# New Millett Hybrid Maxed Amp



## cetoole

Just thought I would post a quick pic of the reason I am still up tonight. Just having real trouble turning Opeth's Deliverance CD off. Had a bit of trouble with way too much gain and getting the volume knob too high with my KSC75's earlier tonight, and even with my HD580s, I cant even make it a quarter turn on the volume knob. This is with DuMont 12ae6a tubes and the cathode resistors unbypassed.


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## tomb

Way to go, Colin! It was nice to come into work this morning and see this.


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## splaz

So I take it prototyping is done ?

 If so, me wants one!


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## tomb

Quote:


  Originally Posted by *splaz* /img/forum/go_quote.gif 
_So I take it prototyping is done ?_

 

I sure hope so, but it's not as if we've had a hard time with it, really. I'll be building one from the new board this weekend. Hopefully, that will have a good result, too.


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## odoe

I've been keeping an eye on these for my main rig project. Looks awesome!


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## jonnywolfet

what are the differences between this and the 'regular' millet?


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## koike

w00t! that is SWEET. cetoole...m(_ _)m


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## tomb

Quote:


  Originally Posted by *jonnywolfet* /img/forum/go_quote.gif 
_what are the differences between this and the 'regular' millet?_

 

Ooh boy - let's see if I can embarass cetoole again! 
	

	
	
		
		

		
		
	


	





 The Millett Hybrid Maxed, or Max for short, was designed by Colin Toole (cetoole, otherwise known as *Mad Max*) to incorporate all of these features and more: 

 * the basic Millett Hybrid circuit 
 * onboard, STEPS-quality Power Supply 
 * onboard, dual Diamond Buffers output stage 
 * onboard, e12 delay circuit (abbreviated for Millett) 

 Also: 
 * extruded TO-220 heat sink footprint for power supply 
 * extruded TO-220 heat sink footprints for all four output transistors 
 * options for MOSFETs on the output transistor positions 
 * CCS has been changed to a feedback transistor pair with selectable resistor sizes for different currents and superior tube regulation 
 * power resistor option for heater circuit, allowing higher voltage supplies without damage to tube heaters 
 * 16mm minimum cap diameter pads throughout, 18mm for the PS 
 (Note: this is spacing for 1000uF-1200uF caps and larger. The Panasonic FM's in cetoole's photo are 1000uF@50V.)
 * 15mm lead spacing for film caps, even larger for cathode bypass films
 * signal input pads front and rear, 5mm spacing for terminal blocks 
 * Noble and Alps adjustable pot positions 
 * onboard Neutrik output jack pads 
 * tube LED and panel LED pads included 
 * PS choice of Schottky rectifier diodes or generic axial diode positions, ceramic snubber caps 
 * board sized for Hammond 1455T1601 case, center post for stability around tubes 

 The Power Supply allows the use of a simple, cheap 24VAC walwart supply (750ma minimum recommended), but results in STEPS-quality power. Capacitor pads allow use of very large boutique electrolytics and film caps. The CCS is superior to the old current-limiting diode, resulting in improved tube current regulation for superior performance. 

 The DB's use only one set of complementary output transistors for each channel, but with the board mounted heat sinks, biasing up to 50ma each and beyond is possible, allowing the transistors to operate within their optimum power range, and lowering distortion for a very clean sound. 

 Finally, for the ultimate in convenience, a small version of Amb's e12 delay circuit is used, resulting in 10-15sec power delay and protective cutoff. No need to unplug your phones upon power on or power off. 

 There is no other DIY amp design that offers as much of a complete package as the Millett Hybrid Max (IMHO). After populating the board, all that is needed are a knob, jacks, the enclosure, and a 750-1000ma 24VAC walwart.

 The sound? Well, it's the best Millett I've ever heard - by a long shot. Initial reports by others are that it competes favorably with many of the best DIY amps.


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## koike

i cant wait to get my hands on the pcbs :drool:


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## regal

Is it possible to bypass the PS section so a Sigma22 can be used ? A design such as this calls for more than a LM317.


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## nysulli

any guesstimate on when the boards will be available, my new hakko is itching for some work, and i've been looking for an excuse to try out tubes


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## tomb

Quote:


  Originally Posted by *regal* /img/forum/go_quote.gif 
_Is it possible to bypass the PS section so a Sigma22 can be used ? A design such as this calls for more than a LM317._

 

Sure, I use an LM338. 
	

	
	
		
		

		
		
	


	




 Seriously, compared to a separate power supply - whether it's the STEPS or one of the SIGMA products, the STEPS-like circuitry on Colin's board is trivial and inexpensive, but it gives nothing away in quality, IMHO. A lot, if not most, of the expense and design of a separate power supply is in the line voltage components, the transformer itself, and the enclosure. 

 More importantly, you circumvent fully half of the advantage in Colin's board trying to do that. A guiding strategy of this board was to have STEPS quality without any of the worries of line voltage filtering/chokes/inductors or expensive toroids. Even with all that stuff - if you put it the STEPS/SIGMA anywhere in the vicinty of the MAX, you'll have worse sound quality than if you hadn't done anything (This has been tested already.)

 It is not a favorable scenario, IMHO.


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## Ace o' Spades

Any estimate on completed cost for a fully populated board?


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## tomb

Quote:


  Originally Posted by *Ace o' Spades* /img/forum/go_quote.gif 
_Any estimate on completed cost for a fully populated board?_

 

*MillettHybridMax.xls 
MHMax BOM Web Page *


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## fierce_freak

This has piqued my interest. I may be DIY'ing again soon


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## regal

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Sure, I use an LM338. ._

 

The problem with the LM317 is it can resonate in the audio band. If you go to the trouble of a discrete buffer it should have a discrete PS, the Millett is especially susceptible to PS quality with the single rail and the argument could be made that you should start with the power supply first. Surely there is a hole on the board where the external regulated DC could be connected?


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## n_maher

Quote:


  Originally Posted by *regal* /img/forum/go_quote.gif 
_The problem with the LM317 is it can resonate in the audio band._

 

Please explain. amb was recently asked if he thought the sigma11 would offer any sort of real world performance benefit over the STEPS with the Millett and his answer was as follows.
  Quote:


  Originally Posted by *amb* 
_If you're referring to RMAA results, I doubt that the change from STEPS to σ11 would make any significant difference, especially in the Millett Hybrid where the amp's limitations still dominate._

 

For the full context of this discussion please see this thread.

  Quote:


 Surely there is a hole on the board where the external regulated DC could be connected? 
 

As far as I understand it yes, there's a fairly simple way to tap whatever power supply you'd like into the board and bypass the on-board PS.


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## regal

I think he is refering to the distortion from the tube making any influence from the power supply hard to measure. Take note that he built a S22 for his Millett. There may be no benefit, but the reviews are that the max is clearer which I am guessing would mean it is more likely to benefit from the S22. The other thing to consider is a filtered power entry module with a choke and capacitors on the AC side.


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## tomb

Quote:


  Originally Posted by *regal* /img/forum/go_quote.gif 
_I think he is refering to the distortion from the tube making any influence from the power supply hard to measure. Take note that he built a S22 for his Millett. There may be no benefit, but the reviews are that the max is clearer which I am guessing would mean it is more likely to benefit from the S22. The other thing to consider is a filtered power entry module with a choke and capacitors on the AC side._

 

Regal, this is not a valid comparison. The Millett is not even Amb's design. His M3 has depended on a STEPS or a TREAD from the beginning. Don't you think he wanted to design his own product for his own amps (Sigma11)? Nate has given you Amb's own answer regarding the Millett, yet you persist. The filtering you mention has next to no benefit when the distance imposed by a walwart is factored in. Here's a question: what did Amb use as a power supply for the CKKIII?

 The Max is a total product. I suggest you build one if you are interested - then see if you want to give up half the board in the interests of bringing an EMF source closer to the tubes.


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## pobrecito

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Regal, this is not a valid comparison. The Millett is not even Amb's design. His M3 has depended on a STEPS or a TREAD from the beginning. Don't you think he wanted to design his own product for his own amps (Sigma11)? Nate has given you Amb's own answer regarding the Millett, yet you persist. The filtering you mention has next to no benefit when the distance imposed by a walwart is factored in. Here's a question: what did Amb use as a power supply for the CKKIII?

 The Max is a total product. I suggest you build one if you are interested - then see if you want to give up half the board in the interests of bringing an EMF source closer to the tubes._

 

I see nothing wrong with what Regal is suggesting. This is DIY. Using a Sigma in close proximity should not be a issue at all as the transformer is not located on the PCB as in the STEPS. On top of that, one can still use the recommended wallwart if needed thus ignoring the issue of EMF. As for the filtering, whether it benefits you or not will depend on your line noise but a simple wallwart without it will definitely be at an disadvantage in the real world.


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## cotdt

Let's see what all this hype is about. I think I'll build one to compare against real tube amps and high end SS amps. Just to see if the hype is justified.


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## bperboy

Quote:


  Originally Posted by *cotdt* /img/forum/go_quote.gif 
_Let's see what all this hype is about. I think I'll build one to compare against real tube amps and high end SS amps. Just to see if the hype is justified._

 

Lets! I've got the last version of the Millett with a STEPS, and I'm planning on building this after this final prototype is... um... prototyped. I'm going to compare it to my old one, and I'll be sure to post pics and impressions. This will probably be a month or so though.


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## tomb

Quote:


  Originally Posted by *pobrecito* /img/forum/go_quote.gif 
_I see nothing wrong with what Regal is suggesting. This is DIY. Using a Sigma in close proximity should not be a issue at all as the transformer is not located on the PCB as in the STEPS. On top of that, one can still use the recommended wallwart if needed thus ignoring the issue of EMF. As for the filtering, whether it benefits you or not will depend on your line noise but a simple wallwart without it will definitely be at an disadvantage in the real world._

 

I agree with what you say in principle - except the filtering part - if a Sigma11 is built without an onboard xfmr. However, "This is DIY" is justifying trashing at least 1/3 of the Max's board when up until a few weeks ago, the STEPS was the best thing going for any PS, anywhere.

 Both of yours and Regal's statements are made without the benefit of testing, or without the benefit of building either one in combination with the Max. You are also both ignoring Amb's own canonical testing of the Millett Hybrid, his own design goals for the Sigma power supplies, and ultimately, _his own statement that it won't make a difference on the Millett_.

 By suggesting this, you are implying that a STEPS-like circuit is not even worthy. Perhaps you also aren't considering the ultimate consequence of this line of discussion: you are setting Amb's Sigma11 design directly against Tangent's STEPS design. That is decidedly _not cool_ in DIY, contrary to what you suggest.


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## n_maher

Quote:


  Originally Posted by *cotdt* /img/forum/go_quote.gif 
_Let's see what all this hype is about. I think I'll build one to compare against real tube amps and high end SS amps. Just to see if the hype is justified._

 

I'd be interested to hear what you think of it, considering that it's total build cost should come in under $200. Although I have no idea what you're talking about referring to "hype". Tomb is excited about the project because he's played a big role in pulling it all together but I don't see any hype.

 And I've said it before and I'll say it again cotdt, your posts have a way of coming across in a very condescending way whether you intend them to or not. Using terms like "real tube amps" doesn't help. 

 I'll never claim that any version of Pete's hybrid regardless of implementation will be the end all in amplification. But for whatever reason it seems to garner and unfair amount of immediate dismissal by folks around here as a giant compromise that can't do anything well either. I'd wager few of the folks making claims like this have ever heard one...


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## koike

and im excited about it because i like the millett's sound! not like anyone cares though...hope i can get boards real soon...


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## tomb

Quote:


  Originally Posted by *koike* /img/forum/go_quote.gif 
_and im excited about it because i like the millett's sound! not like anyone cares though...hope i can get boards real soon..._

 

I care, koike - and I hope we can get the boards to you soon.

 Many thanks for the kind comments, Nate.


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## n_maher

Quote:


  Originally Posted by *koike* /img/forum/go_quote.gif 
_and im excited about it because i like the millett's sound! not like anyone cares though...hope i can get boards real soon..._

 

Actually I care a great deal that you're excited! The only reason most of us (like tomb, cetoole, amb, tangent, etc) do what we do is because it's FUN. The day it stops being so is the day I'll be done.


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## splaz

Well it doesn't look exciting for my bank account...


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## koike

w00t. im gonna get me 5 boards haha!
 im 'taking lessons' from a local amp builder.
 hope i can build one of my own one day


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## naamanf

How does one go about getting a board?


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## tomb

Quote:


  Originally Posted by *naamanf* /img/forum/go_quote.gif 
_How does one go about getting a board?_

 

PM "cetoole".


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## regal

Tomb,

 Don't take offense. I think this new Max board is great and much needed. I think the Millett is an unsung hero and deserves the new CCS and class A buffer.

 Just understand that when you get to higher parts cost and designs the limitations of an LM317 become more apparent. There is nothing wrong with building this as is, but there should be an improvement with a S11. AMB said he can't measure any difference vs the LM317, but you can't measure the benefits of Blackgates either but I'll bet $'s you have used them. 

 As far as Steps vs S11, the question is only where does a S11 become worth the extra parts cost? There is a point where a discrete PS is worth it or people would be using LM317's on everything. We don't know till someone tries each.

 No one is trashing anything. Settle down and realize that if you or I owned a $15000 tube amp, we would look to mod it. And where would I start? The power supply. That's ANY design.


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## pobrecito

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_I agree with what you say in principle - except the filtering part - if a Sigma11 is built without an onboard xfmr. However, "This is DIY" is justifying trashing at least 1/3 of the Max's board when up until a few weeks ago, the STEPS was the best thing going for any PS, anywhere.

 Both of yours and Regal's statements are made without the benefit of testing, or without the benefit of building either one in combination with the Max. You are also both ignoring Amb's own canonical testing of the Millett Hybrid, his own design goals for the Sigma power supplies, and ultimately, his own statement that it won't make a difference on the Millett.

 By suggesting this, you are implying that a STEPS-like circuit is not even worthy. Perhaps you also aren't considering the ultimate consequence of this line of discussion: you are setting Amb's Sigma11 design directly against Tangent's STEPS design. That is decidedly not cool in DIY, contrary to what you suggest._

 


 Nowhere did I say one was better than the other, only that there is nothing wrong with Regal's suggestion. As for the STEPs being unworthy, I have several that I use on a daily basis. Regarding the direct comparison between the power supplies, it is you who is ultimately setting the challenge with such bold statements as "the STEPS was the best thing going for any PS, anywhere." 

 On another note, the MAX is a great design whose time has come. The fact that it integrates so many ideas into a singular package is brilliant. It is very well thought out, offering DIYers everything that they could want in a Millett. However, this doesn't mean there is no more room for improvement/tweaking. 

 You've done a great job on the MAX but you have to learn relax and not to take everything to heart. 

 Peace


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## tomb

Quote:


  Originally Posted by *pobrecito* 
_... snip ... Regarding the direct comparison between the power supplies, it is you who is ultimately setting the challenge with such bold statements as "the STEPS was the best thing going for any PS, anywhere."_

 

That's not a "bold statement". It was a general consensus in the headphone DIY community. Please do not quote me out of context: you very conveniently left out the part of "up until a few weeks ago." This is referring to the fact that Amb's Sigma11 is NEW - as in _didn't exist a few weeks ago._ 

 This is not a helpful or productive line of discussion, however. We are in agreement that the Max is a special design. So, you guys buy some boards from cetoole and chop them up to your heart's content.


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## tomb

OK, I wasn't going to post this again after Colin's fine photo and because I also posted it in the sticky thread at top. However, maybe it will get attention back where it should be: on the Max. This is my version of the 1st prototype. The only issue was a little hum and ripple in the PS, which we solved (totally unrelated to the discussion above). I am running 27V from an 800ma supply. I also have a 1000ma supply and it runs a little cooler. It pulls about 600ma on inrush and 430ma on idle. The DB's are 2SC3422/2SA1359 biased at about 50ma (115mV) ea. Caps are Pana FC's in the PS, Pana FM's on board with Nichicon Muse ES and Wima MKP10's in boutique positions.

 I have lived with this amp every day since March 11th - turning it on every night for several hours, and for most of the day and night every weekend. Listening is mostly through an M-Audio Transit. Music sources tested also include a 1st generation iPod, a Sony D-NE20, and various other PCDP's, including an old "D" model Sony. The combination of the Max with Sony D-NE20 and older D model (using Line Out) highlighted a deficiency in high bit-rate mp3's - something not easily noticed on my other amps. Ever since, I have been using FLAC files almost exclusively.

 In total, it sounds better than any previous Millett - DB's or not (I've built 4). It also sounds better than some other popular DIY amps, but they will remain un-named. Besides the ever-present KSC75's, it drives an HD580 extremely well - detail and slam in abundance. The headphones also stay plugged in without worry of power up or power down. Hopefully, these remarks are free enough from unnecessary embellishment.


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## bperboy

Tomb, your build looks very nice. Are you casing in the Hammond? Whenever you get it cased, please post some more ****! I'm pretty set on this for my next project, but we'll see if there are any more changes to the prototype. As of now, do you think there will be any changes for the final board?


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## n_maher

Quote:


  Originally Posted by *regal* /img/forum/go_quote.gif 
_Just understand that when you get to higher parts cost and designs the limitations of an LM317 become more apparent. There is nothing wrong with building this as is, but there should be an improvement with a S11. AMB said he can't measure any difference vs the LM317, but you can't measure the benefits of Blackgates either but I'll bet $'s you have used them._

 

regal, I appreciate your contributions to the discussion but can you honestly say that you've heard the difference in moving from a STEPS to a better power supply? Which PS? And we're still talking about a sub $200 build even using some boutique parts so I'd hardly say we're into the "higher parts cost" realm of things. The limiting factor with the Millett design is always going to be the tubes. Yes, I completely agree that moving from a wallwart to a good regulated power supply is a huge improvement but I think in this case the designers (cetoole) did a very good job of selecting a complementary topology and didn't throw money at areas just so that they might measure slightly better. Again, I'd ask that you recognize that the STEPS in commercial terms is a _highly_ advanced power supply.

  Quote:


 We don't know till someone tries each. 
 

You're more than welcome to and I'd be interested to hear what you think but some parts of your earlier posts essentially said that if someone was going to bother designing a better Millett than they should have considered a better power supply. A large design consideration (as far as I could tell) with the Millett Max was to bring together known-good existing topologies so that the prototyping expenses kept to a minimum. Please understand that in large part the prototyping costs are born by folks like tomb and myself and not passed onto you, the casual builder. So you'll have to give us a bit of a break if we get a bit tweaked when we go to the trouble of donating money, time and not a little bit of effort into something only to have someone refer to the end result with a "why did you bother if you're not going to do it well" type of reply. 

  Quote:


 Settle down and realize that if you or I owned a $15000 tube amp, we would look to mod it. And where would I start? The power supply. That's ANY design. 
 

Again I would ask that you read what I wrote above and then re-read your previous posts. I think you'll see where tomb is coming from. 

  Quote:


  Originally Posted by *pobrecito* /img/forum/go_quote.gif 
_Regarding the direct comparison between the power supplies, it is you who is ultimately setting the challenge with such bold statements as "the STEPS was the best thing going for any PS, anywhere."_

 

Please point me to another widely used DIY power supply design that both existed and was fully supported two months ago. The STEPS was the best DIY thing going and based on a case by case basis it very may well still be. 

  Quote:


 However, this doesn't mean there is no more room for improvement/tweaking. 
 

I think the idea here is how about letting us get done with this one before you going "tweaking it"? Some of us have been working on/with the Millett for the better part of 2 years now so it's not as if we didn't go into this project without doing a bit of research. 

 Way more than my 2¢ but you don't have to read it if you don't want to.

 Nate


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## regal

Quote:


  Originally Posted by *n_maher* /img/forum/go_quote.gif 
_ some parts of your earlier posts essentially said that if someone was going to bother designing a better Millett than they should have considered a better power supply. only to have someone refer to the end result with a "why did you bother if you're not going to do it well" type of reply. 
_

 

Never even thought such a thing ! The problem with typing replies in forums is people want to jump to conclusions. Heck if I wasn't seriously impressed with this great improvement to the Millett I wouldn't have even made a post.

 Just understand this is the first time Head-fiers have had any exposure on this and the question is pretty benign. 

 For those that don't know diyforums.org is basically closed to new members.


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## infinitesymphony

Will there be links to a parts list, an assembly guide, estimated final cost, etc. for this particular variation of the Millett?

 Second question... I just built a CMoy; how much more knowledge would it take to assemble one of these?


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## pobrecito

Nate, All very valid points, I fully appreciate where you are coming from. I can also clearly see your point of view in regards to the STEPS. As for the statement "the STEPS was the best thing going for any PS, anywhere." I took Tomb's comment to mean the holy grail of power supply design period, not in the context you described. Thus, my comment that it was such a bold statement. I think I might be getting a little bit jaded from reading all of the FOTM/fanboy threads.

 Tomb, In that light, I offer you my sincerest apology.

 PS. Who doesn't like chopped Millett for dinner?


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## tomb

Quote:


  Originally Posted by *bperboy* /img/forum/go_quote.gif 
_Tomb, your build looks very nice. Are you casing in the Hammond? Whenever you get it cased, please post some more ****! I'm pretty set on this for my next project, but we'll see if there are any more changes to the prototype. As of now, do you think there will be any changes for the final board?_

 

Thanks, my photo is just the 1st prototype. I only posted it to get this thread back on track, though. Attention should be paid to cetoole's first post - that's the newer prototype. The back of mine was eventually cut up a little bit in trying to solve the hum/ripple noise. That was fixed, and the changes are incorporated into the new version shown in cetoole's first post.

 Several of us that are building the newer 2nd prototype - the one in cetoole's photo - will be casing them up in a 1455T1601 Hammond. The board is designed to fit in the slots on that case. We will defintiely post photos when they're boxed up.

 According to cetoole's comments and experience thus far with the 2nd prototype, I doubt that there will be any changes to the production boards.

  Quote:


  Originally Posted by *infinitesymphony* 
_Will there be links to a parts list, an assembly guide, estimated final cost, etc. for this particular variation of the Millett?

 Second question... I just built a CMoy; how much more knowledge would it take to assemble one of these?_

 

The links to the current BOM, both in Excel and HTML format was posted in Post #14 of this thread. More info than you'd ever want to know is available at the link in my signature below. Total cost, including case, is less than $150. You'll need to add other things such as jacks and knobs, but that price includes the walwart, too.

 Build a PIMETA next, and perhaps a TREAD to go with it, then building the Max might be possible. There are difficulties dealing with the tubes, matching transistors, the heat sinks, biasing techniques, and then there's quite a parts count. It would not be my choice for a beginner or even a successful CMoy builder, but is well within the skills of someone who has built an M3, for instance.


 P.S. Pobrecito - thanks for the comments. I perhaps reacted too strongly.


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## n_maher

Quote:


  Originally Posted by *regal* /img/forum/go_quote.gif 
_For those that don't know diyforums.org is basically closed to new members._

 

If anyone would like to join that forum all they have to do is shoot me a PM here.


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## tomb

Quote:


  Originally Posted by *n_maher* /img/forum/go_quote.gif 
_If anyone would like to join that forum all they have to do is shoot me a PM here._

 

Yes - I think we all know who "n_maher" is, and that name has been prominently displayed as a moderator at DIYForums.org for as long as I can remember.

 I am trying not to fuel this thread anymore, but - deleted -

 Aw, fudge - I'm gonna go do some yardwork.


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## adfinni

Looks awesome !!!! I love my millett hybrid, but really want to build my own from scratch, and this looks great.

 Few questions though:

 1. If im reading things correct then the boards are still in the prototype phase. How long will these 2nd gen boards be available for and will there be quite a limited run ?

 2. Most importantly 'THE SOUND'. My millett has cerafines throughout and 2 BG standars in directly in the path, plus it's running a tread. What sort of sound improvement am i looking at with this rig:

 Heavily modded marantz cd-63 (probs sounds around the same as $1500-$2000 cd-players) -----------> New MH of course -------------> Grado HF-1 (will eventually get the BEST treatment at headphile like deep woody, blackmaxx recable etc)


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## tomb

Quote:


  Originally Posted by *adfinni* /img/forum/go_quote.gif 
_Looks awesome !!!! I love my millett hybrid, but really want to build my own from scratch, and this looks great.

 Few questions though:

 1. If im reading things correct then the boards are still in the prototype phase. How long will these 2nd gen boards be available for and will there be quite a limited run ?_

 

I believe cetoole has about 10 boards left after sending them to the prototype builders. I may be wrong, though. Easiest thing to do if you want one - PM "cetoole".

  Quote:


 2. Most importantly 'THE SOUND'. My millett has cerafines throughout and 2 BG standars in directly in the path, plus it's running a tread. What sort of sound improvement am i looking at with this rig: 
 

The Cerafines and BG's are great, but there's more to the new Millett Hybrid Max than good caps. You didn't say if yours has the DB's (Diamond Buffers) - that's the single biggest thing that affects the sound on a Millett, besides the tubes, of course. Even so, the Max can run the DB's at a much higher current, and sounds still better than a regular Millett with DB's. There is also more going on with cetoole's circuit around the tube and CCS. Early builders so far are reporting that every detail comes through.

  Quote:


 Heavily modded marantz cd-63 (probs sounds around the same as $1500-$2000 cd-players) -----------> New MH of course -------------> Grado HF-1 (will eventually get the BEST treatment at headphile like deep woody, blackmaxx recable etc) 
 

There is sufficient current and voltage, along with a choice of gain by using different tubes, to satisfy most headphone types - including Grados.


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## pabbi1

Does this design clip as much as the previous incarnation (the Drew & Nate version)? I needed a fair amount of output more than the BUF634 would deliver, so I assume this is better in that regard, though (pardon me Nate) this is still no HA-2? 

 I am tempted to build one, even if I don't have any dynamic phones - just for the fun of it and, maybe, for the office. Me hate you guys - long time... if Pete would just design a DIY electrostat amp... <sigh>.


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## adfinni

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_I believe cetoole has about 10 boards left after sending them to the prototype builders. I may be wrong, though. Easiest thing to do if you want one - PM "cetoole"._

 

OK cool, thanks


  Quote:


 The Cerafines and BG's are great, but there's more to the new Millett Hybrid Max than good caps. You didn't say if yours has the DB's (Diamond Buffers) - that's the single biggest thing that affects the sound on a Millett, besides the tubes, of course. Even so, the Max can run the DB's at a much higher current, and sounds still better than a regular Millett with DB's. There is also more going on with cetoole's circuit around the tube and CCS. Early builders so far are reporting that every detail comes through. 
 

 Yup i have a DB board with them biased around 48mv, and im using GE 12fk6 tubes biased at ~14V.

 Thanks


----------



## splaz

Well, as I hinted at I can't afford to do one right now, I need spending money for a holiday but to make sure I don't put it off I've bought some tubes.

 I figure, the tubes are pretty useless on their own so with them laying around I'll have to put them to use. 
	

	
	
		
		

		
		
	


	




Tubes!

 Probably didn't need 10 but I want spares and I can audition between GE and Westinghouse I guess and the RCA one I can err... look at.


----------



## tomb

Geez - how are you guys finding these Millett tubes on ebay? Gewa posted a photo of a whole box he got the other day. Every time I look, there's only a single here and there.


----------



## splaz

First time lucky for me.


----------



## n_maher

Quote:


  Originally Posted by *pabbi1* /img/forum/go_quote.gif 
_Does this design clip as much as the previous incarnation (the Drew & Nate version)? I needed a fair amount of output more than the BUF634 would deliver, so I assume this is better in that regard, though (pardon me Nate) this is still no HA-2?_

 

What headphones did you have a problem with clipping? In all my experiences with the Milletts I never experienced clipping at my type of listening volumes. That said, I'm don't think any Millett based hybrid will equal the HA-2 for high-impedance headphones.

  Quote:


 I am tempted to build one, even if I don't have any dynamic phones - just for the fun of it and, maybe, for the office. Me hate you guys - long time... 
 

I'm thinking that mine will end up being an office amp too. Course, I'm also having wicked thoughts of deconstructing my current black-gated Millett and moving the parts to the max board. Decisions, decisions...


----------



## mypasswordis

Would you guys happen to have any idea how well the Max would drive an AKG K340, and perhaps compared to the SOHA with discrete buffers (of course, no one has them yet...)? I haven't been listening to it often lately because it just sounds underpowered.


----------



## pabbi1

Quote:


  Originally Posted by *n_maher* /img/forum/go_quote.gif 
_What headphones did you have a problem with clipping? In all my experiences with the Milletts I never experienced clipping at my type of listening volumes. That said, I'm don't think any Millett based hybrid will equal the HA-2 for high-impedance headphones._

 

HD600, of course... and, I am eying the PX450(?) now that I am always on the road... yes, the maxxed I had was with the Black Gates also... it was a sweet memory, but it's cousins, HA-1 and HA-2, were just too seductive with the 600s...

 I talked with Pete about the clipping (and had him listen to it), where he chuckled with a 'What did you expect?', but that naught was to be done, except invest in some heavier iron & glass... good times.


----------



## cotdt

instead of Black Gates, should have used PIO capacitors. So it's not really MAX'ed, is it?


----------



## n_maher

Quote:


  Originally Posted by *cotdt* /img/forum/go_quote.gif 
_instead of Black Gates, should have used PIO capacitors. So it's not really MAX'ed, is it?_

 

As has been clearly shown in the past your truth does not equal my truth. I'm sure every one has their own idea of what a "maxed" configuration of a particular amp would be.


----------



## adfinni

Quote:


  Originally Posted by *n_maher* /img/forum/go_quote.gif 
_ Course, I'm also having wicked thoughts of deconstructing my current black-gated Millett and moving the parts to the max board. Decisions, decisions..._

 

Ditto


----------



## GeWa

Quote:


 Geez - how are you guys finding these Millett tubes on ebay? Gewa posted a photo of a whole box he got the other day. Every time I look, there's only a single here and there. 
 

 Quote:


 First time lucky for me. 
 

Sorry tomb, but I also just stumbled on them doing a long shot search on Ebay.
 I still don't have them though.
 I'm also still waiting on the MillettMax board.

 Regards


----------



## naamanf

I have a local store that has two isles of NOS and used tubes. I plan on seeing what they have tomorrow. Hopefully they have the tubes.


----------



## naamanf

Picked up some tubes today. 12AE6/A 12FK6 and 12FM6. I picked up three different types of the 12FK6 LO, ND, and BV all made by RCA. Any idea what the difference between them is? The BV looks to be the newest of the group.


----------



## tomb

Quote:


  Originally Posted by *naamanf* /img/forum/go_quote.gif 
_Picked up some tubes today. 12AE6/A 12FK6 and 12FM6. I picked up three different types of the 12FK6 LO, ND, and BV all made by RCA. Any idea what the difference between them is? The BV looks to be the newest of the group._

 

 I don't have a clue. The only differences I'm aware of between like-designated Millett tubes are the getters - top or side, round or rectangular. I have never heard of _labeled_ variants.


----------



## n_maher

If I recall correctly there are actually only a couple of actual manufacturers of the tubes used in the Millett (like 3 or 4). Most of what you're going to find are just rebranded tubes with no internal or sonic differences. That said, there may have been production differences throughout the various runs of the tubes but honestly I've put that much stock in trying to roll all that many tubes through my Milletts. Put in a set, bias them and figure out if they sound good to me. Everytime you roll tubes you really should check the bias on the amp, I've had different FK6's (my tube of choice) bias WAY different.

 My 2c,

 Nate


----------



## Listen2this1

Just got my board from Colin, thanks. So its on like donkey kong.


----------



## vixr

I got the last two proto boards... this is gonna be awesome!!!


----------



## tomb

Quote:


  Originally Posted by *vixr* /img/forum/go_quote.gif 
_I got the last two proto boards... this is gonna be awesome!!!_

 

You bet! I think you will be impressed.


----------



## koike

noooooooooooooooooo
 no proto boards for me?


----------



## bperboy

Man, i've finished hte PSU section and i've only got to put in the muting circuit and the buffer then I'm done! I LOVE DIY! SO AWESOME! This right here is why I'm going into electrical engineering. Such an awesome hobby!


----------



## adfinni

Quote:


  Originally Posted by *vixr* /img/forum/go_quote.gif 
_I got the last two proto boards... this is gonna be awesome!!!_

 

group buy coming up eventually i assume ?


----------



## tomb

Quote:


  Originally Posted by *adfinni* /img/forum/go_quote.gif 
_group buy coming up eventually i assume ?_

 

Yes. We're waiting until a couple more of the 2nd proto's get built, just to make double sure it's fully vetted.


----------



## adfinni

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Yes. We're waiting until a couple more of the 2nd proto's get built, just to make double sure it's fully vetted._

 

hehe, so some of us DIY 'noobs' don't get too confused. I'm feeling at a loss as it's been at least 3 months since ive used my soldering iron


----------



## vixr

Quote:


  Originally Posted by *adfinni* /img/forum/go_quote.gif 
_hehe, so some of us DIY 'noobs' don't get too confused. I'm feeling at a loss as it's been at least 3 months since ive used my soldering iron 
	

	
	
		
		

		
		
	


	


_

 

3 months!!! I cant go three days!!! but, I can stop any time I want...


----------



## vixr

is there any significant changes worth mentioning to the BOM posted?


----------



## bperboy

Quote:


  Originally Posted by *vixr* /img/forum/go_quote.gif 
_is there any significant changes worth mentioning to the BOM posted?_

 

Well, so far as teh output buffer goes, I bought the MOSFETs from AMB.org, and we're having some trouble getting it to work. You might want to get the standard MJEs until we get it working...


----------



## tomb

Quote:


  Originally Posted by *vixr* /img/forum/go_quote.gif 
_is there any significant changes worth mentioning to the BOM posted?_

 

Nope - assuming you're referring to the version dated 4/29/07. The cap sizes listed are minimums. You have a lot of latitude if you use your selection of heat sink height as the cap height limit.

 Also, the MOSFET version of the buffer has not been vetted, and Bperboy is having a little trouble trailblazing it. So given a choice, stick with the output transistors. There are several working versions of that option built and performing well. Biasing the transistors for something between 30-50ma should be pretty straightforward. I prefer the higher bias, myself. 
	

	
	
		
		

		
		
	


	




 EDIT: Oops - I see Bperboy has posted already. The MJE's are OK, but the 2SC's are a cut above. BDent or MCMinone are good sources.


----------



## tomb

On other thing to note - the transistor version should jumper out the RB8L/R and RB9L/R resistors. Also, the otuput transistors use the smaller silkscreen outlines.


----------



## The Monkey

Well, count me in and looking forward to the group buy. In the meantime, I'll build my "regular" MH to get back into the swing of DIY, then move on to the Max. 

 Great work, guys, and thank you!


----------



## cronic

Hey guys great work, I really want one of these pcb. They look awesome. Will info be posted in this thread when the pcbs are ready for sale?


----------



## tomb

Quote:


  Originally Posted by *cronic* /img/forum/go_quote.gif 
_Hey guys great work, I really want one of these pcb. They look awesome. Will info be posted in this thread when the pcbs are ready for sale?_

 

Most likely, the GB will be announced in the Head-Fi Group Buy section. It may just be a reference, though, with the actual Group Buy at Headwize.


----------



## tomb

2nd Proto finished:


----------



## naamanf

Looks great! I should be starting mine tomorrow. How does it sound?


----------



## mb3k

It looks as though it comes a tad short to fit snuggly in the hammond case (ie. the pcb touching faceplate to faceplate). I haven't followed the MHMax at all but maybe it could be made longer?


----------



## tomb

Quote:


  Originally Posted by *mb3k* /img/forum/go_quote.gif 
_It looks as though it comes a tad short to fit snuggly in the hammond case (ie. the pcb touching faceplate to faceplate). I haven't followed the MHMax at all but maybe it could be made longer?_

 

Yes, you are correct - it's about 3/16" short. I believe cetoole did this to make room for his Noble pot without pushing it too far back into the heat sinks. When using the Alps and the Neutrik PCB jack, though, that extra space will really help pulling all the test points up from the bottom of the board. We'll have to get cetoole's take on it for the real reason, though.

 This one verified the circuit and final layout for the DB's. We're hoping we have a configuration for the MOSFET's, too - NeilR is working on those with Bperboy as another test case (he was first, actually). The structure, thickness, and perhaps the final length may change some to put it jam up against the endplates, but nothing will alter enough to change from this case.

 The good news is that I used the DB option - the 2SC3422/2SA1359 pairs, and everything worked - the first time out!! I've never had that happen. Everything biases like a charm:

 Walwart: 24VAC, 35VA ($6 surplus Basler Electric) 
 PS: 27.1VDC 
 Tube Bias: 13.5 (12AE6A GE) 
 DB Bias (2SC3422/2SA1359): 109.5mV!!, +or- 0.2mV all four ~50ma ea.


 EDIT: Prior to firing it up:


----------



## bhjazz

Quote:


  Originally Posted by *The Monkey* /img/forum/go_quote.gif 
_Well, count me in and looking forward to the group buy. In the meantime, I'll build my "regular" MH to get back into the swing of DIY, then move on to the Max._

 

Make that two of us. My job has been an absolute bear lately. Gah!!!!! I miss working on this stuff. 

 "But focus, you must."

 Bite me, Yoda. 

 So anway, these protos look gorgeous and I'll keep my eye out for YAGB (yet another group buy!). 

 Thanks, all!


----------



## cotdt

what are the measurement results for this amp?


----------



## tomb

Quote:


  Originally Posted by *cotdt* /img/forum/go_quote.gif 
_what are the measurement results for this amp?_

 

Gee, I don't know. You could take a STEPS PS circuit, add it to a fully vetted Pete Millett Hybrid circuit, and then top it off with PPA Diamond Buffer, except it biases at twice that, if desired. Then stick an e12 delay on it for good measure, what do you think?

 I'm hoping NeilR will RMAA and scope his, but it will be the MOSFET version. Historically, Amb did extensive testing on the original Millett. I've built four of those - all with DB's - and cetoole's is a _major_ improvement.

 'Course it's tubes, so distortion measurements don't portray the real picture. I'm sure that didn't answer your question, but it's the best I can do for the moment.


----------



## cotdt

how about the output impedance and the TIM?


----------



## tomb

I'm not sending you one to review.


----------



## cotdt

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_I'm not sending you one to review. 
	

	
	
		
		

		
		
	


	


_

 

lol =(


----------



## naamanf

Built mine this afternoon. Great little amp and an easy build!


----------



## bperboy

Did you use the BJTs for the output devices on the buffer?


----------



## naamanf

I used the MJE243G and 253.


----------



## tomb

Woo hoo! Great job, Naamanf!


----------



## vixr

still waiting on boards...


----------



## n_maher

Quote:


  Originally Posted by *vixr* /img/forum/go_quote.gif 
_still waiting on boards...
	

	
	
		
		

		
		
	


	


_

 

Don't be sad, the group buy will come soon enough!


----------



## TBomb06

So, you lucky few who have a board...how is this thing working out for you? 
	

	
	
		
		

		
		
	


	




 Any idea when the boards might be ready for a group buy? This may sound silly, but I really plan on matching a set of cans to this amp rather than the other way around...that's how excited I am about it! Sooo...any suggestions for phones for a basshead rocker that were just made to go with this amp, those of you who have been fortunate enough to hear it?


----------



## splaz

Okay this is more of just a general tube question but I have millet tubes now so I guess it's kinda related.

 IIRC don't mix tube brands. However does the location of the getter flash matter, like can you use a side and a top together from the same brand ?


----------



## tomb

Quote:


  Originally Posted by *TBomb06* /img/forum/go_quote.gif 
_So, you lucky few who have a board...how is this thing working out for you? 
	

	
	
		
		

		
		
	


	




 Any idea when the boards might be ready for a group buy? This may sound silly, but I really plan on matching a set of cans to this amp rather than the other way around...that's how excited I am about it! Sooo...any suggestions for phones for a basshead rocker that were just made to go with this amp, those of you who have been fortunate enough to hear it? 
	

	
	
		
		

		
		
	


	


_

 

I think it does very well with the HD580 - plenty of voltage and slew rate to make those phones snap and pop, contrary to the complaints you often hear. 'Course, with the Senn's - it's always about the amp.

 The Max is so detailed, it's also leading me to prefer the old PortaPro's over my beloved and ubiquitious KSC75's. I'm able to clearly hear the grainy midrange now in the KSC's. At the same time, the bloated bass blow in the PP's are very well controlled.

 IMHO, and YMMV, of course.

  Quote:


  Originally Posted by *splaz* 
_Okay this is more of just a general tube question but I have millet tubes now so I guess it's kinda related.

 IIRC don't mix tube brands. However does the location of the getter flash matter, like can you use a side and a top together from the same brand ?_

 

IMHO, the order of preference in distinguishing tubes goes like this:
 1. *Type - *12AE6, 12AE6A, 12FK6, 12FM6 (preference among types is personal and gain-related, but that's the first distinguishing feature that should be considered)
 2. *Brand -* GE, RCA, Sylvania, etc. (This one can get creative, because many of the smaller tube companies subcontracted these tube series to the biggies. Even some of the big ones subcontracted to the others for certain series - for instance, GE didn't list the FM6 in their catalogs. The markings appear to be RCA in origin. Nevertheless, A GE 12AE6A vs. a RCA 12AE6A vs. A Sylvania 12AE6A sound very different.)
 3. *Construction - *as you note, the getter type and location is the distinguishing feature here, and it may vary within the same brand, depending on the vintage. The four types I've seen are:
 1. Circular getters on top (halos)
 2. Circular getters on the side (these are almost always the newest tubes)
 3. Square getters on top
 4. Square getters on the side.
 There doesn't seem to be an advantage/disadvantage in sound among these getter differences, just that there may be a difference.

 P.S. I'll be mentioning this in our web page documentation, but there appears to be a huge anectodal difference in bass according to the size of the cathode bypass cap. That cap for the regular Millett has historically been sized at 220uF, although usually a boutique is recommended. If you run the conventional wisdom equation for RC filtering of the cap, that 220uF is about twice the size as it should be. Nevertheless, I am recommending that a 1000uF cap should be used, or perhaps 470uF at the smallest. It appears to make a huge difference in the very lowest, slamming bass.

 This reasoning is also reflected by Runeight's SOHA design, where he recommended as large a cap as practical in the cathode bypass positions, even though conventional-wisdom says the RC corner frequency needs nothing that large. However, the SOHA never lacked of any bass when following this strategy, and neither does the Max.


----------



## hellomai

Since the output is the same, or almost, as PPAv2. Anyone tried to modify the output buffer to Dyn-O-Bias II? PPL had it post here


----------



## n_maher

Quote:


  Originally Posted by *hellomai* /img/forum/go_quote.gif 
_Since the output is the same, or almost, as PPAv2. Anyone tried to modify the output buffer to Dyn-O-Bias II? PPL had it post here_

 

At this stage of the project we have limited the experimentation to just trying to verify the "base" configurations of the amp. It will be up to enterprising builders like yourself to tweak the amp further.


----------



## hellomai

Quote:


  Originally Posted by *n_maher* /img/forum/go_quote.gif 
_At this stage of the project we have limited the experimentation to just trying to verify the "base" configurations of the amp. It will be up to enterprising builders like yourself to tweak the amp further. 
	

	
	
		
		

		
		
	


	


_

 

waiting for the group buy...


----------



## odoe

Just noticed the BOM was updated last week.
 Time to tweak my mouser project.
 I got a pack of 5 12AE6A tubes off ebay in the mail the other day.
 I'm pretty excited to start putting this thing together!


----------



## vixr

got my boards today!!! they are beautiful... I cant wait to get this thing built. Where are we getting those cute green caps in CA7 L/R ???


----------



## splaz

Quote:


  Originally Posted by *vixr* /img/forum/go_quote.gif 
_got my boards today!!! they are beautiful... I cant wait to get this thing built. Where are we getting those cute green caps in CA7 L/R ???_

 

Nichicon Muse ES ?


----------



## tomb

Quote:


  Originally Posted by *splaz* /img/forum/go_quote.gif 
_Nichicon Muse ES ?_

 

Yes. Handmade Electronics is an excellent source. The 1000uF, 16V is perfect in the cathode bypass (CA2L/R). A perfect output cap (CA7L/R) is the Nichicon Muse ES, 470uF, 35V. Unfortunately, that one is only at Michael Percy and at BDent. BDent happens to be a great source for the 2SC Toshiba and Sanyo output transistors, so that helps. For some reason, Handmade does not carry the 35V line of Muse ES. 50V versions of KZ's and Elna's tend to be 1-1/2" high. There is a high-quality 680uF, 35V Black Gate NX that would be an excellent choice for C7 - same for C2 - there's a 1000uF, 25V that's only 1" high. Of course, if you're using taller heat sinks, this isn't such an issue.


----------



## TBomb06

Quote:


  Originally Posted by *vixr* /img/forum/go_quote.gif 
_got my boards today!!! they are beautiful... I cant wait to get this thing built. Where are we getting those cute green caps in CA7 L/R ???_

 

I'm jealous. Want to sell me a board?


----------



## tomb

Be patient, guys ... the Group Buy is coming ... very shortly.


----------



## bperboy

Quote:


  Originally Posted by *TBomb06* /img/forum/go_quote.gif 
_I'm jealous. Want to sell me a board? 
	

	
	
		
		

		
			



_

 

Teehee! I already have mine! Just you guys wait, its definately worth it!!!


----------



## TBomb06

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Be patient, guys ... the Group Buy is coming ... very shortly._

 

Ok, ok...plus, that will give me time to study up on this amp some more so I will be ready to rock when the boards become available...needless to say, I am excited...


----------



## bperboy

Here's my new Millett Hybrid Max MOSFET Edition, the 2nd one ever built, so far as I know! I feel all special! Sorry for the poor pic quality though. I will try and finish the casing sometime, just need to drill the panels as I'm running this amp topless all the time!


----------



## cronic

looks nice


----------



## tomb

Group Buy is ON!!


----------



## gates_2

WOOT I want one!!

 edit: 2


----------



## vixr

bperboy... that case looks perfect. Im gonna put mine in that one too.


----------



## n_maher

There is now a group buy thread located in the GB Forum.


----------



## TBomb06

Quote:


  Originally Posted by *n_maher* /img/forum/go_quote.gif 
_There is now a group buy thread located in the GB Forum. 
	

	
	
		
		

		
		
	


	


_

 

Woohoo!


----------



## naamanf

Here is my finished Max. Thanks to the group buy I can build a MOSFET version to compare the two


----------



## bperboy

WHOA!! That wood paneling is SEXY!!!! Very nice I love it!


----------



## TBomb06

Quote:


  Originally Posted by *naamanf* /img/forum/go_quote.gif 
_Here is my finished Max. Thanks to the group buy I can build a MOSFET version to compare the two
	

	
	
		
		

		
		
	


	








_

 

Does using the SILMIC caps all around (not just in the signal path) really make a difference, or did you just use them because you wanted to truly "Max" it out? Also, are those the Cardas RCA jacks? Just curious 
	

	
	
		
		

		
		
	


	




 Looks great!!


----------



## TBomb06

Quote:


  Originally Posted by *bperboy* /img/forum/go_quote.gif 
_Here's my new Millett Hybrid Max MOSFET Edition, the 2nd one ever built, so far as I know! I feel all special! Sorry for the poor pic quality though. I will try and finish the casing sometime, just need to drill the panels as I'm running this amp topless all the time! 
	

	
	
		
		

		
		
	


	








_

 

What height heatsinks are those? I noticed in your photos on DIY Forums of the end panels all fabbed up (looks good, BTW 
	

	
	
		
		

		
		
	


	




) that the heatsinks come right up to where the top would be, if it were on.


----------



## naamanf

Quote:


  Originally Posted by *TBomb06* /img/forum/go_quote.gif 
_Does using the SILMIC caps all around (not just in the signal path) really make a difference, or did you just use them because you wanted to truly "Max" it out? Also, are those the Cardas RCA jacks? Just curious 
	

	
	
		
		

		
		
	


	




 Looks great!!_

 

I really couldn't tell you the difference because I built it with them from the get go. They really are not that expensive compared to all the other boutique caps out there. 

 The RCA jacks are actually chepo ratshacks. I plan on getting some Cardas or if I'm feeling froggy WBTs.


----------



## TBomb06

Is it necessary to use a switching jack in order for the muting circuit to work properly, or would it be possible to just run wires from the tip and ring leads on the jack to the spots on the board?


----------



## tomb

Quote:


  Originally Posted by *TBomb06* /img/forum/go_quote.gif 
_Is it necessary to use a switching jack in order for the muting circuit to work properly, or would it be possible to just run wires from the tip and ring leads on the jack to the spots on the board?_

 

The switch is in the relay - no special jack required. If you used two jacks, you could make one of them a switching jack so that the other was switched out in use, but that's not really necessary: the MAX has enough power to run more than one headphone at a time.

 As for the Elna's, its often covenient to order several at once, as Naamanf says. However, I'm a big proponent of Panasonic FM's out of the signal path. Those are hard to beat. Boutiques are definitely warranted for CA7 and CA2.


----------



## bperboy

Quote:


  Originally Posted by *TBomb06* /img/forum/go_quote.gif 
_What height heatsinks are those? I noticed in your photos on DIY Forums of the end panels all fabbed up (looks good, BTW 
	

	
	
		
		

		
			





) that the heatsinks come right up to where the top would be, if it were on._

 

I used the 1.5" heatsinks on the buffers and the voltage regulator. No worries about heat. I'm biased at about 250mV right now, or 113.6mA! Very Nice.


----------



## TBomb06

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_The switch is in the relay - no special jack required. If you used two jacks, you could make one of them a switching jack so that the other was switched out in use, but that's not really necessary: the MAX has enough power to run more than one headphone at a time.

 As for the Elna's, its often covenient to order several at once, as Naamanf says. However, I'm a big proponent of Panasonic FM's out of the signal path. Those are hard to beat. Boutiques are definitely warranted for CA7 and CA2._

 

Thanks! So I could just use a Neutrik locking jack and run wires to the tip, ring, and ground?

 Also, what kind of boutique film caps are most people using for CA9, and if you use a 1000uF cap in CA2 do you need to use a bigger cap than the .22uF one?


----------



## regal

The group buy has started at Headwize.


----------



## tomb

Quote:


  Originally Posted by *regal* /img/forum/go_quote.gif 
_The group buy has started at Headwize._

 

Uh, it's also here at Head-Fi. Check the sig.


----------



## tomb

Quote:


  Originally Posted by *TBomb06* /img/forum/go_quote.gif 
_Thanks! So I could just use a Neutrik locking jack and run wires to the tip, ring, and ground?

 Also, what kind of boutique film caps are most people using for CA9, and if you use a 1000uF cap in CA2 do you need to use a bigger cap than the .22uF one?_

 

The production boards have terminal block pads next to the jack pads. So, wiring in an additional jack will be a snap.

 No, you don't need to use a bigger film cap than the 0.22uF one. However, the pads/space are 50% bigger there than at the other 0.22uF pads. So, a much larger film cap can be used, including some nice boutiques. It's up to you, but the 0.22 Wima's will sound great. The big thing is upsizing that electrolytic - I believe it makes a big difference in bass slam.


----------



## TBomb06

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_The production boards have terminal block pads next to the jack pads. So, wiring in an additional jack will be a snap.

 No, you don't need to use a bigger film cap than the 0.22uF one. However, the pads/space are 50% bigger there than at the other 0.22uF pads. So, a much larger film cap can be used, including some nice boutiques. It's up to you, but the 0.22 Wima's will sound great. The big thing is upsizing that electrolytic - I believe it makes a big difference in bass slam._

 

Sorry mate, I guess I was pretty vague originally...the reason I was inquiring about the headphone jack is that I would like to use a Neutrik locking jack in place of the jack on the BOM, the one that the board is designed around. So, just one headphone jack, and a Neutrik locking jack instead of the Neutrik switching jack listed on the BOM. I'd also like to connect the jack and the ALPS using wire rather than directly on the PCB, that way I have plenty of flexibility when mounting them (mainly so I can vertically center them on the front panel).

 I plan on using the Nichicon Muse ES for the electrolytics in the signal path, and going with 1000uF in place of the 220uF one. I've read that those have the best bass 
	

	
	
		
		

		
		
	


	




 If you think the Wima's on the BOM will work fine, then I will use those


----------



## Alcaudon

Can't wait for the boards!!!!!!!!

 Will someone make some kind of assembly guide for noobs??? This will be my first tube DIY, and I'm unsure about a few things, specially voltages/currents for the tubes and the type/brand.

 Also............ any recommended book to learn the basic principles of tubes???

 This will be very funny...... I hope


----------



## JLMaestro

Quote:


  Originally Posted by *Alcaudon* /img/forum/go_quote.gif 
_Can't wait for the boards!!!!!!!!

 Will someone make some kind of assembly guide for noobs??? This will be my first tube DIY, and I'm unsure about a few things, specially voltages/currents for the tubes and the type/brand.

 Also............ any recommended book to learn the basic principles of tubes???

 This will be very funny...... I hope 
	

	
	
		
		

		
		
	


	


_

 

I've used mb3k's guides, and hopefully he could make one for the MHM


----------



## n_maher

Quote:


  Originally Posted by *JLMaestro* /img/forum/go_quote.gif 
_I've used mb3k's guides, and hopefully he could make one for the MHM_

 

I think you'll be pleased with what Tom (tomb) has come up with for the MAX build. He's put some serious time and effort into it and it shows. Nothing against mb3k's guides of course, they are wonderfully put together as well.


----------



## tomb

There are a couple of sections still under development, but here it is:

http://www.diyforums.org/MAX


----------



## odoe

Nice work tomb. Thanks.

 Question on the neutrik jack though. I have a couple sitting here and have been wondering how you solder it directly to the board. Mine have 6 lugs, not pins. Is there a version with pins?


----------



## tomb

Quote:


  Originally Posted by *odoe* /img/forum/go_quote.gif 
_Nice work tomb. Thanks.

 Question on the neutrik jack though. I have a couple sitting here and have been wondering how you solder it directly to the board. Mine have 6 lugs, not pins. Is there a version with pins?_

 

Yes, this is a heritage part from the revMH Millett and has been used for quite awhile. It is available at Mouser. Check the part# in the BOM on the site.


----------



## Alcaudon

Wow!!!!! Just............ impressive!!!!! 
	

	
	
		
		

		
		
	


	




 Many thanks for this, tomb, it's a great work. Very nice logo too, I'll probably use it on the casing (if you don't mind, of course 
	

	
	
		
		

		
		
	


	




 ).


----------



## tomb

Quote:


  Originally Posted by *Alcaudon* /img/forum/go_quote.gif 
_Wow!!!!! Just............ impressive!!!!! 
	

	
	
		
		

		
		
	


	




 Many thanks for this, tomb, it's a great work. Very nice logo too, I'll probably use it on the casing (if you don't mind, of course 
	

	
	
		
		

		
		
	


	




 )._

 

Thanks for the kind words. No, I don't mind - as long as you don't alter it in anyway. Team Millett MAX has a quality standard to uphold. 
	

	
	
		
		

		
		
	


	




 One of Pete Millett's guiding premises that started the Millett activity was freely sharing with the community. Maybe we can make some money on the T-shirts, though. Nate?


----------



## infinitesymphony

Wow, what a beautiful-looking project website... I'm even more tempted to ignore others' advice to do a Pimeta first and skip directly to this.


----------



## cronic

Fantastic work Tom. Thanks for the wonderful information.


----------



## naamanf

Looks great Tom! I think we are going to see a lot of Maxes in the future.


----------



## TBomb06

I have to go ahead and chime in to sing the praises of Tom, Colin, Nate and the rest of the Millet MAX team...absolutely great work, guys! Thanks for putting in the extra effort to make the MAX something that pretty much all of us can build and enjoy!


----------



## hellomai

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_There are a couple of sections still under development, but here it is:

http://www.diyforums.org/MAX



_

 

Very very impress website. Bravo for the excellent job. 

  Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Maybe we can make some money on the T-shirts, though. Nate? 
	

	
	
		
		

		
		
	


	


_

 

I will buy one!


----------



## curlywoods

I am stoked. Ordered all parts that were available from Mouser today. Will order the extras this week. Can't wait for the PC boards!!!!!!!!!!!!


----------



## mb3k

Quote:


  Originally Posted by *n_maher* /img/forum/go_quote.gif 
_I think you'll be pleased with what Tom (tomb) has come up with for the MAX build. He's put some serious time and effort into it and it shows. Nothing against mb3k's guides of course, they are wonderfully put together as well._

 

I will leave this one to the rightful individuals that made the max possible. I'll enjoy being the receivers' end this one around.

  Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_There are a couple of sections still under development, but here it is:

http://www.diyforums.org/MAX



_

 

Just lovely


----------



## regal

I am a big fan of the Millett and really appreciate what you guys have done to keep it alive.


----------



## NeilR

Quote:


  Originally Posted by *infinitesymphony* /img/forum/go_quote.gif 
_Wow, what a beautiful-looking project website... I'm even more tempted to ignore others' advice to do a Pimeta first and skip directly to this. 
	

	
	
		
		

		
		
	


	


_

 

Although Colin did a great job with this board, giving us a clean and open layout, debugging it if something goes wrong could be a problem if you do not have a lot of building skills. Mainly I'm thinking about the diamond buffers, which are intrinsically no easier to debug than a PPA, which can be a bear to debug (based on what I have seen on various threads- ask Nate), but also the fact that the power supply is very integrally tied into the amp. If you have a short somewhere, for example, you can't even easily pinpoint it between the PSU and the amp, as you could with a Pimeta which requires some sort of off-board power, either battery or a Tread type AC supply.

 I'm not saying don't build it now, and you certainly should get your boards now when they are available, but I personally don't think this is a good beginner project for someone at the level of just considering a Pimeta, for example.

 Just my very HO...

 Neil


----------



## n_maher

Quote:


  Originally Posted by *hellomai* /img/forum/go_quote.gif 
_I will buy one!_

 

I'm going to nip this one in the bud, there are no plans to market T-shirts. It's sort of an inside joke amongst some of us.


----------



## bperboy

Quote:


  Originally Posted by *NeilR* /img/forum/go_quote.gif 
_Although Colin did a great job with this board, giving us a clean and open layout, debugging it if something goes wrong could be a problem if you do not have a lot of building skills. Mainly I'm thinking about the diamond buffers, which are intrinsically no easier to debug than a PPA, which can be a bear to debug (based on what I have seen on various threads- ask Nate), but also the fact that the power supply is very integrally tied into the amp. If you have a short somewhere, for example, you can't even easily pinpoint it between the PSU and the amp, as you could with a Pimeta which requires some sort of off-board power, either battery or a Tread type AC supply.

 I'm not saying don't build it now, and you certainly should get your boards now when they are available, but I personally don't think this is a good beginner project for someone at the level of just considering a Pimeta, for example.

 Just my very HO...

 Neil_

 

I agree very much with Neil. I don't know if you remember Neil, but last year, you helped me out troubleshooting last year with my first Millett. I had only built a CMoy at that point, and it was tough just doing a regular Millett, let alone a maxed out amp with MOSFET buffers. I think maybe you should build a PIMETA as a nice portable amp, and once you are comfortable soldering and with theory, then move on to the Millett. Definately join in on the group buy though!


----------



## threEchelon

Quote:


  Originally Posted by *n_maher* /img/forum/go_quote.gif 
_I'm going to nip this one in the bud, there are no plans to market T-shirts. It's sort of an inside joke amongst some of us. 
	

	
	
		
		

		
		
	


	


_

 

Start selling t-shirts and they'll make you a member of the trade! 
	

	
	
		
		

		
		
	


	








 Actually, they probably would.


----------



## threEchelon

Will anyone be selling matched transistors or even entire kits?

 Also, do you have to choose between the diamond buffers or MOSFETs? If so, what are the differences in sound?


----------



## bperboy

Quote:


  Originally Posted by *threEchelon* /img/forum/go_quote.gif 
_Will anyone be selling matched transistors or even entire kits?

 Also, do you have to choose between the diamond buffers or MOSFETs? If so, what are the differences in sound?_

 

I don't think there are any plans to sell complete kits, although the majority of the parts can be aquired from Mouser, minus Alps pot and some other things. Yes, you can either have the diamond buffer output stage or the MOSFET stage, not both. I have the MOSFET version, the second one to be built, behind Neil, who troubleshot the correct parts list for it. I can't comment on sound differences as I've only got the MOSFET version, but it sounds pretty sweet to me. You can get matched MOSFETs from AMBs site, which is what I did, along with the volume pot. 

 One technical advantage of the MOSFETs is that they can be biased much higher than the BJT diamond buffer. I've got mine set at 250mV or about 114mA current on each channel! Bodacious! 

 Others can probably add more to this than I can, but I hope it provides a good start.


----------



## mb3k

DOes anyone have a source for cheap multimeters that have hfe testers?

 Edit: I usually call it β rather than hfe


----------



## tomb

Harbor Freight - most of the time, they're $2.99 - all I ever use ...

 P.S. Thanks for your comments on the site, mb3k - that's high praise coming from you.


----------



## mb3k

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Harbor Freight - most of the time, they're $2.99 - all I ever use ...

 P.S. Thanks for your comments on the site, mb3k - that's high praise coming from you._

 

Excellent, but I just found out HarborFreight does not ship to Canada 
	

	
	
		
		

		
			




 Anyone up to helping a fellow DIYer?


----------



## splaz

Maybe try some electronics/hardware shops if you have any around. Most should carry cheap multimeters with hfe, maybe not at such a low price but still pocket change.


----------



## NeilR

Quote:


  Originally Posted by *threEchelon* /img/forum/go_quote.gif 
_Also, do you have to choose between the diamond buffers or MOSFETs? If so, what are the differences in sound?_

 

I initially planned on socketing all the buffer parts necessary to make a "convertible" buffer. I got hung up over how to socket the output transistor positions. I bought some nice transistor sockets that accept either the smaller TO-92 leads or the big fat TO-220 leads. The problem is that the sockets are offset from the pin position. Although I think I could physically place the sockets on the board, the transistors would have sat out from the heat sink and I was concerned that I would not get good thermal contact with the sinks. Also, the RB8 pad would have been at least partially underneath the sockets.

 Edit: In addition, you would have to figure out how to set up the elevation of the output transistors such that they either fit one of the available pre-drilled holes on the heat sink or you would have to drill new holes. This would have to be done with at least 8 trannies and sinks, potentially a great deal of effort.

 With a lot of care it might be possible to bend the transistor leads to set up that offset.

 I was able to use those transistor sockets in the QB2/QB3 positions, and I did so, mainly to experiment with the signal drivers in or out, both of which are viable build options. I'm not sure if, for example, the JFET position could be socketed with that part. Can't be sure now without an empty spare board, but it doesn't look good.

 You would also have to socket the JFET (QB1) and almost certainly the two trim pots. I socketed the trim pots because I didn't have 1K trimmers handy (I had not done my breadboard trials before placing my order) and I planned on swapping out my 2K trimmers (which I did thanks to Tomb's help with the needed parts). I know that Steinchen successfully socketed TO-92 parts on the dDB boards and has an image on his web site. I grabbed a couple TO-92 parts at random and tried plugging them into some SIP pins. I wasn't comfortable with the fit. The leads were a little too loose for my comfort factor.

 I was in a hurry to get my build completed because the MOSFET configuration and BOM was dependent on my work, and decided that all the above didn't fit my schedule and time available.

 In summary, though, electrically it is very easy to socket the board such that it can be configured either way and I hope someone does this some day. The problem is with the mechanics of the socketing. If you can get past that hurdle, I can help you with some configuration ideas. Given your casing skills, you could probably figure out these mechanics.

 Although I have a Millett with dDB boards in addition to the Max Millett I have not compared them. I'm probably the wrong person to do that anyway because I don't hear a lot of differences between minor part changes such as transistor swapping and I don't have a good way to quickly A-B two amps (something I have been mulling over for quite some time but haven't built the rig). 

 Neil


----------



## vixr

WOW! tomb... that site is amazing. Thank you for the awesome support.


----------



## tomb

Quote:


  Originally Posted by *threEchelon* /img/forum/go_quote.gif 
_Will anyone be selling matched transistors or even entire kits?_

 

You should do your own transistor matching. Seriously, it's discussed in pretty good detail on the site. Moreover, I was just checking 2n5087/2n5088 prices on Mouser today:
http://www.mouser.com/search/Product...ey512-2N5087BU
http://www.mouser.com/search/Product...ey512-2N5088BU

 There are multiple listings just this cheap: *$2.90 per 100*

 Combine that with a $2.99 DMM from Harbor Freight that measures HFE (also available at many other places for $10 max), and there's no excuse for anyone not to match their own. Buy a hundred of each - you'll never worry about not having enough, stepping on a few, or losing them under the sofa cushion. You will have more than enough for sufficient matching for perhaps a half dozen to a dozen MAX's.

  Quote:


 Also, do you have to choose between the diamond buffers or MOSFETs? If so, what are the differences in sound? 
 

Neil detailed the issues with switching back and forth. The short answer is YES, you must choose. For now, the diamond buffer has been vetted for years with ample support on Steinchen's site, Tangent with the PPA, etc. It is the default choice, but does not short on performance. Keep in mind that you can easily bias up to 50ma or more, perhaps. The PPA is limited to 30ma, not that I'm comparing the two amps - just relative biasing.

 The MOSFET version has been built by two people: NeilR and Bperboy. Along with its huge current demand, it should be considered the more challenging of the two options and may potentially have more teething/troubleshooting issues.


----------



## tomb

Quote:


  Originally Posted by *vixr* /img/forum/go_quote.gif 
_WOW! tomb... that site is amazing. Thank you for the awesome support._

 

Thanks, Vixr. Your tube photographs really add some class to the page on Millett tubes.


----------



## cfcubed

Quote:


  Originally Posted by *threEchelon* /img/forum/go_quote.gif 
_Will anyone be selling matched transistors or even entire kits?<snip>_

 

Looks like jrossel (glassjaraudio) over @ headwize is considering putting together a kit for this... If it's anything like his deal on his Level 1 SOHA (but more $$$ of course) it'd be nice. Even tho I only finished the SOHA a week or so ago, I don't see myself resisting this Millett Max


----------



## abcheng

I have a couple questions about the MH max. 1. Can I use a 24VDC wallwart instead of 24VAC wallwart? 2. Can only the amp portion of the MH max be built, or does the E12 delay circuit, and DB circuit have to be populated?


----------



## tomb

Quote:


  Originally Posted by *abcheng* /img/forum/go_quote.gif 
_I have a couple questions about the MH max. 1. Can I use a 24VDC wallwart instead of 24VAC wallwart?_

 

Hmm ... not recommeded. You can connect the DC walwart and it will work - just dropping a volt or so through the rectifier. Or, you can bypass/jumper the rectifier string completely. However, there's not much of a way to avoid the regulator and expect to have decent performance. The regulator will lose you another 3V. By that time, you'll only have about 19-1/2V, which is substandard for even the regular Millett.

 There are some AC walwarts that are quite powerful and cheap - the kind that have screw terminals and a little screw tab on the top to screw in the center hole of a wall outlet. Those typically range 0.8 - 1.5A, and cost about $6-$9.

 on the web has a good example:<br />
<br />
[URL="http://www.allelectronics.com/matrix/AC_Wall_Transformers.html]http://www.allelectronics.com/matrix/AC_Wall_Transformers.html
 The Type "D" ACTX2420 is 830ma and only $6.50, the ACTX2440 is 1.6A and still only $8.50.

 You should be able to find these in an HVAC supply store, Graingers or McMaster if you don't want to order from All Electronics. Jameco has the 830ma version, too.

 You _gain_ voltage with an AC walwart going through rectification and filtering stage - (1.4 x 24V) - 1.4 - 3 = 29.2VDC

  Quote:


 2. Can only the amp portion of the MH max be built, or does the E12 delay circuit, and DB circuit have to be populated? 
 

No. The MAX's output stage is the DB circuit. There are no BUF634's or DIP-8 sockets for monolithic buffers/opamps. It's possible that the e12 can be jumpered out, but it's there to protect your headphones from driver-destroying DC spikes upon power-on and power-off.


----------



## bperboy

The main benefits of the redesigned Millett is that the buffer and the e12 circuit are built in on the board, as well as the power supply regulation. Thats what makes it a great little amp; only one board needed for all the different features!


----------



## abcheng

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Hmm ... not recommeded. You can connect the DC walwart and it will work - just dropping a volt or so through the rectifier. Or, you can bypass/jumper the rectifier string completely. However, there's not much of a way to avoid the regulator and expect to have decent performance. The regulator will lose you another 3V. By that time, you'll only have about 19-1/2V, which is substandard for even the regular Millett.

 There are some AC walwarts that are quite powerful and cheap - the kind that have screw terminals and a little screw tap on the top to screw in the center hole of a wall outlet. Those typically range 0.8 - 1.5A, and cost about $6.

 on the web has a good example:<br />
<br />
[URL="http://www.allelectronics.com/matrix/AC_Wall_Transformers.html]http://www.allelectronics.com/matrix/AC_Wall_Transformers.html
 The Type "D" ACTX2420 is 830ma and only $6.50, the ACTX2440 is 1.6A and still only $8.50.

 You should be able to find these in an HVAC supply store, Graingers or McMaster if you don't want to order from All Electronics. Jameco has the 830ma version, too.

 You gain voltage with an AC walwart going through rectification and filtering stage - (1.4 x 24V) - 1.4 - 3 = 29.2VDC


 No. The MAX's output stage is the DB circuit. There are no BUF634's or DIP-8 sockets for monolithic buffers/opamps. It's possible that the e12 can be jumpered out, but it's there to protect your headphones from driver-destroying DC spikes upon power-on and power-off._

 

Awesome, thanks for answering my questions. This is off topic, but I just noticed that you live in Atlanta. 
	

	
	
		
		

		
		
	


	




 I haven't seen many people from Atlanta in here.


----------



## vixr

woo hoo!!! got all my parts ordered...my credit card melted into a puddle but I can still make out the numbers!!! I still cant get over how great the MAX site is...


----------



## bperboy

Quote:


  Originally Posted by *vixr* /img/forum/go_quote.gif 
_I still cant get over how great the MAX site is..._

 

QFT! TomB, very nice work! Even though I've already done my Max, this would be an invaluable resource!


----------



## fordgtlover

Big cheers for all those invloved. I join the chorus of praise for the new site. It is excellent.


----------



## adfinni

Truly stunning work on the MAX site, it's soo easy to follow !!!!!!

 IL be pestering you all in about a month when im ready to order parts for my hybrid, but mainly because im in the UK and it's impossible to find the correct 24V AC wallwart. I can find a 24V 1.5A one but that seems about it. 

 anyways, il leave you alone for the time being, and just dream about the time when i can build mine


----------



## amphead

Quote:


  Originally Posted by *mb3k* /img/forum/go_quote.gif 
_I will leave this one to the rightful individuals that made the max possible. I'll enjoy being the receivers' end this one around.


 Just lovely 
	

	
	
		
		

		
		
	


	


_

 

What is the best sounding amp that you have built to date?


----------



## NeilR

Quote:


  Originally Posted by *adfinni* /img/forum/go_quote.gif 
_ IL be pestering you all in about a month when im ready to order parts for my hybrid, but mainly because im in the UK and it's impossible to find the correct 24V AC wallwart. I can find a 24V 1.5A one but that seems about it. _

 

A 1.5A 24VAC wart would work well, and arguably better than a lesser rated wart.


----------



## adfinni

Quote:


  Originally Posted by *NeilR* /img/forum/go_quote.gif 
_A 1.5A 24VAC wart would work well, and arguably better than a lesser rated wart._

 

ahhh excellent, cheers for that 
	

	
	
		
		

		
		
	


	




 Going to read up a lot more in the next month as i have some knowledge and roughly know whats going on, but i really want to be able to understand circuits and exactly what each part does.


----------



## tomb

Quote:


  Originally Posted by *NeilR* /img/forum/go_quote.gif 
_A 1.5A 24VAC wart would work well, and arguably better than a lesser rated wart._

 

Agreed. A 24VAC, 1.5A will be great for the MAX. The published walwart suggestions are _minimums_.

 EDIT: Oops - didn't chime in quickly enough.


----------



## vixr

is it a good idea to socket the resistors for the tube CCS? (RA8 and RA9)


----------



## tomb

Quote:


  Originally Posted by *vixr* /img/forum/go_quote.gif 
_is it a good idea to socket the resistors for the tube CCS? (RA8 and RA9)_

 

If you want to play with different values, yes.

 I didn't, so I didn't socket mine. The BOM listing for those resistors gives you a CCS current that's essentially the same as the traditional Millett.


----------



## NeilR

Quote:


  Originally Posted by *vixr* /img/forum/go_quote.gif 
_is it a good idea to socket the resistors for the tube CCS? (RA8 and RA9)_

 

Rob, I socketed RA8 (only) and that allows me to tinker with the bias value. Colin suggested to me in a private email that RA9 needs to be at least 10X RB8, so I made RB9 51K, which was 10X the highest value I thought I might want to try. Although I have not gotten around to tinkering with that part, RB8=1.13K and RB9=51K is giving me a bias of about 0.59ma., which is just what I expected.

 If you were to socket all 4 parts, I think it would be possible to experiment with many different CCS's, such as the 1N5291 type monolithic CCS used in the older Millett board, or maybe a JFET with a resistor.


----------



## vixr

OK... thanks tomb. it looks to be a tight squeeze anyway. I guess one could push the black stuff off the socket strip... thanks NeilR... I was thinking along those lines too...


----------



## NeilR

Rob,

 RA8 has enough room as long as you use the standard MKP cap or a smaller part, even without stripping the insulation from the SIP pin:


----------



## vixr

oh, perfect! I ordered the wimas too, so it should be no problem. BTW, NeilR that picture is very helpful. thank you.


----------



## soloz2

Neil, what's the PN for the screw terminals you used?


----------



## vixr

soloz2, the part number is in the BOM at the MAX site, but mouser is out of the 3 pos one... digikey has them though.


----------



## amphead

Quote:


  Originally Posted by *NeilR* /img/forum/go_quote.gif 
_Rob,

 RA8 has enough room as long as you use the standard MKP cap or a smaller part, even without stripping the insulation from the SIP pin:




_

 

Nice build, looking forward to my Millet Max!


----------



## amphead

Is that a custom volume knob, or do you have a part number?


----------



## tomb

Quote:


  Originally Posted by *amphead* /img/forum/go_quote.gif 
_Is that a custom volume knob, or do you have a part number_

 

Ebay Store "PARTSPIPE" run by ebay user "hongkongsuperseller":
http://cgi.ebay.com/PKG2-30x22-Alumi...QQcmdZViewItem


----------



## amphead

Quote:


  Originally Posted by *bperboy* /img/forum/go_quote.gif 
_The main benefits of the redesigned Millett is that the buffer and the e12 circuit are built in on the board, as well as the power supply regulation. Thats what makes it a great little amp; only one board needed for all the different features! 
	

	
	
		
		

		
			



_

 

It's very hard not to get involved with the MAX build, so I will be watching/posting in this thread often! Aaaaawsome!!!
 Thanx for the knob info!


----------



## TimmyMac

Is it possible to elevate the tube sockets above the board, say at the level of the top deck of your enclosure? The thought of all that tubey goodness popping out the top of the enclosure is enticing...


----------



## vixr

something like this might work


----------



## bperboy

You could do that, but then you'll run into problems with biasing. You'll need wires running from the top panel down to the board, and those wires will prevent you from opening up the top panel to bias the tubes and buffers. This is all assuming that you're using the Hammond case though. The way I have mine set up, I just mounted the sockets on the board, and then run without a top cover, that way I don't have to worry about issues with stripping out the panel screws and overheating with the MOSFETs. Plus, it just looks cool being able to see all the parts directly. If you're using a different case, you can be creative and think of a way to set up a bracket or something with openings for biasing and such. If you end up still wanting to do this, you'd probably have to drill holes in the top cover for the trimpots and test points, something that I think will make the top look fairly unclean, so far as the design goes.


----------



## vixr

Quote:


  Originally Posted by *bperboy* /img/forum/go_quote.gif 
_ ...If you end up still wanting to do this, you'd probably have to drill holes in the top cover for the trimpots and test points, something that I think will make the top look fairly unclean, so far as the design goes._

 

I think you're right, the top plate was installed on my SOHA for about a day, I took it off to tinker with the new tubes I bought and its been off ever since


----------



## tomb

Positioned correctly, it's possible to have enough of the tube sticking out to actually grasp it for plugging in and unplugging. Also drilling strategic holes in the top for the trimmer screws has been done on a number of occasions. I am uncertain if this works well without a transparent top, but I think it would if one has fairly bright tube lights, or even better - air circulation holes in the sides as well as the top.

 There are also tip jacks that can be installed in the rear plate that allow your DMM probes to simply plug in. Depending on which slot the board is in, you can run all the test point wires underneath. Both strategies may allow complete adjustment and tube removal without taking the top off.

 Caution! this image is not to scale!


----------



## bperboy

Tomb, thats a very nice strategy for getting good clean test points and biasing. I think your solution is much more elegant, but mine easier and maybe more practical. If I had the money, I'd have FrontPanelExpress make up that design, and then the problem would be solved.


----------



## splaz

Well not really max related but wow, the tubes I got for it really are N*O*S.

 I rubbed my thumb on the label and it pretty much disintegrated, it was faded already... maybe like a good wine they improve with age.


----------



## tomb

Quote:


  Originally Posted by *bperboy* /img/forum/go_quote.gif 
_Tomb, thats a very nice strategy for getting good clean test points and biasing. I think your solution is much more elegant, but mine easier and maybe more practical. If I had the money, I'd have FrontPanelExpress make up that design, and then the problem would be solved._

 

Yep - I basically posted that to stimulate some ideas about what's possible. To be honest, I don't have any of mine covered, either. The tip jacks work really well, though - I use them all the time even on my old Milletts - the test points were in some dangerous spots on the old ones.

 There comes a time, though, when you stop fiddling with the tubes and settle on what you want. Then forays into the innards of the case are much less frequent.

  Quote:


  Originally Posted by *splaz* 
_Well not really max related but wow, the tubes I got for it really are NOS.

 I rubbed my thumb on the label and it pretty much disintegrated, it was faded already... maybe like a good wine they improve with age._

 

Yes - some of the lettering will rub right off as if it's just so much dust. I think they probably expected it, though - the important designations seem to always be etched into the glass.


----------



## NeilR

A couple of comments on Tomb's tip jack biasing scheme... because I'm muddling through some kind of solution I can live with but I'm not there yet.

 1) I did that for my old Millett's tube bias but not the dDB bias points. The DrewD boards have 2 pads on 100 mil spacing on each bias point. I used 2 pin Milex KK plugs and sockets, using just one pin. I don't think you can get a one pin molex plug (needed for the Max)although I think one could be rigged up with some butchering and parts substitutions.

 2) You only need 5 bias ports. The board provides for bias points (TB1 and TB2) between the emitter and resistor on both sides of the complimentary pair. The only reason to measure both is on initial startup just to make sure they are close. If the circuit is built right and working, they will be close and they will stay close. You run a port to either TB1 or TB2.

 3) I don't think Tomb's rear panel layout will work when using 1.5" heat sinks, as I did, because the board needs to go in the bottom rail. I doubt you could squeeze pin jacks under the board with it in the bottom rail. I haven't dug out the couple of pin jacks I should have in my bin to see if they will fit on top; I suspect they will with some placement care.

 My main problem with pin jacks here is that I don't want the rear panel permanently attached to the board, as it would be if wires were just soldered to the pin jack and associated bias pad. I've thought about doing some dort of in-line plug and jack with Moles-type connectors, but haven;t taken it any further. the idea being some way to disconnect the bias port wires, either directly at the pad or some inline arrangement. If anyone has any slick ideas I'd like to hear about it


----------



## tomb

It's true that the second set of tip jacks are not critical for the other DB test points, but some of this was an exercise in seeing how everything would fit in a worst case situation - as is often the goal with CAD design work. Certainly, if you locate the board on the bottom slot - due to 1-1/2" heat sinks - this won't work.

 Actually, only 4 tip jacks would be needed over any length of time, perhaps just 3. Those would be the tube bias jacks, gnd, and perhaps V+. Once the DB's are set, as long as you confirm supply voltage, they shouldn't vary that much. I have seen voltages alter enough to change all of your settings at different locations though (like work vs. home) - so the V+ might be useful.

 Having three or four soldered leads hanging off the board is not the best scenario, as Neil says, but again, once buttoned up there's very little reason for getting into the innards again. It's also an impossible scenario to sell the amp to a neophyte without such adjustment features and tip jacks.

 There are single post terminal blocks in existence - at least I've seen some. It could be someone cut a 2-pole in half, but it's been done.

 EDIT: Molex can get expensive unless you combine pins - that could work, though. Another thought is some male/female fully-insulated faston connectors - or those inline bullet connectors used in car wiring. With a little effort, you can probably get the nose of one of those bullet connectors soldered directly onto the end of the tip jack. That way, you wouldn't have any loose connectors rattling around on the bottom of the case. Just a suggestion - I may try it.


----------



## NeilR

Hi Tom,

 I only mentioned the 5 jacks to clarify the minimum needs for buffer biasing.

 I originally wasn't going to bother with biasing ports, more or less for the reasons you mentioned. However, it is becoming more of an issue for me simply because closing up the case radically alters the buffer bias. This is true of the BJT build as well as my MOSFET build, and really it's more important with the BJT build because that circuit is PTC and the bias rises with a closed case. I discovered that when playing with my Steinchen buffers. I'll bet most people running those buffers in closed cases (even with some ventilation) are running them MUCH hotter than they think based on their open case bias measurements.

 Even with the MOSFETS, which should reduce bias when the case is closed, the bias levels are so high that I think it is a good idea to be able to easily measure them with the case closed so that any estimates are confirmed. Just MHO. The more I work with the build, the less confident I am in predicting the closed case bias. 

 I can run mini clips to my test points and out the tube holes, but that forces me to remove the tubes, remove the panels, remove the cover, install the clips, reinstall the cover, reinstall the panels, warm it up for an hour or so, take the measurement, turn it off, let it cool down, remove the tubes, remove the panel screws, remove the cover, remove the clips, reinstall the panels, reinstall the cover, reinstall the tubes, and make sure I didn't swap tubes! Having gone through that process a few times in order to give some accurate biasing advice, it's starting to get old 
	

	
	
		
		

		
		
	


	




 Just wanted to throw all that out so builders can think about all the nagging issues related to bias ports and biasing strategy. It got me thinking.

 Regards,
 Neil


----------



## bperboy

Regards to heat Neil, thats a very good idea, especially coming from you! 
	

	
	
		
		

		
		
	


	




 What was it we call you now? JFET Conflagorous?!


----------



## amphead

Quote:


  Originally Posted by *cetoole* /img/forum/go_quote.gif 
_Just thought I would post a quick pic of the reason I am still up tonight. Just having real trouble turning Opeth's Deliverance CD off. Had a bit of trouble with way too much gain and getting the volume knob too high with my KSC75's earlier tonight, and even with my HD580s, I cant even make it a quarter turn on the volume knob. This is with DuMont 12ae6a tubes and the cathode resistors unbypassed.




_

 

This might be dumb, but I was wondering what would happen, if the volume pot had a 50k resistor added in series, on the high side, to act as a voltage divider and reduce the maximum volume range?


----------



## tomb

Colin's MAX is somewhat of an experiment without the cathode bypass caps. Those will add a bit of negative feedback and tame the gain a bit. It's worth noting that the Millett portion of the circuit is essentially the same as it's ever been with a couple of minor exceptions. Milletts have been around for some time and gain too high has not been a long-standing issue. You might refer to Amb's excellent tests on the original Millett that highlights the gains with the different tubes. They are well within typical DIY headphone amp values.

http://www.ibiblio.org/tkan/audio/millett.html


----------



## tomb

There appears to be the makings of a shortage with the PS electrolytics - 1000uF, 50V. Of course, anyone is more than welcome to use bigger caps. :twisted: Smaller caps would be fine, too, most likely. With four positions, there are many combinations possible and the original design only needed two caps, anyway. What's there now is probably overkill.

 However, I am _not_ going to update the BOM (as someone suggested) if there's a shortage of FM or UPW caps. Those are standard parts and there is no doubt that Mouser and DigiKey will replenish their stock. As a matter of fact, Mouser lists 5/28 as a ship date for the UPW's.

 Meanwhile, for the impatient ones, here are a few suggestions:
 * The Panasonic FC caps at DigiKey are very good and a great substitute: P10333-ND. This is a 1000uF, 50V FC cap and is 16mm dia. x 25mm high. It will work perfectly and would be my first choice after the FM. Unfortunately, they're a little expensive compared to some of the others.

 * Mouser has Nichicon UHE caps - the 647-UHE1H102MHD3 is $0.98 ea. and is 18mm dia x20mm. Be careful - there's another one that is 40mm tall. Some say these may be better than UPW's when used in a power supply.

 I've also heard that one of the Dinkle-style terminal blocks are out at Mouser. There again, there are many others to pick from - Jameco has identical 5mm pitch terminal blocks. I'm not going to update the BOM for that one, either. If there's a legitimate mistake, and a part is incorrect, then please let me know and it will be corrected. Otherwise, this is DIY: be resourceful.

 hope that helps ...


----------



## vixr

handmade has the 470uF 50v caps in KZ but not in ES...they also have the 1000uF 16v ES and 1000uF 50v KZ


----------



## dsavitsk

Tom, 

 A couple of small mistakes on your tweeks page http://www.diyforums.org/MAX/MAXccs.php

 A CCS used as a plate load is a CC Source. It is referred to as a sink when it sinks current, generally when used between cathode and ground as with a cathode follower.

 On the graph, your operating point is misleading -- to have a plate voltage of 27V with a CCS will require a power supply of 35 to 40V or more. That is, the CCS needs to drop some voltage to give it room to swing. The way these are biased (at least on the old one, I have not looked at the new one closely enough) is to about 12 to 14V on the plate (which I think Pete did because it is tricky to bias the grid since it is only at about 0.75V, and even a fraction of a volt change will be a big deal). Thus, with a 27V PS you are dropping ~13V across the CCS for a bias of about 14V, which is where the operating point should be.


----------



## dsavitsk

Another thing, increasing the current to over 1mA will hugely increase Gm and lower ra, which are both generally good things (they improve the ability to drive the next stage -- think of it as doubling up the buffers in a Pimeta or something). Moreover, while the 12ae6a datasheet does not specify plate dissipation, I don't think there is any way you could possibly exceed it (at 14V on the plate and a current of 1mA, you are dissipating 0.014W -- the lowest I have seen a tube capable if dissipating is in the 1 to 1.5W range, so you are not even close and the plates don't look delicate), and these tubes look to be more linear at higher currents (which is generally the case.) So, if I had one of these, I'd try running it at 1 to 2mA to see what happens. Could be a very good thing.

 Edit: 12ae6a suggests 1mA and 12fk6 suggests 1.2mA


----------



## tomb

Quote:


  Originally Posted by *dsavitsk* /img/forum/go_quote.gif 
_Another thing, increasing the current to over 1mA will hugely increase Gm and lower ra, which are both generally good things (they improve the ability to drive the next stage -- think of it as doubling up the buffers in a Pimeta or something). Moreover, while the 12ae6a datasheet does not specify plate dissipation, I don't think there is any way you could possibly exceed it (at 14V on the plate and a current of 1mA, you are dissipating 0.014W -- the lowest I have seen a tube capable if dissipating is in the 1 to 1.5W range, so you are not even close and the plates don't look delicate), and these tubes look to be more linear at higher currents (which is generally the case.) So, if I had one of these, I'd try running it at 1 to 2mA to see what happens. Could be a very good thing.

 Edit: 12ae6a suggests 1mA and 12fk6 suggests 1.2mA_

 

Pete Millett tried 1ma and reported higher distortion in his original Audio Xpress article.

 You are correct about the operating point in your earlier post, and I will make the correction. For some reason, I seem to have a mental block with equating the supply voltage in the Millett to the +or- 13.5V swing at the tubes.

 Note also that our empirical experience with the cathode bypass cap does not follow from the corner frequency equation.


----------



## dsavitsk

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Note also that our empirical experience with the cathode bypass cap does not follow from the corner frequency equation._

 

Could be the low Gm is not enough to drive the next stage? Otherwise you'll need to ask Morgan Jones.

 Pete only tried one tube type I think, so I'd still experiment with higher currents, especially with the other tubes.


----------



## tomb

Quote:


  Originally Posted by *dsavitsk* /img/forum/go_quote.gif 
_Could be the low Gm is not enough to drive the next stage? Otherwise you'll need to ask Morgan Jones.

 Pete only tried one tube type I think, so I'd still experiment with higher currents, especially with the other tubes._

 

Thanks for the tips. Just for the record, "sink" was in reference to the dual transistor, dual resistor circuit, as in "This is a common transistor circuit commonly referred to as a current sink." That reference was not related to its application with the tube at all, but as you say, it was confusing.

 I made the corrections as you suggested and made it clear that in the case of the Millett MAX, it is operating as a constant current _source_.

 You are correct that there is no hard and fast rule about the operating point. Certainly people should try other values if they wish. The CCS makes this pretty easy if you socket the smaller resistor. The other resistor simply needs to be at least 10X. 

 Anyway, thanks for the heads up on the mistakes.


----------



## midnite8791

amp looks great!
 I am a total DIY audio noob, though I do have wiring experience from my Automotive Job, would this be too much of a project for a first timer? This looks very interesting and would be a great summer project for me as ive always wanted a tube amp.


----------



## vixr

midnite8791
 unless you have the ability to do the transistor matching, it probably would be tough to build a great amp...you could probably get it to work though...I just spent a pretty good bit on parts, and I would hate to ruin something due to lack of experience, so you might want to consider something a little easier first, you should consider joining the group buy though... this is like the best Millett ever... I have a board or two from the MH group buy hosted by n_maher last year... Its very easy to build. You too can own one for the low price of 15 dollars! (shipped) PM me if you want one.

 BTW I got my Mouser order in today, Digikey yesterday. Waiting on harbor freight and Handmade!!! Is anybody else sorta disappointed with the quality of the Hammond enclosures? The one I got today has a few blemishes and nicks... I would think they would be better protected, it was covered with a very thin wrapper which allowed some damage...


----------



## pabbi1

Any good sources (besdes partsconnexion) for good pcb mount tube sockets?

 Edit: Gold plated or teflon.


----------



## vixr

www.thetubestore.com


----------



## tomb

Quote:


  Originally Posted by *pabbi1* /img/forum/go_quote.gif 
_Any good sources (besdes partsconnexion) for good pcb mount tube sockets?_

 

As far as I know, PartsConX are the only ones that sell these:






 The availability is different with the chassis mount versions, unfortunately. There are several tube vendors that sell those in gold, but I haven't been able to find anyone else who has gold in PCB 7-pin sockets.

 The tin plated version is available at most tube vendors including TubeDepot, TubeStore, and there's even a guy on ebay who sells them in quantities of 7 and 10 on a regular basis:





 There's a subtle difference noted by the arrow. I used to think that only PartsConX carried the ones that split more evenly in the middle - they are more robust when drilling the center pin out - but it seems simply susceptible to the latest deliveries from the mfr.


----------



## bperboy

I just used the tin plated ceramics from thetubestore, and as to getting the center pin out, I wedged a jeweler's flathead into that little slot, wiggled it a little bit, and this enabled me to grasp the top head of the pin with some pliers, and then I just twisted the damn thing out!


----------



## vixr

this is actually DR3 right?


----------



## daggerlee

Is anybody ordering tube sockets from PartsconX anytime soon? Mind if I jump in on the order for 2 sockets? They aren't responding to my emails for some reason..


----------



## TBomb06

Quote:


  Originally Posted by *vixr* /img/forum/go_quote.gif 
_this is actually DR3 right?





_

 

Yes, that's DR3. If you look at the image of the layout on Tom's MAX site you'll see it labeled correctly there. I'm guessing it was just an oversight during the prototyping...not a big deal.


----------



## tomb

Yep. It was mis-numbered on the 2nd Prototype board, which is what's pictured. The production board has been corrected. Those are simply two generic 1N4002 protection diodes for the tantalums.


----------



## TBomb06

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Yep. It was mis-numbered on the 2nd Prototype board, which is what's pictured. The production board has been corrected. Those are simply two generic 1N4002 protection diodes for the tantalums._

 

Along the same lines, on the 2nd prototype board it looks like the left and right output points (where the headphone jack solders to the board) are tied across like this:

 ._._
 ._._ (relay is here)
 . .

 And in the layout diagram it appears that they aren't connected, like this:

 . ._
 . ._ (relay)
 . . 

 So if you were using the terminal blocks to connect your headphone jack, and not connecting one onto the board, you would have to jumper across those points to the relay, is that right? Hope those rudimentary diagrams make sense


----------



## tomb

Quote:


  Originally Posted by *TBomb06* /img/forum/go_quote.gif 
_Along the same lines, on the 2nd prototype board it looks like the left and right output points (where the headphone jack solders to the board) are tied across like this:

 ._._
 ._._ (relay is here)
 . .

 And in the layout diagram it appears that they aren't connected, like this:

 . ._
 . ._ (relay)
 . . 

 So if you were using the terminal blocks to connect your headphone jack, and not connecting one onto the board, you would have to jumper across those points to the relay, is that right? Hope those rudimentary diagrams make sense 
	

	
	
		
		

		
		
	


	


_

 

They're there - sort of obscured by the "OL" and "OR" text. It's one of the reasons I included different color layout images on the site. One or the other is clearer, depending on what part of the layout you're looking at.


----------



## TBomb06

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_They're there - sort of obscured by the "OL" and "OR" text. It's one of the reasons I included different color layout images on the site. One or the other is clearer, depending on what part of the layout you're looking at.



_

 

What about the connection between the terminal block to the relay? I see the terminal block pads connected to the output jack pads, but I don't see a connection from the output jack pads on the left side over to the output jack pads on the right side, where the output jack is connected to the relay. Sorry if I'm making things more confusing than they need to be...just to clarify, the only output jack I want to use will be connected to the terminal blocks, not to the PCB. It looks like I would have to jumper across the pads where the output jack is supposed to be...


----------



## tomb

Quote:


  Originally Posted by *TBomb06* /img/forum/go_quote.gif 
_What about the connection between the terminal block to the relay? I see the terminal block pads connected to the output jack pads, but I don't see a connection from the output jack pads on the left side over to the output jack pads on the right side, where the output jack is connected to the relay. Sorry if I'm making things more confusing than they need to be...just to clarify, the only output jack I want to use will be connected to the terminal blocks, not to the PCB. It looks like I would have to jumper across the pads where the output jack is supposed to be..._

 

The jack connections are contiguous across the jack. The spring tab contacts cover the width of the jack and the pins are hot on both sides. They are switching, though, so plugging into the jack will disable those side terminals. That sounds like the best way to operate them, though.


----------



## amphead

I am thinking of adding one more piece of eye candy to my build, with a front panel mounted "MAX" logo backlit with blue LEDs. I know, thats getting a little far ahead of the game, but I have been having alot of success lately on my projects.
 Maybe, I'll put a blue led inside the volume knob too. 
 Okay, now that is going too far!


----------



## TBomb06

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_The jack connections are contiguous across the jack. The spring tab contacts cover the width of the jack and the pins are hot on both sides. They are switching, though, so plugging into the jack will disable those side terminals. That sounds like the best way to operate them, though._

 

Ok, but if I don't have the switching jack on the board, only the jack that is connected to the terminal block, then I can just jumper across where the switching jack is supposed to be, right?


----------



## vixr

TBomb06, with only a tiny bit of help the terminal block will fit on the jack pad... I bent the leads just slightly and it fit...


----------



## TBomb06

Quote:


  Originally Posted by *vixr* /img/forum/go_quote.gif 
_TBomb06, with only a tiny bit of help the terminal block will fit on the jack pad... I bent the leads just slightly and it fit..._

 

Ok, but you could do it either way, right? Sorry for the confusion...evidently I am not communicating what I am wanting to do very well. Thanks for your input though, and you too Tomb!


----------



## vixr

no, you are clear... I just figured the block could just as easily go to the jack pad and save you the effort of putting in the jumpers, which would work just fine too.


----------



## vixr

got most of my parts yesterday. still waithing on caps and DMM for DB matching... does anyone else use the customer part number section on the parts order form? sure makes it easy to keep track of a lot of parts...


































 I really like this feature and it only takes a few seconds to add the description of the parts.


----------



## adfinni

lol you won't fit the lid on 
	

	
	
		
		

		
		
	


	




 1.5 inch heatsinks, and what slot of the hammond is your board perched on ? 

 ta


----------



## vixr

I'm going to have one of the machinists at work lay out and cut the holes in the plate for the sinks and tubes, should be an exact fit... within a mil or two...the board sits in slot 3 so the pot and phone jack would be sorta centered... but most likely the plate will end up in a drawer somewhere. I got the bigger heatsinks so they _would_ stick out thru the top plate.


----------



## TimmyMac

Would it be possible to create a balanced version of this amp by making two, then running one off the normal signal and one off the inverted signal from a balanced DAC? Then from the output you would use the normal signal, inverted signal, and ground from both amps into XLR outputs? Does this make sense to anyone?

 edit: Also, would it be worthwhile instead of just building a more expensive better amp?


----------



## tomb

Quote:


  Originally Posted by *vixr* /img/forum/go_quote.gif 
_I'm going to have one of the machinists at work lay out and cut the holes in the plate for the sinks and tubes, should be an exact fit... within a mil or two...the board sits in slot 3 so the pot and phone jack would be sorta centered... but most likely the plate will end up in a drawer somewhere. I got the bigger heatsinks so they would stick out thru the top plate._

 

Sounds neat. Yes, I use the part labeling feature with Mouser and DigiKey all the time. With some appropriate caution, all you have to do is reach for the right parts bag for whatever the silkscreen says.


----------



## adfinni

Quote:


  Originally Posted by *vixr* /img/forum/go_quote.gif 
_I'm going to have one of the machinists at work lay out and cut the holes in the plate for the sinks and tubes, should be an exact fit... within a mil or two...the board sits in slot 3 so the pot and phone jack would be sorta centered... but most likely the plate will end up in a drawer somewhere. I got the bigger heatsinks so they would stick out thru the top plate._

 

Ah very cool, thought you might be trying something to that effect.

 With the centering, i guess that when the pot is centred, the jack will b off, or vise versus, as they have different centres relative to the pcb. Could you please tell me which slot in the hammond would put the pot shaft in the closest to exact centre of the front panel please, trying to work out heatsink sizes, and volume knob diameters?
 Trying to do that with the CAD drawing but would prefer a little 'real life' reassurance.

 cheers


----------



## tomb

Quote:


  Originally Posted by *adfinni* /img/forum/go_quote.gif 
_Ah very cool, thought you might be trying something to that effect.

 With the centering, i guess that when the pot is centred, the jack will b off, or vise versus, as they have different centres relative to the pcb. Could you please tell me which slot in the hammond would put the pot shaft in the closest to exact centre of the front panel please, trying to work out heatsink sizes, and volume knob diameters?
 Trying to do that with the CAD drawing but would prefer a little 'real life' reassurance.

 cheers_

 






 2nd slot from the bottom has the pot shaft closest to the center. As you say, however, the jack is much lower than the center line. So, the whole effect will be that everything is offset onto the bottom half of the endplate. If you air-wired a different jack that might work. However, the RK27 pot combined with the board-mtd jack is a familiar feature of the Millett. 3rd slot from the bottom does not look uncentered at all, IMHO.


----------



## pinkfloyd4ever

Is this too advanced for one's first tube-hybrid amp? So far I've only built a Cmoy and willl be building at least one more SS amp before I'd try this (or any tube amp), so it'd be awhile before I get around to building it. It's just that I kinda want to get in on the PCB group buy.


----------



## TBomb06

Quote:


  Originally Posted by *pinkfloyd4ever* /img/forum/go_quote.gif 
_Is this too advanced for one's first tube-hybrid amp? So far I've only built a Cmoy and willl be building at least one more SS amp before I'd try this (or any tube amp), so it'd be awhile before I get around to building it. It's just that I kinda want to get in on the PCB group buy._

 

I can't really say one way or another as to how qualified you are to build it, as I am not sure how qualified I am to build it 
	

	
	
		
		

		
		
	


	




 I can say that I would go ahead and get in on the group buy because there's no guarantee as to the availability of the boards once the group buy is over.


----------



## tomb

Quote:


  Originally Posted by *TBomb06* /img/forum/go_quote.gif 
_I can't really say one way or another as to how qualified you are to build it, as I am not sure how qualified I am to build it 
	

	
	
		
		

		
		
	


	




 I can say that I would go ahead and get in on the group buy because there's no guarantee as to the availability of the boards once the group buy is over._

 

Yes, by all means - if you think you would ever like to build it, then buy a board. Put it in the drawer or in the file cabinet until you think you're ready.

 Just to avoid confusion with the CAD plot I posted above, this one is with the board in the 3rd slot from bottom, which is pretty much the typical legacy arrangement for the Millett. As you can see, the pot shaft is not much further away, but puts the jack a bit higher so that the overall effect is one where things look centered on the endplate (IMHO):


----------



## vixr

tomb,
 although I dont have that awesome CAD ability, I just set the board in a few different slots and settled on 3...it sorta splits the difference on both centers. Looking at mine, the illusion is that the phone jack is centered and the pot is just slightly higher. Its not too hard on the eyes...how hot does the LM317T get? my A/C in wires are a bit close to the heat sink in the aft center...


----------



## TBomb06

Sooo...TomB, I just read your post over on DIYForums about the heatsink mounting hardware...I noticed that my heatsinks didn't come with any hardware, so that got me wondering what I would use. Anyway, looks like I will be making yet _another_ Mouser order 
	

	
	
		
		

		
		
	


	




. Hope this serves as a reminder to others to make sure you cover all your bases and make sure that when you click on the links in the BOM that you're actually ordering what you want to order. Tom has done a great job getting that BOM together but don't let all the work fall on his shoulders...you have to do some checking for yourself, as I've learned the hard way 
	

	
	
		
		

		
		
	


	




.

 As for thermal paste, I am thinking I will use Arctic Silver, since I have some left from some computer builds. Any reason not to?

 Also, what is the story on the fuse that is shown on the layout (in between the AC input and the power supply section)? I haven't seen anything about it on the BOM or on the MAX site, or anywhere else for that matter. Maybe I just overlooked it, but if I'm going to be making another Mouser order, I'd like to know about this fuse 
	

	
	
		
		

		
		
	


	




 Edit: Since the board takes in AC power, it doesn't matter how your V+ and V- come into the board at the power input, does it? Also, is anyone connecting the "earth ground" on their power jack to anything?


----------



## vixr

TBomb06
 I think they only need to be isolated if they touch the case... I have the kits somewhere in my stash, but I didnt use any yet...


----------



## adfinni

Many thanks tom, just what i was looking for, but im a perfectionist 
	

	
	
		
		

		
		
	


	




 As long as there is nothing stopping me, then i will centre up both the alps and jack in the centre and air-wire them to the pcb. That will allow me to put the pcb in a lower spot, and mount the tube sockets on the chassis top


----------



## vixr

I always wanted to try tubes on top... Please post pics of the construction as you go along...


----------



## adfinni

Quote:


  Originally Posted by *vixr* /img/forum/go_quote.gif 
_I always wanted to try tubes on top... Please post pics of the construction as you go along..._

 

Will do mate, gonna spend my time on this one, looking forward to yours too


----------



## TBomb06

Quote:


  Originally Posted by *vixr* /img/forum/go_quote.gif 
_TBomb06
 I think they only need to be isolated if they touch the case... I have the kits somewhere in my stash, but I didnt use any yet..._

 

Ah, right. So I could just use any nut, bolt and washer combination to hold them together? Thanks


----------



## tomb

Quote:


  Originally Posted by *vixr* /img/forum/go_quote.gif 
_tomb,
 although I dont have that awesome CAD ability, I just set the board in a few different slots and settled on 3...it sorta splits the difference on both centers. Looking at mine, the illusion is that the phone jack is centered and the pot is just slightly higher. Its not too hard on the eyes...how hot does the LM317T get? my A/C in wires are a bit close to the heat sink in the aft center..._

 

Mine gets to 46deg.C. uncovered with a 1" sink. You have to get to a couple of hundred degrees before you have to start worrying about your wires, I would think. You appear to be using 1-1/2" sinks, so you'll have even less of a problem.

 What output transistors are you using - or are you going MOSFETs with those tall sinks?


----------



## tomb

Quote:


  Originally Posted by *TBomb06* /img/forum/go_quote.gif 
_Sooo...TomB, I just read your post over on DIYForums about the heatsink mounting hardware...I noticed that my heatsinks didn't come with any hardware, so that got me wondering what I would use. Anyway, looks like I will be making yet another Mouser order 
	

	
	
		
		

		
			





. Hope this serves as a reminder to others to make sure you cover all your bases and make sure that when you click on the links in the BOM that you're actually ordering what you want to order. Tom has done a great job getting that BOM together but don't let all the work fall on his shoulders...you have to do some checking for yourself, as I've learned the hard way 
	

	
	
		
		

		
		
	


	




._

 

Yes, sorry about that - but as you've noted, you can't include every nut, bolt, input jack, etc. on the BOM. It's already fairly thorough.

  Quote:


 As for thermal paste, I am thinking I will use Arctic Silver, since I have some left from some computer builds. Any reason not to? 
 

Be careful with some of the goos - they may be conductive. Neil just commented over on the other forum that if you buy the Sil-8 (thermasil) insulators, you don't need goo. That's fine, but you can find the mica insulators in bulk for tenths of a penny per. 4-40 screws, nuts, and lock washers are about $2.50 per 100 at your local Ace Hardware. That's why I was saying the kits are a bit of a rip.

  Quote:


 Also, what is the story on the fuse that is shown on the layout (in between the AC input and the power supply section)? I haven't seen anything about it on the BOM or on the MAX site, or anywhere else for that matter. Maybe I just overlooked it, but if I'm going to be making another Mouser order, I'd like to know about this fuse 
	

	
	
		
		

		
		
	


	



 

I've asked Colin to send me the info on this. It was an idea from Neil because of his concern with the high currents on the MOSFETs. I don't necessarily agree with it - but it's there if you want to use it. Most likely, anything from 0.5 to 0.75A (assuming they come in 3/4A - I don't know). My understanding the footprint is for the 5x20mm size. A couple of PCB clips are probably pennies in price. It's easy enough to jumper it out, though, if you don't want to use it.

  Quote:


 Edit: Since the board takes in AC power, it doesn't matter how your V+ and V- come into the board at the power input, does it? Also, is anyone connecting the "earth ground" on their power jack to anything? 
 

Connecting earth ground to your power supply would mean nothing. Connecting it to the power jack on the MAX would be a very bad thing. The MAX is negative DC grounded, connecting earth ground to that will really fork things up. That's why the jack on the BOM is an isolated one. Also, the ground plane for the board is completely separated from not only the AC traces at the back, but from everything else back there except for the final output from the regulator. That is the only thing that has a chance to be hum and ripple-free. This was discovered with considerable effort during the 1st proto builds.

  Quote:


  Originally Posted by *TBomb06* /img/forum/go_quote.gif 
_Ah, right. So I could just use any nut, bolt and washer combination to hold them together? Thanks 
	

	
	
		
		

		
		
	


	


_

 

As long as they're 4-40.


----------



## TBomb06

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Yes, sorry about that - but as you've noted, you can't include every nut, bolt, input jack, etc. on the BOM. It's already fairly thorough._

 

It's quite alright...it seems I won't be having to make a Mouser order anyway, and yes, the BOM is very thorough. Like I said...I guess I have to take some of the responsibility on myself 
	

	
	
		
		

		
		
	


	




.

  Quote:


 Be careful with some of the goos - they may be conductive. Neil just commented over on the other forum that if you buy the Sil-8 (thermasil) insulators, you don't need goo. That's fine, but you can find the mica insulators in bulk for tenths of a penny per. 4-40 screws, nuts, and lock washers are about $2.50 per 100 at your local Ace Hardware. That's why I was saying the kits are a bit of a rip. 
 

The Arctic Silver thermal goo is conductive, so should I avoid it altogether or just be careful when applying it so that it doesn't get on anything else?

 EDIT: Just read Neil's post you mentioned, and it seems as though an electrically conductive thermal paste would be a bad idea. Is it a problem only if the heatsinks touch the top of the case, or should I avoid continuity between the sink and the transistor altogether?

  Quote:


 I've asked Colin to send me the info on this. It was an idea from Neil because of his concern with the high currents on the MOSFETs. I don't necessarily agree with it - but it's there if you want to use it. Most likely, anything from 0.5 to 0.75A (assuming they come in 3/4A - I don't know). My understanding the footprint is for the 5x20mm size. A couple of PCB clips are probably pennies in price. It's easy enough to jumper it out, though, if you don't want to use it. 
 

Thanks for the explanation 
	

	
	
		
		

		
		
	


	




  Quote:


 Connecting earth ground to your power supply would mean nothing. Connecting it to the power jack on the MAX would be a very bad thing. The MAX is negative DC grounded, connecting earth ground to that will really fork things up. That's why the jack on the BOM is an isolated one. Also, the ground plane for the board is completely separated from not only the AC traces at the back, but from everything else back there except for the final output from the regulator. That is the only thing that has a chance to be hum and ripple-free. This was discovered with considerable effort during the 1st proto builds. 
 

That makes sense 
	

	
	
		
		

		
		
	


	




. So since it's alternating current, just hook the jack up so that V+ goes to one terminal pad and V- to the other?

  Quote:


 As long as they're 4-40. 
 

Right-o. Thanks Tom!


----------



## vixr

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_What output transistors are you using - or are you going MOSFETs with those tall sinks?_

 

I bought a couple of lots of 2N5087 and 2N5088 transistors to bias SS amps into class A last year and about 94 of each are just sitting in the bins... I want to try the basic model first then try the MOSFETs on #2. I bought enough parts to build the second one too...WOO HOO!!! after that I get 6 more chances to get it right. I think this amp is going to be insanely popular and will be around a long time... this is just the first GB.


----------



## Alcaudon

One question about tubes.....

 I know that 12AE6 tubes have a gain of 14, and 12FM6 a gain of 10, but, are they different in any other way? How do they sound compared to each other?

 I'm having troubles to find 12AE6 tubes (shipping costs), but I've found some 12FM6, and I just want to be sure that they are fine for my Max. Sorry, I'm a tube noob 
	

	
	
		
		

		
		
	


	




 Thanks!!!!


----------



## tomb

Quote:


  Originally Posted by *Alcaudon* /img/forum/go_quote.gif 
_One question about tubes.....

 I know that 12AE6 tubes have a gain of 14, and 12FM6 a gain of 10, but, are they different in any other way? How do they sound compared to each other?

 I'm having troubles to find 12AE6 tubes (shipping costs), but I've found some 12FM6, and I just want to be sure that they are fine for my Max. Sorry, I'm a tube noob 
	

	
	
		
		

		
		
	


	




 Thanks!!!!_

 

If you don't want to specify brand, Radio Daze has many 12AE6A's for $2.50 ea., and they use USPS Priority Mail, which is only $4.60 for the first pound. If you want FM6's or FK6's those are only $2 ea.

 EDIT: Maybe that doesn't help much if you are not in the US, but I can't tell from your lack of profile. If that's the case, maybe someone else can help. I haven't noticed difficulty with obtaining these from overseas, and we have had many international builders of the Millett through the years.

 This is opinion, although perhaps shared by more than a few, the 12AE6's give up a slight bit of detail over the FK6's in return for more bass punch. The FM6's are somewhere inbetween, but truthfully, not too many have used the 12FM6 by comparison to the other two.


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## vixr

wow... I ordered all my electrolytic caps from handmade to save on some shipping and I got the muse 1000uF@50v KZ for CR1A,B,C and D...they are 1 5/8 inches tall! 1/8th taller than the big heatsink! looks kinda cool though...its got a Mayan pyramid look to it now...tomb you got PM


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## bperboy

I've got a set of each of the three tube types, all GE branded. I've tried both the 12AE6A and the 12FK6, but I've not tried the 12FM6 ever. Maybe I'll swap those in this week.


----------



## tomb

Quote:


  Originally Posted by *bperboy* /img/forum/go_quote.gif 
_I've got a set of each of the three tube types, all GE branded. I've tried both the 12AE6A and the 12FK6, but I've not tried the 12FM6 ever. Maybe I'll swap those in this week._

 

Yes, that's actually the situation I'm in. I didn't mean to imply that the FM6's might not be OK. That's exactly the point: with the few exceptions of really bad tubes or microphonics from bad construction, there are no "bad" or "good" tubes among the 12AE6, 12FM6, and 12FK6.

 If you read through the entire DIYForums.org collection of threads, you will probably find that most prefer the FK6's. I suspect that's because with low gain, they pair well with Grado's, which most Millett builders seem to own. That's all I meant to say. That - and the fact like Bperboy, I haven't actually tried an FM6, yet. That's because despite the FK6 trend (IMHO), the 12AE6A does everything I need. It has the gain necessary to give a pair of Senns that extra "oomph." So, chances are that the FM6 is somewhere in the middle, because its gain is in the middle of the three tubes. Consequently, if you find some saying the FM6 sounds a "little wooly" (one comment I remember vividly), or that the 12AE6 lacks detail, take it with a grain of salt.

 I would definitely recommend that each MAX builder try a pair of each, if possible - at least until you find the ones that satisfy you.


----------



## bperboy

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Yes, that's actually the situation I'm in. I didn't mean to imply that the FM6's might not be OK. That's exactly the point: with the few exceptions of really bad tubes or microphonics from bad construction, there are no "bad" or "good" tubes among the 12AE6, 12FM6, and 12FK6.

 If you read through the entire DIYForums.org collection of threads, you will probably find that most prefer the FK6's. I suspect that's because with low gain, they pair well with Grado's, which most Millett builders seem to own. That's all I meant to say. That - and the fact like Bperboy, I haven't actually tried an FM6, yet. That's because despite the FK6 trend (IMHO), the 12AE6A does everything I need. It has the gain necessary to give a pair of Senns that extra "oomph." So, chances are that the FM6 is somewhere in the middle, because its gain is in the middle of the three tubes. Consequently, if you find some saying the FM6 sounds a "little wooly" (one comment I remember vividly), or that the 12AE6 lacks detail, take it with a grain of salt.

 I would definitely recommend that each MAX builder try a pair of each, if possible - at least until you find the ones that satisfy you._

 

TomB, 
 How high do you usually have the volume set at with the 12AE6As? With that extra gain, I never usually turn it up much past 10oclock. It always seems to be much too loud past that. I'd like to get an SPL meter at some point from Radioshack.


----------



## tomb

Quote:


  Originally Posted by *bperboy* /img/forum/go_quote.gif 
_TomB, 
 How high do you usually have the volume set at with the 12AE6As? With that extra gain, I never usually turn it up much past 10oclock. It always seems to be much too loud past that. I'd like to get an SPL meter at some point from Radioshack._

 

I'd say more like 12 o'clock for over-powering volume. So, put in the 12FK6 or a couple of output resistors, and you're at 3/4 turn. I feel better with my listening between 0 to 1/2 turn, though. More than that and it "feels" like amplifying more noise than music, but that's just my own personal preference.

 EDIT: Keep in mind my comments regarding gain and volume are all based on personal feelings. Saying that higher gain results in more "oomph" is an indefensible statement.

 Oh, those descriptions are also based on HD580's.


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## vixr

OMG... my hfe matching meter is still DAYS down range. My MAX is sitting here with no transistors although I have nearly 200 2n5087/88s in my stash! wish there was a way to do it with my fluke 179... it sucks to be me.


----------



## TBomb06

Quote:


  Originally Posted by *vixr* /img/forum/go_quote.gif 
_OMG... my hfe matching meter is still DAYS down range. My MAX is sitting here with no transistors although I have nearly 200 2n5087/88s in my stash! wish there was a way to do it with my fluke 179... it sucks to be me._

 

I think Harbor Freight ships from the other side of the world, and it gets here via ship, thus the name. If you didn't get your meter from HF then just ignore me, but mine took 2 weeks to get here. And I paid $7 for shipping why???


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## vixr

used some ambiguous ethics and got my hands on a meter!!! 
	

	
	
		
		

		
		
	


	




 my MAX is done...I cant believe the bass! this amp is incredible, setting the bias was not so bad... I wish I was smart enough to figure out what is the setting I need for the DB though. I just picked a number... 90 mV out of the air.. Running some 12FK6s at 13.5 volts. the tubes are hotter than the LM317T. cant turn this monster up past 12:00, and its just perfect... The best Millett ever. I cant wait to try the MOSFET configuration next...You guys waiting for boards are gonna love this amp...my corda cross-1 filters out some volume but the effect is worth it. it should get better with some time on the caps and tubes, right?


----------



## TBomb06

Quote:


  Originally Posted by *vixr* /img/forum/go_quote.gif 
_used some ambiguous ethics and got my hands on a meter!!! 
	

	
	
		
		

		
		
	


	




 my MAX is done...I cant believe the bass! this amp is incredible, setting the bias was not so bad... I wish I was smart enough to figure out what is the setting I need for the DB though. I just picked a number... 90 mV out of the air.. Running some 12FK6s at 13.5 volts. the tubes are hotter than the LM317T. cant turn this monster up past 12:00, and its just perfect... The best Millett ever. I cant wait to try the MOSFET configuration next...You guys waiting for boards are gonna love this amp...my corda cross-1 filters out some volume but the effect is worth it. it should get better with some time on the caps and tubes, right?_

 

From the MAX site that Tom put together, the appropriate bias fro the DB is anywhere from 66-110mV (30ma-50ma). From what I've heard, the closer to 50ma, the better the sound (deeper into Class A, less distortion). Naturally, I can't speak from experience, because I don't have a board yet 
	

	
	
		
		

		
		
	


	




. I've heard 90mV is a good starting point, but personally, I would try pushing it higher, as long as you aren't having any heat issues. Also, from what I've heard, depending on what kind of caps you're rollin with, it will take a few good hours of listening for them to burn in. Just enjoy listening to that bad boy 
	

	
	
		
		

		
		
	


	




 Oh yeah, you forgot pics!!!


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## bperboy

Also, for biasing, it kind of depends on how you enclose the amp. Me, I've not put a top cover on, making it much easier to bias as I won't have to check voltages with the top cover closed.


----------



## tomb

Glad to hear you found some ambiguous ethics, Vixr - at least in the short term - so you could get that MAX finished! 
	

	
	
		
		

		
			





 As a matter of fact about bias - cetoole has told me that fundamentally, the MOSFETs have no advantage over the BJT's in that regard. The BJT's can be biased up to 220mV (100ma), too!
	

	
	
		
		

		
		
	


	




 Only the shorter sinks and the lack of ventilation will prevent them from running at that point. The difference is that at 100ma with the top on, the BJT's may go to 120ma or higher. The MOSFETs on the other hand, may go back down to 80ma with the cover on. This is because of that negative temperature coefficient thing with the MOSFETs.

 I know that the BJT's will probably go another 25% with the default 1" high sinks - that's perhaps 75ma (165mV). I got into the 50ma mode with the 1st prototype for two reasons: 1) it was a good round number that exceeded the Class A bias of the PPAV2 and the original revMH DB's by a large margin, and 2) the JFET's couldn't take anymore. (The JFETs are the PN4392 and 2N5486 for the BJT and MOSFET versions, respectively.)

 The 1st proto, as with Steinchen's revMH DB's, was set up with a current _mirror_. This kept the current through the JFET in the same relative regime as the BJT's. As a result, the two little TO-92 JFETs (L&R) were the hottest things on the board, including the LM317 - by over 10deg. The 2nd proto, MOSFET, and production versions use a current _multiplier_ in the DB circuit that keeps the current way down on the JFET.

 Also, while 50ma for the BJT's is deeper Class A bias than many readily available DIY amps (Dynahi may be the only one AFAIK - but don't quote me), it is only in the 35-40 deg.C range with lowly 1" heat sinks. I don't think there's any danger of thermal runaway even with the lid on. The BJT's are much cooler at this bias than even the revMH DB's. We'll have to experiment with higher settings to see how that goes vs various forms of case ventilation. For the time being, though, 50ma is a good recommendation - that's 110mV at the bias test points.

 The matching procedure is what's used to keep that bias setting the same among the four BJT sections. Hopefully, you don't see much more than 5-10mV difference among the BJT's. However, with the MAX's output capacitors, even larger offsets will be filtered out.


----------



## vixr

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_The 2nd proto, MOSFET, and production versions use a current multiplier in the DB circuit that keeps the current way down on the JFET._

 

I thought that the way the transistors were placed on the board looked a little different... I probably wont be able to use the top plate on mine due to the huge caps I bought, so I dont think heat will play a big part in the DB temp issue. How much adjusting will the trimmers tolerate? Do we want to find a set of tubes we like and leave them in?
 I checked for DC offset at the phone jack and found like 0.1mV in both channels...
 I noticed the Muse ES caps run a little bit warm too...Normal?
 Does this amp suffer from the DB shorting issue like the PPA?
 I also used a 470uF 35V cap in the e12 circuit and see about 16 seconds of turn on delay...


----------



## tomb

Quote:


  Originally Posted by *vixr* /img/forum/go_quote.gif 
_I thought that the way the transistors were placed on the board looked a little different... I probably wont be able to use the top plate on mine due to the huge caps I bought, so I dont think heat will play a big part in the DB temp issue. How much adjusting will the trimmers tolerate? Do we want to find a set of tubes we like and leave them in?
 I checked for DC offset at the phone jack and found like 0.1mV in both channels...
 I noticed the Muse ES caps run a little bit warm too...Normal?
 Does this amp suffer from the DB shorting issue like the PPA?
 I also used a 470uF 35V cap in the e12 circuit and see about 16 seconds of turn on delay..._

 

Not sure what you mean by how much adjusting the trimmers will tolerate - quite a bit, I don't think you have to worry about wearing them out, if that's what you mean.

 Yes, I would settle on a set of tubes and stick with them for awhile. Keep in mind that a "new" set of NOS tubes may take several days to burn out all the gas and settle down into a good sound and reliable bias.

 Your DC offset is fantastic - no problems with that.

 I think the Muse ES pick up the heat from the radiation of the tubes, the PS sink, and the output transistor sinks. I'm not sure they develop heat on their own.

 Yes, depending on which headhpone, a 470uF cap in the e12 is probably a good choice. We've found that the delay is less for low impedance phones. It's not supposed to work that way, but a bigger cap is not a difficulty - especially when quality is not an issue - they can be had for pennies in these sizes and voltage.

 Can you elaborate a little on the DB shorting issue for the PPA? I'm not familiar with that.


----------



## vixr

tomb,
 if you pull the headphone plug out while the PPA is turned on, the right channel ring on the plug shorts to ground in the jack... Tangent says this will destroy the DBs in the PPA, and to never pull the plug out while the amp is on...
 (stolen from Tangent)
 On Output Shorts in PPAv2
 The output buffers in PPAv2 do not have output current limiting. That means that it is theoretically possible for an output short to destroy either the output resistors or the output transistors, or both. Since the tip-ring-sleeve plugs used on headphones have a design flaw that shorts the right channel to ground within the jack while pulling the headphone plug out, it's worth considering the consequences of an output short.


----------



## tomb

Quote:


  Originally Posted by *vixr* /img/forum/go_quote.gif 
_tomb,
 if you pull the headphone plug out while the PPA is turned on, the right channel ring on the plug shorts to ground in the jack... Tangent says this will destroy the DBs in the PPA, and to never pull the plug out while the amp is on...
 (stolen from Tangent)
 On Output Shorts in PPAv2
 The output buffers in PPAv2 do not have output current limiting. That means that it is theoretically possible for an output short to destroy either the output resistors or the output transistors, or both. Since the tip-ring-sleeve plugs used on headphones have a design flaw that shorts the right channel to ground within the jack while pulling the headphone plug out, it's worth considering the consequences of an output short._

 

Well, I can't comment on the PPA. However, neither the revMH Millett with Steinchen's DB's nor the MAX has anything like this tendency. Those BJT's are pretty tough. I am very slow to pull out the headphone plug - especially when it's uncased. Sometimes I lose my grip on the board and it stays stuck in mid-stream for several seconds. There is no issue with this.

 As you may recall on the Millett - without the e12 delay, standard practice is to plug and unplug _with the amp *on*_. Otherwise, you subject the phones to tremendous offset voltages - as much as the power supply itself for a few short seconds. I've seen it stay up around 5-7 volts for 4 or 5 seconds on the regular Millett.

 The MAX also does not have this problem - since the e12 delay is more than sufficient time for the offset to settle down to zero.


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## ericj

steinchen's DBs also have small output resistors, so the output is never a dead short.


----------



## vixr

Well, here it is all finished...I have a better knob on its way from Harry at partspipe...


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## tomb

Wow, Vixr - that's going in the Gallery on the web site tonight!


----------



## tomb

Quote:


  Originally Posted by *ericj* /img/forum/go_quote.gif 
_steinchen's DBs also have small output resistors, so the output is never a dead short._

 

Yes, the MAX has them, but so does the PPAV2, too!?

 I think what's going on here is a bit of confusion with the first PPA - V1. It used monolithic Intersil chips for the buffers and those have no internal output resistors or short circuit protection whatsoever. That's probably where the admonition originated.


----------



## n_maher

Just to elaborate a bit on the output shorting concern here's my take on it after several conversations with folks much more knowledgeable about stuff like this, with any of the iterations of the PPA diamond buffer (V2, Steinchen's layout, the MAX, etc.) there is the theoretical possibility of damaging the buffer if you unplug the headphones while the amp is in use. It is my understanding that no one has ever tried to see how long the output would have to be shorted to cause a buffer to fail but technically it is possible. The reason that none of us has ever experienced this is simply because the time to failure must be longer than the fraction of a second it takes to unplug your headphones (even a slow pull). The output resistors on the buffers act to somewhat isolate the buffer from the shorted output but probably wouldn't last forever. So your best bet is to just be conscious of the possibility and take steps to limit the chances. Pause your source, turn down the volume all the way and then remove the headphones. 

 There's more info somewhere here on this (in PPA threads, I think) so I'd recommend a healthy search for the curious.

 Nate


----------



## vixr

thermal image of the MAX on its side... looks like the whole ground plane is warm. You cant even see the heatsinks or the transistors near the front of the amp...

 stand back from the screen a bit...


----------



## MusicallySilent

Wow those are some big caps 
	

	
	
		
		

		
		
	


	




 This amp looks better by the moment... does anyone have any clue how much wattage these things consume hourly? Also what does the size of caps do to help sound? [im new to the understanding of why it works how it does]


----------



## TBomb06

Quote:


  Originally Posted by *MusicallySilent* /img/forum/go_quote.gif 
_Wow those are some big caps 
	

	
	
		
		

		
		
	


	




 This amp looks better by the moment... does anyone have any clue how much wattage these things consume hourly? Also what does the size of caps do to help sound? [im new to the understanding of why it works how it does]_

 

I'm not sure I am qualified to explain this, but basically, the bigger caps (higher capacitance) in the signal path improve the bass, and that might just be on the cathode bypass caps. It has something to do with the signal frequency, but, like I said, I'm not 100% qualified to explain it.

 As for wattage...I guess that kind of depends, but let's assume you're using the 24V 1A wall-wart:

 W = V*I => W = 24V * 1A = 24W

 Then, taking a formula I found somewhere on the internet:

 kWh = (W * Hrs) / 1000 => kWh = (24W * 1Hr) / 1000 = .024kWh consumed in one hour.

 It's been a while since I've had any electricity classes...and I told myself when I was done with them that I would never even utter the phrase "V = I*R" ever again...figures 
	

	
	
		
		

		
		
	


	




 Anyway, hope this is correct...

 By the way, Vixr, that looks terrific! I can't wait!


----------



## tomb

Those caps are so big because Vixr bought mostly Nichicon KZ's - Nichicon's top-of-the-line boutique audio electrolytic caps. They're monsters in size compared to many other caps! Boutique electrolytic capacitors tend to be much bigger and bulkier than the same size power caps - even very good ones.

 As for the power calcs, TBomb did pretty good. In the absence of real measurements, assuming that the power is the same as the rating on the walwart is a good approach. However, I've done some measurements on the 1st proto - about 600ma inrush and about 400-450ma steady state (DB's biased at 50ma ea.). Also, the point I was measuring was right before entry to the regulator, where the DC voltage was ~33VDC. So:

 33VDC x 0.45A = 14.9W, or 0.015kWH per hour. YMMV, depending on DB bias.

 P.S. Great thermal image, Vixr - that's really neat!!


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## bperboy

How did you take that thermal image by the way?


----------



## MusicallySilent

So it has prettymuch a very low powerusage saying its like 15-50 watts maybe


 I just wanted to make sure i wasnt getting myself into a 100+watt hour beamonth

 This thing looks so much more intresting as time goes buy... i am really thinking about building one but then i was also thinking I can get a really good reciever for the same price and then even hook speakers up to it in the future... will the reciever have similar quality to this i was looking at the pioneer VSX-516-K 7.1 channel receiver with 700watts max power but driving a headphone it probably uses like 50 watts... sadly the impedence for speakers is 8 ior 16 ohms if i remember right... does that mean i can only drive low impedance headphones?

 I will probably try a cheap cmoy or pimeta or something inexpensive first just to gain some experience

 Do you have a good easy to build amp or know of one for a person who has worked with a breadboard before but is new to making something useful out of it?


----------



## bperboy

Quote:


  Originally Posted by *MusicallySilent* /img/forum/go_quote.gif 
_So it has prettymuch a very low powerusage saying its like 15-50 watts maybe


 I just wanted to make sure i wasnt getting myself into a 100+watt hour beamonth

 This thing looks so much more intresting as time goes buy... i am really thinking about building one but then i was also thinking I can get a really good reciever for the same price and then even hook speakers up to it in the future... will the reciever have similar quality to this i was looking at the pioneer VSX-516-K 7.1 channel receiver with 700watts max power but driving a headphone it probably uses like 50 watts... sadly the impedence for speakers is 8 ior 16 ohms if i remember right... does that mean i can only drive low impedance headphones?_

 

For dedicated headphone usage, the Max will definatly have much better quality than any receiver headphone-out, but then again, if you are seriously thinking about a speaker rig, you might want a speaker amp. I'd recommend a Max, but then again, I'm pretty biased (pardon teh pun)!


----------



## MusicallySilent

What about a CMOY or PIMETA will that still sound better than a reciever? Im probably trying to get a relatively cheap amp or just go for the reciever... because i listen alot but i might get screwed over and find myself using the amp more than the potential speakers since it will probably sound better

 Sadly if i really wanted to i could make an amp on my little breadboard with build in pentomitors and crap all i need to do is get the opamp and headphone input and output jacks with connector and im probably good to go since it has a lot of built in stuff and came with a bunch of caps and resistors and whatnot


----------



## bperboy

Quote:


  Originally Posted by *MusicallySilent* /img/forum/go_quote.gif 
_What about a CMOY or PIMETA will that still sound better than a reciever? Im probably trying to get a relatively cheap amp or just go for the reciever... because i listen alot but i might get screwed over and find myself using the amp more than the potential speakers since it will probably sound better

 Sadly if i really wanted to i could make an amp on my little breadboard with build in pentomitors and crap all i need to do is get the opamp and headphone input and output jacks with connector and im probably good to go since it has a lot of built in stuff and came with a bunch of caps and resistors and whatnot_

 

Well if you didn't want to build anything, you could always buy my Millett Hybrid! 
	

	
	
		
		

		
		
	


	




 I think that if its built well, a good solid headphone designed amp will do better than a receiver, but it does depend somewhat on the rest of your chain, i.e. source.


----------



## vixr

Quote:


  Originally Posted by *bperboy* /img/forum/go_quote.gif 
_How did you take that thermal image by the way?_

 

I used the least expensive imager (FLIR) I have in my shop... It doesnt have a zoom function and is focused at infinity. I will take some with the good ($300K) imager and post those... it has a zoom and focus function that should be quite clear... I will leave the amp on awhile and plug everything in, source and phones, to get everything nice and warm. the more things there are at different temps, the better the imager can contrast them...should be very interesting.


----------



## bperboy

Sweeett! Those IR pics are cool! (well, I guess they're hot.. 
	

	
	
		
		

		
		
	


	




)


----------



## vixr

Quote:


  Originally Posted by *bperboy* /img/forum/go_quote.gif 
_Sweeett! Those IR pics are cool! (well, I guess they're hot.. 
	

	
	
		
		

		
		
	


	




)_

 

well...anything above ambient air temp will do


----------



## MusicallySilent

Yea my source is currently wmas 128bit through soundblasterlive to my headphones useing a dynex splitter or some brand like that

 My source for this equipment will be a chaintec a710 or xfi maybe a e-mu card with FLAC or another lossless format at high bit rates


----------



## vixr

here is those thermal images I promised... as you can see, the imager is much better than the first. (seaFLIRII C)



























 this is driving HD-600s, DB set at 110mV, tube heaters at 13.5V, PS set at 27V, the last image was taken at about 15 minutes with the amp switched on...


----------



## tomb

That's very cool ... er, I mean hot. 
	

	
	
		
		

		
		
	


	




 It's interesting to note the PS resistor and the heater resistor - also the BD139 in the e12 delay section. The LED resistor at the top tube looks pretty hot, too - can't tell on the bottom one. I've been thinking of changing the BOM to 2K resistors for the LED's - it would make things a lot simpler and safer.

 So, what are the two circles at the bottom with the blue and yellow thingies that look like little icons of movie projectors?


----------



## vixr

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_That's very cool ... er, I mean hot. 
	

	
	
		
		

		
		
	


	




 It's interesting to note the PS resistor and the heater resistor - also the BD139 in the e12 delay section. The LED resistor at the top tube looks pretty hot, too - can't tell on the bottom one. I've been thinking of changing the BOM to 2K resistors for the LED's - it would make things a lot simpler and safer.

 So, what are the two circles at the bottom with the blue and yellow thingies that look like little icons of movie projectors?_

 

azimuth and elevation indicators... tells you at a glance where the imager is pointing, relative to vessel position...


----------



## vixr

as you can see, I took the pictures from a monitor mounted in the cabin of a vehicle... I used a nikon 5400 digital camera.


----------



## fierce_freak

Wow, that's cool.


----------



## vixr

so far so good on milling the top plate...


----------



## tomb

Vixr, you are amazing!


----------



## daggerlee

Looking at vixr's amp is making me want to spend $20 on boutique nichicon caps...


----------



## vixr

Well, I figure if the MAX team can design something this good, the least I can do is honor that with a decent build.


----------



## pinkfloyd4ever

dude where do u work vixr that you have $300K thermal imaging equipment?


----------



## vixr

Our Government owns the equipment...


----------



## bperboy

Quote:


  Originally Posted by *pinkfloyd4ever* /img/forum/go_quote.gif 
_dude where do u work vixr that you have $300K thermal imaging equipment?_

 

I picked one of those up at a garage sale a few weeks ago... paid $50 for it only because it looked cool.


----------



## vixr

Quote:


  Originally Posted by *bperboy* /img/forum/go_quote.gif 
_I picked one of those up at a garage sale a few weeks ago... paid $50 for it only because it looked cool. 
	

	
	
		
		

		
		
	


	


_

 

You said you wouldn't tell anyone!!!


----------



## MusicallySilent

Yea these amps look so cool along with those pics though im not sure ifi should even get such an amp this close to the beginning of my headfi joining... i might start with a pimeta instead and if i get the upgrade bug ebay it/sell to fellow head-fier/sell to friend along with crapola headphones i have [compared to your headphones (he needs new cans his are 10 year old earbuds and he thinks they sound good !!!! 
	

	
	
		
		

		
		
	


	




 )]


----------



## naamanf

I say just go for it. You will get the upgrade bug.


----------



## MusicallySilent

But then i also need a good pair of headphones to compliment the amps and my listening style

 Music Preferences:
 Classical, Country, Light rock (no metal), Opera (Andrea Bocelli), Rock Classical (Rock music played on classical instruments Bond Apocalyptica (its kinda like metal i just dont like the screaming and whatnot) and the like), Instrumental Music, Soundtracks, No: Rap or metal

 I want something that has nice earpads (pleather [fake leather] makes me sweat real leather might do the same so i might go with velour or cloth) I also want something that goes around the ears with extra space because that is the type of pads my ears stand the most

 The main reason i am asking here is because you know what sounds good with this amp. Im looking for something around 100-150 maybe 175 Max

 I liked the hd580 but its sort of hard to get and has been discontinued and somewhat hard to get

 Im fine with Amazon.com and Newegg.com for buying phones and local shops


----------



## tomb

The HD580 pairs very well with the MAX. There's plenty of voltage slew and power to blow away any hint of a veil. You can still find them at several places - I think B&H Photo still has them, and Amazon, too - although they're up to about $180 at Amazon, now, I think.

 At the very least, you should do what many do: buy the board if you think there's any chance you will ever build one. This isn't a situation like Tangent or Amb where there's an online store and you can order a board anytime you like. Buy it in the Group Buy, or risk the chance of never getting one, period. Put it in the drawer or file cabinet until you're ready to build it after you've had some experience building other amps.


----------



## vixr

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Buy it in the Group Buy, or risk the chance of never getting one, period._

 

pretty much says it all...


----------



## MusicallySilent

So pretty much get the board because i can buy the parts anytime?

 How much is the board again isnt it like 10 bucks according to your site...

 Ill probably buy a board and save everything on your site in a file so i can build in future

 EDIT: So pretty much i am screwed on getting one after tomorrow since the group buy ends?


----------



## TBomb06

Quote:


  Originally Posted by *MusicallySilent* /img/forum/go_quote.gif 
_So pretty much get the board because i can buy the parts anytime?

 How much is the board again isnt it like 10 bucks according to your site...

 Ill probably buy a board and save everything on your site in a file so i can build in future

 EDIT: So pretty much i am screwed on getting one after tomorrow since the group buy ends?_

 

If you want one, I would post in the thread in the group buy forum right now, and email Colin right after that.


----------



## soloz2

Yep, I'm in for 3 boards. I'll probably only build 2, but I got the 3rd just incase


----------



## vixr

I can almost say for a fact, that if you bought a board and didn't build, you could sell it to another builder with no problem... I'm buying 6 extra boards... I would sell a few to those who miss out...


----------



## n_maher

Quote:


  Originally Posted by *vixr* /img/forum/go_quote.gif 
_pretty much says it all..._

 

Yup, and what are we talking, like $15 w/ shipping and fees? (note: I don't know what the actual final price will be, only Colin does)


----------



## MusicallySilent

Wow you have that many boards needing building


----------



## colonelkernel8

I am designing a wooden case for it. What are the board dimensions? How much height should I leave for the caps? (the tubes will be mounted so that they are visible out the top). How big of holes should I leave for the tubes?


----------



## soloz2

Quote:


  Originally Posted by *colonelkernel8* /img/forum/go_quote.gif 
_I am designing a wooden case for it. What are the board dimensions? How much height should I leave for the caps? (the tubes will be mounted so that they are visible out the top). How big of holes should I leave for the tubes?_

 

You can design it after the Hammand case that is standard, then just drill your holes once you know where they need to be


----------



## tomb

Quote:


  Originally Posted by *colonelkernel8* /img/forum/go_quote.gif 
_I am designing a wooden case for it. What are the board dimensions?_

 

160mm wide x 157mm
  Quote:


 How much height should I leave for the caps? (the tubes will be mounted so that they are visible out the top). 
 

This is entirely dependent on your part selection. Your choice of heat sink height really determines this. The standard config with BJT transistor DB's uses 1" high heat sinks. The recommended caps are all 25mm tall or less, but some boutiques, should you choose to use them, may be as tall as 35mm.
  Quote:


 How big of holes should I leave for the tubes? 
 

Millett tubes are 3/4" in diameter. Many people use 1" grommets that have a 7/8" hole, giving 1/16" clearance all around, but this is entirely up to you.

 Note that the board dimensions are in the Technical Highlights and Board section of the Max website. The tube dimensions are also in the Millett Tubes section. I am working on a casework section for the recommended Hammond, but admittedly, it won't be too pertinent if you are making your own wooden case.


----------



## MusicallySilent

Quote:


  Originally Posted by *vixr* /img/forum/go_quote.gif 
_I can almost say for a fact, that if you bought a board and didn't build, you could sell it to another builder with no problem... I'm buying 6 extra boards... I would sell a few to those who miss out..._

 

If I dont get one in time is is possible for you to sell one to me 
	

	
	
		
		

		
		
	


	




 Though im not even sure if i want a 150 dollar amp this soon or if i will ever want one... it is 10 bucks but im not sure if it is worthwhile to spend... i might just make a pimeta or something else instead

 EDIT: I might buy it based on whether or not ill be able to get most of the parts a year for now... (if i have to order a tube or opamp or something that might get discontinued i will


----------



## tomb

*Discontinued tubes?* Gee, that would be unfortunate ... 
	

	
	
		
		

		
		
	


	




 Sorry - I just couldn't resist.


----------



## TBomb06

Quote:


  Originally Posted by *MusicallySilent* /img/forum/go_quote.gif 
_If I dont get one in time is is possible for you to sell one to me 
	

	
	
		
		

		
		
	


	




 Though im not even sure if i want a 150 dollar amp this soon or if i will ever want one... it is 10 bucks but im not sure if it is worthwhile to spend... i might just make a pimeta or something else instead

 EDIT: I might buy it based on whether or not ill be able to get most of the parts a year for now... (if i have to order a tube or opamp or something that might get discontinued i will_

 

I don't mean to be rude, but it's $10...if you decide you want to build one you'll be glad you went ahead and got one. If you decide you don't want to build one, I doubt you'll have much trouble selling the board, as I'm sure there will be someone somewhere who will miss out on the group buy and end up wanting one. My advice, for the second time, is to go ahead and get in on the group buy while you can.


----------



## bperboy

Yes, I'd advise to go ahead and get the board. If you decide not to build, you can always sell it later, and I'm sure there will be a demand when they're not available.


----------



## MusicallySilent

Yea problem is you were supposed to finalize order today....

 Can i still make an order on the 4th in the morning?

 Yea also one last question... If i have all the parts and solder them on in the right places with good joints... is there any real way i can make the amp sound really crappy or would i have to misplace a component or solder poorly

 Also what would you recommend for practice soldering?

 Buying a breadboard and trying to solder on some stuff like wires?


----------



## TBomb06

Quote:


  Originally Posted by *MusicallySilent* /img/forum/go_quote.gif 
_Yea problem is you were supposed to finalize order today....

 Can i still make an order on the 4th in the morning?

 Yea also one last question... If i have all the parts and solder them on in the right places with good joints... is there any real way i can make the amp sound really crappy or would i have to misplace a component or solder poorly

 Also what would you recommend for practice soldering?

 Buying a breadboard and trying to solder on some stuff like wires?_

 

You can make an order until midnight tonight. I'm not sure what time zone though, it wasn't specified in the group buy thread here. I'm sure that tomorrow morning the group buy will be closed, just like it says.

 If all the appropriate parts are properly soldered in the right places I don't really see how you can have a poor performing amp unless you have a malfunctioning component.

 For practice soldering, I would recommend you build an inexpensive CMoy and get that working. It will be good practice if you actually buy a board and plan on building a MAX.


----------



## MusicallySilent

Yea I am probably going to build a cmoy (portable) and a pimeta or Beta 22 (depends on price for building) for desktop amp for 150 total


----------



## vixr

I have a question about transistor matching... I chose the 2n5087s at the most common value I saw over and over, 440. I did the same for the 2n5088s which was 520... should I have chosen different values? I know its a bit late, but at the time I was a little insane. Should they be the same for the type and don't worry about the difference _between_ the types?


----------



## tomb

Quote:


  Originally Posted by *vixr* /img/forum/go_quote.gif 
_I have a question about transistor matching... I chose the 2n5087s at the most common value I saw over and over, 440. I did the same for the 2n5088s which was 520... should I have chosen different values? I know its a bit late, but at the time I was a little insane. Should they be the same for the type and don't worry about the difference between the types?_

 

That sounds like a pretty good match to me. Get all of the same type matched in groups, then pick the two closest groups of each complementary types.

 One good way to tell how well you did is to measure the two test points within each channel. If they're close to the same bias, then you did a good job.


----------



## MusicallySilent

Yea I am in such a debate whether to build a cmoy with a friend for practice for both of us then buy a board off someone and build a millit max or build myself a portable cmoy and desktop pimeta amp/beta 22

 Screw it... all the parts will be available since they are electronic parts and if i really want to i can just buy the tubes...

 I will probably send off an email and payment upon reply promptly tomorrow or buy a board off someone (maybe vixr if he is willing) because i can probably always sell it off if i want to


----------



## vixr

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_That sounds like a pretty good match to me. Get all of the same type matched in groups, then pick the two closest groups of each complementary types._

 

So, if I understand, I would choose exact matches for 2N5087 say at 440... then choose all the 2N5088s at say 450, if I could get that close? I think I could have gotten a lot closer than those 520s. Since that number came up the most, I figured that was about "normal" for those... also, is there a certain number that is better than another? l found enough of each at a given value that could have been used too. I saw a lot of the 87s at 380... and a lot of the 88s at 400. would those have been a better choice?


----------



## TBomb06

Quote:


  Originally Posted by *MusicallySilent* /img/forum/go_quote.gif 
_Yea I am in such a debate whether to build a cmoy with a friend for practice for both of us then buy a board off someone and build a millit max or build myself a portable cmoy and desktop pimeta amp/beta 22

 Screw it... all the parts will be available since they are electronic parts and if i really want to i can just buy the tubes...

 I will probably send off an email and payment upon reply promptly tomorrow or buy a board off someone (maybe vixr if he is willing) because i can probably always sell it off if i want to_

 

Dude, I don't know how much research you have done about the B22 but you are probably going to spend much more than you would to build a really nice MAX. Anyway, my advice, again, is to build you a CMoy to get the basics, and depending on how you do that, maybe go on to the MAX. Anyway...that's my advice...


----------



## bperboy

Quote:


  Originally Posted by *TBomb06* /img/forum/go_quote.gif 
_Dude, I don't know how much research you have done about the B22 but you are probably going to spend much more than you would to build a really nice MAX. Anyway, my advice, again, is to build you a CMoy to get the basics, and depending on how you do that, maybe go on to the MAX. Anyway...that's my advice..._

 

Yes, I was looking into building a B22 also, and I determined that it would be much more than I wanted to spend. I am very happy with the Max, considering it was below $200 IIRC, but only a bit above if it was!


----------



## tomb

Quote:


  Originally Posted by *vixr* /img/forum/go_quote.gif 
_So, if I understand, I would choose exact matches for 2N5087 say at 440... then choose all the 2N5088s at say 450, if I could get that close? I think I could have gotten a lot closer than those 520s. Since that number came up the most, I figured that was about "normal" for those... also, is there a certain number that is better than another? l found enough of each at a given value that could have been used too. I saw a lot of the 87s at 380... and a lot of the 88s at 400. would those have been a better choice?_

 

I'll relate my own experience and reading, but keep in mind I'm no expert. You might refer to Steinchen's revMH dB website. Not only does he describe some important points, but he has some good links that take this into great detail.

 However, to answer your question: from what I've read, the higher the numbers, the better, but matching is more important. First preference is to get all the 5088's matched to an HFE within about 5 and then the same for the 5087's. Sort of as you say, you'll find enough different at that rate to maybe fill 6-10 little cups, but only two or three of those cups will have a bunch in them. Despite which cup has the most, it's probably better to find a 5088 cup that's closet to a 5087 cup - as long as there are enough at those values to build your project, along with a few spares.

 I have built several MH dB's where the 5088's were matched pretty well and so were the 5087's, but not matched so well with each other. It still didn't turn out too bad, but some of them are not as close as I would've liked between the two bias points in the same channel.

 One thing I've started doing is once you've narrowed it down to one group of 5087's and one group of 5088's, check them all again. I've rejected several that didn't measure anywhere close to what they did the first time. The time you have the transistor in the meter's HFE socket has something to do with this. The slight heat buildup will change the reading, but not enough to explain some big differences I've seen. Anyway, the second go-through on my latest MAX gave me DB's that vary no more than about 2mV, which is pretty good when that's at 110mV. So, I think measuring your final groups a second time is a good idea.


----------



## vixr

Tom,
 I think most all of what you say about anything is a good idea... thank you for explaining that and for the tips on the other places to get more info...


----------



## joneeboi

What does one do if Steinchen's website for the revMH's dDBs is down? Are there other websites one can consult?


----------



## tomb

Quote:


  Originally Posted by *joneeboi* /img/forum/go_quote.gif 
_What does one do if Steinchen's website for the revMH's dDBs is down? Are there other websites one can consult?_

 

In a couple of years of looking, I have not had an occasion when Steinchen's site was down. Granted, that doesn't mean it won't happen tomorrow, but the same could be said for almost anyone's site.

 The first place you should look is the Millett MAX website (in the signature below). There's a small discussion about matching transistors in the Construction section. It's really not that big of a deal. Vixr was just asking some very detailed questions. The coupling capacitors on the MAX's output pretty much negate any offset issues between the transistors in the DB's. 

 There are a few people who've just put them together without any matching, I think. Where it comes into play is if you are on the ragged edge of bias, and you don't want one half of one channel to be way off. Even then, pick the high one and bias by that one - then you're assured you don't have a thermal runaway.


----------



## joneeboi

Yeah, I already checked the Max website, but I wanted to learn more about it via the main resource website. I couldn't access it for some reason, and I still can't (linked from the MAX website). But since it's not that big a deal, I won't stress too much about it. Thanks again, Tom.


----------



## tomb

Quote:


  Originally Posted by *joneeboi* /img/forum/go_quote.gif 
_Yeah, I already checked the Max website, but I wanted to learn more about it via the main resource website. I couldn't access it for some reason, and I still can't (linked from the MAX website). But since it's not that big a deal, I won't stress too much about it. Thanks again, Tom._

 

The links work for me, and no one else has reported trouble. The "DIYForums.org" link below the logo in the MAX menu takes you to the same opening page for DIYForums.org that's always been there. You have the option to select from the Forums, the The revMH Millett Hybrid Headphone Amplifier, and the MAX.


----------



## vixr

all the links on every page are active for me...clicked them all.


----------



## joneeboi

I cannot access http://www.diamondstar.de/dDB_overview.html. No one has the same problem?


----------



## tomb

No. I clicked directly on the link in your post and went right to it.


----------



## bperboy

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_No. I clicked directly on the link in your post and went right to it._

 

Also clicked directly on your link and it worked quickly.


----------



## vixr

I had some NOS 12FM6s in my MAX, tube bias @13.5vDC, DB @110mV and it didnt sound good thru my HD-555s. The tubes/caps probably aren't burned in enough to make a factual statement, but the midrange was just thick and muddy. I dropped in 12AE6As at the same bias settings (had to re adjust obviously) and what a difference! the midrange is super clean... If not too clean maybe...almost sterile... IMHO the 12AE6As are the only tube to run in the MAX... on the other hand my HD-600s sounded beautiful with the 12FM6 tubes... my 555s dont have a lot of hours on them either, so maybe its just a combination of things about those phones/tubes/caps/settings... I also re cabled the 555s with Cardas golden reference cable and the nice Cardas 1/4 gold connector about 3 days ago... that mod seemed to improve the bass a little with those phones. I burned the 12AE6As in with a Millett hybrid for months and months @ 12vDC, will it hurt to run them at the higher setting now?


----------



## n_maher

Quote:


  Originally Posted by *vixr* /img/forum/go_quote.gif 
_I had some NOS 12FM6s in my MAX, tube bias @13.5vDC, DB @110mV and it didnt sound good thru my HD-555s._

 

I've never really cared for the FM6. Did you have a pair of FK6's to try out in the MAX, that's been my preferred tube in every Millett I've listened to. I just got 6 more in the other day to keep around as backups. 
	

	
	
		
		

		
			





 And no, it won't hurt to run the tubes at a higher bias. I've run mine as high as 17V as they do sound a bit different at different voltages and I kinda like running them that hot. It will shorten their life span somewhat but at $2 a tube I'm not all that worried.


----------



## vixr

Quote:


  Originally Posted by *n_maher* /img/forum/go_quote.gif 
_I've never really cared for the FM6. Did you have a pair of FK6's to try out in the MAX, that's been my preferred tube in every Millett I've listened to._

 

Yes, I have some FKs to try (Tung-Sol) that I think were produced at the same time...all the painted numbers match exactly, they were out of the same sleeve, and actually had the same faded pattern on the tube boxes... has anyone come up with a good way to clean off the oxidation on these old tube pins? I tried contact cleaner on a Qtip without much improvement... it seems like cycling them in and out of the socket a few times works pretty good. I keep expecting to break a pin someday...


----------



## tomb

On the other hand, I have some FM6's (GE's, of course) in my 2nd proto MAX right now and they sound great - lots of detail and good bass punch. This is all personal preference, but I generally prefer the 12AE6's. I agree that the FK6's generally average more detail, but they also seem to lack some bass punch. They may even have trouble punching through with enough gain for a pair of Senn's.

 Unless, of course, you crank up the voltage like Nate.
	

	
	
		
		

		
			





 I think the FM's got a bad knock from some Millett builders, but they don't seem to be as prevalent, IMHO - so maybe not enough experience has been had with them. Some used to knock the 12AE6's, too.


----------



## n_maher

Quote:


  Originally Posted by *vixr* /img/forum/go_quote.gif 
_has anyone come up with a good way to clean off the oxidation on these old tube pins?_

 

I'd try some high grit sand paper (maybe 400 or so) or steel wool.


----------



## ericj

try deoxit.


----------



## tomb

Colin has been bugging me for awhile to post dimensions and other associated info on the casework for the MAX. I was somewhat reluctant because drawing these up properly encompassed a lot of work. 
	

	
	
		
		

		
		
	


	




 Hopefully, they will be a great help. I am still working on a step-by-step, photo-documented case build-up and will post that shortly. 

 For now, the "Drawings & Templates" page is complete, and has been added to an expanded "Construction" menu selection on the MAX website:

http://www.diyforums.org/MAX


----------



## Jrossel

I have been going over the BOM while ordering parts and found a part that may be incorrect. The CR2 in the power supply section under the digikey list: BC2054-ND comes up as a 0.1 uF not a 1 uF cap.

 I also wonder if substituting 1 uF AVX box caps (478-3367-ND) would be OK for this CR2 part?

 Also can anyone point out where they source the 7 pin tube sockets with holes?

 Thanks for your help.

 JR


----------



## Ferrari

Quote:


  Originally Posted by *Jrossel* /img/forum/go_quote.gif 
_I have been going over the BOM while ordering parts and found a part that may be incorrect. The CR2 in the power supply section under the digikey list: BC2054-ND comes up as a 0.1 uF not a 1 uF cap.

 I also wonder if substituting 1 uF AVX box caps (478-3367-ND) would be OK for this CR2 part?

 Also can anyone point out where they source the 7 pin tube sockets with holes?

 Thanks for your help.

 JR_

 

Jeff, The CR2 serves as bypass capacitor for the electrolytics capacitors CR1x. In this position, any small box caps between 0.1 uF and 1 uF (MKT, MKC, MKP) will work fine here as long as it fits.

 Regarding the 7 pin tube sockets... since tube sockets with hole in the middle are hard to find, most people buy the regular types without hole in the middle and they drill the metal part in the middle out to create a hole for the LED.


----------



## tomb

Ferrari is correct.

 You can find details about different tube sockets and how to drill out the center pin on the MAX website.

 I'll check the parts in the PS, but there is a quasi-inconsistency in Tangent's parts list with the TREAD vs. the STEPS, and it is explained with the range Ferrari gives in his post. The TREAD uses a 1uF, 63V film cap, whereas the STEPS uses a 0.1uF film cap. That said, my intent was to use a 1uF cap from both Mouser and DigiKey. However, a cap in the same series from DigiKey in the 1uF size is almost $1.50, which is way too expensive for this position. So, let me check on it and I'll come up with something appropriate and correct the BOM.

 IMHO, I would order Pana FM caps and the inexpensive Murata trimmers from DigiKey. Everything else should be ordered from Mouser. In fact, you can only get the WIMA signal film caps and the Neutrik PCB phone jack from Mouser. That's obviously a personal preference, though - both are excellent vendors.


----------



## Bigguy

Are there any mini 3.5 headphone jacks that will fit the MAX board or do I have to use an 1/4 to mini adapter?


----------



## soloz2

Quote:


  Originally Posted by *Bigguy* /img/forum/go_quote.gif 
_Are there any mini 3.5 headphone jacks that will fit the MAX board or do I have to use an 1/4 to mini adapter?_

 

you can use whatever jacks you want if you're willing to use some wire


----------



## tomb

The production board has a terminal block position next to the PCB phone jack, which makes other jack connections simple. Of course, soloz2 is correct - you can solder as many jacks in parallel to the PCB jack connections as you can fit.


----------



## kvant

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_For now, the "Drawings & Templates" page is complete, and has been added to an expanded "Construction" menu selection on the MAX website:

http://www.diyforums.org/MAX_

 

That is a hell of a site Tom!

 Browsing it I noticed the recommendation for a huge value of cathode bypass C2 and a statement that 220uF is not sufficient. That sounds a bit strange, since quite a few amps were built within this spec without major complaints. I myself have two revMHs, one with 220uF bypasses and one without C2 altogether. I can't hear any apparent differences between these two. It even does not seem that the gain of the amp without C2 is any lower, which it should according to the common knowledge. (Colin also complained that leaving C2 empty didn't lower the gain, didn't he?)

 Anyway, I decided to have some fun with SPICE and tried to see what simulations have to say on the topic of cathode bypasses. I have found a model for 12FM6. I don't know how good it is, but it doesn't seem to give complete nonsenses. I have ran two simulations, one with 1N5291 as a plate load and one with 20k resistor in the same position. Both these provide cathode current 0.56mA with 12V cathode bias. The simulated circuit contains only tube, C2, R2, R5 and D2. AC signal goes to the tube grid, output is read directly from cathode (see also attached SPICE input file).

 The results (pictures) indicate that C2 has virtually no effect when plate is loaded with constant current diode as there is only negligible difference in gain for bypassed and non-bypassed cathode resitor in this case. This seems to be in line with other arguments. Loading plate with a resistor is another story, however.

 BTW, the case of a plate load with ideal constant current source shows absolutely no low-frequency roll-off irregardless of the the value of C2.

 I find these graphs interesting, but there is no warranty on the quality of used models. Moreover, I have no real education in circuits and their simulations.


----------



## tomb

kvant,

 Your interest is appreciated. However, I think this is a perfect case of being unable to properly define the problem. With every simulation, you have to make some assumptions to define the simulation - or the simulation programmer has made those assumptions for you. This has been discussed ad nausea, _but there are obviously other factors in play_. For example, Runeight (Alex Cavalli) is a pre-eminent and experienced tube amp designer and he recommends the large cap on the cathode bypass in the SOHA (1000uF). When asked about it, he couldn't directly relate it to theory, either - only that the bigger cap was warranted to ensure the best bass response.

 We are 4 out of 4 in votes from MAX builders who each confirm that the larger cap _significantly_ affects the bass response. That number includes me, Colin, NeilR, and bperboy. (You can actually count 5 out of 5 with my two proto's.)

 I strongly suggest that you do not deviate from this recommendation: the MAX CA2 cap should be a 1000uF electrolytic cap.


----------



## tomb

Quote:


  Originally Posted by *Jrossel* /img/forum/go_quote.gif 
_I have been going over the BOM while ordering parts and found a part that may be incorrect. The CR2 in the power supply section under the digikey list: BC2054-ND comes up as a 0.1 uF not a 1 uF cap.

 I also wonder if substituting 1 uF AVX box caps (478-3367-ND) would be OK for this CR2 part?

 Also can anyone point out where they source the 7 pin tube sockets with holes?

 Thanks for your help.

 JR_

 

Jeff,

 The AVX box cap is a great choice. I have altered the BOM accordingly.


----------



## kvant

Well, my problem is that I sort of need to understand things. Otherwise, DIY is only half the fun. Would you have any idea why there were no problems with smaller C2 in the original MH (also designed by an experienced tube designer 
	

	
	
		
		

		
		
	


	




)?


----------



## tomb

Quote:


  Originally Posted by *kvant* /img/forum/go_quote.gif 
_Well, my problem is that I sort of need to understand things. Otherwise, DIY is only half the fun. Would you have any idea why there were no problems with smaller C2 in the original MH (also designed by an experienced tube designer 
	

	
	
		
		

		
			





)?_

 

Well, my first response is that after 4 revMH Milletts with DB's, the MAX has better bass with those caps, period. So does every one of the SOHA's I built. So, the assumption that the original Millett had sufficient bass is not correct.

 We would probably have to scope the design and try various and sundry parts to find out our incorrect assumptions with the theory. There's a lot more different about the MAX vs. the original Millett than that cap. To paraphrase Alex Cavalli, "1000uF electrolytics are cheap and prevalent enough. Why not just use it and be confident that you're getting all the bass you can?"

 It wouldn't be the first time that the model theory didn't agree with the real world example. You're certainly welcome to try to find out why.

 Meanwhile, CA2 should be a 1000uF electrolytic cap.


----------



## Jrossel

Quote:


  Originally Posted by *vixr* /img/forum/go_quote.gif 
_wow... I ordered all my electrolytic caps from handmade to save on some shipping and I got the muse 1000uF@50v KZ for CR1A,B,C and D...they are 1 5/8 inches tall! 1/8th taller than the big heatsink! looks kinda cool though...its got a Mayan pyramid look to it now...tomb you got PM_

 

Hi Vixr

 I am planning on using those Muse UKZ 1000 uF in my kit for the Max, as panasonic FM are currently out of stock at Digikey. I have piles of them, and they are tall to say the least. Let me know how they worked for you.

 JR


----------



## tomb

Quote:


  Originally Posted by *Jrossel* /img/forum/go_quote.gif 
_Hi Vixr

 I am planning on using those Muse UKZ 1000 uF in my kit for the Max, as panasonic FM are currently out of stock at Digikey. I have piles of them, and they are tall to say the least. Let me know how they worked for you.

 JR_

 

Hi, Jeff -
 Just a note for clarification, but there are essentially two primary casing plans that Colin envisioned for the MAX and the Hammond 1455T1601 enclosure:

 1. mount board in 3rd slot from the bottom, 1" heat sinks all around. This allows for 1" high caps as well (actually 32mm may just fit). This is the traditional method for casing a Millett, and it puts the headphone jack and the RK27 volume knob closest to the horizontal centerline of the case.

 2. mount board in bottom slot, 1-1/2" heat sinks all around. This was anticipated for the MOSFET version, but must be used for taller caps. The volume knob and headphone jack will both be below the centerline of the case.

 There are 1" tall Nichicon UPW's in the 1000uF, 50V rating at Mouser. Those are functionally equivalent to the Panasonic FM's. Also, the Panasonic FC's are also a good choice at DigiKey, and there is a 1" tall offering in that rating for those as well.

 P.S. Note that Vixr was actually milling his top plate to let those tall caps stick out. Not many builders are going to have the skills to do that - I know I don't!


----------



## dsavitsk

Quote:


  Originally Posted by *kvant* /img/forum/go_quote.gif 
_Well, my problem is that I sort of need to understand things. Otherwise, DIY is only half the fun. Would you have any idea why there were no problems with smaller C2 in the original MH (also designed by an experienced tube designer 
	

	
	
		
		

		
		
	


	




)?_

 

The explanation of how you pick this cap (in my post you linked to) is in Morgan Jones' Valve Amplifiers, 3rd Ed. on page 78. I'll stay out of the argument regarding what people think they heard other than to say that that cap is directly in the signal path, and if it were my amp I'd do everything I could to avoid its use, perhaps via some sort of fixed battery bias ...


----------



## NeilR

Quote:


  Originally Posted by *kvant* /img/forum/go_quote.gif 
_Well, my problem is that I sort of need to understand things. Otherwise, DIY is only half the fun. Would you have any idea why there were no problems with smaller C2 in the original MH (also designed by an experienced tube designer 
	

	
	
		
		

		
		
	


	




)?_

 

By my way of thinking, half the fun of DIY is learning and understanding the hard theory behind behind the ciurcuits I build; the other half is tinkering with the Voodoo, like caps. It's Voodoo because we don't listen to sine waves, we listen to pulses with transients. Some people think they hear differences from different types of wire (I don't myself). Try running that through a Spice model. Same with pots (continuously variable vs stepped) and resistors (carbon vs film). 

 My own suggestion is that if this issue interests you, order two sets of parts- the standard 200uF and a 1000uF, try both and come to your own conclusions. If you can figure out how to socket the parts, at least temporarily, all the better. If you do that, try to order from the same cap line to minimize other possible variables. And try not to let anything you read here or anywhere else influence what you think you hear.

 Regards,
 Neil


----------



## tomb

Quote:


  Originally Posted by *NeilR* /img/forum/go_quote.gif 
_By my way of thinking, half the fun of DIY is learning and understanding the hard theory behind behind the ciurcuits I build; the other half is tinkering with the Voodoo, like caps. It's Voodoo because *we don't listen to sine waves, we listen to pulses with transients*. Some people think they hear differences from different types of wire (I don't myself). Try running that through a Spice model. Same with pots (continuously variable vs stepped) and resistors (carbon vs film). 

 My own suggestion is that if this issue interests you, order two sets of parts- the standard 200uF and a 1000uF, try both and come to your own conclusions. If you can figure out how to socket the parts, at least temporarily, all the better. If you do that, try to order from the same cap line to minimize other possible variables. And try not to let anything you read here or anywhere else influence what you think you hear.

 Regards,
 Neil_

 

That sentence says a mouthful, and may be one of the reasons why a simulation that appears to only model the same corner frequency equation we're all bouncing around may fall short.

 Very good synopsis and suggestions, Neil.

  Quote:


  Originally Posted by *dsavitsk* 
_The explanation of how you pick this cap (in my post you linked to) is in Morgan Jones' Valve Amplifiers, 3rd Ed. on page 78. I'll stay out of the argument regarding what people think they heard other than to say that that cap is directly in the signal path, and if it were my amp I'd do everything I could to avoid its use, perhaps via some sort of fixed battery bias ..._

 

Dsavitsk, we agree on many things - most of all your own web page reviews of what you think you hear on different capacitors. 
	

	
	
		
		

		
		
	


	










 Notably, I believe Colin's MAX started out without any cathode bypass caps - just as you suggest. I haven't talked to Colin in awhile with the Group Buy in the invoicing phase, but I'm pretty sure he installed a couple of 1000uF Muse ES's and reported better bass than without any caps.


----------



## vixr

I used those huge Muse caps and the Max has the best bass of any amp I've built...


----------



## dsavitsk

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Dsavitsk, we agree on many things - most of all your own web page reviews of what you think you hear on different capacitors. 
	

	
	
		
		

		
		
	


	










 Notably, I believe Colin's MAX started out without any cathode bypass caps - just as you suggest. I haven't talked to Colin in awhile with the Group Buy in the invoicing phase, but I'm pretty sure he installed a couple of 1000uF Muse ES's and reported better bass than without any caps._

 

I'll agree it is a bit of a mystery, and I don't doubt what you heard. But, on the other hand, this particular phenomena is a pretty well understood one. In guitar amp design, these caps are adjusted to alter frequency response, and there are often switches to add/remove them to the circuit for tonal changes.

  Quote:


  Originally Posted by *vixr* /img/forum/go_quote.gif 
_I used those huge Muse caps and the Max has the best bass of any amp I've built..._

 

Perhaps these caps are not particularly linear? And perhaps the larger ones are frequency dependent? That's just a wild guess. Perhaps someone could do a frequency v. ESR graph of one of them. But as I say, something is going on.

 Anyway, I am serious that someone should try battery bias -- or even a Schottky diode (you'll need to figure out where the grids are biased) as it might be a good thing as removing those caps often is.


----------



## tomb

Good guesses, but it may not be about the ES, because NeilR has reported similar results with some 1000uF Elna RFS's that I sent him. Certainly, based on your capacitor listening tests, the ES probably enhances the bass somewhat, but isn't the whole explanation.


----------



## tomb

Quote:


  Originally Posted by *vixr* /img/forum/go_quote.gif 
_I used those huge Muse caps and the Max has the best bass of any amp I've built..._


----------



## seroxatmad

Hi all

 Just built a Kumisa III and after another project.

 Anyone got an extra PCB they don't want and will sell?

 My MSN is seroxatmad@hotmail.co.uk 

 Thanks

 John


----------



## adfinni

Quote:


  Originally Posted by *seroxatmad* /img/forum/go_quote.gif 
_Hi all

 Just built a Kumisa III and after another project.

 Anyone got an extra PCB they don't want and will sell?

 My MSN is seroxatmad@hotmail.co.uk 

 Thanks

 John_

 

O look your in the UK, and i ordered 2 boards. Could be in luck mate 
	

	
	
		
		

		
		
	


	




 I bought one to build and one spare, so i might be willing to sell you my spare one once mine is built, tested and working.


----------



## vixr

Quote:


  Originally Posted by *Jrossel* /img/forum/go_quote.gif 
_Hi Vixr

 I am planning on using those Muse UKZ 1000 uF in my kit for the Max, as panasonic FM are currently out of stock at Digikey. I have piles of them, and they are tall to say the least. Let me know how they worked for you.

 JR_

 

Jrossel,
 I went with the Muse KZ line... The top plate will have 10 holes for caps, and 4 holes for heatsinks...plus two for tubes. I almost have it done except for the paint mask vinyl graphic for the Max logo between the tubes. I'm gonna reverse mask and glass bead the anodize away and leave a bare aluminum logo... it should be totally sick. As far as the SQ goes, I think the Muse caps sound better than the cerafine caps in my SOHA with a lot more bass than any amp I have. I have been giving the amp as much on time as possible (such a chore) and it does improve with time. The Max keeps getting more detailed and smoother in the midrange every day. You guys are gonna love it.


----------



## adfinni

Quote:


  Originally Posted by *vixr* /img/forum/go_quote.gif 
_Jrossel,
 As far as the SQ goes, I think the Muse caps sound better than the cerafine caps in my SOHA with a lot more bass than any amp I have. I have been giving the amp as much on time as possible (such a chore) and it does improve with time. The Max keeps getting more detailed and smoother in the midrange every day. You guys are gonna love it._

 

Im considering going boutique for the x4 1000uf power supply caps too, but am unsure of the gains to be had. In your soha (which i know nothing about), are you comparing the cerafines to KZ's in the main signal path or PSU section ?


----------



## tomb

We'll have to wait for Vixr to reply to know for sure, but I know _he has 1000uF Muse ES's in the CA2 positions - that is the primary recommendation for good bass._ The CA7 caps have an effect, too - but a good selection there more or less ensures no loss of the signal detail and response produced earlier in the circuit. Here, too, Vixr may have chosen the best combination. According to Dsavitsk's capacitor reviews, the ES has the best bass, but may lack a little high-frequency resolution, while the KZ's have a very good high-end response. So, KZ's in the CA7 position after the DB's may be an optimum placement compared to another ES like my MAX's have.

 This is only my personal opinion - although shared by quite a few - but boutique caps in the PS may be overrated, especially when compared to the Panasonic FM. However, DigiKey is still out-of-stock until mid-July. It is sometimes convenient when purchasing something like the ES at Handmade to go ahead and purchase the rest of the caps from there, too (KZ's, FG's, Elna's, etc.).

 Of course, this gets into the "voodoo" that NeilR refers to - it's not something that can be easily measured or tested with instrumentation. *I'll quit saying this eventually, but the 1000uF value at CA2 is the single biggest thing you can do to ensure great bass.* The rest of the voodoo can be mixed to suit your own tastes after that.

 ***
*VIXR:* Your comments are much appreciated. There is no better testament to the MAX performance than comments from builders such as yourself.
 ***

 P.S. Also, please remember the note I gave to JRossel earlier - some of these caps (_not the Muse ES, thankfully_) are much taller than the preferred 1" heat sinks and 3rd-from-bottom slot in the Hammond 1455T1601.


----------



## vixr

I used the Muse caps because tomb said they were a good choice... I don't know enough about "why"... I will stick my neck out and say that the 12FM6 tubes did not sound as good as the 12AE6As. The settings were the same for both tube types, heater voltage @ 14.5, DB voltage @ 110mV and PS voltage @ 29 VDC. I just ordered a sleeve of FK tubes I will try also when they get here. I have been using my HD-600s for all the tests. tomb is waaay more qualified to comment on this than I... I do know it sounds beautiful... I spent hours matching transistors and resistors and doing my best to take advice from the guys who designed the amp, my amp sounds good because it was conceived by smart guys, you should listen to them.


----------



## babbkutz@comcast

what knob is that on there.......any others you like?


----------



## vixr

The knob on the MAX in the slide show is this one... I bought a really cool one from partspipe on ebay, which is on the MAX now...


----------



## adfinni

Quote:


  Originally Posted by *vixr* /img/forum/go_quote.gif 
_The knob on the MAX in the slide show is this one... I bought a really cool one from partspipe on ebay, which is on the MAX now..._

 

PICS PICS PICS 
	

	
	
		
		

		
			





 Cheers for the cap advice, il keep my money for the BG's in more important positions. Will get my stuff ordered up from mouser in about 2 weeks, so it can ship to the UK ready for the board arrival .....


----------



## tomb

Quote:


  Originally Posted by *vixr* /img/forum/go_quote.gif 
_The knob on the MAX in the slide show is this one... I bought a really cool one from partspipe on ebay, which is on the MAX now..._

 

Yeah, hongkongsuperseller (PartsPipe) has some pretty cool knobs:


----------



## vixr

I went with the 40mm black anodized, with the knurled body...it sure didn't want to go on that pot shaft though...


----------



## bperboy

I use a Kilo knob from mouser that I had from a switchbox that I made awhile ago. The pot shaft is too long, but I really don't have the ability to shorten it nicely.


----------



## vixr

Quote:


  Originally Posted by *bperboy* /img/forum/go_quote.gif 
_I use a Kilo knob from mouser that I had from a switchbox that I made awhile ago. The pot shaft is too long, but I really don't have the ability to shorten it nicely._

 

I bought one of these x-acto saws and it cuts thru the pot shaft very nicely... I've cut almost everything from perfboard to aluminum standoffs with it... very handy. oh, it cuts the SIP strips perfect too.


----------



## colonelkernel8

Quote:


  Originally Posted by *vixr* /img/forum/go_quote.gif 
_I bought one of these x-acto saws and it cuts thru the pot shaft very nicely... I've cut almost everything from perfboard to aluminum standoffs with it... very handy. oh, it cuts the SIP strips perfect too._

 

curious, i'll have to add one to my diy toolkit. thanks!


----------



## Jrossel

With your help, I found two vendors for the 7 pin tube sockets.

 Parts Connexion and Cascadesurplus.com 

 I suggested that they stock the PCB mount type at Cascade due to the number of people that may be looking for the sockets.

 JR


----------



## mb3k

Is anyone else building it with a toroid?
 The Amveco [size=x-small][size=x-small]62062 looks like a good candidate:
 2x12V, 1041mA (58mm diameter, 34.5mm height)
[/size][/size]


----------



## tomb

Quote:


  Originally Posted by *mb3k* /img/forum/go_quote.gif 
_Is anyone else building it with a toroid?
 The Amveco [size=x-small][size=x-small]62062 looks like a good candidate:
 2x12V, 1041mA (58mm diameter, 34.5mm height)
[/size][/size]_

 

Nah - no transformer required - especially a toroid. The MAX has its own onboard STEPS-like power supply (minus the xfmr), for the best in AC filtering and DC regulation. All that's needed is a 24VAC walwart - although a fairly juicy one - 750ma minimum. 1A is better and the MOSFET option will probably like more.

 Mine is fed from a 24VAC, 35VA(!) HVAC surplus controls walwart that I got for $6. It seems to like it.
	

	
	
		
		

		
		
	


	




 I've also fed it with a 24VAC, 1000ma walwart and it does fine, but that walwart was retail at $12, I think.


----------



## mb3k

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Nah - no transformer required - especially a toroid. The MAX has its own onboard STEPS-like power supply (minus the xfmr), for the best in AC filtering and DC regulation. All that's needed is a 24VAC walwart - although a fairly juicy one - 750ma minimum. 1A is better and the MOSFET option will probably like more.

 Mine is fed from a 24VAC, 35VA(!) HVAC surplus controls walwart that I got for $6. It seems to like it.
	

	
	
		
		

		
		
	


	




 I've also fed it with a 24VAC, 1000ma walwart and it does fine, but that walwart was retail at $12, I think._

 

I'm not too fond of wallwarts (too much bulk at the wall and powerbar), so I think the 24VAC/1041mA trafo would do me well. The only thing I'm wondering about is the fuse rating for the mains line.


----------



## Ferrari

Quote:


  Originally Posted by *mb3k* /img/forum/go_quote.gif 
_I'm not too fond of wallwarts (too much bulk at the wall and powerbar), so I think the 24VAC/1041mA trafo would do me well. The only thing I'm wondering about is the fuse rating for the mains line._

 

For the same reason as yours I'm buiding this amp with a toroid (was also on my old Milett). 24VAC/1041mA should be more than adequate for this build. Mine is an Amplimo 30VAC/1A since I plan to feed the amp with 30VDC.

 The fuse rating for the mains line (primary fuse) as specified by Amplimo is 160mA, I just put 200mA fuse (closest value I have in my parts bin) in there and it's working fine.


----------



## tomb

You guys are definitely extreme!


----------



## Ferrari

I was busy working on my MH Max this weekend. This is what I have so far... roughly how the internal of my amp will look like.
 Arrr...g, I just realize that I mis 1 transistor (MPSA14) for the ε12 muting delay circuit... 
	

	
	
		
		

		
			





 . Hopefully I can go further next weekend!


----------



## vixr

wow! THAT is nice... I'm sooo jealous.


----------



## tomb

I was wrong when I said "extreme", Ferrari. That looks like only four film caps on the output - albeit a bit large - so you've gone conservative on us.


----------



## Ferrari

Yes, only 4 film caps on the output instead of 60 on my previous build. 
	

	
	
		
		

		
		
	


	



 These 4 MKP film caps (2 per channel) will probably be bypassed with small PIO or teflon but that will be decided after extended listening test.


----------



## Listen2this1

Quick question for the smart ones. Is it a problem to mount the volume pot on the bottom side of the board? The case design I am wanting to use this would help alot.


----------



## Ech0

Just an observation on the BOM that tomb put together. Under "power supply" RR1 = 1/4w and RR2 = 1/2w. Following the Mouser link will take you to RR1 = 1/8w and RR2 = 1/4. 

 Had the values been more I wouldn't have thought a thing about it.

 Thanks for all your effort guys. I can't wait to get started.


----------



## tomb

Quote:


  Originally Posted by *Ech0* /img/forum/go_quote.gif 
_Just an observation on the BOM that tomb put together. Under "power supply" RR1 = 1/4w and RR2 = 1/2w. Following the Mouser link will take you to RR1 = 1/8w and RR2 = 1/4. 

 Had the values been more I wouldn't have thought a thing about it.

 Thanks for all your effort guys. I can't wait to get started._

 

Those are V-D resistors and will easily take twice their 1% rating.


----------



## tomb

Quote:


  Originally Posted by *Listen2this1* /img/forum/go_quote.gif 
_Quick question for the smart ones. Is it a problem to mount the volume pot on the bottom side of the board? The case design I am wanting to use this would help alot._

 

It can't be done ... you would have to air-wire it to make it work.


----------



## Ferrari

It's up and running...






 The output MOSFET's are adjusted to 100 mA (~220 mV). The MOSFET's heatsinks are not too hot... I can put my fingers on it for 10 seconds or more, but the 1.5" heatsink in the PSU is burning hot. I'm now a bit further than the pic above, first listening via my AKG K701 is great, really great 
	

	
	
		
		

		
		
	


	




 .


----------



## n_maher

Quote:


  Originally Posted by *Ferrari* /img/forum/go_quote.gif 
_The output MOSFET's are adjusted to 100 mA (~220 mV). The MOSFET's heatsinks are not too hot... I can put my fingers on it for 10 seconds or more, but the 1.5" heatsink in the PSU is burning hot._

 

You should either find a way to accurately measure how hot the PS heatsink is running and compare it to the allowable specs of the LM317 or you should turn down the mosfets a bit. If you heat the reg up too much it'll go into thermal shutdown and stop regulating until it cools off again. Too much of that will likely cook it for good which could have much worse results than suffering sound quality.

 [edit]It's also very important to remember that your sinks are probably going to run a good bit hotter once you put them inside a case without vents (like the stock hammond that is recommended for the MAX).


----------



## Ferrari

Thanks Nate, the burning hot experience is also partly due to the fact that I adjusted the output MOSFET's to 120 mA first then down to 100 mA within an half hour or so. Turn down the MOSFET's to 80 mA (~176 mV) does reduce the temperature of the PSU heatsink. It's still quite warm but touchable.
 I have got a feeling that the 1.5" PSU heatsink is a bit too small when the output MOSFET's are adjusted to 100 mA or higher.
 Probably a 2" (or 2.5") heatsink is more suitable here.

 This amp + output caps will be cased in an ATI-737U enclosure, so vent is not an issue like the recommended stock Hammond.


----------



## n_maher

Quote:


  Originally Posted by *Ferrari* /img/forum/go_quote.gif 
_Thanks Nate, the burning hot experience is also partly due to the fact that I adjusted the output MOSFET's to 120 mA first then down to 100 mA within an half hour or so. Turn down the MOSFET's to 80 mA (~176 mV) does reduce the temperature of the PSU heatsink. It's still quite warm but touchable.
 I have got a feeling that the 1.5" PSU heatsink is a bit too small when the output MOSFET's are adjusted to 100 mA or higher.
 Probably a 2" (or 2.5") heatsink is more suitable here._

 

If you've got room I'd highly recommend upping the size of the heatsink. Even a vented case will still cause temperatures to rise as there's just no real way to keep the ambient air temperature inside the case the same as outside, even with a fan. 

 Also, it would interesting to see if there's any way to measure the idle current draw of the amp. That would allow you to more accurately size the heatsink for the power supply. Even if you can't measure it you might be able to estimate it (someone has probably already done this). I have a habit of overheating things so I tend to be overcautious when it comes to heatsinks.


----------



## tomb

There are a few things going on here that contribute to the heat in Ferrari's PS sink:

 1. The MOSFETs pull more current (this is obvious).

 2. If you select PS caps that are the same height as the PS heat sink, then most of the fins are blanketed. This has not caused a problem with the lower currents run with the BJT's. As for the MOSFETs, I believe both NeilR and Bperboy used Nichicon UPW's at 1000uF, 50V. Those are only 1" high. When used with the recommended 1-1/2" sinks for MOSFETs, that still gave a considerable fin exposure where most needed - at the top.

 Knowing Ferrari's prediliction for "extreme", those look like they might be 4700uF Nichicon FX's. 
	

	
	
		
		

		
		
	


	




 3. In another "extreme" factor, the transformer is rated for 30V under load. Running the MAX-mosfet at 30V is sort of like running a Millett at 24V with a 24VAC walwart-TREAD/STEPS. Meaning, there's too much voltage being burned off at the sink.

 A quick estimate (Tangent's new power estimator might be a good tool to check this) yields (30VAC x 1.4)-1.4 = 40.6VDC! At approx. 600ma, that's over 10 x 0.6 = 6W. Actually, with that kind of capacitance, the voltage that has to be burned off might be even higher.

 So, sort of like Nate said, reduce the xfmr secondary voltage, reduce the caps, or grow the heat sink.


----------



## Ferrari

Agreed, especially your reasoning regarding the use of 30VAC transformer to feed the amp at 30VDC.
 The power dissipation on the PSU heatsink is probably on the high side.
 I have just found a 24V transformer (EI type) in my parts bin, connect this one to my build and adjust the PSU output to ~28VDC. The PSU heatsink is considerably cooler than previous with the 30V toroid... it's even cooler than the the MOSFET's heatsinks. I think that I will go for this 24V transformer and feed the amp with 28VDC.

 And nahh... I'm not that extreme, the electrolytic capacitors in the PSU are only 2200uF 
	

	
	
		
		

		
		
	


	







 , Nichicon Muse FX indeed.


----------



## tomb

BTW Ferrari, your "extreme" practice of pushing the envelope is commendable and I am always envious. All of the joking is meant in the sincerest way as a compliment! You often set the bar in how far one can really go with a build.

 Why not the 4700uF FX's?


----------



## Ferrari

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Why not the 4700uF FX's?
	

	
	
		
		

		
			






_

 

4700uF... that is really extreme 
	

	
	
		
		

		
		
	


	







 .


----------



## bperboy

Okay, for all those that have finished their Max, what cans do you primarily use with it, and how does it sound?

 I use Senn HD580s and it sounds very smooth and detailed. 

 Mostly, I'm interested in the K701 sound and its synergy with the max, but other cans are very welcome as well.


----------



## tomb

Quote:


  Originally Posted by *bperboy* /img/forum/go_quote.gif 
_Okay, for all those that have finished their Max, what cans do you primarily use with it, and how does it sound?

 I use Senn HD580s and it sounds very smooth and detailed. 

 Mostly, I'm interested in the K701 sound and its synergy with the max, but other cans are very welcome as well._

 

Ditto on the 580's - it probably sounds better with those than any of the other cans below. You can't say that about every amp.

 I also find it sounds great with V6's, PortaPro's and of course - KSC75's.

 The one thing I've noticed is that the MAX is so ruthlessly detailed that any source that's not of the best quality will sound like cr*p. I've changed to listening to FLAC files most often (from an M-audio Transit) - when I can get them in the music I like.


----------



## vixr

Quote:


  Originally Posted by *bperboy* /img/forum/go_quote.gif 
_Okay, for all those that have finished their Max, what cans do you primarily use with it, and how does it sound?

 I use Senn HD580s and it sounds very smooth and detailed. 

 Mostly, I'm interested in the K701 sound and its synergy with the max, but other cans are very welcome as well._

 


 HD-600... the sound is warm and clear, super levels of bass. I filter my Max thru my corda cross-1 and it is my favorite amp right now.

  Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Those are only 1" high. When used with the recommended 1-1/2" sinks for MOSFETs, that still gave a considerable fin exposure where most needed - at the top._

 

I'm not running the MOSFETS, but I am running the buffers at 110mA, tubes @ 14.5V and the 1.5" heatsink barely gets warm...


----------



## tomb

Quote:


  Originally Posted by *Vixr* 
_I'm not running the MOSFETS, but I am running the buffers at 110mA_

 

Holy cow, Vixr! Colin had told me that there's no reason the BJT's can't run as high as the MOSFETs - that's cool, er hot!

 I will post those newer thermal pics when I get a chance - I've just been caught up in some other stuff on the casework. Your running settings will add a nice touch with that image!

 How's that machining going with the lid?


----------



## Listen2this1

Well now that I have got every thing to fit, I am ready for the start of my build. I have designed my amp with all of the needed equiptment. Tell me what you think.

 The case is a Ati enclosure http://www.atiresearch-anodized.com/ATI-737U.html

 There will be a source selector from Twisted Pear which in the long short box in the back left. http://www.twistedpearaudio.com/darwin/darwin.aspx

 The other box will be a basic LM317 power supply for the source selector.

 I will eventually have Front Panel Express do the front with all of the details. I will be posting some pics in the next week as things go along.






[/url][/IMG]


----------



## bperboy

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_The one thing I've noticed is that the MAX is so ruthlessly detailed that any source that's not of the best quality will sound like cr*p. I've changed to listening to FLAC files most often (from an M-audio Transit) - when I can get them in the music I like._

 

I've noticed this too. I listened to Lily Allen's CD, Alright, Still, which isn't the best SQ to begin with, but it sounds horrendous through my system. 
	

	
	
		
		

		
		
	


	




 The only place I can stand to listen to it is in my car. 

 So, anyone have any non-Senn fullsize cans to compare yet?


----------



## tomb

Quote:


  Originally Posted by *Listen2this1* /img/forum/go_quote.gif 
_Well now that I have got every thing to fit, I am ready for the start of my build. I have designed my amp with all of the needed equiptment. Tell me what you think.

 The case is a Ati enclosure http://www.atiresearch-anodized.com/ATI-737U.html

 There will be a source selector from Twisted Pear which in the long short box in the back left. http://www.twistedpearaudio.com/darwin/darwin.aspx

 The other box will be a basic LM317 power supply for the source selector.

 I will eventually have Front Panel Express do the front with all of the details. I will be posting some pics in the next week as things go along.
_

 

WOW!


----------



## vixr

Quote:


  Originally Posted by *Listen2this1* /img/forum/go_quote.gif 
_
 The case is a Ati enclosure

 I will eventually have Front Panel Express do the front with all of the details. I will be posting some pics in the next week as things go along._

 

so, would front panel express fab up a new panel from scratch or could you send them the one from the Ati enclosure?


----------



## Listen2this1

So far they only will fab it if I use their program on their site, that is how they come up with their pricing. So I guess when I get the front panel I will duplicate it and add my alterations to have it milled in the same way as the Ati front panel.


----------



## mb3k

There's going to be many nice looking MHM's soon!
 I can't wait to see them all in the picture thread. Tomb (or any other prototypers) have you tested around with the delay circuit by increasing the value of CM3?
 I'll be trying 470uF and 560uF to see how long I can get the delay - I'm usually in no rush.


----------



## n_maher

Quote:


  Originally Posted by *vixr* /img/forum/go_quote.gif 
_so, would front panel express fab up a new panel from scratch or could you send them the one from the Ati enclosure?_

 

There is an option to send in your own material in the FPE software. But listen2this is correct, as far as I know you *have* to use their software to create the design. It's not all that bad, one of my few gripes is the seriously limited choice of fonts.


----------



## tomb

Quote:


  Originally Posted by *mb3k* /img/forum/go_quote.gif 
_There's going to be many nice looking MHM's soon!
 I can't wait to see them all in the picture thread. Tomb (or any other prototypers) have you tested around with the delay circuit by increasing the value of CM3?
 I'll be trying 470uF and 560uF to see how long I can get the delay - I'm usually in no rush._

 

Well, I just timed 20-22 sec with KSC75's and I have a 330uF on mine. I had noted earlier that higher impedance phones took longer, but concluded that's an effect of not being able to drain the caps completely when testing. From a "standing start" it should be the same for all phones.

 It's easy enough to use the bigger values if you want - the only limitation is the board space. These can be very inexpensive caps, too - some run less than $1 for 10.


----------



## mb3k

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Well, I just timed 20-22 sec with KSC75's and I have a 330uF on mine. I had noted earlier that higher impedance phones took longer, but concluded that's an effect of not being able to drain the caps completely when testing. From a "standing start" it should be the same for all phones.

 It's easy enough to use the bigger values if you want - the only limitation is the board space. These can be very inexpensive caps, too - some run less than $1 for 10._

 

20-22sec seems plenty. I'll socket that cap and test out 470u for starters.
 How fast does the relay disengage on power off?


----------



## tomb

Quote:


  Originally Posted by *mb3k* /img/forum/go_quote.gif 
_20-22sec seems plenty. I'll socket that cap and test out 470u for starters.
 How fast does the relay disengage on power off?_

 

~1.5 seconds? It's like a "klunk", but with no hint of a zap. Again, with a very efficient relatively low impedance phone like the KSC75, the klunk is very obvious, but doesn't sound damaging at all. With a pair of Senns, you may not even hear it - you have to turn off all the sound around you and put your hands over the grilles.

 It took me awhile through the two protos, but I now have no hesitation whatsoever about leaving a pair of phones connected - even my best, most expensive ones. The delay works quite well, and seems 100% reliable.


----------



## Ferrari

I have made a small modification on the MOSFETs output buffer of the MH Max and I think it's worth to tell.
 On the N-channel MOSFET (IRFZ24N), I have added a small compensation capacitor of 220pF between the gate and the source of the MOSFET. Without compensation, the unequal gate capacitance between the N-channel (IRFZ24N) and the P-channel (IRF9Z34N) will result in an asymmetrical slew rates of the output signal (positive/negative pulses). This is also described by AMB on the M³ website earlier. The compensation capacitor can be added neatly this way.







 The BJT's on my build are 180 degrees rotated since I use "Europeans parts" (BC550 / BC560). These BJT's have reversed pinout compared to "US parts" (2n5088 / 2n5087). Not cased yet (probably in the weekend) but I love it!


----------



## cetoole

Quote:


  Originally Posted by *Ferrari* /img/forum/go_quote.gif 
_Agreed, especially your reasoning regarding the use of 30VAC transformer to feed the amp at 30VDC.
 The power dissipation on the PSU heatsink is probably on the high side.
 I have just found a 24V transformer (EI type) in my parts bin, connect this one to my build and adjust the PSU output to ~28VDC. The PSU heatsink is considerably cooler than previous with the 30V toroid... it's even cooler than the the MOSFET's heatsinks. I think that I will go for this 24V transformer and feed the amp with 28VDC.

 And nahh... I'm not that extreme, the electrolytic capacitors in the PSU are only 2200uF 
	

	
	
		
		

		
		
	


	







 , Nichicon Muse FX indeed._

 

Ferrari, I would not want to have a transformer that close to the amplifier, especially an EI core. If you are dead set on having an internal transformer, I would stick with a toroid, ideally shielded. You could unwind some turns from the secondary of the toroid you already have, to drop the secondary voltage down to a suitable level. It also looks like there is plenty of room in that case for the use of larger heatsinks, which would probably be a good idea. I dont know to what extent your mains voltage fluctuates, but if it is significant at all, you want to keep enough voltage drop over the regulator so that it will never fall out of regulation. You could also move to using an LDO regulator. I assume the secondary of your 24v EI core transformer measures around 30-31vdc after rectification, so having the output of your LM317 at 28v may not be sufficient to keep it regulating properly. Also, there will be some voltage drop over the RC filter and CCS feeding the anode of the tubes, so you could measure this, and increase the output of the regulator above 30v potentially to decrease dropout. Very extreme build though, and I bet it is going to be awesome once complete. 

 Bperboy, I am using Senn HD580 with my Max. Sounds nice to me.

 Vixr, I love those thermal images. Simply awesome.

 I do hear both turn on and off clicks from the relay, but neither are loud enough to concern me.

 Current estimate on PCBs from Imagineering is July 10. There is going to be a massive stack of boards for you guys to populate.


----------



## Ferrari

cetoole, I am aware of the magnetic field problem, especially the EI core type.
 The implementation is changed a bit: the 30V/1A EI core power transformer, AC line filter and fuse are now located in a separate "wallwart" to minimize magnetic field interference. Also the PSU heatsink is upsized to 2" and is sufficient for use at 30VDC (also due to the unload voltage of this transformer is ~2 Volt lower than the toroid I used before).


----------



## bperboy

Quote:


  Originally Posted by *cetoole* /img/forum/go_quote.gif 
_Bperboy, I am using Senn HD580 with my Max. Sounds nice to me._

 

Jeese, HD580s are just fine cans! I think the majority of completed max builds are paired with them right now.


----------



## TBomb06

Quote:


  Originally Posted by *bperboy* /img/forum/go_quote.gif 
_Jeese, HD580s are just fine cans! I think the majority of completed max builds are paired with them right now._

 

Anyone tried them with some Grado's and want to comment on the sound?


----------



## amphead

Quote:


  Originally Posted by *cetoole* /img/forum/go_quote.gif 
_Current estimate on PCBs from Imagineering is July 10. There is going to be a massive stack of boards for you guys to populate._

 

Thats an amazing turn around considering how many boards were ordered. I am currently building an aluminum chassis from scratch based on Tom's post for dimensions.
 Thanks for the update Colin!


----------



## adfinni

Quote:


  Originally Posted by *cetoole* /img/forum/go_quote.gif 
_Current estimate on PCBs from Imagineering is July 10. There is going to be a massive stack of boards for you guys to populate._

 

[size=small]WOOOT my birthday[/size]

 Won't be building mine until august because of shipping times for all the boards and me having to get everything from mouser and other US stores, but nevertheless it is going to be my first and a most memorable project


----------



## babbkutz@comcast

pics of the connections.......esp mounted through panel with details Thanks!


----------



## odoe

man
 you guys bought all the 1/4" jacks for the board
 now i have to wire mine up
 damn you head-fi!!

 also, i am working on a case idea, but not sure if it will work how i want. if it does, it should be pretty cool...i hope


----------



## soloz2

I went to radio daze yesterday and bought a pair of GE 12FM6's and a set of GE 6CG7's.

 I was hoping to find some rarer 6CG7's but they only had GE or Sylvania, and didn't see any cleartops 
	

	
	
		
		

		
		
	


	




 oh well.

 The NOS 12FM6's were only $2ea so very reasonably priced.


----------



## mb3k

I was going to buy from RadioDaze but they don't keep records of the tubes.
 What other brands did you see there for the Millett tubes?


----------



## soloz2

Quote:


  Originally Posted by *mb3k* /img/forum/go_quote.gif 
_I was going to buy from RadioDaze but they don't keep records of the tubes.
 What other brands did you see there for the Millett tubes?_

 

I had to wait in the office while someone went back to the wherehouse, but I believe they have lots of GE or Sylvania. I was hoping for RCA, but honestly was more interested in the PPX3 tubes


----------



## tomb

Quote:


  Originally Posted by *mb3k* /img/forum/go_quote.gif 
_I was going to buy from RadioDaze but they don't keep records of the tubes.
 What other brands did you see there for the Millett tubes?_

 

I've received GE, RCA, Sylvania, DuMont, and TungSol - Raytheon, too, I think - all from Radio Daze.

 They're going to raise their price soon like everyone else if we keep ordering from them.


----------



## FallenAngel

Hey guys, lots of great looking builds, and Ferrari, you're crazy man, that looks incredible.

 I'm just building up a BOM for this and was having a little trouble with capacitor choices.

 C2 - Cathode Bypass Electrolytic - 1000uF/16V BlackGate NX (Or perhaps FK - anybody care to comment please). Also considering Elna RFS (read as buying them and decide later).

 C4 / C5 - PSU Caps - 470uF/35V Panasonic FM (Can't get Elna RFS and BlackGate STD in 470uF/50V at $7.75 each maybe not worth it for PSU).

 C3 / C6 - PSU Bypass - 0.22uF Panasonic ECQ-P (Original BOM, again, not sure how important a high quality film cap would be in this position)

 C7 - Output Cap - 680uF/50V BlackGate NX (alternative is 470uF/16V and I'm not sure the voltage requirements are met)

 C8 - Output Bypass - Is this really a good idea with a BlackGate NX or should it be skipped? If it is still a good idea to keep, I'll throw in an AuriCap 0.22uF or Mundorf MCap ZN.

 C9 - Cathode Bypass - Again, same question regarding bypassing an Elna RFS or BackGate NX. If it is still recommended, Mundorf MCap ZN for RFS or AuriCap for BlackGate.


 That just about concludes the main caps in the amp. Pure PSU caps (C1) will be 1000uF/50V Panasonic FM when it comes back in stock on July 17th.

 Also I have a quick (and probably silly) questions about the MOSFET output stage. Is the 2.2 Ohm resistor enough or might it become unstable like the DB? I've had great luck with the PPAv2 and now will be upping the resistor in the amp since it's not perfectly stable with Grado headphones yet.

 Any comments or recommendations on parts choice is greatly appreciated.

 Thanks in advance.


----------



## tomb

Quote:


  Originally Posted by *FallenAngel* /img/forum/go_quote.gif 
_Hey guys, lots of great looking builds, and Ferrari, you're crazy man, that looks incredible.

 I'm just building up a BOM for this and was having a little trouble with capacitor choices.

 C2 - Cathode Bypass Electrolytic - 1000uF/16V BlackGate NX (Or perhaps FK - anybody care to comment please). Also considering Elna RFS (read as buying them and decide later)._

 

 I've been hearing bad things about Elna's lately - like rolled off highs, etc, but I sent a pair to NeilR and he says they helped the bass (he had 220uF's first, like many of us). I just purchased a pair of the 1000uF/25V NX's, but haven't tried them yet. Cetoole seems to think the other series BG's are nothing special at all. Of course, my favorite so far is the Nichicon Muse ES.

  Quote:


 C4 / C5 - PSU Caps - 470uF/35V Panasonic FM (Can't get Elna RFS and BlackGate STD in 470uF/50V at $7.75 each maybe not worth it for PSU). 
 

I haven't mentioned this much, but with the MAX I'm sort of in the Ferrari camp - well, not that far, really: the 470uF's look awfully small. A 1000-1200 at 35V costs hardly anything compared to a boutique. I've used both 1200uF and 1800uF Pana FM's with good results. Whether they make any difference from 470uF's, I don't know - but the price difference is small enough that the investment is worth it just to make the board look symmetrical. 
	

	
	
		
		

		
		
	


	




  Quote:


 C3 / C6 - PSU Bypass - 0.22uF Panasonic ECQ-P (Original BOM, again, not sure how important a high quality film cap would be in this position) 
 

As you suspect, I don't think these have much effect on sound. However, it should be noted that dsavitsk says the Pana ECW's are a little on the harsh and hard side. Whether that translates to the ECQ's, I don't know. I have always stuck with the WIMA's and they've worked very well.

  Quote:


 C7 - Output Cap - 680uF/50V BlackGate NX (alternative is 470uF/16V and I'm not sure the voltage requirements are met) 
 

There's actually a 680uF/35V in the NX series which will help on the height issue. The combo of this one with the 1000uF/16V NX will keep everything below 1" height if you're shooting for that goal (also the Muse ES's will do that). This allows you to put the board at the 3rd slot from the bottom of the case, and has the volume knob and jack just slightly above and below the frontplate centerline, respectively.

  Quote:


 C8 - Output Bypass - Is this really a good idea with a BlackGate NX or should it be skipped? If it is still a good idea to keep, I'll throw in an AuriCap 0.22uF or Mundorf MCap ZN. 
 

Again, this is just from what I've read and from different people who've told me - but no film bypasses with the BG's. The others are a "try and see." The bypasses are better than not with the Muse ES's.

  Quote:


 C9 - Cathode Bypass - Again, same question regarding bypassing an Elna RFS or BackGate NX. If it is still recommended, Mundorf MCap ZN for RFS or AuriCap for BlackGate. 
 

 Ditto the above


  Quote:


 That just about concludes the main caps in the amp. Pure PSU caps (C1) will be 1000uF/50V Panasonic FM when it comes back in stock on July 17th. 
 

Excellent choice.

  Quote:


 Also I have a quick (and probably silly) questions about the MOSFET output stage. Is the 2.2 Ohm resistor enough or might it become unstable like the DB? I've had great luck with the PPAv2 and now will be upping the resistor in the amp since it's not perfectly stable with Grado headphones yet. 
 

We haven't had any stability problems yet. Someone correct me if I'm wrong - but I believe that had more to do with the revMH DB's and the perhaps the PPAV2 because of no heat sinks and lower currents. The instability manifests itself in thermal runaway, which the heat sinks temper.

  Quote:


 Any comments or recommendations on parts choice is greatly appreciated.

 Thanks in advance. 
 

Just MHO on these - others may disagree.


 EDIT: Also - please note Ferrari's photo and note for the bypass cap on the MOSFET legs. That seems very important and I will probably add that to the documentation and BOM for the MOSFET version. It's probably ridiculously cheap and couldn't hurt in any event.


----------



## Ferrari

The compensation capacitor of 220pF on the N-channel MOSFET (IRFZ24N) is a multilayer ceramic type (part number: 80-C315C221J1G) I found in my parts bin. It's also available at Mouser for $28 cent.


----------



## axiom

Would there be any benifit to biasing the DB or MOSFET even higher? (of course requiring more heatsinking/PS ability)

 Where did you find 1000uF/16V BG NX, all I can find is 25V?


----------



## tomb

Doh! You are correct - they are 1000uF/25V BG NX's (16x24mm) ... and there I was correcting FallenAngel for typing the 680uF NX's at 50V! Sorry about that.

 As for the biasing, cetoole says there's no reason the DB's can't be biased at 100ma (220mV). (Actually, I keep mixing up terms - they're both DB's, just one is with BJT "normal" transistors and the other is with MOSFETs.)

 However, there's a limit based on the case and heat sinks. 1-1/2" is probably needed for the MOSFETs at 100ma in a closed case. The negative temperature coefficient means the amperage goes down to 80-90ma when the case is closed - with no vents, I believe (on NeilR's).

 The BJT version is at its limit, I think with 50ma (110mV) and 1" high sinks. They run pretty cool on the board, but heat up pretty quickly when cased. Vent holes are probably a minimum requirement at 50ma and 1" heat sinks.

 There is no limitation on the PS (within reason) - just the walwart. There are several places - All Electronics, MPJA, etc. that sell 35-40VA 24VAC walwarts. These are typically controls transformers used in HVAC or security systems, and most of the time have screw terminals with a mounting screw on top intended to screw into the center hole on an outlet. $6-$7 at most of these places (surplus stores, too) and enough juice to never run out when biasing - 1500-1600ma.


----------



## axiom

So the MOSFETs run cooler at a given bias than the DBs? Perhaps someone could point out (or provide a link to) the differences. I guess MOSFETs handle more current and handle it better (less heat, etc) than the BJTs?

 The reason I'm asking is that I'm thinking of replacing the top of the case with some bent mesh (to allow for larger heat sinks) or getting a taller case and just using a flat piece of mesh (although this seems a waste of money/space...). I would go topless, but I want to avoid pens and other not too heavy objects messing anything up (I don't plan on throwing around any 5 lb weights in the house 
	

	
	
		
		

		
			





 ).

 Is there some kind of bias upper limit that I should be aware of (barring insanity 
	

	
	
		
		

		
		
	


	




 )? Dangers like burning down the house?
	

	
	
		
		

		
		
	


	




 Also is it generally true that the higher the bias the better the sound (I guess this would be giving diminishing returns like stacking buffers?)

 Sorry for all the ?s...


----------



## tomb

Quote:


  Originally Posted by *axiom* /img/forum/go_quote.gif 
_So the MOSFETs run cooler at a given bias than the DBs? Perhaps someone could point out (or provide a link to) the differences. I guess MOSFETs handle more current and handle it better (less heat, etc) than the BJTs?_

 

Whew - Amb is the pre-eminent expert around here on MOSFETs, but I'll try to explain from what I know.

 There is no "one handles heat better than the other" per se, both are limited by how much heat the plastic and the internal junctions can take. That's pretty much constant, regardless of the device, and Watts + heat sinks are the deciding factors. The difference with MOSFETs are two-fold: 1) they have a negative temperature coefficient and 2) they have to run much higher currents to respond to typical audio frequencies without distortion.

 So, while MOSFETs will run decreased current at higher temperatures, a higher current (relative to BJT's) must be maintained to _sound as good._ A typical starting point for the MOSFETs might be 80ma, whereas good response and dynamics can be obtained from the BJT's at only 30ma. So, strictly speaking, a completely successful BJT MAX may be built that runs at much lower temperatures and with smaller heat sinks. This is because milliamp per milliamp and per inch of heat sink - the temperature is the same, within reason - but the BJT's need less to sound good.

  Quote:


 The reason I'm asking is that I'm thinking of replacing the top of the case with some bent mesh (to allow for larger heat sinks) or getting a taller case and just using a flat piece of mesh (although this seems a waste of money/space...). I would go topless, but I want to avoid pens and other not too heavy objects messing anything up (I don't plan on throwing around any 5 lb weights in the house 
	

	
	
		
		

		
		
	


	




 ). 
 

This is reasonable plan either way, it just depends on what you're looking for and what you're using.

  Quote:


 Is there some kind of bias upper limit that I should be aware of (barring insanity 
	

	
	
		
		

		
		
	


	




 )? Dangers like burning down the house?
	

	
	
		
		

		
		
	


	




 Also is it generally true that the higher the bias the better the sound (I guess this would be giving diminishing returns like stacking buffers?) 
 

Yes, there are limits - those are governed by the number of watts burned by the BJT's or MOSFETs: V x A = Watts. Then depending on the heat sink size, this will determine how much current you can run, regardless of device. The difference comes in when you case it up and put the lid on. In the case of the MOSFETs, putting the lid on may reduce the current while raising temperature slightly. The key is that you have to have heat sinks large enough to allow a lot of current pumped into the MOSFETs in the first place.

 In the case of the BJT's, you probably have to cut vent holes in the case top, because as soon as you get things running right on an open board, things will get hotter when you close them up.

 Most of us have been running at 50ma (110mV) with the BJT's. 1" heat sinks are sufficient for this current and probably 20-30ma more, but that's just a guess. They do get hot enough when cased that some vent holes above each heat sink are probably advised - but no more than on the revMH w/DB's.

 The MOSFETs have been biased to 100ma (220mV), and fall back to 80-90ma when cased up. These currents pretty much demand the 1-1/2" heat sinks. Amb has a table of MOSFET bias vs. power supply voltage for 1-1/2" heat sinks on his M3 website here:
M3 Initial Setup & Adjustments - NOTES. He mentions 80ma as a good starting point and then his table shows 120 - 140ma maximum from 30-26V. The MAX is generally setup for 27 to 30V max, and about 100ma falls about in the middle for biases at those voltages and the 80ma starting point.


  Quote:


 Sorry for all the ?s... 
 

No problem - hopefully, this wasn't too confusing (and I didn't screw it up). The thing to remember is that the BJT's can run as much bias current as the MOSFETs, but they don't have to in order to sound good. The MOSFETs will run lower currents when buttoned up in a case, which is helpful, but will require much higher relative current in order to sound as well as they should.


----------



## mb3k

Ferrari, great catch on the compensation cap!
 Like AMB's comments on the M3 site, you could also omit the compensation cap and use RB8=121R, and RB9=75R to maintain symmetrical slew rates


----------



## mb3k

With the MOSFETS IRFZ24N and IRF9Z34N, the datasheets don't indicate the pinouts.
 I was tracing out the MAX layout and schematic it seems to be that looking from the front of the MOSFET (with the screw tab on the back) it is SDG. 

 This is weird because they're usually GDS.

 EDIT: Nevermind! I figured out it is GDS, I was looking at the "wrong" side of the heatsink and thought the MOSFETS mount on the side where the BJT's are suppost to be soldered.


----------



## tomb

Well, dsavitsk threw a little wrench into my answer about capacitor bypasses to Fallen Angel. He posted this just in the last couple of days over on Headwize:

  Quote:


  Originally Posted by *dsavitsk* 
_"Just to add some diversity here, *I have yet to use an electrolytic in the signal path that could not benefit from a good bypass. This has been the case from cheap caps to top of the line blackgates.* And, in fact, rather than spend any real money on the electrolytic, I'd use a cheap one and put the money into the bypass instead.

 As a general rule, I don't like to use caps in the signal path at all preferring designs that use transformers, but if you must cap couple something, and you must use an electrolytic, try a good bypass. The general rule of thumb is 1/100 the value of the larger cap, so 1.5uF is probably too large here."_

 

My experience has agreed with dsavitsk's opinions on caps 100%, so I thought this bore mentioning. I'll report back when I build my MAX with the BG's and experiment a little with bypasses vs. no bypasses.


----------



## n_maher

Tom,

 If you haven't ordered your BG's yet (you probably have) you should pick up a couple of the small value NX-HiQ which are supposed to be excellent bypass caps. That's what I have in my personal Millett (the 'old' version 
	

	
	
		
		

		
		
	


	




) and I'm not at all disappointed in how it sounds.


----------



## tomb

Quote:


  Originally Posted by *n_maher* /img/forum/go_quote.gif 
_Tom,

 If you haven't ordered your BG's yet (you probably have) you should pick up a couple of the small value NX-HiQ which are supposed to be excellent bypass caps. That's what I have in my personal Millett (the 'old' version 
	

	
	
		
		

		
		
	


	




) and I'm not at all disappointed in how it sounds._

 

Interesting - I have heard of this - will give it a try.


----------



## MrMajestic2

Noticed that at least one Vishay Dale value in backordered at Mouser. Any other brands that are recommended, or is it not important since most are not in the signal path, except for RB14? Also, has anyone tried the Evox Rifa PHE as bypass film caps? Remember reading somewhere that they make good bypass caps. They are actually cheaper here in Sweden than the Wima from mouser which is unusual.


----------



## MrMajestic2

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Interesting - I have heard of this - will give it a try._

 

Let us know, and please tell us what value. Cant find a 0.22uf NX-HiQ, so I guess a higher value will have to be used, like 0.47uf maybe.


----------



## tomb

Quote:


  Originally Posted by *MrMajestic2* /img/forum/go_quote.gif 
_Noticed that at least one Vishay Dale value in backordered at Mouser. Any other brands that are recommended, or is it not important since most are not in the signal path, except for RB14? Also, has anyone tried the Evox Rifa PHE as bypass film caps? Remember reading somewhere that they make good bypass caps. They are actually cheaper here in Sweden than the Wima from mouser which is unusual._

 

Actually, RB14 is better off _not_ being a V-D. RB14 is better suited for either jumpering out completely or using a boutique such as a Kiwame, Stackpole, etc. It depends on your taste.

 What is the other value that's backordered? I am going to add a more convenient selection for the CCS resistors - 1K and 10K for RA8L/R and RA9L/R - in addition to the original values spec'd. This pair results in a CCS current of 0.65ma, which is close enough. Buying simple 1K and 10K resistor values is probably way easier, though.

 The only other "weird" value is the 3.32K RM1 in the e12 delay circuit. I'm afraid we're stuck with that - but there's no way it has to be a V-D if that value is out of stock. All it does it alter the delay slightly if the tolerance is not exact - big whoop - so a standard metal film should be fine.


----------



## MrMajestic2

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Actually, RB14 is better off not being a V-D. RB14 is better suited for either jumpering out completely or using a boutique such as a Kiwame, Stackpole, etc. It depends on your taste.

 What is the other value that's backordered? I am going to add a more convenient selection for the CCS resistors - 1K and 10K for RA8L/R and RA9L/R - in addition to the original values spec'd. This pair results in a CCS current of 0.65ma, which is close enough. Buying simple 1K and 10K resistor values is probably way easier, though.

 The only other "weird" value is the 3.32K RM1 in the e12 delay circuit. I'm afraid we're stuck with that - but there's no way it has to be a V-D if that value is out of stock. All it does it alter the delay slightly if the tolerance is not exact - big whoop - so a standard metal film should be fine._

 

Yeah, I was thinking Kiwame for the RB14.

 The value backordered is the 11.3Kohms RA9L/R. If a 10K works then that makes life easier.

 I do like Vishay Dales because they look like little scewered hot dogs 
	

	
	
		
		

		
		
	


	




 Im planning on making on MHM with "boutique" stuff and one using the BOM. Will be interesting to hear the difference.


----------



## tomb

Quote:


  Originally Posted by *MrMajestic2* /img/forum/go_quote.gif 
_Yeah, I was thinking Kiwame for the RB14.

 The value backordered is the 11.3Kohms RA9L/R. If a 10K works then that makes life easier._

 

Yes, I agree. Be sure to change RA8L/R to only 1K, too, though. The relationship of at least 10x between the two must remain.

  Quote:


 I do like Vishay Dales because they look like little scewered hot dogs 
	

	
	
		
		

		
		
	


	




 Im planning on making on MHM with "boutique" stuff and one using the BOM. Will be interesting to hear the difference.


----------



## mb3k

Quote:


  Originally Posted by *MrMajestic2* /img/forum/go_quote.gif 
_Yeah, I was thinking Kiwame for the RB14.

 The value backordered is the 11.3Kohms RA9L/R. If a 10K works then that makes life easier.

 I do like Vishay Dales because they look like little scewered hot dogs 
	

	
	
		
		

		
			





 Im planning on making on MHM with "boutique" stuff and one using the BOM. Will be interesting to hear the difference._

 

Mouser actually carries an 11K version (not shown in the mouser catalog!)
 71-RN55D-F-11K

*EDIT: See Tomb's post above!*


----------



## dsavitsk

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Well, dsavitsk threw a little wrench into my answer about capacitor bypasses to Fallen Angel. He posted this just in the last couple of days over on Headwize:

 My experience has agreed with dsavitsk's opinions on caps 100%, so I thought this bore mentioning. I'll report back when I build my MAX with the BG's and experiment a little with bypasses vs. no bypasses._

 

I should add a point of clarification. The emphasis should be on the modifier to bypass which is *good*.

 The top of the line Blackgates (the N and NX series) are very good for electrolytics. Bypassing with a Wima, to my ear, is not going to do you much good. But, bypassing with a Jensen copper PIO or a Jupiter, or something silly like that will improve it. Further, the limits of this are not well defined in my mind. I bypassed some 4.7uF N series BG's on the output of a DAC with some Russian teflon caps and I thought it was an improvement -- cleaner, less warm. But it was minor, and may have just been different.


----------



## dsavitsk

Quote:


  Originally Posted by *n_maher* /img/forum/go_quote.gif 
_Tom,

 If you haven't ordered your BG's yet (you probably have) you should pick up a couple of the small value NX-HiQ which are supposed to be excellent bypass caps. That's what I have in my personal Millett (the 'old' version 
	

	
	
		
		

		
		
	


	




) and I'm not at all disappointed in how it sounds._

 

FWIW, and sorry to thread crap, these are also excellent in digital circuits.


----------



## FallenAngel

Damn, well that got me really thinking.

 I'm thinking of trying Elna RFS bypassed by Mundorf MCap ZN in one build and BlackGate NX bypassed by AuriCap in the other.

 Hmm... wondering if it's worth it on the NX + AuriCap now, it'll already be $100 just on the caps 
	

	
	
		
		

		
		
	


	




 Maybe a pure BlackGate NX with NX bypass?


----------



## dsavitsk

Quote:


  Originally Posted by *FallenAngel* /img/forum/go_quote.gif 
_Damn, well that got me really thinking.

 I'm thinking of trying Elna RFS bypassed by Mundorf MCap ZN in one build and BlackGate NX bypassed by AuriCap in the other.

 Hmm... wondering if it's worth it on the NX + AuriCap now, it'll already be $100 just on the caps 
	

	
	
		
		

		
		
	


	




 Maybe a pure BlackGate NX with NX bypass?_

 

Often, but not always, the character of the bypass is so dominant that the larger cap is incidental. So, it might be that a cheapo cap bypassed by an Auricap is every bit as good as a BG bypassed by the Auricap -- and it might not be. But it might be worth an experiment?


----------



## MrMajestic2

Quote:


  Originally Posted by *FallenAngel* /img/forum/go_quote.gif 
_Damn, well that got me really thinking.

 I'm thinking of trying Elna RFS bypassed by Mundorf MCap ZN in one build and BlackGate NX bypassed by AuriCap in the other.

 Hmm... wondering if it's worth it on the NX + AuriCap now, it'll already be $100 just on the caps 
	

	
	
		
		

		
		
	


	




 Maybe a pure BlackGate NX with NX bypass?_

 

Yeah, its easy to get carried away with all the choices 
	

	
	
		
		

		
		
	


	




 Im thinking of going BG NX with NX-HiQ bypasses for the "boutique" caps and then Nichicon KZ/FX for the rest.


----------



## Ferrari

Quote:


  Originally Posted by *mb3k* /img/forum/go_quote.gif 
_...you could also omit the compensation cap and use RB8=121R, and RB9=75R to maintain symmetrical slew rates_

 

Yes, the same results can be obtained with 2 resistors with the same ratio 121 : 75 (~ 1.6x), for example RB8 = 82Ω, and RB9 = 50Ω. But keep RB8 = RB9 = 100Ω has the advantage that it makes the parts ordering easier since there are more resistors used in the buffer section with the same value.


----------



## Ech0

Quote:


  Originally Posted by *MrMajestic2* /img/forum/go_quote.gif 
_
 The value backordered is the 11.3Kohms RA9L/R. If a 10K works then that makes life easier.

 I do like Vishay Dales because they look like little scewered hot dogs 
	

	
	
		
		

		
		
	


	


_

 

Would a Xicon 1/8w 11.3Kohms work for RA9L/R? They're available at Mouser. Or would I need to bump that up to a 1/4w for a Xicon?


----------



## tomb

Quote:


  Originally Posted by *Ech0* /img/forum/go_quote.gif 
_Would a Xicon 1/8w 11.3Kohms work for RA9L/R? They're available at Mouser. Or would I need to bump that up to a 1/4w for a Xicon?_

 

1/8W will be plenty, or as suggested earlier - use a 10K and 1K resistor for R9 and R8. Those sizes are stocked in abundance.


----------



## naamanf

I am going to be ordering some caps for my next Max and a couple other projects. What NX HiQ whould be a good size to go with? And am I to under stand that it is used in the CA9 position?. Also what are the thoughts on the coupling caps?


----------



## mb3k

Quote:


  Originally Posted by *ferrari* 
_Yes, the same results can be obtained with 2 resistors with the same ratio 121 : 75 (~ 1.6x), for example RB8 = 82Ω, and RB9 = 50Ω. But keep RB8 = RB9 = 100Ω has the advantage that it makes the parts ordering easier since there are more resistors used in the buffer section with the same value._

 

Yeah, I am going to opt for RB8 = RB9 = 100Ω and do your straddle trick with the cap.


  Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_1/8W will be plenty, or as suggested earlier - use a 10K and 1K resistor for R9 and R8. Those sizes are stocked in abundance._

 

Excellent, I overlooked your post on the last page (I didn't dawn on me that the 11.3k and 1.13K is a 10:1 ratio, duhhh
	

	
	
		
		

		
		
	


	




). It looks like the 10K & 1K is the way to go now.
 A suggestion for the site would be to document ground loop breakers and list transformer options for those who don't use wallwarts (*raises hand* 
	

	
	
		
		

		
		
	


	




)


----------



## zare

Anyone experienced with Kiwame or Mills? For RB10/11 (2.2ohm) I was thinking to get 5W Kiwame, but it will be nightmare getting it positioned nicely. On the other hand, Mills will fit perfectly. I know there will be commotion about boutique resistors, but I've never tried them, so it'll be fun.


----------



## MrMajestic2

Is the Millet Hybrix Max logo available in HPGL or a format that can be converted to HPGL? Would be nice with an engraved logo on the case.


----------



## Ferrari

Quote:


  Originally Posted by *zare* /img/forum/go_quote.gif 
_Anyone experienced with Kiwame or Mills? For RB10/11 (2.2ohm) I was thinking to get 5W Kiwame, but it will be nightmare getting it positioned nicely. On the other hand, Mills will fit perfectly. I know there will be commotion about boutique resistors, but I've never tried them, so it'll be fun._

 


 I usual use Kiwame resistors in the signal path with positive results.
 As far as I know (at least from the shop where I buy it in the Netherlands) Kiwame resistors are not available in small values below 10Ω

 The 5W type with body size: D 9.0 x L 24 (mm) are available from 100Ω to 1MΩ ( +/-5% )
 This type will not (or hardly) fit on the MH Max board.

 The 2W type with body size: D 4.2 x L 12 (mm) are available from 10Ω to 510KΩ ( +/-5% )
 The size will fit on the MH Max board but not available at 2.2Ω.

 For this position I will go for 2W metal film resistors, freferably 1% type if you can find/get and use Kiwame resistors at the output ( RB14L/R).
 (My MH Max is implemented this way 
	

	
	
		
		

		
		
	


	




 )


----------



## tomb

Quote:


  Originally Posted by *naamanf* /img/forum/go_quote.gif 
_I am going to be ordering some caps for my next Max and a couple other projects. What NX HiQ whould be a good size to go with? And am I to under stand that it is used in the CA9 position?. Also what are the thoughts on the coupling caps?_

 

The Martin Colloms paper mentions the 0.47uF NX Hi-Q. There is one of those available at 50V, which would be perfect for the MAX.

 Positions CA9 _and_ CA8 are probably appropriate. These are the bypasses for the CA2 tube cathode bypass and CA7, the output coupling cap, respectively. Both of these areas in the MAX circuit are identified as appropriate boutique cap applications.

 Whether the BG 0.47uF NX Hi-Q is better than a normal boutique film cap in those positions is probably open to interpretation. However, it sounds like a sure method to use for CA8/CA9 if BG's are already used in the CA2 and CA7 positions.

 No doubt, there will be further comment on this, but it's my guess for now.


----------



## zare

Looks like partsconnexion has those:

 KIWAME-66250 2R2 5 Watt

 And for the RB14L/R, I already have in plan kiwames, because I've noticed that even with original Millett the gain very high for my grados and AKG.
 I've checked you builds, and that looks wicked 
	

	
	
		
		

		
			





  Quote:


  Originally Posted by *Ferrari* /img/forum/go_quote.gif 
_I usual use Kiwame resistors in the signal path with positive results.
 As far as I know (at least from the shop where I buy it in the Netherlands) Kiwame resistors are not available in small values below 10Ω
 ....
 For this position I will go for 2W metal film resistors, freferably 1% type if you can find/get and use Kiwame resistors at the output ( RB14L/R).
 (My MH Max is implemented this way 
	

	
	
		
		

		
		
	


	




 )_


----------



## tomb

Quote:


  Originally Posted by *zare* /img/forum/go_quote.gif 
_Looks like partsconnexion has those:

 KIWAME-66250 2R2 5 Watt

 And for the RB14L/R, I already have in plan kiwames, because I've noticed that even with original Millett the gain very high for my grados and AKG.
 I've checked you builds, and that looks wicked 
	

	
	
		
		

		
		
	


	


_

 

Note that Ferrari did _not_ suggest using the Kiwame's for RB10/11. Those are the DB power output resistor positions, and high accuracy and very little coloration is desired. Make sure your DB's are functioning at their best and that they are stable by using the best _precision_ metal film in those positions (metal oxide are OK, but not as good probably). You want something that has little or no drift under a wide temperature range, especially at elevated temperatures.

 I am uncertain whether anyone has used anything like Kiwame's in those positions, or whether the effects are known. Remember that the MAX output stage differs very little from traditional SS amps such as the PPA or the M3, and Kiwame's would be out of the question in those spots on those amps, I think.


----------



## MrMajestic2

Quote:


  Originally Posted by *Ferrari* /img/forum/go_quote.gif 
_I usual use Kiwame resistors in the signal path with positive results.
 As far as I know (at least from the shop where I buy it in the Netherlands) Kiwame resistors are not available in small values below 10Ω

 The 5W type with body size: D 9.0 x L 24 (mm) are available from 100Ω to 1MΩ ( +/-5% )
 This type will not (or hardly) fit on the MH Max board.

 The 2W type with body size: D 4.2 x L 12 (mm) are available from 10Ω to 510KΩ ( +/-5% )
 The size will fit on the MH Max board but not available at 2.2Ω.

 For this position I will go for 2W metal film resistors, freferably 1% type if you can find/get and use Kiwame resistors at the output ( RB14L/R).
 (My MH Max is implemented this way 
	

	
	
		
		

		
		
	


	




 )_

 


 Does your shop in the Netherlands have a online store? Always on the lookout for EU shops


----------



## Ferrari

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Note that Ferrari did not suggest using the Kiwame's for RB10/11. Those are the DB power output resistor positions, and high accuracy and very little coloration is desired. Make sure your DB's are functioning at their best and that they are stable by using the best precision metal film in those positions (ceramic oxide are OK, but not as good probably). You want something that has little or no drift under a wide temperature range, especially at elevated temperatures.

 I am uncertain whether anyone has used anything like Kiwame's in those positions, or whether the effects are known. Remember that the MAX output stage differs very little from traditional SS amps such as the PPA or the M3, and Kiwame's would be out of the question in those spots on those amps, I think._

 

Indeed, _stable behavior of the buffer is very important _here. 
 Not explicitely name it in my previous post, but I suggest to use 2W metal film resistors, preferably 1% for RB10/11.

 @MrMajestic2, the shop I bought from is Acoustic Dimension


----------



## zare

Note taken 
	

	
	
		
		

		
		
	


	



  Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Note that Ferrari did not suggest using the Kiwame's for RB10/11._


----------



## tomb

Quote:


  Originally Posted by *zare* /img/forum/go_quote.gif 
_Note taken 
	

	
	
		
		

		
		
	


	


_

 

OK. 
	

	
	
		
		

		
		
	


	



 Note also that I was mixing terms again 
	

	
	
		
		

		
		
	


	




 - I should've said _metal_ oxide in that previous post for RB10/11. Appropriate wattage metal _film_ are slightly better, however. The MAX BOM has ideal resistors specified for these positions from Mouser or DigiKey.


----------



## curlywoods

Hey,

 Just wondering where the PC boards are for this group buy. I paid for two boards via PayPal around the first week in June and still no boards? I have all the parts and wondering what;s up?


----------



## tomb

Quote:


  Originally Posted by *curlywoods* /img/forum/go_quote.gif 
_Hey,

 Just wondering where the PC boards are for this group buy. I paid for two boards via PayPal around the first week in June and still no boards? I have all the parts and wondering what;s up? 
	

	
	
		
		

		
		
	


	


_

 

Just a thought, but you might try reading the last few posts in the Group Buy thread.


----------



## pabbi1

Originally Posted by cetoole 
 OK guys, here is the latest. I just checked the status of the PCBs, and the boards are expected to ship to me 7/10/2007.


----------



## bhjazz

Quote:


  Originally Posted by *pabbi1* /img/forum/go_quote.gif 
_Originally Posted by cetoole 
 OK guys, here is the latest. I just checked the status of the PCBs, and the boards are expected to ship to me 7/10/2007._

 

What, all of 'em? Aw, geez. Guess I'll be road trippin, then.


----------



## mb3k

Ugh, my eyes are bleeding!
 Finally finished deciding on parts for the MHM... it came out to about $200 w/out casing. I spent most of the day making BOMs for 11 other projects too.
 The stock of some RN55D resistors are scary small! Gotta order quickly


----------



## bperboy

Quote:


  Originally Posted by *mb3k* /img/forum/go_quote.gif 
_Ugh, my eyes are bleeding!
 Finally finished deciding on parts for the MHM... it came out to about $200 w/out casing. I spent most of the day making BOMs for 11 other projects too.
 The stock of some RN55D resistors are scary small! Gotta order quickly_

 

You must be using some premium parts! I think my build total was fairly less than $200 even including shipping costs.


----------



## vixr

my total was less than $200 and I got enough parts to build two amps...


----------



## tomb

Quote:


  Originally Posted by *vixr* /img/forum/go_quote.gif 
_my total was less than $200 and I got enough parts to build two amps..._

 

Yep, the BOM only neglects knob and input jacks - it even includes the Hammond case - for a total of ~$160. As you note, it may be considerably less if some things are ordered in volume.


----------



## MrMajestic2

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Yep, the BOM only neglects knob and input jacks - it even includes the Hammond case - for a total of ~$160. As you note, it may be considerably less if some things are ordered in volume._

 

I think my BOM for a "boutique" version is around $225 including a case. The "standard" BOM is around $160. All excluding shipping from all over the world unfortunetly.


----------



## FallenAngel

So far I'm at $160 (not including PCBs or case) for 2 amps and it's not including the boutique caps, those I'll get from PartsConnexion. Wouldn't be surprised if it ends up being double that because of those caps.


----------



## vixr

Quote:


  Originally Posted by *FallenAngel* /img/forum/go_quote.gif 
_...Wouldn't be surprised if it ends up being double that because of those caps..._

 

I have 4 or 5 more attempts with boards from the group buy. I am absolutely going for some BG caps on at least one of them...I cant believe that the MAX could sound any better than the one I have now though...


----------



## tomb

Yeah, I have some BG's waiting, too. However, "boutique" with Nichicon Muse can be fairly inexpensive with great results. Like Vixr, I am curious to see how much better the BG's will be than those Muse ES's.

 BTW - it's been awhile since I mentioned this, but the 470uF@35V Nichicon Muse ES is available from BDent. That makes it convenient if you are considering ordering any of the Toshiba/Sanyo output transistors. Handmade has the 1000uF@16V ES and then all of the KZ's if you are interested in those.

 P.S. I recently updated the web site with the production board version of the layouts and schematics.


----------



## Alcaudon

Just a few questions....

 Has anyone ever used Evox-Rifa PHE 450 film capacitors? I`m planning to use them in all the film caps positions since I can't find (not locally) those Wima MKP10 that everyone seems to be using. And what about Wima MKS2??

 And about resistors.... What if I use just standard metalised film resistors?? just the ones that you can buy at a local store. Shipping costs from Mouser are about 40$ and I just need a few things that cost less than that.


----------



## FallenAngel

I heard nice things of Wima MKS2 and there should be no problems using any other brand metal film resistors.

 I don't know about the Rifa 450, but I saw them at my local surplus store for really cheap, so I'm only going to assume they aren't great.


----------



## vixr

this guy tested some caps and seems to have a pretty good handle on it...
 click HERE to see his reviews...
 those Rifa 450s are in there...


----------



## naamanf

Just placed all my orders to build my second max. This time it's going to be a MOSFET DB with Blackgates and Auricaps. Also picked up some of the NX Hi-Q caps to try out in place of the Auricaps. Should be fun


----------



## MrMajestic2

Quote:


  Originally Posted by *naamanf* /img/forum/go_quote.gif 
_Just placed all my orders to build my second max. This time it's going to be a MOSFET DB with Blackgates and Auricaps. Also picked up some of the NX Hi-Q caps to try out in place of the Auricaps. Should be fun 
	

	
	
		
		

		
		
	


	


_

 

Will the Auricap with on the board without "creative" mounting methods? Would be interesting to try out.


----------



## tomb

Quote:


  Originally Posted by *MrMajestic2* /img/forum/go_quote.gif 
_Will the Auricap with on the board without "creative" mounting methods? Would be interesting to try out._

 

I have some 0.1's and they're pretty tiny - about like 3 or 4 Smarties stacked together or maybe 2 Altoids. 0.22's are not much bigger. If you go bigger than that you could have problems on the output caps. There's lots of room for the CA9's around the tubes, though.

 While we're at it, I've been meaning to suggest that Jupiters are probably not a good idea - unless you can get them beneath the board and shielded from the heat. Take a look at Vixr's thermal imaging and you get the idea - nothing to be concerned about from normal amp temps, but probably not a good environment for Jupiters' beeswax.

 Also wanted to report that I received an order from Soniccraft just recently, and I can highly recommend them. Lots of BG's and all sorts of film caps. Vixr's capacitor review link up there confirms some of Dsavitsk's listening tests: the Sonicap Gen I/II supposedly has great performance for a very low price among boutique film caps.

 I made a stupid mistake with an item price on an order, and they called me up personally to make sure they sent the right thing - great service!


----------



## FallenAngel

Nice prices at SonicCraft, too bad they're not in Canada. Shipping and import fees to get stuff from there to Canada kills the deals. PartsConnexion it is for me. Oh the joys of blowing $100+ on caps for a single amp


----------



## Ferrari

Quote:


  Originally Posted by *FallenAngel* /img/forum/go_quote.gif 
_...Oh the joys of blowing $100+ on caps for a single amp 
	

	
	
		
		

		
		
	


	


_

 

That's the fun of DIY! You can build an amp just the way you want, but... sometimes it hurts your wallet a bit.
 Mine cost a couple of cents more I guess 
	

	
	
		
		

		
		
	


	




.


----------



## Troyhoot

Getting my bom together and I have a couple questions.

 1. Since I am going to be useing 32ohm cans C7 needs to be 2200uf to get the corner frequency down almost to 2hz. Is this correct?

 2. Is there any reason y'all are useing ES muse over the KZ or even the FG.

 3. Since the 2200uf is only available in the FG series of Muse, is the going to be an inferior choice?

 4. Could I use two 2200uf caps for the power instead of four 1k's ? I would have to put the ac and input termianls on the bottom of the board. Im pretty sure I could make them fit alright. I like the Idea of 2 monster caps instead of 4 smaller ones. 

 Still a little green about all this but im learning fast 
	

	
	
		
		

		
		
	


	




 I was pretty much set on useing Muse caps throughout this build. I can change to something else If the FG's arent up to the job though.


----------



## Ferrari

That is right, but why should you want to go that low? 
	

	
	
		
		

		
		
	


	




 To ensure a linear bass response down to the lowest theoretically audible frequency of 20Hz, a corner frequency at 10Hz is necessary. (at the corner frequency the signal drops 3dB = -3dB point).
 For a 32Ω headphone, a 470uF capacitor if sufficient to guarantee the corner frequency at 10Hz.
 Moreover, it's questionable if your headphone is able to reproduce such low frequencies.


----------



## tomb

Quote:


  Originally Posted by *Troyhoot* /img/forum/go_quote.gif 
_Getting my bom together and I have a couple questions.

 1. Since I am going to be useing 32ohm cans C7 needs to be 2200uf to get the corner frequency down almost to 2hz. Is this correct?_

 

If you just use the equation, yes. However, there is the potential of an output resistor in series with the headphone impedance, and in parallel with the output ground resistor. These aren't normally factored into the equation, but they have a definite effect. The result is that with the judicious use of a quality output resistor, you can achieve the same result. In fact, a V-D might be a good thing here - to tweak the corner frequency and pass the high frequencies at the same time.

 I did some studying just recently about this, and you are correct to want to push the corner frequency as low as it can go with low impedance cans:





 It looks to me though, that you only have to push it (the corner) to 7Hz to have the curve flat at 20Hz.

 Here's the calcs at 32 ohms headphones, with the 1K ground resistor. The table shows the effect with a 470uF coupling output cap and various output resistors:





 I think only a 20ohm resistor might do the job for you.

 If you study the original Pete Millett article, he was actually accomplishing the same thing by using only 220uF coupling caps - the corner frequency is essentially the same for 300ohm Senns with a 22 ohm resistor as with a 470uF coupling cap alone. 

  Quote:


 2. Is there any reason y'all are useing ES muse over the KZ or even the FG. 
 

Yes. 1) Muse ES is known for bass, and 2)the heights allow the use of 1" heat sinks. KZ's are great but they're Giant Sequoias. FG's are borderline audio signal cap and are 3rd down on the list for audio signal caps in the Nichicon Muse line.

  Quote:


 3. Since the 2200uf is only available in the FG series of Muse, is the going to be an inferior choice? 
 

IMHO, yes - you are better off considering the FG's as very nice power caps.

  Quote:


 4. Could I use two 2200uf caps for the power instead of four 1k's ? I would have to put the ac and input termianls on the bottom of the board. Im pretty sure I could make them fit alright. I like the Idea of 2 monster caps instead of 4 smaller ones. 
 

Absolutely. The 1st prototype only had two cap positions, anyway. I had two humongous 2200uF Panasonic FC's back there (still do, but they're off the board - if you look at the thread on DIYForums, you'll see why).

  Quote:


 Still a little green about all this but im learning fast 
	

	
	
		
		

		
		
	


	




 I was pretty much set on useing Muse caps throughout this build. I can change to something else If the FG's arent up to the job though. 
 

Nothing wrong with that idea - at all, but I'd stick to 470uF max on the output coupling caps and play with the output resistors, instead. You almost want a little gain reduction with 32ohm headphones, anyway. BG makes a 680uF, which is reportedly very good, but they're the only boutique in that size, I believe.


----------



## FallenAngel

Troyhoot:

 1) 2200uF will get you down to 2.26Hz, are you sure you need it that low? I don't know any headphones that have anywhere near a flat response anywhere below 16Hz or any music recorded that low anyway. It's up to you of course, but perhaps you would go for quality at the expense of slightly worse corner frequency.

 2) Personal preference again, I'm not, but that's because I can't get them easily. I'm sticking to Elna RFS and BlackGate NX in my 2 builds.

 3) Gotta skip this one, I don't know that line.

  Quote:


  Originally Posted by *Ferrari* /img/forum/go_quote.gif 
_That's the fun of DIY! You can build an amp just the way you want, but... sometimes it hurts your wallet a bit.
 Mine cost a couple of cents more I guess 
	

	
	
		
		

		
		
	


	




._

 

Definitely, your build looks fantastic. I couldn't find those 220uF film caps, largest I can find out of a reasonable line is the AuriCap 100uF at $100 each and it's unfortunately more than I can reasonably spend on it.

 I want to use this amp with both Grados and Sennheisers so to get a nice corner frequency, I would need at to raise the budget to 80% on just the film caps. I'll stick to a smaller budget for now and just drool over your amp 
	

	
	
		
		

		
		
	


	




 On another note, would you guys recommend running at from a 24V wallwart or 30V to get things cooking nicely for MOSFETs?


----------



## Troyhoot

just going by what was in the "Millett MAX Boutique" section on the MAX web guide.

 "_2Hz is a good corner frequency to use, because phase distortions can occur up to 10 times the corner frequency. So if we interested in hearing 20Hz, we should calculate for a corner frequency of 2Hz or less._"

 Well since you talked me into staying at 470 for C7, I can just use KZ's for all the caps and not worry about the FG being inferior quality. I wasn't going to use any output resistor but now I can maybe play with that a bit and see what I like best. And if/when I get some new cans I can just swap resistors if needed.

 Thanks for the quick answers. Im sure I'll have more Q's before this is through


----------



## tomb

Quote:


  Originally Posted by *Troyhoot* /img/forum/go_quote.gif 
_just going by what was in the "Millett MAX Boutique" section on the MAX web guide.

 "2Hz is a good corner frequency to use, because phase distortions can occur up to 10 times the corner frequency. So if we interested in hearing 20Hz, we should calculate for a corner frequency of 2Hz or less."

 Well since you talked me into staying at 470 for C7, I can just use KZ's for all the caps and not worry about the FG being inferior quality. I wasn't going to use any output resistor but now I can maybe play with that a bit and see what I like best. And if/when I get some new cans I can just swap resistors if needed.

 Thanks for the quick answers. Im sure I'll have more Q's before this is through 
	

	
	
		
		

		
		
	


	


_

 

Hmm ... I'll have to look at that - it may be a typo. Ferrari is correct with the basic equation - 10Hz is pretty much the round number answer, and I believe that's what Colin said, too. Ferrari is also correct that a lot of this probably doesn't make much difference, but it's possible that you can hear that difference under certain conditions. For a couple of resistors that you could socket pretty easily, it seems worth the trouble to experiment - especially when some of us are talking about $100s for some boutique caps. Again, in your situation a few ohms or so could lower it another 5-10 Hz without going to those monster size caps.

 BTW, I was working on uploading all those graphs before I saw Ferrari's post, so by no means was I trying to contradict his post. This is just playing with stuff in the margins. 
	

	
	
		
		

		
		
	


	




 Fallen Angel - 
 As long as the components will take it, higher voltage is always better - less current, less heat, etc. for the same power. The tubes will take 30, so go for it. 24V is fairly anemic for the MAX, MOSFETs or not.


----------



## Troyhoot

while I'm asking questions and its fresh in my mind. Is there a reason the bypass film caps are .22uf ? could they be a little smaller or larger or is this size critical ?

 Im sure the answer is in here and I just missed it. But its been bothering me all afternoon


----------



## tomb

Quote:


  Originally Posted by *Troyhoot* /img/forum/go_quote.gif 
_while I'm asking questions and its fresh in my mind. Is there a reason the bypass film caps are .22uf ? could they be a little smaller or larger or is this size critical ?

 Im sure the answer is in here and I just missed it. But its been bothering me all afternoon
	

	
	
		
		

		
		
	


	


_

 

Sizing bypass caps is an empirical thing. I think 1/100 of the larger electrolytic, but this is painting with a broad brush. I think if you get close to single digits, you're in danger of confusing the sound (we're in voodoo with this, so cut me some slack on terms). By the same token, if you're down into the hundredths of microfarads, then it's probably not enough to mean anything. 0.1, .22, .47, are all probably good choices.

 BTW, I stand corrected about the corner frequency - 2Hz is correct! Here is Mad MAX's (cetoole) original quote:
  Quote:


 The greater capacitance, the lower the -3dB point of the filter that is created by the output capacitor and the headphone impedance. This is found by the equation F = 1/(2*pi*R*C), so for me, with my Sennheiser HD580 headphones, with a nominal 300ohm impedance, this is at ~0.78Hz. If instead I was to use my 29ohm Shure E4 IEMs, the cutoff would be at ~8.07Hz. There will be phase distortions 10x higher than this frequency, so to keep this out of the audio frequencies, you must keep the -3dB point under 2Hz. 
 

Again, in your case 1000uF might be OK, the 680uF Black Gate mentioned by Colin is probably ideal. However, as also discussed a couple of posts ago - you may be able to get away with 470uF and the use of a couple of resistors, instead.

 Of course, this is all assuming that 20Hz is audible, and IMHO, YMMV, etc., etc.


----------



## mb3k

Quote:


  Originally Posted by *Troyhoot* /img/forum/go_quote.gif 
_while I'm asking questions and its fresh in my mind. Is there a reason the bypass film caps are .22uf ? could they be a little smaller or larger or is this size critical ?

 Im sure the answer is in here and I just missed it. But its been bothering me all afternoon
	

	
	
		
		

		
		
	


	


_

 

Tomb beat me to it, but ballpark is around 100x less than the electrolytic.
 Here's a little tid-bit from my classic Millett site.





 EDIT: But I read that Solen's aren't that good of performer in this type of application, correct me if I'm wrong about that.


----------



## mb3k

Tomb, I see you've updated the BOM with fuse recommendations.
 Why fast-blo fuses?
 Aren't slow-blow fuses better b/c of the power-on transient can temporarily reach a high enough current to "out-rate" the fuse?


----------



## tomb

Cool chart - lovely style as always, mb3k! Very useful info, to be sure! Heck, it almost indicates that with a 300ohm phone, it's possible to pump most of the music through the film cap. Yes, I've heard that Solen's aren't that good. If you go back a page or two to Vixr's capacitor review reference - they pretty much said the same thing: only a "fair" performance.

 Most of you guys seem to really like the Auricaps. I have some Vitamin Q's I'm going to try and also some of those Sonicap GenII's, since Dsavitsk was so keen on them combined with Muse ES's, which is a great favorite of mine (love the green!). Can't wait to try them all.


----------



## tomb

Quote:


  Originally Posted by *mb3k* /img/forum/go_quote.gif 
_Tomb, I see you've updated the BOM with fuse recommendations.
 Why fast-blo fuses?
 Aren't slow-blow fuses better b/c of the power-on transient can temporarily reach a high enough current to "out-rate" the fuse?_

 

I don't know - you tell me? Seriously, a case can be made for either one. Basically, this grew out of conversations between NeilR and Colin over protecting the MOSFETs. That's why I kind of figured 1A fast blo. If you look at the data, "fast-blo" is kind of a misnomer, anyway. For instance, for the one listed at Mouser it says:

 60 minutes at 150% load
 30 minutes at 210% load

 But then it goes to:
 0.05 seconds at 275% load
 0.01 seconds at 400% load.

 Anyway, the purpose is to save a semiconductor, so a fast-blo is the thing. If it was in the transformer side of things or in the walwart, then by all means: slo-blo.

 It's only a starting point, though - if you guys have a better idea - the pads will be there for clips to put whatever you want in. Or, with the 3-pos terminal block, you can bypass it completely.


----------



## mb3k

Now that you mention it Tomb fusing the secondary seems like the thing to do to protect the MOSsies. I'm also obligated to fuse the primary due to the power inlet module.

 [thinkoutloud]Using my good ol' ideal trafo formula, a 25Vsecondary, 700mAsecondary, running from a perfect 120VAC mains line (primary), the primary current should be 145.83mA.
 When the 1A secondary hits, the primary current will reach 208.3mA... hmm... I'll do a 250mA fuse on the primary.[/thinkoutloud]


----------



## naamanf

nutsack! I did even realize that the production version has a place for a fuse. I hope I can find the clips locally because both my Mouser and Digikey orders just shipped


----------



## tomb

Quote:


  Originally Posted by *naamanf* /img/forum/go_quote.gif 
_nutsack! I did even realize that the production version has a place for a fuse. I hope I can find the clips locally because both my Mouser and Digikey orders just shipped
	

	
	
		
		

		
		
	


	


_

 

Yes, paraphrasing Bones' quote in the first Star Trek movie,

 "You know headphone amp designers: they love to change things."

 One might also say, "You know those Millett monk scribes - too busy brewing beer to keep up with scribing the latest epistle."

 I take full responsibility.


----------



## zare

Quote:


  Originally Posted by *Alcaudon* /img/forum/go_quote.gif 
_. Shipping costs from Mouser are about 40$ and I just need a few things that cost less than that._

 

Well, don't even think about it. Just noticed today on my mouser order for the parts missing in digikey:

 -----------------------------------------------------------------
 MERCHANDISE 80.82
 HANDLING 0.00
*FREIGHT 54.42*
 TAX 0.00
 -----------
 TOTAL $135.24
 -------------------------------------------------------------------






 I give them a call, knowing that I've just ordered some other thing from Allied Electronics, also in US, with same courier (DHL) and have payed only 8.5$.
 Sales rap give me a pap talk how they are concerned about the problem with shipping rate to Canada. So, I guess for us in Canada, we can stick to Digi-Key and local supplier for the bulk of the parts for now.


----------



## amphead

Quote:


  Originally Posted by *curlywoods* /img/forum/go_quote.gif 
_Hey,

 Just wondering where the PC boards are for this group buy. I paid for two boards via PayPal around the first week in June and still no boards? I have all the parts and wondering what;s up? 
	

	
	
		
		

		
		
	


	


_

 

Just look at tomb's signature and you realize the
 complexity of organizing this group buy.


----------



## zare

BTW, has anyone order something like this:TRANSISTOR SOCKET TO-220 ? I have ordered almost all possible transistors to play with, and I was wondering if this will help rolling different types. I know I can not use same PCB for for MOSFET's and BJT without altering the board with corresponding output stage changes.


----------



## tomb

Quote:


  Originally Posted by *zare* /img/forum/go_quote.gif 
_BTW, has anyone order something like this:TRANSISTOR SOCKET TO-220 ? I have ordered almost all possible transistors to play with, and I was wondering if this will help rolling different types. I know I can not use same PCB for for MOSFET's and BJT without altering the board with corresponding output stage changes._

 

A couple have looked at it and the complaint was that perhaps the pads are too close to the heat sinks for the sockets to work right. The "real" TO-220 sockets you sort of rotate and twist the transistor into place, but there's standard mil-max sockets, too.

 It's an idea that should be explored more. As you note, unlike the MOSFETs, there are a number of BJT's that can be used. Existing reviews of the BJT's are pretty much based on 30ma, so there may be differences at the higher currents the MAX can run. Maybe ones that have a good review at 30ma stink at 50ma+ and vice-versa. Sockets would help us find these things out much easier.


----------



## zare

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_It's an idea that should be explored more. As you note, unlike the MOSFETs, there are a number of BJT's that can be used. Existing reviews of the BJT's are pretty much based on 30ma, so there may be differences at the higher currents the MAX can run. Maybe ones that have a good review at 30ma stink at 50ma+ and vice-versa. Sockets would help us find these things out much easier._

 

I've just pulled the trigger, and ordered 10 of those. For testing purpose should be OK I guess. Got some 2'' heatsinks, just in case 
	

	
	
		
		

		
			





 .
 Do you have 2SC2238 / 2SA968 combo? On one older post(diyforums), steinchen mentioned that he might hub some to you?


----------



## FallenAngel

zare - I've been stuck with those rates from Mouser once as well, just don't order from there. Between DFigiKey and Newark, you're covered for all the generic parts. PartsConnexion is nice in Canada for boutiques.


----------



## tomb

Quote:


  Originally Posted by *zare* /img/forum/go_quote.gif 
_I've just pulled the trigger, and ordered 10 of those. For testing purpose should be OK I guess. Got some 2'' heatsinks, just in case 
	

	
	
		
		

		
		
	


	




 .
 Do you have 2SC2238 / 2SA968 combo? On one older post(diyforums), steinchen mentioned that he might hub some to you?_

 

Unfortunately, no - some of the other choices have kept me very happy.


----------



## pabbi1

Only a few left...

http://cgi.ebay.com/7-pin-PCB-Mount-...QQcmdZViewItem


----------



## Ferrari

It's a good idea to experiment with different types of transistors, but keep in mind that Toshiba transistors (2SAxxxx / 2SCxxxx) have a reversed pin-out comparing to BD1xx or MJE2xx. You have to rotate the Toshiba transistors 180 degrees if you are going to try these. In other words, Toshiba transistors should be mounted on the position of the MOSFETs 
	

	
	
		
		

		
		
	


	




 .

 Btw, the graphs Tomb uploaded in post #479 is very good and is more accurate than the quick calculation I deed by head.
 It's my old habit to simplify things when I read, understand and doing quick calculation on electronics circuits.
 It points you to the right direction but sometimes not as accurate as it should be.
 The earlier roll-off characteristic of analogue filters is not taken into account in my quick calculation. One thing we all want to make clear is that it's not necessary to calculate a corner frequency of 1-2Hz due to various reasons that were discussed in some posts on the previous and this page.


----------



## MrMajestic2

Im looking to upsize the PSU and Mosfet heatsinks. I was thinking this for the PSU: http://www.mouser.com/search/product...y567-657-20ABP Will that fit the same footprint?
 Having trouble fiding the correct footprint Mosfet heatsink that is taller than the ones in the BOM.


----------



## tomb

Quote:


  Originally Posted by *MrMajestic2* /img/forum/go_quote.gif 
_Im looking to upsize the PSU and Mosfet heatsinks. I was thinking this for the PSU: http://www.mouser.com/search/product...y567-657-20ABP Will that fit the same footprint?
 Having trouble fiding the correct footprint Mosfet heatsink that is taller than the ones in the BOM._

 

The PS sink is actually the Wakefield 647 series. I can't tell much difference from the one you've selected except that there's only one mounting hole a little higher up from the board, and the space in the middle is a little wider, which may be a good thing - the MAX is pretty packed there inbetween the fins.

 The 647 series only accepts TO-220. It could be that Mouser made the inventory decision to keep the 657 series in the taller sizes. Being more expensive, it probably makes more sense to have one that takes several transistor form factors.

 I think it will work fine.

 EDIT:
 The two inch high version with pins for the DB MOSFETs should be this one:
532-531202B25G . They are basically the Aavid 531 series.


----------



## MrMajestic2

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_The PS sink is actually the Wakefield 647 series. I can't tell much difference from the one you've selected except that there's only one mounting hole a little higher up from the board, and the space in the middle is a little wider, which may be a good thing - the MAX is pretty packed there inbetween the fins.

 The 647 series only accepts TO-220. It could be that Mouser made the inventory decision to keep the 657 series in the taller sizes. Being more expensive, it probably makes more sense to have one that takes several transistor form factors.

 I think it will work fine._

 

Cool, Ill give it a try. Wonder if I can find a taller one for the Mosfets.


----------



## tomb

Quote:


  Originally Posted by *Ferrari* /img/forum/go_quote.gif 
_It's a good idea to experiment with different types of transistors, but keep in mind that Toshiba transistors (2SAxxxx / 2SCxxxx) have a reversed pin-out comparing to BD1xx or MJE2xx. You have to rotate the Toshiba transistors 180 degrees if you are going to try these. In other words, Toshiba transistors should be mounted on the position of the MOSFETs 
	

	
	
		
		

		
		
	


	




 ._

 

True, but among those recommended here:
Millett MAX BJT Transistors Diamond Buffer, there are a couple* of the Toshiba pairs that are normal pinouts.

Normal Pinouts:
 MJE243/MJE253
 BD137/BD138
 *2SC3421/2SA1358
 *2SC3422/2SA1359

Reverse Pinouts:
 2SC2238/2SA968
 2SC2344/2SA1011
 2SC5171/2SA1930


----------



## tomb

Quote:


  Originally Posted by *MrMajestic2* /img/forum/go_quote.gif 
_Cool, Ill give it a try. Wonder if I can find a taller one for the Mosfets._

 

Note the edit up there.


----------



## MrMajestic2

Quote:


  Originally Posted by *MrMajestic2* /img/forum/go_quote.gif 
_Cool, Ill give it a try. Wonder if I can find a taller one for the Mosfets._

 


 To answer my own question:
http://www.mouser.com/search/product...532-531202B25G

 Good thing I have a tall case 
	

	
	
		
		

		
		
	


	




 Edit, Doh didnt see your edit Tom


----------



## Ferrari

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_True, but among those recommended here:
Millett MAX BJT Transistors Diamond Buffer, there are a couple* of the Toshiba pairs that are normal pinouts._

 

Yeah correct! The Toshiba 2SC3421/2SA1358 and 2SC3422/2SA1359 are indeed normal pinouts.
 I have some 2SC3422/2SA1359 (with your help) in my parts bin but never have the opportunity to try it out.
 The 2SC2238/2SA968 I used are reversed pinouts, but not all 2SC/2SA type as I thought.


----------



## MrMajestic2

Quote:


  Originally Posted by *Ferrari* /img/forum/go_quote.gif 
_cetoole, I am aware of the magnetic field problem, especially the EI core type.
 The implementation is changed a bit: the 30V/1A EI core power transformer, AC line filter and fuse are now located in a separate "wallwart" to minimize magnetic field interference. Also the PSU heatsink is upsized to 2" and is sufficient for use at 30VDC (also due to the unload voltage of this transformer is ~2 Volt lower than the toroid I used before).




_

 

Whats the transformers unloaded voltage? Im currently considering going your route as well with an external box. I have either 2x12 volts, which is 2x14,6 unloaded or 2x15 volts at 2x18,3 unloaded.


----------



## Ferrari

The unload secondaire voltage of the transformer I used here is ~ 2x17.5V (~35V).


----------



## MrMajestic2

Quote:


  Originally Posted by *Ferrari* /img/forum/go_quote.gif 
_The unload secondaire voltage of the transformer I used here is ~ 2x17.5V (~35V)._

 

Aha, ok, I guess my 2x18,3 would work then.


----------



## scooot

Anyone looking for tubes and tube sockets should try Roy from the-radio-tube-supply-company on ebay, he is incredibly helpful and can order in any kind of tube for you.

 Oh and props to cetoole, Tomb and and n_maher for finding yet another way for me throw cash at this hobby, you guys have done a spectacular job with this (the website is fantastic) 
	

	
	
		
		

		
			





.


----------



## bperboy

So has anyone heard K701 with the max? How does it compare to the HD580s?


----------



## MrSlacker

If I use the recommended case, will the tubes stick out from top?


----------



## TBomb06

Quote:


  Originally Posted by *MrSlacker* /img/forum/go_quote.gif 
_If I use the recommended case, will the tubes stick out from top?_

 

Yes, they will.


----------



## bperboy

Quote:


  Originally Posted by *TBomb06* /img/forum/go_quote.gif 
_Yes, they will._

 

I just leave the top cover off.


----------



## MrSlacker

Thanks! The reason I asked is because I am planning my case and have some cool ideas for it.

 Also, people who can not do their own case work, are there any companies that do it?

 Thanks again.


----------



## scooot

You can buy pre-made cases and create custom front panels for those cases to your liking.
 Front Panel Express in the company most use for making the panels, website is http://www.frontpanelexpress.com/


----------



## MrMajestic2

Hmm, the Vishay dales are going like hotcakes at Mouser. The 221ohm is on order now 
	

	
	
		
		

		
		
	


	




 I will have to replace it with something else. Is it crucial that it is the 1/8watt or can it be a 1/10watt? By the way, its RB6 & RB7 in the Mosfet Diamond Buffer.

 This is the replacement: http://www.mouser.com/search/Product...71-RN55C-F-221


----------



## ericj

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_As long as the components will take it, higher voltage is always better - less current, less heat, etc. for the same power. The tubes will take 30, so go for it. 24V is fairly anemic for the MAX, MOSFETs or not._

 

The tubes will take 30v B+, but the nominal rating of the filaments is 12.6v. 

 Since these are car radio tubes, we can reasonably assume that the filaments were designed with the knowledge that they would often see as much as 13.8v in a "12 volt" car with the alternator going full out, but generally not more than that. 

 Running the heaters at 15v could potentially limit the lifespan of the tube (by weakening the filament) - by how much i do not know. 

 27v seems like a reasonable recommended voltage for the board.


----------



## Ferrari

If can remember the Max board included a heater resistor (R1). 
 This resistor is used to limit the voltage to the heaters when 30VDC supply voltage is used.
 Take R1 = 20Ω, DC voltage will low down to 27V (theoretically).


----------



## tomb

Yes, Ferrari - you are correct. The MAX includes the heater resistor R1 specifically for the purpose of running the amp at 30VDC, while limiting the voltage to the heaters.

 Sizing the resistor is covered in great detail on the MAX website, but you have it essentially right - 10 or 20 ohms protects the heaters all the way from 24VDC to 30VDC power supplied - for both minimum _and_ maximum heater voltages.

MAX ->Tweaks ->Heater Resistor


----------



## cotdt

what about the BD139/BD140?


----------



## tomb

Quote:


  Originally Posted by *cotdt* /img/forum/go_quote.gif 
_what about the BD139/BD140?_

 

_"slim sound, a little on the bright side ..."_ - Steinchen. In fact, every description I've heard/read of that pair in _any_ amp - when compared with other options - is "overly bright."

 EDIT: This is blasphemy probably, but I don't know why some of our DIY designers continue to specify the BD139/140 pair. The MJE's sound better and also have that rep over on DIYaudio. A recent new portable prototype was even described as "bright" by its designer with those trannies. Even cetoole used the designation in his base MAX schematic, but the other given choices are better - even other BD's not in that series. Of course, the Toshiba's and Sanyo's sound better than either.


----------



## MrMajestic2

Quote:


  Originally Posted by *MrMajestic2* /img/forum/go_quote.gif 
_Hmm, the Vishay dales are going like hotcakes at Mouser. The 221ohm is on order now 
	

	
	
		
		

		
		
	


	




 I will have to replace it with something else. Is it crucial that it is the 1/8watt or can it be a 1/10watt? By the way, its RB6 & RB7 in the Mosfet Diamond Buffer.

 This is the replacement: http://www.mouser.com/search/Product...71-RN55C-F-221_

 

Maybe I should stay on the safe side and get the 1/4watt instead. Will the RN60 package fit on the MHM board?

l.aspx?R=RN60D2210FB14virtualkey61300000virtualkey 71-RN60D-F-221


----------



## tomb

Quote:


  Originally Posted by *MrMajestic2* /img/forum/go_quote.gif 
_Maybe I should stay on the safe side and get the 1/4watt instead. Will the RN60 package fit on the MHM board?_

 

Except where a higher wattage is called for, NO.

 Just curious - what are they running out of and when is the next shipment date?


----------



## MrMajestic2

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Except where a higher wattage is called for, NO.

 Just curious - what are they running out of and when is the next shipment date?_

 


 Just the 221ohm for the RB6/RB7, delivery date August 27 
	

	
	
		
		

		
			





 . So you're saying that the RN60 wont fit, crap.


----------



## tomb

Quote:


  Originally Posted by *MrMajestic2* /img/forum/go_quote.gif 
_Just the 221ohm for the RB6/RB7, delivery date August 27 
	

	
	
		
		

		
		
	


	




 . So you're saying that the RN60 wont fit, crap._

 

OK. The 200ohms or 215ohms is a reasonable option. The ratio of RB6/RB7 with RB4/RB5 is what's important: 2 to 1. However, RB4/RB5 was already a compromise for availability convenience and should've been 110ohm, not 100ohm (technically speaking). So, 200 or 215 for RB6/RB7 is actually closer to the 2 to 1 ratio (200ohm is exact). You don't want to stray too far from the 220 value, but either one is probably OK in this instance.


----------



## MrMajestic2

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_OK. The 200ohms or 215ohms is a reasonable option. The ratio of RB6/RB7 with RB4/RB5 is what's important: 2 to 1. However, RB4/RB5 was already a compromise for availability convenience and should've been 110ohm, not 100ohm (technically speaking). So, 200 or 215 for RB6/RB7 is actually closer to the 2 to 1 ratio (200ohm is exact). You don't want to stray too far from the 220 value, but either one is probably OK in this instance._

 


 Oh cool, the 200ohm is available in large stocks. Gotta get my order in gear before anything else goes runs out 
	

	
	
		
		

		
		
	


	




 Thanks Tom.


----------



## bperboy

Yes, RN60s do NOT fit in most cases. I tried to use some that I had on hand already, and it came out looking pretty bad.


----------



## MrMajestic2

Quote:


  Originally Posted by *bperboy* /img/forum/go_quote.gif 
_Yes, RN60s do NOT fit in most cases. I tried to use some that I had on hand already, and it came out looking pretty bad._

 

Thanks, Ill give the 200ohmer a go instead of forcing the RN60 in there.


----------



## naamanf

Those boards need to hurry up and get done. I threw together some cocobolo end plates for the next MAX.


----------



## bperboy

Quote:


  Originally Posted by *naamanf* /img/forum/go_quote.gif 
_Those boards need to hurry up and get done. I threw together some cocobolo end plates for the next MAX. 




_

 


















 OMG so nice!


----------



## fordgtlover

^ That's beautiful. 

 Would you be flattered or offended if I borrowed from your idea?


----------



## naamanf

Not at all. The tree did all the hard work, I just cleaned it up a bit


----------



## MrMajestic2

I have put in the orders for most parts now, cant wait to build this sucker


----------



## vixr

WOW! have you guys looked at the MAX site lately? its just waaay too cool... thanks tomb. You are what makes DIY great.


----------



## MrMajestic2

Quote:


  Originally Posted by *vixr* /img/forum/go_quote.gif 
_WOW! have you guys looked at the MAX site lately? its just waaay too cool... thanks tomb. You are what makes DIY great._

 

Yeah, thats practically my startup page 
	

	
	
		
		

		
		
	


	




 Go Team MAX!!


----------



## tomb

Thanks guys! Still working on it, too - I finally finished pics of the casework - at least how I did it - and will be uploading the rest and adding the accompanying text soon.


----------



## MrMajestic2

Am I correct in the assumtion that the CR1 Caps are supposed to be rated for at least twice the voltage of the AC input? I think I made a boo-boo in my BOM


----------



## tomb

Quote:


  Originally Posted by *MrMajestic2* /img/forum/go_quote.gif 
_Am I correct in the assumtion that the CR1 Caps are supposed to be rated for at least twice the voltage of the AC input? I think I made a boo-boo in my BOM 
	

	
	
		
		

		
		
	


	


_

 

Not necessarily. All that's really required is that their rating exceed the potential of the rectified AC input. That has to be tempered by the catalog sizes of the caps and by the voltage potential of an unloaded/rectified AC supply, in the worst case.

 50V was chosen because these caps are in front of the regulator, and will see the full rectified voltage of a power supply. 35V, the next lower rating, when adding 1.4 diode drop and dividing by 1.4 recitification increase (calculating recitifed voltage in reverse), results in 26V. It's more than likely that an unloaded 24VAC walwart will produce _more_ than 26V, so a 35V rating does not give sufficient safety factor. The 50V rating was selected.

 This does not even take into account the fact that the MAX was designed for the potential of a 30V regulated supply, which would require an even higher starting AC voltage. However, a 30VAC walwart/xfmr results in approximately 40V under load, perhaps 46V lightly loaded in the extreme case. So, 50V is still adequate.


----------



## MrMajestic2

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Not necessarily. All that's really required is that their rating exceed the potential of the rectified AC input. That has to be tempered by the catalog sizes of the caps and by the voltage potential of an unloaded/rectified AC supply, in the worst case.

 50V was chosen because these caps are in front of the regulator, and will see the full rectified voltage of a power supply. 35V, the next lower rating, when adding 1.4 diode drop and dividing by 1.4 recitification increase (calculating recitifed voltage in reverse), results in 26V. It's more than likely that an unloaded 24VAC walwart will produce more than 26V, so a 35V rating does not give sufficient safety factor. The 50V rating was selected.

 This does not even take into account the fact that the MAX was designed for the potential of a 30V regulated supply, which would require an even higher starting AC voltage. However, a 30VAC walwart/xfmr results in approximately 40V under load, perhaps 46V lightly loaded in the extreme case. So, 50V is still adequate._

 

I actually undersized it with a 35V so I guess I have to change that one. Im planning on running my "boutique" Max at 30VAC so this is no good at all. Dont know what I was thinking. Thanks for the reply.


----------



## ericj

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Not necessarily. All that's really required is that their rating exceed the potential of the rectified AC input. That has to be tempered by the catalog sizes of the caps and by the voltage potential of an unloaded/rectified AC supply, in the worst case.

 50V was chosen because these caps are in front of the regulator, and will see the full rectified voltage of a power supply. 35V, the next lower rating, when adding 1.4 diode drop and dividing by 1.4 recitification increase (calculating recitifed voltage in reverse), results in 26V. It's more than likely that an unloaded 24VAC walwart will produce more than 26V, so a 35V rating does not give sufficient safety factor. The 50V rating was selected._

 

You aluded to, but didn't exactly spell out, there is also the issue of transformer regulation. 

 A given transformer may vary as much as 14% (in really awful cases) from it's nominal rating when unloaded (or overloaded).

 So, take a 30vac transformer, figure a worst-likely-case scenario of 10% regulation, that's 33v RMS, subtract diode drop of 1.4v = 31.6vac RMS, multiply by 1.414 for peak-to-peak full-wave rectified voltage of 44.6 VDC. When completely unloaded. Your actual mileage may vary. 

 So, yes. Caps with a working voltage rating of 50v are necessary in this position.

 If you had a 36vac transformer, the same math leads us to a peak to peak voltage of up to 54vdc, in which case you'd have to go to the next step up and use 63wvdc caps. You could probably get away with 50wvdc caps because this is the *working voltage we're talking about, and it will almost always be considerably below 50v, but for safety and reliability, get the higher rated cap.

 Edit: "When completely unloaded" also includes the initial turn-on spike.


----------



## UglyJoe

Hey guys, I am putting together my BOM for the Max. I've read through the thread here and looked at all of the cap advice, put I think some of it has been a little bit contradictory (not on purpose, and maybe not at all, but I'm fairly new at this).

 For the CA2L/R caps I was planning on using BG NX 1000uF/25V caps

 For the CA7L/R caps I was planning on using BG NX 680uF/35V caps

 For the CA8/CA9 positions I am going with the BG NX HiQ .47uF/50V caps

 Finally for CA4/CA5 I am going with Nichicon FG 1000uF/35vdc caps.

 Here is my question; I am currently using Grado phones, and based on the recent conversation about 32 ohm loads I wasn't sure if the NX 680uF caps were the right thing for CA7, based mostly on tomb's post #479. Any help or comments would be appreciated.


----------



## tomb

Quote:


  Originally Posted by *UglyJoe* /img/forum/go_quote.gif 
_Hey guys, I am putting together my BOM for the Max. I've read through the thread here and looked at all of the cap advice, put I think some of it has been a little bit contradictory (not on purpose, and maybe not at all, but I'm fairly new at this).

 For the CA2L/R caps I was planning on using BG NX 1000uF/25V caps

 For the CA7L/R caps I was planning on using BG NX 680uF/35V caps

 For the CA8/CA9 positions I am going with the BG NX HiQ .47uF/50V caps

 Finally for CA4/CA5 I am going with Nichicon FG 1000uF/35vdc caps.

 Here is my question; I am currently using Grado phones, and based on the recent conversation about 32 ohm loads I wasn't sure if the NX 680uF caps were the right thing for CA7, based mostly on tomb's post #479. Any help or comments would be appreciated._

 

Those are all good choices except for CA8/CA9. I don't think you can get a 1000uF, 35V BG NX, so the 680uF will still get you down below 10Hz for the corner frequency, so you should have plenty of good bass.

 As for the CA8/CA9, I have consulted with a couple of very respected experts and their considered opinion is that a good Auricap, Vitamin Q, or similar high-quality film or PIO cap is still much better than the double BG-bypass method. I've been convinced enough about this that I changed my mind on trying just what you descirbe, and will probably go the Auricap/Vitamin Q route. That's me, though, and I've tried neither method yet, so take your pick. Just be careful that what you purchase will fit in the prescribed board space - there are height limitations as well, depending on which slot you locate the board.


----------



## UglyJoe

Which Auricaps would you suggest, and can I get them from Parts Connexion? The only ones I see on their website are AURICAP-62035, .47uF/400V. I am not sure that I am looking in the right place.


----------



## tomb

Quote:


  Originally Posted by *UglyJoe* /img/forum/go_quote.gif 
_Which Auricaps would you suggest, and can I get them from Parts Connexion? The only ones I see on their website are AURICAP-62035, .47uF/400V. I am not sure that I am looking in the right place._

 

That would be my choice, but I haven't taken a close look at the measurements to see if they will fit. So, please make sure that will be OK before acting on my suggestion. The C9 position - no doubt - but the C8 position is more crowded. It's going to be a creative fit there - maybe a tombstone is the answer, I'm not sure.


----------



## tomb

I hate to contradict again, but since you appear to be spending all that money anyway - 
	

	
	
		
		

		
			








 The 0.47 BG NX's are only $8 for four of them. That's not much to spend to try both and decide which you like best.

 One thing's for sure - just Nichicon Muse ES's and Wima films sound very, very good - so we're talking lots of money for differences that are probably just in the margins.

 Again, wish I could give you a more definitive and less contradictory answer, but I haven't built a BG version yet, either.


----------



## UglyJoe

Well, I figured if I was gonna go for it I was gonna go all out.... sorry about my wallet and all that rot 
	

	
	
		
		

		
		
	


	




 BTW, those Auricaps appear to be approx. 15mm by 20mm.


----------



## cetoole

Well, I received an email from PCBNet today, stating that my order with them had shipped. They also charged my account. The shipment is due to arrive friday via Fedex, and consists of two boxes, one weighing 44lbs, and the other 43lbs. This sure is going to be interesting.

 UglyJoe, the bypass caps shown here in CA8/9 are 13mm x 27mm, 0.47uf PIO. There definitely should be space for your Auricaps mounted in this style.


----------



## UglyJoe

WOOT


----------



## soloz2

I was planning on using the Nichicon Muse caps, but am having difficulty finding ES non-polar caps with 35 or 50v ratings. Where are people getting their Muse caps from? Or do you have to use the KZ polar series?


----------



## TBomb06

Quote:


  Originally Posted by *soloz2* /img/forum/go_quote.gif 
_I was planning on using the Nichicon Muse caps, but am having difficulty finding ES non-polar caps with 35 or 50v ratings. Where are people getting their Muse caps from? Or do you have to use the KZ polar series?_

 

I got mine from Handmade Electronics and Percy Audio...I guess it depends on what size you are talking about. I assume that non-polar is the same as bipolar.


----------



## TBomb06

Quote:


  Originally Posted by *cetoole* /img/forum/go_quote.gif 
_Well, I received an email from PCBNet today, stating that my order with them had shipped. They also charged my account. The shipment is due to arrive friday via Fedex, and consists of two boxes, one weighing 44lbs, and the other 43lbs. This sure is going to be interesting.

 UglyJoe, the bypass caps shown here in CA8/9 are 13mm x 27mm, 0.47uf PIO. There definitely should be space for your Auricaps mounted in this style.



_

 

Sweet! I can't wait, but I definitely don't envy the task ahead of you. Thanks again for all your work!

 One kind of random question...is there something on the jumpers you used in the RB8L/R and RB9L/R? Looks like small heatshrink or something...


----------



## tomb

Quote:


  Originally Posted by *soloz2* /img/forum/go_quote.gif 
_I was planning on using the Nichicon Muse caps, but am having difficulty finding ES non-polar caps with 35 or 50v ratings. Where are people getting their Muse caps from? Or do you have to use the KZ polar series?_

 

Good question. The 470uF @ 35V Nichicon Muse ES is carried at BDent.com:
http://www.bdent.com/search/part.jsp...um=UES1V471MHM
 They also happen to be a great source for the 2SC/2SA high quality Toshiba and Sanyo DB output transistors (except the 2238 pair). Unfortunately, this is the only ES they carry. 
	

	
	
		
		

		
		
	


	




Michael Percy Audio also carries the 470uF, 35V ES, which happens to be great choice for CA7.

Handmade Electronics is the best source of other ES's, including the 1000uF, 16V which is a perfect choice for CA2. They carry a number of ES's, but not all of them and as you noticed - not the 470uF,35V version. Strangely, they carry all of the KZ's.

 I don't know why this strange separation in availability from vendor to vendor. I can confirm that the ES's are worth the effort, though, and any of those vendors above have plenty to pick from of other things as well.


 EDIT: That tubing on Colin's Vitamin Q's is teflon tubing. It's availble from the boutique vendors mentioned above and from PartsConnexion. It works better than heat shrink (what I use), since it won't melt while you're soldering the leads.


----------



## UglyJoe

Tom, where do you get Vitamin Q's? I assume your talking about Colin's CA8 and CA9 caps, and I like the looks of those (never seen a vitamin q before) and the teflon tubing he used for the CA8 positions. The resistors RB8 and RB9 are also odd looking, did he use some kind black teflon tubing on those as well?


----------



## MrMajestic2

Quote:


  Originally Posted by *UglyJoe* /img/forum/go_quote.gif 
_Tom, where do you get Vitamin Q's? I assume your talking about Colin's CA8 and CA9 caps, and I like the looks of those (never seen a vitamin q before) and the teflon tubing he used for the CA8 positions. The resistors RB8 and RB9 are also odd looking, did he use some kind black teflon tubing on those as well?_

 

Im pretty sure that RB8 and RB9 are not actual resistors but jumpers covered in heatshrink.


----------



## tomb

Quote:


  Originally Posted by *MrMajestic2* /img/forum/go_quote.gif 
_Im pretty sure that RB8 and RB9 are not actual resistors but jumpers covered in heatshrink._

 

YEP. RB8 and RB9 are jumpered on the BJT version.

 Vitamin Q's are available at some tube vendors, but the best place - believe it or not - is ebay. There's a bunch in different sizes that sell for about $25 per 20:

Capacitor 0.47mfd 100vdc Vitamin Q (20)


----------



## MrMajestic2

Just realized that I forgot to order extra 2N5087/2N5088 when I ordered from Mouser. Just praying that there will be enough for matching. I ordered for three MHMs, but I totally missed upping the amount for those components. Doh. Might get some extra from Digikey since Im ordering from there for my Mini3 and PPAS projects.


----------



## tomb

There are selections of the 2n5088 and 2n5087 that are less than *$3 per 100*. If you are even considering building more than one MAX, go ahead and order a hundred of each.


----------



## FallenAngel

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_YEP. RB8 and RB9 are jumpered on the BJT version.

 Vitamin Q's are available at some tube vendors, but the best place - believe it or not - is ebay. There's a bunch in different sizes that sell for about $25 per 20:

Capacitor 0.47mfd 100vdc Vitamin Q (20)_

 

If anybody is planning to get these and doesn't need the full batch of 20, I would love to split the batch 
	

	
	
		
		

		
			





 PM or post here if you're getting them. Hopefully I don't thrown this off topic too much


----------



## MrMajestic2

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_There are selections of the 2n5088 and 2n5087 that are less than *$3 per 100*. If you are even considering building more than one MAX, go ahead and order a hundred of each._

 

Yeah, that was the plan, but in all the messing around with orders I missed this point. Double Doh.


----------



## MrMajestic2

Quote:


  Originally Posted by *FallenAngel* /img/forum/go_quote.gif 
_If anybody is planning to get these and doesn't need the full batch of 20, I would love to split the batch 
	

	
	
		
		

		
		
	


	




 PM or post here if you're getting them. Hopefully I don't thrown this off topic too much 
	

	
	
		
		

		
		
	


	


_

 

You've got PM dude


----------



## UglyJoe

A couple of questions for you guys. Is there any *real* benefit to using higher quality caps in the power supply for the Max? And by real I mean the same thing as the slight improvements that the BG and other caps give over the Muses. I know spending more on the caps than the entire rest of the amp is a little silly, but its satisfies my placebo. If so, what caps would you guys suggest (I think I read somewhere that BG's are not good PS caps)?

 Secondly, I need to get a better source for the Max. I would like to build a really nice USB DAC, and was wondering which one is the best option... the DIY DAC scene doesn't seem to me to be nearly as "clean cut" as the amp scene.

 Thanks

 EDIT: BTW, has anyone tried Mundorf's for the CA8/CA9 caps?


----------



## tomb

Quote:


  Originally Posted by *UglyJoe* /img/forum/go_quote.gif 
_A couple of questions for you guys. Is there any *real* benefit to using higher quality caps in the power supply for the Max? And by real I mean the same thing as the slight improvements that the BG and other caps give over the Muses. I know spending more on the caps than the entire rest of the amp is a little silly, but its satisfies my placebo. If so, what caps would you guys suggest (I think I read somewhere that BG's are not good PS caps)?

 Secondly, I need to get a better source for the Max. I would like to build a really nice USB DAC, and was wondering which one is the best option... the DIY DAC scene doesn't seem to me to be nearly as "clean cut" as the amp scene.

 Thanks

 EDIT: BTW, has anyone tried Mundorf's for the CA8/CA9 caps?_

 

I don't think you can do better than Panasonic FM's, FC's or Nichicon UPW's. Boutiques are pretty much wasted in the PS and out of the signal path, IMHO.

 Building your first DAC is an easy answer: the Alien DAC. JRossel is selling kits from his Glass Jar Audio site. MASantos is even selling finished versions with some nice case treatment (in a Head-Fi sponsored thread). I use an M-Audio Transit most of the time with my MAX (haven't built my Alien's yet), and some people say the quality is similar, or a bit better with the Alien. The Transit is great, but I practically stopped listening to mp3's. They just sounded like cr*p on the MAX compared to lossless. Playing a regular CD through the PC's CD Drive and through the Transit was 100% better than any mp3. So, I tried some FLAC files. They sound as good as CD's and I've been using them ever since.

 Can't help you with opinions on the Mundorfs - too expensive for me, I think.


----------



## ruZZ.il

2x on jrossels alien dac kit. really organized little bits. works great, was a fun build and.. i dont really want to use my soundcard or nano's line out. the dac far surpasses that 
	

	
	
		
		

		
		
	


	




 meanwhile... I need to start collecting my MHM bits 
	

	
	
		
		

		
		
	


	




 or speak to jeff, I hear he's packaging things up ? great community this...


----------



## Ferrari

Quote:


  Originally Posted by *ruZZ.il* /img/forum/go_quote.gif 
_... or speak to jeff, I hear he's packaging things up ? great community this..._

 

Actually he is offering a full kit for the MH Max.


----------



## ferds

I'm really excited to start building my millet maxed.. just received my parts from farnell.. 

 But I'm wondering if anyone compared it with MF X-can v2/v3? 

 thanks


----------



## odoe

Oh man. I'm going to have to send Jeff an email.


----------



## babbkutz@comcast

sitting here hoping for word that the PCBs have started shipping........(or more likely CT has them in hand!)


----------



## cetoole

I have received the PCBs and padded envelopes, and purchased the shipping and return labels. I expect to have the first batch out Monday.


----------



## ruZZ.il




----------



## naamanf

Quote:


  Originally Posted by *cetoole* /img/forum/go_quote.gif 
_I have received the PCBs and padded envelopes, and purchased the shipping and return labels. I expect to have the first batch out Monday._


----------



## MrMajestic2

Quote:


  Originally Posted by *cetoole* /img/forum/go_quote.gif 
_I have received the PCBs and padded envelopes, and purchased the shipping and return labels. I expect to have the first batch out Monday._

 

Will you marry me Cetoole


----------



## Ech0

Quote:


  Originally Posted by *cetoole* /img/forum/go_quote.gif 
_I have received the PCBs and padded envelopes, and purchased the shipping and return labels. I expect to have the first batch out Monday._

 

WooooHooooooo!


----------



## MrMajestic2

Parts are slowly trickling in for my Max builds. Man, the Black Gate NX-HiQ 0.47uf/50v are tiny. Half the fun is sourcing parts and unpacking boxes, right?


----------



## amphead

Quote:


  Originally Posted by *cetoole* /img/forum/go_quote.gif 
_I have received the PCBs and padded envelopes, and purchased the shipping and return labels. I expect to have the first batch out Monday._

 

My brain is salivating at the whole idea of building this beauty!


----------



## kklee

All of my parts have come in, now all I need are the PCB's and I can get building!


----------



## Troyhoot

The Joys of matching transistors 
	

	
	
		
		

		
		
	


	




 Been working on these for couple days now and I have a couple concerns/questions.

 I have ran through the 5088's twice and they seemed to level out nicely after the second run. I think i can make 3 pairs within 1 of each other. Going to run through the close ones at least a couple times before final assembly im sure.

 Now the 5087's, after 3 runs they are still going down each test. So im a little concerned if they will ever level out.

 So my questions.. 
 1. How many times is resonable to test the 5087 to get them to level out. 
 2. How close do the sets need to be to each other ? ie: can the 2 sets for the ccs be 20-50 points off the 3 sets for the buffers ? 

 Since my parts are starting to trickle in im getting excited. Almost as excited as I am about my wife being 8 1/2 months pregnant 
	

	
	
		
		

		
		
	


	




 Might get to work on it before we go to the hospital ahaha At least it will give me something to do while the baby takes cat naps. Just hope percy gets back from vaction this weekend so I can get my caps and a few resistors ordered.


----------



## tomb

Quote:


  Originally Posted by *Troyhoot* /img/forum/go_quote.gif 
_The Joys of matching transistors 
	

	
	
		
		

		
		
	


	




 Been working on these for couple days now and I have a couple concerns/questions.

 I have ran through the 5088's twice and they seemed to level out nicely after the second run. I think i can make 3 pairs within 1 of each other. Going to run through the close ones at least a couple times before final assembly im sure.

 Now the 5087's, after 3 runs they are still going down each test. So im a little concerned if they will ever level out._

 

Don't leave them in forever. Yes, they change as the small amount of current from the meter is applied, but a couple of seconds should be enough, I think. The idea is to "match," and if you start holding some in longer, then you should do the others that way, too. Pretty soon it may get out of control and you'd be better off not matching at all. Extreme, for sure, but just trying to illustrate the goal. Ultimately, the large output blocking caps are going to stop all offset.

 The most important matching is actually the two in the CCS for each tube, IMHO.

  Quote:


 So my questions.. 
 1. How many times is resonable to test the 5087 to get them to level out. 
 

I think twice is enough.

  Quote:


 2. How close do the sets need to be to each other ? ie: can the 2 sets for the ccs be 20-50 points off the 3 sets for the buffers ? 
 

Sounds pretty close to me. I've seen the complementary pairs no closer than about 100 before (should've bought more). You do want to pick two sets that are the closest, however. Yes, the CCS's have no relationship to the DB's. There is no need to get them the same. As mentioned above, the two transistors for each CCS are probably the most important ones to match (among the four) on the whole board, however.

  Quote:


 Since my parts are starting to trickle in im getting excited. Almost as excited as I am about my wife being 8 1/2 months pregnant 
	

	
	
		
		

		
		
	


	




 Might get to work on it before we go to the hospital ahaha At least it will give me something to do while the baby takes cat naps. Just hope percy gets back from vaction this weekend so I can get my caps and a few resistors ordered. 
 

I hope you get it built before 9 mos is up. You may not have much of a chance for awhile after that. Or maybe the 3rd or 4th time you get up during the night, you can work on the MAX instead of taking the trouble to go back to bed. 
	

	
	
		
		

		
		
	


	




 Seriously, best wishes on the baby.


----------



## Troyhoot

Thanks TomB. That helped alot. I was leaving them in till the meter stoped dropping instead of just a few seconds. Made a big difference. Now I have plenty for the CCS at 347, and the buffers at 351 and 381 respectively. Thats about as close as I could get with the two types with the 60 each I ordered.

 My tubes came in from RadioDaze today too. Real pleased with them as a vender. I asked for same brand sets and they sent me RCA 12fk6, Raytheon 12ae6a, and Tung-Sol 12fm6. Shipping was fast. Packaging was great too. They answered an email in less then an hour before my order too. Ill use them again im sure.


----------



## tomb

Wow - those trannies all sound really close. You won't have any trouble getting those DB's balanced out!

 Yes, the Radio Daze guys are pretty good. Seeing their packaging when my tubes were delivered for the first time sold me, too! (besides their price and selection, which was already great)


----------



## babbkutz@comcast

tomb......2 questions relating to the casework on the MAX site......(1) part used for the mini plug (female) on the front panel? and (2) parts used for the test points on the rear.......details on connection to the board........Thanks


----------



## tomb

Quote:


  Originally Posted by *babbkutz@comcast* /img/forum/go_quote.gif 
_tomb......2 questions relating to the casework on the MAX site......(1) part used for the mini plug (female) on the front panel?_

 

Mouser #161-7400-EX. Note that this is actually a "commodity" part and is sold under many labels, including Philmore. I've bought many of them at Fry's.
  Quote:


 and (2) parts used for the test points on the rear 
 

Mouser Part #530-105-0801-1. This one is white, there are different part numbers for other colors. Some may call these cheap - and they are - but they are entirely functional for me, are totally insulated being plastic, and have a crimp/solder connection. Higher quality tip jacks sometimes used by others have one of those p2p studs that has to be wire wrapped - yuck.

 I actually bought these in bulk from a local electronics store that was relinqushing their storefront building. I only got the white ones, and then dyed them in the sink with grocery store RIT dye - could've made stripes if I had masked them properly. 
	

	
	
		
		

		
		
	


	




  Quote:


 .......details on connection to the board........Thanks 
 

I have been remiss in finishing pics and text on wiring details - I will try to complete that today. If you are referring to the specific wiring for these tip jacks, I simply soldered them into the bottom of the board at all the test positions. The center gray jack is the ground, the voltage adjust jack is off to the side away from the others. Then the first two on either side are the tube bias - L/R. Then DB bias - L/R, A and B. Of course, you simply use the L or R tube bias test point as the reference for the DB test points for L or R, respectively.

 Others have remarked that there's not enough room between the jacks for typical DMM test probes, but all you need do is plug in the COM jack all the way into the requisite tip jack. Then, even if the test point jack is immediately adjacent, only a partial insertion is plenty to make a measurement - and to stay in place.

 The downside to this is that the tip jacks are soldered to the board, and are installed into the backplate from the outside. This means the backplate is forever attached to the bottom of the board. Accordingly, I built in plenty of slack to remove any issues with ever removing the board, endplate, etc. as necessary:





 This pic is on the MAX website at "Construction -> Casework -> Wiring&Assembly - Pt 3".

 EDIT: I actually positioned the tip jacks a little too close to the bottom of the case. The jacks are so close that the nuts match up flat-to-flat. Unfortunately, the nut corners were far enough down that they were touching the bottom of the case and interfered with closing everything up. I sort of forced the nuts into an inbetween position and finally got everything to fit. I think this happened because the metal is quite a bit thicker on the MAX Hammond case compared to smaller Hammond cases - the clearance was that close. I need to adjust the CAD file drawing on the site accordingly, so keep that in mind.


----------



## n_maher

Tom,

 That's just a heck of a clean build you did there. I start drooling every time I look at those pictures!


----------



## tomb

Thanks, Nate! That's high praise coming from the Uber Millett Guru himself. 
	

	
	
		
		

		
		
	


	




 EDIT: BTW, that B22 pic you put in Clutz's Amp section thread is incredible!


----------



## Blooze

Thanks Tom,

 I've got all the MAX pages printed off except the casework pages (which weren't done yet). I like to have the info on the bench in front of me when working on something.


----------



## amphead

Tom, I have had good luck using teflon/high temp wire in my other builds, say 22 awg. You probably mention somewhere else what you recommend. Do you like teflon wire? Stripping is more of a chore, but audio quality sure seems to benefit. Is it tinned with tin or silver as someone else suggested?


----------



## tomb

Quote:


  Originally Posted by *amphead* /img/forum/go_quote.gif 
_Tom, I have had good luck using teflon/high temp wire in my other builds, say 22 awg. You probably mention somewhere else what you recommend. Do you like teflon wire? Stripping is more of a chore, but audio quality sure seems to benefit. Is it tinned with tin or silver as someone else suggested?_

 

Yep - most of what I use is the silver-coated teflon wire from Navships on ebay: 22 ga. Most is pretty easy to work with. I got some white stuff from him, though, that seems to have insulation as hard and stiff as wood. 
	

	
	
		
		

		
			





 EDIT: I got some orange stuff from a local retailer that sounds similar to what you posted about in the other thread. It's actually my favorite and is much more flexible than even the best Navships stuff - still 22ga and teflon. So there's better stuff out there, but buying small quantities is difficult unless you catch a nice local shop.

 Handmade Electronics carries some Belden teflon silver-coated wire that you can buy in lengths as small as 5 ft:
http://www.hndme.com/productcart/pc/...?idCategory=19
 BTW, they are a great source for Muse ES's or KZ's, Kiwame's, etc.


----------



## amphead

Thanks for the input. I am lucky enough to get any amount I want for peanuts. The salespeople at my source are somewhat limited in their knowledge of what it is. They charge me $0.01 extra for teflon wire per foot.


----------



## Televator

hi all, first of all I'd like to compliment cetoole for the beautiful amp and tomb for a slick looking and very informative website and for all the builders and pic-posters as you've all given me something to daydream about!

 secondly, I hate myself for missing the group buy... I've been looking to get into DIY for a while now, but as I had a hellish time at work lately I kinda figured 'now wasn't the best of times to get started' and I quit reading the DIY section here mostly. Now things have calmed down and I can't wait to get my hands dirty. The Max really is the sort of thing I wanted to go for (evidently after a couple of learning projects like a cmoy, alien dac, pimeta, ...) but I missed the groupbuy completely 
	

	
	
		
		

		
		
	


	




 so after this long intro, is there someone who has got a few extra boards that they won't be building? I am looking for two boards as I would love to build one for a good friend who's helped me through some recent rough times as well.

 Thanks for reading!


----------



## tomb

Colin ordered somewhere around 30+ extra boards. That's not counting the multiples that many ordered who may decide not to build every one of them.

 In addition, we had talked about having another Group Buy around Christmas time, but that depends on a lot of factors: delivery of the first batch, several successful builds, user response, etc. Regardless, I can't imagine that you won't be able to get a board if you keep in touch.


----------



## Televator

great to hear that Tomb! I will certainly be browsing the DIY forums more now and reading up on all the great advice here (as well as drooling over the pics 
	

	
	
		
		

		
		
	


	




 )

 This thread is definitely bookmarked...


----------



## primer

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Colin ordered somewhere around 30+ extra boards. That's not counting the multiples that many ordered who may decide not to build every one of them.

 In addition, we had talked about having another Group Buy around Christmas time, but that depends on a lot of factors: delivery of the first batch, several successful builds, user response, etc. Regardless, I can't imagine that you won't be able to get a board if you keep in touch._

 

Would love one of these extra boards.


----------



## thunder

Speaking about wire, what is the reason for twisting 2 wire's or more together ? Also why do they use a coax style wire for some audio interconnects ?


----------



## tomb

Quote:


  Originally Posted by *thunder* /img/forum/go_quote.gif 
_Speaking about wire, what is the reason for twisting 2 wire's or more together ?_

 

Convenience mostly. It makes for a nicer looking build and keeps errant wires out of the way, allowing you to quickly access important parts of the board. Also, errant wiring has a tendency to go where you don't want it - wrapped around a tube or a heat sink, or stuck inbetween the case panels.[/quote]
  Quote:


 Also why do they use a coax style wire for some audio interconnects ? 
 

There is some suspicion that the signal wires may pick up interference if they are more than an inch or two long. Coax (or more accurately, _shielded cable_) can help protect against that. It's seldom that regular wire ever causes a problem, but using a shielded cable probably never hurts. I would guess that if you have a transformer in the vicinity, then interference is much more of a concern. It's often simply a personal preference.


----------



## thunder

In some amp build pic's, I have seen people using shielded wire going to the rca's on back panel's. Doe's the shield get soldered to the gnd ?


----------



## tomb

Quote:


  Originally Posted by *thunder* /img/forum/go_quote.gif 
_In some amp build pic's, I have seen people using shielded wire going to the rca's on back panel's. Doe's the shield get soldered to the gnd ?_

 

It depends on the amp and how the signal ground compares with the power ground. There is usually a difference between a DC ground and an AC power ground as well.

 Just a suggestion, but this type of question is not limited to the Millett MAX. You might post a separate thread and ask for answers to these questions from the general DIY section. I haven't used shielded wire and am a little uncertain on where/whether it should be connected myself.


----------



## adfinni

Hey tomb quick question

 What size are those alan key type bolts used to hold the front and back panels on, and can they be substituted straight for the screws that come supplied ??

 Also do you flip the front and back panel the opposite way so the countersunk side is touching the case, and allows those small alan key bolts be flush ?

 thanks


----------



## hellomai

Does anyone know how to match tubes? Or anywhere I can buy matched tube set? I have asked RadioDaze, and they can only provide "same brand" tube, but not enough 12FM6, 12AE6A, and 12FK6 to do a match.


----------



## vixr

Quote:


  Originally Posted by *adfinni* /img/forum/go_quote.gif 
_Hey tomb quick question

 What size are those alan key type bolts used to hold the front and back panels on, and can they be substituted straight for the screws that come supplied ??

 Also do you flip the front and back panel the opposite way so the countersunk side is touching the case, and allows those small alan key bolts be flush ?

 thanks_

 

I dont think the end panels are thick enough to allow countersinking of the allen head screws, to be truly flush...


----------



## tomb

Quote:


  Originally Posted by *adfinni* 
_Hey tomb quick question

 What size are those alan key type bolts used to hold the front and back panels on, and can they be substituted straight for the screws that come supplied ??

 Also do you flip the front and back panel the opposite way so the countersunk side is touching the case, and allows those small alan key bolts be flush ?

 thanks_

 

 Quote:


  Originally Posted by *vixr* /img/forum/go_quote.gif 
_I dont think the end panels are thick enough to allow countersinking of the allen head screws, to be truly flush..._

 

Vixr is correct, but the small counter sink on the endpanels works just fine as it is. Socket head cap screws are tough enough to buckle the endplate if you tighten down on it from the reverse side. There would be nothing backing the cap head up if you reversed it. I wouldn't do that.

 A 6-32 x 3/4" will go far enough to cover the length of the threads that a typical 6-32 tap will make. A 1" is too long and will be cutting on untapped metal. 1/2" will not make use of all the threads that are possible. I settled on 3/4" as the best fit. This is probably a good thing to do because the slots only provide a partial thread surface, anyway. The 3/4" length might change if you use a different endplate or forego the end bezel.

 EDIT: Yes, you have to tap the holes, but drilling is not required. This is detailed on the MAX website at Construction -> Casework -> Casework Part 1.


----------



## tomb

Quote:


  Originally Posted by *hellomai* /img/forum/go_quote.gif 
_Does anyone know how to match tubes? Or anywhere I can buy matched tube set? I have asked RadioDaze, and they can only provide "same brand" tube, but not enough 12FM6, 12AE6A, and 12FK6 to do a match._

 

Matching tubes has never really been necessary with the Millett, and the MAX is no different. The Millett design includes tube biasing, so you are able to set every tube exactly.

 Read the tube section on the MAX website. This is discussed a bit. Even brand matching is not critical. Only GE, RCA, and Sylvania made the tubes. Even then, RCA packaged GE's, GE packaged RCA's, and Sylvania's were packaged by many others such as Raytheon, DuMont, etc., along with the GE's and RCA's, too.

 Given a choice, buy the same brand, then try to match construction among the same tube designation. The website discusses the getter shape and position as the primary difference, but there are plate differences as well.

 In the end, however, none of it is that critical - it's more like discussing what color lettering/dot is used on an opamp.


----------



## ericj

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Read the tube section on the MAX website. This is discussed a bit. Even brand matching is not critical. Only GE, RCA, and Sylvania made the tubes. Even then, RCA packaged GE's, GE packaged RCA's, and Sylvania's were packaged by many others such as Raytheon, DuMont, etc., along with the GE's and RCA's, too._

 

It's true that there were only three factories cranking these out. 

 I need to line them up and take pictures, but, I'm pretty sure there are at least five, maybe six different internal constructions in my collection. So, there's *some reason to match at least the internal construction. 

 iirc i'm currently running triple-mica sylvania 12ae6a's.


----------



## adfinni

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Vixr is correct, but the small counter sink on the endpanels works just fine as it is. Socket head cap screws are tough enough to buckle the endplate if you tighten down on it from the reverse side. There would be nothing backing the cap head up if you reversed it. I wouldn't do that.

 A 6-32 x 3/4" will go far enough to cover the length of the threads that a typical 6-32 tap will make. A 1" is too long and will be cutting on untapped metal. 1/2" will not make use of all the threads that are possible. I settled on 3/4" as the best fit. This is probably a good thing to do because the slots only provide a partial thread surface, anyway. The 3/4" length might change if you use a different endplate or forego the end bezel.

 EDIT: Yes, you have to tap the holes, but drilling is not required. This is detailed on the MAX website at Construction -> Casework -> Casework Part 1._

 

Thanks, that's great info, even though ive solely used metric whilst studying degree (except some drilling and tapping in my 1st/2nd year), so all these imperial measurements need some more figuring out 
	

	
	
		
		

		
			





 I love the look of those bolts over the supplied countersunk bolts, and il look into getting a cheaky 6-32 tap.

 O and fantastic job in developing the site even further, so many more updated sections since i last checked. Right off to france for a a few weeks of sun as the flooding in england is horrific and i want a tan. See you lads in a bit, and hopefully when i get back in 2 weeks il have a little package with some pcbs sitting in the house


----------



## tomb

It seems fairly unusual to find taps on sale in single sizes. Usually, it's part of a complete set of taps and dies. There are a few places, however:

 This one is the cheapest at Grainger, but is more than enough to cut the soft aluminum on a Hammond case:




 $6.45 - http://www.grainger.com/Grainger/items/4AKH6

 A better bet is to find your local hobby shop (sorry - I'm an old model airplane builder/flier, so I keep mentioning this specialized stuff that can be found there). 6-32 and 4-40 taps are commonplace. You'll find them sold together with the appropriate numbered drill bit. These are probably the best buys you'll find. Tower Hobbies has a couple of them online:

 $4.79 - http://www2.towerhobbies.com/cgi-bin...?&I=LXE215&P=7, and
 $4.49 - http://www2.towerhobbies.com/cgi-bin...?&I=LXK366&P=7

 They carry a lot of other stuff if you're ever interested - screws in volume and colors(!), gobs of epoxies and CA glues, heat guns that will work for heat shrink (Monokote heat gun), long-handled allen wrenches, etc.

 A tap handle is nice to have, but not necessary with the soft Hammond aluminum. Even a pin vise will work if you use some gloves. 
	

	
	
		
		

		
		
	


	





 P.S. Note the update in the signature.


----------



## n_maher

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_It seems fairly unusual to find taps on sale in single sizes. Usually, it's part of a complete set of taps and dies. There are a few places <snip>_

 

I've had good luck finding them at the local mom and pop hardware store. The big box boys only want to sell you kits so you probably won't find them there. 

  Quote:


 P.S. Note the update in the signature. 
	

	
	
		
		

		
		
	


	



 

Duly noted.


----------



## pabbi1

oops...


----------



## naamanf

Lowes sells taps and the appropriate drill bit in singles.


----------



## UglyJoe

Any update on when the boards are going to be going out? I seem to recall a couple of weeks ago that Colin said the first shipments were going to start going out. Thanks.

 EDIT: Just saw "the pic" on headwize... Guess that means they are shipping soon!


----------



## bperboy

So far as taps go, I didn't tap my Millett, but I have tapped the small Hammond case that is being used for the Mini^3, using 4-40. I think the thread sizes are the same between the different Hammond cases, but correct me if I'm wrong!


----------



## tomb

I haven't used the Mini3 sized Hammond yet, but the J, N, and T cases are all very slightly less than #6 size. Tap yes, Drill no.


----------



## amphead

Quote:


 Matching tubes has never really been necessary with the Millett, and the MAX is no different. The Millett design includes tube biasing, so you are able to set every tube exactly. 
 

Thats one of the beautiful things about this design. No lethal voltages and no problems with biasing!


----------



## MrSlacker

Where is the list for the boutique parts?
 I am not sure if I am calling it correctly, but I am looking for a list of higher quality parts.


----------



## ferds

check here


----------



## MrSlacker

Quote:


  Originally Posted by *ferds* /img/forum/go_quote.gif 
_check here_

 

thanks


----------



## tomb

Apparently, some of you are receiving some nice packages today from Mad MAX.


----------



## Troyhoot

Grats to the lucky ones. Mine didnt arrive today. Maybe monday or tuesday. Still waiting on my order from percy anyway, so not in a big hurry. Now if I can keep my wife from giving birth for another week or two I'll be golden


----------



## MrMajestic2

I have everything waiting in baggies and boxes for the boards to arrive, cant wait. Nice work Colin


----------



## joneeboi

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Apparently, some of you are receiving some nice packages today from Mad MAX. 
	

	
	
		
		

		
		
	


	













_

 

How does one receive packages on the weekend? I never knew they delivered mail on the weekends.


----------



## tomb

Quote:


  Originally Posted by *joneeboi* /img/forum/go_quote.gif 
_How does one receive packages on the weekend? I never knew they delivered mail on the weekends._

 

Hmm ... US Mail always delivers on a Saturday. It depends on the area, but many US Post Offices are open until Noon on Saturdays and postmark up to late afternoon on Saturdays.


----------



## odoe

I was just putting my mouser project together and spec'ing out some res for my hd580s based on the boutique page. I still have a proto board I started to populate with parts that I had around, but got sidetracked with other stuff.


----------



## pabbi1

Quote:


  Originally Posted by *TimmyMac* /img/forum/go_quote.gif 
_Would it be possible to create a balanced version of this amp by making two, then running one off the normal signal and one off the inverted signal from a balanced DAC? Then from the output you would use the normal signal, inverted signal, and ground from both amps into XLR outputs? Does this make sense to anyone?

 edit: Also, would it be worthwhile instead of just building a more expensive better amp?_

 

I'd certainly like to pursue this idea as well... anyone?


----------



## Ech0

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Apparently, some of you are receiving some nice packages today from Mad MAX. 
	

	
	
		
		

		
		
	


	


_

 

Yea, I got my boards today. I was a bit surprised. Sure beats the junk mail I usually get on Saturday. Many many thanks to Colin, the boards are really nice. I'll get started tomorrow. 

 Ech0


----------



## slowpogo

I'm not sure of the appropriate time or place to start asking this, but I learned of this project the day orders were closed. I know many of you ordered 2, 3+ PCBs, and it may be too soon for you to have decided, but is anyone willing to sell off one of their boards at this point? I've been reading this thread a lot and really want this to be my next project. Thanks much..


----------



## n_maher

Quote:


  Originally Posted by *pabbi1* /img/forum/go_quote.gif 
_I'd certainly like to pursue this idea as well... anyone?_

 

I can't think of a reason it wouldn't work.

 And I got a nice little package from Colin yesterday as well!


----------



## pabbi1

Regarding balanced, would I still be able to use the RK27, or would I still need dual stereo pots / attenuators?


----------



## n_maher

Volume matching between the two would be tough with RK27s. I haven't found them to track all that well from unit to unit. Of course they do make a 4-channel RK27 which if you could find it would be ideal for something like this.


----------



## pabbi1

Oh, I am ok with a RK27 on each booard (dual volume), but the RK27 is stereo, and ok for each channel? Just making sure before I go completely out of control.

 Honestly, I'm more after the increased gain from two boards than the balanced signal... I hated how my prior Millett clipped.


----------



## n_maher

Quote:


  Originally Posted by *pabbi1* /img/forum/go_quote.gif 
_Honestly, I'm more after the increased gain from two boards than the balanced signal... I hated how my prior Millett clipped._

 

Remind me, what configuration were you running with your old Millett? I've never had an issue with output clipping on any of my hybrids but I think you and I have talked about this before, curse my failing memory.


----------



## pabbi1

It was mostly with 12fk6, but also with 12ae6a... it was buf634, not db, but I have always needed a bit more gain (why I went to the HA2, which was barely enough). Even Pete laughingly told me it would clip, given my gain requirements.

 The other issue is the wallwart I'm using (and placing in the case (bigger case)) - will this have enough current to drive both channels?

wallwart


----------



## tomb

Quote:


  Originally Posted by *pabbi1* /img/forum/go_quote.gif 
_It was mostly with 12fk6, but also with 12ae6a... it was buf634, not db, but I have always needed a bit more gain (why I went to the HA2, which was barely enough). Even Pete laughingly told me it would clip, given my gain requirements.

 The other issue is the wallwart I'm using (and placing in the case (bigger case)) - will this have enough current to drive both channels?

wallwart_

 

I'm not certain about your specific application, but if it's truly gain that you need, the 12AJ6 is a drop in tube for the Millett design. It has a basic amplification factor of *55*. That's so high it's inappropriate for typical headphone use - unless you have something unusual.

 The walwart current is more or less dependent on the output stage. The MAX benefits from a walwart with more than 1A. However, strictly speaking, current does not relate to gain - that is usually a voltage criterion.

 Don't know if that helps, but there it is ...

 BTW - I use duplicates to that walwart for my MAX's. It is more than enough for 100ma bias in the output stage or much higher, even. (It's a good choice while they have free shipping as mentioned in another thread.)


----------



## dsavitsk

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_I'm not certain about your specific application, but if it's truly gain that you need, the 12AJ6 is a drop in tube for the Millett design. It has a basic amplification factor of *55*. That's so high it's inappropriate for typical headphone use - unless you have something unusual._

 

If it is just a problem with clipping, a higher gain tube will just get him to clipping faster. Instead, you need to increase the power supply voltage (and possibly the grid bias) to allow for more swing in the CCS.


----------



## pabbi1

Granted, that was with the HD600, which won't be the case now... what about the 12EL6?

 Or, I could just turn the volume down, right?


----------



## tomb

Quote:


  Originally Posted by *pabbi1* /img/forum/go_quote.gif 
_Granted, that was with the HD600, which won't be the case now... what about the 12EL6?

 Or, I could just turn the volume down, right? 
	

	
	
		
		

		
		
	


	


_

 

Well, if you have the HD600, I can pretty much assure you that there's no danger of clipping from normal sources with the MAX - either with 12AE6A or 12FM6 tubes. Even 12FK6 tubes appear to reach deafening volumes with either my HD580's or HD600's - and that's on two different MAX's so far. I typically run 27V and bias the tubes to 13.5V That gives them plenty of swing, IMHO.

 One thing you might keep in mind - don't put in any output resistors - just jumper them out. I think you'll find that you have plenty of gain, voltage, current and volume with the basic MAX in that configuration.


----------



## pinkfloyd4ever

I was reading the Max website and was wondering, could the MH be used as a speaker amp with the 12AJ6 tubes? I did see that new adjustable damping amp, but I need to chill on the audio spending at some point before I have to start living in my car to support my addiction 
	

	
	
		
		

		
		
	


	




 btw, does anyone know where to get the PCBs for the adjustable damping millett?


----------



## babbkutz@comcast

looked at the Greenlee punch today (1") and am wondering about that hole punch size (1.12")? How am I going to get a 1" hole? (Machine shop?) The bushings from Mouser measure out to 1" and 1.12" seems to be pushing it.......


----------



## tomb

Quote:


  Originally Posted by *pinkfloyd4ever* /img/forum/go_quote.gif 
_I was reading the Max website and was wondering, could the MH be used as a speaker amp with the 12AJ6 tubes? I did see that new adjustable damping amp, but I need to chill on the audio spending at some point before I have to start living in my car to support my addiction 
	

	
	
		
		

		
		
	


	




 btw, does anyone know where to get the PCBs for the adjustable damping millett?_

 

Didn't see your last question after I replied to your PM -

 Nate has e-mailed Pete about boards, etc. We are expecting his reply. Nate??


----------



## tomb

Quote:


  Originally Posted by *babbkutz@comcast* /img/forum/go_quote.gif 
_looked at the Greenlee punch today (1") and am wondering about that hole punch size (1.12")? How am I going to get a 1" hole? (Machine shop?) The bushings from Mouser measure out to 1" and 1.12" seems to be pushing it......._

 

You are correct to question that. There is a Greenlee punch that is exactly 1" O.D. I have a Greenlee "Slug Buster" #35178 and it is exactly 1" O.D. and is listed as "Hole Size 1"". Look for this one.

 You can pretty much get a Greenlee punch in any diameter, within reason. You just have to be careful to make sure the hole size is 1". Many of the ones for conduit are labeled under nominal sizes only, and will make a hole much larger than their lable indicates. Those will *not* say "hole size," however. Hole size is _hole size_, period.


----------



## amphead

It would seem that increased headroom, as Dsavitsk suggests would solve your clipping problems. Running at say 29V, with a reliable power source.
 Look at Toms spec here:
http://www.diyforums.org/MAX/MAXps.php


----------



## IcantHearU

So, @ midnight Sunday, I realized I hadn't checked the mailbox on Saturday - It's now 4:50 a.m., and I've been at my two Maxxed Milletts for about 4 hours or so - Colin, thanks for your time, effort and enthusiasm and thanks to all the people who helped with everything from the bill if materials to the trials and testing and tweaks - (and of course P. Millett and the original MH DIY group)
 I have to work in 3.5 hours or so - I just don't care - this is just so much better!!
 Will definitely be posting pictures and results after this one - 
 OK, gotta go - my addiction needs to be fed


----------



## n_maher

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Didn't see your last question after I replied to your PM -

 Nate has e-mailed Pete about boards, etc. We are expecting his reply. Nate??_

 

Pete has no problems if we have boards made.

 But Pete and I are working on ideas for a couple of tweaks to the design before production. I don't really want to launch into a full fledged redesign right now and I'll report back as soon as I have anything substantial.


----------



## tomb

Hurry up.


----------



## n_maher

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Hurry up. 
	

	
	
		
		

		
		
	


	





_

 

Sorry, there will be no "hurry" in this operation, Pete's a busy guy and so am I. The frenzied masses are just going to have to hurry up and wait. 
	

	
	
		
		

		
		
	


	




 Seriously I'm hoping the MAX will be plenty to keep folks busy for a good long while. About all you can expect in the near future is that I may start a thread to get some input on what changes if any we might implement but I hope folks will be patient and give us some time to work things out.


----------



## UglyJoe

I'm a very sad diyer right now... 2 beautiful Max boards sitting on my desk and no cash to populate them.... sigh....


----------



## colonelkernel8

Quote:


  Originally Posted by *UglyJoe* /img/forum/go_quote.gif 
_I'm a very sad diyer right now... 2 beautiful Max boards sitting on my desk and no cash to populate them.... sigh...._

 

Same situation, only one board.

 Nice quality boards though, thanks Colin.


----------



## TheRobbStory

I can't believe there aren't any completed builds yet! We've had these boards for more than 48 hours.. 

 I had two shiny new boards sitting on my desk when I got to work this morning. Sadly, I have not even begun to think about ordering parts.


----------



## pabbi1

I have all my parts, well for single ended anyway... balanced reinforcements by Wednesday, well except for casing... oh, and cans.


----------



## soloz2

Quote:


  Originally Posted by *UglyJoe* /img/forum/go_quote.gif 
_I'm a very sad diyer right now... 2 beautiful Max boards sitting on my desk and no cash to populate them.... sigh...._

 

amen brother! I think I'm going to order parts anyway...

  Quote:


  Originally Posted by *TheRobbStory* /img/forum/go_quote.gif 
_I had two shiny new boards sitting on my desk when I got to work this morning. Sadly, I have not even begun to think about ordering parts._

 

I've got 3 and I'm going through finalizing my BOM right now


----------



## UglyJoe

Quote:


  Originally Posted by *soloz2* /img/forum/go_quote.gif 
_amen brother! I think I'm going to order parts anyway..._

 

Yeah, I know it. The wife keeps a pretty tight stranglehold on the ol' wallet, but I might just drop the $300 I am planning on spending on this amp and suffer the consequences. Should be able to climb out of the hole she puts me in after a couple of days....

 *walks off to ponder if MMAX is worth a near death experience...*


----------



## soloz2

Quote:


  Originally Posted by *UglyJoe* /img/forum/go_quote.gif 
_Yeah, I know it. The wife keeps a pretty tight stranglehold on the ol' wallet, but I might just drop the $300 I am planning on spending on this amp and suffer the consequences. Should be able to climb out of the hole she puts me in after a couple of days....

 *walks off to ponder if MMAX is worth a near death experience...*_

 

lol, yeah well I'm kinda broke right now, but my wife has known for some time that I've wanted to build the Max, so she hasn't said anything about me not ordering the parts and I've been very open with her about putting together my BOM so...idk


----------



## UglyJoe

Hey guys, I've got a couple more questions when it comes to caps. I've been reading _Art of Electronics_ lately and I am starting to get a grip on solid state electronics; tube stuff is still beyond me. Why are the CA2/CA9 caps "in the signal pathway", and therefore important to use "nice sounding" ones there? It looks to me like they just go to ground....? Do they provide a pathway to ground for any DC voltage from the input, like a low pass filter? 

 As far as settling on caps goes, I am sticking with BG NX 680uF caps for the CA7 positions, and Auricap .47uF caps for the CA8 positions. If I am calculating correctly that gives me a -3dB point of 4.4 Hz, for the resistance that the two caps in parallel see (RB14 + RA4 in parallel with 32ohm grado cans). If I increase the RB14 resistor to, say, 40 ohms I can drop that down to a -3dB point of 3.3 Hz. In the first case I'd think you would get a flat frequency response from about 40Hz and up; for the second I'd expect one from about 30 Hz and up. For those of you who have worked with the prototype amps, any idea how well the trade-off value is for doing something like that? I understand that you would lose some gain, but a I have read that losing some of the gain would be a pretty good idea for grados anyway.

 If I am right about CA2/CA9 positions being a low pass filter, I thought that for amps where the inputs and outputs are both capacitively coupled you needed to increase the capacitance at both the output and input in order to get the -3dB point at the frequency where you want it? Wouldn't that call for even larger caps at the CA7/CA8 position as well? Or would "overcompensating" at the CA2 position with the 1000uF caps remedy the situation and allow for the typical values at the CA7/CA8 positions.

 One last thing, I've yet to see the symbols on the schematic labeled "TA2L1" and the like. They look kind of like paint brushes or fountain pins. What do they mean?


----------



## pinkfloyd4ever

YEEAHH I got mine too!!

 It's so little, I love it!!! The MH, DBs, delay circuit, and PS all on that little board!! Great job Colin, and thanks again!!

 Just wish I had the time/money/experience to build it now...ahh whatever, this whole head-fi thing is really a journey for each individual anyway. wow I'm gettin all philosophical now


----------



## UglyJoe

I think I figured out the "paintbrush" looking things; those are the points where the biasing measurements are made, correct?


----------



## naamanf

You guys are lucky I am very far away on vacation or I would be sporting a new finished MAX. Should be home soon


----------



## Troyhoot

Well Boards came today and my Percy order did too sooo this is what happened tonight. 
	

	
	
		
		

		
		
	


	





 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 Abought as far as I can go. I ordered the wrong Wallwart so Had to reorder the 1000ma version sunday. nother day or so and I can get it all dialed in. Now to design a case.


----------



## cgrums

Got my boards today, thanks Colin. They look great.

 Sold the extra board.


----------



## UglyJoe

Troyhoot, what caps did you use in the boutique positions? Looks like Muses with auricap bypass, but what capacity are they?


----------



## Troyhoot

Used 1000 KZ muse for all caps. Auricap .22 uf in C9 and 1.00uf in C8. Also a 39ohm Kiwame in R14. Will be running 32 ohm cans.


----------



## zare

Got some Obbligato caps today and plates from local engraving shop:

http://www.flickr.com/photo_zoom.gne...0019090&size=l
http://www.flickr.com/photo_zoom.gne...0019090&size=l
http://www.flickr.com/photo_zoom.gne...0019090&size=l

 Waiting for the weekend


----------



## pddjsteve

Got my boards today. Arg! I've been so busy at work, and I still have to put the finishing touches on my SOHA (1/4" jack instead of 1/8" jack I was testing with and widening the tube hole for a rubber gasket), I was determined to wait on building this for a couple months. Nope. It looks sweet. I want to make it NOW. 

 Curse you, DIY! 

 So I guess I'm making some orders tomorrow. Can anyone think of anything I should be getting from Radio Daze besides the tubes and sockets?


----------



## UglyJoe

Quote:


  Originally Posted by *Troyhoot* /img/forum/go_quote.gif 
_Used 1000 KZ muse for all caps. Auricap .22 uf in C9 and 1.00uf in C8. Also a 39ohm Kiwame in R14. Will be running 32 ohm cans._

 

Interesting. You went with the 1uF Auri at the C8 position for stricter adherence to the 1/100 rule when dealing with bypassing the electrolytic, I am assuming? If you ever get a chance, I'd like to see what difference a BG makes at the bypassed position... seems to me like going your route with the cheaper electrolytic shouldn't have a lot of sonic differences from using BGs, if most of the mids/highs get passed through the film cap anyway. I'd still like some thoughts on my post (651) earlier tonight though, if someone could explain to me exactly what the CA2/CA9 caps actually do....


----------



## dsavitsk

Quote:


  Originally Posted by *UglyJoe* /img/forum/go_quote.gif 
_Hey guys, I've got a couple more questions when it comes to caps. I've been reading Art of Electronics lately and I am starting to get a grip on solid state electronics; tube stuff is still beyond me. Why are the CA2/CA9 caps "in the signal pathway", and therefore important to use "nice sounding" ones there? It looks to me like they just go to ground....? Do they provide a pathway to ground for any DC voltage from the input, like a low pass filter?_

 

No, they are actually a high pass filter. You might find this useful: http://www.nutshellhifi.com/library/ETF.html

 Also, caps never provide a pathway for DC. They provide a pathway for AC.

 Also, if you pick up Morgan Jones' Valve Amplifiers, look on page 78 for how to calculate the cap's value, and remember that the CCS on the plate of this amp presents a near infinite impedance.


----------



## UglyJoe

Quote:


  Originally Posted by *dsavitsk* /img/forum/go_quote.gif 
_No, they are actually a high pass filter. You might find this useful: http://www.nutshellhifi.com/library/ETF.html

 Also, caps never provide a pathway for DC. They provide a pathway for AC.

 Also, if you pick up Morgan Jones' Valve Amplifiers, look on page 78 for how to calculate the cap's value, and remember that the CCS on the plate of this amp presents a near infinite impedance._

 

I'm still confused, because those caps go to ground... how can they be in the signal if the go to ground?

 EDIT: NM, I think I understand... but I might have to think about it a little more....


----------



## tomb

Quote:


  Originally Posted by *UglyJoe* /img/forum/go_quote.gif 
_Hey guys, I've got a couple more questions when it comes to caps. I've been reading Art of Electronics lately and I am starting to get a grip on solid state electronics; tube stuff is still beyond me. Why are the CA2/CA9 caps "in the signal pathway", and therefore important to use "nice sounding" ones there? It looks to me like they just go to ground....? Do they provide a pathway to ground for any DC voltage from the input, like a low pass filter?_

 

No - they work as a "shunt." Think of it as a corridor that the signal must pass through. The cap puts an open door on the back side so the signal can go back and forth as needed (actually the bottom half of the wave form). On the other hand, if the door is closed (no cap) on one end of the corridor, then the signal can go backwards only as far as the length of the corridor.

 The fact that it forms a high pass filter with the tube resistance is ancillary - that dictates the size of this cap in normal situations (see the MAX case below). 

  Quote:


 As far as settling on caps goes, I am sticking with BG NX 680uF caps for the CA7 positions, and Auricap .47uF caps for the CA8 positions. If I am calculating correctly that gives me a -3dB point of 4.4 Hz, for the resistance that the two caps in parallel see (RB14 + RA4 in parallel with 32ohm grado cans). If I increase the RB14 resistor to, say, 40 ohms I can drop that down to a -3dB point of 3.3 Hz. In the first case I'd think you would get a flat frequency response from about 40Hz and up; for the second I'd expect one from about 30 Hz and up. For those of you who have worked with the prototype amps, any idea how well the trade-off value is for doing something like that? I understand that you would lose some gain, but a I have read that losing some of the gain would be a pretty good idea for grados anyway. 
 

This is all true and your reasoning is sound. However, leave room for "impact". Every addition to the output resistor removes a bit of impact from the signal - I can't explain it any other way. This is immediately apparent with something of high impedance such as Senns, but less so with something like Grados. So, there are some diminishing returns in adding resistance. If you think about it, 40 ohms is more than a pair of Grados themselves. It may still be OK - I know the SOHA regularly uses 100-150 ohms on the output. To be honest, you will be trailblazing to a certain extent until we get more experience with this technique. So, by all means - experiment if you can and let us know your results and what you prefer.

  Quote:


 If I am right about CA2/CA9 positions being a low pass filter, I thought that for amps where the inputs and outputs are both capacitively coupled you needed to increase the capacitance at both the output and input in order to get the -3dB point at the frequency where you want it? Wouldn't that call for even larger caps at the CA7/CA8 position as well? Or would "overcompensating" at the CA2 position with the 1000uF caps remedy the situation and allow for the typical values at the CA7/CA8 positions. 
 

Who knows? That may be an explanation for what we've noticed in the prototypes. The 1000uF cap at CA2 definitely improves bass. However, the calculated value of the RC circuit formed by the cap and the resistance of the tube yields a value of something around 100uF for a 20Hz corner. That's why the original Millett used 220uF for maximum assurance. For some reason, the MAX noticeably loses bass with that size, though - and we recommend the 1000uF instead.

 Truth be known, 1000uF is probably best on the output, too. However, there is a higher voltage requirement in the CA7 position. A cap at that rating is much larger and much more expensive. The CA7 does not seem to be as sensitive to this either, and as you have already noted, this is largely "tweakable" with the output resistors, too.

 As for the overall signal input to the MAX, Colin did us a big favor on that one. RA7 works with the pot to set the input impedance of the MAX - it is very high. The original Millett design did not have this resistor and the input impedance was pretty much dictated by the pot alone. So, output caps on the source could make a difference in where the corner frequency occurred. That is not the situation with the MAX.

  Quote:


 One last thing, I've yet to see the symbols on the schematic labeled "TA2L1" and the like. They look kind of like paint brushes or fountain pins. What do they mean? 
 

You figured it out. Those are standard Eagle symbols for board test points - where the bias is adjusted.


----------



## Troyhoot

I picked those values from the discussion and charts on post 477-485. The tube has a high resistance so .22 is way more then enough to get most of the frequencies going through it. My 32 ohm cans on the other hand is different. So I used mb3k's charts http://www.mb3k.com/millettbom.html to figure out what I wanted. I used a 39 ohm resistor in combination with the 1.0 bypass cap to get my corner frequency down and have most of the rest passing through the Bypass cap. Since 1.0 was about the largest size wise cap I could fit I kinda worked around that.

 Will have to wait and see if it all works as planed though. Im still real new to all this and not sure I understand it fully. But I have been trying to ask whenever I dont quite understand, and Im reading everything I possibly can.

 But my overall plan with those sizes was to get the majority of the sound going through the higher quality film bypass caps since the sound better then electrolytic caps (Now this is from everything I read and have been told). This also lets me save a bit on the electrolytics and spend more on the film and kiwame resistors


----------



## tomb

Quote:


  Originally Posted by *cgrums* /img/forum/go_quote.gif 
_Got my boards today, thanks Colin. They look great.

 I forgot i ordered 3. What with other projects backing up, work getting crazy and a particular someone expecting attention I don't think I'll be able to populate all three.

 I'll let this go to the first person I receive a PM from for whatever I paid for the board + shipping._

 

You should refer to the GB thread and PM one of the several people who are begging for a board. The chances of one of them seeing this are very small.


----------



## UglyJoe

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_No - they work as a "shunt." Think of it as a corridor that the signal must pass through. The cap puts an open door on the back side so the signal can go back and forth as needed (actually the bottom half of the wave form). On the other hand, if the door is closed (no cap) on one end of the corridor, then the signal can go backwards only as far as the length of the corridor.

 The fact that it forms a high pass filter with the tube resistance is ancillary - that dictates the size of this cap in normal situations (see the MAX case below)._

 

Is this something only typical of tubes? I still just don't get it, and it might have to remain part of the magic of electronics for a while. It seems to me that you would want the AC frequency that comprises sound at the output to the headphones to be in tact over the frequency range of interest. The output coupling capacitors do that. The ground is *supposed* to be a steady reference voltage . I just don't understand why you would be passing a signal into ground... or am I looking at this completely the wrong way?


----------



## tomb

Quote:


  Originally Posted by *UglyJoe* /img/forum/go_quote.gif 
_Is this something only typical of tubes? I still just don't get it, and it might have to remain part of the magic of electronics for a while. It seems to me that you would want the AC frequency that comprises sound at the output to the headphones to be in tact over the frequency range of interest. The output coupling capacitors do that. The ground is *supposed* to be a steady reference voltage . I just don't understand why you would be passing a signal into ground... or am I looking at this completely the wrong way?_

 

It sounds like you're confusing caps. My description of the shunt is for CA2. CA7 are purely DC-blocking caps to protect your headphones.

 The shunting action of CA2 is complicated background theory involving the waveform of the signal as it hits the tube. Maybe I should've it said it provides "headroom" on the backside of the tube for the bottom of the wave.

 Strictly speaking, it is not necessary and was a design choice made by Pete Millett - as are the cap bypasses. Getting into the pros and cons of that is way beyond me. Accept that CA2 acts as negative headroom and you'll be happier - I hope.

 EDIT: Again, speaking only about CA2, you can combine my description with Dsavitsk's statement that the CCS forms an effective infinite impedance. If that's true, then the peaks of the waveforms have to have somewhere else to go if they are not clipped. (The CCS is on one side of the tube, the CA2 cap is on the other side.) The cap "relaxes" the room for the waveform on the backside of the tube.

 Admittedly, I'm getting into dicey territory on this one.


----------



## UglyJoe

Quote:


  Originally Posted by *Troyhoot* /img/forum/go_quote.gif 
_I picked those values from the discussion and charts on post 477-485. The tube has a high resistance so .22 is way more then enough to get most of the frequencies going through it. My 32 ohm cans on the other hand is different. So I used mb3k's charts http://www.mb3k.com/millettbom.html to figure out what I wanted. I used a 39 ohm resistor in combination with the 1.0 bypass cap to get my corner frequency down and have most of the rest passing through the Bypass cap. Since 1.0 was about the largest size wise cap I could fit I kinda worked around that.

 Will have to wait and see if it all works as planed though. Im still real new to all this and not sure I understand it fully. But I have been trying to ask whenever I dont quite understand, and Im reading everything I possibly can.

 But my overall plan with those sizes was to get the majority of the sound going through the higher quality film bypass caps since the sound better then electrolytic caps (Now this is from everything I read and have been told). This also lets me save a bit on the electrolytics and spend more on the film and kiwame resistors 
	

	
	
		
		

		
		
	


	


_

 

From the way you wrote this I am not sure you exactly understand how to chose the caps... you got the right ones, but I think you got there by a backwards route. The higher capacity cap (the electrolytic) is the one that (mostly) determines the cuttoff frequency. So in your case the total capacitance through your CA7/CA8 caps is 1001uF. As you can see, %99.9 of that is due to the electrolytic, so theoretically most of the bass is passing through the electrolytic. I am still not exactly sure how bypassing with a film cap works; the much smaller capacity film cap has a much smaller time constant, which might have something to do with why the higher frequencies tend to pass through it.. or not, like Tom has said a lot of that is voodoo to me. Regardless, I think I am right in saying the electrolytic is responsible for most of the bottom end of the sound, and it is definitely responsible for determining the cuttoff frequency. Changing the film bypass cap from .47uF to 1.0uF to 10.0uF is not going to change the cuttoff frequency substantially... or really at all, tbh. Just thought you should know the next time something like this comes up for you.

 BTW, that combination gets you a cuttoff frequency of about 2.2 Hz.... something to think about, since the lowest I can get with a similar setup but smaller capacity Black Gates is about 3.3 Hz. I wonder how much audible difference there will be there, and if that will offset the sound difference made up by using a BG in the first place.... *ponders the strange....*


----------



## UglyJoe

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_It sounds like you're confusing caps. My description of the shunt is for CA2. CA7 are purely DC-blocking caps to protect your headphones.

 The shunting action of CA2 is complicated background theory involving the waveform of the signal as it hits the tube. Maybe I should've it said it provides "headroom" on the backside of the tube for the bottom of the wave.

 Strictly speaking, it is not necessary and was a design choice made by Pete Millett - as are the cap bypasses. Getting into the pros and cons of that is way beyond me. Accept that CA2 acts as negative headroom and you'll be happier - I hope.

 EDIT: Again, speaking only about CA2, you can combine my description with Dsavitsk's statement that the CCS forms an effective infinite impedance. If that's true, then the peaks of the waveforms have to have somewhere else to go if they are not clipped. (The CCS is on one side of the tube, the CA2 cap is on the other side.) The cap "relaxes" the room for the waveform on the backside of the tube.

 Admittedly, I'm getting into dicey territory on this one.
	

	
	
		
		

		
		
	


	


_

 

Well, I won't say that makes a heck of a lot more sense, but it gets me there a little bit. I assumed since you are using them as a high pass filter that they were there to block DC offset (I knew thats what the CA7 caps were for), and for the life of me I couldn't figure out why that was needed going from the tube to ground... I won't claim to understand it, or understand exactly why that is still in the signal pathway, but at least it's not quite as painful now.


----------



## tomb

Ugly Joe,

 You may need to look at MB3K's table that Troyhoot referenced. I think his strategy is a good one. As you go up in impedance with headphones, more and more of the signal goes through the film cap instead of the electrolytic.

 It is true that the electrolytic still primarily sets the bass corner frequency, and that the total effective capacitance is what you describe. However, the signal will be divided between the two, depending on the corner frequency of the film cap. Troyhoot has selected sizes that optimize that relationship for his phones.


----------



## UglyJoe

I'll have a look.... the way I read his post made it seem like he thought the overall bass response was due to the film cap. No offense troy if you already knew everything I said in the post above


----------



## tomb

Quote:


  Originally Posted by *UglyJoe* /img/forum/go_quote.gif 
_I'll have a look.... the way I read his post made it seem like he thought the overall bass response was due to the film cap. No offense troy if you already knew everything I said in the post above_

 

There are different schools of thought on cap bypassing - to be sure - and room for every opinion. Troyhoot has selected one and it will be interesting to hear of his results.

 One way to think about the cap bypassing is that the films have a much lower ESR, so the signal current will tend to go through the film cap the most, except for those frequencies that are filtered from the RC relationship. In the frequency range below that, the 'lytic will take over. There is some basis in this thought, because in most cases, bypassing the electrolytic improves the highs and midrange. As with most things, there is probably a point of diminishing returns. If there is one beyond the size and expense of the film cap, Troyhoot's experience may help to tell us that.


----------



## MrMajestic2

Quote:


  Originally Posted by *Troyhoot* /img/forum/go_quote.gif 
_Well Boards came today and my Percy order did too sooo this is what happened tonight. 
	

	
	
		
		

		
		
	


	





 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 Abought as far as I can go. I ordered the wrong Wallwart so Had to reorder the 1000ma version sunday. nother day or so and I can get it all dialed in. Now to design a case._

 

Nice work. Are those 2" heatsinks?


----------



## amphead

Woo Hoo! Time to start building! Excellent build quality!
 I burn alot of my own boards but nothing this good.
 Now Colin can get some much needed rest!


----------



## amphead




----------



## Troyhoot

UglyJoe - I dont know exactly how to chose them but I am learning, thats what I was saying when I said I dont fully understand. But I use the corner frequency equation and those charts I linked to get what I wanted. mb3k's charts made it all very clear to me really.

 You are right in saying I will have a corner frequency of 2.2 with the 1kuf electrolytic cap and the 39ohm resistor. I will also have a 2200 corner frequency with the Film bypass at 1.00uf. Therefore all frequency from 2200 on up will pass through the film and all from 2.2-2200 through the electrolytic . They both have corner frequencies. I changed the Film size to get more frequency passing through the film. _Now this is how I understand it all and I could be completely wrong but from everything I read and the previous discussions this is how I take it._


 MrMajestic2 - Yes those are 2" heatsinks. My large electrolytic caps are 1 5/8" and I wanted my heatsinks to be taller so they wouldnt be totally blocked and overheat by the caps. I also am not using the hammond case so it also fits with my design so far. I am going to have a clear acrylic top with maybe a few holes but didnt want anything sticking through.

 My wife said "it looks like a little city"


----------



## UglyJoe

Quote:


  Originally Posted by *Troyhoot* /img/forum/go_quote.gif 
_UglyJoe - I dont know exactly how to chose them but I am learning, thats what I was saying when I said I dont fully understand. But I use the corner frequency equation and those charts I linked to get what I wanted. mb3k's charts made it all very clear to me really.

 You are right in saying I will have a corner frequency of 2.2 with the 1kuf electrolytic cap and the 39ohm resistor. I will also have a 2200 corner frequency with the Film bypass at 1.00uf. Therefore all frequency from 2200 on up will pass through the film and all from 2.2-2200 through the electrolytic . They both have corner frequencies. I changed the Film size to get more frequency passing through the film. Now this is how I understand it all and I could be completely wrong but from everything I read and the previous discussions this is how I take it.


 MrMajestic2 - Yes those are 2" heatsinks. My large electrolytic caps are 1 5/8" and I wanted my heatsinks to be taller so they wouldnt be totally blocked and overheat by the caps. I also am not using the hammond case so it also fits with my design so far. I am going to have a clear acrylic top with maybe a few holes but didnt want anything sticking through.

 My wife said "it looks like a little city" 
	

	
	
		
		

		
		
	


	


_

 

I think you pretty much have it, though I am unsure about where the frequencies actually pass through the film cap and not the electrolytic, and if that happens at the cuttoff frequency of the smaller film cap or if there is some homogeneous blending of the two caps through part of the midrange with the film cap taking more and more responsibility the higher the frequency is. Thinking about it that way, it seems like the best bypass cap to choose is the biggest one you can find... which is contrary to what I read about choosing a bypass cap that's 1/100 or so of the electrolytic. Doesn't really matter here though, as for a 680-1000uF cap it going to be really hard to find a boutique in the 6-10uF range that will fit. I guess the best options is go for the biggest you can afford/fit.


----------



## tomb

Quote:


  Originally Posted by *UglyJoe* /img/forum/go_quote.gif 
_I think you pretty much have it, though I am unsure about where the frequencies actually pass through the film cap and not the electrolytic, and if that happens at the cuttoff frequency of the smaller film cap or if there is some homogeneous blending of the two caps through part of the midrange with the film cap taking more and more responsibility the higher the frequency is. Thinking about it that way, it seems like the best bypass cap to choose is the biggest one you can find... which is contrary to what I read about choosing a bypass cap that's 1/100 or so of the electrolytic. Doesn't really matter here though, as for a 680-1000uF cap it going to be really hard to find a boutique in the 6-10uF range that will fit. I guess the best options is go for the biggest you can afford/fit._

 

ESR is much lower in the film cap. The signal current will "prefer" to go through it except for the filtering at its individual corner frequency.

 Here's a link that explains some of the differences in types of caps and ESR. In particular, note the table in the middle of the page comparing ESR's of various capacitor types. ESR of a typical film cap is hundreds less ohms than an electrolytic. This is what makes electrolytic-film-cap-bypassing work.

http://www.illinoiscapacitor.com/upl...18FF09455A.pdf


----------



## tomb

Quote:


  Originally Posted by *Troyhoot* /img/forum/go_quote.gif 
_... My wife said "it looks like a little city" 
	

	
	
		
		

		
		
	


	


_

 

Soon to be with a lot of lights, no doubt.


----------



## UglyJoe

BTW, has anyone had a chance to do a side-by-side comparison of the MOSFET output stage option versus the BJT output stage option? I'd love to hear what you guys think about the sonic differences of the two. Tom, you've been talking about using BG as your electrolytics and either Vitamin Q's or Aruicaps for the bypass, are you planning to do that with your next build? I have pretty much decided to go that route myself (once I get some cash-flow, that is) and I'd love to get what your impressions are on sound between the "stock" BOM and the MAX Boutique.

 Also, what is the purpose of the voltage divider after the output coupling caps? Seems to me that it (aside from its use in being able to adjust the 3dB point of the RC circuit) simply results in some gain loss, although admittedly not a whole lot. Also, I was thinking about increasing the value of the RA4 resistors if I increase the value of the RB14 resistors. This should offset any gain loss across the RB14 resistor if I have to increase that value to get the right cutoff frequency... admittedly, it would cost some in power by reducing current, but I don't *think* that would be a big deal.


----------



## tomb

Quote:


  Originally Posted by *UglyJoe* /img/forum/go_quote.gif 
_BTW, has anyone had a chance to do a side-by-side comparison of the MOSFET output stage option versus the BJT output stage option? I'd love to hear what you guys think about the sonic differences of the two. Tom, you've been talking about using BG as your electrolytics and either Vitamin Q's or Aruicaps for the bypass, are you planning to do that with your next build? I have pretty much decided to go that route myself (once I get some cash-flow, that is) and I'd love to get what your impressions are on sound between the "stock" BOM and the MAX Boutique._

 

All good questions - I hope we find out some day. My intent is to build a version of each - MOSFET/BJT/VitQ's/Auricaps/ES-Sonicaps - but it may take awhile.

  Quote:


 Also, what is the purpose of the voltage divider after the output coupling caps? Seems to me that it (aside from its use in being able to adjust the 3dB point of the RC circuit) simply results in some gain loss, although admittedly not a whole lot. Also, I was thinking about increasing the value of the RA4 resistors if I increase the value of the RB14 resistors. This should offset any gain loss across the RB14 resistor if I have to increase that value to get the right cutoff frequency... admittedly, it would cost some in power by reducing current, but I don't *think* that would be a big deal. 
 

RA4 sets a load to ground for the tube in the absence of a pair of headphones. The tube may go unstable without them, I think. Don't go changing values on the amp that are not suggested - unless you get an OK from Colin. The MAX has some serious gain with 12AE6 tubes. I don't think it will be an issue. If you get to where you think you need over 100-150 ohms for RB14, then it may be something to consider if you confirm with cetoole, but I don't think that's going to happen. Put in some 12FK6 tubes, instead.


----------



## UglyJoe

I thought about it, and it was a dumb idea anyway. The RA4 resistor would compensate for increasing the RB14 resistor with no load, but as soon as you plug in the headphones the impedance is dominated by the headphone impedance. It's in parallel with RA4, which means that changing the RA4 resistor would only change the combined resistance by minuscule and unimportant amounts.

 I thought that RA4 must be in there for something without a load plugged in, because once you add the load (especially for low impedance cans like grados) RA4 effectively just disappears.


----------



## amphead

hmmmm........ am I going to go bjt or mosfet. 
 Well I get the feeling that the mosfet version will really crank a set of headphones with lots of current and have a more dynamic presentation.
 But I think the bjt will be easier overall. Ok, call me lazy I am going with bjt! 
 Who's going with mosfet and who's going with bjt?
 Anyone?


----------



## naamanf

I already have a BJT version so the next one will be MOSFET. Then I can do some comparisons.


----------



## mb3k

Quote:


  Originally Posted by *amphead* /img/forum/go_quote.gif 
_hmmmm........ am I going to go bjt or mosfet. 
 Well I get the feeling that the mosfet version will really crank a set of headphones with lots of current and have a more dynamic presentation.
 But I think the bjt will be easier overall. Ok, call me lazy I am going with bjt! 
 Who's going with mosfet and who's going with bjt?
 Anyone?_

 

I've gone BJT on the classic Millett Hybrid Diamond Buffers, so this time around it's going to be MOSFETS. Those should drive HD650's well


----------



## amphead

If the bjt doesn't float my boat, then I might buy or burn another board (if thats ok)  and build the mosfet version. I'll take an educated guess that the bjt does float!


----------



## mb3k

Quote:


  Originally Posted by *amphead* /img/forum/go_quote.gif 
_If the bjt doesn't float my boat, then I might buy or burn another board (if thats ok)  and build the mosfet version. I'll take an educated guess that the bjt does float!_

 

A benefit doing it MOSFET style is that you don't have to go out of your way to buy a cheap DMM that measures hfe for the BJT's. Amb has matched MOSFETs at his shop.

 At the same time, there's more BJT pairs to choose from (compared to the MOSFET choices) which opens up the floor to different listening nirvana.

 I would assume either one WILL be great!


----------



## TBomb06

Welp...it's 2:15AM and I am finally listening to my Max. There were a couple of stupid mistakes made that I'm blaming on my level of tiredness...fortunately they were easily corrected. Now to tidy up the casework and tweak the DB bias. So far so good...


----------



## ruZZ.il

anyone mind recommending a tube socket from RadioDaze for me? 
	

	
	
		
		

		
		
	


	



 or have any other recommendations for an alternative affordable source of both tubes and sockets.. or burning recommendations against those sockets?.. International shipping so I'm trying to keep my sources to a minimum..
 and I'm also stuck between mossies or bjt 
	

	
	
		
		

		
		
	


	



 alot of you guys seem to be doing bjts first, so maybe I'l just try the mossies 
	

	
	
		
		

		
		
	


	







 I got some parts coming from amb anyway...
 thanks


 edit: not sure those lugs are right.. hmm.. ebay?.. anyone willing to share orders of tubes, sockets, and vitamin Q's.. split shipping on all, then ship me my part? 
	

	
	
		
		

		
		
	


	










 Tbomb: congrats on the build!
	

	
	
		
		

		
		
	


	




 I wont sleep from the moment I got all the parts till the time its working either  (though I'm usually up late anyway.. always finding something)


----------



## amphead

There are many sources of sockets(white 7pins),but this source stocks the tubes as well and I have had good success dealing with them.
http://thetubestore.com/7pinminisocket.html


----------



## ruZZ.il

I see they also have a slight lug like connector.. and just outside the circumference of the tube, like on the board.. so I guess none from radiodaze seem to naturally fit.. do some come with pins? thetubestore tubes are almost 3x price of radiodaze.. I think I'll probably just get tubes from rd afterall.. with intl. shipping.. and get the sockets sent to someone who can bring them for me soon. so, I guess any links from anywhere are good. those look good too.. noted. thanks


----------



## tomb

Quote:


  Originally Posted by *amphead* /img/forum/go_quote.gif 
_hmmmm........ am I going to go bjt or mosfet. 
 Well I get the feeling that the mosfet version will really crank a set of headphones with lots of current and have a more dynamic presentation.
 But I think the bjt will be easier overall. Ok, call me lazy I am going with bjt! 
 Who's going with mosfet and who's going with bjt?
 Anyone?_

 

My guess is that the Toshiba BJT's are more detailed than the MOSFETs. There is also no reason that the BJT's can't be run at the same current as the MOSFETs. There is nothing inherent in the MOSFETs that says they can take higher temps. It is all Watts - voltage times current. The difference is that the MOSFETs _require_ a minimum current of about 80ma.

 That means that the MOSFETs need 1-1/2" heat sinks minimum. That also means the board must be located in the case much lower and the volume knob and headphone jack will be well below the centerline. It may also be more difficult to remove the tubes with the lid on, since they won't be sticking out as far, either.

 The BJTs, on the other hand, perform quite well at 30ma - the same current bias used on the PPA and the original Millett w/DB's. However, with only 1" heat sinks, they will take 50ma and perhaps more - much more than any BJT headphone amp except perhaps some of Dr. Gilmore's extreme creations. At least in my experience, too - with the ventilation holes shown in my build on the website - the current does not alter when the case lid is put on and the case is buttoned up. They run slightly hotter, but not enough to alter the bias.

 I am definitely going to build a MOSFET version, but the rep on MOSFETs seems to be "warm" and it will be combining with naturally warm tubes. That's only a guess on my part, based on a lot of the stuff I've read of headphone amps with MOSFETs. The BJT's on the other hand, can have a piercingly detailed edge (Toshiba's for sure) that combines well with a tubey warm gain stage. A perfect analogy is to imagine a PPA with a tube opamp stage, vs. an M3 with a tube opamp stage.

 It will take some of us building both to confirm this, but that's my guess so far.


----------



## tomb

Quote:


  Originally Posted by *ruZZ.il* /img/forum/go_quote.gif 
_I see they also have a slight lug like connector.. and just outside the circumference of the tube, like on the board.. so I guess none from radiodaze seem to naturally fit.. do some come with pins? thetubestore tubes are almost 3x price of radiodaze.. I think I'll probably just get tubes from rd afterall.. with intl. shipping.. and get the sockets sent to someone who can bring them for me soon. so, I guess any links from anywhere are good. those look good too.. noted. thanks 
	

	
	
		
		

		
		
	


	


_

 

ruZZ.il,

 None of the sockets at Radio Daze are appropriate, unfortunately. Please look at the MAX website section on "Tube Lights." It goes into detail about the appropriate sockets. You must use 7-pin PCB sockets, or you will have trouble:
http://www.diyforums.org/MAX/MAXtubelights.php.

 If you don't want to order from another tube vendor and go with Radio Daze instead, you might consider a regular offering that's on e-bay:

Vacuum Tube Sockets 7 Pin PCB Mount (7)


 P.S. The TubeStore is one of the most expensive sources for Millett tubes. A better choice that is almost a mirrored-direct competitor is the Tube Depot:
http://www.tubedepot.com
 While RadioDaze appears to have among the best prices on Millett tubes, the TubeDepot is a wonderful place. I did a review once based on a personal visit I made there:
TubeDepot in Person

 Vacuumtubes.net has prices as good as RadioDaze, but they've been almost bought out by all the Millett builders that have gone before us. I suspect RadioDaze will end up that way, too, by the time most MAX's get built. Vacuumtubesinc.com is another great source, but with a small selection. They are the best for GE 5963's on the SOHA, however.


----------



## tomb

Quote:


  Originally Posted by *mb3k* /img/forum/go_quote.gif 
_A benefit doing it MOSFET style is that you don't have to go out of your way to buy a cheap DMM that measures hfe for the BJT's. Amb has matched MOSFETs at his shop.

 At the same time, there's more BJT pairs to choose from (compared to the MOSFET choices) which opens up the floor to different listening nirvana.

 I would assume either one WILL be great!_

 

Amb lists his MOSFETs as _tested_, not matched. Also, the DMM is needed in either case - the matching is for the small TO-92 2N5087/5088's, which exist in much greater numbers for both cases. Also, the matching is even a better idea with the CCS's, which use the same TO-92 trannies.

 As with the MOSFETs, matching was never really necessary on the large BJT output transistors (MJE's, BD's, or 2SC's).


----------



## tomb

ruZZ.il,

 Also - if you are considering anything boutique, PartsConnexion is the only source for _gold-plated_ 7-pin PCB ceramic sockets. Their prices are quite reasonable for both the gold-plated and regular 7-pin PCB sockets. You could combine that with an order of Black Gates or Auricaps, or whatever you might be considering.


----------



## ruZZ.il

thanks tom! hadn't looked at the Tube Light page for a while. great stuff. The comparisons you just did were also helpful, putting things together..
 today: finish figuring out my caps/tubes.. maybe..


----------



## ruZZ.il

I'm thinking of:
 CA2L/R: BG NX 1000uF 25V 
 CA7L/R: BG NX 680uF 35V
 CA9L/R: Auricap 0.22uF 400V
 along with tube sockets from pcx..

 although, I'll eventually need another set of it all, so, anyone know if the 10x price of the auricaps over the vitamin Q's is worth a noticeable difference(anyone know the diff characteristics?)? since I could split a pack of v-q's for the same price, and have for my next board, and spare.(anyone/two want to split a pack? 
	

	
	
		
		

		
		
	


	




 ) otherwise I'll stick with auris to save the extra shipping..

 also, I'm mostly using ultrasone 40ohm cans, so I'd like to add some kiwames..
 around 50ohm, so I'd get F=~2.6Hz.. (1000uF NX: 25V-tool low, 50V- too tall, so I stuck with 680)
 how much 'gain loss' is expected around there? 
 or is 25V adequate if I'm certain to stick with 12FK6's?
 I still need to ponder the output stage...
 and is upping CA4/5 to 1000uF really going to do much/anything?

 I think thats it for now... any suggestions/objections welcome and appreciated. 

 thanks all.
 -ruZZ


----------



## UglyJoe

Quote:


  Originally Posted by *ruZZ.il* /img/forum/go_quote.gif 
_I'm thinking of:
 CA2L/R: BG NX 1000uF 25V 
 CA7L/R: BG NX 680uF 35V
 CA9L/R: Auricap 0.22uF 400V
 along with tube sockets from pcx..

 although, I'll eventually need another set of it all, so, anyone know if the 10x price of the auricaps over the vitamin Q's is worth a noticeable difference(anyone know the diff characteristics?)? since I could split a pack of v-q's for the same price, and have for my next board, and spare.(anyone/two want to split a pack? 
	

	
	
		
		

		
		
	


	




 ) otherwise I'll stick with auris to save the extra shipping..

 also, I'm mostly using ultrasone 40ohm cans, so I'd like to add some kiwames..
 around 50ohm, so I'd get F=~2.6Hz.. (1000uF NX: 25V-tool low, 50V- too tall, so I stuck with 680)
 how much 'gain loss' is expected around there? 
 or is 25V adequate if I'm certain to stick with 12FK6's?
 I still need to ponder the output stage...
 and is upping CA4/5 to 1000uF really going to do much/anything?

 I think thats it for now... any suggestions/objections welcome and appreciated. 

 thanks all.
 -ruZZ 
	

	
	
		
		

		
		
	


	


_

 

I don't know if you just accidentally left it out, but CA8 is probably the most important caps on the board. I'd follow Troyhoots plan and use the .22uF auricaps for the CA9 position and use 1uF caps for the CA8 position. You'd have to tombstone those at the CA8 (I think you'd have to anyway with the .22uF caps) but it would insure that as much of the signal as possible passes through the film cap. Actually, that's exactly what I was planning for my build as well. I am a little dubious as to the sonic color due to the CA2/CA9 position, so I won't spend the extra cash putting the bigger film caps there, unless cetoole or someone else can give me a really good reason to. I think if a lot of the signal passes through the BG there, I'l be okay with it... I mean, BGs are supposed to sound fantastic anyway, so as far as I can tell it just looks a little overkill to use larger film caps there... although, tbh, the cost difference is probably only about $10 anwyay.. ponders some more.

 As to the gain thing, I am going to buy the standard 22r resistor and probably something between 39-50 ohms. I'll try it with no resistor, and the two other options to decide what sounds best. I don't think it's going to be something that someone can just tell you which way works best, you'll have to experiment to get the sound you like. BTW, I don't know anything about "boutique" resistors. The MAX website seems to imply that you shouldn't use Vishay-Dales at RB14. I was looking at the Mills resistors on sonicraft. Anyone ever used or heard their MRA-5 resistors? Any other suggestions as far as boutiques would be appreciated.


----------



## FallenAngel

Quote:


  Originally Posted by *ruZZ.il* /img/forum/go_quote.gif 
_is 25V adequate if I'm certain to stick with 12FK6's?_

 

I would really love to know this answer as well, Elna RFS 35V are sold out until September and I will be ordering a set of 25V rated caps, is this enough on the output with all tubes? Also of course BlackGate N series doesn't come in 1000uF/35V - only 25V and 50V (crazy priced 
	

	
	
		
		

		
		
	


	




 ).


----------



## tomb

Quote:


  Originally Posted by *ruZZ.il* /img/forum/go_quote.gif 
_I'm thinking of:
 CA2L/R: BG NX 1000uF 25V 
 CA7L/R: BG NX 680uF 35V
 CA9L/R: Auricap 0.22uF 400V
 along with tube sockets from pcx..

 although, I'll eventually need another set of it all, so, anyone know if the 10x price of the auricaps over the vitamin Q's is worth a noticeable difference(anyone know the diff characteristics?)? since I could split a pack of v-q's for the same price, and have for my next board, and spare.(anyone/two want to split a pack? 
	

	
	
		
		

		
		
	


	




 ) otherwise I'll stick with auris to save the extra shipping.._

 

The BG's look great. Note that all the retailers are wrong about the dimensions of the 1000uF/25V - it's 16 x _*26*_, not 16 x 24.

 The Auricaps look good, although it looks like you may be neglecting CA8, the film caps at the output. You might look back at the posts by Troyhoot. He has an interesting strategy in play. Since the headphone resistance seen by CA7 is so much smaller by comparison to the tube CCS at CA2, it made sense to upsize the bypassing film cap at the output. I think he stated he's using 1uF Auricaps there. To be conservative, you might go with 0.47's on the output and stay with 0.22's at the cathode bypass. In any event, I think Troyhoot's strategy makes sense in this regard instead of keeping both pairs of film caps the same. Just a thought.

 As for comparisons between Auricaps and Vitamin Q's, FallenAngel or MrMajestic2 may be in the best position to offer an opinion soon on that - I can't. A guess might be that the Auricap is more detailed but the Vitamin Q probably is more lush with greater bass punch - just a guess from what I've read. 

  Quote:


 also, I'm mostly using ultrasone 40ohm cans, so I'd like to add some kiwames..
 around 50ohm, so I'd get F=~2.6Hz.. (1000uF NX: 25V-tool low, 50V- too tall, so I stuck with 680)
 how much 'gain loss' is expected around there? 
 or is 25V adequate if I'm certain to stick with 12FK6's?
 I still need to ponder the output stage...
 and is upping CA4/5 to 1000uF really going to do much/anything? 
 

I doubt that you will notice the 50ohms. If it's easy for you, though, try to socket those positions. The difference in my hearing is more one of "impact" reduction rather than gain loss. Gain loss becomes noticeable at 100ohms and higher, IMHO. It's hard to tell at less than that. You always want to use as little as you can get away with, however. Personally, I like a hair trigger volume to a certain extent. It may not be that bad, though, depending on how efficient those Ultrasones are. The 12FK6's may do the trick without any output resistors at all.

 As for CA4/5 being 1000uF, it's a psychological-cost thing with me. Those are normal power cap positions and are quite inexpensive at that size. I would always wonder if I did everything I could for the best sound if I stuck 470's in there. They just don't look right in the MAX, IMHO. The two I've built had 1200uF 35V Panasonic FM's the first time, and 1800uF 35V the second time (both are 1" or shorter) - can't tell a difference between the two. 
	

	
	
		
		

		
		
	


	




  Quote:


 I think thats it for now... any suggestions/objections welcome and appreciated. 

 thanks all.
 -ruZZ 
	

	
	
		
		

		
		
	


	



 

I hope it helps - but they are just opinions in the end.


----------



## ericj

Quote:


  Originally Posted by *ruZZ.il* /img/forum/go_quote.gif 
_also, I'm mostly using ultrasone 40ohm cans, so I'd like to add some kiwames..
 around 50ohm, so I'd get F=~2.6Hz.. (1000uF NX: 25V-tool low, 50V- too tall, so I stuck with 680)
 how much 'gain loss' is expected around there? 
 or is 25V adequate if I'm certain to stick with 12FK6's?
 I still need to ponder the output stage...
 and is upping CA4/5 to 1000uF really going to do much/anything?_

 

First, there is almost no information recorded below 20hz. Most of what you can identify as audible bass is between 40 and 70hz. So, with 470uf on the output, there will be almost no actual bass rolled off on your 40ohm cans. So, i sincerely doubt that you would be able to hear a difference between 680uf and 1000uf - even if you only listen to organ drone. 


 And the second point, I'd just been meaning to pop in and say this: 

 The DC voltage seen by the output cap, aside from the initial turn-on pulse, is whatever voltage you bias them to. 

 In any sane millett configuration, this will be between 12 and 15 volts. 

 Moreover, the voltage rating on the cap is the 'working voltage', meaning that occasional transients above that voltage are generally allowable, 

 In general, when working with power circuitry, it's advisable to use a cap that is rated for a voltage somewhat higher than you believe it will ever work at. 

 But the output cap isn't working very hard at all. 

 So, in general, even with a 12ae6a and 30v B+, a 25v output cap should work for at least several years before it starts to degrade.

 About the same time frame as the electrolyte would start to dry out anyway. Over a delta of decades, electrolytic capacitors are consumables. 

 If you can get the cap you want in 35v and have it fit inside the case you want to use, do it, and be assured that you have a very wide safety margin. But if you have to go down to 25wvdc to make it fit, don't lose any sleep over it. It'll be fine. 

 I plan on building my 1st MAX with 470uf 25v Nichicon KZ Muse output caps. 

 I'm considering selling one or two of my four MAX boards as "mini-kits" including just the board, tube sockets, a pair of tested tubes, output caps, and maybe one of those big black Noble volume pots. 

 I figure there's some value in getting the weird bits out of the way for some guy so that he can just get the rest from mouser or digikey. I have enough stuff in my parts bin that i could throw in power supply caps and stuff as well, but i figure that'll only confuse people who expect the kit to exactly match the BOM and annoy people who want to use parts niftier than i consider acceptable.


----------



## tomb

Quote:


  Originally Posted by *ericj* /img/forum/go_quote.gif 
_First, there is almost no information recorded below 20hz. Most of what you can identify as audible bass is between 40 and 70hz. So, with 470uf on the output, there will be almost no actual bass rolled off on your 40ohm cans. So, i sincerely doubt that you would be able to hear a difference between 680uf and 1000uf - even if you only listen to organ drone._

 

There is ample evidence of phase distortion at up to 10 times the corner frequency. That's where this strategy comes from and is documented in many places, including the MAX website. 


  Quote:


 And the second point, I'd just been meaning to pop in and say this: 

 The DC voltage seen by the output cap, aside from the initial turn-on pulse, is whatever voltage you bias them to. 

 In any sane millett configuration, this will be between 12 and 15 volts. 

 Moreover, the voltage rating on the cap is the 'working voltage', meaning that occasional transients above that voltage are generally allowable, 
 

Arguing minimum voltage rating under failure scenarios is a risky business. Black Gates are expensive. There are plenty of reasons to rate the cap for a maximum failure voltage, given the PS supply and the single-sided nature of the Millett design. Get a cranky socket or tube, or a badly adjusted trimmer on the tube bias and you could rack the entire PS voltage through the output caps. I would not want to do that for even a half second with $10 - $15 caps. 

  Quote:


 In general, when working with power circuitry, it's advisable to use a cap that is rated for a voltage somewhat higher than you believe it will ever work at. 

 But the output cap isn't working very hard at all. 

 So, in general, even with a 12ae6a and 30v B+, a 25v output cap should work for at least several years before it starts to degrade. 
 

Your opinion. If you want to risk your money doing this, by all means, but please don't try to convince the rest of us.

  Quote:


 About the same time frame as the electrolyte would start to dry out anyway. Over a delta of decades, electrolytic capacitors are consumables. 

 I plan on building my 1st MAX with 470uf 25v Nichicon KZ Muse output caps. 
 

If you adjust for a 24VDC PS voltage, this might work, but it is ill-advised to flirt that closely with a max rating, IMHO. Plug the thing into a different wall outlet and you may see 26-27V and not know it. There are the previously mentioned scenarios, too. 

  Quote:


 I'm considering selling one or two of my four MAX boards as "mini-kits" including just the board, tube sockets, a pair of tested tubes, output caps, and maybe one of those big black Noble volume pots. 

 I figure there's some value in getting the weird bits out of the way for some guy so that he can just get the rest from mouser or digikey. I have enough stuff in my parts bin that i could throw in power supply caps and stuff as well, but i figure that'll only confuse people who expect the kit to exactly match the BOM and annoy people who want to use parts niftier than i consider acceptable. 
 

 A commendable thought, but I agree with the confusing part.


----------



## dsavitsk

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_As for comparisons between Auricaps and Vitamin Q's, FallenAngel or MrMajestic2 may be in the best position to offer an opinion soon on that - I can't. A guess might be that the Auricap is more detailed but the Vitamin Q probably is more lush with greater bass punch - just a guess from what I've read._

 

I'd actually guess just the opposite -- the Auricaps are generally more lush in the mids, rolled off on both the top and bottom, and less detailed, while the Vit Q's are clearer. Seems odd, I know. 

 The word on the street is that Jensen PIOs, which I have not tried yet, are lush in the way people think oil caps should be, and this is likely where the reputation comes from (also from the fact that Vit Q's are from the same vintage as tubes like the 12AU7 which are themselves lush, and thus amps using VitQ's and 12AU7s will have that characteristic vintage sound) but VitQ's are not particularly lush on their own. They are a bit clearer and more balanced. Blackgates are very lush, and Vit Q's balance them out a bit.

 As a side note, there are a lot of people ordering up Auricaps here. My advice, for what it's worth, is that Sonicap Gen 1s are cheaper, more detailed, and more balanced than Auricaps, and Sonicap Gen 2s have a similar sonic signature to Auricaps, but are also cheaper and a bit more detailed. I would use either over an Auricap, even if they cost the same. Another option is Dynamicaps which are a bit more expensive than Auricaps, but are widely regarded as being the better capacitor.

 Really, as I have lived with a few of these options for a while, I prefer just about anything to an Auricap


----------



## ruZZ.il

eeh. yeah I did kind of overlook it.. makes me consider the vitamin q's more.. wouldn't those fit in CA8 too(or did I read that they shouldn't be tombstoned there?)? 

 aargh I'm getting dragged into 100$ caps too and I'm trrrying to be conservative, but if I'm building the thing, I may as well.. I love/hate this stuff 
	

	
	
		
		

		
		
	


	



 tom you got p.n/links for those CA4/5's you mentoned?

 I need to sleep on the cap ideas I think.. troyhoot had some good reasoning, and since most of the signal will go through the film caps anyway, I may just keep the auri's and save a bit on the blackgates.. but those MUSE KZ seem tall..
 I think in a month or so, when another bunch of ppl have stuff built.. we should all post our BoM's specially the boutique bits.. with sources and prices.. so everyone else can just get ideas, or pick one that suits them.

 I really love the whole discussion that threads from each thought.. I appreciate every bit of info I can ponder on, so thanks again 
	

	
	
		
		

		
		
	


	




 edit: dsavitsk, that recommendation could actually really help me.. thanks.

 looks like I'm sourcing this thing from like 5 places afterall.... whee..


----------



## dsavitsk

Quote:


  Originally Posted by *ruZZ.il* /img/forum/go_quote.gif 
_aargh I'm getting dragged into 100$ caps too and I'm trrrying to be conservative, but if I'm building the thing, I may as well.. I love/hate this stuff 
	

	
	
		
		

		
			



_

 

If I were building one of these, and especially if I didn't have a lot of experience with boutique caps, I'd probably start with Blackgates all around but no bypasses. Live with the amp for a few months, then sneak some bypasses in.


----------



## FallenAngel

Quote:


  Originally Posted by *dsavitsk* /img/forum/go_quote.gif 
_If I were building one of these, and especially if I didn't have a lot of experience with boutique caps, I'd probably start with Blackgates all around but no bypasses. Live with the amp for a few months, then sneak some bypasses in._

 

Interesting idea, I'll try building my 2 like this.

 #1
 Cathode Bypass: ELNA RFS 1000uF/25V
 Output: BlackGate N 680uF/35V

 #2
 Cathode Bypass: ELNA RFS 1000uF/25V
 Cathode Bypass Bypass 
	

	
	
		
		

		
		
	


	




 : 0.47uF Vitamin Q
 Output: BlackGate N 680uF/35V
 Output Bypass: 0.47uF Vitamin Q


 Quick question, would it be worth it to put a BlackGate Standard in the Cathode Bypass position instead of the Elna RFS? I heard it's not recommended over the RFS in the SOHA.


----------



## tomb

Quote:


  Originally Posted by *dsavitsk* /img/forum/go_quote.gif 
_I'd actually guess just the opposite -- the Auricaps are generally more lush in the mids, rolled off on both the top and bottom, and less detailed, while the Vit Q's are clearer. Seems odd, I know. 

 The word on the street is that Jensen PIOs, which I have not tried yet, are lush in the way people think oil caps should be, and this is likely where the reputation comes from (also from the fact that Vit Q's are from the same vintage as tubes like the 12AU7 which are themselves lush, and thus amps using VitQ's and 12AU7s will have that characteristic vintage sound) but VitQ's are not particularly lush on their own. They are a bit clearer and more balanced. Blackgates are very lush, and Vit Q's balance them out a bit._

 

Well, mine was just a guess. Now the Master has spoken. 
	

	
	
		
		

		
		
	


	




  Quote:


 As a side note, there are a lot of people ordering up Auricaps here. My advice, for what it's worth, is that Sonicap Gen 1s are cheaper, more detailed, and more balanced than Auricaps, and Sonicap Gen 2s have a similar sonic signature to Auricaps, but are also cheaper and a bit more detailed. I would use either over an Auricap, even if they cost the same. Another option is Dynamicaps which are a bit more expensive than Auricaps, but are widely regarded as being the better capacitor.

 Really, as I have lived with a few of these options for a while, I prefer just about anything to an Auricap 
	

	
	
		
		

		
		
	


	



 

I think you are right about the Sonicaps. I have four of those GEN II's and can't wait to try them and will order more the first chance it get. Cheap, small, and every report says great - what's not to like?


----------



## MrMajestic2

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_As for comparisons between Auricaps and Vitamin Q's, FallenAngel or MrMajestic2 may be in the best position to offer an opinion soon on that - I can't. A guess might be that the Auricap is more detailed but the Vitamin Q probably is more lush with greater bass punch - just a guess from what I've read._

 

Im afraid I wont be able to compare these two since I didnt get the Auricaps. I opted for the Vitamin Qs, Black Gate NX-HiQs as well as the standard BOM Wimas as bypass caps. Havent decided on the final configuration of my two boards yet though.


----------



## Troyhoot

The right Wallwart came today so I soldered in my inputs and started to bias. and im having some troubles...

 So I biased the power supply to 27 with no troubles. Went to bias in the tubes and they are reading 23volts and 22.8volts a piece and the trimpots are not effecting them. I figured while I was trying to find the problem on my own I would ask for advice too. I did forget to jumper RB1L/R so I fixed that. The only thing I did mount a little differently was the C9 caps. I Used these two points that I circled instead of the original points. I didnt see any reason this would harm anything. But im still learning sooo...



 (just checked this) Either side of R1 is 12.3 and 14.6 . tube is showing 22-24 at pin1 also.
 Also I checked the Mosfet bias and Im getting Nothing at all. Tried some headphones just to see and nothing output either. The delay circuit is audibly clicking on and off also.


----------



## UglyJoe

The circled positions are the bias points, NOT a pad for the cap. Those are the small pads. According to the schematic it ties in right with the signal line there anyway, and even if you had a cold joint there (because of how large the holes are) you should still get signal through the electrolytic, so I dont *think* that that is your problem. I don't think I'd leave the caps in that position though...

 Edit: Is it going to be really hard (because of the radius of the 1uF auricaps) to get the caps to sit in the smaller holes? That might affect my decision to go with those caps... although now I am having second thoughts because of dsavitsk had to say... although, tbh, he's the only person I've ever heard with bad things to say about Auricaps.... but I am a noob when it comes to that kind of stuff, so...


----------



## Troyhoot

yeah I know they are the test points. My big auricap wires fit better though. I didn't see any problem doing it that way. But wanted some more opinions. I'm still kinda stumped. I'm checking over everything for the umptenth time now and Im not seeing any cold joints or any jumped contact points that arent supposed to be. Magnifying glass and bright lights still no help lol. Maybe ill go to bed early and sleep on it. But prolly not


----------



## UglyJoe

BTW, anyone have any opinion on the Mills resistors or other boutique resistors for RB14? Thanks.


----------



## amphead

Quote:


 Dsavitsk:
 The word on the street is that Jensen PIOs, which I have not tried yet, are lush in the way people think oil caps should be, and this is likely where the reputation comes from 
 

I have ten paper in oil copper Jensens, silver leads that were going to be in a build that just never happened. They are all .1uF , axial so not very useful for the MAX unfortunately. Unless someone can think of how they could be used of course.


----------



## tomb

Quote:


  Originally Posted by *Troyhoot* /img/forum/go_quote.gif 
_The right Wallwart came today so I soldered in my inputs and started to bias. and im having some troubles...

 So I biased the power supply to 27 with no troubles. Went to bias in the tubes and they are reading 23volts and 22.8volts a piece and the trimpots are not effecting them. I figured while I was trying to find the problem on my own I would ask for advice too. I did forget to jumper RB1L/R so I fixed that. The only thing I did mount a little differently was the C9 caps. I Used these two points that I circled instead of the original points. I didnt see any reason this would harm anything. But im still learning sooo...


_

 

The second large hole is not supposed to be a bias point, anyway. That one is specifically for tombstoning a Vitamin Q or similar cap that has a "nipple" at the lead intersection with the cap. It will be hard to bias the DB's if you've populated TA2L/R, though. That is the primary reference point for biasing the DB's by measuring from there to TB1L/R and TB2L/R.

 That said, the tube portion of the circuit is pretty much independent of the DB section.

  Quote:


 (just checked this) Either side of R1 is 12.3 and 14.6 . 
 

This much is correct, but as long as you see the heaters in both tubes glowing, that's about all it confirms.
  Quote:


 tube is showing 22-24 at pin1 also. 
 

This is not good. Pin 1 is the tube grid and is connected directly to the signal input from the pot. You should not be reading any DC here at all.

  Quote:


 Also I checked the Mosfet bias and Im getting Nothing at all. Tried some headphones just to see and nothing output either. The delay circuit is audibly clicking on and off also. 
 

Delay circuit is independent too, although if something is wrong with it you won't get signal to the headphones.

 There is something not right with your tubes and that part of the circuit. Sometimes it takes quite a bit of turns before the trimmers start to "take hold." The way they are connected on the MAX, *screwing them counter clockwise will reduce the bias voltage*. Try turning more turns counter-clockwise while watching the bias voltage on your meter. There may be a point where it takes effect. If the CCS is not conducting, you probably won't get any voltage to the DB, anyway.

 Also just in case, can you take a good birds-eye of the center of the board?


----------



## amphead

Quote:


 TomB:
 My guess is that the Toshiba BJT's are more detailed than the MOSFETs. 
 

So for me it will be K701 = detail + Tosh.BJT = DETAIL! The input stage tubes = warmth, so it might be slightly warmer than the solid state amps sound with K701 but definitely a detailed signature.


----------



## Troyhoot

Ok the counterclockwise comment made all the difference with the tube bias. Those biased right down to 13.5 or so. gotta let them settle But i turned it off and took some pics. will upload them in a second. Still getting no readings at the buffer bias points. I dont have anything in the input or output right now if that matters. 

 going to upload some images for you tomb.


----------



## tomb

Well, I'm glad you got the tube bias working, but it sounds like there's still something wrong.

 Just for a test, I racked my tube bias all the way out until it was reading almost 23V and the adjustment no longer had any effect. My tube's Pin 1 still reads zero.

 EDIT: Wait a minute - keep in mind that Pin 1 is the right-most pin going clockwise around the tube. Pin 7 is the one that's connected directly to the CCS and would've been reading 22+ volts awhile ago. So, if you got the pin numbers mixed up, that would mean the bias fixed everything with the tubes.


----------



## Troyhoot

tube voltage
 left tube- 1=14v 2=0 3=0 4=0 5=12.6 6=1.158 7=0 
 right tube 1=13 2=0 3=0 4=14.1 5=27! 6=1.018 7=0

 Doh ok think I have the pins exactly backwards. was going from the picture on the Max site. I was going from looking down at teh tube while it was pluged in. So im all off on the numbers I think. goign to go double check


----------



## tomb

Check those tube numbers again. The last "T" in Millett in my avatar is Pin 1. The "M" is Pin 7. I think that's what you've got going on.

 The 12.6 for for Pin 4 on the Left tube and 27 for Pin 4 on the Right tube is exactly right. Those are the heaters and are in series. It will start at 0, the left tube will burn 12.6V, the R1 resistor about 2-1/2V to ~14.5V, and the right tube will burn the remaining 27-14.5V, or ~12.6V - but Pin 4 on the right tube will read the total PS voltage from ground - 27V. So, all that's correct - you're just reversing the tube pin numbers (they're labeled on the board, btw 
	

	
	
		
		

		
		
	


	




 ).

 Please measure what you read at TB1L/R and TB2L/R, referenced to ground. You have the large Auricaps in this hole, but if you can read the rear lead on RB10L/R and RB11L/R, it should be the same thing.


----------



## vixr

tomb... bravo. you are what makes this hobby so cool. thank you for everything you do for us...


----------



## tomb

I can't see anything wrong on your board, but the pics aren't close enough to read the resistors or check the TO-92's (sorry - I know you went to a big effort on the pics).

 Depending on some measurements such as the one I asked for above, you could be having the same situation with the trimmers on the DB's - there's a spot where they take hold and quite a bit of travel where they are essentially OFF. Adjusting can be touchy, though. I would try to clamp one of your meter leads on the tube bias point wherever your measuring that - the back side of those DB resistors? - that will be your reference for the DB milivolts across the DB resistors. You need to be looking at the meter while you are adjusting so that you don't blow the fuse - or worse.


----------



## Troyhoot

OK IM JUST A NOOB !! I just had to turn those trim pots 20-30 times before I got any reading on the buffers. I biased them at 120 for right now just to test it. Plugged in my cans and WOW ! From my crappy Sansa e140 with some very low rate mp3s it sounds great.

 You say the ES Muse has the best bass.. If they have more then these KZ's I wouldnt want them. Thats coming from a guy with 2 15" subs in a normal cab truck 
	

	
	
		
		

		
			





 I love my bass. cant wait to get is all dialed in and try a good source.

 I was all worried for nothing.


----------



## tomb

Quote:


  Originally Posted by *vixr* /img/forum/go_quote.gif 
_tomb... bravo. you are what makes this hobby so cool. thank you for everything you do for us..._

 

Thank you - but you are being very modest about yourself. While we speak, it looks like you are helping Blooze out - that means a lot to a Millett faithful, no doubt.


----------



## tomb

Quote:


  Originally Posted by *Troyhoot* /img/forum/go_quote.gif 
_OK IM JUST A NOOB !! I just had to turn those trim pots 20-30 times before I got any reading on the buffers. I biased them at 120 for right now just to test it. Plugged in my cans and WOW ! From my crappy Sansa e140 with some very low rate mp3s it sounds great.

 You say the ES Muse has the best bass.. If they have more then these KZ's I wouldnt want them. Thats coming from a guy with 2 15" subs in a normal cab truck 
	

	
	
		
		

		
		
	


	




 I love my bass. cant wait to get is all dialed in and try a good source.

 I was all worried for nothing._

 
























 Another MAX lives!!


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## TBomb06

I finally finished up my casework tonight and got my first Max in it's final (for now) form. I have to say that, thanks to the efforts of Tom and the Max page, along with the rest of the Max crew, the assembly of the amp is pretty straightforward. The casework is definitely what makes DIY challenging for me, at least. It takes a tremendous amount of patience and planning. Needless to say, the casework on this amp is far from perfect but it is together and works...you'd have to look pretty close to see most of my "oh...I didn't think about that until it was too late" mistakes. The good thing is I will probably avoid making those mistakes in the future 
	

	
	
		
		

		
		
	


	




. I'm glad I have some more boards to make a perfect "dream Max" eventually.

 I'm listening to my Max right now as it's burning in and I have to say it sounds absolutely fantastic. Once it has some hours on it I'm going to start cranking the DBs up towards 110mV and I can't wait to see how it sounds there. Thanks to everyone who helped make this project happen!


----------



## UglyJoe

Quote:


 The second large hole is not supposed to be a bias point, anyway. That one is specifically for tombstoning a Vitamin Q or similar cap that has a "nipple" at the lead intersection with the cap. It will be hard to bias the DB's if you've populated TA2L/R, though. That is the primary reference point for biasing the DB's by measuring from there to TB1L/R and TB2L/R. 
 

Slightly confused. That second hole is clearly labeled as TA2L1/TA2R1 test points on the schematic, although it doesn't appear on the board itself. Is this just an artifact due to the way Eagle draws things (i.e., a way to get eagle to have the desired larger hole without going to a lot of trouble)? That was one thing that bothered me a little about the schematic, having a test point just the other side of a capacitor from another test point, and one that wasn't mentioned as being used during the biasing process anyway. Main reason I am asking is because if thats why that "bias" point is there then it seems like a pretty good trick that I might be able to use if I ever design something myself that might require something like that.


----------



## tomb

Quote:


  Originally Posted by *UglyJoe* /img/forum/go_quote.gif 
_TA2L1/TA2R1 ... (i.e., a way to get eagle to have the desired larger hole without going to a lot of trouble)?_

 

YES. These are _not_ identified as bias test points on the MAX website, btw:
MAX Setup and Bias Settings

  Quote:


  Originally Posted by *TBomb06* 
_I'm listening to my Max right now as it's burning in and I have to say it sounds absolutely fantastic. Once it has some hours on it I'm going to start cranking the DBs up towards 110mV and I can't wait to see how it sounds there. Thanks to everyone who helped make this project happen!_

 























 and another MAX lives!


----------



## amphead

Quote:


  Originally Posted by *Troyhoot* /img/forum/go_quote.gif 
_OK IM JUST A NOOB !! I just had to turn those trim pots 20-30 times before I got any reading on the buffers. I biased them at 120 for right now just to test it. Plugged in my cans and WOW ! From my crappy Sansa e140 with some very low rate mp3s it sounds great.

 You say the ES Muse has the best bass.. If they have more then these KZ's I wouldnt want them. Thats coming from a guy with 2 15" subs in a normal cab truck 
	

	
	
		
		

		
		
	


	




 I love my bass. cant wait to get is all dialed in and try a good source.

 I was all worried for nothing._

 

Been there , done that! 
 Well not with the MAX.
 CONGRATS!


----------



## UglyJoe

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_YES. These are not identified as bias test points on the MAX website, btw:
MAX Setup and Bias Settings
























 and another MAX lives!_

 

Oh, I knew that the weren't identified as bias points on the website... I've very carefully read that website up and down. That was part of the reason I was slightly confused when I was looking at my board and the schematic tonight... anyway, its one more trick learned that might come in handy down the road. BTW, thanks, Tom, for taking the time to make such a nice amp site.


----------



## ruZZ.il

sounds like a good day for the MAX! its going to take me some weeks to get started... I don't think I got my boards yet. I've got someone in the states in a week, for a week, so I gotta make all my shipments get there.. hopefully 2 weeks and a day, and I'll be rocking too 
	

	
	
		
		

		
		
	


	




 I think I'm going to try those gen II's too.. they sound like they'd match my cans really well aswell(my cans: great freq. extremes, slightly recessed mids). Dsavitsk, thanks for that advice. what I may just do though, is get them and keep them out for a week or 2 anyway, just to hear the diff. otherwise I wouldn't know whats what(or I'll use the wima's at first). I'll stick with the BG's 1000 and 680 for CA2/7. 

 I'm also unsure that I want to order from yet another source, so I'm not sure about the BJT alternatives.. don't think I'd even meet the min. order at bdent either so I'll probably stay with the BoM standard ON Semiconductor transistors for the DB, and possibly switch them out later on.. (despite the work, but if I get bored/itchy)

 looks like I'm on my way.. slowly 
	

	
	
		
		

		
		
	


	




 edit: tom, do you have a p.n for the led housing you used on the boxed up max you just did? and where can one find the tube protector things that go on the top case? thanks..


----------



## Zyren

Hello, i started building my max earlier today when i received my board and i am about halfway done. However, i still am missing a few pieces that werent on the bom and i am a real novice when it comes to parts and buying them online. This is my first project in the DIY scene but it has gone smoothly so far. The items i am looking for are two female RCA ports, a 1/8" mini port (have the 1/4", but i want to add the 1/8" as well), and a fuse. I am also planning on building interconnects, so any link to the male RCA plugs would be great as well. 
 I am making an order on mouser soon, so it would be preferred if i could get them from mouser. I am willing to spend a few dollars per RCA port/plug. 

 I would also like to give a huge thanks to the forums and everyone who has helped contribute to the millett max. If it wasnt for these forums, the contributions of everyone, and the wonderfully organized millett max site (great work tomb), i don't think i would have even thought about trying a project like this.


----------



## ruZZ.il

in the few mins I got:
 on tangents PIMETA part list, there's a list of a few 3.5mm (1/8'th) stereo mini jacks and RCA inputs.
 the fuse is mentioned as an optional in the BoM:
 Fuse Clips, PCB mount Mouser 534-3519
 Fuse5x20 fast blo, 1 Amp Mouser576-0217001.HXP

 if you're looking to build your interconnects as well, you may as well look at some other kind of stores.. like Take Five Audio, Parts Connection or the sorts (I dont recall too many, that come to mind.. but I've gone through a few, so they're there..).. you should look into what cables and stuff to buy for that too.. but thats a whole new journey  

 there are possibly nicer jacks and stuff than the ones on the pimeta list, but those work great for me 
	

	
	
		
		

		
		
	


	




 maybe just nicer looking ones.. like the 1/4 suggested for the MHM.. dunno.. gotta go, hope this helps you out for a bit


----------



## tomb

Quote:


  Originally Posted by *ruZZ.il* /img/forum/go_quote.gif 
_... edit: tom, do you have a p.n for the led housing you used on the boxed up max you just did? and where can one find the tube protector things that go on the top case? thanks.._

 

Radio Shack Catalog #: 276-080





 Two of these come in a pack for $1.39. If you don't have access to Radio Shack, e-bay's PartsPipe (hongkongsuperseller) is your best bet:
http://cgi.ebay.com/50-x-Copper-Chro...QQcmdZViewItem These are fifty (50) for $4.99 plus $5.50 shipping.

 Mouser has a price problem with these - wanting almost $2 for a single one. I'm not sure that DigiKey even has them. They are nice because even though they are screwed on from the inside, the LED is simply inserted with the rubber stopper behind it. You only have to be careful to remember to have the stopper pushed onto the leads before you solder them to the board (sort of like remembering to put heat shrink on before you solder).

  Quote:


  Originally Posted by *Zyren* 
_Hello, i started building my max earlier today when i received my board and i am about halfway done. However, i still am missing a few pieces that werent on the bom and i am a real novice when it comes to parts and buying them online. This is my first project in the DIY scene but it has gone smoothly so far. The items i am looking for are two female RCA ports,_

 

Straight from MisterX and a post on Headwize:
 Mouser #502-BPJF01AUX and #502-BPJF02AUX

 Neither are really that good. You are better off buying from another source. the cheapest Cardas are a good choice and available from most boutique parts dealers. Also, PartsExpress may have the best available for the lowest price with a low-price shipping option:
http://www.partsexpress.com/pe/showd...364603#reviews (again, a confirmed suggestion from MisterX).

 Personally, I use the Philmore MTG12 that can be found at Fry's. Links to male RCA's can be found at many of those places, but interconnects are not something I've ever fooled with, so I don't know.

  Quote:


 a 1/8" mini port (have the 1/4", but i want to add the 1/8" as well) 
 

This is described in Post #583 of this same thread.

 The fuse has been covered by ruZZ.il, and it is detailed along with the fuse holders on the latest revision of the MAX BOM.


----------



## tomb

Sorry ruZZ.il - forgot that you asked for the tube bushings.

 These are detailed on the MAX website under Drawings and Templates:





 The Millett standard is #561-MP10012. It has a 3/4" diameter opening and requires a 1" hole size. These can also be purchased at pretty much any hardware store in the states in those store sections that carry all the little giblet parts in the special drawers and trays.


----------



## Troyhoot

Well, I got mine all working last night before a I finally passed out thanks to Tomb. I biased the Mosfets on up to 200 and the heatsinks didnt even get very warm through 3 or 4 songs. Will try higher after I get the case done. I have a couple special pieces supposed to be finished today for my case. Hopefully in a day or two I can post some case pictures. I real excited about it. I think its original but will see haha


 I want to Thank You Tomb for all your help with my questions through this project. You are the perfect example of the quality members on this board. Also want to thank Colin and the Team for all they have done to get this project to this stage. I so glad I stumbled upon this board 
	

	
	
		
		

		
			





 Ok enough mushy now back to work..


----------



## ruZZ.il

Tom. muchos gracias... 
 anyone got part numbers for decent pin sockets? till now I've chopped up a few dip-8 op amp sockets and stuff.. looking for those strips 
	

	
	
		
		

		
		
	


	




 (for RB14, and some other little stuff like on a mini^3)
 I just ordered some stuff from sonic caps.. 
 gen II 0.22uF 200v x4
 BG NX 680 x 2
 gonna get the NX 1000's and sockets from pcx soon, tubes from RD, LSDiodes, and mouser, then done, I think
	

	
	
		
		

		
		
	


	




. 
 dankeschun
 -ruZZ


----------



## ericj

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Arguing minimum voltage rating under failure scenarios is a risky business. Black Gates are expensive. There are plenty of reasons to rate the cap for a maximum failure voltage, given the PS supply and the single-sided nature of the Millett design. Get a cranky socket or tube, or a badly adjusted trimmer on the tube bias and you could rack the entire PS voltage through the output caps. I would not want to do that for even a half second with $10 - $15 caps. 

 Your opinion. If you want to risk your money doing this, by all means, but please don't try to convince the rest of us.

 If you adjust for a 24VDC PS voltage, this might work, but it is ill-advised to flirt that closely with a max rating, IMHO. Plug the thing into a different wall outlet and you may see 26-27V and not know it. There are the previously mentioned scenarios, too._

 

Available documentation for audio-grade caps is surprisingly terse, so there are no documented surge ratings for at least Silmic II and KZ-muse caps, but it is quite common for a cap rated at 25wvdc to have a surge rating of 32vdc. 

 In normal use, and if the amp is behaving normally, a 30v turn-on spike isn't likely to damage a 25wvdc rated cap. 

 If i were spending $15/ea on output caps i'd be worried too, but i don't, and i'm not.


----------



## UglyJoe

Quote:


  Originally Posted by *dsavitsk* /img/forum/go_quote.gif 
_I'd actually guess just the opposite -- the Auricaps are generally more lush in the mids, rolled off on both the top and bottom, and less detailed, while the Vit Q's are clearer. Seems odd, I know. 

 The word on the street is that Jensen PIOs, which I have not tried yet, are lush in the way people think oil caps should be, and this is likely where the reputation comes from (also from the fact that Vit Q's are from the same vintage as tubes like the 12AU7 which are themselves lush, and thus amps using VitQ's and 12AU7s will have that characteristic vintage sound) but VitQ's are not particularly lush on their own. They are a bit clearer and more balanced. Blackgates are very lush, and Vit Q's balance them out a bit.

 As a side note, there are a lot of people ordering up Auricaps here. My advice, for what it's worth, is that Sonicap Gen 1s are cheaper, more detailed, and more balanced than Auricaps, and Sonicap Gen 2s have a similar sonic signature to Auricaps, but are also cheaper and a bit more detailed. I would use either over an Auricap, even if they cost the same. Another option is Dynamicaps which are a bit more expensive than Auricaps, but are widely regarded as being the better capacitor.

 Really, as I have lived with a few of these options for a while, I prefer just about anything to an Auricap 
	

	
	
		
		

		
		
	


	


_

 

Problem with most of those choices is that they are too large for the MAX in the standard configuration if you want to use a top without the caps sticking out. The Sonicraft Gen 1 1uF cap at 400 VDC rating is only 1.05 in (26.7 mm) long, so it should work in the case, but that's the only option I see besides the auricaps that work (don't know how big the Vitamin Q's are at 1uF capacity). 

 Another question about using the bypass caps. If phase distortions occur up to 10 times the cutoff frequency, how does that effect the sound in the area where the signal goes from passing through the electrolytic to the film cap? For a 1uF film cap at C8 with 32r cans and a 39r RB14 resistor that puts the cuttoff frequency for the film cap at 2kHz, which means phase distortions could occur all the way up to 20kHz, effectively the entire audible range. With 330 Ohm cans the phase distortions are reduced to 400-4000 Hz range, which is a little more reasonable, but could still cause problems, I assume.


----------



## tomb

Just because Troyhoot is using 1uF on his output bypasses doesn't mean that's become the new standard. It's an interesting strategy, but anything like that has to be weighed with other factors, too. In Troyhoot's case, he has found a specific solution that he's trying - nothing more implied in that.

 The current BOM lists 0.22uF. I built the first proto completely with 0.1's, which were the accepted Millett standard up until the MAX - and I can't honestly tell the difference. There have been some other discussions about going to 0.47's if they fit, but Troyhoot's 1uF is the biggest that I'm aware of ... well, except for Ferrari, that is, and he's his own guide. 
	

	
	
		
		

		
		
	


	







 So, probably all the ones that Dsavitsk mentioned have a solution and a size that will work just fine.


----------



## UglyJoe

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Just because Troyhoot is using 1uF on his output bypasses doesn't mean that's become the new standard. It's an interesting strategy, but anything like that has to be weighed with other factors, too. In Troyhoot's case, he has found a specific solution that he's trying - nothing more implied in that.

 The current BOM lists 0.22uF. I built the first proto completely with 0.1's, which were the accepted Millett standard up until the MAX - and I can't honestly tell the difference. There have been some other discussions about going to 0.47's if they fit, but Troyhoot's 1uF is the biggest that I'm aware of ... well, except for Ferrari, that is, and he's his own guide. 
	

	
	
		
		

		
		
	


	







 So, probably all the ones that Dsavitsk mentioned have a solution and a size that will work just fine. 
	

	
	
		
		

		
		
	


	


_

 

I implied the use of 1uF caps, but I checked on everything from .47uF caps and up as far as size goes, and I think that the only thing besides the Auricaps that fit were the Sonicap gen1s. Going down to .22uF or lower seems a bit useless for me (in the case of 32r cans) because that puts the cutoff frequency at 10kHz. I guess if you think your highs aren't good enough with the electrolytic that's something to look at, but I think it's probably a very large cost solution for a very minor payoff... maybe I am wrong. With Sens or other high impedance cans it's a different animal, as that gets the cutoff frequency at or below 2kHz... a lot more of the audible frequencies will actually pass through the film caps in that case. Course with 1uF film caps the cutoff frequency for Sens could be as low as 400Hz. This gets back to the whole problem with bypass caps... Enough people have reported audible differences for me to believe them; however, the "guide" to sizing a bypass cap is 1/100 of the electrolytic. It seems to me that the guide should be as large of a film cap as fiscally/sterically possible, not some rather random ratio of film cap to electrolytic. I've been trying to find information on cap-bypassing threory, but not had a whole lot of luck, so maybe there are other considerations when choosing the cap that I just don't know about.


----------



## Troyhoot

yeah dont use me as the new guidebook for sizes lol . I picked my sizes for a couple specific reasons.
 1. I have low ohm cans and wanted to get most of my midrange and highs going through the filmcap. Which took a larger film cap.
 2. Also I wanted to use KZ Muse instead of spended 10 times on blackgates. Partially for aesthetic purposes too.

 If your using blackgates I wouldnt use 1.0uf films, .1 or .22 should be more then effective and prolly sound better. You also get your moneys worth on the blackgates by using them in the midrange frequencies. 

 The above is all just my opinion and it could be completely wrong so take it as you will. I am still very new to this side of electronics. But soaking up all I can from the folks around here.

 BTW Im rocking to some Foghat slowride while I write this on my lunch break
	

	
	
		
		

		
		
	


	







 Still waiting on case parts to be finished... My RP-21 never sounded so good. Even in the uncased max lol


----------



## ericj

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_The current BOM lists 0.22uF. I built the first proto completely with 0.1's, which were the accepted Millett standard up until the MAX - and I can't honestly tell the difference. There have been some other discussions about going to 0.47's if they fit, but Troyhoot's 1uF is the biggest that I'm aware of ... well, except for Ferrari, that is, and he's his own guide._

 

I have heard that in some schools of thought - german audio DIYers specifically - nothing higher than 0.068uf is recommended. 

 But i don't have any clue why. 

 I have Nitsuko 4.7uf films that would fit, despite their crazy formfactor and wide lead spacing (they're very thin and flat), but i think they were intended for use in switching power supplies and may not be very linear for audio use. 

 I have 5uf radial polycarbonates that would just barely fit except their leads are too big. 

 There's a good chance I'll just use ERO boxed mylar 0.22uf caps. But i might go nuts and try and use something bigger or, well, different. I have a bunch of 0.68uf axial polypros that i could toombstone in there pretty easily.


----------



## tomb

Yeah, I think all of what you mention may work, eric. There are no hard and fast rules when it comes to bypassing, I guess.

 As said before, I do think Troyhoot has an interesting strategy and I'd like to give it go - more or less asymmetric bypassing between the CA2 and CA7 bypasses - rather than focusing on specific sizes.

 That doesn't mean a lot of other combinations won't work just as well, and it certainly shouldn't stop anyone from trying them. We have a good track record with the 0.1uF and 0.22uF as a baseline. If people want to experiment from there, that's DIY.


----------



## soloz2

well I just ordered all the parts to build 2 
	

	
	
		
		

		
		
	


	




 All except for a couple item's I'll pick up at radio shack and then the Toshiba transisters from B&D. for some reason my order wouldn't go through... I emailed them so we'll see.

 Anyone order extras they'd want to hook me up with?

 so total I ordered from:
 digikey
 mouser
 handmade electronics
 percy audio
 partsconexxion
 vt4c
 lsdiodes
 radio shack (if you count that)
 B&D if I can...

 oh, and I'm doing diamond buffers, muse and wilma caps


----------



## MrMajestic2

Quote:


  Originally Posted by *soloz2* /img/forum/go_quote.gif 
_well I just ordered all the parts to build 2 
	

	
	
		
		

		
		
	


	




 All except for a couple item's I'll pick up at radio shack and then the Toshiba transisters from B&D. for some reason my order wouldn't go through... I emailed them so we'll see.

 Anyone order extras they'd want to hook me up with?

 so total I ordered from:
 digikey
 mouser
 handmade electronics
 percy audio
 partsconexxion
 vt4c
 lsdiodes
 radio shack (if you count that)
 B&D if I can...

 oh, and I'm doing diamond buffers, muse and wilma caps_

 

B&D has a minimum order of $15 from the states and $50 for foreign orders, maybe thats why it didnt go thru. I guess I wont be building a BJT Max any time soon, cause I dont need $50 worth of transistors


----------



## Ferrari

Quote:


  Originally Posted by *MrMajestic2* /img/forum/go_quote.gif 
_B&D has a minimum order of $15 from the states and $50 for foreign orders, maybe thats why it didnt go thru. I guess I wont be building a BJT Max any time soon, cause I dont need $50 worth of transistors 
	

	
	
		
		

		
		
	


	


_

 

If you only need 2 pair Toshiba transistors for your Max build, PM me... I will see if I can do something for you 
	

	
	
		
		

		
		
	


	




 .


----------



## UglyJoe

So, I am a noob when it comes to electronics and I am trying to learn and understand what is going on. I have been reading over the schematic for the MAX and though I understand generally how everything functions, I am having a more difficult time understanding the specifics (ie, predicting what a voltage across or current through a given piece will be). I am having a very difficult time figuring out the CCS and how it results in a constant current of .65mA at the QA1 collector. The CCS looks kind of a like a Darlington connection, but not exactly, and I haven't seen this specific arrangement before, if I recall correctly. Would anyone with the know-how care to explain how one calculates the voltages at the various transistor junctions and the currents that are being pulled through them? Thanks!

 EDIT: So I don't hijack the thread, if anyone wants to PM me with an answer to the above that'd be great.


----------



## ericj

you can get the toshiba transistors from mcminone.com, or from newark, if you want the additional lead time of newark getting them from mcm (who they own). 

 At least, that's where i got mine


----------



## tomb

Quote:


  Originally Posted by *UglyJoe* /img/forum/go_quote.gif 
_EDIT: So I don't hijack the thread, if anyone wants to PM me with an answer to the above that'd be great._

 

It is a common two-transistor constant current source. You can read about the theory, application, and current setting pararmeters here:
http://sound.westhost.com/ism.htm#p5

 It is superior to the diode CCS used in the original Millett, and presents a very high impedance to the tube and better linearity, which is a very good thing - another item with which we owe more thanks to cetoole. Of course - no slight on Pete's original design, either. He didn't have a single TO-92 transistor in the design, so there was a reason for simplicity and going with the CCS diode. However, in the MAX's case, we've got the TO-92's over half the board. Another 2-4 made little difference in convenience, but a big dividend in performance.

 You are correct, though - I think this is getting into the weeds and perhaps you should start a separate thread if you are needing a tutorial on the circuit design. That might give cetoole a better chance to respond to it, anyway.


----------



## soloz2

Quote:


  Originally Posted by *MrMajestic2* /img/forum/go_quote.gif 
_B&D has a minimum order of $15 from the states and $50 for foreign orders, maybe thats why it didnt go thru. I guess I wont be building a BJT Max any time soon, cause I dont need $50 worth of transistors 
	

	
	
		
		

		
			



_

 

I was ordering 15 of each so I could match them. I know it isn't as crucial on these ones, but I wanted to try to get close.

  Quote:


  Originally Posted by *Ferrari* /img/forum/go_quote.gif 
_If you only need 2 pair Toshiba transistors for your Max build, PM me... I will see if I can do something for you 
	

	
	
		
		

		
		
	


	




 ._

 

Thanks!


----------



## UglyJoe

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_It is a common two-transistor constant current source. You can read about the theory, application, and current setting pararmeters here:
http://sound.westhost.com/ism.htm#p5

 It is superior to the diode CCS used in the original Millett, and presents a very high impedance to the tube and better linearity, which is a very good thing - another item with which we owe more thanks to cetoole. Of course - no slight on Pete's original design, either. He didn't have a single TO-92 transistor in the design, so there was a reason for simplicity and going with the CCS diode. However, in the MAX's case, we've got the TO-92's over half the board. Another 2-4 made little difference in convenience, but a big dividend in performance.

 You are correct, though - I think this is getting into the weeds and perhaps you should start a separate thread if you are needing a tutorial on the circuit design. That might give cetoole a better chance to respond to it, anyway._

 

Thanks... the link was some help, but it came down to algebra and pen and paper... just couldn't see it in my head. Good old algebra.... I remember the days!. Anyway, I got it figured out, thanks again Tom.


----------



## ruZZ.il

Got my tubes from RadioDaze, Phil there is nice. they had (edit:atleast, I got 4.. they probably had more..)4 GE FK6's and no GE AE's, got 2 AE RCA's.

 He asked what we're building  seemed to feel something was up. well, I'm sure he's happy.. I hope he finds more 
	

	
	
		
		

		
		
	


	




 forgot to get an estimate on whats left though...

 got stuff from sonicap: 4x 0.22 gen II, 2xNX/680
 from partscon: 2 sets of kiwames, 4 sockets(next amp..), 2xNX1000 25v and some wire..
 mouser(DB's too)&amb.. stuff more 2 mini^3's too.. for my lady and a a friend will build his with me 
	

	
	
		
		

		
		
	


	




 hope this all comes round safely 
	

	
	
		
		

		
		
	


	



 -off to london for the week. 
 thanks guys for helping me figure out some of the stuff... a bit 
	

	
	
		
		

		
		
	


	




)


----------



## Ech0

Quote:


  Originally Posted by *ruZZ.il* 
_Got my tubes from RadioDaze, Phil there is nice. they had 4 GE FK6's and no GE AE's, got 2 AE RCA's.

 He asked what we're building  seemed to feel something was up. well, I'm sure he's happy.. I hope he finds more forgot to get an estimate on whats left though..._

 

I just received some RCA 12AE6A's from RadioDaze. I too tried to get some GE 12AE6's about a week ago (six of them) and Phil said my chances were slim. I told him I'd go for any matched brand. 

 Phil speculated in an email to me that someone must have made a "how to" for something. Nice guy.


----------



## Troyhoot

Case update I wanted to share. After 4 broken pieces I have no more pieces to drill for the back. So Tomorow I have to go buy some more mirrored glass.. joy Joy. At least the front holes are drilled and in decent shape. Still need to sand edges a little though. 2 -1/2" holes are pretty easy but the 3/4" hole is giving me all kinds of trouble in the back panel.


----------



## mb3k

Quote:


  Originally Posted by *Troyhoot* /img/forum/go_quote.gif 
_Case update I wanted to share. After 4 broken pieces I have no more pieces to drill for the back. So Tomorow I have to go buy some more mirrored glass.. joy Joy. At least the front holes are drilled and in decent shape. Still need to sand edges a little though. 2 -1/2" holes are pretty easy but the 3/4" hole is giving me all kinds of trouble in the back panel.


 

 

 

_

 

Cool casing. It's like being stuck in Millett land forever.
 Is it partially see-through from the other side?


----------



## naamanf

Back from vacation. And another MAX lives! Hope to have it cased up this weekend.


----------



## pinkfloyd4ever

Quote:


  Originally Posted by *ruZZ.il* /img/forum/go_quote.gif 
_anyone got part numbers for decent pin sockets? till now I've chopped up a few dip-8 op amp sockets and stuff.. looking for those strips 
	

	
	
		
		

		
		
	


	


_

 

20 pcs
32 pcs
64 pcs


----------



## MrMajestic2

Im just now looking through my components and realizing I might have underdimesioned my toroid a bit. Its rated at 15VA only and 0,50A per secondary (2x15V). Is this on the low side? I can get the same toroid at 30VA also. Those are the only ratings I can get for a PCB mounted toroid, which is what I want in this case.


----------



## tomb

I would argue against a toroid, period - or any in-the-case transformer. I have said this many times, but there is no other DIY headphone amp design that gives the level of performance as the MAX from simply plugging in an AC walwart. I can't emphasize how much the design really benefits from incorporating that feature. You quickly go down the road of modularity once consideration is given to separate power supplies, making the rest of the design theme almost moot. Just MHO, I know - but there it is.

 As to the specifics, I run 40VA walwarts and am quite happy with them. 25VA is the absolute minimum for MOSFETs and I wouldn't dare use anything less than 18VA minimum for a MAX of _any_ configuration.


----------



## soloz2

well now I've been second guessing myself since my first attempt from BD dent didn't go through. Which 2SC/2SA resister option would be best for my Senn's? I'll probably use the amp some with my Beyers as well.

 maybe I'll configure one for senns and the other for grados... hmm... choices choices.

 I was originally going to go with the sanyo transisters, but everyone has been talking about the toshiba's. Which setup would be best? (senn is my priority)


----------



## MrMajestic2

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_I would argue against a toroid, period - or any in-the-case transformer. I have said this many times, but there is no other DIY headphone amp design that gives the level of performance as the MAX from simply plugging in an AC walwart. I can't emphasize how much the design really benefits from incorporating that feature. You quickly go down the road of modularity once consideration is given to separate power supplies, making the rest of the design theme almost moot. Just MHO, I know - but there it is.

 As to the specifics, I run 40VA walwarts and am quite happy with them. 25VA is the absolute minimum for MOSFETs and I wouldn't dare use anything less than 18VA minimum for a MAX of any configuration._

 

Well, the transformer is not going to be mounted inside the case anyway. Hmm, I guess 15VA is a bit on the stingy side then. I have to get a 30VA at least. Ill see if I can dig up a non-toroid transformer with higher VA.


----------



## tomb

Quote:


  Originally Posted by *MrMajestic2* /img/forum/go_quote.gif 
_Well, the transformer is not going to be mounted inside the case anyway. Hmm, I guess 15VA is a bit on the stingy side then. I have to get a 30VA at least. Ill see if I can dig up a non-toroid transformer with higher VA._

 

Yes - sorry I keep harping on that point about the power supply. You are correct, though 15VA is not enough.


----------



## MrMajestic2

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Yes - sorry I keep harping on that point about the power supply. You are correct, though 15VA is not enough._

 


 Dang, its hard to find PCB mounted transformers that doesnt cost an arm and a leg. Do you think a 30VA will do the trick or should I go even higher? By the way, why did you advice againt toroids? Any special reason or just when they are in-case mounted?


----------



## ruZZ.il

Quote:


  Originally Posted by *MrMajestic2* /img/forum/go_quote.gif 
_Dang, its hard to find PCB mounted transformers that doesnt cost an arm and a leg._

 

Dang, its hard to find the right one, period. I'm looking for an amveco 70062 and they're out of stock at digikey. rs sells them here, for.. well, and arm and a leg  I havent even got myself a ps for the max yet. I'll be looking around for some 240v ones now.. I think that other than that, I've ordered everything I need 
	

	
	
		
		

		
		
	


	





 PinkFloyd: thanks 
	

	
	
		
		

		
		
	


	




 noted for next time. I had to get my orders out in a jiffy so I just ordered a bunch of opamp sockets.. I needed some anyway.


----------



## tomb

Quote:


  Originally Posted by *MrMajestic2* /img/forum/go_quote.gif 
_Dang, its hard to find PCB mounted transformers that doesnt cost an arm and a leg. Do you think a 30VA will do the trick or should I go even higher? By the way, why did you advice againt toroids? Any special reason or just when they are in-case mounted?_

 

30VA is great. My advice was based on the fact that a separate PS, a Toroid, etc., will have no advantage whatsoever over a $6.99 surplus walwart. Everything is already on the board to completely regulate and remove ripple down to the quality of a STEPS - with the cheapest of AC input.


----------



## FallenAngel

Hey guys (and especially tomb)

 I'm having some serious trouble finding any 30VAC transformer other than a toroidal. I've found the wallwart enclosures (GPB483) at Jameco and am thinking of grabbing a few, but the transformers themselves is another story. Any recommendations?

 EDIT: Ah, I see when I was thinking about this message before lunch, during my lunch, people already pushed this idea


----------



## MrMajestic2

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_30VA is great. My advice was based on the fact that a separate PS, a Toroid, etc., will have no advantage whatsoever over a $6.99 surplus walwart. Everything is already on the board to completely regulate and remove ripple down to the quality of a STEPS - with the cheapest of AC input._

 

Great, Ill get one of those. The reason Im getting a toroid is that the most powerful AC wallwart I can find here is 24v/1A and I want to use 30V for my "pimped" Max 
	

	
	
		
		

		
		
	


	




 I building another one that uses the wallwart.

 Was going to use a line filter also, but I think Ill skip that one for this build.


----------



## motherone

I like to use the 24VAC 1.13 amp wall warts available at the various internet surplus shops. Rectified, that would give you 34 volts before you factor in the diode drop. The voltage will be even higher if you're not pulling the full current.

 A nice one from All Electronics (if you don't mind using screw terminals):
http://www.allelectronics.com/cgi-bi...NSFORMER_.html

 And here's one from Skycraft Surplus with a connector you'll have to replace:
http://www.skycraftsurplus.com/index...OD&ProdID=1596

 It looks like the cheap ones that used to be available at Allelectronics, Halted, and Herbach & Rademan have dried up.


----------



## MrMajestic2

Quote:


  Originally Posted by *motherone* /img/forum/go_quote.gif 
_I like to use the 24VAC 1.13 amp wall warts available at the various internet surplus shops. Rectified, that would give you 34 volts before you factor in the diode drop. The voltage will be even higher if you're not pulling the full current.

 A nice one from All Electronics (if you don't mind using screw terminals):
http://www.allelectronics.com/cgi-bi...NSFORMER_.html

 And here's one from Skycraft Surplus with a connector you'll have to replace:
http://www.skycraftsurplus.com/index...OD&ProdID=1596

 It looks like the cheap ones that used to be available at Allelectronics, Halted, and Herbach & Rademan have dried up._

 

Would love to have more options, but I we are a bit short of those here in Sweden.


----------



## tomb

Jameco has a 830ma version of the one in Motherone's first link. Also, MPJA Online has them, too -
http://www.mpja.com/prodinfo.asp?number=12637+PA
 This is an exact duplicate of the ones I use, except mine are light tan in color. They are made by Basler Electric.

 Security systems and HVAC controls contractors use these supplies as a standard. 24V is the maximum they can run without an Electrician's license and the AC lets them route the wire over long distances without worrying too much about voltage drop.


----------



## FallenAngel

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Jameco has a 830ma version of the one in Motherone's first link. Also, MPJA Online has them, too -
http://www.mpja.com/prodinfo.asp?number=12637+PA
 This is an exact duplicate of the ones I use, except mine are light tan in color. They are made by Basler Electric.

 Security systems and HVAC controls contractors use these supplies as a standard. 24V is the maximum they can run without an Electrician's license and the AC lets them route the wire over long distances without worrying too much about voltage drop._

 

Hold up, am I having a complete brainfreeze and you're saying that a nice amperage 24VAC transformer will let me run the MAX at 30V DC? No horrible searching for 30VAC transformers?


----------



## tomb

Quote:


  Originally Posted by *FallenAngel* /img/forum/go_quote.gif 
_Hold up, am I having a complete brainfreeze and you're saying that a nice amperage 24VAC transformer will let me run the MAX at 30V DC? No horrible searching for 30VAC transformers?_

 

No. Sometimes the numbers get fudged up a little higher than they should. "Loaded" in my experience may be as little as 20% of the rating and unfortunately, that's enough to keep it from flaring up much higher than 24V on its own.

 So, start with 24V even with that high amperage. Then you have:
 24V * 0.9 = 21.6VDC when rectified.
 Add the smoothing/filtering 'lytics, then you get close to VACp-p, so:
 21.6VDC * 1.414 = 30.54VDC
 However, there's the voltage drop from the rectifiers, so:
 30.54VDC - 1.4 = 29.14VDC.

 You still need to take at least 2V from the regulator, maybe more, so:
 29.14VC - 2 = 27.14VDC.

 My experience with the prototypes getting to 30V was not very fruitful. I think you can only count on 1 or 2 Volts above the 27.14 just calculated. In fact, my 40VA walwart measures 31.1VDC directly after the smoothing caps. So, only 31.1 - 29.14 = 1.96 Volts over the rating. 31.1VDC is also not enough to provide the voltage drop needed by the regulator to regulate (or remove ripple) at 30VDC.

 The huge walwarts do, however, provide much added protection against ripple and provide oodles of current for much higher DB biasing. This is with no loss of voltage at 27, or any loss of ripple reduction. IOW, that 1 or 2 extra volts never goes away, giving the regulator more voltage for ripple reduction under the greatest range. They are also cheap. 
	

	
	
		
		

		
		
	


	




 For the time being, I am quite happy with 27VDC on the MAX's. If you want more, though, you will need a higher voltage transformer.


----------



## ericj

Remember, transformer regulation both giveth and taketh away. 

 Transformers vary in how well they regulate their magnetic fields. A 'good' EI core transformer has maybe 6% regulation, and a cheap one has as much as 10% or 12%. 

 When you hook your transformer up to the wall, and read the AC input and output without any load, the percentage above it's rated output voltage can be considered it's regulation percentage, more or less. 

 SO, you will often see voltages 6% to 12% higher than Tom's calculations would suggest - when there is no load. 

 Under the full rated load, the AC output can be pessimistically expected to fall by the same percentage under it's rated output. 

 Toroidal transformers exhibit far better regulation than EI, R, or split-bobbin core transformers - but i agree with several posters that you're better off spending less money on an external wall wart or power brick with a higher VA rating than you absolutely need.

 Edit: Some transformer manufacturers actually give regulation specs, but in general you can't really trust them. The only way to be sure is to test the actual transformer. An EE friend of mine tells me that he's fond of sinking the transformer and a resistive dummy load in a vat of motor oil (to keep 'em cool) for this purpose.


----------



## TBomb06

Hey those who are more knowledgeable than I...I am having difficulty reaching a 110mV bias point on my right channel. The left I have no problem getting that high but the right trimpot "bottoms out" at ~96mV. Could it be a possibility that I just have a bad trimpot or is it something more complicated than that?


----------



## tomb

Quote:


  Originally Posted by *TBomb06* /img/forum/go_quote.gif 
_Hey those who are more knowledgeable than I...I am having difficulty reaching a 110mV bias point on my right channel. The left I have no problem getting that high but the right trimpot "bottoms out" at ~96mV. Could it be a possibility that I just have a bad trimpot or is it something more complicated than that?_

 

It should not be the trimmer. A pic would help, but in the meantime you might check the following (assuming you're doing the BJT's):

 1. 220 ohm resistors in for RB6R and RB7R? 
 2. 100 ohm resistors in for RB4R and RB5R?
 3. Trim pot the same value for both the L and R DB's?
 4. Is PN4392 in the correct position instead of a 2N5087/88?
 5. RB8R and RB9R jumpered out?
 6. A 2N5087 mixed up with a 2N5088 or vice-versa?


----------



## ratso

i am as noob as noob gets to this game (have my copy of 'electronics for dummies' in front of me now). i would like to build a max after figuring out what i'm doing, but seem to be too late for these group buys. is there anywhere to
 download the pcb files to get our own made? seeing as how i have never done this, is it gerber, eagle or other files needed? thanx.


----------



## TBomb06

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_It should not be the trimmer. A pic would help, but in the meantime you might check the following (assuming you're doing the BJT's):

 1. 220 ohm resistors in for RB6R and RB7R? 
 2. 100 ohm resistors in for RB4R and RB5R?
 3. Trim pot the same value for both the L and R DB's?
 4. Is PN4392 in the correct position instead of a 2N5087/88?
 5. RB8R and RB9R jumpered out?
 6. A 2N5087 mixed up with a 2N5088 or vice-versa?_

 

Thanks for the suggestions. I have used a meter to verify the parts I have in place.

 I have 220 ohm resistors in for RB4R,5R,6R and 7R which was taken from the BOM I placed my order from. However, both sides of the buffer are the same so I don't see why I could hit 110mV on one side and not the other.

 The trim pot is the same part number for both sides, however, when I measure resistance between the far right and far left legs of the trimmers I get 70 ohms on the left channel and 3 ohms on the right channel. This is with both trimmers adjusted to provide 95mV to their respective buffer. For the right side this is basically full out while the left side still has some adjustment left.

 The PN4392s are in the correct position as well. I don't know if measuring resistance values between the legs of those means anything but the right one measured much lower resistance values than the left.

 RB8R and 9R are jumpered out.

 The 2N5087 and 5088s are in the correct places.

 I appreciate your troubleshooting help...hopefully that information is beneficial as right now the only thing I can think of is that I might have damaged the right PN4392 because I installed it backwards and then had to de-solder it and reinstall it after scrutinizing the board before initial fire-up.


----------



## TBomb06

Quote:


  Originally Posted by *ratso* /img/forum/go_quote.gif 
_i am as noob as noob gets to this game (have my copy of 'electronics for dummies' in front of me now). i would like to build a max after figuring out what i'm doing, but seem to be too late for these group buys. is there anywhere to
 download the pcb files to get our own made? seeing as how i have never done this, is it gerber, eagle or other files needed? thanx._

 

I know that Colin (cetoole) ordered several extra boards so you should check with him not only to see if he has any leftovers but also to see if he would be OK with sharing the PCB files and you having your own printed.


----------



## tomb

Quote:


  Originally Posted by *TBomb06* /img/forum/go_quote.gif 
_Thanks for the suggestions. I have used a meter to verify the parts I have in place.

 I have 220 ohm resistors in for RB4R,5R,6R and 7R which was taken from the BOM I placed my order from. However, both sides of the buffer are the same so I don't see why I could hit 110mV on one side and not the other._

 

Tests with the prototype indicated things are fairly unstable when RB4 and RB5 are 220ohm. Just a hint - but try seeing how hot the JFETs (PN4392) are. They may not last under this scenario. What happens is that they get so hot with that amount of current, it's like balancing on the top of a basketball. The surprise is that you reliably got the Left channel to 110mV, not necessarily that the Right channel can't get there.

 I would try replacing those resistors first, then see how the trimmers operate - assuming that you've checked all those other things. It's still possible that you have a bad trimmer, or a bad JFET (from over-temps) - but changing those resistors will make things more stable and easier to tell what's going on.

 I'm sorry that this was changed - but it was a very early change - even before the Group Buy started. We decided on those resistors with the successful testing of the 2nd prototype. It was incorporated into the BOM a long time ago. I'm curious - where did you get a copy that didn't have this change? It's probably my fault somewhere, but I'd like to know where it is so that I can correct it.


----------



## tomb

Quote:


  Originally Posted by *TBomb06* /img/forum/go_quote.gif 
_I know that Colin (cetoole) ordered several extra boards so you should check with him not only to see if he has any leftovers but also to see if he would be OK with sharing the PCB files and you having your own printed._

 

Colin has posted in both Group Buy threads - here and on Headwize. He asked not to e-mail him because he'll lose track of it right now - wait until he offers the extra boards for sale in a couple of weeks. He says he has close to 50, but by all means, please read his posts to be certain.

 As for the Gerber files, we've discussed that he may release those after the next Group Buy, which will probably be at Christmas time.


----------



## ruZZ.il

Quote:


  Originally Posted by *ratso* /img/forum/go_quote.gif 
_i am as noob as noob gets to this game (have my copy of 'electronics for dummies' in front of me now). i would like to build a max after figuring out what i'm doing, but seem to be too late for these group buys......_

 

since you're new to building these things, you may like to try a kit. This one is offered by Jeff Rossel at Glass Jar Audio  (its not on his site yet, but email him if you're ineterested). specially with a large part count like this, where you could get lost just trying to order the right parts.
 Probably the most recommended way to start would be to build a CMoy on perf board(figuring things out)! 
 You could (and should) try building something like a PIMETA or a Mini³ too. The functionality of each part will be easier to learn, as would troubleshooting and dealing with the parts list to begin with (I ordered parts for my MHM from 5 sources after all... and I still need to pick up a thing or 2..). Either way, take a look at Tangents Tangentsoft.net, plenty of great tutorials and in depth talk about a lot of stuff...
 If you do decide to build something else and are still very interested in the MAX, you should definitely pick up a board or 2 when you can, either when Collin announces that he'll sell off what he has left, from someone who may sell a spare or 2 of theirs, another group buy when/if(there seems to be growing demand, and nice enough ppl to conduct them!), or a kit while they last.
 We'll still be here (probably) to help, on any of those amps too.
 good luck


----------



## amphead

Tom,
 This is primarily for you. I am considering a custom case build, in order to fit 3/4 inches of standoff at the bottom of the board. Why? You ask. I have six .1uf Jensen copper foil, paper in oil caps, with silver lead out. If I mount them underneath the board I can just about get the (solid silver)leads to 15mm length(Caps are 35mm x 16mm). I would put teflon sleeves on the leads also. You mentioned an earlier build where you used .1uf film caps. In your humble opinion, is it worth it for the sound quality?
 I think .1uf vs .22uf moves the frequency hump slightly toward treble from midrange. Top view on the board will be a little sparser. But thats eye candy vs ear candy!
 The bottom cap is the one that I have.


----------



## tomb

ruZZ.il - Thank you for mentioning those excellent suggestions for ratso!

 Amphead - I think we saw Dsavitsk mention a few posts back that the Jensens are getting rave reviews. As stated in a reply to that post, he is the Master when it comes to sampling boutique caps. 
	

	
	
		
		

		
		
	


	




 So, by all means - give those things a try.

 A couple of points, though - the Wima's are just fine in the other positions, so save the rest of those Jensens for just the CA9 and CA8 positions. As for 0.1uF vs. 0.22uF, it's an easy bet that a 0.1uF Jensen is better than a 0.22 Wima. We've talked about many caps and related many opinions gathered from Dsavitsk, Colin, and others, but my 1st and 2nd prototype MAX's have nothing but Wima's. The 1st proto has 0.1uF's in every position and the 2nd proto has 0.22uF's in every position.

 As also mentioned, I can barely tell the difference between the two amps. If pressed for a distinction, maybe the 2nd proto is slightly smoother and not as "steely." That most likely has much more to do with the fact that the 1st proto used metal oxide output resistors in the DB's. We went with metal-film output resistors in the DB's on the 2nd proto.

 Don't worry about your case design right now. Go ahead and solder those caps where you think you can live with them and see if you like the sound. If convinced or not, it's fairly easy to unsolder them. (Leave most of the leads untrimmed until you're certain.) It's possible that if they are too tall on top in a tombstone position, you may still be able to make them work in a kneeling position. Or as you say, mount them underneath. The recommended board height is 1/2", so that's only another 1/4".

 However, the concern about putting them underneath - especially with metal can caps - would be the potential for shorting the can out on the exposed board leads/solder under the board. All that stands between you and a dead short is the thin, colored film layer covering the can (assuming the Jensens are made that way - I don't know for sure). If you use spacers or a separation distance, that puts the board even higher.

 Just some things to consider - but you can probably get them to work one way or another and they are probably worth it.


----------



## Kruspe

I’m up to the “Setup and Biasing” part of my build. I’ve never done any electronics work before, so I’m not sure if I am using the DMM correctly, specifically with the DB Bias part.

 On the DMM I have the red lead in the V(Omega Sign)mA, and the black one is in the COM. I set the dial to 200 DCV for reading the PS voltage by touching the red on the +V hole on the board, and the black to one of the grounds. It was in the low twenties, so I figured I was measuring it right and used the trimmer to get it to 27.

 For the Tube Bias, I changed the dial to 20 DCV, and touched the red to the TA2L, and black to the ground. I set these to the recommended 13.5.

 Now for the DB Bias, I was originally touching the TB1R to ground, but that was giving around the same reading as the Tube Bias. This morning I noticed at the bottom of the page you actually listed TB1L/TB2L to TA2L. So I set the DMM dial to 2000m in the DCV section, and tried using that instead of ground, and it seemed more reasonable. I set both the left and right to ~66. 

 Is this correct, or is my amp going to explode?


----------



## TBomb06

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Tests with the prototype indicated things are fairly unstable when RB4 and RB5 are 220ohm. Just a hint - but try seeing how hot the JFETs (PN4392) are. They may not last under this scenario. What happens is that they get so hot with that amount of current, it's like balancing on the top of a basketball. The surprise is that you reliably got the Left channel to 110mV, not necessarily that the Right channel can't get there.

 I would try replacing those resistors first, then see how the trimmers operate - assuming that you've checked all those other things. It's still possible that you have a bad trimmer, or a bad JFET (from over-temps) - but changing those resistors will make things more stable and easier to tell what's going on.

 I'm sorry that this was changed - but it was a very early change - even before the Group Buy started. We decided on those resistors with the successful testing of the 2nd prototype. It was incorporated into the BOM a long time ago. I'm curious - where did you get a copy that didn't have this change? It's probably my fault somewhere, but I'd like to know where it is so that I can correct it._

 

No, it's not your fault at all, it's my fault for not checking the latest BOM before making my orders. It was probably one of the earliest BOMs that was available and I just didn't pay close enough attention to the updated one to notice the difference. I have noticed that the JFETs do get rather warm at times so I will try replacing those resisters and see what happens. Again, I really appreciate your help and I'll let you know what my results are.

 Edit: Well, wouldn't you know it...I don't have enough 100 ohm resistors to change out both sides. I will have to wait until I can place a Mouser order. In the meantime, would it be OK to run the amp with the buffers dialed back? I don't want to damage anything.


----------



## naamanf

Sounds like you did it all right. If the trimmers are adjusting the corresponding voltages it more then likely means you are doing it correctly.


----------



## TBomb06

Quote:


  Originally Posted by *Kruspe* /img/forum/go_quote.gif 
_I’m up to the “Setup and Biasing” part of my build. I’ve never done any electronics work before, so I’m not sure if I am using the DMM correctly, specifically with the DB Bias part.

 On the DMM I have the red lead in the V(Omega Sign)mA, and the black one is in the COM. I set the dial to 200 DCV for reading the PS voltage by touching the red on the +V hole on the board, and the black to one of the grounds. It was in the low twenties, so I figured I was measuring it right and used the trimmer to get it to 27.

 For the Tube Bias, I changed the dial to 20 DCV, and touched the red to the TA2L, and black to the ground. I set these to the recommended 13.5.

 Now for the DB Bias, I was originally touching the TB1R to ground, but that was giving around the same reading as the Tube Bias. This morning I noticed at the bottom of the page you actually listed TB1L/TB2L to TA2L. So I set the DMM dial to 2000m in the DCV section, and tried using that instead of ground, and it seemed more reasonable. I set both the left and right to ~66. 

 Is this correct, or is my amp going to explode?_

 

All of that looks/sounds correct to me...I see no reason why you should have an exploding amp


----------



## tomb

Quote:


  Originally Posted by *TBomb06* /img/forum/go_quote.gif 
_No, it's not your fault at all, it's my fault for not checking the latest BOM before making my orders. It was probably one of the earliest BOMs that was available and I just didn't pay close enough attention to the updated one to notice the difference. I have noticed that the JFETs do get rather warm at times so I will try replacing those resisters and see what happens. Again, I really appreciate your help and I'll let you know what my results are.

 Edit: Well, wouldn't you know it...I don't have enough 100 ohm resistors to change out both sides. I will have to wait until I can place a Mouser order. In the meantime, would it be OK to run the amp with the buffers dialed back? I don't want to damage anything._

 

By all means - you will get very good results at 30ma, which should measure out to ~66mV. 5-10mV either way is probably close enough down in that range. That will also let you confirm that everything else is OK before you do that work on the resistors.


----------



## tomb

Quote:


  Originally Posted by *TBomb06* /img/forum/go_quote.gif 
_ Quote:


  Originally Posted by *Kruspe* 
I’m up to the “Setup and Biasing” part of my build. I’ve never done any electronics work before, so I’m not sure if I am using the DMM correctly, specifically with the DB Bias part.

 On the DMM I have the red lead in the V(Omega Sign)mA, and the black one is in the COM. I set the dial to 200 DCV for reading the PS voltage by touching the red on the +V hole on the board, and the black to one of the grounds. It was in the low twenties, so I figured I was measuring it right and used the trimmer to get it to 27.

 For the Tube Bias, I changed the dial to 20 DCV, and touched the red to the TA2L, and black to the ground. I set these to the recommended 13.5.

 Now for the DB Bias, I was originally touching the TB1R to ground, but that was giving around the same reading as the Tube Bias. This morning I noticed at the bottom of the page you actually listed TB1L/TB2L to TA2L. So I set the DMM dial to 2000m in the DCV section, and tried using that instead of ground, and it seemed more reasonable. I set both the left and right to ~66. 

 Is this correct, or is my amp going to explode?

 

All of that looks/sounds correct to me...I see no reason why you should have an exploding amp 
	

	
	
		
		

		
		
	


	


_

 

Ditto. You have done it exactly right. What's happening is that you are actually measuring the voltage across the DB output resistors, not from ground. The object is to set the Class A bias on the DB circuits so that they are always flowing current. That makes them sound better by removing any switching noise that occurs when the transistors turn on and off. (We want them ON all the time)

 We've spec'd the BJT versions of the MAX at 50ma - but you can go higher, depending on the height of the heat sinks you've used. 50ma is the recommended normal current for BJT's and 1" heat sinks.

 Anyway, the output resistors of the DB's are 2.2ohms. I = V/R. So, to get 50ma through the DB's, we want 0.050 = V/2.2, or V = 110mV across each of the resistors. You've set them for 66mV, which is I = 0.066/2.2 = 30ma, which is a good conservative amount while you're checking out the amp and breaking it in.

 Good job!!


----------



## ruZZ.il

all this talk... 
	

	
	
		
		

		
		
	


	







 I want to build my aaamplifier, aamplifier aamplifier..
 I want to build my amplifier 
 I want to build my aaamp
 I want to build my amplifier
 I want to build it... now 

 Amplifier builders are coming your way
 So forget all your duties oh yeah (hey, that bit fits in..)
 Fat bottomed tubes will be built today
 So look out for those boutiques oh yeah 
 On your marks get set go
 amplifier building amplifier building amplifier building


 hm.. k.. enough..


----------



## Kruspe

Ok, thanks. Sounds great btw, night and day difference for the bass on my DT880s.

 All that’s left now is to clean up the case a little and put the top plate on.


----------



## TheRobbStory

Quote:


  Originally Posted by *ruZZ.il* /img/forum/go_quote.gif 
_all this talk... 
	

	
	
		
		

		
		
	


	







 I want to build my aaamplifier, aamplifier aamplifier..
 I want to build my amplifier 
 I want to build my aaamp
 I want to build my amplifier
 I want to build it... now 

 Amplifier builders are coming your way
 So forget all your duties oh yeah (hey, that bit fits in..)
 Fat bottomed tubes will be built today
 So look out for those boutiques oh yeah 
 On your marks get set go
 amplifier building amplifier building amplifier building


 hm.. k.. enough.. 
	

	
	
		
		

		
		
	


	


_

 

Plug in your soldering iron and ride!


----------



## TBomb06

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_By all means - you will get very good results at 30ma, which should measure out to ~66mV. 5-10mV either way is probably close enough down in that range. That will also let you confirm that everything else is OK before you do that work on the resistors._

 

What does "confirming everything else is OK" consist of? To me, an electronics project turns out OK if nothing smokes or melts when I turn it on 
	

	
	
		
		

		
		
	


	




 That, and if all of my measurements come out right (PS voltage, tube bias, DB bias). I might actually try replacing the right PN4392 first since the one that is in there has been de-soldered and re-soldered, which might have gotten it too hot. The left one seems to be holding up OK. Thanks again Tom!


----------



## ruZZ.il

my guess, it plays the music you make it to.. and sounds good 
	

	
	
		
		

		
		
	


	




 if anything is dysfunctional, it probably wouldnt do that too well..
 play for a little while, then make sure nothing is smolderingly hot (dont touch the tubes though, they may be  )


----------



## TBomb06

Quote:


  Originally Posted by *ruZZ.il* /img/forum/go_quote.gif 
_my guess, it plays the music you make it to.. and sounds good 
	

	
	
		
		

		
			





 if anything is dysfunctional, it probably wouldnt do that too well..
 play for a little while, then make sure nothing is smolderingly hot (dont touch the tubes though, they may be  )_

 

Well, yeah 
	

	
	
		
		

		
		
	


	




 I've been playing the amp for a couple of days now and everything sounds fine. I have noticed that today, for the first time, I seem to get some hum from touching the sides of the case or the volume knob, and that the tubes are kind of microphonic as well anytime my hands get near them. I only notice it without anything playing, though.

 Edit: I believe that the hum and tube microphonics are related to the outlet I have the amp plugged into. I plugged it into a different outlet when I first noticed the noise, and after plugging it into a third outlet the noise is much less noticeable.


----------



## ruZZ.il

the tube microphonics are probably from a field you create by the charge in your body, altering the movement of electrons that are emitted from the cathode towards the anode, which is usually the functionality of the grid thats connected to the audio signal.. but if you disturb that field, you would probably hear it..

 edit: doh, grounding.. I was thinking in the (electron) clouds for a second


----------



## ericj

Quote:


  Originally Posted by *TBomb06* /img/forum/go_quote.gif 
_ I have noticed that today, for the first time, I seem to get some hum from touching the sides of the case or the volume knob, and that the tubes are kind of microphonic as well anytime my hands get near them. I only notice it without anything playing, though._

 


 This actually sounds like classic grounding issues. 

 I'm assuming you have a big Alps pot, right? Get some thin wire, back out one of the screws on the back of the pot a bit, wrap wire around it, put the screw back in, and connect the other end of the wire to ground. 

 I can almost 100% guarantee that this will end the hum when you touch the knob. 

 If it does, and you still have hum when touching the side of the case, you need to do something to ground the case, too.


----------



## tomb

Quote:


  Originally Posted by *ericj* /img/forum/go_quote.gif 
_This actually sounds like classic grounding issues. 

 I'm assuming you have a big Alps pot, right? Get some thin wire, back out one of the screws on the back of the pot a bit, wrap wire around it, put the screw back in, and connect the other end of the wire to ground. 

 I can almost 100% guarantee that this will end the hum when you touch the knob. 

 If it does, and you still have hum when touching the side of the case, you need to do something to ground the case, too._

 

Agree 100%.

 As for microphonics, it takes an actual touch and contact - moving your hand within the proximity of the tube doesn't do it - as Eric says, that's a grounding issue.

 That said, it's possible to get a tube that's so microphonic it will almost never stop ringing from the mechanical echo of simply flipping the power switch. If a tube is that badly microphonic, ditch it immediately. In other cases, you may have a tube that can be pretty bad, but any ringing stops quickly and sounds quite good as long as you don't touch anything. It always involves contact from something, though.


----------



## tomb

Quote:


  Originally Posted by *TBomb06* /img/forum/go_quote.gif 
_What does "confirming everything else is OK" consist of? To me, an electronics project turns out OK if nothing smokes or melts when I turn it on 
	

	
	
		
		

		
		
	


	




 That, and if all of my measurements come out right (PS voltage, tube bias, DB bias). I might actually try replacing the right PN4392 first since the one that is in there has been de-soldered and re-soldered, which might have gotten it too hot. The left one seems to be holding up OK. Thanks again Tom!_

 

Aha! Now we have a confession. 
	

	
	
		
		

		
		
	


	







 Yes, I bet that JFET is your problem. As for the rest of your comment - there are always unforseen issues that could crop up. Having a runaway DB would not be a pretty picture, for instance. Some of the grounding issues metioned in the other post is another. Just have one little tantalum let go and you could ruin a bunch of stuff. All of these things will be exacerbated if you are running your MAX to the max, so to speak. A minimum of caution and prudence could mean the difference between an "aw shucks" or an "oh crap."

 Now, maybe that caution lasts only a day or a few hours - whatever it takes to make many measurements, note the heat and whether it's something unusual, try several headphones, make sure the delay is working, etc., etc. Your choice, though.


----------



## TBomb06

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Agree 100%.

 As for microphonics, it takes an actual touch and contact - moving your hand within the proximity of the tube doesn't do it - as Eric says, that's a grounding issue.

 That said, it's possible to get a tube that's so microphonic it will almost never stop ringing from the mechanical echo of simply flipping the power switch. If a tube is that badly microphonic, ditch it immediately. In other cases, you may have a tube that can be pretty bad, but any ringing stops quickly and sounds quite good as long as you don't touch anything. It always involves contact from something, though._

 

I appreciate both eric and your suggestions. I'll give that a try when I get a chance as well. I should have just grounded the Alps to begin with but I forgot to when the time came.


----------



## amphead

Quote:


 TomB:
 Jensens for just the CA9 and CA8 positions. As for 0.1uF vs. 0.22uF, it's an easy bet that a 0.1uF Jensen is better than a 0.22 Wima. 
 

Thats enough encouragement for me, just wanted to sanity check the idea. The cans on the Jensens have an insulated sleeve, so I will just sleeve the leads for extra protection. 
 Thanks Tom!


----------



## amphead

Hey Tom,
 Colins layout Rocks! I can just barely mount all four Jensen caps(35mm x 16mm) on top of the board laying down. I will be pushing the 15/20mm max lead length spec. I am at 21mm for CA9R and 22mm for CA8R (solid silver leads). How warm are the heatsinks with BJT? The caps at CA8L/R are 5mm from the heatsinks. 
 Thanks!


----------



## ericj

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_As for microphonics, it takes an actual touch and contact - moving your hand within the proximity of the tube doesn't do it_

 


 There have been tubes that sensitive - the CK5886 requires a 100000 megohm grid resistor, and has to be installed in a dark chamber because ambient light is enough to make it misbehave. Dust on the tube could conceivably interfere with the biasing. But unless you're counting indivdual coulombs it's a pretty worthless tube.


----------



## Sixer

You guys sound like you're having so much fun - I can't wait for my boards to arrive 
	

	
	
		
		

		
		
	


	




 Ok I'm just about to make my orders from mouser and a few other places - but can someone check that this looks ok for my caps:

 CA2: 1000uF Muse ES 25V
 CA9: 0.22uF Auricap 450V

 CA7: I was going to socket this position and try a 470uF 35V Muse ES and 1000uF 25V Muse KZ
 CA8: I think I'll go with the larger 1uF 200V Auricap here, the theory makes sense to put as much of the sound as you can through the film cap.
 RB14: Was going to socket and try with and without a Kiwame, maybe 33ohm? or should I go for higher?

 I'll be using 32ohm grados with this amp.

 I still need to find a nice volume knob - tomb, what is the knob you have on your build on the max site?

 Oh and could someone please give me mouser part numbers for the RCA input jacks I should be using?

 Thanks


----------



## ruZZ.il

in the last few pages (around 37-9) we spoke again about some of the caps, including some suggestions made by dsavitsk who's.. listened to alot of caps before 
	

	
	
		
		

		
		
	


	




 I was looking at the auricaps, and trying to keep costs down a little.. I settled on some sonic caps after all. tom posted some stuff about RCA jacks, something I need to pick up too I'm just going to use a minijack in the meantime.. or maybe solder my alien DAC directly 
	

	
	
		
		

		
		
	


	



 with the grado's you couldnt do any harm by having some resistors there.. you dont need too much gain with them anyway, I'm using 40ohm cans, and I'll socket the output resistors too.. going to play with 24ohm and 51ohm.. will benefit a bit in the lower cutoff frequency (trying to take it as low as possible.. around 2hz.. since some distotion is supposedly audible up to 10x that value.. so, keeping it below the 'audible' level can only be good).. anyway, my bit  wait till they all wake up to get theirs


----------



## Sixer

Thanks ruZZ.il. Yeah I have read pretty much the whole thread - I just wanted someone to make sure I wasn't going to do something entirely stupid.


----------



## tomb

Quote:


  Originally Posted by *amphead* /img/forum/go_quote.gif 
_Hey Tom,
 Colins layout Rocks! I can just barely mount all four Jensen caps(35mm x 16mm) on top of the board laying down. I will be pushing the 15/20mm max lead length spec. I am at 21mm for CA9R and 22mm for CA8R (solid silver leads). How warm are the heatsinks with BJT? The caps at CA8L/R are 5mm from the heatsinks. 
 Thanks!_

 

That's good news! Don't worry about the heat. It's not an environment for Jupiters and their beeswax, but you won't have a problem as long as they are not actually _touching_ the heat sinks.


----------



## tomb

Quote:


  Originally Posted by *Sixer* /img/forum/go_quote.gif 
_You guys sound like you're having so much fun - I can't wait for my boards to arrive 
	

	
	
		
		

		
		
	


	




 Ok I'm just about to make my orders from mouser and a few other places - but can someone check that this looks ok for my caps:

 CA2: 1000uF Muse ES 25V
 CA9: 0.22uF Auricap 450V

 CA7: I was going to socket this position and try a 470uF 35V Muse ES and 1000uF 25V Muse KZ_

 

Hmm ... interesting question here. You might let your decision on the heat sink height and your case make it for you, though. The KZ's won't fit regardless if you are casing it in the 3rd slot of the Hammond with 1" heat sinks.

 The Muse ES 470uF 35V is an ideal choice, but they are only available at BDent and Michael Percy. At Handmade, they have the 470uF, 25V ES and also a 1000uF, 25V ES. If you are going to take the risk with 25V caps (see the exchange between ericj and myself awhile back), then the 1000uF might be best, especially with Grados. The 1000uF 25V ES is 32mm high. If I'm not mistaken, that will fit. I measure 33.5mm in the CAD file for the recommended Hammond. That's close, for sure - you might try just slipping the board in the third slot and measuring yourself from the top surface of the board to the underside of the top plate.

 Ericj is correct that if everything works correctly, and you have no hiccups, the 25V cap may suffice - if you want to take the risk. The failure mode is not catastrophic, either - if it starts failing, you may notice a slight swelling - perhaps nothing more than that (that would still mean the cap went bad and needed replacement).

 All things being equal, 35V is best, but if you go into this eyes wide open you may be successful. The Nichicon Muse ES is a very high quality cap, so you would expect some safety factor on their part, too. Again, too much for me to risk with Black Gates - but this is a different situation. It's up to you.

 BTW - socketing electrolytics is never recommended - just too much charge and voltage, and not enough dependability in the socket. Just trim your leads so that you leave about 1/4" under the board. That will make removing them with the soldering iron much easier.

  Quote:


 CA8: I think I'll go with the larger 1uF 200V Auricap here, the theory makes sense to put as much of the sound as you can through the film cap.
 RB14: Was going to socket and try with and without a Kiwame, maybe 33ohm? or should I go for higher? 
 

Socketing the output resistor positions is a good idea if you are uncertain. Since it often comes to a personal taste anyway, even more so. You will want to focus on 12FK6 tubes in any case. Whatever's the lowest you can live with (including -0-) is best. 33 is as good a start as anything - maybe 50, 75, and 100. If you are ordering the Muse ES from Handmade, they also have Stackpole resistors - get the 2W versions. These are very cheap and give you close to the quality of Kiwame's. You could buy several sizes and experiment until you have a good idea what you want, then buy the Kiwame's later. Just a suggestion. Quote:


 
 I'll be using 32ohm grados with this amp. 
 

The MAX will pair quite nicely with Grados - crank those BJT DB's up to 50ma and rock. 
	

	
	
		
		

		
		
	


	




  Quote:


 I still need to find a nice volume knob - tomb, what is the knob you have on your build on the max site? 
 

E-bay seller PartsPipe - also known as hongkongsuperseller. Here's a current listing for a pair - 30mm diameter:
2 PCS 30mmDIAx22 Aluminum Hi-Fi VOLUME CONTROL KNOB

  Quote:


 Oh and could someone please give me mouser part numbers for the RCA input jacks I should be using? 
 

This was discussed in Post #734 in this thread.

 Note that the _best_ Mouser RCA jacks are not very good. Since you are obviously ordering from some boutique dealers to get those caps, you should buy them there. The Cardas CTFA's are fairly reasonable and at most boutique dealers. As noted in that post, I use the Philmore MTG12 - $4.99 a pair at Fry's and elsewhere. Parts Express probably has the best/cheapest that are readily available if you don't have a Fry's that has those jacks. This was also mentioned in that post.

  Quote:


 Thanks 
	

	
	
		
		

		
		
	


	



 


 EDIT: Please understand I am only suggesting the lower voltage caps if you are wanting the Muse ES, but are unable to order from BDent or M.Percy. The 25V is not an approved design selection, but if you want to experiment and take the risk, those are a few things you can try.


----------



## TBomb06

Ok, I grounded the Alps and the hum is gone. Should have done that to begin with.

 As for the right DB bias issue...I replaced the right PN4392 and now I am only able to reach 105mV max. If I back the trimmer out any more it actually starts dropping back down to ~103mV until the trimmer bottoms out. I currently am running both channels at 90mV and the JFETs don't seem any hotter than anything else on the board. Hopefully replacing the RB4 and RB5 resistors will fix the problem.


----------



## tomb

Quote:


  Originally Posted by *TBomb06* /img/forum/go_quote.gif 
_Ok, I grounded the Alps and the hum is gone. Should have done that to begin with.

 As for the right DB bias issue...I replaced the right PN4392 and now I am only able to reach 105mV max. If I back the trimmer out any more it actually starts dropping back down to ~103mV until the trimmer bottoms out. I currently am running both channels at 90mV and the JFETs don't seem any hotter than anything else on the board. Hopefully replacing the RB4 and RB5 resistors will fix the problem._

 

What you describe is exactly what should happen with the resistors you have. Rest assured, changing those out will fix it.

 EDIT: Be sure to back those trimmers off before powering up after changing those resistors - your current will be doubled.


----------



## TBomb06

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_What you describe is exactly what should happen with the resistors you have. Rest assured, changing those out will fix it.

 EDIT: Be sure to back those trimmers off before powering up after changing those resistors - your current will be doubled._

 

Thank you for all your help, Tom! I will make sure and crank the trimmers back down. So I guess this is what you meant when you said they were "unstable". Anyway, I will get some more 100 ohms in and replace them and then report back.


----------



## Sixer

Wow thank you for such a comprehensive reply tomb!

 Ah of course I wasn't thinking about the voltage specs for CA7 - I guess it's worth a try to see if the 25v 1000uF sounds any better, and if it does, hopefully it won't fail. I'll have the 35V 470uF muse ES on hand in case they aren't happy.
 You're right (of course) the KZ will be a difficult fit, I'll go the 1000uF 25V ES - it might just fit. I intend to build the MOSFET version at this stage - so the board will be on the lower slot of the Hammond anyway to accommodate the 1.5" heatsinks. I'm going to be getting my caps from Micheal Percy, since it means I can get them all from the one place. I'll get a couple of different values of the 2W Kiwame too and experiment - they are only a bit more than $1 each.

 Thanks for the tip about not socketing the caps too - it makes sense not to 
	

	
	
		
		

		
			





 That volume knob is exactly what I'm after 
	

	
	
		
		

		
		
	


	




 I'll report back my findings on the caps and resistors once I have it all up and running.


----------



## tomb

Quote:


  Originally Posted by *Sixer* /img/forum/go_quote.gif 
_Wow thank you for such a comprehensive reply tomb!

 Ah of course I wasn't thinking about the voltage specs for CA7 - I guess it's worth a try to see if the 25v 1000uF sounds any better, and if it does, hopefully it won't fail. I'll have the 35V 470uF muse ES on hand in case they aren't happy.
 You're right (of course) the KZ will be a difficult fit, I'll go the 1000uF 25V ES - it might just fit. I intend to build the MOSFET version at this stage - so the board will be on the lower slot of the Hammond anyway to accommodate the 1.5" heatsinks. I'm going to be getting my caps from Micheal Percy, since it means I can get them all from the one place. I'll get a couple of different values of the 2W Kiwame too and experiment - they are only a bit more than $1 each.

 Thanks for the tip about not socketing the caps too - it makes sense not to 
	

	
	
		
		

		
		
	


	




 That volume knob is exactly what I'm after 
	

	
	
		
		

		
		
	


	




 I'll report back my findings on the caps and resistors once I have it all up and running._

 

My measurements show that the 1000uF, 50V KZ's will fit. They are 40mm tall. Placing the board in the bottom slot measures 40.55mm from the top of the board to the bottom surface of the lid. I'd use those and remove any doubt of whether the voltage rating will be enough.

 Most of my comments were based on your using the BJT's and placing the board in the 3rd slot.


----------



## tomb

Frankly, I am a little surprised at the number of MOSFET MAXes. It seems that MOSFET builders are in a substantial majority in this thread.

 It's an interesting feature that Colin provided for us, but MOSFETs were not my first choices for the MAX. (Obviously - I built both prototypes with BJT's.) The only thing that determines the current capability, re MOSFETs vs. BJTs, is the height of the heat sinks - nothing more. The fact that MOSFETs are _required_ to run at the higher current doesn't mean the BJT's can't.

 Others have said it, but tubes + MOSFETs = warm + warm, whereas tubes + BJTs = warm + detail.

 Just MHO - no criticism intended - especially to the previous poster - but I'm really curious - where's all this interest for the MOSFETs coming from?


----------



## Sixer

Ok well this is probably a rather naive reason, but basically I figured that all the highly regarded diy amps must use mosfet output stages for a reason, so they must be good! And that it pretty much didn't matter either way. 
	

	
	
		
		

		
		
	


	




 If you think this is a mistake i'll seriously consider the BJT version instead.


----------



## tomb

It's certainly not a _mistake_ ... I was just making an observation. I personally don't know for sure which pairs better with the MAX at all - just surmising from some of the comments I've been reading in other places that perhaps MOSFETs add more warmth to the warmth that's already there.

 I wonder if part of this is the admitted difficulty in finding some of the favorite Toshibas. There are other options for the BJT's, though. For instance, the MJE243/253 BJT pair is very cheap and easy to get at Mouser - 70 and 58 cents, respectively. This will get you to 90% of the detail from the hard-to-find Toshibas. Regardless, I need to build a MOSFET version so that I can speak with a more qualified opinion on this question.


----------



## ericj

I've pointed out before, mcminone.com has the 2SC3421 and 2SA1358 in stock. About $1.50 each, but in stock. Since they're an InOne company, this means that you can also order them through Newark for the same price but a few days more lead time. You could potentially stuff the whole MAX board with parts from Newark. 

 Edit: Farnell is also part of the InOne empire, so they can probably be ordered through there as well. 

 They also have 2SC2344 and 2SA1011 but in sanyo rather than toshiba. 

 And Electronix.com likely has them as well, but doesn't say what maker. Probably Rohm, in my experience with them.


----------



## tomb

Quote:


  Originally Posted by *ericj* /img/forum/go_quote.gif 
_I've pointed out before, mcminone.com has the 2SC3421 and 2SA1358 in stock. About $1.50 each, but in stock. Since they're an InOne company, this means that you can also order them through Newark for the same price but a few days more lead time. You could potentially stuff the whole MAX board with parts from Newark. 

 Edit: Farnell is also part of the InOne empire, so they can probably be ordered through there as well. 

 They also have 2SC2344 and 2SA1011 but in sanyo rather than toshiba. 

 And Electronix.com likely has them as well, but doesn't say what maker. Probably Rohm, in my experience with them._

 

True, eric. Although mcminone has the best BJT pair - the 2SC2238/2SA968. The 2SC3422/2SA1359 is better than the ones you mentioned - although 2SA3421/2SA1358 is awfully close. These are all at BDent - except for the 2SC2238 pair - which is why your mention of MCMinone is important. 
	

	
	
		
		

		
		
	


	




 BDent also has the 35V version of the 470uF Muse ES (mentioned this before a few times). You can also get many of these pairs in my neck of the woods at the AudioLab of Georgia here in Atlanta. 
	

	
	
		
		

		
		
	


	




 As for the maker, most are Toshiba transistors, but several of them are Sanyo's. In either case, they are each the respective original mfr from what I've read. I don't know about the case you mention with Rohm, but we refer to these by their mfr for convenience. There's no reason there would be any difference if they are the same transistor model.


----------



## vixr

hey guys... could the RXE050 fuse from the Millett Hybrid be used on the MAX?


----------



## tomb

Quote:


  Originally Posted by *vixr* /img/forum/go_quote.gif 
_hey guys... could the RXE050 fuse from the Millett Hybrid be used on the MAX?_

 

I think it's rated too low for the MAX. The fuse is optional, regardless - you can wire to the outside and middle terminals on the AC input and that will bypass the fuse position.


----------



## ericj

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_As for the maker, most are Toshiba transistors, but several of them are Sanyo's. In either case, they are each the respective original mfr from what I've read. I don't know about the case you mention with Rohm, but we refer to these by their mfr for convenience. There's no reason there would be any difference if they are the same transistor model._

 


 The thing about electronix.com is that they cater to the electronics repair industry. The prices are good, they have all sorts of hard-to-find japanese transistors, but they don't tell you who made them. 

 I once got the idea in my head to make a Kumisa III on perfboard - this was way before the Cavalli-Kan version of it. I bought all the needed transistors from Electronix for about $9, but some of them were mixed lots. Like five Rohm and one Sanyo but all the same number. And with different package types in the same bag. 

 They probably all perform the same, but it was a little off-putting. 

 I'm gonna go ahead and build a C-K kumisa 3, but i'm gonna use bc550c for the small-signal parts and the Rohm output transistors, per conversations with amb dissuading me from using the original K3 to92 parts. I forget what the output transistors are at the moment, though.

 Rohm seems to make a lot of clones of japanese transistors. I haven't heard anything good or bad about them as a manufacturer.


----------



## vixr

thanks for the message Tom...I have a few of the RXE050s laying around and was just wondering. Another MAX lives! I just finished the basic tweaks and everything adjusted like a dream...


----------



## Ferrari

From this side of the ocean... MH Max boards arrived today in good shape 
	

	
	
		
		

		
		
	


	




 . Many thanks, Colin !


----------



## ruZZ.il

tomb, basically. I didn't feel like using another source. I was going to get my mosfets from amb or something, though in the end, I didn't feel like having to deal with current (like for my M^3, I'm still waiting to figure out where to get an amveco 70062 for my STEPS.. instead of the 70053 that I have..).. I got the MJE243/253 BJT pairs in th meantime and I'll just switch them out when I get a batch for my next board or something.. and I have a mosfet amp already anyway, so.. 
	

	
	
		
		

		
		
	


	




 and by switching them out, I'd at least maybe pick up on the differences..


----------



## Ferrari

ruZZ.il, 

 Have you take a look at reichelt.de ? This 25VA (2x12V) transformer has the same specs as the Amveco 70062 you are looking for 
	

	
	
		
		

		
			





 .


----------



## MrMajestic2

Boards arrived safe and sound today. Many thanks Colin


----------



## ruZZ.il

hoi. thanks 
	

	
	
		
		

		
		
	


	




 I found the same one at RS, rsisrael, at double the price though. I'll have to call reichelt to see whats up then 
	

	
	
		
		

		
		
	


	




 thanks for that..


----------



## Bigguy

I got my boards last week. I have yet to order a single part. I am still dumbfounded (or just dumb) by all the combinations or opinions on the boutique cap parts. I suppose I should just get the BOM recommended standard parts. I would probably never hear the difference anyway. Great job Colin on the board design and Tomb on the web design.


----------



## bperboy

Quote:


  Originally Posted by *Bigguy* /img/forum/go_quote.gif 
_I got my boards last week. I have yet to order a single part. I am still dumbfounded (or just dumb) by all the combinations or opinions on the boutique cap parts. I suppose I should just get the BOM recommended standard parts. I would probably never hear the difference anyway. Great job Colin on the board design and Tomb on the web design._

 

I have all the recommended caps to begin with, and it sounded great. I then got some Green Muse's for two of the positions which increased the bass significantly.


----------



## ericj

CR5 is out of stock at Digikey - that's the 1.0uf 50v high-stability low-esr tantalum - 399-3547-ND. 

 Looks to me like this one will work: 399-3622-ND

 Same specs, except lead spacing is 5.08mm. So it won't be ideal. but it'll probably work anyway. 

 Any thoughts from the rest of you?

 Edit: Also, DM1 is given as 1N5242B-TPCT-ND but this part is qty10 minimum. I suppose paying 75 cents for 10 of them isn't much worse than paying 35 cents for one of 1N5242BDICT-ND.


----------



## tomb

Quote:


  Originally Posted by *ericj* /img/forum/go_quote.gif 
_CR5 is out of stock at Digikey - that's the 1.0uf 50v high-stability low-esr tantalum - 399-3547-ND. 

 Looks to me like this one will work: 399-3622-ND

 Same specs, except lead spacing is 5.08mm. So it won't be ideal. but it'll probably work anyway._

 

478-1836-ND looks like a perfect match - by AVX - 2.08mm spacing.

  Quote:


 Any thoughts from the rest of you?

 Edit: Also, DM1 is given as 1N5242B-TPCT-ND but this part is qty10 minimum. I suppose paying 75 cents for 10 of them isn't much worse than paying 35 cents for one of 1N5242BDICT-ND. 
 

#1N5242BDICT-ND may not have been available when I made the BOM - some of these parts trace back to well before the 1st prototype. That one looks fine - if all you want is one. As soon as you purchase three, the other one is a better deal - by a mile.


----------



## Picodeloro

2 MH Max boards arrived today in good shape, they look great.

 Many thanks, Colin !


----------



## tomb

FYI - I made some changes on the website for the casework drilling templates. The clearance beneath the board is small enough that the tips of the tip jack nuts did not have clearance between the board and the bottom of the case. I've given them more spacing so that the nut flats are parallel with the board and the bottom of the case.

 Of course, all of that is predicated on using the 3rd slot from the bottom and a max component height of 33mm or less (1" heat sinks). _The BJT version, in other words ..._


----------



## vixr

Colin,Tom, Neil... it must be a pretty good feeling to know your efforts will be enjoyed all over the _world_...


----------



## odoe

Yeah, thanks a lot guys.
 I'm learning a lot just putting my parts list together.


----------



## ruZZ.il

Quote:


 Colin,Tom, Neil... it must be a pretty good feeling to know your efforts will be enjoyed all over the _world_... 
 

yep. I just got word that I have a square padded envelope in good shape, waiting for me at home 
	

	
	
		
		

		
		
	


	















 I also just picked up a 1.5 amp 24ac supply..


 also, at mouser (RB2/3)
 71-RN55D-F-10.2 1/8watt 10.2ohms 4 
 MHM-DB RB2/3 Vishay/Dale 1/8W Metal Film Resistors
 This product is expected to be in stock by 09-17-07.

 I didnt even look for appropriate subs, I just managed to find 1/2w 1% 10ohm resistors at some local place... I'll get some v.d's with my next order..

 Tom meantime maybe you could add a little section after the BoM with reported backorders and the such, with appropriate substitutes, or maybe you could add a wiki section there so we could do it, with a common password for everyone on the forum or something (I mean, unless part number PwNd exists).


----------



## tomb

Quote:


  Originally Posted by *vixr* /img/forum/go_quote.gif 
_Colin,Tom, Neil... it must be a pretty good feeling to know your efforts will be enjoyed all over the world..._

 

You are too kind as usual, Vixr. 
	

	
	
		
		

		
		
	


	




 Someone could turn this entire process into a Master's Thesis or Doctoral Dissertation about spontaneous project development in a digital community. Ponder this thought: Colin and I have never met, never laid eyes on each other, and never even talked on the telephone. Neither of us have met Nate, either - as far as I know (I know I haven't). I think Colin did meet Neil at a meet once, but that was totally by happenstance and had nothing to do with the MAX.

 The idea that a community of interested people can gather together, communicate, and spontaneously create, manage, and participate in a project such as the MAX - without any face-to-face interaction - is just mind-boggling. Of course, most of it is due to a couple of very gifted Creators - Pete Millett and Colin Toole - freely sharing their creations with the community.


----------



## ericj

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Of course, all of that is predicated on using the 3rd slot from the bottom and a max component height of 33mm or less (1" heat sinks). The BJT version, in other words ..._

 


 Of course, we still have the option of wiring the volume pot and the jack offboard and using the template anyway when building the mosfet version.


----------



## GeWa

Quote:


 Of course, most of it is due to a couple of very gifted Creators - Pete Millett and Colin Toole - freely sharing their creations with the community. 
 

Don't rule yourself out tomb. What you do on the forum and especially this tread is just amazing. You're always here to help everybody out with there various questions whether it's design, wiring, parts or where to get parts and so on. Also what you accomplished with the MillettMax website is truly awesome. It's not only looking great but also very useful to all "Max" builders, a work of art.
 I think I'm not the only one who feels this way.

 Regards

 P.S. I hope I get my amp finished someday


----------



## soloz2

I got a couple more packages in the mail today and so I have almost all the parts I need to build a couple amps


----------



## vixr

hey guys,
 I am seeing the trimmers RA1 not staying at my desired setting unless I trim up to the setting... If I start out higher than the desired setting and trim down, it wont hold... if I trim up its fine...am I just seeing things? the part is the stock one from the BOM


----------



## tomb

Quote:


  Originally Posted by *vixr* /img/forum/go_quote.gif 
_hey guys,
 I am seeing the trimmers RA1 not staying at my desired setting unless I trim up to the setting... If I start out higher than the desired setting and trim down, it wont hold... if I trim up its fine...am I just seeing things? the part is the stock one from the BOM_

 

This can vary a lot depending on the tubes. The tubes aren't the fastest things in the world and can overshoot/undershoot by a couple turns on the trimmers sometimes, depending on which direction you come from. With patience, they should always settle eventually.

 If you've put new tubes in there lately, it may take a day or two before they settle down. NOS tubes collect small bits of gas particles that infiltrate into the tube after sitting for the last 30-40 years. It may take a few days for the getter to burn off those gas molecules when you plug in a NOS tube for the first time. The bias will continue to creep while that process is going on.

 Also, the bias on broken-in tubes may still vary by a volt or more over a period of a few hours - that may just mean that their bias was set before waiting long enough to warm up.

 There are also a lot of anectodal reference to some Millett tubes being easier to bias than others. Generally speaking, the 12FK6's reportedly bias easier and more consistently and the 12AE6's are the worst. I don't know that I believe that one, though.

 EDIT: Don't know if that helps, but maybe you can find something in that discussion that fits your situation.


----------



## ericj

Quote:


  Originally Posted by *vixr* /img/forum/go_quote.gif 
_hey guys,
 I am seeing the trimmers RA1 not staying at my desired setting unless I trim up to the setting... If I start out higher than the desired setting and trim down, it wont hold... if I trim up its fine...am I just seeing things? the part is the stock one from the BOM_

 

I concurr with tomb - it may take several hours, but eventually they'll settle down. My experience is mostly with RCA 12fm6 and Sylvania 12ae6a.


----------



## Troyhoot

Im basicly through with my mosfet max. Just need a knob. Biased mosfets up to 310mv after a good warm up. They start out a little higher at first power on when cold. Cased up the heatsinks get to about 150f degrees. So everything seems great. Just couple observations.

 The 1000ma wallwart is having trouble keeping up with my mosfets biased so high. Cant get the power supply to bias above 26.2volts or so. Tried a 750ma just to make sure my wallwart wasnt bad. The 750 wouldnt get about 25volts. I might look for a little bigger wallwart. But everything is running good and sounding great. Tubes biased at 13.1-2 and fets at 310 as stated above. Was this observed in any of the prototypes ? Just curious.

 Now I am running 2" sinks on everything so thats prolly letting me go a bit higher with the mosfets. I didnt have any problem going to 29V before I biased my mosfets when it was first built. Basicly with no power to the mosfets yet. I also tried different power outlets in different rooms on different circuits to rule that out.

 1 more Q, Anyone know where I can find a 2" black knob. Found one maybe on ebay but not having any luck with other sources.


----------



## tomb

310mV? You're blazing a trail with that. Before you let 'em run too long at that, you might want to refer to Amb's table of recommended _maximum_ quiescent current for those MOSFETs:
http://www.amb.org/audio/mmm/setup.html

 At 26V, he recommends a max of 140ma and the recommendation _drops_ as the voltage gets higher. With the MAX's 2.2 ohm output resistors, that's 308mV. You're above that, but you're running those way-tall sinks. So, before anybody gets an idea to do this, too - don't - unless you run those taller sinks.

 I'm not surprised your walwart is choking. Typically, a rule-of-thumb for loading a transformer is 2/3 down to only 1/2 of the maximum rating. You're probably running around 650ma total on your MAX. So, best case for you is probably around 975ma, worst case would be 1.3A. I tend to think of best case as a quality toroid, whereas a cheap walwart is probably closer to 1/2 loading to run easily. This sounds like what you're finding: In other words, a 750ma won't cut it and a 1000ma may barely do it, but questionable.

 I can't help you on the knob - except AlcoSwitch makes a huge one with a spinner indentation - but it's ~$20 or something like that. You could go industrial, but they tend to look pretty ugly - molded bakelite or something like that with finger/thumb notches.


----------



## tomb

PS - Troyhoot - one of those Basler Electric security systems/HVAC controls walwarts would be perfect for you - 40VA - that's 1.67A. I think I mentioned it in a post awhile back - and others did, too - MPJA.com and All Electronics are two of them that I can think of - still only about $7.95 ea.


----------



## Troyhoot

thanks for that link. That helps. looks like I'm right on the edge anyway. So getting a bigger powersupply would cause me to lower the bias. Been running like this cased since friday evening. Everything good so far. Ill just let it be. Need to take some good pics of my case to let y'all get a look at what I'm workign with for a knob. Just not alot of time atm. 

 My Daughter was born sunday evening at 5:43 so thats where my time is going 
	

	
	
		
		

		
		
	


	




 They came home today. I just get some time while they sleep.


----------



## ruZZ.il

MAZEL TOV!!


----------



## tomb

Quote:


  Originally Posted by *ruZZ.il* /img/forum/go_quote.gif 
_MAZEL TOV!! 
	

	
	
		
		

		
		
	


	




































_

 

X10


----------



## dsavitsk

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_There are also a lot of anectodal reference to some Millett tubes being easier to bias than others. Generally speaking, the 12FK6's reportedly bias easier and more consistently and the 12AE6's are the worst. I don't know that I believe that one, though._

 

First, there is a little misnomer here. Bias is the voltage difference between the grid and the cathode, not the plate and ground. On this amp, you read the bias from the plate because small changes to the grid cause large changes on the plate, and while it is difficult to adjust settings between 0.75V and 0.78V, adjusting between 12V and 14V is pretty easy.

 Because the 12FK6 has a much lower mu (mu is the amplification factor) than the 12AE6A (less than half), adjusting the 12AE6A is more sensitive. That is, identical changes in the bias of a 12AE6A will cause larger changes on the plate than on a 12FK6.


----------



## colonelkernel8

Finally ordered my parts (kit) sans the hammond, I dont want the hammond. Will the Galaxy case that is 40mm tall be tall enough?


----------



## naamanf

Almost done. Just need to finish drilling a couple more holes in the top and it will be complete. Here is what I have so far.


----------



## mb3k

You made the bland Hammond case look very elegant!
 Nice build.


----------



## MrMajestic2

Quote:


  Originally Posted by *colonelkernel8* /img/forum/go_quote.gif 
_Finally ordered my parts (kit) sans the hammond, I dont want the hammond. Will the Galaxy case that is 40mm tall be tall enough?_

 

If you are using 1" heatsinks it will be enough I think. If youre building the Mosfet version with 1.5" or 2" heatsinks they will have to stick out of the top cover. Needless to say that the tubes will poke out on either version on a 40mm case. I just ordered the 80mm version so nothing will stick out.


----------



## tomb

Very nice, Naamanf! I love that LED in the knob!


----------



## Troyhoot

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Very nice, Naamanf! I love that LED in the knob! 
	

	
	
		
		

		
		
	


	


_

 

X2 The Dark wood looks great too.


----------



## tomb

Quote:


  Originally Posted by *MrMajestic2* /img/forum/go_quote.gif 
_If you are using 1" heatsinks it will be enough I think. If youre building the Mosfet version with 1.5" or 2" heatsinks they will have to stick out of the top cover. Needless to say that the tubes will poke out on either version on a 40mm case. I just ordered the 80mm version so nothing will stick out._

 

Well, that sounds like you may have room for those VitaminQ's. Those things are huge!


----------



## Troyhoot

got some time to take a few pictures. Dont mind all the papertowel fuzz from cleaning 
	

	
	
		
		

		
		
	


	




 I also think I will have to polish up some edges after I see this pictures. But im still happy with this result for the most part.


 

 

 

 

 

 

 

 

 

 

 



 Mirrored inside 4 walls. Clear bottom and top. Just painted the back of the sides to give it the depth. Mosfet heatsinks dont get over 150f degrees. I might add some more leds later. Just did this at our shop at work. Only non-hand tool I used was the Mill for the top. Screw holes could have been alittle better. But overall im happy with it.


----------



## tomb

Holy cow, Troyhoot! That's pretty neat. I am behind in my postings to the MAX website gallery, but this will definitely go there.

 Another MAX lives!!!


----------



## Listen2this1

Looks good naamanf, the dark wood gives it a one-off look. What leds did you use under the tubes? I like that look better than the blue leds. 

 There should be a thread started on pictures of the Max builds. I have a feeling as the boards become populated this thread will get out of control.


----------



## naamanf

I used the orange LEDs from LS diodes. My BJT max has the blue LEDs and I like the orange ones better. 

 X2 on starting a picture thread for the MAXs.


----------



## soloz2

I started to build one of mine this morning. I've got a couple people coming over for a mini-meet on Saturday and was hoping to have it done so we could listen to it... but I realized that I don't think my order from partsconnexion will be here in time 
	

	
	
		
		

		
		
	


	




 so no tube sockets or Kiwame resisters


----------



## Ferrari

It's good to see that more and more MH Max are buildt (or almost finished). Nice work guys! 
*naamanf*, did you create the LED on the volume knop yourself ? very nice!

 It reminds me that I still have to case up my MH Max build... still no time for that due to very busy work schedule lately 
	

	
	
		
		

		
		
	


	




 .
 Also the use of MKP//Teflon caps (these are huge) at the output of my build requires a bit more time to do the case work, but hopfully I will have more time in the coming weeks. Of course I will be back with pics 
	

	
	
		
		

		
		
	


	




 .


----------



## MrMajestic2

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Well, that sounds like you may have room for those VitaminQ's. Those things are huge!_

 

Yeah, big suckers those things. I havent decided if I should do my first build with the Vitamn Qs or Black Gates, which, by comparison, are really tiny


----------



## soloz2

I just looked through my mouser shipment and realized I didn't get any wallwarts... a quick inspection shows that even though they were on hand when I ordered, they sold out before they shipped my order (normally Mouser ships next day for me... but it took them several days this time for some reason) and now they aren't getting any more in stock till the end of the month! Likewise the 10ohm vishay Dale's aren't going to be in stock until mid Sept! man this sucks 
	

	
	
		
		

		
		
	


	




 I might have to order a .8a wallwart like what's on the BOM instead of the 1a one I ordered


----------



## FallenAngel

For those who can't order from Mouser (like us Canadians here who don't want to deal with those shipping fees), you can get some nice wallwarts off eBay. I just picked up a pair of these 24VAC 50VA (2Amps). There are a few other 40VA ones as well - 1.6A is definitely more than enough.


----------



## naamanf

Quote:


  Originally Posted by *Ferrari* /img/forum/go_quote.gif 
_*naamanf*, did you create the LED on the volume knob yourself ? very nice!
_

 

Yep. So far I have made all the knobs for my amps. This time I wanted something a little different and so far so good. 

 Pretty simple to make as long as you have a drill press


----------



## Bigguy

How do you power the LED in the knob?


----------



## naamanf

If you look in the picture you should see a small black wire running from the volume pot to where the LED pads are on the board.


----------



## Ferrari

Quote:


  Originally Posted by *naamanf* /img/forum/go_quote.gif 
_Yep. So far I have made all the knobs for my amps. This time I wanted something a little different and so far so good. 

 Pretty simple to make as long as you have a drill press_

 

Yes, it's do-able with a drill press. I have tried something similar before but on aluminium.


----------



## tomb

Quote:


  Originally Posted by *FallenAngel* /img/forum/go_quote.gif 
_For those who can't order from Mouser (like us Canadians here who don't want to deal with those shipping fees), you can get some nice wallwarts off eBay. I just picked up a pair of these 24VAC 50VA (2Amps). There are a few other 40VA ones as well - 1.6A is definitely more than enough._

 

Hey - that looks pretty good. Thanks for the link! I've been searching on e-bay through wall adapters and such - no luck. I didn't think to look for an e-bay section on security systems.


----------



## FallenAngel

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Hey - that looks pretty good. Thanks for the link! I've been searching on e-bay through wall adapters and such - no luck. I didn't think to look for an e-bay section on security systems._

 

Anytime.

 There is another seller that is selling the same 24VAC 40VA versions here. 5 Left for this one.


----------



## colonelkernel8

Once I get my parts, this is my idea:

 Get a case from Galaxy, one of the 80 tall ones so I have breathing room, and mount the tube sockets on the lid so it look like a true tube amp. What do you think?


----------



## tomb

I've updated the website with every photo of a built MAX that I could find - that was several dozen more pics. They are organized into individual pages per user and my intent is to continue that practice. So, keep 'em comin - and let me know if there's someone I've missed so far.


----------



## tomb

Quote:


  Originally Posted by *colonelkernel8* /img/forum/go_quote.gif 
_Once I get my parts, this is my idea:

 Get a case from Galaxy, one of the 80 tall ones so I have breathing room, and mount the tube sockets on the lid so it look like a true tube amp. What do you think?_

 

You might give Blooze a PM - he is pretty good at mounting tubes on the outside and did that with a Millett years ago.


----------



## soloz2

what was the mouser part for the tube grommets?


----------



## tomb

Quote:


  Originally Posted by *soloz2* /img/forum/go_quote.gif 
_what was the mouser part for the tube grommets?_

 

Post #735 and on the MAX website on the Templates page.


----------



## soloz2

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Post #735 and on the MAX website on the Templates page._

 

I'm so blind! I looked at that page first lol


----------



## Blooze

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_You might give Blooze a PM - he is pretty good at mounting tubes on the outside and did that with a Millett years ago._

 

Well, I don't know about that 
	

	
	
		
		

		
			




 But I do like to see all of the tube.

 I kind of homemade rigged my original Millet for connections to the tubes and it worked ok if you weren't going to be tearing into the build very often, which I wasn't unless something happened to it.

 If I was going to do it again (which I will be for the MAX), I think I would use some 8 pin connectors (the rectangular plug and sockets from Jameco for instance) to connect/disconnect the tube socket from the main board just to make it easy to get the top panel out of the way. If you're not going to have a removable top panel for some reason, then just leads that are long enough to let you move stuff out of the way should suffice. I never noticed any hum problem with the slightly longer leads in my original Millett before I made them "quick connect".

 I'm still dreaming of an enclosure for mine. Wood and metal for sure, but not so "Dr. Who'ish" like my SOHA. Thinking copper and padauk for the moment. But I have a couple of other projects in the works as well. I've got a 1626 Darling I need to finsh this fall, and I'm going through a 6L6 organ amp to scavange parts for a SE EL34 utilizing Tubelab's pcb as well. Plus I still have CKIII boards I've never populated. And a version of the Sijosae's MHHA using an octal tube I'm wanting to play with. Never mind the ART array's I need to build cabinets for.

 This hobby drains me like no other, I swear!!!


----------



## tomb

It was pointed out to me that I neglected to increase the quantity of 3-position terminal blocks to "2" on the BOM. The production version uses only 3-position terminal blocks - the AC input allowing a choice between a position that goes through the fuse or one that completely bypasses the fuse.

 That change meant that the 2-position terminal block was deleted, but I neglected to change the quantity on the 3-position blocks. Sorry about that.


----------



## ruZZ.il

NP, I was going to solder my inputs in anyway 
	

	
	
		
		

		
		
	


	




 wouldn't terminal blocks effect signal though? I mean, ppl use good solder, expensive wire/plugs.. 
 maybe I'll look for nice gold contact ones for my next order..

 I've gotta say, I'm really impressed with the case work and skill/effort that's gone into things around here.. 

 AND.. I GOT MY BOARDS 
	

	
	
		
		

		
		
	


	




 **All due respect to everyone!! <tips hat>**

 say, what's a normal unloaded measurement of the common type 24Vac wallwart (has the block type core)? 

 I have a 24VAC 36VA that measures round 24.8. I know the toroidals output bout 5v more than rated(in that range) while unloaded, no? didnt someone recently post the loaded/unloaded deviance of different types?
	

	
	
		
		

		
		
	


	




 I should have all my bits by mid week, and hopefully soon after, another MAX will live


----------



## tomb

Quote:


  Originally Posted by *ruZZ.il* /img/forum/go_quote.gif 
_say, what's a normal unloaded measurement of the common type 24Vac wallwart (has the block type core)? 

 I have a 24VAC 36VA that measures round 24.8. I know the toroidals output bout 5v more than rated(in that range) while unloaded, no? didnt someone recently post the loaded/unloaded deviance of different types?
	

	
	
		
		

		
		
	


	




 I should have all my bits by mid week, and hopefully soon after, another MAX will live 
	

	
	
		
		

		
		
	


	





_

 

I've not seen the variance that many talk about in AC walwarts. Perhaps the unregulated DC versions are the ones that shoot up so high when lightly loaded. Like you have noticed, my experience with even these monster walwarts are that the AC voltage may only peak at about 2 volts higher than rating without load. It also gives pause to the supposed inherent regulation quality of toroids - if a simple block of steel is this consistent, instead. Or, maybe these larger industrial walwarts are built with much more quality that we realize.


----------



## Listen2this1

Tomb: There is no reason you should be saying sorry for something you missed on the BOM. All of this time that you put into this build I will say, and I am sure that many others will to, is that you should be rewarded for what you have done . I am pretty new at this and I am glad for your site and especially glad to have the BOM with the links to the sites, you probably cut about 5 hours off of the ordering process.

 Thanks again and you keep this Diy hobby fun for all.


----------



## ericj

Quote:


  Originally Posted by *ruZZ.il* /img/forum/go_quote.gif 
_say, what's a normal unloaded measurement of the common type 24Vac wallwart (has the block type core)? 

 I have a 24VAC 36VA that measures round 24.8. I know the toroidals output bout 5v more than rated(in that range) while unloaded, no? didnt someone recently post the loaded/unloaded deviance of different types?
	

	
	
		
		

		
		
	


	


_

 

Assuming your mains voltage is correct, that's a variance of about 4% from the rated output. 

 So, it's a good quality trafo.

 Edit: All I've been trying to say is, it's a small factor that ought to be remembered when determining power supply capacity. Give Duncan Amps' PSU designer a look - they always include a regulation factor for the transformer (default is 6% iirc) and I've found, when designing my own power supplies, that the simulation only really matches reality when i determine and then plug in the actual regulation percentage of the actual trafo I'm using. 

 The difference between 24.0 and 24.8 when applying the 1.414 multiplier when converting from the AC RMS voltage to the DC peak to peak voltage is only about 2 volts, but the significance of transformer regulation increases greatly with the output voltage of the transformer. 

 For example, the transformer i bought for my Bender 6N1P build has a 285v secondary with about 11% regulation. Do the math on that one and you'll see what i mean.


----------



## ruZZ.il

Thanks guys.
 I found this, about voltage regulation and a more thorough glance at Wikipedia:Transformer interesting, and helpful somewhat


----------



## MrMajestic2

I have a huge problem. I was desoldering a trimpot that I turned the wrong way and one solder pad came off 
	

	
	
		
		

		
		
	


	




 Have I ruined the board? I dont know what to do now, this is basically the worst DIY day of my life.


----------



## tomb

Quote:


  Originally Posted by *MrMajestic2* /img/forum/go_quote.gif 
_I have a huge problem. I was desoldering a trimpot that I turned the wrong way and one solder pad came 
	

	
	
		
		

		
		
	


	




 Have I ruined the board? I dont know what to do now, this is basically the worst DIY day of my life._

 

There's almost no way you can totally ruin a board. Find where the trace is that feeds this pad. Gently scrape away some of the green mask behind where the trace feeds the pad. Bend an extra trimmed capacitor lead so that it follows the contour of the trace and solder it in place. You should have the lead stop over the hole where you tore the pad. The lead from the trimmer, your fabricated trace lead, and a solder blob should put it all together.

 Give us a pic when you can and we can be more specific with the advice. 
	

	
	
		
		

		
		
	


	




 EDIT: Or, you can use an insulated wire jumper soldered from the last good trace spot to the trimmer lead - depends on the area. I like the bare lead when I can make it work - you can solder it almost along the whole lenght, making it as strong/stronger as the rest of the board.


----------



## MrMajestic2

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_There's almost no way you can totally ruin a board. Find where the trace is that feeds this pad. Gently scrape away some of the green mask behind where the trace feeds the pad. Bend an extra trimmed capacitor lead so that it follows the contour of the trace and solder it in place. You should have the lead stop over the hole where you tore the pad. The lead from the trimmer, your fabricated trace lead, and a solder blob should put it all together.

 Give us a pic when you can and we can be more specific with the advice. 
	

	
	
		
		

		
		
	


	




 EDIT: Or, you can use an insulated wire jumper soldered from the last good trace spot to the trimmer lead - depends on the area._

 

Thanks Tomb, I ll give that a try. I dont have a camera at hand at the moment though.


----------



## MrMajestic2

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_There's almost no way you can totally ruin a board. Find where the trace is that feeds this pad. Gently scrape away some of the green mask behind where the trace feeds the pad. Bend an extra trimmed capacitor lead so that it follows the contour of the trace and solder it in place. You should have the lead stop over the hole where you tore the pad. The lead from the trimmer, your fabricated trace lead, and a solder blob should put it all together.

 Give us a pic when you can and we can be more specific with the advice. 
	

	
	
		
		

		
		
	


	




 EDIT: Or, you can use an insulated wire jumper soldered from the last good trace spot to the trimmer lead - depends on the area. I like the bare lead when I can make it work - you can solder it almost along the whole lenght, making it as strong/stronger as the rest of the board._

 

Its by the way the solder pad for RA1L pin3 which doesnt have a trace going to it. Is this perhaps a pin on the trimpot that is not in use?


----------



## MrMajestic2

I think Im going to desolder the "boutique" parts on this board and start over on my second board. I have a second batch of components so I can leave the rest of the stuff on this board until I can patch up the solder pad. It'll be a pain in the butt to desolder the heatsink though.


----------



## tomb

Quote:


  Originally Posted by *MrMajestic2* /img/forum/go_quote.gif 
_Its by the way the solder pad for RA1L pin3 which doesnt have a trace going to it. Is this perhaps a pin on the trimpot that is not in use?_

 

Shoot! You're home free!

 That's the ground pad. Just solder a lead on the bottom of the board from the edge of the "GND" test point nearby to the bottom of the trimmer Pin 3. You'll be able to solder the trimmer flush to the board and it will be rock-solid.

 No one will ever know.


----------



## tomb

Like this:


----------



## thunder

This link may be helpful to some , who are new to DIY ! >http://www.epemag.wimborne.co.uk/solderfaq.htm


----------



## MrMajestic2

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Shoot! You're home free!

 That's the ground pad. Just solder a lead on the bottom of the board from the edge of the "GND" test point nearby to the bottom of the trimmer Pin 3. You'll be able to solder the trimmer flush to the board and it will be rock-solid.

 No one will ever know. 
	

	
	
		
		

		
		
	


	


_

 

Ah yeah, thats what it looked like, I just wasnt sure. I'll fix it tonight, thanks mate.


----------



## MrMajestic2

Ok, I know Im gonna come off as a complete n00b, but I just have to ask. Last night a desoldered all my trimmers convinced that they were mounted the wrong way. I based my decision on the layout picture on the Max site:






 It shows where PIN3 is supposed to be, and all my trimmers were facing the wrong way. Pin3 is clearly marked on the Vishay trimmers:





 And according to the layout picture, PIN3 is at the following places on the Max board:





 These markings are not on the actual production board though. When looking at the various builds on the website gallery and the forum, it seems to me that most mounted their trimmers the opposite way. I might be completely coo-coo in the head after a way too long and irritating night of soldering, so please help me out here.


----------



## tomb

I'm sorry to say ... knowing the trouble you've gone through ... it doesn't make any difference which way the trimmers are oriented. If you look at the schematic for a typical trimmer, you'll see why:






 Reverse this schematic from left to right and it's the same. The only thing that makes a difference is which way you turn the screw. Even a volume pot is the same way, but unlike a trimmer, which way you turn the volume knob is important and the _most_ critical point.

 It does look like the image on the layout is reversed from the normal way of thinking. _This may be exactly why Colin deleted the pin number and arrow from the production board._ I have always faced the epoxy side of the trimmer toward the "wings" on the board silkscreen. This makes sense, because many trimmers have these little wings on the epoxy side. It probably serves as the sprue attachment while the epoxy is poured/potted in place. Orienting them this way has never given me any trouble on any amps/TREADS/etc.:






 Actually, if you look at cetoole's, he didn't particularly care about which way the trimmers were turned (he also told me the same thing 
	

	
	
		
		

		
		
	


	




 ). His tube bias trimmers are oriented in the same direction. However - as we know, they are mirror imaged in terms of the actual circuit. This means that he has to turn the trimmer one way to reduce bias on one tube, but turn the trimmer screw the other way to reduce bias on the other tube:






 Honestly, I can't ever remember which way to turn a trimmer from one tube to the next anyway. I just watch the meter and if it goes up when I'm trying to make it go down, then I turn the screw the other way - literally.


----------



## TzeYang

^tomb, i was about to say the same but you beat me to it.

 Sigh, times like these makes a DIY junkie sad.


----------



## Ferrari

What Tomb described is correct. NO need to be sad or panic and to desolder the trimpots if it's mounted 180 degrees vertically rotated. Just turn the trimmer screw, put the DMM on the testpoint and follow what you read 
	

	
	
		
		

		
		
	


	




 .
 If the trimpot is mounted 180 degrees vertically rotated, turn the trimmer screw counter clockwise insteed of clockwise (an vice versa).

 An trimpot doesn't behave like an electrolytic capacitor or something like that, it will not smoke if it's accidentally mounted 180 degrees vertically rotated.


----------



## odoe

The first time, I built a tread and tried to figure which way to turn the trimmer, I was like oh crap. I just remembered, left loosey, righty tighty and it all worked out in the end.


----------



## pabbi1

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_




_

 

Well, while we are here, I have a question about mounting the caps like this - are the VitaminQs simply soldered to the 'center hole' (presumably to ground), or is something jumpered underneath? And, how does this work?

 I have those same VQ, and that is a REALLY tight fit, especially against one of the tube legs. Otherwise, I guess I can tombstone them, but this is an elegant solution that took some real skill.


----------



## tomb

Look closely and you will see a short loop of transparent teflon tubing bending under each end - separate from the screw. I'm pretty sure Colin had the screw installed before he ever attached the Vitamin Q's. So, they loop underneath within the teflon tubing and to the pads on the board.


----------



## MrMajestic2

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_I'm sorry to say ... knowing the trouble you've gone through ... it doesn't make any difference which way the trimmers are oriented. If you look at the schematic for a typical trimmer, you'll see why:

 Reverse this schematic from left to right and it's the same. The only thing that makes a difference is which way you turn the screw. Even a volume pot is the same way, but unlike a trimmer, which way you turn the volume knob is important and the most critical point.

 It does look like the image on the layout is reversed from the normal way of thinking. This may be exactly why Colin deleted the pin number and arrow from the production board. I have always faced the epoxy side of the trimmer toward the "wings" on the board silkscreen. This makes sense, because many trimmers have these little wings on the epoxy side. It probably serves as the sprue attachment while the epoxy is poured/potted in place. Orienting them this way has never given me any trouble on any amps/TREADS/etc.:

 Actually, if you look at cetoole's, he didn't particularly care about which way the trimmers were turned (he also told me the same thing 
	

	
	
		
		

		
		
	


	




 ). His tube bias trimmers are oriented in the same direction. However - as we know, they are mirror imaged in terms of the actual circuit. This means that he has to turn the trimmer one way to reduce bias on one tube, but turn the trimmer screw the other way to reduce bias on the other tube:

 Honestly, I can't ever remember which way to turn a trimmer from one tube to the next anyway. I just watch the meter and if it goes up when I'm trying to make it go down, then I turn the screw the other way - literally._

 

Thanks for your reply, but I have to slightly disagree that it doesnt matter which way the trimmer is mounted. On the Max website under "Setup and Bias Settings" it states the following:

 "Before applying power to the amp for the first time, screw the trimmers down to their minimums. This is usually 20-25 turns. Either count 20 turns or listen for a click, if your trimmer clicks." The Vishay trimmer have a clutch.

 If the trimmer is turned the "wrong" way, then doing this will actually maximise the voltage, not minimizing it. I think it would be a good idea to mention the orientation of the trimmers on the website to stop people from doing the same mistake as I did, even if it would still work. But saying that, I would rather have the trimmers oriented the way they are supposed to be, so that the turning action is always the same. So to do that, would I have to orient them with the pin3 marking on the pin3 of the board? Since I already desoldered, and ruined them in the process, I might as well do it right this time around. I put them on the same way you did, the epoxy side facing the wing markings on the board, which seemed logical to me at the time. But this is the in fact the "wrong" way, right?


----------



## MrMajestic2

Quote:


  Originally Posted by *Ferrari* /img/forum/go_quote.gif 
_What Tomb described is correct. NO need to be sad or panic and to desolder the trimpots if it's mounted 180 degrees vertically rotated. Just turn the trimmer screw, put the DMM on the testpoint and follow what you read 
	

	
	
		
		

		
		
	


	




 .
 If the trimpot is mounted 180 degrees vertically rotated, turn the trimmer screw counter clockwise insteed of clockwise (an vice versa).

 An trimpot doesn't behave like an electrolytic capacitor or something like that, it will not smoke if it's accidentally mounted 180 degrees vertically rotated._

 

If I had been doing this when I was actually in a sane state of mind, and not dead tired, I would have asked in the forum BEFORE desoldering anything, but its too late now 
	

	
	
		
		

		
		
	


	




 But on the other hand, Im here to learn, even if it is the hard way.


----------



## tomb

Quote:


  Originally Posted by *MrMajestic2* 
_But this is the in fact the "wrong" way, right?_

 

No it's correct - as stated earlier, I believe Colin deleted the arrow and pin # in the silkscreen for a purpose. Ultimately, however, as with the theme in the last several posts by several people, there is no "right" or "wrong" way.

 As for the website, you will note that I did not specify a direction in the cautionary statement about the DB trimmers. That was on purpose.

 A good precautionary technique might be to check the DB trimmers first when you cut it on. When you are satisfied which direction is which, turn it off and adjust it to a minimum. This only takes a couple of seconds. In any event, with the combination of the fuse and the heat sinks, this is not as critical an item as it used to be with the original revMH Millett DB's.


----------



## MrMajestic2

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_No it's correct - as stated earlier, I believe Colin deleted the arrow and pin # in the silkscreen for a purpose. Ultimately, however, as with the theme in the last several posts by several people, there is no "right" or "wrong" way.

 As for the website, you will note that I did not specify a direction in the cautionary statement about the DB trimmers. That was on purpose.

 A good precautionary technique might be to check the DB trimmers first when you cut it on. When you are satisfied which direction is which, turn it off and adjust it to a minimum. This only takes a couple of seconds. In any event, with the combination of the fuse and the heat sinks, this is not as critical an item as it used to be with the original revMH Millett DB's._

 

I understand that there is really no "right" or "wrong". But since pin3 is marked on the trimmer, this is most likely the way the manufacturer intended them to be mounted, even if you could mount them the other way around. I mean to say that I would rather have them mounted in a way that would make it work like a volume pot. That way, I dont have to guess which way to turn it. That said, if I had known that it wouldnt really matter which way they where mounted, I would have left them in, and not desoldered them. Sorry for blabbering on about trimpots, Ill shut up now 
	

	
	
		
		

		
		
	


	




 Thanks everyone for the help, I really appreciate it.

 Ill be cleaning up the board tonight, put the trimmers in, oriented the "right" way 
	

	
	
		
		

		
		
	


	




 And Bias the crap out of my fist Max build 
	

	
	
		
		

		
		
	


	




 I have black gates as bypass caps by the way, hope it sound good.


----------



## pabbi1

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Look closely and you will see a short loop of transparent teflon tubing bending under each end - separate from the screw. I'm pretty sure Colin had the screw installed before he ever attached the Vitamin Q's. So, they loop underneath within the teflon tubing and to the pads on the board._

 

Yep, I see it now - question is, where to get the teflon tubing?


----------



## Televator

Quote:


  Originally Posted by *pabbi1* /img/forum/go_quote.gif 
_Yep, I see it now - question is, where to get the teflon tubing?_

 

I know quables carries some (just follow the link) but it might not be the cheapest solution


----------



## pabbi1

Quote:


  Originally Posted by *Televator* /img/forum/go_quote.gif 
_I know quables carries some (just follow the link) but it might not be the cheapest solution_

 

Ah, price is not an object, but time and convenience is...

 Anyone know a US vendor? RS, Frys, or ????


----------



## tomb

Quote:


  Originally Posted by *pabbi1* /img/forum/go_quote.gif 
_Ah, price is not an object, but time and convenience is...

 Anyone know a US vendor? RS, Frys, or ????_

 

Handmade Electronics:
http://www.hndme.com/productcart/pc/...?idCategory=89
 Parts Connexion:
http://www.partsconnexion.com/catalog/wire.html  - under the last tab labeled "Polyester Sleeving - Teflon Tubing"

 Yeah, technically PartsConnexion is them Canadian folk, but all of us order from them anyway.


----------



## zare




----------



## tomb

Cool - looks like you've been taking hints from Ferarri. 
	

	
	
		
		

		
		
	


	




 Those Obligattos are huge. 
	

	
	
		
		

		
		
	


	




 Questions:
 Fine Gold power caps, ES on the output, KZ on the cathode, right?
 Kiwames on the output resistors ...
 What are the film caps on the cathode bypasses?
 Also, looks like you're running at 50ma on the DB's and you've got the 2SC type BJT's, but I can't tell which ones?

 So how does it sound?

 Oh yeah - another MAX lives!!


----------



## zare

Questions:
 Fine Gold power caps, ES on the output, KZ on the cathode, right?

 3300uF FW for PS
 1000uF FG for power rail 
 KZ on cathode + Obligatto film (0.22uF)
 ES on output + Obligattos oil (4.7uF)
 0.22uF EVOX MMK for the rest
 PRP resistors for most of the signal path
 LM338, just in case

 Kiwames on the output resistors ... 22R

 Also, looks like you're running at 50ma on the DB's and you've got the 2SC type BJT's, but I can't tell which ones?

 2SC3422/SA1359

 So how does it sound?

 hmm.. sweet ... .I'll try FK or FM tube tonight.

 BUT, BG and MOSFET are just around the corner ..


----------



## tomb

Quote:


  Originally Posted by *zare* 
_PRP resistors for most of the signal path_

 

Oh yeah - I missed the PRP resistors ... love that red!


----------



## soloz2

percy audio also has teflon tubing


 I just got a spool of 1000' so if you only need a little bit just send me a PM


----------



## MrMajestic2

Hi, its me again, your resident DIY idiot 
	

	
	
		
		

		
			




 Soldered on the trimmers and fixed the broken solder pad as per Tombs advice. Switch it on, LEDs light up, PSU voltage seemed ok. Tube bias around 18v, which seems high, considering that the PSU voltage was only 22 at the time since I turned the trimmers to minumum setting. MOSFET test point showed no voltage reading whatsoever 
	

	
	
		
		

		
		
	


	




 Was going to check PSU voltage again, and everything went dead. Turned off and back on after a while, LEDs go on again, turned up PSU voltage to 25, still no reading on the MOSFET bias points. LEDs started blinking and all went dead again. Regulator heatsink a bit warm, but no too bad I think. By chance I put my multimeter in connector mode, or whatever its called when you check if two points are connected, and V+ and ground can now talk to each other 
	

	
	
		
		

		
		
	


	




 Something clearly is shorted somewhere and I cant for the love of god find where. First thought that comes to mind is that I really messed something up beyond a mear solderpad, but what? My first choice of error would be the trimmers, or more precisely, the solderpads for the trimmers. Are pin3 ground on all trimmers? Wow, this is turning out to be a bit long, so Ill round off by posting some photos. They are not very good, but maybe someone cant see something that I cant.


----------



## tomb

Offhand, I don't see anything wrong - even your repair with the pin jumper on the trimmer looks OK.

 One thing - I don't think you can get valid readings on a lot of things if you don't load the tubes with the pot. Put the volume pot in the circuit next time you measure things.

 A few things:
 1. It is not unusual at all to see the tubes with initial bias very close to, or equal to, the power supply voltage. Depending on where the trimmers are set, it can take 5-10 full turns before you see a response.
 2. The DB's may be in the same position as the tubes in #1 - it may take many turns of the trimmers before you see and movement across the resistors.
 3. If it worked, then it didn't, and you didn't blow a fuse - it's in the power supply. Make several measurements of your transformer until you are confident that it's producing the correct voltage.
 4. Unplug the tubes, screw down the DB trimmers and focus on the PS until you find out what's wrong.

 If you have time - maybe you can take a more detailed photo of just the PS. Let's focus on this for the time being.


----------



## ericj

A couple errors in the digikey column of the BOM webpage

 RB12L/R for Mosfet output is given as 490-2880-ND - that's a 2k trimmer instead of the 1k specified. Should be 490-2874-ND. 

 RB2L/R, RB3L/R also in the Mosfet section are specified as 390ohm but the part number listed is 10.0XBK-ND. Yaego doesn't seem to sell a 390ohm resistor, Panasonic does - P390CACT-ND.


----------



## MrMajestic2

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Offhand, I don't see anything wrong - even your repair with the pin jumper on the trimmer looks OK.

 One thing - I don't think you can get valid readings on a lot of things if you don't load the tubes with the pot. Put the volume pot in the circuit next time you measure things.

 A few things:
 1. It is not unusual at all to see the tubes with initial bias very close to, or equal to, the power supply voltage. Depending on where the trimmers are set, it can take 5-10 full turns before you see a response.
 2. The DB's may be in the same position as the tubes in #1 - it may take many turns of the trimmers before you see and movement across the resistors.
 3. If it worked, then it didn't, and you didn't blow a fuse - it's in the power supply. Make several measurements of your transformer until you are confident that it's producing the correct voltage.
 4. Unplug the tubes, screw down the DB trimmers and focus on the PS until you find out what's wrong.

 If you have time - maybe you can take a more detailed photo of just the PS. Let's focus on this for the time being. 
	

	
	
		
		

		
		
	


	


_

 

Once again, thanks for replying. 

 I did try to turn the Bias setting up on the MOSFET section before it died again, but it didnt affect the reading, still zero.

 Im mostly worried about the fact that ground and V+ are somehow connected.

 I will try to put the volume pot in also before checking again, It uses header pins so it doesnt require any additional soldering.

 I will also double check the transformer, but Im pretty sure its ok and putting out around 30V.

 EDIT:
 Here are some pictures of the PSU section, both top and bottom. Havent had a chance to switch it on since I have small kids running around.


----------



## tomb

I took a quick look - I'll be out for most of the day. However - gosh - I don't see anything. Your work looks fine, and it doesn't look like any parts are messed up.

 Just a guess - are you connecting the transformer leads to the inside two terminals of the terminal block? If you use the middle and inside, the power goes through the fuse. If you use the middle and outside terminals, the power bypasses the fuse.

 * If you use the inside and outside terminals, you will have a dead short with the power supply. I would've thought that would blow the fuse, though.

 * If that's not it, verify that every transistor is in the correct position. That's a little tedious, but the only other thing I can think of at the moment - perhaps there are a couple of transistors that got mixed up. Include the MOSFETs in this, too. If you've checked that and you're confident they're correct, then plug the power supply back in without the tubes. With the MOSFET trimmers turned down, the lack of tubes should prevent some of the current from going through the rest of the board.

 Start measuring your power supply at that point and let's see if we can get that working.

 P.S. The LED in the center of the board looks a little weird in the pic - is that OK?


----------



## MrMajestic2

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_I took a quick look - I'll be out for most of the day. However - gosh - I don't see anything. Your work looks fine, and it doesn't look like any parts are messed up.

 Just a guess - are you connecting the transformer leads to the inside two terminals of the terminal block? If you use the middle and inside, the power goes through the fuse. If you use the middle and outside terminals, the power bypasses the fuse.

 * If you use the inside and outside terminals, you will have a dead short with the power supply. I would've thought that would blow the fuse, though.

 * If that's not it, verify that every transistor is in the correct position. That's a little tedious, but the only other thing I can think of at the moment - perhaps there are a couple of transistors that got mixed up. Include the MOSFETs in this, too. If you've checked that and you're confident they're correct, then plug the power supply back in without the tubes. With the MOSFET trimmers turned down, the lack of tubes should prevent some of the current from going through the rest of the board.

 Start measuring your power supply at that point and let's see if we can get that working.

 P.S. The LED in the center of the board looks a little weird in the pic - is that OK?_

 

I was using the middle and inside terminals for the power. 

 Ill check all the transistors tonight. I pretty sure they are correct, but I cant be 100% sure at this point.

 Ill try without tubes if all checks out. The PSU section measured just fine and responded to the trimmer pot as well last night before it died.

 The LED is mounted on header pins so I can remove it later when I get my case work done. So its supposed to look like that


----------



## tomb

There is one other possibility - depending on the power of your transformer and the size of the caps on your board, it may be putting too much stress (current) on the LM317. The LM317 has protective internal circuitry that will shut it down if the current capacity (1A) is exceeded. You stated your transformer is 30V. If it's a whopper in the amperage category, the voltage may shoot up much higher than that and cause the LM317 to dissipate much more power (Vdelta x current). The shutdown may not occur until the tubes' heaters kick in, which could be up to 10 seconds or more after power on.

 No tubes should help you confirm this. If this turns out to be the case, I may have an extra LM338 I can send you. Amb went through this on the M3 and started recommending the LM338 as a replacement - 3A capability. I actually used one on the first prototype before we had a better handle on the current. However, you may be the first with both MOSFETs and a 30V supply. Again - depending on your transformer, it may be exacerbating this effect.

 Just another thought - might not be the answer, though. We thought this would not be an issue after NeilR's MOSFET prototype. His current left a few hundred milliamps in reserve, but he wasn't running 30V.

 For that matter, if you do have something shorted out, it may shut down the LM317 before it blows the fuse.


----------



## tomb

Quote:


  Originally Posted by *ericj* /img/forum/go_quote.gif 
_A couple errors in the digikey column of the BOM webpage

 RB12L/R for Mosfet output is given as 490-2880-ND - that's a 2k trimmer instead of the 1k specified. Should be 490-2874-ND. 

 RB2L/R, RB3L/R also in the Mosfet section are specified as 390ohm but the part number listed is 10.0XBK-ND. Yaego doesn't seem to sell a 390ohm resistor, Panasonic does - P390CACT-ND._

 

Eric - thank you! I haven't forgotten this while MrMajestic2 is having his troubles. I will make the corrrections when I get a chance.


----------



## naamanf

Quote:


  Originally Posted by *MrMajestic2* /img/forum/go_quote.gif 
_
 Im mostly worried about the fact that ground and V+ are somehow connected._

 

How many ohms are you reading between V+ and ground?

 If its 0.0 then I would say there is a problem. If its in the neighborhood of 30-40 ohms then I would say your fine.


----------



## MrMajestic2

Quote:


  Originally Posted by *naamanf* /img/forum/go_quote.gif 
_How many ohms are you reading between V+ and ground?

 If its 0.0 then I would say there is a problem. If its in the neighborhood of 30-40 ohms then I would say your fine._

 

Around 3ohm now between ground and v+. Oddly enough the continuity test fails today between them. Good, but weird.

 EDIT.
 The measurement is without tubes in it.

 EDIT2:

 With the tubes in, I get 0.03 ohm reading, that cant be good. And the continuity test does not fail, arghh.


----------



## MrMajestic2

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_There is one other possibility - depending on the power of your transformer and the size of the caps on your board, it may be putting too much stress (current) on the LM317. The LM317 has protective internal circuitry that will shut it down if the current capacity (1A) is exceeded. You stated your transformer is 30V. If it's a whopper in the amperage category, the voltage may shoot up much higher than that and cause the LM317 to dissipate much more power (Vdelta x current). The shutdown may not occur until the tubes' heaters kick in, which could be up to 10 seconds or more after power on.

 No tubes should help you confirm this. If this turns out to be the case, I may have an extra LM338 I can send you. Amb went through this on the M3 and started recommending the LM338 as a replacement - 3A capability. I actually used one on the first prototype before we had a better handle on the current. However, you may be the first with both MOSFETs and a 30V supply. Again - depending on your transformer, it may be exacerbating this effect.

 Just another thought - might not be the answer, though. We thought this would not be an issue after NeilR's MOSFET prototype. His current left a few hundred milliamps in reserve, but he wasn't running 30V.

 For that matter, if you do have something shorted out, it may shut down the LM317 before it blows the fuse._

 

My transformer is a 2x15V 30VA PCB mounted toroid. Its rated at 2x1.0 amps maximum. I will give it a shot without the tubes in it tonight. I could be the LM317 as you say, because the PSU heatsink was the only thing that was hot to the touch quite quickly. If its too much ampage, then I would gladly accept your kind offer on the LM338. I also have a 24V AC wallwart lying around that I could try too. I was going to use it for my standard build MAX, but I forgot I had it until now.


----------



## naamanf

I would think you have a problem if your reading 3 ohms with the tubes out. I would look over everything on the top and bottom and make sure nothings bridged. When installing the components if they are forced into the holes the pads can shave off slivers of metal that can cause problems.

 Also are you using a auto-ranging DMM?


----------



## MrMajestic2

Quote:


  Originally Posted by *naamanf* /img/forum/go_quote.gif 
_I would think you have a problem if your reading 3 ohms with the tubes out. I would look over everything on the top and bottom and make sure nothings bridged. When installing the components if they are forced into the holes the pads can shave off slivers of metal that can cause problems.

 Also are you using a auto-ranging DMM?_

 

I will go over it tonight with a loupe. I was thinking the same thing as you but I didnt find anything, but I will double check. Also, my multimeter is not auto-range. I set it to the lowest range which is 20K.

 EDIT.

 Double doh. It struck me that the reading I was getting was misinterpreted by me. Since my multimeter is not auto-ranging, the 0.03 reading is in fact 30 ohm, Im an idiot I know


----------



## naamanf

Quote:


  Originally Posted by *MrMajestic2* /img/forum/go_quote.gif 
_ Also, my multimeter is not auto-range. I set it to the lowest range which is 20K._

 

So on the 20K setting its reading 3.000 or 0.003?


----------



## MrMajestic2

Quote:


  Originally Posted by *naamanf* /img/forum/go_quote.gif 
_So on the 20K setting its reading 3.000 or 0.003?_

 

See my edit, but its 0.03, which would make it 30ohm, not actually 0.03ohm. I've never used the ohm setting before, so I got it wrong.

 EDIT once more. I found that I do have a lower range on my meter and now I get a 35.7ohm reading. I just have a single word to sum it up, RTFM. Ill go shoot myself now.


----------



## naamanf

If that is with the tubes installed I would say your good. If the tubes are removed then you have a problem.


----------



## MrMajestic2

Quote:


  Originally Posted by *naamanf* /img/forum/go_quote.gif 
_If that is with the tubes installed I would say your good. If the tubes are removed then you have a problem._

 

Its with tubes installed. So im hoping that the problem is the LM317 as Tomb described. I have an exciting night ahead of me


----------



## naamanf

Just out of curiosity what is it with the tubes removed?


----------



## MrMajestic2

Quote:


  Originally Posted by *naamanf* /img/forum/go_quote.gif 
_Just out of curiosity what is it with the tubes removed?_

 

Around 1.6K, can that be right?


----------



## MrMajestic2

Ok, good news. The problem with my board is definetly the voltage regulator. I took out the tubes and presto, it doesnt shut down. I managed to get some reaction from the MOSFET trimmers as well. I switched to my 24V wallwart instead and running it with the tubes in works as well. The tube bias voltage is however around 23 volts and thats with the trimmer turn all the way down. Turning it will only make the voltage go up. Any ideas what could be causing this.


----------



## tomb

Quote:


  Originally Posted by *MrMajestic2* /img/forum/go_quote.gif 
_Ok, good news. The problem with my board is definetly the voltage regulator. I took out the tubes and presto, it doesnt shut down. I managed to get some reaction from the MOSFET trimmers as well. I switched to my 24V wallwart instead and running it with the tubes in works as well. The tube bias voltage is however around 23 volts and thats with the trimmer turn all the way down. Turning it will only make the voltage go up. Any ideas what could be causing this._

 

I would say one of two things:

 1. You're turning the trimmers the wrong way - try about 20 turns in the opposite direction and see if it catches and starts changing after about 10-15 turns.
 2. The tube pins/sockets are messed up. Try wiggling the tubes - after you've tried #1 and see if that makes a difference. Usually, however, this shows up as the heaters blinking or not on in both tubes.

 Anyway, glad you find out the power problem. YGPM.


----------



## Ech0

Quick question, I have finished my Max build and have set the voltage, tube and db bias. Is it okay to continue to listen to my headphones through the amp as I tweak the tube bias? In between "tweaks" I mean.

 It's taking quite awhile for the tube bias to settle down. FWIW, voltage and db bias is set and stable.

 Edit: Changed the above to say "tube bias" not "DB bias"


----------



## n_maher

I probably wouldn't adjust anything while listening to your headphones. Murphy has to have a law on the books about that. And yes, it'll take a bit of time for the tube bias to settle, IME especially if they're tubes that haven't been used before are were true NOS. 

 If you mean _in between_ to mean can you listen when you're not adjusting I would say sure. I for one wouldn't stress all that much about the bias drifting a bit, you'll drive yourself crazy if you do. Set it, listen, and as long as it's sounding good forget about it for a while. 

 My 2¢,

 Nate


----------



## Ech0

Thanks Nate, I just didn't want to screw up my headphones. And yeah I meant to adjust the tube bias, then listen for awhile, and repeat. 

  Quote:


  Originally Posted by *n_maher* 
_I for one wouldn't stress all that much about the bias drifting a bit, you'll drive yourself crazy if you do. Set it, listen, and as long as it's sounding good forget about it for a while_

 

I needed that reality check, I can get a bit obsessive at times. Now I can take the multimeter out of the living room.


----------



## soloz2

well I just need to put the voltage regulator and transisters on my Max, what size bolts work well for those heatsinks?


----------



## tomb

Quote:


  Originally Posted by *soloz2* /img/forum/go_quote.gif 
_well I just need to put the voltage regulator and transisters on my Max, what size bolts work well for those heatsinks?_

 

4-40


----------



## xmokshax

i realize that people are only just receiving their boards from the group buy, but did anyone order extra MAX boards? are any of the online shops selling them? i missed the group buy, but realized shortly thereafter that i would end up wanting to build a MAX.


----------



## MasiveMunkey

Quote:


  Originally Posted by *xmokshax* /img/forum/go_quote.gif 
_i realize that people are only just receiving their boards from the group buy, but did anyone order extra MAX boards? are any of the online shops selling them? i missed the group buy, but realized shortly thereafter that i would end up wanting to build a MAX._

 

You could buy a kit from glassjaraudio.com, you'd have to email jeff though since he hasn't posted it up on the main site yet.

 I have a couple questions with the max build. Can you explain how to wire in the power connector and switch? (There are three metal prongs on the power connector and you only use two right?)

 Can you explain how to drill out the middle pin of the tube sockets so the LED light will shine through?

 Do you want the resistance on the trimmers to be small or large when you turn on the amp for the first time? Large would be my guess for less current right?

 On the board I received one of the holes came partially closed, too closed for a pin to fit though, what's the best way to clear the hole?

 Thanks for your help again tomb


----------



## tomb

Quote:


  Originally Posted by *MasiveMunkey* /img/forum/go_quote.gif 
_You could buy a kit from glassjaraudio.com, you'd have to email jeff though since he hasn't posted it up on the main site yet.

 I have a couple questions with the max build. Can you explain how to wire in the power connector and switch? (There are three metal prongs on the power connector and you only use two right?)_

 

This is explained on the MAX website at Construction -> Casework -> Wiring & Assembly Pt.3.

  Quote:


 Can you explain how to drill out the middle pin of the tube sockets so the LED light will shine through? 
 

This is explained on the MAX website at Tweaks -> Tube Lights.

  Quote:


 Do you want the resistance on the trimmers to be small or large when you turn on the amp for the first time? Large would be my guess for less current right? 
 

Experience is making this moot. The heat sinks will handle most anything. Check the DB bias within the first minute just to make sure it's in range. If you are running some outrageous transformer/walwart with 30V and lots of amps, then check the PS voltage in the first minute, too. It won't hurt anything if you turn it off and on within the first minute or so.

  Quote:


 On the board I received one of the holes came partially closed, too closed for a pin to fit though, what's the best way to clear the hole? 
 

Use a _hot_ pin. 
	

	
	
		
		

		
		
	


	




 Seriously, if it's actually closed with solder, some wire braid and flux should clean it out. You might share a pic with us to make sure. I've not heard of this happening.

  Quote:


 Thanks for your help again tomb
	

	
	
		
		

		
		
	


	



 

No problem - my hope is to get as many MAXes living as possible.


----------



## tomb

Quote:


  Originally Posted by *xmokshax* /img/forum/go_quote.gif 
_i realize that people are only just receiving their boards from the group buy, but did anyone order extra MAX boards? are any of the online shops selling them? i missed the group buy, but realized shortly thereafter that i would end up wanting to build a MAX._

 

According to the last post I saw from Colin, he has about 50 extra boards. He also specifically requested NO e-mails. He will offer them for sale as soon as he gets a chance.

 This is a very busy time for many people with colleges, universities, and K-12 schools starting everywhere in the US. Try to be patient - he's not going to hold on to 50 boards just for the heck of it.


----------



## tomb

Quote:


  Originally Posted by *ericj* /img/forum/go_quote.gif 
_A couple errors in the digikey column of the BOM webpage

 RB12L/R for Mosfet output is given as 490-2880-ND - that's a 2k trimmer instead of the 1k specified. Should be 490-2874-ND._

 

DONE - thank you. 

  Quote:


 RB2L/R, RB3L/R also in the Mosfet section are specified as 390ohm but the part number listed is 10.0XBK-ND. Yaego doesn't seem to sell a 390ohm resistor, Panasonic does - P390CACT-ND. 
 

Yageo has a 392 ohm - that's close enough. I changed it to that in the interests of keeping them all the same brand. Of course, everyone may make their own choices of brands as they see fit (or make fit 
	

	
	
		
		

		
			





 ).


----------



## nysulli

just finishing up my parts list for my max, few questions though

 what spots if any would see a noticeable benefit from a higher end resistor then vishney's on a transistor DB MAX?

 as for caps, heres my thoughts so far

 ca2 - 1000uf muse KZ
 ca4/5, 7 - 470uf muse KZ
 ca3/6/8 - Black Gate NX-hiq
 ca9 - auricap's

 2sc3422/2sa1359 transistors, 1.5" heat sinks bias to 75-100ma


----------



## tomb

Quote:


  Originally Posted by *nysulli* /img/forum/go_quote.gif 
_just finishing up my parts list for my max, few questions though

 what spots if any would see a noticeable benefit from a higher end resistor then vishney's on a transistor DB MAX?

 as for caps, heres my thoughts so far

 ca2 - 1000uf muse KZ
 ca4/5, 7 - 470uf muse KZ
 ca3/6/8 - Black Gate NX-hiq
 ca9 - auricap's_

 

Why not make it simple? Put the 1000uF KZ's everywhere. The board can easily take it and you've already accepted the height penalty with one.

 CA9 and CA8 should be the same type cap. I'm not sure I would use the tiny BG NX-HiQ's as bypassing caps on other caps - unless you are using BG's as CA7 and CA2, which you're not. The Auricaps should be put on CA8 as well. Just use Wima's on the other bypasses - it won't make a difference.

  Quote:


 2sc3422/2sa1359 transistors, 1.5" heat sinks bias to 75-100ma 
 

Great choice on transistors. The 1.5" tall heat sinks will easily take 100ma with a ventilated case, maybe more.


----------



## soloz2

I forgot how nasty the flux in Cardas solder is to clean up!


----------



## ruZZ.il

while we're talking about h.sinks and screws.. etc.. what're the right type of thermal pastes to use for DBs? I'll have all my parts tomorrow


----------



## ericj

Quote:


  Originally Posted by *ruZZ.il* /img/forum/go_quote.gif 
_while we're talking about h.sinks and screws.. etc.. what're the right type of thermal pastes to use for DBs? I'll have all my parts tomorrow 
	

	
	
		
		

		
		
	


	








_

 


 You can really use any kind you like.

 If you're using a metal enclosure, and your transistors have a metal tab, be aware that the heatsink will be electrically connected to the transistor, and you really don't want to short it out to your case. 

 I'm probably going to be using silpad insulators. Admittedly i used Arctic Silver 5 on my M3, but i think it was silly to do so.


----------



## nysulli

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Why not make it simple? Put the 1000uF KZ's everywhere. The board can easily take it and you've already accepted the height penalty with one.

 CA9 and CA8 should be the same type cap. I'm not sure I would use the tiny BG NX-HiQ's as bypassing caps on other caps - unless you are using BG's as CA7 and CA2, which you're not. The Auricaps should be put on CA8 as well. Just use Wima's on the other bypasses - it won't make a difference.

 Great choice on transistors. The 1.5" tall heat sinks will easily take 100ma with a ventilated case, maybe more._

 

well, i guess i could bump up to BG NX's in CA2/7, but i'm trying to build a high end max without letting the budget get to out of control, so i'll probably stick with the KZ's, and add a second set of auricaps for CA8, should be lots of fun packing them down there

 as for 1000uf KZ's everywhere, easy enough to do, but any benefit to maybe putting in 2200uf FG's in cr1a-d?


----------



## soloz2

I used some of the free white thermal material that often comes with computer heatsinks. I gave my tube of AS5 to my bro and he hasn't returned it yet...


----------



## ruZZ.il

hmpf. I dont have the insulating pads or those screw things.. I guess I'll just use whatever I have in the meantime. I plan on switching my transistors a little later on anyway. I'll do them right then. any P/N's for the insulating pads, etc.. ? Thanks..


----------



## ericj

Quote:


  Originally Posted by *ruZZ.il* /img/forum/go_quote.gif 
_hmpf. I dont have the insulating pads or those screw things.. I guess I'll just use whatever I have in the meantime. I plan on switching my transistors a little later on anyway. I'll do them right then. any P/N's for the insulating pads, etc.. ? Thanks.._

 

I bought 100x Berquist pads for a little over $6 - digikey BER168-ND - they're slightly self-adhesive, just enough to stick to either the transistor or the heatsink once or twice. 

 The shoulder bushing is 3049K-ND and has to be bought 100 at a time, but at just over 4 cents each. 

 So, you end up paying about $11 for 100 pads and 100 bushings, which seems like a lot until you look at how much the pre-packaged Thermalloy kits cost. If you're doing more than one or two transistors, buying in bulk rapidly makes sense. 

 Would you rather buy enough hardware for 100 transistors at less than 15 cents each, or enough hardware for 5 transistors at $2.50 each? 

 I don't have part numbers for screws and nuts just at the moment. you want 4-40 screws maybe 3/8" or half an inch long, and matching nuts. You can get these from digikey or from the hardware store. I'm not sure who's cheaper.


----------



## ruZZ.il

So far I got my screws and nuts for free 
	

	
	
		
		

		
		
	


	




 (okay, I never got ANY nuts, just free screws) went to some elec. repair store and they let me scavenge through their screw boxes.. I'll have to do this again though. 
 I'll add the ins. stuff to my next order. Not sure if I'll find anything right till my build though, which I start tomorrow 
	

	
	
		
		

		
		
	


	




 so I'll just use any thermal stuff for the meantime.
 Thanks.


----------



## soloz2

oh, I should mention that "It's Alive!"


----------



## zare

You mean 100mV? In my case with 110mV DB's are running cool, the problem is LM317/LM338, which is starting to sweat.
  Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Great choice on transistors. The 1.5" tall heat sinks will easily take 100ma with a ventilated case, maybe more._


----------



## nysulli

i'm pretty sure he means 100ma, I know theres another MAX or 2 running DB bias that high, otherwise i don't know if i'd try it myself, but i think i'll be opting for a 2" heatsink on LM317 just to avoid that issue


----------



## MrMajestic2

Another Max lives 
	

	
	
		
		

		
		
	


	




 Its up and running finally, although with just 24V at the moment. It does however distort when I turn up the volume, even on fairly low volume. Anybody care to guess what could be the cause of this? Its not my source and DC offset is very low, except when starting up when it shoots passed 200mv 
	

	
	
		
		

		
		
	


	




 right after the relay opens up. It settles down after a a short while though. May need to adjust the relay to wait longer before opening up.

 EDIT:

 Buffers are at ~180mv at the moment.


----------



## tomb

Quote:


  Originally Posted by *MrMajestic2* /img/forum/go_quote.gif 
_Another Max lives 
	

	
	
		
		

		
			





 Its up and running finally, although with just 24V at the moment. It does however distort when I turn up the volume, even on fairly low volume. Anybody care to guess what could be the cause of this? Its not my source and DC offset is very low, except when starting up when it shoots passed 200mv 
	

	
	
		
		

		
		
	


	




 right after the relay opens up. It settles down after a a short while though. May need to adjust the relay to wait longer before opening up.

 EDIT:

 Buffers are at ~180mv at the moment._

 

EDIT: Never mind - you're using the MOSFETs. I can't keep track of the MAXes. 
	

	
	
		
		

		
		
	


	




 Measure your voltage, measure your tube biases and measure the DB's again. If that's all OK - check again if you're getting distortion. There should be some harshness with all those new caps and your tubes may be far from broken in. "Distort" is a pretty strong term, though.

 Got everything grounded - including the wire to the pot?

 Also - did you install the compensation capacitors on the outside MOSFETs? I don't remember seeing them in your pics. That might contribute to the distortion, but it wouldn't cause it all.


----------



## MrMajestic2

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_EDIT: Never mind - you're using the MOSFETs. I can't keep track of the MAXes. 
	

	
	
		
		

		
		
	


	




 Measure your voltage, measure your tube biases and measure the DB's again. If that's all OK - check again if you're getting distortion. There should be some harshness with all those new caps and your tubes may be far from broken in. "Distort" is a pretty strong term, though.

 Got everything grounded - including the wire to the pot?

 Also - did you install the compensation capacitors on the outside MOSFETs? I don't remember seeing them in your pics. That might contribute to the distortion, but it wouldn't cause it all._

 

Yeah, Ill keep measuring the voltages. The tube voltage fluctuates quite a bit, but thats to be expected. It doesnt really sound "harsh", it more like distortion when having too high input volume, which I know Im not having. But Im going to let it run for a while before passing final judgement. Besides the "distortion" it sounds really great, which is comforting, considering the amount of cash I have put into it 
	

	
	
		
		

		
		
	


	




 Im going to start construcing the standard BOM max soon to compare with. Gotta get me some more tubes too.

 By the way, should I worry about the DC offset shooting up at startup?


----------



## tomb

Quote:


  Originally Posted by *nysulli* /img/forum/go_quote.gif 
_well, i guess i could bump up to BG NX's in CA2/7, but i'm trying to build a high end max without letting the budget get to out of control, so i'll probably stick with the KZ's, and add a second set of auricaps for CA8, should be lots of fun packing them down there_

 

Good choices - nothing wrong with what you've described.

  Quote:


 as for 1000uf KZ's everywhere, easy enough to do, but any benefit to maybe putting in 2200uf FG's in cr1a-d? 
 

I don't think you can get FG's in that size at 50V. Remember the voltage rating needed for the Power Supply caps. All the others come after the regulator and it's not such a big deal.

 Forgot about your resistor question. The output resistors are special because they're right in the signal path. I prefer none and use jumpers, but if you use some, you want a good Kiwame or Stackpole in there - something like that.

 As for the other resistors (excluding the DB and tube heater power resistors), V-D is standard. The PRP brand has already been used by Zare, and I have a set, too, that I was going to use with my BG-version MAX. They cost about twice as much as V-D's - about 30 cents. You can get them at Soniccraft. I've seen them other places as well, but I can't remember where right now - maybe someone else will suggest another source.


----------



## MrMajestic2

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_EDIT: Never mind - you're using the MOSFETs. I can't keep track of the MAXes. 
	

	
	
		
		

		
		
	


	




 Measure your voltage, measure your tube biases and measure the DB's again. If that's all OK - check again if you're getting distortion. There should be some harshness with all those new caps and your tubes may be far from broken in. "Distort" is a pretty strong term, though.

 Got everything grounded - including the wire to the pot?

 Also - did you install the compensation capacitors on the outside MOSFETs? I don't remember seeing them in your pics. That might contribute to the distortion, but it wouldn't cause it all._

 

Forgot to mention that its not cased up right now. Still waiting for my latest batch of Galaxy cases. And the compensation caps are installed.


----------



## tomb

Quote:


  Originally Posted by *MrMajestic2* /img/forum/go_quote.gif 
_Yeah, Ill keep measuring the voltages. The tube voltage fluctuates quite a bit, but thats to be expected. It doesnt really sound "harsh", it more like distortion when having too high input volume, which I know Im not having. But Im going to let it run for a while before passing final judgement. Besides the "distortion" it sounds really great, which is comforting, considering the amount of cash I have put into it 
	

	
	
		
		

		
		
	


	




 Im going to start construcing the standard BOM max soon to compare with. Gotta get me some more tubes too._

 

Well, not sure what that means. If it sounds great but has distortion, but yet it's not harshness, I'm confused. 
	

	
	
		
		

		
		
	


	




  Quote:


 By the way, should I worry about the DC offset shooting up at startup? 
 

YES. Jump that large electrolytic to 470uF. BTW, you wouldn't be listening with IEM's would you? That would cause a lot of this. Super high efficiency/low impedance on the output might not be a good thing and if I remember correctly, the delay will not be nearly as long.

 Vixr had a similar problem in the beginning with one pair of his headphones. I don't know that he ever found out what was causing it because I think it went away. My guess is that this is a lot more capacitance than many of us are used to and it takes some time for those cans to calm down - a few days before I stopped hearing a bit of harshness.

 Now, if it's a lack of or intermittent grounding in the signal path, that can sound horrible. Just some more guesses.

 EDIT: Never mind - I think it's the tubes. It's one of those things that some of take for granted, but if you've never experienced it, it would seem like something is wrong.


----------



## tomb

Another thing - tube voltage should not fluctuate if they're broken in. If they aren't broken in, you will get distortion. Maybe that's it?


----------



## nysulli

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Good choices - nothing wrong with what you've described.

 I don't think you can get FG's in that size at 50V. Remember the voltage rating needed for the Power Supply caps. All the others come after the regulator and it's not such a big deal.

 Forgot about your resistor question. The output resistors are special because they're right in the signal path. I prefer none and use jumpers, but if you use some, you want a good Kiwame or Stackpole in there - something like that.

 As for the other resistors (excluding the DB and tube heater power resistors), V-D is standard. The PRP brand has already been used by Zare, and I have a set, too, that I was going to use with my BG-version MAX. They cost about twice as much as V-D's - about 30 cents. You can get them at Soniccraft. I've seen them other places as well, but I can't remember where right now - maybe someone else will suggest another source._

 

Micheal Percy audio has the PRP resistors as well, think I might use those rather then the vishey's, seems like every value is available and the respective wattage requirements, i was planing on kiwame for the output resistors, but PRP should work i presume, or maybe i'll go with Mills, seems to be the highend of what percy carries


----------



## MrMajestic2

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_YES. Jump that large electrolytic to 470uF. BTW, you wouldn't be listening with IEM's would you? That would cause a lot of this. Super low impedance on the output might not be a good thing and if I remember correctly, the delay will not be nearly as long.

 Vixr had a similar problem in the beginning with one pair of his headphones. I don't know that he ever found out what was causing it because I think it went away. My guess is that this is a lot more capacitance than many of us are used to and it takes some time for those cans to calm down - a few days before I stopped hearing a bit of harshness.

 Now, if it's a lack of or intermittent grounding in the signal path, that can sound horrible. Just some more guesses.

 EDIT: Never mind - I think it's the tubes. It's one of those things that some of take for granted, but if you've never experienced it, it would seem like something is wrong._

 

Tubes are not broken in, never been used until now. I've never used tubes before so this is kinda new to me. Im going to let them settle in first and hopefully the distortion will go away.

 The electrolytic you mention, is that the 330uf one in the E12 delay circuit? As it happens I have a couple of 470uf lying around, since my supplier gave me the wrong ones when I started collection parts.

 Im using Beyer DT770/80 with it by the way.

  Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Well, not sure what that means. If it sounds great but has distortion, but yet it's not harshness, I'm confused. 
	

	
	
		
		

		
		
	


	


_

 

It sounds great until the the sound goes up in volume. As in a ballad sounds great, but something bassy and loud distorts.


----------



## tomb

Quote:


  Originally Posted by *MrMajestic2* /img/forum/go_quote.gif 
_Tubes are not broken in, never been used until now. I've never used tubes before so this is kinda new to me. Im going to let them settle in first and hopefully the distortion will go away._

 

Yeah, the more I think about your description - it must be the tubes. A good hint: when the bias voltage is stable over a number of hours, then they're broken in and should sound "sweet." It's also one reason why you shouldn't listen until the amp's been on for awhile. They will always have distortion until they've run for an hour or two. For well broken in tubes, 90% of it goes away in the first 1/2 hour, but 1-2 hours are probably needed to sound best.

 It may take a couple of days to burn in _new_ tubes, though.

  Quote:


 The electrolytic you mention, is that the 330uf one in the E12 delay circuit? As it happens I have a couple of 470uf lying around, since my supplier gave me the wrong ones when I started collection parts. 
 

Yep - that's the one. The time may increase with some running on the one you've got, but it sounds like you're way too close, anyway. Plop that 470uF in there.

  Quote:


 Im using Beyer DT770/80 with it by the way. 
 

OK - then we can remove your headphones from any consideration as a source of trouble.


----------



## MrMajestic2

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Yeah, the more I think about your description - it must be the tubes. A good hint: when the bias voltage is stable over a number of hours, then they're broken in and should sound "sweet." It's also one reason why you shouldn't listen until the amp's been on for awhile. They will always have distortion until they've run for an hour or two. For well broken in tubes, 90% of it goes away in the first 1/2 hour, but 1-2 hours are probably needed to sound best.

 It may take a couple of days to burn in new tubes, though.

 Yep - that's the one. The time may increase with some running on the one you've got, but it sounds like you're way too close, anyway. Plop that 470uF in there.

 OK - then we can remove your headphones from any consideration as a source of trouble. 
	

	
	
		
		

		
		
	


	


_

 

Ok, Ill "plop" that cap in tomorrow. Good thing I was careful enough not to have my phones plugged in when powering up 
	

	
	
		
		

		
		
	


	




 Ill let it run a few hours tomorrow to give the tubes some time to wake up.


----------



## Ech0

Pics of my Millet Max....
















 I've yet to decide on a volume knob.

 Many thanks guys. 

 Ech0


----------



## tomb

Beautiful, Echo!! Your ventilation holes look much cleaner than mine!

 What BJT's did you use?


----------



## MrSlacker

Very nice looking amp!
 I am trying to decide which case to get... black or silver


----------



## colonelkernel8

I've decided to make a case out of wood.


----------



## Troyhoot

Back on post 845 I was talking to tomb about my 1000ma wallwart not keeping up with the mosfets at 310mv. I couldnt get it to bias above 26.2V after biasing the tubes and fets. 
 Later someone found some larger ones on ebay. I ordered one of the 24VAC 50VA wallwarts. It came today 
	

	
	
		
		

		
		
	


	




 Had to make a power cable and kinda redesign my ac input jack. Everything working good though. Biased upto 27v on power supply no problems. tubes at 13.5 and fets still at 300 for right now. Running about 145f degrees on the fet heatsinks. So I might go up a little more in a week or so.
 Just wanted to share my experience with the larger 50VA wallwart with mosfets. In case anyone else if having trouble getting the power supply to bias up to 27V like I was.

 Tomb- I see you talk about grounding the volumn pot. Is that only an issue with the metal cases ? I havent grounded mine and havent had any issue with distortion or anything. So was curious if that was mandatory.

 zare- that max looks great. Those tubes look so clean and pristine. All mine the writing is half rubbed off and such.
	

	
	
		
		

		
		
	


	




 MrMajestic2- Good luck getting all your kinks ironed out. You will be up and running in no time im sure.

 echo- nice clean looking case. I still havent found a knob yet either.

 Oh Yeah. Caylin is now a week old !! I am the sleepiest I have ever been. Wouldnt change anything though


----------



## Ech0

Hey, thanks for the kind words guys.

 I obviously liked the way Tomb did the vents on the top of his case. A drill press certainly made drilling those holes easier. Thanks for the case layout / pdf files Tomb they were extremely helpful.

  Quote:


  Originally Posted by *Tomb* 
_What BJT's did you use?_

 

 I used the MJE243/53 straight from the BOM. I have another board and there are a few things I would like to change and one is different trans. for Q8/9. 

 It sounds great btw and the best part is the dead silence when no sound is coming through.

 @ colonelkernel8 -- I actually have the legs and sides cut for a wooden case and then changed my mind.

 edit: And if it's helpful to anyone out there I used a radioshack motherboard insulated standoff (cut in half) for the post in the center of the board.


----------



## zare

So brief comparison to original Millett after almost 12 hours:

 1. Quickly got rid of RB14L/R(kiwame), it tame the sound to my ears.
 2. CA8L/R: Only Hovland made a bigger difference in mid and high section.
 3. Stick to 12FK with low Z cans, even thou 12AE have a better bass punch. FK more details for me.
 4. Very sensitive on source quality, which can be good and bad
 5. Someone asked about K701 with MAX. Compared to original Millett, I am not very impressed, but my 701 are new, so maybe I'll need some time.

 Summary: MAX has definitely archived the level I was expecting, with lot's of details and precise presentation. Well, except one small digression: I am somewhat missing the warm tube sound. MOSFET MAX, here I come !


----------



## Sixer

Is anyone ordering parts from Micheal Percy Audio? He isn't responding to any of my emails


----------



## tomb

Quote:


  Originally Posted by *zare* /img/forum/go_quote.gif 
_So brief comparison to original Millett after almost 12 hours:

 1. Quickly got rid of RB14L/R(kiwame), it tame the sound to my ears.
 2. CA8L/R: Only Hovland made a bigger difference in mid and high section.
 3. Stick to 12FK with low Z cans, even thou 12AE have a better bass punch. FK more details for me.
 4. Very sensitive on source quality, which can be good and bad
 5. Someone asked about K701 with MAX. Compared to original Millett, I am not very impressed, but my 701 are new, so maybe I'll need some time.

 Summary: MAX has definitely archived the level I was expecting, with lot's of details and precise presentation. Well, except one small digression: I am somewhat missing the warm tube sound. MOSFET MAX, here I come !_

 

Thanks, Zare. So, the Obligattos didn't work out?

 I think some of this will "sweeten" up when the caps have more time. The K701 has excellent midrange from what I've been told, and that is usually most affected by the new caps.

 I don't use the output resistors, either - it loses some of the brutal impact the MAX is capable of providing on high impedance phones. As for the tubes - welcome to the Millett owners' quandry - detail with the FK6's or bass punch with the 12AE6's. If you can find some good FM6's, they should be inbetween.

 Thanks for sharing your impressions!!


----------



## tomb

Quote:


  Originally Posted by *Sixer* /img/forum/go_quote.gif 
_Is anyone ordering parts from Micheal Percy Audio? He isn't responding to any of my emails 
	

	
	
		
		

		
		
	


	


_

 

Unfortunately, I have heard of this before - one reason I don't go out of my way to recommend him as a source. I have never had one bit of trouble with Handmade Electronics on _several_ orders. My first Soniccraft experience was absolutely outstanding. PartsConnexion can be a little peculiar with Paypal orders and they are delayed by 3 or 4 days compared to others - but always impeccably reliable.


----------



## ruZZ.il

PAGE 50!
 we're catching up to the "There's Something About Ultrasone" thread! 
	

	
	
		
		

		
		
	


	




 (I kind of belong there too.. but its way more fun here!)

 anyway.. this all came in this morning:




 enough to build a MAX and 2 mini^3's... plus some spare parts 
	

	
	
		
		

		
		
	


	



 btw, custom p/n's... mmmm I liike


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## ruZZ.il

Regarding the Power Supply resistors, I noticed the P/N's (mouser) are for 1/8 and 1/4 watt though the bom calls for 1/4 and 1/2.. they look the same size as what tom is using in his one on the construction page, so I'm using them anyway 
	

	
	
		
		

		
		
	


	




 assuming its.. ok..


----------



## tomb

Quote:


  Originally Posted by *ruZZ.il* /img/forum/go_quote.gif 
_Regarding the Power Supply resistors, I noticed the P/N's (mouser) are for 1/8 and 1/4 watt though the bom calls for 1/4 and 1/2.. they look the same size as what tom is using in his one on the construction page, so I'm using them anyway 
	

	
	
		
		

		
		
	


	




 assuming its.. ok.._

 

This is typical for Vishay-Dale resistors. They are underrated by 100% compared to "normal" resistors. RN60's will easily take 1/2W, RN55's will go 1/4W - no problem.

 So, you got some Sonicaps to go with those Black Gates?


----------



## adfinni

OOOOOOO ruzz.il, lots and lots of bits 
	

	
	
		
		

		
		
	


	










 Thanks for the boards colin, now i need to trawl back through the thread after my french holiday trip and alter my mouser order, as about 4 parts from the BOM are out of stock.

  Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_So, you got some Sonicaps to go with those Black Gates?_

 

Can't wait to hear your impressions, im going to try some 0.47uf and 0.22uf GEN 1's.


----------



## zare

Obligattos are doing very good job, but Hovlands are better. But I think that I am not judging them correctly. More time is needed.
 I have RCA and GE 12FM, I'll try them soon. 

 One think that I don't like before casing this guy: the PS heat sink.With 110mV DB bias, it's running very hot. How hot? I don't exactly know, I don't have thermometer, but my finger can not hold that heat sink(it's 1.5'' tall) for more them 5-6 seconds. Plus, the PS caps are so close to the sink, preventing any airflow. 
 2'' is very tall for hammond case, so no plans to render the top plate ugly 
	

	
	
		
		

		
		
	


	





  Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Thanks, Zare. So, the Obligattos didn't work out?

 I think some of this will "sweeten" up when the caps have more time. The K701 has excellent midrange from what I've been told, and that is usually most affected by the new caps.

 I don't use the output resistors, either - it loses some of the brutal impact the MAX is capable of providing on high impedance phones. As for the tubes - welcome to the Millett owners' quandry - detail with the FK6's or bass punch with the 12AE6's. If you can find some good FM6's, they should be inbetween.

 Thanks for sharing your impressions!!_


----------



## Sixer

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Unfortunately, I have heard of this before - one reason I don't go out of my way to recommend him as a source. I have never had one bit of trouble with Handmade Electronics on several orders. My first Soniccraft experience was absolutely outstanding. PartsConnexion can be a little peculiar with Paypal orders and they are delayed by 3 or 4 days compared to others - but always impeccably reliable._

 

How annoying, Percy has all the stuff I wanted in the one place. Thanks for the suggestions, it seems that Handmade want me to order at least $100 before they ship overseas, which isn't going to happen. The other two don't have the Muse caps, so either I'll have to go black gates, or find somewhere else that sells the Muses. Any other suggestions?


----------



## odoe

Speaking of heatsink heat and airflow. I've pondered adding something like a 60mm panaflo fan into my case. I haven't seen any amps with fans, but just coming from a computer building background, would there be any detriment to doing so? I got a thing about heat, I don't like it


----------



## tomb

Quote:


  Originally Posted by *odoe* /img/forum/go_quote.gif 
_Speaking of heatsink heat and airflow. I've pondered adding something like a 60mm panaflo fan into my case. I haven't seen any amps with fans, but just coming from a computer building background, would there be any detriment to doing so? I got a thing about heat, I don't like it 
	

	
	
		
		

		
		
	


	


_

 

The general consensus is that this is a bad idea. There was a very recent thread about this on Headwize with input from Amb and MisterX:
http://headwize.com/ubb/showpage.php?fnum=3&tid=7018

 It seems that both mechanical/emf noise _and_ air velocity noise are a problem with our super-quiet background and small signal needs.


----------



## ruZZ.il

hm. whoops.. I was so organized, but leaving the 1/1.5" choice till last led me to get the h.sink for the regulator, but not the other 4.. guess I'll be looking/waiting again. hmpf.. guess they were hiding under the DB options 
	

	
	
		
		

		
		
	


	




 edit: cant paste a link.. but how does rsisrael.com P/N: 507-4769 look?


----------



## tomb

Quote:


  Originally Posted by *Sixer* /img/forum/go_quote.gif 
_How annoying, Percy has all the stuff I wanted in the one place. Thanks for the suggestions, it seems that Handmade want me to order at least $100 before they ship overseas, which isn't going to happen. The other two don't have the Muse caps, so either I'll have to go black gates, or find somewhere else that sells the Muses. Any other suggestions?_

 

Well, I haven't heard of him failing to fulfill an order eventually.

 Have you actually sent an order? Or are you just e-mailing with questions? There are a number of vendors who tend to ignore anything that's not a real order. I can't guarantee that will help, but given your international location, you may need to be patient.

 There are some international vendors that sell Muse ES's, but not a lot of the other stuff. I've just reconciled myself to making multiple orders. PartsConnexion has had a note on their site for quite awhile stating that they will be carrying Nichicon caps in the future, but they're not saying which ones or when.

 Int'l ES Dealers I've found:
http://http://minisemi.com/Nichicon%...apacitors.html
http://http://shop.diyrealaudio.com/...products_id=94
 I can't give you any references as to the above vendors - just some results from Google.


----------



## tomb

Quote:


  Originally Posted by *zare* /img/forum/go_quote.gif 
_Obligattos are doing very good job, but Hovlands are better. But I think that I am not judging them correctly. More time is needed.
 I have RCA and GE 12FM, I'll try them soon. 

 One think that I don't like before casing this guy: the PS heat sink.With 110mV DB bias, it's running very hot. How hot? I don't exactly know, I don't have thermometer, but my finger can not hold that heat sink(it's 1.5'' tall) for more them 5-6 seconds. Plus, the PS caps are so close to the sink, preventing any airflow. 
 2'' is very tall for hammond case, so no plans to render the top plate ugly 
	

	
	
		
		

		
			



_

 

The PS heat sink temp is almost entirely dependent on your walwart/transformer. We tested the prototypes - including NeilR's MOSFET version with commercially available walwarts. As noted in some of the earlier posts, these tend not to shoot up in voltage as much as one would think. If however, you are using a powerful toroid or other some such at 30V, you may have problems.

 Keep in mind that the normal, "old" Millett's DB's were so hot that they could not be touched - even a second or two - at least the metal MJE243/253's were that way. If you are still 60-70deg. C. or less, it will run forever.

 Cetoole and I traded a couple of comments about the heat sink being blocked by those caps. I have to take responsibility for some of it. I thought having the capability for 4 caps was important to equal the quality of a STEPS. However, the original design, 1st prototype, etc., only had two caps. The MAX will run quite nicely with only two PS caps, as a matter of fact. With the 1.5" heat sink, you can actually put in two 2200uF Panasonic FC's, which is what I'm running on the 1st prototype.

 If you are even able to hold it for 5-6 seconds, though, I don't think you have a problem.


----------



## Sixer

Ah excellent, thanks for those links tomb.
 I'll give Percy a couple more days to respond (yes I sent an actual order), then I might have to go with one or more of the other suppliers.


----------



## zare

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_The PS heat sink temp is almost entirely dependent on your walwart/transformer. We tested the prototypes - including NeilR's MOSFET version with commercially available walwarts. As noted in some of the earlier posts, these tend not to shoot up in voltage as much as one would think. If however, you are using a powerful toroid or other some such at 30V, you may have problems._

 

Currently running with 229D24 from Hammond , which unloaded comes to 26.4V. Before the REG I have almost 32V, which is what I was hoping. I am planing to run 30V for the mosfet version, but 2'' heat sinks on REG and DB's.


----------



## ericj

Quote:


  Originally Posted by *zare* /img/forum/go_quote.gif 
_Currently running with 229D24 from Hammond , which unloaded comes to 26.4V. Before the REG I have almost 32V, which is what I was hoping. I am planing to run 30V for the mosfet version, but 2'' heat sinks on REG and DB's.
	

	
	
		
		

		
		
	


	


_

 

So what you're saying is, after heater power and mosfet bias, you expect the rectified DC to dip less than half a volt? 

 I don't think it's gonna work out that way.

 Edit: I do, in fact, predict that you'll be running somewhere between 28v and 29v after regulation, best case scenario.


----------



## nysulli

if you read percy's catalog at the top he says the following

 "My apologies for any delay in replying to your emails and faxes. We are
 experiencing an extremely high volume of emails, and it is almost impossible
 to answer all of them. Please be patient, and inquire again if you do
 not receive a response within a few days."

 i'm not defending the guy or saying your being impatient, just pointing out if you haven't seen it that he seems to very busy and might take a few days


----------



## Troyhoot

About Percy. He has 2 emails. One he checks on vacation the other i dont think he does. I had to send stuff to both emails to finally get a response that he was on vacation. Then it took about a week and another reminder to get my order. Hes real busy and im sure vacationing this summer. So make sure you try both his emails. The one on the webpage and the one in the catalog.


----------



## zare

Quote:


  Originally Posted by *ericj* /img/forum/go_quote.gif 
_So what you're saying is, after heater power and mosfet bias, you expect the rectified DC to dip less than half a volt? 

 I don't think it's gonna work out that way.

 Edit: I do, in fact, predict that you'll be running somewhere between 28v and 29v after regulation, best case scenario._

 

All the measurement on full load:

 -Hammond output 27.8V
 -Before LM338, 32.9
 -After REF currently set to 28V
 -Tube are 14V
 -BJT DB are 110mV

 With min 1.5V for REG to work, I still have buffer to 30V. Mosfets will definitely drain more current, but that's why I have 2A transformer and 13200uF in filtering PS caps. Well, I guess I'll have to build it before I claim anything


----------



## tomb

Keep in mind the regulator wants 5V for the greatest ripple reduction. The huge caps in the PS help reduce the ripple and push the voltage to the theoretical maximum. However, with a minimum voltage drop across the regulator you may start to hear some noise.


----------



## Sixer

Yeah I have sent emails to both of Percy's addresses, my first one a week ago and got nothing back - I sent him another one then - if I get no reply by tomorrow I'll go somewhere else.


----------



## n_maher

Just bear in mind that he's a one man show so if he's on vacation you're not going to get a reply until he gets back. This is a popular time of year to take vacation in the states as it's the end of the summer holiday for folks with kids.


----------



## ericj

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_The PS heat sink temp is almost entirely dependent on your walwart/transformer._

 

It's entirely dependent on Ohm's Law. 

 If you drop 7 volts at 400ma you dissipate 2.8 watts as heat. 

 So, yeah, it's closely related to the transformer, but it's easy to calculate and plan for.


----------



## tomb

Quote:


  Originally Posted by *ericj* /img/forum/go_quote.gif 
_It's entirely dependent on Ohm's Law. 

 If you drop 7 volts at 400ma you dissipate 2.8 watts as heat. 

 So, yeah, it's closely related to the transformer, but it's easy to calculate and plan for._

 

Actually, NO. It's _Joule's Law_:
 P = I x V, where Power also equals Heat dissipated by the regulator.

 It's also not easy to calculate because it depends on the voltage and amperage rating of the transformer _and_ its inherent regulation. Predicting the final voltage becomes one of predicting how much over-voltage the transformer will produce at a given percentage of its load rating. That more or less involves a direct measurement - not something that is easy to plan for.

 I'm sure you knew all of that, but instead wanted to make the 1000th post in this thread.


----------



## ruZZ.il

Tom, on the construction thread regarding the heat sinks: "You should use an insulating shoulder washer on the regulator, but it will not fit on most of the suggested transistors.", 
 I'm not entirely sure how one goes about electrically insulating them then. I mean, with the insulating thermal conductive pads, but if those shoulder washers don't fit, what's to be used to prevent the screw from touching the transistors on the inside of the hole? (EDIT: Never mind, I took a look at the transistors. They don't have the tongue like the regulator and diodes, like I somehow thought they did..) 

 also, I'll soon have a whole bunch of matched transistors.. of both types (only done 5088s so far) I'll probably find quiet a few matched ones within the range (got between 375 and 430) with the most around 390, 415.... I suppose the others will have a slightly higher range? say I get groupe there at 450, 500, 530.. am I supposed to use groups closer together (like 415/450) ? or doesnt it matter there, as long as they're matched?

 and yep.. got the sonicap gen II's 0.22 with BGs... I expect it all to sound good even with the standard caps, but it'll probably take a while to get another MAX to compare them to.. looking forward to it all 
	

	
	
		
		

		
		
	


	




 (though it'll probably take a while for me to get them heatsinks, dangit)

 Thanks.


----------



## tomb

Quote:


  Originally Posted by *ruZZ.il* /img/forum/go_quote.gif 
_Tom, on the construction thread regarding the heat sinks: "You should use an insulating shoulder washer on the regulator, but it will not fit on most of the suggested transistors.", 
 I'm not entirely sure how one goes about electrically insulating them then. I mean, with the insulating thermal conductive pads, but if those shoulder washers don't fit, what's to be used to prevent the screw from touching the transistors on the inside of the hole?_

 

The ones that won't allow a shoulder washer are plastic and inherently insulated. I probably should've added that statement.

  Quote:


 also, I'll soon have a whole bunch of matched transistors.. of both types (only done 5088s so far) I'll probably find quiet a few matched ones within the range (got between 375 and 430) with the most around 390, 415.... I suppose the others will have a slightly higher range? say I get groupe there at 450, 500, 530.. am I supposed to use groups closer together (like 415/450) ? or doesnt it matter there, as long as they're matched? 
 

It matters. So, your 415/450 example would be best - given a choice. If you don't have matching as close as that between the 5087-5088 groups it'll still be OK. Matching within type is still most important. It's probably very critical for the pairs that form the CCS.

  Quote:


 and yep.. got the sonicap gen II's 0.22 with BGs... I expect it all to sound good even with the standard caps, but it'll probably take a while to get another MAX to compare them to.. looking forward to it all 
	

	
	
		
		

		
		
	


	




 (though it'll probably take a while for me to get them heatsinks, dangit)

 Thanks. 
 

Good luck!


----------



## tomb

We've gone over 1000 posts in this thread - that bests the Alien DAC thread, which I thought might be a record-breaker for the DIY section, but I'm not sure. I would encourage some of you to also participate at DIYForums.org, the basis for Millett development. I've made some changes that may make things easier for registering, etc. I will continue to monitor things over here, though, and actively participate. Head-Fi has been/is the Big Kahuna for the MAX. We would never have achieved 400+ boards without it.


----------



## jamess71

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_We've gone over 1000 posts in this thread - that bests the Alien DAC thread, which I thought might be a record-breaker for the DIY section, but I'm not sure. I would encourage some of you to also participate at DIYForums.org, the basis for Millett development. I've made some changes that may make things easier for registering, etc. I will continue to monitor things over here, though, and actively participate. Head-Fi has been/is the Big Kahuna for the MAX. We would never have achieved 400+ boards without it._

 

Tom are there any more boards available? 

 James


----------



## tomb

Quote:


  Originally Posted by *jamess71* /img/forum/go_quote.gif 
_Tom are there any more boards available? 

 James_

 

Colin has close to 50 extras. However, it's school registration at many colleges across the US. I think he'll get back to us with a sale notice eventually.


----------



## jamess71

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Colin has close to 50 extras. However, it's school registration at many colleges across the US. I think he'll get back to us with a sale notice eventually._

 

Cool Is there some kind of list to get on or should I PM someone? Thx


----------



## tomb

Quote:


  Originally Posted by *jamess71* /img/forum/go_quote.gif 
_Cool Is there some kind of list to get on or should I PM someone? Thx_

 

Sorry, no.


----------



## ericj

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_The ones that won't allow a shoulder washer are plastic and inherently insulated. I probably should've added that statement._

 

You already know this, but just so others aren't confused: if the plastic package has a metal plate on the back, you should still insulate between the transistor and the heatsink. But you don't need the shoulder bushing. 

 My bd series transistors (fairchild, I think) have exposed metal on the back, I don't recall if my mje series transistors do.


----------



## tomb

Quote:


  Originally Posted by *ericj* /img/forum/go_quote.gif 
_You already know this, but just so others aren't confused: if the plastic package has a metal plate on the back, you should still insulate between the transistor and the heatsink. But you don't need the shoulder bushing. 

 My bd series transistors (fairchild, I think) have exposed metal on the back, I don't recall if my mje series transistors do._

 

Yes, that is a very good point. The MJE's I've had all had metal backs - TO-216's, I think.


----------



## DanPash

Just finished my soha and its sounding sweet! I really want a board to build one of these!


----------



## soloz2

I took the output resisters out today... opens the amp up a bit. before it sounded a tad constrained. I like it better jumpered 
	

	
	
		
		

		
			





 now I just need to look into getting the endpannels engraved...


----------



## tomb

Quote:


  Originally Posted by *soloz2* /img/forum/go_quote.gif 
_I took the output resisters out today... opens the amp up a bit. before it sounded a tad constrained. I like it better jumpered 
	

	
	
		
		

		
		
	


	




 now I just need to look into getting the endpannels engraved..._

 

Yeah, I like it better without output resistors, too. Use the different tubes to adjust gain and leave them out.


----------



## ericj

I was under the impression that the output resistors provided some protection.


----------



## tomb

Quote:


  Originally Posted by *ericj* /img/forum/go_quote.gif 
_I was under the impression that the output resistors provided some protection._

 

The DB has power output resistors. These are the legacy Millett output resistors and they are truly optional.


----------



## tomb

Quote:


  Originally Posted by *DanPash* /img/forum/go_quote.gif 
_Just finished my soha and its sounding sweet! I really want a board to build one of these!_

 

HeadphoneJunkie won't like me saying this again, but I have the following sitting on my coffee table for direct comparison as I type this:

*SOHA:* GE 5963 tube, 100uF, 100V Panasonic FC caps, 1200uF Panasonic FM caps on the 12V opamp supply, with 47uF Panasonic FM's on the opamp side of the regs. Muse ES on the cathode bypass positions, Opamp is OPA2107 with Wima 0.1uF MKP10's.

*MAX Proto #1:* RCA 12AE6A tubes, 2-2200uF FC's in the PS, 1200uF Pana FM's for the general caps, Muse ES on cathode bypass and output, Wima MKP10's all around, 2SC3422/2SA1359 BJT's biased to 110mV (50ma)

 Both are fed with an Alien DAC and flac files from the PC I'm typing on. The Alien DAC has Muse ES's on the output. So, it's most definitely a bass heavy table. 
	

	
	
		
		

		
		
	


	




 Ummm ... guess which one just blows the other one away? In every aspect: detail, resolution, bass definition, bass extension, dynamics, _slam_, etc.? Yet, both have a distinctly tube-driven frequency response flair.


----------



## ericj

Ahh. Yeah, then leaving them out does make sense.


----------



## odoe

Got all my parts now except for some orange drops I'm waiting on from ebay. I accidentally ordered two cases, which is ok because I have two boards


----------



## c0nsumer

Hey there... This weekend I finished up my Millett Hybrid Max (with MOSFETs) and while it was working great at first (Saturday), I'm now having some problems. I'm hoping that someone here can give me some pointers on where to look.


 First off, here are photos of the top and bottom of the PCB: Bottom Low Res, Bottom High Res, Top Low Res, Top High Res.


 My soldering is generally pretty good, but please note that all the connections look dull because I'm now using lead-free solder for board work. As can be seen on this page my enclosure is almost exactly the same as cetoole's, including the vent holes for the heatsinks. When it was working the chassis never rose above slightly warm (around 100°F) in a 75°F room, so it seems to be vented well enough.

 The power supply is a Jameco-brand 24VAC 1A wall wart. I've used their supplies before and they've been quite good in the past. For fuses I've been using either 800mA or 1A fast-blow fuses. When the amp was working the 800mA was sufficient at levels as high as the maximum I could stand (about 10 o'clock).

 Power, audio inputs, and headphone jack are all isolated from the chassis, and their isolation has been confirmed with a continuity meter.


 Here's a rough timeline of how the build / testing went and problems I had along the way, which will hopefully help point the way:

 - Finished assembling everything, and on powering it on I found only ~2.6VDC from the power supply, regardless of the position of RR3.
 - Found that I was bit by the backwards silkscreen on the trimmers, so when I thought I had everything turned down all the way for initial setup it was actually all the way up.
 - Properly turned all the trimmers down, powered things on, set the power supply to 27.00 VDC.
 - Biased the tubes to 13.50 VDC.
 - Biased the MOSFETs to 200mV, which is right in the middle of the range suggested on the MAX Setup and Bias Settings page.
 - Hooked up a CD player (random Yamaha changer) and headphones (Sennheiser HD570) and confirmed that I could hear audio.
 - Left the CD player playing Radiohead's Kid A on repeat for 4-5 hours with the volume at listening levels.
 - Checked the power supply voltage, tube bias, and MOSFET bias and returned them to the settings previously mentioned, as they had drifted slightly.
 - Checked the heatsinks with a thermocouple and found them to be around 125°F.
 - Listened to a few different CDs and some DVD audio and was happy with the sound.
 - The next day I went to hook up my iPod, but I wasn't getting any audio from the left channel. Turned everything off, removed the tubes, looked around, reinserted the tubes, and noted that everything seemed to work.
 - Listened to a few more CDs, then found the left channel to be a bit lower than the right. I figured that the MOSFETs needed to be biased again, so I decided to set it aside and open the case the next morning.
 - Listening more the left channel started dropping out completely, and during a test while listening to Squarepusher's Tetra-Sync (a 10 minute track) I could hear the left channel fade in and out, and occasionally get a bit static-y / fuzzy.
 - The next morning I began thinking the problem might be with the 1/4" to 3.5mm headphone adapter I was using, so I plugged in a different one and turned on the amp. It wasn't working, nor was it warming up.
 - Opening up the amp I found that the fuse (800mA) was blown. From this point on it blew every fuse I've inserted.


 In testing, I tried the following with no success, with fuses continuing to blow each time:

 - Replaced the left tube with a spare NOS 12AE6A.
 - Removed the board from the enclosure.
 - Replaced both tubes with spare NOS 12FM6 pieces.
 - With the tubes in place, VCC to GND is at about 33.8Ω, which just about matches the two tube heaters (~12Ω each) plus R1 (~10Ω). No dead short there.


 Any ideas? I'm pretty lost at this point...

 Thanks very much...

 -Steve


----------



## amphead

Quote:


 TomB:
 Ummm ... guess which one just blows the other one away? In every aspect: detail, resolution, bass definition, bass extension, dynamics, slam, etc.? Yet, both have a distinctly tube-driven frequency response flair. 
 

Begins with M and ends with an X?


----------



## tomb

Quote:


  Originally Posted by *amphead* /img/forum/go_quote.gif 
_Begins with M and ends with an X?_

 

Give that man a cigar.


----------



## nysulli

Quote:


  Originally Posted by *c0nsumer* /img/forum/go_quote.gif 
_
 - Replaced the left tube with a spare NOS 12AE6A.
 - Removed the board from the enclosure.
 - Replaced both tubes with spare NOS 12FM6 pieces.
 - With the tubes in place, VCC to GND is at about 33.8Ω, which just about matches the two tube heaters (~12Ω each) plus R1 (~10Ω). No dead short there.


 Any ideas? I'm pretty lost at this point...

 Thanks very much...

 -Steve_

 

not that i'm an expert or anything, but it doesn't look like your using shoulder washers on the mosfet heatsinks, it also appears that the bolts for the 2 center mosfets are very close if not touching

 could they possibly be providing an electrical contact between the mosfets and heatsinks, or possibly from one mosfet to the other?

 other then that, i don't see anything obvious, soldering looks fine, don't see anything on the top of the board otherwise either


----------



## c0nsumer

Quote:


  Originally Posted by *nysulli* /img/forum/go_quote.gif 
_not that i'm an expert or anything, but it doesn't look like your using shoulder washers on the mosfet heatsinks, it also appears that the bolts for the 2 center mosfets are very close if not touching

 could they possibly be providing an electrical contact between the mosfets and heatsinks, or possibly from one mosfet to the other?

 other then that, i don't see anything obvious, soldering looks fine, don't see anything on the top of the board otherwise either_

 

Thanks for the idea, but all of the TO-220 parts are actually isolated from the sinks with insulating pads and shoulder washers. Those bolts are actually touching, but as they are isolated it doesn't matter. (This too has been confirmed with a meter.)

 If you look here (click on the image if you want it larger, and look at the center of the front edge) you can see one of the insulating sheets and shoulder washer which came with the Aavid 4880SG Thermalsil III Mounting Kits.


----------



## ericj

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_
*SOHA:* GE 5963 tube, 100uF, 100V Panasonic FC caps, 1200uF Panasonic FM caps on the 12V opamp supply, with 47uF Panasonic FM's on the opamp side of the regs. Muse ES on the cathode bypass positions, Opamp is OPA2107 with Wima 0.1uF MKP10's._

 


 For whatever it's worth: My SOHA (which also sports a GE 5963) is the only thing I've plugged an opa2107 into where i didn't like it. 

 I've got it in the mu-follower configuration with an lm4562 and 0.82uf Electrocube polypro coupling caps, and it really sounds pretty good - except for the fact that the lm4562 struggles to drive low-impedance headphones. 

 Does a grand job with 250-600ohm cans. Less so between 120 and 250 ohms. With planar magnetic cans it can go down further but it's not ideal. 

 12au7 types *should be able to outperform 12ae6 types quite handily. The SOHA suffers from a weak output stage and the design needs an update. 

 With 15v to220 regulators on the output power supply and a good discrete output stage it should perform much better, but there's certainly no easy way for the average joe to do that now. At the moment it seems to be the exclusive domain of people with the time & interest to forge ahead without a printed board. 

 Alex Cavalli indicated that he's working on a much improved output stage but hasn't leaked any details. 

 Just sayin, is all. I find my SOHA to be very smooth and relaxed.


----------



## tomb

Quote:


  Originally Posted by *c0nsumer* /img/forum/go_quote.gif 
_Thanks for the idea, but all of the TO-220 parts are actually isolated from the sinks with insulating pads and shoulder washers. Those bolts are actually touching, but as they are isolated it doesn't matter. (This too has been confirmed with a meter.)

 If you look here (click on the image if you want it larger, and look at the center of the front edge) you can see one of the insulating sheets and shoulder washer which came with the Aavid 4880SG Thermalsil III Mounting Kits._

 

I'm sorry I missed this post earlier. However, after studying your photographs my first reaction was that of Nysulli's. I noted the shoulder washers, but it seems having the bolts touch in the center is just tempting fate. I wonder if they measure OK now because the Left channel MOSFET in that position is fried.

 That's just a guess, for sure - your work looks splendid, otherwise. However, other than the voltage regulator - and it has its own thermal protection - the MOSFETs are the only thing on the board that could be blowing the fuse, IMHO.

 If it's not the bolt - just curious where you got the MOSFETs? If you bought them from Amb, no problem. If not, they have been known to run pretty high with rejects. That's why Amb sells them as "tested" (not matched). Perhaps that's another possibility. It does sound like one of those MOSFETs.

 Maybe I'll have some other suggestions tomorrow.

 EDIT: One thing you might try is to zero out the DB trimmers. If that stops the fuse from blowing, at least you know for sure the issue is in the DB's.


 P.S. Your CA2 caps look pretty small - what size are they?
 Also, you may need to add those compensation caps on the outside MOSFETs. That wouldn't cause this problem, though. You may have them already, but I can't tell from the bird's eye.


----------



## amphead

Tom,
 The only item I have not purchased yet, are the 12AE6/A's. Best source for GE's?.....Radio Daze?


----------



## tomb

Quote:


  Originally Posted by *amphead* /img/forum/go_quote.gif 
_Tom,
 The only item I have not purchased yet, are the 12AE6/A's. Best source for GE's?.....Radio Daze?_

 

I don't know at this point. Certainly, Radio Daze is worth a shot, but they're running low with specific branding - esp. GE's. If you try them, please let us know how their stock is doing.

 Roy and Dale at Vacuumtubes.net have a pretty good stock of Olsons - which were repackaged GE's. Their prices are as good as Radio Daze. James Cross at vacuumtubesinc.com has the Olsons, too. He's a tad higher but still quite reasonable. Antique Electronic Supply (tubesandmore.com) used to have the GE's, but they've been sold out for awhile, I think. 

 After that, you're dealing with higher prices, I'm afraid - perhaps $5 a tube or more - but the GE's in GE boxes can be found. At the higher prices, I can highly recommend TubeDepot.com - they also have our sockets, and have impeccable and reliable service.

 To be honest, the tube branding really doesn't make much of a difference with the MAX. It's sort of like those DB's simply suck out every last bit of detail from the tubes, regardless. With the old Millett - especially without DB's - it was a little easier to distinguish the subtle differences between tube brands. There is nothing whatsoever wrong with the RCA's and the Sylvanias (or the re-packaged ones). Despite my GE fanboy stance, I've been listening more to RCA's and Sylvania's recently.

 Anyway, tell us what luck you have with purchasing tubes and the dealer's stock that you select.


----------



## soloz2

where's the best place to get the shoulder washers? I should pick up some


----------



## c0nsumer

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_I'm sorry I missed this post earlier. However, after studying your photographs my first reaction was that of Nysulli's. I noted the shoulder washers, but it seems having the bolts touch in the center is just tempting fate. I wonder if they measure OK now because the Left channel MOSFET in that position is fried._

 

I didn't like having these bolts touch, but at that point with the mounting kits I had the only choice was to go this route, or attempt to shorten the bolt and re-thread the bolts. I set it up, checked to be sure everything was isolated properly, then went ahead and powered it on. The contact is so light that I'm not actually able to determine the resistance between the two bolts. So, I'm hesitant to think that this is the problem.

 I'd also be surprised that everything could run great for 6 hours powered on and sounding fine if the issue was a simple short like that.

 On a side note, after doing this assembly I really dislike the positioning of the two center heatsinks (RB9L/R), because it makes it very difficult to actually tighten down mounting bolts unless one fits one part completely, then the other. (this photo shows my doing this, before I fitted QB9L.) With the heatsinks being soldered in place I'm not yet sure of the procedure I'll use if I need to remove / replace the MOSFETs, as re-bolting them will be a problem.


  Quote:


 That's just a guess, for sure - your work looks splendid, otherwise. However, other than the voltage regulator - and it has its own thermal protection - the MOSFETs are the only thing on the board that could be blowing the fuse, IMHO.

 If it's not the bolt - just curious where you got the MOSFETs? If you bought them from Amb, no problem. If not, they have been known to run pretty high with rejects. That's why Amb sells them as "tested" (not matched). Perhaps that's another possibility. It does sound like one of those MOSFETs.

 Maybe I'll have some other suggestions tomorrow.

 EDIT: One thing you might try is to zero out the DB trimmers. If that stops the fuse from blowing, at least you know for sure the issue is in the DB's. 
 

Thank you. I've actually done quite a bit of electronics assembly / board design work, but this is the first all-analog audio project I've done so it's a bit... frustrating.

 I actually picked up the MOSFETs from Amb as the matched pair sets. I've got another set here, but they are being shipped off to the UK tomorrow for a friend who is building one.

 This morning before leaving for work I tried turning the DB trimmers (RB12L/R) all the way down (clockwise, because of the backwards installation due to the silkscreen) and went through another fuse. Just for completeness sake I tried spinning it all the way counterclockwise as well, and that also blew a fuse.


  Quote:


 P.S. Your CA2 caps look pretty small - what size are they?
 Also, you may need to add those compensation caps on the outside MOSFETs. That wouldn't cause this problem, though. You may have them already, but I can't tell from the bird's eye. 
 

Those are the Nichicon 1000μF 16V (Mouser Part 647-UPW1C102MPD) caps mentioned in the BOM. The compensation caps are there too, but they are hard to see, sorry. If you look at this image you can see the one in QB8L.

 Thanks very much for the help / ideas on this. I've just sort of hit a wall. I'm half-tempted to assemble a second on one of the other PCBs, or just toss this and build a β22 / σ22 combo, but I know that wouldn't be the smart thing to do.

 I'm also wishing for a power supply where I can set both the voltage and amperage output, because then I could just feed the board just under 1A and wait for whatever is causing the short to smoke, then replace that.

 (One other thing I noticed when originally doing the assembly, which I forgot to mention last night, is that when I powered the board up without the tubes in place, the fuse blew. After fitting the tubes this didn't happen. I chalked it up to something I don't understand in the design, but is this right? Could powering it up without the tubes have potentially damaged something else?)

 Thanks again...


----------



## ericj

Quote:


  Originally Posted by *soloz2* /img/forum/go_quote.gif 
_where's the best place to get the shoulder washers? I should pick up some_

 

dunno about 'best place' but i posted digikey part numbers for berquist insulating pads and some generic shoulder washers a couple pages back. 

 digikey sells the berquist pads in whatever quantity, but the shoulder washers start at qty100 (just over 4 cents each)


----------



## nysulli

Quote:


  Originally Posted by *soloz2* /img/forum/go_quote.gif 
_where's the best place to get the shoulder washers? I should pick up some_

 

mouser part #561-04006 or 561-04012 depending on the thickness of the heatsink, not sure which is needed myself


----------



## tomb

Quote:


  Originally Posted by *c0nsumer* /img/forum/go_quote.gif 
_I didn't like having these bolts touch, but at that point with the mounting kits I had the only choice was to go this route, or attempt to shorten the bolt and re-thread the bolts. I set it up, checked to be sure everything was isolated properly, then went ahead and powered it on. The contact is so light that I'm not actually able to determine the resistance between the two bolts. So, I'm hesitant to think that this is the problem.

 I'd also be surprised that everything could run great for 6 hours powered on and sounding fine if the issue was a simple short like that._

 

True, and I'm guessing, but it may be heat related - something expanded where not having touched before, it touches now. It certainly sounds like a dead short somewhere. We agree that there's nothing on the bottom of your board that could be causing this, so the top must be where this is happening, and the bolts seem the likely suspect.

  Quote:


 On a side note, after doing this assembly I really dislike the positioning of the two center heatsinks (RB9L/R), because it makes it very difficult to actually tighten down mounting bolts unless one fits one part completely, then the other. 
 

We may be in agreement that the positioning of some of the heat sinks may not be optimum, but there are important design considerations that led to this arrangement.

 Regardless, this is easily solved with shorter screws and making sure that the nuts are on the inside in both cases. There's nothing that says the screw head has to go on the front side of the MOSFET, or that you have to use screws that are this long in this case. In any event, you should attach the transistors to the heat sink prior to soldering the assembly on the board. Replacement is a little more difficult, but not with the nuts on the inside in both cases.

  Quote:


 (this photo shows my doing this, before I fitted QB9L.) With the heatsinks being soldered in place I'm not yet sure of the procedure I'll use if I need to remove / replace the MOSFETs, as re-bolting them will be a problem. 
 

Again, this is a simple solution as noted above. Almost any Hardware store should have cheap 4-40 screws - most likely Philips heads and at 3/8" lengths. Socket head cap screws are even better, and can be accessed on the inside between the sinks as well with the use of a ball tip allen wrench. 

  Quote:


 Thank you. I've actually done quite a bit of electronics assembly / board design work, but this is the first all-analog audio project I've done so it's a bit... frustrating.

 I actually picked up the MOSFETs from Amb as the matched pair sets. 
 

Again - not "matched", but "tested." The reason for this is that some MOSFET brands are known for failures.

  Quote:


 I've got another set here, but they are being shipped off to the UK tomorrow for a friend who is building one.

 This morning before leaving for work I tried turning the DB trimmers (RB12L/R) all the way down (clockwise, because of the backwards installation due to the silkscreen) and went through another fuse. Just for completeness sake I tried spinning it all the way counterclockwise as well, and that also blew a fuse. 
 

We are definitely sorry with the trouble you are having. Please take comfort in the fact that there are quite a few MAXes running fine at the moment, and that we went through a rigorous design and prototyping process.

  Quote:


 Those are the Nichicon 1000μF 16V (Mouser Part 647-UPW1C102MPD) caps mentioned in the BOM. The compensation caps are there too, but they are hard to see, sorry. If you look at this image you can see the one in QB8L. 
 

OK - just wondering - not too many people are going with non-boutiques. I wasn't used to seeing them. 
	

	
	
		
		

		
		
	


	




 The regular electrolytics should be smallish in this rating and with the Wima bypasses will still sound pretty good. That was part of the genius in Pete Millett's original design.

  Quote:


 Thanks very much for the help / ideas on this. I've just sort of hit a wall. I'm half-tempted to assemble a second on one of the other PCBs, or just toss this and build a β22 / σ22 combo, but I know that wouldn't be the smart thing to do.

 I'm also wishing for a power supply where I can set both the voltage and amperage output, because then I could just feed the board just under 1A and wait for whatever is causing the short to smoke, then replace that.

 (One other thing I noticed when originally doing the assembly, which I forgot to mention last night, is that when I powered the board up without the tubes in place, the fuse blew. After fitting the tubes this didn't happen. I chalked it up to something I don't understand in the design, but is this right? Could powering it up without the tubes have potentially damaged something else?)

 Thanks again... 
 

Please be patient. We're here to help. I would not advise building another MAX board until you get this one fixed - the mistake may be repeatable. A B-22 is a great amp, but you will gain nothing in the potential for mistakes - it's much more complicated.

 One thing you mentioned here at the last that might be suspect: There's a huge amount of caps on the board and if you have biased up the MOSFETs, it's quite possible that you could blow the fuse without the tubes. The tubes take quite a bit of current, but the heaters are slow to come up. This may have the effect of "tempering" the huge inrush presented by the caps and the MOSFETs. You might try a 1.5A fuse, put the tubes in, and see if that makes a difference. Get those screws fixed first, though.

 Let us know your results.


----------



## vixr

Quote:


  Originally Posted by *c0nsumer* /img/forum/go_quote.gif 
_On a side note, after doing this assembly I really dislike the positioning of the two center heatsinks (RB9L/R), because it makes it very difficult to actually tighten down mounting bolts unless one fits one part completely, then the other. (this photo shows my doing this, before I fitted QB9L.) With the heatsinks being soldered in place I'm not yet sure of the procedure I'll use if I need to remove / replace the MOSFETs, as re-bolting them will be a problem._

 


 tomb shows the heatsinks all pre-built as an assembly in this pic from the MAX site...I did it this way with no problem. getting the tiny tip I use on my hakko to solder those huge posts on the sinks was the hard part.


----------



## c0nsumer

Quote:


  Originally Posted by *vixr* /img/forum/go_quote.gif 
_tomb shows the heatsinks all pre-built as an assembly in this pic from the MAX site...I did it this way with no problem. getting the tiny tip I use on my hakko to solder those huge posts on the sinks was the hard part._

 

I saw that, but I was a bit concerned about possibly overheating the MOSFETs while soldering the heatsinks, so I did three of the heatsinks stand-alone, then bolted in the MOSFETs, then soldered their leads. This way there wasn't any stress on the solder joints.

 Then I fitted the fourth MOSFET (QB9L) to the heatsink, soldered the MOSFET leads, then the heatsink legs. I had no problem doing it with a Weller WES51 and an ETA tip, even with lead-free.

 I can't see any reason for a problem with how I fitted the heatsinks, and I still don't believe that the touching mounting bolt is a problem as the MOSFETs are wholly electrically isolated from the heatsinks and bolts.


----------



## c0nsumer

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_True, and I'm guessing, but it may be heat related - something expanded where not having touched before, it touches now. It certainly sounds like a dead short somewhere. We agree that there's nothing on the bottom of your board that could be causing this, so the top must be where this is happening, and the bolts seem the likely suspect._

 

I'm still in disagreement about the bolts being the problem as I've repeatedly made sure they aren't electrically connecting to anything but the heatsinks, and I can't believe that thermal expansion would defeat the isolation provided by the shoulder washers and insulting film, but I'll still be sure to rule them out. (Then I'll also then have shorter mounting hardware to send along with the kit to the friend in the UK...)


  Quote:


 We may be in agreement that the positioning of some of the heat sinks may not be optimum, but there are important design considerations that led to this arrangement. 
 

Yep, I can see how the bushings around the tubes are allowed clearance during assembly thanks to this mounting arrangement. And it seems fine for cooling, so I can understand that...

  Quote:


 Regardless, this is easily solved with shorter screws and making sure that the nuts are on the inside in both cases. There's nothing that says the screw head has to go on the front side of the MOSFET, or that you have to use screws that are this long in this case. In any event, you should attach the transistors to the heat sink prior to soldering the assembly on the board. Replacement is a little more difficult, but not with the nuts on the inside in both cases. 
 

What I'm not understanding is why they should be attached prior to heatsink mounting. I can't see a reason, as long as the assembly is done without stressing any joints. That length of screws was used because they were provided with the mounting kits, and it didn't seem like it would be a problem.




> Again, this is a simple solution as noted above. Almost any Hardware store should have cheap 4-40 screws - most likely Philips heads and at 3/8" lengths. Socket head cap screws are even better, and can be accessed on the inside between the sinks as well with the use of a ball tip allen wrench.
> 
> Quote:
> 
> ...


----------



## ruZZ.il

damn those tube socket bolts are tough to get out.. I ended up 'melting' my way through them.. not sure I had the right bit hmm.. I cracked one got some spares, but I'll just epoxy it and use it anyway 
	

	
	
		
		

		
		
	


	









 c'mon lsdiodes.. I'm waiting..


----------



## tomb

Quote:


  Originally Posted by *c0nsumer* /img/forum/go_quote.gif 
_... I still don't believe that the touching mounting bolt is a problem as the MOSFETs are wholly electrically isolated from the heatsinks and bolts._

 

The shoulder washer and insulating pad are precautions, they aren't foolproof. It's conceivable that the shoulder washer doesn't cover the entire MOSFET tab thickness. If the screws are wedged in there, there may be a torque that under heat allows portions of the screws to come into contact with the MOSFETs.

 There were other things mentioned as well, but its up to you about whether to try the suggestions. There's no guarantee either way, but those screws are the very first thing I would remove from the list of possible suspicions.

 Heck - poke a Dremel cutoff wheel in there and cut the stubs off if you can - or a hack saw.


----------



## vixr

Quote:


  Originally Posted by *ruZZ.il* /img/forum/go_quote.gif 
_damn those tube socket bolts are tough to get out.. I ended up 'melting' my way through them.. not sure I had the right bit hmm.. I cracked one got some spares, but I'll just epoxy it and use it anyway 
	

	
	
		
		

		
		
	


	









 c'mon lsdiodes.. I'm waiting.._

 

I used a stepped drill bit to drill out the head of the rivet...its soft aluminum and once it drills out, the little ring of left over material starts to spin... the remaining headless rivet just drops right out after that...


----------



## tomb

Quote:


  Originally Posted by *ruZZ.il* /img/forum/go_quote.gif 
_damn those tube socket bolts are tough to get out.. I ended up 'melting' my way through them.. not sure I had the right bit hmm.. I cracked one got some spares, but I'll just epoxy it and use it anyway 
	

	
	
		
		

		
		
	


	









 c'mon lsdiodes.. I'm waiting.._

 

Yes - it's still tricky - you have to be very careful with the pressure applied on the socket. I still break about 1 out of every 3 or 4.


----------



## vixr

tomb, your MAX is famous....click HERE


----------



## tomb

Thanks. Yes - Colin actually sent me an e-mail about it awhile back. It's a little bit scary, to tell the truth - never talked to anyone about this.


----------



## ericj

Quote:


  Originally Posted by *vixr* /img/forum/go_quote.gif 
_I used a stepped drill bit to drill out the head of the rivet...its soft aluminum and once it drills out, the little ring of left over material starts to spin... the remaining headless rivet just drops right out after that..._

 

My sockets have a solid aluminum rivet - if i drill through the cap on the underside, it comes off as a little ring and the whole thing falls apart. 

 And then i just superglue the halves together.


----------



## ruZZ.il

I think the rivets expanded inside mine for some reason, I got the underside shoulder off from drilling, the rest just never came out.. well.. till..  say, tom, do you still use the broken ones? I don't think a bit of epoxy would have any ill effect, if applied as to avoid the pins..


----------



## c0nsumer

Quote:


  Originally Posted by *ericj* /img/forum/go_quote.gif 
_My sockets have a solid aluminum rivet - if i drill through the cap on the underside, it comes off as a little ring and the whole thing falls apart. 

 And then i just superglue the halves together._

 

For what it's worth I just stuck the sockets in a drill press vise and started into them with a 3/16" bit. Within 3mm of drilling the rivet separated, then I'd just use a few small spots of epoxy to hold things together.

*UPDATE:* Oh, and this was with the plain ceramic sockets from tubedepot.com. I did six in a row with no problems whatsoever.


----------



## tomb

Quote:


  Originally Posted by *ruZZ.il* /img/forum/go_quote.gif 
_I think the rivets expanded inside mine for some reason, I got the underside shoulder off from drilling, the rest just never came out.. well.. till..  say, tom, do you still use the broken ones? I don't think a bit of epoxy would have any ill effect, if applied as to avoid the pins.._

 

http://http://www.diyforums.org/MAX/MAXtubelights.php Middle of the page - where it says "Socket Take-Apart Methods". No, I don't use the broken ones. The sockets take a lot of stress. It's pretty difficult to glue them structurally without enveloping the pins.

 Personally, I think the 3/32" bit is best. You can end up mashing the melted center pins into the hole or busting a part of the ceramic around the hole with a larger bit. The idea is to push the bottom pin out. So, the 3/32" is only used to punch through the top pin and push out the bottom pin from the inside.


----------



## c0nsumer

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_The shoulder washer and insulating pad are precautions, they aren't foolproof. It's conceivable that the shoulder washer doesn't cover the entire MOSFET tab thickness. If the screws are wedged in there, there may be a torque that under heat allows portions of the screws to come into contact with the MOSFETs.

 There were other things mentioned as well, but its up to you about whether to try the suggestions. There's no guarantee either way, but those screws are the very first thing I would remove from the list of possible suspicions.

 Heck - poke a Dremel cutoff wheel in there and cut the stubs off if you can - or a hack saw._

 

Yep, I understand... I think at this point the best thing for me to do is to simply replace all the MOSFETs and bolts, just to be sure. It'll be less than $8 in parts at most, and hopefully it'll fix things.

 I was going to be ordering a set of ß22 boards and such anyway, so throwing on another set of MOSFETs will be trivial.

 At least this time I'll know the proper minimum positions for the trimmers too.

 Thanks for your help.


----------



## amphead

Quote:


 TomB:
 Radio Daze is worth a shot, but they're running low with specific branding - esp. GE's. If you try them, please let us know how their stock is doing. 
 

Tom, I didn't check with Radio Daze due to the availability issues. I ordered from TubeDepot, without checking their stock level. Backordered for 2 weeks. My bad  So, now that I'm in the shark feeding frenzy mode, I have ordered 3 tubes from TheTubeStore. I will post my findings on that order. Tube availability at this point, is starting to become frightening 
	

	
	
		
		

		
		
	


	




 and its not even Oct 31st.


----------



## ruZZ.il

we need new new stock


----------



## Blooze

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_I don't know at this point. Certainly, Radio Daze is worth a shot, but they're running low with specific branding - esp. GE's. If you try them, please let us know how their stock is doing._

 


 SHHHHH. I've been buying tubes from them for quite a while now. I can tell you what's going to happen to the prices. It's gonna be just like the 1626's. A few people build an amp with $1-2 tubes and like it, then a few more, and a few more, and soon enough they're going for $10 ea on fleabay. 
	

	
	
		
		

		
		
	


	




 Or 300B's that used to sell for $5 each 30 years ago and now go for $300+ a piece. Although I can't see these tubes actually making that 
	

	
	
		
		

		
		
	


	




 Honestly, there ought to be a pretty good supply of these out there just due to the availability and usage they had in the past. I bet some of these old mom and pop auto parts stores that have been around forever in the small towns might even have some wasting away in some corner.

 I've never tried the GE's. But I like the Sylvania 12FK6's and the Tung-Sol 12FK6's I've had. Never tried a 12AE6 yet as I liked the other well enough not to want to change. I do have a couple left so I better get on the stick and get some ordered for rolling and backup.


----------



## c0nsumer

Tonight I went ahead and replaced all four MOSFETs in the board, using shorter screws this time. I still am not convinced the touching, isolated screws caused the problem, but I figured that I may as well install shorter screws since I was removing the MOSFETs anyway. (Here's an image of the MOSFET area with the new, shorter screws fitted.)

 Unfortunately as this was my only spare set of MOSFETs, it means that my friend won't be getting his kit for a little while longer. It also didn't solve the problem.

 After a bit more poking I did get the problem solved, though. Well, sort of.

 So, what was it? A combination of things... Most notably, the suggested fuses and power supply. The BOM specifies a 1A quick-blow fuse and a 1A power supply, but as can be seen in this photo the inrush current was over 1.7A. (That's with the MOSFET bias (RB12L/R) turned all the way down and with 12FM6 tubes. With 12AE6A tubes and the bias equally low the max was around 1.6A. I haven't yet tested it with the MOSFET bias set for normal use.)

 I found this after running out of the straight-wire fuses I was using and giving things one last go with one of the new 576-0217001.HXP fuses (1A, 250V) I received from Mouser this afternoon. This fuse happens to have a zig-zag pattern element (photo of the fuse up close), but I figured I would hook up my meter, try one more fuse, and see exactly what the inrush current peaks at before the fuse blows. When I powered the amp on I didn't see the telltale flash of a blowing fuse, but I instead saw the wire twitch and look as if it almost broke, except when I glanced at the meter I saw a ~1.7A maximum reading. After 15 seconds or so things settled out at about 300mA.

 I think that the fuses I was using were just a bit too sensitive and couldn't handle the inrush current. I'm not sure why it took a few hours to start happening, but once it did, things were pretty consistent. I only wish I had tried this before. (It may be because the room the amp was sitting in before the problem arose was about 15°F warmer than the basement where the amp was first built. If I recall correctly MOSFETs consume more power as they get warmer. Maybe things were right on the edge? I'm not sure about this part of it yet...)

 Going forward I think that it would be best to recommend both much higher amperage power supplies and higher amperage fuses. Realistically the power supply and fuse should be able to handle the full inrush current. I suspect that many individuals out there who have built Millett Hybrid Maxes and are using a 1A supply without fuses are very briefly (1-2 seconds) overloading their supplies and risking cooking them.

 I personally am going to order some slow-blow 1A and 2A fuses next time I place an order with Mouser. I'll use the 1A fuses for now and just wait for the day that the wall-wart power supply fails, then I'll replace it with a 2A supply and 2A fuses. There's a good chance it may be able to take the sudden spike, and I'll stick with it, although I'm still not completely comfortable with its sizing.

 Oh, two other things...

 One, the Kobiconn 161-073SP-EX from Mouser seems to be a really nice gold-plated snap-in front panel 3.5mm (1/8") jack. It's an attractive black plastic lump which snaps solidly into a 3/8" hole drilled in one of the Hammond 1455T1601 metal front panels. I'll post photos of it later once I've got everything set up and ready to use.

 Second, if the Millett Hybrid Max boards ever undergo a revision, I have one design suggestion: Set the groudplane back a bit from the sides so that there is less of a risk of the grooves on the sides of the suggested enclosure (Hammond 1455T1601-series) scraping through the soldermask and making contact with the groundplane. I did this on the MIDIbox SID-NUXX mainboard PCBs which were designed for the same enclosure and it worked out great (scan of top of PCB here).

 Anyway, thanks for the suggestions, everyone. I'm just glad it's working. Now, time to go wire in that new 3.5mm front panel jack and get it ready for initial listening / burn-in / biasing.


----------



## Blooze

On the inrush current problem, could a NTC CL-** thermistor be utilized in this instance to slow that down a bit? We use them on full tube amps to slow the B+ down a bit and let the heaters warm up a little more before slamming the tubes.


----------



## joneeboi

Hey guys,

 I'm getting 27VDC for PS, 66mV at the DB, but when I twist the trimpot knob for RA1L/R, it just sits at 24.3VDC. I tried flipping the trimpot but nothing changes. Anything I should check before uploading some pics?


----------



## Troyhoot

Speaking of fuses and wallwarts. ill relay my experience. When I ordered the 1 amp fuses were out of stock. So i got 1.25 amp fuses. They are the zigzag ones. I bought wrong transformer first off so I had a 750ma. Quickly replaced it with a 1a. Now running a 2a and i have had zero problems with my fuses. Im also pushing 300-310mv on my mosfets. heatsink temps hover around 150-160f degrees also.

 I would agree you probably got some weak fuses. I also would agree the Mosfet version really needs a higher transformer. I couldnt hold 27v with the 1a version. So far my 1.25a fuse is holding with the 2a transformer(been 3 or 4 days). But I would have to think somthing else was contributing to the fuse blowing. But I dunno. Just giving you what Info I gathered on my build.


----------



## Troyhoot

Quote:


  Originally Posted by *joneeboi* /img/forum/go_quote.gif 
_Hey guys,

 I'm getting 27VDC for PS, 66mV at the DB, but when I twist the trimpot knob for RA1L/R, it just sits at 24.3VDC. I tried flipping the trimpot but nothing changes. Anything I should check before uploading some pics?_

 

You might have to give those 10-20 turns before you see a change in the readings. I had that problem with mine too. You may have already tried that, if not its wortha shot.


----------



## joneeboi

I have tried spinning the trimpot from fully clockwise to fully counterclockwise and no change at all. I've tried it with the toobs in and out but it didn't affect anything.


----------



## tomb

Quote:


  Originally Posted by *Troyhoot* /img/forum/go_quote.gif 
_Speaking of fuses and wallwarts. ill relay my experience. When I ordered the 1 amp fuses were out of stock. So i got 1.25 amp fuses. They are the zigzag ones. I bought wrong transformer first off so I had a 750ma. Quickly replaced it with a 1a. Now running a 2a and i have had zero problems with my fuses. Im also pushing 300-310mv on my mosfets. heatsink temps hover around 150-160f degrees also.

 I would agree you probably got some weak fuses. I also would agree the Mosfet version really needs a higher transformer. I couldnt hold 27v with the 1a version. So far my 1.25a fuse is holding with the 2a transformer(been 3 or 4 days). But I would have to think somthing else was contributing to the fuse blowing. But I dunno. Just giving you what Info I gathered on my build._

 

Yeah, I would have to agree that something else was going on.

 That's way too much inrush relative to the steady state. The prototypes - including NeilR's MOSFET version ran about 50% higher on inrush. According to c0nsumer's measurements he's running 300ma steady state with a 1700ma inrush. That's an inrush more than _five times_ the steady state current - almost like LRA on a motor. 
	

	
	
		
		

		
			





 Of course, my 50ma BJT version pulls ~450ma steady state, so I'm not sure what's going on with the numbers here, but they are definitely strange.

 At any rate, I'm glad c0nsumer found his problem.


----------



## c0nsumer

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_That's an inrush more than five times the steady state current - almost like LRA on a motor. 
	

	
	
		
		

		
		
	


	




 Of course, my 50ma BJT version pulls ~450ma steady state, so I'm not sure what's going on with the numbers here, but they are definitely strange.

 At any rate, I'm glad c0nsumer found his problem._

 

I'm just curious, have you hooked up a fairly responsive meter with automatic logging of the maximums just to see what the inrush really is on yours?

 I'd be really curious what other people are finding... All the parts I used are from the formal BOM, except for the power supply and a few external connectors / knobs.


----------



## tomb

Quote:


  Originally Posted by *joneeboi* /img/forum/go_quote.gif 
_I have tried spinning the trimpot from fully clockwise to fully counterclockwise and no change at all. I've tried it with the toobs in and out but it didn't affect anything._

 

I agree with Troyhoot. Depending on the tubes, you may only get an adjustment range in the last 5 turns or so. If the tubes aren't conducting and the CCS's working properly, the trimmers have nothing to adjust. So, it's pointless to try it without the tubes.

 Sometimes the tubes and sockets are not making good contact. Look to see if you see the orange glow from the vertical rod in the very center of the tubes - that's the heater/cathode. If it's not glowing, then the tube is not working - regardless of whether the LEDs are on.

 If those things check out, I would keep trying to turn the trimmer - remember you've got 25 turns total, so even if you turned 20, you may not have hit the adjustment range, depending on the tube.


----------



## c0nsumer

Quote:


  Originally Posted by *Troyhoot* /img/forum/go_quote.gif 
_I would agree you probably got some weak fuses._

 

Perhaps I should restate that. When I said "too sensitive" I didn't mean weak, I meant too sensitive for this application. I, personally, would want fast-blow fuses to fail quickly upon current across them reaching 170% of their rated value. I'd think they were doing their job.

 If other people are seeing inrush currents this high (mind you, it's for a very short period of time) I would really believe that the specified parts are. I'm the sort of individual who feels you should design everything to run within its rated values.


----------



## tomb

Quote:


  Originally Posted by *c0nsumer* /img/forum/go_quote.gif 
_I'm just curious, have you hooked up a fairly responsive meter with automatic logging of the maximums just to see what the inrush really is on yours?

 I'd be really curious what other people are finding... All the parts I used are from the formal BOM, except for the power supply and a few external connectors / knobs._

 

A fast response doesn't mean much if my steady state BJT's biased at 50ma each are pulling 150ma more than your MOSFETs.


----------



## tomb

Note also that I suggested using a higher amp fuse at one point. Frankly, I don't agree with the fuse, period, and suspected that it may cause as many problems as it supposedly protected. However, that was one design discussion that I didn't win.


----------



## c0nsumer

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_A fast response doesn't mean much if my steady state BJT's biased at 50ma each are pulling 150ma more than your MOSFETs._

 

Er, I said a fairly responsive meter, so that you could actually determine what the inrush current is on your amp overall. You need one that samples frequently enough to see the spike and note it as the maximum.


----------



## c0nsumer

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Note also that I suggested using a higher amp fuse at one point. Frankly, I don't agree with the fuse, period, and suspected that it may cause as many problems as it supposedly protected. However, that was one design discussion that I didn't win._

 

May I ask why you don't agree with fuses? I personally think they are very important, as they (should) protect the external power supply, and it's fusing (hopefully self-resetting) or being designed to fail open keeps the breaker in your house from blowing or a fire from starting.

 Fuses are there for safety reasons and are pretty darn important, in my opinion.


----------



## ericj

IMHO the biggest contributing factor to inrush current is probably capacitance. 

 Modern low-ESR caps are almost a dead short when they're first powered up. 

 So, how much rail capacitance ya got there?


----------



## tomb

Quote:


  Originally Posted by *c0nsumer* /img/forum/go_quote.gif 
_Er, I said a fairly responsive meter, so that you could actually determine what the inrush current is on your amp overall. You need one that samples frequently enough to see the spike and note it as the maximum._

 

You missed the point. How can you be running 300ma steady state when my BJT versoin MAX biased to only 50ma is running 150ma more than yours? The inrush is not necessarily the issue. We seem to be discussing wacky numbers all the way around, but I only use a $2.99 meter for everything I build, so I'm probably the one in error I suppose.

  Quote:


  Originally Posted by *c0consumer* 
_May I ask why you don't agree with fuses? I personally think they are very important, as they (should) protect the external power supply, and it's fusing (hopefully self-resetting) or being designed to fail open keeps the breaker in your house from blowing or a fire from starting.

 Fuses are there for safety reasons and are pretty darn important, in my opinion._

 

The power supply needs no protection - it's supposed to be a walwart, which is already fused. If you used your own transformer/PS fabrication, then you still should use a fuse on the line inlet as a minimum good practice.

 When it comes to the fuse on the board, it was put there to protect the MOSFETs, not the PS. There is no other major DIY amp that has a fuse on the board, either. No M3 ever had an onboard fuse, neither did Sheldon Stokes' original MOSFET headphone amplifier. I don't know why we have to cripple the MAX and give people such as yourself a needless headache over it.

 I've said my piece on it several times, though, and supplied several extra fuses to an individual - not doing that anymore. I'll do without, thank you. 
	

	
	
		
		

		
			





 EDIT: As Eric just implied, the inrush can be totally arbitrary - dependent on your own choice of bias, your own choice of capacitance in your electrolytics, etc. And there I am trying to suggest an amp size starting point for a fuse and getting blamed for it.


----------



## joneeboi

So the tube sockets are soldered in and I tested every tube I have (a pair each of the big 3) and no orange lights coming out. Any other possibilities?


----------



## c0nsumer

Quote:


  Originally Posted by *ericj* /img/forum/go_quote.gif 
_So, how much rail capacitance ya got there?_

 

More than my meter can determine, or i'm not holding the probes on long enough (the 1mm annular-rings-as-test-pads are hell).

 I'm not set up to model it, either.


----------



## c0nsumer

Quote:


  Originally Posted by *joneeboi* /img/forum/go_quote.gif 
_So the tube sockets are soldered in and I tested every tube I have (a pair each of the big 3) and no orange lights coming out. Any other possibilities?_

 

Not all tubes have visible glow. The 12FM6s I have here are just barely visible.


----------



## tomb

Quote:


  Originally Posted by *joneeboi* /img/forum/go_quote.gif 
_So the tube sockets are soldered in and I tested every tube I have (a pair each of the big 3) and no orange lights coming out. Any other possibilities?
_

 

When you wiggle, cant the tube slightly to the side or to the back and let it sit that way for a few seconds. It will take 5 seconds or so for the heater to kick in and start glowing.


*Forget that! I see your problem.* The heater resistor is optional, but if you don't put it in, you still have to jumper the position. Otherwise, you have a broken circuit to the heaters.

 Put a power resistor in that spot or jumper it with a bare wire - the heaters should glow after that.


----------



## joneeboi

Giant "never mind." Seems R1 would do the trick.

 She LIVES! I'll call her Maxine. Thanks, Tom and Troyhoot.

 Edit: Okay, the orange comes, but the trimmers still don't work. *wrinkles eyebrows*

 Edit 2: Apologies to all for so quickly claiming that it is living. It doesn't actually play music. I was just so excited when I saw orange. It reminded me of Arrested Development.


----------



## tomb

Like so:





 EDIT: Oops - can't edit a photo and post it fast enough.


----------



## tomb

Quote:


  Originally Posted by *joneeboi* /img/forum/go_quote.gif 
_Giant "never mind." Seems R1 would do the trick.

 She LIVES! I'll call her Maxine. Thanks, Tom and Troyhoot.

 Edit: Okay, the orange comes, but the trimmers still don't work. *wrinkles eyebrows*

 Edit 2: Apologies to all for so quickly claiming that it is living. It doesn't actually play music. I was just so excited when I saw orange. It reminded me of Arrested Development._

 

Go back to my earlier post. You've got at least 25 turns in those trimmers, I believe. Try backing them out with the meter connected and see if there's a point where a reaction takes place. Again, depending on the tube, it may within the last 5 turns or so before the bias kicks in.


----------



## joneeboi

Right. So I was turning the trimmers only one way...
	

	
	
		
		

		
		
	


	




 Tubes are now biased, but music still isn't coming out. Weird thing happened with the trimmers: I couldn't get back up to 27VDC. Only would go to 26.1V (did this already happen to someone?). Maybe my wall just wasn't givin' her like it used to. Alas...

 I also got a loud DC pop when I turned it off. Blast it all!

 Also, can't I use the fuse positions as a place for my on/off switch?


----------



## c0nsumer

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_You missed the point. How can you be running 300ma steady state when my BJT versoin MAX biased to only 50ma is running 150ma more than yours? The inrush is not necessarily the issue. We seem to be discussing wacky numbers all the way around, but I only use a $2.99 meter for everything I build, so I'm probably the one in error I suppose._

 

In the example back there the MOSFETs were at 0, because I'd just finished putting the new ones in and I didn't want to risk them. That all was an example of the drastic difference between inrush and some manner of steady state.


  Quote:


 The power supply needs no protection - it's supposed to be a walwart, which is already fused. If you used your own transformer/PS fabrication, then you still should use a fuse on the line inlet as a minimum good practice.

 When it comes to the fuse on the board, it was put there to protect the MOSFETs, not the PS. There is no other major DIY amp that has a fuse on the board, either. No M3 ever had an onboard fuse, neither did Sheldon Stokes' original MOSFET headphone amplifier. I don't know why we have to cripple the MAX and give people such as yourself a needless headache over it. 
 

Wallwarts are not always fused. When they are, quite often it is a single-shot. All those other amps you mention have some sort of external power supply in their design, and normally these would have a removable fuse in (or right near) the mains connection. This is just good practice. Sure, the amp board itself doesn't have a fuse on it, but the amp+power supply assembly has something replaceable, just like a fused Max does. 

 I think the fuse on the Max is a good thing, because beyond potential safety issues it (if properly sized) is a great failsafe, protecting the not-cheap wallwarts and the boards. Anyone not using it is likely setting themselves up for potential problems.

 Sure, it caused me some issues, but it helped me identify the deeper problem of the recommendations being off. I'd definitely prefer that the fuse go as opposed to the wallwart. (I'm still surprised at how I found the problem... The wire in the fuse visibly bounces like a spring.)

 I'm just surprised there weren't inrush measurements taken of a number of different development configurations and fuse/supply recommendations made off of that, as opposed to steady-state. Perhaps the BOM / website should be updated to reflect this, along with the silkscreen errors?


----------



## tomb

Quote:


  Originally Posted by *joneeboi* /img/forum/go_quote.gif 
_Right. So I was turning the trimmers only one way...
	

	
	
		
		

		
		
	


	




 Tubes are now biased, but music still isn't coming out. Weird thing happened with the trimmers: I couldn't get back up to 27VDC. Only would go to 26.1V (did this already happen to someone?). Maybe my wall just wasn't givin' her like it used to. Alas...

 I also got a loud DC pop when I turned it off. Blast it all!

 Also, can't I use the fuse positions as a place for my on/off switch?_

 

Yes - good idea about the fuse positions on the terminal block.

 Maybe you should give us more details about your DB bias and your walwart. Not being able to bias up to 27VDC is a good sign your walwart isn't big enough.

 Some of you guys - not saying you are, Joneeboi - are really trying to supercharge the MAX. That's fine, but don't expect the part selection to work in every case. Even the MOSFET bias is setup for a midpoint of 100ma in the basic design, the BJT's for 40ma. There is no issue with the parts selection at those values - at least none of the previous builders have any.

 Sorry for that digression ...

 About your loud pop - that may mean something wrong with your relay. How many seconds does it take to trip? Also, something that's a bit disconcerting, but it gives a somewhat loud sound when clicking off sometimes. You should note, however, that there's no real power or buzz behind it. So, it's not damaging for even the best headphones if setup properly.


----------



## c0nsumer

Quote:


  Originally Posted by *Blooze* /img/forum/go_quote.gif 
_On the inrush current problem, could a NTC CL-** thermistor be utilized in this instance to slow that down a bit? We use them on full tube amps to slow the B+ down a bit and let the heaters warm up a little more before slamming the tubes._

 

Would you happen to have a schematic readily available to show how this is done? I'm pretty new to tube-based things, so I just can't picture it.

 Thanks very much. 
	

	
	
		
		

		
		
	


	




*UPDATE:* Never mind, sorry. I just found some examples of doing it. I'm just trying to find appropriate parts so I can incorporate them now.


----------



## amphead

Ok, try this! Replace all of the resistors with jumpers. Warm up the VOM, and check the peak inrush current. Oh, but don't forget to jumper the fuse.
	

	
	
		
		

		
		
	


	




 Edit: Ok, so that wasn't very useful. Instead this is for those nervous nellies, such as myself who can't wait to get their Max parts. Copy/paste your tracking number at this site:http://isnoop.net/tracking/ . Isnoop tracks UPS,FedEx and USPS, with rss feeds which are always up to date.


----------



## joneeboi

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Yes - good idea about the fuse positions on the terminal block.

 Maybe you should give us more details about your DB bias and your walwart. Not being able to bias up to 27VDC is a good sign your walwart isn't big enough.

 Some of you guys - not saying you are, Joneeboi - are really trying to supercharge the MAX. That's fine, but don't expect the part selection to work in every case. Even the MOSFET bias is setup for a midpoint of 100ma in the basic design, the BJT's for 40ma. There is no issue with the parts selection at those values - at least none of the previous builders have any.

 Sorry for that digression ...

 About your loud pop - that may mean something wrong with your relay. How many seconds does it take to trip? Also, something that's a bit disconcerting, but it gives a somewhat loud sound when clicking off sometimes. You should note, however, that there's no real power or buzz behind it. So, it's not damaging for even the best headphones if setup properly._

 

My wallwart is the 750mA one from the BOM, and my DB bias is sitting at 85.7mV. Sinks aren't even getting hot just yet, except maybe QB8L/R, which are the MJE243s running generally hotter than not.

 Weird. Now my MAX's max voltage goes up to 26.7, which isn't bad, I suppose. But what if I wanted to go to 27.1?


----------



## tomb

Quote:


  Originally Posted by *joneeboi* /img/forum/go_quote.gif 
_My wallwart is the 750mA one from the BOM, and my DB bias is sitting at 85.7mV. Sinks aren't even getting hot just yet, except maybe QB8L/R, which are the MJE243s running generally hotter than not.

 Weird. Now my MAX's max voltage goes up to 26.7, which isn't bad, I suppose. But what if I wanted to go to 27.1? 
	

	
	
		
		

		
		
	


	


_

 

Well, I would bias the MJE's up to 110mV if you can - that much more milliamps is not going to have that big of effect on the walwart now.

 Joneeboi - What's your AC voltage at the input terminal block?


----------



## thunder

Can anyone explain why RB 10 & 11 are 2watt when followed by RB14 which is a 1/2 watt? Also can a 10 ohm be used in place of a 2.2 ohm in the 10 & 11 positions ? If so what if any changes are needed ? The reason for the question is I was thinking of using a Tantalum resistor in those position's but cant source anything smaller than a 10 ohm. Also most boutique's are usually 1 watt or less !


----------



## tomb

Quote:


  Originally Posted by *thunder* /img/forum/go_quote.gif 
_Can anyone explain why RB 10 & 11 are 2watt when followed by RB14 which is a 1/2 watt? Also can a 10 ohm be used in place of a 2.2 ohm in the 10 & 11 positions ? If so what if any changes are needed ? The reason for the question is I was thinking of using a Tantalum resistor in those position's but cant source anything smaller than a 10 ohm. Also most boutique's are usually 1 watt or less !_

 

I answered your PM about this over on DIYForums.org ...


----------



## bperboy

So, If I've got a balanced source, can I just build myself another identical millett to the one I've got and set it so the left channel goes through one and the right through the other?


----------



## tomb

Quote:


  Originally Posted by *bperboy* /img/forum/go_quote.gif 
_So, If I've got a balanced source, can I just build myself another identical millett to the one I've got and set it so the left channel goes through one and the right through the other?_

 

It may be more complicated than that, but maybe I'm misinterpreting some of this (I know I don't understand all of it!):

Balanced Millett Hybrid

 Maybe cetoole or dsavitsk can give us more insight if they see this.


----------



## n_maher

Building two amps should work fine to create a balanced amp. You'd feed one the in-phase signal and one the out-of-phase signal. I swear I've already posted that in this thread...


----------



## tomb

Quote:


  Originally Posted by *n_maher* /img/forum/go_quote.gif 
_Building two amps should work fine to create a balanced amp. You'd feed one the in-phase signal and one the out-of-phase signal. I swear I've already posted that in this thread..._

 

Yep - you did now that you mention it ... and I don't understand it any better now. 
	

	
	
		
		

		
			





 Could you elaborate on the phases of the signals? Also, there isn't any problem with bridging the outputs on the Millett?


----------



## pabbi1

Well, I am doing a balanced version, with the Opus DAC / Ballsie module, all in a single case (http://www.surplussales.com/Cab-Rack...re/encl_2.html, the Nabu, with a wood front panel), and the combo jacks, so I can go SE or balanced. The main design goal for me is an office rig that I can use with a reasonably cheap transport, and a variety of cans, and possibly 2 cans at the same time.

 Oh, and with 2 toroids (one 2x25v for the boards, and the other for the DACs), which is all about MY wiring convenience / fit.


----------



## tomb

Quote:


  Originally Posted by *pabbi1* /img/forum/go_quote.gif 
_Well, I am doing a balanced version, with the Opus DAC / Ballsie module, all in a single case (http://www.surplussales.com/Cab-Rack...re/encl_2.html, the Nabu, with a wood front panel), and the combo jacks, so I can go SE or balanced. The main design goal for me is an office rig that I can use with a reasonably cheap transport, and a variety of cans, and possibly 2 cans at the same time.

 Oh, and with 2 toroids (one 2x25v for the boards, and the other for the DACs), which is all about MY wiring convenience / fit._

 

Cool! If you can write up a "how-to" with some pics, I'll post it as an article on the MAX website. That goes for you, too, Bperboy. 
	

	
	
		
		

		
		
	


	




 I'm sure there are a lot of MAX builders (like me) who would like to know how to do this.


----------



## pabbi1

But of course... the main delay is in the Opus DAC, hopefully just a week or two out...


----------



## colonelkernel8

I got my parts today. Mmmmm, building time.


----------



## joneeboi

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Joneeboi - What's your AC voltage at the input terminal block?_

 

Interestingly enough, I'm not getting any power at all from the wallwart. Did I blow a fuse or something? Tried 3 different plugs and it doesn't seem to give any power anywhere. I checked the V+ and GND for DCV and also the terminal block for ACV and 00.0 every time. Does this mean I have to get a new one? *sigh*


----------



## MasiveMunkey

I was just wondering which caps will sound better, the Nichicon Muse ES or KZ for CA2?


----------



## amphead

Quote:


  Originally Posted by *joneeboi* /img/forum/go_quote.gif 
_Interestingly enough, I'm not getting any power at all from the wallwart. Did I blow a fuse or something? Tried 3 different plugs and it doesn't seem to give any power anywhere. I checked the V+ and GND for DCV and also the terminal block for ACV and 00.0 every time. Does this mean I have to get a new one? *sigh*_

 

If you are motivated, you could remove the plastic housing around the wallwart plug. In my case, I had to drill out the screws, holding the plastic housing together. Then test for step down voltage after the transformer. If that is bad you will need a new wallwart. If that is good, then move to points on the little pcb that are connected to the output of the transformer. You should find a bad component or even more likely an open in the wires leaving the pcb. In my case I had to splice a broken wire leaving the pcb. Good luck!


----------



## tomb

I agree with Amphead's instructions completely. Also, Joneeboi - you mentioned in a post further back that you experienced a "loud DC pop". That should not happen, so it may be that you have a short somewhere in the board. You should probably look for that before plugging in another walwart. If you can post some pics, we may be able to spot a solder bridge or something else untoward.


----------



## tomb

Quote:


  Originally Posted by *MasiveMunkey* /img/forum/go_quote.gif 
_I was just wondering which caps will sound better, the Nichicon Muse ES or KZ for CA2?_

 

Ask Dsavitsk. 
	

	
	
		
		

		
		
	


	




 I know the ES are very good and have lots of bass. I think I read where Doug once said the KZ's tended more toward a slight hardness with sharp highs, but my memory could be mistaken on that. If so, they may also be a great combo with tubes which have a natural warmth and bass tendency anyway. There are plenty of people who have used KZ's - Vixr is one that comes to mind. Also, JRossel's kits defaulted to the KZ's as well. 

 I don't know if we have anyone who has tried both for a direct comparison. Dsavitsk is probably the best one to ask about that.


----------



## soloz2

bradley is using KZ's as well (colonelkernal8)


----------



## Troyhoot

Im using 1000 kz's all around on mine. If it had more bass I would have to make adjustments to the equalizer. Im very pleased so far. I dont really have anythign else to compare it too, but I have zero complaints with kz's. My highs dont seem harsh at all, everything is clear and smooth to me. But Im running a 1.0 auricap as bypass so most of my mid/highs should be going through there.


----------



## joneeboi

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_I agree with Amphead's instructions completely. Also, Joneeboi - you mentioned in a post further back that you experienced a "loud DC pop". That should not happen, so it may be that you have a short somewhere in the board. You should probably look for that before plugging in another walwart. If you can post some pics, we may be able to spot a solder bridge or something else untoward._

 

I unsuspectingly checked the terminal block voltage using the DCV setting, but changed to ACV as soon as I realized. Could this have damaged the wallwart?


----------



## tomb

Quote:


  Originally Posted by *joneeboi* /img/forum/go_quote.gif 
_I unsuspectingly checked the terminal block voltage using the DCV setting, but changed to ACV as soon as I realized. Could this have damaged the wallwart?_

 

NO - and you would read zero DC volts if you did this.


----------



## babbkutz@comcast

I have mounting kits T0-220 from Aavid in three flavors (Mica,SG, and Thermalloy..MG SG AND G). Could you go into detail about the use of thermal paste and shoulder washers? I'm using 1" sinks on a MAX with DBs...thanks!


----------



## ruZZ.il

Quote:


  Originally Posted by *babbkutz@comcast* /img/forum/go_quote.gif 
_I have mounting kits T0-220 from Aavid in three flavors (Mica,SG, and Thermalloy..MG SG AND G). Could you go into detail about the use of thermal paste and shoulder washers? I'm using 1" sinks on a MAX with DBs...thanks!_

 

not sure bout MG/SG/G but what you're trying to do is electrically insulate the output transistors and the voltage regulator from the heat sink, while allowing thermal conduction. A very little bit of the thermal paste is optionally used on both sides of the thermally conductive insulating pad to allow better heat transfer by achieving better contact(filling in the gaps).

 The shoulder washer is to prevent the mounting screw from coming in contact with the metal tongue of the voltage regulator, since it's connected to the center pin of the regulator, which is at a different voltage than the grounded case, so you wouldn't want contact between them. The washer is unnecessary with the output transistors (that I'm familiar with) since the mounting bit of it is the transistors housing which is non conductive (when you look at it, you'll see), but you should still use a washer to spread the clamping force and prevent damage.

 Hope this helps a bit, maybe someone else will fill in about the differences in the pads though you'd probably find this in their datasheets..

 edit: looks like tomb was typing while I was posting too 
	

	
	
		
		

		
			





 (fortunately slightly diff. stuff)


----------



## tomb

Quote:


  Originally Posted by *babbkutz@comcast* /img/forum/go_quote.gif 
_I have mounting kits T0-220 from Aavid in three flavors (Mica,SG, and Thermalloy..MG SG AND G). Could you go into detail about the use of thermal paste and shoulder washers? I'm using 1" sinks on a MAX with DBs...thanks!_

 

I'm not exactly sure of the designations you're quoting. Thermalloy is just part of the Aavid name, as in Aavid Thermalloy. I'm not sure of the SG, MG, and G designations.

 In the last catalog I got from Aavid, they listed three types of transistor mounting insulators:

 1. Mica
 2. ThermaFilm
 3. ThermaSil

 The ThermaFilm is just an upgrade from Mica - better electrical insulating quality with better heat transfer. The ThermaSil are pads that are meant to be used without any grease.

 For the Mica and ThermaFilm, I apply a thin coating on the back of the transistor first with a small toothpick - sort of swab it around like spreading butter on toast. 
	

	
	
		
		

		
		
	


	




 Then line up the Mica insulator hole-to-hole with the back of the transistor and place it on the grease. Don't squish it down. You want all of this to just lay together inline. Screwing the assembly down will mash it all together. Anyway, apply some more grease to the back of the Mica insulator just as you did the transistor. In every case, the Mica insulator is bigger than the transistor. Regardless, I apply the grease to the entire surface of the Mica. It's too much trouble to do otherwise.

 Then place the assembly on the surface of the heat sink - again, lining up the holes. Insert the shoulder washer into the tab on the front side of the transistor - the large flat part should face outward from the front of the transistor. Insert the screw through the entire assembly, attach a metal washer if you have one, a lock washer, and the nut. At this point, it really doesn't matter from which direction you insert the screw - just do it in the way that makes it most convenient for removal if needed. In particular, study the two sinks in the center on the MAX, and make your decision on how to orient the screw assemblies on each - they need not be the same.

 I like to torque it down pretty good - within reason, given the small precision tools you may be using - don't use a automotive breaking bar tool or something silly like that, though. As mentioned elsewhere in this thread, the shoulder washer will not fit on many of the recommended BJT transistors. Usually ones with the metal tabs (TO-220) can use the shoulder washers. In the cases where the shoulder washer won't fit - don't use it. More than likely the transistor is self insulated from the screw anyway.

 Hope that helps ...


 EDIT: Looks like ruZZ.il was posting while I was typing.


----------



## babbkutz@comcast

that clears things up alot....hopefully we'll have another live MAX tomorrow!


----------



## soloz2

so how would the max work as a preamp? Like could you run a line from the output pads to be used as a preamp out?


----------



## tomb

Quote:


  Originally Posted by *soloz2* /img/forum/go_quote.gif 
_so how would the max work as a preamp? Like could you run a line from the output pads to be used as a preamp out?_

 

Yes, I believe so. Since the MAX has the relay delay circuit, it should perform splendidly as a preamp.


----------



## soloz2

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Yes, I believe so. Since the MAX has the relay delay circuit, it should perform splendidly as a preamp._

 

thanks! that's what I thought, but I wanted to make sure 
	

	
	
		
		

		
		
	


	




 I'll be adding that feature to mine.

 I also started pricing up custom engraved endpanels 
	

	
	
		
		

		
		
	


	




 btw, has anyone made a front panel express file for the max?


----------



## bperboy

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Yes, I believe so. Since the MAX has the relay delay circuit, it should perform splendidly as a preamp._

 

I wonder.. I was asking in another thread if my Mini3 would be useful to get the passive pickup on my violin to a line level for my computer. Would the Max serve the same purpose?


----------



## scooot

*She lives!:*

 Front




 [size=small](Wood front panels made by forum user naamanf, they look gorgeous btw)[/size]

 Back






 Guts






 And to think, all it took was a whole pile of money, some burned fingers and a bit of cursing and swearing.


----------



## tomb

Looks great! I was hoping someone took advantage of Naamanf's deal over on DIYForums - those wood end panels look very nice.


----------



## odoe

Excuse my cap noobness, but what kind of film caps are those?


----------



## tomb

Quote:


  Originally Posted by *odoe* /img/forum/go_quote.gif 
_Excuse my cap noobness, but what kind of film caps are those?_

 

Interesting -
http://www.seas.co.uk/acatalog/SAX_Capacitors.html


----------



## vixr

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Interesting -
http://http://www.seas.co.uk/acatalo...apacitors.html_

 

tomb... bad gateway error message on the link...double http


----------



## tomb

Quote:


  Originally Posted by *vixr* /img/forum/go_quote.gif 
_tomb... bad gateway error message on the link...double http_

 

Oops - I keep copying links and forget Head-Fi already prefixes with "http://". It's fixed.


----------



## ruZZ.il

woohoo lsdiodes arrived!
	

	
	
		
		

		
			





 I can continue with the sockets now, and everything taller. rsisrael has my forgotten heat sinks that I'll pick up tomorrow and all being well, another one will live 
	

	
	
		
		

		
		
	


	




 nice build scoot, but I'm wondering what led you to load CA3 with those caps?


----------



## Ferrari

Quote:


  Originally Posted by *scooot* /img/forum/go_quote.gif 
_*She lives!:*

 Guts



_

 

Hee... I'm not the only one who uses huge MKP's on the MH Max


----------



## scooot

Quote:


  Originally Posted by *ruZZ.il* /img/forum/go_quote.gif 
_nice build scoot, but I'm wondering what led you to load CA3 with those caps?_

 

Well I had planned to use those Soniqs on all film cap places just for the heck of it but ran out of space at CA8, those sinks get fairly toasty and I didnt want to shove a film cap right up next to one.

 As for the Soniqs, they can be picked up off eBay cheap as


----------



## babbkutz@comcast

Why would some MAXs need the grounding wire from the pot when others don't? (Yeah I've got a live one here (DB) but touching the pot at full volume (12AE6A tubes) produces ground hum......no touch no hum......wire seems to solve the problem)......all my setup measurements came off without a hitch 27V/13.5V/70mV


----------



## Ferrari

Quote:


  Originally Posted by *babbkutz@comcast* /img/forum/go_quote.gif 
_Why would some MAXs need the grounding wire from the pot when others don't? (Yeah I've got a live one here (DB) but touching the pot at full volume (12AE6A tubes) produces ground hum......no touch no hum......wire seems to solve the problem)......all my setup measurements came off without a hitch 27V/13.5V/70mV_

 

If the Alps pot is mounted on a metal face plate (assuming the face plate is conductive), the Alps pot is already connected to GND via the face plate... thus grounding wire is superfluous. But if the Alps pot is mounted on a non-metal face plate (wooden, plastics...) or an uncased amp, then a grounding wire is necessary to connect the Alps pot to GND.


----------



## amphead

Quote:


 Scooot:
 She lives! 
 

Thats one swanky case! How do you like your sound with the big film caps?


----------



## amphead

Quote:


 ruZZ.il:
 woohoo lsdiodes arrived! I can continue with the sockets now, and everything taller. rsisrael has my forgotten heat sinks that I'll pick up tomorrow and all being well, another one will live 
 

Congrats! Looks like you beat me by one week.


----------



## tomb

Quote:


  Originally Posted by *Ferrari* /img/forum/go_quote.gif 
_If the Alps pot is mounted on a metal face plate (assuming the face plate is conductive), the Alps pot is already connected to GND via the face plate... thus grounding wire is superfluous. But if the Alps pot is mounted on a non-metal face plate (wooden, plastics...) or an uncased amp, then a grounding wire is necessary to connect the Alps pot to GND. 
	

	
	
		
		

		
		
	


	


_

 

Ferrari is correct.

 Also, the recommended Hammond case is insulated by the anodizing. Unless the pot shaft makes contact with the edges of the drilled hole, the grounding wire is needed.


----------



## odoe

I think I expected these orange drops to be smaller. Deceiving name.





 I'm guessing I'm going to leave these until last to install creatively, heh


----------



## tomb

Quote:


  Originally Posted by *odoe* /img/forum/go_quote.gif 
_I think I expected these orange drops to be smaller. Deceiving name.

 I'm guessing I'm going to leave these until last to install creatively, heh_

 

A few of us got some Vitamin Q's that are a little worse than that. That said, they look pretty flat. If you're doing a BJT version, you may have room to mount them under the board.


----------



## ruZZ.il

Quote:


  Originally Posted by *amphead* /img/forum/go_quote.gif 
_Congrats! Looks like you beat me by one week. _

 

Not so quickly 
	

	
	
		
		

		
		
	


	




 I hadnt been around most of the day, but I got around to 'finishing it up' 
	

	
	
		
		

		
		
	


	




 The PS works and is set to 22v in the meantime, LED's... bright 
	

	
	
		
		

		
		
	


	




 but I'm having issues biasing the tube voltages, and the right channel DB current. QB8/9R bias at a minimum of around 170ma and respond to the trimpot going upwards. With a tube in, this just shoots to around 1A
	

	
	
		
		

		
		
	


	




 , and gets too hot(unplug). I've made sure I got the right value components(visually) in their places, and the transistors read sane values when I check the 2 forward bias (diode check) values too (the left seem to bias as expected). I think it may be cause I had all my trimpots completely loosened(anti clockwise) when I powered up, instead of 'trimmed down'(clockwise, it seems) for about 20~30s till I got to that check. The tube voltages both seems to be at at about 18.5v, and don't respond to trimming(throughout the whole range) 
	

	
	
		
		

		
		
	


	




 so I'll troubleshoot some more tomorrow, with more detail/pics to see if anyone can pick anything up too. I have a feeling I'll be waiting for some transistors now 
	

	
	
		
		

		
		
	


	




 off to zzz though and thanks to anyone who has anything to say in the meantime 
	

	
	
		
		

		
		
	


	



 Also, are these sonicap genIIs polarized
	

	
	
		
		

		
		
	


	




? 
 -ruZZ


----------



## c0nsumer

Quote:


  Originally Posted by *odoe* /img/forum/go_quote.gif 
_I think I expected these orange drops to be smaller. Deceiving name.

 I'm guessing I'm going to leave these until last to install creatively, heh_

 

Don't forget the possibility of mounting them vertically. The leads look long enough that you may be able to upend them. I've done this before with smaller parts and had no problems.


----------



## Blooze

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_A few of us got some Vitamin Q's that are a little worse than that. That said, they look pretty flat. If you're doing a BJT version, you may have room to mount them under the board._

 


 Those are pretty decent sized, aren't they? I've got some sitting in wait for my Darling amp. I've heard a few tube amps with them and they do sound nice. The Russian PIO are nice as well.

 I think someone should use some motor run caps in the PS. Now some of those are HUGE. Come to think of it I've got some...hmmmm


----------



## scooot

Quote:


  Originally Posted by *amphead* /img/forum/go_quote.gif 
_Thats one swanky case! How do you like your sound with the big film caps?_

 

Cheers! All I had to do was drill holes, naamanf did the rest.

 Caps sound awesome, an absolute pain to install but I think it was worth it


----------



## amphead

Since I have the recommended hammond case, I will take some sandpaper and carefully remove the black anodized film where the Alps pot makes contact with the faceplate. I don't know though, maybe I will be better off with a wire connected to the case.


----------



## Superpong

Hello do we (or did we) have a group buy of this PCB? It looks really interesting.


----------



## amphead

Welcome Superpong! You are about 6 weeks too late, but boards may become available. You will have to check with TomB. Sorry for your wallet.


----------



## tomb

Quote:


  Originally Posted by *ruZZ.il* /img/forum/go_quote.gif 
_Also, are these sonicap genIIs polarized
	

	
	
		
		

		
			





? 
 -ruZZ_

 

No.

  Quote:


  Originally Posted by *amphead* 
_Since I have the recommended hammond case, I will take some sandpaper and carefully remove the black anodized film where the Alps pot makes contact with the faceplate. I don't know though, maybe I will be better off with a wire connected to the case. _

 

The pad is there next to the pot for the ground wire. There should be no need to purposefully ground the case. In fact, the case/ground is isolated from the power supply (AC). We only made reference to the case in case of happenstance. It is only important that the pot is grounded to the signal ground (DC negative) on the board. That's the purpose of the pad.

 Solder a wire to the pad and tie the end of the lead to the screw on the Alps pot. The Alps pot screws go all the way the length of the pot and are visible on the front of the pot. So, when you unscrew them, there's gracious plenty room to wrap the wire around and screw it all back in.

  Quote:


  Originally Posted by *superpong* 
_Hello do we (or did we) have a group buy of this PCB? It looks really interesting_

 

Yes - one of the biggest Group Buys (biggest?) ever made for a DIY headphone amp. Check the stats in my signature below.

  Quote:


  Originally Posted by *amphead* 
_Welcome Superpong! You are about 6 weeks too late, but boards may become available. You will have to check with TomB. Sorry for your wallet. _

 

Actually, it's still Cetoole (Colin) that has the boards. He is still too busy to answer my e-mails, either - so don't send him any. He always gets back to us when he can.

 It's a fact that he has ~50 extra boards. He may still be working with some people who've been shorted or had shipping errors. He can't hang on to that many boards, so he will sell them at some point. Also, we have talked many times about having another Group Buy around Christmas, perhaps. So, please stay tuned ...


----------



## adfinni

My 2 boards are framed and hanging on the wall


----------



## Steve Cat

Didn"t read this thread< and know little about electronics< but have had my share of tube guitar amps< and the voltages stored here can kill< be careful>


----------



## tomb

Quote:


  Originally Posted by *Steve Cat* /img/forum/go_quote.gif 
_Didn"t read this thread< and know little about electronics< but have had my share of tube guitar amps< and the voltages stored here can kill< be careful>_

 

Nope - That's what makes the Millett so great: 24-27VDC max.


----------



## FallenAngel

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_A few of us got some Vitamin Q's that are a little worse than that. That said, they look pretty flat. If you're doing a BJT version, you may have room to mount them under the board._

 

You don't say. 
	

	
	
		
		

		
		
	


	




 Just wait until I post pics of my board, it definitely looks interesting.


----------



## babbkutz@comcast

I just got my K701s plugged into the MAX............THANKS EVERYONE!


----------



## tomb

Quote:


  Originally Posted by *babbkutz@comcast* /img/forum/go_quote.gif 
_I just got my K701s plugged into the MAX............THANKS EVERYONE!
	

	
	
		
		

		
		
	


	


_

 

Hey! This is news, I hope. Several of us can confirm the MAX does great with the HD580 and HD600. May we now state that the K701's sound great with the MAX??


----------



## babbkutz@comcast

into k701s and my initial impression is WOW! (it's still not cased) Yeah they definitely work!


----------



## daggerlee

I went away for a few months on vacation and wow this thread has gotten large. I assume there have been a few more people who have built both MOSFETs and DBs, can any of them weigh in on the comparison?


----------



## babbkutz@comcast

the range is large.......what do you guys suggest? I'm running 12AE6As at 13.5 right now.......71mV bias.......


----------



## ruZZ.il

Alright, maybe someone can help me out..
 the entire left channel seems to be behaving, the tube voltage sets, and the bias is within range. The right channel, not quiet. With a tube inserted, the tube bias range is from 16~19.8v (Main voltage set to 22v), while the DB bias starts at around 180mV, and climbs to about 1.3V, before I promptly disconnect it all. I have a feeling the output transistors may be damaged since the trimpots were 'maxed' in the wrong way for a bit when I first powered up.. I found a local place with the least recommended BD139/140s that I'll pick up tomorrow and see how that works for now... meanwhile, maybe someone can spot something else?
 Thanks.
 -Russ.

Top-Large, Bottom-Large.











 Thanks guys..

 (the 3 wire braid is temporary, and the fuse blew so I bypassed 
	

	
	
		
		

		
		
	


	




)


----------



## tomb

I don't see anything from the pics, ruZZ.il. It's immaculate work, by the way - outstanding. 
	

	
	
		
		

		
		
	


	




 It's possible the JFET gave out before any of the output transistors. 1/2 of the total current passes through that one tiny transistor. It's the weak spot in the DB, not the output transistors.

 What are you biasing the left side at? 50ma is a proven current. Colin has stated 100ma shouldn't be a problem, but I'm not sure he's considered the consequences to that little JFET. (That's the PN4392 transistor - one per channel.)

 EDIT: This guess is questionable. I'm not so sure of my facts and the voltage that JFET sees. It was an issue in the 1st prototype. So, we turned the current mirror into a current multiplier. That lowers the current seen by the JFET.


----------



## tomb

Also, even if 100ma is attainable, it's not with 1" high heat sinks. 50ma (110mV) bias is just about maximum, IMHO. The output transistors are hot enough at that size heat sink and current.

 What you describe at 180mV is thermal runaway. The BJT's are positive temperature coefficient devices, so as temperature climbs, so will their current, ala voltage. So, they are burning up toward the 1.3V.

 My first guess may be all wet.


----------



## ruZZ.il

I checked QB1L vs QB1R (with the diode check on my DMM, for forward bias voltage), and they measure up pretty much the same, but then so did qb8/9. I'll see if I can pick up one/two of those anyway. I haven't set my left DB bias yet, just to minimum till the right is sorted out too, but it starts at 22mv and biases up seemingly alright, so I'll leave it at that for now. I'll go over all my resistors and stuff again too.. anyway, just for fun heres a pic from my Adobe x-ray cam 
	

	
	
		
		

		
		
	


	



 Thanks.. and if you think of anything else I should ckeck let me know. (will be back home later, and am bound to be the night owl that I am...)






 edit: also, any idea why one side tube bias wouldn't set right?.. would something in the DB section effect this?


----------



## tomb

Quote:


  Originally Posted by *ruZZ.il* /img/forum/go_quote.gif 
_edit: also, any idea why one side tube bias wouldn't set right?.. would something in the DB section effect this?_

 

There's a few volts that drop on the way to the CCS and tube. The voltage difference you cite of 22 to 19.8 just sounds like it's not biased, period (can't speak for your range down to 16 - that sounds like it's "caught" and is starting to bias) ... and no, nothing in the DB section would affect this.


----------



## ruZZ.il

hm. my next option is to start switching components between L and R and see if I can follow the problem.. fun fun 
	

	
	
		
		

		
		
	


	







 any risk at powering up with a missing QB1/8/9 ?


----------



## [AK]Zip

What do you guys think about VitamineQ caps for CA3 and CA6 as well?


----------



## tomb

Quote:


  Originally Posted by *ruZZ.il* /img/forum/go_quote.gif 
_hm. my next option is to start switching components between L and R and see if I can follow the problem.. fun fun 
	

	
	
		
		

		
		
	


	







 any risk at powering up with a missing QB1/8/9 ?_

 

ruZZ.il, let's try a more cautious approach if you're up to it. To be honest, I'm going to be worthless helping anyone troubleshoot separate transistors. You are almost better off to just replace the whole bank of 2n5087's and 2n5088's (it's what I'd do and have done), but before you do that:

 - Shoot for a bias of about 20-30ma to start. Despite what Colin suggested, no one that I'm aware of has tested the BJT's at higher than 50ma bias - and they're positively great at that point, anyway.

 - You might go over all your resistors - make sure they didn't get switched.

 - Turn the Left channel down to about 20-30ma. Then turn it off and measure the pins of the Left DB trimmer (ohms). Then try to adjust the Right DB trimmer for the same values. Turn the power back on and try it that way.


----------



## tomb

Quote:


  Originally Posted by *[AK]Zip* /img/forum/go_quote.gif 
_What do you guys think about VitamineQ caps for CA3 and CA6 as well?_

 

Probably a waste - they're not in the signal path. Ferrari uses them or something similar, I think - maybe Russian teflons - but his extreme builds are not something to recommend for everyone. He'd probably say that, too.


----------



## ruZZ.il

tom, I did that already 
	

	
	
		
		

		
		
	


	




 (the trimmer thing) I've also checked my resistor values, and compared the resistance checks of each side. I've also switched QB1 between sides, and the problem stayed on the right. I'm in the process of switching QB8/9, will see if it follows.. otherwise I suppose I'll replace the rest of the transistors (good thing I got hundreds of those..)


----------



## [AK]Zip

Here is where I am so far.











 I am just waiting on some better parts for QB8 and QB9 and some tube sockets. Volume controller will be a stepped attenuator. I really am thinking about changing out the Wima caps for the VitamineQ's for fun.
	

	
	
		
		

		
		
	


	




 Also, thinking about installing the R1 instead of the jumper..

 -Alex-


----------



## Ferrari

Yes indeed! For these positions you can best stick on the recommended MKP's as specified in the BOM (Wima, Ero MKP).
 If you consider VitamineQ caps... you can best put them on C8-9 L/R, where the audio signal has the most benefit from them.

 I put Russian PIO on C3 and C6 just because I have got the whole box of these caps for my birth day.
 (A good friend knew that I'm a DIY junky 
	

	
	
		
		

		
		
	


	




 ). For C8 I use Russian teflon and for C9 polystyrene (the yellow caps I used in my first Millett).

 Ah... you posted when I'm writing this. I see that you already put VitamineQ on C8-9 L/R, very wise !


----------



## ruZZ.il

My problem followed QB8 from the right to the left, including the tube bias voltage. bugger. thanks again for the suggestions.. and I guess now we know a problematic QB8 can effect tube bias too  now, anyone got a few spare output transistors to send me? 
	

	
	
		
		

		
		
	


	




 I'll pick up a few of the fairchild ones in the meantime.. but ordering from BDent is a problem for me ;/ on that note, if anyone is about to make an order and wouldnt mind adding a few in for me, and shipping them snail mail, I'll paypal you for it. 
	

	
	
		
		

		
		
	


	




 thanks..


----------



## tomb

ruZZ.il,
 YGPM.


----------



## babbkutz@comcast

I'm using dayton RCA jacks from Parts Xpress....they have dual teflon washers (front and back) with a ground ring. I'm thinking washer/panel/washer/ground ring/nut......is this correct? or should the ring touch the case panel?


----------



## ruZZ.il

Thanks, Tom. I'll get back to you on that shortly 
	

	
	
		
		

		
			




 I actually don't mind to have gone through a bit of trouble. Ultimately, I feel a little more acquainted with my new little buddy now(assuming it was that). I think what you stated about keeping the dmm on the DB's while initially firing up is good. 
	

	
	
		
		

		
		
	


	




 2 dmm's are better 
	

	
	
		
		

		
		
	


	




 I think I'll take notes sometime as to what the resistance readings should be between certain points while everything is trimmed to minimum, which could be helpful to know beforehand and avoid confusion with the trimmers. I've got to say, the support here is very comforting. thanks again 
	

	
	
		
		

		
		
	


	



 -ruZZ


----------



## tomb

Quote:


  Originally Posted by *babbkutz@comcast* /img/forum/go_quote.gif 
_I'm using dayton RCA jacks from Parts Xpress....they have dual teflon washers (front and back) with a ground ring. I'm thinking washer/panel/washer/groung ring/nut......is this correct? or should the ring touch the case panel?_

 

The washers aren't needed. It's fine to screw them down directly to the case. The ground ring should be on the inside, of course. The only thing that must be isolated on the case is the power jack, because that's accepting AC.


----------



## tomb

Quote:


  Originally Posted by *ruZZ.il* /img/forum/go_quote.gif 
_Thanks, Tom. I'll get back to you on that shortly 
	

	
	
		
		

		
		
	


	



 I actually don't mind to have gone through a bit of trouble. Ultimately, I feel a little more acquainted with my new little buddy now(assuming it was that). I think what you stated about keeping the dmm on the DB's while initially firing up is good. 
	

	
	
		
		

		
		
	


	




 2 dmm's are better 
	

	
	
		
		

		
		
	


	




 I think I'll take notes sometime as to what the resistance readings should be between certain points while everything is trimmed to minimum, which could be helpful to know beforehand and avoid confusion with the trimmers. I've got to say, the support here is very comforting. thanks again 
	

	
	
		
		

		
		
	


	



 -ruZZ_

 

You bet!

 Just for the benefit of everyone else, here's a paraphrase of the suggestion I gave ruZZ.il earlier:

One thing you can try that's worked for me is to have the probes on your DMM sitting in the test points for one of the DB's - you can see the voltage and flip the amp on and off until you're certain which way the adjustment is going, then turn it off and do it for the other side. It takes a finite number of seconds (or more) to fry the transistors unless they're installed with a dead short - plenty of time to figure out which way things are heading.

 In any event, you can leave the tubes on all day without biasing them properly - it's not going to hurt them. So, forget about the tubes until you get the DB's behaving.

 I'm sorry if I can't remember all these things at once, but some of you may find this method useful. As ruZZ.il implies, you could buy another one of those $2.99 DMM's and have them both connected. 
	

	
	
		
		

		
		
	


	





 P.S. Nice looking build so far, [AK]Zip! We'll be interested in seeing how your stepped attenuator works on the MAX.


----------



## amphead

ruZZ.il :

 You installed RA1R backwards!
 Hope that helps.


----------



## tomb

Quote:


  Originally Posted by *amphead* /img/forum/go_quote.gif 
_ruZZ.il :

 You installed RA1R backwards!
 Hope that helps.
	

	
	
		
		

		
		
	


	


_

 

Good point! The tube trimmers must be mirror-imaged relative to one another, or you will be adjusting the bias in opposite directions from one tube to the other.

 The DB trimmers are both oriented in the same direction on the board and turn in the same direction to adjust bias.


----------



## ruZZ.il

hehe yeah, I noticed that.. good thing the tube bias isnt so critical at first.. its a pity I hadnt made that mistake with my right DB trimmer, then I'd have started all sane 
	

	
	
		
		

		
		
	


	




 seems like I've located my problem though, and it should all get straightened out soon 
	

	
	
		
		

		
		
	


	




 I'll probably turn that around anyway though to keep a decent symmetry for the trimmer holes on the case top.
 AK, those vit Q's look (I'm scared to say this about an amp...hhe) kinda sexy in there


----------



## MrMajestic2

Ok, Im back again 
	

	
	
		
		

		
		
	


	




 The tubes are now stable in their voltage, but the distortion problem is still there. One question I have though is that when adjusting the tube bias, should the volume pot be turned up or down, because that affects the voltage. If I have 13.5v with the pot turned down, I will have between 16.5 and 17.5V when turned up, depending on which channel I measure. Oh, and I also still have the DC offset spiking big time at startup.


----------



## tomb

Quote:


  Originally Posted by *MrMajestic2* /img/forum/go_quote.gif 
_Ok, Im back again 
	

	
	
		
		

		
		
	


	




 The tubes are now stable in their voltage, but the distortion problem is still there. One question I have though is that when adjusting the tube bias, should the volume pot be turned up or down, because that affects the voltage. If I have 13.5v with the pot turned down, I will have between 16.5 and 17.5V when turned up, depending on which channel I measure. Oh, and I also still have the DC offset spiking big time at startup._

 

The volume should be down/off. I can't recall anyone ever measuring what happens to tube bias when the volume is turned up. That's risky business anyway - you'd have to have probes connected and be sticking a screwdriver or trimmer tool into the board while the amp is actively amplifiying (volume turned up) - not a good practice, IMHO.


----------



## MrMajestic2

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_The volume should be down/off. I can't recall anyone ever measuring what happens to tube bias when the volume is turned up. That's risky business anyway - you'd have to have probes connected and be sticking a screwdriver or trimmer tool into the board while the amp is actively amplifiying (volume turned up) - not a good practice, IMHO._

 

I have been measuring it with the pot turned down. I just forgot to turn it down once, and realizing it made quite a difference in the readout. So the mystery of my distortion still persists. Im going to try swapping tubes from 12AE6 to 12FK6 to see if that changes anything.


----------



## MrMajestic2

I tried putting in some 12FK6 tubes and the distortion went away. My guess is either the tubes 12AE6 tubes are damaged or the gain is too much for my headphones.


----------



## tomb

Quote:


  Originally Posted by *MrMajestic2* /img/forum/go_quote.gif 
_I tried putting in some 12FK6 tubes and the distortion went away. My guess is either the tubes 12AE6 tubes are damaged or the gain is too much for my headphones._

 

Could be they just aren't broken in. NOS tubes collect a lot of gas molecule infiltration from sitting on the shelf unused for 30-40 years(!). It may take 2 or 3 days of solid running for the getter to burn out all the gas and let the tube sound as it should. Even a new tube may take a few days of running - it just depends.


----------



## MrMajestic2

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Could be they just aren't broken in. NOS tubes collect a lot of gas molecule infiltration from sitting on the shelf unused for 30-40 years(!). It may take 2 or 3 days of solid running for the getter to burn out all the gas and let the tube sound as it should. Even a new tube may take a few days of running - it just depends._

 

Yeah, I was thining that they are not broken in as well, so I will keep em running for a while longer. But with the 12FK6 it sounded amazing straight out of the box, not broken in at all. Im finally beginning to hear the potential of this little amp. Will start building my second one this weekend, probably with VitaminQs


----------



## Ferrari

A little note regarding the setting of the buffer trimpots RB12L/R at first power up.
*(Assuming the trimpots are mounted the same way as showed on the circuit board silkscreen).*

 To avoid toasted transistors in the output buffer section of your Max build at first power up, the buffer trimpots RB12L/R should be set to full clockwise.
 At full clockwise, the current flows through the power resistor RB10-11 L/R is minimum, thus lowest output buffer bias.
 From this starting point, you can set the output buffer bias to a higher, desired level by using a DMM while carefully turning the trimpots RB12L/R counter-clockwise, first the left channel then the right channel (or vice versa). Hope that this will help a bit.

 The MOSFET’s and BJT’s (2SC2238/2SA968) output buffers of my 2 Max build are biased this way.


----------



## bperboy

What does everyone else with the MOSFET edition have their bias at? I've got the 1.5" sinks and am running at ~250mV, or ~113mA.


----------



## tomb

Quote:


  Originally Posted by *Ferrari* /img/forum/go_quote.gif 
_A little note regarding the setting of the buffer trimpots RB12L/R at first power up.
*(Assuming the trimpots are mounted the same way as showed on the circuit board silkscreen).*

 To avoid toasted transistors in the output buffer section of your Max build at first power up, the buffer trimpots RB12L/R should be set to full clockwise.
 At full clockwise, the current flows through the power resistor RB10-11 L/R is minimum, thus lowest output buffer bias.
 From this starting point, you can set the output buffer bias to a higher, desired level by using a DMM while carefully turning the trimpots RB12L/R counter-clockwise, first the left channel then the right channel (or vice versa). Hope that this will help a bit.

 The MOSFET’s and BJT’s (2SC2238/2SA968) output buffers of my 2 Max build are biased this way._

 

Thanks, Ferrari.
 I'm sure that will help a lot. 
	

	
	
		
		

		
		
	


	




 EDIT: Matter of fact, with your permission, I'll post it on the website when I get a chance.


----------



## odoe

I'm glad you said that, because I just assumed it would go counter-clockwise. Thanks.


----------



## Troyhoot

Quote:


  Originally Posted by *bperboy* /img/forum/go_quote.gif 
_What does everyone else with the MOSFET edition have their bias at? I've got the 1.5" sinks and am running at ~250mV, or ~113mA._

 

2" sinks. Mosfets running at 300mv, 136ma. Runs around 145-150 degrees fahrenheit with a probe in between the 2 center sinks.


----------



## thunder

Not to change the subject, But can a 25v cap work in the CA7 position w/o causing a problem?


----------



## amphead

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Thanks, Ferrari.
 I'm sure that will help a lot. 
	

	
	
		
		

		
			





 EDIT: Matter of fact, with your permission, I'll post it on the website when I get a chance._

 

That will help alot, because its counter-intuitive for many builders who haven't biased an amp.


----------



## ericj

Quote:


  Originally Posted by *thunder* /img/forum/go_quote.gif 
_Not to change the subject, But can a 25v cap work in the CA7 position w/o causing a problem?_

 

Mostly. 

 Usually it's a good idea to run a 35v cap in a 24v system. But there are other factors at play here. 

 When the amp is behaving normally - tubes installed and biased down properly - the DC they are exposed to will be the DC you have biased the tubes to - usually 1/2 of the full power supply voltage. 

 At power up, for the second or two before the tubes get warm, they will see the full power supply voltage. 

 If you run your millett max at 24 or 25 volts, you will never exceed the rated working voltage of the capacitor, and it will spend the majority of it's working life at 12 or 13 volts DC. And this, generally speaking, will be A-OK. 

 If you run higher than that, you're hedging your bets that the capacitor can handle momentary surges above it's WVDC rating. Usually a surge rating 20% higher than WVDC is documented, but many manufacturers don't publish a surge rating for most of their capacitors. 

 And as the audiophile quality of capacitors go up, the datasheet says less and less. The Black Gates don't even have a traditional datasheet. 

 So, IMHO, even when running the millett max at a B+ of 30vdc, worst case scenario you are only slightly limiting the lifespan of the capacitor. 

 If we're talking about $3 worth of Silmic II's or Nichicon Muze's, that's probably not an issue for anybody. The 25v Silmic II's in my current RevMH board (which runs at about 27v) have been there for a year in semi-regular use and show no signs of wear.

 If your capacitors cost $12/ea, well, you have a right to worry about them i guess.

 Edit: And if you're really concerned, parallel the capacitor with a 25v varistor.


----------



## tomb

Quote:


  Originally Posted by *thunder* /img/forum/go_quote.gif 
_Not to change the subject, But can a 25v cap work in the CA7 position w/o causing a problem?_

 

If you run 24V, maybe.

 The issue is that CA7 sees exactly the bias voltage of one tube in a properly operating amp. The trouble is that on startup, both CA7 caps see the full voltage of the power supply. Only when the tube heaters kick in and the tubes start to conduct does this voltage drop. This may also happen if one of the tubes burn out, or you get a loose connection on the sockets, etc., etc.

 We talked about this awhile back, but if anything at all causes that voltage to go above 25V, your cap may be damaged or worse - toasted. If you're running anything greater than 24VDC in the power supply, then I'd say it's out of the question.

 EDIT: I guess Eric and I were posting at the same time. Pick your opinion - he and I aren't that far off from each other.


----------



## amphead

Tom, what would it sound like to plug in a headphone into each of those output connections at the same time?


----------



## tomb

Quote:


  Originally Posted by *amphead* /img/forum/go_quote.gif 
_Tom, what would it sound like to plug in a headphone into each of those output connections at the same time?_

 

Bad, unless the headphones were the same - then it might be OK. If different, you get some intermediate impedance that doesn't suit either the headphones or the amp.

 Besides, the Neutrik jack switches out the little one if something's plugged into it.


----------



## amphead

Quote:


 TomB:
 Besides, the Neutrik jack switches out the little one if something's plugged into it. 
 

Good point! Not a good way to A/B phones.


----------



## thunder

Tom & Ericj Thank's for the quick reply and as usual very good advice! Getting ready for my final part's order, just wanted to double check all option's. Everyone's build pic's look really great, hope to get thing's together soon!


----------



## ruZZ.il

Its really great to see all these amps being created, and all the details of each thing discussed. Thanks, this time to everyone!

 hm.. and I just got back from a Jethro Tull concert.. wow!


----------



## Ferrari

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_... Matter of fact, with your permission, I'll post it on the website when I get a chance._

 

Sure, feel free to post it on the website.


----------



## tomb

Quote:


  Originally Posted by *Ferrari* /img/forum/go_quote.gif 
_Sure, feel free to post it on the website._

 

Thanks. I already took the liberty -
Setup and Biasing


----------



## amphead

Waiting on (4) 220 ohm resistors and (4) 10 ohm resistors, for RB6 L/R , RB7 L/R, RB2 L/R and RB3 L/R. Could have powered up today, but parts are still 1200 miles away.  I found a 30VAC /1000ma walwart. Is that too much?


----------



## daggerlee

Can anybody comment on using the MAX as a preamp to run two sets of outputs. One set to my T-amp (which will act as a power amp) and one set to my powered sub (as a line level input). Do I have to match impedances or something like that, and what would that entail exactly? Thanks


----------



## ruZZ.il

SHE IS ALIIIIIIIVE!! 
	

	
	
		
		

		
			


























 I put in some temporary BDs on the one channel, solved the prob. MJE's in the other.. not sure I care for the imbalance for a little while unless it gets to me. (cant notice it now, it sounds.. mmm.. umm... oooh.. mmmmmmm.. damn ephin good!) till I get more attuned. a middle solder pad from one of those transistors got a little messed.. so I'll actually try keep switching to a minimum.. or something.. for now.. either way, rock on! 

 Thanks everyone for the support.. and I hope I can be of some to anyone who needs sometime too... meanwhile, I'm enjoying some Tull..


----------



## tomb

Quote:


  Originally Posted by *amphead* /img/forum/go_quote.gif 
_Waiting on (4) 220 ohm resistors and (4) 10 ohm resistors, for RB6 L/R , RB7 L/R, RB2 L/R and RB3 L/R. Could have powered up today, but parts are still 1200 miles away.  I found a 30VAC /1000ma walwart. Is that too much?_

 

Expect to dissipate a whole lot of heat in the PS heat sink. 30VDC is max for the MAX, and only with the use of R1, the heater resistor. See the MAX website for Tweaks -> Heater Resistor for details. You will cook the tubes at 30VDC without the resistor.

 Voltage Estimate, minimum = ((30 x .9) x 1.414) - 1.4 = 36.8VDC. So, you'll need to burn off about 7VDC x whatever current your MAX is pulling. With BJT's at 50ma, that's a little over 3W, with MOSFETs, that's about 4.5W minimum. You may need a taller heat sink.


----------



## babbkutz@comcast

if you're using the templates for the rear panel on the MAX web site be aware that the use of the fuse requires you move the power entry position (I found out the hard way!)


----------



## tomb

Quote:


  Originally Posted by *babbkutz@comcast* /img/forum/go_quote.gif 
_if you're using the templates for the rear panel on the MAX web site be aware that the use of the fuse requires yow move the power entry position (I found out the hard way!)_

 

Figures ... I'd like to blow away that fuse forever.


----------



## babbkutz@comcast

I checked with Mouser....no luck......anyone have a source? (clear.plain al)


----------



## kklee

Try e-sonic, I've ordered end panels for other Hammond cases from them before.


----------



## amphead

Quote:


 TomB:
 Expect to dissipate a whole lot of heat in the PS heat sink. 
 

Thats really the opposite of where I want to be, so 24V PS it is!


----------



## amphead

Quote:


  Originally Posted by *ruZZ.il* /img/forum/go_quote.gif 
_SHE IS ALIIIIIIIVE!! 
	

	
	
		
		

		
		
	


	

























 I put in some temporary BDs on the one channel, solved the prob. MJE's in the other.. not sure I care for the imbalance for a little while unless it gets to me. (cant notice it now, it sounds.. mmm.. umm... oooh.. mmmmmmm.. damn ephin good!) till I get more attuned. a middle solder pad from one of those transistors got a little messed.. so I'll actually try keep switching to a minimum.. or something.. for now.. either way, rock on! 

 Thanks everyone for the support.. and I hope I can be of some to anyone who needs sometime too... meanwhile, I'm enjoying some Tull.._

 

Congrats again! Looking forward to listening to some Tull myself!


----------



## Bigguy

Somebody (scooot) posted a pic showing a fuse mounted in the back panel for outside access like most consumer electronics. That would solve the problem and make another hole to drill.


----------



## joneeboi

Quote:


  Originally Posted by *amphead* /img/forum/go_quote.gif 
_If you are motivated, you could remove the plastic housing around the wallwart plug. In my case, I had to drill out the screws, holding the plastic housing together. Then test for step down voltage after the transformer. If that is bad you will need a new wallwart. If that is good, then move to points on the little pcb that are connected to the output of the transformer. You should find a bad component or even more likely an open in the wires leaving the pcb. In my case I had to splice a broken wire leaving the pcb. Good luck!
	

	
	
		
		

		
		
	


	


_

 

Haven't set aside time to really get down to troubleshooting this mother but now that I'm thinking about it a little bit, how in the heck do I reversibly open the wallwart? Surely I can take a hacksaw to it but I still want to use it. Assuming the problem is the wallwart, I've already ordered another one *crosses fingers* but I'd still like to see what's wrong with this one. I always assumed they melted the plastic parts together all around so you couldn't open it and unleash the Pandora's box that lies inside. But perhaps that's what true DIY trailblazing is: discovering that the Pandora's box is a mere treasure chest that someday one will turn into a beautiful case for an amp project. Now, how do I open it? Can it be opened?


----------



## ericj

Quote:


  Originally Posted by *joneeboi* /img/forum/go_quote.gif 
_Haven't set aside time to really get down to troubleshooting this mother but now that I'm thinking about it a little bit, how in the heck do I reversibly open the wallwart?_

 


 Sometimes they're glued, sometimes they're solvent welded, sometimes they're ultrasonically welded. 

 I've cracked open WAY too many of them myself. 

 First, come to terms with the fact that it's going to get a little messed up. But you'll be able to seal it again. 

 I usually start by putting it in a vise, with the edge of the jaw about a quarter inch from the seam, and i gently squeeze. Generally, unless I'm squeezing on the wrong side, i'll hear a crack. 

 This will loosen it up a bit, and sometimes allow you to open it easily after doing all four sides. 

 Aside from that, It's a matter of prying and jimmying with a flat tool. 

 Oh, have we mentioned that you can get empty wallwart housings from jameco? so, you have the option of just sawing the damn thing open and repotting it. 

 If the wart is totally dead, there's a good chance that there's a fuse in it. But there's also a good chance that you overloaded the transformer, and instead of an external fuse it has an internal fuseable link in the winding. In which case it's garbage.


----------



## amphead

Yeah, no step down voltage is definitely a bad indicator. Don't worry about beauty, just get it open and you will learn something. The transformer winding is very thin so be careful not to break it.


----------



## tomb

Joneeboi,
 I thought you said a few posts back that you were trying to read DC with your DMM on that AC walwart. If so, it may be fine.

 I agree with these other guy's methods about opening it up, but unless you're comfortable working with a transformer and mains wiring, it's not worth your trouble. I use the Jameco walwart cases all the time, but it's to fabricate a brand new walwart with the stuff I want to put it in it. There's only a small chance you can repair your present walwart - assuming there's anything wrong with it. On the other hand, you can get walwarts for the MAX for only $7-$8 anyway.


----------



## ruZZ.il

bumped up Vreg to 28v to keep the temp there down a little.. still got about 3.5v regulating margin. sounds good.. a little cooler.. whats the call on higher voltage anyway?.. 5v reg diff for max ripple filtering?


----------



## bperboy

Would performance increase if I upped the supply voltage and then the tube voltage?


----------



## ruZZ.il

I can't really hear any performance increase, no decrease though 
	

	
	
		
		

		
			





 but its still burning in, and with cheaper temporary transistors. V@28v, and my 1" ps sink is much more 'touchable' (than 27, I guess about 20% cooler). tubes@14v. bjts@43ma, will increase soon.. but they're already rather warm, QB8 more so. say, do the SC/SA transistors dissipate less heat than the MJE/BDs?


----------



## tomb

Quote:


  Originally Posted by *ruZZ.il* /img/forum/go_quote.gif 
_I can't really hear any performance increase, no decrease though 
	

	
	
		
		

		
		
	


	




 but its still burning in, and with cheaper temporary transistors. V@28v, and my 1" ps sink is much more 'touchable' (than 27, I guess about 20% cooler). tubes@14v. bjts@43ma, will increase soon.. but they're already rather warm, QB8 more so. say, do the SC/SA transistors dissipate less heat than the MJE/BDs? 
	

	
	
		
		

		
		
	


	


_

 

No - keep in mind, though, that these things can get plenty hot and still be fine. You are in great territory with 1" heat sinks for the time being. Keep in mind that you still want to case it up, which will make things run hotter all the way around.

 With the vent holes I drew up in the templates on the website, 1" heat sinks all around, 27VDC, and DB's biased to 50ma, there was no change in bias from the increased heat when it was buttoned up, which is saying a lot. If you bias more than that, maybe OK - but you may have some unintended consequences when you case it up. The old revMH DB's that had no heat sinks would draw another 10-20ma when the case was shut.


----------



## ruZZ.il

I dont think I'll push past 50.. even 43 sounds great.. and theres still upgrading those, and to 50. 28v is cooler though, but still hot. its the PS I like keeping cool 
	

	
	
		
		

		
		
	


	




 and higher voltage does that, a little.. so I'd like to hover just below its upper limit before regulation quality drops.. anything else I should try look out for at higher voltages?


----------



## joneeboi

So here are the surgery photos:




































 I'm not sure what help this is. Should I take off the tape? I didn't see any fuses or PCBs. Perhaps it's all in there in the tape. Hm.


----------



## amphead

If their isn't a fuse anywhere and you don't measure any "AC" voltage, then the windings have opened. That would be basically impossible to fix. When I talked about fixing a walwart that had a pc board inside, that was a "DC" supply not used on the MAX. Make sure you are using the AC setting on your DMM, as TomB mentioned earlier. Looking at your photos I don't see much more than a transformer in the 24VAC walwart. Hmmm.... I have a 24VAC 40V/A transformer on my bench. You like that rating for the MAX Tom? I think thats equivalent to 24VAC at 2000ma.


----------



## ruZZ.il

hm.. I'd just carefully measure the AC voltage, while its in the bottom part of the case. Make sure its getting 120 at where the leads from the main connect to it. There should also be around 27Vac or so at the secondary output too. If there is primary and no secondary voltage.. hmmm 
	

	
	
		
		

		
		
	


	




 Make sure to measure while its in a stable position, and with easily accessible terminals. Preferably on an extension cord so it wont have to be touched. And I'd be careful..

 Edit: and what amphead said!.. (its ~1.7amps. its what I've got 
	

	
	
		
		

		
		
	


	




 works great.. what v do you get unloaded? )


----------



## amphead

Edit: Actually P/V = I, therefore 40 VA is 40W and this would be 40/24 = 1.66 so its 24VAC at 1600ma. That too much for the MAX?


----------



## tomb

No, I'm running 40VA walwarts on mine. Strictly speaking the 24V, 1A should be enough. We vetted the prototypes at 750ma for the BJT's when biased at 50ma. NeilR's MOSFET version was built using the same transformer - with his MOSFETs biased at 100ma. Colin had something similar, too, with his BJT version. NeilR's was really pushing it, though. So, that's how we came up with the 1A for the MOSFET version.

 Since then, however, I found the inexpensive 40VA walwarts and I've been using them ever since. A small walwart will probably work, but they're most likely more expensive.

 Joneeboi -
 You've never confirmed whether you were just trying to read DC on an AC walwart. I thought you had stated that awhile back.

 As for the guts of that thing, it looks like the leads on the plug blades are not the same. (great photography, btw) I suspect that one of those leads goes to a PolyFuse under the tape.


----------



## odoe

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Thanks. I already took the liberty -
Setup and Biasing_

 

Now, does that apply to all the trimmers? Is it best to apply this practice to PS and Tube bias before powering up? I mean as in turning them clockwise?

 I also had a general question, maybe someone could answer.
QM1 was and looks like it still is out at mouser. Can I substitute the same transistor that was an option for Q8LR?

 The specs look the same to me.
 The only difference seems to be in the descriptions.
 Am I missing something?

 Thanks folks.


----------



## ruZZ.il

yeah, it'll usually only be around 30% loaded.. or less? bjt or millet? anyway.. its great for either..


----------



## joneeboi

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Joneeboi -
 You've never confirmed whether you were just trying to read DC on an AC walwart. I thought you had stated that awhile back._

 

Yeah, I did mention that. I did try DC for a second but quickly went to AC. My most recent tests were with AC.

 As for this wallwart, I'm ready to pronounce time of death. For the next one (same model), how might I avoid such a disaster?

 Edit: Thanks for the compliment, Tom.


----------



## tomb

Quote:


  Originally Posted by *joneeboi* /img/forum/go_quote.gif 
_Yeah, I did mention that. I did try DC for a second but quickly went to AC. My most recent tests were with AC.

 As for this wallwart, I'm ready to pronounce time of death. For the next one (same model), how might I avoid such a disaster?

 Edit: Thanks for the compliment, Tom._

 

Follow the new instructions on DB bias that I added from Ferrari's post a short while back:

MAX - Biasing and Setup

 Only shoot for the minimums at first, building up to the standard bias of 50ma for the BJT's, and 80-100ma for the MOSFETs. Do this carefully and don't exceed those currents unless you know what you are doing and are prepared to take the consequences.

 Another good read is Steinchen's instructions regarding DB bias for the original revMH Diamond Buffers:
_
do the adjustments in small increments. The output transistors are BJTs which have strongly positive thermal coefficient, which means that as you increase the bias, the current through the transistors increase, and that will heat up the transistor and cause its DC current gain to go up, which would then in turn cause the current to further increase.
it would be best not to aim for 20mA right away, or else a few minutes later you'd find that the current had gone up to more than 40mA. Increase the bias slowly and in small steps, let the transistors warm up and settle at a stable current before making more adjustments. Do this with at least 5 minute wait time between each adjustment until you get to the target without drift.

 Further, even more:
if voltage measures zero continue with left (counter-clockwise) turns, you will probably have to do some turns until the bias suddenly kicks in
when the bias kicks in give the buffers a minute to warm up and settle, don't turn the pots any further unless the bias has become stable
carefully increase (turn left = counter clockwise) or decrease (turn right = clockwise) the bias by half turns until the target bias is reached. Wait a few minutes after every adjustment to give the buffer time to settle. With the temperature changing the bias current changes, too. Be patient while adjusting the bias.
fine adjust the last 5mV by quarter turns
_
 Note the extreme caution that's readily apparent in those biasing descriptions. It's not enough to adjust then measure. You must adjust, *then wait*, then measure. Even if you think it's adjusted correctly, the temperature may climb at the setting and increase the current significantly.

 Note also that he says adjust the last 5mV (!) by only quarter turns at a time with the trimmer, stopping between each one to allow the heat to come up.

 It's not just a matter of dialing in a number.

 I'm not saying you didn't do any of this, Joneeboi - these are just the precautions that should be taken regardless. The DB's are like a tiger - handle with care, or they could turn, bite, or kill (some component).


----------



## tomb

Quote:


  Originally Posted by *odoe* /img/forum/go_quote.gif 
_Now, does that apply to all the trimmers? Is it best to apply this practice to PS and Tube bias before powering up? I mean as in turning them clockwise?

 I also had a general question, maybe someone could answer.
QM1 was and looks like it still is out at mouser. Can I substitute the same transistor that was an option for Q8LR?

 The specs look the same to me.
 The only difference seems to be in the descriptions.
 Am I missing something?

 Thanks folks._

 

"BD139" is the operative term. Type that into Mouser's Search field. The result is a list of 10. When making up the BOM, I start from that basis and then look for the cheapest one. However, transistors such as these change production lots on a regular basis. Those lots often have different number qualifiers that append to the primary string "BD139". Just pick one that has similar case and mounting dimensions and it will work.


----------



## amphead

Thanks Tom, that 24VAC 40 VA transformer is a standard item at Fry's.


----------



## odoe

Awesome.
 Thanks.


----------



## NoPants

Hey I ordered three of these boards and I've been playing around with the idea of using these as monoblocks...would there be anything wrong with strapping two boards together for L+/- and R+/-? Disregard the fact that I'm a noob when it comes to DIY plzkthx haha


----------



## ruZZ.il

Quote:


  Originally Posted by *NoPants* /img/forum/go_quote.gif 
_Hey I ordered three of these boards and I've been playing around with the idea of using these as monoblocks...would there be anything wrong with strapping two boards together for L+/- and R+/-? Disregard the fact that I'm a noob when it comes to DIY plzkthx haha_

 

If you're thinking of balanced, take a look at some of the posts on page 55, starting here.
 But, theoretically, each channel is independent (except for the volume being tied together for 2 channels)..

 EDIT: maybe you mean like, bridging the channel to get 'double' th output power?.. I'm not quiet sure how the output would handle that... nor which headphones would benefit from it...


----------



## Ferrari

What is your question exactly? Not clear what your question is ???
 You are talking about mono blocks => non strapping => each board drives 1 channel independently (like each mono power amp drive 1 speaker, usually in Hi-end audio). But in the same question, you are also talking about strapping 2 boards => Non mono 
	

	
	
		
		

		
		
	


	




 Btw, what are you going to use it (your strapping thing...) for ? Balanced headphone or ...?


----------



## odoe

This is where I'm at so far.





 I'm just waiting on some stuff my heatsinks, my LEDs and some gold plated sockets. Then I'm probably going to mount my orange drops underneath the board. I have to figure out the wiring, because I'm also waiting on the test jacks to mount to the back and wire underneath. I like that idea. Thanks to everyone. This has been a great learning experience so far.


----------



## kklee

Just finished casing it up. This is my first build using Lexan to replace aluminum panels. I learned some interesting things about working with Lexan, like how far it can shoot across the room when the table saw blade 'grabs' it (I had the blade cranked up too far).


----------



## tomb

Very cool, guys!

 That Lexan is really neat, kklee. More MAXes living every day!


----------



## Listen2this1

Is there a place that carries voltages of the Muse es'. I am having a hard time to find someone that carries the 35v and the 16v. Thanks


----------



## ruZZ.il

I really like that stuff.. nice work! I've also been thinking of something transparent.. I'll probably get the aluminum done first. I've still got to case up my M^3 too..


----------



## tomb

Quote:


  Originally Posted by *Listen2this1* /img/forum/go_quote.gif 
_Is there a place that carries voltages of the Muse es'. I am having a hard time to find someone that carries the 35v and the 16v. Thanks_

 

Handmade Electronics carries plenty of the 16V and 50V ES's and KZ's (they have the entire line of KZ's). The 470uF 35V ES is available at BDent (lots of BJT output transistors) and Michael Percy.


----------



## amphead

The higher current capable power transformers, should not sag as much under load. Therefore, If a builder is looking to get the upper voltage range from the 317 regulator, say 28, 29 volts, they might want to use the 40 VA rated trannies.


----------



## Ech0

Quote:


  Originally Posted by *kklee* /img/forum/go_quote.gif 
_Just finished casing it up. This is my first build using Lexan to replace aluminum panels. I learned some interesting things about working with Lexan, like how far it can shoot across the room when the table saw blade 'grabs' it (I had the blade cranked up too far)._

 


 kklee, 

 Very, very cool. I'm curious about something. Are those 1 1/2 inch heat sinks? I was going to do my top (not fronts) like that (I changed my mind about 3 times on how to make the case), but, I didn't think the lexan would clear the heat sinks. If those are indeed 1 1/2 heat sinks, um, I guess I was wrong! Once again I really like the look. That Max board looks so good populated that your lexan was a great choice. 

 Ech0


----------



## Listen2this1

Would anybody be interested in selling me 2- 1000uf 16v Nichicon caps. Do not mind paying a little extra. I just do not need 15 dollars of product from Handmade. If so please pm me. I can pay via paypal or check. 
 Thanks


----------



## kklee

Quote:


  Originally Posted by *Ech0* /img/forum/go_quote.gif 
_kklee, 

 Very, very cool. I'm curious about something. Are those 1 1/2 inch heat sinks? I was going to do my top (not fronts) like that (I changed my mind about 3 times on how to make the case), but, I didn't think the lexan would clear the heat sinks. If those are indeed 1 1/2 heat sinks, um, I guess I was wrong! Once again I really like the look. That Max board looks so good populated that your lexan was a great choice. 

 Ech0_

 

Those are the 1.5" heat sinks spec'd in the BoM. With the PCB in the bottom slots of the case, there's about 1.5mm clearance between the heat sinks and the Lexan.

 I was getting tired of the plain Hammond look, so I decided the Lexan would be a nice change. Besides that, the LED in the center of the board lights up everything quite nicely.


----------



## nysulli

Quote:


  Originally Posted by *kklee* /img/forum/go_quote.gif 
_Those are the 1.5" heat sinks spec'd in the BoM. With the PCB in the bottom slots of the case, there's about 1.5mm clearance between the heat sinks and the Lexan.

 I was getting tired of the plain Hammond look, so I decided the Lexan would be a nice change. Besides that, the LED in the center of the board lights up everything quite nicely.




_

 

i was thinking if doing the lexan thing myself, what thickness or work do you need to do to get it to slide in like the normal hammond top?


----------



## daggerlee

Hey if anybody needs some parts for their Max built let me know. For caps, I have PAnasonic FC 1000uf 50V caps for the power supply, FM 470 50V caps, Silmic II 470uf 35V caps. I also have 2K trimmers and PN4392, MJE253G, and MJE243G transistors for a Diamond DB build (I went MOSFET which is why they're left over). These are all for free 
	

	
	
		
		

		
		
	


	




 Just take them off my hands if you need them.


----------



## tomb

Quote:


  Originally Posted by *kklee* /img/forum/go_quote.gif 
_Those are the 1.5" heat sinks spec'd in the BoM. With the PCB in the bottom slots of the case, there's about 1.5mm clearance between the heat sinks and the Lexan.

 I was getting tired of the plain Hammond look, so I decided the Lexan would be a nice change. Besides that, the LED in the center of the board lights up everything quite nicely.
_

 

That is just too cool, kklee - very cool!! 
	

	
	
		
		

		
			







 If you can write a description of working with Lexan, I'll post it on the MAX website. I'm sure there are several of us who've wanted to do something like yours or Amb's transparent casetops. Steinchen's revMH Millett had a transparent lid, too. Drilling holes for adjusting bias works much easier if the lid is see-through and you can see the trimmer screw. 
	

	
	
		
		

		
		
	


	




  Quote:


  Originally Posted by *daggerlee* 
_Hey if anybody needs some parts for their Max built let me know. For caps, I have PAnasonic FC 1000uf 50V caps for the power supply, FM 470 50V caps, Silmic II 470uf 35V caps. I also have 2K trimmers and PN4392, MJE253G, and MJE243G transistors for a Diamond DB build (I went MOSFET which is why they're left over). These are all for free Just take them off my hands if you need them._

 

That's very generous of you, daggerlee. Thanks for helping out the Millett builder community.


----------



## kklee

Quote:


  Originally Posted by *nysulli* /img/forum/go_quote.gif 
_i was thinking if doing the lexan thing myself, what thickness or work do you need to do to get it to slide in like the normal hammond top?_

 

Since this was the first time I worked with Lexan and didn't know if it was going to turn out, I used the smallest sheet I could find at Home Depot. I think it was 1/8", I'll have to check.

 I used a non-ferrous saw blade on a radial arm saw to shave down the edges of the Lexan(total overkill, but I have the equipment, so why not? 
	

	
	
		
		

		
		
	


	




).

  Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_That is just too cool, kklee - very cool!! 
	

	
	
		
		

		
		
	


	






 If you can write a description of working with Lexan, I'll post it on the MAX website. I'm sure there are several of us who've wanted to do something like yours or Amb's transparent casetops. Steinchen's revMH Millett had a transparent lid, too._

 

I actually found that working with Lexan was more labour intensive than working with aluminum since you have to be much more careful with drilling and cutting it.

 I'll type something up. I'm thinking about re-doing the top plate because the holes didn't come out all that straight, and although you can't see the marks in the photos, there are some nast gouges from when the table saw shot it across the garage. I can take some photo's of the process.

  Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Drilling holes for adjusting bias works much easier if the lid is see-through and you can see the trimmer screw. 
	

	
	
		
		

		
		
	


	


_

 

Unfortunately, the Lexan I bought comes with a paper coating on one side and plastic coating on the other, so it's pretty opaque.

 ...Ken


----------



## tomb

Quote:


  Originally Posted by *kklee* /img/forum/go_quote.gif 
_ Quote:


  Originally Posted by *tomb* 
Drilling holes for adjusting bias works much easier if the lid is see-through and you can see the trimmer screw.

 

Unfortunately, the Lexan I bought comes with a paper coating on one side and plastic coating on the other, so it's pretty opaque.

 ...Ken_

 

Umm, yeah - my comment didn't come out quite right. I would never drill holes over a populated board. I meant that having the trimmer adjustment holes would work a lot better if you could see the trimmer screws when you inserted a trimmer adjustment wand.


----------



## tomb

Quote:


  Originally Posted by *Listen2this1* /img/forum/go_quote.gif 
_Would anybody be interested in selling me 2- 1000uf 16v Nichicon caps. Do not mind paying a little extra. I just do not need 15 dollars of product from Handmade. If so please pm me. I can pay via paypal or check. 
 Thanks_

 

YGPM


----------



## adfinni

Gorgeous work klee !!!!!!

 One question i have wanted to ask, and finally remembered after seeing the board mounted in the bottom slot of the hammond. What is the distance between the top of the case and the top tip of the tubes ?

 cheers


----------



## amphead

Good work kklee! I was thinking that you could make a template out of a spare piece of hardwood or aluminum and then apply it to the new piece of lexan. This would give both sides a uniform look as well and be pretty much foolproof. The aluminum template can be scored with a scribe and straight edge to give a perfectly aligned straight line.


----------



## Bigguy

Daggerlee YGPM


----------



## Listen2this1

kklee Looks great, you should be very proud. I have seen a couple people use the amber/red Leds and I really like them.


----------



## Ech0

Quote:


  Originally Posted by *nysulli* /img/forum/go_quote.gif 
_i was thinking if doing the lexan thing myself, what thickness or work do you need to do to get it to slide in like the normal hammond top?_

 

I think I saw a post at the diy forums about this (re: lexan). If I remember right, the answer was 1/16 of an inch. 


 Ech0


----------



## kklee

Quote:


  Originally Posted by *Listen2this1* /img/forum/go_quote.gif 
_kklee Looks great, you should be very proud. I have seen a couple people use the amber/red Leds and I really like them._

 

Thanks. I prefer red/orange since the tubes glow that colour anyways. Besides that, I listen to my amps in bed and blue lights up the room too much and annoys my wife.

  Quote:


  Originally Posted by *Ech0* /img/forum/go_quote.gif 
_I think I saw a post at the diy forums about this (re: lexan). If I remember right, the answer was 1/16 of an inch. _

 

I used 1/8" and I thought it was kinda thin. I think 1/16" might have too much flex to it. The end bezels of the Hammond case have little tabs sticking out that keep the lid from bowing in and the 1/8" fits into them perfectly. Although 1/16" may fit right into the slots, it won't be flush with the top of the case or the bezels.

  Quote:


  Originally Posted by *amphead* /img/forum/go_quote.gif 
_Good work kklee! I was thinking that you could make a template out of a spare piece of hardwood or aluminum and then apply it to the new piece of lexan. This would give both sides a uniform look as well and be pretty much foolproof. The aluminum template can be scored with a scribe and straight edge to give a perfectly aligned straight line._

 

I had this exact conversation with a coworker today. The end result of that chat was that a drill press attachment for a hand drill may be an easier solution. I'm seriously considering modding my drill press to run slower as another solution.

 Since I had a couple of requests about measurements, here's a picture with a ruler:


----------



## tomb

From now on, any questions about spare parts, boutique parts, or anything else you may need for the MAX will not be discussed by me on this forum - and in particular, in a PM. 
	

	
	
		
		

		
		
	


	







 You all know where to reach me.


----------



## daggerlee

Quote:


  Originally Posted by *daggerlee* /img/forum/go_quote.gif 
_Hey if anybody needs some parts for their Max built let me know. For caps, I have PAnasonic FC 1000uf 50V caps for the power supply, FM 470 50V caps, Silmic II 470uf 35V caps. I also have 2K trimmers and PN4392, MJE253G, and MJE243G transistors for a Diamond DB build (I went MOSFET which is why they're left over). These are all for free 
	

	
	
		
		

		
		
	


	




 Just take them off my hands if you need them._

 

Just to be clear I intend for this to help out those who are in the middle of building their millets but realize that they are missing or need some extra parts and don't want to have to pay $7+ for shipping on a part from mouser or the digikey under-$25 $5 handling charge...or for those who are trying to get parts that aren't in stock at mouser or digikey. sorry if I wasn't clear. Thanks


----------



## ruZZ.il

Nothing scientific, but I just thought I'd share what I captured in electroacoustic toolbox. Generating a frequency of about 220hz through the Alien DAC, through the MHM and to my audio input. Sure, output isn't perfect, nor is the input, but its a worthy comparison. The images are of a triangular oscillation. One is captured while both channels are about equally biased at about 45mA, whereas the other is when the left (green) channel is biased at about 7ma and the right at 45mA. One can see the 'linearity' deviation appear as the lines become nonparallel. Hopefuly I'll get a real scope/f.generator sometime.. but I'm more likely to get some free lab time and play a bit.. it'll be a while.. but maybe a little more accuracy then..


----------



## tomb

Quote:


  Originally Posted by *daggerlee* /img/forum/go_quote.gif 
_Just to be clear I intend for this to help out those who are in the middle of building their millets but realize that they are missing or need some extra parts and don't want to have to pay $7+ for shipping on a part from mouser or the digikey under-$25 $5 handling charge...or for those who are trying to get parts that aren't in stock at mouser or digikey. sorry if I wasn't clear. Thanks_

 

Daggerlee - just to be clear, my post up there had nothing whatsoever to do with your post or your generous offer - assuming you even thought that. By all means, help to the DIY Community and to Millett builders is always appreciated. Again, thank you.

  Quote:


  Originally Posted by *ruZZil* 
_<snip>Nothing scientific, but I just thought I'd share what I captured in electroacoustic toolbox. Generating a frequency of about 220hz through the Alien DAC, through the MHM and to my audio input. Sure, output isn't perfect, nor is the input, but its a worthy comparison.<snip>_

 

So, for an electronics analysis know-nothing like me, is that good or bad for the MAX?


----------



## ruZZ.il

well, it just shows a little of what class A does. not really specific to the MAX.
 For those that are less familiar, Class A biased basically means running your signal on top of a constant voltage, so the oscillation is in the linear response region, creating a current thats a lot more true to the source (alike, but maybe amplified). whilst a non biased amps output would be.. a little different. here are some characteristics (different tube though similar behaviour) so basically, if there is a linear increase in voltage above 0v, one would get an increase in current that behaves in proportion (theoretically) to V^(3/2) (it realistically does something similar).. whilst a linear increase in voltage above say a few volts, would be a linear increase in current. One can also see that there generally is a wider region of linearity with a higher temperature filament .. anyway, the more linear response of a class A biased amp is just a lot more 'true' to the source.. hmm.. I need to learn more 
	

	
	
		
		

		
		
	


	




 anyway..


----------



## ruZZ.il

hm. anything ill in tapping in another little regulator+bits to get ~6v for an alien dac? I'm thinkig basically in parallel to the other regulators in and ground. wondering if this would effect the MAX, and if a regulator is cool with a 25v drop with probably hm.. how much current does the a.dac draw? I'm assuming it'd be less than 5w dissipation.. maybe need a heatsink.. hm. so, anywhere I could tap into to get some voltage?


----------



## ericj

Quote:


  Originally Posted by *ruZZ.il* /img/forum/go_quote.gif 
_hm. anything ill in tapping in another little regulator+bits to get ~6v for an alien dac? I'm thinkig basically in parallel to the other regulators in and ground. wondering if this would effect the MAX, and if a regulator is cool with a 25v drop with probably hm.. how much current does the a.dac draw? I'm assuming it'd be less than 5w dissipation.. maybe need a heatsink.. hm. so, anywhere I could tap into to get some voltage?_

 

The MAX wouldn't mind, or even notice, probably. At least if external s/pdif connections are transformer-coupled. 

 Edit: You'd be amazed by the weirdness that can occur due to direct-coupled S/PDIF. Before i added a pulse transformer to the s/pdif output on my diy usb dac, sometimes when i turned off the (fluorescent) lights in that room, the Sony DTS receiver it was plugged into would reset itself. 

 As for dropping so many volts in the regulator - you can avoid some of that uglyness by using a resistor to drop the voltage down before it gets to the regulator.


----------



## daggerlee

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Daggerlee - just to be clear, my post up there had nothing whatsoever to do with your post or your generous offer - assuming you even thought that. By all means, help to the DIY Community and to Millett builders is always appreciated. Again, thank you.


 So, for an electronics analysis know-nothing like me, is that good or bad for the MAX? 
	

	
	
		
		

		
			



_

 

Don't worry tom I wasn't talking about you 
	

	
	
		
		

		
		
	


	




 thanks for all the help you've provided for this project you've been invaluable!


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## ruZZ.il

<the new me 
	

	
	
		
		

		
		
	


	




 ...also, thanks ericj. any suggested resistance? I'll probably need something twice the 'resistance' of the reg. to get about 10v to it.. though I'm guessing it may be more complicated than that.. maybe I'll just build some voltage divider and play around to get some decent values first..


----------



## daggerlee

another Max lives... 
	

	
	
		
		

		
		
	


	




 Pics to come soon


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## ruZZ.il

enjoy!


----------



## daggerlee

Some pics:











 The LED is actually white, so try to imagine it like that...

 MOSFET version, biased at around 215 mV. Don't really care to go higher 
	

	
	
		
		

		
		
	


	




 So far sounds really great. Will be using primarily as a preamp which explains the set of RCA outs. I bought the aluminum mesh at a crafts store (AC Moore), it's a little too thin/flexible to use as a cover, sometimes it won't stay flat. I'd recommend something more stiff if you want to go this route. Thanks to everyone who made the Max possible 
	

	
	
		
		

		
		
	


	




 Also, once it's biased I don't have to touch anything do I if I turn it off and turn it on again?


----------



## Troyhoot

after you burn it in (week or so) you should at least check your biases. other then that you shouldnt need to touch it. all looks great now time to enjoy


----------



## amphead

In the wee hours of the morning......... SHE LIVES! 
 Well sort of. I adjusted the PS for 27V with all of the other trimmers set to full clockwise. I let that burn -in for 10 minutes. The tubes filaments glowing orange. Tubes quite warm to the touch. Measuring TA2L to GND gave me 24.3 volts. Moving RA1L slowly counter-clockwise gave no change in voltage. Turned off power to look up other biasing posts. Decided to turn RA1L 20 turns counter-clockwise. Turned on power. Well there goes the fuse immediately. Err Umm don't do that! Power on first and then adjust trimmers slowly! No extra fuses at this late hour. Tommorrows another day.  Oh, also NICE WORK daggerlee!!!!


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## ruZZ.il

Congrats, amphead! 
 Happened to me when my db bias was set at the max. I bypassed the fuse after all, and burnt a transistor. You can bypass it though, as long as what look out for at first is the output transistor bias. Set your dmm (or 2) there when you power up and make sure those are in the lower end of the bias scale. If not, either trim quickly or power down, trim, power up. Once your output stage is safe, move on to the tubes. Once everything is safe, take your time with incremental adjustments. I don't have a fuse in now and all is good, but I'll probably put a new one in now that its stable, to protect from accidental shorts and stuff. 
 Happy Listening!


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## tomb

Good advice, ruZZ.il! I'm sure Amphead appreciates it. Here's some additional thoughts, based on some of the questions I've been receiving in other areas:

*Tube Care*
 Yes, I have had some questions in other places about the tubes and how to take care of them: _forget it_!

 They can stay on indefinitely unbiased, badly biased - whatever - and yes, they get very, very hot. They are not analogous to light bulbs on several accounts, but when it comes to heat, they _are_ like light bulbs. Not to worry - they can go on like that for 10,000+ hours - including at a bad bias. As mentioned before, if I have a set of new tubes just put in, I'll turn it on and let it sit for a couple of hours. In many cases, it's a waste of time to start adjusting bias before then.

 Also - tubes distort, period. If the tubes are broken-in, that distortion can be quite musical. If not broken in, it may sound like you've built a bad amp. Give it time. 

 About the best you can do for the life of the tube:
 1. Use the heater resistor (R1). What burns out most often on a tube is the cathode - or heater. Colin gave us R1 in the MAX specifically to temper the heater voltage. Be sure you look at the Tweaks -> Heater Resistor page on the MAX website, though. There is a maximum _and_ minimum that should not be exceeded. There are plenty of calcs and a graph to help you select this resistor, depending on the voltage of your power supply - and precision is not needed.
 2. Clean the glass - this maybe one of those unproven bits of advice, but I try to make sure the top half of the tubes are clean. This makes sure there are no hot spots and that their ability to radiate heat is not hampered. I don't think it matters much on the side - the lettering prevents much of this, and some of these tubes are old enough that a little Windex to the glass will completely dissolve any lettering that's there. I just use a lens-cleaning cloth to clean them as best as I can. Again, no proof here - just a common sense precaution.
 3. Check the pins. Sometimes they are really bent - that doesn't help the tube or the socket. Also, many of these old tubes have corrosion or dirt on the pins. A little bit of steel wool, emory cloth - or even a pencil eraser can help clean them up. The pin contact is not necessarily a function of the life of the tube, but you can get some nasty DC transients if contact is intermittent on some pins. Thankfully, this is a _very_ infrequent occurrence (about as much as having the same thing happen with an opamp), and is usually a sign of a bad socket, not the tube.

*DB's*
 By all means _worry_ about the DB's. That's where damage can occur - quite easily depending on where the trimmers are set. They are also like tubes with their positive temperature coefficient. They will undershoot and overshoot. You can get them adjusted, and then because you've been turning up the current for that adjustment, they will start to get hotter. As they get hotter, the "adjustment" climbs to a still higher voltage (current).

 Thankfully, unless they are really out of whack, they aren't as bad as on the original revMH DB's or the CKKIII - something like that. The heat sinks provide a bit of "heat inertia" and temper these changes to a certain extent.

 Once set and proven out over a couple of hours, you may never have to adjust the DB's for _years_. They really are a situation where you may want to paint a little fingernail polish on the trimmer screw - so that they stay put from now on.


----------



## joneeboi

Here's something I've been curious about: which parts and part values does one tune in the MAX to maximize Grado-impedanced headphones?


----------



## tomb

Quote:


  Originally Posted by *joneeboi* /img/forum/go_quote.gif 
_Here's something I've been curious about: which parts and part values does one tune in the MAX to maximize Grado-impedanced headphones?_

 

My personal opinion? Grados love warmth and deep bass. So, I would go for the ES's and either the stock Wima's or some Sonicap GEN II's (~$3.50 ea in 0.22, 0.33, 0.47uF sizes - small, too).

 As for the impedance - all you really need do is use the 12FK6 tubes. They have the least gain (most detail, too - btw). You might want to play around with the output resistors if you still have a problem, but the SR-80's I had once really weren't that efficient. Using the 12FK6 tubes is probably the single best thing you can do in using the MAX with Grados.

 The basic Millett has always paired well with Grados - the MAX is no different. The MAX sounds great with the HD580 and HD600, too. For normal listening, I still use the KSC75 for everything - and those sound great with the MAX, too. There is probably a full octave of bass available from the MAX that the KSC75's can't get, though. I have a pair of Sony V6's with Beyer pads and with the MAX and an ES-equipped Alien DAC, the bass is frightening.


----------



## c0nsumer

Reading through all of this is tempting me to make another MAX, this time in a silver Hammond case with wood ends, 12FK6 tubes, a BJT output stage, and some sort of special caps.

 Lessons learned from the previous MAX I built should make this one go even more smoothly, and it'd be interesting to A/B them. I just happen to have a spare volume pot, sockets, and two MAX PCBs. I'd just need to snag some parts from Mouser, eBay, Jameco, and Digi-Key... Hmm...

 If you all were doing this, is there anything special you'd do cap and transistor-wise? I'm thinking just Muse ES caps, 1.5" heatsinks (why not -- it all still fits in the chassis nicely), again no LEDs (saves on power, makes for cooler power supply, etc), maybe a thermistor in series with (or in place of) the fuse... I've got no idea about which pairings of transistors might be best, though.

 For what it's worth I've got a set of Sennheiser HD570 headphones and the next set will likely either be the 600s or 650s. I personally really prefer over the ear, open ear headphones.


----------



## ruZZ.il

try look at the characteristics of the caps and transistors. ie, I chose the gen II's for their 'mid bloom', and slightly recessed highs. my cans have slightly recessed mids, and pronounced highs(slightly too much for me).. perfect match 
	

	
	
		
		

		
		
	


	




 bg's sounded like they'd compliment the tubes, too..


----------



## babbkutz@comcast

off your short list of headphones (the 650s are great just not as comfortable as the 600s...tight on the head)


----------



## tomb

Quote:


  Originally Posted by *c0nsumer* /img/forum/go_quote.gif 
_Reading through all of this is tempting me to make another MAX, this time in a silver Hammond case with wood ends, 12FK6 tubes, a BJT output stage, and some sort of special caps.

 Lessons learned from the previous MAX I built should make this one go even more smoothly, and it'd be interesting to A/B them. I just happen to have a spare volume pot, sockets, and two MAX PCBs. I'd just need to snag some parts from Mouser, eBay, Jameco, and Digi-Key... Hmm...

 If you all were doing this, is there anything special you'd do cap and transistor-wise? I'm thinking just Muse ES caps, 1.5" heatsinks (why not -- it all still fits in the chassis nicely), again no LEDs (saves on power, makes for cooler power supply, etc), maybe a thermistor in series with (or in place of) the fuse... I've got no idea about which pairings of transistors might be best, though.

 For what it's worth I've got a set of Sennheiser HD570 headphones and the next set will likely either be the 600s or 650s. I personally really prefer over the ear, open ear headphones._

 

Based on your description, a really nice set of BJT's may be the best improvement. The MJE's are no slouch, but the Toshiba and Sanyo pairs are really superior. The best resource - as always - is Steinchen's original revMH DB website. Scroll down to the bottom of this page and you will see his reviews for the various BJT pairs:

http://www.diamondstar.de/dDB_partslist.html

 I have used the 2SC3422/2SA1359 pair many times and can personally vouch for their "rockability" and "slam". 
	

	
	
		
		

		
			








 They are very, very nice.

 The 2SC3421/2SA1358 I've also used and they have tremendous bass extension - organ pedal deep. They also happen to have been used on the Dynahi and cetoole's first proto. Again, a very good choice - and if asked, I would have to say that the highs are not necessarily "rough" as Steinchen mentions.

 The 2SC2238/2SA968 pair became Steinchen's all-time favorite. I have yet to use them, but have no doubt they will be among the best - every other BJT I've tried has tracked Steinchen's reviews pretty well.

 About the wood panels - Naamanf had a thread on DIYForums.org where he was selling ready made wooden front and back plates for the Hammond.


----------



## slowpogo

This has been asked before (by myself and others) but at this point, is anyone willing to sell off a board? I thought maybe someone is deciding they don't really need 3 or 4 PCBs after all.


----------



## fc911c

Quote:


  Originally Posted by *slowpogo* /img/forum/go_quote.gif 
_This has been asked before (by myself and others) but at this point, is anyone willing to sell off a board? I thought maybe someone is deciding they don't really need 3 or 4 PCBs after all._

 


 Yes I'd be interested in one as well.

 Thanks
 Frank


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## amphead

Hmmmmmmm..............Ever since I turned RA1L counter-clockwise 20 turns, she is now quite a fuse blower. All trimmers except PS are fully clockwise. The PS trimmer is turned down. The next step is to put a fuse holder/ fuse in my diy power supply and jumper the fuse in the MAX, to see if its inrush or something not so nice.
	

	
	
		
		

		
		
	


	




 Sniff test and visual on trannies good.


----------



## britishbane

Quote:


  Originally Posted by *slowpogo* /img/forum/go_quote.gif 
_This has been asked before (by myself and others) but at this point, is anyone willing to sell off a board? I thought maybe someone is deciding they don't really need 3 or 4 PCBs after all._

 


 What they said. Interested as well.


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## amphead

Note to self, no more inrush current jokes. Thats probably going to be *my* problem.


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## tomb

I suggest taking the fuse clips out and stomping on them once or twice. You could throw in a couple of the fuses for good measure. Then put your one AC lead in the other terminal block position and forget about it.

 OK - a moment of weakness ... Seriously, it sounds like your power supply is supplying a lot of volts that are getting burned off in the PS. If the temperatures are OK and the LM317 doesn't shut down, you can live with it. Go up to my previous post about biasing the DB's and carefully check, measure, wait, measure and then adjust until you get them where you want.


----------



## ooeric

anyone still building these too sell?
 ive been looking for one, i cant diy. my hands just cant it do.


----------



## c0nsumer

Quote:


  Originally Posted by *babbkutz@comcast* /img/forum/go_quote.gif 
_off your short list of headphones (the 650s are great just not as comfortable as the 600s...tight on the head)_

 

Hmm... I've never tried AKG headphones... They look quite comfortable, though...

 I'm just having a hard time shelling out that much, especially as I happened to get the 570s for about US$36 as a local shop was going out of business and clearancing everything.


----------



## c0nsumer

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Based on your description, a really nice set of BJT's may be the best improvement. The MJE's are no slouch, but the Toshiba and Sanyo pairs are really superior. The best resource - as always - is Steinchen's original revMH DB website. Scroll down to the bottom of this page and you will see his reviews for the various BJT pairs:

http://www.diamondstar.de/dDB_partslist.html

 I have used the 2SC3422/2SA1359 pair many times and can personally vouch for their "rockability" and "slam". 
	

	
	
		
		

		
		
	


	







 They are very, very nice.

 The 2SC3421/2SA1358 I've also used and they have tremendous bass extension - organ pedal deep. They also happen to have been used on the Dynahi and cetoole's first proto. Again, a very good choice - and if asked, I would have to say that the highs are not necessarily "rough" as Steinchen mentions.

 The 2SC2238/2SA968 pair became Steinchen's all-time favorite. I have yet to use them, but have no doubt they will be among the best - every other BJT I've tried has tracked Steinchen's reviews pretty well.

 About the wood panels - Naamanf had a thread on DIYForums.org where he was selling ready made wooden front and back plates for the Hammond._

 

I had been looking through there, and while I originally was looking at his default recommendations, I don't think it'd be too hard to hook in the 2SC2238/2SA968 set. Hmm.

 I found someone who has six 12FK6 tubes for a reasonable price, NOS. I might pick up four of them or so...

 I like those wood end panels, but I think I'm going to grab some veneer tomorrow (not sure what sort yet) and attempt to laminate it cleanly on to aluminum. I figure surface hit with some 440 grit or so should do well with contact cement, the veneer, and a decent setup for pressing it all together. We'll see, I'll definitely post about how its done and such.

 Right now I'm thinking a light wood, but maybe not zebra... I'll see what Woodcraft has. Oh, and some wipe-on urethane...


----------



## amphead

Ok, so knock on wood it was peak inrush current causing my problem so far. 2A regular blo 250VAC fuse on the primary of my trafo. Jumpered fuse position on the MAX. For now I am just warming my hands by the tubes.  After the tubes burn-in for an hour, I will attempt to bias.


----------



## amphead

Tube and DB bias trimmers fully clockwise. DB bias currently at ~29mv. Regulator heat sink very warm 5 second touch maximum. No burned plastic smell, so far. Still not ready to jump in, I'm waiting for the water temp to be just right! Tom, I wonder how much cooler the PS heatsink will be once I get the tube bias to 13.75, assuming that I ever get there? Can't imagine ever putting the lid on, the way it feels now, without moving to Alaska or maybe Sweden.


----------



## bperboy

Quote:


  Originally Posted by *amphead* /img/forum/go_quote.gif 
_Tube and DB bias trimmers fully clockwise. DB bias currently at ~29mv. Regulator heat sink very warm 5 second touch maximum. No burned plastic smell, so far. Still not ready to jump in, I'm waiting for the water temp to be just right! Tom, I wonder how much cooler the PS heatsink will be once I get the tube bias to 13.75, assuming that I ever get there? Can't imagine ever putting the lid on, the way it feels now, without moving to Alaska or maybe Sweden._

 

Personally, I leave the top off mine all the time. No worries about heat, and no worries about trying to align the tube holes perfectly!


----------



## amphead

Mmmm..Hmmm..., so the consensus is that sinks and tubes will stay quite warm, even at proper bias.


----------



## tomb

Measurements are your friend. 
	

	
	
		
		

		
			





 The DB's will run within a certain milliamp range, and the voltage and the 2.2 ohm DB output resistors determine those milliamps. Yes, things get hot, but it varies from amp to amp and component choice to component choice.

 BTW, the tubes don't care - leave them unbiased until you get the DB's right - it won't affect them.


----------



## bperboy

Quote:


  Originally Posted by *amphead* /img/forum/go_quote.gif 
_Mmmm..Hmmm..., so the consensus is that sinks and tubes will stay quite warm, even at proper bias._

 

Definitely! Its like a mini campfire in my room for the wintertime!


----------



## amphead

Thanks Tom, I will leave the tubes biased at 24V and then bias the DBs verrry carefully. Any idea what the filament voltage might be with the tube bias at 24V? Those are some meaty filaments!


----------



## tomb

While you are waiting for your latest bias adjustment change to take place on the DB's, it's an easy enough matter to reach over and adjust the tubes. Technically, an unbiased tube is not in a range that can hurt the grid, but I guess it's not something you'd want to do for days and days - besides the fact that you wouldn't be getting any music out all that time.

 As for the filaments - those are the heaters, cathodes, etc. - all the same thing. There is no music signal in the heaters. They split the voltage between the power supply - each taking one-half of the total voltage, minus whatever the R1 resistor takes. Keep in mind that the purpose of the heaters is to _heat_.


----------



## amphead

Yep, the heaters throw off electrons into the vacuum to create current flow from cathode to the plate and are slowed by the grid bias and then swing with the music.  Currently left DB bias at 45mV. My large Jensen bypass cap on the right channel is in the way of 2A1R testpoint. I am cooling the tubes and pulling the board from the enclosure to solder a wire underneath the board to get the right channel biased.


----------



## amphead

Another MAX LIVES!!!!!!!!
	

	
	
		
		

		
		
	


	






























 Analysis:shocking detail, I'm speechless really. But with K701 and Jensen bypass caps, clarity, crisp without harshness. Soundstage is wider than I am used to hearing. I left my headphones and descended into a room with the musicians! Vocals with outstanding presence. Strings are natural, with a more realistic sound. One faux pais, I have to admit to was the use of BD139 and BD140s. I should have looked at the BOM more closely. I guess at some point I'll upgrade to the top of the line trannies. I won't be in a hurry to do that though, enjoying the Tull too much! Ok, now for the credits.....
 Thanks Colin, you did one awesome layout and logistical process!
 Thanks Tom, detailed, authoritative website and dilligent online help!
 Thanks Ti, for the delay circuit! No pops on power! Fast parts shipper!
 Thanks also goes to Pete Millett for the original design and sharing it! 
 I'm sure I forgot to thank someone. Oh yeah, thanks ruZZ.il,bperboy and Dsavitsk!

 Ron


----------



## tomb

Way to go! 
	

	
	
		
		

		
		
	


	










 It's nice to hear that another K701 user confirms that the MAX pairs well with them.


----------



## ruZZ.il

rock on! 
	

	
	
		
		

		
		
	


	




 I'm also pretty impressed with the BD/MJE. I've actually got the BD pair on the left, and MJE on the right.. its kind of confusing to try pick up differences.. but I'm looking forward to changing those too. meanwhile, I didn't feel like chopping up the aluminum endplates/top yet.. I'm thinking of even taking it to someone with a proper press drill, etc. yesterday I took a piece of mdf from some big packaging box just to play around (hehe, playing with wood
	

	
	
		
		

		
		
	


	




) but its kinda cool.. hmm.. so maybe I could get some nice wood, or get naamanfs plates. I need a workshop too now 
	

	
	
		
		

		
		
	


	




 and my lounge can barely tolerate the 'lab'..


----------



## vixr

almost done!!! just a little wiring left.


----------



## ruZZ.il

umm... wow! 
	

	
	
		
		

		
		
	


	




 good stuff...


----------



## kklee

Nice, I like how it has a kind of industrial/architectural look to it.


----------



## Listen2this1

Vixr, Looks awesome. I like to see variations in case work. I am going to use a little of lexan as well. Since I have Toms permission I am going to have the Millett Max logo laser etched into the lexan. You will see through the lexan to see the tubes. Here is a little taste.




 By listen2this1


----------



## odoe

This is some awesome casework guys.
 My max should be up by tonight, last of parts came in the mail.
 I'm not even done with this one yet and I'm looking at parts combos for my next build


----------



## tomb

Awesome work, Vixr! It's really cool watching you guys come up with this original casework.


----------



## Ferrari

I'm quite picky when it comes to case work but... I must say that I'm impressed. Realy nice and original mechanical work, vixr.


----------



## vixr

thanks guys... the case has a wonderful weight to it.


----------



## adfinni

God im jealous..... Mine isn't coming along soo well, still can't figure out why there is no sound coming from it 
	

	
	
		
		

		
			








 Pic to see if you can see the problem


----------



## naamanf

Thats obvious and I am sure your going to smack yourself once you read this. The lines are going the wrong direction.


----------



## joneeboi

I'm not sure if this has already been posted, but it would be a great resource for the beginner DIYer working on the MAX. I kinda just stumbled on it through Google. *shrug*

http://nuxx.net/wiki/Millett_Hybrid_Maxed


----------



## Listen2this1

Adfinni, with this pic it is hard to say, but it looks like the left side of the right cap is not soldered. 

 That is my suggestion.


----------



## bperboy

Adfinni, it may be that you've got the wrong caps. I think the real ones need to be black-colored. Or maybe red.


----------



## adfinni

Quote:


  Originally Posted by *bperboy* /img/forum/go_quote.gif 
_Adfinni, it may be that you've got the wrong caps. I think the real ones need to be black-colored. Or maybe red. 
	

	
	
		
		

		
		
	


	


_

 

O i like yellow, the yellowness apparently gives a great sound making the best mundorffs sound like swiss cheese 
	

	
	
		
		

		
		
	


	







 Il be ordering everything this weekend so soon you will have another MAX to help bring to life


----------



## tomb

Quote:


  Originally Posted by *joneeboi* /img/forum/go_quote.gif 
_I'm not sure if this has already been posted, but it would be a great resource for the beginner DIYer working on the MAX. I kinda just stumbled on it through Google. *shrug*

http://nuxx.net/wiki/Millett_Hybrid_Maxed_

 

Yep - that's c0nsumer's site! He did an oustanding job. Considering he came into this new, it's downright amazing. Sorry I haven't gotten around to telling you guys, but I did load all his pics on the MAX website gallery last night (that was a job - he had a bunch!).

 There are a few things he did non-standard, so if in doubt, ask or refer to the MAX website for a different take. We all do things a little differently, though - as evidenced by the wide variances you guys have been doing on casework. It's all great!


----------



## tomb

I also got a very nice note from Phil Hazen at Radio Daze today. He's a good businessman that's trying to say as nicely as he can that he can't offer specific brands anymore for the Millett tubes. We have bought so much of his stock that it takes his guys half a day to hunt up these tubes in specific brands, so please keep that in consideration - or else he will be raising his price, most likely (he didn't say that, though).

 Those of you who've bought a passel of these tubes have probably come to the same conclusion as me: pursuing certain brands with Millett tubes is almost self-defeating. There are only 3 mfrs who made the tubes as far as anyone knows - GE, RCA, and Sylvania. They also sold these to resellers and amongst themselves. I have Sylvania GE's, RCA GE's, GE RCA's, Sylvania RCA's etc., etc. You may in fact discover that you are just as likely to get the same mfr in a pair of tube types by not specifying as you are when specifying brand.

 So, by all means, order from Radio Daze, but not by brand for Millett tubes.

 Thanks.


----------



## babbkutz@comcast

maybe make a note (on the MAX site) that the "official" templates for the back panel don't work with the fuse.....just a suggestion


----------



## tomb

I'll rework them when I get a chance. In the meantime, I'll add a note.


----------



## n_maher

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_I'll rework them when I get a chance._

 






 SLACKER!


----------



## babbkutz@comcast

the MAX is too good for that....and this fuse dispute has to be put to bed.


----------



## tomb

Quote:


  Originally Posted by *babbkutz@comcast* /img/forum/go_quote.gif 
_the MAX is too good for that....and this fuse dispute has to be put to bed._

 

Right. The hole would not be drilled wrong. It's the fuse that's wrong.


----------



## tomb

Seriously, it's not a trivial issue, and I'm not in a position right now to check it. I haven't even populated a production board, neither do I have the fuse clips. So, changing those templates are not going to happen overnight - even if I wasn't a slacker. 
	

	
	
		
		

		
		
	


	




 An interim solution may be to use an "outtie" instead of an "innie":





 Jameco part #151590

 EDIT: The note has been added to the website.


----------



## [AK]Zip

The amp is now alive and sounds quite nice.... 
	

	
	
		
		

		
			





 Pics to follow soon. Then I will rewire everything and case it all up.

 EDIT: Using RCA 12FK6 now. Will try Sylvania 12AE6A's next.

 -Alex-


----------



## Picodeloro

Quote:


  Originally Posted by *naamanf* /img/forum/go_quote.gif 
_Back from vacation. And another MAX lives! Hope to have it cased up this weekend.




_

 

Hi:

 The application notes of the Auricap web put "In signal path applications the black lead is "in" and the red lead is "out". " and "In power supplies the black lead should be connected to ground and the red lead to the + or – voltage".

 I think that C8 and C9 is in the signal path, if we see the photos of the amplifier of naamanf or the one of troyhoot, auricaps is in the right direction?

 I want for this positions (C8-C9) 0.22mfd/200v Auricap, what caps you advise me for C2L/R and C7L/R?


----------



## odoe

I'll get pics up tomorrow, but something is wrong with my build. I can't even get it to power on, even after bypassing the fuse. Not sure what's wrong, but I'll delve deeper into it tomorrow.
 Thanks folks.


----------



## c0nsumer

Quote:


  Originally Posted by *joneeboi* /img/forum/go_quote.gif 
_I'm not sure if this has already been posted, but it would be a great resource for the beginner DIYer working on the MAX. I kinda just stumbled on it through Google. *shrug*

http://nuxx.net/wiki/Millett_Hybrid_Maxed_

 

Er... That already made it to Google? Damn my site is well indexed... I just came by here to make a post announcing that I finished adding most of the info and pictures and such to it.

 I guess I'll go do that now.


----------



## tomb

Quote:


  Originally Posted by *Picodeloro* /img/forum/go_quote.gif 
_Hi:

 The application notes of the Auricap web put "In signal path applications the black lead is "in" and the red lead is "out". " and "In power supplies the black lead should be connected to ground and the red lead to the + or – voltage".

 I think that C8 and C9 is in the signal path, if we see the photos of the amplifier of naamanf or the one of troyhoot, auricaps is in the right direction?

 I want for this positions (C8-C9) 0.22mfd/200v Auricap, what caps you advise me for C2L/R and C7L/R?_

 

Yes, he's put the Auricaps in the right direction. So did Troyhoot, where he had the Auricaps pointing up, the green side was on top.

 C2L/R should be 1000uf. We've spec'd 16V, but it may be possible to run less than that. The voltage going through that part of the circuit is less than 6V from some of our measurements. Don't know if it stays at that under every case, though.

 C7L/R should be 470uF and 35V minimum.

 Standard boutique caps are recommended for these positions:
 - Nichicon Muse ES (my favorite),
 - Nichicon Muse KZ,
 - Elna Cerafine or Silmic RFS, or
 - Black Gate - N, NX preferred. 
 That said, several MAX builders have used the standard, quality power caps such as the Nichicon UPW, Panasonic FC, or Panasonic FM. The fact that all of these caps are bypassed with film caps helps to level these differences to a certain extent and good sound is the result even if the boutique electrolytics are _not_ used.

 In selecting the boutique electrolytics, you may find height is the determining factor. In that regard, the ES's and the BG's have an advantage - they are shorter in the desired sizes. (The BG for C7 is actually a 680uF, 35V NX that's only 25mm high.)


----------



## tomb

Quote:


  Originally Posted by *odoe* /img/forum/go_quote.gif 
_I'll get pics up tomorrow, but something is wrong with my build. I can't even get it to power on, even after bypassing the fuse. Not sure what's wrong, but I'll delve deeper into it tomorrow.
 Thanks folks._

 

Yes - bring those pics! Don't worry - we'll be here to figure it out, one way or another.


----------



## c0nsumer

Metering peak inrush current on my Millett Hybrid Maxed
 along with a Sony Playstation SCPH-1001 CD player.
 Also, beer (Michigan Brewing Company's Pale Ale, specifically.)

 Well, it seems that joneeboi and tomb happened to come across my write-up on the Millett Hybrid Maxed a little earlier than I had originally anticipated. Not that I mind, though. Additionally, thanks for the nice comments about it.

 For those of you who haven't seen those posts I figured I'd just mention, and sort of officially announce, the write-up I did on my experiences with my assembly of the Millett Hybrid Maxed.

 Most of the time when I build something a bit in-depth, be it from a kit, partial kit, or a new creation, I try to write up a bit of info about it. This info is generally just an amalgamation of my notes, thoughts, and pictures, but I find that other people end up finding them useful. I also personally like to use them for reference materials.

 I'm not exactly new to DIY-ish electronics, having done a bunch of music related things (Sequentix P3, whole new hardware design for the MIDIbox SID called the MIDIbox SID-NUXX, x0xb0xes) an a bunch of other crap. (Visit nuxx.net if you are really bored/interested.)

 Anyway, I'd never made a headphone amp nor done much with tubes, so when I saw the MAX it looked like a pretty easy first headphone amp, so I acquired parts for me and kitted up some for a friend in the UK. He just got the parts today and began working on his (it'll be in some manner of different enclosure).

 The result? I've got a headphone amp that I rather like and the write-up on it was done. I just added the power consumption section tonight, which is what I was waiting on before posting it here.

 I've also got a bunch of photos about it here if you are interested.

 (Before anyone asks, that Playstation there is the niche audiophile favorite SCPH-1001 I finished adding play/pause, stop, prev, next, rw, and ff buttons to tonight. Except for in my LiveJournal I haven't written anything up about it yet. Although there are a bunch of photos from this project here, though. I'm also not so sure of how good it actually sounds yet. It _seems_ nice, but more listening and possibly objective testing is needed.)

 Oh, and finally, if you see any errors or things that should be corrected on that MAX write-up, please contact me and let me know. Most of that was just thrown together over the past weekend, and it has received minimal polishing / adding this week, so it's likely still a bit rough.

 -Steve


----------



## tomb

Quote:


  Originally Posted by *c0nsumer* /img/forum/go_quote.gif 
_Oh, and finally, if you see any errors or things that should be corrected on that MAX write-up, please contact me and let me know. Most of that was just thrown together over the past weekend, and it has received minimal polishing / adding this week, so it's likely still a bit rough.

 -Steve_

 

It's an outstanding job - unbelievably so from someone who wasn't intimately involved in the history.

 I hope that's a good microbrew from your extensive list that you used to toast your completed MAX - the head could be better, though.


----------



## c0nsumer

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_I hope that's a good microbrew from your extensive list that you used to toast your completed MAX - the head could be better, though. 
	

	
	
		
		

		
		
	


	








_

 

Hehe... Naw... That one isn't particularly special. It's Michigan Brewing Company's Pale Ale. It's really... meh. Not bad, by any stretch, but not great. I'm actually waiting until a better night when I can crack open something top-notch, hook the MAX up to the DVD audio player (that Oppo DV-970HD sounds really good for being as cheap as it is) and get lost in a dark room, some music, and tasty beer.

 Got any suggestions for anything in particular? I'm not sure how much of what is distributed by you is here, but I'm sure there's some crossover. (Beyond DFH, Rogue, etc.)

 For now it's bed time for me, though. 
	

	
	
		
		

		
		
	


	




 Goodnight...

 (Also, hoppier beers have more oils which kills head, and this is a run of the mill 5% or so, and the lower amount of malt keeps it less viscous. Thusly, no good head. 
	

	
	
		
		

		
		
	


	




 I could really use a good oatmeal stout or something where the glass is coated with foam by the time I'm done. Especially now that it's getting cool in the evenings... Mmm...)


----------



## Ferrari

Quote:


  Originally Posted by *Picodeloro* /img/forum/go_quote.gif 
_Hi:

 The application notes of the Auricap web put "In signal path applications the black lead is "in" and the red lead is "out". " and "In power supplies the black lead should be connected to ground and the red lead to the + or – voltage"._

 






 Huh ... Auricaps are metalized polypropylene capacitors and this type of capacitor is NON-polar (does not have + / - poles like electrolytics capacitors) => it doesn't matter how to mount this type of capacitor. 

 In my humble opinion, the Auricap application notes is very questionable 
	

	
	
		
		

		
		
	


	




 ?
 I have been in electronics for more than 20 years (as college student, engineer and now as DIY-junkie) and have never seen "polar metalized polypropylene capacitors".


----------



## amphead

Yes, I agree. Film caps are of the non-polarized variety almost exclusively. He is in the learning mode, and is in one of the best places to do that.


----------



## amphead

Well, I took my MAX on its first road trip. I wanted to have my brother-in-law evaluate the design. He was an audio engineer by trade, but is now moving from electronic design manager at a major elevator control firm to a vice-president position. He is one of those jaded types that doesn't like anything. So I set-up the MAX with some good tunes and he did a quick analysis. He was impressed! He was tapping his foot, bobbing his head and humming. I think he was in a state of musical hypnosis.We have a winner!


----------



## Picodeloro

Quote:


  Originally Posted by *Ferrari* /img/forum/go_quote.gif 
_In my humble opinion, the Auricap application notes is very questionable 
	

	
	
		
		

		
		
	


	




 ?
 I have been in electronics for more than 20 years (as college student, engineer and now as DIY-junkie) and have never seen "polar metalized polypropylene capacitors"._

 

Yes, I think the same, but some audio brands put a signal direction in some components, like film caps or cables and I don't understand it.


  Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Yes, he's put the Auricaps in the right direction. So did Troyhoot, where he had the Auricaps pointing up, the green side was on top.

 C2L/R should be 1000uf. We've spec'd 16V, but it may be possible to run less than that. The voltage going through that part of the circuit is less than 6V from some of our measurements. Don't know if it stays at that under every case, though.

 C7L/R should be 470uF and 35V minimum.

 Standard boutique caps are recommended for these positions:
 - Nichicon Muse ES (my favorite),
 - Nichicon Muse KZ,
 - Elna Cerafine or Silmic RFS, or
 - Black Gate - N, NX preferred. 
 That said, several MAX builders have used the standard, quality power caps such as the Nichicon UPW, Panasonic FC, or Panasonic FM. The fact that all of these caps are bypassed with film caps helps to level these differences to a certain extent and good sound is the result even if the boutique electrolytics are not used.

 In selecting the boutique electrolytics, you may find height is the determining factor. In that regard, the ES's and the BG's have an advantage - they are shorter in the desired sizes. (The BG for C7 is actually a 680uF, 35V NX that's only 25mm high.)_

 


 Excuseme but I don't understand it...

 In the CA8L/R I thought that the signal path direction is "in" in the nearest position to RB11L/R and "out" to RB14L/R, and in the amp of naamanf I see the "red" lead in the "in" position.

 In the CA9L/R, what's the direction of the signal path?, gnd to tube?, tube to gnd?


----------



## amphead

ruZZ.il: Are you sure the bottom of your board wasn't wave soldered? Some very artistic iron work! My board works good, but I bend my leads for mechanical strength and that makes it strong but not that visually appealing. I nominate you as the winner for the best soldering job! I apologize to some other builders in advance, but his build quality just rocks!


----------



## ruZZ.il

Hey, thanks 
	

	
	
		
		

		
		
	


	




 I just try to snip the leads as flush as possible.. and my flat nose (?) cutter kind of sucks. I even ended up taking some components out and snipping another fraction of a mm before soldering. My iron also sucks, and I just use decent solder, very thin. I get a little more of a buldge than I'd like. I had plenty of time cause I had to wait for another bit here and there, too. Its actually not at perfect as it seems from directly above though, although, most joints are smooth and rounded (still slightly bulgy, and not as flat as I like..).. I also cared a lot less for joints not in any signal applications.. like the e12 bit, bits of the p.s.. etc.. its what a few classes on point charge accumulation did to me 
	

	
	
		
		

		
		
	


	




 Meanwhile, I'm learning $h17loads of cool stuff around here from everyone else 
	

	
	
		
		

		
		
	


	




 I<3DIY.....

 Also, I don't always get it to flow through to the other side perfectly. It often either doesn't seep through enough, or seeps through too much. I've seen some others here that that the seeping through seems a lot more consistent. I'm guessing its got to do with my solder and iron.. any suggestions?


----------



## tomb

Quote:


  Originally Posted by *Picodeloro* /img/forum/go_quote.gif 
_Excuseme but I don't understand it...

 In the CA8L/R I thought that the signal path direction is "in" in the nearest position to RB11L/R and "out" to RB14L/R, and in the amp of naamanf I see the "red" lead in the "in" position.

 In the CA9L/R, what's the direction of the signal path?, gnd to tube?, tube to gnd?_

 

I think if you research what Auricap says, if _polarity_ is specified, then red goes to positive and black to negative.

 In the case of the Millett MAX, yes - these are in the signal path - but primarily, they are bypasses to the electrolytics in the adjacent positions. If you look at the schematic, the polarity and the _positive_ end of the cap is clearly indicated:





 This means the red lead goes toward the RB10/RB11 end and the black lead goes toward the RB14 end. This is actually intuitive, since *red means positive* is a worldwide convention.

 The same applies to the cathode bypass position - the black lead goes toward the screw, which is the _negative_ ground.

 Ultimately, however, Ferrari is correct - it's probably just a marketing ploy by Audience.


----------



## odoe

Ok, so tried a few things when I got up this morning. I decided to do what made sense and followed the current. I tested each point from where the power comes in to see where it might dip or stop and I found something.
 I made diagrams to help 
	

	
	
		
		

		
		
	


	




 Something is wrong with CR3D and DR1D. There is current at the top line, but it doesn't seem to be flowing through each component into the other areas. (refer to diagram). 










 This diagram here shows where flow from one point to the next, as I would have expected. The non-arrow lines show where I have current at the top, but it doesn't make it over to the bottom.





 I don't know if that means that both, or just one component is bad. I don't see how a ceramic cap can be bad, but I guess you never know. The diode could be bad I guess, but I would expect to see some current at it's bottom point if the ceramic cap was ok. I went through and reflowed the solder on both components and no change. I checked, they are not backwards. Ceramic caps are non-polar, as far as I know and diode direction matches with board.
 At least I know it's not the fuse 
	

	
	
		
		

		
		
	


	




 If anyone has any ideas, I'd appreciate it. I've waited this long to put my MAX together, if I have to order more ceramic caps and diodes, I can wait a little more. I'm off to work, but I can troubleshoot more when I get home.


----------



## Picodeloro

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_This means the red lead goes toward the RB10/RB11 end and the black lead goes toward the RB14 end. This is actually intuitive, since *red means positive* is a worldwide convention.

 The same applies to the cathode bypass position - the black lead goes toward the screw, which is the negative ground.

 Ultimately, however, Ferrari is correct - it's probably just a marketing ploy by Audience. 
	

	
	
		
		

		
		
	


	


_

 

Yes, I know "red means positive", but Audience put red lead in positive positions in the supply, and opposite in the signals, and that has confused to me.

 I have the same problem with the "YBA Diamond Interconnect" cable, YBA tell that this is a directional cable?¿?¿?







 Many thanks tomb


----------



## MrSlacker

Hey guys. Does anyone have any Cerafine caps they are willing to sell? I got everything except caps...


----------



## tomb

Odoe,

 Measuring DC across snubber caps is only going to give your the voltage difference across the traces - same for the rectifiers, but those may be a problem. You should definitely read DC across the traces straddling DR1D.

 I am curious, though. What do you get if you measure* AC* at the two pads shown below?


----------



## odoe

Thanks tomb. I'll try that when I get home. I should have probably said that I measured AC at all points by hooking up one lead from my dmm to a lug on the power socket and touching the solder points on the board with the other the other lead. So if I had the lead on the +lug of the socket, I measured the points where the - current was going and vice versa. My AC current was around 26-27 and even 29 a couple of times. I'll try those two points when I get home.


----------



## tomb

Quote:


  Originally Posted by *odoe* /img/forum/go_quote.gif 
_Thanks tomb. I'll try that when I get home. I should have probably said that I measured AC at all points by hooking up one lead from my dmm to a lug on the power socket and touching the solder points on the board with the other the other lead. So if I had the lead on the +lug of the socket, I measured the points where the - current was going and vice versa. My AC current was around 26-27 and even 29 a couple of times. I'll try those two points when I get home._

 

OK, I see. Well, you are correct that the DR1D rectifier may be suspect. Again, keep in mind with the traces going all that length, you may still reading current through any number of the components that bridge those traces. Ultimately, the little ceramic snubber caps are trivial and not critical to the circuit - you can simply delete them with little effect. The rectifier is a different matter - it is a critical component. However, if you just lose one, you'd still have a half wave of DC on that side, so your power voltage would still be something other than zero.

 You might try reflowing those joints - they still look a little cold. Also, more pics of the overall power supply might help. The truth is, in the realm of possibilities a bad rectifier is _very_ improbable. It almost never happens unless some real damage/breakage has occurred.


----------



## joneeboi

Greetings knowledgeable MAX builders,

 My shipment from Mouser just got in and I got a new wallwart. After running it a while all the heatsinks are pretty warm and so are the tubes (some are actually pretty hot). Running off my ZVM lineout and some Air Canada headphones, when I turn the volume up to the MAX I can hear a humming, and very, very quietly the music kind of whispering. I checked the voltage across most of the components except the transistors (QA1/2, VREG, QM1/2, QB1/2/3/4/5/6/7/8/9) and trimmers (RA1, RR1, RB12). There doesn't seem to be any solder bridges so far, but I really cannot figure out what is going on here. I will post pictures sometime today.


----------



## vixr

this may be dumb, but is your source turned up?


----------



## tomb

Quote:


  Originally Posted by *joneeboi* /img/forum/go_quote.gif 
_Greetings knowledgeable MAX builders,

 My shipment from Mouser just got in and I got a new wallwart. After running it a while all the heatsinks are pretty warm and so are the tubes (some are actually pretty hot). Running off my ZVM lineout and some Air Canada headphones, when I turn the volume up to the MAX I can hear a humming, and very, very quietly the music kind of whispering. I checked the voltage across most of the components except the transistors (QA1/2, VREG, QM1/2, QB1/2/3/4/5/6/7/8/9) and trimmers (RA1, RR1, RB12). There doesn't seem to be any solder bridges so far, but I really cannot figure out what is going on here. I will post pictures sometime today._

 

Measure your voltages at all the test points, first. If those are OK, then re-check your input/output connections. What you describe can sometimes occur if the input lines are crossed with the ground. (BTW - the tubes should be to hot to touch - that's normal.)


----------



## joneeboi

vixr:

 I was using the ZVM's lineout, so it's as loud as can be (as far as I understand lineouts to work). I was just listening to some music on it through my SI T-amp, so that's working fine.

 tomb:

 The test points all work fine. V+ and GND still give me 26.5VDC max but I suspect that I can tune this with RR1(?). DBs are operating pretty warm at 85mV, tubes at a healthy 13.3V. And when you mean input and ground are crossed, do you mean the wire for ground is actually hooked up to signal and signal is hooked up to ground?


----------



## Ferrari

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_... - it's probably just a marketing ploy by Audience. 
	

	
	
		
		

		
		
	


	


_

 

Yes, definitely ! On the same application notes, Audience also writes _"Do not use bypass capacitors in the signal path"._

 If we blindy follow their application notes... no one of us should consider to buy Auricaps and put them on the critical positions of our MH Max 
	

	
	
		
		

		
		
	


	




 . (I wouldn't recommend anybody to follow this notes blindy! ). We all know the truth... 
	

	
	
		
		

		
		
	


	




 .


----------



## tomb

Quote:


  Originally Posted by *joneeboi* /img/forum/go_quote.gif 
_tomb:

 The test points all work fine. V+ and GND still give me 26.5VDC max but I suspect that I can tune this with RR1(?). DBs are operating pretty warm at 85mV, tubes at a healthy 13.3V. And when you mean input and ground are crossed, do you mean the wire for ground is actually hooked up to signal and signal is hooked up to ground?_

 

Yes - possibly - either on input or output. If you have proper voltages - and you do - that's the only explanation, IMHO. Something's messed up in your input/output connections.

 I once had a horrible intermittent DC spike - buzz ... or so it seemed. Upon inspection, the signal ground wire had worked itself halfway out of the input terminal block. I've also panicked after building an amp and only getting weak sound out of one channel - the input wires were crossed.


----------



## pinkfloyd4ever

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_C2L/R should be 1000uf. We've spec'd 16V, but it may be possible to run less than that. The voltage going through that part of the circuit is less than 6V from some of our measurements. Don't know if it stays at that under every case, though.

 C7L/R should be 470uF and 35V minimum.

 Standard boutique caps are recommended for these positions:
 - Nichicon Muse ES (my favorite),
 - Nichicon Muse KZ,
 - Elna Cerafine or Silmic RFS, or
 - Black Gate - N, NX preferred. 
 That said, several MAX builders have used the standard, quality power caps such as the Nichicon UPW, Panasonic FC, or Panasonic FM. The fact that all of these caps are bypassed with film caps helps to level these differences to a certain extent and good sound is the result even if the boutique electrolytics are not used.

 In selecting the boutique electrolytics, you may find height is the determining factor. In that regard, the ES's and the BG's have an advantage - they are shorter in the desired sizes. (The BG for C7 is actually a 680uF, 35V NX that's only 25mm high.)_

 

I'm sure it's been said before, but could you or anyone else discuss the audible differences between these common botiques, as well as the other potential boutique caps and resistors? I tried searching the thread and got mostly stuff I wasn't looking for, and I didn't see anything discussing audible differences b/t different boutique options on the MAX site. If someone knows where to find it, a link is good too. Thanks


----------



## odoe

It just occured to me after looking over some things while at work, that all my trimmers are installed reverse of the silk screen, but I turned them all full clockwise. After reading consumers wiki, it hit me. I hope my problem is that simple. Chalk that one up to a bonehead move. I'm armed with layouts and schematics, almost ready to troubleshoot.


----------



## tomb

Quote:


  Originally Posted by *pinkfloyd4ever* /img/forum/go_quote.gif 
_I'm sure it's been said before, but could you or anyone else discuss the audible differences between these common botiques, as well as the other potential boutique caps and resistors? I tried searching the thread and got mostly stuff I wasn't looking for, and I didn't see anything discussing audible differences b/t different boutique options on the MAX site. If someone knows where to find it, a link is good too. Thanks
	

	
	
		
		

		
			



_

 

Dsavitsk's Notes on Output Coupling Capacitors

 I can only help you in general terms from there, based on other posts that Dsavitsk has made and my limited experience. I will tell you that my limited experience tracks very well with Dsavitsk's opinions.

*Electrolytics*
*MUSE ES -* these are the kings of bass. Their highs are not as resolving as others, but with a good bypass, they can sing. I also have them bare in an Alien DAC and they seem to do both well without any help - actually preferring them to an identical DAC with Black Gates. The slam and deep extension is incredible.

*MUSE KZ's -* Admittedly, I have little experience with these. They've usually been so large that I've made other choices to keep case heights in reason. Nichicon lists them as their best audio choice. Dsavitsk has said - if I remember - they tend a little toward the hard side on the highs. If that's true, then they may pair very well with tubes. There are many MAX builders who've already used them - perhaps they'll chime in and give us their impressions.

*ELNA Silmics -* These are the latest versions of ELNA Cerafines. Prized for their similarity to Black Gates but at a much lower price, some of the latest statements I've read about them indicates that they may trade rolled off highs for smoothness. Still, it's a pretty sure bet that they sound better than the typical Nichicon UPW, Panasonic FM or FC's (in the signal path). I think I've read that some prefer them in the Alien DAC. Again, there are several Millett builders who've used them and perhaps they can relate their impressions.

*Black Gates -* Super rich, super detailed, and very dynamic. They can make a relatively flat pre-digital rock recording sound as dynamic as a modern digital one. There is nothing better. Still, they don't seem to have as much bass extension as the ES's to me.

 EDIT: Of the electrolytics, the ES's and the BG's are the shortest in the recommended ratings. They will allow the use of 1" sinks and mounting the board in the 3rd slot of the recommended Hammond case.

 As for the film bypassing, there are so many choices it's hard to keep up. Again, I encourage you to research Dsavitsk's capacitor reviews. I believe he's also got quite a few posts here and in the Alien DAC thread. Some of the things - if memory serves - that he recommends in pairing with the caps above (at least the ES's and BG's):

 1. *Sonicap GEN II's for the ES's.* This review is on Dsavitsk's web site. According to his statements, one might deduce that this pairing with ES's results in a sterling combination: not adversely affecting any of the bass, but opening up the combo with sterling highs.
 2. *Vitamin Q's for the Black Gates* Contrary to popular opinon, Dsavitsk says the VitQ's are fairly neutral. So, they pair well with BG's, refraining from traditionally rich film caps that may end up making the BG's sound syrupy.
 3. *0.47, 50V BG's* These are also a good bypass option for BG's, according to reports. I believe Nate Maher stated that this was how he build his ultimate revMH Millett Hybrid. I believe the technique is to follow the logic of the Black Gate "Super E" method, which connects the small bypass in opposite polarity from the larger caps they are bypassing. 'Course, the BG's in consideration are supposed to be the N, NX type, which are bipolar.
 4. *Auricaps* test out in Dsavitsk's reviews as having both rolled off highs and rolled off lows. That seems quite a price to pay for its infamous mid-range bloom. I think Dsavitsk has stated he would rather use almost any film cap than an Auricap. That may be an exagerration on my part and I'm nor trying to start anything - only relating what I've read and heard.
 5. *Wima MKP10 -* There is nothing wrong with these in a basic configuration. Following Pete Millett's original strategy, they can even make standard power caps like Nichicon UPWs, Panasonic FM's and FC's sound pretty good in the MAX. They are certainly the economical choice, although the Sonicaps are pretty close.

 Of course, most of this is gleaned from memory, so IMHO and YMMV x10!

 P.S. The Jupiters and the Mundorf Silver Oil are at the top of Dsavitsk's rating. However, I personally believe the Jupiters are inappropriate for most MAXes - the temperatures are simply too high. Also keep in mind that ultimately, the MAX is a hybrid - pairing the best in discrete solid state output stage with a tube gain stage. So, to a certain extent, _flavoring_ with a very expensive boutique may have quickly diminishing returns.


----------



## tomb

Quote:


  Originally Posted by *c0nsumer* /img/forum/go_quote.gif 
_Hehe... Naw... That one isn't particularly special. It's Michigan Brewing Company's Pale Ale. It's really... meh. Not bad, by any stretch, but not great. I'm actually waiting until a better night when I can crack open something top-notch, hook the MAX up to the DVD audio player (that Oppo DV-970HD sounds really good for being as cheap as it is) and get lost in a dark room, some music, and tasty beer.

 Got any suggestions for anything in particular? I'm not sure how much of what is distributed by you is here, but I'm sure there's some crossover. (Beyond DFH, Rogue, etc.)

 For now it's bed time for me, though. 
	

	
	
		
		

		
		
	


	




 Goodnight...

 (Also, hoppier beers have more oils which kills head, and this is a run of the mill 5% or so, and the lower amount of malt keeps it less viscous. Thusly, no good head. 
	

	
	
		
		

		
		
	


	




 I could really use a good oatmeal stout or something where the glass is coated with foam by the time I'm done. Especially now that it's getting cool in the evenings... Mmm...)_

 

I missed this earlier ... it's off topic, but as long as this thread is, it can't hurt too much.

 I'm an IPA man myself, although not as much anymore as in the past. 
	

	
	
		
		

		
		
	


	




 Micro breweries are one of the best things to happen to America in the last few decades. I regularly ask for a local microbrew when I travel - what better way to sample the local flavor? In Atlanta, Sweetwater Brewing makes a bunch of good stuff - I like their IPA and Pale Ale when I can't get the IPA. Dogwood Brewery also made some really good IPA, but I can't find their stuff as much anymore - I'm afraid Sweetwater has blown them away in the market around here. Of course, there are many great IPA's all over the country now. 
	

	
	
		
		

		
		
	


	







 Again - sorry for the off-topic diversion.


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## odoe

Ok, so I'm home now and I'm trying to troubleshoot away here.

 I tested the AC at the points tomb suggest and I get a reading of 21.7. I reflowed the solder on those rectifiers and still no go. Since I noticed that my trimmers are backwards of al the silkscreen, I turned all my trimmers full counter-clockwise and still no go when i power up.

 I took some pics which I'll link, because it's a lot.
 At this point, I'm not sure where else to test or measure.
http://www.odoe.net/mine/audio/max_troubleshoot_4.jpg
http://www.odoe.net/mine/audio/max_troubleshoot_5.jpg
http://www.odoe.net/mine/audio/max_troubleshoot_6.jpg
http://www.odoe.net/mine/audio/max_troubleshoot_7.jpg
http://www.odoe.net/mine/audio/max_troubleshoot_8.jpg
http://www.odoe.net/mine/audio/max_troubleshoot_9.jpg

 At least it looks good 
	

	
	
		
		

		
		
	


	

















 Thanks folks. I'd appreciate any help.


----------



## tomb

I know you're having trouble, Odoe, so I apologize - EDIT: Never mind - I misread you - it looks all you did was rack the screws one way and then another.

 Please let me study what you've got and I'll get back to you - nothing obvious so far in the images that appear in the post. A reading of 21.7VAC seems low, but there's been some voltage drop there already from the rectifiers. What do you read right off the screws on the terminal block?

 Meanwhile, let me look at the links to the other pics and I'll get back to you.


----------



## odoe

Thanks tomb.
 My only concern on the trimmers was that I had left them open full and burned something out, but I think I found it. I had a bad solder joint on the vreg. It was almost impossible to tell until I got my flashlight out. It turned on!!!

 Time to bias.

 I have to say thank you for your patience!
 Also, one thing I love about the DIY, is the learning experience. It's the most fun. Time for biasing.


----------



## ruZZ.il

mmm does look good those orange drops look mighty mighty 
	

	
	
		
		

		
		
	


	




 one thing I do see though, is that you've soldered a lot before trimming the leads.. it could get risky if any bend and short with others.. I'd suggest trimming it all and rechecking the solder, check for any solder that may have flowed over to ground or something, on both sides. your trimmers look good though.. if they're the standard bom ones, I think clockwise is minimum. you really need to have a dmm or 2 hooked up to the db test points, and see if they respond to trimming.. try get a shot of the back, from directly above the back.. meanwhile, 4am for me.. so zzz.. but we'll see..

 edit: looks like you're getting somewhere
	

	
	
		
		

		
		
	


	




 I'd still trim those leads.. thats risky ****. and dont power up for long before you got the trimmers right! I think clockwise is where you should be staring ?


----------



## tomb

As for screwing the trimmers - the voltage trimmer is not a zero adjust. So, if you've got any power at all, you should be reading voltage at V+.

 Is there any possibility that you could have CR4 or CR5 reversed in polarity or reversed with each other? Those items often cause trouble in a TREAD or STEPS.

 BTW - I appreciate all the effort at the photos of the PS - those are very helpful - I think - still studying them ...


----------



## odoe

Yeah, I left the trimming of leads for last because it would be easier for me to desolder them if I had to that way. I'm now getting 26.5v DC at test points. Thanks so much guys.


----------



## ruZZ.il

keep your eyes more on the DBs! dont want them burning out.. like mine


----------



## tomb

Yes - I misread what you had done with the trimmers - sorry about that.

 Glad you found your issue!! However, I would not have guessed a bad solder joint on the VR.

 Be careful biasing those BJT's. Let us know how you're doing. Good luck!


----------



## odoe

So.
 Dumb question.
 Which range of the cenntech dmm do I use to measure bias?
 The DC volt range? I can have it on 20 or 200 dcv on the dmm and I get a reading of about 7 for tb2 and 3.5 for tb1.

 I just realized those numbers are pretty high. I was measuring wrong, my bad.


----------



## ruZZ.il

more like 2v dc or basically, the lowest dcv setting. you should be measuring less than 100mv (0.1v) to begin with.
 you may need a more sensitive/accurate dmm if it only does 20/200.


----------



## odoe

It does less. It's just to orange drops block all my test points from the top, so I have to measure from below and got confused. I'm biasing right now, and I threw some cheapie headphones on to try and no buzz, hum or other audible oddities. Music sounds good too. I'm probably going to shoot for 90mv and let it run all night to burn in.

 heehee, i feel giddy


----------



## joneeboi

Time for troubleshooting fun!




















 Power Supply





 Right Channel





 Left Channel





 Deeeeeeeeeeeeeeeeeeeeeeelaaaaay!













































 What lurks inside the jack?


 While I have your attention, where does an Edmontonian find heatsink goop either locally or otherwise? I've checked the Rona and Canadian Tire and The Source by Circuit City, but not much luck.


----------



## tomb

Joneeboi,

 Your problem is the phone jack you are using for input!! You have the input wires soldered to the left side of the jack. Those contact points on the left side are _switched out_ when there's a plug plugged into the jack.


----------



## tomb

Quote:


  Originally Posted by *odoe* /img/forum/go_quote.gif 
_It does less. It's just to orange drops block all my test points from the top, so I have to measure from below and got confused. I'm biasing right now, and I threw some cheapie headphones on to try and no buzz, hum or other audible oddities. Music sounds good too. I'm probably going to shoot for 90mv and let it run all night to burn in.

 heehee, i feel giddy_

 

I may be too late in stating this, but don't leave it running all night to burn in. The cheapie headphones are a great idea, but I wouldn't leave it unattended overnight. There's too much that can go wrong until you've lived with it a few days. It takes a good hour or two before you can even say with certainty that the DB bias doesn't move. Just a suggestion.


----------



## mb3k

Quote:


  Originally Posted by *joneeboi* /img/forum/go_quote.gif 
_While I have your attention, where does an Edmontonian find heatsink goop either locally or otherwise? I've checked the Rona and Canadian Tire and The Source by Circuit City, but not much luck._

 

Go to MemoryExpress and pick up some ArcticSilver. Or any other computer shop.


----------



## ruZZ.il

joneeboi, I recently bought 50 little insulation pads that go between the heatsink and the BJT's/VReg I could send you 5 of them if you like.. you could use basically any heat sink compound with them.. or even go without. also, try cleaning up the flux a bit more. the little bits of solder that are on the board can just be picked off with your nail when the board is soaking in some solvent. I didnt have anything better to clean with that 95% alcohol from a chemist.. used an old toothbrush rigorously.. and again and again. alcohol leaves a sticky residue though, so when I was done I used a bit more alcohol, then used a mildly damp cloth to wipe it off.. then some glasses cleaner  (there are better options than alcohol) but everything looks right, I guess 
	

	
	
		
		

		
			





 change that jacks contacts around that tom picked up (I'd probably have missed that
	

	
	
		
		

		
		
	


	




) and careful with the biasing! (plenty has been posted here bout that..) and.. woohoo! 
	

	
	
		
		

		
		
	


	




 let us know how it goes


----------



## thunder

Looking at different option's, what are good some product's, methods and technique's used in flux removal cleaning & care of PCB's ?


----------



## joneeboi

tomb:

 ...that's it? *blank stare*

 *hangs head and cues Charlie Brown Christmas theme*

 I will try that input jack switch-up sometime later today.

 ruZZ.il:

 Sure, I'll take you up on that offer. YGPM. I'll clean up that flux when I'm completely finished. Then time for unoriginal casework! Huzzah!


----------



## headphonejunkie

I use isopropyl alcohol and a small brush. This can get messy though . Then I find myself really cleaning off the whole board with alcohol. I am not sure if there is a perfect and great way to clean of flux. I am open to suggestions too.I suppose if you try to minmize the area where you are cleaning the flux residue should stay localized until you can remove it all.


----------



## tomb

I've tried some of the commercial flux cleaners - they're no better than $1/qt 90% isopropyl and the fumes are worse, to boot - IMHO.

 A large board like the MAX may take a half dozen rinses or more. You're essentially trying to dissolve the rosin, but it has nowhere to go unless you continue to dilute with rinse after rinse. I typically get a plastic bowl, about a half cup of alcohol and an old toothbrush. I use the toothbrush to dip into the alcohol and spread it so that the board is completely covered. Let it evaporate, then do it again - until the white stuff is gone and the board is shiny. The action of dissolving the flux and transferring it from toothbrush to cup is about the only thing that gets rid of it.

 Something like the Alien DAC might be clean in 2 or 3 rinses. The MAX board will take quite a bit longer, most likely.


----------



## ruZZ.il

Quote:


  Originally Posted by *thunder* /img/forum/go_quote.gif 
_Looking at different option's, what are good some product's, methods and technique's used in flux removal cleaning & care of PCB's ?_

 

Try taking a look at Tangents Tutorials, specifically #5. but tom basically summed it up


----------



## joneeboi

She LIVES! I'll call her Maxine.

 For real this time.


----------



## c0nsumer

Quote:


  Originally Posted by *headphonejunkie* /img/forum/go_quote.gif 
_I use isopropyl alcohol and a small brush. This can get messy though . Then I find myself really cleaning off the whole board with alcohol. I am not sure if there is a perfect and great way to clean of flux. I am open to suggestions too.I suppose if you try to minmize the area where you are cleaning the flux residue should stay localized until you can remove it all._

 

A while back I did a write-up on how I remove flux from PCBs. If you want to read it, it can be found here:

Flux Removal

 More specifically, what I did for the MAX soldered with a lead-free solder with Kester 331 (and 2331-zx) was as follows:

 - Solder down everything except the volume pot and one of the two center heatsinks. Also leave out other non-sealed parts if you have any. For the MAX I also left the MOSFETs off at this stage, because I didn't want water seeping in between them and the insulating film via capillary action.
 - Scrub the board down with warm tap water and a toothbrush. (I do this in the laundry tub.)
 - Rinse the board thoroughly.
 - Rinse the board with distilled water.
 - Dry the board with a combination of hot air (to dry faster) and compressed air (to get water out of small crevices).
 - Solder the volume pot, fit all the MOSFETs (BJTs would also apply here) and final heatsink.
 - Use a towel dampened with distilled water to remove the new bits of flux.

 This is similar to what is used in many test labs, except they'll often have an automated system which is water with cleaner, plain water, then deionized water.

 Also, I'm not sure if it was noted here already, but I've seen flux conduct just enough to trigger FETs and other parts, causing all sorts of problem. Not to mention that flux is generally corrosive...


----------



## odoe

My max lives and oh man, this thing can thump. My HD580's sound awesome!


----------



## tomb

Quote:


  Originally Posted by *odoe* /img/forum/go_quote.gif 
_My max lives and oh man, this thing can thump. My HD580's sound awesome!_

 

Way to go, Odoe! I can't tell you how great it feels to help and see you guys solve the little problems so that you can get the BIG sound. Yes, the MAX can thump with the best of them and can really make those HD580's bounce. Another MAX lives!!


----------



## ruZZ.il

x2


----------



## vixr

I've been listening to mine off and on all day, just letting it run... This is a very enjoyable amplifier. I can't believe I built something this cool...


----------



## ericj

Alright. Almost done, got some problems. 

 The big problem i have is that the left tube won't bias above 8.3v. Right one biases fine. The tubes are a pair with a few hundred hours on them in my revMH, and the problem stays with the socket rather than the tube. 

 What should i look for? Everything looks ok to me. 

 The other problem i have is an inability to bias up the mosfet output - but that's probably because i forgot to order 2n5486's and the highest idss 2n5484 i have just isn't high enough to do anything.


----------



## Pingunugnug

Hi,

 This is my first amp build - noob (I can hear uh-ohs already)
	

	
	
		
		

		
			





 I am pretty much at the point where I have finished populating the board but I am kinda confused about how the heat sink should be mounted on the transistors and vreg. 

 Should there be an insulation pad in between those? 
 From what I have read the answer is yes but:

 - Doesn't the screw that goes though both items conduct.
 > So should I be using nylon screws? (But I see on the MAX site that metal bolts were used. 

 -Doesn't the use of an insulation pad reduce the effectiveness of the heatsink?

 What will happen if I leave it that way?

 Thx


----------



## tomb

Quote:


  Originally Posted by *ericj* /img/forum/go_quote.gif 
_Alright. Almost done, got some problems. 

 The big problem i have is that the left tube won't bias above 8.3v. Right one biases fine. The tubes are a pair with a few hundred hours on them in my revMH, and the problem stays with the socket rather than the tube. 

 What should i look for? Everything looks ok to me._

 

Got to be the CCS circuit. Make sure you have the right resistors in the right place. You might check the transistors, but I think if you had those messed up it wouldn't work, period. Also, make sure you didn't get the trimmer mixed up with one of a different value.

  Quote:


 The other problem i have is an inability to bias up the mosfet output - but that's probably because i forgot to order 2n5486's and the highest idss 2n5484 i have just isn't high enough to do anything. 
 

Yep. That would do it - gotta have the 2N5486.


----------



## tomb

Quote:


  Originally Posted by *Pingunugnug* /img/forum/go_quote.gif 
_Hi,

 This is my first amp build - noob (I can hear uh-ohs already)
	

	
	
		
		

		
		
	


	




 I am pretty much at the point where I have finished populating the board but I am kinda confused about how the heat sink should be mounted on the transistors and vreg. 

 Should there be an insulation pad in between those?_

 

Yes. 
  Quote:


 From what I have read the answer is yes but:

 - Doesn't the screw that goes though both items conduct. 
 

Not if you use the nylon shoulder washer. This is assuming you have a metal tab transistor - some of them are inherently insulated.
  Quote:


 > So should I be using nylon screws? 
 

Absoutely NOT. Nylon will creep under the heat and you'll have a blown transistor on your hands in no time. Mounting transistors and other devices to a heat sink is a common technique. The metal bolt and nylon shoulder washer have been used for as long as there have been transistors:




 The above is taken straight out of the Aavid Heat Sink Catalog. Note that grease is not shown because it's not part of the mounting kit and sold separately. Also, there are silicone pads that do not require thermal grease - "Thermasil" is one. They are more expensive, but it's a trivial cost for one amp and may be cheaper than a tube of grease if you think you will never build another amp.

 Also, it can be advantageous to use a flat washer between the screw head and the shoulder washer. For many transistors that are plastic and have no metal tab, a flat washer should be mandatory - the shoulder washer will probably not fit anyway.

 Finally, note that the orientation of the mounting kit may be reversed - with the screw head on the other side (the shoulder washer should always go on the metal tab side). Again, a flat washer behind the screw head is probably a good practice, regardless.
  Quote:


 (But I see on the MAX site that metal bolts were used. 
 

Right. 

  Quote:


 -Doesn't the use of an insulation pad reduce the effectiveness of the heatsink? 
 

No. A mica insulator combined with heat transfer grease has a higher thermal conductivity than without. "Insulate" is electrically insulated, not thermally.

  Quote:


 What will happen if I leave it that way? 
 

It won't work as well and you may burn up your transistors. This may manifest itself fairly quickly by an inability to hold bias in the circuit, or it may be harder to adjust.

  Quote:


 Thx 
 

 You're welcome - good luck!


----------



## amphead

Congrats Joneeboi and Odoe!!!
	

	
	
		
		

		
		
	


	









 The MAX is an advanced build! You can be proud of your talent and the advancement in building prowess that this project gives! I know that for myself I have built other tube projects, but not at this level of sophistication or sound quality.


----------



## amphead

One of our esteemed colleagues, who shall go unnamed for now anyway, has sent me 6 of the high-end trannies pro bono and unsolicited. When I get them, I will replace the BD139s and BD140s. This reflects the character and heart that most members possess on this forum, especially the DIYers! I am proud to be TEAM MILLETT MAX, and I know many of you are also.


----------



## nysulli

parts finally on order, i've ordered KZ's, ES, and when i make out my mouser order, i might even order silmic's for more swapping fun

 original thoughts of auricaps have been ditched for Gen 2 sonicaps

 parts also ordered for 2 alien dacs (need one for work now) ordered BG's and ES's for that, along with 2 sonicaps for coupling bypass's


----------



## ruZZ.il

I'm happy with those gen II's. I can't pinpoint their contributions though since they're in the only max I've ever heard.
 I need to order some a.dacs soon too. I need to start getting all my lists ready soon for the next time someone I know comes from the states. I have about a month I think. need to think of another amp 
	

	
	
		
		

		
		
	


	







 or maybe my other max. I'll probably either build it for someone per request, or build it for myself if someone wants mine.. so maybe not yet. ~I need to build it build it I need to build it build it!


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## tomb

Some of the brain trust around here have been pooh-poohing the Alien DAC lately. Certainly, the Opus is FOTM without question.

 Yet, the two little Alien's I built in mint tins - one with BG's, the other with ES's - sound as good with the MAX as any source I own. That includes a number of CD players, including an old D model Sony portable (not bad), the Sony D-NE20, a number of iPods, and the M-Audio Transit. The Transit specifically, supposedly tests for better noise numbers, but mine sounds lifeless with a notable lack of detail compared to the Aliens. (The Transit does sound better than all the other things listed.)

 The MAX is very sensitive to sources. I think anything with an opamp in the path is going to suffer going through the MAX. Also, in my experience, most mp3's - even low compression types - sound bad. Either FLAC files played through the Aliens or original CD's played through a PC's drive and the Aliens sound best. 'Course, I don't own any really high end sources like a Rega CD player and such. IMHO and YMMV, of course.


----------



## odoe

On my next MAX, I'm thinking of using sockets in the caps positions and playing around with some cap rolling. I'll never know what I like unless I start trying some different ones out.

 I'm using a basic alien dac at the moment and it sounds great to me. I do have a TC-7510 and a Transit I'm going to play with when I get a spare SPDIF cable though, and a couple of alien dac boards I'm planning to put together with some boutique caps too big for their own good which I want to try too


----------



## nysulli

Quote:


  Originally Posted by *odoe* /img/forum/go_quote.gif 
_On my next MAX, I'm thinking of using sockets in the caps positions and playing around with some cap rolling. I'll never know what I like unless I start trying some different ones out.

 I'm using a basic alien dac at the moment and it sounds great to me. I do have a TC-7510 and a Transit I'm going to play with when I get a spare SPDIF cable though, and a couple of alien dac boards I'm planning to put together with some boutique caps too big for their own good which I want to try too 
	

	
	
		
		

		
		
	


	


_

 

i personally wouldn't socket caps, and others in this thread have posted similar opinions, to much charge imo, if you had to replace a resistor thats come loose thats one thing, but if you grab hold of a cap thats got some charge stored the wrong way you could be in for a little surprise

 not to mention if you use polar caps and accidentally put it in the wrong way


----------



## joneeboi

In case you need ideas where to pick up those boutiques 
	

	
	
		
		

		
		
	


	




 : 

Boutique Capacitors - Where to buy?


----------



## Picodeloro

Quote:


  Originally Posted by *Ferrari* /img/forum/go_quote.gif 
_Yes, definitely ! On the same application notes, Audience also writes "Do not use bypass capacitors in the signal path".

 If we blindy follow their application notes... no one of us should consider to buy Auricaps and put them on the critical positions of our MH Max 
	

	
	
		
		

		
		
	


	




 . (I wouldn't recommend anybody to follow this notes blindy! ). We all know the truth... 
	

	
	
		
		

		
		
	


	




 ._


----------



## kklee

I re-did the Lexan panels on my Millett Max for a bunch of reasons:
 - I wasn't happy with the crooked vent holes
 - Tomb asked me to document the process
 - I didn't like the Neutrick locking jack blocking the internal view
 - I cut the panel a little too short and it didn't fit quite right


----------



## tomb

Wow!


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## thunder

First I must 2end that WOW!!!! Now for anyone like me trying to learn here is some really nice stuff on capacitor's> http://industrial.panasonic.com/www-...A0000PE190.pdf None of the usual hype or sorted market claim's ect...


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## amphead

Thats one mean looking case kklee! The sinister red glow belies its ballsy sonic capabilities!
	

	
	
		
		

		
			











 Edit: Acrylic is one of the most transparent 92% solid material that currently exists, even more than window glass, crystal and diamond! Edit: Lexan is highly transparent and more crack resistant than acrylic.There are specialized optical glass with transparency of 98%


----------



## amphead

First rebias 10 minutes ago. Rebiased left channel, for left tube bias which drifted to 15.3 VDC and right channel tube bias did not drift and measured 13.7 VDC. DB bias did not drift at all from the 48mv left and right that I had them originally. I forgot that the Jensen bypass caps that were installed are 0.1uF. My evaluation on these caps are that they are neutral sounding, but 0.1uF versus 0.22uF moved the frequency response hump slightly towards treble, quite predictably. Eeexxtteennddeeddd Highs! Resolution is pronounced in the treble region. The saliva is quite audible on a singers lips! My next build will use 0.22uF bypass caps per the MAX spec.


----------



## joneeboi

That sounds great, amphead. Now you never mention if that extension is appreciated or not...
	

	
	
		
		

		
		
	


	




 On another note, I thought I'd post my theory on why my earlier wallwart destructo-ed. The second one I ordered after my first busted included a little slip of paper I had not received in the first, "This power unit is intended to be correctly orientated in a vertical or floor mount position." Setting aside the various grammar goofs, I remember plugging this bad boy in upside down; that is, fat side away from the ground (err, the floor). One conclusion is that these bad boys shouldn't be plugged in this way. Then of course, we could spend pages debating what the real meaning is behind those cautionary words, or we could settle with a relatively safe assumption that these power supplies should be only used in a certain way. Again, I have no idea why that really makes any difference (plugging it in "normally" would make it seem as though it were plugged in upside down anyway since it's AC...right?), but my knowledge is limited. Perhaps someone can enlighten me. Anyway, that's my theory: I plugged it in with the wrong pin orientation.


----------



## amphead

The sound with extended highs is an apples and oranges situation. Both sound good. However imagine that you prefer oranges, and you have apples. he he ! On a more serious note: You did not destroy the walwart by installing it in the plug the way you did. The most likely cause of failure was that too much current burned the winding of the transformer open, or an internal fuse(not replaceable) located on the windings. If you really want to avoid problems, you can create your own power supply. It consists of five things 24VAC step-down transformer rated at 40VA, 2A fuse w/fuse holder, spst switch 3A at 250VAC and the input plug/output wiring. It should be mounted inside of a metal project box. This power supply will run forever.


----------



## amphead

Stop the presses! Some astute builder will notice that I biased my DBs for 48mv instead of 48ma. My true intention was to start with about 50ma~66mv. I have now biased the DBs for 66mv. Another evaluation is underway. Quick impression is: midrange boost!


----------



## tomb

Quote:


  Originally Posted by *amphead* /img/forum/go_quote.gif 
_Stop the presses! Some astute builder will notice that I biased my DBs for 48mv instead of 48ma. My true intention was to start with about 50ma~66mv. I have now biased the DBs for 66mv. Another evaluation is underway. Quick impression is: midrange boost! _

 

You're mixing millivolts and milliamps interchangeably.

 E=IR, and the output resistors are 2.2 ohms. Therefore, "E" or in other words, "mV", equals 2.2 x milliamps. Like so: mV = 2.2 x ma. So, if you want 48ma, then you should adjust to measure 105.6mV on your meter (105.6mV = 2.2 x 48ma).

 Some quick numbers you're referencing:

*Meter voltage *............... *ma Bias*
 ..........48mV ................. 22ma bias
 ..........66mV ................. 30ma bias
 ......105.6mV ................. 48ma bias
 .........110mV ................. 50ma bias

 EDIT: Most likely, the DB's have barely kicked in at 22ma bias. Minimum is 66mV - 30ma bias, recommended is 110mV - 50ma bias.


----------



## amphead

You are absolutely right Tom! What I should have said was that I wanted to work my way up to 48ma in steps, starting at 66mv~30ma then after another 24 hours going to 106mv~48ma. I'm still over-cautious of the thermal runaway possibility, if there is such a thing as being over-cautious when it comes to biasing DBs.  Edit: he he, I deserved the ohms law posting, what was I thinking? I was missing alot of sound with the weakly biased DBs. Now Its reeaally kicking in!


----------



## amphead

Slam, dynamic range, drums, guts! Thats what I now have, biased at 103mv left and right channels/DBs. That may be all I need. My head nearly bounces off the wall if you know what I mean!


----------



## amphead

Who's using V-caps in their MAX? Apparently they have a long burn-in, before they sound good. I was thinking that the V-caps could be mounted in a spare amp and allowed to burn-in before being installed in your primary listening amp. I know that teflon dielectrics are highly resistant to heat degradation, and are supposed to be superior sonically to other types. Dsavitsk?


----------



## tomb

Kklee was gracious enough to provide a complete web page with pics about constructing his Lexan see-thru case panels. I was able to add them to the MAX website today:

MAX Construction -> Casework -> Lexan see-thru Option

 Many thanks to forum user Kklee.


----------



## ruZZ.il

x2!
 I'd like to do use that stuff for my top panel.. on quiet a few things.
 meanwhile, I didnt want to use the aluminum yet, so I decided to use some mdf wood that was just lying around.. it actually turned out kinda cool. will add pics.
 I may even varnish it and stuff.. but I still like that lexan stuff. good stuff. respect.


----------



## babbkutz@comcast

as the bias of the DBs is adjusted upward from 70mv to 86mv I'm hearing more midrange grain....am I nuts?


----------



## tomb

Quote:


  Originally Posted by *babbkutz@comcast* /img/forum/go_quote.gif 
_as the bias of the DBs is adjusted upward from 70mv to 86mv I'm hearing more midrange grain....am I nuts?_

 

No. As the DB's kick in with a higher bias, they'll reveal every shortcoming of your amp and system. Most likely, you will hear this if you haven't let the tubes warm up for at least a couple of hours. In some cases, it may never go away - those tubes just may not have a sweet midrange. In other cases, it may be your bypassing capacitors. It can be hard to pinpoint, but it gives you an idea why there is so much emphasis on boutique caps, quality sources, and even higher quality tubes in tube headphone amplifiers.

 Also keep in mind - many people will never hear what you describe even with the most rudimentary components. 9 times out of 10 it's the tubes, anyway.


----------



## odoe

I've been listening to my MAX pretty consistently since I got it up and I've DB biased up to 100mv and tubes at 13.75v with PS at 27.5v. My music has a lot more clarity over my pimeta and I don't know the proper terminology, but the music is very "airy", not in a distorted sense, but almost like it has more breathing room. It's also like some of the bass is "blowing" at me. I like it a lot.


----------



## tomb

Nice going Odoe! Glad you solved your problems and that you've been sharing time for awhile now with a living MAX! Yes, a properly tuned MAX can be quite impressive and your terminology is just fine.


----------



## Pingunugnug

I finally finished the enclosure side panels (have some minor clearance problems, that can be fixed with an exterior fuse holder); got to setup last night and the first flick of the switch the fuse blows. I bypassed it and so far it hasn't have smoke come out of it...yet. The DB biased ok; at 50mV. However, I don't know what to do with the tube bias. 

 The tube stays around 2V~3V below the PS and which ever direction I turn the trimpots. 
	

	
	
		
		

		
			





 I have 
 PS at 25.7V
 TAs - Grnd at 22.9

 It stays the same with or without the tubes. 
 What should I look for? Right now I don't have tubes (accident). Is it still possible to find out what's wrong without them?

 TIA


----------



## tomb

Quote:


  Originally Posted by *Pingunugnug* /img/forum/go_quote.gif 
_I finally finished the enclosure side panels (have some minor clearance problems, that can be fixed with an exterior fuse holder); got to setup last night and the first flick of the switch the fuse blows. I bypassed it and so far it hasn't have smoke come out of it...yet. The DB biased ok; at 50mV. However, I don't know what to do with the tube bias. 

 The tube stays around 2V~3V below the PS and which ever direction I turn the trimpots. 
	

	
	
		
		

		
		
	


	




 I have 
 PS at 25.7V
 TAs - Grnd at 22.9

 It stays the same with or without the tubes. 
 What should I look for? Right now I don't have tubes (accident). Is it still possible to find out what's wrong without them?

 TIA_

 

1. It's good that you bypassed the fuse - I'll not comment further on that.
 2. You probably should get those DB's up to 66mV. That's 30ma. They almost need 30ma before they're even actively biased. This is assuming, of course, that you are not mixing terms. That's 66mV, which you read on your meter. The 30ma is the quantity that you really want - at a minimum - but that number is calculated. Ultimately, you want to get to 110mV, which is 50ma calculated.
 3. Tube bias -
If the tubes are glowing orange, then most likely the plates are conducting. The orange comes from the heater, or cathode. It's a rod about 1/16" diameter that runs vertically through the center of the tube. It should be easy to see regardless of tube construciton - either at top, on the sides, or at the bottom.
If the tubes are not conducting (no heater glow), then your problem is with the tubes or the sockets. For checking the sockets, gently cant the tubes one way or another in the socket. Usually canting forwards or backwards works best, since the front two pins have a space between them anyway. You need to wait a minute - if canting the tubes makes a good connection, it will take 15-30sec for the heaters to glow.
Most likely - you simply can't believe how far you have to turn the trimmers. Please remember those trimmers are meant to work with three different types of tubes, each of which have their own bias point. So, you may have to turn them quite a bit. I believe the trimmers spec'd are 25 turn trimmers. Turn the trimmers counter-clockwise to lower the bias voltage if you've oriented the trimmers correctly. You may need to turn them out 20 turns out of the 25 before you notice a difference, depending on the tubes.

 Count to make yourself more confident that you are turning the turns available. Again, if you ordered the spec'd trimmers, they should have a clutch so you won't damage them. As long as the heaters are glowing, I'm pretty sure you will get a measureable reaction eventually.

 Also - nothing will work for biasing the tube circuit if the tubes are not in the sockets, the heaters are warmed up, and the tube plates are conducting. It's a waste of time otherwise.

 EDIT: One other noobie piece of advice - don't even think of doing any of this with heapdhones connected. As a final check - even when you think you have everyting working correctly - you should measure whether any offset exists between ground and the output channels on the headphone jack. Finally, use a cheap pair of headphones for the first time you attempt to play music. Follow these precautions and you won't have any disappointing damage in case something is still wrong.


----------



## ruZZ.il

I don't think you can bias without the tubes. once you have the tubes in there, if everything else is good, it should bias correctly. that being said, try power up with a lower bias. since the tubes are rather tolerant, I'm guessing you could even just set the trim pots to about the middle (~10 turns from either min/max), and let us know.. meanwhile, pics?


----------



## ruZZ.il

what..lol


----------



## tomb

Quote:


  Originally Posted by *ruZZ.il* /img/forum/go_quote.gif 
_what..lol 
	

	
	
		
		

		
		
	


	


_

 

Well, I'm glad someone else is watching this thread besides me. Thanks!


----------



## pinkfloyd4ever

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_[*MUSE KZ's -* There are many MAX builders who've already used them - perhaps they'll chime in and give us their impressions.
 ...........
*ELNA Silmics -* Again, there are several Millett builders who've used them and perhaps they can relate their impressions.

 ...............
 As for the film bypassing, there are so many choices it's hard to keep up. Again, I encourage you to research Dsavitsk's capacitor reviews. I believe he's also got quite a few posts here and in the Alien DAC thread. Some of the things - if memory serves - that he recommends in pairing with the caps above (at least the ES's and BG's):

 1. *Sonicap GEN II's for the ES's.* This review is on Dsavitsk's web site. According to his statements, one might deduce that this pairing with ES's results in a sterling combination: not adversely affecting any of the bass, but opening up the combo with sterling highs.
 2. *Vitamin Q's for the Black Gates* Contrary to popular opinon, Dsavitsk says the VitQ's are fairly neutral. So, they pair well with BG's, refraining from traditionally rich film caps that may end up making the BG's sound syrupy.
 3. *0.47, 50V BG's* These are also a good bypass option for BG's, according to reports. I believe Nate Maher stated that this was how he build his ultimate revMH Millett Hybrid. I believe the technique is to follow the logic of the Black Gate "Super E" method, which connects the small bypass in opposite polarity from the larger caps they are bypassing. 'Course, the BG's in consideration are supposed to be the N, NX type, which are bipolar.
 4. *Auricaps* test out in Dsavitsk's reviews as having both rolled off highs and rolled off lows. That seems quite a price to pay for its infamous mid-range bloom. I think Dsavitsk has stated he would rather use almost any film cap than an Auricap. That may be an exagerration on my part and I'm nor trying to start anything - only relating what I've read and heard.
 5. *Wima MKP10 -* There is nothing wrong with these in a basic configuration. Following Pete Millett's original strategy, they can even make standard power caps like Nichicon UPWs, Panasonic FM's and FC's sound pretty good in the MAX. They are certainly the economical choice, although the Sonicaps are pretty close.

 Of course, most of this is gleaned from memory, so IMHO and YMMV x10!

 P.S. The Jupiters and the Mundorf Silver Oil are at the top of Dsavitsk's rating. However, I personally believe the Jupiters are inappropriate for most MAXes - the temperatures are simply too high. Also keep in mind that ultimately, the MAX is a hybrid - pairing the best in discrete solid state output stage with a tube gain stage. So, to a certain extent, flavoring with a very expensive boutique may have quickly diminishing returns._

 

anyone else got boutique opinions/comparisons?


----------



## tomb

Quote:


  Originally Posted by *pinkfloyd4ever* /img/forum/go_quote.gif 
_anyone else got boutique opinions/comparisons?_

 

You're welcome? I didn't know I was preparing a flame flag, but so be it.


----------



## Pingunugnug

Thanks for the help. Here is some pictures of the build:
http://www.flickr.com/gp/11073745@N08/162EvN

 It pretty much looks like the one on the MAX site (except noobfied). (In fact without this thread ,that site, and Jeff Rossel putting it into a kit, the build would be pretty much impossible for me.) I recieved Jeff Rossel's kit (very nicely packaged) on Friday and just started building. 


 I can't test until Thursday, when the new tubes arrive. I did notice when they were slightly glowing at the tip (I didn't check if whole length was glowing) when it was at 22.9V. How long should I keep it there to trim it down without damage? 

 I just measured the trimpot at the connection end. Both of them is very near 5k Ohms. If I put in the tubes, turn it on and it still reads ~22V. That is the situation that I am in right now with out the tubes. With the tubes, will that value go down?


----------



## ericj

install the tubes for crying out loud.


----------



## pinkfloyd4ever

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_You're welcome? I didn't know I was preparing a flame flag, but so be it.
	

	
	
		
		

		
		
	


	


_

 

oh no I didn't mean that tomb, sorry I forgot to say THANKS A TON for the info you gave. I was just wondering if anyone who'd built the MAX with one or more of the caps you said you had limited experience with or hadn't heard in the MAX had thoughts or camparisons to share. Don't get me wrong, I know your information is legit, and I certainly don't have enough experience to disagree with any of it. Just hoping someone else could "chime in and give us their impressions"


----------



## ruZZ.il

Pingunugnug, the solder points that can be seen look good. try cleaning the back up a little bit more.. pick off all the little bits of stray solder, etc.. meanwhile, since the DB's trim and your voltage is set, most everything is good. once those tubes are in, we can check the rest.. but that 22v in the meantime sounds right. mine was like that when I had no tubes in, so it seems right..


----------



## dsavitsk

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_I think Dsavitsk has stated he would rather use almost any film cap than an Auricap. That may be an exagerration on my part_

 






 a little bit. I have a pair as parafeed caps in my preamp -- they were small enough to fit easily and sound pretty good there. They were pulled from my DAC in favor of the Silver/Oils which I think work better as couplers. I might upgrade them at some point, but then again, I might not.

 I have a bunch of new caps to try including some cheapo Clarity Caps that I am pretty excited about, but I was exposed to an obscenely loud noise for an obscenely long time on a flight the other day (did it really save Northwest Air that much cash to put me that close to the engine? Sadly, probably yes.), and I still can't hear that well. Hopefully the ringing and numbness go away in another day or so and I can get back to this listening business.


  Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_ I regularly ask for a local microbrew when I travel - what better way to sample the local flavor?_

 

I like that idea. If you are in Wisconsin, try a Spotted Cow. They make an IPA too, but I've not had it.


----------



## amphead

Dsavitsk: I know V-caps teflon/foil may be a tad expensive, but have you had a listen? Too pricey for the MAX build?


----------



## amphead

Well, I know the tubes/caps are young in this build, but I had to know. I paralleled another set of Jensen bypass caps 0.1uF across CA8L/R for a total 0.2uF per side. Could I hear the difference? Yes, the vocals have a more liquid presence. Piano strings vibrate with a deeper timbre. Snare drums are more laid back in the mix, with a less percussive sound. Everything appears a shade darker/pleasing to my ears.  Edit: this is of course what the BOM required: 0.22uF film, and for good reason.


----------



## amphead

There weren't any more Jensens in my stash, but I did have 2 more Wima 0.22uf film caps. Now, these are installed across my Jensens 0.1uF at CA9L/R, for a total 0.32uF. Another change in the sound, which I perceive as more forward mids. Stronger dynamic content overall. Electric guitar passages more forward. Piano roars with sound! Vocals are warmer, and still liquid. More apparent volume. Edit: I might remove the Wimas and go back to 0.1uF for CA9R/L. I'm not sure if I hear a slight veil overall. Edit: There seems to be too much distortion, with 0.32uF in this position. They have to go tomorrow. I was happy with the sound before trying this configuration.


----------



## ruZZ.il

good stuff.. keep it coming


----------



## tomb

Quote:


  Originally Posted by *ericj* /img/forum/go_quote.gif 
_install the tubes for crying out loud._

 

Agreed. 
	

	
	
		
		

		
		
	


	




  Quote:


  Originally Posted by *pinkfloyd4ever* 
_oh no I didn't mean that tomb, sorry I forgot to say THANKS A TON for the info you gave. I was just wondering if anyone who'd built the MAX with one or more of the caps you said you had limited experience with or hadn't heard in the MAX had thoughts or camparisons to share. Don't get me wrong, I know your information is legit ... <snip>_

 

Actually, my info is not necessarily legit - that's why I was a bit chagrinned at seeing you re-quote it and ask for comments. 
	

	
	
		
		

		
		
	


	




 It was only summarizing what I've read and heard, but by no means does that make me an expert. We have Dsavitsk for that.
	

	
	
		
		

		
		
	


	




  Quote:


  Originally Posted by *Dsavitsk* 
_<snip> ... but I was exposed to an obscenely loud noise for an obscenely long time on a flight the other day (did it really save Northwest Air that much cash to put me that close to the engine? Sadly, probably yes.), and I still can't hear that well. ... </snip>_

 

Been there, done that - it's easy to see why no one wants to sit back there next to the engine on the DC-9/727 derivative type planes.

  Quote:


 <snip> ... If you are in Wisconsin, try a Spotted Cow. They make an IPA too, but I've not had it. 
 

Thanks. I'll keep an eye out for it.

  Quote:


  Originally Posted by *amphead* 
_<snip> ... There weren't any more Jensens in my stash, but I did have 2 more Wima 0.22uf film caps. Now, these are installed across my Jensens 0.1uF at CA9L/R, for a total 0.32uF._

 

You could try what Ferrari did on his original Millett Hybrid - parallel enough box film caps that they totaled up to sufficient value to replace the electrolytic. 'Course, I think he had to build another case to fit the film caps - it looked like one of those banks of solar cells you might see for a power application - rows and rows of box film caps.


----------



## ruZZ.il

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_..
 You could try what Ferrari did on his original Millett Hybrid - parallel enough box film caps that they totaled up to sufficient value to replace the electrolytic. 'Course, I think he had to build another case to fit the film caps - it looked like one of those banks of solar cells you might see for a power application - rows and rows of box film caps. 
	

	
	
		
		

		
		
	


	


_

 

nuu, Ferrari how did that sound?


----------



## dsavitsk

Quote:


  Originally Posted by *amphead* /img/forum/go_quote.gif 
_Dsavitsk: I know V-caps teflon/foil may be a tad expensive, but have you had a listen? Too pricey for the MAX build? _

 

I wouldn't use them for a couple of reasons. The first, and simplest, is that Sonicap Platinums are cheaper, and according to people I've talked to, better.

 But, more importantly, I think they are a little overkill in this spot. Basically, a grounded cathode amplifier, which is what the front half of this amp is, can drive headphones in 4 ways. The first is that the rp of the tube can be low enough to simply drive the phones from the plate. The second is that you can add a cathode follower of some sort. The third is that you can use a solid state buffer, and the fourth is that you can use a transformer, either single feed or parallel feed connected.

 Each of these options has advantages and drawbacks. The Millett uses a solid state buffer. The advantages of this option are cost and the ability to rely less on the tube stage for drive, so low voltages and high rp tubes work fine. But, at the point that you are dumping a lot of money into the project, then I think it is reasonable to consider some of the advantages offered by the other options, or by improvements to the Millett topology.

 So, before buying really expensive caps, I would, at a minimum -- even keeping the solid state buffer option around --, modify the circuit to place the cap (or an interstage transformer) between the tube and the buffer and DC couple the output to eliminate the electrolytic entirely. Additionally, I would switch tubes to something more linear (which would likely entail some higher voltages). This is a lot of work, but you are talking about throwing $200+ of caps at this amp. If you want to stick with the Millett, then I think it is probably not a good use of money to buy these caps as, once you have something decent (Wima, Sonicap, whatever), they are not the weak spot of the amplifier.

 -d


----------



## tomb

I certainly second Dsavitsk's opinions here about the investment in caps. I just usually don't express an opinion in that regard because I'm a cheapskate compared to many of you guys. The MAX is the first thing I've ever bought BG's for (well, outside of the teeny ones for the Alien DAC), but purchasing several of these big-time boutique film caps is out of the question for me. I will stick with the Wima's, the Sonicaps, and the 0.47uF 50V BG's - also the Vitamin Q's if I can ever figure out how they'll fit. 
	

	
	
		
		

		
		
	


	




 I may try the Auricaps - simply because they do run fairly small (not as small as the Sonicaps), which is an advantage in the MAX.

 About the design - I think you'll find that the MAX is about as far as one can get and still remain a Millett. The problem with DC coupling the output stage is that it does nothing for controlling offset. There is no feedback in the Millett design. So, unless a DC servo or something similar is used, the offset will be uncontrollable. Those big electrolytics on the output are performing a very useful service - they automatically block any offset that might occur.

 Steinchen found out the same thing with his SOHA buffers. Just as suggested, the SOHA uses a DC coupled film cap that connects the tube output with the opamp output stage. There are no output coupling caps, per se. Anyway, Steinchen tried several types of discrete output buffers for the SOHA - a MOSFET, BJT Diamond Buffer, and Amb's Jisbos current buffer. The MOSFET was never stable and was abandoned. The Diamond Buffer was eventually abandoned, too. The problem was in having to dial out so much offset with the DC servo that there was hardly any left to bias the buffer. Most likely, this would also occur on the MAX.

 The Jisbos are still in the offing, supposedly. Amb designed those buffers from the ground up specifically for zeroing offset without a servo. They "preserve" much of the voltage for use in biasing the buffer.

 Anyway, Dsavitsk is certainly right about not spending too many bucks on the caps. IMHO, you can alter the sound quality tremendously by using a set of the upgrade BJT's on that version:

 2SC3422/2SA1359 - Rock and hard slam (very nice!)
 2SC2238/2SA968 - Ultimate detail, very neutral and well balanced (best of all)
 2SC3421/2SA1358 - Deepest bass extension, some slam (very good)

 These are all a major upgrade considered against the BD's and MJE's, yet a full set will probably set you back ~$8 at the most, $4 on some if you don't count shipping.

 There are also many others on Steinchen's DB page that may sound very good in the MAX. With the MAX's much higher bias, "dark" may get light and "fat bottoms" may trim up. In any event, you could experiment a lot with little investment.


----------



## Ferrari

Quote:


  Originally Posted by *ruZZ.il* /img/forum/go_quote.gif 
_nuu, Ferrari how did that sound? 
	

	
	
		
		

		
		
	


	


_

 

Hmm... the output caps on my original Millett... it looks like this:






 It sounds very good in terms of sound balance and resolutions, of course within the ability of the original Millett board construction (limited current bias with drop in Diamond Buffer). I prefer the sound of these output caps above Blackgate NX 680uF or Nichicon Muse ES 470uF//small MKP. However the combination Nichicon Muse ES//small MKP is the ultimate winner when price/performance is taken into account 
	

	
	
		
		

		
		
	


	




 . 

 Probably it was the best Millett I could build at that time. My current Millett Max build with MKP//Russian Teflon output caps is clearly of a higher level though (hope to post some pics next weekend).


----------



## ericj

Quote:


  Originally Posted by *tomb* 
_You could try what Ferrari did on his original Millett Hybrid - parallel enough box film caps that they totaled up to sufficient value to replace the electrolytic. 'Course, I think he had to build another case to fit the film caps - it looked like one of those banks of solar cells you might see for a power application - rows and rows of box film caps. 
	

	
	
		
		

		
		
	


	


_

 


 I've seen high-voltage OTL tube amps that just had a big bank of motor run caps on the output. Less wiring to do, at least.


----------



## bennet

nice...


----------



## ruZZ.il

nice++, that's a really cool build. I'd like to play with more caps.. I just made myself a pimeta bass boost with the spare wima 0.22s from the BOM though  but differently... anyway, great craftsmanship too!


----------



## pinkfloyd4ever

Quote:


  Originally Posted by *Ferrari* /img/forum/go_quote.gif 
_Hmm... the output caps on my original Millett... it looks like this:




_

 

Now that is just OBSCENE 
	

	
	
		
		

		
		
	


	




  Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_ I also the Vitamin Q's if I can ever figure out how they'll fit. 
	

	
	
		
		

		
		
	


	


_

 

Ahh crap I didn't realize they were that big, I was thinkin about tryin those

  Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Anyway, Dsavitsk is certainly right about not spending too many bucks on the caps. IMHO, you can alter the sound quality tremendously by using a set of the upgrade BJT's on that version:

 2SC3422/2SA1359 - Rock and hard slam (very nice!)
 2SC2238/2SA968 - Ultimate detail, very neutral and well balanced (best of all)
 2SC3421/2SA1358 - Deepest bass extension, some slam (very good)

 These are all a major upgrade considered against the BD's and MJE's, yet a full set will probably set you back ~$8 at the most, $4 on some if you don't count shipping._

 

OOHHHH yeah now that's what I'm talkin about...man I love this hobby
 wait, what do you mean by "on that version" tho tomb?

  Quote:


  Originally Posted by *dsavitsk* /img/forum/go_quote.gif 
_I have a bunch of new caps to try including some cheapo Clarity Caps that I am pretty excited about_

 

oooo ya I've seen all the DIY hi-fi sites hypin those up & wondering how they sound, as I haven't read much about em from those not selling them

 also, tomb & dsavitsk, do you think it's really that bad of an idea to socket caps on the MAX? could something get fried if you accidently fire it up with a cap out? (I which I did building my first cmoy, but hey that's why we start with those and not a MHM, right?) What about socketing BJTs?

 thanks in advance and sorry for bein all over the place, but whatever, it is head-fi


----------



## tomb

Quote:


  Originally Posted by *pinkfloyd4ever* /img/forum/go_quote.gif 
_Now that is just OBSCENE 
	

	
	
		
		

		
		
	


	





 Ahh crap I didn't realize they were that big, I was thinkin about tryin those_

 

Yeah, really - we're limited to about 1/2" x 1" for the CA9's and about 1/2" x 3/4" in the CA8 positions. CA8 is actually setup for tomb-stoning, but that's limited to the height of the heat sinks, pretty much (IOW, that dictates your free height in the case).


  Quote:


 OOHHHH yeah now that's what I'm talkin about...man I love this hobby
 wait, what do you mean by "on that version" tho tomb? 
 

I meant the BJT version of the MAX. You have many BJT's to pick from and that will have more effect on the final sound than any cap. On the other hand, you're stuck with only one particular set of MOSFETs (AFAIK) if you build the MOSFET version.


  Quote:


 oooo ya I've seen all the DIY hi-fi sites hypin those up & wondering how they sound, as I haven't read much about em from those not selling them

 also, tomb & dsavitsk, do you think it's really that bad of an idea to socket caps on the MAX? could something get fried if you accidently fire it up with a cap out? (I which I did building my first cmoy, but hey that's why we start with those and not a MHM, right?) 
 

Yeah, I think it's a bad idea. The caps are way too big in the MAX. Just unpluggin them might put burn spots in the board.

  Quote:


 What about socketing BJTs? 
 

That's definitely do-able. Whether it's worth the trouble considering the heat sink mounting is a different question, but that may be something you can put up with.

  Quote:


 thanks in advance and sorry for bein all over the place, but whatever, it is head-fi 
 

No problem.


----------



## vixr

hey guys, I have a sony walkman digital FM tuner, model#SRF-M37V, that I was just listening to while I had my fluke hooked up to the tube heater test points and I notice every time I change FM channels, the heater voltage changes too...it drops about 1/2 a volt then slowly creeps back up to around 13.5 VDC. what gives?


----------



## colonelkernel8

Havent been following the thread too closely, but if you arent using mosfets, do you jumper RB8LR and RB9LR?


----------



## thunder

If someone wanted to use a boutique capacitor for the c7 pos remotely mounted What special if any thing's would need to be considered ? The reason is I would like to use a 1000uf in that pos, but most are to tall so I thought about remote mounting a pair of 470's.


----------



## amphead

Thanks dsavitsk for the advice! I may be willing to try the platinum teflon caps. The V-caps won't happen. 
 Tom, I have all of those high-end trannies coming from someone who ordered too many in NYC, and is giving them to me pro bono. Thanks for your advice!
 Ferrari, awesome configurations, I'm speechless!


----------



## tomb

Quote:


  Originally Posted by *vixr* /img/forum/go_quote.gif 
_hey guys, I have a sony walkman digital FM tuner, model#SRF-M37V, that I was just listening to while I had my fluke hooked up to the tube heater test points and I notice every time I change FM channels, the heater voltage changes too...it drops about 1/2 a volt then slowly creeps back up to around 13.5 VDC. what gives?_

 

Maybe the tubes just don't like you changing the channels. 
	

	
	
		
		

		
			








 Other than that, I don't have a clue.

  Quote:


  Originally Posted by *colonelkernel8* 
_Havent been following the thread too closely, but if you arent using mosfets, do you jumper RB8LR and RB9LR?_

 

Yes.

  Quote:


  Originally Posted by *thunder* 
_If someone wanted to use a boutique capacitor for the c7 pos remotely mounted What special if any thing's would need to be considered ? The reason is I would like to use a 1000uf in that pos, but most are to tall so I thought about remote mounting a pair of 470's._

 

Generally speaking, it's probably not a good idea to remotely mount electrolytics. I could be wrong, but since these caps carry the signal, you are into the same issues that cause people to spend $$$ on special headphone cables and interconnects.

 You could always just lower the board into one of the bottom slots on the recommended Hammond case. In the bottom slot, you've got over 40mm from the board surface to the bottom of the lid. That would handle any 1000uF cap, AFAIK - even a 1000uF, 50V Muse KZ (40mm). Every MOSFET version of the MAX has located the board in the bottom slot and nobody seems to mind too much. 
	

	
	
		
		

		
		
	


	




  Quote:


  Originally Posted by *amphead* 
_<snip> ... Tom, I have all of those high-end trannies coming from someone who ordered too many in NYC, and is giving them to me pro bono. Thanks for your advice! ...</snip>_

 

 That's great! I also meant to say that the high-end trannies will definitely _improve_ the sound, not just _alter_ it.


----------



## thunder

Tomb, I wish things were that simple my case is not a hammond it's a teko # DS2470.18. I've already invested to much time modding this case ! The only obstacle left is to address is the cap section c7 which I have about 30mm to play with. Moving the caps seems the only option sense I really like using Muse ES caps. I had thought about using the BG 680's but can't bring myself to spend another 30+ $ with shipping ect... As far as cable I have aquired to many pair's of interconnect's to count over the year's. I'm open to any new Idea's someone may have. Thanks


----------



## nysulli

well, sorry to anyone trying to pick up FM6's from radiodaze, i seem to have drained their supply, oops

 and the parts have begun to arrive, Handmade got here first, ordered late monday night, even with billing issues got here wed. afternoon


----------



## tomb

Quote:


  Originally Posted by *nysulli* /img/forum/go_quote.gif 
_well, sorry to anyone trying to pick up FM6's from radiodaze, i seem to have drained their supply, oops

 and the parts have begun to arrive, Handmade got here first, ordered late monday night, even with billing issues got here wed. afternoon_

 

I suspected as much after that nice e-mail I got from Phil Hazen. Maybe someday he'll get some more. As it is, he's been a great and wonderful source for Millett builders. He certainly has plenty of tubes if anyone contemplates building other tube amps and deserves consideration after all of his great service.

 AFAIK, the FM6's are the rarest breed. I wonder how long his AE6's and FK6's will last, now?


----------



## Pingunugnug

The tubes arrived early; recieved them today. I figured out why I can't get the tubes below 20ish volts; turned the wrong way. 

 I am now listening with it.

 <In Monty Burn's voice> Excellent

 Thx for the help guys!!


----------



## amphead

Congrats! Remember the tubes sound good when you first get it running, but the sound will improve after your components burn-in.


----------



## ruZZ.il

congrats!


----------



## nysulli

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_I suspected as much after that nice e-mail I got from Phil Hazen. Maybe someday he'll get some more. As it is, he's been a great and wonderful source for Millett builders. He certainly has plenty of tubes if anyone contemplates building other tube amps and deserves consideration after all of his great service.

 AFAIK, the FM6's are the rarest breed. I wonder how long his AE6's and FK6's will last, now?_

 

it sounded like they had a fair amount of the others, just that they had run out of the FM6's

 now watch, the way getting parts for this project has been it'll be my favorite tube, and i'll only have the 3 i currently have to last a lifetime

 oh yeah, i'm also the prick that bought the last 2SC3422's from newark since BD was out of them, estimated date for BD's next patch is 10-31


----------



## amphead

Quote:


  Originally Posted by *nysulli* /img/forum/go_quote.gif 
_it sounded like they had a fair amount of the others, just that they had run out of the FM6's

 now watch, the way getting parts for this project has been it'll be my favorite tube, and i'll only have the 3 i currently have to last a lifetime

 oh yeah, i'm also the prick that bought the last 2SC3422's from newark since BD was out of them, estimated date for BD's next patch is 10-31_

 

Ok Tom, you get the rope and I'll find a good tree. Maybe ruZZ.il would like to smack the horse on the backside! 
	

	
	
		
		

		
		
	


	




 Seriously though, maybe the suppliers need more of a heads up, as to the restocking issues ahead.


----------



## tomb

"Restocking" NOS tubes is not something that's accomplished by just calling up your supplier. I tried my best with Phil Hazen at Radio Daze, but I respect his reasoning. If the design needed some 300B's along with these $2-$3 car radio tubes, it might make a difference. 
	

	
	
		
		

		
		
	


	




 I don't think we're even close to diminishing returns yet, but there has to be a point where the existing availability of Millett tubes is exceeded by the number of MAX builds. Certainly, we did this with Radio Daze and the 12FM6. Vacuumtubes.net has been out of 12FM6's for awhile, now. I think Antique Electric Supply ran out of Millett tubes last year. This will probably continue, rather than get better.


----------



## ruZZ.il

hey I dont smack animals (well, my lady someti... nevermind 
	

	
	
		
		

		
		
	


	




 ) but I sure hope the MAX is supported for years and years to come cause I enjoyed building it, and am loving listening to it. It would be a pity if cant be shared, when that's partly what it was built for. 

 ..Meanwhile, one of the AE's I have got knocked a bit after I got it (3" drop onto wood table) and doesn't work. The heater resistance measures infinite, so it seems its dead.. I only had 2 ;/ good thing I have 2 spare FKs for my other board, but I should definitely get some spares for both..

 [size=xx-small]
 *no ladies were hurt in the making of this post[/size]


----------



## vixr

I finally got my top plate all cut out... looks pretty good. Ready for paint!!!


----------



## ruZZ.il

nice! looks perfect, which tools?


----------



## Troyhoot

Wish I had access to the tools you do Vixr !! That looks great !! I really likey


----------



## tomb

Quote:


  Originally Posted by *ruZZ.il* /img/forum/go_quote.gif 
_hey I dont smack animals (well, my lady someti... nevermind 
	

	
	
		
		

		
		
	


	




 ) but I sure hope the MAX is supported for years and years to come cause I enjoyed building it, and am loving listening to it. It would be a pity if cant be shared, when that's partly what it was built for. 

 ..Meanwhile, one of the AE's I have got knocked a bit after I got it (3" drop onto wood table) and doesn't work. The heater resistance measures infinite, so it seems its dead.. I only had 2 ;/ good thing I have 2 spare FKs for my other board, but I should definitely get some spares for both..

 [size=xx-small]
 *no ladies were hurt in the making of this post[/size]_

 

Yes, well - we can hope that enough MAX's are built and sold that Electro-Harmonix, JJ, or EI will decide to make Millett tubes again ... but I don't think that's happening anytime soon. Not to fear - that was a big list of tube vendors I posted aways back. There are still good deals to be had - we're just going to have to try harder. After all, no Millett builder had heard of Radio Daze a few months ago. 
	

	
	
		
		

		
		
	


	




 About the bad tube - I've gotten about 1 out of every two dozen to be bad, anyway. So, it could happen whether you dropped that one or not.


----------



## tomb

Quote:


  Originally Posted by *vixr* /img/forum/go_quote.gif 
_I finally got my top plate all cut out... looks pretty good. Ready for paint!!!
_

 

Nice!


----------



## vixr

I used the milling machine at work...


----------



## ruZZ.il

does mouser sell those? 
	

	
	
		
		

		
		
	


	







 hmm.. I've got to find someone with one of those.. I could always bug the w.shop on campus..


----------



## kklee

Quote:


  Originally Posted by *vixr* /img/forum/go_quote.gif 
_I finally got my top plate all cut out... looks pretty good. Ready for paint!!!_

 

This was originally how I wanted to do my Max case, but I don't have access to the appropriate tools and settled for Lexan instead. Looks great!


----------



## vixr

done!!!


----------



## Televator

Quote:


  Originally Posted by *vixr* /img/forum/go_quote.gif 
_done!!!
 (snip)_

 

Drool! that is just ... eh ... the MAX!


----------



## tomb

Quote:


  Originally Posted by *Televator* /img/forum/go_quote.gif 
_Drool! that is just ... eh ... the MAX!_

 

x10 - Too cool!! This is two extreme MAXes for you now, Vixr!


----------



## ruZZ.il

reeeally cool vixr! 

 ..meanwhile, back in my lair, I received the output transistors Tom so kindly sent me. I'd previously only had MJE's, and burnt one out. I found some BDs and changed one channel while I waited.. yes, I was impressed with the 
 max.. but these things really put the cherry on top! 
	

	
	
		
		

		
		
	


	




 I have a bunch here so I hope to play around with them sometime. I've got BG/Gen II's and since I also like my bass I started off with the the 3422s to bump up the bottom. Well?.. definitely noticeable differences. A lot more clarity all round seems to be shining through and the bass extends further down, more controlled and empowering I can actually feel it, almost as if the BD/MJE's were really veiling.. bias@40ma, will climb tomorrow. All in all, I think its a pity to be building the MAX with the other transistors when for only a few bucks these could be had. definitely a worth while upgrade.

 Also, if anyone finds themselves switching transistors, take a little length of some string or hookup wire and loop it through the hole, flip the board and heat all 3 pins simultaneously while pulling down on the string (I used wire
	

	
	
		
		

		
		
	


	




)


 ...Thanks tom


----------



## Ferrari

Nice mechanical work indeed.


----------



## holland

OMG Vixr, that's SEXY!!! You should make custom front plates though. The plastic detracts from the sexiness of the top plate.

 You can probably make a solid billet aluminum case with those tools. Man, the mind races....


----------



## Blooze

Nice Vixr! I wish I had access to a lathe and milling machine as I've got some top plate work to do as well.

 I better get on the stick and get some tubes ordered before they're all gone or too much $$$. See Tomb, told you it's gonna be just like the 1626's 
	

	
	
		
		

		
		
	


	




 I just checked my stash and I've got 3 Tung-sol 12FK6's, two Raytheon 12FK6's, two RCA 12FK6's, one Arcturus 12FK6, and two Sylvania 12FM6's. One bad 12AE6. So I need to find some 12FM6's and some 12AE6's at least.


----------



## Ech0

Very, very cool indeed vixr! I love it fired up with the lights on. 

 Ferrari, I really like your "power on" light you build into your casework. That's a classic example of less is more. If I remember right you've detailed how to do this in a post here at HeadFi. I'm surprised it hasn't been copied more or maybe it has and I just don't know it.


----------



## amphead

Kool Vixr! Keep em coming, you are inspiring me to do something special too!


----------



## amphead

Just fired up my UV exposure lamp. My next build will be the first MAX built with a board that I exposed/etched. I won't silkscreen the top, but Pete, Colin, Tom and Ti will be properly credited in copper on the bottom in scrolled text! Edit: Not knowing what Colin has in mind with the boards from the group buy, I can not offer any of these for sale, sorry.


----------



## matt303

Got mine working last night, first thing I've built since leaving the electronics industry 8 years ago and it worked first time 
	

	
	
		
		

		
		
	


	







 click image for bigger version

 Sounds really good running my SR-60s, case and transformer housing are the next bits to sort out.


----------



## tomb

Way to go! It looks really great!

 Another MAX lives!!


----------



## c0nsumer

I just ordered an Alien DAC kit, and I think I figured out what I'm going to do for the second MAX I put together: Use the 1455T2201 and fit the Alien DAC in there as well, with an input switch. There would be plenty of room in the case, I just need to figure out where/how to integrate the switch, how to mount the Alien DAC, boutique parts and tubes to use, case/knob color, things like that.

 I think this will make a good all-around headphone listening box.


----------



## amphead

matt303, great timing! You get yours up and running and then make it your first post! Congrats!


----------



## amphead

TomB, kudos for wearing 2 hats! he he


----------



## Pingunugnug

I have been listening to the amp for a while and I am noticing some things that I don't know if it's normal.

 When I turn the volume I can actually hear a the "friction of it rotating". Not sure if I can describe it better.

 Also, can the volume go full range?
 Lowest at 7 o'clock, by the time it gets to 12:30 the Left channel cuts out and then further up both gets cut out. It is more than enough for regular use by then but should I be concerned about it?


----------



## tomb

Quote:


  Originally Posted by *Pingunugnug* /img/forum/go_quote.gif 
_I have been listening to the amp for a while and I am noticing some things that I don't know if it's normal.

 When I turn the volume I can actually hear a the "friction of it rotating". Not sure if I can describe it better.

 Also, can the volume go full range?
 Lowest at 7 o'clock, by the time it gets to 12:30 the Left channel cuts out and then further up both gets cut out. It is more than enough for regular use by then but should I be concerned about it?_

 

Yes, you should be concerned. The MAX should literally pump out enough volume to blow your headphones up (most headphones, anyway). The "friction" you describe may simply be a dirty pot.

 However, the rest of what you describe is not a dirty pot and actually sounds serious. Please post us some pics when you can. Meanwhile, please confirm the test point voltages - voltage supply, tube bias, and DB bias. Are you running BJT's or MOSFET's, what kind of power supply, etc., etc.?


----------



## bhjazz

Quote:


  Originally Posted by *Pingunugnug* /img/forum/go_quote.gif 
_When I turn the volume I can actually hear a the "friction of it rotating". Not sure if I can describe it better._

 

Definitely sounds like you have a cold soder joint somewhere. You'll want to reheat joints, starting with the ones for the volume pot. Post a few pics, as tomb suggest, which will help us figure out just which joint might be the culprit.


----------



## tomb

Those of you interested in boutique caps for the MAX may be interested in this exchange:
http://www.diyforums.org/phpBB2/view...hp?p=3308#3308


----------



## Ferrari

Some quick shots with my "point-and-shot" camera. I will take some neat pics later, probably in the weekend.


----------



## ruZZ.il

holy sh.. 

 good stuff!


----------



## tomb

Quote:


  Originally Posted by *ruZZ.il* /img/forum/go_quote.gif 
_holy sh.. 

 good stuff! 
	

	
	
		
		

		
		
	


	


_

 









 Definitely ... boutique to the MAX!


----------



## Televator

seeing the first pic I thought: "wow, that's a nice case, but it is very 'standard' for a Ferrari-build" until I realized the 1/4" socket looked a bit small compared to the case ... wait a sec ... what the fudge? Did he stash some soda cans in there as well?


----------



## soloz2

I like that case! what is it?


----------



## Ferrari

Quote:


  Originally Posted by *soloz2* /img/forum/go_quote.gif 
_I like that case! what is it?_

 

The enclosure is an ATI-737U (same type used for my β22).


 To answer some email/PM I have received regarding the capacitors I used in my MH Max build:

 Electrolytics capacitors in the PS and CA4+5L/R are Nichicon Muse FX; 
 Cathode bypass caps (CA2+9LR) are BG NX//polystyrene 1%; On the output, MKP//Russian Teflon are used for CA7+8L/R.
 Unless the amp is just case up, it has more than 300 listening (test) hours already. 
 Many types of bypass capacitors are tried out and I finally decide to settle on the caps combinations for the output CA7+8L/R and cathode bypass CA2+9LR as they are on my MH Max currently.


----------



## smegger

hi guys i just ordered some alien dacs of jeff over at glass jar i asked him about kits for my new k601s and he said he had kits for these, now i have a something missing in my life, tube amps and i have been dying to build one!

 has anyone any experience with the kit jeff offers or would i be better getting all my kit from farnell?


----------



## ruZZ.il

Jeffs kits are great. Iäve built an Alien DAC and the M3 that he offers. very concise and organized. just call him to get the latest on options and stuff that he has, very nice guy. Ill be ordering more dac kits from him soon.

 Russ

 (excuse my usage of this strange keyboard)


----------



## tomb

Quote:


  Originally Posted by *smegger* /img/forum/go_quote.gif 
_hi guys i just ordered some alien dacs of jeff over at glass jar i asked him about kits for my new k601s and he said he had kits for these, now i have a something missing in my life, tube amps and i have been dying to build one!

 has anyone any experience with the kit jeff offers or would i be better getting all my kit from farnell?_

 

Jeff lifted my BOM straight from the MAX website. He has put together an outstanding selection of parts for the MAX.

 If there is anything at all to make note of - and it's not much - is that he is including KZ's for the boutique cap choices. Keep in mind, now - the fact that he is providing a set of boutique caps is stupendous by itself! The only reason I mention it is that those caps are tall, so you will have to locate the board at the bottom slot in the recommended Hammond case. Many builders have built the MAX that way, so it's not a problem.

 If you want to go with caps that are shorter and still boutique - you can refer to the post on the Millett Forum that I referenced earlier:

http://www.diyforums.org/phpBB2/view...hp?p=3308#3308


----------



## smegger

damn it guys my wallet already felt on the light side!!! well what upgrades would people recommend for getting the best out of some k601s which i have or k701s which are similar!


----------



## tomb

Quote:


  Originally Posted by *smegger* /img/forum/go_quote.gif 
_damn it guys my wallet already felt on the light side!!! well what upgrades would people recommend for getting the best out of some k601s which i have or k701s which are similar!_

 

Again, Jeff's parts are great. However, the ES's are best for killer bass slam and they are short at 1". Trouble is, unless you order both from Michael Percy, you have to get one pair at Handmade (CA2 - 1000uF@16V), and the other pair at BDent.com (CA7 - 470uF@35V).


----------



## smegger

Tomb i am in the uk do those places ship to here?


----------



## tomb

Quote:


  Originally Posted by *smegger* /img/forum/go_quote.gif 
_Tomb i am in the uk do those places ship to here?_

 

Don't know for sure - YGPM.


----------



## eddiewalker

I'm still trying to figure out what I'm going to do with my Max before I solder the heatsinks down. I ended up with taller sinks than will fit in the standard Hammonds case, but I dont have the means to pull off anything as neat as Vixr's. Perhaps plexi or lexan would be easier to work by hand (and less risky than taking the chance of ruining my one Hammonds lid.)

 One thought I've had though, is has anyone considered mounting the trimpots on the bottom of the board and drilling holes for them and the test points on the bottom of a case? I think it'd make for a much cleaner build with less fuss.


----------



## Listen2this1

Quote:


 One thought I've had though, is has anyone considered mounting the trimpots on the bottom of the board and drilling holes for them and the test points on the bottom of a case? I think it'd make for a much cleaner build with less fuss 
 

The usage problems that I can see is that in order to adjust the pots you would need to turn the amp over, 1. The tubes would be in the way 2.If you are going to be doing alot of adjustments at a time I would rather just remove a cover to do all of the adjustments.


----------



## eddiewalker

Quote:


  Originally Posted by *Listen2this1* /img/forum/go_quote.gif 
_The usage problems that I can see is that in order to adjust the pots you would need to turn the amp over, 1. The tubes would be in the way 2.If you are going to be doing alot of adjustments at a time I would rather just remove a cover to do all of the adjustments._

 

I'd considered that, but propping the amp up between two stacks of books to get access to the bottom is still much easier that removing the tubes and the back cover to slide the top off of a Hammonds case.

 I dont have room for the trim pots on the bottom since i have to mount the board in the bottom slot, but I still think i'm going to drill holes for the test points on the bottom and drill the "normal" adjust holes on the top just to avoid having to mess with mounting test point jacks (or disassembling the amp)

 If i can find some small grommets for the bottom holes that will still let the case sit on its feet I will use them to avoid shorting a test point to the case with a probe. Otherwise I'll just wrap my meter probes in electrical tape to accomplish the same.


----------



## tomb

A few things:

 1. A 3/16" hole centered above the trimmer screw (as per the layout templates I provided) is sufficient to adjust the trimmers with a trimmer wand. There's enough light from the LED's and overhead to see the position of the trimmer screw slot. Line up your trimmer tool tab with this screw slot, insert and turn. Sometimes you have to fish around a bit, but it's very easy to tell which is the trimmer screw and what's not. The 3/16" hole doesn't allow for a lot of twisting around, so it all works together.

 It should be noted that once you have the DB's biased and you've run them in for a few days - taking readings every once in awhile to confirm all is well - you should have little reason for adjusting them - ever - again.

 Same for the voltage adjustment in the PS.

 So essentially, the tube bias trimmers are what you really need to adjust things on a regular basis. That's three 3/16" holes in the lid, and three 1/4" holes in the backplate for three tip jacks. I only use plastic tip jacks, so they're very cheap. 

 2. Unless you have 2" sinks, it will all fit in the recommended Hammond case. 1-1/2" sinks will fit beneath the lid if the board is located in the bottom slot. Most MOSFET builders have done it this way. The volume knob and phone jack are a bit below the centerline, but it's not objectionable. There are many examples in the galleries on the MAX website.

 P.S. You may have trouble sticking the trimmer wand far enough into the case with 3/16" holes - if you locate the board in the bottom slot. You might want 1/4" diameter holes, instead. A good, insulated trimmer wand (about $1.50 at Jameco) helps to build confidence when sticking it into the case. I've done this hundreds of times with the MAX and Milletts before that. It's definitely safer than an open case while using a screwdriver.


----------



## Pingunugnug

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Yes, you should be concerned. The MAX should literally pump out enough volume to blow your headphones up (most headphones, anyway). The "friction" you describe may simply be a dirty pot.

 However, the rest of what you describe is not a dirty pot and actually sounds serious. Please post us some pics when you can. Meanwhile, please confirm the test point voltages - voltage supply, tube bias, and DB bias. Are you running BJT's or MOSFET's, what kind of power supply, etc., etc.?_

 

I redid the Pot but it is still cutting out.

 Here are the pics:

http://www.flickr.com/gp/11073745@N08/czb080

 I am running BJT's.
 Tubes: 12AE6 (Motorola) 
 - I just noticed this it says 12AE6 on the carton but it says 12AJ6 on the tube - diff name same thing or totaly different thing?
 Wall wart: 120VAC /23.5W Output: 24VAC @ 750ma


 Voltage: 27V
 Tube: R 13.3V / L 13.3V
 DB: R 71.9 (71.4)mv / L 72.2 (72.2) TA2R-TB2R(TB1R) / TA2-TB2L(TB1L)

 Thx


----------



## tomb

Quote:


  Originally Posted by *Pingunugnug* /img/forum/go_quote.gif 
_Here are the pics:

http://www.flickr.com/gp/11073745@N08/czb080

 I am running BJT's.
 Tubes: 12AE6 (Motorola) 
 - I just noticed this it says 12AE6 on the carton but it says 12AJ6 on the tube - diff name same thing or totaly different thing?

 Voltage: 27V
 Tube: R 13.3V / L 13.3V
 DB: R 71.9 (71.4)mv / L 72.2 (72.2) TA2R-TB2R(TB1R) / TA2-TB2L(TB1L)_

 

Ack! 
	

	
	
		
		

		
		
	


	




 That's your problem! The 12AJ6 has a gain of about 55. It's probably overdriving your output stage. The effects you describe on your volume knob may actually be happening to the amp.

 Hopefully, it didn't damage anything. Put the proper tubes in there and it may work: 12AE6, 12AE6A, 12FK6, or 12FM6.

 P.S. I once got a 6JH6 in an RCA box marked "12AE6A." So, it happens.


 EDIT: Thanks for posting the pics, but what happened to the top half of your tube sockets?


----------



## amphead

Tom, I have become a member of the "dark" side. You will see me soon. he he
 Seriously though posts coming to increase traffic there.


----------



## Pingunugnug

I replaced the tubes with the spare that I ordered and it solved both the rotating pot sound and the volume range problem. 

 Thanks 
	

	
	
		
		

		
		
	


	




 The tube sockets were drilled out for the leds when I flip it over for the picture the top part fell off and the pics were taken with them off.


----------



## ruZZ.il

You should epoxy them on, just careful with the pins. Get the 15/30 minute clear stuff thats good for ceramics. Glad your MAX is up! congrats!


----------



## amphead

Congrats again! I'm happy to hear that somehow the MAX, was able to sustain the battering from that monster gain!


----------



## amphead

Just got these in the mail from a generous head-fi member in NYC. Hmmm....what do I wan't to install.
 2x2SC3421
 2x2SA1358
 2x2SC3422
 2x2SA1359
 1x2SC2344
 1x2SX1011

 I will be replacing BD139/140s
 Edit: Tom, I remember seeing a comparison for these but couldn't find it with the search.


----------



## tomb

Quote:


  Originally Posted by *amphead* /img/forum/go_quote.gif 
_Just got these in the mail from a generous head-fi member in NYC. Hmmm....what do I wan't to install.
 2x2SC3421
 2x2SA1358
 2x2SC3422
 2x2SA1359
 1x2SC2344
 1x2SX1011

 I will be replacing BD139/140s_

 

Out of that list, the 2SC3422/2SC1359. Those rock with slam. 
	

	
	
		
		

		
			





 The 2SC3421/2SA1358 are a very close second, with enormous bass extension, but just a tad less musicality.

 The 2SC2344/2SA1011 are not quite as good as the other two, a little fat on the bottom end, but quite fun with Grados. I'm not that familiar with the K701's you use, but it may be interesting with those, too - something to color up the sterility, perhaps. (That's not a knock - I'd love to get some K701's when I can afford them!)


----------



## Blooze

I've tried to skim over this long thread, but what is the consensus on the 12FM6's so far with the better PSU in the MAX? I've got a few of the12FK6's, and a couple FM6's. Got a source that has a few FM6's I can get (and no, I'm not telling who or where 
	

	
	
		
		

		
		
	


	




 , ya'll snag 'em up before me!!) I remember with my old Rev.1 millett they were a little more smooth than the 12FK6's, but not quite as detailed. And I never did try any 12AE6's. Still running my 50 ohm AKG's and the little KSC-75s.

 I won't be building these till this winter when I can get some of the 2SC3422 pairs, but I'm gonna get some more tubes before the price goes up and availability goes down. I figure if I have 10 of each type that ought to last me a lifetime.


----------



## tomb

Quote:


  Originally Posted by *Blooze* /img/forum/go_quote.gif 
_I've tried to skim over this long thread, but what is the consensus on the 12FM6's so far with the better PSU in the MAX? I've got a few of the12FK6's, and a couple FM6's. Got a source that has a few FM6's I can get (and no, I'm not telling who or where 
	

	
	
		
		

		
		
	


	




 , ya'll snag 'em up before me!!) I remember with my old Rev.1 millett they were a little more smooth than the 12FK6's, but not quite as detailed. And I never did try any 12AE6's. Still running my 50 ohm AKG's and the little KSC-75s._

 

The FM's got a bad knock for some reason during the Rev. 1 days. After trying a dozen or so each of these, they're fairly consistent - the 12AE6's have the most punch, the FK6's the most detail, with the FM6's inbetween with a bit of both. Smoothness and airiness come down to the tube construction, since there were only 3 mfrs (we believe), but I'm hard pressed to tell you which is which. Some have noticeable airiness, but not much in the bottom end and vice-versa. YMMV x 10.

 I will say that the FM6's seem to be the rarest. So if you have a good source, protect it. 
	

	
	
		
		

		
		
	


	




  Quote:


 I won't be building these till this winter when I can get some of the 2SC3422 pairs, but I'm gonna get some more tubes before the price goes up and availability goes down. I figure if I have 10 of each type that ought to last me a lifetime. 
 

YGPM


----------



## pinkfloyd4ever

Quote:


  Originally Posted by *amphead* /img/forum/go_quote.gif 
_Just got these in the mail from a generous head-fi member in NYC. Hmmm....what do I wan't to install.
 2x2SC3421
 2x2SA1358
 2x2SC3422
 2x2SA1359
 1x2SC2344
 1x2SX1011

 I will be replacing BD139/140s
 Edit: Tom, I remember seeing a comparison for these but couldn't find it with the search._

 

this what you're looking for?
http://www.head-fi.org/forums/showth...postcount=1415


----------



## odoe

I am very happy with my combo of ES and 2SC3422/2SC1359. I don't know how much the orange drops impact the sound as I have no real comparisons to make, but that punch is definitely there. My tubes have settled in a bit and the airiness of the amp has really gotten more refined.


----------



## amphead

2SC3422/2SC1359 it is!
 Thanks Tom!


----------



## tomb

Quote:


  Originally Posted by *odoe* /img/forum/go_quote.gif 
_I am very happy with my combo of ES and 2SC3422/2SC1359. I don't know how much the orange drops impact the sound as I have no real comparisons to make, but that punch is definitely there. My tubes have settled in a bit and the airiness of the amp has really gotten more refined._

 

I agree with you, but I don't think the orange drops have anything to do with it. 
	

	
	
		
		

		
		
	


	




 My guess? 75% ES caps, 25% 2SC3422's. The orange drops should help preserve the cymbal crashes. The ES's will break up a bit on their own with that type of high-frequency impact. That's why they _need_ the bypasses. 

 The ES's pair up quite nicely with the 2SC3421 pair, too - for very, very deep bass extension.

 I still haven't tried those 2SC2238's yet, but they may be the pairing for the ultimate in detail with BG-equipped MAX. just a guess ...


----------



## amphead

Still working on the mask, it is about 95% complete. A little rough in spots. Fellow head-fiers, don't rely on this mask, because it is incomplete.


----------



## amphead

2SC3422/2SC1359 have just replaced the BD139/140s. Have not biased them yet, but the trimmers are full clockwise. It wasn't any fun doing the surgery, but needing to verify that I didn't destroy any traces, I plugged in the phones. Whooaa! This is what it sounds like unbiased? Its kicking some major ass. I have to solder a wire underneath the board to access my right channel testpoint. Here goes. Be right back!


----------



## adfinni

Quote:


 2SC3422/2SC1359 
 

Does anyone in the US have a pair or two of those transistors that they would be willing to ship over to the UK for a price, as i contacted B&D enterprises who confirmed the minimum $50 international order amount. Im not ready to spend that much as the costs for my boutique are spiralling out of control anyway 
	

	
	
		
		

		
		
	


	




 Anyhow, ordering my bits from mouser, and every other supplier around the world this week, so should hopefully be building by the end of next week.


----------



## amphead

adfinni, I wish I could help, TomB can sometimes find them, but no guarantees. Well, I biased left and right DBs for 70mv. I was starting to get thermal runaway at 90mv so I backed off! Soundstage and fidelity have come alive! I highly recommend the 2SC3422/2SC1359 pairing! 
 Thanks again Tom!


----------



## tomb

Quote:


  Originally Posted by *amphead* /img/forum/go_quote.gif 
_adfinni, I wish I could help, TomB can sometimes find them, but no guarantees. Well, I biased left and right DBs for 70mv. I was starting to get thermal runaway at 90mv so I backed off! Soundstage and fidelity have come alive! I highly recommend the 2SC3422/2SC1359 pairing! 
 Thanks again Tom! _

 

Thermal runaway? I have two MAX's set at 110mV with those pairs - one MAX is buttoned up in a case with only 1" sinks. Are you using some good thermal goo? Caution is advised, but you should _not_ have any trouble with stable operation at higher than that if you go 1/4 turn and wait a few minutes each time.

 Anyway, glad you like those trannies. 
	

	
	
		
		

		
		
	


	




  Quote:


  Originally Posted by *adfinni* 
_2SC3422/2SA1359_

 

Adfinni - YGPM


----------



## amphead

Well, not thermal runaway that can not be tamed. I am just being my usual cautious self. I wanted to listen to some tunes in a hurry, so I left them there until tommorrow. I will be going to at least 103mv on the next session.


----------



## tomb

OK, makes sense - nice work on the mask, btw.


----------



## soloz2

Quote:


  Originally Posted by *adfinni* /img/forum/go_quote.gif 
_Does anyone in the US have a pair or two of those transistors that they would be willing to ship over to the UK for a price, as i contacted B&D enterprises who confirmed the minimum $50 international order amount. Im not ready to spend that much as the costs for my boutique are spiralling out of control anyway 
	

	
	
		
		

		
			





 Anyhow, ordering my bits from mouser, and every other supplier around the world this week, so should hopefully be building by the end of next week._

 

I should have an extra pair around here somewehre


----------



## bou

Would anybody have an extra set of 2SC3422/2SC1359 to spare, I would really like to try those. BDent don't have the 2SC3422 in stock... I just ordered a kit from Jeff Rossel and I really look forward to build this amp. 

 Thank You
 Bou

 Edit : I forgot to say, I can pay with paypal for the transistors and the shipping to Canada.


----------



## tomb

Quote:


  Originally Posted by *bou* /img/forum/go_quote.gif 
_Would anybody have an extra set of 2SC3422/2SC1359 to spare, I would really like to try those. BDent don't have the 2SC3422 in stock... I just ordered a kit from Jeff Rossel and I really look forward to build this amp. 

 Thank You
 Bou

 Edit : I forgot to say, I can pay with paypal for the transistors and the shipping to Canada._

 

check with Soloz2 above. I'm committed to Adfinni and a couple of others right now and am running low myself. If that falls through, send me a PM and I'll see where I stand.


----------



## bou

Thank you Tomb for the response. I will contact soloz2.

 Soloz2 YGPM.

 Bou


----------



## adfinni

Quote:


  Originally Posted by *soloz2* /img/forum/go_quote.gif 
_I should have an extra pair around here somewehre_

 

Thanks for the offer, but ive already sorted it out with tom


----------



## Ferrari

Quote:


  Originally Posted by *c0nsumer* /img/forum/go_quote.gif 
_A while back I did a write-up on how I remove flux from PCBs. If you want to read it, it can be found here:

Flux Removal

 More specifically, what I did for the MAX soldered with a lead-free solder with Kester 331 (and 2331-zx) was as follows:

 - Solder down everything except the volume pot and one of the two center heatsinks. Also leave out other non-sealed parts if you have any. For the MAX I also left the MOSFETs off at this stage, because I didn't want water seeping in between them and the insulating film via capillary action.
 - Scrub the board down with warm tap water and a toothbrush. (I do this in the laundry tub.)
 - Rinse the board thoroughly.
 - Rinse the board with distilled water.
 - Dry the board with a combination of hot air (to dry faster) and compressed air (to get water out of small crevices).
 - Solder the volume pot, fit all the MOSFETs (BJTs would also apply here) and final heatsink.
 - Use a towel dampened with distilled water to remove the new bits of flux.

 This is similar to what is used in many test labs, except they'll often have an automated system which is water with cleaner, plain water, then deionized water.

 Also, I'm not sure if it was noted here already, but I've seen flux conduct just enough to trigger FETs and other parts, causing all sorts of problem. Not to mention that flux is generally corrosive..._

 

Ever heard about Electro Static Discharge (ESD)? Especially water: water can be regarded as a good conductor ( = electrons/charges transfer). What described here (use a towel to remove flux... 
	

	
	
		
		

		
		
	


	







 ) may generate charges transfer that are potentially harmful to sensitive components (MOSFETs, transistors) mounted on the board.

 ESD damaging of sensitive components is not always visible directly as toasted MOSFETs/transistors or somthing like that, but it can be latent also... things to keep in mind.


----------



## amphead

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_OK, makes sense - nice work on the mask, btw._

 

Ok, time to bias those DBs and give the full sonic evaluation. The mask is being worked with Paint Shop Pro, as opposed to the "proper" electronics software. It is in some ways more difficult, but in many ways easier for me to use.


----------



## c0nsumer

Quote:


  Originally Posted by *amphead* /img/forum/go_quote.gif 
_Ok, time to bias those DBs and give the full sonic evaluation. The mask is being worked with Paint Shop Pro, as opposed to the "proper" electronics software. It is in some ways more difficult, but in many ways easier for me to use.
	

	
	
		
		

		
		
	


	


_

 

This is a pretty simple board. Laying it out again in EAGLE wouldn't be too difficult, but the license to do a schematic+board of that size runs US$800. 
	

	
	
		
		

		
		
	


	




 I'd gladly do it, but I only have a commercial license for 80mm x 100mm boards, and a non-profit license for 160mm x 100mm.


----------



## ericj

RA8L and RA9L check out just fine. 

 RA1L checks out ok too. 

 Replaced QA1L and QA2L. 

 Replaced the tube socket. 

 Whereas before i could bias VTL between about 7.6v and 8.5v, now i can bias it between about 9.5v and 10.4v. 

 Anybody got any ideas? 


 Mosfets aren't biasing the way they ought either. 

 I got proper 1n5486's into QB1L/R. RB12L/R are 1k as specified. 

 There's a point on both sets of mosfets where, when rotating RB12, the voltage between TA2 and TB1/2 jumps from 30mv to over 1v. 

 I've never had this much trouble with a printed board amp before.

 Edit: Oh, using the min/max function of my Wavetek DMM, i've measured the inrush at as high as 1.7 amps. These fast-blowing fuses don't have a snowcone's chance in heck.


----------



## ruZZ.il

hm. is that with the tubes in? what happens when you switch the tubes between L/R? does VTR bias right? do you have a function to check diodes with your dmm? go over all the transistors and make sure you have 2 diodes in them.. with about 0.3~0.8v forward bias voltage(I dont think you can check the mosfets with your dmm so simply though). just look at the NPN as 2 diodes, NP and PN. the PNP as PN and NP. when you initially fired up, what were the trimmers orientation? other than caps, did you get any parts not from the BOM? 
 got pics?


----------



## tomb

Quote:


  Originally Posted by *ericj* /img/forum/go_quote.gif 
_RA8L and RA9L check out just fine._

 

Just to be sure, RA9L must be 10 times RA8L. The BOM specifies:
 RA8L: 1.13K ohm
 RA9L: 11.3K ohm

 Alternatively, 
 RA8L: 1K ohm
 RA9L: 10K ohm

 So, are your values similar - or do you have "K" values? 

  Quote:


 RA1L checks out ok too. 
 

Just for kicks, is this trimmer 5K? The PS trimmer is 2K, BJT trimmers are also 2K, the MOSFET trimmers should be 1K. However, the tube trimmers should be *5K*. 

  Quote:


 Replaced QA1L and QA2L. 
 

Are these both 2n5087's? They are both the same, _not_ a complementary pair. 

  Quote:


 Replaced the tube socket. 
 

I doubt that had anything to do with it, IMHO. 

  Quote:


 Whereas before i could bias VTL between about 7.6v and 8.5v, now i can bias it between about 9.5v and 10.4v. 
 

Almost sounds like the wrong trimmer to me - just a guess. 

  Quote:


 Anybody got any ideas? 
 

See the above. 
	

	
	
		
		

		
		
	


	





  Quote:


 Mosfets aren't biasing the way they ought either. 

 I got proper 1n5486's into QB1L/R. RB12L/R are 1k as specified. 
 

Just for the record, they should be 2n5486's, but I'm sure that's a typo.

  Quote:


 There's a point on both sets of mosfets where, when rotating RB12, the voltage between TA2 and TB1/2 jumps from 30mv to over 1v. 
 

Again - just asking the obvious - but do you have the MOSFETs on the _left_ side of the sinks as you face the front of the board? Are RB1L/R jumpered out? These are _not_ used for the MOSFETs. Are you using R84L/R and RB9L/R? These should be 100ohm, but are not used in the BJT version. Are RB2L/R and RB3L/R 390ohm? These values of RB2 and RB3 are unique to the MOSFET version. Finally, are RB12L/R *1K* trimmers? Again, this value is unique to the MOSFETs.

  Quote:


 I've never had this much trouble with a printed board amp before. 
 

Sorry for your trouble.

  Quote:


 Edit: Oh, using the min/max function of my Wavetek DMM, i've measured the inrush at as high as 1.7 amps. These fast-blowing fuses don't have a snowcone's chance in heck. 
 

No comment.


----------



## c0nsumer

Quote:


  Originally Posted by *ericj* /img/forum/go_quote.gif 
_Edit: Oh, using the min/max function of my Wavetek DMM, i've measured the inrush at as high as 1.7 amps. These fast-blowing fuses don't have a snowcone's chance in heck._

 

I'm not trying to stir up discussion over this, I just wanted to mention Mouser part number 576-0218001.HXP which is a slow-blow 1A fuse whose datasheet  seems to indicate that it can sit at just over 2A for a bit more than one second. I ordered a few of these and I'll see how they work out. I presume the results will be good. I also ordered the 800mA analog for the new BJT MAX I'm putting together. I'll provide inrush and such for that one once it is complete.

 -Steve


----------



## ericj

Quote:


  Originally Posted by *ruZZ.il* /img/forum/go_quote.gif 
_hm. is that with the tubes in? what happens when you switch the tubes between L/R? does VTR bias right?_

 

Yes. Whatever tube is in the right socket biases fine. These are United 12FM6 tubes I've used in my RevMH. 

  Quote:


  Originally Posted by *ruZZ.il* 
_do you have a function to check diodes with your dmm? go over all the transistors and make sure you have 2 diodes in them.. with about 0.3~0.8v forward bias voltage(I dont think you can check the mosfets with your dmm so simply though). just look at the NPN as 2 diodes, NP and PN. the PNP as PN and NP. when you initially fired up, what were the trimmers orientation? other than caps, did you get any parts not from the BOM? 
 got pics? 
	

	
	
		
		

		
		
	


	


_

 

I guess i could check the transistors that way. 

 Trimmer orientation is correct. 

 Several caps aren't identical to the BOM but that's to be expected. R1 is 20ohm but since V+ is 27.8v that's fine. 

 RA5C and LEDC are not populated. 

 Bridge rectifier is built with ultrafast to220 diodes you've never heard of, but that's ok. 

  Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Just to be sure, RA9L must be 10 times RA8L. The BOM specifies:
 RA8L: 1.13K ohm
 RA9L: 11.3K ohm

 Alternatively, 
 RA8L: 1K ohm
 RA9L: 10K ohm

 So, are your values similar - or do you have "K" values?_

 

RA8L reads 1.146k, RA9L reads 11.45k.

  Quote:


  Originally Posted by *tomb* 
_Just for kicks, is this trimmer 5K? The PS trimmer is 2K, BJT trimmers are also 2K, the MOSFET trimmers should be 1K. However, the tube trimmers should be *5K*._

 

They are Murata type PV36 5K trimmers. I've measured from pin 2 of the tube socket to ground while adjusting it, and i have full range of adjustment between 0 and 5k. 

  Quote:


  Originally Posted by *tomb* 
_Are these both 2n5087's? They are both the same, not a complementary pair._

 

Yup. 

  Quote:


  Originally Posted by *tomb* 
_I doubt that had anything to do with it, IMHO._

 

I figured there was a possibility that I'd fouled something while gluing the halves together after drilling out the rivet. 

  Quote:


  Originally Posted by *tomb* 
_Almost sounds like the wrong trimmer to me - just a guess._

 

Yeah, but it aint. 

  Quote:


  Originally Posted by *tomb* 
_Just for the record, they should be 2n5486's, but I'm sure that's a typo._

 

Right. i don't think 1n5486 even exists. 

  Quote:


  Originally Posted by *tomb* 
_Again - just asking the obvious - but do you have the MOSFETs on the left side of the sinks as you face the front of the board? Are RB1L/R jumpered out? These are not used for the MOSFETs._

 

Yes and Yes. 

  Quote:


  Originally Posted by *tomb* 
_Are you using R84L/R and RB9L/R? These should be 100ohm, but are not used in the BJT version._

 

Yup. They look like 100r to me (have the right bands). 

  Quote:


  Originally Posted by *tomb* 
_Are RB2L/R and RB3L/R 390ohm? These values of RB2 and RB3 are unique to the MOSFET version. Finally, are RB12L/R *1K* trimmers? Again, this value is unique to the MOSFETs._

 

yes, and yes. 

 I'll post pics after work.


----------



## tomb

Quote:


  Originally Posted by *ericj* /img/forum/go_quote.gif 
_<snip> ... I'll post pics after work._

 

Yep. Based on your answers, that's the next step. Again, sorry you're having trouble.


----------



## ruZZ.il

hm. try comparing measurements between L/R channels around the tube area.. it still wouldn't solve the DB biasing issue, but maybe you'll spot something bout the tubes. The first(tube) stage may be fine though, and the biasing prob caused by an issue in the second stage.. I had tube biasing probs with a burnt out QB8. But its funny cause you're getting the same mosfet biasing issue on both sides.. so its less likely to be a faulty joint or some short.. but different tube behaviour.. so.. dunno.. something seems asymmetrical though, maybe we can start by finding that..


----------



## joneeboi

Reporting that I switched out boutique positions with some Solens I had from my RA-1 Clone project and some 1000uF Pannies I received from a generous head-fier today. Before I was kinda skeptical of all this boutique stuff, but no longer. Soundstage has widened, noise floor blackened, bass levels risen, and overall clarity and transparency. It's revealed a lot of clicks I never knew I had in a bad encoding of Rachmaninoff Piano Concerto No. 2. I had heard a few of those clicks unamped, but I just assumed they were the noises from the maestro constantly tapping his music stand. 
	

	
	
		
		

		
			





 Alas, the double edged sword of detail! Pictures to come maybe tomorrow.


----------



## amphead

Quote:


  Originally Posted by *c0nsumer* /img/forum/go_quote.gif 
_This is a pretty simple board. Laying it out again in EAGLE wouldn't be too difficult, but the license to do a schematic+board of that size runs US$800. 
	

	
	
		
		

		
		
	


	




 I'd gladly do it, but I only have a commercial license for 80mm x 100mm boards, and a non-profit license for 160mm x 100mm._

 

Thanks for the offer, but contrary to what others experiences have been with consumer imaging software, I have had many positive builds doing it this way. The boards built with Paint Shop Pro, will be 90% of the quality of the commercial version, but will still be 100% functional. The real challenge for me is after the mask is done. Doing a quality photoresist develop/etch! 
	

	
	
		
		

		
		
	


	



 Edit: I am encouraging those who have not built the Max yet, to use boards from the group buy if more become available. They were built to 110% quality standards, and will last a long time with a proper build.The ones that I do, will allow me to experiment a little. If using my final mask, and etching your own board, just think of it as for experimental purposes, because its extremely difficult to match the quality of a first rate commercial board.


----------



## ericj

Sorry no pics yet. I got home and my shipment of Sanyo transistors finally turned up, so i finished building my CKKIII instead.


----------



## tomb

Quote:


  Originally Posted by *ericj* /img/forum/go_quote.gif 
_Sorry no pics yet. I got home and my shipment of Sanyo transistors finally turned up, so i finished building my CKKIII instead._

 

Bad choice. 
	

	
	
		
		

		
		
	


	







 Anyway, we're waiting to help when you get a chance.


----------



## tomb

Quote:


  Originally Posted by *joneeboi* /img/forum/go_quote.gif 
_Reporting that I switched out boutique positions with some Solens I had from my RA-1 Clone project and some 1000uF Pannies I received from a generous head-fier today. Before I was kinda skeptical of all this boutique stuff, but no longer. Soundstage has widened, noise floor blackened, bass levels risen, and overall clarity and transparency. It's revealed a lot of clicks I never knew I had in a bad encoding of Rachmaninoff Piano Concerto No. 2. I had heard a few of those clicks unamped, but I just assumed they were the noises from the maestro constantly tapping his music stand. 
	

	
	
		
		

		
		
	


	




 Alas, the double edged sword of detail! Pictures to come maybe tomorrow._

 

Sounds good, but please - give us some more details: which Solens? (rating, etc.) What positions on the MAX? What Pannies and in which positions? Just so somebody else can replicate your experience.


----------



## joneeboi

In the spirit of using grossly overspec'ed components, I grabbed 6 Solens from PartsExpress of the 5.1uF 400V variety, plopped them into CA8LR, CA9LR. I didn't have enough to finish off CA3, CA6, but I don't think I would have had room for them anyway. The other two are in my CMoy which has yet to be finished. I also replaced CA2LR, CA7LR with 1000uF Panasonic FCs, up from my Nichicon 470uF off the BOM. My MAX was already pretty punchy and fun in the bass department, but now I think they are overstaffed. I'm beginning to believe this is how the Grado bass should sound. Now if only I could get some realistic reproduction of the highs.

 Allow me to attempt to make this into a pico-review:

 The noise floor has never been this quiet. Source silenced, volume knob down, hum was definitely still audible. This situation has since changed. Channels are as far apart as they've ever been. I've heard the K701, HD650, GS1K separation, and it's not quite as clear on the lowly SR60s. Nevertheless, I find myself turning my eyes to the side to visualize the guitars, drums, vocalists. They aren't all around or above or below me, but they are in front of me as though I'm sitting close to stage. It still sounds like they're packed into a minivan and opened the door to let me hear their music, but this time the door opening is bigger. Hi-hats and cymbals are clearer and more resolved, and I hear patterns I've never figured out via the HP jack. The difference is almost like someone has stepped out of the way and I can see what the drummer is doing, although he is pretty far away and there's stage smoke and people are jumping up and down and he's behind his drum kit and people are walking around on stage. Overall, my aural eyes are beginning to open, and I like what I see. Except for the darn clicks in the track. If I didn't have the Grado mids, this setup would be unbearable.

 Hm, do I sound like Patrick82 now?


----------



## joneeboi

It'll be hard to bias this whenever the occasion arrives. I guess I just won't tube roll 
	

	
	
		
		

		
		
	


	








 ruZZ.il's sil pads


----------



## tomb

Joneeboi,

 The heck with sounding like Patrick, you're on your way to Ferrari's DIY-Extreme territory. 
	

	
	
		
		

		
		
	


	




 Seriously, thanks for the specs and thanks for the pics. That makes me think I can fit those 0.47uF VitQ's in one of mine.

 BTW, I tried to emphasize to everyone that C2 should be a 1000uF cap, anyway. Most likely, that's where your bass is coming from. Upping C2 to 1000uF makes a huge difference. Those Solens are responsible for all the rest of your flowery prose, though.


----------



## ericj

You know, noise floor and channel separation are aspects that we can easily and accurately measure. 

 Just sayin.


----------



## adfinni

Very nice joneeboi but what's that in the background ???

  Quote:


 Illustrated Catwatching


----------



## britishbane

deleted


----------



## ruZZ.il

hey Jon, looks like a mean amp now 
	

	
	
		
		

		
		
	


	




 mind jumpering over the output resistors and letting us know if those V-D's are steamy, smokey or a bunch of jumpy teenagers? they may just be a transparent mist... nice metaphors 
	

	
	
		
		

		
		
	


	




. I'm yet to experiment with the kiwames I have waiting..

 edit: you could flip those trimmers around to make it easier.. if you do, when they're out just measure the resistance between 2 adjacent pins, then trim to get the same resistance between the middle and other pin to make sure you power up in the same ballpark. it'll just trim in the other way, but thats okay.. I'm sure you know what I mean..


----------



## _atari_

Hi,

 I m just wondering if there are any Europian tubes as a replacement or alternatives for the American 12AE6 or similar.

 Any experience or suggestions?

 Thanks in advance

 _atari_


----------



## tomb

Quote:


  Originally Posted by *britishbane* /img/forum/go_quote.gif 
_Can those of you who have completed the amp and logged a few hours compare it to a current production amp? For example the gilmore lite or a tube amp like the raptor. Just a few quick impressions would help me make up my mind, whether or not I want to make this amp._

 

No offense, but answering questions like that around here (Head-Fi) is a good way to get this whole thread locked.

 I would suggest either posting this question in a separate thread or PM'ng someone who's built one and has a frame of reference you're interested in (look at their sig for equipment with which to compare).


----------



## tomb

Quote:


  Originally Posted by *_atari_* /img/forum/go_quote.gif 
_Hi,

 I m just wondering if there are any Europian tubes as a replacement or alternatives for the American 12AE6 or similar.

 Any experience or suggestions?

 Thanks in advance

 _atari__

 

No, but all of the Millett tubes enjoyed worldwide distribution, AFAIK. I just bought a bunch of 12AE6's from French Quebec if that means anything, and through the years there have been several Millett builders from Germany, Belgium, Netherlands (Ferrari, for instance), the UK, etc.


----------



## amphead

I am going to call this the final mask. Use it to build experimental boards. That is, use good components to experiment, but not the extreme boutique. Or, go ahead if you want.
	

	
	
		
		

		
			




 Edit - To use this image copy the image and paste it to word. Resize in word and print. Change the size until the posts of your heatsink line up on the mask. Edit: Image is updated, but you will need to hit your refresh button to see the current version.


----------



## ruZZ.il

how do you do the grounding?


----------



## c0nsumer

I decided to build another MAX better suited for my desk at work. With the Hammond 1455T2201 there should be no problem fitting an Alien DAC in the box, and I'm hoping to fit an input switch on the front panel, for selecting between USB, Input 1, and Input 2.

 I'm planning on using the pictured Elna RFS caps for CA2L/R and CA7L/R, 2SC2238/2SA968s in a BJT output stage, 12FK6 tubes, and everything else pretty stock off the BOM.

 Hopefully it'll work out well. My biggest concern right now is fitting the input switch. It should arrive tomorrow, and if it doesn't seem to fit I might bang something together with a PIC, selector button, indicator LEDs, and a few relays. We'll see.

 -Steve


----------



## MrSlacker

Hey guys, does anyone have an extra headphone jack? I got a different one, but turns out it wont really fit the case. I'll pay for the jack and everything.. just don't want to pay $5 shipping from mouser.

 Thanks


----------



## ericj

OK, took pics. Board still needs a final alcohol rinse to get the rest of the rosin off, which is why you see some smudges here and there. 

 11 megs of pics, and i figured they should be left big, so, I'm not attaching them or even linking them directly. 

 Go here: http://166.70.233.190/MAX/


----------



## tomb

Quote:


  Originally Posted by *ericj* /img/forum/go_quote.gif 
_OK, took pics. Board still needs a final alcohol rinse to get the rest of the rosin off, which is why you see some smudges here and there. 

 11 megs of pics, and i figured they should be left big, so, I'm not attaching them or even linking them directly. 

 Go here: http://166.70.233.190/MAX/_

 

One thing I see right off - you have the MOSFET compensation caps shorting across the wrong terminals on the MOSFETs. Here's Ferrari's pic from the MAX website:





 I'll keep studying, though - and thanks for the pics!


----------



## tomb

QB2L is reversed, eric.

 I didn't think it was possible, but some of the guys are confirming that if you have bad problems in the DB's, it can affect the tube bias. Since that's the left channel, it might be the problem.


----------



## amphead

Nice work Joneeboi! I have to say that 5.1uF in those positions would usually be a little too flabby and reduce the higher frequency response, but I'm glad that you are enjoying them. You have outdone yourself with the review. Hope to hear some more!


----------



## Sixer

Got mine all up and running a couple of days ago - still not cased but humming along. 
	

	
	
		
		

		
		
	


	




 However it doesn't sound as good as I expected, from all reports, it should sound brilliant, but my one has a rather disappointing amount of detail and the highs aren't great either - neither are terrible, just no where near as good as I expected. Now i'm not comparing this to anything amazing - it even sounds on par or only a little better compared to the headphone out on my ipod with both my RS-2s and ER-6is. On the other hand, bass is pretty good and midrange punch is good too - just lacking detail and highs. It's kinda harsh at times too.

 Everything should be biased ok, using 12AE6A tubes at 13.5-13.7v bias each, MOSFETs at 220mv. Power supply is 27v.

 Have I made poor choices in terms of caps? Is this what tubes inherently sound like? Could I have actually done something wrong in my construction?

 Caps are:
 CA2: 1000uF 25v Blackgate NX
 CA9: 0.22uF Sonicap genII
 CA7: 680uF 35v Blackgate NX
 CA8: Sonicap 0.82uF genII

 Would be great if someone could shed some light on this


----------



## tomb

Quote:


  Originally Posted by *Sixer* /img/forum/go_quote.gif 
_Got mine all up and running a couple of days ago - still not cased but humming along. 
	

	
	
		
		

		
		
	


	




 However it doesn't sound as good as I expected, from all reports, it should sound brilliant, but my one has a rather disappointing amount of detail and the highs aren't great either - neither are terrible, just no where near as good as I expected. Now i'm not comparing this to anything amazing - it even sounds on par or only a little better compared to the headphone out on my ipod with both my RS-2s and ER-6is. On the other hand, bass is pretty good and midrange punch is good too - just lacking detail and highs. It's kinda harsh at times too.

 Everything should be biased ok, using 12AE6A tubes at 13.5-13.7v bias each, MOSFETs at 220mv. Power supply is 27v.

 Have I made poor choices in terms of caps? Is this what tubes inherently sound like? Could I have actually done something wrong in my construction?

 Caps are:
 CA2: 1000uF 25v Blackgate NX
 CA9: 0.22uF Sonicap genII
 CA7: 680uF 35v Blackgate NX
 CA8: Sonicap 0.82uF genII

 Would be great if someone could shed some light on this 
	

	
	
		
		

		
		
	


	


_

 

A few things to try:

 1. IMHO, and I've already had this conversation with someone, but the GEN II's are a poor choice for the BG's. They were only recommended for the ES's, which are an entirely different cap.

 BG's should use an ultra boutique (translated means very expensive), the small NX Hi-Q's (0.47@50V) in a "Super E" configuration, or NO bypass caps at all. There are, in fact, many articles making reference to bypass caps actually ruining the response of BG's. Not saying that's what's happening, but again, the GEN II's were never mentioned as a good combo with the BG's.

 Even after you do all of that, it may take quite awhile for the BG's to break in - they are notorious - like 200hrs worth.

 2. Put some 12FK6's in there and see if that helps. The 12FK6's are generally speaking, the most detailed tubes. They are a little light on the bass, however, and may not have enough gain to adequately punch through a Sennheiser veil. Low gain and a Sennheiser veil are obviously not your issues with Grados and IEM's, however.

 3. Take out the RB14L/R resistors, if you have any in there. These will reduce impact and soften detail to a certain extent. That's preferred in some situations, but not yours from what it sounds like.

 4. Finally, the MAX is very sensitive to source. MP3's sound like crap, IMHO. An iPod or PDCP may sound just fine with revealing headphones or IEM's, but very disappointing on the MAX (as in "not much difference"). Try FLAC files from a DAC, an iPod, or direct CD from a decent CD player - hopefully one with a true line out and a discrete output stage.

 "4." may be a difficult thing for you, but items 1 - 3 should have the most immediate effect and in that order.

 Let us know how it turns out. We want everyone to be happy with their MAX. I'm pretty sure it's the GEN II's and maybe some deader-than-usual 12AE6A's.

 P.S. To add another that was mentioned for bypassing BG's - Vitamin Q's. This is because as Dsavitsk as said, the VitQ's are actually on the neutral side with extended high ends. As stated, though, the default should be no bypasses or perhaps the little NX Hi-Q's popped in reverse polarity (all these caps are supposed to be non-polar, but what the hey - that's what BG says to do, and it's a proven method).


----------



## Sixer

Thanks for that tomb 
	

	
	
		
		

		
		
	


	




 #1 Ahh right! - I'll try removing the sonicaps and see what kind of difference that makes!

 #2 Yeah I'm intending on getting some 12FK6s - I should have got them first - I just couldn't find any locally.

 #3 No resistors - jumpered out 
	

	
	
		
		

		
		
	


	




 #4 I have been running the max from a NAD cdp - so I think I should be OK source wise.

 In fact I'll remove those sonicaps right now - expect a report in a little while


----------



## ruZZ.il

I'm running a similar config caps wise, just with 0.22 in CA8. I've got the FK tubes though. I cant say I'm lacking detail, nor highs though. I can say I'm noticing ups and downs, with a general upward trend in sound quality as it clocks play time.. the tubes need a few hours and the BG's supposedly need a few hundred. Also significant difference after its warmed up. The BG's supposedly don't play well with bypass caps unless they're top end and are meant to sound pretty good on their own. I'll see how they behave without them soon.. if everything is stable in your setup, I'd let it play for a while and see how it plays out..

 edit: hehe beat me to it.. Tom, you're the man! I cant compete 
	

	
	
		
		

		
		
	


	



 and sixer, looks like you'll beat me to that report too.. I'm looking forward to it.


----------



## Sixer

Haha - thanks anyway ruZZ! 
	

	
	
		
		

		
		
	


	




 Ok - sonicaps are out. Definitely an improvement on first impressions. There are actually some decent highs now! 
	

	
	
		
		

		
		
	


	



 I'll let the BGs burn in and get some 12FK6s and I think I should be very happy. 
	

	
	
		
		

		
		
	


	




 Ooh it is sounding rather nice!
 I'll give you an updated report when the 12FK6s are in.

 Thanks Tomb! 
	

	
	
		
		

		
		
	


	




 PS. anyone wanna buy some slightly used sonicaps?


----------



## soloz2

Quote:


  Originally Posted by *Sixer* /img/forum/go_quote.gif 
_Haha - thanks anyway ruZZ! 
	

	
	
		
		

		
		
	


	




 Ok - sonicaps are out. Definitely an improvement on first impressions. There are actually some decent highs now! 
	

	
	
		
		

		
		
	


	



 I'll let the BGs burn in and get some 12FK6s and I think I should be very happy. 
	

	
	
		
		

		
		
	


	




 Ooh it is sounding rather nice!
 I'll give you an updated report when the 12FK6s are in.

 Thanks Tomb! 
	

	
	
		
		

		
		
	


	




 PS. anyone wanna buy some slightly used sonicaps? 
	

	
	
		
		

		
		
	


	


_

 

I might be interested depending on what shipping would be


----------



## ericj

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_QB2L is reversed, eric.

 I didn't think it was possible, but some of the guys are confirming that if you have bad problems in the DB's, it can affect the tube bias. Since that's the left channel, it might be the problem._

 

Hmm, surprised i missed that. 

 Must have read the instructions wrong wrt. the caps.


----------



## Sixer

Quote:


  Originally Posted by *soloz2* /img/forum/go_quote.gif 
_I might be interested depending on what shipping would be_

 

Probably not worth it - the leads have all been snipped anyway.

 ericj: actually the instructions in the BOM are wrong. They say the cap should be between the gate and drain of the mosfet, where it should be gate and source.


----------



## ruZZ.il

Quote:


  Originally Posted by *Sixer* /img/forum/go_quote.gif 
_... Ok - sonicaps are out. Definitely an improvement on first impressions. There are actually some decent highs now! 
	

	
	
		
		

		
			




 I'll let the BGs burn in and get some 12FK6s and I think I should be very happy. 
	

	
	
		
		

		
		
	


	




 ..._

 

I did something slightly different. I wouldn't advise doing it, but I unsoldered one leg of each of the bypass caps on one side of the amp and bent the caps back just a little so that the one leg would 'hover' just above the solder point. While listening, I carefully pushed down on the cap/s so that the leg would be pushed against the solder point while perking my ear for differences. Thing is, I cant really make out any difference, even after numerous A/Bing. This could mean a few things, and one of them being that the BG's are quiet fine as is. Alternatively, I just can't hear the difference, but that just leaves the question being how much of a difference is actually audible (or how sensitive my ears are, but I'd rate myself as rather finicky 
	

	
	
		
		

		
		
	


	




). Amongst how I tried to pick off diffs' was by using a mono input signal and having everything positioned pretty much smack in the middle of my head, and trying to hear anything get lopsided.. hmm.. <shrugs>. Anyway, since _I_ cant pick up much difference, I'll probably use these Gen II's for my next MAX that I hope to use ES's on. I'll repeat the little experiment then too. meanwhile, for my purposes, I'm concluding that the BG's are rather happy on their own. oddly enough, in contrary to your experience, I didn't hear any deterioration due to the presence of the bypass caps either. hmm.. maybe the AEs have something to do with this...<shrugs>.


  Quote:


  Originally Posted by *Sixer* /img/forum/go_quote.gif 
_PS. anyone wanna buy some slightly used sonicaps? 
	

	
	
		
		

		
		
	


	


_

 

well, I plan to use mine on my other MAX. it was also suggested that these could be used as bypass caps in an alien DAC, so I plan to get some others for that purpose too (I guess for the ES's, atleast). the pre-clipped legs would be problematic for me though. Talking about alien DACs, I'm planing on building atleast another 2. one with BG's and one with ES's. I'd really like to personally get more familiar with the differences each cap has to offer, and how the combinations pair up. maybe later on, I'll play with other caps too


----------



## ruZZ.il

Quote:


  Originally Posted by *Sixer* /img/forum/go_quote.gif 
_Probably not worth it - the leads have all been snipped anyway.._

 

this would be no problem at all if they're intended to be put in a MAX, specially if they were positioned rather well to begin with.


----------



## tomb

Quote:


  Originally Posted by *Sixer* /img/forum/go_quote.gif 
_Probably not worth it - the leads have all been snipped anyway.

 ericj: actually the instructions in the BOM are wrong. They say the cap should be between the gate and drain of the mosfet, where it should be gate and source._

 

Thanks for that bit of info. I'm bad about mixing terms - I guess my brain works on a graphical level - knowing that it was the outer two pins. I'll make the correction.

 EDIT: It's corrected. Sorry if that messed anybody else up.


----------



## ericj

Well, at least my mistakes are relatively easy to fix. 

 Good to hear that the mistake with the caps wasn't due to lack of attention.


----------



## Listen2this1

I come to this forum this time with a frown. Just finished assembly on the max and after plugging it in I was able to set the Ps voltage just fine. Moved onto the Tube Bias went well. Went to adjust the Db bias and then it all did not go well. Before plugging it in I did turn in the pots, But after trying to back them out Rb11-10 started to smoke the solder joints. So i unplugged it and turned the pots all the way out, then went in 20 turns. Plugged it back in and the same thing happened. So I desoldered the resistors and measured them, Perfect 2.2ohms. It only seems to happen on the right channel I do not get a chance to check the left.

 I really do appreciate any help






 By listen2this1


----------



## Ferrari

Quote:


  Originally Posted by *Listen2this1* /img/forum/go_quote.gif 
_I come to this forum this time with a frown. Just finished assembly on the max and after plugging it in I was able to set the Ps voltage just fine. Moved onto the Tube Bias went well. Went to adjust the Db bias and then it all did not go well. Before plugging it in I did turn in the pots, But after trying to back them out Rb11-10 started to smoke the solder joints. So i unplugged it and turned the pots all the way out, then went in 20 turns. Plugged it back in and the same thing happened. So I desoldered the resistors and measured them, Perfect 2.2ohms. It only seems to happen on the right channel I do not get a chance to check the left.

 I really do appreciate any help_

 

What do you mean with turn in/out the trimpot 
	

	
	
		
		

		
		
	


	




 ? What is the definition of your "turn in" ? clockwise? counter-clockwise? What do you expect when you turn the trimpot 20 turns?
 Why don't just keep the buffer bias at its minimum at first powerup by turning the buffer trimpots RB12L/R full clockwise?


----------



## ruZZ.il

with the DB trimpots orientation, minimum bias is when they're turned all the way clockwise. also, when initially firing up they should be the first thing to bias since they're the most sensitive. now, if you did what I did 
	

	
	
		
		

		
		
	


	




 and had them biased to their max, taking too much time to get to them... you may have burnt out an output transistor (like i did). what happened after that is that the channels minimum bias started at 170mv(/2.2=~77mA) but quickly shot up to just over 1.5V (over half an amp!). so, make sure you trim them clockwise all the way, then power up, ideally with your dmm set to check voltage on its most sesitive(lowest voltage) scale. dont keep it on for long if you see a prob, just note down your measurements and power down. if your problem is anything similar to mine, it may be qb8 and that would need changing.. also, you say one side biases right? then next maybe start to look at whats different between the 2 sides.. resistor values, checking with a dmm, etc.. comparing each side rigorously. I managed to pinpoint my problematic qb8 after switching components between left and right one by one, but with some info we can start with the right components.. good luck and keep us updated 
	

	
	
		
		

		
		
	


	




 ..say, when did you get your board?


----------



## Listen2this1

I went clockwise all the way in until i heard a little clicking noise, I took it that was all the way in. I have a feeling that I did burn up a output transistor.

 I was one of the first to get a proto board. I Just now got around to putting this together.


----------



## ruZZ.il

well, one way to make sure is to start switching them between the left and right channels and seeing if the problem follows. I'd wait for Tom to come around though. He knows a lot more about this stuff and this amp specifically than I do, and is bound to have some ideas for you.. but it is likely that you burnt up one of those transistors and this shouldn't have happened if you started up with them trimmed correctly, in which case something else may have caused it.. no worries, seeeeek and deeeestroy!
	

	
	
		
		

		
		
	


	



 (okay, seek and solve 
	

	
	
		
		

		
		
	


	




 )


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## tomb

Yep - that's a prototype board.

 ruZZ.il and Ferrari gave good advice and pointers. As Ferrari says - clockwise all the way down - which is 25 turns, by the way. Also as ruZZ.il says - don't let the amp sit there while you check all these other things - the DB's come first. They're the only thing that will smoke on their own simply from a bad setting.

 By all means, check the trannies in the DB - make sure you haven't swapped a 2n5087 for a 2n5088 and vice-versa. Some of the resistors are critical - RB4 and RB6, for instance. If one of those are switched, it could throw the symmetry off in the DB.

 Good luck and let us know how you are doing.


 EDIT: What ruZZ.il suggested at first makes a lot of sense. Is the left side OK? If so, leave those resistors out on the right and see if the Left side can be biased correctly. If so, then start studying the right side and see what doesn't match up.


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## Listen2this1

Does anyone know the reading that i should get when testing the Qb8 With the NpN settings on my dmm? I am getting 1695 Good or Bad?


----------



## tomb

Quote:


  Originally Posted by *Listen2this1* /img/forum/go_quote.gif 
_Does anyone know the reading that i should get when testing the Qb8 With the NpN settings on my dmm? I am getting 1695 Good or Bad?_

 

What QB8 do you have? Most of them should be about 240 HFE.


----------



## ericj

Quote:


  Originally Posted by *Listen2this1* /img/forum/go_quote.gif 
_Does anyone know the reading that i should get when testing the Qb8 With the NpN settings on my dmm? I am getting 1695 Good or Bad?_

 

Some DMMs read insanely high numbers like that when the transistor isn't plugged in correctly. 

 my waveteks just screech at me until i pull them out . . .


----------



## Listen2this1

I am using the je243g's, Afer removing the left channel qb8 It read 840, So I thought that was good. So I re-installed it and tried to bias the left. It also has problems. Is it possible that I put the trimmers to far clockwise. Can they create a dead short? All 5088-5087 are in their right positions. I think on Monday I will order new qb8's Rb14/10's and new trim pots. Exchange those and see where that gets me. Should I order anything else?

 Thanks again guys.


----------



## ericj

oh, btw, the Murata trimmers i have don't click. or don't click so much that i can hear or feel it. So, stick with bourns or whoever. I find it pretty annoying to have no clue save for counting turns whether I've reached the end or not.


----------



## tomb

The nice thing about the Muratas is that you can't over-turn them and tear them up. So, in effect - you don't have to count. 
	

	
	
		
		

		
			





 They're less than half the price of the Bourns, too.

 MJE243/253 HFE = 180 max

 You didn't mention checking the resistors - I'd give them a pretty good look, too. A wrong value here and there can really screw up the currents in the DB's. Also the PN4392 - it's a very critical part. IMHO, bad Murata trimmers are pretty unlikely. It's easy enough to check them with your DMM.


----------



## amphead

Listen2this1, don't forget that a cold solder joint can increase resistance significantly wherever it occurs. Depending on where that is, it could drive a transistor past its maximum rating. I usually give the most critical areas(what isn't) one more quick application of heat from my soldering iron.


----------



## ericj

Correcting those three mistakes cleared up my issues. Thanks for all the help!

 Now i just have to enclose it. i'd been thinking of doing something creative and original, but now I'm thinking that that's overrated. 'cause i have no good ideas.


----------



## tomb

Way to go, Eric!

 So, how well does it drive those K340's in your pic there? I've heard those things are infamous in their demand on an amp.


----------



## ericj

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Way to go, Eric!

 So, how well does it drive those K340's in your pic there? I've heard those things are infamous in their demand on an amp._

 

Pretty well. 12fm6 didn't have enough gain, so i installed some RCA 12ae6a - which is enough. 

 Plenty of bass, as others have mentioned. But crystal clear treble, too. 

 Output is Nichicon KZ 470uf 25v. Even with v+ at 29v and 12ae6a tubes, i actually can't set the tube bias higher than just under 26v, so i have no concerns about their lifespan. Admittedly things would be different w/o tubes or with something wrong in the circuit. 

 btw, 20-ohm R1 at 29v is running at about 125f. As you can see from my earlier pics, I went up one watt in size, too. It's the hottest thing on the board.

 Probably won't be an issue, but if someone was concerned they might be able to get a to220 resistor and heatsink it. Probably have to air-wire the resistor and drill extra holes in the board to mount it. 

 CA2 are nichicon upw 1000uf, CA9 are CDE polycarbonate 0.68uf. CA3 and CA6 are Nitsuko stacked metalized polyester 4.7uf. They're big and fast - which is good 'cause they're power caps, right? I wouldn't use them in the signal path, but they seem to be doing well on the power rails. CA8 are ERO boxed mylar 0.22uf and nothing special. I might replace these if at some point for some reason I'm dissatisfied with the sound, but by now you know i'm not really entirely a capacitor guy. 

 RB14 are big honkin ferrites. I have no specs for them - got something like 200 of them, leaded, on tape, on ebay a few years ago. 

 CA4 and CA5 are relatively cheap Nichicon RS 1000uf 35v. They're good but nothing special. I figure the giant film caps paralleling them make up for any shortcomings they have. 

 Oh, and the to220 diodes in the power supply are Unitrode SES-5404. They're old-ish. Precursor to the MUR420 iirc. Ultrafast diodes of the early 90's. The voltage drop across them is only about .4v each. Paralleled with unknown-brand .1uf boxed mylar. 

 I'm driving them with a modified Skynet power brick. Used to be rated 30vdc 1A. Cracked open and pulled out the rectifier board. There's enough room in there that i'll piece together a STEPS-alike AC line filter w/ common mode choke and the works. 

 With everything biased up and music playing i have almost 33v after rectification, so I'm dropping 4 volts and the regulator doesn't get particularly hot.


----------



## amphead

Excellent ericj! Another MAX Lives!!!!
	

	
	
		
		

		
		
	


	










 Your determination showed on this build. Kudos to the Millett Max Teamwork!


----------



## amphead

Now, on to the not so fun ground plane, (top mask) for the experimental MAX mask. The registration marks have to line up perfectly to get that right. I may even have to alter the "final" mask if things get rough. One "cheat" is to leave ground plane around the pad areas slightly wide, which will still keep the board quiet. Remember this is the "experimental" MAX board, not the "uber" MAX that many of us have built.


----------



## fordgtlover

A quick trimmer question

 I have seen the other advice regarding starting with the RB12L/R trimmers set at the minimum (full clockwise) setting to start with. I have not been able to find comments on reasonable starting points for the other trimmers.

 Is it reasonable to set RR3 and RA1L/R to the half way point of their adjustment as a starting (installation) setting?


----------



## tomb

Quote:


  Originally Posted by *fordgtlover* /img/forum/go_quote.gif 
_A quick trimmer question

 I have seen the other advice regarding starting with the RB12L/R trimmers set at the minimum (full clockwise) setting to start with. I have not been able to find comments on reasonable starting points for the other trimmers.

 Is it reasonable to set RR3 and RA1L/R to the half way point of their adjustment as a starting (installation) setting?_

 

it doesn't really matter. The tubes don't care, and RR3 is only a fine-adjust: RR1 and RR2 actually set the range. If you look at Tangent's STEPS schematic, when RR1 and RR2 are 120 and 2K, respectively, then the voltage range is approximately 22 - 27VDC. None of the voltages in that range are going to hurt anything in the short term.

 So - not to worry. 
	

	
	
		
		

		
		
	


	




 EDIT: Tangent's STEPS is slightly different - it uses a 500 ohm trimmer, but the principle is the same: an interval of voltage is set by the resistors, depending on the incoming voltage, and the trimmer is only a fine adjust within that range.


----------



## Ferrari

Here are some neater pics of my MH Max 
	

	
	
		
		

		
		
	


	




 :











 and more here:

http://i72.photobucket.com/albums/i1...H/P1010063.jpg
http://i72.photobucket.com/albums/i1...H/P1010064.jpg
http://i72.photobucket.com/albums/i1...H/P1010067.jpg
http://i72.photobucket.com/albums/i1...H/P1010068.jpg
http://i72.photobucket.com/albums/i1...H/P1010070.jpg

 The BJT version still needs to be cased up and it will be totally differerent 
	

	
	
		
		

		
		
	


	




 .


----------



## tomb

Very, very nice, Ferarri! I'll post these on the website when I get a chance.

 Speaking of the website, ruZZ.il suggested that I put a warning on the Setup and Bias page stating to *bias the DB's first*. Seemed like a good idea based on what we've been seeing and the recent question from fordgtlover. That change has been added.


----------



## ruZZ.il

Quote:


  Originally Posted by *Listen2this1* /img/forum/go_quote.gif 
_... Should I order anything else?_

 

as stated before, the trimmers themselves may be unaffected. You did mention both RB10 and RB11 getting excessively hot, so there is a possibility that QB9 is damaged too. You could go about removing the BJTs that you already have, checking what's functional, trying to use the good ones, etc.. if you find a good pair you'll be able to make sure the rest of the circit is good, but all the inserting/resoldering could pay its toll on the board, so you may not be too bad off just ordering spare QB9s too, specially for their price. I suggest getting a pair of nicer transistors, but you may like to make sure everything else is fully functional before putting nicer ones in. Once you're interested in getting some, mention it around here, or better yet, at the DIYForums. You may find someone to share orders with. If you do manage to find a good pair in the meantime and can make sure everything is good, maybe just go straight for a good bunch. since you'll be removing quiet a few transistors, may I suggest looking at this tip. It was also noted to me that QB1 is in a sensitive position, or at least in one that could be effected by excessively high currents in the DBs, since most of it would go through it. 

 Rest assured, you'll get it all solved soon enough. I was recently in exactly your situation but the support here keeps you going 
	

	
	
		
		

		
		
	


	




 (thanks guys) Anyway, you're bound to learn more this way


----------



## daggerlee

My Millet w/ the Triad 1A 24VDC wallwart won't get past 26.7V. This is with MOSFETs biased at around 230 mV each. Is this normal?


----------



## ruZZ.il

when its powered up, what is the AC input voltage? the transformers voltage may drop too much under load to get a good enough margin for regulation.. also, could you set it higher when the mossies were biased at less than that?


----------



## tomb

Quote:


  Originally Posted by *daggerlee* /img/forum/go_quote.gif 
_My Millet w/ the Triad 1A 24VDC wallwart won't get past 26.7V. This is with MOSFETs biased at around 230 mV each. Is this normal?_

 

It's possible that this is the case. 1A is actually pretty close at 80-90ma. Add the extra current you're running, all three potential LED's, a heater resistor more than 10ohms, and you may be over. This also depends on your home's line voltage. If your wall voltage is close to 110 than 120, this will subtract from the mix.

 It may be another item I should note on the BOM. The biggest/cheapest capacity is had from one of these Security/Camera systems walwarts - there is one that's fairly plentiful in the industry that has screw terminals and is rated at 24VAC, 40VA (1.67A). It's what I use for the BJT's (haven't built a MOSFET) and others report it works for the MOSFETs. They can usually be found for less than $10, plus any shipping, of course.

 Of course, this is all predicated on setting 27VDC, not 24VDC.

 Here's one of these walwarts at MPJA Electronics:
http://www.mpja.com/prodinfo.asp?number=12637+PA
 and one at e-bay:
http://cgi.ebay.com/ws/eBayISAPI.dll...MEWA:IT&ih=008







 EDIT: Can't type as fast as you, ruZZ.il


----------



## daggerlee

Quote:


  Originally Posted by *ruZZ.il* /img/forum/go_quote.gif 
_when its powered up, what is the AC input voltage? the transformers voltage may drop too much under load to get a good enough margin for regulation.. also, could you set it higher when the mossies were biased at less than that?_

 

Hmm I can't really measure because I heatshrinked the input/switch for safety.

 I guess I'll just assume it's the case it can't handle the load at 235 mV for the mosfets. I think it was able to before at 210 mV but I'm not sure. 

 FWIW, I'm only running one LED and no heater resistor...Not really sure what the voltage at the wall is, it's very possible that it's only 110V. Oh well, I'll learn to live with it


----------



## tomb

Quote:


  Originally Posted by *daggerlee* /img/forum/go_quote.gif 
_Hmm I can't really measure because I heatshrinked the input/switch for safety.

 I guess I'll just assume it's the case it can't handle the load at 235 mV for the mosfets. I think it was able to before at 210 mV but I'm not sure. 

 FWIW, I'm only running one LED and no heater resistor...Not really sure what the voltage at the wall is, it's very possible that it's only 110V. Oh well, I'll learn to live with it_

 

Turn it back down to 210mV, then.
	

	
	
		
		

		
		
	


	




 There are only a few headphones ever made that might not remain Class A at that current. Everything else will never come close.


----------



## bperboy

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Turn it back down to 210mV, then.
	

	
	
		
		

		
		
	


	




 There are only a few headphones ever made that might not remain Class A at that current. Everything else will never come close._

 

Is it the lower impedance headphones require higher biasing? Or is it the other way around?


----------



## TzeYang

lower impedance requires higher biasing as it eats away more current.


----------



## bperboy

Quote:


  Originally Posted by *TzeYang* /img/forum/go_quote.gif 
_lower impedance requires higher biasing as it eats away more current._

 

Ahh, thank you for the explanation!


----------



## daggerlee

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Turn it back down to 210mV, then.
	

	
	
		
		

		
		
	


	




 There are only a few headphones ever made that might not remain Class A at that current. Everything else will never come close._

 

I'm actually using the Millet as a pre-amp to drive two sources (my t-amp and a powered sub). Does this still apply? I'm assuming since it's acting as a source, the current requirement shouldn't be that high?


----------



## tomb

Quote:


  Originally Posted by *daggerlee* /img/forum/go_quote.gif 
_I'm actually using the Millet as a pre-amp to drive two sources (my t-amp and a powered sub). Does this still apply? I'm assuming since it's acting as a source, the current requirement shouldn't be that high?_

 

An amplifier presents a very high impedance as load (10K - 1Meg or higher). Current requirements are minimal.


----------



## joneeboi

I've been doing some reading for some time and I can't really grasp the concept of a pre-amp. Voltage amplifier, current amplifier, power amplifier something something. Can you guys explain this to me?


----------



## fordgtlover

Quick question on choices for the CA7 caps. I have access to either 35V 330uf or 25V 470uf Silmics. I only intend to run it at 24V.

 I saw the previous post on using 25V caps, but I'm wondering whether it wouldn't be better to use the 35V - for a bit more flexibility in voltage - and drop a bit of capacitance. Thoughts?


----------



## tomb

Quote:


  Originally Posted by *fordgtlover* /img/forum/go_quote.gif 
_Quick question on choices for the CA7 caps. I have access to either 35V 330uf or 25V 470uf Silmics. I only intend to run it at 24V.

 I saw the previous post on using 25V caps, but I'm wondering whether it wouldn't be better to use the 35V - for a bit more flexibility in voltage - and drop a bit of capacitance. Thoughts?_

 

If you're sure that you will only run 24VDC in the Power Supply, then by all means: the 25V 470uF Silmics.

 The MAX loses about 1-2V on startup, probably due to the current inrush. That means for about 2-3 seconds, the CA7 caps will see about 22-23VDC. This steadily decreases for about 6-7 seconds down to approximately the tube bias setpoint. My MAXes run at 27VDC, and the CA7 caps sit at about 13.7VDC during normal operation.

 The problem with 27VDC and a 25V rating for CA7 caps is that they would see ~26V for a few seconds _every single time_ you turned on the amp.

 Be sure that you keep that PS set at 24VDC, however, and you should check it occasionally.


----------



## amphead

Quote:


 TzeYang: lower impedance requires higher biasing as it eats away more current. 
 

So if you wan't to drive your headphones harder, bias the output lower?


----------



## amphead

As it turns out creating the top mask/ ground plane for the experimental mask, is going to be quite easy. I also realized a way to get the top mask and the bottom mask to line up. I use the tranparency for the final/bottom mask to overlay a print of the top mask and change size until nothing is "shorting" out at the pads. This means that registration marks also look "perfect" from top to bottom. When developing the mask on a double sided board, you need to use cool water in your mix. This slows down the developer solution, allowing you to keep turning the board to make sure both sides finish at the same rate. Warm water can cause the reaction to completely strip the resist on one side before the other side finishes.


----------



## fordgtlover

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_If you're sure that you will only run 24VDC in the Power Supply, then by all means: the 25V 470uF Silmics.

 The MAX loses about 1-2V on startup, probably due to the current inrush. That means for about 2-3 seconds, the CA7 caps will see about 22-23VDC. This steadily decreases for about 6-7 seconds down to approximately the tube bias setpoint. My MAXes run at 27VDC, and the CA7 caps sit at about 13.7VDC during normal operation.

 The problem with 27VDC and a 25V rating for CA7 caps is that they would see ~26V for a few seconds every single time you turned on the amp.

 Be sure that you keep that PS set at 24VDC, however, and you should check it occasionally._

 

Cheers Tomb. 

 I'll use the 25V 470uf caps and keep a close eye on the PS voltage.

 BTW - my Digikey order arrived today. I expect my Mouser order in the next few day - then I'll build


----------



## bperboy

So, I was thinking about my Millett today, and I was wondering what those little caps do on the BJT position for the MOSFET edition. I've been running it however long without them, should I add them in?


----------



## ericj

They give that FET gate capacitance equal to it's mate.


----------



## bperboy

Quote:


  Originally Posted by *ericj* /img/forum/go_quote.gif 
_They give that FET gate capacitance equal to it's mate._

 

Ehh? So I should get a few of those?


----------



## IcantHearU

Just a quickie - aren't the recommended heatsinks generally the anodized aluminum type and therefore they really don't conduct from either the transistors or the regulator - so, aside from being cautious, there really is no 'need' for the insulating mounting kits?
 I ask becasuse I've been guilty of touching the heatsinks on two different MOSFETS/etc.(on my M^3) on numerous occasions with no ill effect, whereas if the heatsinks were electrically tied to the transistor, there would exist the possibility of creating a bridge and therefore a short? 
 Thanks


----------



## ericj

Quote:


  Originally Posted by *bperboy* /img/forum/go_quote.gif 
_Ehh? So I should get a few of those?_

 

Not sayin you don't know this, but, i'm sure some others don't, so, here's a basic overview. 

 People sometimes overlook the way that most discrete components exhibit some electrical characteristics other than their primary characteristic. 

 Thus, resistors generally exhibit some inductance, capacitors have an equivalent resistance, inductors exhibit some ohmic resistance, and nearly everyone agrees that many capacitors exhibit some tiny amount of inductance. But there's at least one guy who insists that capacitors can't have inductance. 

 Inherent in the construction of FETs is some capacitance on the gate. 

 irfz24 and irfz34 are complementary but one has more gate capacitance than the other. Adding that capacitor makes their performance more similar.


----------



## tomb

Quote:


  Originally Posted by *ericj* 
_They give that <MOS>FET gate capacitance equal to it's mate._

 

 Quote:


  Originally Posted by *bperboy* /img/forum/go_quote.gif 
_Ehh? So I should get a few of those?_

 

Amb says without them, it results in an assymmetric wave of the signal from the N-channel MOSFETs. I'm not exactly sure what effects you may hear from that that, if anything, but it probably wouldn't test well.


----------



## tomb

Quote:


  Originally Posted by *IcantHearU* /img/forum/go_quote.gif 
_Just a quickie - aren't the recommended heatsinks generally the anodized aluminum type and therefore they really don't conduct from either the transistors or the regulator - so, aside from being cautious, there really is no 'need' for the insulating mounting kits?
 I ask becasuse I've been guilty of touching the heatsinks on two different MOSFETS/etc.(on my M^3) on numerous occasions with no ill effect, whereas if the heatsinks were electrically tied to the transistor, there would exist the possibility of creating a bridge and therefore a short? 
 Thanks_

 

I assure you I'm not trying to be flippant about it, but heat shrink vs. exposed leads is "cautious," too. You're technically correct, but it's a small scratch away from disaster without the insulator kits - something as simple as too tight with the nut and lock washer, for instance.


----------



## amphead

Quote:


  Originally Posted by *IcantHearU* /img/forum/go_quote.gif 
_Just a quickie - aren't the recommended heatsinks generally the anodized aluminum type and therefore they really don't conduct from either the transistors or the regulator - so, aside from being cautious, there really is no 'need' for the insulating mounting kits?
 I ask becasuse I've been guilty of touching the heatsinks on two different MOSFETS/etc.(on my M^3) on numerous occasions with no ill effect, whereas if the heatsinks were electrically tied to the transistor, there would exist the possibility of creating a bridge and therefore a short? 
 Thanks_

 

Steve, its just not worth the risk, as Tom said. You will be better off with the "insurance policy". Also,it's time to thank you again for those boutique DBs.


----------



## TzeYang

Quote:


  Originally Posted by *amphead* /img/forum/go_quote.gif 
_So if you wan't to drive your headphones harder, bias the output lower? _

 

my understanding is that it depends on the load you're driving and the voltage level you're listening at.

 Just bias it higher so it has a larger headroom and not easily drop out of class A.


----------



## tomb

Quote:


  Originally Posted by *TzeYang* /img/forum/go_quote.gif 
_my understanding is that it depends on the load you're driving and the voltage level you're listening at.

 Just bias it higher so it has a larger headroom and not easily drop out of class A._

 

I think amphead's smiley-wink got lost in the translation. I looked hard at that comment and decided he wasn't asking/looking for a correction.


----------



## thunder

For any 1st time builders I've found what looks like a really good priced soldering station that comes with a bonus deal multi-meter if purchase is over 50.00 us$ >http://www.circuitspecialists.com/prod.itml/icOid/7307 This seems like good priced way to get started ! If anyone has had experience with this Co and or its products please let me know. Thanks


----------



## ruZZ.il

although if 'harder' means to be 'pushing to the limits of loudness without concern of maximum quality', whilst trying not to overheat/burn out the transistors.. then I'd guess bias lower, yes. but you may as well build a different type of amp then  or, I may be wrong..


----------



## eddiewalker

It was a close call after I got everything set up and biased, then couldn't get any sound output. Luckily all it took to make my new Max live was to reorient one of the diodes in the muting circuit.

 Thanks to everyone involved. I'm enjoying this thing so much I'm going to have a hard time turning it off to figure out casing.


----------



## ruZZ.il

congrats! 
	

	
	
		
		

		
		
	


	




 glad you got it figured out.
 specs?


----------



## amphead

My guess, is that biasing the DBs at a lower voltage produces more boom with less clarity, maybe more harmonic distortion. The available voltage swing would be less, as TzeYang says about the headroom. This results in clipping of the signal if driven harder, with the extra current pumping the headphones drivers. Usually not what you would want. Thus biasing the DBs higher, resulting in less current flow, but without harmonic distortion induced by clipping of the signal? Thoughts?


----------



## amphead

Quote:


  Originally Posted by *eddiewalker* /img/forum/go_quote.gif 
_It was a close call after I got everything set up and biased, then couldn't get any sound output. Luckily all it took to make my new Max live was to reorient one of the diodes in the muting circuit.

 Thanks to everyone involved. I'm enjoying this thing so much I'm going to have a hard time turning it off to figure out casing._

 

Another MAX lives! Congrats!
	

	
	
		
		

		
			










 I know, it is hard to turn it off, the sound is beautiful.


----------



## ruZZ.il

Quote:


  Originally Posted by *amphead* /img/forum/go_quote.gif 
_My guess, is that biasing the DBs at a lower voltage produces more boom with less clarity, maybe more harmonic distortion. The available voltage swing would be less, as TzeYang says about the headroom. This results in clipping of the signal if driven harder, with the extra current pumping the headphones drivers. Usually not what you would want. Thus biasing the DBs higher, resulting in less current flow, but without harmonic distortion induced by clipping of the signal? Thoughts? _

 


 I'm nor sure I view things so similarly.. a transistor is kind of like a 'variable switch', or a dimmer.. it is a junction between 2 circuits, one usually lower current/voltage, and one higher. lets stick to current.. its pretty much the same with voltage though. anyway, by changing the current in the low current circuit, you're controlling the current flow in the high current circit in an almost analogous way. Now, the 'high current' circuit has its own limitations, and so does the transistor.. resulting in a 'saturation current', being the maximum current that can flow through it. so lets say it simply 'doubles' the current, ie, by allowing a small current in circuit a, it allows double the current to flow in circuit B. so(all numbers as examples alone), 0.5amp-> 1amp, 1amp->2amp... but lets say the saturation current is 3amps, so 1.2->2.4, 1.5->3, 1.6->3, 2->3 you get what I mean(clipping).. the thing is, its not a linear device, so it cant just double. invision a parabolic climb that straightens out somewhere for a bit then suddently becomes flat. kind of like:
 0->0
 0.1>0.05
 0.2>0.2
 0.3>0.4
 0.4>0.7
 0.5>1 (here its double, lets say it has becomes linear here...)
 0.6>1.2 ....1>2.. 1.5>3 (now, saturation) 1.6>3 ... which is, basically, clipping.

 so, the way I see it is that you can get larger current swings if you oscillate between (0..1.5)->(0..3) but it wont be linear, so a sin wave would look kind of funny. but if your oscillations would be between say (0.9...1.1)->(1.8->2.2) you would have an almost identical sin wave of double the current flow.. thing is, there is always current flowing (dc), but thats another paragraph, and what capacitors are for 
	

	
	
		
		

		
		
	


	




 but basically, unbiased.. the current swing can be higher, the headroom that I think he meant was the margin of linearity.. like, if its linear between (input of) 0.5 and 1.5, you can oscillate around 1amp(bias current) with a headroom of half an amp before you either start clipping or dropping out of class A linearity.....
 anyway, I havent actually studied this stuff yet, so I'm likely to think differently in a year from now(ask me then
	

	
	
		
		

		
		
	


	




) and I may be wrong/innacurate/whatevere.. or just making a mess with numbers.. I think google will get you further than I did


----------



## tomb

Voltage is constant throughout the DB, regardless of current. The voltage is set by the PS. The _signal_ voltage is set by the tube. That's called gain. The bias plus or minus the supply voltage is the amount of voltage/gain swing possible by the tube, minus a bunch of parts inbetween - most important the impedance of the headphone.

 Amb made the following measurements on the original revMH Millett (without DB's):

** Maximum output voltage*
 (prior to onset of clipping, 12AE6A tubes, 27VDC supply, 13.5V bias)
 5.85Vrms (16.5Vp-p) into 330Ω
 2.85Vrms (8.06Vp-p) into 33Ω

 This sort of gives you the idea. Signal voltage is set by the PS, tube bias, and the headphone impedance.

 The real value the DB's Class A bias provides is how much current, therefore, power - since voltage is set by gain in the tube stage - the output stage is prepared to supply without _transistor switching._ That's what's meant by "remaining in Class A" with a heavy load. A very inefficient headphone may draw instantaneous current that exceeds the bias setting of the buffer. When that happens, the capacitors supply the instantaneous current and the transistors add switching noise when they respond to the greater current.

 If the signal continues at that peak, the capacitors may deplete. Then voltage will also drop and clipping will start. All of this happens in the blink of an eye, of course.

 A good example is if you've ever had experience with a variable flash on a camera. Flash at full power and you may only get one or two flashes before the batteries are called on to re-charge the capacitor. At a small flash power setting (as in more efficient headphone to the amplifier), you can get many more flashes before it has to stop to re-charge. However, get a professional flash with a special power pack, and you may be able to fire off dozens of full power flashes without any delay.

 A deep Class A bias amplifier does the same thing for your headphones: fires off continuous, full-power "flashes" with no switching noise or clipping.

 EDIT: I think what ruZZ.il explains is correct, too - but this is the way I understand it. I've probably said some things that are not technically accurate, but hope that it helps, anyway ...


----------



## adfinni

Quote:


  Originally Posted by *ericj* /img/forum/go_quote.gif 
_Correcting those three mistakes cleared up my issues. Thanks for all the help!

 Now i just have to enclose it. i'd been thinking of doing something creative and original, but now I'm thinking that that's overrated. 'cause i have no good ideas.




_

 

LOOKS awesome, don't suppose you have a picture from above, im trying to figure out if i can get some obligato 0.22uf's in there for CA8's and CA9's.

 Also can someone explain about the corner frequency. Ive read it, and with the caps im going to be using (BG NX 680uf/35v) at CA7's will give a fequency of 7.31hz, not the recommended 2hz. How do i choose an output coupling cap as im considering the 630v 0.22uf obligatos ????? o and btw im using grado's.


----------



## n_maher

Quote:


  Originally Posted by *adfinni* /img/forum/go_quote.gif 
_Also can someone explain about the corner frequency. Ive read it, and with the caps im going to be using (BG NX 680uf/35v) at CA7's will give a fequency of 7.31hz, not the recommended 2hz. How do i choose an output coupling cap as im considering the 630v 0.22uf obligatos ????? o and btw im using grado's._

 

I'm going to go out on a limb and say that not only can you probably not hear 7Hz but your headphones probably roll off at a far higher frequency so I wouldn't worry about that in the least. It's all well and good for some folks to take this design to the extreme with their choice of caps and whatnot but I think we've gone well past 11 when we start talking about a corner freq. of 7Hz being an unacceptable compromise.


----------



## ruZZ.il

what nate said.
 but anyway.. hm.. grados?
 looks like you calculated it right. 1/(2*pi*r*c) while r=your cans. you can add an x ohm resistor if you like, so then its 1/(2*pi*(Rcans+Rres)*c). if you'd liek to, get some kiwames or other good resistors, and experiement.. you may get a lower corner frequency, but other side effects you dislike more. so, do your own balancing act


----------



## tomb

Adfinni - YGPM.

 What these other guys said x10. To bypass if you're using BG's:

 1. Nothing.
 2. Vitamin Q's if you can get them to fit (not easy)
 3. Buy the 0.47uF, 50V NX HiQ Black Gates and connect them in reverse polarity (Super E) as bypasses. These are only $2.50 ea where BG's are sold.

 I believe #3 is how Nate did his old Millett, and at least one other has done the MAX this way. If it turns out the Super E is not as good as "nothing", at least you've only spent $10, and you can turn around and put them on a couple of Alien DACs. 
	

	
	
		
		

		
		
	


	




 P.S. Stay away from the Obligato's. The MAX's response and transients are way too quick for those things and they're huge, anyway. One other user (Zare?) tried Obligatto's and quickly changed to Hovlands. Hovlands are very expensive btw, and pretty large, too. Their claim to fame is very neutral, flat with extended to harsh highs. I'm not recommending them, just saying it's an example that the MAX doesn't necessarily do that well with the generally accepted sweet, syrupy old-style film tube cap. As Dsavitsk noted a ways back, Vitamin Q's are an exception, being surprisingly uncolored with extended, somewhat unfiltered highs.


----------



## adfinni

Thanks for all those reply boys, it's horrific trying to choose the correct cap combinations. 

 1.) im leading towards bypassing the NX's with some little 0.47uf NX HI-Q's, which i actually use in my old millett to bypass some BG standards. But if using these is not as good as nothing then it seems quite pointless.

 2.) Im considering saving money on caps and going for 1000uF nichicon KZ's all round (even the PSU section) then using some 0.22uf hovlands in CA8's and 9's. But as you say they have extended highs and my grado's certainly don't need any more.

 3.) FOund some 0.22uf vitamin Q's for sale here in england so am tempted to get 4 of them, but wouldn't know whether they would pair better with the KZ's or NX's...

 O and obviously i have the 2SC3422 / 2SA1359 combo so it should be nice and bassy.

 Lol isn't this fun


----------



## tomb

There's almost no cap, nohow, better than a Panasonic FM out of the signal path. So, don't waste your money on boutiques in those positions. Better to buy as much capacitance as possible, within reason. I have 1800uf, 35V Panasonic FM's in one MAX, and 1200uf, 35V FM's in the other. The 1800uF's are the same size and height as the 1000uF, 50V FM's in the PS, so it looks "symmetrical."

 Also, I didn't say that NO bypasses would be better than the 0.47uF BG's. I believe it's a matter of expense. From what we're learning, you have to put a very high quality film cap in there or it detracts from the quality of the BG's in the first place. However, I don't know first hand. Again, Dsavitsk is the master when it comes to this and is the only one to have done testing of any import. He said awhile back much the same - given a choice, he would always bypass the BG's, but if it came to a cheap bypass vs. no bypass, then no bypass.

 I'm sorry that a lot of this is guesswork. I've got several orders pending, but it will be awhile before I have some test cases built. Honestly, it's hard to beat the ES's and the Wima's.


----------



## ruZZ.il

Quote:


  Originally Posted by *adfinni* /img/forum/go_quote.gif 
_....
 3.) FOund some 0.22uf vitamin Q's for sale here in england so am tempted to get 4 of them..._

 

how much are they there? there are a few on e-bay for pretty cheap.. just that you have to get a whole bunch. I'd be willing to share some with someone or 2..


----------



## adfinni

Quote:


  Originally Posted by *ruZZ.il* /img/forum/go_quote.gif 
_how much are they there? there are a few on e-bay for pretty cheap.. just that you have to get a whole bunch. I'd be willing to share some with someone or 2.._

 

They are £8.95 each for the new ones 0.22uf 400v (have fancy chrome and black outer skin), or £5 for the USA made ones that look like NOS. The NOS ones have a single nut fixing at the end but no leads ???


----------



## tomb

Vitamin Q's on e-bay:

http://cgi.ebay.com/capacitor-0-22mf...QQcmdZViewItem
http://cgi.ebay.com/Capacitor-0-27mf...QQcmdZViewItem
http://cgi.ebay.com/Capacitor-0-18mf...QQcmdZViewItem
http://cgi.ebay.com/Capacitor-0-15mf...QQcmdZViewItem
http://cgi.ebay.com/Capacitor-0-47mf...QQcmdZViewItem

 These are all from "LA Surplus Electronics Co.", and I can personally vouch for their good service, having ordered from them twice with excellent service. Those listed above are genuine "Vitamin Q" and stamped as such by Sprague. However, they're pretty big. There are others that are smaller that are "Vitamin Q - like" but not having tried any of these yet, I can't say for sure. MrMajestic2 and FallenAngel have some, but I don't know if they've tried them yet, either.

 You will note that Colin prepared the board in the front specifically for these type of capacitors. The CA8 positions have a little more room, but the CA9 positions are more cramped. So, the pseudo test point was included in the CA9 positions. The Vitamin Q's are bead-soldered at the terminals coming out of the cans. The beads make a perfect fit in those holes when you tombstone one of them.


----------



## adfinni

http://cgi.ebay.co.uk/22UF-400V-DC-S...QQcmdZViewItem

 ^^^ THat's the confusing one.

 Cheers for that tom, il pick up some like in the link above, then put them in once ive run in the millett. WIll start with just the BG NX's in C7 and C2, then burn them in and sub in the vit Q's to compare.


----------



## tomb

Quote:


  Originally Posted by *adfinni* /img/forum/go_quote.gif 
_http://cgi.ebay.co.uk/22UF-400V-DC-S...QQcmdZViewItem

 ^^^ THat's the confusing one.

 Cheers for that tom, il pick up some like in the link above, then put them in once ive run in the millett. WIll start with just the BG NX's in C7 and C2, then burn them in and sub in the vit Q's to compare._

 

Yeah, most of those with the threads and the nut are pretty big - like maybe 2" long and 3/4" in diameter. They're not showing it in the pic in your link, but those usually have a lead on the other end, too. The ones I ordered from those links might be too big, too - I got some 0.47uf's that probably don't have in prayer of fitting and then the 0.22uf's are just as long but only about 1/4" in diameter. So, I might have a chance with those if I get creative.

 So, watch those sizes and compare with what you've got room for on the board. If you're in the bottom slot of the Hammond case and going for 1-1/2" sinks, you can probably fit most of those by standing them up. That might be one way to do it.


----------



## Pingunugnug

I have been trying out the other tubes.

 I was surprised the 12FM6 would "have less decay" as if it's cut off(I'm not sure if I used the term correctly but it's that echoey trail) but, the FK6 seems to have that right amount (for me). I thought it would be proportional to the gain value of each tube. (Kind of like the next in line will be less and so on...) FK6 seem to be the least brassy (that certain jazzy timbre when the sax plays). I am not sure if I can even say it's the coolest sounding of the 3 (if the expression of warm is given to the sound of the tubes) but somehow it also sounds more precise and detailed. 

 By now you probably think I'm the most confused person here. 
	

	
	
		
		

		
		
	


	




 I have been taking measurements for tube bias since I am changing tubes and here is what I noticed.

 As I adjust the vol knob up on the 12AE6 the voltage across the test points goes up but, with the other two, the voltage remains the same no matter how I adjust the volume. What is different between the 12AE6 and the other 2 type of tubes?


----------



## tomb

Quote:


  Originally Posted by *Pingunugnug* /img/forum/go_quote.gif 
_I have been trying out the other tubes.

 I was surprised the 12FM6 would "have less decay" as if it's cut off(I'm not sure if I used the term correctly but it's that echoey trail) but, the FK6 seems to have that right amount (for me). I thought it would be proportional to the gain value of each tube. (Kind of like the next in line will be less and so on...) FK6 seem to be the least brassy (that certain jazzy timbre when the sax plays). I am not sure if I can even say it's the coolest sounding of the 3 (if the expression of warm is given to the sound of the tubes) but somehow it also sounds more precise and detailed. 

 By now you probably think I'm the most confused person here. 
	

	
	
		
		

		
			





 I have been taking measurements for tube bias since I am changing tubes and here is what I noticed.

 As I adjust the vol knob up on the 12AE6 the voltage across the test points goes up but, with the other two, the voltage remains the same no matter how I adjust the volume. What is different between the 12AE6 and the other 2 type of tubes?_

 

Just checked mine - nope, no bias change with volume, and I listen to 12AE6/A's all the time - they're my favorite. I'm in the minority, though. Most people agree with your tastes in Millett tubes.

 Just out of curiosity, what's the rating of the caps you used for C4L/R and C5L/R?


----------



## c0nsumer

Yay, it's working. Tonight I got my second MAX going, this one with 2SC2238/2SA968 transistors in the BJT diamond bridge and Du Mont 12FK6 tubes. (I've got some RCAs which I may use, but I wanted to try these for now.)

 Because of lessons learned with the previous MAX I built this one went together a lot better. I reversed the trimmers as needed to make counter-clockwise always equal the lower value, fitted wire loop test points and filled the test pads to make biasing easier, used slow-blow fuses, and temporarily borrowed a few parts from my older MAX until I get the new case finished. All in all it's working out great.

 I ended up using 25V caps for CA7L/R, which is pushing it, but I don't have a chance to get 35V parts yet. As soon as I do I'll replace them. (I watched these positions ramp up to 25V-26V then back down on powerup on my MOSFET MAX, so I know this is risky... I'll meter the BJT version later.)

 I did stupidly cut my thumb trying to remove the serrated washer from a 4-40 sems machine screw, but strangely it didn't hurt and is already healing.

 I'm just glad this is working, because now I can get on to fashioning the piece of bubinga acquired on Sunday into some nice wood end caps. Oh, and get to work on the relay-based, microcontroller driven input switch... (This may turn into a bigger open-source hardware and software project.)


----------



## amphead

Quote:


 TomB: the output stage is prepared to supply without transistor switching. That's what's meant by "remaining in Class A" with a heavy load. 
 

Hmmm..........Constant current source plus buffering. 
 Edit: I do remember hearing the sound being articulate with the DBs underbiased ~44mV.


----------



## amphead

c0nsumer, Congrats! Max + Max = MAAAXX 

 A bit of the brown stuff is a great way to celebrate!


----------



## ruZZ.il

amphead, if you got access to a freq. generator and an oscilloscope you should compare input/output at different bias currents. I did this with a little with an application through my line in (page 63 on this thread).. not as good as proper equip, but nonetheless indicative... when I get access to equip, I'm certain to play around 
	

	
	
		
		

		
		
	


	




 c0ns: congratsX2! 
	

	
	
		
		

		
		
	


	




, and all the rest you do.. really cool stuff. good documentation too!


----------



## amphead

ruZZ.il, good point, I have access at my brother-in-laws workbench. He's an elevator controls manager, soon to be vice-president. Out of town at an elevator convention in Florida. When he gets back, I'll take a look on his workbench. You have brought to mind a good idea. You could take pictures of waveforms on your o-scope, with testpoint references and they could be posted on Tom's website. Edit: I have found that if I give my ears a 2 day rest and then re-evaluate the sound, component changes have a more pronounced effect. Kind of like a coffee bean taster who rinses with water between sessions!  I think it reduces the noise floor and creates a black ambient space between notes within our eardrums/aural nerves.


----------



## ruZZ.il

when I have access to proper equipment, I may. meanwhile, my alien dac as a frequency generator and line in as an o.scope don't quiet cut it for me  I guess the dac is decent as a source cause I'm more interested in comparing in to out, but my line in doesn't quiet cut it. it would be interesting to look at a whole bunch of responses though.. switching, non-linearities, etc... problem is, by the time I have access to the stuff.. I don't have the time to play. hmpf. I've actually had my eyes open for an old scope and f.generator for a while now.. btw, elevators are cool.. I like watching the relays switch stuff then manually push the things around sometimes muahahah 
	

	
	
		
		

		
		
	


	




 pwnd. have fun with the equip! see if he has some export tools.. screenshot stuff or smtn, maybe you can update us


----------



## adfinni

Do all international packages cost loads to ship from the USA as radiodaze have just quoted $23 for shipping to the UK. With parts for mine coming from parts express, michael percy, and my main mouser order il be paying close to $100 for shipping 
	

	
	
		
		

		
		
	


	
















 Any idea if it's possible to get 2 pairs of 12fk6 tubes and x2 7-pin mini ceramic sockets with mount sent cheaper than $23?


----------



## MrMajestic2

Quote:


  Originally Posted by *adfinni* /img/forum/go_quote.gif 
_Do all international packages cost loads to ship from the USA as radiodaze have just quoted $23 for shipping to the UK. With parts for mine coming from parts express, michael percy, and my main mouser order il be paying close to $100 for shipping 
	

	
	
		
		

		
		
	


	
















 Any idea if it's possible to get 2 pairs of 12fk6 tubes and x2 7-pin mini ceramic sockets with mount sent cheaper than $23?_

 

Try http://www.thetubestore.com/
 I was quoted $7 for 3 tube pairs and 6 sockets with Air Parcel Post. I went with UPS though for $27.


----------



## c0nsumer

So, would any of you have an interest in an audio input switch which can fit inside a Hammond enclosure along with the MAX?

 I'm starting to work something up for my own use, and as soon as the microcontroller sample arrives I'll finish up the software.

 This will be a full-on BSD-licensed software / creative commons board designs project, and I might sell PCBs and pre-programmed microcontrollers...


----------



## Pingunugnug

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Just checked mine - nope, no bias change with volume, and I listen to 12AE6/A's all the time - they're my favorite. I'm in the minority, though. Most people agree with your tastes in Millett tubes.

 Just out of curiosity, what's the rating of the caps you used for C4L/R and C5L/R?_

 

For C4 and C5, I used 50V, 470uF caps.

 You are right about the 12AE6/A. I got a chance to check with mine; the pair that is changing with the volume is 12AE6 non /A. 

 So that begs the question, what is different between the /A's and non /A's? or Is something wrong with my non /A tubes?

 Forgot to add,

 The range that I measured goes from 13.5V to ~18V (full volume).


----------



## adfinni

Quote:


  Originally Posted by *MrMajestic2* /img/forum/go_quote.gif 
_Try http://www.thetubestore.com/
 I was quoted $7 for 3 tube pairs and 6 sockets with Air Parcel Post. I went with UPS though for $27._

 

Cheers, but their 12fk6's are $7.95 each 
	

	
	
		
		

		
		
	


	




 Ive sent a message to another tube store, totally forgotten their name but they have a red background on their website and only sell tubes (no accessories).


----------



## ruZZ.il

Quote:


  Originally Posted by *c0nsumer* /img/forum/go_quote.gif 
_So, would any of you have an interest in an audio input switch which can fit inside a Hammond enclosure along with the MAX?
 ...._

 

that would be cool! specially if its applicable to a lot of amps. I'd think it's even possible on a simpler system of gates, momentary switch, a 5v supply and some good relays.. a led or 2.. hmm but I'd really like to see something come along!


----------



## c0nsumer

Quote:


  Originally Posted by *ruZZ.il* /img/forum/go_quote.gif 
_that would be cool! specially if its applicable to a lot of amps. I'd think it's even possible on a simpler system of gates, momentary switch, a 5v supply and some good relays.. a led or 2.. hmm but I'd really like to see something come along! 
	

	
	
		
		

		
		
	


	


_

 

My current thought is the following:


> Two to five inputs. This is selected by soldering / omitting two jumpers.
> 
> Support for two buttons, one for next input, one for previous input. (You could just fit the next button if you didn't want to go back.)
> 
> ...


I'm thinking a single-piece rectifier, LM7805, small cap for smoothing power, PIC16F630, 5 (or 10) cheap NPN transistors, 8-pin header, five 4-pole relays, maybe some screw terminals, five resistors, bit of cable, one or two switches, five LEDs.

 Uhm... that's about it, I think.

 The most expensive thing here will be the relays.


----------



## tomb

Quote:


  Originally Posted by *Pingunugnug* /img/forum/go_quote.gif 
_For C4 and C5, I used 50V, 470uF caps.

 You are right about the 12AE6/A. I got a chance to check with mine; the pair that is changing with the volume is 12AE6 non /A. 

 So that begs the question, what is different between the /A's and non /A's? or Is something wrong with my non /A tubes?

 Forgot to add,

 The range that I measured goes from 13.5V to ~18V (full volume)._

 

I don't think it's the tubes, per se, except that some tubes may have a propensity toward a stronger bass boom and perhaps more current.

 Here's what I think is happening, but it's purely conjecture on my part:
 I've been suspecting for awhile that the 470uf's may be marginal in the decoupling positions. CA4 and CA5 essentially ensure that the + rail and ground remain apart. In other words, they ensure that the ground stays at a lower potential than the rest of the circuit and also ensure that the + rail voltage doesn't dip from the power supply, through the CCS/tube, and on to the DB's. However, with the very powerful DB's in the output stage, it may be possible to overdrive the CCS through the tube. IOW, the high gain is sucking the current out of the CCS's, which are allowing the tube bias to climb as you turn the volume up.

 Anyway, like I said - conjecture - we'll see if someone blows it full of holes. In the meantime, you might do all us a favor if you are able to change out those caps to larger values and see if those old 12AE6's do the same thing after that.


----------



## amphead

Quote:


  Originally Posted by *adfinni* /img/forum/go_quote.gif 
_Cheers, but their 12fk6's are $7.95 each 
	

	
	
		
		

		
			





 Ive sent a message to another tube store, totally forgotten their name but they have a red background on their website and only sell tubes (no accessories)._

 

Thats alot of money for some, but I enjoy the sound so much, that it *almost* seems worth it.


----------



## ruZZ.il

c0ns, sounds cool. I think I'd just need something like DAC/RCA. would be cool to find maybe a good switching mini jack kind of like the neutrik 1/4'th we use cause I sometimes use mini-minis. I had some ideas bout having the 5v from usb feed a gate that switches a relay.. anyway, keep me updated 
	

	
	
		
		

		
		
	


	




 btw, where are there the gold plated neutrik 1/4'th input switching jacks? I've seen some in some builds or something..


----------



## Pingunugnug

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_In the meantime, you might do all us a favor if you are able to change out those caps to larger values and see if those old 12AE6's do the same thing after that._

 

Just need to confirm. I took a look at the KZ line and the next up would be the 50V, 1000uF. So I should swap out the current ones for these?


----------



## tomb

Quote:


  Originally Posted by *Pingunugnug* /img/forum/go_quote.gif 
_Just need to confirm. I took a look at the KZ line and the next up would be the 50V, 1000uF. So I should swap out the current ones for these?_

 

1st - This is only conjecture. I can't guarantee it will make a difference.
 2nd - Remember that these caps are CA4L/R and CA5L/R. Those are plain old power caps all the way. So, Panasonic FM's will have better performance, but again - it's up to you. They also only need to be 35V.


----------



## c0nsumer

Quote:


  Originally Posted by *ruZZ.il* /img/forum/go_quote.gif 
_c0ns, sounds cool. I think I'd just need something like DAC/RCA. would be cool to find maybe a good switching mini jack kind of like the neutrik 1/4'th we use cause I sometimes use mini-minis. I had some ideas bout having the 5v from usb feed a gate that switches a relay.. anyway, keep me updated 
	

	
	
		
		

		
		
	


	




 btw, where are there the gold plated neutrik 1/4'th input switching jacks? I've seen some in some builds or something.._

 

The reason there are four pins switching is so that you can just use two if you want. 
	

	
	
		
		

		
		
	


	




 I haven't looked closely enough at the relays yet, but I think I can probably make it so you can drop in DPST relays if you are only going to be switching two lines.

 If things go as I hope, the cost from me for PCB + IC will be something like $10. Or you can just etch your own board and run the IC on that.

 This is all still in the planning phases, of course... More will be known after I get the software finished. (I haven't started yet, but I figure it's a day or so to get the basics down, then a bit of polishing.)


----------



## amphead

Double post, my bad ;-(


----------



## amphead

Test etch on the photo mask for the experimental MAX went well. Picture not so good.


----------



## Blooze

Looks good.

 I've gotta learn how to etch someday.


----------



## 04BluMach

Its ALIVE....!

 First of two Millet MAX builds is up, biased and running smoothly. Flipped the switch and it came up smoothly with no problems.

 Adjusted PS output level to 27V checking to make sure that DB bias current wasn't off the wall. Biased tubes 13.5V. 
 Then adjusted DB bias up in stages to current 105mV (50mA) for burn-in and to stabilize. 

 Fitted with FM7's. The DB QA8/QA9 are the 2SA1011/2SC2344 Sanyo BJT pairs. 
 ICW Clarity SA 0.47uF 630V Film Caps are Tombstoned into the CA7 & CA8 positions for a little uniqueness. Not quite up to par with Ferrari's 
 HYPER build levels... but a little different personality 
	

	
	
		
		

		
		
	


	




 All I’ve got to say at this point is WOWWWWWWWWWWWW.......
	

	
	
		
		

		
		
	


	




 And this is only with a couple of hours on the Caps and those NOS FM7’s. This thing is going to kick some kind of TAIL when it is fully burned in!

 Will try to post up some Pics soon.


----------



## amphead

04BluMach, Congrats! Another MAX lives!


----------



## tomb

Quote:


  Originally Posted by *04BluMach* /img/forum/go_quote.gif 
_Its ALIVE....!
 ..._

 

Way to go!


----------



## amphead

Test your Millett Max with this tune! 

http://www.magatune.com/artists/albu...onic/hifi_play


----------



## adfinni

Quote:


  Originally Posted by *amphead* /img/forum/go_quote.gif 
_Test your Millett Max with this tune! 

http://www.magatune.com/artists/albu...onic/hifi_play_

 

Awesome tune, let's see if the MAX will give my grado's soundstage


----------



## adfinni

Quote:


  Originally Posted by *amphead* /img/forum/go_quote.gif 
_Test your Millett Max with this tune! 

http://www.magatune.com/artists/albu...onic/hifi_play_

 

Awesome tune, let's see if the MAX will give my grado's soundstage


----------



## tomb

Looks like you're trying for a balanced approach already.


----------



## odoe

I have a proto board, the last version before the final as far as I know. Is there anything I should take into consideration when building it that's different from the final, aside from the lack of fuse 
	

	
	
		
		

		
			





 ?


----------



## vixr

I built both a proto and a production from TomBs BOM without any problems...


----------



## tomb

Quote:


  Originally Posted by *odoe* /img/forum/go_quote.gif 
_I have a proto board, the last version before the final as far as I know. Is there anything I should take into consideration when building it that's different from the final, aside from the lack of fuse 
	

	
	
		
		

		
		
	


	




 ?_

 

*Differences between the final prototype board and the Group Buy production board:*
 1. The fuse position was added.
 2. The power input was changed to a 3-position terminal block so that the fuse position could be bypassed if desired.
 3. The optional input pads on the outside of the volume pot were enlarged to a full-size terminal block position.
 4. A terminal block position was added to the outside of the headphone jack pads.
 5. Two duplicate test points were added for Gnd for convenience.

 Except for the fuse, none of these changes have any impact on the operation of the circuit. As I've repeated many times, my recommendation is that you bypass the fuse and not get caught up in trying to protect something that was supposed to protect either the walwart or the rest of the circuit, but can't really do either because of its location.


----------



## adfinni

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Looks like you're trying for a balanced approach already. 
	

	
	
		
		

		
		
	


	


_

 












 Don't confuse me further, im still learning about the basics of the millett and how and why certain parts are chosen. Anyhow, 20 vit Q's in total heading to RuZZ.il and myself, plus im ordering the rest of the parts today for mine.....

 COsts are really mounting up, but i know it's going to sound amazing !


----------



## c0nsumer

Quote:


  Originally Posted by *amphead* /img/forum/go_quote.gif 
_Test etch on the photo mask for the experimental MAX went well. Picture not so good.




_

 

Something in the rectifier isn't right. If you note, that entire row of top holes are connected. They aren't that way in the actual MAX. The way you have it will take the two AC lines and tie them directly together.

 This error is in the  image you posted earlier.

 I haven't looked at the rest of the layout to look for other errors.


----------



## tomb

Quote:


  Originally Posted by *c0nsumer* /img/forum/go_quote.gif 
_Something in the rectifier isn't right. If you note, that entire row of top holes are connected. They aren't that way in the actual MAX. The way you have it will take the two AC lines and tie them directly together.

 I haven't looked at the rest of the layout to look for other errors._

 

Yes, you are correct. The reason there are two traces feeding those pads for the rectifiers is that one trace connects to the first 4 pads and the other trace connects to the last 4 pads.

 I'm still astounded that Amphead is trying this, though.


----------



## c0nsumer

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Yes, you are correct. The reason there are two traces feeding those pads for the rectifiers is that one trace connects to the first 4 pads and the other trace connects to the last 4 pads.

 I'm still astounded that Amphead is trying this, though._

 

Scans of the boards and Illustrator's raster to vector converter should make it trivial.

 That said, if someone were to just ask cetoole to run the CAM processor on his boards again, dumping each layer as postscript (also: don't fill pads), it'd be trivial to make PDF masks. (This is how I make masks whenever I'm etching boards...)


----------



## adfinni

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Vixr is correct, but the small counter sink on the endpanels works just fine as it is. Socket head cap screws are tough enough to buckle the endplate if you tighten down on it from the reverse side. There would be nothing backing the cap head up if you reversed it. I wouldn't do that.

 A 6-32 x 3/4" will go far enough to cover the length of the threads that a typical 6-32 tap will make. A 1" is too long and will be cutting on untapped metal. 1/2" will not make use of all the threads that are possible. I settled on 3/4" as the best fit. This is probably a good thing to do because the slots only provide a partial thread surface, anyway. The 3/4" length might change if you use a different endplate or forego the end bezel._

 

Im looking at using the socket head cap screws, but am having a little trouble converting the imperial to metric that we use here in the UK. Was a lot easier at uni as we had the tables on the workshop walls.

 From my browsing around an M3.5 socket head cap screw is equivalent to a 6-32 version. Also, from the MAX site im having trouble understanding if the holes in the hammond have to be tapped again, or the correct length socket head cap screws can be screwed straight in ?


----------



## tomb

Quote:


  Originally Posted by *adfinni* /img/forum/go_quote.gif 
_Im looking at using the socket head cap screws, but am having a little trouble converting the imperial to metric that we use here in the UK. Was a lot easier at uni as we had the tables on the workshop walls.

 From my browsing around an M3.5 socket head cap screw is equivalent to a 6-32 version. Also, from the MAX site im having trouble understanding if the holes in the hammond have to be tapped again, or the correct length socket head cap screws can be screwed straight in ?_

 

The Hammond case is NOT tapped. They come with cheap little self-tapping sheet-metal screws that are worthless and shouldn't be used, IMHO. The slot/hole has enough meat to work for a 6-32 tap without drilling - but probably not if you use one of the screws that come with it, first. Although, you can probably cut threads beyond whatever those little screws tear up. I've found 3/4" long 6-32 socket head cap screws to work best.

 I don't know how all that relates to metric, however. You'd have to also use a metric tap, too, if that's the way you're going.


----------



## bperboy

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_The Hammond case is NOT tapped. They come with cheap little self-tapping sheet-metal screws that are worthless and shouldn't be used, IMHO. The slot/hole has enough meat to work for a 6-32 tap without drilling - but probably not if you use one of the screws that come with it, first. Although, you can probably cut threads beyond whatever those little screws tear up. I've found 3/4" long 6-32 socket head cap screws to work best.

 I don't know how all that relates to metric, however. You'd have to also use a metric tap, too, if that's the way you're going._

 

I don't know if I got a freak, but my Hammond was already tapped. This wasn't the case on my hammond for the mini3, but my Millett Max hammond that I ordered from mouser already had threads. A nice little surprise, but I wouldn't count on it in the future.


----------



## tomb

Quote:


  Originally Posted by *bperboy* /img/forum/go_quote.gif 
_I don't know if I got a freak, but my Hammond was already tapped. This wasn't the case on my hammond for the mini3, but my Millett Max hammond that I ordered from mouser already had threads. A nice little surprise, but I wouldn't count on it in the future._

 

Maybe somebody tapped it but returned it.


----------



## adfinni

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_The Hammond case is NOT tapped. They come with cheap little self-tapping sheet-metal screws that are worthless and shouldn't be used, IMHO. The slot/hole has enough meat to work for a 6-32 tap without drilling - but probably not if you use one of the screws that come with it, first. Although, you can probably cut threads beyond whatever those little screws tear up. I've found 3/4" long 6-32 socket head cap screws to work best.

 I don't know how all that relates to metric, however. You'd have to also use a metric tap, too, if that's the way you're going._

 

Ah right......... I assumed it would be tapped, but now there is no way im using some cheapy self tapping screws that will probably end up stripping the thread they bore.

 Well found a model shop online here that do metric and imperial taps.... But itl be $20 for all 3 taps, so i think im only going to buy the Taper tap and just use that to make a hole deep enough.


----------



## amphead

Quote:


 c0nsumer:
 that entire row of top holes are connected. They aren't that way in the actual MAX. The way you have it will take the two AC lines and tie them directly together. 
 

Yes, you and Tom are correct, just don't give me more than 20 lashes for my infraction. 
 Thats what I need, more eyes to get this board right.
 As far as getting Colin to supply us with his mask, that may not be possible. IMHO, he deserves to get paid whatever can happen from selling boards from the group buys for his hard work. The boards that we can build outside of his original effort is up to us. Thoughts?
 Corrections on the way!


----------



## c0nsumer

Quote:


  Originally Posted by *amphead* /img/forum/go_quote.gif 
_Yes, you and Tom are correct, just don't give me more than 20 lashes for my infraction. 
 Thats what I need, more eyes to get this board right.
 As far as getting Colin to supply us with his mask, that may not be possible. IMHO, he deserves to get paid whatever can happen from selling boards from the group buys for his hard work. The boards that we can build outside of his original effort is up to us. Thoughts?
 Corrections on the way!_

 

I think if you just ask him for PS outputs of each layer you'll have what you want and everyone will be happy. If he doesn't want to give them out, then keep going...

 Masks as images (even vector images) aren't particularly useful to anyone mass producing boards. They'd only be good for those who are etching their own boards. Anyone having boards mass produced illicitly would do better off redrawing it. It wouldn't be too difficult.

 All he'd have to do is give out the PS files and state that they are for personal, non-commercial use only, and for any clarification of this, people should contact him.


----------



## amphead

Well, you may have a point. He is busy with his studies at the university right now. So this may not work, but here goes.
 Colin may we have your MAX mask images for non-commercial reproduction please?


----------



## amphead

The experimental MAX mask has been corrected for the error in the power supply. I looked the mask over again and didn't see anything, so I will once again call it final.  Still working on the ground plane/ top mask.Edit: Nothing is really final until top and bottom masks line up correctly. I can't say that I enjoy this process, because I would rather be populating a board, soldering, testing and listening! There will be a huge payoff, knowing that you have created a MAX from scratch and it sounds sooooo good! Almost like reaching outer space on your own amateur rocket!


----------



## vixr

this fade circuit is kinda interesting... I built it to see if it would work under the MAX tubes. I think the center LED pad on the MAX board could power the fader... I used a 100K trimpot to be able to change the speed of the fade. the chip is a LM1458









 here is a little video (sorry I'm no Tangent)


----------



## tomb

Very enterprising, Vixr!


----------



## tomb

I don't know if you guys caught this (I'm usually the last to know), but Pete Millett updated his "low-voltage hybrid headphone amp" pages to include a note about the MAX board and a link to the MAX website:

http://www.pmillett.com/hybrid_head.htm


----------



## amphead

Thats really great that Pete, was able to see the MAX. It looks like he was extremely busy and only just recently became aware of it. It seems that he was really blown away by it. Awesome!


----------



## amphead

Good idea Vixr!


----------



## bhjazz

Quote:


  Originally Posted by *vixr* /img/forum/go_quote.gif 
_this fade circuit is kinda interesting... I built it to see if it would work under the MAX tubes. I think the center LED pad on the MAX board could power the fader... I used a 100K trimpot to be able to change the speed of the fade. the chip is a LM1458



_

 

vixr that's awesome! I have seen some circuits that take a far larger chip to do what you just designed, so kudos to you. This is something I want to incorporate into a design later this year, so may I use it? (I'll definitely give you a shoutout!)

 bhjazz...the LED monkey


----------



## vixr

Quote:


  Originally Posted by *bhjazz* /img/forum/go_quote.gif 
_This is something I want to incorporate into a design later this year, so may I use it?_

 

by all means, use it... I'm glad to see I wasn't the only one who thought it was cool. the litte proto board measures 1.750"x 1.50", radioshack P/N 276-0150... You could probably do a much neater job building it...BTW the trimpot is in place of the bottom center 47K resistor in the schematic, right above the "D" in Drawn by...the video shows the fader in its slowest rate, the fastest rate just stays on...


----------



## n_maher

Quote:


  Originally Posted by *amphead* /img/forum/go_quote.gif 
_Thats really great that Pete, was able to see the MAX. It looks like he was extremely busy and only just recently became aware of it. It seems that he was really blown away by it. Awesome!
	

	
	
		
		

		
		
	


	


_

 

Pete's been aware of the MAX concept from the moment that we (Colin really) started experimenting with the design again. And like every other revision of the hybrid I sent him a copy of the pcb (both the proto and final production version) so that he has a record of how the design progresses. I only mention this because I think asking permission is an important part of the process and shouldn't be overlooked.


----------



## tomb

Quote:


  Originally Posted by *n_maher* /img/forum/go_quote.gif 
_Pete's been aware of the MAX concept from the moment that we (Colin really) started experimenting with the design again. And like every other revision of the hybrid I sent him a copy of the pcb (both the proto and final production version) so that he has a record of how the design progresses. I only mention this because I think asking permission is an important part of the process and shouldn't be overlooked._

 

Of course! Many thanks for you doing just that, Nate.


----------



## c0nsumer

Hrm. Well, the software for my MAX input switch is working... Now to finish selecting parts and design the PCB.


----------



## amphead

Thanks for the info Nate! Its very interesting to know the twists and turns that preceded the building of the first MAX.  Edit: Also, thank you for your efforts/contributions that helped to bring the MAX to life! btw, what is your feeling about the sharing of the official MAX mask images, both top and bottom? It would be better quality than what the "experimental" mask is going to be. You are absolutely right about the permission being sought, for any designers intellectual property. Pete Millett's site describes very well what he expects from those who use his designs.
 .

 Ron


----------



## vixr

removed a really dumb post...


----------



## matt303

Anyone used AKG K601 headphones with their MAX?

 I normally use Grado SR60s but I rather like the idea of giving a pair of K601s a go.


----------



## tomb

Quote:


  Originally Posted by *matt303* /img/forum/go_quote.gif 
_Anyone used AKG K601 headphones with their MAX?

 I normally use Grado SR60s but I rather like the idea of giving a pair of K601s a go._

 

We have a couple of builders confirm that the MAX drives K701s very well. If the headphones are similar, the MAX shouldn't have any problem with them.


----------



## amphead

There are probably a few builders, who currently have built the Millett Hybrid and the Millett Max. What are the similarities in sound and what are the differences? Is there a night and day difference in the sound? Thoughts?


----------



## ruZZ.il

I'm going to a little meet in 2 weeks and will try out a whole bunch of cans on both my MAX and M³. Will update. I wont be too familiar with most cans though, so I don't expect much


----------



## tomb

Quote:


  Originally Posted by *amphead* /img/forum/go_quote.gif 
_There are probably a few builders, who currently have built the Millett Hybrid and the Millett Max. What are the similarities in sound and what are the differences? Is there a night and day difference in the sound? Thoughts?_

 

Well, I built 4 Milletts - used single BUF's, double-stacked BUF's, the OPA551 and finally - the Intersil HA-5002, stacked and unstacked. Then I proceeded to add Diamond Buffers to each: one with the 2S3422/2SA1359, one with the 2SC3421/2SA1358, one with the MJE 243/253, and one with the BD135/136. All were powered by upgraded Treads.

 The sound signature is identical to the MAX except the MAX has an unbelievable reserve of power. The Millett, even with highly detailed Diamond Buffers, did not have the authority needed to maintain the very deep and strong bass of the MAX. The Millett also seemed to choke a bit on higher impedance cans, while the MAX seems to push through every last bit of detail to the phones.

 Keep in mind that there are those who said the Millett Hybrid with DB's performs better than a Melos, is better than almost all the familiar Asian tube amps, and when equipped with Black Gates was up there with an M3. So, take the slightly negative comments compared to the MAX in perspective, please. 
	

	
	
		
		

		
			





 None of that should be viewed as a criticism of the older Millett Hybrid - either Pete's or Drew's and Nate's version. Colin Toole's MAX is the next stage of refinement - one should expect that it is an improvement in many respects. 
	

	
	
		
		

		
		
	


	

















 EDIT: Given a choice of amps, I would always want to have a Millett of some sort - Hybrid or MAX.


----------



## xmokshax

i'm planning on starting to build a MAX at some point soon, and since i'm placing an order with soniccraft for a few other caps, i figured i might as well take care of my boutique cap needs for the MAX as well. however, i need some advice - i've done a few searches of this thread (obviously sifting through the whole thing is out of the question), and here's what i've gleaned:

 -CA3 and CA6 can be populated with the box film caps recommended in the BOM, despite the fact that they're "consensus boutique cap" locations according to the notes on the BOM.

 -it may be a good idea to use a slightly higher film cap value (~1.0uF) at CA8 than at CA9

 assuming these two things are true, i still have a couple of questions. first, does anyone have any suggestions about which line of caps to use at the CA8 and CA9 locations? i don't have much experience with boutique film caps, and unfortunately, the cost is somewhat prohibitive of experimentation. i'd like to get the caps i need from Soniccraft if possible, and i've been looking at the Auricap, Dynamicap, and Sonicap Gen II lines. are any/all of those suitable? any favorites?

 second, has anyone built a MAX using smaller (~0.47uF) blackgates at CA8/9 rather than film caps? if so, how do they perform?


----------



## tomb

Quote:


  Originally Posted by *xmokshax* /img/forum/go_quote.gif 
_i'm planning on starting to build a MAX at some point soon, and since i'm placing an order with soniccraft for a few other caps, i figured i might as well take care of my boutique cap needs for the MAX as well. however, i need some advice - i've done a few searches of this thread (obviously sifting through the whole thing is out of the question), and here's what i've gleaned:

 -CA3 and CA6 can be populated with the box film caps recommended in the BOM, despite the fact that they're "consensus boutique cap" locations according to the notes on the BOM._

 

Look more closely at that BOM. Those double asterisks "**" are only on the CA8L/R and CA9L/R.

  Quote:


 -it may be a good idea to use a slightly higher film cap value (~1.0uF) at CA8 than at CA9 
 

I remarked at the time that Troyhoot's strategy was interesting, but it hasn't been proven out. As Dsavitsk told me recently, there may be more going on with bypassing than simply selecting a cutoff frequency for the big cap (where the film bypass takes over).

  Quote:


 assuming these two things are true, i still have a couple of questions. first, does anyone have any suggestions about which line of caps to use at the CA8 and CA9 locations? i don't have much experience with boutique film caps, and unfortunately, the cost is somewhat prohibitive of experimentation. i'd like to get the caps i need from Soniccraft if possible, and i've been looking at the Auricap, Dynamicap, and Sonicap Gen II lines. are any/all of those suitable? any favorites? 
 

If you're using Muse ES caps at CA2 and CA7, no question according to Dsavitsk - the Sonicap GEN II's. I've also been talking with him lately and I get the impression that he likes those film caps as the inexpensive choice, period.

  Quote:


 second, has anyone built a MAX using smaller (~0.47uF) blackgates at CA8/9 rather than film caps? if so, how do they perform? 
 

MrMajestic2 has done this. Unfortunately, like a lot of us - he doesn't have another MAX built yet to provide a frame of reference.

 I've been having much the same conversation with Dsavitsk offline. I'm going to try to build a few more MAXes in the next couple of weeks and hopefully will get the chance to test some of these things out.

 EDIT: Rest assured, the MAX with the basic Wima's sounds very good ... with ES's in CA7 and CA2, even better. So, that's a killer - cheap - combo that sounds very, very good.


----------



## amphead

Tom, that was an outstanding comparison. Although the preceding designs were important for the evolution of the MAX, for me the MAXs bass extension, especially with K701, means I will build the MAX again with other quality components. Just the most bang for the buck. I was considering building one of the others, but I just can't justify the effort, with everything the MAX offers.  Kudos to Pete, Nate, Drew and of course Colin, whos efforts allow me to do so!


----------



## xmokshax

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Look more closely at that BOM. Those double asterisks "**" are only on the CA8L/R and CA9L/R.

 ...

 EDIT: Rest assured, the MAX with the basic Wima's sounds very good ... with ES's in CA7 and CA2, even better. So, that's a killer - cheap - combo that sounds very, very good._

 

ok, i was misinterpreting the BOM. i was just assuming that the double asterisk applied to C3 and C6 as well, since they were all on the same line and the asterisk followed the last one. i'm quite relieved that a premium configuration won't involve 8 high-quality film caps! 
	

	
	
		
		

		
		
	


	




 out of curiosity, around how much is the MAX costing people to build, for relatively standard configurations (or perhaps with a few boutique caps)? looks like jeff rossel's BOM comes out to around $170 in parts - are people spending a lot more than that, or is that pretty reasonable?


----------



## amphead

ruZZ.il, hope you get to listen to some awesome audio equipment! If you can, bring your digital camera and show your fellow MAXers.


----------



## amphead

So, the mighty MAX is at the top of the heap! Who has built both AMBs Beta 22 and the MAX. How would you compare the sound? I know I know, the Beta 22 is high end, but we still need to put the available diy builds into perspective. So please pony up a review.


----------



## tomb

Quote:


  Originally Posted by *xmokshax* /img/forum/go_quote.gif 
_<snip>out of curiosity, around how much is the MAX costing people to build, for relatively standard configurations (or perhaps with a few boutique caps)? looks like jeff rossel's BOM comes out to around $170 in parts - are people spending a lot more than that, or is that pretty reasonable?_

 

Building it yourself, that's a reasonable cost to populate the board with a few other component parts. However, as with any amp, there are a number of miscellaneous parts such as mounting bolts, washers, heat sink insulating pads/heat sink grease or silpads, The Knob, RCA jacks, extra output jacks, miscellaneous wiring, tip jacks, tube bushings, upgrade transistors, - not to mention the cost of several tubes. Those things may or may not end up costing quite a bit more, depending on how you budget and what you purchase in volume. For instance, pay retail price and shipping for a complete set of tubes, a high quality knob, and price/shipping for boutique output transistors and you can easily spend another $50-$70 just for those items alone. Some people may pay that just for a pair of RCA jacks. 
	

	
	
		
		

		
		
	


	




 Now, having said all of that, the onboard power supply, the delay circuit, the footprint for heat sinks, the fact that the board is engineered to fit perfectly in a standard Hammond with no extra components needed - all those things combine along with outstanding - even surprising - performance to make the MAX an unbeatable combination. IMHO, you can't purchase an amp with this level of performance for this price - either retail _or_ DIY.


----------



## babbkutz@comcast

with the DBs (MJE243/MJE253) using 12AE6A tubes and it sounds great into Senn 650s, Senn 600s, and AKG K701s.....rest assured you won't be disappointed!


----------



## c0nsumer

Not sure if this is interesting or not, but the software for the audio input switch for my MAX is complete. It's being released under the MIT license, and you can grab a copy of the source here: http://nuxx.net/files/nuxx_input_swi...board.pbas.txt

 It's written in mikroBasic (I can bang stuff out fast this way), designed for a PIC16F630 running from the internal 4 MHz osc, and is currently set up for my dev board. Defines for pins will change in order to better facilitate better routing of traces and such.

 I'll be working up a full-on project page for the nuxx Audio Input Switch after I get more of the hardware design done.

 Hmm... Maybe I should start a new thread about this.


----------



## Ferrari

I have built and owning the MH Max (both versions) and the β22/σ22 (3- and 4-channel) for a while and this is my thought...

 These 2 amps are from totally different sort. The MH Max is a good hybrid 2-channel amp with its own sound signature, relatively inexpensive and easy to build... lots of amp for the buck. The sound signature is much depending on various factors: BJTs or MOSFETs output buffer, the DC voltage level applied on the output buffer, the choice of the output caps...

 On the other hand, the β22 with its partner σ22 are true high-end Solid State amp and PS, with the flexibility to configure it as 2-, 3- or 4-channel amp and different PS combinations. From electronics design viewpoint, the β22 and σ22 are definitely belonging to the best what a hardware designer can do: _"la crème de la crème"_.
 Soundwise, this amp belongs to top notch audio... 
	

	
	
		
		

		
		
	


	




 no doubt.

 To my opinion, these 2 amps are from totally different sorts that makes it not easy to compare them directly to each other. You are not going to compare a good _Volkswagen Golf _to a _Porsche_ or something like that... 
 Unless they are all vehicle on 4 wheels, it's simply unfair to do so.


----------



## fierce_freak

Haha, thanks Ferrari


----------



## nysulli

contruction finally began last night, depending on a pending business trip next week (which would require me finishing my mini^3 first) yet another MAX will be alive and well, BJT biased to 100 mA (yes, thats mA)

 final chance to decide, i have both muse KZ and ES caps for the output, 3422 trannies, and soniccap gen 2's for bypass, main phones are HF-1's, suggestions?


----------



## amphead

Ferrari, thanks for the review! Now I realize how good the beta 22 sounds, because the MAX kicks some serious ass with boutique components.


----------



## tomb

Quote:


  Originally Posted by *nysulli* /img/forum/go_quote.gif 
_contruction finally began last night, depending on a pending business trip next week (which would require me finishing my mini^3 first) yet another MAX will be alive and well, BJT biased to 100 mA (yes, thats mA)

 final chance to decide, i have both muse KZ and ES caps for the output, 3422 trannies, and soniccap gen 2's for bypass, main phones are HF-1's, suggestions?_

 

Well, the height of the case would make the decision for me - the KZ's are Giant Sequoias. However, if that's not your concern - you might try mixing them up. ES's on the cathode bypass to emphasize bass and then KZ's on the output to pass everything unaltered. You really can't lose whatever you do if height is not a consideration.


----------



## nysulli

it really isn't, as CA4 and 5 are 1000uf KZ's, along with the 1.5" heatsinks on the trannies, but the extra bass might be nice 
	

	
	
		
		

		
		
	


	




 something tells me i'll be experimenting with the ES/KZ combo and tubes for a little while, should be a good time


----------



## amphead

So, in the diy horse race for the best sound, the winners circle consists of:
 1st Place - Beta 22
 2nd Place - Millett Max
 3rd Place - M³
 Is this the consensus? I personally don't know having only built the MAX. Thoughts?


----------



## ruZZ.il

M³ also has character of its own, I'm not sure I'd rate either MAX or M³ below or above each other.. I find myself listening to the max more often, but the M³ has its points and wins a fair deal of my time too 
	

	
	
		
		

		
		
	


	




 it seems more authoritative, accurate, but less 'musical' in some senses.. its definitely a bit more 'powerful', or so it seems..


----------



## amphead

A photo finish for second and third place! 
 Edit: with the Max by a nose!


----------



## vixr

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_You really can't lose whatever you do if height is not a consideration._

 

even if height _is_ a consideration, do it anyway!!! WOO HOO!!!


----------



## tomb

Of course! 
	

	
	
		
		

		
		
	


	




 When someone has your milling abilities, component height is not a problem.


----------



## joneeboi

Question about the e12 delay circuit:

 What value for CM1 can be used aside from the BOM's 47uF, 25V electrolytic? I'm making a Mouser project and the standard value is backordered until Christmas Eve. I'm not saying I'll build another one between the time, but I'd just like to know for the sake of understanding a bit more how the circuit works.


----------



## bperboy

Quote:


  Originally Posted by *joneeboi* /img/forum/go_quote.gif 
_Question about the e12 delay circuit:

 What value for CM1 can be used aside from the BOM's 47uF, 25V electrolytic? I'm making a Mouser project and the standard value is backordered until Christmas Eve. I'm not saying I'll build another one between the time, but I'd just like to know for the sake of understanding a bit more how the circuit works._

 

Try Mouser p/n 647-UPW1E470MDD. Should be the equivalent. Someone else might care to check, but I'm pretty sure this will work.


----------



## tomb

Bperboy is correct that almost any 'ol 47uF 25V electrolytic will work - certainly, a UPW will work fine, but that kind of quality is not really necessary. I use Xicons in mine -they're a little under $1 for 10 of them. You don't need a high performance cap here - only a dependable one. Xicon, Mallory, United Chem-con, Nichicon VX, etc. It might be good to stick with a 105deg. rating, though, simply because of the heat from all those heat sinks nearby.

 The 1st prototype actually used a 22uF 25V Tantalum. The delay was quite a bit slower with that cap. However, the equivalent Tantalum probably should've been smaller and that might have something to do with the difference in the circuit. At any rate, that particular size Tantalum was $2.22! So Colin - thankfully - substituted something cheaper.

 As it is working out, we may be better off with a 470uF in CM3. That sort of equalizes the circuit back to the delay times we had with the tantalum, I think. Again - as cheap as you can find, but not an off-brand that might fail.

 EDIT: Increasing the size of RM2 and CM3 is the most direct way to increase the delay. My own experience is that the delay alters with the impedance of the can. You want about 10 seconds of delay with the lowest impedance can you will use, but the delay will be much longer for higher impedance cans.


----------



## ericj

For the delay circuit? I used jamicons from my parts bin. 







 Don't look at me that way - some of my diy projects are purely slow digital logic, applications where super-high-quality caps are wasted.


----------



## amphead

Finally a pic of my rigs innards.


----------



## amphead

Lets zoom out! Edit: Thats my teflon power jack mod(upper left) to keep it isolated.


----------



## amphead

My listening rig! I know thats a guitar trainer used for my cd player/dac.


----------



## MrMajestic2

Quote:


  Originally Posted by *amphead* /img/forum/go_quote.gif 
_My listening rig! I know thats a guitar trainer used for my cd player/dac.
http://i207.photobucket.com/albums/b...cide/bfour.jpg_

 

How are those K701´s working out with the Max? Planning on getting me a pair too.


----------



## amphead

Night view!


----------



## amphead

Quote:


 MrMajestic2:
 How are those K701´s working out with the Max? Planning on getting me a pair too. 
 

The combination with the MAX and boutique film/foil bypass caps really shines. Remember, you get clarity(no veil) and sounds come out that didn't exist before. Not a headphone for absolute bassheads. The bass is good/tight, but not the jarring type that a basshead is used to. It really is an equally divided response, because treble, mids and bass are all there.
 Going from bass heavy phones, you would have to readjust, but the clarity is worth every bit IMHO. Cymbals, voice, piano, guitar strings have presence and an "in the same room" type of sound! Guitar strings and strings in general resonate. Piano sounds natural and resonant! Vocals sparkle!


----------



## ruZZ.il

looks good. nice way of mounting those caps!


----------



## MrMajestic2

Quote:


  Originally Posted by *amphead* /img/forum/go_quote.gif 
_The combination with the MAX and boutique film bypass caps really shines. Remember, you get clarity(no veil) and sounds come out that didn't exist before. Not a headphone for absolute bassheads. The bass is good/tight, but not the jarring type that a basshead is used to. It really is an equally divided response, because treble, mids and bass are all there.
 Going from bass heavy phones, you would have to readjust, but the clarity is worth every bit IMHO. Cymbals, voice, piano, guitar strings have presence and an "in the same room" type of sound! Guitar strings and strings in general resonate. Piano sounds natural and resonant! Vocals sparkle! _

 

Sounds like my kinda phones 
	

	
	
		
		

		
		
	


	




 Nice build by the way.


----------



## amphead

Thanks, for the compliments! Yes it seemed to be the way the Jensens wanted to be oriented in the MAX. There are six of them. Two pairs are stacked in the DBs, for 0.2uF there. That rounded the sound a bit more than when I had 0.1uF.

 Cheers, Ron ( Jethro Tull on Oct. 4th! )


----------



## thunder

Does anyone know why when using a Nichicon ES w/sonicap offer better or more bass response, Is it becuase it's a by-polar cap ? If not what makes this combo provide it's unique response ?


----------



## tomb

Quote:


  Originally Posted by *thunder* /img/forum/go_quote.gif 
_Does anyone know why when using a Nichicon ES w/sonicap offer better or more bass response, Is it becuase it's a by-polar cap ? If not what makes this combo provide it's unique response ?_

 

It's the ES, period. The Sonicap actually tames a bit of the breakup and lack of resolution that exists in the ES's top end, without destroying the bass. It actually does this with a slight roll-off on the high and low end, with a fairly good midrange. The ES predominates in the low end, anyway, so the Sonicap doesn't detract from the bass.

 That's an anectodal description of what's happening, but the same thing happens with a plain 'ol Wima - only not quite as well (still pretty d*mn good, though). Actually, the same thing happens with a Panasonic FM or a Nichicon UPW - the bypass cap is smoothing the high end breakup and distortion that exists in many power caps in the high end audio frequency region. It's just that the ES is a fairly decent boutique cap and does pretty well on its own - very, very good in bass.

 Why is the ES inherently so strong in bass? You'd have to ask Nichicon that one, I guess.

 EDIT: Bi-polar doesn't have anything to do with it, IMHO. You can compare the ES to a bi-polar Black Gate: the Black Gate NX is probably the most detailed and dynamic electrolytic in existence, but the ES is still the bass monster.


----------



## tomb

Quote:


  Originally Posted by *amphead* /img/forum/go_quote.gif 
_Finally a pic of my rigs innards. _

 

Very impressive! What are the electrolytics you're pairing with those Jensens?


----------



## amphead

Tom, Originally I planned on using these capacitors temporarily, which is what is in the MAX right now. Panasonic HFS 470uF 63v 105 degrees and Panasonic SU 1000uF 50v. I am confident with the HFS, which is comparable to Panasonic FC, and is specified as "low impedance". The SU series will probably get rolled for something better. I think the SU are "general purpose". They were caps that I had left over from another audio project. Thinking about going Nichicon ES, based on reviews!


----------



## thunder

Has anyone tried using the Std Blackgate series cap's ? If so how do they compare to Nichicon Muse ES or KZ, Elna Silmic or the Blackgate NX ? If possible I would like to get some idea how each rank from good better best ect... when being used with a film bypass. Thanks


----------



## tomb

Quote:


  Originally Posted by *thunder* /img/forum/go_quote.gif 
_Has anyone tried using the Std Blackgate series cap's ? If so how do they compare to Nichicon Muse ES or KZ, Elna Silmic or the Blackgate NX ? If possible I would like to get some idea how each rank from good better best ect... when being used with a film bypass. Thanks_

 

Black Gate NX's are the best in the signal path.

 As a power cap, Black Gate Stds are not as good as your typical Panasonic FM or Nichicon UPW power cap - this has been told to me from several sources. Now, if you believe that the MAX's circuit can distinguish between a cap with a decent tonal quality vs. one without _outside_ the signal path (I don't), then maybe a Black Gate Std would work well. Personally, I think they would be a waste of money. I don't think they compare to any of the others as a boutique cap in the signal path, either, but maybe there's some that will disagree with that. IOW - IMHO - BG Stds are a waste of money in either case for the MAX. Again, there are a few who've told me this same thing - including cetoole.

 Of course - watch to see if that statement attracts Dsavitsk's attention.


----------



## fordgtlover

Sorry for the dumb question. Which is the front of the BD139? Based on what I can figure the writing is at the back. Is this correct.

 So close with the build and then I get tripped up on such a little thing.


----------



## tomb

Quote:


  Originally Posted by *fordgtlover* /img/forum/go_quote.gif 
_Sorry for the dumb question. Which is the front of the BD139? Based on what I can figure the writing is at the back. Is this correct.

 So close with the build and then I get tripped up on such a little thing._

 

NO. The writing is always on the front.


----------



## fordgtlover

Tomb - thanks.


----------



## fordgtlover

Has anyone tried, or know anything about, the PIO caps listed in this sale at ebay.
http://cgi.ebay.com/ws/eBayISAPI.dll...m=260163732519

 Are they likely to be any good for CA8/9?

 I will be running Elna Silmics in CA2/7.


----------



## tomb

Quote:


  Originally Posted by *fordgtlover* /img/forum/go_quote.gif 
_Has anyone tried, or know anything about, the PIO caps listed in this sale at ebay.
http://cgi.ebay.com/ws/eBayISAPI.dll...m=260163732519

 Are they likely to be any good for CA8/9?

 I will be running Elna Silmics in CA2/7._

 

They look like a pretty good deal to me - and it appears that they are less than an inch. I may try a purchase myself.

 It looks like you may need to sand the nipples when putting them in the positions on the front of the board - those large pseudo-test point holes are for tombstoning caps such as these. However, it appears that the green paint covers the nipples, too.


----------



## amphead

*[size=large]CORNER FREQUENCY![/size]*
 After thinking hard about what could improve the sound, I thought about what my brother-in-law(formerly audio engineer by trade) said. "Sounds great but it still needs something". Disappointed with that response, I remembered how important the output coupling capacitors are. I had panasonic hfs(like fc) there at 470uF. Took my last set of panasonic su caps at 1000uF(not boutique) and rolled those into CA7L/R. 
	

	
	
		
		

		
			



















 Ever heard K701s in Basshead mode? Freakin awesome!
	

	
	
		
		

		
		
	


	

























 Dont hesitate on the K701s with the MAX. It rocks so hard with corner frequency correction(64 ohms/1000uF) its unbelievable. Oh, don't forget to rebias the DBs, I nearly cooked my trannies, while listening to some tunes. Current flow has changed of course.
	

	
	
		
		

		
		
	


	



 Now to locate some boutique output coupling caps at 1000uF!


----------



## tomb

Yeah, the MAX is causing us to re-evaluate the reasoning behind corner frequency effects. If you calculate for a 64 ohm pair of headphones and 470uf, you get something like 5.3Hz, which should be low enough even with phase distortion.

 The calculation is even worse when considering the transconductance of the tubes and trying to size for CA2. Traditionally, this calculation has resulted in something around ~120uf for 5-10Hz. So, the traditional practice on the old Millett Hybrid was to use 220uf (!). Yet, such a value in the MAX results in noticeably anemic bass - which is why I changed the recommendation to 1000uf minimum for CA2 in all builds.

 The problem is that you will find that searching for 1000uf boutique caps with a 35V rating and higher is not so simple. The BG's have the 680uf at 35V, but after that, the caps become huge. I haven't noticed any lack of bass with the 1000uf on the back end, though - and voltage can be as low ~10V in the CA2 positions. That makes it a little easier to get high capacitance on the back end.

 In any event, glad to hear you made a big difference in your listening results!!


----------



## thunder

Tomb, Now you understand the basis for all my cap related question's. I merely wondered about Std Blackgate's for making a size and cost vs performance comparison ! The CA7 pos is tough to fill with anything other than a 680 NX. My favorite HP's are 600 ohm. Also here goes another new-be brainstorm, What do you think about using Mills noninductive wirewound 3 watt 2.2 ohm res in the RB10 & 11 position's ?


----------



## Troyhoot

thats why i ran 1k KZ caps all around and even the 1.0 bypass with a 32 ohm resistor. All to lower my corner frequency for 32 ohm cans. I havent been disapointed at all.


----------



## thunder

How do the KZ's compare to the ES series as far as sound quality ect... ? Just wondering which would be the better choice for the CA2 position. As for CA7 it's a toss-up for either a 1000uf KZ or a BG 680 NX.


----------



## Troyhoot

I havent compared them personally. Everyone says the ES have more bass. If my Max had more bass I would have to play with my eq 
	

	
	
		
		

		
		
	


	




 Seriously though, I have zero complaints with the KZ's. Plenty of bass, everything seems very clear and precise through all frequency range. The KZ is supposed to be the top of the line Nichicon cap though in that category. Im sure Tomb or one of the others with experience with both can give you a better response.

 I wanted to go with 1k caps on all positions to lower my corner frequency and for easy of ordering too. Since ES dont have 1k cap choice I went with what I thought would be a premium cap without paying a fortune (IE: 1k black gates). 

 Now my setup is kinda against the grain with most since I used KZ's with Auricap bypass. This combination worked fine with me. I am enjoying my amp with no regrets. My guess is the Auricaps dont work well in combination with some caps as a bypass. The characteristics of the KZ's though match very well with them IMHO. This was discussed a ways back in this gigantic thread a little bit.


----------



## Alcaudon

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_
 The problem is that you will find that searching for 1000uf boutique caps with a 35V rating and higher is not so simple. The BG's have the 680uf at 35V, but after that, the caps become huge. I haven't noticed any lack of bass with the 1000uf on the back end, though - and voltage can be as low ~10V in the CA2 positions. That makes it a little easier to get high capacitance on the back end.
_

 

Tomb, do you think that would be safe to use 25V caps in CA7 positions? I was planning to use some 1000uF-25V muse es there.


----------



## thunder

Thanks guys this really helps narrow the field some before I decide as to or not cut the case I'm using. To bad there is no room for a 2 deck rotary sw for cap's in my case ! I then could try different combo's w/o the pain of trial and error cap swapping ! For CA7 
	

	
	
		
		

		
		
	


	










 KZ/NX KZ/NX KZ/NX Someone please help make up my mind !!!! Thank's again guy's PS> (To bad we couldn't use a 25v cap in that position it would solve everything.)


----------



## Ferrari

Theoretically you guys are (almost) right about the corner frequency calculation (... don't forget RA4L/R = 1KΩ // with your headphone impedance! ) But it seems to be that the focus here is abit too much on the quantity: how large the value should be? 470µF, 680µF or 1000µF ??? The _"true audio quality"_ of the output caps: pulse response as function of the audio frequencies (non-lineair characteristic), unwanted memory effect... is somewhat overlooked. I agreed that you can't put a small capacitor (i.e. 1µF) at the output when you are expecting good bass response.

 Besides the apprepriated value, the _"true audio quality"_ of the capacitor can break or make the sound, "good bass" included! I have tried many electrolytics capacitors at the output (including BG NX, Elna Silmic II and Nichicon Muse ES/KZ as mentioned here) but I use this on one of my MH Max... and only 330µF.







 Keep in mind that human ears can NOT hear frequencies below ~20Hz and probably the roll-off of many headphones (the best ones included) start at a far higher frequency than the calculated corner frequency.


----------



## thunder

Ferrari, Please explain more on how RA4 L&R effect thing's, I'm currently planning to use 600 ohm HP's. Also could you shed some light on the results found using various other cap's in the CA7 position ? I have very limited knowledge if any of electronic's, just hope to get the best result's out of this build w/o spending mega $$$$ or trying to obtain a degree on line. Thank-you very much for all or any help !


----------



## tomb

Quote:


  Originally Posted by *Ferrari* /img/forum/go_quote.gif 
_Theoretically you guys are (almost) right about the corner frequency calculation (... don't forget RA4L/R = 1KΩ // with your headphone impedance! ) But it seems to be that the focus here is abit too much on the quantity: how large the value should be? 470µF, 680µF or 1000µF ??? The "true audio quality" of the output caps: pulse response as function of the audio frequencies (non-lineair characteristic), unwanted memory effect... is somewhat overlooked. I agreed that you can't put a small capacitor (i.e. 1µF) at the output when you are expecting good bass response.</snip>_

 

Yes - we discussed this in Post #479 and some of the surrounding posts before and after. That's been awhile, but the chart and calcs I displayed in that post indicated that a corner frequency of 7Hz was needed just to keep the total rolloff at 20Hz or below. This is remembering of course, that the corner frequency represents the -3dB point. So, the response is falling off before then - all the way up at 90Hz or higher. R4L/R was factored in with the table in the above post. As you correctly state, it's in parallel with the headphone impedance. 

 Ordinarily, I'd agree that it shouldn't make a big difference. Yet, the MAX has been stubborn in its resistance to rigid adherence of the corner frequency calculation. The anecdotal experience has been proven out by several builders with "before and after" tests with CA2 (perhaps explained in part by the pulse capability you reference). I think all I was trying to say was that because of that experience, I was not really surprised if Amphead discovered it made a big difference at CA7, too.

 BTW, now that you mention it - some of us compensate to get maximum performance in different ways. 
	

	
	
		
		

		
		
	


	







 Perhaps a 1000uF electrolytic is just one man's reaction to your extreme film caps.


----------



## tomb

Quote:


  Originally Posted by *thunder* /img/forum/go_quote.gif 
_Ferrari, Please explain more on how RA4 L&R effect thing's, I'm currently planning to use 600 ohm HP's. Also could you shed some light on the results found using various other cap's in the CA7 position ? I have very limited knowledge if any of electronic's, just hope to get the best result's out of this build w/o spending mega $$$$ or trying to obtain a degree on line. Thank-you very much for all or any help !_

 

RA4 is in parallel with the headphone impedance. So, for instance, if you used Grado's, you'd have:

 1/Rtotal = 1/RA4 + 1/HeadphoneOhms, or
 1/Rtot = 1/1000 + 1/32 = 0.001 + 0.03125 = 0.03225, and
 Rtot = 31

 It makes a bigger difference when using high impedance phones such as 300ohm Senns:

 1/Rtot = 1/1000 + 1/300 = 0.0043, Rtot = 230ohms. This says that because of that resistor to ground, the output stage (including the CA7 caps) actually see 230ohms, not 300. That's quite a difference.

 Of course, you must also include the output resistor, RB14, if it's used. That one is in series, of course - so you would add it to the resistance total you calculated for the parallel resistance of the headphone and RA4.

 EDIT: Thor, if you're using 600ohm cans, you could probably get away with 100uf in the CA7 position:

 1/Rtot = 1/1000 + 1/600 = 0.0027, Rtot = 375ohms

 So, using 7Hz as a corner frequency, we'd have:
 C= 1/(2pi * f * R), C = 1/(2*pi * 7 *375), 
*C = 60uf!!*

 EDIT: Ferrari - please check that for me - I think it's right.


----------



## tomb

Quote:


  Originally Posted by *Alcaudon* /img/forum/go_quote.gif 
_Tomb, do you think that would be safe to use 25V caps in CA7 positions? I was planning to use some 1000uF-25V muse es there._

 

Only if you never exceed 24VDC for your power supply setting. (V+). On powerup, the CA7 caps see full supply voltage minus a a couple volts of drop through the whole circuit. This happens every single time you turn the amp on - until the tubes begin to conduct. Then the caps see approximately the reference bias of 1/2 of the total voltage. So, if you set V+ at 24VDC, then they would see ~23-24VDC at powerup, and settle down to ~12-13V after the tubes warm up.

 However, there is a reason not to run higher voltage: all other things being equal, the tubes have better performance at higher voltages. Likewise, the Diamond Buffer output stage performs better at higher voltage and can drive more difficult loads. As a matter of fact, for the first time with a Millett design, the MAX has provision to go to 30VDC in the supply - if your walwart can support it. The heater resistor makes this possible, since the real voltage limitation is on the heater circuit. As documented in many places, however, 27VDC is the accepted MAX standard.


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## thunder

Tomb, As usual I find your help extremely valuable ! Today I plan to use my 600 ohm HP's who knows if later I'll switch to something else with less impedance. Is it possible to use a low value in R14 pos say 10 ohm, then construct a plug-in style set-up for RA4 if swapping HP's from time to time ? Once again and always thank-you !!!


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## tomb

Quote:


  Originally Posted by *thunder* /img/forum/go_quote.gif 
_Tomb, As usual I find your help extremely valuable ! Today I plan to use my 600 ohm HP's who knows if later I'll switch to something else with less impedance. Is it possible to use a low value in R14 pos say 10 ohm, then construct a plug-in style set-up for RA4 if swapping HP's from time to time ? Once again and always thank-you !!!_

 

Well, to tell the truth - all those calcs are just a long way around to end up saying: "Put a 470uf in there and forget about it." 
	

	
	
		
		

		
			





 Certainly - you can put sockets in a resistor position, or better yet - run leads from the resistor pads to a switch, but ultimately, you'd be better off just putting 470uf's in there when it's all said and done.

 You really only have a problem in the low bass when doing that with Grados or similar. However, most Grados aren't going to reproduce bass in that region anyway. 
	

	
	
		
		

		
		
	


	




 Don't get mad at me folks - I may buy some Grados again sometime. 
	

	
	
		
		

		
		
	


	




 Most of the time I listen with KSC75's, anyway - they're just so d*mn convenient.


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## amphead

Is there a down side to the use of the mediocre panasonic su 1000uF cap in place of the panasonic hfs(fc) 470uF in the CA7L/R position? In a word, yes. While it helped to identify the range of frequency response, it has a harshness and lacks the detail that a boutique replacement will have. I will also consider that 680uF may be sufficient there, depending on what I find for a replacement. I could also probably go back to the panasonic hfs( fc ) 470uF and replace the 22 ohm resistors at RB14L/R with 100 ohm, to see what that does right? Is their a performance loss in doing it that way? Dsavitsk?


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## Alcaudon

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_
 On powerup, the CA7 caps see full supply voltage minus a a couple volts of drop through the whole circuit. This happens every single time you turn the amp on - until the tubes begin to conduct. Then the caps see approximately the reference bias of 1/2 of the total voltage. So, if you set V+ at 24VDC, then they would see ~23-24VDC at powerup, and settle down to ~12-13V after the tubes warm up.
_

 

Thanks for your help Tomb, that's exactly what i thought so I asked to a teacher (Believe me when I tell you that he is an electronics master) and he told me that it was absolutely safe specially using good quality caps.
 Anyway I will take your advice and stick with 470uF-35V, I prefer to run it at 27V-28V without being afraid of blowing up the caps everytime I turn on the Max 
	

	
	
		
		

		
		
	


	




 Thanks again!!!


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## amphead

Quote:


  Originally Posted by *Alcaudon* /img/forum/go_quote.gif 
_Thanks for your help Tomb, that's exactly what i thought so I asked to a teacher (Believe me when I tell you that he is an electronics master) and he told me that it was absolutely safe specially using good quality caps.
 Anyway I will take your advice and stick with 470uF-35V, I prefer to run it at 27V-28V without being afraid of blowing up the caps everytime I turn on the Max 
	

	
	
		
		

		
		
	


	




 Thanks again!!!_

 

What are your headphones and their rated impedance?


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## Alcaudon

Quote:


  Originally Posted by *amphead* /img/forum/go_quote.gif 
_What are your headphones and their rated impedance?_

 

I will use the Max mainly with a pair of HD595 and some other low impedance cans, so that makes an impedance range of 32-50 Ohms aprox. I'm planning to buy a pair of HD600 in a near future, but I will probably build another Max for those.

 So using 470uF caps will produce a corner frequency range of aprox 10Hz-7Hz, taking into account phase distorsions: 100Hz-70Hz (considering the worst case, maybe its a bit too much distorsion 
	

	
	
		
		

		
		
	


	




) is this correct??. That seems to me a quite high frequency and maybe this results in a lack of bass, but I'm quite new to all this. Maybe you could bring some light to my dark head 
	

	
	
		
		

		
		
	


	




.

 Thanks!!!


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## tomb

A couple of things and Ferrari sort of alluded to it:

 - This discussion is all in the margins, actually. The 470uf has been used in the revMH practically from the very beginning.
 - Starting from that basis, I can't recall anyone _ever_ having trouble with bass using Grados. In fact, you would think from most Millett Hybrid builders that Grados are the ideal pairing with a Millett - simply because of the amount of bass and warmth that a Millett imparts.

 {Well, there was one instance with the old Millett where someone used 100uf caps everywhere and he definitely noticed a lack of bass. However, those were not recommended values by any version of the BOM.)

 - Reading through Amphead's posts, I think he was using some rather non-standard caps. Non-standard for a Millett, that is.
 - Go back and read some of the many threads - you will find that many claim the MAX has some of the best bass they've heard. Vixr, for instances, claims the MAX has the best bass of any of his amps - and he has quite a few.

 Finally, and this again alludes to what Ferrari has said:
 I recall testing some of my revMH Millett Hybrids without the traditional Wima caps bypassing the C7 output coupling position. There were 470uf ES's in those positions. However, without the little Wima films, the result was _less bass_ not less highs. One might think from this - as Ferrari mentioned in his post a short while ago - that there's something more going on with the film caps than just providing a "crossover" at higher frequencies. I don't pretend to understand it, either - but there it was.

 So rest assured, build the MAX with a quality 470uf and 0.22uf Wima MKP10's, and also the 1000uf's on CA2 with the Wima's, and you won't have any lack of bass - pretty much regardless of headphone. It's when we deviate from that in an attempt to get even more spectacular performance that things start getting a little tricky in the margins.

 You might also reference Steinchen's original post about calculating corner frequency for the orig. Millett Hybrid: http://www.diyforums.org/phpBB2/viewtopic.php?t=16 In that link he calculates the corner frequency for a few headphone impedances:

 300R 1000uF -> 0.5Hz 
 300R 470uF -> 1.1Hz 
 300R 220uF -> 2.5Hz 
 300R 100uF -> 5.3Hz 

 120R 1000uF -> 1.3Hz 
 120R 470uF -> 2.8Hz 
 120R 220uF -> 6.0Hz 
 120R 100uF -> 13.3Hz 

 75R 1000uF -> 2.1Hz 
 75R 470uF -> 4.5Hz 
 75R 220uF -> 9.6Hz 
 75R 100uF -> 21.2Hz 

 32R 1000uF -> 5.0Hz 
 32R 470uF -> 10.6Hz 
 32R 220uF -> 22.6Hz 
 32R 100uF -> 49.7Hz

 Not to confuse things, we discussed a few posts back the fact that there may be a couple of other resistors in there, but they don't make a bean's worth of difference at low headphone impedances, where the concern for corner frequency exists. We could also talk about where the rolloff begins and whether phase distortions actually have an effect and where, but I'm not sure anyone is certain whether these effects are audible, anyway.


----------



## Alcaudon

Again another clear explanatory post. Thanks for all your advices Tomb.


----------



## Ferrari

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_RA4 is in parallel with the headphone impedance. So, for instance, if you used Grado's, you'd have:

 1/Rtotal = 1/RA4 + 1/HeadphoneOhms, or
 1/Rtot = 1/1000 + 1/32 = 0.001 + 0.03125 = 0.03225, and
 Rtot = 31

 It makes a bigger difference when using high impedance phones such as 300ohm Senns:

 1/Rtot = 1/1000 + 1/300 = 0.0043, Rtot = 230ohms. This says that because of that resistor to ground, the output stage (including the CA7 caps) actually see 230ohms, not 300. That's quite a difference.

 Of course, you must also include the output resistor, RB14, if it's used. That one is in series, of course - so you would add it to the resistance total you calculated for the parallel resistance of the headphone and RA4.

 EDIT: Thor, if you're using 600ohm cans, you could probably get away with 100uf in the CA7 position:

 1/Rtot = 1/1000 + 1/600 = 0.0027, Rtot = 375ohms

 So, using 7Hz as a corner frequency, we'd have:
 C= 1/(2pi * f * R), C = 1/(2*pi * 7 *375), 
*C = 60uf!!*

 EDIT: Ferrari - please check that for me - I think it's right. 
	

	
	
		
		

		
		
	


	


_

 


 Tomb, your calculation is correct!

 It’s indeed based on the basic formular: f = 1/(2π.R.C)
 => C = 1/(2π.f.R); with R = [RB14 + (RA4 // RH)]; RH = Headphone impedance by approximation. 
 => C = 1/{2π.f.[RB14 + (RA4 // RH)]} = 1/{2π.f.[RB14 + (RA4.RH)/(RA4+RH)]}

 The reason why I call RH = Headphone impedance by approximation is that: in real life, headphone/speaker impedance is not real Ohms but rather complex and looks like (R+ jωL+ 1/jωC) and thus depending on the frequencies (ω = 2π.f).

 => C = 1/(2π.R.f); with R = {RB14 + [RA4 // (R+ jωL+ 1/jωC)]}
 => f = 1/{2π.[RB14 + (RA4 // (R + jωL + 1/jωC))].C}
 => f = 1/{2π.[RB14 + (RA4.(R + jωL + 1/jωC))/(RA4 + (R + jωL + 1/jωC))].C}

 But let me stop the calculations this way since it becomes quite lo…..ong 
	

	
	
		
		

		
		
	


	




 . 
 For the convenience, we can keep it simple and use:

 f = 1/{2π.C.[RB14 + (RA4.RH)/(RA4+RH)]}

 Steinchen calculations is also based on this simplified formula but it does give a good insight on the use of the output capacitor on the MH Max. Note that Steinchen assumes that the output resistor RB14 = 0 in his calculations.


----------



## tomb

Thanks, Ferrari. I lose it when I start seeing those imaginary numbers, though.


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## ruZZ.il

mmm.. phasors.. phun.
 anyway, I love this amp, it makes me melt 
	

	
	
		
		

		
		
	


	



 just had to say that..


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## nysulli

construction complete, all thats left is to fire it up, troubleshoot and bias, and casework when i get around to it, but i think i'll be to busy enjoying this one for a few days to do the work

 i'll post back in a little while after I eat dinner and get the biasing done


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## ruZZ.il

yeeha! remember to be quick checking the DB's! 
 <keen for the update>


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## c0nsumer

In case any of you are interested, here is my first draft of the audio input switch I've been working on. It's designed to fit in a Hammond enclosure right behind a MAX and easily piggyback off of the power / feed audio to it, but it'll also be a nice stand-alone device.

 Yes, it's just still a draft, and I have to finish validating all the part choices, but hopefully I'll order the first run of PCBs by the end of the weekend.

 -Steve


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## ruZZ.il

if they're inexpensive it would be nice to just build in the case.. I'm guessing you can expect to find a few buyers, me included. looks neat! how long does it take to switch sources? ie, for the relays to switch.. break before make? also, is there a delay between selecting a source and its activation? cause if its a momentary toggle switch to rotate between sources, it should have a bit of a delay so it'll only switch once even between say, I1 and I3.. or is it rotary toggle to hook up to J4? also.. momentary toggle needs some extra circuitry with some caps and stuff, cause 1 press can make and break quiet a few times to these fast gates.. or did you say that already?  anyway, looks like fun to put together.. and a nice project. thanks! and kudos.


----------



## nysulli

well, first powerup went without a hitch, all trimmers full clockwise, all voltages nice and low, just bumped the PS up to 27V, now going to finish up things and give it a listen, 12FK6 tubes in right now, just to have something in

 final configuration

 3422/1359 trannies
 1000uf Muse ES in CA2
 1000uf Muse KZ in CA4,5,7
 1000uf panny FM in CR1's
 soniccap gen2's in CA8,9
 PRP resistors throughout with the exception of RB10/11 which are Mills wire-wounds
 DB's biased at 50ma for the time being, final bias should be around 100ma

 things aren't even remotely warm with the 1.5" heatsinks, but theres no way to fit a top on here without cutting holes for the KZ's and heatsinks along with the tubes

 so far i like it, definitly more detail then my old PINT, cleaner sound, screw that, i don't like this thing, i love it so far, i'll have to do some tube swapping later this week after i give it a chance to burnin the trannies and caps


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## ruZZ.il

congrats! good to hear it all went smoothly. Mostly thanks to the MAX team in the first place! Enjoy!


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## c0nsumer

Quote:


  Originally Posted by *ruZZ.il* /img/forum/go_quote.gif 
_if they're inexpensive it would be nice to just build in the case.. I'm guessing you can expect to find a few buyers, me included. looks neat! how long does it take to switch sources? ie, for the relays to switch.. break before make? also, is there a delay between selecting a source and its activation? cause if its a momentary toggle switch to rotate between sources, it should have a bit of a delay so it'll only switch once even between say, I1 and I3.. or is it rotary toggle to hook up to J4? also.. momentary toggle needs some extra circuitry with some caps and stuff, cause 1 press can make and break quiet a few times to these fast gates.. or did you say that already?  anyway, looks like fun to put together.. and a nice project. thanks! and kudos._

 

I figure that if one is setting up the board with on-board power supply (AC to DC) and five relays for switching unbalanced stereo the part cost should be around US$30. There's nothing too expensive on there, and all the parts are very standard.

 The way it works is that when you press NEXT (or PREVIOUS, for that matter) all inputs are disconnected, a 100ms delay occurs, then the next input is connected. There is enough logic in place to be sure that holding a button only switches the input once, inputs can't be switched when the device is muted, and holding one button and pressing others (or multiples at once) doesn't bind things.

 I spent lots of time being sure that the buttons have a combination of good, responsive feeling, enough time for debouncing (70ms felt really comfortable), and enough time for the relays to switch. Changing any of these timeouts will be easy to do, as it's just a couple lines in the firmware.

 The pinout for J4 is as follows:

 I5 - I1: Anode connection for LED to indicate which input is selected. Cathode connects to common ground (G).
 PW: Anode connection for Power indication LED. Cathode connects to common ground (G).
 M: Mute switch connection, other half of switch connects to common ground (G).
 P: Previous Input switch connection, other half same as mute.
 N: Next Input switch connection, other half same as mute.
 G: Common ground.

 It can be powered from your choice of 5VDC (via the 5VDC connector) or from AC, around 5VAC to ~24VAC. If you power it from AC, 5VDC will be available from the 5V connector to power something else in the enclosure. I'm going to use this to power an Alien DAC.

 On the suggestion of a friend I may change the pinout a bit, so that each LED connection and each switch connection has its own ground pin available. This shouldn't be hard to do, and as the friend suggested it'll make wiring easier for some people, especially those who just want to connect a pair of flying wires from each switch or LED straight back to the board. I think this is a good plan, as this input switch can (obviously) be used in far more places than the MAX. I've just sized it for the MAX to make it easier for me to initially use, and give myself a target size.

 The size of the board is 160mm x 50mm and this is unlikely to change, as I've just about run out of vertical space. This should give around 15mm of space between the MAX PCB and this switch PCB when both boards are slid into a Hammond 1455T2201.


----------



## ruZZ.il

sounds solid...[size=xx-small]<removed silly stuff>[/size]..anyway, any option for an input range of 30 to 7dcv, regulate it down to 5.. depending on current draw and the heatsink used... and have a 5v output for any aux devices(ie alien).. it could just have dc in after that ac>dc chip (what chip is that? or just a rectifier, in which case dc and ac input can be the same) it would be easier to add to amps that dont ave any AC around, nor 5v. anyway, maybe I should chatter more on the diyforums thread.. maybe you should start a thread on here too.. it would be a good interest chek and you'd get some great feedback.. check up on the regulator thing too?
 ..also, if the output were between the main circuitry and the inputs, one would be able to trim the board if need be.. cutting out unnecessary inputs..(though it would suit the MAX less perfectly)


----------



## nysulli

yeah, i can't thank tom and colin enough for starting this project and posting the support site. Not to mention everyone in this thread for all the helpful hints from their trials and tribulations getting their max's running

 after 1.5 hours of breaking in, it just keeps sounding better and better, more detail, deeper bass, better extension in the highs, the most seperation i recall hearing on my HF-1's

 DB bias now up to 135mV, just going up slowly, and the sinks are still barely warm


----------



## ruZZ.il

135mV? did you do MOSFETS in the end? cause I'm not sure you really need to be biasing bjts that high.. atleast not too much higher. Also, most of the improvements that you're hearing, burn in aside, are probably the tubes warming up.. mmm.. my tubes are hot 
	

	
	
		
		

		
			





 but power down now.. 'night guys.


----------



## c0nsumer

Quote:


  Originally Posted by *ruZZ.il* /img/forum/go_quote.gif 
_sounds solid...[size=xx-small]<removed silly stuff>[/size]..anyway, any option for an input range of 30 to 7dcv, regulate it down to 5.. depending on current draw and the heatsink used... and have a 5v output for any aux devices(ie alien).. it could just have dc in after that ac>dc chip (what chip is that? or just a rectifier, in which case dc and ac input can be the same) it would be easier to add to amps that dont ave any AC around, nor 5v. anyway, maybe I should chatter more on the diyforums thread.. maybe you should start a thread on here too.. it would be a good interest chek and you'd get some great feedback.. check up on the regulator thing too?
 ..also, if the output were between the main circuitry and the inputs, one would be able to trim the board if need be.. cutting out unnecessary inputs..(though it would suit the MAX less perfectly)_

 

That's a good idea. I'll find a way to get power in before the reg nicely, I think. I hadn't thought that people might have some DC other than 5V hanging around.

 That chip is a DIP-package 1A bridge rectifier. I don't remember the part number, but it's pretty common and costs about US$0.50/each. It should be nice and easy to solder.

 I could have made this loads smaller, but I'm intentionally sticking to easy to solder through-hole parts to make assembly easy, even if it costs a little bit more.

 I may start a thread here... I've got one going on diyaudio.com already, but it's getting no response. We'll see. For now I'm thinking I'll get it where I'm happy with it, then start asking around in larger circles.

 I understand what you're saying about trimming the board to size, but I'm hesitant to do that. I like how the board is spaced now, and I don't think the 2cm savings per cut-off input will be worth it for most uses. On a side note, I originally designed this as just a three-input device using a much smaller PIC, but doing five didn't cost much more and fit the enclosure better. Having the extra IO pins spawned the ideas for a previous and mute buttons.

 I've also thought that I could do it with a PIC with a bit more IO and use all latching relays, so that there is never any power going to the coils once the relays are set (a common audiophile complaint, it seems). I'd also then do LEDs on their own separate pins (not tied to the driver) so I could do things like have them all fade in and out when the device is muted. The LEDs could be done off two pins and a shift register, and four latching relays could be driven from a single driver chip and eight IO pins.

 Then I started to think that the latching relays, PWMd LEDs, and all of that is a bit of feature creep and went back to my original idea of what you see there.


----------



## nysulli

Quote:


  Originally Posted by *ruZZ.il* /img/forum/go_quote.gif 
_135mV? did you do MOSFETS in the end? cause I'm not sure you really need to be biasing bjts that high.. atleast not too much higher. Also, most of the improvements that you're hearing, burn in aside, are probably the tubes warming up.. mmm.. my tubes are hot 
	

	
	
		
		

		
		
	


	




 but power down now.. 'night guys._

 

no, i'm using the DB's, i went with the taller heatsinks to push the buffers a bit further to see what i could get out of them, with the end goal of 220mV (100mA)


----------



## tomb

Quote:


  Originally Posted by *nysulli* /img/forum/go_quote.gif 
_no, i'm using the DB's, i went with the taller heatsinks to push the buffers a bit further to see what i could get out of them, with the end goal of 220mV (100mA)_

 

Glad to hear you've got another MAX alive. 
	

	
	
		
		

		
		
	


	




 However, you're entering into uncharted territory running >50-60ma with BJT's. They should be able to take it with the taller sink, but go cautiously. They have a positive temperature coefficient and can fall off the cliff suddenly - with little warning. One setting appears to be OK, but another 10-20ma sends it into thermal runaway.

 If it were me, I'd get it to 60ma then live with it for a few days. Try another 10ma after that. The buffers will develop considerably more heat while playing music compared to just sitting there. Operating the amp for a couple of days might be a prudent and cautious approach. Remember that you will probably have to worry about this all over again when you case it up, too.

 You might find out in the end that there was nothing at all to worry about, but just in case ...


----------



## amphead

Great news Nysulli! Another MAX lives!!!
	

	
	
		
		

		
		
	


	










 Well, I removed the mediocre panasonic su 1000uF and installed the panasonic hfs(fc) 470uF 63v 105 degrees caps in CA7L/R. Frequency response good however, not as good as 1000uF, but clarity has returned. Therefore, I have 75 ohm 1 watt dales, that are going into RB14L/R to replace the 22 ohm. Here goes.


----------



## nysulli

thats my plan as of now tomb, their sitting nicely at ~62mA, i know one or 2 other builders have pushed into this range as well, but i'll be upping the current slowly just to see if theres even an audible difference

 but after about 1.5 hours of constant music, the heatsinks are still cool enough to keep my finger on them

 but better safe then sorry, i have a spare set of transistors, but i'd rather not have to go about changing them out


----------



## pinkfloyd4ever

Quote:


  Originally Posted by *c0nsumer* /img/forum/go_quote.gif 
_In case any of you are interested, here is my first draft of the audio input switch I've been working on. It's designed to fit in a Hammond enclosure right behind a MAX and easily piggyback off of the power / feed audio to it, but it'll also be a nice stand-alone device.
 ......................
 [lots of technical jargon b/t consumer & ruzz.il that I don't understand]_

 

JEEEEZZZUSSS christ, why not just use a rotary switch??


----------



## nysulli

Quote:


  Originally Posted by *pinkfloyd4ever* /img/forum/go_quote.gif 
_JEEEEZZZUSSS christ, why not just use a rotary switch??
	

	
	
		
		

		
		
	


	








_

 

but where's the fun in doing that?


----------



## amphead

Nice studio switchbox c0nsumer!

 Well, if you want to roll components in the MAX, watch out! Remember it has a ground plane on top, that surrounds the pads that exist on the top as well. Whats the distance between pads and ground plane? Maybe a nats ass. When restoring my 22 ohm resistors at RB14, I managed to get an embedded solder bridge(not a nice one!) across pad/ground plane on the left side, which had to be fixed by cutting a trace on the bottom of the board and then a jumper to one side of RB14L. Of course there was no sound in the left side of the phones until that was fixed. Its possible that *some would never find it*, not realizing that it can even happen. 

 Moving on, so what did it sound like when I used 75 ohm resistors instead of 22 ohm? Well, the available volume was cut by 33%, with no apparent bass boost. Therefore with K701/64ohms, you have to increase the size of CA7L/R to at least 680uF and possibly 1000uF. I won't know until I find the right boutique caps. What does my rig sound like right now? It is still a killing machine, with that one last upgrade awaiting it.
	

	
	
		
		

		
		
	


	




 Edit: Laid back signature with 470uF(sounds really good/smooth) and forward signature with 1000uF(sounds very good/dynamic).


----------



## tomb

Hmm ... 1000uf at CA2 and 470uf at CA7 on two MAXes gives me _frightening_ bass with a Sony V6 (beyer pads). Those phones are 63 ohms. I wonder what size your CA2 is and whether boutique caps such as the ES just produce lower frequencies anyway. Well, in the case of the Muse ES's, that's a given - but I'm just wondering ...

 I haven't tested any Black Gates yet on the MAX (this weekend, hopefully). However, it's a fact that with a 33uf Muse ES vs a 47uf Black Gate NX HiQ in the Alien DAC, the 33uf ES reaches much lower bass - perhaps a whole octave, IMHO. 'Course, the BG's are still better with dynamics and details.

 What you found with the resistors is not surprising. Some people like a good Kiwame there, but to me the impact is noticeably reduced with even 10-22 ohms.

 EDIT: The transistors can make a difference with this, too. The 2SC3421/2SA1358 pair have noticeably deeper bass extension. The 2SC3422/2SA1359 pair go pretty deep as well (not quite as deep, though).


----------



## amphead

Right now, because I haven't ordered any boutique caps, I'm just experimenting, to nail down a few things. I paralleled another set of 470uF at CA7 to see what that does with the slightly better panasonic hfs/fc(not boutique of course) caps, and it improves in some ways, but imaging seems to suffer some. I have the mediocre panasonic su 1000uF at CA2. What I might do, is order Blackgate NX for both CA2 and CA7(1000uF 35v).Well, maybe not the NX is 25v.


----------



## tomb

Your headphones certainly deserve the investment in the Black Gates. Be attuned to whether your Jensens end up detracting from the BG's, though. BG's are apparently tricky to pair up with bypasses.


----------



## tomb

Amphead,

 I did some further research and found an interesting bit of info on DIYHiFi.org. As a matter of fact, this statement came from their Moderator of the "Passive Parts" section:

  Quote:


 _Have in mind that if you use polar caps, you need to use higher capacitance, to minimize distortion at low frequencies. 
 You had what, an 100uF Panasonic FC? That makes sense. 
 With bipolar caps you can use much lower capacitance. _ 
 

That would explain the differences in my experience vs. yours. Apparently, bipolar caps such as the Muse ES (or Black Gate NX) offer more bass per capacitance. So, my 470uF ES for CA7 may equate to your 1000uf "normal" cap, or at least to a 680uf normal cap, perhaps.


----------



## ruZZ.il

great tom, now I want to build speakers and their amps too. I need a job  
 oh.. and time ;( well, never mind then.. I'll just contently build H.P amps for the next few years


----------



## tomb

Quote:


  Originally Posted by *ruZZ.il* /img/forum/go_quote.gif 
_great tom, now I want to build speakers and their amps too. I need a job  
 oh.. and time ;( well, never mind then.. I'll just contently build H.P amps for the next few years 
	

	
	
		
		

		
		
	


	





_

 

Oh? Maybe you'd be interested in this latest from Pete Millett:





Low Voltage Hybrid Amplifier with Adjustable Damping
 It even looks like a Millett. 
	

	
	
		
		

		
		
	


	







 Edit: Nate posted this first - I think in this thread ... somewhere ...


----------



## adfinni

[size=large]FUN FUN FUN[/size]


----------



## c0nsumer

Quote:


  Originally Posted by *nysulli* /img/forum/go_quote.gif 
_but where's the fun in doing that?_

 

Rotary switches also require lots of flying wires, take up a bunch of front panel space (or rear, with a long rod) and are more prone to corrosion. It's also not as elegant. Not to mention the difficulties in finding a nice rotary switch which will do enough poles on enough inputs with the number of positions you want, in a break-before-make version, with the shaft you like, etc.

 This board, assembled, should cost not-much-more than a comparable rotary switch and is a good bit more flexible. It also only took me about two days of spare-time work for the software, and three for the board.

 -Steve


----------



## ruZZ.il

<scribbles his name up on the interested wall>..


 hey adfinni, welcome back 
	

	
	
		
		

		
		
	


	




 looks like.. fun I still have mine stuck on my window! I used a long strip of tape, marked up a scale in the range, and placed each transistor on the scale.. helped cause I could easily see where they bunched up. I need to put them in a little box already, they're slowly falling onto my floor (I had nowhere else to stick the strip) anyway.. find a little box man, and send me your P.Pal @


----------



## amphead

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Amphead,

 I did some further research and found an interesting bit of info on DIYHiFi.org. As a matter of fact, this statement came from their Moderator of the "Passive Parts" section:

 That would explain the differences in my experience vs. yours. Apparently, bipolar caps such as the Muse ES (or Black Gate NX) offer more bass per capacitance. So, my 470uF ES for CA7 may equate to your 1000uf "normal" cap, or at least to a 680uf normal cap, perhaps._

 

Thanks for the heads up! I really need to have 1000uF with at least 35v at CA7 positions, but possibly with bipolar I could go 680uF there. The K701s seem to resist changes in signature compared to other phones IMHO.
	

	
	
		
		

		
		
	


	




 Edit: running wire to the top of the board to parallel the 2nd set of 470uF at CA7, increased bass response, with a small amount of veil on vocals, and pronounced midrange on electric guitars. I am going to parallel another set of 470uF at CA7, for 3x470uF there. Smoke em, if you got em. 
 I know its probably crazy, he he. Be right back.


----------



## amphead

Ok, so what is the verdict with 3x470uF = (1410uF of course) at CA7. Slam, bass extension, clarity on vocals. Dynamic presentation, no veil, no distortion, musical! Remember this is with K701s. I would gladly ship TomB the whole kit and kaboodle to verify what I am saying, if I could stand to be without for a couple of weeks. he he  Now to get it tidy looking with 6 capacitors at CA7L/R. I can just barely do it(think Houdini). My DBs are currently underbiased at 80mv L/R and I will try keeping them there because I think the temp is quite warm on the power supply sink. Couldn't believe that I would like this configuration, but there it is. I should ship TomB my rig for verification, because it really is hard to believe.


----------



## tomb

Aw gee - you're making me feel like I don't believe you - I do. It's just that I'm worried about everyone going out and putting 6 electrolytics on the output of their MAX. For your MAX and your phones, I have no doubt that you've discovered what works best for you. 
	

	
	
		
		

		
		
	


	




 As noted awhile back, there are some strange things going on with the MAX that defie rote equations. The CA2 cap sizing in particular, does not follow the standard prescription.


----------



## amphead

Well, I think I'm probably within striking range of what my rig might sound like with boutiques, or I could be wrong of course. Looks like I will keep this configuration and order up boutiques for my second Max, and then see what the real situation is. Nothing to lose doing things that way. I have to agree that I consider this a strange situation with the Max and K701s. Like you said in your earlier post, polarized caps might need a larger value to remove bass distortion. Note, I think you believe me Tom, I'm the one who can't believe it, and still can't.  If you have an experimental Max to try these out, I'll ship you six of these (panasonic hfs 470uF), pro bono. However, we are talking about them being used with K701s, so the impedance of your phones might not work well with them. Or the boutiques that you are using might make them irrelevant, who knows. Well, I should send them anyway, let me know Edit: I still have the garbage panasonic su 1000uF at CA2, so I have to double/triple up there with 470uF hfs(yes, they will fit yikes!) I certainly don't recommend that anyone follow me down this path of insanity, its just to see if it can be done with good results!


----------



## amphead

Nevermind, they(panasonic 3x470uF hfs) are not so good when listening to other cds that I had not tested them on. Its a slight phase distortion and some lack of imaging combined. Back to the boutique cap search. Tally ho! Edit: snipped the wires creating the 3x470uF bringing it back to 470uF at CA7 and imaging/clarity returned. he he enough to drive me insane.


----------



## thunder

This is what I had thought of doing when posting #1424. I did not get a good response to my question ! I lack the knowledge to understand what is going on, but I got the idea trying to find a solution for 1000 uf worth of boutique caps for the C7 position. I didn't wont to spend the money on BG NX cap's and end up with 680uf @ $30.00 later ! Please keep us up to date on the result's especially because your using 701's. I have been saving for some time for a new set of HP's ! I love "AKG" Mine are the 240 Sextett 600 ohm and still sound good ! This is some of the best new's I've heard in some time. Thank's: eggo: Amphead did not catch your edit, back to square 1 again. Never the less I really enjoy reading about various result's. My 240's are 20 yrs old by x-mas I hope to be using 601 or 701's. Trying to build a amp for both is no easy task !


----------



## amphead

Quote:


  Originally Posted by *thunder* /img/forum/go_quote.gif 
_This is what I had thought of doing when posting #1424. I did not get a good response to my question ! I lack the knowledge to understand what is going on, but I got the idea trying to find a solution for 1000 uf worth of boutique caps for the C7 position. I didn't wont to spend the money on BG NX cap's and end up with 680uf @ $30.00 later ! Please keep us up to date on the result's especially because your using 701's. I have been saving for some time for a new set of HP's ! I love "AKG" Mine are the 240 Sextett 600 ohm and still sound good ! This is some of the best new's I've heard in some time. Thank's
	

	
	
		
		

		
		
	


	


_

 

Sorry Thunder, apparently theres no free lunch when it comes to getting the best sound. I am going to have to order boutique $$$ caps to get the sound where I want it.


----------



## thunder

Amphead, I understand the lunch thing ! Actually I believe perseverance will truly bring the best result's. For what its worth, what direction would you go if currently using hi imp HP's later probably ending up with something between 60-120 ohm range ? I wrote santa a letter asking for a crystal ball, but got no reply ! Once again Thank's for listening


----------



## tomb

I thought this excerpt from one of Dsavitsk's links was worth repeating (link at bottom):

  Quote:


 _[size=x-small]The real problem is the reliability. According to Jensen website, these oil caps only have a measly 250 hour life at maximum temperature of 85°C. You may jump in with, “since the actual temperature inside a chassis is much lower than this, the life must be exponentially prolonged”. Such is not the experience for several manufacturers using Jensen. I’m withholding their names here because I don’t want them to be swamped with inquires about the Jensen reliability questions. If you are really interested in the horror experience of these poor manufacturers, just Google or a blog search at audioasylum.com and so on. Therefore, if you want to use Jensen, please make sure your chassis is cool inside, and inspect your Jensen visually at least quarterly, after one year. If you see deformation, discoloration, or oil creep, you should replace them immediately.[/size]_ 
 

The MAX stays pretty hot inside the case. The back positions are irradiated with heat from the PS and the tubes, the front from the line of four output trannie heat sinks. So, please be vigilant if you are using Jensens (Amphead?) If I had known this before, I probably would've put out a warning like I did for Jupiters.

 We've discounted some of this guy's reviews where the quote came from, but nevertheless - he could be right on this one.
http://www.vhaudio.com/21capacitorshootout.pdf


----------



## c0nsumer

By the way, I emailed Colin about this, but I'm wondering if someone here can answer me quicker:

 Do any of you know which board house / company was used to make the MAX PCBs? I want to get my audio input switches done somewhere reliable, but hopefully cheaper than my old-standby for commercial work, Advanced Circuits. So I'm looking for some other place...

 Worst case I'll just fall back to using pcbex.com, who contracts boards out to China. They are cheap and of good quality, but I don't trust them for RoHS compliance.

 Thanks!


----------



## tomb

PCBNet


----------



## c0nsumer

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_PCBNet_

 

Thanks very much... From an initial glance their prices look great. I just have to wait until I get the parts from Mouser so I can validate the power supply and driver implementation, then I'll order the first run of boards.


----------



## amphead

Tom, yeah thanks, I saw that article about Jensens after I had already installed them. Keeping a close eye on that situation. I was able to get some Panasonic FC 680uF, so all locations that currently have 470uF hfs will get these for a trial period.

 Thunder, I believe that with high impedance phones, that you don't neccessarily need more than 470uF in CA7, but you should have 1000uF at CA2. I have low impedance phones, with less bass in the frequency curve, therefore its neccessary for me to use a larger cap in CA7. But just as important is that it has lower ESR(equivalent series resistance) or sound will suffer.


----------



## nysulli

just an update on running high bias with the DB's

 currently biased at 166mV without any issues, bear in mind i opted to use the 1.5" tall heatsinks

 also just wondering what everyones favorite tube is?

 personally I've only had the chance to extensively listen to the FK6, but in burning in a new pair of dumont AE6A's i've found them to be a little thin sounding, definitly prefer the FK6's at this point, but i'll give the AE6A's another day or 2 before moving on to the FM6's

 btw, this is with HF-1's, so i'm not surprised that the FK6 is my tube of choice so far


----------



## fordgtlover

Was there any consensus (or at least a general view) on the use of 1000uf in CA7 compared to the standard 470uf?

 Cheers


----------



## tomb

Quote:


  Originally Posted by *steinchen* 
_300R 1000uF -> 0.5Hz
 300R 470uF -> 1.1Hz
 300R 220uF -> 2.5Hz
 300R 100uF -> 5.3Hz

 120R 1000uF -> 1.3Hz
 120R 470uF -> 2.8Hz
 120R 220uF -> 6.0Hz
 120R 100uF -> 13.3Hz

 75R 1000uF -> 2.1Hz
 75R 470uF -> 4.5Hz
 75R 220uF -> 9.6Hz
 75R 100uF -> 21.2Hz

 32R 1000uF -> 5.0Hz
 32R 470uF -> 10.6Hz
 32R 220uF -> 22.6Hz
 32R 100uF -> 49.7Hz_

 

 Quote:


  Originally Posted by *steinchen* 
_please note that at the corner frequency the signal already drops 3dB. To get a linear bass response down to 20Hz without roll off you want the corner frequency (-3dB) to be at 10Hz or below.

 Therefore the recommended minimum capacitances are:
 300R -> 100uF
 120R -> 150uF
 75R -> 220uF
 32R -> 470uF

*A 470uF cap is a good choice in any case. It suits every headphone, fits the pcb and is easily available in any line of caps.*_

 

That is the original recommendation for C7 on the Millett Hybrid from Steinchen back in 2005. Some of the previous posts are dealing with some rather non-standard caps that could be confusing things. There is nothing going on with the MAX that has changed the above recommendation (*for CA7*).


----------



## fordgtlover

cheers tomb


----------



## fordgtlover

I have finished my board, but I can't bias the mosfets.

 Power is 27V. Both tubes are around 13.5V (but moving around a little). The mosfets are sitting at 0mV. I started with the RB12 trimmers set to full clockwise on power up as previously suggested. With the DMM probes in TA2L & TB1L and winding the pot anti-clockwise - nothing. Both channels are the same.

 I've checked for solder bridges, and incorrect part positioning - but nothing obvious to my eyes.

 Any thoughts?



 BTW - I had the 1A fast blow fuse installed; it fried in a micro-second. I installed a 500mA slow blow fuse and it's fine.


----------



## amphead

Fordgtlover, are you able to read a schematic? If so, I would take a look at various components on the schematic, to find where to take measurements. You would confirm where voltage exists as expected and where it drops out, that should identify the problem. I hope you didn't smoke any transistors on power up. You would normally smell burnt plastic if you want to do the sniff check, but the DMM(digital multimeter) is your friend.


----------



## tomb

Quote:


  Originally Posted by *fordgtlover* /img/forum/go_quote.gif 
_I have finished my board, but I can't bias the mosfets.

 Power is 27V. Both tubes are around 13.5V (but moving around a little). The mosfets are sitting at 0mV. I started with the RB12 trimmers set to full clockwise on power up as previously suggested. With the DMM probes in TA2L & TB1L and winding the pot anti-clockwise - nothing. Both channels are the same.

 I've checked for solder bridges, and incorrect part positioning - but nothing obvious to my eyes.

 Any thoughts?_

 

We need some good pics of your Diamond Buffers. There is no explanation for this except that you have some sort of part mixup.


----------



## amphead

Well, now to replace some 470uF hfs with 680uF FC. btw,ruZZ.il and crew(everyone else),I just got back from the Jethro Tull concert. It was very good, and was sold out. Ian Anderson signed my strat! It says "Hello! Ian Anderson Tull.". I had to wait in the dark and cold for 30 minutes near his tour bus, after being told by a roadie, "no autographs". Ian Anderson then swaggered over and signed it! Cor Blimey!


----------



## grawk

Colin's apparently bringing some extra boards with him to today's DC meet, in addition to an assembled amp, and his HPDAC, which is a usb dac integrated with a mini3.


----------



## fordgtlover

Here are some photos of my problem build.
http://img229.imageshack.us/img229/9074/pict2433yq5.jpg
http://img401.imageshack.us/img401/1724/pict2428pj1.jpg
http://img211.imageshack.us/img211/8322/pict2429fs4.jpg
http://img50.imageshack.us/img50/3131/pict2439km6.jpg
http://img213.imageshack.us/img213/1220/pict2441gs6.jpg

 I can confirm that there are no strange smells (I toasted an op-amp last week and there are none of those smells). The heatsinks on the mosfets are stone cold.


----------



## Ferrari

Post deletted!


----------



## tomb

Quote:


  Originally Posted by *grawk* /img/forum/go_quote.gif 
_Colin's apparently bringing some extra boards with him to today's DC meet, in addition to an assembled amp, and his HPDAC, which is a usb dac integrated with a mini3._

 

Grawk,
 You and Colin got PM.


----------



## tomb

Quote:


  Originally Posted by *fordgtlover* /img/forum/go_quote.gif 
_Here are some photos of my problem build.
http://img229.imageshack.us/img229/9074/pict2433yq5.jpg
http://img401.imageshack.us/img401/1724/pict2428pj1.jpg
http://img211.imageshack.us/img211/8322/pict2429fs4.jpg
http://img50.imageshack.us/img50/3131/pict2439km6.jpg
http://img213.imageshack.us/img213/1220/pict2441gs6.jpg

 I can confirm that there are no strange smells (I toasted an op-amp last week and there are none of those smells). The heatsinks on the mosfets are stone cold._

 

I've got to leave for awhile. I'll study these in detail when I get back. Unfortunately, first glance doesn't reveal anything obvious.


----------



## ruZZ.il

Quote:


  Originally Posted by *fordgtlover* /img/forum/go_quote.gif 
_.. nothing. Both channels are the same...._

 

Both channels behaving the same makes me also think it could be in part selection or something.. a solder bridge or freak dysfunctional part isn't likely to lead to much symmetry. anyway.. just to get the obvious out the way, is your dmm on its lowest Vdc setting?.. also, do the sinks even get warm?


----------



## tomb

Fordgtlover,

 RB1-L/R must be jumpered out on the MOSFET version. That's the resistors you have with the black band in the middle - in between the trimmers and little transistors. Take those out and solder a wire lead in their place and see if that makes a difference.


----------



## pabbi1

Braindead response of the day - since I am wiring balanced and single to Neutrik combo jacks, what all _can_ I utilize on the outs? What would be my best path, as I need two distinct lines out for each oG, oR, and oL? Is this as simple as using both sides of the panel jack connector holes? Is it also GRL front to back?


----------



## Ferrari

Quote:


  Originally Posted by *pabbi1* /img/forum/go_quote.gif 
_Braindead response of the day - since I am wiring balanced and single to Neutrik combo jacks, what all _can_ I utilize on the outs? What would be my best path, as I need two distinct lines out for each oG, oR, and oL? Is this as simple as using both sides of the panel jack connector holes? Is it also GRL front to back?_

 

Assuming you are using 2 Neutrik NCJ6FI-S combo jacks, each containing a 3-pin female XLR and one 1/4" stereo phone jack.

 It's sufficient to connect the 1/4" stereo phone jack part of the Neutrik NCJ6FI-S to the right side (viewing from front) of the panel jack connector holes on the first MH Max board. Do the same with the second NCJ6FI-S combo jacks and the second MH Max board. It's indeed G-R-L from front to back.


----------



## pabbi1

Thanks... but, since I am using the combo for both 1/4" single AND balanced, can I use both sidesz, OR use the right side of the panel mount and the connections to the left? Ideally, I'd use the panel mount right for either single or balanced, THEN left for the other. This would give me either channel for 1/4 out, and both, of course, for balanced.


----------



## Ferrari

I know that you are using the combo for both 1/4" single ended output AND balanced output.

 What I described earlier is applied for what you call _"ideally"... _use the panel mount right for either single or balanced, and use panel mount left the same way of course. Each channel serves as 1/4 output and/or balanced output.


----------



## Fitz

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Fordgtlover,

 RB1-L/R must be jumpered out on the MOSFET version. That's the resistors you have with the black band in the middle - in between the trimmers and little transistors. Take those out and solder a wire lead in their place and see if that makes a difference. 
	

	
	
		
		

		
		
	


	


_

 

Those "resistors" with a single black band in the middle *are* wire jumpers.


----------



## pabbi1

Quote:


  Originally Posted by *Ferrari* /img/forum/go_quote.gif 
_I know that you are using the combo for both 1/4" single ended output AND balanced output.

 What I described earlier is applied for what you call "ideally"... use the panel mount right for either single or balanced, and use panel mount left the same way of course. Each channel serves as 1/4 output and/or balanced output._

 

Thanks, and sorry I seemed harsh - I just want to make sure that both sides of the panel mount out are hot individually, and that the signal is not impacted by only using one side or the other depending on single or balanced. Otherwise. I'd just run two wires from each of the screw terminal outs.


----------



## Ferrari

Quote:


  Originally Posted by *pabbi1* /img/forum/go_quote.gif 
_... I'd just run two wires from each of the screw terminal outs._

 

You can do that but don't forget to connect the screw terminal output pins to the _right_ side of the headphone connector holes on the MH Max board (viewing from top/front). The screw terminal output pins are not directly connected to the output relay ( = output of the amp). Take a look at the board layout and you will see how to connect 
	

	
	
		
		

		
		
	


	




 .


----------



## pabbi1

That was my original curiosity, as the left side of the panel mount looks to have no signal, correct?

 Someday, I will learn to phrase my real questions better.


----------



## tomb

Quote:


  Originally Posted by *Fitz* /img/forum/go_quote.gif 
_Those "resistors" with a single black band in the middle *are* wire jumpers. 
	

	
	
		
		

		
		
	


	


_

 

I don't get it Fitz - somebody makes brown sausage resistors with black bands and zero resistance?

 EDIT: Oops. OK - so they do. Back to studying fordgtlover's pics, then.


----------



## Ferrari

With a 1/4" stereo phone jack mounted: yes. But without a 1/4" stereo phone jack mounted : no. 
 The left side of the headphone connector holes is not connected to the right side => not connected to the output relay => no output signal.


----------



## amphead

Hmmm......Well, I installed the panasonic fc 680uF at CA7. What was my conclusion? Bass improves, but I really can't deal with the veil that it brings to the higher frequencies. I have to get it all, rich bass, prominent mids and crystal clear highs. I might use the fc in other positions, but as an output coupling capacitor, they truly suck! 
	

	
	
		
		

		
			








 Edit: Rolling capacitors, over and over again will make the traces/pads lift from the board at those locations, which I am able to bridge with a larger bead of solder, but don't do it unless you have to. Just put the right capacitor in that position the very first time!


----------



## Ferrari

I'm not going to tell anything new: *use quality caps with sufficient capacity at the output.*
 Forget about focusing on the quantity (the more µF, the better 
	

	
	
		
		

		
		
	


	




 ????) of some low grade, with hopeless non-lineair characteristics of some vague electrolytics.


----------



## tomb

Fordgtlover - some guesses:

 1. Bad MOSFETs
 2. Check the signal transistors - these can result in total failure of the DB's if they are messed up - do you have 2n5087 for QB2L and QB2R? And is a 2n5088 in QB3L and QB4R?
 3. Might as well check the other ones two. One way I keep track is Odd-Even and Even-Odd. It's a silly little bit of logic, but 5087 is Odd - it goes only in the Even spots - QB2, QB4, QB6. 5088 is Even - it goes only in the Odd spots - QB3, QB5, QB7. Then QB1 is the JFET (2N5486).
 4. Wrong JFET - did you use 2N5486?
 5. The trimmers are the wrong value - should be 1K

 Except for getting tripped up on the zero resistors, I can't see anything amiss.


----------



## amphead

Quote:


  Originally Posted by *Ferrari* /img/forum/go_quote.gif 
_I'm not going to tell anything new: *use quality caps with sufficient capacity at the output.*
 Forget about focusing on the quantity (the more µF, the better 
	

	
	
		
		

		
		
	


	




 ????) of some low grade, with hopeless non-lineair characteristics of some vague electrolytics._

 

Couldn't agree with you more Ferrari! I like to prove the need for the cost of a component before taking the plunge with the $$$$$ cash. In this case , where I have cleary described what happens with capacitors of dubious quality, It saves some other builders from wasting their time, so it wasn't a total loss. 
	

	
	
		
		

		
		
	


	




 Edit: Another point to consider, is that when you think that there has been an improvement in sound, based on personal expectations for a component, you will often be fooled for awhile. But long lasting listening enjoyment only occurs when the improvement in sound is real.


----------



## fordgtlover

Quote:


  Originally Posted by *ruZZ.il* /img/forum/go_quote.gif 
_Both channels behaving the same makes me also think it could be in part selection or something.. a solder bridge or freak dysfunctional part isn't likely to lead to much symmetry. anyway.. just to get the obvious out the way, is your dmm on its lowest Vdc setting?.. also, do the sinks even get warm?_

 

I have tried the DMM on Vdc auto range setting and on the mV setting - no difference in reading. The heatsink on the LM317 gets warm, but the mosfet sinks are stone cold.

 cheers


----------



## fordgtlover

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_I don't get it Fitz - somebody makes brown sausage resistors with black bands and zero resistance?

 EDIT: Oops. OK - so they do. Back to studying fordgtlover's pics, then. 
	

	
	
		
		

		
		
	


	


_

 

They are Vishay Zero Ohm resistors from Mouser (PN: 71-FRJ-55-0 )


----------



## fordgtlover

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Fordgtlover - some guesses:_

 

 Quote:


 1. Bad MOSFETs 
 

I got them from AMB and only took them out of their packaging to mount them. While I don't know if this is the cause yet, would it require a failure on all four or just one on each channel to cause this?

  Quote:


 2. Check the signal transistors - these can result in total failure of the DB's if they are messed up - do you have 2n5087 for QB2L and QB2R? And is a 2n5088 in QB3L and QB4R? 
 

I was pretty careful with these as I installed them, but I'll double check them all as best I can.

  Quote:


 3. Might as well check the other ones two. One way I keep track is Odd-Even and Even-Odd. It's a silly little bit of logic, but 5087 is Odd - it goes only in the Even spots - QB2, QB4, QB6. 5088 is Even - it goes only in the Odd spots - QB3, QB5, QB7. Then QB1 is the JFET (2N5486). 
 

As for 2 above, I will go back through them and check them all again. I had the signal transistors all separated in the correct quantities after matching and didn't have any left over after installing them.

  Quote:


 4. Wrong JFET - did you use 2N5486? 
 

I ordered the 2N5486 and checked it off as I installed it, but I will check it again.

  Quote:


 5. The trimmers are the wrong value - should be 1K 
 

Triple checked. I can confirm that the RB12 trimmers are 1K. As I wind them anti-clockwise the voltage through RB13 changes (can't remember if it increased or decreased).

 Thanks for the suggestions. I'll go back through it all again today.

 What voltages should I expect to see at QB8 and QB9?


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## fordgtlover

I have been checking the parts as best I could. Out of desperation I swapped the tubes for a second set I have. The left channel is now working. I have been able to bias it up to 88mV - no problems. 

 I will continue to work on the right channel.


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## amphead

Wow, thats not what I would have guessed. But, as you said, there was a big change. Remember one channel should mirror the other, so take readings in different positions on the left channel(not just the testpoints of course) and on the corresponding point in the right channel see what it reads. Just put the negative lead of the DMM on a ground test point and poke around with the positive lead carefully, comparing sides. I hope you find it!


----------



## fordgtlover

Thanks amphead.

 In some vain hope that the new tube had somehow "influenced" the channel to work (yes I know this is silly), I swapped the tubes. The left continues to work, but the right still doesn't.

 I have been doing exactly what amphead has suggested, now that I have the left channel as a reference. The voltage to RB8, RB9, RB10 & RB11 are all in the same ballpark left and right. That suggests the CCS is OK. I can see voltages change when I work the RB12R trimmer. This brings it down to the mosfets. 

 I'll go and reflow the mosfets and keep working my way through.

 Thanks for all the help.


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## grawk

So I listened to Colin's Max today at the DC meet. Remarkable what can be done with those cheap little tubes. Great job everyone who worked together on that design, it sounds great. If I could possibly justify another amp, this would be on my short list.


----------



## amphead

Grawk, Yeah, its worth the build. If you purchase a board from Colin and don't need it, I would take it. I need to build the mosfet version, now that I have the bjt working.


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## fordgtlover

It's alive!!!!!


 After reflowing the mosfets I still couldn't see any changes to the measurements at the test points while adjusting the RB12R trimmer. I was measuring the voltages at the mosfets and found that the voltages on each of the pins on the right channel were in the same ballpark as the ones in the working left channel. So, I decided to bias pin 1 of the IRF9Z34N mosfet against ground. I then went back to the test points and sure enough I had a reading and it was about right.

 I have biased both sets of mosfets to 180mV and it all looks stable. I'll let it run for a while, fine tune the biases, then connect up the RCA jacks and have a listen.

 Thanks to all for your help.


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## fordgtlover

At the risk of being a post whore I will make this brief.

 Given how difficult it is to check that the correct transistors are in the correct place after everythng has been installed, and that when the build doesn't work first time the need to confirm placement. In the future I will get some different colour paint markers and put a little dot of a different colour on the top of each type. That way I will be able to see the placement of each type from the top rather than trying to look between parts. Quick and easy.

 I am now moving onto the B22. I'll try this out.


----------



## tomb

Quote:


  Originally Posted by *fordgtlover* /img/forum/go_quote.gif 
_At the risk of being a post whore I will make this brief.

 Given how difficult it is to check that the correct transistors are in the correct place after everythng has been installed, and that when the build doesn't work first time the need to confirm placement. In the future I will get some different colour paint markers and put a little dot of a different colour on the top of each type. That way I will be able to see the placement of each type from the top rather than trying to look between parts. Quick and easy.

 I am now moving onto the B22. I'll try this out._

 

I'm confused (besides sleepy). So what was the problem in the end?


----------



## fordgtlover

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_... So what was the problem in the end?_

 

I'm not really sure what the problem ended up being. I didn't actually fix anything as such.

 All I can think is that it was taking more turns of the trimmers than I was giving before I could get a reading from the test points.



 The other comments about marking the tops of the transistors would have allowed me to skip over (triple) checking these and fast-tracked the result.


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## amphead

Congrats fordgtlover! Another MAX lives!!!! 
	

	
	
		
		

		
			











 Aaah, so the trimmers were just so far off that you didn't read any voltage. Thats interesting and because you didn't listen for sound, you didn't realize that it was actually probably working. Edit: or maybe the solder reflow fixed it, but probably not.


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## amphead

Well, at the risk of going absolutely insane, I have to say that reinstalling 470uF panasonic hfs caps at CA7. Removing 470uF caps at CA4 and CA5, then replacing those with panasonic fc 680uF has produced a rich bass, slightly recessed mids, and articulate highs. Its nicely musical and sounded good on a variety of CDs. Will I like the way it sounds tommorrow? I think I will, but its better to give it a couple of days to see if I'm being fooled once again.  Edit: Does it sound as good as yours Ferrari? Of course not, but pretty damn good!


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## pabbi1

Well, it lives not... 28v in, tubes <14v for now, but 0mv both across TA(r&l) to either TB1 or TB2... and 0mv between TB1 and TB2.

 How ugly is this most likely? Same result across 2 boards.


----------



## tomb

Quote:


  Originally Posted by *pabbi1* /img/forum/go_quote.gif 
_Well, it lives not... 28v in, tubes <14v for now, but 0mv both across TA(r&l) to either TB1 or TB2... and 0mv between TB1 and TB2.

 How ugly is this most likely? Same result across 2 boards._

 

Not ugly. 
	

	
	
		
		

		
		
	


	




 We just lived through this with fordgtlover. Are you running MOSFETs or BJT's in the output stage? If you are sure that the small transistors are correct and that you've jumpered out and populated the proper positions depending on MOSFETs vs. BJT's, then perhaps you simply haven't turned out the trimmers far enough. Because of the dual-purpose circuit, there is not complete adjustment throughout the travel of the trimmer.

 If you haven't gotten out 25 turns, there may be some adjustment travel left. At least - that seems to be what happened with fordgtlover and his MOSFETs.


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## pabbi1

Oy... power transistors inverted... more tomorrow. Bonehead of the year.

 RTFM.


----------



## tomb

Quote:


  Originally Posted by *pabbi1* /img/forum/go_quote.gif 
_Oy... power transistors inverted... more tomorrow. Bonehead of the year.

 RTFM._

 

Not bonehead - especially with the power transistors. Depending on which BJT pairs you got, they could be mounted on either side of the heat sinks. It can be easy to lose track. One thing is constant, though - whichever complementary pair is used, they are all on the same side of the sinks. Here's the legend from the MAX website:






 I had a list prepared, but I got distracted before you figured it out on your own:
 [size=xx-small]_1. Check to make sure the transistors are in the correct positions.
 2. Which BJT's did you use? Most should be mounted on the right side of the heat sink (all positions are the same) when looking from the front of the board.
 3. In particular, make sure that the signal transistors, QB2 and QB3 are correctly oriented and are the right parts.
 3. Make sure you jumpered the RB8-L/R and RB9-L/R positions. These are not populated for BJT's, but they must be jumpered.
 4. If you are able to actually bias the tubes, then that pretty much means voltage and signal is getting to the DB's._[/size]
 Number 1 and 2 just about covers it.
	

	
	
		
		

		
		
	


	




 Stick those things in an HFE meter to see if they got fried from being reversed. Most should read ~240.


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## joneeboi

Question about gain:

 Using SR60s and occasionally E4s, I would like to reduce the gain to maybe around 4 or 5. Tubes are FKs and RB14L/R are the BOM 22ohm V-Ds. I want to replace the V-Ds with some Kiwames just for fun. What value should I get for the typical Grado gain level, which I'm thinking is around 4, and where should I buy them from? DIYhifisupply has the minimum 10 resistors, $17 for really 2 resistors. I'm okay with paying it, it's just I don't really have any need for the other resistors.


----------



## tomb

Quote:


  Originally Posted by *joneeboi* /img/forum/go_quote.gif 
_Question about gain:

 Using SR60s and occasionally E4s, I would like to reduce the gain to maybe around 4 or 5. Tubes are FKs and RB14L/R are the BOM 22ohm V-Ds. I want to replace the V-Ds with some Kiwames just for fun. What value should I get for the typical Grado gain level, which I'm thinking is around 4, and where should I buy them from? DIYhifisupply has the minimum 10 resistors, $17 for really 2 resistors. I'm okay with paying it, it's just I don't really have any need for the other resistors._

 

PartsConnexion carries the Kiwames in your country. I don't know if the price will be any better, though - those things are expensive. A cheaper alternative are the Stackpoles you can find at Handmade Electronics. I've used them on SOHA's and they're definitely better than the Vishay-Dales.

 **People, please don't misinterpret this - this is a special case for the output resistors just prior to the headphone connection - these are historically boutique resistor positions.**

 With Grados, I'm afraid you'll have to go 50ohms before you can tell a difference, but that's just a guess. If you have the extras, you might try putting in some cheap resistors at various sizes - 50 ohms, 75 ohms, 100, 120, etc. It'll sound like cr*p, but it should give you an accurate measure of which value will give you the gain you want - then you can go buy the right value of those expensive Kiwames that sound so sweet.


----------



## joneeboi

Is there some sort of equation you're consulting that I can get in on here, Tom?


----------



## tomb

Quote:


  Originally Posted by *joneeboi* /img/forum/go_quote.gif 
_Is there some sort of equation you're consulting that I can get in on here, Tom?_

 

Nope. Gain is fixed in the tube. There's nothing you can do once you're using the lowest gain tubes - 12FK6's - except attenuate the signal at the output with resistors.

 As I said, it was a guess based on experience - but it's not too hard to figure out. What you're doing is adding resistance to the impedance of the phones. So if you have 32 ohm Grados and you add 30 ohms, you've turned them into the same impedance as Sony V6's.

 Attenuation is the correct term, too - it will attenuate everything - including impact and detail. However, with Kiwame's or similar, you will lose less of that and gain some sweetness. The MAX will pair greatly with Grados - regardless - but using IEMs is pushing it, IMHO.


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## joneeboi

The reason I ask is because I'm already using my bro's Ety P-to-S cable and the knob (lowest setting is at 12:00) sits around 2:30. Somehow I feel this should not be, and I've already go 22ohms at RB14. Anything else I can do besides the Kiwames?


----------



## tomb

Quote:


  Originally Posted by *joneeboi* /img/forum/go_quote.gif 
_The reason I ask is because I'm already using my bro's Ety P-to-S cable and the knob (lowest setting is at 12:00) sits around 2:30. Somehow I feel this should not be, and I've already go 22ohms at RB14. Anything else I can do besides the Kiwames?_

 

 Quote:


  Originally Posted by *tomb* 
_There's nothing you can do once you're using the lowest gain tubes - 12FK6's - except attenuate the signal at the output with resistors._


----------



## joneeboi

Makes enough sense. Thanks for the help.


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## amphead

Earlier I installed 680uF caps in CA4/CA5, which had replaced 470uF there. This configuration provided less detail/presence in vocals. Installed 470uF into CA4 and left 680uF in CA5. Vocal definition/presence returned. So this is the best compromise so far. To get extended bass, I have to compromise on vocals, which for me is less enjoyable. Back to analyzing.


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## joneeboi

I spent a bit of time cleaning up my MAX today. Nothing special but it'll stay this way for the most part until I order the Kiwames.

















 Changes to note:
 - Reversed RA1 tube trimpots
 - Tombstoned the Solens
 - Added orange tube lights
 - Revised switch and DC jack wiring
 - Jumpered RB14s
 - Replaced jumpered R1 with 1/2W 10ohm
 - Secured pot's ground wire

 SR60 without the Ety 75ohm adapter into output gives me about 12:00 to 1:00 volume range on my Sony CE235. Maybe I should switch to a 100K Alps Blue or Black Beauty instead of splurging on the Kiwames. Is there something I did wrong? With the FKs and 50K Alps blue, I can't imagine everyone having this small of a volume range on Grados if they and the MAX are supposed to pair well together.


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## amphead

Nice work Joneeboi! I can't say, not having tried FK6 in the Max, but my gut feeling is money well spent, is going to be in something with higher gain. The 12ae6 or the fm6 might be available at thetubestore.com in Ontario. You should be getting raucous volume out of the Max at full volume.


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## tomb

Amphead, Joneeboi is looking for less gain, not more.

 I can't say I've ever had an amp that I could turn the volume more than about halfway - the 12 o'clock position - as you describe. Most of the time it's around 9 o'clock, but that's because I default to 12AE6's most of the time and with KSC75's. With Senns, 10 to 11 o'clock is normal listening. If memory serves, 12FK6's gives you another 2-3 hours on the volume dial, so to speak - like 10 o'clock with KSC75's and maybe 2 o'clock with Senns.

 I sold my only Grados, but they were usually higher on the volume knob than the KSC75's, due to lower sensitivity. I have a pair of PIMETAs that I down-tuned to gains of 5, and they correspond to about 12 o'clock for medium-loud listening with KSC75's. They have 10K pots.

 Don't know if that helps you much, but I think this is a reasonable reference. Admittedly, I personally prefer sort of a hair-trigger volume control rather than attenuating the signal with output resistors. Maybe I've just gotten used to it - the SOHA is about twice as bad as any of these references - never getting past 9 o'clock even with Senns. 
	

	
	
		
		

		
		
	


	




 Some of the most prominent builders of Milletts use the Kiwames and it seems to help. I know Colin is using them on his MAX.


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## amphead

Sorry Joneeboi, the kiwames are in order for sure, as TomB said. I was easily able to cut volume with larger resistors at RB14. I think that the kiwames will still provide you with proper detail, with the attenuation that a larger value provides.


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## bperboy

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Amphead, Joneeboi is looking for less gain, not more.

 I can't say I've ever had an amp that I could turn the volume more than about halfway - the 12 o'clock position - as you describe. Most of the time it's around 9 o'clock, but that's because I default to 12AE6's most of the time and with KSC75's. With Senns, 10 to 11 o'clock is normal listening. If memory serves, 12FK6's gives you another 2-3 hours on the volume dial, so to speak - like 10 o'clock with KSC75's and maybe 2 o'clock with Senns.

 I sold my only Grados, but they were usually higher on the volume knob than the KSC75's, due to lower sensitivity. I have a pair of PIMETAs that I down-tuned to gains of 5, and they correspond to about 12 o'clock for medium-loud listening with KSC75's. They have 10K pots.

 Don't know if that helps you much, but I think this is a reasonable reference. Admittedly, I personally prefer sort of a hair-trigger volume control rather than attenuating the signal with output resistors. Maybe I've just gotten used to it - the SOHA is about twice as bad as any of these references - never getting past 9 o'clock even with Senns. 
	

	
	
		
		

		
		
	


	




 Some of the most prominent builders of Milletts use the Kiwames and it seems to help. I know Colin is using them on his MAX._

 

I use mine with 12FK6s and 100ohm output resistors, and I still find it quite loud at 9 o'clock. I've got a SPL meter and its only about 80db at that volume, but its pretty loud for me.


----------



## nysulli

tomb, how hot is too hot for the transistors?

 at 75mA mine are really starting to get warm to the touch, and almost getting to the point where its to hot to keep my fingers on the heatsinks


----------



## tomb

That sounds too hot. IMHO, the sinks should cook pretty good - but not enough that you can't lay a finger on them. In any event, they should run that cool out of the box at least - things will get much worse when you case it up.

 What size sinks are you using? Sounds like 1" high sinks. If you're running 1-1/2" tall sinks, this could be a bad problem.

 A measurement might be a good idea if you can manage it. If the sinks are hotter than the plastic case of the transistors, that's ideal. I think if you are under 70 deg.C. (~160 deg.F.), you're OK. Much more than that and I'd worry. That's from memory when I had an amp that would go into thermal runaway and shutdown with an LM317 higher than that. I think it's fairly conservative, but I could be wrong.

 At 110mV on mine running with 1" tall sinks, I get about 45 deg.C. on the transistors _and_ the LM317. I'm sure it runs a bit hotter cased up, but the current draw and bias settings remained the same and I've checked it quite a bit (lots of ventilation holes in the top, though).

 On the old revMH Millett with DB's, the metal-backed MJE's would get so hot you couldn't touch them at all - and that was running about 25ma bias. So, my references with the MAX may be way, way too conservative.


----------



## joneeboi

My volume control starts at 12:00 (edit: meaning no volume at 12) and finishes around 1:30 to 2:00. If that's relatively normal I can live with it. Where are your volume controls starting, Tom? I'd think something around 7:00 is typical, which is where I put mine earlier. Mind you the 12 to 2 range is with 75 ohms in series. Raw Grado impedance is only 12 to 1.

 What size RB14 is liveable for Grados and FKs? 

 amphead: Which value did you install and which headphones are you using?

 bperboy: Which headphones are you listening with?

 tomb: You were right (from what I read on the MAX site) about using V-Ds in RB14. The highs seemed so synthetic and fake, like they were pulled out of a loop track almost. Attack and decay were very chalky as the cymbals just blinked in and out real fast. Now I'm getting a more realistic rise and decay. Again, I'm able to pick up those minute, extremely subtle "quiet-time" drumming bits that really reveal the skill of the drummer. Will report back on the Kiwames whenever I get around to ordering them.

 I think I'm really taking to the tube sound. Just the other day I was in my parent's CR-V and I turned down the treble knob past the "normal" position cause I wasn't feeling the sound. I think my ears were actually reaching out for the MAX. Mmmm, toobz. Plus the orange tube lights aren't as distracting as I imagined for night-time listening. They're very sensual.


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## pinkfloyd4ever

we are talking about the Carbon Film Kiwames that partsconnexion sells right? I don't know that there are any other kinds, just checking. How do they compare to other "boutique" resistors like vishay(not V-D), caddock, holco, dale(again, not V-D), riken, roederstein, etc? How about Allen-Bradley carbons? Audio Note (or other) tantalums?


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## tomb

Quote:


  Originally Posted by *joneeboi* /img/forum/go_quote.gif 
_My volume control starts at 12:00 (edit: meaning no volume at 12) and finishes around 1:30 to 2:00. If that's relatively normal I can live with it. Where are your volume controls starting, Tom? I'd think something around 7:00 is typical, which is where I put mine earlier. Mind you the 12 to 2 range is with 75 ohms in series. Raw Grado impedance is only 12 to 1._

 

If you are truly saying your volume knob is set at about 7 o'clock for zero position, but you have no volume whatsoever until you turn it to 12 o'clock, then something major is wrong. It almost sounds like you have a linear pot, not an audio pot.

 Did you use an RK27? Where did you get it? What you describe is not normal - it's normal for a linear pot, but not a log/audio pot.


----------



## amphead

Joneeboi, I am using K701, 12ae6, and 22ohms. Volume starts about 8 oclock and continues to uncomfortable at full volume. I tried dale 75ohms at RB14 and volume dropped 33% and detail dropped 40%, and I could listen at full volume but didn't want to. Those are ballpark figures of course. I can't recommend Dale resistors for RB14. Edit: Remember however, that I dial the volume out on the CD player for the least distortion, which is about 1/3 of its volume. If I put that to full volume then I would probably have sound almost through the full range of the pot on the Max.


----------



## joneeboi

Sorry for the lack of clarity, Tom. The pointer on my knob, when turned fully counterclockwise, sits at 12:00. It *used* to be at 7, but I changed it to begin at 12. The volume pot is Tangent's RK27.

 Amphead: I'm just trying to gauge what value I should get for RB14. I should probably go with tomb's suggested swapping of cheap resistors to gauge relative sound level. 75 ohms doesn't seem like enough. Then again I ought to think of the future when, who knows, I buy a headphone with 250ohm impedance. Maybe I should get a gain switch. Now wouldn't that be pretty?


----------



## amphead

Its hard for me to imagine what your system needs, because the 12ae6 with K701s, is a completely different situation than yours. The 75 ohms is much too large on my system and too small for yours apparently.


----------



## amphead

Update on my experimentation with the Max. I increased 0.1uF Jensen cap with 0.1uF Tex-Cap 250v metalized polyester, in parallel for 0.2uF there(CA9L/R). Then I increased from 0.2uF worth of Jensen caps with 0.22uF Tex-Cap 250v metalized polyester, in parallel for 0.42uF in that position(CA8L/R). So far I think I like the more forward upper mids. Bass is slightly more forward. The tempo of the music seems to sound right, kind of dynamic/lively. Just more of everything, like removing anything that had a recessed response. A little more detail in the mids. The reverberation and resonance increased for piano and some vocals. Quite nice! Oh by the way Ian Anderson says hello to Team Millett Max! I briefly mentioned what we were doing when he signed my guitar! I should have had him sign the Max in silver marker over black!  Edit: Probably too large of a value for capacitance at CA8L/R for some songs, you get a small amount of sibilance on louder vocals. Oh well, I knew 0.42uF was pushing things a bit too much. Yeah, once again not the sound I'm after. Back to the drawing board. I'll find the right configuration eventually.


----------



## fordgtlover

Is there a thread discussing listening impression of the Millett Max?


----------



## tomb

Quote:


  Originally Posted by *fordgtlover* /img/forum/go_quote.gif 
_Is there a thread discussing listening impression of the Millett Max?_

 

Good idea. Why don't you start one?


----------



## nysulli

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_That sounds too hot. IMHO, the sinks should cook pretty good - but not enough that you can't lay a finger on them. In any event, they should run that cool out of the box at least - things will get much worse when you case it up.

 What size sinks are you using? Sounds like 1" high sinks. If you're running 1-1/2" tall sinks, this could be a bad problem.

 A measurement might be a good idea if you can manage it. If the sinks are hotter than the plastic case of the transistors, that's ideal. I think if you are under 70 deg.C. (~160 deg.F.), you're OK. Much more than that and I'd worry. That's from memory when I had an amp that would go into thermal runaway and shutdown with an LM317 higher than that. I think it's fairly conservative, but I could be wrong.

 At 110mV on mine running with 1" tall sinks, I get about 45 deg.C. on the transistors and the LM317. I'm sure it runs a bit hotter cased up, but the current draw and bias settings remained the same and I've checked it quite a bit (lots of ventilation holes in the top, though).

 On the old revMH Millett with DB's, the metal-backed MJE's would get so hot you couldn't touch them at all - and that was running about 25ma bias. So, my references with the MAX may be way, way too conservative._

 

i'm using 1.5" heatsinks, and their nowhere near that hot, i can still put my finger on them, it just that now it gets a little uncomfortable after 5-10 seconds, i'd say their running 35-40c


----------



## tomb

Quote:


  Originally Posted by *nysulli* /img/forum/go_quote.gif 
_i'm using 1.5" heatsinks, and their nowhere near that hot, i can still put my finger on them, it just that now it gets a little uncomfortable after 5-10 seconds, i'd say their running 35-40c_

 

You have no problem, then.


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## adfinni

A cheeky pic of mine......... No more piccies until it's done 
	

	
	
		
		

		
		
	


	











 O and a question.... Does it matter (electronically) if the top of the power supply capacitors touch the top of the hammond case ?????


----------



## tomb

Quote:


  Originally Posted by *adfinni* /img/forum/go_quote.gif 
_<snip>O and a question.... Does it matter (electronically) if the top of the power supply capacitors touch the top of the hammond case ?????_

 

It could - some caps have the case grounded to the negative supply. Although, I think all the ones recommended for the MAX are isolated.

 However, I'd be more worried because they were touching, period. It can't be very easy to get them all at the exact height - the plastic film itself has some variance in how much pops up around the opening. So, it would seem that at least a few would almost get sheared off every time you removed the lid and get banged around every time the case got bumped. One of the things that distinguishes a quality electrolytic with one that's not is the rubber cushioning at the interface between the cap and the board - sort of like shock absorbtion. If they were touching, you'd lose all mechanical isolation and may put a lot of stress on the leads and their solder joints - perhaps resulting in stress cracks, slight breaks, etc. - and bad sound because of the imperfect connection.

 Nice work so far, though.


----------



## adfinni

Cheers tom, it looks even better with all the electrolytic caps and heatsink assemblies in place now.

 I won't tell you what caps i have, but they are 40mm tall, and the hammond i have has a slightly bowed top panel. I calculated that with these caps there should be about 0.5mm clearance but the hammond doesn't have tolerances this tight me thinks. I might consider putting a thin layer of selotape on top of the caps in question just to be sure.

 They are good quality caps so the rubber cushion should be decent enough.... Ok ok ok a slight hint.... Lets just say they begin with a 'K' and end with a 'Z'


----------



## vixr

mine wouldn't fit... the caps were all slightly different, and the board was a little warped too...


----------



## tomb

Yeah, I'm beginning to see what others complain about with the Hammond cases. I still like them a lot, but you'd think with the metal as thick as it is on these MAX cases that they could extrude that stuff without the bow in the middle. 
	

	
	
		
		

		
		
	


	







 Of course, Vixr's solution is most ingenious - I wish we could all do that. My solution is using ES or BG caps, although I'm going to build one with KZ's at some point. Those caps are Giant Sequoia's, that's for sure.


----------



## nysulli

the KZ's are huge, unfortunitly i have the added problem of the 1.5" heatsinks as well, thus my top, whenever i get around to drilling all the holes, will look much like vixr's, with the heatsinks physically sticking out of the case as well

 but given that i'll be doing the casework with a cordless drill and a dremel, I somehow don't think its going to come out looking as nice as vixr's, but maybe once its cased up i'll post pictures

 after all i'm doing something a little goofy with the biasing points being wired to the outside of the case


----------



## tomb

I finally got around to making some small tests, guys - thanks to some help from Vixr and others who've gone into some parts purchases with me. Here's what I've discovered so far:

*Keep the boutique film caps away from the cathode bypass position (CA9) - unless you have some very, very good ones that are very, very flat.*

 I finally got some Sonicaps to try out and plunked them right into all four positions - it was as if a muffler had been put on the MAX. Mids and highs were absolutely beautiful - crystal clear, with great depth. However, all that deep, deep bass and fantastic slam I've grown to love these last several months was gone!

 What to do? Well, going over the things I knew:
 1. Dsavitsk couldn't be that far off about the ES + Sonicap GEN II - he was the one that clued me in on the Muse ES bass to begin with ... so something else must be going on besides the simple coupling arrangement at the output: CA7 and CA8. (His tests are for coupling caps, not tube-cathode-bypass-caps.)
 2. The MAX has always been sensitive to the cap in the cathode bypass positions - that's why we went with the 1000uf size, and it made a big difference in deep bass and slam.
 3. The SOHA design doesn't even use a bypass film cap with its cathode bypass electrolytics and doesn't seem to suffer. The film coupling cap at the tube output and entry to the opamp makes a big difference, however.

 So, those three things indicated that the thing to do was remove the Sonicaps from the cathode bypass positions. That's what I did, but also replaced the Wima's, since there was never any lack of bass and impact before. It worked. Highs are still fairly open - maybe a little bit more harshness, but no muffler and oodles of deep, deep bass, impact and slam: the stuff that made me love the MAX from the very beginning.

 Anyway, I think many of us have wondered the relative importance of the film caps in those positions, vis-a-vis, cathode bypass vs. output coupling - which was more important? As stated above, don't mess with the Wima caps at the CA9 positions unless you have something that has a very, very flat frequency response - most "boutique" film caps probably do not. The Sonicap GEN II's actually have a rolloff in the highs and lows - similar to an Auricap. So, an Auricap might be suspect in that position, too - as Dsavitsk also mentioned somewhere in this giant thread ...


----------



## nysulli

interesting, i've got a spare pair of wima's, i might just have to give that a shot over the weekend, i'll try to compare it to leaving out CA9 as well if I have the time


----------



## pabbi1

Well, it lived for a few minutes... voltage 28v, check, tubes biased to 14v, check, db biases ~35mv, check.

 Then...

 I start biasing my first right channel... moving slowly up to about 60mv, sipke to infinity, rb2r glows into flame, smoke, ick... immediate power down...

 Thoughts?


----------



## nysulli

unless i'm reading the schematic wrong i would lean towards one of 2 things, either a bad transistor in qb4r, or a short

 or a short at QB8R

 as far as i can tell those are the only current paths to RB2R, and i've seen bad transistors toast resistors on the output end in other electronic gear before


----------



## joneeboi

Perhaps it was just a bad transistor. Or maybe there is a short at QB2. There could be a direct path from V+ to GND at QB2 through QB4, 6, or 8 and their associated resistors.


----------



## tomb

Pabbi,

 Did you determine that your output transistors were bad from the first time and are these new ones? After considering my comments from the first time, I don't think there's anyway the output trannies would've survived in those reversed positions. Perhaps that's what smoked the resistor.

 Or, if you did replace the transistors, perhaps the previously reversed condition weakened the power resistors so that one blew when you hit it with some significant current. Just a guess ...


----------



## amphead

Quote:


 TomB:
 As stated above, don't mess with the Wima caps at the CA9 positions unless you have something that has a very, very flat frequency response - most "boutique" film caps probably do not. 
 

Thats something that I want to try, now that you mention it. I have 2 extra Wimas, which will roll the Jensens there. 

 Nothing against the visually impaired, but should they be driving automobiles. I got in a fender bender, hitting the guy in front of me at about 7-8 miles an hour after screeching on my brakes. Amazingly there was no damage to his car or mine, except my front license plate was bent a little. I offered him $100.00 and he took it. That came out of my Max fund, now the boutique caps have to wait awhile. 
	

	
	
		
		

		
			




  Quote:


 rb2r glows into flame, smoke, ick... immediate power down... 
 

wth, thats amazing! Sorry to hear that! I definitely suspect those trannies that its connected to.


----------



## smegger

hi there about to order a max kit now i know it don't need a toroid but i am from the uk so will be using a 240v supply and i figure a toroid maybe as cheap and i intend on using a case big enough anyway,so can somerone point me in the right direction for one as i have never bought one before.

 Also i was wondering has anyone ever combined a switch box with an max to have say 3 selectable inputs?


----------



## joneeboi

I can't help you with the toroid, but I know that c0nsumer is working on an audio switch.


----------



## adfinni

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_I finally got around to making some small tests, guys - thanks to some help from Vixr and others who've gone into some parts purchases with me. Here's what I've discovered so far:

*Keep the boutique film caps away from the cathode bypass position (CA9) - unless you have some very, very good ones that are very, very flat.*_

 

Very interesting tom.

 I was going to try my boutique caps in CA7 and CA2 before bypassing them with the other caps ive bought. My MAX won't be complete until next week as im still waiting for some silver wire and RCA sockets to come, and then theres the burn in time for the caps (tubes already sorted). IL then do my own tests and get some impressions posted up.


  Quote:


  Originally Posted by *smegger* /img/forum/go_quote.gif 
_hi there about to order a max kit now i know it don't need a toroid but i am from the uk so will be using a 240v supply and i figure a toroid maybe as cheap and i intend on using a case big enough anyway,so can somerone point me in the right direction for one as i have never bought one before.

 Also i was wondering has anyone ever combined a switch box with an max to have say 3 selectable inputs?_

 

Ive purchased an AC-AC 24V 1500mA adapter from maplins for about £15 which should be ample to power the MAX.

 FUnny you should asked about a switchbox, im building one alongside the MAX albeit in a separate hammond enclosure. A separate one is easier to build and use in the future if i ever feel the need to upgrade from the MAX..... I reckon that'l be doubtful


----------



## smegger

what specs do i need for a power supply, would summit like this be ok, i just like the cleaner look of a kettle lead input, i dunno just don't like wall warts! if i was ordering parts for a switch box would this power my max total bargin cause not rohs? 

http://uk.farnell.com/jsp/search/pro...sp?sku=4334103


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## joneeboi

Typically MAXes have been run from 24V to 30V and sit around 600-700mA depending on the configuration. You're going to need a larger secondary voltage than that.


----------



## ruZZ.il

22 is pretty much borderline too low, it would only leave you with a bit under a volt to regulate down to 27vdc (note: unregulated Vdc=~Vac*1.4*0.9). Also, 1.6VA is way too low. Try narrow your search for toroidals down to anything with either 2x12v secondaries, or a 25v secondary. 2x25v secondary is good too (you could parallel the outputs). Look for something with a VA rating above 20, too. Something like this looks good.

 edit: This also looks good and at a relatively unbelievable price. Too good? Not sure. Anyone?


----------



## smegger

its not rohs compliant so thats why its so cheap. i may go for that one and see thanks guys, if anyone else wants one let me know and it should help me and you get round the £20 minimum order.


----------



## n_maher

FYI - someone just listed 4 MAX PCB's for sale...


----------



## tomb

Quote:


  Originally Posted by *adfinni* /img/forum/go_quote.gif 
_Very interesting tom.

 I was going to try my boutique caps in CA7 and CA2 before bypassing them with the other caps ive bought. My MAX won't be complete until next week as im still waiting for some silver wire and RCA sockets to come, and then theres the burn in time for the caps (tubes already sorted). IL then do my own tests and get some impressions posted up.</snip>_

 

Well, I am convinced that there is a particular synergy between ES's and Wima's now more than ever. I've remarked in other threads, but I recall trying to go it alone with the ES's and no Wima's on one of my old Millett Hybrids - I immediately lost the bass. Doesn't make sense, but I've trading some e-mails with Dsavitsk, and as he says, bypassing cap combinations can sometimes lead to unpredictable results.

 All this time, both of my MAXes have been running with ES's and Wima's. From day one, I've experienced more deep bass and hard, hard slam than I've ever heard in a headphone amp. So, when that disappeared with the Sonicaps in both positions, I was very concerned. Of course, there is a bit of graininess with the Wima's in the mids and highs, so that's why the attempt was made in the first place.

_I am happy to report that after a lot of further testing, I have absolutely settled on ES + Wima at CA2 and CA9 and the ES's + Sonicaps on the output. The sound is wonderfully detailed, with all the tremendous bass and hard slam that I've grown to love._

 I told Dsavitsk that I knew his tests would prove out one way or another - it's just the hyper-sensitivity of those cathode bypass positions that did't follow suit.


----------



## pabbi1

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Pabbi,

 Did you determine that your output transistors were bad from the first time and are these new ones? After considering my comments from the first time, I don't think there's anyway the output trannies would've survived in those reversed positions. Perhaps that's what smoked the resistor.

 Or, if you did replace the transistors, perhaps the previously reversed condition weakened the power resistors so that one blew when you hit it with some significant current. Just a guess ..._

 


 Yep, all new output transistors... I'll look at the other paths mentioned above as well... 

 Thanks, all,

 al


----------



## fordgtlover

Just posted a few pics of my partially cased Max over in this thread

http://www.head-fi.org/forums/showthread.php?t=265075


----------



## amphead

Quote:


  Originally Posted by *n_maher* /img/forum/go_quote.gif 
_FYI - someone just listed 4 MAX PCB's for sale..._

 

Didn't see it Nate. Probably too late.


----------



## tobias_svensk

So.. I should take up my build to again and I really want the whole thing to fit in a 40mm high chassi (Galaxy/HiFi2000) and I'm building the MOSFet version.

 Have somebody tried 1" heatsinks on a MOSFet version and does it get to hot? I guess the 1.5" heatsinks I allready have don't fit (havent got the case yet) but they could be cut down to 1.3-1.4"

 And would the ES 470uF/35V be a bad choice in the CA4/CA5 spot? I can't find another cap that has the same height/dia as the rest (I don't want a skinny cap there 
	

	
	
		
		

		
		
	


	




) The only alternative is the KZ 470uF/25V but maybe the voltage rating would be too low.

 Cheers


----------



## tomb

Quote:


  Originally Posted by *tobias_svensk* /img/forum/go_quote.gif 
_So.. I should take up my build to again and I really want the whole thing to fit in a 40mm high chassi (Galaxy/HiFi2000) and I'm building the MOSFet version.

 Have somebody tried 1" heatsinks on a MOSFet version and does it get to hot? I guess the 1.5" heatsinks I allready have don't fit (havent got the case yet) but they could be cut down to 1.3-1.4"_

 

Cutting down would be your only option, IMHO. The MOSFETs need 80ma - absolute minimum - to operate correctly. That's pushing it too far with a 1" sink.

  Quote:


 And would the ES 470uF/35V be a bad choice in the CA4/CA5 spot? I can't find another cap that has the same height/dia as the rest (I don't want a skinny cap there 
	

	
	
		
		

		
			





) The only alternative is the KZ 470uF/25V but maybe the voltage rating would be too low.

 Cheers 
 

Yes and no. ES's would be OK, but would not be the best choice. CA4/CA5 are _not_ boutique positions. The best choice are Panasonic FM's, Nichicon UHE's, UPW's, or Panasonic FC's - probably in that order. For me personally, I use 1800uf 35V FM's - they are 25mm tall. You can actually get 1200uf's that are only 20mm tall. I would not put less than 1000uf in there, given a choice - and more is better up to that 1800uf, depending on your power supply (I use a 40VA walwart).


----------



## thunder

If using 470 uf cap's in position's C4 & C5 gives you 940 uf per side, What improvements can be had by going higher ? Also did you mean a total of 1800 uf ? Is the additional capacitance you speak of used for the mos-fet version only ?


----------



## tomb

Quote:


  Originally Posted by *thunder* /img/forum/go_quote.gif 
_If using 470 uf cap's in position's C4 & C5 gives you 940 uf per side, What improvements can be had by going higher ? Also did you mean a total of 1800 uf ? Is the additional capacitance you speak of used for the mos-fet version only ?_

 

1. No, that's 7200uf combined in the CA4 and CA5 positions.
 2. There is a case to be made that CA4 and CA5 maintain the stored voltage potential for the Tube CCS and the DB, respectively. To the extent that isolates those two things from the other it results in better performance. Besides, it keeps you from using skinny caps and fills the circles on the board. 
	

	
	
		
		

		
		
	


	



 3. I only use the BJT versions. The BJT versions are a better match up for the tubes, IMHO. The MOSFET DB without global feedback sounds tubey already. So, tubey + tubey = syrup (maybe). The BJT's on the other hand, are very dynamic and detailed. There are even a few selections that provide very good slam. So, the BJT's provide a good contrast to the tube gain stage.

 IMHO and YMMV.


----------



## nysulli

well, your definitly onto something with the bass and slam with the ES/wima combo, without a doubt theres more bass, the question is the high end.

 like you said, its a bit more grainy, and I'm already missing the amazing highs the soniccaps gave me, but I'm also really enjoying the new found bass, god damnit tomb, now I need to build a second MAX so I can switch between the 2 at will


----------



## tomb

Quote:


  Originally Posted by *nysulli* 
_<snip> ... I'm also really enjoying the new found bass, god damnit tomb, now I need to build a second MAX so I can switch between the 2 at will_

 









 Just promoting the slam for everybody. 
	

	
	
		
		

		
		
	


	







 Seriously, the compromise is to keep the ES + Wima in the cathode bypass positions on the tube, then use the ES + Sonicap on the output coupling positions. I think it's a near perfect combo so far w/o going to Black Gates. I don't think the Black Gates are going to have the slam of the ES's, but I'll report back when I get to that point.

 Meanwhile, rock on with that slam.


----------



## odoe

I'm thinking of switching to that combo on my current build just so casing would be easier.


----------



## ruZZ.il

hm. Makes me want to play around with mixing up a max with BG's and ES's 
	

	
	
		
		

		
		
	


	




 ...Looks like I'll be ordering from digikey sometime soon too 
	

	
	
		
		

		
		
	


	




 Specially since they're back in stock with the amveco toroidal I was waiting for. 

 And Tom, I saw your Millet Hybrid last week, sounds damn good too. Didn't get to listen seriously, but good stuff!


----------



## tomb

Quote:


  Originally Posted by *ruZZ.il* /img/forum/go_quote.gif 
_<snip>
 And Tom, I saw your Millet Hybrid last week, sounds damn good too. Didn't get to listen seriously, but good stuff!_

 

Cool - I thought about asking if you knew AudioBully, but then I thought, "Naa, that's silly - it's a whole country." Small world, I guess.


----------



## ruZZ.il

Well, I popped in to a little meet 
	

	
	
		
		

		
		
	


	




 took my max along which got some thumbs up.. and a pic:






 yep, I got around to kind of casing it up 
	

	
	
		
		

		
		
	


	




 used some plywood 'temporarily', which worked out kinda nicely.. still needs to be treated, but I think I'll keep it.. I'll get around to taking proper pics sometime.
 note how nothings quiet finished  ... need knobs, to top off my M³ (and unseen steps).. hm.. need to make a new panel for my PIMETA too since I added a bass boost 
	

	
	
		
		

		
		
	


	




 oh.. and go to class.. fun


----------



## amphead

Awesome ruZZil! You could glue a veneer onto the plywood. Nobody would know it wasn't solid hardwood. Stain that and add a clear satin coat of polyurethane. Whatever you do I'm sure it will look good.


----------



## MrMajestic2

Quote:


  Originally Posted by *tobias_svensk* /img/forum/go_quote.gif 
_So.. I should take up my build to again and I really want the whole thing to fit in a 40mm high chassi (Galaxy/HiFi2000) and I'm building the MOSFet version.

 Have somebody tried 1" heatsinks on a MOSFet version and does it get to hot? I guess the 1.5" heatsinks I allready have don't fit (havent got the case yet) but they could be cut down to 1.3-1.4"

 And would the ES 470uF/35V be a bad choice in the CA4/CA5 spot? I can't find another cap that has the same height/dia as the rest (I don't want a skinny cap there 
	

	
	
		
		

		
		
	


	




) The only alternative is the KZ 470uF/25V but maybe the voltage rating would be too low.

 Cheers_

 

If you are going to get shorter heatsinks I would recommend switching from Mosfet to BJT instead. Maybe someone around here has a set left over. I have a 1" heatsink for the PSU section lying around if you want it, but you still need 1" for the trannies.


----------



## pabbi1

Completely out of my depth, and need intervention... I replaced the QB4R, and the rb2r (well twice, but that is yet another story)... checked rb4r and rb6r which both measured properly (100 and 220 ohm, respectively).

 Rb8r (and L) is jumpered.

 Trimmer is fully clockwise, as it was for the first initial power on, prior to any biasing, which gave me less than 30mv across the bias points.

 Still, rb2r smokes before I can turn off the power switch - 1 second or so.

 Recommendations? How can I tell if this board is worth saving or if it needs scrap, and replace? 

 The ugly side of DIY - demoralized, beaten down, but not yet defeated...


----------



## tomb

Pabbi - have no fear. We have solved several tempermental MAXes. It's a proven design and a proven board. There simply has to be something you're not seeing that maybe some of the rest of us might.

 You've heard it before, but please take some pics for us - ones that are reasonable enough to discern the parts. I'm sure we can figure it out.


----------



## pabbi1

Well, this is a start... let me know if better pics are needed. Click on the pic to enlarge.

Front
Front 2
Front 3
Back


----------



## amphead

Pabbi, in the worst possible case, (which we probably won't need to do,btw), you can ship the board with parts to one of us who likes the challenge. It will, become a beautiful killing machine! I for one would do it. TomB would do it( right? ). But lets get this thing fixed online! I would like to see a close-up of the pads at RB2R, there might be a solder bridge from the topside of the pad to the ground plane on top of the board.
 Even more likely would be a short from the trannie in series to the ground plane.


----------



## ruZZ.il

hey does your other board work? time to start comparing measurements between points on board a to the same measurements on board b.. that would be points on each side of resistors, from ground to multiple points, and try get the forward bias readings of the 2 diodes in the transistors (ie, NPN = NP - PN, PNP=PN-NP) if your dmm can do this. compare board visually bit by bit, etc. though if both boards behave similarly, there must be a part mix up or something.. also, did the symptoms appear in both channels equaly? that also sounds like a parts culprit, or something being fundamentally mistaken, rather than a bad joint or something..
 looks like you'll have one mean setup pretty soon! 
	

	
	
		
		

		
			




 ..and, try get more shots of underneath.. maybe macro focus or something?


----------



## tomb

That's a nice thought, Amphead - I actually PM'd Pabbi and told him that before he posted the pics. You're right, though, we should be able to solve it here.

 Pabbi - tell us more about those PIO's on the front output positions. Both of them look like they could be shorting the RB14 position - especially the one on the right side. It's canted sideways and looks like the edge of the can may be touching the RB14 jumper.

 I've seen a thick plastic film on some of those, but they usually don't cover the ends. It's on the right channel, too - so I'd take a look at that.

 Exactly which BJT's are you using? They look like maybe the 2SC3422/2SA1359 pair. Have you checked the obvious such as the positions of each? The 2SC1359's go in the middle two sinks. The 2SC3422's go on the outside.

 Anyway, that's all I see for now - I'll keep looking.

 P.S. ruZZ.il has an excellent point, too. If the other board works, then you have a perfect reference with which to make measurements and pointpoint the problem position/


----------



## pabbi1

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_That's a nice thought, Amphead - I actually PM'd Pabbi and told him that before he posted the pics. You're right, though, we should be able to solve it here.

 Pabbi - tell us more about those PIO's on the front output positions. Both of them look like they could be shorting the RB14 position - especially the one on the right side. It's canted sideways and looks like the edge of the can may be touching the RB14 jumper.

 I've seen a thick plastic film on some of those, but they usually don't cover the ends. It's on the right channel, too - so I'd take a look at that.

 Exactly which BJT's are you using? They look like maybe the 2SC3422/2SA1359 pair. Have you checked the obvious such as the positions of each? The 2SC1359's go in the middle two sinks. The 2SC3422's go on the outside.

 Anyway, that's all I see for now - I'll keep looking.

 P.S. ruZZ.il has an excellent point, too. If the other board works, then you have a perfect reference with which to make measurements and pointpoint the problem position/_

 


 You guys are great - lest I forget, much love to all helping - and, even to others getting a chuckle - I'll find this quite humorous someday as well.

 Indeed it is the 3422/1359 combo, and they are oriented correctly. This was all OK for the corrected biasing run, where things went wonky after moving the bias up after about 20 minutes of good activity, until I hit 60mv on the right side, then something gave out.

 The left side of that board seems fine, so I can measure the NPN & PNP for each transistor - is there a reference for what they should be? 2n5087, and 2n5088, which I should be able to measure on the left channel, and both channels on the left board. I just would not try biasing again without some feeling that all is right with the transistors.

 I am curious about the ground plane short, as I did hear a snap once when measuring voltage (ONLY on this board), but also found a couple of unsoldered joints (how did that happen? 
	

	
	
		
		

		
		
	


	




 ), and hoped that had fixed that issue.

 Ok, more data - some of it quite ugly...

One
Two
3
4
5
6
7
Back 1
Back 2
Back 3
Back 4

 Oh, don't ask me how it comes to this... we'll call it an acquired talent, of sorts.


----------



## tomb

Your BD139 transistor in the delay circuit is reversed (QM1).

 Also - you didn't address the question I had about the PIO/VitQ/Russian film cap in the right output position - I could sware it's touching the silver multistrand you're using to jumper RB14, the output resistor.

 I'll keep looking - meanwhile, fix that QM1. I don't think that's all of your problem, but it can't be helping.


----------



## amphead

Pabbi, I see something quite troubling or good depending how you look at it. Did this board ever have transistors mounted in the Mosfet positions? QB8R shows evidence of solder activity in the Mosfet position in picture "one". There could be a short to the ground plane at those pads.


----------



## pabbi1

Quote:


  Originally Posted by *amphead* /img/forum/go_quote.gif 
_Pabbi, I see something quite troubling or good depending how you look at it. Did this board ever have transistors mounted in the Mosfet positions? QB8R shows evidence of solder activity in the Mosfet position in picture "one". There could be a short to the ground plane at those pads._

 

Yep, I had all the output transistors mounted in the wrong holes... question is, simply remove the balance of the old leads, as I simply cut them off, or is that not really necessary?

 Tom, good catch, as it is indeed touching the jumper - so it looks like that could be the ground short? I'll get that fixed, and the QM1... then replace the Rb2r... again. I am guessing all was OK, and when I was biasing the first time probably pushed the VitQ into the jumper - good lesson to use shielded wire on jumpers, huh? On the other board, I have the angle much more severe, so the VitQ is nowhere near the jumper.

 Thanks, guys - I'll have at that tomorrow, and report back... oy...


----------



## amphead

If the problem is still there, after the other fix. Take your ohm meter with the board powered down and put the negative lead in a ground test point and see if those pads are shorted to ground with your positive lead. I have to look at the schematic again but one pin might actually be grounded intentionally on the diamond buffers, so this is not a completely foolproof test. I'll get back to you on that.


----------



## amphead

The center pin at QB8R will show ground, but the outside pins should read infinite resistance/open.


----------



## amphead

btw, I really enjoy the sound with the Wimas replacing Jensens at CA9! Wimas are boutique for that position!  Thanks again for the heads up TomB. I still use Jensens and Panasonic hfs 470uF at CA8/CA9(I know theres better out there). The bass sounds nice and extended without any detectable loss of highs. Mids are not forward nor recessed. Aaah just right! I use "bungle in the jungle" to test highs,mids,bass linearity. Sorry you had to find that out.


----------



## amphead

If there is a short to the ground plane, they can be a real b*tch to fix. Just wicking up the solder doesn't always work, as I found out. So what did I do? I cut the trace on the bottom of the board to release/float the pad connected to ground plane. Its not "purdy", but is quite effective.  If that was my board, I couldn't wait to do just that. Cut across all three traces separating mosfet side from bjt's. At least you could eliminate that as a possible cause. Not nice burning resistors, transistors more than once!


----------



## fordgtlover

Quote:


  Originally Posted by *pabbi1* /img/forum/go_quote.gif 
_You guys are great - lest I forget, much love to all helping - and, even to others getting a chuckle - I'll find this quite humorous someday as well._

 

No chuckling here - we are all very supportive. I would offer advice if I thought it would help. Tomb, amphead ruZZ.il and others provide great support and will get you through.


----------



## fordgtlover

I have continued working through eliminating the graininess in the mids. I built mine with Elna Silmics at CA2/7 bypassed by the standard WIMA MKP caps. As suggested by Tomb, I removed the WIMAs from CA8/9 - no change, hmmmm.

 Thinking that perhaps the Silmics just don't work well in this amp, I decided to put some Panasonic FMs in place of the Silmics at CA7, and reinstalled the WIMAs in CA8. The result - a significant reduction in grain. 

 I'll keep on it. I have some of those Russian K42 PIOs on the way - I'll try these with a combination of the Panasonic and Elna caps.


----------



## tomb

Fordgtlover,

 That may confirm some of what I've heard about Elna Silmics. On the one hand, I've always heard that they're great boutiques - almost as good as Black Gates, etc. However, I've also heard that the Silmics are no replacement for Cerafines and that the Silmics are grainy/rough. Maybe you've found out which is really true, at least for the MAX.

 In any event, your experience and mine is creating a new-found respect for the Wima's. Obviously, Pete Millett knew what he was doing in using them all along.


 P.S. Thanks for the help with Pabbi, guys. I hope he's found the problems. Then maybe we can get on with learning more about his trailblazing OPUS-fed balanced MAX.


----------



## thunder

Tomb, If your using a combined total of 7200 uf or 4 x 1800 in CA4 & CA5, What kind of results can be expected if using 4 x 1000 instead ? Also does this combo have anything to do with the killer bass you've got or is that purely a ES-Wima thing ? Has anyone tried doubling the power supply cap size from 1000 uf to say 2200 uf and if so, What were the results ? Just looking for thunder mixed with some lighting quick transients and sparkle ! (Edit) What I mean by doubling the caps in the PS section is 4 x 2200 !


----------



## gychang

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_I have lived with this amp every day since March 11th - turning it on every night for several hours, and for most of the day and night every weekend. Listening is mostly through an M-Audio Transit. Music sources tested also include a 1st generation iPod, a Sony D-NE20, and various other PCDP's, including an old "D" model Sony. The combination of the Max with Sony D-NE20 and older D model (using Line Out) highlighted a deficiency in high bit-rate mp3's - something not easily noticed on my other amps. Ever since, I have been using FLAC files almost exclusively._

 

Looks like a first class sculpture, thanks for description of sound. This may be in my future project.

 gychang


----------



## tomb

Quote:


  Originally Posted by *thunder* /img/forum/go_quote.gif 
_Tomb, If your using a combined total of 7200 uf or 4 x 1800 in CA4 & CA5, What kind of results can be expected if using 4 x 1000 instead ? Also does this combo have anything to do with the killer bass you've got or is that purely a ES-Wima thing ? Has anyone tried doubling the power supply cap size from 1000 uf to say 2200 uf and if so, What were the results ? Just looking for thunder mixed with some lighting quick transients and sparkle !_

 

Honestly, I have 1200uf's in my 1st prototype and I cannot really tell the difference in the strength of the bass between those and the 1800uf's I use now. If I remember correctly, the 1800uf's are just pennies more and as I said previously, seem to fill out the circles better. They are also the same relative diameter/height as the ES's and the higher voltage 1000uf 50V FM's in the power supply. So, the whole thing combines for a very consistent look and I have no doubt whatsoever that there's enough capacitance on board. 
	

	
	
		
		

		
			








 As for whether you can go down to 1000uf and get the same effect, bass-wise, I would guess so. I have considered "officially" recommending 1000uf as a minimum (my gut says there would be a definite improvement over 470uf's), but can't justify it on the basis of testing. What I am guessing is happening with the 470uf's is that some people, especially with high current MOSFETs, are reporting that adjusting the DB bias can have some effect on the tube bias, or that adjusting volume can affect the tube bias. This should not be so. The only thing I can surmise is that the smaller caps are not large enough to completely support some of the current demand and the DB's are sucking current out of the CCS's. Certainly, with the caps I've described - I can confirm that I've _never _seen any of this.

 I did do an "official" recommendation with CA2 and will continue to warn everyone that if they don't put 1000uf in that position the bass will suffer.

 I'm going to add to that recommendation to be very careful what they put in for a film cap bypass at that position, too. Things have giant effects on the sound at that cathode bypass position. You can really destroy the sound there if you're not careful, apparently. Only the flatest caps should be put in that position and even if the Wima's have a bit of grain, you are better off with them than some boutique film cap like a Auricap that bloats the mids and falls off in the bass (especially). This includes Sonicap GEN II's, also, which is how I made this discovery.

 As for the PS caps - I still stick with the 1" maximum height on my MAXes, so that pretty much limits me to the 1000uf FM's at 50V, and you definitely need the 50V rating there. However, I am using 2200uf 50V Panasonic FC's on the 1st prototype and am building another just like it. However, the 1st prototype board only had positions for two caps, so it seemed like a good combination to use those - they're expensive for power caps, though. Of course, on paper the 4 x 1000uf FM's are better than the 2 x 2200uf FC's, simply because the FM's have better ratings (by a pretty good amount). I can't tell a difference in sound between the two.

 Where I can tell the difference is in the Wima's. The 1st prototype had room for 0.1uf Wima MKP10's. The 2nd proto and production boards use the 0.22uf Wima's. There is a definite difference in smoothness and lack of grain - in favor of the larger Wima's and the production boards.


----------



## KWS

hi all,i am going to join this project but have few questions to ask.
 1.Is it possible to replace the diamond buffers by the normal buffers like BUF634?I think it would be quite troublesome to match the transistors.
 2.I would like to use separated power supply to avoid the oscillation and heat from it.Would it be worth to do it?
 3.which one would be better for the CA2,Cerafine or PANS FM?I wouldn't consider Blackgate...LOL
 Thank you very much.


----------



## tomb

Quote:


  Originally Posted by *KWS* /img/forum/go_quote.gif 
_hi all,i am going to join this project but have few questions to ask.
 1.Is it possible to replace the diamond buffers by the normal buffers like BUF634?I think it would be quite troublesome to match the transistors._

 

This feature was rejected between the 1st and 2nd prototypes. Matching transistors is not that big a deal and even if you don't - the output coupling caps stop any offset that might occur. Quote:


 2.I would like to use separated power supply to avoid the oscillation and heat from it.Would it be worth to do it? 
 

NO. However, combine this question with your first one, and you may actually want the older revMH Millett, instead. That's because if you take the BUF634 outputs (OPA551's work with a small mod) and the separate power supply, and you pretty much have the original Millett, not the MAX. The MAX also adds the onboard E12 delay circuit, but that could be added to the older one, too. Quote:


 3.which one would be better for the CA2,Cerafine or PANS FM?I wouldn't consider Blackgate...LOL 
 

Cerafine if you can find them - it's important to make them 1000uf unless you are building the older Millett, then you can get away with 220uf. The jury is hung right now on the Elna Silmic - I get about as many comments from people not liking them as from some that do.

 The FM's will perform quite nicely, too - if you include the Wima bypass cap. Quote:


 Thank you very much.


----------



## pabbi1

Quote:


  Originally Posted by *pabbi1* /img/forum/go_quote.gif 
_Tom, good catch, as it is indeed touching the jumper - so it looks like that could be the ground short?_

 

Well, the cold reality of the new day shows me that the VitQ is NOT touching the jumper, and I cannot make it do so no matter how I try, so that is a dead end.I'll fix the QM1, and replace the r2 again, but need to remeasure something prior to powering up again.

 In looking closer, QB1r and QB6r look white and scorched (enough that I can't read the part number) - so replacement of those is also a good bet, though I'd like to know how to check them with the meter first.

 One interesting observation - no opens on ground test points, BUT... on the wholly good board, measuring from G to any of the buffer bias points gives me a reading of 1.1v. On the 'bad' board, the same measurement gives me .56v on the left channel, and 0v on the right (bad channel). Sure this tells me something, just no clue what.


----------



## tomb

Quote:


  Originally Posted by *pabbi1* /img/forum/go_quote.gif 
_Well, the cold reality of the new day shows me that the VitQ is NOT touching the jumper, and I cannot make it do so no matter how I try, so that is a dead end.I'll fix the QM1, and replace the r2 again, but need to remeasure something prior to powering up again._

 

Well, that's good news - sort of. It's possible that QM1 was leveraging current back in the other direction and causing RB2R to blow.

  Quote:


 In looking closer, QB1r and QB6r look white and scorched (enough that I can't read the part number) - so replacement of those is also a good bet, though I'd like to know how to check them with the meter first. 
 

I don't know of any way without removing them. Honestly, you may not like to hear this, but at this point I would remove every single TO-92 on that side of the circuit and trash them. Do the same for the resistors. Clean the bottom of that board where all the damage was taking place, while soldering in jumper leads at positions that might look suspect. I'd remove the output transistors on that side as well. You can stick them (or the TO-92's) in a meter to check for HFE. Again, the output transistors generally average about ~240 HFE, but you can check this specifically on the MAX website with the spec sheets for the 2SC3422/2SA1359 pair -
http://www.diyforums.org/MAX/MAXbjt.php  The spec sheets are at the bottom of the page.

 If the HFE checks out with the output transistors, then it's probably OK to put them back in. When you do, be careful with the mounting - it's not trivial. Without a good connection to the heat sink, you may experience some instability and thermal runaway. Ditch the shoulder washers - they don't work on the 2SC3422's, nor are they necessary. I like to put a flat washer on the transistor side so that the screw force is not concentrated right around the hole.

 If you need the 2N5087's or 2N5088's, please give me a PM. I'll send you a whole set that are matched (within reason). Hopefully, you bought them in a hundred, though - they're $2 and change for 100 now at Mouser.

  Quote:


 One interesting observation - no opens on ground test points, BUT... on the wholly good board, measuring from G to any of the buffer bias points gives me a reading of 1.1v. On the 'bad' board, the same measurement gives me .56v on the left channel, and 0v on the right (bad channel). Sure this tells me something, just no clue what. 
 

There is some small current - probably from the caps - that the circuit pushes through the DMM, so it will have a small affect if you're attempting to make an absolute measurement like that. I have measured similar amounts and the difference in channels/boards may just be the combined differences in the parts tolerances. The 0V is sort of telltale, though and it could explain the 0.56V on the left instead of the 1.1V for both. I'll try to make a measurement on one of mine if/when I get a chance.


----------



## pabbi1

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Well, that's good news - sort of. It's possible that QM1 was leveraging current back in the other direction and causing RB2R to blow.

 I don't know of any way without removing them. Honestly, you may not like to hear this, but at this point I would remove every single TO-92 on that side of the circuit and trash them. Do the same for the resistors. Clean the bottom of that board where all the damage was taking place, while soldering in jumper leads at positions that might look suspect. I'd remove the output transistors on that side as well. You can stick them (or the TO-92's) in a meter to check for HFE._

 

Yep, as QB2 and qB3 look toasted as well. I did get 50 each, so I do have a few left handy.

 This will take a while, so I may have to follow up in a day or two. 

 Thanks again, as this is really a character building exercise. 
	

	
	
		
		

		
		
	


	




 Al


----------



## ruZZ.il

and learning one 
	

	
	
		
		

		
		
	


	




 (sorry I cant help too much, I'm limited in knowledge, and time lately ;/ )


----------



## thunder

If using the MAX what would be needed to use the max as a pre-amp ? If possible I would like to be able to also use it with a power-amp for driving speaker's. Could it be done with a dpdt toggle sw to switch between HP's or pre-out ? If so aside from alot of gain will there be any sort of impedance issues hooking it up to a power-amp ? If needed is there a simple type of circuit that can be implemented ? From every thing I've read the MAX is a lively a dynamic amp, So why not expand on it's potential by having the option of HP's or speaker's ?


----------



## joneeboi

Anyone have an idea how to get those protecty tube thingers? I've searched head-fi, Google (imagine I couldn't find it), eBay, and nothing. I searched tube protector, cover. I'm on drugs since I got the wisdom teeth yoinked, so I'm at a loss of ideas =T Help?


----------



## Listen2this1

Joneeboi, are you talking about something like this http://www.vt4c.com/shop/program/mai..._id=2&hit_cat=

 These are one of the few that I have found for the smaller tubes. 

 Hope this helps.


----------



## pinkfloyd4ever

ok I'm sort of MHM straggler I guess since I haven't had time or money to build mine yet. But I have a few questions and points for clarification as I'm putting together my Mouser & other orders. I plan on using BG NX's for the CA7L/R and CA2L/R and using a .47 uF NX as the bypass. I'd like to (if possible, however SQ is foremost here of course) get all my boutique parts from one place, meaning the BG's, Kiwame resistors, and any of following stuff that Mouser doesn't have...

 1) Are Panasonic FM's better than Nichicon UPWs or Pana FCs for all the big out-of-signal (meaning CA4L/R, CA5L/R, CR1A, CR1B, CR1C, and CR1D) electrolytics?

 2) In regards to tomb's post at the top of this page, which ones are recommended to have higher values than is listed on the BOM, and what are those values & voltages?

 3) In regards to the "upgrade" QB8/QB9 transistors discussed before...
  Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Anyway, Dsavitsk is certainly right about not spending too many bucks on the caps. IMHO, you can alter the sound quality tremendously by using a set of the upgrade BJT's on that version:

 2SC3422/2SA1359 - Rock and hard slam (very nice!)
 2SC2238/2SA968 - Ultimate detail, very neutral and well balanced (best of all)
 2SC3421/2SA1358 - Deepest bass extension, some slam (very good)

 These are all a major upgrade considered against the BD's and MJE's, yet a full set will probably set you back ~$8 at the most, $4 on some if you don't count shipping._

 

the ones listed on the BOM don't entirely correspond to those listed above, but when I search on Mouser for the middle pair (the one I'm interested in) I get this and this. Tomb's description of the 2SC2238/2SA968 pair sounds alot like Steinchen's description of the third upgrade pair (2SC2344/2SA1011) in the BOM AND when I search Mouser for 2SC2344 I get THIS, one of the same results I get searching for the 2SC2238. What's the dealio? Are they the same?
 EDIT: AHHH, crap, nevermind, I just figured it out searching on B&D's site...the 2SC2238/2SA968 pair has been replaced by the 2SC2344/2SA1011 pair. Maybe I should just order my trannies from B&D? Dammit, looks like this ordering my parts from only 2 places isn't going to happen, except B&D has a $15 min order. Do they not have Panasonic FM caps? I saw they were listed in that "where to buy boutique stuff" thread as having Pana caps, but I can't seem to find FMs on their site

 4) Which cap position do I use the 0.47uF BG NX/Vit-Q/whatever? Just CA8L/R & CA9L/R? Or also CA3L/R & CA6L/R?

 5) If I do try to get some Vitamin Q's to fit, should I get .22, .33, or .47 uF?


----------



## pinkfloyd4ever

Quote:


  Originally Posted by *Listen2this1* /img/forum/go_quote.gif 
_http://www.vt4c.com/shop/program/mai..._id=2&hit_cat=_

 

wow thet guy nose englis good


----------



## thunder

Found this post over at DIY> http://www.diyforums.org/phpBB2/viewtopic.php?t=445 Can anyone help to resolve this ? See also post # 1928 on this page. Any ideas would be greatly appreciated ! Thank's


----------



## tomb

Quote:


  Originally Posted by *joneeboi* /img/forum/go_quote.gif 
_Anyone have an idea how to get those protecty tube thingers? I've searched head-fi, Google (imagine I couldn't find it), eBay, and nothing. I searched tube protector, cover. I'm on drugs since I got the wisdom teeth yoinked, so I'm at a loss of ideas =T Help?_

 

Are you referring to these:




 ?

http://www.vt4c.com

 Keep in mind they probably won't work very well unless you do a top-mounted socket.

 EDIT: Oops - didn't see Listen2This1's post next. Oh well - we think alike.


----------



## tomb

Quote:


  Originally Posted by *pinkfloyd4ever* /img/forum/go_quote.gif 
_ok I'm sort of MHM straggler I guess since I haven't had time or money to build mine yet. But I have a few questions and points for clarification as I'm putting together my Mouser & other orders. I plan on using BG NX's for the CA7L/R and CA2L/R and using a .47 uF NX as the bypass. I'd like to (if possible, however SQ is foremost here of course) get all my boutique parts from one place, meaning the BG's, Kiwame resistors, and any of following stuff that Mouser doesn't have...

 1) Are Panasonic FM's better than Nichicon UPWs or Pana FCs for all the big out-of-signal (meaning CA4L/R, CA5L/R, CR1A, CR1B, CR1C, and CR1D) electrolytics?_

 

YES - FM's are better than both of the other caps. Whether they're better enough to make a difference in sound, you'll have to decide yourself. I would ask you that you look at the difference in impedance and ripple current between an FM and UPW, then make your own decision. (The difference is not small.)

  Quote:


 2) In regards to tomb's post at the top of this page, which ones are recommended to have higher values than is listed on the BOM, and what are those values & voltages? 
 

I would definitely make CA4L/R and CA5L/R at 1000uf 35V, minimum. As a matter of fact, I will alter the BOM later today for those ratings. They're only pennies more and there's no reason to leave any suspicion about whether the MAX's performance might be degraded by the small size of these caps.

 BTW, 1800uf 35V FM's will max out the positions at 1" height. Nichicon has a couple of UPW selections at 1800uf 35V that will probably work, too. Whether you want to go that far is up to you, but 1000uf minimum is not going to put a hurt on anything or anybody.
  Quote:


 3) In regards to the "upgrade" QB8/QB9 transistors discussed before...

 the ones listed on the BOM don't entirely correspond to those listed above, but when I search on Mouser for the middle pair (the one I'm interested in) I get this and this. Tomb's description of the 2SC2238/2SA968 pair sounds alot like Steinchen's description of the third upgrade pair (2SC2344/2SA1011) in the BOM AND when I search Mouser for 2SC2344 I get THIS, one of the same results I get searching for the 2SC2238. What's the dealio? Are they the same?
 EDIT: AHHH, crap, nevermind, I just figured it out searching on B&D's site...the 2SC2238/2SA968 pair has been replaced by the 2SC2344/2SA1011 pair. Maybe I should just order my trannies from B&D? Dammit, looks like this ordering my parts from only 2 places isn't going to happen, except B&D has a $15 min order. Do they not have Panasonic FM caps? I saw they were listed in that "where to buy boutique stuff" thread as having Pana caps, but I can't seem to find FMs on their site 
 

I think you are confusing things. One, the BJT transistor model#'s are very specific. A substition is NOT the same thing, just as each one of the transistors listed have different sound qualities. Except for reverse pinouts on a couple of models, they could ALL be considered replacements for each other - but we know they don't sound the same. So, there is no such thing as a substition/replacement.

 Also, it sounds like you got things figured out, but there is no discrepancy on the BOM about these transistors, AFAIK. None of them will be found at Mouser or DigiKey except the MJE's and BD's.

 B&D carries Sanyo caps almost exclusively with one major exception - they have the Nichicon Muse ES 470uf 35V boutique cap. No one else except Michael Percy has that cap which happens to be the best choice for CA7 that's 1" or under, save for a Black Gate NX.
  Quote:


 4) Which cap position do I use the 0.47uF BG NX/Vit-Q/whatever? Just CA8L/R & CA9L/R? Or also CA3L/R & CA6L/R? 
 

Yes, that is where you may use them, although they would be wasted at CA3L/R and CA6L/R - the Wima's are all you ever need at the CA3 and CA6 positions. However, based on some recent experience, I would leave the small BG's _or any other boutique film cap_ out of the CA9 positions. Along with CA2, those positions form the cathode capacitor bypass for the tube. There is a possibility that the little 0.47uf will overwhelm the larger cap in CA2 - to the detriment of most of the bass frequencies. I haven't tried it, but my gut feel and experience with other caps is that CA2 should sit alone (1000uf is a given). 
  Quote:


 5) If I do try to get some Vitamin Q's to fit, should I get .22, .33, or .47 uF? 
 

I doubt that even the 0.22uf's will fit without extreme measures of board mounting acrobatics.

 1. If you use BG electrolytics for CA2 and CA7, leave them alone. You might try the small 0.47uf BG NX to bypass CA7, but it may be better without it.
 2. If you don't use BG's, then the Wima MKP10 0.22uf's are pretty d*mn good and have a special synergy with ES caps - they _enhance_ the bass.
 3. The ideal non-BG combo I've found so far are ES's in CA2 and CA7, bypassed with a Wima at CA2, and a Sonicap GEN II 0.22uf at CA7. The Wima preserves the tremendous bass slam and blow from the ES at CA2, and the Sonicap GEN II brings out the last bit of high frequency detail and mids at CA7.

 Warning: Using a Sonicap to bypass CA2 (CA9) will destroy the bass and put a major muffler on the whole MAX. This may be the same for many boutique film caps, so use the utmost caution. Save the boutique film cap to bypass the electrolytic at the output - CA7 (CA8).


----------



## tomb

Quote:


  Originally Posted by *thunder* /img/forum/go_quote.gif 
_Found this post over at DIY> http://www.diyforums.org/phpBB2/viewtopic.php?t=445 Can anyone help to resolve this ? See also post # 1928 on this page. Any ideas would be greatly appreciated ! Thank's_

 

There are others who've used the MAX and the older Millett Hybrid as a preamp. The older Millett Hybrid had a major issue with turn-on/turn-off offset, but of course that's solved with the delay circuit in the MAX.

 I suspect that the heat that MrBubbs refers to is a consequence of using the MAX for a movie. Most likely, the length of time _and_ volume is much greater for a full-length movie than most of us use for casual headphone listening. So, I'm not sure his experience is an actual problem. The MAX can definitely get toasty with extended listening, but there should not be an issue if you don't go crazy on the bias and include a ventilated case such as that shown in the construction section on the MAX website.

 His description of the connection would be a perfect way to do it - wire the secondary pads at the headphone jack to the preamp outputs. When a headphone is plugged in, it will disconnect those connections - no selector switch needed.


----------



## Televator

received my Farnell order this morning... found some time this evening and (nearly) finished my first Max... well, I have not cased it yet, nor have I soldered on all connectors and I haven't even listened to it yet... but I have been busy biasing and so far so good... (PS was piece o' cake, tubes still fluctuate a bit... but they are NOS and the DB's are almost up to 66mV now)

 I have to prepare dinner first (so I don't get lynched by my hungry family) but then I will go back and put it through its first listening test

 ...until then, here's some Max-tube-a-licious-ness for y'all:


----------



## tomb

Nice pic!

 As mentioned in one of my posts this morning, I have updated the BOM and the BOM page on the MAX website. CA4L/R and CA5L/R are now shown as 1000uf 35V minimum. However, as luck would have it, Mouser is out of the Nichicon UPW's in 1000uf 35V until late November. There was only one or two others to pick from. So, I sized both the Mouser and DigiKey part #'s for CA4-5L/R as 1500uf 35V and 1800uf 35V, respectively, which are just about the largest available that have been tested and are 1" in height. As noted this morning, I use the Panasonic FM 1800uf 35V caps in mine and they are the same size as the 1000uf 50V PS caps in FM's.

 I also added a listing for the 2SC2238/2SA968 BJT output transistors. They are readily available for not much expense at MCMinone - when they are in stock, which they currently are not. I contacted them a few days and they told me mid-October, so they should have some more anytime now.


----------



## smegger

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Are you referring to these:




 ?

http://www.vt4c.com

 Keep in mind they probably won't work very well unless you do a top-mounted socket.

 EDIT: Oops - didn't see Listen2This1's post next. Oh well - we think alike. 
	

	
	
		
		

		
		
	


	


_

 

i really would like to mount my tubes like this how wuld i goabout mounting them off the board


----------



## luvdunhill

does anyone happen to have a part number handy for those panel mount test probe recepticles I see on your builds for tube biasing? I looked at the MM BOM and at Mouser under the test equipment section and came up empty handed.

 Thanks!


----------



## pinkfloyd4ever

crap tomb, I forgot to mention one important thing last night, I was really tired. I prefer less bass than most. I mean, I like the sound of deep, impactful bass, but it hurts my ears after more than a few seconds. So, while I do like some quality bass, I'm more of a mids & highs guy. Most of all however, I love crisp, clean, minute detail. These are the reasons I decided to go with the BG NXs and the 2SC2238/2SA968 BJT pair. So, since neither B&D or Mouser have that BJT pair and Newark only offers it with a factory lead time of "less than 97 days"
	

	
	
		
		

		
		
	


	




 I'm guessing it's obsolete? Newark has a few of the 2SC2344/2SA1011 pair in stock and (in case thy sell out before I get around to ordering) the lead time for those is only 7 days. Soooo I think I might get my common parts there. 

 Also, with regards to the Vitamin Q's, the .22uFs are only 1.5" long x 5/8" dia. and the .47s are even smaller. I know that's too tall for tombstoning, but wouldn't they fit horizontally? I'm getting those figures here.

 EDIT: ahhh I just saw your last post before I made this one. Man I type too slow  Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_I also added a listing for the 2SC2238/2SA968 BJT output transistors. They are readily available for not much expense at MCMinone - when they are in stock, which they currently are not. I contacted them a few days and they told me mid-October, so they should have some more anytime now._

 

That's good news, MCMOne is the same as Newark right? (i.e. Newark will have them in stock when MCMOne does?)

 Also, maybe I'm dumb, but where do you get your Panasonic FM's? I looked On that "where to buy boutique caps" list and can only find a couple values, none of which are the right ones

  Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_I think you mean 0.47's are larger. Regardless, there is room for 1" at CA9 in the back and 3/4" for CA8 in the front. They won't fit without those acrobatics I mentioned._

 

Yes and no, I keep getting confused b/c they have these Mudorfs that they have titled as VitQs, but the for the real Qs .47uf is 1 1/8”x7/16” or 1 1/2”x1/2” and the .22uF is 1 1/2”x3/8” They also have a .27uF that's 1 1/2”x3/8”.


----------



## tomb

Quote:


  Originally Posted by *pinkfloyd4ever* /img/forum/go_quote.gif 
_crap tomb, I forgot to mention one important thing last night, I was really tired. I prefer less bass than most. I mean, I like the sound of deep, impactful bass, but it hurts my ears after more than a few seconds. So, while I do like some quality bass, I'm more of a mids & highs guy. Most of all however, I love crisp, clean, minute detail. These are the reasons I decided to go with the BG NXs and the 2SC2238/2SA968 BJT pair. So, since neither B&D or Mouser have that BJT pair and Newark only offers it with a factory lead time of "less than 97 days"
	

	
	
		
		

		
		
	


	




 I'm guessing it's obsolete? Newark has a few of the 2SC2344/2SA1011 pair in stock and (in case thy sell out before I get around to ordering) the lead time for those is only 7 days. Soooo I think I might get my common parts there._

 

I know I post an awful lot, so if you don't read carefully, you may not see some things. Those transistors are not obsolete. I have talked to MCMinone and they assured me they were getting more in mid-October - that's imminent. There is also a local vendor in Atlanta who has 10 pairs right now. Finally, there were several links to these on e-bay.

 That said, the 2SC2344/2SA1011 pair may be brighter than most, so maybe you would prefer them. 

  Quote:


 Also, with regards to the Vitamin Q's, the .22uFs are only 1.5" long x 5/8" dia. and the .47s are even smaller. I know that's too tall for tombstoning, but wouldn't they fit horizontally? I'm getting those figures here. 
 

I think you mean 0.47's are larger. Regardless, there is room for 1" at CA9 in the back and 3/4" for CA8 in the front. They won't fit without those acrobatics I mentioned.

 EDIT: Panasonic FM caps are not "boutique," some of Amphead's comments notwithstanding. 
	

	
	
		
		

		
		
	


	




 They're at DigiKey and all the electrolytics listed on the MAX BOM under the DigiKey section are FM's.


----------



## tomb

Quote:


  Originally Posted by *luvdunhill* /img/forum/go_quote.gif 
_does anyone happen to have a part number handy for those panel mount test probe recepticles I see on your builds for tube biasing? I looked at the MM BOM and at Mouser under the test equipment section and came up empty handed.

 Thanks!_

 

On the MAX website under the case construction - wiring and assembly - about midway on the page under "Tip Jacks":
http://www.diyforums.org/MAX/MAXcasework3.php


----------



## tomb

Quote:


  Originally Posted by *smegger* /img/forum/go_quote.gif 
_i really would like to mount my tubes like this how wuld i goabout mounting them off the board_

 

You have to use chassis mounted sockets on the case lid and wire down to the pads on the board below. It's been done ... several times.


----------



## luvdunhill

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_On the MAX website under the case construction - wiring and assembly - about midway on the page under "Tip Jacks":
http://www.diyforums.org/MAX/MAXcasework3.php_

 

Tom:

 Thanks, and what a fantastic website!!


----------



## bou

So TomB, what you mean is that CA4 and CA5 are better with pana 1800uF FM than with 470uF Muse KZ??? That is what I have in wright now and I was wondering if I should change them for the 1800uF...

 Thank you
 Bou


----------



## pinkfloyd4ever

GAH!! Look at my edits tomb, I feel like we're playing ring-around-the rosie here
	

	
	
		
		

		
		
	


	




 Sooo is there someplace I can get all of the "common" parts including the 2 BJT pairs we've been discussing and the Panasonic FM's? Does digikey carry the both the 2SC2238/2SA968 and the 2SC2344/2SA1011 BJT pairs? I tend to shy away from Digikey cause Mouser & Newark's project managers & site designs are so much nicer & easier to use (and they're a bit cheaper) buuutt if they do have everything I'll go with em, after all i guess I do already have the links to all the parts right there on the BOM page


----------



## IcantHearU

Check out post #583 - I believe Tom gives the part number for the test points (the white ones at least) - Sorry I'm so lazy and can't cut and paste the link directly

 Directly from Max website - casework/wiring part 3

 The tip jacks used are about as cheap as they come - Mouser #530-105-0801-1. There are much better tip jacks available - but these are entirely functional, are totally insulated being plastic, and have a crimp/solder connection


----------



## n_maher

Quote:


  Originally Posted by *bou* /img/forum/go_quote.gif 
_So TomB, what you mean is that CA4 and CA5 are better with pana 1800uF FM than with 470uF Muse KZ??? That is what I have in wright now and I was wondering if I should change them for the 1800uF...

 Thank you
 Bou_

 

I'd be shocked if you could hear a difference. 

 You know, I feel like it's worth someone stepping in here and saying that I appreciate the lengths that folks are going to create the best sounding amp possible by cap-tweaking but there is no one-best-configuration. And considering that we don't all hear the same way it's even a bit more crazy. Don't get me wrong, I've experienced the difference between using UPW's on the output vs. much better caps but I'm more of a mind to think that once you get into the good range of caps (Cerafines, Silmic II's, BGs, Muze's, etc) that more than anything you're pretty much going to end up with a great sounding amp. I think I've heard 20 or so odd configurations of Milletts now and honestly, none have sounded bad. Some have certainly sounded better than others but more along the lines of preferring one to another rather than thinking one sounded deficient in a particular area.

 I respect what others are doing and saying in this thread, I just felt like a voice in semi-opposition was necessary since it seems like people are starting to stress about cap choices WAY more than I think is necessary.

 Just my 2¢.


----------



## tomb

Quote:


  Originally Posted by *bou* /img/forum/go_quote.gif 
_So TomB, what you mean is that CA4 and CA5 are better with pana 1800uF FM than with 470uF Muse KZ??? That is what I have in wright now and I was wondering if I should change them for the 1800uF...

 Thank you
 Bou_

 

No, I didn't say that. The Muse KZ's are boutique caps. I'm sure they're just fine. What I was referring to was about pennies-on-the-dollar UPW's, UHE's, FM's, and FC's. If you've followed the website and many of these posts, I've mentioned 1000uf power caps (which are still way smaller than those KZ's) are probably a minimum selection. After all, people put 4 x 1000uf in a PIMETA and 2 x 1000uf in a CMoy, sometimes. These are power caps. You can put the KZ's in there and probably get the same result, as Dsavitsk has posted previously.

 As sort of implied in Nate's post, which I generally agree with, it seems a poor savings to save $0.50 a cap for four caps at Mouser or DigiKey when many of you are spending much more elsewhere for less effect.

 I would also emphasize what I've been saying about the CA2 and CA9 positions. For some reason on the MAX, it has a huge effect. What I've said from the beginning is put 1000uf cap in CA2 and now I'm saying the plain old Wima may be better than anything else in CA9. So, to that extent, Nate and I are in agreement.

 Put another way, you'd be better off spending a couple of bucks extra to upsize those CA4/5 caps than spending $10, $20, etc. on boutique film caps.


----------



## tomb

Quote:


  Originally Posted by *pinkfloyd4ever* /img/forum/go_quote.gif 
_GAH!! Look at my edits tomb, I feel like we're playing ring-around-the rosie here
	

	
	
		
		

		
			





 Sooo is there someplace I can get all of the "common" parts including the 2 BJT pairs we've been discussing and the Panasonic FM's? Does digikey carry the both the 2SC2238/2SA968 and the 2SC2344/2SA1011 BJT pairs? I tend to shy away from Digikey cause Mouser & Newark's project managers & site designs are so much nicer & easier to use (and they're a bit cheaper) buuutt if they do have everything I'll go with em, after all i guess I do already have the links to all the parts right there on the BOM page_

 

Please read the BOM - all the info is there, and always has been:
http://www.diyforums.org/MAX/MAXbom.php

 There is an additional discussion on the Tweaks-MAX Boutique section of the website:
http://www.diyforums.org/MAX/MAXboutique.php

 If I'm personally stressing about anything, it's for some of you to pull out the Sonicap in the CA9 positions. That means you, too, Nate. Then be very careful what you might put back in there - a $1 Wima is fine, for instance. In the output position the Sonicap does wonders. In the cathode bypass area it stinks and ruins the sound of the amp.


----------



## Televator

well, dinner was nice, the family is happy, so I could go back to the Max and 

 ...

 it's alive... ALIVE I tell you! 
	

	
	
		
		

		
		
	


	









 Current configuration is the standard Jrossel kit: Panasonic FC 1000µF for CA2 / Muse UKZ 470µF for CA4, 5 & 7 / WIMA MKP10 .22µF for CA8 & 9 and MJE243/MJE253 transistor pairs.

 I just did a quick listening test, just to see if everything works ... so I hooked an old Panasonic PCDP (with no real line-out) to the inputs using a generic mini-mini and cheapo gator-clips (I will solder on the phono sockets when the rear plate is drilled); then I went through the usual suspect (my line-up of test-phones)

 - earphones of the Panasonic PCDP (just to see if it won't destroy my headphones):
 I needed to turn down the PCDP volume to 1-2/20 or the buds would have blown... but no (amp-induced) distortion, so on to the next one

 - Sennheiser HD497 (only used for testing nowadays): I listened to some Eels and I was constantly thinking "did Eels always have THIS much bass?" I was nearly shaking in my seat! So I did the logical thing... I put on some Laurent Garnier 
	

	
	
		
		

		
		
	


	




 I was in a freaking Nightclub! I avoid the HD497 mostly because they are way too muddy to my taste, but this was pure fun... the bass was hitting harder (and cleaner) than I've ever heard it through these Senns, though of course it still clouded most other frequencies. After 5 minutes, I had had enough of this sensation though and I switched to pair n°3

 - SR-60 (recabled/rescreened): back to Eels... the bass was still there 
	

	
	
		
		

		
		
	


	




 ... it didn't muddy the other frequencies anymore... but there was lots of it (relatively speaking for listening with a grado of course) and it was deep and punchy. I hardly listen to Beautiful Freak nowadays and only dug it up again to test my Cmoys/Alien DAC... but (uncritically) listening now I discovered unheard bass-lines on at least three songs on this album. Mids and highs were very good as well (pretty lush but still very detailed).

 To state the obvious, it sounded WAY better (well, better and beyond...squared...times 5 and a bit more) than the Cmoy I had used recently with these same cds but what was much more surprising to me was that it sounded soooo good already while I was only listening to a bad source connected through ultra-low-quality cables and bloody gator-clips!

 I am so much looking forward to listening to it with my NAD C542 as a source hooked up with decent cables and with my MS2i 
	

	
	
		
		

		
		
	


	




 but I will not try this until I have finished casing it (that is my incentive to get on with it...otherwise it'll stay half-finished like my cmoys/alien dac, which I really need to case up...right after I've done my Max 
	

	
	
		
		

		
		
	


	




 ) Once I've set it up in my home system, I'll try and write down some more critical impressions and perhaps do a comparison to the H5 in the Max impressions-thread.

 Thanks again to Colin, Tomb and all the others contributing to this project through co-designing, providing guidance or even asking the right questions in this thread (without you I wouldn't have been able to build this without real problems this early in my DIY-career)... and of course to Jrossel for providing kits which make this a very economic build for me as a non-US resident.

 PS: Sorry for the long post, but I'm really stoked with my (apparently successfully built) Max
 PS2: Sorry for this extra unnecessary glow-pic... but I just love seeing this stuff!


----------



## tomb

Excellent - Televator. Thank you for that fine post. We needed to hear that after some of this distracting capacitor discussion. 
	

	
	
		
		

		
		
	


	




 Big honkin KZ's, inexpensive little Wima films all around and another MAX lives!!


----------



## amphead

Awesome Televator! Another MAX lives! 
	

	
	
		
		

		
		
	


	










 I hope no one uses Panasonic FMs as boutique. They are not of course. On my system, the only boutiques that I have are the Jensens at CA8, and the Wimas at CA9(yes Wimas). Panasonic FMs are the ones used for Power Supply caps. Thats my view.


----------



## amphead

Feebleminded, I got your pm, but prefer to answer here. You will just have to keep waiting for the Max boards to become available again. I need a board myself.


----------



## fordgtlover

Quote:


  Originally Posted by *amphead* /img/forum/go_quote.gif 
_Awesome Televator! Another MAX lives! 
	

	
	
		
		

		
		
	


	










 I hope no one uses Panasonic FMs as boutique. They are not of course. On my system, the only boutiques that I have are the Jensens at CA8, and the Wimas at CA9(yes Wimas). Panasonic FMs are the ones used for Power Supply caps. Thats my view. 
	

	
	
		
		

		
		
	


	


_

 

Curiously, as I previously posted, the FMs in CA7 bypassed with the WIMAs sounded much better to my ears than the Elna Silmics, bypassed or not.

 [Shrugs]


----------



## ruZZ.il

So the bottom line is everyone experiment for themselves? sounds like more fun to me.. 
	

	
	
		
		

		
		
	


	



 Meanwhile.. I'm thinking we should start a post on diyforums, only with part numbers and locations.. no chitchat. I may get around to this sometime, but you're all welcome to beat me to it! 
	

	
	
		
		

		
		
	


	




 edit: Bits and Pieces!.

 I'll try contribute when I find my bits and pieces, and thank you in advance to everyone who does.


----------



## tomb

Quote:


  Originally Posted by *amphead* /img/forum/go_quote.gif 
_Feebleminded, I got your pm, but prefer to answer here. You will just have to keep waiting for the Max boards to become available again. I need a board myself. _

 

I am working with Colin on setting up purchases of more MAX boards from a web store. If I said more here, it would probably violate Head-Fi rules, so pay attention elsewhere if you can.


----------



## tomb

Quote:


  Originally Posted by *fordgtlover* /img/forum/go_quote.gif 
_Curiously, as I previously posted, the FMs in CA7 bypassed with the WIMAs sounded much better to my ears than the Elna Silmics, bypassed or not.

 [Shrugs]_

 

Not really too curious if you think about it - this is something Pete Millett has done for years - bypassing regular electrolytics with Wimas. That's where the practice of cap bypassing and the Wimas in Milletts came from. He had probably tested all of this many years before.

 To the extent that the FM caps are superior in its ratings to an Elna Silmic, if the Wima tempers the FM to make it suitable for an audio signal, then it stands to reason that the combination could end up better overall. After all - that was one of the guiding principles in Pete's Millett design: no expensive boutique caps needed.

 Yet, many of these combinations are unpredictable and defy any sort of independent measurement. What probably happens most often is the experience I had putting the Sonicap in CA9 - yuck. So when trying it and getting a similar result, some people may complain for the rest of their audiophile lives that bypassing with film caps sucks, smears the signal, etc., etc. Finding a truly good combination may be harder than it looks.

 Even so, the practice of bypassing large electrolytics with tiny box film caps goes way back - but it's probably been closely held and specific results remained unshared until people like Dsavitsk and the Humble Homemade HiFi guy came along. I hope Doug tests the Wima in the future, since that is the traditional Millett bypass cap and we could establish that as a baseline comparison with his other tests - hint, hint.


----------



## pinkfloyd4ever

DAMMIT!!! Digikey (the only place that has Panasonic FMs) doesn't have V-D resistors, Wimas, or wallwarts. Newark (the only place that has both the BJT transistors and other stuff I need) doesn't have Wimas, Panasonic FMs. Mouser (the only place with Wimas and wallwarts under $15) doesn't carry the BJTs or Panasonic FMs!!!! AAAHHHHHH 
	

	
	
		
		

		
		
	


	










 And then of course I hafta go to pCx to get BG's, tube sockets, & Kiwames. this is the part of DIY I hate, and I don't have time for it now with school. This is all gonna hafta wait awhile till thanksgiving or christmas or something. Why can't anyone else in the world give a crap about really hearing their music so all this stuff wouldn't be so spotty in the suppliers' selections? 
	

	
	
		
		

		
		
	


	




Sorry I just had to vent...


----------



## ruZZ.il

welcome  but.. we do make it easier..


----------



## amphead

Quote:


  Originally Posted by *fordgtlover* /img/forum/go_quote.gif 
_Curiously, as I previously posted, the FMs in CA7 bypassed with the WIMAs sounded much better to my ears than the Elna Silmics, bypassed or not.

 [Shrugs]_

 

Sorry Fordgtlover! I didn't mean to rain on your parade. If the Panasonic FM sounds good properly bypassed, then so be it. I was speaking in more general terms, not having tried it. I am using Panasonic HFS, in CA7 and it sounds good as well. Technically not boutique however. 
	

	
	
		
		

		
		
	


	



 Edit: In general, the rule of thumb, for boutique electrolytics is that they are bipolar, not of the polarized type.


----------



## Listen2this1

Since I have found time to work on the Max again after having problems, is it ok to run one channel at a time? Like not putting in Qb8/9 on one channel so I can see if the other is working properly first.


----------



## fordgtlover

Quote:


  Originally Posted by *amphead* /img/forum/go_quote.gif 
_Sorry Fordgtlover! I didn't mean to rain on your parade. If the Panasonic FM sounds good properly bypassed, then so be it. I was speaking in more general terms, not having tried it. I am using Panasonic HFS, in CA7 and it sounds good as well. Technically not boutique however. 
	

	
	
		
		

		
		
	


	



 Edit: In general, the rule of thumb, for boutique electrolytics is that they are bipolar, not of the polarized type._

 

No problems amphead. I didn't take the comments as a personal attack. I'm excited by the fact that I can roll a few different cap combinations through the Millett Max and assess the impacts. 

 We all think that we can build a better bikeshed (or mousetrap). We may all end up back at a similar (and perhaps already known) point - but the journey was fun.

 I currently have the 470uf FMs in CA4/5. I'll swap in some spare 1000uf Silmics (because I don't have any 1000uf FMs) and see how it sounds.


----------



## 04BluMach

Quote:


  Originally Posted by *pinkfloyd4ever* /img/forum/go_quote.gif 
_Also, with regards to the Vitamin Q's, ... but the for the real Qs .47uf is 1 1/8”x7/16” or 1 1/2”x1/2” and the .22uF is 1 1/2”x3/8” They also have a .27uF that's 1 1/2”x3/8”._

 


 Here is a Sprague VitaQ PIO 0.47uf 100V cap sourced from the EBay storefront LA SurplusElectronics - that's the real Sprague NOS Part too! 
	

	
	
		
		

		
		
	


	



 It is one of the 20 that came in the pack. All were of the same first quality NOS components. Excellent Ebay source - great communicator, super fast delivery. (No personal connection on my part)






 The basic dimensions, including the wire interconnection nipple points on each end, are approximately 1.5"x.5". To install on the MAX board will in all likelihood require tombstoning the CAP at boutique CA7 & CA9 bypass positions. Here is the VitaQ Snugged up to its ELNA SILMIC 470uf 50V Output Cap partner in my in process second MAX build. Note the height shown on the ruler indicates that this board needs to be slammed to the basement (first notch) to allow the top cover to slide in place with the standard Hammond case listed in the MAX BOM.






 Note that the VitaQ wire needs to be run through (encased) in either Teflon tube or very high quality Heat Shrink to protect from shorting out against the top of the case and maintain signal quality. The ELNA's originated from Handmade, Mouser was out at the time. But they got a free shipping ride since Handmade was the ready source for the Nichicon MUSE KZ's that are on the other end of this MAX's Board PS section.


----------



## tomb

Thanks for illustrating that, 04BluMach. Yes, those are the "genuine" Sprague Vitamin Q's. In addition, I have read that those with the numbers starting with 196P are the best, too - and that's also what those are.

 As you say, if you slam the board down to the bottom slot, many of these issues go away. You can tombstone them with enough clearance to work. If using 1" high parts and locating the board in the 3rd slot, then the real McCoy VitQ's are very problemmatic. You can fit almost anything in with enough preparation and effort, but it won't be easy going.

 Be attuned to those VitQ's in the CA9 positions. Colin seems to like his (he's got some off-brands that are 1-1/8"), but I haven't had much of a chance to ask how it sounds in detail. If you suspect anything less than singularly outstanding bass, you might try it without the VitQ's in the CA9 positions.

 That said, Dsavitsk has told us that the VitQ's, contrary to conventional wisdom, are actually quite flat in frequency response. If that's true, they may do very well - but I'd like more feedback if you can.


----------



## pinkfloyd4ever

I know u guys already said socketing the electrolytics is a bad idea, but how about the CA8 & CA9 film caps & the RB14 output resistors? Would those be ok to socket?


----------



## pinkfloyd4ever

Quote:


  Originally Posted by *04BluMach* /img/forum/go_quote.gif 
_








_

 

SWEEEETTT I can't believe nobody else has used em yet(or if they have, they haven't shown pix). I figured you'd prob wanna heatshrink the leads, but do you think shielding is a good idea too? Prob it's insignificant, but just wondering your (and others') opinions. You gonna be using all of those Q's?


----------



## 04BluMach

Well it may be a little over the top 
	

	
	
		
		

		
		
	


	




 But here is the second MAX build I currently have in process as seen from a front view.






 Elna Silmic 470uf 50V Output Caps are bypassed by Sprague VitQ 0.47uf 100V PIO Caps feeding to a Neutrik 1/4" Locking Panel Jack through Kiwami 20 Ohms 2W Carbon Resistors to add a little lushness to the tunes.






 Toshiba 2SC2238/2SA968 Bipolar Transistor Pairs (QB8/9) provide the driving force for the output buffer current in this MAX. They were sourced from MCM. 
 I have always wanted to try these BJT's in a Millet Buffer ever since reading Steinchen's glowing recommendation as his top pick for the dDB. Cost was reasonable with fast delivery through MCM. Actually - WHO CARED How Much $'s 
	

	
	
		
		

		
		
	


	



 (Don't go through Newark for these since they don't stock them - they are really dropped shipped via parent Company MCM).

 CA2 Caps are the Nichicon ES 1000uf 16V bypassed by Sprague VitaminQ PIO .15uf 100V. Nichicon KZ 470uf 50V are located in CA4 & CA5 board positions, bypassed by WIMA 0.01uf MKP10 Caps. Four Nichicon KZ 1000uF 50V Caps Tower over the PS regulator in the CR1 Slots. The Vreg on this build is a 3A Fairchild LM-350 since it is being fed by an AMSECO 24VAC 40VA Wall Transformer capable of 1.67A. Shooting for 29VDC at Veg output.






 TOMB.... There will be NO FUSES installed on this MAX


----------



## 04BluMach

Quote:


  Originally Posted by *pinkfloyd4ever* /img/forum/go_quote.gif 
_SWEEEETTT I can't believe nobody else has used em yet(or if they have, they haven't said here that they had & showed pix). I figured you'd prob wanna heatshrink the leads, but do you think shielding is a good idea too? Prob it's insignificant, but just wondering your (and others') opinions. You gonna be using all of those Q's?_

 


 The Tombstoned VitaQ's absolutely need insulation covering their bare wire leads if you are planning on using the Hammond Case's metal top. The wire can come in contact with top when closed up with any pressure applied to the top plate. 

 I really should have run it through Teflon Tubing (PFTE).

 I haven't decided exactly how the Cherry Wood for the top of the case is going to be mounted at this point. I may cut a larger opening in the metal so the wire will have no way of shorting out. 

 Anyway, I have some air dried Local Cherry selected for the Front/Rear and top panel.


----------



## amphead

04BluMach, Thats some beautiful work! Yeah we all want to know how it sounds.

 Well, it turns out that the Panasonic HFS, were a highly regarded type that was discontinued in 2000. Their claim to fame was low esr(equivalent series resistance)/low impedance. They are polarized, but they do sound heavenly. Without knowing where I originally obtained mine, I had put them in the Max out of convenience. Low esr is where its at, for sound quality!  Edit: Don't discount the effect that low esr caps will have at CA4/CA5. I notice a huge effect in soundstage/imaging/detail putting Panasonic HFS there! 

 TomB, off the top of your head, what electrolytic currently being used in the MAX has the lowest esr rating? Whatever it is, I will need to get some.


----------



## fordgtlover

I don't know where the fuse issue got to, but I have been running a slo-blo 1A since I built mine up - no problems.

 Cheers


----------



## 04BluMach

Quote:


  Originally Posted by *amphead* /img/forum/go_quote.gif 
_04BluMach, Thats some beautiful work! Yeah we all want to know how it sounds.
 Well, it turns out that the Panasonic HFS, were a highly regarded type that was discontinued in 2000. Their claim to fame was low esr(equivalent series resistance)/low impedance. They are polarized, but they do sound heavenly. Without knowing where I originally obtained mine, I had put them in the Max out of convenience. Low esr is where its at, for sound quality! _

 

Thanks for the compliment....! 

 Its actually been an easy build with tomb's PHENOMENAL website and cetoole's fantastic board layout. Plus, being the second board I've stuffed increases the confidence factor a little also.

 My born first MAX uses Panasonic FC's for the CR1's which aren't as low an ESR as the HFS nor even close to the current FM's. Digikey was out of the FM's at the time of order. That MAX sounds awesome.

 The Nichicon KZ's may not even be a better component than the Panny FM's for this PS Cap requirement.... But they sure look GOOD! Like FM's on Steroids
	

	
	
		
		

		
		
	


	




 Just wanted to have something a little over the top...


----------



## pinkfloyd4ever

Quote:


  Originally Posted by *pinkfloyd4ever* /img/forum/go_quote.gif 
_I figured you'd prob wanna heatshrink the leads, but do you think shielding is a good idea too? Prob it's insignificant, but just wondering your (and others') opinions. Quote:


  Originally Posted by *04BluMach* /img/forum/go_quote.gif 
The Tombstoned VitaQ's absolutely need insulation covering their bare wire leads if you are planning on using the Hammond Case's metal top. The wire can come in contact with top when closed up with any pressure applied to the top plate. 

 

_

 

just to clarify, I actually meant EMI shielding with something like this<click the "Tin Copper Braid" tab at bottom of the page] b/c I thought I read on this thread (maybe around when ferrari first posted in the MH Max thread) that remote-mounting caps can be a bad idea because the long wires can pick up EMI and it has a much greater effect on the sound when its in the middle of the signal path of an amp as opposed to at either end (i.e. wires going from the board to input/output jacks). SOOOO I'm just wondering how far that goes, if the long wire coming out the top when tombstonig an axial-leaded cap can have any such effect. I definitely agree that they should be electrically insulated with heat shrink, but that doesn't do much for EMI does it? I guess when using that copper braid shielding you'd first put a piece of heatshrink on the wire or lead, then the braid over that, and then a bigger piece of heatshrink?

 Am I going way overboard here? Though I do plan on upgrading sometime in the future, for now I'm a broke college student and I currently only have my computer with a Cotdt-modded Audigy 2ZS as a source and MS-1s as my primary cans. Holy crap I need to get to bed


----------



## Televator

wow, I thought my Max looked impressive with those Muse KZ's... great build there 04BluMach!

 well, regarding the fuse-issue: I had installed my fast-blow 1A that came with the Jrossel kit and at first few power-ups it all went smoothly (managed to bias everything and had it playing for a couple of hours).

 Shut it off for the night and powered back up next day (PCDP was playing already on power-up and HD497 was connected)... fuse blew with a nice flash!

 Switched power cable-entry around (avoiding the fuse) and switched back on. Checked everything and all voltages were still pretty close to biased values. Everything works just fine, but I haven't put a fuse back in... 

 I know Tomb isn't really pro-fuse 
	

	
	
		
		

		
		
	


	




 ... but what exactly am I risking if I just lose the fuse? (would make the layout for the back-plate easier and as I blew one fuse already without an evident reason, I guess there will be more to come)

 If you really think I should try to keep the fuse, what might have caused it to blow and how can I avoid this...


----------



## adfinni

Quote:


  Originally Posted by *amphead* /img/forum/go_quote.gif 
_04BluMach, Thats some beautiful work! Yeah we all want to know how it sounds._

 

Id love to know how these sound, but we'll let you enjoy the sound of the MAX as it is, because that's what it's for


----------



## tomb

Quote:


  Originally Posted by *Televator* /img/forum/go_quote.gif 
_wow, I thought my Max looked impressive with those Muse KZ's... great build there 04BluMach!

 well, regarding the fuse-issue: I had installed my fast-blow 1A that came with the Jrossel kit and at first few power-ups it all went smoothly (managed to bias everything and had it playing for a couple of hours).

 Shut it off for the night and powered back up next day (PCDP was playing already on power-up and HD497 was connected)... fuse blew with a nice flash!

 Switched power cable-entry around (avoiding the fuse) and switched back on. Checked everything and all voltages were still pretty close to biased values. Everything works just fine, but I haven't put a fuse back in... 

 I know Tomb isn't really pro-fuse 
	

	
	
		
		

		
		
	


	




 ... but what exactly am I risking if I just lose the fuse? (would make the layout for the back-plate easier and as I blew one fuse already without an evident reason, I guess there will be more to come)

 If you really think I should try to keep the fuse, what might have caused it to blow and how can I avoid this..._

 

Current inrush blew it. Most likely, amplfication of the signal with a connected load was just enough to send it over the edge.

 Saying I'm not pro-fuse is correct. It was a late change submitted by a third party. I was not in total agreement until Colin added the 3-pos terminal block that allowed one to bypass the fuse. It has caused a lot of problems - including messing up the backplate template.

 There are basically two main areas that one might want to protect with a fuse - 1) the transformer or walwart, and 2) the output transistors on the DB's. The only other item might be the LM317, but it already has internal thermal shutdown capability. There was a strange set of circumstances that caused the LM317's in STEPS and TREAD supplies to blow with the M3, but I think that it was relatively rare. If any of you ever suspect that, the immediate solution is the same as it was with the M3: use an LM338, which has a 5 Amp rating. I have only heard of one person having trouble with the LM317 on the MAX and it's not certain that was the issue.

 Anyway, the location on the board doesn't protect either of the two desired places very well, IMHO:

 1. The transformer and line-side wiring.
 Current inrush demands are 2 to 3 times the normal steady-state operation of the MAX, depending on your cap selection. Slo-Blo is the only way to protect the transformer or walwart. However, the best and only way to protect a walwart or line-connected transformer is to put the fuse _between_ the source and the load. That means the fuse should be on the line side ahead of the transformer primary. This is critical because the primary may remain connected for extended periods when the secondaries may not even be connected (iow, the amp is turned off). The location on the board does not meet that requirement. In any event, most walwarts are legally required to already have this fuse.

 It so happens that some walwarts have irreplaceable fuses, so it was suggested that this fuse would help protect that. However, it's still in the wrong place and will never protect for an outright short because of the current inrush, which is _after_ the fuse. It is possible, however, to set the fuse as a slo-blo at some value less than the walwart's rating (0.75A, 1A, 1.5A, etc.). That is the one way this fuse has any value, IMHO. Any other PS application for the fuse is confusing a STEPS configuration with the MAX's onboard Power Supply. This would come from a failure to recognize that unlike the STEPS, the MAX does not include an onboard transformer connected to line power.

 I suppose the fuse might protect the walwart/transformer secondaries, but again, this is not a recognized practice - the single fuse on the line side is supposed to do that. If it's drawing current through the secondaries, it's drawing current through the primary and line side.

 2. Protect the DB's
 As some of us unfortunately know, one can smoke the DB's if not careful during setup - even if everything is installed correctly.

 However, we already know that the current inrush on the MAX maybe as much as 2-3 times the steady state current draw. Since the fuse is located _prior_ to every bit of the capacitance on the board, it is impossible to size the fuse low enough to protect the DB's transistors, but high enough to withstand the current inrush. Most likely, the best way to apply a fuse to the DB's would be to fuse the V+ supply just ahead of each of the Left and Right channel DB's and use a minimum-sized, fast-blo fuse. (I am not aware of any DIY headphone amp that does this, btw.) Slo-blo is useless in protecting the DB's, IMHO.

 So, IMHO, losing the fuse loses you very little. That's just my opinion, though - others may disagree.


----------



## c0nsumer

Quote:


  Originally Posted by *fordgtlover* /img/forum/go_quote.gif 
_I don't know where the fuse issue got to, but I have been running a slo-blo 1A since I built mine up - no problems.

 Cheers_

 

Slow-blow fuses sort it out. Check the data sheet for most slow-blow fuses and you'll see that they can easily handle the inrush current I'd observed for a second or two, which is plenty.

 For reference I'm using Mouser part number 576-0218001.HXP (1A) and 576-0218.800HXP (800mA) in my two MAXes and things are great.

 -Steve


----------



## Televator

Thanks a lot for the quick and comprehensive answers guys... this is really why I love the Max-project!

 hm, decisions decisions... slo-blo or ditching it? I haven't drilled my plates yet, so I could look for an alternative placing and keep the slo-blo (doing some serious customization anyway as I'm moving the board to the second slot) or I could just desolder the clips so they are out of my way and ignore this feature...


----------



## n_maher

Hopefully I'll have the first MAX I'm building done by tomorrow night, the only board mounted component is the pot so it strays quite a bit from Tom's excellent layout.


----------



## vixr

Quote:


  Originally Posted by *n_maher* /img/forum/go_quote.gif 
_Hopefully I'll have the first MAX I'm building done by tomorrow night, the only board mounted component is the pot so it strays quite a bit from Tom's excellent layout._

 


 PICTURES!!! PICS PICS PICS!!!


----------



## n_maher

It's not gonna be anything all that special, just a variation on a theme and showing what can be done in a given chassis.


----------



## c0nsumer

Quote:


  Originally Posted by *n_maher* /img/forum/go_quote.gif 
_Hopefully I'll have the first MAX I'm building done by tomorrow night, the only board mounted component is the pot so it strays quite a bit from Tom's excellent layout._

 

You even got the resistors and small caps and stuff off the board? I'm really interested to see how you did that...

 -Steve


----------



## tomb

I think Nate means my casework layout, not the PCB layout - which of course, was cetoole's design.


----------



## nysulli

finally got around to making cables for the MAX, nothing special, just a 6 wire litz RCA to RCA 1 signal, 1 ground, 1 dummy wire grounded to a single end, basic replication of a kimber PBJ cable

 lower end got a nice boost, tightened up a tad as well, highs just as clear as they were before, maybe a tad cleaner

 now back to finishing up the casework, hopefully this weekend, but I actually have to force myself to stop listening to the MAX before i can get that done, i'll post pics when its finished, won't be anything out of the ordinary

 btw tomb, DB bias is up to 90 mA, sound seems to have a bit more fullness to it, little extra low end slam, with the highs its so hard to tell, maybe if i put the sonicaps back in it would be more noticable in that range, but at this point i think the wima's are the limiting factor for the highs


----------



## amphead

Can't wait to see your Max, Nate! 
 You've peaked my curiosity with only the volume pot mounted on the board. 

 Another exciting event, was the installation of some free Blackgate NX(N) 470uF at CA7. I know thats way too much luck for one builder since my boutique BJTs were given to me by another Headfier. Sure sounds good with Blackgate NX. Guess what? I'm risking a 16V rating there. I will let everybody know, if they don't burn up! I have 12 hours of tunes on them so far and they don't show any strain under the load.
 One of our esteemed fellow headfiers is shipping me his rig to get up and running. I'm doing it pro bono of course. Passing on the goodwill that has come my way!


----------



## amphead

Update: I tried another Blackgate NX(N) in parallel at CA7 and this sounded good also. But I didn't leave it that way for long, because I removed the extra set(NX) and replaced CA2 panasonic su 1000uF with them. So the boutiques are in all the best positions and the sound is very nice. Interestingly enough, I can't hear any loss of bass with 470uF (NX) at CA2. Just a nice linear response and low distortion. So far I'm bypassing the Blackgates, but might try removing those film/foil bypass caps.


----------



## Televator

quick question as I'm going to drill my plates in a few moments and all of a sudden I'm a bit confused... which connectors/chassis components need to be isolated? I'll make it a bit more specific...

 I know the PS-components (on/off switch and more importantly AC-in) need to be isolated from the chassis and from the pics in the builds gallery and going from the size of the holes in the chassis layout, the RCA-jacks don't need to be isolated (so grounded to chassis is ok I guess)

 But does the 1/4" socket need isolation or can it be grounded to the chassis as well? (in concretu: does the suggested neutrik jack _need_ the rounded black plastic rivet underneath the silver screw at the outside of the chassis or is it only _optional_?)


----------



## tomb

Quote:


  Originally Posted by *Televator* /img/forum/go_quote.gif 
_quick question as I'm going to drill my plates in a few moments and all of a sudden I'm a bit confused... which connectors/chassis components need to be isolated? I'll make it a bit more specific...

 I know the PS-components (on/off switch and more importantly AC-in) need to be isolated from the chassis and from the pics in the builds gallery and going from the size of the holes in the chassis layout, the RCA-jacks don't need to be isolated (so grounded to chassis is ok I guess)

 But does the 1/4" socket need isolation or can it be grounded to the chassis as well? (in concretu: does the suggested neutrik jack need the rounded black plastic rivet underneath the silver screw at the outside of the chassis or is it only optional?)_

 

The board-mtd Neutrik needs two of the plastic washers behind the endplate and the tapered plastic washer under the nut in front of the endplate. This is simply the way the geometry lines up, not anything to do with grounding.

 EDIT: The front edge of the board is lined up with the front edge of the Hammond body extrusion. The plastic bezels holding the endplate add about ~1/4" beyond that. If you don't use the bezels, that would put the endplate flush against the edge of the case and the board. You wouldn't need the two back washers in that instance. In either case, the plastic housing that the jack nut screws into ends up being the contact on the edges of the hole. The tapered front washer is meant to be used in every case for appearance. So, the end effect of the phone jack is that it is always isolated, anyway. :end EDIT

 The MAX, like every Millett before it, is negatively grounded, so "ground" may touch any part of the case. So, yes, the RCA jack's ground may be grounded to the case. In practice, this doesn't really occur except through the edges of the drilled hole, since the Hammond case is anodized (insulated). This would occur at the pot too, except that since the pot shaft must turn, there is usually too much clearance at the hole. That's why the ground wire is used on a screw on the back of the pot.

 The really important items you noted: the AC input must be totally isolated and the power switch as well - since it's switching AC. If the AC ever corrupts the negative ground of your MAX, you'll probably get a horrible hum that won't go away.


----------



## Televator

thanks Tomb... now I know all I need to know to finish my first Max!


----------



## joneeboi

I've been having a problem with my biased voltage. I mentioned it before but only managed a band-aid solution.

 Problem: I max out the trimmer and the highest voltage I can get is ~24.4V. All PS parts are BOM, although I did take out the LM317 once to add a silpad that ruZZ.il sent me.

 Should I just reflow everything and check back again later? I haven't seen this problem pop up in this thread yet except for when I first complained about it. I just want my MAX to sound its best, and it's kind of annoying to know that the only option I have is the minimum recommended voltage. Initial ideas?


----------



## tomb

Quote:


  Originally Posted by *joneeboi* /img/forum/go_quote.gif 
_I've been having a problem with my biased voltage. I mentioned it before but only managed a band-aid solution.

 Problem: I max out the trimmer and the highest voltage I can get is ~24.4V. All PS parts are BOM, although I did take out the LM317 once to add a silpad that ruZZ.il sent me.

 Should I just reflow everything and check back again later? I haven't seen this problem pop up in this thread yet except for when I first complained about it. I just want my MAX to sound its best, and it's kind of annoying to know that the only option I have is the minimum recommended voltage. Initial ideas?_

 

The voltage attained is largely dependent on the over-voltage present in the AC walwart, which is in turn dependent on the amperage rating.

 For instance, a loaded walwart that only produces 24VAC at its output, would only deliver - (0.9 * 24 * 1.414) - 1.4 Volts, or ~ 29Volts. However, the LM317 will burn at least 2V, perhaps 3. This is why we recommend 27V as the normal voltage setting on the MAX.

 If you're not getting that, there's an issue. I doubt seriously that it has anything to do with re-flowing the solder.

 What do you measure for AC Volts when the MAX is running? You can measure this at the screws on the AC input terminal block. If you've got less than 24VAC, then there's something wrong.


----------



## pinkfloyd4ever

Quote:


  Originally Posted by *amphead* /img/forum/go_quote.gif 
_Can't wait to see your Max, Nate! 
 You've peaked my curiosity with only the volume pot mounted on the board. 

 Another exciting event, was the installation of some free Blackgate NX(N) 470uF at CA7. I know thats way too much luck for one builder since my boutique BJTs were given to me by another Headfier. Sure sounds good with Blackgate NX. Guess what? I'm risking a 16V rating there. I will let everybody know, if they don't burn up! I have 12 hours of tunes on them so far and they don't show any strain under the load.
 One of our esteemed fellow headfiers is shipping me his rig to get up and running. I'm doing it pro bono of course. Passing on the goodwill that has come my way! _

 

ya I too noticed that there's no such thing as a 35V 470uf BG NX, but as expensive as they are (for those that dont know, 12.50 for the 16V 470uf), I think Im going to play it safe and spend the extra $1.45 for the 35V 680 uf


----------



## tomb

Generally speaking, the CA7 caps will sit constantly at approximately the bias voltage - whatever you've adjusted that to. So, depending on how you configured things, 12-15VDC. However, everytime you turn on the amp, until the tubes warm up and start to conduct (10-15sec?), those caps see the entire V+ voltage: 24-30VDC.

 EDIT: The V+ voltage is actually a peak that gradually declines over that 10-15 seconds until they settle in at the bias voltage.


----------



## amphead

Yeah, there is risk involved with 16V at CA7, and I am not going to recommend that everyone go out and get some. These were pro bono, and that was just enough incentive to spin the roulette wheel. If they fail, the most likely scenario is the loss of the cap that fails first. Then again since it is a premium cap, it may have a large margin of safety. Time will tell. After a three hour listening session they were dead cold to the touch, but this is definitely "experimentation".


----------



## Listen2this1

I am trying to Bias my amp. After I put the trimmers in 25 turns, how many out until I see any change?


----------



## Listen2this1

Ok I am having troubles again. I am wondering where I have gone wrong. This may take some thinking. My TA2R and TB1R are reading the same 13.6volts. Even with this reading the tubes glow a little and the heat sinks are not getting warm? I am wondering when I had the problem before if something serious did not happen? I hope someone out there can help. Thanks again


----------



## joneeboi

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_The voltage attained is largely dependent on the over-voltage present in the AC walwart, which is in turn dependent on the amperage rating.

 For instance, a loaded walwart that only produces 24VAC at its output, would only deliver - (0.9 * 24 * 1.414) - 1.4 Volts, or ~ 29Volts. However, the LM317 will burn at least 2V, perhaps 3. This is why we recommend 27V as the normal voltage setting on the MAX.

 If you're not getting that, there's an issue. I doubt seriously that it has anything to do with re-flowing the solder.

 What do you measure for AC Volts when the MAX is running? You can measure this at the screws on the AC input terminal block. If you've got 24VAC, then there's something wrong._

 

Checked the terminal block screws and I am indeed getting ~24VAC. In fact I'm getting 23.6VAC if that matters. I guess this means I need another wallwart (again). Any recommendations? Digikey have anything good?


----------



## fordgtlover

Well after much soldering and desoldering of caps I have finally finshed.

 For reference, I am running mosfets.

 I upgraded the CA4/5 caps from 470uf to 1000uf. I didn't notice any audible difference.

 I originally had Silmics in CA2/7 bypassed by WIMAs; I found this far too grainy for my taste. I bought some K42 PIOs off ebay as bypass caps. While they did help, it was still too grainy for my liking.

 Then, I replaced the Silmics with Panasonic FMs. These sounded OK bypassed by the WIMAs, but still a little too grainy. 

 The best combination I have found is Panasonic FMs in CA2/7 bypassed by the little PIOs.

 I have nice highs, solid mids and good bass. Nothing lacking, nothing over emphasised - sweet.


----------



## tomb

Quote:


  Originally Posted by *joneeboi* /img/forum/go_quote.gif 
_Checked the terminal block screws and I am indeed getting ~24VAC. In fact I'm getting 23.6VAC if that matters. I guess this means I need another wallwart (again). Any recommendations? Digikey have anything good?_

 

Oops - I meant to say "less than" 24VAC. I've edited the first post accordingly.

 You do have less than 24VAC - technically - it's enough to keep you from getting 27VDC after the reg. With that voltage, you should have ~28.6VDC feeding the regulator. Counting the drop across the regulator, you should be able to support 25-26VDC for V+. You're stating only 24VDC, but I wonder if it's really slightly higher, but not high enough to get to 27VDC.

 Knowing your history, you already blew one walwart - it's possible that you do have enough current draw in the amp that the current walwart simply can't support the voltage. I don't know - that's just a guess. Remind me what current you're drawing in the DB's.

 There are some walwarts at e-bay, but the best deal I've seen from an online dealer is from MPJA Electronics. This walwart is similar to the ones I use - 40VA - that's 1.67Amps:
http://www.mpja.com/prodinfo.asp?number=12637+PA


----------



## tomb

Quote:


  Originally Posted by *Listen2this1* /img/forum/go_quote.gif 
_Ok I am having troubles again. I am wondering where I have gone wrong. This may take some thinking. My TA2R and TB1R are reading the same 13.6volts. Even with this reading the tubes glow a little and the heat sinks are not getting warm? I am wondering when I had the problem before if something serious did not happen? I hope someone out there can help. Thanks again_

 

Remind me of your problem before and how it went away. 
	

	
	
		
		

		
			





 If TA2R and TB1R are at the same voltage, the the DB circuit is open on that side. You should be drawing ~10-20ma even at the lowest trimmer setting, I think. Look to see if there's a bad solder connection or whether something's come loose.


----------



## vixr

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Remind me of your problem before and how it went away..._

 

sounds like tomb needs to get rid of his plate and get a buffet platter...


----------



## Alcaudon

Has anybody ever used wima black box caps???? I`m plannning to try them at CA9 and CA8.


----------



## tomb

Alcaudon, YGPM.

 (I think it's a great idea.)


----------



## Listen2this1

My problem before is I smoked qb8/9. So I replaced them and rb10/11. Solder connections seem to be good. I went over them before I powered it up. I have a proto board, has there been any problems with them? This project just has me scratching the hair off of my head.


----------



## Ferrari

Quote:


  Originally Posted by *Listen2this1* /img/forum/go_quote.gif 
_... I have a proto board, has there been any problems with them? This project just has me scratching the hair off of my head._

 

There is no problem with the proto board. I have used this proto board on my build, even with Europeans transistors (BC550/560)... it works perfect!


----------



## joneeboi

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Oops - I meant to say "less than" 24VAC. I've edited the first post accordingly.

 You do have less than 24VAC - technically - it's enough to keep you from getting 27VDC after the reg. With that voltage, you should have ~28.6VDC feeding the regulator. Counting the drop across the regulator, you should be able to support 25-26VDC for V+. You're stating only 24VDC, but I wonder if it's really slightly higher, but not high enough to get to 27VDC.

 Knowing your history, you already blew one walwart - it's possible that you do have enough current draw in the amp that the current walwart simply can't support the voltage. I don't know - that's just a guess. Remind me what current you're drawing in the DB's.

 There are some walwarts at e-bay, but the best deal I've seen from an online dealer is from MPJA Electronics. This walwart is similar to the ones I use - 40VA - that's 1.67Amps:
http://www.mpja.com/prodinfo.asp?number=12637+PA_

 

I rechecked the terminal block voltage after letting it run for a bit and it got up to 25.2VAC, but it only put out 24.4VDC. I think the other one blew up because I stuck in the wall upside down. When I ordered the second one from Mouser that one came with a slip of paper telling me not to put it in upside down. Woopsies. At any rate my DBs are running at 106mV, so just about 50mA.


----------



## tomb

Quote:


  Originally Posted by *Listen2this1* /img/forum/go_quote.gif 
_My problem before is I smoked qb8/9. So I replaced them and rb10/11. Solder connections seem to be good. I went over them before I powered it up. I have a proto board, has there been any problems with them? This project just has me scratching the hair off of my head._

 

Yeah, Ferrari is correct - sort of. Actually, the 1st proto board has some issues - but not with the DB's. There are so few of us that even have the 1st proto boards, I probably shouldn't have even mentioned it. There are no problems whatsoever with the 2nd proto board, which is what most people have - if they have a proto.

 Anyway - it's picture time, I suppose. Right side only and underneath would probably suffice. That's all I can think of - unless you smoked the trannies again. Did you at least get some use out of them and then this happened suddenly again or what?


----------



## Listen2this1

I left the camera in my wifes jeep so pics will need to wait till tomorrow.


----------



## tomb

Quote:


  Originally Posted by *Listen2this1* /img/forum/go_quote.gif 
_I left the camera in my wifes jeep so pics will need to wait till tomorrow._

 

's OK. I'll be out of touch the rest of the day. Although, there are others who can help, too.


----------



## naamanf

Not sure if this has been covered but has anyone found a good source for 1000+mah walwarts? I let a friend barrow one of my MAXs and he has my power supply.


----------



## Troyhoot

I had wallwart troubles way back in the thread. Ended up getting a 2.0 amp off of ebay and had zero troubles keeping enough voltage since. The .75 and 1.0 amp ones just wouldnt cut it for my particular setup. 

 Got mine off ebay http://cgi.ebay.com/ws/eBayISAPI.dll...m=290145365981

 Thats about easiest place to find the larger ones IMO.


----------



## Ferrari

Thanks for being specific on the proto versions Tomb. 
 I'm indeed talking about the second version proto board and I knew that Listen2this1 is using this version as he post it earlier on post #1552.


----------



## tomb

Quote:


  Originally Posted by *naamanf* /img/forum/go_quote.gif 
_Not sure if this has been covered but has anyone found a good source for 1000+mah walwarts? I let a friend barrow one of my MAXs and he has my power supply._

 

From the previous page - these are 1.67Amps and only $7.95, but Troyhoot's version is an even better deal:

  Quote:


  Originally Posted by *tomb* 
_There are some walwarts at e-bay, but the best deal I've seen from an online dealer is from MPJA Electronics. This walwart is similar to the ones I use - 40VA - that's 1.67Amps:
http://www.mpja.com/prodinfo.asp?number=12637+PA_


----------



## tomb

Quote:


  Originally Posted by *Ferrari* /img/forum/go_quote.gif 
_Thanks for being specific on the proto versions Tomb. 
 I'm indeed talking about the second version proto board and I knew that Listen2this1 is using this version as he post it earlier on post #1552._

 

Yes, of course - I was just shooting the breeze about the 1st proto, probably because I'm building another one right now.

 Listen2this1 - What is that transistor you're using in the E12 delay? Thanks to Ferarri dredging up your original post and photo, I can see that's not a BD139. If it happens to have a reverse pinout compared to a BD139, that may be your problem. The delay circuit seems to dump back into the Right channel DB if something's at odds. That seems to be what's been happening with Pabbi on his BalMax or FrankenMAX, whichever he decides to call his balanced MAX.

 Let us know what that is so we can check it out. Again, if it's been leveraging current backwards, that may be what's blowing out your DB resistors.


----------



## thunder

With all other values of capacitors increased, Why has the power supply section not been altered or capacitance increased there to ?


----------



## pinkfloyd4ever

Quote:


  Originally Posted by *Troyhoot* /img/forum/go_quote.gif 
_I had wallwart troubles way back in the thread. Ended up getting a 2.0 amp off of ebay and had zero troubles keeping enough voltage since. The .75 and 1.0 amp ones just wouldnt cut it for my particular setup. 

 Got mine off ebay http://cgi.ebay.com/ws/eBayISAPI.dll...m=290145365981

 Thats about easiest place to find the larger ones IMO._

 

what do you do for the actual power cord from the transformer to the amp? I didn't see any, at least in that seller's store, and I couldn't find much besides AC-DC adapters when I searched


----------



## Televator

Cased my Max up (still going to do some things like shortening the pot shaft and some extra stuff to the top-plate which was slightly damaged due to my lack of carefulness 
	

	
	
		
		

		
			





 )

 but here she is (it definitely is a she 
	

	
	
		
		

		
		
	


	




 ) ...











 I took a bit of Vixr's layout but I slotted the board in the second slot so the Muse UKZ's fit underneath the top plate. I can still grab the tubes enough to switch 'em easily. The heatsinks wouldn't fit though... but hopefully this way they will cool a bit more as well than just with the holes. I've also added a bunch of test-points to the rear (like in Tombs layout) so it can be biased without opening.

 It is still running pretty hot with 40°C side buffer heatsinks (1.5"), 45° mid-buffer sinks (1.5") and 55° PS-sink (1") at 27Vdc, 13.5V 12FK6-tubes and 90mV DB's after running some 6 hours straight. But not too hot I guess.

 I'll take some better/more pics tomorrow and also again when I've finished modding the case (dunno when that's going to be) and I have a few more in-construction pics ... but perhaps Ill just upload them somewhere and link it all (or you can put them in the gallery if you're interested Tomb) in stead of clogging this thread further

 BTW: it sounds amazing with my NAD C542 + MS2i... but I'll keep the details for the review thread


----------



## tomb

Quote:


  Originally Posted by *pinkfloyd4ever* /img/forum/go_quote.gif 
_what do you do for the actual power cord from the transformer to the amp? I didn't see any, at least in that seller's store, and I couldn't find much besides AC-DC adapters when I searched_

 

Mouser sells 2.1mm plug/wire assemblies. I've bought many of these - they're 6 ft long and terminate in the typical 2.1mm plug:

172-4101

 EDIT: Very nice, Televator!!


----------



## tomb

Quote:


  Originally Posted by *thunder* /img/forum/go_quote.gif 
_With all other values of capacitors increased, Why has the power supply section not been altered or capacitance increased there to ?_

 

Nothing has changed. The board allowed that size of capacitors all along. I didn't change the BOM to 1000uf because Mouser's UPW's are out until late November. It's just a few pennies either way, though, but it does not affect the power section. There is no symmetrical relationship between the caps in the power supply and the caps that are used to decouple V+ from Ground at strategic points in the amp circuit.


----------



## adfinni

QUICK HELP PLZ !!!!!!!!!!!!!!!

 Is the way iv wired the AC input correct.... I know there is no switch, but im getting the amp up and running before the casework and don't wana blow it on the first switch on ?


----------



## Televator

looks ok to me (the ground is unused as should be and as far as I know, as it is AC it doesn't matter which thread connects which pole in regards to the other two connectors)... though I'd use some heatshrink on those exposed contacts so you do not accidentally short something against the AC


----------



## bperboy

Quote:


  Originally Posted by *Televator* /img/forum/go_quote.gif 
_looks ok to me (the ground is unused as should be and as far as I know, as it is AC it doesn't matter which thread connects which pole in regards to the other two connectors)... though I'd use some heatshrink on those exposed contacts so you do not accidentally short something against the AC_

 

Yes, since the AC alternates between the positive and negative, it doesn't matter which way its wired.


----------



## pinkfloyd4ever

Quote:


  Originally Posted by *bperboy* /img/forum/go_quote.gif 
_Yes, since the AC alternates between the positive and negative, it doesn't matter which way its wired._

 

really? I thought you were still supposed to run the hot through the switch and leave the neutral unswitched? The voltage doesn't actually switch back and forth between the 2 wires. The hot alternates between positive and negative voltage and the neutral is the return path. I don't know, maybe that doesn't matter in this case? Somebody who knows for sure (tomb, n_maher, or another EE), could you jump in here?


----------



## adfinni

cheers

 Well its the first power up and it's only temporary so i can get it biased and run in whilst i make the casework this weekend.

 now im gonna turn the trimpots to 0 ish before i turn it on. I know the trimpots for the db's have to be at minimum, but does it matter what the voltage reg trimmer and both the tube trimmers are set at on powerup ?


 edit:
 when i bump it on the tube led's come on, but in either db the multimeter shoots up and sits at 1 on the far left of the screen out of range. That is on either the voltage setting of 2000m or 200m......... Any advice what i should do as i don't wana blow these 3422's.

 another edit:
 im using db's so what ive jsut realised does it matter which way round the heatsinks are mounted with the attached db's ?


----------



## thunder

Tomb, What I meant to say was there is a provision for 4) 1000uf caps in that section, has anyone used more than 4000uf combined ? Say 4) 1500uf's ect...If so, What effect's would it have on performance, sonics ect... ?


----------



## bperboy

Quote:


  Originally Posted by *pinkfloyd4ever* /img/forum/go_quote.gif 
_really? I thought you were still supposed to run the hot through the switch and leave the neutral unswitched? The voltage doesn't actually switch back and forth between the 2 wires. The hot alternates between positive and negative voltage and the neutral is the return path. I don't know, maybe that doesn't matter in this case? Somebody who knows for sure (tomb, n_maher, or another EE), could you jump in here?_

 

All I know is that either way I wire it, it works and measures out correctly. Maybe I'm not right, who knows?


----------



## tomb

Quote:


  Originally Posted by *adfinni* /img/forum/go_quote.gif 
_cheers

 Well its the first power up and it's only temporary so i can get it biased and run in whilst i make the casework this weekend.

 now im gonna turn the trimpots to 0 ish before i turn it on. I know the trimpots for the db's have to be at minimum, but does it matter what the voltage reg trimmer and both the tube trimmers are set at on powerup ?


 edit:
 when i bump it on the tube led's come on, but in either db the multimeter shoots up and sits at 1 on the far left of the screen out of range. That is on either the voltage setting of 2000m or 200m......... Any advice what i should do as i don't wana blow these 3422's.

 another edit:
 im using db's so what ive jsut realised does it matter which way round the heatsinks are mounted with the attached db's ?
_

 

Adfinni - the 2SC3422/2SA1359's should be mounted on the right side of the heat sinks - _*in every case.*_ So, you've got a couple of them reversed there.

 Refer to the MAX website and the board legend at the bottom of the page here:
http://www.diyforums.org/MAX/MAXbjt.php

 Note that a complementary pair of BJT's go only on one side of the heat sinks in every case. They may be on the left - like MOSFETs, depending on the type, or they may be on the right - but they are all on one side or the other, period.


----------



## adfinni

Cheers tom, thought id got it wrong as ive just seen pics of everyones millett with them all on one side or the other.

 I hope nothing is blown !


----------



## tomb

Quote:


  Originally Posted by *bperboy* /img/forum/go_quote.gif 
_ Quote:


  Originally Posted by *pinkfloyd4ever* 
really? I thought you were still supposed to run the hot through the switch and leave the neutral unswitched? The voltage doesn't actually switch back and forth between the 2 wires. The hot alternates between positive and negative voltage and the neutral is the return path. I don't know, maybe that doesn't matter in this case? Somebody who knows for sure (tomb, n_maher, or another EE), could you jump in here?

 

All I know is that either way I wire it, it works and measures out correctly. Maybe I'm not right, who knows? 
	

	
	
		
		

		
		
	


	


_

 

You're both right - it really doesn't make a difference. One of the reasons the high-powered AC walwarts we've been talking about lately are available is that CCTV and security systems installers can run 24VAC without a license (and without knowing which is which). The AC can be transformed anywhere along the system for pennies so voltage drop is not the issue it would be with DC. So, they get the best of both worlds.

 However, for good practice - I put the hot leg on the center pin and switch that. That sort of follows the center-positive logic for DC, too.

 EDIT: But since I use screw-terminal walwarts, I don't know which one is the hot leg anyway!


----------



## tomb

Quote:


  Originally Posted by *thunder* /img/forum/go_quote.gif 
_Tomb, What I meant to say was there is a provision for 4) 1000uf caps in that section, has anyone used more than 4000uf combined ? Say 4) 1500uf's ect...If so, What effect's would it have on performance, sonics ect... ?_

 

I can't answer that. If height is not a restriction, I say go for it. Better get one of those high-powered walwarts, though, or you'll never get it turned on. 
	

	
	
		
		

		
		
	


	




 Whether you can hear any difference - I seriously doubt it. IMHO, the PS is perfect. Just build it exactly as spec'd and fuhgeddaboudit.


----------



## thunder

That's good to hear! I've got 1000 uf KZ's for that position, I didn't want to read later that someone struck sonic bliss 
	

	
	
		
		

		
		
	


	




 with something larger. Again I would like to express my many thank's I believe a great many of us would be lost w/o Dr. Tomb! Thank-you


----------



## adfinni

Well switched round the two tannies that were the wrong way round and am soldering up again. Also just noticed that i forgot to solder 1 leg on each of the caps at C7 positions. silllly me.


----------



## amphead

Great work Televator! Nice to see all the variations on the MAX!

 Update: After 24 hours, I am still very happy with Blackgate N 16V at CA2 and CA7. I guess Blackgate N are equivalent to NX, but don't know. One website lumped the description: Black Gate (N NX NX Hi-Q) - "The king of Black Gate realizes perfect non-polarized operation for the first time, holds a revolutionary features. Improves any equipment performance a great deal. No capacitor can be equal in digital pulse transfer at super high speed." A typo in their description, because it came from Japan. I was listening to some CDs that previously sounded too veiled without the Blackgates. 20 hours on the 16V caps so far.


----------



## adfinni

ok my multimeter has x2 voltage regions on it. One has a solid line with a dotted line under it and 1000,200,20,2000m,200m settings, the other has V with a wiggly line under it and 750,200 settings. Which one should i be using ?????????????

 readings (V with soid line and dotted under)

 VREG = 27V
 Vtube left = 17.7V .........right =17.5V (this is with both trimpots ALL way anti clockwise until clicks)
 db's left = 17.8V.... right =17.5V (trimpots about all way clockwise)


 readings (V with wiggly line)

 VREG = 58.8V
 Vtube left = 38.5V .........right =37.8V (this is with both trimpots ALL way anti clockwise until clicks)
 db's left = 38.6V.... right =37.9V (trimpots about all way clockwise)


 How should i be measuring these bad boys, o and btw music coming out thru the grados for 20 secs and it sounds ok to me.


----------



## tomb

Adfinni:

 1. The straight line and dotted line indicate a two way voltage with different polarity on each leg. That's DC and is the scale you should use. The squiggly is a wave, meaning a sine wave and AC/alternating current.

 2. It looks like you are still using Ground as your reference point to measure the DB's. This is incorrect. Your reference points for measuring bias are the ends of the power resistors, RB10L/R and RB11L/R.

 So for the Left channel, you put one probe at TA2L and one probe at _either_ TB1L or TB2L.

 For the right channel, you put one probe at TA2R and one probe at _either_ TB1R or TB2R.

 There are two "ending" reference points for each DB since there are two transistors - a PNP and a NPN. The thing to do is measure the highest of the two and go by that to be safe. Chances are that they are close, but not exactly the same.

 What's going on is that you are measuring the bias (constant) current going through the DB by referencing the voltage across the output power resistors (RB10L/R and RB11L/R). Since those resistors are 2.2ohms, dividing the measured voltage in mV by 2.2 gives you your current. For instance, if you are looking to bias up to 50ma, then you would *gradually *work up to about 110mV.

 All of this is explained, including a photo legend of the measuring points for your probe, on the MAX website under "Bias and Setup":
http://www.diyforums.org/MAX/MAXsetup.php
 (click on the photo to see a large size version of the board and the bias points).

 P.S. The tube trimmers should turn _counter-clockwise_ to _lower_ the bias voltage.


----------



## adfinni

Hahahaha no more cider for me tonight. You know i have actually been using the page you linked to for the last hour anyway..... coming up to 3.30am so i should go to bed.

 Vreg @ 27v
 db's at 90ma

 BUT tubes stuck at 17.6 V each and that's with it all the way anti-clockwise until clicks... hmmmmmmm

 well the amp is on my desk and have my cd-player on my lap listening to some orbital, and WOW...... better than my boutiqe rev millett, greater accuracy, wider soundstage even with these HF-1's, and loads of BOOOM BOOOM.

 Just put on some howling bells and screw*** HELL 
	

	
	
		
		

		
		
	


	






















 My god this is a big step up from a boutique old skool millett.... Can't wait for the tubes and BG's to burn in.


----------



## Troyhoot

Quote:


  Originally Posted by *pinkfloyd4ever* /img/forum/go_quote.gif 
_what do you do for the actual power cord from the transformer to the amp? I didn't see any, at least in that seller's store, and I couldn't find much besides AC-DC adapters when I searched_

 

Heh, I just used some starquad myself. 2wires per terminal and hard wired it in. Then covered it in some gold techflex to match my Solid brass knob.
http://img134.imageshack.us/my.php?image=img3463yt1.jpg


----------



## pinkfloyd4ever

Quote:


  Originally Posted by *Troyhoot* /img/forum/go_quote.gif 
_Heh, I just used some starquad myself. 2wires per terminal and hard wired it in. Then covered it in some gold techflex to match my Solid brass knob.
http://img134.imageshack.us/my.php?image=img3463yt1.jpg_

 

holy crap, I was gonna say that's bordering on something ferrari would do, but then again, you are using it with Equations. Anyway, very nice. I'll probably stick with something a little cheaper though, for now anyway


----------



## adfinni

IT OFFICIALLY LIVES !!!!!!!!!!!!!!!!!

 Well ive lowered my Vreg voltage to 24V which has brought the tube voltages down to a safe 15.8V. Any suggestions on which resistor size for r1 i should try for R1 as my readings are a lot higher for this 10ohm resistor than the instructions on the MAX page. tempted to try a 30ohm as at 27V voltage my tubes don't go lower than 17.8V and that's with the trimmers at minimum.

 Anyhow the sound..... Well still only got a few hours on it, and have just put on 'nerina pallot - fires' and at the beginning of tracks 7+8 i can hear somethings ive never heard before. On one track i think it's her foot tapping and on the other it seems to be a squeak from one of the peddles on the piano she's playing... What a resolving amp


----------



## tomb

Quote:


  Originally Posted by *adfinni* /img/forum/go_quote.gif 
_IT OFFICIALLY LIVES !!!!!!!!!!!!!!!!!

 Well ive lowered my Vreg voltage to 24V which has brought the tube voltages down to a safe 15.8V. Any suggestions on which resistor size for r1 i should try for R1 as my readings are a lot higher for this 10ohm resistor than the instructions on the MAX page. tempted to try a 30ohm as at 27V voltage my tubes don't go lower than 17.8V and that's with the trimmers at minimum.

 Anyhow the sound..... Well still only got a few hours on it, and have just put on 'nerina pallot - fires' and at the beginning of tracks 7+8 i can hear somethings ive never heard before. On one track i think it's her foot tapping and on the other it seems to be a squeak from one of the peddles on the piano she's playing... What a resolving amp 
	

	
	
		
		

		
			



_

 

Adfinni - 
 What size trimmers did you put for the tube bias at RA1L and RA1R? Those should be 5K, because what you describe for the bias on your tubes _should not be happening._

 R1 has _absolutely nothing_ to do with the bias voltage on the tubes. Also, let's look at your CCS. The default configuration is 11.3*K* for RA9L/R and only 1.13K for RA8L/R. So, RA9L/R must be ~10 times RA8L/R. Also, did you use two 2N5087's for the CCS transistors - QA1L/R and QA2L/R?

 Lastly, are you measuring the tube bias in VDC from Gnd to TA2L and TA2R? There are three GND test points on the board with the production version, so they should be easy to hit. Then measure from there to TA2L for the left tube, adjusting with RA1L. For the right channel, measure from one of the GND test points to TA2R, adjusting with RA1R.

 The tubes are remarkably lenient with voltage bias, but we need to fix this before you go further, I think. 
	

	
	
		
		

		
		
	


	







 EDIT: Sorry for being a downer on the enthusiasm - Congratulations on finishing it!! It's just that there is something in error and you shouldn't be thinking about changing the heater resistor to adjust the bias on the tubes.


----------



## tomb

I sort of believe in the MAX. 
	

	
	
		
		

		
		
	


	




 What I've been working on lately (and it's going so slooow):


----------



## MrMajestic2

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_I sort of believe in the MAX. 
	

	
	
		
		

		
		
	


	




 What I've been working on lately (and it's going so slooow):

 [URL="http://www.beezar.com/misc/MAX/5MAXes-large.jpg"[/URL]_

 

Wow, thats a s**t load of Millets 
	

	
	
		
		

		
		
	


	




 Very nice indeed. Are you just trying different configurations or are you building them for someone else?

 My Millet building is going quite slow also. Started my second one today. Hopefully it will be finished this weekend with some VitaminQs in it 
	

	
	
		
		

		
		
	


	




 By the way, I swapped my LM317 in my first build for the LM338 and I will try to fire this baby up tomorrow using 30V, wohoo.


----------



## adfinni

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Adfinni - 
 What size trimmers did you put for the tube bias at RA1L and RA1R? Those should be 5K, because what you describe for the bias on your tubes should not be happening.

 R1 has absolutely nothing to do with the bias voltage on the tubes. Also, let's look at your CCS. The default configuration is 11.3*K* for RA9L/R and only 1.13K for RA8L/R. So, RA9L/R must be ~10 times RA8L/R. 

 Lastly, are you measuring the tube bias in VDC from Gnd to TA2L and TA2R? There are three GND test points on the board with the production version, so they should be easy to hit. Then measure from there to TA2L for the left tube, adjusting with RA1L. For the right channel, measure from one of the GND test points to TA2R, adjusting with RA1R._

 

Those bits are all fine and reading points are all correct, i just followed the BOM. O and i tried biasing the tubes way outta spec last night, from 17V to about 23V. AS i got higher the sound lost the soundstage, dynamics, highs, mids and just about everything else.

  Quote:


 Also, did you use two 2N5087's for the CCS transistors - QA1L/R and QA2L/R? 
 

No there are x2 5088's each side... Why i don't know, i was the most methodical iv ever been when sorting those out.... I phail at life 
	

	
	
		
		

		
		
	


	




 Where would i be without you 
	

	
	
		
		

		
		
	


	





  Quote:


 EDIT: Sorry for being a downer on the enthusiasm - Congratulations on finishing it!! It's just that there is something in error and you shouldn't be thinking about changing the heater resistor to adjust the bias on the tubes. 
 

hehehe that's a good thing, and cheers for the correction, you pinpointed it in the 2nd paragraph of your post with it being the wrong trannies. 

 O and x5 boards with ranks of capacitors like soldiers in their units... NICE !


----------



## tomb

Quote:


  Originally Posted by *MrMajestic2* /img/forum/go_quote.gif 
_Wow, thats a s**t load of Millets 
	

	
	
		
		

		
		
	


	




 Very nice indeed. Are you just trying different configurations or are you building them for someone else?</snip>_

 

One of the two BG versions is for someone else. All the rest are mine - at least for as long as I can afford to keep them. 
	

	
	
		
		

		
		
	


	




 Except for the duplicate BG versions, this is mostly a test of transistors: four different combinations of BJT's. The two BG versions have 2SC2238/2SA968. Then there are separate versions using ES caps and 2SC3421/2SA1358, 2SC3422/2SA1359, and 2SC2344/2SA1011. When finished and combined with my existing MAXes, I'll have two versions of the 2SC3422/2SA1359 BJT's so that I can make one-to-one comparisons with different film caps in the future. At least that's the plan.


----------



## tomb

Quote:


  Originally Posted by *adfinni* /img/forum/go_quote.gif 
_Those bits are all fine and reading points are all correct, i just followed the BOM. O and i tried biasing the tubes way outta spec last night, from 17V to about 23V. AS i got higher the sound lost the soundstage, dynamics, highs, mids and just about everything else._

 

Just for future reference, this is how a biased tube works. As you approach the supply voltage, the tubes stop conducting until there is zero sound. The ideal is halfway between the supply voltage and zero (ground). What that does is let the signal wave swing equal amounts in both positive and negative directions, centered around the bias voltage as the effective zero line of the signal wave.

  Quote:


  Quote:


  Originally Posted by *tomb* 
_Also, did you use two 2N5087's for the CCS transistors - QA1L/R and QA2L/R?_

 

No there are x2 5088's each side... Why i don't know, i was the most methodical iv ever been when sorting those out.... I phail at life 
	

	
	
		
		

		
		
	


	




 Where would i be without you 
	

	
	
		
		

		
		
	


	



  Quote:


  Originally Posted by *tomb* 
_EDIT: Sorry for being a downer on the enthusiasm - Congratulations on finishing it!! It's just that there is something in error and you shouldn't be thinking about changing the heater resistor to adjust the bias on the tubes._

 

hehehe that's a good thing, and cheers for the correction, you pinpointed it in the 2nd paragraph of your post with it being the wrong trannies. 
 

Thanks - just wanted to make sure you're getting the MAX enjoyment out of your MAX. 
	

	
	
		
		

		
		
	


	



  Quote:


 O and x5 boards with ranks of capacitors like soldiers in their units... NICE ! 
 

Yeah, and they better follow the plan of attack!


----------



## adfinni

Thanks, and does it matter if the 5087's in the ccs arnt matched closely to the other ones in the dB section?

 I know that in the CCS matching is critical.


----------



## tomb

Quote:


  Originally Posted by *adfinni* /img/forum/go_quote.gif 
_Thanks, and does it matter if the 5087's in the ccs arnt matched closely to the other ones in the dB section?

 I know that in the CCS matching is critical._

 

Correct and correct. 
	

	
	
		
		

		
		
	


	




 'Course, matching two 5087's together is almost trivial probably within 10-20 HFE is fine. The ones for the Left tube should probably be close to the HFE's of the ones for the Right tube, but even that's not that critical.


----------



## pinkfloyd4ever

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_I sort of believe in the MAX. 
	

	
	
		
		

		
		
	


	




 What I've been working on lately (and it's going so slooow)_

 

hah, no way I woulda never guessed
	

	
	
		
		

		
		
	


	



  Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_ The two BG versions have 2SC2238/2SA968. Then there are separate versions using ES caps .... and 2SC2344/2SA1011._

 

ooo verry niace!(Borat style) You wouldn't happen to also have a BG version using the 2SC2344/2SA1011 pair would you? Cause I'd def be interested in a comparison
	

	
	
		
		

		
		
	


	




 I'm guessing that one board closest to the camera is the prototype board you were talking about? Oh and those wouldn't happen to be VitQs peeking into the corner of that pic would it?

 I'm finally done with those midterms, and man I really wish I had money to get all the parts for at least one of my MAXes. Oh well, they say patience is a virtue, I wish it seemed like it now, rather than torture


----------



## tomb

Quote:


  Originally Posted by *pinkfloyd4ever* /img/forum/go_quote.gif 
_hah, no way I woulda never guessed
	

	
	
		
		

		
		
	


	





 ooo verry niace!(Borat style) You wouldn't happen to also have a BG version using the 2SC2344/2SA1011 pair would you? Cause I'd def be interested in a comparison
	

	
	
		
		

		
		
	


	




 Obviously you know, but for those who don't, the 2SC2238/2SA968 BJT pair is back in stock @ MCM. I'm guessing that one board closest to the camera is the prototype board you were talking about? Oh and those wouldn't happen to be VitQs peeking into the corner of that pic would it?_

 

Actually, MCMinone is still out of stock on the 2SA968.
	

	
	
		
		

		
		
	


	




 No, both BG versions are using the 2SC2238 pair - that one tests out as most neutral and detailed (on previous Millett Hybrids). My favorite pair is still the 2SC3422/2SA1359, but I may change my mind when I get these BG's built - we'll have to see. I also think the 2SC3421/2SA1358 is a good second choice, but who knows - I may change my opinions when these get built.

 Yes, that little one is the 1st prototype - it's sized to fit into a Lansing case - there's only about 1/8-1/4" clearance on the top and the bottom. I have to put the PS caps and rectifiers offboard inside a Jameco walwart case. There are other ways to do it, but this is the way I've chosen. The ground plane went the length and width of the board and it picks up the hum from the AC input and ripple from the PS caps. So, essentially, I turn it into a DC-fed MAX. Hopefully, it will excite enough of you when I get it cased up to be another option for building a MAX. It's an easy matter for Colin to fix the ground plane and order more boards that would work the way they're supposed to.

 There are some other limits - not much room for caps, for instance, and MOSFETs are out of the question if you use the Lansing case. Still, it's pretty cute at the smaller size and low profile shape. I'm charged about getting it done. 
	

	
	
		
		

		
		
	


	



  Quote:


 I'm finally done with those midterms, and man I really wish I had money to get all the parts for at least one of my MAXes. Oh well, they say patience is a virtue, I wish it seemed like it now, rather than torture


----------



## Listen2this1

Tomb the trans in the delay circuit is http://www.mouser.com/search/refine.aspx?Ntt=nte375, this was the replacement to the one on the BOM I quess I should of checked it out before I installed it, but you said the E12 circuit feeds back into the right channel. I am getting the same voltage on the left channel as well. This build is really making me feel that I am a Dumb A**. It has really killed some brain cells. Here are the new pics:


----------



## pinkfloyd4ever

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Actually, MCMinone is still out of stock on the 2SA968.
	

	
	
		
		

		
		
	


	




 No, both BG versions are using the 2SC2238 pair - that one tests out as most neutral and detailed (on previous Millett Hybrids)._

 

really? crap, I guess I just looked at the 2SC2238 and saw the "other people bought 2SA968" thing and assumed they were both in stock. What are those big red electrolytics, Cerafines?
 And is it just an illusion or is that upper left board really wide?


----------



## smegger

hi would this be ok for chassis mounting the tubes for a max?
http://cgi.ebay.co.uk/ws/eBayISAPI.d..._promot_widget


----------



## n_maher

Quote:


  Originally Posted by *pinkfloyd4ever* /img/forum/go_quote.gif 
_What are those big red electrolytics, Cerafines?_

 

BlackGate nonpolars.

 My MAX is complete, shame that this one isn't sticking around long.


----------



## pinkfloyd4ever

Quote:


  Originally Posted by *n_maher* /img/forum/go_quote.gif 
_BlackGate nonpolars._

 

oh really? NX's are red? Hmm, news to me, for some reason I thought they were navy blue or something


----------



## tomb

Quote:


  Originally Posted by *n_maher* /img/forum/go_quote.gif 
_
 My MAX is complete, shame that this one isn't sticking around long.
_

 

Very, very nice, Nate! I like the variation on the holes. Those RCA jacks look very "MAXey" - large and substantial. Who makes those?


----------



## n_maher

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Those RCA jacks look very "MAXey" - large and substantial. Who makes those?_

 

Partsconnexion (sponsor link at top of the forum for those interested), very reasonably priced for how good they are to work with.


----------



## joneeboi

And THAT's why I asked vacuumtubes.net for only halos. Oh well, 5 pairs of non-haloed getters is just as impressive looking.

 I guess.


----------



## tomb

Quote:


  Originally Posted by *Listen2this1* /img/forum/go_quote.gif 
_Tomb the trans in the delay circuit is http://www.mouser.com/search/refine.aspx?Ntt=nte375, this was the replacement to the one on the BOM I quess I should of checked it out before I installed it, but you said the E12 circuit feeds back into the right channel. I am getting the same voltage on the left channel as well. This build is really making me feel that I am a Dumb A**. It has really killed some brain cells. Here are the new pics:
_

 

OK - let's dismiss the power transistor in the E12, then. I just thought it looked odd, so I mentioned it.

 Looking at your pics - very good top view, btw - I honestly can't see anything out of place. So, the only thing I know to do is go through a list. Some of these will probably seem obvious, but here goes:

 1. Your main problem is no apparent voltage difference from TA2 to TAB1 or TAB2 (Left and Right). Please tell me that you are not measuring both of these points referenced from Ground and expecting to subtract the difference.

 The DB's are current buffers - meaning, they add no more voltage to MAX's output from the tubes. So, referenced to Ground, the output of the DB (at the output power resistors) will be the very same voltage as the tube bias point referenced to Ground. That's why your DB bias is referenced not from a new point that might be the starting lead of the resistors, but the very same bias test point used for biasing the tubes.

 However, what you are biasing is the current, not the total voltage. The way this is measured is by measuring the current across the output power resistors. You do this by measuring mV from TA2 to TAB and dividing by the value of the resistor - 2.2 ohms. This mV that you are measuring is the local voltage across the resistor only - it has nothing to do with the voltage level referenced to Ground - and referenced to Ground means nothing in this instance.

 Come to think of it, I'll stop with the list right there. Please tell me if this is what you were doing. If so, then start measuring those mV across TA2 and TAB and bias the DB's accordingly. Let us know in either case and we'll go from there.


----------



## tomb

Made a bit of progress today:





 EDIT: Phew! Just finished the 5th board.


----------



## Listen2this1

Ok I am biased THANKS GUYS, I have tried to read the pin config on the Qm1 in the BOM and the QM1 that I got as a out of stock sub, but the drawing on the one I got http://www.nteinc.com/specs/300to399/pdf/nte375.pdf is hard to understand (My trans does not have any chamfered edges to go off of) and the one on the BOM http://www.fairchildsemi.com/ds/BD/BD139.pdf Since Tomb brought it up ealier I am trying to see if I have the pins reversed. All because I think the e12 is not working correcty.


----------



## tomb

Quote:


  Originally Posted by *Listen2this1* /img/forum/go_quote.gif 
_Ok I am biased THANKS GUYS, I have tried to read the pin config on the Qm1 in the BOM and the QM1 that I got as a out of stock sub, but the drawing on the one I got http://www.nteinc.com/specs/300to399/pdf/nte375.pdf is hard to understand (My trans does not have any chamfered edges to go off of) and the one on the BOM http://www.fairchildsemi.com/ds/BD/BD139.pdf Since Tomb brought it up ealier I am trying to see if I have the pins reversed. All because I think the e12 is not working correcty._

 

Looking at the spec sheets you reference, the NTE goes Base-Collector-Emitter. Unfortunately, the BD139 goes Emitter-Base-Collector. So, the pinouts are reversed.


----------



## amphead

Nice view TomB! An army of MAXs in formation, ready to do battle. he he
 I think I spy some Blackgate NXs. Did you prefer the sound of the NXs or the Muse ES? Or was it apples and oranges, both good but different?
 I'm looking forward to some more boards when they become available.


----------



## tomb

Quote:


  Originally Posted by *amphead* /img/forum/go_quote.gif 
_Nice view TomB! An army of MAXs in formation, ready to do battle. he he
 I think I spy some Blackgate NXs. Did you prefer the sound of the NXs or the Muse ES? Or was it apples and oranges, both good but different?</snip>_

 

Those pics are of the work I _just_ completed yesterday. Gimme a minute to wire them up and turn them on and I'll tell ya.


----------



## adfinni

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Those pics are of the work I just completed yesterday. Gimme a minute to wire them up and turn them on and I'll tell ya. 
	

	
	
		
		

		
		
	


	








_

 

Don't forget that those BG's might change significantly during burn in. Im not gonna give any real sonic impressions + reviews until the UK hi-fi meet, as mine should be nicely run in then for a good 200 hours.

 And boy does this Vreg put out a serious amount of heat. The heatsink is too hot to touch for more than 3 seconds. At least it shows the thermasil pad is doing its job. The dBs don't feel too hot, but the centre 2 heatsinks are hotter than the outer one, and that's with them biased at 103mV.

 Tom: changing those 5088s to 5087s have allowed my tubes to balance out nicely at 13.5V


----------



## tomb

Quote:


  Originally Posted by *adfinni* /img/forum/go_quote.gif 
_Don't forget that those BG's might change significantly during burn in. Im not gonna give any real sonic impressions + reviews until the UK hi-fi meet, as mine should be nicely run in then for a good 200 hours._

 

Yes, of course - I was being toungue-in-cheek with Amphead, there. With BG's, Dsavitsk suggested that I just hook the amp up and let it run for a week before I even listen to it for the first time. 
	

	
	
		
		

		
		
	


	




  Quote:


 And boy does this Vreg put out a serious amount of heat. The heatsink is too hot to touch for more than 3 seconds. At least it shows the thermasil pad is doing its job. The dBs don't feel too hot, but the centre 2 heatsinks are hotter than the outer one, and that's with them biased at 103mV. 
 

Yes, as with any design, there are compromises. I'm not sure that Colin could have located the center sinks any better - there are serious downsides with locating them another way, and it was tried before. What is happening, of course, is that there isn't enough airflow betwen the two sinks. As you say, if the heat sink is not getting hot, then something is wrong. If you have any doubt, the thing to do is measure the plastic part on the reg or the transistor. This is just my own rule-of-thumb judgment, but if it's less than about 70deg.C. (~160deg.F.), you're OK. To be truthful, all of the parts can withstand probably twice that much. A good reference is to remember that on the little DB boards in the original revMH Millett Hybrid, the transistors were literally too hot to touch - even for a second. Ones with a metal back were very close to rendering a burn. Still, they would operate that way for years.

  Quote:


 Tom: changing those 5088s to 5087s have allowed my tubes to balance out nicely at 13.5V 
	

	
	
		
		

		
		
	


	









 

I'm glad to hear it. Now we can truly say it:
 Another MAX lives!!!


----------



## adfinni

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Yes, of course - I was being toungue-in-cheek with Amphead, there. With BG's, Dsavitsk suggested that I just hook the amp up and let it run for a week before I even listen to it for the first time. 
	

	
	
		
		

		
		
	


	


_

 

 Ive had a few cheeky listena but am just running it in during all hours im awake and might leave it on overnight the next few days if all seems stable.



  Quote:


 Yes, as with any design, there are compromises. I'm not sure that Colin could have located the center sinks any better - there are serious downsides with locating them another way, and it was tried before. What is happening, of course, is that there isn't enough airflow betwen the two sinks. As you say, if the heat sink is not getting hot, then something is wrong. If you have any doubt, the thing to do is measure the plastic part on the reg or the transistor. This is just my own rule-of-thumb judgment, but if it's less than about 70deg.C. (~160deg.F.), you're OK. To be truthful, all of the parts can withstand probably twice that much. A good reference is to remember that on the little DB boards in the original revMH Millett Hybrid, the transistors were literally too hot to touch - even for a second. Ones with a metal back were very close to rendering a burn. Still, they would operate that way for years. 
 

I remember the day when i used to cook bacon on the dB board in my rev. millett 
	

	
	
		
		

		
		
	


	




 i have some cooling designs for my casing which should help out the VREG with its heat disapation, but the transistors still remain quite cool to the touch, and that's a very good thing.

  Quote:


 i'm glad to hear it. Now we can truly say it:
 Another MAX lives!!!










 

TOOOOT


----------



## amphead

Congrats Adfinni! Krikey another MAX Lives!


----------



## ruZZ.il

Been away for a bit(Paris) but I've seen a lot's gone on. Congrats on all the new MAXes! 
	

	
	
		
		

		
		
	


	




 I'll try catch up sometime and see if I can offer any help too, but back to school though, so.. hmm. I've also added some of the P/N's I picked up while scanning through here to this bits and pieces post, and a note at the bottom.. hope it comes handy sometime 
	

	
	
		
		

		
		
	


	



 cheers.
 ruZZ


----------



## amphead

Hope you did all of the usual tourist activities. Musee du Louvre, Musee d'Orsay, Eiffel Tower. I had a good time there. The French weren't rude as is sometimes reported. They were friendly enough. Welcome Back!  Parlez vous francaise?


----------



## amphead

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Made a bit of progress today:



 EDIT: Phew! Just finished the 5th board._

 

Wow, thats some quick work! You are getting close to the A/B with BG NX vs Muse ES.


----------



## tomb

Ya'll may find a recent discussion on Headwize of the MAX's e12 Delay interesting. It starts with post #232 (Click on the "View Post In Thread".)


----------



## thunder

Is anyone working on a way to rectify the problem, or is it to minor to worry about ?


----------



## n_maher

It doesn't appear to really be a problem, more of a minor annoyance that you get a bit of a pop through the headphones on shut down. I actually think that it might be the sound of the relay closing but more investigation is needed. On my next MAX I'll be using a 10uF cap to see if it affects this at all.


----------



## tomb

Quote:


  Originally Posted by *thunder* /img/forum/go_quote.gif 
_Is anyone working on a way to rectify the problem, or is it to minor to worry about ?_

 

You apparently need to read all of the posts. 
	

	
	
		
		

		
		
	


	




 There's no problem if you use the right parts. 
	

	
	
		
		

		
		
	


	










 I posted it in case another enterprising builder starts measuring offset at the headphone jack on turn-off. You may get some interesting numbers depending on what you have connected or not connected. Bottom line, it's not an issue - as Amb confirms in a later post.


----------



## Listen2this1

Which is better with the e12 circuit. Leaving the headphones in on power down or reducing the volume all the way down, removing the headphones, then powering down. I try to do the later all the time on any headphone amp.


----------



## tomb

Quote:


  Originally Posted by *Listen2this1* /img/forum/go_quote.gif 
_Which is better with the e12 circuit. Leaving the headphones in on power down or reducing the volume all the way down, removing the headphones, then powering down. I try to do the later all the time on any headphone amp._

 

I think turning the volume down is probably prudent in any case. As for the rest - fuhgeddaboudit. You can leave them plugged in with confidence. I have been listening for months on a couple of MAX's with HD580's and HD600's and never noticed anything untoward. 

 I didn't mean to cause trouble with this. (I'll learn one of these days. 
	

	
	
		
		

		
		
	


	




 ) The point is - build it with the right parts and there should not be an issue. Amb has confirmed this and even with the observed voltage effect on higher-impedance cans. It's the normal operation - not to worry.

 As said, if you go and start measuring your headphone jack offset without anything connected, the first thing you'll notice is an alarming 4+VDC that appears for something less than a second. However, that's with _nothing_ plugged in. Plug in something around 50ohms or less (KSC75's, Grado's, etc.) and that less-than-one-second offset is in the one to two digit mV range - trivial. Plug in something around 300ohms and you may see something barely over 1V for a split second. As Amb comfirmed, that's trivial for a high impedance can.

 The problem is when measuring the offset at the jack with an infinite impedance load (nothing connected).


----------



## colonelkernel8

Bah, I have my max done, but I dont have an enclosure. I refuse to use that hammond case...


----------



## ruZZ.il

Quote:


  Originally Posted by *amphead* /img/forum/go_quote.gif 
_Hope you did all of the usual tourist activities. Musee du Louvre, Musee d'Orsay, Eiffel Tower. I had a good time there. The French weren't rude as is sometimes reported. They were friendly enough. Welcome Back!  Parlez vous francaise?_

 

Was there for my girlfriends cousins wedding.. well.. and to meet the fam. I'd done most of the touristy stuff before so we were just chilling.. rented a city bicycle(that we doubled up on, and got stopped by a cop for going through a red light, who just said don't do it again) and wine, cheese, baguettes, flan, around the eiffel. Pics for a new panoramic somewhere on the sein..etc..
 The whole europeans/french hating americans thing is generally b.s(I think) It really depends on how polite you are to them to begin with(its.. cultural(etiquette))... but when a rowdy crowd comes back complaining about them being snobs.. just wonder why  fortunately, my gf speaks french. I just look innocent 
	

	
	
		
		

		
		
	


	




 ....okay, fine, they are kinda snobbish.. but really not terrible.


----------



## adfinni

Starting to loosen up as ive been running it in since yesterday afternoon. Only about 30 hours total on it and it's definately less harsh and is somewhat mellower.

 Drilled the frontpanel today, tapped screw thread even though they arn't concentric holes in the hammond so are more like 4 taps down 4 ridges.... hehe.

 Backpanel and top plate will be done by wednesdayl, and hopefully my sexy RCA plugs will arrive on friday so i can fully assemble ready for the meet at the weekend.

 O and building my new silver IC's too... Can't wait to hear em... The bits:


----------



## amphead

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Ya'll may find a recent discussion on Headwize of the MAX's e12 Delay interesting. It starts with post #232 (Click on the "View Post In Thread".)_

 

The sound that I get on power down is pretty mild. Kind of a "Pffft". But I always thought that was the electric field collapsing in the electrolytic caps as they drop to zero volts. Just my theory(IMHO). I can't imagine how nasty the pop is without the delay circuit, and don't want to risk my phones to do an A/B.
	

	
	
		
		

		
		
	


	




 Edit: Thats to avoid the pop on power up of course. On power down the delay obviously isn't doing anything.


----------



## c0nsumer

Ooh... What's that there in my second MAX? Could it be the first assembled nuxx Audio Input Switch? Why yes, it is!

And yes, it works as expected... So, I expect there to be a group buy put together pretty soon...

 Hrm, I think the design needs a few improvements...


----------



## pinkfloyd4ever

while we're on the topic of CM1, what's the reason it's a Panny EB rather than FM?


----------



## pinkfloyd4ever

Quote:


  Originally Posted by *c0nsumer* /img/forum/go_quote.gif 
_Ooh... What's that there in my second MAX? Could it be the first assembled nuxx Audio Input Switch? Why yes, it is!

And yes, it works as expected... So, I expect there to be a group buy put together pretty soon...

 Hrm, I think the design needs a few improvements..._

 

once the source is switched, the signal path doesn't actually pass thru any of the components does it? As I said before, I don't know jack about this..


----------



## c0nsumer

Quote:


  Originally Posted by *pinkfloyd4ever* /img/forum/go_quote.gif 
_once the source is switched, the signal path doesn't actually pass thru any of the components does it? As I said before, I don't know jack about this.._

 

Erm... What? I'm a bit confused by your question.


----------



## naamanf

It goes through a relay.


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## amphead

The switch connects one from a group of multiple audio sources with the push of a button!  Edit: Nice work C0nsumer!


----------



## Listen2this1

*IT IS ALIVE 
	

	
	
		
		

		
			



*

















 Thanks everyone for the help, I really could not do this with out all the help.

 Tomb- when do you think I can work my way up from 50ma? By the way it was the BD139 that was causing the issues in the E12.

 So far Sounds Great!


----------



## tomb

Quote:


  Originally Posted by *Listen2this1* /img/forum/go_quote.gif 
_*IT IS ALIVE 
	

	
	
		
		

		
		
	


	


*

 Thanks everyone for the help, I really could not do this with out all the help.

 Tomb- when do you think I can work my way up from 50ma? By the way it was the BD139 that was causing the issues in the E12.

 So far Sounds Great!_

 

Nice - very nice! Congrats on your new MAX!

 As for more than 50ma? You've got the standard 1" heat sinks and I'm getting conservative after some people have smoked theirs. Realize, of course, that I haven't dialed in more than 50ma on any of mine. So, I think maybe 75ma would still be OK to try - but keep a close eye on temperature. Also, when you case it up - all bets are off. With the 1" sinks, the vent holes, and 50ma, a cased up MAX doesn't overheat - but even the volume knob will get fairly warm after a few hours. Strong caution is advised over 50ma.

 P.S. I think you meant the _NTE equivalent_ for the BD139 was causing the problem.


----------



## tomb

Quote:


  Originally Posted by *amphead* /img/forum/go_quote.gif 
_The switch connects one from a group of multiple audio sources with the push of a button!  Edit: Nice work C0nsumer!_

 

Yes - you guys should take a look at his website link. It appears to be a very professional project - very.

nuxx Audio Input Switch


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## Listen2this1

Quote:


 P.S. I think you meant the NTE equivalent for the BD139 was causing the problem. 
 

Yes that is correct. I learned a lesson on just taking mousers link for the subsitution, I should of looked on the spec sheet for the pin config.


----------



## amphead

Listen2this1 Congrats! - Another MAX Lives! 
	

	
	
		
		

		
		
	


	










 Love the macro photography! I can almost reach out and touch that tube!


----------



## amphead

Pabbi, I'm not quite ready to pop the cork on the champagne bottle, but the outside pins on QB8R are connected to the top ground plane on the Mosfet pads. Probably only one pin, but I won't know until after I pull the heatsink and DB. Because there is only a few human hairs between pads and ground plane on the top of the Max, an accumulation of solder can short out the pads there. So I am going to pull that and do some dremel surgery to remove the short. See ya later.  Edit: I will PM you if it fixes your Max.


----------



## amphead

Ok Pabbi, more info: QB9R on that same board has one outside pin shorted to the ground plane at the mosfet pad. So I will fix both of those and check it. Edit: On the second board that you sent me for the balanced Max configuration, one outside pin on QB9R is shorted to ground also. This shows how often this happens and should help other builders who don't realize that this could happen. Be back after the dremel surgery.


----------



## c0nsumer

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Yes - you guys should take a look at his website link. It appears to be a very professional project - very.

nuxx Audio Input Switch_

 

Thank you. 
	

	
	
		
		

		
		
	


	




 I'm having a combination of problems with the design (the analog / switching side is not as noise free as I'd like, particularly when muted or switching to unconnected inputs) so I need to work on that, I also need to get the power supply design done better.

 On top of that real-world work responsibilities have changed a bit, and I'm considerably busier than I was last week. OS X 10.5 is also coming out on Friday, so that'll take up the weekend.

 It's coming along, just a little slower than expected. Thanks for the support on it all everyone, though. I'll be sure to let you all know if / when the group buy will be available. It won't be until I'm happy with the design, though.

 -Steve


----------



## joneeboi

I'm down. Can't wait.

 I wouldn't have to program it or anything, would I?


----------



## pinkfloyd4ever

Quote:


  Originally Posted by *c0nsumer* /img/forum/go_quote.gif 
_Thank you. 
	

	
	
		
		

		
		
	


	




 I'm having a combination of problems with the design (the analog / switching side is not as noise free as I'd like, particularly when muted or switching to unconnected inputs) so I need to work on that, I also need to get the power supply design done better.

 It won't be until I'm happy with the design, though.
 -Steve_

 

ahh, ya that's what I was concerned about when I asked about it above, I don't really know what a relay is or how it (or anything else in the circuit) effects the signal. I don't know, does the signal in the MAX pass thru the relay in the delay circuit?

 Anyway, it would be sweet to have something like this. I'd be interested in one when you get the kinks worked out, as long as all I have to do is copy the parts list & follow the silkscreen to solder them where they go


----------



## eddiewalker

Quote:


  Originally Posted by *pinkfloyd4ever* /img/forum/go_quote.gif 
_I don't really know what a relay is or how it (or anything else in the circuit) effects the signal._

 

Consider it an electrically controlled mechanical switch.

  Quote:


  Originally Posted by *pinkfloyd4ever* /img/forum/go_quote.gif 
_ I don't know, does the signal in the MAX pass thru the relay in the delay circuit?_

 

Yes.


----------



## c0nsumer

Quote:


  Originally Posted by *joneeboi* /img/forum/go_quote.gif 
_I'm down. Can't wait.

 I wouldn't have to program it or anything, would I?_

 

Nope, my hope is to offer PCBs and preprogrammed microcontrollers for around US$20. You'd just have to source the rest of the parts, but as I'm keeping the parts common and (as of thus far) sticking to things only available from Mouser, this should be trivial. People outside of the US shouldn't have a problem either, as everything on the board is a fairly common component.

 I'm holding off on doing any work on it until after the weekend, though. I just need a bit of a break from electronics, especially with how life has been otherwise. Hehe. 
	

	
	
		
		

		
		
	


	




 -Steve


----------



## c0nsumer

Quote:


  Originally Posted by *pinkfloyd4ever* /img/forum/go_quote.gif 
_ahh, ya that's what I was concerned about when I asked about it above, I don't really know what a relay is or how it (or anything else in the circuit) effects the signal. I don't know, does the signal in the MAX pass thru the relay in the delay circuit?

 Anyway, it would be sweet to have something like this. I'd be interested in one when you get the kinks worked out, as long as all I have to do is copy the parts list & follow the silkscreen to solder them where they go
	

	
	
		
		

		
		
	


	


_

 

Thanks. 
	

	
	
		
		

		
		
	


	




 And yes, that's all that will need to be done... Order the list of parts, solder the stuff in place, test it to be sure the power supply is working as it should be, plug in the microcontroller, and use it.

 Well, you'll have to sort out the mounting of the controls yourself, of course, as this is just the switch / PCB, but that part isn't difficult at all.


----------



## amphead

Pabbi, another update on the bad board. I removed the burnt resistor at RB2R and removed RB10R, which had a solder accumulation at the top/ground plane. Dremeled away the pads on the top for those resistors, due to the shorting. Found shorts at QB4R and QB1R on single pins with accumulation on the ground plane. I have to remove those QBs and dremel those pads off. Back to dremel surgery.


----------



## MrMajestic2

Just finished up my second MAX. Worked straight away with just a bias tuning needed 
	

	
	
		
		

		
			

























 Everything is from the standard BOM except the 0.47uf VitaminQs. It sounds awesome and the bass is very powerful, which I wasnt expecting.


----------



## ruZZ.il

Good stuff going on


----------



## amphead

Pabbi, the QB8R DB (2SC3422) is bad, so I wouldn't trust the DBs in the right channel. I didn't find a replacement for that in the parts that were sent, so I would need replacements there. Thanks

 MrMajestic2, thats some nice work! How does it sound?


----------



## eddiewalker

Quote:


  Originally Posted by *MrMajestic2* /img/forum/go_quote.gif 
_Just finished up my second MAX. Worked straight away with just a bias tuning needed 
	

	
	
		
		

		
		
	


	




 (IMG)

 Everything is from the standard BOM except the 0.47uf VitaminQs. It sounds awesome and the bass is very powerful, which I wasnt expecting._

 

What's that you used to lift up the pot? I've been trying to find an elegant way to give mine a tiny bit of height so the knob will land vertically centered on the front panel.


----------



## pabbi1

Quote:


  Originally Posted by *amphead* /img/forum/go_quote.gif 
_Pabbi, the QB8R DB (2SC3422) is bad, so I wouldn't trust the DBs in the right channel. I didn't find a replacement for that in the parts that were sent, so I would need replacements there. Thanks_

 


 Boy. I should have quit while I was behind... how humiliating I could screw this up so bad.

 So, total recap of what is needed: Some 2sc3422 & 2sc1359 - any resistors?

 I am indebted to Ron for helping me on this - absolute shame it has come to this. I promise, to all, this is my last DIY.


----------



## ruZZ.il

You'll be back


----------



## MrMajestic2

Quote:


  Originally Posted by *amphead* /img/forum/go_quote.gif 
_MrMajestic2, thats some nice work! How does it sound? _

 

Thanks, Im pretty happy with it. Was kind of tricky to figure out how to mount the VitaminsQs though.It sounds great, much better than I expected compared to my other MAX with boutique parts. I didnt listen for very long last night, but it has a very pleasant sound with plenty of bass.

  Quote:


  Originally Posted by *eddiewalker* /img/forum/go_quote.gif 
_What's that you used to lift up the pot? I've been trying to find an elegant way to give mine a tiny bit of height so the knob will land vertically centered on the front panel._

 

Its just sitting on header pins with socket strips soldered on the pot. Its just a temporary thing until I get the casing done. It will then be connected with wires. Im not using a Hammond case so I cant have the pot soldered on the board. I f you just want to raise it a little bit then the legs on the pot will fit in to socket strips directly. I used header pins on the board side so I couldnt do that.


----------



## tomb

Quote:


  Originally Posted by *MrMajestic2* /img/forum/go_quote.gif 
_Thanks, Im pretty happy with it. Was kind of tricky to figure out how to mount the VitaminsQs though.It sounds great, much better than I expected compared to my other MAX with boutique parts. I didnt listen for very long last night, but it has a very pleasant sound with plenty of bass.</snip>_

 

Nice work! You've removed much of my guilt after seeing that you somehow figured out how to fit those VitQ's in.

 This sort of answers/confirms a few things we're learning:
 1. What you describe is _supposed_ to be what a MAX sounds like. It's always sounded like that with ES's and plain ol' Wimas.

 2. Dsavitsk was right about the VitQ's (natch!) and contrary to conventional wisdom, they must be very, very flat and neutral in frequency response. This is because of the findings lately about the cathode bypass-bypass cap. Actually, the bass is always there and has always been there. The trick is to keep the cathode bypass caps from destroying it.

 I think a typical boutique film cap (translated: exagerrated mids, with high and low rolloff) _does_ destroy the bass - when placed in that very sensitive cathode bypass position.

 3. This leads to your experience with your Black Gate MAX. Try removing those little 0.47 bypasses - it may sound much better and the bass may start to approach the other one. Just a guess, but it may be that the little one overwhelms the 1000uf in that cathode bypass position. On the other hand, it's quite possible that bypassing with the little one on the output has no effect at all.

 This may explain why ruZZ.il noticed no difference with the film bypasses connected or disconnected - he may have been doing this at the output, instead of that uber-sensitive cathode bypass position. That's just a guess, though.

 Anyway, glad you've discovered the true sound of the MAX!!


----------



## amphead

Pabbi, at least one set of 2sc3422 & 2sc1359, but it would be a good idea for 2 sets. As far as you were saying, about this being your last diy, you could build a MAX anytime you want, once you watch out for solder dribbling from the back side of the board, to the fronts side. Just by being stingy with the amount of solder, you would have been up and running from what you have done so far, so no big deal. You can definitely build another Max yourself, just by being stingy with the solder.


----------



## MrMajestic2

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_3. This leads to your experience with your Black Gate MAX. Try removing those little 0.47 bypasses - it may sound much better and the bass may start to approach the other one. Just a guess, but it may be that the little one overwhelms the 1000uf in that cathode bypass position. On the other hand, it's quite possible that bypassing with the little one on the output has no effect at all.

 This may explain why ruZZ.il noticed no difference with the film bypasses connected or disconnected - he may have been doing this at the output, instead of that uber-sensitive cathode bypass position. That's just a guess, though.

 Anyway, glad you've discovered the true sound of the MAX!! 
	

	
	
		
		

		
		
	


	





_

 

The first thing I will do is remove the Kiwames in the RB14 position. I think that veils the sound a lot. But I didnt have a problem with my Black Gates after I changed the tubes. I was getting what I would call distortion before that, probably due to the tubes not being burned in.


----------



## fordgtlover

Quote:


  Originally Posted by *MrMajestic2* /img/forum/go_quote.gif 
_Thanks, Im pretty happy with it. Was kind of tricky to figure out how to mount the VitaminsQs though.It sounds great, much better than I expected compared to my other MAX with boutique parts. I didnt listen for very long last night, but it has a very pleasant sound with plenty of bass.
_

 

Yep... I found that the only boutique part that actually made a positive difference is the C8 bypass cap. As I recently stated, I found that the Elna Silmics in CA2/7 were much less pleasant than the Panasonic FMs, and there was no difference between using the WIMA and a PIO in CA9

 I am currently trying to decide whether I like the little russian K42 PIO or the Vit Q better in CA8 - this really is a last 1% issue.

 Tomb has been absolutely correct the whole time on the issue of using boutique parts in the Millet MAX - Oh, why didn't we listen to you tomb (just joking).

 I have really enjoyed rolling various parts through mine.


----------



## ruZZ.il

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_This may explain why ruZZ.il noticed no difference with the film bypasses connected or disconnected - he may have been doing this at the output, instead of that uber-sensitive cathode bypass position. That's just a guess, though._

 

I was playing with both bypasses. Neither one, the other, or both disconnected had any observable effect at the time. These were sonicap Gen II's bypassing BGs. 

 I'm not sure if I stated this then, but the amp had only been on for about 10 minutes before I started playing around, for about 15 minutes, so the lack of enough heat in the tubes may have contributed to a lesser/harder to observe difference, but still indicates that its not a big one. I may re-do this with some hotties.

 I'm not yet able to state that the BG's wouldn't benefit by a wima or vitQ in either position yet (yet, but I just shared some vit Q's with adam that I'll get around to soon 
	

	
	
		
		

		
		
	


	




), just that the BG's seem hard to beat by themselves, and bypassing with gen II's had little to no effect observable by me (ill or good, ymmv). 

 on another note, I found myself a decent bargain on a pretty old.. oscilloscope
	

	
	
		
		

		
		
	


	




. this could potentially keep me busy if I weren't already busy, but I'm certain to play around sometime, and hopefuly see things and try correlate them to what I hear. I've also got a bunch of mini^3s and Alien DACs waiting to be built. I put together a mini^3 for myself and got to listen quiet a bit.. with my 40ohm cans, it contends quiet nicely with my pimped out PIMETA. the differences are little, but there. not too easy to pinpoint so quickly, so I'll do some extensive A/Bing sometime 
	

	
	
		
		

		
		
	


	




 For one, its standard bass response is punchier than the 8610s in my pimeta, but I got a bass boost there, so it compensates well 
	

	
	
		
		

		
		
	


	




 one of them also gave me an ever so slight feeling of being in a larger room. I still like my pimeta more, but marginally. I ended up traveling with the mini though cause, well, its smaller, sleeker, and looks less like a bomb. It's also new, and almost matches my girlfriends one
	

	
	
		
		

		
		
	


	




 I've got my pimeta with me for the w.end though.


----------



## tomb

Quote:


  Originally Posted by *ruZZ.il* /img/forum/go_quote.gif 
_I was playing with both bypasses. Neither one, the other, or both disconnected had any observable effect at the time. These were sonicap Gen II's bypassing BGs._

 

OK - I thought perhaps you had just tried it with the outputs. My bad - thanks for the correction.

 Your MAX may be an anomaly, though, because if you recall, we had another BG user complain about it sounding awful with BG's until he _removed_ the Sonicaps. 

  Quote:


 I'm not sure if I stated this then, but the amp had only been on for about 10 minutes before I started playing around, for about 15 minutes, so the lack of enough heat in the tubes may have contributed to a lesser/harder to observe difference, but still indicates that its not a big one. I may re-do this with some hotties. 
 

No, you didn't start this. I observed a horrible effect with the Sonicap in the cathode bypass spot myself - with lowly ES's. That's what started this. 
	

	
	
		
		

		
		
	


	




  Quote:


 I'm not yet able to state that the BG's wouldn't benefit by a wima or vitQ in either position yet (yet, but I just shared some vit Q's with adam that I'll get around to soon 
	

	
	
		
		

		
		
	


	




), just that the BG's seem hard to beat by themselves, and bypassing with gen II's had little to no effect observable by me (ill or good, ymmv). 
 

Yes, we agree on your first statement. My thought (I'll find out soon) is that the BG's shouldn't be bypassed, period.

 I believe when Dsavitsk first mentioned that he would _always_ bypass - even BG's - he was speaking in a theoretical sense, and assuming that one would find the proper cap (translated: uber-expensive, flat, and pristine). For instance, I found a statement where the Soniccraft people recommended nothing but Multicap RTX for bypassing BG's, a polystyrene film cap that sounds very different (flat and peaky) from most boutique film caps. Before that, I was recommending the standard practice with BG's: don't bypass them.

 The MAX's output caps - when something other than BG's - seem to follow the accepted practice - very often, a reasonable boutique film cap will add a desireable affect to the sound, including a Sonicap GEN II (especially!). However, and this is the important thing - I don't think testing or bypass experience applies in that cathode bypass position. It's not a coupling application and is just not the same thing.

  Quote:


  Originally Posted by *MrMajestic2* /img/forum/go_quote.gif 
_The first thing I will do is remove the Kiwames in the RB14 position. I think that veils the sound a lot. But I didnt have a problem with my Black Gates after I changed the tubes. I was getting what I would call distortion before that, probably due to the tubes not being burned in._

 

I understand, but I would still pull them out of the CA9 position (cathode bypass) and just see if that sounds better. I could be wrong, but I think it will.

 We are in agreement with the Kiwames, depending on how big they are. 22ohm or less probably won't make much of a difference either way, but I could be wrong.


----------



## ruZZ.il

hehe no, I mean if I'd stated that the little experiment I did wasn't with properly warmed up tubes. I was driven to experiment by the previous statements by you, and other users BG experience to begin with. meanwhile, its probably me being more of an anomaly than there being no difference, since I know these things have an effect, some effect. I'll have to play around a lot more before I can start pinpointing parts..


----------



## tomb

Quote:


  Originally Posted by *ruZZ.il* /img/forum/go_quote.gif 
_hehe no, I mean if I'd stated that the little experiment I did wasn't with properly warmed up tubes. I was driven to experiment by the previous statements by you, and other users BG experience to begin with. meanwhile, its probably me being more of an anomaly than there being no difference, since I know these things have an effect, some effect. I'll have to play around a lot more before I can start pinpointing parts.._

 

Yep - you and me both need to make some more tests - one of the reasons I'm building so many MAX's.

 I'm just concerned that we come up with some dependable combos for the general masses of MAX builders. So far, I think it's safe to say:

*For Non-Black Gates -*
 1. WIMAs are enough to give impressive results in a basic configuration.
 2. The VitQ's and the WIMA's are good to go in CA9 (cathode bypass).
 3. Other film caps and boutiques may improve the sound in the CA8 positions (output coupling), but the same is NOT true in CA9 and the sound may be adversely affected. (see #2 above).
 4. The Sonicap GEN II seems to work very well and improves the sound noticeably in CA8, but NOT in CA9.

*For Black Gates*
 1. It may be best to let these stand on their own.
 2. If you want to try bypassing, try the little 0.47 BG NX's first
 3. Polystyrene - RTX - may be a good choice for bypassing BG's, along with Vitamin Q's, but none of this certain and hasn't been tested.
 4. Item #3 may work for CA8, but be bad for CA9. YMMV.


 EDIT: Ya'll correct me if you disagree or have different experiences.


----------



## vixr

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Yep - you and me both need to make some more tests - one of the reasons I'm building so many MAX's.

 I'm just concerned that we come up with some dependable combos for the general masses of MAX builders..._

 


 Thanks Tom... I smell some new BOMs cooking.


----------



## Listen2this1

After 14 hours. I am overall happy with the Millett. I wish mine had more bottom end. I can live with what it has, but just a little more. I am going to try different cables and some other combos to see if this can help. Well see what happens. Maybe if I am able to build another one I will try some different caps.

 How long until tubes are considered broke in?

 Hey *vixr*, I was trying to click on the links in your signature and all of the links are crashing my browser (Safari). Thought you would like to know.


----------



## vixr

Quote:


  Originally Posted by *Listen2this1* /img/forum/go_quote.gif 
_
 Hey *vixr*, I was trying to click on the links in your signature and all of the links are crashing my browser (Safari). Thought you would like to know._

 

hmmmm... I dont have a clue. Its a slideshow offered by photobucket. I removed them, sorry about the PITA


----------



## adfinni

YES YES YES 

 Cased it all up, and ready for the UK meet tomorrow. And the best bit is that nothing has shorted or blown, and it sounds, and looks sensational. Do you ladies want to see it or shall i leave you in suspense and make you wait for the meet pics ? 
	

	
	
		
		

		
			





 Only problem is that i wired my RCA jacks the wrong way around. lol.


----------



## tomb

Quote:


  Originally Posted by *fordgtlover* /img/forum/go_quote.gif 
_Yep... *I found that the only boutique part that actually made a positive difference is the C8 bypass cap*. As I recently stated, I found that the Elna Silmics in CA2/7 were much less pleasant than the Panasonic FMs, *and there was no difference between using the WIMA and a PIO in CA9*_

 

Somehow I missed this earlier, but I think it's very important. It feeds right into what I've been thinking/saying: a WIMA is just fine in CA9.

  Quote:


 I am currently trying to decide whether I like the little russian K42 PIO or the Vit Q better in CA8 - this really is a last 1% issue. 
 

This is just as important, too, because for many of us, the genuine Sprague VitQ's are really too big. MrMajestic2 got away with it because he's using the taller sinks.

 Thanks to you, I can now see that those little K42 PIO's can fit in fairly easy at CA8 - both lying down or standing up, I believe.

 So, my further testing will focus on whether the little Russian PIO's are appreciably better than Sonicap GEN II's in that position. The GEN II's really shine with the ES's there. I don't know if the PIO's have the same synergy - they may be a better match with the BG's.

  Quote:


 Tomb has been absolutely correct the whole time on the issue of using boutique parts in the Millet MAX - Oh, why didn't we listen to you tomb (just joking). 
 

Not really. By my recollection I sidetracked a bit with trying to apply bypasses to Black Gates and also putting the Sonicaps in CA9, but I appreciate the thought - and the joke. 
	

	
	
		
		

		
		
	


	







  Quote:


 I have really enjoyed rolling various parts through mine.


----------



## tomb

Quote:


  Originally Posted by *Listen2this1* /img/forum/go_quote.gif 
_After 14 hours. I am overall happy with the Millett. I wish mine had more bottom end. I can live with what it has, but just a little more. I am going to try different cables and some other combos to see if this can help. Well see what happens. Maybe if I am able to build another one I will try some different caps._

 

You should not be complaining about a lack of bass with the MAX. Tell us more about the specs of what you put in. I can see that you put ES caps in CA4 and CA5 - are those the 470uf's? Did you say what output transistors you were using? If you're using the BD's, you might get the impression of less bass. Anyway, we can probably help this with a few changes.

  Quote:


 How long until tubes are considered broke in? 
 

Honestly? It can be as bad as Black Gates - maybe a week or two before some pairs become completely dependable. Some of this has to do with the fact that gas molecules collect in the tubes over the years and the getter has to burn them out. That takes a _number_ of hours. Generally speaking, if the bias doesn't vary after a couple of hours and you can't detect high-end harshness, they're broken in. Broken-in tubes will also heat up and give good sound pretty quickly - maybe within an hour.


----------



## jerrygp

Would like to socket the RB14 position, but boutique resistor leads are larger than the standard sip socket. Can anyone help with a vendor and p/n for a suitable replacement? This is my first post, but just completed one millet and am tweaking it before moving on to my second with boutique Black Gates in place of the Nichicon ES setup in my first. Couldn’t have done it without the invaluable posts and subsequent responses of the faithful folks that frequent this forum.


----------



## vixr

jerrygp, solder a smaller diameter lead clipping to the existing one that _will_ fit in the sip socket...


----------



## jerrygp

Thank you vixr...sometimes the solutions are simple. The reduction in the diameter of the lead is not an issue. I am going to experiment with different Kiwame resistor values to see what effect they have, but volume levels are decent now with my HD580's and my old untrained ears may not notice any decrease in upper frequency harshness.


----------



## pabbi1

Quote:


  Originally Posted by *amphead* /img/forum/go_quote.gif 
_Pabbi, at least one set of 2sc3422 & 2sc1359, but it would be a good idea for 2 sets. As far as you were saying, about this being your last diy, you could build a MAX anytime you want, once you watch out for solder dribbling from the back side of the board, to the fronts side. Just by being stingy with the amount of solder, you would have been up and running from what you have done so far, so no big deal. You can definitely build another Max yourself, just by being stingy with the solder._

 

Parts enroute... should be there by Wednesday. 

 Note to self: Stingy with solder...


----------



## tomb

Quote:


  Originally Posted by *pabbi1* /img/forum/go_quote.gif 
_<snip>Note to self: Stingy with solder... 
	

	
	
		
		

		
		
	


	


_

 

Don't kick yourself. 
	

	
	
		
		

		
		
	


	




 The MAX is one of the most wickable boards designed. Colin did it that way on purpose to ensure good connections and solderability across such a large board.


----------



## amphead

Ok thanks Pabbi!
 Yeah TomB, thats probably the better way to visualize what happens. The solder wicks up to the top of the board through gravity and capillary action.


----------



## ruZZ.il

being finicky almost solves it


----------



## ferds

I've finally finished my maxed... thanks to all you guys..

 here are some pics (sorry for the quality, only have my phone camera right now)














 see more pictures here


----------



## tomb

Very nice!
 Another MAX lives!


----------



## Televator

good work ferds (no need for air/cooling holes?)

 I'm currently burning in my 12FK6 tubes (did a while with the 12AE6, but their gain was too high for my NAD C542/MS2i-combo)

 the AE seem to have a bit more bass than the FK, but I still think the FK's provide a good low-end in the Max. Just listened to some Boris & Sunn O))) and it was clean and punchy but at the right times almost rummmblin' deep 
	

	
	
		
		

		
		
	


	




 Will the 12FM6's be somewhere in the middle? (they are gain-wise, I believe, but what about sound?)

 At the moment my NOS 12FK6's are still slightly unstable in their bias voltage (even after being on for 6 hours straight, each evening this past week)


----------



## amphead

Congrats Ferds! Another MAX Lives!
	

	
	
		
		

		
		
	


	










 Hows your sound? 

 Maligayang bati sa iyong pagtatapos! he he


----------



## tomb

Quote:


  Originally Posted by *Televator* /img/forum/go_quote.gif 
_good work ferds (no need for air/cooling holes?)

 I'm currently burning in my 12FK6 tubes (did a while with the 12AE6, but their gain was too high for my NAD C542/MS2i-combo)

 the AE seem to have a bit more bass than the FK, but I still think the FK's provide a good low-end in the Max. Just listened to some Boris & Sunn O))) and it was clean and punchy but at the right times almost rummmblin' deep 
	

	
	
		
		

		
		
	


	




 Will the 12FM6's be somewhere in the middle? (they are gain-wise, I believe, but what about sound?)

 At the moment my NOS 12FK6's are still slightly unstable in their bias voltage (even after being on for 6 hours straight, each evening this past week)_

 

You describe the quality of the different tubes exactly. There are tradeoffs and advantages with each one. Yes - the 12FM6 is in the middle.

 Yep for the bias voltage, too. As they break-in, the bias will become more or less rock-solid (after an hour or so)


----------



## ferds

Thanks guys.. 

 I will surely put some holes on top.. it runs a little hotter than i expected..

 hey amphead nice to see another pinoy here (are you?) hehe

 bout the sound? hmmm i still used to the sound of my PPAv2 (637 +627) but definitely loving it..


----------



## amphead

No, but I thought I would congratulate you in tagalog. 
 Not exactly a graduation but almost.


----------



## amphead

Pabbi, I have decided to get as far as I can on the bad board before the replacement DBs arrive. So far with those parts removed, I have plugged your board into my power supply. Its showing signs of life. The fuse does not blow. The tubes and leds light up (nice green glow). I adjusted voltage from 27.9V to 27V on the power supply. I biased left tube to 13.7V. Checked bias on left DBs/channel and currently its at 30mv. I won't bias left DBs, until I can bias the right channel. I am going to listen to the left channel alone with my phones. More info to come.  If all goes well as I expect, I want to get your amps back to you in good working order as soon as possible.


----------



## amphead

Pabbi, update: So there is a bit of nice music eminating from the left channel, even though it is still supremely underbiased at 30mv on those DBs.  That means I can concentrate on getting the right channel up to spec. - more info later. Edit: I need some information on setting up the 2 Maxes in a balanced configuration. Anybody?


----------



## ruZZ.il

I'd guess feeding them from a balanced source, + to one channel, - to the other.. or whatever the terms are with one amp L, one amp R.. but I haven't done anything balanced yet, so my guess is as good as a fleas


----------



## pabbi1

Quote:


  Originally Posted by *amphead* /img/forum/go_quote.gif 
_Pabbi, update: So there is a bit of nice music eminating from the left channel, even though it is still supremely underbiased at 30mv on those DBs.  That means I can concentrate on getting the right channel up to spec. - more info later. Edit: I need some information on setting up the 2 Maxes in a balanced configuration. Anybody?_

 


 For balanced, both channels on both boards should match - I'll use R as +, and L as -, which is all the magic there is to this. I have dual leads from the outs that will go to Neutrik combo jacks, following Ti's guidance (though he is referencing Beta22, the concept is the same) here, under 'Other Options', using the 'Combined Balanced / Unbalanced' diagram: 

Balanced / Unbalanced wiring

 The balanced input to the boards is coming from the Twisted Pear OPUS dac.

 I am using Denon AH-D2000 (with the markl mod) balanced, so I doubt there needs to be more bias than the bottom end of the range, especially with the 12AE6A. I also have 12fk6 (my real preference in the Millett, as determined with my prioor Millett), which will be my permanent tubes.

 Much love to Amphead - without you, this is a heap of parts headed for the recycle bin.


 So, for the $64k question - do the buffer biases change with different tubes? If so, how does the buffer bias change when changing 12ea6a to 12fk6?


----------



## tomb

Quote:


  Originally Posted by *pabbi1* /img/forum/go_quote.gif 
_<snip>So, for the $64k question - do the buffer biases change with different tubes? If so, how does the buffer bias change when changing 12ea6a to 12fk6?_

 

NO. The buffer bias is absolutely unaffected by the tube bias. We have had a couple of reports where the reverse has happened - biasing the buffers has had an effect on the tube bias. Neither should be the case, although I would believe it sooner in the case where the DB's may be able to suck current out of the CCS and perhaps drop the voltage slightly on the tubes.

 Neither should happen, however. That's one reason I changed the parts recommendation for the CA4 and CA5 caps to 1000uf minimum. I've actually used 1800uf FM's except for 1200uf FM's in the 1st proto - never had a problem with either situation.

 EDIT: Colin would probably say either case is impossible, but hey - it's only a few pennies for some extra uf's and they look better bigger, anyway.


----------



## pabbi1

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_NO. The buffer bias is absolutely unaffected by the tube bias. We have had a couple of reports where the reverse has happened - biasing the buffers has had an effect on the tube bias. Neither should be the case, although I would believe it sooner in the case where the DB's may be able to suck current out of the CCS and perhaps drop the voltage slightly on the tubes.
_

 

As I had hoped - I will be really gun shy abiut touching buffer bias...


----------



## odoe

I have to change out one of my tubes later today. At least I think it's a tube issue. If I tap on my desk or tap the amp, I get nasty static in the left channel. But, if I do it enough, like tap on my desk for 5-10 seconds, it slowly fades away not to return. The only thing I can think of is that I got a funky tube.

 This happened after I switched out a couple of orange drops for wimas in CA9, but touched nothing else. I thought maybe it was a grounding issue and wired the ALPS to ground, but it still happens. It's the fact that the static goes away after some tapping that makes me think it's a tube thing.


----------



## tomb

Quote:


  Originally Posted by *odoe* /img/forum/go_quote.gif 
_I have to change out one of my tubes later today. At least I think it's a tube issue. If I tap on my desk or tap the amp, I get nasty static in the left channel. But, if I do it enough, like tap on my desk for 5-10 seconds, it slowly fades away not to return. The only thing I can think of is that I got a funky tube.

 This happened after I switched out a couple of orange drops for wimas in CA9, but touched nothing else. I thought maybe it was a grounding issue and wired the ALPS to ground, but it still happens. It's the fact that the static goes away after some tapping that makes me think it's a tube thing._

 

It's possible. One way to know for sure is to swap the tube out or switch the tubes from one channel to the other.

 If that doesn't stop it, it's possible that you might have something shorted to ground if it was case up. Sometimes taking one apart and putting it back together is enough to short something that wasn't shorted before, perhaps.

 If the tube is microphonic - which is what one normally thinks of when a tube reacts to tapping on an adjacent surface - it usually manifests itself in ringing or echoing in the sound output. 99 times out of 100, it's very, very obvious.


----------



## tomb

My first foray into Black Gates on a Millett MAX:



_[size=xx-small](click for a larger pic)[/size]_

 Panasonic FM's all around, Wimas, etc.
 1" or less parts all around
 1000uf 25V BG NX's in CA2
 680uf 35V BG NX's in CA7
 BJT's - 2SC2238/2SA968's

 27VDC, for the PS, DB biasing was straightforward - started out at about 40mV and worked up to 110mV (50ma) in about an hour - everything stable. LM317 is running at about 42deg.C. on the plastic, about 50deg.C on the metal tab. The sink is very hot - almost burning hot to the hand, but more like automobile-door-in-the-sun hot. It should run like that indefinitely. DB's are considerably cooler - 37deg. C. on the plastic, about 42deg.C. on the metal tabs (the 2SC2238's have metal tabs).

 It sounds OK so far - it's obvious that the frequency response on the BG's is very extended - both extended highs and bass. However, things sound a bit metal and harsh for the time being. I haven't decided whether to put film caps on the output - have some Russian PIO's I'm itching to try, but will probably let it run this way for a week, at least.

 EDIT: The relay is sounding pretty harsh in the left channel, but I've measured both turn-on and turn-off and the offset is within previously seen values - it just sounds bad. Maybe the caps need to break-in some more. If it continues like that, I may replace the smaller electrolytic with a 10uf 25V tantalum - something Amb recommended over on Headwize in the E12 thread - and see if that helps. I may have a not-so-good relay.

 EDIT2: Wow - it doesn't take too long for those things to start smoothing out - sounds very good!


----------



## MrMajestic2

Looking good there Tomb. Wish I had more boards/money to experiment with BJT buffers and different caps. Money is running dry from my Opus and B22 builds 
	

	
	
		
		

		
			





 and I still dont have the cases done for my Maxs.


  Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_My first foray into Black Gates on a Millett MAX:
http://www.paintedpostcards.com/misc1/BG-MAX-1a-sm.jpg
[size=xx-small](click for a larger pic)[/size]

 Panasonic FM's all around, Wimas, etc.
 1" or less parts all around
 1000uf 25V BG NX's in CA2
 680uf 35V BG NX's in CA7
 BJT's - 2SC2238/2SA968's

 27VDC, for the PS, DB biasing was straightforward - started out at about 40mV and worked up to 110mV (50ma) in about an hour - everything stable. LM317 is running at about 42deg.C. on the plastic, about 50deg.C on the metal tab. The sink is very hot - almost burning hot to the hand, but more like automobile-door-in-the-sun hot. It should run like that indefinitely. DB's are considerably cooler - 37deg. C. on the plastic, about 42deg.C. on the metal tabs (the 2SC2238's have metal tabs).

 It sounds OK so far - it's obvious that the frequency response on the BG's is very extended - both extended highs and bass. However, things sound a bit metal and harsh for the time being. I haven't decided whether to put film caps on the output - have some Russian PIO's I'm itching to try, but will probably let it run this way for a week, at least.

 EDIT: The relay is sounding pretty harsh in the left channel, but I've measured both turn-on and turn-off and the offset is within previously seen values - it just sounds bad. Maybe the caps need to break-in some more. If it continues like that, I may replace the smaller electrolytic with a 10uf 25V tantalum - something Amb recommended over on Headwize in the E12 thread - and see if that helps. I may have a not-so-good relay.

 EDIT2: Wow - it doesn't take too long for those things to start smoothing out - sounds very good!_


----------



## pabbi1

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_It sounds OK so far - it's obvious that the frequency response on the BG's is very extended - both extended highs and bass. However, things sound a bit metal and harsh for the time being. I haven't decided whether to put film caps on the output - have some Russian PIO's I'm itching to try, but will probably let it run this way for a week, at least.

 EDIT: The relay is sounding pretty harsh in the left channel, but I've measured both turn-on and turn-off and the offset is within previously seen values - it just sounds bad. Maybe the caps need to break-in some more. If it continues like that, I may replace the smaller electrolytic with a 10uf 25V tantalum - something Amb recommended over on Headwize in the E12 thread - and see if that helps. I may have a not-so-good relay.

 EDIT2: Wow - it doesn't take too long for those things to start smoothing out - sounds very good!_

 

My experience is that the BG will 'bloom' at a couple of stages - about 100 hours, then somewhere around 300 hours... oh and some rebloom if it ever stays off for a week or so... all casual observation, of course. I wouldn't even listen for the first 24 hours, or so. Definitely give it a month or so to really burn in before making changes, as it really will take that long to fully settle out.


----------



## tomb

Quote:


  Originally Posted by *pabbi1* /img/forum/go_quote.gif 
_My experience is that the BG will 'bloom' at a couple of stages - about 100 hours, then somewhere around 300 hours... oh and some rebloom if it ever stays off for a week or so... all casual observation, of course. I wouldn't even listen for the first 24 hours, or so. Definitely give it a month or so to really burn in before making changes, as it really will take that long to fully settle out._

 

Thanks, pabbi - you, too, MrMajestic2. Unfortunately, I probably won't be able to keep it that long since I'm building it for someone else. I'm going to keep it long enough to determine if it's better with some PIO caps than without, though. To tell the truth, it sounds awfully good right now - it lost a lot of the metallic harshness after about 2 hrs. Right now, it's slightly but pleasantly fuzzy. It helps that those RCA 12AE6's have about 500 hrs on them.


----------



## ruZZ.il

I liked them.. I loved them... I wondered, cause they seemed just good.. then, I loved them again. they really do need their time. 

 Meanwhile, I'm finalizing a digikey+mouser order tomorrow. Mostly my second max bits. I've also got a better transformer for my steps so I can finally turn up the bias on my M^3. a bunch of knobs too.. and some spares for minis, etc. anyone have any parts suggestions that could come in handy? nice knobs? got knob?  I'll have to do some pcx and tube shopping too.. wheee.


----------



## tomb

Quote:


  Originally Posted by *ruZZ.il* /img/forum/go_quote.gif 
_I liked them.. I loved them... I wondered, cause they seemed just good.. then, I loved them again. they really do need their time. 

 Meanwhile, I'm finalizing a digikey+mouser order tomorrow. Mostly my second max bits. I've also got a better transformer for my steps so I can finally turn up the bias on my M^3. a bunch of knobs too.. and some spares for minis, etc. anyone have any parts suggestions that could come in handy? nice knobs? got knob?  I'll have to do some pcx and tube shopping too.. wheee._

 

Get those 1800uf 35V FM's at DigiKey (for CA4 and CA5) - very nice caps and at 1" if you're building a MAX for the 3rd slot.

 You might try that 10uf 25V tantalum for the relay, too. Amb recommended it over on Headwize after Nate had similar trouble. I haven't had an issue with the relays until this one, but it may be more common than I thought. It really has an un-nerving punch on turn-on and turn-off. Measurements seem OK - only a volt for a split second or so with KSC75's on turn-off. Still, the tantalum should speed things up a lot.

 We had a 20uf 25V tantalum on the 1st proto and it worked very well. Trouble was, it was $2.20 ea.(!) or thereabouts. The 10uf should put us in a lot cheaper territory. I'll try to make the change tomorrow night and see if makes a big difference.

 Again, nothing we've measured so far would indicate that there's anything that could be damaging and Amb confirmed as much. I'd just rather that we had as sharp a turn-off with all of the relays, but the quality control may not be that rigid on those things. (could be the cheap Xicon's I'm using, too)


----------



## joneeboi

Question:

 I know the BJTs can bias up to 50mA, but I got 1.5" heat sinks for my BJT setup as opposed to the recommended 1" heat sinks. Can I safely bias them higher in that case? Is the current limit more a matter of heat sink size or of which transistor I chose? (Running both MJEs, the middle two of which are considerably hotter than the outer pair.)


----------



## ruZZ.il

ah, thanks 
	

	
	
		
		

		
		
	


	




 I'll try that cap and I'll scope my relays behavior out sometime soon too. Got the 1800's down already 
	

	
	
		
		

		
		
	


	




 I'm going to use 1.5" sinks and have them stick out the top.. kind of like vixr's I guess, just not quiet like it  probably some cheap plywood again, or something better if I find it. 

 So anyone have a good recommendation on rca jacks from pcx, not on the looney expensive side? 
	

	
	
		
		

		
		
	


	




 hmm.. I should get some cable too.. need to make new i.connects. 

 hey adam how'd all your new ones turn out? looks like you're wired. maybe you can send me some ~? 
	

	
	
		
		

		
		
	


	




 what wire is that? pics if you're done!


 edit: jon, you could bias a bit more, just make sure they don't get much hotter. remember that they have a negative temperature coefficient, ie.. as they heat up, they conduct better, current rises, more heat, etc.., unlike the MOSFETS that as they heat up, the current drops. So thermal runaway is more likely with the BJTs (unikely with mosfets?). something to watch out for. The question also is, how much more would be beneficial and how beneficial, if it all. I'd take it slow and stay away from 'too hot'. I'd also rather get better transistors, than to try push those (there are substantially better, imho). but hey, if you burn them.. you could get better ones


----------



## tomb

Quote:


  Originally Posted by *joneeboi* /img/forum/go_quote.gif 
_Question:

 I know the BJTs can bias up to 50mA, but I got 1.5" heat sinks for my BJT setup as opposed to the recommended 1" heat sinks. Can I safely bias them higher in that case? Is the current limit more a matter of heat sink size or of which transistor I chose? (Running both MJEs, the middle two of which are considerably hotter than the outer pair.)_

 

Power is the important parameter. In the case of the output transistors, that's V+ times the bias current. That's the same whether it's a BJT or a MOSFET. We know the MOSFETs can easily run 100ma, or 2.7W at 27VDC. However, we also know the MOSFETs require the 1.5" sinks. So, one would think that there's no reason the BJT's can't run the same - 100ma with a 1.5" sink. However, as ruZZ.il says, the BJT's have a positive temp coefficient. They also have different cases in some instances. So, you're in trail-blazing territory to a certain extent and I can't guarantee anything. The best thing to do is look at the table that Amb devised for biasing the M3 relative to supply voltage and the height of the heat sinks:

 PSU voltage Maximum recommended quiescent current (w/1.5" sinks) 
 24V 160mA 
 26V 140mA 
 28V 130mA 
 30V 120mA 
 32V 115mA 
 34V 110mA 
 36V 105mA 
 38V 100mA 
 40V 95mA.

 So, you can take from that you might be able to attain 135ma maximum with 1.5" sinks. However, this is with a genuine metal-backed, metal-tabbed TO-220. It will be slightly less for the MJE's and less even more for the totally plastic 2SC3422, 2SC3421 pairs, etc. So, as stated in the beginning - 100ma, no question with 1.5" sinks. After that, it's up to you.


----------



## thomaskuhn

Tomb,

 I am curious as to what you have enjoyed more so far? The SE - wima combination or the BG combination (based on your current break-in period and possibly an extrapolation)?

 Tom Kuhn


----------



## tomb

Quote:


  Originally Posted by *thomaskuhn* /img/forum/go_quote.gif 
_Tomb,

 I am curious as to what you have enjoyed more so far? The SE - wima combination or the BG combination (based on your current break-in period and possibly an extrapolation)?

 Tom Kuhn_

 

Well, this is a timely question because I'm close to modifying the website with what's been found so far.. I'm still in the thick of trying many things out and have yet to really try the PIO caps. I've had a bunch of Vitamin Q's for awhile, but they're so big - even if I could find a way to make them work, I think they would be unrealistic to recommend to everyone. However, fordgtlover sent me some of the green Russian PIO caps (0.22uf 160V) that will fit. So, they may be a realistic alternative if they sound good and fordgtlover seems to think they do already. I'm also still testing quite a few of the transistors. I'm pretty familiar with several of them, but not others.

 So, keep in mind that my opinion may be modified over the next week or two.

 1. 1st config - budget conscious, realiable spectacular results:
 ES caps at CA2 and CA7, WIMAs all around, hefty* caps for CA4 and CA5
 2SC3422/2SA1359 BJT's

 This combo simply rocks. Bass slams the doors off and highs are reasonably effective. It's a very rocking combination that goes well with everything from Senns to KSC75's and inbetween. The WIMA's only have a slight graininess in the mids and a bit of harshness on the top end, but are very tolerable and competitive with amps easily costing twice as much (more than that if commercial).

 Frankly, despite that slight deficiencie with the WIMA's, I have heard nothing to compare with the bass in one of these short of a cranked up subwoofer in the car trunk. It can almost be intimidating with certain headphones (Beyer-padded Sony V6's, for instance). 
	

	
	
		
		

		
		
	


	




 2. Same as 1st config, except add Sonicap GEN II's to byppas CA7 instead of the WIMAs - WIMAs everywhere else. This is sort of the minimum upgrade to #1. Bass is slightly less, but highs are superlative and mids are soothing. Highs are the sort that my poor ears often hear only as a semi-constant fluttering or dog whistle in the ears, but it's something that adds airiness and an incredible sense of hearing every detail that exists. The Sonicaps are only $3.30 each, about $2 more than the WIMAs. So for about $4 more, you can supercharge the highs of #1. The only down side is that some of that subwoofer slam is missed.

 3. 3rd config - high cost, audiophile special:
 Black Gate NX's at CA2 and CA7, hefty caps at CA4 and CA5
 2SC2238/2SA968 BJT's

 This seems to be the Audiophile special. To my ears, it's as flat and detailed as a solid state amp - nothing exagerrated, but nothing lost. I think the BJT's add to this effect a lot, since they have always been listed as the ultimate neutral and extended response BJT's. The only downside that I can see to this combo so far is the slight fuzziness in the Black Gates. That may decrease with further running - as pabbi has indicated. Or, it might be corrected immediately with a pair of those PIO caps. I will try them by next weekend and let you know.

 The Sonicaps are out of the question for this and so would be just about every other popular cap such as Auricaps - IMHO, it would ruin the wonderful neutrality that this combination seems to have (already). Bass is very, very deep and firm, yet highs are splendid. They don't seem quite as extended yet as the effect gained with the Sonicaps on the ES's, but either further run-in or those PIO caps may address that. The slight fuzziness and tendency toward a bit of metallic sound makes guitar work sound glorious.

 So, there's three combos that work very, very well - from inexpensive to expensive. Time will tell if the PIO caps add to this combo, but everyone who's tried them seems to like them. Other than that and perhaps the Sonicaps on the output ES's (or the Millett-standard WIMAs), I would be very, very stingy with any mid-range bloom "boutique" film cap. They seem to do more harm than good - especially in bypassing the CA2 electrolytics, perhaps less so on the output.


 * This goes back to some of my recent recommendations. I have always used giant caps in the CA4 and CA5 positions, even though Millett tradition has called for 470uf's in these positions. It's only pennies more when using FM's up to 1200uf and 1800uf (what I use). Other caps are more expensive, so this route may not be as beneficial to some. One day we'll be paying premium prices for those FM's, but until then - get 'em while you can. 
	

	
	
		
		

		
		
	


	




 EDIT: Didn't answer the question as to which was more enjoyable, did I? Well, I will always have a soft spot for those ES's and 2SC3422 BJT's and their rockin' slam. Are the BG's better? Yes. Are the ES's and 2SC3422's more fun? To me, yes.

 EDIT: As I type this, the BG's are sounding worse and worse. That's sort of typical - what pabbi and others have reported and the same thing that happened with my BG Alien DAC. It'll probably be a week's worth of running before they sound good again and continue to improve.


----------



## amphead

Nice work on the BG Maxes TomB!

 I was tempted to install a 2sc3421 in place of the 2sc3422, to test your "bad" amp Pabbi. But I think it would be prudent to wait for that 2sc3422 shipment.


----------



## pabbi1

Quote:


  Originally Posted by *amphead* /img/forum/go_quote.gif 
_Nice work on the BG Maxes TomB!

 I was tempted to install a 2sc3421 in place of the 2sc3422, to test your "bad" amp Pabbi. But I think it would be prudent to wait for that 2sc3422 shipment. _

 

Yes, should be Tuesday or Wednesday, as I opted for an expedited shipment... mainly to respect your time, and I am all but insensitive to cost penalties. 

 Tom, the Black Gate bloom really is a wonderous thing - you wonder what all the fuss is about, they turn dull, then downright icky, then wham - where did that come from? It is a truly mysterious experience, but something you just have to experience to join the believers. In fact, I didn't go BG mainly because this is an office rig, and I just travel too many weeks to live through all the bloom cycles I would be faced with. So, I thought the Cerrafines would suit my application better. This was not an economic decision for me.


----------



## amphead

Pabbi, Well I couldn't wait and I went ahead and installed 2sc3421 for purposes of troubleshooting. The right channel tube, heats up properly, but there is no bias voltage at TA2R. Measuring the plate voltage at pin 7 of the right tube, gives .9V . Therefore I'll replace QA1R and QA2R, looking at what is the likely culprit upstream on the schematic.


----------



## Listen2this1

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_You should not be complaining about a lack of bass with the MAX. Tell us more about the specs of what you put in. I can see that you put ES caps in CA4 and CA5 - are those the 470uf's? Did you say what output transistors you were using? If you're using the BD's, you might get the impression of less bass. Anyway, we can probably help this with a few changes._

 


 Tomb In position CA4/5 they are Muse 470uf 35v, In position CA2 it is a Muse 1000uf 16v. The output trannies are the ones direct linked from the BOM. I was wanting to get some of the Toshiba's but then you had that shipping problem, so I went with the ones from the link. I am currently using Rca 12fk6 tubes. Bias is staying really stable. 

 Should the mje253's run warmer than the mje243's? 

 Also I am using the Grado 325i's, I know they are slightly on the bright side, this is why I am wanting a little more bottom end.


----------



## joneeboi

I'm all for biasing up to 150mA, but I just don't have any clue how many mVs I need to hit that mark. I'm running ~24.5Vs so I can easily hit that 150mA mark, I just don't know how carefully I should tread. There's got to be something I can consult wrt to this matter. The MAX website says 264mV for MOSFETs will give me 120mA. Does this transfer over for BJTs? I checked the MAX site, Steinchen's dB site and the M^3 site but I couldn't find anything.

 edit: Also, I'm running with the top of the Hammond enclosure removed, so the greenhouse effect will be avoided.


----------



## Listen2this1

Quote:


  Originally Posted by *joneeboi* /img/forum/go_quote.gif 
_I'm all for biasing up to 150mA, but I just don't have any clue how many mVs I need to hit that mark. I'm running ~24.5Vs so I can easily hit that 150mA mark, I just don't know how carefully I should tread. There's got to be something I can consult wrt to this matter. The MAX website says 264mV for MOSFETs will give me 120mA. Does this transfer over for BJTs? I checked the MAX site, Steinchen's dB site and the M^3 site but I couldn't find anything._

 

Joneeboi, I learned this calculation the hard way. If you are using a 2.2ohm resistor for RB10/11 you will use the multiplier of 2.2 for your calculations. ie: if you are reading 200mV on a Dmm you would divide this by 2.2 and get 90.9mA. You will be making these readings from TA2-L/R to TB-L/R, Not to ground.

 Hope this helps


----------



## IcantHearU

Quote:


 The MAX website says 264mV for MOSFETs will give me 120mA. Does this transfer over for BJTs? I checked the MAX site, Steinchen's dB site and the M^3 site but I couldn't find anything. 
 

Joneeboi,

 DB Bias
 Measurement Points:TB1L or TB2L tu TA2L, TB1R to TB2R with TA2R
 Adjustment Device:RB12L, RB12R
 Acceptable Values:66mV - 110mV (30ma - 50ma)
http://www.diyforums.org/MAX/MAXsetup.php

 That's from the MAX site - the setup and biasing page
 Although not as high as you're going, I'm sure the math still holds true - (mAx2.2=mV)


----------



## pinkfloyd4ever

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_My first foray into Black Gates on a Millett MAX:



[size=xx-small](click for a larger pic)[/size]

 Panasonic FM's all around, Wimas, etc.
 1" or less parts all around
 1000uf 25V BG NX's in CA2
 680uf 35V BG NX's in CA7
 BJT's - 2SC2238/2SA968's_

 

*YUMMMYY*

  Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_The relay is sounding pretty harsh in the left channel, but I've measured both turn-on and turn-off and the offset is within previously seen values - it just sounds bad. Maybe the caps need to break-in some more. If it continues like that, I may replace the smaller electrolytic with a 10uf 25V tantalum - something Amb recommended over on Headwize in the E12 thread - and see if that helps. I may have a not-so-good relay._

 

 would it make sense or even be possible to use 2 10uf tantalums in parallel? Seems like that might be a little faster than 1 20uf? Maybe; I'm just guessing, I don't actually know What i'm talkin about
	

	
	
		
		

		
			





  Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_3. 3rd config - high cost, audiophile special:
 Black Gate NX's at CA2 and CA7, hefty caps at CA4 and CA5
 2SC2238/2SA968 BJT's

 This seems to be the Audiophile special. To my ears, it's as flat and detailed as a solid state amp - nothing exagerrated, but nothing lost. I think the BJT's add to this effect a lot, since they have always been listed as the ultimate neutral and extended response BJT's. The only downside that I can see to this combo so far is the slight fuzziness in the Black Gates. That may decrease with further running - as pabbi has indicated. Or, it might be corrected immediately with a pair of those PIO caps. I will try them by next weekend and let you know._

 

sounds like that is in fact the one for me. Damn tho, I hope everywhere doesnt sell outta BG's before I get a chance to buy em...def next on the list to buy when I get the money to spare. Should be by late Dec (after I get x-mas money), do I have anything to worry about?

  Quote:


  Originally Posted by *ruZZ.il* /img/forum/go_quote.gif 
_So anyone have a good recommendation on rca jacks from pcx, not on the looney expensive side?_

 

Ha, aren't those mutually exclusive?


----------



## pinkfloyd4ever

Quote:


  Originally Posted by *jerrygp* /img/forum/go_quote.gif 
_Thank you vixr...sometimes the solutions are simple. The reduction in the diameter of the lead is not an issue. I am going to experiment with different Kiwame resistor values to see what effect they have, but volume levels are decent now with my HD580's and my old untrained ears may not notice any decrease in upper frequency harshness._

 

Ya I've been wondering about this too, because at $1 each they're not cheap. I'd like to be able to use the full range of the pot but I have no idea what values would work best with my cans (ya I know somewhere b/t 10-150 ohms). For now (meaning at least for a yearish) I just have an MS-1 & some KSC-75s, which are both 32 ohms, correct? But when/if i get new cans I might wanna change em...crap. Goodbye money, hello ton of $1 resistors that I'll end up using exactly 2 of...


----------



## amphead

Well Pabbi, that was not where the problem lies. QB2R & QB3R are my next possible culprits.


----------



## amphead

Pabbi, So now you have 2sc3421 in the right DB. I have replaced QB2R & QB3R. I had to create a jumper to ground for QB2R, because the ground plane does not make contact on one of its pins that is supposed to be grounded. Checked for tube bias voltage in the right channel. You now have 23.4V. So I biased the right tube to 13.7V. Checked the right DB bias and it was 25mv. Brought it slowly up to 30mv to match the left DBs. Plugged in my phones. YEEAAOOOW! Its a slammin, killing machine! Another MAX Lives! 
	

	
	
		
		

		
		
	


	










 Articulate vocals, crushing bass and all around great sound. With Cerafine(CA7), Silmic II(CA2), Sprague .47uF bypass caps all around.


----------



## adfinni

Quote:


  Originally Posted by *pabbi1* /img/forum/go_quote.gif 
_
 Tom, the Black Gate bloom really is a wonderous thing - you wonder what all the fuss is about, they turn dull, then downright icky, then wham - where did that come from? It is a truly mysterious experience, but something you just have to experience to join the believers. In fact, I didn't go BG mainly because this is an office rig, and I just travel too many weeks to live through all the bloom cycles I would be faced with. So, I thought the Cerrafines would suit my application better. This was not an economic decision for me._

 

Agreed here, they sounded ok when i first ut my amp on and biased it, actually better than my old millett hybrid. Left them running in for a week and they sounded a bit better, plus they sounded quite good at the meet. Plugged everything back in last night and my amp does just sound 'icky'. perfect wording there pabbi. 

 This is with about 120-130 hours on them, so il keep them running in, and will eventually try some vit-q's in ca8 + ca9 position combinations.


----------



## tomb

Quote:


  Originally Posted by *joneeboi* /img/forum/go_quote.gif 
_I'm all for biasing up to 150mA, but I just don't have any clue how many mVs I need to hit that mark. I'm running ~24.5Vs so I can easily hit that 150mA mark, I just don't know how carefully I should tread. There's got to be something I can consult wrt to this matter. The MAX website says 264mV for MOSFETs will give me 120mA. Does this transfer over for BJTs? I checked the MAX site, Steinchen's dB site and the M^3 site but I couldn't find anything.

 edit: Also, I'm running with the top of the Hammond enclosure removed, so the greenhouse effect will be avoided._

 

Others have given you the formula. What's happening is that the current across the transistors (the bias, IOW) is determined by the voltage across the 2.2 ohm output power resistors. Since I = V/R, then I(ma) = V(mV)/2.2. Or:
 mV measured = Desired Current Bias * 2.2.

 You may be taking a mile after getting an inch, though. Yes, you are correct from Amb's table that perhaps 150ma should be possible with 24V and 1.5" heat sinks (actually 155ma, interpolating correctly from your 24.5V). However, keep in mind that those are for TO-220 MOSFETs. MOSFETs have that positive temperature coefficent, making them more stable and much more tolerant of heat + high bias. The TO-220, with its full metal back and tab will also have better heat transfer characteristics than the TO-225 of the MJE's.

 So, to be conservative and safe, 100ma should be easy to obtain. Higher than that could be risky, IMHO. So, tread carefully.


----------



## fordgtlover

Tomb

 those BGs look absolutely stunning.

 The BJTs are mounted on the Mosfet side. Are they a different package to the usual ones? (demonstrating an absolute lack of knowledge of BJTs)


----------



## Televator

Quote:


  Originally Posted by *amphead* /img/forum/go_quote.gif 
_YEEAAOOOW! Its a slammin, killing machine! Another MAX Lives! 
	

	
	
		
		

		
		
	


	








_

 

good work amphead, good fortune pabbi! another MAX lives!!(it was a close call, but some first aid revived it without too much problems 
	

	
	
		
		

		
		
	


	




 )


----------



## tomb

Quote:


  Originally Posted by *Listen2this1* /img/forum/go_quote.gif 
_Tomb In position CA4/5 they are Muse 470uf 35v, In position CA2 it is a Muse 1000uf 16v. The output trannies are the ones direct linked from the BOM. I was wanting to get some of the Toshiba's but then you had that shipping problem, so I went with the ones from the link. I am currently using Rca 12fk6 tubes. Bias is staying really stable._

 

You should be getting fantastic bass, based on your parts selection. I'm somewhat at a loss to suggest things that could help - you should already be there. However, here are the guesses in no particular order:

 1. You might try some upsized power caps instead of the ES's in the CA4 and CA5 positions. Those positions aren't necessarily supposed to affect the bass, but perhaps the fact that the ES's are bi-polar is messing up the application at that point. Those caps are supposed to ensure decoupling between the V+ and Ground, which maintains the voltage differential. Bipolar caps will let current flow in either direction, perhaps defeating the entire purpose of caps at those positions.

 Use some regular power caps - FM, FC, UPW, or UHE's, 1000uf minimum. I like those 1800uf 35V Panasonic FM's here. They're not very expensive and are 1" in height - very potent.

 2. You might try the Nichicon FG 1000uf 35V at the CA7 positions. It's an audio grade cap that's only 1" high and is inexpensively available at Handmade Electronics. I'm not sold on this, though, because I've heard nothing but good reports from Grado owners all the way back to the old revMH Millett Hybrid - using a 470uf for the output cap. The difference between a 470uf and a 1000uf combined with Grados may only be 5Hz within the audible frequencies, so I doubt that this would have a noticeable affect on increasing bass, but there it is. Plus, bipolars (ES's) in this position would be superior, whereas the FG would not.

 EDIT: If you don't have height restrictions, there are many possibilities - 1000uf 50V KZ's would be an excellent choice. There's also the 1000uf 50V Elna Silmic RFS's at DigiKey. For that matter, you can try a simple power cap such as the Panasonic FM, as long as it's bypassed with the WIMA. The FM would be well under 1", too. Lots of possibilities ...

 3. Have you verified your source? Perhaps it has a bass rolloff that you've never really tested until you built the MAX. 

  Quote:


 Should the mje253's run warmer than the mje243's? 
 

Not in principle, but anything located on the center two sinks will run hotter. That's the nature of the tradeoffs in designing the board - the middle two sinks don't have enough air space between them and will run hotter. This is as it should be, given the design. 
  Quote:


 Also I am using the Grado 325i's, I know they are slightly on the bright side, this is why I am wanting a little more bottom end. 
 

Again, you should not be experiencing a lack of bass, even with the lower impedance Grados. There is nothing particularly deficient with the MJE's. They may not slam as with the 2SC3422's, but they are not going to be lacking in bass.


----------



## tomb

Quote:


  Originally Posted by *fordgtlover* /img/forum/go_quote.gif 
_Tomb

 those BGs look absolutely stunning.

 The BJTs are mounted on the Mosfet side. Are they a different package to the usual ones? (demonstrating an absolute lack of knowledge about BJTs)_

 

Thanks.

 Actually, that's demonstrating a _very good_ knowledge about BJT's. 
	

	
	
		
		

		
		
	


	




 It just so happens that there are a few pairs with reversed pinouts. The 2SC2238/2SA968's are one of those pairs.


----------



## tomb

Quote:


  Originally Posted by *pinkfloyd4ever* /img/forum/go_quote.gif 
_Ya I've been wondering about this too, because at $1 each they're not cheap. I'd like to be able to use the full range of the pot but I have no idea what values would work best with my cans (ya I know somewhere b/t 10-150 ohms)._

 

to be honest, I'm not sure "the full range of the pot" is a realistic expectation. I can't even get above 1/2 volume with Sennheisers on a portable PIMETA with a gain of ~4. The rest of that volume travel should be reserved for those instances where you might have weak sources such as an iPod, etc., IMHO - but maybe that's just me.
  Quote:


 For now (meaning at least for a yearish) I just have an MS-1 & some KSC-75s, which are both 32 ohms, correct? 
 

Actually, the KSC75's are 60 ohms, but they are so efficient that the volume travel needed maybe less than the Grados (Allessandros).
  Quote:


 But when/if i get new cans I might wanna change em...crap. Goodbye money, hello ton of $1 resistors that I'll end up using exactly 2 of...
	

	
	
		
		

		
		
	


	



 

It will take 150ohms to get anywhere close to what you're describing. Remember that you can always run leads to the resistor pads and connect them to a DPDT switch. That will give you two choices of resistance.

 Also, you want to be using a 12FK6 if you're not already. That tube has the lowest inherent gain (7).


----------



## joneeboi

Hello all,

 I bring yet again power supply woes to the Wise in Millett. I was already going to get the www.mpja.com wallwart that tomb recommended and that others have already employed, except that when I plugged in a set of KSC75s with impedance adaptor (DMM showed ~130ohms per channel), a low frequency hum was very apparent. The volume knob doesn't affect it, so my guess is that it has to do with the 60Hz hum from the wallwart I have right now. You can hear the hum putting your ear next to the wallwart, and now I have the fun of having it being transmitted through the audio chain. Yeah!

 Now my question is whether I should go with the mpja wallwart or go with a higher quality one in a separate and matching Hammond case? Is there a workaround for this hum? Is anyone else noticing a hum? It's almost inaudible with my SR60s, and it was okay with my KSC75 at its regular impedance. Will a higher quality toroid eliminate this hum? Hum hum hum hum hum hum hum. Stupid hum.


----------



## tomb

Quote:


  Originally Posted by *joneeboi* /img/forum/go_quote.gif 
_Hello all,

 I bring yet again power supply woes to the Wise in Millett. I was already going to get the www.mpja.com wallwart that tomb recommended and that others have already employed, except that when I plugged in a set of KSC75s with impedance adaptor (DMM showed ~130ohms per channel), a low frequency hum was very apparent. The volume knob doesn't affect it, so my guess is that it has to do with the 60Hz hum from the wallwart I have right now. You can hear the hum putting your ear next to the wallwart, and now I have the fun of having it being transmitted through the audio chain. Yeah!

 Now my question is whether I should go with the mpja wallwart or go with a higher quality one in a separate and matching Hammond case? Is there a workaround for this hum? Is anyone else noticing a hum? It's almost inaudible with my SR60s, and it was okay with my KSC75 at its regular impedance. Will a higher quality toroid eliminate this hum? Hum hum hum hum hum hum hum. Stupid hum._

 

You have a problem with your PS on the MAX board, and it is the source of the same trouble you've had all along. There is no reason that you can't get 27VDC and you will not have _any_ hum with a properly constructed PS section on the MAX board.

 Give us some pics of the PS section only - that's the big sink, the rectifiers and the four caps - top, bottom, and side facing the LM317. There's something wrong.

 EDIT: By design, _every_ walwart used for the MAX will have hum, because the MAX uses only AC walwarts. It's the purpose of the onboard PS to remove all of that hum - the ripple, too - until it's completely inaudible and effectively the same as that using a STEPS-like power supply.


----------



## adfinni

No inside pics until i can be bothered to take the top off the case. il explain later on when i get the main pics up why it's such a PITA 
	

	
	
		
		

		
			





 Here's the first one shot in a dark light on purpose. Il get the other ones up later or wait until daylight tomorrow and take my sisters better digi camera.


----------



## Televator

I just added some 25 pics of my Millet Max (as thumbnails of course 
	

	
	
		
		

		
		
	


	




 ) in the DIY gallery thread here: link

 some of the pics have been posted in this thread as well, but there are quite a couple extra (including from case design and of my final version) and behind the thumbnails are high res versions as well...

 @ Tomb: feel free to add them to your MAX-pages if you want to

 BTW: typing these words while enjoying Puscifer (with Maynard James Keenan) through my NAD C542 -> MAX -> 75Ω adapter -> MS2i ... the only thing humming here is me


----------



## amphead

Pabbi, now I can check out the other Max board that you sent. More info later. I want to get these boards shipped back asap.

 Thanks Televator, I'll probably do a pro bono repair again. If anyone else gets into a similar fix.


----------



## pabbi1

Quote:


  Originally Posted by *amphead* /img/forum/go_quote.gif 
_Pabbi, now I can check out the other Max board that you sent. More info later. I want to get these boards shipped back asap.

 Thanks Televator, I'll probably do a pro bono repair again. If anyone else gets into a similar fix. _

 

I am just simply astounded with the overwhelming generousity of this community. There are simply not words to express my gratitude to Ron for bailing me out - no other way to put it.

 We can only hope no one else has a cluster like this - mostly preventable by RTFM, and not wicking on too much solder.

 Let's hope the other board is less problematic. Oh, and Ron, let me know your Paypal to cover the shipping back when that is applicable. Finally, keep all the extra parts in case a pro bono pops up - or, you wanna do another personal build - I'll certainly not be using them.


----------



## joneeboi

Well, I have some bad news to report.

 I biased up my dBs as per the past two pages and things were going great for a while. The left channel actually would only go up to 230mV (~104.5mA) while the right could go right up near 300, but I decided they should probably be equally biased. At any rate, I unsuspectingly put even more strain on an already struggling wallwart which died on me not more than 10 minutes ago. I will be putting a rush on the mpja wallwart, as I want my music and I'm having a mini-meet this Saturday just to showcase the MAX. *sigh* AND I was listening through the very annoying humming. I'll take those pictures and what not eventually, Tom, don't worry


----------



## ruZZ.il

did you hear much difference? I'm really not sure how much difference there really is.. also, not that I'm familiar with the other side, but if you bias too much, you could be dropping out of linearity as the transistor reaches its saturation current (which may be a lot more than we're using anyway.. I haven't looked at the specs too much ). I still think you should look into getting better transistors. They may satisfy your need to push more. When I changed my BD139/140's to the 3422 pair (I think), it was like taking a pillow case off my head.


----------



## tomb

Quote:


  Originally Posted by *joneeboi* /img/forum/go_quote.gif 
_Well, I have some bad news to report.

 I biased up my dBs as per the past two pages and things were going great for a while. The left channel actually would only go up to 230mV (~104.5mA) while the right could go right up near 300, but I decided they should probably be equally biased. At any rate, I unsuspectingly put even more strain on an already struggling wallwart which died on me not more than 10 minutes ago. I will be putting a rush on the mpja wallwart, as I want my music and I'm having a mini-meet this Saturday just to showcase the MAX. *sigh* AND I was listening through the very annoying humming. I'll take those pictures and what not eventually, Tom, don't worry 
	

	
	
		
		

		
		
	


	


_

 

 Quote:


  Originally Posted by *ruZZ.il* 
_did you hear much difference? I'm really not sure how much difference there really is.. also, not that I'm familiar with the other side, but if you bias too much, you could be dropping out of linearity as the transistor reaches its saturation current (which may be a lot more than we're using anyway.. I haven't looked at the specs too much ). I still think you should look into getting better transistors. They may satisfy your need to push more. When I changed my BD139/140's to the 3422 pair (I think), it was like taking a pillow case off my head._

 

-Sigh-
 Yes, ruZZ.il is correct to question whether it would make a difference in sound, although I think the MJE's can take 15W under the right scenario and max collector current is 4A.

 Regardless, I think the thing to say is to repeat that there's something more going on - especially with your onboard PS. This may not be the time to tread untested ground by seriously hiking up the current bias on your transistors. In any case, I had thought that perhaps my recommended limit was 100ma - even before we confirmed that you have a problem in the PS. Yet, you went to ~136ma on the right channel. 
	

	
	
		
		

		
		
	


	




 There is another transistor that is probably more of a limiting factor than the output trannies - the JFETs at QB1 and QB2. I'm not entirely certain what they can take or support in terms of current. It's quite possible that they reach a saturation current as ruZZ.il describes. As a lowly TO-92, that may not be much and heat sink options are certainly limited. As we've all seen when matching trannies, the ratings (as in current saturation) can also vary from one TO-92 to another, which probably explains the difference in adjustment range you noticed between channels. The DB current mirror is actually setup as a current multiplier, so the JFETs see much less current than the output trannies. That means only a small variance in current saturation at the JFETs might result in the 30-40ma difference betwen channels. Still - it's probably certain that those are the limiting devices in this whole experiment.

 While you're waiting for that MPJA walwart, let's figure out what's wrong with your PS. You should never have blown your first walwart in the first place. My guess is that your LM317 is bad, and is not regulating at all - just passing through the voltage with a sizable drop. In that case, the 4000uf caps may not be enough to absorb all the hum and ripple. Just a guess, but there's something wrong (sorry for being redundant).


----------



## amphead

Pabbi, don't worry about the shipping. I'll just set aside 2 silmic IIs,2 cerafines and a single 12ae6. You have a nice sound going with silmic II(CA2) and cerafine(CA7).

 TomB, what are your thoughts regarding those caps in those positions? I like Pabbis configuration.


----------



## tomb

Quote:


  Originally Posted by *amphead* /img/forum/go_quote.gif 
_Pabbi, don't worry about the shipping. I'll just set aside 2 silmic IIs,2 cerafines and a single 12ae6. You have a nice sound going with silmic II(CA2) and cerafine(CA7).

 TomB, what are your thoughts regarding those caps in those positions? I like Pabbis configuration. _

 

It probably makes an oustanding configuration. I don't often recommend them for two reasons:
 1. I try to adhere to the 1" height and the board in the 3rd slot. That pretty much limits things to the ES's, Black Gates, or a normal cap bypassed with the Wima's such as an FM, UPW, etc.
 2. The Cerafines are particularly hard to find these days - probably Welborne is the only place anymore, and they've been sold out of the 470uf 35V for a long, long time. They've also had a number of bad reports lately.

 You can see that none of those reasons have anything to do with sound. 
	

	
	
		
		

		
		
	


	




 Pabbi's configuration completely does away with the typical casework for obvious reasons (balanced amp), so reason #1 doesn't apply. As for the Cerafines, that's the book choice given his reasoning about liking Black Gates but not being able to tolerate the repeated break-in cycle.

 Most likely his Vitamin Q's have as much do with the signature as anything else. As we've learned, they may be much more linear and uncolored than the typical blooming-mids boutique film cap, which is the important thing for the MAX - especially in that position near the tubes. The Vitamin Q's may be safest bet for the MAX other than Wima's - and considerably better. The catch again that doesn't apply to Pabbi - is fitting them in.

 These Russian caps that Fordgtlover has found on e-bay have a lot of potential. They're only 24mm long without the nipples, but the nipple fits perfectly (maybe some sanding) in the tombstone spot on the output positions and they fit horizontally back by the tubes, anyway. I'm going to test them, too, and will report back.


----------



## tomb

Just to reiterate until I get a chance to update the website:

 1. CA9 (film cap position by the tubes): Either something very linear like Vitamin Q's, Wima's, or NOTHING.

 Beware the use of commonly accepted boutiques with blooming mids - they will destroy the MAX's frequency response in the CA9 position

 2. CA8 (film bypass on the output caps): whatever you like that sounds best. A blooming-mids boutique can sound very good here, but be mindful of the degradation to the frequency response.

 The MAX has a tremendous bass slam that may be _adversely_ affected by blooming-mids film caps, especially in the CA9 position.


----------



## adfinni

Here are my first set of external pics. Unfortunately it was hard to get all the dust off the case, but il try again when i get the internal pics. I think the bright sun gives some cool effects


----------



## joneeboi

Nice pictures, adfinni. That PSU window is pretty snazzy 
	

	
	
		
		

		
		
	


	




 tomb: I didn't actually bias the right channel all the way up to 136mA, I just meant that it could go up that far to show the strange difference between the channels. They were both sitting right around 230mV give or take a few mV when the wallwart exploded. I only crossed the line by a tiny bit 
	

	
	
		
		

		
		
	


	




 In any case, I was about to checkout my order at MPJA when I read their international shipping policy. I have to order a minimum 100USD before shipping which is totally bunk. I only need about 20USD worth of stuff, but I can't exactly get it without an American address. Is there someone who's willing to purchase my stuff for me (after I send some dough through Paypal of course) and send it to my location? I think you may need an American billing address too, but we can talk about that if anyone is willing to do it for me. Pretty please?

 Cherries, whipped cream and sprinkles included with pleading.


----------



## pabbi1

Quote:


  Originally Posted by *amphead* /img/forum/go_quote.gif 
_Pabbi, don't worry about the shipping. I'll just set aside 2 silmic IIs,2 cerafines and a single 12ae6. You have a nice sound going with silmic II(CA2) and cerafine(CA7).

 TomB, what are your thoughts regarding those caps in those positions? I like Pabbis configuration. _

 

Oh, and there are plenty of VitQ in case you want a few of those - I had to buy 25, and unfortunately, also bought 25 of the 1.5" size as well.


----------



## ruZZ.il

sweeet case, adam!


----------



## pinkfloyd4ever

Quote:


  Originally Posted by *adfinni* /img/forum/go_quote.gif 
_Here are my first set of external pics. Unfortunately it was hard to get all the dust off the case, but il try again when i get the internal pics. I think the bright sun gives some cool effects 
	

	
	
		
		

		
		
	


	


_

 

yes, very nice case indeed, prolly the nicest utilization of the stock Hammond case I've seen yet. How'd you make those rails? And that big hole in back? U using a machine shop?


----------



## colonelkernel8

The rails look like cabinet door handles from a hardware store possibly.


----------



## ruZZ.il

despite PCXs rep. for sometimes taking their time, I just got a shipping confirmation, so thats within 24hrs. Second time they've worked out quickly for me. I took you up on the PRP suggestion, Tom. Along with some tube sockets, cheap rca jacks, and 2x0.47 BGs. Will order some spare tubes sometime


----------



## adfinni

Quote:


  Originally Posted by *pinkfloyd4ever* /img/forum/go_quote.gif 
_yes, very nice case indeed, prolly the nicest utilization of the stock Hammond case I've seen yet. How'd you make those rails? And that big hole in back? U using a machine shop?_

 

hehe, thanks 
	

	
	
		
		

		
		
	


	




 the hole in the back was simply made with my dads dremel substitute. I went through x2 cutting discs too. The surround rubber was some spare window trim that i use to cut and finish side windows on pc side panels, not glued or attached in anyway, the interference fit holds it in place well enough.

 For the handle question, well that's already been answered 
	

	
	
		
		

		
		
	


	




:

  Quote:


  Originally Posted by *colonelkernel8* /img/forum/go_quote.gif 
_The rails look like cabinet door handles from a hardware store possibly._

 

One problem i totally overlooked is the assembly and disassembly. the handles have their own M4 bolts that i trimmed down. But unfortunately my caps touch the top of the case and i totally forgot about the heads of the bolts. this means that if i want to take off the top, the pcb must come along with it. the same vise versa.

 But by using large nylon sockets around where the tubes exit the chassis i can adjust the dB and tube bias voltages relatively easy with my jewlers screwdrivers. Plus i have drilled holes in the bottom of the chassis so i can read the voltages from the test points, but i do have to turn the chassis on its side. I couldn't use the tip jacks as the board is already in the bottom slot, and bunching them up around where the RCA sockets are would have been messy.

 But the internal pics are much better than the external ones


----------



## amphead

Ok thanks Pabbi!
 Thanks TomB!
 Adffini, thats beautiful! Built like a tank! I think it needs a Hummer logo.


----------



## Ech0

adfinni, that's one cool case for all the reasons stated above. I like the interconnects too. I took a look at your "how to" on the IC's. Nicely done. 

  Quote:


  Originally Posted by *amphead* 
_I think it needs a Hummer logo. _


----------



## smegger

just made the plunge and payed for my max kit!!! woo cant wait till it gets here
	

	
	
		
		

		
		
	


	










, 

 i have bought a toroid for it could someone check it will work ok?

http://onecall.farnell.com/jsp/searc...sp?SKU=4335041


----------



## amphead

The price is good smegger, but I think the 30VA rating is a little low for long life. I would go for something rated at 40VA. I think Ferrari could answer that better though.


----------



## joneeboi

Quote:


  Originally Posted by *joneeboi* /img/forum/go_quote.gif 
_In any case, I was about to checkout my order at MPJA when I read their international shipping policy. I have to order a minimum 100USD before shipping which is totally bunk. I only need about 20USD worth of stuff, but I can't exactly get it without an American address. *Is there someone who's willing to purchase my stuff for me (after I send some dough through Paypal of course) and send it to my location?* I think you may need an American billing address too, but we can talk about that if anyone is willing to do it for me. Pretty please?

 Cherries, whipped cream and sprinkles included with pleading._

 

Bump. I of course will pay shipping both to your location and to mine.


----------



## pinkfloyd4ever

Quote:


  Originally Posted by *joneeboi* /img/forum/go_quote.gif 
_Bump. I of course will pay shipping both to your location and to mine._

 

what else do you need from them besides the walwart? Check this out... http://search.ebay.com/Class-2-Trans...MEFSRCHQ3aSRCH

  Quote:


  Originally Posted by *smegger* /img/forum/go_quote.gif 
_just made the plunge and payed for my max kit!!! woo cant wait till it gets here
	

	
	
		
		

		
		
	


	










, 

 i have bought a toroid for it could someone check it will work ok?

http://onecall.farnell.com/jsp/searc...sp?SKU=4335041_

 

same for you smegger


----------



## tomb

30VA should be plenty for a BJT MAX, as long as you don't go turning up the bias to some crazy amount. 50ma is plenty.


----------



## joneeboi

Hey all. PS update. Yay!


----------



## amphead

Pabbi, update: the second amp you sent was fine with your build. I biased both amps up to spec. The audio test was close to the first amp, very nice!  I will try to get them shipped to you tomorrow. I think that you are on your way to some listening bliss real soon! I didn't have time to wire them in balanced configuration, so you will be first to hear them that way.


----------



## tomb

OK - thanks for the pics, Joneeboi.

 I would say that you need to re-do that LM317. It looks quite possible that the leads are not making good contact with the traces on the bottom. It's possible that one lead is not making contact at all, but it's hard to tell - that's sort of an indicator by itself (hard to tell). Depending on whether you've replaced this or re-soldered it any, the plating in the holes may or may not be there. So, it's important to get that thing down in the holes and soldered well. I know that's difficult with a fixed hole in the heat sink, but you can remove the LM317 entirely and solder "extensions" on the leads. Better yet, get a new one. Do they have Radio Shacks in Canada? You can get one there, although at a premium for $2.50. Or, I can send you another one in your walwart order. Just let me know.

 You also need to use a proper insulating washer and keep that screw isolated from the metal tab. The heat sink is actually isolated from the ground plane in the PS, but there's no telling what may come in contact with the sink when you case it up or you are adjusting things.

 I think if you get those two things fixed, it should solve a lot of your problems.

 EDIT: One way to look at it is that the entire current flow for the entire amp goes through that voltage reg. It's important that it has good contact all around, and that it's insulated/isolated.


----------



## pabbi1

Quote:


  Originally Posted by *amphead* /img/forum/go_quote.gif 
_Pabbi, update: the second amp you sent was fine with your build. I biased both amps up to spec. The audio test was close to the first amp, very nice!  I will try to get them shipped to you tomorrow. I think that you are on your way to some listening bliss real soon! I didn't have time to wire them in balanced configuration, so you will be first to hear them that way._

 

Well, one outta two ain't bad... 

 I am so pumped, as I bit off more than I could chew this time... and, I can't wait to show the final working product. I was serious about you keeping and retaining / redistributing the 'spares' as you see fit, including the wallwart, which is useless to me. Oh, and I'll get the spare VitQ, and all the caps I can't use headed your way.

 Again, without your help, this would be simply not have happened.


----------



## ruZZ.il

kudosX2


----------



## colonelkernel8

wow, nice pictures, holy **** macro.


----------



## smegger

i am using a toroid cause i need 240v and i hate wall warts! i looked at 240 v wall warts and my toroid was as cheap, i will consult further when i am building but just wanted to check it is possible for me to use this with a kettle lead.


----------



## tomb

Quote:


  Originally Posted by *pinkfloyd4ever* /img/forum/go_quote.gif 
_what else do you need from them besides the walwart? Check this out... http://search.ebay.com/Class-2-Trans...MEFSRCHQ3aSRCH



 same for you smegger_

 

Good link! Thanks!


----------



## thomaskuhn

I thought I saw in some post somewhere about Mouser carrying a heatsink bolt kit? I thought the post said something about it containing washer, mica, bolt, and nut. Does this exist? I swear I saw it somewhere but have searched and can not find it.

 Tom


----------



## tomb

Quote:


  Originally Posted by *thomaskuhn* /img/forum/go_quote.gif 
_I thought I saw in some post somewhere about Mouser carrying a heatsink bolt kit? I thought the post said something about it containing washer, mica, bolt, and nut. Does this exist? I swear I saw it somewhere but have searched and can not find it.

 Tom_

 

Mouser -
 SilPads (no grease req'd): 532-4880SG
 Thermafilm (upgraded insulator - still needs grease): 532-4880
 Mica (economical choice, grease req'd): 532-4880M

 EDIT: These are all kits, not just the insulator. If you plan on building more than one MAX, you might want to just buy the insulators and the shoulder washers. They are cheaper in bulk. The screw hardware can be purchased for $2-$3 per hundred (washers, lock washers, 4-40 screws, and nuts).


----------



## amphead

Ok Pabbi, the boards left here this afternoon, Priority Mail. 
 You might want to test them with your phones as individual amps, before wiring them in balanced configuration, however I will be interested in your review with a balanced source.


----------



## pabbi1

Quote:


  Originally Posted by *amphead* /img/forum/go_quote.gif 
_Ok Pabbi, the boards left here this afternoon, Priority Mail. 
 You might want to test them with your phones as individual amps, before wiring them in balanced configuration, however I will be interested in your review with a balanced source. _

 

I definitely will as they will be wired balanced and as two seperate amps with the Neutrik combo jacks... I have both a balanced source (Eastsound E5, with a Zap filter), and with an OPUS DAC in the enclosure from the digital put on an inexpensive DVD source. So, the journey isn't quite over... but I can see the end from here.

 A review will definitely be published, with a summary of the journey - all the pieces have been published here and there.

 Oh, and I am adding yet one more altruistic piece to the fabric - more when finished.


----------



## tomb

Quote:


  Originally Posted by *pabbi1* /img/forum/go_quote.gif 
_I definitely will as they will be wired balanced and as two seperate amps with the Neutrik combo jacks... I have both a balanced source (Eastsound E5, with a Zap filter), and with an OPUS DAC in the enclosure from the digital put on an inexpensive DVD source. So, the journey isn't quite over... but I can see the end from here.

 A review will definitely be published, with a summary of the journey - all the pieces have been published here and there.

 Oh, and I am adding yet one more altruistic piece to the fabric - more when finished._

 

We'll stay tuned. 
	

	
	
		
		

		
			





 Many thanks to Amphead for helping you through this.


----------



## tomb

I thought this was of particular interest in the DIY build thread for the MAX. Mainly because in all of these discussions about boutique caps - which ones work, which ones don't, etc., etc. - we lose sight of the fact that the MAX in only a basic configuration is a _very_ respectable amp.

 What I took note of in the following pic and quotes is that Soloz2's MAX is equipped with only ES caps on CA2/CA7 and WIMA's all around. Also, It sounds like he hadn't even reached standard bias on his BJT DB's during the meet. That makes the performance even more impressive.

 Hopefully, he doesn't mind, but the following are quotes and a pic that can be found in a "Meet Impressions" thread recently posted here:
http://www.head-fi.org/forums/showthread.php?t=268454

 The MAX is in the company of at least a B22 and one Aikido, maybe two - I can't really figure out from reading the thread, but maybe some of you recognize some of the very serious equipment in that thread. Of course, no one is really saying that the MAX is as good as those amps - just that it's not out of place in that company and acquits itself very well. Anyway, I picked out the best overal pic of the equipment, I think, and the salient quotes:






  Quote:


 I do have to say that I was impressed with my Max's ability to keep up with the other amps we had on hand. I need to get my butt in gear and finish it! I built it a while ago, but had been working on a mini review for a couple computer forums since Marshal sent me a Mini3 and XP so my Millet got no love for the last month. The Max is a great amp for the price and while it was not as detailed or refined as the other amps we had present, it was in no way outclassed by any of them in my book and Jay seemed to think the same. I'll have to dial up the diamond buffers and see what it's capable of in the upcoming weeks. 
 

 Quote:


 Millet Max:
 Though not quite as good as other full size home amps, I was surprised as to how close it really was. It was a little rough on the high end, but it smoothed out nicely when we switched digital cables to the zhaolu source, which was feeding it. Which just goes to show you how important system matching can be. Even a digital cable can make or break the synergy of a combo. 
 

 Quote:


 btw, I turned the db up to 75mv last night and she sounds smoother than ever with my beyers 
 

 Quote:


 I dialed up the bias on the diamond buffers on my Max a bit more and the highs seem a bit smoother now. I'm really wishing that I had had the time to tweak it a bit more before the meet or that we had busted out one of Jim's meters while we were there. I think you'd like to give it another listen. Hopefully it won't be too long before we can do this again! 
 

As I say, hopefully Soloz2 doesn't mind. I thought it was important to put some of our discussion in perspective and give you guys an idea of what's possible without spending $$megabucks on boutique caps, etc., etc.


----------



## fordgtlover

I'm sure these type of comments will be echoed many times.


----------



## pabbi1

Just to really ratchet the comparisons up a notch, I will be comparing balanced Maxx to the Blue Hawaii. Normally, red flags go off all over (12xx6 ve el34, dynamic v electrostatic, Denon v Senn/Stax, $$$ v $$$$, home v office), but what the heck? That is all I have to compare against. But, both will be fully balanced, so let's see all the heads spinning on this one.


----------



## Ooztuncer

Hi guys,
 I have couple of questions if I may.

 is it feasible 
 1) to modify millett max to utilize 6AS7G tubes?

 2) to modify so that it will have an optical in and a built in dac

 3) to add balanced out option

 unfortunately, I have very very limited knowledge on diy stuff, so please bear with me.

 PS: I don't have a millett and even if I had I wouldn't try to modify it with my butcher skills, I am just wondering. Thanks...


----------



## ruZZ.il

I think the max is already pretty tube specific but regarding all the rest, basically, yes. There are little dacs or bigger dacs that one could add on, like an alien DAC or twisted pear opus DAC that can. be for either USB or optical in. Pabbi1 here is using an opus to feed 2 amps in balanced mode. Can be done with some experience skill and knowledge.. And friendly help 
	

	
	
		
		

		
		
	


	




 btw this is my first time on an ipod touch and its fn cool 
	

	
	
		
		

		
		
	


	




 read a bit.back here and search those dacs


----------



## bperboy

Quote:


  Originally Posted by *ruZZ.il* /img/forum/go_quote.gif 
_btw this is my first time on an ipod touch and its fn cool 
	

	
	
		
		

		
		
	


	




 read a bit.back here and search those dacs_

 

LuckY!! I'm gonna try and get one for xmas this year; they look fn awesome!


----------



## amphead

Thanks Pabbi!
 Thanks TomB!

 I don't have a balanced source per say just a Rega P2 TT(which it is of course). Need to build a second Max to hear that in balanced mode. Will need another Max board to get that done. Looking forward to it.

 Will be receiving my Sony NWZ- A818 8GB flash tomorrow. I returned a Creative Zen V 2GB, last week. It sounded quite good through the Max, but had to be reset 2 times in a week. The new Sony product got good reviews for sound. I'll describe the sound when I get it. 

 The thread seems to have gotten quiet concerning build problems. Anyone having major trouble getting their Max going, can get it fixed online or by the hired gunslingers/pro bono techs monitoring this thread.


----------



## amphead

So I pulled 470uF BGs from CA2 and replaced those with Silmic II 1000uF and replaced Wimas at CA9 with Vitamin Qs. Thanks again Pabbi. Paralleled the BGs 470uF at CA7 with those pulled from CA2, for 940uF. Pulled the Jensens at CA8 and removed RB14 resistors. So how does it sound? Detailed highs, musical mids, clear vocals, tight bass. Presence is better. I put a jumper on one side of the Jensens at CA8, and while listening I snipped the wires connecting them. No audible difference without them. Just wasted space. I have rolled so many different combinations that its made my head spin. This configuration will stand, unless a ufo crashes and I salvage some advanced capacitors from the smoking wreckage.  Edit: Or would they be using SMD.


----------



## pinkfloyd4ever

Quote:


  Originally Posted by *amphead* /img/forum/go_quote.gif 
_So I pulled 470uF BGs from CA2 and replaced those with Silmic II 1000uF and replaced Wimas at CA9 with Vitamin Qs. Thanks again Pabbi. Paralleled the BGs 470uF at CA7 with those pulled from CA2, for 940uF. Pulled the Jensens at CA8 and removed RB14 resistors. So how does it sound? Detailed highs, musical mids, clear vocals, tight bass. Presence is better. I put a jumper on one side of the Jensens at CA8, and while listening I snipped the wires connecting them. No audible difference without them. Just wasted space. I have rolled so many different combinations that its made my head spin. This configuration will stand, unless a ufo crashes and I salvage some advanced capacitors from the smoking wreckage.  Edit: Or would they be using SMD. _

 

wow that's alot of stuff to change at once. I like to change one thing at a time so you can tell what is causing any audible differences. Anyway I'd be interested in hearing your opinion on how the Silmics compare with the BG's if you get time to swap just those back & forth maybe a few times w/o changing other stuff...once the Silmics have time to burn in. How many hours you got on your BGs?

 tomb, for that BG version you built last weekend, did you use 35v 680ufs at CA7 and 25v 1000ufs at CA2? or 1000 ufs for both?
 EDIT: nvmd, I looked where you posted it...duh
 I know it is possible to have too much capacitance. Would it possibly be detrimental to use 1000ufs at CA7? I don't recall seeing anyone do that until amphead (well 2 paralleled 470s anyway) just now. 

 Oh and are the trimpots that click the ones from Digikey, the Muratas?


----------



## fordgtlover

Quote:


  Originally Posted by *amphead* /img/forum/go_quote.gif 
_So I pulled 470uF BGs from CA2 and replaced those with Silmic II 1000uF and replaced Wimas at CA9 with Vitamin Qs. Thanks again Pabbi. Paralleled the BGs 470uF at CA7 with those pulled from CA2, for 940uF. Pulled the Jensens at CA8 and removed RB14 resistors. So how does it sound? Detailed highs, musical mids, clear vocals, tight bass. Presence is better. 
 snip_

 

Interesting about the Silmic IIs. I can't say that I was fond of them in CA2 or CA7, regardless of bypassing with any of the WIMA, K42 Russian PIO or VitQ. I liked them the least in CA7, but in CA2 they were still causing the sound to be grainy (just a little less so).

 I admit that I didn't allow them more than about 30 or so hours to settle in. During all of that time they sounded the same.

 Others are using the Silmics and presumably are having success.

 Is it possible that they lack synergy with the Mosfet version?

 I am still keen to try the Nichicon ES caps in both positions. I have offered a trade on the For Sale / Trade forum offering a capacitor trade, but no takers yet.


----------



## tomb

Quote:


  Originally Posted by *pinkfloyd4ever* /img/forum/go_quote.gif 
_<snip>

 tomb, for that BG version you built last weekend, did you use 35v 680ufs at CA7 and 25v 1000ufs at CA2? or 1000 ufs for both?
 EDIT: nvmd, I looked where you posted it...duh
 I know it is possible to have too much capacitance. Would it possibly be detrimental to use 1000ufs at CA7? I don't recall seeing anyone do that until amphead (well 2 paralleled 470s anyway) just now._

 

Yes, those are pretty much the available sizes in the Black Gate NX's anyway - 1000uf 25V and 680uf 35V. There's a 1500uf 10V that would also work in CA2, but comparing with caps that actually report their numbers
	

	
	
		
		

		
			





, the 1000uf 25V should have lower ESR. 

 Besides going tall with an Elna Silmic or Nichicon KZ, both of which have 1000uf 50V (the KZ is 40mm tall
	

	
	
		
		

		
		
	


	




), there's a Nichicon Muse Fine Gold (FG) that's 1000uf 35V. It's very inexpensive at Handmade Electronics at $1.05 ea.
  Quote:


 Oh and are the trimpots that click the ones from Digikey, the Muratas? 
 

No. The Muratas don't click - thank goodness. The ones that click break. I use the Muratas all the time and just turn in 15 clockwise (by counting) turns on the DB trimmers before kicking on a new MAX. The other trimmers don't matter until you check those DB's.

 *******************************************
*DB Biasing (BJT's)*

*Startup:*
 Generally speaking, the differences in JFETs will determine the minimum current which seems to be anywhere from 20-40mV. It should take several turns to get a reaction from that point once you've turned them on.

 Kick it on and off and move your probes to the other DB's until you're sure that both sets are asleep. Then adjust the PS voltage to the desired value. Once that's set, then go back to the DB's.

*Start Adjusting - One DB, Then Another:*
 It should take several turns after that to notice the mV climb. Once the voltage starts to change, it will go 2 or 3mV per turn. Once you get to around 50mV on the DB's, the change may be 5mV per half-turn. When you're in the 60mV range, you can be pretty sure that the DB's are running in a minimum Class A and actually pulling DB current compared to the unadjusted position.

 When you get to 90mV or thereabouts, you'll notice that the change may be 5mV _per quarter turn_. This may be where some people get into trouble. If you kept turning it from the lower positions and never gave it a chance to run for awhile and heat up, it's fairly easy to get it to 150mV or more without hardly trying. _One good way to keep from doing this is to try to keep the DB's even - adjust for 20mV or so, then go to the other one. In the time it takes to adjust the second DB, the first has had some heat on it for awhile.

 Be sure to check both test points on each DB - there will be a slight difference, depending on how well you did your matching, and how well the output transistors are matched (sort of out of your control). Pick the high one if the settings differ and use that as your guide.

*Adjust to 90mV, Adust Other Settings, Start Listening:*
 So, 80-90mV, ease up with a half-turn at a time, waiting about 5minutes inbetween until you get to about 90mV. I actually stop at this point and check all the other settings - bias the tubes, re-check the PS Voltage, etc. For a final check, measure the offset from Input Ground to Output Left, Right, and Ground - this should be in single-digit mV or just -0-. Then I plug headhones in and start listening at this point - probably for about an hour.

 Continuously check the DB settings for evidence of runaway (I unplug the headphones and turn the volume down for a measurement.) They should be hot on the sinks, but unchanging.

*Adjust for Final Setting:*
 When you're satisfied that the adjustments are stable (don't worry if the tubes keep bouncing around), then go back to adjusting the DB's for that final bit to 110mV (50ma current bias). At this point, the trimmers should be fairly close to a hair-trigger adjustment, especially when you close in on 110mV. You may notice that 1/8 turn can mean the difference between 110mv - 115mV. So, you need to be careful at that point.

 I've done four of them that way so far with the Murata trimmers - not a problem.

*Relative Adjustment Comparisons:*
 For reference, the PS voltage adjust moves about 0.1V every quarter turn. The tubes are similar to the DB's in that it takes quite a bit of turning to get them down to the half-voltage point (e.g., 27V PS, then 13.5V tube bias). However, they have a lot of undershoot and overshoot and may react in different ways depending on which direction you come at them. This is perfectly normal. At the desired bias point, the voltage may change by 1/2 volt per half-turn - sometimes, but then not other times. 
	

	
	
		
		

		
		
	


	







 They're tubes - you should get used to it. 
	

	
	
		
		

		
		
	


	




*Heat:*
 Another thing you will also notice is that the sinks should get slightly cooler with run-in - including the PS sink. Burn-in definitely makes a difference. They will also run cooler with high-impedance phones compared to low impedance phones or just sitting unloaded. None of those conditions should be risky, however. The sinks can be hot enough that it should feel very uncomfortable to the touch for even a few seconds - this is more on the PS sink than the DB's, which should run about 10deg.C. hotter than the DB sinks. Because the center two DB sinks are so close together, they will run noticeably hotter than the outside sinks. This is perfectly normal (it's called a design tradeoff).
 *******************************************

 I don't know why I wrote all of that except that it was fresh in my mind after doing a couple recently. 
	

	
	
		
		

		
		
	


	


_


----------



## ruZZ.il

Helpful nonetheless. There's even insight as to how they behave, heat wise. Am I wrong to assume then that MOSFETs would be able to be biased to around their destined point a lot more rapidly as their nature is to conduct less as the heat rises.. so less likely to run away. That would probably be good on the MAX pages too.. it'll eventually get lost in here


----------



## tomb

Thanks, Russ. Yeah, the MOSFET comment sounds good to me, too.

 I'll get all this stuff on the website eventually, but I've got too many irons in the fire right now. I'm in the middle of testing some Russian PIO's I got from fordgtlover and trying to get some of this stuff ready for the Atlanta Mini-Meet next week.

 Unlike the Sonicaps, the Russian PIO's definitely preserve the bass in the ES's.
	

	
	
		
		

		
		
	


	







. However, I can't figure out yet whether they roll off in the highs. I think not, but they're not exagerrated like the Sonicaps. The Sonicaps bring out every detail, making it seem as if every phone is a Grado. 
	

	
	
		
		

		
		
	


	




 I'm not sure that's reality, though.

 The Russian PIO's are small and smooth - I'm about to declare them the winner. Tombstoned and even with the lead bent up, over and down, they're maybe 1/16" higher than the 1" sinks. The body, not counting the nipple, is shorter than the ES's. No hint of grain even with WIMA's still in the cathode bypass.

 Hmm ... the highs are getting better as they're run in ... that's nice. 
	

	
	
		
		

		
		
	


	







 [size=xx-small]_Click for a bigger pic ..._[/size]


----------



## MrMajestic2

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_ The body, not counting the nipple, is shorter than the ES's._

 

I always count the nipples


----------



## Listen2this1

Tomb that is some good info. What do you think about putting something like that on the Max site. That would really be helpful in the future for many people, since if there will be another chance to buy boards. I have a really good feeling, with all of this talk about this amazing amp there will be alot more built.

 By the way. The bass thing has been resolved.
 1. I was using my Denon cd recorder as my player, and the Macbook
 2. I decided to try my Denon 5900, and the bass was there.
 I think the cd recorder is having some issues on playback.
 The Mac can not explain why the bass was not there.


----------



## Listen2this1

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Mouser -
 SilPads (no grease req'd): 532-4880SG
 Thermafilm (upgraded insulator - still needs grease): 532-4880
 Mica (economical choice, grease req'd): 532-4880M_

 



 I am using the Thermafilm with no grease, according to the site it is not needed. My heatsinks seem to be getting the heat pretty well.


----------



## tomb

Quote:


  Originally Posted by *Listen2this1* /img/forum/go_quote.gif 
_I am using the Thermafilm with no grease, according to the site it is not needed. My heatsinks seem to be getting the heat pretty well._

 

Thermafilm is not the same as ThermaSil (Silpads) and needs grease. It's a Kapton replacement for Mica, that's all.


----------



## tomb

Quote:


  Originally Posted by *Listen2this1* /img/forum/go_quote.gif 
_Tomb that is some good info. What do you think about putting something like that on the Max site. That would really be helpful in the future for many people, since if there will be another chance to buy boards. I have a really good feeling, with all of this talk about this amazing amp there will be alot more built.

 By the way. The bass thing has been resolved.
 1. I was using my Denon cd recorder as my player, and the Macbook
 2. I decided to try my Denon 5900, and the bass was there.
 I think the cd recorder is having some issues on playback.
 The Mac can not explain why the bass was not there._

 

Good news on your source - or at least that you found the problem.

 Yes, I will put much of this on the website soon - but I have a lot of things going on right now, so it will have to wait for awhile. When you guys find out, though, I hope you'll agree my priorities were in the right place.


----------



## fordgtlover

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Unlike the Sonicaps, the Russian PIO's definitely preserve the bass in the ES's.
	

	
	
		
		

		
		
	


	







. 

 ...

 However, I can't figure out yet whether they roll off in the highs. I think not, but they're not exagerrated like the Sonicaps.

 ...

 No hint of grain even with WIMA's still in the cathode bypass.

 Hmm ... the highs are getting better as they're run in ... that's nice. 
	

	
	
		
		

		
		
	


	







 [size=xx-small]Click for a bigger pic ...[/size]_

 

Nice job mounting them (much nicer than mine), and a nice picture.

 Tomb, your initial impressions are 100% consistent with my experience with these little Russian caps. They don't seem to take anything away, or over emphasise anything, but they do control the grain I could hear in the upper-mids with the WIMAs in CA8.

 After swapping between these and the VitQs about 4 times now - probably 20 - 30 hours listening time on each, I can't hear any noticable difference between them. I actually think they sound as good as each other. As I noted in a previous post, I don't think I could pick between them in a DBT.


----------



## tomb

Quote:


  Originally Posted by *fordgtlover* /img/forum/go_quote.gif 
_Tomb, your initial impressions are 100% consistent with my experience with these little Russian caps. They don't seem to take anything away, or over emphasise anything, but they manage to control the grain I could hear in the upper-mids while using the WIMAs in CA8.

 After swapping between these and the VitQs about 4 times now - probably 20 - 30 hours listening time on each, I am unable to articulate any noticable difference between them. I actually think they sound as good as each other._

 

Considering that the VitQ's are about 50% larger, that makes these the winners, period in my mind. They will become one of 2 or 3 "Sure Thing Builds" that I plan to add to the website. 

 Many, many thanks for the samples and steering me toward these.


----------



## fordgtlover

No probs. I took a punt on them and liked what I heard.

 I'm really pleased that you like them too.


----------



## fordgtlover

Somebody (tomb - I think) posted recently about using boutiqe resistors at RB14 to 'tune' the highs. I can't for the life of me find that post. Does anyone know which post that was.


----------



## tomb

Quote:


  Originally Posted by *fordgtlover* /img/forum/go_quote.gif 
_Somebody (tomb - I think) posted recently about using boutiqe resistors at RB14 to 'tune' the highs. I can't for the life of me find that post. Does anyone know which post that was._

 

Yeah, it's buried in this thread somewhere. The output depends on the corner frequency equation:
*F = 1/(2 * pi * C * R) *

 You can adjust C, but you can also adjust R - making either one of them bigger has the effect of forestalling any loss of bass frequencies. However, carbon-based resistors have a habit of blocking highs. Harshness and tube noise in some instances can be the undesired amplification of high frequency noise. This occurs when audible harmonics are formed, even though the noise's primary frequency is above the audible spectrum. The judicious use of carbon output resistors can help to tame this.

 On the other hand, some boutique resistors supposedly have an extended "audio quality" high frequency response. Kiwames are reportedly known for this. So it may be possible to increase the bass (from the equation above) with low impedance phones, but also to make the highs sound "sweeter."

 Keep in mind except for the purely mathematical corner frequency equation above, most of the rest of those two paragraphs are unsupported. There's no way to test for "boutique". You either like the way it sounds or not.

 Most often, however, the reason to use output resistors is to tame the gain. Even the 12FK6's gain of 7 may prove to be too much with efficient low impedance phones and a strong source.


----------



## ruZZ.il

anyone got some of these caps spare?


----------



## fordgtlover

whoops - answered my own silly question.


----------



## nysulli

Quote:


  Originally Posted by *fordgtlover* /img/forum/go_quote.gif 
_No probs. I took a punt on them and liked what I heard.

 I'm really pleased that you like them too._

 

just curious as to where you picked those up, i'd be game for a few if i could find them


----------



## fordgtlover

Quote:


  Originally Posted by *ruZZ.il* /img/forum/go_quote.gif 
_anyone got some of these caps spare? 
	

	
	
		
		

		
		
	


	


_

 

PM sent


----------



## fordgtlover

They are sold by on eBay from Russia or the Ukraine.


----------



## colonelkernel8

I just hooked up my max for biasing but resistor RB2L went up in smoke, any ideas?


----------



## pabbi1

Quote:


  Originally Posted by *colonelkernel8* /img/forum/go_quote.gif 
_I just hooked up my max for biasing but resistor RB2L went up in smoke, any ideas?_

 

Very familiar... Trail of tears

 Thanks to the extreme generosity of others, mine was fixed - no real final root cause as to how / why, and no guarantees mine was the same issue...


----------



## tomb

Quote:


  Originally Posted by *colonelkernel8* /img/forum/go_quote.gif 
_I just hooked up my max for biasing but resistor RB2L went up in smoke, any ideas?_

 

Ditto pabbi. Bottom line, we'll get it fixed one way or the other. 
	

	
	
		
		

		
		
	


	




 Right now, it's time for pics, please ...


----------



## colonelkernel8

Well, ill get some pics, all you'll see is a perfect soldering job and a fried resistor.


----------



## colonelkernel8




----------



## naamanf

What is the value of those Russian PIOs? .22uf 160V?


----------



## tomb

To colonelkernel8:

 Arrgh - it's way past my bedtime. I'll have to study these tomorrow.

 A couple of questions in the meantime:

 1. What output transistors are those? If they're MJE's, they have a metal back and you may have a direct short to ground if you didn't use an insulator behind them.
 2. Can you measure a connection between that trace and what appears to be a scratch in the groundplane? I can't tell - it may be a lighting issue in the photo.

 Maybe some others will have some thoughts while I get some sleep.


----------



## tomb

Quote:


  Originally Posted by *naamanf* /img/forum/go_quote.gif 
_What is the value of those Russian PIOs? .22uf 160V?_

 

Yep - you got it. K42Y-2


----------



## naamanf

Thanks. I now have 50 of those on their way. I hate Ebay


----------



## amphead

colonelkernel8, This is what worked to fix Pabbi1s bad board. I removed RB2R and cleaned up the holes at the ground plane. I put the negative lead of the DMM into the ground test point and probed for shorts to ground on top of the board. It is unlikely that you would have the exact same problem, but you might. Check RB10L, QB2L and QB3L. If you are proficient with a schematic look at all points that feed RB2L. Give that a try. Edit: I wouldn't trust the DBs in the left channel unfortunately. Pabbi1 had a bad DB at QB8R, after that episode(burnt RB2R).


----------



## amphead

Well, I installed Cerafine 470uF in parallel at CA7 with BGs 470uF. Later I removed the extra set of BGs there, and noticed profound bass response, with the best clarity yet. Yes, I recommend Cerafine at CA7 if you can find them. Thanks again Pabbi!  Interestingly enough I installed the Cerafine caps in the CA8 positions watching polarity of course. This better be the final mod.


----------



## fordgtlover

^

 Final Mod?


----------



## el_matt0

k question guys. i just got mine all hooked up and went to do the initial setup and biasing. i get 27.0V on the dot for my PSU - all good. however, even starting with both RA1 and RB12 trimpots all the way clockwise, i get 0.0V as DB bias and i cant for the life of me seem to get any voltage reading for the tubes either. they are warming up, but im getting NOTHING close to 13.5V. if i crank my dmm down in sensitivity between TA2L and GND reads about 17.0 mV regardless of how i change those RA1 trimpots. seems to be fairly similar problem on both channels. changing the RB12 trimpots doesnt seem to do much either! the tubes ARE warming up, the PSU heatsink is warming up, the other 4 sinks are not however. help!!


----------



## el_matt0

ugh nevermind what a stupid mistake. im way too damn sleepy to be doign this, its like 4AM but i just wanted to get it done - im SURE u guys know the feeling eh!? anyways, forgot to jumper across RB8 and RB9! 
	

	
	
		
		

		
			





! *sheepish grin*


----------



## ruZZ.il

is it fixed now?


----------



## odoe

Are you going to try those PIOs on your BG MAX Tomb?


----------



## tomb

Quote:


  Originally Posted by *odoe* /img/forum/go_quote.gif 
_Are you going to try those PIOs on your BG MAX Tomb?_

 

Yep - they're going in there today. I'll post some pics dealing how I mount these. Not that it's some special technique, but I've seen some not even use those tombstone points that Colin provided - even for tombstoned caps. That's sort of a waste. Also, it might help to show what we're really talking about in terms of clearance from the case when mounting the board in the 3rd slot. So, maybe some pics will help. 
	

	
	
		
		

		
		
	


	




 EDIT: Dang! These caps are good - I've got to get to work instead of listening to more music. 
	

	
	
		
		

		
		
	


	



 The highs continue to extend as they burn in more - with no loss of bass at all. Very nice.


----------



## pinkfloyd4ever

Quote:


  Originally Posted by *nysulli* /img/forum/go_quote.gif 
_just curious as to where you picked those up, i'd be game for a few if i could find them_

 

http://search.stores.ebay.com/SOVCOM...574324QQsofpZ0
 ahh those crazy russians
	

	
	
		
		

		
		
	


	




 EDIT: actually, we're clearly not the first audiophiles to discover these... http://search.ebay.com/search/search...trypage=search


----------



## ruZZ.il

they are also here. $(6.50+5) for 10 opposed to $(16+14) for 50 above. I'm in for 10 since I cant efficiently split 50's with anyone from here.. thanks for the h.u


----------



## colonelkernel8

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_To colonelkernel8:

 Arrgh - it's way past my bedtime. I'll have to study these tomorrow.

 A couple of questions in the meantime:

 1. What output transistors are those? If they're MJE's, they have a metal back and you may have a direct short to ground if you didn't use an insulator behind them.
 2. Can you measure a connection between that trace and what appears to be a scratch in the groundplane? I can't tell - it may be a lighting issue in the photo.

 Maybe some others will have some thoughts while I get some sleep. 
	

	
	
		
		

		
		
	


	


_

 

Yeah, they are MJE's. Its possible they are shorting, I used Arctic Silver 5 as the thermal compound, which I am assuming is electrically conductive. There are no scratches in the groundplane, what I think you are referring to is one of my eyelashes, lol.


----------



## colonelkernel8

Frankly, I don't even feel like troubleshooting this, I have a feeling it will be tedious and take a very long time. It sucks being OCD and impatient, and an audiophile to boot.


----------



## tomb

Quote:


  Originally Posted by *colonelkernel8* /img/forum/go_quote.gif 
_Yeah, they are MJE's. Its possible they are shorting, I used Arctic Silver 5 as the thermal compound, which I am assuming is electrically conductive. There are no scratches in the groundplane, what I think you are referring to is one of my eyelashes, lol._

 

Well, the direct connection formed by the MJE's and the heat sinks could be a potential problem. I'm not saying that's it, but the DB heat sinks on the MAX sit directly over the ground plane. The pins are technically isolated from the ground plane, but the mask on top of the board is very, very thin. That means that if the sinks have a few burrs - which they often do - then the metal back MJE could make contact with ground.

 Obviously, you have trouble with the left channel. You might disconnect the jumpers at RB8L and RB9L (I'm assuming those are zero-ohm ferrites?). That should disconnect the Left DB. Then see if you have the same issue on the right side. If not, that's halfway there. You can then make direct comparisons between sides to see what's different.


----------



## amphead

colonelkernel8, try insulating those DBs first as TomB suggested, and then look at the ground plane for shorting by using the right channel as a model/mirror of the left channel to look for differences. If all else fails and you can't fix it online, you could always ship it economically to one of us to fix (pro bono of course). When a component burns on a board. thats when I'm willing to do it(resistors make bad fuses).


----------



## fordgtlover

Quote:


  Originally Posted by *pinkfloyd4ever* /img/forum/go_quote.gif 
_http://search.stores.ebay.com/SOVCOM...574324QQsofpZ0
 ahh those crazy russians
	

	
	
		
		

		
		
	


	




 EDIT: actually, we're clearly not the first audiophiles to discover these... http://search.ebay.com/search/search...trypage=search_

 

When you search for the K42 Russian PIO caps through google you can find reults back a few years now. The tube guys have been onto Russian caps for a while, but surprisingly there is not a lot of information available on them; perhaps becuase all of the technical information is in Russian.

 People have had good results with these in tube amps, power supplies and speaker crossovers. You can find a few comparisons to the brand name PIOs.

 The K42y seems to be generally well regarded. The K40Y is considered to be almost identical in sound to the VitQ, but honestly in the Max I can't tell the difference between the K42y and the VitQ. And, the K40y is about as big as the VitQ, which is far less suitablefor those who want to stay under 1" for the Hammond case - the K42 is small and sounds great. 

 The ultimate is the K75, but these are very rare (those tube guys probably have them stashed 
	

	
	
		
		

		
		
	


	




, and I haven't seen any small k75s at all on ebay - only the really big ones.

 Ferrari used the K40y in his Max. 

 Here is a post from a Russian user over at diytube explaining the differences in the Russian caps:
http://www.diytube.com/phpBB2/viewtopic.php?=&p=7514

 K15-4 Ceramic HV "doorknobs"
 K15-5 Ceramic HV Disc

 K31 Silver Mica "kidney bean" style cap

 K40P-2B Paper in Oil, 5% tol.
 K40U-9V Paper In Oil , Silver body, 10% tol.

 K41-1A PIO, High Voltage "Pulse" caps

 K42U-2 PIO, green painted body
 K42Y-2 PIO, green painted body

 K50 Aluminum Electrrolytic

 K71-7V Polystyrol "High Tolerance" 1% or 2% tol.

 K72P-6 Teflon Dielectric 5% tol.

 K73-14 PETP High Voltage
 K73-15 PETP / Dry Mylar
 K73-16 PETP / Dry mylar
 K73P-4 "tub " style AC capacitors (may be paper or mylar, still TBD)

 K74 HV caps

 K75-10 PIO, Green body
 K75-15 PIO, High Voltage "tub"
 K75-17 PIO High Voltage "tub"
 K75-24 PIO Green body tubular
 K75-28 PIO High Voltage "tub"

 BMT-2 Paper In Oil

 FGT High Voltage Teflon Dielectric, Ceramic body (almost beer can size)

 KBG PIO

 KBI HV "doorknob" RF / Transmitting cap

 KSO Silver-Mica "precision" caps

 MBG Paper-Aluminum "tub" AC caps

 The letters OTK are initials for "Otdiel Technicheskovo Kontrolya" or Bureau of Technical Control
 which indicates that special mil-spec or industrial testing standards are applied. In other words, "Top Shelf"


----------



## tomb

Well, in the true spirit of the Millett, I am quite happy with the apparent *mid-level* K42's that you have discovered for us. These sound great. I am listening to them in a BG MAX as I type this, and couldn't be happier with the sound. They've lifted the congestion of BG caps that still need break-in and have made them sound much smoother.

 Even if the K75's are supposed to be better - so are the teflons. Neither is a realistic option in the Millett. Besides, maybe the "OTK" means these have very high grade paper and only the best oil.


----------



## fordgtlover

Yes, they fit that rare but desired combination of synergy, size, and cost that we seek in components.


----------



## colonelkernel8

I have decided to sell my millett for $65 shipped as is to someone who would like to fix it. It has essentially all the recommended parts and with all Nichicon Muse UKZ's (except powersupply and CA2, which are Panasonic FC). This will include the Triad Magnetics 24v 750mA wallwart.


----------



## Ferrari

Very interesting to know a bit more about Russian caps. Actually, I experimented with Russian caps for a while.
 Some types I'm currently using are: K40Y-9 PIO in the MH Max, K75-10 PIO in the Bijou (these K75-10's are excellent 
	

	
	
		
		

		
		
	


	




) and of course... K72 Teflon in another MH Max.


----------



## tomb

Quote:


  Originally Posted by *colonelkernel8* /img/forum/go_quote.gif 
_I have decided to sell my millett for $65 shipped as is to someone who would like to fix it. It has essentially all the recommended parts and with all Nichicon Muse UKZ's (except powersupply and CA2, which are Panasonic FC). This will include the Triad Magnetics 24v 750mA wallwart._

 

You know, I wish we could type some magic words and make your problem go away. But we can't.

 Please understand that there are many who will help you fix this - as evidenced by the size of this thread and the many posts - one of the largest of its type on Head-Fi to date. This help has even gone so far as shipping one person's amp(s) to another DIYer for repair - with successful results. I'm fairly certain those opportunities exist for you, too - if you want them.

 On the other hand, attempting to sell your mistakes and expecting a purchase by one of those same DIYers within this thread may not meet with the same favor. I could be wrong about that, but in any event, this is the _Millett MAX build-support thread_ in the Head-Fi "Do-It-Yourself" section, not a for sale thread where you can market the deal, lower the price, etc., etc. 

 If you have truly given up - without trying to accept the help that is freely offered - please post this in one of the many Head-Fi For Sale threads, instead. Thank you.


----------



## ruZZ.il

don't give up!


----------



## colonelkernel8

Well, its not that I can't or do not want to fix it, its that my interest (and resources) has strongly been shifted to another, non-FOTM DIY audio project. I appreciate the help, and I understand my timing was a little suspicious, but its just that the Dynalo has piqued my interest very much.


----------



## tomb

I've placed a new page on the MAX website for the K42Y-2 caps.

 It can be found at Tweaks->K42 PIO Caps
 I've put them on three MAX builds so far, including a BG MAX and see no reason to not recommend them as a basic part for the MAX. Many thanks, fordgtlover!

 I will also be modifying the "MAX Boutique" page based on some important facts we've learned and also transferring that blow-by-blow account of biasing DB's when I get a chance.


----------



## fordgtlover

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_I've placed a new page on the MAX website for the K42Y-2 caps.

 It can be found at Tweaks->K42 PIO Caps
 I've put them on three MAX builds so far, including a BG MAX and see no reason to not recommend them as a basic part for the MAX. Many thanks, fordgtlover!_

 


 Tomb

 Excellent guide; above and beyond - once again.

 Many thanks to you for your [huge] role in this excellent DIY project. 

 Cheers


----------



## naamanf

Goodness. You either don't sleep, don't work, or both. Great job. The MAX by far has the best website for a DIY product.


----------



## ruZZ.il

Nice write up, Tom.
 And while I'm writing.. anyone got a P/N for those center of board support stubs that go underneath? I forgot to get some.. I need to get some of that good hookup wire too (naviships, I spose..). maybe someone has some spare of both?


----------



## tomb

Thanks for all the comments, guys. You've really bowled me over. Sometimes I start thinking nobody notices, but then you guys post comments like that. Many thanks!


----------



## TVaudio

Just curious. I have a non Max MH with BG's, would these caps be a recommended try with this amp. I'm not unhappy, but as we all know, can always be happier "maybe".
 What do you think?


----------



## tomb

Quote:


  Originally Posted by *ruZZ.il* /img/forum/go_quote.gif 
_Nice write up, Tom.
 And while I'm writing.. anyone got a P/N for those center of board support stubs that go underneath? I forgot to get some.. I need to get some of that good hookup wire too (naviships, I spose..). maybe someone has some spare of both? 
	

	
	
		
		

		
		
	


	


_

 

Nothing magical about the center post - just a 4-40 screw with a combination of spacers and a plastic nut on the end. You can do the same thing with a metal nut, though - just flex the board slightly as you push it in the case, then release when you've got it in place - assuming you care whether you get scrape marks on the inside bottom of your Hammond case.

 The main point is that you have enough screw/bolt/washers so that whatever you put on the bottom - nut, plastic nut, standoff, etc. - is positively touching the bottom of the case. That's all that's needed to prevent the center part of the board from flexing in the downward direction. There's some flex upward when you remove tubes, but not nearly as much as pushing the tubes into the sockets.

 I don't know if anyone has some Navships wire to spare, but it's very cheap on e-bay. John from Navships has impeccable service and reliability, too - highly recommended.


----------



## Televator

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Thanks for all the comments, guys. You've really bowled me over. Sometimes I start thinking nobody notices, but then you guys post comments like that. Many thanks!_

 

well, I just wanted to pitch in some thanks to you and fordgtlover as well... thanks to the trial and error you guys put in and the nice write-up, I (as a low-level DIY'er) feel confident enough to try those myself.

 I just ordered some and will put them in my second MAX (coupled with Nichicon KZ) and if I do like them after comparison, I still can replace my WIMAs in my first build as well.

 Can't wait to try them!


----------



## tomb

Quote:


  Originally Posted by *TVaudio* /img/forum/go_quote.gif 
_Just curious. I have a non Max MH with BG's, would these caps be a recommended try with this amp. I'm not unhappy, but as we all know, can always be happier "maybe".
 What do you think?_

 

So far, the BG's in a MAX seem resistant to cap bypassing. It's as if they can't be hurt by bad ones (note Russ's several comments about no difference in Sonicaps vs NO Sonicaps), and yet can't be helped by good ones (meaning, the K42's).

 I've got them on a brand new BG MAX where the BG's are not fully broken in. The best I can say about them is that they have no effect as far as I can tell. I have about 40-50 hours on the BG's and they still sound "congested." The K42's don't seem to have much effect, to be truthful. Nevertheless, for BG's, that may be saying a lot.

 One thing - the revMH Millett Hybrid board does not have enough room on the board to fit one of these caps, IMHO. They wouldn't fit in the MAX sitting horizontal - it's the tombstone positions that Colin included that make the difference. You'd have to do something pretty special to shoehorn them in there.


----------



## TVaudio

Thanks for the answer. I'm not going to bother then.


----------



## amphead

TomB, thats what I noticed too, as far as film/foil caps go, for CA8 and BGs at CA7. Although I have done the experimental thing with the Cerafine 470uF in parallel with BG 470uF there with very good results. As we know Cerafines are getting harder to find though. btw,I also appreciate your support on this thread! Edit: Thats a very definitive instruction guide on the Russian PIO cap modification/installation, but just another example of the high quality you consistently provide.


----------



## amphead

btw, I am in negotiations with some local electronic engineers/technicians to help buy a surplus electronics store. We have just incorporated and for the first time in my life I am a sitting member on a board of directors. I purposely avoided the primary positions of President, Secretary and Treasurer, in order to become the primary buyer/CTO. Unfortunately, we decided not to pay ourselves for six months(hmm...peanut butter and jelly sandwiches, ramen noodles) until we reach a predetermined cash flow. In two months, if all works out, I can stock the capacitors, transistors, tubes, resistors, connectors and wire that I think will sell. Then I will see what arrangements I can make for discounts to members of this forum through the appropriate channels. Edit: Tom B., you will be rewarded for your time on this thread, once I get the power to buy.


----------



## gates_2

Quote:


  Originally Posted by *amphead* /img/forum/go_quote.gif 
_btw, I am in negotiations with some local electronic engineers/technicians to help buy a surplus electronics store. We have just incorporated and for the first time in my life I am a sitting member on a board of directors. I purposely avoided the primary positions of President, Secretary and Treasurer, in order to become the primary buyer/CTO. Unfortunately, we decided not to pay ourselves for six months until we reach a predetermined cash flow. In two months, if all works out, I can stock the capacitors, transistors, tubes, resistors, connectors and wire that I think will sell. Then I will see what arrangements I can make for discounts to members of this forum through the appropriate channels._

 

SWEET
	

	
	
		
		

		
			







 now we can have a legit corp buy stuff in bulk, and we'll reap the benefits!
	

	
	
		
		

		
		
	


	





 in all seriousness, congrats on your new business endeavor... hope it works out well for you


----------



## fordgtlover

Quote:


  Originally Posted by *Televator* /img/forum/go_quote.gif 
_well, I just wanted to pitch in some thanks to you and fordgtlover as well... thanks to the trial and error you guys put in and the nice write-up, I (as a low-level DIY'er) feel confident enough to try those myself.

 I just ordered some and will put them in my second MAX (coupled with Nichicon KZ) and if I do like them after comparison, I still can replace my WIMAs in my first build as well.

 Can't wait to try them!_

 

Thanks Televator - I gratefully accept a small part of the appreciation. 

 The MAX is a great project and I am pleased to have added to it in a small way. 

 I am still a relative newbie to DIY myself. So, it goes to show that improvements don't always need to come from those guys with considerably more experience. Curiosity takes you a long way. 

 I think it's a low cost tweak that many will enjoy. I can't wait for you and others to hear what Tomb and I have heard with these nice little caps.

 I certainly hope they keep finding wharehouse in Russia with such treasures


----------



## jamess71

Quote:


  Originally Posted by *amphead* /img/forum/go_quote.gif 
_btw, I am in negotiations with some local electronic engineers/technicians to help buy a surplus electronics store. We have just incorporated and for the first time in my life I am a sitting member on a board of directors. I purposely avoided the primary positions of President, Secretary and Treasurer, in order to become the primary buyer/CTO. Unfortunately, we decided not to pay ourselves for six months(hmm...peanut butter and jelly sandwiches, ramen noodles) until we reach a predetermined cash flow. In two months, if all works out, I can stock the capacitors, transistors, tubes, resistors, connectors and wire that I think will sell. Then I will see what arrangements I can make for discounts to members of this forum through the appropriate channels. Edit: Tom B., you will be rewarded for your time on this thread, once I get the power to buy._

 

Sounds good. I'll be keeping an eye out. BTW whats the name of your company and do you have a web site up yet?


----------



## smegger

woo my max kit just arrived!!!!! 
	

	
	
		
		

		
		
	


	

















 pity i now have to wait till wednesday to get it cause i am up at uni


----------



## amphead

Quote:


  Originally Posted by *jamess71* /img/forum/go_quote.gif 
_Sounds good. I'll be keeping an eye out. BTW whats the name of your company and do you have a web site up yet?_

 

HFE, and no not yet. Give me 2 months. 
	

	
	
		
		

		
		
	


	




 Edit: Thats good news Smegger, take your time!


----------



## smegger

Anyone in the uk interested in some of the Russian caps mentioned by tomb i am currently ordering some is anyone would want me to order some for them.

http://cgi.ebay.co.uk/ws/eBayISAPI.d...MEWA:IT&ih=016


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## tomb




----------



## joneeboi

Sign me up! I can pay you when you send me the money request for the wall wart and LM317.


----------



## odoe

Haha. That's awesome!


----------



## amphead

Nice work TomB! I can just imagine you with an army of Maxes at a Head-Fi meet in one of those beauties.


----------



## pabbi1

Uh, I need one in 'balanced'... 
	

	
	
		
		

		
		
	


	




 All in on that, and I need _at least_ two... in XL, por favor.


----------



## tomb

I added a bunch of new galleries on the MAX website.

 Ya'll let me know if I missed somebody.


----------



## ruZZ.il

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_









_

 

You doing some group buy of those? pretty cool stuff. I'd be in for 1. It may also be cool with the logo big at the back, and a small one in the front or smtn. If you're not doing a whole thing, maybe you can send me the logo file?


----------



## tomb

Quote:


  Originally Posted by *ruZZ.il* /img/forum/go_quote.gif 
_You doing some group buy of those? pretty cool stuff. I'd be in for 1. It may also be cool with the logo big at the back, and a small one in the front or smtn. If you're not doing a whole thing, maybe you can send me the logo file? 
	

	
	
		
		

		
		
	


	


_

 

Yep - that's a good idea, but it would've cost me too much this time. If these are popular, maybe the next batch. There are 36 ... er, 34 left, so I'm not about to keep all of those for myself. Next week, hopefully - more boards and other stuff will be available. I can't go into details here, because of MOT and all that junk. Watch the website and the Millett forum.

 EDIT: Another one:


----------



## Televator

nice work on the gallery... looks great with all those different builds...also good fun on the shirts: go team-MAX!

 on a different note, I was just looking for other changes I can make to JRossel's standard kit for my second build (or perhaps to switch in my first build as well). I already ordered some K42's as said above, but I was also looking to try some different transistors in the DB's.

 I have MJE243/253 now and I was pretty interested in the 2SC3422/2SA1359 and/or 2SC2238/2SA968. I can find the latter set @ RS-components (for pretty high prices though), but no luck on the former (not at RS, nor Farnell.be). I'd love to try the 2SC3422/2SA1359 though as it's more prominent bass might compensate for the slight loss of lower freqs impact by using 12FK6 tubes in stead of 12AE6...

 also, I have experimented with a 75Ω adapter (with already 22Ω at RB14) and while it gave a bit more 'twisting room' on the knob, it darkened (veiled) the sound a bit.

 I'm still wondering what the best solution (well, for me at least) is for the MAX + grado/alessandros:
 - 12AE6 + very little vol adjustment or lots more Ω @ RB14 (not too happy with this)

 - 12FM6 + slightly more than 22Ω @ RB14

 - 12FK6 and stick with 22Ω @ RB14

 all help/input welcome evidently


----------



## tomb

Quote:


  Originally Posted by *Televator* /img/forum/go_quote.gif 
_nice work on the gallery... looks great with all those different builds...also good fun on the shirts: go team-MAX!

 on a different note, I was just looking for other changes I can make to JRossel's standard kit for my second build (or perhaps to switch in my first build as well). I already ordered some K42's as said above, but I was also looking to try some different transistors in the DB's.

 I have MJE243/253 now and I was pretty interested in the 2SC3422/2SA1359 and/or 2SC2238/2SA968. I can find the latter set @ RS-components (for pretty high prices though), but no luck on the former (not at RS, nor Farnell.be). I'd love to try the 2SC3422/2SA1359 though as it's more prominent bass might compensate for the slight loss of lower freqs impact by using 12FK6 tubes in stead of 12AE6..._

 

YGPM

  Quote:


 also, I have experimented with a 75Ω adapter (with already 22Ω at RB14) and while it gave a bit more 'twisting room' on the knob, it darkened (veiled) the sound a bit.

 I'm still wondering what the best solution (well, for me at least) is for the MAX + grado/alessandros:
 - 12AE6 + very little vol adjustment or lots more Ω @ RB14 (not too happy with this)

 - 12FM6 + slightly more than 22Ω @ RB14

 - 12FK6 and stick with 22Ω @ RB14

 all help/input welcome evidently 
	

	
	
		
		

		
		
	


	



 

The best that you can do - and I'm going from memory here with my old Milletts before I sold my Grados - is stay with the 12FK6. You've already dug yourself a hole from higher gain with the 12FM6 and 12AE6. The best thing to do is find the volume range you think you want. Then go and buy Kiwames of that value. Try to get as little as you can stand - the combination of that and the quality of the Kiwames will minimize the loss in dynamics. I don't use them, period, but then I like the 12AE6 and a hair-trigger volume control. (The 12AE6's have more bass punch, too.) Most of the time I listen to KSC75's, which if memory serves, are still lower on the volume dial than a pair of Grados - due to the higher sensitivity. Of course, none of this is an issue with high-impedance phones.

 Black Gates will help, too - although that's sort of the last reason in the world to spend that much money on them. Yet, the BG's are like putting little amplifiers in those cap positions - the dynamics increase such that the more detail gets pushed through. So, you will start at a much higher level of dynamics before the output resistor will start to veil the output.

 BTW, the reason I'm mentioning that is that my BG's turned the corner last night. That's after about 50 hours, so it wasn't as long as I had thought - because there's a big difference. The dynamics and detail were always there, but they don't sound like they have a head cold anymore - much more transparent. 
	

	
	
		
		

		
		
	


	




 Also, another BTW - I'm running the 2SC2238/2SC968 with the BG's.


----------



## joneeboi

I had the same problem, what with the high gain of the 12FK6s. As good as Kiwames or Stackpoles may be, I figured I'd just go with the jumper at RB14. I was also considering getting a 100K Black Beauty or Blue Velvet pot, but I board-mounted my 50K blue which would make it kind of tricky to remove. I compromised with the jumpers. Sometimes the best solutions are the simplest. With RB14 jumpered, I get about "2 hours" control.

 You could also try a different knob.


----------



## thunder

Are BG really as good as many claim? How do they far against the Nichicon ES with a really good by-pass cap ect... Please give comparitive detail's ! If BG's are as good as many claim, why then is the company going out of buiness ?


----------



## Televator

thanks tomb for your info and all the help 
	

	
	
		
		

		
		
	


	




 and joneeboi for the tip and the laugh 
	

	
	
		
		

		
		
	


	




 I have a 50K blue velvet on board as well, but I could opt for something else on my second build... still I wonder whether it is worth it (I believe Amb once explained using a higher Ω pot raises the noise level, though I might be mistaken as I have no clue what I'm talking about 
	

	
	
		
		

		
		
	


	




 )

 I should be looking for other knobs actually as the one I've got isn't that good looking 
	

	
	
		
		

		
		
	


	




 but enough innuendo 
	

	
	
		
		

		
		
	


	




 At the moment it looks like I'll be going for a second build with:
 - 12FK6 tubes
 - 470µf UKZ caps on CA7 with 
 - K42 PIO bypass on CA8
 - WIMA's for the other film caps
 - 2SC3422/2SA1359 transistors and 
 - either a low value resistor (I've only got the 22Ω Vishay Dale from the JRossel kit though) or a jumper at RB14.

 This should give me a bit more bass than the current MJE243/MJE253 setup and remove the slight grain from the WIMA's at CA8 and give me about 2 hours of movement on the pot as well... I'll just have to learn to work with minimal adjustments 
	

	
	
		
		

		
		
	


	




 edit: I just compared the renewed BOM on the MAX-site to my JRossel order and noticed some things:
 - for CA4/5 a 1000µf minimum is recommended now... I guess this used to be 470µf and that's what I got with the kit (470µf UKZ's there as well) Any problems with this?... I remember this was discussed before and I'll look it up, but a quick pointer to where in this humongous thread is always welcome

 - for CA2 a boutique is recommended: the kit comes with a Panasonic FC-series 1000µf cap... is this a good option here? Better options?

 - CA9 is also a possible boutique position... would it make any difference to use Russion K47 PIO's there as well?

 Sorry for all the questions... just that I want to make my second build my home amp and now that I've fallen in love with the MAX (standard JRossel kit) I'd love to take it to the MAX (well, not really Ferrari's MAX... nor will I go for Blackgates I guess)


----------



## tomb

Quote:


  Originally Posted by *thunder* /img/forum/go_quote.gif 
_Are BG really as good as many claim? How do they far against the Nichicon ES with a really good by-pass cap ect... Please give comparitive detail's !_

 

 YES. They are better, although the ES may still have a tad more bass. Mine took about 50hrs to stop sounding "congested", but the resulting sound is worth it. I will still use ES's (because I can't afford BG's in every case), but the BG's are worth the cost.

 Using BG's is sort of like putting little amplifiers in the cap positions - it amplifies every detail and seemingly brings the minutest sound to the same level as the rest of the music. That description sounds weird, I know, but it's the best analogy I can think of at the moment.

  Quote:


 If BG's are as good as many claim, why then is the company going out of buiness ? 
 

The company knows how to market.


----------



## tomb

Quote:


  Originally Posted by *Televator* /img/forum/go_quote.gif 
_thanks tomb for your info and all the help 
	

	
	
		
		

		
		
	


	




 and joneeboi for the tip and the laugh 
	

	
	
		
		

		
		
	


	




 I have a 50K blue velvet on board as well, but I could opt for something else on my second build... still I wonder whether it is worth it (I believe Amb once explained using a higher Ω pot raises the noise level, though I might be mistaken as I have no clue what I'm talking about 
	

	
	
		
		

		
		
	


	




 )_

 

I don't have much of a clue, either, but you're right - he has said that. I think what happens traditionally in a tube amp is that the input impedance is relatively low. They used higher impedance pots to compensate - I think.

 However, I could be wrong, but the volume level is not going to be affected, if at all, with a higher impedance pot. They work on a logarithmic scale, and the final increased impedance is not proportional in that case - I think.
	

	
	
		
		

		
		
	


	




  Quote:


 I should be looking for other knobs actually as the one I've got isn't that good looking 
	

	
	
		
		

		
		
	


	




 but enough innuendo 
	

	
	
		
		

		
		
	


	




 At the moment it looks like I'll be going for a second build with:
 - 12FK6 tubes
 - 470µf UKZ caps on CA7 with 
 - K42 PIO bypass on CA8
 - WIMA's for the other film caps
 - 2SC3422/2SA1359 transistors and 
 - either a low value resistor (I've only got the 22Ω Vishay Dale from the JRossel kit though) or a jumper at RB14.

 This should give me a bit more bass than the current MJE243/MJE253 setup and remove the slight grain from the WIMA's at CA8 and give me about 2 hours of movement on the pot as well... I'll just have to learn to work with minimal adjustments 
	

	
	
		
		

		
		
	


	



 

All sounds good ...
  Quote:


 edit: I just compared the renewed BOM on the MAX-site to my JRossel order and noticed some things:
 - for CA4/5 a 1000µf minimum is recommended now... I guess this used to be 470µf and that's what I got with the kit (470µf UKZ's there as well) Any problems with this?... I remember this was discussed before and I'll look it up, but a quick pointer to where in this humongous thread is always welcome 
 

Yes, I have used 1800uf 35V Panasonic FM's in all my MAXes. They're only about 50 cents more than a 1000uf. I think the 470uf's are too small for such an amp as the MAX. I have never had a problem with bass - quite to the contrary - the problem is holding the headphones from bouncing off my head. 
	

	
	
		
		

		
		
	


	






  Quote:


 - for CA2 a boutique is recommended: the kit comes with a Panasonic FC-series 1000µf cap... is this a good option here? Better options? 
 

If you apply the WIMA as the bypass, this will be good. It might even be OK without the WIMA and standing on its own - you'll have to find out. The thing about these positions by the tubes is that there is very little you can do to improve the music there, but there are many things you can do to really wreck the signal. Essentially, a very big cap is needed to remove any doubt whatsoever than the signal might clip or have the low bass filtered out. Other than that, don't fool with it , IOW.

  Quote:


 - CA9 is also a possible boutique position... would it make any difference to use Russion K47 PIO's there as well? 
 

Of course - the K42's would be a great choice. I suppose you can fit even bigger ones since the KZ's already pretty much dictate the height of the board components.

  Quote:


 Sorry for all the questions... just that I want to make my second build my home amp and now that I've fallen in love with the MAX (standard JRossel kit) I'd love to take it to the MAX (well, not really Ferrari's MAX... nor will I go for Blackgates I guess) 
 









 Good Luck!


----------



## thunder

Tomb, Are you using any by-pass cap's with the BG's ? If so what size or sizes are being used ? I'm still trying to unwind the mysteries of obtaining the greatest sound, My mouth water's everytime I see what other's are building, I just cant afford to do all the trial and error investing in caps ect... I may at best try a couple combos. Being new to DIY at my rate it may take years to build a parts arsenal ! Once again thank's for all your wisdom and help!


----------



## Televator

thanks again for the quick and thorough answer... this really is my favorite thread
	

	
	
		
		

		
		
	


	



  Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_However, I could be wrong, but the volume level is not going to be affected [...]- I think.
	

	
	
		
		

		
		
	


	


_

 

I kinda thought so, so I'll just learn to live with little turning (should actually be better for my wrists 
	

	
	
		
		

		
		
	


	




 )

  Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_ Yes, I have used 1800uf 35V Panasonic FM's in all my MAXes [...] I think the 470uf's are too small for such an amp as the MAX._

 

I'll get some 1800µf's from RS... (I now all of a sudden have 8 x 470µf Muse KZ's left over 
	

	
	
		
		

		
		
	


	




 ). I will link the passage on the MAX site and your answer for JRossel, so he can change his kits if he wants.

  Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_ If you apply the WIMA as the bypass, this will be good. [...] Essentially, a very big cap is needed to remove any doubt whatsoever than the signal might clip or have the low bass filtered out. Other than that, don't fool with it , IOW._

 

ah, I get it. It's not that much a real boutique position but rather a "some big things work, smaller won't and some seemingly good options will sound lousy"-position. It works, so I'll keep it as it is (well, just perhaps bypass them with the K42 PIO's in stead of WIMA's)

 I have just found out that as I have to remove the four Muse KZ's in the CA4/5 positions as they are too small (in capacitance of course, they are huge otherwise 
	

	
	
		
		

		
		
	


	




 ) I only have two of those Sequoias left on my board. I was wondering whether I should keep those for the second build (the Muses do sound great on my current build) or try something else (just found some dutch online shops selling Elna Silmic II's and another one selling Blackgates) ... This way I could also use a bigger cap (perhaps nearer to 1000µf) to raise the corner frequency for my low impedance Alessandros. I actually only just realized that I would in fact only need two of those boutique caps (only for CA7L/R) so I would even be willing to splurge on some Blackgate NX's (35V 680µf at €13.15/pp) and I definitely would consider the Elna Silmic II's (35V 1000µf at €6.48/pp) which would also make a third slot MAX possible with less difficult casework to be done ... ah decisions decisions 
	

	
	
		
		

		
		
	


	




 so to recap; the crucial positions (and my current doubts):
 - 12FK6 tubes (at least one certainty in my life 
	

	
	
		
		

		
		
	


	




 )
 - CA2 = Panasonic FC 16V 1000µf 
 - bypassed by CA9 = WIMA or K42 PIO
 - CA4/5 = Panasonic FM 35V 1800µf (changed my typo)
 - CA3/6 = WIMA's
 - CA7 = Muze KZ (35V 470µf) or Elna Silmic II (35V 1000µf) or Blackgate NX (35V 680µf)
 - bypassed by CA8 = K42 PIO (also for Elnas and Blackgates?)
 - BJT's = 2SC3422/2SA1359 (or perhaps 2SC2238/2SA968 as I have to order the Pana FMs from RS anyway so I can get those as well)

 Perhaps I should just consider building a third one? But I can only really use one... my friends don't even listen to headphones anymore, so I can't even give them away (planned to do that with one actually, showed it to my good friend so he knew what he could expect and he could even determine the looks... but he graciously declined as he didn't have any time for headphone listening anymore and he felt he didn't deserve such a big gift) and my level of DIY might not inspire enough trust for a sale of the ones I decide not to keep (for parts prices only of course). Or just skip the second JRossel kit and sell that on (unbuilt/with Panasonic FM caps) ... and wait for the next shift of boards or just mod my existing build... aaargh

 oh yeah... sorry for all these BOM-doubts. Quite funny actually that I'm having them now after I've completed a MAX already 
	

	
	
		
		

		
		
	


	




 But this is actually my first own BOM (I built a Cmoy following Tangent and an Alien DAC and a MAX both from unaltered JRossel kits)...so again sorry for my noobness 
	

	
	
		
		

		
		
	


	




  Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_








 Good Luck!_

 

I think I'll need it 
	

	
	
		
		

		
		
	


	




 (and my wallet too 
	

	
	
		
		

		
		
	


	




 )


----------



## tomb

Quote:


  Originally Posted by *thunder* /img/forum/go_quote.gif 
_Tomb, Are you using any by-pass cap's with the BG's ? If so what size or sizes are being used ? I'm still trying to unwind the mysteries of obtaining the greatest sound, My mouth water's everytime I see what other's are building, I just cant afford to do all the trial and error investing in caps ect... I may at best try a couple combos. Being new to DIY at my rate it may take years to build a parts arsenal ! Once again thank's for all your wisdom and help!_

 

I've put the Russian K42's as bypasses on the BG's at the output (CA7), but the BG's at CA2 are standing pat.

 Personally, I think putting the K42's at the tube positions (CA9) are overkill. The thing is, the BG's have all the frequency response you need. They just need a little sweetness and something to remove some of the crunchiness. However, I have a feeling that putting the K42's at the CA9 positions would be too much.

 If you're using regular power caps at those positions, then maybe the Wima's are needed to ensure a smooth frequency response - but that's it. As long as the tubes have enough capacitance backing up the signal - 1000uf at CA2, then the output positions really govern everything else. At least it appears that way to me now after some of the testing I've done.

 I would keep the Wima's on ES's at CA2, by the way - because the ES's have a deficiency in the highs. It seems to be fully correctable with the Wima bypass, however. For Black Gates at CA2 - no film or PIO bypass.


----------



## pinkfloyd4ever

edit: crap, nvmd tomb already got it, I'm too slow as usual


----------



## tomb

Quote:


  Originally Posted by *Televator* /img/forum/go_quote.gif 
_thanks again for the quick and thorough answer... this really is my favorite thread
	

	
	
		
		

		
		
	


	



 I kinda thought so, so I'll just learn to live with little turning (should actually be better for my wrists 
	

	
	
		
		

		
		
	


	




 )

 I'll get some 1800µf's from RS... (I now all of a sudden have 8 x 470µf Muse KZ's left over 
	

	
	
		
		

		
		
	


	




 ). I will link the passage on the MAX site and your answer for JRossel, so he can change his kits if he wants.

 ah, I get it. It's not that much a real boutique position but rather a "some big things work, smaller won't and some seemingly good options will sound lousy"-position. It works, so I'll keep it as it is (well, just perhaps bypass them with the K42 PIO's in stead of WIMA's)

 I have just found out that as I have to remove the four Muse KZ's in the CA4/5 positions as they are too small (in capacitance of course, they are huge otherwise 
	

	
	
		
		

		
		
	


	




 ) I only have two of those Sequoias left on my board. I was wondering whether I should keep those for the second build (the Muses do sound great on my current build) or try something else (just found some dutch online shops selling Elna Silmic II's and another one selling Blackgates) ... This way I could also use a bigger cap (perhaps nearer to 1000µf) to raise the corner frequency for my low impedance Alessandros. I actually only just realized that I would in fact only need two of those boutique caps (only for CA7L/R) so I would even be willing to splurge on some Blackgate NX's (35V 680µf at €13.15/pp) and I definitely would consider the Elna Silmic II's (35V 1000µf at €6.48/pp) which would also make a third slot MAX possible with less difficult casework to be done ... ah decisions decisions 
	

	
	
		
		

		
		
	


	


_

 

Couple of things:
 1. It's possible that the Sequoia KZ's are enough in the CA4/CA5 positions. That recommendation is really for those who go and buy 470uf UPW's, FM's or FC's. I would say that ES's are probably not optimum in those positions, either - because they're bipolar. That doesn't meet the intent of those caps, which is to preserve the voltage difference between V+ and Gnd and prevent any possible coupling. However, the KZ's may be OK because so much of their frequency response is "tuned" for the audio band. I haven't tested them personally, so I don't really know this, however.

 Strictly speaking, the difference between the price of a 470uf KZ and an 1800uf is about 40cents. From a capacitance standpoint, that's no comparison - and "audio quality" is not really the purpose - "power quality" is. Ultimately however, it _all_ becomes signal, so that's why I give the disclaimer - I just don't know. 

  Quote:


 so to recap; the crucial positions (and my current doubts):
 - 12FK6 tubes (at least one certainty in my life 
	

	
	
		
		

		
		
	


	




 )
 - CA2 = Panasonic FC 16V 1000µf 
 - bypassed by CA9 = WIMA or K42 PIO 
 

Actually, the way things work I think a K42 would be wasted in the CA9 position, but that's just MHO. There seems to be no detriment whatsoever with having a Wima in there and then using the K42 just on the output. Quote:


 - CA4/5 = Panasonic FM 35V 1000µf 
 

 I'm confused with this one, since you were talking 1800uf earlier up there (which is what I use), but yeah, 1000uf should be minimum.
  Quote:


 - CA3/6 = WIMA's 
 

Yep - never a need to change these at all - in any case. Quote:


 - CA7 = Muze KZ (35V 470µf) or Elna Silmic II (35V 1000µf) or Blackgate NX (35V 680µf)
 - bypassed by CA8 = K42 PIO (also for Elnas and Blackgates?) 
 

Yes - the K42 works for Black Gates and obviously for ES's. I haven't personally tried Elna's, but there's no reason the K42 wouldn't work there as well. If it works for ES's, but then also BG's, that pretty much covers the differences.
  Quote:


 - BJT's = 2SC3422/2SA1359 (or perhaps 2SC2238/2SA968 as I have to order the Pana FMs from RS anyway so I can get those as well) 
 

Here's just my opinion, but when I use ES's, I limit myself to the 2SC3422/2SA1359 -or- the 2SC3421/2SA1358. If using Black Gates, then the 2SC2238/2SA968 are a perfect choice. Just MHO and YMMV.

 Also, it's more money for sure, but IMHO - if you purchase the BG's for CA7, it seems a waste not to have the BG's in CA2. Sort of a twofer/fourfer as it were. 
	

	
	
		
		

		
		
	


	




 I'm not one to mix the type of caps in those two positions - they should probably be the same brand, but I guess there's no law about it - just no guarantees, either. The combinations could be endless, as witness some of Amphead's many experiments. 
	

	
	
		
		

		
		
	


	



  Quote:


 Perhaps I should just consider building a third one? 
 

There's the answer!

  Quote:


 But I can only really use one... my friends don't even listen to headphones anymore, so I can't even give them away (planned to do that with one actually, showed it to my good friend so he knew what he could expect and he could even determine the looks... but he graciously declined as he didn't have any time for headphone listening anymore and he felt he didn't deserve such a big gift) and my level of DIY might not inspire enough trust for a sale of the ones I decide not to keep (for parts prices only of course). Or just skip the second JRossel kit and sell that on (unbuilt/with Panasonic FM caps) ... and wait for the next shift of boards or just mod my existing build... aaargh 
 

There's a Compact MAX coming, but it's not that different - just sized for a different case. There may be some minor changes in the big board, but I wouldn't expect much. I have one of my nicest Black Gate versions installed in the 2nd prototype board, so I wouldn't worry about using an older version and missing features, per se.

  Quote:


 oh yeah... sorry for all these BOM-doubts. Quite funny actually that I'm having them now after I've completed a MAX already 
	

	
	
		
		

		
		
	


	




 But this is actually my first own BOM (I built a Cmoy following Tangent and an Alien DAC and a MAX both from unaltered JRossel kits)...so again sorry for my noobness 
	

	
	
		
		

		
		
	


	



 

No problem. Just realize the Jeff offers an unbelievable deal on his kits. One way he might be able to do that is to offer a specific selection of parts that he purchased in volume. The individual builder could perhaps select a more optimum set of parts than he might be able to offer in a kit. There is nothing wrong with Jeff's basic kit and it will/should perform impressively, but it is not necessarily true to the BOM. KZ's were never mentioned in the BOM, for instance, because of their height. Colin and I tried to adhere to a 1" height in all instances except for the MOSFET version.


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## ruZZ.il

Jeff is also great when it comes to customizing things. He has no problem taking a few things off the BoM for you if you ask, and if he has anything else around, no problem adding them. He even threw in a few other extra goodies for me that I needed around irrelevant to the dacs/minis he last sent me. I'm sure that if he sees enough demand for the 1800's, he may just keep a little pack around to keep ppl happy. Best is to give him a call or an e-mail to see where he's flexible. Also, leave him some feedback. Strangely enough, he's done so much and received very little of it..


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## tomb

I've made some more changes in the basic BOM - please check the website as always for updates:
Millett MAX BOM

 Changes are:
_1. DigiKey part numbers for the resistors have been changed to the CMF55 series. This is the Vishay-Dale commercial equivalent of the mil-spec RN55 series at Mouser. Note, however, that the larger CMF60 (RN60) is not carried in the size needed for RR2. That part number remains as before. As always, Team Millett MAX selects normally stocked items at the listed vendors, but out-of-stock items will occur from time to time.

 2. The LED resistors have been changed to 2K. This gets them easily in the 1/2 Watt power rating and knocks the current down slightly. The resistor has greater availability in this size, also. Several of the LED's burned out on the prototype using 1K, which was close to the previous BOM recommendation. The part still remains as an inexpensive carbon-film type. _

 Also, please note the previous changes, one of which ocurred yesterday. Thanks.


----------



## Jrossel

Quote:


  Originally Posted by *ruZZ.il* /img/forum/go_quote.gif 
_Jeff is also great when it comes to customizing things. He has no problem taking a few things off the BoM for you if you ask, and if he has anything else around, no problem adding them. He even threw in a few other extra goodies for me that I needed around irrelevant to the dacs/minis he last sent me. I'm sure that if he sees enough demand for the 1800's, he may just keep a little pack around to keep ppl happy. Best is to give him a call or an e-mail to see where he's flexible. Also, leave him some feedback. Strangely enough, he's done so much and received very little of it.._

 


 Hey, speaking of customizing...

 I have ordered some of these little green Russian buggers (K42s) for future kits. If I could shrink the UKZs I would. BTW I read and see that the BOM has morphed a bit on the C4 /C5 cap. I will hunt for something larger than the 470 uF UKZ that I have been using. But not as "large" as the 50V 1000uF UKZ I have sitting around begging to be put into a kit. Maybe 1800 uF Panasonic FM, I already have 35V FC 2200 uF, too large?


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## tomb

Quote:


  Originally Posted by *Jrossel* /img/forum/go_quote.gif 
_Hey, speaking of customizing...

 I have ordered some of these little green Russian buggers (K42s) for future kits. If I could shrink the UKZs I would. BTW I read and see that the BOM has morphed a bit on the C4 /C5 cap. I will hunt for something larger than the 470 uF UKZ that I have been using. But not as "large" as the 50V 1000uF UKZ I have sitting around begging to be put into a kit. Maybe 1800 uF Panasonic FM, I already have 35V FC 2200 uF, too large?_

 

I try to adhere to the 1" height by and large, to get the board in the 3rd slot where the volume knob is more or less centered. That reduces some options because the only boutique caps at that height and rating are the Nichicon Muse ES and the Black Gates. The BG's are very expensive, of course, and the ES's have to be purchased from two vendors or from Michael Percy - but they are not too expensive in either case.

 Like some of the rest of us, you have business decisions to make and it continues to amaze many of us with the low prices that you offer. Of course, there is nothing inherently wrong with lowering the board and many builders have done that with great success. The KZ is a great cap, no doubt - just a bit huge. 
	

	
	
		
		

		
		
	


	







 Many thanks for what you do in offering such great kits to the community - including the Millett MAX. You also have e-mail.


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## fordgtlover

Tom 

 I have been meaning to post about this for ages - oh well a bit distracted.

 The BOM lists the power supply CR3 caps from Digikey as 399-4141-ND , which has a 2.5mm lead spacing. Perhaps the better fit is the 399-4199-ND, which is the same part with a 5.08mm lead spacing.

 Cheers


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## dsavitsk

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_I don't have much of a clue, either, but you're right - he has said that. I think what happens traditionally in a tube amp is that the input impedance is relatively low. They used higher impedance pots to compensate - I think._

 

Actually, input impedance (of a tube's grid) is very high. Usually, you want the pot to be at most 1/10th of the input impedance of the next stage. With tubes, you can use a 250K pot because the tube's input impedance is so high -- often well into the MOhms. 

 The noise level does increase as the pot size is increases, but this is really a solid state issue where you can have a crazy low noise floor. Tubes always have a higher noise floor, so a higher value pot doesn't do any harm. So, why use one? Because you can get away with a smaller coupling cap before it, and to relieve strain on the previous stage.


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## Televator

thanks all for the responses!

 First of all a bit of a clarification: I really love Jeff's kits (I have bought numerous already 
	

	
	
		
		

		
		
	


	




 and left very positive feedback for it as well) and I have no problem with them whatsoever! The CA4/5 recommendation was changed after the kits were bought so I just wanted to keep Jeff posted so he could adapt the kits (for future sales) if he deemed necessary... but as he reads the forum as well, he has already noticed and even posted his intentions ... which is clearly why I love those kits!

 I have also gotten some customizations in my (Alien DAC kits) already... but at the moment I'm actually talking about a (standard) MAX kit I have already bought and received (but not built yet; I bought two right away) 
	

	
	
		
		

		
		
	


	




 I just love the MAX even more than I expected and I don't mind spending a bit more on it, so I was thinking of adapting my second kit to further 'Boutique' it up a bit... no critique on Jeff('s offerings) at all!
  Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_It's possible that the Sequoia KZ's are enough in the CA4/CA5 positions [...]_

 

well, they do sound great in my first build... don't really notice any problems... but as I do have a second build coming and don't mind experimenting a bit, I will try FM 1800µf (the 1*0*00µf was actually just a typo in my summary 
	

	
	
		
		

		
		
	


	




 ) as well. I don't know how much I'll change at once (bit afraid of de/resoldering too much and damaging traces) but I'll try and compare if I can isolate certain differences.
  Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Actually, the way things work I think a K42 would be wasted in the CA9 position, but that's just MHO._

 

But I have ordered 10 of those K42's 
	

	
	
		
		

		
		
	


	




 so I have to do something with them (but I have other options to 'dispose' of the leftovers of course and the WIMA's did work fine... and if I opt for a full-BG version I won't even need them at all 
	

	
	
		
		

		
		
	


	




 )
  Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Here's just my opinion, but when I use ES's, I limit myself to the 2SC3422/2SA1359 -or- the 2SC3421/2SA1358. If using Black Gates, then the 2SC2238/2SA968 are a perfect choice._

 

at the moment I'm leaning towards a KZ-version + 2SC3422/2SA1359 and a BG-version + 2SC2238/2SA968 which I will compare...
  Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Also, it's more money for sure, but IMHO - if you purchase the BG's for CA7, it seems a waste not to have the BG's in CA2. Sort of a twofer/fourfer as it were. 
	

	
	
		
		

		
		
	


	




 I'm not one to mix the type of caps in those two positions - they should probably be the same brand, but I guess there's no law about it - just no guarantees, either._

 

The kit with Pana FC for CA2 and Muse KZ for CA7 did work very well actually, so at least one more mix that doesn't ruin anything at all 
	

	
	
		
		

		
		
	


	




 ...my wallet is hiding somewhere, but I kinda feel like splurging on some BG's

  Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_There [= building a third MAX] is the answer!_

 

see, now you've really scared my wallet away for good 
	

	
	
		
		

		
		
	


	




  Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_There's a Compact MAX coming, but it's not that different - just sized for a different case. There may be some minor changes in the big board, but I wouldn't expect much._

 

this does sound interesting and I'm looking forward to learning more about those new versions... but for now I guess I'll focus on building a second one first...

  Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_No problem. Just realize the Jeff offers an unbelievable deal on his kits. [...] Colin and I tried to adhere to a 1" height in all instances except for the MOSFET version._

 

As I said above, I do realize Jeff offers a brilliant deal (and it does sound wonderful already for relatively very little money) but if I (with my limited experience) can help to improve those a tiny bit I'll be happy beyond belief (and if not, I'll just stick to building a second full-boutique version)

 I actually noticed the KZ's do fit the second slot (which still offers a possibility to fit some slim test points underneath the board and looks relatively centered on the front panel) but the heatsinks for the BJT's didn't fit by a fraction of an inch. So I just let them poke through the top plate (well, they actually didn't stick out at all and came to about halfway the thickness of the top plate) but this is of course extra encasing work (but I guess one could also use smaller heatsinks).


----------



## tomb

Quote:


  Originally Posted by *dsavitsk* /img/forum/go_quote.gif 
_Actually, input impedance (of a tube's grid) is very high. Usually, you want the pot to be at most 1/10th of the input impedance of the next stage. With tubes, you can use a 250K pot because the tube's input impedance is so high -- often well into the MOhms. 

 The noise level does increase as the pot size is increases, but this is really a solid state issue where you can have a crazy low noise floor. Tubes always have a higher noise floor, so a higher value pot doesn't do any harm. So, why use one? Because you can get away with a smaller coupling cap before it, and to relieve strain on the previous stage._

 

Thanks for explaining that! I had it exactly backwards.


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## tomb

Quote:


  Originally Posted by *fordgtlover* /img/forum/go_quote.gif 
_Tom 

 I have been meaning to post about this for ages - oh well a bit distracted.

 The BOM lists the power supply CR3 caps from Digikey as 399-4141-ND , which has a 2.5mm lead spacing. Perhaps the better fit is the 399-4199-ND, which is the same part with a 5.08mm lead spacing.

 Cheers_

 

Thanks. This has been changed, along with some incorrect links for a couple of parts that pinkfloyd4ever pointed out.

 Also, I changed the brand names for the electrolytics in the e12 circuit to cheap Xicons at Mouser and Nichicon UVZ's at DigiKey. The cheapest sort of cap can be used in these positions as long as the rating is met and the 105deg. temperature rating is also selected.

 Also, I've had good luck using a 470uf 16V for CM3 instead of a 330uf. That will increase the delay a few more seconds. You can do this by increasing the value of RM2, too, but resistors greater than 1M are sometimes hard to find.


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## Televator

I stumbled across my wallet (hiding behind the couch 
	

	
	
		
		

		
		
	


	




 ) and quickly ordered some BG NX's (25V 1000µf and 35V 680µf) for my second build 
	

	
	
		
		

		
		
	


	




 seems I'll go for real boutique anyway ... darn, I already ordered and now I realize I should have gotten some extra BG's for my Alien 
	

	
	
		
		

		
		
	


	




 -----------------------

 On a completely different note: the MAX and tube/panel-LED's!

 I was wondering what everybody preferred (/used)... 
 - for tube lights: yes or no ; what color ; what specs ; what sources you get them from etc...

 - for panel/internal LED: panel and/or internal ; color ; special gimmicks (somewhere early in this thread someone (Vixr?) mentioned a backlit Millet MAX logo... did it get built? But also knobs with lights (any links to how-to's?) or other wow-ideas...) ; etc...

 I'm really just interested in most everything as I have to decide what to do for MAX#2 and now I still have a chance to change from the standard blue LED's all round (which I have implemented in my MAX#1 already)

 In general I kinda do like white LED's, but as tube-lights they would kill the glow-effect I guess. Red or orange might be extra 'glowy', but how would I be able to see if my MAX caught fire? 
	

	
	
		
		

		
		
	


	




 Would a bare MAX look good. No (or very low intensity) tube-lights and only a very low-intensity white LED in the volume knob?... What do you all like/think/have built/wish to change in your build if you had the chance?


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## smegger

just came home to get my max kit form glass jar today its awesome! i just ordered some russian pio caps too, (i have 10 so anyone after them pm me).

 since i ordered my kit the bom in relation to ca4 and 5 seems to have changed i asked jeff to change mine to muse ukzs but i have 470uf here atm should i change these?


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## tomb

Quote:


  Originally Posted by *smegger* /img/forum/go_quote.gif 
_just came home to get my max kit form glass jar today its awesome! i just ordered some russian pio caps too, (i have 10 so anyone after them pm me).

 since i ordered my kit the bom in relation to ca4 and 5 seems to have changed i asked jeff to change mine to muse ukzs but i have 470uf here atm should i change these?_

 

This is a hard question to answer. We have had reports of some MAXes not having enough bass, with seemingly no difference from well-established MAXes that have bigger values in those positions. More worrisome is that there have been some reports that increasing bias on the DB's has affected the bias on the tubes. That should _never_ happen. At the same time, the purpose of the CA4 and CA5 caps is to de-couple the V+ from ground. So, my only guess is that under extreme conditions, smaller versions of those caps are not enough to maintain the voltage differential between V+ and ground.

 That may not be technically correct, but after firing up 5 MAXes so far, I can tell you for sure that with ES caps or BG caps along with 1200uf - 1800uf caps in CA4/CA5, the bass is nothing short of _intimidating_. If that isn't the case, then the first things to look for are the following:

 1. Too small selection at CA7 - 470uf has never been a problem here, even with Grados.
 2. Too small selection at CA2 - this has been addressed by making 1000uf the _required_ selection.
 3. A "blooming-mids" boutique film cap in CA9. I think I've publicized this enough now that most know about this pitfall.
 4. CA4 and CA5 caps too small.

 Another bit of anecdotal evidence for this: there was a relatively recent instance of someone building a revMH Millett Hybrid and using 100uf caps (that's one hundred) in C4 and C5. His C7 cap was 470uf and C2 was 220uf, the prescribed amount at the time for the older Millett. He was complaining about a lack of bass!

 The conclusion was that the C4 C5 caps were too small at 100uf. You see, there have been statements in the past that the C4 and C5 caps have no effect on bass, so it was thought that perhaps a smaller size would be OK. In any event, at a guess, he changed them out to 470uf's and was then happy with the bass.

 Now, considering that with the MAX, everything is more or less super-sized, it stands to reason that this may be another bit of evidence that smaller caps - relatively speaking - could be a cause of lighter bass than expected.

 I hope that clarifies where my judgment is coming from ... those caps are only 50-75 cents more for each of four caps on a DIY project that costs you ~$175 for parts alone. Rather than make exhaustive comparison tests to prove this absolutely (time is better spent on testing $expensive boutiques), it makes a lot more sense to just tell everyone not to skimp on those caps. 
	

	
	
		
		

		
		
	


	










 EDIT: Sorry for being so verbose about this subject. The fact remains that everyone of you who build a MAX should be exclaiming, "WOW!" when you hear the MAX's bass for the first time. So, we want to make sure that those of you who don't - soon will. 
	

	
	
		
		

		
		
	


	







 [end rant]


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## smegger

no worries tomb i do understand what you are saying better safe than sorry.

 um anyone want to swap some 470 muse ukz for some 1000-1800 ones? or can anyone point me in the right direction of where to get em in the uk?


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## Televator

I have built a pure Glassjar kit (including 470µf KZ's @ CA4/5) and coming from the HeadFive I already went "WOW that bass" (with a 470µf output cap and grado/alessandros)

 I don't really feel urged to switch those 470µf's in my existing build... but as I'm starting my second build, I'm interested to try the other option as well (I'll try some Panasonic 35V FM 1800µf's) as those spots aren't mentioned as boutique locations. I found some Pana FM's of the correct values with RS-components in Belgium (part n° 5261812) so I guess they should be available in the UK as well...

 All this said, I do think the KZ's do a great job already and I'm just wondering if this could even be improved (just like I'm going more boutique in other places as well) but if the BOM hadn't changed (or if I hadn't noticed the change) I definitely wouldn't have felt that something was(/might be) missing! Including mildly ear-shaking bass even with MS2i's and relatively low capacitance output caps...

 My current MAX is clearly the best amp I have ever heard... just hoping/trying to make sure my second MAX can top this still 
	

	
	
		
		

		
		
	


	




 PS: I also ordered 10x K42 PIO's (and will probably only need 4 or 6 max), so if someone feels the need to try those perhaps check here first to see if you can't get them in precise amounts


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## tomb

Thanks, Televator. Yes, as mentioned previously, the KZ's are probably different. I'm actually referring to the typical little 470uf power caps such as FM's, FC's, UPW's, etc., when I say perhaps not as big as they should be on the MAX.


----------



## odoe

Using 2SC3422/2SA1359 and ES's in CA7 with orange drops in CA8, my HD580s will reverberate at 12 o clock with bass. Its like someone is blowing in my ears. The MAX is not short on bass, that's for sure.

 My next MAX, which will be a BG build is on hold for the holidays, but for now, this current build serves me well and is extrememly fun.


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## ruZZ.il

woohoo. I got a whole bunch of parts to start my next MAX with 
	

	
	
		
		

		
			





 I'm going to move my BG's over to it and use 1.5" sinks. I should have some of the Russian caps soon too to try. I'll be comparing them with the vit Q's I've obtained and am yet to try, while I'm at it. I've got a set of ES's that Tom sent me to stick into my first max (what was the verdict with the Gen IIs with these, if any?). I've got some PRP resistors to outfit most significant positions too, which I hope will prove their worth though they do at least look good 
	

	
	
		
		

		
		
	


	




. I'll probably use some cheap wood for the case again too since it actually looks kinda cool (I'll eventually update my pics). I'll probably extrude the heat sinks kind of like vixr style. fortunately my caps are still short enough though since I doubt I could cut that clean (rspct, vixr). got some knobs while I'm at it too.. still need more knobs
	

	
	
		
		

		
		
	


	




. I still need to get a pot and to make some new cables. need more wire too I guess
	

	
	
		
		

		
		
	


	




. I'm really taking my time with this one though, since, well.. I've just got less of it lately ;/ so no pot.. not wired. yet.

 edit: Thankfully, I also have a bunch of BJT pairs I'll still try out


----------



## tomb

Quote:


  Originally Posted by *ruZZ.il* /img/forum/go_quote.gif 
_<snip>I've got a set of ES's that Tom sent me to stick into my first max (what was the verdict with the Gen IIs with these, if any?)._

 

I posted up there in one of my recent posts, but I've been posting books lately so maybe they're hard to read. 
	

	
	
		
		

		
		
	


	




 The GEN II's will cut some of the bass and falsely exaggerate the highs (IMHO). The K42's are the thing to use - ES's or Black Gates. Since KZ's are in the same family as ES's, then I bet they work with those, too.

 I still use the Wimas in CA8, except with BG's - I let the CA2 caps stand alone in that case. I wasn't even going to add any bypasses on CA7 with BG's, but the K42 actually helps clear up some of the BG congestion.

  Quote:


 I've got some PRP resistors to outfit most significant positions too, which I hope will prove their worth though they do at least look good 
	

	
	
		
		

		
		
	


	




. 
 

I've used them on a couple of MAXes already and can't tell a difference with the V-D's - but they sure look better than that ugly brown.


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## amphead

Quote:


  Originally Posted by *ruZZ.il* /img/forum/go_quote.gif 
_woohoo. I got a whole bunch of parts to start my next MAX with 
	

	
	
		
		

		
		
	


	




 I'm going to move my BG's over to it and use 1.5" sinks. I should have some of the Russian caps soon too to try. I'll be comparing them with the vit Q's I've obtained and am yet to try, while I'm at it. I've got a set of ES's that Tom sent me to stick into my first max (what was the verdict with the Gen IIs with these, if any?). I've got some PRP resistors to outfit most significant positions too, which I hope will prove their worth though they do at least look good 
	

	
	
		
		

		
		
	


	




. I'll probably use some cheap wood for the case again too since it actually looks kinda cool (I'll eventually update my pics). I'll probably extrude the heat sinks kind of like vixr style. fortunately my caps are still short enough though since I doubt I could cut that clean (rspct, vixr). got some knobs while I'm at it too.. still need more knobs
	

	
	
		
		

		
		
	


	




. I still need to get a pot and to make some new cables. need more wire too I guess
	

	
	
		
		

		
		
	


	




. I'm really taking my time with this one though, since, well.. I've just got less of it lately ;/ so no pot.. not wired. yet.

 edit: Thankfully, I also have a bunch of BJT pairs I'll still try out 
	

	
	
		
		

		
		
	


	


_

 

Sounds good, I will be interested in the new boards when they become available, to get my second Max started.


----------



## pinkfloyd4ever

Quote:


  Originally Posted by *smegger* /img/forum/go_quote.gif 
_no worries tomb i do understand what you are saying better safe than sorry.

 um anyone want to swap some 470 muse ukz for some 1000-1800 ones? or can anyone point me in the right direction of where to get em in the uk? 
	

	
	
		
		

		
		
	


	


_

 

 Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Thanks, Televator. Yes, as mentioned previously, the KZ's are probably different. I'm actually referring to the typical little 470uf power caps such as FM's, FC's, UPW's, etc., when I say perhaps not as big as they should be on the MAX. 
	

	
	
		
		

		
		
	


	


_

 

so in case you (or anyone else) are still confused, you should be fine with 470uf at the CA4, CA5, and CA7 positions if they're Muse KZ's, assuming you still have the spec'd 1000uf for CA2 and CR1A/B/C/D, which you do if you're using JRossel's Glass Jar kit

 from tomb's post #2311: Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Couple of things:
 1. It's possible that the Sequoia KZ's are enough in the CA4/CA5 positions. That recommendation is really for those who go and buy 470uf UPW's, FM's or FC's. I would say that ES's are probably not optimum in those positions, either - because they're bipolar. That doesn't meet the intent of those caps, which is to preserve the voltage difference between V+ and Gnd and prevent any possible coupling. However, the KZ's may be OK because so much of their frequency response is "tuned" for the audio band. I haven't tested them personally, so I don't really know this, however.

 Strictly speaking, the difference between the price of a 470uf KZ and an 1800uf is about 40cents. From a capacitance standpoint, that's no comparison - and "audio quality" is not really the purpose - "power quality" is. Ultimately however, it all becomes signal, so that's why I give the disclaimer - I just don't know._


----------



## Ferrari

For those who are considering a balanced MH Max, be aware that the balanced amp will have an effective gain that 2x higher than the single ended version. As a result, the volume controle range will be more limited comparing to single ended version.

 In this build, the gain is determined by the used tube and thus fixed. Even when the 12FK6 with a gain of ~5x is used (assuming with 300 Ω headphone), the effective gain is still 10x !!!

 One might implement a level converter which allows pre-attenuation of -6dB, -12dB or -18dB to decrease (lowering) the input signal level a bit. By doing this way the volume controle range can be enlarge. However from audio viewpoint, this is a not a neat (desired) solution.

 I am happy with the sound of the balanced version I have built... but, the volume controle range is quite limited as I described here.


----------



## pinkfloyd4ever

ferrari, have u tried using some Kiwames or other high quality output resistors? (at RB14 for those who don't know) Or a higher R pot? I'm too lazy to look up the exact links, but both have been discussed in the last few pages of the thread


----------



## pabbi1

Quote:


  Originally Posted by *Ferrari* /img/forum/go_quote.gif 
_For those who are considering a balanced MH Max, be aware that the balanced amp will have an effective gain that 2x higher than the single ended version. As a result, the volume controle range will be more limited comparing to single ended version._

 

Precisely why I built balanced - my original Max simply did not have enough output, and I have stocked up very well on 12fk6. The output resistors are also an option, if needed.


----------



## smegger

finally got underway and this is how far i have got






 then ran out of solder!!!!!
 anyone got any leaded eutectic in the uk i have asked this before i know but now im desperate! think i am just gona have to go lead free.


----------



## tomb

Quote:


  Originally Posted by *pabbi1* /img/forum/go_quote.gif 
_Precisely why I built balanced - my original Max simply did not have enough output, and I have stocked up very well on 12fk6. The output resistors are also an option, if needed._

 

Yes, I regularly listen to 12AE6's and KSC75's with an Alien DAC as source. I get to 9 o'clock or thereabouts for normal listening and it's acceptable - close to 12 o'clock for Senns.

 The 12FK6 is half the gain of the 12AE6's (7 vs. 14). So, if you substitute one of those in a balanced version, the volume control should be similar to the above. I'm only guessing of course, but I don't think it should deter anyone from building a balanced version if they want one.
 EDIT #2: That's with jumpering the output resistor positions, by the way.


 EDIT: Lookin' good, Smegger!!


----------



## pinkfloyd4ever

Quote:


  Originally Posted by *smegger* /img/forum/go_quote.gif 
_think i am just gona have to go lead free._

 

NOOOOO resist the Dark Side!!!

 some head-fier in the UK has to have been stockpiling REAL solder...one o u Brits wanna jump in here & help him plz?


----------



## amphead

Quote:


  Originally Posted by *pabbi1* /img/forum/go_quote.gif 
_Precisely why I built balanced - my original Max simply did not have enough output, and I have stocked up very well on 12fk6. The output resistors are also an option, if needed._

 

Hope all is working out well for your balanced Max!


----------



## pabbi1

Quote:


  Originally Posted by *amphead* /img/forum/go_quote.gif 
_Hope all is working out well for your balanced Max! 
	

	
	
		
		

		
		
	


	


_

 

Amp sections are fine - troubleshooting the S/PDIF receiver for the DAC... getting closer... I think / hope / have no freaking idea...


----------



## smegger

please im drunk hit me with eutictic solder


----------



## pinkfloyd4ever

Quote:


  Originally Posted by *smegger* /img/forum/go_quote.gif 
_please im drunk hit me with eutictic solder_

 

HAHHH Yessss I can def identify w/that. Sorry dude, I'd send you some at cost if I had more than one spool, plus it'd take awhile to get there. Maybe post a new thread in the DIY section asking ppl from the UK if they could help you out?

 EDIT: resist the urge to work on your MAX when you come home by yourself drunk and want to do something. Soldering + alcohol = costly ****-ups you'll regret in the morning...trust me, I've done it


----------



## Ferrari

Quote:


  Originally Posted by *pabbi1* /img/forum/go_quote.gif 
_Precisely why I built balanced - my original Max simply did not have enough output, and I have stocked up very well on 12fk6. The output resistors are also an option, if needed._

 

Pabbi1, I have got a feelling that you are mixing the limited "current ability" of your original MH Millett with "voltage gain" I am talking about. Your original MH Millett was clipping at a certain volume level. The problem there was the limited current ability of the original Diamond Buffer. Adjust original Diamond Buffer at ~20mA or so and it's already melting hot. Dial the output current to a higher level is impossible !!! 

 If I can remember, you have contacted Pete Millett for the clipping problem of your original MH Millett and his answer was: hee, _what do you expect from this amp?_ The good man was thinking and talking in terms of "current ability".

 About the output resistor, I have not mentioned it explicitely in my previous post but it was already considered (tried out). You can temper the output level a bit but not a byte. You might put a couple of hundred Ohms at the output but not KOhms.

 Btw, it's not my intention to dicourage anyone to build a balanced version of the Max. Just a little experience I want to share.
 Sad to know that you have got so much trouble with your build, but try to complete it!


----------



## Televator

Quote:


  Originally Posted by *smegger* /img/forum/go_quote.gif 
_please im drunk hit me with eutictic solder_

 

I use Multicore's eutectic 62/36/2 (Sb/Pb/Ag) solder (22swg/0.75mm thickness) and it is very easy to work with... you can get it from RS-components (I use Belgium, but there is a UK version as well 
	

	
	
		
		

		
			





 and the part n° is 551-671 for a reel of .5kg)

 your build is looking good so far... I'm quite eager to get going on my second MAX, but I'm waiting on some parts and I still have to place one last order with RS-comps myself

 no-one has responded yet to my question on MAX-lights though... I was thinking of going without tube lights (I know n_maher prefers this as there's no risk for them malfunctioning/burning out underneath the tube sockets) or using lower intensity yellow/amber ones and I'd love to add a LED to my volume knob (but I wouldn't have a clue how to do this though so links to instructions are welcome)

 I was just thinking: if I go boutique on the internals, why not improve outer looks a bit as well? so what have you done (I've seen the Gallery on the MAX-site, but please comment on your choices shown there as well) or are you planning to do?


----------



## tomb

Quote:


  Originally Posted by *Televator* /img/forum/go_quote.gif 
_no-one has responded yet to my question on MAX-lights though... I was thinking of going without tube lights (I know n_maher prefers this as there's no risk for them malfunctioning/burning out underneath the tube sockets)_

 

That's not really the case. Most of the time, I remove components with leads from the bottom by poking a spare lead into the hole while melting the solder joint. This pushes the part through from the other side. Extra solder or making a blob between the two leads makes this even easier, since it will keep both joints melted at the same time.

 As it happens, the LED, when pushed, will drop completely through the hole in the tube socket and drop right out. Installing a new one is just as easy - you can drop the LED in from the top through the hole in the socket.

 This is made easier if you mount the LED so that it sits up in the tube socket hole, but it's not completely necessary.

 Also, that's one of the things I changed on the BOM the other day: using a 2K resistor for the LED's. This puts the power rating down into the 1/2W rating, and the 2K resistor is easier to find. It only drops the current down to ~12ma, which has very little effect on the brightness of the LED. Yet, it will increase LED life tremendously.

 Seriously, the hardest part about using tube LED's is drilling the hole in the sockets - without breaking them. 
	

	
	
		
		

		
		
	


	




  Quote:


 ... or using lower intensity yellow/amber ones and I'd love to add a LED to my volume knob (but I wouldn't have a clue how to do this though so links to instructions are welcome) 
 

Ferrari revealed how to do this once. Simply drill the knob in the front to fit the LED. Use some silicon caulk or similar to secure it from the back. (This is also how it works if you want to backlight the knob or back light a shape you've cut through the endplate.) Wire up some flexible leads while placing the knob in a medium volume position so that you'll have a bit of movement either way for adjustment.

 What happens is that full movement is not possible once soldering the leads through an enlarged front plate hole and routing them along the pot shaft. However, as we've been discussing lately with MAX gains, etc. - you may only need about 90 deg. of full travel on the knob, anyway.

  Quote:


 I was just thinking: if I go boutique on the internals, why not improve outer looks a bit as well? so what have you done (I've seen the Gallery on the MAX-site, but please comment on your choices shown there as well) or are you planning to do? 
 

One thing - the Hammond case can be painted/finished quite easily if you start with a silver one and use a coat of primer first.


----------



## Televator

ah, thanks Tomb... no worries about the tube-leds anymore for me because the socket drilling worked just fine thanks to the good description on the site (good as I didn't want to miss the glow actually 
	

	
	
		
		

		
		
	


	




 )

 I reckon the 2k led-resistors can be any cheap kind ... I have some 1/4W metal film 2k resistors left over, or do I need a higher W-rating (1/2 min)?

 the knob-led sounds easy enough as well (will have to try that one) and I know for sure my knob won't have to spin too much 
	

	
	
		
		

		
		
	


	




 Will think some more about finishing the outside, but for now I know enough to order the last parts... MAX n°2 here I come


----------



## tomb

Quote:


  Originally Posted by *Televator* /img/forum/go_quote.gif 
_ah, thanks Tomb... no worries about the tube-leds anymore for me because the socket drilling worked just fine thanks to the good description on the site (good as I didn't want to miss the glow actually 
	

	
	
		
		

		
		
	


	




 )_

 

My second favorite tube light color is green - it's a very nice glow and is not overpowering like the blue. I wish LSDiodes had their "aqua" color in 3mm LEDs - I'd use that one all the time.

  Quote:


 I reckon the 2k led-resistors can be any cheap kind ... I have some 1/4W metal film 2k resistors left over, or do I need a higher W-rating (1/2 min)? 
 

You must've missed it in the post up there: 1/2W is _minimum_. It's actually ~0.29W at a PS voltage of 27VDC, but that's definitely more than 1/4W. You always want a big safety factor in something like this, anyway (catastrophic failure). Cheap as you can find will work as long as it has that power rating.

  Quote:


 the knob-led sounds easy enough as well (will have to try that one) and I know for sure my knob won't have to spin too much 
	

	
	
		
		

		
		
	


	



 

I haven't done one, but it stands to reason that the bigger the knob, the easier this will be. If memory serves, Ferrari did it on one of his HiFi2000 cases with a humongous knob.

  Quote:


 Will think some more about finishing the outside, but for now I know enough to order the last parts... MAX n°2 here I come


----------



## kvant

Quote:


  Originally Posted by *Ferrari* /img/forum/go_quote.gif 
_Your original MH Millett was clipping at a certain volume level. The problem there was the limited current ability of the original Diamond Buffer. Adjust original Diamond Buffer at ~20mA or so and it's already melting hot. Dial the output current to a higher level is impossible !!! _

 

I don't think this is correct. The bias current only determines, how long the buffer stays in class A. When the voltage swing exceeds certain limit, the buffer switches over to class B, but that does not mean that it clips. BTW, the bias 20mA per transistor in the original buffers actually means 40mA per channel, since there were paralleled output devices. This, in turn, is not that much lower than the general recommendation of 50mA per transistor for MH MAX, that has only one pair of output devices per channel.


----------



## smegger

televator be stupid like me and save for a custom hifi 2000 case, it will prob cost more than the amp


----------



## tomb

Quote:


  Originally Posted by *kvant* /img/forum/go_quote.gif 
_I don't think this is correct. The bias current only determines, how long the buffer stays in class A. When the voltage swing exceeds certain limit, the buffer switches over to class B, but that does not mean that it clips. BTW, the bias 20mA per transistor in the original buffers actually means 40mA per channel, since there were paralleled output devices. This, in turn, is not that much lower than the general recommendation of 50mA per transistor for MH MAX, that has only one pair of output devices per channel._

 

Good catch!

 Yes, there was even a possibility to bias to 30ma, which with the parallel output transistors, would be 60ma per channel, actually exceeding the general MAX recommendation. The MAX can go quite a bit higher, though, whereas that was pretty much the absolute with the revMH DB's.

 As you say, though, this is only the Class A bias value, not an indication of peak currents that the transistors could supply with switching.


----------



## pinkfloyd4ever

is it at all possible to fit a 5mm led under the sockets?
  Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_My second favorite tube light color is green - it's a very nice glow and is not overpowering like the blue. I wish LSDiodes had their "aqua" color in 3mm LEDs - I'd use that one all the time._

 

I wish LSDiodes site was up.. 
	

	
	
		
		

		
		
	


	




 On an unrelated note, why exactly would one want a CCS current of .65ma as opposed to the standard .575mA? I looked all over here & on the MAX site and couldn't find _why_ one would want the higher current. Is it just for MOSFETs?


----------



## pabbi1

Quote:


  Originally Posted by *Ferrari* /img/forum/go_quote.gif 
_Pabbi1, I have got a feelling that you are mixing the limited "current ability" of your original MH Millett with "voltage gain" I am talking about. Your original MH Millett was clipping at a certain volume level. The problem there was the limited current ability of the original Diamond Buffer. Adjust original Diamond Buffer at ~20mA or so and it's already melting hot. Dial the output current to a higher level is impossible !!! 

 If I can remember, you have contacted Pete Millett for the clipping problem of your original MH Millett and his answer was: hee, what do you expect from this amp? The good man was thinking and talking in terms of "current ability".

 About the output resistor, I have not mentioned it explicitely in my previous post but it was already considered (tried out). You can temper the output level a bit but not a byte. You might put a couple of hundred Ohms at the output but not KOhms.

 Btw, it's not my intention to dicourage anyone to build a balanced version of the Max. Just a little experience I want to share.
 Sad to know that you have got so much trouble with your build, but try to complete it!_

 

No problems at all - I never used DB in the old amp, just buf634, and was constantly driving my HD600 at 3-4 o'clock... just maddening. This time I'm running Denons (though the HD600 will come back), so we'll see. The BH is fully balanced, so the concept of balanced isn't scaring me at all, just having a receiver, DAC, and balanced amps all at once just isn't yet coming together as fast as I had hoped...


----------



## Televator

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_You must've missed it in the post up there: 1/2W is minimum._

 

misinterpreted it indeed


----------



## Ferrari

Quote:


  Originally Posted by *kvant* /img/forum/go_quote.gif 
_I don't think this is correct. The bias current only determines, how long the buffer stays in class A. When the voltage swing exceeds certain limit, the buffer switches over to class B, but that does not mean that it clips. BTW, the bias 20mA per transistor in the original buffers actually means 40mA per channel, since there were paralleled output devices._

 

Thanks for remembering me... I almost forget that I have build this stuff in the past 
	

	
	
		
		

		
		
	


	




.
 And thanks god, I still not forget the Class A-B operation thing of this buffer or power amplifier in general... unless electronics design is not my main profession anymore for years.


----------



## tomb

Quote:


  Originally Posted by *pinkfloyd4ever* /img/forum/go_quote.gif 
_is it at all possible to fit a 5mm led under the sockets?_

 

Unfortunately, no. It's possible that one could come up with something custom, but with the standard board and tube socket - no.

  Quote:


 I wish LSDiodes site was up.. 
	

	
	
		
		

		
		
	


	



 

It was up and running when I checked awhile ago.

  Quote:


 On an unrelated note, why exactly would one want a CCS current of .65ma as opposed to the standard .575mA? I looked all over here & on the MAX site and couldn't find _why_ one would want the higher current. Is it just for MOSFETs? 
 

What context is this from? As a matter of fact, CCS current is largely arbitrary within a certain range. Pete Millett actually tried a full milliamp (1.0ma) on the original, but said that the result was "slightly higher distortion." The guide for this are the tube curves for the various Millett tubes. Those can be found in the tube data sheets which are on the MAX website under Millett MAX tubes.

 The object is to pick a CCS current point (line) that generally intersects at the linear portion of the tube curves. You don't want to pick a CCS point that's down in the part of the curves that are curved. 
	

	
	
		
		

		
		
	


	




 Those curves are different for each tube, too. For instance, one might look at the 12AE6 and it might look as if 0.3ma would be sufficient for the CCS. However, look at the 12FM6 curves, and 0.3ma is down in the region where the lines are still currving sharply. So, a higher point is selected, but not too high up around 1ma where Pete noted some distortion.


----------



## tomb

Quote:


  Originally Posted by *Ferrari* /img/forum/go_quote.gif 
_Thanks for remembering me... I almost forget that I have build this stuff in the past 
	

	
	
		
		

		
		
	


	




.
 And thanks god, I still not forget the Class A-B operation thing of this buffer or power amplifier in general... unless electronics design is not my main profession anymore for years. 
	

	
	
		
		

		
		
	


	


_

 

I built 4 of them and still didn't catch what you had said. Luckily, I can't make the claim of being an EE - just an ignorant ME.


----------



## Ferrari

Quote:


  Originally Posted by *Televator* /img/forum/go_quote.gif 
_... I'd love to add a LED to my volume knob (but I wouldn't have a clue how to do this though so links to instructions are welcome)_

 

The construction of the knop with LED on an ATI-735U enclosure as can be seen on page 90 of the "Post pics of your builds" thread is described here. Hope that it will help a bit.


----------



## amphead

Quote:


  Originally Posted by *kvant* /img/forum/go_quote.gif 
_I don't think this is correct. The bias current only determines, how long the buffer stays in class A. When the voltage swing exceeds certain limit, the buffer switches over to class B, but that does not mean that it clips. BTW, the bias 20mA per transistor in the original buffers actually means 40mA per channel, since there were paralleled output devices. This, in turn, is not that much lower than the general recommendation of 50mA per transistor for MH MAX, that has only one pair of output devices per channel._

 

Good info! I had posted concerns a couple of months ago, about the possibility of clipping with an overloaded input signal. But didn't realize that the trannies were working the way that you describe. Thanks, very enlightening.


----------



## Troyhoot

Just burnt out my second tube led.. Did I notice a change to the led resistor ? some way to remedy this from happening more ? Im using ultraviolet leds and not the ultrabright blue ones.


----------



## pinkfloyd4ever

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_What context is this from? As a matter of fact, CCS current is largely arbitrary within a certain range. Pete Millett actually tried a full milliamp (1.0ma) on the original, but said that the result was "slightly higher distortion." The guide for this are the tube curves for the various Millett tubes. Those can be found in the tube data sheets which are on the MAX website under Millett MAX tubes._

 

it was in the context of the CCS page on the site, combined with the BOM where it has "Optional selection: Results in CCS current of 0.65 mA" in reference to the alternate values of RA8/9. From the graph on the CCS page and the associated info, I was under the impression that .575 was the ideal CCS current for maximum performance and tube longevity in most cases, and I just guessed that the .65ma was intended for mosfets since they use more current.  Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_The object is to pick a CCS current point (line) that generally intersects at the linear portion of the tube curves. You don't want to pick a CCS point that's down in the part of the curves that are curved. 
	

	
	
		
		

		
		
	


	




 Those curves are different for each tube, too. For instance, one might look at the 12AE6 and it might look as if 0.3ma would be sufficient for the CCS. However, look at the 12FM6 curves, and 0.3ma is down in the region where the lines are still currving sharply. So, a higher point is selected, but not too high up around 1ma where Pete noted some distortion._

 

So, just to make sure, you're saying that anywhere on that I(V) graph is as good as the next as long as it's around the middle of the parts of the curves that are long and straight? EDIT: If you're totally confused by that description (as I prob would be too) the region circled in green:
	

	
	
		
		

		
		
	


	




  Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_I built 4 of them and still didn't catch what you had said. Luckily, I can't make the claim of being an EE - just an ignorant ME. 
	

	
	
		
		

		
		
	


	





_

 

WORD, me too...well, ME student anyway

  Quote:


  Originally Posted by *Troyhoot* /img/forum/go_quote.gif 
_Just burnt out my second tube led.. Did I notice a change to the led resistor ? some way to remedy this from happening more ? Im using ultraviolet leds and not the ultrabright blue ones._

 

ooo really, I was gonna do that, didn't think anyone else had. Is it as awesome as I hope it will be, as in like a fluorescent blacklight? Where'd you get your LEDs?


----------



## pinkfloyd4ever

OOO I see, so assuming I'm using a PS voltage of 27V (which I will be), it'd be more accurate to say along the blue line AND inside the green area? So, for whatever tube this graph is for, that'd be somewhere between .4 and .9 mA? Or am I just making sh!t up?


----------



## amphead

Duplicate post of below.......... V


----------



## amphead

Quote:


  Originally Posted by *Troyhoot* /img/forum/go_quote.gif 
_Just burnt out my second tube led.. Did I notice a change to the led resistor ? some way to remedy this from happening more ? Im using ultraviolet leds and not the ultrabright blue ones._

 

Remember to use caution with UV leds. You can get away with longwave UV, as long as you don't stare at it too long. Shortwave UV, will damage the corneas of your eyeballs however.


----------



## willisv

Well I finished building my millet max tonight (Big thanks to Jeff for the kit). When I powered it up everything looked good... no smoke, I had the DB bias pots turned all the way clockwise. The problem is, with the pots at their minimum setting I'm still reading 160 mA for the left side and 127 mA for the right side. Does anyone have any ideas what the problem might be?


----------



## willisv

I figured it out... i had a 243 and 253 transister mixed up. Hope I didn't fry anything.


----------



## amphead

Quote:


  Originally Posted by *willisv* /img/forum/go_quote.gif 
_I figured it out... i had a 243 and 253 transister mixed up. Hope I didn't fry anything._

 

If you can get your system to bias properly now, then you didn't fry anything. Sniff test for burnt plastic and visual for bubbled plastic. If it biases properly give it a listen!


----------



## willisv

Well I'm happy to say that everything is O.K. I got all my settings where their supposed to be and plugged in some headphones for a listen. This amp sounds amazing, I'm very happy with it so far. I think my next step will be to take out the dale vishay resistors at RB14 and see if that improves the sound. I'll post some pics tomorrow, I gotta get some sleep


----------



## Televator

good work willisv, for the built and also for the auto-troubleshooting! Another MAX lives!

 The glassjar kit does indeed sound great, doesn't it? Just let it burn in for a while (so the tubes burn their gases and all components settle down a bit)... it really improves with a bit of usage and good biasing of the buffers.


----------



## tomb

Quote:


  Originally Posted by *Troyhoot* /img/forum/go_quote.gif 
_Just burnt out my second tube led.. Did I notice a change to the led resistor ? some way to remedy this from happening more ? Im using ultraviolet leds and not the ultrabright blue ones._

 

Yes, I changed the LED resistors to 2K. It was more a matter of convenience, though - offering a better safety factor for a 2K, 1/2W resistor, which is easier to find.

 I'm not sure it's going to help the UV LEDs, though. If you're talking the UVs from LSDiodes, I've burned every one that I ran near the recommded current - all three burned up on the 1st MAX prototype. I asked Vixr if he had the same problem - he uses the UVs often - but no, no problem.

 Maybe we're just unlucky. I've never burned out any other LED.


----------



## tomb

Quote:


  Originally Posted by *pinkfloyd4ever* /img/forum/go_quote.gif 
_OOO I see, so assuming I'm using a PS voltage of 27V (which I will be), it'd be more accurate to say along the blue line AND inside the green area? So, for whatever tube this graph is for, that'd be somewhere between .4 and .9 mA? Or am I just making sh!t up?_

 

Yes, but there are a couple of facts, mentioned earlier, that you have to roll into your choice of CCS current:

 1. Pete has documented that going up as high as 1.0ma caused a noticeable increase in distortion. One can deduce from that the lower values are probably better than the 0.9ma.
 2. From the perpspective of the designer, you want to pick something that is able to utilize all three tubes. So, if you pick a number from that graph - it looks like one for a 12AE6 - you should compare it with the graphs from the other tubes and make certain the CCS current is in an acceptable regime.

 As noted earlier, numbers around 0.3 or perhaps even 0.4 are not in the linear area of the tube curve for the 12FK6.


----------



## Troyhoot

[size=xx-small] Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Yes, I changed the LED resistors to 2K. It was more a matter of convenience, though - offering a better safety factor for a 2K, 1/2W resistor, which is easier to find.

 I'm not sure it's going to help the UV LEDs, though. If you're talking the UVs from LSDiodes, I've burned every one that I ran near the recommded current - all three burned up on the 1st MAX prototype. I asked Vixr if he had the same problem - he uses the UVs often - but no, no problem.

 Maybe we're just unlucky. I've never burned out any other LED._

 

[/size]

 Hmm well if I burn another one out Im going to either change colors or just take them out completly. Might just be an UV thing, or a bad batch this time. The first one I replaced is already dimmer then the one I replaced last night.


----------



## tomb

Quote:


  Originally Posted by *Troyhoot* /img/forum/go_quote.gif 
_
 Hmm well if I burn another one out Im going to either change colors or just take them out completly. Might just be an UV thing, or a bad batch this time. The first one I replaced is already dimmer then the one I replaced last night._

 

One thing - I have a UV on an Alien DAC from the same batch and it's going strong. However, by my calcs the resistor selection on the Alien puts it down around ~7.5ma. So, I guess they will last if the current is severely reduced. The Alien's not very bright, however - it would be about like a power-on LED if it wasn't transparent and directional. That would make it 3.5Kohms on the MAX to run that same current, but I'm not sure they would be very useful at that - for the panel LED, yes, but nothing great for tube lighting. As you know, the UV's are already way down on the MCD's compared to high output LED's.

 You might try a 2K resistor such as on the revised BOM or perhaps a 3K - it may keep them from burning out at any rate.

 By the way, the MAX's original LED resistors were sized according to LSDiode's referenced LED calculator. So, there's definitely something weird going on with these UV's.


----------



## thomaskuhn

By any chance does anyone have an extra set of the 2SC2238/ 2SA968 power transistors, they might be able to sell me? I ordered some a while ago from MCM, but they are still out of stock. Does anyone know of another supplier for them?

 Tom


----------



## Possede

Just finished building the Max. Plugged it into the power supply. The LED's glow, but when I plug in some headphone (No matter if a music source is connected) all I can hear is a lowish hum. When connected to a music source, nothing can be heard apart from the hum. I noticed QB8L heatsink becomes very warm, whilst the rest stay cold. Help would be appreciated. 

 Most likely you will want some pictures, so I'll post them in a min.

 Thanks.


----------



## naamanf

Quote:


  Originally Posted by *Possédé* /img/forum/go_quote.gif 
_
 Most likely you will want some pictures, so I'll post them in a min._

 

Please do.


----------



## Possede

I'll replace this with some better pictures in a min or two, sorry. The tubes become a little warm, not much though. What component voltages should I check over?


----------



## naamanf

You might want to try and get better pictures that are a bit brighter. Also some pictures of the bottom traces would help. Are the tubes also heating up? Have you checked all the voltages?


----------



## willisv

Quote:


  Originally Posted by *amphead* /img/forum/go_quote.gif 
_If you can get your system to bias properly now, then you didn't fry anything. Sniff test for burnt plastic and visual for bubbled plastic. If it biases properly give it a listen! 
	

	
	
		
		

		
		
	


	


_

 

Thanks amphead, I got lucky... no damage as far as I can tell.

  Quote:


  Originally Posted by *Televator* /img/forum/go_quote.gif 
_good work willisv, for the built and also for the auto-troubleshooting! Another MAX lives!

 The glassjar kit does indeed sound great, doesn't it? Just let it burn in for a while (so the tubes burn their gases and all components settle down a bit)... it really improves with a bit of usage and good biasing of the buffers._

 

Yes this kit is very good, highly recommended if your a first timer like myself. Thanks very much for the info! If I only knew how fun this diy stuff was I would have done this long ago!

 Here's a picture 



][/url]


----------



## willisv

Quote:


  Originally Posted by *Possédé* /img/forum/go_quote.gif 
_I'll replace this with some better pictures in a min or two, sorry. The tubes become a little warm, not much though. What component voltages should I check over?





_

 

Did you get the right tube bias trim pot mixed up with the power supply trim pot?
 It kinda looks like a glass jar kit that I just built.


----------



## jerrygp

Quote:


  Originally Posted by *thomaskuhn* /img/forum/go_quote.gif 
_By any chance does anyone have an extra set of the 2SC2238/ 2SA968 power transistors, they might be able to sell me? I ordered some a while ago from MCM, but they are still out of stock. Does anyone know of another supplier for them?

 Tom_

 

I am on my second Millet build and am also interested if anyone might have a lead on where I might purchase a set of the 2SC2238/2SA968 power transistors? I have looked high and low and am having trouble finding a supplier that has them both in stock. Any help?


----------



## naamanf

Look hear for setting it all up.
http://www.diyforums.org/MAX/MAXsetup.php

 And it does look you might have swapped the pots by mistake. Also double check all the solder joints on the bottom side to make sure you don't have any cold ones. It's hard to tell in the pictures but you might have a couple.


----------



## willisv

Possede, you may want to check the resister RB7R. It looks like it got a little toasty.


----------



## Possede

Double post


----------



## naamanf

Quote:


  Originally Posted by *Possédé* /img/forum/go_quote.gif 
_
 Does it matter that I am running it off of a 20V DC power supply? It's the only one I could find in my house at the moment._

 

That is going to be your first problem. It needs a A/C power supply. It internally converts the A/C to D/C. 

 As for the pots you can look on the sides and they should have numbers that represent their resistance. Make sure that they are all in the proper place by those numbers not the color.

 Edit: The power supply whould have a "1k", the tube bias a "5k",a and the DB bias a "2k"


----------



## Televator

Quote:


  Originally Posted by *jerrygp* /img/forum/go_quote.gif 
_I am on my second Millet build and am also interested if anyone might have a lead on where I might purchase a set of the 2SC2238/2SA968 power transistors? I have looked high and low and am having trouble finding a supplier that has them both in stock. Any help?_

 

some European RS-Components (I checked the Belgian branch) have both in stock... I just ordered some for my own second (BG) MAX

 UK RS is out of the 2SC2238 but has got the 2SA986


----------



## willisv

Quote:


  Originally Posted by *Possédé* /img/forum/go_quote.gif 
_Yeah, I bought this off of Jeff. 
	

	
	
		
		

		
		
	


	




 Great guy. 

 Since this is theoretically my first time building anything, I am virtually uneducated when it comes to circuits. I'm pretty sure the problem with the amplifier is an obvious mistake - on my part. Thanks for pointing that out - I just realised that the right side tube bias is a different colour to the rest, so should I swap the right side tube bias with the power supply's bias? So they are both equally the lighter blue colour?

 Does it matter that I am running it off of a 20V DC power supply? It's the only one I could find in my house at the moment._

 

The power supply pot (RR3) is a 1K ohm and the tube bias pots (RA1 l/r) are 5K ohm. As far as power supply, I'll leave that to someone smarter than me but I think 27 volts is optimum.


----------



## Ferrari

Quote:


  Originally Posted by *jerrygp* /img/forum/go_quote.gif 
_I am on my second Millet build and am also interested if anyone might have a lead on where I might purchase a set of the 2SC2238/2SA968 power transistors? I have looked high and low and am having trouble finding a supplier that has them both in stock. Any help?_

 

Take a look at this shop.


----------



## Televator

Quote:


  Originally Posted by *Ferrari* /img/forum/go_quote.gif 
_Take a look at this shop. 
	

	
	
		
		

		
			



_

 

looks interesting they do also offer 2234/986 pairs (5 pairs) combined for about the same price... must remember this for if I manage to fry some of my current ordered ones (forgot to order spares 
	

	
	
		
		

		
		
	


	




 )


----------



## jerrygp

Quote:


  Originally Posted by *Ferrari* /img/forum/go_quote.gif 
_Take a look at this shop. 
	

	
	
		
		

		
		
	


	


_

 

Thanks Televator and Ferrari...I ordered 10 of the set from ALLPARTSPIPE on Ebay October 9th, but have yet to receive them. They are attempting to locate my order, but no luck yet. Coming from Hong Kong, I may be out of luck. I will try RS Components Europe though, and see what happens...I'm really wanting to try that configuration with the BG setup in this build.


----------



## Possede

Quote:


  Originally Posted by *willisv* /img/forum/go_quote.gif 
_Did you get the right tube bias trim pot mixed up with the power supply trim pot?
 It kinda looks like a glass jar kit that I just built._

 

Yeah, I bought this off of Jeff. 
	

	
	
		
		

		
		
	


	




 Great guy. 

 Since this is theoretically my first time building anything, I am virtually uneducated when it comes to circuits. I'm pretty sure the problem with the amplifier is an obvious mistake - on my part. Thanks for pointing that out - I just realised that the right side pot is a different colour to the rest, so should I swap it with the power supply's pot so they are both equally the lighter blue colour?

 Does it matter that I am running it off of a 20V DC power supply? It's the only one I could find in my house at the moment.


----------



## tomb

Looks like some of these posts are messed up after the Head-Fi rebuild. I believe Naamanf stated that the 20VDC power supply is a problem before Possédé posted that he was using it. 
	

	
	
		
		

		
		
	


	




 It's worse than that, though: 20VDC will not be enough to support the minimum voltage requirement on the tube heaters. It's possible that the tubes will be damaged if you run them on that. You need 24V*AC*, minimum.

 A couple of you guys need to verify those trimmers - it looks like some Vishay-BC's(?) are mixed up with some Muratas. It's possible that Jeff used different brands for trimmers with the same rating, but it looks confusing.

 Post again if you are still having problems.


----------



## tomb

Here's another Millett MAX that I finished last week. This one is equipped with Black Gates on the signal positions with Russian K42's bypassing the output Black Gates. The BJT Diamond Buffer output uses 2SC2238/2SA968 complementary pairs. The switch on the left of the frontplate is a two-position Low-Z/High-Z switch. There is also a set of pre-amp outputs on the back that are switched from the headphone jack (OFF when a headphone is plugged in).

 The tip jacks cover all of the important test points - Gnd, V+, L&R tube bias, and L&R DB bias. There are adjustment holes in the top plate so that all of these settings may be adjusted without taking the lid off.

 In the past, I've stayed away from Black Gates because of the price and hype, but they really sound great. They took about 40-50 hours before they stopped sounding very "congested," however. Another 50 hours and they sound very, very nice.

_[size=xx-small](click for larger pics)[/size]_


----------



## naamanf

Looks great TomB! I have a bunch of the those Russian PIOs on the way. I look forward to trying them in my MOSFET Max.


----------



## tomb

Quote:


  Originally Posted by *naamanf* /img/forum/go_quote.gif 
_Looks great TomB! I have a bunch of the those Russian PIOs on the way. I look forward to trying them in my MOSFET Max._

 

Thanks, Naamanf! So, are you in CO or Iraq?


----------



## naamanf

Iraq. I imagine thats why it's taking so long for those caps to get here.


----------



## tomb

Quote:


  Originally Posted by *naamanf* /img/forum/go_quote.gif 
_Iraq. I imagine thats why it's taking so long for those caps to get here._

 

Not really - I only got mine Friday and I think several of us ordered them at the same time. (EDIT: my first ones came from fordgtlover!) They came wrapped up in several layers of brown paper with tape and stickers that had cryllic Russian writing all over it - weird/old and interesting at the same time. The caps look great, though.

 Anyway, thanks for what you guys are doing for us over there! Shoot me a PM if you need any MAX parts - really.


----------



## ruZZ.il

And on another note.. nice box, tom! I've been running a similar config for the last week or 2.. good stuff.


----------



## Bigguy

Tomb, what is the switch on the front panel for? 2 inputs?


----------



## tomb

Quote:


  Originally Posted by *Bigguy* /img/forum/go_quote.gif 
_Tomb, what is the switch on the front panel for? 2 inputs?_

 

It's a dual-impedance switch, switching between 10ohm and 47ohm Stackpole output resistors. It offers a minimum of attenuation adjustment while preserving most of the impact. Ordinarily, I like to run bare on output resistors, but this one is built for someone else and they wanted more useful travel on the volume knob.


----------



## Televator

well, this will be a pretty large post... in the style of the old-fashioned western: "The Good, The Bad and The Ugly"


*The Good*: my second Max is alive!

 It'is a Black-Gates version with Russian K42Y PIO bypass caps (used at CA8 & CA9), Pana FM 1800µ's at CA4&5 and 2SC2238/2SA968 transistors. I still need to replace the V-D resistors at RB14 by Kiwame's...

 Leds are high intensity Orange (amber) leds raised to sit in the hole of the tube sockets, which gives a great glow-effect. As for now it isn't cased yet (still thinking on the case).

 It has been running for a couple of days straight to burn in the caps/tubes and it already sounds great (even from a bad Panasonic PCDP hooked up through gator-clips

 I'll be hooking up some neutrik RCA-sockets soon so I'll be able to test it with my NAD CDP... but I'm very confident it'll sound amazing!

 Just a quick few pics...
















*The Bad:* my first Max has died!

 I got hold of some 2SC3422/2SA1359 transistors (thanks Tomb!) for my Muse KZ version. I installed them without any problems and ran it for a couple of days. This version (with 480µ KZ's + WIMA's all around as in the Jrossel/glassjaraudio-kit) sounded "mucho fun" with those BJT's!

 However I had ordered some extra tubes for backup and wanted to test them to see if none were DOA (see further). As my KZ-version is fitted in the second Hammond slot from below, switching tubes isn't that easy when cased up...so I opened her up for a while. I unfortunately didn't screw the back-plate back on after removing the top and one of the test-points (TBR2) shorted with the case (=ground) through a badly isolated screw on the probe-socket in the back-panel... I saw a bright spark at the short-location, heard a pop and my Max was dead!

 I haven't found the guts to try and turn it back on, because I guess that it wouldn't help anyway and I might damage it further doing so. So my *question* is *what parts have been fried* (BJT's? How many? other parts?...) and if there is no sure answer to that (which I guess there isn't) *how I can check this myself* without replacing stuff blindly (no visual damage at all but I can always take some pics anyways). I have got a DMM with most standard functions, though no HFE...

 Thank you all in advance for troubleshooting my sick Max!


*The Ugly:* you have got to love the postal services

 As said above, I love the Max for my MS2i with 12FK6-tubes...so I decided to order some extra for back-up. The five tubes I ordered arrived pretty quickly given they had to travel from the US to Belgium... but unfortunately they arrived like this:






 The tubes themselves (and their individual boxes) didn't look damaged... but I wasn't sure whether the innards had survived as well. I decided to test them ... but while my tubes are OK, I unfortunately killed my first Max testing them


----------



## tomb

Televator - a couple of things:

 1. Did you incorporate a fuse? It's likely that burned out if you shorted something. I'm curious, because you say the MAX is dead. I would've thought something shorted and smoked in the right channel DB - probably the JFET or one of the small signal transistors. The power transistors can take a lot. They probably won't die unless you hooked them up backwards in the circuit and left them that way for an extended period (a few seconds?) - which you didn't do.

 So, I guess I'd like some more details - crack that thing open, plug it up and start making measurements - do the test points first. For instance, do you get voltage on the PS, do the tubes light, what are the tube bias points reading, do any resistors look fried, etc., etc.? We may be able to figure it out, but it will take more information.

 2. This is just an "oh, by the way", but the recommended way to mount those K42's is to clip the leads and solder on some hookup wire, silver or silver plated if possible. Even if you found a way to mount them with the existing leads, we're pretty sure they're magnetic - so you don't want them anyway.

 If you use the leads and tombstone them, you'll find that in those back positions you can tombstone them in the two extra "Gnd" test points just behind the cap positions. Use a hookup wire length on top to snake around the front of the trimmers and solder into the "+" positions on the CA9 positions.

 Just a suggestion - it depends on whether they're stable the way you've got them.


----------



## dbfreak

Great idea with the tip jacks and I look forward to the Millet Max board being offered for groupbuy again, one day.


----------



## tomb

The MAXes are multiplying at my house 
	

	
	
		
		

		
			





 :



_[size=xx-small](click for a big pic)[/size]_

 The one in the left rear you've all seen before - my MAX production prototype. The one in the right rear was the one I finished just prior to the Atlanta Mini-Meet a couple of weeks ago. Both of these have ES electrolytics and 2SC3422/2SA1359 transistors. The production proto had all WIMA bypass caps, while the newer one has the Russian K42's in the output bypass position.

 The silver MAX you've seen just a few posts back. The green tube one I just finished yesterday. It has ES caps and Russian K42's on the output, but has the 2SC3421/2SA1358 transistors. I'd have to say that those are my favorite transistors so far.

 Colin and I had several discussions during the design of the MAX about the bias currents on the BJT's versus the DB board used in the revMH Millett. Steinchen used parallel output pairs (8 transistors total) to get a reasonable current output without heatsinks in a small area. While each BJT would only bias to 20-30ma ea, the parallel configuration meant that there was 2X the bias current seen by the headphones. It was/is a pretty ingeneous solution.

 In the case of the MAX, we only have a single complementary pair and depend on the heat sinks to run higher biases to get the same depth of Class A bias. However, what Colin and I postulated was that this meant each individual transistor might be operating in a more favorable current position on its performance curves. IOW, Steinchen's reviews on these transistors may or may not be consistent with the MAX's higher individual bias currents.

 That's a long way of saying that the 2SC3421/2SA1358 pair were described as _"strong bass, hard punch, recessed mids. highs tend to sound a little rough and pronounced." _ Well, that may be true to a point, but the highs are anything but "rough" in the MAX. Instead, they seem to have a truly smooth and long-lasting sheen to cymbal hits and crashes. The bass has always had unbeatable extension, but I'm liking these transistors very much at the moment - a very nice alternative to the other ones.
	

	
	
		
		

		
		
	


	




 Oh, BTW - another interesting discovery: the cabinet wire pulls, which I like to use for their heft and tube protection - _actually improve the heat transfer._ They radiate significant heat from conduction through the case top. I've cranked up the DB's another 10ma in the blue one and it still runs cooler than the production prototype without the wire pulls.


----------



## Televator

Thanks Tomb for the quick reply... here's a couple of answers already and I'll check some things later...

 1. no fuse, no wrongly installed power transistors (they ran for a couple of days before the short) and while I said "dead"... you've got me thinking now: I might have actually just turned it off quite quickly in an almost instantaneous reaction...but I can't really remember (it's been a while, this happened right as Head-Fi died 
	

	
	
		
		

		
		
	


	




 ) ... so dead might be the wrong word choice... alas I can't really check right now if it is indeed dead or not...

 I will try to fix it... but it'll have to wait a couple of days I'm afraid, as I just remembered I've actually desoldered the 1µF tantalum cap in the PS to build my second Max (I've lost one somewhere... afraid I vacuumed it into oblivion) and I still have to get a new one before I can power on again and do some tests. I was too eager to build the B-G version and was waiting for Head-Fi to revive before trying to fix my first Max (afraid of doing more damage).

 First visual inspection didn't reveal any obvious fried components, but i'll go over the right DB-section with the jewelers glasses later (you've given me some areas to look into closely).

 2. It might not show through in my pics, but my Rusky PIO's only have about 5mm of their own leads left (just enough for a strong lead/hookup wire solder connection). The rest is (deep purple) Navships 24awg teflon coated SPC. The clear heatshrink that covers the entire wire does give a silver shine (in the pic at least) as if it was a bare lead underneath.

 Tombstoning the back K42Y's still sounds like a decent idea, but as they are installed now, they actually are quite stable... but I'll definitely look into that some more (also for the KZ-version once it's up and running again).


----------



## fordgtlover

Nice job tomb.

 Do you have a favourite Max configuration yet?


----------



## willisv

I finally got mine cased up.


----------



## tomb

Quote:


  Originally Posted by *willisv* /img/forum/go_quote.gif 
_I finally got mine cased up.

 [<URL=http://imageshack.us][<IMG]http://img218.imageshack.us/img218/1323/mg5415od8.jpg[/IMG][/URL]

 [<URL=http://imageshack.us][<IMG]http://img232.imageshack.us/img232/4264/mg5418wr9.jpg[/IMG][/URL]

 [<URL=http://imageshack.us][<IMG]http://img232.imageshack.us/img232/7180/mg5409hl2.jpg[/IMG][/URL]>_

 

Very cool - I love all those tip jacks. I think you're the first one I've seen do that besides myself. They're a bit of a hassle to put in at first, but they sure make things convenient for adjustment, don't they?

  Quote:


  Originally Posted by *fordgtlover* 
_Nice job tomb.

 Do you have a favourite Max configuration yet?_

 

NO. 
	

	
	
		
		

		
		
	


	









 I can't decide - I keep going back and forth. The K42 versions are all definitely better than the production prototype, but other than that - even the Black Gates are just light enough in the bass to make the ES's almost an even tradeoff.

 Heck - I don't know - I've got more testing to do ... thank goodness.


----------



## nysulli

finally finished up the casework besides the top, which may never be used anyways, i'll post pics when I get my hands on a digicam (mine died a few weeks back)

 while i didn't use tipjacks, i still have outside access to the biasing points through a serial port connection and cable with alligator clips, allows for a neat case, while allowing me to monitor both left and right channels for biasing should i need to


----------



## amphead

Nice work Willisv! Yeah those tip jacks will definitely keep your Max in top working order.

 Televator, sorry to hear about that Max! Yeah definitely post some pics. Do the sniff test for burnt components. Make sure you have a fuse, before attempting to power up again. If you have not damaged the power supply, you could power up and adjust for 27V. Sometimes one channel is blown and the other is still functioning. As is usual, testpoint voltages will narrow down the problem, if you can get that far.


----------



## amphead

Yes verrry nice TomB! I don't know anyone who owns more working and properly housed Maxes.


----------



## willisv

Thanks for the nice comments guys, this was my first DIY amp build and I'm definitely hooked... I just ordered an Alien Dac from Jeff. The tip jacks are a lot of work but they work great (Big thanks to Tomb for the great tutorials, templates, etc.).


----------



## 04BluMach

Great to see the HeadFi Site back up!!!! Thanks to all for their efforts...

 Really nice clean build Willisv! 
	

	
	
		
		

		
		
	


	





  Quote:


 Very cool - I love all those tip jacks. 
 

No doubt that using Tip Jacks as laid out by TOMB within the MAX website for carrying test points to the rear panel raises 
 the fit and finish of the MAX build. 
 It really adds that Professional build look to the MAX. 
 Not to mention how it really increases the ease of adjusting bias especially when changing tubes. 

 Had my MAX build#1 open the other day so took some pics...

 Under Board wiring and rear panel mounting for Tip Jacks:







 All of the test points carried to Tip Jacks mounted on the rear panel...
 ......... Rear Panel Layout Template by TOMB!






 Unfortunately, I had to use a stainless pan head on the rear panel since one
 of the cap screws went missing...??


----------



## joneeboi

Boy, it's good to be back.

 I just installed the Toshiba 2SC3422/2SA1359 BJT combo that I bought off tomb (thanks again, Tom; YGPM via diyforums.org). Goodness me, what an improvement over the MJE243/MJE253 setup. Allow me to share my thoughts and feelings on the swap:

 Who knew you could get both bass punch and high frequency detail at once? Not only is there this (for me) unusual coexistence, but there is also an unheard of separation of instruments. I have never enjoyed my music so much! All this listening is through my special 4G Apple iPod and my Grado SR60s. This MAX is tuned specifically to the glue-modded GS1K pads and rescreening I have performed on these bad boys. While the current bass extension and depth is not totally what I'm looking for, I think it comes very close to a level that I'm satisfied with. Listening to my reference track, the overall PRaT wasn't what I remembered it to be. I feel that a good bass and drum synergy will really drive a song along, and while I was looking for the awesome bass that the transistors were supposed to bring, I think I missed out on actually enjoying the song. Bass test not 100%, more like 78%. In an attempt to rectify my bass problem, I returned to a dark past that involved a love/hate relationship: the Grado Bowls. What amazingly uncomfortable accessories. Even when my enthusiasm from the new purchase was nigh, it could not sustain me through the pain of wearing bowls. Revbowls didn't help either. I was very surprised that Grado used these pads on their headphones at all. Just then, kramer5150's came out with his basshead mod. Tape a bit of clear tape around the circumference of the bowls, and magically, bass shall crystallize before thee! I came back to the bowls in order to get the bass, and I ended up sacrificing everything for it; no more soundstage (yes, I remember I'm talking about Grados here), snare drums sounded cheaper than normal, highs seemed squished, comfort levels gone. I figured that the sacrifice of the many for the one wasn't fair and overall not as pleasing to the ear, so I came back to the Jumbos. At that point, I figured that in every system there ought to be some constants and some variables, and that the Jumbos would remain constants. But perhaps if I opened the Black Gates, the floods of bass will flow...*devious smile*

 Passing my setup through the enjoyability test, I have never been this impressed. I haven't yet heard many of the Headphone-dom giants yet, but this setup has allowed me to enjoy my music as best as I ever have, exaggeration excluded. I saw drumming patterns appear out of nowhere, whole choirs showing up much earlier than they were expected, acoustic guitars being clearly strummed amidst the busyness, and an impressive overall separation of the band. Stepping back a bit and taking away the scrutiny for the bass, PRaT returned to its orginal Grado infamy, and I couldn't help but share with my brother the fruits of my tweaking. Such sweet fruit it was! That's what real music is, it moves you in a way that requires you share with everyone. I believe this insight can be observed in this community as well as some others.

 Now I must listen some more. Tweaking is great, but you never seem to finish. Thanks goes again to Tom for supplying me with "clean water" so I could enjoy the fruits of my labour.


----------



## amphead

btw, allow me to go off-topic for a minute. My avatar had shrunken after the outage, and I had to go to edit my avatar and reload it to get the proportions back. So if you have not, I highly recommend it.


----------



## ruZZ.il

Quote:


  Originally Posted by *nysulli* /img/forum/go_quote.gif 
_..i still have outside access to the biasing points through a serial port connection..._

 

Great idea! I think I'm tempted to follow.. rspct.


----------



## tomb

Wow - you guys are embarassing me with the compliments. Many thanks.

 Great job, 04BluMach! Besides those excellent tip jacks, your wiring "harness" looks great! We both know how much work it is to drill all those holes in the case lid, too - great job!

 Joneeboi - great review and nice to hear that the stuff arrived fairly quickly! Thanks for compliments!


 P.S. -
  Quote:


  Originally Posted by *joneeboi* /img/forum/go_quote.gif 
_Boy, it's good to be back.

 I just installed the Toshiba 2SC3422/2SA1359 BJT combo that I bought off tomb (thanks again, Tom; YGPM via diyforums.org).<snip>_

 

I answered it a day before you posted this.


----------



## Cellsplicer

I really wanted to build this amp for my 4 month long holiday (I finished high school). It seems however that I missed out on the PCB group buy


----------



## nysulli

Quote:


  Originally Posted by *ruZZ.il* /img/forum/go_quote.gif 
_Great idea! I think I'm tempted to follow.. rspct._

 

i used all off the shelf radioshack stuff, board has to be mounted on the third space up to have space for the serial port

 i personally just like to keep case holes to a minimum for aesthetics, and the serial port allows you to put all the test leads in a tight, detachable package

 i was tempted to try a rj-45 connection, but i couldn't find a jack that i could mount on the case, but if i were to do it all over, i'd go with a more professional looking limo style connector


----------



## willisv

Hey does anyone have any russian K42's they want to sell ? (I don't need 40 of them). Also I am trying to source out the 2SC3422/2SA1359 transistors... if anyone knows where I can buy them it would be appreciated. This is what I'm planning for my Millet Hybrid Max:

 1: Muse ES 1000uF 16v at CA2

 2: Muse ES 470uF 35v at CA7

 3: Russian K42's @ CA8 and CA9

 4: 2SC3422/2SA1359 transistor's

 5: Nichicon KZ 1000uF/50vdc at C4/C5

 Suggestions and criticism welcome.


----------



## 04BluMach

Quote:


  Originally Posted by *willisv* /img/forum/go_quote.gif 
_Thanks for the nice comments guys, this was my first DIY amp build and I'm definitely hooked... I just ordered an Alien Dac from Jeff. The tip jacks are a lot of work but they work great (Big thanks to Tomb for the great tutorials, templates, etc.)._

 


 Wow! Very impressive for a first DIY amp build. 

 I think anyone involved with this thread would tell you this is a fairly complex electronic build. Not too many of the online MAX mentors would recommend the MAX as your first DIY amp to tackle.

 Kudos 
	

	
	
		
		

		
			





 to you for what appears to be a very clean build 
	

	
	
		
		

		
		
	


	




.






 Again, it points out the excellent build documentation site that TOMB has assembled for the MAX...!


----------



## willisv

Quote:


  Originally Posted by *04BluMach* /img/forum/go_quote.gif 
_Wow! Very impressive for a first DIY amp build. 

 I think anyone involved with this thread would tell you this is a fairly complex electronic build. Not too many of the online MAX mentors would recommend the MAX as your first DIY amp to tackle.

 Kudos 
	

	
	
		
		

		
		
	


	




 to you for what appears to be a very clean build 
	

	
	
		
		

		
		
	


	




.






 Again, it points out the excellent build documentation site that TOMB has assembled for the MAX...! 
	

	
	
		
		

		
		
	


	


_

 

Thanks BluMach, you are exactly right about the Max site. All the information you need is there step by step, that paired with a Glass Jar Audio kit makes it pretty easy for anybody with a little patience.


----------



## bperboy

Tom, how do you have those 'rollbars' screwed in? Are they in contact with the heatsinks to improve the heat transfer? I'm still running my Max topless, but if I ever decide to cloth it up, I like the idea of additional heat transferance.


----------



## tomb

Quote:


  Originally Posted by *bperboy* /img/forum/go_quote.gif 
_Tom, how do you have those 'rollbars' screwed in? Are they in contact with the heatsinks to improve the heat transfer? I'm still running my Max topless, but if I ever decide to cloth it up, I like the idea of additional heat transferance._

 

They're nothing special - just brush-chrome-plated brass wire pulls. The ones on the outside are 3-1/2" on centers. The inside wire pulls are 3". The Silver MAX uses 3" for all four because I couldn't find 3-1/2" in Black.
	

	
	
		
		

		
		
	


	




 The inside ones are shorter so that they don't interfere with the PS ventilation holes.

 All the wire pulls are held on with 8-32 x 1/2" phillips head screws with a lock washer and flat washer where the vent holes aren't close enough to be blocked by the flat washer.

 The heat transfer occurs because despite the vent holes, the case gets hot enough over a few hours to even heat up the volume knob (on the production prototype). However, the solid connection through the large screws and contact surface of the wire pulls is enough to conduct the heat away from the case lid, enhancing the overall heat transfer of the amp. You can't feel the heat from the roll bars, either, because they're so extended and totally exposed to any air circulation. So, the transfer from the roll bars/wire pulls is almost ideal. It's possible that they absorb a lot of radiated heat from the tubes as well.

 I wouldn't have guessed that it made that much difference, but it's easily noticeable with direct comparisons. As I said, the roll-bar equipped MAX runs so cool at 50ma that I cranked one of them up to 60ma, but it still doesn't get as hot as the production prototype that's still biased at 50ma.


----------



## tomb

Quote:


  Originally Posted by *willisv* /img/forum/go_quote.gif 
_Hey does anyone have any russian K42's they want to sell ? (I don't need 40 of them). Also I am trying to source out the 2SC3422/2SA1359 transistors... if anyone knows where I can buy them it would be appreciated. This is what I'm planning for my Millet Hybrid Max:

 1: Muse ES 1000uF 16v at CA2

 2: Muse ES 470uF 35v at CA7

 3: Russian K42's @ CA8 and CA9

 4: 2SC3422/2SA1359 transistor's

 5: Nichicon KZ 1000uF/50vdc at C4/C5

 Suggestions and criticism welcome._

 

Looks good except for the KZ's as power caps. I know that's what Jeff puts in his kits and they work well, but you can put in four 1800uf-35V or 1000uf-50V Panasonic FM's for less money and end up at 1" height. Everything you have listed will remain at ~1" except for those KZ's.

 Strictly speaking, CA4 and CA5 are not signal positions and the FM's probably provide better performance.


----------



## tomb

Dang you, Amphead!
	

	
	
		
		

		
		
	


	










 I'm going to be fiddling with this avatar for hours - once you get me going on something like that I can't stop because of all the variations.


----------



## willisv

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Looks good except for the KZ's as power caps. I know that's what Jeff puts in his kits and they work well, but you can put in four 1800uf-35V or 1000uf-50V Panasonic FM's for less money and end up at 1" height. Everything you have listed will remain at ~1" except for those KZ's.

 Strictly speaking, CA4 and CA5 are not signal positions and the FM's probably provide better performance._

 

O.k. Thanks Tomb, I will order panasonics instead. I tried to get some 470uF muse es's from bdent but they were out of stock, so I ordered from michael percy and he sent me a quote a couple hours later. (Also got the four blackgates cause I can't decide). I will order the 1000uF muse es's from handmade, and some guy from hong kong on ebay had 5ea of 2SC2238/2SA968 for $5.00 plus shipping.


----------



## amphead

TomB, perfection is a disease, thats probably why we like the MAX! he he Avatar looks good so far!


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## tomb

I don't know if you guys noticed, but I did a major re-write of the MAX Boutique page on the MAX website:
Millett Hybrid MAX Boutique

 I guess the most important item is the addition of the "Can't Miss MAX Builds" table. I felt it important because we've discussed so many combinations that it probably got confusing to some of the newcomers (hopefully, we'll have more of those now that Head-Fi is back online!).


----------



## 04BluMach

Quote:


  Originally Posted by *willisv* /img/forum/go_quote.gif 
_O.k. Thanks Tomb, I will order panasonics instead. I tried to get some 470uF muse es's from bdent but they were out of stock, so I ordered from michael percy and he sent me a quote a couple hours later. (Also got the four blackgates cause I can't decide). I will order the 1000uF muse es's from handmade, and some guy from hong kong on ebay had 5ea of 2SC2238/2SA968 for $5.00 plus shipping._

 

The Toshiba transitors are highly desirable in the international market. Unfortunately there are rampant FAKES strewn throughout the marketplace. 
	

	
	
		
		

		
		
	


	




 Supposedly so many that they have even tainted the OEM stocks in the supply chain.

 ********** Buyer Beware ***********

 Would highly caution to know your buyer. Make it simpler on yourself - use reputable suppliers who are expert in their field. The commercial suppliers like BDENT, MCM, Digikey, Mouser, etc. And the speciality suppliers like Handmade, Percy, etc. Definitely check out the HeadFi Supporters first! 
	

	
	
		
		

		
		
	


	




 Remember, if the deal is too good to be believed - It Probably IS NOT a good deal!!!


----------



## 04BluMach

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_I don't know if you guys noticed, but I did a major re-write of the MAX Boutique page on the MAX website:
Millett Hybrid MAX Boutique

 I guess the most important item is the addition of the "Can't Miss MAX Builds" table......_

 

Great update to the MAXBoutique section....
	

	
	
		
		

		
		
	


	




 For the Build#1, using BlackGate NX's on CA2 & CA7 along with the Russian K42 or VitaQ PIO for CA8, you recommend leaving the CA9 bypass as Blank.

 From your direct experience with this config, did you notice any degradation in Sig Quality when CA8 would be filled by a K42? Or using a K42 in CA8 just didn't really provide any appreciable improvement - so you might as well leave out?

 Since the Russian K42's (and VitaQ's) are only sold in min packs of 5, 10, or 20 - any reason not to use these high quality PIO's in place of the WIMAs since you have them anyways? Understand, that numerous well known Botique Film caps don't play well together in the CA8 Cathode Bypass position.
	

	
	
		
		

		
		
	


	




 ......Inquiring minds and ears are searching for the Perfect Chord!


----------



## tomb

Quote:


  Originally Posted by *04BluMach* /img/forum/go_quote.gif 
_Great update to the MAXBoutique section....
	

	
	
		
		

		
		
	


	




 For the Build#1, using BlackGate NX's on CA2 & CA7 along with the Russian K42 or VitaQ PIO for CA8, you recommend leaving the CA9 bypass as Blank.

 From your direct experience with this config, did you notice any degradation in Sig Quality when CA8 would be filled by a K42? Or using a K42 in CA8 just didn't really provide any appreciable improvement - so you might as well leave out?_

 

Yep - no difference. Some caps - big difference, in the wrong direction! I think best to leave out completely when using Black Gates. I ran the one I just built for weeks without any bypass caps at all on all four BG's until fordgtlover came up with the K42's. I tried them and what you describe was the result at CA8 - not much difference. I think they help a bit on the output, though.

 One dirty little secret is that the CA2 position is much different than a signal coupling cap (as you relate below). I would guess that any reasonable quality cap would work just as well in that position - as long as it's 1000uf. So, if you are debating the huge cost of BG's, it might be just as well to just go with them only on CA7. That's only a guess, mind you - it wasn't tested. It may be just as valid to purchase them for all four positions for consistency - but I thought I'd mention that might be the case.

  Quote:


 Since the Russian K42's (and VitaQ's) are only sold in min packs of 5, 10, or 20 - any reason not to use these high quality PIO's in place of the WIMAs since you have them anyways? Understand, that numerous well known Botique Film caps don't play well together in the CA8 Cathode Bypass position.
	

	
	
		
		

		
		
	


	



 

Umm - I'm hoping to address that quantity ordering thing soon with our webstore. However in the meantime, there's nothing easier than plopping a rectangular Wima in the existing pads and soldering them in. The K42's take a lot of work with those leads, heat shrink, etc. Since they're wasted in those positions anyway, I'd throw them in your parts bin for a rainy day or the next project. Alternatively, you might share them with other MAX builders or drop them in an envelope to me. 
	

	
	
		
		

		
		
	


	




  Quote:


 ......Inquiring minds and ears are searching for the Perfect Chord!


----------



## tomb

Quote:


  Originally Posted by *04BluMach* /img/forum/go_quote.gif 
_The Toshiba transitors are highly desirable in the international market. Unfortunately there are rampant FAKES strewn throughout the marketplace. 
	

	
	
		
		

		
		
	


	




 Supposedly so many that they have even tainted the OEM stocks in the supply chain.

 ********** Buyer Beware ***********

 Would highly caution to know your buyer. Make it simpler on yourself - use reputable suppliers who are expert in their field. The commercial suppliers like BDENT, MCM, Digikey, Mouser, etc. And the speciality suppliers like Handmade, Percy, etc. Definitely check out the HeadFi Supporters first! 
	

	
	
		
		

		
		
	


	




 Remember, if the deal is too good to be believed - It Probably IS NOT a good deal!!!_

 

Good admonition, but as you say, it's possible that the OEM stocks are tainted everywhere. I'm not really sure that any of these BJT's are still made by the original mfr. Some of the vendors I've talked to personally about these transistors have indicated that they're all too old to be original manufacture and are only made by the off-brand mfrs. I think that's one reason they're hard to find and aren't carried in the normal Mouser/DigiKey/etc. stock. They're pretty much only used by the electronics/appliance repair suppliers.

 As for the 2SC2238/2SA968 pair, I've bought many from MCMinone and I think they are of Chinese manufacture (I'll check for sure tonight). I've also bought them personally from a local vendor who I trust and have purchased from going back almost 30years. They are all Chinese manufacture as well:
Audio Lab Shopping Cart

 So, not saying for sure, but the e-bay deal could be legit.


----------



## willisv

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Good admonition, but as you say, it's possible that the OEM stocks are tainted everywhere. I'm not really sure that any of these BJT's are still made by the original mfr. Some of the vendors I've talked to personally about these transistors have indicated that they're all too old to be original manufacture and are only made by the off-brand mfrs. I think that's one reason they're hard to find and aren't carried in the normal Mouser/DigiKey/etc. stock. They're pretty much only used by the electronics/appliance repair suppliers.

 As for the 2SC2238/2SA968 pair, I've bought many from MCMinone and I think they are of Chinese manufacture (I'll check for sure tonight). I've also bought them personally from a local vendor who I trust and have purchased from going back almost 30years. They are all Chinese manufacture as well:
Audio Lab Shopping Cart

 So, not saying for sure, but the e-bay deal could be legit._

 


 That's pretty interesting, I would have never even thought about fake transistors. I guess the only way to find out is to try them and hear how they sound. I have all my upgrade parts sourced except the 1000uF 16v muse es's... I live in Canada so handmade needs a $100 order min, I have searched high and low for another vendor that sells these caps but haven't found anything yet. How important is the voltage rating, Michael Percy has a 1000uF 25v es... would that work O.K.?


----------



## thomaskuhn

Well, I finally got the chance to power up my max for the first time. What a thrill when smoke snakes up from the board!! Well, it ended up being a solder bridge on the BD139. I have started to dial in the bias and such and thus have a question. I am measuring the test points from:

 TB1L to TA2L = 65mV
 TB2L to TA2L = 65mV
 TB1R to TA2R = 65mV
 TB2R to TA2R = 65mV

 But from the instructions, I should be looking at about 44mV with the pots turned all the way clockwise. Is this normal?

 Tom

 PS, using 2sc2238/9xx


----------



## thomaskuhn

Although I am reading a bit out of wack on the bias, I decided to test out the audio. No sound. I will have to carefully step through it and see what is wrong. For some reason, I want to think it is the muting circuit. I did short out the transistor there, not to mention that there is not sound/hum/hiss/grumble when increasing the volume at all. I tested out the DAC and all is in order there.


 Tom


----------



## tomb

Quote:


  Originally Posted by *thomaskuhn* /img/forum/go_quote.gif 
_Well, I finally got the chance to power up my max for the first time. What a thrill when smoke snakes up from the board!! Well, it ended up being a solder bridge on the BD139. I have started to dial in the bias and such and thus have a question. I am measuring the test points from:

 TB1L to TA2L = 65mV
 TB2L to TA2L = 65mV
 TB1R to TA2R = 65mV
 TB2R to TA2R = 65mV

 But from the instructions, I should be looking at about 44mV with the pots turned all the way clockwise. Is this normal?

 Tom

 PS, using 2sc2238/9xx_

 

How low the starting voltage/current bias depends on the JFET, and they can vary widely. Actually, you're quite lucky to have them that close. Mine are usually ~40mV on one side and then about 60mV something on the other.

 EDIT: OK - that's why they were so close that they were the same - something's wrong.

 First thing to look for might be if you jumpered out RB8L/R and RB9L/R?


----------



## thomaskuhn

"The Vigilant Tomb, Guardian of the wayward amplifier builder"

 Thanks Tomb,

 I guess I too quickly read the values. They are not all exact. After letting the board sit, the values are (And I hope this is right) 

 TB1L to TA2L = 70.9
 TB2L to TA2L = -71.1
 TB1R to TA2R = 64.5
 TB2R to TA2R = -64.6

 I have not adjusted the Bias resistor yet, so these are the minimum values with the variable resistors turned all the way to the right. Power into the board is 27.0. Tube voltage is 13.36/13.39 with new tubes. 

 Tom


----------



## thomaskuhn

Tomb, 

 It is interesting that this was brought up, I recently ordered 5 pairs of 2SC2238/2SA968 from that guy in Hong Kong from ebay. I have them in and just added them to the board. I wondered myself if there was a possibility of fakes, as I think I read the same post as Willisv about fakes. If anyone is interested in testing a set of the ones I purchased, I can send them free of charge.

 Tom


  Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Good admonition, but as you say, it's possible that the OEM stocks are tainted everywhere. I'm not really sure that any of these BJT's are still made by the original mfr. Some of the vendors I've talked to personally about these transistors have indicated that they're all too old to be original manufacture and are only made by the off-brand mfrs. I think that's one reason they're hard to find and aren't carried in the normal Mouser/DigiKey/etc. stock. They're pretty much only used by the electronics/appliance repair suppliers.

 As for the 2SC2238/2SA968 pair, I've bought many from MCMinone and I think they are of Chinese manufacture (I'll check for sure tonight). I've also bought them personally from a local vendor who I trust and have purchased from going back almost 30years. They are all Chinese manufacture as well:
Audio Lab Shopping Cart

 So, not saying for sure, but the e-bay deal could be legit._


----------



## thomaskuhn

It is definitely in the muting circuit. I ran a quick jumper from RB14 to the L/R out on the jack (just held it there), and sound came through. Although, I only received a small sampling of sound, I must say that the BASE ON THIS is GOOD. 

 Tom


----------



## tomb

Quote:


  Originally Posted by *thomaskuhn* /img/forum/go_quote.gif 
_It is definitely in the muting circuit. I ran a quick jumper from RB14 to the L/R out on the jack (just held it there), and sound came through. Although, I only received a small sampling of sound, I must say that the BASE ON THIS is GOOD. 

 Tom_

 

Well, that's good news - sort of - I guess that BD139 is blown. If you don't have anymore of those, you could probably put one of those 2SC2238's in there - in reverse - and it would probably work - just as any TO-220/216/etc. NPN BJT would. 
	

	
	
		
		

		
			








 About fakes - I have those from two different sources as noted and can tell no difference. I don't really know what we'd test, though. There are many transistors that have similar ratings, but they won't sound the same - that's sort of the point of selecting certain BJT's.

 The question of whether they're fake maybe a hornet's nest without a resolution.


----------



## joneeboi

Good to see more MAX lovin'.

 I just wanted to report that I did a double swap at CA4 and CA5. I originally had 470uF Nichicon UPWs from an earlier BOM and swapped for some 1000uF UPWs that just came in. Doing a quick listening test, I fired up the iron as quickly as I had switched it off. The bass was too far forward and rolled off the highs. I was wondering when the cymbals were coming in during the chorus, but it never really happened for me. Swapped back to the 470uFs and life is good again. I feel I'm in territory that doesn't really have any hard and fast rules, and now I'm reconsidering modding anything that will affect the sound. I like it the way it is, and it'll stay that way for quite some time.


----------



## 04BluMach

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_The question of whether they're fake maybe a hornet's nest without a resolution._

 

The last thing I ever wanted to do is derail this very impressive thread from its focus on the build support for the Millet Hybrid MAX. 
	

	
	
		
		

		
		
	


	




 Certainly not my intent at all! Was only trying to bring some awareness to how you shop for components - just as you would for a used car, a watch, or an appliance. 
 Part of the very impressive MAX build support, has been the component sourcing recommendations that provide excellent guidelines for types, part numbers and vendor source alternatives. Typically for a complex DIY electronic project that can be a very daunting and time consuming task. Especially when trying to add some boutique components into the mix can really raise the efforts and price.

 EBay has in many ways, radically changed our electronic marketplaces. Affording small niche vendors an international bazaar to operate out of. Certainly, a great benefit for us DIYers trying to source 10, 20 30 or even older parts or small quantiry niche items. Unfortunately, there are not a lot of regulators out in those markets getting rid of the false parts or unreputable dealers. So everyone should be cautious and do their research appropriately.

 As far as the BJT Transitors - TOMB is correct, these are old components with a greatly reduced worldwide demand. The OEMs - Toshiba, SANYO, and others - long since ended production in their extremely high quality manufacturing plants located in Japan to outlying pacific rim production plants (ie China, India, etc). Typically, these are subsidiery companies and/or licensed for manufacturing by the OEM with QA monitoring to maintain the standards/specs and thereby maintaining the good name of the OEM. As far as Fakes, the concern is for very shoddy components that are intentially mislabelled or manufacturing rejects that get out the back door into the grey market.

 My Millet BJTs (both MAX & dDB), were all sourced from BDent. They all carried the appropriate OEM name on the case (Toshiba or Sanyo). My latest sets of the Toshiba 2SC2238/2SA968 I sourced from MCM (BDent was out of stock again) were case marked Toshiba. Of course they are probably of Chinese origin likely licensed for manufacture by Toshiba. 
	

	
	
		
		

		
		
	


	




 Of course the Ebay source in Hong Kong as mentioned in a prior thread might be good source for these components. I really don't know one way or another. I would just suggest that unless you have broad experience you really should use the recommended component sources that are given throughout this thread first. 

 Again, lets tell that idiot 04BluMach to keep his mouth shut and take his hornets nest somewhere else. And get the thread focus back on the *MAX*....


----------



## willisv

Thanks for the heads up BluMach 
	

	
	
		
		

		
		
	


	




  Quote:


  Originally Posted by *04BluMach* /img/forum/go_quote.gif 
_The last thing I ever wanted to do is derail this very impressive thread from its focus on the build support for the Millet Hybrid MAX. 
	

	
	
		
		

		
		
	


	




 Certainly not my intent at all! Was only trying to bring some awareness to how you shop for components - just as you would for a used car, a watch, or an appliance. 
 Part of the very impressive MAX build support, has been the component sourcing recommendations that provide excellent guidelines for types, part numbers and vendor source alternatives. Typically for a complex DIY electronic project that can be a very daunting and time consuming task. Especially when trying to add some boutique components into the mix can really raise the efforts and price.

 EBay has in many ways, radically changed our electronic marketplaces. Affording small niche vendors an international bazaar to operate out of. Certainly, a great benefit for us DIYers trying to source 10, 20 30 or even older parts or small quantiry niche items. Unfortunately, there are not a lot of regulators out in those markets getting rid of the false parts or unreputable dealers. So everyone should be cautious and do their research appropriately.

 As far as the BJT Transitors - TOMB is correct, these are old components with a greatly reduced worldwide demand. The OEMs - Toshiba, SANYO, and others - long since ended production in their extremely high quality manufacturing plants located in Japan to outlying pacific rim production plants (ie China, India, etc). Typically, these are subsidiery companies and/or licensed for manufacturing by the OEM with QA monitoring to maintain the standards/specs and thereby maintaining the good name of the OEM. As far as Fakes, the concern is for very shoddy components that are intentially mislabelled or manufacturing rejects that get out the back door into the grey market.

 My Millet BJTs (both MAX & dDB), were all sourced from BDent. They all carried the appropriate OEM name on the case (Toshiba or Sanyo). My latest sets of the Toshiba 2SC2238/2SA968 I sourced from MCM (BDent was out of stock again) were case marked Toshiba. Of course they are probably of Chinese origin likely licensed for manufacture by Toshiba. 
	

	
	
		
		

		
		
	


	




 Of course the Ebay source in Hong Kong as mentioned in a prior thread might be good source for these components. I really don't know one way or another. I would just suggest that unless you have broad experience you really should use the recommended component sources that are given throughout this thread first. 

 Again, lets tell that idiot 04BluMach to keep his mouth shut and take his hornets nest somewhere else. And get the thread focus back on the *MAX*....
	

	
	
		
		

		
		
	


	


_


----------



## 04BluMach

Returning to the Focus on the MAX build, here are some pics of Build1...
















 I tried out the 0.47uF ICW Clarity SA Film Caps for this MAX version for both the output and cathode film bypass components. The cathode bypass cap is a Nichicon 1000uf ES along with a Nichicon 470uf ES as the output cap.






 ...and last but not least the rear panel view.





 I am typically so enjoying the Music through this amp that I haven't often critically listened. I think that its strength is its smoothness - there is real music coming out the other end that you can really get involved with and really thumps when it is called for 
	

	
	
		
		

		
		
	


	



 Yeah, it offers fairly good resolution and dynamics to go with it too. Will often find myself listening intently focused to a single instrument or persussion sound then snap back to the total sounstage. The SA's are Tuneful without midrange bloom nor rolled off. They definitely have good flat response without harshness. Not the ultimate in resolution. They are good budget (inexpensive) Film Caps. These were sourced from DIYCable.com.

 I may drop some 0.15uf VitaQ PIO caps in place of the Clarity Caps just to give a good comparison in this configuration. Coupling Capacitor Review info .


----------



## tomb

Thanks 04BluMach! That's a great looking MAX! You guys are fantastic. It seems everyone is using those tip jacks now! Great job on all those ventilation holes, too. You and I and several other people know what a job that is to drill all those holes! Great work!

 You also gave us another great link to Dsavitsk's Notes on Coupling Capacitors! I forgot to mention while Head-Fi was down, Doug updated his reviews and added some great comments on the Vitamin Q's. He wanted to do the Russian K42's and asked me for some, but the ones we are using don't meet his voltage requirement - he's running some rather high tube voltages in his setup, I think.

 He also included some comments on the MultiCap RTX polystyrenes. These are supposedly the cap of choice to team up with Black Gate NX's - if anyone is interested in trying. It would have to be a non-standard build, though, because I haven't seen any small enough to fit without some creative, very-tall tombstoning.

 Anyway - great stuff, 04BluMach, and thanks for the post on the other stuff, too.


----------



## soloz2

what voltage does he need? I just ordered 50 160v ones from ebay. 
	

	
	
		
		

		
		
	


	




 I need enough for 3 amps and it was cheaper to order 50 than 20 lol.


----------



## tomb

Quote:


  Originally Posted by *soloz2* /img/forum/go_quote.gif 
_what voltage does he need? I just ordered 50 160v ones from ebay. 
	

	
	
		
		

		
		
	


	




 I need enough for 3 amps and it was cheaper to order 50 than 20 lol._

 

He is using 250V for his capacitor tests - he states that on his web page. 
	

	
	
		
		

		
		
	


	







 P.S. Odoe is wanting about a half-dozen K42's over on the Millett Forum. You might PM him there or here if you want to get rid of or sell your extras.


----------



## 04BluMach

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Thanks 04BluMach! That's a great looking MAX! You guys are fantastic. It seems everyone is using those tip jacks now! Great job on all those ventilation holes, too._

 


 Actually, Born on Date of this MAX was announced on 9/21/07 so it has a lot of hours on it already. Just been very lame in following up with some Pics and details ( like the Tip Jacks).

 Yeah, the ventilation holes are very time consuming..... Since I have access to a drill press, they aren't as tedious as they could be if done by only hand tools.

 However, there are actually double the number of holes in this case. The bottom of the case has a mirror image of the top!
	

	
	
		
		

		
			




 For some reason, I didn't take a photo of its underbelly. I'll flip it over this PM for a shot and post it up to the thread this evening 
	

	
	
		
		

		
		
	


	




 Since it was indicated that the temperatures were running relatively high when cased up - I thought why not try to get some air flow going inside the unit. There must be enough air flow through the case since this unit really doesn't run hot. Have never noticed significant heat transfer say to the volume knob, etc. even though it is fully biased up to 115mv. I leave the unit powered up all the time so it doesn't need to "warm up" ...
	

	
	
		
		

		
		
	


	




 Actually, had considered to drill some holes through the PCB next to the heat sinks to provide more air flow. But since I had already installed components on the board - thought better of it.

 May want to consider adding a couple of additional "Test Points" strategically near the Heat Sinks in any future Board production. That would really help to achieve moving a little air flow across the heat sinks when coupled with some underbelly cross ventilation holes. 
	

	
	
		
		

		
		
	


	




 Speaking of "future boards" - I would really like to get my hands on another board to try out the high value BlackGate NX caps configuration you have labeled as your Can't Miss MAX Build #1





 ....Hint! Hint! On His Knees with Bowed Head he grovels with meek sounds issuing forth that sound like BegBeggggPPPPPPlease....I need just *ONE MORE!*
 ...........you see the pathetic addict in front of you. He is hooked to the *MAX*!


----------



## tomb

I don't know if you guys have seen this thread or not, but it's the impressions from our recent Atlanta Mini-Meet. The thread is actually highlighted right now on the Head-Fi.org home page (Thanks, Jude):

ATL Nov 10th Meet

 PiccoloNamek hosted the event at the the Holy Cross Anglican Church in Loganville, GA, sort of around the corner from me (so to speak). Many, many thanks to him.

 Anyway, the MAX got some nice comments. If there were any bad ones, at least everyone was polite enough not to express them. 
	

	
	
		
		

		
		
	


	







 The MAX was in some pretty heady company, too. All this with just some flac files and Alien DACs as sources. I wish I had MexicanDragon's HF-1's to audition them, too. Those things have made me re-evaluate Grados and regret mightily that I didn't get onboard with that Group Buy when it occurred.

 Anyway - here's one of Fitz's pics that shows an old fart with a MAX t-shirt (
	

	
	
		
		

		
		
	


	




 ) talking to Hoppergrass:





 ... and a nice close shot from PiccoloNamek:





  Quote:


  Originally Posted by *BigAmish* 
_"I have yet to hear a tube amp that I dislike. Every tube amp that I listened to (through my Grado RS-1s) at the meet had its merits and are very worthy purchases, especially considering their respective price ranges. Aside from the MAD Ear+ HD that I own (I am biased of course), I was particularly floored by the Darkvoice 336 (Fitz modded) & the Millett Max Hybrid amp. For the $$$, both were very very very nice. The Darkvoice had *unbelievably* luscious liquidy mids. I can't say that the Millett Max Hybrid did any one thing particularly well, but the music I listened to just sounded 'right' across the sonic spectrum. Perhaps that is the greatest compliment of all! No overt weaknesses as far as I could tell. I suggest the Darkvoice 336 or the Millett Max Hybrid to anyone just getting started in the world of tube amps who is on a budget."_

 

 Quote:


  Originally Posted by *MexicanDragon* 
_"I spent most of my time with my HF-1's headphone wise, as I was really more interested in finding out what went well with those than listening to gear I won't be aquiring any time soon. I did get to put them up against RS-2's (I stayed away from the RS-1's, as I'd heard them before, and wanted them then. RS-2s were unfamiliar to me completely). They fared quite well with the Millett Max, where I prefered them to the RS-2s. The RS-2s seemed a bit more lust, and with a presentation that was a bit further back than what I was used to with the HF-1's... not as much edge, I guess one could say. I think I've found my amp."
 ....

 "I AM, however, QUITE impressed with the Millett Max. The guys did a great job on it, and I am looking forward to picking one up in the not-too-distant future. Thanks tomb for letting me try it out with my source there at the end (and staying over to talk a few minutes)."_

 

Many thanks for those kind words and especially to MexicanDragon for sharing a quality pair of Grado headphones with me. They seem to have an especially good synergy with the MAX.


----------



## ferds

Has anyone tried the Russian teflon caps?


----------



## thomaskuhn

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Well, that's good news - sort of - I guess that BD139 is blown. If you don't have anymore of those, you could probably put one of those 2SC2238's in there - in reverse - and it would probably work - just as any TO-220/216/etc. NPN BJT would. 
	

	
	
		
		

		
		
	


	





_

 

I replaced the 139 last night, as I had an extra. I still do not have sound, and I am not hearing the relay click (I am not sure if you can actually hear it though). I am not seeing 12V at the relay inputs, so I am gathering that some other part of the circuit is broken, possibly in relation to the BD139 shorting out. Well clumsy me, while testing to see if voltage was getting to the 139, shorted it out again with the test probe. So it might be shot again, not sure. 

 does anyone know what are some good test points to begin diagnosing this. I know the circuit is simple, but a little guidance would really help me out. 

 Thanks,
 Tom


----------



## tomb

Quote:


  Originally Posted by *thomaskuhn* /img/forum/go_quote.gif 
_I replaced the 139 last night, as I had an extra. I still do not have sound, and I am not hearing the relay click (I am not sure if you can actually hear it though). I am not seeing 12V at the relay inputs, so I am gathering that some other part of the circuit is broken, possibly in relation to the BD139 shorting out. Well clumsy me, while testing to see if voltage was getting to the 139, shorted it out again with the test probe. So it might be shot again, not sure. 

 does anyone know what are some good test points to begin diagnosing this. I know the circuit is simple, but a little guidance would really help me out. 

 Thanks,
 Tom_

 

The only other part of any importance is the MPSA14. You can de-solder and check the HFE - you can do that with the BD139, too, for that matter. The data sheets are on the MAX website and you can use that to compare the HFE reading you get.

 As for parts that might smoke, I'd suspect the MPSA14 before _anything_. That's just a little TO-92 trannie that might fry in an instant from a short.

 The only other possibility is that you might have burned the relay out. You should be able to trace the coil and check for continuity by confirming zero resistance. Again, the data sheet is on the MAX website, but you should see zero resistance (more or less) between the first two pins - on the volume pot side.

 As you say, there's not much too it.

 Here's some more- you can refer to the MAX website at Tweaks-e12 Delay. Here's the schematic:






 Keep in mind that the 2N5088 was changed to the MPSA14. Colin was trying to keep the parts count down and it would've been nice to use a 2N5088, but it wouldn't handle the load. Anyway, you can see two things about the transistors from the schematic:

 1. the BD139 is providing the voltage regulation. So, if you lose the BD139, you shouldn't read any voltage across the caps or the resistor RM2.
 2. It appears the MPSA14 (the 2N5088 in the schematic) fires the coil. If you lose that, the coil's not going to close.


----------



## thomaskuhn

I can already tell you that I bet bottom dollar I have a 2N5088 sitting in there. I do not remember buying a MPSA14 at all. I will swing by the local surplus store and see if I can get one.

 Tom


----------



## amb

The diode DM1 in the above schematic should be a 12V zener (e.g., BZX55C12 or 1N5242B), _not_ 1N4001 as shown.


----------



## tomb

Quote:


  Originally Posted by *amb* /img/forum/go_quote.gif 
_The diode DM1 in the above schematic should be a 12V zener (e.g., BZX55C12 or 1N5242B), not 1N4001 as shown._

 

It is a 1N5242B and always has been. Colin never updated the schematic.

 Guess I'll get to work on Photochopping the schematic text so there won't be any confusion.


----------



## ferds

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_It is a 1N5242B and always has been. Colin never updated the schematic.

 Guess I'll get to work on Photochopping the schematic text so there won't be any confusion.
	

	
	
		
		

		
		
	


	


_

 


 how about this tomb?


----------



## tomb

Quote:


  Originally Posted by *ferds* /img/forum/go_quote.gif 
_how about this tomb? 
	

	
	
		
		

		
		
	


	


_

 

Thanks, but it's done (in the original post and on the website) - and you missed the conversation about QM2 being an MPSA14, too. You could do the other five for me, though.
	

	
	
		
		

		
		
	


	




 Seriously, it really needs to be changed in the Eagle software. I had intended to ask Colin to do it, but I guess it's one of those things that fell through the crack.

 EDIT: While we're at it, both diodes are wrong. DM2 is a 1N4148. So, the whole schematic was messed up. Luckily, everyone up until now has gone by the BOM:

*E12 DELAY*
 RM13.32K ohm
 RM21M ohm
 CM147uF, 25V Electrolytic
 CM20.1uF X7R
 CM3330uF 16V Electrolytic (10mm dia. Max)
 DM11N5242B Zener
 DM21N4148
 QM1BD139
 QM2MPSA14
 G6AOmron 12V DPDT Relay G6A-234P

 I've also had good luck with a 470uf as CM3. CM1 can also be a 22uf Tantalum, but those are $2 a piece, while a 47uf electrolytic costs pennies.


----------



## 04BluMach

As mentioned a couple threads earlier....

  Quote:


 However, there are actually double the number of holes in this case. The bottom of the case has a mirror image of the top! 
 For some reason, I didn't take a photo of its underbelly. I'll flip it over this PM for a shot and post it up to the thread this evening 
 

The top of the unit which follows TOMB's template from the MAX Website.






 The case bottom includes the mirror image array of ventilation holes.






 The cross ventilation appears to be working since the unit seems to only reach a warm temperature on top over each of the heat sink areas. The BJT's are fully biased to 115mv and remains continuosly powered up ready at a moments notice.


----------



## joneeboi

04BluMach:

 Have you considered cutting off a portion of the Alps Blue shaft to get your knob to sit flush to the front panel? It's a 20 second job to measure and Dremel.


----------



## 04BluMach

Quote:


  Originally Posted by *joneeboi* /img/forum/go_quote.gif 
_04BluMach:

 Have you considered cutting off a portion of the Alps Blue shaft to get your knob to sit flush to the front panel? It's a 20 second job to measure and Dremel._

 

Now that is embarrasing...
	

	
	
		
		

		
		
	


	




 But that isn't the final front panel that I had planned for the amp. A friend of mine recently gave me some small pieces of wood to "improve" my metal cases.

 Anyway, this is the piece planned for the front, rear, and top (maybe). 






 I need to link up with a friend who has the wood shop to plane, cut, etc this piece to fit so I can complete this MAX.
	

	
	
		
		

		
		
	


	




 As happens, stuff just interferes with both of our schedules to work on this bad boy.

 Anyway, the shaft will be cut when fit to the final front panel....till then it will continue to look goofy


----------



## ferds

just finish my 2nd maxed.. hehe

 no case yet.. I used 2SC3421/2SA1358 for this built and i must say they are much better than the one i used before, mje243/253.. Very nice highs and good bass.. I also use Russian teflon caps..


----------



## Ferrari

Good to know that you like these Russian Teflon. I used it as bypass caps for the MKPs here... excellent in terms of details and resolution with very good extended, controlled bass 
	

	
	
		
		

		
		
	


	




 .

 Also in my 3-channel active ground MH as signal coupling cap (NOT bypass), these caps (besides the K75 PIO) demonstrates their excellent qualities... probably the best sounding MH I have ever built so far.


----------



## tomb

Quote:


  Originally Posted by *ferds* /img/forum/go_quote.gif 
_just finish my 2nd maxed.. hehe

 no case yet.. I used 2SC3421/2SA1358 for this built and i must say they are much better than the one i used before, mje243/253.. Very nice highs and good bass.. I also use Russian teflon caps.. 

 [<IMG]http://i75.photobucket.com/albums/i297/ferds_calma/Millet%20%20Maxed/2nd%20millett/DSC00867.jpg[/IMG]
 [<IMG]http://i75.photobucket.com/albums/i297/ferds_calma/Millet%20%20Maxed/2nd%20millett/DSC00869.jpg[/IMG]





_

 

Yes - I am liking the 2SC3421/2SA1358 combination more and more each day! They sound much nicer than they did in the original Millett/DB's - perhaps because of the higher bias as mentioned earlier. Very nice!

 As for your teflons, they look like rocket boosters on the sides. 
	

	
	
		
		

		
		
	


	




 Early on, this was a pretty famous pic from Colin about whether Russian Teflons would fit:


----------



## pinkfloyd4ever

hey tomb, i searched for info about the BJT heatsink mounting hardware & grease, but now I'm just more confused. what's the most common config? could u give mouser part #s? (maybe a good addition to the BOM on the site?) I don't mind using grease & stuff as opposed to the pads, just whatever's cheapest-i don't mind a little extra labor.


----------



## fordgtlover

I got my BJT MAX up an running tonight using the 2SC2238/2SA968 combination with Pana FC/FM caps throughout except for the Nichicon ES in CA2/7 and WIMA caps on all but CA8 where I have K42s. I have jumpers on the output resisters.

 I built the Mosfets version a few months back, and really liked it. But given the amount of positive discussion on the BJT build, I figured that I needed to hear it for myself. The build was very painless.

 A couple of points on the biasing. The BJTs were much easier to bias. In my Mosfet version just about every adjustment effected the others; biasing was like hearding cats. The BJTs on the other hand simply required two rounds, and they're done.

 Using the same Raytheon 12FM6 tubes that I have really liked in the Mosfet version, I am now listening to my new one and it is really quite different. There is no harshness at all, and while I never thought that my first Max lacked bass, this one has even more. This one does everything I liked about the Mosfet Max, but this one does it all just a bit better as far as I can tell so far.

 It seems to work very well regardless of the genre of music, from male to female vocal, blues and rock and metal. Very nice.

 I think I'll kick back and enjoy it...

 Thanks once again to Tomb for his tireless work


----------



## amphead

Thats interesting to know! I think I will stick with building the BJT versions, since I haven't built the mosfet MAX.


----------



## tomb

Quote:


  Originally Posted by *pinkfloyd4ever* /img/forum/go_quote.gif 
_hey tomb, i searched for info about the BJT heatsink mounting hardware & grease, but now I'm just more confused. what's the most common config? could u give mouser part #s? (maybe a good addition to the BOM on the site?) I don't mind using grease & stuff as opposed to the pads, just whatever's cheapest-i don't mind a little extra labor._

 

To be honest, I've switched to the Bergquist pads at DigiKey. They're pretty much the cheapest and easy to install. They seem to have a bit better heat transfer compared to grease + mica.

 It's not rocket science, though. You need a 4-40 screw, preferrably a flat washer under the screw head to keep from damaging the transistor underneath, then after the heat sink - a flat washer, _lock washer_ (important), and the nut.

 The only question then becomes what to use as the insulator between the transistor and the heat sink. If the transistor is a true TO-220 - meaning it has a metal tab - then it needs a shoulder washer to keep the screw from making contact between the transistor and the heat sink. If not a TO-220, a shoulder washer won't fit anyway - so don't use it.

 The choice of pad becomes one of convenience. Mica is the cheapest by far, but needs grease. Thermafilm has better heat transfer than Mica, but costs more and _still need grease._ Therma*sil* is the one that does not need grease, and often comes with an adhesive back, making it very convenient. You line up the hole with the heat sink hole and press down - very similar to applying a stamp these days (I remember when you had to always lick. 
	

	
	
		
		

		
		
	


	




 ). My personal opinion is that they take a bit more torque on tightening the screw assembly - so as to make the pad material "flow" into the joint - but other than that, easy as pie.

 This is the standard diagram used by Avid:





 And the parts list legend:





 This diagram, the parts list, and complete explanations for mounting, selecting, and using heat sinks is in the Aavid catalog. It's available for free download on their website - 2007 Standard Products Catalog

 It's also listed as a hot link reference to every Aavid heat sink at Mouser and DigiKey if you click on "data sheet."

 Sorry, but mounting transistors to heat sinks is technique that is referenced in many places - akin to soldering or similar building techniques. Everything can't be put on the MAX site, nor should it be.


----------



## tomb

Quote:


  Originally Posted by *fordgtlover* /img/forum/go_quote.gif 
_I got my BJT MAX up an running tonight using the 2SC2238/2SA968 combination with Pana FC/FM caps throughout except for the Nichicon ES in CA2/7 and WIMA caps on all but CA8 where I have K42s. I have jumpers on the output resisters.

 I built the Mosfets version a few months back, and really liked it. But given the amount of positive discussion on the BJT build, I figured that I needed to hear it for myself. The build was very painless.

 A couple of points on the biasing. The BJTs were much easier to bias. In my Mosfet version just about every adjustment effected the others; biasing was like hearding cats. The BJTs on the other hand simply required two rounds, and they're done.

 Using the same Raytheon 12FM6 tubes that I have really liked in the Mosfet version, I am now listening to my new one and it is really quite different. There is no harshness at all, and while I never thought that my first Max lacked bass, this one has even more. This one does everything I liked about the Mosfet Max, but this one does it all just a bit better as far as I can tell so far.

 It seems to work very well regardless of the genre of music, from male to female vocal, blues and rock and metal. Very nice.

 I think I'll kick back and enjoy it...

 Thanks once again to Tomb for his tireless work_

 

Glad to hear you like it! 
	

	
	
		
		

		
		
	


	




 Yes, I think the sterile detail of the BJT's are the mustard to the tube's ketchup. The BJT's apparently perform much better without feedback (the Millett is a zero-feedback design), whereas the MOSFETs become a bit peaky in the bass and roll off in the highs. A guess is that your improved bass is actually the BJT's better control over the headphone drivers without feedback compared to the MOSFETs.

 So, are those orange-pad Sony MDR's in your avatar? I had a pair like that once - they came on a dark blue Sony FM/AM Walkman - might've been Sony's first - I can't remember back that far anymore.


----------



## Possede

I need to purchase a power supply for the Max. Would this one do? Does it have the correct input plug? 

AC Power Supply 24V AC (1000mA) ** FREE DELIVERY ** on eBay, also, Other Security Equipment, Security Equipment, Consumer Electronics (end time 04-Dec-07 17:03:56 GMT)


----------



## soloz2

Quote:


  Originally Posted by *Possédé* /img/forum/go_quote.gif 
_I need to purchase a power supply for the Max. Would this one do? Does it have the correct input plug? 

AC Power Supply 24V AC (1000mA) ** FREE DELIVERY ** on eBay, also, Other Security Equipment, Security Equipment, Consumer Electronics (end time 04-Dec-07 17:03:56 GMT)_

 

the jack is easy enough to change. I believe the stock jack is 2.5mm, but you'd have to check to be sure.


----------



## fordgtlover

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_ So, are those orange-pad Sony MDR's in your avatar? I had a pair like that once - they came on a dark blue Sony FM/AM Walkman - might've been Sony's first - I can't remember back that far anymore. 
	

	
	
		
		

		
		
	


	


_

 

I'm not sure what they are; I found the picture on the web somewhere. I had many sets like this over the years on Sony and other brand portable cassette players. Most of these headphones were very forgettable. 

 I liked them when I saw the picture. I thought that it offerered an amusing (to me at least) lo-fi counter point to the hi-fi ideal pursued by most head-fi members. I guess they were pretty much the iPod buds of the '80s.


----------



## tomb

Quote:


  Originally Posted by *Possédé* /img/forum/go_quote.gif 
_I need to purchase a power supply for the Max. Would this one do? Does it have the correct input plug? 

AC Power Supply 24V AC (1000mA) ** FREE DELIVERY ** on eBay, also, Other Security Equipment, Security Equipment, Consumer Electronics (end time 04-Dec-07 17:03:56 GMT)_

 

It says 2.1mm plug, so that should be fine. I'm not familiar with your wall outlet over in the UK, though - looks weird to me, but maybe it's OK.

 EDIT: Soloz2 is correct, though - it's easy enough to wire another one up if it doesn't match - or change the socket on the MAX. You don't even have to worry about polarity with AC.


----------



## el_matt0




----------



## Ech0

el Matt0,

 Really nice casework (very neat). I like the screen in the back. Congrats!


----------



## willisv

Looks good el Matt0, whats under the hood?


----------



## el_matt0

ah at this point its just stock parts from glassjaraudio's kit with the upgraded muse caps. im definitely considering adding some upgrades though. ive never really tried boutique caps etc, but id definitely look into it if only i knew where to begin! thanks for the compliments guys


----------



## pinkfloyd4ever

Quote:


  Originally Posted by *el_matt0* /img/forum/go_quote.gif 
_ah at this point its just stock parts from glassjaraudio's kit with the upgraded muse caps. im definitely considering adding some upgrades though. ive never really tried boutique caps etc, but id definitely look into it if only i knew where to begin!_

 

how about here Millett Hybrid MAX Boutique





 I'd go with the modifications of one of the "can't miss builds" 1-4, depending on your tastes

 If you like huge bass, stick with one with Muse ES's (which you already have half of obv), or if you like a more flat response & crystal-clear detail, go with Blackgate NX's


----------



## amphead

Verrry nice El-matt0! I like the ka-nob too. Those phones finally have something worthy to plug into. he he


----------



## el_matt0

hey guys, so yea im definitely going to try out one of the "cant miss" builds, see what kind of differences i notice. im going to try the blackgate NXs, which ive found i can order either from parts connexion or THL audio in HK. i am however at quite a loss as to where to get a few things. id like to try the VitQ's although i remember reading they can be hard to find. anyone got a good place to order from? if not that, what about the russian K42s? with regards to the WIMA caps for CA9, i know THL audio sells wima caps, thlaudio web site pages , but im not sure which rating i would want to grab. lastly. im new to the tube world and have NO idea where good places to order tubes are. im interested in perhaps trying a pair of NOS FK6's, where would i go about ordering those. is there any ONE place that i can get most of this stuff from, or am i going to hafta do the ol' order from 4 different places routine?


----------



## willisv

I got this info from a post tomb made on the diy forums. I hope he doesn't mind me posting this:

 Outside of the straight power caps such as Pana FM/FC, Nichicon UPW/UHE, there are two recommended boutique combinations that fit at 1":

 CA2: Nichicon Muse ES, 1000uF - 16V - 25mm
 Black Gate NX 1000uF - 25V - 26mm
 (note that BG also has a 1500uF - 10V that will also fit, but the specs are better on the previous one)

 CA7: Nichicon Muse ES, 470uF - 35V - 25mm
 Black Gate NX 680uF - 35V - 24mm


 The best place to buy BG's are at Soniccraft.com or at PartsConnexion. Right now, they must be strong competitors - because PartsConx has reduced their BG prices to the same as Soniccraft: $12.50 for the 1000uF listed above, and $13.95 for the 680uf.

 Handmade is the best source for Nichicon ES's and also KZ's and FG's. However, Handmade does not carry any 35V ES's. The 470uF 35V Muse ES is only available at BDent.com ($1.41) or at PercyAudio.com ($2.25). Michael Percy also carries most of everything else, but his response is often catch as catch-can. He may go incognito for a few weeks at certain times of the year. The other vendors mentioned have impeccable service and communication.

 BDent, unfortunately, carries no other ES cap - or any other boutique - save for some small Os-Cons for use in digital circuits. However, BDent carries most of the upgrade BJT's - the 2SC3422 pair, the 2SC3421 pair, and the 2SC2344 pair. They are out of the 2SC3422's until end of Sept or Oct. The 2SC2238 pairs are at MCMinone.com (or Newark with a handoff).

 PartsConnexion, Soniccraft, and Michael Percy carry almost every boutique film cap you would want, except Sonicaps, which are only at Soniccraft. Handmade only carries AudioCap (RelCap) and Solen. Vitamin Q's are pretty much only on E-bay, except that there are some tube vendors that carry them.

 Hope that helps you, mrbubbs.


 P.S. The CA8 film cap position will fit a 1" long film cap with no trouble. The CA9 film cap position will fit a 3/4", but 1" will work if tombstoned. That actually limits most film caps if you are looking for 0.22, 0.33, or 0.47uF:

 Sonicap GEN II's - no problem (400V), GEN I - OK for 0.22 and 0.33.
 Auricaps - no problem (for 400V versions)
 Cardas - only 0.1uF
 AudioCap - PCU OK up to 0.33uF (400V)
 Dynamicap - 0.1uF - maybe
 Jupiter - not recommended at all (too hot)
 Kimber Kap - OK up to 0.47uF (450V - maybe on the 0.47uF)
 Multicap - 0.1uF - maybe
 Mundorf Silver-Oil - no, Silver-Gold - no
 Hovland - no
 Jensen - no


----------



## willisv

Just to add to that... Vitq's and russian k42's pretty much have to be bought on ebay. The russian caps are usually sold in large lots which makes them a little pricey, you can ask someone in the forums if they have any extra's to sell. All this info is in this thread, I'm just repeating it.


----------



## el_matt0

watabout wimas, i have no idea what im looking for even (what rating and such), im planning on trying out the "cant miss build 1". what exactly does this last bit imply
 CA9: blank (Wimas elsewhere)
 2SC2238/2SA968 BJT Diamond Buffer
 i leave CA9 just jumpered? where does wimas elsewhere indicate, and what are those 2 part numbers, are those WIMAS? i think im good to go on ordering the blackgates but if someone can offer a little help with the wimas, either K42's or VitQs (that on the ODD chance someone might have lying around? 
	

	
	
		
		

		
		
	


	




) it would be muccch appreciated! oh and again, where would i go about ordering up some FK6 tubes?


----------



## pinkfloyd4ever

Wimas are the red rectangular caps you have in there already
 those part numbers are for the BJT transistors, which are the 4 in front with the heatsinks. The only place that has both right now is 5x 2SC2238 +5X 2SA968 TOSHIBA Pwr AMP Transistor TO-220 - (eBay item 220176917126 end time Dec-02-07 21:06:56 PST) here on ebay, tho there has recently been some question as to whether they're fakes or not, but I'd go for em if I currently had the $$
 CA9: (blank) means exactly that- leave it empty, no jumper is required
 the ratings for the BG caps are listed right there, just go to partsconnexion.com & find their SKUs, & call em up & order em


----------



## willisv

Quote:


  Originally Posted by *el_matt0* /img/forum/go_quote.gif 
_watabout wimas, i have no idea what im looking for even (what rating and such), im planning on trying out the "cant miss build 1". what exactly does this last bit imply
 CA9: blank (Wimas elsewhere)
 2SC2238/2SA968 BJT Diamond Buffer
 i leave CA9 just jumpered? where does wimas elsewhere indicate, and what are those 2 part numbers, are those WIMAS? i think im good to go on ordering the blackgates but if someone can offer a little help with the wimas, either K42's or VitQs (that on the ODD chance someone might have lying around? 
	

	
	
		
		

		
		
	


	




) it would be muccch appreciated! oh and again, where would i go about ordering up some FK6 tubes?_

 

CA9 is left empty - no jumpers, 2SC2238/2SA968 are power transistors you need two of each. Wima's are those red boxy caps that are already in your amp so you shouldn't need to buy any. The FK6 tubes, I'm not sure where to buy them but the 12AE6 tubes seem to be very popular with a lot of people here.


----------



## vixr

got all camera happy again...sorry.


----------



## fordgtlover

Quote:


  Originally Posted by *el_matt0* /img/forum/go_quote.gif 
_watabout wimas, i have no idea what im looking for even (what rating and such), im planning on trying out the "cant miss build 1". what exactly does this last bit imply
 CA9: blank (Wimas elsewhere)
 2SC2238/2SA968 BJT Diamond Buffer
 i leave CA9 just jumpered? where does wimas elsewhere indicate, and what are those 2 part numbers, are those WIMAS? i think im good to go on ordering the blackgates but if someone can offer a little help with the wimas, either K42's or VitQs (that on the ODD chance someone might have lying around? 
	

	
	
		
		

		
		
	


	




) it would be muccch appreciated! oh and again, where would i go about ordering up some FK6 tubes?_

 

 Quote:


 i leave CA9 just jumpered? 
 

Tomb states on his boutique  page:
 # CA9 Cathode Bypass (film bypass) - highly sensitive, use a Wima *or leave empty if in doubt*, a typical "blooming mids" (roll off in bass and highs) can destroy the MAX response. 


 See
http://www.head-fi.org/forums/f6/new...ml#post3428250 for more information on the Blackgate and CA8/9 issue.


----------



## thomaskuhn

IT WORKS!!!

 I finally had a chance to sit down and replace some parts. It was DM1. I guess I fried it when it shorted, and now I am up and running. I will have to wait for tomorrow to try it with my RS-1's, but if it sounds as good as it does with the crap cans I was sampling it though, and it has not even been broken in yet, I am in for a big suprise. Thanks Tomb for all your help! Will post a pic or two soon!

 Tom


----------



## rhester

Where can you souce the tube led's now that lsdiodes is not in business?


----------



## tomb

Quote:


  Originally Posted by *thomaskuhn* /img/forum/go_quote.gif 
_IT WORKS!!!

 I finally had a chance to sit down and replace some parts. It was DM1. I guess I fried it when it shorted, and now I am up and running. I will have to wait for tomorrow to try it with my RS-1's, but if it sounds as good as it does with the crap cans I was sampling it though, and it has not even been broken in yet, I am in for a big suprise. Thanks Tomb for all your help! Will post a pic or two soon!

 Tom_

 

Way to go, Tom! That's great!

 Send us some pics when you get it cased up. I'm also expecting some new comments in an upcoming episode of Spilled Whine. Let me know when to tune in!


----------



## tomb

Quote:


  Originally Posted by *rhester* /img/forum/go_quote.gif 
_Where can you souce the tube led's now that lsdiodes is not in business?_

 

OH FUDGE!!! 
	

	
	
		
		

		
		
	


	













 They've been my exclusive source for LED's since Vixr (nice pic, man! - get camera-happy anytime you want!) told us about them.

 Tell you what - I'll do the best thing we can: ask for help from fellow DIY-ers with a new thread. We need to come up with a great LED source - no volume buys, cheap and dependable. Hopefully there will be such a thing.


----------



## bperboy

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_OH FUDGE!!! 
	

	
	
		
		

		
		
	


	













 They've been my exclusive source for LED's since Vixr (nice pic, man! - get camera-happy anytime you want!) told us about them.

 Tell you what - I'll do the best thing we can: ask for help from fellow DIY-ers with a new thread. We need to come up with a great LED source - no volume buys, cheap and dependable. Hopefully there will be such a thing. 
	

	
	
		
		

		
		
	


	


_

 

Oh man!!! That's too bad they closed... what a great source for great LEDs!


----------



## willisv

congrats thomaskuhn, enjoy your max!!


----------



## joneeboi

Congrats, Thomas. Welcome to the club 
	

	
	
		
		

		
			





 What's the delay with the RS1s?


----------



## amphead

Congrats Thomas! Another MAX Lives!   

 You will become addicted to the sound with a good source and good cans!


----------



## soloz2

lsdiods isn't in business anymore?!?! 
	

	
	
		
		

		
		
	


	




 I was going to order from them a couple days ago but the site said down for maintenance so I figured I'd order this week... crap. I've gotta get some white LEDs now


----------



## tomb

pinkfloyd4ever,

 After seeing what I posted on heat sinks, I came to the conclusion that you were correct: I added it to the MAX website. It's another selection under the "Output Stage" section of the menu - Heat Sink Mounting .


----------



## xmokshax

hi all, i'm finally going to take the plunge and build myself a MAX, but i have just a couple of questions. first, Jeff Rossel let me know that a different board layout was forthcoming, although he doesn't know when - will this "new" MAX be improved enough that i'll want to wait for it, or is it just the more compact version that i think i've read about?

 second, does anyone have a couple of Muse ES 1000uf 16 or 25V caps that they'd be willing to part with (for a fair price, of course)? i'd like to put them in place of the Pana FCs that Jeff uses for CA2L/R, but i don't need anything else that would justify an order from Percy or Handmade. does anyone know if the ESs play well with UKZs at CA7L/R, or if they'd be a significant upgrade over the FCs?


----------



## tomb

Quote:


  Originally Posted by *xmokshax* /img/forum/go_quote.gif 
_hi all, i'm finally going to take the plunge and build myself a MAX, but i have just a couple of questions. first, Jeff Rossel let me know that a different board layout was forthcoming, although he doesn't know when - will this "new" MAX be improved enough that i'll want to wait for it, or is it just the more compact version that i think i've read about?

 second, does anyone have a couple of Muse ES 1000uf 16 or 25V caps that they'd be willing to part with (for a fair price, of course)? i'd like to put them in place of the Pana FCs that Jeff uses for CA2L/R, but i don't need anything else that would justify an order from Percy or Handmade. does anyone know if the ESs play well with UKZs at CA7L/R, or if they'd be a significant upgrade over the FCs?_

 

It's just the more compact version. Colin has dubbed it the "MiniMAX," so I'll be calling it that from now on. It's about 2/3 the size of the regular MAX. It's made for a Lansing case and is really slick when fit into the case. However, the 1" height rule is not negotiable and the part selection is pretty rigid - just not enough room to offer much flexibility. Hopefully, there will be enough interest to offer both.

 Colin's main project right now is a Tube DAC. It will be next year before you see prototypes, though.


----------



## amphead

Just can't wait to build that tube DAC!


----------



## pinkfloyd4ever

Any ETA on the next round of regular MAX boards? Did you say you guys were gonna set up a webstore to sell them from?

 Just to be sure, I should stick with the 680uf 35V BG at CA7, rather than the 1000uF 25V, right? I swore I saw a pic where you had Wima's in at CA9 (can't find it now since the big site crash) have you since removed them, and did you already try the K42's at CA2?

 I think a while back you said the one thing you might consider bypassing BG's with at CA9 was small value NX Hi-Q's...is that correct? I was thinking about getting 2 0.1uf's for each channel (so 4 total per amp) and trying the Super-E, which is 2 BG NX's paralleled in opposite orientation (which kinda doesn't make sense to me; if they're non-polar, shouldn't they not have an orientation?) Looks like Jelmax finally took down the BG website, but thankfully there's Google's cache. Anyway, I thought this would be easy to do since there's 4 holes for each CA9 position, and at about $2 each, it's worth a shot right? Sooo, you see any reason not to do this? I can't remember anyone doing this, or for that matter using one .47uf NX Hi-Q per channel(as I think you suggested), can you? Would you use 2 paralled .47ufs or stick with 2 .1ufs?Alright, I promise that's really all..for now.

 Keep on rockin in the free world (can we PLEASE get a rock on devil ears hand in the smilies?!?!??


----------



## ferds

wow tube dac... cant wait...


----------



## tomb

Quote:


  Originally Posted by *pinkfloyd4ever* /img/forum/go_quote.gif 
_Any ETA on the next round of regular MAX boards? Did you say you guys were gonna set up a webstore to sell them from?_

 

First, I hope you noticed that you changed my mind on the heatsink mounting. After looking at that post, I thought, "Sheesh - why the heck not post that on the website?" Anyway, I hope you don't mind my crediting your username on that web page, but you were the instigator. 
	

	
	
		
		

		
		
	


	










 Yes, there is a store in the works and I am working on it every day. Anybody who says web e-commerce is easy is mistaken, but I digress. It's not abiding by forum rules to discuss something like that. So, let me state that after sending 10 more boards to Jeff a few days ago, I have about two dozen left. We will be making a large order soon, but I wanted to get that thing I just mentioned up and running, first. (I'm getting close. 
	

	
	
		
		

		
		
	


	




 )

 Anyway, that's where things stand. Of course, Colin and I are going to add more things as time goes on. The MiniMAX will be part of that large order I will make in a few weeks. Then Colin should have the tube DAC ready to prototype after the new year. We will be adding more things as well as time goes on.

  Quote:


 Just to be sure, I should stick with the 680uf 35V BG at CA7, rather than the 1000uF 25V, right? 
 

Yes. You mentioned a quote in your earlier PM, but I was only talking about CA2 in that reference. You really need 35V minimum on CA7 unless you set the amp at 24V maximum, and that's not getting the best performance.

 There is a Nichicon Muse Fine Gold that's 1000uf 35V. I have a pair but haven't tested them. Seriously, though, anyone who puts in the recommended caps that I have listed in those "Can't Miss MAX Builds" on the MAX website will never complain about a lack of bass - including with Grados.

 MexicanDragon let me listen to his Grado HF-1's at the recent Atlanta meet connected to one of my Muse ES MAXes - the bass is fantastic - deep, tight, and punchy ... very, very nice. I'm in the market for an HF-1, by the way, but may settle for an SR-225 by Christmas. His impressed me that much, even though I had sold my only Grado months ago (SR-80). People have told me that the SR-80's were not representative of the higher-level models, but it's so expensive to get any really good Grados - but I digress.

  Quote:


 I swore I saw a pic where you had Wima's in at CA9 (can't find it now since the big site crash) have you since removed them, and did you already try the K42's at CA2? 
 

I've put the Russian K42's as bypasses on the BG's at the output (CA7), but the BG's at CA2 are standing pat ......
 Personally, I think putting the K42's at the tube positions (CA9) are overkill. The thing is, the BG's have all the frequency response you need..... For Black Gates at CA2 - no film or PIO bypass.

 Yes - I put the Wima's in CA9 when using ES's. Again, my testing has shown that the K42's are sort of wasted at CA9. They may even hurt slightly, because they may have just the teeniest bit of rolloff in the highs. The Wima's have no rolloff anywhere and are quite flat and neutral. It's just that there's a bit of grain and squeekiness in the mids. That comes through if they're on the output in the CA8 position, but not in CA9.

 Again, you sort of have to think of CA2 and CA9 as keeping the door open in case the signal gets big. 
	

	
	
		
		

		
		
	


	




 - but it's not filtering through every bit of the signal. So, it's sort of like what you put there can really hurt, but it's never going to really improve things (unless you've hurt them in the first place).

 Hope that makes sense.

  Quote:


 I think a while back you said the one thing you might consider bypassing BG's with at CA9 was small value NX Hi-Q's...is that correct? I was thinking about getting 2 0.1uf's for each channel (so 4 total per amp) and trying the Super-E, which is 2 BG NX's paralleled in opposite orientation (which kinda doesn't make sense to me; if they're non-polar, shouldn't they not have an orientation?) Looks like Jelmax finally took down the BG website, but thankfully there's Google's cache. Anyway, I thought this would be easy to do since there's 4 holes for each CA9 position, and at about $2 each, it's worth a shot right? Sooo, you see any reason not to do this? I can't remember anyone doing this, or for that matter using one .47uf NX Hi-Q per channel(as I think you suggested), can you? Would you use 2 paralled .47ufs or stick with 2 .1ufs?Alright, I promise that's really all..for now. 
 

Here's the deal - the way I understand it, at least:
 I would only use one 0.47uf. You're forgetting that CA2 and CA7 are already there as the first cap in the "Super E" configuration. Technically, to follow the Black Gate strategy as they intend, you'd put two 680uf's in CA7 and CA8, mounted in opposite polarity. See - it's just another marketing ploy to make you buy twice the number of ridiculously expensive Black Gates.
	

	
	
		
		

		
		
	


	




 However, the idea of using the 0.47uf as the "film bypass" at CA9 and CA8 is a good one. MrMajestic2 is one that I know for sure that's built a MAX that way. It's pictured in the gallery on the MAX website. He's built two, though - one with the very large 0.47uf Vitamin Q's. You could PM him to find out his opinions, but I'm not sure he has anything to compare with for a reference. The one he built that way is using MOSFETs, too, so that may render any comparison moot. Anyway, I think the single bypass on a large BG electrolytic with the smaller, super high-quality 0.47uf NX Hi-Q is a safe bet. Be wary of that CA9 position, though - it still may be better to just do it on CA8 at the output and leave CA9 blank.

 I really think the Black Gates at CA2 are just fine to stand by themselves. I wouldn't even put the Wima's there with the ES's except that the ES's have a known issue with resolution in the highs, and the Wima's fix that without rolling off in the frequencies anywhere.

  Quote:


 Keep on rockin in the free world (can we PLEASE get a rock on devil ears hand in the smilies?!?!??
	

	
	
		
		

		
		
	


	



 

EDIT: The red resistors you asked about in your PM are PRP resistors. Available at both Soniccraft and PartsConnexion, they're the same quality as Vishay-Dales, but are a snappy red color with white lettering. PRP claims they're specifically made for audio and sound better, but I buy them for the red color. They're about twice as much as V-D's, but that's still only 30 cents each. Here's a page at Soniccraft that explains their characteristics and the sizes available:
PRP Resistors at Soniccraft.com


----------



## pinkfloyd4ever

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_First, I hope you noticed that you changed my mind on the heatsink mounting. After looking at that post, I thought, "Sheesh - why the heck not post that on the website?" Anyway, I hope you don't mind my crediting your username on that web page, but you were the instigator. 
	

	
	
		
		

		
		
	


	








_

 

wow, I thought it might help some people, but I never thought I'd be immortalized by being credited on the MAX website
	

	
	
		
		

		
		
	


	




 I'm glad they have those kits or I still wouldn't be totally sure I'm ordering all the correct parts

  Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Yes, there is a store in the works and I am working on it every day. Anybody who says web e-commerce is easy is mistaken_

 

ya, I can imagine, I'm taking my first programming class now (C++) and just that is killing me. Good to hear though
  Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Yes. You mentioned a quote in your earlier PM, but I was only talking about CA2 in that reference. You really need 35V minimum on CA7 unless you set the amp at 24V maximum, and that's not getting the best performance.

 There is a Nichicon Muse Fine Gold that's 1000uf 35V. I have a pair but haven't tested them. Seriously, though, anyone who puts in the recommended caps that I have listed in those "Can't Miss MAX Builds" on the MAX website will never complain about a lack of bass - including with Grados._

 

Well then, if bass is all it might effect, I think I'll stick with the 680uf BG since I'm no basshead

  Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Here's the deal - the way I understand it, at least:
 I would only use one 0.47uf. You're forgetting that CA2 and CA7 are already there as the first cap in the "Super E" configuration. Technically, to follow the Black Gate strategy as they intend, you'd put two 680uf's in CA7 and CA8, mounted in opposite polarity. See - it's just another marketing ploy to make you buy twice the number of ridiculously expensive Black Gates.
	

	
	
		
		

		
		
	


	




 However, the idea of using the 0.47uf as the "film bypass" at CA9 and CA8 is a good one. MrMajestic2 is one that I know for sure that's built a MAX that way. It's pictured in the gallery on the MAX website. He's built two, though - one with the very large 0.47uf Vitamin Q's. You could PM him to find out his opinions, but I'm not sure he has anything to compare with for a reference. The one he built that way is using MOSFETs, too, so that may render any comparison moot. Anyway, I think the single bypass on a large BG electrolytic with the smaller, super high-quality 0.47uf NX Hi-Q is a safe bet. Be wary of that CA9 position, though - it still may be better to just do it on CA8 at the output and leave CA9 blank.

 I really think the Black Gates at CA2 are just fine to stand by themselves. I wouldn't even put the Wima's there with the ES's except that the ES's have a known issue with resolution in the highs, and the Wima's fix that without rolling off in the frequencies anywhere._

 

Allrighty, sweet, empty CA9 it is, at least until I've given everything a hundred hours or so to burn in, then I might experiment with the NX Hi-Q's a bit. Thanks again for all your helpful insight


----------



## pinkfloyd4ever

oh and I almost forgot...on the topic of heatsinks, do those pins that go into the board come with them, or are they even necessary?


----------



## tomb

Quote:


  Originally Posted by *pinkfloyd4ever* /img/forum/go_quote.gif 
_oh and I almost forgot...on the topic of heatsinks, do those pins that go into the board come with them, or are they even necessary?_

 

Yes, the heat sink part #'s listed on the BOM are the heat sinks that come with pins. There are others that can be threaded and secured with screws, but pinned heat sinks seem to be used most often.


----------



## 04BluMach

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Colin's main project right now is a Tube DAC. It will be next year before you see prototypes, though._

 


 Tube DAC....
	

	
	
		
		

		
		
	


	




 Been very interested in building a DAC to improve SQ of CD collection. Was leaning to Non-Oversampling NOS DAC for the tonality and lushness that is offered by that Topology. Most impressed with the Monica3 DAC offered by DIYParadise.

 But if Colin is working a Tube DAC - may need to wait for the MAX Tube DAC. 
	

	
	
		
		

		
		
	


	




 Is there a design thread up on the tube dac currently? If not, any further details such as target Dig Converter chip? Input for both SPIDF and USB?

 Might want to start a separate thread for interest check and further details. Would not want to derail the intended topic of this great MAX Build Thread.


----------



## jerrygp

Finished up my second Millet Hybrid, powered it up, checked the DB bias, and had plugged my multimeter probes into the V+ and GRD tip jacks to check voltage, and then CR1D ruptured at the seam and steam spewed forth like a small geyser. The top of the cap is slightly distorted but there are no other obvious signs of trauma. One possibility is that I jumpered the fuse-not knowing if I needed to or not, and hooked the power wires up to position 1 and 2 on the 3 pos terminal block. Maybe I should have removed the jumper? I've included some Pixs of my board. Can anyone offer up any help? I can provide any component info if needed.


----------



## amphead

We need better pictures of the top of the board. Close-ups of the power supply and of the DBs/transistors.


----------



## IcantHearU

Quote:


  Originally Posted by *jerrygp* /img/forum/go_quote.gif 
_Finished up my second Millet Hybrid, powered it up, checked the DB bias, and had plugged my multimeter probes into the V+ and GRD tip jacks to check voltage, and then CR1D ruptured at the seam and steam spewed forth like a small geyser. The top of the cap is slightly distorted but there are no other obvious signs of trauma. One possibility is that I jumpered the fuse-not knowing if I needed to or not, and hooked the power wires up to position 1 and 2 on the 3 pos terminal block. Maybe I should have removed the jumper? I've included some Pixs of my board. Can anyone offer up any help? I can provide any component info if needed._

 


 From here it looks like it's just one of the electrolytic caps installed backwards - look at the stripe(negative side) on the one that blew - 
 Hope that helps.


----------



## fordgtlover

IcantHearU would appear to be on the money. It sure looks like CR1D is reversed.


----------



## tomb

Quote:


  Originally Posted by *fordgtlover* /img/forum/go_quote.gif 
_IcantHearU would appear to be on the money. It sure looks like CR1D is reversed._

 

Agreed - I hope those aren't polarized Black Gates.

 Looks like a great build, though, jerrygp - nice Black Gates at CA2 and CA7!


----------



## vixr

this LED supplier looks promising... they have a pretty good selection of stuff.


----------



## n_maher

Can you guys seriously not find what you need for LED's at Mouser? And I have to say, I'm generally trying to make LED's *less* bright not more.


----------



## tomb

Quote:


  Originally Posted by *n_maher* /img/forum/go_quote.gif 
_Can you guys seriously not find what you need for LED's at Mouser? And I have to say, I'm generally trying to make LED's *less* bright not more. 
	

	
	
		
		

		
		
	


	


_

 

Hey - you broke the rules, anyway - you didn't even drill your tube sockets and install the tube LED's on that last MAX you built.


----------



## slowpogo

I'm probably going to try the "Can't Miss Build #1". Somewhere in this swamp of a thread, I read that CA2 was not as important as CA7, in terms of its affect on the SQ.

 Another thing I've read is that the different BG types generally play very well together in the signal path. Given those two ideas, would it be acceptable to use a standard polarized Black Gate 1000uf, 25v cap in CA2, and the expensive 680uf NX in CA7?

 I plan on using Panasonic FC or FM for all the other electrolytics, if that's important.


----------



## tomb

Quote:


  Originally Posted by *slowpogo* /img/forum/go_quote.gif 
_I'm probably going to try the "Can't Miss Build #1". Somewhere in this swamp of a thread, I read that CA2 was not as important as CA7, in terms of its affect on the SQ.

 Another thing I've read is that the different BG types generally play very well together in the signal path. Given those two ideas, would it be acceptable to use a standard polarized Black Gate 1000uf, 25v cap in CA2, and the expensive 680uf NX in CA7?

 I plan on using Panasonic FC or FM for all the other electrolytics, if that's important._

 

You might do just as well _or better_ with one of those FM's in the CA2 position, but yes - you are correct about the general strategy. Keep in mind I haven't actually tested it, but given what we know and the large numbers of Jeff's kits that were built with FC's in that position - it's a good bet.


----------



## n_maher

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Hey - you broke the rules, anyway - you didn't even drill your tube sockets and install the tube LED's on that last MAX you built. 
	

	
	
		
		

		
		
	


	











_

 

True enough, I have an aversion to installing parts that I can never remove later on. 
	

	
	
		
		

		
		
	


	




 I like the older implementation of the tube LED's with the installation done on the bottom of the board so that if one ever wanted to remove/change/replace one of the LED's they could do so without having to remove the entire tube socket.


----------



## joneeboi

To remove my tube lights, I just need to tip it upside down, apply heat to the pads and poke around a bit with a screwdriver or toothpick. It's not that much trouble.


----------



## ruZZ.il

you can do it all with the tube sockets still in..

 edit: err, yeah.. what joneeboi said


----------



## thomaskuhn

Quote:


  Originally Posted by *joneeboi* /img/forum/go_quote.gif 
_Congrats, Thomas. Welcome to the club 
	

	
	
		
		

		
		
	


	




 What's the delay with the RS1s?_

 

I think you are refering to the e12 relay circuit? I still have it as stock. If you are wondering the delay in trying the amp out with them, they were at the office, and I finished the amp at the house. I will say the whole thing sounds great! I am really loving it! I am contemplating the idea of swapping out the 2sc2238/9xx with the ones I got from MCM. The first set was from the Hong Kong ebay guy. I also just got some K42's in, and should soon have them installed. If anyone needs a pair, just PM me. I should have about 6 left, after myself and some I am giving away. I was walking around Orlando's awsome surplus store, and looking at the capacators, I came upon some Sprague .22mF 200V 2TM-p22 caps. They look similar to the VitQ's I haave seen in pictures, but have a black coating on the outside. If anyone would like to audio test them, just PM me and I send them to you.

 Tom


----------



## tomb

Quote:


  Originally Posted by *thomaskuhn* /img/forum/go_quote.gif 
_I think you are refering to the e12 relay circuit? I still have it as stock. If you are wondering the delay in trying the amp out with them, they were at the office, and I finished the amp at the house. I will say the whole thing sounds great! I am really loving it! I am contemplating the idea of swapping out the 2sc2238/9xx with the ones I got from MCM. The first set was from the Hong Kong ebay guy. I also just got some K42's in, and should soon have them installed. If anyone needs a pair, just PM me. I should have about 6 left, after myself and some I am giving away. I was walking around Orlando's awsome surplus store, and looking at the capacators, I came upon some Sprague .22mF 200V 2TM-p22 caps. They look similar to the VitQ's I haave seen in pictures, but have a black coating on the outside. If anyone would like to audio test them, just PM me and I send them to you.

 Tom_

 

Sounds like you found some Sprague Black Beauties. 
	

	
	
		
		

		
		
	


	




 About the 2SC2238/2SA968's - let us know if it makes a difference swapping them out - but try to be sure that it's not psychological. I have a habit of claiming "better" just because I put the sweat into doing it. That may or may not be reality. I have one on the building board right now with the Chinese versions I got from that local vendor that I trust ... ed. 
	

	
	
		
		

		
		
	


	




 I'll swap 'em out if you think there's a difference.


----------



## jerrygp

Thank you all for your help. CR1D is reversed. I don't know how that slipped by...I am usually very...anal about my DIY stuff. (Have to be with no electronics training or experience.) Tomb mentioned polarized Black Gates, the side of the canister has "nonpolar" markings, so I assume I am alright there? Would reversing the CR1D cap have damaged anything else?

 And thank you Tomb, for your attaboy. I am using the Russian PIO's in there as well at CA8. Hope it breaks in sweetly. You folks are part of a great community.


----------



## el_matt0

anyone have any spare vitQs or russians they could spare, im hoping to try out the "cant miss 1 build" but im not too keen on having to order a whole lot of them just to match them! :| if anyone has any spares it would be a huge and greatly appreciated favor lol! pm me if so cheers


----------



## thomaskuhn

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Sounds like you found some Sprague Black Beauties. 
	

	
	
		
		

		
			





 About the 2SC2238/2SA968's - let us know if it makes a difference swapping them out - but try to be sure that it's not psychological. I have a habit of claiming "better" just because I put the sweat into doing it. That may or may not be reality. I have one on the building board right now with the Chinese versions I got from that local vendor that I trust ... ed. 
	

	
	
		
		

		
		
	


	




 I'll swap 'em out if you think there's a difference._

 


 Well, If anyone is interested in any of the "Black Beauties", There were quite a few left, maybe 10 -20 in the box. I am not sure of their audio quality, but I will keep the offer out there if anyone is interested.

 Tomb, I know what you mean about the psychological aspect. I might not be able to tell the difference at all..

 Tom


----------



## tomb

Quote:


  Originally Posted by *jerrygp* /img/forum/go_quote.gif 
_Thank you all for your help. CR1D is reversed. I don't know how that slipped by...I am usually very...anal about my DIY stuff. (Have to be with no electronics training or experience.) Tomb mentioned polarized Black Gates, the side of the canister has "nonpolar" markings, so I assume I am alright there? Would reversing the CR1D cap have damaged anything else?_

 

Nah - the cap would only hurt itself.

 As for your Black Gates, yes - those are non-polarized and should be OK installed in either direction. As it happens, even non-polar or bi-polar caps have one lead longer than the other. As a general rule, the long lead on a polarized cap goes into the positive side. I always put bi-polars in that way, too, but they'll be OK, regardless.

  Quote:


 And thank you Tomb, for your attaboy. I am using the Russian PIO's in there as well at CA8. Hope it breaks in sweetly. You folks are part of a great community. 
 

Sweetly and _longly_. 
	

	
	
		
		

		
		
	


	




 Dsavitsk has suggested just running BG's for a week before you even listen. That might not be a bad idea - they will take 50-100 hours before they stop sounding "thick and conjested" and will continue to improve for many hours beyond that.

 You are welcome for the attaboys. As for the "community", others have said it, but that's the big thing that Jude's created: a headphone community. Some of us tend to forget that when we complain about the rules or other things.


----------



## el_matt0

noobish question, can someone elaborate on the black beauties? what are they and where are you guys trying them in the max?


----------



## tomb

Quote:


  Originally Posted by *el_matt0* /img/forum/go_quote.gif 
_noobish question, can someone elaborate on the black beauties? what are they and where are you guys trying them in the max?_

 

I didn't want to be discouraging, but I haven't seen a Black Beauty anywhere near the size small enough to fit in the MAX. They're probably not as good as VitaminQ's and the construction is not reliable. Black Beauties are more popular with the guitar folks who want something that adds more brraatt and preserves vintage sound




_[size=xx-small](click for a big pic)[/size]_

 Here's an excerpt from the March, 2007 issue of the New Jersey Antique Radio Club Newsletter - it has everything you wanted to know about Sprague Black Beauties:
How Beautiful Are Those Black Beauties?


----------



## el_matt0

thanks tom, all i needed/ wanted to know! was just curious more than anything else. well - unfortunately im still on the hunt for some vitQs or russians it looks like!


----------



## pinkfloyd4ever

Quote:


  Originally Posted by *el_matt0* /img/forum/go_quote.gif 
_thanks tom, all i needed/ wanted to know! was just curious more than anything else. well - unfortunately im still on the hunt for some vitQs or russians it looks like! 
	

	
	
		
		

		
		
	


	


_

 

umm ever try reading previous posts in the thread? like a whole page ago...
	

	
	
		
		

		
		
	


	




 (damn this new rolleyes smiley doesn't look cynical enough)
  Quote:


  Originally Posted by *thomaskuhn* /img/forum/go_quote.gif 
_ I also just got some K42's in, and should soon have them installed. If anyone needs a pair, just PM me. I should have about 6 left, after myself and some I am giving away._

 

or have all his already been claimed? if so, mybad, just disregard this. Actually, if so, PM me, I personally don't have any but I may be able to hook you up


----------



## naamanf

I have about 46 extra. Only problem is it might take a bit long to get to you do to my present location. If you can't find anyone else and don't mind waiting let me know.


----------



## jerrygp

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Nah - the cap would only hurt itself.

 As for your Black Gates, yes - those are non-polarized and should be OK installed in either direction. As it happens, even non-polar or bi-polar caps have one lead longer than the other. As a general rule, the long lead on a polarized cap goes into the positive side. I always put bi-polars in that way, too, but they'll be OK, regardless.

 Sweetly and longly. 
	

	
	
		
		

		
		
	


	




 Dsavitsk has suggested just running BG's for a week before you even listen. That might not be a bad idea - they will take 50-100 hours before they stop sounding "thick and conjested" and will continue to improve for many hours beyond that.

 You are welcome for the attaboys. As for the "community", others have said it, but that's the big thing that Jude's created: a headphone community. Some of us tend to forget that when we complain about the rules or other things. 
	

	
	
		
		

		
		
	


	


_

 

Thanks, tomb. Didn't have any extra UPW's, so I had to order more from Mouser. While I wait, I might as well start on my third board...either that or start the new Dean Koontz novel...


----------



## amphead

Quote:


 I am usually very...anal about my DIY stuff. (Have to be with no electronics training or experience.) 
 

The hits that you take when installing a cap backwards and learning from that is what electronics "experience" is all about. It isn't fun, but the school of hard knocks is valuable training!


----------



## tomb

Quote:


  Originally Posted by *amphead* /img/forum/go_quote.gif 
_The hits that you take when installing a cap backwards and learning from that is what electronics "experience" is all about. It isn't fun, but the school of hard knocks is valuable training!_

 

Yes, Amphead is right - it happens to all of us. I once installed an entire bank of TO-92's in reverse on one of the Millett DB boards. I couldn't understand why it was burning and smelling when it was plugged in. 
	

	
	
		
		

		
		
	


	







 I had been so careful to get the 2N5087's and 2N5088's in their respective positions, it never dawned on me that they were reversed. It fried every one of the TO-92's on that channel - had to replace them all.


----------



## slowpogo

Is there any place in the Max where boutique resistors might work well? I recall someone used Kiwames in their Max but didn't care for the sound. I'm thinking of tantalums, MK-132s or Rikens.

 I'm planning on using PRP resistors for most of the amp, but thought maybe some boutiques in the input stage might not be a bad idea.


----------



## el_matt0

i believe where people have reported kiwames having a positive impact is on the output stage. i could be wrong though. out of random curiousity, i notice some people use MASSIVE caps in their mhmax, ferraris build for example with those huge black audyn caps. what position are those being used in? and i assume those are those massive russian teflons being used @ CA8?


----------



## tomb

Quote:


  Originally Posted by *slowpogo* /img/forum/go_quote.gif 
_Is there any place in the Max where boutique resistors might work well? I recall someone used Kiwames in their Max but didn't care for the sound. I'm thinking of tantalums, MK-132s or Rikens.

 I'm planning on using PRP resistors for most of the amp, but thought maybe some boutiques in the input stage might not be a bad idea._

 

 Quote:


  Originally Posted by *el_matto* 
_i believe where people have reported kiwames having a positive impact is on the output stage. i could be wrong though. out of random curiousity, i notice some people use MASSIVE caps in their mhmax, ferraris build for example with those huge black audyn caps. what position are those being used in? and i assume those are those massive russian teflons being used @ CA8?_

 

I agree with el_matto - I'm not aware of _anyone_ who did not like the Kiwame's. Now, keep in mind that if the choice is *no* resistor on the output vs. *some* resistor on the output, the Kiwame may lose in that choice - but probably not otherwise. So, jumpered output resistors will definitely sound superior than say a 75ohm or 100ohm Kiwame. Down around 22-10ohms, the Kiwame may actually help rather than hurt compared to just jumpers. I've heard that the Rikens may be just as good, but we don't have any direct reports - yet. The cheap Stackpole carbon films at Handmade can get you 80-90% of the effect of a Kiwame for about 1/10 the price.

 The output positions are the only place on a MAX where boutique resistors may make a difference. PRP or V-D's are as good as it gets for the rest - excluding the three LED resistors. Nothing more than simple carbon films should be used there.

 Ferrari (pardon my speaking for him, here) pursues the principle that any electrolytic in the signal path is bad. So, he chooses to make combinations of film capacitors in parallel that add up to the capacitance of the electrolytic output coupling caps. For instance, in the original Millett Hybrid, he tied together enough film caps to total 470uf - the banks of film caps were larger than the rest of the amp. The Audyns he's using in his MAX follow the same priniciple. It's just that he was able to get the Audyns in much larger sizes so that it only took two or three - or however many it was.

 Again, he is using them in the CA7 position instead of the 470uf electrolytics. (He may, in fact, have a larger value total than that - I'm not really sure.) I'd have to look at the pics again to see what you're talking about in the back. At one point he was using the Russian K40 PIO's, I think, but changed to something else, later.


----------



## 04BluMach

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_I didn't want to be discouraging, but I haven't seen a Black Beauty anywhere near the size small enough to fit in the MAX. They're probably not as good as VitaminQ's and the construction is not reliable. Black Beauties are more popular with the guitar folks who want something that adds more brraatt and preserves vintage sound_

 


 Yeah, TOMB is right on those Caps being desired by the guitar folks...
 Not by the MAX folks!

 I don't think anyone would want to put a Black Beauty (or Bumble Bee) in their MAX. Their claim to fame is their tonal coloration and distortion products that they produce within Guitar AMP tone circuits are highly sought for that Vintage Signature Sound. They are also know for being very prone to leaking acid and oil out of them through age and heat exposure. YUK 
	

	
	
		
		

		
		
	


	




 Can't imagine anyone intentionally wanting to distort or color that dynamic music stream pouring through their MAX. On top of that they aren't cheap because the Vintage Guitar crowd has driven the prices up!
	

	
	
		
		

		
		
	


	




 Here is another article that is short, sweet and to the point.. Black Beauty 

 It also contains some very highly respected reference links on Capacitor construction data, selection criteria and highly regarded test documentation for those that want to Geeky on the subject.


----------



## 04BluMach

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_I agree with el_matto - I'm not aware of anyone who did not like the Kiwame's. Now, keep in mind that if the choice is *no* resistor on the output vs. *some* resistor on the output, the Kiwame may lose in that choice - but probably not otherwise. So, jumpered output resistors will definitely sound superior than say a 75ohm or 100ohm Kiwame. Down around 22-10ohms, the Kiwame may actually help rather than hurt compared to just jumpers._

 

I am using 20 ohm Kiwames in the outputs of my second build. Definity has very sweet and crystaline highs. No harshness at all. The unit is still breaking in the caps (ELNA SILMICII 470uf w/ 0.47uf VitaQ Bypass caps) and uses the 2SC2238/2SA968's. Initial listening was with well burned in 12AE6A.
 Tried jumpering across the Kiwames - had a little grain and lost a little sweetness. Maybe the Caps still need a little cooking in to reach WellDone 
	

	
	
		
		

		
			





 Not sure about the potential loss of Dynamics since I haven't put a lot of listening time on this yet since it hasn't been cased-up and completed! But the MAX has GOBS of dynamics - so who knows. I probably need much a much younger Head-Fi member with golden ears to try it out to get a better read 
	

	
	
		
		

		
		
	


	




 Think I will add a front panel switch to be able to cut the resistor out or into the circuit...
	

	
	
		
		

		
		
	


	




 To gain better Volume control adjustment range you probably need about 100 to 150 Ohms in output circuit... that level will probably reduce dynamics somewhat. 

  Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_I've heard that the Rikens may be just as good, but we don't have any direct reports - yet. The cheap Stackpole carbon films at Handmade can get you 80-90% of the effect of a Kiwame for about 1/10 the price._

 

Yeah, the Rikens should be right up there with the Kiwame's since they are both very high quality Carbon FILM resistors. TOMB is probably right on the money about those Stackpoles too. Avoid both Metal Film (harshness) and Carbon Composition (Noise/Distortion) in the output position.


  Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Ferrari (pardon my speaking for him, here) pursues the principle that any electrolytic in the signal path is bad. So, he chooses to make combinations of film capacitors in parallel that add up to the capacitance of the electrolytic output coupling caps. ....
 Again, he is using them in the CA7 position instead of the 470uf electrolytics. (He may, in fact, have a larger value total than that - I'm not really sure.) I'd have to look at the pics again to see what you're talking about in the back. At one point he was using the Russian K40 PIO's, I think, but changed to something else, later._

 

Ferrari is an _*ANIMAL*_. His builds are not just Awesome.... they are _*OVER THE TOP*_











 I am so jealous of his style and finish on his builds. Certainly, puts a Target out there for us to strive to achieve even anywhere close to those levels...


----------



## slowpogo

I have some 15ohm Rikens I will try on the output.

 I may be missing something, but the Max board has test points, of course, for biasing...yet the BOM does not show any test points that I see.

 Would the Keystone test points work here? They make three sizes I believe, Tangent's stuff uses the middle size...


----------



## bperboy

Quote:


  Originally Posted by *slowpogo* /img/forum/go_quote.gif 
_I have some 15ohm Rikens I will try on the output.

 I may be missing something, but the Max board has test points, of course, for biasing...yet the BOM does not show any test points that I see.

 Would the Keystone test points work here? They make three sizes I believe, Tangent's stuff uses the middle size..._

 

The test points are just holes in the boards, not specific parts for test sockets. As long as they fit, any kind of socket that you can stick a probe into should work. I'm not sure about the size of the kind you're talking about.


----------



## tomb

The Keystone test points slowpogo refers to are the loop-clip-on type. I remember Vixr showed a simple way to do the same thing with a spent lead bent into a loop and a small piece of teflon insulation under the loop. Those Keystone test points are expensive for what you get.
 EDIT: correction - it was a glass bead, not a piece of teflon insulation - like the kind used to make little jewelry in the craft store.

 Ultimately, you may find that simply poking a probe through the test holes works just as well. Another option is to use tip jacks wired so that you can install them on the back plate - my preference. It's a hassle to wire them up and install them, but very convenient once it's done. Details are on the MAX website under "Construction -> Casework -> Wiring & Assembly"

 04BluMach - nice posts!


----------



## thomaskuhn

Quote:


  Originally Posted by *04BluMach* /img/forum/go_quote.gif 
_Yeah, TOMB is right on those Caps being desired by the guitar folks...
 Not by the MAX folks!

 I don't think anyone would want to put a Black Beauty (or Bumble Bee) in their MAX. Their claim to fame is their tonal coloration and distortion products that they produce within Guitar AMP tone circuits are highly sought for that Vintage Signature Sound. They are also know for being very prone to leaking acid and oil out of them through age and heat exposure. YUK 
	

	
	
		
		

		
		
	


	




 Can't imagine anyone intentionally wanting to distort or color that dynamic music stream pouring through their MAX. On top of that they aren't cheap because the Vintage Guitar crowd has driven the prices up!
	

	
	
		
		

		
		
	


	




 Here is another article that is short, sweet and to the point.. Black Beauty 

 It also contains some very highly respected reference links on Capacitor construction data, selection criteria and highly regarded test documentation for those that want to Geeky on the subject._

 

It is so interesting that some caps I found in a small bin have so much "history" of audio quality. Every time I go to the surplus store and look upon row after row of caps, I always wonder what might it give to audio quality. I usually head over there once a week for work purposes, so if anyone is looking for anything special (you never know what they have) I can keep an eye out.

 Tom


----------



## jerrygp

I jumpered the fuse position on the production board on my almost complete second build, and hooked up my power leads to positions 1 and 2 while leaving position three on the terminal block unused. I am thinking the jumper is unnecessary in this config. Can anyone give me a yay or nay on the jumper? I blew up my CR1D yesterday as I posted earlier, but I'm thinking the jumpered fuse position is not an issue...(I tried using the fuse clips from digikey but the outermost one fouled with backside of the power socket when everything was in place and the endplates were installed...again with me thinking...the fuse and it's clips maybe are only used during testing when the board is out of the case...)


----------



## tomb

Quote:


  Originally Posted by *jerrygp* /img/forum/go_quote.gif 
_I jumpered the fuse position on the production board on my almost complete second build, and hooked up my power leads to positions 1 and 2 while leaving position three on the terminal block unused. I am thinking the jumper is unnecessary in this config. Can anyone give me a yay or nay on the jumper? I blew up my CR1D yesterday as I posted earlier, but I'm thinking the jumpered fuse position is not an issue...(I tried using the fuse clips from digikey but the outermost one got in the way of my power switch when everything was in place and the endplates were installed...again I am assuming the fuse maybe is only used during testing when the board is out of the case...)_

 

The first two positions (from left to right looking from the volume pot end) of the power input terminal block completely bypass the fuse - jumpered or not.


----------



## amphead

Quote:


 I have some 15ohm Rikens I will try on the output. 
 

Ok, let us know. I am jumpered with good results.


----------



## slowpogo

I want to use Front Panel Express for my panels. The drawings on the site will allow me to plot everything I want in the FPE software, except the heat sink vent holes.

 Can someone point me to some FPE template files for the Hammond case? Or explain how to plot the holes like they are in tomb's top panel drawing?

 As I said, the tube locations are measured out in the drawings, but the heat sinks are not.


----------



## tomb

Quote:


  Originally Posted by *slowpogo* /img/forum/go_quote.gif 
_I want to use Front Panel Express for my panels. The drawings on the site will allow me to plot everything I want in the FPE software, except the heat sink vent holes.

 Can someone point me to some FPE template files for the Hammond case? Or explain how to plot the holes like they are in tomb's top panel drawing?

 As I said, the tube locations are measured out in the drawings, but the heat sinks are not._

 

The template drawings are done to scale and have graphic scales on the drawings, even if your printer is off in scaling. So, you should be able to measure from that. The holes are all 3/16", except the trimmer adjustment holes, but I'd make them 3/16" at this point, too. I'd offer to dimension them for you, but it may be awhile before I can get to it.

 Too bad FPE uses a proprietary format and charges $$ for importing DXF or DWG files. Those are also available from the MAX website.

 EDIT: I believe FPE prices according to how many holes you have. I think something like the MAX toplate will be very expensive because of that. You also have to consider what to do without the z-bend in the lip of the Hammond top plate. Without that, the top plate will sit lower in the case. The Hammond top plates look like they're extruded that way, but I doubt FPE is setup to do that.


----------



## ruZZ.il

wood is nice. I need to find some wood.


----------



## slowpogo

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_EDIT: I believe FPE prices according to how many holes you have. I think something like the MAX toplate will be very expensive because of that. You also have to consider what to do without the z-bend in the lip of the Hammond top plate. Without that, the top plate will sit lower in the case. The Hammond top plates look like they're extruded that way, but I doubt FPE is setup to do that._

 

I've done a quick version of a top panel with FPE...you're right, unless you're willing to pay $120 for a huge cavity to recreate a z-bend, the panel will sit a little lower than the top edge. 

 But if you have a 3mm panel and use cavities to thin out the part that slides into the slot, it will be only around 1mm lower, which I can live with. Actually, it will compensate visually for the tube bushings, which have some thickness above the panel.

 Assuming two 1" tube holes, and around 30 3/16" holes, the cost will be around $50. Really, not too bad IMO. 

 The front and rear panels should be only around $65 together. So, $115 for the panels...considering that I don't own a drill or bits, and would very likely screw something up to the point of wanting to buy another case and try again, I can live with it.


----------



## tomb

Quote:


  Originally Posted by *slowpogo* /img/forum/go_quote.gif 
_I've done a quick version of a top panel with FPE...you're right, unless you're willing to pay $120 for a huge cavity to recreate a z-bend, the panel will sit a little lower than the top edge. 

 But if you have a 3mm panel and use cavities to thin out the part that slides into the slot, it will be only around 1mm lower, which I can live with. Actually, it will compensate visually for the tube bushings, which have some thickness above the panel.

 Assuming two 1" tube holes, and around 30 3/16" holes, the cost will be around $50. Really, not too bad IMO. 

 The front and rear panels should be only around $65 together. So, $115 for the panels...considering that I don't own a drill or bits, and would very likely screw something up to the point of wanting to buy another case and try again, I can live with it._

 

Well, yes - I agree. Somtimes I think it would be worth it to pay $50 for a lid rather than drill all those holes. Still, I've never used them and don't understand the pricing - seems cheap compared to the endplates or compared to what we paid on the Mini3. Maybe the lettering costs even more.
	

	
	
		
		

		
		
	


	




 Please take pics and let us have a look when you get them.


----------



## el_matt0

with respect to this front panel express issue. heres the best advice i can offer, based on my experience with them. to avoid paying for the z-bend, simply select the option to use your own material, pay the 8 bucks or whatever it costs to get a nice fresh top plate, and mail that over to them to be used for your order. tomb is right in saying that they basically charge per hole, per piece of work done. basically just print out the template from the MHMAX site as close to scale as you can get it (shouldnt be hard, i was able to print exactly to scale) and just use a ruler to measure your distances. you can even just do this right on your MHMax board. the exact location of those vent holes for the sinks doesnt have to be right on the money by any means, so long as they are generally above the heatsinks the function will still be the same. i dont know if the idea appeals to you at all, but you might look into getting long "slits" cut in or something as opposed to 5 holes x 4. 20x 3/16" holes might in fact be more expensive than simply 4 longitudinal slits cut in, one above each heatsink. if you check out my max, ull see that i didnt opt to drill out the rear holes in the same manner either, i found creating a larger hole and adding a screen to it allows for much better air flow and cooling of the sinks. honestly id say if you are going "all the way" and getting FPE to do your panels for you, be a little creative man. whats the point in paying all the extra money only to end up with a MHMax that looks just like everyone elses who has simply taken the time to carefully drill their own holes by hand? if it was me personally doing it via FPE i would want to create something unique. basically the only "critical" factors on the top plate is the z-bends along the sides and getting the location of the tube holes right, but that shouldnt be hard too do with some careful measuring. in terms of the front and back plates just make sure you are using the correct height. i drilled out one front panel based on the templates from the MHMax build site, only to realize that those are based on the max being on the 3rd step up in a hammond case. for whatever reason i guess my sinks are slightly taller than the ones used in those examples on the site, so mine can ONLY fit on the very bottom "shelf" in the hammond case. that would be my route if i were going FPE....and it really shouldnt cost u too much i dont think. just as you go, keep an eye on the running total cost. it gives the specific price for each piece of work done, some speciifc things are REALLY expensive and can be cleverly avoided (ie countersunk holes for one, which u can work your way around by drilling 2 partial holes one from the back one from the front, of differing diameters). anyways, hope that helps, and hopefully we will be seeing a groovy looking unique max in not too long!


----------



## slowpogo

If I understand correctly, I could mail the *existing* top plate from the Hammond case to FPE and have them drill that, based on a template made with their software? Huh, it's unsurprising but I just hadn't considered that it was possible. 

 Yes, I plan to be a little creative. At least with the front panel, it will have some lettering and a logo. Good call on using slits for the top. Maybe I'll try two opposing, trapezoidal slits per heat sink. And I'll probably put some kind of mesh underneath, just so any tiny spill of liquid won't rocket directly into the case.


----------



## el_matt0

Quote:


  Originally Posted by *slowpogo* /img/forum/go_quote.gif 
_If I understand correctly, I could mail the *existing* top plate from the Hammond case to FPE and have them drill that, based on a template made with their software? Huh, it's unsurprising but I just hadn't considered that it was possible. 

 Yes, I plan to be a little creative. At least with the front panel, it will have some lettering and a logo. Good call on using slits for the top. Maybe I'll try two opposing, trapezoidal slits per heat sink. And I'll probably put some kind of mesh underneath, just so any tiny spill of liquid won't rocket directly into the case._

 

haha 
	

	
	
		
		

		
			





 well i wouldnt like to think that your planning to be spilling liquids all over your amp or anything! but it seems like it would be a clever idea. and yea, im not sure EXACTLY where the option is, but its on the menu where you select the dimensions and color etc for your plate. theres a little checkbox that says "use my own material". ive never tried it personally but i assume its just a simple matter of choosing that option and shipping them the plate to be used. i think you would DEFINITELY save some money that way as opposed to like you said, getting them to plane out one entire side so that the z-bends are present. i find lettering and whatnot isnt too expensive, mostly cutting and drilling etc is. but yea, i really woud not be surprised if cutting trapezoidal slats like you said is cheaper than drilling 20 precision holes. good luck with it man, if you are careful and measure everything meticulously, i have no doubt u will be receiving a brilliant looking case from them. best of luck


----------



## amphead

Another option for the top plate, is to use black plastic 1/4 inch square stock and cut a thin channel for the top plate. The 4 plastic pieces are screwed into the top of the box at the corners and after sliding the top plate in place, the front piece is screwed down. This provides about another 1/4 clearance for capacitors, without expensive bends on the top plate.


----------



## villekille

Is it possible to have a bass boost with millett hybrid? Like the one in PPA v2?


----------



## bperboy

Quote:


  Originally Posted by *villekille* /img/forum/go_quote.gif 
_Is it possible to have a bass boost with millett hybrid? Like the one in PPA v2?_

 

Put some nice big Caps in there, and IMHO there is no need for Bass boost! Plenty to go around already!


----------



## amphead

Yeah plenty of bass in the Max. Well nothing to work on right now. I can't commit to a 4 board design like the Beta-22 right now, so here I am with gears in neutral. My Max sounds awesome with the new Walkman as source(1410KBPS files). No further refinements neccessary on the Max. 

 TomB YGPM


----------



## soloz2

I'll go in w/ whoever to get some nice endpannels done. It would probably be cheaper then doing it all individual anyway. Let me know.


----------



## slowpogo

The discount isn't that great. If 20 people went in, they'd each save about $5 per panel.


----------



## el_matt0

Quote:


  Originally Posted by *slowpogo* /img/forum/go_quote.gif 
_The discount isn't that great. If 20 people went in, they'd each save about $5 per panel._

 

x2, ive looked into that option as well but its just not really worth the hassle of rounding up 20 people who want to commit to such a thing as opposed to just getting it over with and paying the extra 5 yourself. plus having something unique is well - unique!


----------



## ruZZ.il

Quote:


  Originally Posted by *villekille* /img/forum/go_quote.gif 
_Is it possible to have a bass boost with millett hybrid? Like the one in PPA v2?_

 

Definitely not in the way the PPA or M^3 do. They use op-amps to 'amplify' the voltage from the source with a feedback loop with some resistance that controls the gain. The opamp has 2 inputs, one from the source and one from the feedback from the output. It tries to equalize the 2 inputs, so it will alter the output in any way necessary to do this. With a resistor in the feedback path, the outputs voltage drops on the way to the other input, so the opamp just increases the outputs voltage so the inputs are equalized. If one puts a high pass filter on that feedback loop the lower frequencies are 'muted' a bit, so the amp compensates more for the lower frequencies in order to equalize the inputs. The output is also connected to a current multiplier stage, like the BJTs or the MOSFETs, which complete the amps voltage/current amplification.

 The MAX uses a tube for voltage amplification, which has no feedback. it basically uses the source voltage to create a field which excels expelled electrons from the heater element into a cylindrical anode that absorbs them, where they continue in a 'completed' circuit whose current is in proportion to the input voltage. This current is 'amplified' in a similar current amplification stage as the other amps (the transistors are more like dimmers, so the small current controls a circuit with more current, creating a proportional, 'stronger' current. The gain is an inherent property of the tube that cant really be altered, though one could supply it with an efficient stock of electrons to disperse as it needs, which is what the capacitors function is, along with the capacitors own inherent response. so basically, all you can do is try compliment it with a sufficient circuit so that it can work at its optimal inherent manner.. no more. as far as I know.
 But I don't know it all too well, and I'd love to learn more, or otherwise, so please excuse inaccuracies and my misconceptions, though its the basic idea. sorry I couldn't be as explicit 'bout the tube bass bit, but hopefully the insight to the differences will help you understand why it cant be the same 
 Maybe something else could be done that I don't know about?.. Though.. I must say, I'm happy with my bass 
	

	
	
		
		

		
		
	


	




 Py black gates took some time, but they're thumping now 
	

	
	
		
		

		
		
	


	




, probably not like ES's (I'll soon find out though..)...


----------



## tomb

ruZZ.il is absolutely correct. His technical explanation of a solid-state amp with feedback and bass boost is much better than anything I could explain.

 However, I'm full of jargon 
	

	
	
		
		

		
		
	


	




:
 If you build one of the "Can't Miss MAX Builds" on the Tweaks -> MAX Boutique on the MAX website, I would be shocked if you'd want a bass boost.

 Bass boost is one of those artifacts from the solid-state amp community. 
	

	
	
		
		

		
		
	


	




 Solid-state clips so readily and so harshly that it takes massive amounts of power and over-sized power-to-load ratios to accurately reproduce the full strength of bass notes. When people refer to bass _slam_, they're talking about a low frequency _transient_. A transient like that requires massive amounts of current burst or voltage swing, depending on the impedance of the load. Unless the solid-state amplifier is built to supply this current burst or voltage swing, the bass suffers quickly.

 Obviously, some of the very best (and expensive) solid-state amps have no issue with bass at all and will out-perform the MAX. However, the MAX does it at a very low price - perhaps more competitvely than any other amp. I'm a certified basshead and have always wanted a bass boost with the solid-state amps I've built - but not with the MAX. The MAX has so much bass already that any kind of boost (or equalization) makes it immediately sound fake and artificial. I can still remember that after I built the first MAX prototype, I turned my equipment's bass equalization down to zero for the first time. At that instant, I was sold on the MAX!

 As ruZZ.il says, the Black Gate version of the MAX may seem a tad light on bass by comparison, trading enormous detail for slightly less bass - but only slightly. However, when building one of the ES versions of those "Can't Miss MAX Builds," I would guess that you can't get more or better bass with any other amp at this price.


----------



## amb

tomb, I understand your enthusiasm for tubes but your statement above is flat out false in the case of the Millett Hybrid (MAX or otherwise). When the amp clips, it does so just as harshly as any SS amp. Have you looked at a spectrum analyzer and/or a scope to see what happens before you wrote that paragraph? Also, on what basis do you claim that SS amp clip more readily than the Max (given the same supply rail voltage)? I don't need to remind you that the Millett MAX design has a SS output stage that's lifted straight out of the PPAv2...


----------



## slowpogo

I'm curious, how much would you have to spend to get a commercially produced amp that is definitely better than the Millett Max?


----------



## el_matt0

Quote:


  Originally Posted by *slowpogo* /img/forum/go_quote.gif 
_I'm curious, how much would you have to spend to get a commercially produced amp that is definitely better than the Millett Max?_

 

i think you are generally going to get a wide variety of (somewhat meaningless) answers to a question like this. as is the case with most DIY amps, there is a wide range of components that people choose to incorporate into their builds. id say some have spend around $180 to put together a MH hybrid, where as i wouldnt be surprised in the slightest if some of the more modded builds including boutique caps and what not are closer to the $500 or above range. and as is always the case with audio, ultimately its purely subjective preference when deciding on which is "better". then you have to also factor in synergy of the amp with the remainder of your setup (source, cans, etc). i could be wrong, but i have a feeling most will agree with me on this one


----------



## slowpogo

I understand, but as an example, most people would agree that the Sennheiser HD595 is a good headphone but not quite in the same class as the top models from Beyer, AKG, the HD650 etc. This is general and not universal, but still useful information. An Acura Integra is pretty much better than a Ford Taurus, etc.

 I'm kind of wondering what the analogous "higher class" of non-balanced headphone amps would be, compared to a typical Millett Max build. I mean, would it take $600, or more like $2500 to beat the Max? I'm just looking for generalities, not trying to start a debate.

 It would just be nice to have a point of reference, in regards to DIY vs. commercial/professional amps.


----------



## Ferrari

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_...

 Bass boost is one of those artifacts from the solid-state amp community. 
	

	
	
		
		

		
		
	


	




 Solid-state clips so readily and so harshly that it takes massive amounts of power and over-sized power-to-load ratios to accurately reproduce the full strength of bass notes. When people refer to bass slam, they're talking about a low frequency transient. A transient like that requires massive amounts of current burst or voltage swing, depending on the impedance of the load. Unless the solid-state amplifier is built to supply this current burst or voltage swing, the bass suffers quickly.
 ..._


----------



## tomb

Quote:


  Originally Posted by *amb* /img/forum/go_quote.gif 
_tomb, I understand your enthusiasm for tubes but your statement above is flat out false in the case of the Millett Hybrid (MAX or otherwise). When the amp clips, it does so just as harshly as any SS amp. Have you looked at a spectrum analyzer and/or a scope to see what happens before you wrote that paragraph? Also, on what basis do you claim that SS amp clip more readily than the Max (given the same supply rail voltage)? I don't need to remind you that the Millett MAX design has a SS output stage that's lifted straight out of the PPAv2..._

 

Specifically, I was talking about the soft clipping characteristics of a tube, not the output stage, and I was definitely in error when I used the specific word "readily." One might interpret "more harshly" as encompassing like characteristics of "readily," but perhaps that was too strong a term.

 That a SS amp would clip _more harshly_ is not something I made up. This characteristic can be found in most literature that ever compares the two. It seems to me that in the MAX, the tube will clip way before the output stage, since the tube is acting as the amplification device in the circuit - but perhaps I'm wrong on that account.

 I was not comparing specific amps in that post and I'm not going to do that anymore, even though others have. I think the MAX competes very well in its price category and that was the essence of what I was trying to convey, albeit rather enthusiastically. 

 Rather than incur further objection from you, however, I'll refrain from the jargon in the future, too. The MAX's great success is due in large part from not only your e12 design, but also your MOSFET diamond buffer design. I would rather do anything else than make you think I've insulted your designs after what you've contributed to the community. That was the furthest thing from my mind.


----------



## ruZZ.il

I want to build a beta22


----------



## tomb

Quote:


  Originally Posted by *ruZZ.il* /img/forum/go_quote.gif 
_I want to build a beta22 _

 

I can guarantee you that a Beta22 never entered my mind in any comparison with the MAX.
	

	
	
		
		

		
			





 Maybe I should've been more specific, but I'm in enough trouble already.


----------



## dsavitsk

Quote:


  Originally Posted by *amb* /img/forum/go_quote.gif 
_When the amp clips, it does so just as harshly as any SS amp. ... Also, on what basis do you claim that SS amp clip more readily than the Max (given the same supply rail voltage)?_

 

 Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Specifically, I was talking about the soft clipping characteristics of a tube, not the output stage ... That a SS amp would clip more harshly is not something I made up. This characteristic can be found in most literature that ever compares the two. It seems to me that in the MAX, the tube will clip way before the output stage, since the tube is acting as the amplification device in the circuit - but perhaps I'm wrong on that account._

 

tomb, you are right that tubes clip in a more pleasing way than transistors. But, with the Millett, any clipping is likely in the CCS, which is solid state. In order to get tube type clipping, you would need to overdrive the grid. But, because of the way that the amp is designed, this won't likely happen until well after the CCS's room to swing has been passed.

 As a (very) simplified example, with the 12AE6A, with .6mA of current and a 13V plate bias, the cathode is at ~0.5V. Assuming that the supply voltage is 26V, this means that the CCS has 13V to swing, if it can go right up to the rail ... which it can't. Optimistically, it might have 8V of swing in it. So, the tube can swing ~1V before clipping, and with a mu of 16, this would require the CCS to swing 16V, which it clearly can't do. To extract the full gain of the tube, and get to the tube's clipping, you would need a CCS that dropped more like 30V, which would mean a plate supply of 45V or so with that same 13V plate bias.


----------



## tomb

OK, I see, Doug. Thank you for the explanation.

 I am sorry for my blatant bias and jargonistic suppositions. Please accept my apology for the trouble I caused, guys.


----------



## amphead

All good discussion TomB, Dsavitsk, Amb,ruZZ.il! This is what brings the characteristics of the Max into sharp focus. Really interesting stuff. Another post about 8 weeks ago, from someone I can't recall, talked about the output stage. He mentioned that when the output is overdriven, that rather than clipping it moved from Class A operation to Class B. Whats your understanding of that statement? Amb? Dsavitsk?


----------



## amb

amphead, the push-pull output stage will transition from class A to class AB when it's asked to deliver more than double the (peak) current than its quiescent current. This may occur with low-Z loads well below clipping threshold.

 You have to understand that clipping happens when the output voltage swing would exceed what's available from the supply voltage minus internal losses. It's a voltage swing phenomenon that would occur when you turn up the volume high enough, even without a load at its output.

 The transition from class A to class AB, on the other hand, is load-dependent and quiescent-current dependent.


----------



## amphead

Thanks Amb, that makes sense! Higher output impedance couples more voltage swing, which could translate into the peaks being flattened hence clipping. And lower output impedance(with an overdriven signal), tends to degrade operation from Class A to Class AB, which can introduce crossover distortion. Two different ways to lose clarity, one when headroom is exceeded and the other when current flow pushes operation into the AB region.


----------



## amb

amphead, replace "output impedance" with "load impedance" in your post above and it would be mostly right. Clipping is nasty -- instant harshness in the sound. It should be avoided completely. On the other hand, class AB operation, despite onset of crossover distortion, may not be so bad, depending on the amp design. In an amp with global negative feedback (which the Millett isn't) such distortion would be corrected by the feedback, albeit not completely.


----------



## amphead

Yeah, load impedance is the correct term. I stand corrected. The crossover distortion probably isn't much of a factor in the Max, due to its lower power(current density), compared to speaker driving amplifiers.(scratch this theory it doesn't match what I just read about the effect of biasing)


----------



## tomb

A work in progress on the MiniMAX -










_[size=xx-small](click for big pics)[/size]_

 The Lansing case is really cool except for the color. I made the mistake of thinking it might be neat to try white for once. As you can see, however, it's a refrigerator almond color, instead. 
	

	
	
		
		

		
		
	


	




 I'm probably going to paint it and be sure to order a black one next time. 
	

	
	
		
		

		
		
	


	




 The Lansing case bottom is the key to the whole case and is of very high quality. However, the top is thin gray steel covered with a grained-vinyl. It all seems to come together very nicely, though, and the overall effect is tight and compact.


----------



## willisv

Very cool Tomb!! The board looks very compact, I imagine the cap choices would be pretty limited.


----------



## ruZZ.il

hey that does look nifty! any circuitry changes? I think you mentioned it was pretty much the same..


----------



## tomb

Quote:


  Originally Posted by *ruZZ.il* /img/forum/go_quote.gif 
_hey that does look nifty! any circuitry changes? I think you mentioned it was pretty much the same.._

 

Yep, pretty much the same - just some tweaks here and there. The 1" height is a rigid constraint, though - and the Wima's and boutique caps are 0.1uf's. Those are some Sonicap GEN II's in there now, but I've got some 0.1uf K42's that will be going in. Colin is working on some more refinement.

 It's basically a nice mixup with the big one, and the case is kind of interesting to work with - but we'll see when I go to punch holes in it.


----------



## slowpogo

What do you all think about this design for the top panel? If I send in my own metal to Front Panel Express, it's only $23.

 I think it looks kind of busy and angular on the computer screen, with the stark black and white contrast. But laying down flat with some wire mesh under the heatsink holes, it should be more subtle.


----------



## ruZZ.il

looks pretty cool.. and efficiently thought out slits.. how's the overlay with the board look?


----------



## slowpogo

I still have to check that. I'm going to make a transparency to put over the board, so I can know for sure that the heat sink parts are lined up correctly. It will probably be tweaked further.


----------



## joneeboi

I thought I might go a little camera crazy amidst all the joyful debating.


----------



## fordgtlover

Fantastic macro photography. What camera are you using?


----------



## joneeboi

It's a Canon Powershot A720 IS. We're actually looking at getting into them DSLRs, namely the Nikon D40X and the Canon EOS 400D. We actually were taking a look at them today. I hope to get camera crazy much more often


----------



## amphead

Slowpogo, thats tribal!

 Nice orange glow Joneeboi!


----------



## amphead

Nice work on the miniMax TomB/CeToole (Team miniMax)! The miniMax is a candidate for a balanced configuration, due to its even smaller size(right Pabbi?). Let me know when you need some cash for that other board TomB.


----------



## joneeboi

Thanks, amphead. I thought the orange would complement the heater glow better than the other colours. I tried green but it wasn't as uniform.

  Quote:


  Originally Posted by *amphead* /img/forum/go_quote.gif 
_Slowpogo, thats tribal!_

 

I actually thought it looked more like a robotic Tweety with a bowtie.


----------



## tomb

Joneeboi - 
 You always have some of the best macro-photography I've seen. Great job!


 Amphead -
 YGPM


----------



## joneeboi

Thanks, Tom. Do you think it's good enough to make it onto the MAX site?


----------



## tomb

Quote:


  Originally Posted by *joneeboi* /img/forum/go_quote.gif 
_Thanks, Tom. Do you think it's good enough to make it onto the MAX site? 
	

	
	
		
		

		
		
	


	


_

 

Of course! First chance I get.


----------



## joneeboi

Sounds great, Tom.

 While I'm at it, does anyone have extra K42Ys?


----------



## tomb

Quote:


  Originally Posted by *joneeboi* /img/forum/go_quote.gif 
_Sounds great, Tom.

 While I'm at it, does anyone have extra K42Ys?_

 

Joneeboi, YGPM.


----------



## tobias_svensk

Lol, my first powerup and 27VDC from PSU but 22.5VDC TA2L-> GND 
	

	
	
		
		

		
		
	


	




 and trimmer doesn't respond.

 The fuse went directly at powerup and I didn't have anotherone so I just tapped the screwterminal, I wonder if I have burned the MOSFets? but no smoke or smell 
	

	
	
		
		

		
		
	


	




 And I did have RB12L/R at fully CW.


----------



## tomb

Quote:


  Originally Posted by *tobias_svensk* /img/forum/go_quote.gif 
_Lol, my first powerup and 27VDC from PSU but 22.5VDC TA2L-> GND 
	

	
	
		
		

		
		
	


	




 and trimmer doesn't respond.

 The fuse went directly at powerup and I didn't have anotherone so I just tapped the screwterminal, I wonder if I have burned the MOSFets? but no smoke or smell 
	

	
	
		
		

		
		
	


	




 And I did have RB12L/R at fully CW._

 

Oops! Measuring Diamond Buffer bias is from TB1L OR TB2L to TA2L. TA2L -> GND is measuring the bias on the LEFT tube, in which case you would adjust RA1L, not RB12L. To be specific, counterclockwise on RA1L should lower that 22.5VDC to something closer to 13.5VDC.

 However, don't mess with that until you check the Diamond Buffer bias. Refer to this pic on the MAX website for reference:



_[size=xx-small](click for bigger pic) [/size]_


----------



## tobias_svensk

Hello Tom

 Well It's me who gives poor explanation.

 I did it like this:

 First of all the fuse went poff.

 1. Before anything I screwed the DB-buffer pot fully CW.
 2. Inserted 24VAC and checked kinda quickly the rail (~27VDC)
 3. Checked TB1L -> TA2L (~22VDC) had to put my meter to 200VDC instead of 20VDC 
	

	
	
		
		

		
			





 and adjusting RB2L didn't had any effect.
 4. Checked TA2L - GND (~22VDC)
 5. Realized I had forgotten R1, soldered it but no change.
 6. Stopped everything until tomorrow 
	

	
	
		
		

		
		
	


	




 Cheers


----------



## tomb

Quote:


  Originally Posted by *tobias_svensk* /img/forum/go_quote.gif 
_Hello Tom

 Well It's me who gives poor explanation.

 I did it like this:

 First of all the fuse went poff.

 1. Before anything I screwed the DB-buffer pot fully CW.
 2. Inserted 24VAC and checked kinda quickly the rail (~27VDC)
 3. Checked TB1L -> TA2L (~22VDC) had to put my meter to 200VDC instead of 20VDC 
	

	
	
		
		

		
		
	


	




 and adjusting RB2L didn't had any effect.
 4. Checked TA2L - GND (~22VDC)
 5. Realized I had forgotten R1, soldered it but no change.
 6. Stopped everything until tomorrow 
	

	
	
		
		

		
		
	


	




 Cheers_

 

OK. Well, give us some more specific measurements tomorrow and pics of the DB's, if you can. We're ready to help you with whatever it takes to get your MAX alive.


----------



## amphead

We have your back Tobias. Plenty of eyes to go around and brains to get you up and running.


----------



## tobias_svensk

Hello again 
	

	
	
		
		

		
		
	


	




 Well here are some pictures, not so good I'm afraid.. it's from my cellphone.

 /T


----------



## tobias_svensk

.


----------



## tobias_svensk

..


----------



## tobias_svensk

...


----------



## tomb

Quote:


  Originally Posted by *tobias_svensk* /img/forum/go_quote.gif 
_Hello Tom

 Well It's me who gives poor explanation.

 I did it like this:

 First of all the fuse went poff.

 1. Before anything I screwed the DB-buffer pot fully CW.
 2. Inserted 24VAC and checked kinda quickly the rail (~27VDC)
 3. Checked TB1L -> TA2L (~22VDC) had to put my meter to 200VDC instead of 20VDC 
	

	
	
		
		

		
		
	


	




 and adjusting RB2L didn't had any effect.
 4. Checked TA2L - GND (~22VDC)
 5. Realized I had forgotten R1, soldered it but no change.
 6. Stopped everything until tomorrow 
	

	
	
		
		

		
		
	


	




 Cheers_

 

Tobias,

 Those pics are small, even when clicking on them. However, from what I can see, you have a perfect build.

 I think maybe we should focus more on your procedure. #2. and #4 above make sense if you haven't adjusted bias on the tube. They really make sense if you didn't put in R1, because it would mean that the tubes weren't even on or conducting.

 So, I am still curious about #3. For your #3., you should, indeed, have to change the scale on your meter - but to 200mv or less, not over 200V. You see, those two points are measuring the voltage across the ends of the resistor, RB11L. I don't think it's even possible to measure 22VDC across that resistor - not without it exploding, anyway (assuming it's 2.2ohm).

 Please check your meter and how you are measuring between those two points. Again, please refer to that layout key on the measurement points I posted a few posts back.

 Bottom line, I don't see anything wrong with your build from here.


----------



## Televator

just put in the finishing touch (kiwame output resistors, thanks fordgtlover!) in my Black-Gates Max... cased it up (unfortunately my 8mm drill was bad and the air holes aren't as well aligned as I would have liked), but nevertheless it looks great together with my 3-input / 3-output switchbox with matching style ... and much more importantly: it sounds even better!


----------



## n_maher

Nice work!


----------



## slowpogo

There are genuine Vitamin Q caps on ebay, in .18 and .27uf values. The recommended value for the film bypasses is .22uf, but would either of these Vitamin Q's still work?


----------



## tobias_svensk

Oh man.. 
	

	
	
		
		

		
		
	


	




 Please forgive me Tom.. It's nothing wrong with my MAX 
	

	
	
		
		

		
		
	


	




 Now I have 27V / 13.5V / 190mV running.

 But were do you have some information about R1? I guess it's there to lower the heatercurrent if you're running a high rail?

 /T


----------



## ferds

Congrats tobias... another MAX lives!!!!


----------



## J.D.N

If i wanted to build a Millet Max, where would i get a PCB? Do i need to wait for another group buy? 

 The answer to this question may be very obvious, but this Max thread/cult is rather over whelming!


----------



## tobias_svensk

Quote:


  Originally Posted by *ferds* /img/forum/go_quote.gif 
_Congrats tobias... another MAX lives!!!!_

 

Thanks man 
	

	
	
		
		

		
		
	


	




 Remember to always turn your trimmers ALL the way and test... I had like all my adjustment on the last 10-20% of the turns.

 My PSU heatsink is madly hot but I guess 25.5VAC in under load is a bit on the steep side.

 Sadly I have to sleep now but tomorrow I will compare it to my QRV-04 (OPA627 + BUF634)

 Cheers


----------



## Televator

Quote:


  Originally Posted by *J.D.N* /img/forum/go_quote.gif 
_If i wanted to build a Millet Max, where would i get a PCB? Do i need to wait for another group buy?_

 

for now there's only the Glassjaraudio kits (member Jrossel sells them through his site, but you have to PM or email him for an order form). These kits offer everything (not just the PCB) and they sound GREAT as they come (one of the "can't miss"-builds on the MAX site). If you are certain you want to go extra boutique you can always ask for a less complete kit.

 Besides that, a new group-buy (for MAX or MAX-mini) will come pretty soon, I guess


----------



## J.D.N

Quote:


  Originally Posted by *Televator* /img/forum/go_quote.gif 
_for now there's only the Glassjaraudio kits (member Jrossel sells them through his site, but you have to PM or email him for an order form). These kits offer everything (not just the PCB) and they sound GREAT as they come (one of the "can't miss"-builds on the MAX site). If you are certain you want to go extra boutique you can always ask for a less complete kit.

 Besides that, a new group-buy (for MAX or MAX-mini) will come pretty soon, I guess_

 


 Cheers, i'd love to build a MAX, it really doesnt need to be extra boutique or anything. Just got to weigh up if it's over my head and i should start with a SOHA.


----------



## Televator

I went for a Max as it deals with low voltages only, so I could ruin the amp but not much more if I screwed up good ... but I built a JRossel-kit successfully after having only built a Cmoy (well two) and an alien DAC before...

 Just follow the instructions on Tombs MAX-site (they are very precise and easy to follow) and double (no triple) check every part before mounting (correct part, orientation, ...)

 For me, the MAX kit was even easier than a cmoy in certain ways as it comes in one complete package and it is very well documented and supported (here in this thread 
	

	
	
		
		

		
			





 )


----------



## tomb

A friend has shared with me some data and calculations about the Millett's car radio tubes. It seems that there's not a bean's worth of difference in the performance values between a 12AE6A and a 12AU7A (GE, 1954/56) when the 12AU7A is run at reduced voltage - say 50V or so.

 I'll try to get the tube curves and operating points worked up for comparison and post it when I get a chance.

 EDIT: Now, keep in mind, that I've always loved the tube-rolling that's possible in the SOHA. but my bias is well-known and documented in this thread. 
	

	
	
		
		

		
		
	


	





 P.S. Great work Televator! That's a cool-looking MAX!


----------



## tomb

Quote:


  Originally Posted by *tobias_svensk* /img/forum/go_quote.gif 
_Thanks man 
	

	
	
		
		

		
		
	


	




 Remember to always turn your trimmers ALL the way and test... I had like all my adjustment on the last 10-20% of the turns.

 My PSU heatsink is madly hot but I guess 25.5VAC in under load is a bit on the steep side.

 Sadly I have to sleep now but tomorrow I will compare it to my QRV-04 (OPA627 + BUF634)

 Cheers_

 

Congrats! You may find that the sinks will get cooler with run in. Colin and I have been comparing notes on that lately and it seems to be the case with most of our builds.


----------



## tomb

Quote:


  Originally Posted by *slowpogo* /img/forum/go_quote.gif 
_There are genuine Vitamin Q caps on ebay, in .18 and .27uf values. The recommended value for the film bypasses is .22uf, but would either of these Vitamin Q's still work?_

 

Yes. Either of them would probably work very well. The problem with Vitamin Q's are their size. Now, if you are putting the MAX board on the bottom slot of the Hammond, that gives you plenty of room to tombstone even 0.47uf Sprague Vitamin Q's. If you are trying to keep things under 1" and put the board in the Hammond's 3rd slot from bottom (~center for the volume shaft), then the K42's are the choice.

 EDIT: This is assuming low-voltage VitQ's (150-250V, I think) from that e-bay seller in LA. If you get up into the several-hundred volt range, then they get gigantic. Something around 1-1/4" to 1-1/2" long may be OK. You only have about 1-1/8" height clearance in the 3rd slot and about 1-1/2" in the bottom slot - but I haven't checked the bottom slot clearance as much, so I maybe off on that.


----------



## SmartBomb

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Congrats! You may find that the sinks will get cooler with run in. Colin have been comparing notes on that lately and it seems to be the case with most of our builds._

 

I can confirm that both of my MAX builds got noticeably cooler after running in for 48 hours.


----------



## rhester

Got my power supply tonite and hooked it up. All mV were adjusted correctly and have a nice little glow from the tubes. Just waiting on my K42Ys to come in and some good hook up wire. Used BGs as the boutiques so I plan to let it burn in a good while before any critical listening.

 This forum was invaluable for all the pointers and tips (and tomb specifically).

 This proves that even us Mechanical Engineers can build things right.


----------



## ruZZ.il

Quote:


  Originally Posted by *tobias_svensk* /img/forum/go_quote.gif 
_..
 My PSU heatsink is madly hot but I guess 25.5VAC in under load is a bit on the steep side..._

 

Firstly, congrats! 
	

	
	
		
		

		
		
	


	




 Now, what kind of AC converter are you using? You should be able to turn the voltage up a bit, say to 27v. This would mean the regulator has to regulate the voltage to a closer value to its input, so it would dissipate less heat. Generally, a 24vAC output, when rectified, gives about 24*1.4=33.6v, though the rectifiers are diodes, so theres about a 1.5v drop (thats about 0.7v on each diode, and the current goes through 2 each cycle) so, 24*1.4-1.5=32 after the caps, you're left with a rough DC voltage of about (24*1.4-1.5)*0.9=28.9vDC the regulator needs about 2 volts to regulate down to a steady 27, which is just fine (note, the output of a 24vAC regulator is a little more than 24v, so its actually around 30v unregulated DC at this point). now lets say your amp draws half an amp(of current), the regulator would be dissipating 3 volts(30-27) time half an amp, (P=VI), about 1.5 watts of heat. If you're regulating down to 25.5V, thats about (30-25.5) times half an amp, so about 2.25 watts.. thats 50% more heat.. so, I suggest bumping your regulated DC value up a bit, and the regulator should run a little cooler.. hope this helps a bit 
	

	
	
		
		

		
		
	


	




 edit: I just found this, not sure what it says(I'm running out the door..) but it looks like it should graphically explain most of what's going on..


----------



## tobias_svensk

ruZZ.il;3503997 said:
			
		

> Firstly, congrats!
> 
> 
> 
> ...


----------



## ruZZ.il

strange toroidal configuration you have but 25.5vAC is good. I thought you meant your DC was set to 25.5. Anyway, with your toroid, the regulator would probably work sufficiently and coolest at around 28v.. sorry bout my confusion, but I hope you understand what I meant anyway


----------



## amphead

Quote:


  Originally Posted by *tobias_svensk* /img/forum/go_quote.gif 
_Thanks man 
	

	
	
		
		

		
		
	


	




 Remember to always turn your trimmers ALL the way and test... I had like all my adjustment on the last 10-20% of the turns.

 My PSU heatsink is madly hot but I guess 25.5VAC in under load is a bit on the steep side.

 Sadly I have to sleep now but tomorrow I will compare it to my QRV-04 (OPA627 + BUF634)

 Cheers_

 

Tobias congrats! Another Max Lives   

 About 50% who build the Max for the first time have the exact same experience you had, myself included.


----------



## slowpogo

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Now, if you are putting the MAX board on the bottom slot of the Hammond, that gives you plenty of room to tombstone even 0.47uf Sprague Vitamin Q's._

 

Should I infer from this that for the boutique film bypass positions, more capacitance is better? Could you hear a difference between .18uf and .47uf versions of the same cap? (Assuming size is no issue)

 I will be using the bottom slot, since I have a TKD pot I need to hand-wire anyway...so I will go nuts with the .47uf, if it's advantageous.


----------



## tomb

Quote:


  Originally Posted by *slowpogo* /img/forum/go_quote.gif 
_Should I infer from this that for the boutique film bypass positions, more capacitance is better? Could you hear a difference between .18uf and .47uf versions of the same cap? (Assuming size is no issue)

 I will be using the bottom slot, since I have a TKD pot I need to hand-wire anyway...so I will go nuts with the .47uf, if it's advantageous._

 

Generally speaking, the higher values may offer some additional smoothness, but bypassing is a highly variable experiment in each case. There's no guarantee that any combination of sizes works better than another without trying it for sure.

 I'm not aware of any downside with the larger bypasses, but there is bound to be a point of diminishing returns. Technically, the film bypasses are only there to make up for the limitations of the electrolytics, which are pretty much required because of the RC filtering efffect. This limitation is mostly in the higher frequencies where more distortion or harsh harmonics are formed in some electrolytics (I believe from what I've read). The guiding principle of the original Millett was that the Wima bypasses allowed regular power caps to work just as well as something boutique and expensive.

 All that's to say that improvements are probably slight. Bigger changes may be completely unpredicatable and you may be better off investing in better electrolytics.

 EDIT: There are at least two builders who've used 0.47uf Vitamin Q's (there may be more): MrMajestic2 and Colin Toole. Colin's are Philco brand, however, and no larger than 0.22uf K42's. I know he his quite happy with is. I would be recommending them to everyone as with the K42's, but have not found a reliable, steady source for them.


----------



## slowpogo

Thanks tomb, super helpful as always. One more capacitor question...Welborne Labs has Wima MKP10 .22uf at 160v. They are smaller than the 250v on the BOM (still 15mm spacing), and there's the advantage that Welborne will match pairs for $1.

 Is there any audible advantage to matching the Wimas, or is it plenty good to just go with the unmatched ones on the BOM?


----------



## tobias_svensk

Quote:


  Originally Posted by *ruZZ.il* /img/forum/go_quote.gif 
_strange toroidal configuration you have but 25.5vAC is good. I thought you meant your DC was set to 25.5. Anyway, with your toroid, the regulator would probably work sufficiently and coolest at around 28v.. sorry bout my confusion, but I hope you understand what I meant anyway 
	

	
	
		
		

		
			



_

 

Yeah I know, but it will work perfectly if I want to run my MAX and USBDAC that needs +5 & +/-15V and I found it in a dumpster 
	

	
	
		
		

		
		
	


	




 Today I bumped up the DC to 29V and set the DB bias to 200mV for now.

 Hard to compare it to my OPA627/BUF634 amp but the power and oumph in drums are better so far. But I guess it's hard to say something because my HD650 has been playing maybe 10-15h and in my dac I have new BG's and they are maybe 3h old.

 But it sure does sound great so far.

 /T


----------



## tobias_svensk

Quote:


  Originally Posted by *amphead* /img/forum/go_quote.gif 
_Tobias congrats! Another Max Lives   

 About 50% who build the Max for the first time have the exact same experience you had, myself included. _

 

Thanks man

 I had even more strange things going on today when I fired it up but that's classified 
	

	
	
		
		

		
		
	


	




 So it's time to dust off the other board I have.. 
	

	
	
		
		

		
		
	


	




 have to build the BJT version I guess. Are Jeff selling the components for that one? and do he have the bass slam BJT's that Tom have been talking about? And does somebody have some ES (and someother candy?) left over because I don't just want to order some ES only.

 Cheers


----------



## tomb

Quote:


  Originally Posted by *slowpogo* /img/forum/go_quote.gif 
_Thanks tomb, super helpful as always. One more capacitor question...Welborne Labs has Wima MKP10 .22uf at 160v. They are smaller than the 250v on the BOM (still 15mm spacing), and there's the advantage that Welborne will match pairs for $1.

 Is there any audible advantage to matching the Wimas, or is it plenty good to just go with the unmatched ones on the BOM?_

 

I don't know that anything other than the small transistors in the DB's are worth matching. Even then, the trimmers will compensate to a certain extent.

 I was going to say use the smaller voltage to buy a bigger uf rating at the same size, but that looks like the only one they have that's even close.

 There was another user and I that were exploring the possibility of Black Wima's. Unlike most who seem to put Wima's in the category of "cheap and common", I like the Wima's a lot - so does Pete Millett, I think 
	

	
	
		
		

		
		
	


	




. Consequently, I don't think anyone suffers much at all by building a complete-Wima MAX. So, the Black Wima's intrigued me if they were the same but better, but man - are they expensive!! VitQ's and K42's just beat them all to h*ll on price and it would've been a total experiment with no guarantee, to boot.

 Anyway, when it comes to the MAX, I don't think you give up anything by just buying them at Mouser, IMHO.


----------



## dsavitsk

Quote:


  Originally Posted by *slowpogo* /img/forum/go_quote.gif 
_Welborne Labs has Wima MKP10 .22uf at 160v. They are smaller than the 250v on the BOM (still 15mm spacing), and there's the advantage that Welborne will match pairs for $1._

 

Before you order for Welborne, search at Audio Asylum, here, diyaudio, etc. for lots of stories of people not getting parts or refunds -- sometimes in the 4 or 5 figure range. Also, cap matching makes no difference here.


----------



## jamess71

I'm getting ready to order the parts for my 1st Millet Max, 1 of 2. 

 Is the BOM on the MAX site up to date? Are there any substitutions you would recomend with the bom?

 Thanks
 James


----------



## ruZZ.il

Can't go wrong with the BOM but you may want to take a look at the cant miss boutique section to see if you'd like to seek some alternatives. I'd still suggest getting the whole bom anyway cause the boutique section would just substitute a 5-10$ chunk, if that.. Also, theres a little list in progress of bits and pieces here, some of which you may find you'd like to order too.. namely the tube bushings and silpads/thermasil insulating pads for the transistors and the regulator (you'd need 5).. posibly little nylon shoulder washers too depending on the transistors you use.. the part numbers can be found on the data sheets for the insulation kits there... hmm.. probably lots of other little bits and pieces too.. so while Im at it:
 Anyone, please feel free to contribute any interesting bits and pieces part numbers/locations you think may be relevant.


----------



## soloz2

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_EDIT: There are at least two builders who've used 0.47uf Vitamin Q's (there may be more): MrMajestic2 and Colin Toole. Colin's are Philco brand, however, and no larger than 0.22uf K42's. I know he his quite happy with is. I would be recommending them to everyone as with the K42's, but have not found a reliable, steady source for them._

 

 I got a package of 30 yesterday


----------



## el_matt0

does anyone know a P/N for those elegant looking stainless steel "tube guards"? Ive seen them in numerous builds around here but cant dig up any photos ATM. basically they look like 2 or 3 stainless steel rings supported by 3 or so vertical pieces. basically like a cylindrical cage surrounding the tube, but with the tops exposed. not sure if that was a great description (in fact i KNOW it wasnt) but hopefully someone knows what im talking about! anyone know where to order those? its basically in place of a tube bushing, although i know to use "tube guards" like this that the tube socket would have to be mounted up high, not like is commonly done on the MAX, so that the tube would be basically almost fully extruded from the top of the case.


----------



## IcantHearU

Here's a link to a set on ebay I came across recently

Tube Guard Protector tube Pre amp 12ax7 12au7 6922 5687 - (eBay item 290190951294 end time Dec-19-07 01:01:28 PST)

 And here's the VT4C site - this seller also carries the guards which have been linked in a previous post.

HiFi DIY Site - VT4C/211 Power Triode

 Good luck


----------



## GeWa

Almost there. I'm just a bit scared to fire it up though 
	

	
	
		
		

		
		
	


	



 Oh yeah, today I bought myself an AKG K-701, hope the two will match together.

 Regards


----------



## tobias_svensk

Looking good GeWa 
	

	
	
		
		

		
		
	


	




 just don't forget R1 like I did 
	

	
	
		
		

		
		
	


	




 Tjoho


----------



## el_matt0

Quote:


  Originally Posted by *tobias_svensk* /img/forum/go_quote.gif 
_Looking good GeWa 
	

	
	
		
		

		
		
	


	




 just don't forget R1 like I did 
	

	
	
		
		

		
		
	


	




 Tjoho_

 

x2 wheres R1


----------



## TheRobbStory

Noo! I built my Millett Hybrid Max last night, squeezed it into an ATI case, but I don't have a 24VAC walwart to power it! I thought I had one at work, but I was wrong. Looks like it's going to be a few more days waiting


----------



## IcantHearU

Quote:


  Originally Posted by *TheRobbStory* /img/forum/go_quote.gif 
_Noo! I built my Millett Hybrid Max last night, squeezed it into an ATI case, but I don't have a 24VAC walwart to power it! I thought I had one at work, but I was wrong. Looks like it's going to be a few more days waiting _

 

I did the same thing - doh - Then I couldn't wait for the delivery, so I ran to Radio Shack and picked up their 25.2volt 2 amp trafo (not plug in, wired) for $10 or so - works fine, but it's huge,ugly and I have nothing to case it up in as of now - but if you can't wait...


----------



## tomb

Quote:


  Originally Posted by *GeWa* /img/forum/go_quote.gif 
_Almost there. I'm just a bit scared to fire it up though 
	

	
	
		
		

		
		
	


	



 Oh yeah, today I bought myself an AKG K-701, hope the two will match together.

 Regards_

 

Yep - the guys are right about R1. You have an open circuit to the tube heaters without it. It's OK to put in a jumper, though, if you want. It's probably better for the heaters in the long run to have R1, but "long run" could be quite awhile. 
	

	
	
		
		

		
		
	


	




 It looks like you have the RB8 and RB9 resistors jumpered, so those should be BJT's in the diamond buffer. This description may help you as you start to bring your MAX alive 
	

	
	
		
		

		
		
	


	




 :

*DB Biasing (BJT's)*

*Startup:*
 Generally speaking, the differences in JFETs will determine the minimum current which seems to be anywhere from 20-40mV. It should take several turns to get a reaction from that point once you've turned them on.

 Put your probes in the test points for the DB's on one side. Kick the MAX on and off long enough to read your meter. Then move your probes to the other DB's, while kicking it on and off until you're sure that both sets are asleep (20-40mv or less). Then turn it back on and adjust the PS voltage to the desired value. Leave the amp on. Once that's set, then go back to the DB's.

*Start Adjusting - One DB, Then Another:*
 It should take several turns after that to notice the mV climb. Once the voltage starts to change, it will go 2 or 3mV per turn. Once you get to around 50mV on the DB's, the change may be 5mV per half-turn. When you're in the 60mV range, you can be pretty sure that the DB's are running in a minimum Class A and actually pulling DB current compared to the unadjusted position.

 When you get to 90mV or thereabouts, you'll notice that the change may be 5mV _per quarter turn_. This may be where some people get into trouble. If you kept turning it from the lower positions and never gave it a chance to run for awhile and heat up, it's fairly easy to get it to 150mV or more without hardly trying. One good way to keep from doing this is to try to keep the DB's even - adjust for 20mV or so, then go to the other one. In the time it takes to adjust the second DB, the first has had some heat on it for awhile.

 Be sure to check both test points on each DB - there will be a slight difference, depending on how well you did your matching, and how well the output transistors are matched (sort of out of your control). Pick the high one if the settings differ and use that as your guide.

*Adjust to 90mV, Adust Other Settings, Start Listening:*
 So, 80-90mV, ease up with a half-turn at a time, waiting about 5minutes inbetween until you get to about 90mV. I actually stop at this point and check all the other settings - bias the tubes, re-check the PS Voltage, etc. For a final check, measure the offset from Input Ground to Output Left, Right, and Ground - this should be in single-digit mV or just -0-. Then I plug headhones in and start listening at this point - probably for about an hour.

 Continuously check the DB settings for evidence of runaway (I unplug the headphones and turn the volume down for a measurement.) They should be hot on the sinks, but unchanging.

*Adjust for Final Setting:*
 When you're satisfied that the adjustments are stable (don't worry if the tubes keep bouncing around), then go back to adjusting the DB's for that final bit to 110mV (50ma current bias). At this point, the trimmers should be fairly close to a hair-trigger adjustment, especially when you close in on 110mV. You may notice that 1/8 turn can mean the difference between 110mv - 115mV. So, you need to be careful at that point.

 I've done six of them that way so far with the Murata trimmers - not a problem.

*Relative Adjustment Comparisons:*
 For reference, the PS voltage adjust moves about 0.1V every quarter turn. The tubes are similar to the DB's in that it takes quite a bit of turning to get them down to the half-voltage point (e.g., 27V PS, then 13.5V tube bias). However, they have a lot of undershoot and overshoot and may react in different ways depending on which direction you come at them. This is perfectly normal. At the desired bias point, the voltage may change by 1/2 volt per half-turn - sometimes, but then not other times. 
	

	
	
		
		

		
		
	


	







 They're tubes - you should get used to it. 
	

	
	
		
		

		
		
	


	




*Heat:*
 Another thing you will also notice is that the sinks should get slightly cooler with run-in - including the PS sink. Burn-in definitely makes a difference. They will also run cooler with high-impedance phones compared to low impedance phones or just sitting unloaded. None of those conditions should be risky, however. The sinks can be hot enough that it should feel very uncomfortable to the touch for even a few seconds - this is more on the PS sink than the DB's, which should run about 10deg.C. hotter than the DB sinks. Because the center two DB sinks are so close together, they will run noticeably hotter than the outside sinks. This is perfectly normal (it's called a design tradeoff).

 I haven't had a chance to post this on the website yet, but maybe it will help you now.


----------



## GeWa

Quote:


 just don't forget R1 like I did 
 

Done! Thanks Tobias
	

	
	
		
		

		
			





*tomb*

 Yes I'm using the 2SC2238/2SA968 combo. I'm gonna read your post a few times to make sure I don't screw up when I finally will fire it up.

 Regards


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## el_matt0

regardless of the amp at hand , the first power up is ALWAYS a bit of a nervewracking step! more often than not it goes well though! 
	

	
	
		
		

		
		
	


	




 best of luck Quote:


  Originally Posted by *GeWa* /img/forum/go_quote.gif 
_Done! Thanks Tobias
	

	
	
		
		

		
		
	


	




*tomb*

 Yes I'm using the 2SC2238/2SA968 combo. I'm gonna read your post a few times to make sure I don't screw up when I finally will fire it up.

 Regards_


----------



## pinkfloyd4ever

Quote:


  Originally Posted by *GeWa* /img/forum/go_quote.gif 
_Almost there. I'm just a bit scared to fire it up though 
	

	
	
		
		

		
		
	


	



 Oh yeah, today I bought myself an AKG K-701, hope the two will match together.

 Regards_

 

are those socket strips in the RB14 positions? I'm guessing you already know this, but don't forget to put either a jumper or a resistor (preferably HQ boutique like a Kiwame) in there, or you won't get any sound at the output!


----------



## el_matt0

good eye, x2 on that


----------



## ferds

@Gewa

 You forgot the most important part. the LED at the tube socket.
	

	
	
		
		

		
		
	


	




 Good Luck!!


----------



## slowpogo

Quote:


  Originally Posted by *pinkfloyd4ever* /img/forum/go_quote.gif 
_are those socket strips in the RB14 positions?_

 

Are those simply chopped up IC sockets, or actual "resistor sockets"?

 I was actually going to do the same thing to compare Kiwame vs Riken.


----------



## pinkfloyd4ever

ha, I dunno it's not my project, but I don't think there are sockets made specifically for resistors. They look like either one side of a DIP IC socket with all the actual sockets other than at the ends removed from the housing, or a SIP socket strip with the same deal, all but the sockets at each end removed from the casing they come in


----------



## GeWa

@ferds

 There are no LED's underneath the tube sockets. Power LED will be integrated in the front panel (3mm flat white LED).

 @pinkfloyd4ever and slowpogo

 Those are indeed "chopped up" IC sockets. Probably I will end up with two pieces of silver wire anyway but doing it like this gives room to experiment.
	

	
	
		
		

		
		
	


	




 Regards


----------



## TheRobbStory

Quote:


  Originally Posted by *IcantHearU* /img/forum/go_quote.gif 
_I did the same thing - doh - Then I couldn't wait for the delivery, so I ran to Radio Shack and picked up their 25.2volt 2 amp trafo (not plug in, wired) for $10 or so - works fine, but it's huge,ugly and I have nothing to case it up in as of now - but if you can't wait..._

 

Ah, thanks for the tip! Rat Shack carries an 18/24vac walwart for $22, but your post reminded me of the 25v torroid in my M^3 power supply. I'll give that a shot tonight. Hopefully I can breathe life into my Millett!


----------



## amphead

Quote:


  Originally Posted by *GeWa* /img/forum/go_quote.gif 
_Almost there. I'm just a bit scared to fire it up though 
	

	
	
		
		

		
		
	


	



 Oh yeah, today I bought myself an AKG K-701, hope the two will match together.

 Regards_

 

If you use a can't miss build from TomBs web site, the K701s will make you very happy. Thats what I use most of the time.


----------



## jamess71

Ok I ordered all the parts from mouser to build 2 Millet Max's. Parts should arrive on tuesday. 
	

	
	
		
		

		
		
	


	




 All parts from the BOM on the MM site. I still need to order pot/tubes. I know I can get the pot from Amb or Tangents site. 

 Where should I order the tubes and sockets? Any recomendations for store and also what type I should get? My main headphones are ATH-A900LTD. I would like at least one set for low gain. Thanks for any pointers.

 James


----------



## ruZZ.il

Tom recommended Vacuumtubes.net to me a little while ago. My last purchase was from Radio Daze, and they were great. I think they were running out of the tubes we used.. I think we killed them  I got the gold plated sockets from parts conneXion  along with some black gates and RCA jacks I think.. I need more tubes too..
 Tom maybe you should get a big box of tubes and sockets for your front too?

 From the max site(here):
 There are 3 tubes commonly referenced for the Millett and Millett MAX:
 # 12AE6 (later version: 12AE6A) .... basic amplification factor of 14
 # 12FM6 ............................................... basic amplification factor of 10
 # 12FK6 ............................................... basic amplification factor of 7

 FKs are probably your best bet. I'm not sure how sensitive your cans are, but at 40ohm, the FKs should be fine. I'm not sure about the sonic differences, but supposedly the FK's are favorable in most ways.. I'm sure someone else could elaborate more..


----------



## tomb

Great post as usual, ruZZ.il - and very informative, too!

 Nah, I'll leave tubes to the guys who know it best. Being able to keep track of old tubes, purchasing from liquidating stores, old estate sales, etc., etc. - that kind of salvage and scavenging takes a special talent. I mightily respect what these tube vendors do. The fact that they are willing to fool with us and our little $3-$5 tubes is even more amazing.

 So, ya'll please keep that in mind when you're dealing with the vacuumtubes.net's, Radio Daze's, etc. of the world. They probably exert the utmost patience when they receive a request for "2 - GE's with halo top getters in original boxes that are matched" - or whatever else one of you may specify (myself included in the past).

 I suppose if you're paying $5 or more for a Millett tube, then maybe that buys you the right to specify a preference. However, I've taken to buying what I can get - then picking out the good from the bad. Hopefully, we can keep the vendors that do supply us, happy - so that they'll continue to purchase and supply us with more of these tubes.


----------



## slowpogo

Speaking of tube sockets...I apologize if this info is on the Max site and I'm missing it (and search is too massive), but what's the tried and true procedure for removing the center part of the socket so the LEDs can shine through?


----------



## ferds

i used plier or cutter plier to removed the "rivet" in the center of the socket. Then i used superglue or epoxy to bond them together. HTH


----------



## soloz2

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Great post as usual, ruZZ.il - and very informative, too!

 Nah, I'll leave tubes to the guys who know it best. Being able to keep track of old tubes, purchasing from liquidating stores, old estate sales, etc., etc. - that kind of salvage and scavenging takes a special talent. I mightily respect what these tube vendors do. The fact that they are willing to fool with us and our little $3-$5 tubes is even more amazing.

 So, ya'll please keep that in mind when you're dealing with the vacuumtubes.net's, Radio Daze's, etc. of the world. They probably exert the utmost patience when they receive a request for "2 - GE's with halo top getters in original boxes that are matched" - or whatever else one of you may specify (myself included in the past).

 I suppose if you're paying $5 or more for a Millett tube, then maybe that buys you the right to specify a preference. However, I've taken to buying what I can get - then picking out the good from the bad. Hopefully, we can keep the vendors that do supply us, happy - so that they'll continue to purchase and supply us with more of these tubes._

 


 I just email Radio Daze what I want and they have it ready for me to pick up later that day!


----------



## naamanf

I just drill it out form the top. Then used a bit of super glue to hold it all together.


----------



## tomb

Quote:


  Originally Posted by *slowpogo* /img/forum/go_quote.gif 
_Speaking of tube sockets...I apologize if this info is on the Max site and I'm missing it (and search is too massive), but what's the tried and true procedure for removing the center part of the socket so the LEDs can shine through?_

 

This is covered on the MAX website under *Tweaks -> Tube Lights*


----------



## tomb

BTW - CA glue is fine if you use the thick or GEL, IMHO. However, 15 minute epoxy is probably best. 5-minute is fine if you've only two sockets and work fast. 
	

	
	
		
		

		
		
	


	




 Rubber bands to hold the halves together while curing works well for me.

 The problem with certain types of glue is that the sockets undergo a huge amount of flexing stress. As Naamanf will probably agree, it's more of a center-wing-joint than a rib joint or sheeting joint. 
	

	
	
		
		

		
		
	


	







 EDIT: As noted on the MAX site reference above, DO NOT USE Gorilla glue. It will expand into the socket pins and render the socket useless. You'll get some on the pins even when using epoxy, but those glues do not expand and will break away from any pin-to-ceramic joint after a few flexes.


----------



## joneeboi

Drilling it shouldn't be a problem. I tried desoldering mine from my board since I wasn't planning on having tube LEDs at first, but I'll be darned if that giant ground plane wouldn't keep sucking all the heat out of the joints. Turning the heat up all the way didn't seem to matter. I just drilled it while it sat on the board and things turned out great. The top popped right off, and I think I permanently ruined the drill bit because it seems the metal tab melted right onto it.

 And who can resist the draw of that orange aura?


----------



## el_matt0

on the topic of taking apart the tube sockets. i saw ferds mentioned it above, but i dont believe its mentioned on the MHMAX site. i had a ton of success just simply using a fine pair of wire snips. i started out with a small flat tipped jewelers screwdriver like is recommended on the mhmax site, but as u will see if you try it, once u pry it open a bit you can basically "see" the part of the center pin that you need to cut. easy as pie, cut that and the halves fall apart with the pin falling out either side. id say this is far easier than drilling it out or the other techniques recommended. although there MIGHT be some slight risk to the socket itself, at no point in doing this did I feel like i was putting enough tension on the socket or the pins of the socket to break either or - so id say realistically if your careful this is a pretty damn safe and FAST way to get this done. superglue worked fine for me to glue em back together - however i find with superglue its always better to err on the side of too little rather than too much glue 
	

	
	
		
		

		
		
	


	




! good luck!
 PS just got my hands on a couple 0.22mF K42's (thanks to thomaskuhn 
	

	
	
		
		

		
		
	


	




) and ive got my blackgates on the way from PCX, just a matter of finding 2SC2238/2SA968 now 
	

	
	
		
		

		
		
	


	




 . anyone have spares, or is ebay my only option haha!


----------



## tomb

Well, caution is advised.
	

	
	
		
		

		
		
	


	




 I have never been able to pry the pins apart far enough to get anything in them - small screwdriver or otherwise - and have destroyed quite a few sockets in the process. There is a wide variance in these things as mentioned on the MAX website. The gold-pin ones at Parts Connexion have a bottom half that's only 1/16" thick or less. Only the utmost care will prevent breaking one.

 Pulling apart the pins with a plier is even worse. The metal is so soft it's like trying to grab silly putty with the pliers - they deform rather than allow any kind of grip. Drilling is the only thing I've found that consistently works for all the sockets. Even then, I break 1 out of 5 or so.

 Maybe I'm just ham-handed.


----------



## el_matt0

@ tomb, well i DEFINITELY never suggested grabbing the pins with pliers, if i did that was a typo lol. i imagine like you say there is probably quite a ton of variance in the builds of the tube sockets. i did have the feeling that the ones i was working with (stock from jrossels kit) were necessarily of the utmost highest build quality, which is why i could maybe so easily fit a fine pair of snips in there. 
 question, 2SC2238/2SA968 diamond buffers, this is a terribly clueless question but what position do those go in and how many do i need for the boutique build? all the other parts for cant miss #1 seem pretty well specified but i was slightly unclear on the diamond buffer front! also, would u suggest just going with ebay to get those (ive heard some mention of fakes etc, but......is that a realistic concern). thanks 4 the help


----------



## tomb

The legend for BJT positions can be found on the MAX website at *Output Stage -> BJT Diamond Buffer*

 This is what it looks like 
	

	
	
		
		

		
		
	


	




 :


----------



## bperboy

Hah, I've done it by grabbing the central pin with pliers before; you're right, it just falls apart. I just kept doing that until the damn thing fell apart!


----------



## el_matt0

Quote:


  Originally Posted by *bperboy* /img/forum/go_quote.gif 
_Hah, I've done it by grabbing the central pin with pliers before; you're right, it just falls apart. I just kept doing that until the damn thing fell apart!_

 

lol, kinda wanna try that


----------



## el_matt0

question, is there any reason i dont see more MHMax's using chassis-top mount tube sockets, and showing off the tubes and tube lights more? i was thinking I might switch to that, as I'm really not seeing a ton of my tube or tube lights right now (obviosuly not that that effects SQ in the slightest), but i assume its a perfectly viable option right?


----------



## slowpogo

Maybe the worry is that the wires from socket to board would introduce noise? Just a guess. Also, from dealing with tube guitar amps with the tube sockets connected remotely by wire, I can tell you, it can potentially be a real pain.


----------



## jamess71

el_matto the 2SC2238/2SA968 are for QB8/QB9 and you'll need 2 of each one. you can get them at Newark.com It looks like there is a 10 day lead time for the the 68 though. 

 James


----------



## b17m4p

Capacitor 0.0047mfd 200vdc VitaminQ type(20) - (eBay item 320129310199 end time Dec-16-07 14:10:36 PST)

 So is something like this what I could use for CA8 a la Can't Miss Built #1?


----------



## slowpogo

Quote:


  Originally Posted by *b17m4p* /img/forum/go_quote.gif 
_Capacitor 0.0047mfd 200vdc VitaminQ type(20) - (eBay item 320129310199 end time Dec-16-07 14:10:36 PST)

 So is something like this what I could use for CA8 a la Can't Miss Built #1?_

 

Those are actually way too small..."mfd" is the same as "uf," and the BOM calls for 0.22uf.

 I have 20 Vitamin Q's coming in the mail, 0.27uf 100v. They are about 1 1/4" tall. I'll be keeping 4 for myself and selling the rest in pairs.

 ...but it will probably be a week or so before that happens. Thought I'd let you know, since what I just bought off eBay is what you're looking for, basically.

 *I have also seen 0.18uf Vitamin Q's on ebay from the same seller...those would work well too (was discussed a few pages back)


----------



## bperboy

Quote:


  Originally Posted by *slowpogo* /img/forum/go_quote.gif 
_Maybe the worry is that the wires from socket to board would introduce noise? Just a guess. Also, from dealing with tube guitar amps with the tube sockets connected remotely by wire, I can tell you, it can potentially be a real pain._

 

Yeah, probably most people don't want to bother with it; it'd be a pain to setup, and a Hammond probably wouldn't be the first choice of casing, which is one of the nice features of this board revisions..


----------



## n_maher

Quote:


  Originally Posted by *el_matt0* /img/forum/go_quote.gif 
_question, is there any reason i dont see more MHMax's using chassis-top mount tube sockets,_

 

It's a huge pain in ass for one thing.


----------



## Ferrari

Quote:


  Originally Posted by *el_matt0* /img/forum/go_quote.gif 
_question, is there any reason i dont see more MHMax's using chassis-top mount tube sockets, and showing off the tubes and tube lights more?_

 

It can be done with a little bit more work but I'm agreed... for some people it can be a huge pain in ass 
	

	
	
		
		

		
			





 as n_maher said.
 Most people (probably > 95%) take the easy way and go for the standard Hammond box, the result is what you see !
 I have done that before on my old 2-channel MH (now converted into a 3-channel active ground version without the output capacitor C7L/R). No noise/hum noticed BTW.


----------



## pabbi1

Well, it has been a long time, and nothing attributed to site availability...

 The FrankenMaxx lives, in thanks to many here or at least close by. Amphead for fixing my aborted left channel, Alex (APureSound) for troubleshooting _something_ in the S/PDIF receiver, then figuring out the right channel on the OPUS was whacked, and to Brian (Twisted Pear) for shipping me a new unit with the utmost dispatch.

 Final specs: 2x MillettMax boards, wired balanced to Neutrik combo jacks (1 balanced, or 2 SE), fed by an Twisted Pear OPUS DAC from their S/PDIF receiver. Powered by two toroids - main at 26v, the Twisted Pear stack at 15v.

 To wit:






 Now, all cased up, and it's innocuous appearance to the outside world:






 I have no firm impressions yet as it needs to burn for a week or so, but the Denon 2k is probably not the best fit. We'll see about a balanced RP-21 (I REALLY like those for closed phones), but the DAC is really nice so far - not up to the Azur 840c, but nor should it. Already great imaging, air, seperation and detail. I am already thinking balanced HD600 - my true dynamic love.

 Good enough for the office (damn near anyone's office, dynamically speaking), and thoughts of giving it to the son in law for Christmas have vanished.

 Now to burn a bit, then change out the 12ae6a to the 12fk6 for some serious evaluations. Time to fork over for some Tung Sol fk6 - dirt cheap compared to chasing Mullard el34.

 Ready for a Dallas meet in January.


----------



## joneeboi

That's some really impressive work, pabbi. Glad it worked out for you in the end. That thing is a beast!


----------



## tomb

Wow, pabbi! That's fantastic. You fought long and hard for that glorious thing - very, very nice!! I envy the folks in Dallas.


----------



## amphead

Woo Hoo, Pabbi thats going to be a serious contender at the Dallas meet. Good to see results from lots of hard work. Looking forward to the sonic evaluation!


----------



## slowpogo

I just noticed something new (to me) on the Max site..the part about the center support hole in the PCB.

 Does anyone have some part numbers of appropriate spacers for that? Or any general advice about creating some support under the PCB?


----------



## el_matt0

i just used a standard bolt with 3 or 4 nuts underneath since the gap in a hammond case is a little bit too small for even the smallest sized brass spacers my local store carries. my local place also has simple white plastic spacers which im sure you could cut to the right length if you would rather go that route. but, simply just using 2 or 3 nuts together on one bolt has the same effect, and if u use a long enough bolt that u can keep one nut on the top side of the board as well, that will allow you to "tweak" it to the exact right height.


----------



## n_maher

Quote:


  Originally Posted by *slowpogo* /img/forum/go_quote.gif 
_I just noticed something new (to me) on the Max site..the part about the center support hole in the PCB.

 Does anyone have some part numbers of appropriate spacers for that? Or any general advice about creating some support under the PCB?_

 

Search mouser for "aluminum standoff" and you should be able to locate what you're looking for.


----------



## slowpogo

Quote:


  Originally Posted by *n_maher* /img/forum/go_quote.gif 
_Search mouser for "aluminum standoff" and you should be able to locate what you're looking for. 
	

	
	
		
		

		
		
	


	


_

 

Ya, I figured that much out. I was wondering if anyone knew the specific length the standoffs need to be (I'd measure it but I don't have the hammond case yet). I guess they're cheap enough that I'll just order a variety, and some washers.


----------



## tomb

I use a 1/2" long 4-40 screw with a combination of washers and spacers and a nylon lock nut on the end. A metal nut is OK, but it will scrape when you slide the board into the case. That's not really a problem, either, because you can still lift up on the board when sliding it in, then release the tension when you get it in place. A thick nylon nut on the bottom is ideal, though, IMHO.

 What you want is something long enough to touch bottom so that it prevents the board from flexing in the middle when you push down to plug in the tubes. That's when it recieves the most stress - it's not too bad when pulling tubes out.

 Anyway, it's about 1/2" from the top of the board to the inside bottom of the case. So a lock washer and flat washer on top of the board under the head of the screw and some combination of washer/spacer/nut underneath does the trick.

 You can always drill a hole in the bottom of the case and secure it clean through, but I've never trusted myself to drill the hole in the right place. 
	

	
	
		
		

		
		
	


	





 EDIT: As Structural Engineer Nate will tell you 
	

	
	
		
		

		
		
	


	




, please don't build your MAX without something supporting through that center hole. The board is awfully wide and sometimes it takes some real force to plug those tubes in the socket - especially the first time or two. It's possible to weaken or crack some of the traces if you don't.


----------



## rhester

Is there any consensus on wether a boutique resistor will help in RB14 vs a jumper? And if so, is there nayplace in the states to get them (kiwame or stackpole)?


----------



## tomb

Quote:


  Originally Posted by *rhester* /img/forum/go_quote.gif 
_Is there any consensus on wether a boutique resistor will help in RB14 vs a jumper? And if so, is there nayplace in the states to get them (kiwame or stackpole)?_

 

Yeah, I think a case can be made for something like a 10ohm Stackpole or Kiwame. It can filter out just enough tube noise and harshness to perhaps sound better than jumpering, but you'd have to try on an individual basis. It probably depends on one's own particular build.

 I think when you get up to 47ohms or more, the attenuation effects outweigh any perceived benefit in "sweetening" the sound. People may still want that much resistance or more, though, depending on whether they are using very low impedance phones and desire a lot of volume knob travel.

 Kiwame's are at PartsConnexion (Canada) and HiFiDIYSupply(? - Hong Kong) or something like that - whichever are the ones that carry the Obligatto caps. Stackpoles are at Handmade Electronics (Pennsylvania). IMHO, the Stackpoles get you pretty close to Kiwames and cost pennies. Some people have mentioned Rikens, too, but I've never had the privilege of trying those.


----------



## amphead

While thinking about what a stepped attenuator might sound like on the Max, I thought of something else. If a switch could "switch in" the volume pot and also "switch out" the volume pot, while switching in a single value kiwame/stackpole resistor for each channel that produced the same attenuation/resistance value most often used for listening with the pot. This would produce a very low priced version of a stepped potentiometer. Is it crazy? Yes, but if done properly it might be a good mod.


----------



## vixr

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_
 You can always drill a hole in the bottom of the case and secure it clean through, but I've never trusted myself to drill the hole in the right place. 
	

	
	
		
		

		
			



_

 

use the bare PCB and mark all the holes in the case before you build the pcb up. the PCB will lay flat on the bottom of the case and then just pencil mark thru the holes in the PCB...


----------



## n_maher

Quote:


  Originally Posted by *vixr* /img/forum/go_quote.gif 
_use the bare PCB and mark all the holes in the case before you build the pcb up. the PCB will lay flat on the bottom of the case and then just pencil mark thru the holes in the PCB..._

 

That's exactly how I do it too. 
	

	
	
		
		

		
		
	


	




 One more reason to always buy 2 pcbs.


----------



## UglyJoe

Hey guys,

 I've had zero cash flow for about 5 months, and I've avoided this thread like the plague since then (I can't bare to look at everyone's builds when I have two lonely boards just sitting there, waiting to be populated). Finally got some money to stuff the MAX, so I've gone back to looking at the website and trying to piece together all the new information that has come out since then. The first thing I note is the major differences in the Boutique builds, and of course some cap changes, etc. So, I've put together a BOM for myself, and hoped you guys could comment on it, plus answer a few questions.

 Everything else as per the standard BOM

 CA4,CA5: Nichicon 1000uF 50V Electrolytic UPW1H102MHD
 CA2: Black Gate NX 1000uF, 25V Boutique
 CA7: Black Gate NX 680uF, 35V Boutique
 CA9: WIMA (or none)
 CA8: Russian PiO K42Y-2 0.22uF 160V +/-10%

 I've noticed that the recommendation for CA4/5 is 1800uf 35V Panasonic FM's. How much better (if at all) would this be than the Nichicons? I'm trying to keep all of my order except for the boutiques from Jeff Rossell to keep down the shipping costs, and I don't think he carries the FMs. 

 Speaking of caps, is there any way of getting a hold of the Russian K42s besides buying them in bulk from ebay?

 For the DBT's I'll be using the MJE243/MJE253 transistors at first (those are the ones available from Jeff) as well as the 12ae6/a tubes. Any other combination of tubes/transistors that would work better with the proposed Caps I've chosen from above?

 Lastly, I'll be using Grados; has anyone had experience with a MAX/Grado combination and what is the best resistor values at RB14 to get the correct bass response out of the amp for the 32 ohm cans?

 Thanks,
 UJ


----------



## joneeboi

I'll give it a shot.

 The 1800uF CA4,5 recommendation AFAIK was made just because it can fit the 1" height limitation of the Hammond. Bass response will be minimally appropriate at 1000uF; the 1800uF and 2200uF caps were just recommended because the height works. Unless you have a provision for avoiding height limitations, 1000uF, 1800uF, and 2200uF will work fine. The sound difference will probably be negligible, as will the cost.

 Grados require a pretty low gain, and the 12FK6 tube will be your best bet at good component interaction. If you want to use the 12AE6 with RB14s, then Stackpoles off eBay, partsconneXion, Handmade Electronics, etc, will be good in terms of price/quality. Kiwames are a bit pricier, so you'll want to avoid those. The RB14s boutiques tend to reduce high end harshness, so if you want to tame some of the Grado brightness, that might work well for you. I believe Colin populated RB14, but I couldn't tell you with what. As for resistor values, I think 20ohms has worked well (for someone), but I may just be spewing hot gas at this point.

 As for the K42s, PM tomb. I don't want to speak for him, but I think he'll be okay with supplying you with some. He should have quite a few extras. 
	

	
	
		
		

		
		
	


	




 The only builders I can think of that worked with the Black Gates were tomb and pabbi, so you can ask them for impressions. Again, boutique combinations as well as sound signatures can be as personal as human voices, so YMMV is in strong effect here. There is the famous BG break-in period to worry about, so you'd have to wait to get the full sonic signature of your MAX.

 The MAX is a difficult project in that it requires the steady application of the basics of electronics, ie. avoid cold solder joints, don't flip transistors, remember when and where to jumper, make sure your resistor values are correct, etc. The board is beautifully made and is of high Olimex quality, so you don't have to worry too much about burning it up. The ground plane can be very annoying to work with too, so be sure to be careful when soldering things like the tube sockets to the ground points. Heatsinks will be annoying to remove if you don't do it right, so be sure to do them right the first time. An annoying thing about kits, I've found, is that they only supply you with exactly what you need. If you misplace or destroy any of the parts, you may be in trouble. We've seen a trend for RB2 to burn up unexpectedly, so make sure your DB transistors are all correctly matched and correctly oriented.

 Mr. Toole has done a very good job of designing the board, so everything should be pretty straightforward. We're here when you need us, and the willingness of past builders to continually contribute to this thread is something you only see in select build threads. Either way, we're all here to help.


----------



## willisv

Quote:


  Originally Posted by *UglyJoe* /img/forum/go_quote.gif 
_Hey guys,

 I've had zero cash flow for about 5 months, and I've avoided this thread like the plague since then (I can't bare to look at everyone's builds when I have two lonely boards just sitting there, waiting to be populated). Finally got some money to stuff the MAX, so I've gone back to looking at the website and trying to piece together all the new information that has come out since then. The first thing I note is the major differences in the Boutique builds, and of course some cap changes, etc. So, I've put together a BOM for myself, and hoped you guys could comment on it, plus answer a few questions.

 Everything else as per the standard BOM

 CA4,CA5: Nichicon 1000uF 50V Electrolytic UPW1H102MHD
 CA2: Black Gate NX 1000uF, 25V Boutique
 CA7: Black Gate NX 680uF, 35V Boutique
 CA9: WIMA (or none)
 CA8: Russian PiO K42Y-2 0.22uF 160V +/-10%

 I've noticed that the recommendation for CA4/5 is 1800uf 35V Panasonic FM's. How much better (if at all) would this be than the Nichicons? I'm trying to keep all of my order except for the boutiques from Jeff Rossell to keep down the shipping costs, and I don't think he carries the FMs. 

 Speaking of caps, is there any way of getting a hold of the Russian K42s besides buying them in bulk from ebay?

 For the DBT's I'll be using the MJE243/MJE253 transistors at first (those are the ones available from Jeff) as well as the 12ae6/a tubes. Any other combination of tubes/transistors that would work better with the proposed Caps I've chosen from above?

 Lastly, I'll be using Grados; has anyone had experience with a MAX/Grado combination and what is the best resistor values at RB14 to get the correct bass response out of the amp for the 32 ohm cans?

 Thanks,
 UJ_

 

I just finished upgrading my millet max that was a stock glassjar audio kit.
 I ended up going with:

 CA4,5: Haven't had a chance to change these yet (kit came with 470uF 50v nichicon kz's) but will upgrade to 1800 fm's soon to hopefully increase bass.

 CA2: Muse ES 1000uF 16v

 CA7: Muse ES 470uF 35v

 CA9: stock Wima's

 CA8: Russian K42's .22uF

 Tubes: 12FK6 GE

 DBT's: 2SC2238/2SA968

 This combination sounds very good, much better than the stock version. The highs are crystal clear and don't sound harsh at all. I also have the blackgates to try but it sounds so good already I will save them for a different build. The bass isn't too pronounced but that is probably due to not changing C4,5 yet. The 12FK6 tubes are nicer sounding than the 12AE6 that came in the kit in my opinion. The only thing I am not sure about is the 2SC2238/2SA968 transistors, I was expecting big changes from these but they didn't really impress me that much... I think the 243/253 works just as good. I would recommend getting the right DB transistor's the first time because they are a huge pain to change out later.


----------



## joneeboi

x2 on the transistor changing.

 I personally liked how the 2SC3422/2SA1359 transistors fit into my MAX. They gave a very nice balance of sound, with quick and precise highs combined with punchier and fuller bass. As they broke in, the bass took over quite a bit, but that faired well in my system. The 2SC2388 seems to be quite popular though.


----------



## pinkfloyd4ever

Quote:


  Originally Posted by *willisv* /img/forum/go_quote.gif 
_.........
 .................
 This combination sounds very good, much better than the stock version. The highs are crystal clear and don't sound harsh at all. I also have the blackgates to try but it sounds so good already I will save them for a different build. The bass isn't too pronounced but that is probably due to not changing C4,5 yet. The 12FK6 tubes are nicer sounding than the 12AE6 that came in the kit in my opinion. The only thing I am not sure about is the 2SC2238/2SA968 transistors, I was expecting big changes from these but they didn't really impress me that much... I think the 243/253 works just as good. I would recommend getting the right DB transistor's the first time because they are a huge pain to change out later._

 

Where did you get your DB transistors? If it was off eBay, there's a very good chance they're counterfeit, which could be at least part of the absence of a major change in sound from the standard BJTs. If you're using the 2SC2238/2SA968 pair, I'd assume you're going for the ultimate in clarity and detail, so I'd go ahead and use your Blackgates, unless you plan on building another with the 2SC2238/2SA968 or the 2SC2344/2SA1011 pair(MCM actually has both of that pair in stock, so u can be sure you're getting the genuine one). And yes, Panasonic FMs should help with the bass, as well as everything else. Finally, how long have you given all this to burn in? NOS tubes take quite awhile to burn off all the crap that's slowly built up over the years. Also, just to warn you, the BG NX's take at least a good 200 hours to get close to their potential, and they will at times sound downright crappy at times up to that point. As long as you're confident that you've got everything dialed in well & don't have to worry about anything nasty like thermal runaway, I don't see any reason not to leave music or some good ol' pink noise looping on your Max (while connected to a pair of cans) overnight or while you're gone to work or whatever during the day. Quote:


  Originally Posted by *joneeboi* /img/forum/go_quote.gif 
_Kiwames are a bit pricier, so you'll want to avoid those. The RB14s boutiques tend to reduce high end harshness, so if you want to tame some of the Grado brightness, that might work well for you. I believe Colin populated RB14, but I couldn't tell you with what. As for resistor values, I think 20ohms has worked well (for someone), but I may just be spewing hot gas at this point._

 

I'm gonna have to respectfully disagree with you on that one jonee. My philosophy is that if you're building this in such a way as most of us are, willisv included, you want it to sound the best it can (with the exception of going wayyy all-out like ferrari) so to me, $2 for 2 kiwames is worth the ~10% (quoting tomb there) difference they give over 2 stackpoles at .20 cents...with shipping, its almost gonna even out anyway. If it was one of those last fraction of 1% things, then I'd prolly agree with you, but I've heard more than a couple people say they had experience with the 2 and that the difference b/t Kiwames and Stackpoles was at least more than "just noticable"....anyway, just my 3 cents (that's right baby, 3 
	

	
	
		
		

		
		
	


	




 )


----------



## pinkfloyd4ever

crap, mybad, duplicate post


----------



## joneeboi

I'm sure in terms of sound quality, the Kiwames will stack (that's right, baby 
	

	
	
		
		

		
		
	


	




) better against the Stackpoles. It just seemed to me UJ was trying to go for a relatively low cost, high quality MAX, so I was trying to suggest the more cost-sensitive approach. You're right about shipping evening things out though, which is funny considering I just paid $22(ouch) for shipping from AMB for two Mini3s-worth of parts. I personally haven't had any experience with either as I ultimately jumpered my RB14s, but it seems more people than none want to reduce their effective gain in the MAX boutique resistor style. I've ever only seen the Kiwames at DIY HiFi Supply, though they are carried elsewhere, and they have a 10 piece minimum order with $7 shipping (for resistors?) which was taken into account when I was telling UJ to avoid them. I don't know where DIYing head-fiers usually get them, so I guess that's where my miscalculation comes in. Thanks for chiming in.


----------



## xmokshax

I posted this in the FS/FT forums a while back, and i think in this thread too, but got no responses, so I figure I'll give it one more shot:

 does anyone have any 470uF/35V or 1000uF/16V or 25V Muse ES caps that they'd be willing to part with? 

 I haven't soldered the KZ's from Jeff's MAX kit into my board yet, but it seems that they'll necessitate mounting the board in a lower slot than recommended (moving all the panel components off-center). I'd really appreciate it if anyone can help me out - I was trying to finish this amp in time for Christmas for someone. Thanks!


----------



## pinkfloyd4ever

Quote:


  Originally Posted by *joneeboi* /img/forum/go_quote.gif 
_I'm sure in terms of sound quality, the Kiwames will stack (that's right, baby 
	

	
	
		
		

		
		
	


	




) better against the Stackpoles._

 

heh, well played, sir 
	

	
	
		
		

		
		
	


	




  Quote:


  Originally Posted by *joneeboi* /img/forum/go_quote.gif 
_ I've ever only seen the Kiwames at DIY HiFi Supply, though they are carried elsewhere, and they have a 10 piece minimum order with $7 shipping (for resistors?) which was taken into account when I was telling UJ to avoid them. I don't know where DIYing head-fiers usually get them, so I guess that's where my miscalculation comes in._

 

partsconnexion has Kiwames


----------



## tomb

Good posts all three - Joneeboi, Willisv and Pinkfloyd4ever!!

 I concur with everything you guys have said.

 The only question seems to be between the Stackpoles and Kiwames, but that is a difference of opinion, nothing more. Yes, the Kiwames are better but more expensive. Is that difference very much at 10ohms? Probably not. At 47ohms and greater? Probably. So, it depends - it's an individual preference, for sure.

 You can summarize by what we've suggested a few times before: buy the Stackpoles in varying sizes until you find the resistance that gives you the volume knob travel you like - then go buy the Kiwames at that rating. 
	

	
	
		
		

		
		
	


	




 BTW, Kiwame's are at PartsConnexion, Stackpoles at Handmade Electronics. Both vendors in my experience are absolutely reputable, reliable and fast.

 Ugly Joe - 
 Using the 1000uf 50V, which I'm assuming are the same ones used in the PS, is a good choice if that's the one available. Any differences with the FM's will be in the margins.

 About the transistors - The jury is out concerning the 2SC2238/2SA968's. I will attempt to do further testing when I get a chance. I have both the Chinese variety and the supposedly "genuine" Toshibas from MCMinone. I'll let you know if I find a difference. For the time being, I would have to agree with Willisv that the MJE 243/253's are perhaps as good. That may mean there's something to the counterfeit rumors.

 In the meantime, however, I can assure you that the 2SC3422/2SA1359 and 2SC3421/2SA1358 pairs are at the same time, better and different. The rockin slam (both lows and highs) are a dependable upgrade with the 2SC3422/2SA1359. The unequalled bass extension and pronounced highs of the 2SC3421/2SA1358 are likewise dependable. You can use either and be assured that the change is equal parts noticeable and an improvement, IMHO.


----------



## pinkfloyd4ever

does Handmade have a minimum order for people within the US?


----------



## slowpogo

Uh-oh. I just bought "Toshiba" 2SC2238/2SA968's off ebay. If they're just generic transistors labeled Toshiba, I can live with it I guess, as long as they are in fact 2SC2238/2SA968's.

 But is someone suggesting that they're not even that?


----------



## pinkfloyd4ever

Quote:


  Originally Posted by *slowpogo* /img/forum/go_quote.gif 
_Uh-oh. I just bought "Toshiba" 2SC2238/2SA968's off ebay. If they're just generic transistors labeled Toshiba, I can live with it I guess, as long as they are in fact 2SC2238/2SA968's.

 But is someone suggesting that they're not even that?_

 

crap. I need to watch what I say. I'm guessing you got em from allpartspipe? I wouldn't fret too much about it. I could tell you what I _think_ the deal is, but that's not worth much; I'm no EE. Could one of our resident EEs jump in and tell us about em? Are they the same basic construction just with lower quality materials & construction? n_maher, 04blumach, soloz2, dsavitsk, tangent? (or anyone else I'm forgetting)


----------



## slowpogo

I actually got them from goodbuy711. I didn't get them for the Toshiba name, I got them because that's the only place I could get both transistors at once. As long as they work, I'll be OK.


----------



## tomb

All of these transistors are functional replacements for one another. That's the problem - although functionally equivalent, the tonal qualities vary greatly.

 For instance, if one were to look at Steinchen's review list, the 2SC5171/2SA1930 look to be the fastest with the best ratings. Yet, Steinchen calls them "warm and dark." He's made at least one forum post stating the same thing: very dark.

 So, testing and rating are no guarantee of tonal quality, IMHO - unfortunately. That makes it difficult to ever make a determination short of listening from one to the other. 
  Quote:


  Originally Posted by *pinkfloyd4ever* /img/forum/go_quote.gif 
_crap. I need to watch what I say. I'm guessing you got em from allpartspipe? I wouldn't fret too much about it. I could tell you what I think the deal is, but that's not worth much; I'm no EE. Could one of our resident EEs jump in and tell us about em? Are they the same basic construction just with lower quality materials & construction? n_maher, 04blumach, soloz2, dsavitsk, tangent? (or anyone else I'm forgetting)_


----------



## joneeboi

A package from partsconneXion is waiting for me at home.

 Huzzah!


----------



## willisv

pinkfloyd4ever:

 I think you may be right about the ebay transistors being fake, Blumach warned me about that right after I posted where I bought them. I will probably try to source some from elsewhere just to be sure. I guess the only way to know for sure is to buy them from the same place Steinchen did.

 TomB:

 I would be very interested to find out how those tests go with the Chinese and the "real" 2SC 2238/2SA 968 transistors. I wish Jeff or someone would sell a boutique kit in various flavours so that a person doesn't have to order parts from 10 different places... I would gladly pay more for these parts if I could get them from 1 spot. Also thanks for the heads up on Radio Electric, these guys sell their tubes for cheap and are very reasonable on shipping.


----------



## tomb

Quote:


  Originally Posted by *willisv* /img/forum/go_quote.gif 
_pinkfloyd4ever:

 I think you may be right about the ebay transistors being fake, Blumach warned me about that right after I posted where I bought them. I will probably try to source some from elsewhere just to be sure. I guess the only way to know for sure is to buy them from the same place Steinchen did.

 TomB:

 I would be very interested to find out how those tests go with the Chinese and the "real" 2SC 2238/2SA 968 transistors. I wish Jeff or someone would sell a boutique kit in various flavours so that a person doesn't have to order parts from 10 different places... I would gladly pay more for these parts if I could get them from 1 spot. Also thanks for the heads up on Radio Electric, these guys sell their tubes for cheap and are very reasonable on shipping._

 

AFAIK, Steinchen bought his at Fibra-brandt. The only reasonable source other than that - that are definitely Toshiba - are from MCMinone, but the stock is spotty at best. (Note Newark sub-purchases from MCMinone.) Someone stated a few posts back that they're in stock - they're not. There are few 2SC2238's, but the 2SA968's have been out for awhile. As we all know, they're pretty much useless without the other.

 Jeff is the kit man. As for the rest, I'm working on it. 
	

	
	
		
		

		
			





 Yeah, Radio Electric Supply - otherwise known as vacuumtubes.net - are one of the good guys. Dale and Roy are always very helpful and as you say: lots of selection and good prices. However, the Millett tubes are starting to get a little scarce. Ruzz.il once suggested to start a blog for parts. I'm thinking it may be a good idea for tubes. To be honest, I've discovered a few here and there - but then bought all their stock. One had a couple dozen, another about the same - that's the way it goes. There are more finds to be made, but it will take some effort.


----------



## willisv

Quote:


  Originally Posted by *slowpogo* /img/forum/go_quote.gif 
_I actually got them from goodbuy711. I didn't get them for the Toshiba name, I got them because that's the only place I could get both transistors at once. As long as they work, I'll be OK._

 

Allpartspipe and goodbuy711 are the same guy, that's where I bought mine from also. They don't sound bad at all, maybe my expectations were too high.


----------



## joneeboi

When I stocked up on tubes, I emailed vacuumtubes.net about 12FK6s and they replied that they had found 200 more a little before I emailed. I bought 10 tubes from them asking for all RCA, GE, or Sylvania with halo getters; a pretty tall order for $2 or $3 per tube for any tube supplier. I ended up with 3 RCAs, 7 unbranded, and no haloes. On the receipt the extra notes actually had "NO HALOS." I emailed them and they didn't answer back. I probably shouldn't have asked in the first place, but they at least could have said that it was too much trouble so I wouldn't have ended up disappointed. I understand where they're coming from, but dang, those haloes look too cool.


----------



## willisv

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_AFAIK, Steinchen bought his at Fibra-brandt. The only reasonable source other than that - that are definitely Toshiba - are from MCMinone, but the stock is spotty at best. (Note Newark sub-purchases from MCMinone.) Someone stated a few posts back that they're in stock - they're not. There are few 2SC2238's, but the 2SA968's have been out for awhile. As we all know, they're pretty much useless without the other.

 Jeff is the kit man. As for the rest, I'm working on it. 
	

	
	
		
		

		
		
	


	




 Yeah, Radio Electric Supply - otherwise known as vacuumtubes.net - are one of the good guys. Dale and Roy are always very helpful and as you say: lots of selection and good prices. However, the Millett tubes are starting to get a little scarce. Ruzz.il once suggested to start a blog for parts. I'm thinking it may be a good idea for tubes. To be honest, I've discovered a few here and there - but then bought all their stock. One had a couple dozen, another about the same - that's the way it goes. There are more finds to be made, but it will take some effort._

 

Thanks for the Info TomB, looking forward to seeing what you got cooking!


----------



## willisv

Quote:


  Originally Posted by *joneeboi* /img/forum/go_quote.gif 
_When I stocked up on tubes, I emailed vacuumtubes.net about 12FK6s and they replied that they had found 200 more a little before I emailed. I bought 10 tubes from them asking for all RCA, GE, or Sylvania with halo getters; a pretty tall order for $2 or $3 per tube for any tube supplier. I ended up with 3 RCAs, 7 unbranded, and no haloes. On the receipt the extra notes actually had "NO HALOS." I emailed them and they didn't answer back. I probably shouldn't have asked in the first place, but they at least could have said that it was too much trouble so I wouldn't have ended up disappointed. I understand where they're coming from, but dang, those haloes look too cool._

 

I ordered 2- 12FM6, 2- 12AE6A, and 2- 12FK6. I ended up with GE's for the FK's (1 top getter and 1 side getter), RCA's for the AE6'6 (both top getter's), and GE's for the FM's (1 top getter and 1 side getter). It would have been nice to have exact matching sets, but I was happy to get the same brand per set.


----------



## amphead

Just ordered 2 GEs w/halo and 2 RCA w/halo and 4 sockets. Someplace in Canada. I will let you know how I do.


----------



## 04BluMach

Quote:


  Originally Posted by *joneeboi* /img/forum/go_quote.gif 
_I'll give it a shot......

 Grados require a pretty low gain, and the 12FK6 tube will be your best bet at good component interaction. If you want to use the 12AE6 with RB14s, then Stackpoles off eBay, partsconneXion, Handmade Electronics, etc, will be good in terms of price/quality. Kiwames are a bit pricier, so you'll want to avoid those. The RB14s boutiques tend to reduce high end harshness, so if you want to tame some of the Grado brightness, that might work well for you. I believe Colin populated RB14, but I couldn't tell you with what. As for resistor values, I think 20ohms has worked well (for someone), but I may just be spewing hot gas at this point...

 ....The only builders I can think of that worked with the Black Gates were tomb and pabbi, so you can ask them for impressions. Again, boutique combinations as well as sound signatures can be as personal as human voices, so YMMV is in strong effect here. There is the famous BG break-in period to worry about, so you'd have to wait to get the full sonic signature of your MAX._

 


 The Kiwames can be sourced from Parts Connexion - they are a cut above the Stackpoles. Since there are only the two RB14's in the signal path its not a big price to pay for SQ. 
 I have used 22 Ohms for RB14 - my burned out ears prefer the Kiwame smoothness over the jumpered out option. I plan to go with a switched selection for this third planned build. This should be a great way to have the option of either with or without Resistor in the sig path. May find it a great way to feed your mood at the moment - Lushness vs Rock Slam.
 Parts Connexion is a convinient source for Boutique MAX components beyond the mainstream Mouser & Digikey components....




 Those components just arrived in less than a weeks time via standard ship - Kiwame, Black Gates, Vampire Connectors, Ceramic Gold contact PCB Tube Sockets.

 So we are about to add at least another Boutique Black Gate build to the MAX community...
	

	
	
		
		

		
		
	


	





  Quote:


  Originally Posted by *joneeboi* /img/forum/go_quote.gif 
_Mr. Toole has done a very good job of designing the board, so everything should be pretty straightforward. We're here when you need us, and the willingness of past builders to continually contribute to this thread is something you only see in select build threads. Either way, we're all here to help._

 

Couldn't agree more with this.... this board exudes CETOOLE craftmanship and excellent build quality. Immediate on-line support is nearly unparalleled with an outstanding MAX Build information and guide website.


----------



## 04BluMach

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_......

 About the transistors - The jury is out concerning the 2SC2238/2SA968's. I will attempt to do further testing when I get a chance. I have both the Chinese variety and the supposedly "genuine" Toshibas from MCMinone. I'll let you know if I find a difference. For the time being, I would have to agree with Willisv that the MJE 243/253's are perhaps as good. That may mean there's something to the counterfeit rumors.

 In the meantime, however, I can assure you that the 2SC3422/2SA1359 and 2SC3421/2SA1358 pairs are at the same time, better and different. The rockin slam (both lows and highs) are a dependable upgrade with the 2SC3422/2SA1359. The unequalled bass extension and pronounced highs of the 2SC3421/2SA1358 are likewise dependable. You can use either and be assured that the change is equal parts noticeable and an improvement, IMHO._

 

Steinchen's Diamond Buffer Transistor Review is still the most authoritative and complete informational source on this subject that is available to the Head-Fi'r DIY community. His audio observations on each pair are concise and provide a consistent comparison and terminology for each pairings audio qualities.

 2x on the 2SC3422/2SA1359 and 2SC3421/2SA1358 pairs...!
	

	
	
		
		

		
		
	


	



 I would add the Sanyo 2SC2344/2SA1011 to that list as one my favorite pairs.
	

	
	
		
		

		
		
	


	




 Of course YMMV! They offer a clear and airy sound with good detail and seperation. Dynamic and detailed bass. With the Ncihicon ES & Clarity SA Caps they do not have "piercing highs" since they are a very smooth coupling cap pair. Could be a good choice for Auricaps Films and others that may have highs rolled off! 

 I really can't comment on the MJE's since I have never used those with either the Rev Millet Hybrid dDB or the MAX. 

 However, it has been postulated that the MAX may be bringing out the best in all BJT's that are placed in this circuit since the higher Bias current is bringing them closer to their optimum and operating points. That is they are approaching their most dynamic and sweeter capabilities in the MAX vice the Rev Millet Buffer.

 Certainly something to be said for this - the MAX is certainly a dynamic cut above the dDB Buffer outfitted Rev Millet Hybrid...
	

	
	
		
		

		
		
	


	




  Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_AFAIK, Steinchen bought his at Fibra-brandt. The only reasonable source other than that - that are definitely Toshiba - are from MCMinone, but the stock is spotty at best. (Note Newark sub-purchases from MCMinone.) Someone stated a few posts back that they're in stock - they're not. There are few 2SC2238's, but the 2SA968's have been out for awhile. As we all know, they're pretty much useless without the other._

 

From the very long design & build thread, it appeared that Steinchen sourced all of his BJT's from Fibra-Brandt. At the time, they were the only consistent and available source for the 2SC2238/2SA968 - which appeared IMHO to be Steinchen's favorite for the dDB application. Since I didn't want to pay the shipping cost to the US for a couple of transitors...

 I was fortunate to catch the 2SC2238/2SA968 pairs when they were in stock at MCM for a brief period. Yes, they are BETTER and different than the other BJT pairs (sorry TOMB just had to use your quote!). 

 Steinchen, I feel, very accurately captures their audio signature as... "neutral and balanced sound, tight bass. detailed and clear highs without being bright, easy to listen to excellent choice but note reversed pinout!"



			
				willisv;3532195 said:
			
		

> pinkfloyd4ever:
> 
> I think you may be right about the ebay transistors being fake, Blumach warned me about that right after I posted where I bought them. I will probably try to source some from elsewhere just to be sure. I guess the only way to know for sure is to buy them from the same place Steinchen did.
> 
> ...


----------



## tomb

Great posts, 04BluMach!!

 Yeah, I'm thinking there's a fairly noticeable difference between the Toshiba vs. Chinese 2SC2238's. At least that vendor I trust was honest about them being Chinese copies. 
	

	
	
		
		

		
		
	


	




 On a different note, here's a challenge to you talented guys with the tube sockets.
	

	
	
		
		

		
		
	


	







 Take a look at the sockets 04BluMach purchased from PartsConx - can you pry those pieces apart without breaking that bottom section? 
	

	
	
		
		

		
		
	


	









 All the ones with gold pins are like this, AFAIK.


----------



## naamanf

I have the same ones and just drilled out the top. I think I used 1/8" bit. It's very soft metal and I can't imagine breaking the socket doing it this way.


----------



## ruZZ.il

I broke 2.. though I had this really cheap drill bit that would heat up before getting far, cease up and.. well.. though I got a proper drill bit set which goes through them like butter


----------



## kklee

I just dismantled four of these over the weekend. I drilled out the bottom and they came apart easily. Judging by the amount of stamped metal holding them together, prying won't be very helpful.


----------



## slowpogo

(whoops)


----------



## willisv

For all those with 2SC2238/2SA968 pairs in their Max:

 I have been doing some tube rolling because I wasn't really happy with the sound I was getting. The GE 12FK6's sounded O.K. but it was almost like the highs were overly bright and maybe smeared a bit, bass was very weak. I tried the 12AE6's (two different sets, RCA and Standard Brand) and it was pretty much the same thing... the highs just sounded unnatural and there was no bass. I put the GE 12FM6's in there not expecting much since they don't seem too popular with the Millet Max crowd. This actually shocked me how good it sounded, I listened for a while and decided that these were the best sounding tubes for my Max. The bass was very strong with these tubes, the highs sounded very natural and forward and the sound stage increased dramatically. I let them burn in overnight and they seem to be holding up nicely... very sweet sounding and musical. Keep in mind I have Muse Es's in CA7 and CA2 with K-42's in CA8, Wima's in CA9, and RB-14's jumpered.


----------



## joneeboi

Quote:


  Originally Posted by *04BluMach* /img/forum/go_quote.gif 
_Immediate on-line support is nearly unparalleled with an outstanding MAX Build information and guide website._

 

We're actually just a few replies shy of being "The Most Replied to Thread in the DIY Subforum."

 Most views is another matter, sadly.


----------



## tomb

Quote:


  Originally Posted by *joneeboi* /img/forum/go_quote.gif 
_We're actually just a few replies shy of being "The Most Replied to Thread in the DIY Subforum."

 Most views is another matter, sadly._

 

Shhhh .... you'll jinx it.


----------



## ruZZ.il

not of we can help it


----------



## xmokshax

i have a question for anyone who's ordered a MAX kit from Jeff: does anyone know what kind of matching he does on the transistors? must they still be matched when received, or are all the ones he sends of a certain type pretty well matched with one another?


----------



## amphead

Thats probably a question for TomB. Speaking of TomB, thanks package received today.


----------



## tomb

Quote:


  Originally Posted by *amphead* /img/forum/go_quote.gif 
_Thats probably a question for TomB. Speaking of TomB, thanks package received today. _

 

That's great news!

 No, I can't tell you if Jeff matches transistors. Truth is, the MAX is pretty tolerant and will do fairly well without matching. Matching is probably one of those things in the last 10% of improvements, but someone will have to ask him to know for sure.

 If he does, then there's more evidence of the quality he puts in his kits. If not, then that tells you the MAX will give you great sound without a lot of effort - witness the many satisfied customers of Jeff's kits.

 Seems as if the answer is a win-win either way.


----------



## willisv

Quote:


  Originally Posted by *xmokshax* /img/forum/go_quote.gif 
_i have a question for anyone who's ordered a MAX kit from Jeff: does anyone know what kind of matching he does on the transistors? must they still be matched when received, or are all the ones he sends of a certain type pretty well matched with one another?_

 

Jeff does match transistors. After I ordered my Millet max kit from him he said he would ship it but first he had to match 100 transistors.


----------



## xmokshax

Quote:


  Originally Posted by *willisv* /img/forum/go_quote.gif 
_Jeff does match transistors. After I ordered my Millet max kit from him he said he would ship it but first he had to match 100 transistors._

 

excellent. Jeff did label the bag containing the CCS parts as "match transistors", but i wasn't sure if that was a direction (as in, "make sure you match them yourself"), or if it was a descriptor (as in, "these four are all matched well to one another"). it's good to hear that he does match, but it's also nice that the MAX design is pretty tolerant. i actually soldered the CCS transistors in last night before realizing that matching might be an issue, and actually stopped stuffing the board because was worried that i might be compromising the amp's quality. i'm glad that i wasn't.

 oh, and on a side note, i did e-mail Jeff first to ask him myself, but i'm sure he's pretty busy and i'm trying to complete the MAX in time for Christmas, so i figured i'd ask on here as well. if he gives me more information on precisely which transistors he matches (all, or just the CCS, or what), i'll post it on here for the common good.

 and now, off to solder like mad and hopefully get to biasing tonight as well!


----------



## amphead

One thing that I am wondering about, is......when we eventually run out of the standard mini 7 pin tubes for the Max, will we be able to create a version that uses 12au7. The 12au7 has a gain from 14 - 20, can run at 48v B+, and runs at higher current of course, and is 9 pin which can be worked around. There will be no end to the availability of the 12au7, which is used in the SOHA of course. What are the chances of Colin pulling that off? Anyone?


----------



## jerrygp

Just put about thirty hours on my 2nd max with Black Gates and the Russian K42's at CA8...breaking in verrry sweetly. You guys are the best. Got parts for a third and will be doing "can't miss" build #2 or 3. Thought I was overdoing it buying three boards at the beginning, but...


----------



## amphead

Yeah, thats the way the Max effects most of us. Our not so secret audio addiction. he he


----------



## ruZZ.il

hmpf, I only got 2.. I'll have to do some of the miniMax's when the come out 
	

	
	
		
		

		
			





 ... I'll probably have to start selling some too since I've got more amps than I can listen to.. and *need* to make more.
 I wonder what the market calls for for the can't miss builds built well.. my neurotic perfectionistic soldering should be worth.. something..


----------



## Hubbard0

There's a lot of pages, but these last few make it sound like there is a place to pick up PCBs for the Millet. Is that the case, cause if so I'll pick one up very soon?


----------



## tomb

Quote:


  Originally Posted by *amphead* /img/forum/go_quote.gif 
_One thing that I am wondering about, is......when we eventually run out of the standard mini 7 pin tubes for the Max, will we be able to create a version that uses 12au7. The 12au7 has a gain from 14 - 20, can run at 48v B+, and runs at higher current of course, and is 9 pin which can be worked around. There will be no end to the availability of the 12au7, which is used in the SOHA of course. What are the chances of Colin pulling that off? Anyone?_

 

Probably not. The design belongs to Runeight and he's working on a Super SOHA. My guess is that it will _not _be in the direction that Colin likes to go, however - single, all in one board - but that's Runeight's decision to make.

 I will have to post those specs we ran on the 12AU7 and the 12AE6. It's true that the availability is much better for the 12AU7, but the advantages quickly diminish after that. As noted earlier, running the 12AU7 at reduced voltage results in numbers that become a splitting-hairs-difference when compared to the 12AE6 at 24+V.

 We keep looking at the 6GM8, so that may be an option in the future. It's a really sterling tube, but there are some particular problems with implementing it in the Millett - no more than using the 12AU7, however. 

 Interestingly, we just learned a few posts ago that vacuumtubes.net stumbled onto over 200 Millett tubes recently. They haven't raised the price yet, either (they have some of the lowest prices around). Radio Daze may yet have a bunch - we were just killing them on specifying brands, construction, etc. - at the price that they charge. So, we may have a ways to go before the Millett tubes become really scarce.

 Still, it may be of benefit to start posting good vendors who source these tubes, (as mentioned earlier). When I get through with current projects, I'll try to implement a blog on the MAX site for tube vendors.

 EDIT: In the meantime, ruZZ.il has started a nice thread on DIYforums, where he is listing sources and parts not normally availble for Mouser/DigiKey, et al.


----------



## slowpogo

Anyone know anything about Consolidated Electronics (Consolidated Electronics, Incorporated)? Also called the "The Amazing Semiconductor Store."

 They have Toshiba 2SA968/2SC2238's. They claim they have been carrying Toshiba semiconductors for years, because hardly anyone else imports them. They also carry all the other major brands, Sanyo, Fairchild, Motorola, etc.

 I called them and they only have a dozen 2SA968's, but have many 2SC2238. Their prices are cheap, perhaps suspiciously so. Around 80-90 cents each.

 Anyone have a gut reaction to this? I considered flat-out asking the guy, "There's a well-known problem with counterfeit power transistors, are yours legit?" Maybe I should have.


----------



## el_matt0

Quote:


  Originally Posted by *slowpogo* /img/forum/go_quote.gif 
_Anyone know anything about Consolidated Electronics (Consolidated Electronics, Incorporated)? Also called the "The Amazing Semiconductor Store."

 They have Toshiba 2SA968/2SC2238's. They claim they have been carrying Toshiba semiconductors for years, because hardly anyone else imports them. They also carry all the other major brands, Sanyo, Fairchild, Motorola, etc.

 I called them and they only have a dozen 2SA968's, but have many 2SC2238. Their prices are cheap, perhaps suspiciously so. Around 80-90 cents each.

 Anyone have a gut reaction to this? I considered flat-out asking the guy, "There's a well-known problem with counterfeit power transistors, are yours legit?" Maybe I should have._

 

...uh oh, dont send me those then! 
	

	
	
		
		

		
		
	


	







 lol, im jk if its legit its all good, but hows it lookin on your ebay lot?


----------



## amphead

Quote:


 Probably not. The design belongs to Runeight and he's working on a Super SOHA. My guess is that it will not be in the direction that Colin likes to go, however - single, all in one board - but that's Runeight's decision to make. 
 

Well thats Ok, since we are finding more Millett tubes. Looking forward to building the miniMax in balanced configuration, now that I have tubes in hand for that build.


----------



## slowpogo

Quote:


  Originally Posted by *el_matt0* /img/forum/go_quote.gif 
_...uh oh, dont send me those then! 
	

	
	
		
		

		
		
	


	







 lol, im jk if its legit its all good, but hows it lookin on your ebay lot?_

 






 There doesn't seem to be any conclusive evidence that the ones commonly found on ebay are fake. I've been doing a lot of googling and reading on other forums. 

 All I really know at this point is, fake semiconductors exist; Toshiba power transistors are a popular target for this; and, I just bought Toshiba power transistors, so I can only wonder if they're real!

 They haven't arrived yet, but I've found a few definite tip-offs of whether they're real or fake...involving the lettering and the quality of its printing, the color of the backplate, and some other things. I'll have to check mine against these details. 

 According to other Max builders, they do *work* at least. Which suggests to me, at the worst they're Chinese functional copies.

 I don't know el_matto, I wasn't aware of this stuff at all when I bought the ebay lot, or when I offered to sell you the spares. If you have second thoughts that's totally understandable, PM me and we'll work it out.


----------



## el_matt0

lol no no you misunderstood me im just poking fun. haha. im with you on that one, if they ARE ultimately fakes im sure at least that they are functional replicas. albeit obviously i would prefer thats NOT the case but in the end hey what can you do right?


----------



## xmokshax

another quick question: what's the mimimum acceptable gauge for the wiring from the board to the AC jack? i know that i've used 22AWG solid-core wire in past amps with no problem, but the MAX is pulling significantly more current than other amps i've built. will 22AWG still be OK, or do i need to get something bigger? if the latter, can i just use multiple strands of 22AWG, or will that add some sort of parasitics that will negatively impact the sound?


----------



## el_matt0

im 99% sure 22AWG should be adequate. IF you were really worried about it u could either go to 18 or 20 AWG. or like you said you could just use dual strands of 22 awg per each. i dont think that would affect SQ at all. just make sure all your pairs are twisted or braided to avoid hum but thats about it. honestly i think u should be fine with the 22awg as is though, im pretty sure thats all im using in my MHMAX.


----------



## xmokshax

thanks, el_matt0. i'll probably go ahead and use a single strand of 22AWG.


----------



## tomb

Quote:


  Originally Posted by *xmokshax* /img/forum/go_quote.gif 
_thanks, el_matt0. i'll probably go ahead and use a single strand of 22AWG._

 

el_matto is correct. However, just to ease your mind: Most wire mfrs rate the ampacity of 22ga with teflon insulation (the insulation we seem to use most around here) at *4.5A*. I think we have a ways to go with the MAX at even half that amount.


----------



## 04BluMach

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Probably not. The design belongs to Runeight and he's working on a Super SOHA. My guess is that it will not be in the direction that Colin likes to go, however - single, all in one board - but that's Runeight's decision to make._

 

I have been anxiously awaiting further info on Runeight's "Super" SOHA and of course its final unveiling. I would assume that he is further developing the SOHA off line in his own Skunk Works to maintain close hold to his intellectual property this time around. I have stayed away from the current available SOHA PCB till we have a true "Runeight" PCB available.
	

	
	
		
		

		
		
	


	




 TOMB do you have any personal insight or knowledge on the status of Runeight's SOHA?

 I was very sorry to see Runeight decide to no longer participate in the DIY forumns (or at least to very infrequently participate). He always cheerfully offered so much of his knowledge and would go out of his way to help impart an understanding of various projects that he would become involved with. He was (and still is) a major contributor to the DIY community.

  Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_....We keep looking at the 6GM8, so that may be an option in the future. It's a really sterling tube, but there are some particular problems with implementing it in the Millett - no more than using the 12AU7, however._

 

If I remember correctly, there is a 6GM8 "Millet Inspired" prototype that has been floated by Dsavitsk . The MEHA and also originally as the Millett 2?

 Would be sweet to have Dsavitsk and CETOOLE to collaborate on a 6GM8 MEHA possibly with a Balance PS using just a small Film cap at the Tube output into a set of MAX'd Out Diamond Buffers thereby eliminating the need for the large Output Caps. 
	

	
	
		
		

		
		
	


	




 ....Stop it I'M DROOLING...
	

	
	
		
		

		
		
	


	




 Where do we sign up....? 
 Any other interested Head Amp Fiends out there for what could be the Ultimate "Millet Like" Amp?

 I believe also that John Broskie has a low voltage 6GM8 version of his Akido available.


----------



## pinkfloyd4ever

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_el_matto is correct. However, just to ease your mind: Most wire mfrs rate the ampacity of 22ga with teflon insulation (the insulation we seem to use most around here) at *4.5A*. I think we have a ways to go with the MAX at even half that amount. 
	

	
	
		
		

		
		
	


	


_

 

ya, I was just about to order some wire from Navships, and I thought I'd go up to 24 ga. just to be sure...so, you'll be fine with 22. Is there any reason that my results using 24 ga would be any different than using 22? Also, solid or stranded? Or is that another big can o' worms?


----------



## slowpogo

Quote:


  Originally Posted by *pinkfloyd4ever* /img/forum/go_quote.gif 
_Also, solid or stranded? Or is that another big can o' worms?_

 

In this case I would say it doesn't really matter. It's not in the signal path so the tenuous arguments about sq don't play into it. Wire inserted into terminal blocks horizontally will not strain as much as a vertical pcb connection...so the argument about solid wire breaking easily is kind of muted.

 The biggest consideration for me would be, what are you going to use the other 49 feet of wire for? 
	

	
	
		
		

		
		
	


	




 If you want to make interconnects or headphone cable, stranded might be preferable. But some prefer solid for that stuff too...

 Hell, get whatever color you like best.


----------



## dBel84

Quote:


  Originally Posted by *04BluMach* /img/forum/go_quote.gif 
_I have been anxiously awaiting further info on Runeight's "Super" SOHA and of course its final unveiling. ....

 TOMB do you have any personal insight or knowledge on the status of Runeight's SOHA?_

 

not to thread-jack but rumours spread so quickly ... it has gone through several design phases and after a few distractions has been finalised. The concept amp sounds phenomenal and so should SOHA II which is in prototype phase. runeight will post more news in good time. 

  Quote:


  Originally Posted by *04BluMach* /img/forum/go_quote.gif 
_I believe also that John Broskie has a low voltage 6GM8 version of his Akido available._

 

 Runeight has not been completely idle .. The EHHA is a low voltage tube amp which utilises the 6GM8. I have it biased 150mA into class A - I don't need a heater in my office 
	

	
	
		
		

		
			





 ..dB


----------



## amphead

Update: Specifying (12AE6A) 2 GE and 2 RCA with Sylvania as a third choice, I received 2 RCA (side halo) and 2 Sylvania(trapezoidal getter). So this is the availability from Tube Depot currently. Popped the Sylvanias into the functional Max expecting a lesser tone and........very nice! Don't be afraid to use Sylvanias.


----------



## tomb

Quote:


  Originally Posted by *amphead* /img/forum/go_quote.gif 
_Update: Specifying (12AE6A) 2 GE and 2 RCA with Sylvania as a third choice, I received 2 RCA (side halo) and 2 Sylvania(trapezoidal getter). So this is the availability from Tube Depot currently. Popped the Sylvanias into the functional Max expecting a lesser tone and........very nice! Don't be afraid to use Sylvanias. _

 

Yes - you're right. In my experience, the Sylvania 12AE6 probably has the best highs of any 12AE6. I'm a certified bass head, though, and they seemed to lack the punch of the GE's. 
	

	
	
		
		

		
		
	


	




 Also, Amphead - your post emphasizes a good point. Just because the MAX has those killer DB's and a lot of our discussion has been on BG's, ES's, VitQ's, K42's, etc. - that doesn't mean that tube changes aren't noticeable. Rolling tubes in the Millett is a worthwhile effort and may effect a large part of the sound of the amp.

 Rolling is a bit more difficult in a Millett, however, because the tubes were so widely sub-contracted from one company to the other. RCA's telltale is the squished octagon with the tube designation. GE's are the etched dots. The other mfr was either Sylvania or Tung-Sol - or both. There's a very good web page by Jeff Duntemann that explains many of the space-charge tubes:

Space Charge Tubes: Tube Projects Without Lethal Voltage!

 On this page, he states that Tung-Sol was the originator of the space-charge tubes, so maybe they have to be the other mfr. Tung-Sol Millett tubes seem to have the most "air" IMHO, but they also seem to be the most scarce. I've always had trouble believing that they were the 3rd or 4th mfr of these tubes because of their scarcity. I suppose research and development doesn't parallel manufacturing ability.

 Colin also clued me into another tube on this list: the *12FT6*. It appears to be a one-to-one equivalent of the 12AE6 (unlike the 12AJ6 which has a gain of 55!). Another one for you guys to investigate, neither Colin nor me have found it listed at any tube vendor. I even sent an e-mail to Dale and Roy at Radio Electric Supply (vaccumtubes.net):

_Thomas,

 Must be a really obscure tube. We have never seen one, but it is in the databases. I sure wouldn't engineer anything around it. You would have a really tough time finding replacement tubes.

 Dale_






 Let me know if any of you spot one.


----------



## amphead

Yeah, I noticed exactly the same signature change with the Sylvanias, lots of detail, tight recessed bass, but most importantly no "mid bloom". The RCAs that I tried were more punchy/dynamic and very good overall. Where we go down the road, will depend on our tube availability and future circuit design breakthroughs.


----------



## joneeboi

Update on my MAX:

 Changes:
 - CA2/7 Panasonic FC 1000uF to Black Gate Standard 1000uF 
 - CA4/5 Nichicon UPW 470uF to Panasonic FM 1800uF
 - Removed CA8/9

 Glittering Generalities:
 - More minute bass detail passed through to my ears and brain
 - Soundstage changed (wider?)

 Burning it in as I leave for a party soon 
	

	
	
		
		

		
		
	


	




 (stupid finals...*grumble*)


----------



## jerrygp

This is not the correct forum for this, but I searched the computer-as-source forum and could find no help. Can someone pm me and explain what a DAC's function is in a computer audio environment? As far as I've been able to decipher, it converts digital information to analog information for the purpose of what? I have a high end home audio system and a high end self built computer with sound card, but mainly get my audio through headphones via an IAudio X5L and a number of DIY headphone amps - the Millet Hybrid being one of them. Does a DAC fit into this scenario at all or is it strictly for providing a signal to a home preamp or amp setup through a computer cd player or some sort of cd transport system? I know this is not the right forum for this question and if someone can point me to the right place, I would appreciate it. I am trying to further my audio education at the expense of you guys...


----------



## amphead

Well, you are almost there. Yes a dac is a (digital to analog converter). There are dac's and then there are DAC's. The quality of the conversion process impacts the resulting sound greatly. What conversion process you ask? Well digital encoded audio is ones and zeros, which are square waves. Analog signals are variations of sine waves, which transmit frequencies of sound. Therefore using a mathematical algorithm, the digital square wave is transformed into the analog waveform. Speakers/headphones work with analog waveforms, to produce sound, where voltage is converted to current in the amplifier, to move the coil of the headphone/speaker which in turn pushes air to give you music. Interestingly enough there may be a tube dac project coming this spring. That would be a DAC!!!!!


----------



## tomb

Quote:


  Originally Posted by *jerrygp* /img/forum/go_quote.gif 
_This is not the correct forum for this, but I searched the computer-as-source forum and could find no help. Can someone pm me and explain what a DAC's function is in a computer audio environment? As far as I've been able to decipher, it converts digital information to analog information for the purpose of what? I have a high end home audio system and a high end self built computer with sound card, but mainly get my audio through headphones via an IAudio X5L and a number of DIY headphone amps - the Millet Hybrid being one of them. Does a DAC fit into this scenario at all or is it strictly for providing a signal to a home preamp or amp setup through a computer cd player or some sort of cd transport system? I know this is not the right forum for this question and if someone can point me to the right place, I would appreciate it. I am trying to further my audio education at the expense of you guys..._

 

You had it right - it converts digital information to analog information. There are many esoteric uses for any device that serves as a source for digital music files. Connect a DAC with compatible inputs for the source's outputs, and it will convert those digitial files to analog. Most high-end DACs also include an elaborate I/V conversion, because a DAC in its purest form outputs small levels of current - way too low to be used as a source for most audio equipment.

 But that's getting too far into the nits. In it's most prevalent use (IMHO), it allows the use of a computer as your primary music source. Connect a DAC to your computer - then mp3 files, FLAC files, wav files, CD drives, etc. - may be used to connect directly to your preamp or headphone amp setup. In simple terms, it serves the same purpose as your computer's sound card, but at a much, much higher level of detail and quality.

 For instance, a high-end quality DAC will easily blow away any sound card. Even a low-end DAC, such as the Alien DAC, will better most all built-in sound cards and some after-market sound cards. I don't have super-expensive sources - mostly Sony and Technics CD and DVD players, both portable and home component versions, and a few iPods. However, my Alien DAC blows away all of them in sound quality with superior detail and frequency response. Only a line-out iPod comes close. An M-Audio Transit is comparable - better in noise, but not in detail, IMHO. _For instance, all I listen to with my Millett MAXes are FLAC files on the computer played through Foobar and an Alien DAC connected via a USB cable._

 You can imagine my excitement when you realize that the Alien is down at the bottom of quality for most DACs - so there's huge improvements to be had.

 You'll also see DAC's used in high-end systems where CD players or DAPs are used as transport mechnisms only. They'll have digital outs such as optical or SPDIF for use in connecting to a separate component DAC, where the signal is converted to analog and lifted to line levels. The combination serves as high-quality source to your preamp or headphone amp systems.

 EDIT: Yes, Amphead is correct - there's some exciting stuff coming, especially in DACs. DIY has only scratched the surface in DAC technology.

 There are a couple of MAX builders who've placed a DAC directly in the case with a MAX. For instance, Pabbi just posted pics of his balanced MAX with an OPUS DAC as the source in the same case. All he has to do is connect a PC or CD transport directly, I believe. Some have built simpler versions that just have a USB plug on the back of a MAX in addition to RCA connectors. Connect a USB cable between the MAX and your PC, fire up Foobar or some other Media Player and away you go.


----------



## willisv

You wouldn't be able to plug your IAudio X5L into a standalone Dac because it doesn't have a digital output. But you could bypass the dac in your sound card by plugging in an alien dac or something similar to the usb port in your computer and then into your amplifier. This would give you better quality sound than your IAudio X5L could provide.


----------



## amphead

Yeah, good point Willisv! He needs to bypass that sound card, and use an Alien dac as TomB mentions in his post. Great explanation TomB! I think that puts to bed any gaps in knowledge that anyone had.  btw, look at my post count.


----------



## willisv

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Yes - you're right. In my experience, the Sylvania 12AE6 probably has the best highs of any 12AE6. I'm a certified bass head, though, and they seemed to lack the punch of the GE's. 
	

	
	
		
		

		
		
	


	




 Also, Amphead - your post emphasizes a good point. Just because the MAX has those killer DB's and a lot of our discussion has been on BG's, ES's, VitQ's, K42's, etc. - that doesn't mean that tube changes aren't noticeable. Rolling tubes in the Millett is a worthwhile effort and may effect a large part of the sound of the amp.

 Rolling is a bit more difficult in a Millett, however, because the tubes were so widely sub-contracted from one company to the other. RCA's telltale is the squished octagon with the tube designation. GE's are the etched dots. The other mfr was either Sylvania or Tung-Sol - or both. There's a very good web page by Jeff Duntemann that explains many of the space-charge tubes:

Space Charge Tubes: Tube Projects Without Lethal Voltage!

 On this page, he states that Tung-Sol was the originator of the space-charge tubes, so maybe they have to be the other mfr. Tung-Sol Millett tubes seem to have the most "air" IMHO, but they also seem to be the most scarce. I've always had trouble believing that they were the 3rd or 4th mfr of these tubes because of their scarcity. I suppose research and development doesn't parallel manufacturing ability.

 Colin also clued me into another tube on this list: the *12FT6*. It appears to be a one-to-one equivalent of the 12AE6 (unlike the 12AJ6 which has a gain of 55!). Another one for you guys to investigate, neither Colin nor me have found it listed at any tube vendor. I even sent an e-mail to Dale and Roy at Radio Electric Supply (vaccumtubes.net):

Thomas,

 Must be a really obscure tube. We have never seen one, but it is in the databases. I sure wouldn't engineer anything around it. You would have a really tough time finding replacement tubes.

 Dale






 Let me know if any of you spot one. 
	

	
	
		
		

		
		
	


	





_

 


 These guys may have this tube in stock (12FT6), It's listed on their site. I was going to give them a call but I'm over budget this month. 
	

	
	
		
		

		
		
	


	




Leeds Electronics : Tubes 8KA8 - 12HG7


----------



## jerrygp

Thank you folks for the valued info. I'm in the process of building a new PC and haven't purchased a sound card yet or know yet if I even need to, but have a solid motherboard/cpu/memory configuration. I've been reading posts in different forums about how to "best get the most" out of the various audio processing and playback choices I will have to be making. So many choices to make. I need a mentor. I mentor at work and never thought I would need one myself. Should have been boning up on audio when I was younger instead of some of the crazy other stuff. I'm fortunate that so much info is available online. I just gotta keep reading and asking questions and maybe I will get lucky and have the right amount of skill to put something together that pleases my ears and intellect, and scratches that itch I have and the folks in this forum have to create.


----------



## amphead

Hey TomB, the Bijou looks interesting! A nice addition to the Millett Max collection. 

 Look at my post count fellow Head-Fiers!


----------



## tomb

Quote:


  Originally Posted by *amphead* /img/forum/go_quote.gif 
_Hey TomB, the Bijou looks interesting! A nice addition to the Millett Max collection. _

 

Don't know about that. Maybe you meant something else, but the Bijou is not affiliated with the MAX, the Millett, Colin or myself.

 EDIT: Your post count looks good, though!


----------



## jamess71

Quote:


  Originally Posted by *amphead* /img/forum/go_quote.gif 
_Look at my post count fellow Head-Fiers! _

 

Congrats on the 1500. Man Im a long way off. 10X and i'm there.....
	

	
	
		
		

		
		
	


	




 I got the rest of my parts in yesterday for my holiday max X 2 build. I ended up getting 10 - 12FK6 from ? man now I can't remember. I'll check tonight. It wasn't VacuumTubes.net though. He said someboby built a board back in the spring that used these tubes and they have been selling like hotcakes ever since.
	

	
	
		
		

		
		
	


	




 I wonder what that board was.... 
	

	
	
		
		

		
		
	


	




 He said they probably didn't sell 1 in 7 years prior to the MM. He does have a few mix and match left.


----------



## amphead

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Don't know about that. Maybe you meant something else, but the Bijou is not affiliated with the MAX, the Millett, Colin or myself.

 EDIT: Your post count looks good, though! 
	

	
	
		
		

		
			



_

 

Yeah, its not a Millett in any way shape or form. Don't know how it sounds in relation to the MAX. Edit: All tube sometimes = mid hump, good star grounding is needed to avoid 60 hz hum, and it runs at 300v B+, therefore the lethal voltages need to be dealt with. I have been hit with 480v, and my body was convulsed violently...need we say more?..........There are careful high voltage amp builders and then the are the.......dead.

 Thanks for noticing my graduation!


----------



## willisv

Quote:


  Originally Posted by *amphead* /img/forum/go_quote.gif 
_Yeah, its not a Millett in any way shape or form. Don't know how it sounds in relation to the MAX. Edit: All tube sometimes = mid hump, good star grounding is needed to avoid 60 hz hum, and it runs at 300v B+, therefore the lethal voltages need to be dealt with. I have been hit with 480v, and my body was convulsed violently...need we say more?..........There are careful high voltage amp builders and then the are the.......dead.

 Thanks for noticing my graduation! _

 

LOL, congrats on the post count!


----------



## slowpogo

Another probably-already-answered question...what are the negatives of using 1" heatsinks for the BJT output or power supply, as opposed to 1.5"?

 Obviously the shorter ones won't dissipate as much heat, but what does that mean in terms of what you hear? I do want to bias the power transistors as high as I can.

 My main concern is that I wanted to put some screening under the vent holes on the top panel, but the 1.5" sinks will literally scrape the top panel--no room for metal screening. The screening will allow big fat vent holes, so I'm wondering if the excellent ventilation will offset the need for a bigger heatsink.


----------



## tomb

Quote:


  Originally Posted by *slowpogo* /img/forum/go_quote.gif 
_Another probably-already-answered question...what are the negatives of using 1" heatsinks for the BJT output or power supply, as opposed to 1.5"?

 Obviously the shorter ones won't dissipate as much heat, but what does that mean in terms of what you hear? I do want to bias the power transistors as high as I can.

 My main concern is that I wanted to put some screening under the vent holes on the top panel, but the 1.5" sinks will literally scrape the top panel--no room for metal screening. The screening will allow big fat vent holes, so I'm wondering if the excellent ventilation will offset the need for a bigger heatsink._

 

The base configuration is _supposed_ to be with 1" high heat sinks.

 I have had my BJTs up to 60ma when using the rollbars - they tend to enhance the heat transfer effect, but I'm sure another 10-15ma is possible with care. 50ma with no ventilation whatsoever is a reasonable build. It will get a little toasty, but nothing more than that. 

 I have not cased up a MAX yet with anything other than 1" sinks and 1" parts.


----------



## Hubbard0

I've got another question too. I'm building an Alien to go along with this and on that board there are 2 capacitors that do not need to be populated if the amp has input DC protection. Does the Millet have this?


----------



## slowpogo

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_The base configuration is supposed to be with 1" high heat sinks.

 I have not cased up a MAX yet with anything other than 1" sinks and 1" parts. 
	

	
	
		
		

		
		
	


	


_

 

Great, no worries then, I will add some 1-inchers to my mouser order. My kit from Jeff has 1.5" heat sinks, so I wasn't sure. If it weren't for my obsessively crafted top panel I wouldn't even have asked.


----------



## tomb

Quote:


  Originally Posted by *slowpogo* /img/forum/go_quote.gif 
_Great, no worries then, I will add some 1-inchers to my mouser order. My kit from Jeff has 1.5" heat sinks, so I wasn't sure. If it weren't for my obsessively crafted top panel I wouldn't even have asked._

 

Yep - my use of the phrase "supposed to be" may be a bit strong. Jeff's kits are a primary build option - it's just that 1" sinks don't work well with the giant KZ's that Jeff uses in his kits. ES caps or Black Gates will get you down to the 1" maximum part height.


----------



## rhester

tomb, where do those sporty rollbars come from? Add a nice touch to the build.


----------



## tomb

Thanks! Believe it or not, they are standard cabinet wire pulls from Home Depot or Lowes. I use 3" or 3-1/2". They are typically brass and plated with another color - brushed steel or black. The brushed steel are very common.

 They have plastic ones, too, but they wouldn't do much except add some protection for the tube tops. The metal ones add heft and ruggedness to the amp and most importantly, improve heat transfer from the case.

 They are about $2.50 or $3 ea. and come threaded for 8-32 screws. However, you'll need to purchase some of your own screws. The ones that come with them are sized for 1/2"-3/4" wood thicknesses and will never screw far enough to clamp down on a 1/16" case lid. 
	

	
	
		
		

		
		
	


	





 EDIT: I've attached a PDF CAD layout of the top plate incorporating the rollbars. I'll try to get this posted on the MAX website sometime today. 3" rollbars are used in the center, while the option to use 3-1/2" are on the sides. Again, this was mainly due to availability at HD/Lowes in Atlanta. The black ones are only at a couple stores and only at 3". There are online places where you can order different colors and lengths and are not too expensive, however. This is one that I bookmarked recently, but I haven't ordered anything, yet:
865 - Wire Pull, Contemporary Cabinet Pulls Amerock, www.knobsandhardware.com

 Layout/PDF Template: MAXtopPlate-rollbars.pdf


----------



## jerrygp

Want to wish everyone that celebrates Christmas, a Merry Christmas...and to all, a creative new year. Thank you everyone for this forum over the past year...


----------



## xmokshax

so i've finished stuffing my MAX board, and so i went right on to biasing, but encountered a problem immediately. i plugged in the wallwart and flipped the switch, and the fuse blew immediately. i've seen quite a bit of discussion regarding fuses blowing earlier in this thread (which i'm wading through as we speak), and i'm not sure if i should just bypass the fuse and continue with testing, or if the fuse blowing on first startup should be an indication that something is wrong. any thoughts?

 the fuse is the one that was supplied in Jeff's kit - i'm not sure if he's still supplying fast-blow fuses or he's switched to slow-blow.


----------



## tomb

Quote:


  Originally Posted by *xmokshax* /img/forum/go_quote.gif 
_so i've finished stuffing my MAX board, and so i went right on to biasing, but encountered a problem immediately. i plugged in the wallwart and flipped the switch, and the fuse blew immediately. i've seen quite a bit of discussion regarding fuses blowing earlier in this thread (which i'm wading through as we speak), and i'm not sure if i should just bypass the fuse and continue with testing, or if the fuse blowing on first startup should be an indication that something is wrong. any thoughts?

 the fuse is the one that was supplied in Jeff's kit - i'm not sure if he's still supplying fast-blow fuses or he's switched to slow-blow._

 

Yep - if you size the fuse to handle the inrush current it won't blow, but then it won't protect anything on the board, either. Better to go without it, IMHO. Screw your AC leads into the first two terminal positions and bypass the fuse, instead.

 Bump the amp on and off while checking for minimum DB bias on the left and right channel. When you're comfortable those are at minimum, then turn it on for good and start measuring the PS and set the voltage as desired. If all appears well, then go on to biasing the DB's carefully using the procedure outlined earlier. (I'll try to post it on the website right now.)


----------



## xmokshax

thanks for the reply, tom. by the way, thanks also for the package that i received on friday. 
	

	
	
		
		

		
		
	


	




 i bypassed the fuse and checked the DB biases - at maximum RB12L/R, i read 25.8 and 26.5 mV for the two channels, well below the estimated 50mV. is this cause for concern? in light of some other results, it seems like it should be.

 after finding the DB biases to be very low, i quickly set the PS voltage to 27V. so far, so good. however, when i measured the tube biases, both clocked in at around 24V. i played with the trimpots, but they didn't seem to make much difference. i think i've read some other posts about this problem, so i'll go back and look. the odd thing is that if i leave the amp on for a few seconds, the bias voltages plummet (not sure how far down they go, because i shut the amp off when this happened). i figured this might be a thermal shutdown of the LM317, but both the chip and the sink feel cool to the touch. any idea what might be going on?


----------



## tomb

Quote:


  Originally Posted by *xmokshax* /img/forum/go_quote.gif 
_thanks for the reply, tom. by the way, thanks also for the package that i received on friday. 
	

	
	
		
		

		
		
	


	




 i bypassed the fuse and checked the DB biases - at maximum RB12L/R, i read 25.8 and 26.5 mV for the two channels, well below the estimated 50mV. is this cause for concern? in light of some other results, it seems like it should be._

 

No, that sounds good. As a matter of fact, it shows that you have well-matched JFET's. I'm pretty sure they are what govern the actual minimum voltage through the DB's and difference. That difference is very small in your case - 0.7mV. I've had as much as 20mV difference in mine. 
	

	
	
		
		

		
		
	


	




 By the way, I finished posting that blow-by-blow on DB biasing on the MAX website:
MAX Setup and Bias Settings

  Quote:


 after finding the DB biases to be very low, i quickly set the PS voltage to 27V. so far, so good. however, when i measured the tube biases, both clocked in at around 24V. i played with the trimpots, but they didn't seem to make much difference. i think i've read some other posts about this problem, so i'll go back and look. the odd thing is that if i leave the amp on for a few seconds, the bias voltages plummet (not sure how far down they go, because i shut the amp off when this happened). i figured this might be a thermal shutdown of the LM317, but both the chip and the sink feel cool to the touch. any idea what might be going on? 
 

Did you install R1, the heater resistor? The tube heater circuit is open if that resistor is not installed or jumpered - the tubes will never conduct. It almost sounds like that's what's going on.

 I'm not sure if that's a reason for the bias voltages to fall - can't answer that one. However, you are correct to conclude that without lots of heat, chances are the LM317 is not shutting down. It sounds like you are in the safe range for the DB's - let's see if you can get those tubes to conduct.

 BTW, be sure you're not mixing up the trimmers - I've caught myself a couple of times trying to adjust the DB trimmers, thinking they were the tube trimmers. Also, be sure you're measuring the proper test points - the key is on that same "MAX Setup and Biasing" page referenced above.

 All I can think of so far ...


----------



## heatmizer

edit found the answer on the other forum
 Have quick question about the max in bjt configuration. Why does qb1 require such a higher idss than the original rev db.


----------



## xmokshax

i actually did catch myself accidentally adjusting a DB trimmer rather than a tube trimmer last night, but i've definitely adjusted the tube trimmers all the way up and seen essentially no change in the tube bias voltage. the heater resistor is installed, and there's definitely voltage flowing through the tubes, it seems. i don't know enough about tube "anatomy" to say specifically what part it is, but there's a piece that looks like the end of a filament at the top of the tube that begins glowing orange shortly after i turn the amp on - is this the end of the heater? in any case, it definitely seems that there's voltage flowing to at least certain components of the tube.

 i've made a couple of other seemingly strange observations that might shed a bit more light on the subject. first, even when the wallwart isn't plugged in, my meter shows between 1.4 and 1.7V between ground and TA2L or TA2R. this appears to persist for some time after the amp is unplugged - i'm not sure if there are capacitors in that path that are just remaining charged, or what. second, i decided to measure the tube trimmers' resistance with my meter to ensure that they're changing, and set as i expect them to be. they both read the appropriate ~5k when turned all the way clockwise, but it takes a long time for the meter to reach that reading. it starts at around 1k and creeps up for about 10 or 20 seconds before it levels off. i've never experienced this type of behavior before when measuring a resistor, and it seems like there must be some other component in the circuit that's influencing the reading. i'm not sure if this is normal or not.

 i'll take pictures of the board when i have a chance - there's still a good bit of flux on it that i suppose COULD be causing problems, so i'll try to get that cleaned off first.


----------



## tomb

Quote:


  Originally Posted by *xmokshax* /img/forum/go_quote.gif 
_i actually did catch myself accidentally adjusting a DB trimmer rather than a tube trimmer last night, but i've definitely adjusted the tube trimmers all the way up and seen essentially no change in the tube bias voltage. the heater resistor is installed, and there's definitely voltage flowing through the tubes, it seems. i don't know enough about tube "anatomy" to say specifically what part it is, but there's a piece that looks like the end of a filament at the top of the tube that begins glowing orange shortly after i turn the amp on - is this the end of the heater? in any case, it definitely seems that there's voltage flowing to at least certain components of the tube._

 

Then this means your heaters are working. 
	

	
	
		
		

		
			





 There are a couple of other things to check -
 1. One builder made the mistake of using 2N5088's in the CCS circuit instead of the 2N5087's. You might check that - also make sure that you have the right resistors in their positions - RA9 and RA8 should be 11.3K ohm and 1.13K ohms, respectively - or alternatively, 10K ohms for RA9 and 1K for RA8.

 2. There's always the possibility that you've got bad connections in the tube socket. If everything else checks out, but you still can't adjust a bias, then the plates are not conducting in the circuit. That means the pins for the plates are not connecting to the pins in the socket. Those are pins 2 and 7. You might try wiggling the tubes or canting them sideways a bit and see if that makes a difference.

 Other than pics showing some misplaced parts, that's all I can think of for now.

  Quote:


 i've made a couple of other seemingly strange observations that might shed a bit more light on the subject. first, even when the wallwart isn't plugged in, my meter shows between 1.4 and 1.7V between ground and TA2L or TA2R. this appears to persist for some time after the amp is unplugged - i'm not sure if there are capacitors in that path that are just remaining charged, or what. second, i decided to measure the tube trimmers' resistance with my meter to ensure that they're changing, and set as i expect them to be. they both read the appropriate ~5k when turned all the way clockwise, but it takes a long time for the meter to reach that reading. it starts at around 1k and creeps up for about 10 or 20 seconds before it levels off. i've never experienced this type of behavior before when measuring a resistor, and it seems like there must be some other component in the circuit that's influencing the reading. i'm not sure if this is normal or not. 
 

None of this seems too strange, really - you can get some strange readings, especially with as many caps as the MAX has - after it's been charged once or twice. For instance, I've never gotten 0V at the test points once it's been populated. I'm not even sure you wouldn't still get something like that even if it's never been plugged in. (Your meter can affect some readings.)

  Quote:


 i'll take pictures of the board when i have a chance - there's still a good bit of flux on it that i suppose COULD be causing problems, so i'll try to get that cleaned off first. 
 

I doubt that flux could be causing a problem this early - it usually takes some aging to develop conductance. Most likely, there's some parts misplaced or those tube sockets are causing a problem. You could also have bad tubes, but I think two of those at once are unlikely.

 Not to worry - the tube circuit is the simplest of them all. It's almost always something out of place - there's not much else that can go wrong with it. 
	

	
	
		
		

		
		
	


	







 Merry Christmas!! Hopefully we'll help you birth a new MAX before New Year's!!


----------



## joneeboi

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_You might try wiggling the tubes or canting them sideways a bit and see if that makes a difference._

 

x2. I have a fully functional MAX with one wonky tube socket.


----------



## xmokshax

merry christmas to you too! 
	

	
	
		
		

		
		
	


	




 i'd thought that it might be the sockets - i'll go and jiggle the tubes around a bit and see if that helps. i was a little dubious that i'd be able to glue the sockets back together with cyanoacrylate without affecting any of the pins. perhaps one of the pins did get caught up in the glue and isn't making good contact. i'll also take pics and post them up here in just a few minutes, to see if you guys can spot any misplaced parts that i've missed. thanks again for the help.

 EDIT: pics! as i said, the bottom of the board is still pretty nasty. also, i tried jimmying the tubes around in the sockets a bit, to no effect. Jeff supplies small-package Vishays for RA5L/C/R, so they're much smaller than the silkscreen, but they're still the spec'ed 1W. i'm about to go back through and hand-check the resistors in the tube circuit with my meter.

 EDIT 2: ok, i think i've found the problem - or at the very least, another symptom thereof. R7L/R measure at 1.0 and 1.7 OHMS, respectively, while they're supposed to be 1.0 MEGAohms. they're marked correctly as 1.0Mohm ("1004F"). is this typical of a fried resistor (~1 ohm remaining resistance), and is it at all likely that those resistors would have gotten fried? if so, where should i look next for a problem?


----------



## regal

Quote:


  Originally Posted by *amphead* /img/forum/go_quote.gif 
_. Interestingly enough there may be a tube dac project coming this spring. That would be a DAC!!!!! _

 


 I hope so. We have all these awesome amp projects, we go to great lengths to have diamound buffers and avoid opamps at all cost. But we feed our masterpieces with opamp I/V and opamp buffers in our DAC's or CDP's.

 This is greatly needed.


----------



## tomb

Quote:


  Originally Posted by *xmokshax* /img/forum/go_quote.gif 
_merry christmas to you too! 
	

	
	
		
		

		
		
	


	




 i'd thought that it might be the sockets - i'll go and jiggle the tubes around a bit and see if that helps. i was a little dubious that i'd be able to glue the sockets back together with cyanoacrylate without affecting any of the pins. perhaps one of the pins did get caught up in the glue and isn't making good contact. i'll also take pics and post them up here in just a few minutes, to see if you guys can spot any misplaced parts that i've missed. thanks again for the help.

 EDIT: pics! as i said, the bottom of the board is still pretty nasty. also, i tried jimmying the tubes around in the sockets a bit, to no effect. Jeff supplies small-package Vishays for RA5L/C/R, so they're much smaller than the silkscreen, but they're still the spec'ed 1W. i'm about to go back through and hand-check the resistors in the tube circuit with my meter.

 EDIT 2: ok, i think i've found the problem - or at the very least, another symptom thereof. R7L/R measure at 1.0 and 1.7 OHMS, respectively, while they're supposed to be 1.0 MEGAohms. they're marked correctly as 1.0Mohm ("1004F"). is this typical of a fried resistor (~1 ohm remaining resistance), and is it at all likely that those resistors would have gotten fried? if so, where should i look next for a problem?_

 

You're fighting a losing battle trying to measure resistances on a populated board. Too many components are in parallel with each other. The 1M resistors, RA7L/R in particular, are paralleled with the grid on the tube (among other things), which is almost zero resistance until the tubes are on and biased. So, don't mess around trying to measure resistance.

 I hesitate to ask this, but I don't see anything wrong with your pictures at first glance - but exactly what test points are you using to set the bias on the tubes? You should refer to the legend photograph and description on the MAX website:
MAX Setup and Bias Settings

 The tube bias is referenced to Gnd. So you would stick your probes in TA2L and Gnd for the Left Tube and TA2R and Gnd for the Right Tube. Keep in mind that the trimmers are sized for three different tubes, each with varying bias set points. So, you may have to unscrew (counter-clockwise) the trimmers perhaps 20 turns or more on a 25-turn trimmer, depending on the tubes.

  Quote:


 [>URL=http://imageshack.us][>IMG]http://img297.imageshack.us/img297/2876/fullboardbc3.jpg[/IMG][/URL]

 [>URL=http://imageshack.us][>IMG]http://img170.imageshack.us/img170/6495/tubeareabi8.jpg[/IMG][/URL]

 [>URL=http://imageshack.us][>IMG]http://img170.imageshack.us/img170/6876/bottomofboardlg3.jpg[/IMG][/URL] 
 

Again, don't see anything wrong with your work at this point that would be causing your problem. Try biasing the tubes again, but be patient - remember that unscrewing the trimmers will lower the voltage on the tubes, but that screwing them in (clockwise) will increase the voltage. If you're already measuring 24-27VDC, then screwing anymore clockwise will never register a thing.


----------



## xmokshax

the tubes were out when i made those measurements on RA7, so it isn't likely to be the grid resistance i'm measuring, but your point is well taken. i won't mess around with measuring resistances on the board. i think i'll go back and turn those trimmers a good distance counterclockwise, to see if i can't get some adjustment at the far end of the trimmer's range. i did have them most of the way clockwise, so maybe i've just been ouside of the adjustable range for the 12AE6 tubes all this time. i'll feel pretty stupid if that's the case. 
	

	
	
		
		

		
		
	


	




 i'm definitely using the right test points - i followed the instructions on the site very closely (they're excellent, by the way, and even better now that you've further fleshed out the DB biasing section).

 EDIT: ...well, i DO feel stupid, and i'm sorry for wasting your time. :/ on the bright side, all that was happening this entire time was that the dynamic range for these tubes is closer to the full-counterclockwise position of the trimmers than i had apparently ventured. the voltage started changing rather quickly once i got close to 20 turns counterclockwise of the full-clockwise position. i'm still not sure what was happening when the bias voltage was dropping unexpectedly last night, but if it doesn't happen again, i won't complain. just so you don't have to deal with any more fools like me, tom, it might be worth putting a note in the tube biasing section that the voltage may be pretty close to the power supply voltage (perhaps particularly with 12AE6 tubes?) until you've turned the trimmer fairly far counterclockwise, and that the bias voltage changes fairly rapidly once you reach the dynamic range of the trimmer for that particular tube. this is probably common sense for many MAX builders, but i'm still very green when it comes to these things and i wasted everyone's time because of it. i actually had a similar "problem" when building a TREAD a while back, so i should have learned by now to explore the entire range of a trimmer before assuming something else is wrong. 
	

	
	
		
		

		
		
	


	




 in any case, thanks for bearing with me. hopefully the rest of the biasing process will go off without a hitch, and the amp will work right off the bat.


----------



## amphead

One really common mistake is to be out of adjustment on the trimpots, when trying to bias. They often start adjusting at the far end of their travel. Sorry I can't help more right now, got to get into bed. I have a sore throat and feel weak. Hope its not the flu. Merry Christmas! Try not to get sick. ;-(


----------



## Ech0

I'm starting a case(s) for my 2nd MilletMax. I've always done the amp construction first and the casework last on the other amps I've built. This time I thought I'd switch it up and do the casework first. 






 This is going to be a SwitchBox and MilletMax. Hopefully, they'll come out decent. If it comes out respectable I'll post the final pics, otherwise, I'll just quietly slink away.


----------



## xmokshax

Quote:


  Originally Posted by *amphead* /img/forum/go_quote.gif 
_One really common mistake is to be out of adjustment on the trimpots, when trying to bias. They often start adjusting at the far end of their travel. Sorry I can't help more right now, got to get into bed. I have a sore throat and feel weak. Hope its not the flu. Merry Christmas! Try not to get sick. ;-(_

 

yep, that turned out to be precisely my problem. merry christmas to you too, and hope you feel better.


 Ech0: looking good so far. i, for one, will be hoping you post final pics rather than quietly slinking away.


----------



## tomb

Quote:


  Originally Posted by *xmokshax* /img/forum/go_quote.gif 
_the tubes were out when i made those measurements on RA7, so it isn't likely to be the grid resistance i'm measuring, but your point is well taken. i won't mess around with measuring resistances on the board. i think i'll go back and turn those trimmers a good distance counterclockwise, to see if i can't get some adjustment at the far end of the trimmer's range. i did have them most of the way clockwise, so maybe i've just been ouside of the adjustable range for the 12AE6 tubes all this time. i'll feel pretty stupid if that's the case. 
	

	
	
		
		

		
		
	


	




 i'm definitely using the right test points - i followed the instructions on the site very closely (they're excellent, by the way, and even better now that you've further fleshed out the DB biasing section).

 EDIT: ...well, i DO feel stupid, and i'm sorry for wasting your time. :/ on the bright side, all that was happening this entire time was that the dynamic range for these tubes is closer to the full-counterclockwise position of the trimmers than i had apparently ventured. the voltage started changing rather quickly once i got close to 20 turns counterclockwise of the full-clockwise position. i'm still not sure what was happening when the bias voltage was dropping unexpectedly last night, but if it doesn't happen again, i won't complain. just so you don't have to deal with any more fools like me, tom, it might be worth putting a note in the tube biasing section that the voltage may be pretty close to the power supply voltage (perhaps particularly with 12AE6 tubes?) until you've turned the trimmer fairly far counterclockwise, and that the bias voltage changes fairly rapidly once you reach the dynamic range of the trimmer for that particular tube. this is probably common sense for many MAX builders, but i'm still very green when it comes to these things and i wasted everyone's time because of it. i actually had a similar "problem" when building a TREAD a while back, so i should have learned by now to explore the entire range of a trimmer before assuming something else is wrong. 
	

	
	
		
		

		
		
	


	




 in any case, thanks for bearing with me. hopefully the rest of the biasing process will go off without a hitch, and the amp will work right off the bat._

 

Don't knock yourself so hard - the important thing is that it sounds like another MAX Lives!!!
	

	
	
		
		

		
		
	


	




 Seriously, it's not an uncommon issue - as Amphead says. I'll take a look and see if there's a bit of explanation that I can offer on the website and will add it when I can.

 As I said, this goes back to the fact that the circuit is designed to handle three different kinds of tubes that have very different bias adjustments. The MAX is no different than the original Millett in this regard - only the CCS is slightly different. The result is that the travel is limited to a few turns, but at different locations in the total trimmer travel, depending on the tubes.

 Anyway, it's no reason to feel the fool - far from it! Let us know how the rest of it went and how it sounds when you get a chance.


----------



## joneeboi

I wonder what the victim count is for "I didn't turn the trimpot enough."

 Don't worry, xmoshax. Just about every single mistake seems stupid once you figure it out.


----------



## xmokshax

joneeboi, that's a good way to look at it. good to know that i'm not the only victim of this one.

 tom, upon further inspection, it looks like you've mostly covered the issue i was having in your new, in-depth pop-out section on DB biasing. perhaps just moving some of the tube biasing specifics back out to the tube bias section would be good, or even just a bold "make sure you explore the trimpot's entire range" would do the trick. i think you do have all the salient info in there somewhere, though.


----------



## ruZZ.il

off the bat, they may be more responsive if they were logarythmic trimmers? <shrugs>.. I'll look at it later too :>


----------



## tobias_svensk

Well I to was a victim of it that's for sure


----------



## slowpogo

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Yep - no difference. Some caps - big difference, in the wrong direction! I think best to leave out completely when using Black Gates. I ran the one I just built for weeks without any bypass caps at all on all four BG's until fordgtlover came up with the K42's. I tried them and what you describe was the result at CA8 - not much difference. I think they help a bit on the output, though._

 

This is an old post, but it confuses me. The "Can't Miss Build #1" recommends leaving CA9 blank, but using a PIO cap for CA8.

 But in this post, tomb you basically say there's no point in using the PIO in CA8. Were you (and the previous poster) confusing CA8 with CA9, or do you really mean, it's best to leave _both_ blank?

 And when you say they "help a bit on the output," which cap position are you referring to (where they help)?


----------



## tomb

Quote:


  Originally Posted by *slowpogo* /img/forum/go_quote.gif 
_This is an old post, but it confuses me. The "Can't Miss Build #1" recommends leaving CA9 blank, but using a PIO cap for CA8.

 But in this post, tomb you basically say there's no point in using the PIO in CA8. Were you (and the previous poster) confusing CA8 with CA9, or do you really mean, it's best to leave both blank?

 And when you say they "help a bit on the output," which cap position are you referring to (where they help)?_

 

Sorry for the confusion. It's true that I get the positions mixed up. You see - intuitively, the "lower" number designations should be at the tubes. So, CA8 should go with CA2. That's not the case, however, and is the source for my sometimes confusing the issue.

 Let me try to say it plainly while I'm referring to a board in the other hand. 
	

	
	
		
		

		
			





*Cathode Bypass Position:*
 CA2 - electrolytic
 CA9 - film bypass

 Uses: BG's - nothing in CA9. Other Boutique and Power Caps - Wima's.
 K42's or VitQ's may be substituted for the Wima's, but you will not notice an improvement.

 These positions form what is known as a cathode bypass for the tube. The capacitors act in a shunting mode, providing headroom for the expanding signal. It's a little more complicated than that and I would try to explain it if I knew it thoroughly. The point is, some of the signal may _encroach_ into these caps, but this is highly variable and most often occurs with very strong amplitude signals.

 What this means is that these two caps have less an effect on the sound quality than the output positions - assuming that they are flat and don't offer a "restricted headroom" for the signal wave in the tube. That's where the film bypass comes in. Boutique film caps often have exagerrated mids with rolled off highs and lows. Any cap in these two positions that is not completely flat through the audio spectrum will damage the signal at it's source of amplification: the tube. Damage or lose the signal here and you never get it back.

 I had often wondered which two positions were more important in the sound signature of the Millett. Reading _all_ of the posts about the Millett many times over failed to answer this question. With the MAX, however, we did enough testing to know: _there is very little you can do to enhance the music signal in these positions, but it is very easy to destroy the quality of the music signal._

 Consequently, my recommendation is to forego all but the flattest film caps in the CA9 position. With most electrolytics, the Wima's work great. They are still needed because there is a lack of resolution in the highs using most electrolytics (including ES and other non-BG boutiques). The Wimas don't impart enough of their own coloration to affect anything adversely, so they are a good choice and recommended in every non-BG case. If you insist on Vitamin Q's or K42's, they will not adversely affect the sound quality, but you'd be hard-pressed to determine if they helped it, either.

 With BG's, I would (and do) use nothing. The K42's probably add or subtract nothing here - they are a great neutral cap. However, that also means they are somewhat redundant. Again, if you insist - Vitamin Q's would be OK and will not adversely affect anything. (They may have a tad more sparkle in the high end, but this is highly debatable.) The BG's are so good and fast that the Wimas have little effect or even a bad effect - as do many other caps paired with the BG's. So overall, using film caps with BG's in these positions - even if they are flat - is probably redundant and ineffective. That's my opinion.

 The electrolytics have a big effect on bass in these positions, but that's more of a size issue than anything else. Although, the ES's will always be the bass kings, IMHO.

*Output Coupling Cap Positions*
 CA7 - electrolytic
 CA8 - film bypass

 Uses: BG's - bypass with K42's or VitQ's. Other Boutique and Power Caps - K42's or VitQ's. Wimas are acceptable with only the slightest roughness in the mids.

 Things are much simpler for these positions. All signal passes through these caps and the signal is constantly affected by the quality of these caps. The MAX is at heart a hybrid, however, and without a flat film bypass cap in this position, the extended response of the MAX suffers. The Wimas do a great job, but they possess a bit of graininess in the mids. Nevertheless - they are a great choice. The Vitamin Q's are probably ideal here, but as posted many times - their size does not lend themselves to an easy install. There are some that are not too big, but they are not predominantly available nor are they the "genuine" Sprague variety.

 Enter Forum User Fordgtlover and his "discovery" of the K42's with the MAX. They offer almost indistinguishable sound quality from the VitQ's at a much smaller size. So, they are the _de rigueur_ choice for the CA8 (output) positions on the MAX. That's my recommendation.

 Other film caps have been tested and have some deleterious frequency response effects - not as much as in the cathode bypass positions and the result may be enhanced in other areas. A great example of this is a cap used in our early recommendations - the Sonicap GEN II's. Highs and mids will be greatly enhanced for a penalty in bass. Some of you may think the MAX has too much bass already, so this may be a solution for some.

 The electrolytic is simpler still - size for the corner frequency equation and put a good quality boutique so that the sound quality is affected least. There is no lack of bass with 470uf's in this position, but the BG's are pretty much only in 680uf's in a size and rating that will fit. Keep in mind that most of my comments about size are directed at achieving a 1" high part height. If you case your MAX up in such a way where that's not an issue, then you have a little more flexibility in choosing caps - but you will find that what's available at 1" is not going to be beat.

 The "bit of help" thing comes again in the case of the Black Gates. Very little effect is had by any film cap bypasing BG's in the MAX, but I believe the addition of the K42's or VitQ's add a bit of smoothness and transparency. This helps with the characteristic congestion of Black Gates that are under-run. I hope that explains things thoroughly and I apologize for confusing those CA8 and CA9 caps. I've probably done it many times and frustrated many of you.

 By the way, the last time I posted this much "opinion," I got slammed pretty good. 
	

	
	
		
		

		
		
	


	




 So, keep in mind that these opinions are my own, but they are the result of many hours of building, listening, and testing different caps on the MAX. 
	

	
	
		
		

		
		
	


	




 EDIT: These opinions and recommendations apply only to the BJT version of the MAX. I'm not familiar enough with the MOSFET version to comment.


----------



## joneeboi

Essentially, I believe it comes down to what the "Can't Miss Builds" table states. Don't populate CA9, and CA8 should only be populated by a very neutral cap, so neutral that it wouldn't sound any different if you added it. From my reading, it seems the K42 adds a bit of smoothness to the sound, but I think what it means is that the BGs are so good you don't need to bypass them. If you do want to bypass them, try the K42 or other PIOs because they usually have good synergy with tubes, plus most other film caps destroy the great mids brought to you by Rubycon. I'm out on a limb with most of what I'm saying here, but I'm just parroting Tom and other online resources. I didn't bypass my BGs, partly because I want to compare unbypassed and bypassed with K42, partly because they haven't arrived yet 
	

	
	
		
		

		
		
	


	




. I have a two other sets of cans to roll (Muse ES, Silmic II), plus experiment with K42 and Wimas. With three sets of electrolytics and two sets of films, that means the number of possible arrangements is...24? All BGs with no bypassing, all BGs with CA8 bypassing, all BGs with CA9 bypassing, one pair BG and one pair Muse ES with no bypassing, etc. What have I gotten myself into?

 Did I answer your question? When opening the Black Gates of Doom, bypass at CA8 with PIOs or nothing at all. K42s are cool because of their 1" size and relatively steady inventory.

 [Yikes. Seems Tom beat me to it.]


----------



## tomb

Quote:


  Originally Posted by *ruZZ.il* /img/forum/go_quote.gif 
_off the bat, they may be more responsive if they were logarythmic trimmers? <shrugs>.. I'll look at it later too :>_

 

 Quote:


  Originally Posted by *tobias_svensk* 
_Well I to was a victim of it that's for sure. 
	

	
	
		
		

		
		
	


	


_

 

Well, I apologize for the lack of emphasis in warnings about the tube trimmers, but keep in mind that little or nothing has changed in the tube circuit since Pete's original. It's possible that the MAX has caused some over-exposure to this issue that wasn't there before. I have noticed no difference in the way the tubes bias from Nate and Drew's revMH Millett.


----------



## tomb

Quote:


  Originally Posted by *joneeboi* /img/forum/go_quote.gif 
_<snip>

 [Yikes. Seems Tom beat me to it.]_

 

Doesn't matter - you got it essentially correct - in less words than me.


----------



## slowpogo

Not sure if this is proper, but I have a few spare pairs of Vitamin Q's to sell, which are listed in the for sale forum. 
	

	
	
		
		

		
		
	


	




 I'm not trying to spam, I honestly would just like people to know about them so they can get them and enjoy them.


----------



## slowpogo

Here are two pairs of 2SA968/2SC2238 transistors. Both are claimed to be "genuine Toshiba." Any ideas as to which are authentic, if any of them are?

 The one on the top right has the same color and type of lettering as the top left, it just doesn't show. The heatsink tabs on the top pair are kind of frosty and weathered looking, while the bottom pair are mirror shiny. The bottom pair also feels *slightly* heavier to me.


----------



## 04BluMach

Quote:


  Originally Posted by *slowpogo* /img/forum/go_quote.gif 
_Here are two pairs of 2SA968/2SC2238 transistors. Both are claimed to be "genuine Toshiba." Any ideas as to which are authentic, if any of them are?

 The one on the top right has the same color and type of lettering as the top left, it just doesn't show. The heatsink tabs on the top pair are kind of frosty and weathered looking, while the bottom pair are mirror shiny. The bottom pair also feels *slightly* heavier to me._

 

The original 2SA968's came in 2SA968, 2SA968A, and 2SA968B. I am not entirely sure what the minute differences may be between the three versions. However, all were the full TO-220 case. A heavier full metal heat sink to allow for higher power disipation (1.5Amp vs 1A for BD139). They also have a higher F(t) of 100Mhz. Of course, since they are old production pieces they do not meet new lead free standards (non-ROHS compliant). And as such are no longer in production nor been in production for some time. They are no longer listed on the Toshiba Web Site for even specs or substitute info (at least as far as I saw from a quick search). Spec sheets are still available from many third party sources though.

 Here are a couple of the 2SA968A that I received from MCM. (I didn't pull out their complementary pair - the 2SC2238's). 
 A shot with the MCM shipping pack. 





 A much closer view of the 2SA968A. The heavy TO-220 case is very apparent along with the full metal heat sink. And yes, they clearly do feel heavier compared to some of the other BJT's recommended for the MAX. And the " T " is the very simple Toshiba Semiconductor label.





 I know I have seen the product symbol on your cases before - I seem to remember that it was used by Toshiba at one point. 

 But the best way to tell is installed in your MAX! Assuming that you have other BJT's (or another MAX) to compare, you should be able to hear the diffence. The MAX is very revealing of the BJT sound sigs - if you listen closely and analytically.

 Don't fret over the BJT's. If you source indicates they are "genuine", they probably are - put em in and enjoy!
	

	
	
		
		

		
		
	


	




 Remember... If it Sounds Good - It Must be GOOD!


----------



## slowpogo

Quote:


  Originally Posted by *04BluMach* /img/forum/go_quote.gif 
_I know I have seen the product symbol on your cases before - I seem to remember that it was used by Toshiba at one point._

 

The top pair has a symbol resembling a "T", while the bottom pair just has those arrows. Which symbol do you recognize?

 The bottom, heavier pair seems to be made with higher quality plastic, like a typical DIP opamp. Whereas the top ones are more of a shiny, soft and light plastic.

 I'm a perfectionist, so hearing about counterfeit transistors made me a little paranoid. I'm sure either of the types I have will function OK, they just look completely different from one another, so I can't help but wonder if one of them isn't genuine.


----------



## 04BluMach

Quote:


  Originally Posted by *slowpogo* /img/forum/go_quote.gif 
_The top pair has a symbol resembling a "T", while the bottom pair just has those arrows. Which symbol do you recognize?

 The bottom, heavier pair seems to be made with higher quality plastic, like a typical DIP opamp. Whereas the top ones are more of a shiny, soft and light plastic.
 ._

 

The arrows on the bottom pair are the symbols that I recognize.

 Remember, these were an "Industrial" Transistor used throughout commercial practice (from control systems to RF Amplification). They were heavy duty and handled higher currents. Nothing fancy about them. No gold or glitter.

 Toshiba made them originally in Japan and I believe later they were made in other Pacific Rim plants, both in their subsidiery plants and under license to others.

 Again, if your source has indicated they are Genuine - they probably are. Give em a go - I'm sure they will sound great in your MAX. So ENJOY


----------



## tomb

The ones at Beezar.com are sourced from BDent exclusively, except for the 2SC2238/2SA968 pairs, which are from MCMinone. You can compare pics there for the Toshiba logos. _All_ have the slanted, thick "T" except for the 2SA968's, which have the simple cross "T" as 04BluMach shows in his pics. Of course, the 2SC2344/2SA1011 pairs are Sanyo - often referenced as a drop in replacement for the 2SC2238/2SA968 Toshiba's. The Sanyo's apparently are a tad brighter on the high end, but otherwise have a similar sound signature.


----------



## slowpogo

Wow, how long has that store been there? Very nice!!


----------



## joneeboi

And it is a very good store. My MAX shirt, LED bezels and caps just got in. Thanks, Tom.


----------



## 04BluMach

Quote:


  Originally Posted by *joneeboi* /img/forum/go_quote.gif 
_And it is a very good store. My MAX shirt, LED bezels and caps just got in. Thanks, Tom. 
	

	
	
		
		

		
		
	


	


_

 

Got's to have the MAX shirt....
	

	
	
		
		

		
		
	


	




 Great looking and well laid out store front! Another excellent source for the DIY community.
	

	
	
		
		

		
		
	


	




 The MAX Board looks very lonely though!!! Some sibling boards would help fill out the family - like Tube DAC PCB's and other Millet like Topology (eg 6GM8 version) with the MAX touch.


----------



## slowpogo

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_They are still needed because there is a lack of resolution in the highs using most electrolytics (including ES and other non-BG boutiques).

 With BG's, I would (and do) use nothing._

 

I'm curious, does your suggestion that Black Gates don't need a cap in CA9 apply to the FK series as well? Or just the non-polar series? 

 I was thinking about trying the 1000uf 16v FK in CA2; it's basically the same price as the NX cap, and some say the FK series sounds better, sometimes. (And, I have this compulsion to do things just a little differently than the norm.)


----------



## tomb

Quote:


  Originally Posted by *04BluMach* /img/forum/go_quote.gif 
_Got's to have the MAX shirt....
	

	
	
		
		

		
			





 Great looking and well laid out store front! Another excellent source for the DIY community.
	

	
	
		
		

		
		
	


	




 The MAX Board looks very lonely though!!! Some sibling boards would help fill out the family - like Tube DAC PCB's and other Millet like Topology (eg 6GM8 version) with the MAX touch.
	

	
	
		
		

		
		
	


	


_

 

Thanks. You are right in line with the strategy. 
	

	
	
		
		

		
		
	


	




 After the Tube DAC, Colin will be working on a serious re-design of the Millett topology. One thing he will probably incorporate are his bipolar discrete regulators, something that's gotten nice comments from a VIP designer. We've talked about the 6GM8 for quite some time, too - among other things. He's also been experimenting with a speaker option for the MAX. 
	

	
	
		
		

		
		
	


	




 However, these changes will take much longer than anticipated for just a new revision. So, we will order more regular MAX boards in the meantime, plus the MiniMAX - right after New Year's. The major re-design will probably take a few months longer.


----------



## tomb

Quote:


  Originally Posted by *slowpogo* /img/forum/go_quote.gif 
_I'm curious, does your suggestion that Black Gates don't need a cap in CA9 apply to the FK series as well? Or just the non-polar series? 

 I was thinking about trying the 1000uf 16v FK in CA2; it's basically the same price as the NX cap, and some say the FK series sounds better, sometimes. (And, I have this compulsion to do things just a little differently than the norm.)_

 

Well, BG's are a bit expensive for experimentation - especially if the FK's aren't any cheaper. Go for it if you want, though, but I can't offer any experience except for the NX's.


----------



## Negatron

Quote:


  Originally Posted by *slowpogo* /img/forum/go_quote.gif 
_I'm curious, does your suggestion that Black Gates don't need a cap in CA9 apply to the FK series as well? Or just the non-polar series? 

 I was thinking about trying the 1000uf 16v FK in CA2; it's basically the same price as the NX cap, and some say the FK series sounds better, sometimes. (And, I have this compulsion to do things just a little differently than the norm.)_

 

Excuse me for jumping in, but I have uses Blackgates quite a bit, (qualifying that with saying I hate EL caps) The Blackgates do not like being bypassed with film caps. You can use the NX .1uf to good advantage for BG bypass and they are cheap enough and not in short supply. The NX are to MY ears the best sounding of the lot and they both tend to just go away after break-in. 
 the 1000uf or 470uf N or NX are excelent K bypass caps
 Most all of my experience though is with higher voltage filter and OP coupling. And naturaly, other opinions are many.


----------



## amphead

Website looks excellent TomB! Nice work. Well I didn't get the flu but this cold isn't too good.  No soldering on the second Max board until I'm over this beast, I want to have my solder joints look like ruZZ.il's meticulous work.


----------



## tomb

Quote:


  Originally Posted by *amphead* /img/forum/go_quote.gif 
_Website looks excellent TomB! Nice work. Well I didn't get the flu but this cold isn't too good.  No soldering on the second Max board until I'm over this beast, I want to have my solder joints look like ruZZ.il's meticulous work._

 

Thanks! Get well soon!!

 EDIT: Yep - the bottom of Russ's board looks as good as the top on others!


----------



## ruZZ.il

Hey thanks 
	

	
	
		
		

		
		
	


	




 feel better quick!

 ....you should see my second board, I've really been taking my time.. I've been pretty busy and I've already got a MAX to listen to in the meantime so no rush 
	

	
	
		
		

		
		
	


	




 I usually stick a bunch of bits in, snip them, then take them out and snip them just a little more so its truly flush (marginally sub flush).. but I've gotten the hang of snipping most bits to size after just bending their legs right.


----------



## joneeboi

Quote:


  Originally Posted by *Negatron* /img/forum/go_quote.gif 
_the 1000uf or 470uf N or NX are excelent K bypass caps_

 

How come you suggest such huge capacitance caps for bypassing? For instance, the BOM Wimas at 0.22uF are used for bypassing, but you're saying the 1000uF or 470uF nonpolar BGs would work. Along the idea of bypassing, you want something fast, so is quickness the only thing that matters? AFAI understand, electrolytics are slow and films are quick. Does the fact that the N/NX series come in such high capacitances add to the beauty of their speed and relatively small packaging?


----------



## slowpogo

I've still got a few pairs left of .27uf Vitamin Q's..PM me or check the for sale forum if you're interested.


----------



## cetoole

Quote:


  Originally Posted by *joneeboi* /img/forum/go_quote.gif 
_How come you suggest such huge capacitance caps for bypassing? For instance, the BOM Wimas at 0.22uF are used for bypassing, but you're saying the 1000uF or 470uF nonpolar BGs would work. Along the idea of bypassing, you want something fast, so is quickness the only thing that matters? AFAI understand, electrolytics are slow and films are quick. Does the fact that the N/NX series come in such high capacitances add to the beauty of their speed and relatively small packaging?_

 

In this case, I believe Negatron is using 'K' to refer to the Kathode of the tube, as opposed to Black Gate K series capacitors.


----------



## Negatron

Quote:


  Originally Posted by *joneeboi* /img/forum/go_quote.gif 
_How come you suggest such huge capacitance caps for bypassing? For instance, the BOM Wimas at 0.22uF are used for bypassing, but you're saying the 1000uF or 470uF nonpolar BGs would work. Along the idea of bypassing, you want something fast, so is quickness the only thing that matters? AFAI understand, electrolytics are slow and films are quick. Does the fact that the N/NX series come in such high capacitances add to the beauty of their speed and relatively small packaging?_

 

I apologize for any confusion. My communication skills are sorely lacking. 'K' is referring to the cathode and old reference used by some of us 'geezers' The reason for such a large value of bypass for the K (cathode) resistor is to lower the Fc of Rk to as close to zero as possible. As noted by the developers of this effort, bigger is better and something I have found to be true in other design as well. I may have confused further by using the term bypass in 2 different contexts, The 'bypassing' of electrolytic's with small value film caps is not the same thing as 'bypassing' the cathode resistor with a cap.

 The math is complex, though simple Fc calcs suffice and all will tell you that a much smaller value of C is required for good low Freq response. The ears will argue! Large works well, but with standard caps much larger than 470uf messes with the upper mids and HF detail suffers to a small extent. With High quality caps 1000uf works fine. The Blackgate N and NX series are the best or most invisible cap I have encountered.

 As most have discovered, the BG's don't really need or want bypassing with a small value of C to counter inductance, BG's work by Ion transfer rather than Electron transfer. However, I have found a small gain by bypassing BG's that are 470uf or larger with the .1uf BG's but we are in real subjective territory here.

 I hope I haven't made things worse.


----------



## tomb

Quote:


  Originally Posted by *Negatron* 
_<snip>The math is complex, though simple Fc calcs suffice and all will tell you that a much smaller value of C is required for good low Freq response. The ears will argue! Large works well, but with standard caps much larger than 470uf messes with the upper mids and HF detail suffers to a small extent. With High quality caps 1000uf works fine.</snip>_

 

Shoot - that pretty much sums up the whole scenario with CA2 on the MAX and C2 on the Millett. Good info!

 Glad to see Colin posting again, too! 
	

	
	
		
		

		
		
	


	




 Also, I posted an Interest Check thread in the MAX section (stickied) on DIYForums.org. We will be ordering more boards, but the question is the variance of standard MAX boards vs. Mini MAX boards. Please post (not here!) and let us know your preferences and intent. Thanks.


----------



## joneeboi

Thanks, cetoole and Negatron. I'm just glad I could learn something here.


----------



## slowpogo

I've seen some pictures of Max builds that use a certain bluish-green LED for the tubes. It kind of looks like the ocean in the tropics. It's not the bright granny smith-looking green, or the deep powerful blue color, but inbetween.

 I've seen some LED's called "aqua." Are these what I'm describing?


----------



## tomb

Quote:


  Originally Posted by *slowpogo* /img/forum/go_quote.gif 
_I've seen some pictures of Max builds that use a certain bluish-green LED for the tubes. It kind of looks like the ocean in the tropics. It's not the bright granny smith-looking green, or the deep powerful blue color, but inbetween.

 I've seen some LED's called "aqua." Are these what I'm describing?_

 

You mean like these?


----------



## pinkfloyd4ever

Quote:


  Originally Posted by *slowpogo* /img/forum/go_quote.gif 
_I've seen some LED's called "aqua." Are these what I'm describing?_

 

I would say so. If you're looking for some try here


----------



## slowpogo

That's exactly it tomb, where did you get those? From the source given above (superbrightleds) or somewhere else?

 I once bought a "cyan" LED for my Pimeta, but it ended up looking plain old green. So I'm confused over that spectrum.


----------



## tomb

Quote:


  Originally Posted by *slowpogo* /img/forum/go_quote.gif 
_That's exactly it tomb, where did you get those? From the source given above (superbrightleds) or somewhere else?

 I once bought a "cyan" LED for my Pimeta, but it ended up looking plain old green. So I'm confused over that spectrum._

 

Sadly, LSDiodes. I'd tell you what wavelength they were, but that was on the LSDiodes site, too.


----------



## cetoole

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Sadly, LSDiodes. I'd tell you what wavelength they were, but that was on the LSDiodes site, too.
	

	
	
		
		

		
		
	


	


_

 

Using the Wayback Machine, from archive.org, it appears that the Sea Green 5mm LED from LSDiodes had a peak emission wavelength of 495nm.
http://web.archive.org/web/200610220...products_id=11

 Tom said something about me experimenting with a speaker option for the Max a few pages ago. So far, this "experimenting" has just been me having some old (~10 years) Sony 3 way bookshelf speakers I had sitting around as part of a mini system, and powering them instead using my Max. I havnt really done anything different with this, though a note to any trying it is that you cant have any additional output resistance for it to sound like anything. I prefer the sound though to what I get from the Sony amp. I bet the Sony can go louder, as it is rated for 100WPC (at 10% THD 
	

	
	
		
		

		
		
	


	




), but this sounds better to me, at the levels I prefer in my bedroom.


----------



## tomb

That _Wayback Machine_ is pretty cool!

 I was able to look up the wavelength the LSDiodes still in my parts box. The tricky thing has always been to match up a low-power panel LED with the high power ones under the tubes. It's been suggested before to use a much higher value resistor on the panel LED, but this is not an ideal solution. The panel LED should be _diffuse_. Also, the panel LED should be a 5mm (IMHO), whereas the 3mm's are under the tubes. All that conspires to mean that the panel LED is different.

 Anyway, here are the wavelengths of the other 3mm LSDiodes for those that are interested:

 Blue ...... 468 nm
 Green .... 515 nm
 Amber ... 586 nm
 Red ....... 625 nm

 I recently used the Green on a new MAX and that wavelength is a little difficult to find, too, unfortunately.


----------



## slowpogo

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_The tricky thing has always been to match up a low-power panel LED with the high power ones under the tubes...The panel LED should be diffuse._

 

My solution to this was to use a white LED for the panel. But, I've found that it's hard to find a low power white LED for some reason (most are at least 1000mcd), and even harder to find one that has a diffuse or "milky" lens. I'm still looking...


----------



## amb

I have "converted" clear-lens LEDs to milky-diffused by sprayting a few coats of matte-clear finish over the lens. Krylon makes something like that (usually available at hardware or automotive supply stores), and there are also others that could be found at hobby stores. Allow each coat to dry thoroughly before the next coat until the desired finish is reached.


----------



## slowpogo

Thanks amb, I will probably try that.

 So I'm waiting on parts for the can't miss build #1. I plan on following the suggestion of a PIO cap in CA8 and nothing in CA9. But, is there any advantage at all to using boutique caps in any of the other Wima positions? (CA3, CA6)

 I ask because I have some Auricaps from another project that I never used, and I thought I might as well put them in the Max.


----------



## tomb

Quote:


  Originally Posted by *slowpogo* /img/forum/go_quote.gif 
_<snip>So I'm waiting on parts for the can't miss build #1. I plan on following the suggestion of a PIO cap in CA8 and nothing in CA9. But, is there any advantage at all to using boutique caps in any of the other Wima positions? (CA3, CA6)</snip>_

 

No.


----------



## pinkfloyd4ever

hey I finally got all my parts to start my amp (thanks a TON to 04blumach) and I'm almost done soldering all the resistors and the small diodes, but I'm wondering, is it necessary to clean the flux, and if so, will alcohol hurt any of the other components? (if so I'll do it now, otherwise I think I'll wait till I'm done soldering on the board). I like to think I've been doing a pretty good job soldering, as nice as most that I've seen here, before cleaning flux anyway. Plus soldering on this board is SO MUCH easier than the ratshack protoboard most of us build cmoys on.


----------



## xmokshax

just thought i'd let everyone know that, after a misdiagnosed non-problem, my MAX is indeed alive and sounding excellent! 
	

	
	
		
		

		
		
	


	




 everything's up and running, DBs biased to 100mV... just needs to be cased up. i do have a couple of questions, though - perhaps someone can answer them for me.

 first: i'm hearing a good bit of scratchiness from my volume pot (standard RK27). this is especially noticeable when i change the volume with no music playing - it sounds like the wiper is grinding along the contacts. i don't have a lot of experience with the RK27 yet, but is this normal? i'm not using unusually sensitive headphones, it happens with both Senn HD535 and AKG K240.

 second: it takes a little while for the tube bias voltages to settle down to the ~13.5V set point, perhaps on the order of 3 to 5 minutes to get all the way down. i assume this is normal for tubes as they warm up, but i just want to make sure. there isn't any danger in listening to the amp when the tube biases are up in the higher teens rather than at 13.5V, is there?

 third (related to the above): how important is it to have the tube biases precisely at 13.5V (i know that the tubes CAN run without damage at much higher voltages, but does this affect the amp's sound?)? also, must the two tubes be biased very closely to one another in order for the two channels to sound the same? my tubes seem to be taking quite a while to settle down and stop drifting.

 fourth: how has everyone constructed the center support for the PCB? i read through the casework section of the MAX construction page, but i was still a bit uncertain what parts people use to make a nice, stable support and i couldn't quite glean this information from the pics on the site. is it just a screw with a nylon cap and a few washers stacked in between? what size screw fits best in the hole in the PCB?


----------



## slowpogo

Quote:


  Originally Posted by *xmokshax* /img/forum/go_quote.gif 
_fourth: how has everyone constructed the center support for the PCB? i read through the casework section of the MAX construction page, but i was still a bit uncertain what parts people use to make a nice, stable support and i couldn't quite glean this information from the pics on the site. is it just a screw with a nylon cap and a few washers stacked in between? what size screw fits best in the hole in the PCB?_

 

I can tell you what I've constructed..my pcb is in the first slot of the Hammond case. I got it all from Mouser:

 Nylon 4-40 thumb screw (1/2 inch, cut to size): 561-T0440050
 Standard nylon washer: 561-D432

 The screw and washer go through the top of the board, then on the bottom:

 Lock washer (against pcb): 534-4693
 Thick nylon washer: 561-D462
 Nylon hex nut: 561-G440

 If you're using a higher slot, you'd have to add some washers or a spacer under the board of course..maybe get a longer screw just in case. The thumb screw is nice because it gives you a little handle to slide the board out with.


----------



## tomb

Quote:


  Originally Posted by *xmokshax* /img/forum/go_quote.gif 
_just thought i'd let everyone know that, after a misdiagnosed non-problem, my MAX is indeed alive and sounding excellent! 
	

	
	
		
		

		
		
	


	




 everything's up and running, DBs biased to 100mV... just needs to be cased up. i do have a couple of questions, though - perhaps someone can answer them for me.

 first: i'm hearing a good bit of scratchiness from my volume pot (standard RK27). this is especially noticeable when i change the volume with no music playing - it sounds like the wiper is grinding along the contacts. i don't have a lot of experience with the RK27 yet, but is this normal? i'm not using unusually sensitive headphones, it happens with both Senn HD535 and AKG K240._

 

It definitely sounds like you have a problem pot. I believe if you remove the screws from the back, the front plate can be removed and you can spray in some contact cleaner. Sometimes if you aren't careful with the flux or with rinsing the board, you can get some flux into the pot. That can cause the scratching. Similar questions have been asked on the general DIY forum - you might do a search if that's working.

 If none of that works, it may be a bad pot.

  Quote:


 second: it takes a little while for the tube bias voltages to settle down to the ~13.5V set point, perhaps on the order of 3 to 5 minutes to get all the way down. i assume this is normal for tubes as they warm up, but i just want to make sure. there isn't any danger in listening to the amp when the tube biases are up in the higher teens rather than at 13.5V, is there? 
 

You're lucky - it sounds like your tubes are broken in. 
	

	
	
		
		

		
		
	


	




 I suspect, though, that if you were to check it some 3-4 hours later you may find that they're running at 12.5V instead of 13.5. Regardless, it's perfectly normal. In some cases with new tubes, it may take a week of running before they calm down - taking an hour or two to settle into a semi-constant bias.

  Quote:


 third (related to the above): how important is it to have the tube biases precisely at 13.5V (i know that the tubes CAN run without damage at much higher voltages, but does this affect the amp's sound?)? also, must the two tubes be biased very closely to one another in order for the two channels to sound the same? my tubes seem to be taking quite a while to settle down and stop drifting. 
 

Technically speaking, the bias provides the center point for the swing of the audio wave. We set our Millett and MAX tubes at 1/2 of the supply voltage. That gives a maximum voltage swing in both directions for the music signal sine wave.

 However, if the bias is too high, then the music may clip - Supply voltage minus bias voltage is your signal swing capability in the positive direction. Conversely, if the bias is too low, then the music may clip in the other direction.

 Is this precise? Heck no. Your bias can vary 2, 3 volts or more without you ever noticing it. Now, the reason I say always check bias if you change tubes is because going from a 12AE6 to a 12FK6 can sometimes result in a bias change of 8 or 9V. I think that's more than enough to make a difference.

 My tubes probably vary between 13 and 14 all the time. I tend to set them a little high - maybe 13.6 to 13.7, knowing that they typically drop a bit over a period of hours - but none of this is hard and fast - _or precise_ when it comes to tubes.

  Quote:


 fourth: how has everyone constructed the center support for the PCB? i read through the casework section of the MAX construction page, but i was still a bit uncertain what parts people use to make a nice, stable support and i couldn't quite glean this information from the pics on the site. is it just a screw with a nylon cap and a few washers stacked in between? what size screw fits best in the hole in the PCB? 
 

Slowpogo already gave you a great answer. I've also posted an answer further back. I typically use a 4-40 x 1/2" long screw and some combination of washers and spacers so that a thick nylon nut is just scraping along the bottom of the case.


----------



## xmokshax

slowpogo: thanks. i think i have most or all of those parts lying around. i'll also have the pcb in the bottom slot (Jeff's kit with the big tall KZs and 1.5" sinks), so what you've described will work perfectly. much appreciated.

 tom: thanks for the explanations. i haven't logged any serious listening hours on the amp yet, so it may well be that the tube biases will change a good bit after a few hours, as you say. i'm hoping i don't have to replace the pot, but we'll see.


----------



## cetoole

Quote:


  Originally Posted by *pinkfloyd4ever* /img/forum/go_quote.gif 
_hey I finally got all my parts to start my amp (thanks a TON to 04blumach) and I'm almost done soldering all the resistors and the small diodes, but I'm wondering, is it necessary to clean the flux, and if so, will alcohol hurt any of the other components? (if so I'll do it now, otherwise I think I'll wait till I'm done soldering on the board). I like to think I've been doing a pretty good job soldering, as nice as most that I've seen here, before cleaning flux anyway. Plus soldering on this board is SO MUCH easier than the ratshack protoboard most of us build cmoys on._

 

I like to clean as I go, since taller parts make it difficult to access the flux on the component side of the board. Wont hurt anything, though I like to be careful around the pot, since that is pretty much the only part that isnt hermetically sealed. If you use acetone like I sometimes do though, it will remove all of the ink from parts, especially capacitors.

 As to the board being easier than ratshack protoboard, you will get no arguments from me on that number, but I like to use pad-per-hole protoboard for prototyping, with all connections made using component leads as traces, and this, at least for me, is also much easier than struggling with that ratshack ****.
  Quote:


  Originally Posted by *xmokshax* /img/forum/go_quote.gif 
_just thought i'd let everyone know that, after a misdiagnosed non-problem, my MAX is indeed alive and sounding excellent! 
	

	
	
		
		

		
		
	


	




 everything's up and running, DBs biased to 100mV... just needs to be cased up. i do have a couple of questions, though - perhaps someone can answer them for me.

 first: i'm hearing a good bit of scratchiness from my volume pot (standard RK27). this is especially noticeable when i change the volume with no music playing - it sounds like the wiper is grinding along the contacts. i don't have a lot of experience with the RK27 yet, but is this normal? i'm not using unusually sensitive headphones, it happens with both Senn HD535 and AKG K240.

 second: it takes a little while for the tube bias voltages to settle down to the ~13.5V set point, perhaps on the order of 3 to 5 minutes to get all the way down. i assume this is normal for tubes as they warm up, but i just want to make sure. there isn't any danger in listening to the amp when the tube biases are up in the higher teens rather than at 13.5V, is there?

 third (related to the above): how important is it to have the tube biases precisely at 13.5V (i know that the tubes CAN run without damage at much higher voltages, but does this affect the amp's sound?)? also, must the two tubes be biased very closely to one another in order for the two channels to sound the same? my tubes seem to be taking quite a while to settle down and stop drifting.

 fourth: how has everyone constructed the center support for the PCB? i read through the casework section of the MAX construction page, but i was still a bit uncertain what parts people use to make a nice, stable support and i couldn't quite glean this information from the pics on the site. is it just a screw with a nylon cap and a few washers stacked in between? what size screw fits best in the hole in the PCB?_

 

Glad you got it working; it feels great for me to see these things come online.

 The scratchiness could be a result of a bad or dirty pot, but it also could be a due to DC voltage on the input. I would measure this, and quickly, since it can do damage to the pot, and generally isnt good to have DC on the input of the amp. It may be that you are one of the cases where input capacitors are advisable. If this is the case, there isnt a board location for these caps, but you just replace the input wire from the RCA jacks. I recommend ~1.5uf or so, but this is pretty flexible.

 As for the bias, the other guys covered this pretty well. I will say I am running Tung Sol 12FK6 right now, and each are holding constant at 13.5v on the plate after some hours of operation. I rolled these in about a week ago; they had been NOS prior to that.

 I am a bit different when it comes to the center hole than some of the others here; I use an aluminum standoff, screwed tightly to both the board and case, and use this as my only ground connection to the case. RCA jacks are isolated, as is the output jack. Makes a good, solid connection, which is the main reason I use it, and I have no worries about board flex when inserting or removing tubes. Really though, any of the listed methods work.


----------



## xmokshax

colin: i hear scratchiness only when i turn the shaft of the pot. i wasn't terribly specific about this in my initial post. is this still a symptom that would be consistent with DC on the input? i've only used an iPod as the source thus far, and i've measured very little DC on its output in the past.

 i'm thinking of ordering some 12FK6 tubes for the next MAX i build (this one is a gift, so now i have to take care of "number one"). where do you recommend buying them online? i'm sure this information can be found readily on the forums, and i'm doing a search as we speak, but i thought i might as well ask since your mention of your own 12FK6es reminded me.


----------



## cetoole

Quote:


  Originally Posted by *xmokshax* /img/forum/go_quote.gif 
_colin: i hear scratchiness only when i turn the shaft of the pot. i wasn't terribly specific about this in my initial post. is this still a symptom that would be consistent with DC on the input? i've only used an iPod as the source thus far, and i've measured very little DC on its output in the past.

 i'm thinking of ordering some 12FK6 tubes for the next MAX i build (this one is a gift, so now i have to take care of "number one"). where do you recommend buying them online? i'm sure this information can be found readily on the forums, and i'm doing a search as we speak, but i thought i might as well ask since your mention of your own 12FK6es reminded me._

 

DC offset on the pot is noticeable when turning the pot. Measuring the DC offset is a real quick way of determining if this is a problem with your amp. Also, is your pot grounded? Some funny sounds can ensue if it isnt. You can test for this if you are unsure with your DMM, by measuring resistance from some metal portion of the pot's case to ground.

 No idea where to buy Max tubes these days, I bought mine from vacuumtubes.net and radiodaze. Have GE, Tung Sol, Raytheon, RCA, DuMont, and Sylvania, in various different models. Probably have between 2-3 dozen Millett appropriate tubes in total, so I havnt had need to look for any more lately.


----------



## amphead

One small point that probably wont be affecting Max builders but is something to keep in mind, is........The heater voltage on the tubes should not be allowed to drop too low, say 10-20% lower than the tubes spec. The heaters which are a part of the filament, provide thermionic emmission. Sooooo they boil off electrons into the vacuum of the tube. This is essentially the electrons used to produce current flow from the cathode to the anode/plate. If the heaters voltage is too low, there is not enough available electrons sooooo.......the cathode slowly becomes pitted as electrons are stripped from its metallic surfaces, and eventually fails. This phenomenon is called cathode-stripping. Just some tube 101...... I don't know how much of a problem this is with low voltage tubes like the ones we use however. Dsavitsk?


----------



## tomb

Quote:


  Originally Posted by *cetoole* /img/forum/go_quote.gif 
_<snip>DC offset on the pot is noticeable when turning the pot. Measuring the DC offset is a real quick way of determining if this is a problem with your amp. Also, is your pot grounded? Some funny sounds can ensue if it isnt. You can test for this if you are unsure with your DMM, by measuring resistance from some metal portion of the pot's case to ground.
 </snip>_

 

Xmoshakx,
 Cetoole has a good point with the pot. If it really only happens when you touch and turn it, then it could very well be grounding as cetoole suggests. Did you install that wire from the pot ground pad to a screw on the pot?

 Amphead, 
 I think most of us run the MAX at 27V. For those that don't and run lower voltages, your post is a good admonition. The Millett tubes all have definite warnings that heater voltage should never be below 10V. Even with a heater resistor of 20 ohms (most use 10 ohms, I think), 24VDC in the PS would still result in about 10.7V per heater. So as you say, MAX builders shouldn't be affected.


----------



## xmokshax

cetoole and tomb: i haven't grounded the pot yet. i know that the buzzing sound i hear when i touch the pot's shaft is from lack of grounding, but didn't realize that the scratchiness might be caused by the same thing. i'll install the ground wire and see if it goes away.

 EDIT: ok, minimal DC on the inputs w/ my iPod - <1mV on each channel. soldered in a ground wire, which eliminated the buzzing (of course), but the scratchiness is still there when i turn up the volume. sounds like a (VERY) softened version of the sound you hear when you clean a record player's needle while the amp is on.


----------



## tomb

Xmokshax,
 I think you have a dirty pot. Buzz when you touch without grounding, but as you've found out - scratch stays. Most likely, you've got some dried flux in there.

 Same thing with my latest here 
	

	
	
		
		

		
			





 - 






 [size=xx-small]_(click for bigger pics)_[/size]

 I've got a scratching on the left channel when I adjust the pot. I haven't attached the ground strap yet, but just for a test: I attached a test jumper from ground to the pot. No go - the scratch is still there. It probably happened when I had to replace a couple of transistors a few hours ago.

 I should be working on drilling the holes in the MiniMAX case, but hey - it's a holiday. 
	

	
	
		
		

		
		
	


	




 Anyway, this is another Black Gate MAX I had built, but had never fired it up. I decided to work on it last night so that I could fire it up this morning.

 So first thing this morning - carefully, I screwed down the DB trimmers, stuck my probes in the left DB test points and fired it up. Hmm ... the meter says 0.0 - that can't be right - checked the meter setting, that was OK - checked the probes to see if they were making contact - that was OK. That's when I smelled it - burning plastic! 
	

	
	
		
		

		
		
	


	




 I cut everything off and began the troubleshooting. First, I suspected that maybe the Vitamin Q's that Colin gave me were contacting the opposite pads in their tombstone position, but no - measurements checked out. Everything else looked great, so I started checking the transistor numbers vs. their silkscreen locations. Even-numbered transistor, odd numbered silkscreen and vice-versa. Then I saw it: the two small signal transistors QB2L and QB3L were reversed. I had a 2N5088 in QB2L and a 2N5087 in QB3L. That was even-even and odd-odd - not right!

 About an hour's worth of surgery later (those little pins are tough to get out of the board holes!), I fired it up again and it sounds great. I can't tell whether it's Colin's Vitamin Q's or the 2SC2238/2SA968 transistor pairs, but it sounds better than my other Black Gate MAX did. The Vitamin Q's add a tiny bit of sparkle over the K42's perhaps, but they wouldn't sparkle if the sparkle wasn't there to begin with. I guess I'd have to say that the Chinese-Toshiba thing mentioned by 04BluMach is real. The other BG-MAX had Chinese versions. I'm still not convinced that these pairs are any better than the 2SC3422/2SC3421/etc. transistors - just different. However, I don't think there's any doubt the Chinese versions are not as good - noticeably. I'm starting to wonder if the "conjestion" I reported with BG's was simply the Chinese transistors. 
	

	
	
		
		

		
		
	


	




 Anyway, specs:
 Black Gate NX's for CA2 and CA7, Panasonic FM's all around - 1000uf in PS, 1800uf elsewhere, Wimas in the unimportant positions, Philco 0.47uf Vitamin Q's (I think that's what Colin said they were) - about 1-1/4" tall, 10ohm Kiwames on the output. I have a couple of Tung-Sol 12AE6A's in there right now, but the one on the right is irritatingly microphonic. It's only biased to 40ma so far - being extra specially careful after smoking those two trannies. Despite that, it sounds great already. What BG break-in?


----------



## Negatron

You might also check the continuity of RA7. It's also easy enough to paralell another 1M R between the grid pin of the tube socket and gnd.

 It's not uncommon for the neg V on the grid to cause noise from a pot if the grid R is not adequate.


----------



## tomb

Quote:


  Originally Posted by *Negatron* /img/forum/go_quote.gif 
_You might also check the continuity of RA7. It's also easy enough to paralell another 1M R between the grid pin of the tube socket and gnd.

 It's not uncommon for the neg V on the grid to cause noise from a pot if the grid R is not adequate._

 

Well, you may have something there. 
	

	
	
		
		

		
		
	


	




 After basically drenching the pot in flux remover and contact cleaner, it had no effect.

 After populating 7 of these boards so far, I'm fairly certain that RA7 is both sufficient and connected well on this board. However, the pins on the left tube are pretty bad. I've been straightening them all day on and off because the slightest twist in the socket bends them. They have some corrosion near the glass base. So, guessing that you were right - only maybe it's the pin connection to the grid - I switched tubes with their sockets. The scratching is almost gone except at very high volume travel and at that point, the very slight scratching is in both channels. So, maybe a little steel wool on the pins is in order - assuming that one tube doesn't drop its pins altogether, which I suspect will happen soon. 
	

	
	
		
		

		
		
	


	




 Gotta put me some good GE's in there. Meanwhile, problem solved - thanks.


----------



## Negatron

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Well, you may have something there. 
	

	
	
		
		

		
		
	


	




 After basically drenching the pot in flux remover and contact cleaner, it had no effect.

 After populating 7 of these boards so far, I'm fairly certain that RA7 is both sufficient and connected well on this board. However, the pins on the left tube are pretty bad. I've been straightening them all day on and off because the slightest twist in the socket bends them. They have some corrosion near the glass base. So, guessing that you were right - only maybe it's the pin connection to the grid - I switched tubes with their sockets. The scratching is almost gone except at very high volume travel and at that point, the very slight scratching is in both channels. So, maybe a little steel wool on the pins is in order - assuming that one tube doesn't drop its pins altogether, which I suspect will happen soon. 
	

	
	
		
		

		
		
	


	




 Gotta put me some good GE's in there. Meanwhile, problem solved - thanks. 
	

	
	
		
		

		
		
	


	


_

 


 I get a lucky guess sometimes. I realize you know, but for the benefit of others, steel wool for cleaning tube pins should be 4/0 or at least no more than 2/0. I mention this because I cringe when I hear people say they will 'wire brush' the pins to clean 'em. BTW, for bad corrosion, CLR or even 409 and a toothbrush works OK with a GOOD after rinse of H2O and then pure Isopropyl alky.


----------



## tomb

Agreed. It was a poor choice of phrase (key words:"maybe" and "little") - I don't own any steel wool, anyway. 
	

	
	
		
		

		
		
	


	




 More than likely, it will be a little alcohol and a soft toothbrush. 
	

	
	
		
		

		
		
	


	




 Biased up to 50ma now and it's burning in nicely.

 BTW, your solution helps explain another issue that pops up from time-to-time that I couldn't explain: cutoff noise in the delay circuit. The cutoff on the delay circuit almost always has a small pop or click. However, every once in awhile I get one with quite a "whoosh" in one channel on cutoff. Up till now, I assumed it was a problem with the relay.

 Well, this one had it in the left channel. After switching the tubes, now it doesn't. 
	

	
	
		
		

		
		
	


	




 I would've never guessed a poor connection with the tube grid was causing it.

 EDIT: Argggh - Head-Fi's changing smileys on me while posting this. Now "allteeth" is "big grin" - ":" and "D" instead of "
	

	
	
		
		

		
		
	


	




".


----------



## Negatron

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Agreed. It was a poor choice of phrase (key words:"maybe" and "little") - I don't own any steel wool, anyway. 
	

	
	
		
		

		
		
	


	




 More than likely, it will be a little alcohol and a soft toothbrush. 
	

	
	
		
		

		
		
	


	




 Biased up to 50ma now and it's burning in nicely.

 BTW, your solution helps explain another issue that pops up from time-to-time that I couldn't explain: cutoff noise in the delay circuit. The cutoff on the delay circuit almost always has a small pop or click. However, every once in awhile I get one with quite a "whoosh" in one channel on cutoff. Up till now, I assumed it was a problem with the relay.

 Well, this one had it in the left channel. After switching the tubes, now it doesn't. 
	

	
	
		
		

		
		
	


	




 I would've never guessed a poor connection with the tube grid was causing it.

 EDIT: Argggh - Head-Fi's changing smileys on me while posting this. Now "allteeth" is "big grin" - ":" and "D" instead of "
	

	
	
		
		

		
		
	


	




"._

 

The 'Smileys' have been interesting, but the site reconstruction was quite an impressive undertaking. I'm starting to write my own in brackets <g>

 I think my 4 most used tools with tubes has come down to Toothbrush, Alchohol, Caig DeOxit and most called upon of the lot - patience. (large grin)


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## regal

With film bypass caps degrading the bass on the cathode caps I wonder if it would make sense to try no CA2 cap at all. I know many times designers just use a resistor on the cathode. Has anyone tried this?


----------



## tomb

Quote:


  Originally Posted by *regal* /img/forum/go_quote.gif 
_With film bypass caps degrading the bass on the cathode caps I wonder if it would make sense to try no CA2 cap at all. I know many times designers just use a resistor on the cathode. Has anyone tried this?_

 

Regal,
 What the MAX reveals is that many, if not most boutique film caps roll off in the bass and highs. That's not a damaging scenario unless paired as a bypass to the electrolytic cap in the cathode bypass. If the film cap in that scenario is not flat and neutral, then frequency response of the entire amplifier suffers.

 This can be gleaned from places other than experience with the MAX. Dsavitsk first mentioned it in this thread and his excellent Notes on Output Coupling Capacitors reference gives some inkling to this.

 So, bottom line - a boutique is not as good as a plain Wima in this scenario, where the Wima at least provides some highs resolution in contrast to the electrolytic it bypasses. Go further than that, and the blooming mids - tuned "boutique" film cap does almost nothing but damage the response.

 PIO's such as the Russian K42 or Vitamin Q's - contrary to conventional wisdom (also confirmed by Dsavitsk) - are actually very neutral. These are fine bypassing the electrolytic in the CA2 position, but offer little over the plain Wima - except when it comes to Black Gates. Black Gates are good enough that the slight squeekiness and grain in the Wima's degrades the BG's. In that case, the K42's or the VitQ's will do a good job.

 IMHO and YMMV, of course - but this is what we have found with the MAX.

 P.S. Colin actually experimented with his MAX just using a resistor (an adjustable one, though) in the cathode bypass position. He eventually went to ES electrolytics and VitaminQ's - for a better sound, I think.


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## Negatron

A few comments regarding cathode caps in the MH or Max. As a rule over time I have come to avoid the use of cathode caps as an detriment to detail and further, I regard electrolytics as no more than a sometimes necessary evil. That being said, I can make a case for EL K bypass in the MH or Max.

 One of the effects of a cathode cap is reduction of effective plate resistance or rp and the increase of transconductance or gm. In the case of the automotive tube used in the Max the gm is already extremely low. The omission of the cathode cap lowers the gm of the tube to very low levels as well as a pretty good apparent raise in rp and the tube already exhibits a pretty strange distortion spectrum with unusually high odd order distortion products to a level usually seen only in solid state devices. The large drop in gm and a major increase of rp by not using the K cap don't help the condition at all. The tube requires an almost zero load to operate under these conditions.

 The original MH used an opamp buffer presenting a load to the tube greater than 100Meg, and the lack of load was a condition the tube benefited from. The buffer BJT input in the max presents a considerably lower input impedance and much greater load for the tube to drive. And the tube is not up to the task without a (large) cap on K. To my ears the original MH sounded best without a K cap. When I replaced the 551's with a DB I found the sound to degrade quite a bit. I'm not a fan of solid state but the change was hard to accept even with SS prejudice. The problem was fixed by the addition of a K cap. Drat, foiled again! (frowning icon)

 I don't know if this clouds the waters worse or makes sense, I can't write worth a darn. Once it leaves my head and hits type it gets muddled up. But I am an avowed enemy of the cathode cap and yet recommend one with the Millett. There are contributors to this thread who have a far better understanding than I about this, as well as a lot more experience with the Max. Hopefully they can simplify this better than I can. (confused Icon)


----------



## steinchen

The load on the tubes is definitely a problem that degrades performance. While prototyping buffers about a year ago a tried several buffers with my revMH I owned that time, although the buffer was meant for my SOHA amp. To me the JISBOS (with its high impedance JFET input stage) sounded best. Colin, Tom, you may consider a JISBOS buffer output stage for the next evolution.

 Nevertheless, Kudos and thanks to Colin and Tom for the MAX project. I just completed my MAX a week ago during the holidays: pic1 pic2


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## tomb

As you both imply, the cathode cap is important, if not critical in the MAX. This is why we went to the 1000uf rating. The MAX suffers if the cap is not that big. The original Millett and revMH Millett used a 220uf cap for C2. That size was thought to be about twice what was needed, according to the corner frequency equation. As far as I know, no revMH Millett with Diamond Buffers had a bigger C2 cap than 220uf - it simply wouldn't fit. (Actually, if memory serves, Bperboy built one with rather large Elna Cerfines that canted out from the edges of the buffer board in a horizontal direction.)

 Through extensive prototyping, we found certain aspects of the MAX that were needed to ensure optimum performance. Some of these items didn't follow the perceived theory: sizing the CA2 cap is one of them. CA4 and CA5 are important as well. That's why we included the selection of "Can't Miss MAX Builds" on the MAX website - to emphasize that there are some important differences from what went before. Perhaps Negatron's posts finally explain what's going on with CA2. I'm guessing that some of Amb's recent posts on power rail variance probably explain the importance of CA4 and CA5 as well.

 At any rate, each MAX that I've built performs better than the four Millett Hybrids I built before (one was pictured earlier with the aqua LED's). With Steinchen's DB boards, they were no slouches, either, and were my favorites!! I hope you found the same, Steinchen, but with the level of superlative amps in your collection - it may be hard to tell. 
	

	
	
		
		

		
		
	


	







 That's definitely a great looking MAX to add to your collection!

 BTW, your development, testing, and reviews of the DB's and DB transistors has been critical to the MAX's success. Your work has been referenced numerous times in the MAX's documentation. Thanks for the kudo's and all of the work you did that we built on!
	

	
	
		
		

		
		
	


	







 P.S. Colin is going to work on further MAX refinement. I'm pretty sure one of the first things he will include will be his Bipolar Discrete Shunt Regulators. They recently got some nice comments from Jan Didden over on DIYAudio. There are some other things that may be pretty surprising, but we'll have to wait!!


----------



## cetoole

I find it kinda interesting that you guys are finding such a difference depending on buffer input impedance. While not as high as JFETs, the BJT diamond buffer doesnt exactly have a low input impedance. Yeah, there is the base current requirement, but this should be pretty low. I do imagine though that it becomes significant when the cathode resistor is completely unbypassed. The reason I wouldnt have thought it would be as important as you seem to feel is because the impedance of the CCS is in parallel with the impedance of the output buffer, and neither CCS, that used in the RevMH or the MHMax, are _that_ high impedance circuits. Seems to be one of the major tradeoffs to get good performance with minimal voltage drop. Changing the CCS was one of the things I am considering though for the next version, probably to voltage reference diode biased BJT, which is then cascoded with a P-Channel JFET. Since the current requirements are quite low here, we can utilize some very good, low capacitance parts. I have looked at the voltage swing on the output of my MHMax, while driving loads varying from my 300ohm Sennheiser HD580 headphones to a pair of 8ohm 3 way bookshelf speakers, and it never got even close to the limits imposed by the supply, so I feel that the tradeoff to get better CCS performance are probably worth it. Of course, this CCS isnt nearly as high impedance as something like the Pimm Self Biased Cascoded Mosfet CCS circuits I built for the parafeed 6c45pi spud amp I am working on, but those require about as much voltage be dropped across them as the whole B+ of the MHMax. Performance is exceptional though.

 The other major change I am working on are a new regulator, as TomB mentioned, though he posted a link to some shunt regulators I am working on for my DAC project, specifically the +/-15v regulators meant to power the discrete I/V output stage and buffer. Lower versions are also configured for the digital supplies. However, I am not nearly crazy enough to attempt a 250mA CCS loaded shunt regulator for this amp. Call me crazy (or sane, or whatever?). I have been working on a series regulator, of similar topology to that TomB linked, but being the stupid git I often am, left the simulation files on my work computer in my school's library, so I will have access to them again tomorrow when UMBC reopens for January term. Performance is quite similar to the shunt regulators, but impedance is lower, almost certainly due to the increased current through the pass transistor. Dropout voltage is very similar to the LM317. I will also be doing some minor layout changes, mainly to improve cooling, and adding positions for grid stopper resistors. Not sure how much these tubes really need grid stoppers, but I figure they cant really hurt, and will definitely help the layout be more direct.

 Steinchen, while I am sure the JISBOS sounds great as a buffer for the MH, I prefer not to adopt it for several reasons. First, it makes parts sourcing much more difficult, because of those matched complimentary audio JFETs. I have a number of 2SK170BL and 2SJ74BL, but many people do not, and dont wish to place an order with some place like BDent. Also, I prefer not to use a feedback buffer in an amp with an output coupling capacitor. Rest assured, when I do something similar to the SOHA with bipolar supplies for the buffers and an interstage coupling capacitor, I will almost certainly use something like the JISBOS. Are you sure it was really the increased input impedance you attribute the improved sound to that was making the difference, not something like the different topology or feedback, or the decreased output impedance caused by the feedback? Have you tried a similar topology to the diamond buffer ever, but using FET devices? There are the Toshiba audio JFETs that could be used for input transistors, or maybe some of the zetex complimentary MOSFETs, which look to be pretty good for that. I forget the Zetex part numbers, but I can look them up if there is interest. I think I have some of them here too. BTW, great looking Max you have there Steinchen. FPE perspex for the front panel? I dont recognize the case, is it custom?

 Negatron, good point about the gm of these tubes being low (~1000uS) even in optimal operating conditions. As TomB said, I originally used my Max with the cathode resistors unbypassed, but eventually changed that to how it is now (1000uf Nichicon Muse ES, 0.47uf Philco PIO bypass), but this was due to H-K leakage problems I had with some tubes. I dont clearly remember the sonic changes the bypassing made, but I do remember the sound got darker. Probably because rp was high enough to be relatively close to the parallel impedance of the CCS load and diamond buffer. Dunno for sure though. I have thought of just adding a small input coupling cap after the pot, and implementing an opamp integrator servo providing fixed bias a couple times. I am still thinking this might be the best set of tradeoffs of any of the possibilities. Autobias circuit would be able to be extremely simple here, because of the low voltage SE class A nature of the tube stage of the amp.


----------



## steinchen

Quote:


  Originally Posted by *cetoole* /img/forum/go_quote.gif 
_Are you sure it was really the increased input impedance you attribute the improved sound to that was making the difference, not something like the different topology or feedback, or the decreased output impedance caused by the feedback?_

 

Impossible to say :/ I just figured the higher impedance played a (major) role in it. 

  Quote:


  Originally Posted by *cetoole* /img/forum/go_quote.gif 
_Have you tried a similar topology to the diamond buffer ever, but using FET devices?_

 

not yet, but that's a good idea worth to be investigated

  Quote:


  Originally Posted by *cetoole* /img/forum/go_quote.gif 
_BTW, great looking Max you have there Steinchen. FPE perspex for the front panel? I dont recognize the case, is it custom?_

 

yup, front and rear panels are made of perspex by FPE. I got the case from elcal.de, a good source for affordable cases here in Germany.


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## dsavitsk

Quote:


  Originally Posted by *cetoole* /img/forum/go_quote.gif 
_ I dont clearly remember the sonic changes the bypassing made, but I do remember the sound got darker. Probably because rp was high enough to be relatively close to the parallel impedance of the CCS load and diamond buffer._

 

I'd tend to doubt it. Even the worst CCS still has pretty high impedance at audio frequencies. You are adding maybe 18K to rp by not bypassing (Rk * mu) which brings it up to 36K or so. The CCS must be at least an order of magnitude higher than that.

 My recent experiments, especially with this design seems to, at least in part, confirm my suspicions that the "warm" and "mellow" characteristics of most tube amps has more to do with the caps in the signal path rather than the tubes. That particular amp more or less gets all the caps out of the signal path, and it is not warm or mellow in the least bit -- fast and clear is more like it. It is simple enough to put some caps back, and when I do the character takes on that familiar "tubey" sound. I'd bet that the darker tone is from the ES's. 

 -d


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## tomb

My bad on the link, Colin. Told you it was too technical for this ME.


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## Negatron

Quote:


  Originally Posted by *cetoole* /img/forum/go_quote.gif 
_I find it kinda interesting that you guys are finding such a difference depending on buffer input impedance. While not as high as JFETs, the BJT diamond buffer doesn't exactly have a low input impedance. Yeah, there is the base current requirement,_

 


 dsavitsk sort of nailed it with his comments about the role caps play in the audible characteristics of the amp. The Millett can be tweaked far more by caps than much else. As to the R load the tube sees and the role that plays, I personally believe it to have a bearing on that particular tube family. With me the solution is simple, I ordered MOSFETS from AMB and am omitting QB2 & QB3, problem solved. On to the fun of the build. I was going to ask about a jfet input in the Diamond Buffer but the circuit itself is fine. And I'm kinda' afraid to ask now anyway. 
	

	
	
		
		

		
		
	


	




  Quote:


  Originally Posted by *cetoole* /img/forum/go_quote.gif 
_The reason I wouldn't have thought it would be as important as you seem to feel is because the impedance of the CCS is in parallel with the impedance of the output buffer, and neither CCS, that used in the RevMH or the MHMax, are that high impedance circuits._

 

It isn't so much the actual calculated or measured impedance but rather what the tube thinks it sees. And in the case of the MH or MAX it is a VERY large rp. That's all the tube needs to know to work in the circuit. One of the beauties of this circuit is it's simplicity and the way things work together to bring out something special. When someone falls into the trap of measurements and tubes in the same arena they are on the road to the 'rubber room' "Alice, down the rabbit hole" (L. Carroll), comes to mind.

 Change this little amp too much and it is not going to be the same amp and it is not going to have the same Magic. Please keep in mind my observations about the MAX and load the tube sees comes from a brain that has been nailed far too many times with 5 and 6 hundred volts over the years. I certainly have no business commenting very seriously on devices that run on compressed smoke. I am far better suited playing with my Vacuum devices and the Crayons they let me have to draw with. 
	

	
	
		
		

		
		
	


	




 An observation I have made over time with amps is a lesson that has stayed with me and embedded itself. Take the design of 3 major old amps, a McIntosh, a Fisher and a Scott in that order. I have listened to them all extensively and studied their designs. The Mac wins hands down as the finest Lab amp built. The engineering is involved and elegant. The measurements are without peer (almost).

 But the amps are un-involving, sterile to the point of boredom. Enter Avery Fisher, again Elegant EE, but the amps are trimmed to death, they looked good, and were a very well measuring and designed, alternative to the Macs. Very well regarded indeed. Kind of boring though also when you listen to them. Then there is Herman Hosmer Scott,. Fishers nemesis. His designs are studies in simplicity, they don't measure as well as the former two, but.... They are more 'Musical', the un-defined, can't quantify, subjective quandry. All 3 used good iron, that was the commonality. But from massively designed elegance down to 'stripped to only what is necessary to work' school, coincides with a steady improvement in 'Musicality"
 (PLEASE don't follow up with these particular comments, it is Holy War territory and I just mention it as personal observation.)

 JMO YMMV


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## amphead

Quote:


 But from massively designed elegance down to 'stripped to only what is necessary to work' school, coincides with a steady improvement in 'Musicality" 
 

Probably the inherent shorter signal path, improving musicality. Fewer losses and less introduction of unwanted noise from excessive circuitry.


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## pinkfloyd4ever

so I was soldering the 4 CR3s in the power supply and I pulled on one of em too hard (mine had like 3 mm lead spacing) to try to get it down close to the board and cracked the yellow casing of the cap. It's not real bad, just a couple mm around the leads. Should I replace it or will it be ok? I don't know much about ceramic caps, do they have any liquid in em like electrolytics or PIOs? I'm working on getting some good pics, but the macro mode isn't great on point n shoots

 EDIT:


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## tomb

Quote:


  Originally Posted by *pinkfloyd4ever* /img/forum/go_quote.gif 
_so I was soldering the 4 CR3s in the power supply and I pulled on one of em too hard (mine had like 3 mm lead spacing) to try to get it down close to the board and cracked the yellow casing of the cap. It's not real bad, just a couple mm around the leads. Should I replace it or will it be ok? I don't know much about ceramic caps, do they have any liquid in em like electrolytics or PIOs? I'm working on getting some good pics, but the macro mode isn't great on point n shoots_

 

No, they don't have liquid. Just venturing a guess here, but I doubt that you'll ever notice a difference. They're only there to take out some of the switching noise in the rectifiers, which with the MBR's is probably negligible, anyway. I smashed quite a few of them on several TREADS with little audible effect. Order some more when you get a chance or pick some up at Radio Shack. They're only pennies at Mouser and DigiKey, but if you have a minimum order and pay shipping then maybe this outrageous price at Radio Shack is a better deal:
100pF 50V 10% Hi-Q Ceramic Disc Capacitor  ($1.49/pr)


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## amphead

Thats verrrry nice Dsavitsk!


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## Negatron

Quote:


  Originally Posted by *amphead* /img/forum/go_quote.gif 
_Thats verrrry nice Dsavitsk!




_

 

JMO, but that is how an tube amp should look. Stunning!


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## tomb

Yes, Dsavitsk knows how to build (and design) a good tube amp.


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## Negatron

Since I've already wandered down a dead end with the plate resistor excercise, I thought I would inquire from the vast experience here rather than just rip up something else and ask if anyone had played with the detector diodes as relating to the unusual quantity of odd order distortion products. 

 Since the anodes are in effect negativly charged, bass-ackwards from where they are supposed to, be could their coupling with the cathode be causing some anolomoly in the distortion spectra?

 As the cathode is above ground, the plates of the Diodes are negative in respect to the cathode. They are, it seems to me to being a pair of very poorly constructed grounded grids. Anyone tried tying them to the cathode?


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## tomb

The diodes have always been grounded this way in the Millett, AFAIK.

 I will have to disagree slightly about the theme when it comes to the Millett with BJT Diamond Buffers and the MAX, however. After 11 of these things (counting 4 of the revMH Milletts), and dozens of tubes, I'd have to say that tube variations are slight at best. The primary variation in the tubes is the change from a 12AE6/A to a 12FK6, with the 12FM6 inbetween - that being that the 12AE6 is more punchy with better bass, whereas a 12FK6 is a bit airy with more extended highs, but less bass.

 Brand distinctions are so muddied with the wide subcontracting/re-branding that went on between mfrs, that it's difficult to distinguish any consistent difference. These differences are easier to hear with the older Millett running BUF's, Intersil's, or OPA551's. Again, the primary difference being between punchy bass vs. airy highs.

 The BJT DB-equipped Millett changed a lot of that and the MAX goes even further down that road. IMHO, almost the entire signature of the amp is controlled with the choice of BJT's. Those differences follow Steinchen's BJT reviews almost down the line. The difference between a 2SC3422/2SA1359 MAX vs. one with 2SC3421/2SA1358 is extreme. 2SC2238/2SA968 is still different from those, too. It's one of the reasons I've built so many. Each one with different BJT's is distinctly different in sound signature. It's as if they are _different_ amps - giving you the ability to pick and choose according to mood, music, and headphones. 
	

	
	
		
		

		
		
	


	




 EDIT: Even with caps - I'd have to say the choice is one of "good" vs. "better," not "different."


----------



## Negatron

Tomb, I think my question may have been mis-understood in meaning. I have no issue with the SQ of the Millett over all, truly, I'm impressed by it. My point of curiosity is that the tube itself, each of them actually, exhibit unusually high 3rd order harmonics, a condition not at all normal for a single stage non-global feedback triode.

  Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_The diodes have always been grounded this way in the Millett, AFAIK._

 

This is my point, "Always". Something Pete Millett did probably for the sake of simplicity and then it has been forgotten. A simple solution to deal with unwanted elements is to ground them. But is there perhaps an effect of grounding an anode, meant to be at positive potential in proximity to a negative cathode and the surrounding electron cloud.

  Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_I'd have to say that tube variations are slight at best. <snip>_

 

That is pretty much as it should be, tubes do tend to produce the same base sound signature BUT there are usually greater variations than exist here. But again they all share the unusual distortion distribution. Granted the space charge tube is a bit of an unusual tube and it may well be that's all this is.

  Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_The BJT DB-equipped Millett changed a lot of that and the MAX goes even further down that road. IMHO, almost the entire signature of the amp is controlled with the choice of BJT's. Those differences follow Steinchen's BJT reviews almost down the line. <snip> It's one of the reasons I've built so many. Each one with different BJT's is distinctly different in sound signature._

 

This goes back to what dsavitsk mentioned previously, that being the change Caps have on the amp and I agree also that choice of semi conductors has an effect as well. I agree that tubes are essentially neutral, though differing tubes can vary greatly in interaction with surrounding topology.

 Please understand I am NOT taking issue with the amp. I am not putting the tubes at issue either. All this stems from a simple question, being essentially "Has anyone ever tried to connect the anodes of the tubes un-used diodes to the cathode" or even ground them through a large R. Has common practice never been questioned? Triodes exhibit primarily second harmonic products. period. You have to coax them to go further. These little guys are spewing out 3rd harmonic right out of the gate. Why?

 I'm a 'tube guy' I normally could care less about distortion numbers in the tenths of a percent. But my ears perk up when I see an odd order harmonic where it should not be.
 That's all this is, curiosity. My scopes are old, my plug-ins are tired, I don't own a spectrum analyzer. I'm impressed with the design just as it is. I merely asked a question about diodes. 

 What if elimination of an unusual 3rd harmonic was simple?


----------



## soloz2

what voltage do the tube LEDs need to be? I forget. I'm looking for some white and some amber ones.


----------



## dsavitsk

I doubt that the grounded anodes of the diode sections are making any difference -- it is pretty common practice to simply ground unused portions of a tube to prevent interference, but it should be an easy enough thing to test. These tubes don't show much, if any, tendency to oscillate, so instead of adding a tube socket, add a few short wires and connect the tubes via clip leads. Then, connect the anodes however you like -- my guess is no change, at least not for the better.

 I think it is a little bit of an overstatement to say that tubes don't have odd harmonics. What they don't seem to have are 17th order harmonics, but 3rd is not uncommon. Some of the most commonly used audio tubes -- 6dj8 for example -- have a pretty high 3rd harmonic. These little tubes are designed for low voltage, were designed and manufactured at the very end of the "tube era", and were never intended to be good performers in terms of distortion being made for car radios. I think it is these factors that are leading to the highish numbers.


----------



## tomb

Quote:


  Originally Posted by *Negatron* /img/forum/go_quote.gif 
_<snip>Tomb, I think my question may have been mis-understood in meaning. I have no issue with the SQ of the Millett over all, truly, I'm impressed by it.</snip>_

 

 Oh no - didn't mean that! I just meant that the idea of messing with the tubes - or even the caps - is not going to have nearly the effect on sound signature as the BJT's. It just seems to me after comparing to other amps that there are certain things that one needs to be careful with in selecting tubes and caps, but it's more or less to make certain that the BJT's sound quality isn't impeded - not the other way around. (from my humble experience)

 This is directly counter to the basic SOHA, for instance, where the tube is probably 75% of the sound signature of the amp. I've enjoyed rolling many different tubes and writing tube reviews on the SOHA myself. From that aspect, the Millett tubes are very different, IMHO. They just don't vary that much - except perhaps the previously referenced change from 12AE6 to 12FK6. The 12AU7, 5963, 5814, 6189 etc., tubes can have extreme differences in sound signature, especially at the SOHA's reduced plate voltage. I'm guessing the Jisbos may have a similar effect to the SOHA as the DB's did to the Millett: making the buffer contribution to sound signature much more significant. I don't know that yet, though, and not enough people have reported specifics yet.

 Anyway, I'm getting way too sensitive about comparisons to the MAX and I apologize to everyone!! I wasn't getting at that at all this time.


----------



## tomb

Quote:


  Originally Posted by *soloz2* /img/forum/go_quote.gif 
_what voltage do the tube LEDs need to be? I forget. I'm looking for some white and some amber ones._

 

Voltage is set by the LED resistors, but the resistors are really there to set current. You are looking for high MCD's (thousands) at something around a 10-20ma rating on the LED's.

 I changed the BOM awhile back because the original RLED's were a bit too high in current. It's been said that with high-MCD LED's, you can decrease current quite a bit with little decrease in light. I guess that's right - the new RLEDs are 2Kohm for simplicity and seem to work well.

 At 27VDC, that would work out to 13.5ma per LED.


----------



## Negatron

Quote:


  Originally Posted by *soloz2* /img/forum/go_quote.gif 
_what voltage do the tube LEDs need to be? I forget. I'm looking for some white and some amber ones._

 

A diode will drop in the range of 1 1/2 to 2 volts, If you figure 2 volts @ 20ma you'd drop about 10.6v or need a 530 ohm resistor so a 470 would be fine, 220 ohm would be nice and bright and use about a 1/2watt so a 1 watt R would be used. That's just a baseline, the specific diode specs will give you more exact values for your needs.

 EDIT: Ignore post - See tomb's above


----------



## Negatron

Quote:


  Originally Posted by *dsavitsk* /img/forum/go_quote.gif 
_I doubt that the grounded anodes of the diode sections are making any difference -- it is pretty common practice to simply ground unused portions of a tube to prevent interference, but it should be an easy enough thing to test. These tubes don't show much, if any, tendency to oscillate, so instead of adding a tube socket, add a few short wires and connect the tubes via clip leads. Then, connect the anodes however you like -- my guess is no change, at least not for the better.

 I think it is a little bit of an overstatement to say that tubes don't have odd harmonics. What they don't seem to have are 17th order harmonics, but 3rd is not uncommon. Some of the most commonly used audio tubes -- 6dj8 for example -- have a pretty high 3rd harmonic. These little tubes are designed for low voltage, were designed and manufactured at the very end of the "tube era", and were never intended to be good performers in terms of distortion being made for car radios. I think it is these factors that are leading to the highish numbers._

 

Everything going at once and I'm a hunt and peck typist. I over simplified, what I usually find with tubes and my primitive gear is that the third is way down in relation to the 2nd compared to most BJT's I have dealt with. I just wondered if anyone had played with it before. It's easy enough to lift pins, I just didn't want to wast time on another dead end. (Anode R vs CCS)


----------



## amphead

I tend to think that the signature of the MAX, has hit its peak, and that the only improvements have been the quality of the BJTs and caps used to build it. The tube brands having a slight impact on the "flavor" of the sound. As far as any major redesigns, I think that only for a completely different animal would they be desirable. Such as, some of those other tubes that might be used. And then it is no longer the Max as we know it. Just(mho).


----------



## tomb

Quote:


  Originally Posted by *amphead* /img/forum/go_quote.gif 
_I tend to think that the signature of the MAX, has hit its peak, and that the only improvements have been the quality of the BJTs and caps used to build it. The tube brands having a slight impact on the "flavor" of the sound. As far as any major redesigns, I think that only for a completely different animal would they be desirable. Such as, some of those other tubes that might be used. And then it is no longer the Max as we know it. Just(mho)._

 

Your humble opinion is seconded. 
	

	
	
		
		

		
		
	


	




 The only caveat I would add that was being discussed in the last few posts is that IMHO, the type of BJT's may add more "flavoring" than the tubes at this point.

 You are absolutely correct - the MAX is "maxed" out. We can shrink it some, as in the Mini MAX, but a major re-design will result in a new amp altogether.


----------



## powertoold

Would the Max be suitable for use with sensitive IEMs at all? I have this particular bias against tube amps for having too much background hiss.


----------



## cetoole

Quote:


  Originally Posted by *powertoold* /img/forum/go_quote.gif 
_Would the Max be suitable for use with sensitive IEMs at all? I have this particular bias against tube amps for having too much background hiss._

 

Probably would want to use an output resistor. I know that without one, I heard some noise when I had my Shure E4's plugged in to my Max. It may have been residual H-K leakage, not sure exactly, since I dont hear it with any other headphones. Using 100ohm Stackpole resistors now (for headphones, speaker outputs are taken before the resistors or relay), mainly to lower the gain, but IIRC, it also eliminated the noise for my IEMs. Still, I am not sure I would recommend this amp for you if you are only going to be using it with IEMs. The gain is rather high, there is more noise than most SS circuits have (which isnt usually an issue, just with ubersensitive IEMs), and it is about as portable as a pair of bricks on a leash.


----------



## slowpogo

Just wanted to share something I learned...RS-Components sells all the Toshiba transistor types used in the Max. They are sold under the Toshiba name, but, are really generic.

 The RS rep actually told me they were genuine Toshiba in an email. After a little digging I discovered they are sourced from a place called Magnatec in the UK, who manufacture their own in-house equivalents of these transistors.

 So they're probably good quality, better than Chinese rush jobs, but are not actual Toshiba so who knows how they would sound.

 Wow, I'm glad I picked mine up from Beezar before Tom ran out. These suckers are hard to find.


----------



## fran

err, I've only got as far as page 60 in this thread, but have to buy some parts for the max!!

 So 2 quick questions:

 Can I use a 100K pot instead of 50K?

 CA7 is down as 470uF/35V electrolytic. I have 600V PIO 470uF caps here that would do nicely. Would it be OK to use them? (other than the space issues).


----------



## tomb

Quote:


  Originally Posted by *slowpogo* /img/forum/go_quote.gif 
_Just wanted to share something I learned...RS-Components sells all the Toshiba transistor types used in the Max. They are sold under the Toshiba name, but, are really generic.

 The RS rep actually told me they were genuine Toshiba in an email. After a little digging I discovered they are sourced from a place called Magnatec in the UK, who manufacture their own in-house equivalents of these transistors.

 So they're probably good quality, better than Chinese rush jobs, but are not actual Toshiba so who knows how they would sound.

 Wow, I'm glad I picked mine up from Beezar before Tom ran out. These suckers are hard to find._

 

I should have bunches more by the end of the month. 
	

	
	
		
		

		
		
	


	




  Quote:


  Originally Posted by *fran* 
_err, I've only got as far as page 60 in this thread, but have to buy some parts for the max!!

 So 2 quick questions:

 Can I use a 100K pot instead of 50K?

 CA7 is down as 470uF/35V electrolytic. I have 600V PIO 470uF caps here that would do nicely. Would it be OK to use them? (other than the space issues)._

 

No. Generally speaking, anything from 10K to 100K is OK.

 As for the caps, there's no issue as long as the uf's are enough for your headphones. If the R of your headphones times the C of the capacitor is not large enough, it will filter some of the bass frequencies. If all you ran were 300ohm Senns, you can actually get away with 220uf. 470uf is enough for almost all headphones, including 32ohms. You're right, though, I think you will have space issues with PIO caps that big. What are they - beer can size, maybe?


----------



## cetoole

Heck no, 470uf 600v PIO caps are gonna be much larger than beer cans I bet. I have some 55uf 250v dry MKP caps, and they are about beer can size. Probably closer to 6 pack size, or mini keg.


----------



## fran

Eh, well I got that one wrong! The ones I have here are 47uF and PP, not PIO. Funny what memory does to ya.

 Anyhow, I went and bought a 100k stepped pot. Dunno if its gonna be crap but got it from ebay and it uses SMT resistors (vishay dale if you can believe that). Claims are for a shorter signal path. Probably crap, but I said I'd give it a try. 

 My case will be different anyway, so I will be using some flying wires for the attenuator and headphone jack anyway.


 Another question: There appears to be 2 options for the CCS current (0.65mA vs ?). Which gives the best sound and is there any other factors to watch out for?

 TIA and I know most of this is probably buried in here, but time is against me.

 Fran


----------



## tomb

Quote:


  Originally Posted by *fran* /img/forum/go_quote.gif 
_<snip>Another question: There appears to be 2 options for the CCS current (0.65mA vs ?). Which gives the best sound and is there any other factors to watch out for?

 TIA and I know most of this is probably buried in here, but time is against me.

 Fran_

 

Actually, I assume most people know this, but most of the information is "buried" on the MAX website. 
	

	
	
		
		

		
		
	


	




 There's quite a discussion on the CCS under "Tweaks -> CCS/Tube Bias".

 You'll also find Pete Millett's original Millett Hybrid Audio Xpress magazine article, linked from the "History" section. In that, Pete discusses some of the testing he did with CCS currents. I believe he remarked that a CCS current of 1ma gave him more distortion than lower values. Neither CCS current option mentioned on the Bill Of Materials is different enough to be noticeable. The second CCS option was selected for convenient resistor sizes. The 1K resistor, in particular, is ubiquitous. The 10K is also more plentiful than either of the other two sizes in the original CCS.

 Just make sure to look at the website. Another good page to focus on is the "Tweaks -> MAX Boutique" section, where I recently added the "Can't Miss MAX Builds" table.


----------



## fran

Thanks TomB,

 I had read the site, but didn't remember seeing anything about the CCS bit. Mouser seem to have all the appropriate value resistors so the "normal" CCS should be OK for me.

 It looks like I'll be going with build 6 - regular build, just because getting the boutique caps is such a PITA here. Mouser don't seem to stock them either. I do have some 0.22uF caps that would be nice for bypasses, but I have read the warnings about not everything working in there, so I might just order up the wima ones anyway.

 Who is everyone buying tubes and bases from? (don't think I will light the tubes with LEDs, so that won't matter)

 Fran


----------



## tomb

*Tubes*

 Radio Electric Supply: Vacuum Tubes Radio Tubes - 5,000 different tubes in stock - Over 10 million tubes!
 Radio Daze: Radio Daze
 Antique Electronic Supply: Antique Electronic Supply
 The Tube Depot: Welcome to TubeDepot.com!
 The Tube Store: Vacuum tubes @ thetubestore. New and NOS electron tubes for any amplifier.
 Vacuum Tubes Inc.com: Vacuum Tubes, Inc. Homepage, Electron Tubes

 You can also drive yourself crazy checking every tube source listed in Head-Fi's Headphone Amps sub-forum. It's a sticky at the top of that forum section: TUBES SITES faq - add your fav's here

*Sockets*

 About half of the sources listed above have the proper socket: a "7-pin, miniature, ceramic PCB socket." Also:
 e-bay: 7-pin Ceramic PCB Mount Mini Tube Socket - Qty 8 
 Cascade Surplus: 7-pin Ceramic PCB Mount Tube Socket
 (this is actually the same company as the e-bay listing)
 Parts Connexion: Socket #SOCKET-59029


 EDIT: OK - this is a little freaky. Head-Fi has changed the code so that it reads the web site and retrieves its own description for a linked address - no matter what you type in. Weird.


----------



## fran

Thanks again TomB,

 I have shot off an email to radio daze and also to another guy that I've bought from before. I didn't realise you had the muse caps in beezar.com, so you'll be getting another email about that soon!

 thanks for the help,

 Fran


----------



## ruZZ.il

fran, please update us with their response regarding tube stock, types, or whatever info you get from them. I've got to snag some tubes soon too =D.


----------



## slowpogo

After months of research and gradual part ordering, I've now built 95% of my Max...still waiting on my BG caps and a TKD pot. Seemingly, it's gone perfectly. I triple-checked everything that I was soldering in, my new CS soldering station made it a pleasure. It was very fun and thrilling to watch it come together. And to think, a year ago my snap judgment of DIY electronics was that it was geeky and boring. Many hundreds of dollars later... 
	

	
	
		
		

		
			





 I'll be ordering my panels from FP express next week. It's gonna be beautiful. Hopefully, it will work without much fuss. Thanks guys.


----------



## amphead

Quote:


  Originally Posted by *slowpogo* /img/forum/go_quote.gif 
_After months of research and gradual part ordering, I've now built 95% of my Max...still waiting on my BG caps and a TKD pot. Seemingly, it's gone perfectly. I triple-checked everything that I was soldering in, my new CS soldering station made it a pleasure. It was very fun and thrilling to watch it come together. And to think, a year ago my snap judgment of DIY electronics was that it was geeky and boring. Many hundreds of dollars later... 
	

	
	
		
		

		
		
	


	




 I'll be ordering my panels from FP express next week. It's gonna be beautiful. Hopefully, it will work without much fuss. Thanks guys._

 

Thanks for letting us re-live the excitement from our first build. We certainly will be interested as to your impression of the sound.


----------



## pinkfloyd4ever

hey which direction is QM1 supposed to face, with the printed glossy side or the matte side towards the front of the board?


----------



## naamanf

I think it should be the printed side toward the front. Look at the outline on the board. The heavy line is to the rear.


----------



## tomb

This has happened more than once. So, here are a couple of images that should help. The BD139 has subtle differences between front and back, but the molding line is the clincher. Anyway:


----------



## pinkfloyd4ever

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_This has happened more than once. So, here are a couple of images that should help. The BD139 has subtle differences between front and back, but the molding line is the clincher. Anyway:_

 

cool thanks


----------



## luvdunhill

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_The BD139 has subtle differences between front and back, but the molding line is the clincher_

 

Tom:

 do you have any recommendations on sockets that can be used for TO-220 packages? I was thinking about finding the type of IC sockets that look like this "| |" as opposed to the round sockets, as often the pins on the transistors are flat.


----------



## TheRobbStory

My boutiqe caps and power supply showed up today. As soon as I powered it up, the tube lights flicked on for an instant and the fuse popped.

 I did a very clean soldering job, and I can't see any bridged traces or shorts.

 Thoughts?


----------



## ruZZ.il

The Fuses don't deal well with the inrush currents. Most of us here have bypassed it.. with caution. After going over all your bits and making sure all the right transistors are in the right places, and in the right directions and that all the caps are right, diodes, etc and making sure you know exactly what/how to setup correctly (detailed wonderfully here). I'd bypass the fuse, checking the output transistors bias levels at first power on. If everything is good, then you're good to go. if anything is out of range, power down quickly, re-adjust, re-try. If nothing works.. come back with measurements and pics. Also note: it may take quiet a lot of turns for bias to respond.. start with them turned fully clockwise if they're in in the right way.. and slowly turn counter clockwise from there..


----------



## TheRobbStory

Thanks for the tip! For some reason I couldn't find any information on why there was an onboard bypass for the fuse. Just got the bias' set and everything sounds incredible! Will post some pics once I have it cased up.

 Another MAX lives!


----------



## ruZZ.il

Enjoy! pics and specs


----------



## tomb

Quote:


  Originally Posted by *luvdunhill* /img/forum/go_quote.gif 
_Tom:

 do you have any recommendations on sockets that can be used for TO-220 packages? I was thinking about finding the type of IC sockets that look like this "| |" as opposed to the round sockets, as often the pins on the transistors are flat._

 

Molex makes several. This one is probably the best candidate and is at DigiKey:
Digi-Key Technical Information
http://rocky.digikey.com/WebLib/Mole...10-18-2031.jpg (pic)
http://www.molex.com/pdm_docs/sd/010182031_sd.pdf

 Most likely Mouser has similar offerings - I just happened to be looking at DigiKey right now. There may be some conflict with heat sinks, depending on your application. So, you need to look carefully at the dimensions in the drawing.

 EDIT: That pic was ridiculously big, so I just included the link, instead.


----------



## tomb

Quote:


  Originally Posted by *TheRobbStory* /img/forum/go_quote.gif 
_Thanks for the tip! For some reason I couldn't find any information on why there was an onboard bypass for the fuse. Just got the bias' set and everything sounds incredible! Will post some pics once I have it cased up.

 Another MAX lives!_

 

Kudos to ruZZ.il for the explanation on the fuse. 
	

	
	
		
		

		
			





 I won't add anything except to say congratulations on getting your MAX working!!


----------



## TheRobbStory

Thanks for the lightning fast shipping on those caps and PS, Tom!

 Here's two quickie pics:











 Louis Prima has never sounded better!


----------



## 04BluMach

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Molex makes several. This one is probably the best candidate and is at DigiKey:
Digi-Key Technical Information
http://rocky.digikey.com/WebLib/Mole...10-18-2031.jpg (pic)
http://www.molex.com/pdm_docs/sd/010182031_sd.pdf

 Most likely Mouser has similar offerings - I just happened to be looking at DigiKey right now. There may be some conflict with heat sinks, depending on your application. So, you need to look carefully at the dimensions in the drawing.

 EDIT: That pic was ridiculously big, so I just included the link, instead._

 


 Wow - Tom, I am impressed with how fast you found these and responded to this request! Definitely showing your Digikey search prowess.....
	

	
	
		
		

		
		
	


	




 I think the real operative statement above is ....

_There may be some conflict with heat sinks_

 The tops of these sockets are going to sit approximately 3/8" above the board for the Transitors to plug into (Really can't expect to smash these completely to the surface of the PCB). So the transitors will either sit VERY far above the board when plugged into these sockets or you will need to clip the transitor leads to near nubs (even then they will be riding pretty high). But I think the Heat Sinks will then be floating above the Board surface only connected to the TO-220 cases which will only be supported by the leads plugged into these sockets. This would be an unsatisfactory mounting method for long term use since the Heat Sinks are quite hefty for the transitors to support alone.

 If you want to just use these in a near "bread board" set up to test out mutliple transitor types without fully casing up it might be a worthwhile experiment. It would save you from having to solder/unsolder the Transitor pairs for the tests. But you would still want to unsolder these to put in your final desired pairs for permanent install. 

 Unless you are planning on trialing say three or more pairs, I really dont think these sockets will be something you would want to mess with (along with the expense). Just IMHO that is! 
	

	
	
		
		

		
		
	


	




 But these are interesting find for a bread board build up though!


----------



## 04BluMach

Quote:


  Originally Posted by *TheRobbStory* /img/forum/go_quote.gif 
_Thanks for the tip! For some reason I couldn't find any information on why there was an onboard bypass for the fuse. Just got the bias' set and everything sounds incredible! Will post some pics once I have it cased up.

 Another MAX lives!_

 


 Congrats! 
	

	
	
		
		

		
		
	


	




 And if you think it sounds incredible now...... Just wait till those Tubes and components fully burn in! The MAX really Sings with surprising dynamics and substantial musical details offered.

 From your Pics it looks like a very nice solid build - well done! It appears from the Pics that you have Nich ES's for both Cathode Bypass and Output Coupling ECaps with WIMAs used for bypasses throughout. A very solid MAX config...

 Enjoy!


----------



## slowpogo

whoops, never mind, didn't read clearly enough..


----------



## amphead

That's really awesome TheRobbStory! Another Max Lives!


----------



## pinkfloyd4ever

YESSSSSSSSSSS FINALLY I got mine done and up and running!!! Just using Panasonic FMs everywhere for now till my pCx order arrives, but it still sounds awesome with those and un-broken-in tubes, K42s and everything else. I'll post pics tom if I can ever stop listening
	

	
	
		
		

		
		
	


	




 Man, I need to order that Alien...crap


----------



## amphead

Congrats pinkfloyd4ever! Another Max Lives!


----------



## tomb

Quote:


  Originally Posted by *pinkfloyd4ever* /img/forum/go_quote.gif 
_YESSSSSSSSSSS FINALLY I got mine done and up and running!!! Just using Panasonic FMs everywhere for now till my pCx order arrives, but it still sounds awesome with those and un-broken-in tubes, K42s and everything else. I'll post pics tom if I can ever stop listening
	

	
	
		
		

		
		
	


	




 Man, I need to order that Alien...crap 
	

	
	
		
		

		
		
	


	


_

 

That's awesome! Yeah, mine sounds best with the Alien, but the rest of my sources are cr*p. Except, I do have an M-Audio Transit. There is a very-slight level of hiss that you can detect through the MAX with the Alien that's not there with the Transit, but the Alien has more detail, IMHO. So, my Transit goes unused.

 Good sources are important with the MAX. I quite listening to mp3's a long time ago - unless it's some music that I like and can't get anywhere else. Other than that, it's been FLAC all the way with me since the MAX.


----------



## rhester

What devices are people using to socket resistors, especially the otput resistors on the Max?


----------



## luvdunhill

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Molex makes several. This one is probably the best candidate and is at DigiKey_

 

wow, they are actually called transistor sockets!! I see there are even TO-3 sockets, crazy ...

  Quote:


  Originally Posted by *04BluMach* /img/forum/go_quote.gif 
_This would be an unsatisfactory mounting method for long term use since the Heat Sinks are quite hefty for the transitors to support alone._

 

I have to admit these are not for the Millet Max. Tom has the best ideas of these sorts (for example, the tip jack) so I figured he'd be the right person to ask. I apologize for the confusion.


----------



## luvdunhill

Quote:


  Originally Posted by *luvdunhill* /img/forum/go_quote.gif 
_wow, they are actually called transistor sockets!! I see there are even TO-3 sockets, crazy ..._

 

check these out:






Datasheet


----------



## tomb

Quote:


  Originally Posted by *rhester* /img/forum/go_quote.gif 
_What devices are people using to socket resistors, especially the otput resistors on the Max?_

 

Either a couple of sockets broken off of a SIP strip or cutting the cross-members away on DIP-socket. I like the DIP-socket better, because the single SIP-sockets are not very rugged compared to the strength of a 2W resistor lead. I've broken them before several times and quit using them. What you'd do with the DIP-sockets is snip away the intervening socket leads and just leave the ones on the ends. Then the plastic and unused sockets inbetween add much more strength.

 I don't know if the side of a DIP-8 fits the board pads, though - but you can always buy sockets with more pins. Maybe someone else has done it and can tell us which one. If not, I'll measure it when I get home tonight.

 EDIT: Here's a pic where NeilR used the break-off SIP strips on his MOSFET MAX prototype. Apparently, he wanted to play around with the resistor-capacitor combo to adjust the delay. (The delay resistor is the small one in back that's elevated on the sockets. The delay capacitor is the one in front - a 330uf in this case.) Note that the relay is also socketed, although I'm guessing that just a regular DIP-16 would've worked - not sure about that, though:


----------



## 04BluMach

Quote:


  Originally Posted by *pinkfloyd4ever* /img/forum/go_quote.gif 
_YESSSSSSSSSSS FINALLY I got mine done and up and running!!! Just using Panasonic FMs everywhere for now till my pCx order arrives, but it still sounds awesome with those and un-broken-in tubes, K42s and everything else. I'll post pics tom if I can ever stop listening
	

	
	
		
		

		
		
	


	




 Man, I need to order that Alien...crap 
	

	
	
		
		

		
		
	


	


_

 


 Congrats....!!!!
	

	
	
		
		

		
		
	


	










 Glad to hear that you've been able to finally join the MAX build community. You've been an advocate and avid (rabid even?
	

	
	
		
		

		
		
	


	




) proponent and enthusiast from the earliest portion of this immense thread till your MAX birth announcement! 
	

	
	
		
		

		
		
	


	




 I am really starting to fully agree with tomb on the MAX signature really being driven or characterized more so by the BJT's used in its output stage than the Caps or Tubes. Even with the Panny FM's, especially when Bypassed by the K42's, the MAX will sing when used in conjunction with one of the top pick BJT's pairings.

 Make sure you let those Caps and tubes burn in fully before you replace out with your planned BG caps in the future. That way you will be able to provide all a good read on the improvement made by the BG's. I am sure it will be characterized as a veil lifted across the entire freq band with improved Mids, sweetned highs, and details that you've never heard before.... 

 Yeah this thing is addictive - once you've started improving the chain.... then need to improve the source, then need those new Cans, need to tweak those cables, need to get more money for that....

 The MAX is a H*** of a way to start down the road though...
	

	
	
		
		

		
		
	


	



 I am sure it will impress quite a few at the upcoming St Louis Meet!

 Enjoy! More PICS!!!! SPECS and Impressions needed!

 Thanks to Pete Millet, cetoole, tomb, and many others for bringing us to the MAX!


----------



## slowpogo

My last parts are scheduled to arrive today, so hopefully my Max will be alive and kicking later tonight.

 What are people finding to be the burn-in threshold, where things pretty much sound like they're gonna sound? 50 hours? 300 hours? Just curious what to expect.


----------



## 04BluMach

Quote:


  Originally Posted by *slowpogo* /img/forum/go_quote.gif 
_My last parts are scheduled to arrive today, so hopefully my Max will be alive and kicking later tonight.

 What are people finding to be the burn-in threshold, where things pretty much sound like they're gonna sound? 50 hours? 300 hours? Just curious what to expect._

 

Normally, a lot less than 50 hrs. The first 2 to 4 hours is really to allow your BJT bias current to stabilize, tubes to warm up, Tube bias voltage to stabilize, and the Caps to fully form and start to breakin. During this time also, depending on the tube condition, the sound could be very mediocre till the Tubes Getter captures the impurities that have leaked within the vacumn.

 Depending on the condition of the tubes and the particular Caps used - probably get to at least the 90 to 95% SQ within 10-20 hrs.

 Now if they are Black Gate Caps.... then you could expect possibly expect 50 or more hours.

 I think tomb has quite a bit of real hands on history across all the build configs since he has personally built nearly each one. So he should be able to better quantify based on your specific build what to expect.


----------



## slowpogo

OK. I did Build #1 straight down the line w/ Vitamin Q's. The other electrolytics are Panasonic FM's, output resistors are 15ohm Rikens. I also sprung for a TKD pot; if it sounds half as good as it feels to turn, I'm in for a treat.

 50 hours isn't too bad..after breaking in my K701's for 400 hours, it will be easy.


----------



## slowpogo

One more question...the instructions for biasing the BJT buffers are really thorough, but there's one basic and probably obvious thing I'm not sure about.

 To test the BJT voltage on the left channel, I would put one test lead from my DMM in TB1L or TB2L, and the other DMM lead in...Ground? Or TA2L, the "L DB Reference" point? I'm not sure what that one is for.


----------



## TheRobbStory

you measure between TB1L/R and TB2L/R. I made the same mistake, measuring between ground and the test points. I freaked out when I saw around 22VDC instead of mV.

 My MAX sounds infinitely better after about six hours of burn in last night and about 8 hours at work today. Really warm and lively. I'm in love.


----------



## tomb

Copied and pasted directly from MAX Setup and Biasing:






 EDIT: OK - I take that back. There was an issue with the typo and the wording. Hopefully, it's clearly stated now.

 Slowpogo -

 You will absolutely love the Black Gates and Vitamin Q's. They are a sterling, but somewhat expensive combination. The bass is not as hard slamming as the ES caps, but after several of these, I've found out it really takes the 2SC3422/2SA1359 transistor pairs to fully complete the really fun rockin' slam in the Can't Miss Build #2. 
	

	
	
		
		

		
		
	


	




 On the other hand, the Build #3 (ES's, K42's, and 2SC3421/2SA1359) is very similar to #1: deep and extended - just not as smooth. Besides smooth, the BG's with the genuine 2SC2238's and VitQ's are deep and super-detailed with a very extended high end.


----------



## ruZZ.il

Talking about cant miss builds, I'm a few heat-sink mounting screws and a few solder joints short of build #2.. I've had a bit of a mix and match with BGs/k42s/3422s till now that I was really happy with, but I've done some re-arranging. New build will be a 1.5" cant miss #1 while my older build will conform into cant miss #2.. unfortunately my PL750s right driver seems to be acting up, which will probably get changed as soon as I send it in.. hmpf. Congrats on all the new MAXs around!! I'm glad to see those boards come to life.. meanwhile, I really enjoy the actual building process more than I can afford.. anyone know the going market price for these things? I need some circulation


----------



## tomb

I can't add much to 04BluMach's excellent post. However, the BG version we're both talking about is what I've been listening to constantly ever since I posted the pics a couple of pages back - Build #1 with 0.47uf Vitamin Q's (Philco brand from Colin) in all four positions. Here's sort of what I remember:

 1. First turn-on, bias set, etc. - WOW.
 2. Couple of days later - bass gone, harshness in high end.
 3. Several days of 8-10hrs running, bass comes back, but highs medium harsh.
 4. The last couple of days - bass deep, super-detail, transparent extended highs, harshness almost completely gone.

 I'd say there's somewhere close to 100 hrs on the BG's now and I think they're as good as they will get, which is great! I still wish the bass were a bit stronger, but the detail is every bit as impressive as ES bass-slam. Sort of what I've always said, though - you need more than one MAX to fit your mood (or several).


----------



## Gross

Hey there Fellahs! I don't post much, but I had to let everyone know, Another MAX LIVES! 
 Right now I am biased to 70mV on the DBs, I think I will tweak them up in a bit. Although it already sounds so powerful. Thanks Cetoole, TomB, AMB, and Pete!


----------



## tomb

Quote:


  Originally Posted by *Gross* /img/forum/go_quote.gif 
_Hey there Fellahs! I don't post much, but I had to let everyone know, Another MAX LIVES! 
 Right now I am biased to 70mV on the DBs, I think I will tweak them up in a bit. Although it already sounds so powerful. Thanks Cetoole, TomB, AMB, and Pete!_

 

Congrats! Way to go!!


----------



## slowpogo

My Max is alive! Everything went _perfectly_--I can't believe it. The DB's are biased up to 110mv, and it sounds spectacular, and it's only been running an hour and a half! It puts every other amp I've used to absolute shame.

 I've actually only been listening on my somewhat crappy Audio Technica phones, but they sound two or three levels better than I've ever heard them sound. My plan is to let it burn in several days, and then, plug in the AKG K701's. I'm almost scared, honestly, at what I'll hear...!!


----------



## 04BluMach

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_snip.....

 You will absolutely love the Black Gates and Vitamin Q's. They are a sterling, but somewhat expensive combination. The bass is not as hard slamming as the ES caps, but after several of these, I've found out it really takes the 2SC3422/2SA1359 transistor pairs to fully complete the really fun rockin' slam in the Can't Miss Build #2. 
	

	
	
		
		

		
		
	


	




 On the other hand, the Build #3 (ES's, K42's, and 2SC3421/2SA1359) is very similar to #1: deep and extended - just not as smooth. Besides smooth, the BG's with the genuine 2SC2238's and VitQ's are deep and super-detailed with a very extended high end._

 

All the parts for my third MAX, a Can't Miss Build #1, are sitting here in a box..... 
	

	
	
		
		

		
		
	


	




 My Wife just doesn't understand my need to have solder wafting in our Sun Room (Audio WorkShop?). Instead she expects me to finish the Family room wood reflooring, repainting, trim work, curtain hanging, and other trivial Home stuff by this weekend. Daughters impending bridal shower is just interfering with my important DIY stuff - My MAX MAX build 
	

	
	
		
		

		
		
	


	




 So what happens - tomb, waxes on about the sweet sounds I should be anticipating shortly. Then SLOWPGO and ruZZ.il rub the salt further in the wound on their impending/inprogress Builds 
	

	
	
		
		

		
		
	


	




 Well at least the flooring project is donating Brazilian Cherry for front and rear Hammond panels. So I guess it has some value in the overall scheme of things 
	

	
	
		
		

		
		
	


	




 The Box has all the good stuff - BG's for Cathode Bypass and Output coupling, four Russian K42 PIO's as the BG Bypasses and the Real Deal Toshiba 2SC2238/2SA938 BJT pairs.
	

	
	
		
		

		
		
	


	




 Can't let that threatened Kitchen repainting wifey task interfere with that is a very important winter project!
	

	
	
		
		

		
		
	


	




 Now if I can only get my hands on a cetoole Tube DAC prototype board and BOM I will able to improve that source in time for those BG's to Burnin, and those HD650's would look cool (..or the rumored HD700s may be out???).....
	

	
	
		
		

		
		
	


	










 Yeah! Need to get the trading paper lined up for the next batch of TOYS...
	

	
	
		
		

		
		
	


	




 Actually, keep the info coming on the builds and impressions (tomb, ruZZ.il, and slowpogo) - can't wait to hear how they are fleshing out...
	

	
	
		
		

		
		
	


	




 PS: ruZZ.il I think these Can't miss MAX Build #1'S will become classic legends in their time at both HeadFi and Headwize. With very few to show up on the For Sale Forumns since they will be real keepers...


----------



## cetoole

Quote:


  Originally Posted by *TheRobbStory* /img/forum/go_quote.gif 
_Thanks for the tip! For some reason I couldn't find any information on why there was an onboard bypass for the fuse. Just got the bias' set and everything sounds incredible! Will post some pics once I have it cased up.

 Another MAX lives!_

 

 Quote:


  Originally Posted by *pinkfloyd4ever* /img/forum/go_quote.gif 
_YESSSSSSSSSSS FINALLY I got mine done and up and running!!! Just using Panasonic FMs everywhere for now till my pCx order arrives, but it still sounds awesome with those and un-broken-in tubes, K42s and everything else. I'll post pics tom if I can ever stop listening
	

	
	
		
		

		
		
	


	




 Man, I need to order that Alien...crap 
	

	
	
		
		

		
		
	


	


_

 

 Quote:


  Originally Posted by *Gross* /img/forum/go_quote.gif 
_Hey there Fellahs! I don't post much, but I had to let everyone know, Another MAX LIVES! 
 Right now I am biased to 70mV on the DBs, I think I will tweak them up in a bit. Although it already sounds so powerful. Thanks Cetoole, TomB, AMB, and Pete!_

 

 Quote:


  Originally Posted by *slowpogo* /img/forum/go_quote.gif 
_My Max is alive! Everything went perfectly--I can't believe it. The DB's are biased up to 110mv, and it sounds spectacular, and it's only been running an hour and a half! It puts every other amp I've used to absolute shame.

 I've actually only been listening on my somewhat crappy Audio Technica phones, but they sound two or three levels better than I've ever heard them sound. My plan is to let it burn in several days, and then, plug in the AKG K701's. I'm almost scared, honestly, at what I'll hear...!! 
	

	
	
		
		

		
		
	


	








_

 

W00T! 
	

	
	
		
		

		
		
	


	







 Wonder what is up with the sudden rush of Maxes being built up? This is four in half as many days, and I know it isnt just you guys only now getting boards 
 from Tom, because I remember shipping to a couple of you dudes. Anyways, it is great seeing these babies come alive.


----------



## 04BluMach

Quote:


  Originally Posted by *slowpogo* /img/forum/go_quote.gif 
_My Max is alive! Everything went perfectly--I can't believe it. The DB's are biased up to 110mv, and it sounds spectacular, and it's only been running an hour and a half! It puts every other amp I've used to absolute shame.

 I've actually only been listening on my somewhat crappy Audio Technica phones, but they sound two or three levels better than I've ever heard them sound. My plan is to let it burn in several days, and then, plug in the AKG K701's. I'm almost scared, honestly, at what I'll hear...!! 
	

	
	
		
		

		
		
	


	








_

 

CONGRATS.....!!!!!!!!!!!!
	

	
	
		
		

		
		
	


	




 Or should I say after that long last post above - I am crushed! 
	

	
	
		
		

		
		
	


	




 LOL

 Can't wait to hear how it progresses to completition and final burnin...

 .........Soooooooooooo keep the info and impressions coming with lots of PICS!


----------



## cetoole

Quote:


  Originally Posted by *04BluMach* /img/forum/go_quote.gif 
_All the parts for my third MAX, a Can't Miss Build #1, are sitting here in a box..... 
	

	
	
		
		

		
		
	


	


_

 

Heck, same here, whoda thunk it?
  Quote:


 Well at least the flooring project is donating Brazilian Cherry for front and rear Hammond panels. So I guess it has some value in the overall scheme of things 
	

	
	
		
		

		
		
	


	



 

Yum, I bet that will look amazing. I checked out a flooring store once looking for nice wood to make front and rear panels for my Max once, but didnt come up with anything really. Guess I coulda done shag carpet endpanels. Glad to hear you found a good source for yourself. I bet that case will look great. The Hammond is reasonably nice looking alone, but hardwood endpanels sure do dress it up. You will be what, the second person do have done this for a Max, after naamanf?
  Quote:


 Now if I can only get my hands on a cetoole Tube DAC prototype board and BOM I will able to improve that source in time for those BG's to Burnin, and those HD650's would look cool (..or the rumored HD700s may be out???).....
	

	
	
		
		

		
		
	


	









 

I wanna get my hands on one of those tubedac prototype board and BOMs you mentioned too. Anyone got a source for 'em yet?


----------



## 04BluMach

Quote:


  Originally Posted by *cetoole* /img/forum/go_quote.gif 
_W00T! 
	

	
	
		
		

		
			








 Wonder what is up with the sudden rush of Maxes being built up? This is four in half as many days, and I know it isnt just you guys only now getting boards 
 from Tom, because I remember shipping to a couple of you dudes. Anyways, it is great seeing these babies come alive._

 

It must be a new winter sport...
	

	
	
		
		

		
		
	


	




 Maybe the Writers Guild Strike has caused us all to head to the Work Bench to escape Family bonding activities since nothing is on TV 
	

	
	
		
		

		
		
	


	




 Think it is just the bent up desire finally broke through to some free time availability during the Winter (after Christmas) down times
	

	
	
		
		

		
		
	


	




 By the way.... put me on the list for at least 2 Tube DAC boards (maybe 4)...
	

	
	
		
		

		
		
	


	




 .....and send a Proto Board this way if ya need a test build (hint, hint,...)


----------



## 04BluMach

Quote:


  Originally Posted by *cetoole* /img/forum/go_quote.gif 
_
 Yum, I bet that will look amazing. I checked out a flooring store once looking for nice wood to make front and rear panels for my Max once, but didnt come up with anything really._

 

Ya got a PM!


----------



## amphead

Congrats Gross! Another Max Lives!


----------



## amphead

That great news Slowpogo! Another Max Lives!   

 You are in for a treat. The Max will sound reasonably good with low hours, but it will be one killing machine when it burns in, especially with those K701's.


----------



## ruZZ.il

Quote:


  Originally Posted by *04BluMach* /img/forum/go_quote.gif 
_All the parts for my third MAX, a Can't Miss Build #1, are sitting here in a box..... 
	

	
	
		
		

		
		
	


	



 .....Then SLOWPGO and ruZZ.il rub the salt further in the wound on their impending/inprogress Builds 
	

	
	
		
		

		
		
	


	




..._

 

I'd feel bad if I hadn't just done the same thing. I've basically had all the bits lying around for a good 3 months already.. well, till about a month ago, then I had a board lying around with just resistors till 2 weeks ago, when I finally got the transistors sorted and on. It's been.. a work in progress but I'm so close now, so hopefully it'll get done soon 
	

	
	
		
		

		
		
	


	




 though, I need to start thinking about filling my next box or 2 too.. I've got 2 weeks off coming up in about 2 months


----------



## pinkfloyd4ever

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_That's awesome! Yeah, mine sounds best with the Alien, but the rest of my sources are cr*p. Except, I do have an M-Audio Transit. There is a very-slight level of hiss that you can detect through the MAX with the Alien that's not there with the Transit, but the Alien has more detail, IMHO. So, my Transit goes unused.

 Good sources are important with the MAX. I quite listening to mp3's a long time ago - unless it's some music that I like and can't get anywhere else. Other than that, it's been FLAC all the way with me since the MAX. 
	

	
	
		
		

		
		
	


	


_

 

ya, right now I have my cotdt-modded Audigy 2ZS, which is decent for the small amount of work and money I put into it after buying it with the computer. And I've been getting all my favorite music in flac, so I've got a good flac collection now.


----------



## Gross

I have built a few AlienDACs now and I thoroughly enjoy them. Honestly so far my favorite has 4.7uf KimberKaps on the output. Real smooth baby.


----------



## Roee2807

I am new to DIY,
 Can I by somewhere complete KIT for that AMP ?

 Thanks


----------



## ruZZ.il

Quote:


  Originally Posted by *Roee2807* /img/forum/go_quote.gif 
_I am new to DIY,
 Can I by somewhere complete KIT for that AMP ?

 Thanks_

 

I believe Jeff (Jrossel) at GlassJarAudio has a good kit (maybe not on his page, nor in stock.. but contact him about it). Though this may not be the best first amp but if you're serious get one if you can, when you're ready to tackle it the support is here. hope to see you join us soon


----------



## fran

Just placed my order with mouser this morning!

 Looking forward to this build.

 Fran


----------



## slowpogo

After about 20 hours, my Max is following tomb's chart exactly. It was really WOW once it was first biased. Now, the bass has gotten softer with less punch, it's less detailed and it's pretty harsh. I don't really enjoy listening to it right now, actually. Definitely sounds like a different amp than it did yesterday.

 I think I read about this many pages back, but there is a slight buzz that increases when I touch the volume knob. Actually, it increases just when my hand is close to the knob. If I turn the knob all the way up, it disappears. If the knob is sitting the right way (it's TKD, so connected with about 1.5 inches of wire) the buzz all but disappears.

 I haven't grounded the pot yet (and it's not in a case), is that the cause?


----------



## naamanf

Quote:


  Originally Posted by *slowpogo* /img/forum/go_quote.gif 
_
 I haven't grounded the pot yet (and it's not in a case), is that the cause?_

 

Yes.


----------



## pinkfloyd4ever

Quote:


  Originally Posted by *naamanf* /img/forum/go_quote.gif 
_Yes._

 

ooohh I'm having the same thing happening. Is that what that little hole labeled "GND" behind the pot is for? What on the pot do you connect it to, one of the screws on back?


----------



## naamanf

Quote:


  Originally Posted by *pinkfloyd4ever* /img/forum/go_quote.gif 
_ooohh I'm having the same thing happening. Is that what that little hole labeled "GND" behind the pot is for? What on the pot do you connect it to, one of the screws on back?_


----------



## pinkfloyd4ever

damn that was fast! thanks!


----------



## [AK]Zip

Does anyone have an extra Alps pot or some other that they aren't using and are willing to sell? Let me know I am looking for one. I want to test it against the stepped attenuators.

 Thanks,
 Alex


----------



## tomb

Quote:


  Originally Posted by *[AK]Zip* /img/forum/go_quote.gif 
_Does anyone have an extra Alps pot or some other that they aren't using and are willing to sell? Let me know I am looking for one. I want to test it against the stepped attenuators.

 Thanks,
 Alex_

 

??

Tangent's Notes on Audio Attenuators
 Tangent's Tests in Excel Spreadsheet


----------



## [AK]Zip

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_??

Tangent's Notes on Audio Attenuators
 Tangent's Tests in Excel Spreadsheet_

 

I want to test sound differences between the stepped attenuators I have and a standard pot just for fun.


----------



## 04BluMach

Quote:


  Originally Posted by *[AK]Zip* /img/forum/go_quote.gif 
_Does anyone have an extra Alps pot or some other that they aren't using and are willing to sell? Let me know I am looking for one. I want to test it against the stepped attenuators.

 Thanks,
 Alex_

 

I could part with one of my still sealed ALPS Pots for say a straight up trade of one of your nice v3 cables for my HD580's or maybe a replacement cable for my IM716's (understand they are ety er4's in disguise).
	

	
	
		
		

		
		
	


	




 Hey I would even consider some used versions ... LOL


----------



## Negatron

T 1 3/4 LED's in ceramic sockets? Nothings impossible.

 I got tired of looking for high output T-1 LED's so out comes the trusty rotary tool and some Harbor Freight Diamond Burrs, I picked up a few sets last year on sale for $3.99. They no longer have 'em, but do have something that will work. Here is a link.
Harbor Freight Tools - Quality Tools at the Lowest Prices

http://farm3.static.flickr.com/2003/...2ce25c1c_o.jpg
http://farm3.static.flickr.com/2345/...d67be9fe_o.jpg
http://farm3.static.flickr.com/2115/...2c565a04_o.jpg
http://farm3.static.flickr.com/2034/...e099dfb3_o.jpg


 So......
 These 18,000 mcd 5mm's should let me make hand shadow puppets on the ceiling. 
	

	
	
		
		

		
		
	


	



Jameco Electronics Opto & Illumination: AVAGO TECHNOLOGIES: HLMP-EG08-Y2000
 (I'm really not running 'em full out, but it's tempting)

 The second build is coming along with BG's NX's at OP and K w/BG 0.47 bypass also BG N 4.7's at CR5, 470 Silmics w/PIO@CA4, 1800FC's@CR1 and 2700FC's@CA5. Mills non Inductive R's@RB10,11 on MOSFETS w/QB2,3 jumped and Kiwame 10R's@RB14.

 This is fun, the possibilities are endless. No wonder tomb is building 20 or 30.


----------



## Negatron

It seems a good number of MAX's have been born recently so I thought I would add another to the population.
 (And more of the little critters yet to be birthed)






 Poor ears, with the BG's and the Silmic, it is going to take some time to hit it's stride. Pink noise time.....
 (Silmics are worse than BG's in that respect). 2700FC's and PIO's on the rail.

 And I don't know if anyone has done it, but probably. A smaller (4.7) BG N at the output of a regulator is a plus.

 Fun and fast to build. Great layout colin.


----------



## ruZZ.il

its ALIIIIVE! 
	

	
	
		
		

		
		
	


	




 New pics and comparisons between my 2 builds to come..


----------



## tomb

Quote:


  Originally Posted by *Negatron* /img/forum/go_quote.gif 
_<snip>
 This is fun, the possibilities are endless. No wonder tomb is building 20 or 30. 
	

	
	
		
		

		
		
	


	


_

 

Not 20 or 30 ....... yet. 
	

	
	
		
		

		
		
	


	







  Quote:


  Originally Posted by *ruZZ.il* /img/forum/go_quote.gif 
_its ALIIIIVE! 
	

	
	
		
		

		
		
	


	




 New pics and comparisons between my 2 builds to come.._

 

Cool - be sure you include pics of the bottom. We want to see more of that picture-perfect soldering you do.


----------



## pinkfloyd4ever

Quote:


  Originally Posted by *Negatron* /img/forum/go_quote.gif 
_T 1 3/4 LED's in ceramic sockets? Nothings impossible.

 I got tired of looking for high output T-1 LED's so out comes the trusty rotary tool and some Harbor Freight Diamond Burrs, I picked up a few sets last year on sale for $3.99. They no longer have 'em, but do have something that will work. Here is a link.
Harbor Freight Tools - Quality Tools at the Lowest Prices

http://farm3.static.flickr.com/2003/...2ce25c1c_o.jpg
http://farm3.static.flickr.com/2345/...d67be9fe_o.jpg
http://farm3.static.flickr.com/2115/...2c565a04_o.jpg
http://farm3.static.flickr.com/2034/...e099dfb3_o.jpg


 So......
 These 18,000 mcd 5mm's should let me make hand shadow puppets on the ceiling. 
	

	
	
		
		

		
		
	


	



Jameco Electronics Opto & Illumination: AVAGO TECHNOLOGIES: HLMP-EG08-Y2000
 (I'm really not running 'em full out, but it's tempting)

 The second build is coming along with BG's NX's at OP and K w/BG 0.47 bypass also BG N 4.7's at CR5, 470 Silmics w/PIO@CA4, 1800FC's@CR1 and 2700FC's@CA5. Mills non Inductive R's@RB10,11 on MOSFETS w/QB2,3 jumped and Kiwame 10R's@RB14.

 This is fun, the possibilities are endless. No wonder tomb is building 20 or 30. 
	

	
	
		
		

		
		
	


	


_

 

nnIIIIICCCEEE, show us pics of em in action too. I've been wanting to do that cause obv the high output leds are alot easier to find in the 5mm size, but I don't have the tools


----------



## Negatron

Quote:


  Originally Posted by *pinkfloyd4ever* /img/forum/go_quote.gif 
_nnIIIIICCCEEE, show us pics of em in action too. I've been wanting to do that cause obv the high output leds are alot easier to find in the 5mm size, but I don't have the tools_

 

"This is overseas calling, is Mr Floyd there?"

 It's really hard to show a pic that gives the brightness since they are a 6 deg LED and illuminate almost straight up, but here's a grainy pic':




 19ma-1.32k Rled & Jameco LED's-4x1800 FC's B+, MOSFETS w/2x2700, 470 Silmic w/PIO on plates, 1000BG /K, 680BG /OP

 As for the moto tool, you want cheap?
Harbor Freight Tools - Quality Tools at the Lowest Prices

 It would not stand up to much hard duty, but for small projects it should do fine. I love Harbor Freight! After many years of mail order. they finally built a store 5 miles from me. 
	

	
	
		
		

		
		
	


	




 (Try going in and buy just what's on your list! <evil icon>


----------



## ruZZ.il

Didn't have my tripod handy, so I'll have to update with better shots of the amp sometime(hence the flash reflection, my paper diffuser didnt help too much).. got some mad me in there too while I was at it 
	

	
	
		
		

		
		
	


	



 So, specs: mostly PRPs, PW 1000uf, FM 1800uf, NX 1000uf, NX 470uf, vit Q 0.22uf, Wima 0.22uf elsewhere, 2SC2238/2SA968 BJTs and for now GE 12FK6s (positions are obvious). 1.5" heatsinks V=28v, Tubes@14v, BJTs@43.2ma running luke warm to the touch, detailed and clean to the ear..

 Meantime fed with an alien dac with ES caps, so I've got fair bass 
	

	
	
		
		

		
		
	


	




 I'd like to try the BGs on an alien too sometimes but I stuck them in a diyMod for my nano(thanks joneeboi
	

	
	
		
		

		
		
	


	




), which sounded wonderful till I wore the ribbon on the clickwheel out.. but I should have a new one soon...aanyway:


----------



## Negatron

That's really nice work ruZZ. Looks like you ran the board through a solder bath machine. Makes my work look like I used an old buzz box stick welder.


----------



## ruZZ.il

thanks 
	

	
	
		
		

		
		
	


	




 I dunno what a 'buzz box' stick welder is, but mine probably aint much better.. I really need a better one with some proper tips and stuff. The only bath I gave it was with some alcohol though.. not even the cleanest stuff (leaves nasty residue).. the good thing is though, that I really try avoid having any pointy bits, so I can just wipe the alcohol off with some tissue..


 <wondering if he meant radio shack..>


----------



## tomb

A "buzz-box" stick welder is exactly as described: an arc welder where the power supply box buzzed when running, as they often do. Been there, done that - but not too much, thank goodness. 
	

	
	
		
		

		
		
	


	




 I remember being excited after learning how to do it in class. I brought an old exercise bike up to the college. The pedal bearing assembly had broken off at the weld joint. So, I was going to fix it with my newly acquired welding skills. Firing up the buzz-box, I promptly blew a half-dozen holes right through the thin steel tubing that made up the bike frame. 
	

	
	
		
		

		
		
	


	




 That's a great job squeezing those Vit Q's in there. I had thought about trying to do that a couple of times, but those trimmers get in the way. It looks like you can still reach the screw on the Left channel, though.

 You may want to try to put them in the back, too, if you're game. I think with the VitQ's, things sound better on the BG's putting them in the back, too. I don't think that philosophy holds with the K42's. Anyway, I'd thought about just putting the ground lead on the pad for the _other_ cap and vice versa. Since the ground is common throughout the board, there's no reason the ground lead has to be put in its own silkscreen area. They could both straddle each other. Just an idea - haven't tried it, though. That's about the only way to make it work with those type VitQ's - they're about 1-3/8" long.

 Nice job!!


----------



## ruZZ.il

It would actually be really easy to stick these vit Qs@CA9 like you said. They look like they'd fit really snug parallel to each other right between the tubes.. will try it out after the w.end
	

	
	
		
		

		
		
	


	




 thanks. 

 In the meantime, I'm a little confused with the differences. I'd been listening to the BGs for a while with my first build but with the 3422 pair, then I had a quick listen to my old build with the ESs instead of the BGs. I think the ESs may need to burn in a bit before I judge or I may need to take a listen with different dac caps but the ES/ES dac/amp was a little too muddy for me.. they're new ESs in the amp though, so I'll give them time.. (new, hehe.. you sent them to me like 4 months ago I think).. but I've been enjoying the BG and 2238 pair.. a little smoother to listen to maybe?.. I dunno.. I'm confused with all the changing, and I hadn't been listening too much lately so its not all too fresh for a comparison;/. I'll be mixing and matching my dacs/amps and see where that takes me.. I need to get another power supply too.. mm but this sounds good 
	

	
	
		
		

		
		
	


	




 the 1.5" makes a BIG diff.. medium HOT to luke warm.. will bump up the bias soon..


 edit: something like this:

(not actually done yet) though I'd turn the tube trimmers around.. btw, talking bout tube trimmers, I inserted these orientated as illustrated and they actually behave in the opposite manner to the V and DB bias, ie, when fully clockwise, they were at max. Turning them around would unify their behavior with everything else, and have both the trimmer screws closer to the tubes, giving me space to conveniently stick the vitq's in like that..


 edit2: okay, I am somewhat a bashead too 
	

	
	
		
		

		
		
	


	




 the ES/ES dac/amp combo will kicks ass with electronic music.. much more to feel. Still a little too muddy for everything else, though it definitely needs its time. They still have a nasty harshness and are a little veiled.. but I'm comparing them directly to nicely burnt in BGs.. not fair


----------



## Negatron

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_ <snip>
 You may want to try to put them in the back, too, if you're game. I think with the VitQ's, things sound better on the BG's putting them in the back, too. I don't think that philosophy holds with the K42's. Anyway, I'd thought about just putting the ground lead on the pad for the other cap and vice versa. Since the ground is common throughout the board, there's no reason the ground lead has to be put in its own silkscreen area. They could both straddle each other. Just an idea - haven't tried it, though. That's about the only way to make it work with those type VitQ's - they're about 1-3/8" long.

 Nice job!!_

 

With exceptional soldering skills, 
	

	
	
		
		

		
			





 bottom connection would be simple to do with a loop around the pos lead of CA2, neg of the VitQ to the ground plane or even the opposing CA2 neg. Insulate the caps from the leads on the botton between caps with a piece of plastic milk carton or other suitable insulator.

 There is benefit to the most direct connection. The shortest path, etc.


----------



## 04BluMach

Quote:


  Originally Posted by *;3635877* 
_Didn't have my tripod handy, so I'll have to update with better shots of the amp sometime(hence the flash reflection, my paper diffuser didnt help too much).. got some mad me in there too while I was at it 
	

	
	
		
		

		
		
	


	







_

 

Oh YEAH............... 
	

	
	
		
		

		
		
	


	










You are the Soldering MACHINE
	

	
	
		
		

		
		
	


	










 And from closer inspection - We have a Lead PRE-CLIPPER among our midst!!!

 Very impressive work. Talking ArtWork here. 

 I BOW before ruZZ.il the master.

  Quote:


  Originally Posted by *;3635877* 
_So, specs: mostly PRPs, PW 1000uf, FM 1800uf, NX 1000uf, NX 470uf, vit Q 0.22uf, Wima 0.22uf elsewhere, 2SC2238/2SA968 BJTs and for now GE 12FK6s (positions are obvious). 1.5" heatsinks V=28v, Tubes@14v, BJTs@43.2ma running luke warm to the touch, detailed and clean to the ear.._

 

Sweet, talking all the good stuff here. And color coordinated with that PRP / BG thing going. Wait till you Crank that BJT Bias current up since you are running with 1.5" HeatSinks! Those Tosh BJTs are really going to rattle your your brain bones... BassHead Extreme LOL

 Those VitaQ's are awesome! Are those .22uf @150V or so? What are the case size on those bad boys?

  Quote:


 
 Originally Posted by tomb 
 <snip>
 You may want to try to put them in the back, too, if you're game. I think with the VitQ's, things sound better on the BG's putting them in the back, too. I don't think that philosophy holds with the K42's. Anyway, I'd thought about just putting the ground lead on the pad for the other cap and vice versa. Since the ground is common throughout the board, there's no reason the ground lead has to be put in its own silkscreen area. They could both straddle each other. Just an idea - haven't tried it, though. That's about the only way to make it work with those type VitQ's - they're about 1-3/8" long. 
 

 Quote:


 Originally Posted by Negatron
 With exceptional soldering skills, bottom connection would be simple to do with a loop around the pos lead of CA2, neg of the VitQ to the ground plane or even the opposing CA2 neg. Insulate the caps from the leads on the botton between caps with a piece of plastic milk carton or other suitable insulator. 
 

I mean we are talking abot the SOLDERING MACHINE here 
	

	
	
		
		

		
		
	


	




. I think he could have them floating in 3D space if needed


----------



## 04BluMach

Quote:


  Originally Posted by *ruZZ.il* /img/forum/go_quote.gif 
_It would actually be really easy to stick these vit Qs@CA9 like you said. They look like they'd fit really snug parallel to each other right between the tubes.. will try it out after the w.end
	

	
	
		
		

		
		
	


	




 thanks. 
 ...snip

 edit: something like this:

(not actually done yet) though I'd turn the tube trimmers around.. btw, talking bout tube trimmers, I inserted these orientated as illustrated and they actually behave in the opposite manner to the V and DB bias, ie, when fully clockwise, they were at max. Turning them around would unify their behavior with everything else, and have both the trimmer screws closer to the tubes, giving me space to conveniently stick the vitq's in like that.._

 


 Looks like you could move those two (CA9's) in parallel down (from top torwards the bottom of pic) a little closer to the lower heat sink (ie locating the one approximately just over the LED contacts) to easily clear your trimmers.
	

	
	
		
		

		
		
	


	




 EDIT:
 Since the VitaQ's in your build are not that large in diameter you could actually stack them parellel to one another one on top of the other. That way you could move them a little closer to the LED contacts while still providing clearance from the Heat Sinks. That way if you crank the Bias current up you won't need to be concernced about heat damage to those very nice PIO Caps...


 I am so jealous 
	

	
	
		
		

		
		
	


	




. Just an incredible build. CONGRATS...


----------



## tomb

Quote:


  Originally Posted by *ruZZ.il* /img/forum/go_quote.gif 
_It would actually be really easy to stick these vit Qs@CA9 like you said. They look like they'd fit really snug parallel to each other right between the tubes.. will try it out after the w.end
	

	
	
		
		

		
		
	


	




 thanks. 

 In the meantime, I'm a little confused with the differences. I'd been listening to the BGs for a while with my first build but with the 3422 pair, then I had a quick listen to my old build with the ESs instead of the BGs. I think the ESs may need to burn in a bit before I judge or I may need to take a listen with different dac caps but the ES/ES dac/amp was a little too muddy for me.. they're new ESs in the amp though, so I'll give them time.. (new, hehe.. you sent them to me like 4 months ago I think).. but I've been enjoying the BG and 2238 pair.. a little smoother to listen to maybe?.. I dunno.. I'm confused with all the changing, and I hadn't been listening too much lately so its not all too fresh for a comparison;/. I'll be mixing and matching my dacs/amps and see where that takes me.. I need to get another power supply too.. mm but this sounds good 
	

	
	
		
		

		
		
	


	




 the 1.5" makes a BIG diff.. medium HOT to luke warm.. will bump up the bias soon..<snip>_

 

Well, after tons of listening, I've modified my opinion some on the Alien DAC combinations. MASantos built and sold a lot of them. He's right when he says the Black Gate Alien DACs beat all other "normal" combinations, including one with ES's. The ES Alien is great for something like a PIMETA, which already has great detail, but may be missing that last octave of bass. More than that, though, once you have plenty of bass, the ES Alien DAC just doesn't compete well with really excellent sources. The BG Alien is very similar to the MAX, IMHO - a surprising performer that often holds its own with components costing much more.

 Back to the much larger Black Gates on the MAX, there is a reason that they cost _more than ten times_ the cost of an ES cap: they have fantastic detail. OTOH, as you've mentioned in the past - sometimes you wonder where the bass has gone. It's all the more reason to build several flavors. 
	

	
	
		
		

		
		
	


	




 EDIT: The VitQ's look interesting there in the back. Again, I was worried about the trimmers when considering it. Maybe they could move over the center LED resistor, or even pop that resistor out and flip onto the back side. Just a thought - but even placing them in the position is further than I got. 
	

	
	
		
		

		
		
	


	




 EDIT2: Oops! 04BluMach beat me to the suggestion.

 P.S. I was wondering how you made that soldering look so good!! Nice!


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## ruZZ.il

will be back later, but the reason I thought of keeping them that far back was to keep them away from heat sinks, as cool as possible, although on average they are closer to the tubes.. and since the sinks really aren't hot (yet), I'm not sure what's better to keep them further from...also, each ones others ground point would probably be the shortest path to a ground point for each cap since its end point doesn't hover over the center anyway.. actually, hovers closer to over the other ground than the center, so.. and since its each ones length, and not the average combined length that matters, it'd still probably be shorter to go to the opposite ground..


----------



## Negatron

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Well, after tons of listening, I've modified my opinion some on the Alien DAC combinations. MASantos built and sold a lot of them. He's right when he says the Black Gate Alien DACs beat all other "normal" combinations, including one with ES's. The ES Alien is great for something like a PIMETA, which already has great detail, but may be missing that last octave of bass. More than that, though, once you have plenty of bass, the ES Alien DAC just doesn't compete well with really excellent sources. The BG Alien is very similar to the MAX, IMHO - a surprising performer that often holds its own with components costing much more.

 Back to the much larger Black Gates on the MAX, there is a reason that they cost more than ten times the cost of an ES cap: they have fantastic detail. OTOH, as you've mentioned in the past - sometimes you wonder where the bass has gone. It's all the more reason to build several flavors. 
	

	
	
		
		

		
		
	


	




 <snip>_

 

It is JMHO, but I have found that with one exception ALL el caps are additive within their freq limits.
 Some components or combinations can easily be subtractive, they remove a part or parts of, the music. But in the case of electrolytics, they release information into the music that was not there to start with.
 Sure it's subjective but far too many people hear the same thing to be ignored just because we haven't figured out yet how or what to measure.

 Blackgates, once broken in are neutral, they neither take away or add. What you hear is what you got. Others come into that area but none I have listened to quite get there. Thus if an el cap has slam, it is the cap and not the amp that is doing it. If an el cap lacks bass and is used well above the limits of Fc, then again, it is the amp and instantaneous peak current capability, not the el cap.that is lacking bass. Oddly enough much live music lacks bass also. Can't blame a cap there.

 That leads me to a personal bias, in that I believe an amp should be as neutral as possible and then tweak elsewhere, and if an el cap must be used anywhere near the signal path, a Blackgate is best way to accomplish that. That's not to say though that with a given design, caps can't or shouldn't be used to tune. I don't like silver IC's but I sure as heck will tune an amp design with silver wire and other tricks when needed and the same with cap choice, but the end intention is to get an amp that is neutral.

 That a vitaminQ is about the only cap other than another Blackgate that will work and play at all with another BG speaks volumes of the neutrality of both caps. So being additive, it may be helpful to think of el caps as prosthetics in an amp, used to aid in deficiencies. And thus placed accordingly.

 Edit: By being 'additive' I also mean to imply that artifacts are introduced into the music that may obscure and cloud detail and low level information.


----------



## 04BluMach

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Well, after tons of listening, I've modified my opinion some on the Alien DAC combinations. MASantos built and sold a lot of them. He's right when he says the Black Gate Alien DACs beat all other "normal" combinations, including one with ES's. The ES Alien is great for something like a PIMETA, which already has great detail, but may be missing that last octave of bass. More than that, though, once you have plenty of bass, the ES Alien DAC just doesn't compete well with really excellent sources. The BG Alien is very similar to the MAX, IMHO - a surprising performer that often holds its own with components costing much more.

 Back to the much larger Black Gates on the MAX, there is a reason that they cost more than ten times the cost of an ES cap: they have fantastic detail. OTOH, as you've mentioned in the past - sometimes you wonder where the bass has gone. It's all the more reason to build several flavors. 
	

	
	
		
		

		
		
	


	



 snip....
_

 

British Bookshelf Monitor Loudspeakers are well known for using the Spendor developed for the BBC monitors frequency responce curve that included a mid-bass hump. Very impressive Bass sound from a relatively small speaker. It fools our psychoacoustic hearing system into believing we are hearing a MUCH larger speaker for that amount of bass output.

 The ES's remind me exactly of that same Mid-Bass Hump in their frequency response. It is just enough not to sound too exaggerated - that is, as tomb has noted, until you add a couple in the sound chain. Then you will probably end up with too much of a good thing - bloated sounding bass.

 I don't think the BG's are lacking in Bass. They just have a very flat response from the lowest bottom to the top. What goes in is what comes out with all the detail (sweetness or warts and all). As such, you just feel like there is something less when compared to the ES's humped up response. 

 Is it 10x the improvement of performance to the 10x the increase in cost. Well -not really. But it is what the cost is to get there. You are rapidly approaching the diminishing returns factor with the NX BG's over the ES's. (Even less for ELNA Silmics & such). The cost to own is only worth it to those who are seeking the last 10 to 20% improvement in SQ at the big cost markup demanded for the "Best".

 Just IMHO -YMMV

 Edit: Negatron beat me to this subject. Very well stated along with some more detail I might add also! 

 PS: The BG cost/perfomance thing is a flamewar subject on other forumns. I Hope this doesn't start here. It just is what it is - high cost for an extra edge in performance.


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## slowpogo

Here are a few pics of my build. I did Can't Miss #1, with 0.27uf Vitamin Q's in all four spots, TKD pot, Panasonic FM's, PRP resistors, 15 ohm Rikens for output, and Mills wirewound power resistors (probably pointless, but so much prettier than those ugly brown Vishays).

 I didn't even try to get the Vitamin Q's flat to the board, but I like the way they look, all pointing inward. I was using some halo GE FK6 tubes at first, but after switching to RCA, I really prefer those, even un-broken-in.

 It doesn't show up well in the pics, but I'm proud of how neat and aligned everything is...I made sure all the resistor values were face up, oriented the same way as the writing on the board, etc., all that anal stuff.


----------



## Negatron

Quote:


  Originally Posted by *slowpogo* /img/forum/go_quote.gif 
_Here are a few pics of my build. I did Can't Miss #1, with 0.27uf Vitamin Q's in all four spots, TKD pot, Panasonic FM's, PRP resistors, 15 ohm Rikens for output, and Mills wirewound power resistors (probably pointless, but so much prettier than those ugly brown Vishays).

 I didn't even try to get the Vitamin Q's flat to the board, but I like the way they look, all pointing inward. I was using some halo GE FK6 tubes at first, but after switching to RCA, I really prefer those, even un-broken-in.

 It doesn't show up well in the pics, but I'm proud of how neat and aligned everything is...I made sure all the resistor values were face up, oriented the same way as the writing on the board, etc., all that anal stuff._

 

Very nice build, and BTW, I think the Mills non-inductive WW's are a very good choice and have found them to be an audible improvement to the Dales in other amps. No reason why not here also. I used 'em.

 I like the canted caps. Real nice overall work.

 EDIT: Those look suspiciously like Rikens up front.


----------



## amphead

Oh Yeah, Slowpogo......turquoise leds, BG's and Vitamin Q's. No arguments here on your component selection. Nice build quality, 45 degree "Q's" are nice. Once the BG's are broken in then it really doesn't get any better.


----------



## xnothingpoetic

I recently bought a Max off of someone here and it has green LEDs, which looks very nice. 

 But has anyone found any LEDs that enhance the natural glow of the tubes?


----------



## Negatron

Quote:


  Originally Posted by *xnothingpoetic* /img/forum/go_quote.gif 
_I recently bought a Max off of someone here and it has green LEDs, which looks very nice. 

 But has anyone found any LEDs that enhance the natural glow of the tubes?_

 

These are Aveco HLMP-EG08-Y2000 available from Jameco @ 68 cents.
http://www.head-fi.org/forums/f6/new...ml#post3635693.
 The photo is running at around 19ma, pretty bright. The LED's are spec'd to go to 50ma. at around 12-15ma (the stock Rled) they are more subdues and orange. At 20ma more red/orange, by 25 they start getting RED.

 You're going to have to de-solder the tube sockets to change them and surgery will be required to fit those LED's or other T-1 3/4's as outlined in a previous post. There is a much wider selection of orange and amber LED's in T-1 3/4. A 5 to 15 degree viewing angle helps too.


----------



## ruZZ.il

Quote:


  Originally Posted by *04BluMach* /img/forum/go_quote.gif 
_..We have a Lead PRE-CLIPPER among our midst!!!...
 Those VitaQ's are awesome! Are those .22uf @150V or so? What are the case size on those bad boys?.._

 

uhoh, they're on to me! <hides>.. you're spot on! I mentioned this a few pages ago too, having the leads either flush or very close to flush is key. Since my wire clippers don't do the job too well, I've resided to pre-snipping almost everything. Time consuming at first, but after a few components you get a feeling for how short things have to be..

 0.22@100v, they're L~1.2", R~0.2".

  Quote:


  Originally Posted by *slowpogo* /img/forum/go_quote.gif 
_...It doesn't show up well in the pics, but I'm proud of how neat and aligned everything is...I made sure all the resistor values were face up, oriented the same way as the writing on the board, etc., all that anal stuff..._

 

Nice build too!
	

	
	
		
		

		
		
	


	




 which trannies are you using? What casing option have you got up your sleeve there?.. I've really taken a liking to the BG characteristics.. You'll love them
	

	
	
		
		

		
		
	


	




 btw, all that anal stuff is what makes a diff after-all 
	

	
	
		
		

		
		
	


	




 wow.. there really has been a sudden surge of new builds.. good stuff 
	

	
	
		
		

		
		
	


	




 I also(since I doubt I'm not the first to think this) think the max has really hit a winning combo from the segments designs by their respective designers, the master modular combiner and super support/documentation all the way down to the cumulative end users contributions. My first encounter with tubes has been a pleasure, so thank you all 
	

	
	
		
		

		
		
	


	




 (<nudges Collin for the next encounter> )


 Also, regarding the recent conversation about BG cost/performance.. yeah, they cost around 10x most competitors, but their total price is about 25% of the amp, for a '10%' difference.. its at-least the same order of magnitude, not diminishing yet 
	

	
	
		
		

		
		
	


	







 ..And thanks for the kind words guys. I think the mere fact that any of us build these is pretty neat!


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## fordgtlover

Quote:


  Originally Posted by *slowpogo* /img/forum/go_quote.gif 
_snip 

 It doesn't show up well in the pics, but I'm proud of how neat and aligned everything is...I made sure all the resistor values were face up, oriented the same way as the writing on the board, etc., all that anal stuff.
_

 

Quality is in the detail - it shows you care.


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## jamess71

Slopogo are those LED's the from SUPER BRIGHT LEDS home


 RL3-A4018 Aqua 3mm LED
 3mm Aqua Super Bright LED
 505 nm / 4000 mcd / 18 Degree Viewing Angle

 Will this led produce the same effect? I love yours.

 james


----------



## tomb

Great builds and posts, guys. 

 I don't want to start a flame war, either, so let me say up front: I agree with what's being said.

 However, none of this contradicts the "Can't Miss Builds" on the MAX website. Just remember that using BG's comes with a price - both monetarily and in building skill - if you want to eke out the very last bit of performance with VitQ's. In the last few sets of pics, we've been looking at some _very good builders._ In each case, it shows that VitQ's require a _creative_ build. There's no way VitQ's at the desired rating will fit in a straightforward manner. You can also forget about trying to get them to fit in a MiniMAX. (Well, Colin is Mad MAX - a Creative Genius - so it's possible he'll surprise us about that claim.)

 Also, no one should feel that they have to purchase Black Gates to build a highly enjoyable, high-fidelity MAX. Just my humble opinon, but the Nichion Muse ES is still my favorite cap to use in a MAX or a Millett (Alien DAC conversations notwithstanding). They are cheap, the build is simple, and the effect is impressive. They may even pair better with punchy and slightly peaky phones such as Grados and KSC75's, IMHO.

 Nevertheless, the path is there to build a very high-level MAX.

_Lots of _Another MAX Lives!!


----------



## slowpogo

Quote:


  Originally Posted by *jamess71* /img/forum/go_quote.gif 
_Slopogo are those LED's the from SUPER BRIGHT LEDS home


 RL3-A4018 Aqua 3mm LED
 3mm Aqua Super Bright LED
 505 nm / 4000 mcd / 18 Degree Viewing Angle

 Will this led produce the same effect? I love yours.

 james_

 

That's the same one I used. But be warned, the pics make them look more blue than they are. In real life they're basically light green, with just a touch of blueness--the pics show them as I was hoping they'd look. 
	

	
	
		
		

		
		
	


	




 They're also not that bright, probably significantly dimmer than what a lot of people are using. Still, I'm not complaining, they do look nice!

 I'm using a Hammond case, but will be using FP Express for the front, rear and top panels. It'll probably be a month or two before I actually have it cased up. The case will be black, with black rear panel and natural aluminum front panel. It will be nice and simple, knob and output centered vertically, LED in the middle toward the top...I decided to not use an LED holder, just drill a hole 3mm wide and let just the curved portion of the LED stick out (the top 1.5mm or so).

 I'm also going to put some fairly big vent holes in the top panel, with wire mesh behind them. There will be an air vent in the back panel too. I'm hoping to find some quality aluminum-colored "feet" too.


----------



## cetoole

Quote:


  Originally Posted by *Negatron* /img/forum/go_quote.gif 
_It seems a good number of MAX's have been born recently so I thought I would add another to the population.
 (And more of the little critters yet to be birthed)

http://farm3.static.flickr.com/2401/...8d7c7a9e_o.jpg

 Poor ears, with the BG's and the Silmic, it is going to take some time to hit it's stride. Pink noise time.....
 (Silmics are worse than BG's in that respect). 2700FC's and PIO's on the rail.

 And I don't know if anyone has done it, but probably. A smaller (4.7) BG N at the output of a regulator is a plus.

 Fun and fast to build. Great layout colin. 
	

	
	
		
		

		
		
	


	


_

 

Good looking MHMax so far Negatron, but what I really wanna see is that thingie in the background. Plus, Amperex 12AE6A tubes 
	

	
	
		
		

		
		
	


	




. Thanks for the compliment too.
  Quote:


  Originally Posted by *ruZZ.il* /img/forum/go_quote.gif 
_uhoh, they're on to me! <hides>.. you're spot on! I mentioned this a few pages ago too, having the leads either flush or very close to flush is key. Since my wire clippers don't do the job too well, I've resided to pre-snipping almost everything. Time consuming at first, but after a few components you get a feeling for how short things have to be..

 0.22@100v, they're L~1.2", R~0.2".


 Nice build too!
	

	
	
		
		

		
		
	


	




 which trannies are you using? What casing option have you got up your sleeve there?.. I've really taken a liking to the BG characteristics.. You'll love them
	

	
	
		
		

		
		
	


	




 btw, all that anal stuff is what makes a diff after-all 
	

	
	
		
		

		
		
	


	




 wow.. there really has been a sudden surge of new builds.. good stuff 
	

	
	
		
		

		
		
	


	




 I also(since I doubt I'm not the first to think this) think the max has really hit a winning combo from the segments designs by their respective designers, the master modular combiner and super support/documentation all the way down to the cumulative end users contributions. My first encounter with tubes has been a pleasure, so thank you all 
	

	
	
		
		

		
		
	


	




 (<nudges Collin for the next encounter> )


 Also, regarding the recent conversation about BG cost/performance.. yeah, they cost around 10x most competitors, but their total price is about 25% of the amp, for a '10%' difference.. its at-least the same order of magnitude, not diminishing yet 
	

	
	
		
		

		
		
	


	







 ..And thanks for the kind words guys. I think the mere fact that any of us build these is pretty neat! 
	

	
	
		
		

		
		
	


	


_

 

ruZZ.il, sounds like you need to get some decent flush cutters. I do my soldering this way too, mainly to ease flux cleanup. I have had 3 different ones so far, and really like my Xcelite 170D cutters, which are ~$5 from Mouser or Digikey.

 Next encounter is coming. Hope I dont have to start wearing a fake mustache and glasses at meets (cant grow a proper, non scruffy one yet).
  Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Great builds and posts, guys. 

 I don't want to start a flame war, either, so let me say up front: I agree with what's being said.

 However, none of this contradicts the "Can't Miss Builds" on the MAX website. Just remember that using BG's comes with a price - both monetarily and in building skill - if you want to eke out the very last bit of performance with VitQ's. In the last few sets of pics, we've been looking at some very good builders. In each case, it shows that VitQ's require a creative build. There's no way VitQ's at the desired rating will fit in a straightforward manner. You can also forget about trying to get them to fit in a MiniMAX. (Well, Colin is Mad MAX - a Creative Genius - so it's possible he'll surprise us about that claim.)_

 

Who you calling Mad MAX? You guys have crazier builds than I. Though I probably am still the only one who has ever listened to a Max with parafed autoformer outputs, driving 8ohm 3 way speakers 
	

	
	
		
		

		
		
	


	




. Nightingale sounded great like that, though IMO, Nightingale always sounds great.
  Quote:


  Originally Posted by *slowpogo* /img/forum/go_quote.gif 
_I'm also going to put some fairly big vent holes in the top panel, with wire mesh behind them. There will be an air vent in the back panel too. I'm hoping to find some quality aluminum-colored "feet" too._

 

Feet, you mean like this?


----------



## slowpogo

Quote:


  Originally Posted by *cetoole* /img/forum/go_quote.gif 
_Feet, you mean like this?_

 

Exactly cetoole, where are those from? Are they an appropriate size for a Hammond-cased Max?


----------



## tomb

Quote:


  Originally Posted by *cetoole* /img/forum/go_quote.gif 
_Who you calling Mad MAX?_


----------



## dragontooth67

A couple questions for you guys...and I apologize if these were answered before in this thread but its a bit of a monster to read through (especially for a DIY newbie). 

 For those of you who have used it, how well does the Glass Jar Audio kit stack up (cost, ~$180, vs. sound) compared to some of these other builds? 

 Please keep in mind this is not only my first DIY amp, but my first amp in general (so I don't really need the beez-neez, if you will, just something that will pair well with my new hd650s). I don't think I would really notice, or appreciate, the difference it would cost for high-end caps until I get to know the new headphones and the amp in general. Anyways, advice from anybody who has used this kit before or who knows something about it would be appreciated. 

 ps. how well does this amp work with the hd650s, anyways? I notice alot of K701 users in this thread....


----------



## willisv

The glass jar kit sounds great, It's one of the can't miss builds on the Max site. Even if you want to upgrade caps later, it's still one of the best ways to start.


----------



## tomb

Quote:


  Originally Posted by *dragontooth67* /img/forum/go_quote.gif 
_A couple questions for you guys...and I apologize if these were answered before in this thread but its a bit of a monster to read through (especially for a DIY newbie). 

 For those of you who have used it, how well does the Glass Jar Audio kit stack up (cost, ~$180, vs. sound) compared to some of these other builds? 

 Please keep in mind this is not only my first DIY amp, but my first amp in general (so I don't really need the beez-neez, if you will, just something that will pair well with my new hd650s). I don't think I would really notice, or appreciate, the difference it would cost for high-end caps until I get to know the new headphones and the amp in general. Anyways, advice from anybody who has used this kit before or who knows something about it would be appreciated. 

 ps. how well does this amp work with the hd650s, anyways? I notice alot of K701 users in this thread...._

 

Jeff's kit is an excellent buy. It's listed in one of the "Can't Miss MAX Builds" - #5, to be exact. I haven't built one, but we have had many good reports.

 FYI, the film bypass caps is one of the great features of Pete Millett's Millett, and Colin Toole's great evolution of that design, the Millett MAX. The bypass caps allow you to use regular quality power electrolytics and gain very much the same sound as you do with boutique caps. Jeff's Glass Jar Audio kit uses full-fledged boutique electrolytics anyway - the Nichicon Muse KZ's. The KZ is the best in Nichicon's line - meaning better overall than the ES.

 Part of the reason I posted that post this morning was a gentle reminder that we all get carried away singing the praises of these high-dollar caps, but you can't go wrong with any of those Can't Miss MAX Builds, including Jeff's kit. Jeff's prices are always outstanding, too. I believe the MAX BOM is at about $160 and change, but there's a lot of hardware that's not included in that price. Many of us continue to wonder how Jeff does it at his prices. 
	

	
	
		
		

		
		
	


	




 P.S. I often use HD580's and HD600's with my MAXes. Although, I confess that what's on my ears most often are KSC75's. 
	

	
	
		
		

		
		
	


	




 EDIT: willisv beat me to it!


----------



## willisv

I forgot to mention - if you want to substitute some of the parts in the Glass Jar kit for different parts like the ones in tomb's site, he will do that for you. He is really good that way. Speaking of Jeff, my Bijou kit just showed up!


----------



## tomb

While I was posting photos (nobody thought that was funny?), cetoole had mentioned Negatron's Amperex 12AE6. I happen to have one, too, although it's only a single, unfortunately. I picked it up along with a group of very old and uncommon tube boxes. I'm hoping to post a collection of Millett tube box graphics on the MAX site in the future. So, if you guys have any you'd like to contribute, please send them to me.

 BTW, scanning works as well as a camera 
	

	
	
		
		

		
		
	


	




 :





 The actual tubes in the boxes - despite the painted brand name - from left to right are: Sylvania/Tung Sol, GE, RCA, GE, Sylvania/Tung Sol.


----------



## willisv

Here's mine Tom.


----------



## Negatron

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_














_

 

ROFL!!! I gotta' have a T-shirt, Poster and I'm gonna' print up lablels for 'MAX' boxes. 

 WHO on this forum is a copyright Lawyer? We desperately need some Pro-Bono permission work.

 I just stopped in for a few min and checked my email and the forum. Worth every second spent!

 I'll be back!


----------



## cetoole

Quote:


  Originally Posted by *slowpogo* /img/forum/go_quote.gif 
_Exactly cetoole, where are those from? Are they an appropriate size for a Hammond-cased Max?_

 

They came from Jaycar Electronics, way down under. Shipping, surprisingly, wasnt bad. These are 30mm diameter. They may be a little much with regards to their height, though if you go with an oversized front panel, from FPE or something, they would look great IMO. I did a lot of foot searching when sourcing parts for the balanced M³ I built for another member here. These (well, larger ones for that amp) were the best I could find at the time. I may be able to be persuaded to take a photo of a 1455T1601 sitting ontop of them, if that would be helpful.

 Dragontooth67, I use Sennheiser HD580 headphones almost exclusively (besides speakers) with my MHMax. Had the HD650 for a bit, but preferred the HD580.


----------



## slowpogo

To me, 30mm by around 9-10mm (best guess) is perfect. Do you remember what hardware works well to mount them? I will be ordering from McMaster-Carr soon so it would be cool to include that stuff too.


----------



## cetoole

Well, my calipers say ~30.5mm by ~9.5mm. 6-32 screws and appropriate nuts work great. I prefer hex screws, either socket head or button head. Dont get too long screws, or they will hit the PCB. Just an estimate, but maybe go for 3/8" or a bit less. That will work just fine, unless the Max PCB will be in the bottom slot.


----------



## dragontooth67

Thanks for the replies. TomB, I think you just sold me on Jeff's kit. Sounds perfect for what I want! 

 Man, this is a great forum....I got headphone advice from the designer of the amp, himself! To me, thats like going to Bill Gates and asking him what he thinks of using Foobar with Windows XP.


----------



## Negatron

Quote:


  Originally Posted by *dragontooth67* /img/forum/go_quote.gif 
_Thanks for the replies. TomB, I think you just sold me on Jeff's kit. Sounds perfect for what I want! 

 Man, this is a great forum....I got headphone advice from the designer of the amp, himself! To me, thats like going to Bill Gates and asking him what he thinks of using Foobar with Windows XP._

 

Actually Pete Millett of Wheatfield Audio fame was the original designer, cetoole did the board layout with the input from a collection of great talent. tomb is likened to General Eisenhower in WWII, the general coordinator (my puns are bad) of great minds to a single task

 Welcome to the blackhole that sucks in time & money. BTW, Jeff puts together great kits

 I refrain from mentioning Bill Gates <evil icon>


----------



## Negatron

Quote:


  Originally Posted by *cetoole* /img/forum/go_quote.gif 
_Good looking MHMax so far Negatron, <snip>_

 

Thanks!

  Quote:


  Originally Posted by *cetoole* /img/forum/go_quote.gif 
_but what I really wanna see is that thingie in the background. Plus, Amperex 12AE6A tubes 
	

	
	
		
		

		
			





. Thanks for the compliment too. <snip>_

 

As per tomb's post, the tubes are only a re-brand (Boo) as to the 'thingie':
 Very OT, me bad....
 3 input, 6SN7 driven, direct coupled 6H6p White Cathode Follower: Mains filtered, T=250v 200ma, 5U4, LCRC, 10mH, 800uf, 100R, 800uf. 1st gen .47 MIT Multicap PS bypasses, 30,000uf CLCRC DC heaters, .1 Auricap@upper K to Lower G, 50R AB grid stops, 100R plate 80R K, BG+BG OP coupling. R=Mills, Holco, Kiwame, Riken. Amp presently in pre-op for (yet another) update.
 When I do Surgery in the near future, I'll post a few photos of the 'Guts' and details in another thread.

http://farm3.static.flickr.com/2017/...9236d742_o.jpg


----------



## tomb

Quote:


  Originally Posted by *Negatron* /img/forum/go_quote.gif 
_Actually Pete Millett of Wheatfield Audio fame was the original designer, cetoole did the board layout with the input from a collection of great talent. tomb is likened to General Eisenhower in WWII, the general coordinator (my puns are bad) of great minds to a single task_

 

Hmm ... I'll accept the General part as far as managing some things, but only if cetoole is The President. 
	

	
	
		
		

		
		
	


	




 As long as we're drawing analogies, Pete Millett started things - no doubt whatsoever - he's the "Great God Millett" who bequethed his creation to the masses. "Go forth and multiply and be thou great stewards of this creation" or something like that. At the same time, he gave us all "free will" over his creation to do with as we please. Thank you, Pete!!! (Sorry for the religious analogy - I don't mean to offend anyone.)

 When it comes to cetoole's _free will_ achievement with the MAX, it's somewhat easy to think of it as just designing another layout of the existing Millett design. However, it's quite rare to have someone accomplish the near-perfect integration of disparate components as Colin has done with the MAX. Actually, the pure Millett portion is only one part of a very large and complicated package. Granted, that part happens to be the basis of the whole design - but still only a part.

 Very often with a DIY design, (there are notable exceptions, to be sure) the separate circuits have existed as _general knowledge_. It takes creative genius to put these all together so that the combination is something more than the separate pieces. The MAX is a complete package: it fits a standard case exactly and requires only the connection of an inexpensive AC walwart. At the same time, it incorporates just about every component accessory ever associated with or desired for the basic Millett design. Integration and package design on that sort of level is every bit a creation. IOW, _the board is the thing_. Without that, General Eisenhower is _nothing_, I can guarantee you! 
	

	
	
		
		

		
		
	


	




 So again, not referencing your post per se, but I just wanted to make it clear to everyone the context and importance of what Colin has done here - at least from my own personal perspective.


----------



## Aldyrin2

A few questions about the construction materials:

 1. Can anyone recommend a good place to get something similar to the front chrome bezel LED holder (T-1-3/4 LED panel bezel) like the one shown in the construction pictures?
 2. I have the ALPS RK27 pot for my volume control. What is a good knob to use with this? Where would I buy this?
 3. Can you buy the bushings for the tube chassis holes at Home Depot or Lowes?


 Is it really worth it to install the tip jacks on the back? 

 This is my first DIY audio amp, although I've had a lot of soldering/electronics lab work in the past. Got most of the soldering done, just getting the finishing touches on at this point.

 Sorry if these questions have been addressed already. I tried searching, but this thread is huge!

 Also, should I be able to use any cans with this amp, or will I need to make adjustments to get optimum output? I have some grado SR-80's I was planning on using when I get finished, but I am thinking about getting AKG-701's soon.

 Thanks for the help!


----------



## tomb

Quote:


  Originally Posted by *Aldyrin2* /img/forum/go_quote.gif 
_A few questions about the construction materials:

 1. Can anyone recommend a good place to get something similar to the front chrome bezel LED holder (T-1-3/4 LED panel bezel) like the one shown in the construction pictures?_

 

Beezar.com has them in stock along with many other hard-to-get MAX parts. Quote:


 2. I have the ALPS RK27 pot for my volume control. What is a good knob to use with this? Where would I buy this? 
 

The knobs that I use are from ebay store "Partspipe" (ebay user "hongkongsuperseller"). Buy the ones that are 30mm diameter x 22mm. They are made specifically for the Alps pots. Be careful, however, he has a lot to pick from. I was disappointed to realize that the gold versions of these knobs are push-on type, only. So be sure it's one with a set screw and has those dimensions. He is quite reliable, but don't expect any answers to questions. Quote:


 3. Can you buy the bushings for the tube chassis holes at Home Depot or Lowes? 
 

No, but they're at Mouser and most Ace Hardware stores.

  Quote:


 Is it really worth it to install the tip jacks on the back? 
 

That's up to you. It's definitely a tremendous convenience. DB's and the PS Voltage adjustment should not vary, but every time you change to a different tube you should check the tube bias. (Voltage adjustment may actually vary if you move the amp to another location that has a different line voltage - say 120VAC instead of 110VAC.) 

  Quote:


 This is my first DIY audio amp, although I've had a lot of soldering/electronics lab work in the past. Got most of the soldering done, just getting the finishing touches on at this point.

 Sorry if these questions have been addressed already. I tried searching, but this thread is huge! 
 

The MAX website is usually the first resource, but the MAX forum section on DIYForums.org may help, too.

  Quote:


 Also, should I be able to use any cans with this amp, or will I need to make adjustments to get optimum output? I have some grado SR-80's I was planning on using when I get finished, but I am thinking about getting AKG-701's soon.

 Thanks for the help! 
 

Either of those cans will do fantastically with the MAX. The MAX can force plenty of current to drive either one with authority.


----------



## tomb

BTW - about biasing/tip jacks. Without the tip jacks, it means that you have to take the lid off to do any biasing adjustments. That's possible by removing six screws and taking the lid out of the case. The six screws are the 4 on the back plate and the top two on the frontplate - because the screws on top actually cut into the edges of the lid.

 Again, you'll have to determine for yourself whether tip jacks are worth it to you. There are many Millett and Millett MAX owners who've just left the lid off permanently. Others have just installed a type of wire mesh for the lid. So, there are other possibilities if the thought of the tip jacks are troubling. Course, 3 are all it would take to cover what's needed for tube bias. You could leave the rest off.


----------



## ruZZ.il

Although you may want to have a few sets of tubes that you may like to use. With the Grado's, which are a lower impedance pair of headphones, you may want to use a lower gain set of tubes. The tubes govern the voltage gain in the amp. Generally, you need a higher voltage gain to power higher impedance headphones to a certain volume(They do require less current though). You'd still be able to use either gain with either headphones, but the 'volume response' will differ. 12FK6 seem to be the most commonly used lower gain tubes here, while the 12AE6s for higher gain (I think). Take a look at the MAXs Tubes page.


----------



## Aldyrin2

Sounds good. Thanks for the feedback.

 The current tubes I have are 12AE6. Should those be fine for the 701's? That is mainly what I am building this amp to be used with.


----------



## slowpogo

With a typical CD (DVD) player, the 12FK6 are more than enough with my K701's. With the volume halfway up, it borders on too loud for rock music. Even with quiet classical music I still only turn it up 3/4 of the way.

 I haven't tried them but the 12AE6 would probably be way too much. You'd only be turning up your volume knob a small amount, and the best tracking in pots is the middle area.


----------



## Aldyrin2

Well my source is my computer at work (for now, thinking about a diy USB DAC in the near future), so hopefully I can tweak the output to be in the best tracking range of the pot...

 We'll see!
 Thanks again.


----------



## pabbi1

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_While I was posting photos (nobody thought that was funny?), cetoole had mentioned Negatron's Amperex 12AE6. I happen to have one, too, although it's only a single, unfortunately. I picked it up along with a group of very old and uncommon tube boxes. I'm hoping to post a collection of Millett tube box graphics on the MAX site in the future. So, if you guys have any you'd like to contribute, please send them to me.

 The actual tubes in the boxes - despite the painted brand name - from left to right are: Sylvania/Tung Sol, GE, RCA, GE, Sylvania/Tung Sol. 
	

	
	
		
		

		
		
	


	


_

 

With the 12fk6, I am finding the balanced Maxx to love it some Pink Floyd... velvety is the correct term, I think.

 OK, these are the 12fk6 I have today, and another batch incoming...


----------



## slowpogo

I don't think I've seen this mentioned..what about mixing the boutique electrolytics? Like, using Nichicon ES for CA2 and Black Gates for CA7? Or vice versa?

 Could this split the difference between detail and powerful bass slam? Has anyone tried it? I've never seen it advocated here and it's an obvious idea, so I have the feeling the answer is "no"...


----------



## Negatron

Quote:


  Originally Posted by *slowpogo* /img/forum/go_quote.gif 
_I don't think I've seen this mentioned..what about mixing the boutique electrolytics? Like, using Nichicon ES for CA2 and Black Gates for CA7? Or vice versa?

 Could this split the difference between detail and powerful bass slam? Has anyone tried it? I've never seen it advocated here and it's an obvious idea, so I have the feeling the answer is "no"..._

 

I don't personaly believe the answer is "no", but the difference is going to be subtle. I frequently mix caps in an design and though my experience with the sound of the MAX is more based on the revMH. My first MAX build was in the de-soldering process right after 2 days of pink noise as soon as I started the #2 build. I opted for BG's on both OP & K but used a Silmic with PIO on CA4 to smooth/warm the current source, but we are talking very minor change. CA7 and CA2 are absolutely the most critical caps in the circuit as for SQ. My personal choice if using an 470-680uf ES on CA7 would be a 1000uf BG N or a Nichicon KZ on CA2.

 I am sure there are those with far more experience with the MAX that have recommendations but as always with this hobby, my opinon only is based on my ears. YMMV.

 Edit: I could add that the signal passes through CA7, but is actually working in parallel in CA2 and thus it is my personal opinion that CA2 should be as neutral as possible.


----------



## jamess71

I have my first almost done. Realized yesterday I never ordered the alps from ambs site. duh. I was hoping to get it running today but no luck. Have the order in for 2 and hopefully I'll have them later this week. 

 Where are you guys finding the 12fk6 tubes? I bought a lot of 10. They all came in white boxes, I was told they are all GE. I don't think a pic of these would help your cause Tomb. 
	

	
	
		
		

		
		
	


	




 James


----------



## pinkfloyd4ever

Quote:


  Originally Posted by *pabbi1* /img/forum/go_quote.gif 
_With the 12fk6, I am finding the balanced Maxx to love it some Pink Floyd... velvety is the correct term, I think.

 OK, these are the 12fk6 I have today, and another batch incoming...

 <awesome pic of tubes>_

 

mmmmm sounds like a good idea. nice tubes


----------



## tomb

Quote:


  Originally Posted by *jamess71* /img/forum/go_quote.gif 
_Where are you guys finding the 12fk6 tubes? I bought a lot of 10. They all came in white boxes, I was told they are all GE. I don't think a pic of these would help your cause Tomb. 
	

	
	
		
		

		
			





 James_

 

Yep - I've gotten several like that from vacuumtubes.net, but they were RCA's. It's easy enough to tell:

 - GE's have a series of white dots near the top of a tube that are etched into the glass.
 - RCA's all have the "squished" octagon near the top of the tube (the octagon is much wider than tall) with the tube designation inside, as in "{12FK6}".
 - If the tubes have neither of those indicators, most likely it's a Sylvania/Tung-Sol production.

 Those three possibilities are pretty much all that exists for Millett tubes, regardless of the box or the name brand that's painted on the tube.


----------



## amphead

I have yet to try 12FK6 in the Max, and I am using the efficient(64ohm) K701's. Pabbi's got me jonesin to give that a try. I like the 12AE6 in all the flavors that I have tried grape, cherry, lime and rootbeer, paired with K701's.


----------



## slowpogo

I just tried 12FM6 tubes for the first time. I had been using 12FK6, GE then RCA, but something wasn't quite right about them. I'm listening on K701's, and with the FK6 tubes, the sound was just too cool. Super detailed, but missing much of that musical low-mid sound that I like. Bass was a little light too.

 After putting in some RCA 12FM6's...WOW. Now, I'm impressed. The amp has been running about 100 hours now, so it should be pretty well broken in, apart from the tubes, but even with totally new tubes in it sounds much better to my ears. The bass has just the right amount of beefiness and impact, but is still tight, and significantly deeper than the FK6's. The highs are still extended and quite clear, and there is much detail, but overall the mids are just so much more musical. I hesitate to call it "warm"; it still sounds basically neutral, but just balanced much better for me.

 And, the FM6 added a negligible amount of gain, really. I turn the knob up only about 10 degrees less. It seems like the extra juice is mostly just making the K701's sound better, not really adding volume.


----------



## Negatron

Quote:


  Originally Posted by *slowpogo* /img/forum/go_quote.gif 
_I just tried 12FM6 tubes for the first time. I had been using 12FK6, GE then RCA, but something wasn't quite right about them. I'm listening on K701's, and with the FK6 tubes, the sound was just too cool. Super detailed, but missing much of that musical low-mid sound that I like. Bass was a little light too.

 After putting in some RCA 12FM6's...WOW. Now, I'm impressed. The amp has been running about 100 hours now, so it should be pretty well broken in, apart from the tubes, but even with totally new tubes in it sounds much better to my ears. The bass has just the right amount of beefiness and impact, but is still tight, and significantly deeper than the FK6's. The highs are still extended and quite clear, and there is much detail, but overall the mids are just so much more musical. I hesitate to call it "warm"; it still sounds basically neutral, but just balanced much better for me.

 And, the FM6 added a negligible amount of gain, really. I turn the knob up only about 10 degrees less. It seems like the extra juice is mostly just making the K701's sound better, not really adding volume._

 


 Good thing you haven't read how the 'FM6 is a poor performer in the Millett .
	

	
	
		
		

		
		
	


	




 I really like the 'FM' RCA's with my modded K501's also. The decay on cymbals, and bells is natual among other things, I just mention that because I was listening earlier to a pair - not trying to get a tube rolling thing going but they are under-rated. I am not quite as pleased with them using Senns tho'. If it is easy for you to do, kick up the CCS to 0.065ma with RA8 & 9 to 1K & 10K. The 'FM6 responds better with the higher current to my ears and the AKG's. My overall choice is still the 12AE6 but the FM is a nice tube.
 Great to hear you are enjoying it.


----------



## jamess71

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Yep - I've gotten several like that from vacuumtubes.net, but they were RCA's. It's easy enough to tell:

 - GE's have a series of white dots near the top of a tube that are etched into the glass.
 - RCA's all have the "squished" octagon near the top of the tube (the octagon is much wider than tall) with the tube designation inside, as in "{12FK6}".
 - If the tubes have neither of those indicators, most likely it's a Sylvania/Tung-Sol production.

 Those three possibilities are pretty much all that exists for Millett tubes, regardless of the box or the name brand that's painted on the tube. 
	

	
	
		
		

		
		
	


	


_

 

Thanks tomb, so I have RCA's. I have 10 of them. Does anybody want to try them out? I would like to trade some of these 12fk6 for any other flavor. 

 Thanks 
 James


----------



## tomb

Quote:


  Originally Posted by *Negatron* /img/forum/go_quote.gif 
_Good thing you haven't read how the 'FM6 is a poor performer in the Millett .
	

	
	
		
		

		
		
	


	




 I really like the 'FM' RCA's with my modded K501's also. The decay on cymbals, and bells is natual among other things, I just mention that because I was listening earlier to a pair - not trying to get a tube rolling thing going but they are under-rated. I am not quite as pleased with them using Senns tho'. If it is easy for you to do, kick up the CCS to 0.065ma with RA8 & 9 to 1K & 10K. The 'FM6 responds better with the higher current to my ears and the AKG's. My overall choice is still the 12AE6 but the FM is a nice tube.
 Great to hear you are enjoying it._

 

Yep. The 12FM6 got a bad rap during some of the original revMH discussions on DIYForums.org. Again, probably attributable to the relative rarity of the tube - the early reports may have been due to some bad examples. Comments such as "wooly", "fuzzy", and so on were unjustified.

 I have found that the 12FM6 is just about mid-way between the characteristics of the 12FK6 and the 12AE6 (clear highs vs. punch). I agree with Negatron that the 12AE6/A is still my favorite, though, even with low impedance cans. I don't mind having a hair-trigger volume control and often live in the space from 7 to 10 o'clock. 
	

	
	
		
		

		
		
	


	




 The Grado SR80's I had at one time sucked enough current to be happy in the high side of that range with a 12AE6, anyway.


----------



## GeWa

Does anybody have any comments on those red PRP resistors Partconnexion sels? Are they any good or should I just stick to normal metal film resisors?

 Regards


----------



## slowpogo

PRP are non-magnetic, which is good. In my experience they are a little less harsh than the Vishay-Dales that Mouser sells. They also look a lot nicer, if that matters to you.

 Personally, I think it's worth spending ~$7 for PRP's in the Max.


----------



## tomb

Quote:


  Originally Posted by *slowpogo* /img/forum/go_quote.gif 
_PRP are non-magnetic, which is good. In my experience they are a little less harsh than the Vishay-Dales that Mouser sells. They also look a lot nicer, if that matters to you.

 Personally, I think it's worth spending ~$7 for PRP's in the Max._

 

I agree completely. Plus, they look kinda cool. 
	

	
	
		
		

		
		
	


	




 BTW - besides PartsConX, you can order both PRP's and Black Gates at Soniccraft.com - highly recommended.


----------



## pinkfloyd4ever

hey tomb (or AMB, colin, or anybody else who knows) what's the equation for the DB current? I'm just curious as to how many mA mine are biased to at whatever voltage I've got them set at(100mV right now). Is it just a simple ohms law equation? Does a higher bias current/voltage give better performance? Is there any disadvantage to setting it to the prescribed max of 110 mV, like a decrease in the life of the BJTs?


----------



## Gross

I finished my MAX sometime last week, I used Nichicon Muse KZ as CA7 and Panasonic FC for CA2, while I left CA8 and 9 open until I received my K42s...

 Well I got the K42s installed. Wow. The high end just open up and got twinkley! It was worth the wait. 

 I have a Q though, I used the MJE 243/253 setup for the DBs, am I going to hear a nice difference if I switch to the 2SC2238/2SA968 combo or something else?

 I still love this amp. Maybe I will post pics, as I think I did a fairly nice job on it.


----------



## willisv

Quote:


  Originally Posted by *Gross* /img/forum/go_quote.gif 
_I finished my MAX sometime last week, I used Nichicon Muse KZ as CA7 and Panasonic FC for CA2, while I left CA8 and 9 open until I received my K42s...

 Well I got the K42s installed. Wow. The high end just open up and got twinkley! It was worth the wait. 

 I have a Q though, I used the MJE 243/253 setup for the DBs, am I going to hear a nice difference if I switch to the 2SC2238/2SA968 combo or something else?

 I still love this amp. Maybe I will post pics, as I think I did a fairly nice job on it._

 

I did exactly what you are asking, I took the 243/253's out of my max and put the 2SC2238/2SA968's in. The only problem is that I am pretty sure that they were fakes. (I got them on ebay from a hong kong seller) The sound quality went way down. If you do this make sure you get the real ones.


----------



## ruZZ.il

Quote:


  Originally Posted by *pinkfloyd4ever* /img/forum/go_quote.gif 
_....what's the equation fo the DB current? ...._

 

Yep, ohms law. Its I=V[size=xx-small](RB10/11)[/size]/(RB10/11). In a standard build with RB10/11 being 2.2Ohms, you just devide the measured voltage by 2.2. So, 100mV is almost 45.5mA, for instance.

 The advantage of a higher current (within the recommended range, that is) is utilizing a more linear region of response of the transistors, which is truer to the source and slightly better performance. The disadvantage is heat and the risk of thermal runaway. Since the BJTs conduct better at higher temps, as they heat up, more current is passed through, hence.. more heat, and so on.. poof!. So, as long as they're kept cool enough, you're good. I'm not sure what 'cool enough' is though, but I don't like too hot to the touch. Their temp and max current is govourned by the heatinks, ventilation, etc.. Also, I havent experimented too much with the sound of deeper bias, maybe someone else can elaborate more on the differences, and the current limits you should expect out of your configuration (what is your configuration?).. hope this helps some..


----------



## pinkfloyd4ever

Quote:


  Originally Posted by *Gross* /img/forum/go_quote.gif 
_I have a Q though, I used the MJE 243/253 setup for the DBs, am I going to hear a nice difference if I switch to the 2SC2238/2SA968 combo or something else?_

 

 Quote:


  Originally Posted by *willisv* /img/forum/go_quote.gif 
_I did exactly what you are asking, I took the 243/253's out of my max and put the 2SC2238/2SA968's in. The only problem is that I am pretty sure that they were fakes. (I got them on ebay from a hong kong seller) The sound quality went way down. If you do this make sure you get the real ones._

 

right. I think you will definitely hear a difference, as the BJT pairs used in the Max are said to have the biggest effect on its sound signature. However, beware of fakes. From what people here have told me, (not that I think any of them aren't trustworthy, just that I've only ordered from one of these places) you can always be sure they're genuine if they're from B&D Enterprises fibra-brandt or MCM


----------



## amphead

I will be representing TEAM MILLETT MAX at this meet. No one there has the mighty MAX. 







 Attendees:

 Voltron
 JP11801
 Tyrion
 Boomana
 Agile_One
 Thrice
 blessingx
 Iron_Dreamer
 Icarium
 Bigguy + The Boss
 foo_me
 mikeymad
 Grahame
 utep10
 Ori
 neilvg
 ironbut
 calaf
 ronin74
 episiarch
 rhythmdevils
 FZfan
 NightWoundsTime
 immtbiker
 Wmcmanus
 bobcn
 manhattanproj
 Rakthar
 pdennis
 teros1
 amphead
 guzziguy
 Jhokur + 1
 MaloS + 1


 Possible Attendees:

 The Monkey
 Humanflyz
 granodemostasa
 justin w.
 thelittleprince
 clarke68


----------



## tomb

Quote:


  Originally Posted by *Gross* /img/forum/go_quote.gif 
_I finished my MAX sometime last week, I used Nichicon Muse KZ as CA7 and Panasonic FC for CA2, while I left CA8 and 9 open until I received my K42s...

 Well I got the K42s installed. Wow. The high end just open up and got twinkley! It was worth the wait. 

 I have a Q though, I used the MJE 243/253 setup for the DBs, am I going to hear a nice difference if I switch to the 2SC2238/2SA968 combo or something else?

 I still love this amp. Maybe I will post pics, as I think I did a fairly nice job on it._

 

Glad to hear it!

 Yes, you will notice a difference with the 2SC2238/2SA968 combo. However, since that pair is very neutral, the difference will be somewhat subtle - more detail, with a very wide extension, almost nothing is lost. These qualities are present much more so than the MJE's, but because the difference is in one of neutrality plus detail with extension, the change is not as obvious as some of the other transistor pairs. Using the 2SC3422/2SA1359, for instance, the rocking slam is immediately apparent. The 2SC3421/2SA1358's extended bass and prominent highs are also immediately obvious.

 Again, all the "special" transistors are definitely an upgrade, but each has their own special signature and quality. IMHO, Black Gates should use the 2SC2238/2SA968 combo where the exquisite detail reinforces each other, whereas the 2SC3422/2SA1359 are particularly well suited with the ES's - the rockin' slam complementing each other. Just a couple of examples - again, back to the Can't Miss MAX Builds. 
	

	
	
		
		

		
		
	


	




 Yet, DIY by its very nature is experimentation. So feel free to come up with your own combination if you are game.


----------



## tomb

Quote:


  Originally Posted by *pinkfloyd4ever* /img/forum/go_quote.gif 
_right. I think you will definitely hear a difference, as the BJT pairs used in the Max are said to have the biggest effect on its sound signature. However, beware of fakes. From what people here have told me, (not that I think any of them aren't trustworthy, just that I've only ordered from one of these places) you can always be sure they're genuine if they're from B&D Enterprises fibra-brandt or MCM_

 

Just to be clear, and I've stated this before, but all of mine for sale on beezar are from B&D and MCMinone. Both guarantee the source is genuine Toshiba. (2SC2344/2SA1011 are Sanyo transistors, however.)

 I have made the direct comparison with the Chinese versions of the 2SC2238/2SA968 pairs. This was because the very-reputable source from where I purchased the Chinese versions (not for sale!!) were completely honest about their source: China. The Chinese versions sound "congested", perhaps due to a higher level of inherent distortion.


----------



## tomb

Quote:


  Originally Posted by *ruZZ.il* /img/forum/go_quote.gif 
_Yep, ohms law. Its I=V[size=xx-small](RB10/11)[/size]/(RB10/11). In a standard build with RB10/11 being 2.2Ohms, you just devide the measured voltage by 2.2. So, 100mV is almost 45.5mA, for instance.

 The advantage of a higher current (within the recommended range, that is) is utilizing a more linear region of response of the transistors, which is truer to the source and slightly better performance. The disadvantage is heat and the risk of thermal runaway. Since the BJTs conduct better at higher temps, as they heat up, more current is passed through, hence.. more heat, and so on.. poof!. So, as long as they're kept cool enough, you're good. I'm not sure what 'cool enough' is though, but I don't like too hot to the touch. Their temp and max current is govourned by the heatinks, ventilation, etc.. Also, I havent experimented too much with the sound of deeper bias, maybe someone else can elaborate more on the differences, and the current limits you should expect out of your configuration (what is your configuration?).. hope this helps some.._

 

This is exactly right. However, the primary reason for biasing is to keep the output stage in Class A - meaning there is no switching by the transistors to supply more current. The transistors are alread "ON" and supplying all the current that the headphones need for any peaks and transients (hopefully). Switching is often a source of higher distortion and other artifacts, often resulting in poorer sound.

_Or so I've read - ruZZ.il can no doubt explain it better than me._





 Just my experience, but there's no issue at all running 50ma (110mV) with 1" high sinks. Using the cabinet-wire-pull "roll bars" as I do, you can eke out another 10ma, perhaps more. Mine actually run cooler cased up with the roll bars than they do un-cased. I believe I notice a difference with just the extra 10ma (60ma total, 132mV), but that may very well be psychological. 
	

	
	
		
		

		
		
	


	




 It also varies with the headphones, depending on impedance - but there may also be the effect that ruZZ.il mentions: an improvement by running the transistors in a better performance regime.


 P.S. Big names on that list, Amphead!! I'm sure your MAX will do us proud!


----------



## amphead

Quote:


 P.S. Big names on that list, Amphead!! I'm sure your MAX will do us proud! 
 

Makes sense doesn't it, since I was the first customer on Beezar.com. 
	

	
	
		
		

		
		
	


	




 Thanks Tom, I will of course direct attention to Beezar.com


----------



## tomb

Quote:


  Originally Posted by *amphead* /img/forum/go_quote.gif 
_Makes sense doesn't it, since I was the first customer on Beezar.com. 
	

	
	
		
		

		
		
	


	


_

 

You bet! Without your help I would not have been able to fix many things.


----------



## jamess71

Hey tomb I see on beezar.com you are out of the 2sc2238/2sa968. It says they will be in on monday. Is that correct? 

 I want to do the boutique build # 1 for my second Max. So I'll also be ordering the k42's. Will you be carrying wima's? I need them also, the .22uf for the elsewhere. 

 These are the only parts I havn't got yet and I was hoping to do a one stop shop @ beezar. 
	

	
	
		
		

		
		
	


	




 James


----------



## tomb

Quote:


  Originally Posted by *jamess71* /img/forum/go_quote.gif 
_Hey tomb I see on beezar.com you are out of the 2sc2238/2sa968. It says they will be in on monday. Is that correct? 

 I want to do the boutique build # 1 for my second Max. So I'll also be ordering the k42's. Will you be carrying wima's? I need them also, the .22uf for the elsewhere. 

 These are the only parts I havn't got yet and I was hoping to do a one stop shop @ beezar. 
	

	
	
		
		

		
		
	


	




 James_

 

Monday is an estimate, but it could be sooner. The order has been in for awhile, so they should send them to me as soon as they receive them.

 No Wimas - Mouser has plenty.


----------



## jamess71

Another question. In the can't miss build #1 it states C9 blank (Wimas elsewhere) 

 Does this mean nothing in the C9 position? And what is the elsewhere refering to?

 James


----------



## ruZZ.il

Quote:


  Originally Posted by *jamess71* /img/forum/go_quote.gif 
_Another question. In the can't miss build #1 it states C9 blank (Wimas elsewhere) 

 Does this mean nothing in the C9 position? And what is the elsewhere refering to?

 James_

 

yep, just leave C9's blank. Elsewhere means everywhere else the BOM advises the use of Wimas. I believe thats just 4 of them then, CA6 and CA3, while K42/VitQs are in CA8.


----------



## tomb

Yes, again - ruZZ.il is correct, but I probably need to qualify that slightly. With VitQ's, it's probably better to populate CA9. I did that in my current build (posted pics a few pages back), and they are working quite well. There is still a question in my mind whether the bass is very slightly affected. Unfortunately, it takes so long for BG's to break-in, it's not an easy determination: Do the VitQ's take away some bass at CA9 or are the BG's just not broken-in? The answer could take _weeks_.

 You might try both yourself to find out. The recommendation is just not that certain in this case. The BG's on mine don't seem to punch KSC75's like ES's do, but when I put on a pair of HD600's or 580's, the bass is very deep. (The highs are splendid, of course.) So, my guess if you use VitQ's with Black Gates - put them also in CA9.

 With ES's you can tell right away - they need something to help the highs - but the Wima's do just fine in CA9 for that. At the same time, _any_ cap that hurts the bass is also noticed right away.


----------



## jamess71

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Yes, again - ruZZ.il is correct, but I probably need to qualify that slightly. With VitQ's, it's probably better to populate CA9. I did that in my current build (posted pics a few pages back), and they are working quite well. There is still a question in my mind whether the bass is very slightly affected. Unfortunately, it takes so long for BG's to break-in, it's not an easy determination: Do the VitQ's take away some bass at CA9 or are the BG's just not broken-in? The answer could take weeks.

 You might try both yourself to find out. The recommendation is just not that certain in this case. The BG's on mine don't seem to punch KSC75's like ES's do, but when I put on a pair of HD600's or 580's, the bass is very deep. (The highs are splendid, of course.) So, my guess if you use VitQ's with Black Gates - put them also in CA9.

 With ES's you can tell right away - they need something to help the highs - but the Wima's do just fine in CA9 for that. At the same time, any cap that hurts the bass is also noticed right away._

 

tomb when you are refering to the VitQ's does that also apply to the K42's?


----------



## Negatron

It's just a suggestion, but it works for me with BG's. Try using an 0.47 Blackgate N as a bypass on CA7 and NO bypass with a BG on CA2. This was determined by my favored test instrument, my ears, after extended Blackgate breakin with 24hr / 5 day pink noise.

 On CA2, Russian PIO's are horrible and Vit Q's ever so slightly muck up the bottom end. (with BG's)
 As always, this is by my opinion only. Gonna' go for a MAX #3 w/ jfet input DB. Dang you Beezar.


----------



## tomb

Quote:


  Originally Posted by *jamess71* /img/forum/go_quote.gif 
_tomb when you are refering to the VitQ's does that also apply to the K42's?_

 

With K42's, leave them out at CA9. That's where the original recommendation for Can't Miss MAX Build #1 comes from.

 The difference being that VitQ's seem to add a slight bit of sparkle that enhances the upper response of the Black Gates without impacting the bass (perhaps). K42's are so neutral that they seem to make no difference in CA9 - meaning they would be a wasted investment. However, they work well in the CA8 position by seeming to smooth out some of the Black Gate's sound.

 VitQ's are not an easy build and are much more expensive than K42's. That's why K42's are the first choice for most MAX builds. However, VitQ's seem to work well in both positions with Black Gates and would be my first choice if you can make them fit.

 EDIT: Negatron's comments agree with mine. His suggestion of using the smaller 0.47NX HiQ BG as a bypass is a good one and one we recommended it early on with the MAX. It would certainly be easier to install than VitQ's.


----------



## n_maher

One quick note about the Russain Ebay PIO caps. I purchased some on Dec. 3rd from the recommended seller, they never arrived. I only heard from the seller once confirming my order and that was it. I'm now in the midst of a Paypal dispute with them and they haven't responded to that either. So just be cautious if you do deal with them. I know most have had good luck, clearly I have not.


----------



## Negatron

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_With K42's, leave them out at CA9. That's where the original recommendation for Can't Miss MAX Build #1 comes from.

 The difference being that VitQ's seem to add a slight bit of sparkle that enhances the upper response of the Black Gates without impacting the bass (perhaps). K42's are so neutral that they seem to make no difference in CA9 - meaning they would be a wasted investment. However, they work well in the CA8 position by seeming to smooth out some of the Black Gate's sound.

 VitQ's are not an easy build and are much more expensive than K42's. That's why K42's are the first choice for most MAX builds. However, VitQ's seem to work well in both positions with Black Gates and would be my first choice if you can make them fit.

 EDIT: Negatron's comments agree with mine. His suggestion of using the smaller 0.47NX HiQ BG as a bypass is a good one and one we recommended it early on with the MAX. It would certainly be easier to install than VitQ's._

 


 My build must be odd. I found the Russian PIO's to impart a grit or diffuseness in midrange massed passages bypassing CA2 (in CA9). Removal smoothed things up. This is after a fair break-in. Same source was used.


----------



## tomb

Quote:


  Originally Posted by *Negatron* /img/forum/go_quote.gif 
_My build must be odd. I found the Russian PIO's to impart a grit or diffuseness in midrange massed passages bypassing CA2 (in CA9). Removal smoothed things up. This is after a fair break-in. Same source was used._

 

This much I bet we can agree on: weird things happen with film caps down there in the cathode bypass position. When in doubt, leave it out. 
	

	
	
		
		

		
			





 P.S. I don't think you have an "odd build" at all.


----------



## Negatron

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_This much I bet we can agree on: weird things happen with film caps down there in the cathode bypass position. When in doubt, leave it out. 
	

	
	
		
		

		
		
	


	


_

 

That about sums it up. Just to be clear, my comments were solely based on the Blackgates, but the K cap in theory is used essentially as a DC voltage source to hold the cathode at constant X volts above the grid..But in effect the darn thing is in parallel with the circuit AND out of phase with the output. They can be a bag of worms and in most every thing I build I avoid them like the plague. However as discussed earlier in the thread, the space charge tubes need a very high effective ra + RLoad >100meg without the cap on K. So it has to be there. 
 No free Lunch.


----------



## bperboy

Tom, I've got the green Muse's that you sent me awhile back in my build, but you mentioned something about them needing help with the highs (or was that a different kind of muse?). I've got the red Wimas in right now, but is there something that you would recommend like removing some?


----------



## 04BluMach

Quote:


  Originally Posted by *n_maher* /img/forum/go_quote.gif 
_One quick note about the Russain Ebay PIO caps. I purchased some on Dec. 3rd from the recommended seller, they never arrived. I only heard from the seller once confirming my order and that was it. I'm now in the midst of a Paypal dispute with them and they haven't responded to that either. So just be cautious if you do deal with them. I know most have had good luck, clearly I have not._

 

Thanks for getting the word of caution on the Russian cap EBay source out!

 My K42's took over three weeks to arrive after my PayPal payment was executed for the transaction. By the time they showed up with all those funny looking stamps all over the package - I had nearly forgotten about them. Yeah, not hardly!
	

	
	
		
		

		
		
	


	




 Sure hope your transaction gets completed with your parts in hand!
	

	
	
		
		

		
		
	


	




 Hopefully, he has just been swamped by all of those crazy American MAX'ists!
	

	
	
		
		

		
		
	


	




 Keep us informed on the resolution so we know if we still have or have lost a viable source for the Russian film caps!!! Another of those buyer beware instances.... Nobody wants to see anyone get burned. 

 Anyway - shoot me a PM if a couple K42's would tied you over for your MAX build till you get some product. I've got a couple spare in the parts box just incase...


----------



## 04BluMach

Quote:


  Originally Posted by *bperboy* /img/forum/go_quote.gif 
_Tom, I've got the green Muse's that you sent me awhile back in my build, but you mentioned something about them needing help with the highs (or was that a different kind of muse?). I've got the red Wimas in right now, but is there something that you would recommend like removing some?_

 

Since tomb appears offline - I'll take a shot at trying to answer your question/concerns.

 The Green Muse's are the Nichicon Muse "ES" caps. They are considered as the highly recommended Value Performance Caps for the CA2 and CA7 position. Along with the "Red" Wima film caps in all film cap positions form the basis of the Can't Miss MAX Build #4 that tomb has personally built and tested. The Wima's are a very good film cap that has the Flat Frequency response that is required to let the MAX Sing!
	

	
	
		
		

		
		
	


	




 Do not be at all concerned with our Cap ramblings! You have a great Build Combo for your MAX - it has excellent bass and dynamic slam to boot. Enjoy the Music!!!! 

 If after a period of time and if you have an oppurtunity to hear some other MAXes with some of the other Can't Miss MAX Build CAP combos (like the #2 or #3) you have the base Green Nichicon ES's to build upon by changing out a couple of the WIMA Caps with PIO caps (the Russian K42's or VitaQ caps). BUT - Don't loose any sleep over this! You really do have a very good combo to enjoy right now.

 Hope this info helps to answer your questions and any concerns you may have!


----------



## bperboy

Quote:


  Originally Posted by *04BluMach* /img/forum/go_quote.gif 
_Since tomb appears offline - I'll take a shot at trying to answer your question/concerns.

 The Green Muse's are the Nichicon Muse "ES" caps. They are considered as the highly recommended Value Performance Caps for the CA2 and CA7 position. Along with the "Red" Wima film caps in all film cap positions form the basis of the Can't Miss MAX Build #4 that tomb has personally built and tested. The Wima's are a very good film cap that has the Flat Frequency response that is required to let the MAX Sing!
	

	
	
		
		

		
		
	


	




 Do not be at all concerned with our Cap ramblings! You have a great Build Combo for your MAX - it has excellent bass and dynamic slam to boot. Enjoy the Music!!!! 

 If after a period of time and if you have an oppurtunity to hear some other MAXes with some of the other Can't Miss MAX Build CAP combos (like the #2 or #3) you have the base Green Nichicon ES's to build upon by changing out a couple of the WIMA Caps with PIO caps (the Russian K42's or VitaQ caps). BUT - Don't loose any sleep over this! You really do have a very good combo to enjoy right now.

 Hope this info helps to answer your questions and any concerns you may have!_

 

Thanks for the response! I've just been checkin in on this thread periodically, and I've been getting rumblings to do some more electronics. I'm going to CanJam, so hopefully there's another Max there I can listen to!


----------



## 04BluMach

Quote:


  Originally Posted by *bperboy* /img/forum/go_quote.gif 
_Thanks for the response! I've just been checkin in on this thread periodically, and I've been getting rumblings to do some more electronics. I'm going to CanJam, so hopefully there's another Max there I can listen to!_

 

If you are heading to the CanJam, make sure you take your MAX along with your Darth HD580's! The MAX seems to have a synergy thing going with the HD580's. It appears to take the 580's to the best level I've ever heard.

 I think anyone at the CanJam having the oppurtunity to hear the MAX will be blown away by its level of performance for the cost. Anyone who wants to Jam - your MAX will definitely feed the BASSHeads that show up 
	

	
	
		
		

		
		
	


	




  Quote:


 .........and I've been getting rumblings to do some more electronics. 
 

 Sounds like you will soon have a PocketBook lightening experience


----------



## pinkfloyd4ever

Quote:


  Originally Posted by *amphead* /img/forum/go_quote.gif 
_I will be representing TEAM MILLETT MAX at this meet. No one there has the mighty MAX. 






 Attendees:

 <crapload of people>_

 

ahhhahaa verry nice, I'm jealous, I've really been wanting to be 'that guy' with the millett at a meet since I finished mine. How'd you guys get so many people in Fairfax? Have you been having meets regularly for awhile? I'm in St Louis and we were only able to get like 4 people to come to the meet I put together, though it was in June so I guess people are less likely to spend their saturday inside than in the middle of winter. Love the pic too. Ever get really high and rock the Max? I highly recommend it
	

	
	
		
		

		
		
	


	




 Esp late at night, with most of the lights off except a blacklight and your monitor on the visualizer. WOWW it's *****in AMAZING


----------



## joneeboi

I just wanted to report my cap findings in the midst of the Muse and K42 talk. I don't know how many of you are tomb-stoning (chuckle) the K42s in the CA8 and CA9 positions, but I actually found it to be unnecessary. At CA9, you can lay the K42s flat with the grounding lead crossing from the left side to the right and vice versa. For instance, the CA9R K42 will connect from pin 2 of the tube and land on the ground pad for CA9L and the same will happen for the other. For CA8, if you aren't using RB14, you can send the lead to the giant CA8 hole to the RB14 pad, jumpering underneath the board to hide the ugliness. That way you can lay the K42s flat and you don't have to worry about its length/height.

 I actually just switched my STD BGs from CA2 and CA7 (didn't know what I was thinking when ordering; should have gotten the NX series) to Muse ES. I found the BGs to be too bass shy on my setup, though levels have wavered constantly (ironic) throughout the burn-in process. I don't know if they're finished burning in, but I wanted to give the Muses a shot. They have almost sufficient bass levels, a boost over the BGs. Maybe it's because my BGs aren't NXs, but everything sounded too harsh. I'll give the Muses a shot and maybe I'll throw in the old BGs after a while. I don't know when I'll be starting my other MAX build, but I will be picking up my NX BGs and Alps Blues/Noble from parts conneXion to save on shipping. On that topic, pCx only has 100K Nobles. I read before that 100K over 50K pots will increase noise floor. Anyone want to comment/confirm?


----------



## tomb

Quote:


  Originally Posted by *joneeboi* /img/forum/go_quote.gif 
_<snip>I don't know how many of you are tomb-stoning (chuckle) the K42s[/B] in the CA8 and CA9 positions ... </snip>_

 

Hey - it's TomB-stoning. 
	

	
	
		
		

		
		
	


	










 I thought it needed that clarification.


----------



## fran

I hope not... my 100K stepped attenuator arrived today!

 Fran


----------



## Hubbard0

I just finished my Alien so I'll be ordering my Millet from Glass Jar in a week or two. My first SMD work was a complete success.


----------



## amphead

Quote:


  Originally Posted by *pinkfloyd4ever* /img/forum/go_quote.gif 
_ahhhahaa verry nice, I'm jealous, I've really been wanting to be 'that guy' with the millett at a meet since I finished mine. How'd you guys get so many people in Fairfax?_

 

Well, this is my first Head-Fi meet. And this is the first time that Voltron has held one at his home in Fairfax. Apparently, it is going to be one half frat party. Think "Animal House". Well maybe some will go "that" crazy. There is going to be some hi end audio gear there, and thats the reason I wanted to go. 

*Gear:*
 Voltron:
 SinglePower SDS-XLR
 EMM Labs DCC2 and CDSD SE Stack
 Balanced Edition 9
 Balanced Equinox HD650
 Balanced Wyvern Audio HD600
 Balanced Black Dragon K701
 Balanced (?) PS-1
 Moth Audio 300B Paradigm
 Dual 505 TT
 Squeezebox 3 w/Nugget Audio PS
 Channel Islands Audio VDA-1
 Hardwire Equinox'd K1000
 Pico #055!
 Stax SRM-1/MkII
 Stax ED-1 Equalizer
 Stax Lambda Professional Earspeakers
 Boomana:
 LaRocco PRII
 LaRocco Diablo
 Headamp Pico
 RSA SR-71
 Rockhopper mini^3
 STAX SR-001
 ATH-ESW9
 Yuin PK1
 Ety ER4P/S (got some Shure olives and the new baby blue tips)
 MacBook Pro
 5.5g imod
 4g imod
 ipod nano
 Denon DCP-100
 Agile_One:
 Stax Omega II Mk.2 Earspeaker
 SRM-007tII Vacuum Tube Driver
 foo_me:
 Zanden 7000-300B Amplifier
 K1000 with Equinox and cage mod
 MikeyMad:
 Marantz SA-7S1 - SACD
 SinglePower ES-1
 Woo Audio WA5
 Stax Omega II Mk.1
 K1000
 ATH - L3000
 calaf:
 Onix XCD-88
 Corda Opera
 Woo Audio 3
 AKG K340
 Sennheiser HD25-1
 ironbut:
 Technics RS1500 heavily modded reel-to-reel tape player
 Tape Projects first 10 releases! Awesomeness itself!
 Bottlehead custom all tube repo amp (Blackgates, teflon caps, carbon pots, shunt regulated PS)
 Eddie Current Zana Deux
 ATH AD2000
 K701
 ronin74:
 Half case of assorted wines. Nice gear indeed!
 neilvg:
*NWO 3.0G -- perhaps the best digital source in the world*
 SinglePower ES-2
 Sennheiser HE90
 HEAUDIO Eh-1.3 Chinese electrostat headphone
 utep10:
 Affordable K1000 rig in collaboration with Ori
 Ori:
 *Oritek Audio DAC/headamp/preamp in full-size case with remote (2 digital, 2 analog sources, 100-step relay-based volume control)
 *Similar product in the smaller Zhaolu enclosure, using a motorized ALPS potentiometer and remote
 *Prototype amplifier for K1000
 Thrice:
 Cannoli Kan Kamikaze III (aka Cavalli-Kan Kumisa III)
 mini3
 ATH-W3000 (those are ATH-W100s with L3000 driver in them)
 jp11801:
 Laptop into Wavelength Audio Cosecant DAC
 Expressimo Turntable
 Eddie Current HD-2
 Naked K1000
 Grado HP2 with SAA balanced cable
 K701 with ALO Jena Wire
 tyrion:
 Pico
 Rockhopper Mini3
 Corda Headsix
 Ety ER-6i
 Kipsch Image (?)
 Sony Vaio notebook
 iPod Classic 160gb
 bobcn
 Grado HP-1
 K1000 w/equinox hardwire
 RWA Sig 30.2 (!)
 [Needs a source to share]
 immtbiker:
 HeAudio 1.2 Chinese electrostat headphone
 Possibly HeAudio 1.3 Chinese electrostat headphone
 Will need to use Stax compatible amp to drive them
 pdennis
 Macbook Pro (iTunes/AIFF)
 Echo Audiofire 4
 QSC PLX1202
 SRD-7
 SR-X mk. III
 amphead:
 K701
 DIY Millett Max
 Walkman
 guzziguy:
 Singlepower Platinum Extreme
 Rockhopper Pimeta
 eXemplar Denon 2900
 iPod
 MS1
 Leopardwood Darth Beyers
 mtkversion:
 HeadFive


----------



## n_maher

Quote:


  Originally Posted by *04BluMach* /img/forum/go_quote.gif 
_Thanks for getting the word of caution on the Russian cap EBay source out!

 Keep us informed on the resolution so we know if we still have or have lost a viable source for the Russian film caps!!! Another of those buyer beware instances.... Nobody wants to see anyone get burned._

 

Thanks for the kind offer of the caps but I think I'll just stick with more pedestrian offerings for now. 
	

	
	
		
		

		
		
	


	




 And I've since learned of another person who's stuck in the same situation that I am. 
	

	
	
		
		

		
		
	


	




 The seller of the caps was "ussr_tubes" on ebay and I found them via a link from tomb in this thread I think.


----------



## tomb

Quote:


  Originally Posted by *n_maher* /img/forum/go_quote.gif 
_Thanks for the kind offer of the caps but I think I'll just stick with more pedestrian offerings for now. 
	

	
	
		
		

		
			





 And I've since learned of another person who's stuck in the same situation that I am. 
	

	
	
		
		

		
		
	


	




 The seller of the caps was "ussr_tubes" on ebay and I found them via a link from tomb in this thread I think._

 

I've had good experience with the guy. Granted, it took about 4 wks in shipping, regardless. I also think he told me he would be gone for Christmas and New Years for quite awhile, but perhaps that doesn't explain all of it.

 He operates out of WesternBid.com, so you might try that route. Also, there's ebay user "alexer1", who operates the ebay store "SOVCOM", but he's out of the 0.22uf's right now. 
	

	
	
		
		

		
		
	


	




 EDIT: I still have them - for as long as they last.


----------



## Negatron

FWIW, I have had VERY good success in dealings with the Sov. surplus dealers from Latvia (EU). Georgia is fair, when I order from the the Russian Federation, I put it in the back of my mind and when a package shows up I am pleased if I remember ordering it. There are exceptions of course and the bulk of my dealings have been tubes and caps.

 Try this link:
eBay Store - KW TUBES: Capacitors: 0.047uF 200V PIO Capacitors K40Y9. Lot of 20
 (Disregard the link title, it's just how their ebay store Cap section shows linked here)


----------



## 04BluMach

Quote:


  Originally Posted by *n_maher* /img/forum/go_quote.gif 
_Thanks for the kind offer of the caps but I think I'll just stick with more pedestrian offerings for now. 
	

	
	
		
		

		
		
	


	




 And I've since learned of another person who's stuck in the same situation that I am. 
	

	
	
		
		

		
		
	


	




 The seller of the caps was "ussr_tubes" on ebay and I found them via a link from tomb in this thread I think._

 

 Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_I've had good experience with the guy. Granted, it took about 4 wks in shipping, regardless. I also think he told me he would be gone for Christmas and New Years for quite awhile, but perhaps that doesn't explain all of it.

 He operates out of WesternBid.com, so you might try that route. Also, there's ebay user "alexer1", who operates the ebay store "SOVCOM", but he's out of the 0.22uf's right now. 
	

	
	
		
		

		
		
	


	




 EDIT: I still have them - for as long as they last._

 

I used the same eBay source "ussr_tubes" for my K42's. As both I and tomb indicated -very long shipping time was experienced (about 4wks). Checked my PayPal record and transaction was via Western Bid Europe. Sellers Email as "europe AT westernbid.com"

 Hopefully, he is has just "out of pocket" for the Holidays as indicated to tomb. And will soon get A_ROUND_TUIT!! 
	

	
	
		
		

		
		
	


	




 Good Luck....!

 Cap Offer still stands! I've enjoyed some of the fruits of your very substantial amount of uncompensated labor for us Head-Fi'ers 
	

	
	
		
		

		
		
	


	




 Sounds like beezar may be the safest and quickest way to go for latching onto the K42 PIO Caps. Let the ShopKeeper handle dealing with the details and delays involved in International Transit of these Caps...


----------



## ruZZ.il

ussr_tubes sent me my 10 caps.. don't remember how long it took, but I generally expect things to take ages. I think it took less than ages though, I guess about 2 weeks. Sometime in november. The package did look like it was sent in 1962.. I hope they get around to you..


----------



## jamess71

Quote:


  Originally Posted by *Negatron* /img/forum/go_quote.gif 
_FWIW, I have had VERY good success in dealings with the Sov. surplus dealers from Latvia (EU). Georgia is fair, when I order from the the Russian Federation, I put it in the back of my mind and when a package shows up I am pleased if I remember ordering it. There are exceptions of course and the bulk of my dealings have been tubes and caps.

 Try this link:
eBay Store - KW TUBES: Capacitors: 0.047uF 200V PIO Capacitors K40Y9. Lot of 20
 (Disregard the link title, it's just how their ebay store Cap section shows linked here)_

 

Thats funny you mention that store negatron. I just ordered an assortment of k42's 100 caps total. under $20 total. Gotta love the prices. Hope they ship quickly.

 James


----------



## ferds

I also ordered PIO and teflon caps from kwtubes last november.. I received them in about 2weeks..


----------



## Negatron

Quote:


  Originally Posted by *jamess71* /img/forum/go_quote.gif 
_Thats funny you mention that store negatron. I just ordered an assortment of k42's 100 caps total. under $20 total. Gotta love the prices. Hope they ship quickly.

 James_

 

I thought some might be interested in a clip from his shipping notification from KW Tubes:

 <snip>
 Thank you for your purchase. Should you have any troubles, please
 don't hesitate to ask, we will rectify the problems asap. Your
 feedback on eBay would be much appreciated.

 All items we ship are delivered to the post office on a bicycle in
 my JUMBO backpack.

 ==========================
 My order was shipped the same day as purchase.
 Is this guy priceless or what? Most people I have dealt with from Latvia have been like this.


----------



## naamanf

I'm 1/4 Latvian. Maybe that's why I'm funny. Sometimes.


----------



## tomb

Quote:


  Originally Posted by *naamanf* /img/forum/go_quote.gif 
_I'm 1/4 Latvian. Maybe that's why I'm funny. Sometimes._

 

I suppose that explains the rubber chicken on your head that's about to get shot.


----------



## Negatron

Quote:


  Originally Posted by *naamanf* /img/forum/go_quote.gif 
_I'm 1/4 Latvian. Maybe that's why I'm funny. Sometimes._

 

Don't trust that chicken, you can't be too carefull. 
	

	
	
		
		

		
		
	


	



 BTW, I and Most people I know are very grateful for your service in Kirkuk.
 Thanks man, from an old River Rat.


----------



## naamanf

Quote:


  Originally Posted by *Negatron* /img/forum/go_quote.gif 
_Don't trust that chicken, you can't be too carefull. 
	

	
	
		
		

		
		
	


	



 BTW, I and Most people I know are very grateful for your service in Kirkuk.
 Thanks man, from an old River Rat._

 

Appreciated. It's actually a turkey. Can't trust them either. Funny thing about turkeys. Everyone here has them. Always thought that a bit funny.


----------



## tomb

News Update:
 Negatron got me thinking about the VitQ's with Black Gates. He had mentioned that he thought VitQ's might rob a bit of the bass in the cathode bypass. It seemed plausible after comparing with the bass in ES MAXes: there was a lack of authoritative bass.

 So, I popped out the VitQ's that were in CA9. I'm listening right now and the bass is definitely back - not as much as ES's - but enough to be able to tell that the CA9 VitQ's were robbing some of the bass.

 So: CA9 in "Can't Miss MAX Build #1" should go blank - with K42's OR VitQ's.


----------



## slowpogo

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_So, I popped out the VitQ's that were in CA9. I'm listening right now and the bass is definitely back - not as much as ES's - but enough to be able to tell that the CA9 VitQ's were robbing some of the bass._

 

So it was a completely positive change--better bass, no drawbacks?


----------



## pinkfloyd4ever

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_So: CA9 in "Can't Miss MAX Build #1" should go blank - with K42's OR VitQ's._

 

eh? You mean blank when using K42s/Qs at CA8?


----------



## tomb

Quote:


  Originally Posted by *slowpogo* /img/forum/go_quote.gif 
_So it was a completely positive change--better bass, no drawbacks?_

 

It seems so. The splendid highs seem to be there in all the right places, but the stronger, punchier bass makes the highs less noticeable in normal passages - probably as it should be.

 In my own defense, the BG's are fully broken in, now - there is punchy bass now that the VitQ's are gone at CA9. Removing them earlier had no effect - or so it seemed - the BG's were probably never really broken in.

  Quote:


  Originally Posted by *pinkfloyd4ever* 
_eh? You mean blank when using K42s/Qs at CA8?_

 

Yes.


----------



## n_maher

Well, in a bizzare twist of fate, after still not receiving anything in the way of a response from Paypal, my caps showed up today???
 So I guess the lesson here is that 7 weeks is not outside the normal delivery window.


----------



## Negatron

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_It seems so. The splendid highs seem to be there in all the right places, but the stronger, punchier bass makes the highs less noticeable in normal passages - probably as it should be.

 In my own defense, the BG's are fully broken in, now - there is punchy bass now that the VitQ's are gone at CA9. Removing them earlier had no effect - or so it seemed - the BG's were probably never really broken in.

 Yes._

 

BG's have bitten me more than once, thinking they had become broken-in when the subtle little critters rested and then went a bit farther. I guess it's like if you think you may hear a cap there, they still aren't fully broken in. 
 Cerafines and Silmics pretty much let you know, Blackgates just want to see if they can get you committed to the 'Padded room'.


----------



## Negatron

2nd MAX attempt: I offer - Mighty MAX











 R1 1800uf FC's w/ Wima@CR2, CA5 2700 FC's w/Wima@CA6, CA4 is a 470uf Silmic w/PIO@CA3, CA2 is a 1000uf Blackgate, nothing at CA9, CA7 is a 680uf Blackgate w/0.47 Blackgate@CA8. Outputs on the DB are MOSFETS with QB2 & 3 jumpered. Tubes are biased at .065ma, 27 volt supply, MOSFETS biased at 110ma.


----------



## pinkfloyd4ever

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_It seems so. The splendid highs seem to be there in all the right places, but the stronger, punchier bass makes the highs less noticeable in normal passages - probably as it should be.

 In my own defense, the BG's are fully broken in, now - there is punchy bass now that the VitQ's are gone at CA9. Removing them earlier had no effect - or so it seemed - the BG's were probably never really broken in._

 

ahh but what about some BG NX Hi-Q's 
	

	
	
		
		

		
		
	


	




 (I know you've already answered that like 8 times) I guess I'll just have to find out myself 
	

	
	
		
		

		
		
	


	




 I forgot, did you say it'd be ok to socket CA8 & 9?

  Quote:


  Originally Posted by *n_maher* /img/forum/go_quote.gif 
_Well, in a bizzare twist of fate, after still not receiving anything in the way of a response from Paypal, my caps showed up today???
 So I guess the lesson here is that 7 weeks is not outside the normal delivery window._

 

wow well thats good to hear. It doesn't really surprise me that it'd take that long. For those that don't already know, I went to Russia for 3 weeks about 5 years ago, and if you think government services are slow and inefficient here in the ol US of A, go to Russia. Hell when their cops wanna pull you over all they do is hold up this black and white striped stick while they're standing on the sidewalk. The exception is if you're a strong public opponent of the government, then they'll poison you with polonium in a jiffy 
	

	
	
		
		

		
		
	


	




 anyway, back to music.. Colin, Nate, and anybody else who uses 580s with their Max, what kind of music do you listen to? I have MS-1s which I like the sound of (though I haven't thoroughly compared them with much else) but they're so damn uncomfortable and I know Senns are among the most comfy cans out there. I listen almost exclusively to classic rock, pink floyd (obv) and led zeppelin are my 2 all time faves. I'm also big on Jimi Hendrix and Metallica but I listen to just about anything that can be called rock. I don't really have money for new cans now, but what are good with this music that doesn't feel like a vice after about 20 minutes? I know this is a question more suited to the headphone forum, but I thought I'd ask all of you Team MAXers out there since it's my new main amp


----------



## tomb

Quote:


  Originally Posted by *n_maher* /img/forum/go_quote.gif 
_Well, in a bizzare twist of fate, after still not receiving anything in the way of a response from Paypal, my caps showed up today???
 So I guess the lesson here is that 7 weeks is not outside the normal delivery window._

 

Somehow I had a feeling that was going to happen. 
	

	
	
		
		

		
		
	


	




 Yeah, 7wks if you put Christmas and New Years in there. Heck, there are some places that just shut down for a couple of weeks during that time.


----------



## tomb

Quote:


  Originally Posted by *Negatron* /img/forum/go_quote.gif 
_2nd MAX attempt: I offer - Mighty MAX

 [<IMG>]http://farm3.static.flickr.com/2316/2201243892_8da498105e_o.jpg[/IMG]

 [<IMG>]http://farm3.static.flickr.com/2083/2200450425_95c9379323_o.jpg[/IMG]

 R1 1800uf FC's w/ Wima@CR2, CA5 2700 FC's w/Wima@CA6, CA4 is a 470uf Silmic w/PIO@CA3, CA2 is a 1000uf Blackgate, nothing at CA9, CA7 is a 680uf Blackgate w/0.47 Blackgate@CA8. Outputs on the DB are MOSFETS with QB2 & 3 jumpered. Tubes are biased at .065ma, 27 volt supply, MOSFETS biased at 110ma._

 

Wow! Another MAX Lives!!! 
	

	
	
		
		

		
		
	


	







 Those handles are great! Is that a crinkle finish on that endplate? Cool.


----------



## slowpogo

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_It seems so. The splendid highs seem to be there in all the right places, but the stronger, punchier bass makes the highs less noticeable in normal passages - probably as it should be._

 

I went ahead and pulled the Vitamin Q wire leads out for CA9, and you're right, there is more bass. It's a subtle increase but it adds just the right amount of weight and thickness, too. Kick drums now have that subtle, penetrating punch to them.

 It also removed a glassy quality that was bugging me. Things like chimes and bells still have a really great sparkle to them, but sibilance is tamed and things aren't quite so airy anymore (which is good IMO). It also seems to reinforce the low mids, which I was also missing, more tubey warmth.

 I have some GE 12FM6's coming in the mail, and my prediction is they will be the perfect tube for me, my favorite. Assuming they come close to what I think they will, I should be about done experimenting and can confidently case it up.

 I've never heard a MAX with an Alps blue pot, but I have to say the TKD pot I'm using is awesome. I may be stretching it but I feel like I can hear a difference even without a comparison, just having used the Alps in a few other amps. The sound is so clear and uninhibited. If you don't mind paying $60 and hand wiring to the board, it's really nice...and smooth as could possibly be to turn.


----------



## Negatron

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Wow! Another MAX Lives!!! 
	

	
	
		
		

		
		
	


	







 Those handles are great! Is that a crinkle finish on that endplate? Cool._

 

Thanks for the kind words, The paint is old Hammer Tone, sort of a grey/aged bronze. I kinda' think it looks like big amp up close. These are fun!


----------



## pinkfloyd4ever

Quote:


  Originally Posted by *Negatron* /img/forum/go_quote.gif 
_2nd MAX attempt: I offer - Mighty MAX

 <sweet pics>

 R1 1800uf FC's w/ Wima@CR2, CA5 2700 FC's w/Wima@CA6, CA4 is a 470uf Silmic w/PIO@CA3, CA2 is a 1000uf Blackgate, nothing at CA9, CA7 is a 680uf Blackgate w/0.47 Blackgate@CA8. Outputs on the DB are MOSFETS with QB2 & 3 jumpered. Tubes are biased at .065ma, 27 volt supply, MOSFETS biased at 110ma._

 

wow NICE front panel there. Did you build your first with MOSFETs too? I've got a pair of BGs that I'm eventually gonna try at CA8, but for now I'm still burning everything else in. I've got the 2SC2344/2SA1011 BJT pair, BGs at CA2 & CA7, FMs for the rest of the electrolytics, Wimas at CA3 & 6, and K42s at CA8. CA9 is blank. I'm using a pair of RCA-made FK6 tubes now, which I thought I'd try in addition to the GE-made pair I had running 24/7 for about a week. What tubes r u using?

 OUCH, $60 for a pot? It better sound good. Why not just go for the Alps RK50? It's only what, like $500
	

	
	
		
		

		
		
	


	




 j/k, I'm sure it does sound better than the Alps


----------



## tomb

Quote:


  Originally Posted by *pinkfloyd4ever* /img/forum/go_quote.gif 
_<snip>anyway, back to music.. Colin, Nate, and anybody else who uses 580s with their Max, what kind of music do you listen to? I have MS-1s which I like the sound of (though I haven't thoroughly compared them with much else) but they're so damn uncomfortable and I know Senns are among the most comfy cans out there. I listen almost exclusively to classic rock, pink floyd (obv) and led zeppelin are my 2 all time faves. I'm also big on Jimi Hendrix and Metallica but I listen to just about anything that can be called rock. I don't really have money for new cans now, but what are good with this music that doesn't feel like a vice after about 20 minutes? I know this is a question more suited to the headphone forum, but I thought I'd ask all of you Team MAXers out there since it's my new main amp
	

	
	
		
		

		
		
	


	


_

 

I'll admit that Grados are not my favorite phones, but they have a special synergy with Milletts and the MAX - Just MHO. It may sound silly, but if you want something that sounds similar but is comfortable for hours, slip a couple of KSC75's over your ears. That's what I listen to most, although I'm in the market for a pair of SR225's. I figured those might be the ones to get. I was really impressed with a pair of HF-1's that Mexican Dragon had at the Atlanta meet - wow! However, getting one of those will probably be like getting tickets to the upcoming Radiohead tour. 
	

	
	
		
		

		
		
	


	




 The HD580's are another pair that do wonderfully with the MAX. Colin and I both were using them in developing the prototype. However, I think you need to re-cable them. The stock cable is pretty poor - the cans will sound a bit bassy with details and highs recessed. Once tuned with the right cable, they're a bit less open than HD600's, but punchier (better). I never thought I'd say that about cables, but it makes a difference. I had used a Cardas until I switched it to a pair of HD600's. Going back to the stock cable on the HD580 has been disappointing, to say the least. It may be that the HD650 cable could be a cheap alternative - $11 from Sennheiser I've read - but I haven't tried one. I'm going to be making my own with some Navships SPC. But I digress ...

 There's no question that comfort with Senns is outstanding.


----------



## amphead

Quote:


 2nd MAX attempt: I offer - Mighty MAX 
 

Negatron Congrats! Another Max Lives!   

 The Mighty Max is the rackmount configuration.


----------



## tomb

Quote:


  Originally Posted by *Negatron* /img/forum/go_quote.gif 
_2nd MAX attempt: I offer - Mighty MAX

 [<IMG>]http://farm3.static.flickr.com/2316/2201243892_8da498105e_o.jpg[/IMG]

 [<IMG>]http://farm3.static.flickr.com/2083/2200450425_95c9379323_o.jpg[/IMG]

 R1 1800uf FC's w/ Wima@CR2, CA5 2700 FC's w/Wima@CA6, CA4 is a 470uf Silmic w/PIO@CA3, CA2 is a 1000uf Blackgate, nothing at CA9, CA7 is a 680uf Blackgate w/0.47 Blackgate@CA8. Outputs on the DB are MOSFETS with QB2 & 3 jumpered. Tubes are biased at .065ma, 27 volt supply, MOSFETS biased at 110ma._

 

Couple of questions, Negatron -

 How do you like your MOSFETs? I have yet to try them, but there have been a few reports on the side that they may have a bit of bottom-end peakiness with a slight rolloff in the highs. In some places I've read that may be due to the lack of feedback, but have seen some other things lately that contradict that.

 If yours performs well, do you think deleting Q2 and Q3 helps flatten them out?

 What's your explanation for taking them out? I know NeilR played with both during his MOSFET development of the MAX, but I think he settled on leaving them in there because it marginally improved the bias adjustment precision.

 EDIT: I haven't had much opportunity to develop support for the MOSFET since NeilR did the original vetting. It sounds like you may be able to answer some of these questions before I build my own. 
	

	
	
		
		

		
		
	


	




 Again, nice looking MAX - I love metal hardware!


----------



## Negatron

Quote:


  Originally Posted by *pinkfloyd4ever* /img/forum/go_quote.gif 
_wow NICE front panel there. Did you build your first with MOSFETs too? I've got a pair of BGs that I'm eventually gonna try at CA8, but for now I'm still burning everything else in. I've got the 2SC2344/2SA1011 BJT pair, BGs at CA2 & CA7, FMs for the rest of the electrolytics, Wimas at CA3 & 6, and K42s at CA8. CA9 is blank. I'm using a pair of RCA-made FK6 tubes now, which I thought I'd try in addition to the GE-made pair I had running 24/7 for about a week. What tubes r u using?
 <snip>_

 

I started with the 2SC3422 & 2SA1359 BJT's and soon changed to the MOSFETS on the first MAX, I began with BG's on both. CA5 started at 2200 FC but went to 2700 with MAX2. My 2 favorite tubes are RCA 12AE6 & GE 12FM6,
 oddly my 'FM6's are branded RCA but are GE. 

 When you try HiQ BG 0.47's on CA9 leave the leads a bit longer so they can be easily re-used later after you figure out they didn't make any difference at all. Tom pinned it down earlier, the BG's on CA2 just need lotsa' breakin. (I found bypassing them is a waste of time and money.) I do like the Silmic w/PIO at CA3 and 470uf gives an fc of 0.3hz., the CS isn't quite neutral and a bigger cap just clouds the 'air' to my ears. But I think you would have to go WAY off the beaten path to make this thing sound bad, no matter what build you went with.


----------



## Negatron

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Couple of questions, Negatron -

 How do you like your MOSFETs? I have yet to try them, but there have been a few reports on the side that they may have a bottom-end peakiness with a slow rolloff in the highs. In some places I've read that may be due to the lack of feedback, but have seen some other things lately that contradict that.

 If yours performs well, do you think deleting Q2 and Q3 helps flatten them out?

 What's your explanation for taking them out? I know NeilR played with both during his MOSFET development of the MAX, but I think he settled on leaving them in there because it marginally improved the bias adjustment precision.

 Again, nice looking MAX - I love metal hardware!_

 

I prefer the MOSFETS, but there is a penalty in the highs with Q2, Q3 jumped.
 That is due to the high input capacitance of the MOSFETS. My reason was I prefered the overall response of the tube with higher Z loading and was willing to sacrifice the bit on top for what was gained elsewhere. I think feedback would ruin this amp. It ain't an opamp. 
	

	
	
		
		

		
		
	


	




 Also I found no bass peakiness, I suspect that would come from choice of caps and also with MOSFETS and their current demand, you could probably use more capacitance on the rail than I am using now for better very Low Freq response but very little music goes there.

 Bias Adj isn't that hard. It would be a nightmare with 2k pots. Once all settles in, I've had no trouble getting the bias where I want it and it stays there. I'm playing now with replacing Q2 & Q3 with jfets to raise the Z that the tube sees, I think that will get me where I want with this. NOTE: jfets are not drop-in and I'm still trying to find decent PSpice lib's so don't ask.
	

	
	
		
		

		
		
	


	




 I much prefer the MOSFETS but you may not find that many fans. I am hard core tube and they sound better to my ears. It's just a matter of having a (ready for this?) TUBE BIAS.

 The handles I made from some .300" alum rod I had laying around, chucked it in the lathe and drilled it and cut it off for cheap spacers. The 1/2 flat stock was more scrap. Easy to do. Wonder if Bud makes Mini-Rack cabinets?


----------



## amb

Yes, Negatron is right, the MOSFETs have a significant amount of gate capacitance which, with Q2B and Q3B jumpered, would be driven from the Millett's tube stage directly. The tube has a high output Z, which forms a low-pass filter with the MOSFET gate capacitance and causes a rolloff of the high frequency response.

 With QB2/QB3 installed, there is now a complementary emitter follower between the tube and the MOSFETs. The emitter follower has low output Z and moves the rolloff frequency well into the ultrasonics.

 At Negatron's request I did some simulations of the Millett Max diamond buffer section (alone by itself, sans the tube stage) with MOSFETs. The new twist is that QB2/QB3 are replaced with 2SJ74BL and 2SK170BL JFETs, respectively, making them a complementary source follower. This dramatically increases the buffer's input Z as compared to BJTs. As "seen" from the tube, the buffer becomes a negligible load, which is a good thing.

 To make this work, the RB4/RB6 and RB5/RB7 resistance ratios must go back to 1:1 (use 100 ohms for all of these), and RB2/RB3 should be increased to around 1K-1.2K ohms. QB1 should be 2N5486 and RB12 should be 1K ohms per the Millett Max BOM (MOSFET option). This change prevents the operating current through QB2/QB2 from coming too close to the 2SJ74BL/2SK170BL's Idss low range limit (6mA), yet still allows the output MOSFETs to be properly biased within RB12's adjustment range.

 The result is quite good. Here is the frequency response of the buffer section from the simulator. Note that the -3dB point is up near 1MHz, which is significantly higher than the tube's frequency response.






 For people who contemplate doing the MOSFET option on the Millett Max, I recommend this configuration.


----------



## jamess71

Negatron that Mighty Max looks great. Hopefully you'll be able to try out some Sylvania 12fk6 this weekend. 
	

	
	
		
		

		
			





 James


----------



## Negatron

I want to personaly thank Amb for his excelent work (as well as congratulate the superior skill at sourcing .lib files ) 
	

	
	
		
		

		
		
	


	




 Great looking Sim. With the AMB jfet mod, the tube should open up and also the idosyncracies with the K cap should change (more to drive one nuts.) If what I believe is so with the tube seeing a very high Z it should be possible to delete CA2,9 completely, there will be a small penalty in gain but the addition of local feedback through the degeneration on RA1 should be of benefit. Thanks again AMB!


----------



## n_maher

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Somehow I had a feeling that was going to happen. 
	

	
	
		
		

		
		
	


	




 Yeah, 7wks if you put Christmas and New Years in there. Heck, there are some places that just shut down for a couple of weeks during that time._

 

It became more an issue of them first never sending an email that was supposed to come 48hrs after the close of the auction then not responding to additional emails or the Paypal dispute that had me concerned. One simple message saying, "We've shipped your caps" would have put me at ease.


----------



## tomb

Quote:


  Originally Posted by *amb* /img/forum/go_quote.gif 
_Yes, Negatron is right, the MOSFETs have a significant amount of gate capacitance which, with Q2B and Q3B jumpered, would be driven from the Millett's tube stage directly. The tube has a high output Z, which forms a low-pass filter with the MOSFET gate capacitance and causes a rolloff of the high frequency response.

 With QB2/QB3 installed, there is now a complementary emitter follower between the tube and the MOSFETs. The emitter follower has low output Z and moves the rolloff frequency well into the ultrasonics.

 At Negatron's request I did some simulations of the Millett Max diamond buffer section (alone by itself, sans the tube stage) with MOSFETs. The new twist is that QB2/QB3 are replaced with 2SJ74BL and 2SK170BL JFETs, respectively, making them a complementary source follower. This dramatically increases the buffer's input Z as compared to BJTs. As "seen" from the tube, the buffer becomes a negligible load, which is a good thing.

 To make this work, the RB4/RB6 and RB5/RB7 resistance ratios must go back to 1:1 (use 100 ohms for all of these), and RB2/RB3 should be increased to around 1K-1.2K ohms. QB1 should be 2N5486 and RB12 should be 1K ohms per the Millett Max BOM (MOSFET option). This change prevents the operating current through QB2/QB2 from coming too close to the 2SJ74BL/2SK170BL's Idss low range limit (6mA), yet still allows the output MOSFETs to be properly biased within RB12's adjustment range.

 The result is quite good. Here is the frequency response of the buffer section from the simulator. Note that the -3dB point is up near 1MHz, which is significantly higher than the tube's frequency response.






 For people who contemplate doing the MOSFET option on the Millett Max, I recommend this configuration._

 

Nice work, Amb! I will try a build with this configuration as soon as possible and report back the results! 
	

	
	
		
		

		
		
	


	







 I feel another "Can't Miss MAX Build" coming.


----------



## tomb

Quote:


  Originally Posted by *amb* /img/forum/go_quote.gif 
_<snip>For people who contemplate doing the MOSFET option on the Millett Max, I recommend this configuration._

 

Amb - one question, please - are the N-Channel compensation caps still needed in this configuration?


----------



## amb

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Amb - one question, please - are the N-Channel compensation caps still needed in this configuration?_

 

The P-channel device gate capacitance is greater than the N-channel's, so that capacitor equalizes the two, and makes the buffer's positive-going slew rate the same as the negative. However, in the Millett, the tube is far slower than the MOSFETs, so you won't actually see a real difference. I'd say the capacitor is an "optional" part here.


----------



## amb

Oh, and one more thing, the 2SJ74/2SK170 JFETs have D-G-S pinout, so they must be mounted in reverse orientation compared to 2N5087/2N5088.


----------



## rockcod




----------



## tomb

Wow - you guys are coming up with some impressive work!

 Another MAX lives!! 
	

	
	
		
		

		
		
	


	







 BTW, what are those film caps you're using? They look like wax capacitors, but they're too small to be Jupiters, I think. Also, it looks like Cerafines in front, but what are those monsters in the CA2 positions?

 Very nice!


----------



## 04BluMach

Quote:


  Originally Posted by *amb* /img/forum/go_quote.gif 
_Yes, Negatron is right, the MOSFETs have a significant amount of gate capacitance which, with Q2B and Q3B jumpered, would be driven from the Millett's tube stage directly. The tube has a high output Z, which forms a low-pass filter with the MOSFET gate capacitance and causes a rolloff of the high frequency response._

 

Great pick up by Negatron's perception of MOSFET HF rolloff. (Yet he contends that his ears have limited sound perception - don't think so 
	

	
	
		
		

		
		
	


	




) And of course, seat of the pants intuition that something was just not right with K Caps characteristics potentially due to tube output impedence loading. 

 AMB, excellent simplistic description of what's going on within the MAX's MOSFET circuit.

  Quote:


  Originally Posted by *amb* /img/forum/go_quote.gif 
_With QB2/QB3 installed, there is now a complementary emitter follower between the tube and the MOSFETs. The emitter follower has low output Z and moves the rolloff frequency well into the ultrasonics.

 At Negatron's request I did some simulations of the Millett Max diamond buffer section (alone by itself, sans the tube stage) with MOSFETs. The new twist is that QB2/QB3 are replaced with 2SJ74BL and 2SK170BL JFETs, respectively, making them a complementary source follower. This dramatically increases the buffer's input Z as compared to BJTs. As "seen" from the tube, the buffer becomes a negligible load, which is a good thing.

 To make this work, the RB4/RB6 and RB5/RB7 resistance ratios must go back to 1:1 (use 100 ohms for all of these), and RB2/RB3 should be increased to around 1K-1.2K ohms. QB1 should be 2N5486 and RB12 should be 1K ohms per the Millett Max BOM (MOSFET option). This change prevents the operating current through QB2/QB2 from coming too close to the 2SJ74BL/2SK170BL's Idss low range limit (6mA), yet still allows the output MOSFETs to be properly biased within RB12's adjustment range.._

 

Sounds like the JFETS, with the resistance ratios back to 1:1, are nearly a drop in solution to achieve a hiZ Buffer input to make the Space Charge Tubes Happy when playing with the MOSFET Buffer Outputs. 

  Quote:


  Originally Posted by *amb* /img/forum/go_quote.gif 
_The result is quite good. Here is the frequency response of the buffer section from the simulator. Note that the -3dB point is up near 1MHz, which is significantly higher than the tube's frequency response._

 

That is a Very Impressive freq response SIM Curve with the AMB JFET Mod for MOSFET MAX's......
	

	
	
		
		

		
		
	


	



 Is the current target range Bias (110mA or so) still considered optimal with this approach to achieve lowest distortion results?
 Also, AMB & Negatron, do you feel that with this Mod approach that the Cathode Cap now may become a liabilty to improved SQ and should be left blank?

  Quote:


  Originally Posted by *amb* /img/forum/go_quote.gif 
_For people who contemplate doing the MOSFET option on the Millett Max, I recommend this configuration._

 

Certainly have convinced me that the MOSFET MAX has great potential...........
	

	
	
		
		

		
		
	


	




 Sounds like I will soon have a PocketBook Lightening Experience for Build #4 
	

	
	
		
		

		
		
	


	



 Dam you AMB & Negatron for opening up another Sonic Experience Oppurtunity.......
	

	
	
		
		

		
		
	


	




 Negatron - let us know soon of your results of implementing the AMB JFET Buffer mod and also with either deleting or Tweaking the K Cap value 
	

	
	
		
		

		
		
	


	




 Super Circuit Mod by AMB 
	

	
	
		
		

		
		
	


	










 Any potential to mod BJT buffer circuit with JFET input also to achieve similar results? Understand that the gate cap HF rolloff response is not a problem with the BJT's. But potentially lowering distortion products due to tube output loading could be a goal along with eliminating the Cathode Cap requirement.


----------



## rockcod

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Wow - you guys are coming up with some impressive work!

 Another MAX lives!! 
	

	
	
		
		

		
		
	


	







 BTW, what are those film caps you're using? They look like wax capacitors, but they're too small to be Jupiters, I think. Also, it looks like Cerafines in front, but what are those monsters in the CA2 positions?

 Very nice!_

 

Thanks!
 Yes, they are NOS Tex-Cap wax caps. CA2s are Nichicon KZ -- I used the 50V version because I didn't have anything smaller on hand.


----------



## fran

A Q on the PS: I am going to mount a Tx in the case with the millet max, much as per rockcods pics above. I have a Tx with a 28V output. I think I read somewhere that I will need to fit a dropping resistor to drop the heater voltage a bit somewhere. Could someone point to some info on this, R position on the board and what values anyone with a 30v supply have used?

 thanks

 Fran


----------



## 04BluMach

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Wow - you guys are coming up with some impressive work!

 Another MAX lives!! 
	

	
	
		
		

		
		
	


	





_

 

X2 on the Impressive work!

 Great build on the latest MAX rockcod 
	

	
	
		
		

		
		
	


	




 Looks like you've got KZ's as ur C1's and those appear to be 1.5" Heat Sinks
	

	
	
		
		

		
		
	


	



 Edit: Ooooops - meant C2's. Noted you just indicated above they are KZ's for C2's!
 Is it a MOSFET build? ....or just to keep the Temps down on BJT's?

 Again - Congrats on an impressive looking MAX


----------



## amb

Quote:


  Originally Posted by *04BluMach* /img/forum/go_quote.gif 
_Is the current target range Bias (110mA or so) still considered optimal with this approach to achieve lowest distortion results?_

 

I recommend 80mA as a minimum, but not much more than that on 1" heatsinks. With taller heatsinks you could go a little higher.

  Quote:


 Any potential to mod BJT buffer circuit with JFET input also to achieve similar results? Understand that the gate cap HF rolloff response is not a problem with the BJT's. But potentially lowering distortion products due to tube output loading could be a goal along with eliminating the Cathode Cap requirement. 
 

Yes, you can also do the JFET input mod on the BJT diamond buffer with a similar increase in input Z. I recommend using 2N5486 for QB1, 1K ohms for RB12, 100 ohms for RB4-RB7, and 330 ohms for RB2/RB3. Dial the output quiescent current up to about 30mA for the BJT buffer.


----------



## rockcod

Quote:


  Originally Posted by *fran* /img/forum/go_quote.gif 
_A Q on the PS: I am going to mount a Tx in the case with the millet max, much as per rockcods pics above. I have a Tx with a 28V output. I think I read somewhere that I will need to fit a dropping resistor to drop the heater voltage a bit somewhere. Could someone point to some info on this, R position on the board and what values anyone with a 30v supply have used?

 thanks

 Fran_

 

Here is what you need:
MAX Tube Heaters Resistor


----------



## cetoole

If you use JFETs for the input transistors, with BJT output transistors, you lose the error correction benefit of the diamond topology. AMB, thanks for running the numbers for a JFET/MOSFET diamond buffer. It is something I have thought about for a while, but never got around to doing. This may be the best bet for use in this and similar amps.


----------



## rockcod

Quote:


  Originally Posted by *04BluMach* /img/forum/go_quote.gif 
_X2 on the Impressive work!

 Great build on the latest MAX rockcod 
	

	
	
		
		

		
			





 Looks like you've got KZ's as ur C1's and those appear to be 1.5" Heat Sinks
	

	
	
		
		

		
		
	


	



 Edit: Ooooops - meant C2's. Noted you just indicated above they are KZ's for C2's!
 Is it a MOSFET build? ....or just to keep the Temps down on BJT's?

 Again - Congrats on an impressive looking MAX 
	

	
	
		
		

		
		
	


	








_

 

Thanks!
 The heatsinks are actually 2" as it is a MOSFET build and heavily biased at 110mA.

 PS. I think I will do the mods AMB suggested.


----------



## 04BluMach

Quote:


  Originally Posted by *amb* /img/forum/go_quote.gif 
_I recommend 80mA as a minimum, but not much more than that on 1" heatsinks. With taller heatsinks you could go a little higher._

 

AMB thanks for reply. Yep - I meant with the 1.5" Heatsinks
	

	
	
		
		

		
		
	


	




 Those MOSFETS want to run deep in quiscent current...
 Appreciate the info from the MOSFET master!
	

	
	
		
		

		
		
	


	




 Negatron - now I understand why you've got those Howitzer size Caps in place to feed current to those hungry MOSFET beasts whith plenty of dynamic peak voltage on hand when demanded. 
	

	
	
		
		

		
		
	


	




  Quote:


  Originally Posted by *amb* /img/forum/go_quote.gif 
_Yes, you can also do the JFET input mod on the BJT diamond buffer with a similar increase in input Z. I recommend using 2N5486 for QB1, 1K ohms for RB12, 100 ohms for RB4-RB7, and 330 ohms for RB2/RB3. Dial the output quiescent current up to about 30mA for the BJT buffer._

 

Edit: Per cetoole's post... sounds like need to back off a JFET mod to the BJT Buffs.... 

 AMB, Again thanks for the Mod Inputs!


----------



## tomb

Quote:


  Originally Posted by *cetoole* /img/forum/go_quote.gif 
_If you use JFETs for the input transistors, with BJT output transistors, you lose the error correction benefit of the diamond topology. AMB, thanks for running the numbers for a JFET/MOSFET diamond buffer. It is something I have thought about for a while, but never got around to doing. This may be the best bet for use in this and similar amps._

 

Echoing what you are stating, cetoole, the BJT Diamond Buffer is excellent as it stands. It is a tried and true configuration with a long line of excellent performing Milletts and MAXes. IMHO, there is no need to change anything on the BJT's. Of course, this is DIY, so if you guys want to experiment - go right ahead. There's an old saying though, "If ain't broke ..."

 However, double thanks to Amb for the mods to the MOSFET. I am still busy ordering parts to make a couple of them. In the meantime, please continue to reference the MAX website for "official" information. (Unless you are prepared to experiment. 
	

	
	
		
		

		
		
	


	




 ) When we get a couple of Amb's JFET MOSFET Mods working, I will update the site accordingly.

 P.S. Just as a reminder, we have always recommended 1-1/2" heat sinks and 80ma minimum for MOSFETs on the MAX.


----------



## cetoole

Quote:


  Originally Posted by *n_maher* /img/forum/go_quote.gif 
_Well, in a bizzare twist of fate, after still not receiving anything in the way of a response from Paypal, my caps showed up today???
 So I guess the lesson here is that 7 weeks is not outside the normal delivery window._

 

Nate, glad you finally got your caps. I have ordered several times from eastern european sellers for capacitors and tubes, and my order for 6n1p and 6n6p tubes probably took close to this length of time. I did end up getting them though, and I am quite glad your saga had a happy ending as well.

  Quote:


  Originally Posted by *pinkfloyd4ever* /img/forum/go_quote.gif 
_anyway, back to music.. Colin, Nate, and anybody else who uses 580s with their Max, what kind of music do you listen to? I have MS-1s which I like the sound of (though I haven't thoroughly compared them with much else) but they're so damn uncomfortable and I know Senns are among the most comfy cans out there. I listen almost exclusively to classic rock, pink floyd (obv) and led zeppelin are my 2 all time faves. I'm also big on Jimi Hendrix and Metallica but I listen to just about anything that can be called rock. I don't really have money for new cans now, but what are good with this music that doesn't feel like a vice after about 20 minutes? I know this is a question more suited to the headphone forum, but I thought I'd ask all of you Team MAXers out there since it's my new main amp
	

	
	
		
		

		
		
	


	


_

 

Well, I tend to listen to stuff like Nightingale, Opeth, Dan Swano, Edge of Sanity, Dark Tranquillity, Cynic, Nightwish, Epica, Tristania, Bloodbath, Arch Enemy, November's Doom, Therion, and Iron Maiden, so I guess you could say Prog Rock/Metal. I have a little Pink Floyd and Led Zeppelin here, though I havnt tried either on the Max/HD580 rig yet. I prefer pretty much everything I listed on the Senn HD580 to any other headphones I have tried for long term, which admittedly, isnt very many pairs. Headphones I have used for over a month only include HD580, HD650 (sold, had slight preference for HD580 on everything), Grado PS1 (borrowed, preferred for minimal amount of music, but generally bested by HD580).


----------



## amb

Quote:


  Originally Posted by *cetoole* /img/forum/go_quote.gif 
_If you use JFETs for the input transistors, with BJT output transistors, you lose the error correction benefit of the diamond topology._

 

I ran some simulations which will surely raise your eyebrows. If there is any "error correction" benefit in the BJT-BJT configuration, it certainly doesn't show in simulation.

 Here is the BJT-input BJT-output diamond buffer harmonic distortion spectrum (output voltage is 1Vrms or 2.8Vpp, into 32 ohm load). The primary distortion spike is the 3rd harmonic, at 1.8mV, which corresponds to 0.13%.






 Here is the distortion spectrum for the JFET-input, BJT-output diamond buffer, under the same conditions. There are two spikes, the 2nd harmonic at 251uV corresponds to 0.018% and the 3rd harmonic at 561uV is 0.04%. This is less than 3x less distortion than the BJT-BJT configuration.






 The stunner is the JFET-input, MOSFET-output diamond buffer. NONE of the harmonics are greater than 30uV, or 0.002%. Note the expanded Y-axis.






 Sometimes it's all too easy to speculate, but when in doubt, prove it . So, I think we have a winner here. All that said, however, _all_ of these distortion results are below those of the tube's, even though the BJT-BJT version comes pretty close, at least for the 2nd harmonic. As I have tested before, the Millett's tubes all exhibit high distortion, at even _and_ odd harmonics well up the spectrum.


----------



## Negatron

The jfets AMB sent came in the mail yesterday afternoon.
 Well it bias's up, nothing went up in flames and the power company hasn't sent anyone by.

 The AMB jfet Mod works! The R values I used are a hair off, but close enough for Gov't work. Heck, they are old mil spec Dale aerospace surplus I had in my box anyway. 
	

	
	
		
		

		
		
	


	




 The highs are smooth and extended, effortless is a good word. I have been up all night and it's dawn. The extended listening eval is going to have to wait. I'm not 25 anymore. But what I hear is an improvement. Not subtle, and nothing bothers me about the SQ, but then I'm tired. Maybe Later tonight I will hate it. (Fat chance!) G'night.


----------



## Ferrari

Indeed, the JFET/MOSFET mod works fine!
 This morning I use an half of the balanced MH Max I built a while back (but didn't like it) and modified it as suggested by AMB some posts back, then adjust the quiescent current to 100mA as previous without any problem. Note that this is not the teflon/MKP output version I built but the simplified version with lower quality electrolytics (Black Gate NX) at the output.

 Also AMB is correct, the distortion- and slew rate figures (within the audio band and there outside) of the MH Max are simlpy poor... All the crap that caused by the used tubes will shadowed the subtle improvement of the output buffer (more or less) completely. Nevertheless, this JFET/MOSFET mod is worth to try. Great work AMB 
	

	
	
		
		

		
		
	


	




 .


----------



## tomb

Quote:


  Originally Posted by *AMB* 
_<snip>So, I think we have a winner here. All that said, however, all of these distortion results are below those of the tube's, even though the BJT-BJT version comes pretty close, at least for the 2nd harmonic.</snip>_

 

 Quote:


  Originally Posted by *Ferrari* 
_<snip>All the crap that caused by the used tubes will shadowed the subtle improvement of the output buffer (more or less) completely. </snip>_

 

Let's control ourselves guys. It's great that AMB has come up with an improvement on the MOSFET buffer, but some of these comments are simply tube _bias_, pardon the pun. In particular, there's no reason to resort to piling on by cursing and using vulgarities in slamming the Millett tubes.

 If lower distortion was the goal, we wouldn't be using tubes in the first place. There is ample evidence that the lack of odd-order harmonics in some tubes doesn't explain the benefits of "tube sound," anyway. So, if they exhibit odd-order harmonics, that's no confirmation that somehow the Millett tubes are worse on sound. Moreover, the stated issue in this case had nothing to do with distortion - frequency response was the issue with regard to MOSFETs in a non-feedback situation.

 Since Amb referenced his excellent Millett Hybrid article, perhaps a few of his comments that I've carried with me for a long time are worth repeating:

"The clipping behavior is classic tube-gear soft. When mildly overdriven this amplifier will not sound overly harsh."  (Note that I got slammed awhile back for paraphrasing that one. 
	

	
	
		
		

		
		
	


	




 )

"This amplifier has a low noise floor. When used with a ripple-free DC power supply, the spectrum is devoid of hum or noise spikes."

"The high frequency response of this amplifier is quite extended, -3dB at 535KHz (I only tested this with the 12AE6A). This is in stark contrast to the rolled-off highs found on many tube amps."

 Finally, this last paragraph by AMB:
The measurements show an amplifier's technical strengths and weaknesses, but it doesn't describe the sound. I am happy to report that despite the measurements, *this neat little amplifier is fine-sounding, in a euphonic kind of way.** It doesn't break new ground in dynamics, resolution or soundstage, nor was it ever intended to. *This is a different kind of audio project, simple, safe and easy on the wallet.** The sense of nostalgia when examining the vintage NOS tube boxes is a pleasure to behold. Moreover, no solid state device evokes the visual enjoyment that tubes provide, especially when displayed in their full glory with a clear-top case, and lit from below with blue light! 
	

	
	
		
		

		
		
	


	




 "
 [size=xx-small]* my emphasis[/size]

 There is no doubt in my mind after building 4 Millett Hybrids w/DB's and now 7 Millett MAXes and counting, that Colin Toole has greatly improved all of those qualities in the MAX.


----------



## amb

Hmm, TomB, nowhere in my post did I make any remarks that could be construed as "cursing and using vulgarities". What I posted are simply facts. Any value judgements you or anyone else makes, based on those sim results, are entirely your own.


----------



## tomb

Quote:


  Originally Posted by *amb* /img/forum/go_quote.gif 
_Hmm, TomB, nowhere in my post did I make any remarks that could be construed as "cursing and using vulgarities". What I posted are simply facts. Any value judgements you or anyone else makes, based on those sim results, are entirely your own.




_

 

Amb, it's easy enough for anyone to read who I was referring to about piling on with vulgarities, and it wasn't you.


----------



## Ferrari

Tomb, I can understand that you are very sensitive for comments or words that are not positive about (or related to) the MH Max as you PM-ed sometime ago. (I don't need to post your old PM here). All I said are based on facts, nothing more or less! There are many good audio tubes on the market but the tubes used here are unfortunately not belong to that category. That is the truth as we all know!

 Also... not one single word I said has the intention of what you called "using vulgarities, cursing or slamming" nor was my message intended to. I never feel the need for that. It's a pity that you interpret my message that way.


----------



## ruZZ.il

hmm.. I'm just glad there are plenty bright minds around here, and especially in the past few pages. I know the MAX is a great package for what it is as true as it may be that there are designs around components that on their own probably cost a MAX or a half and *should* outperform, for what they're worth. _*Even*_ if there are better components to work around in the range, then the MAX is even more of a marvel for taking the lesser of goods and making so so much out of it. I hope no misunderstandings or little differences get in the way of what a great crowd we have around here. I'm certain nobody meant any ill and I hope to see more 'battles' of the minds in such a constructive way as of late..


----------



## Negatron

What a great way to wake up, after falling asleep from a marathon session, happy as hell over an major improvement. Sadly, one of the reasons I generally 'Lurk' rather than participate in Forums is that invariably there ends up from perfectly sensible and generally highly intelligent people, a subtle, low level 'P*ssing match' between SS & Tube.

 I recognized and identified a needed improvement in the SS-Tube interface of a very civil project. Voiced views, requested assistance in solving the problem. Saw the problem solved and when the improvement came to fruition, witnessed this degeneration from adults. Lurking has merit.


----------



## 04BluMach

Quote:


  Originally Posted by *Negatron* /img/forum/go_quote.gif 
_Snip.....
 The AMB jfet Mod works! .....The highs are smooth and extended, effortless is a good word. I have been up all night and it's dawn. The extended listening eval is going to have to wait. I'm not 25 anymore. But what I hear is an improvement. Not subtle, and nothing bothers me about the SQ, but then I'm tired. Maybe Later tonight I will hate it. (Fat chance!) G'night._

 

 Quote:


  Originally Posted by *Ferrari* /img/forum/go_quote.gif 
_Indeed, the JFET/MOSFET mod works fine!
 This morning I use an half of the balanced MH Max I built a while back (but didn't like it) and modified it as suggested by AMB some posts back, then adjust the quiescent current to 100mA as previous without any problem. Note that this is not the teflon/MKP output version I built but the simplified version with lower quality electrolytics (Black Gate NX) at the output.
 .......... Great work AMB 
	

	
	
		
		

		
		
	


	




 ._

 

The AMB JFET Mod for the MOSFET Buffer MAXs initial builds by Negatron & Ferrari appear to confirm AMBs SIMs. Initial thumbs up from both seem to indicate thay we have a very viable Mod for the MOSFET MAX Buffer.

 Thanks for your efforts to try the Mod out so rapidly and getting the word out.
	

	
	
		
		

		
		
	


	




 Thanks AMB for the Mod developement and the great SIM presentations
	

	
	
		
		

		
		
	


	




 Ferrari - I don't think my snips of your posts takes it out of context as far as the JFET Mod of the Buffer circuit is concerned....


----------



## slowpogo

Does anyone have experience using Multicap RTX caps for bypass? They are polystyrene, supposedly really neutral and clinical.

 I have a pair of .1uf's sitting around, and have thought about trying them, either in CA9, or in CA2 parallel with the existing Vitamin Q's.


----------



## tomb

Quote:


  Originally Posted by *slowpogo* /img/forum/go_quote.gif 
_Does anyone have experience using Multicap RTX caps for bypass? They are polystyrene, supposedly really neutral and clinical.

 I have a pair of .1uf's sitting around, and have thought about trying them, either in CA9, or in CA2 parallel with the existing Vitamin Q's._

 

The owner of Soniccraft has stated that they are the best for bypassing Black Gates, but I haven't found any small enough to work in a "normal" casing arrangement. Dsavitsk reviewed some recently on his excellent Notes On Output Coupling Capacitors web page and really likes them.


----------



## tomb

Quote:


  Originally Posted by *04BluMach* /img/forum/go_quote.gif 
_The AMB JFET Mod for the MOSFET Buffer MAXs initial builds by Negatron & Ferrari appear to confirm AMBs SIMs. Initial thumbs up from both seem to indicate thay we have a very viable Mod for the MOSFET MAX Buffer.

 Thanks for your efforts to try the Mod out so rapidly and getting the word out.
	

	
	
		
		

		
			





 Thanks AMB for the Mod developement and the great SIM presentations
	

	
	
		
		

		
		
	


	




 Ferrari - I don't think my snips of your posts takes it out of context as far as the JFET Mod of the Buffer circuit is concerned....
	

	
	
		
		

		
		
	


	


_

 

Good summary.

 For what it's worth, I ordered parts for the JFET MOSFET Mod from Amb as soon as he posted the _first_ post on the mod. I will update the MAX website with complete details, photos, and official changes to the BOM as soon as I build a couple of them and am sure that I can support the changes. Assuming that all works out - and I have no reason to believe it won't - I will post a recommendation on the home page that all MOSFET MAX owners make this change.

 In particular, I'm going to experiment with casing up a 1" heat sink version and see how far we can push the bias on short sinks with heat-transfer-enhanced "rollbars." As many of you know, I am a big proponent of locating the board in that 3rd slot from bottom on the Hammond. Nevertheless, we have many happy builders using that bottom slot and 1-1/2" heat sinks.

 The official BJT version of the Diamond Buffers will remain as is, unless Colin disagrees. It has a long and proven history dating all the way back to Walt Jung. With very minor differences (mostly to boost current-biasing capability), it is the very same buffer on the PPA and the original revMH Millett Hybrid DB. Having now built a number of the different BJT's, I'll try to give a review of the differences in sound quality among those many options vs. the new version of the MOSFETs.

 Speaking of different BJT's, here's a pic of a MiniMAX prototype that I just finished setting up and running for the first time yesterday. This one has the Sanyo 2SC2344/2SA1011 BJT's that are often listed as replacements for the Toshiba 2SC2238/2SA968's. Steinchen describes them as "_crystal clear and airy, rather bright but not piercing bright. good detail and instrument seperation. well defined bass. sounds clean and analytical."_ Those are 0.1uf 160V K42's tombstoned inbetween the center heat sinks. ES's and 0.1uf Wima's all around. You might notice a lack of caps around the power supply. It's a long story, but those of you who know the history will remember the explanation for that. 
	

	
	
		
		

		
		
	


	




 This is actually the very 1st MAX prototype board.





[size=xx-small](click for a bigger pic)[/size]


----------



## pinkfloyd4ever

are those spaces for IC buffer sockets?


----------



## tomb

Quote:


  Originally Posted by *pinkfloyd4ever* /img/forum/go_quote.gif 
_are those spaces for IC buffer sockets?_

 

Yep. We originally thought there might be a need to have a monolithic buffer option for the BUF634's or OPA551's. However, the discrete BJT buffer has always sounded _way_ superior (at least with the better transistors). Plus, once the discrete buffer got populated there was no turning back to the BUF's. So, the option was dismissed with the second prototype and the current production MAX.


----------



## slowpogo

I just put my 0.1uf Multicap RTX's in CA9..and I think it's a winner.

 It does not seem to affect the bass like the Vitamin Q's did, maybe a _tiny_ bit, but not nearly as noticeable. I think the benefits outweigh this easily; everything is just tighter and more focused. It's much "blacker between the notes," and the dynamic detail is improved. Before, the Max was very dynamic in terms of the big picture; an ensemble could get very quiet or very loud. Now it's like that has extended more to the individual instruments. The cymbals and things are more finely detailed, I can hear the different timbres as the stick hits different places.

 The highs are slightly sweetened, but not airy, like with the Vitamin Q's. Very controlled. There is a small downside to this, without any caps in CA9, I'd listen to jazz stuff and feel like I was in the studio with them. Now that feeling is a little diminished, as if the music was engineered better, or something.

 They're exactly as tall as the Black Gates, so I tombstoned 'em. They are pretty expensive, though, so they're probably not a "must." But definitely worth experimenting with if you have some from another project to try.


----------



## tomb

That's great news, slowpogo! Glad to hear they worked out!

 There is another option I haven't experimented with, but probably will eventually. The same Russians we love to do business with have something called a "HiTol" cap (Hi-Tolerance, whupeedoo 
	

	
	
		
		

		
		
	


	




 ), but the important part is that they are polystyrene.

 They look like large green Wima's. It's hard to tell from the pics what the exact dimensions are. I've worked out a graphic measure with the 0.12uf's and they appear to be 25mm long, which would be a tad too big for CA8. If some of you are game, though, here's one of the links:
0,12uF 250V HI-TOL. +/- 2% AUDIO capacitors Lot of 30






 EDIT: That's $24 shipped for 30, resulting in about 80 cents per cap. 
	

	
	
		
		

		
		
	


	




 EDIT2: That looks like the same cap he has pictured for the 0.1uf's, so the 0.12uf's may be even bigger. I've had good luck dealing with Oleg here and USSR-Tubes, but like the HongKong ebay-ers, they will _not_ answer questions - probably too risky if they get the translation wrong.


----------



## jamess71

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_




[size=xx-small](click for a bigger pic)[/size]_

 

TomB what knob is that and where did you get it? thanks

 James


----------



## tomb

Quote:


  Originally Posted by *jamess71* /img/forum/go_quote.gif 
_TomB what knob is that and where did you get it? thanks

 James_

 

Another from my favorite knob dealer on ebay 
	

	
	
		
		

		
		
	


	




 :
Partspipe/hongkongsuperseller - SOLID ALLOY GOLD HI-FI VOLUME CONTROL KNOBS
 Don't know what "solid alloy gold" means 
	

	
	
		
		

		
		
	


	




 , but it's a nice knob for the smaller Lansing case.


----------



## soloz2

well I'm waiting on a few last parts for build #2 and 3, and so I started on the casework for #1 and #2 today... but sadly my drill press bit the dust.


----------



## pinkfloyd4ever

Quote:


  Originally Posted by *soloz2* /img/forum/go_quote.gif 
_well I'm waiting on a few last parts for build #2 and 3, and so I started on the casework for #1 and #2 today... but sadly my drill press bit the dust._

 

that sucks..I'm looking at getting a drill press, which is why my Max is still just sitting in the case w/o the top or end panels. What kind was yours? (so I know what to avoid)


----------



## slowpogo

How difficult is it to remove the tube sockets on a fully-populated Max board? I was worried my tube LED's would be too bright, but they're actually pretty tame, to the point I wouldn't mind spending an hour to redo the sockets/LED's. I may even mod them for 5mm lights.

 If I had some kind of thin snipping tool, maybe even the scissors on a Swiss Army Knife, it seems easy enough to snip the ceramic off the socket legs...or even just crush the ceramic with a pliers, pick it apart, and desolder. Anyone have a good method? (I have more sockets to use, and don't care if I have to destroy the current ones)


----------



## tomb

Quote:


  Originally Posted by *slowpogo* /img/forum/go_quote.gif 
_How difficult is it to remove the tube sockets on a fully-populated Max board? I was worried my tube LED's would be too bright, but they're actually pretty tame, to the point I wouldn't mind spending an hour to redo the sockets/LED's. I may even mod them for 5mm lights.

 If I had some kind of thin snipping tool, maybe even the scissors on a Swiss Army Knife, it seems easy enough to snip the ceramic off the socket legs...or even just crush the ceramic with a pliers, pick it apart, and desolder. Anyone have a good method? (I have more sockets to use, and don't care if I have to destroy the current ones)_

 

I'm not sure I understand the problem. A typical 3mm LED should fall right through the socket's center hole. Get yourself a snipped lead, hold it with a pair of needlenoses and push it into the hole from the bottom side while you're heating the solder joint with your iron. Do that for both of the LED pads and it should pop out through the tube socket hole without a problem. 
	

	
	
		
		

		
		
	


	




 I've played with soldering mine into various positions with several MAXes - either flush against the board, in the middle of the tube socket hole, and at the very top just under the top surface of the socket and the tube. The 3mm slides right through at any point.

 I suppose you can remove the tube sockets if you want to put a 5mm in there, but having built Millett Hybrids before this (which used 5mm LED's), it's my opinion that the 3mm's are more focused into lighting the tubes - especially if you position the LED somewhere inside the socket.


----------



## slowpogo

I put one of those rubber things on my LEDs, that normally would be used for an LED holder, and then, glued the rubber thing inside the tube socket. This put the LEDs right below the edge of the hole. Chances are high they are in there permanently.

 The 5mm LED I'm looking at is 20 degree off axis, and almost twice the mcl of my current ones. So, they should definitely be brighter. I'll try your method, and maybe the LEDs will still come out, but I'm pretty sure they were glued along with the rubber piece.


----------



## soloz2

Quote:


  Originally Posted by *pinkfloyd4ever* /img/forum/go_quote.gif 
_that sucks..I'm looking at getting a drill press, which is why my Max is still just sitting in the case w/o the top or end panels. What kind was yours? (so I know what to avoid)_

 

well it's pretty old. It was my Grandpa's but when he moved to FL full time and couldn't use it anymore my dad got it and he gave it to me last summer. 

 I talked with my dad and he said it's an 'easy' fix and he told me what to do, but for the life of me I can't get it so I must be doing something wrong. lol. The entire chuck fell off so... it's apparently a compression fitting so you just have to push it on but I can't get it to stay even using a board and hitting it w/ my hammer. lol.


----------



## tomb

Quote:


  Originally Posted by *slowpogo* /img/forum/go_quote.gif 
_I put one of those rubber things on my LEDs, that normally would be used for an LED holder, and then, glued the rubber thing inside the tube socket. This put the LEDs right below the edge of the hole. Chances are high they are in there permanently.

 The 5mm LED I'm looking at is 20 degree off axis, and almost twice the mcl of my current ones. So, they should definitely be brighter. I'll try your method, and maybe the LEDs will still come out, but I'm pretty sure they were glued along with the rubber piece._

 

OK - didn't know that. I have drilled out a tube socket after it was already installed on the board, though. So, that may be a solution to get the LED holder out - even if glued. It's best to use a drill press or use a depth collar on the drill bit if using a hand drill. That will keep you from going too far and drilling through the board. Although, it probably wouldn't be the end of the world if you did that. There are some traces under the right tube that are important if the hole is too big, though.

 Short of that, I don't think you'll have much luck removing the tube socket in one piece. You might be able to snip through several of the pin legs with some standard flush cutters. Then you could perhaps get the rest of it off.

 Good luck.


----------



## cetoole

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Short of that, I don't think you'll have much luck removing the tube socket in one piece. You might be able to snip through several of the pin legs with some standard flush cutters. Then you could perhaps get the rest of it off.

 Good luck._

 

I have done it once, successfully pulling both sockets from one of the first proto pcbs intact, and without lifting any pads. Basically add a ton of solder to each, and do your best to heat all pads, you may be able to make it fall out, then cleanup is easy. Otherwise, and what I did, is careful cleaning of each pin, then heating the pins and centering them in their holes while hot so they dont re-adhere to the pads. Then do more cleanup around them, with spacers in place. Sockets survived fine, and I am using them in my current Max. Board pads also lived to tell the tale.

  Quote:


  Originally Posted by *soloz2* /img/forum/go_quote.gif 
_I talked with my dad and he said it's an 'easy' fix and he told me what to do, but for the life of me I can't get it so I must be doing something wrong. lol. The entire chuck fell off so... it's apparently a compression fitting so you just have to push it on but I can't get it to stay even using a board and hitting it w/ my hammer. lol._

 

That is actually part of the assembly steps for a drill press, at least my new Craftsman. You probably are just going too easy. Fully retract the bits that hold the drill bit in place so as not to damage them, then use either a rubber mallet or a board between the head and a standard hammer, and whack it good.


----------



## Negatron

After several days to evaluate the AMB jfet DB mod with modded HD580's and K501's and good source, I have determined my board indicator LED is still at 610nm and tube LED's at 635 nm, as indicated by my Systron Donner 8368Lmp prototype, LED analyzer 
	

	
	
		
		

		
			





 However, a new twist after some extended eval.- The BASS is tighter and more defined as well. I believe that to be a direct consequence of tube plate loading. A benefit I suspected, but it was greater than I thought. Not huge, but noticeable 
	

	
	
		
		

		
		
	


	




 (Previous posts indicate build components)

 As initially stated after completion of the AMB mod, the highs were seeming extended and 'effortless'. That has also proven itself out with extended listening and comparing what I hear now to the chicken scratchings that pass for my notes. (yes I still use paper. I worked maintenance on computers for some time and believe them to be put on this planet to prove Murphy's Law.)

 Anyone who contemplate MOSFETS will gain the total effect they can bring, unless of course you prefer BJT SS sound. For those who love tubes and prefer MOSFETS this is a no-Brainer.
 I highly, well actually, very highly recommend this mod. <Big thumbs up>

 I'm tied up with several tube power amp projects I neglected while playing with this, so my posting is limited. Those interested in constructive, hands-on dialog about the jfets or mods feel free to PM me, when I have free time I will answer.


----------



## wkwlb

Hi, I am building my first Millet Max. juz curious, has anyone used 2200uF caps on C4/C5? and basically the cap values difference on C4/C5 will have what kind of effect on output? thx


----------



## tomb

Quote:


  Originally Posted by *wkwlb* /img/forum/go_quote.gif 
_Hi, I am building my first Millet Max. juz curious, has anyone used 2200uF caps on C4/C5? and basically the cap values difference on C4/C5 will have what kind of effect on output? thx_

 

If you're talking about the UPW's that are 18 x 25mm high, it's a little extreme, but not much more than the 1800uf FM's that I use. The reason I mention UPW's is of course, they don't have 1800uf's. So, you might be thinking up or down from there. However, the important thing, IMHO, is to keep these at or above 1000uf. You probably won't tell any difference going up in size except on current inrush. Inrush could increase beyond your walwart's capability. If you use one of the 50VA Class 2 walwarts, though, it shouldn't be an issue.


----------



## amphead

Just a heads up. We were successful opening a brick and mortar electronics surplus/new stock store. The web site won't be functional for a while. I am the CTO/Buyer for the store. I plan on stocking hifi resistors/caps/tubes/transistors/wire etc. The name is HFE Electronics. We chose HFE for obvious reasons. I put this here because I will be trying to get discounts for Head-Fi members, and thought that some of you might appreciate that. Edit: with Beezar.com online now from TomB/CeToole, the builder community gets a great choice of materials.


----------



## tomb

Quote:


  Originally Posted by *amphead* /img/forum/go_quote.gif 
_Just a heads up. We were successful opening a brick and mortar electronics surplus/new stock store. The web site won't be functional for a while. I am the CTO/Buyer for the store. I plan on stocking hifi resistors/caps/tubes/transistors/wire etc. The name is HFE Electronics. We chose HFE for obvious reasons. I put this here because I will be trying to get discounts for Head-Fi members, and thought that some of you might appreciate that._

 

Thanks - maybe we can work out some bulk purchases. 
	

	
	
		
		

		
		
	


	




 Speaking of which, I hope everyone grants me a little patience on the Toshiba BJT's. I have a standing order at MCMinone, but they received only the 2SA968's last week. They told me the 2SC2238's were due in to MCMinone yesterday, but they're a no-show so far. So, the due date at beezar.com may get revised again. 
	

	
	
		
		

		
		
	


	




 Meanwhile, I received some MOSFETs and JFETs today from AMB - fast service as usual. However, my Mouser and DigiKey orders will be lagging behind. I depleted my parts bin after the last 5 MAXes, so it's been difficult figuring out what I have left and what I need - every spare penny has been going into beezar.


----------



## tomb

Besides updating the MAX site for the JFET-MOSFET mod, I still want to follow up on the tube box collection. This is similar to what would be used for the MAX site, only for the Millett tubes, specifically:
Tube Box Art
 Here's another one:
Tube Box Art Gallery

 Those sort of give you the idea.


----------



## amphead

Quote:


 Thanks - maybe we can work out some bulk purchases. 
 

Definitely!  It will take me some time to get the hang of this buyer thing. All five board members are electronic types as opposed to bean counters.  Edit: one member used to work for Nelson Pass.


----------



## slowpogo

FWIW I did an A/B comparison between Rikens and Kiwames in R14.

 I started out with 15ohm Rikens installed, and have been listening to that setup for a few weeks now. Tonight, I switched in some 15ohm Kiwames.

 Hmmm...I know a lot of people here seem to like the Kiwames, but it was a noticeable step down to me. I only left them in for about three hours, the amp playing the whole time, so I don't know if I'm missing out on some big burn-in transformation. But they really fuzzed things up. It sounded pleasant and warm and tubey, but in comparison the Kiwames really blunt the leading edge of notes and just kind of smeared things slightly. Things like timpani really brought out the difference. With the Kiwames in it literally sounded like the timpanist had changed from a firm mallet to a big soft mallet.

 Not unpleasant, again, but fidelity took a step down, for sure. I tried them with several tube types (and I have can't miss build #1 by the way).

 Now with the Rikens back in, my thoughts upon hearing the Kiwames hold true. The smearing is gone, it's nice and crisp and lively, but the highs are still sweetened and not harsh.

 It's $5-6 for a pair of Rikens, but honestly, to my ears it's really worth the extra $4 over the Kiwames.


----------



## Negatron

Quote:


  Originally Posted by *slowpogo* /img/forum/go_quote.gif 
_FWIW I did an A/B comparison between Rikens and Kiwames in R14.

 I started out with 15ohm Rikens installed, and have been listening to that setup for a few weeks now. Tonight, I switched in some 15ohm Kiwames.

 Hmmm...I know a lot of people here seem to like the Kiwames, but it was a noticeable step down to me. I only left them in for about three hours, the amp playing the whole time, so I don't know if I'm missing out on some big burn-in transformation. But they really fuzzed things up. It sounded pleasant and warm and tubey, but in comparison the Kiwames really blunt the leading edge of notes and just kind of smeared things slightly. Things like timpani really brought out the difference. With the Kiwames in it literally sounded like the timpanist had changed from a firm mallet to a big soft mallet.

 Not unpleasant, again, but fidelity took a step down, for sure. I tried them with several tube types (and I have can't miss build #1 by the way).

 Now with the Rikens back in, my thoughts upon hearing the Kiwames hold true. The smearing is gone, it's nice and crisp and lively, but the highs are still sweetened and not harsh.

 It's $5-6 for a pair of Rikens, but honestly, to my ears it's really worth the extra $4 over the Kiwames._

 

The Rikens are worth every bit spent in that location. They are the only thing I know that gives sweet AND detailed. They are also great as plate and cathode R's in amps that can use them there. It's likely whatever internal lead connection they use, but I don't have a clue how. And I bet they ain't telling.


----------



## 04BluMach

Quote:


  Originally Posted by *slowpogo* /img/forum/go_quote.gif 
_FWIW I did an A/B comparison between Rikens and Kiwames in R14..........
 Hmmm...I know a lot of people here seem to like the Kiwames, but it was a noticeable step down to me. I only left them in for about three hours, the amp playing the whole time, so I don't know if I'm missing out on some big burn-in transformation. But they really fuzzed things up. It sounded pleasant and warm and tubey, but in comparison the Kiwames really blunt the leading edge of notes and just kind of smeared things slightly. Things like timpani really brought out the difference. With the Kiwames in it literally sounded like the timpanist had changed from a firm mallet to a big soft mallet.

 Not unpleasant, again, but fidelity took a step down, for sure. I tried them with several tube types (and I have can't miss build #1 by the way).

 Now with the Rikens back in, my thoughts upon hearing the Kiwames hold true. The smearing is gone, it's nice and crisp and lively, but the highs are still sweetened and not harsh.

 It's $5-6 for a pair of Rikens, but honestly, to my ears it's really worth the extra $4 over the Kiwames._

 

 Quote:


  Originally Posted by *Negatron* /img/forum/go_quote.gif 
_The Rikens are worth every bit spent in that location. They are the only thing I know that gives sweet AND detailed. They are also great as plate and cathode R's in amps that can use them there. It's likely whatever internal lead connection they use, but I don't have a clue how. And I bet they ain't telling. 
	

	
	
		
		

		
		
	


	


_

 


 Hmmmmmm Is right! 

 I had never tried directly pitting the Kiwames against the Rikens. I was more a fan of sprinkling a few Kiwames strategically in the Sig Path to soften some of the Metal resistor harshness that typically builds up. Didn't really consider that Rikens would hold a significant advantage over the Kiwames as Tants do (for some big $$$). I guess it is one of those - well they are both well made Carbon film resistors they couldn't sound that different...
	

	
	
		
		

		
		
	


	




 Based on the Riken cheer leading squad...
	

	
	
		
		

		
		
	


	




 Think I will give them a shot as the Output resistors with a MOSFET conversion I have planned for build#2. While I am at it - will pick up values for Plate and Cathode to try out after it gets well burned in to see if my burned out ears can identify a Riken difference. 

 SInce I have been delayed so long already with the MAX #3 build (that I finally just started), I guess it will wait a little while longer for a couple of Rikens on its output too....
	

	
	
		
		

		
		
	


	




 Thanks for the info....... 
 ..............._and after all its only more paper to trade for better Toys!_


----------



## Negatron

Quote:


  Originally Posted by *04BluMach* /img/forum/go_quote.gif 
_Hmmmmmm Is right! 

 <snip>
 Based on the Riken cheer leading squad...
	

	
	
		
		

		
		
	


	




 Think I will give them a shot as the Output resistors with a MOSFET conversion I have planned for build#2. While I am at it - will pick up values for Plate and Cathode to try out after it gets well burned in to see if my burned out ears can identify a Riken difference. 
 <snip>
 Thanks for the info....... 
 ...............and after all its only more paper to trade for better Toys!_

 

They (Rikens) will be a bit of a pleasant surprise on RB14. Regarding the Rikens on the plate though, there is really no true plate R and replacing RA8 with a Riken will be overridden by the following signature of the CS. and the cathode is an VR so no go there. However, with the AMB jfet mod w/MOSFETS, replacing RB2,3 with 1.2K Rikens is another place you can go with benefit that you will hear. JMHO

 Edit: Though not tried, there may be a gain from using 100R Rikens at RB8,9 though you may find once used there is a law of diminishing return unless RB14 is jumpered. So it is likely a waste if already replacing RB14.


----------



## Tyne

Hey, I've been enjoying my Max for quite some time now, but I've recently been having a problem with the left channel. Usually when I turn the amp on only the right channel works. I have to turn the amp off and turn it back on to get them both on. Sometimes after a few hours of listening the left channel will go dead again.

 Any advice on what might be the problem? I went with BJT Diamond Buffer for the output stage btw.


----------



## ruZZ.il

check for solder bridges and proper connection, make sure the back of the board is nice and clean, check that the tubes are in nice and snug, check input connections, etc.. there may be some faulty part though, but try get all the other factors out the way.. I guess after that, it would be down to trying to trace a signal with a scope while the problem is present, if you have access to one. Its often hard to find problem that aren't always there ;( and since you say it often works, its hard to blame something specific or do a spot check comparison between sides.. but maybe there are some tricks I'd be glad to learn here too


----------



## Negatron

Quote:


  Originally Posted by *Tyne* /img/forum/go_quote.gif 
_Hey, I've been enjoying my Max for quite some time now, but I've recently been having a problem with the left channel. Usually when I turn the amp on only the right channel works. I have to turn the amp off and turn it back on to get them both on. Sometimes after a few hours of listening the left channel will go dead again.

 Any advice on what might be the problem? I went with BJT Diamond Buffer for the output stage btw._

 

The problem may well be as simple as a bad solder joint. Just look at the bottom and I/O connectors (if you have screw down headers check them too) Use a magnifying glass and look for grey colored solder joints (that are not shiny). Solder joints and very small solder bridges from splashes that heat expansion could be bringing into play may well be the cause. If you see a suspect joint reflow it with flux. Hopefully it's an easy one.

 One more thing. In the absence of an occiloscope you can use a DMM on millivolt scale and being carefull not to short out anything, trace an input signal to where it stops. http://www.diyforums.org/MAX/schematic/MAXsch75.jpg
 It's usually simple. (That does not always mean fast. 
	

	
	
		
		

		
			





)

 On the otherhand, if your luck is like mine, it is a problem that one on earth has ever seen before and evil spirits from outer space are wagering on the outcome of your sanity.


----------



## amphead

Quote:


 On the otherhand, if your luck is like mine, it is a problem that one on earth has ever seen before and evil spirits from outer space are wagering on the outcome of your sanity. 
 

Ha Ha.....so true! 
 Good luck Tyne, we will get it fixed eventually. If you don't see anything you could post some pics. Edit: try swapping tubes from left to right, eventhough that probably won't be your problem.


----------



## tomb

Quote:


  Originally Posted by *amphead* /img/forum/go_quote.gif 
_Ha Ha.....so true! 
 Good luck Tyne, we will get it fixed eventually. If you don't see anything you could post some pics. Edit: try swapping tubes from left to right, eventhough that probably won't be your problem._

 

Actually, that's usually my first suspect - bad pin connections on the tube or the socket. There are up to five pins on the tube that if loose, would cause you to lose a channel completely. Two of them are the heater connections - if you see the tube glow (other than the LED's), then you can dismiss that. However, the plate and grid pins could have a bad/intermittent connection. If you can measure a bias, then you can dismiss the plate pins. You can refer to the tube pin diagram on the MAX website:
MAX Tubes
 Pins 3 & 4 are the heater connections, pins 2 and 7 are the plates, and pin 1 is the signal input (pin 7 is also the signal output). Remember that these designations are reversed from how you see them on the board - the pin diagram is referenced by looking at the _bottom_ of the tube. You might try wiggling or canting the tube slightly if anything is amiss with your measurements. That can confirm some bad pins. Often, either a cleanup or bending the pins out slightly can fix the situation.

 I've also had intermittent issues with a signal-input terminal block on one MAX, but it came down to the wire being flattened out so bad that the screws were clamping down on the insulation (it's a well-used prototyping board). 

 It might be a good idea to stop and check those things the next time the Left channel is _not _working. 
	

	
	
		
		

		
		
	


	




 If those things all check out, then follow ruZZ.il's and Negatron's advice and start looking for some bad solder connections.


----------



## naamanf

Seeing that it works if you cycle power I would also take a look at the one mechanic part on the board. The relay.


----------



## jimmyjohn

Another troubleshooting question:

 I bought a used unit a couple of weeks ago, and it's been working fine. However, yesterday I checked the bias voltages (normally 14.5V), and one channel was 9.9V while the other was around 20V. There was a pretty equal voltage change in opposite directions. Any ideas as to what would cause this? 

 Over the weekend I noticed that most of the nuts for the volume knob, headphone jack, and input jacks were loose so I tightened everything. Could a loose ground connection at the chassis have caused my original bias adjustments to be incorrect?

 Also, how stable should these bias settings be? I have adjusted them to 14.5 volts several times, but they always drift about +/- 0.5V when I check them again.

 Thanks,
 Jim D.


----------



## Negatron

Quote:


  Originally Posted by *jimmyjohn* /img/forum/go_quote.gif 
_Another troubleshooting question:

 I bought a used unit a couple of weeks ago, and it's been working fine. However, yesterday I checked the bias voltages (normally 14.5V), and one channel was 9.9V while the other was around 20V. There was a pretty equal voltage change in opposite directions. Any ideas as to what would cause this? 

 Over the weekend I noticed that most of the nuts for the volume knob, headphone jack, and input jacks were loose so I tightened everything. Could a loose ground connection at the chassis have caused my original bias adjustments to be incorrect?

 Also, how stable should these bias settings be? I have adjusted them to 14.5 volts several times, but they always drift about +/- 0.5V when I check them again.

 Thanks,
 Jim D._

 

Power supply and ground are on the board so probably not.
 Did you by any chance remove the tubes and mistakenly put them in the opposite sockets?


----------



## jimmyjohn

Quote:


  Originally Posted by *Negatron* /img/forum/go_quote.gif 
_Power supply and ground are on the board so probably not.
 Did you by any chance remove the tubes and mistakenly put them in the opposite sockets?_

 

Yes, that's certainly a possibility, since I removed the tubes to get the case open when I tightened everything. 

 What about the bias voltage drift? Is it a concern? Like I said, it's usually +/- 0.3 - 0.6 volts.


----------



## Negatron

Quote:


  Originally Posted by *jimmyjohn* /img/forum/go_quote.gif 
_Yes, that's certainly a possibility, since I removed the tubes to get the case open when I tightened everything. 

 What about the bias voltage drift? Is it a concern? Like I said, it's usually +/- 0.3 - 0.6 volts._

 

Just for curiosities sake, swap the tubes back and see if you get the same thing. Bet it goes right back. As to the drift, no big deal. as the transistors in the CS change temp there will be a slight current shift and the tubes will change some as they stabilize also .3 volts is not much.


----------



## slowpogo

I don't think this is mentioned on the Max site...is there any benefit in paying for matched tubes? Or does adjusting the tube bias basically "match" them?


----------



## Negatron

Quote:


  Originally Posted by *slowpogo* /img/forum/go_quote.gif 
_I don't think this is mentioned on the Max site...is there any benefit in paying for matched tubes? Or does adjusting the tube bias basically "match" them?_

 

I have a Hickok 600A and I never bother to match them. Just adjust the Bias.
 They are just $2 tubes, no need to worry abour small stuff.
 Matching is generally for push pull amps where there is a need, and the anal retentive. If you meet neither qualification just listen and enjoy.


----------



## rockcod

while we are on the subject of tubes, I have problem sourcing 12AE6/A in larger quantity. Most of the usual places (tubedepot, tubeworld, the tubestore, vacuumtubes.net, etc.) offer only singles, or at the most, single pairs. Are there any other vendors that'd offer more, say, 5-10 pairs of the same type?


----------



## slowpogo

I would suggest trying Consolidated Electronics:

Consolidated Electronics, Incorporated

 The website looks kind of low-rent and shady, but I've dealt with them before and they're pretty good. The guy who runs it is a nice guy and easy to deal with, and I know they have 12AE6's; and I suspect they have a bunch of them. Just a suggestion.


----------



## 04BluMach

Quote:


  Originally Posted by *04BluMach* /img/forum/go_quote.gif 
_Snip ..............While I am at it - will pick up values for Plate and Cathode to try out after it gets well burned in to see if my burned out ears can identify a Riken difference............_

 

 Quote:


  Originally Posted by *Negatron* /img/forum/go_quote.gif 
_They (Rikens) will be a bit of a pleasant surprise on RB14. Regarding the Rikens on the plate though, there is really no true plate R and replacing RA8 with a Riken will be overridden by the following signature of the CS. and the cathode is an VR so no go there. However, with the AMB jfet mod w/MOSFETS, replacing RB2,3 with 1.2K Rikens is another place you can go with benefit that you will hear. JMHO

 Edit: Though not tried, there may be a gain from using 100R Rikens at RB8,9 though you may find once used there is a law of diminishing return unless RB14 is jumpered. So it is likely a waste if already replacing RB14._

 

How stupid on my part, well thats what happens when you are too tired and just blathering trying to think of something cute to say versus intelligent.....

 Of course with a CS on the plate - the resistor is buried under the CS signature. And the cathode resistor is a trimmer (DUH!!!). 
 [It certainly would provide some impovement replacing the trimmer by a Riken - but wouldn't allow much adjustment range for bias afterwards....LOL]


----------



## rockcod

Quote:


  Originally Posted by *slowpogo* /img/forum/go_quote.gif 
_I would suggest trying Consolidated Electronics:

Consolidated Electronics, Incorporated

 The website looks kind of low-rent and shady, but I've dealt with them before and they're pretty good. The guy who runs it is a nice guy and easy to deal with, and I know they have 12AE6's; and I suspect they have a bunch of them. Just a suggestion._

 

Thanks! I will check them out.


----------



## 04BluMach

Quote:


  Originally Posted by *Negatron* /img/forum/go_quote.gif 
_I have a Hickok 600A and I never bother to match them. Just adjust the Bias.
 They are just $2 tubes, no need to worry abour small stuff.
 Matching is generally for push pull amps where there is a need, and the anal retentive. If you meet neither qualification just listen and enjoy._

 

Yeah, no benefit matching these triodes in SE circuit. 

 Speaking of matching - if you are considering implementating the JFET Mod be aware that you need to match the JFETS Complemenatery pairs preferably as a fully matched/balanced "Quad" set.

 So, either -
 plan on buying a substantial quantity to roll your own QUAD sets by matching IDSS values to maintain desired current levels and keep the channels balanced (and store all the leftover unmatched JFETS in a jar ???)
 ...or 
 head over to the AMB store site to order your two sets of JFET complementary pairs and the additional item for JFET Quad matching service. 

 The price for the JFETS and the service are very reasonable. I couldn't imagine spending all that time to match them (assuming you already have the test jig setup) and only charging $4. Maybe he has Elfs come in at night....


----------



## 04BluMach

Quote:


  Originally Posted by *slowpogo* /img/forum/go_quote.gif 
_I would suggest trying Consolidated Electronics:

Consolidated Electronics, Incorporated

 The website looks kind of low-rent and shady, but I've dealt with them before and they're pretty good. The guy who runs it is a nice guy and easy to deal with, and I know they have 12AE6's; and I suspect they have a bunch of them. Just a suggestion._

 


 Well, now that the word is out.... I guess he won't have too many left by the end of the weekend!!
	

	
	
		
		

		
			





 Sounds like rockcod has moved his money out of the stock market and is reinvesting in 12AE6's .....


----------



## amphead

Quote:


 I don't think this is mentioned on the Max site...is there any benefit in paying for matched tubes? Or does adjusting the tube bias basically "match" them? 
 

Sorry to beat a dead horse, but matching tubes in Class AB/push-pull amps is keeping the "weaker" tube from burning out due to higher current demand. Matched tubes share current flow equally and age at roughly the same rate.


----------



## amb

I've seen two Millett tubes of the same manufacturer and type exhibit as much as a dB or more difference in gain, so if anything, this is something to look out for when buying.


----------



## amb

Quote:


  Originally Posted by *amphead* /img/forum/go_quote.gif 
_Sorry to beat a dead horse, but matching tubes in Class AB/push-pull amps is keeping the "weaker" tube from burning out due to higher current demand. Matched tubes share current flow equally and age at roughly the same rate._

 

But that doesn't really apply to the Millett Hybrid...


----------



## amphead

Right you are! The Max is Class A. Just a little tube 101 (I try to give those who are learning, some idea of what physics are happening in a general sense).


----------



## tomb

Quote:


  Originally Posted by *Negatron* /img/forum/go_quote.gif 
_I have a Hickok 600A and I never bother to match them. Just adjust the Bias.
 They are just $2 tubes, no need to worry abour small stuff.
 Matching is generally for push pull amps where there is a need, and the anal retentive. If you meet neither qualification just listen and enjoy._

 

Actually, Antique Electronic Supply had a few 12FK6's for $1.30 awhile back. 
	

	
	
		
		

		
		
	


	







 There have been some aspersions cast toward these tubes lately that I don't necessarily agree with. Regardless, Negatron's comments are good advice: matching tubes that are this inexpensive is beyond the point of diminishing returns. You are much more likely to have issues with simple break-in or microphonics than mismatched tubes.

 I have seen some of these tubes take several hours - if not a couple of days - before even being able to bias them. Yet once that gas was burned off, they often turned into sterling tubes. Testing/matching under those circumstances and these prices are problemmatic at best, even if a vendor agreed to do it.

 Speaking of which, we need to respect our tube vendors and the prices they offer on these tubes. We have gone from being able to select brand to simply finding stock wherever we can. The demand has been that great because of the MAX. I have received more than a few e-mails from vendors asking for relief from some of these requests.

 So, simply buy multiples if you can. Give the tubes time and try to adjust for proper bias - but if you don't like the sound you're getting, then just swap them out. Above all, the Millett MAX is supposed to be _fun_. Worrying over the tubes is just not worth the sweat.


----------



## amphead

btw, Thanks TomB! The extra-large Max t-shirt is a beauty! Should have pics on Head-Fi after the Fairfax meet when those become available. I actually wear something between a large and extra-large, so I wash an extra large in hot water and it shrinks to the right size.


----------



## Negatron

A few additions to TomB's tube comments. There are not that many different mfg'd tubes in the line. If you find a $1.50-$2.00 single, grab it. you will find a match down the line.
 (Hamfests are a great 50 cent source) Buying 2 RCA's does not guarantee you will get tubes that are made by the same factory, just branded the same. Also there is something that has not come up yet to my knowledge, but it may yet.

 When a tube has excess gas from age, the getter, the silver part can turn dark. That is no indication of a bad tube. In reality a dark getter is very efficient. It's when they shrink that they stop being effective. So if you get a pair and one darkens,don't jump on the phone and raise h*ll with the seller, the getter is just doing it's job. No problem exists usually.

 An up-side to MAX tubes is there is really a small number of MAX's compared to the number of available tubes. But they are readily available in the hands of the usual vendors, So supplies locally shrink. Some will capitalize on the current run, but it won't last and by then more tubes will be sourced, the demand stabilizes and guess what ? A wealth of cheap tubes again..

 (Wait 'till gas regulators come back in style. I'm gonna' be a RICH man!)


----------



## tomb

Quote:


  Originally Posted by *amphead* /img/forum/go_quote.gif 
_btw, Thanks TomB! The extra-large Max t-shirt is a beauty! Should have pics on Head-Fi after the Fairfax meet when those become available. I actually wear something between a large and extra-large, so I wash an extra large in hot water and it shrinks to the right size. _

 

I hope that will work. Those t-shirts are high-quality _pre-shrunk_. Let me know if it still doesn't fit and we'll work something out.


----------



## 04BluMach

Quote:


  Originally Posted by *Negatron* /img/forum/go_quote.gif 
_Snip........
 When a tube has excess gas from age, the getter, the silver part can turn dark. That is no indication of a bad tube. In reality a dark getter is very efficient. It's when they shrink that they stop being effective. So if you get a pair and one darkens,don't jump on the phone and raise h*ll with the seller, the getter is just doing it's job. No problem exists usually.\_

 

As far as to why matching these tubes is not really required/recomended - we are really talking the law of diminishing returns for a number of reasons:

 These tubes are ALL between 46 and 50 years old. 
	

	
	
		
		

		
		
	


	




 As such, if they are NOS (Never been used), they have been sitting in wharehouses, etc for a long time slowly having their vacumn degrade.
	

	
	
		
		

		
		
	


	




 As noted by tomb, they take hours up to a couple of days of burn-in to stabilize. Negatron describes the process that these tubes go through during burn-in to reach a stable point. If the tubes aren't stable - you can't accurately determine their operational values to find a pair that come close to matching together.
	

	
	
		
		

		
		
	


	




 These tubes are only being sold for a couple of bucks. No where near the $30, 50, 80, 120, and up big $$$ that high demand HV Triodes are going for. Vendors offer pair "Matching" as a service to their customers of expensive tubes at a NOMINAL charge! For balanced operation - matching extends the potential life of an (very) expensive tube!!! 
	

	
	
		
		

		
		
	


	




 Since these tubes takes so long to stabilize - there is no way the vendors nominal fee is covering the cost to match these "cheap" tubes. For an expensive Mullard - it is a labor of love by one of these tube vendors. Not so for these funky car radio tubes that these Can nerds are clamoring for...
	

	
	
		
		

		
		
	


	




 The 12VDC Tubes being used for the Millet (MAX, etc) are some of the last tubes to be developed and produced within the US (till the transistor rapidly took over). They were developed by TungSol purposely for 12VDC Car Radios to eliminate the need for those POS HV vibrators. They were MASS produced from 1958 to 1962 by three companies in "State of the ART" assembly plants. As such, the tolerances between specific manufacturers plant tubes are fairly good. They are, surprisingly, pairly well matched already as long as they labeled by the same company (and we can adjust the bias voltage!). 
	

	
	
		
		

		
		
	


	




 If you really want to get tweaky for that important bit of bragging rights (and last ounce of balanced channel to channel performance). Burn-in a number of tubes - carry them to a Hamfest or a Geeky friend who has a tube tested siting on their kitchen table (like Negatron - LOL: allteeth
	

	
	
		
		

		
		
	


	




 to have them matched into pairs for you. There are even a few store/shops around with tube testers on their floor (don't ask, I don't know of any specifically!). But I wouldn't expect to get very good pair matching results from one of our NOS Tube vendors - its just too time consuming and they don't have the stock to pull from like they did before. Remember, the matching process is plug tube into tester, wait till stabilized, test and note values, pull tube out of tester, plug next tube into tester, etc, etc till you have a couple that have characeristic values that are close enough to each other to be declared a PAIR.....Yech!!! 
	

	
	
		
		

		
		
	


	




 And you thought HFE matching some little Transitors was a PITA and timeconsuming!!!
	

	
	
		
		

		
		
	


	




 Anyone who wants to get Geeky and learn more about this class of tubes, I dug deep into my URL favorites listings and pulled out this article on Space Charge Tubes .
 Edit:
 And no, the list at the bottom of the article is not all of the possible tubes that would work in your MAX. Only the 12AE6, 12AE6A, 12FK6, and 12FM6 are approved tube options. The rest of the list will not work, so don't try them!!!
 When all else fails and you have worried yourself sick - [size=small][size=medium]*Just Enjoy the Music!*[/size][/size]


----------



## rockcod

Quote:


  Originally Posted by *04BluMach* /img/forum/go_quote.gif 
_Well, now that the word is out.... I guess he won't have too many left by the end of the weekend!!
	

	
	
		
		

		
		
	


	




 Sounds like rockcod has moved his money out of the stock market and is reinvesting in 12AE6's .....
	

	
	
		
		

		
		
	


	


_

 

I did. I basically cleaned out their inventory


----------



## ruZZ.il

I hope you're keeping them for us


----------



## rockcod

Don't worry -- more is coming ... I hope


----------



## soloz2

well I was just casing up a Max this morning and I put the plastic gromets in the tube holes but they stick down to far... when I tried to slide the top off again the gromet got caught on some caps and pulled one or two out.


----------



## tomb

Quote:


  Originally Posted by *soloz2* /img/forum/go_quote.gif 
_well I was just casing up a Max this morning and I put the plastic gromets in the tube holes but they stick down to far... when I tried to slide the top off again the gromet got caught on some caps and pulled one or two out. 
	

	
	
		
		

		
		
	


	


_

 

Oops - sorry to hear that! Yes, it is a tight fit. Howver, you can push/pull the tube bushings up about 1/8-1/4" before pushing the lid in/pulling the lid out. That's usually enough to clear everything unless you have some caps taller than 1" (assuming 3rd slot from bottom in the Hammond).


----------



## n_maher

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Oops - sorry to hear that! Yes, it is a tight fit. Howver, you can push/pull the tube bushings up about 1/8-1/4" before pushing the lid in/pulling the lid out. That's usually enough to clear everything unless you have some caps taller than 1" (assuming 3rd slot from bottom in the Hammond). 
	

	
	
		
		

		
			



_

 

You can also use a small jeweler's screw driver and remove them if you're careful. 
	

	
	
		
		

		
		
	


	




 Just gently pry back on the clip on one side to get it started, then work on the other side.


----------



## slowpogo

How long can you expect tubes to last in the Max? Is it really necessary to have a stockpile of 20 tubes?


----------



## n_maher

Quote:


  Originally Posted by *slowpogo* /img/forum/go_quote.gif 
_How long can you expect tubes to last in the Max? Is it really necessary to have a stockpile of 20 tubes?_

 

Depends on a lot of factors really, rough guess several thousand hours.


----------



## amphead

Quote:


 Depends on a lot of factors really, rough guess several thousand hours. 
 

And then the Black Gates will have finally broken in.


----------



## Listen2this1

So, I am in the final stage of finishing the case for my Max, and I came up with a situation that I have a question about. First the case is all wooden except a the top plate which is aluminum. The tubes fit through the top plate. I am getting a hum when I put my hand above the amp, not even touching. This being my first tube build I am coming across some very interesting scenario's. If I ground the signal to the aluminum plate this goes away. So my question is, I understand that a ground is a ground, but is there a better place than others to ground a system Ie: ground at the signals ground, on one of the brass risers, at the same spot as the pot? Also is it a problem if the tubes rest on the aluminum plate, the hole is pretty tight tolerence, so they touch the sides a little.


----------



## tomb

Quote:


  Originally Posted by *Listen2this1* /img/forum/go_quote.gif 
_So, I am in the final stage of finishing the case for my Max, and I came up with a situation that I have a question about. First the case is all wooden except a the top plate which is aluminum. The tubes fit through the top plate. I am getting a hum when I put my hand above the amp, not even touching. This being my first tube build I am coming across some very interesting scenario's. If I ground the signal to the aluminum plate this goes away. So my question is, I understand that a ground is a ground, but is there a better place than others to ground a system Ie: ground at the signals ground, on one of the brass risers, at the same spot as the pot? Also is it a problem if the tubes rest on the aluminum plate, the hole is pretty tight tolerence, so they touch the sides a little._

 

First, let me qualify my statements to say that I am no expert in grounding. There are many people around here that can explain different grounding scenarios - I can't.

 There's no question that grounding the signal in the MAX is important. Grounding the pot is also important. However, I wouldn't count on a small jumper wrapped around a tiny screw in a plastic-bodied pot to ground the whole amp. In most cases, simply bolting the RCA jacks directly to the case (and through the bare metal in the drilled holes) is sufficient to ground the signal in the MAX. That's one of the reasons why I use and sell the RCA jacks without insulators.

 It's also the case that while the MAX is the same as the Millett Hybrid in being negative grounded, the MAX takes away that convenient path through the case by virtue of the AC supply connection: it must be isolated or 60Hz hum will result and you'll never get rid of it. If the grounding path is not there through the signal ground, though, that AC connection may still be picked up by the amplifier circuit.

 Since you don't have that with a wooden case, I would run a wire from the common connection of the RCA jacks to some sort of screw directly attached to the aluminum plate.

 As for touching the plate, that's not an issue per se, except for microphonics. I hate to say it, but a microphonic Millett tube is not that rare. However, it's quite possible to enjoy good sound with a slightly microphonic tube if the case is well supported. However, if the tubes are touching the metal case lid, the problems will be exacerbated. There's more than one reason for using the tube bushing besides covering a potentially unslightly hole edge.


----------



## el_matt0

hey all, im just in the process of re-casing and upgrading my millet to a a boutique build - just a quick question. to be honest - mainly for aesthetics - i am planning on putting 2 single ended outputs on the front plate, rather than just 1 as is standard practice in the millet max. is there any special consideration i should take when doing this (should i NOT do this), or can i simply just wire up two 1/4 jacks in series and voila? i realize you would only be able to listen to similar impedence headphones simultaneously at reasonable volumes, but could one persay drive two pairs of grados from the MHMax or is the mhmax specifically only "powerful" enough to drive one pair of cans at a time?


----------



## tomb

Quote:


  Originally Posted by *el_matt0* /img/forum/go_quote.gif 
_hey all, im just in the process of re-casing and upgrading my millet to a a boutique build - just a quick question. to be honest - mainly for aesthetics - i am planning on putting 2 single ended outputs on the front plate, rather than just 1 as is standard practice in the millet max. is there any special consideration i should take when doing this (should i NOT do this), or can i simply just wire up two 1/4 jacks in series and voila? i realize you would only be able to listen to similar impedence headphones simultaneously at reasonable volumes, but could one persay drive two pairs of grados from the MHMax or is the mhmax specifically only "powerful" enough to drive one pair of cans at a time?_

 

You may be stating "series" in a figurative sense, because you would want them wired in parallel. 
	

	
	
		
		

		
		
	


	




 There's no issue AFAIK, as long as the headphones are the same. Even different headphones with the same impedance would probably not be a good idea, because different sensitivies would still be involved. Also, if the two you use are Grado's, then you'd have 16ohms as the load. You might have to beef up the bias currents on the DB's to stay in Class A on the peaks.

 That's my guess, anyway. 
	

	
	
		
		

		
		
	


	




 The terminal block on the side of the headphone jack is already wired in parallel and may be the better way to go. However, the way it's setup is that the standard MAX headphone jack will switch that terminal block out when a pair of headphones is plugged into the board-mounted jack.


----------



## Negatron

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_< snip > The terminal block on the side of the headphone jack is already wired in parallel and may be the better way to go. However, the way it's setup is that the standard MAX headphone jack will switch that terminal block out when a pair of headphones is plugged into the board-mounted jack._

 

It'd probabably be easiest to put jumpers across the 2 rear most pad sets of the 1/4 jack and use the 3 terminal block for 2 front mounted Neutric panel jacks or whatever your choice is. If you need to revert later it would be simple to remove the cross jumpers and install the BOM spec'd jack.


----------



## ruZZ.il

with low impedance cans the bass may suffer a little too as the corner frequency is doubled, which may be negligible since we try to keep them so low to refrain from phase shift around 20hz anyway. So, there may be a little more phase shift around 20hz. Again, this may be negligible too since the caps are usually valued pretty high to prevent the effects mentioned above. This would only be an issue when using, say, 2 grados, or other low impedance cans. Clipping may indeed be a much bigger problem at louder volumes and a beefy amount of power-caps would be nice though we all already have those. For the few times that its nice to share the tunes it's probably worth doing and I wouldnt worry toooo much about the effects. For something a little more permanent if using similar low impedance cans: higher bias, larger heat sinks and more output capacitance may help.. or another MAX


----------



## Ech0

Hey, I've finished up my 2nd Millet Max and ran into a snag. When measuring the DB Bias, TB2L to TA2L & TB1R to TA2R, I got a reading of 0.00. I have set my DMM to 200m and/or 2000m (DCV) and I get zilch. Thoughts?? 

 The voltage is fine as is the tube bias, btw. 

 I did hear a "pop" after I had the Max on for a second or two. I looked over the board carefully and did not see anything that looked burnt or smelled anything. I don't know what other relevant information you may need.

 Any help would be appreciated. 

 Thanks,
 Echo

 Edit: I also turned the trimmers down until I heard a "click" before i started.


----------



## tomb

For your purview, the completed *MiniMAX*:
















_[size=x-small](click on the pics for bigger images)[/size]_

 Muse ES electrolytics,
 0.1uf 160V K42's on the output,
 RCA 12FM6 tubes,
 Sanyo 2SC2344/2SA1011 BJT's.

 I tend easily toward exaggeration, but it sounds very, very good. Another MAX lives!! 
	

	
	
		
		

		
		
	


	







 EDIT: That case is only 1-3/8" thick - total. 5-1/2" wide, 6-1/2" long.


----------



## soloz2

looks good too!


----------



## tomb

Quote:


  Originally Posted by *Ech0* /img/forum/go_quote.gif 
_Hey, I've finished up my 2nd Millet Max and ran into a snag. When measuring the DB Bias, TB2L to TA2L & TB1R to TA2R, I got a reading of 0.00. I have set my DMM to 200m and/or 2000m (DCV) and I get zilch. Thoughts?? 

 The voltage is fine as is the tube bias, btw. 

 I did hear a "pop" after I had the Max on for a second or two. I looked over the board carefully and did not see anything that looked burnt or smelled anything. I don't know what other relevant information you may need.

 Any help would be appreciated. 

 Thanks,
 Echo

 Edit: I also turned the trimmers down until I heard a "click" before i started._

 

It sounds like we need pics. Something's wrong. If you are using the right scale on the DMM (sounds like you are), you should read anywhere from 20-50mV on the DB's with the trimmers set to minimum. It will not be zero.


----------



## Ech0

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_It sounds like we need pics. Something's wrong._

 

Thanks for the fast response. Here's a pic. The pics average, hopefully, it will help. I can get one that's more clear (I must've been shaking.)






 The new Max looks very nice TomB. It's compact. Very neat as usual on the build. 

 Echo

 Edit: Changed the picture to a better one.


----------



## wquiles

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_For your purview, the completed *MiniMAX*:

 (snip)

 Muse ES electrolytics,
 0.1uf 160V K42's on the output,
 RCA 12FM6 tubes,
 Sanyo 2SC2344/2SA1011 BJT's.

 I tend easily toward exaggeration, but it sounds very, very good. Another MAX lives!! 
	

	
	
		
		

		
			








 EDIT: That case is only 1-3/8" thick - total. 5-1/2" wide, 6-1/2" long. 
	

	
	
		
		

		
		
	


	


_

 

Outstanding work TomB !!!

 Will


----------



## Negatron

Quote:


  Originally Posted by *Ech0* /img/forum/go_quote.gif 
_Hey, I've finished up my 2nd Millet Max and ran into a snag. When measuring the DB Bias, TB2L to TA2L & TB1R to TA2R, I got a reading of 0.00. I have set my DMM to 200m and/or 2000m (DCV) and I get zilch. Thoughts?? 
 <snip>
 Edit: I also turned the trimmers down until I heard a "click" before i started._

 

Just as a 'rule it out' check voltage across TB1 & TB2, since that gives total bias but likely 0 in your case. Then check for voltage on your jumpers at 8 & 9 to see if you've lost the DB.

 Hopefully (fingers crossed) it will turn out to be one of those 'head slapping' "That's all it was" things.


----------



## Negatron

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_For your purview, the completed *MiniMAX*:

http://www.paintedpostcards.com/misc3/MiniMAX-1-sm.jpg[/url]
 [url=http://www.paintedpostcards.com/misc3/MiniMAX-3.jpg][IMG]http://www.paintedpostcards.com/misc3/MiniMAX-3-sm.jpg[/url]
 [url=http://www.paintedpostcards.com/misc3/MiniMAXinside.jpg][IMG]http://www.paintedpostcards.com/misc3/MiniMAXinside-sm.jpg[/url]

 Muse ES electrolytics,
 0.1uf 160V K42's on the output,
 RCA 12FM6 tubes,
 Sanyo 2SC2344/2SA1011 BJT's.

 I tend easily toward exaggeration, but it sounds very, very good. Another MAX lives!! [img]http://www.head-fi.org/forums/images/smilies/http://hfimage.head-fi.org/smilies/biggrin.gif
	


 EDIT: That case is only 1-3/8" thick - total. 5-1/2" wide, 6-1/2" long. 
	
_

 
 


You are just plain evil! More to tempt the "build your own inclined"
 Conversation at the schoolyard....
 "C'mere Kid. Here is a free Millett. Ya' understand of course that you gotta' buy any more if you decide ya' like 'em"

 I can see it now, my friends saying "He had such a nice house, now he lives in that cardboard box under the overpass with all those headphone amps."

 Really, Really, nice looking amp Tom!


----------



## Ech0

Quote:


  Originally Posted by *Negatron* /img/forum/go_quote.gif 
_Hopefully (fingers crossed) it will turn out to be one of those 'head slapping' "That's all it was" things._

 

Yep, me slaps head, twice for good measure. 
	

	
	
		
		

		
		
	


	




 It just dawned on me, I used Toshiba 2SC2238 & 2SA968 transistors and forgot the very explicit footnote in the BOM.* "note reversed pinout"*. I'm a goof sometimes. 

 Now I guess the question becomes, did this ruin my transistors? I guess I can take them off the board and test them with the DMM? Any thoughts? And I'll have to figure out what's the best way to mount them on the board if they're okay. 

 Thanks all,
 Echo


----------



## tomb

Quote:


  Originally Posted by *Ech0* /img/forum/go_quote.gif 
_Yep, me slaps head, twice for good measure. 
	

	
	
		
		

		
		
	


	




 It just dawned on me, I used Toshiba 2SC2238 & 2SA968 transistors and forgot the very explicit footnote in the BOM.* "note reversed pinout"*. I'm a goof sometimes. 

 Now I guess the question becomes, did this ruin my transistors? I guess I can take them off the board and test them with the DMM? Any thoughts? And I'll have to figure out what's the best way to mount them on the board if they're okay. 

 Thanks all,
 Echo_

 

OK - little bit more than a head slap, but you may still be OK. Check the transistors with your DMM for HFE - they should register about 240 or thereabouts. If that's still OK, they may be alright. I would guess that one or more of them has fried, unfortunately. It's pretty hard to overcome a _soldered_ shorted connection.

 Remember that there is the location key diagram on the MAX website under Output Stage -> BJT Diamond Buffer:






 I wish I had more of those things for you. I have a standing order with MCMinone, but they've been projecting the delivery of the 2SC2238's for a couple of weeks, now. To be honest, though, the 2SC2344/2SA1011 pair is about 95% there if not equal to the Toshiba pair. You might give those a try until the others appear. (Assuming that yours are bad.)


----------



## tomb

Thanks for the comments on the MiniMAX, guys!! You are all very kind!


----------



## Negatron

Quote:


  Originally Posted by *Ech0* /img/forum/go_quote.gif 
_Yep, me slaps head, twice for good measure. 
	

	
	
		
		

		
		
	


	




 It just dawned on me, I used Toshiba 2SC2238 & 2SA968 transistors and forgot the very explicit footnote in the BOM.* "note reversed pinout"*. I'm a goof sometimes. 
 <snip>_

 

When computers became more common, I decided I wanted to take an advanced computer repair course at a local VoTech. Being a longtime 'E' hobbyist, I saw no need for the required 2 year electronics program required to take the advanced course. I was then interviewed by the Electronics instructors to find if I was 'qualified'.

 When asked why I thought I was experienced enough to skip the prerequisite courses, I replied:
 "Experience is directly proportional to the amount of equipment destroyed"
 "And I have destroyed a lot of crap in my life"
 After the laughter subsided, I was accepted.

 We have all been there or if not, will.


----------



## Ech0

Tomb, thanks for the quick reply. 

 I don't relish the idea of replacing the transistors more than once. So, I'll probably just order the 2sc2344/2sa1011's to replace them. I don't think it's worth taking a chance the Toshiba's are still good. Besides, I'm not going to hear the 5% difference between the two. 

 I'm going to check a local electronics place on the off chance they have the Toshibas and if not I'll be stopping by Beezar tomorrow morning.


----------



## Ech0

Quote:


  Originally Posted by *Negatron* /img/forum/go_quote.gif 
_
 When asked why I thought I was experienced enough to skip the prerequisite courses, I replied:
 "Experience is directly proportional to the amount of equipment destroyed"
 "And I have destroyed a lot of crap in my life"
 After the laughter subsided, I was accepted.

 We have all been there or if not, will._

 

LMAO & thanks.


----------



## pinkfloyd4ever

if you touch several or all of the metal tabs of the diodes in the PS would you get a little AC shock? Cause I've been shocked with 120 VAC before and it def felt like that, but weaker obv. Is that bad for the amp?

 edit: hmm maybe I was imagining things


----------



## amphead

Congrats TomB! Congrats CeToole! The miniMAX Lives!


----------



## fordgtlover

Very nice miniMAX Tomb. Your build quality is superb as usual.


----------



## luvdunhill

Tom:

 When using rubber cement to secure the drilling template, is it difficult to remove? Is it key to do the whole process in one sitting, or can I secure the template and do the drilling a day or two (or week) later? I'm thinking about using this technique on a large heatsink that I need to tap a number of holes in, with a decent amount of precision.

 Thanks!


----------



## tomb

Quote:


  Originally Posted by *luvdunhill* /img/forum/go_quote.gif 
_Tom:

 When using rubber cement to secure the drilling template, is it difficult to remove? Is it key to do the whole process in one sitting, or can I secure the template and do the drilling a day or two (or week) later? I'm thinking about using this technique on a large heatsink that I need to tap a number of holes in, with a decent amount of precision.

 Thanks!_

 

No - it's a piece of cake to remove from the metal or any non-porous surface. It rubs off in little balls similar to Play-Do or Silly Putty. 
	

	
	
		
		

		
		
	


	




 There is absolutely no chance that any of it will remain when you want to clean it off. It only takes few seconds to do it, too.

 The paper is a different story, however, but there's no need to save that anyway. The only thing you need to do is let the rubber cement dry on the metal and the paper before you put the two together. You will need some center alignment points on big pieces, though, because you absolutely can't re-position the paper if you get it wrong. Even that's no big deal - just rub the cement off the metal, print out another sheet of paper, paint on the rubber cement (let dry) and try it again.

 One tip is to maybe buy some rubber cement thinner - it can get fairly thick and you want the paper to lay as flat as possible on the metal. Part of the advantage of doing this is that the paper forms a pretty good protection for the surface against all those errant metal chips. It can't do that as well if pockets form underneath.

 Note that I still use a center punch just in case. 
	

	
	
		
		

		
		
	


	




 The principle of this technique came from painting cars and airplanes - you can come up with some very intricate designs using drafting vellum, which is semi-non-porous. When you stick the template down on a surface, you can use your fingers to rub away the rubber cement from the open surfaces. Then you seal the edges with some clear sealer and spray away. You're only limited by the complexity of the design that you can draw/plot and cut on the vellum. An important advantage is that this method will follow compound curved surfaces, too.

 I just updated the idea for use as drilling templates. Plus, it's pretty easy to use the same technique on some card stock to make up some actual endplate mockups.

 Sorry for the long-winded response, but thanks for the interest!!


----------



## luvdunhill

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_The only thing you need to do is let the rubber cement dry on the metal and the paper before you put the two together._

 

Tom:

 Thanks for the long reply. The only confusion I have is the above. By dry, do you mean dry completely, or just wait 60 seconds or so...


----------



## tomb

Quote:


  Originally Posted by *luvdunhill* /img/forum/go_quote.gif 
_Tom:

 Thanks for the long reply. The only confusion I have is the above. By dry, do you mean dry completely, or just wait 60 seconds or so..._

 

You shouldn't see any wet reflections. Otherwise, you'll be working with a gooey mess. 
	

	
	
		
		

		
			





 As you say, it takes about 60 seconds or so, but it depends on how thick it went on.


----------



## n_maher

Nice work as usual Tomb. I actually finished the board work on my second MAX last night.


----------



## tomb

Quote:


  Originally Posted by *n_maher* /img/forum/go_quote.gif 
_Nice work as usual Tomb. I actually finished the board work on my second MAX last night. 
	

	
	
		
		

		
		
	


	


_

 

Thanks, Nate!


----------



## slowpogo

Probably a well-covered topic, but I just got some Sylvania 12AE6's in the mail today, and one of them has a rattle. Nothing seems totally detached, since I can't see anything bouncing around. It seems to work fine, but I'm just wondering if it matters at all, if its life may be shortened by something being loose.


----------



## fran

Something I've noticed - since I started to build tonight, I gone back a few times to check out that I have pieces oriented Ok etc. Going through the build gallery it seems that loads of people have RA1L and RA1R and RR3 inserted in different ways. Just something I saw!

 Fran

 Fran


----------



## pinkfloyd4ever

look at tomb's build pics on the website for the correct orientation


----------



## tomb

Quote:


  Originally Posted by *fran* /img/forum/go_quote.gif 
_Something I've noticed - since I started to build tonight, I gone back a few times to check out that I have pieces oriented Ok etc. Going through the build gallery it seems that loads of people have RA1L and RA1R and RR3 inserted in different ways. Just something I saw!

 Fran

 Fran_

 

 Quote:


  Originally Posted by *pinkfloyd4ever* /img/forum/go_quote.gif 
_look at tomb's build pics on the website for the correct orientation_

 

Yes - it's been awhile since someone brought this subject up. If I remember correctly, there may in fact be an error with the direction of the arrow on the silkscreen. Whether that's true or not, the important key is the slight wing tabs on the silkscreen for the trimmers. That represents the epoxy side of the trimmer and sets the orientation.

 Because of the way the traces worked out in order to orient both tubes to the front, the trimmers for the L and R tubes are directly reversed from each other. That is as it should be.

 EDIT: Went too far and got confused as usual. Refer to Negatron's post if you read this before I edited it. The above statements are correct now.


----------



## tomb

Quote:


  Originally Posted by *slowpogo* /img/forum/go_quote.gif 
_Probably a well-covered topic, but I just got some Sylvania 12AE6's in the mail today, and one of them has a rattle. Nothing seems totally detached, since I can't see anything bouncing around. It seems to work fine, but I'm just wondering if it matters at all, if its life may be shortened by something being loose._

 

Sometimes bits of the mica spacers may break off or were bent/folded during assembly. That may be what's going on. If it biases and it sounds good, then it's probably OK. It depends on what you spent for it, though. If you spent $5 - $6 or more, then I'd ask for a replacement. If down in the $2-$3 range, then I'd just go ahead and use it.


----------



## Negatron

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_<snip>
 Because of the way the traces worked out in order to orient both tubes to the front, *the trimmers for the L and R tubes are directly reversed from each othe*r. That is as it should be.

 Another way to think about it is that the voltage set PS trimmer, and the tube trimmers all face to the front of the board. IOW, *when viewed from the front* of the board (Volume Pot end), [the plastic face of the trimmers - with printed designations, etc. are facing forward._

 

At least with my three boards there was/is a slight difference from that description. regarding* tube bias trimmers*
 With the outboard pins of the trimmers tied to the cathodes, both are reversed BUT,* one printing side is forward and one epoxy side is forward*. in each trimmer* the adjustment screw is inboard
*


----------



## tomb

Quote:


  Originally Posted by *Negatron* /img/forum/go_quote.gif 
_At least with my three boards there was/is a slight difference from that description. regarding* tube bias trimmers*
 With the outboard pins of the trimmers tied to the cathodes, both are reversed BUT,* one printing side is forward and one epoxy side is forward*. in each trimmer* the adjustment screw is inboard
*_

 

Oops. I woke up from conking out on the couch again and realized I made that mistake. It's been a long day. 
	

	
	
		
		

		
		
	


	




 Should've just posted this to begin with:


----------



## 04BluMach

Quote:


  Originally Posted by *Negatron* /img/forum/go_quote.gif 
_At least with my three boards there was/is a slight difference from that description. regarding* tube bias trimmers*
 With the outboard pins of the trimmers tied to the cathodes, both are reversed BUT,* one printing side is forward and one epoxy side is forward*. in each trimmer* the adjustment screw is inboard
*_

 


 Errrr, bet you can't say that three times really fast..... 
	

	
	
		
		

		
		
	


	




 Actually, I think the easiest way to remember is that all of the trimmers have their adjustment screw aligned closest to the center of the board. With the PS trimmer aligned to the right when viewed from the front panel. 

 Edit: Yep. thats it! Just like is shown in the pic tomb just posted... lol

 Or at least they do on my builds....


----------



## Negatron

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Oops. I woke up from conking out on the couch again and realized I made that mistake. It's been a long day. 
	

	
	
		
		

		
		
	


	


_

 

If I had a dollar for every time I got something mixed up when I was tired, I would have had a courier get out of a Bentley and hand deliver the orientation to Fran in Erie before his soldering iron got hot.


----------



## 04BluMach

Quote:


  Originally Posted by *Negatron* /img/forum/go_quote.gif 
_If I had a dollar for every time I got something mixed up when I was tired, I would have had a courier get out of a Bentley and hand deliver the orientation to Fran in Erie before his soldering iron got hot. 
	

	
	
		
		

		
		
	


	


_

 


 ..............Mine would be by Lear Jet


----------



## Negatron

Quote:


  Originally Posted by *04BluMach* /img/forum/go_quote.gif 
_..............Mine would be by Lear Jet 
	

	
	
		
		

		
		
	


	


_

 

Must be nice not to have made so many mistakes. 
	

	
	
		
		

		
		
	


	



 I never did say how I flew the Bentley over there on such short notice.


----------



## amphead

Ha Ha, you guys are nuts!
	

	
	
		
		

		
		
	


	










 You think I'm funny, as in I amuse you. Bang Bang. Dance dance. Spider go get me that drink.


----------



## fran

Thanks guys, I do have them in the correct way, but I was wondering!


 Fran


----------



## jamess71

TomB on the pics of your build on the max site. Where did you get the bushings for the tubes through the case? How about the pot knob? Thanks

 I'm at a standstill at the moment with my build. I figure if I post about it I'll get motivated to finish it. I'm still waiting on knockout punch set from harbor for the case work. Should I finish final assembly and test it without the case? Just do some loose wiring for all the IO's ? 

 On another note. My workbench has become such a mess It's not inviting anymore. 
	

	
	
		
		

		
			




 I really need to get it all straightend out again. What type of system do you guys use for sorting/organizing all you parts pieces and tools? I got a few of those drawer and cases for small parts I just need to figure out how to put them into action. 
	

	
	
		
		

		
		
	


	




 Later
 James


----------



## fordgtlover

^

 The information on the bushings can be found at:
MAX Drawings & Templates

 From memory Tomb's favourite knob supplier is:
eBay Store - PARTSPIPE: SWITCHES, Electronic accessories, Plugs Connectors

 I'm sure Tomb will correct me if this is incorrect.

 As to the question of whether you should finish before the case arrive - hell yes. I finished mine months ago and still listen to it everyday even though it's only partly cased up


----------



## tomb

Quote:


  Originally Posted by *fran* /img/forum/go_quote.gif 
_Thanks guys, I do have them in the correct way, but I was wondering!


 Fran_

 

It took quite an effort for us to tell you, didn't it? 
	

	
	
		
		

		
		
	


	











 EDIT: Exactly correct on James' questions fordgtlover!


----------



## Negatron

Quote:


  Originally Posted by *jamess71* /img/forum/go_quote.gif 
_<snip>

 On another note. My workbench has become such a mess It's not inviting anymore. 
	

	
	
		
		

		
		
	


	



 I really need to get it all straightend out again. What type of system do you guys use for sorting/organizing all you parts pieces and tools? I got a few of those drawer and cases for small parts I just need to figure out how to put them into action. 
	

	
	
		
		

		
		
	


	


_

 

It's really quite simple. Keeps lots of boxes labeled Digi-Key, Mouser, different size things from Newark, don't forget the 4 year old Mouser box labeled in felt tip pen marked Current project and the Digi-Key box with Dyna Mod on it (which one , I have 7) Priority mail boxes are great lots of room to scratch out labels and write amended ones. Lots of boxes from Triode electronics are good too.

 Then there are the new Beezar boxes marked MAX, MAX + Alien parts, MAX2 + revMH parts + Alien SCA35, and alway keep track of the parts removed from the boxes when you were searching last time and decided they needed to be in another box, but you weren't sure where it was buried at the time, so the parts got put in a bare spot on one of the benches.

 Never clean up often because it screws up your memory of what pile of stuff the things were in, even it if seemed to make no sense at the time. Lots of plastic containers, coolwhip tubs, butter tubs, lots of flip lid boxes with bunches of small compartments that used to make sense are a big plus. Big plastic buckets are good for transformers in smaller boxes or in plastic bags.with newspaper.

 Most importantly always know where the soldering station is and the solder and and extra wands plus the magnifying glass and tweezers. Keep at least 15" x 15" clear.

 If you have more than 6 projects going at once, set one or two lower priority items on top of the ones from last year that you can't find the critical parts for yet. But know you have them somewhere. (If that last damned girlfriend hadn't tried to be nice and straighten up.)

 Hope this helps. :
	

	
	
		
		

		
		
	


	




 Edit: Parts Connection has really nice boxes too.


----------



## jamess71

Thanks guys. Ok Negatron I get it. I guess I'm not in that bad a shape after all. 
	

	
	
		
		

		
		
	


	




 thanks for the tips. 
	

	
	
		
		

		
		
	


	




 I'm gonna get back to work on my 1st Max build tonight. Now I have to double check the trim pots too. That ebay store looks like a great place for knobs. Good prices too.


----------



## slowpogo

Quote:


  Originally Posted by *jamess71* /img/forum/go_quote.gif 
_That ebay store looks like a great place for knobs. Good prices too._

 

I have some solid aluminum knobs from there that I really like. But be prepared to wait about 3 weeks from the time you order to get them.


----------



## fran

Another Q:

 I'm doing the mosfet version. So I will be installing the compensation cap for the IRFZ24N. So I want to double check: Do the legs of the cap go to the 2 outside pins of the IRFZ24?

 Fran


----------



## tomb

Quote:


  Originally Posted by *fran* /img/forum/go_quote.gif 
_Another Q:

 I'm doing the mosfet version. So I will be installing the compensation cap for the IRFZ24N. So I want to double check: Do the legs of the cap go to the 2 outside pins of the IRFZ24?

 Fran_

 

This is highlighted on the MAX website at Output Stage -> MOSFET Diamond Buffer

 There is a pic of one of Ferrari's MAXes in the middle of the page. It shows the compensation cap attached to the outer legs.

 If you're building the MOSFET version, be sure you substitute the 2SJ74BL and 2SK170BL JFETs for QB2 and QB3, respectively. Also, RB2 and RB3 should be 1K. RB6 and RB7 should also be changed back to 100ohms.

 This information has not been updated yet on the MAX website.


----------



## slowpogo

Could someone briefly describe the main sonic differences between the BJT and the newly modified MOSFET buffers?


----------



## tomb

Quote:


  Originally Posted by *slowpogo* /img/forum/go_quote.gif 
_Could someone briefly describe the main sonic differences between the BJT and the newly modified MOSFET buffers?_

 

You'll have to wait until I build them. AFAIK, there's no one that has a good selection of both to compare. 
	

	
	
		
		

		
		
	


	




 P.S. I finally ordered the parts. I'm planning on a surprise or two, also.


----------



## slowpogo

OK, how about just the difference between BJT and the "standard" MOSFET build? I've never built anything with MOSFETs so I don't know what they sound like.

 A surprise or two? Cryptic..I'm intrigued


----------



## n_maher

Maybe Tom's going to liquid cool one of his MAX's so he can run unlimited bias? Muuuaaahahahahahahaha!


----------



## tomb

Quote:


  Originally Posted by *n_maher* /img/forum/go_quote.gif 
_Maybe Tom's going to liquid cool one of his MAX's so he can run unlimited bias? Muuuaaahahahahahahaha!_

 

Now, there's an idea!
	

	
	
		
		

		
		
	


	




 Nothing so dramatic, though - just a new look or two. Also, I've got high hopes for the JFET MOSFET mod, so I want to be sure to document it properly. I'll see if I can get that BOM changed this weekend, at least.

 P.S. As slowpogo has asked, it'd be nice to have a sound signature comparison of all of the different MAXes, too.


----------



## Negatron

I finally got the flock of Carbide Teeth Beavers to chew me a top to cool the MOSFETS. Thought I would post the finished piece. 
 Since the MOSFETS run about 6 watts I've been running without a top. For evaluation purposes, not laziness of course. Finally got off my butt tho...









 Edit:: Email inquiries have been made re: adjustment holes. The MOSFET bias across TB1,2 are through neoprene grommets on the bottom. Tube bias is adjusted by 'cheating' the twiddle stick at an angle through the Vreg TP holes, which are large enough to do so. everything was layed out symmetrically for aesthetics and hole count was what I thought was a minimum for the heat.


----------



## tomb

Whoa! Very nice!!


----------



## fran

Thanks TomB - I saw that picture but didn't realise you could click on it to make it bigger - I had tried that with the bottom pic. 

 I used the SJ74/SK170 from AMB and have them in reversed (compared to the original). Saw the bit about the resistors too - although I'm waiting on a few more parts from mouser. I'm about an hour away from firing this thing up, hope those parts come soon.

 Fran


----------



## fran

Negatron - nice work there! We posted simulatneously.

 The rack mount clone handles are a nice touch.


 BTW, I bought and have wired in a stepped attenuator from ebay. I haven't used it yet, but I'm not so sure about the feel of it. I don't know if I'm going to be able to live with the clicks! Anyway, we'll give a run for a while and see how it works out. I was at a hifi show last weekend and there was some gear there with stepped attenuators too - likewise there, I don't think I really like the feel of them. Theres something nice and slick about a nice smooth pot with a bit of resistance in the turn.

 Anyway, maybe it will be god in practice....

 Fran


----------



## joneeboi

Quote:


  Originally Posted by *Negatron* /img/forum/go_quote.gif 
_



_

 

Impressive work, Negatron. Makes me want to get one of those newfangled drill presses. How did you pull off that job?


----------



## soloz2

well I figure I'll post some pictures of one of the amps I built since I haven't posted pictures yet


----------



## wquiles

Quote:


  Originally Posted by *Negatron* /img/forum/go_quote.gif 
_I finally got the flock of Carbide Teeth Beavers to chew me a top to cool the MOSFETS. Thought I would post the finished piece. 
 Since the MOSFETS run about 6 watts I've been running without a top. For evaluation purposes, not laziness of course. Finally got off my butt tho..._

 

Outstanding work!


----------



## tomb

Quote:


  Originally Posted by *soloz2* /img/forum/go_quote.gif 
_well I figure I'll post some pictures of one of the amps I built since I haven't posted pictures yet
_

 

Very nice, Soloz! That CD goes really great with a MAX, too.
	

	
	
		
		

		
		
	


	




 Her voice just pours into the phones - sounds almost like she's breathing on you!


----------



## Negatron

TomB, Fran, wquiles, Thanks for the kind words.. 
 Soloz, really clean amp, it looks great!

 Tom is dead on target, Dianna Krall is incredible on the MAX as are many Female vocals. I've even dug out some older stuff because of this amp to see what it would do. Things I know by heart on speaker amps but havent listened to in a long time. Phoebe Snow, Early Grace Slick, early Allison Krause, I even dug out the old Linda Ronstadt, Nelson Riddle "What's New"(1983) great old stuff. AND! If you want shivers, listen to Enya's 'Shepherd Moons'.

 All of this is with the AMB jfet mod. Several have asked about sound signature and differences with both the AMB mod as well as MOSFETS alone.
 I suspect (hope) Tomb is going to do a side by side and so having converted both existing amps to jfet / MOSFET. I cannot compare directly, nor can I write as well either, so I'll be hoping to hear a side-by-side as well.

 My personal impressions are that the AMB jfet mod opens up the Space Charge tube.
 The change is not so much measurable as it is audible and thus subjective, so YMMV.
 I find it to have more natural ambiance and 'air'. The attack and decay of transients to be more natural than with the heavier loading of the BJT front end buffer The tube was never designed with an Audiophile in mind, but it is still a triode and more triode like it becomes with less load being presented to it's plate. A small degree of change I hear is in a different area, I can hear more clearly when I make a small change elsewhere in the amp. A cap change or a Bias change is 'easier' for me to detect with the mod. The tube seems less constrained and allows more subtleties to present themselves. 

 I gave up Hybrids a long time ago as not to my liking. Pete Millett's design and the efforts of all the people who tweaked his gift to where it is now changed that prejudice, And I'm glad, because I was running out of space for my tube monsters. 
	

	
	
		
		

		
		
	


	




 THANKS to all of you!

 --


----------



## Negatron

Quote:


  Originally Posted by *fran* /img/forum/go_quote.gif 
_<snip>
 BTW, I bought and have wired in a stepped attenuator from ebay. I haven't used it yet, but I'm not so sure about the feel of it. I don't know if I'm going to be able to live with the clicks! Anyway, we'll give a run for a while and see how it works out. I was at a hifi show last weekend and there was some gear there with stepped attenuators too - likewise there, I don't think I really like the feel of them. Theres something nice and slick about a nice smooth pot with a bit of resistance in the turn.

 Anyway, maybe it will be god in practice....

 Fran_

 

I started with a 36 stepped ladder with the Walnut based Ref amp you saw pics of. I purposefully designed the spacing of the output tube pair to accommodate it. It lasted about 2 weeks before I went back to an Alps.
 Surprisingly tiny difference in SQ and almost no difference in tracking, most all the Aps 27's I have used are no worse. If you can access the detentes, try using a Teflon lube and a 'Q-Tip' swab or the like to lube the 'clicks'. Over here, Break Free or Tri-Flow are good, but what ever you have access to.
 I have heard rumors that the Leprocauns have a process to distill the green mold that grows under the Blarney stone that is very slippery indeed.

 Patiently waiting for reports and photos of the final wooden masterpiece.


----------



## soloz2

Thanks! yeah, last night I just turned off the lights and laid down on the couch for a while before going to bed and listened to Diana Krall.


----------



## Negatron

Quote:


  Originally Posted by *joneeboi* /img/forum/go_quote.gif 
_http://farm3.static.flickr.com/2014/...6f873334_o.jpg
 Impressive work, Negatron. Makes me want to get one of those newfangled drill presses. How did you pull off that job?_

 

Well, you make dents with a big nail and use an old garage sale Craftsman drill and make sure to run the bit back and forth over a concrete block to sharpen it, and then.....
 Couldn't resist. Us dumb Southern boys at it again. I do a Layout on masking paper or 2" tape works good (3x). 
 An auto center punch really speeds things up, then pre-drill all with a 1/16" bit and deburr. For the holes a SHARP cutter or bit is a must, as well as clamping the work stationary for each cut. The sneaky part is cutting narrow strips of Scotch Brite pads and taping them to 1/8" & 1/4" arbors as buffers for a die grinder (or Dremel) to smooth up the holes. WAY cheaper than buying ready made wheels.

 Look close though and you'll see a couple of 'Oh, hell's' when the small bit walked anyway. A drill press or mill is almost a must but if you get a cheap one make sure the chuck doesn't walk or move at all from side to side, an older used one may be better than the real cheap ones that are around lately..

 Edit: Not to imply you have to have a drill press. A hand drill works if you clamp the work and work carefully.


----------



## thomaskuhn

Thanks for getting the Store up. I finally ordered a board for my brother in law. 

 Quick question, I had not checked the settings on my amp for some time, and finally decided to double check. Well the left tube was at 16.5V, while the other was down to 10V. Adjusted that, and finally readjusted the bias to 110mv from the 90mv I was running. Here is the strage thing, just before doing all this, I noticed that when I dragged my headphone cable across the desk, I would hear a little bit of static/noise in the left ear. When I turned the plug in the jack, I could hear it again, butit is not static but a tiny amplified version of the sound itself. Same thing touching the tubes. Which leads me to believe that it is... I can not remember the name of it... where physical vibrations cause the tube to make additional noise. What could be the reason for only hearing it in the left channel only. Could it be that the tube was running too hot for a while?

 Another strange behavior, is that when moving from 90mv to 110mv, the voltage just increased to 110, almost linearly. I still have the meter hooked up, and I am not seeing any post adjustment increase. It was also quite a few twists to get it there. 

 Tom


----------



## ruZZ.il

Microphonics? Some tubes are more sensitive than others. I'm sure someone can chirp about them better than me though. The tube variation over time is natural, specially with tubes that haven't been used for around 50 years. They should settle down though. Also, if the Transistors were already warm, re-adjusting them at that range by about 20% may not make a huge difference to their temp so they wont deviate too much when settling into their new bias current. Its when you re-bias and temps change a lot that you need to keep re-adjusting. You don't want to go over the hill though! but 110mv seems a tested and safe spot. Enjoy! And if the microphonics really bother you, you can try some other tubes..

 Also, while I'm posting, I haven't yet mentioned the outstanding builds and casework I've seen popping up lately, which deserves mentioning. Good work guys! 
	

	
	
		
		

		
		
	


	




 I hope to someday reach the great craftsmanship around, and I'm fortunate to have you guys as inspiration.


----------



## amphead

Quote:


 What could be the reason for only hearing it in the left channel only. Could it be that the tube was running too hot for a while? 
 

One procedure that I like to use for troubleshooting left vs right channel issues, is to just swap tubes left to right to see if the problem follows the tube swap. In this case it would probably pin down a single microphonic tube issue. Good Luck.


----------



## thomaskuhn

Thats it. The one tube was microphonic. I will just swap it out. Thanks everyone!

 Tom


----------



## Ech0

I finally finished up my MilletMax. I had a little setback when I incorrectly mounted my Toshiba Transistors. When I removed/tested them, every single one was toast. Anyway, now I have the 2SC2344/2SA1011's on the board and some Silmic II's. Other than that everything is pretty much straight off the BOM. 

 Thanks TomB / Beezar.com for getting the second set of transistors out to me quickly. 

 I made the top removable for easy adjustments....







 I'll post some more pics in the Picture/Build thread for anyone that's interested. 

 Ech0


----------



## Negatron

Quote:


  Originally Posted by *Ech0* /img/forum/go_quote.gif 
_I finally finished up my MilletMax. I had a little setback when I incorrectly mounted my Toshiba Transistors. When I removed/tested them, every single one was toast. Anyway, now I have the 2SC2344/2SA1011's on the board and some Silmic II's. Other than that everything is pretty much straight off the BOM. 

 Thanks TomB / Beezar.com for getting the second set of transistors out to me quickly. 

 I made the top removable for easy adjustments....

http://img406.imageshack.us/img406/9...ntanglenl4.jpg

 I'll post some more pics in the Picture/Build thread for anyone that's interested. 

 Ech0_

 

Incredibly detailed and magnificently executed build, Congratulations!
 One of the best looking MAX's posted. BTW, I very much like the sound (once broken in 
	

	
	
		
		

		
		
	


	




 ) of the Silmic's in the Millett circuit.


----------



## tomb

Quote:


  Originally Posted by *Ech0* /img/forum/go_quote.gif 
_I finally finished up my MilletMax. I had a little setback when I incorrectly mounted my Toshiba Transistors. When I removed/tested them, every single one was toast. Anyway, now I have the 2SC2344/2SA1011's on the board and some Silmic II's. Other than that everything is pretty much straight off the BOM. 

 Thanks TomB / Beezar.com for getting the second set of transistors out to me quickly. 

 I made the top removable for easy adjustments....

 <IMG>http://img406.imageshack.us/img406/9797/frontanglenl4.jpg</IMG>

 I'll post some more pics in the Picture/Build thread for anyone that's interested. 

 Ech0_

 

Very, very nice, Echo! The rest of your pics in the pics-of-your-build thread look fantastic! As one of the posters said, a great combination of metal, wood, and acrylic. Each component works to enhance the other. 

 I think you will enjoy those Sanyo transistors. They are very worthy substitutes for the Toshiba's. Strong and very deep bass, excellent mids, and a slightly more prominent high end to provide lots of air without tizziness.


----------



## rhester

tomb, how close are the 2SC2344/2SA1011's to the 968/2238 combo? I am finishing up my newest with BG and VitaQ and wanting something very nice to finish off.


----------



## tomb

Quote:


  Originally Posted by *rhester* /img/forum/go_quote.gif 
_tomb, how close are the 2SC2344/2SA1011's to the 968/2238 combo? I am finishing up my newest with BG and VitaQ and wanting something very nice to finish off._

 

This is subjective, of course, but I would say that they're 90-95%. They give up nothing in the bass and mids and are very neutral. Steinchen describes them as slightly bright:

  Quote:


  Originally Posted by *Steinchen* 
_crystal clear and airy, rather bright but not piercing bright. good detail and instrument seperation. well defined bass. sounds clean and analytical._

 

This may be one of those language difference things, however. 
	

	
	
		
		

		
		
	


	




 Instead of "rather bright," I would refer to the highs as _detail-enhanced_. When combined with the natural warmth and strong low-end of the MAX, I think it's a great combination. Ordinarily, something like this would have recessed mids or a fall-off in bass - these don't. "Clean and analytical" has it pegged.


----------



## Ech0

Hey Guys,

 Thanks! I can tell already that I will like the sound. The 2SC2344/2SA1011's / Max seems to pair up good with my K701's. 

 I have a matching switchbox that needs the end plates drilled and internals hooked up and then I'm really done. And, Nate made a suggestion that I intend to do re: ventilation.


----------



## tomb

Quote:


  Originally Posted by *Ech0* /img/forum/go_quote.gif 
_Hey Guys,

 Thanks! I can tell already that I will like the sound. The 2SC2344/2SA1011's / Max seems to pair up good with my K701's. 

 I have a matching switchbox that needs the end plates drilled and internals hooked up and then I'm really done. And, Nate made a suggestion that I intend to do re: ventilation._

 

That's great news!

 Oh - and I forgot:





 Another MAX lives!!


----------



## slowpogo

What are those little circular things on the heatsinks?


----------



## ruZZ.il

I believe they're ventilation holes in an acrylic case top. Really well done casework btw!


----------



## slowpogo

Ahh... 
	

	
	
		
		

		
		
	


	




 I thought they were some kind of thermal thing to make contact with the cover.


----------



## jamess71

Beautiful Casework ech0 

 So I finally got my Max fired up this weekend. Its an all stock BOM. At first I was unimpressed with the sound, no burn in and 12fk6 tubes. Well after a bit of burn in it really started to open up. Then I switched the tubes to 12AE6 and man what a difference. Thanks Negatron. The soundstage grew bigtime. 
	

	
	
		
		

		
		
	


	




 and also a bit more clarity and seperation between the instruments. 

 I'm gonna build a boutiqe next but in the meantime can I swap any of the caps out with k42's for an improvement? I have a large assortment of the russian K42's ranging from 0.047uF to 1.0uF 160V. If anybody wants to expreiment with them I have extras of most of them. 

 James


----------



## tomb

Quote:


  Originally Posted by *jamess71* /img/forum/go_quote.gif 
_Beautiful Casework ech0 

 So I finally got my Max fired up this weekend. Its an all stock BOM. At first I was unimpressed with the sound, no burn in and 12fk6 tubes. Well after a bit of burn in it really started to open up. Then I switched the tubes to 12AE6 and man what a difference. Thanks Negatron. The soundstage grew bigtime. 
	

	
	
		
		

		
		
	


	




 and also a bit more clarity and seperation between the instruments. 

 I'm gonna build a boutiqe next but in the meantime can I swap any of the caps out with k42's for an improvement? I have a large assortment of the russian K42's ranging from 0.047uF to 1.0uF 160V. If anybody wants to expreiment with them I have extras of most of them. 

 James_

 

Exchanging 0.22uf 160V K42's for the WIMA's in CA8 will effect a noticeable improvement in extended highs and smooth mids. Full details are on the MAX website at Tweaks -> K42 PIO Caps


----------



## vixr

Ech0, simply beautiful case work...another (stunning) MAX lives!


----------



## jamess71

TomB is beezar gonna have the 2SC2238/2SA968 BJT Diamond Buffers in this week? Where else can I get em if not? thanks

 James


----------



## tomb

Quote:


  Originally Posted by *jamess71* /img/forum/go_quote.gif 
_TomB is beezar gonna have the 2SC2238/2SA968 BJT Diamond Buffers in this week? Where else can I get em if not? thanks

 James_

 

The supplier (MCMinone) told me they shipped them to me today. So, I may have them in a few more days. Their website still says out-of-stock, so maybe they gave us dealers first crack at them. 
	

	
	
		
		

		
		
	


	




 Needless to say, I will update beezar as soon as I have them in my hands - but not before.

 I am not aware of anyone else that both sells them _and_ guarantees that they are the originals from Toshiba-Japan. There was another thread on Head-Fi about the perils of the Chinese versions. I have several of the those - from a reputable dealer who stated that they were Chinese - and there's a definite difference in sound quality. (I'm not selling them, though.) Otherwise, you would never know from appearance.


----------



## jamess71

Thanks TomB I'll wait to place my order then. I created an account and my order is ready to go when they arrive.


----------



## amphead

Well, the Fairfax show was incredible. Imagine listening with Orpheus phones to the APL NWO cd player. Very fluid sound with a real black between notes. Phenomenal. Another amp used the largest power tubes I have seen. The Russian GM70. The heaters are so large that the builder Frank Cooter uses a bench power supply to feed them current.





 It sounded awesome through some HP-1s. I did a fair amount of manning the Millett MAX display, explaining the build and most of those who listened to the MAX were quite impressed. Every time I left the MAX station I would come back to someone else, giving it a try. I managed not to get drunk, considering I tasted a little 144 proof bourbon. Just the fumes from the glass made my eyes water! The official Millett MAX t-shirt got some looks and a few mentioned that they are going to attempt to build a MAX of their own. Overall a very impressive show!


----------



## tomb

Wow! Them's some BIG tubes! Just looking at them compared to the "normally large" bakelite-based tubes next to them - one gets some idea of how large they really are. 
	

	
	
		
		

		
		
	


	




 Many, many thanks for your efforts in displaying the MAX!!


----------



## ruZZ.il

One of my tubes acted up. it started by suddenly just 'clicked' out of action.. well, it actually barely worked the volume on that side was VERY low. I didn't know it was the tube yet. What was strange was that when I turned the pot volume up, it just blended back into action. Every now and then, I can turn the pot down again and it sticks for a while. I figured it was either the pot or something bias-able. Switched the tubes around and it followed. Strange problem though, maybe somethings strange with the plate.. I'll just 'plop' ( 
	

	
	
		
		

		
		
	


	




 ) in a new one, but I'm all out of tubes.. EEEEK  
 Anyone had this kind of tube failure before? it seems odd...
 meanwhile, if its on max vol, and the source is low, I still listen comfortably, albeit with a higher noise level I guess which I cant really pickup anyway. I'll use a tube from my other MAX in the meantime anyway...


----------



## Negatron

Quote:


  Originally Posted by *ruZZ.il* /img/forum/go_quote.gif 
_One of my tubes acted up. it started by suddenly just 'clicked' out of action.. well, it actually barely worked the volume on that side was VERY low. I didn't know it was the tube yet. What was strange was that when I turned the pot volume up, it just blended back into action. Every now and then, I can turn the pot down again and it sticks for a while. I figured it was either the pot or something bias-able. Switched the tubes around and it followed. Strange problem though, maybe somethings strange with the plate.. I'll just 'plop' ( 
	

	
	
		
		

		
		
	


	




 ) in a new one, but I'm all out of tubes.. EEEEK  
 Anyone had this kind of tube failure before? it seems odd...
 meanwhile, if its on max vol, and the source is low, I still listen comfortably, albeit with a higher noise level I guess which I cant really pickup anyway. I'll use a tube from my other MAX in the meantime anyway..._

 

It is more likely the grid or the cathode, cranking it up re-establishes current flow. Have you cleaned the pins well?
 Also place a 600deg F or so soldering iron on the bottom of the tube pins to re-flow a possible cold pin solder joint. Those tubes were not high priority in the quality control department in their day. 
	

	
	
		
		

		
		
	


	




 If all else fails at least they are not 300B's, thus very cheap.


----------



## ruZZ.il

Thanks. That gives some insight 
	

	
	
		
		

		
		
	


	




 I'll try the solder>pin thing out next time I fire up my iron. It's had enough for today. I really need to get a new iron, too. For now, I'm sitting back listening to some g.dead with the tube I took from my other max. Tom ignited some incentive for me to bypass the ESs on my alien dac with some sonicaps gen IIs.. much better. The bass was drowning out the mid-> high detail before, the gen IIs bring it back forward again. I'm liking the ES/gen II Alien feeding BG/vit Qs. No equalization at all and it's exactly how I like it 
	

	
	
		
		

		
		
	


	




 The way it's meant to be.. where to from now, I dunno, but for now, I like the flow.


----------



## Listen2this1

Well I am Finally done with all of the case work, sort of. While I was doing some polishing I chipped the plexi, so when I get a chance to get back into the shop I will cut some more and try again.

 Thanks again Tom and the folks on the site for the help.


----------



## fran

Lovely case. The plexi is a nice touch and with the text - even nicer.

 Lovely build, well done.

 Fran


----------



## ruZZ.il

That.. is.. nice!


----------



## tomb

Quote:


  Originally Posted by *ruZZ.il* /img/forum/go_quote.gif 
_Thanks. That gives some insight 
	

	
	
		
		

		
		
	


	




 I'll try the solder>pin thing out next time I fire up my iron. It's had enough for today. I really need to get a new iron, too. For now, I'm sitting back listening to some g.dead with the tube I took from my other max. Tom ignited some incentive for me to bypass the ESs on my alien dac with some sonicaps gen IIs.. much better. The bass was drowning out the mid-> high detail before, the gen IIs bring it back forward again. I'm liking the ES/gen II Alien feeding BG/vit Qs. No equalization at all and it's exactly how I like it 
	

	
	
		
		

		
		
	


	




 The way it's meant to be.. where to from now, I dunno, but for now, I like the flow._

 

"ES/gen II Alien feeding BG/vit Qs" Exactly what I've been doing.


----------



## tomb

Quote:


  Originally Posted by *Listen2this1* /img/forum/go_quote.gif 
_Well I am Finally done with all of the case work. Sort of while I was doig some polishing I chipped the plexi, so when I get a chance to get back into the shop I will cut some more and try again.

 Thanks again Tom and the folks on the site for the help.





_

 

Oh wow!! I didn't see this until I posted that reply to ruZZ.il. Sometimes you are shocked about what happens while you're taking your time in editing a post. 
	

	
	
		
		

		
		
	


	




 Another MAX lives - with a logo, too! Very, very cool!


----------



## Negatron

Absolutly stunning build. The last several amps pictured have been very exceptional examples of the Craft. BTW, Fran (woodcraftsman) It would be a good time for a photo shoot.


----------



## amphead

Great job, TomB, Listen2this1, and Echo! 3 MAX's Live!


----------



## ruZZ.il

You guys in the states may have better finds, but I just got myself a little package of LEDs from besthongkong. I'm no candle meter, but I'm seeing spots 
	

	
	
		
		

		
		
	


	




 I'm not sure if they're the cheapest, but for a handful of leds I didn't really care.. and they got here. Happy camper


----------



## amphead

Quote:


  Originally Posted by *ruZZ.il* /img/forum/go_quote.gif 
_You guys in the states may have better finds, but I just got myself a little package of LEDs from besthongkong. I'm no candle meter, but I'm seeing spots 
	

	
	
		
		

		
		
	


	




 I'm not sure if they're the cheapest, but for a handful of leds I didn't really care.. and they got here. Happy camper 
	

	
	
		
		

		
		
	


	


_

 

That looks like a really good source RuZZ.il, and I might use it myself. Thanks


----------



## ruZZ.il

NP. There are probably places around you with no min, orders and stuff though. I saw a couple with either min orders, or 100pcs. I just wanted a little assortment without ordering 500pcs, so it suited me..
 I don't get the minimum order thing. Just add another 5$ or something.. it's like we're aliens, and there's some special procedure to ship to us... hmpf. USPS really isn't that expensive for little boxes to almost anywhere..


----------



## tomb

Well, I'm sad to report that the trials and tribulations of the Toshiba 2SC2238/2SA968 transistors continue. I received a big package from MCMinone today. Unfortunately, upon opening I found that the 2SC2238's were CDIL (Continental Device India Limited) transistors, not Toshibas. I thought perhaps something was fishy when they were sending me some, but at the same time failing to update their website to an "in stock" status for the 2238's. I'm going to be having a long phone call with them in the morning about returning these. I'll also find out the expectations of ever receiving the real thing. I will let you all know, but in the meantime, there's no predicting when they may appear.

 I may have to change beezar's expected delivery notice to "lead time 67 days."


----------



## pinkfloyd4ever

I thought firbra-brandt had them? or are those not genuine?


----------



## dragontooth67

I had an idea for you intrepid and experienced DIY MAX builders....

 Having gradually put together a Glass Jar Audio MAX kit over the last couple of weeks, today was the day when I finally plugged it in and saw the tubes light up for the first time....if only for a split second before my fuse blew. This was after reading the "Blow-by-Blow" biasing guide on the Max website, and thinking I had taken every precaution in the world to prevent possible damage to my new baby. After bypassing the fuse and "bumping" the amp on and off...more times than I care to admit, after reading pages and doing search upon search to find biasing help, I am as stuck as I was hours ago when my fuse blew. But my objective isn't to troubleshoot my particular build (that will probably come later...
	

	
	
		
		

		
		
	


	




); I have a suggestion/request that I believe would benefit many future generations of charitable MAX builders:

*What would one of you more experienced MAXers think about putting together a video that demonstrates how to properly bias a new MAX?* From initially setting the trimpots, showing a noob [like me] how to use a DMM, locating the test points, and showing what type of voltages one should be seeing. 

 Don't get me wrong, I do recognize that there is tons of info on this topic already contained in this thread, and on the MAX website. However, with the large number of MAX builders, and the relative ease with which one can burn out their valuable parts, one video might save dozens of future posts (and probably some new threads, for that matter) and much builder heartache/money. 

 Thanks for reading...I hope one of you builders will be inspired to undertake this task! Standby for more posts from me in the coming days...may Maxy is in a sorry state right now (and I swear it isn't the soldering!).

 ps: Needless to say I did do a quick YouTube search with a hope that such a video might exist, and was rather disappointed when a "millet max" search only returned a video about a vicious hamster named Max attacking his food (also needless to say I watched said video...).


----------



## willisv

This might be what your looking for:

Beezar.com


----------



## dragontooth67

willisv, looks like you are right. I had never seen that disk before, but its description is dead on. Looks like I might have to shell out an extra 8 bucks for such a video....I didn't expect something like that to exist in the DIY world.

 For anyone who has purchased the MAX's Owner's Manual cd, was it worth the purchase?


----------



## tomb

Quote:


  Originally Posted by *dragontooth67* /img/forum/go_quote.gif 
_willisv, looks like you are right. I had never seen that disk before, but its description is dead on. Looks like I might have to shell out an extra 8 bucks for such a video....I didn't expect something like that to exist in the DIY world.

 For anyone who has purchased the MAX's Owner's Manual cd, was it worth the purchase?_

 

Dragontooth, the MAX Owner's Manual CD is exactly that: an Owner's Manual. It's not a specific instruction manual for _building_. There are generalized videos for how to bias a _proven_ and operating MAX, but I'm not sure it would address your situation in _troubleshooting_ a build. The MAX website is the reference for that. Specifically, the Setup and Biasing page. Near the middle of that page, you will find a link for a Blow-by-Blow description of the biasing process. I think you will find that account to be as detailed as any you may find for a DIY headphone amp.

 Now, please don't lose heart. There are many of us who will help you - here, on DIYForums.org, and through PM's or e-mail. One of us has even taken delivery on a problem unit, fixed it, and returned it to a grateful builder. However, we need to start here first (since you posted here , first) - by defining your problem and going through it step-by-step. That's the first thing to do: exactly what is the trouble?

 Once we know that, we can offer several possibilities on how to fix it and will walk you through it the whole way. In the meantime, it's always helpful to post a good photograph or two - very often, we've been able to spot the problem in the first photo and fix it.

 P.S. I apologize for the fuse. Those that are familiar with this story can give you some insight. Suffice to say that it may be useful for saving your walwart. Every Class 2 plug-in transformer has protective circuitry. Unfortunately, most have protection that is non-resettable, meaning once tripped - the walwart is ruined. In that light, it should be sized at about 1A slo-blo. It is a useful feature when that is done, but it probably isn't necessary unless you are building up to a very high bias.


----------



## tomb

BTW, the Owner's Manual CD does have the entire MAX website on the CD, including the page and references I gave above, along with just about every historical reference for a Millett that exists. It's just that the videos are not done from a builder's perspective - more from an operational standpoint: how to disassemble the case, how to bias when the amp is cased up, how to adjust the tubes vs. DB's and the scales for each, etc.


----------



## dragontooth67

Thanks for the replies, TomB. I will probably post later this evening or tomorrow with some pictures and a more detailed description of my problems. I have just been double checking my build and searching through this thread a bit more to see if I can find a solution so I don't waste anyone's time. Its good to hear that this forum is here for me, though.

 One quick question so I have something to think about in the mean time....how long does it take of having too much voltage through the DB before you fry something? The longest I have had it on for at one time couldn't be more than 30 seconds, most of the time I do 5-10 second bumps. I realize this probably largely depends on how much voltage is going through the DB, but I was just hoping for a rough estimate (I know the Blow-by-blow says a "few minutes"). Thanks again.


----------



## tomb

Quote:


  Originally Posted by *dragontooth67* /img/forum/go_quote.gif 
_Thanks for the replies, TomB. I will probably post later this evening or tomorrow with some pictures and a more detailed description of my problems. I have just been double checking my build and searching through this thread a bit more to see if I can find a solution so I don't waste anyone's time. Its good to hear that this forum is here for me, though._

 

First - absolutely the forum is here for you. Second - please don't think you are wasting anyone's time. That is the point of this thread and the ones on DIYforums.org. We want to birth every MAX we can and make it an enjoyable experience for you. 
	

	
	
		
		

		
		
	


	




  Quote:


 One quick question so I have something to think about in the mean time....how long does it take of having too much voltage through the DB before you fry something? The longest I have had it on for at one time couldn't be more than 30 seconds, most of the time I do 5-10 second bumps. I realize this probably largely depends on how much voltage is going through the DB, but I was just hoping for a rough estimate (I know the Blow-by-blow says a "few minutes"). Thanks again. 
 

Well, again - a couple of things:

 1. The fact of the matter is that if you have the transistors actually installed and soldered in the board incorrectly, frying them is pretty much instantaneous. There's nothing you can do in that instance except replace them. Don't worry, though - that's not an intimidating thing to do: basically unscrew them from the heat sink, make a solder blob large enough to cover all three pins so that it stays melted, and pull. Some have suggested tying a string through the legs of the transistor so that you can pull at the same time you're melting and that may help. Cleanup with wick and lots of flux and you should be OK.

 2. The other way to fry the DB's is through heat (literally). If you encounter #1, they will only get warm once. If they are installed OK, though, and if you have taken care to screw down the trimmers (clockwise about 20 turns), then you have to actively adjust them to fry them. As long as you are watching the meter the entire time and only adjusting one, then the other, about 10mV at a time - the chances of burning them up are very slim.

 I'm hazarding a guess, but I think a few people may have just dialed those trimmers up like a volume knob without measuring each one, one-at-a-time, or walked off and grabbed a cup of coffee (or worse) while they burned up.

 If you are watching them the whole time, feeling with your hands, watching the meter etc., it's no big deal. Dial them immediately up to 100+mV and walk away, they probably won't be there when you get back. Poor heat sink mounting probably contributed to this in a few cases, too.

 I know that doesn't answer your question very well. All I can say is that anywhere over about 50mV, you need to let them settle for 1-2 minutes. Typically, adjusting the other channel another 10mV and then coming back to the previous channel for a check is sufficient. With proper heat sink mounting, there's no reason you should have to worry about anything until they get close to 100mV and above. With proper caution, that's no issue, either. At 110mV on the BJT's, they still run cooler than the LM317 in the back. Both are far less than their limits, too.


----------



## tomb

About the Toshiba's - 

 I've been on the phone with MCMinone a couple of times today. It turns out that 25 of what they shipped me are absolutely genuine. I'll adjust the in-stock status tonight accordingly (along with some coming additions).


----------



## pinkfloyd4ever

I have a muting circuit question. The delay seems way longer than necessary, to the point that it's kind of annoying. Which cap it is to use a smaller value of to make this faster? Was it CM3?


----------



## dragontooth67

Just an update on my Maxy....

 I was looking over the parts again, and it turns out, in my excitment upon receiving my heatsink mounting kits from TomB, I didn't pay attention to where I mounted those transistors (MJE243 vs MJE253). Turns out I needed to swap two of them....which I was able to do without actually removing the heatsinks (just unscrewed them, globed the soldering together as per your suggestion TomB, and it wasnt too bad). 

 After, my values started making sense. I have succesfully set the tube bias and the PS bias. Right now both my DB baises are in the mid 30mV, and I haven't started adjusting them yet, but everything seems to be as it should.

 I am stoked! I will update once I finally plug my hd650s into this bad boy...


----------



## tomb

Quote:


  Originally Posted by *pinkfloyd4ever* /img/forum/go_quote.gif 
_I have a muting circuit question. The delay seems way longer than necessary, to the point that it's kind of annoying. Which cap it is to use a smaller value of to make this faster? Was it CM3?_

 

It may be irritating, but the tubes aren't ready for good sound before 1/2 hr to 1 hr, anyway. Honestly, the delay could be 5 minutes and it wouldn't be a bother compared to how long the tubes really take before they sound their smoothest.

 The problem is that we are trying to protect headphones. Left sitting turned off, the delay may be 30-45 seconds. The problem is that if you happen to turn it off, and then turn it back on a few minutes later, that delay may be half of that 30-45 seconds. Then you're getting into the danger point.

 Turn your MAX on before anything else and forget about it - then listen later on when you're able. The tubes will be at their best if you do that.

 If you're determined to alter the delay, however, the number of seconds is determined by the RC product of RM2 x CM3. Reduce the size of either one, and you reduce the delay. Details may be found on the MAX website at Tweaks -> e12 Delay.


----------



## tomb

Quote:


  Originally Posted by *dragontooth67* /img/forum/go_quote.gif 
_Just an update on my Maxy....

 I was looking over the parts again, and it turns out, in my excitment upon receiving my heatsink mounting kits from TomB, I didn't pay attention to where I mounted those transistors (MJE243 vs MJE253). Turns out I needed to swap two of them....which I was able to do without actually removing the heatsinks (just unscrewed them, globed the soldering together as per your suggestion TomB, and it wasnt too bad). 

 After, my values started making sense. I have succesfully set the tube bias and the PS bias. Right now both my DB baises are in the mid 30mV, and I haven't started adjusting them yet, but everything seems to be as it should.

 I am stoked! I will update once I finally plug my hd650s into this bad boy..._

 

Hey, that's great news! Thankfully, I guess swapping PNP with NPN is not as bad as actually mis-orienting them.

 Keep us updated!


----------



## fran

Yes, another one lives!!!!


 Had a few little heart attacks biasing up - and I have a bit of ground buzz - but I'm fairly certain thats due to my power transformer. Other than that it sounds pretty OK!

 I did the amb mosfet mod, running 12AE6 right now with PS at 27V, and mosfet bias at 220mV. Once set the mosfet bias has stayed bang on, the tube bias has varied a bit though. Anyway, I need to leave it on for a while and let it run to make sure things are OK.

 Sounds nice so far, but need to do some comparisons between it and my revMH.

 Photos when I get a chance!

 Fran

 EDIT: a question I meant to ask earlier and couldn't see on the site: Does the e12 delay on the max protect against DC after the relay has clicked, ie like the full e12 from amb?


----------



## amphead

Congrats Fran! Another Max Lives!   

 Somewhere in the picture below is Amphead at the Fairfax meet. Can you spot Waldo?


----------



## dragontooth67

The latest....

 So I have everything biased to the T: And it was good. I checked the offset from the input ground to all the outputs, and everything was as the "blow-by-blow" said it should be (<1mV). So, just make things as simple as possible, I plugged my rat-shack interconnect into my iPod (at medium volume), put my Max volume at the min, slipped on my headphones (and plugged them in, duh) and pressed play. I gradually turned up the volume, expecting a new wave of audio-goodness to ooze out....and what happens.....?

 Nothing. I reach max volume, and I don't hear a thing coming out. I try plugging the interconnect into my computer, no difference. I unplug the RCA inputs and turn the volume up to see if there is any hiss or anything, and there is nothing. I used my DMM and did a continuity check between the mini-end of the interconnect and the top of the input terminal block on the PCB, just to make sure something wasn't grounding out where it shouldn't be, and everything is right as rain. I double checked my biases after my MAX has been "idling" for a few minutes, and everything is right were it should be (27V, about 13.5V on each tube, and around 90 mV for each DB). So now I am just confused and I return to Head-Fi.org....

 I suppose something could be blown, given my little transistor mix-up. But it seems like if that were the case, there would be some kind of hissing, some sort of burn mark on the PCB or a component, something. But there are none of these. 

 EDIT: I also just tried plugging in some low-impedance IEMs to see if I could hear any hissing, and there was still nothing (it was as if I hadn't plugged in my IEMs at all). I was under the impression that a higher-powered amp would produce some kind of hiss on IEMs without some type of gain switch...I don't know if this clue helps at all, but there it is.

 Any thoughts/ideas? I am not really sure what the next step is...I already combed the bottom of the board over before, looking for solder bridges, etc, and I don't think that is an issue (but if problems carries on for long I will post some pics and let you all be the judge). Thanks for the support...I will be here, wistfully gazing into these blue LEDs...


----------



## tomb

Quote:


  Originally Posted by *dragontooth67* /img/forum/go_quote.gif 
_The latest....

 So I have everything biased to the T: And it was good. I checked the offset from the input ground to all the outputs, and everything was as the "blow-by-blow" said it should be (<1mV). So, just make things as simple as possible, I plugged my rat-shack interconnect into my iPod (at medium volume), put my Max volume at the min, slipped on my headphones (and plugged them in, duh) and pressed play. I gradually turned up the volume, expecting a new wave of audio-goodness to ooze out....and what happens.....?

 Nothing. I reach max volume, and I don't hear a thing coming out. I try plugging the interconnect into my computer, no difference. I unplug the RCA inputs and turn the volume up to see if there is any hiss or anything, and there is nothing. I used my DMM and did a continuity check between the mini-end of the interconnect and the top of the input terminal block on the PCB, just to make sure something wasn't grounding out where it shouldn't be, and everything is right as rain. I double checked my biases after my MAX has been "idling" for a few minutes, and everything is right were it should be (27V, about 13.5V on each tube, and around 90 mV for each DB). So now I am just confused and I return to Head-Fi.org....

 I suppose something could be blown, given my little transistor mix-up. But it seems like if that were the case, there would be some kind of hissing, some sort of burn mark on the PCB or a component, something. But there are none of these. 

 Any thoughts/ideas? I am not really sure what the next step is...I already combed the bottom of the board over before, looking for solder bridges, etc, and I don't think that is an issue (but if problems carries on for long I will post some pics and let you all be the judge). Thanks for the support...I will be here, wistfully gazing into these blue LEDs..._

 

I think we need a pic of your relay-delay area. It sounds like the relay is not firing to close the circuit to the headphone jack.

 1. Did you jumper or install the output resistors?
 2. Is the BD139 in the relay circuit installed correctly? The molding line on the transistor edge is the rear - it faces to the back of the amp.

 Those are a couple of the common mistakes, assuming the tubes are lit, the DB's bias correctly, etc., etc.

 EDIT: A really bad possibility is that those MJE's you switched are actually fried. It may be possible if they were on the center sinks and you're only using the outside test holes to check the bias.


----------



## tomb

Quote:


  Originally Posted by *amphead* /img/forum/go_quote.gif 
_Congrats Fran! Another Max Lives!   

 Somewhere in the picture below is Amphead at the Fairfax meet. Can you spot Waldo? 

 <IMG>http://i207.photobucket.com/albums/bb308/tungstensilicide/moa.jpg</IMG>_

 

I believe I see a MAX t-shirt on some guy in the back. 
	

	
	
		
		

		
		
	


	




 Does that count or is it cheating?


----------



## dragontooth67

Good call on the BD139 TomB. I am pretty sure I have it in backwards, if I understand you correctly. The label on the relay should face the front of the amp, correct? I am currently in the process of desoldering it, but its a pain...I had to remove CM3 to get at the solder that keeps draining to the top of the board....ugh. With luck I will have it turned around by the time you read this. Also, I have 6 jumpers in right now....two for the output resistors (I think, not sure if those are the output resistors or not) and 4 for not using the MOSFET configuration (they are diagonal across the board). 
 Wish me luck...thanks again.


 EDIT: ITS ALIVE! After I finished soldering up, popped the tubes back in and slid it into the Hammond enclosure (minus front/back, and top of course) I plugged my iPod in and went through the same rigamarole. Once I pressed play, I heard nothing (the profanity did flow, you might say). But, as I was increasing the volume....BOOM it popped to life (and I remembered reading about the power on delay it has to prevent damage to headphones). 

 So I am proud to say...another MAX lives.


----------



## tomb

Quote:


  Originally Posted by *dragontooth67* /img/forum/go_quote.gif 
_Good call on the BD139 TomB. I am pretty sure I have it in backwards, if I understand you correctly. The label on the relay should face the front of the amp, correct? I am currently in the process of desoldering it, but its a pain...I had to remove CM3 to get at the solder that keeps draining to the top of the board....ugh. With luck I will have it turned around by the time you read this. Also, I have 6 jumpers in right now....two for the output resistors (I think, not sure if those are the output resistors or not) and 4 for not using the MOSFET configuration (they are diagonal across the board). 
 Wish me luck...thanks again._

 

Yep - definitely sounds like the BD139. The good news is that it's never been damaged for anyone that's had to turn it around.


----------



## tomb

Quote:


  Originally Posted by *dragontooth67* /img/forum/go_quote.gif 
_EDIT: ITS ALIVE! After I finished soldering up, popped the tubes back in and slid it into the Hammond enclosure (minus front/back, and top of course) I plugged my iPod in and went through the same rigamarole. Once I pressed play, I heard nothing (the profanity did flow, you might say). But, as I was increasing the volume....BOOM it popped to life (and I remembered reading about the power on delay it has to prevent damage to headphones). 

 So I am proud to say...another MAX lives._

 

Yay! Another MAX lives!! 
	

	
	
		
		

		
		
	


	







 Now I can go to bed.


----------



## amphead

Congrats Dragontooth67! Another Max Lives!   

 It will only sound better as it burns in. Then it will be hard to turn it off! 

 Yeah, that was Waldo on the second floor of Voltrons house. He called that the listening room. No loud talking, just equipment evaluating in there. Downstairs he had about 75% of the equipment, to give you some idea.


----------



## franky_s

Hello,

 in the last time I built a MHMax (a kit from Jeff Rossel). Unfortunatelly Jeff shipped some wrong resistors (10k instead of 1k for RA2L/R, RA4L/R and RB1L/R). He wrote me a mail about that and was so fast in his informations that I got his mail before his kit reached me!!! He prommised me to send the right resistors. Really great service, isn't it?
 Needless to say that I was not able to wait and built the amp with 6 cheap resistors I had on hand.
 The amp is alive and I am very satisfied with the sound! In fact I heared some of my CDs never with more satisfaction! 
 Meanwhile the 6 resistors reached me and I was able to swap the resistors in carefully.
 And now this is my question:
 Is it possible that I can hear a difference in SQ? For me the sound is now more detailed and less intrusive. Also the soundstage semms now more balanced. Is this possible or is it just my imagination? Waht do you think?

 Here are some pics (I will post some more pics in the "post pics of your builds"-thread later today):








 Right now I am listening to the CD "Arie Antiche" from Cecilia Bartoli and I can tell you: I never heared her so wonderful! My blood runs cold! The other CD I never heared so clear and enjoyable is the CD "Nwe Seasons" from Albrecht Meyer, Solo-Oboist of the Berlin Philh. Orchestra. If you like wood-wind instruments (and I like them - I am playing Bassoon) this CD is very very highly recommended.

 Last but not least I want to thank all the people involved in developing this great amp! Thank you very much! I am very happy with my MHMax.

 Regards,
 Frank

 p.s.: I forgot: How hot is the voltage regulator LM317 allowed to be? I heared from the "5 seconds finger on it rule of thumb", but if I'm honest, I can barely put my finger on the heatsink for 5 seconds. Is this OK? Now I'm a little bit afraid of closing the amp with my case-top.
 I use a wallwart with 24VAC/1000mA and I put a adhesive silikon insulator pad between the LM317 and the heatsink.


----------



## ruZZ.il

Firstly: CONGRATS on the new MAXs! Both dragontooth and franky!
 dt: Mistakes are a great way of learning, congrats on your new max and your newly acquired skills and knowledge in fixing things when they go wrong, and what to look out for next time 
	

	
	
		
		

		
		
	


	




. Also, good job on sticking with us. We've sadly had some that would have just quit where you went on..

 Franky:
 I dont believe RA2/4 would have much effect by using cheaper resistors but RB1 is directly in the signal path and probably does have some effect on the shound. Although I suspect what you're hearing may be due to the caps and tubes being a little more burnt in too. It really depends how bad the RB1s you were using were.. also, if the change was significant and discrete, it's most likely RB1s anyway.

 Regarding the Vreg. May I ask what the AC voltage measured on the input is, and what your DC voltage on the board is regulated to? The sink does get a little hot and its proportional partly to the difference between the effective input voltage and the DC output voltage. If your AC input is rather high (say, 24.5 even) it may be worth bumping up the regulated DC with the trimmer to 28 or so. Give us some measurements and we'll see what's good. Dont worry too much though, they do get HOT..

 And worthy of no less praise is Tom! Congrats on getting yet ANOTHER MAX alive!


----------



## slowpogo

Quote:


  Originally Posted by *franky_s* /img/forum/go_quote.gif 
_p.s.: I forgot: How hot is the voltage regulator LM317 allowed to be? I heared from the "5 seconds finger on it rule of thumb", but if I'm honest, I can barely put my finger on the heatsink for 5 seconds. Is this OK? Now I'm a little bit afraid of closing the amp with my case-top._

 

My power heat sink was the same way at first. But this definitely gets better with burn-in. After 150 hours or so, I could leave my finger on it indefinitely.


----------



## teNtiOn

Feel like building my first millette max with the Can't Miss MAX Build #1, using blackgate. But not sure to use MOSFET Diamond Buffer or the BJT Diamond Buffer. Which is the better choice and which transistor works better for blackgate?


----------



## franky_s

Quote:


  Originally Posted by *ruZZ.il* /img/forum/go_quote.gif 
_Firstly: CONGRATS on the new MAXs! 
 Franky:
 I dont believe RA2/4 would have much effect by using cheaper resistors but RB1 is directly in the signal path and probably does have some effect on the shound. Although I suspect what you're hearing may be due to the caps and tubes being a little more burnt in too. It really depends how bad the RB1s you were using were.. also, if the change was significant and discrete, it's most likely RB1s anyway.

 Regarding the Vreg. May I ask what the AC voltage measured on the input is, and what your DC voltage on the board is regulated to? The sink does get a little hot and its proportional partly to the difference between the effective input voltage and the DC output voltage. If your AC input is rather high (say, 24.5 even) it may be worth bumping up the regulated DC with the trimmer to 28 or so. Give us some measurements and we'll see what's good. Dont worry too much though, they do get HOT..

 And worthy of no less praise is Tom! Congrats on getting yet ANOTHER MAX alive! 
	

	
	
		
		

		
		
	


	


_

 

ruZZ.il, thanks for the reply. 
 About your questions concerning my power supply, I measured the following:
 28,6 VAC wallwart, unloaded (amp off)
 26,8 VAC wallwart, loaded (amp on)
 27,0 VDC regulated power supply for the amp

 some more infos:
 13,5V heater voltage at the tubes
 100mV bias voltage in the DBs

 At first, the heater voltage was not really stable, but now I think the tubes broke in a little bit and the 13,5 or 13,6V are nearly stable after lets say half an hour.

 I hope, this will help.

 @slowpogo:
 I hope you are right. I made this experience some months ago with a STEPS I built on perfboard. But there the heatsink was a little bit bigger. Indeed, this STEPS is running very cool now.


----------



## ruZZ.il

Franky: 
 The heat is most probably a result of the wallwart. To get an idea of how much power the regulator is dissipating in heat, we look at the difference in voltage between its unregulated DC in and its regulated DC out times the current (from P=V*I with an assumption that the regulator acts more or less like a resistive load). 
 To calculate the unregulated DC input we use:
 [(AC input under load)-1.4)]*sqrt(2)*0.9
 This is effective(measured) AC , minus 1.4v from the voltage drop on the 2 diodes that the current goes through in each direction, times sqrt(2) to get to the peak of it times 0.9 to get the effective dc after the caps.. IIRC and am thinking straight.
 In order to get optimum performance, the voltage regulator needs a margin of about 3 volts between its input and output.
 So, optimally, to calculate the best working voltage to use, we'd be looking at:
 [(AC input under load)-1.4)]*sqrt(2)*0.9-3
 In your case, that equals 29.3 volts which is still a safe working voltage for the MAX.
 Assuming you have 600mA running through your amp, that would be 0.6*3=1.8Watts.
 At 27 volts, you have [[(AC input under load)-1.4)]*sqrt(2)*0.9-27]*0.6~=3.2Watts.
 by re-adjusting your voltage to 29v you'll effectively be dissipating only about 40% heat of what you currently are!

 It's what I'd do, but I'd wait for the green light from the more knowledgeable MAXers around here before you get going.

 edit: I may have the order in the equation a little mixed up, but the difference isn't that much. I still believe that changing the regulated DC to 29v will leave adequate headroom for good regulation and drop the heat dissipation by a good watt and a half or so. you may even get away with 29.5, but I'd go gradually.. sides, it can handle quiet a bit of heat anyway, so no harm playing it safe.

 teNtiOn: I'm not sure anyones compared the 2 configurations using blackgates, although possibly someone with more experience using different combinations of the 2 could help you out.


----------



## tomb

ruZZ.il,

 Your calcs are correct and impressive as always. However, a 26.8VAC walwart loaded is _below_ the range we anticipated in the MAX power supply. There should be no issue with this input voltage and the associated wattage burned off by the heat sink - at 27VDC (assuming a 1" sink). For most of the ones I've experimented with, a 3V drop through the LM317 is really a bit low. I think the LM317 needs more than that. So, he may be on the ragged edge attempting to bump up to 28VDC on the Vset.

 It is true that the LM317 is the hottest device on the board - even including the tubes, if I remember from my last measurements. However, if the sink is that hot to the touch, I would think it's doing the job and carrying away most of the heat from the LM317. Most of my measurements with MAX sinks almost too hot to touch result in about ~50-60 deg.C. I think we can all go to 70 deg.C. or more before even starting to worry. 

 It is also true that "burning in" will result in a little cooler temperatures. That seems to be the nature of the adhesive Bergquist-like heat sink pads. It may take a little while for the material to "form" to the surface imperfections on the sink and the transistor back.

 All that still may mean he needs some cooling holes in that case lid. It looks like that's finished, but I've seen at least one other builder cut a hole through the backplate - that will probably work just as well. EDIT: A second look shows plenty of holes - it should be fine!!


 EDIT: Note that for "break-in" of any mechanical/thermal device, the cool down is just as important as burn-in. You will probably need to let it cool completely down a couple of times for the pads to have maximum effect. Straight burning-in is not as advantageous in this regard.


----------



## tomb

Quote:


  Originally Posted by *teNtiOn* /img/forum/go_quote.gif 
_Feel like building my first millette max with the Can't Miss MAX Build #1, using blackgate. But not sure to use MOSFET Diamond Buffer or the BJT Diamond Buffer. Which is the better choice and which transistor works better for blackgate?_

 

teNtiOn,
 ruZZ.il is correct in this, too. I am working on two MOSFET builds using Amb's JFET MOSFET mod, but it will be next week before I have anything specific to report. We obviously have a couple of builders who are have lavished outstanding praise on the JFET MOSFET version, but that's not really a comparison to the BJT versions. I'm probably the only one who has built so many MAXes that will be in the position to judge. (that's embarassment for that, not bragging) 
	

	
	
		
		

		
			





 I'm also working on some testing procedures for each to see if the various BJT versions and MOSFET versions actually have measureable differences (as ruZZ.il can probably guess from my Alien DAC experiments).

 That said, I would highly recommend the BJT version for the time being. The MOSFET versions use a bias so much higher than the BJT's that I would call any MOSFET build "advanced." Part of what I am working on is a mini-website section devoted exclusively to a MOSFET build. So, I am hopeful that will help things tremendously. However, that is not available for the time being.

 My personal opinion is that everyone needs more than one MAX. 
	

	
	
		
		

		
		
	


	




 So, I would recommend a BJT version, first - in most circumstances.


----------



## franky_s

@ ruZZ.il and tomb:

 Thanks for the detailed calculation and for the informations on burning in. 
 Tomb, if I understand you right you would NOT trimm the Vreg to 28VDC? Is this right? Maybe I should only be patient and wait a couple of working-hours.


----------



## tomb

Quote:


  Originally Posted by *franky_s* /img/forum/go_quote.gif 
_@ ruZZ.il and tomb:

 Thanks for the detailed calculation and for the informations on burning in. 
 Tomb, if I understand you right you would NOT trimm the Vreg to 28VDC? Is this right? Maybe I should only be patient and wait a couple of working-hours._

 

Yes, IMHO, you should leave it at 27VDC. The LM317 performs better with a bigger voltage drop - up to 5V. Your walwart doesn't appear to have voltage any higher than most MAXes (probably less). I would guess you could get about 28.5VDC or 29VDC max, but you may be losing some of the ripple reduction in the LM317 at that. Leave it at 27VDC and see if the heat gets better.


----------



## ruZZ.il

I stand corrected with my recommendation then 
	

	
	
		
		

		
		
	


	




 Though, I'm quiet surprised most wallwarts have such a high unloaded output. I guess mine is pretty good then with 25.1 unloaded and 24.6 loaded with my MAX, though it does give me quiet a tight margin for regulation. That being said, with just a 2~3v regulation, I have no complaints with its performance.


----------



## tomb

Quote:


  Originally Posted by *ruZZ.il* /img/forum/go_quote.gif 
_I stand corrected with my recommendation then 
	

	
	
		
		

		
		
	


	




 Though, I'm quiet surprised most wallwarts have such a high unloaded output. I guess mine is pretty good then with 25.1 unloaded and 24.6 loaded with my MAX, though it does give me quiet a tight margin for regulation. That being said, with just a 2~3v regulation, I have no complaints with its performance._

 

Oh - no corrections! We are only talking opinions here ... and you know what they say about opinions ... 
	

	
	
		
		

		
		
	


	




 My walwarts measure about 26VAC loaded, so maybe I'm splitting the difference.

 Franky_s - just to be sure, if you don't have a thermocouple-equipped multi-meter, stick the tip of a cooking thermometer to the heat sink and tell us what it is. EDIT: Better forget that one - mine is covered with enough shortening that it doesn't make good contact.


----------



## fran

OK I said some pics would be forthcoming:























 I got the hum issues sorted handy enough, all I hear now with the volume right up is some rushing - which I presume is thermal noise.

 Amp seems stable too, although I'll give it another few hours before resetting bias etc.

 Fran


----------



## Negatron

Quote:


  Originally Posted by *fran* /img/forum/go_quote.gif 
_<snip>

 I got the hum issues sorted handy enough, all I hear now with the volume right up is some rushing - which I presume is thermal noise.

 Amp seems stable too, although I'll give it another few hours before resetting bias etc.

 Fran_

 

A really nice looking Amp Fran. And I do believe you have re-defined the term for "Hum-Bucket" Quite an creative solution. 
	

	
	
		
		

		
		
	


	




 Nice looking 'step', hope you get used to it. BTW the rushing noise may burn off as the tubes settle in.

 It seems officially "Another MAX Lives!"


----------



## ruZZ.il

Fran, congrats! looks like a solid build, and yeah, x2 on the "Hum Bucket"  hows the heat buildup in there with no ventilation?..

 Meanwhile, I did some power-on scoping to see what the whole tube-issue is, and came up with these:

 This is at 5 second for the whole line. The blur is about 3v peak to peak. The rest are other time/voltage variations I was to lazy to record, but some can be made out anyway. 













 Anyone got an explanation for the voltage blur?
 I assume the different timing that it took to occur was due to the start-up temp and stuff. I'm guess it has something to do with an initial charging of the space before it gets constant.. maybe thats when the thermal energy is around equal to the work function?.. someone?


----------



## fran

Hum-bucket!

 Actually hum-paint-can-with-end-cut-off! Its coated with a special type of paint which effectively cuts down on EMI. All the internal wires are coated in the same stuff. I had forgotten to do the back of the stepped attenuator and that was the source of the hum I spoke of earlier. 
	

	
	
		
		

		
		
	


	










 ruzz.il - theres a good bit of ventilation, the board is on 12mm standoffs and underneath that is a panel of 6mm holes in the alu base that the whole thing sits on. There are more holes then in a pattern in the plexi top.

 its actually amazing to hear the burn in. I reckon its been on now for about 6 hours and its improved quite a bit in that time. Its easy to be skeptical of burn in - and I have had different experiences of it. On a phonostage I built one time the burn in period was about 3 weeks - very clearly defined changes over that 3 weeks. On my aikido preamp, absolutely nothing changed form the first moment I powered it up.

 Its really odd how somethings change so much and others so little. No wonder there are such arguments about it.


 Fran


----------



## Negatron

Quote:


  Originally Posted by *ruZZ.il* /img/forum/go_quote.gif 
_<clip from previous post:
 I stand corrected with my recommendation then Though, I'm quiet surprised most wallwarts have such a high unloaded output. I guess mine is pretty good then with 25.1 unloaded and 24.6 loaded with my MAX, though it does give me quiet a tight margin for regulation. That being said, with just a 2~3v regulation, I have no complaints with its performance._

 

Just to ad to the 'data pool' my Jameco 1250ma 'line' wart puts out 27.8 unloaded and 26.6 loaded (Fluke meter) With an LM338, the reg output goes south at 29.2 running 110ma bias on the MOSFETS. I've scoped V with dynamic E-Dance music @ 28v regOut and rock stable it is.

  Quote:


  Originally Posted by *ruZZ.il* /img/forum/go_quote.gif 
_Fran, congrats! looks like a solid build, and yeah, x2 on the "Hum Bucket"  hows the heat buildup in there with no ventilation?..

 Meanwhile, I did some power-on scoping to see what the whole tube-issue is, and came up with these:

 This is at 5 second for the whole line. The blur is about 3v peak to peak. The rest are other time/voltage variations I was to lazy to record, but some can be made out anyway. 
http://i262.photobucket.com/albums/i.../DSC_00081.jpg
http://i262.photobucket.com/albums/i.../DSC_00041.jpg
http://i262.photobucket.com/albums/i...p/DSC_0016.jpg

 Anyone got an explanation for the voltage blur?
 I assume the different timing that it took to occur was due to the start-up temp and stuff. I'm guess it has something to do with an initial charging of the space before it gets constant.. maybe thats when the thermal energy is around equal to the work function?.. someone? 
	

	
	
		
		

		
		
	


	


_

 

A wild guess is the electron cloud forming on cathode warm up, but space charge tubes are a bit strange, it may be a very temporary connection to the 13th dimension. 
	

	
	
		
		

		
		
	


	




 But very interestings data, thanks for taking the time. More food for thought.


----------



## soloz2

Just listened to a Max with a pair of Beyer 880's with a silver cable. Very detailed with some slam 
	

	
	
		
		

		
		
	


	




 great match!


----------



## franky_s

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Franky_s - just to be sure, if you don't have a thermocouple-equipped multi-meter, stick the tip of a cooking thermometer to the heat sink and tell us what it is. EDIT: Better forget that one - mine is covered with enough shortening that it doesn't make good contact. 
	

	
	
		
		

		
		
	


	


_

 

I had tried to measure the temperature with my multimeter, but thought, the contact area was to small to make a good measurement. And if you press the end of the thermo-wire with your finger onto the heatsink, your finger will get very hot...
 Now, after your post tomb, I thought of using a small stick of wood (not metall because of the high heat conductivity) to press it down.
 And I think it worked! I read a stable value of about 55°C and if this is the correct value (maybe I had to add for example 5°C) the LM317 should survive this, right?

 p.s.: Unfortunatelly I have no cooking thermometer...


----------



## tomb

Quote:


  Originally Posted by *franky_s* /img/forum/go_quote.gif 
_I had tried to measure the temperature with my multimeter, but thought, the contact area was to small to make a good measurement. And if you press the end of the thermo-wire with your finger onto the heatsink, your finger will get very hot...
 Now, after your post tomb, I thought of using a small stick of wood (not metall because of the high heat conductivity) to press it down.
 And I think it worked! I read a stable value of about 55°C and if this is the correct value (maybe I had to add for example 5°C) the LM317 should survive this, right?

 p.s.: Unfortunatelly I have no cooking thermometer...
	

	
	
		
		

		
		
	


	


_

 









 Your 55°C is exactly what I'd expect. Actually, the LM317 is good for 125°C, but we want a sizable safety factor. That's why I was suggesting that we're fine until it gets into 70°C territory. Even then, as long as it stabilizes, it should be OK. The real question is whether it spirals into runaway. Bottom line, the PS sink - even at 1" high - will tolerate higher temperatures without damaging the LM317.

 BTW, the thermocouple should be sensitive enough to work by just holding the tip on the body of the LM317. Typically, the metal tab is hotter and you should not detect a significant difference between the metal tab temp and the surrounding sink.

 Bottom line: you are fine. Also - nice case top!!


----------



## tomb

Quote:


  Originally Posted by *fran* /img/forum/go_quote.gif 
_Hum-bucket!

 Actually hum-paint-can-with-end-cut-off! Its coated with a special type of paint which effectively cuts down on EMI. All the internal wires are coated in the same stuff. I had forgotten to do the back of the stepped attenuator and that was the source of the hum I spoke of earlier. 
	

	
	
		
		

		
		
	


	










 ruzz.il - theres a good bit of ventilation, the board is on 12mm standoffs and underneath that is a panel of 6mm holes in the alu base that the whole thing sits on. There are more holes then in a pattern in the plexi top.

 its actually amazing to hear the burn in. I reckon its been on now for about 6 hours and its improved quite a bit in that time. Its easy to be skeptical of burn in - and I have had different experiences of it. On a phonostage I built one time the burn in period was about 3 weeks - very clearly defined changes over that 3 weeks. On my aikido preamp, absolutely nothing changed form the first moment I powered it up.

 Its really odd how somethings change so much and others so little. No wonder there are such arguments about it.


 Fran_

 

Hum-bucket, indeed!!
	

	
	
		
		

		
		
	


	




 Your coating reminds me of the stuff we used at Lockheed on the F-22 - but I can't talk about that. 
	

	
	
		
		

		
		
	


	




 I was only involved in the design of the facilities used to coat it, though - not the plane itself.

 Anyway, very nice build, Fran!!

 Yes, there's no doubt in my mind that burn-in helps the MAX. Tubes aside (which may take days to burn-in properly), ES caps and even the Russian K42's benefit from at least 6 hrs run-in, IMHO. You can tell a major difference after about 2-4hrs. Of course, Black Gates are worse than the tubes.


----------



## tomb

I've added some resistors to you-know-where that you may find very interesting. 
	

	
	
		
		

		
			





 However, we must respect Head-Fi sponsors. *So, do not ask me questions or discuss the subject in this thread or elsewhere on Head-Fi.* I would not mention it at all, except that someone is bound to post something and may still do it, anyway. Thanks.

 12AE6 and 12FK6 tubes will be added in a couple of days. 
	

	
	
		
		

		
		
	


	





 EDIT: Gosh. I didn't mean to scare anyone - just requesting that you not ask questions about those resistors on the open Head-Fi forum. It's one of those things like asking about how to clone certain name-brand amps, etc.


----------



## tomb

EDIT: Double post.


----------



## franky_s

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_








 Your 55°C is exactly what I'd expect. Actually, the LM317 is good for 125°C, but we want a sizable safety factor. That's why I was suggesting that we're fine until it gets into 70°C territory. Even then, as long as it stabilizes, it should be OK. The real question is whether it spirals into runaway._

 

Thanks tomb for the confirmation. I will stay with Vreg 27VDC. And just to be on the safe side, I will drill some holes in the back side of the case as you suggested. Just to get a little bit of a air flow.

  Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Also - nice case top!!_

 

Thanks. It took me quite some time to drill these holes. But you know that...


----------



## tomb

Quote:


  Originally Posted by *franky_s* /img/forum/go_quote.gif 
_Thanks tomb for the confirmation. I will stay with Vreg 27VDC. And just to be on the safe side, I will drill some holes in the back side of the case as you suggested. Just to get a little bit of a air flow._

 

You might want to slide that lid on first and snake your thermocouple through one of the cooling holes to check the temp. You may be surprised to find that you'll be fine.

 As a matter of fact, I suspect that there's quite a potential for radiative heat transfer between the sinks and the case lid. Your cabinet-pull rollbars will end up rejecting tons of heat. I've found on mine that I can actually bias much higher with the rollbars than without.

 Just something to consider before you go drilling more holes. Another think to consider: unlike the BJT's or MOSFETs in the output stage, the LM317 is actually an integrated chip. It has its own thermal protection circuitry. So, it will shut itself down if it gets too hot. The bottom line is that what you're seeing with heat is the norm - not an unusual case.

  Quote:


 Thanks. It took me quite some time to drill these holes. But you know that...
	

	
	
		
		

		
		
	


	



 

Yes, well mine usually show some defects if you look closely. Yours don't - great job!


----------



## amphead

Good info TomB! Well, sorry to say that I am no longer CTO at HFE Electronics. There were 5 board members and now there are 4. The secretary instigated a coup de etat, while I was at the Fairfax show and I was voted off of the board. He was jealous of the fun and success that we all enjoy here. It would have been nice to order the electronic parts that we use at a discount, but there you have it. Just a heads up, that if you form a corporation, watch out for rats! 
	

	
	
		
		

		
		
	


	




 I'm over it now, but believe me I was steamed at first. 
	

	
	
		
		

		
		
	


	




 I didn't lose my investment capital, just a little pride. I was handed a check for the $5,000.00 I paid to be on the board, and I handed him my keys to the store.


----------



## tomb

Quote:


  Originally Posted by *amphead* /img/forum/go_quote.gif 
_Good info TomB! Well, sorry to say that I am no longer CTO at HFE Electronics. There were 5 board members and now there are 4. The secretary instigated a coup de etat, while I was at the Fairfax show and I was voted off of the board. He was jealous of the fun and success that we all enjoy here. It would have been nice to order the electronic parts that we use at a discount, but there you have it. Just a heads up, that if you form a corporation, watch out for rats! 
	

	
	
		
		

		
		
	


	




 I'm over it now, but believe me I was steamed at first. 
	

	
	
		
		

		
		
	


	




 I didn't lose my investment capital, just a little pride. I was handed a check for the $5,000.00 I paid to be on the board, and I handed him my keys to the store. _

 

Gee whiz - what a crummy thing to do!
	

	
	
		
		

		
		
	


	







 I won't buy from them, now - no matter what they carry.

 That really stinks.
	

	
	
		
		

		
		
	


	




 I would also think that they owe you more money. If it was investment capital, there's a time value of money. IOW, they rented your money for awhile. So, you are due interest


----------



## joneeboi

That's crummy news, amphead. I was looking forward to what you could have brought to the table, but now it doesn't look like it'll happen. I'm tempted to blame the one secretary dude for instigating the coup, but if everyone voted you out, then you're better off without them. Besides, who needs them when you have us?


----------



## ruZZ.il

yes, you have us 
	

	
	
		
		

		
		
	


	




 edit: you're still welcome to buy some parts for us btw


----------



## amphead

Thanks for the support. I had one Russian speaking supporter, who voted for me to stay, at the risk of being voted off from the board himself. He is the treasurer, but that was still 3 against 1. The secretary who is a ham radio guy, wasn't invited by me to go to the show and protested that I shouldn't be allowed to go, because the store had not opened its doors yet. However for 2 months worth of board meetings, I mentioned that I would be going.  Edit: a head-fier(rhythmdevils) from the show wants to buy a Max kit. Any available? I told him, that I would build it pro bono. I love to build the Max.


----------



## ruZZ.il

Well, there are Jeffs kits which many people are happy with, and Tom helps getting most other upgrades in one place.


----------



## amphead

Thanks, I just sent Jeff an e-mail inquiring about kit availability.


----------



## ruZZ.il

If you plan to upgrade, ask jeff to drop a few wimas and the other coupling caps, along with the output transistors. He's very helpful in customizing orders, and it'll save you a few bucks.
 On the other hand, its not a bad idea to have a few spare parts around either.


----------



## amphead

This is the infamous secretary. 
 Instructions: copy picture, then print, then apply to your dart board.


----------



## tomb

It sounds like some silly ham-radio vs. audio electronics prejudice. I've seen people even "select" their customers that way in a different hobby, but it doesn't last long. If that's the kind of shenanigans that go on before the business has even opened its doors, it will be a short-lived enterprise.

 On a different note - yes, I can confirm first hand that Jeff should have plenty of boards for MAX kits.


----------



## thomaskuhn

I was thinking of a cool upgrade to my MAX, and thought that a real cool feature would be a very small analog gauge on it, circular, backlit in blue or red. I hunted around my local surplus store, and they had a few cool gauges, but only a few small ones. Does anyone know of a supplier for them. What type of meter would one use? where on the board would it be connected?

 Tom


----------



## tomb

Quote:


  Originally Posted by *thomaskuhn* /img/forum/go_quote.gif 
_I was thinking of a cool upgrade to my MAX, and thought that a real cool feature would be a very small analog gauge on it, circular, backlit in blue or red. I hunted around my local surplus store, and they had a few cool gauges, but only a few small ones. Does anyone know of a supplier for them. What type of meter would one use? where on the board would it be connected?

 Tom_

 

The most obvious way to implement a gauge would be for the tube bias. Many have talked about it in the past - all the way back to the original Millett, but I'm not sure anyone has really done it. You would wire a panel voltage gauge between ground and the two tube bias points - TA2L and TA2R. You could use one meter connected to ground and an SPDT to switch between TA2L and TA2R. It would be nice to use a couple of panel mounted 1/4" shaft linear pots - with a small knob mounted on either side of the meter. Leads would run to the corresponding trimmer positions on the board. Put the switch in the middle under the gauge, Then you could switch between Right and Left, and adjust the bias by turning the corresponding knob.

 There are many Voltmeter gauges available that are inexpensive - less than $15 in some cases. I've never seen one smaller than about 2-1/2" square, however - that's the real problem. If you're making up your own case, though, it might be fairly trivial to do.

 This is an example I just found pecking around at All Electronics:
30V DC PANEL METER | All Electronics Corp - Parts, Supplies and Components






 The scale goes to 30VDC on this one, so it's probably ideal for tube bias. There is probably no need to be much more accurate than that with tube bias.


----------



## el_matt0

am i on my own in thinking that 12FK6's sound better than 12AE6's when paired up with the boutique build 1, with blackgates and vitQ's? i found that the added detail from the FK6s only further brought out the strengths of the blackgate NXs...have any of you found otherwise, preferring the 12AE6 in this kinda situation?


----------



## slowpogo

Quote:


  Originally Posted by *el_matt0* /img/forum/go_quote.gif 
_i found that the added detail from the FK6s only further brought out the strengths of the blackgate NXs...have any of you found otherwise, preferring the 12AE6 in this kinda situation?_

 

With K701's, I find the FK6 to be more detailed, but thin-sounding. It lacks punch, especially in the bass. The 12AE6 is less-detailed, but there's still plenty of it for me, and overall it sounds more musical.

 I thought the way you did until I got some nice top-getter GE 12AE6s (only had RCA before). Now I vastly prefer the GE; I only wish I knew where to find another pair or two.


----------



## tomb

Quote:


  Originally Posted by *el_matt0* /img/forum/go_quote.gif 
_am i on my own in thinking that 12FK6's sound better than 12AE6's when paired up with the boutique build 1, with blackgates and vitQ's? i found that the added detail from the FK6s only further brought out the strengths of the blackgate NXs...have any of you found otherwise, preferring the 12AE6 in this kinda situation?_

 

Yep. It's a general consensus that the 12AE6 has more punch, the 12FK6 more top end. It's up to the individual and his own amp, music, and listening preferences to decide which he prefers.


----------



## jamess71

Where do the fm's fall compared to the others? I'm using a almost stock BOM with k42's in pIace of C8 & C9. I prefer the AE's now but my fk's need much more burn in. I guess they should mellow out a bit.


----------



## tomb

Quote:


  Originally Posted by *jamess71* /img/forum/go_quote.gif 
_Where do the fm's fall compared to the others? I'm using a almost stock BOM with k42's in pIace of C8 & C9. I prefer the AE's now but my fk's need much more burn in. I guess they should mellow out a bit._

 

Inbetween the other two tube types.


----------



## jamess71

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Inbetween the other two tube types. 
	

	
	
		
		

		
		
	


	


_

 

haha that works.

 I'm glad to see you got some of the real 238/968's in. I placed the order yesterday. 
	

	
	
		
		

		
		
	


	



 Might have to start on the Boutique Max next weekend.

 James


----------



## rhester

I just finished my 3rd build with NXs and VitaQ, the 12FK6 so far sounds better to me (still very early in the burn in process). They so far have more bottom end presence, maybe not puch per se, but plenty of extension and very well defined, not bloated or exaggerated.

 Looking for a great way to case this one up and add an alien dac to it at the same time. Any suggestions?


----------



## el_matt0

hehe, i find the max doesnt really need any more punch, but it DOES really benefit i find from the added detail in the high end. maybe thats just my setup/preference though, i do have a balanced b22 to cover what my max cant, so, its probably partially to do with the fact that the b22 is clearly my "bassy-oomph" amp, and my millet is the lower level listening detail amp.


----------



## xnothingpoetic

don't know where else to post this, so...

 I was using the 12fk6 tubes, like most people but with the way the EQ is set up and the 100ohm adapter, I got the 12ae6a tubes- higher gain so volume pot is at a lower position which means less hiss- blacker BG.

 Only been 10 mins warm up after probably 40 years of being idle, but the bass extends much deeper with these tubes. 

 That's only my first, quick, impression- I will AB test both and see which better suits me.


 EDIT:
 I see from the above posts, this seems about right. But when paired with my er4s', it seems like a good match so far.


----------



## jamess71

Finally took a couple of pics It's a standard BOM with k42's in C8 & C9. Sounds Great...... 
	

	
	
		
		

		
		
	


	




 Just got my knockout punch set so I'll get the cover done soon. Then on to my Boutique.


----------



## pinkfloyd4ever

ok so I'm trying to put in some Kiwames (or KOAs...those bastards) at RB14 but make them switchable so that I can easily compare the sound with and without them. How would I go about doing this? I have a spare DPDT switch, will that work? The only way I can think of is to use two DPDT switches


----------



## tomb

Quote:


  Originally Posted by *pinkfloyd4ever* /img/forum/go_quote.gif 
_ok so I'm trying to put in some Kiwames (or KOAs...those bastards) at RB14 but make them switchable so that I can easily compare the sound with and without them. How would I go about doing this? I have a spare DPDT switch, will that work? The only way I can think of is to use two DPDT switches_

 

KOA is OK - it's Triode, but I'm breaking my own rule. 
	

	
	
		
		

		
		
	


	




 Give me a bit and I'll draw up a schematic. It's easier than you think and your DPDT is all you need. 
	

	
	
		
		

		
		
	


	




 EDIT: Nice pics, James, but the 2nd one isn't showing.


----------



## pinkfloyd4ever

cool thanks. And I've got a pair each of 10, 16 and 22 ohms, which would you recommend I try first? Again, I've got MS1s and I'm using FK6 tubes. Obv I'm trying them to see how they improve the sound, not to increase attenuation


----------



## tomb

Quote:


  Originally Posted by *pinkfloyd4ever* /img/forum/go_quote.gif 
_cool thanks. And I've got a pair each of 10, 16 and 22 ohms, which would you recommend I try first? Again, I've got MS1s and I'm using FK6 tubes. Obv I'm trying them to see how they improve the sound, not to increase attenuation_

 

I doubt that you'll notice any difference at all going from 10 to 16. From 10 to 22 ohms will be subtle, at best. You may definitely notice a smoothing going from jumpered to 10, though.

 Anyway, here's the best I can do on short notice. A little smaller than I'd like, but my AutoCAD skills are very rusty:






 This is for one channel only, but hopefully you get the idea. I think it's best to put wire leads on both ends of the resistor leads so that the whole assembly can flex. It will get pretty cramped around the switch, too, so heat shrink should be used all around.


----------



## pinkfloyd4ever

ahhh ok cool thanks, thats what I was thinking but I wasn't sure if it was ok to leave the one end of the resistor thats switched off in contact with the one thats switched on. I was actually going to compare a resistor to no resistor at all, so one side will just be wire


----------



## 04BluMach

Quote:


  Originally Posted by *pinkfloyd4ever* /img/forum/go_quote.gif 
_ahhh ok cool thanks, thats what I was thinking but I wasn't sure if it was ok to leave the one end of the resistor thats switched off in contact with the one thats switched on. I was actually going to compare a resistor to no resistor at all, so one side will just be wire_

 

The eaiest way is to put the resistor in its position and wire the switch as either open or to apply a short across the resitor (ie jumper).
	

	
	
		
		

		
			





 For test - you can temporarily tack solder the resistor in position then apply a a jumper wire (or test leads) across the resistor to "remove" it from the circuit (ie Short across it)...

 Edit: Just make sure ya don't pull an OOOPS by accidently shorting your output to GROUND (like your case, etc)!

 Also, agree 100% withe tomb that the values are way too close together to "hear" a difference. Try these approx values 22, 47, 100 or so...


----------



## Negatron

Quote:


  Originally Posted by *04BluMach* /img/forum/go_quote.gif 
_The eaiest way is to put the resistor in its position and wire the switch as either open or to apply a short across the resitor (ie jumper).
	

	
	
		
		

		
		
	


	




 For test - you can temporarily tack solder the resistor in position then apply a a jumper wire (or test leads) across the resistor to "remove" it from the circuit (ie Short across it)... <snip>_

 

Yep! Pretty easy. Also, you could use 100R for R14 and jump as you posted the 'short' with a wire, at the Switch and solve a minor issue for those who want to have switchable sensitivity.


 BTW: Nice Clean looking Amp a few posts up James!


----------



## el_matt0

couldnt u also just use small IC sockets...? just do the testing with the top off just swapping in and out the resistors by hand, no soldering needed once sockets are in! not as nice as a switch if it was going to be a long term thing...but this would definitely get the job done just fine sofar as i see it, just so long as u wouldnt mind doing the testing with the lid off.


----------



## tomb

In the interests of full disclosure, I have to tell you that Dsavitsk has given the K42's a bad review: Notes On Output Coupling Capacitors

 However, keep in mind that they are being used in a different application on the MAX (bypassing ES electrolytics). Many builders, including myself, have found the K42's to be simply superb in combination with bypassing ES caps. The bass is tremendous - punchy with loads of impact, while the highs are sweetened and extended slightly compared to the basic-build Wima's. They also remove any hint of the Wima's slight mid-range graininess.

 As a for instance that not all comparisons are equal, Dsavitsk's recommendation for bypassing ES's with the Sonicap GEN II's does _not_ work in the MAX. The GEN II's audibly cut the bass - basically destroying it in the CA9 positions, a bit less in CA8. However, the combination works _superbly_ in the Alien DAC, where the sizes are very similar to what Doug tested. Dsavitsk's ES-GEN II combo sounds and _tests better_ in the Alien than Black Gates. See some of the latest posts from myself and ruZZ.il in the Alien DAC thread (not the one with the ant attack! 
	

	
	
		
		

		
		
	


	




 )

 Bottom line, Team Millett MAX will continue to recommend the K42's as optimum for use with ES's and Vitamin Q's for use with Black Gates (no discrepancy with Dsavitsk on that one). We will also continue to recommend Dsavitsk's excellent Capacitor Reviews, with the caveat that not everything applies to every situation.


----------



## el_matt0

is there a huge diff between VitQ's and russian K42s? they are both PIO caps...how diff do they sound? I have a couple of k42s that I plan to incorporate with my blackgate NXs - is that suitable? I know it says its a possible option on the max boutique site, so i assume it should still sound good right? Or if im using blackgate nxs, should i stay on the hunt for some real VitQs? i plan to leave CA9 blank (build #1).


----------



## jamess71

Quote:


  Originally Posted by *el_matt0* /img/forum/go_quote.gif 
_is there a huge diff between VitQ's and russian K42s? they are both PIO caps...how diff do they sound? I have a couple of k42s that I plan to incorporate with my blackgate NXs - is that suitable? I know it says its a possible option on the max boutique site, so i assume it should still sound good right? Or if im using blackgate nxs, should i stay on the hunt for some real VitQs? i plan to leave CA9 blank (build #1)._

 

Same exact question.


----------



## tomb

If you are interested in building the absolute best build possible - e.g., investing in Black Gates, then I would hunt the Vitamin Q's. By the same token, I think VitQ's may be a bit of overkill with ES's.

 The K42's are absolutely better than Wima's IMHO, and stack up very well against the Vit Q's as a bypass cap on the MAX. However, the VitQ's may have just a bit better high end sparkle. You probably need the BG NX's to make use of that. Keep in mind that the VitQ's are more expensive than the K42's, too.

 Just MHO, of course, but that's all in keeping with a certain philosophy:
 1. FM's, FC's, UPW's with Wima's as a very good basic build.
 2. ES's with K42's as a rocking/slamming, good detail upgrade, and
 3. BG NX's with Vitamin Q's as the ultimate build.
 BJT's and MOSFETs could be in all mixes. 

 I'll try to load some VitQ's onto Beezar tonight. I have some that I think are suitable and the supply line is somewhat dependable - bought in bulk from LA Surplus Electronics on e-bay. They are 0.47uf's Sprague Vitamin Q's, but are only about 1-1/8" long. If one is careful with that double heat shrink on bending over the top lead, they should tombstone OK. IOW, they could come close enough to arc onto the top plate if some care is not taken.

 EDIT: That's sort of the additional problem with VitQ's and one of the things that make the K42's so nice. The VitQ's are almost all too large (at the ratings needed) to fit in a straightforward manner in the MAX. There are a few exceptions such as the ones mentioned above.


----------



## el_matt0

wow that would be fantastic if you could post some up on beezar! 
	

	
	
		
		

		
		
	


	




 the height is not an issue as im not casing it in a hammond case anyways. cheers, thx for the help, and definitely keep me posted about those vitqs


----------



## teNtiOn

Maybe post up the blackgate to beezar as well? lol


----------



## el_matt0

lol, now THAT might be too much to ask for


----------



## tomb

I have tested this genuine Sprague paper-in-oil, "Vitamin Q" type cap in my Black Gate MAX. This particular cap is the only Vitamin Q-style cap that I've found that is both readily available and will fit in the MAX with the board in the Hammond's 3rd slot from bottom. It is Vitamin Q in every way - hermetically sealed, glass ends, including being genuine NOS Sprague - save for having "Vitamin Q" stamped on the body along with "Sprague".

 The sound is superior to the Philco Vitamin Q-types that Colin had given me, with lots of "air" and sparkling highs. Bass seems to have no loss whatsoever, as long as you keep these out of the CA9 positions. They should go in CA8, and should probably only be paired with Black Gate NX's.


----------



## el_matt0

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_I have tested this genuine Sprague paper-in-oil, "Vitamin Q" type cap in my Black Gate MAX. This particular cap is the only Vitamin Q-style cap that I've found that is both readily available and will fit in the MAX with the board in the Hammond's 3rd slot from bottom. It is Vitamin Q in every way - hermetically sealed, glass ends, including being genuine NOS Sprague - save for having "Vitamin Q" stamped on the body along with "Sprague".

 The sound is superior to the Philco Vitamin Q-types that Colin had given me, with lots of "air" and sparkling highs. Bass seems to have no loss whatsoever, as long as you keep these out of the CA9 positions. They should go in CA8, and should probably only be paired with Black Gate NX's.



_

 

are those the ones, dare i ask, that you were referring to when you said you might be throwing some up on beezar? PLEASE let me know if you do, you as well as i know im dying to get my hands on 2x those.


----------



## ruZZ.il

Tom how do they compare to the bigger in size, more common .22's that some of us (me!) have?. And, have you tried it in your alien yet?


----------



## tomb

Quote:


  Originally Posted by *ruZZ.il* /img/forum/go_quote.gif 
_Tom how do they compare to the bigger in size, more common .22's that some of us (me!) have?. And, have you tried it in your alien yet? 
	

	
	
		
		

		
		
	


	


_

 

I'm sort of inflexible when it comes to the bigger caps - if they don't fit with the MAX board in the 3rd slot, I don't try them. So, I don't have a comparison with the larger, stamped "Vitamin Q" versions. These are excellent sounding as it is, though, and can be made to fit by following the K42 installation procedure.

 NOTE: For those not aware, the Vitamin Q caps made by Sprague - that are actually stamped "Vitamin Q" - are larger in each dimension than the ones on Beezar. Even a 0.1uf-100V is about 1-1/4" long, plus the lead nipples on the end - all but impossible to fit in a 3rd-slot MAX. That's why the Sprague 118P is such a nice selection for a top-end MAX. 

 Your second question is key, however, the larger VitQ's (0.22uf and 0.47uf) are reserved for Alien DAC experiments (yet to occur). There's a surprising bit of room in a mint tin.


----------



## fault151

Quote:


  Originally Posted by *cetoole* /img/forum/go_quote.gif 
_Just thought I would post a quick pic of the reason I am still up tonight. Just having real trouble turning Opeth's Deliverance CD off. Had a bit of trouble with way too much gain and getting the volume knob too high with my KSC75's earlier tonight, and even with my HD580s, I cant even make it a quarter turn on the volume knob. This is with DuMont 12ae6a tubes and the cathode resistors unbypassed.





_

 

Hi im new to this thread, is the amp pictured a kit design? If so where can you get them?

 Looks cool by the way!


----------



## joneeboi

You can get a kit from glassjaraudio.com. Also, check out index while you're at it.


----------



## fault151

Quote:


  Originally Posted by *joneeboi* /img/forum/go_quote.gif 
_You can get a kit from glassjaraudio.com. Also, check out index while you're at it._

 

Ok cheers, i'll have a look now.


----------



## el_matt0

AHH VitQ's 
	

	
	
		
		

		
		
	


	










 ty tomb

 -does it make a huge difference that the VitQ's up for sale on beezar are 0.47uF rather than 0.22 as indicated they should be on the max boutique page? I need 2 of them for my CA8 positions in my "Can't Miss Boutique Build #1", I'll be leaving CA9 blank as directed. Will the 0.47 VitQ's be OK / Good
	

	
	
		
		

		
		
	


	




?


----------



## fault151

is it the one that says *Level 2 SOHA kit*?


----------



## joneeboi

I felt like taking a picture of mine. I'm running ES + K42 in my MAX, so these Vit Qs will get some use with my diyMod. I'll try bypassing the BGs, replacing the BGs and see what the huge deal is.


----------



## el_matt0

...i still await an answer to my question regarding whether or not the 0.47pF VitQ's are OK to use instead of the indicated 0.22uF ones


----------



## joneeboi

pF? You mean uF? Sure, you can use them.

 fault151, you may have to email Jeff and ask for a Millett MAX kit. While you're at it, you can customize your order with him as well. I've read that he's pretty good about it. Ask him about boutique options, though you may want to stick to the original plan just to keep things simple.


----------



## tomb

Quote:


  Originally Posted by *el_matt0* /img/forum/go_quote.gif 
_...i still await an answer to my question regarding whether or not the 0.47pF VitQ's are OK to use instead of the indicated 0.22pF ones_

 

Sorry - I do have a job during the day. I can sneak in on the forum without too much trouble, but every once-in-awhile, I have to go to meetings.
	

	
	
		
		

		
		
	


	







 At any rate, the description I put on beezar says specifically, "_... we are confident that you will find this cap to be among the very finest that you can use for bypassing the output electrolytics on the MAX._" I wrote that because I tested them specifically in my BG MAX last night - and said so in the earlier post with the pic. I would not sell them for the MAX if I hadn't tested them myself. That goes the same for all of the stuff I sell - especially if I'm going to invest a few $hundred to keep them in stock. 
	

	
	
		
		

		
		
	


	




 Higher uf's are better than lower uf's anyway - up to a point. I don't know what that point is, but maybe Joneeboi is fixing to find out.
	

	
	
		
		

		
		
	


	




 Ordinarily, I would've guessed up to about 1.0uf. Who knows what the limit is, though? 

 It's all voodoo when it comes to bypassing caps.

 ... ting tang walla walla bing bang.


----------



## el_matt0

...excellent. I am very excited to give them a try then.


----------



## fault151

Quote:


  Originally Posted by *joneeboi* /img/forum/go_quote.gif 
_pF? You mean uF? Sure, you can use them.

 fault151, you may have to email Jeff and ask for a Millett MAX kit. While you're at it, you can customize your order with him as well. I've read that he's pretty good about it. Ask him about boutique options, though you may want to stick to the original plan just to keep things simple._

 

Are they fairly simple to put together? Do they come with everything needed?

 Cheers for your help!


----------



## tomb

Quote:


  Originally Posted by *el_matt0* /img/forum/go_quote.gif 
_...excellent. I am very excited to give them a try then. 
	

	
	
		
		

		
		
	


	


_

 

Well, thank you for spurring me on to put them out there. It was quite a bit of work after a long day to try them out, but when I discovered that they sounded better than the already best-I'd-tried Philco VitQ's, that clinched it. Anyway, hope you enjoy them.

  Quote:


  Originally Posted by *fault151* 
_Are they fairly simple to put together? Do they come with everything needed?

 Cheers for your help!_

 

Millett Hybrid MAX


----------



## jamess71

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Well, thank you for spurring me on to put them out there. It was quite a bit of work after a long day to try them out, but when I discovered that they sounded better than the already best-I'd-tried Philco VitQ's, that clinched it. Anyway, hope you enjoy them.


Millett Hybrid MAX






_

 

Hey TomB can you give a little info on the differences between the k42's vs vitQ's with BG's? thanks james


----------



## joneeboi

Quote:


  Originally Posted by *fault151* /img/forum/go_quote.gif 
_Are they fairly simple to put together? Do they come with everything needed?

 Cheers for your help!_

 

What TomB said. 
	

	
	
		
		

		
		
	


	




 It all really depends on how much experience you have and how confident you are in your abilities. If you have to ask, I'm guessing you're still a beginner, but correct me if I'm wrong. I had only built a CMoy and 3/4 of a PIMETA before tackling the MAX, and I managed to pull through with the build. It wasn't all me, however. The friendly folks on this thread were eager to walk me through the parts of the build I messed up on, so you're in good company and good hands with the MAX crowd. The real fun is learning stuff along the way to completion, so try to do your own research at first, taking notes and making personal adjustments along the way. We're here to clue you in on whatever you need, so you're only really limited by how many questions you ask. And don't worry about annoying us; we've been going 3300 posts strong, and there's no sign of us slowing down. Good luck on your build!


----------



## tomb

Quote:


  Originally Posted by *jamess71* /img/forum/go_quote.gif 
_Hey TomB can you give a little info on the differences between the k42's vs vitQ's with BG's? thanks james_

 

Please see Post #3353 a couple of pages back. That explains it better than I can repeat it again.


 Great post, Joneeboi! It can't be said better than that.


----------



## slowpogo

Tomb, I've ordered some of the .47 Q's from Beezar. I've been using .27uf genuine Spragues in C8 and want to see if the extra capacitance makes a difference.

 My question is about tomb-stoning them. My caps are thinner and longer, so I had to angle them, which worked fine. But I noticed that their "nipples" were a little too thick to fit through the large hole in the PCB (without taking a tack hammer to them or something). Are the .47 caps the same way, and if so what did you do to make them fit? If possible I'd like to tomb-stone them, they could be too wide to angle the way I'm doing it currently.

 Also, since I'll be adding them to a burned-in amp, do paper in oil caps need time to burn in? I had no way of knowing with my current caps, since the black gates were also burning in.


----------



## tomb

Quote:


  Originally Posted by *slowpogo* /img/forum/go_quote.gif 
_Tomb, I've ordered some of the .47 Q's from Beezar. I've been using .27uf genuine Spragues in C8 and want to see if the extra capacitance makes a difference.

 My question is about tomb-stoning them. My caps are thinner and longer, so I had to angle them, which worked fine. But I noticed that their "nipples" were a little too thick to fit through the large hole in the PCB (without taking a tack hammer to them or something). Are the .47 caps the same way, and if so what did you do to make them fit? If possible I'd like to tomb-stone them, they could be too wide to angle the way I'm doing it currently.

 Also, since I'll be adding them to a burned-in amp, do paper in oil caps need time to burn in? I had no way of knowing with my current caps, since the black gates were also burning in._

 

TomB-stoning
	

	
	
		
		

		
			





 must be carefully done. The nipples aren't the best in quality control. You are correct that some of them are too big to fit in the TomB-stoning holes. Get out your trusty Boy Scout pocket knife and start whittling until they do. 
	

	
	
		
		

		
		
	


	




 The cap has to be flush to the board.

 Also, you need to be sure that you absolutely attach the wire lead to the nipple or just above. Any bend over above that and you'll be touching the inside top of the case. There's a bit more than 1/16" clearance assured if you do those two things. If not, solder the lead directly under the nipple and snip it off. (ouch!)

 Yes, they do burn-in, but it's not like several hours that an ES might take or weeks for a BG. I noticed a significant difference in about an hour, a little less in two hours - the highs getting less scratchy and smoother. They probably continue to change after that but my ears are not capable of anything more subtle than that.


----------



## el_matt0

hey tomb, out of curiousity (forgive me if this is prying too far) but what is your relation to the designer of the millet colin (correct me if im wrong there)? Ive always been curious with regards to your ever-so-central role in the millet world! One might even say you are the "Sun" of this "universe" we all know with such familiarity as the wonderful world of the Millet Max. 
	

	
	
		
		

		
		
	


	




 i think its really fantastic what the kind of resources and information you (and many others) pour into this amp, not to mention all of the hours! Speaking from experience, having built several other DIY amps, of both harder and easier difficulty, the "support" for the MHMax (from all of you guys, and TomBs sites) is just in a world and class of its own IMHO. This makes it a superb choice for your inexperienced DIYer looking to get their hands wet on a second project or something, and it also is simply a fantastic way for even more experienced builders to simply find out what all those other proud max owners out there are up to with their creations!


----------



## joneeboi

What I did to fit the K42s into the C8 position was to slip the south lead to the RB14 hole, extending from the test point. Since I'm jumpering RB14, I just used the extra lead length to be the jumper across RB14. Even if you're not jumpering RB14, you can solder it to a slightly elevated and exposed resistor lead. This makes TomBstoning unnecessary, keeping your cap from ever touching the roof of the Hammond. From the beezar image, it looks like the Sprague could fit the same way. IOW, lay capacitor down on board into TA2L/R and into one of the RB14L/R holes.

 What do you think, Tom? Maybe we should just keep TomBstoning so we can say that we're TomBStoning.


----------



## amphead

Quote:


 out of curiousity (forgive me if this is prying too far) but what is your relation to the designer of the millet colin (correct me if im wrong there)? Ive always been curious with regards to your ever-so-central role in the millet world! One might even say you are the "Sun" of this "universe" 
 

"I am Oz, the Great and Terrible. Who are you, and why do you seek me?"


----------



## el_matt0

Quote:


  Originally Posted by *amphead* /img/forum/go_quote.gif 
_"I am Oz, the Great and Terrible. Who are you, and why do you seek me?" 
	

	
	
		
		

		
		
	


	


_

 

my point precisely.


----------



## tomb

So, I leave for a school board meeting and now I'm OZ, the Great and Terrible? Gee whiz.

 About the Sprague caps:
 It's been brought to my attention that they are not truly paper-in-oil. First, strictly speaking, K42's are not paper-in-oil, either. However, there is a common tendency to refer to many of these caps as PIO. They are not electrolytics, they are not teflons, they are not box films or orange drops. Even though the medium may be a different material than paper and the fluid a different material than oil, there is a common consensus that lets one know the type of cap that's being discussed.

 Actually, it makes little difference IMHO. I think it's plain that they are not stamped "Vitamin Q", but they _are_ genuine Sprague caps of an apparent similar nature. They definitely sound better than the Philco's, which also sounded better than the K42's, which also sounded better than the Wima's. All that sounds a little silly, but you are welcome to check the source of these caps yourself:

 I mentioned it a little earlier when I said LA Surplus Electronics on ebay. The guy happens to be the biggest supplier on the bay for VitQ's (genuine stamped, trademarked ones). For these caps, he states
*"They are made by Sprague, part number 118P47492S2. They are glass sealed, insulated, paper-oil, and are 1 1/8”x7/16”. They are new, and excellent for audio applications."*

 One might note that he also has Dublier's and Goodmans with similar descriptions. You can look at the link and decide for yourself:
Capacitor 0.47mfd 200vdc Vitamin Q (10) - eBay (item 320193409824 end time Mar-06-08 15:05:49 PST)

 As stated earlier, I have tested these caps in the MAX, and IMHO, they are worthy of Black Gates. Sorry about taking up space repeating all of this.


----------



## tomb

Quote:


  Originally Posted by *el_matt0* /img/forum/go_quote.gif 
_hey tomb, out of curiousity (forgive me if this is prying too far) but what is your relation to the designer of the millet colin (correct me if im wrong there)? Ive always been curious with regards to your ever-so-central role in the millet world! One might even say you are the "Sun" of this "universe" we all know with such familiarity as the wonderful world of the Millet Max. 
	

	
	
		
		

		
		
	


	




 i think its really fantastic what the kind of resources and information you (and many others) pour into this amp, not to mention all of the hours! Speaking from experience, having built several other DIY amps, of both harder and easier difficulty, the "support" for the MHMax (from all of you guys, and TomBs sites) is just in a world and class of its own IMHO. This makes it a superb choice for your inexperienced DIYer looking to get their hands wet on a second project or something, and it also is simply a fantastic way for even more experienced builders to simply find out what all those other proud max owners out there are up to with their creations!_

 

I appreciate some of these comments - I think.
	

	
	
		
		

		
		
	


	




 I may need to clear the air with this one, too - you're getting a knack, el_matto.
	

	
	
		
		

		
		
	


	




 First, "designer of the millett colin" is incorrect. Pete Millett designed the original and published it in AudioXpress magazine. We are forever grateful, not only because he created it, but because he bequethed the design to the DIY community.

 Much of this and what followed is detailed extensively under Millett History on the MAX website.

 Colin designed the Millett MAX, which is currently the ultimate refinement of the basic Millett Hybrid design. Sort of un-noticed here and on Headwize, when Colin posted the new layout on DIYForums.org, I pounced on it and wouldn't let him go. 
	

	
	
		
		

		
		
	


	




 I was hooked on the Millett after building four of Drew Dunn/Nate Maher's revMH Milletts - and adding Steinchen's Diamond Buffer boards, too. However, for the first time, Colin's design included every feature anyone ever desired for the Millett. It's still one of the most singular boards in its complete package design: hookup a simple AC walwart and you're ready to go. Along with a few others, we stuck with him and bugged him mercilessly until his layout became a real prototype board run. 
	

	
	
		
		

		
		
	


	




 At some point along the way, I asked him if I could make a website and our collaborative relationship took off.

 There were many others, though - I don't mean to make my contribution sound like more than it was. Nate Maher was instrumental all along the way. First, as a major contributor in setting up the revMH Millett in the first place. Running several Group Buys, prototyping the original, etc. He and Drew setup DIYForums.org in the first place and laid the groundwork for the Millett MAX that followed. Somewhere along the way when I was getting more heavily involved with Colin's design, Nate made me an Administrator over on DIYfourms. Drew also gave me development access to the website, and I created the MAX website as a result.

 Pretty soon, Colin had his Guinness World Record Group Buy - over 400 boards and 175 users in 20 countries. You know the rest.

 You can read most of this directly in the actual, original design thread on DIYForums.org, and see for yourself how the involvement between the two of us began. There is also a large portion where NealR proved the MOSFET version. Of course, AMB just recently devised some refinements to that version. So, the MAX continues to grow and refine. I posted pics a few pages back of the finished build of the prototype MiniMAX. We hope to have that ready in mid-to-late Spring. Colin is also working on a Super MAX, although he doesn't like that name and will probably think of something else to call it. 
	

	
	
		
		

		
		
	


	




 Colin and I trade e-mails often and a few phone calls inbetween, but we have never met in person. The age of the Internet is amazing in some respects when you think of what was accomplished. Anyway, Colin remains the braintrust as the very gifted layout/circuit designer that he is, while I try to bring up the rear with website skills, promotion, and the time to support problems that come up with builds. (He's a student with two jobs!)

 Hope that helps, and ... pay no attention to that man behind the curtain ...


----------



## 04BluMach

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_So, I leave for a school board meeting and now I'm OZ, the Great and Terrible? Gee whiz.._

 

All hail OZ, the Great and Terrible.......
	

	
	
		
		

		
		
	


	




 Give you great credit to search out a product to the needs of the Millet MAX C8 position when BG Output Coupling Caps are used. And openly clarify that these may not be PIOs...

 The Key point are these are Sprague NOS items with their Top of the Line CAP Signature construction Tubular metal with Glass sealed ends. This was reserved for their best of type Caps with at or near Mil-Spec build quality. Along with near legendary performance across their lines. 

 And the second Key point - OZ Tested for In-Circuit Performance: 

  Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_ As stated earlier, I have tested these caps in the MAX, and IMHO, they are worthy of Black Gates._

 

That is what it is all about! Ultimately, its all about the MUSIC.
	

	
	
		
		

		
		
	


	



 If it takes a little VooDoo to get there - Who Cares! 
 Just NO SNAKE OIL allowed!

 I hope to have a chance to try these out in my BG equipped MAX....
	

	
	
		
		

		
		
	


	




 ... ting tang walla walla bing bang.


----------



## 04BluMach

Deleted Double Post.


----------



## amphead

I am still amazed at how reliable the Max is. I don't know how many times I rolled caps, trying to nail down the best configuration for my ears/HPs and just like a timex it keeps on tickin. Really an awesome feat of engineering, to have a great sounding and reliable piece of kit for such a reasonable price. Kudos again to Colin, TomB, Nate, Pete, Amb and any others I may have missed.


----------



## el_matt0

Quote:


  Originally Posted by *amphead* /img/forum/go_quote.gif 
_\Kudos again to Colin, TomB, Nate, Pete, Amb and any others I may have missed._

 

a BIG BIG x2 FROM ME!


----------



## fault151

Quote:


  Originally Posted by *joneeboi* /img/forum/go_quote.gif 
_What TomB said. 
	

	
	
		
		

		
		
	


	




 It all really depends on how much experience you have and how confident you are in your abilities. If you have to ask, I'm guessing you're still a beginner, but correct me if I'm wrong. I had only built a CMoy and 3/4 of a PIMETA before tackling the MAX, and I managed to pull through with the build. It wasn't all me, however. The friendly folks on this thread were eager to walk me through the parts of the build I messed up on, so you're in good company and good hands with the MAX crowd. The real fun is learning stuff along the way to completion, so try to do your own research at first, taking notes and making personal adjustments along the way. We're here to clue you in on whatever you need, so you're only really limited by how many questions you ask. And don't worry about annoying us; we've been going 3300 posts strong, and there's no sign of us slowing down. Good luck on your build!_

 

Cheers, yeh im a beginner to building amps. I have a mate who is a lot more experienced at putting them together so i could get him to help me through the physical making of the thing. No doubt i will need your advice too! I'll get in touch with the person you sent me in the link earlier and see what kits they have.

 cheers!


----------



## tomb

OK - Russ, 04BluMach, el_matt0,

 I'm baring my soul, here, but I will soon list 0.22uf-100V Sprague 196P-series, genuine "Vitamin Q's".
	

	
	
		
		

		
		
	


	




 These are even stamped with "[size=medium]V[/size]itamin [size=medium]Q[/size]" (see pic below). I have a deal working with LA Surplus Electronic and hope to list them sometime this weekend (I told him about the other caps, too, so we'll see what he says - if anything.)




_[size=xx-small](click for big pic)[/size]_

 Meanwhile, I stayed up late again last night because this issue had me so worried. Taking the cue from Joneeboi, I tried a similar technique with the 1-1/2" long 0.22 Vit Q's. Surprisingly, the installation is even simpler. Using the leads they're born with, you can angle them down in back and point them up slightly toward center. They will look like a couple of battleship guns pointing toward the center of the front panel, so to speak. (Note that the TomB-stone points are _not_ used - just the two outer-most standard pads.) The leads are heavy enough that they provide some structural support - especially in the back. The trick is to pull the back lead through the bottom so that the edge of the can is _firmly_ resting on the board. Ideally, you may want to insulate the forward lead where it bends under and down to the front pad, but it's not absolutely necessary, perhaps. Once soldered in that position, they are very solid. Nothing could be simpler unless they could somehow actually fit on the pads. As you see them here, they are not blocking any test points or trimmers. The top edge of the caps are about 1/8" above the top level of the 1" sinks.




_[size=xx-small](click for big pic)[/size]_

 I'm not going to state what these sound like this time - I'll jinx it, and I've been wrong before - just night before last, it seems. 
	

	
	
		
		

		
		
	


	




 So, I'll just refer you to Dsavitsk's always excellent "Notes on Output Coupling Capacitors" page, and you can read for yourself.

 I am impressed enough at these and embarrassed enough to find out that the others are not paper-in-oil, that I'll be shipping a pair of these to everyone who has purchased the 0.47uf 118P's so far. The 118P's will still remain for sale, but are no longer my top recommendation for Black Gates. Sorry for the mixup and I hope this resolves things for the better for everyone.

 Those of you that install these things would really do a service to the Millett MAX community if you share your listening experiences with them. I think many will be quite surprised.


----------



## el_matt0

ooh oooh ooh! so i get the REAL vitQs now instead? (tomb, incase you didnt put 2+2 together my last name's carr 
	

	
	
		
		

		
		
	


	




, although im sure someone of your infinite wisdom had already deduced that hehe 
	

	
	
		
		

		
		
	


	




)


----------



## tomb

Quote:


  Originally Posted by *el_matt0* /img/forum/go_quote.gif 
_ooh oooh ooh! so i get the REAL vitQs now instead? (tomb, incase you didnt put 2+2 together my last name's carr 
	

	
	
		
		

		
			





, although im sure someone of your infinite wisdom had already deduced that hehe 
	

	
	
		
		

		
		
	


	




)_

 

Yep - figured that. However, no - you are not getting real VitQ's _instead_, but _in addition_. I'm packaging it up now along with a couple of others, and am sending a pair to Slowpogo who actually had some of the 118P's already ship.


----------



## el_matt0

well thanks for the generosity, much appreciated as always, i cannot wait to try these out and will definitely share impressions once i do.
 my main decision right now is whether to go with the FK6 or the AE6 once i have BG NXs, vitqs and 238/968s in there. we will haaaave to see i guess!


----------



## joneeboi

Quote:


  Originally Posted by *fault151* /img/forum/go_quote.gif 
_Cheers, yeh im a beginner to building amps. I have a mate who is a lot more experienced at putting them together so i could get him to help me through the physical making of the thing. No doubt i will need your advice too! I'll get in touch with the person you sent me in the link earlier and see what kits they have.

 cheers! 
	

	
	
		
		

		
		
	


	


_

 

Glad to know I could help. I just can't wait to see what you do with it; I just ran through your design page and I was blown away. All your work is really amazing! Simply stunning. Maybe you could make some illustrations of the MAX to put on your page once you're done.


----------



## el_matt0

yes i just flipped through the designs too and wow, x2 on that, incredible work man. youve done some really great looking stuff!


----------



## 04BluMach

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_OK - Russ, 04BluMach, el_matt0,

 I'm baring my soul, here, but I will soon list 0.22uf-100V Sprague 196P-series, genuine "Vitamin Q's".
	

	
	
		
		

		
		
	


	




 These are even stamped with "[size=medium]V[/size]itamin [size=medium]Q[/size]" (see pic below). I have a deal working with LA Surplus Electronic and hope to list them sometime this weekend (I told him about the other caps, too, so we'll see what he says - if anything.)_

 

Tom, you do not need to do any soul baring here! You are a stand up guy. As I said before, I am very impressed by your desire and efforts to support the MAX Ccommunity by searching out and trying out all these combos of components. Searching for specific parts takes time, effort and $'s to find just the right combo to allow such a varied group of skill levels to complete these builds with great results!
	

	
	
		
		

		
		
	


	




 Excellent build for the 0.22 VitaQ's. You need to get tweaky to get the full 196P VitaQ's in position if you absolutely want to keep the PCB in the third slot. Its not easy and takes patience and thinking outside the box to wedge them in there.

  Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_
 Meanwhile, I stayed up late again last night because this issue had me so worried. Taking the cue from Joneeboi, I tried a similar technique with the 1-1/2" long 0.22 Vit Q's. Surprisingly, the installation is even simpler. Using the leads they're born with, you can angle them down in back and point them up slightly toward center. They will look like a couple of battleship guns pointing toward the center of the front panel, so to speak. (Note that the TomB-stone points are not used - just the two outer-most standard pads.) The leads are heavy enough that they provide some structural support - especially in the back. The trick is to pull the back lead through the bottom so that the edge of the can is firmly resting on the board. Ideally, you may want to insulate the forward lead where it bends under and down to the front pad, but it's not absolutely necessary, perhaps. Once soldered in that position, they are very solid. Nothing could be simpler unless they could somehow actually fit on the pads. As you see them here, they are not blocking any test points or trimmers. The top edge of the caps are about 1/8" above the top level of the 1" sinks.




[size=xx-small](click for big pic)[/size]_

 

Not very many others will stay up all hours of the night to try out a new build combo to bring the word back than you have done on a continuous basis. Amazingly, this thread has seen not only yourself, but many others who have done the same on numerous occassions. It is impressive to see so many get so excited over a DIY project like what has occurred with this MAX.

  Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_I am impressed enough at these and embarrassed enough to find out that the others are not paper-in-oil, that I'll be shipping a pair of these to everyone who has purchased the 0.47uf 118P's so far. The 118P's will still remain for sale, but are no longer my top recommendation for Black Gates. Sorry for the mixup and I hope this resolves things for the better for everyone.

 Those of you that install these things would really do a service to the Millett MAX community if you share your listening experiences with them. I think many will be quite surprised.
	

	
	
		
		

		
		
	


	


_

 

Agree 100% that the VitaQ's are impressive, anyone who trys them will be impressed.... If you want to better them - be prepared to pay an arm and leg!!!

 Also, you do not need to feel embarresed at all. You represented the 118P's exactly as listed by the vendor. And immediately got the word out that they may not be PIO's. I would have hoped that the vendor would be willing to work with you on their replacement by the 196P's. 

 You have handled this in a spectacular manner. Hope you don't stick yourself financially! You don't deserve that in anyway.

 Anyway - thanks for all your efforts aqnd interest in the DIY community. It is well appreciated!!!


----------



## erickytam

I really like the design of the amp, and was wondering if this would be a good setup?

 Sennheiser HD280 Pro
 Millet Hybrid Max
 Sony CDP-CX355 300-Disc CD changer
 Creative Zen Vision M

 Right now I mostly listen to my Zen, and will be getting the 300 cd changer (unless you guys would recommend something else). I also have an old record player made by Aiwa, I might plug that in too. I was wondering, could you change the tubes to something larger later on? I liked the KT-88's. What would I have to add/remove/switch?

 Thanks
 Eric


----------



## fran

Has anyone done some listening tests with regard to the pot?

 I ask because I have just done some swapping around on my preamp and there was a huge difference between the alps pot and a stepped attenuator. So much it wasn't funny. Now I haven't tried the alps in my max (another stepped attenuator in there) but I do have one in my revMH. 

 So has anyone done any listening test on this?

 Fran


----------



## tomb

04BluMach,

 That was a very, very kind post. I don't know what to say, except: Thank you. Thank you very much.


----------



## tomb

Quote:


  Originally Posted by *erickytam* /img/forum/go_quote.gif 
_I really like the design of the amp, and was wondering if this would be a good setup?

 Sennheiser HD280 Pro
 Millet Hybrid Max
 Sony CDP-CX355 300-Disc CD changer
 Creative Zen Vision M

 Right now I mostly listen to my Zen, and will be getting the 300 cd changer (unless you guys would recommend something else). I also have an old record player made by Aiwa, I might plug that in too. I was wondering, could you change the tubes to something larger later on? I liked the KT-88's. What would I have to add/remove/switch?

 Thanks
 Eric_

 

Eric,
 Thank you for interest in the Millett Hybrid MAX.

 The MAX is similar to many DIY amps in that the sound signature can be tweaked. In fact, the MAX can be tweaked more than most. For instance, there are several types of buffer transistors that can be used that will significantly alter the sound signature. That's not even counting the tubes. There are three main tube types that may be used in the MAX, and that's the same as any Millett. They range from punchy to airy, extended highs and even inbetween, depending on your preference.

 All that's to say that you can probably tweak one to sound good whatever your setup might be. 
	

	
	
		
		

		
		
	


	




 As for your question on tubes, one reason the Millett and now the MAX, is so popular is that Pete Millett's original creation was based on a significant premise: the Millett tubes are special, low-voltage tubes. There is nothing in the Millett or MAX that is more than 24-30Volts. Most tubes, including the KT88, use from 200-300 volts or more. So, you can't use that tube, unfortunately.

 If you are interested in building one, you should refer to the MAX website for more information. However, it's probably a project that needs at least some DIY amp experience. On the other hand, there are a few of us who have built MAXes for sale - Nate Maher is one. I'm sort of booked at the moment, but perhaps someone else will see this and shoot you a PM. A couple have shown up on the For Sale section, but not many so far.


----------



## ruZZ.il

They're too hard amp to let go off! 

 erickytam: Are you more interested in building or getting one built?


----------



## erickytam

I would like to build it myself, so I know what goes into it incase I need to make repairs or want to upgrade any parts. I wouldn't mind buying a Max built, as long as the shipping charges aren't too high.

 Does anyone know about the CD changer?

 Thanks again
 Eric


----------



## slowpogo

Quote:


  Originally Posted by *erickytam* /img/forum/go_quote.gif 
_Does anyone know about the CD changer?

 Thanks again
 Eric_

 

A lot of people here seem to go with lossless files playing from their computer. What kind of sound card do you have?

 I don't know how much a 300-disc CD changer costs, but for about $160 you could get a basic audiophile sound card (thinking E-mu 0404) and 160GB hard drive (which would hold probably over 400 CDs in FLAC format). Just an idea.


----------



## BoilermakerFan

Well, my Mouser order showed up today. I had already ordered a lot of parts and boutique bits from Beezer. My Digi-Key shipment showed up almost 2 weeks ago, but my Mouser order was on hold waiting for a back-ordered item. I ordered extras of everything, usually more than doubling the BOM quantity so I'll have everything except the MAX PCB and wall wart needed to build a second MAX amp. But one item is back-ordered. The one item is the MPSA14. Yep, a 30 cent part is holding up my build. I made the newbie mistake of entering my Digi-Key order two days before the Mouser order so D-K had already shipped before I knew Mouser was out of stock of the MPSA14 until May. 
	

	
	
		
		

		
		
	


	




 I'm also going to be building several hybrid gainclone amps for my remodeled turntable consoles, so I'm going to order the MPSA14 with the chip amp parts early next week from D-K. It just chaps me that Mouser was out of stock of such a basic transistor.


----------



## ruZZ.il

start building anyway 
	

	
	
		
		

		
		
	


	




 since you have doubles.. 
 anyone: would a spare QB3/5/7 work instead of that QM2?


----------



## tomb

Quote:


  Originally Posted by *ruZZ.il* /img/forum/go_quote.gif 
_start building anyway 
	

	
	
		
		

		
		
	


	




 since you have doubles.. 
 anyone: would a spare QB3/5/7 work instead of that QM2?_

 

No. The MPSA14 is a Darlington transistor. Those have an extremely high continuous collector current - over an amp in the case of the MPSA14. We've also had someone put in a 2N5088 by mistake, and the relay would not work.

 I'll send a note to Colin and see if he can suggest alternates.


----------



## tomb

OK - haven't heard from Colin yet, but AMB's e12 pages list the following as alternates for the MPSA14:

 KSP13, KSP14, KSP25, KSP26, KSP27,
 MPSA13, MPSA27, MPSA28, MPSA29,
 2N6426, 2N6427, 2N7052, 2N7053,
 BC372 or BC373

 That should give us plenty of possibilities. 
	

	
	
		
		

		
			





 Meanwhile, I will update the e12 web pages on the MAX website.


----------



## BoilermakerFan

Thanks guys. One of the other members sent me a PM and is sending a couple my way.

 I do plan to start building very soon. I'm just refreshing my soldering skills before I start building the MAX. I'm also digging through all the info on Beezer's CD. 

 The final step is to decide on which headphones I want to pair with it. I have it down to the AKG601s and the Denon 3000's... for now.


----------



## fault151

Quote:


  Originally Posted by *joneeboi* /img/forum/go_quote.gif 
_Glad to know I could help. I just can't wait to see what you do with it; I just ran through your design page and I was blown away. All your work is really amazing! Simply stunning. Maybe you could make some illustrations of the MAX to put on your page once you're done. 
	

	
	
		
		

		
		
	


	


_

 

cheers! illustrations/design is what i do best, i just wish i knew what i was doing with making amps! Im making another valve amp with a friend and im designing a logo that i'm going to get printed on to the case. i can't wait for that! Ill post a pic when i'm done. 

 Oh i was looking on the glass jar audio, is it the soha level 2 kit that im after to build this amp? I emailed them but no reply.


----------



## ruZZ.il

Nope. I don't think the MAX kit is on the site. Ask him about the MAX kit specifically, if it's what you're after. If Jeff gets your e-mails, he'll get back to you. He may just be busy or away for the w.end..


----------



## fault151

Quote:


  Originally Posted by *ruZZ.il* /img/forum/go_quote.gif 
_Nope. I don't think the MAX kit is on the site. Ask him about the MAX kit specifically, if it's what you're after. If Jeff gets your e-mails, he'll get back to you. He may just be busy or away for the w.end.._

 

Yeh i've sent him an email so hopefully he will get it. I can't wait to get hold of one and start my build! Have you got one of them?


----------



## tomb

Jeff lists the MAX kit as a Bill Of Materials on his geocities site:
index

 EDIT: Man, sometimes that automatic link lookup that they enabled here is a real pain.

 --http://www.geocities.com/jeffrossel-- - that's what should appear up there instead of "index." I've tried editing it a couple of times, to no avail.


----------



## ruZZ.il

A kit or the MAX? I've MAXed myself out twice so far 
	

	
	
		
		

		
		
	


	



 I haven't used Jeff's MAX kit, but I've used some of his other kits that have been very good. His MAX kit is a very solid combination of parts, but there is still room for personal tweaking. If you're relatively new to all, don't think too much about the parts. Build the kit, enjoy it, and do some upgrades later on! Else, you'll never get one built.. you'll just be stuck trying to figure it all out...

 edit: haha yeah, that link thing has zapped me a few times to.. pretty annoying.


----------



## fault151

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Jeff lists the MAX kit as a Bill Of Materials on his geocities site:
index_

 

yeh i saw that, is it just a list of parts needed with prices or does he actually provide them all? If i could id rather get the majority of parts and just upgrade any other bits via suggestions from the rest of you guys. 

 Any ideas on how much it would come to for a full kit?


----------



## tomb

Quote:


  Originally Posted by *fault151* /img/forum/go_quote.gif 
_yeh i saw that, is it just a list of parts needed with prices or does he actually provide them all? If i could id rather get the majority of parts and just upgrade any other bits via suggestions from the rest of you guys. 

 Any ideas on how much it would come to for a full kit?_

 

As I understand it, that is the price of the kit: the total on that parts list at Jeff's site. He's provided the kit to many builders. I know, because he buys the boards from me. 
	

	
	
		
		

		
		
	


	




 The "list of parts" is the Bill Of Materials on the MAX website.


----------



## fault151

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_As I understand it, that is the price of the kit: the total on that parts list at Jeff's site. He's provided the kit to many builders. I know, because he buys the boards from me. 
	

	
	
		
		

		
		
	


	




 The "list of parts" is the Bill Of Materials on the MAX website. 
	

	
	
		
		

		
		
	


	


_

 

Oh right, i guess i'll just wait to hear from jeff then and buy a kit. Are all the components he sell what most people use? Or do they upgrade them as they go on? I can't believe i haven't discovered this amp before! Im looking forward to having a go at it.


----------



## fault151

Quote:


  Originally Posted by *ruZZ.il* /img/forum/go_quote.gif 
_A kit or the MAX? I've MAXed myself out twice so far 
	

	
	
		
		

		
		
	


	



 I haven't used Jeff's MAX kit, but I've used some of his other kits that have been very good. His MAX kit is a very solid combination of parts, but there is still room for personal tweaking. If you're relatively new to all, don't think too much about the parts. Build the kit, enjoy it, and do some upgrades later on! Else, you'll never get one built.. you'll just be stuck trying to figure it all out...

 edit: haha yeah, that link thing has zapped me a few times to.. pretty annoying._

 

yeh i think i will. Do most just use a wallwart power supply for it?


----------



## tomb

Quote:


  Originally Posted by *fault151* /img/forum/go_quote.gif 
_yeh i think i will. Do most just use a wallwart power supply for it?_

 

Well, that's supposed to be a major design feature: nothing but a 24VAC Class 2 Walwart for audiophile quality power.


----------



## fault151

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Well, that's supposed to be a major design feature: nothing but a 24VAC Class 2 Walwart for audiophile quality power. 
	

	
	
		
		

		
		
	


	


_

 

i read through the info on the max overview page, it makes for a really interesting read! wish all amp designs had such a good technical info page to look through for new comers like me. Its amazing to see so many variations on looks for the same amp!


----------



## BoilermakerFan

Quote:


  Originally Posted by *ruZZ.il* /img/forum/go_quote.gif 
_A kit or the MAX? I've MAXed myself out twice so far 
	

	
	
		
		

		
		
	


	



 I haven't used Jeff's MAX kit, but I've used some of his other kits that have been very good. His MAX kit is a very solid combination of parts, but there is still room for personal tweaking. If you're relatively new to all, don't think too much about the parts. Build the kit, enjoy it, and do some upgrades later on! Else, you'll never get one built.. you'll just be stuck trying to figure it all out...

 edit: haha yeah, that link thing has zapped me a few times to.. pretty annoying._

 

Or you can order the boutique parts from Beezer for two different Must Build MAXes and start with one, then plan to build the second later for yourself or a friend. 
	

	
	
		
		

		
		
	


	




 That's what I did. I could decided between two of the builds, but I knew I wanted the ES caps and the K42 bypass caps for both, so I ordered enough to build two except for the PCB board and wall wart. This way I have spares if I let the magic smoke out, but I also have the majority of parts to build a second tweaked MAX. I also ordered two sets of each of the tubes, but Radio Daze only had one of the 12FM6's, but I did get the (4) 12FK's and 12AE's, which were the two tubes I planned to start with anyways. 

 It wasn't difficult to use the BOM from the MAX site and order the parts individually. I just made sure I filled in the Customer Reference sections with the MAX locations for the parts so everything is labeled from Mouser or Digi-Key. My only mistake was not completing two shopping carts at the same time to cover myself if something was out of stock at one shop.


----------



## fault151

Quote:


  Originally Posted by *BoilermakerFan* /img/forum/go_quote.gif 
_Or you can order the boutique parts from Beezer for two different Must Build MAXes_

 

Do they provide a full kit on beezer or just certain parts?


----------



## tomb

Quote:


  Originally Posted by *fault151* /img/forum/go_quote.gif 
_Do they provide a full kit on beezer or just certain parts?_

 

Jeff's business is kits. 
	

	
	
		
		

		
			





 The niche for Beezar is providing the boards and those parts that you can't get from Mouser or DigiKey. I don't quite have them all, yet - but I'm working on it.


----------



## fault151

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Jeff's business is kits. 
	

	
	
		
		

		
		
	


	




 The niche for Beezar is providing the boards and those parts that you can't get from Mouser or DigiKey. I don't quite have them all, yet - but I'm working on it. 
	

	
	
		
		

		
		
	


	


_

 

So would you recommend just to get the full kit from Jeff instead? 

 Thanks for your help by the way!


----------



## ruZZ.il

To avoid the confusion in ordering all the parts yourself, I suggest you just get the kit from jeff. You could get a select few alternative parts from beezar either later, or once you've made the move.


----------



## fault151

Quote:


  Originally Posted by *ruZZ.il* /img/forum/go_quote.gif 
_To avoid the confusion in ordering all the parts yourself, I suggest you just get the kit from jeff. You could get a select few alternative parts from beezar either later, or once you've made the move._

 

ok thanks for your help. Im sorry if i sound a bit thick i was just getting slightly confused as to what i buy from where. Last question, are all of Jeff's parts standard quality or can you buy better parts from beezar?


----------



## tomb

Quote:


  Originally Posted by *ruZZ.il* /img/forum/go_quote.gif 
_To avoid the confusion in ordering all the parts yourself, I suggest you just get the kit from jeff. You could get a select few alternative parts from beezar either later, or once you've made the move._

 

Yep. Russ suggested this once before a page or two back and I totally agree with his advice.

 Better to get the whole thing if you're starting out into DIY. We'll still help with whatever problem you might have, but the documentation is already about as extensive as you will find. (I hope.) 
	

	
	
		
		

		
		
	


	




 EDIT: You can buy better parts at Beezar, but it's not extensive - just a few special ones.


----------



## fault151

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Yep. Russ suggested this once before a page or two back and I totally agree with his advice.

 Better to get the whole thing if you're starting out into DIY. We'll still help with whatever problem you might have, but the documentation is already about as extensive as you will find. (I hope.) 
	

	
	
		
		

		
		
	


	




 EDIT: You can buy better parts at Beezar, but it's not extensive - just a few special ones. 
	

	
	
		
		

		
		
	


	


_

 

Ok cheers guys, ill wait to hear back from Jeff then. Looking forward to it. I'll give you a shout if i need a bit of advice! Thanks for your help!!!! and patience!!! ha ha


----------



## erickytam

Which guy is Jeff, so I can email him about the kit too.

 Eric


----------



## tomb

Quote:


  Originally Posted by *erickytam* /img/forum/go_quote.gif 
_Which guy is Jeff, so I can email him about the kit too.

 Eric_

 

index
 (<www.geocities.com/jeffrossel>)


----------



## John Wilson

Has anyone tried the BG NX 0.1's as bypass (Millett H. M.) in place of the Wima's? Thank's. JW


----------



## tomb

Quote:


  Originally Posted by *John Wilson* /img/forum/go_quote.gif 
_Has anyone tried the BG NX 0.1's as bypass (Millett H. M.) in place of the Wima's? Thank's. JW_

 

0.1uf are too low in rating. If you are going to use this method to bypass Black Gates (Negatron likes it.), the proper choice is the NX Hi-Q, 0.47uf at 50V. The BG electrolytics in the MAX are rather on the large size and will benefit from the slightly larger bypass. It's only 10 cents more for the 0.47uf's.


----------



## tomb

I've added some minor things to DIYForums.org to show the way we're headed with some hopeful timelines.

 Also, I added an extensive web page for VitaminQ's on the MAX website at *Tweaks -> VitaminQ PIO Caps.*

 These are the genuine (really!) 0.22uf 196P Sprague VitaminQ's. Included are a couple of new pics and an elaborate detail that can form as a template for bending the leads to get these things installed.








 There's a shipment on the way to me, now. I will post them on Beezar when I receive them. I'll also try to have the tubes ready by then, too.


----------



## rhester

I am puting the finishing touches on my latest build. It has BlackGates and Vitamin Q's in CA8, and uses 2238/968 driving it.

 Also included is a Alien DAC with BlackGates. Switching between Alien and RCAs with a switch.

 Sounding very good and still buring in.


----------



## fault151

rhester;3817609 said:
			
		

> I am puting the finishing touches on my latest build. It has BlackGates and Vitamin Q's in CA8, and uses 2238/968 driving it.
> 
> Also included is a Alien DAC with BlackGates. Switching between Alien and RCAs with a switch.
> 
> ...


----------



## John Wilson

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_0.1uf are too low in rating. If you are going to use this method to bypass Black Gates (Negatron likes it.), the proper choice is the NX Hi-Q, 0.47uf at 50V. The BG electrolytics in the MAX are rather on the large size and will benefit from the slightly larger bypass. It's only 10 cents more for the 0.47uf's. 
	

	
	
		
		

		
		
	


	


_

 

Thank's Tomb! (0.47 BG) I get to start on mine today. It's nice working with a board. 99 percent of the time I hard-wire. I'm a true believer that all large caps must be by- passed. Being an old audiophile for 34 years, by-passing has been drilled into my head. JW


----------



## fault151

Does anyone know where i can get a Uk 3 pin power adaptor for the millet max design? It needs to be a wallwart (24V 1000 mA). Iv looked on ebay but can't find any that are actually sold within the UK.


----------



## ruZZ.il

Quote:


  Originally Posted by *fault151* /img/forum/go_quote.gif 
_Does anyone know where i can get a Uk 3 pin power adaptor for the millet max design? It needs to be a wallwart (24V 1000 mA). Iv looked on ebay but can't find any that are actually sold within the UK._

 

I use the L55BR from maplin. 
 There are probably cheaper ones around, but I found it when I needed it and it serves me really well 
	

	
	
		
		

		
			





 edit: if you are picking stuff up from maplin, or even anywhere else, may I suggest you look at some rotary tool kit? something like this. I picked up a similar rotacraft kit (doesn't seem to be there but it's basically the same thing. I had a flexible extension, that broke). The actual motor is a solid tool though, and it comes with quiet a lot of useful pieces. I've used it for so much stuff .. great buy. 
 I got a little set of good drill bits too (locally), for metal specifically, which I used with the rotary tool to bore out the middle bit of the tube sockets..


----------



## fault151

ok cheers, i'll have a look at it.


----------



## tomb

Quote:


  Originally Posted by *rhester* /img/forum/go_quote.gif 
_I am puting the finishing touches on my latest build. It has BlackGates and Vitamin Q's in CA8, and uses 2238/968 driving it.

 Also included is a Alien DAC with BlackGates. Switching between Alien and RCAs with a switch.

 Sounding very good and still buring in.

 <IMG]http://i247.photobucket.com/albums/gg140/rhester19/IMG_1414.jpg[/IMG>

 <IMG]http://i247.photobucket.com/albums/gg140/rhester19/IMG_1423.jpg[/IMG>

 <IMG]http://i247.photobucket.com/albums/gg140/rhester19/IMG_1425.jpg[/IMG>

 <IMG]http://i247.photobucket.com/albums/gg140/rhester19/IMG_1430.jpg[/IMG>_

 

Nice work on your MAX, Max!

 That Alien looks pretty cool in there - so do those PRP resistors, the Black Gates, and the VitaminQ's. Your part selection is the best. I'm sure it will sound very good after about 200hrs. 
	

	
	
		
		

		
		
	


	




 Seriously, mine took about that long for resolution to come in on the highs, and about another 200 before the bass was slamming like ES's. The ultimate sound has been well worth it, however.

 Great job!


----------



## rhester

My other BlackGate / K42Y is still changing subtly, but perciptably. It has probably 250 hrs on it. But this new one sounds decidely better so far. A little more bottom end presence and the stackapoles have taken a slight edge off the hi end. can't wait till it finished burning in.

 Also just finished a Bijou. It is great to be able to hear differences between the 2 approaches.


----------



## ruZZ.il

rhester: Solid parts selection indeed! and well put together. congrats on the new build! 
	

	
	
		
		

		
		
	


	




 Regarding the twisted signal wires you have.. it wasn't bought up by me initially here, but generally one would usually twist a signal with a ground since the ground signal is basically the same current going in the opposite direction, so, a signal and ground pair's net current is much closer to 0, so the EM field it creates is greatly reduced, and its cross talk with other signal cables is reduced too. 
 The common litz braid tries to keep the cable from being in parallel as little as possible, and thats cause the EM field created doesn't effect the signal thats traveling perpendicularly to the current direction, reducing cross talk too. 

 I'm not sure how noticeable of an effect practicing either of these are, but it's general consensus to use one of them rather than twisting 2 signals together, which is the antithesis of this all.


----------



## fault151

Iv placed an order of the kit from Jeff, im just looking in to buying a few other bits whilst im at it. Where can i get the black gate capacitors from? And what value is needed for them?

 Thanks.


----------



## tomb

Quote:


  Originally Posted by *fault151* /img/forum/go_quote.gif 
_Iv placed an order of the kit from Jeff, im just looking in to buying a few other bits whilst im at it. Where can i get the black gate capacitors from? And what value is needed for them?

 Thanks. 
	

	
	
		
		

		
		
	


	


_

 

1000uf 25V Black Gate NX for CA2L/R
 680uf 35V Black Gate NX for CA7L/R

Sonic Craft High-End DIY Audio Parts
parts conneXion - The authority on hi-fi DIY parts and components


----------



## fault151

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_1000uf 25V Black Gate NX for CA2L/R
 680uf 35V Black Gate NX for CA7L/R

Sonic Craft High-End DIY Audio Parts
parts conneXion - The authority on hi-fi DIY parts and components_

 

How many of each do i need please. Sorry but i don't have a part list or diagram to hand. I'll order of parts connexion i think.

 Cheers for you help!


----------



## ruZZ.il

2 of each (yeah, about 50$).
 Also, I suggest you print out both the schematic and parts list. you'll need to be looking at them both a lot soon 
	

	
	
		
		

		
		
	


	




 no problem
	

	
	
		
		

		
		
	


	




 And, if you plan to build yourself an alien DAC or something sometime, may I suggest you buy yourself 2x47uF 6.3v BG NX caps while you're at it.
 And, add an Alien DAC kit to your order from jeff too! You may not be ready to build it yet, but when you are (and there are plenty places to look for tips on how to solder that tiny stuff), the Alien DAC will be a great companion to your MAX.


----------



## fault151

is the alien dac purely usb based? I already have a beresford dac and a zero that i was planning to use with the millet. I suppose the added alien dac would always be another means of input. I take it id have to wire it up via a switch for rca's and the dac?


----------



## ruZZ.il

or use it externally, with RCAs. Jeffs kit comes with a little hammond enclosure and Tom has decent RCA females. If you already have a proper DAC, you may not need an alien.. its just another fun good sounding project


----------



## Aldyrin2

Ok, so I finally got finished with drilling on my case, and wired the whole thing up this weekend. I turned the RB12R/L trimmers all the way down, as the instructions say. When I bumped the power on (for the first time) for a few seconds, I got no voltage readout on the multimeter when checking the left DB bias voltage. All three LED's did turn on, however. I then checked the right DB bias voltage and similarly got no voltage readout. 

 I then checked to make sure the power supply voltage was high enough. It was sitting at about 26 volts, which I adjusted to 27. 

 I then checked the tube voltage, which was at 0 volts, same as the db bias voltages. 

 Any help or suggestions you guys can give would be greatly appreciated. I think I am done troubleshooting for tonight. All this drilling takes a lot out of you. Wish I had a drill press.

 I don't need a dummy load connected in order to test these voltages, do I? 

 Thanks in advance!


----------



## tomb

Quote:


  Originally Posted by *Aldyrin2* /img/forum/go_quote.gif 
_Ok, so I finally got finished with drilling on my case, and wired the whole thing up this weekend. I turned the RB12R/L trimmers all the way down, as the instructions say. When I bumped the power on (for the first time) for a few seconds, I got no voltage readout on the multimeter when checking the left DB bias voltage. All three LED's did turn on, however. I then checked the right DB bias voltage and similarly got no voltage readout. 

 I then checked to make sure the power supply voltage was high enough. It was sitting at about 26 volts, which I adjusted to 27. 

 I then checked the tube voltage, which was at 0 volts, same as the db bias voltages. 

 Any help or suggestions you guys can give would be greatly appreciated. I think I am done troubleshooting for tonight. All this drilling takes a lot out of you. Wish I had a drill press.

 I don't need a dummy load connected in order to test these voltages, do I? 

 Thanks in advance!_

 

Did you install R1? R1 is the heater resistor. Even if you decided you didn't need one, you must install a jumper or the circuit to the tube heaters is broken.


----------



## Aldyrin2

R1 is installed, and I'm seeing 1.5 volts across it when the amp is powered on. Any suggestions on things to check to see if the circuit to the tube heaters is the problem?


----------



## tomb

Quote:


  Originally Posted by *Aldyrin2* /img/forum/go_quote.gif 
_R1 is installed, and I'm seeing 1.5 volts across it when the amp is powered on. Any suggestions on things to check to see if the circuit to the tube heaters is the problem?_

 

You should see a vertical rod that goes through the center of the tube from top to bottom - it should glow red-orange. Those are the heaters/cathode. If those are glowing, then your tubes are "lit."

 I'm curious - are you measuring the test points as shown on the MAX website Setup and Biasing page? Refer to the pic of the board for the measurement points:

 Tube Bias: GND to TA2L for the Left tube and GND to TA2R for the right
 DB Bias: TA2L to TB2L _or_ TB1L for the Left DB,
 TA2R to TB2R _or_ TB1R for the Right DB.


----------



## Aldyrin2

Yes, I'm measuring from those points. I noticed that the tubes do seem to be lit. They weren't glowing brightly, the tip was the brightest, but it seemed the rod further down was getting more red as time passed. I'm a bit wary of leaving it on for a long period of time to see if it heats up more.


----------



## tomb

Quote:


  Originally Posted by *Aldyrin2* /img/forum/go_quote.gif 
_Yes, I'm measuring from those points. I noticed that the tubes do seem to be lit. They weren't glowing brightly, the tip was the brightest, but it seemed the rod further down was getting more red as time passed. I'm a bit wary of leaving it on for a long period of time to see if it heats up more._

 

I'm at a loss for explaining your not reading any voltage from GND to TA2L and TA2R - if the tube heaters are glowing. There are several things that could be going wrong with the buffers, but the tubes are pretty straightforward. If those cathodes are glowing, there's voltage on the tubes. If anything, you should be reading 27V, not 0.

 Did you install 2N5087's for the CCS? Some people have put in 2N5088's by mistake.

 Put one probe in the GND test point and touch the other probe to the bottom leg of RA9. That's the outer most resistor on the outside of the two CCS transistors. The bottom lead (facing to the front of the board) should read close to 23-24VDC.

 Also, with the probe still in GND, measure the voltage at the 1st tube socket leg on the left. That's pin 7 and it should be close to the bias voltage, whatever that may be.


----------



## Aldyrin2

Ok, well I took the measurements again, this time with a little more precision for the Tube bias measurements. I confirmed that I have 2N5087's installed in the CSS.

 TA2R - GND = 35 mV
 TA2L - GND = 5mV
 Bottom leg of RA9R/L - GND = 23.1 V
 From the tube socket pin positioned between 6 and 9 o'clock, looking at the amp from the front - GND = 23.7 V on both sides.


----------



## tomb

Quote:


  Originally Posted by *Aldyrin2* /img/forum/go_quote.gif 
_Ok, well I took the measurements again, this time with a little more precision for the Tube bias measurements. I confirmed that I have 2N5087's installed in the CSS.

 TA2R - GND = 35 mV
 TA2L - GND = 5mV
 Bottom leg of RA9R/L - GND = 23.1 V
 From the tube socket pin positioned between 6 and 9 o'clock, looking at the amp from the front - GND = 23.7 V on both sides._

 

OK - the voltage is OK, then. My guess is that there is something wrong in your CCS circuit. I believe that even if the trimmer is racked all the way in one direction, you should still read 2 or 3 whole Volts. At minimum in the other direction, they should register the same as that ~23VDC you're measuring.

 EDIT: scratch what I had before - let me do a bit more measuring on mine.

 EDIT: Nope, that's right. So what I asked before - have you possibly switched RA8 and RA9 with each other? RA9 is the higher-rated resistor and should be 10 times the resistance of RA8.

 EDIT3: I'm guessing too much at this point. Maybe it's time for some pics.


----------



## Ech0

Curious if anyone has used the K42's in C8 L/R in tamden with Elna RFS Silmic II's? 

 I'm thinking about doing this, replacing the Wimas with these assuming I don't get any negative feedback. They fit the board fairly well which is part of my consideration vs. Vit Q's.


----------



## tomb

Quote:


  Originally Posted by *Ech0* /img/forum/go_quote.gif 
_Curious if anyone has used the K42's in C8 L/R in tamden with Elna RFS Silmic II's? 

 I'm thinking about doing this, replacing the Wimas with these assuming I don't get any negative feedback. They fit the board fairly well which is part of my consideration vs. Vit Q's._

 

The K42's are a definite step up from the Wima's, regardless of the electrolytic in CA7L/R.


----------



## tomb

Aldyrin2,

 After making many more measurements, the stuff I read on my board is not that different than yours (except for the lack of tube bias). One might suspect the tubes, but it's very unusual that both would be bad at the same time. Indeed, the fact that you are registering a difference - even in mV - is an indication of that.

 If you can confirm all the right parts in the CCS section, then maybe there's something wrong with the trimmers and the way they're being turned?

 Remember that _clockwise_ raises the voltage on the tube bias. If you have them turned completely counter-clockwise, they would read minimum volts. I still think you'd read 2-3 Volts, not something in the millivolt range, but it's worth a check.


----------



## Ech0

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_The K42's are a definite step up from the Wima's, regardless of the electrolytic in CA7L/R._

 

Thanks for the super fast response TomB! 

 A bit of a night owl I see...


----------



## Aldyrin2

Well, I switched the tubes just to see if the voltage discrepancy would shift as well, but the voltages stayed the same. I had trouble confirming the part numbers of RA8 and RA9, but I measured their values to be 1.13k and 11.27k, respectively, while they were still attached to the board. I normally wouldn't do this, but these were the values I was expecting, so I guess in this case, there wasn't much if any parallel resistance to mess up the reading.

 I also previously confirmed that the transistors were 2N5087, so all the CSS parts seem to be correct. 

 I tried messing with the tube bias pots, but the tube bias voltage did not change.

 Something even more interesting: the tube bias voltage readings I posted earlier are present even if the power to the amp is turned off. Must be some juice in some of the caps that keep the voltage alive.

 I'll try to get you some images somehow.


----------



## Aldyrin2

Here are some pics. If I need higher resolution, let me know and I can get some more tomorrow. Thanks for the help!


----------



## Nebby

After reading up on this amp I'm tempted to build one; for balanced use are any modifications necessary aside from changing the input and output wiring? (Ie. from L/R/G to +/-/G per board)


----------



## pinkfloyd4ever

Aldryin, you gotta jumper your RB8s & RB9s


----------



## amphead

Quote:


  Originally Posted by *Nebby* /img/forum/go_quote.gif 
_After reading up on this amp I'm tempted to build one; for balanced use are any modifications necessary aside from changing the input and output wiring? (Ie. from L/R/G to +/-/G per board)_

 

You won't be disappointed Nebby! btw, pabbi1 built a balanced max, if you want to PM him. Otherwise we will get you through it!


----------



## ruZZ.il

^^, and just to note, you'd have to build 2 identical amps as each amp is only 2 channels. You need 4 channels for a balanced set-up.


----------



## tomb

Quote:


  Originally Posted by *pinkfloyd4ever* /img/forum/go_quote.gif 
_Aldryin, you gotta jumper your RB8s & RB9s
	

	
	
		
		

		
		
	


	


_

 

Good one, pink! I believe that breaks the circuit from V+ back to the output of the tube. Put jumpers there, and Aldryin should be OK.

 Night Owl - heck - I had to go to bed! Glad you guys were checking in the meantime!


----------



## fault151

Iv just been looking through the cant miss max builds, which is the most popular choice? i guess the sound is a mattaer of personal preference rather than which sounds 'the best'. Are there any which are more sort after than others? I think im going to go with build number 1.


----------



## BoilermakerFan

Quote:


  Originally Posted by *fault151* /img/forum/go_quote.gif 
_Iv just been looking through the cant miss max builds, which is the most popular choice? i guess the sound is a mattaer of personal preference rather than which sounds 'the best'. Are there any which are more sort after than others? I think im going to go with build number 1._

 

I have the parts to make the Build #2 or Build #3 so I can decide just how much bass emphasis I want once I decide on a pair of headphones.


----------



## fault151

Quote:


  Originally Posted by *BoilermakerFan* /img/forum/go_quote.gif 
_I have the parts to make the Build #2 or Build #3 so I can decide just how much bass emphasis I want once I decide on a pair of headphones._

 

Which build provides the most bass? 

 Does anyone have a brief overview on the type of sound i could expect from each build number?


----------



## slowpogo

Build #1, with Black Gates, is probably the "finest" (and most expensive) overall. I built one...it sounds very balanced and neutral with amazing detail. Bass is pretty robust too.

 The other builds using Nichicon ES caps are going to have more bass with a lot of impact.

 But the BG build still has plenty of bass. It's really deep and rich and tight with my K701's. I haven't heard an ES build but it's supposed to have really impressive bass slam.


----------



## ruZZ.il

build #2 will have more bass than #1, but it wont be as balanced and detailed. The clarity of build #1 is really nice though.. it's a cant miss build for sure 
	

	
	
		
		

		
			





 I think #1 has enough bass, too. #2 may be just a tad too much for me, its a little less controlled, the bass.


----------



## BoilermakerFan

Quote:


  Originally Posted by *fault151* /img/forum/go_quote.gif 
_Which build provides the most bass? 

 Does anyone have a brief overview on the type of sound i could expect from each build number?_

 


 From Beezer.com:

 The 3421/1358:

 "The 2SC3421/2SA1358 BJT pair has perhaps the most bass extension of any of the BJT output transistors you may use with the MAX. The highs seem to also be extended and clear on the MAX with these transistors, more so than with the 2SC2238 or 2SC3422. Some say they do this in return for some reduced mids. Regardless, these are a very fine alternate to the 2SC3422 and for combining with the Nichicon ES caps. They are a great complement to a 2SC3422/ES MAX if you want to build two."

 The 3422/1359:

 "the transistors offered for the MAX on this site. In my opinion, they compete very well with the detail of the 2SC3421/2SA1358 pair, but add bunches of dynamic slam in trade for slightly reduced highs. They are a perfect combination with the Nichicon ES capacitors and when properly installed with suitable bypassing caps, the combo of these transistors with ES caps is outstanding. Along with the 2SC3421/2SA1358 pair, it's a tough choice for which is more-suited with an ES-equipped MAX."

 But, the transistors are only part of the whole. The tubes will also influence the sound, so I'm starting with the 12FK6's since they appear to be the majority favorite for good, flat response. I'll be starting with the 3422/1359 combo which is the Build #2 setup initially. Finally, you have to consider your headphones too. If you have 'phones like the DT880's that are known for a strong bass emphasis, then you don't need to build an amp to further the bass boost unless you're a bass addict. I'm planning to go with Denon or AKG 601/701s so my build will place some emphasis on bass since my 'phones will be a little weaker in that range.


----------



## fault151

cheers for all your replies. I think ill go with build 1, just hope it has enough bass and impact. I like the sound to have a lot of presence and weight to it.


----------



## BoilermakerFan

It's quickly becoming obvious that the Millett MAX is like a can of Pringles, once you open it, you can't stop at just one! 

 Going back and looking at Build #1, I'm now rethinking my planned second build to the BGs and Vitamin Q's. I might change my ES/K42 build to incorporate a Alien DAC. Luckily, I ordered the longer Hammond enclosure.


----------



## tomb

Quote:


  Originally Posted by *fault151* /img/forum/go_quote.gif 
_Which build provides the most bass? 

 Does anyone have a brief overview on the type of sound i could expect from each build number?_

 

Looks like I'm behind on this, but let's see if I can synopsize it. The sound signature is controlled by three things:
*1. Output Transistors
 2. Electrolytic and Film Caps at CA2, CA7, CA8, and CA9
 3. Tubes.*
 I think I'd rank them in that order, too, but that maybe because I tend to stick with one tube type and don't vary too much with rolling.

*TRANSISTORS*
 I can't add much to Steinchen's excellent reviews, but:
*1.a. 2SC2238/2SA968 or 2SC2344/2SA1011* - The 2SC2238 pairs are the famous Toshibas. Extremely neutral, extended bass and highs, excellent mids, and tons of detail. Simply, it's just a fantastic all-around transistor pair. The problem is that they are very scarce, and sub-par counterfeits are rampant on the market.

*1.b. The 2SC2344/2SA1011* are a Sanyo pair that comes very close to the Toshibas. The difference is that the highs are a tad more prominent - but only a tad. IMHO, this is a very worthy competitor to the Toshibas, expecially because they are inexpensive and easy to get.

 Both of these are excellent choices for an high-end build with Black Gates and Vitamin Q's.

*2. 2SC3422/2SA1359* - another Toshiba pair, these are the ultimate for rockin' slam. Paired with ES's and Wimas or K42's, these are unparalleled for pure punchy fun. Great detail, neutral, but something to bounce Grado's right off your head with a smile. 
	

	
	
		
		

		
		
	


	




*3. 2SC3421/2SA1358* - still another Toshiba pair, but with a very different sound. These possess perhaps the deepest bass extension of any recommended transistor pair, but without the exagerrated punch of #2. Highs are also extended and prominent, although they may lack a bit of resolution. These are a great pairing with phones that need extended highs to sound lively. Note: these are the output transistors used on the Dynahi.

*4. MJE 243/253* are a very good pair similar to the 2SC2238/2SA968, in that they are fairly neutral, but extension and detail is not quite up the to the Toshiba level.

 My personal opinion is that 1a. and 1b. are great with Black Gates, but perform well with any cap combination. 2., 3., and 4. are excellent pairings with ES caps and power caps equipped with film bypasses.

*CAPACITORS*
*Electrolytics*
*1. Nichicon Muse ES* - Best bass is with ES caps, bar none - they really slam and punch with reverberation. Highs lack resolution but are good with bypassing. Muse KZ's are similar with perhaps a bit less bass, but with a mroe resolute/hard high end.

*2. Black Gates* are right there after about a month of solid listening every night (take that long to break-in), but background is blacker, highs much more resolving - cymbal crashes don't break up, but echo and reverberate in addition to the bass. Downside is that you must be _very_ patient with these. The full frequency response may seem to take forever to come in. Some people even complain about a lack of bass when building with these caps, but they just don't live with them long enough. When building with these, it's better to set the amp up, connect some music then walk away for a week before you even listen. 
	

	
	
		
		

		
		
	


	




*Film Bypasses*
*1. Wima MKP10* - excellent all around film bypass, these make power caps acceptable in the signal path for the Millett and the MAX and fix the highs resolution of ES's. Wima's are sort of traditional in the Millett heritage. Excellent neutrality with no loss of bass whatsoever, highs are also extended. The only downside is that experienced listeners may detect some graininess in the mids, with a tad bit of squeekiness in the highs.

*2. Russian K42's *- a MAX discovery by fellow Head-Fier fordgtlover, these film caps are a decided upgrade over the Wima's. Referred to as a PIO (Paper-In-Oil), they may actually use polyester and a vaseline type gel as the medium. Neutrality is the same, with far less grain. No loss whatsoever in bass, highs are probably 95%, but that works well in combination with ES caps or the 2SC3422 and 2SC3421 transistor pairs. Both these and Wima's are excellent choices for a build with those transistors and the ES caps.

*3. Vitamin Q's* - the ultimate in transparency and low distortion with excellent bass and a sparkly, very detailed high end, these are the ultimate bypass caps for Black Gates. Of course, they will work great with anything else, too.

 WARNING: Do not use any of these film caps in CA9, except for the Wimas. Even then, leave the positions blank if you are using Black Gates. You will kill the bass if you don't do this.

*TUBES*
 The Millett tubes are simple:
*12AE6/A *- Most gain, most punch with the most bass. Good ones have good high-end detail, too.
*12FK6* - Least gain, with best inherent high-end detail. Bass can be lacking with not as much punch, but good to tame too strong bass or bassy phones.
*12FM6* - Inbetween the other two in every way, including gain.

 EDIT: Of course, realize that I haven't included any reference to the MOSFETs. I am currently working on those and will report when I get them built. They have the potential to be as good or better as any of the other transistors.


----------



## fault151

Quote:


  Originally Posted by *BoilermakerFan* /img/forum/go_quote.gif 
_Luckily, I ordered the longer Hammond enclosure. 
	

	
	
		
		

		
		
	


	


_

 

Where did you get the hammond enclosure from?


----------



## fault151

Well cheers for your replies, makes it much easier for me to understand whats what on the build guide. Im liking the sound of the vit Q's with the black gates!


----------



## amb

Quote:


  Originally Posted by *tomb* 
_Looks like I'm behind on this, but let's see if I can synopsize it. The sound signature is controlled by three things:
 1. Output Transistors
 2. Electrolytic and Film Caps at CA2, CA7, CA8, and CA9
 3. Tubes.
 I think I'd rank them in that order, too, but that maybe because I tend to stick with one tube type and don't vary too much with rolling._

 

Sorry to be a spoiler, and I'm glad you threw in that last qualifier. But I would rank them in exactly the opposite order. If there is going to be a change in sound character, there has to be a measurable difference in the output. Take the output stage out of the Millett MAX and make them standalone, equip them with different transistor types, and then measure them. Be it THD, IMD, frequency response, whatever else. You will find very little difference amongst them, especially within the audio band.

 On the other hand, measure the tubes. You'll see large differences between tube types. or amongst the same type (but different brand). These tubes even vary significantly from sample to sample in the same type and manufacturer.

 The capacitors' effects are also measurable, but less than those of the tube.

 I am not saying that the changing output devices produce no differences, but those differences are small and way over-hyped around here.


----------



## BoilermakerFan

Quote:


  Originally Posted by *fault151* /img/forum/go_quote.gif 
_Where did you get the hammond enclosure from?_

 

I ordered the standard silver one called out in the BOM from Digi-Key and I ordered the longer one in black from Mouser. I originally ordered the longer one so I can use some industrial switches and indicator lights I have that almost look retro or art deco. I plan to use art deco cabinet pulls as my tube protectors too, so I'm going for an overall look that is a little different that the standard MAX.

 I may have to order my volume knob from Korea!


----------



## fault151

so there are 3 basic tubes makes that you can use on this design?


----------



## BoilermakerFan

Quote:


  Originally Posted by *fault151* /img/forum/go_quote.gif 
_so there are 3 basic tubes makes that you can use on this design?_

 

Yes, but the 12FM6 tubes are really hard to find. As AMB said, there are sound variations even within a tube type based on the manufacturer.


----------



## n_maher

Just wanted to point out that today is Colin's birthday and it'd be nice if a few of you stopped by the thread I started in the members lounge to wish him well.


----------



## tomb

Quote:


  Originally Posted by *amb* /img/forum/go_quote.gif 
_I am not saying that the changing output devices produce no differences, but those differences are small and way over-hyped around here._

 

We'll have to agree to disagree, AMB. After trying literally dozens of these things, I think the Millett tubes are surprisingly consistent. They're not at all like a 12AU7 which may vary wildly in sound signature, depending on manufacturer. Yes, the change from 12AE6 to 12FK6 can be significant, but that's about it. Sub-contracting was so incestuous among the 3 or 4 tube mfrs that differences were muddied long ago. The qualification I gave was as intended. Most Millett and now MAX builders decide on a tube type and pretty much stick with it. From there on, the differences are elsewhere - which is why I put tubes at the bottom of the list.

 As for the output transistors, we'll just have to disagree on that one, too. Build them and see - many agree that there are notable differences besides just the reference I gave.


----------



## tomb

Quote:


  Originally Posted by *BoilermakerFan* /img/forum/go_quote.gif 
_Yes, but the 12FM6 tubes are really hard to find. As AMB said, there are sound variations even within a tube type based on the manufacturer._

 

I disagree strongly. At any rate, the point is moot because there's no way to tell unless you inspect the tubes. The manufacturing was incestuously sub-contracted among only 3 or 4 mfrs. There's no rhyme or reason to it. Yes, there are differences from 12AE6 to 12FM6 to 12FK6, but that's as much as anyone can guarantee.

 Implying that there are differences from one mfr to another within the same tube type is setting someone up for disappointment, IMHO.


----------



## pinkfloyd4ever

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Night Owl - heck - I had to go to bed! Glad you guys were checking in the meantime! 
	

	
	
		
		

		
		
	


	


_

 

ya I'm lucky. My school is one of the few that give President's day off, or I normally wouldn't have been up that late. Thank you Washington and Lincoln!!


----------



## erickytam

Can someone help me measure the size of the PCB with the heatsinks on? I am going to buy a cigar box and use it as an enclosure, but I want to make sure it isn't too tall. The tubes will be sticking out of the top. If worst comes to worst, I'll maybe get larger heat sinks so they stick out of the top too so they won't look so funny.

 Thanks
 Eric


----------



## BoilermakerFan

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_I disagree strongly. At any rate, the point is moot because there's no way to tell unless you inspect the tubes. The manufacturing was incestuously sub-contracted among only 3 or 4 mfrs. There's no rhyme or reason to it. Yes, there are differences from 12AE6 to 12FM6 to 12FK6, but that's as much as anyone can guarantee.

 Implying that there are differences from one mfr to another within the same tube type is setting someone up for disappointment, IMHO._

 


 Fair enough, but I still wouldn't mix tubes from two manufacturers on one amp.

 I know that you didn't recommend paying for tube matching for these tubes, but isn't that because we adjust the bias voltages to "match" the tubes?


----------



## tomb

Quote:


  Originally Posted by *erickytam* /img/forum/go_quote.gif 
_Can someone help me measure the size of the PCB with the heatsinks on? I am going to buy a cigar box and use it as an enclosure, but I want to make sure it isn't too tall. The tubes will be sticking out of the top. If worst comes to worst, I'll maybe get larger heat sinks so they stick out of the top too so they won't look so funny.

 Thanks
 Eric_

 

From the MAX website under Layout and Board -> Board:
"Board Dimensions: 6.3" wide x 6.2" (160mm wide x 157mm),
 Board Specs: 2oz copper on an 0.062" (1.6mm) FR4 dielectric"

 That means if you use 1" tall sinks (standard), then 1.062" high. For 1.5" sinks, then 1.562" high. I hope you're calculating some sort of standoffs, too (including one in the center hole), because the board won't be stable resting on the heat sink pins, snipped leads, and solder blobs. So, you'd need to add in that height, too.


----------



## tomb

Quote:


  Originally Posted by *BoilermakerFan* /img/forum/go_quote.gif 
_Fair enough, but I still wouldn't mix tubes from two manufacturers on one amp.

 I know that you didn't recommend paying for tube matching for these tubes, but isn't that because we adjust the bias voltages to "match" the tubes?_

 

Well, what I'm saying is that the manufacturers aren't determined by the box or even the stamped label on the tube. 
	

	
	
		
		

		
		
	


	




 IOW, you may very well be using tubes from two different mfrs even if they are stamped with the same label. Some day I'm going to have to document these differences on the website, but it will have to wait until I have time. There are some things to look for if you are interested.

 You are generally correct about biasing the tubes vs. matching. There are many amplifier circuits out there that don't provide adjustable trimmers for the bias. Consequently, "matching" is in demand. With the Millett and the MAX, you can get the response of the tubes within 1/4dB of each other by careful biasing with most tubes. It takes a lot more than that for your ears to hear the difference.

 Again, these things are pretty consistent if one takes reasonable care to use tubes of the same construction, stay away from ones that are microphonic, etc. Even then, it takes some pretty wild differences to be noticed, IMHO.


----------



## erickytam

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_From the MAX website under Layout and Board -> Board:
"Board Dimensions: 6.3" wide x 6.2" (160mm wide x 157mm),
 Board Specs: 2oz copper on an 0.062" (1.6mm) FR4 dielectric"

 That means if you use 1" tall sinks (standard), then 1.062" high. For 1.5" sinks, then 1.562" high. I hope you're calculating some sort of standoffs, too (including one in the center hole), because the board won't be stable resting on the heat sink pins, snipped leads, and solder blobs. So, you'd need to add in that height, too. 
	

	
	
		
		

		
		
	


	


_

 

Thanks tomb, that helped. The cigar box is about 2.5" tall inside, so there's plenty of room. There are probably smaller cigar boxes I can fit it into, actually. I'll probably be using the pins that seperate Motherboards from computer cases to hold it up.

 Eric


----------



## Listen2this1

It has been really crazy around my house lately, but I wanted to say thanks for the comments on my case. I hope to do another one soon.


----------



## Aldyrin2

Well, it seems that jumpering RB8 and RB9 solved part of the problem. I can now see and adjust the tube bias voltage using the test points. 

 However, I am still seeing a DB Bias voltage of 0 mV for both sides. Any suggestions on things to check, now that the circuit is a little better?

 Thanks in advance!

 -Ald


----------



## tomb

Quote:


  Originally Posted by *Aldyrin2* /img/forum/go_quote.gif 
_Well, it seems that jumpering RB8 and RB9 solved part of the problem. I can now see and adjust the tube bias voltage using the test points. 

 However, I am still seeing a DB Bias voltage of 0 mV for both sides. Any suggestions on things to check, now that the circuit is a little better?

 Thanks in advance!

 -Ald_

 

Uh-oh. This legend from the MAX website is your problem:






 From your pics, it appears that you've installed either the 3422's, 3421's, or perhaps the MJE's. Those go on the right side of the sinks when facing the front of the board.

 EDIT: Don't panic. We've had some folks do the same thing and the transistors were OK. Pull them out, if you have a meter with an HFE measurement, check them out - they should all more or less be at 240 HFE. If that checks out, put them back in on the other side.

 Make a blob of solder big enough to cover all three pins on the back of the board, then pull the transistor out. Some people even tie a string around the transistor so that they can pull and melt the solder around the pins at the same time.


----------



## Aldyrin2

TomB, you are my hero. I installed the MJE253/243's. I will flip them tomorrow, and report back! Serves me right for just reading the PCB construction portion of the website, instead of reading all the sections in depth. If you have any control over the site, a link to the output stage page in the PCB Construction section might save others trouble who are similarly negligent.

 Thanks again!


----------



## tomb

We'll be waiting to hear the report. Good luck - you're almost there!


----------



## fakeplasticpete

Admittedly O/T, might have been posted here before, just thought it was cool...

 French dude rolls his own tubes....

MAKE: Blog: Make your own vacuum tubes?


----------



## pinkfloyd4ever

Quote:


  Originally Posted by *fakeplasticpete* /img/forum/go_quote.gif 
_Admittedly O/T, might have been posted here before, just thought it was cool...

 French dude rolls his own tubes....

MAKE: Blog: Make your own vacuum tubes?_

 

it is amazing but yes it has been, most recently just a few days ago http://www.head-fi.org/forums/f6/ult...-diyer-296585/


----------



## Aldyrin2

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Uh-oh. This legend from the MAX website is your problem:







 From your pics, it appears that you've installed either the 3422's, 3421's, or perhaps the MJE's. Those go on the right side of the sinks when facing the front of the board.

 EDIT: Don't panic. We've had some folks do the same thing and the transistors were OK. Pull them out, if you have a meter with an HFE measurement, check them out - they should all more or less be at 240 HFE. If that checks out, put them back in on the other side.

 Make a blob of solder big enough to cover all three pins on the back of the board, then pull the transistor out. Some people even tie a string around the transistor so that they can pull and melt the solder around the pins at the same time._

 

Well, I'm a little disheartened tonight. I pulled out the power transistors and checked their HFE. The PNP and NPN values matched up on the right and left; however, they were not around 240. One pair was around 140, and I don't remember the other pair's values. I think it may have been 170, but I'm not 100% sure.

 Since the values matched up, I decided to go ahead and put them in the correct places and give it a shot. This was very difficult to do, since I couldn't get the heatsinks to detach from the board.

 Long story short, I get them all back in place, switch on the power, and immediately blow the fuse. I didn't smell any smoke, so hopefully there was no damage. I inspected the board bottom to see if I had left any contacts bridged, but did not see any. 

 I know I sound like a broken record, but anyone have any suggestions?


----------



## pinkfloyd4ever

I would order a couple 2SC2238/2SA968 or 2SC2344/2SA1011 BJT pairs from beezar, I hear their shipping is pretty quick 
	

	
	
		
		

		
		
	


	




 plus they'll sound better than even non-fried MJEs


----------



## tomb

Quote:


  Originally Posted by *Aldyrin2* /img/forum/go_quote.gif 
_Well, I'm a little disheartened tonight. I pulled out the power transistors and checked their HFE. The PNP and NPN values matched up on the right and left; however, they were not around 240. One pair was around 140, and I don't remember the other pair's values. I think it may have been 170, but I'm not 100% sure._

 

That may still be OK, I haven't used MJE's for quite awhile and don't even have any to measure HFE. The 240 is pretty typical for all of the Toshibas. Looking at the MJE data sheets, I see now that the HFE is given as 180. So, I think it's enough of a register to say they're working. 
	

	
	
		
		

		
		
	


	




  Quote:


 Since the values matched up, I decided to go ahead and put them in the correct places and give it a shot. This was very difficult to do, since I couldn't get the heatsinks to detach from the board. 
 

Ooh - I hope you weren't trying to remove the sinks. All that was needed was a switch from one side to the other. You can buy some more insulating pads later if those got messed up.

  Quote:


 Long story short, I get them all back in place, switch on the power, and immediately blow the fuse. I didn't smell any smoke, so hopefully there was no damage. I inspected the board bottom to see if I had left any contacts bridged, but did not see any. 
 

Actually, this is a good thing. 
	

	
	
		
		

		
		
	


	




 The fuse has always been problemmatical. Until you replace it with a 1A Slo Blo, go ahead and bypass it by putting that one AC lead in the other terminal spot. I bet you'll be going in no time. 

  Quote:


 I know I sound like a broken record, but anyone have any suggestions? 
 

Have heart. You're almost there. Blowing the fuse is a good indicator in a perverse sort of way. Just bypass that thing and get a 1A Slo Blo later on, or leave it bypassed for good. It's really there to protect walwarts with non-resettable circuit protection. 
	

	
	
		
		

		
		
	


	





 EDIT: Of course, pinkfloyd4ever's suggestion is a good one 
	

	
	
		
		

		
		
	


	







, but I bet you can do this without having to go that route first.


----------



## tomb

We all know that they are car tubes, but this is ridiculous:






 Does this mean _unsafe at any speed_?
	

	
	
		
		

		
		
	


	



 (Yeah, I know there's no Chevron trademark, but it still struck me as cute.)


----------



## joneeboi

Happy post #3500, TomB and Team MAX. Let the good tubes roll.


----------



## amphead

Thats a collector set if there ever was one! 

  Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_We all know that they are car tubes, but this is ridiculous:






 Does this mean unsafe at any speed?
	

	
	
		
		

		
		
	


	



 (Yeah, I know there's no Chevron trademark, but it still struck me as cute.)_


----------



## tomb

Quote:


  Originally Posted by *amphead* /img/forum/go_quote.gif 
_Thats a collector set if there ever was one! _

 

Maybe there's some Studebaker tubes out there somewhere, too!


----------



## Aldyrin2

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Ooh - I hope you weren't trying to remove the sinks. All that was needed was a switch from one side to the other. You can buy some more insulating pads later if those got messed up._

 

I wouldn't have been doing this, but I was finding it exceedingly difficult to screw the transistors onto the heatsinks for the two in the middle. I find a general rule of thumb is that you should never, ever have to use two pairs of needle nose pliers at the same time.

 I guess when I get home tonight I'll bridge the fuse with some wire and see what happens. We'll see if we get any magic blue smoke.


----------



## tomb

Quote:


  Originally Posted by *Aldyrin2* /img/forum/go_quote.gif 
_I wouldn't have been doing this, but I was finding it exceedingly difficult to screw the transistors onto the heatsinks for the two in the middle. I find a general rule of thumb is that you should never, ever have to use two pairs of needle nose pliers at the same time.

 I guess when I get home tonight I'll bridge the fuse with some wire and see what happens. We'll see if we get any magic blue smoke._

 

No need to bridge the fuse with a wire. Just use the 1st and 2nd terminals instead of the last two.


----------



## pinkfloyd4ever

Quote:


  Originally Posted by *Aldyrin2* /img/forum/go_quote.gif 
_I guess when I get home tonight I'll bridge the fuse with some wire and see what happens_

 

 you don't even have to do that, just move your yellow wire to the other side of your red one (assuming you have them the same as in your earlier pics)


----------



## Aldyrin2

Will do. Now, if it turns out I had a Slo-blow fuse in place, do you recommend I try this, or not? I got this kit from Jeff, so I will have to wait till I get home to see whether or not it is a slow or fast fuse. He sent me a spreadsheet a while back covering the kit's contents, and I think that information was included. If not, is there any way to tell if it is slow or fast by looking at the fuse itself?

 I may just go to radio shack and see if they are selling them for not too outrageous of a price. I don't go there much any more since they tried to sell me a 80 dollar optical audio cable 6 feet long


----------



## tomb

Quote:


  Originally Posted by *Aldyrin2* /img/forum/go_quote.gif 
_Will do. Now, if it turns out I had a Slo-blow fuse in place, do you recommend I try this, or not? I got this kit from Jeff, so I will have to wait till I get home to see whether or not it is a slow or fast fuse. He sent me a spreadsheet a while back covering the kit's contents, and I think that information was included. If not, is there any way to tell if it is slow or fast by looking at the fuse itself?

 I may just go to radio shack and see if they are selling them for not too outrageous of a price. I don't go there much any more since they tried to sell me a 80 dollar optical audio cable 6 feet long 
	

	
	
		
		

		
		
	


	


_

 

Radio Shack is quite reasonable with these. They come 4 to a pack for $2.99:
RadioShack.com - Cables, Parts & Connectors: Fuses: Slow-blow fuses: 1.0A 250V 5x20mm Slow-Blow Glass Fuse (4-Pack)

 The ones I get from them have what looks like solder blob in the middle of the filament - it takes a lot longer to burn through, IOW.

 That said, I'm sure you'll be fine with bypassing it.


----------



## Aldyrin2

That makes me feel better. Mine just had a wire about the width of a hair in the middle. I assume that makes it a fast-blow fuse. Looks like I'll be heading to radio shack on the way home!

 I'll report back tonight. Thanks for all the help.


----------



## fran

Hah, my tubes came in corvair boxes just like the pics above!

 Fran


----------



## Aldyrin2

Well, I got the fuses, and these seem to work better than the kind I previously used. The amp will stay on now, but it looks like something else is still wrong. When I checked the DB bias voltage, it was about one volt on both sides. Head, meet wall. This is far from the 40 mV goal. 

 Just for kicks, I turned the DB bias pots all the other way till it clicked, and it still reads way over what it should. I didn't give the meter enough time to stabilize since I was concerned about ruining something with the pot wide open.

 Any thoughts on things to check?


----------



## Listen2this1

So I am putting a new design that will be interesting. Now I have built one I am confident doing this design starting with the design of the enclosure and internals. So in doing this I have came up with a concern. Is it possible to have the Lm317 mounted to a heatsink that is remotely mounted, so there will be extension wires between the board and the Lm317? 

 If so, what problems might I encounter.


----------



## tomb

Quote:


  Originally Posted by *Aldyrin2* /img/forum/go_quote.gif 
_Well, I got the fuses, and these seem to work better than the kind I previously used. The amp will stay on now, but it looks like something else is still wrong. When I checked the DB bias voltage, it was about one volt on both sides. Head, meet wall. This is far from the 40 mV goal. 

 Just for kicks, I turned the DB bias pots all the other way till it clicked, and it still reads way over what it should. I didn't give the meter enough time to stabilize since I was concerned about ruining something with the pot wide open.

 Any thoughts on things to check?_

 

Review the points you are measuring. Refer to that diagram of test points and the ones you should be referencing. Unless something is really screwed up, it perhaps sounds like you're measuring the wrong points? 1V across the power resistors would be something like 450ma. You could probably fry eggs on the heat sinks if the transistors were rejecting that much wattage.

 Remember when biasing the DB's, you are not referencing Ground. For the left channel, one probe is in the TA2L test point - the same one used for biasing the left tube. The other is either in TB1L or TB2L. These points are actually measuring only the voltage across a single resistor - RB10L (w/TB1L) or RB11L (w/TB2L). The right channel is identical with the appropriate "R."

 Let us know if that's it.


----------



## tomb

Quote:


  Originally Posted by *Listen2this1* /img/forum/go_quote.gif 
_So I am putting a new design that will be interesting. Now I have built one I am confident doing this design starting with the design of the enclosure and internals. So in doing this I have came up with a concern. Is it possible to have the Lm317 mounted to a heatsink that is remotely mounted, so there will be extension wires between the board and the Lm317? 

 If so, what problems might I encounter._

 

Yes, it's possible. However, you want to keep the leads within reason. The data sheets say 6 inches unless you use an input bypass cap. The MAX already uses CR2, the film cap in the back. So I suppose that even 6 inches is not a limit.

 However, remember that the LM317 is an IC, not a transistor. It's possible that lead length could be extended such that inductance/capacitance increases enough to cause oscillation. I don't have a clue what that length might be, though. I've gone a couple of inches with remote leads on TREADS before, with no ill effects whatsoever.


----------



## ruZZ.il

PM bomb jrossel, its (still) his birthday! HAPPY BIRTHDAY! 
	

	
	
		
		

		
		
	


	





 and look outside, right now, full lunar eclipse in the brew


----------



## Aldyrin2

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Review the points you are measuring. Refer to that diagram of test points and the ones you should be referencing. Unless something is really screwed up, it perhaps sounds like you're measuring the wrong points? 1V across the power resistors would be something like 450ma. You could probably fry eggs on the heat sinks if the transistors were rejecting that much wattage.

 Remember when biasing the DB's, you are not referencing Ground. For the left channel, one probe is in the TA2L test point - the same one used for biasing the left tube. The other is either in TB1L or TB2L. These points are actually measuring only the voltage across a single resistor - RB10L (w/TB1L) or RB11L (w/TB2L). The right channel is identical with the appropriate "R."

 Let us know if that's it. 
	

	
	
		
		

		
		
	


	


_

 

I double checked my measuring points and even checked the voltage across the resistors you mentioned. When I turn on the amp, it starts out at 1 volt, and settles down around .6ish volts. 

 I also noticed that QB3R and QB2L are really damn hot. Do you think I might have damaged some of the transistors in the DB section of the circuit by having the power transistors flipped? 

 The heatsinks didn't seem particularly hot, btw. The heatsinks for QB8R and QB9L seem to progressively get warmer, but the other two heatsinks remain pretty cold.


----------



## tomb

Quote:


  Originally Posted by *Aldyrin2* /img/forum/go_quote.gif 
_I double checked my measuring points and even checked the voltage across the resistors you mentioned. When I turn on the amp, it starts out at 1 volt, and settles down around .6ish volts. 

 I also noticed that QB3R and QB2L are really damn hot. Do you think I might have damaged some of the transistors in the DB section of the circuit by having the power transistors flipped? 

 The heatsinks didn't seem particularly hot, btw. The heatsinks for QB8R and QB9L seem to progressively get warmer, but the other two heatsinks remain pretty cold._

 

OK. This blind squirrel (me) is having a tough time finding this nut.
	

	
	
		
		

		
		
	


	




 I looked back at your photographs and don't see anything untoward, save the output power transistors which you've already changed. So, the next step I think before you go replacing anything is to make absolutely certain that you don't have any more parts reversed.

 This took some work, but hopefully these images will help. Please verify that you have the designated parts in their correct locations. If you need to slightly bend over a TO-92 transistor to see the designation, then do so. Most of the ones I've seen will take 2 or 3 bends back and forth before they break - so you should be OK to do this.

 As for the resistors, I just hope that you installed them with the designation right-side up.
	

	
	
		
		

		
		
	


	




 The V-D way of designating may take a little getting used to, but the last digit is scientific notation - as in, EXP+1, EXP+2, etc. IOW, the last number is how many tens to multiply. There's a few that you can check with your meter - the 1K's and 10R's should be measureable, for instance, but the rest are paralleled, I believe.

 At any rate, as a last step before replacing anything, please check these out and don't assume anything. 
	

	
	
		
		

		
		
	


	
















 Good luck!!


----------



## Aldyrin2

Wow I'm sure that took a while to put together. Thanks for the help. Tonight I'm going to unsolder all the resistors and ohm them out to confirm they are the right values. I double checked the transistors last night, and they were correct.


----------



## ruZZ.il

did I miss the pics?.. what resistors did you use? you may be able to tell a lot of their values anyway, without removing them.. I think removing them would be a tedious task, and bound to bring some trouble. There must be easier ways around it all...
 Meanwhile.. one exam left


----------



## Aldyrin2

They aren't all right-side up, so I can't tell the values without desoldering them. Tedious, I know, but I think this is probably the last step before I buy all new components for the DB section. 

 TomB, are you fairly certain that is where the problem lies?


----------



## ruZZ.il

I'll be with my MAX on Sat. night. I could measure the resistance from ground to a few selected spots, which would verify if the connected batch is alright or so, at-least.. there are a few that can be calculated..


----------



## tomb

Quote:


  Originally Posted by *Aldyrin2* /img/forum/go_quote.gif 
_They aren't all right-side up, so I can't tell the values without desoldering them. Tedious, I know, but I think this is probably the last step before I buy all new components for the DB section. 

 TomB, are you fairly certain that is where the problem lies?_

 

No, I'm not. It could just as easily be that the power output transistors in the wrong positions shorted some of the small ones out.

 I'm hopeful that maybe you have some resistors turned around, though, and that could be causing the high bias that you seem to be reading - 272ma now, I believe (600mV)?

 Either situation could be the issue, however. As stated, there's nothing obvious in your pics now, once you got those output transistors switched around.


 EDIT: I'd pinch myself a couple of times if I were you and see if there's something I forgot to check, whether I'm turning the trimmers in the wrong direction, whether I'm reading the wrong scale on the meter, etc.

 Your description of heat on the transistor-sink assemblies sounds about right. The middle two develop a decent amount of heat due to their close quarters, while the outer two may get slightly warm. As long as they aren't burning skin, maybe you should try to plug some headphones in and see if sound comes out (make sure there's no offset, first). Don't leave things turned on for long, though, if your numbers are correct.

 Another option before you go and start de-soldering resistors is another couple of photos for us. Try one with a lot of ambient light using macro and a tripod. The pics of your soldering on the bottom of the board are not really detailed enough to see if you have solder bridges. I'm assuming that you don't, but there are still things to check before we resort to too much actual work in replacement.


----------



## Aldyrin2

Something I guess I wasn't clear enough on before:

 The two small transistors I mentioned earlier as really damn hot actually burned my finger a little. 

 And the two power transistors I mentioned getting warm were the inner transistor on the left side and the outer transistor on the right side. So unless I'm missing something, there seems to be a different problem on either side?


----------



## jamess71

I got my first Max build where I'm gonna keep it. Nichicon Muse in C2 & C7 and K42's in C8 and C9 blank per Tomb, thanks. It's still breaking in but sound is great. How long for the muse to burn in? 

 I'm going to build my second max per Boutique #1 Still not 100% sure on a couple things.

 Should use the k42's for C8 or not? 

 I'll be leaving C9 empty.

 100 Ohm output resistors to knock the gain down a bit. Would I be better off with the Stackpole or the KOA's??

 Thnaks
 James


----------



## tomb

Quote:


  Originally Posted by *Aldyrin2* /img/forum/go_quote.gif 
_Something I guess I wasn't clear enough on before:

 The two small transistors I mentioned earlier as really damn hot actually burned my finger a little. 

 And the two power transistors I mentioned getting warm were the inner transistor on the left side and the outer transistor on the right side. So unless I'm missing something, there seems to be a different problem on either side?_

 

Well, I was dismissing the small signal transistors. QB2 and QB3, as an overall current issue, Actually, however, they should never see anything that would get them hot.

 Your description of the power transistors also indicates that something is seriously off-balance.

 1. Either you missed a transistor in the wrong position,
 2. One or more of the resistors are wrong, or
 3. You have some solder bridges somewhere that's causing a short.

 There could still be the issue that the power transistors were actually damaged, but I'm uncertain at this point - especially with the new info you just gave. See if you can get us some better photos as suggested and maybe we can take a closer look at some things.


----------



## tomb

Quote:


  Originally Posted by *jamess71* /img/forum/go_quote.gif 
_I got my first Max build where I'm gonna keep it. Nichicon Muse in C2 & C7 and K42's in C8 and C9 blank per Tomb, thanks. It's still breaking in but sound is great. How long for the muse to burn in?_

 

That's good news! 
  Quote:


 I'm going to build my second max per Boutique #1 Still not 100% sure on a couple things.

 Should use the k42's for C8 or not? 
 

Depends on your electrolytics. If you use Black Gates, I'd use VitaminQ's.
  Quote:


 I'll be leaving C9 empty.

 100 Ohm output resistors to knock the gain down a bit. Would I be better off with the Stackpole or the KOA's?? 
 

Uh ... *cough*cough* ... Kiwames have always been the better choice. It's just that price has usually been a problem. *cough*cough* 
	

	
	
		
		

		
			





  Quote:


 Thnaks
 James


----------



## fault151

God i can't wait to get hold of my kit jeff! i wanna get building! i just hope i can manage it!


----------



## jamess71

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Kiwames have always been the better choice. It's just that price has usually been a problem. *cough*cough* 
	

	
	
		
		

		
		
	


	


_

 

Kiwames it is then I have both on hand thanks to Beezar. 
	

	
	
		
		

		
		
	


	




  Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Depends on your electrolytics. If you use Black Gates, I'd use VitaminQ's._

 

I am using BG's but I have all these extra k42's on hand. 
	

	
	
		
		

		
		
	


	




 Is it worth anything to use these in place of the other wimas? And order a couple of vitQ's for C8?

 James


----------



## tomb

Quote:


  Originally Posted by *jamess71* /img/forum/go_quote.gif 
_Kiwames it is then I have both on hand thanks to Beezar. 
	

	
	
		
		

		
		
	


	






 I am using BG's but I have all these extra k42's on hand. 
	

	
	
		
		

		
		
	


	




 Is it worth anything to use these in place of the other wimas? And order a couple of vitQ's for C8?

 James_

 

The Wima's will make a cleaner build. This is just a guess, but they may be superior to the K42's in bypassing power caps. It's sort of like the question about whether to use ES's in the power cap positions rather than low-ESR/high-ripple Panasonic FM's.


----------



## thomaskuhn

So lately I have been staring at my amp and thinking of some cool looking case mods, and as an earlier post mentioned, I really wanted to add an analog gauge of some sort. I was at the local surplus store today and found a cool looking old analog gauge that I could not resist. I then went back and found a cool SS bezel that it fit perfectly into. I will just need to get a little bit welded, and I think this will look super cool! But, of course my artistic mind is racing way ahead of my logical side. What to hook the gauge to????

 So here is the story on it. It is a 1 mA gauge, so it is 0.0 - 1.0 mA with a resistance across the posts are 130 ohms. Pretty small amount, So where could it be connected? Or did I get ahead of myself? I would really like it not to interfere with the signal, but it the needle danced around a bit, that would be super cool.

 Tom Kuhn


----------



## ruZZ.il

maybe connect a small op-amp circuit to the input that can drive a dummy load with it in its path.. it'll be a parallel device to the whole amp and wont really effect anything.


----------



## fault151

Quote:


  Originally Posted by *thomaskuhn* /img/forum/go_quote.gif 
_So lately I have been staring at my amp and thinking of some cool looking case mods, and as an earlier post mentioned, I really wanted to add an analog gauge of some sort. I was at the local surplus store today and found a cool looking old analog gauge that I could not resist. I then went back and found a cool SS bezel that it fit perfectly into. I will just need to get a little bit welded, and I think this will look super cool! But, of course my artistic mind is racing way ahead of my logical side. What to hook the gauge to????

 So here is the story on it. It is a 1 mA gauge, so it is 0.0 - 1.0 mA with a resistance across the posts are 130 ohms. Pretty small amount, So where could it be connected? Or did I get ahead of myself? I would really like it not to interfere with the signal, but it the needle danced around a bit, that would be super cool.

 Tom Kuhn_

 

post a pic up if you get it working, id like to see it!


----------



## thomaskuhn

Quote:


  Originally Posted by *fault151* /img/forum/go_quote.gif 
_post a pic up if you get it working, id like to see it!_

 

Will Do!


----------



## odoe

Well, I have been enjoying my Muse ES/Orange Drops MAX for a few months now and I have a couple of boards that have been staring me in the face for the same amount of time. I'm going to go ahead and take a shot at a Blackgate MAX. I got my russian PIO's over the holidays and I'm just thinking of some little tweaks here and there.

 Has anyone successfully socketed the transistors or is that just trouble to try and do? Also, what was the mouser/digikey ID on the 0 ohm VD resistors I saw someone using for jumpers? I think they looked pretty cool.


----------



## slowpogo

Quote:


  Originally Posted by *jamess71* /img/forum/go_quote.gif 
_Kiwames it is then I have both on hand thanks to Beezar. 
	

	
	
		
		

		
		
	


	


_

 

I suggest Riken Ohm resistors. They're a little pricey, I think $2.70 each at Parts Connexion, but better than the Kiwame types. Not many people have used them on the Max (at least, they haven't posted about it) but the few who have really like them a lot.

 They are as detailed as metal film, and have a similar sweetening effect like the Kiwames, but without the "wooly" quality. Some people like this warm wooly sound, I prefer the clearer sound of Rikens.


----------



## Negatron

Quote:


  Originally Posted by *slowpogo* /img/forum/go_quote.gif 
_I suggest Riken Ohm resistors. They're a little pricey, I think $2.70 each at Parts Connexion, but better than the Kiwame types. Not many people have used them on the Max (at least, they haven't posted about it) but the few who have really like them a lot.

 They are as detailed as metal film, and have a similar sweetening effect like the Kiwames, but without the "wooly" quality. Some people like this warm wooly sound, I prefer the clearer sound of Rikens._

 

Another thing to consider is that if you intend to use the RB14 as attenuation and not a tuning tool, then the Riken will have an even greater advantage at the larger values (100R) at around 10R the Riken out performs the Kiwame but the margin is smaller in detail, the larger you go, the softer and more diffuse the Kiwames become with greater dissipation, the Rikens seem unaffected.
 But in other spots, such as RA8,9 Kiwames are a great tweak.

 It's a financial call, the K's tend to envelope the signal with a semi transparent mask, it is not at all unpleasant, but not neutral. But slowpogo is right, the R's have the detail of quality MF's with the sweetness of the best carbons without the low level noise riding the signal.
 BTW, if you run MOSFETS use Rikens - or nothing. You can hear the difference easier with Bells, close mic'd Flute, tenor sax and so on. As always JMO.


----------



## slowpogo

Quote:


  Originally Posted by *Negatron* /img/forum/go_quote.gif 
_But in other spots, such as RA8,9 Kiwames are a great tweak._

 

Can you expand on this? What might I hear if I replaced the mouser Vishay I have in RA8 with a 1.1k Kiwame? (I assume 1.1 is close enough to 1.13)


----------



## Negatron

Quote:


  Originally Posted by *slowpogo* /img/forum/go_quote.gif 
_Can you expand on this? What might I hear if I replaced the mouser Vishay I have in RA8 with a 1.1k Kiwame? (I assume 1.1 is close enough to 1.13)_

 

It's all real subjective, as well as subtle. MY ears hear a small amount of hardness in the CS and the diffuseness of the Kiwames soften that a bit. Since the amplification is from the varying plate r of the CS'd tube, the detail is unaffected. Since the current is so low I have even used Alan Bradley carbons replacing Dales there, and even though it is feeding the base of QA2, noise from the carbon has not been a factor. And 1.1K is no problem at all. (2%)


----------



## fordgtlover

Quote:


  Originally Posted by *odoe* /img/forum/go_quote.gif 
_...
 Also, what was the mouser/digikey ID on the 0 ohm VD resistors I saw someone using for jumpers? I think they looked pretty cool._

 

FRJ55 from Mouser


----------



## odoe

awesome, thanks!


----------



## Aldyrin2

Well, I checked all the resistor values in the DB section of the BOM, and they all are correct. Do you think it would be worthwhile to check out the resistors in the other sections? 

  Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Well, I was dismissing the small signal transistors. QB2 and QB3, as an overall current issue, Actually, however, they should never see anything that would get them hot.

 Your description of the power transistors also indicates that something is seriously off-balance.

 1. Either you missed a transistor in the wrong position,
 2. One or more of the resistors are wrong, or
 3. You have some solder bridges somewhere that's causing a short.

 There could still be the issue that the power transistors were actually damaged, but I'm uncertain at this point - especially with the new info you just gave. See if you can get us some better photos as suggested and maybe we can take a closer look at some things. 
	

	
	
		
		

		
			



_


----------



## tomb

Quote:


  Originally Posted by *Aldyrin2* /img/forum/go_quote.gif 
_Well, I checked all the resistor values in the DB section of the BOM, and they all are correct. Do you think it would be worthwhile to check out the resistors in the other sections?_

 

No. You already have.
	

	
	
		
		

		
		
	


	




 Voltage is adjustable and set within parameters, and your tubes are able to bias. The only other section with resistors is the relay circuit, but until we get your DB's working, we probably can't confirm there's any issue with that.


----------



## thomaskuhn

Well I am on my way with my mini project of adding an analog meter to the Max case. I posted previously about finding an old meter I liked, and have since gotten a bit of work done on it. The picture is not flattering by any means.















 The rails are standard SS cabinet handles. I cut the ends off of the two middle ones and welded on the bezel. It kind if gave it that floating look. There was another design that would have looked better, but I had never welded these materials before and did not want to ruin what I had. (Note: the bezel in the picture is actually the outside keep of a giant bearing that I found at the surplus store) The gauge is not in yet, because for some reason, I left it at work. But you can imagine and old black faced gauge with blue illumination (To be added) sitting in the hole. 

 My real dilemma is coming up with the circuit to drive the meter. RuZZ.il came up with the opamp idea, and I have been reading my "Electrical Engineering for Inventors" book on opamps. I have been through the chapter 4 times, along with the audio section. I have looked at the schematics... and I think I know what to do, but could use a little help (perhaps privately, as this is a little off topic). I am currently looking at using a OPA2234 driven off the 24V supply. I want to use a single supply for simplicity, but if I do that, I would have to add an DC level to the input. If I did this, would any of the offset get into the main input of the amp? My other idea was to use a split power supply to drive the opamp, and apply the DC offset (half of the 24V) after the feedback loop into the meter circuit and go from there. I am REALLY trying to learn this and figure it out on my own. But maybe a little nudge on the right track would help. 

 Thanks,

 Tom


----------



## Aldyrin2

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_No. You already have.
	

	
	
		
		

		
		
	


	




 Voltage is adjustable and set within parameters, and your tubes are able to bias. The only other section with resistors is the relay circuit, but until we get your DB's working, we probably can't confirm there's any issue with that._

 

Ok, well I guess I will wait till the transistors get in then and just replace all of them in the DB circuit. Do you think I should replace the CCS ones as well?

 Also, do you know if taking HFE measurements would reveal if there are any issues with the transistors?

 I'm pretty sure I've been hearing the relay switching when I turn the power to the amp on or off, so hopefully at least that part is good.


----------



## MrMajestic2

Finally got around to swap out my Black Gate bypass caps for VitQs on my Black Gate Max. Wow, what a difference, really detailed and smooth. I need to let it run for a while though, cause the BGs are not run in. I also removed the Kiwame RB14s while I was at it.


----------



## MrMajestic2

I was on a roll today, so I finished my Millet Max frontpanel:





 Night shot





 Day shot


 Maroon Audio is my own "brand" 
	

	
	
		
		

		
		
	


	



 Both the panel and window were made at Front Panel Express. The case is a Galaxy Maggiorato from Hifi2000.


----------



## odoe

wow
 that is an awesome piece of work Majestic
 nice job


----------



## ruZZ.il

ugh. wow.
 respecteroo!


----------



## tomb

Ulp - Oh Man - WOW! 
	

	
	
		
		

		
		
	


	







 You've got to give us details on how you did that!


----------



## MrMajestic2

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Ulp - Oh Man - WOW! 
	

	
	
		
		

		
		
	


	







 You've got to give us details on how you did that!_

 


 Thank you guys. Well, its a plexi window with the Millet Max logo engraved on it then lit up with 2 blue LEDs from behind. The window is countersunk from behind.


----------



## odoe

it almost looks like neon strips, i can't even tell where the blue LEDs are.

 nice work


----------



## MrMajestic2

Quote:


  Originally Posted by *odoe* /img/forum/go_quote.gif 
_it almost looks like neon strips, i can't even tell where the blue LEDs are.

 nice work_

 

Yeah, the engravings really glow when lit from the sides. I was hoping this would work, and it did. Thank god, because the window and panel cost a fortune


----------



## fault151

wow that looks great! i think we should start a thread to show of the millet max designs people have customised! How did you create the logo on the pannel?


----------



## MrMajestic2

Quote:


  Originally Posted by *fault151* /img/forum/go_quote.gif 
_wow that looks great! i think we should start a thread to show of the millet max designs people have customised! How did you create the logo on the pannel?_

 

I converted the logo to HPGL using Corel Draw. I had the window made at Front Panel Express.


----------



## MrMajestic2

Here is an inside shot of the window. Its actually a lot simpler than it looks. Sorry about the tape, but that was all I had at home
	

	
	
		
		

		
		
	


	









 The Millet in all its glory.






 A few gratuitous tubeshots thrown in for good measure.











 For some reason the last one turned out orange, but it still looks cool


----------



## fault151

Quote:


  Originally Posted by *MrMajestic2* /img/forum/go_quote.gif 
_I converted the logo to HPGL using Corel Draw. I had the window made at Front Panel Express._

 

What is HPGL? Is i a vector format logo that can be re sized easily? You've done a good job. Was it expensive to have made? Im a graphic designer and im looking to design my own logo for an amp im making, pls i could have something done for my millet when i make it.


----------



## MrMajestic2

Quote:


  Originally Posted by *fault151* /img/forum/go_quote.gif 
_What is HPGL? Is i a vector format logo that can be re sized easily? You've done a good job. Was it expensive to have made? Im a graphic designer and im looking to design my own logo for an amp im making, pls i could have something done for my millet when i make it._

 

Its a format that was originally used for HP plotters. Its also the format that is used for automated engraving at, for example, Front Panel Express. I also did an EPS version of it. I will let TomB decide wether it can be relased into the wild


----------



## fault151

Quote:


  Originally Posted by *MrMajestic2* /img/forum/go_quote.gif 
_Its a format that was originally used for HP plotters. Its also the format that is used for automated engraving at, for example, Front Panel Express. I also did an EPS version of it. I will let TomB decide wether it can be relased into the wild 
	

	
	
		
		

		
		
	


	


_

 

yeh good idea. Would you have to buy it as a complete front face panel? Is it hard to use the program the you design the face plates in? 

 Hw much did it cost to make it?


----------



## MrMajestic2

Quote:


  Originally Posted by *fault151* /img/forum/go_quote.gif 
_yeh good idea. Would you have to buy it as a complete front face panel? Is it hard to use the program the you design the face plates in? 

 Hw much did it cost to make it?_

 

Well, the window and panel are 2 separate parts. There is also a backpanel that I havent photographed yet. The Front Panel Designer is free from Front Panel Express and quite easy to use. Total cost including back panel was around 130 Euro with shipping 
	

	
	
		
		

		
		
	


	




 The cost was high partly due to the fact that I have work done on the backside of the front panel.


----------



## tomb

Quote:


  Originally Posted by *MrMajestic2* /img/forum/go_quote.gif 
_Its a format that was originally used for HP plotters. Its also the format that is used for automated engraving at, for example, Front Panel Express. I also did an EPS version of it. I will let TomB decide wether it can be relased into the wild 
	

	
	
		
		

		
		
	


	


_

 

Of course, release it to anyone that you want. 
	

	
	
		
		

		
		
	


	




 The logo is my design, but I would never copyright or trademark it with Pete's name in it.


----------



## MrMajestic2

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Of course, release it to anyone that you want. 
	

	
	
		
		

		
		
	


	




 The logo is my design, but I would never copyright or trademark it with Pete's name in it. 
	

	
	
		
		

		
		
	


	


_

 

Great


----------



## fault151

so is the logo on a plastic plate that drops in to place within the metal panel? Was the rest of the box an existing box that you just switched with the new panel?


----------



## MrMajestic2

Quote:


  Originally Posted by *fault151* /img/forum/go_quote.gif 
_so is the logo on a plastic plate that drops in to place within the metal panel? Was the rest of the box an existing box that you just switched with the new panel?_

 

Yes, its a separate piece of plexiglas with the engraving on it. It also has cutouts for the LEDs in all four corners, although I just used 2 LEDs so far. The rest of the case is a Galaxy Maggiorato from Hifi2000.


----------



## fault151

oh right sounds good! i havn't got my kit yet, but when i do i'll definitely be looking in to getting some nice box made. Are you thinking of putting an order in for a few of the plastic panels, or would ou be able to provide me the details and design if i was to get one made?


----------



## MrMajestic2

Quote:


  Originally Posted by *fault151* /img/forum/go_quote.gif 
_oh right sounds good! i havn't got my kit yet, but when i do i'll definitely be looking in to getting some nice box made. Are you thinking of putting an order in for a few of the plastic panels, or would ou be able to provide me the details and design if i was to get one made?_

 

I have no plan on mass ordering the panels. But I can help you later on if you want. Be aware that the Hifi2000 cases cost a lot to ship to the states if that where you are located. Im in europe myself, so its not too bad.


----------



## fault151

Quote:


  Originally Posted by *MrMajestic2* /img/forum/go_quote.gif 
_I have no plan on mass ordering the panels. But I can help you later on if you want. Be aware that the Hifi2000 cases cost a lot to ship to the states if that where you are located. Im in europe myself, so its not too bad._

 

im in the UK. i really like the look of the one you bought, it looks pretty good quality. Could hifi2000 engrave a logo for me that ive designed. Can the use screen printing methods do you know? I may just get a nice logo put on the the box and hav done. take it you managed to fit the millet in the box no probs?

 cheers for your help.


----------



## MrMajestic2

Quote:


  Originally Posted by *fault151* /img/forum/go_quote.gif 
_im in the UK. i really like the look of the one you bought, it looks pretty good quality. Could hifi2000 engrave a logo for me that ive designed. Can the use screen printing methods do you know? I may just get a nice logo put on the the box and hav done. take it you managed to fit the millet in the box no probs?

 cheers for your help._

 

I know that Hifi2000 does custom jobs on panels. Not sure if they do engraving or screen printing, but you can always ask. The webshop is here: Modushop I doubt that they do jobs on the top of the case since that is steel, not aluminium.
 I like the Hifi2000 cases, I have more then 10 of them at home 
	

	
	
		
		

		
		
	


	



 The Max fits with room to spare in the case.


----------



## fault151

Quote:


  Originally Posted by *MrMajestic2* /img/forum/go_quote.gif 
_I know that Hifi2000 does custom jobs on panels. Not sure if they do engraving or screen printing, but you can always ask. The webshop is here: Modushop I doubt that they do jobs on the top of the case since that is steel, not aluminium.
 I like the Hifi2000 cases, I have more then 10 of them at home 
	

	
	
		
		

		
		
	


	



 The Max fits with room to spare in the case._

 

That link is just for the panels and not the complete box? Am i missing where it says boxes or are they just panels? I looked on the following link, i think they sell the box as well. 

Hi-Fi 2000 contenitori per l'elettronica, case modding HTPC, Galaxy, rack, DIYaudio, computer cases, knobs,milled Handles, milled fronts, hi-end,


----------



## MrMajestic2

Quote:


  Originally Posted by *fault151* /img/forum/go_quote.gif 
_That link is just for the panels and not the complete box? Am i missing where it says boxes or are they just panels? I looked on the following link, i think they sell the box as well. 

Hi-Fi 2000 contenitori per l'elettronica, case modding HTPC, Galaxy, rack, DIYaudio, computer cases, knobs,milled Handles, milled fronts, hi-end,_

 

Modushop is Hifi2000s webshop. Its the same company. Click on the name Galaxy Maggiorato highlighted in blue. I know it looks like a title, but its actually a link to the cases. The website is very confusing.


----------



## fault151

Quote:


  Originally Posted by *MrMajestic2* /img/forum/go_quote.gif 
_Modushop is Hifi2000s webshop. Its the same company. Click on the name Galaxy Maggiorato highlighted in blue. I know it looks like a title, but its actually a link to the cases. The website is very confusing._

 

on the link you sent me the page loads up with just the panel for sale. All of the pages just sell panels, i cant see any mention of the rest of the box for sale.


----------



## MrMajestic2

Quote:


  Originally Posted by *fault151* /img/forum/go_quote.gif 
_on the link you sent me the page loads up with just the panel for sale. All of the pages just sell panels, i cant see any mention of the rest of the box for sale._

 

Did you click here:







 You have to register to see the correct prices.


----------



## tomb

OK, that tears it. Now I'm jealous of that avatar.


----------



## amphead

That is just gorgeous MrMajestic! It bumps the appearance up to commercial release grade Max. Sitting on the shelf of the nearest upscale hifi shop, who would know that it wasn't factory tooled/produced. Aaaaawsome!


----------



## cetoole

Frikkin' amazing work MrMajestic2 
	

	
	
		
		

		
		
	


	




. That is simply about the best, most professional looking DIY project I have ever seen. Amphead is right, that would not look at all out of place on the shelf of any hifi retailer, selling for several thousand $/€. I hope it sounds even close to as good as it looks.


----------



## fault151

Quote:


  Originally Posted by *MrMajestic2* /img/forum/go_quote.gif 
_Did you click here:






 You have to register to see the correct prices._

 

yeh i did, it came up with lots of shots of the panel. Ill try registering and seeing what i get. Thanks for your help!


----------



## MrMajestic2

Quote:


  Originally Posted by *amphead* /img/forum/go_quote.gif 
_That is just gorgeous MrMajestic! It bumps the appearance up to commercial release grade Max. Sitting on the shelf of the nearest upscale hifi shop, who would know that it wasn't factory tooled/produced. Aaaaawsome! _

 

 Quote:


  Originally Posted by *cetoole* /img/forum/go_quote.gif 
_Frikkin' amazing work MrMajestic2 
	

	
	
		
		

		
		
	


	




. That is simply about the best, most professional looking DIY project I have ever seen. Amphead is right, that would not look at all out of place on the shelf of any hifi retailer, selling for several thousand $/€. I hope it sounds even close to as good as it looks._

 

Thank you guys, your comments makes it worth the effort 
	

	
	
		
		

		
		
	


	




 The Black Gate version inside sounds amazing, although it still requires some more burn-in. Together with the Opus its a great combo.


----------



## MrMajestic2

Quote:


  Originally Posted by *fault151* /img/forum/go_quote.gif 
_yeh i did, it came up with lots of shots of the panel. Ill try registering and seeing what i get. Thanks for your help!_

 

You can always do a search for GX283 and you will get the case I used.


----------



## John Wilson

Here is were I'm at...so far. JW


----------



## pinkfloyd4ever

Quote:


  Originally Posted by *John Wilson* /img/forum/go_quote.gif 
_Here is were I'm at...so far. JW_

 

wow that's quite a variety of electrolytics you got there...I know the BGs and the ESs, what are the rest of those? And what are those blue resistors? That's a HUGE CM3 you got there. And is that a Kiwame/KOA R1?


----------



## fault151

Quote:


  Originally Posted by *MrMajestic2* /img/forum/go_quote.gif 
_You can always do a search for GX283 and you will get the case I used._

 

Ok i will do. Thanks for your help!


----------



## Daveze

MrMajestic2, you make me sad... 1) your case is far, far nicer than mine (for now?); and

 2) (the real reason behind my post) I can't even really get mine up and running yet. I'm just pre-checking the DB bias (BJT), one side is good (~30mV), the other is getting up in the multi V region (higher than the 200m range, higher than 2V, might even out in the 20V but I'm not game to leave it on for long enough...). Hoping to get some ideas on what might be wrong.


----------



## fault151

Quote:


  Originally Posted by *Daveze* /img/forum/go_quote.gif 
_MrMajestic2, you make me sad... 1) your case is far, far nicer than mine (for now?); and

 2) (the real reason behind my post) I can't even really get mine up and running yet. I'm just pre-checking the DB bias (BJT), one side is good (~30mV), the other is getting up in the multi V region (higher than the 200m range, higher than 2V, might even out in the 20V but I'm not game to leave it on for long enough...). Hoping to get some ideas on what might be wrong._

 

I have to say, im getting a bit worried as to whether i can accomplish the millet build, i keep reading how people ar estuggling with the tube biasing and other bits. Is the build not as simple as soldering the parts in the correct places and thats it? How come theres so many problems with the designs? 

 Or is this a one off incident?


----------



## tomb

Quote:


  Originally Posted by *Daveze* /img/forum/go_quote.gif 
_MrMajestic2, you make me sad... 1) your case is far, far nicer than mine (for now?); and

 2) (the real reason behind my post) I can't even really get mine up and running yet. I'm just pre-checking the DB bias (BJT), one side is good (~30mV), the other is getting up in the multi V region (higher than the 200m range, higher than 2V, might even out in the 20V but I'm not game to leave it on for long enough...). Hoping to get some ideas on what might be wrong._

 

The only thing that will result in what you describe is some misplaced parts. Check the two sides Left and Right to see what's different - especially since you have one side that's working well. That 30mV is perfectly within the range you should see for a DB at idle. So, that one is done correctly.

 If you can take some good pics of your DB section, post them. Different eyes are always helpful in spotting a mistake.


----------



## tomb

Quote:


  Originally Posted by *fault151* /img/forum/go_quote.gif 
_I have to say, im getting a bit worried as to whether i can accopmlish the millet build, i keep reading how people ar estuggling with the tube biasing and other bits. Is the build not as simple as soldering the parts in the correct places and thats it? How come theres so many problems with the designs? 

 Or is this a one off incident?_

 

Well, it's true that we've had a couple of hard nuts to crack lately (the MAXes, not the builders!). However, I'll stand by the claim that we haven't failed yet for someone who really wants to fix one that's had trouble.

 Daveze's problem is fresh. Let's hope that he/we spots the problem soon. Aldyrin2 has been in a waiting mode until he receives the new transistors I sent him. That should fix his MAX. We should also note that he's been steadily progressing. Any issue with his tubes was simply leaving those two resistors out. The DB's were damaged from reversing the positions of the output transistors. The question now is how much to replace to make it work. 
	

	
	
		
		

		
		
	


	







 By and large, the builds go without a hitch. However, there's no denying that it's an advanced build. I would not and have not recommended the MAX as a 1st build. One has enough to worry about with the great number of parts in the MAX. The tubes are fairly simple - they either work or they don't, and nothing burns up if they don't. However, the DB's can be a little daunting because they will fry if you're not careful. 

 With eyes wide open, some previous DIY experience, and with careful attention to the documentation, the chances are pretty good for a successful build.


----------



## tomb

Quote:


  Originally Posted by *pinkfloyd4ever* /img/forum/go_quote.gif 
_wow that's quite a variety of electrolytics you got there...I know the BGs and the ESs, what are the rest of those? And what are those blue resistors? That's a HUGE CM3 you got there. And is that a Kiwame/KOA R1?_

 

Looks like ES's, FG's, and KZ's in progressive heights - very beautiful photography, too.
	

	
	
		
		

		
		
	


	




 I meant to mention that Tom Kuhn's Heavy Metal project looks interesting, too. We're being treated to some great eye candy with the MAXes lately.


----------



## fault151

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Well, it's true that we've had a couple of hard nuts to crack lately (the MAXes, not the builders!). However, I'll stand by the claim that we haven't failed yet for someone who really wants to fix one that's had trouble.

 Daveze's problem is fresh. Let's hope that he/we spots the problem soon. Aldyrin2 has been in a waiting mode until he receives the new transistors I sent him. That should fix his MAX. We should also note that he's been steadily progressing. Any issue with his tubes was simply leaving those two resistors out. The DB's were damaged from reversing the positions of the output transistors. The question now is how much to replace to make it work. 
	

	
	
		
		

		
			








 By and large, the builds go without a hitch. However, there's no denying that it's an advanced build. I would not and have not recommended the MAX as a 1st build. One has enough to worry about with the great number of parts in the MAX. The tubes are fairly simple - they either work or they don't, and nothing burns up if they don't. However, the DB's can be a little daunting because they will fry if you're not careful. 

 With eyes wide open, some previous DIY experience, and with careful attention to the documentation, the chances are pretty good for a successful build. 
	

	
	
		
		

		
		
	


	


_

 

Right i see. I wonder if i should try something else first before attempting the build? I have a kit on order form Jeff.


----------



## tomb

Quote:


  Originally Posted by *fault151* /img/forum/go_quote.gif 
_Right i see. I wonder if i should try something else first before attempting the build? I have a kit on order form Jeff._

 

Yes.

 I recommend this one first for everyone:

How to Build the CMoy Pocket Amplifier

 Very cheap ($25?) and you get to learn almost all techniques at once. More than that, it's actually a bit harder than a good through-hole PCB, which of course describes the MAX.


----------



## fault151

Iv actually got a grado ra-1 clone amp that im going to build, thats a very similar design to a cmoy isn't it? 

 I can also get a mate to help me out with building the max. He's put together a few valve amps so should know what to do and with your help i guess we should be able to solve any probs. I think i'll go ahead and get the kit, just get my mate to help out so i don't damage anything.


----------



## tomb

Quote:


  Originally Posted by *fault151* /img/forum/go_quote.gif 
_Iv actually got a grado ra-1 clone amp that im going to build, thats a very similar design to a cmoy isn't it? 

 I can also get a mate to help me out with building the max. He's put together a few valve amps so should know what to do and with your help i guess we should be able to solve any probs. I think i'll go ahead and get the kit, just get my mate to help out so i don't damage anything._

 

That sounds like a good plan.


----------



## ruZZ.il

J.W good looking build, and thats some GREAT photography independently!


----------



## Daveze

I've swapped QB8R and QB9R around. You wouldn't believe how frustrated/furious I am right now, I even soldered them during the day so that I'd be paying more attention.

 If I can successfully unsolder them, can I just swap them back or are they gonna be toast?


----------



## tomb

Quote:


  Originally Posted by *Daveze* /img/forum/go_quote.gif 
_I've swapped QB8R and QB9R around. You wouldn't believe how frustrated/furious I am right now, I even soldered them during the day so that I'd be paying more attention.

 If I can successfully unsolder them, can I just swap them back or are they gonna be toast?_

 

Well, I'm glad you found the problem, but sad that there's not a good answer: no.

 I suggested that with Aldyrin2's, but we're learning that there's just no way. The power output transistors are very tough. Installed correctly, there's almost nothing that will kill them unless they burn up. However, soldered in reverse is an unsurvivable exception.


----------



## Daveze

I had read his experience, it was making me feel sad.

 I'm really quite sad now.


----------



## Daveze

But a glimmer of hope, I have the same transistors left over from some JISBOS that haven't been completed...


----------



## ruZZ.il

lucky! I had to wait a whole weekend to get some spare MJEs from a local elec. shop that got me running till I got my BJT variety pack from Tom. luckily I'd only burnt MJEs anyway  ultimately, we live, we learn, and fortunately, the support and help makes is much easier 
	

	
	
		
		

		
		
	


	




 Thanks again!


----------



## BoilermakerFan

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Well, I'm glad you found the problem, but sad that there's not a good answer: no.

 I suggested that with Aldyrin2's, but we're learning that there's just no way. The power output transistors are very tough. Installed correctly, there's almost nothing that will kill them unless they burn up. However, soldered in reverse is an unsurvivable exception.
	

	
	
		
		

		
		
	


	


_

 

Hmmm... I just realized I ordered multiples of everything except the transistor multi-pack from Beezer.

 But I've also decided to use the MAX as my pre-amp/headphone amp in all 3 or 4 of my console rebuilds, so I need to put in a new order to Beezer for more boards and bits anyways. I'll just make sure I order (6) of the multi-packs...

 Slightly off topic, but I can't decide which headphones to order. I was leaning towards the AKG K271s or K601s with plans to re-cable both, but I have a set of Denon C700 canal phones now and I really like them, but they are bit bass heavy. So the Denon D2000s are on the list for full size phones, as are the AT 900Ti's. I'd have Grado's on the list, but I listen to a lot of female folk/accoustic and the 225/325i's just slaughtered female voices, so the were dropped off the list. Any recommendations? My primary headphone build will be the Build #2, but I am planning to do one Build#1 with the BG's and VitQ's for the dining room console since it will be used the most often. 

 Send me PM's so this doesn't drift too far off topic, but I want the opinions of MAX listeners versus everyone else on HF. Thanks.


----------



## Daveze

Okay, new BJT's are in.

 Next problem: no test voltages for the right channel at all anymore. I've got V+ (27V) up to and across (small drop) RA2R but thats about it. I'm a bit stuck for ideas and quite tired...help is appreciated.


----------



## tomb

Quote:


  Originally Posted by *Daveze* /img/forum/go_quote.gif 
_Okay, new BJT's are in.

 Next problem: no test voltages for the right channel at all anymore. I've got V+ (27V) up to and across (small drop) RA2R but thats about it. I'm a bit stuck for ideas and quite tired...help is appreciated._

 

are you saying you lost tube bias, as well?

 Sounds like the incident may have blown some of the smaller transistors, too, although I haven't really seen that happen, yet.


----------



## Daveze

Yup. I've given up on it for tonight, I'll have a look in the morning but probably won't really get around to fixing it until Thursday...except that smaller transistors will take longer than that. Any ideas on what I should be checking?


----------



## tomb

Quote:


  Originally Posted by *Daveze* /img/forum/go_quote.gif 
_Yup. I've given up on it for tonight, I'll have a look in the morning but probably won't really get around to fixing it until Thursday...except that smaller transistors will take longer than that. Any ideas on what I should be checking?_

 

Well, truthfully, there's no explanation for losing the bias on the tubes unless something else got messed up when you replaced the BJT's. I suspect that's the case if you've lost tube bias, too. That doesn't make sense, otherwise. The tubes are essentially independent of the buffers as long as the voltage path through the DB resistors to ground is complete.

 I agree it's best not to work on it when you are tired. That can cause mistakes and even more frustration. We'll be here when you're ready to take a crack at it again. I'd focus on some good pics in the meantime, perhaps, and go over those parts in the Right buffer and see if something else is mixed up.

 EDIT: It could just as easily be something that was messed up all along and changing the BJT's only changed the meter readings.


----------



## John Wilson

Quote:


  Originally Posted by *pinkfloyd4ever* /img/forum/go_quote.gif 
_wow that's quite a variety of electrolytics you got there...I know the BGs and the ESs, what are the rest of those? And what are those blue resistors? That's a HUGE CM3 you got there. And is that a Kiwame/KOA R1?_

 

The blues are 0.1 Dales. Kiwame...Yes. Fine gold 2200 uf. CM 3 is a BG 330 uf 16V. JW


----------



## John Wilson

Quote:


  Originally Posted by *ruZZ.il* /img/forum/go_quote.gif 
_J.W good looking build, and thats some GREAT photography independently!_

 

Thank you sir. JW


----------



## John Wilson

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Looks like ES's, FG's, and KZ's in progressive heights - very beautiful photography, too.
	

	
	
		
		

		
			





 I meant to mention that Tom Kuhn's Heavy Metal project looks interesting, too. We're being treated to some great eye candy with the MAXes lately. 
	

	
	
		
		

		
		
	


	


_

 

Hi Tom. The photos are quick and dirty. Saturation was a little high. So the color was off on the PS caps which are 1 K 50 V Silmics. JW


----------



## ruZZ.il

what lighting did you use? I think thats an important element I'm seriously missing


----------



## BoilermakerFan

Quote:


  Originally Posted by *John Wilson* /img/forum/go_quote.gif 
_Hi Tom. The photos are quick and dirty. Saturation was a little high. So the color was off on the PS caps which are 1 K 50 V Silmics. JW_

 

Wow, I wish I had similar results on my "quick and dirty" pictures! 
	

	
	
		
		

		
		
	


	




 ruZZ.il, with the influence of eBay, there are some pretty nice little tabletop "studios" on the market with two lights and a shadow box backdrop that go for under US$200 from the major NYC online camera dealers like Adorama. Seeing JW's pics makes me want to invest in one of these little kits for all my hobby photography. Of course, I would also want the Canon Rebel XTi to go with it, but then there goes the money for the diy audio projects. 
	

	
	
		
		

		
		
	


	





 - BMF


----------



## MrMajestic2

Quote:


  Originally Posted by *BoilermakerFan* /img/forum/go_quote.gif 
_Wow, I wish I had similar results on my "quick and dirty" pictures! 
	

	
	
		
		

		
		
	


	




 ruZZ.il, with the influence of eBay, there are some pretty nice little tabletop "studios" on the market with two lights and a shadow box backdrop that go for under US$200 from the major NYC online camera dealers like Adorama. Seeing JW's pics makes me want to invest in one of these little kits for all my hobby photography. Of course, I would also want the Canon Rebel XTi to go with it, but then there goes the money for the diy audio projects. 
	

	
	
		
		

		
		
	


	





 - BMF_

 

Im thinking of making something like this:
Homemade Light Box for Product Photography » StudioLighting.net
 DIY all the way


----------



## fault151

Quote:


  Originally Posted by *BoilermakerFan* /img/forum/go_quote.gif 
_Wow, I wish I had similar results on my "quick and dirty" pictures! 
	

	
	
		
		

		
		
	


	




 ruZZ.il, with the influence of eBay, there are some pretty nice little tabletop "studios" on the market with two lights and a shadow box backdrop that go for under US$200 from the major NYC online camera dealers like Adorama. Seeing JW's pics makes me want to invest in one of these little kits for all my hobby photography. Of course, I would also want the Canon Rebel XTi to go with it, but then there goes the money for the diy audio projects. 
	

	
	
		
		

		
		
	


	





 - BMF_

 

I have a light tent and a couple of studio lights that i got of ebay, they really help to get good pics. Lighting is everything when it comes to photography. You need the most natural light bulbs possible to the sunlight.


----------



## ruZZ.il

Quote:


  Originally Posted by *MrMajestic2* /img/forum/go_quote.gif 
_Im thinking of making something like this:
Homemade Light Box for Product Photography » StudioLighting.net
 DIY all the way 
	

	
	
		
		

		
		
	


	


_

 

wheee


----------



## amphead

Looks like a nice photography project MrMajestic2!

 Fault151, if you have a little soldering experience and want to build the Max, I would give it a try. If you get stuck, just post pictures and we will get you through.

 Davese, keep on banging away on it. Post some good closeup pictures if you can and if not then keep those testpoint voltages coming.


----------



## Daveze

Thanks, I intend to keep going with it, just running short of time for it at the moment...

 I'm at work at the moment so I can't actually do anything but got any ideas of test voltages that'd help pinpoint the problem? I'm going to do a comparison between the two channels tonight or tomorrow but wondering if there's anything specific that would indicate a particular problem...


----------



## Aldyrin2

Well, I think swapping out the power transistors may have been just what the doctor ordered. After doing so, the DB Bias currents were about 30 mV, and I was able to get them up to 110 mV without any issues.

 I borrowed my girlfriend's ipod because I needed a source to test with and didn't have anything better immediately available. I think I might have been hearing some distortion when the gain was pretty high, but I'm not 100% sure because I was listening to some electronic techno-ish music she has on it for running. Is this normal? 

 Is the Millet Max affected by burn-in? If so, about how long does it generally take?

 Thanks for your help everyone!


----------



## amphead

The Max is very clean, when all is as it should be. I dont know that your build is out of the woods yet. The iPod shoud give a verrry nice sound, even though I lean towards my 8gb Walkman for hi-fidelity. So unless something obvious comes up, you will need to do some more troubleshooting.


----------



## Daveze

I had a general suggestion from one of my EE colleagues...Oscillation. Is this a possible candidate for my problem? This leads me towards the tubes, as they're the high gain components of the circuit...


----------



## John Wilson

Quote:


  Originally Posted by *ruZZ.il* /img/forum/go_quote.gif 
_what lighting did you use? I think thats an important element I'm seriously missing _

 

Bouncing the flash...my walls are white. JW Try this one. Light Box / Light Tent Photo Gallery by Bill Huber at pbase.com


----------



## amphead

One way to troubleshoot right channel vs left channel problems, is to swap tubes from left to right, and see if the problems follows. Also, I like to do mirror testpoint voltage checks from left channel to right channel. This sometimes helps to locate a problem. Just put the negative lead of your DMM on a ground point and leave it there, while moving your positive lead from left to right channel testpoints. Hope this helps.


----------



## Daveze

Tubes are fine, the swap check was the first thing I did after everything went weird...

 Homeward in 10min, I think I'm free enough tonight to run some tests and post some info.


----------



## Daveze

Okay, first significant strange thing: the bad channel only gets to ~148mV at the test points (all points), which stays after power is removed.

 The test point underneath CA8 I read 0mV for bad channel, compared to several volts that decrease for the good channel. However, the resistance between that point and ground is the same for both channels (1.022k).

 Above voltages referenced to ground.

 For reference to V+: ~26.7V at the test points on the bad channel.


----------



## tomb

Quote:


  Originally Posted by *Daveze* /img/forum/go_quote.gif 
_Okay, first significant strange thing: the bad channel only gets to ~148mV at the test points (all points), which stays after power is removed._

 

What you're reading is just the residual charge potential left in the caps on a powered off circuit.

  Quote:


 The test point underneath CA8 I read 0mV for bad channel, compared to several volts that decrease for the good channel. However, the resistance between that point and ground is the same for both channels (1.022k).

 Above voltages referenced to ground. 
 

Measuring the DB test points to ground doesn't clue us into anything. Let's get back to the recommended points so you can start with fundamentals.

  Quote:


 For reference to V+: ~26.7V at the test points on the bad channel. 
 

This doesn't make any sense either - V+ is V+ for the whole board, there is no "channel"


 Let's back up and have you give us the proper test points (no resistances):

 V+ to Ground: ?
 TA2L to Ground?
 TA2R to Ground?
 TB1L to TA2L?
 TB2L to TA2L?
 TB1R to TA2R
 TB2R to TA2R?

 What about those pics - something for the bottom of the board, too?

 EDIT: I see that Amphead suggested that you measure like this. That's fine once we have an understanding of your baseline condition. I'm not clear on that at all, yet. 
	

	
	
		
		

		
			





 P.S. Oscillation is near-impossible with tubes in a non-feedback circuit such as the Millett. I'm not sure we could make it happen even if we wanted it.


----------



## Daveze

Sorry, test point results as requested:

 V+ to GND: 27V
 TA2L to GND: 23.9V
 TA2R to GND: 62mV
 TB1L to TA2L: -30mV
 TB2L to TA2L: 28.9mV
 TB1R to TA2R: 0
 TB2R to TA2R: 0

 I've tried to get photos but I've only got a phone and it can't get it to focus past the heatsinks and tall caps.


----------



## Daveze

Its just as hard to get photos of the bottom too, you can see that there are soldering joints but not any detail beyond that.


----------



## tomb

Quote:


  Originally Posted by *Daveze* /img/forum/go_quote.gif 
_Sorry, test point results as requested:

 V+ to GND: 27V
 TA2L to GND: 23.9V
 TA2R to GND: 62mV
 TB1L to TA2L: -30mV
 TB2L to TA2L: 28.9mV
 TB1R to TA2R: 0
 TB2R to TA2R: 0

 I've tried to get photos but I've only got a phone and it can't get it to focus past the heatsinks and tall caps._

 

No, don't apologize - I hadn't seen Amphead's post up there asking you to measure like that. The thing is, once you start doing that, you are really looking for the bad part and should be measuring the leads around a component.

 For instance, if you wanted to check if some of the transistors were bad, you'd measure the leads referenced to ground and compare them to the same transistor on the good channel. most likely, you'd want to follow the circuit from beginning to end.

 You'd start with QB1, the PN4392 JFET, then proceed to QB2 and QB3 - checking each time to see if there were differences in the measurements on the transistor leads referenced to ground.


 Actually, you may be at that point. What your test point measurements show is something we probably already knew, but need to restate: The circuit to ground is broken somewhere in the Right channel DB. The tube output (Pin 7) references its voltage - and therefore, the ability to bias that voltage - to ground. This path reference to ground is through the DB circuit. That's why not jumpering the RB8 and RB9 resistors on another MAX resulted in an inability to bias the tubes (Aldyrin2's MAX).

 You've lost both the ability to bias the Right channel DB, but also the ability to bias the Right Tube. I can't explain why you were able to do it before, unless having the output trannies in backwards caused some perverted path to ground that didn't exist before. Whatever, that path is gone now - because that's the only thing that would stop your tube from biasing at this point, I believe.

 Let's try this - see if you can measure the voltage difference between the leads/pads with the white arrows from the black arrows. Alternatively, the white arrows should measure "0" Volts when referenced to V+. The black arrows should measure "0" Volts when referenced to Ground. You can reference them to the V+ and Gnd test points, but that's only going to prove that the traces are OK, and we pretty much know that. However, the difference from one of those white leads to anyone of those black arrows should be 27VDC, unless you've got some bad parts:






 Try that for now and tell us what you get - you can probably just describe the exceptions. This may still just confirm the traces, but it may find some solder bridges, if you have any.

 We'll go for some intermediate voltages, next.

 Is there a camera you can borrow from someone? This is going to continue to be difficult if we can't even see your board.

 EDIT: Check the parts again while you're at it:

 QB1R: PN4392 JFET
 QB2R, QB4R, QB6R: 2N5087
 QB3R, QB5R, QB7R: 2N5088
 RB1R: 1K ohm
 RB2R, RB3R: 10 ohm
 RB4R, RB5R: 100 ohm
 RB6R, RB7R: 220 ohm
 RB8R, RB9R: JUMPERED
 RB10R, RB11R: 2.2 ohm Power Resistor


----------



## tomb

Please note the edits above if you check the thread again. Thanks, good luck, and hang in there!!


----------



## Daveze

Every combo of white to black gives 27V.


----------



## Daveze

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_EDIT: Check the parts again while you're at it:

 QB1R: PN4392 JFET
 QB2R, QB4R, QB6R: 2N5087
 QB3R, QB5R, QB7R: 2N5088
 RB1R: 1K ohm
 RB2R, RB3R: 10 ohm
 RB4R, RB5R: 100 ohm
 RB6R, RB7R: 220 ohm
 RB8R, RB9R: JUMPERED
 RB10R, RB11R: 2.2 ohm Power Resistor






_

 

All parts are as you've described.


----------



## tomb

OK, let's do this - measure the Voltage across each resistor, first the good channel, then your bad one (Right):

 RB13L: ?V RB13R: ?V (Also verify for 100 ohms - forgot this one earlier)
 RB1L: ?V RB1R: ?V
 RB2L: ?V RB2R: ?V
 RB3L: ?V RB3R: ?V
 RB4L: ?V RB4R: ?V
 RB5L: ?V RB5R: ?V
 RB6L: ?V RB6R: ?V
 RB7L: ?V RB7R: ?V

 Try mV first, then switch to whole volts if that exceeds the scale.


----------



## Daveze

I suspect we're close with this one:

 RB13L: 108.5mV RB13R: 106.3mV (verified for 100 ohms - ok)
 RB1L: 1.3mV RB1R: 409mV DING DING DING DING
 RB2L: 21.1mV RB2R: 23.4mV
 RB3L: 22.5mV RB3R: 22mV
 RB4L: 219mV RB4R: 231mV
 RB5L: 230mV RB5R: 218mV
 RB6L: 240mV RB6R: 235mV
 RB7L: 240mV RB7R: 234mV

 Something screwy with RB1R methinks.


----------



## Daveze

Unfortunately its pretty much way past my bed time now. I won't do any more work now because I need a few hours of sleep before work but I might attack the thing tomorrow morning if its an easy fix...


----------



## tomb

Quote:


  Originally Posted by *Daveze* /img/forum/go_quote.gif 
_I suspect we're close with this one:

 RB13L: 108.5mV RB13R: 106.3mV (verified for 100 ohms - ok)
 RB1L: 1.3mV RB1R: 409mV DING DING DING DING
 RB2L: 21.1mV RB2R: 23.4mV
 RB3L: 22.5mV RB3R: 22mV
 RB4L: 219mV RB4R: 231mV
 RB5L: 230mV RB5R: 218mV
 RB6L: 240mV RB6R: 235mV
 RB7L: 240mV RB7R: 234mV

 Something screwy with RB1R methinks._

 

Well, I doubt that anything's wrong with RB1R, specifically. That resistor is not paralleled with anything else. Measure it for resistance - you should get 1K ohms or close.

*I believe that's telling us that you've blown QB2R and QB3R.* There is nothing that RB1R is connected to, except the tube output and the junction of the QB2R/QB3R pair, which are otherwise known as the signal transistors. That sort of makes sense, since they are directly connected to the voltage and ground legs of QB8R and QB9R, respectively. They probably got fried when those output transistors were switched.

 Replace those and we'll cross our fingers.

 Be *very* careful about doing this - don't get them mixed up at this point! Always remember: EVEN transistor-ODD pad and ODD transistor-EVEN pad. So QB*2* is a 2N508*7* and QB*3* is a 2N508*8*. This logic follows for the TO-92's through the entire buffer.


----------



## Daveze

Blast. Those I don't have spare.

 Order placed. I wonder how the PIO will go as the tone cap in a bass guitar....


----------



## fault151

*Tomb,* if i buy a ready made millet from America will i need to do anything to get it working here in the UK other than just buying a UK power supply? Theres no internal features to change is there?


----------



## tomb

Quote:


  Originally Posted by *fault151* /img/forum/go_quote.gif 
_*Tomb,* if i buy a ready made millet from America will i need to do anything to get it working here in the UK other than just buying a UK power supply? Theres no internal features to change is there?_

 

There are many international MAX builders who can answer this question better than me.

 The MAX needs 24VAC, preferrably from a source capable of at least 1 Amp.

 ruZZ.il checks in pretty frequently and Israel uses the same as the UK, I think. So, let's see what he says. I sold an older Millett Hybrid to another Head-Fier in Israel, and I believe he was able to purchase an International convertor to 110VAC/60Hz. If you go that route, then you can buy any normal 24VAC walwart from here in the states and plug into that device.

 There are a couple of MAX builders in the UK, too. Maybe they'll have an answer, too.


----------



## fault151

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_There are many international MAX builders who can answer this question better than me.

 The MAX needs 24VAC, preferrably from a source capable of at least 1 Amp.

 ruZZ.il checks in pretty frequently and Israel uses the same as the UK, I think. So, let's see what he says. I sold an older Millett Hybrid to another Head-Fier in Israel, and I believe he was able to purchase an International convertor to 110VAC/60Hz. If you go that route, then you can buy any normal 24VAC walwart from here in the states and plug into that device.

 There are a couple of MAX builders in the UK, too. Maybe they'll have an answer, too._

 

Well Jeff said to get a specific wallwart (24V 1000 mA). He never mentioned the internal bits. The version im buying has been made for use in the US. If its a case of just swapping the power supply then it will be fine to buy his and get my own supply for over here.


----------



## fran

I built a MAX and I'm in Ireland. Once you have a PS that will give you 24V AC then you are set. There is nothing else to worry about in the circuit. Once the power from the wallwart hits the max PCB, it is converted to DC so any differences are gone.

 Just check that the wallwart/power supply is giving you 24VAC - not 24VDC!

 I say this because although there seems to be 24VAC wallwarts 10 a penny in the USA, I couldn't find any here (eg Maplin) - until you hit about €70+VAT (RS components). So just watch out for that. So the PS you are looking for is 240VAC input/24VAC output.


 If the worst comes to the worst and you can't find one, you could build one fairly easily prob will run to about £30 to make one up.

 Fran


----------



## fran

Actually, I just reread your post. The easiest route here for you is to get the US power supply from the seller and then go to Maplin a buy a step down transformer. See here:

Maplin > 100W UK to USA Voltage Convertor


----------



## Daveze

I'd be really surprised if it wasn't easier to jump on ebay and find the appropriate 24V supply from a local seller...you'll save on having the ship the US 24V supply and save on having to buy that expensive step down trafo (my 24V supply was shipped to me for ~$30AU).


----------



## amphead

Sorry Davese, I only meant reference to ground on the testpoints for the tubes. I should have made that clear. TomB has you on the right track. Hope you find it soon.


----------



## Daveze

Thats no drama, by day I'm a process engineer: when trying to troubleshoot a plant that isn't working right, you can never have too much info. I'm just not a good enough EE to know what info is useful and what is not, so I was just highlighting things that were weird. I reckon if I knew the mechanism by which transistors failed I could nearly figure out the problem, I built up a spice model with that intent but didn't know what to do with it...


----------



## Daveze

Hmm, 1k resistors between Base and Emitter of both transistors gives similar numbers to what I get in real life...


----------



## thomaskuhn

I have most all of the schematics and hardware done for driving my "VU" analog meter. Thanks Ruzz.il for the tip. I am driving the meter through an op-amp coupled with a rectifier. Working good so far. I just have one quick question, I am splitting off the input signal with two channels and ground going to the MAX, and then splitting the left channel and ground to go to the meter driver. To power the op-amp, I am splitting the voltage from the power supply to +13.5V and - 13.5V with a ground in the middle (using two resistors). This circuit only works when the audio ground is connected to this "floating" ground. Could this in any way cause any audio issues with the MAX itself? 

 Tom Kuhn


----------



## adfinni

Quote:


  Originally Posted by *fault151* /img/forum/go_quote.gif 
_Well Jeff said to get a specific wallwart (24V 1000 mA). He never mentioned the internal bits. The version im buying has been made for use in the US. If its a case of just swapping the power supply then it will be fine to buy his and get my own supply for over here._

 

I got my 24V PS from maplins.co.uk. Works fine for my MAX, and comes with a multitude of different connection sizes, with about 3/4 actually fitting in the power socket.

 I used to BOM and got most of my bits from mouser in the USA (and got buggered by customs), but the rest of my bits and capacitors from all over the shop.


----------



## fault151

Quote:


  Originally Posted by *fran* /img/forum/go_quote.gif 
_I built a MAX and I'm in Ireland. Once you have a PS that will give you 24V AC then you are set. There is nothing else to worry about in the circuit. Once the power from the wallwart hits the max PCB, it is converted to DC so any differences are gone.

 Just check that the wallwart/power supply is giving you 24VAC - not 24VDC!

 I say this because although there seems to be 24VAC wallwarts 10 a penny in the USA, I couldn't find any here (eg Maplin) - until you hit about €70+VAT (RS components). So just watch out for that. So the PS you are looking for is 240VAC input/24VAC output.


 If the worst comes to the worst and you can't find one, you could build one fairly easily prob will run to about £30 to make one up.

 Fran_

 


 ok cheers for your help, i'll have a quick look on ebay too.


----------



## Aldyrin2

I took another listen to my MAX last night, and I think the distortion I heard previously must have been in my head. I'm still concerned something might be wrong with some of the components due to all the work i've been doing on it, though. 

 Are there any general integrity tests to run on the MAX to determine its "healthiness"? I'm wondering if I should replace the transistors in the diode bridge that were hot enough to burn my finger a while back, at the minimum. 

 I might be able to use an oscilloscope in the lab where I work, but i'm not 100% sure they would be ok with it, so I was hoping for a different way to confirm all is well.

 Thoughts?


----------



## tomb

Quote:


  Originally Posted by *Aldyrin2* /img/forum/go_quote.gif 
_I took another listen to my MAX last night, and I think the distortion I heard previously must have been in my head. I'm still concerned something might be wrong with some of the components due to all the work i've been doing on it, though. 

 Are there any general integrity tests to run on the MAX to determine its "healthiness"? I'm wondering if I should replace the transistors in the diode bridge that were hot enough to burn my finger a while back, at the minimum. 

 I might be able to use an oscilloscope in the lab where I work, but i'm not 100% sure they would be ok with it, so I was hoping for a different way to confirm all is well.

 Thoughts?_

 

I think some of this may be getting used to tubes. Every NOS tube has sat on the shelf a minimum of what - 30 yrs, perhaps 40 yrs for Millett tubes? The vacuum in the tube is impossible to maintain over that period of time. Some gas molecules will infiltrate the moment it left the production line, much less 30-40 years later. That's why they have "getters" and "getter flashes" - to catalyze the errant gas molecules to the compound in the getter flash. Such a reaction takes time - more time for more molecules, etc., etc. Until those gas molecules are catalyzed to the getter flash, they block and carrom some of the transmission of electrons from the cathode to the plates, so distortion will be higher for a tube that needs more burn-in _and cool-down_. Remember, we're talking about stabilizing a material system at elevated temperatures - cool-down is just as important as burn-in.

 That's not even counting the fact that it takes about an hour for the tubes to stabilize in heating, anyway. Any MAX will sound boomy upon turn-on, with harsh highs that break-up (i.e., _distortion_). This lasts for 1/2hr - 1hr, depending on the amp and the tubes.

 Anyway - sorry to hammer that home, but some of our supposed experts don't seem to get that.
	

	
	
		
		

		
			





 About your solid-state devices, failures are often complete or non-existent - with very little inbetween. However, there are some instances where you might hear what sounds like buzzes, crackling, or static discharges in the music. I doubt that you have anything else damaged unless you are hearing something like that. The ultimate rating of a typical MBR1035 rectifier or similar is at least 150deg.C. at the junction. That's 302 deg.F., or almost 100 degrees over boiling water. Now, the internal junction temperature will be reached long before the temperature on the plastic case rises that high. Even so, skin burns at only 111 deg. F. A full thickness, 3rd degree burn can occur at only 149deg.F. in 2 seconds. That's gracious plenty below the danger point of the MBR1035. So, I wouldn't worry about it.

 If you've been following the conversation with Daveze, it looks like your QB2 and QB3 may be burned out. That's probably what's wrong if memory serves about your MAX's problems. IOW, the power output transistors may have been OK all along. That might be something to check while you're waiting for those parts. Take a look at the readings I asked Daveze to do and tell us what you get measuring those resistors.


----------



## Aldyrin2

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_I think some of this may be getting used to tubes. Every NOS tube has sat on the shelf a minimum of what - 30 yrs, perhaps 40 yrs for Millett tubes? The vacuum in the tube is impossible to maintain over that period of time. Some gas molecules will infiltrate the moment it left the production line, much less 30-40 years later. That's why they have "getters" and "getter flashes" - to catalyze the errant gas molecules to the compound in the getter flash. Such a reaction takes time - more time for more molecules, etc., etc. Until those gas molecules are catalyzed to the getter flash, they block and carrom some of the transmission of electrons from the cathode to the plates, so distortion will be higher for a tube that needs more burn-in and cool-down. Remember, we're talking about stabilizing a material system at elevated temperatures - cool-down is just as important as burn-in.

 That's not even counting the fact that it takes about an hour for the tubes to stabilize in heating, anyway. Any MAX will sound boomy upon turn-on, with harsh highs that break-up (i.e., distortion). This lasts for 1/2hr - 1hr, depending on the amp and the tubes.

 Anyway - sorry to hammer that home, but some of our supposed experts don't seem to get that.
	

	
	
		
		

		
		
	


	




 About your solid-state devices, failures are often complete or non-existent - with very little inbetween. However, there are some instances where you might hear what sounds like buzzes, crackling, or static discharges in the music. I doubt that you have anything else damaged unless you are hearing something like that. The ultimate rating of a typical MBR1035 rectifier or similar is at least 150deg.C. at the junction. That's 302 deg.F., or almost 100 degrees over boiling water. Now, the internal junction temperature will be reached long before the temperature on the plastic case rises that high. Even so, skin burns at only 111 deg. F. A full thickness, 3rd degree burn can occur at only 149deg.F. in 2 seconds. That's gracious plenty below the danger point of the MBR1035. So, I wouldn't worry about it.

 If you've been following the conversation with Daveze, it looks like your QB2 and QB3 may be burned out. That's probably what's wrong if memory serves about your MAX's problems. IOW, the power output transistors may have been OK all along. That might be something to check while you're waiting for those parts. Take a look at the readings I asked Daveze to do and tell us what you get measuring those resistors. 
	

	
	
		
		

		
		
	


	


_

 

This is my first time using tubes, so that little brief helps a lot. The first test that I did when I noticed distortion was when the amp had probably been on for 5-10 minutes, so it probably just hadn't warmed up yet. 

 You confused me with that last paragraph. I put in the new power transistors you sent me and it has been working fine since. Do you think I should still replace QB2 and QB3? Maybe you missed my previous post about it. Or maybe I'm crazy 
	

	
	
		
		

		
		
	


	




 QB3R and QB2L were the really hot transistors back when I was having problems. Do you think I should replace them? What I got from your post was that if there was something wrong with them, it just wouldn't work.


----------



## tomb

Quote:


  Originally Posted by *Aldyrin2* /img/forum/go_quote.gif 
_<snip>

 You confused me with that last paragraph. I put in the new power transistors you sent me and it has been working fine since. Do you think I should still replace QB2 and QB3? Maybe you missed my previous post about it. Or maybe I'm crazy 
	

	
	
		
		

		
		
	


	


_

 

I'm the one that's confused. Yeah, I obviously missed your post. Dang! I should've realized that you had it fixed if you were asking about distortion in the music. 
	

	
	
		
		

		
		
	


	










  Quote:


 QB3R and QB2L were the really hot transistors back when I was having problems. Do you think I should replace them? What I got from your post was that if there was something wrong with them, it just wouldn't work. 
 

Yes - forget I mentioned anything about your MAX not working.

 Thank goodness!! Now, if we get Daveze squared away, all will be right with the MAX world.


----------



## Aldyrin2

Good deal 
	

	
	
		
		

		
			





 Do you guys perform voltage checks when plugging in the amp at a different location? I think I read something about that somewhere, but I would think that the power supply would take care of any differences.

 Thanks for all the help!


----------



## tomb

Quote:


  Originally Posted by *Aldyrin2* /img/forum/go_quote.gif 
_Good deal 
	

	
	
		
		

		
		
	


	




 Do you guys perform voltage checks when plugging in the amp at a different location? I think I read something about that somewhere, but I would think that the power supply would take care of any differences.

 Thanks for all the help!_

 

The PS regulates based on a _difference_. So, if the line voltage is low enough at a different location to lower the 24VAC walwart by a couple of volts, it could make a difference.

 For instance, 120V -> 24VAC, perhaps 32VDC rectified, minus 3V in the LM317, that gives 29VDC maximum at V+. Go to an office that is running as low as 110V, then, 22VAC, perhaps 31VDC rectified, and there may not be enough voltage to maintain the difference the LM317 needs. In that case, you would lose regulation and may start to hear 120Hz ripple below the music.

 Typically, if you are at 27VDC, there's enough pucker factor at most locations to keep it from being an issue.


----------



## BoilermakerFan

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_The PS regulates for a difference. So, if the line voltage is high enough at a different location to boost the 24VAC walwart by a couple of volts, it could make a difference.

 For instance, 110V -> 24VAC, perhaps 32VDC rectified, minus 3V in the LM317, that gives 29VDC maximum at V+. Go to an office that is running as high as 120V, then, 26VAC, perhaps 35VDC rectified, minus 3V in the LM317, that gives 32VDC with the same setting. That might expose the tube heaters to more than 15VDC each and damage them.

 Just estimates, of course, and I probably have some numbers off - but you can see what's involved with an absolute worst case: assuming your house ran on the low end of 110VAC and your office was on the high end at 120VAC. The reverse may happen if you've adjusted your MAX at home for the highest possible voltage while still regulating with the LM317, then you go to the office and the line voltage is on the low side. In that case, you would lose regulation and may start to hear 120Hz ripple below the music.

 Typically, if you are at 27VDC, there's enough pucker factor on both sides to keep it from being an issue._

 

OK, I'm out in Seattle and fighting off a killer headache, but let me see if I understand your post...

 The PS circuit in the MAX was designed around 110V nominal and not 120V? The 110V was the old nominal voltage to account for voltage drop in the lines and housing, but most power companies have quietly bumped their transmission voltages up without changing transformers in the grid as a way to deliver more power to meet America's ever hungry power demand. I rewired my house in 2000 and every outlet in my house puts out 120VAC in the Fall, Winter, and Spring. In Summer it might go up 1-2 Volts during very high demand periods because the utility boosts their line voltages again to eliminate drops when everyone's air conditioners are running. Other parts of the U.S. are even worse and see greater seasonal fluctuations with their nominal voltages actually going over 126VAC! 

 That being said, I have the 26-27VAC wallwart from Beezer and plan to buy (3) more of them for my other three MAX-based builds. Should I change any component values in my builds since I know my incoming voltage will be a minimum of 120VAC? I don't want to burn out components or damage tubes because of "high" voltage.

 EDIT: Nevermind, I re-read Tom's post and realized that is why we bias our tubes! Tom's comments were related to moving a MAX between two locations that could have more than a 10VAC variation. Doh! I'm fortunate that my utility doesn't vary too much so my amps should stay pretty consistent.


----------



## tomb

Quote:


  Originally Posted by *BoilermakerFan* /img/forum/go_quote.gif 
_OK, I'm out in Seattle and fighting off a killer headache, but let me see if I understand your post...

 The PS circuit in the MAX was designed around 110V nominal and not 120V? The 110V was the old nominal voltage to account for voltage drop in the lines and housing, but most power companies have quietly bumped their transmission voltages up without changing transformers in the grid as a way to deliver more power to meet America's ever hungry power demand. I rewired my house in 2000 and every outlet in my house puts out 120VAC in the Fall, Winter, and Spring. In Summer it might go up 1-2 Volts during very high demand periods because the utility boosts their line voltages again to eliminate drops when everyone's air conditioners are running. Other parts of the U.S. are even worse and see greater seasonal fluctuations with their nominal voltages actually going over 126VAC! 

 That being said, I have the 26-27VAC wallwart from Beezer and plan to buy (3) more of them for my other three MAX-based builds. Should I change any component values in my builds since I know my incoming voltage will be a minimum of 120VAC? I don't want to burn out components or damage tubes because of "high" voltage._

 

Dang! I knew as soon as I ran out to lunch that I mis-spoke.

_It regulates as long as the differential is there_. There is no issue on the high side, except for heat.

 Sorry about that. I will edit the original in case I misled someone else.


----------



## BoilermakerFan

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Dang! I knew as soon as I ran out to lunch that I mis-spoke.

It regulates as long as the differential is there. There is no issue on the high side, except for heat.

 Sorry about that. I will edit the original in case I misled someone else. 
	

	
	
		
		

		
		
	


	





_

 

No worries. I also missed the critical statement in post being the changing location of the MAX and the possible large difference in nominal voltages at the recepticles. 

 One comment I would make is that anyone planning to use a MAX amp at the office definitely check the nominal voltage at their desk recepticle. In the States, 98% of office buildings were built by the lowest bidder and to the minimum NEC requirements, so the seasonal (or daily in some cases) voltage swings will be worse in the office. I'm fortunate in that my office is in my house and I know the individuals that did all my electrical work.


----------



## tomb

Let's see if I can repair the damage I did. 
	

	
	
		
		

		
		
	


	










 Quote:


  Originally Posted by *BoilermakerFan* /img/forum/go_quote.gif 
_OK, I'm out in Seattle and fighting off a killer headache, but let me see if I understand your post...

 The PS circuit in the MAX was designed around 110V nominal and not 120V? The 110V was the old nominal voltage to account for voltage drop in the lines and housing, but most power companies have quietly bumped their transmission voltages up without changing transformers in the grid as a way to deliver more power to meet America's ever hungry power demand. I rewired my house in 2000 and every outlet in my house puts out 120VAC in the Fall, Winter, and Spring. In Summer it might go up 1-2 Volts during very high demand periods because the utility boosts their line voltages again to eliminate drops when everyone's air conditioners are running. Other parts of the U.S. are even worse and see greater seasonal fluctuations with their nominal voltages actually going over 126VAC!_

 

No. What I described was wrong. I was thinking of differential needed for the LM317 to regulate, not some constant "difference." It wouldn't be regulation the way I described it - sorry.

 What happens is that the LM317 maintains 1.25V between its output pin and its adjustment pin. It needs ~3V to regulate, but ~5V for greatest ripple removal. So, going from a higher to lower line voltage is the concern, assuming you've adjusted on the edge at high voltage - 28.5, 29, 30 - something like that.

 What happens is that the LM317 will attempt to regulate under all conditions, but if it loses enough voltage on the entering side compared to the output setting, it will lose regulation and ripple may intrude into the music.

  Quote:


 That being said, I have the 26-27VAC wallwart from Beezer and plan to buy (3) more of them for my other three MAX-based builds. Should I change any component values in my builds since I know my incoming voltage will be a minimum of 120VAC? I don't want to burn out components or damage tubes because of "high" voltage. 
 

No, my stupid mistake.

  Quote:


 EDIT: Nevermind, I re-read Tom's post and realized that is why we bias our tubes! Tom's comments were related to moving a MAX between two locations that could have more than a 10VAC variation. Doh! I'm fortunate that my utility doesn't vary too much so my amps should stay pretty consistent. 
 

My blind squirrel luck let you arrive at the correct conclusion, anyway.

 Sorry for the mis-spoken BS.


----------



## tomb

Quote:


  Originally Posted by *BoilermakerFan* /img/forum/go_quote.gif 
_No worries. I also missed the critical statement in post being the changing location of the MAX and the possible large difference in nominal voltages at the recepticles. 

 One comment I would make is that anyone planning to use a MAX amp at the office definitely check the nominal voltage at their desk recepticle. In the States, 98% of office buildings were built by the lowest bidder and to the minimum NEC requirements, so the seasonal (or daily in some cases) voltage swings will be worse in the office. I'm fortunate in that my office is in my house and I know the individuals that did all my electrical work. 
	

	
	
		
		

		
		
	


	


_

 

Yep. The reason all this came up goes back to the very first MAX prototype. It had a ripple problem, so I sort of became familiar with what the problem sounded like.

 Way back last year, I was preparing a couple of older Millett Hybrids for sale. One TREAD that I was using for a power supply was tempermental for some reason. It worked fine at home, but I was shocked to hear the familiar ripple on the Millett at work. Found out it was a broken solder joint from my packing the TREAD's large cap (I had up-sized it) into a very small box. In bending the leads to fit, I had put a hairline crack in the solder joint. The cap was not even in the circuit. I couldn't get rid of the ripple until I had dialed in at least a 5V difference between supply and output. My line voltage at home had just enough to make it work without my noticing anything wrong until I took it to work, where the line voltage was lower.

 Anyway, I repaired the lead and it would adjust to a much smaller voltage difference without hearing any ripple. So, now you know what those big power caps in the PS are for. Besides reducing the ripple below audible, it gives you extra wiggle room on adjusting the voltage.


----------



## slowpogo

I'm finally working on the case for my MAX. I'm using the standard Hammond case, but will be having Front Panel Express make the front, rear and top panels.

 I got my screws and a tap from McMaster-Carr, and tried tapping one of the holes. It's a standard 6-32 tap, 3/4" long. I don't have a tap handle, so I just used a vice grip to drill it in. It seemed to work well and was pretty easy, only took a few minutes.

 Only one thing has me worried. I'm able to screw in a socket head screw no problem, using just my fingers. But it's not a sturdy, tight fit until the last few millimeters. Before then it will rattle side to side pretty easily, and even all the way in it's a little loose.

 This was one of the top holes. Is it loose because of the open space used by the top plate? Should I have tapped the hole with the top plate inserted? As it is, it seems that if I were to screw on a 4mm panel it would not be very secure, unless the bottom holes are tighter.


----------



## tomb

Quote:


  Originally Posted by *slowpogo* /img/forum/go_quote.gif 
_I'm finally working on the case for my MAX. I'm using the standard Hammond case, but will be having Front Panel Express make the front, rear and top panels.

 I got my screws and a tap from McMaster-Carr, and tried tapping one of the holes. It's a standard 6-32 tap, 3/4" long. I don't have a tap handle, so I just used a vice grip to drill it in. It seemed to work well and was pretty easy, only took a few minutes.

 Only one thing has me worried. I'm able to screw in a socket head screw no problem, using just my fingers. But it's not a sturdy, tight fit until the last few millimeters. Before then it will rattle side to side pretty easily, and even all the way in it's a little loose.

 This was one of the top holes. Is it loose because of the open space used by the top plate? As it is, it seems that if I were to screw on a 4mm panel it would not be very secure, unless the bottom holes are tighter._

 

It should be tight about 1/4 to half-way in, not the last few millimeters. I wonder if your use of vice grips augered out the hole more than usual. The tap threads will always cut. So if most of the force was in a torquing motion to the outside of the hole, it may have cut more than intended.

 A pin vise will work if you can't find a tap handle, but you should have something that sort of works to stay on center. Harbor Freight sells tap handles, too. So does Sears.


----------



## vixr

you can also chuck the tap in a cordless drill...I have a adjustable drill that lets you select the drill's speed, which I set to low, and the drilling force, which I assume is for using the drill to drive screws...I just set the force to around 5 on the drill's collar and it starts to ratchet when the tap gets too tight. reverse the drill to clear the cutting edges and back to forward to resume cutting. Works for me...


----------



## slowpogo

Well, I went to the hardware store and got a basic tap handle. I tried it on another hole, and attempted to be as stable as possible, with the case on its end and going straight down.

 This one is better, but it's still loose, even all the way in. It jiggles a a millimeter or so.

 Hopefully I can figure it out and the other holes don't end up loose, but for those that are, would using a lock washer tighten things up some when I get my panel?


----------



## tomb

Quote:


  Originally Posted by *slowpogo* /img/forum/go_quote.gif 
_Well, I went to the hardware store and got a basic tap handle. I tried it on another hole, and attempted to be as stable as possible, with the case on its end and going straight down.

 This one is better, but it's still loose, even all the way in. It jiggles a a millimeter or so.

 Hopefully I can figure it out and the other holes don't end up loose, but for those that are, would using a lock washer tighten things up some when I get my panel?_

 

Are you tapping all the way up to the shoulder? You shouldn't see any threads showing on that tap by the time you get it screwed all the way in. It will open up the very front of the opening some, but it will run the taps deep where the screw will have enough meat to grip well. If you don't do that, the only "tight" threads are at the opening where it's loose, anyway.

 If that's not doing it, maybe the tap is no good. The Hammond slots aren't the best, but you might remember that once you slide the lid in, the screws will be self tapping along the edge of the lid. The fit will be very tight, indeed.


----------



## Nebby

This is how I do my tapping; my patience wore out doing it with the hand crank, particularly with the cheap handle that I got with my kit!


----------



## Aldyrin2

At least you didn't use pliers like I did. I just bought the bit, not a kit 
	

	
	
		
		

		
		
	


	




 Anywho, my 7 year old grado SR-80's finally bit the dust, so I'm going to take a big step up and am thinking about buying either the AKG 701, the HD-650/600, or the Beyer DT 880's. 

 I know this is a bit off topic, but I figured it was a question best asked here since i'm shooting for synergy with the MAX. Which can do you think pairs the best with our amp? If you have other suggestions in that price range, i'm all ears!


----------



## John Wilson

Almost done. Waiting on a case. JW


----------



## tomb

Wow - gorgeous photography, as before!!


----------



## jamess71

JW those are some awesome pics. Nice build too. Great work, I think you inspired me to get started on my second Max build this weekend. 

 James


----------



## ruZZ.il

edit: disregard this post, I missed something.

 JW: I just want take make sure you have enough space between the 2 bolts that are used to clamp the output transistors to their heat sinks.
 what looks like maybe just enough to get a craft knife through may be problematic when things get hot. I doubt they'd expand more than a craft knifes thickness though, but if you cant get one clearly through there, I'd either flip the bolt around (would be hard to tighten though), or file it down a little. Also, I notice you don't have the insulating shoulder washers (index 2 here) on the transistors. With these the bolt contact woudnt be an issue, just a precautionary step.. 
 Otherwise, you've got one hell of a good looking amp coming along! 
	

	
	
		
		

		
			





 P.S: don't try stick a craft knife through there while it's on! That'd be exactly what we're trying to avoid 
	

	
	
		
		

		
		
	


	




 I'm not sure it would grant it's own order either, if you need some I'm sure someone would send you a few. I would if I had some. on that note, I'll be adding a handful to my next order too


----------



## tomb

Good suggestions, Russ, but you can't use shoulder washers on those type transistors.


----------



## slowpogo

Quote:


  Originally Posted by *Aldyrin2* /img/forum/go_quote.gif 
_Anywho, my 7 year old grado SR-80's finally bit the dust, so I'm going to take a big step up and am thinking about buying either the AKG 701, the HD-650/600, or the Beyer DT 880's._

 

Maybe this isn't that helpful, since I haven't listened with the Senns or Beyers...but the K701s sound *wonderful* with my Max. I did Can't Miss Build #1 BTW w/ Vitamin Q's.

 I've found that the 12AE6 tubes are best for the K701's as a side note.


----------



## ruZZ.il

DOH! and it wont even matter if those bolts touch 
 I've been away for a few days, it must have been too long. I need to solder something damnit! need some fumes..

 Still a good looking hunka electronics there hubba hubba


----------



## tomb

Quote:


  Originally Posted by *ruZZ.il* /img/forum/go_quote.gif 
_DOH! and it wont even matter if those bolts touch 
 I've been away for a few days, it must have been too long. I need to solder something damnit! need some fumes..

 Still a good looking hunka electronics there hubba hubba 
	

	
	
		
		

		
		
	


	


_

 

's OK - not as bad as my telling everyone yesterday that, in effect, the MAX's regulated supply doesn't regulate.
	

	
	
		
		

		
		
	


	







 (Of course, it _does_ regulate!)


----------



## ruZZ.il

yeah, though all the discussion and speculation that arises often gets the idea across better in the end anyway


----------



## jamess71

I'm planning on using 100 ohm resistors to reduce the gain. How much will the 100 ohm lower it? I also have the kiwame and stackpole to choose from. Thnaks

 James


----------



## tomb

Quote:


  Originally Posted by *jamess71* /img/forum/go_quote.gif 
_I'm planning on using 100 ohm resistors to reduce the gain. How much will the 100 ohm lower it? I also have the kiwame and stackpole to choose from. Thnaks

 James_

 

Hmm ... that's a hard one to answer. First, it doesn't really change gain. Gain is fixed by the tubes: 12AE6 the greatest, 12FM6 lower, and 12FK6 lowest.

 Resistors on the output do two things:
 1. Filter some of the "tizziness" from the tubes, and
 2. Attenuate the signal.

 For #1, 10-22ohms is sufficient. Others and myself have commented many times that it's quite possible that this small amount of output resistor value may actually make the amp sound better than without.

 #2 attenuates - it reduces the signal level. It's possible to find the right value of resistor in this case to "simulate" a lower gain if the lowest gain tube doesn't result in the volume knob travel desired. Values here may range from 47ohms to 100ohms or more. However, it won't sound as good as less resistance - some impact is lost.

 Frankly, starting at 7 o'clock as OFF, I normally do all my listening between 8 and 10 o'clock using either 10ohm resistors or just jumpers. The Alps RK27 tracks extremely well at all positions and the small value of output resistance gives the most impact. You'll find that this is more important with high impedance phones, whereas low impedance phones can tolerate the higher value output resistors. That makes sense, since the amp is seeing the total impedance anyway.

 To be specific in answering your question, though, I have been told be another user over on DIYForums.org that 100ohms on the MAX resulted in the same volume levels as 150ohms on the SOHA. That also makes sense, since the SOHA's 12AU7 is higher gain than even the MAX's 12AE6. So, if you are interested in getting full travel of the volume knob, or predominate listening at the 12 o'clock position, then 100 ohms may do the trick.

 As for quality, the Kiwame's are better than the Stackpoles. There are a couple of MAX builders who sware by Rikens, but those are $3.60 a piece at the sizes the MAX board uses. Thanks to Mouser and Beezar, the other two resistors are quite a bit lower than that.


----------



## John Wilson

Quote:


  Originally Posted by *ruZZ.il* /img/forum/go_quote.gif 
_edit: disregard this post, I missed something.

 JW: I just want take make sure you have enough space between the 2 bolts that are used to clamp the output transistors to their heat sinks.
 what looks like maybe just enough to get a craft knife through may be problematic when things get hot. I doubt they'd expand more than a craft knifes thickness though, but if you cant get one clearly through there, I'd either flip the bolt around (would be hard to tighten though), or file it down a little. Also, I notice you don't have the insulating shoulder washers (index 2 here) on the transistors. With these the bolt contact woudnt be an issue, just a precautionary step.. 
 Otherwise, you've got one hell of a good looking amp coming along! 
	

	
	
		
		

		
		
	


	




 P.S: don't try stick a craft knife through there while it's on! That'd be exactly what we're trying to avoid 
	

	
	
		
		

		
		
	


	




 I'm not sure it would grant it's own order either, if you need some I'm sure someone would send you a few. I would if I had some. on that note, I'll be adding a handful to my next order too 
	

	
	
		
		

		
		
	


	


_

 






 I have the insulators on,,,on the back side. They were a hair large and had to ream the hole by a hair. JW


----------



## jamess71

Thnaks once again TomB, It sounds like I'm going to have to do some experimenting to get what I want. I have a few sets of tubes of the 3 varieties that I want to try. I guess I'll use a socket of some sort to swap out resistors. Any reccomendations for small sockets I could use?

 James


----------



## Ech0

I just snipped the gold socket out of a dip socket I had laying around.


 Edit-
 Something like this:

Digi-Key - AE10175-ND (Assmann Electronics Inc - AR08-HZL/01-TT-R)

 I could have sworn Radio Shack had something similiar, but, didn't see anything.

 The more experienced guys will probably have a more elegant solution.


----------



## IceClass

Quote:


  Originally Posted by *MrMajestic2* /img/forum/go_quote.gif 
_




 Night shot




 Day shot

_

 

Dude that is simply the sexiest damn headphone amplifier I've ever seen.
 At this point, it could sound like a flushing toilet and I'd still be lusting madly for one.
	

	
	
		
		

		
		
	


	










 If you ever get bored of yours and want to sell it or if you ever need someone to leave it to in your will, just let me know.


----------



## MrMajestic2

Quote:


  Originally Posted by *IceClass* /img/forum/go_quote.gif 
_Dude that is simply the sexiest damn headphone amplifier I've ever seen.
 At this point, it could sound like a flushing toilet and I'd still be lusting madly for one.
	

	
	
		
		

		
		
	


	










 If you ever get bored of yours and want to sell it or if you ever need someone to leave it to in your will, just let me know.






_

 


 Thanks mate 
	

	
	
		
		

		
		
	


	




 Thankfully it doesnt sound like a toilet. I might actually have to put it up for sale soon. My wife is getting tired of the large pile of amps, dacs and other things stacking up.


----------



## soloz2

hmm... I've got a Max in progress with one scheduled to begin hopefully next week. I've been using Muse ES caps and have a whole bunch of the k42 caps and have been enjoying the results with them, but am toying about using Blackgates in the next build...


----------



## ruZZ.il

do it.


----------



## MrMajestic2

Quote:


  Originally Posted by *ruZZ.il* /img/forum/go_quote.gif 
_do it._

 

X2


----------



## tomb

The K42's are definitely a step-up from the Wima's in the output position. This is in spite of the fact that Dsavitsk didn't like them too much - maybe the higher-volt versions are not as good? At any rate, not quite as detailed or smooth as VitaminQ's, I've found that at the same time, the K42's have an extremely extended, dog-whistle-type, high frequency response. This is similar to the Soniccap GEN II's that we were initially recommending, but rejected because the Sonicaps damage the bass response. The K42's don't do that - as Dsavitsk admits, the bass is strong and punchy - a perfect combo for the ES's.

 As for the VitaminQ's, those are still the optimum choice for Black Gates, IMHO. I don't know if you guys caught it or not (I was trying to keep a low profile after the VitQ-notVitQ episode), but I put a special page on the MAX website for these things:

Tweaks -> VitaminQ PIO Caps

 Also included are some photos and a detail I drew that demonstrates the mounting technique and does double-duty as a template for bending the leads. 
	

	
	
		
		

		
		
	


	










 P.S. Needless to say, available for some time now on you-know-where.


----------



## pinkfloyd4ever

hey tomb, can you hear a difference with your PRP resistors? do you have another BG max with the 2SC2238/2SA968 BJT pair to compare it with? 

 I've been running mine with K42s, but now I'm itching to try out my Qs, and I also wanna try out some .47uf BGs NX Hi-Qs. My pads at CA8 are already showing some wear and tear. I need to figure out a good way to use some sockets there w/o soldering smaller diameter leads onto the Qs


----------



## BoilermakerFan

Has anyone tried tube dampers from Herbie's Audio Lab? Do you guys think they would make an audible difference in a MAX? Is one of the MAX tubes more prone to microphonics than the others? Would the aluminum ring style be better since they would dissipate some heat?

 I realize there are better areas to spend "upgrade" money in the MAX, but what about on an ultimate BG, VitQ, Riken, build? 

 Again, just curious, I'm not necessarily sold on spend $30+ on tube dampers that may not make much of a difference, but some of them sure are nice eye candy!


----------



## John Wilson

Quote:


  Originally Posted by *pinkfloyd4ever* /img/forum/go_quote.gif 
_hey tomb, can you hear a difference with your PRP resistors? do you have another BG max with the 2SC2238/2SA968 BJT pair to compare it with? 

 I've been running mine with K42s, but now I'm itching to try out my Qs, and I also wanna try out some .47uf BGs NX Hi-Qs. My pads at CA8 are already showing some wear and tear. I need to figure out a good way to use some sockets there w/o soldering smaller diameter leads onto the Qs 
	

	
	
		
		

		
		
	


	


_

 

I'm going with the .47's. Still waiting on a case for the board. JW


----------



## BoilermakerFan

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_The K42's are definitely a step-up from the Wima's in the output position. This is in spite of the fact that Dsavitsk didn't like them too much - maybe the higher-volt versions are not as good? At any rate, not quite as detailed or smooth as VitaminQ's, I've found that at the same time, the K42's have an extremely extended, dog-whistle-type, high frequency response. This is similar to the Soniccap GEN II's that we were initially recommending, but rejected because the Sonicaps damage the bass response. The K42's don't do that - as Dsavitsk admits, the bass is strong and punchy - a perfect combo for the ES's.

 As for the VitaminQ's, those are still the optimum choice for Black Gates, IMHO. I don't know if you guys caught it or not (I was trying to keep a low profile after the VitQ-notVitQ episode), but I put a special page on the MAX website for these things:

Tweaks -> VitaminQ PIO Caps

 Also included are some photos and a detail I drew that demonstrates the mounting technique and does double-duty as a template for bending the leads. 
	

	
	
		
		

		
		
	


	










 P.S. Needless to say, available for some time now on you-know-where. 
	

	
	
		
		

		
		
	


	


_

 

Tom

 My builds will not have a height restriction, so are the leads on the VitQ's long enough to allow a true vertical tombstoning mount?


----------



## Aldyrin2

How long-ish should I expect it to take in order for the tube bias voltages to settle down? 

 Am I correct in thinking that I should wait until this stabilizes before adjusting it to half the V+ value?

 Thanks,
 Ald


----------



## tomb

Quote:


  Originally Posted by *Aldyrin2* /img/forum/go_quote.gif 
_How long-ish should I expect it to take in order for the tube bias voltages to settle down? 

 Am I correct in thinking that I should wait until this stabilizes before adjusting it to half the V+ value?

 Thanks,
 Ald_

 

It depends on the tubes. I've had some go a week before they locked into the bias voltage. However, that was definitely a worst case. Most take a day or two of running. Dropping a volt every hour or so is not at all unusual after you fire them up for the first time. After a day, they may drop a volt every 2-3 hours - something like that. That's for the 12AE6. 12FM6's or FK6's may go up, I forget. I'd go on and adjust them initially if you can, but then check them every hour or two for the first couple of days. You'll get a feel for when they lock into a constant bias.

 Even broken in, they'll probably take an hour or two before the bias settles down each time - before they sound their best, too. Welcome to tubes.


----------



## tomb

Quote:


  Originally Posted by *pinkfloyd4ever* /img/forum/go_quote.gif 
_hey tomb, can you hear a difference with your PRP resistors? do you have another BG max with the 2SC2238/2SA968 BJT pair to compare it with?_

 

 I have several builds using the PRP resistors. I can't tell the difference. It's strictly a "looks" thing, IMHO. More bling for the MAX. 
	

	
	
		
		

		
		
	


	




  Quote:


 I've been running mine with K42s, but now I'm itching to try out my Qs, and I also wanna try out some .47uf BGs NX Hi-Qs. My pads at CA8 are already showing some wear and tear. I need to figure out a good way to use some sockets there w/o soldering smaller diameter leads onto the Qs 
	

	
	
		
		

		
		
	


	



 

Sockets are a bad idea for caps. Even the small K42's will arc and blow a hole right through a solder joint. I've seen it happen.


----------



## tomb

Quote:


  Originally Posted by *BoilermakerFan* /img/forum/go_quote.gif 
_Has anyone tried tube dampers from Herbie's Audio Lab? Do you guys think they would make an audible difference in a MAX? Is one of the MAX tubes more prone to microphonics than the others? Would the aluminum ring style be better since they would dissipate some heat?

 I realize there are better areas to spend "upgrade" money in the MAX, but what about on an ultimate BG, VitQ, Riken, build? 

 Again, just curious, I'm not necessarily sold on spend $30+ on tube dampers that may not make much of a difference, but some of them sure are nice eye candy!_

 

I'm not familiar with the particular ones you mention, but Nate Maher seems to like them and has used them in the past on his Milletts. Maybe he'll see this and let us know if it makes a difference. Frankly, from the looks of some of them, you could go down to the hardware store and find an o-ring that might fit for a lot cheaper. 
	

	
	
		
		

		
		
	


	




 There are no MAX/Millett tubes that are more prone to microphonics than others - it's strictly a random element in the manufacturing process.


----------



## tomb

Quote:


  Originally Posted by *BoilermakerFan* /img/forum/go_quote.gif 
_Tom

 My builds will not have a height restriction, so are the leads on the VitQ's long enough to allow a true vertical tombstoning mount?_

 

Yes, they are long enough, but that's not a factor in limiting tombstoning. You'll see from the MAX website section on K42's that we snip the leads and solder on hookup wire, anyway. It probably helps the electrical characteristics, considering the material used for some of these NOS capacitor leads.


----------



## BoilermakerFan

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Yes, they are long enough, but that's not a factor in limiting tombstoning. You'll see from the MAX website section on K42's that we snip the leads and solder on hookup wire, anyway. It probably helps the electrical characteristics, considering the material used for some of these NOS capacitor leads._

 

Thanks Tom. I haven't had a chance to dig through the CD or the web site. I'm hoping to have some time tomorrow night to read through a lot of it again. 

 Oh, can you guys recommend a good brand of input selector switches? I'll have 3-5 sources that I need to select between. I'm also assuming I'll need a 2 pole selector switch correct for right and left channels, or do I need a 4 pole to keep the ground connections switched as well?


----------



## tomb

Quote:


  Originally Posted by *BoilermakerFan* /img/forum/go_quote.gif 
_Thanks Tom. I haven't had a chance to dig through the CD or the web site. I'm hoping to have some time tomorrow night to read through a lot of it again. 

 Oh, can you guys recommend a good brand of input selector switches? I'll have 3-5 sources that I need to select between. I'm also assuming I'll need a 2 pole selector switch correct for right and left channels, or do I need a 4 pole to keep the ground connections switched as well?_

 

Many of use the e-bay Navships SPC wire for hookup wire, which is why I was stating it probably helps, rather then hurts compared to the leads that come on the caps. There's a rumor going around that says the leads on the K42's are magnetic, so you probably would want to snip those, anyway. I don't think the VitQ's are that way, though.

 You'll have to get an answer from some of these other guys on the multi-pole selector switches. I haven't progressed to building preamps with multiple sources, yet.


----------



## pinkfloyd4ever

I was looking at some tube dampers too... I found these 8 TUBE DAMPERS 6BA6/5749/6AU6/6GK5/6FQ5 FITS MARANTZ 8b - eBay (item 320223105583 end time Mar-09-08 20:36:19 PDT) I'm pretty sure they're the same thing as some O-rings at Mcmaster for 4.45 for a 10 pack. I can't get a link to work cause their site is all java based (i think), but ya I'm sure tombs right that you could find them at a hardware store somewhere. You want an inside diameter of 5/8" and as thick as you can find


----------



## cronic

Hello, I finally built my unit over the past week. I did the boutique build 2. I have the following voltage settings
 psu: 27.047v
 tb: 13.518v
 db: 0.040v
 My left tube led is not glowing but the right one is. The measured voltage at the right positive led is 3.30v However the left led positive measures 27.041v! The ledc positive also measures 27.041v. All led locations have 2k resisters installed. Any ideas on this?

 I measured across each resistor and those are the same as the respective led positive legs. I measured all three resistors before they were installed and they checked out fine. Not really sure of the possibly of two bad resistors? 
 I also re soldered the troublesome resistors, but it made no difference.



 EDIT!
 I guess it makes a difference if you have all the leds installed! lol I soldered headers for the power led and did not have it attached. Oh well. Time to take the left tube socket off to get to the led to replace it.


----------



## tomb

Glad you found your problem, Cronic!

 Your other readings look fine. Sounds like you're ready to turn up the bias on the DB's, next. Take your time by adjusting one side a bit then the other - waiting inbetween to let the heat stabilize. Good luck and let us know how it goes!

 EDIT: Good tip on the o-rings, Pinkfloyd4ever! Let us know if you try any and it makes a difference.


----------



## cronic

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Glad you found your problem, Cronic!

 Your other readings look fine. Sounds like you're ready to turn up the bias on the DB's, next. Take your time by adjusting one side a bit then the other - waiting inbetween to let the heat stabilize. Good luck and let us know how it goes!

 EDIT: Good tip on the o-rings, Pinkfloyd4ever! Let us know if you try any and it makes a difference. 
	

	
	
		
		

		
		
	


	


_

 

Got the tube socket up and the led replaced. Everything is good now. I am waiting on my 701s to come in so I am headphone less until Monday
	

	
	
		
		

		
		
	


	




. I went with the 1.5" heat sinks all the way around. What is the upper limit on DB's?


----------



## tomb

Quote:


  Originally Posted by *cronic* /img/forum/go_quote.gif 
_Got the tube socket up and the led replaced. Everything is good now. I am waiting on my 701s to come in so I am headphone less until Monday
	

	
	
		
		

		
		
	


	




. I went with the 1.5" heat sinks all the way around. What is the upper limit on DB's?_

 

We recommend 120ma as the absolute maximum with 1-1/2" sinks. That's 264mV. However, if you get it to 100ma (220mV), I'd stop and quit while you were ahead.


----------



## cronic

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_We recommend 120ma as the absolute maximum with 1-1/2" sinks. That's 264mV. However, if you get it to 100ma (220mV), I'd stop and quit while you were ahead. 
	

	
	
		
		

		
		
	


	


_

 

Cool, all of the voltages were with the 12fk6 tubes. I tried out a set of 12ae6a tubes that I bought and am getting some very weird tube voltages. No matter were I set the pot I get 24 volts. What am I missing here? I realize they have twice the gain but the voltage doesn't seem right. I would assume that the voltage should act the same with either tubes.


----------



## BoilermakerFan

Quote:


  Originally Posted by *pinkfloyd4ever* /img/forum/go_quote.gif 
_I was looking at some tube dampers too... I found these 8 TUBE DAMPERS 6BA6/5749/6AU6/6GK5/6FQ5 FITS MARANTZ 8b - eBay (item 320223105583 end time Mar-09-08 20:36:19 PDT) I'm pretty sure they're the same thing as some O-rings at Mcmaster for 4.45 for a 10 pack. I can't get a link to work cause their site is all java based (i think), but ya I'm sure tombs right that you could find them at a hardware store somewhere. You want an inside diameter of 5/8" and as thick as you can find_

 

I think I'll go with the stacked metal ring heat sink design instead of the O-Rings.


----------



## fault151

Quote:


  Originally Posted by *BoilermakerFan* /img/forum/go_quote.gif 
_I think I'll go with the stacked metal ring heat sink design instead of the O-Rings._

 

I have a set of the o rings,im not sure if they even make a difference, they look quite nice though! Mine are white.


----------



## ruZZ.il

cronic: Do you mean the tube bias trimmers? They may need quiet a few turns before you see response. They're 20 turn trimmers.
 most importantly, make sure your db's are biased right. 0.04v like you said above is good to start. Try use the mV scale and get them accurately matched, too.


----------



## chilly

Hey all, Started populating my Max board today.

 I have a question on CA4 and CA5...

 can I use 1000uf 50volt as opposed to 1000uf 35volt?

 I have the 50 volt... and already put them on.... I don't know what I was thinking... 
	

	
	
		
		

		
		
	


	




 thanks,

 chilly


----------



## tomb

Quote:


  Originally Posted by *chilly* /img/forum/go_quote.gif 
_Hey all, Started populating my Max board today.

 I have a question on CA4 and CA5...

 can I use 1000uf 50volt as opposed to 1000uf 35volt?

 I have the 50 volt... and already put them on.... I don't know what I was thinking... 
	

	
	
		
		

		
		
	


	




 thanks,

 chilly_

 

Absolutely! Good choice and it probably gets you a discount by ordering more of the same.


----------



## chilly

excellent!!!! Thanks Tomb, Also thanks for the quick delivery on my order!!!

 -chilly


----------



## John Wilson

Are we running a ground wire from the board to the case? JW


----------



## ruZZ.il

Essentially, yes. The RCAs arent insulated, for instance, nor is the volume pot prevented from touching the case.
 So, the case is essentially tied to the *signal* ground. 

 Note: The signal ground is NOT the DC ground as marked on the test point in the center of the board. The signal ground is at the input, output and just behind the pot. 

  Quote:


  Originally Posted by *John Wilson* /img/forum/go_quote.gif 
_Are we running a ground wire from the board to the case? JW_


----------



## soloz2

I don't remember seeing this posted anywhere, but is there any reason not to use k42 caps instead of wilmas throughout?


----------



## ruZZ.il

yes, supposedly wimas have very flat response curves which is ideal for most positions that it's called for. Using caps with non-neutral response in those positions could negatively effects some things. I really cant comment much, just echoing what I've read as a preliminary note. Maybe someone will emphasize the differences..


----------



## tomb

Good advice about the grounding, ruZZ.il.
	

	
	
		
		

		
			





 Except technically speaking, the signal ground _is the same_ as the DC Ground test point on the board.

 The Millett, and now the MAX, has always been negatively grounded. In the case of the older revMH Millett Hybrid, which was fed from DC, it was a good practice to use a metal DC power jack where the ground was commonly shared. However, the difference in the MAX is that the rectified-regulated DC power is onboard, so the actual power input jack is 24VAC. In that case, the AC must be isolated from the DC ground of the board and as you correctly point out - is also shared with the enclosure. That's why a plastic power input jack is specified on the MAX's Bill Of Materials (BOM). That AC/DC difference is probably what you were thinking.


----------



## tomb

Quote:


  Originally Posted by *ruZZ.il* /img/forum/go_quote.gif 
_yes, supposedly wimas have very flat response curves which is ideal for most positions that it's called for. Using caps with non-neutral response in those positions could negatively effects some things. I really cant comment much, just echoing what I've read as a preliminary note. Maybe someone will emphasize the differences.._

 

Yes, ruZZ.il is correct.
	

	
	
		
		

		
		
	


	




 Also, the big difference for me is that I'm lazy.
	

	
	
		
		

		
		
	


	




 There's no more easier part to solder in the board than the Wima caps. The same cannot be said about the K42's. Wimas are cheaper, too. So in those positions where the _very _slight squeeky-graininess of the Wima has no effect (everywhere but CA8), it's much easier to use them.


----------



## John Wilson

Thank you Russ! JW


----------



## ruZZ.il

hm. I see.. So you're saying the regulator is basically 'standing' on the signal ground, always holding the V+ about ~27v above?
 alright


----------



## tomb

Quote:


  Originally Posted by *ruZZ.il* /img/forum/go_quote.gif 
_hm. I see.. So you're saying the regulator is basically 'standing' on the signal ground, always holding the V+ about ~27v above?
 alright 
	

	
	
		
		

		
		
	


	


_

 

Yep - and the tubes are adjusted so that their bias is in the middle, allowing the sine wave of the music to swing between those two points. Assuming you set V+ to 27VDC, the zero point of the Left and Right signal sits at 13.5VDC, which is why there are output caps to block that DC from your headphones. When you bias the tubes, you are actually measuring the Left and Right signal voltage and its reference to Ground.


----------



## slowpogo

I'm finalizing the back panel for my Max. Would a small vent in the back be a good idea, or is it basically unnecessary (mine uses BJT with 1" sinks)? The top panel will have pretty good sized vent holes, with metal mesh beneath.


----------



## tomb

Quote:


  Originally Posted by *slowpogo* /img/forum/go_quote.gif 
_I'm finalizing the back panel for my Max. Would a small vent in the back be a good idea, or is it basically unnecessary (mine uses BJT with 1" sinks)? The top panel will have pretty good sized vent holes, with metal mesh beneath._

 

None of mine have vents in the back. They seem to suffer no ill effects.


----------



## jimmyjohn

Does anyone need a power supply? I sold my MAX to a gentleman in the UK, and he has no use for the power supply. It's a Radio Shack unit:

RadioShack.com - Power & Batteries: Home & office power: AC (Home) adapters: 18/24VAC 1000mA AC-to-AC Adapter

 Let me know if you're interested, and we'll work something out.

 Jim D.


----------



## fault151

Hey Jim, any idea when you will be posting out the amp? Theres no mad rush, just wondered? Ill have to arrange for someone to be in and sign for it.

 Looking forward to listening to it, iv been following the millet thread for ages. Im even in the process of getting a custom box made.



  Quote:


  Originally Posted by *jimmyjohn* /img/forum/go_quote.gif 
_Does anyone need a power supply? I sold my MAX to a gentleman in the UK, and he has no use for the power supply. It's a Radio Shack unit:

RadioShack.com - Power & Batteries: Home & office power: AC (Home) adapters: 18/24VAC 1000mA AC-to-AC Adapter

 Let me know if you're interested, and we'll work something out.

 Jim D._


----------



## thomaskuhn

I finished up the circuit for the VU meter. It worked great when I hooked the inputs to my iPod, so this morning I began installing it in the MAX (I was supposed to be painting the house, and there was hell to pay) Well lo and behold, it does not work. I was wondering if any one could help me out? Below is a simple diagram I made in SPICE. 






 Please note that the values are correct and the bridge is actually a chip, but I did not find one in the library, so I just drew 4 diodes. My meter is the between the bridge and resistor.

 The problem I am having is that when I connect the signal ground to the MAX, it seems to remove my floating ground, so that the input to the op-amp is now 27V, where as when it is hooked to the iPod, the power is properly split +13.5/-13.5. I am sure it has to do with using a floating ground in this setup. Can anyone help me out?

 Tom Kuhn


----------



## ruZZ.il

we were just speaking about it, that the signal ground voltage = "Max ground" voltage so it would need a seperate power supply, maybe a battery? or a different type of op amp.. basically, you're shorting that bottom 10k resistor when hooked up to the max like that..
 <scratches head>
 I have to learn more about op-amps...
 can't help too much yet
 soon..


----------



## soloz2

Quote:


  Originally Posted by *ruZZ.il* /img/forum/go_quote.gif 
_yes, supposedly wimas have very flat response curves which is ideal for most positions that it's called for. Using caps with non-neutral response in those positions could negatively effects some things. I really cant comment much, just echoing what I've read as a preliminary note. Maybe someone will emphasize the differences.._

 

 Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Yes, ruZZ.il is correct.
	

	
	
		
		

		
		
	


	




 Also, the big difference for me is that I'm lazy.
	

	
	
		
		

		
		
	


	




 There's no more easier part to solder in the board than the Wima caps. The same cannot be said about the K42's. Wimas are cheaper, too. So in those positions where the very slight squeeky-graininess of the Wima has no effect (everywhere but CA8), it's much easier to use them._

 


 Thanks for the info guys. I'm not too worried about what's easier as I find it only takes an extra couple minutes to install a pair of k42's over a pair of Wilmas and I have a box of I think 36 k42's left 
	

	
	
		
		

		
		
	


	




 So I should just use the Wilmas anyway then.... no biggie


----------



## tomb

Quote:


  Originally Posted by *ruZZ.il* /img/forum/go_quote.gif 
_we were just speaking about it, that the signal ground voltage = "Max ground" voltage so it would need a seperate power supply, maybe a battery? or a different type of op amp.. basically, you're shorting that bottom 10k resistor when hooked up to the max like that..
 <scratches head>
 I have to learn more about op-amps...
 can't help too much yet
 soon.._

 

Russ,
 You know more about this than I do, but couldn't he just forget the voltage splitter? The tube already splits the voltage. If he just connected the V+ and Gnd to the V+ and V- on the opamp, the signal + would be at 13.5 and the signal Gnd would be the same as Signal -.

 That presents a bit of a problem, because the opamp has to burn a diode drop, I believe, because it can't swing rail-to-rail. This is why Runeight installed a set of four 1N4148 switching diodes around the opamp on the SOHA - to insure that the opamp wasn't burned out with a signal that exceeded its maximum voltage differential.

 I'm guessing, though.


----------



## joneeboi

I was wondering, as I often do when staring at the insides of my MAX, and I thought about what it would be like to have a 3 channel MAX. How would that work? One way would be to populate a board and a half and use one channel as the GND. Does that make sense electrically or pragmatically? We currently use a huge ground plane, so how does that affect the implementation of a 3rd channel? How would input and output grounds be connected to the board? Wouldn't you just wire the input ground to, say, the left channel and take output ground to be the left output? I don't have any balanced sources nor do I plan on having any in the near future, so pulling a pabbi would be so very nice and useless for me. I don't suppose Team Millett wants to focus on a 3CH design anytime soon. 
	

	
	
		
		

		
		
	


	




 What do we allegedly have on tap at the moment? MiniMAX, Super MAX, 12AU7/12AX7 (or whatever) MAX? Is a 3rd channel even worth my internet chat breath?


----------



## tomb

Quote:


  Originally Posted by *joneeboi* /img/forum/go_quote.gif 
_I was wondering, as I often do when staring at the insides of my MAX, and I thought about what it would be like to have a 3 channel MAX. How would that work? One way would be to populate a board and a half and use one channel as the GND. Does that make sense electrically or pragmatically? We currently use a huge ground plane, so how does that affect the implementation of a 3rd channel? How would input and output grounds be connected to the board? Wouldn't you just wire the input ground to, say, the left channel and take output ground to be the left output? I don't have any balanced sources nor do I plan on having any in the near future, so pulling a pabbi would be so very nice and useless for me. I don't suppose Team Millett wants to focus on a 3CH design anytime soon. 
	

	
	
		
		

		
			





 What do we allegedly have on tap at the moment? MiniMAX, Super MAX, 12AU7/12AX7 (or whatever) MAX? Is a 3rd channel even worth my internet chat breath?_

 

As for the 3rd channel, I've discussed the possibility with Colin, but the single-ended, negative ground topology presents some problems. The easiest way to do it is to make the buffers into 3 channels using a TLE or a voltage divider of some sort. Sinking lots of current will become an issue that way, so I'm not sure.

 Ferrari has built one like that - I'd send him a note and see if he can explain it to you.

 As for what's on tap - I'm in the middle of creating two new websites for the MAX. One is projected for mid-March, although that may slip a little due to the IRS.
	

	
	
		
		

		
		
	


	




 My intent is to focus on a much more step-by-step set of instructions for building one from the board up - especially for the MOSFETs. Also, I sort of hinted at this earlier, but I'm going to use a couple of new cases that will be detailed as well. Hopefully, the design will also incorporate a method for building and installing an Alien DAC in the case - which will be no bigger than the standard MAX. There are a few tricks that I've come up with to make it work.

 Beezar will carry the MOSFETs and JFETs, too.

 The MiniMAX is due probably a month later, but we'll be depending on Colin for that one. He's had a little trouble with trace routing around the middle heat sinks. I believe he's been trying to open the distance up between them because on the Mini, the output bypass caps go between the middle two sinks.

 Beezar added 12AE6 and 12FK6 tubes tonight, along with a few other trinkets. RK27's are still slated for March 31st.


----------



## Ampersand

Hello,

 Just finished my 2nd MAX build and I'm having a bit of a problem. BTW, the first build went flawlessly 
	

	
	
		
		

		
		
	


	




.

 Tubes and buffers bias fine. I don't hear the relay click like I do in the first MAX. Could the relay be faulty?? Is there a voltage I can check??

 In the meantime, I'll double check my resistor values within the Delay circuit.

 Thanks,
 Mike


----------



## joneeboi

That sounds really great, Tom. It's a bummer to hear about the IRS thing. What do they have a problem with? And thanks for the update on the website stuff. As most newbies would agree, it's always better to have a detailed, step-by-step instruction guide to help through the build. Just for kicks, we could go through the pages of the thread and count the number of times people have accidentally flipped the buffer trannies. 
	

	
	
		
		

		
		
	


	




 Also, it'll be cool to see how you intend to incorporate the Alien DAC into the MAX. I think we're all aware of how much you enjoy it, so it's good to see how those projects are naturally fusing together through your continued participation on these forums. I'm so glad I got to be part of this chapter in history. 
	

	
	
		
		

		
		
	


	




 Finally, I'm sure I speak on behalf of everyone on Team Millett MAX when I say, "Thank you, Colin and Tom, for all your incredible and immeasurable contribution and commitment to this project."


----------



## chilly

Hey everyone,

 just wanted to let everyone know, another Max lives... I just finished around 4 this afternoon, I did have some minor problems biasing.... but once I figured out how to read a DMM. (This is only my second electronics project, The soha was my first)

 The 2 problems I have now, one is that the gain is probably to high ( I am using UE-5c's as my headphones and their really low ohm 24 or so I think.), I'm using the 12ae6's I have just ordered the other 2 sets. So we will see how that goes. 

 The other problem I have is I have a noisy pot. Not sure what to do about that as its already soldered to the board.

 SO my thanks to all of you, and Tomb, as I couldn't have dones this without you and the website.

 Thanks

 chilly


----------



## pabbi1

Quote:


  Originally Posted by *joneeboi* /img/forum/go_quote.gif 
_I was wondering, as I often do when staring at the insides of my MAX, and I thought about what it would be like to have a 3 channel MAX. How would that work? One way would be to populate a board and a half and use one channel as the GND. Does that make sense electrically or pragmatically? We currently use a huge ground plane, so how does that affect the implementation of a 3rd channel? How would input and output grounds be connected to the board? Wouldn't you just wire the input ground to, say, the left channel and take output ground to be the left output? I don't have any balanced sources nor do I plan on having any in the near future, so pulling a pabbi would be so very nice and useless for me. I don't suppose Team Millett wants to focus on a 3CH design anytime soon. 
	

	
	
		
		

		
		
	


	




 What do we allegedly have on tap at the moment? MiniMAX, Super MAX, 12AU7/12AX7 (or whatever) MAX? Is a 3rd channel even worth my internet chat breath?_

 


 Keep in mind I also added in the balanced source (OPUS DAC) into the solution. While I do have a balanced source player as well, my implementation was to also get balanced source with a very modest transport. I am thinking you want something along the lines of Millett output with a m³ or Beta22topology? You might also ping Ti Kan (Amb) about how to do this with two boards, and, if there is any gain, or severe downside.

 Now, I am curious about the status of that all tube DAC...


----------



## cronic

Quote:


  Originally Posted by *ruZZ.il* /img/forum/go_quote.gif 
_cronic: Do you mean the tube bias trimmers? They may need quiet a few turns before you see response. They're 20 turn trimmers.
 most importantly, make sure your db's are biased right. 0.04v like you said above is good to start. Try use the mV scale and get them accurately matched, too._

 



 Yes its the tube bias. I can only get 24 v no matter where the trimmer is set with the 12ae6a tube. I have the db set to 50.02mV. The 12fk6 tb sets the way it should, but with the 12ae6a tubes installed only 24 volts. Is that a sign of bad tubes?


----------



## tomb

Quote:


  Originally Posted by *cronic* /img/forum/go_quote.gif 
_Yes its the tube bias. I can only get 24 v no matter where the trimmer is set with the 12ae6a tube. I have the db set to 50.02mV. The 12fk6 tb sets the way it should, but with the 12ae6a tubes installed only 24 volts. Is that a sign of bad tubes?_

 

I think what Russ is saying is that it doesn't make sense. The chances of having two 12AE6's that won't bias is small to impossible. I'm speaking for him, too, but I think we both suspect that you're not turning the trimmers far enough. Most of the ones spec'd for the MAX and Millett are _25_-turn trimmers. The 12AE6 biases at the other end of the trimmers, if I remember correctly - and it may only bias in the last 4 or 5 turns.

 I'd try while listening for a click to be sure you don't tear up the trimmers. If you have Murata's (recommended), they won't break. Anyway, leave the tubes up and running for about a half-hour, then try it again.

 Like I said, it's almost impossible that they could both be bad and also have your 12FK6's bias fine.


----------



## tomb

Quote:


  Originally Posted by *chilly* /img/forum/go_quote.gif 
_Hey everyone,

 just wanted to let everyone know, another Max lives... I just finished around 4 this afternoon, I did have some minor problems biasing.... but once I figured out how to read a DMM. (This is only my second electronics project, The soha was my first)

 The 2 problems I have now, one is that the gain is probably to high ( I am using UE-5c's as my headphones and their really low ohm 24 or so I think.), I'm using the 12ae6's I have just ordered the other 2 sets. So we will see how that goes. 

 The other problem I have is I have a noisy pot. Not sure what to do about that as its already soldered to the board.

 SO my thanks to all of you, and Tomb, as I couldn't have dones this without you and the website.

 Thanks

 chilly_

 

Thanks for the compliment!

 I hate to say this, but using IEM's is probably not the best choice with a tube amp, even if it is a hybrid. You may need 100ohm output resistors or more to tame the gain and also the noise.

 Most likely, the noise in the pot you're hearing is tube noise. Scratchiness occurs if the tubes aren't completely stable and/or have some less-than-optimum connections on the pins. Try switching the tubes and see if that alters the pot noise slightly. If it's an ALPS, it's probably the tubes plus your IEMs.


----------



## tomb

Quote:


  Originally Posted by *Ampersand* /img/forum/go_quote.gif 
_Hello,

 Just finished my 2nd MAX build and I'm having a bit of a problem. BTW, the first build went flawlessly 
	

	
	
		
		

		
		
	


	




.

 Tubes and buffers bias fine. I don't hear the relay click like I do in the first MAX. Could the relay be faulty?? Is there a voltage I can check??

 In the meantime, I'll double check my resistor values within the Delay circuit.

 Thanks,
 Mike_

 

The most common cause of this problem with most MAX builders is installing the BD139 backwards. Take a look on the MAX website at Tweaks -> e12 Delay. At the bottom of the page, I included a key plan and detail of how to recognize the proper orientation of the BD139 in the relay circuit.

 One good thing is that the BD139 doesn't seem to damage itself in this condition if that's what your problem is. So, just take it out and turn it around.

 Let us know if that's it.


----------



## cronic

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_I think what Russ is saying is that it doesn't make sense. The chances of having two 12AE6's that won't bias is small to impossible. I'm speaking for him, too, but I think we both suspect that you're not turning the trimmers far enough. Most of the ones spec'd for the MAX and Millett are 25-turn trimmers. The 12AE6 biases at the other end of the trimmers, if I remember correctly - and it may only bias in the last 4 or 5 turns.

 I'd try while listening for a click to be sure you don't tear up the trimmers. If you have Murata's (recommended), they won't break. Anyway, leave the tubes up and running for about a half-hour, then try it again.

 Like I said, it's almost impossible that they could both be bad and also have your 12FK6's bias fine._

 

Yes, I understand what you are saying. I have tried them all the way to either side. Click to click either way I get 24 v. I also noticed that I get no glow at all out of the 12ae6a, whereas the 12fk6 have a nice glow at the tip. The 12ae5a are also dead cold, whereas the 12fk6 get nice and warm after bing on for a while. Bad tubes?


----------



## tomb

Quote:


  Originally Posted by *joneeboi* /img/forum/go_quote.gif 
_<snip>Finally, I'm sure I speak on behalf of everyone on Team Millett MAX when I say, "Thank you, Colin and Tom, for all your incredible and immeasurable contribution and commitment to this project."_

 

Thank you so much for such a complimentary post, Joneeboi! It means a lot from someone like you, who's been with the project for so long. 
	

	
	
		
		

		
		
	


	










 Not to worry about me and the IRS (I hope, anyway). It's just that it takes me about two solid months of weekends to do my taxes.


----------



## Ampersand

Thanks for the quick response. No, the BD139 is in there correctly. I have the two MAXs side-by-side. All components in the Delay circuit are in the correct orientation. 

 Any other ideas?

 BTW, the tubes I'm using to test this 2nd MAX are the ones I just pulled from the 'working' MAX.

 Thanks,
 Mike


----------



## cetoole

Quote:


  Originally Posted by *cronic* /img/forum/go_quote.gif 
_Yes, I understand what you are saying. I have tried them all the way to either side. Click to click either way I get 24 v. I also noticed that I get no glow at all out of the 12ae6a, whereas the 12fk6 have a nice glow at the tip. The 12ae5a are also dead cold, whereas the 12fk6 get nice and warm after bing on for a while. Bad tubes?_

 

My money (nickel) says one of your 12AE6A tubes has an open heater. Use your DMM (you have one, right) on continuity, or resistance mode, and test the heater pins on each tube. I bet you will find one that is quite low and one that is infinite resistance. Its rare, but happens, and if you find one like this, you just gotta pony up the few bucks and replace it.


----------



## cronic

Quote:


  Originally Posted by *cetoole* /img/forum/go_quote.gif 
_My money (nickel) says one of your 12AE6A tubes has an open heater. Use your DMM (you have one, right) on continuity, or resistance mode, and test the heater pins on each tube. I bet you will find one that is quite low and one that is infinite resistance. Its rare, but happens, and if you find one like this, you just gotta pony up the few bucks and replace it._

 

Thanks man, I measured continuity between pin 2 and pin 3 on both tubes. One reads up to 110 ohms and then falls at a constant rate ohms and the other reads 0 ohms. Looks like thats the issue.


----------



## Daveze

Quote:


  Originally Posted by *joneeboi* /img/forum/go_quote.gif 
_I was wondering, as I often do when staring at the insides of my MAX, and I thought about what it would be like to have a 3 channel MAX. How would that work? One way would be to populate a board and a half and use one channel as the GND. Does that make sense electrically or pragmatically? We currently use a huge ground plane, so how does that affect the implementation of a 3rd channel? How would input and output grounds be connected to the board? Wouldn't you just wire the input ground to, say, the left channel and take output ground to be the left output? I don't have any balanced sources nor do I plan on having any in the near future, so pulling a pabbi would be so very nice and useless for me. I don't suppose Team Millett wants to focus on a 3CH design anytime soon. 
	

	
	
		
		

		
		
	


	




 What do we allegedly have on tap at the moment? MiniMAX, Super MAX, 12AU7/12AX7 (or whatever) MAX? Is a 3rd channel even worth my internet chat breath?_

 

I've considered this a wee tad. I was thinking that an original Millet with 3 x JISBOS on the back end might work nicely. Using two tubes for voltage gain, then implementing the 3rd channel just on the current stage.


----------



## Ampersand

Well, I jumpered a pin from RA4L to the jack and got sound!!! So I guess the delay circuit is the culprit. Now I must figure out which part. Any ideas??

 Earlier in the build, I mistakenly soldered the CM1 47uF elec cap in a spot in the power supply and had to desolder it and move it. Its possible I burned up the cap. Would a burned up cap in CM1 cause this problem???

 Thanks,
 Mike


----------



## Ampersand

Well, I swapped out CM1 for another 47uF cap I had laying around. That didn't work, so I swapped out the BD139 for another and BINGO, I have sound. Thank goodness, because that Relay looked like a #@&%* to desolder.

 So finally i can enjoy my BG version of the MAX. BTW, I know the Can't Miss Max Build #1 bypasses the BGs with K42's or VitQ's, but what was the consensus of using BG's to bypass BG's?? I'm currently not bypassing at all 
	

	
	
		
		

		
			





 Thanks,
 Mike


----------



## pinkfloyd4ever

Quote:


  Originally Posted by *Ampersand* /img/forum/go_quote.gif 
_Well, I swapped out CM1 for another 47uF cap I had laying around. That didn't work, so I swapped out the BD139 for another and BINGO, I have sound. Thank goodness, because that Relay looked like a #@&%* to desolder.

 So finally i can enjoy my BG version of the MAX. BTW, I know the Can't Miss Max Build #1 bypasses the BGs with K42's or VitQ's, but what was the consensus of using BG's to bypass BG's?? I'm currently not bypassing at all 
	

	
	
		
		

		
		
	


	




 Thanks,
 Mike_

 

good to hear. I wish I could comment on the bypassing issue, but I just replaced my K42s with vitamin Qs last night and still haven't gotten around to trying my .47uf BG NXs...plus I haven't been able to hear with my left ear for like a week and a half cause of this damn ear infection...def need to call the doctor back tomorrow

 btw, anyone know if theres much of a break-in period for VitQs?


----------



## amphead

Quote:


 Thanks man, I measured continuity between pin 2 and pin 3 on both tubes. One reads up to 110 ohms and then falls at a constant rate ohms and the other reads 0 ohms. Looks like thats the issue. 
 

Cronic, that would actually show working heaters on both of those tubes. Colin was telling you that if you measured infinite resistance on the heater that it was bad(open circuit). However, the tube that measured 110 ohms, might be having problems anyway.

 Ampersand, kudos on your fix. Another Max Lives!!!


----------



## John Wilson

Sad news...I can't get the DB's on one side below .940 mv and the other side below .835 mv!!! The tubes bias fine at 13.5 v, And ps at 27v. For what it's worth the MJE 243 and 253's are about 9 years old...never used..stored in there bags. May I;ll get new ones. JW


----------



## tomb

Quote:


  Originally Posted by *amphead* /img/forum/go_quote.gif 
_Cronic, that would actually show working heaters on both of those tubes. Colin was telling you that if you measured infinite resistance on the heater that it was bad(open circuit). However, the tube that measured 110 ohms, might be having problems anyway.

 Ampersand, kudos on your fix. Another Max Lives!!!   _

 

It may be that he measured those pins with the tubes in the board.

 Cronic, try measuring the pins on your tubes when they're pulled from the sockets. Colin made a great guess based on your description of the problem. It can also be caused by bad contact with the tube pins in the socket. After you've checked the pins when the tubes are out, try canting them in the socket until the LEDs light.


----------



## tomb

Quote:


  Originally Posted by *John Wilson* /img/forum/go_quote.gif 
_Sad news...I can't get the DB's on one side below .940 mv and the other side below .835 mv!!! The tubes bias fine at 13.5 v, And ps at 27v. For what it's worth the MJE 243 and 253's are about 9 years old...never used..stored in there bags. May I;ll get new ones. JW_

 

I've looked at your pic on page 366 of this thread. You've got a real good pic there of the DB section. A visual inspection doesn't indicate anything wrong. So, let's start the standard drill, John:

 1. Verify the test points that you are trying to measure. The test points do nothing but measure the voltage at the leads of the RB10 or RB11 resistors.

Left Channel: One probe is in TA2L. The other probe is in TB1L or TB2L.
Right Channel: One probe is in TA2R. The other probe is in TB1R or TB2R.

 2. If that's correct, you need to verify your parts.

Trimmers:
 RB12L and RB12R are 2K trimmers

Transistors:
 Even to Odd on the small transistors to the pads on the board. 2N5088's go on QB3, QB5, and QB7. 2N5087's go on QB2, QB4, and QB6.

 QB1 is the PN4392 JFET.

 MJE253's go on the middle sinks on the Right side of the sinks.
 MJE243's go on the outboard sinks on the Right side of the sinks.

Resistors:
 RB1R: 1K ohm
 RB2R, RB3R: 10 ohm
 RB4R, RB5R: 100 ohm
 RB6R, RB7R: 220 ohm
 RB8R, RB9R: JUMPERED
 RB10R, RB11R: 2.2 ohm Power Resistor

 Please, DON'T CHEAT - make an honest attempt at this and let us know. If this doesn't indicate something, there are other things that we can try.


----------



## cronic

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_It may be that he measured those pins with the tubes in the board.

 Cronic, try measuring the pins on your tubes when they're pulled from the sockets. Colin made a great guess based on your description of the problem. It can also be caused by bad contact with the tube pins in the socket. After you've checked the pins when the tubes are out, try canting them in the socket until the LEDs light._

 

They were measured out of the board. I wiggled them to and fro while in the socket and nothing changed.


----------



## tomb

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_It may be that he measured those pins with the tubes in the board.

 Cronic, try measuring the pins on your tubes when they're pulled from the sockets. Colin made a great guess based on your description of the problem. It can also be caused by bad contact with the tube pins in the socket. After you've checked the pins when the tubes are out, try canting them in the socket until the LEDs light._

 

Try putting the 12AE6 that measured good in one socket and one of your good 12FK6's in the other. See if you can bias the 12AE6 under that scenario. At least it will prove that one 12AE6 tube is good (needless to say, the amp won't sound very good doing that, but it won't hurt it).


----------



## cronic

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Try putting the 12AE6 that measured good in one socket and one of your good 12FK6's in the other. See if you can bias the 12AE6 under that scenario. At least it will prove that one 12AE6 tube is good (needless to say, the amp won't sound very good doing that, but it won't hurt it)._

 

Good deal, I will try that when I get home tonight. Thanks everyone for your awesome help.


----------



## chilly

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Thanks for the compliment!

 I hate to say this, but using IEM's is probably not the best choice with a tube amp, even if it is a hybrid. You may need 100ohm output resistors or more to tame the gain and also the noise.

 Most likely, the noise in the pot you're hearing is tube noise. Scratchiness occurs if the tubes aren't completely stable and/or have some less-than-optimum connections on the pins. Try switching the tubes and see if that alters the pot noise slightly. If it's an ALPS, it's probably the tubes plus your IEMs._

 

 Hey Tomb,

 I agree, IEM's are probably not the best for tubes... with harmonics and hashyness( is that a word? ) My problem is, over the ear and on the ear phones tend to hurt over a very short time. where as my IEM's I can wear all day with no discomfort.

 I do have the Soha working very nicely now, with 22ohm resistors in the output, that still gives me pretty good bass, although I might change a couple of the caps for a more accurate bass.

 The Max, obviously needs more time to burn in, and I just ordered other tubes to give them a shot...

 The pot noise is not too big of a problem, as I usualy don't turn the amp up and down a lot, it pretty much stays in one place.

 Plus I only use my headphone amps at work, and the IEMS totally isolate me from my loud game playing co-workers. They are really into team fortress 2.

 Again, thanks to you tomb, and everyone else for all your hard work.

 -chilly


 I also had purchased a second Max board... maybe I'll build a very fancy one... like Ferrari's.... ideas anyone???


 hmmmmmm


----------



## John Wilson

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_I've looked at your pic on page 366 of this thread. You've got a real good pic there of the DB section. A visual inspection doesn't indicate anything wrong. So, let's start the standard drill, John:

 1. Verify the test points that you are trying to measure. The test points do nothing but measure the voltage at the leads of the RB10 or RB11 resistors.

Left Channel: One probe is in TA2L. The other probe is in TB1L or TB2L.
Right Channel: One probe is in TA2R. The other probe is in TB1R or TB2R.

 2. If that's correct, you need to verify your parts.

Trimmers:
 RB12L and RB12R are 2K trimmers

Transistors:
 Even to Odd on the small transistors to the pads on the board. 2N5088's go on QB3, QB5, and QB7. 2N5087's go on QB2, QB4, and QB6.

 QB1 is the PN4392 JFET.

 MJE253's go on the middle sinks on the Right side of the sinks.
 MJE243's go on the outboard sinks on the Right side of the sinks.

Resistors:
 RB1R: 1K ohm
 RB2R, RB3R: 10 ohm
 RB4R, RB5R: 100 ohm
 RB6R, RB7R: 220 ohm
 RB8R, RB9R: JUMPERED
 RB10R, RB11R: 2.2 ohm Power Resistor

 Please, DON'T CHEAT - make an honest attempt at this and let us know. If this doesn't indicate something, there are other things that we can try.
	

	
	
		
		

		
		
	


	


_

 

Thanks Tom. Followed your instructions vehemently. All is correct per build instuction. No cheat. JW


----------



## tomb

Well, dadgum, John!

 Maybe we're looking at this the wrong way.

 You say that for one DB that you "_can't get the DB's on one side below .940 mv_" and also, "_the other side below .835 mv!!!"_

 Well, let's review something I didn't catch before:

 Desired bias on DB's: 66.000 mV to 110.000 mV.
 You're measuring 00.940 mV and 000.835 mV, but you're trying to go lower?

 I think we're a couple of decimal points behind. Actually, I'm surprised that you can get them to go that low. 25.000 mV to 40.000 mV is typical with the trimmers turned about 20 turns down.

 I hope this is the issue. Sorry I didn't catch it before making you go through all that trouble.


----------



## John Wilson

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Well, dadgum, John!

 Maybe we're looking at this the wrong way.

 You say that for one DB that you "can't get the DB's on one side below .940 mv" and also, "the other side below .835 mv!!!"

 Well, let's review something I didn't catch before:

 Desired bias on DB's: 66.000 mV to 110.000 mV.
 You're measuring 00.940 mV and 000.835 mV, but you're trying to go lower?

 I think we're a couple of decimal points behind. Actually, I'm surprised that you can get them to go that low. 25.000 mV to 40.000 mV is typical with the trimmers turned about 20 turns down.

 I hope this is the issue. Sorry I didn't catch it before making you go through all that trouble. 
	

	
	
		
		

		
		
	


	


_

 

I was hoping I was miss reading the meter. I V is 1000MV,Right? I was thinking I was almost at 1V at .940. Let me go back and try it again. JW


----------



## John Wilson

tb2l to ta2l=0.84VDC~tb1l to ta2l=0.87VDC~TB1R to TA2R= 0.98VDC~TB2R to TA2R=0.99VDC. JW


----------



## tomb

Quote:


  Originally Posted by *John Wilson* /img/forum/go_quote.gif 
_tb2l to ta2l=0.84VDC~tb1l to ta2l=0.87VDC~TB1R to TA2R= 0.98VDC~TB2R to TA2R=0.99VDC. JW_

 

How's the heat on those? That's almost 500ma per DB, adding up to almost 1Amp in the output stage alone. Add in 0.15A for the tube heaters, and the PS is blowing off over 6W! I'm not sure that 1" heat sinks can even support that. It seems to me you'd be damaging components all over at that current, even if on for just a few seconds. Unless you're running one of those huge walwarts from Beezar, you'd be blowing the secondary protections in the walwart, too.

 I was running the numbers earlier and came to that conclusion - which is why I suspected the decimal point shift. So, how's the heat?

 EDIT: If things are not burning up/melting, then I'd have to conclude that those MJE's are toast.


----------



## John Wilson

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_How's the heat on those? That's almost 500ma per DB, adding up to almost 1Amp in the output stage alone. Add in 0.15A for the tube heaters, and the PS is blowing off over 6W! I'm not sure that 1" heat sinks can even support that. It seems to me you'd be damaging components all over at that current, even if on for just a few seconds. Unless you're running one of those huge walwarts from Beezar, you'd be blowing the secondary protections in the walwart, too.

 I was running the numbers earlier and came to that conclusion - which is why I suspected the decimal point shift. So, how's the heat?

 EDIT: If things are not burning up/melting, then I'd have to conclude that those MJE's are toast._

 

Last night I took reading on the MJE's and it hit 117 degrees. JW


----------



## John Wilson

Also I'm useing the 1.8 amp WallW. JW


----------



## tomb

Quote:


  Originally Posted by *John Wilson* /img/forum/go_quote.gif 
_Also I'm useing the 1.8 amp WallW. JW_

 

OK - that tells us why you haven't blown the walwart up, yet. 
	

	
	
		
		

		
			





  Quote:


  Originally Posted by *John Wilson* /img/forum/go_quote.gif 
_Last night I took reading on the MJE's and it hit 117 degrees. JW_

 

Well, see - that's another confusing point.

 With a typical MAX running 27VDC for V+, and 50ma bias (110mV), the temp of the transistors on the middle two heat sinks will be about 45 deg.C. Converting, that's 113 deg.F.

 I guess I should ask: is that Farenheit or Celcius you've measured?


----------



## tomb

I guess whether it's Fahrenheit or Celcius doesn't matter - your MAX still has a problem.

 Here's the next step I tried with Daveze the other day. Please check the voltage difference between the black and white arrows. You should get 27VDC in each case. This really only checks that the traces are OK, but it's a start.






 2nd, you can measure voltage across the leads of each of the resistors in the DB's:

 RB13L: ?V RB13R: ?V
 RB1L: ?V RB1R: ?V
 RB2L: ?V RB2R: ?V
 RB3L: ?V RB3R: ?V
 RB4L: ?V RB4R: ?V
 RB5L: ?V RB5R: ?V
 RB6L: ?V RB6R: ?V
 RB7L: ?V RB7R: ?V

 Here's a ballpark on the measurements that Daveze made on his:
 RB13L: 108.5mV RB13R: 106.3mV
 RB1L: 1.3mV RB1R: 409mV DING DING DING DING _-> this was the bad one, so I'd expect ~1.3mV to be correct._
 RB2L: 21.1mV RB2R: 23.4mV
 RB3L: 22.5mV RB3R: 22mV
 RB4L: 219mV RB4R: 231mV
 RB5L: 230mV RB5R: 218mV
 RB6L: 240mV RB6R: 235mV
 RB7L: 240mV RB7R: 234mV

 Daveze's MAX was working on the Left, so the "L" reading numbers should be a reasonable expectation. A lot of work, but your photos and MAX look so good that I'm deeply puzzled at what's going on.


----------



## cronic

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Try putting the 12AE6 that measured good in one socket and one of your good 12FK6's in the other. See if you can bias the 12AE6 under that scenario. At least it will prove that one 12AE6 tube is good (needless to say, the amp won't sound very good doing that, but it won't hurt it)._

 

You guys are AWESOME. 
	

	
	
		
		

		
		
	


	




 One of the 12ae6a worked correctly and adjusted fine with the 12fk6, the other did not. Looks like I need to order a set.
	

	
	
		
		

		
		
	


	




 I got my new AKG 701 phones in today and am very impressed with the sound of the amp and phones with zero burn in, so I guess it only gets better from here on out. Thanks again guys for the awesome help. I hope have enough time to get the edges of the black cast acrylic polished tomorrow and have my custom case finished except for the top panel. I will post pics as soon as I get it done. But for now its time to jam some pink floyd.


----------



## pinkfloyd4ever

Quote:


  Originally Posted by *cronic* /img/forum/go_quote.gif 
_ But for now its time to jam some pink floyd. 
	

	
	
		
		

		
		
	


	


_

 

WOOOOOORRRRDDD 
	

	
	
		
		

		
		
	


	




 anyone know if there's much of a burn-in period for Vit Qs?


----------



## tomb

Quote:


  Originally Posted by *pinkfloyd4ever* /img/forum/go_quote.gif 
_WOOOOOORRRRDDD 
	

	
	
		
		

		
		
	


	




 anyone know if there's much of a burn-in period for Vit Qs?_

 

an hour or two? maybe less ...


----------



## amphead

Quote:


 Try putting the 12AE6 that measured good in one socket and one of your good 12FK6's in the other. 
 

Good call TomB! You knocked that ball out of the park!


----------



## John Wilson

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_OK - that tells us why you haven't blown the walwart up, yet. 
	

	
	
		
		

		
		
	


	




 Well, see - that's another confusing point.

 With a typical MAX running 27VDC for V+, and 50ma bias (110mV), the temp of the transistors on the middle two heat sinks will be about 45 deg.C. Converting, that's 113 deg.F.

 I guess I should ask: is that Farenheit or Celcius you've measured?_

 

Tom! I'm from Cleveland Ohio. JW


----------



## tomb

Quote:


  Originally Posted by *John Wilson* /img/forum/go_quote.gif 
_Tom! I'm from Cleveland Ohio. JW_

 

Well, I'm in Hotlanta, but my meter still reads in Celcius. 
	

	
	
		
		

		
		
	


	







 Seriously, please tell us how you're doing with your MAX today. Some of us will continue to worry until you get it fixed.


----------



## John Wilson

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Well, I'm in Hotlanta, but my meter still reads in Celcius. 
	

	
	
		
		

		
		
	


	







 Seriously, please tell us how you're doing with your MAX today. Some of us will continue to worry until you get it fixed. 
	

	
	
		
		

		
		
	


	


_

 

Mine has both....But can't relate to C. It was 64 here in Cleveland yesterday...today it's 30! All in F. I'll get to all the test today Tom. And thanks! You are magnanimous in more ways then one. This Yankee thanks you for your Southern hospitality! JW


----------



## tomb




----------



## John Wilson

Stop the presses! SO FAR!! RB2L=0V~ RB2R=0V...RB 3L=293mv~ RB3R=6.49V. Yes..Volts! RB7L=302mv~ RB7R=295mv. JW


----------



## John Wilson

It's time to eat humble pie....RB2L,2R,3L,3R. I have 10K ohm instread of 10 ohm!! I am a twit. JW


----------



## tomb

Quote:


  Originally Posted by *John Wilson* /img/forum/go_quote.gif 
_It's time to eat humble pie....RB2L,2R,3L,3R. I have 10K ohm instread of 10 ohm!! I am a twit. JW_

 

's OK. Sometimes it takes going through the process of troubleshooting before we ever notice that a part is wrong. The nice thing is that we are lucky when that happens, because the solution is pretty certain.

 Glad to see you found something! Success is around the corner, hopefully!


----------



## cronic

Well another one lives. Here is how far I am so far. I still have to etch the front and rear panels and make the top panel. I also need to get the rest of the polishing compound out of the side recesses. 
	

	
	
		
		

		
		
	


	




 All in all I am super pleased with the max. It sounds incredible and makes me want to listen to all my music again. Big thanks to everyone who was and is involved with bringing the max to the DIY community.


----------



## pinkfloyd4ever

cronic, are those 1.5" sinks? You usin mosfets or is that just the kit from jeff? I might recommend replacing your output resistors (RB14s) with jumpers, as I've heard that the V-Ds can crapify the sound some in those positions

 edit: actually I got that from the max site Millett Hybrid MAX Boutique at the bottom of that page


----------



## cronic

Quote:


  Originally Posted by *pinkfloyd4ever* /img/forum/go_quote.gif 
_cronic, are those 1.5" sinks? You usin mosfets or is that just the kit from jeff? I might recommend replacing your output resistors (RB14s) with jumpers, as I've heard that the V-Ds crapify the sound in those positions

 edit: actually I got that from the max site Millett Hybrid MAX Boutique at the bottom of that page_

 

Yes, they are 1.5". I am not using mosfets yet, but I may in the future. In hind site I should have gotten a kit from jeff, but I did it the old fashion way and ordered from 4 different places.
	

	
	
		
		

		
		
	


	




 I will jumper rb14l/r very shortly. That was an oversight on my part. Thanks for the good eye bud. 
	

	
	
		
		

		
		
	


	




 I got them jumpered now and the music seems to have more pop or impact ( for lack of a better term ) than it did before. Thanks for the help.


----------



## John Wilson

Thankyou Tom! Put in the four 10 ohmer's and it's all systems go. 110 mv per side. PS 27V. Tubes 13.5 V. Input and output offset all 0 mv! I'll do glammer shots later. JW


----------



## amphead

Thats great news JW! Another Max Lives!!!   

 How do you like the sound?


----------



## tomb

Yayyyy Cronic!

 Yayyyy John!

 Another two MAXes live!!!


----------



## John Wilson

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Yayyyy Cronic!

 Yayyyy John!

 Another two MAXes live!!!
	

	
	
		
		

		
		
	


	





_

 

And sounds fantastic...wait till it burns in. JW


----------



## John Wilson

Quote:


  Originally Posted by *amphead* /img/forum/go_quote.gif 
_Thats great news JW! Another Max Lives!!!   

 How do you like the sound?_

 

Thanks AH! Sounds great! Some Paul Simon.Dave Grusin,Jean-Luc Ponty,Steely Dan,Johnny Adams,Sting etc. I'm glad I put in the TKD pot. I've always used Noble ( still a great choice). I went with a 250k ohm TKD. JW


----------



## joneeboi

Congratulations, cronic and John. Enjoy your MAXes.

 I just wanted to inquire of the gurus. I used to have Muses bypassed with K42s, but I wasn't getting enough bass information. I thought the Muses were the bass monsters, but I definitely wasn't getting the slam like my PIMETA and car system typically give me. I threw in some Silmic IIs bypassed only at CA7 with the K42s. It is all currently burning in, but I'm wondering what I can do to increase the bass. I have 1000uF at CA2, 470uF at CA7, but some of my reference tracks are coming up shy. I have the ES, Std BGs, some Panny FCs and FMs, and there are the Slimic IIs already inside them. Something went wrong with the VitQs, so I took them out because I didn't feel like troubleshooting that. I feel kind of bad going to my PIMETA all the time because the MAX leaves me kind of hungry for bass. I love the MAX, but it's not doing what I want it to. =T


----------



## amphead

Yeah, congrats Cronic!!! Another Max Lives!   

 Nice looking build!


----------



## John Wilson

Quote:


  Originally Posted by *joneeboi* /img/forum/go_quote.gif 
_Congratulations, cronic and John. Enjoy your MAXes.

 I just wanted to inquire of the gurus. I used to have Muses bypassed with K42s, but I wasn't getting enough bass information. I thought the Muses were the bass monsters, but I definitely wasn't getting the slam like my PIMETA and car system typically give me. I threw in some Silmic IIs bypassed only at CA7 with the K42s. It is all currently burning in, but I'm wondering what I can do to increase the bass. I have 1000uF at CA2, 470uF at CA7, but some of my reference tracks are coming up shy. I have the ES, Std BGs, some Panny FCs and FMs, and there are the Slimic IIs already inside them. Something went wrong with the VitQs, so I took them out because I didn't feel like troubleshooting that. I feel kind of bad going to my PIMETA all the time because the MAX leaves me kind of hungry for bass. I love the MAX, but it's not doing what I want it to. =T_

 

Hey Jonee. Mine from the start isn't to bad. I can hear a little sibilance...just a little. But that's the caps...after burn in it should sound better. So many factors! I have the 680 uf BG's at the output bypassed by the 0.47 uf BG NX. I'm using my Sony DAT with a batt power supply. (4.5 amps) And had some monster cable made for ipods (single 1/8 in. to two RCA's) By the way I'm not into ipods. Ok bass. Then I used a 1/8 inch with two FRCA's and put on my Kimber Hero interconnect with locking WBT ends...WOW more bass! More detail, more air and attack! So many factors! JW


----------



## jgonino

I am sure this has been covered before, but searching this thread is really hard!:

 Is it possible to build a one of these at a lower gain (say around 3) without degrading SQ due to resistors?


----------



## pinkfloyd4ever

In short, no.

 The millett tube with the lowest gain is the 12FK6, which has a gain of about 7, but the Millett has some negative gain so I believe its around 5 with the FK6. Adding output resistors isn't reducing the gain, but rather attenuating, and like you said, to do it that much will hurt the dynamics of the amp. What do you need a gain that low for? I use mine with MS-1s and KSC75s, both very easy to drive cans, and I don't find the gain to be too high at all..in fact I'm considering trying one of the higher gain tubes. It is an awesome amp and I'd definitely recommend it, particularly Boutique Build #1 from the Max site


----------



## jgonino

my current amp gets too loud at around 9 oclock, so I am looking for a lower gain. If you are using 7, that should work for my dx1000's


----------



## pinkfloyd4ever

joneeboi, do you have K42s at CA9? As tomb's said before, many times the best thing there is Wimas or nothing, as the bass can be killed by having anything other than a Wima there Millett Hybrid MAX Boutique read the 3rd paragraph under Cathode Bypass Caps


----------



## amphead

Quote:


  Originally Posted by *jgonino* /img/forum/go_quote.gif 
_my current amp gets too loud at around 9 oclock, so I am looking for a lower gain. If you are using 7, that should work for my dx1000's_

 

The Millett Max's forte is that LOUD, is not what comes to mind while listening. Even with 12AE6 and a gain of 14, the words CLARITY and TIGHT but EXTENDED BASS come to mind, even with my K701's, which are very linear. You would thank yourself for building one. (JMHO)


----------



## jgonino

I am considering having one of these built by a member here. I am looking to sell my PPX3, and use this as my main amp. As for configuration, it looks like I should go with the lowest gain tubes. I am also going to have the builder make this thing "maxxed" with all possible options, as well as a nice case. Is it possible to have a loop out as well as as an input?


----------



## tomb

Quote:


  Originally Posted by *jgonino* /img/forum/go_quote.gif 
_I am considering having one of these built by a member here. I am looking to sell my PPX3, and use this as my main amp. As for configuration, it looks like I should go with the lowest gain tubes. I am also going to have the builder make this thing "maxxed" with all possible options, as well as a nice case. Is it possible to have a loop out as well as as an input?_

 

Yes, of course. Colin has provided ample terminal block positions on the board for just such a purpose. The easiest is to use the board-mtd headphone jack in conjunction with preamp outs connected to the adjacent terminal block. Since the headphone jack is switched, it will operate as a pre-amp until a pair of headphones are plugged in.

 There are other ways to do it, too.


----------



## slowpogo

I know this has been discussed before, but what exactly are the Max's capabilities as a preamp? There is an older, used NAD speaker amp I've been eying up at the store...could the Max function as a preamp in this capacity?


----------



## cronic

I have noticed that with the amp on and no source playing I get a noise when the volume pot is turned all the way to either end of its rotation when you reach the end of the pots travel. It sounds like a ping or ringing sound through the headphones. Is this normal or is there an issue with the pot?


----------



## joneeboi

Quote:


  Originally Posted by *pinkfloyd4ever* /img/forum/go_quote.gif 
_joneeboi, do you have K42s at CA9? As tomb's said before, many times the best thing there is Wimas or nothing, as the bass can be killed by having anything other than a Wima there Millett Hybrid MAX Boutique read the 3rd paragraph under Cathode Bypass Caps_

 

I left CA9 open. I think I'll try going back to the Panasonic FCs to see if that will help, because I was getting loads of bass with it before. Or maybe it's just a different category of bass I'm getting between the PIMETA and MAX altogether. I like the slam and forwardness from the PIMETA, whereas the MAX would probably serve more as a softer listening medium, spinning some Bach during the cold winter months by the fireplace, curled up in a airy, fluffy, brown blanket, sipping a toasty cocoa with soaking stale marshmallows. Alas, spring is finally upon us and the PIMETA and Mini^3 will probably see more use. Tragic.


----------



## joneeboi

Quote:


  Originally Posted by *cronic* /img/forum/go_quote.gif 
_I have noticed that with the amp on and no source playing I get a noise when the volume pot is turned all the way to either end of its rotation when you reach the end of the pots travel. It sounds like a ping or ringing sound through the headphones. Is this normal or is there an issue with the pot?_

 

It's probably a microphonic tube/two microphonic tubes reacting to the physical jolt made by turning the pot to each end. Lightly tap on either tube to see which is problematic and replace as you desire.


----------



## tomb

Quote:


  Originally Posted by *cronic* /img/forum/go_quote.gif 
_I have noticed that with the amp on and no source playing I get a noise when the volume pot is turned all the way to either end of its rotation when you reach the end of the pots travel. It sounds like a ping or ringing sound through the headphones. Is this normal or is there an issue with the pot?_

 

That's a slightly microphonic tube pinging you when the pot hits it's travel. 
	

	
	
		
		

		
		
	


	




 Take your fingernail to the tubes and slightly flick them and see if that gives you a similar sound.
	

	
	
		
		

		
		
	


	




 EDIT: Oops. Joneeboi and I were doing mental telepathy.


----------



## ruZZ.il

Thats some slow traveling thought 
	

	
	
		
		

		
		
	


	



 I bet it felt like it was just in your head without you ever realizing how, or when, it got there, ha?


 <returns to dividing binary>.. hrm..


----------



## tomb

Quote:


  Originally Posted by *ruZZ.il* /img/forum/go_quote.gif 
_Thats some slow traveling thought 
	

	
	
		
		

		
		
	


	



 I bet it felt like it was just in your head without you ever realizing how, or when, it got there, ha?


 <returns to dividing binary>.. hrm.._

 












 Obviously, I hadn't refreshed my screen lately.


----------



## cronic

Quote:


  Originally Posted by *joneeboi* /img/forum/go_quote.gif 
_It's probably a microphonic tube/two microphonic tubes reacting to the physical jolt made by turning the pot to each end. Lightly tap on either tube to see which is problematic and replace as you desire._

 

You guys have troubleshooting down pat on this amp. It is the tubes. 
	

	
	
		
		

		
		
	


	




 I will change them out when I get some more. Thanks again guys for your awesome help and real time troubleshooting.


----------



## BoilermakerFan

Tom

 I was spreading the Millett MAX gospel today. I was on a flight from Brownsville, TX to Houston, TX and the guys sitting next to me asked me about my DAP and my headphones (I had my Shure E2Gs out instead of the Denon C700s because I had planned to sleep). We started discussing headphones and their differences, then discussed amps. I told him about my plans for the four different MAX amps and he started asking some more questions. I asked if he was a member of Head-Fi and he said he was, so I asked for his user name and told him to check out this thread and to visit the MAX site. 

 His user name is Panigraphi and he lives in Atlanta! I asked if he made it to any of the GTGs and e said he hasn't yet, but I told him you were in ATL and suggested he contact you and make it to the next GTG you guys have so he can listen to a couple of different MAX amps with his K701s and HF1s. 

 On a side note, I think I've decided on the two headphones I'm going to go with initially. The AKG K601s and the Ultrasone HFI-780s. Both are in the right price point so I can get both at the same time and both have reports of significant improvements with sub-$300 cable upgrades and tweaks. I'll have ALO mod the 780s, and I'll have the K601s done by a guy in Nashville that used to work for AKG, but I can't remember his name now. I want to order both as stock 'phones and break them in and listen to them for some time before I upgrade them so I can have a better appreciation for the improvements. The AKGs have been ordered tonight, but I'm looking into the HFI-780s and leaning towards just ordering them from ALO...

 - BMF


----------



## tomb

Wow, BoilermakerFan! Small world! I'll keep an ear out for him. If he has a pair of HF-1's, wow. The MAX and the HF-1's are an outstanding combo. I wish I could get a pair, in fact. I remember listening to MexicanDragon's when he hooked them up to my MAX at the Atlanta meet - very, very nice. I don't know if he ever did, but he was talking about getting Nate to build him one - he was likewise impressed with the MAX.

 HopperGrass had a pair of K701's at that same meet - that's how I got to hear those with the MAX - also very nice. Of course, Fitz was there, too - so every AKG you could imagine and then some you couldn't were all laid out on a couple of tables. They didn't "travel" around to the other amps as much as HopperGrass's did, though.


----------



## tomb

Quote:


  Originally Posted by *cronic* /img/forum/go_quote.gif 
_You guys have troubleshooting down pat on this amp. It is the tubes. 
	

	
	
		
		

		
		
	


	




 I will change them out when I get some more. Thanks again guys for your awesome help and real time troubleshooting._

 

Actually, one of the things about using tubes is learning to accept some faults - they all have their own personality, so to speak. Sometimes those faults are sort of like having a stain on a guitar - it doesn't mean it will make it sound bad. 
	

	
	
		
		

		
		
	


	




 If the microphonics are where you only hear it when you rack the pot, the tubes may perform well for you a good long time.

 Some microphonic tubes, on the other hand, can be so bad that they pick up the slight noise of paper rustling on the tabletop.


----------



## BoilermakerFan

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Wow, BoilermakerFan! Small world! I'll keep an ear out for him. If he has a pair of HF-1's, wow. The MAX and the HF-1's are an outstanding combo. I wish I could get a pair, in fact. I remember listening to MexicanDragon's when he hooked them up to my MAX at the Atlanta meet - very, very nice. I don't know if he ever did, but he was talking about getting Nate to build him one - he was likewise impressed with the MAX.

 HopperGrass had a pair of K701's at that same meet - that's how I got to hear those with the MAX - also very nice. Of course, Fitz was there, too - so every AKG you could imagine and then some you couldn't were all laid out on a couple of tables. They didn't "travel" around to the other amps as much as HopperGrass's did, though._

 

Yes it is. I didn't get my nap, but it was a lot nicer to talk to somebody about headphone audio that actually "gets it" so it made the short flight pass very quickly. I just emailed Ken at ALO on the 780s too. I figure if I have the headphones sitting there waiting to be used, it will help me stay focused on getting at least the first one built and I can always move it to it's new home later when the console mods are finished. I just hope the weather stays warmer consistently soon. My garage isn't heated and I don't have room for mad scientist solder work in the house.


----------



## amphead

Quote:


  Originally Posted by *cronic* /img/forum/go_quote.gif 
_You guys have troubleshooting down pat on this amp. It is the tubes. 
	

	
	
		
		

		
			





 I will change them out when I get some more. Thanks again guys for your awesome help and real time troubleshooting._

 

Hey Cronic, try putting high-temp o-rings on the tubes. They dampen vibration. You just find the size that fits the diameter of the glass. Vibration often initiates microphonics of course.


----------



## cronic

Quote:


  Originally Posted by *amphead* /img/forum/go_quote.gif 
_Hey Cronic, try putting high-temp o-rings on the tubes. They dampen vibration. You just find the size that fits the diameter of the glass. Vibration often initiates microphonics of course._

 

Thats a good idea. I will try to pick some up and give it a spin.


----------



## MexicanDragon

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_If he has a pair of HF-1's, wow. The MAX and the HF-1's are an outstanding combo. I wish I could get a pair, in fact. I remember listening to MexicanDragon's when he hooked them up to my MAX at the Atlanta meet - very, very nice. I don't know if he ever did, but he was talking about getting Nate to build him one - he was likewise impressed with the MAX._

 

Hey tom,

 Never got that MAX from Nate, but I know where it went, and its in good hands. I wish I would have, since he's now retired, but maybe one day. (I know Colin too... <g>) The Max is still on my list to own, though.

 I know we put it up against RS-2s in a Toshiba SD-3950 (stock)->TomB's Max-> My HF-1s and it sounded REALLY good. On the RS-2 owner's rig, the 2's were better... but IIRC, the HF-1s just worked with the Max, and though I conceded defeat to the 2s on the owner's Darkvoice, the HF-1s seemed to be the perfect fit for that amp.

 I've actually found myself recommending a MAX to a few other people. But bang-for-the-buck, its tough to beat.

 **BRENT**


----------



## John Wilson

New change. Hi...remember me? ( Pretend you do). In CA 5 I have the FG ( Fine Gold) 2200 uf and in CA 4 the muse 470 uf. I replaced the 470 with another FG 1000 uf. WOW! Bass was good before. But now it's GREAT. Tight, deeper,fast and better dynamics from top to bottom. Midrange has even more air and detail. P. S. at 24 V. 12FM6's at 12 V. All MJE's at 110 mv. JW


----------



## ruZZ.il

Glad you're all up and running! I missed a few congrats on some new MAXes, CONGRATS ALL! 
	

	
	
		
		

		
		
	


	



 JW: wait till you switch out those BJTs


----------



## Daveze

Man, got me feeling pretty cold and alone now, its painful just how close I am but at the same time aren't...


----------



## amphead

Hey no worries! Where are you at now, in the troubleshooting process? You know it would cost a fortune to ship it to me to fix, but I do fix them pro bono. However, let's get it fixed online!


----------



## tomb

Quote:


  Originally Posted by *MexicanDragon* /img/forum/go_quote.gif 
_Hey tom,

 Never got that MAX from Nate, but I know where it went, and its in good hands. I wish I would have, since he's now retired, but maybe one day. (I know Colin too... <g>) The Max is still on my list to own, though.

 I know we put it up against RS-2s in a Toshiba SD-3950 (stock)->TomB's Max-> My HF-1s and it sounded REALLY good. On the RS-2 owner's rig, the 2's were better... but IIRC, the HF-1s just worked with the Max, and though I conceded defeat to the 2s on the owner's Darkvoice, the HF-1s seemed to be the perfect fit for that amp.

 I've actually found myself recommending a MAX to a few other people. But bang-for-the-buck, its tough to beat.

 **BRENT**_

 

Thanks for kind words on the MAX, Brent. Likewise, your HF-1 was mightily impressive. I keep hoping there'll be another Grado/Head-Fi special like that, but I may be out of luck. I was clueless the first time.


----------



## tomb

Quote:


  Originally Posted by *John Wilson* /img/forum/go_quote.gif 
_New change. Hi...remember me? ( Pretend you do). In CA 5 I have the FG ( Fine Gold) 2200 uf and in CA 4 the muse 470 uf. I replaced the 470 with another FG 1000 uf. WOW! Bass was good before. But now it's GREAT. Tight, deeper,fast and better dynamics from top to bottom. Midrange has even more air and detail. P. S. at 24 V. 12FM6's at 12 V. All MJE's at 110 mv. JW_

 

That's one of the reasons we changed that part specification to 1000uf minimum at CA4 and CA5. 
	

	
	
		
		

		
		
	


	




 Glad you're liking your MAX.


----------



## tomb

Quote:


  Originally Posted by *amphead* /img/forum/go_quote.gif 
_Hey no worries! Where are you at now, in the troubleshooting process? You know it would cost a fortune to ship it to me to fix, but I do fix them pro bono. However, let's get it fixed online! _

 

Amphead, you're a champ! I can't tell you how much that standing offer helps the Millett MAX community. What you've already done for Pabbi's Balanced MAX is tremendous!!

 However, I had sent Daveze a bunch a parts - some purchased, some not. He wasn't too specific in that last post, but I'm hoping he's still waiting on those parts. If not, we need to get an idea what he's replaced and what he hasn't. We had narrowed down the issue to some wild voltage around QB2 and QB3 and the possibility that his output transistors are bad. He originally had the power output transistors reversed, but I am suspecting that doing that also burned out QB2 and QB3.

 However, after John's finding that the some of the DB resistors were sized incorrectly, I'm wondering if that same thing could be going on with Daveze's (it's always possible that some are mistaken even after checking).

 Lots of questions ... hopefully, Daveze will give us more details.


----------



## Daveze

Its the waiting game that I'm playing...its a big pond to cross.

 Thats the most frustrating bit about it, there isn't anything I can really do other than wait, so I'm just spinning my wheels while everybody else is fixing theirs. 

 Sorry guys, just venting a little.


----------



## Nebby

Quote:


  Originally Posted by *Daveze* /img/forum/go_quote.gif 
_Its the waiting game that I'm playing...its a big pond to cross.

 Thats the most frustrating bit about it, there isn't anything I can really do other than wait, so I'm just spinning my wheels while everybody else is fixing theirs. 

 Sorry guys, just venting a little._

 

If it's any consolation, my Millet Maxis still in the planning stages


----------



## Daveze

Thanks, it does help a little, at least I have a left channel that I can marvel at...
	

	
	
		
		

		
		
	


	




 It might be somewhat 'sucker for punishment-ish' but I too have a MAX in planning stages. Ma-ma-ma-Mosfet anyone?


----------



## Aldyrin2

Has anyone had any experience with Audio Technica HP's with the MAX? I was thinking about getting AKG 701's to use with the MAX at the office, but I think some closed can's might be the best idea, and was thinking about the ATH-W1000's.

 Anyone heard these driven from a MAX?


----------



## Nebby

Quote:


  Originally Posted by *Daveze* /img/forum/go_quote.gif 
_Thanks, it does help a little, at least I have a left channel that I can marvel at...
	

	
	
		
		

		
			





 It might be somewhat 'sucker for punishment-ish' but I too have a MAX in planning stages. Ma-ma-ma-Mosfet anyone?_

 

Strangely enough, the one I'm planning also has mosfets involved too


----------



## BoilermakerFan

Quote:


  Originally Posted by *Aldyrin2* /img/forum/go_quote.gif 
_Has anyone had any experience with Audio Technica HP's with the MAX? I was thinking about getting AKG 701's to use with the MAX at the office, but I think some closed can's might be the best idea, and was thinking about the ATH-W1000's.

 Anyone heard these driven from a MAX?_

 

I haven't heard the W1000s, but at the W1000 price point, I would put the ALO modified HFI-780s with the Vampire wire on the list. I'm planning to buy the stock HFI-780s from ALO next week, listen to them and break them in, then send them back to ALO for the upgrades in 2-3 months so I can truly appreciate the changes done by Ken. I'm also ordering a pair of AKG 601s that I will have re-cabled with a 701 pad replacement in the future (again, about the same price point as the W1000s after re-cabling). I looked at the AT 'phones, but from my interpretation of all the review opinions, I wouldn't like their sound compared to the HFI-780s or AKGs. Another alternate for you would be the AKG K271Studios which are closed and cables are very easily upgraded due to the mini-XLR connector on the headphone. The 271s and new cable would be about the same or slightly less than the W1000s. 

 The thing that I really drew me to the MAX amp in particular is how much we can alter the sound signature just be changing the caps or the DB transistors. I think there is a combination that can make any good or great headphone sound even better, but that's JMHO... I couldn't decide which one I wanted to build, so I've already decided to build four. I'm sure one or two will become overall favorites, but I want to be able to do side-by-side comparisons with four amps and two different sets of headphones with different types of music.


----------



## fault151

Hi, im after a power supply for the millet. Which of the two is best for me?

 I live in the UK.

AC 220V 240V to DC 24V ADAPTOR Converter 1000mA on eBay, also, Power Plug Adaptors, Accessories, Consumer Electronics (end time 14-Mar-08 07:39:28 GMT)

AC/DC MAINS POWER ADAPTOR/SUPPLY 1 AMP/1A 24V/24 VOLT on eBay, also, Power Plug Adaptors, Accessories, Consumer Electronics (end time 28-Feb-08 11:30:18 GMT)


----------



## tomb

Quote:


  Originally Posted by *fault151* /img/forum/go_quote.gif 
_Hi, im after a power supply for the millet. Which of the two is best for me?

 I live in the UK.

AC 220V 240V to DC 24V ADAPTOR Converter 1000mA on eBay, also, Power Plug Adaptors, Accessories, Consumer Electronics (end time 14-Mar-08 07:39:28 GMT)

AC/DC MAINS POWER ADAPTOR/SUPPLY 1 AMP/1A 24V/24 VOLT on eBay, also, Power Plug Adaptors, Accessories, Consumer Electronics (end time 28-Feb-08 11:30:18 GMT)_

 

Neither, unfortunately. Both convert to 24VDC. Most likely, they're switching supplies, too, which would be inappropriate for the MAX even if you forego the onboard power supply.

 I'll look to see if I can find you something ...


----------



## tomb

You need one of these:

REVERE RT-2440SL/M 24VAC 40VA PLUG-IN TRANSFORMER 2 EA on eBay, also Passive Components, Electronic Components, Industrial Electrical Test, Business Industrial (end time 12-Mar-08 21:49:34 GMT)

 plugged into one of these:

45W US to UK Stepdown Transformer Voltage Converter on eBay, also, Other Electronics Accessories, Accessories, Consumer Electronics (end time 14-Mar-08 11:22:31 GMT)

 There may be something that does it all in one box, but that's the best I could find on short notice.


----------



## fault151

ok thanks for your help. What are the key features im looking for? Ill have detailed search on eby tonight. I m glad i asked now, nearly bought the other one thinking it war the right thing.


----------



## ruZZ.il

24V *A*C output. around 30 VA (1.25Amps, more here is better, but no need for much more). I mentioned the LB55R, who's specs are just right.

 Input, i assume, preferably 220-240Vac ?


----------



## fault151

Quote:


  Originally Posted by *ruZZ.il* /img/forum/go_quote.gif 
_24V *A*C output. around 30 VA (1.25Amps, more here is better, but no need for much more). I mentioned the LB55R, who's specs are just right.

 Input, i assume, preferably 220-240Vac ?_

 

do maplin do a slightly higher powered version? If not i'll just get this. The detatchable ends wont cause any problems with sound will it? Interference/noise?


----------



## ruZZ.il

Nope, thats what they got. I think its plenty powerful enough, even for a hungry MAX. I don't have any problems with that plug thing, it can come out sometimes if i move things around and aren't careful, but I don't do it much when the amp is on, so I don't care. It's been good to me.


----------



## fault151

i ordered one anyway. :0) Thanks


----------



## John Wilson

Question: My V-reg heat sink seems to be running hot,I can,t keep my index finger on it more then 6 seconds. It's 135.8 degrees F. at 24 Volts. JW


----------



## tomb

Quote:


  Originally Posted by *John Wilson* /img/forum/go_quote.gif 
_Question: My V-reg heat sink seems to be running hot,I can,t keep my index finger on it more then 6 seconds. It's 135.8 degrees F. at 24 Volts. JW_

 

It will run cooler at 27VDC than 24.

 2nd, I noticed you used the very tall KZ's for the PS caps, but you used a 1" sink, if memory serves. That will make your PS run a bit hotter than normal, because more of the heat sink is "shaded." Extra cooling holes - perhaps in the back plate may be warranted.

 Still, running 27VDC will cool it down faster than anything else at this point.


----------



## John Wilson

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_It will run cooler at 27VDC than 24.

 2nd, I noticed you used the very tall KZ's for the PS caps, but you used a 1" sink, if memory serves. That will make your PS run a bit hotter than normal, because more of the heat sink is "shaded." Extra cooling holes - perhaps in the back plate may be warranted.

 Still, running 27VDC will cool it down faster than anything else at this point.
	

	
	
		
		

		
		
	


	


_

 

Thanks Tom! Will do. JW


----------



## Daveze

Tom, you're lucky I can't reach you from here, because I'd be planting one big sloppy kiss on your face.

 New QB2/3 arrived yesterday and were installed this morning. I have both tubes biased and am in the middle of DB bias.

 My girlfriend won't like me saying it but I think I love you...


----------



## tomb

Sloppy kiss?! 
	

	
	
		
		

		
		
	


	







 Good thing you're Australia!! 
	

	
	
		
		

		
		
	


	




 Seriously, keep us in touch with how it's going - glad to help.


----------



## Daveze

Thats right, big sloppy kiss. Its love and thats just how I roll 
	

	
	
		
		

		
			





 More seriously though, I'm...amped...
	

	
	
		
		

		
		
	


	




 Okay okay, enough jocularity...for now. I'm sitting at 85mV for each DB bias point and its hardly cracking a sweat, though its sitting out in the open at the moment and we have a nicely cool breeze happening, so I'm a little reluctant to push too much higher just yet.

 You wouldn't believe just how content I feel right now.


----------



## tomb

Sounds good! Dare I say it?

 Another MAX lives!!


----------



## Daveze

It most certainly does live. I pushed it out to 100mV, reaching about 40C. Punches through the SR-80's. 

 Now to finish the case...


----------



## fault151

Hey all, just got my power supply through from Maplins ready for when the millet arrives. Theres one thing im not sure about. 

 On the mini adapter end that you plug in, there i + and - marked on the plug. It doesn't line up with the connector. The two symbols on each part contradict each other. Im not sure which way it needs to be plugged in? I think one way is enabling positive to the center and the other way enables positive to the outside? Am i making any sense? Ill try take a pic and post it up.

*ruZZ.il - how have you connected yours up?*


----------



## amphead

Congrats Daveze! Another Max Lives!!   

 Give a full report on your sound when you get a chance.

 Fault151, if you are talking about the output of the 24v AC power supply, then it doesn't matter. Remember polarity switches back and forth every half cycle.


----------



## Daveze

Quote:


  Originally Posted by *amphead* /img/forum/go_quote.gif 
_Congrats Daveze! Another Max Lives!!   

 Give a full report on your sound when you get a chance...._

 

I'll give as much of a report as I can. For reference, my build is from Jeff Rossel's kit. Source is an AlienDAC with film caps, playing FLAC files through Winamp on Vista. The last link is kinda the weakest, I don't think I have audio working with Vista quite as well as I'd hoped.

 JVC "something-something" IEM: I used these as the expendable first test 'phones. I haven't actually sat and listened to these for a while but I was really tempted to spend quite some time just listening to these.

 VSonic R02Pro IEM: These were second in line after the JVC's. After being quite impressed with the JVC's I was a bit disappointed that these didn't blow them out of the water. Its not that they're bad, its just that they didn't outshine the JVC's like they do when I just use my MP3 player.

 IEM summary: The Max was the ground leveler. For me, IEM's are my traveling headphones, not for serious listening. Its not fair on all IEM's but I wouldn't bother building a Max just for IEM's, its a wasted effort.

 Grado SR-80: These are my home listening cans, normally I doze off at night to the tunes of Davis or Mingus, through a Go-Vibe 3. With the Max, the slam was the first thing I noticed, I think I'm beginning to see why people say Grado's are current thirsty devices. Theres also the fine details too, like the little nuances in the bass tone of a Cure song that were previously not so obvious. 

 Grado SR-225: These are brand spanking new. The first time I'd listened to them was with the Max, and as a result: they sucked. The highs were brittle and irritating, the rest was probably nice but I couldn't get over how much I didn't like listening to the highs. I however have complete faith that with the opportunity to burn-in, they will come fantastic.

 AKG-240S: I didn't think that I would have the Max running over the weekend, so these are still at work. I have a strong suspicion that these will be very good fun.

 Summary: As the first step up from portable amps like the Go-Vibe and the Mini3, the Max really kicks some donkey. I play bass as an instrument, so I love listening to the low end, which is fantastic because the Max with the SR-80's is a very formidable force for slam and definition in the lows. Other than that, I'll avoid going into great detail because I don't really have much to compare with. A really great, fun amp, I can't really bear to stop on any one cd for more than a few tracks, like a kid in a candyshop.

 If anybody is debating whether or not the Max is worthwhile, give in, it most certainly is. I'll hope to provide more details after I regain the ability to think more objectively...


----------



## headphonejunkie

The 225's will sound even better than your 80's once they burn-in. You wait.


----------



## BoilermakerFan

Quote:


  Originally Posted by *Daveze* /img/forum/go_quote.gif 
_AKG-240S: I didn't think that I would have the Max running over the weekend, so these are still at work. I have a strong suspicion that these will be very good fun._

 

Congrats on getting your MAX alive and kicking!

 Did you have Jeff upgrade your DBs and caps to the Muse ES? 

 Also, let me know how the 240S's sound with the MAX. I'll be ordering Ultrasone HFI-780s from ALO and AKG K601s, but I'm also interested in the AKG K270Ss. The ALO modded Grado 225s are starting to whisper my name too, but I need to draw the line at the HFI-780s and K601s for now. I need to upgrade my IEMs for use with my Sony A816 DAP. My Denon C700s are great, but they offer little isolation, however, they have made the poor SQ of my Shure E2Gs obvious, so I need to upgrade. The Klipsch Images are on the short list for my next IEMs.


----------



## odoe

Maybe it's just me, but I actually think my K240S are more "fun" with my MAX than my HD580s. This is on a ES/Orange Drop with 2SC3422/2SA1359. The 580s are great and bassy, but I like the 240S enough that I am very interested in some higher level AKGs to try out with my MAX.


----------



## fran

Fault151 --

 From your description of the plug it seems likely that you have a 24V *DC* adaptor rather than a 24V AC adaptor. What was the part number in maplins?

 Fran


----------



## Daveze

Quote:


  Originally Posted by *BoilermakerFan* /img/forum/go_quote.gif 
_Congrats on getting your MAX alive and kicking!

 Did you have Jeff upgrade your DBs and caps to the Muse ES? 

 Also, let me know how the 240S's sound with the MAX. I'll be ordering Ultrasone HFI-780s from ALO and AKG K601s, but I'm also interested in the AKG K270Ss. The ALO modded Grado 225s are starting to whisper my name too, but I need to draw the line at the HFI-780s and K601s for now. I need to upgrade my IEMs for use with my Sony A816 DAP. My Denon C700s are great, but they offer little isolation, however, they have made the poor SQ of my Shure E2Gs obvious, so I need to upgrade. The Klipsch Images are on the short list for my next IEMs._

 

Thanks. Its the stock kit from Jeff, which has me a little undecided on whether to start afresh with a specifically boutique Max or just retrofit my current...with all the other projects going on I think the retrofit is the go.

 I really love my K240S, they have a fair few detractors but they're just a really nice pair of headphones and I reckon they'll pair fantastically with the Max.


----------



## ruZZ.il

Quote:


  Originally Posted by *fran* /img/forum/go_quote.gif 
_Fault151 --

 From your description of the plug it seems likely that you have a 24V *DC* adaptor rather than a 24V AC adaptor. What was the part number in maplins?

 Fran_

 


 It's just that the end bits are standard, and would work with a DC supply too. When coupled with a DC supply, the polarity indicators would actually have meaning. The AC supply that he has doesn't have the complimentary indicators cause, as amphead mentioned, it's meaningless with this supply. Whichever which way they're attached, it will be fine.


----------



## pinkfloyd4ever

Quote:


  Originally Posted by *cronic* /img/forum/go_quote.gif 
_Thats a good idea. I will try to pick some up and give it a spin._

 

8 TUBE DAMPERS 6BA6/5749/6AU6/6GK5/6FQ5 FITS MARANTZ 8b - eBay (item 320223105583 end time Mar-09-08 20:36:19 PDT)
 and no that's not me
 mcmaster.com has what I'm pretty sure are the same thing for $4.50 for a pack of 10. I'd give a link but it wont work, it's part number 9396K283

 or if you wanna go more expensive Herbie's Audio Lab: Tube Dampers you want the "7" size (no I don't work for them either)


----------



## fault151

Quote:


  Originally Posted by *ruZZ.il* /img/forum/go_quote.gif 
_It's just that the end bits are standard, and would work with a DC supply too. When coupled with a DC supply, the polarity indicators would actually have meaning. The AC supply that he has doesn't have the complimentary indicators cause, as amphead mentioned, it's meaningless with this supply. Whichever which way they're attached, it will be fine._

 

oh right thats ok then. I thought they must be generic plug ends that could e swapped with other similar power supplies, but i wanted to make sure first before i caused any damage. 

 Thanks for your replies!


----------



## fran

FWIW, 

 I've started to use a new volume pot in the last preamp I built and am very pleased with it. I haven't mentioned it here before but it seems logical to use it in a max. I hope to put one into mine pretty soon. Theres a long thread about this type of attenuation pot over on diyaudio - with all the usual claims etc etc etc. Link

 The pot is based on a pair of light dependant resistors to get the attenuation. Results to my ears (which aren't golden) are superb. Great clarity especially at the treble end, no dulling of the sound at all. If you follow the thread linked above you can easily make your own, or there is a kit available from a lad in Oz ska audio. He calls his kit optivol and I think its about AUS$27 for the kit - a bit more than an alps pot, but it is streets ahead of an alps. 

 The thing is a no-name pot with a pair of matched LDRs and the various other bits needed to make it work. As it comes its made to work off a 30V supply, but it will work off anything >5V, you just need to adjust a resistor for your supply voltage. Easy to put together and make it work. It draws about 13mA so I think would easily work off the max, just need to tap into the +27V supply.

 I have no connection with the thing (other than having bought 2 of them and am a happy customer), but hadn't seen it mentioned here and I think it would provide a great high quality solution for a really good volume pot at low cost.

 If anyone else already has one of these, I'd love to hear your comments.

 Fran


----------



## Alcaudon

Hi all,

 Finished my max a month ago. Sorry for the delay, I know you want to keep record of every new born max, but couldn't find time to take some pics.......... 
	

	
	
		
		

		
			





. Some pics:
















 All that I can say, it's that i can feel my melted brain flowing through my ears 
	

	
	
		
		

		
		
	


	




. Love the bass, as LCD soundsytem said: "Daft punk it's playing at my house".

 Thanks everyone for the incredible support in this thread, my building went smooth (actually scaringly smooth) but it's always nice to know that there's a legion of maxers ready to troubleshoot down anything (specially you tomb 
	

	
	
		
		

		
		
	


	




).

 BTW, I'm curious.... how's that tube DAC going? Should I start an Alien or wait for it? And wat about the mini max? cant wait to put my hands on one of these.


----------



## tomb

Wow - how about a belated, "Another MAX lives!"
	

	
	
		
		

		
		
	


	







 ?

 Great job!

 About your questions - Colin is busy and is working as we post, but that's about as much as I feel free to say for the time being.


----------



## amphead

Verrrry Cooool Alcaudon!! Another Max Lives!!   

 Viva Millett Max Team España! 

 Daft Punk really pumps through the Max.


----------



## BoilermakerFan

Quote:


  Originally Posted by *fran* /img/forum/go_quote.gif 
_FWIW, 

 I've started to use a new volume pot in the last preamp I built and am very pleased with it. I haven't mentioned it here before but it seems logical to use it in a max. I hope to put one into mine pretty soon. Theres a long thread about this type of attenuation pot over on diyaudio - with all the usual claims etc etc etc. Link

 The pot is based on a pair of light dependant resistors to get the attenuation. Results to my ears (which aren't golden) are superb. Great clarity especially at the treble end, no dulling of the sound at all. If you follow the thread linked above you can easily make your own, or there is a kit available from a lad in Oz ska audio. He calls his kit optivol and I think its about AUS$27 for the kit - a bit more than an alps pot, but it is streets ahead of an alps. 

 The thing is a no-name pot with a pair of matched LDRs and the various other bits needed to make it work. As it comes its made to work off a 30V supply, but it will work off anything >5V, you just need to adjust a resistor for your supply voltage. Easy to put together and make it work. It draws about 13mA so I think would easily work off the max, just need to tap into the +27V supply.

 I have no connection with the thing (other than having bought 2 of them and am a happy customer), but hadn't seen it mentioned here and I think it would provide a great high quality solution for a really good volume pot at low cost.

 If anyone else already has one of these, I'd love to hear your comments.

 Fran_

 

Looks interesting... Now I just need to find the time to read a 50 page thread and do more research! 
	

	
	
		
		

		
		
	


	




 I didn't see the kit on SKA though, do you have to email Greg and ask for it?


----------



## BoilermakerFan

Tom is aware of my intents with a couple of MAX amps, but I have a question for you guys.

 Below is a pic of a console that I'm retrofitting behind the faceplate. It's trashed enough that it's not worth the trouble trying to refurbish or restore it, but I like the look of it enough that I want to keep the front panel as intact as possible. So, I have the Tuning Eye tube location in the top center of the panel. What ways can I reallocate this? The tuner is mono and I can't see how to easily upgrade it to stereo and use it as an additional input. Could I setup a permanent tube bias comparison circuit? One that would make the tuning eye glow the brightest when both tube bias match the closest? This would be a visual indicator that the tubes have drifted from each other. I realize I could modify it to be a simple power on indicator, but I'm looking for more creative or useful uses since I can convert the FM dial backlight to be my power on indicator.

 Here's the pic:





 Thanks for your creative ideas in advance!

 - BMF


----------



## fran

Yes, just email greg and ask him for it. I'm nearly certain its AUS$27 incl postage anywhere in the world - paypal.

 I still think its a clear winner, but at that kind of money its worth taking a punt on it. I would like to hear what others think too.

 Fran


----------



## cronic

TomB, I got the 12ae6 tubes today and they are fantastic! Thanks for the great customer support. You are a true asset to the diy community. My k701 really came to life with the 12ae6 compared to the 12fk6. Just alot more impact for lack of a better term. 160 hours so far on the max and the 701s and boy am I loving it. Next up alien dac.........


----------



## tomb

Quote:


  Originally Posted by *cronic* /img/forum/go_quote.gif 
_TomB, I got the 12ae6 tubes today and they are fantastic! Thanks for the great customer support. You are a true asset to the diy community. My k701 really came to life with the 12ae6 compared to the 12fk6. Just alot more impact for lack of a better term. 160 hours so far on the max and the 701s and boy am I loving it. Next up alien dac........._

 

Glad to hear it!!

 BoilermakerFan,

 That's a great looking console. I can remember growing up and the Magnavox consoles were the best. I can't help you with the light, but I wonder if the FM tuner would be OK if you just doubled up on the mono connections. It might make for some nostalgic sound if the radio worked.

 Your idea sounds like a good one, though. Maybe some sort of analog circuit that would invert the voltage difference between the two tube biases - such that the lower the difference, the more voltage went to the light up to its maximum voltage at zero difference in tube biases. I don't know how to do it, though.


----------



## BoilermakerFan

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Glad to hear it!!

 BoilermakerFan,

 That's a great looking console. I can remember growing up and the Magnavox consoles were the best. I can't help you with the light, but I wonder if the FM tuner would be OK if you just doubled up on the mono connections. It might make for some nostalgic sound if the radio worked.

 Your idea sounds like a good one, though. Maybe some sort of analog circuit that would invert the voltage difference between the two tube biases - such that the lower the difference, the more voltage went to the light up to its maximum voltage at zero difference in tube biases. I don't know how to do it, though. 
	

	
	
		
		

		
		
	


	


_

 

Thanks. Best part is, it was free and it still has all it's tubes. I have four consoles in total, but this one is definitely in the best shape. It's a mono unit with (2) 12" full range woofers stacked on the left side behind the grill cloth. It had two blown tubes in the PSU, but I replaced them with two from the other units. It needs a new power cord so I haven't had a chance to turn it on and see what happens. Unfortunately, the turntable for it is trashed or I would use it as it is. 

 I looked briefly at the tuner and it looks like it has provisions to output stereo since there is a blank for a second RCA output jack. I'll have to remove the tuner and see what's actually missing from the circuit, but I also just thought about using a 2-to-1 splitter and just run the mono signal into both channels of the MAX pre-amp. I have to figure out what voltage is being fed to the tuner because the system is a little different. There are both rectifier and signal tubes on the PSU and the signal from the preamp with the tuner feeds back into the PSU signal tubes before the transformers for the speakers. I think everything is wired P2P too so I should be able to upgrade the switches on the front bezel without too much trouble. 

 All the transformers and rectifier tubes will be recycled later into a UL tube amp of some type, I just need to continue to do my research and keep learning, but I'm cutting my DIY audio teeth with the MAX (pre)amps.


----------



## Ampersand

hey guys,

 My MAX has been up and running for a week or so now and I'm loving it. However, I have a slight hum in the right channel only (really low frequency hum). When i move my hand near the tube itself, the hum intensifies. But when i put my hand completely on the case, any gournd point, or the CDplayer itself then the hum completely goes away. 

 Is this what happens when a tube becomes microphonic??

 Or is this a ground problem? (I have my signal ground connected to the case currently) 

 Thanks,
 mike


----------



## tomb

Quote:


  Originally Posted by *Ampersand* /img/forum/go_quote.gif 
_hey guys,

 My MAX has been up and running for a week or so now and I'm loving it. However, I have a slight hum in the right channel only (really low frequency hum). When i move my hand near the tube itself, the hum intensifies. But when i put my hand completely on the case, any gournd point, or the CDplayer itself then the hum completely goes away. 

 Is this what happens when a tube becomes microphonic??

 Or is this a ground problem? (I have my signal ground connected to the case currently) 

 Thanks,
 mike_

 

Microphonics respond to touch, not an EM field. It sounds like a ground problem to me, but it could be as simple as a bad tube - maybe a pin fixing to give way, etc. Other possibilities include not grounding the pot, or perhaps a less-than optimum solder joint on the signal ground somewhere.

 Try switching the tube with the other one and see if the problem follows the tube.


----------



## Ampersand

Strange,

 I finally put the lid on the case and the hum is greatly reduced now. Almost completely inaudible. 

 I'll try switching the right tube with the left one tomorrow. But I should note that this 'hum' doesn't exist with 12AE6 tubes, only the 12FM6 tubes. Not sure if that clears things up or just makes it more confusing....

 mike

 edit: the pot IS grounded, btw


----------



## tomb

Quote:


  Originally Posted by *Ampersand* /img/forum/go_quote.gif 
_Strange,

 I finally put the lid on the case and the hum is greatly reduced now. Almost completely inaudible. 

 I'll try switching the right tube with the left one tomorrow. But I should note that this 'hum' doesn't exist with 12AE6 tubes, only the 12FM6 tubes. Not sure if that clears things up or just makes it more confusing....

 mike

 edit: the pot IS grounded, btw_

 

Actually, that does clear it up. It sounds more like the tubes. The 12AE6 tubes have more gain. So, if the hum was somewhere else in the amp, it would be more prominent with those. However, since it only exists with the 12FM6 tubes, it would make sense if one those tubes were bad. It could still be something as simple as a dirty or bent pin. Or, the tube might simply be bad.


----------



## Solecs

Quote:


  Originally Posted by *Ampersand* /img/forum/go_quote.gif 
_Strange,

 I finally put the lid on the case and the hum is greatly reduced now. Almost completely inaudible. 

 I'll try switching the right tube with the left one tomorrow. But I should note that this 'hum' doesn't exist with 12AE6 tubes, only the 12FM6 tubes. Not sure if that clears things up or just makes it more confusing....

 mike

 edit: the pot IS grounded, btw_

 

I had the same problem, hum in one of the channels, and it turned out to be one of the tubes. I switched it out and the hum disappeared. It was a 12FK6 tube for the record. Also, I guess I'm another happy owner of a MilletMAX. I finished my Black Gate and VitaminQ (basically boutique build #1) MAX last week, a big thanks to everyone involved in the project. All of the provided info made the project very easy and fun.

 A few pics:











 I still need to do the top plate, but I'll need to wait until I'm home for the weekend since I don't have a good way of making a big enough hole for the tubes at the moment. As for sound, I think it sounds amazing 
	

	
	
		
		

		
		
	


	




. Although if previous experience is anything to go by, the sound is still changing and will get even better. Thanks again for making this project possible everybody!


----------



## tomb

Quote:


  Originally Posted by *Solecs* /img/forum/go_quote.gif 
_I had the same problem, hum in one of the channels, and it turned out to be one of the tubes. I switched it out and the hum disappeared. It was a 12FK6 tube for the record. Also, I guess I'm another happy owner of a MilletMAX. I finished my Black Gate and VitaminQ (basically boutique build #1) MAX last week, a big thanks to everyone involved in the project. All of the provided info made the project very easy and fun.

 A few pics:

 <IMG]http://members.cox.net/sounaken123/MillettMAX/MAX1.JPG[/IMG>

 <IMG]http://members.cox.net/sounaken123/MillettMAX/MAX2.JPG[/IMG>

 I still need to do the top plate, but I'll need to wait until I'm home for the weekend since I don't have a good way of making a big enough hole for the tubes at the moment. As for sound, I think it sounds amazing 
	

	
	
		
		

		
		
	


	




. Although if previous experience is anything to go by, the sound is still changing and will get even better. Thanks again for making this project possible everybody!_

 

Very nice! Another MAX lives!!
	

	
	
		
		

		
		
	


	







 Those BG's and VitQ's are the best!


----------



## Alcaudon

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Very nice! Another MAX lives!!
	

	
	
		
		

		
			







 Those BG's and VitQ's are the best!_

 

Really? I'm considering this combination (basically can't miss build #1) for my second MAx, but I'm a basshead (I can't help being a basshead 
	

	
	
		
		

		
		
	


	




) and I'm afraid this combination will sound too "cold" to my ears. How much does this combination vary sq from........ lets say one with muses, pios, and 2sc2238/2sa2968 transistors (the one I have 
	

	
	
		
		

		
		
	


	




)?


----------



## tomb

Quote:


  Originally Posted by *Alcaudon* /img/forum/go_quote.gif 
_Really? I'm considering this combination (basically can't miss build #1) for my second MAx, but I'm a basshead (I can't help being a basshead 
	

	
	
		
		

		
		
	


	




) and I'm afraid this combination will sound too "cold" to my ears. How much does this combination vary sq from........ lets say one with muses, pios, and 2sc2238/2sa2968 transistors (the one I have 
	

	
	
		
		

		
		
	


	




)?_

 

You have to give the BG's time to get clear highs and still longer to get full bass, but they will attain about 90% of the bass with ES's. However, the BG's are superior across the spectrum. I would hope so, at $12-$13 per cap.
	

	
	
		
		

		
		
	


	




 I love the ES's a lot and will continue to build MAXes with them - just used them recently in the MiniMAX I posted a ways back. However, the ES's are only $2 caps. Are the BG's enough better to equal the price difference? Probably not, but they _are_ better.

 The sound of any of the MAX combinations is still far from "cold". I don't know that I've ever built one that could be described that way. 
	

	
	
		
		

		
		
	


	




 More to the point, the ES's with 2SC3422/2SA1359 will have the most rocking slam. However, ES's with 2SC3421/2SA1358 will have the most bass extension - I'd put the 2SC2344/2SA1011 pair in that category, too. I know it's difficult to see the distinction, but take a look at a response graph for a Grado on Headroom. The bass has a rolloff at 50Hz and below, yet Grado's can give great punch and slam - there is no sensation of missing bass (at least on the better models). On the other hand, Senn's have much less of a rolloff, so you can actually hear those lower notes if they're there, but the sound will be much more refined than simple rock and slam. That's sort of the difference between the 2SC3422 pair and the other two pairs mentioned.

 That said, the BG/VitQ's and 2SC2238 or 2SC2344 pairs will produce the best, overall amp signature and will approach the sensation of a good, but _warm_, solid-state amp.

 However, don't take any of this too seriously, though, or you-know-who will come over here with his scope-ruler and slap my knuckles again. 
	

	
	
		
		

		
		
	


	




 EDIT: Sorry - I deleted some specific references. I'm getting MAXes and people mixed up. There's so many of them now!


----------



## Nebby

I just recently put some blackgates in my opus, how long would you say it takes for them to get clear highs/full bass?


----------



## tomb

Quote:


  Originally Posted by *Nebby* /img/forum/go_quote.gif 
_I just recently put some blackgates in my opus, how long would you say it takes for them to get clear highs/full bass?_

 

Sorry, I think there a couple devices called "Opus", and I don't know what BG's you used, or where in the circuit they may be.

 Generally speaking, BG NX's in the direct signal path take anywhere from 100hrs to 200 hrs of run-in, depending on size. Unfortunately, the sizes used in the MAX are quite large, relatively speaking, and they seem to take more like the 200hrs or more. Something like the 47uf BG-NX's used in an Alien DAC are probably where they need to be in a couple of days.

 If you are referring to the Opus DAC, perhaps the BG's are small and they won't take very long.

 Just my non-scientific impressions and experience.


----------



## fault151

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Very nice! Another MAX lives!!
	

	
	
		
		

		
		
	


	







 Those BG's and VitQ's are the best!_

 

Tomb on your website, do the vitQ's come in sets of 2 or separate? I'm going to order some for my max. Also do you sell the blackgates to with them? or will i have to get them off parts connex?

 Iv bought a second hand max which has the muse installed and I'm keen to see what the blackgates sound like with the vitQ's.


----------



## tomb

Quote:


  Originally Posted by *fault151* /img/forum/go_quote.gif 
_Tomb on your website, do the vitQ's come in sets of 2 or separate?_

 

AFAIK, the only things sold in pairs at beezar.com are the RCA jacks. 
	

	
	
		
		

		
		
	


	




  Quote:


 I'm going to order some for my max. Also do you sell the blackgates to with them? or will i have to get them off parts connex? 
 

Soniccraft.com is an absolutely reliable source as well. No, I don't sell them - the vendors are holding fast to the "No more Black Gates" storyline. I couldn't get them to sell on beezar even if I tried - which I did, once.
	

	
	
		
		

		
		
	


	




  Quote:


 Iv bought a second hand max which has the muse installed and I'm keen to see what the blackgates sound like with the vitQ's. 
 

Well, I would listen to it first before you went and spent over $50 on the Black Gates.* You may like it just fine. Black Gates are a tremendous investment. Given a choice, the amp should probably be built with those in mind, IMHO.


 * Four caps at approx. $12-$13 each.


----------



## Nebby

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Sorry, I think there a couple devices called "Opus", and I don't know what BG's you used, or where in the circuit they may be.

 Generally speaking, BG NX's in the direct signal path take anywhere from 100hrs to 200 hrs of run-in, depending on size. Unfortunately, the sizes used in the MAX are quite large, relatively speaking, and they seem to take more like the 200hrs or more. Something like the 47uf BG-NX's used in an Alien DAC are probably where they need to be in a couple of days.

 If you are referring to the Opus DAC, perhaps the BG's are small and they won't take very long.

 Just my non-scientific impressions and experience. 
	

	
	
		
		

		
		
	


	


_

 

I was indeed referring to the Opus DAC, which uses tiny 22uF caps 
	

	
	
		
		

		
		
	


	




 Thanks for the info, I was mainly looking for a time range, as running a search came up with plenty of cap debates, but no useful info. Sorry for going OT!


----------



## fault151

yeh i will try it out, but i also can't resist listening to the other option after hearing so many good comments on it. I too like bass so i hope they both sound as good in that department. 

 heres the inside of the millet i have. Do i need to remove/ do anything else to its current state if i decide to fit the blackgates and vitQ's?


----------



## tomb

Wow, that's a great looking build. If you don't mind my asking, who was the builder (Head-Fi username)?

 If you are bound and determined, all you need do is remove the four big green capacitors and replace them with the proper BG-NX's. 1000uf 25V go in the rear and 680uf 35V go in the front. The ratings are slightly different because the BG-NX's don't follow standard sizes all the way through.

 The dark green cylinders next to the light green cans in front are the Russian K-42's. You'd take those out and put in the Vitamin Q's. Refer to the MAX website at Tweaks -> VitaminQ PIO Capacitors for details on how to install the Vitamin Q's.

 There is again an issue I should warn you and everyone else about. When considering removing the large electrolytic capacitors, terminal blocks, and a few other items, you need to be careful. The only contact with the ground plane for those parts are through the hole plating. Since the caps/terminal blocks completely cover the pads on top, the only way to get the connection is from the solder joint on bottom and through the hole plating.

 Sometimes (at least for me, anyway), you may end up removing the hole plating when you desolder a part. You can see this on the leads of the removed part. It happens on larger parts like this because you often have to melt then push/pull on one lead, then melt and push/pull on the other lead. During this process, it can be easy to rip out the hole plating while you're trying to remove the part. So be careful. If you suspect this has happened, then your new cap may not be contacting ground and will be out of the circuit. You may need to solder a jumper to another good ground pad on the bottom of the board.


----------



## fault151

Well i bought it of Jimmy John. But im not sure whether he made it or bought it of another user? 

 I will listen to the amp as it is to see what it sounds like first. The amp does look nice, i can't wait to get it. Its somewhere amongst customs at the mo. :0(


----------



## tomb

I'm guessing it was el Matto's.


----------



## fault151

Im after a slightly more impressive box to go with it once it arrives. I wouldn't mind getting something a bit more customised.


----------



## BoilermakerFan

Quote:


  Originally Posted by *fault151* /img/forum/go_quote.gif 
_Well i bought it of Jimmy John. But im not sure whether he made it or bought it of another user? 

 I will listen to the amp as it is to see what it sounds like first. The amp does look nice, i can't wait to get it. Its somewhere amongst customs at the mo. :0(_

 


 fault, I think I would leave it alone and put the money towards a second one that you could build yourself... 

 My guess is that that MAX has the 3422/1359 DBs BJTs with the Muse ES/K42 caps. That is the same setup as the first MAX I'm going to build. To take the full advantage of the BGs and VitQs you'd probably want to change out the DB transistors to the 2SC2238/2SA968 BJTs. That's a lot of rework on an already great build, IMHO. I think you'll be very happy with the MAX you are receiving paired with your Senns. Heck, I think I would put the $100 (after freight to the UK) towards a cable upgrade for your headphones first. Again, just MHO...


----------



## fault151

yeh, i suppose it makes more sense to build another, rather than mess with an existing design. Plus it would be more fun. 

 I bought the sennheiser hd650 cable so far for my h600's. Im not sure if id spend much more on something like the cardas cable.


----------



## BoilermakerFan

Quote:


  Originally Posted by *fault151* /img/forum/go_quote.gif 
_yeh, i suppose it makes more sense to build another, rather than mess with an existing design. Plus it would be more fun. 

 I bought the sennheiser hd650 cable so far for my h600's. Im not sure if id spend much more on something like the cardas cable._

 

So the ALO Vampire cable is out of the running?
http://aloaudio.com/store/catalog/pr...roducts_id=213






 At least you would get to take advantage of the weak US dollar...


----------



## fault151

would that really make much difference over my 650 cable?


----------



## BoilermakerFan

Quote:


  Originally Posted by *fault151* /img/forum/go_quote.gif 
_would that really make much difference over my 650 cable?_

 

To keep the thread on topic, I sent you a PM...


----------



## fault151

yeh no problem, i just got it thanks.


----------



## joneeboi

I am happy to report that my MAX has returned to head-exploding levels of bass. I have the Silmic IIs bypassed with K42s right now, and I feel that this config brings me closer to my recordings than I have ever heard. I should like to try the BG NXs some time, but at this point, I'm really enjoying the MAX. The bass is way overloaded, just the way I like it for its niche in my audio rig. It brings a level of clarity to the highs that I haven't often heard, and is now actually competing with my PIMETA for my attention and affection. It's almost as if I can hear the limitations of my 320kbps LAME CBR MP3, but I may just be imagining that. I'm working on the whole 'converting library to FLAC' thing, so you can put down your torches and pitchforks. 
	

	
	
		
		

		
			





 I guess what I'm saying is, "diyMod with MAX with 12FK6, Silmic IIs/K42s,RB14 jumpers through my SR60s are grade A awesome to my ears."


----------



## tomb

Glad to hear that you found the combination you like.


----------



## amphead

Quote:


 I'm working on the whole 'converting library to FLAC' thing, so you can put down your torches and pitchforks. I guess what I'm saying is, "diyMod with MAX with 12FK6, Silmic IIs..... 
 

I like the Silmic IIs as cathode bypass with my Vitamin Qs. LOL torches and pitchforks.


----------



## pabbi1

Quote:


  Originally Posted by *amphead* /img/forum/go_quote.gif 
_I like the Silmic IIs as cathode bypass with my Vitamin Qs. LOL torches and pitchforks. _

 

Me two...


----------



## amphead

Yeah, that was one of the benefits I received from your amp fix Pabbi! I would not have tried it, until listening to both of your amps convinced me. I have one weird output cap setup. Cerfines bypassed with 16v BGs. I liked the sound so much, that I stopped rolling caps. Good to hear from you!  Edit: I talked to Wmcmanus at the Fairfax show.


----------



## John Wilson

Hey all. Starting my second built soon...waiting on some parts. Went a little crazy this time. For resitors I'm going to use all Mills, Caddock and Vishay. Also went with the BG FK's for the tubes. And 3422/1358. JW


----------



## tomb

Quote:


  Originally Posted by *John Wilson* /img/forum/go_quote.gif 
_Hey all. Starting my second built soon...waiting on some parts. Went a little crazy this time. For resitors I'm going to use all Mills, Caddock and Vishay. Also went with the BG FK's for the tubes. And 3422/1358. JW_

 

Sounds good, but I hope you mean 3422/135*9*.


----------



## John Wilson

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Sounds good, but I hope you mean 3422/135*9*.
	

	
	
		
		

		
		
	


	


_

 

Ops...number 9. Yes. JW


----------



## tomb

Quote:


  Originally Posted by *John Wilson* /img/forum/go_quote.gif 
_Ops...number 9. Yes. JW_

 

Just kidding you - I'm sure you had the right ones. 
	

	
	
		
		

		
		
	


	




 BTW, please let us know how the BG FK's compare to the NX's. I've read very contradictory opinions on that.


----------



## Ampersand

Quote:


  Originally Posted by *Ampersand* /img/forum/go_quote.gif 
_Strange,

 I finally put the lid on the case and the hum is greatly reduced now. Almost completely inaudible. 

 I'll try switching the right tube with the left one tomorrow. But I should note that this 'hum' doesn't exist with 12AE6 tubes, only the 12FM6 tubes. Not sure if that clears things up or just makes it more confusing....

 mike

 edit: the pot IS grounded, btw_

 


 Finally got around to opening the case and switching the tubes. Now the hum is in the other channel, so i think we can conclude its a bad tube.

 Thanks again for all your help. I'm awaiting new tubes - hopefully they'll arrive tomorrow.

 On a side note, I'm not bypassing the output BG's with anything. Has anyone else NOT bypassed their BG's (CA7L/R)? My thought was that i didn't want to introduce any phase issues with the addition of a bypass cap. Am I wrong with this logic? Also, I don't have any vitamin Q's laying around, but i do have some Auricaps. Has anyone tried Auricaps with BG's? 

 Thanks,
 mike


----------



## tomb

Quote:


  Originally Posted by *Ampersand* /img/forum/go_quote.gif 
_Finally got around to opening the case and switching the tubes. Now the hum is in the other channel, so i think we can conclude its a bad tube.

 Thanks again for all your help. I'm awaiting new tubes - hopefully they'll arrive tomorrow.

 On a side note, I'm not bypassing the output BG's with anything. Has anyone else NOT bypassed their BG's (CA7L/R)? My thought was that i didn't want to introduce any phase issues with the addition of a bypass cap. Am I wrong with this logic? Also, I don't have any vitamin Q's laying around, but i do have some Auricaps. Has anyone tried Auricaps with BG's? 

 Thanks,
 mike_

 

Phase issue problems with bypassing assume that the two caps act independently of one another. There's a school of thought that says a bypassed cap acts as a single device. Personally, I don't think results are consistent enough to make a conclusion one way or another.

 As for trying the BG's without bypassing - yes, I've done that. It was better with bypassing - but only with the right cap. Some bypass caps on a BG seem to have no effect at all, others sound worse. That's one reason I came up with the "Can't Miss MAX Builds" - to try to document known-good combinations. 

 Most likely, there will be better choices on the MAX than Auricaps, IMHO. Because of the highly-detailed solid-state output buffers, the MAX needs neutral or flat caps, probably not ones with a midrange bloom and rolled off highs and lows. The VitQ's, polystyrene such as Multicap RTX's (recommended for BG's by Soniccraft), Black Gate 0.47uf NX's, or other such flat-frequency-response caps are good candidates.

 Without a doubt, the easiest thing to install for bypasses on Black Gates are the 0.47uf BG NX's. I don't know if they're better than VitQ's, but it's possible. By all means, though, experiment if you can and let us know what you find.


----------



## Ampersand

Thanks, I guess i'll eventually get around to bypassing them. I'm only the Vit Q's away from 'Can't Miss Build #1', but i was looking to try something different. Maybe i'll give the RTX's a try.

 edit: Since my BG's are 680uF, should I bypass them with .68uF instead of the .47uF ?


----------



## pinkfloyd4ever

I've got .47ufs with my BGs (also 680uf, since 35v 470uf BG NXs don't exist) as I think alot of people do. If you can find any .68uf VitQ's I doubt it would hurt, but you can probably find .68 in another cap if you're looking for something else. If you do try something else, I'd at least give the VitQs a shot also...man I think I'm gonna get a couple rotary switches to compare all these output bypass caps


----------



## tomb

Quote:


  Originally Posted by *Ampersand* /img/forum/go_quote.gif 
_Thanks, I guess i'll eventually get around to bypassing them. I'm only the Vit Q's away from 'Can't Miss Build #1', but i was looking to try something different. Maybe i'll give the RTX's a try.

 edit: Since my BG's are 680uF, should I bypass them with .68uF instead of the .47uF ?_

 

Nope - I just use the 0.22uf VitQ's. If you're talking about the 0.47uf BG's, those are a special size that also have a "HiQ" rating. There's nothing else close that also has that rating. So, if using another Black Gate to bypass a Black Gate, the 0.47uf 50V NX HiQ is optimum.


----------



## Ampersand

Well, i was actually considering the RTX's, which come in both .47uF and .68uF. I was just wondering since the BG's I have are 680uF if its 'optimal' to be some factor of that such as the .68uF value.


----------



## pinkfloyd4ever

no it's not really like that, probably anything from .22 up to 1.0 should work


----------



## xnothingpoetic

Hello all,

 I am in the process of upgrading the parts in my MAX. I was going to put in the VitQ's, 2SC2238/2SA968, Wimas and eventually BG's 

 It seems to original builder put 100uf caps in ca4 & ca5, which if I read correctly, is not recommended- 1000uf min there. 

 Question: which MUSE caps should I put there? (temporary until BG) 
 I thought I read many using FG but don't recall seeing it often in builds.. 

 This is the board (i've dusted since pic)




 Using this amp with my D2000's, so I am not looking to make the bass much more punchy. Actually it is pretty weak in the bass punch department now, and I figure that is due to the 100uf's and some of the caps used?


----------



## John Wilson

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Just kidding you - I'm sure you had the right ones. 
	

	
	
		
		

		
		
	


	




 BTW, please let us know how the BG FK's compare to the NX's. I've read very contradictory opinions on that._

 

On this one I' m going to by pass the FK's with the .1 or .47 NX. JW


----------



## tomb

Yep - CA4L/R and CA5L/R should be 1000uf minimum. However, any good quality, low-ESR/high ripple power capacitor is all that's needed - Panasonic FM's (good choice), FC's, or Nichicon UPW's, UHE's. Of course, you can also put boutique electrolytics there, too - Muse ES, KZ or FG, Elna RFS Silmic or Cerafine, or even Std Black Gates. However, anything more than a good power cap is probably money spent better elsewhere.


----------



## John Wilson

For what it's worth...I picked up a bottle of " Rail-Zap" today. It's a cleaner and electrical enhancer. Try it on your NOS tube pins. You will hear a difference. And the tube pins glide in and out of the sockets. Only about 5 bucks. JW


----------



## tomb

Quote:


  Originally Posted by *John Wilson* /img/forum/go_quote.gif 
_On this one I' m going to by pass the FK's with the .1 or .47 NX. JW_

 

Yes, well it's the FK's period, that I'm curious about. There are some statements over on the Alien DAC forum that don't follow Black Gate's (Jelmax?) own recommendations. BG has always recommend NX's as their best choice audio capacitor. There are some scaling effects going on with the caps in the Alien - evidence Dsavitsk's recommendation of bypassing ES's with Sonicap GEN II's: it works great in the Alien. However, that combo did not translate very well to the cap sizes in the MAX. The Sonicap GEN II's bypassing Muse ES's resulted in a skewed frequency response with deficient bass - and that's just using them in the front positions.

 So, I guess what I'm saying is that even though someone suggests the FK's are good in the Alien, doesn't mean they will be in the MAX - instead of BG NX's, especially. However, if you're willing to experiment ... perhaps the results will benefit all of us. 
	

	
	
		
		

		
		
	


	








 EDIT: Good tip on the Rail Zip. I still have a bottle lying around somewhere - used it mostly for cranky 1/8 jacks on portable FM Walkmans and such. I gave up my railroad layout a number of years ago.


----------



## John Wilson

The FK's are for the tubes. Suggestions are a very good starting point...I just like to experiment. So far so good on my first one. It's also time for some new headphones. JW


----------



## pinkfloyd4ever

nothingpoetic, I'd also suggest replacing your RB14s with jumpers or low valued (10-22 ohm) KOA Speer carbon film resistors, Rikens, or some other boutique resistor. And if you do get the 2SC2238/2SA968 set, remember that they go on the opposite side of the heatsinks as the ones you have in there now


----------



## cronic

Well, I made some more progress on my max yesterday. I got the top cut out and the front milled on a cnc router. I still have to polish the edges of the top, maybe this weekend.... Then I can start on the dac-1, which will be an alien dac and a darwin selector in the same type of enclosure as the max, so the max can stack on top.


----------



## John Wilson

Quote:


  Originally Posted by *cronic* /img/forum/go_quote.gif 
_Well, I made some more progress on my first max yesterday. I got the top cut out and the front etched on a cnc router. I still have to polish the edges of the top, maybe this weekend.... Then I can start on the dac-1, which will be an alien dac and a darwin selector in the same type of enclosure as the max, so the max can sit on top. 



_

 

Nice!!! And how do the 701's sound? I'm thinking of buying them. But not sure yet. JW


----------



## cronic

John, I have really enjoyed the 701s so far. They will not blow you away with bass, but they do have plenty for me. I would defiantly recommend them them if you want an accurate sound.


----------



## tomb

Wow, Cronic!

 You guys are something else. The level of craftsmanship that's been displayed lately for the Millett MAX is just tremendous.


----------



## BoilermakerFan

I just received a shipping notice from Mouser. My (2) MPSA-214 transistors shipped via FedEx. They spent $6.64 to send my $0.30 in back-ordered parts. Crazy! 

 My soldering station is scheduled to arrive Monday too, so I get to start building next weekend after I run by my local electronics store and pick up a 1/4lb spool of Kester "44" solder. Last bits I need is a illuminated magnifier and a set of X-Acto X-tra hands since a buddy is letting me borrow one of their PCB vices from his work.


----------



## ruZZ.il

ooh the FUN bit 
	

	
	
		
		

		
			





 Enjoy the build, take it easy and keep us up to date!


----------



## BoilermakerFan

Quote:


  Originally Posted by *ruZZ.il* /img/forum/go_quote.gif 
_ooh the FUN bit 
	

	
	
		
		

		
		
	


	




 Enjoy the build, take it easy and keep us up to date!_

 

Thanks. I will, I'm actually planning to go down to the dungeon and sort all my bits. Everything from Mouser and Digi-Key is referenced to the correct parts on the MAX, but I order anywhere from 2-4 extra pieces and I need to take inventory of what I have and what I need for 3 more builds. Two will be built in short order, the other two will be build later. 

 Unfortunately, I don't really have a good workstation or workbench at the moment, so I need to decide how to resolve that issue or wait till it stays warm enough at night to work in the garage since I think my wife may complain about the fumes if I try to solder in the basement without a vent hood. Of course I will try to solder in the basement at our craft table, I just think I will be allowed to continue to solder there after the first night! 
	

	
	
		
		

		
		
	


	




 QUESTION: What is the generally recommended tip size and style for a newbie to use on their iron for a MAX build? I have .8mm, 1.6mm, and 3.2mm screwdriver-style chisel tips as well as 1mm, 2mm, and 3mm, chamfered round tips (as well as a couple others that I can remember) coming with my iron. 

 - BMF


----------



## BoilermakerFan

One more question:

 Is there a cap that falls somewhere between the cost of the Muse ES or Muse KZ and the Black Gates? One that the general MAX builder consensus favors?


----------



## rockcod

Quote:


  Originally Posted by *BoilermakerFan* /img/forum/go_quote.gif 
_One more question:

 Is there a cap that falls somewhere between the cost of the Muse ES or Muse KZ and the Black Gates? One that the general MAX builder consensus favors?_

 

Elna Cerafine & Silmic II would fit your bill


----------



## slowpogo

Quote:


  Originally Posted by *rockcod* /img/forum/go_quote.gif 
_Silmic II would fit your bill_

 

Well, Silmics are also cheap, cheaper than the Muse KZ. And Cerafines are basically the same cost as KZ, pennies difference.

 I think the question is, is there something significantly better than the Nichicons that doesn't cost $12 a pop like the Black Gates, even if it's not quite as good as those? As far as I know, the answer is no.

 The Black Gates are definitely better than Nichicon/Elna. But they are not really "10x better" as their price might suggest. Still, I'm glad I put them in my Max. I've only done one build so I can't compare them to anything else, but I do know that my amp sounds wonderful.


----------



## slowpogo

I'm having a ground buzz problem. Until recently my Max was just a populated board, no case. The amp buzzed when I touched the knob, and there was a slight, much quieter buzz when I wasn't touching it.

 I grounded the pot between a screw and the pad on the circuit board. The buzz when *not* touching the knob all but disappeared, but it still buzzed upon touch.

 I just got my front panel from FP Express, and put the board in the Hammond case and mounted the front panel. So now input ground is grounded to the entire case. There is now no buzz when I'm not touching anything, it's absolutely silent and pure. However, it STILL buzzes when I touch the volume knob. There is still no top or back panel attached.

 The amp sounds great otherwise. How do I get this buzz to go away?


----------



## tomb

Quote:


  Originally Posted by *slowpogo* /img/forum/go_quote.gif 
_I'm having a ground buzz problem. Until recently my Max was just a populated board, no case. The amp buzzed when I touched the knob, and there was a slight, much quieter buzz when I wasn't touching it.

 I grounded the pot between a screw and the pad on the circuit board. The buzz when *not* touching the knob all but disappeared, but it still buzzed upon touch.

 I just got my front panel from FP Express, and put the board in the Hammond case and mounted the front panel. So now input ground is grounded to the entire case. There is now no buzz when I'm not touching anything, it's absolutely silent and pure. However, it STILL buzzes when I touch the volume knob. There is still no top or back panel attached.

 The amp sounds great otherwise. How do I get this buzz to go away?_

 

This could be a tricky situation to solve completely {i.e., grounding issues}.

 It's been my experience that buzzes _without_ touching the knob are caused by problems with the signal ground. Either the RCA Jacks are not really contacting the case, or the signal ground is not really contacting (or contacting intermittently) the ground plane on the board.

 On the other hand, if you are getting a buzz _with_ contacting the pot, I'd have to guess that the pot is still not making good contact with the ground plane. Or, there could be an issue with the tubes. The pot is connected directly to the input of the tubes. If the tube is not quite right, or the contact is not optimum through its pins to the ground pins and the pot traces, then you might see this scenario. It's somewhat similar to hearing scratches or static when you turn the pot: everything may appear to be connected, but there's something either internally or externally going on with how the tube is connected to the circuit.

 If the buzz is confined to only one channel, I'd suspect that channel's tube. Switch it with the other one and see if that changes things. If not, then it may still be the ground connection to the pot.

 I've mentioned this before, but Colin has configured the MAX with very heavy traces on the bottom of the board. That's a superior way (IMHO) to run the signal circuit, but one very slight disadvantage is that the ground plane is only on one side of the board. So, ground connections that are soldered underneath depend on the through-hole plating, or on wicking to the top surface of the board. That's normally not an issue, unless you've unsoldered and re-soldered to the point that the ground plating got ripped out. Or, in the case of an insulated lead, it might be possible that the insulation was pushed into the hole, with only the tip of the wire making contact with the soldered pad underneath.

 You might try re-flowing the solder on that ground wire lead or checking the screw to make sure it's screwed in securely and is making contact with the tip of the wire where the insulation is removed. Regardless, it sounds like the pot maybe finding a more convenient path to ground through your fingers than it is to the board. Hopefully, one of those scenarios I've described will help you pinpoint the problem.


----------



## xnothingpoetic

Would I be correct that the CR1's need to be 1000uf?

 While looking at my MAX to see what needs to be upgraded, I noticed my CR1 caps are 470uf. Since I'm replacing CA4/CA5 to 1000uf, I want to know if I should order for CR1(x4) too?


  Quote:


  Originally Posted by *pinkfloyd4ever* /img/forum/go_quote.gif 
_nothingpoetic, I'd also suggest replacing your RB14s with jumpers or low valued (10-22 ohm) KOA Speer carbon film resistors, Rikens, or some other boutique resistor. And if you do get the 2SC2238/2SA968 set, remember that they go on the opposite side of the heatsinks as the ones you have in there now_

 

Thanks for the tip. I believe I have some Kiwames laying around.


----------



## tomb

Quote:


  Originally Posted by *xnothingpoetic* /img/forum/go_quote.gif 
_Would I be correct that the CR1's need to be 1000uf?

 While looking at my MAX to see what needs to be upgraded, I noticed my CR1 caps are 470uf. Since I'm replacing CA4/CA5 to 1000uf, I want to know if I should order for CR1(x4) too?_

 

Yep. The CR1's have always been 1000uf 50V, since the days of the earliest prototype. CA4 and CA5 were upsized later in the process.


 On a different note, some of you guys have been asking what may be used to get the ES's to sound more like Black Gates. Here's a short list that can get them close:

*1. 12FK6 tubes.*
*2. Jumpers only on RB14L/R.* 
*3. Vitamin Q's for CA8L/R.* 

 1. We've talked a long time about tubes and the fact that the 12FK6 is the most airy and detailed. Depending on your particular setup, you may take a very slight hit in bass and punchiness. This will become more pronounced with high-impedance headphones, but will probably go un-noticed in low impedance headphones. Generally speaking, high-impedance headphones should probably use the 12AE6's, but the MAX is very forgiving in this instance. There are some differences in tubes within types, where some have a better high-frequency response vs. bass. Due to the rampant sub-contracting in their manufacture, however, this is very difficult to predict. As with any tube amp, you should probably get several tubes and try them out until you find a pair to your liking.

 2. You will have to take the hit on these if you don't like adjusting the volume in the 1st-third of the pot's rotation. There's no doubt that jumpers only will pass every bit of detail. They may pass some bad things, too, but I think the belief in audible tube noise is probably over-rated.

 3. The K42's are similar to ES's in that they are the punch and slam kings. However, their upper response may not be quite as smooth as a VitQ. If you already have more than enough slam and feel that you can trade a bit for more detail, then perhaps the VitQ's will work for you paired with ES's. Certainly, the VitQ's take nothing away from bass. On the contrary, it's their neutrality that's so impressive.

 Besides the 0.22uf's already at Beezar, smaller 0.18uf's will soon be available. These are almost identical, except for being a full 1/4" shorter. I've been testing these with ES's of late, and combined with the other two items, it can bring them close to Black Gate sound. (It can also make KSC75's sound like raw Grados, too - so be careful with this strategy. 
	

	
	
		
		

		
		
	


	




 ) As an added advantage, break-in on the VitQ's and ES's seems to occur at somewhere around 4-8 hrs _instead of 4-8 weeks_.

 Note that numbers "2" and "3" assume that you've already selected which tube you prefer.


----------



## BoilermakerFan

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Yep. The CR1's have always been 1000uf 50V, since the days of the earliest prototype. CA4 and CA5 were upsized later in the process.


 On a different note, some of you guys have been asking what may be used to get the ES's to sound more like Black Gates. Here's a short list that can get them close:

*1. 12FK6 tubes.*
*2. Jumpers only on RB14L/R.* 
*3. Vitamin Q's for CA8L/R.* 

 1. We've talked a long time about tubes and the fact that the 12FK6 is the most airy and detailed. Depending on your particular setup, you may take a very slight hit in bass and punchiness. This will become more pronounced with high-impedance headphones, but will probably go un-noticed in low impedance headphones. Generally speaking, high-impedance headphones should probably use the 12AE6's, but the MAX is very forgiving in this instance. There are some differences in tubes within types, where some have a better high-frequency response vs. bass. Due to the rampant sub-contracting in their manufacture, however, this is very difficult to predict. As with any tube amp, you should probably get several tubes and try them out until you find a pair to your liking.

 2. You will have to take the hit on these if you don't like adjusting the volume in the 1st-third of the pot's rotation. There's no doubt that jumpers only will pass every bit of detail. They may pass some bad things, too, but I think the belief in audible tube noise is probably over-rated.

 3. The K42's are similar to ES's in that they are the punch and slam kings. However, their upper response may not be quite as smooth as a VitQ. If you already have more than enough slam and feel that you can trade a bit for more detail, then perhaps the VitQ's will work for you paired with ES's. Certainly, the VitQ's take nothing away from bass. On the contrary, it's their neutrality that's so impressive.

 Besides the 0.22uf's already at Beezar, smaller 0.18uf's will soon be available. These are almost identical, except for being a full 1/4" shorter. I've been testing these with ES's of late, and combined with the other two items, it can bring them close to Black Gate sound. (It can also make KSC75's sound like raw Grados, too - so be careful with this strategy. 
	

	
	
		
		

		
		
	


	




 ) As an added advantage, break-in on the VitQ's and ES's seems to occur at somewhere around 4-8 hrs instead of 4-8 weeks.

 Note that numbers "2" and "3" assume that you've already selected which tube you prefer.
	

	
	
		
		

		
		
	


	


_

 

Tom

 I'm assuming those 3 items are to be combined with the 2SC2238/2SA968 BJT DBs, or would the 2344/1011 be a better choice?


----------



## tomb

Quote:


  Originally Posted by *BoilermakerFan* /img/forum/go_quote.gif 
_Tom

 I'm assuming those 3 items are to be combined with the 2SC2238/2SA968 BJT DBs, or would the 2344/1011 be a better choice?_

 

Neither, they are independent of your transistor choice.

 Actually, all the transistor selections have great detail. It just depends on where the focus is: rockin' slam (3422/1359), bass and highs extension (3421/1358), outstanding neutrality(2238/968), or outstanding neutrality with a slight emphasis in highs (2344/1011).


----------



## BoilermakerFan

I've been putting together my planned BOMs for my first three MAX Pre-amp builds, so I'm about to place an order with Beezer and do some damage to their RCA jack supply! 
	

	
	
		
		

		
		
	


	




 I already have the Muse ES/K42 caps to pair with the 3422/1359 DBs. My second build will be Silmic II/VitQ with 2238/968. The third will be Muse KZ/VitQ with the 2344/1011 DBs. I have a second spare set of Muse ES caps so if either the second or third build doesn't meet my listening preferences, the caps will be swapped out. I'm also going to order a second set of VitQs for thefirst build if I decide I want to open up the highs more. I need to thank Tom for his email discussions of the cap/DB combo discussions that help bring me to these decisions. 

 Why no Black Gates? Because I won't be using any of the units on a daily basis, so the burn in time and short memory when their not used daily actually turned me away from them. If I can get even 80% of the sound without the long burn in and not have to worry about losing the burn in over time, then that sealed the deal for me.

 In order to switch input sources I'm assuming I need a 4 pole selector switch, correct? Or is it an 8pole?


----------



## John Wilson

I spent $140.00 on resistors for MAX number two built. JW


----------



## BoilermakerFan

Quote:


  Originally Posted by *John Wilson* /img/forum/go_quote.gif 
_I spent $140.00 on resistors for MAX number two built. JW_

 

IMO, that depends on your source and your headphones...

 My sources are all over the board, from the highly compressed signal of XM radio to my Pro-Ject 1.2 turntable with Grado Gold cartridge, so I'd have a hard time justifying uber-high-end resistors and BGs for any of my builds (until I order an OPPO 981 and build Colin's Tube DAC), but I can easily justify a $30 or $40 upgrade to the overall amp on caps and resistors. I actually enjoy the challenge of finding the absolute best bang for the buck for my personal tastes. This applies to everything I buy, not just audio bits for DIY. 

 My first set of headphones will be ALO-780 with Vampire wire, then a set of AKG K601s or maybe, maybe Senn HD650s since I can cash in airline miles for gift cards to Crutchfield. Then I can buy a Senn cable upgrade from ALO.


----------



## John Wilson

Quote:


  Originally Posted by *BoilermakerFan* /img/forum/go_quote.gif 
_ so I'd have a hard time justifying uber-high-end resistors and BGs for any of my builds (until I order an OPPO 981 and build Colin's Tube DAC ._

 

Ah HA! JW


----------



## BoilermakerFan

Quote:


  Originally Posted by *John Wilson* /img/forum/go_quote.gif 
_Ah HA! JW_

 

LOL! I still won't use any BGs because we wouldn't listen to any single console often enough to keep them burned in. The extra $50 can be put to better upgrades in the system.


----------



## pinkfloyd4ever

Quote:


  Originally Posted by *John Wilson* /img/forum/go_quote.gif 
_I spent $140.00 on resistors for MAX number two built. JW_

 

yes you probably are crazy....or maybe just overly sane
	

	
	
		
		

		
			





 What kind of resistors?


----------



## John Wilson

Quote:


  Originally Posted by *pinkfloyd4ever* /img/forum/go_quote.gif 
_yes you probably are crazy....or maybe just overly sane
	

	
	
		
		

		
		
	


	




 What kind of resistors?_

 

Mills, Caddock, Vishay and still have some 5 PPM Dales. I've always experimented with resistors caps and diodes. Good diodes can change the sound. Built #2 I'm going with soft recover diodes. And beef up the power supply caps. No output resistors this time. JW


----------



## tomb

Well, going without the output resistors is a good option for more detail, but I'm not sure about beefing up the power caps. The Mini uses only two 1000uf, 50V caps as opposed to the regular MAX's four. Can't say that I notice any difference at all - at least audibly, anyway.


----------



## soloz2

well it seems one of the tube LEDs is bad (doesn't light) on the Max I'm building now... thing is the amp is complete. Anyone have any good ideas for getting it out? my Tweezers aren't quite small enough to reach in and pull it out. 
	

	
	
		
		

		
		
	


	





 well looking more at the build the LED is seeing the full 27v across it so that's the problem. Swapping rled should fix this... will I still need to replace the LED or should it still work?


----------



## tomb

Quote:


  Originally Posted by *soloz2* /img/forum/go_quote.gif 
_well it seems one of the tube LEDs is bad (doesn't light) on the Max I'm building now... thing is the amp is complete. Anyone have any good ideas for getting it out? my Tweezers aren't quite small enough to reach in and pull it out. 
	

	
	
		
		

		
		
	


	





 well looking more at the build the LED is seeing the full 27v across it so that's the problem. Swapping rled should fix this... will I still need to replace the LED or should it still work?_

 

I'd guess that if it saw a full 27V, it's toast, but you never know. Be sure you use a 2K resistor - that cuts down on the current a bit and lets you get away with a 1/2W resistor.

 About removing the LED's under the tube sockets - I always use a spent lead held with a pair of needlenose pliers while heating the solder pad with the board turned upside down. Use the spent lead to push into the hole when you melt the solder and it will push out the LED from the bottom. (You have to do the second hole before it will drop out, of course.) Be sure you poke the lead far enough through the hole. If you don't push far enough, you can get the part's lead stuck to the very top of the pad on the top side of the board. That may make it difficult inside the tube socket. You may also get the spent lead stuck in the hole from time-to-time, but it's easy enough to heat it up and pull it out.

 When you're trying to remove the part, don't apply heat to the spent lead while you're holding it in the pliers - just apply heat to the soldered pad. If the pliers are holding the lead, it will act as a giant heat sink and prevent you from heating things up.


----------



## John Wilson

In CA3 and CA6 is a 0.01 or 0.033 ok to use? JW


----------



## tomb

Quote:


  Originally Posted by *John Wilson* /img/forum/go_quote.gif 
_In CA3 and CA6 is a 0.01 or 0.033 ok to use? JW_

 

Film cap bypassing is not an exact science. However, both of the sizes you mention are a full magnitude smaller than the recommended 0.22uf. CA3L/R and CA6L/R are all supposed to be the same size, too. So, no - I can't recommend it.


----------



## John Wilson

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Film cap bypassing is not an exact science. However, both of the sizes you mention are a full magnitude smaller than the recommended 0.22uf. CA3L/R and CA6L/R are all supposed to be the same size, too. So, no - I can't recommend it._

 

For a lack of better words how do you think 4- 0.01 uf caps would act? JW


----------



## BoilermakerFan

Quote:


  Originally Posted by *John Wilson* /img/forum/go_quote.gif 
_For a lack of better words how do you think 4- 0.01 uf caps would act? JW_

 

Like a single 0.04uF cap. Still way too small. Twenty 0.01uF caps would get you in the ballpark...


----------



## soloz2

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_I'd guess that if it saw a full 27V, it's toast, but you never know. Be sure you use a 2K resistor - that cuts down on the current a bit and lets you get away with a 1/2W resistor.

 About removing the LED's under the tube sockets - I always use a spent lead held with a pair of needlenose pliers while heating the solder pad with the board turned upside down. Use the spent lead to push into the hole when you melt the solder and it will push out the LED from the bottom. (You have to do the second hole before it will drop out, of course.) Be sure you poke the lead far enough through the hole. If you don't push far enough, you can get the part's lead stuck to the very top of the pad on the top side of the board. That may make it difficult inside the tube socket. You may also get the spent lead stuck in the hole from time-to-time, but it's easy enough to heat it up and pull it out.

 When you're trying to remove the part, don't apply heat to the spent lead while you're holding it in the pliers - just apply heat to the soldered pad. If the pliers are holding the lead, it will act as a giant heat sink and prevent you from heating things up._

 

well I replaced RLED hoping to see a voltage drop but no dice... still 27v Am I missing something?


----------



## cronic

Quote:


  Originally Posted by *soloz2* /img/forum/go_quote.gif 
_well I replaced RLED hoping to see a voltage drop but no dice... still 27v Am I missing something?_

 

do you have the pwr led (ledc) populated? I had 27v as well until I installed the pwr led (ledc).


----------



## soloz2

Quote:


  Originally Posted by *cronic* /img/forum/go_quote.gif 
_do you have the pwr led (ledc) populated? I had 27v as well until I installed the pwr led (ledc)._

 

no. but that can change easily enough!


 it is odd though that the left side is reading 3.3v while the right side is 27v. The amp works and sounds fine.


 Update: Power LED is reading 27v too. hooked up a LED no go, measured sure enough 27v... shoulda measured before throwing the LED in. It was only in for a few seconds so hopefully it didn't get fried.


----------



## cronic

Quote:


  Originally Posted by *soloz2* /img/forum/go_quote.gif 
_no. but that can change easily enough!


 it is odd though that the left side is reading 3.3v while the right side is 27v. The amp works and sounds fine._

 


 Mine was the ledl that read 27v without the ledc installed.


----------



## John Wilson

Quote:


  Originally Posted by *BoilermakerFan* /img/forum/go_quote.gif 
_Like a single 0.04uF cap. Still way too small. Twenty 0.01uF caps would get you in the ballpark..._

 

No..I meant one .01 OR .033 film in CA3R/L and CA6R/L. Would there be a problem with ringing? Too unstable? Distortion? Roll the bass or high end off? Gain?? Less dynamic? JW


----------



## BoilermakerFan

Off topic, but do any of you MAX owners/builders have a ADC to bring in their analog to their PC via USB or Firewire? I'm just starting my search, but did come across this DIY half-kit:
Hagerman Technology LLC: The Ripper

 I have about 7 albums that I received from a friend that have yet to be released on CD. He would like me to convert these albums to WAV files for him and I get to keep all his albums (about 60 that I wanted to keep). 
	

	
	
		
		

		
			





 I'm negotiating a similar deal with two other coworkers, but they want a representative sample of my "work" before they are willing to part with their vinyl. Luckily, I have a couple of Who albums in fantastic condition that have since been remuddled, oops, I mean remastered on CD that I'll use for my proof of quality to get my hands on some amazing classic rock and folk albums of the '60's.


----------



## slowpogo

Quote:


  Originally Posted by *John Wilson* /img/forum/go_quote.gif 
_No..I meant one .01 OR .033 film in CA3R/L and CA6R/L. Would there be a problem with ringing? Too unstable? Distortion? Roll the bass or high end off? Gain?? Less dynamic? JW_

 

Not to be condescending, but it sounds like you already possess the .01 and .033 caps..and presumably would rather use those than spend the $, or go to the trouble to buy the spec'd .22 caps?

 If the ones you have were closer, like .18, I'd say go ahead and try them. But you're WAY below the specs...I would suggest spending $5 on some Wimas and avoiding the worry.


----------



## John Wilson

Quote:


  Originally Posted by *slowpogo* /img/forum/go_quote.gif 
_Not to be condescending, but it sounds like you already possess the .01 and .033 caps..and presumably would rather use those than spend the $, or go to the trouble to buy the spec'd .22 caps?

 If the ones you have were closer, like .18, I'd say go ahead and try them. But you're WAY below the specs...I would suggest spending $5 on some Wimas and avoiding the worry._

 

 I have all of them. And even more...think of me as a small parts shop. Question still not answered. JW P. S. I guess you miss the one how I just spent $140.00 on resistors, LOL.


----------



## BoilermakerFan

Quote:


  Originally Posted by *John Wilson* /img/forum/go_quote.gif 
_No..I meant one .01 OR .033 film in CA3R/L and CA6R/L. Would there be a problem with ringing? Too unstable? Distortion? Roll the bass or high end off? Gain?? Less dynamic? JW_

 

I snipped this right off the MAX website:

_Bypassing Principles with Capacitors
 Note that the film caps in the Millett MAX follow the Millett heritage by "bypassing" the electrolytic in each case. This is a common practice for many amp designs, although hotly debated in some circles. The idea is to combine the film cap with the electrolytic so as to pass the higher frequencies through the film cap, whose sound quality is generally much better than the electrolytic. Most electrolytics, even boutique ones, suffer from some harshness in the higher frequencies. The philosophy of bypassing can have such good results that boutique electrolytics may not be needed - common power electrolytics may suffice. Conversely, it has been documented in several places that using bypass film caps with Black Gate NX's may actually degrade the quality of sound. Some of us who've had a chance to test different combinations with the Black Gates have also found that many film cap bypasses have absolutely no effect at all. Typical practice is to delete the film bypass caps when investing in Black Gates. However, this may not work with the other boutiques and film bypasses may still offer better results than none at all. For instance, the Nichicon Muse ES is one that works well with a good film bypass, but not as good without.

 NOTE: As noted in the "Can't Miss MAX Builds" above, the K42 Russian PIO seems to add some transparency and smoothness to the Black Gate NX's. This is in keeping with a general consensus that Vitamin Q's also do well with Black Gate NX's, since the K42's are similar."_

 I'm not an expert and all the electronics theory isn't coming back to me as fast as I would like, but I think the small value caps you've mentioned will just not add anything to the sound. If your using BGs again, then you might as well leave them out. If your using a different electrolytic cap, then the highs may be congested or simply rolled off.


----------



## pinkfloyd4ever

CA3 & CA6 aren't bypass caps, boilermakerfan, though I still wouldn't use that small of caps there as John is talking about


----------



## tomb

Quote:


  Originally Posted by *John Wilson* /img/forum/go_quote.gif 
_I have all of them. And even more...think of me as a small parts shop. Question still not answered. JW P. S. I guess you miss the one how I just spent $140.00 on resistors, LOL._

 

Yep. Seeing the parts selection in those pics you've posted, one knows that money spent on parts is not your issue. 
	

	
	
		
		

		
		
	


	







 Boilermakerfan sort of answered your question, but that quote is probably more specific to bypassing the signal caps. In the case of the rail caps, the best that I can use to compare is the older Millett Hybrid or the 1st prototype MAX, or the MiniMAX prototype. Each of those examples use 0.1uf Wima's instead of 0.22uf. There's a certain "blackness" or smoothness that the higher value bypasses impart. I doubt seriously that there's any speed difference between 0.1uf and 0.22uf, so I don't think we can mistake added blackness/smoothness for slower caps.

 In the case of the rail caps, bypassing is reducing the high-frequency noise that exists in many electrolytics. To a certain amount, the bypasses reduce noise all across the spectrum. Very small bypasses will approach the effect of having none at all - rendering them superfluous, while very large bypasses will overtake the electrolytics and produce phase distortions. Where those breaks occur is anyone's guess, but as referenced, I can tell you that going from 0.1uf to 0.22uf is an improvement. I doubt that going the other direction would be the same.

 EDIT: There is a school of thought that all the rail caps may be considered in the signal path at some point or another. You can think of it as whether the power used by the tube/transistors to amplify or leverage current is clean or noisy.


----------



## John Wilson

Thanks Tom! JW


----------



## kvant

Quote:


  Originally Posted by *pinkfloyd4ever* /img/forum/go_quote.gif 
_CA3 & CA6 aren't bypass caps..._

 

CA3 & CA6 are bypass caps to electrolytics CA4 & CA5. Or, perhaps, CA4 & CA5 are bypass caps to CA3 & CA6.


----------



## tomb

Quote:


  Originally Posted by *kvant* /img/forum/go_quote.gif 
_*CA3 & CA6 are bypass caps to electrolytics CA4 & CA5*. Or, perhaps, CA4 & CA5 are bypass caps to CA3 & CA6._

 

Yes, that first statement is correct. 
	

	
	
		
		

		
		
	


	




 Thanks!


----------



## fault151

Hi guys i read on the max website that the tubes need setting up when you first use them (tube biasing). If i have an amp coming form America, do i need to do anything before i turn it on to get it set up properly, or, should i be able to just use it straight away? 

*I just wanted to check before i did anything. *


----------



## tomb

Quote:


  Originally Posted by *fault151* /img/forum/go_quote.gif 
_Hi guys i read on the max website that the tubes need setting up when you first use them (tube biasing). If i have an amp coming form America, do i need to do anything before i turn it on to get it set up properly, or, should i be able to just use it straight away? 

*I just wanted to check before i did anything. *_

 

It depends on how the owner sends it to you. 
	

	
	
		
		

		
		
	


	




 I always include instructions with mine, and clearly identify which two tubes are set for the current bias setting and which ones are Left and Right. (I wouldn't recommend shipping one with the tubes installed.)


----------



## fault151

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_It depends on how the owner sends it to you. 
	

	
	
		
		

		
		
	


	




 I always include instructions with mine, and clearly identify which two tubes are set for the current bias setting and which ones are Left and Right. (I wouldn't recommend shipping one with the tubes installed.)_

 

Im not sure, i'll contact him too.

 Hes removed the tubes out and wrapped them up. If i find out which ones are left and right, will it be ok then?


----------



## fault151

Ok heres what Jim said:

 There is a hand-written set of instructions for bias adjustment, as well as a meter for checking the voltages, so it's pretty simple. Nothing to do before you turn it on, except install the tubes. I would let it warm up for an hour or so before checking the bias, since the tubes have been out for a while. Once it's adjusted, it should be fine, although I checked the voltages for the first couple of days, just out of curiosity.

 There is one thing to check for with that unit: When you check the voltage for the 1st time, if one channel is around 0.5 volts high, and the other is 0.5 volts low, swap the tubes side-to-side.

 Is this what i should do then?


----------



## tomb

There's more to it than that, like where to stick the probes, which trimmers to turn (there are 5 of them) total voltage, etc. Whatever - we'll walk you through when you get it.


----------



## fault151

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_There's more to it than that, like where to stick the probes, which trimmers to turn (there are 5 of them) total voltage, etc. Whatever - we'll walk you through when you get it. 
	

	
	
		
		

		
			






_

 

cheers! I haven't got a clue! I shall let you know when i get it.

 Thank you!


----------



## slowpogo

For those who have used Front Panel Express for their amps...

 I just got my front panel a few days ago, and I love it, it's beautiful. It's plain anodized aluminum; my Hammond case is black, and I just ordered a black back panel. My intention is it will be all black, except for the front panel (and feet).

 I was expecting that the inner parts of cavities and holes would not be finished like the front of the panel. But I was surprised to find that my front panel was also not finished along the edges; it was "raw" and I needed to use my Dremel with a fine brush to smooth the edges out. (They were already "smooth" but I wanted a more muted color, not so shiny)

 As far as BLACK panels go -- is it the same way with them? Will mine have a nice black front and raw, silvery edges? Is the back also finished black, or just the front?

 I thought I had considered everything but these questions just popped up. Thanks for any help.


----------



## MrMajestic2

Quote:


  Originally Posted by *slowpogo* /img/forum/go_quote.gif 
_As far as BLACK panels go -- is it the same way with them? Will mine have a nice black front and raw, silvery edges? Is the back also finished black, or just the front?_

 

Both the front and back will be black, but the edges are the same as the silver ones. This is due to the fact that FPE anodizes the aluminium before cutting it. I guess this is one thing that keeps the price down.


----------



## GeWa

Well, that's because they use plates that are already anodized. If you drill holes or make countersinks those edges are just plain aluminum colored. Same goes for the outer edges of the plates. For the kind of money you pay for there stuff they should reconsider an other way of manufacturing. Machining first and than anodizing.

 Regards


----------



## slowpogo

Well, it looks like I have some painting to do, of the edges. I haven't painted much--will typical cheap spray paint work alright on aluminum? Or does it need to be Rustoleum or something like that?


----------



## BoilermakerFan

Quote:


  Originally Posted by *slowpogo* /img/forum/go_quote.gif 
_Well, it looks like I have some painting to do, of the edges. I haven't painted much--will typical cheap spray paint work alright on aluminum? Or does it need to be Rustoleum or something like that?_

 

How important is the end finish to you? You can send the entire case with FPE panels out to an annodizer and have them strip off the existing black from all parts, electro-polish it again, and then re-annodize the case any color you want. If you want a satin textured finish, then you can skip the electro-polish. This was my plan for the Hammond cases before I decided to take my MAX builds in different directions entirely. I found an annodizer near Nashville, TN that will do custom work including fades if you really want to go crazy. They can do other custom work too such as 3 or more distinct colors, but it would involve multiple shippings or price adders to you. PM me for the info if your interested in taking it that far and I will dig out their contact info.


----------



## cetoole

Quote:


  Originally Posted by *slowpogo* /img/forum/go_quote.gif 
_For those who have used Front Panel Express for their amps...

 I just got my front panel a few days ago, and I love it, it's beautiful. It's plain anodized aluminum; my Hammond case is black, and I just ordered a black back panel. My intention is it will be all black, except for the front panel (and feet).

 I was expecting that the inner parts of cavities and holes would not be finished like the front of the panel. But I was surprised to find that my front panel was also not finished along the edges; it was "raw" and I needed to use my Dremel with a fine brush to smooth the edges out. (They were already "smooth" but I wanted a more muted color, not so shiny)

 As far as BLACK panels go -- is it the same way with them? Will mine have a nice black front and raw, silvery edges? Is the back also finished black, or just the front?

 I thought I had considered everything but these questions just popped up. Thanks for any help._

 

Yeah, that was pretty much my experience with FPE, great work, but a bit disappointed by the edge finish for a $100 panel. I would only use it for natural anodize color, and then you really do need to go back and clean up the edges. Black should be black on the front and back, but not the edges or anywhere they cut. I have been kinda tempted to get a FPE panel for my Max, but held off thus far due to cost. I have no useful experience in painting aluminum, but if you figure out something that works well, I would be interested to hear it, as I would like to refinish my Hammond case.


----------



## BoilermakerFan

Quote:


  Originally Posted by *cetoole* /img/forum/go_quote.gif 
_Yeah, that was pretty much my experience with FPE, great work, but a bit disappointed by the edge finish for a $100 panel. I would only use it for natural anodize color, and then you really do need to go back and clean up the edges. Black should be black on the front and back, but not the edges or anywhere they cut. I have been kinda tempted to get a FPE panel for my Max, but held off thus far due to cost. I have no useful experience in painting aluminum, but if you figure out something that works well, I would be interested to hear it, as I would like to refinish my Hammond case._

 

A local body shop that does motorcycle work or custom airbrushing would be a good choice too. They just need to use an etching primer before the paint for a solid bond, but I bet you could get it re-annodized in a solid color for less than having it painted, even factoring a small amount of shipping both ways.


----------



## fault151

The problem with aluminium is getting the paint to stay stuck to it. Its a bit of a pain. 


  Quote:


  Originally Posted by *BoilermakerFan* /img/forum/go_quote.gif 
_A local body shop that does motorcycle work or custom airbrushing would be a good choice too. They just need to use an etching primer before the paint for a solid bond, but I bet you could get it re-annodized in a solid color for less than having it painted, even factoring a small amount of shipping both ways._


----------



## tomb

I had great luck painting the Hammond lid on a Millett Hybrid, once. As long as you use brown primer, it goes on great. You need to let the final coat dry about a week before using it, though. It takes that long to get a reliable hard shell.

 Edit: I used Rustoleum, too.


----------



## fault151

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_I had great luck painting the Hammond lid on a Millett Hybrid, once. As long as you use brown primer, it goes on great. You need to let the final coat dry about a week before using it, though. It takes that long to get a reliable hard shell._

 

Is it not easier to get a black box?

 I'm having a panel made by front panel. Hope it comes out ok. I haven't even got my millet yet! 
	

	
	
		
		

		
		
	


	




 The panel is being made very soon so i shall let you know how it turns out. I had lots of help from Mr Majestic2 on the design, cheers for that!


----------



## amphead

Yeah, go for the anodized black aluminum box as first choice and painting as a second choice. Powder coating is the most reliable other than anodizing with aluminum. Its good to know that the primer solution is available as a backup plan. Edit: I guess you survived the freakish tornado in Atlanta TomB!


----------



## BoilermakerFan

Quote:


  Originally Posted by *fault151* /img/forum/go_quote.gif 
_The problem with aluminium is getting the paint to stay stuck to it. Its a bit of a pain._

 

That's were the _etching_ primer comes in. It physically bonds to the aluminum and then the paint bonds to the primer. An automotive urethane paint can be cured in a make shift insulation oven with a 150W bulb to speed up the curing/hardening process without making it brittle if you want to keep it DIY, but you'll still get the best results from a Pro. 
	

	
	
		
		

		
		
	


	




 Edit: The panels are annodized black, as is the enclosure, but every exposed edge were the aluminum was drilled or cut out will be unannodized raw aluminum. Even the "plain" silver aluminum enclosures are actually clear annodized.


----------



## tomb

Quote:


  Originally Posted by *fault151* /img/forum/go_quote.gif 
_Is it not easier to get a black box?

 I'm having a panel made by front panel. Hope it comes out ok. I haven't even got my millet yet! 
	

	
	
		
		

		
		
	


	




 The panel is being made very soon so i shall let you know how it turns out. I had lots of help from Mr Majestic2 on the design, cheers for that! 
	

	
	
		
		

		
		
	


	


_

 

Actually, it was silver. 
	

	
	
		
		

		
		
	


	




 The reason I painted it is because I cut a huge gouge in the lid while punching the tube holes. That was with Harbor Freight hole punches - I went out and bought a Greenlee punch after that and never looked back.

 That still left me with a lid that was hideously gouged. After several coats of primer with lots of wet-sanding inbetween, I put a few coats of silver and did some more wet-sanding. I repeated that for several coats before the final top coat. It turned out very nice. Actually you couldn't see the gouge after wet-sanding/painting about two coats of primer, anyway - but all the rest of the work made the finish very nice.

 Anyonw can do the same with a can of brown primer and color Rustoleum from Walmart. Add a couple sheets of wet-dry sandpaper, and you're in business. This was during the summer, so I cheated by leaving the lid out in the sunlight during the day. It cooked pretty good in Hotlanta. 
	

	
	
		
		

		
		
	


	




 Here's a pic - wish I had made one with better light - the lid was very glittery. 
	

	
	
		
		

		
		
	


	




 I sold it, unfortunately, so no more pics:






 Amphead - thanks for the thought, but I'm pretty far away from downtown - in my house, anyway - luckily it wasn't during working hours.


----------



## Nebby

Hey tomb, where did you pick up your Greenlee punches? I was getting ready to pick up the Harbor freight ones, but lucky you posted about them here


----------



## tomb

Quote:


  Originally Posted by *Nebby* /img/forum/go_quote.gif 
_Hey tomb, where did you pick up your Greenlee punches? I was getting ready to pick up the Harbor freight ones, but lucky you posted about them here 
	

	
	
		
		

		
			



_

 

Grainger. It's a Greenlee Slug-Buster #35178 - makes a 1" diameter hole. You have to be careful to pick one with the hole size specified. Many of the punches are made for conduit and the nominal size is actually the O.D. of the conduit.

 Yeah, I had a 1/2" breaking bar about a foot and a half long and couldn't put enought torque on the Harbor Freight punch to punch the hole. They're really pathetic. What happens is that the threads are not very precise. The cutter will slip sideways slightly while wrenching it down. When it does that, it gets misaligned so that part of the cutter is line with the outside edge of the die. No amount of force will punch it through when it does that.

 The Greenlee stays true every time. Except for the small snap when the cutter finally breaks through, you can almost finger-tighten it. Unfortunately, they are pretty expensive. I think mine cost me about $55. I haven't looked at prices lately, but it's worth every penny if you want clean holes.


----------



## BoilermakerFan

Does your Greenlee warp or dimple the top? I've always experienced an uneven surface after using a punch on steel enclosures for electrical panels, so I switched to Unibits. Aluminum is probably more forgiving though.

IRWIN Unibit Unibit Cobalt Step Drill

 I'm sure the Cobalt version is as much as the Greenlee punch, but this way you have more than one hole size too. The best part about them is that they work in steel, aluminum, plastic, even wood in a pinch. I have 3 TiNitride coated ones that range from 1/16" up to 3/4", but my best friend is a journeyman electrician, so I can get my hands on just about any Unibit made.


----------



## fault151

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Actually, it was silver. 
	

	
	
		
		

		
		
	


	




 The reason I painted it is because I cut a huge gouge in the lid while punching the tube holes. That was with Harbor Freight hole punches - I went out and bought a Greenlee punch after that and never looked back.

 That still left me with a lid that was hideously gouged. After several coats of primer with lots of wet-sanding inbetween, I put a few coats of silver and did some more wet-sanding. I repeated that for several coats before the final top coat. It turned out very nice. Actually you couldn't see the gouge after wet-sanding/painting about two coats of primer, anyway - but all the rest of the work made the finish very nice.

 Anyonw can do the same with a can of brown primer and color Rustoleum from Walmart. Add a couple sheets of wet-dry sandpaper, and you're in business. This was during the summer, so I cheated by leaving the lid out in the sunlight during the day. It cooked pretty good in Hotlanta. 
	

	
	
		
		

		
		
	


	




 Here's a pic - wish I had made one with better light - the lid was very glittery. 
	

	
	
		
		

		
		
	


	




 I sold it, unfortunately, so no more pics:






 Amphead - thanks for the thought, but I'm pretty far away from downtown - in my house, anyway - luckily it wasn't during working hours. 
	

	
	
		
		

		
		
	


	


_

 

Yeh you did a good job of it, looks good!


----------



## Marzie

OK, I got to around page 100 and I don't think I found what I was looking for. I am planning to use the suggestion under the boutique page for using 
 Nichicon Muse ES at CA2 (1000uF 16V from handmade)
 and CA7 (470uF 35V from BD)
 Wima's at CA9 (250V .22uF from Mouser)
 and Sonicap GEN II at CA8 (200, 400, or 600 V from Sonicraft???)

 Is this correct? Which voltage on the gen IIs? Is it ok to follow the BOM for the rest of the caps? Where else should there be wimas? Also, I notice some BJT suggestions to go along with the can't miss builds, what is recommended for my configuration?


----------



## tomb

Quote:


  Originally Posted by *Marzie* /img/forum/go_quote.gif 
_OK, I got to around page 100 and I don't think I found what I was looking for. I am planning to use the suggestion under the boutique page for using 
 Nichicon Muse ES at CA2 (1000uF 16V from handmade)
 and CA7 (470uF 35V from BD)
 Wima's at CA9 (250V .22uF from Mouser)
 and Sonicap GEN II at CA8 (200, 400, or 600 V from Sonicraft???)

 Is this correct? Which voltage on the gen IIs? Is it ok to follow the BOM for the rest of the caps? Where else should there be wimas? Also, I notice some BJT suggestions to go along with the can't miss builds, what is recommended for my configuration?_

 

Marzie,

 Your best bet is to refer to the MAX website: MAX. It has all the latest info. Things have evolved quite a bit over time and as we built more MAXes and tested various combos. We junked the idea of the Sonicap's a long time ago. Refer to the Tweaks -> MAX Boutique and also the most current notes listed on the Bill Of Materials page on the MAX website.

 Check beezar.com (beezar.com welcome page) for those parts that are not available at Mouser and DigiKey. ALPS RK27's are due in at the end of the month and a new, smaller version of VitaminQ's will be added sometime this week.

 To be specific, the ES's are appropriate but Vitamin Q's or the Russian K42's are best for the CA8 positions. We are recommending only Wima's in the CA9 positions, or, when using Black Gates - leave CA9 blank. Info and mounting instructions are on the Tweaks -> K42 PIO Caps page and the Tweaks -> VitaminQ PIO Caps page on the MAX website.

 Keep the questions coming.


----------



## tomb

Also, to answer your questions about BJT's, refer to beezar.com for a description of the different traits of each BJT.

 As for voltage, nothing on the board past the power supply ever sees anything more than 30VDC. However, the power caps are sized at 50V, since they see something between 30-40VDC at the input to the voltage regulator in the power supply.

 Film caps are rated for much higher voltages. In those cases, however, you want the smallest physical size that will fit on the board. The Wima's happen to be 250V, but the board is designed specifically for the model number listed in the BOM. Boutique is different and sometimes you have to use some creativity to make them fit, which is why we included special pages for the K42's and the VitaminQ's on the MAX website.


----------



## Dark_Shadow

Quote:


  Originally Posted by *fault151* /img/forum/go_quote.gif 
_The problem with aluminium is getting the paint to stay stuck to it. Its a bit of a pain._

 

The trick is to use a surface preparation like chemical film (Alodine or Iridite) this will ensure that the paint stick to the surface. It the kind of stuff used in aerospace to help the adhesion of paint on the surface when we can not anodize a part.


----------



## soloz2

Alright, I'm sure it's just something I overlooked but I'm still getting 27v for both the poer LED and right tube LED.


----------



## tomb

Quote:


  Originally Posted by *soloz2* /img/forum/go_quote.gif 
_Alright, I'm sure it's just something I overlooked but I'm still getting 27v for both the poer LED and right tube LED.

 <img]http://img522.imageshack.us/img522/1598/img4082zc9.jpg[/img>

 <img]http://img442.imageshack.us/img442/5931/img4083kq2.jpg[/img>_

 

You have an open circuit when the LED is not in there. It will probably measure 27VDC at the very slight current that the meter pulls. It takes current flowing through the resistor to drop the voltage.

 There's nothing in parallel with the LED resistors, so check the resistance from V+ to the positive LED pad in each case. If you get the supposed value of the resistor (should be 2K ohm), you should be OK.


----------



## soloz2

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_You have an open circuit when the LED is not in there. It will probably measure 27VDC at the very slight current that the meter pulls. It takes current flowing through the resistor to drop the voltage.

 There's nothing in parallel with the LED resistors, so check the resistance from V+ to the positive LED pad in each case. If you get the supposed value of the resistor (should be 2K ohm), you should be OK._

 

I'm about to head to work so I'll check when I get back. I've got 1.2k resisters in there now. I'll see if I have some 2k ones that will work.

 I have LEDs in both tube positions and I tried putting a LED in the power position and it didn't fix the problem. Left tube LED is working as it should.


----------



## dsavitsk

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Grainger. It's a Greenlee Slug-Buster #35178 - makes a 1" diameter hole._

 

Check Mouser, too. They have the Greenlees as well as some off brands that are not nearly as good, but can work in a pinch (like when there is no Greenlee in the correct size.)


----------



## fault151

Hi guys, my millet has just arrived. Im dying to switch it on and have a listen, but before i do, is there anything i need to do first? The amps ready made and came from US to me in UK. The forum member i bought it of left me a list of instructions for tube biasing and set up. I guess need to do these first?


----------



## tomb

Quote:


  Originally Posted by *fault151* /img/forum/go_quote.gif 
_Hi guys, my millet has just arrived. Im dying to switch it on and have a listen, but before i do, is there anything i need to do first? The amps ready made and came from US to me in UK. The forum member i bought it of left me a list of instructions for tube biasing and set up. I guess need to do these first?_

 

Yep - by all means, read the instructions, first. You need to focus on the tip jacks in back. That green one in the middle is ground. Put the black probe of your meter in that one and let it stay. Then, I'd check voltage with the amp on by placing the red probe in the black (if I remember the colors exactly) tip jack over by itself on the end. That should be your voltage and it should read 27VDC, but anything from 24VDC to about 28VDC is OK. Remember what the voltage is, because you want the tubes to bias at 1/2 of that value.

 Keeping the black probe in the center green tip jack, begin by checking tube bias on the left tube. To do that, put the red probe in the white tip jack immediately adjacent to the green one in the middle. Similarly, the right tube will be measured by the red tip jack immediately adjacent to the green tip jack.

 Both tubes should measure about 1/2 of the supply voltage you measured. To adjust the left tube bias - turn the trimmer that's furthest in back on the left side. Similarly, to adjust the right tube, turn the trimmer that's furthest in back on the right side. Turning clockwise will raise the voltage, counterclockwise will lower it.

 Tell us when you get to this point and we'll help you further. If you're lucky, all these will be set already. 
	

	
	
		
		

		
		
	


	





 WARNING! Don't adjust the trimmers that are farthest forward. Those are the DB trimmers - they should need no adjustment!!


----------



## fault151

My instructions say to adjust it up to 29v, that ok too?

 Will i need to completely remove the board out of the hammond case to do all this?




  Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Yep - by all means, read the instructions, first. You need to focus on the tip jacks in back. That green one in the middle is ground. Put the black probe of your meter in that one and let it stay. Then, I'd check voltage with the amp on by placing the red probe in the black (if I remember the colors exactly) tip jack over by itself on the end. That should be your voltage and it should read 27VDC, but anything from 24VDC to about 28VDC is OK. Remember what the voltage is, because you want the tubes to bias at 1/2 of that value.

 Keeping the black probe in the center green tip jack, begin by checking tube bias on the left tube. To do that, put the red probe in the white tip jack immediately adjacent to the green one in the middle. Similarly, the right tube will be measured by the red tip jack immediately adjacent to the green tip jack.

 Both tubes should measure about 1/2 of the supply voltage you measured. To adjust the left tube bias - turn the trimmer that's furthest in back on the left side. Similarly, to adjust the right tube, turn the trimmer that's furthest in back on the right side. Turning clockwise will raise the voltage, counterclockwise will lower it.

 Tell us when you get to this point and we'll help you further. If you're lucky, all these will be set already. 
	

	
	
		
		

		
		
	


	





 WARNING! Don't adjust the trimmers that are farthest forward. Those are the DB trimmers - they should need no adjustment!!_


----------



## fault151

oh i see there are 5 holes over 5 different trimmers. Don't adjust the ones at the front nearest the face panel? That right? Just the other 3.


----------



## tomb

Quote:


  Originally Posted by *fault151* /img/forum/go_quote.gif 
_oh i see there are 5 holes over 5 different trimmers. Don't adjust the ones at the front nearest the face panel? That right? Just the other 3._

 

Yes - don't dare touch the the two near the front!

 Look down in the holes and you should see a small brass screw on top of the light-blue rectangular trimmer. You need to use a trimmer adjustment tool or a jeweler's type screwdriver. The adjustment tool is better because they're always insulated, but the screwdriver will work if you are careful.

 I'd plug it in and measure through the tip jacks, first - that won't cause any damage if it was setup at all before it was sent to you. 
	

	
	
		
		

		
			






 EDIT: 29VDC is too high if it's fed from a 24VAC source. You should set it probably go ahead and set it for 27VDC - that's the typcial DIY Millett standard.

 The single hole through the lid in the rear is the trimmer to set voltage.


----------



## fault151

Ok i'll give it a go. I'll be back on as soon as i get it done. 10min or so, don't wanna rush 
	

	
	
		
		

		
		
	


	




 cheers for your help!




  Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Yes - don't dare touch the the two near the front!

 Look down in the holes and you should see a small brass screw on top of the light-blue recatangular trimmer. You need to use a trimmer adjustment tool or a jeweler's type screwdriver. The adjustment tool is better because they're always insulated, but the screwdriver will work if you are careful.

 I'd plug it in and measure through the tip jacks, first - that won't cause any damage if it was setup at all before it was sent to you. 
	

	
	
		
		

		
		
	


	





 EDIT: 29VDC is too high if it's fed from a 24VAC source. You should set it probably go ahead and set it for 27VDC - that's the typcial DIY Millett standard._


----------



## tomb

Typing too fast - sorry for the fractured English.


----------



## fault151

ok i now have 27 . 14.5V and the front trims read 110v. Everything ok with that set up?


----------



## tomb

Quote:


  Originally Posted by *fault151* /img/forum/go_quote.gif 
_ok i now have 27 . 14.5V and the front rims read 110v. Everything ok with that set up?_

 

I hope you mean the front trimmers are set at 110*m*V. 
	

	
	
		
		

		
		
	


	




 You need to set the 14.5V tube bias to 13.5VDC on both tubes (1/2 of 27VDC). Counter-clockwise will reduce that voltage on each tube. Don't get mixed up about which tip jack is reading from which trimmer. You should see immediate changes when you turn the trimmer.

 Don't get too upset about adjusting the tubes, too. They're the mules of the audio world. 
	

	
	
		
		

		
		
	


	




 They react slowly to the turns and will overshoot and undershoot. They also will react differently depending on which direction you're coming from with the trimmer ... all normal. It's probably good to do 1/4 turn at a time and you may find that 1/8 turn either way will give you the final adjustment.

 Final tuning may be done with your ears - adjust so that the sound level is equal in both ears and the centered sound is centered.


----------



## fault151

yeh i mean 110mv. Im so excited i missed the 'm' off. 
	

	
	
		
		

		
		
	


	




 I best lower the tube bias then. Be right back


----------



## fault151

Right i think it seems ok now. One other thing, the left tube at the top has part of a black area forming??? This ok? Everything reads as it should on the amp and i haven't done anything else.


----------



## tomb

Quote:


  Originally Posted by *fault151* /img/forum/go_quote.gif 
_Right i think it seems ok now. One other thing, the left tube at the top has part of a black area forming??? This ok? Everything reads as it should on the amp and i haven't done anything else._

 

Yep, some mules have blemishes. 
	

	
	
		
		

		
		
	


	




 Enjoy it, then.

 Remember the tubes will exhibit a bit of distortion and won't come into their own for about 1/2hr to 1hr.


----------



## fault151

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Yep, some mules have blemishes. 
	

	
	
		
		

		
		
	


	




 Enjoy it, then.

 Remember the tubes will exhibit a bit of distortion and won't come into their own for about 1/2hr to 1hr._

 

Thats ok then. I love the bass this thing produces! Im going to sit here and have a listen for a while see how it sounds.

 Cheers for you help!

 I just need my custom box now then it will be set up perfect!


----------



## fault151

Wow the amp is really starting to sound nice now! Iv had it on a few hours now. I m comparing the sound to my Graham Slee solo amp. 

 I love the way it sounds really detailed and i can hear the most smallest sounds of detail in songs. 

 Pleased i bought it.


----------



## amphead

Congrats Fault151! Another Max Lives!   

 That's great that you are enjoying your sound. Remember, you can always roll tubes to replace that one. But I wouldn't worry about it if you are getting good sound. Awesome!


----------



## tomb

Quote:


  Originally Posted by *fault151* /img/forum/go_quote.gif 
_Wow the amp is really starting to sound nice now! Iv had it on a few hours now. I m comparing the sound to my Graham Slee solo amp. 

 I love the way it sounds really detailed and i can hear the most smallest sounds of detail in songs. 

 Pleased i bought it._

 

It's always great to read/hear that reaction.
	

	
	
		
		

		
		
	


	







 Colin gets a kick out of seeing compliments about his design like that, too. He may not post as much with all his school and work, but he reads everything. He'll like reading this.


----------



## John Wilson

Working on Max #2. Got alot done today. JW


----------



## fault151

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_It's always great to read/hear that reaction.
	

	
	
		
		

		
		
	


	







 Colin gets a kick out of seeing compliments about his design like that, too. He may not post as much with all his school and work, but he reads everything. He'll like reading this. 
	

	
	
		
		

		
		
	


	


_

 

Yeh it does sound really impressive. I didn't want to come to work this morning, i wanted to sit there flicking through all my cds, trying them out!

 If i ever needed some new valves for it, where would i get them from and what chioces do i have, bearing in mind im in the UK.

 Im very tempted to have a go at making another one now! Thats if i can manage it.


----------



## fault151

Quote:


  Originally Posted by *amphead* /img/forum/go_quote.gif 
_Congrats Fault151! Another Max Lives!   

 That's great that you are enjoying your sound. Remember, you can always roll tubes to replace that one. But I wouldn't worry about it if you are getting good sound. Awesome! _

 

Cheers!


----------



## tomb

Quote:


  Originally Posted by *John Wilson* /img/forum/go_quote.gif 
_Working on Max #2. Got alot done today. JW 
 <IMG]http://i42.photobucket.com/albums/e332/jw1954/jw1954-2/DSC_0011-2.jpg[/IMG>
 <IMG]http://i42.photobucket.com/albums/e332/jw1954/jw1954-2/DSC_0012-1.jpg[/IMG>
 <IMG]http://i42.photobucket.com/albums/e332/jw1954/jw1954-2/DSC_0023-3.jpg[/IMG>
 <IMG]http://i42.photobucket.com/albums/e332/jw1954/jw1954-2/DSC_0005.jpg[/IMG>
 <IMG]http://i42.photobucket.com/albums/e332/jw1954/jw1954-2/DSC_0002-1.jpg[/IMG>
 <IMG]http://i42.photobucket.com/albums/e332/jw1954/jw1954-2/DSC_0015.jpg[/IMG>_

 

Good grief!!
	

	
	
		
		

		
			








 What photography!


----------



## BoilermakerFan

Quote:


  Originally Posted by *John Wilson* /img/forum/go_quote.gif 
_Working on Max #2. Got alot done today. JW 
	

	
	
		
		

		
		
	


	

















_

 

JW

 Can you post up the part numbers and source of the wire loop test points you use on your MAX (TB1L, TB2L, etc)? I like those a lot and for my builds they would be just as easy as test jacks at the back of the amp with less work. 
	

	
	
		
		

		
		
	


	




 Thanks.


----------



## tomb

This is a typical red one at Mouser:
534-5005. John may have used bigger ones, though.


 EDIT: Yeah, looks like he used the ones with longer wire loops:
534-5010


----------



## Marzie

CM1 and CM3 are backordered at mouser, I was thinking of using digikey for CM1 CM2 and CM3, so I get all Kemet, rather than a mix kemet and xicon. Any comments on this? Also, CA4L/R, CA5L/R are backordered at both sites, should I go with the Panasonics from Digikey or the Nichicons from Mouser, since I have to choose one...


----------



## fault151

On my new design for a box, i want to include a few leds inside as lighting. Where would the best place be to get a feed from?


----------



## tomb

Quote:


  Originally Posted by *Marzie* /img/forum/go_quote.gif 
_CM1 and CM3 are backordered at mouser, I was thinking of using digikey for CM1 CM2 and CM3, so I get all Kemet, rather than a mix kemet and xicon. Any comments on this? Also, CA4L/R, CA5L/R are backordered at both sites, should I go with the Panasonics from Digikey or the Nichicons from Mouser, since I have to choose one..._

 

CM1 and CM3 are electrolytics. I'm not sure Kemet even makes electrolytics. 
	

	
	
		
		

		
		
	


	




 Regardless, any ol' electrolytic cap will do at those ratings and preferrably with a 105 deg. temperature rating - Nichicon UPW, UHE, UVZ, maybe even the Vishay-Sprague 517D's.

 Similarly for CA4L/R and CA5L/R, but you want a high-quality power cap with low ESR and high ripple. The cap must have at least 1000uf minimum plus 35V minimum and fit within the dimensions you want (careful that they're not too tall if you're using the 3rd slot from bottom with the Hammond case (1" or 25mm height restriction. With those requirements, the following caps will work:

At Mouser:
 Nichicon UPW 1000uf 35V - UPW1V102MHD
 Nichicon UPW 1500uf 35V - UPW1V152MHD
 Nichicon UPW 2200uf 35V - UPW1V222MHD6
 Nichicon UPW 1000uf 50V - UPW1H102MHD

 Nichicon UHE 1000uf 35V - UHE1V102MHD

At Digikey:

 Panasonic FM 1000uf 35V - P12405-ND
 Panasonic FM 1200uf 35V - P12407-ND
 Panasonic FM 1800uf 35V - P12410-ND (I use these and/or the 1200uf's)
 Panasonic FM 1000uf 50V - P12393-ND (a great choice if used for CR1's, too)

 Panasonic FC 1000uf 35V - P10876-ND
 Panasonic FC 1000uf 35V - P10305-ND
 Panasonic FC 1200uf 35V - P11242-ND
 Panasonic FC 1500uf 35V - P11243-ND
 Panasonic FC 1500uf 35V - P10306-ND
 Panasonic FC 1800uf 35V - P11246-ND
 Panasonic FC 1800uf 35V - P11245-ND
 Panasonic FC 2200uf 35V - P10310-ND

 Panasonic FC 1000uf 50V - P10333-ND
 Panasonic FC 1200uf 50V - P11265-ND

 All of those caps above are 25mm in height. Depending on where you ordered CR1A,B,C, and D, you might just want to get four more 1000uf 50V - that's probably the most economical choice. Be careful with some of these - there are often two choices of size in the same rating - one taller, one shorter. You want the shorter ones at 25mm or less.

 At any rate, I trust that's enough of a selection to work for you.


----------



## tomb

Quote:


  Originally Posted by *fault151* /img/forum/go_quote.gif 
_On my new design for a box, i want to include a few leds inside as lighting. Where would the best place be to get a feed from?_

 

There are two ground test points on the board and two test points for each buffer. You only need one for each left and right buffer and only one ground for testing and biasing. So, you could use one of the ground points and one of the DB test points - that will give you 27VDC. Combine a 2K, 1/2W resistor in series and you have a source. You would want to reduce the resistor in kind for each LED that you add.


----------



## John Wilson

Quote:


  Originally Posted by *BoilermakerFan* /img/forum/go_quote.gif 
_JW

 Can you post up the part numbers and source of the wire loop test points you use on your MAX (TB1L, TB2L, etc)? I like those a lot and for my builds they would be just as easy as test jacks at the back of the amp with less work. 
	

	
	
		
		

		
		
	


	




 Thanks._

 

http://www.mouser.com/catalog/633/1758.pdf
 Tom got it right...It's # C. JW


----------



## fault151

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_There are two ground test points on the board and two test points for each buffer. You only need one for each left and right buffer and only one ground for testing and biasing. So, you could use one of the ground points and one of the DB test points - that will give you 27VDC. Combine a 2K, 1/2W resistor in series and you have a source. You would want to reduce the resistor in kind for each LED that you add._

 

Ok cheers. i'll give it a go.

 Just trying to decide what other colours to use.


----------



## tomb

Quote:


  Originally Posted by *fault151* /img/forum/go_quote.gif 
_Ok cheers. i'll give it a go.

 Just trying to decide what other colours to use._

 

Nope - check that. The test points are at signal voltage, which would be 13.5VDC. I'll look at it tonight and also see if Colin has a suggestion.


----------



## Marzie

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_CM1 and CM3 are electrolytics. I'm not sure Kemet even makes electrolytics. 
	

	
	
		
		

		
		
	


	


_

 

Doh! I don't know how I got mixed up, CM2 is the only Kemet of the three on digikey. I went with the Nichicon on the bom from Digikey. I got the enclosure and LED from there also, so I ducked the $5 handling fee.

 EDIT: Scratch that, I just realized the bom calls for the "clear" model, and digikey doesn't carry the black model

 I also went with the UPW1H102MHD from Mouser for CA4L/R and CA5L/R.


 I should have started from the end of this thread and worked my way backwards (which is what I am going to do now), I had no idea beezar had so many of the hard to find parts! I can limit my order to three sources, which is great!


----------



## n_maher

Quote:


  Originally Posted by *fault151* /img/forum/go_quote.gif 
_On my new design for a box, i want to include a few leds inside as lighting. Where would the best place be to get a feed from?_

 

Not to be a wise guy but what's wrong with the LED position at the center of the PCB? There's no reason several LED's can't be air-wired from that position.


----------



## fault151

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Nope - check that. The test points are at signal voltage, which would be 13.5VDC. I'll look at it tonight and also see if Colin has a suggestion. 
	

	
	
		
		

		
		
	


	


_

 


 ok, yeh let me know please. Id like to add maybe 2-4 leds. Anyone know where i can get purple leds? I only need about 4. Iv found a load on ebay, but they are in batches of 100. Also i take it standard leds are all pretty much the same? Im going to go for 3mm in size non flashing.


----------



## tomb

Quote:


  Originally Posted by *n_maher* /img/forum/go_quote.gif 
_Not to be a wise guy but what's wrong with the LED position at the center of the PCB? There's no reason several LED's can't be air-wired from that position._

 

You're always a wise guy.
	

	
	
		
		

		
		
	


	










 Yep - I just hesitated to offer that because I was just looking for some bigger holes. I've had trouble putting LED's in series if they're different colors: any differences at all in the current rating, one gets very bright while the other one's dim. They should be paralleled, IMHO, each with their own resistor. There's no reason they still couldn't use those pads - maybe branch off with a terminal block or something to distribute the LED's.

 Good suggestion.


----------



## ruZZ.il

BestHongKong.com has a bunch of colors. No purple, but they have UV..
 Maybe not the best price but for a handful assortment, I didn't care. they had what I was looking for. Came through pretty quickly and they're good LEDs too.. or so they seem so far 
	

	
	
		
		

		
		
	


	



 I googled across some UK resellers at the time, You may find em if you look..


----------



## tobias_svensk

John Wilson posted beautiful pictures and i don't think I have posted any yet so here's a couple showing the Motorola tube that I'm thinking of replacing.

















 And source is laptop -> foobar -> asio4all -> usbdac (PCM2702) -> MAX






 Everything uncased (as usual 
	

	
	
		
		

		
		
	


	




) on a woodtable 
	

	
	
		
		

		
		
	


	



 This is a perfect companion in the evenings after work as I'm working away from home Mon-Thur.
 Now I just have to find a goog place to buy some BG's for my second board that gonna be with BJT's.

 Cheers


----------



## fault151

Quote:


  Originally Posted by *ruZZ.il* /img/forum/go_quote.gif 
_BestHongKong.com has a bunch of colors. No purple, but they have UV..
 Maybe not the best price but for a handful assortment, I didn't care. they had what I was looking for. Came through pretty quickly and they're good LEDs too.. or so they seem so far 
	

	
	
		
		

		
		
	


	



 I googled across some UK resellers at the time, You may find em if you look.._

 

cheers, ill take a look. Id like pink if i cant get purple. I just want something a little different.


----------



## MrMajestic2

Quote:


  Originally Posted by *n_maher* /img/forum/go_quote.gif 
_Not to be a wise guy but what's wrong with the LED position at the center of the PCB? There's no reason several LED's can't be air-wired from that position._

 

Yeah, thats what I did on my windowed Max. I paralleled 2 bright blue LEDs, worked great without changing the default LED resistor. Dont go too bright, it will be irritating 
	

	
	
		
		

		
		
	


	




 Mine are around 400mcd I think.


----------



## fault151

Quote:


  Originally Posted by *MrMajestic2* /img/forum/go_quote.gif 
_Yeah, thats what I did on my windowed Max. I paralleled 2 bright blue LEDs, worked great without changing the default LED resistor. Dont go too bright, it will be irritating 
	

	
	
		
		

		
		
	


	




 Mine are around 400mcd I think._

 

Where did you get yours from?


----------



## MrMajestic2

Quote:


  Originally Posted by *fault151* /img/forum/go_quote.gif 
_Where did you get yours from?_

 

Local company Elfa. Its Everlight EL1254UBC if I remember correctly.


----------



## fault151

Yeh i found them. I'll try to get some pink/purple ones first, if not i'll get more blue. 

 cheers


----------



## tomb

Quote:


  Originally Posted by *tobias_svensk* /img/forum/go_quote.gif 
_John Wilson posted beautiful pictures and i don't think I have posted any yet so here's a couple showing the Motorola tube that I'm thinking of replacing.

 <IMG]http://www.ettnet.se/~tobias/photos/diy/motorola.jpg[/IMG>

 <IMG]http://www.ettnet.se/~tobias/photos/diy/max1.jpg[/IMG>

 <IMG]http://www.ettnet.se/~tobias/photos/diy/mosfet.jpg[/IMG>

 And source is laptop -> foobar -> asio4all -> usbdac (PCM2702) -> MAX

 <IMG]http://www.ettnet.se/~tobias/photos/diy/unisonus_uscdac.jpg[/IMG>

 Everything uncased (as usual 
	

	
	
		
		

		
		
	


	




) on a woodtable 
	

	
	
		
		

		
		
	


	



 This is a perfect companion in the evenings after work as I'm working away from home Mon-Thur.
 Now I just have to find a goog place to buy some BG's for my second board that gonna be with BJT's.

 Cheers_

 

Nice pics, Tobias!!


----------



## John Wilson

Wonderful photos tobias! Thanks. JW


----------



## BoilermakerFan

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_This is a typical red one at Mouser:
534-5005. John may have used bigger ones, though.


 EDIT: Yeah, looks like he used the ones with longer wire loops:
534-5010_

 


  Quote:


  Originally Posted by *John Wilson* /img/forum/go_quote.gif 
_http://www.mouser.com/catalog/633/1758.pdf
 Tom got it right...It's # C. JW_

 

Thanks guys! I'll have to add those to my order with Mouser.


----------



## John Wilson

Built two is done. Don't hate me gentlemen...but it sounds GREAT! Smooooth, airy, and sweet. This time I'm using a board mount Nobel pot and phone jack. TKD in #1. And all those fancy resistors. Soft recovery diodes. Solid core pure silver in this. Kimber stranded solid silver in #1. JW


----------



## joneeboi

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Colin gets a kick out of seeing compliments about his design like that, too. He may not post as much with all his school and work, but he reads everything. He'll like reading this. 
	

	
	
		
		

		
		
	


	


_

 

In that vein, I have to confess a weird thing I've been doing with my unused MAX boards. Sometimes...*sigh*...I stay up late at night just staring at the bare board. It's hard for me to believe the amazing symmetry and overall neatness and cleanliness of the routing. The entire top board is entirely ground except for one trace; each module is physically separated into its own section (PSU, amplifier, DB output, muting); the manufacturing of the board itself is stunning; everything is very flexible in allowing for extreme modding for things like boutique caps and bypass caps, either 1" or 1.5" max height configurations. Really the list goes on, and I can't really fully express my awe in what's been accomplished in the MAX. All of the amazement and wonder is amplified even further with my attempts at designing my own stuff. I probably won't ever be able to wrap my head around it, nor do I really want to. This kind of work really is inspiring, getting me out of bed each morning to go to class to learn about this stuff. Which reminds me, I have to get to bed soon so I can get to my catch-up lab tomorrow morning so I don't fail this course so I can get my BSc. in EE in the normal allotted time. 
	

	
	
		
		

		
		
	


	




 I just finished a lab today on opamps, one of the first times in my degree where I really took an interest in what I was learning (since it overlaps with this DIY thing I dabble in ). Very interesting stuff. Only 3 more years to go. 
	

	
	
		
		

		
		
	


	




 You rock, Colin!


----------



## John Wilson

My jaw keeps hitting the floor! WOW!! And it's only been alive four hours! I wish you could hear #2. It's perfect, and so musical. You have to try the BG FK's 1000 uf 16V in CA2L/R with the BG 0.47 bypassing them. Trust me on this. Vishay's and Caddock's are the way to go in this one. No kidding. JW


----------



## John Wilson

Quote:


  Originally Posted by *joneeboi* /img/forum/go_quote.gif 
_In that vein, I have to confess a weird thing I've been doing with my unused MAX boards. Sometimes...*sigh*...I stay up late at night just staring at the bare board. It's hard for me to believe the amazing symmetry and overall neatness and cleanliness of the routing. The entire top board is entirely ground except for one trace; each module is physically separated into its own section (PSU, amplifier, DB output, muting); the manufacturing of the board itself is stunning; everything is very flexible in allowing for extreme modding for things like boutique caps and bypass caps, either 1" or 1.5" max height configurations. Really the list goes on, and I can't really fully express my awe in what's been accomplished in the MAX. All of the amazement and wonder is amplified even further with my attempts at designing my own stuff. I probably won't ever be able to wrap my head around it, nor do I really want to. This kind of work really is inspiring, getting me out of bed each morning to go to class to learn about this stuff. Which reminds me, I have to get to bed soon so I can get to my catch-up lab tomorrow morning so I don't fail this course so I can get my BSc. in EE in the normal allotted time. 
	

	
	
		
		

		
		
	


	




 I just finished a lab today on opamps, one of the first times in my degree where I really took an interest in what I was learning (since it overlaps with this DIY thing I dabble in ). Very interesting stuff. Only 3 more years to go. 
	

	
	
		
		

		
		
	


	




 You rock, Colin!_

 

It's just a board..nothing more..nothing less. JW


----------



## amphead

Don't forget its Colins' blood, sweat and late nights! And the reason we have all come to this party!


----------



## ruZZ.il

Happy birthday Rob! 
	

	
	
		
		

		
		
	


	



 (fordgtlover)


----------



## BoilermakerFan

Quote:


  Originally Posted by *John Wilson* /img/forum/go_quote.gif 
_My jaw keeps hitting the floor! WOW!! And it's only been alive four hours! I wish you could hear #2. It's perfect, and so musical. You have to try the BG FK's 1000 uf 16V in CA2L/R with the BG 0.47 bypassing them. Trust me on this. Vishay's and Caddock's are the way to go in this one. No kidding. JW_

 

In which locations did you use the Caddock resistors?


----------



## tomb

Quote:


  Originally Posted by *BoilermakerFan* /img/forum/go_quote.gif 
_In which locations did you use the Caddock resistors?_

 

From his pics on pg. 399 and 401 (that one's quoted in your post 
	

	
	
		
		

		
			





 ), it looks like all of them except the heater, LED, and DB power output resistors.
	

	
	
		
		

		
		
	


	




 EDIT:
 And I thought the Mills resistors on the DB outputs were expensive ... those Caddocks are ~$7 a piece!!


----------



## John Wilson

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_From his pics on pg. 399 and 401 (that one's quoted in your post 
	

	
	
		
		

		
		
	


	




 ), it looks like all of them except the heater, LED, and DB power output resistors.
	

	
	
		
		

		
		
	


	




 EDIT:
 And I thought the Mills resistors on the DB outputs were expensive ... those Caddocks are ~$7 a piece!! 
	

	
	
		
		

		
		
	


	





_

 

You are correct. All the 1K ohm...8 total, are the Vishay S102's. JW


----------



## joneeboi

Quote:


  Originally Posted by *John Wilson* /img/forum/go_quote.gif 
_It's just a board..nothing more..nothing less. JW_

 

You're right. There really isn't anything special about this board that would make anyone's "jaw keep hitting the floor."

 One man's garbage...


----------



## John Wilson

Quote:


  Originally Posted by *joneeboi* /img/forum/go_quote.gif 
_You're right. There really isn't anything special about this board that would make anyone's "jaw keep hitting the floor."

 One man's garbage..._

 

I was patiently waiting for this. Please don't over analyzes my statement. I was joking with BMF. JW


----------



## joneeboi

BMF...bad motor finger? bone marrow foundation? Belgian MoOo Farm? BMF - What does BMF stand for? Acronyms and abbreviations by the Free Online Dictionary.

 Apologies if I misunderstood your statement. I've learnt the hard way that the lack of tone of voice and body language makes it harder to joke on the internet.

 But yeah, isn't the MAX board so cool?


----------



## Daveze

BMF => Boilermakerfan? Or maybe Bad Mother Fire-trucker? Big Mal the Fishmonger?


----------



## BoilermakerFan

Quote:


  Originally Posted by *Daveze* /img/forum/go_quote.gif 
_BMF => Boilermakerfan? Or maybe Bad Mother Fire-trucker? Big Mal the Fishmonger?_

 

Yep, that's me, BMF. I love my username, but it is rather long and BMF can be interpreted in a few funny ways, so I've always just signed my posts with -BMF

 My favorite was one somebody posted on another forum, a homebrew forum to be precise, which was Belgian Malted Frosty. I liked that one the best since I tend to favor the Belgium brews...

 Thanks to Tom and JW for pointing out that it was all of them except for the Vishays, I'm a newbie, so I didn't want to make assumptions, but I can almost populate two MAX boards with Muse ES, Muse KZ or Silmic caps; VitQs; and RD55 Vishay-Dale resistors for what JW was willing to spend on just resistors. I'm ok with that, as I'm sure JW is too. I need to build (4) MAX boards, (2) Phono stages, and (2) DACs so I'm trying to get the best bang for the dollar. Oh, I almost forgot to add the (2) pairs of speakers, a sub, and(4) stereo tube buffered gainclone amps too. 

 JW, are you going to replace either of your volume pots with a LDR from SKA? I'm planning to use the SKA LDR kit on my Silmic/VitQ/2238 DB build just to see how different it sounds from a ALPS on the same unit.

 - BMF


----------



## amphead

Quote:


  Originally Posted by *John Wilson* /img/forum/go_quote.gif 
_I was patiently waiting for this. Please don't over analyzes my statement. I was joking with BMF. JW_

 

Sorry man.....seems I'm too touchy when it comes to the MAX!


----------



## John Wilson

Quote:


  Originally Posted by *BoilermakerFan* /img/forum/go_quote.gif 
_JW, are you going to replace either of your volume pots with a LDR from SKA? I'm planning to use the SKA LDR kit on my Silmic/VitQ/2238 DB build just to see how different it sounds from a ALPS on the same unit.

 - BMF 
	

	
	
		
		

		
		
	


	


_

 

Maybe sometime in the future. A good pot is VERY important. JW


----------



## ruZZ.il

good pot is important


----------



## fran

Without wanting to pee anyone off here or affect anyones business - IMHO the LDR is clearly head and shoulders above an alps blue. So much better it ain't even funny. I have one now installed in a valve pre and also in my new 24V aikido HPA. They work perfectly and sound very clear. When I did a comparison the alps sounded muffled by comparison. And that was just with a MP3 player and crappy POS speakers in the workshop.

 A decent stepped pot might give it a better run for its money. The other thing about the LDR is that it is very quiet, ie no added noise. No grounding issues either as the pot is isolated from the circuit and only supplies voltage to the LDRs.

 Of course, this won't fit on the max PCB - and I'm not sure if it would fit in one of the hammond cases either. Its not big, but I'm not familiar with those cases. It would be smaller than most stepped pots. Thinking about it, it would be about the same height and depth as the alps pot, but would be wider. There are also input and output wires, PS wiring and a ground wire too. 

 Fran


----------



## pinkfloyd4ever

What's LDR? All I could find was light dependent resistor and I'm pretty sure that's not it


----------



## fran

Yes, thats it!

 The idea is like this:

 A resistor in the signal path will attenuate that signal. This is basically what the LDR does, except the resistor that is soldered in, is a special Light Dependent Resistor (LDR) which according how much light is shone on it by a LED can vary it's resistance, so you can have control over the level of music by controlling the amount of brigtness of the LED by a pot which varies the voltage going to the LED. (substantially taken from a post in that thread)

 The PITA bit of putting one of these together is that the LDR must be matched for each side and you need to buy a bunch of them to get closely matched ones. Thats why the kit is such a bonus. So the built kit is then powered from your main supply, with an appropriate resistor to adjust for the voltage you have to hand. 

 Theres a looong thread over on diyaudio:

LDR thread - diyaudio

 The kit is available from SKA Audio and he calls it optivol. There is a thread on the ska audio forum about it too.

 Disclaimer: I'm not in any way connected with the site - just happy customer and think thats its a great solution to a high quality pot for just AUS$27 (which by my calculation is about USD25).

 Fran


----------



## BoilermakerFan

Quote:


  Originally Posted by *fran* /img/forum/go_quote.gif 
_Yes, thats it!

 The idea is like this:

 A resistor in the signal path will attenuate that signal. This is basically what the LDR does, except the resistor that is soldered in, is a special Light Dependent Resistor (LDR) which according how much light is shone on it by a LED can vary it's resistance, so you can have control over the level of music by controlling the amount of brigtness of the LED by a pot which varies the voltage going to the LED. (substantially taken from a post in that thread)

 The PITA bit of putting one of these together is that the LDR must be matched for each side and you need to buy a bunch of them to get closely matched ones. Thats why the kit is such a bonus. So the built kit is then powered from your main supply, with an appropriate resistor to adjust for the voltage you have to hand. 

 Theres a looong thread over on diyaudio:

LDR thread - diyaudio

 The kit is available from SKA Audio and he calls it optivol. There is a thread on the ska audio forum about it too.

 Disclaimer: I'm not in any way connected with the site - just happy customer and think thats its a great solution to a high quality pot for just AUS$27 (which by my calculation is about USD25).

 Fran_

 

Based on pic on SKA for his LDR, it definitely will not fit in the standard Hammond MAX case, but you should be able tomake it fit in the 2" longer case without too much difficulty. The pic of the SKA LDR in the forum thread shows how tiny it actually is.


----------



## John Wilson

Light Dependent Resistors Light Dependent Resistor - Electric Circuit http://www.biltek.tubitak.gov.tr/gel..._NSL19_M51.pdf


----------



## amphead

LDR, sounds like an interesting mod for the MAX. I'm certainly tempted to try it. If the standard MAX hammond case is modified a little, it should fit. Using MrMajestic2s case would seem to fit even easier. Ouch my wallet.


----------



## BoilermakerFan

Quote:


  Originally Posted by *amphead* /img/forum/go_quote.gif 
_LDR, sounds like an interesting mod for the MAX. I'm certainly tempted to try it. If the standard MAX hammond case is modified a little, it should fit. Using MrMajestic2s case would seem to fit even easier. Ouch my wallet. _

 

I think it will fit in the longer case, with room for the Alien DAC on the other side. Just have to remote mount the potentiometer to the front.


----------



## mik000000

I have finished my max otherthan the tube sockets. Can i apply power to check voltages (and tube led brightness) without tubes installed? or will that damage the transistors?


----------



## tomb

Quote:


  Originally Posted by *mik000000* /img/forum/go_quote.gif 
_I have finished my max otherthan the tube sockets. Can i apply power to check voltages (and tube led brightness) without tubes installed? or will that damage the transistors?_

 

It won't damage anything, but you won't have any voltage through the buffer without the tubes. Unlike the revMH Millett, though, which took the LED power from the heater circuit, the MAX's will light up fine without the tubes.

 EDIT: Scratch that. You will get voltage through the buffers, but it will be greatly reduced. That makes it dangerous to attempt biasing the buffers. The MAX I just checked had almost a 30mV difference between no tubes and with tubes - with the complete w/tubes condition having a much higher bias reading.


----------



## tomb

*Volume Pots -*
 The Opti-Vol could be an interesting option for those ultimate MAX builds or for anyone who's contemplating wiring an offboard pot. However, it's probably for someone who's interested in an advanced build. Besides the fit problem - as Fran mentioned , you have to power it too: + and - 15VDC @ 13ma. As best I can tell, Gary Ball is referring to -15VDC and +15VDC. I don't know that for sure, but looking at his other stuff, when he quotes "+/- VDC," he's also referencing AC and CT transformer options. That makes me think he's really talking a voltage divider from a 30VDC supply. I could be wrong about that - because obviously, Fran has one working. If true, though, it would be very difficult to get that kind of voltage from a regular MAX. 

 For those wishing to compare with the ALPS and other pots, Tangent's tests are here: http://www.tangentsoft.net/audio/misc/pot-curves.zip

 If you are interested in looking at Tangent's spreadsheet in that zip file, the formula for minimum dB is LOG(E2)*20, where "E2" is the cell on the ALPS worksheet tab. For some reason, Tangent left that off of the ALPS sheet. For instance, the minimum dB range (volume range) for the Panasonic EVJ is -43.5dB. One of those fake ALPS attenuators is -48dB, while a DACT CT2 is -46dB. When you plug that equation into the ALPS page, it results in 84.3dB, easily the best of the lot. The SKA Opti-Vol quotes a dB control range of 50dB.

 The average channel difference is much better on the DACT and even the fake ALPS Stepped Attenuators. That could be the reason stepped attenuators seem to sound better, but I'm no expert on pots. It does seem that the ALPS tests quieter than the rest. It would be nice to see some tested data on the Opti-Vol.

 Another thing to consider - part of the reason the ALPS is nicknamed the "Blue Velvet" is the feel that you get when turning the knob. One of the features of the Opti-Vol is its inexpensive potentiometer. I believe that means you would give up the positive feel of the ALPS, but not having tried an Opti-Vol, I can't say that for certain. Looking at the pics, though, it looks like a push-on type shaft. It's possible he may be able to substitute something different, but I don't know.

 I'm not trying to be skeptical per se, just mentioning some of the things that perhaps should be considered before anyone goes abandoning the long-accepted ALPS. 
	

	
	
		
		

		
			





*MiniMAX -*
 The Opti-Vol will not fit in the MiniMAX, btw, which will have precious little room for anything but the specified parts in the Lansing case. Colin has been working on the board design lately, btw - we've traded comments on a couple of layouts. He is currently working on making sure the new, smaller 0.18uf Vitamin Q's will fit without tombstoning or kneeling. The new MiniMAX board will also accomodate 0.22uf Wima's all around, something different than the proto, which used 0.1uf's. The 0.22uf's impart a bit more smoothness.

 As for the 0.18uf 96P series VitaminQ, I've been testing it lately with an ES version MAX. When using FK6 tubes, it closely approaches the detail of Black Gates - _very closely_. So, I may be editing some of the "Can't Miss Builds" a bit.
	

	
	
		
		

		
		
	


	




*MAX Review -*
 Meanwhile, you might check out the nice Mini-Review Colin found in the Head-Fi Amplifiers section. I was hoping he'd post it himself, but maybe he's been too busy with school and work lately. He and I have both been a little sick of late and you know how that puts you behind with work and school.
	

	
	
		
		

		
		
	


	




Mini Review: PPX3 and Bada PH-12 with comparisons to the Millet Max 

 I wonder if that was user Listen2This's MAX? I think he helped organize that Lawrence, Kansas meet.


----------



## Fitz

Quote:


  Originally Posted by *ruZZ.il* /img/forum/go_quote.gif 
_good pot is important 
	

	
	
		
		

		
		
	


	


_

 

Indeed.


----------



## mik000000

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_It won't damage anything, but you won't have any voltage through the buffer without the tubes. Unlike the revMH Millett, though, which took the LED power from the heater circuit, the MAX's will light up fine without the tubes.

 EDIT: Scratch that. You will get voltage through the buffers, but it will be greatly reduced. That makes it dangerous to attempt biasing the buffers. The MAX I just checked had almost a 30mV difference between no tubes and with tubes - with the complete w/tubes condition having a much higher bias reading._

 

understood, but i can verify the power supply stage, and get the led's working before i solder in the tube sockets?


----------



## tomb

Quote:


  Originally Posted by *mik000000* /img/forum/go_quote.gif 
_understood, but i can verify the power supply stage, and get the led's working before i solder in the tube sockets?_

 

YEP


----------



## kvant

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_...you have to power it too: + and - 15VDC @ 13ma. As best I can tell, Gary Ball is referring to -15VDC and +15VDC. I don't know that for sure, but looking at his other stuff, when he quotes "+/- VDC," he's also referencing AC and CT transformer options. That makes me think he's really talking a voltage divider from a 30VDC supply. I could be wrong about that - because obviously, Fran has one working. If true, though, it would be very difficult to get that kind of voltage from a regular MAX._

 

I haven't seen the schematic of the OptiVol, but I think that it is reasonable to assume that you could power it single rail and lift the signal up between the rail and ground with a capacitor and a couple of resistors. The rail we have on board here should be just fine to power it then.

  Quote:


 Another thing to consider - part of the reason the ALPS is nicknamed the "Blue Velvet" is the feel that you get when turning the knob. One of the features of the Opti-Vol is its inexpensive potentiometer. I believe that means you would give up the positive feel of the ALPS, but not having tried an Opti-Vol, I can't say that for certain. 
 

Well, I have a bunch of Panasonic EVJs and they feel pretty good too. Anyway, is the feeling while turning the knob that important feature of a pot? Besides that, there is another pot from ALPS known as Black Beauty. I don't know what is beautiful about it, but since it is typically hidden inside an enclosure, you don't get to admire it too often. I guess there is only that much information in a nickname.


----------



## tomb

Quote:


  Originally Posted by *kvant* /img/forum/go_quote.gif 
_I haven't seen the schematic of the OptiVol, but I think that it is reasonable to assume that you could power it single rail and lift the signal up between the rail and ground with a capacitor and a couple of resistors. The rail we have on board here should be just fine to power it then._

 

Yes, if there were 30VDC to work with - there's not unless you build a transformer-supplied MAX. I did mention a voltage divider - again, another reason why I stated perhaps it's an advanced build.
  Quote:


 Well, I have a bunch of Panasonic EVJs and they feel pretty good too. Anyway, is the feeling while turning the knob that important feature of a pot? Besides that, there is another pot from ALPS known as Black Beauty. I don't know what is beautiful about it, but since it is typically hidden inside an enclosure, you don't get to admire it too often. I guess there is only that much information in a nickname. 
	

	
	
		
		

		
		
	


	



 

Perhaps the push-on shaft is enough to bother your sensibilities?
	

	
	
		
		

		
		
	


	







 For what it's worth, I agree that the EVJ has a nice feel as long as you're not looking at it.


----------



## kvant

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Yes, if there were 30VDC to work with - there's not unless you build a transformer-supplied MAX. _

 

I don't quite understand this statement. What voltage do you have after the regulator? 27V? There is surely enough wiggle room with the OptiVol so that 27V will do. I mean, the signal we are attenuating is line-level, some 3V peak, so there is hardly a real need for such a high rail. That +/-15V is probably just a convenient value, which is typically available in a preamp.

  Quote:


 Perhaps the push-on shaft is enough to bother your sensibilities?
	

	
	
		
		

		
		
	


	






 

Well, yes, that looks... ugly. But then again, chances are that one can buy a pot with slightly different part number that will be absolutely equivalent, just with a more convenient shaft.


----------



## tomb

Quote:


  Originally Posted by *kvant* /img/forum/go_quote.gif 
_I don't quite understand this statement. What voltage do you have after the regulator? 27V? There is surely enough wiggle room with the OptiVol so that 27V will do. I mean, the signal we are attenuating is line-level, some 3V peak, so there is hardly a real need for such a high rail. That +/-15V is probably just a convenient value, which is typically available in a preamp._

 

I'm certainly no expert on the Opti-Vol. If you state that it will perform to specifications with only +/-13.5V, then I won't dispute that.
	

	
	
		
		

		
		
	


	




  Quote:


 Well, yes, that looks... ugly. But then again, chances are that one can buy a pot with slightly different part number that will be absolutely equivalent, just with a more convenient shaft. 
 

Well, yes - but doesn't that get you back into the selection-of-a-quality-pot business all over again?


 EDIT: It wasn't my intent to debate about this - only to offer some opposing items that didn't seem to be considered. It might be an interesting thing to try.


----------



## kvant

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_If you state that it will perform to specifications with only +/-13.5V, then I won't dispute that.
	

	
	
		
		

		
		
	


	


_

 

Just found a post by Greg Ball on his forum that clears the fog, check post #125 at 'http://ska-audio.com/Forum/YaBB.pl?num=1178438672/120'


----------



## fran

On the optivol:

 You only need single rail voltage. The standard kit comes with a current limiting resistor sized for 30VDC supply - which is whats available in Gregs other DIY amp offerings. It will work of any supply >6VDC - you just need to resize that resistor. If you want to do that, you know that the thing needs 13mA, you will know your voltage, plug the 2 into an online ohms law calculator and it will give you the right resistor. I told Greg what I wanted it for and he included the appropriate resistor in the kit for me. I am using one in my 24V aikido (at 24V) and I'm using another in a valve preamp and I have it running off the 6.3VDC heater supply. Both work perfectly.

 So to summarise:

 1. Single rail voltage anywhere from 6VDC upwards. Cleaner the supply the better. Resize resistor to suit voltage.

 2. The pot is a basic one, but feels pretty OK to me. Don't think you would really notice it any different to an alps blue if you weren't told. Feels way better than a stepped pot.

 3. It is a simple push-on type splined pot, if you want to use a knob with screw fixing you may need to slip a shim into the slot in the shaft to stop it closing under the screw.

 4. It is very easy to build, certainly if you can build a max you can do this.

 5. It most likely won't fit in the standard hammond case, but since I don't have one I can't say for sure. It might just clear the board but that wouldn't leave you much room for in/out wiring.

 6. Cost seems to be AUS$28 which from XE.com turns into US$25. Way cheaper than a stepped pot and not that much more than a alps blue ($16+shipping)


 As usual YMMV. Not on a crusade here or anything! Alps pot is very well supported and thought of here and elsewhere. I suppose this would be good for someone who wanted to do something a little different or who had used the alps before and would like to experiment a bit. 


 Fran


----------



## Ampersand

forgive me for butting in, but what was the concensus on best moderate-to-low gain tube for the MAX? I remember reading in one of these posts, but i can't remember now if it was the 12Fm6 or 12Fk6. I know the 12fk6 has the higher gain, but is one slightly better than the other for overall sound? I'm currently running the Can't Miss Build #1 through Grados. 

 Thanks,
 mike


----------



## fran

I've just been outside doing some other work and a light bulb lit over my head:

 The optivol can easily be made to fit the case. The pot can be mounted as usual on the front panel and then just fly wire it to the optivol PCB. Fully built as stock, it measures 50mm by 25mm (2" x 1").

 Wiring it:

 1. your power supply: + and PS ground.

 2. Left - hot and ground in and out

 3. Right - ground in and out

 4. Another ground wire which connects the ground plane of the PCB to your main PS ground.

 If you are fly wiring it, just a matter of 3 wires to essentially extend the legs of the pot.

 Fran


----------



## tomb

Quote:


  Originally Posted by *Ampersand* /img/forum/go_quote.gif 
_forgive me for butting in, but what was the concensus on best moderate-to-low gain tube for the MAX? I remember reading in one of these posts, but i can't remember now if it was the 12Fm6 or 12Fk6. I know the 12fk6 has the higher gain, but is one slightly better than the other for overall sound? I'm currently running the Can't Miss Build #1 through Grados. 

 Thanks,
 mike_

 

By all means - butt in. It'd be nice to get back to discussing the MAX. 
	

	
	
		
		

		
			








 The 12FK6 has the lowest gain of all of the Millett tubes. Chances are you'd want those for Grados. Here's the list:

*Tube*....*Amplification Factor(gain)*
 12FK6.........7
 12FM6........10
 12AE6/A......14

 Now, the actual results in the MAX are quite a bit lower and depend on the impedance of the load - but that gives you the breakout comparison among the tubes.

 As for detail/bass slam, the 12FK6 has the most detail and "air", while the 12AE6/A has the most bass slam. The 12FM6 is sort of inbetween, but probably closer to the 12AE6 in my experience. These are very generalized listening experiences, of course.


----------



## fran

we are discussing the max


----------



## Ampersand

Right, the 12fk6 has the lowest gain - what i meant to type. And in fact, these are my current tubes. Just wasn't sure if people preferred the FM's over the FK's if there wasn't a preference for gain.


----------



## tomb

Quote:


  Originally Posted by *fran* /img/forum/go_quote.gif 
_we are discussing the max_

 

Actually, we've been discussing pots for so long that I've had people PM'ing me for help on their MAX instead of posting in this thread. This was because they didn't think we were providing support anymore.

 Ampersand might've been another case of that, since he "apologized for butting in." You'll just have to forgive me if I get a bit concerned when I start seeing comments and PM's like that.
	

	
	
		
		

		
		
	


	




  Quote:


  Originally Posted by *Ampersand* 
_Right, the 12fk6 has the lowest gain - what i meant to type. And in fact, these are my current tubes. Just wasn't sure if people preferred the FM's over the FK's if there wasn't a preference for gain._

 

I think you'll find that MAX builders run the gamut on tubes. Everyone has a favorite. Generally speaking, though, the differences run as I mentioned in the previous post - it just depends on which you prefer and how those tube tendencies match up with your headphones.


----------



## Ampersand

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_I think you'll find that MAX builders run the gamut on tubes. Everyone has a favorite. Generally speaking, though, the differences run as I mentioned in the previous post - it just depends on which you prefer and how those tube tendencies match up with your headphones. 
	

	
	
		
		

		
		
	


	


_

 

Great! I've been really enjoying this MAX build (my 2nd actually). Just wanted to make sure i wasn't missing something profound by using the 12fk6's.


----------



## BoilermakerFan

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_By all means - butt in. It'd be nice to get back to discussing the MAX. 
	

	
	
		
		

		
		
	


	





_

 

LOL! 
	

	
	
		
		

		
		
	


	




 I don't know, I think this is part of what makes the Millet hybrid and Colin's MAX design in particular so amazing. I haven't built mine yet, but based on all the posts and comments, I think it's safe to say it's a very good sounding amp if built to the standard BOM and it becomes a great sounding amp with relatively low cost upgrades. Then you can add another $100 and take it over the top of headphone amps that cost 3 to 10 times more. 

 I certainly know that nobody implied the design or BOM as spec'd was flawed and it requires a LDR to "fix" the problem. I'm planning t o build one with the LDR and two with the ALPS pots. I'll decide which volume attenuator I like the best with each individual build and decide if it's worth the $10 difference to add it to all the builds and reallocate the ALPS pots to better uses. It all comes down to my challenge of the best bang for the buck for my personal listening tastes. 

 The one potential "drawback" to the LDR that I saw was is it potentially limited attenuation that may not be low enough for certain speaker/amp combinations. This could potentially be an issue with easy to drive cans or IEMs like my Denon C700s, so that will be something I'll take into consideration for my office MAX console build. It's a non-issue for me since my gainclone amps will all be built on the LM3886 chip with mute, so I can just flip a switch to ground the mute pin and it will be quiet enough...

 And in my case, for at least two of my console builds, the push on volume pot is a benefit and very welcome because my vintage knobs are all push-on types! 

 But, as Tom pointed out, my builds fall into the "advanced" category and I won't using the stock BOM enclosure for at least 3 of them. 

 - BMF


----------



## BoilermakerFan

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Actually, we've been discussing pots for so long that I've had people PM'ing me for help on their MAX instead of posting in this thread. This was because they didn't think we were providing support anymore.

 Ampersand might've been another case of that, since he "apologized for butting in." You'll just have to forgive me if I get a bit concerned when I start seeing comments and PM's like that.
	

	
	
		
		

		
		
	


	


_

 

Missed your post when I was typing my last one, so I wasn't trying to pull it off topic any more. I am disappointed to hear that peeps thought they couldn't post their requests for help because they were afraid of interrupting a side discussion of the MAX building process.


----------



## tomb

Quote:


  Originally Posted by *BoilermakerFan* /img/forum/go_quote.gif 
_Missed your post when I was typing my last one, so I wasn't trying to pull it off topic any more. I am disappointed to hear that peeps thought they couldn't post their requests for help because they were afraid of interrupting a side discussion of the MAX building process._

 

Well, in truth - some of it has been the horsing around about John's expensive builds, but the pot discussion entered that, too. Regardless, your post didn't seem out of place to me.


----------



## Migroo

Hi guys.

 This has probably been covered before, so apologies. I've read through a great deal of this thread, but I've probably missed parts as its so long!

 I have a question on insulating the heatsinks. I've read the page on the MMax site - MAX Heat Sink Mounting but I'm still not too clear.

 Must I insulate the parts from the heatsinks, or is it optional? I have some thermal compound, but I guess that isn't the issue...


----------



## ruZZ.il

Quote:


  Originally Posted by *Migroo* /img/forum/go_quote.gif 
_Hi guys.

 Must I insulate the parts from the heatsinks, or is it optional? I have some thermal compound, but I guess that isn't the issue..._

 


 It's optional, but heavily advised! to the point that one could define it as a mandatory precautionary measure. Thermal pads should be put between the transistor and the heatsink and depending on the transistor type, possibly insulating shoulder washers too. What type of transistors are you using?


----------



## BoilermakerFan

Quote:


  Originally Posted by *Migroo* /img/forum/go_quote.gif 
_ I have some thermal compound, but I guess that isn't the issue..._

 

I'd be careful there too, as Artic Silver is a very common CPU thermal compound, but it is conductive and could cause problems if you plan to use it or a similar compound.


----------



## Migroo

I got a kit from Jeff Rossel at Glass Jar Audio - so I believe I have:

 LM317T for power supply regulator
 QB8L/R = MJE243 NPN power transistor
 QB9L/R = MJE253 PNP power transistor

 Thanks!
 Chris


----------



## Thomas_K

Seems like a nice little amp this. I have sent an e-mail to Jeff to inquire about shipping costs. 

 In the meantime i have been looking for a wall wart to power the thing with, but i can't find anything locally. I do however have a few toroidal transformers lying around. A 230V primary with 2x 24V secondary windings should be good, should it not? Or maybe one with 2x12V secondary windings and couple them in series to get the required 24V. I have both 2x12V and 2x24V available. Both are 20VA. Can i use one of these, or do i need something more powerful?


----------



## tomb

Quote:


  Originally Posted by *Migroo* /img/forum/go_quote.gif 
_I got a kit from Jeff Rossel at Glass Jar Audio - so I believe I have:

 LM317T for power supply regulator
 QB8L/R = MJE243 NPN power transistor
 QB9L/R = MJE253 PNP power transistor

 Thanks!
 Chris_

 

Yeah, the guys are right on this. The MJE243/253's have a metal back, so they will come into contact with the heat sink. There's anodizing involved, but the screw, lockwasher and nut sort of mess that up in terms of insulating.

 In the MAX, the heat sinks sit on the ground plane. So, any slight scratch in the anodizing or in the PCB's green mask (green mask controls solder, it doesn't insulate) could make contact with the heat sink. If the transistor is not insulated from the sink, then you could potentially have a short if anything touches the sinks - like your DMM probe, your biasing screwdriver, the case lid, etc.


----------



## tomb

Quote:


  Originally Posted by *Thomas_K* /img/forum/go_quote.gif 
_Seems like a nice little amp this. I have sent an e-mail to Jeff to inquire about shipping costs. 

 In the meantime i have been looking for a wall wart to power the thing with, but i can't find anything locally. I do however have a few toroidal transformers lying around. A 230V primary with 2x 24V secondary windings should be good, should it not? Or maybe one with 2x12V secondary windings and couple them in series to get the required 24V. I have both 2x12V and 2x24V available. Both are 20VA. Can i use one of these, or do i need something more powerful?_

 

You'd need to wire the 2X12 in series or the 2x24 in parallel, but other than that, 20VA at 24V should be 833ma, enough for most BJT MAXes that top out at 50-60ma buffer bias.


----------



## Thomas_K

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_You'd need to wire the 2X12 in series or the 2x24 in parallel, but other than that, 20VA at 24V should be 833ma, enough for most BJT MAXes that top out at 50-60ma buffer bias. 
	

	
	
		
		

		
		
	


	


_

 

Thanks, *tomb*.
 I guess, since i have everything i need, i'll be ordering a MAX from Jeff tomorrow. Or maybe two..


----------



## fran

Absolutely the last thing I'd want is for anyone to be scared off asking a Q here. Thats what the thread is for!! and may I say, it is _*absolutely singular*_ in the DIY world IMHO. Nowhere do you get this kind of help and variety of builds. The very fact that there are so many different builds leads to huge levels of info and experience with the max and makes it an even better amp - no easy feat. I know the max is not advertised as a first time build, but with the help here, and primarily from TomB, it could be. Did I mention that its a great amp too! 

 A back-on-topic Q: last time I bought some tubes, the 12fm6 were out of stock in my usual places. Is this a harder to find tube do you think or did I just hit a scarce patch? Funny thing is I would like to lay hands on a pair, even though when I built my max I put in the 12FK6 first and have yet to change them out for the 12AE6 even though I said I would at the time. They sound very good.


 OT: Side discussions can be helpful too - even if they do take up 17 posts out of 4069. 

 Fran


----------



## pinkfloyd4ever

fran, check ebay


----------



## cronic

Anyone looking for heatsink mounting options, I suggest taking a look at the HiQ Heat Sink Mounting Kit at beezar.com. I used them in my build and they are absolutely top notch. I should also add that everything I have gotten from beezar.com has been incredible. 
	

	
	
		
		

		
		
	


	




 At this point I have 450 plus hours on the max and 701s. It is unbelievable how great this setup sounds.


----------



## tomb

Quote:


  Originally Posted by *fran* /img/forum/go_quote.gif 
_Absolutely the last thing I'd want is for anyone to be scared off asking a Q here. Thats what the thread is for!! and may I say, it is *absolutely singular* in the DIY world IMHO. Nowhere do you get this kind of help and variety of builds. The very fact that there are so many different builds leads to huge levels of info and experience with the max and makes it an even better amp - no easy feat. I know the max is not advertised as a first time build, but with the help here, and primarily from TomB, it could be. Did I mention that its a great amp too! 

 A back-on-topic Q: last time I bought some tubes, the 12fm6 were out of stock in my usual places. Is this a harder to find tube do you think or did I just hit a scarce patch? Funny thing is I would like to lay hands on a pair, even though when I built my max I put in the 12FK6 first and have yet to change them out for the 12AE6 even though I said I would at the time. They sound very good.


 OT: Side discussions can be helpful too - even if they do take up 17 posts out of 4069. 

 Fran_

 

Fran,

 Those are very kind words. Thank you very much.

 About the 12FM6's - yes, they are getting very rare. They've always been that way, but with the popularity of the Millett and now the MAX, even more so. If you've had a chance to read the thread all the way from the beginning, you'll see that MAX builders personally cleaned out a couple of vendors of 12FM6's. Phil at Radio Daze even sent me a personal e-mail requesting that I tell everyone - among other things (a very nice e-mail, btw).

 YGPM.


----------



## tomb

Quote:


  Originally Posted by *cronic* /img/forum/go_quote.gif 
_Anyone looking for heatsink mounting options, I suggest taking a look at the HiQ Heat Sink Mounting Kit at bezzar.com. I used them in my build and they are absolutely top notch. I should also add that everything I have gotten from bezzar.com has been incredible. 
	

	
	
		
		

		
		
	


	




 At this point I have 450 plus hours on the max and 701s. It is unbelievable how great this setup sounds._

 

Thanks for the plug, cronic! However, it's *beezar*.com.

 Glad you are enjoying your MAX - thanks again!


----------



## Migroo

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Yeah, the guys are right on this. The MJE243/253's have a metal back, so they will come into contact with the heat sink. There's anodizing involved, but the screw, lockwasher and nut sort of mess that up in terms of insulating._

 

Hi Tom (And others who responded) - thanks.

 I've ordered some insulating kits.

 I'll post up pics when I'm done


----------



## jarensberg

Hi all! I'm been lurking for a while and need some help.

 I'm finishing up my second MAX and got everything in and had a gray moment while doing the initial DB bias. I had my meter on AC voltage instead of DC. When I finally noticed that and switched to DC the reading was high (around 200mv or so). i quickly powered everything off and reset the trimmers all the way down. Now I can't get less than 70 mv or so. So, how bad did I fry things?

 Thanks in advance


----------



## BoilermakerFan

Quote:


  Originally Posted by *fran* /img/forum/go_quote.gif 
_I know the max is not advertised as a first time build, but with the help here, and primarily from TomB, it could be._

 

It will be a first time build for me! But, I'll be building three at the same time, so does that make it easier or harder? 

  Quote:


  Originally Posted by *fran* /img/forum/go_quote.gif 
_A back-on-topic Q: last time I bought some tubes, the 12fm6 were out of stock in my usual places. Is this a harder to find tube do you think or did I just hit a scarce patch? Funny thing is I would like to lay hands on a pair, even though when I built my max I put in the 12FK6 first and have yet to change them out for the 12AE6 even though I said I would at the time. They sound very good.

 Fran_

 

I found a source in the States that had them, but they wanted over $20 a piece for them. I actually was the one who bought the very last tube from Radio Daze. I ordered 4 and was only shipped 1. 
	

	
	
		
		

		
		
	


	




 A member here is working to help me out and try to match up a tube with my existing one... Speaking of which, I need to go take a pic of that lone tube!


----------



## joneeboi

I don't know if you necessarily fried anything. The fact that you get a voltage at all is a good sign. Set it to 110mV or so and see if you can get sound at the output.


----------



## manaox2

I'm checking out Beezar.com and working out what to order. I want to build a reasonable quality (high, but don't have a budget for good stepped attenuators) BALANCED Millett Max. I'm planning to order enough extra parts to make an extra SE Millett Max for if or maybe I think when I might mess up.

 I don't have much over $900 to spend on this project alone, this seems like an good challenge for a first time amp builder. I am still greedy and want the Bass slam and good highs... I am wondering about blackgates or nicholen muse caps bypassed with a good film cap, and I know the gain is going to be kind of high with even the 12fk6 tubes, but don't want to add resistors that would lower dynamics. 

 Based on what I think I will also use two rk27 Alps Blue Velvet pots, Neutrik combo xlr jacks, and a standard drop power unit with a switch. I got great advice (thanks pabbi1) on a Nabu casing to separate the transformer from the boards and have enough room.

 I'm going to try to start ordering parts on April 2nd and don't want to go too far all over the place for shipping. I'm going to be ordering two 2 toroids - one an OPUS DAC to make my source and the other to power the amp boards. I 

 I'm going to be deciding next on what transistors to order. I'd appreciate any tips others can give me, this DIY amp has the best community and support which makes me really put my faith it it.


----------



## tomb

Quote:


  Originally Posted by *joneeboi* /img/forum/go_quote.gif 
_ Quote:


  Originally Posted by *jarensberg* 
Hi all! I'm been lurking for a while and need some help.

 I'm finishing up my second MAX and got everything in and had a gray moment while doing the initial DB bias. I had my meter on AC voltage instead of DC. When I finally noticed that and switched to DC the reading was high (around 200mv or so). i quickly powered everything off and reset the trimmers all the way down. Now I can't get less than 70 mv or so. So, how bad did I fry things?

 Thanks in advance

 

I don't know if you necessarily fried anything. The fact that you get a voltage at all is a good sign. Set it to 110mV or so and see if you can get sound at the output._

 

Yes - Joneeboi is probably correct. You'll get up to 40mV or more with the trimmers at dead zero. If you only screwed them down 20 turns instead of 25 turns, then 70mV may still be OK.

 I'm with Joneeboi - see if you can start adjusting upwards and they change accordingly - go 5-10mV at a time until you get to 90-100mV. Let it sit there for a few hours, checking it every once in awhile and listening to the sound. If all's well, then boost it up to 110mV - you're done!

 They should be able to take 200mV for short periods. That's on the low side for MOSFETs, for instance, but we normally recommend 1-1/2" sinks in that case. Still, it's not that bad - assuming you don't find something wrong.


----------



## tomb

Quote:


  Originally Posted by *manaox2* /img/forum/go_quote.gif 
_I'm checking out Beezar.com and working out what to order. I want to build a reasonable quality (high, but don't have a budget for good stepped attenuators) BALANCED Millett Max. I'm planning to order enough extra parts to make an extra SE Millett Max for if or maybe I think when I might mess up.

 I don't have much over $900 to spend on this project alone, this seems like an good challenge for a first time amp builder. I am still greedy and want the Bass slam and good highs... I am wondering about blackgates or nicholen muse caps bypassed with a good film cap, and I know the gain is going to be kind of high with even the 12fk6 tubes, but don't want to add resistors that would lower dynamics. 

 Based on what I think I will also use two rk27 Alps Blue Velvet pots, Neutrik combo xlr jacks, and a standard drop power unit with a switch. I got great advice (thanks pabbi1) on a Nabu casing to separate the transformer from the boards and have enough room.

 I'm going to try to start ordering parts on April 2nd and don't want to go too far all over the place for shipping. I'm going to be ordering two 2 toroids - one an OPUS DAC to make my source and the other to power the amp boards. I 

 I'm going to be deciding next on what transistors to order. I'd appreciate any tips others can give me, this DIY amp has the best community and support which makes me really put my faith it it. 
	

	
	
		
		

		
		
	


	


_

 

Welcome to the MAX! You're already talking to the best person about a balanced MAX with user pabbi. However, you might also talk to the fella that fixed it for him - Amphead. Between the both of them, you should end up with a fine amp. 
	

	
	
		
		

		
		
	


	




 Remember that the balanced version will double the gain, so the 12FK6 is definitely your best bet. Other than that, I don't know too much about balanced. Pabbi still owes us that article on how to build a Balanced MAX. 
	

	
	
		
		

		
		
	


	







 As for Beezar parts, I'll be putting up a 0.18uf 96P-series Vitamin Q shortly that pairs very, very well with Nichicon Muse ES's. It makes them sound very close to Black Gates. Motherone on DIYForums.org also has had great experience with the ES's using Xicon MKP's, of all things. So, the ES's can give great performance with the right bypass. They're pretty good with Wima's, too.

 As for transistors, my personal favorites are the Toshiba 2SC3422/2SA1359's. However, the Toshiba 2SC2238/2SA968's win the cult status as the most neutral-detailed/hardest-to-get. So hard, in fact, that I don't have them - neither does anyone else, AFAIK - and counterfeits are rampant, so be careful if you go to another source. I also think that the Sanyo 2SC2344/2SA1011's are very similar, but with a slight emphasis on the high end. That works well with the warmth of the tubes. I hope to have the MOSFET MAX option worked out by then and will be selling parts for those, too.

 ES's with those VitQ's in front and Wima's elsewhere, 12FK6's, and 2SC3422/2SA1359's is very hard to beat and not very expensive, either - at least $100 cheaper in parts than using Black Gates. Black Gates are very nice and unbeatable if you have the time for break-in and use them often (they will lose their break-in if you let them sit too long). So, take your pick, I guess.


----------



## manaox2

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_As for Beezar parts, I'll be putting up a 0.18uf 96P-series Vitamin Q shortly that pairs very, very well with Nichicon Muse ES's. It makes them sound very close to Black Gates. Motherone on DIYForums.org also has had great experience with the ES's using Xicon MKP's, of all things. So, the ES's can give great performance with the right bypass. They're pretty good with Wima's, too.

 ES's with those VitQ's in front and Wima's elsewhere, 12FK6's, and 2SC3422/2SA1359's is very hard to beat and not very expensive, either - at least $100 cheaper in parts than using Black Gates. Black Gates are very nice and unbeatable if you have the time for break-in and use them often (they will lose their break-in if you let them sit too long). So, take your pick, I guess. 
	

	
	
		
		

		
			






_

 

Thanks for the great summary, I've added it to my notes. I'll be happy to save the $100, capacitor rolling could be a future option. Thats great news about adding the 0.18uf VitaminQ's to Beezar, I remember reading about that discovery earlier too(I'm reading through the thread backwards currently). I'm really happy to be at the front line for the improvements, if only everything in DIY was this well researched as a community. 
	

	
	
		
		

		
		
	


	




 I'll try to contact Amphead tomorrow to ask about possible impending problems and the balanced implementation. If I get this done properly guys, I'll be happy to provide some notes on the experience.


----------



## joneeboi

I'm wondering if anyone, who bought those used 50VA wallwarts from Beezar, is getting crazy loud humming from the unit. I tried opening it up, but it really isn't cooperating. I wanted to just secure the toroid somehow that is fire-safe, but I couldn't even get it opened. Since I rearranged my room, it sits right next to where I listen to my music, and the sound can be transmitted well across the room (I switched out carpet for fake laminate hard wood). I can hear it everywhere, and now I have to start unplugging it, a hassle. Should I chop it open or buy a new one, find a new one in a dumpster, dip it in a vat of epoxy?


----------



## fault151

has anyone got any pics of the alien dac that they have made? Im thinking about making one. Was it a fairly easy build?


----------



## ruZZ.il

Quote:


  Originally Posted by *fault151* /img/forum/go_quote.gif 
_has anyone got any pics of the alien dac that they have made? Im thinking about making one. Was it a fairly easy build?_

 

here are some I have floating around:











 These are actually a little more than the standard board, with the additional board that helps mounting it securely in a hammond case, and with bypass caps on one too. basically, the build is pretty straight forward if you have steady hands and some tweezers. read through some techniques for smd soldering (tangents site for instance) and you should be ok. I use flood and absorb for the main chip (with solder wick braid).


----------



## fault151

cheers for the pics. How does the dac sound overall? It looks pretty small and compact.


----------



## tomb

Quote:


  Originally Posted by *joneeboi* /img/forum/go_quote.gif 
_I'm wondering if anyone, who bought those used 50VA wallwarts from Beezar, is getting crazy loud humming from the unit. I tried opening it up, but it really isn't cooperating. I wanted to just secure the toroid somehow that is fire-safe, but I couldn't even get it opened. Since I rearranged my room, it sits right next to where I listen to my music, and the sound can be transmitted well across the room (I switched out carpet for fake laminate hard wood). I can hear it everywhere, and now I have to start unplugging it, a hassle. Should I chop it open or buy a new one, find a new one in a dumpster, dip it in a vat of epoxy?_

 

Joneeboi, it's a code violation to even open one. I know that doesn't stop most of us DIY-er's, but you will more or less have to destroy one to open it up.

 It's quite possible that yours has gone bad. Since they're used, I plug everyone one of them in to test that they work and that there's not something unusual like you're describing. Nevertheless, they are used and there's a small chance that something like that can happen to them. I've personally used about 5 of them - have one at work with me now - and have never had a problem.

 Nevertheless, the supply has dried up. So I started carrying -brand new- versions of these monsters that are fully guaranteed (at a correspondingly higher price, unfortunately).


----------



## tomb

Quote:


  Originally Posted by *manaox2* /img/forum/go_quote.gif 
_Thanks for the great summary, I've added it to my notes. I'll be happy to save the $100, capacitor rolling could be a future option. Thats great news about adding the 0.18uf VitaminQ's to Beezar, I remember reading about that discovery earlier too(I'm reading through the thread backwards currently). I'm really happy to be at the front line for the improvements, if only everything in DIY was this well researched as a community. 
	

	
	
		
		

		
		
	


	




 I'll try to contact Amphead tomorrow to ask about possible impending problems and the balanced implementation. If I get this done properly guys, I'll be happy to provide some notes on the experience._

 

Forgot to mention the Russian K42 capacitors. Sound and quality go something like Wima -> K42 -> VitaminQ's. The K42's are not as detailed as the VitQ's, but have more punch. So, they make a good pairing with 12AE6's if you want the basshead treatment.


----------



## jarensberg

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Yes - Joneeboi is probably correct. You'll get up to 40mV or more with the trimmers at dead zero. If you only screwed them down 20 turns instead of 25 turns, then 70mV may still be OK.

 I'm with Joneeboi - see if you can start adjusting upwards and they change accordingly - go 5-10mV at a time until you get to 90-100mV. Let it sit there for a few hours, checking it every once in awhile and listening to the sound. If all's well, then boost it up to 110mV - you're done!

 They should be able to take 200mV for short periods. That's on the low side for MOSFETs, for instance, but we normally recommend 1-1/2" sinks in that case. Still, it's not that bad - assuming you don't find something wrong._

 

Thanks! I'll give it a shot and see how it goes.


----------



## Migroo

Hi guys

 Some progress tonight!

 I've also added the WIMA caps since taking the photo, but that can wait for another evening. This is a glass-jar audio kit 
	

	
	
		
		

		
		
	


	




 I'm just waiting for a couple of items to come in and I'm ready to go!

 Want to clarify something - I currently use a PSU which my Dad made a few years ago. It outputs DC (and can do 24v). According to Dad, putting DC into the Millet Max should be OK, but I wanted to check with you guys too. From what I can see, the DC will just pass through (half of) the bridge rectifier and into the amp without problem.


----------



## tomb

Quote:


  Originally Posted by *Migroo* /img/forum/go_quote.gif 
_Hi guys

 Some progress tonight!

 I've also added the WIMA caps since taking the photo, but that can wait for another evening. This is a glass-jar audio kit 
	

	
	
		
		

		
		
	


	




 I'm just waiting for a couple of items to come in and I'm ready to go!

 Want to clarify something - I currently use a PSU which my Dad made a few years ago. It outputs DC (and can do 24v). According to Dad, putting DC into the Millet Max should be OK, but I wanted to check with you guys too. From what I can see, the DC will just pass through (half of) the bridge rectifier and into the amp without problem._

 

Looks good so far!

 About the DC supply. What your Dad says is completely true, of course! However, there's the regulator to worry about. Quality, linear regulation is extremely important for the MAX because that supply voltage is carried throughout the rest of the amp with no more regulation - supplying heaters, tubes, and DB's. It has a great deal to do with the quality of sound produced by the MAX.

 Unfortunately, the LM317 will need to burn about 3 volts to give you linear regulation. That means you'll be down to 21VDC probably under load. Cut that in half (10.5VDC per tube), and it's not enough to support the minimum voltage needed by the heaters. _You need more voltage._

 The reason 24V*AC* is such an advantage is that when rectified and smoothed by the big power caps, the resulting DC voltage is (1.414 x 24) - 1.4 = *32.5VDC*. From there, the regulator burns its 3 Volts leaving a maximum of 29.5VDC to supply the MAX. We tune it down from there to 27VDC and burn a bit extra through the regulator heat sink. That's because there are variances in line level voltages from place to place in the US (some are 110VAC, others 120VAC). If the line voltage is not high enough, but you have the MAX board set to that ~29.5 maximum, you may lose that 2-3V burn through the regulator, and the supply may drop out of regulation. Setting it at 27VDC pretty much guarantees the regulator will always have plenty of volts to burn and that the MAX will always be under total linear regulation - ensuring good quality sound.


----------



## Migroo

Hi Tom,

 Thanks - an interesting read. I'll have to do some investigating and see how much voltage I can get out of this thing. Its currently happily powering my Pimeta at about 18v.

 If I have to find / buy a 24vAC wall wart it isn't the end of the world


----------



## ruZZ.il

I'm not sure the diodes can handle the full load cycle? Anyway, thats not the ideal way of powering it. The MAX could be adapted to work with an external DC supply but I wouldn't just feed it straight through. Inputting 24vdc through 2 diodes, through a regulator, etc will have quiet a voltage drop and a redundant regulator leaving you with less than 24v, far from ideal. You could probably leave out the diodes and regulator and patch the 24vdc straight in but you're still left with 24v. Just build up the PSU on the MAX and use a transformer. you'll get a solid 27~28Vdc and leave it as is, IMHO. unless you really cant find a trafo..

 edit: I'm beat, I cant compete, you're fit for the feat and just too damn neat! 
	

	
	
		
		

		
		
	


	




 (kudos for that)


----------



## tomb

Quote:


  Originally Posted by *ruZZ.il* /img/forum/go_quote.gif 
_edit: I'm beat, I cant compete, you're fit for the feat and just too damn neat! 
	

	
	
		
		

		
		
	


	




 (kudos for that)_

 

You got me beat on the poetry for sure.
	

	
	
		
		

		
		
	


	




 Nice to know you had my back, though.


----------



## slowpogo

I'm using a 1 amp Triad wall wart, with my BJT Max. Would there be any audible advantage to using one of the larger Beezar wall warts, or is it just more juice that my amp wouldn't use?


----------



## Marzie

Anyone have any extra superbright blue or violet LEDs for the tube lights? I didn't order them and if anyone has some or a source to get some fast (I will be checking my local place on the weekend) I am all ears!

 Mike


----------



## manaox2

What hookup wire is recommended for the Max from Navships? And is there any other wire that anyone recommends? Also, what heatstrink in the case of tombstoning? I may have to borrow a blowdryer...


----------



## jarensberg

Quote:


  Originally Posted by *Marzie* /img/forum/go_quote.gif 
_Anyone have any extra superbright blue or violet LEDs for the tube lights? I didn't order them and if anyone has some or a source to get some fast (I will be checking my local place on the weekend) I am all ears!

 Mike_

 

I have some extra blue LEDs if you're interested. Just PM me your address and I'll send you a couple.
Attachment 3281


----------



## tomb

Quote:


  Originally Posted by *slowpogo* /img/forum/go_quote.gif 
_I'm using a 1 amp Triad wall wart, with my BJT Max. Would there be any audible advantage to using one of the larger Beezar wall warts, or is it just more juice that my amp wouldn't use?_

 

As stated earlier, around 750 ma is probably plenty for any BJT MAX at 50-60ma bias. 1 amp gives more of a safety margin.

 You probably don't want a walwart's transformer loaded to more than 2/3 of its rating - 1/2 is even better. 1 Amp is typically plenty of headroom for a typical MAX. I made current measurements early in the MAX development and reported them in the original design thread over on DIYForums.org. Typical current draw at 50ma bias is about 450ma. So, a 0.75 to 1A walwart gives you 2/3 to 1/2 rating on the walwart.

 When you get into very high biases or powering a MOSFET MAX, then that cushion disappears rather quickly. You can get core saturation and the transformer may vibrate/buzz, make more power noise, and generally speaking, just mess up the quality of the power.

 I suspect that may still be going on with Joneeboi's MAX since he's complaining about his walwart buzzing and vibrating. He was one of the early builders and had trouble blowing up a couple of walwarts. So, there's probably something still going on with his MAX, but he's been listening to it for quite awhile now - maybe we should leave well enough alone.
	

	
	
		
		

		
			





 We'll have to see if the buzzing of his walwart gets intolerable.


----------



## tomb

Quote:


  Originally Posted by *manaox2* /img/forum/go_quote.gif 
_What hookup wire is recommended for the Max from Navships? And is there any other wire that anyone recommends? Also, what heatstrink in the case of tombstoning? I may have to borrow a blowdryer..._

 

I use the 22ga Navships exclusively. However, be sure to compare among what he has and get the thinnest. I wasn't paying attention once and got some white that was very thick and stiff. John always lists the diameter of his wire, so that helps. IMHO, anything close to 0.05 inches in diameter or less is just fine.

 Unfortunately, he hasn't had much 22ga to pick from lately. As I write this reply, he has four listings for 22ga, but two of them are twisted pair. The other two are OK for diameter (0.047 in.), but are some odd color arrangements: white-red and white-brown-violet. He's had much more than that in the past. 
	

	
	
		
		

		
		
	


	




 EDIT: for heatshrink, I think the 3/32" is the stuff I use most. Most heat shrink has a 2 to 1 shrinkage. You can use that to size for long lengths of wire. Since we're usually trying to cover up a wire/lug/solder-blob joint, though, a much larger size is often needed.


----------



## fault151

I received some new valves today for my millet. I now have 12fk6 and 12 ae6. Which is th recommended valve for the millet? At the minute i have a different model number of tube installed that cam with the amp.


----------



## tomb

Quote:


  Originally Posted by *fault151* /img/forum/go_quote.gif 
_I received some new valves today for my millet. I now have 12fk6 and 12 ae6. Which is th recommended valve for the millet? At the minute i have a different model number of tube installed that cam with the amp._

 

The Millett MAX, as with the rest of the Millett line, can use three tube types: 12AE6/A, 12FM6, and 12FK6. The 12AE6/A has the most gain and bass slam, whereas the 12FK6 has the least gain with more detail and high end. The 12FM6 are between the other two in gain and in sound characteristics. It's up to you to decide which one you want.

 Sometimes people suggest the 12FK6 for Grados, for instance, because of its low relative gain and high-end detail. However, just as many recommend the 12AE6 for Grados, because it adds quite a punch and bass slam that helps to fill-in the Grado's preceived deficiencies. Other headphones are different, of course, it all depends on what you want.

 Note that the tube bias is not similar at all with the three types of tubes, so you need to re-bias if you switch tube types. You should do that in any case - even with new tubes within the same type - but the bias is different enough between the 12AE6 and the 12FK6 that the amp may not even work if you don't re-adjust the bias. Yours has those tip jacks in the back, so re-bias should be a piece of cake.


----------



## pinkfloyd4ever

it's a matter of personal preference really, but the differences have been discussed several times recently http://www.head-fi.org/forums/f6/new...ml#post3986737


----------



## tomb

Quote:


  Originally Posted by *pinkfloyd4ever* /img/forum/go_quote.gif 
_it's a matter of personal preference really, but the differences have been discussed several times recently http://www.head-fi.org/forums/f6/new...ml#post3986737_

 

Wow - you're really watching!


----------



## fault151

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_The Millett MAX, as with the rest of the Millett line, can use three tube types: 12AE6/A, 12FM6, and 12FK6. The 12AE6/A has the most gain and bass slam, whereas the 12FK6 has the least gain with more detail and high end. The 12FM6 are between the other two in gain and in sound characteristics. It's up to you to decide which one you want.

 Sometimes people suggest the 12FK6 for Grados, for instance, because of its low relative gain and high-end detail. However, just as many recommend the 12AE6 for Grados, because it adds quite a punch and bass slam that helps to fill-in the Grado's preceived deficiencies. Other headphones are different, of course, it all depends on what you want.

 Note that the tube bias is not similar at all with the three types of tubes, so you need to re-bias if you switch tube types. You should do that in any case - even with new tubes within the same type - but the bias is different enough between the 12AE6 and the 12FK6 that the amp may not even work if you don't re-adjust the bias. Yours has those tip jacks in the back, so re-bias should be a piece of cake.
	

	
	
		
		

		
		
	


	


_

 

Ok cheers, at the minute i have the fm6 installed. It came with them. i Might change them for the 12ae6, i love bass! If i install them, when bias levels do i need it to be set to? Could you give me the details for all the figures i need to set it to please. I dont wanna **** it up.

 Thank you.


----------



## Migroo

Bit of an update for tonight.

 Just waiting for the insulators for the heatsink chips now


----------



## tomb

Quote:


  Originally Posted by *fault151* /img/forum/go_quote.gif 
_Ok cheers, at the minute i have the fm6 installed. It came with them. i Might change them for the 12ae6, i love bass! If i install them, when bias levels do i need it to be set to? Could you give me the details for all the figures i need to set it to please. I dont wanna **** it up.

 Thank you._

 

Well, correct me if I'm wrong, but we set your bias earlier at 13.5VDC (your supply voltage is 27VDC).

 The thing is, each of the Millett tubes should be biased at that _same_ value: one-half of the supply voltage. What's different is that the trimmers will need to be turned to a different position to attain that value. So, after changing tubes, plug your DMM into the appropriate tip jacks - one probe in the center ground tip jack and the other probe in the immediately adjacent tip jack, on the right for the Right channel tube and on the left for the Left channel tube.

 Then turn the appropriate trimmer to adjust the bias. It will never be at 13.5 if you've replaced tubes to a different type, so watch the DMM as you turn the trimmer - you'll be able to quickly tell which way to turn it and how far. If the trimmers were installed in a standard fashion, clockwise will raise the bias voltage and counter-clockwise will lower it.


----------



## Marzie

Ok, if this has been discussed elsewhere in the thread, someone let me know, but I am testing the db bias and right away I get about 350 mv (and it goes up from there) on both sides. Any suggestions?

 EDIT: More info, I turned them (and all trimmers) down all the way before turning it on, and only bumped it to see the values.


----------



## xnothingpoetic

I just replaced 18 caps today with zero problems! (Rubycons in the back and wimas across the board with VitQ's up front and kept the 4 ES's the way they were)

 Hurray for me! 

 Bass is now crazzy deep with good punch and the midrange is to die for!


----------



## tomb

Quote:


  Originally Posted by *Marzie* /img/forum/go_quote.gif 
_Ok, if this has been discussed elsewhere in the thread, someone let me know, but I am testing the db bias and right away I get about 350 mv (and it goes up from there) on both sides. Any suggestions?

 EDIT: More info, I turned them (and all trimmers) down all the way before turning it on, and only bumped it to see the values._

 

Well, that's not good.
	

	
	
		
		

		
		
	


	




 First thing, make sure that you are measuring the bias from the proper test points. Look at the photographic key on the MAX website:
MAX Setup and Bias Settings
 When measuring the DB bias, you are only trying to measure the voltage (and thus convert to milliamps) across the DB output resistors - RB10L/R and RB11L/R. You do that by putting one probe in TA2L and either TB1L or TB2L for the Left Channel DB. For the Right Channel DB, that's putting one probe in TA2R. The other probe then goes in TB1R or TB2R.

 It's quite possible you'll read some strange voltages if you have one probe in Ground.

 Check that first.


----------



## Marzie

Well I went back to retest because the site said "figure out whether the trimmers are operating correctly" so I went to check the resistances. I checked it initially and saw 1.2 ohms. at first I thought they might be bad, but 2 bad trimmers? So I started to adjust them and as I turned the trimmers, well I noticed something strange, I turned the trimmers "up" (clockwise) and saw the resistance increase...? Well I went and reread the site and discover that clockwise is down, not what I expected... Off to try again... 
	

	
	
		
		

		
		
	


	




 EDIT: I know the up, down terminology may be confusing, but I expected the mV to go "up" as I turned the trimmer clockwise, not the inverse... anyway, I'm gonna go change this.


----------



## tomb

Quote:


  Originally Posted by *Marzie* /img/forum/go_quote.gif 
_Well I went back to retest because the site said "figure out whether the trimmers are operating correctly" so I went to check the resistances. I checked it initially and saw 1.2 ohms. at first I thought they might be bad, but 2 bad trimmers? So I started to adjust them and as I turned the trimmers, well I noticed something strange, I turned the trimmers "up" (clockwise) and saw the resistance increase...? Well I went and reread the site and discover that clockwise is down, not what I expected... Off to try again... 
	

	
	
		
		

		
			





 EDIT: I know the up, down terminology may be confusing, but I expected the mV to go "up" as I turned the trimmer clockwise, not the inverse... anyway, I'm gonna go change this._

 

Just to confuse you further 
	

	
	
		
		

		
		
	


	




your description is correct for the tube trimmers - it's an artifact from how the original revMH Millett's operated. However, DB trimmers are always analogous to opening or closing flood gates, along with the right-hand rule, of course.

 So bottom line, what you're saying is that you had hit bias limit at 350mV or 160ma!
	

	
	
		
		

		
		
	


	




 Still, that would've been OK as long as you didn't let it run for more than a few moments. 
	

	
	
		
		

		
		
	


	




 Tell us what you get after you reset and re-measure.


----------



## Marzie

I got around 30 on one side and about 40 on the other. I did the PS check then the tube bias, then adjusted both db to about 55. I am going to wait 5 mins, then go to 75 on one, 75 on the other. Then I will wait another 5 mins, go to 80, then 1/2 turn every 5 mins till 90, recheck all other settings, check the offset, then 1 hour listening with a db check every 10 mins, then 110 mV, followed by rechecking the ps and tubes, then some more listening then call it a night. 
	

	
	
		
		

		
		
	


	




 EDIT: yes, I only ran it for under 15 seconds each time at first.


----------



## Marzie

Any advice on moving the max? Right now it's plugged in in the living room and I was thinking of moving it to the office where I have my dac and do most of my listening. What issues could this cause? My other option is to plug my dvd/sacd player into it and stay in the living room. I am speaking of just for tonight, at the end of the night its coming in here anyway.


----------



## tomb

Quote:


  Originally Posted by *Marzie* /img/forum/go_quote.gif 
_I got around 30 on one side and about 40 on the other. I did the PS check then the tube bias, then adjusted both db to about 55. I am going to wait 5 mins, then go to 75 on one, 75 on the other. Then I will wait another 5 mins, go to 80, then 1/2 turn every 5 mins till 90, recheck all other settings, check the offset, then 1 hour listening with a db check every 10 mins, then 110 mV, followed by rechecking the ps and tubes, then some more listening then call it a night. 
	

	
	
		
		

		
		
	


	




 EDIT: yes, I only ran it for under 15 seconds each time at first._

 

Sounds like you've got things well in hand, now - good luck!


----------



## Fitz

Keep it level when you move it, so you don't trip the mercury switch and cause it to explode. It'll be fine otherwise.


----------



## tomb

Quote:


  Originally Posted by *Fitz* /img/forum/go_quote.gif 
_Keep it level when you move it, so you don't trip the mercury switch and cause it to explode. It'll be fine otherwise._

 

You weren't supposed to tell him about the tilt switch. 
	

	
	
		
		

		
		
	


	




 Seriously, as Fitz says - no problem. I take mine to work all the time. Just be careful about those tube tips - one reason I put roll bars on my cases.


----------



## Marzie

Quote:


  Originally Posted by *Fitz* /img/forum/go_quote.gif 
_Keep it level when you move it, so you don't trip the mercury switch and cause it to explode. It'll be fine otherwise._

 

 Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Just be careful about those tube tips - one reason I put roll bars on my cases._

 


 LOL at those two posts! What movie was it that had a bomb with a mercury switch? I tried imdb but couldnt find it... maybe it was a tv show. Whenver I hear (or read) something that triggers a memory that I know was from childhood, I get nostolgic and try to find the source of the quote or scene or whatever. 

 I know yours wasn't meant to be funny, tomb, but I never thought of them as "roll bars" before. I picture your amp in an offroad race like a dune buggy, plowing over dirt hills and rolling, but low and behold! The tubes are safe!

 Anyway, everything is going great, been listening to Raising sands for about 50 mins now, and it sounds great!! Thank you all (esp tomb) for your help! The board is wonderful and although I didn't put much thought to it before building, during the build I was more and more impressed with the layout of the board. It really is stunning how it looks before and after it is populated (more so after! 
	

	
	
		
		

		
		
	


	




) but during the process of building, you get feel like this part belongs here, everything is orientated properly, there were no real points of confusion. I was a little worried reading the build instructions beforehand because it wasn't what I was used to. But during the build everything just sort of clicked. Thanks tomb for the excellent site, without it and the great pics, I would not have gotten through it with so few questions. Thanks to all the max builders for testing out the various configurations, etc. Thanks to Colin for the great design, and thanks again to tomb for beezar, which made ordering very easy (and once again for "fixing" all the mistakes with my order! 
	

	
	
		
		

		
		
	


	




)


----------



## Fitz

Quote:


  Originally Posted by *Marzie* /img/forum/go_quote.gif 
_LOL at those two posts! What movie was it that had a bomb with a mercury switch? I tried imdb but couldnt find it... maybe it was a tv show. Whenver I hear (or read) something that triggers a memory that I know was from childhood, I get nostolgic and try to find the source of the quote or scene or whatever._

 

I was thinking of an episode of MacGyver when I wrote that. I forget how the situation was resolved though.


----------



## Marzie

Quote:


  Originally Posted by *Fitz* /img/forum/go_quote.gif 
_I was thinking of an episode of MacGyver when I wrote that. I forget how the situation was resolved though._

 

Quote from tv.com "But the mercury switch resists being frozen and the casing can't be opened without detonating it. They try to move the bomb to the elevator so it can explode in the basement but get trapped in the elevator with the bomb. With only a minute left, MacGyver strips wires from the elevator control panel and arcs them beneath the switch to destroy it before time runs out."


----------



## Beefy

Now I managed to read the first 125 pages briefly before my eyes started bleeding, but I didn't see any info specifically relating to my question........ so hopefully this isn't just regurgitating a whole heap of stuff!

 I'm keen on building this amp as my second DIY project. My previous project, an M^3 with S11, is just in the final wrapping up right now. I did this myself with hand-picked parts and showed little restraint; things like an expensive all-in-one IEC/fuse/switch/EMI filter, Amphenol connectors for the power umbilical, and a whole swag of different OPAMPs. The result was a good learning experience, but MUCH more expensive than I initially wanted - particularly after picking up various tools like a crimper and drill bits for case work. Also, I live in Australia and local parts sources are crap - so international shipping from AMB, Mouser and Digikey came very close to US$100.

 So for the Millett Max, I was thinking of a kit to make things much easier and cheaper. Naturally, Jeff Rossel's kits came up. They seem to tick all the right boxes - 1000µF at CA2, Muze KZ at CA4,5,7 Wima films at CA3,6,8,9, Nichicon UPW in power supply, Vishay resistors in the signal path, Alps pot - without going completely nuts with rare, boutique parts. The kit seems to include everything except for RCA inputs and a volume knob, so I should be able to finish the shopping locally. My only significant issue would be the wallwart supplied for US use, because my local supply is 230V 50Hz.

 So I guess my most important question for you folks is whether anybody knows of a better kit option for a relatively high end Millett Max?

 I guess I'm also keen to know whether Jeff's kits have matched transistors, and whether I can dump/swap the wallwart...... I don't want to bother him with these more specific question until I have the cash ready to go......

 Thanks people!


----------



## tomb

A MacGyver MAX? I think it took MacGyver talent to build those amp boards that Fitz is displaying in the Post-Pics-of-Your-Build thread. Very nice work - everyone should go take a look. 
	

	
	
		
		

		
		
	


	




 Thanks for the kind comments, Marzie - and thanks, too, for describing what a wonderful design Colin has created with this board. As noted before, he doesn't always have time to post, but he always keeps current with reading this thread.

 Raising Sand by Robert Plant and Allison Krauss? Boy, that thing has got some crusher bass, as much as I've heard in a long time - perfect for the MAX. 
	

	
	
		
		

		
		
	


	




 When you get a chance, post some pics so we can say the magic words.


----------



## tomb

Quote:


  Originally Posted by *Beefy* /img/forum/go_quote.gif 
_Now I managed to read the first 125 pages briefly before my eyes started bleeding, but I didn't see any info specifically relating to my question........ so hopefully this isn't just regurgitating a whole heap of stuff!

 <snip></snip>

 Thanks people! 
	

	
	
		
		

		
		
	


	


_

 

Jeff is quite flexible in how he sells the kits, from what everyone has said. I'm speaking a bit for him, of course, but many people have stated that he will leave out certain parts and adjust the price if you want to order from other sources.

 Swapping may be a bit difficult from his perspective, so I don't know that I'd ask him to do that - it might be a bit unfair to expect him to get something that he doesn't already stock - especially an Australian walwart or similar. BTW, someone has posted before and confirmed that his small transistors are all matched.

 Take a look at Beezar, Parts Connexion, or Soniccraft and pick out what you want, then tell Jeff to leave those parts out and adjust accordingly. Or, as you say, get what you need locally. From everything I hear, you shouldn't have any problem doing that.


----------



## Beefy

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_it might be a bit unfair to expect him to get something that he doesn't already stock_

 

Yes, realistically I wouldn't even ask unless it was specifically offered. Just leaving out the wallwart would be fine for me, because with a quick look it seems like I can get something locally quite easily:
Jaycar Electronics
Altronics - Your One Stop Electronics Shop
 Considering the onboard LM317, I assume that unregulated is OK?

  Quote:


 Take a look at Beezar, Parts Connexion, or Soniccraft and pick out what you want, then tell Jeff to leave those parts out and adjust accordingly 
 

You know, I really don't think that there is any other component that I would want to change from his kit. Like I said - he seems to tick all the boxes for a good build, without going too nuts. Unless you see something particularly offensive in there? 
	

	
	
		
		

		
		
	


	



 [EDIT] Actually, looking back to your website, it seems that Jeff's kit is the 'Can't Miss #5'......


----------



## amphead

Quote:


 So I guess my most important question for you folks is whether anybody knows of a better kit option for a relatively high end Millett Max? 
 

Get Jeff's kit and purchase some Black Gate NX caps, if you can find them and you will have your high-end Max.


----------



## Beefy

Are they *that* much better than the Muse KZ? Considering it would be the cost of the caps, AND another lot of international shipping?


----------



## tomb

Quote:


  Originally Posted by *Beefy* /img/forum/go_quote.gif 
_Are they *that* much better than the Muse KZ? Considering it would be the cost of the caps, AND another lot of international shipping?_

 

I can't speak for the Muse KZ's - they're great caps, but too tall for me. However, put some good VitQ's on the output bypasses with Muse ES's, and they come very close to Black Gates. There's no reason the Muse KZ's wouldn't work the same.

 That said, the Black Gates are still the best - but you asked the correct question: are they that much better considering the cost?


----------



## Beefy

And I think that the answer is "not better enough for me".

 I feel like I've already had my exercise in excess with the M^3. The Muze KZ with Wima bypass should be a good enough start for my venture into valve amps, with the least amount of fuss coming as a kit.

 Thanks for the advice folks - even if I did ignore it


----------



## fault151

Yeh thats right we did. I had the buffers at 110. So as long as it ends up at the same 13.5vdc and 27vdc it will be ok?

 Thanks for your help.



  Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Well, correct me if I'm wrong, but we set your bias earlier at 13.5VDC (your supply voltage is 27VDC).

 The thing is, each of the Millett tubes should be biased at that same value: one-half of the supply voltage. What's different is that the trimmers will need to be turned to a different position to attain that value. So, after changing tubes, plug your DMM into the appropriate tip jacks - one probe in the center ground tip jack and the other probe in the immediately adjacent tip jack, on the right for the Right channel tube and on the left for the Left channel tube.

 Then turn the appropriate trimmer to adjust the bias. It will never be at 13.5 if you've replaced tubes to a different type, so watch the DMM as you turn the trimmer - you'll be able to quickly tell which way to turn it and how far. If the trimmers were installed in a standard fashion, clockwise will raise the bias voltage and counter-clockwise will lower it._


----------



## tomb

Quote:


  Originally Posted by *fault151* /img/forum/go_quote.gif 
_Yeh thats right we did. I had the buffers at 110. So as long as it ends up at the same 13.5vdc and 27vdc it will be ok?

 Thanks for your help._

 

Yep. Your 27VDC supply voltage won't change in any event, but as soon as you put a different tube in, the 13.5VDC will. This is true even if it's just a different tube of the same type, it's just that the difference won't be as much.

 Some of the Amp-Buyer-non-DIY-ers will just switch tubes on a Millett and never re-adjust, accepting the sound for what results (not too good). We're DIY-er's, though, and there's no excuse for not adjusting it back to 13.5VDC every time. 
	

	
	
		
		

		
		
	


	




 If they're new tubes, remember that bias point will change over time. Just referencing the 12AE6, its bias will continue to drop as the tube breaks in (some of the other tube types may go in a different direction). So, I'd check it every few hours for the first couple of days. If the bias no longer drifts after being turned on for an hour or two, that means the tube is broken-in.


----------



## fault151

Ok then, i'll swap them over and keep checking them. Cheers :0)



  Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Yep. Your 27VDC supply voltage won't change in any event, but as soon as you put a different tube in, the 13.5VDC will. This is true even if it's just a different tube of the same type, it's just that the difference won't be as much.

 Some of the Amp-Buyer-non-DIY-ers will just switch tubes on a Millett and never re-adjust, accepting the sound for what results (not too good). We're DIY-er's, though, and there's no excuse for not adjusting it back to 13.5VDC every time. 
	

	
	
		
		

		
		
	


	




 If they're new tubes, remember that bias point will change over time. Just referencing the 12AE6, its bias will continue to drop as the tube breaks in (some of the other tube types may go in a different direction). So, I'd check it every few hours for the first couple of days. If the bias no longer drifts after being turned on for an hour or two, that means the tube is broken-in. 
	

	
	
		
		

		
		
	


	


_


----------



## tomb

I should qualify that statement a bit. Yes, the tubes will be broken-in from the standpoint of bias. However, it can sometimes take a week for subtle things to improve - like slightly harsh highs, etc. It depends on your headphones and the criticality of your listening. But no re-adjustment will ever be required.


----------



## xnothingpoetic

Can someone help these guys find their way home?




 I sadly don't know where the positive and negitive leads go on the switch.. 
 I know it's the bottom two but I don't want to reverse it by mistake.

 oh yeah: the top left is the switch- the upper right is where the AC adapter plugs into- and the bottom is the MAX board where they connect.


----------



## pinkfloyd4ever

not that it's deficient in performance or anything, but anyone know if there's much performance gain to be had by cranking up the PS & tube bias voltages to say 28v and 14v respectively? or maybe 29 and 14.5? Would this cause shorter tube life?


----------



## mik000000

Quote:


  Originally Posted by *xnothingpoetic* /img/forum/go_quote.gif 
_Can someone help these guys find their way home?




 I sadly don't know where the positive and negitive leads go on the switch.. 
 I know it's the bottom two but I don't want to reverse it by mistake.

 oh yeah: the top left is the switch- the upper right is where the AC adapter plugs into- and the bottom is the MAX board where they connect._

 

the walwart is 24vac so it doesn't matter which way you connect them


----------



## tomb

Quote:


  Originally Posted by *xnothingpoetic* /img/forum/go_quote.gif 
_Can someone help these guys find their way home?
 <IMG]http://img87.imageshack.us/img87/9573/ohnoesna3.jpg[/IMG>
 I sadly don't know where the positive and negitive leads go on the switch.. 
 I know it's the bottom two but I don't want to reverse it by mistake.

 oh yeah: the top left is the switch- the upper right is where the AC adapter plugs into- and the bottom is the MAX board where they connect._

 

mik000000 is correct, but using your diagram, this is more specific and all that's needed:


----------



## tomb

Quote:


  Originally Posted by *pinkfloyd4ever* /img/forum/go_quote.gif 
_not that it's deficient in performance or anything, but anyone know if there's much performance gain to be had by cranking up the PS & tube bias voltages to say 28v and 14v respectively? or maybe 29 and 14.5? Would this cause shorter tube life?_

 

A tad higher performance. However, you have to be careful that you've got plenty of extra voltage in the supply and that you don't throw the regulator out of regulation. It needs to burn 3V, at least.

 Colin's incorporation of the heater resistor prevents the tubes from being over-volted up to 30V. Check the MAX website for the graph on the Tweaks -> Heater Resistor to be sure, but I think 10ohms is enough for safety.


----------



## xnothingpoetic

Thanks for the help guys. I got her up and running again


----------



## Marzie

Quote:


  Originally Posted by *Beefy* /img/forum/go_quote.gif 
_*snip* The kit seems to include everything except for RCA inputs... *snip*_

 

Just FYI, I get my RCA jacks from DIY Fidelity They used to be only $3 or so, they have since TRIPLED the price, but they are on sale now for $6 AUD. I bought 5 pairs of them (last time I bought 3 pairs) and I am thinking about getting more while they are still on sale. I plan on making a switchbox and possibly a dac in the same case... or not... but they are great jacks, imho.


----------



## Beefy

Quote:


  Originally Posted by *Marzie* /img/forum/go_quote.gif 
_Just FYI, I get my RCA jacks from DIY Fidelity_

 

Thanks Marzie, That is handy to know! They've also the same nice RCA plugs used in my Goldenjacks, so I might put in an order.


----------



## Marzie

Listening to the who - Who's Next, it sounds just awesome, I did some of the panel work today, I am disappointed, I may have to widen the front panel jack, it is REALLY hard to plug in my headphones. the jack was lower than the hole (or vice versa), so it was tough to screw the outer part in, now I think I will just have to either get a file or... (this is bad but) take out the drill and drill into it at an angle. Also, because my drill has too small of a chuck for the right size bits, I can't drill the switch or power jack holes either. I might just have someone at work with a cnc mill do the work for me, I think I can just grab the autocad files off the site, anyway this weekend I think I'll get some pics taken so you can say it 
	

	
	
		
		

		
		
	


	




 EDIT: I posted it here a few days ago, but I am still looking for LEDs. I got a response, but he/she hasn't responded to my pms. 
	

	
	
		
		

		
		
	


	




 Anyone have any spare blue LEDs?


----------



## jarensberg

Quote:


  Originally Posted by *Marzie* /img/forum/go_quote.gif 
_Listening to the who - Who's Next, it sounds just awesome, I did some of the panel work today, I am disappointed, I may have to widen the front panel jack, it is REALLY hard to plug in my headphones. the jack was lower than the hole (or vice versa), so it was tough to screw the outer part in, now I think I will just have to either get a file or... (this is bad but) take out the drill and drill into it at an angle. Also, because my drill has too small of a chuck for the right size bits, I can't drill the switch or power jack holes either. I might just have someone at work with a cnc mill do the work for me, I think I can just grab the autocad files off the site, anyway this weekend I think I'll get some pics taken so you can say it 
	

	
	
		
		

		
			





 EDIT: I posted it here a few days ago, but I am still looking for LEDs. I got a response, but he/she hasn't responded to my pms. 
	

	
	
		
		

		
		
	


	




 Anyone have any spare blue LEDs?_

 

Marzie,
 I've got you covered. Sorry for the slow response but I'll have them in the mail to you tomorrow.


----------



## Marzie

Quote:


  Originally Posted by *jarensberg* /img/forum/go_quote.gif 
_Marzie,
 I've got you covered. Sorry for the slow response but I'll have them in the mail to you tomorrow._

 

Hey, no problem that's awesome! Now I just can't wait to get my HD600s! I bet they'll sound awesome with this. Not that the DT770s are bad, I just think an open can, especially the 600 will pair nicely with the tubiness of the amp.


----------



## pabbi1

Quote:


  Originally Posted by *Marzie* /img/forum/go_quote.gif 
_Hey, no problem that's awesome! Now I just can't wait to get my HD600s! I bet they'll sound awesome with this. Not that the DT770s are bad, I just think an open can, especially the 600 will pair nicely with the tubiness of the amp._

 

Yes, it does - you are in for a treat.


----------



## regal

Are the 3422/1359 foward and slightly sharp in the upper midrange?


----------



## tomb

Quote:


  Originally Posted by *regal* /img/forum/go_quote.gif 
_Are the 3422/1359 foward and slightly sharp in the upper midrange?_

 

Slightly forward, perhaps, with reverberating bass punch/slam and cymbal crashes, but I wouldn't call them _sharp_ in the least. I keep defaulting to Steinchen's descriptions, but he is largely accurate with most of these. For the 2SC3422/2SA1359, he states,

 "strong bass, neutral to warm sound. 
good choice if you prefer rocky sound with slam"

 Note that he says _neutral to warm_ - that's about as accurate as can be, and I've built 4 amps with them, dating back to the revMH Millett w/DB's. This Toshiba pair has always been my personal favorite, too.


----------



## jarensberg

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Yes - Joneeboi is probably correct. You'll get up to 40mV or more with the trimmers at dead zero. If you only screwed them down 20 turns instead of 25 turns, then 70mV may still be OK.

 I'm with Joneeboi - see if you can start adjusting upwards and they change accordingly - go 5-10mV at a time until you get to 90-100mV. Let it sit there for a few hours, checking it every once in awhile and listening to the sound. If all's well, then boost it up to 110mV - you're done!

 They should be able to take 200mV for short periods. That's on the low side for MOSFETs, for instance, but we normally recommend 1-1/2" sinks in that case. Still, it's not that bad - assuming you don't find something wrong._

 

I finally got time to finish everything and... it works perfectly! "Another MAX lives!"

 This is my second and I went with the boutique #1 build (BG, Vit Q, 2sc2238, 2SA968) and a blacked out case.


----------



## Marzie

I like how, when covered, you can see the leds especially bright in the tips, it actually looks like the tube is filled. I think I am boing to leave mine uncovered, though, to keep things nice and cool, and because I hate casework


----------



## tomb

Quote:


  Originally Posted by *jarensberg* /img/forum/go_quote.gif 
_I finally got time to finish everything and... it works perfectly! "Another MAX lives!"

 This is my second and I went with the boutique #1 build (BG, Vit Q, 2sc2238, 2SA968) and a blacked out case._

 

Nice work, John!! I bet those components sound very good!


----------



## jarensberg

Quote:


  Originally Posted by *Marzie* /img/forum/go_quote.gif 
_I like how, when covered, you can see the leds especially bright in the tips, it actually looks like the tube is filled. I think I am boing to leave mine uncovered, though, to keep things nice and cool, and because I hate casework_

 

If you want that look you'll need tubes with side getters. If you don't know what that means look at the pictures of the tubes on beezar.com. The 12AE6 has the getter on top and the 12FK6 is on the side. I've found tubes of all types with side getters though.


----------



## cronic

Quote:


  Originally Posted by *jarensberg* /img/forum/go_quote.gif 
_If you want that look you'll need tubes with side getters. If you don't know what that means look at the pictures of the tubes on beezar.com. The 12AE6 has the getter on top and the 12FK6 is on the side. I've found tubes of all types with side getters though._

 

I would love to find a set of 12ae6 with side getters.


----------



## jarensberg

Quote:


  Originally Posted by *cronic* /img/forum/go_quote.gif 
_I would love to find a set of 12ae6 with side getters._

 

I bought 4 12AE6As from Antique Electronics Supply and they all had side getters. They're also the best sounding AE6s I've tried.


----------



## cronic

Quote:


  Originally Posted by *jarensberg* /img/forum/go_quote.gif 
_I bought 4 12AE6As from Antique Electronics Supply and they all had side getters. They're also the best sounding AE6s I've tried._

 

good deal, I will give them a shot. Thanks


----------



## Marzie

Quote:


  Originally Posted by *jarensberg* /img/forum/go_quote.gif 
_If you want that look you'll need tubes with side getters. If you don't know what that means look at the pictures of the tubes on beezar.com. The 12AE6 has the getter on top and the 12FK6 is on the side. I've found tubes of all types with side getters though._

 

Perfect! I started with the 12FK6s and I think that's what I'm going to stick with.


----------



## tomb

Quote:


  Originally Posted by *jarensberg* /img/forum/go_quote.gif 
_If you want that look you'll need tubes with side getters. If you don't know what that means look at the pictures of the tubes on beezar.com. The 12AE6 has the getter on top and the 12FK6 is on the side. I've found tubes of all types with side getters though._

 

Interesting ... the 12FK6 doesn't have a top getter? You know, I've never really thought about, but you may be right. I'll have to look through my stock and see if there is such a thing.

 I'm certainly trying to find out more of the history of these things. Certainly as you say, the 12AE6A is commonly a side getter, but the 12AE6 seems to always be a top getter. The 12AE6 was the early version, while the 12AE6A was later. I think I've still seen later versions with top getters, though, but I will check. I don't know what the difference is between the 12AE6 and the 12AE6A, either. Bottom line, there's still a lot we don't know about these tubes.

 The best source I've found on space-charge tube history is Jeff Duntemann's excellent web page:
Space Charge Tubes: Tube Projects Without Lethal Voltage!
 He doesn't get into the details we're interested in with the Millett tubes, however.


----------



## jarensberg

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Interesting ... the 12FK6 doesn't have a top getter? You know, I've never really thought about, but you may be right. I'll have to look through my stock and see if there is such a thing.

 I'm certainly trying to find out more of the history of these things. Certainly as you say, the 12AE6A is commonly a side getter, but the 12AE6 seems to always be a top getter. The 12AE6 was the early version, while the 12AE6A was later. I think I've still seen later versions with top getters, though, but I will check. I don't know what the difference is between the 12AE6 and the 12AE6A, either. Bottom line, there's still a lot we don't know about these tubes.

 The best source I've found on space-charge tube history is Jeff Duntemann's excellent web page:
Space Charge Tubes: Tube Projects Without Lethal Voltage!
 He doesn't get into the details we're interested in with the Millett tubes, however._

 

I'll have to check my stock at work and see what have. I only have 6 sets of tubes at home. I think I've become a tubeaholic
	

	
	
		
		

		
		
	


	




 If anybody is looking for 12FM6s, I recommend eBay My World - the-radio-tube-supply-company. I've purchased several sets of tubes from him. His stuff is all NOS. No guarantee that you'll get a matching set though.


----------



## manaox2

For balanced operation, I figure that I need a two pots, a big quad Alps Pot or a stepped attenuator. Maybe something like this without the motor:

ALPS Quad Potentiometer RK27114MC motorized Pot RK27 - eBay (item 260216970470 end time Apr-01-08 22:49:34 PDT)

 This or a stepped attenuator are pretty big. Any recommendations on how to mount this or two stepped attenuators?


----------



## pinkfloyd4ever

Quote:


  Originally Posted by *manaox2* /img/forum/go_quote.gif 
_This or a stepped attenuator are pretty big. Any recommendations on how to mount this or two stepped attenuators?_

 

You can get 4 channel stepped attenuators, you'd need a bigger case than the standard hammond, but I'm assuming that you're already using something bigger since you'll have 2 boards. I see you're already following that stepped attenuator thread so I won't bother linking to it, but the balanced Twisted Pear Joshua Tree is another option to consider 


 anyhooters, I'm having some weird sh!t going on with my PS voltage. I've been trying to crank it up to 29 or 30v so I can bias the tubes to 14.5-15v, but when I'm turning the trimpot the PS voltage stops going up at a certain point and just kinda sticks at that voltage(+/- .02 volts or so) no matter how much I turn it. This point seems to vary between 27.3 and 27.9v. I'm using a 24VAC Triad wallwart from Mouser and I have Murata trimpots. I'm measuring about 24.8VAC at the power terminal blocks. I haven't noticed any other abnormal opreation, and everything else is staying biased fine


----------



## tomb

Quote:


  Originally Posted by *manaox2* /img/forum/go_quote.gif 
_For balanced operation, I figure that I need a two pots, a big quad Alps Pot or a stepped attenuator. Maybe something like this without the motor:

ALPS Quad Potentiometer RK27114MC motorized Pot RK27 - eBay (item 260216970470 end time Apr-01-08 22:49:34 PDT)

 This or a stepped attenuator are pretty big. Any recommendations on how to mount this or two stepped attenuators?_

 

I think you'd want the quad ALPS without the motor from FamilyGate. I'm pretty sure that's what Nate used on his Balanced Mini3. It looked to me as if he just had it mounted to a Hammond frontplate. Maybe he'll see this and tell exactly what he used and how he did it.
	

	
	
		
		

		
			





 Again, this is from memory, too, but I think Pabbi built his with duplicate normal ALPS so that the L and R channel were individually controlled. I've seen pics of a lot of balanced amps done that way, too. That would be simpler and give you more control, at the price of a bit of convenience.


----------



## tomb

Quote:


  Originally Posted by *pinkfloyd4ever* /img/forum/go_quote.gif 
_<snip>

 anyhooters, I'm having some weird sh!t going on with my PS voltage. I've been trying to crank it up to 29 or 30v so I can bias the tubes to 14.5-15v, but when I'm turning the trimpot the PS voltage stops going up at a certain point and just kinda sticks at that voltage no matter how much I turn it. This point seems to vary between 27.3 and 27.9v. I'm using a 24VAC Triad wallwart from Mouser and I have Murata trimpots. I'm measuring about 24.8VAC at the power terminal blocks. I haven't noticed any other abnormal opreation, and everything else is staying biased fine_

 

Yep. When it "just kinda sticks", you've hit maximum. Better back it off another volt to make sure it doesn't drop out of regulation.

 This varies for everyone's individual MAX, but there is a limited number of volts available. It depends on two things:
 1. primarily the voltage of the walwart (should be 24VAC) and then 
 2. the current draw of your MAX.
 More current draw means less over-voltage available from the walwart due to light-loading. It's one of the reason I use and sell those big-honkin 50VA walwarts.

 The arithmetic says rectified and smoothed VDC = 1.414 * VAC minus 1.4V for the drop through the rectifiers. However, depending on your cap arrangement, loading etc., it may have an additional 0.9 factor multiplier, too.

 For the typical 24VAC walwart, that comes to (24VAC * 0.9 * 1.414) - 1.4 = 30.54VDC. However, the LM317 wants to burn at least 3V to maintain regulation, so your final voltage ends up at 30.54 - 3 = *27.5VDC*, give or take a volt. Sounds like that's what you're finding. 
	

	
	
		
		

		
		
	


	




 One of those big honkin walwarts will give you about another 1 to 1-1/2V, depending on your particular MAX, but it's highly variable. To get to 30VDC on the board, you'd have to have a higher voltage-rated transformer, period.


----------



## pinkfloyd4ever

hmm that's weird cause I just have BJTs, no caps bigger than 1000uf, 12FK6 tubes and 32ohm cans. So having additional available current but the same voltage from the wallwart will allow the PS voltage to go higher?


----------



## tomb

Quote:


  Originally Posted by *pinkfloyd4ever* /img/forum/go_quote.gif 
_hmm that's weird cause I just have BJTs, no caps bigger than 1000uf, 12FK6 tubes and 32ohm cans. So having additional available current but the same voltage from the wallwart will allow the PS voltage to go higher?_

 

Not weird, really - your experience fits the calcs almost perfectly.

 Yes, having additional current available preserves more of the _natural_ over-voltage that occurs due to light loading. However, as I mentioned up there - light loading is usually 50% or less. Even then, you're only going to get 1 to 1-1/2 more volts at best. Even with the big honkin' walwarts that I run, I still set the voltage at 27VDC. The reason is that cushion will guarantee a better PS and more quieting. You see, the LM317 will burn at least 3V, but it really wants 5V for maximum ripple removal. I'm probably giving it about 4 to 4-1/2V. The last time I tried, I could hit about 28.5 or so before turning the trimmer made no difference.

 As mentioned earlier, to get to 30VDC, you'd need a transformer rated for more than 24VAC.


----------



## manaox2

6 x Nichicon Muse ES 470uf 35V
 6 x Nichicon Muse ES 1000uf 16V
 6 x 7-pin Gold Miniature Ceramic PCB Tube Socket
 4 x 12FK6 Tube
 6 x 12AE6 Tube
 3 x Millett Hybrid MAXed PCB
 12 x Wima MKP10 0.22uf 250V
 6 x 2SC3422 BJT NPN Transistor
 6 x 2SA1359 BJT PNP Transistor
 6 x KOA (Kiwame) SPR 2W 47R Resistor
 6 x 22R 2W Stackpole Carbon Film Resistor
 6 x KOA (Kiwame) SPR 2W 100R Resistor
 1 x HiQ RCA Jack (1 pr Black and Red)
 3 x Eight (Qty 8) 6-32 x 3/4" Socket Head Cap Screws
 6 x LED Chrome Bezel HiQ
 1 x Millett Hybrid MAXed Owner's Manual
 1 x Bourns Trimpot Adjustment Tool
 6 x VitaminQ PIO 0.18uf, 100V

 Here is the current plan for my beezer order before I go to mouser or digikey. I'm waiting on that last item to make my order. I tried to pick out enough to make a balanced and a single ended Millett Max (for comparison and extra parts in case of mistakes). There are also a couple of different output resistors in there, I'm going to try a few after jumping RB14 because of the gain doubling when going balanced. It will be nice to be able to build an amp to my specification to know for certain how much a difference going balanced actually makes.

 Let me know if you see any mistakes.


----------



## Marzie

I don't know why you would need 6 LED bezels... If I were you, I would get the right LED resistance and wire a single LED between the 2 boards, not sure of the exact mechanics of doing this. you would need a second bezel for your single ended amp. Unless you have more RCA jacks, you will need a second set for your single ended (or vice versa)... wait, ignore the last comment, it is due to my limited knowledge of balanced equipment...

 BTW, good luck with your build! I can't wait to see pics of a balanced Millet (I have never seen pabbi's)

 EDIT: I would also suggest going with the heatsink mounting packages from beezar. you would need 12 without shoulder washer and 3 with. And depending on whether or not you are going to do tube lighting, and how you plan to take the sockets apart, I would get a few extra sockets. I bought three. The first one I used a precision screwdriver and it came apart pretty easily. The second one I broke using the same method. The third I drilled through the center pin, and I was sweating a bit because it was my last one and it isn't exactly a cut-and-dry operation, but it worked just fine. Took a lot longer and was a lot more difficult than I thought it would be. To hold it steady, I popped it through the top of a shoebox and drilled it. It went through and had to be reinserted in a new spot a couple times.


----------



## manaox2

Quote:


  Originally Posted by *Marzie* /img/forum/go_quote.gif 
_I don't know why you would need 6 LED bezels... If I were you, I would get the right LED resistance and wire a single LED between the 2 boards, not sure of the exact mechanics of doing this. you would need a second bezel for your single ended amp. Unless you have more RCA jacks, you will need a second set for your single ended (or vice versa)... wait, ignore the last comment, it is due to my limited knowledge of balanced equipment...

 BTW, good luck with your build! I can't wait to see pics of a balanced Millet (I have never seen pabbi's)

 EDIT: I would also suggest going with the heatsink mounting packages from beezar. you would need 12 without shoulder washer and 3 with. And depending on whether or not you are going to do tube lighting, and how you plan to take the sockets apart, I would get a few extra sockets. I bought three. The first one I used a precision screwdriver and it came apart pretty easily. The second one I broke using the same method. The third I drilled through the center pin, and I was sweating a bit because it was my last one and it isn't exactly a cut-and-dry operation, but it worked just fine. Took a lot longer and was a lot more difficult than I thought it would be. To hold it steady, I popped it through the top of a shoebox and drilled it. It went through and had to be reinserted in a new spot a couple times._

 

Thanks for the heads up. I was thinking that you needed a bezel for each LED to be mounted inand one LED per tube, so I planned 6. I had no clue how to install the heatsink mounting packages, therefore how many I needed. I think I will also want some thermal compound.

 Thanks for the count and I'll get those extra tube sockets. I might mount them in a scrap piece of wood before drilling on the press.

 EDIT: Just noticed I'm going to need A LOT more of those output capacitors for matching.... N/M scratch that. 
	

	
	
		
		

		
		
	


	




 Where in the world does anyone find a 3mm 5500 mcd LED? geez, highest I can find is 1500.


----------



## tomb

Yep - I think that's 18 of the Wima's you'd need - 6 per MAX if you're using the ES's. I think the 0.18uf VitQ's go best with the ES's, but I don't have them listed, yet. If you can wait a couple of days, I should have them added and some ALPS, too. They were supposed to arrive yesterday, but they shipped them to my salesman, instead.
	

	
	
		
		

		
		
	


	




 He told me today that he shipped them back out to me yesterday.

 About the heat sink mounting kits - no thermal compound needed. In fact, it would hurt rather than help with the pads that are in the kit. There's a detail at Output Stage -> Heat Sink Mounting for heat sink kits on the MAX website. Just delete the shoulder washer for the non-TO-220 type output transistors. The LM317 in the PS will use one, though.

 P.S. I use a standard drill press vise for my sockets. The lip at top holds it in place with a minimum of clamping. Marzie's right, though - I still break at least one every time I drill them.


----------



## Marzie

Quote:


  Originally Posted by *manaox2* /img/forum/go_quote.gif 
_Thanks for the heads up. I was thinking that you needed a bezel for each LED to be mounted inand one LED per tube, so I planned 6. I had no clue how to install the heatsink mounting packages, therefore how many I needed. I think I will also want some thermal compound._

 

Nope, and actually, I didn't use any, I am leaving mine topless, so I just mounted the main LED right on the board as well (just like the tube LEDs that I will mount soon.) The heatsink packages are just a set of washers, a nut, and a screw, as well as shoulder washers for the main voltage regulater, to help with insulation and prevent shorts. One for each of the 4 bjts, and one for the voltage regulator (that is the one that will need the shoulder washer.) Thermal compound is necessary or definately suggested by me. I forgot about this, as I usually use arctic silver (a computer thermal compound) but decided against this as it contains silver which has a greater chance of causign a short than other thermal material. I just used a tube of Zalman brand I had that came from a computer heatsink, but Radioshack and other places carry this. (BTW, I didn't know about the mounting packages until Tomb told me when I placed my order. He can be a good "extra" set of eyes in case you do miss anything)

  Quote:


  Originally Posted by *manaox2* /img/forum/go_quote.gif 
_Thanks for the count and I'll get those extra tube sockets. I might mount them in a scrap piece of wood before drilling on the press._

 

I didn't understand the "wood" mounting technique described on the site, but I'm sure there are many ways to do it. Ahh, and using a press is much better than the black and decker corded hand drill (is that the proper terminology?) that I have.

  Quote:


  Originally Posted by *manaox2* /img/forum/go_quote.gif 
_EDIT: Just noticed I'm going to need A LOT more of those output capacitors for matching.... N/M scratch that. 
	

	
	
		
		

		
		
	


	




 Where in the world does anyone find a 3mm 5500 mcd LED? geez, highest I can find is 1500._

 

I suppose you realized you don't have to match the output capacitors. I don't know if Tomb matches the BJTs, but I think they come out fine anyway. As far as LEDs, I just posted here and in the FS forum and got a few takers. I will ask one of them if they would like to pass some on to you...


----------



## manaox2

Thank you very much about the advice and help. I think as soon as I have those VitQ, I have that order ready. Working on Digikey now.

 I guess two 25 x 25v transformer will be good for my power. I shouldn't need a wall wart.

 Is 1N4002DICT-ND a good substitute for 1N4002/54GICT-ND? The listed part is obsolete(?) and no longer sold by Digikey.


----------



## pinkfloyd4ever

that just won that lot of 25 12AE6A tubes on ebay? I won a lot of 5 FK6s yesterday, if anyone was wondering who that was


----------



## Beefy

So it looks like I might end up placing an order with Beezar in addition to a Jeff Rossel kit. I would probably buy some FK6 tubes, spare tube sockets, RCA jacks and TO-220 mounting kits - plus more cap options.

 For the latter, lets say I were to get some Muse ES at CA2 and CA7, and Vitamin Q at CA8...... it would make for a formidable amp, yes?


----------



## pinkfloyd4ever

did you already build one with ES's beefy? If so I can't stop myself from suggesting you try some BGs. Yeah they're really expensive but for the ultimate in detail they can't be beat...esp with the 2344/1011 BJT pair


----------



## Beefy

Quote:


  Originally Posted by *pinkfloyd4ever* /img/forum/go_quote.gif 
_did you already build one with ES's beefy?_

 

No, this will be my first Millett.

  Quote:


 Yeah they're really expensive but for the ultimate in detail they can't be beat 
 

A single Black Gate for the price of the whole ES/VitQ setup really is just a bit too nutty for me. This project is intended to be my _cheap_ intro to tubes.


----------



## fault151

Quote:


 Here is the current plan for my beezer order before I go to mouser or digikey. I'm waiting on that last item to make my order. I tried to pick out enough to make a balanced and a single ended Millett Max 
 

Wow a balanced millet, i can't wait to see that! Id love to make one!!!! I was talking to TomB about it yesterday. If i could id like to make b22 balanced amp or a millet balanced amp. 

 Please post up a few pics when you get cracking. Good luck!


----------



## pinkfloyd4ever

Quote:


  Originally Posted by *Beefy* /img/forum/go_quote.gif 
_No, this will be my first Millett.



 A single Black Gate for the price of the whole ES/VitQ setup really is just a bit too nutty for me. This project is intended to be my cheap intro to tubes._

 

then by all means, go with the ES's


----------



## amphead

Quote:


 A single Black Gate for the price of the whole ES/VitQ setup really is just a bit too nutty for me. This project is intended to be my cheap intro to tubes. 
 

Another way to make your wallet scream would be to get some HD600s to listen to your max. Highly recommended.


----------



## fault151

Quote:


  Originally Posted by *amphead* /img/forum/go_quote.gif 
_Another way to make your wallet scream would be to get some HD600s to listen to your max. Highly recommended. _

 

And buy a cardas cable to go with them like i just did. I bought the millet max then realised my 595's weren't as good so i bought some 600's then thought, hey why not try the decent cable too. A few hundred pounds later i have a set up i really like!!! Next i want a balanced amp. It never stops!


----------



## tomb

Quote:


  Originally Posted by *manaox2* /img/forum/go_quote.gif 
_Thank you very much about the advice and help. I think as soon as I have those VitQ, I have that order ready. Working on Digikey now.

 I guess two 25 x 25v transformer will be good for my power. I shouldn't need a wall wart.

 Is 1N4002DICT-ND a good substitute for 1N4002/54GICT-ND? The listed part is obsolete(?) and no longer sold by Digikey._

 

Yes. The 1N4002 is a generic diode. Pretty much anything that has that number will work. Unfortunately, that also means it's treated as a commodity. So, it's difficult to maintain consistent part numbers in the BOM as DigiKey and others buy in huge lots from all over the world.

 I'll try to get the 0.18 96P-series VitQ's on the store site tonight.


----------



## fault151

S**T, I have just noticed my millet has some wiring that is wrong somewhere in the amp. the sound from the left and right channels are the wrong way round. I purposely put on a song i know starts in the left channel, on my solo and x can it plays in the left on my millet its the right!

 I didn't make the amp so where would i start in trying to figure out which is wrong? Could i just swap the rca's over or is it bit more seriuos?


----------



## manaox2

Here is the BoM for the balanced and single ended millett for mouser: (main differences being 3x everything except only two panel LED and switches, well 400 of the small transistors for matching, the XLR female jacks (2 normal, 2 1/4th combo)). Thought this might help those who might want to also try building a boutique balanced. 
	

	
	
		
		

		
		
	


	




 Notice CA2, CA7, CA8, CA9, and RB14 are not included as they are ordered from beezar as boutique components.

 BoM Mouser:
 72-T93YA-5K|6
 71-RN55D-F-1.0K|18
 71-RN55D-F-1.0M|6
 647-UPW1V152MHD|12
 512-2N5087_J18Z|400
 71-RN55D1131F|10
 71-RN55D-F-11.3K|10
 282-10-RC|3
 293-2K-RC|9
 859-LTL42UB6N|2
 571-2828363|6
 550-22302|1
 71-RN55D-F-121|3
 71-RN60D-F-2K/R|3
 72-T93YA-1K|3
 647-UPW1H102MHD|12
 75-MKT1817510064|3
 140-50N5-101J-RC|12
 581-TAP106K035SCS|3
 581-TAP105K050SCS|3
 821-MBR1035|12
 512-1N4002|6
 511-LM317T|3
 567-647-15ABP|3
 103-R13-135A-02-EV|2
 71-RN55D-F-3.32K|3
 71-RN55D-F-1.0M|3
 140-HTRL25V47-RC|3
 21RX310-RC|3
 140-HTRL25V330-RC|3
 78-1N5242B|3
 78-1N4148|3
 512-BD1396STU|3
 512-MPSA14|3
 653-G6A-234P-DC12|3
 71-RN55D-F-221|12
 71-RN55D-F-10.2|12
 594-5083NW2R200J|12
 72-T93YA-2K|6
 71-RN55D-F-100|18
 512-PN4392|6
 512-2N5088TA|18
 532-531102B25G|18
 568-NCJ5FI-S|2
 NC3FBY-B|2


----------



## manaox2

Quote:


  Originally Posted by *fault151* /img/forum/go_quote.gif 
_S**T, I have just noticed my millet has some wiring that is wrong somewhere in the amp. the sound from the left and right channels are the wrong way round. I purposely put on a song i know starts in the left channel, on my solo and x can it plays in the left on my millet its the right!

 I didn't make the amp so where would i start in trying to figure out which is wrong? Could i just swap the rca's over or is it bit more seriuos?_

 

I'm no tech-know-how guy on this, but it could be something as simple as a miswiring of the RCA or jack.


----------



## fault151

Quote:


  Originally Posted by *manaox2* /img/forum/go_quote.gif 
_I'm no tech-know-how guy on this, but it could be something as simple as a miswiring of the RCA or jack._

 

Yeh thats what i thought/hoping! I haven't taken it apart yet to have a look, bts getting late here. I just wondered where would be the best places to look. I guess is should try headphone jack and rca's first?


----------



## el_matt0

howabout this. i bet a more likely scenario is that you potentially just have the detachable cable of your senn hd600s reversed..? try with different cans to confirm its the amp first. If not, then yes it is simply either the RCA inputs wired in reverse, or the L and R channels to the 1/4 output that are flipped (both a 2 second fixer upper, but a silly mistake by the builder nonetheless).


----------



## MrMajestic2

Quote:


  Originally Posted by *fault151* /img/forum/go_quote.gif 
_Yeh thats what i thought/hoping! I haven't taken it apart yet to have a look, bts getting late here. I just wondered where would be the best places to look. I guess is should try headphone jack and rca's first?_

 

If the pot and headphone jack arent airwired, then the inputs are pretty much the only place that can be wrong. Could also be the headphones as el_matt0 suggests.


----------



## el_matt0

oh yea forgot most people dont even airwire the pot, that narrows things down substantially as mr.majestic correctly points out. should be a simple problem to solve by all means - although my moneys still on the senns to be honest.


----------



## Migroo

Another MAX lives! 
	

	
	
		
		

		
		
	


	




 I've only had it running for about half an hour... Its improving constantly. Its still caseless and connected temporarily.

 Thanks for everyone's help! I've been very impressed with the level of support available on this DIY amp.

 Pics at the weekend when I've had chance to neaten it up!


----------



## Beefy

Well I've placed an order at Beezar for 12FK6 tubes, ES and VitQ caps, spare transistors, spare sockets, jacks and TO-200 mount kits. I'm fleshing out the final details of my kit with Jeff, namely adding some extra 1000µF caps.

 I'm excited.... but the G/F is going to be p%&#ed!


----------



## tomb

Quote:


  Originally Posted by *fault151* /img/forum/go_quote.gif 
_Yeh thats what i thought/hoping! I haven't taken it apart yet to have a look, bts getting late here. I just wondered where would be the best places to look. I guess is should try headphone jack and rca's first?_

 

Both the headphone jack and the pot are board mounted in a standard-build MAX. I'm pretty sure yours was that way. That means the L and R wires from the RCA jacks are switched in the input terminal block.

 It's trivial - a small screwdriver to loosen the outer two screws on the terminal block and swap the wires. I have some sort of mental block and get them switched on a regular basis.
	

	
	
		
		

		
			





 I sort of gave up trying to keep them straight on mine.


----------



## chilly

Hey everyone,

 I had finished my Max about a month and a half ago, it was my second DIY electronics project. The soha was my first. ok so I got bit by the bug... damn you all... 
	

	
	
		
		

		
		
	


	




 I'd post pic's but it looks like all the black maxes out there.

 I (well actually my wife did) ordered another Max kit from Jeff at Glass Jar (thanks Jeff). But I am going to jazz it up a bit this time. My first max was with the Nichicon Muse ES's and VitQ's from Beezar ( thanks Tom). I'm very happy with the sound, but I feel maybe just maybe I can squeak out even better performance...

 Since I have no clue about electronic circuitry... I'm going on what is written in these forums and well all of you, who I value so much. 


 SO I think I'm going to do the boutique build #1 using Black Gates, and VitQ's as well, leaving C9 blank.


 CA7 - black gate
 CA2 - black gate
 CA8 - VitQ .22uf or the .18uf if those would be better
 CA9 - blank

 I also have the transitors 2344 and 1011, but am wondering if the 3422 and 1359 is a better match for me as I do like good strong but accurate bass.

 I have already purchased a pair of WBT next gen sockets, and will soon be purchasing a neutrik locking plug, and Wire from Navships.

 My questions are:

 Are the VitQ's the best for the job in CA8 or is there a better film cap? ( like cardas, or mundorf, or angela )

 could I use VitQ's for CA3 and CA6 instead of the wima's? would it improve the sound?

 I'm making a custom case for this amp as well, I will be air wiring the Pot, and the headphone jack, and I will also be air wiring the tubes to fully poke them out of the case. Does anyone see any problem with airwiring the tubes? it will only be like 3 inches at the most. 

 My case will be wood will that be a problem? only the top plate and the rear will be metal, probably stainless steel.

 I will probably be using 12ae6a's as I think they have the tightest bass, I love the 12fm6's but the bass can get a little mushy to me, but oh, the midrange is heavenly.


 If anyone has any ideas for making this an even better amp, please let me know, I can't say this is a money no object amp, cause its not but I would be willing to spend a little more. Please keep in mind that I use IEM's UE-5c's to be exact. Yes I know IEM's may not be the best for a tube amp.... but the current Max I have is virtually silent with the exception of an occasional cell phone interference buzz. I do have a 10ohm resistor at RB14.

 Ok enough rambling,

 cheers


----------



## Beefy

Quote:


  Originally Posted by *chilly* /img/forum/go_quote.gif 
_Are the VitQ's the best for the job in CA8 or is there a better film cap? ( like cardas, or mundorf, or angela )

 could I use VitQ's for CA3 and CA6 instead of the wima's? would it improve the sound?_

 

I read about 100 forum pages about the MHM last night, before placing my orders. Hopefully, this is an accurate summary.......

 Vitamin Q 0.22µF at CA8 is about as good as you can get. Anything better is simply too large to fit on the PCB. Everywhere else, Wima is the best choice. Even CA9 should be a Wima - unless you have BG NX, in which case you leave it out, as you correctly intend to do.

  Quote:


 Does anyone see any problem with airwiring the tubes? it will only be like 3 inches at the most. 
 

I really don't think that will be a good idea. Not any specific info, just a very big hunch.

  Quote:


 If anyone has any ideas for making this an even better amp, please let me know, I can't say this is a money no object amp, cause its not but I would be willing to spend a little more. 
 

You might want to use larger caps than Jeff provides at CA4 and CA5. By default Jeff supplies 470µF Muze KZ, which are nice caps but tomb thinks they are simply too small. I'm swapping mine to 1000µF Panasonic FM or Nichicon UPW. You can go up to 1800µF if you really want to.... perhaps I'm a bit naive, but I don't see how 7200µF of capacitance could POSSIBLY be required there - my M^3 has nowhere near that, and is almost capable of driving speakers.

 I can't help you out with transistor selections, because I didn't really research that. Only other major suggestions is perhaps a stepped attenuator instead of the volume pot? Its a very popular upgrade in many DIY amps.

 Hope this helps!


----------



## amphead

Congrats Migroo! Another Max Lives!   

 So many ways to box it up, but the Hammond enclosure works very well.


----------



## tomb

0.18uf, 100V 96P-series ("THE" Vitamin Q) VitQ's are also up.


----------



## tomb

Quote:


  Originally Posted by *Beefy* /img/forum/go_quote.gif 
_You might want to use larger caps than Jeff provides at CA4 and CA5. By default Jeff supplies 470µF Muze KZ, which are nice caps but tomb thinks they are simply too small. I'm swapping mine to 1000µF Panasonic FM or Nichicon UPW. You can go up to 1800µF if you really want to.... perhaps I'm a bit naive, but I don't see how 7200µF of capacitance could POSSIBLY be required there - my M^3 has nowhere near that, and is almost capable of driving speakers._

 

Hmm ... I thought Jeff had started putting bigger caps in there. FYI, the M3 uses a capacitance multiplier in the circuit so that the effective on-board capacitance is over 10,000uf. That's why AMB has a lot of warnings about don't dare increase the size and number of the capacitors.

 That said, I think 1000uf is a happy medium. If you go on and use the same 50V caps that are in the PS, that sends the number to 8, and it's a small matter to order two more to get the per-10 price break.

 I use 1800uf in mine, but the bigger you go, the bigger the voltage spike your headphones see at turn off.

  Quote:


 I can't help you out with transistor selections, because I didn't really research that. Only other major suggestions is perhaps a stepped attenuator instead of the volume pot? Its a very popular upgrade in many DIY amps.

 Hope this helps! 
	

	
	
		
		

		
		
	


	



 

Steinchen's transistor reviews for his revMH Millett DB's are still the standard reference. I basically describe them the same way on beezar with a bit of embellishment.


----------



## Beefy

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_0.18uf, 100V 96P-series ("THE" Vitamin Q) VitQ's are also up.


_

 

Ah crap, I bought the 0.22µF just 3 hours ago, to go with Muse ES. And now you have these better ones, at just $1 more for the pair? 
	

	
	
		
		

		
		
	


	




 Is it possible to swap them, even after my order has been confirmed? Last communication I got was that the order was 'Processing'.......

 [EDIT] Emailing you directly.....


----------



## Beefy

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_FYI, the M3 uses a capacitance multiplier in the circuit so that the effective on-board capacitance is over 10,000uf. That's why AMB has a lot of warnings about don't dare increase the size and number of the capacitors._

 

I thought it was because of inrush current causing a temporary short circuit in the S11 PSU. Might have to research capacitance multipliers.....

  Quote:


 I thought Jeff had started putting bigger caps in there 
 

Jeff's email says "I have switched out some of the 470uF already to 1000uF Panasonic FM caps". That's fairly ambiguous as to whether they come with it by default. Perhaps best to check as I did


----------



## tomb

Quote:


  Originally Posted by *Beefy* /img/forum/go_quote.gif 
_I thought it was because of inrush current causing a temporary short circuit in the S11 PSU. Might have to research capacitance multipliers....._

 

Well, yeah - but something causes that current inrush. 
	

	
	
		
		

		
		
	


	




 Remember also that 4000uf of the onboard capacitance in the MAX is the Power Supply. The M3 doesn't even count that.


----------



## Beefy

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Remember also that 4000uf of the onboard capacitance in the MAX is the Power Supply. The M3 doesn't even count that._

 

Sorry to keep dragging this off-topic, but I'm still learning 
	

	
	
		
		

		
		
	


	




 I was thinking that post-voltage-regulator C7 on the M^3 board (3000µF max) is analogous to CA4/5 on the MHM (4000-7200µF).

 And that pre-voltage-regulator C5 on the S11 board (3000µF) is analogous to CR1 on the MHM (4000µF).


----------



## tomb

Quote:


  Originally Posted by *Beefy* /img/forum/go_quote.gif 
_Sorry to keep dragging this off-topic, but I'm still learning 
	

	
	
		
		

		
		
	


	




 I was thinking that post-voltage-regulator C7 on the M^3 board (3000µF max) is analogous to CA4/5 on the MHM (4000-7200µF).

 And that pre-voltage-regulator C5 on the S11 board (3000µF) is analogous to CR1 on the MHM (4000µF)._

 

Yes, but the 10,000uf effective capacitance on the M3 board should only be compared to the MAX's CA4L/R and CA5L/R caps, in order to do apples to apples. If you compare by also including the MAX's PS caps, then you have to add the M3's 10,000uf plus whatever is in the S11 or STEPS, meaning you're comparing about 14,000uf for the M3 to that supposedly over-loaded 7200uf on the MAX.

 1800uf caps on the MAX doesn't seem like that much put in that context.


----------



## Beefy

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Yes, but the 10,000uf effective capacitance on the M3 board....._

 

That's fine, I'll have to learn about how this effective capacitance trickery actually works! 
	

	
	
		
		

		
		
	


	




 Oh, and I tried responding to your PM you re: the Vit Q's, but you've exceeded your quota. Sent an email to tomb AT beezer.com instead.......


----------



## tomb

Quote:


  Originally Posted by *Beefy* /img/forum/go_quote.gif 
_That's fine, I'll have to learn about how this effective capacitance trickery actually works! 
	

	
	
		
		

		
		
	


	




 Oh, and I tried responding to your PM you re: the Vit Q's, but you've exceeded your quota. Sent an email to tomb AT beezer.com instead......._

 

Yep - I cleaned it up, but it was too late.


----------



## Beefy

Ok, I think I've now got the skinny on capacitance multipliers..... 

 The big 3000µF capacitance at C7 on the M^3 supplies power to the MOSFETs. This appears to have no capacitance multiplication.

 But the M^3 does use a capacitance multiplier on the 100µF capacitors at C5 (or is it technically C4?). This cap provides a source of clean power to the OPAMPs, effectively filtering away any ripple introduced by the MOSFETs.

 This is all very interesting.... so many different ways to skin a cat


----------



## fault151

Cheers for alll your replys guys. It's definitely not the headphones the wrong way. checked them + my other two amps i tried them work fine. I guess it must be the rca's. 

 I'll take them apart tonight and swap them over. Hope it works!

 I'll update you all. 

 Cheers. 
	

	
	
		
		

		
		
	


	






  Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Both the headphone jack and the pot are board mounted in a standard-build MAX. I'm pretty sure yours was that way. That means the L and R wires from the RCA jacks are switched in the input terminal block.

 It's trivial - a small screwdriver to loosen the outer two screws on the terminal block and swap the wires. I have some sort of mental block and get them switched on a regular basis.
	

	
	
		
		

		
		
	


	




 I sort of gave up trying to keep them straight on mine.
	

	
	
		
		

		
		
	


	


_


----------



## chilly

Thanks Beefy,

 I have also read through this thread like 4 times... and still learn something each time I read it.

 I'm not too worried about what fits on the PCB as I can always put them under the PCB. I'm making a custom case that will be large enough to fit almost anything. and gotcha on the Wima's will do on that.

 Its too bad about airwireing the tube sockets... anyone else have an opinion on this?

 Also still looking at tranistor choices with the Black Gates.

 cheers


----------



## tomb

OK - this may have gotten overlooked in all the discussion about VitQ's and capacitance multipliers (not on the MAX), 
 but this: 

 is this: 



 Sorry for the blatant plug 
	

	
	
		
		

		
			








, but it's been three solid months of waiting for these to come off the manufacturing line at ALPS in Japan.


----------



## tomb

Quote:


  Originally Posted by *chilly* /img/forum/go_quote.gif 
_Thanks Beefy,

 I have also read through this thread like 4 times... and still learn something each time I read it.

 I'm not too worried about what fits on the PCB as I can always put them under the PCB. I'm making a custom case that will be large enough to fit almost anything. and gotcha on the Wima's will do on that.

 Its too bad about airwireing the tube sockets... anyone else have an opinion on this?

 Also still looking at tranistor choices with the Black Gates.

 cheers_

 

Air-wiring is definitely possible. There have been a few builders who've done it. Bloozer is the one I always think of - he did it with the original Millett. Someone has done it on the MAX, too - I just can't remember who at the moment.

 As for transistor choices, MCMinone tells me it will be May before they get anymore 2SC2238's (I have plenty of 2SA968's). IMHO, the Sanyo 2SC2344/2SA1011's are very worthy substitutes. They're almost identical with a tad more emphasis on the high end - but bass is very strong and midrange, too. They're a very good selection. Steinchen describes them this way:

_"crystal clear and airy, rather bright but not piercing bright. good detail and instrument seperation. well defined bass. sounds clean and analytical." _

 The "rather bright" is tempered by the strong bass that's inherent in the MAX. I'm still working on comprehensive testing, but almost every MAX shows a very slight (<0.25dB) response increase starting at midbass and continuing in a linear fashion down to 20Hz. IOW, the combination complements each other and sounds very good. I currently have the ES's with those transistors in the MiniMAX. It gives up nothing to the big MAXes, except for the BG's.

*Black Gates and the MAX -*
 Speaking of which - I left my BG MAX (still uncased) unused for about a month while I've been doing taxes and a small bit of development work. I pulled it out about three days ago to start listening again - I'm using it to build the Alien DAC version that will fit in the same Hammond case as a normal MAX. Anyway, it's taken those last three days for the sound to come back without being harsh on the peaks and in the highs. I was beginning to think something was wrong until it came back into prime last night. So, something to think about if you're contemplating BG's - great sound, but lots of TLC to keep them in shape.


----------



## BoilermakerFan

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_*Black Gates and the MAX -*
 Speaking of which - I left my BG MAX (still uncased) unused for about a month while I've been doing taxes and a small bit of development work. I pulled it out about three days ago to start listening again - I'm using it to build the Alien DAC version that will fit in the same Hammond case as a normal MAX. Anyway, it's taken those last three days for the sound to come back without being harsh on the peaks and in the highs. I was beginning to think something was wrong until it came back into prime last night. So, something to think about if you're contemplating BG's - great sound, but lots of TLC to keep them in shape. 
	

	
	
		
		

		
		
	


	


_

 

Thanks for that note. The previous comments about the long burn-in made me shy away from the BGs, but that just confirms that BGs are not for me, at least not until there is a battery powered portable version of the MAX! Oh, to have a job that doesn't involve 80% travel and 60% of that on airlines... Of course, if I was a desk jockey I'd go crazy. 
	

	
	
		
		

		
		
	


	




 I think I'm pushing the time constants with a Silmic build since I've read that they need a little longer to burn in than the Muse caps, but they will be used on the main dining room console that the family uses every night at dinner, so once they are burned in they stay in use.

 Has anyone tried to build in cross feed to their MAX? I know HeadRoom added it to their commercial version, so I guess we have to be a little careful about stepping on toes, but the concept of crossfeed has me intrigued. Any links or pointers on it would be great.


----------



## BoilermakerFan

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_OK - this may have gotten overlooked in all the discussion about VitQ's and capacitance multipliers (not on the MAX), 
 but this: 

 is this: 



 Sorry for the blatant plug 
	

	
	
		
		

		
		
	


	







, but it's been three solid months of waiting for these to come off the manufacturing line at ALPS in Japan._

 

If it makes you feel better, I just stared at the pic of the box for about the last 25 minutes while I was on a conference call. Over $1,300 in ALPS goodness. 
	

	
	
		
		

		
		
	


	




 I'm certainly glad they're in so I can just add them to my Beezer order instead of ordering them from a third-party source.


----------



## tomb

Tangent has always had a neat little crossfeed board available -
Modified Linkwitz Crossfeed PCB
 There are complete instructions on his site and you can buy the boards from his store.

 I haven't tried his board, but then I'm not a crossfeed fan, anyway.
	

	
	
		
		

		
		
	


	




  Quote:


  Originally Posted by *BoilermakerFan* /img/forum/go_quote.gif 
_If it makes you feel better, I just stared at the pic of the box for about the last 25 minutes while I was on a conference call. Over $1,300 in ALPS goodness. 
	

	
	
		
		

		
		
	


	




 I'm certainly glad they're in so I can just add them to my Beezer order instead of ordering them from a third-party source._

 

Yes, it makes me feel better.
	

	
	
		
		

		
		
	


	




 There's more than what you counted in the pic, though.


----------



## BoilermakerFan

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Tangent has always had a neat little crossfeed board available -
Modified Linkwitz Crossfeed PCB
 There are complete instructions on his site and you can buy the boards from his store.

 I haven't tried his board, but then I'm not a crossfeed fan, anyway.
	

	
	
		
		

		
		
	


	


_

 

Thanks. I like that board design, but I didn't realize the design inherently has a 6-10dB signal drop, so that could have an impact on the MAX's output volume. I was thinking about using it as a separate "input" option on the preamp, but it has a "bypass" option to minimize the crossfeed. 

 It's definitely only an option for a dedicated MAX headphone amp and not a good fit for my consoles which will be feeding speakers as well as 'phones. Looks like it goes into the holding que for integration into the future mosfetMAX build which will be a dedicated headphone amp. I have the 8" long Hoffman box, so I'd have room for an AlienDAC, LDR, and the crossfeed boards in that enclosure if the mosfetMAX board will be the same size as the current boards.


----------



## chilly

Hey Tom your turning me off to the black gates.... although I use my amp 6-8 hours every day (desk jocky at work). I just don't think I would have what it takes for the black gates. I might just buy the .18 VitQ's and use the ES's I bought from you a couple of weeks ago.

 Although how do the KZ's compare to the ES's since the KZ's are supposed to be there top of the line... again, size isn't an issue for me here.

 cheers


----------



## tomb

BoilermakerFan;4034053 said:
			
		

> Thanks. I like that board design, but I didn't realize the design inherently has a 6-10dB signal drop, so that could have an impact on the MAX's output volume.<snip>
> 
> 
> 
> ...


----------



## tomb

Quote:


  Originally Posted by *chilly* /img/forum/go_quote.gif 
_Hey Tom your turning me off to the black gates.... although I use my amp 6-8 hours every day (desk jocky at work). I just don't think I would have what it takes for the black gates. I might just buy the .18 VitQ's and use the ES's I bought from you a couple of weeks ago.

 Although how do the KZ's compare to the ES's since the KZ's are supposed to be there top of the line... again, size isn't an issue for me here.

 cheers_

 

I don't know exactly - they're too big for me. I have _read_ that they are very similar, with KZ's better overall and in the highs, but not quite as much bass as the ES's.


----------



## manaox2

Ready to place my order, and the heatsink mounting kits with the should washers are out of stock. 
	

	
	
		
		

		
		
	


	




 Where can I find these?


----------



## tomb

Quote:


  Originally Posted by *manaox2* /img/forum/go_quote.gif 
_Ready to place my order, and the heatsink mounting kits with the should washers are out of stock. 
	

	
	
		
		

		
		
	


	




 Where can I find these?_

 

Whoops.
	

	
	
		
		

		
		
	


	




 I have plenty, just not bagged up and labeled. I can do that tonight, though. There's more there now.

 Dadgum IRS has put me way behind.


----------



## manaox2

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Whoops.
	

	
	
		
		

		
		
	


	




 I have plenty, just not bagged up and labeled. I can do that tonight, though. There's more there now.

 Dadgum IRS has put me way behind.
	

	
	
		
		

		
		
	


	


_

 

Thanks Tom!


----------



## Beefy

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_I don't know exactly - they're too big for me. I have read that they are very similar, with KZ's better overall and in the highs, but not quite as much bass as the ES's._

 

Interesting to hear..... just a theory, but perhaps KZ are better with the 'bassy' 12AE6 tubes, and ES are better with the thinner bass of the 12FK6?


----------



## slowpogo

I finally got all the paneling done for my case. Here she is in all her glory:


----------



## bperboy

Whoa! I love those top plate grills!


----------



## Beefy

The nice and chunky front and back panels are great too. Front panel express?


----------



## fault151

slowpogo= love the case! Looks great!


----------



## slowpogo

Thanks guys. The front, back and top were done by Front Panel Express. The grill under the vent holes came from an old computer case, as did the gold-colored feet.

 I wanted the top vents to be basic and geometric, but still have some character. I'd do it slightly differently (more rounded) if I could do it over but I'm happy with what I have. 

 I started planning for this amp about 6 months ago, and it's finally done. It's a good feeling. Not only do I love how it sounds, but it's now a sturdy little thing that looks as good as something you'd buy in a hi-fi shop (in my opinion).


----------



## tomb

Quote:


  Originally Posted by *slowpogo* /img/forum/go_quote.gif 
_<snip>I started planning for this amp about 6 months ago, and it's finally done. It's a good feeling. Not only do I love how it sounds, but it's now a sturdy little thing that looks as good as something you'd buy in a hi-fi shop (in my opinion)._

 

Agreed. You did a great job!!


----------



## soloz2

anyone have some 2k 1/2w resisters? I need a few for RLED positions. I don't have any on hand, and the 1.2k resistors aren't playing nicely w/ my LEDs 
	

	
	
		
		

		
		
	


	




 I don't want to place an order for only a handful of resisters so any help would be appreciated. I can pp the funds


----------



## manaox2

Would a 10 ohm resistor be safe in R1 for a 30VDC trafo? Working on making sure I have parts right for the tweaks.

 EDIT: seems from the graph that I would probably be better off using a 30 Ohm, right?


----------



## tomb

Quote:


  Originally Posted by *manaox2* /img/forum/go_quote.gif 
_Would a 10 ohm resistor be safe in R1 for a 30VDC trafo? Working on making sure I have parts right for the tweaks.

 EDIT: seems from the graph that I would probably be better off using a 30 Ohm, right?_

 

Maybe split the difference and use a 20ohm?


----------



## chilly

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_I don't know exactly - they're too big for me. I have read that they are very similar, with KZ's better overall and in the highs, but not quite as much bass as the ES's._

 

could one use both the KZ's and the ES's in a build, i.e. put the ES's in CA2 position and the KZ's in the CA7 position, or vice versa, depending on which has more impact on bass.


 to be honest I don't know much about circuitry to really understand if it would help or hurt.



 and do resistors make that much of a difference, such as if I used the fancy Caddock or Mills resistors? or would I be flushing money down the toilet.

 cheers


----------



## ruZZ.il

NICE ONE(!), Slowpogo. congrats!


----------



## joneeboi

Quote:


  Originally Posted by *chilly* /img/forum/go_quote.gif 
_could one use both the KZ's and the ES's in a build, i.e. put the ES's in CA2 position and the KZ's in the CA7 position, or vice versa, depending on which has more impact on bass._

 

One could do that. This is the stage where everything comes down to personal experience, so take every recommendation with a grain of salt. What may work for one person may not necessarily turn out for another, so do what's best for your sound preference.

  Quote:


  Originally Posted by *chilly* /img/forum/go_quote.gif 
_and do resistors make that much of a difference, such as if I used the fancy Caddock or Mills resistors? or would I be flushing money down the toilet._

 

It depends on where you use them. The biggest impact would be to put them directly in the signal path, which corresponds to RB14. For other positions, you'd have a harder time justifying it based purely on theoretical sound difference per dollar. Some people hear a big difference while others "hear" a big difference. Best way to find out is to try it for yourself.


----------



## amphead

Stunning Slowpogo! It certainly would look at home in an upscale hi-fi shop. Congrats on a beautiful design!


----------



## Beefy

So over the last week, instead of writing grant applications 
	

	
	
		
		

		
		
	


	




 , I've read the entire thread here on Head-Fi, as well as about 100 pages in total over at diyaudio.org. I understand most things happening with the tweaks, but still have a couple of lingering issues.

 Firstly, output resistors. I understand some people don't like them because they hurt dynamics...... but isn't that a direct result of most people using carbon film resistors? I know that the likes of Stackpole, KOA etc. are the tube-enthusiasts-darling, but it was my understanding that carbon film is inferior to metal film across pretty much all measured characteristics.

 Secondly, power transistors. How are people _honestly_ comparing the different options? I find it difficult to believe that you can get such big distinctions as people claim between these parts, when so much time and effort passes between testing one versus another in the same amp. Unlike testing between caps, where plenty of people have identical builds except for the caps, nobody seems to have rigs where the only difference is the transistors. Or if they do, they are Black Gate models which would probably sound subtly different even with the same transistors, depending on burn in status and individual tube characteristics.

 Thoughts?


----------



## regal

the output transistors can be socketed, making comparison possible.


----------



## Beefy

How many have done that, in this amp, and 'published' their findings?


----------



## chilly

joneeboi,

 Thanks for the info. Alright Here is what I'm doing... I think.

 I'm going to use the KZ's in the CA7 position
 ES's in the CA2 position

 with .18 VitQs in the CA8 bypass


 do you think the .18 VitQs would be ok in the CA9 or stick with the WIMA's...

 I just ordered the 2sc3422 and its complement for my BJT's I think this may be a great compliment to the ES and KZ's, plus I think the warm midrange that could happen will be very pleasing.

 cheers again

 TomB Thanks in advance for my order I just placed!!!


----------



## FallenAngel

Quote:


  Originally Posted by *chilly* /img/forum/go_quote.gif 
_joneeboi,

 Thanks for the info. Alright Here is what I'm doing... I think.

 I'm going to use the KZ's in the CA7 position
 ES's in the CA2 position

 with .18 VitQs in the CA8 bypass


 do you think the .18 VitQs would be ok in the CA9 or stick with the WIMA's...

 I just ordered the 2sc3422 and its complement for my BJT's I think this may be a great compliment to the ES and KZ's, plus I think the warm midrange that could happen will be very pleasing.

 cheers again

 TomB Thanks in advance for my order I just placed!!!_

 

Vitamin Q's are somewhat nicer than Wima, definitely go with them if you can.


----------



## regal

Quote:


  Originally Posted by *Beefy* /img/forum/go_quote.gif 
_How many have done that, in this amp, and 'published' their findings?_

 


 here:

discrete diamond buffer - parts list


----------



## tomb

Quote:


  Originally Posted by *Beefy* /img/forum/go_quote.gif 
_So over the last week, instead of writing grant applications 
	

	
	
		
		

		
			





 , I've read the entire thread here on Head-Fi, as well as about 100 pages in total over at diyaudio.org. I understand most things happening with the tweaks, but still have a couple of lingering issues.

 Firstly, output resistors. I understand some people don't like them because they hurt dynamics...... but isn't that a direct result of most people using carbon film resistors? I know that the likes of Stackpole, KOA etc. are the tube-enthusiasts-darling, but it was my understanding that carbon film is inferior to metal film across pretty much all measured characteristics._

 

Decent guess, but no. Metal film just sounds bad in the output positions, period - and yes, I've tried both on identical amps at the same time. A high value metal film will sound noisy and lose dynamics - a very bad sounding combination.

 It's true that it hurts dynamics. This is immediately apparent on high impedance phones such as Sennheisers. With low impedance - something like KSC75's or Grado's, the dynamics are not noticeably hurt at low resistor values, but some of the "tizziness" goes away and there's a soft sheen on the highs (with some sort of carbon resistor, there).

  Quote:


 Secondly, power transistors. How are people _honestly_ comparing the different options? I find it difficult to believe that you can get such big distinctions as people claim between these parts, when so much time and effort passes between testing one versus another in the same amp. Unlike testing between caps, where plenty of people have identical builds except for the caps, nobody seems to have rigs where the only difference is the transistors. Or if they do, they are Black Gate models which would probably sound subtly different even with the same transistors, depending on burn in status and individual tube characteristics. 
 

The differences are not subtle, and yes - I have 6 MAXes right now, each with different output transistors - also had four regular Milletts before that, each with different transistors in the DB's. With the Millett, you could take the same amp and plug/unplug as many different DB's as you had on hand. That's probably how Steinchen made his original reviews. 
	

	
	
		
		

		
		
	


	




 Moreover, I've heard nothing to dispute Steinchen's original work on such reviews (as referenced in Regal's link), except that I disagree slightly with his description of "rough highs" on the 2SC3421/2SA1358. (I think with the right output cap and higher bias currents on the MAX, the highs are fairly smooth - they're definitely emphasized in those transistors, though - so is the bass, but in extension, not in slam.) If you read the older Millett threads over on DIYForums.org, Steinchen at one point declared the 2SC34221/2SA1358 pair his favorite. So, things change as you try other transistors and note the differences.

 There's also a point I made not too far back in this very same thread. AMB took issue with it because it read as if I was saying that the tubes did not make the most difference with sound. That's true to an extent - what happens in my experience with these things is that differences in tubes of the same type are more or less overwhelmed by the buffer. This was obvious in the older Millett, since you could plug and unplug the DB's versus a monolithic buffer. With the monolithics, even small differences in the tubes between brands seemed to make a difference. That goes away, IMHO, when a strong discrete buffer is applied.

 Now, that said, changing from a 12AE6 to a 12FK6 will affect a huge difference in sound. Personally, I still think it's debatable in some instances whether that difference is greater than the difference between changing from a 2SC3422/2SA1359 pair to a 2SC3421/2SA1358 pair. Those two are very different, for instance. Whereas, differences between the 2SC2238/2SA968 and the 2SC2344/2SA1011 are much more subtle.

 As stated in some of those posts, though, the gain and sound difference are large enough between the 12AE6 and 12FK6 that many people settle on one or the other. That makes any changes from then on are effected almost entirely by the transistors.

 Keep in mind that at this point, there are very few amps that have as much history and refinement in the DIY headphone community as the Millett Hybrid. The basic circuit has been built for years now, and some of us are on our way to building a dozen or more.
	

	
	
		
		

		
		
	


	




  Quote:


 Thoughts? 
 

Yep.


----------



## tomb

Quote:


  Originally Posted by *chilly* /img/forum/go_quote.gif 
_joneeboi,

 Thanks for the info. Alright Here is what I'm doing... I think.

 I'm going to use the KZ's in the CA7 position
 ES's in the CA2 position

 with .18 VitQs in the CA8 bypass


 do you think the .18 VitQs would be ok in the CA9 or stick with the WIMA's..._

 

Don't put anything in CA9 but Wima's, or it will kill the bass - that includes VitQ's. The only exception to this is when using Black Gates. Either nothing or perhaps the little 0.47uf, 50V BG NX-HiQ's are appropriate.

  Quote:


 I just ordered the 2sc3422 and its complement for my BJT's I think this may be a great compliment to the ES and KZ's, plus I think the warm midrange that could happen will be very pleasing. 
 

If you choose ES's, use Wima's everywhere except those VitQ's at the CA8 output positions, you are in for a real treat.
	

	
	
		
		

		
		
	


	




  Quote:


 cheers again

 TomB Thanks in advance for my order I just placed!!! 
 

It's on the way!
	

	
	
		
		

		
		
	


	




 BTW, about the KZ vs. ES. The biggest difference will be which one you use at CA7. CA2, as a shunting cathode bypass, has very little direct effect on sound. You can just as well put an FC, FM, UPW there as long as it's 1000uf and is bypassed by the Wima. There will be an improvement with ES's, KZ's, or some other boutique electrolytic, but any differences will be very subtle. Paradoxically, the choice of film cap at CA9 can have a huge and immediate effect on bass - most will kill it. That's why I recommend almost nothing back there except a Wima.

 Changes at CA7 (or CA8), on the other hand, are immediate and significant at all frequencies.


----------



## Beefy

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Decent guess....

 The differences are not subtle...._

 

Well, I'm a lot more convinced now with all that info in one place - rather than alluded to on different occasions in a 400+ page thread 
	

	
	
		
		

		
		
	


	




 I'll cogitate on all this over the weekend. Maybe I should place another Beezar order for some transistors to replace the BJE 243/253 in Jeff's kit (if Jeff ever sends me an invoice or his PayPal details), and some KOAs. I would be able to drop some extra $$$ on the order for those extra VitQ's as well to bring my karma back into balance 
	

	
	
		
		

		
		
	


	




 Its all going to be a tough call when I come to build, really. I'll have a choice between KZ and ES at CA7, 0.18 and 0.22µF VitQ's at CA8, possibly make a decision between a slamming 2SC3422/2SA1359 and a neutral/detailed 2SC2238/2SA968, and decide whether I want any taming of the output.

 *sigh* too many choices to make, too little time to test any of them for myself, and too little money to pay for it all


----------



## chilly

Beefy,

 My first max was a Jeff kit, and I built it stock with the exception of putting in ES's and VitQ's in the appropriate places. I have to say that it makes a very nice sounding amp. I use 10ohm resistors in output to tame some tube noise(i'm using IEM's).

 I'm sure you have read my above posts as well, and I am building another amp... with maybe a bit better sonics. we shall see, Hopefully I can start today.... But I just got another freelance rush project that I need to finish before Monday, ARGH!!!. Life always gets in the way.

 Well I can vouch for jeff's kit it sounds great and neutral. Its also a Can't miss build on the MAX site!

 -cheers


----------



## Beefy

Quote:


  Originally Posted by *chilly* /img/forum/go_quote.gif 
_Well I can vouch for jeff's kit it sounds great and neutral. Its also a Can't miss build on the MAX site!_

 

Oh, I'm sure it does sound great. But I am only ever going to build one of these, and I don't really want to tweak once it is built if I can avoid it. Get it _right_ the first time.

 And the best thing is, I can buy a few extra parts for the DB and still come up at about the same cost as _just_ Black Gates.

 [EDIT] Thinking about it now, I've already got an awesome solid state amp with my M^3. So as I said much earlier, I'm guess I'm really looking for an introduction to tubes through the MHM. With the boutique parts that I've already got (Muse at CA2 and CA7, Wima at CA9, VitQ at CA8), are there any particular transistor/output resistor combos that will give the best tubey sound? I suspect that the warmth of the 2SC3422/2SA1359 would probably be the closest, with just 10R on the output to smooth it off?


----------



## chilly

Beefy,

 Thats the direction I'm going... 

 sounds like it will be a great build, I'm quite anxious to build mine.

 cheers


----------



## tomb

Quote:


  Originally Posted by *Beefy* /img/forum/go_quote.gif 
_<snip>
 [EDIT] Thinking about it now, I've already got an awesome solid state amp with my M^3. So as I said much earlier, I'm guess I'm really looking for an introduction to tubes through the MHM. With the boutique parts that I've already got (Muse at CA2 and CA7, Wima at CA9, VitQ at CA8), are there any particular transistor/output resistor combos that will give the best tubey sound? I suspect that the warmth of the 2SC3422/2SA1359 would probably be the closest, with just 10R on the output to smooth it off?_

 

The 10R on the output is a highly subjective thing. With Senns, I wouldn't use it. With IEM's, it's probably a necessity. It may change with 12AE6 (needed) vs. 12FK6 (not needed), too. It just depends on how much you value details vs. desiring the ability to have more travel in the volume knob plus more of a "tubey" sound. If you suspect in the least a bit less dynamics than you were expecting, take them out and use jumpers. A DPDT switch is a great idea if you have a wide range of headphones.

 I think you are definitely headed in the right direction, though. Those parts and caps should give you a very good contrast with the M3. I'd go for the Panasonic 1200uf or 1800uf 35V at CA4/5 with Wima's and the Panasonic 1000uf 50V in the power supply. Use good RN55 Vishay-Dales everywhere (or red PRP's for a nice touch), with metal film 2.2ohm power resistors at the R10/11 positions, and you'll have great detail plus oodles of rockin' slam. Detail may not be quite up to the M3, but you'll have a seductive resonance in the mids (Diana Krall, yum!) with a deep, reverberating bass slam.


----------



## slowpogo

I have a small problem with the metal grille on my amp case (pics a few pages back). It came from an old PC case, and is slightly bowed. I want it to be perfectly flat. I attached it to the top panel with Gorilla tape, which seemed to hold it flat no problem, but a day later it has bowed up again. I don't think Krazy glue will really hold wire mesh against aluminum too well.

 How can I flatten it? I tried to tap it out with a tack hammer but it didn't work. If I put it between some books with a heavy weight on top of it, will that eventually flatten it after a few days or so?


----------



## BoilermakerFan

A little off topic, but I just wanted to post up about an amazing singer/songwriter artist I happened to catch in concert this week in Minneapolis. Actually, her opening act was really good too, so I came home with three new CDs. Her name is Tristan Prettyman. Her sound is folk/folk rock or a little folk pop, but not to the extent of Cheryl Crow. The newspaper article described her as a less edgy Chan Marshall (Catpower) but I don't think that's quite a fair comparison and I'm a huge Catpower fan. Anyways, you can hear Tristan's entire first two albums on her website via streaming audio which is pretty cool, but the SQ is obviously lacking. The opening act was a band from Australia called Whitley. They are a foklktronic sound, but only their front man opened for Tristan with a great acoustic set. Anyways, just wanted to share about these two artists because they are definitely motivating me to get on the ball and get at least one of MAXes built and get my Oppo HD-981 / 'phones on order so I can enjoy the full benefit of their CDs and MAX amp! Tristan's voice was made for Senns or AKGs and Whitley will sound great on a pair of Grados or Ultrasones, but they both sound darn great on my Sony A816 with Denon C700 canal phones. 
	

	
	
		
		

		
		
	


	




 If anybody else listens to a lot of folk rock, folk pop, new folk, or folktronic; please send me a PM with new recommendations to check out, I'm really starting to dig this music genre!

 BMF


----------



## Migroo

Guys, I bought some 12FK6 tubes from Beezar and I'm going to swap them tonight.

 I'm expecting to have to re-bias the tubes, but do I have to take the same precautions with the DB bias as I did when setting up the trimmers for the first time? I don't want to risk smoking my DBs! 
	

	
	
		
		

		
		
	


	




 I'm looking forward to the sound of the FK6s as the AE6s sound quite bass heavy on my Senn HD500s - a fault definately with the headphones, not the Max - but swapping the tubes to calm the bass down is a quick fix that I can't resist!!

 Cheers
 Chris


----------



## BoilermakerFan

Quote:


  Originally Posted by *slowpogo* /img/forum/go_quote.gif 
_I have a small problem with the metal grille on my amp case (pics a few pages back). It came from an old PC case, and is slightly bowed. I want it to be perfectly flat. I attached it to the top panel with Gorilla tape, which seemed to hold it flat no problem, but a day later it has bowed up again. I don't think Krazy glue will really hold wire mesh against aluminum too well.

 How can I flatten it? I tried to tap it out with a tack hammer but it didn't work. If I put it between some books with a heavy weight on top of it, will that eventually flatten it after a few days or so?_

 

Is it just polished metal like aluminum? If it's polished and not painted you can torch it to relax the memory, then flatten it under very heavy weight, books won't be enough. The other option is to use JB Weld to bond it to the case top, but it might bow again before the JB cures, so I'd try to flatten it first.


----------



## Beefy

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_The 10R on the output is a highly subjective thing. With Senns, I wouldn't use it. With IEM's, it's probably a necessity._

 

I currently use Audio Technica ATH-AD900, which are 32 ohm and quite sensitive. My next phones, if any, will probably be Alessandro (also 32 ohm). 10R it will be.

  Quote:


 Those parts and caps should give you a very good contrast with the M3. 
 

I look forward to the comparison. The bass with OPA627BP in L/R, and AD8610 in GND is already incredibly staccato - even with my smooth/airy/sparkly phones and using a gain of only 2. Female vocals and horns are spine tingling to boot......


----------



## FallenAngel

Quote:


  Originally Posted by *Beefy* /img/forum/go_quote.gif 
_I currently use Audio Technica ATH-AD900, which are 32 ohm and quite sensitive. My next phones, if any, will probably be Alessandro (also 32 ohm). 10R it will be._

 

Consider adding this later, and only if necessary, any resistor will be worse than no resistor so unless you get some kind of hum/hiss (which you shouldn't), why use it, it'll only give you an extra little bit of room on the volume control. I had absolutely no problem with 32 Ohm Grado SR225 with no resistor.


----------



## Beefy

Quote:


  Originally Posted by *FallenAngel* /img/forum/go_quote.gif 
_Consider adding this later, and only if necessary, any resistor will be worse than no resistor_

 

People keep saying this...... but you can consistently read on Head-Fi and other places about how much better the ER-4P sounds when you use the 'S' adapter, which puts 73 ohms in series with the drivers. Or how the Beyer DT880 sounds better from the 120 ohm output of the Corda Opera, than the 0 ohm output.

 Obviously it is phones/amp dependent, but how can opinions vary so wildly about a thing that is so simple to test?


----------



## fordgtlover

Quote:


  Originally Posted by *Beefy* /img/forum/go_quote.gif 
_People keep saying this...... but you can consistently read on Head-Fi and other places about how much better the ER-4P sounds when you use the 'S' adapter, which puts 73 ohms in series with the drivers. Or how the Beyer DT880 sounds better from the 120 ohm output of the Corda Opera, than the 0 ohm output.

 Obviously it is phones/amp dependent, but how can opinions vary so wildly about a thing that is so simple to test? 
	

	
	
		
		

		
		
	


	


_

 

I believe the principle is that there should be as few component in the path as possible - hence the 'no resistor' view.

 However, this is always balanced by the 'What's the benefit' question. Where the benefit is of greater value - you have your answer.

 So, if adding a resistor does reduce some hum/hiss, and doesn't cause an even greater problem then put it in. If you don't 'need' the resistor then leave it out.

 The RB14 resistors in the Max falls in to the category. Some people have some noise that they would like to address, some people add the RB14 to modify (sweeten) the output while many people just jumper it.

 We all have different gear and different ears. DIY gives you choices to build things that suits your preferences and your gear 
	

	
	
		
		

		
		
	


	




.


----------



## tomb

Quote:


  Originally Posted by *Migroo* /img/forum/go_quote.gif 
_Guys, I bought some 12FK6 tubes from Beezar and I'm going to swap them tonight.

 I'm expecting to have to re-bias the tubes, but do I have to take the same precautions with the DB bias as I did when setting up the trimmers for the first time? I don't want to risk smoking my DBs! 
	

	
	
		
		

		
		
	


	




 I'm looking forward to the sound of the FK6s as the AE6s sound quite bass heavy on my Senn HD500s - a fault definately with the headphones, not the Max - but swapping the tubes to calm the bass down is a quick fix that I can't resist!!

 Cheers
 Chris_

 

You should never have to change the DB bias again. Tubes are different. Every one of them will have a different bias - some worse than others. As long as you don't bump the DB trimmers, though, they should never get out of adjustment. Some people have been known to paint a little fingernail polish on the trimmer screw to mark it and seal it place (assuming you don't _want_ to change it again).


----------



## Phil Townsend

Has anyone tried V Caps?

Tempo Electric : The Great Capacitor Shoot-Out

 Phil
 Santa Fe


----------



## CountChoculaBot

How much could I expect to pay to get someone to construct a standard build with MOSFET DB's? The BOM says it's all approx. $160... could I expect to pay $200-$250?


----------



## Migroo

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_You should never have to change the DB bias again. Tubes are different. Every one of them will have a different bias - some worse than others. As long as you don't bump the DB trimmers, though, they should never get out of adjustment. Some people have been known to paint a little fingernail polish on the trimmer screw to mark it and seal it place (assuming you don't want to change it again)._

 

Hi Tom,

 Thanks for clarification. I went ahead and changed the valves - and you were right. PS and Db bias were rock solid. Tube bias was all over the place! Quick adjustment and we're back to half of PS voltage again.

 The 12FK6s are great btw 
	

	
	
		
		

		
		
	


	




 Chris


----------



## tomb

Quote:


  Originally Posted by *Phil Townsend* /img/forum/go_quote.gif 
_Has anyone tried V Caps?

Tempo Electric : The Great Capacitor Shoot-Out

 Phil
 Santa Fe_

 

The MAX community prefers to use this reference as a baseline (Even though Doug was hard on the K42's.):

Dsavitsk's Notes on Output Coupling Capacitors

 In addition, there are a couple of other famous capacitor reviews, but they all disagree on some things one way or another.

 That said, the V-Cap and the reference you gave seems to follow the ideal needed for the MAX: neutral and detailed. On the other hand, so many boutique caps add a flavor that results in significant fall-off in the bass and the highs - e.g., Auricaps or Sonicap GEN II's (ironically, we used to recommend both in the early life of the MAX history). The MAX is a tube hybrid: a low voltage tube gain stage combined with a very aggressive, deep Class A fully-discrete output stage. That output stage demands the very best in open neutrality - particularly because we have to slap a giant electrolytic on the end of it, anyway. That's another factor to consider - there are no single cap positions in the MAX: they're all in a bypass mode. Bypassing does not follow hard and fast rules of typical boutique-signal-cap applications. The end result is that caps that vary from the best of a neutral, linear response have a very bad effect in the MAX.

 At the same time, the MAX competes at a very low price point compared to its performance. Unfortunately, the V-cap violates that theme by a wide margin. Looking at the V-Cap price list, the 0.22uf is _only_ $89.99!
	

	
	
		
		

		
		
	


	




 2X of those exceeds the basic parts cost of the entire MAX!
	

	
	
		
		

		
		
	


	




 Are they that much better than a couple of VitaminQ's sold at $3? No way. There are people who rank a good pair of VitQ's as good as the very best (see the same Dsavitsk's reference above). With that potential comparison, it makes it very difficult to justify a difference in cost of that magnitude.


  Quote:


  Originally Posted by *CountChoculaBot* 
_How much could I expect to pay to get someone to construct a standard build with MOSFET DB's? The BOM says it's all approx. $160... could I expect to pay $200-$250?_

 

Well, that parts cost is true in an absolute sense. However, one has to consider that up until a couple of months ago, you had to order from up to four different sources to get those parts. If you count the shipping on also adding a boutique capacitor or upgraded output transistors - then that's even more. So, that's an unlisted shipping cost potential of $30-$40, or more. So to consider a fair cost to the seller, you're closer to $200 for the basic parts cost.

 Add to that some miscellaneous items such as the Volume knob, RCA jacks, wiring, case hardware, etc., and I'd say the $250 is a bottom _theoretical_ purchase price for a finished amp. $275 is more like it _as a starting point_ for a commissioned build, and I think that's what Nate Maher used for a brand new one he built. I know we don't count labor (
	

	
	
		
		

		
		
	


	




) in the Head-Fi For Sale forums, but heck - it's worth $100 to someone just to drill all the holes in that case lid!

 Bottom line, yes - a DIYer would compare the parts cost to other DIY amps at $160. Buying a completely built one is a different process of adding up costs, however.


----------



## Kenneth S

Hi Tom,

 How goes the integration of the Alien DAC with the Max coming along? Any luck? I am planning to begin on the MOSFET Max build and also planning to finish up the first Alien build and hook it up to the other one. Clue me in, I get electronic noise when i push the pot up to abt the 12 - 2 o'clock position. Is this something that can be fixed with a magnetic filter on the cables? How much change will the DAC make to the problem?


----------



## Phil Townsend

Thanks Tom...
 I guess the first job is to build The Max...
 I'll pop over and order the board.

 Phil
 Santa Fe


----------



## tomb

Quote:


  Originally Posted by *Kenneth S* /img/forum/go_quote.gif 
_Hi Tom,

 How goes the integration of the Alien DAC with the Max coming along? Any luck? I am planning to begin on the MOSFET Max build and also planning to finish up the first Alien build and hook it up to the other one. Clue me in, I get electronic noise when i push the pot up to abt the 12 - 2 o'clock position. Is this something that can be fixed with a magnetic filter on the cables? How much change will the DAC make to the problem?_

 

Believe it or not, static in the pot is more than likely caused by the tubes. I never considered it until Negatron suggested it awhile back. These RK27's are very resistant to pot noise in the normal course of soldering. I flushed one out one time, only to loose some of the important grease around the shaft (no longer a blue _velvet_). Turned out, it was the tubes - both the left and right would do it to some degree, so switching them had no luck. The tubes weren't that bad, either - sounded OK to me, but not among the best I've had. It was something in the pins and how they connected to the plates or even just slight corrosion on the pins and their contact with the sockets.

 You might try:
 1. Switching the Left and Right tubes with each other and see if the scratchiness changes.
 2. Try a different set of tubes - 12FK6's don't seem as susceptible with their lower gain.
 3. Use a toothbrush and some 91% rubbing alcohol (99cents a quart at Walmart) on the pins to see if that changes things.

 I keep trying to work on the Alien DAC MAX - I have the Alien running - fine and FLAT (slightly less than 3/8" thick at its thickest).
	

	
	
		
		

		
		
	


	




 So, it will work, it's just documenting all of it. It's tops on my list, so hopefully it will not be much longer.
	

	
	
		
		

		
		
	


	




 EDIT: That remedy is for a scratchy pot, maybe. If you're having _constant_ noise at the 12-2 o'clock position, it's probably something else.


----------



## mik000000

I have been through (most) of this thread, but can find no discussion of th relative merits of MOSFET buffers vs Diamond buffers. I understand the MOSFET version is more difficult to build and adjust. Is there a sonic difference?


----------



## denden88

i'm having some problems with completing my max 
	

	
	
		
		

		
		
	


	




. when i power it on, the LEDs come on and the tubes glow but when i plug in my headphones all i hear is hum. and for some reason i can only bias the left side. the right side seems to stay exactly the same, no matter what i do. also when i first turned it on before adjusting the powersupply voltage, the resistor in RB2R slot smoked up a bit. here are the voltages i'm getting:

 V+ to GND: 24.7v
 TA2L to GND: -13.1v
 TB1L to TA2L: -67.5mv
 TB2L to TA2L: -67.5mv

 TA2R to GND: -8.35v (can't regulate)
 TB1R to TA2R: -1.12v (can't regulate)
 TB2R to TA2R: 1.12v (can't regulate)

 i'll take some pictures when i figure out where my camera is

 edit: the resistor that smoked up reads 9ohms


----------



## tomb

Quote:


  Originally Posted by *mik000000* /img/forum/go_quote.gif 
_I have been through (most) of this thread, but can find no discussion of th relative merits of MOSFET buffers vs Diamond buffers. I understand the MOSFET version is more difficult to build and adjust. Is there a sonic difference?_

 

We'll have to wait until someone's built all of them. That would probably be me since I've done six and counting - all with different BJT's. However, stuffing an Alien DAC into one of my existing MAXes comes first. I have the parts ready for two MOSFET MAXes using AMB's JFET mod. Colin is working on one, too - he can compare it to his 2SC3421/2SA1359/ES-VitQ MAX.


----------



## tomb

Quote:


  Originally Posted by *denden88* /img/forum/go_quote.gif 
_i'm having some problems with completing my max 
	

	
	
		
		

		
		
	


	




. when i power it on, the LEDs come on and the tubes glow but when i plug in my headphones all i hear is hum. and for some reason i can only bias the left side. the right side seems to stay exactly the same, no matter what i do. also when i first turned it on before adjusting the powersupply voltage, the resistor in RB2R slot smoked up a bit. here are the voltages i'm getting:

 V+ to GND: 24.7v
 TA2L to GND: -13.1v
 TB1L to TA2L: -67.5mv
 TB2L to TA2L: -67.5mv

 TA2R to GND: -8.35v (can't regulate)
 TB1R to TA2R: -1.12v (can't regulate)
 TB2R to TA2R: 1.12v (can't regulate)

 i'll take some pictures when i figure out where my camera is

 edit: the resistor that smoked up reads 9ohms_

 

Others have smoked that resistor and if memory serves, it was always an output transistor reversed or out of position. Give us those pics when you can.


----------



## tomb

denden88,

 Please refer to this pic from the MAX website to see if you've oriented your output transistors properly:


----------



## denden88

pictures: 
http://farm4.static.flickr.com/3220/...76c60809_o.jpg
http://farm4.static.flickr.com/3269/...9438032c_o.jpg

 ack didnt take any of the output transistors, ill check them real quick


----------



## tomb

I'm concerned that the way you've mounted those output transistors is causing problems. With those standoffs sticking out like that, it's probably very easy to short them out with a probe or something. In any event, you'll never be able to bias them properly without better mounting to the sinks.

 Please verify that the MJE253's are on the middle heat sinks and that the MJE243's are on the outside sinks. Those are the only things I can see from here - except as you say, RB2R is smoked.
	

	
	
		
		

		
		
	


	




 Did you turn the DB trimmers all the way clockwise (about 20-25 turns) before you turned it on? It's possible that they developed enough heat to burn that resistor out, if not. I really think it's a short somewhere, though.


----------



## fran

If you're using MJE253/243 you have them mounted in the wrong positions. And definitely something is wrong with the way the 2 are mounted in the centre of the board.

 Have a look again at Tomb's earlier post above.


 Fran


----------



## slowpogo

Quote:


  Originally Posted by *BoilermakerFan* /img/forum/go_quote.gif 
_Is it just polished metal like aluminum? If it's polished and not painted you can torch it to relax the memory, then flatten it under very heavy weight, books won't be enough. The other option is to use JB Weld to bond it to the case top, but it might bow again before the JB cures, so I'd try to flatten it first._

 

I think it's painted; it's not shiny metal colored, more a flat gray finish. I will try putting it between some books with about 75 pound of barbells on top for a few days. Hopefully it should be close enough to flat that the JB Weld will work. I'd forgotten about the "cold weld" stuff, thanks!


----------



## slowpogo

I read a ways back that it's possible to use the Max as a preamp..IIRC you can just run some RCA jacks to the extra output pads.

 My question is, what DIY power amp project out there would go well with the Max as preamp? I'm thinking of something basic, two-channel and modest power, but with good enough sound to take advantage of the Max (and hopefully, a similarly great price/performance ratio). Any suggestions? Thanks!


----------



## BoilermakerFan

Quote:


  Originally Posted by *slowpogo* /img/forum/go_quote.gif 
_I read a ways back that it's possible to use the Max as a preamp..IIRC you can just run some RCA jacks to the extra output pads.

 My question is, what DIY power amp project out there would go well with the Max as preamp? I'm thinking of something basic, two-channel and modest power, but with good enough sound to take advantage of the Max (and hopefully, a similarly great price/performance ratio). Any suggestions? Thanks!_

 

Yep. Colin's MAX board is pretty amazing and has a lot features built in that most peeps don't even use! My priority is headphone SQ, so that's why I'm using the MAX as a preamp for 3 out of 4 of my MAX builds. 

 My personal choice for my main MAX console build is a hybrid, tube-buffered inverted gainclone amp that uses a single 6992 tube for a stereo pair of LM3875 chips. It can also be built with the higher power LM3886 chip, but you lose a little of the SQ of the LM3875 chip. There are other chip amp kits or designs out there, but I like the simplicity of the tube buffer inverted gainclone. Output is 35W/ch or 50W/ch. SKA Audio also has a nice discrete stereo amp kit for 150W/ch that I'll be using in another build with his 300W/ch mono amp for a 2.1 system. The third build will be another 2.1 system with the LM3875 hybrid tube gainclones feeding a full range pair of speakers and the SKA 150W mono feeding a sub to cover the very low end bass, but with SQ being the priority. The LM3875 and LM3886 definitely top most peeps lists for best sounding chip amps though, so I wouldn't stray far from those for now if you are interested in the gainclone amps.

 Twisted Pear audio also makes really nice amp kits that get rave reviews, so if your looking for kits, I'd start with SKA or TP. If you want a more challenging, but IMHO, better amp design, they go for the tube buffered inverted chip amp. FWIW, I'm going to be using Twisted Pear's Darwin Selector as my input switches for my console builds instead of higher end rotary switches. 

 Tomb has been helping me with this very long process of deciding what to do with these consoles for some time now and he's been a great help. I just wish I was further along in the process, but I still need to order my parts for the other two builds from Beezer, DK, Mouser, and Handmade Electronics among others. 

 I'll put together the links to all the relevant threads and web sites and I'll send them to you in a PM tomorrow... I've been down and out for the last three days with a nasty virus, so I'm behind on my paperwork and many other things like my electronics orders.


----------



## Beefy

Jeff hasn't got back to me yet with details of my kit, so I thought I'd have a bit of a play around on Mouser to see what I could do with my own BOM.

 I'm finding that the cost of the Vishay Dale resistors has decreased by up to a half compared to both the offical and Jeff's BOM...... or have I just gone mad?


----------



## Beefy

Oh, and I saw it asked many pages back, but didn't see an answer. Now that LEDs - LSDiodes Optoelectronics is no more, are there any drop-in replacements for the MHM from the usual suppliers? Mouser would be preferred.......


----------



## tomb

Quote:


  Originally Posted by *Beefy* /img/forum/go_quote.gif 
_Jeff hasn't got back to me yet with details of my kit, so I thought I'd have a bit of a play around on Mouser to see what I could do with my own BOM.

 I'm finding that the cost of the Vishay Dale resistors has decreased by up to a half compared to both the offical and Jeff's BOM...... or have I just gone mad?_

 

No, that's right, by gosh -8 cents for a RN55D1001FB14 (1K RN55 V-D resistor). It's nice to see prices going down for once. I doubt that we're going to see too much of that in the coming months. 
	

	
	
		
		

		
		
	


	




  Quote:


  Originally Posted by *Beefy* /img/forum/go_quote.gif 
_Oh, and I saw it asked many pages back, but didn't see an answer. Now that LEDs - LSDiodes Optoelectronics is no more, are there any drop-in replacements for the MHM from the usual suppliers? Mouser would be preferred......._

 

I just thought LSDiodes was a cool vendor and listed them on purpose. However, 3mm LED's are pretty much a commodity - anything with an mcd >1000 will probably work. It's been my experience, though, that "super-bright" LED's are more easily found elsewhere (and at a lower price) than Mouser or DigiKey. Here's one that many people have used instead of LSDiodes:
SUPER BRIGHT LEDS home

 Note that I use 5mm, low power diffused LED's for the panel LED. These from Mouser have given me great results:
 78-TLHB5400 Blue
 78-TLHG5400 Green
 78-TLHR5400 Red
 78-TLHY5400 Yellow


----------



## tomb

Quote:


  Originally Posted by *fran* /img/forum/go_quote.gif 
_If you're using MJE253/243 you have them mounted in the wrong positions. And definitely something is wrong with the way the 2 are mounted in the centre of the board.

 Have a look again at Tomb's earlier post above.


 Fran_

 

I think denden88 has them correct. It's just that we can't tell 253 from 243 from here, which is why I asked him to check which transistors were which. His photo is upside down relative to the image legend posted from the MAX website, so it looks wrong - but the MJE's are on the volume pot side of the heat sinks.


----------



## Beefy

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_It's been my experience, though, that "super-bright" LED's are more easily found elsewhere (and at a lower price) than Mouser or DigiKey._

 

I suspected that, but I'd still be trying to keep things from one supplier.

  Quote:


 Note that I use 5mm, low power diffused LED's for the panel LED. These from Mouser have given me great results: 
 

Don't recommend the one in the BOM anymore? 
	

	
	
		
		

		
		
	


	




 I used a really expensive Lumex one in my M^3, but it is pretty.

 Oh, related question...... any problems with changing RA5C independent of RA5L/R?


----------



## tomb

Quote:


  Originally Posted by *Beefy* /img/forum/go_quote.gif 
_I suspected that, but I'd still be trying to keep things from one supplier.



 Don't recommend the one in the BOM anymore? 
	

	
	
		
		

		
		
	


	


_

 

Hmm ... actually, no. That one is "clear." I guess I need to change that. 
	

	
	
		
		

		
		
	


	




 Quote:


 
 I used a really expensive Lumex one in my M^3, but it is pretty.

 Oh, related question...... any problems with changing RA5C independent of RA5L/R? 
 

No, each LED is independently sourced - but the ones I just posted do fine with the same 2K resistor.


----------



## Kenneth S

I am mulling over popping in a stepped attenuator in its place. You reckon that will improve things? 
	

	
	
		
		

		
		
	


	




 Gonna start on the second build am going for a full sized wooden chassis. With blackgates and MOSFETs, how you reckon it will sound? And yeah maybe a stepped attentuator.


----------



## fault151

Quote:


  Originally Posted by *Kenneth S* /img/forum/go_quote.gif 
_I am mulling over popping in a stepped attenuator in its place. You reckon that will improve things? 
	

	
	
		
		

		
		
	


	




 Gonna start on the second build am going for a full sized wooden chassis. With blackgates and MOSFETs, how you reckon it will sound? And yeah maybe a stepped attentuator. 
	

	
	
		
		

		
		
	


	


_

 

What does a stepped attenuator actually do to the sound? How is it better than say a decent alps pot?


----------



## tomb

Quote:


  Originally Posted by *Kenneth S* /img/forum/go_quote.gif 
_I am mulling over popping in a stepped attenuator in its place. You reckon that will improve things? 
	

	
	
		
		

		
			





 Gonna start on the second build am going for a full sized wooden chassis. With blackgates and MOSFETs, how you reckon it will sound? And yeah maybe a stepped attentuator. 
	

	
	
		
		

		
		
	


	


_

 

Be sure you build it with Amb's JFET-MOSFET mod. I think it's significant enough to warrant a separate website for the MOSFET-MAX, but I'm running way behind these days. Unfortunately, that means I've been mortified to find some who are still building the MOSFET version without incorporating this mod.

 Luckily, it's a very easy thing to retrofit. Just to refresh our memory - before I get a chance to update the websites - here's the jist of the mod:

"... the MOSFETs have a significant amount of gate capacitance which, with Q2B and Q3B jumpered, would be driven from the Millett's tube stage directly. The tube has a high output Z, which forms a low-pass filter with the MOSFET gate capacitance and causes a rolloff of the high frequency response. With QB2/QB3 installed, there is now a complementary emitter follower between the tube and the MOSFETs. The emitter follower has low output Z and moves the rolloff frequency well into the ultrasonics. At Negatron's request I did some simulations of the Millett Max diamond buffer section (alone by itself, sans the tube stage) with MOSFETs. The new twist is that QB2/QB3 are replaced with 2SJ74BL and 2SK170BL JFETs, respectively, making them a complementary source follower. This dramatically increases the buffer's input Z as compared to BJTs. As "seen" from the tube, the buffer becomes a negligible load, which is a good thing. To make this work, the RB4/RB6 and RB5/RB7 resistance ratios must go back to 1:1 (use 100 ohms for all of these), and RB2/RB3 should be increased to around 1K-1.2K ohms. QB1 should be 2N5486 and RB12 should be 1K ohms per the Millett Max BOM (MOSFET option). This change prevents the operating current through QB2/QB2 from coming too close to the 2SJ74BL/2SK170BL's Idss low range limit (6mA), yet still allows the output MOSFETs to be properly biased within RB12's adjustment range. The result is quite good. Here is the frequency response of the buffer section from the simulator. Note that the -3dB point is up near 1MHz, which is significantly higher than the tube's frequency response." 

 And the simulation result:





 NOTE: the 2SJ74BL and 2SK170BL JFET's are turned around backwards from the silkscreen on the board for QB2 and QB3, respectively.


----------



## BoilermakerFan

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Be sure you build it with Amb's JFET-MOSFET mod. I think it's significant enough to warrant a separate website for the MOSFET-MAX, but I'm running way behind these days. Unfortunately, that means I've been mortified to find some who are still building the MOSFET version without incorporating this mod.

 Luckily, it's a very easy thing to retrofit. Just to refresh our memory - before I get a chance to update the websites - here's the jist of the mod:

"... the MOSFETs have a significant amount of gate capacitance which, with Q2B and Q3B jumpered, would be driven from the Millett's tube stage directly. The tube has a high output Z, which forms a low-pass filter with the MOSFET gate capacitance and causes a rolloff of the high frequency response. With QB2/QB3 installed, there is now a complementary emitter follower between the tube and the MOSFETs. The emitter follower has low output Z and moves the rolloff frequency well into the ultrasonics. At Negatron's request I did some simulations of the Millett Max diamond buffer section (alone by itself, sans the tube stage) with MOSFETs. The new twist is that QB2/QB3 are replaced with 2SJ74BL and 2SK170BL JFETs, respectively, making them a complementary source follower. This dramatically increases the buffer's input Z as compared to BJTs. As "seen" from the tube, the buffer becomes a negligible load, which is a good thing. To make this work, the RB4/RB6 and RB5/RB7 resistance ratios must go back to 1:1 (use 100 ohms for all of these), and RB2/RB3 should be increased to around 1K-1.2K ohms. QB1 should be 2N5486 and RB12 should be 1K ohms per the Millett Max BOM (MOSFET option). This change prevents the operating current through QB2/QB2 from coming too close to the 2SJ74BL/2SK170BL's Idss low range limit (6mA), yet still allows the output MOSFETs to be properly biased within RB12's adjustment range. The result is quite good. Here is the frequency response of the buffer section from the simulator. Note that the -3dB point is up near 1MHz, which is significantly higher than the tube's frequency response." 

 And the simulation result:





 NOTE: the 2SJ74BL and 2SK170BL JFET's are turned around backwards from the silkscreen on the board for QB2 and QB3, respectively._

 

Is the MOSFET-MAX going to have a new, revised board, or is it just an incorporation of these subtle changes and the additional MOSFETS before the buffers with changed resistor or cap values? I'm planning to build the MOSFET-MAX as a dedicated headphone amp incorporated into the larger Hammond box to fit an Alien DAC, LDR, and crossfeed boards for use with my PC. The MOSFET-MAX will be the last one I build, so I have time to wait for the new website and updated info. I was waiting to order the board because there was going be a revision to it, but now I think I've misunderstood the differences.


----------



## tomb

Quote:


  Originally Posted by *fault151* /img/forum/go_quote.gif 
_What does a stepped attenuator actually do to the sound? How is it better than say a decent alps pot?_

 

Generally speaking (very generally), they are more transparent with wider separation than a "regular" pot. However, the low-volume quieting is not as good. A DACT stepped attenuator has a dB range of about -50dB, but an ALPS RK27 is over -80dB.

 There was quite a bit of talk awhile back in this thread about an LDR attenuator, too - Light Dependent Resistor. This principle is used in some electric guitar volume controls - it removes any mechanical connection contact in the signal path of the attenuator circuit.

 However - and I don't want to _*ever*_ hamper discussion on the MAX, but ... Something like a discussion on pot technologies would benefit everyone in the DIY section on Head-Fi and should perhaps be in its own thread.


----------



## tomb

Quote:


  Originally Posted by *BoilermakerFan* /img/forum/go_quote.gif 
_Is the MOSFET-MAX going to have a new, revised board, or is it just an incorporation of these subtle changes and the additional MOSFETS before the buffers with changed resistor or cap values? I'm planning to build the MOSFET-MAX as a dedicated headphone amp incorporated into the larger Hammond box to fit an Alien DAC, LDR, and crossfeed boards for use with my PC. The MOSFET-MAX will be the last one I build, so I have time to wait for the new website and updated info. I was waiting to order the board because there was going be a revision to it, but now I think I've misunderstood the differences._

 

NO - no board change. However, the MOSFET build has always been an _advanced_ build, with special considerations given to heat rejection, high bias current and power supply demands, etc. The JFET-MOD just added another good reason to give the MOSFET MAX its own supported website.

 We may be drilling some holes in the board, though. 
	

	
	
		
		

		
		
	


	




 If you use 1-1/2" sinks, that's not an issue, though.


----------



## BoilermakerFan

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_NO - no board change. However, the MOSFET build has always been an advanced build, with special considerations given to heat rejection, high bias current and power supply demands, etc. The JFET-MOD just added another good reason to give the MOSFET MAX its own supported website.

 We may be drilling some holes in the board, though. 
	

	
	
		
		

		
		
	


	




 If you use 1-1/2" sinks, that's not an issue, though.
	

	
	
		
		

		
		
	


	


_

 

Good deal, thanks for the clarification Tom. 

 I have 1-1/2" heatsinks for my BJTs already, so I'd just stick with those and the case has the room. I plan to incorporate a couple of other "controversial" add-ons as well such as brass tube dampers. 

 "Advanced-schmanced", sometimes the magic smoke just wants to be free! 
	

	
	
		
		

		
		
	


	




 I'll build my other MAXes first, then order new bits from Beezer when I'm ready to actually build the MOSFET-MAX amp. I think I would rather incorporate Colin's tube DAC instead of the Alien DAC too, so all the more reason to wait. I have my eye on a couple of larger cases from overseas too. 

 - BMF


----------



## Kenneth S

Talking of dampers, read about this oil damper mod too. Maybe I will try that? Was thinking of building a mod with the tube mounted on the case and dampen with a oil sleeve. Think that will rock. :


----------



## BoilermakerFan

Quote:


  Originally Posted by *Kenneth S* /img/forum/go_quote.gif 
_Talking of dampers, read about this oil damper mod too. Maybe I will try that? Was thinking of building a mod with the tube mounted on the case and dampen with a oil sleeve. Think that will rock. :
	

	
	
		
		

		
		
	


	


_

 

I think I would stay away from oil. It will only create a huge mess if it leaks and a lot of oil is actually conductive, so you'd be at a very high risk of a short. The tube dampers I plan to use are from Mapleshade records and they are really more like heatsinks and tube protectors than dampers per say. I just figured I would try them on a MAX since any sonic differences would be easier to hear on headphones than my console speakers.


----------



## pinkfloyd4ever

WRT dampers: http://www.head-fi.org/forums/f6/new...ml#post3920319 you can probably find something like those silicone rings if you look at hardware stores, plumbing supply places, or I know Grainger has them if you have one near you, they're AS568A Dash Number 312 (I don't really know what that means either but if you walk into one and tell them that they should be able to quickly find what you're looking for...and it's the 312 that's important)

 I agree with BMF, oil and electronics don't play well together

  Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_ Something like a discussion on pot technologies would benefit everyone in the DIY section on Head-Fi and should perhaps be in its own thread.
	

	
	
		
		

		
		
	


	


_

 

for Kenneth S, fault151, and anyone else who's interested
http://www.head-fi.org/forums/f6/ste...s-alps-311879/


----------



## fault151

Quote:


  Originally Posted by *pinkfloyd4ever* /img/forum/go_quote.gif 
_

 for Kenneth S, fault151, and anyone else who's interested
http://www.head-fi.org/forums/f6/ste...s-alps-311879/_

 

cheers i'll take a look in a min.


----------



## tomb

Quote:


  Originally Posted by *pinkfloyd4ever* /img/forum/go_quote.gif 
_WRT dampers: http://www.head-fi.org/forums/f6/new...ml#post3920319 you can probably find something like those silicone rings if you look at hardware stores, plumbing supply places, or I know Grainger has them if you have one near you, they're AS568A Dash Number 312 (I don't really know what that means either but if you walk into one and tell them that they should be able to quickly find what you're looking for...and it's the 312 that's important)<snip>_

 

Hmm ... there are four options with that series and Dash Number: depending on whether you want Buna N, Viton, Silicone, or EPDM. From what I've read, you want the one that's Silicone - it has the highest temperature resistance at 450 deg.F. There are some separate o-rings made out of PTFE (teflon) with higher temperature resistance, but they're very hard.

 Specifically, the AS568A, Dash Number 312 in Silicone is Grainger Part #*1RFF3*. I'll pick some up tomorrow and try them out. If I can tell whether they seem to do anything, I'll start carrying them at Beezar.

 Thanks for the tip!


----------



## fran

The millet tubes don't seem to get that hot - so tube cooling is not that big an issue (ref the heatsinks mentioned above). The other thing is that I have tried using the o-ring type dampers and didn;t hear any difference. YMMV but I wouldn't be spending much money. Jim McShane used to do them for 50c apiece.

 Fran


----------



## fran

simul-post!!

 The ones I used were viton - and on tubes that got a lot hotter than the millet ones. No problems with them.

 fran


----------



## tomb

Quote:


  Originally Posted by *jarensberg* /img/forum/go_quote.gif 
_If you want that look you'll need tubes with side getters. If you don't know what that means look at the pictures of the tubes on beezar.com. The 12AE6 has the getter on top and the 12FK6 is on the side. I've found tubes of all types with side getters though._

 

OK. Sorry, John - but I have a top-getter 12FK6 sighting. In fact, I've got a bunch (several?) of top-getter 12FK6's. Most appear to be GE construction with "J" plates as a matter of fact. It looked a bit inconvenient to build them that way, because these also happen to be the style where the plates are held together at the top with a small disc. It's practically concentric with the halo getter.


----------



## jarensberg

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_OK. Sorry, John - but I have a top-getter 12FK6 sighting. In fact, I've got a bunch (several?) of top-getter 12FK6's. Most appear to be GE construction with "J" plates as a matter of fact. It looked a bit inconvenient to build them that way, because these also happen to be the style where the plates are held together at the top with a small disc. It's practically concentric with the halo getter._

 

Right. The point I was trying to make, but did a poor job, was that there is no guarantee of getting a side or top getter for any tube type. If you want a particular look you'll need to ask about the getter type or see the tube for yourself before you buy.


----------



## tomb

Quote:


  Originally Posted by *jarensberg* /img/forum/go_quote.gif 
_Right. The point I was trying to make, but did a poor job, was that there is no guarantee of getting a side or top getter for any tube type. If you want a particular look you'll need to ask about the getter type or see the tube for yourself before you buy._

 

Oh no! You did not do a poor job! Sorry - I wasn't even looking because I thought you might be right. I couldn't remember ever seeing any. In fact, I only stumbled on them by accident - just thought it was interesting to report and quoted your post again as a reference.

 Another one of those tasks you've made me think about wanting to do - draw up details on the various Millett tube constructions and try to make some sense out of all of them.


----------



## Kenneth S

Would this be right for the Amb MOSFET BOM?

 RB1L/RNOT USED - DB Version ONLY - jumper out
 RB6L/R, RB7L/R 100 ohms4
 RB2L/R, RB3L/R 1.2K ohms4
 RB10L/R, RB11L/R2.2 ohm 2W Metal Film4
 RB12L/R 1K ohm Trimmer Pot - different value2
 RB4L/R, RB5L/R, 
 RB8L/R, RB9L/R, 
 RB13L/R 100 ohm10
 RB14L/R 22 ohm2
 QB1L/R 2N54862
 QB2L/R, QB4L/R, 
 QB6L/R 2SJ74BL JFET6
 QB3L/R, QB5L/R, 
 QB7L/R 2SK170BL JEFT6
 QB8L/R alt. MOSFET IRFZ24N2
 QB9L/R alt. MOSFET IRF9Z34N2
 CB8 220pF C0G ceramic - 5mm lead spacing2

 Heat Sink Aavid #531002B02500G (1-1/2"h.)4


----------



## Kenneth S

Hi Tom,

 Do you happen to offer the amb mosfet components for sale thru beezar.com? If so, will they be matched ones?


----------



## tomb

Quote:


  Originally Posted by *Kenneth S* /img/forum/go_quote.gif 
_Would this be right for the Amb MOSFET BOM?

 RB1L/R...........................NOT USED - DB Version ONLY - jumper out
 RB2L/R, RB3L/R................1K ohms.....4 *(1K is sufficient and matches others on the board)*
 RB10L/R, RB11L/R.............2.2 ohm 2W Metal Film....4
 RB12L/R..........................1K ohm Trimmer Pot - different value....2
 RB4L/R, RB5L/R,
 RB6L/R, RB7L/R 
 RB8L/R, RB9L/R, 
 RB13L/R..........................100 ohm....12
 RB14L/R..........................22 ohm....2 *(optional - try jumpers, first)*
 QB1L/R...........................2N5486....2
*QB2L/R.......................2SJ74BL JFET....2*
*QB4L/R, QB6L/R............2N5087....4* 
*QB3L/R.......................2SK170BL JFET....2*
*QB5L/R, QB7L/R............2N5088....4*
 QB8L/R...........................MOSFET IRFZ24N....2
 QB9L/R...........................MOSFET IRF9Z34N....2
 CB8L/R...........................220pF C0G ceramic - 5mm lead spacing....2

 Heat Sink........................Aavid #531002B02500G (1-1/2"h.)....4 (*1" may work for 80-90ma, but this will be tested)*_

 

Note the changes. You misunderstood about the JFETs - they are only used at the QB2 and QB3 positions. 2N5087/2N5088's are still used elsewhere. (Acutally, the 2N5486 is a JFET, too - but its use goes all the way back to the revMH Diamond Buffers.)


  Quote:


  Originally Posted by *Kenneth S* /img/forum/go_quote.gif 
_Hi Tom,

 Do you happen to offer the amb mosfet components for sale thru beezar.com?_

 

Yes, but soon - not right now. Quote:


 If so, will they be matched ones? 
 

Yes - they *must* be matched. You can order them from AMB for the time being, but be sure you get the matching service. Keep in mind that I won't be able to support the build until I get the website, BOM, etc. built. So, you may be taking a slight risk to do the build if you are not an experienced builder.


----------



## BoilermakerFan

Quote:


  Originally Posted by *Kenneth S* /img/forum/go_quote.gif 
_Hi Tom,

 Do you happen to offer the amb mosfet components for sale thru beezar.com? If so, will they be matched ones?_

 


 Edit: tomb already replied... I guess I should have refreshed my screen before posting.


----------



## tomb

Quote:


  Originally Posted by *BoilermakerFan* /img/forum/go_quote.gif 
_Edit: tomb already replied... I guess I should have refreshed my screen before posting._

 

pro'lly my fault - I have a habit of editing, re-editing, re-editing, re-editing ...


----------



## Cloud

is it possible with a 3 channel, active ground built with 2 boards? is it as simple as populating one board with a single channel components and wire the ground through it?


----------



## tomb

Quote:


  Originally Posted by *Cloud* /img/forum/go_quote.gif 
_is it possible with a 3 channel, active ground built with 2 boards? is it as simple as populating one board with a single channel components and wire the ground through it?_

 

I believe Ferrari made one with a 3-channel output buffer, but you run into issues if you want to include the tube. It's just as likely that building a balanced MAX would be easier if you do that. The tubes in the MAX split the power supply voltage in a series circuit. You'd have to burn all that off if you had a board with only one tube in it. It would be easier to just populate the rest of it and get a fully-balanced amp in the bargain.


----------



## BoilermakerFan

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_I believe Ferrari made one with a 3-channel output buffer, but you run into issues if you want to include the tube. It's just as likely that building a balanced MAX would be easier if you do that. The tubes in the MAX split the power supply voltage in a series circuit. You'd have to burn all that off if you had a board with only one tube in it. It would be easier to just populate the rest of it and get a fully-balanced amp in the bargain. 
	

	
	
		
		

		
		
	


	


_

 

So...

 First we'll see the release of the MiniMAX, followed by the MOSFET-MAX. The Tube DAC comes after that. But, when can we expect a Balanced-MAX? Seems like a nice evolution of the family to me! Too bad I don't have any balanced sources or headphones. I'm working on the Console-MAX or Integrated-MAX too, but it won't fit in a Hoffman enclosure.


----------



## BoilermakerFan

I have a couple of questions for the guys that have built the MAX with both 1/4" and 1/8" jacks.

 First, which jack works the best? 

 Second, did you put resistors in line to lower the output to make it more compatible with canal or IEM phones? I'm getting ready to order more bits from Mouser and Digi-Key, so I figured I might add a 1/8" jack for my Denon C700 canal phones, but they are very easy to drive off my Sony A816 DAC so I'd need a good way to drop the level down at the jack so I can use more of the volume pot range.


----------



## slowpogo

One quick question -- are the 1k resistors in the delay circuit in the signal path? I have two Vishay S102 resistors laying around that I might as well put in if they are.


----------



## rockcod

Quote:


  Originally Posted by *slowpogo* /img/forum/go_quote.gif 
_One quick question -- are the 1k resistors in the delay circuit in the signal path? I have two Vishay S102 resistors laying around that I might as well put in if they are._

 

The default BOM has only two resistors in the delay circuit: 3.32K and 1M. And none of them are in the signal path.


----------



## slowpogo

OK, I'm referring to RA4 L/R. They're right on either side of the relay, so I assumed they were part of the delay circuit, sorry.

 They are after R14 but right before the delay, and short to ground. I don't know what that means; do they have any effect on the sound?


----------



## rockcod

Quote:


  Originally Posted by *slowpogo* /img/forum/go_quote.gif 
_OK, I'm referring to RA4 L/R. They're right on either side of the relay, so I assumed they were part of the delay circuit, sorry.

 They are after R14 but right before the delay, and short to ground. I don't know what that means; do they have any effect on the sound?_

 

The only resistors in the signal path you have to worry about are RB14L/R.


----------



## slowpogo

Quote:


  Originally Posted by *rockcod* /img/forum/go_quote.gif 
_The only resistors in the signal path you have to worry about are RB14L/R._

 

Please, just humor me here...is RA4 in the signal path or not?

 And actually, the other resistors *do* impact the sound. I tried putting a 1k Kiwame in the CCS circuit, and it was a fairly drastic difference, no question it changed things. I'd like to similarly experiment on RA4 since I have the nice resistors just sitting here--as long as it's in the signal path.


----------



## joneeboi

The RA4 resistors form a high pass filter with the CA7 caps and RB14 resistors, if present. With BOM specs, you don't have to worry about RA4 so much as you should with RB14 as the corner frequency is well below 1Hz (0.15915494309189533576888376337251Hz, give or take 0.00000000000000000000000000000001Hz ). RA4 can be found in Pete Millett's original Millett Hybrid schematic, labelled R3 and R7. You could toy with it if you want, but you'd have to pay closer attention to your values for RA4, CA7 and RB14 since you'd be juggling three variables instead of two. rockcod still makes a valid point though: RB14 is the resistor you want to be jiggling around with, not so much RA4. Nevertheless, it's your life/funeral and you can do what you like to get the sound you like.


----------



## rockcod

Quote:


  Originally Posted by *slowpogo* /img/forum/go_quote.gif 
_Please, just humor me here...is RA4 in the signal path or not?

 And actually, the other resistors *do* impact the sound. I tried putting a 1k Kiwame in the CCS circuit, and it was a fairly drastic difference, no question it changed things. I'd like to similarly experiment on RA4 since I have the nice resistors just sitting here--as long as it's in the signal path._

 

Please don't take my opinion as authortative, but RA4 is not in the signal path, IMHO -- I believe tomb can provide a much better answer here.

 To a certain extend, everything impacts the sound. But you just have to try it to found out if you like it or not -- that's what makes DIY fun (or frustrating ) And I am sad to report that these tin ears cannot hear the difference among various exotic non-signal path resistors


----------



## pabbi1

Quote:


  Originally Posted by *BoilermakerFan* /img/forum/go_quote.gif 
_So...

 First we'll see the release of the MiniMAX, followed by the MOSFET-MAX. The Tube DAC comes after that. But, when can we expect a Balanced-MAX? Seems like a nice evolution of the family to me! Too bad I don't have any balanced sources or headphones. I'm working on the Console-MAX or Integrated-MAX too, but it won't fit in a Hoffman enclosure. 
	

	
	
		
		

		
			



_

 

Dude - WITH an OPUS balanced out DAC...

Maximus


----------



## manaox2

Quote:


  Originally Posted by *pabbi1* /img/forum/go_quote.gif 
_Dude - WITH an OPUS balanced out DAC...

Maximus_

 

Haha, I've already ordered the parts to make another.


----------



## tomb

Millettus MAXimus ... that fits.


----------



## pabbi1

Perfect case for a balanced Max

Surplus Sales


----------



## manaox2

Quote:


  Originally Posted by *pabbi1* /img/forum/go_quote.gif 
_Perfect case for a balanced Max

Surplus Sales_

 

Bought it, it even has free shipping. Can't beat a shielded case with a built in power supply for $18... Geez.


----------



## tomb

Quote:


  Originally Posted by *rockcod* /img/forum/go_quote.gif 
_Please don't take my opinion as authortative, but RA4 is not in the signal path, IMHO -- I believe tomb can provide a much better answer here.

 To a certain extend, everything impacts the sound. But you just have to try it to found out if you like it or not -- that's what makes DIY fun (or frustrating ) And I am sad to report that these tin ears cannot hear the difference among various exotic non-signal path resistors _

 

It may be that slowpogo is very sensitive to resistor changes.
	

	
	
		
		

		
		
	


	




 On the other hand, there are some old tube hands I've seen claim that V-D's are susceptible to picking up EMF and RF. They claim the PRP's do not.

 I think slowpogo has already changed the RB14's to Rikens and says he prefers those over Kiwame's. It's quite possible that a boutique at the CCS may sound better, but it may be at the expense of some linearity in the CCS, which would lower the impedance and affect tube performance. There may be some middle ground and perhaps he's discovered a spot that works.

 However - IMHO, if someone is looking for resistor upgrades:

 1. I'd change the metal film DB output resistors to the non-inductive wire-wound Mills - something Negatron suggested awhile back. That would be the first one I'd try to change out other than the RB14's.
 2. Maybe change all the V-D's to PRP's and see if that makes a difference. (I think there may be a subtle difference, but it could just be the cool red color.) This is at minimal expense - at least until the prices dropped so dramatically on V-D's. The PRP's are about 30 cents a piece, I think, the last time I looked (Soniccraft and Parts Connexion). So, this move is quite affordable.
 3. It may be that the 1K resistor between the tubes and the DB's may benefit as a boutique resistor. That one carries all the signal and the resistance is not insignificant. That's RB1L/R.

 These are just guesses. IMHO, there are other parts on the board that will benefit more with upgrades. Besides the obvious capacitors, it's useful to find a very good pair of tubes, too. Of course, most of us know that John Wilson used the Caddocks and some Vishay TO-220 resistors throughout and reports a noticeable change. I guess that just confirms what we've always known: the Millett is eminently tweakable and continues to improve as the quality of the parts improve. How much you want to spend is up to you.

 About the RA4L/R resistors. Joneeboi is correct that they benefit the bass filtering on the output by increasing the R x C product. However, if I'm not mistaken the real reason they're there is to drain down the output caps so that your headphones (or other things) don't get zapped. The relay circuit prevents this most of the time, but I suppose the relay's contacts could get zapped, too, if these caps don't drain down.


----------



## Phil Townsend

I tried the PRPs a year or so ago in my homebrew parafeed 45 amp. ( silver wound magnequest irons, Vcaps, silver wire. low dcr supply etc...etc...yadi yadi etc. . I did not like them one bit. I went back to my drifty Allen Bradleys and Audio notes.
 But then it is a hollow state thing.
 The Max is a very different thing and they may work quite well... But they(PRP) do make a very nice pot. 

 Phil
 Santa Fe


----------



## BoilermakerFan

Quote:


  Originally Posted by *manaox2* /img/forum/go_quote.gif 
_Bought it, it even has free shipping. Can't beat a shielded case with a built in power supply for $18... Geez._

 

Where did you see the free shipping? I didn't see free shipping noted on the web site and they have a note that shipping is added to the order after they ship your order. Man, if the shipping is free, I'll order more than two of them.


----------



## manaox2

Quote:


  Originally Posted by *BoilermakerFan* /img/forum/go_quote.gif 
_Where did you see the free shipping? I didn't see free shipping noted on the web site and they have a note that shipping is added to the order after they ship your order. Man, if the shipping is free, I'll order more than two of them._

 

Your probably right then. I just saw the shipping: 0.00 on my receipt.


----------



## bperboy

So, I've got some VD output resistors on my MAX right now. If I were to jumper those, would I get a clearer sound at the loss of Pot turning space?


----------



## pabbi1

Quote:


  Originally Posted by *manaox2* /img/forum/go_quote.gif 
_Bought it, it even has free shipping. Can't beat a shielded case with a built in power supply for $18... Geez._

 


 Before anyone goes too crazy, the toroids I used do NOT come with that case.... but the shielding is perfect for isolating the PSU / toroids. But, it is a VERY sturdy steel case, where the plastic front bolts on (steel underneath) making for a very easy front panel.


----------



## kvant

Quote:


  Originally Posted by *joneeboi* /img/forum/go_quote.gif 
_The RA4 resistors form a high pass filter with the CA7 caps and RB14 resistors, if present. With BOM specs, you don't have to worry about RA4 so much as you should with RB14 as the corner frequency is well below 1Hz (0.15915494309189533576888376337251Hz_

 

 Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_About the RA4L/R resistors. Joneeboi is correct that they benefit the bass filtering on the output by increasing the R x C product._

 

I don't see much point in calculating the corner frequency from CA7 and RA4 alone, i.e., for unloaded amp (BTW, BOM now specifies 1000uF for output caps?). The RA4 actually _increases_ the corner frequency (_decreases_ the R x C product) because it is _in parallel_ with phones. But the effect is pretty marginal - 32 ohm phones look like 31 ohm, 300 ohm phones look like 230 ohm (the second case is seemingly a big drop, but since the output cap covers well even those 32 ohm phones, who cares).

  Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_However, if I'm not mistaken the real reason they're there is to drain down the output caps so that your headphones (or other things) don't get zapped. The relay circuit prevents this most of the time, but I suppose the relay's contacts could get zapped, too, if these caps don't drain down._

 

Without RA4 it could be scratchy during plugging in the phones, perhaps with a bit of thump, but I seriously doubt it would be strong enough to damage any phones.


----------



## BoilermakerFan

Quote:


  Originally Posted by *pabbi1* /img/forum/go_quote.gif 
_Before anyone goes too crazy, the toroids I used do NOT come with that case.... but the shielding is perfect for isolating the PSU / toroids. But, it is a VERY sturdy steel case, where the plastic front bolts on (steel underneath) making for a very easy front panel._

 

I noticed that, I actually thought it was an empty case until I read the description. I like the provision for the voltage regs outside on the heat sink and the built in PSU supplies regulated 5VDC and 18VDC, so I won't scrap it, it will just be put to other uses in the future. It's actually a really nice case for my consoles and I'll need a pair to house the MAX-based preamp and the tube-buffered inverted gainclone amps for the speakers. At the price structure, buying (5) is only $7 more than (4) so I'll opt for (5).

 I'm still not sure I'd reap the full benefit of a balanced MAX build since the only dedicated, stand-alone headphone amp I'll have will be used with my PC and my ripped music. Not all of it is in WAV or lossless formats either. 

 pabbi, I'm also going to send you a PM with an off topic question.


----------



## tomb

Quote:


  Originally Posted by *kvant* /img/forum/go_quote.gif 
_I don't see much point in calculating the corner frequency from CA7 and RA4 alone, i.e., for unloaded amp (BTW, BOM now specifies 1000uF for output caps?). The RA4 actually increases the corner frequency (decreases the R x C product) because it is in parallel with phones. But the effect is pretty marginal - 32 ohm phones look like 31 ohm, 300 ohm phones look like 230 ohm (the second case is seemingly a big drop, but since the output cap covers well even those 32 ohm phones, who cares)._

 

... not sure where you're seeing that the BOM says 1000uf for output caps, but let me know and I'll correct it.

 Also, you may be forgetting that "C" is also less than 1 in that R x C product (uf is 10E-6). So, as "R" gets smaller, the product gets larger. The second case you cite for headphone impedance is still large enough to drop a cap size or two, so I'm not sure I would call that marginal.
	

	
	
		
		

		
		
	


	




  Quote:


 Without RA4 it could be scratchy during plugging in the phones, perhaps with a bit of thump, but I seriously doubt it would be strong enough to damage any phones. 
 

As stated, the relay will prevent this in most instances. Although I was stupid enough to pull the plug out once after the relay had tripped, but before the cap had discharged - "zapped" is the term I used and I'll stand by that.


----------



## tomb

Quote:


  Originally Posted by *bperboy* /img/forum/go_quote.gif 
_So, I've got some VD output resistors on my MAX right now. If I were to jumper those, would I get a clearer sound at the loss of Pot turning space?_

 

Hi, bperboy! I haven't seen you post around here in awhile!

 "Clearer" is a subjective term. For some it may mean "noisier." I think I stated a few posts back that this resistor is a highly subjective item. It depends on several factors, not the least of which is your headphone impedance. I think if you're running high impedance Senns, going without it may make a noticeable difference in dynamics. With lower impedance phones, not so much. That assumes you're using something around 22ohms or below. Higher than that compared to jumpering, and it's probably noticeable with any pair of headphones. However, volume travel is always proportional to the resistor value, regardless of effect on dynamics.

 I've also made the statement many times that a smallish value boutique resistor such as a Kiwame may actually have the effect of improving the sound compared to jumpering - because it's possible that it "tempers" a slight bit of tube noise and tizziness compared to whatever dynamics might be lost (minimal at 10ohms, for instance).

 Sorry if that wasn't more definitive, but it's why many people socket those positions. Personally, I have MAXes with both: jumpers vs. 10 ohm Kiwames.


----------



## kvant

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_... not sure where you're seeing that the BOM says 1000uf for output caps, but let me know and I'll correct it._

 

From _joneeboi_, he says "_With BOM specs...the corner frequency is...0.15915494309189533576888376337251Hz_". That works out with 1k for RA4 and 1000uF for CA7. You don't need to correct it anywhere.

  Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Also, you may be forgetting that "C" is also less than 1 in that R x C product (uf is 10E-6). So, as "R" gets smaller, the product gets larger._

 

Interesting algebra you promote here. As far as I know, R x C is a linear function of R and as such it grows with increasing R, as long as C is positive (which capacitances use to be).

  Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_The second case you cite for headphone impedance is still large enough to drop a cap size or two, so I'm not sure I would call that marginal._

 

Right. But it depends on the way you look at it. If you hold CA7 at BOM value (and you typically suggest people doing so) then the drop in resistance is not important for performance.


----------



## tomb

Quote:


  Originally Posted by *kvant* /img/forum/go_quote.gif 
_<snip>
 Interesting algebra you promote here. As far as I know, R x C is a linear function of R and as such it grows with increasing R, as long as C is positive (which capacitances use to be)._

 

Yep, perhaps I did state it wrong. Yes, R X C is linear, and R is the reciprocal sum of the individual reciprocal resistances, RA4 and the headphone impedance. However, the corner frequency is also proportional to the _reciprocal_ of the R*C product. 
	

	
	
		
		

		
		
	


	




 BTW, I did all these calcs some time ago. The graph on the MAX website illustrates it a bit better:





 RA4 is still there primarily for other reasons and appears to be a common practice on OTL tube amps. A tube hybrid operates under similar circumstances when it comes to offset at the output.


----------



## slowpogo

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_It may be that slowpogo is very sensitive to resistor changes.
	

	
	
		
		

		
		
	


	


_

 

Hehe, joking aside, my hearing is pretty sensitive I think--people have always told me so, as I sometimes hear things I shouldn't 
	

	
	
		
		

		
		
	


	




. I can't fathom how some people can't hear or "don't believe in" headphone burn-in. I think if I were half-deaf I could still hear a difference between my K701's when new and now after 5-600 hours.

 Thanks for the info, tomb...sounds like if I'm gonna experiment I should put my 1k's in RB1L/R. Though those are kind of entrenched in surrounding parts, and will be tricky to get out, compared to the RA4's. When I do it I'll post back with my impressions.


----------



## tomb

Quote:


  Originally Posted by *slowpogo* /img/forum/go_quote.gif 
_Hehe, joking aside, my hearing is pretty sensitive I think--people have always told me so, as I sometimes hear things I shouldn't 
	

	
	
		
		

		
		
	


	




. I can't fathom how some people can't hear or "don't believe in" headphone burn-in. I think if I were half-deaf I could still hear a difference between my K701's when new and now after 5-600 hours.

 Thanks for the info, tomb...sounds like if I'm gonna experiment I should put my 1k's in RB1L/R. Though those are kind of entrenched in surrounding parts, and will be tricky to get out, compared to the RA4's. When I do it I'll post back with my impressions._

 

Ha - yes, I think we can officially declare that the RA4 resistors have been beaten to death.


----------



## joneeboi

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_... not sure where you're seeing that the BOM says 1000uf for output caps, but let me know and I'll correct it._

 

Cripes, that's my bad, Tom. I was a bit too hasty with the calculator. 
	

	
	
		
		

		
		
	


	




 Plus, I missed that paralleling effect with the headphones connected. I didn't mean to spread any bad blood.  That frequency again is 10.91Hz with parameters R = 1000||32 = 31.01 and C = 470.22uF. Without paralleling the 1K and adding the bypass cap, you'd get that 10.58Hz on the graph.

 kvant, Tom's still alluding to the -3db frequency equation. R decreases, f increases.

 Wow, a lot happened between starting to reply and previewing my post.


----------



## tomb

Quote:


  Originally Posted by *joneeboi* /img/forum/go_quote.gif 
_Cripes, that's my bad, Tom. I was a bit too hasty with the calculator. 
	

	
	
		
		

		
		
	


	




 Plus, I missed that paralleling effect with the headphones connected. I didn't mean to spread any bad blood.  That frequency again is 10.91Hz with parameters R = 1000||32 = 31.01 and C = 470.22uF. Without paralleling the 1K and adding the bypass cap, you'd get that 10.58Hz on the graph.

 kvant, Tom's still alluding to the -3db frequency equation. R decreases, f increases.

 Wow, a lot happened between starting to reply and previewing my post._

 

Not to worry - no bad blood from anyone here! It's past my bedtime, though, and that's pretty bad since my brain quits working about noon most days now.


----------



## bperboy

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Hi, bperboy! I haven't seen you post around here in awhile!

 "Clearer" is a subjective term. For some it may mean "noisier." I think I stated a few posts back that this resistor is a highly subjective item. It depends on several factors, not the least of which is your headphone impedance. I think if you're running high impedance Senns, going without it may make a noticeable difference in dynamics. With lower impedance phones, not so much. That assumes you're using something around 22ohms or below. Higher than that compared to jumpering, and it's probably noticeable with any pair of headphones. However, volume travel is always proportional to the resistor value, regardless of effect on dynamics.

 I've also made the statement many times that a smallish value boutique resistor such as a Kiwame may actually have the effect of improving the sound compared to jumpering - because it's possible that it "tempers" a slight bit of tube noise and tizziness compared to whatever dynamics might be lost (minimal at 10ohms, for instance).

 Sorry if that wasn't more definitive, but it's why many people socket those positions. Personally, I have MAXes with both: jumpers vs. 10 ohm Kiwames.
	

	
	
		
		

		
		
	


	


_

 

Thanks for that Tomb! I've got 100ohms on there now I believe, so I'll try jumpering and see what I think...


----------



## kvant

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_So, as RA4 increases, "R" decreases, R*C decreases, but F increases. If I didn't get it right now, I give up. 
	

	
	
		
		

		
		
	


	


_

 

I am sorry, but you didn't. As RA4 increases, "R" also increases. The formula says:

 "R" = 1 / ( 1/RA4 + 1/Rphones )

 When RA4 is zero then "R" is zero as the output is shorted, and if RA4 is infinity (no RA4 populated) then the amp sees just "R"=Rphones as a load. Now adding RA4 to the circuit means decreasing its value from infinity, which causes total load "R" to decrease and that makes the corner frequency to increase, i.e., make the low-frequency performance slightly worse with given CA7. In view of this, the RA4 does not look like any extra insurance on frequency response...

  Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_RA4 is just a bit of added insurance on this particular subject._

 

 Quote:


  Originally Posted by *joneeboi* /img/forum/go_quote.gif 
_I didn't mean to spread any bad blood._

 

No bad blood. It's just that things like Ohm's law and mathematics are not a matter of opinion... but they are quite prone to be influenced by certain circumstances...

  Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_It's past my bedtime..._


----------



## BoilermakerFan

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_
 RA4 is still there primarily for other reasons and appears to be a common practice on OTL tube amps. 
_

 

Can we agree that RA4 serves other purposes besides those discussed above, leave the RA4 value as specified in the BOM, and accept that Colin's design and it's performance is sound (pun intended)? 
	

	
	
		
		

		
		
	


	




 pabbi

 Do you have pics of your balanced MAX in the NABU case? I did a quick search, but didn't see them. Did you remove the front plastic bezel and use a FPE panel in it's place? For one of my builds I'll need to use a large FPE panel to fill in an opening on a console, so I figured the NABU case would work very well for this application while housing a MAX, TPA Darwin source selector, and Colin's Tube DAC once that design is finished.


----------



## tomb

Quote:


  Originally Posted by *kvant* /img/forum/go_quote.gif 
_<snip>

 No bad blood. It's just that things like Ohm's law and mathematics are not a matter of opinion... but they are quite prone to be influenced by certain circumstances..._

 

When the heck did I state that it was _opinon_? If I got it wrong, I got it wrong. Balancing multiple reciprocal fractions in my head late at night wasn't a good idea. Many people have issues with that even in daylight.
	

	
	
		
		

		
		
	


	




 Sorry.
	

	
	
		
		

		
		
	


	




  Quote:


  Originally Posted by *kvant* 
_From joneeboi, he says "With BOM specs...the corner frequency is...0.15915494309189533576888376337251Hz". That works out with 1k for RA4 and 1000uF for CA7. You don't need to correct it anywhere._

 

Still not sure where you're getting that, though. If you take "BOM specs" literally, "R" would be 51.23 with 32ohm phones. In fact, we had a discussion awhile back where adusting RB14 could be a significant advantage to the corner frequency for low impedance phones. Even if you don't do that, I can't seem to get those numbers (more like 4 or 5Hz with 1022uf or 1000uf), but maybe we've confused everyone enough for now.


----------



## joneeboi

Quote:


  Originally Posted by *kvant* /img/forum/go_quote.gif 
_I am sorry, but you didn't. As RA4 increases, "R" also increases. The formula says:

 "R" = 1 / ( 1/RA4 + 1/Rphones )

 When RA4 is zero then "R" is zero as the output is shorted, and if RA4 is infinity (no RA4 populated) then the amp sees just "R"=Rphones as a load. Now adding RA4 to the circuit means decreasing its value from infinity, which causes total load "R" to decrease and that makes the corner frequency to increase, i.e., make the low-frequency performance slightly worse with given CA7. In view of this, the RA4 does not look like any extra insurance on frequency response..._

 

I'm going to go back to the "draining the caps" response as mentioned earlier. It would appear that the paralleling of the headphones with RA4 gives an upper limit to R in the corner frequency equation, namely the headphone impedance. Frankly, I can't tell what its use is beyond keeping the caps drained, but I figure it's there for a reason.

 I believe there has been a mix-up between increasing R in the corner frequency equation and increasing R in the parallel resistor equation. Raising R in the -3db equation would indeed drop the rolloff point, but raising RA4 in the parallel resistor equation indeed lifts the effective resistance seen after the output caps. Raising R in the filter equation has its limits, but I believe RA4 was chosen as something that would work for most, if not all, headphones. Granted, the paralleling effect is much pronounced in higher imp'ed headphones, but I don't think the effect on frequency is all that great, all things considered. Pairing 600ohms with 1000 only gives a total resistance of 375ohms, but that value spits out such a low cutoff frequency that it becomes a non-issue. With lower imp. headphones like Grados, the difference in corner frequency is very small, as shown in the graph in Tom's post and in my previous calculation (10.58Hz compared with 10.91Hz, respectively). I think we can say at this point that the frequency response is not the main focus of this resistor, but as already mentioned, it's for the purposes of keeping those output caps and protecting your headphones from the ghastly effects of "zapping." The relay also keeps one's headphones safe and sound, but I figure it's better to include RA4 than to completely omit it despite its frequency response characteristic.

 This whole discussion has been fun so far, hasn't it? Sorry for misquoting the BOM, TomB. I don't even know where I got that value from - I'm using 470uF Silmic IIs in my MAX.

 *shrug*


----------



## tomb

Quote:


  Originally Posted by *joneeboi* /img/forum/go_quote.gif 
_<snip>This whole discussion has been fun so far, hasn't it? Sorry for misquoting the BOM, TomB. I don't even know where I got that value from - I'm using 470uF Silmic IIs in my MAX._

 

Unless I'm getting things wrong again, you never stated the values the first time. kvant backed those numbers out from your result, but I don't see how. I'm not batting 1000 right now, so it's likely something else I missed.

  Quote:


 *shrug* 
 

Yeah. Me, too.


----------



## kvant

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Unless I'm getting things wrong again, you never stated the values the first time. kvant backed those numbers out from your result, but I don't see how._

 

All I did was to guess the equation joneeboi used but never explicitly showed and then inferred the values (1k for resistance and 1000uF for capacitance) he put in there to get his frequency. As simple as that. Or perhaps I looked into a crystal ball. It doesn't matter that much, joneeboi later confirmed he really used those values. 

  Quote:


  Originally Posted by *joneeboi* /img/forum/go_quote.gif 
_Frankly, I can't tell what its use is beyond keeping the caps drained, but I figure it's there for a reason._

 

To further extend the funny discussion that makes you shrugging: the only reason for the resistor is to hold the output at (or close to) ground. Its value is a compromise - it has to be there to do its job but cannot be too small in order not to force coupling cap too large. But the compromise is more theoretical than real, since...

  Quote:


  Originally Posted by *joneeboi* /img/forum/go_quote.gif 
_...Pairing 600ohms with 1000 only gives a total resistance of 375ohms, but that value spits out such a low cutoff frequency that it becomes a non-issue. With lower imp. headphones like Grados, the difference in corner frequency is very small, as shown in the graph in Tom's post and in my previous calculation (10.58Hz compared with 10.91Hz, respectively)._

 

However, to keep the statements precise - RA4 does not keep the output caps drained, but charged. Drained cap would have zero voltage across it and that certainly is not the case here.


----------



## regal

How much is the phase distortion which is present up to 10x the corner feq really an issue with headphones?


----------



## tomb

Quote:


  Originally Posted by *kvant* /img/forum/go_quote.gif 
_<snip>However, to keep the statements precise - RA4 does not keep the output caps drained, but charged. Drained cap would have zero voltage across it and that certainly is not the case here._

 

Good point. Thanks for that explanation.


----------



## tomb

Quote:


  Originally Posted by *regal* /img/forum/go_quote.gif 
_How much is the phase distortion which is present up to 10x the corner feq really an issue with headphones?_

 

I know Colin's a believer in it. However, as noted many times before, higher impedance phones have enough "clearance" from the corner frequency at 470uf that there's no need for worry.

 As for Grados, they seem to pair better with Milletts and MAXes than many other phones, anyway. I have not heard any complaints about lack of bass with Grados all the way back to the revMH Millett Hybrid. I suspect that any potential phase distortion is mitigated by the basic response of a Grado. According to the Headroom graphs, response is down about 10-15db at 20Hz with an SR225. That doesn't mean that they sound bass-light, far from it. It just looks like most of the energy is directed at the 80-120Hz mid-bass.

 That's just a guess. As I told Joneeboi - I've had a couple of strike-outs lately.


----------



## joneeboi

I'm glad we all got that out of our systems. Thanks for sharing your pearls, kvant and Tom.


----------



## Beefy

Quote:


  Originally Posted by *slowpogo* /img/forum/go_quote.gif 
_I can't fathom how some people can't hear or "don't believe in" headphone burn-in. I think if I were half-deaf I could still hear a difference between my K701's when new and now after 5-600 hours._

 

Not wanting to drag things off-track or start an argument...... but I'm curious as to what you use as a specific point of reference over that 600 hours.

 Do you have a non-burnt-in pair of K701 that you listen to for short periods?
 Or is it just what you 'remember' they sound like?


----------



## slowpogo

Quote:


  Originally Posted by *Beefy* /img/forum/go_quote.gif 
_Not wanting to drag things off-track or start an argument...... but I'm curious as to what you use as a specific point of reference over that 600 hours.

 Do you have a non-burnt-in pair of K701 that you listen to for short periods?
 Or is it just what you 'remember' they sound like?_

 

Eh, I've been through this too many times. No, I'm not conducting a scientific experiment, and I don't have a brand new pair of K701s to compare with. But when I first heard them I almost sent them back. They gave me a headache. The highs were _grating_, almost physically irritating. Songs I knew to have deep bass simply...didn't. The imaging was worse than my $50 Audio Technica phones.

 I didn't listen to them again for a few weeks (they were hooked up and playing constantly). Either I belong in a mental hospital, or those headphones sounded a helluva lot better when I picked them up after burning in. All the above complaints were gone, I felt happy and pleased, and a big grin spread on my face, and I spent the next hour sitting in the laundry room listening to music.

 I feel like I'm in a courtroom in these discussions...nowhere else is my basic human capacity for memory of experience questioned so severely. Like, if I told you I knew someone who was learning a piece on piano, who didn't sound so good with it at first...then two months later I heard them play, and thought they sounded spectacular. Would you demand proof, question the subjective nature of experience? Or would you trust that as a person with ears I can remember that where there were bunked notes in the first performance, they were now correct, that where the person had to slow down for difficult passages the first time, now they are played up to tempo...it's really not different in my view.


----------



## Beefy

Quote:


  Originally Posted by *slowpogo* /img/forum/go_quote.gif 
_I feel like I'm in a courtroom in these discussions...nowhere else is my basic human capacity for memory of experience questioned so severely._

 

I don't mean it to sound like that at all, and I apologise if it came across that way. And I do think that people too eagerly dismiss the *massive* power of their own brains, but in a completely different way to what you think.

 I've have a PhD in Physiology, and currently work as a Biomed research scientist. In my undergrad days I studied a little neuroscience and a lot of audiology. In my learned opinion, our brain has many orders of magnitude more capacity for adaptation to sound than a headphone driver. I believe you insult yourself by saying that the effect is purely because of the headphones, while at the same time over-estimating the power of your memory relative to this.

  Quote:


 subjective nature of experience? 
 

My point exactly. It is the subjective experience, in combination with the actual, physical sound. Are you sure they were bung notes? Or was your brain listening for something else? Or are you enjoying the music so much now, that what it sounded like before just seems worse than it was?

 Don't be afraid to question the power of your mind to adapt! 
	

	
	
		
		

		
		
	


	




 [EDIT] Oh, and for the record, I do believe in physical burn-in - at least some effects over the short term. But something on the order of 600 hours hits my skepticism button. Multiple times


----------



## slowpogo

What you say makes sense, but when can the brain be trusted? If you hold up two fingers, say "How many fingers am I holding up?" and I tell you two...then two days later ask me, "How many fingers was I holding up the other day?" and I say "two"...is even that questionable? It gets ridiculous at a certain point, IMO.

 Anyway, I used the example in my other post because I have taught piano lessons. I have also recorded myself playing at the start of learning a piece, then much later, listened to it to compare. Occasionally I'll think, "Well, it wasn't as bad back then as I thought"--but I'm never totally blown away by how my memory is completely wrong and my brain totally threw me for a loop or anything. I've developed a trust in myself that way.

 BTW, I think the most change happened in my K701's in the first 100 or 200 hours. That much I'm sure of. Since then, I *think* I have heard subtle improvement but I can't be sure...just thought I'd clarify that in some contexts I am willing to admit when it could just be my own mind.


----------



## Beefy

Quote:


  Originally Posted by *slowpogo* /img/forum/go_quote.gif 
_What you say makes sense, but when can the brain be trusted?_

 

And therein lies the paradox. I would generally argue that our brain can't be trusted very often at all...... but only because it generally adapts so incredibly well to small changes, in order to make us feel better about the world around us.

 If our brains didn't adapt, we certainly could trust every little minute difference in the senses - but we wouldn't like how that felt at all because even the slightest change in our environment would be unbearable. Think severe OCD.

  Quote:


 BTW, I think the most change happened in my K701's in the first 100 or 200 hours. That much I'm sure of. Since then, I *think* I have heard subtle improvement but I can't be sure...just thought I'd clarify that in some contexts I am willing to admit when it could just be my own mind. 
 

I can certainly live with that assessment. If they do, genuinely sound better to you, that's fantastic, and I can't - and don't want to - deny that.

 But please don't dismiss the power of your own brain as a big source of that apparent improvement


----------



## amphead

Yeah, the brain certainly does play games with our hearing, based on what we expect to hear. Sometimes an apples or oranges change in sound just sounds better, because we need it too. There is alot of evidence to suggest, that K701s have a very rigid driver, that needs to loosen up to sound its best. It was designed that way to maintain tight bass, among other things. Rigidity is great for some tones but not for all tones, and they do get better over a very extended break-in period. That period will be longer for some than others, due to not only the objective experience(time based), but the subjective experience our brains put us through.


----------



## BoilermakerFan

Quote:


  Originally Posted by *pabbi1* /img/forum/go_quote.gif 
_Dude - WITH an OPUS balanced out DAC...

Maximus_

 

pabbi

 I think my question about your front panel was lost in the "discussion" over the last 5 pages...

 Are you using the stock NABU plastic front panel, did you just remove the plastic panel, or did you have FPE manufacture a custom panel? Also, I noticed you have two separate ALPS pots for volume, is there any reason why a single pot, or other "volume control alternative" couldn't be used to control both boards at once? Would hooking up both boards in parallel to one ALPS pot require a 100K pot vs. 50K?


----------



## regal

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_I know Colin's a believer in it. However, as noted many times before, higher impedance phones have enough "clearance" from the corner frequency at 470uf that there's no need for worry.

 As for Grados, they seem to pair better with Milletts and MAXes than many other phones, anyway. I have not heard any complaints about lack of bass with Grados all the way back to the revMH Millett Hybrid..

 That's just a guess. As I told Joneeboi - I've had a couple of strike-outs lately.
	

	
	
		
		

		
		
	


	


_

 

Thanks Tomb, I value your opinion as you are one who tests things and lsitens instead of going soley on "theory." I love your Boutque Max section btw.


----------



## manaox2

Quote:


  Originally Posted by *BoilermakerFan* /img/forum/go_quote.gif 
_Also, I noticed you have two separate ALPS pots for volume, is there any reason why a single pot, or other "volume control alternative" couldn't be used to control both boards at once? Would hooking up both boards in parallel to one ALPS pot require a 100K pot vs. 50K?_

 

Sorry to butt in, but you would need a quad pot for that, its now four channels instead of two. The standard ALPS pot is designed for two. When you go balanced, the gain is also doubled, so the 100k pot might also not be a bad idea (correct me if I'm wrong).


----------



## Gross

Well, I let a buddy of mine borrow my MAX and my SR-225s. He has informed me that I have converted another to the world of head-fi, and he refuses to give back my Grados or my MAX. Looks like I am going to be Forced to buy some RS-1s and build a Mosfet-MAX. 
	

	
	
		
		

		
		
	


	




 Hows the Mosfet-MAX site coming? I see it has a logo now. Oh yeah, thanks again to all those involved for the design and support of such an awesome amp.


----------



## BoilermakerFan

Quote:


  Originally Posted by *Gross* /img/forum/go_quote.gif 
_Well, I let a buddy of mine borrow my MAX and my SR-225s. He has informed me that I have converted another to the world of head-fi, and he refuses to give back my Grados or my MAX. Looks like I am going to be Forced to buy some RS-1s and build a Mosfet-MAX. 
	

	
	
		
		

		
		
	


	




 Hows the Mosfet-MAX site coming? I see it has a logo now. Oh yeah, thanks again to all those involved for the design and support of such an awesome amp._

 

You did mark up the cost of your SR225s and MAX to cover your labor and "break-in" services right?



 manaox2

 No problem, thanks for the help. I figured it would need a different volume attenuator, but I wasn't sure. Now that I've had my coffee, it makes sense since the paralleled pot would combine the two signals and screw it all up, besides defeating the whole purpose of a balance signal.


----------



## pabbi1

Quote:


  Originally Posted by *BoilermakerFan* /img/forum/go_quote.gif 
_pabbi

 I think my question about your front panel was lost in the "discussion" over the last 5 pages...

 Are you using the stock NABU plastic front panel, did you just remove the plastic panel, or did you have FPE manufacture a custom panel? Also, I noticed you have two separate ALPS pots for volume, is there any reason why a single pot, or other "volume control alternative" couldn't be used to control both boards at once? Would hooking up both boards in parallel to one ALPS pot require a 100K pot vs. 50K?_

 


 I replaced the plastic with wood - for example, my choice was bloodwood...

Bloodwood Thin lumber - eBay (item 140223289177 end time Apr-16-08 13:59:48 PDT)

 The proper search on ebay is 'thin lumber' - you can usually find something that is close enough to just require a crosscut with a fine-toothed saw, then a drill press for the bolt holes.

 Sorry, this is a little dark, but... Bloodwood panel

 Oh, and I was lazy on the pots - should have air wired them for maintenance and case fitting purposes - would have saved a LOT of time and effort.


----------



## tomb

Quote:


  Originally Posted by *Gross* /img/forum/go_quote.gif 
_Well, I let a buddy of mine borrow my MAX and my SR-225s. He has informed me that I have converted another to the world of head-fi, and he refuses to give back my Grados or my MAX. Looks like I am going to be Forced to buy some RS-1s and build a Mosfet-MAX. 
	

	
	
		
		

		
			





 Hows the Mosfet-MAX site coming? I see it has a logo now. Oh yeah, thanks again to all those involved for the design and support of such an awesome amp._

 

There are some who believe that nirvana is already attained with SR-225. Regardless, it's hard to deny the synergy between a Grado and the Millett MAX. I have to admit that myself and I'm pretty much a Sennheiser/Koss guy.

 Argh - you're all putting pressure on me.
	

	
	
		
		

		
		
	


	




 I got delayed so bad from taxes, but I'll try my best to knock out some of the website out this weekend, if I can. 'Course, it means I have to build one, too.


----------



## BoilermakerFan

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_There are some who believe that nirvana is already attained with SR-225. Regardless, it's hard to deny the synergy between a Grado and the Millett MAX. I have to admit that myself and I'm pretty much a Sennheiser/Koss guy.

 Argh - you're all putting pressure on me.
	

	
	
		
		

		
		
	


	




 I got delayed so bad from taxes, but I'll try my best to knock out some of the website out this weekend, if I can. 'Course, it means I have to build one, too. 
	

	
	
		
		

		
		
	


	





_

 

Yep. I'm starting to come to the realization that I need to add SR225s to the list of headphones to acquire. 

 Just send me all the parts to build it, I already have an unused Hoffman case though, so I won't need that; just everything else- VD RDs, Muse ESs, and VitQs will be fine. I'll take one for the team and let you know if the magic smoke comes out! 
	

	
	
		
		

		
		
	


	




 - BMF


----------



## BoilermakerFan

Quote:


  Originally Posted by *pabbi1* /img/forum/go_quote.gif 
_I replaced the plastic with wood - for example, my choice was bloodwood...

Bloodwood Thin lumber - eBay (item 140223289177 end time Apr-16-08 13:59:48 PDT)

 The proper search on ebay is 'thin lumber' - you can usually find something that is close enough to just require a crosscut with a fine-toothed saw, then a drill press for the bolt holes.

 Sorry, this is a little dark, but... Bloodwood panel

 Oh, and I was lazy on the pots - should have air wired them for maintenance and case fitting purposes - would have saved a LOT of time and effort._

 

Nice, I like that. I think it would be sweet with a bamboo panel front and turned walnut or madrone wood knobs too. 

 Is there an easy way to "balance" or bias the two sides when using a single quad volume control so that the signal strength to both channels is as close to equal as it can be? I guess you could always mount the two ALPS close enough and turn them both all the way up or all the way down first, then mount gears on both shafts that are turned by a central knob in the center, but it would need it's own shaft and four gears... Which end of the ALPS pot has more error?


----------



## xnothingpoetic

My AC adapter say 24v 0.83A

 Is that sufficient? I don't know what that equates to the 750ma minimum.


----------



## Gross

Quote:


  Originally Posted by *xnothingpoetic* /img/forum/go_quote.gif 
_My AC adapter say 24v 0.83A

 Is that sufficient? I don't know what that equates to the 750ma minimum._

 


 Well, yours specifies 830ma, so you are fine if you need 750ma.


----------



## tomb

Quote:


  Originally Posted by *xnothingpoetic* /img/forum/go_quote.gif 
_My AC adapter say 24v 0.83A

 Is that sufficient? I don't know what that equates to the 750ma minimum._

 

750ma is 0.75A. So 0.83A is the same as 830ma. It gets a little tougher if they only quote VA, because then you have to divide the voltage into it to get the amperage Regardless 1Amp = 1000milliamps.
	

	
	
		
		

		
		
	


	




 EDIT: Oops - took too long to reply. Gross is absolutely correct.


----------



## xnothingpoetic

Quote:


  Originally Posted by *Gross* /img/forum/go_quote.gif 
_Well, yours specifies 830ma, so you are fine if you need 750ma._

 

Thanks, that was easy 
	

	
	
		
		

		
		
	


	




 I feel like an idiot now 
	

	
	
		
		

		
		
	


	




 And the MAX website was min of 750ma, so I wasn't sure if I was getting that or not.

  Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_1Amp = 1000milliamps.
	

	
	
		
		

		
		
	


	


_

 

Duly noted.


----------



## Gross

Quote:


  Originally Posted by *xnothingpoetic* /img/forum/go_quote.gif 
_Thanks, that was easy 
	

	
	
		
		

		
		
	


	




 I feel like an idiot now 
	

	
	
		
		

		
		
	


	



_

 

We are all here to have fun and learn


----------



## manaox2

Quote:


  Originally Posted by *pabbi1* /img/forum/go_quote.gif 
_I replaced the plastic with wood - for example, my choice was bloodwood...

Bloodwood Thin lumber - eBay (item 140223289177 end time Apr-16-08 13:59:48 PDT)

 The proper search on ebay is 'thin lumber' - you can usually find something that is close enough to just require a crosscut with a fine-toothed saw, then a drill press for the bolt holes.

 Sorry, this is a little dark, but... Bloodwood panel_

 

*IMPORTANT*

 Bloodwood sawdust is very toxic. If you cut it, you don't want to inhale it, get it in your mouth, eyes, on your skin, etc. That eBay auction listing says that he offers recutting services. I suggest taking advantage of them.


----------



## amphead

Nice work Pabbi!

 The balanced Max front view.


----------



## slowpogo

Looks nice amphead. Is that the DVP-NS775V sitting on top? I have that player (or one that looks exactly like it), and am curious what you think about it, particularly mated with the Max.


----------



## amphead

Sorry Slowpogo, I was showing a lightened up photo of Pabbi's balanced Max.


----------



## Mr. Tadashi

Hi Everybody. I managed to bust the tirmmer pots for the DB bias and my readings for it is way to high(300ma range) I have some new ones on order to swap out and I was wondering what resistors should I check to see if they are blown and would my transistors be alright and if need be is there an recommended way to check them.

 Thanks

 Edit: I forgot to mention it uses DJB DB's(I followed cant miss build #2) Also form my check sound is comming through too as if it is all working.


----------



## Phil Townsend

The output transistors...QB9 and QB8 left and right...
 There are holes for 2 sets of transistors at each position...
 one set of holes is on theleft side of the heat sink the other set of holes are on the right of the heatsink...

 Question is do BOTH sets of holes get filled? 
 OR just one set?
 The schematic shows Both hole sets loaded.

 What is right if I am Not building the MOSFET version?


 Many thanks
 Phil


----------



## tomb

Quote:


  Originally Posted by *Mr. Tadashi* /img/forum/go_quote.gif 
_Hi Everybody. I managed to bust the tirmmer pots for the DB bias and my readings for it is way to high(300ma range) I have some new ones on order to swap out and I was wondering what resistors should I check to see if they are blown and would my transistors be alright and if need be is there an recommended way to check them.

 Thanks

 Edit: I forgot to mention it uses DJB DB's(I followed cant miss build #2) Also form my check sound is comming through too as if it is all working._

 

Sounds like it is (working).
	

	
	
		
		

		
		
	


	




 We've had some others hit 300ma for short periods. If you didn't leave it that way long enough to melt something, I'm sure its fine.

 I guess this is too late to suggest if you have some on order already, but I sure love the Murata's at DigiKey. Not only do they cost half as much as any other trimmer, but they use a clutch that makes it impossible to break by turning it too much. When you hit the limit of travel, it continues turning with no change in resistance. As soon as you turn the screw the other direction, it starts changing resistance again. Very nice.

 I'm sure you'll be fine, though. Go take a look at the MAX website's "Setup and Biasing" page. There's a link in the middle of the page that says, "Click here for a blow-by-blow detail on biasing the DB's." That should pretty much walk you through the whole process of biasing the buffers for the first time.

 Good luck and let us know how it goes!


----------



## tomb

Quote:


  Originally Posted by *Phil Townsend* /img/forum/go_quote.gif 
_The output transistors...QB9 and QB8 left and right...
 There are holes for 2 sets of transistors at each position...
 one set of holes is on theleft side of the heat sink the other set of holes are on the right of the heatsink...

 Question is do BOTH sets of holes get filled? 
 OR just one set?
 The schematic shows Both hole sets loaded.

 What is right if I am Not building the MOSFET version?


 Many thanks
 Phil_

 

Hi, Phil!

 The MAX website is your friend. 
	

	
	
		
		

		
			





 There's a diagram legend for the different kinds of output transistors at the bottom of the Output Stage -> BJT Diamond Buffer page.

 It looks like this 
	

	
	
		
		

		
		
	


	




 :


----------



## Mr. Tadashi

Thanks for the advice tomb. I have the murata's on order already(one set to replace the current one and ones for my next build) I managed to bust them since I was trying to figure out why the readings were comming in at zero for the DB bias test points. Well due to my overlooking things I forgot to put in the jumpers for RB8L/R and RB8L/R and I over rotated the trimmers and busted those ones.


----------



## Phil Townsend

So...all slots get filled!
 Thank You!


----------



## tomb

Quote:


  Originally Posted by *Phil Townsend* /img/forum/go_quote.gif 
_So...all slots get filled!
 Thank You!_

 

NO. There's only one transistor per heat sink. Go back and look at that pic and compare it with the transistors you have - the 2SC2344/2SA1011 pairs. You will have the 2SC2344's on the outside sinks - on the left side as you look from the volume pot end of the board. The 2SA1011's go on the center sinks facing the same way - to the left.

 Regardless of the type of output transistor pairs, you will have four transistors - two of PNP and two of NPN. Each one is dedicated to a single heat sink each. They all face the same way - either to the left or to the right, depending on which ones you have.

 When you look at the schematic, you are seeing an either/or option for the mosfets, but there's only one transistor per junction - two per channel and four per board/MAX.


----------



## Beefy

A question of etiquette...... but first, the story.......

 8 days ago, after a little bit of back and forward correspondence, I sent a BOM/order to Jeff Rossel for a MHM kit. I asked how I could make the payment. Minutes after sending the last email, I ordered some parts from Beezar.

 4 days later, I hadn't heard anything from Jeff. I sent him an email checking that he had got my order. He replied that tax season was on him. OK, I said.

 4 more days later, I got note that my Beezar order has arrived and is ready to pick up from the post office. Still no word from Jeff.

 So back to the question of etiquette. At what point do you all think I could cancel my order with Jeff - relatively guilt-free - and just pick the parts myself from Mouser? Obviously I don't want to screw Jeff around, because he does good work for the community.

 But I've added it all up, and it would cost me less than $2 more to do it myself (the only part I'd be missing is tube lighting). I've submitted, paid for, modified, shipped and received (almost) an order from Beezar in the same time as not hearing anything from Jeff 
	

	
	
		
		

		
		
	


	




 Thoughts?


----------



## amphead

Jrossel, is a very good source for Max kits. Try sending another PM. If you don't get a response, for whatever reason, he won't hold it against you to order directly from Mouser. Good Luck! Edit: Be sure to cancel your order first, if you intend to purchase directly from Mouser. That's probably the most important etiquette.


----------



## BoilermakerFan

Quote:


  Originally Posted by *Beefy* /img/forum/go_quote.gif 
_
 But I've added it all up, and it would cost me less than $2 more to do it myself (the only part I'd be missing is tube lighting). I've submitted, paid for, modified, shipped and received (almost) an order from Beezar in the same time as not hearing anything from Jeff 
	

	
	
		
		

		
		
	


	




 Thoughts?_

 

Well, if you do cancel with Jeff and order from Mouser, I bet you will have to order a few bits from Digi-Key too, or have to wait for back-ordered parts. Mouser was out of stock of the black case and a transistor for me. You can get the tube lighting LEDs from Mouser too, tomb posted recommendations a few pages ago. The mistake I made was ordering from Digi-Key, then waiting 2 days before entering my Mouser order. I would definitely put together orders for both at same time so you can see what is in stock at both sites. 

 Second, Jeff should be finished up with his taxes by Tues. next week, or at least he has to file for an extension by then. I can feel his pain, I'm still working on my taxes and I have to have them done tonight so I can mail them tomorrow because I'm out of town next Mon. through Thurs.


----------



## fault151

Quote:


  Originally Posted by *BoilermakerFan* /img/forum/go_quote.gif 
_Well, if you do cancel with Jeff and order from Mouser, I bet you will have to order a few bits from Digi-Key too, or have to wait for back-ordered parts. Mouser was out of stock of the black case and a transistor for me. You can get the tube lighting LEDs from Mouser too, tomb posted recommendations a few pages ago. The mistake I made was ordering from Digi-Key, then waiting 2 days before entering my Mouser order. I would definitely put together orders for both at same time so you can see what is in stock at both sites. 

 Second, Jeff should be finished up with his taxes by Tues. next week, or at least he has to file for an extension by then. I can feel his pain, I'm still working on my taxes and I have to have them done tonight so I can mail them tomorrow because I'm out of town next Mon. through Thurs._

 

Funny enough, i too tried to order from Jeff but got the same response. Im after the b22 kit. He said hes sorting his taxes and will deal with it hopefully soon. Hope he manages to get the kits sorted. I understand he is busy.


----------



## BoilermakerFan

Quote:


  Originally Posted by *fault151* /img/forum/go_quote.gif 
_Funny enough, i too tried to order from Jeff but got the same response. Im after the b22 kit. He said hes sorting his taxes and will deal with it hopefully soon. Hope he manages to get the kits sorted. I understand he is busy._

 

Man, fault, you're crazier than I am jumping into DIY with a b22!


----------



## fault151

Quote:


  Originally Posted by *BoilermakerFan* /img/forum/go_quote.gif 
_Man, fault, you're crazier than I am jumping into DIY with a b22! 
	

	
	
		
		

		
		
	


	


_

 

ha ha, well im buying it now whilst i have the money and when i get brave i'll attempt to build it. I have a mate that hopefully will be able to help out if i get stuck. 

 I attempt to work my way up starting with a cmoy amp, then mayb an alien dac. I also have a valve headphone amp i am building with my mate so hopefully i will gain a lot of knowledge doing that.


----------



## Beefy

Quote:


  Originally Posted by *BoilermakerFan* /img/forum/go_quote.gif 
_Well, if you do cancel with Jeff and order from Mouser, I bet you will have to order a few bits from Digi-Key too, or have to wait for back-ordered parts._

 

Actually, the BOM I made myself for Mouser was completely in stock..... minus the boutique parts like VitQ's, ES, transistors and pot from Beezar of course.

 I'll pop Jeff an email tomorrow and see what he says.


----------



## Beefy

Quote:


  Originally Posted by *fault151* /img/forum/go_quote.gif 
_Im after the b22 kit._

 

I wouldn't even think of touching the B22 myself at this point in my DIY career. Too much part matching.

 But the MHM is actually *really* easy to make up yourself (certainly easier than the BOM that I did for my M^3), thanks to the boutique parts and matched transistors available at Beezar. If they could offer good tube LEDs, tube rings and MOSFETs....... well, you couldn't possibly ask for more!


----------



## Mr. Tadashi

Quote:


  Originally Posted by *Beefy* /img/forum/go_quote.gif 
_I wouldn't even think of touching the B22 myself at this point in my DIY career. Too much part matching.

 But the MHM is actually *really* easy to make up yourself (certainly easier than the BOM that I did for my M^3), thanks to the boutique parts and matched transistors available at Beezar. If they could offer good tube LEDs, tube rings and MOSFETs....... well, you couldn't possibly ask for more!_

 

I agree there and also there is a great wealth on information that makes trouble shooting it a breeze.(Ordering the parts for a boutique build using the blackgates can be a bit of a hassle since parts have to be ordered from various vendors but, it is not all that difficult afterall.)


----------



## pabbi1

Quote:


  Originally Posted by *slowpogo* /img/forum/go_quote.gif 
_Looks nice amphead. Is that the DVP-NS775V sitting on top? I have that player (or one that looks exactly like it), and am curious what you think about it, particularly mated with the Max._

 

Running it through the OPUS DAC, I like it just fine... 
	

	
	
		
		

		
		
	


	




 Regarding wood, I have Koa on the Blue Hawaii (totally native), but wanted rosewood or cocobolo for the Max - but, alas, only bloodwood was handy. My first millett had ebony (and old fretboard), which was uber cool... naamanf made several series of exotic (padouk?) endplates for the Hammond enclosures, which were also very nice.


----------



## manaox2

Quote:


  Originally Posted by *Beefy* /img/forum/go_quote.gif 
_Actually, the BOM I made myself for Mouser was completely in stock..... minus the boutique parts like VitQ's, ES, transistors and pot from Beezar of course.

 I'll pop Jeff an email tomorrow and see what he says._

 

X2, ordered the BoM for 3 Millett Max's from Mouser on Monday, it shipped Wednesday.


----------



## tomb

Quote:


  Originally Posted by *Beefy* /img/forum/go_quote.gif 
_I wouldn't even think of touching the B22 myself at this point in my DIY career. Too much part matching.

 But the MHM is actually *really* easy to make up yourself (certainly easier than the BOM that I did for my M^3), thanks to the boutique parts and matched transistors available at Beezar. If they could offer good tube LEDs, tube rings and MOSFETs....... well, you couldn't possibly ask for more!_

 

Hmm ... thanks for some of the kind words I've been seeing. I'll consider what you suggest - I'm already working on the tube rings. We'll see about the LEDs. If I could purchase from the stock at LSDiodes (or wherever they got theirs), that would be ideal.

 The MOSFETs and JFETs are definitely coming - I've had a stock for quite awhile. I just haven't set up the matching circuit for the JFETs, yet. It's not at all like doing HFE for little BJT's.
	

	
	
		
		

		
			





 About Jeff - I appreciate what he's going through. My taxes were 37 pages, and that was just one envelope out of several. It's the reason I'm behind on the AlienDAC-MAX, the MOSFET-MAX website, and the parts above. I was practically cursing last night, in fact, because I was still making up the envelopes to IRS, state, etc.
	

	
	
		
		

		
		
	


	










 I support Jeff 100%, though, especially since the boards come from Colin and me. I'm sure he'll come through eventually as BoilermakerFan said.


----------



## BoilermakerFan

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Hmm ... thanks for some of the kind words I've been seeing. I'll consider what you suggest - I'm already working on the tube rings. We'll see about the LEDs. If I could purchase from the stock at LSDiodes (or wherever they got theirs), that would be ideal.

 The MOSFETs and JFETs are definitely coming - I've had a stock for quite awhile. I just haven't set up the matching circuit for the JFETs, yet. It's not at all like doing HFE for little BJT's.
	

	
	
		
		

		
		
	


	




 About Jeff - I appreciate what he's going through. My taxes were 37 pages, and that was just one envelope out of several. It's the reason I'm behind on the AlienDAC-MAX, the MOSFET-MAX website, and the parts above. I was practically cursing last night, in fact, because I was still making up the envelopes to IRS, state, etc.
	

	
	
		
		

		
		
	


	










 I support Jeff 100%, though, especially since the boards come from Colin and me. I'm sure he'll come through eventually as BoilermakerFan said.
	

	
	
		
		

		
		
	


	


_

 

I just finished my taxes. A decent refund from the Fed that goes to the State and I had to pay penalties and interest for underpaying my State taxes. Yet, our roads still suck, the parks suck, and we have some of the worst air pollution in the country from coal fired power plants and big corporations. 
	

	
	
		
		

		
		
	


	




 Anyways, Tom, have you checked into ledtronics.com? They have minimum order quantities of 25, 50, or 100, but depending on the LED, prices aren't too bad. Maybe just stock the blue and green ones since that seems to be the two dominant colors of choice?


----------



## Mr. Tadashi

Well I got my new Murata trimmers in the amp and it is now alive. 
	

	
	
		
		

		
		
	


	




 Pictures will be taken later.(After I start my Max mosfet build started)


----------



## Beefy

Well, I just sent an email to cancel my order with Jeff. I feel pretty bad because he provides a good service..... but ultimately I think 8+ days is a bit too much, and doing my own BOM is going to work out better for me 
	

	
	
		
		

		
		
	


	




 Anyway, putting the final touches on things, I'm going with some Lumex LED's under the tubes:
 Blue option: SSL-LX3044USBC 
 Orange option: SSL-LX3044SOC

 They are pretty pricey, and nowhere near 5500mcd. But I look at it this way..... the blue one is the 3mm, clear version of the 5mm diffused that I use on the front panel of my M^3. In this role, it is running at 24V behind a 10k resistor for a current of 2mA - this is VERY bright, almost too bright for a front panel. In the MHM I will run it at 27V behind a 1.2k 1W resistor for a current of ~17mA (or ~18mA for the lower Vf orange), which is well below the specified maximum of 30mA. With drilled out tube sockets, it should be A-O-K! 
	

	
	
		
		

		
		
	


	




 Other decisions of note...... going with Nichicon UPW exclusively for electrolytics (including in the E12, but not at CA2/7 of course - Muse ES from Beezar are going there), and despite my skepticism I'm springing for 1800µF at CA4/5. Already got VitQ's from Beezar, and I'll also grab various KOA output resistors, different transistor options and some other goodies when I order the board and pots.

 So, as is *always* the case with me, a simple matter of buying a kit and putting it together snowballed into something much bigger. Ah well, I'm actually much more excited about it now!


----------



## Beefy

Got a reply from Jeff, and he seemed happy enough. I feel a bit better now 
	

	
	
		
		

		
		
	


	




 So I have just one last question before I place my Mouser order......

 The BOM specifies 120 ohm 1/4W at RR1, and 2k ohm 1/2W at RR2. The Mouser-linked part are Vishay Dale metal films at the correct resistance, but only rated at 1/8W and 1/4W respectively.

 Strangely, the linked Digikey parts are 1/2W and 1W.

 Are the linked Mouser ones OK, or should I find higher rated one?


----------



## n_maher

The VD resistors, by virtue of their mil-spec lineage are fine when operated at twice their rated current. So those 1/8's are fine at 1/4 and the 1/4's are fine at 1/2. I think Tangent goes into more depth about this on his site somewhere but I'm 99% sure you're all set using the values in Tom's BOM.


----------



## Beefy

Cheers!

 If I have time when I go to order, I'll find some chunkier resistors. If I don't, I should be right anyway. If something blows up, I'll find you n_maher..........


----------



## BoilermakerFan

Quote:


  Originally Posted by *Beefy* /img/forum/go_quote.gif 
_Well, I just sent an email to cancel my order with Jeff. I feel pretty bad because he provides a good service..... but ultimately I think 8+ days is a bit too much, and doing my own BOM is going to work out better for me 
	

	
	
		
		

		
		
	


	




 Anyway, putting the final touches on things, I'm going with some Lumex LED's under the tubes:
 Blue option: SSL-LX3044USBC 
 Orange option: SSL-LX3044SOC

 They are pretty pricey, and nowhere near 5500mcd. But I look at it this way..... the blue one is the 3mm, clear version of the 5mm diffused that I use on the front panel of my M^3. In this role, it is running at 24V behind a 10k resistor for a current of 2mA - this is VERY bright, almost too bright for a front panel. In the MHM I will run it at 27V behind a 1.2k 1W resistor for a current of ~17mA (or ~18mA for the lower Vf orange), which is well below the specified maximum of 30mA. With drilled out tube sockets, it should be A-O-K! 
	

	
	
		
		

		
		
	


	




 Other decisions of note...... going with Nichicon UPW exclusively for electrolytics (including in the E12, but not at CA2/7 of course - Muse ES from Beezar are going there), and despite my skepticism I'm springing for 1800µF at CA4/5. Already got VitQ's from Beezar, and I'll also grab various KOA output resistors, different transistor options and some other goodies when I order the board and pots.

 So, as is *always* the case with me, a simple matter of buying a kit and putting it together snowballed into something much bigger. Ah well, I'm actually much more excited about it now! 
	

	
	
		
		

		
		
	


	


_

 

I'm kind of partial to the orange with a black case, but then again, I was born the day before Halloween. 
	

	
	
		
		

		
		
	


	




 I ordered orange, yellow-orange, and green. Planned to power them up on a bread board @ 27VDC with the resistors to see which one I like the best. But now I have time to wait since I won't need tube lighting for my first three MAXes. 

 I've decided the fourth will be a MOSFET-MAX in a larger enclosure like the NABU. I'll make sure there is room for Colin's Tube DAC and I think I'm going to setup the crossfeed circuit for an 1/8" mini jack since the attenuation of the circuit will be a benefit when using my Denon C700 canal phones. This will be my desktop unit so it will have tube lighting and case lighting.


----------



## BoilermakerFan

Quote:


  Originally Posted by *Beefy* /img/forum/go_quote.gif 
_Cheers!

 If I have time when I go to order, I'll find some chunkier resistors. If I don't, I should be right anyway. If something blows up, I'll find you n_maher.......... 
	

	
	
		
		

		
		
	


	


_

 

Nate is correct, the RD's are the MIL-SPEC version so their published power handling is half that of their commercial twin. As long as you solder the correct value in the correct locations, they'll be just fine.

 If you would feel more comfortable, read the data sheets and the references to the commercial line and their different power handling ratings.


----------



## tomb

Yep - what Nate says - he knows. 
	

	
	
		
		

		
		
	


	




 A couple of things, though, after trying the 1.2K resistors for the LED's and burning out all 3 LED's on the first prototype, I think 2K is a little better. It keeps the current down slightly instead of running on the edge of the LED's limit. You can easily exceed their limit just while you're setting up and adjusting things. Plus, it gives a better safety factor on the power dissipation of the resistors. The 1.2K's will run tremendously hot. I changed to the 2K's on the BOM quite awhile ago because of this.

 Also, I don't think you're going to find 1800uf 35V caps in the Nichicon UPW - it's an inbetween size for them. I'd go down a size - or if you're really daring, they have some 2200uf's that are still at 1" height. If you use those, be mindful of the current draw at turn-on and the potential output spike at turnoff. If either becomes an issue, you'll have to drop down a size. I think a couple of builders have used them, but I personally haven't tested anything bigger than the 1800uf FM's.

 EDIT: Chunkier resistors won't fit - stick with the RN55's. The only exceptions are the Vset resistor on the LM317 - that's an RN60, the LED resistors (make them cheapo carbons), the buffer output resistors - high-power 2W metal film, and the RB14 boutique output positions.


----------



## Beefy

Quote:


  Originally Posted by *BoilermakerFan* /img/forum/go_quote.gif 
_I'm kind of partial to the orange with a black case, but then again, I was born the day before Halloween. 
	

	
	
		
		

		
		
	


	


_

 

My M^3 is a silver case with black bezels, blue LEDs, and it will have black aluminium knobs it my Partspipe order ever arrives. I'm going for the exact same effect with my Max 
	

	
	
		
		

		
		
	


	




  Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_I don't think you're going to find 1800uf 35V caps in the Nichicon UPW - it's an inbetween size for them._

 

Unless I've got something very wrong, they are right here in all their 16x25mm glory UPW1V182MHD

  Quote:


 A couple of things, though, after trying the 1.2K resistors for the LED's and burning out all 3 LED's on the first prototype, I think 2K is a little better. 
 

I didn't say, but my BOM actually has both 1.2 and 2k resistors, and spare LED's 
	

	
	
		
		

		
		
	


	




 For my build, I was planning on leaving out the tube sockets, powering up, getting the PS voltage right, then installing 1.2k ohm resistors and LEDs. If it goes pear shaped, I can increase the resistance and replace LEDs easily. Tube sockets will go in only after I'm happy everything is OK.


----------



## tomb

Quote:


  Originally Posted by *Beefy* /img/forum/go_quote.gif 
_<snip>Unless I've got something very wrong, they are right here in all their 16x25mm glory UPW1V182MHD_

 

Well I'll be - too much competition from Panasonic, I guess. That's a new offering. I have a not-too old Mouser catalog right in front of me and the UPW's jump from 1500uf to 2200uf. We have had numerous discussions in the past because of that lack of size at Mouser.

 EDIT: Uh, that happens to be a Feb-April 2008 Mouser catalog - must've been a _very_ recent addition.


----------



## Beefy

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_EDIT: Chunkier resistors won't fit - stick with the RN55's._

 

Ah, that's handy to know!

  Quote:


 The only exceptions are the Vset resistor on the LM317 - that's an RN60, the LED resistors (make them cheapo carbons), the buffer output resistors - high-power 2W metal film, and the RB14 boutique output positions. 
 

In my BOM, everything is RN55 as per BOM except for:
 R1 - 10 ohm, 2W, metal oxide
 RA5 L/R - 2k ohm, 1/2W, carbon film OR 1.2k ohm, 1W, metal film (Vishay BC - same as Jeff's kit)
 RA5 C - 10k ohm, RN55 (same LED, voltage and resistance as my M^3 - go OCD!)
 RR2 - 2k ohm, 1/4W (RN60)
 RB10/11 - 2.2 ohm, 2W metal film (Vishay BC)
 RB14 - various values of KOA from Beezar

 I think I'm good to go......


----------



## Beefy

Well I placed my second Beezar order and a Mouser order. Now I play the waiting game! 
	

	
	
		
		

		
		
	


	




 Everything ended up costing me US$334. That included everything on the BOM, plus: shipping, a few extra parts from Mouser unrelated to the Max, 3 sets of tubes in total, double-ups on *all* boutique caps, at least 1 extra of every transistor and diode, at least 1 extra of every resistor (but not trimmers), RCA jacks, extra tube sockets.... even a trimpot tool, and surely other extras I've forgotten. The only item that I need to get locally is the Wallwart.

 It was quite a bit more money than I'd planned on, but I didn't expect to be doing my own BOM. This ultimately meant I had to pay for 2 lots of shipping to Beezar. Actually, the annoying and/or funny thing is.... shipping was almost a third of the total money. But it was still FAR cheaper than buying things locally at Farnell or RS Components. They really are crooks down here 
	

	
	
		
		

		
		
	


	




 Thanks for all the help up to this point everyone. I'll keep an eye on this thread, and report back when everything starts to come together.

 Cheers!


----------



## pinkfloyd4ever

not really


----------



## Beefy

Quote:


  Originally Posted by *pinkfloyd4ever* /img/forum/go_quote.gif 
_YESSSSS I got all 126 of them....SUCKAAAAAAAAAAZZZZZZZZZZZ_


----------



## BoilermakerFan

I have a question about transistors. I was given an old SS Garrard integrated receiver and it has Matsus-h-i-t-a C1226/A699 sets of NPN/PNP transistors for it's output power. I've Googled them and found an online seller that sells them $5 each, but that is it. Could these be used on the MAX DBs or perhaps on a different headphone amp? 

 Does anybody have a link to a good online resource for transistor information as it relates to audio equipment?

 Edit: LOL! The profanity censor put in astericks on the transistor manufacturers name...


----------



## tomb

Quote:


  Originally Posted by *BoilermakerFan* /img/forum/go_quote.gif 
_I have a question about transistors. I was given an old SS Garrard integrated receiver and it has Matsus-h-i-t-a C1226/A699 sets of NPN/PNP transistors for it's output power. I've Googled them and found an online seller that sells them $5 each, but that is it. Could these be used on the MAX DBs or perhaps on a different headphone amp? 

 Does anybody have a link to a good online resource for transistor information as it relates to audio equipment?

 Edit: LOL! The profanity censor put in astericks on the transistor manufacturers name..._

 

You're taking a risk, IMHO, to use anything that's not on Steinchen's list. Even then, there are a few he didn't test. You can find the list here:
discrete diamond buffer - parts list
 Look under "Note 2: Output Transistors"

 I suppose if you can find the specs on the transistors you mention and if they match up with the general specs for most of those in Steinchen's list - then they may work. Between MOSFETs and BJT's, I've still got a long way to go to build examples of Milletts or MAXes for all the transistors on that list. 
	

	
	
		
		

		
		
	


	




 Steinchen references a good start for trying to find the data for those trannies at ::: ALLDATASHEET - Datasheet search site, Datasheet search site for Electronic Components and Semiconductors and other semiconductors.. Here are the links to the ones you mention: 2SC1226, 2SA699


----------



## BoilermakerFan

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_You're taking a risk, IMHO, to use anything that's not on Steinchen's list. Even then, there are a few he didn't test. You can find the list here:
discrete diamond buffer - parts list
 Look under "Note 2: Output Transistors"

 I suppose if you can find the specs on the transistors you mention and if they match up with the general specs for most of those in Steinchen's list - then they may work. Between MOSFETs and BJT's, I've still got a long way to go to build examples of Milletts or MAXes for all the transistors on that list. 
	

	
	
		
		

		
		
	


	




 Steinchen references a good start for trying to find the data for those trannies at ::: ALLDATASHEET - Datasheet search site, Datasheet search site for Electronic Components and Semiconductors and other semiconductors.. Here are the links to the ones you mention: 2SC1226, 2SA699_

 

Thanks Tom. I figured you or a couple of the others in here could help me out. I haven't posted it on DIYaudio yet either. Crazy day today... Ah, life with a two year old!


----------



## chilly

Another Max Lives!!!!!


 Well I went to work early this morning to finish a freelance gig, which gave me from 4pm till now to work on the MAX... 

 and no problems... everything went together like clockwork... 

 so this is what I have done...

 CA2 Nichicon Muse ES
 CA7 Nichicon Muse KZ
 CA9 Wima
 CA3 VitQ .22uf
 CA6 VitQ .22uf
 CA8 VitQ .18uf

 RB14 KOA 10ohm

 tubes are 12ae6a

 Transistors are the 3422 and 1359

 Navships shielded two conducter wire for audio inputs and WBT RCA Jacks.

 I'll let this run for a while and let it burn in before I make any decisions about changing anything.

 Right now I have to say is that it is very detailed but not as bassy as I like... it may need some burn in. I might switch the KZ with a ES, But I wanna make sure I give it a chance.


 Thanks TomB, for everything at Beezar, and all your help through out this thread. Thanks Jeff Rossel for the Max Kit.

 This is my third amp kit, my First was a Soha and my Second was a Max and now this Max.

 Thanks again for everyones help!

 chilly


----------



## BoilermakerFan

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_You're taking a risk, IMHO, to use anything that's not on Steinchen's list. Even then, there are a few he didn't test. You can find the list here:
discrete diamond buffer - parts list
 Look under "Note 2: Output Transistors"

 I suppose if you can find the specs on the transistors you mention and if they match up with the general specs for most of those in Steinchen's list - then they may work. Between MOSFETs and BJT's, I've still got a long way to go to build examples of Milletts or MAXes for all the transistors on that list. 
	

	
	
		
		

		
		
	


	




 Steinchen references a good start for trying to find the data for those trannies at ::: ALLDATASHEET - Datasheet search site, Datasheet search site for Electronic Components and Semiconductors and other semiconductors.. Here are the links to the ones you mention: 2SC1226, 2SA699_

 

OK, what are the critical specs to compare? These old transistors are for 5W outputs as are the 3422s and the voltage tables seem to align closely, but I need to print them out and really compare them. Definitely not trying to be cheap with the DBs, as I have 4 out of the 5 pairs Beezar carries. Two are in my possession and 2 will be on there way shortly. My main concern is what collateral damage could occur if, IF, I tried these in an amp for grins? Besides smoking a pair of old, freebie transistors and a few resistors, what other bits should I worry about?


----------



## Beefy

Quote:


  Originally Posted by *chilly* /img/forum/go_quote.gif 
_CA3 VitQ .22uf
 CA6 VitQ .22uf_

 

Just curious, but why did you put expensive caps in this position? They are out of the signal path.....

 Oh, and your post isn't worth diddly-squat without PICS!


----------



## tomb

Quote:


  Originally Posted by *BoilermakerFan* /img/forum/go_quote.gif 
_OK, what are the critical specs to compare? These old transistors are for 5W outputs as are the 3422s and the voltage tables seem to align closely, but I need to print them out and really compare them. Definitely not trying to be cheap with the DBs, as I have 4 out of the 5 pairs Beezar carries. Two are in my possession and 2 will be on there way shortly. My main concern is what collateral damage could occur if, IF, I tried these in an amp for grins? Besides smoking a pair of old, freebie transistors and a few resistors, what other bits should I worry about?_

 

I can't tell you exactly, except for those specs that Steinchen lists - HFE, Idss, and MHz. I'm not trying to be flippant, but seriously, that's why I said you'd be taking a risk. 
	

	
	
		
		

		
		
	


	




 By the time you bolt these onto heat sinks with thermal pads or grease and solder them all in, it's not that easy to change them out. They could sound like dog do-do as soon as you tried them out - even if everything was correct.

 As long as you keep PNP and NPN correct, I can't see that there's anything you could do to hurt the rest of the circuit, but that's assuming you have everything absolutely correct with no mistakes. They may have reversed pinouts, etc. MAX builders have burned out resistors and other transistors if anything goes wrong with the orientation of the output transistors - even when they use the recommended types. So, from that aspect, you could damage a lot.

 Maybe after you've built 2 or 3 and are comfortable with biasing and setup, etc., the risk may be more acceptable. It's possible that you could tack-solder them - without heat sinks, standing naked so to speak - and bias them for no more than 30ma. TO-220's are able to dissipate about that much without heat sinks, as in the revMH Diamond Buffers, the PPA, the CKKIII, or the JISBOS. That might be an easier way to determine if they sound good enough to invest the rest of the heat sink parts, etc., and mount them permanently.

 However, as stated before, there are already plenty to pick from the list and some that have not even been tried yet, but are at least listed as an acceptable substitute. I can't say I would recommend it, so please tread carefully if you are determined to do this.


----------



## tomb

Quote:


  Originally Posted by *chilly* /img/forum/go_quote.gif 
_Another Max Lives!!!!!


 Well I went to work early this morning to finish a freelance gig, which gave me from 4pm till now to work on the MAX... 

 and no problems... everything went together like clockwork... 

 so this is what I have done...

 CA2 Nichicon Muse ES
 CA7 Nichicon Muse KZ
 CA9 Wima
 CA3 VitQ .22uf
 CA6 VitQ .22uf
 CA8 VitQ .18uf

 RB14 KOA 10ohm

 tubes are 12ae6a

 Transistors are the 3422 and 1359

 Navships shielded two conducter wire for audio inputs and WBT RCA Jacks.

 I'll let this run for a while and let it burn in before I make any decisions about changing anything.

 Right now I have to say is that it is very detailed but not as bassy as I like... it may need some burn in. I might switch the KZ with a ES, But I wanna make sure I give it a chance.


 Thanks TomB, for everything at Beezar, and all your help through out this thread. Thanks Jeff Rossel for the Max Kit.

 This is my third amp kit, my First was a Soha and my Second was a Max and now this Max.

 Thanks again for everyones help!

 chilly_

 

Congrats! Just an FYI, but that many VitQ's may decrease the bass. They are only recommended at CA8. Typically, VitQ's are a tad bass-light, but with ES's and plenty of caps elsewhere, it's not usually enough to affect anything and the benefits of their sweet highs and detail are worth it. However, using them elsewhere - even in the supposed non-signal positions, will have an effect.

 What's the size you used for CA4/CA5? That can also affect the bass, but it may just be the VitQ's there. CA4/CA5 are not actually that far removed from the signal path in the Millett circuit, and can affect the bass under certain conditions - less-than-optimum bypassing, too small, etc.


----------



## Beefy

Oh, while you're online tomb...... 
	

	
	
		
		

		
		
	


	




 I see no mention of any screw mounting for the heatsinks. In the M^3, the heatsinks are tapped for M3 or #4-40, and screwed down to the board, and it was a fairly painless procedure. Is there anything stopping people from doing this on the Max? I'm going for 1.5" sinks on my Max, and feel that the mechanical support is important. There are holes on board that definitely look like they are in the right position......

 Cheers!


----------



## amphead

Beefy, those are solder holes for the heatsinks, where the sink is mounted to the board. While turning the board upside-down with sink in place you will attach it with solder.


----------



## MrMajestic2

Quote:


  Originally Posted by *Beefy* /img/forum/go_quote.gif 
_Oh, while you're online tomb...... 
	

	
	
		
		

		
		
	


	




 I see no mention of any screw mounting for the heatsinks. In the M^3, the heatsinks are tapped for M3 or #4-40, and screwed down to the board, and it was a fairly painless procedure. Is there anything stopping people from doing this on the Max? I'm going for 1.5" sinks on my Max, and feel that the mechanical support is important. There are holes on board that definitely look like they are in the right position......

 Cheers!_

 

there is nothing stopping you from mounting them with screws instead of solder. I will do that on my next build for sure. Its a pain do remove them if they are soldered.


----------



## Beefy

Quote:


  Originally Posted by *amphead* /img/forum/go_quote.gif 
_Beefy, those are solder holes for the heatsinks, where the sink is mounted to the board. While turning the board upside-down with sink in place you will attach it with solder._

 

Hmmm, that never even occurred to me, and it seems like a strange way to do it...... but ok then 
	

	
	
		
		

		
		
	


	




  Quote:


  Originally Posted by *MrMajestic2* /img/forum/go_quote.gif 
_there is nothing stopping you from mounting them with screws instead of solder. I will do that on my next build for sure. Its a pain do remove them if they are soldered._

 

Yeah, if there is no specific reason why I can't, I'll definitely tap the heatsinks and screw them down.


----------



## amphead

Beefy, you can follow MrMajestic2's suggestion as well. He does incredible work. Take a look at his Max below.


----------



## Beefy

Yeah, I've seen that. Fantastic stuff! 
	

	
	
		
		

		
		
	


	




 Unfortunately, my case work will *always* be my weak point. I've never had an electronics project go wrong, but my mechanical skills are truly awful


----------



## MrMajestic2

Quote:


  Originally Posted by *amphead* /img/forum/go_quote.gif 
_Beefy, you can follow MrMajestic2's suggestion as well. He does incredible work. Take a look at his Max below. 
http://i5.photobucket.com/albums/y19...x/02240016.jpg_

 

Thank you, now Im blushing 
	

	
	
		
		

		
			





  Quote:


  Originally Posted by *Beefy* /img/forum/go_quote.gif 
_Yeah, I've seen that. Fantastic stuff! 
	

	
	
		
		

		
		
	


	




 Unfortunately, my case work will *always* be my weak point. I've never had an electronics project go wrong, but my mechanical skills are truly awful 
	

	
	
		
		

		
		
	


	


_

 

Anyone can order from Front Panel Express


----------



## Beefy

Quote:


  Originally Posted by *MrMajestic2* /img/forum/go_quote.gif 
_Anyone can order from Front Panel Express 
	

	
	
		
		

		
		
	


	


_

 

Fair call 
	

	
	
		
		

		
		
	


	




 I'd be interested to see what the prices are like to kit my M^3, S11 and a MHM with front and rear panels. I suspect it is a LOT more than I want to spend though.....


----------



## tomb

Quote:


  Originally Posted by *Beefy* /img/forum/go_quote.gif 
_Hmmm, that never even occurred to me, and it seems like a strange way to do it...... but ok then 
	

	
	
		
		

		
		
	


	


_

 

Actually, it seems to be the most common way. Even with AMB's M3 heat sinks, some come with pins. I have a set myself. During the early phase of selling the M3, there was some issue about whether to included tapped sinks - it was and is a stumbling block for some users to do that.

  Quote:


 Yeah, if there is no specific reason why I can't, I'll definitely tap the heatsinks and screw them down. 
 

MrMajestic2 is totally correct - just be sure you order the correct heat sinks.


----------



## BoilermakerFan

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_I can't tell you exactly, except for those specs that Steinchen lists - HFE, Idss, and MHz. I'm not trying to be flippant, but seriously, that's why I said you'd be taking a risk. 
	

	
	
		
		

		
		
	


	




 snip

 As long as you keep PNP and NPN correct, I can't see that there's anything you could do to hurt the rest of the circuit, but that's assuming you have everything absolutely correct with no mistakes. They may have reversed pinouts, etc. MAX builders have burned out resistors and other transistors if anything goes wrong with the orientation of the output transistors - even when they use the recommended types. So, from that aspect, you could damage a lot.

 Maybe after you've built 2 or 3 and are comfortable with biasing and setup, etc., the risk may be more acceptable. It's possible that you could tack-solder them - without heat sinks, standing naked so to speak - and bias them for no more than 30ma. TO-220's are able to dissipate about that much without heat sinks, as in the revMH Diamond Buffers, the PPA, the CKKIII, or the JISBOS. That might be an easier way to determine if they sound good enough to invest the rest of the heat sink parts, etc., and mount them permanently.

 However, as stated before, there are already plenty to pick from the list and some that have not even been tried yet, but are at least listed as an acceptable substitute. I can't say I would recommend it, so please tread carefully if you are determined to do this.
	

	
	
		
		

		
		
	


	


_

 

"But I want an Umpa Loompa Daddy!" 

 I know you weren't being flippant, and I'm not being stubborn and saying I will use them. I'm just trying to learn a little along the way and you guys are great at helping newbies understand and correct mistakes.

 I definitely won't be using these on a first build, I'll probably use them on the third build. I plan to build it with Muse KZ or Silmic II's and VitQs. I'll start with one of the other DB combos to make sure all is well in the MAX, then swap in these IF they look like they will work. I'll use your suggestion about 30mA free-air mounting to see how they sound. I'm also going to compare specs of some of the others that haven't been tested. 

 Other than the base set and the four combos on Beezar, are there others that you have already tried? I'd like to pick a couple that nobody else has tried just for the fun of experimenting. 
	

	
	
		
		

		
		
	


	




 And thanks for the suggestions on the tapped heatsinks. I think I'll go that route with this test mule build.


----------



## Beefy

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Actually, it seems to be the most common way. Even with AMB's M3 heat sinks, some come with pins._

 

Oh, I see now. I looked at the mechanical drawing for height etc. on both the power and output heatsinks to check I was getting the 1.5" ones, and didn't even notice the pins on the drawing. That's why I was confused about why soldering was a good idea - I was thinking they just had the holes.

 Its all good now!


----------



## chilly

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Congrats! Just an FYI, but that many VitQ's may decrease the bass. They are only recommended at CA8. Typically, VitQ's are a tad bass-light, but with ES's and plenty of caps elsewhere, it's not usually enough to affect anything and the benefits of their sweet highs and detail are worth it. However, using them elsewhere - even in the supposed non-signal positions, will have an effect.

 What's the size you used for CA4/CA5? That can also affect the bass, but it may just be the VitQ's there. CA4/CA5 are not actually that far removed from the signal path in the Millett circuit, and can affect the bass under certain conditions - less-than-optimum bypassing, too small, etc._

 

The CA4/CA5 are 1000uf 50volts i believe... they are the ones that came with Jeff's kit.

 Yeah I had thought that all VitQ's maybe a bit pushing it, but I still wanted to try it... I can easily take them out and put wimas in... I just wanted to try something new. I had thought of using Mundorfs for CA8 but it was cost prohibitive that I might not be able to hear the quality. I didn't want to risk the loss of cash.

 I'll have pictures later... maybe in a few days


 -chilly


----------



## mik000000

It is stock buiild. And those are Nichicon 1800uf's


----------



## Beefy

Nice work on the acrylic case - those tubes must look awesome at night!

 And that is the Hammond 2201 instead of the 1601? The extra room must be a godsend for all of those test-point wires......


----------



## tomb

Quote:


  Originally Posted by *chilly* /img/forum/go_quote.gif 
_The CA4/CA5 are 1000uf 50volts i believe... they are the ones that came with Jeff's kit.

 Yeah I had thought that all VitQ's maybe a bit pushing it, but I still wanted to try it... I can easily take them out and put wimas in... I just wanted to try something new. I had thought of using Mundorfs for CA8 but it was cost prohibitive that I might not be able to hear the quality. I didn't want to risk the loss of cash.

 I'll have pictures later... maybe in a few days


 -chilly_

 

Those caps should be fine. 
	

	
	
		
		

		
		
	


	




 I'd expect the VitQ's to be cutting into the bass in that case, then. It could be tubes, too - 12FK6's are a tad light on bass as opposed to the 12AE6's. I go back and forth between both, though, depending on mood.
	

	
	
		
		

		
		
	


	





 EDIT: Nice job, mik000000!! Great look on the acrylic - did you follow Kklee's tutorial on the MAX website?


----------



## mik000000

EDIT: Nice job, mik000000!! Great look on the acrylic - did you follow Kklee's tutorial on the MAX website?[/QUOTE]

 i followed to the letter, including his drill templates
	

	
	
		
		

		
		
	


	




. Until i read his tutorial, i had no idea you could cut the stuff with a table saw. It was brilliant. Thansk KkLEE!!!

 I am doing another with the boutique parts and am going to redo the template for the top panel as i found some of the holes did not line up after i rescaled.


----------



## mik000000

Quote:


  Originally Posted by *Beefy* /img/forum/go_quote.gif 
_Nice work on the acrylic case - those tubes must look awesome at night!

 And that is the Hammond 2201 instead of the 1601? The extra room must be a godsend for all of those test-point wires......_

 

Yes it is the 2201. I wanted to use the 1 1/2" heat sinks which means the board has to be in the bottom slot and would interfere with the test points. And the cost difference is only $3


----------



## Phil Townsend

Has anyone tried the Cree zero recovery diodes in the Max?


----------



## bperboy

I've gone through and taken out the output resistors and just jumpered the position. I'm not sure that I can actually tell any difference, but it makes me feel better inside! 
	

	
	
		
		

		
		
	


	




 I also went through and clipped all my leads shorter with a new pair of cutters I got, cleaned up the underside a bit, and reflowed a few joints! I've got all the operating voltages reset, and I just feel better doing it!


----------



## chilly

Ok so I replaced the .22 VitQ's with wimas... everything is so zero'd it sounds great... It sounded great with the VitQ's as well.... maybe a bit more detailed. (i felt the pressure) 
	

	
	
		
		

		
		
	


	





 I have 2 sets of tubes that are burned in, 12ae6's I got from Beezar, and a set of 12fm6's that I forgot where I got them... unfortunately the 12fm6's are a little harmonic not to bad and only when I bump the amp do I hear it, and the 12fm6's also differ between the 2, 1 is a side getter and the other is a top getter. Oh well. I do love both sets of tubes, I do have some FK's that I will play with over the coming week.

 I use these amps at work almost all day long.

 I'll take some pictures sometime this week... I just put it in a hammond case for now, I'll consider a custom case in the future... or just try my hand at a Bijou.

 -chilly


----------



## rhester

For those who have built the MOSFET version of the MAX, what are the sonic benefits? Is it worth the extra effort?


----------



## bperboy

Quote:


  Originally Posted by *rhester* /img/forum/go_quote.gif 
_For those who have built the MOSFET version of the MAX, what are the sonic benefits? Is it worth the extra effort?_

 

I had the first attempted MOSFET edition, and while I had some extra effort waiting for others to figure out why the darn thing didn't work, I believe the MAX site details pretty well what part changes are needed to get a working amp. I can't comment on the sound differences, as the MOSFET edition is the only one I have heard; it sounds pretty good at any rate!


----------



## tomb

Keep in mind that AMB's JFET-MOSFET mod addressed a weakness in the original implementation. Reports from some who've built the new version indicate that it may be very good _and fast._


----------



## bperboy

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Keep in mind that AMB's JFET-MOSFET mod addressed a weakness in the original implementation. Reports from some who've built the new version indicate that it may be very good and fast._

 

Tom, what is this change? Anything I should consider? Is that the caps that go on the mosfet pins?


----------



## tomb

Quote:


  Originally Posted by *bperboy* /img/forum/go_quote.gif 
_Tom, what is this change? Anything I should consider? Is that the caps that go on the mosfet pins?_

 

There is a capacitive load presented by the MOSFETs. Combined with the output impedance of the tube, it forms a high pass filter that cuts some of the high frequency response and detail.

 I made a recent post about it in Post #4276

 I definitely recommend it for ALL MOSFET MAX builds and am building a new website and a couple of MAXes based on it. It's a fairly inexpensive change and not too much trouble for someone who's already got a built MOSFET MAX.


----------



## tomb

Just as an FYI - the original MOSFET Diamond Buffer was taken from a schematic that AMB published on DIYAudio, I believe, in August, 2005. However, AFAIK, it had never been built until Bperboy tried it. He had problems with it at a time when no one had much experience yet on the MAX. Head-Fi user NeilR spent quite awhile building some perfboard test circuits to prove out the original AMB schematic, allowing Bperboy to make his MAX work. The story is all described on the MAX website at Tweaks -> MOSFET Configuration. That is the design that's existing on the MAX website. The JFET MOSFET mod by AMB takes the MOSFET diamond buffer circuit to the next step of high-performance.


----------



## bperboy

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_There is a capacitive load presented by the MOSFETs. Combined with the output impedance of the tube, it forms a high pass filter that cuts some of the high frequency response and detail.

 I made a recent post about it in Post #4276

 I definitely recommend it for ALL MOSFET MAX builds and am building a new website and a couple of MAXes based on it. It's a fairly inexpensive change and not too much trouble for someone who's already got a built MOSFET MAX._

 

So the things I should have to do are change QB2/3 to 2SJ74BL and 2SK170BL JFETs, respectively, RB6/7 to 100ohms, and change RB2/3 to 1k ohms?


----------



## tomb

Quote:


  Originally Posted by *bperboy* /img/forum/go_quote.gif 
_So the things I should have to do are change QB2/3 to 2SJ74BL and 2SK170BL JFETs, respectively, RB6/7 to 100ohms, and change RB2/3 to 1k ohms?_

 

Yes - you've got it.


----------



## Marzie

Hey, tomb, any info on the tube DAC that Colin is working on?


----------



## tomb

Quote:


  Originally Posted by *Marzie* /img/forum/go_quote.gif 
_Hey, tomb, any info on the tube DAC that Colin is working on?_

 

I probably should let Colin answer questions like this. However, I wouldn't expect it before mid-Summer at best, probably. I am hoping the MiniMAX is his first priority and will be done before long - it's about 99.95% done.

 When we last traded e-mails, he indicated that the Tube DAC is giving him issues with the power supply. The design needs 100VDC, 12.6V, +/-15VDC, 5VDC, and 3.3VDC. He's been wrestling with how to handle that without requiring a builder to buy 4 or 5 transformers.


----------



## BoilermakerFan

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_I probably should let Colin answer questions like this. However, I wouldn't expect it before mid-Summer at best, probably. I am hoping the MiniMAX is his first priority and will be done before long - it's about 99.95% done.

 When we last traded e-mails, he indicated that the Tube DAC is giving him issues with the power supply. The design needs 100VDC, 12.6V, +/-15VDC, 5VDC, and 3.3VDC. He's been wrestling with how to handle that without requiring a builder to buy 4 or 5 transformers._

 

Multi-tap transformer group buy?


----------



## tomb

Quote:


  Originally Posted by *BoilermakerFan* /img/forum/go_quote.gif 
_Multi-tap transformer group buy? 
	

	
	
		
		

		
		
	


	


_

 

We've discussed that possibility. Trouble is, custom transformer buys - even if done under a group buy - are still very expensive. I'm hoping he can come up with a different solution.


----------



## slowpogo

Here's a quick question: I have my input RCAs connected to the amp with three wires..left, right, and one shared for ground.

 Would there be any benefit to using a separate ground wire for each channel? I know the wires are only a few inches long anyway but I was just curious, since everywhere else in the amp the ground wire is doubled.


----------



## tomb

Quote:


  Originally Posted by *slowpogo* /img/forum/go_quote.gif 
_Here's a quick question: I have my input RCAs connected to the amp with three wires..left, right, and one shared for ground.

 Would there be any benefit to using a separate ground wire for each channel? I know the wires are only a few inches long anyway but I was just curious, since everywhere else in the amp the ground wire is doubled._

 

Only if the wires traveled long enough to cause twisting. In that case, you should probably run 4 wires so that you can Litz-braid them. The two ground wires provide a grounded path for both signal wires in the braid. If you twist/braid with only one ground wire, then you could get cross-talk.

 At least that's what I've been told - can't say that I've ever noticed the difference either way, but I do it now as described above - just in case.
	

	
	
		
		

		
		
	


	




 If the wire lengths are short, and there's no wound-in twist, then I wouldn't worry about it.


----------



## BoilermakerFan

Has anyone built a MAX using the 2SC4935/2SA1869 or 2SD669d/2SB649d combos from Steinchen's list? I was reviewing the list an noticed these were not tested by him. However, based on my Google search, they appear to be even more elusive than the 2238s/968s combo.


 Will a 30mA bias versus 50mA bias change the sound of the DBs on the same transistor pairs? The reason for the higher bias is to ensure the amp will stay in Class A with very low impedance headphones, correct? Does the additional bias power allow the amp to maintain tighter control of the headphones and react faster as well?


----------



## Beefy

I've seen Class A biasing described as the idle speed of a car's engine. Set it too low, and it bogs down when you accelerate. Set it too high, and you waste fuel and run hot.

 As you say, 'bogs down' in this instance is low impedance loads at very high volume. My understanding is that it isn't an issue until you actually get a transistor switch as it drops out of Class A, so I doubt you'll hear the difference unless you specifically enjoy hearing damage.


----------



## amb

Quote:


  Originally Posted by *BoilermakerFan* /img/forum/go_quote.gif 
_Will a 30mA bias versus 50mA bias change the sound of the DBs on the same transistor pairs? The reason for the higher bias is to ensure the amp will stay in Class A with very low impedance headphones, correct?_

 

Not only does changing the bias alter how deeply the output stage operate in class A, it also shifts the region of the output transistors' transfer curves that we operate in. Since no active device is completely linear, and this is an open loop buffer without the benefit of global negative feedback to help linearize the effective curve, the distortion profile of the buffer would vary with the bias setting, and it could be audible.

  Quote:


 Does the additional bias power allow the amp to maintain tighter control of the headphones and react faster as well? 
 

No, the control of the headphone diaphragm is a function of the output impedance. The lower the output impedance, the better the control. The output impedance does not vary with bias setting. Here again, without the benefit of global feedback, the output impedance of the DB here is relatively high compared to other amps.

 As for "react faster", if you're referring to speed/bandwidth, it is also not influenced by the bias setting. In this amp, the tube is ultimately the bottleneck as far as bandwidth/speed is concerned.


----------



## BoilermakerFan

Quote:


  Originally Posted by *amb* /img/forum/go_quote.gif 
_Not only does changing the bias alter how deeply the output stage operate in class A, it also shifts the region of the output transistors' transfer curves that we operate in. Since no active device is completely linear, and this is an open loop buffer without the benefit of global negative feedback to help linearize the effective curve, the distortion profile of the buffer would vary with the bias setting, and it could be audible.


 No, the control of the headphone diaphragm is a function of the output impedance. The lower the output impedance, the better the control. The output impedance does not vary with bias setting. Here again, without the benefit of global feedback, the output impedance of the DB here is relatively high compared to other amps.

 As for "react faster", if you're referring to speed/bandwidth, it is also not influenced by the bias setting. In this amp, the tube is ultimately the bottleneck as far as bandwidth/speed is concerned._

 

Thanks amb, I'm just trying to understand the impact of the bias current and it's effect on what we hear in the headphones. It stemmed from Tom's suggestion to bias an untested/non-recommended BJT to 30mA before mounting it to a heat sink. I was wondering what benefit there would be to raising the bias to 40mA or 50mA later if the 30mA bias current sounded good. Your answers helped a lot. Thanks. 

 I'll have to go back and look at the curves for a few of the recommended BJTs and see how much they differ, then I'm sure I'll have more questions, but I'll send them to you in a PM.


----------



## Beefy

Quote:


  Originally Posted by *amb* /img/forum/go_quote.gif 
_and this is an open loop buffer without the benefit of global negative feedback to help linearize the effective curve, the distortion profile of the buffer would vary with the bias setting, and it could be audible._

 

Ah, of course. I now remember reading on your site that MOSFETs have less distortion with higher quiescent current.


----------



## tomb

Quote:


  Originally Posted by *Beefy* /img/forum/go_quote.gif 
_Ah, of course. I now remember reading on your site that MOSFETs have less distortion with higher quiescent current._

 

Well, to bring it back from the other side, Kevin Gilmore has commented that increased current on any part causes more noise. That's one reason he uses multiple paralleled output BJT's instead of MOSFETs.

 There's a camp that disagrees with the higher bias, period, in the BJT's. Personally, I think it's a difference in design philosophy (as evidenced by Gilmore's differing design practices). On the one hand, we talk about the high bias currents of MOSFETs being an advantage, where on the other hand we talk about it being a disadvantage with BJT's. Remember that low distortion is only one quality in getting good sound, and is not necessarily the most important one. No feedback is also a feature, not a disadvantage, depending on what you're trying to attain.

 A design requirement for the MAX was to emulate the capability of the original revMH diamond buffer boards with single output transistors and heat sinks. The original revMH DB's had the equivalent of 60 ma buffer bias with the paralleled output transistors. If we don't bias the MAX's buffer up to nearly that point, then it may not have the same capability as the original DB's. This goes back to Beefy's comments about ensuring that the transistors don't enter into a switching mode with low impedance phones. There are a lot of undesireable effects when that occurs, so we can't have that. 
	

	
	
		
		

		
			








 Continuing to comment on the tube being a bottleneck when we all know that's the primary feature of the amp reveals a bit, too - since we're talking about bias.


----------



## slowpogo

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Only if the wires traveled long enough to cause twisting. In that case, you should probably run 4 wires so that you can Litz-braid them. The two ground wires provide a grounded path for both signal wires in the braid. If you twist/braid with only one ground wire, then you could get cross-talk.

 At least that's what I've been told - can't say that I've ever noticed the difference either way, but I do it now as described above - just in case.
	

	
	
		
		

		
		
	


	




 If the wire lengths are short, and there's no wound-in twist, then I wouldn't worry about it.
	

	
	
		
		

		
		
	


	


_

 

I had 23AWG silver Jupiter wire on the RCA inputs (cotton), and replaced the single ground wire with two stranded copper wires (Auric, stolen from a defunct Pimeta). I put the four wires in a very short litz braid. Before the three wires were just twisted together.

 The good news is, this solved my buzzing problem (when the case or pot was touched). No more buzz whatsoever. There is still a mild hissing/scraping sound though in the right channel when I turn the pot.

 The bad news is, I can hear a difference between the wires. Yeah, I know I'm not supposed to be able to, but I do. The Auric wire is bigger (20awg) and has polyethylene insulation. The amp now sounds warmer and kind of tubby. I wasn't expecting more than a very subtle difference, if any at all but when I first listened I was like "Whoa--definite change". I may try some Jupiter copper wire and see if I can split the difference; the amp was slightly shrill before with all silver wire.


----------



## tomb

Quote:


  Originally Posted by *slowpogo* /img/forum/go_quote.gif 
_I had 23AWG silver Jupiter wire on the RCA inputs (cotton), and replaced the single ground wire with two stranded copper wires (Auric, stolen from a defunct Pimeta). I put the four wires in a very short litz braid. Before the three wires were just twisted together.

 The good news is, this solved my buzzing problem (when the case or pot was touched). No more buzz whatsoever. There is still a mild hissing/scraping sound though in the right channel when I turn the pot.

 The bad news is, I can hear a difference between the wires. Yeah, I know I'm not supposed to be able to, but I do. The Auric wire is bigger (20awg) and has polyethylene insulation. The amp now sounds warmer and kind of tubby. I wasn't expecting more than a very subtle difference, if any at all but when I first listened I was like "Whoa--definite change". I may try some Jupiter copper wire and see if I can split the difference; the amp was slightly shrill before with all silver wire._

 

You definitely have some sensitive, critical ears. My oldest daughter is like that - she's a Junior majoring in piano at college right now.

 About the hissing/scraping sound in the pot - most likely, that's the tube. 12AE6's with Black Gates seem the worst combination. The high gain combined with the super low noise floor of the BG's work together to make many 12AE6's noisy when the volume is adjusted. It goes away instantly when you don't move the pot, but sounds like the pot is dirty while in motion. Negatron explained the phenomenon awhile back, but I forget the exact cause. Some tubes are worse than others. You can try swapping tubes - that will confirm it right away. The problem seems to go away with 12FM6 and 12FK6 tubes, too.

 I tolerate it the same as microphonics. Sometimes microphonics can be so bad that the tube is worthless. Other times, the tube sounds so good that you decide that you can live with the slight irritation of hearing an echo when you rack the pot or bump the amp. The scratching seems the same way. I've got a couple of 12AE6's that are as powerful as anything I've tried in awhile. They scratch in both channels when the volume is adjusted (even with ES's), but the sound is so good, I'll put up with the slight irritation.
	

	
	
		
		

		
		
	


	




 Things like that confound tests and measurements.
	

	
	
		
		

		
		
	


	





 P.S. I use 22ga Navships SPC for everything, so I wouldn't know how it sounds otherwise.


----------



## slowpogo

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_You definitely have some sensitive, critical ears. My oldest daughter is like that - she's a Junior majoring in piano at college right now.
 .....

 P.S. I use 22ga Navships SPC for everything, so I wouldn't know how it sounds otherwise._

 

I was a music major in college too, played piano and trombone. That does really develop your ears, and creates a sophisticated mind/body connection with sound. It's similar to the way meditation will enhance your senses with practice...actually, playing an instrument, esp. a wind instrument basically _is_ meditation in many ways.

 Yeah, if I'm reading a book and someone's talking to me up to several feet away, I can often just tilt the book a little and hear a different quality of sound, from the changed reflection.

 Re: the pot scratchiness, it's actually kind of a pleasant and soothing sound, more of a very warm hiss than scratching. So I don't mind it, as long as it's not an indication of trouble.


----------



## Beefy

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_There's a camp that disagrees with the higher bias, period, in the BJT's. Personally, I think it's a difference in design philosophy (as evidenced by Gilmore's differing design practices)._

 

Yeah, there's so many ways to swing a cat. A constant trade-off between multiple factors. Personally, I'm developing a like for anything that has a lot of finesse in a small part count...... but that might have something to do with all the money I'm spending on international shipping! 
	

	
	
		
		

		
		
	


	




 At the end of the day, my ears tell me that my M^3 rocks, and they will likely tell me that my MHM rocks as well - hopefully, they will just rock in different ways.

  Quote:


 Continuing to comment on the tube being a bottleneck when we all know that's the primary feature of the amp reveals a bit, too - since we're talking about bias. 
	

	
	
		
		

		
		
	


	



 

I don't think that there is any denying what AMB says is true. But it doesn't make the amp any less fun! 
	

	
	
		
		

		
		
	


	




  Quote:


  Originally Posted by *slowpogo* /img/forum/go_quote.gif 
_I had 23AWG silver Jupiter wire on the RCA inputs (cotton), and replaced the single ground wire with two stranded copper wires (Auric, stolen from a defunct Pimeta). I put the four wires in a very short litz braid. Before the three wires were just twisted together._

 

I've got bog standard 26AWG copper hookup connecting the RCA inputs to my M^3, and I intend to use the same on my Max


----------



## dsavitsk

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Continuing to comment on the tube being a bottleneck when we all know that's the primary feature of the amp reveals a bit, too - since we're talking about bias. 
	

	
	
		
		

		
		
	


	


_

 

Lots of tubes will operate well into the MHz range, and triodes are inherently more linear than any solid state device yet devised. Tubes went away, not because they worked poorly, but because they were large, expensive to manufacture and power, needed to be replaced frequently, and solid state's inherent crudiness could be compensated for with feedback.


----------



## bperboy

Is there a way to directly measure the output impedance of the amplifier with a DMM? Or is that something that needs to be calculated from the circuit?


----------



## amphead

Love the tubey sounds. Organic and when done well are not midrangey at all, but verrry smooth and linear. Reproducing highs and bass in all their glory. The only downside for me are filaments and the meticulous craftsmanship and design to prevent them from injecting noise. This shows how ingenious the Max is, because that beautiful backplane/ground provides us with the blackest sound around. 

  Quote:


 You definitely have some sensitive, critical ears. My oldest daughter is like that - she's a Junior majoring in piano at college right now. 
 

Sorry about your wallet.  Couldn't resist.


----------



## Ferrari

Quote:


  Originally Posted by *bperboy* /img/forum/go_quote.gif 
_Is there a way to directly measure the output impedance of the amplifier with a DMM? Or is that something that needs to be calculated from the circuit?_

 

Since the nature of amplifier output is AC (assuming DC component = 0), the output impedance of an amp is the opposition of the AC current flows through its output terminals and is frequency dependent. 
	

	
	
		
		

		
		
	


	




 It’s therefore not possible to measure the output impedance of an amp with a DMM.


----------



## bperboy

Quote:


  Originally Posted by *Ferrari* /img/forum/go_quote.gif 
_Since the nature of amplifier output is AC (assuming DC component = 0), the output impedance of an amp is the opposition of the AC current flows through its output terminals and is frequency dependent. 
	

	
	
		
		

		
		
	


	




 It’s therefore not possible to measure the output impedance of an amp with a DMM._

 

Ahh, thanks. And the frequency that is changing is that of the music and when it changes, it will change the impedence values for all the caps and inductors, etc. correct?


----------



## Ferrari

Quote:


  Originally Posted by *bperboy* /img/forum/go_quote.gif 
_Ahh, thanks. And the frequency that is changing is that of the music and when it changes, it will change the impedence values for all the caps and inductors, etc. correct?_

 

Yes, you are correct. The number is not real Ohms but rather complex (RCL).


----------



## tomb

Quote:


  Originally Posted by *bperboy* /img/forum/go_quote.gif 
_Is there a way to directly measure the output impedance of the amplifier with a DMM? Or is that something that needs to be calculated from the circuit?_

 

Actually, there are several methods for measuring the output impedance of an amp.

 1. Measure the unloaded output voltage.
 2. Measure the voltage loaded with a resistor.
 3. Determine current using the measured value of the resistor:
 I = V/R, using V measured in #2.
 4. The difference in voltage is #1 minus #2. The output impedance can then be calculated:
 Z = (V1 - V2)/I

 It helps to have a low value resistor so that the voltages are higher - that makes the measurement more accurate (larger numbers). The resistance of the resistor should be measured at the elevated temperature of #2. Also, the DMM has to be reliable in measuring RMS AC Volts. So, this is one time where a Fluke may be necessary.
	

	
	
		
		

		
		
	


	




 This is somewhat similar to a discussion on Power Factor that I posted in early yesterday morning: http://www.head-fi.org/forums/f77/po...r-amps-316159/ I wasn't considering the amp's output impedance, though. From a utility's perspective, that's fixed (0.9?) and the customer's load is the side that must be corrected.
	

	
	
		
		

		
		
	


	




 Still, if the load can be assumed that it's all "R" and no "Z", then the discussion results in the output impedance of the amp, instead.

 There are other methods, but this is the simplest one I found. Unfortunately, we'd need some frame of reference and I'd rather not digress that far into the discussion. If someone is looking for an amp with cutting-edge tested measurements, then look elsewhere. On the other hand, if someone is looking for a very good performing amp with "musicality" and "personality," then the Millett MAX can fit that bill. It is the very latest refinement of Pete Millett's original, magical design.

 Colin's tremendous design layout gets lost in some of these performance/theory discussions, too. IMHO, the MAX has the most complete features on a single board - Power supply, relay-delay, Millett tube circuit, plus full-size extruded heat sink layout for the diamond buffers. It is also unique in incorporating the option of using BJT's or MOSFETs on the same board - whichever of those one might prefer.


 P.S. Thanks for that post, Dsavitsk! Yours too, Amphead!


----------



## BoilermakerFan

Quote:


  Originally Posted by *dsavitsk* /img/forum/go_quote.gif 
_Lots of tubes will operate well into the MHz range, and triodes are inherently more linear than any solid state device yet devised. Tubes went away, not because they worked poorly, but because they were large, expensive to manufacture and power, needed to be replaced frequently, and solid state's inherent crudiness could be compensated for with feedback._

 

Good point. I'll restate that my original questions weren't aimed at pointing out a perceived weakness, I'm just trying to understand how all the parts fit together to make the MAX what it is. 

 I do find it a bit confusing that some people act like you have to chose sides (not implying anyone in this thread either, I spend a lot of time on DIYaudio were this occurs often), pick the better team, etc. I think the hybrid designs are the best thing since sliced bread! The warmth and second harmonics of tubes at low signal levels with an analytical (or lowest possible alteration of the existing sound) SS output to keep the tube signature. That's why I was so blown away by the MAX design and John Rassmusen's JLTi tube-buffered inverted gain clone amps. 

 What fascinates me the most is the emotional aspect of it all. We don't all have to agree that one way is better than another. We just need to respect each others decisions and tastes for what they are, an individual's emotional opinion based on what sounds (or tastes, or looks) great to that individual.


----------



## Ferrari

Quote:


  Originally Posted by *dsavitsk* /img/forum/go_quote.gif 
_Lots of tubes will operate well into the MHz range, and triodes are inherently more linear than any solid state device yet devised. Tubes went away, not because they worked poorly, but because they were large, expensive to manufacture and power, needed to be replaced frequently, and solid state's inherent crudiness could be compensated for with feedback._

 

Agreed... lots of tubes, but unfortunately NOT all tubes!
 There are lots of good tubes (in any price classes) which are excellent for audio applications but some others are simply inferior for audio, especially when important parameters for audio (besides band width) such as slew rate and distortions are considered, (the same is true for semi-conductors).

 Inferior tubes are (and stay) inferior tubes! Excessive marketing craps will and can not disguise the real nature of these inferior tubes.


----------



## tomb

Ferrari - it's a moot point.

 Pick a single channel tube that uses 24V on the plate and 12.6V heater voltage ...

 You see, it's a remark against the design, because there are no other tubes that can be used, despite your opinion of them. 

 One might as well go over in the M3 thread and say that you hate MOSFETs, that they don't sound as good as BJT's, they have more noise, etc. ... not a very polite thing to do.


----------



## bperboy

Thanks Ferrari and Tomb for putting up with my questions! 
	

	
	
		
		

		
			





 I've been taking a introduction to electric circuits class this semester before I start college in the fall, and I've been trying to use some of the stuff I've learned to better understand how my gear works... DIY is one of the big reasons that I've chosen to go into EE, so props to the DIY forum at Head-Fi!


----------



## Beefy

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Pick a single channel tube that uses 24V on the plate and 12.6V heater voltage ...

 You see, it's a remark against the design, because there are no other tubes that can be used, despite your opinion of them._

 

But the original Millett design was always a compromise in this regard, wasn't it? The aim of the design was to *specifically* use low voltage commodity tubes, and make something listenable.

 BUT

 The fact that the Millett and its successors are so highly regarded, with these otherwise useless tubes, IS NOT a remark against the design. It is proof of a massively successful design, isn't it? That the design has managed to do something spectacular, despite the 'weak' point?


----------



## tomb

Quote:


  Originally Posted by *Beefy* /img/forum/go_quote.gif 
_But the original Millett design was always a compromise in this regard, wasn't it? The aim of the design was to *specifically* use low voltage commodity tubes, and make something listenable._

 

Exactly.

  Quote:


 BUT

 The fact that the Millett and its successors are so highly regarded, with these otherwise useless tubes, IS NOT a remark against the design. It is proof of a massively successful design, isn't it? That the design has managed to do something spectacular, despite the 'weak' point? 
 

Yes, you have superbly turned the point on its end.


----------



## pinkfloyd4ever

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Exactly.

 Yes, you have superbly turned the point on its end.
	

	
	
		
		

		
		
	


	


_

 

x2....I don't know much about circuits and electronics design, but I challenge anyone to listen to a Max and not find the sound amazing, especially for its price...I can't tell you how many songs I'd sort of worn out my appreciation for I've been so turned on to again because of the detail, clarity, and just damn good reproduction of music (however you like to describe it) of my Max

 also, let's not forget here that one of the original goals of the Millett (to which the Max is no exception) was to use LOW VOLTAGE tubes, making a design much safer for tube newbies than the several hundreds of volts encountered in traditional tube amps


----------



## n_maher

All you hybrid lovers should come to CanJam. You'll find a new little something sitting on my table...


----------



## Beefy

Quote:


  Originally Posted by *n_maher* /img/forum/go_quote.gif 
_All you hybrid lovers should come to CanJam. You'll find a new little something sitting on my table..._

 

You've got something more exciting than 'The Menace'?


----------



## bperboy

Quote:


  Originally Posted by *n_maher* /img/forum/go_quote.gif 
_All you hybrid lovers should come to CanJam. You'll find a new little something sitting on my table..._

 

Uh oh... actually I think I'm at the table next to yours nate!


----------



## BoilermakerFan

Quote:


  Originally Posted by *n_maher* /img/forum/go_quote.gif 
_All you hybrid lovers should come to CanJam. You'll find a new little something sitting on my table..._

 

I can't make it to CanJam, and the wife won't approve the purchase of TTVJ's Millett Hybrid amp. 
	

	
	
		
		

		
		
	


	




 But I look forward to reading the reviews and seeing the comments. I am assuming that is what you are posting about and not a reference to certain agriculture hybrids. LOL! 

 bperboy, any chance you could schlep your MAX down there and do a side by side comparison of the two? After all, it will be right next to you...


----------



## n_maher

Quote:


  Originally Posted by *Beefy* /img/forum/go_quote.gif 
_You've got something more exciting than 'The Menace'? 
	

	
	
		
		

		
		
	


	


_

 

All depends on what excites you. The "new" hybrid should set new standards for price/performance, it costs about the same as a Cmoy to build including the chassis and power supply. 
	

	
	
		
		

		
		
	


	




 There's nothing hybrid about the Menace either, so that doesn't really count. Folks who enjoy Pete's designs should stop by and check that out as well. In truth there's still a chance that the Menace won't make it, I just finished the power supply wiring and I'll be starting the amplifier section tomorrow night but it's an uphill battle I'm facing.


----------



## Beefy

Quote:


  Originally Posted by *n_maher* /img/forum/go_quote.gif 
_The "new" hybrid should set new standards for price/performance, it costs about the same as a Cmoy to build including the chassis and power supply. 
	

	
	
		
		

		
		
	


	


_

 

Intriguing!

  Quote:


 In truth there's still a chance that the Menace won't make it, I just finished the power supply wiring and I'll be starting the amplifier section tomorrow night but it's an uphill battle I'm facing. 
 

Best of luck then! I look forward to seeing some impressions of that beasty thing.......


----------



## tomb

Quote:


  Originally Posted by *n_maher* /img/forum/go_quote.gif 
_All you hybrid lovers should come to CanJam. You'll find a new little something sitting on my table..._

 

Well, you've really got my curiosity going with that. Unfortunately, it doesn't look like I'll make it to CanJam, either. The wife has a bit of a conflict with her annual charitable fund-raising event. I'll be dead meat if I leave at that time of year.


----------



## n_maher

Sorry to hear that you won't be making the trip Tom, that's a bummer. I think that details will be coming out pretty soon about the amp that Pete calls "Millett Starving Student" amp. 
	

	
	
		
		

		
		
	


	




 I've been using one for the last couple of weeks at work and it's a solid performer.


----------



## tomb

Quote:


  Originally Posted by *n_maher* /img/forum/go_quote.gif 
_Sorry to hear that you won't be making the trip Tom, that's a bummer. I think that details will be coming out pretty soon about the amp that Pete calls "Millett Starving Student" amp. 
	

	
	
		
		

		
			





 I've been using one for the last couple of weeks at work and it's a solid performer._

 

Sounds cool, Nate!


----------



## manaox2

Quote:


  Originally Posted by *n_maher* /img/forum/go_quote.gif 
_Sorry to hear that you won't be making the trip Tom, that's a bummer. I think that details will be coming out pretty soon about the amp that Pete calls "Millett Starving Student" amp. 
	

	
	
		
		

		
		
	


	




 I've been using one for the last couple of weeks at work and it's a solid performer._

 

My hero!


----------



## n_maher

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Sounds cool, Nate! 
	

	
	
		
		

		
		
	


	


_

 

Looks cool too! This is my version, I think it cost ~$50 including the tubes, chassis and PS. I need to get a better picture with the knob on it so it looks a bit less ghetto.


----------



## el_matt0

haha yo nate thats awesome man! can i see pics of the internals by any chance? did you do the board yourself or...whats in there?


----------



## el_matt0

oh and how does it sound compared with a full sized millet - comparable at least??


----------



## n_maher

Quote:


  Originally Posted by *el_matt0* /img/forum/go_quote.gif 
_haha yo nate thats awesome man! can i see pics of the internals by any chance? did you do the board yourself or...whats in there?

 oh and how does it sound compared with a full sized millet - comparable at least??
_

 

No PCB, it's wired point to point. And I'll post internal pictures once it's been officially released for public consumption. I served as the "any idiot can build it" test and it passed so I think it's just a matter of Pete finding the time to publish it. 
 Sound wise I'd put it on par with the original hybrid design, maybe a touch better. But really I haven't heard any of the low-voltage hybrids recently enough to make a valid comparison. There's certainly nothing about it that jumps out as wrong.


----------



## el_matt0

very nice work anyhow, i look forward to throwing one of these together! cant wait till this gets released to the public! if you happen to have a schematic or anything prior to that, please PM me with any info possible, it was my cousins bday last week and i was trying to think of the perfect amp to put together for him, and i think this might just be it. guess itll be a little belated though...lol!


----------



## kvant

Quote:


  Originally Posted by *n_maher* /img/forum/go_quote.gif 
_...I think it's just a matter of Pete finding the time to publish it._

 

In the meantime... from the outside (and from the "priceside") it looks a lot like this one. I guess the internal concept is pretty close too.


----------



## n_maher

In concept it's similar, yes. The tube and B+ are different though.


----------



## tomb

I'm guessing not. I could be wrong, but Nate's tubes don't look like 12AE6's - 12FK6's or 12FM6's, either. It's hard to tell at this angle, but the top mica spacer is too far down and the getter flash is in the wrong place. Side getters are between the mica spacers, while top getters usually have the flash predominately on the dome.

 'Course, it may just be another bad guess on my part.
	

	
	
		
		

		
		
	


	




 EDIT: Oops. He beat me to it.
	

	
	
		
		

		
		
	


	




 Anybody ever notice you get one shot at an edit before Head-Fi rings the "Last edited by ..." bell? It seems time related.


----------



## dsavitsk

Quote:


  Originally Posted by *BoilermakerFan* /img/forum/go_quote.gif 
_I think the hybrid designs are the best thing since sliced bread! The warmth and second harmonics of tubes at low signal levels with an analytical (or lowest possible alteration of the existing sound) SS output to keep the tube signature. That's why I was so blown away by the MAX design and John Rassmusen's JLTi tube-buffered inverted gain clone amps._

 

So, what I'm telling you is that this _2nd harmonic myth_ of the internet is incorrect. Tubes sound good not because of the highish 2nd harmonics, but in spite of them. Indeed, the best tubes (45's to give the standard example) have extraordinarily low second harmonics. When I say that a triode is more linear than a transistor, what this means is that it is a lower distortion device. Transistors, in order to achieve these low levels of distortion must use feedback or some other clever means that many people feel are degrading to the sound. If you want to convince yourself that this second harmonic business is nonsense, build a solid state amplifier with very low measured distortion. Use a computer to generate second harmonic distortion and listen to it. It won't sound like a tube amp. All of this is to say, there is more going on than harmonic distortion.

 Now, this is not to evangelize or say that solid state is all bad. Quite frankly, if people stopped buying tubes and thus driving up the prices, I'd be much happier. There are many very good solid state designs. It is to say that solid state is not better in some analytical sense.


----------



## BoilermakerFan

Quote:


  Originally Posted by *dsavitsk* /img/forum/go_quote.gif 
_So, what I'm telling you is that this 2nd harmonic myth of the internet is incorrect. Tubes sound good not because of the highish 2nd harmonics, but in spite of them. Indeed, the best tubes (45's to give the standard example) have extraordinarily low second harmonics. When I say that a triode is more linear than a transistor, what this means is that it is a lower distortion device. Transistors, in order to achieve these low levels of distortion must use feedback or some other clever means that many people feel are degrading to the sound. If you want to convince yourself that this second harmonic business is nonsense, build a solid state amplifier with very low measured distortion. Use a computer to generate second harmonic distortion and listen to it. It won't sound like a tube amp. All of this is to say, there is more going on than harmonic distortion.

 Now, this is not to evangelize or say that solid state is all bad. Quite frankly, if people stopped buying tubes and thus driving up the prices, I'd be much happier. There are many very good solid state designs. It is to say that solid state is not better in some analytical sense._

 

I have always heard or read that the distortion present in tubes was primarily in the second harmonic, which is pleasant to most human ears. So perhaps I've bought into this myth that this 2nd harmonic is the key to the tube sound. I'm ok with that and your explanation helps. All I know is, I like the sound of tubes, so don't worry, I wasn't trying to imply SS is better. 

 New technology or new products do not necessarily indicate better quality. Crappy components and poor workmanship will result in a crappy product, regardless of whether it's a tube, transistor, house, car, piano, or glass of wine. 

 It seems like this thread has drifted off topic a lot in last 20 pages or so. My original question was related to the bias levels for the DB transistors simply to educate myself and learn about it's impact on the performance of the amp. It was not intended to bring up yet another off topic discussion or argue the merit of the design or specific components in the MAX.


----------



## tomb

Don't mind Dsavitsk, I believe he is correct. It's one of those things that people have conjectured all along but may be incorrect (even-order harmonics resulting in the pleasing "tube sound") . I think he's also mentioned that OTL push-pull tube amps will cancel out even order distortion, yet they still have "tube sound."

 Meanwhile, based on many comments I've received in the past few months, I've updated the MAX BOM. Details are here:

MAX BOM

 In addition to some parts updates, the MOSFET section has been completely removed, in preparation for the MOSFET-MAX website and updating to the JFET-MOSFET mod parts. I should have that done shortly. If not, thanks for your patience, but I was getting a bit fretful at discovering several builders continuing to select the MOSFET option with the old parts.


----------



## bperboy

TomB, the transistors that I'll be replacing are to go in reverse of the silkscreen, correct?


----------



## tomb

Quote:


  Originally Posted by *bperboy* /img/forum/go_quote.gif 
_TomB, the transistors that I'll be replacing are to go in reverse of the silkscreen, correct?_

 

Yes - turned backwards within the same location - the flat part of the TO-92 case will face the opposite direction of the silkscreen's flat part.


----------



## bperboy

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Yes - turned backwards within the same location - the flat part of the TO-92 case will face the opposite direction of the silkscreen's flat part._

 

Awesome! I received my trannies today, and hopefully resistors will arrive tomorrow or friday... I'll be sure to note any differences if my lead ears can actually hear any!


----------



## BoilermakerFan

Well, I had a lot of time to kill in airports this morning, so I reviewed my "old" MAX BOM that I had printed off along with copies of my original Mouser and Digi-Key orders. I had pretty much ordered doubles of everything except for the Panasonic caps from D-K, which for some reason I only ordered (6) instead of (4) or (8). But I noticed I missed the WIMA caps for CA4L/R and CA6L/R completely. Probably because I planned to order K42s and VitQs from Beezar for the CA8L/R. 

 Anyways, I'll be ordering those WIMAs and the additional BOM bits for a third MAX. However, in the interim, can I use K42s for CA4 and CA6 without a negative impact on the sound so I can start building? This build will be the 3422s DB pair with Muse ES caps and VitQ bypass caps. If it is a try it and see situation, I will and I'll swap in the WIMAs in a week if I have too.

 Thanks.


----------



## tomb

If I had to guess, the K42's are closer to the Wima's performance than they are to VitQ's. So yes, go ahead and use them - but try it and see (or listen).


----------



## BoilermakerFan

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_If I had to guess, the K42's are closer to the Wima's performance than they are to VitQ's. So yes, go ahead and use them - but try it and see (or listen).
	

	
	
		
		

		
		
	


	


_

 

Great! I'll let you know how it sounds in five months when I finally get it built and order headphones!


----------



## Beefy

Ooooh, my Mouser order just arrived through internal mail at work. Hurry up Beezar!


----------



## tomb

Quote:


  Originally Posted by *Beefy* /img/forum/go_quote.gif 
_Ooooh, my Mouser order just arrived through internal mail at work. Hurry up Beezar! 
	

	
	
		
		

		
		
	


	


_

 

Well, you know when it shipped. It's probably up to Australia at this point.


----------



## fault151

Hi guys, what would be the best thickness for hook up cable on the millet or any amp for that matter? Would 28AWG be a bit thick?


----------



## tomb

Quote:


  Originally Posted by *fault151* /img/forum/go_quote.gif 
_Hi guys, what would be the best thickness for hook up cable on the millet or any amp for that matter? Would 28AWG be a bit thick?_

 

28AWG is too small, IMHO. Wire gauge designations are inverted from the physical wire size. So, 28AWG is smaller than 26AWG, which is smaller than 24AWG, etc. 22AWG is the size I use most and it will fit in every through hole pad on DIY boards. It gets somewhat thick when twisted or braided in multiples - perhaps too heavy for headphone cable for instance, so the smaller 24AWG is commonly used, too.


----------



## Beefy

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Well, you know when it shipped. It's probably up to Australia at this point.
	

	
	
		
		

		
		
	


	








_

 

Yeah, it's all good! 
	

	
	
		
		

		
		
	


	




 The Mouser order contained the resistor I needed to increase the voltage on my S11 power supply to 27V. So I'll do that first, before drilling out my tube sockets and testing all the resistor and tube LED combos for brightness and heat from that 27V source.......


----------



## fault151

So for hook up wire inside the amp you would use 24AWG.

 Would you use shielded 22AWG for interconnects and to connect to the rca's?

 What would be good for headphones?


----------



## MrMajestic2

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_28AWG is too small, IMHO. Wire gauge designations are inverted from the physical wire size. So, 28AWG is smaller than 26AWG, which is smaller than 24AWG, etc. 22AWG is the size I use most and it will fit in every through hole pad on DIY boards. It gets somewhat thick when twisted or braided in multiples - perhaps too heavy for headphone cable for instance, so the smaller 24AWG is commonly used, too._

 

I agree with Tomb, 28 is way too small. 22 or 24 is a good size.


----------



## tomb

Quote:


  Originally Posted by *fault151* /img/forum/go_quote.gif 
_So for hook up wire inside the amp you would use 24AWG.

 Would you use shielded 22AWG for interconnects and to connect to the rca's?

 What would be good for headphones?_

 

No, actually - I use 22AWG for everything but headphone cable itself.
	

	
	
		
		

		
		
	


	




 That's because, generally you're hanging all of that wire from your head. I've seen some people use 22AWG, though - even for headphone cable.

 EDIT: Generally speaking, as long as you can bend it and work with it, the bigger the wire, the better. 22AWG seems to fit that bill for me.


----------



## fault151

Ok cheers. I'll see what i can find.


----------



## fault151

one other thing, is shielded cable only really used for interconnects and internal rca links? Anyone know of any good places to buy wire from in the UK?


----------



## tomb

Quote:


  Originally Posted by *fault151* /img/forum/go_quote.gif 
_one other thing, is shielded cable only really used for interconnects and internal rca links?_

 

Yep, but there are always exceptions. 
	

	
	
		
		

		
		
	


	




 Typically, teflon-insulated wire is not used in shielded cable. So, soldering is not as convenient for DIY hookup.

  Quote:


 Anyone know of any good places to buy wire from in the UK? 
 

Can't help you on that one.


----------



## Beefy

Well my S11 is now at 26.6V, and powering a blue Lumex LED at 19mA without breaking a sweat. The 1.2kohm 1W resistor does get pretty toasty, but I can still touch it for a few seconds.

 I think I will go with this combo for my tube LED. When It comes to build time on the Max, I'll just mount the resistor a touch off-board to be safe.


----------



## BoilermakerFan

Quote:


  Originally Posted by *pabbi1* /img/forum/go_quote.gif 
_Perfect case for a balanced Max

Surplus Sales_

 

Thanks again for the tip to these cases pabbi. I should have plenty of room to turn it into a nice integrated amp for my consoles. I put my order in for (5) of them. Asked them to ship them the cheapest way possible since the combined shipping weight is 80 pounds and they ship 4 to a case. Under $16 each for a project case this big is just too darn cool.


----------



## luvdunhill

Tom:

 Will rubber cement, a paper template, and a Bubinga front panel play well together? I don't see why not, but I didn't know if the glue might leave markings on the panel that couldn't be easily removed with light sanding, or perhaps effect the look after the wood has been finished...


----------



## naamanf

I would use some double sided tape.


----------



## BoilermakerFan

Quote:


  Originally Posted by *luvdunhill* /img/forum/go_quote.gif 
_Tom:

 Will rubber cement, a paper template, and a Bubinga front panel play well together? I don't see why not, but I didn't know if the glue might leave markings on the panel that couldn't be easily removed with light sanding, or perhaps effect the look after the wood has been finished..._

 

You could always mirror or inverse the image on your printer and glue it to the backside of the front panel. Then drill small pilot holes to locate the correct positions on the front and drill the correct sized holes from the front so you don't tear out the finished side.


----------



## luvdunhill

Quote:


  Originally Posted by *naamanf* /img/forum/go_quote.gif 
_I would use some double sided tape._

 

they are your panels 
	

	
	
		
		

		
		
	


	







 thanks again!


----------



## tomb

Rubber cement should work well if the grain is sealed. If not, the solvent will soak in and may leave a stain.

 Boilermaker's idea is an interesting one. If the bit is sharp and the underside is well-supported and clamped to a good piece of scrap wood, I would just drill the hole clean through. Don't do that unless you use a drill press - even a small mis-alignment could be disastrous. With wood, though, the paper could just be taped long enough to center punch the holes. Then refer to a key plan for the correct hole sizes at their locations.

 One of the big reasons for using paper with rubber cement templates on aluminum is that the glued down paper protects the overall finish from the metal chips that sometimes get whipped around by the drill bit.


----------



## naamanf

Quote:


  Originally Posted by *luvdunhill* /img/forum/go_quote.gif 
_they are your panels 
	

	
	
		
		

		
		
	


	







 thanks again!_

 

That's what I thought


----------



## tomb

Then he should know the best way to do them.


----------



## swt61

Speaking as the bloke who will be drilling the holes in these panels, I like BoilermakerFan's idea best. I also agree with tomb that tape should suffice. I've done some pretty intricate faceplates with nothing but measurements. I'll have no problem with tear out. I have a drill press, my Forstners are sharp, and I always use backer boards. Should be a slam dunk Marc, no need to fret.


----------



## fordgtlover

Could you first cover the timber faceplate with blue painter's tape to completely cover the grain and then glue the template on to the tape?


----------



## rhester

Just finished my lateste build, this one with the AMB-JFet modified MOSFET version. Everything fired up great, mains where they are suppsoed to be and tubes biased fine. Adjusted MOSFET bias to 264mV. everything is glowing, but there is NO music coming out whatsoever. Should you be able to hear the E12 relay pull in (thru headphones or externally)? Will post pics later if I don't find somehting wrong.


----------



## BoilermakerFan

Quote:


  Originally Posted by *swt61* /img/forum/go_quote.gif 
_Speaking as the bloke who will be drilling the holes in these panels, I like BoilermakerFan's idea best. I also agree with tomb that tape should suffice. I've done some pretty intricate faceplates with nothing but measurements. I'll have no problem with tear out. I have a drill press, my Forstners are sharp, and I always use backer boards. Should be a slam dunk Marc, no need to fret. 
	

	
	
		
		

		
		
	


	


_

 

I will be having a friend of a friend make a faceplate out of Pacific Northwest Madrone for one of my NABU enclosures, so I'll mention "our" techniques to him, but I have a question for you. What kind of edge finish or shape will you use? A simple chamfer, cove, or something more intricate?


----------



## tomb

Quote:


  Originally Posted by *rhester* /img/forum/go_quote.gif 
_Just finished my lateste build, this one with the AMB-JFet modified MOSFET version. Everything fired up great, mains where they are suppsoed to be and tubes biased fine. Adjusted MOSFET bias to 264mV. everything is glowing, but there is NO music coming out whatsoever. Should you be able to hear the E12 relay pull in (thru headphones or externally)? Will post pics later if I don't find somehting wrong._

 

Yes - you can hear the relay click in through the headphones and you can hear it click externally on the board, although the external click is pretty faint. It can take up to 45 seconds, depending on your part selection.

 I'd say if your MOSFETs are biased correctly, then your suspicion is a good one: the relay circuit. The most common problem we've had is soldering the BD-139 in backwards. There's a detail on the MAX website under the Tweaks -> e12 Delay section - at the bottom of the page. It shows how to properly orient the BD-139.

 Just in case, did you remember to solder the JFETs in backwards? Their pinouts are opposite of the BJT silkscreen for QB2L/R and QB3L/R. It's possible that you could bias the MOSFETs properly, but the JFETs could prevent any signal from propagating through the buffer if they're in backwards. Just a guess - I haven't had much experience with them, yet.


----------



## rhester

JFETs are in backwards, I did remeber that and have checked it. Also looks like the 139 is in correct (taper towards the volume control). I definitely do not hear the relay kick in (either thru phones or without them on).


----------



## tomb

Quote:


  Originally Posted by *rhester* /img/forum/go_quote.gif 
_JFETs are in backwards, I did remeber that and have checked it. Also looks like the 139 is in correct (taper towards the volume control). I definitely do not hear the relay kick in (either thru phones or without them on)._

 

OK - I guess we need pics of your delay relay section. That seems to be the problem. If you have some jumper cables, you might try to connect to the ends of the RB14 resistors and to ground - then connect to a headphone plug and see if you get sound. If you do, then something's wrong with the relay.


----------



## rhester

Should the QB1L/R be in backwards to the silkscreen also or in the normal way?


----------



## tomb

Quote:


  Originally Posted by *rhester* /img/forum/go_quote.gif 
_Should the QB1L/R be in backwards to the silkscreen also or in the normal way?_

 

Normal.


----------



## rhester

Here are a couple of pics of the E12 circuit.


----------



## rhester

It is definitely in the E12 circuit. Jumped off the RB14 resistors and ground to another output and have glorious music. Now to find where in the circuit is the problem.


----------



## tomb

Quote:


  Originally Posted by *rhester* /img/forum/go_quote.gif 
_It is definitely in the E12 circuit. Jumped off the RB14 resistors and ground to another output and have glorious music. Now to find where in the circuit is the problem._

 

Well, that's great news - we have it narrowed down pretty good.

 Things that appear correct:
 1. diodes
 2. electrolytic caps
 3. ceramic cap
 4. resistors - can't tell, it looks like you have the rating label rotated to the side.
 5. relay is oriented correctly.

 The thing I would suspicion/guess is perhaps the QM1 transistor. Did you put in an MPSA14? That's a Darlington transistor. One of the 2N5087/88's will not work.

 If that's not it, then perhaps we might suspect that the relay is bad. Confirm that transistor. If it's the MPSA14, then we should probably try to measure some voltages - particularly across the DM2 diode.


----------



## fault151

Hi guys im after a new switch for my Millet max. Will this one be ok to use?

Cool Switch

 Its for the power on/off button.


----------



## rhester

It is MPSA14.


----------



## tomb

Quote:


  Originally Posted by *rhester* /img/forum/go_quote.gif 
_It is MPSA14._

 

Can you measure voltage across the DM2 diode? That's the one that sits across the rails feeding the relay coil. Mine is a little bit more than 10VDC. If you don't have something close to 12VDC there, the relay coil will not shut.

 If you do have ~10VDC there, and you still can't get sound, then something's wrong with the relay.


----------



## tomb

Quote:


  Originally Posted by *fault151* /img/forum/go_quote.gif 
_Hi guys im after a new switch for my Millet max. Will this one be ok to use?

Cool Switch

 Its for the power on/off button._

 

EDIT: Check that. I'm curious about the Normally Closed, and whether there may be a momentary open. Can you give us more literature on this switch?


----------



## fault151

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_EDIT: Check that. I'm curious about the Normally Closed, and whether there may be a momentary open. Can you give us more literature on this switch?_

 

Its off ebay.

 here's a little more info:

 THIS AUCTION IS FOR ONE PACK OF 1 PCS ALTERNATE/latching ON/ON SPDT [ 3-TERMINAL /3-PIN ] HEAVY-DUTY PUSH BUTTON SWITCH [ IDEAL FOR YOUR CAR ELECTRONIC PROJECT ]. [ high quality products,UL,CE ,ECT VERIFIED ]-- NOS [BRAND NEW ]

switch


----------



## rhester

I have almost 11V DC across it so I will swap relays, whenever my Mouser order gets here.


----------



## tomb

Quote:


  Originally Posted by *fault151* /img/forum/go_quote.gif 
_Its off ebay.

 here's a little more info:

 THIS AUCTION IS FOR ONE PACK OF 1 PCS ALTERNATE/latching ON/ON SPDT [ 3-TERMINAL /3-PIN ] HEAVY-DUTY PUSH BUTTON SWITCH [ IDEAL FOR YOUR CAR ELECTRONIC PROJECT ]. [ high quality products,UL,CE ,ECT VERIFIED ]-- NOS [BRAND NEW ]

switch_

 

OK - latching should be fine. The MAX only needs a SPST, so you won't use two of those pins, but that's not uncommon for upgrade-style switches. You should be fine.

 Be careful that you have enough depth to fit it, though, those pushbuttons can be rather long.


----------



## fault151

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_OK - latching should be fine. The MAX only needs a SPST, so you won't use two of those pins, but that's not uncommon for upgrade-style switches. You should be fine.

 Be careful that you have enough depth to fit it, though, those pushbuttons can be rather long._

 

You mean inside the case? Yeh i do. What does SPST stand for. Which two pins do i need? Do you think it will come with some sort of drawing? 

 Cheers.


----------



## naamanf

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_EDIT: Check that. I'm curious about the Normally Closed, and whether there may be a momentary open. Can you give us more literature on this switch?_

 

I have some of the DPDT version of that switch. So you can use on pole for NC. Not momentary though. It's a latched switch. If you want one tomb shoot me a PM.


----------



## tomb

Quote:


  Originally Posted by *rhester* /img/forum/go_quote.gif 
_I have almost 11V DC across it so I will swap relays, whenever my Mouser order gets here._

 

OK - you have put your ear down to it and never hear a click, right? Anything on the back of the board that could be amiss? It sounds like a bad relay, but just making sure.
	

	
	
		
		

		
			





 I'm not sure, but I think these things are rather fragile when it comes to soldering. It may be possible to heat them up too much. Not saying that's the reason, or otherwise we'd have heard of this happening more often. In fact, I don't think we've had a reported case of someone ruining one. So, you should try to see if Mouser will replace/refund it.

 While you're unsoldering/ordering, you might try a DIP-16 socket, or two DIP-8 sockets put end-to-end. The relay will plug into one of those arrangements. You'll have to trim the legs of the socket where there are no holes in the board for them, but it could make things more convenient if this happens to be a recurring problem.


----------



## rhester

Problem fixed (I admit to being a dumbass now). Went to desolder the relay and flipped the board over and found that I had not soldered the pin going out of the relay. Soldered it and everythig is hunky dory.


----------



## Gaso

I finally started and finished my Max (minus the case) couple of days ago and I can't forgive me for not completing this project sooner... All I'm going to say first time I heard this little marvel of an amp I got rooted to my seat and realized I haven't moved a muscle in two hours straight. Denon D2000+12FM6 were OK, but pair those phones with 12AE6 and oh boy... Now I'm afraid to touch the volume knob, because I know I'll just jinx this whole thing and lose what I'm hearing for good.

 Thanks Colin, Tomb and everyone else involved!


----------



## tomb

Quote:


  Originally Posted by *rhester* /img/forum/go_quote.gif 
_Problem fixed (I admit to being a dumbass now). Went to desolder the relay and flipped the board over and found that I had not soldered the pin going out of the relay. Soldered it and everythig is hunky dory._

 

Yay! Always cause to celebrate when a MAX problem is solved.


----------



## tomb

Quote:


  Originally Posted by *Gaso* /img/forum/go_quote.gif 
_I finally started and finished my Max (minus the case) couple of days ago and I can't forgive me for not completing this project sooner... All I'm going to say first time I heard this little marvel of an amp I got rooted to my seat and realized I haven't moved a muscle in two hours straight. Denon D2000+12FM6 were OK, but pair those phones with 12AE6 and oh boy... Now I'm afraid to touch the volume knob, because I know I'll just jinx this whole thing and lose what I'm hearing for good.

 Thanks Colin, Tomb and everyone else involved!_

 

Glad you enjoy the MAX!
	

	
	
		
		

		
		
	


	







 Yeah, I go back and forth depending on the mood - been listening to the detail on 12FK6's for the last few weeks. Then I plugged in a set of Dumont 12AE6's and WOW! The dynamic slam is just incredible. Response is great and cymbal crashes are just as strong as bass slam. It's as if any note with a percussive hit is uber-amplified. Just outstanding.


----------



## BoilermakerFan

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Glad you enjoy the MAX!
	

	
	
		
		

		
		
	


	







 Yeah, I go back and forth depending on the mood - been listening to the detail on 12FK6's for the last few weeks. Then I plugged in a set of Dumont 12AE6's and WOW! The dynamic slam is just incredible. Response is great and cymbal crashes are just as strong as bass slam. It's as if any note with a percussive hit is uber-amplified. Just outstanding.
	

	
	
		
		

		
		
	


	


_

 

Have anymore of those Dumont tubes?


----------



## slowpogo

The past week or two I've spotted some 12AE6's on ebay. One was a batch of Westinghouse tubes, the other Tung-Sol. The pictures for these auctions didn't have 360 degree coverage, but I couldn't see the familiar GE etching or RCA octagon on either of them. The Tung-Sols seemed to have some numeric indication painted on, matching the logo.

 Do we know for sure at this point how many companies made the 12AE6 (as in manufacture, not rebranded)? I know there are GE, RCA and Sylvania models out there. Could there also be Tung-Sol and/or Westinghouse too?


----------



## amphead

Congrats Gaso! Another Max Lives!   

 I know exactly how you feel. The Max is outstanding with 12AE6 and really pumps out tone!


----------



## tomb

Quote:


  Originally Posted by *BoilermakerFan* /img/forum/go_quote.gif 
_Have anymore of those Dumont tubes?_

 

Luck of the draw ... you have as much chance as I did to draw a couple of superlative tubes. They exist - an occurrence perhaps where every part came together just right. As a matter of fact, Dumont didn't make any of their own tubes. The ones I've spoken about are Sylvania's. Colin has a pair of Dumonts and the construction is entirely different - either GE's or RCA's.

  Quote:


  Originally Posted by *slowpogo* 
_The past week or two I've spotted some 12AE6's on ebay. One was a batch of Westinghouse tubes, the other Tung-Sol. The pictures for these auctions didn't have 360 degree coverage, but I couldn't see the familiar GE etching or RCA octagon on either of them. The Tung-Sols seemed to have some numeric indication painted on, matching the logo.

 Do we know for sure at this point how many companies made the 12AE6 (as in manufacture, not rebranded)? I know there are GE, RCA and Sylvania models out there. Could there also be Tung-Sol and/or Westinghouse too?_

 

I didn't catch the Westinghouse tubes, but the ten Tung-Sol 12AE6's that went last night were either RCA or GE side-getters. It's quite possible the GE markings were on them, because the one pictured had the little clear disc connecting the plates at the top - that's a GE feature. It's also quite possible that none of the ones in the other boxes were similar except for a painted-on "Tung-Sol" label.

 I've gotten several Westinghouses, but there is no indication that they made any - every one could be identified as one of the Big Three. As one of the big three, Sylvania/Tung-Sol is different: the story is that that Tung-Sol invented space-charge tubes (low voltage tubes). However, all of the Tung-Sol's I've ever received could be indentified as one of the three: RCA, GE, or Sylvania. The belief is that Tung-Sol sub-contracted perhaps _all of_ their manufacture to Sylvania and others. I believe Negatron mentioned that Tung-Sol and Sylvania had a "special" arrangement.

*Sylvania ID:*
 Of the three constructions, the Sylvania is the one that's least common, IMHO. AFAIK, no Sylvania used anything but square getters - either side or top. The top getter style is often off-kilter, perhaps being as much as a side getter as top getter - just at the top, instead of somewhere in the middle between the two mica spacers as with every other side getter. The grid box is usually more elaborate, often with extra supports above the top mica space. The designator on the tube is simply the tube type in small black letters, or placed within a small rectangle (I'm going from memory here - I don't have the tubes in front of me).

*GE/RCA ID:*
 GE's and RCA's are much more easily identified. If the tube has the designation etched in the glass, along with a series of etched dots, then the tube was manufactured by GE, period. RCA's have the tube designation contained with a squished octagon. What makes this doubly confusing is that you can find GE tubes where the RCA designator was applied later. I can't imagine that GE would etch the glass if the the RCA designation was on there first, though, so one can assume that the RCA's in that case are GE, period. 

*Sound Differences:*
 Typically, I've found the Sylvania's have the best highs of most 12AE6's, but are often light in the bass department. It happens every once in awhile that you find one with strong bass, as with the Dumonts I mentioned. The same can be said of the other two mfrs, except in reverse: GE and RCA 12AE6's seem bass-strong, so one is looking for that outstanding pair that also have great highs. It's seemed to me that RCA's have a boomy bass that mellows out after break-in, leaving a rich mid-range. GE's remain very punchy. Those are very generalized statements, though, for sound differences - and only apply to the 12AE6.

 Meanwhile, Colin and I have talked about my drawing up some details on the tube construction to give everyone a reference (which I'm going to do). One big reason to do that is that at Beezar, I endeavor to match construction, not the name that's painted on the tube. The 12FK6 top getters that I mentioned several pages back are two different "painted-on" brands that I've been using for weeks in the MiniMAX - one RCA, one GE. However, there's no doubt that both are identical GE construction. Matching in that way (tube construction) is much more important than matching the name painted on the label - the two things have no consistent relationship.


----------



## BoilermakerFan

Quote:


  Originally Posted by *fault151* /img/forum/go_quote.gif 
_You mean inside the case? Yeh i do. What does SPST stand for. Which two pins do i need? Do you think it will come with some sort of drawing? 

 Cheers._

 

SPST = Single Pole, Single Throw. There are only one set of contact points and the switch only has two positions, On and Off.

 I would see if the pins are numbered and if it has a switch circuit diagram with it. If it doesn't, you can use a continuity checker on a DMMV or wire it to one set of contacts on either side and see if it works. If it does, you're good to go. If it doesn't, move the center wire one pin away and try again. Move the wire to the outer pin if that doesn't work either.

 Are you planning to relocate the switch to the front faceplate of the MAX? It's a cool looking power switch, but you usually won't see it since the stock location is on the back of the MAX.


----------



## BoilermakerFan

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Luck of the draw ... you have as much chance as I did to draw a couple of superlative tubes. They exist - an occurrence perhaps where every part came together just right. As a matter of fact, Dumont didn't make any of their own tubes. The ones I've spoken about are Sylvania's. Colin has a pair of Dumonts and the construction is entirely different - either GE's or RCA's.

 I didn't catch the Westinghouse tubes, but the ten Tung-Sol 12AE6's that went last night were either RCA or GE side-getters. It's quite possible the GE markings were on them, because the one pictured had the little clear disc connecting the plates at the top - that's a GE feature. It's also quite possible that none of the ones in the other boxes were similar except for a painted-on "Tung-Sol" label.

 I've gotten several Westinghouses, but there is no indication that they made any - every one could be identified as one of the Big Three. As one of the big three, Sylvania/Tung-Sol is different: the story is that that Tung-Sol invented space-charge tubes (low voltage tubes). However, all of the Tung-Sol's I've ever received could be indentified as one of the three: RCA, GE, or Sylvania. The belief is that Tung-Sol sub-contracted perhaps all of their manufacture to Sylvania and others. I believe Negatron mentioned that Tung-Sol and Sylvania had a "special" arrangement.

*Sylvania ID:*
 Of the three constructions, the Sylvania is the one that's least common, IMHO. AFAIK, no Sylvania used anything but square getters - either side or top. The top getter style is often off-kilter, perhaps being as much as a side getter as top getter - just at the top, instead of somewhere in the middle between the two mica spacers as with every other side getter. The grid box is usually more elaborate, often with extra supports above the top mica space. The designator on the tube is simply the tube type in small black letters, or placed within a small rectangle (I'm going from memory here - I don't have the tubes in front of me).

*GE/RCA ID:*
 GE's and RCA's are much more easily identified. If the tube has the designation etched in the glass, along with a series of etched dots, then the tube was manufactured by GE, period. RCA's have the tube designation contained with a squished octagon. What makes this doubly confusing is that you can find GE tubes where the RCA designator was applied later. I can't imagine that GE would etch the glass if the the RCA designation was on there first, though, so one can assume that the RCA's in that case are GE, period. 

*Sound Differences:*
 Typically, I've found the Sylvania's have the best highs of most 12AE6's, but are often light in the bass department. It happens every once in awhile that you find one with strong bass, as with the Dumonts I mentioned. The same can be said of the other two mfrs, except in reverse: GE and RCA 12AE6's seem bass-strong, so one is looking for that outstanding pair that also have great highs. It's seemed to me that RCA's have a boomy bass that mellows out after break-in, leaving a rich mid-range. GE's remain very punchy. Those are very generalized statements, though, for sound differences - and only apply to the 12AE6.

 Meanwhile, Colin and I have talked about my drawing up some details on the tube construction to give everyone a reference (which I'm going to do). One big reason to do that is that at Beezar, I endeavor to match construction, not the name that's painted on the tube. The 12FK6 top getters that I mentioned several pages back are two different "painted-on" brands that I've been using for weeks in the MiniMAX - one RCA, one GE. However, there's no doubt that both are identical GE construction. Matching in that way (tube construction) is much more important than matching the name painted on the label - the two things have no consistent relationship._

 

Thanks Tom. I sent you an email with a Beezar related question.


----------



## BoilermakerFan

A large box from Beezar showed up today. 
	

	
	
		
		

		
		
	


	




 I heard the mailman pull up so I was able to sign for it. 

 Now I just need to get the gosh darned PCB vise from my buddy and let the fumes fly.


----------



## n_maher

Don't let the vise stop you, I've built many a project were using the vice was more trouble that it was worth.


----------



## BoilermakerFan

Quote:


  Originally Posted by *n_maher* /img/forum/go_quote.gif 
_Don't let the vise stop you, I've built many a project were using the vice was more trouble that it was worth._

 

OK, now my newbie side is coming out, how do you hold the component in place in order to solder from the bottom? Or do you just insert the component and solder from above? I just figured I would have much better results soldering on the bottom with the board inverted since I haven't done PCB electronics projects in a few years (more than 12) and I'm just getting started again.


----------



## tomb

Quote:


  Originally Posted by *BoilermakerFan* /img/forum/go_quote.gif 
_OK, now my newbie side is coming out, how do you hold the component in place in order to solder from the bottom? Or do you just insert the component and solder from above? I just figured I would have much better results soldering on the bottom with the board inverted since I haven't done PCB electronics projects in a few years (more than 12) and I'm just getting started again._

 

Nate is right - one of those vises may be more trouble that it's worth for the MAX. Take a look at the construction article on the MAX website.

 1. Get yourself a 1 x 8 or 1 x 10 board about 10" long.
 2. Arrange your parts according to height: RN55 resistors first, then diodes and RN60 resistor, small trannies, Wima caps, tube sockets, large electrolytics, then heat sinks (I may have a couple out of order).
 3. Starting with the lowest height parts first - the RN55 resistors, bend the leads and put them through the holes in the board. While holding the part against the board, bend the leads sideways so that they don't fall out when you turn the board upside down. If you're lucky, many of them will fit with enough friction that they won't move anyway. Also:
 .........a. Bend the RN55's right at the joint of the body - a 90 deg. bend.
 .........b. Make sure you bend the leads so that the rating number is face up!This will help you troubleshoot when/if something goes wrong.
 4. Turn the board over and while pressing the board down to keep the resistors flush against the board, solder the leads one at a time. You should press in the general vicinity of the resistor that you're soldering each time. Slightly "roll" the resistor by moving the board a bit back and forth to keep the resistor leads as perpendicular as you can to the board.
 5. Turn the board back over every now and then to make sure they're getting soldered OK.
 6. Repeat for the rest of the parts as needed.
 7. For the big caps, put your board on top of the caps after placing them in the board. Then with both hands holding the top and bottom, turn the whole assembly upside down. Begin soldering while pressing down slightle at each capacitor just as you did before. You might solder one lead each of each capacitor, then turn it over to check for adjustment if they've twisted a bit.
 8. The heat sinks will go last, and in much the same way as #7. Turn the whole assembly over and while pressing down with each sink (trying to keep things as level as possible, solder only one pin on each heat sink. Turn the board over when done and readjust the sinks to match the silkscreen outlines. Turn it back over again and solder the remaining pins.

 As long as you can keep track of what's shorter and higher, this procedure goes really quick, and it's quite easy to keep everything flush against the board. No fancy vise needed.


----------



## Gross

I use this head and a custom weighted base. To hold the parts on, I have a roll of blue masking tape, and I tape the components down and then flip the pcb over to solder. Works pretty good for me.


----------



## BoilermakerFan

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Nate is right - one of those vises may be more trouble that it's worth for the MAX. Take a look at the construction article on the MAX website.

 1. Get yourself a 1 x 8 or 1 x 10 board about 10" long.
 2. Arrange your parts according to height: RN55 resistors first, then diodes and RN60 resistor, small trannies, Wima caps, tube sockets, large electrolytics, then heat sinks (I may have a couple out of order).
 3. Starting with the lowest height parts first - the RN55 resistors, bend the leads and put them through the holes in the board. While holding the part against the board, bend the leads sideways so that they don't fall out when you turn the board upside down. If you're lucky, many of them will fit with enough friction that they won't move anyway. Also:
 .........a. Bend the RN55's right at the joint of the body - a 90 deg. bend.
 .........b. Make sure you bend the leads so that the rating number is face up!This will help you troubleshoot when/if something goes wrong.
 4. Turn the board over and while pressing the board down to keep the resistors flush against the board, solder the leads one at a time. You should press in the general vicinity of the resistor that you're soldering each time. Slightly "roll" the resistor by moving the board a bit back and forth to keep the resistor leads as perpendicular as you can to the board.
 5. Turn the board back over every now and then to make sure they're getting soldered OK.
 6. Repeat for the rest of the parts as needed.
 7. For the big caps, put your board on top of the caps after placing them in the board. Then with both hands holding the top and bottom, turn the whole assembly upside down. Begin soldering while pressing down slightle at each capacitor just as you did before. You might solder one lead each of each capacitor, then turn it over to check for adjustment if they've twisted a bit.
 8. The heat sinks will go last, and in much the same way as #7. Turn the whole assembly over and while pressing down with each sink (trying to keep things as level as possible, solder only one pin on each heat sink. Turn the board over when done and readjust the sinks to match the silkscreen outlines. Turn it back over again and solder the remaining pins.

 As long as you can keep track of what's shorter and higher, this procedure goes really quick, and it's quite easy to keep everything flush against the board. No fancy vise needed.
	

	
	
		
		

		
			



_

 

Now you know I have the CD... but, I haven't looked at the pages on the site or CD in some time... 
	

	
	
		
		

		
		
	


	




 As always, thanks again for the great support. 

 And a quick semi - off topic - I was walking my daughter home from school minutes ago and my neighbor had brought two old textured glass windows to the curb for large item trash day. 
	

	
	
		
		

		
		
	


	




 This is glass from the 1930's that isn't made anymore. I asked him if I could grab it for a CD cabinet and a stereo project I was working on. He said of course, so I have this awesome antique glass pane that I need to incorporate into my stand-alone MOSFET-MAX build!


----------



## fran

If you fill a smallish bag with some sand it works well to hold odd shaped pieces in place when soldering.

 Fran


----------



## bperboy

Jeese, all this talk of vices and clamps and sandbags... be a man, hold your finger on each and every component while soldering! Thats how real men do it!


----------



## Beefy

Well I picked up my Beezar order from the post office today. Immaculately packed, and I was pleasantly surprised that the 12AE6A's had side getters. The PCB was also larger than I expected.

 I now have everything to put it together. Might start this Friday, since it is a public holiday down under.....


----------



## amphead

Take your time and measure each resistor with your meter before installing them on the board. Pay close attention to orientation for caps and especially transistors. Transistors seem to get installed backwards now and then. Since you've already had success with an M3 build, this will be like shooting fish in a barrel. But you want to make sure to do it right the first time so that you can listen to the Max for the first time, as soon as possible. Thats the "real" payoff. Good Luck!


----------



## tomb

I have a bit of bad news to announce concerning a parts shortage - something I hope will only last a couple of weeks:

 The specified headphone jack for the MAX - the Neutrik NMJ6CD2 - is out of stock at Mouser. They have 6,711 on the way that are due in on 5/15/2008.

 Unfortunately, after searching numerous local and national vendors, there doesn't appear to be a good substitute. Some of the guys have used the NMJ-series jack with the black plastic nut, but that one is out of stock at Mouser until July. There is another one that has short threads, but I don't think the threads go far enough to work with the Hammond endplates and bezels. Also, Neutrik's "NYS" series will not fit the pads on the board.

 The NMJ6CD2 jack is traditional for the Millett. It's been used all the way back to the original Pete Millett version that first appeared in Audio Xpress magazine. I'm not sure any of us realized how limited the options were for additional sources. In any event, when they are back in stock at Mouser - beezar will carry them, too, just in case.
	

	
	
		
		

		
		
	


	





 P.S. Of course in the meantime, any jack may be air-wired using the existing pads or the terminal block. If you use the terminal block, remember to jumper the headphone jack pads. The terminal block is not energized by default.


----------



## BoilermakerFan

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_I have a bit of bad news to announce concerning a parts shortage - something I hope will only last a couple of weeks:

 The specified headphone jack for the MAX - the Neutrik NMJ6CD2 - is out of stock at Mouser. They have 6,711 on the way that are due in on 5/15/2008.

 Unfortunately, after searching numerous local and national vendors, there doesn't appear to be a good substitute. Some of the guys have used the NMJ-series jack with the black plastic nut, but that one is out of stock at Mouser until July. There is another one that has short threads, but I don't think the threads go far enough to work with the Hammond endplates and bezels. Also, Neutrik's "NYS" series will not fit the pads on the board.

 The NMJ6CD2 jack is traditional for the Millett. It's been used all the way back to the original Pete Millett version that first appeared in Audio Xpress magazine. I'm not sure any of us realized how limited the options were for additional sources. In any event, when they are back in stock at Mouser - beezar will carry them, too, just in case.
	

	
	
		
		

		
		
	


	





 P.S. Of course in the meantime, any jack may be air-wired using the existing pads or the terminal block. If you use the terminal block, remember to jumper the headphone jack pads. The terminal block is not energized by default._

 

My back-order experience with Mouser was better than expected too, so the 5/15 date is a worst case scenario. If you have already placed an order for them for Beezar, I bet they will expedite their order to get them in as soon as possible. Thanks for the heads up though, I was putting together my order for both Mouser and D-K this week, but I have a couple of those jacks already and the locking style is my "standard" jack.


----------



## BoilermakerFan

OK, I have another question for you guys...

 I will have my integrated, MAX-based amp enclosed in a NABU case along with the other boards for input selection and the amp to the speakers. My control panel will be above this case inside the console next to the turntable. The input selector switch wiring and volume attenuation wiring will not be in the signal path so I'll be fine with just using braided or twisted hook-up wire. However, the cable to the headphone jack is going to mounted to the control panel 12"-18" above the amp case. Will Mogami cable be the best cable to use? Should I only ground the shield wire inside the amp to the common signal ground, or should I ground it to the main case/PSU ground? I'm assuming I would want it tied to the S ground only inside the amp so it functions as a drain and not ground loop, correct?

 Thanks.

 BMF


----------



## Beefy

Quote:


  Originally Posted by *amphead* /img/forum/go_quote.gif 
_Good Luck!_

 

Cheers, Amphead! I'm pretty anal retentive about everything, so hopefully it will turn out fine. I usually check each resistor with my DMM before it goes in AND after it is soldered (good for checking for cold joints on ground - see below). Transistors/caps are checked for part number and orientation twice before soldering (and once after for good measure). Where possible, everything is mounted so that I can read it.

 I actually started the build tonight anyway. I was hoping to get my M3 and S11 front and back panels from my mate who was doing the cutouts, but not go. I've managed to get every low-profile part installed up to the tube sockets, bar RB14 - I'm still deciding what to do there, but will probably just put 10 ohm KOA in and go with the whole ignorance is bliss angle....... I HATE desoldering.

 So drill out the tube sockets tomorrow, then LEDs, rectifiers, electrolytics, CA8 VitQ's, Vreg, output BJTs, pot and H/P socket. It all seems so easy once the parts are picked, ordered and on-hand! 
	

	
	
		
		

		
		
	


	




 Oh, and as I hinted at above.... I HATE soldering small components like resistors to ground. My technique just isn't good enough for the massive ground planes on boards like the Max and the M3......


----------



## tomb

Careful with those tube sockets.
	

	
	
		
		

		
		
	


	




 I still break one whenever I drill.

 When you drill through the top pin, your bit will actually be pushing the bottom pin out. So when you start, you'll get resistance at the top (obviously). Once it drills through, let up until you feel resistance at the bottom. At that point, it helps to push the bit slightly - otherwise you'll have drilled through both pins and they'll remain together, accomplishing nothing. The bottom half of the ceramic is very thin, though, so be careful. The point is, there is no need to _drill_ anymore once you've made through the top pin. If you're lucky, the bottom pin will just fall out.


----------



## joneeboi

On the topic of tube sockets, when I was drilling mine out, I didn't apply enough force through the pin, so my drill bit got super hot and eventually melted through the pin. The thing eventually came out, but now I have one unusable drill bit covered in tube socket pin metal.


----------



## Gaso

Great Scott! I just accidentally measured AC amps across GND and V+ instead of VDC. This sent some spectacular blue sparks flying. Let it be clear that I intended to measure VDC instead, but misread the dial from the opposite side (It's safe to assume I'm blind as a bat) 
	

	
	
		
		

		
		
	


	




 Nothing serious happened, but somehow the sound stage collapsed somewhat and the sound distorts a bit on some occasions and bass is less extented, not on a big scale though. 

 So... Could someone explain me what just happened? What might I have broken? 
	

	
	
		
		

		
		
	


	




 EDIT: I feel like an idiot now... should have left the amp running a bit more, because the symptoms seem to have disappeared. Did I somehow manage to drain the caps or am I just imaging things now? 

 EDIT 2: OK, the distortion is definitely there. I checked with another amp and another pair of phones and it still distorts. It seems the source is the culprit. Oh well, I needed a proper DAC anyway...


----------



## tomb

Quote:


  Originally Posted by *Gaso* /img/forum/go_quote.gif 
_Great Scott! I just accidentally measured AC amps across GND and V+ instead of VDC. This sent some spectacular blue sparks flying. Let it be clear that I intended to measure VDC instead, but misread the dial from the opposite side (It's safe to assume I'm blind as a bat) 
	

	
	
		
		

		
		
	


	




 Nothing serious happened, but somehow the sound stage collapsed somewhat and the sound distorts a bit on some occasions and bass is less extented, not on a big scale though. 

 So... Could someone explain me what just happened? What might I have broken? 
	

	
	
		
		

		
		
	


	




 EDIT: I feel like an idiot now... should have left the amp running a bit more, because the symptoms seem to have disappeared. Did I somehow manage to drain the caps or am I just imaging things now? _

 

I'd say it's a good bet that you did at least that.
	

	
	
		
		

		
		
	


	




 I think connecting a meter in that fashion is the same as creating a dead short between V+ and Gnd.

 I'm guessing here, but caps draining wouldn't last that long. I think what you might have done is engaged the protective circuitry of the LM317 in the power supply. That might explain some of this. If so, maybe you didn't hurt anything. I would think the blue sparks came from your meter - surely you blew a meter fuse?

 I tend not to make any measurements on a MAX with the headphones connected, except for biasing the tubes. I finally understand what Drew meant by making the fine adjustment of left and right bias by ear. 
	

	
	
		
		

		
		
	


	




 EDIT: Well, that's good there's no damage, apparently. The MAX can be quite revealing, so a good source helps.

 Stuff happens - I've blown a hole in a few solder joints by touching a grounded probe on VitaminQ's and K42's. You wouldn't think they carry that much charge until you see the spark.


----------



## bperboy

What exactly do you hear when fine-tuning the tube bias? What kind of music are you listening to when you do it?


----------



## Gaso

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Im guessing here, but caps draining wouldn't last that long. I think what you might have done is engaged the protective circuitry of the LM317 in the power supply. That might explain some of this. If so, maybe you didn't hurt anything. I would think the blue sparks came from your meter - surely you blew a meter fuse?_

 

Yes, the sparks flew from V+ contact point and left a small burn mark there for a reminder. The meter fuse held, I don't know if it's a bad or a good thing though . 
	

	
	
		
		

		
			





  Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_
 I tend not to make any measurements on a MAX with the headphones connected, except for biasing the tubes. I finally understand what Drew meant by making the fine adjustment of left and right bias by ear. 
	

	
	
		
		

		
		
	


	


_

 

Believe me, lesson learned.


----------



## tomb

Quote:


  Originally Posted by *bperboy* /img/forum/go_quote.gif 
_What exactly do you hear when fine-tuning the tube bias? What kind of music are you listening to when you do it?_

 

I always thought he could hear a lot more things than me, because I never seemed to notice a difference.

 However, when you get the tubes very close to the same bias, you can detect a slight off-center focus in your headphones. Centered music (mono-like) works best for this, instead of something multiple-miked. Anyway, I'll be danged, but you can hear the center of the soundstage move as you slightly adjust the trimmer on one side or another. So, you want to get it centered, regardless of meter reading. Your ears are a lot more sensitive than the meter, believe it or not - at least for perfectly matching the bias of one tube to the other. 
	

	
	
		
		

		
		
	


	




 Case in point:









 The top image is my BG MAX where I paid close attention to the bias between tubes. I submit that the human ear may balance that bias even closer with the right music.

 The bottom image is an ES MAX where one of the tubes had a constantly lowering bias. At first, there wasn't even enough travel in the trimmer to bias it properly. I left it connected for a few hours and was able to adjust it. Trouble was, it kept lowering as it burned in more and more over time. As you can see, the levels between the two are quite different. The meter reading is probably off by a volt or two on that Right tube.

 Anyway, you can easily see what differences in bias can do the levels between channels. Don't let anyone tell you that you don't have to re-bias when changing tubes.
	

	
	
		
		

		
		
	


	




 P.S. The drop off at 20KHz is a limitation of my M-Audio Transit. The loopback test on the Transit follows that curve and drop at 20KHz exactly. The rest of the curve is fairly typical for most MAXes I've tested so far - a slight elevation on the bass end, but by and large, fairly flat. You can also see an ever-so-slight rise in bass with the ES's.
	

	
	
		
		

		
		
	


	




 Earlier Millett designs were not flat down to 20Hz like that - they had some drop off. That's no criticism, but one would expect some improvement with the MAX. 
	

	
	
		
		

		
		
	


	




 Anyway, my testing so far leaves much to be desired, so the comparisons are more important than any absolute.


----------



## Beefy

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Don't let anyone tell you that you don't have to re-bias when changing tubes.
	

	
	
		
		

		
		
	


	


_

 

I was thinking about this last night.......

 Originally, I wasn't going to run any test points for technical reasons - I was sticking with the 160mm deep Hammond case, and went with 1.5" sinks because I didn't care about the volume knob being centered. But considering that adjustments to power and DB will rarely, if ever, be made after initial setup, I figured that I might try and run test points just for the tube bias. I could position them above or next to the rectifiers - IF I could be bothered.

 However, I think that your post has just sealed the deal. I'll try and buy some tip jacks locally.


----------



## BoilermakerFan

Look what the nice UPS man left on my back patio...






 I few future homes for MAX amps. Thanks again pabbi, and now I'm really thinking about a balanced MOSFET-MAX to be paired with TPA's Buffalo DAC when it's released.


----------



## Beefy

Of all the ridiculous things, I can't seem to find anywhere that has tip jacks near me. Would an insulated banana socket be OK?
Altronics - Your One Stop Electronics Shop (preferred - only 8mm hole)
Jaycar Electronics

 Or can someone think of a better cheap, easily available alternative?


----------



## pinkfloyd4ever

I don't think banana jacks would work too well

 where u @ beef? Australia?


----------



## Beefy

Yes, Australia - Perth specifically.

 I can't see what would be wrong with them, other than the fact that they are bigger than the tip jacks? I just need something with hookup wire on one end, insulated, and room to stick a multimeter probe......

 [EDIT] Oh, I suppose they are probably a little bit electrically exposed on the outside. I was thinking the inside would be fine, because I'd just heatshrink it. What about a captive head binding post? We use these all over the lab for electrical field stimulation:
Altronics - Your One Stop Electronics Shop
 I was swaying away from them because of how far they protrude...... but they are probably a good option if the bananas are a no-go.


----------



## Beefy

Total brain-fart moment...... I think I was up too late last night with the Max.....

 The anode of an LED connects to the positive of the power supply? And that is usually the longer lead?


----------



## fordgtlover

^ 

 Beefy, I found some tip jacks at Dick Smith. They seem to be getting out of electronics, but they had some green, black and red ones. 

 I think I have some that I didn't use. I can have a look for them if you like.

 Cheers


----------



## Beefy

I checked Dickies website, but couldn't find anything. The navigation is atrocious. Maybe I just wander down the aisles and see what I can see.

 Don't worry about looking - for such a simple thing unrelated to amp performance, it just isn't worth it. Worst comes to worst I'll get some of the covered binding posts from Altronics.


----------



## fordgtlover

^

 I couldn't find them on the website either. They were located in the shop near the banana plug sockets.


----------



## tomb

Quote:


  Originally Posted by *Beefy* /img/forum/go_quote.gif 
_Total brain-fart moment...... I think I was up too late last night with the Max.....

 The anode of an LED connects to the positive of the power supply? And that is usually the longer lead?_

 

Yes - but not _usually_ - _every_ time, AFAIK.


----------



## fault151

Hi guys, i want to wire in two leds to the board for my mileet. Whats the best way to do it, and do i need to use a certain led size and resistor?

 I already have one led wired to the led hole in the middle of the board. I bought a load of leds of ebay but not sure if certain ones will effect the way the millet works???


----------



## Kenneth S

Talking of which, i know tube amps tend to sound warmer than the others, but why is it that when I setup my millet as a preamp, i don't get that rich warmth? Well not as mellow as when I listen with my ATH plugged in. I run the millet thru to a Harmon Kardon 6650R and connected to a pair of Wharfedale Diamonds 9.0. Am also having some probs with the output which I figure to be a shonky connection (Maybe the contact is broken or loose somewhere)


----------



## tomb

Quote:


  Originally Posted by *Kenneth S* /img/forum/go_quote.gif 
_Talking of which, i know tube amps tend to sound warmer than the others, but why is it that when I setup my millet as a preamp, i don't get that rich warmth? Well not as mellow as when I listen with my ATH plugged in. I run the millet thru to a Harmon Kardon 6650R and connected to a pair of Wharfedale Diamonds 9.0. Am also having some probs with the output which I figure to be a shonky connection (Maybe the contact is broken or loose somewhere)_

 

There's a much different impedance in play when connecting in as a preamp - different cables, input impedance of the speaker amp vs. the headphones, etc.

 When I've tried it, I found the combo to be much tighter, with gobs more detail than I ever heard from the receiver itself. You're right, though - the first impression is not one of mellowness. I guess if we had to classify the MAX, it's high-performance solid-state with a _flavoring_ of tubey mid-range warmth and bass. Some of that flavoring may get obscured in the overall performance jump by connecting it in as a pre-amp. As mentioned, the sound detail was so night and day improved over my regular receiver that warmth and tubeyness was lost in the comparison.


----------



## tomb

Quote:


  Originally Posted by *fault151* /img/forum/go_quote.gif 
_Hi guys, i want to wire in two leds to the board for my mileet. Whats the best way to do it, and do i need to use a certain led size and resistor?

 I already have one led wired to the led hole in the middle of the board. I bought a load of leds of ebay but not sure if certain ones will effect the way the millet works???_

 

Did you use the LED pads under the tubes? Those are two more connections that are available to you. You can also wire in from the V+ and any Ground point with a 2K, 1/4 resistor. That should work for most LED's.


----------



## fault151

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Did you use the LED pads under the tubes? Those are two more connections that are available to you. You can also wire in from the V+ and any Ground point with a 2K, 1/4 resistor. That should work for most LED's._

 

Well i didnt build the amp, but it does have two leds unde rthe tubes, im guessing thats what you mean. I was told i could solder the leds fromt eh centre in parralel? Would that be fine?

 My leds already come wired with resistors installed under heat shrink. i have no idea what size the resistor is. Will i still need to add another resistor? i'll try dig out the link and post it up for you to see. 

 Cheers.


----------



## fault151

Quote:


  Originally Posted by *fault151* /img/forum/go_quote.gif 
_i'll try dig out the link and post it up for you to see. 

 Cheers. 
	

	
	
		
		

		
		
	


	


_

 

I think this is them....


LEDS ON EBAY


----------



## Beefy

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Yes - but not usually - every time, AFAIK._

 

Cheers.

 I drilled out my sockets tonight, and had 4 from 4 success. The way I did it was to wrap the sockets around the outside with two layers of thin rag (old t-shirt). Then I VERY carefully clamped it all together with a set of hand-held vise grips - not too tight obviously. My lady friend held the vice grips and I drilled it out with a 4mm drill bit. The bottom of the pin just fell out, but the socket was held by the vice grips.

 They're all cleaned up with isopropanol now and I just need to glue them. I honestly think that _this_ is going to be the hard part..... getting good coverage without gluing the pins. I'll be using 5 minute epoxy resin (Araldite) - the only other option was 72 hour stuff!


----------



## BoilermakerFan

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_There's a much different impedance in play when connecting in as a preamp - different cables, input impedance of the speaker amp vs. the headphones, etc.

 When I've tried it, I found the combo to be much tighter, with gobs more detail than I ever heard from the receiver itself. You're right, though - the first impression is not one of mellowness. I guess if we had to classify the MAX, it's high-performance solid-state with a flavoring of tubey mid-range warmth and bass. Some of that flavoring may get obscured in the overall performance jump by connecting it in as a pre-amp. As mentioned, the sound detail was so night and day improved over my regular receiver that warmth and tubeyness was lost in the comparison._

 

Which DB combo and boutique caps did you use on your pre-amp? I have four DB combos on hand and three boutique capacitor combos (Muse ES, KZ, and Silmic II). The MAX will be feeding this amp: DIY Chip Amplifier Kits, PCB's, Components and Information. with the primary source being my Pro-Ject TT with Grado and Ortofon cartridges, but it will also see a CDP, iPod, XM Radio, and maybe a FM tuner. I'm planning to use the 12AE6A tubes for this amp.


----------



## tomb

Quote:


  Originally Posted by *BoilermakerFan* /img/forum/go_quote.gif 
_Which DB combo and boutique caps did you use on your pre-amp? I have four DB combos on hand and three boutique capacitor combos (Muse ES, KZ, and Silmic II). The MAX will be feeding this amp: DIY Chip Amplifier Kits, PCB's, Components and Information. with the primary source being my Pro-Ject TT with Grado and Ortofon cartridges, but it will also see a CDP, iPod, XM Radio, and maybe a FM tuner. I'm planning to use the 12AE6A tubes for this amp._

 

It was BG MAX running 2SC2238/2SA968's and Russian K42's.

 Colin has been using his MAX almost exclusively as a small speaker amp lately, from what he's been telling me (he likes it!). If memory serves, his has ES's with 2SC3421/2SA1358's and Philco VitQ's.


----------



## fault151

TomB= are these leds any good for what i need?



LEDS ON EBAY

 Cheers


----------



## BoilermakerFan

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_It was BG MAX running 2SC2238/2SA968's and Russian K42's.

 Colin has been using his MAX almost exclusively as a small speaker amp lately, from what he's been telling me (he likes it!). If memory serves, his has ES's with 2SC3421/2SA1358's and Philco VitQ's._

 

Perhaps Colin can confirm that he just used the terminal block next to the headphone jack to wire up speaker jacks? Did he change anything else to bump the output power? The BJT sets used in the DB were all used in 5W amplifiers, so they should be able to do a nice job with small, efficient speakers. Hmmm... I think the 3421/Muse ES combo would be great with a FR loaded horn speaker. 
	

	
	
		
		

		
		
	


	




 Have I mentioned lately how much I _LOVE_ this amp design?


----------



## cetoole

Quote:


  Originally Posted by *BoilermakerFan* /img/forum/go_quote.gif 
_Perhaps Colin can confirm that he just used the terminal block next to the headphone jack to wire up speaker jacks? Did he change anything else to bump the output power? The BJT sets used in the DB were all used in 5W amplifiers, so they should be able to do a nice job with small, efficient speakers. Hmmm... I think the 3421/Muse ES combo would be great with a FR loaded horn speaker. 
	

	
	
		
		

		
		
	


	




 Have I mentioned lately how much I LOVE this amp design?_

 

Colin is actually using a prototype board without the terminal block, but he modded the board to give that same functionality. Jumpered the output resistors, and bumped the bias up a bit (60mA now, IIRC). Tom got my parts correct. From the switched output off the headphone jack, it is wired to four banana jacks on the back panel (22awg internal hookup wire, and 14awg speaker wire 
	

	
	
		
		

		
		
	


	




). Speakers are 90dB/W efficient. I enjoy it much more than my modded sonic impact t-amp, but havnt really tried anything else.


----------



## BoilermakerFan

Quote:


  Originally Posted by *cetoole* /img/forum/go_quote.gif 
_Colin is actually using a prototype board without the terminal block, but he modded the board to give that same functionality. Jumpered the output resistors, and bumped the bias up a bit (60mA now, IIRC). Tom got my parts correct. From the switched output off the headphone jack, it is wired to four banana jacks on the back panel (22awg internal hookup wire, and 14awg speaker wire 
	

	
	
		
		

		
		
	


	




). Speakers are 90dB/W efficient. I enjoy it much more than my modded sonic impact t-amp, but havnt really tried anything else._

 

Thanks Colin!


----------



## tomb

Quote:


  Originally Posted by *BoilermakerFan* /img/forum/go_quote.gif 
_Thanks Colin!_

 

Told you guys - Colin doesn't miss anything.


----------



## Kenneth S

THis is my first millet. Its a DB and Muse setup. The next one will be a MOSEFT version with blackgates NX. Am waiting for the MOSFET site to be online before the build. 
	

	
	
		
		

		
		
	


	




  Quote:


  Originally Posted by *BoilermakerFan* /img/forum/go_quote.gif 
_Which DB combo and boutique caps did you use on your pre-amp? I have four DB combos on hand and three boutique capacitor combos (Muse ES, KZ, and Silmic II). The MAX will be feeding this amp: DIY Chip Amplifier Kits, PCB's, Components and Information. with the primary source being my Pro-Ject TT with Grado and Ortofon cartridges, but it will also see a CDP, iPod, XM Radio, and maybe a FM tuner. I'm planning to use the 12AE6A tubes for this amp._


----------



## slowpogo

Just wanted to share that I replaced RB1L/R with tantalum resistors (audio note), which had previously been PRP. A ways back it had been discussed that this position could potentially benefit from boutiques, because it's in the signal path and has significant resistance.

 Anyway, it did make a difference on my amp. It seems my ears are pretty sensitive but I think it's worthwhile in general.

 What it did was tame some of the glassy edge from the metal film resistors, and add just a bit of warmth. It gives the effect I was hoping Kiwames might have in the output position...but where Kiwames kind of put a general veil over things, the tantalums do not veil but de-emphasize some sibilance and high end harshness. Also, things like distorted guitar riffs now seem to have a little more shape and chunkiness to them, more inner spatial detail I guess you'd say.

 Tantalums are expensive ($5 a pop) but if you're trying to squeeze the last .5% of sound from your Max, I'd recommend it.


----------



## BoilermakerFan

Quote:


  Originally Posted by *slowpogo* /img/forum/go_quote.gif 
_Just wanted to share that I replaced RB1L/R with tantalum resistors (audio note), which had previously been PRP. A ways back it had been discussed that this position could potentially benefit from boutiques, because it's in the signal path and has significant resistance.

 Anyway, it did make a difference on my amp. It seems my ears are pretty sensitive but I think it's worthwhile in general.

 What it did was tame some of the glassy edge from the metal film resistors, and add just a bit of warmth. It gives the effect I was hoping Kiwames might have in the output position...but where Kiwames kind of put a general veil over things, the tantalums do not veil but de-emphasize some sibilance and high end harshness. Also, things like distorted guitar riffs now seem to have a little more shape and chunkiness to them, more inner spatial detail I guess you'd say.

 Tantalums are expensive ($5 a pop) but if you're trying to squeeze the last .5% of sound from your Max, I'd recommend it._

 

Most important bit of info was missing... What value did you select? Also, I can't remember which tubes you're using, AE6As or FK6s?


----------



## slowpogo

Quote:


  Originally Posted by *BoilermakerFan* /img/forum/go_quote.gif 
_Most important bit of info was missing... What value did you select? Also, I can't remember which tubes you're using, AE6As or FK6s?_

 

I didn't know the value was variable..I just used 1k, from the BOM. I'm using 12AE6 tubes.


----------



## BoilermakerFan

Quote:


  Originally Posted by *slowpogo* /img/forum/go_quote.gif 
_I didn't know the value was variable..I just used 1k, from the BOM. I'm using 12AE6 tubes._

 

Oops. 
	

	
	
		
		

		
			





 I thought you were referring to RB14L/R...


----------



## Beefy

In a rare stroke of luck, I managed to pick up everything I needed to complete my Max over the ANZAC Day holiday. 24VAC 1A plugpack, 2.1mm plug, hookup wire AND some tip jacks from Dick Smith. I even managed to find some 6.35mm quick connectors with the loose rubber cover/insulation, rather than the fixed plastic insulation, to hook up the IEC connector on my S11.

 So for any Australian who needs to get them locally, go to DICK SMITH ELECTRONICS dse.com.au and search for part numbers P1756 and P1758. Thanks for the tip fordgtlover!


----------



## fordgtlover

^

 No probs. I'm glad you found soemthing useful before DS gets rid of all of their electronics parts.


----------



## fault151

Does anyone know where i can get some* pink *resistors to work with the millet max? I can only seem to ever find blue red n green.


----------



## BoilermakerFan

Quote:


  Originally Posted by *fault151* /img/forum/go_quote.gif 
_Does anyone know where i can get some* pink *resistors to work with the millet max? I can only seem to ever find blue red n green._

 

A quick Google search indicates they are no longer made, they are vintage resistors...

 Expired Italian eBay auction though:
eBay.ie: VINTAGE PAINTON TYPE 73/74 PINK RESISTORS (item 320234909347 end time 11-Apr-08 18:25:29 BST)


----------



## fault151

Quote:


  Originally Posted by *BoilermakerFan* /img/forum/go_quote.gif 
_A quick Google search indicates they are no longer made, they are vintage resistors...

 Expired Italian eBay auction though:
eBay.ie: VINTAGE PAINTON TYPE 73/74 PINK RESISTORS (item 320234909347 end time 11-Apr-08 18:25:29 BST)_

 

Crap i meant to put LED's not Resistors! ha ha. Sorry!!! 
	

	
	
		
		

		
		
	


	




*Pink Led's* is what i need.

 I can find loads of pink ones on ebay, but im not sure if they are Ok with the millet design.


----------



## fault151

would these work ok???

PINK LEDS


 HERE IS THE SPEC:
*
 ALL LEDS ARE RoHS COMPLAINT

 FULL SPECS CAN BE GIVEN ON REQUEST

 THIS ITEM IS ALSO AVAILABLE IN 3mm FROM OUR SHOP

 DESCRIPTION

 20 PINK 5mm LED’S 

 TECHNICAL SPECIFICATIONS

 INTENSITY 1000--1500mcd

 FORWARD VOLTAGE 3.0—3.6v

 FORWARD CURRENT 20m/a

 DOMI WAVELENGTH nm

 HOUSING WATER CLEAR

 VIEWING ANGLE 20 degrees

 RESISTORS SUPPLIED FOR USE ON 12 VOLTS UNLESS OTHERWISE REQUESTED FREE OF CHARGE*


----------



## MrMajestic2

Quote:


  Originally Posted by *fault151* /img/forum/go_quote.gif 
_Crap i meant to put LED's not Resistors! ha ha. Sorry!!! 
	

	
	
		
		

		
		
	


	




*Pink Led's* is what i need.

 I can find loads of pink ones on ebay, but im not sure if they are Ok with the millet design._

 

3mm Pink LED 10 Pack - Free shipping


----------



## MrMajestic2

Quote:


  Originally Posted by *fault151* /img/forum/go_quote.gif 
_would these work ok???

PINK LEDS


 HERE IS THE SPEC:
*
 ALL LEDS ARE RoHS COMPLAINT

 FULL SPECS CAN BE GIVEN ON REQUEST

 THIS ITEM IS ALSO AVAILABLE IN 3mm FROM OUR SHOP

 DESCRIPTION

 20 PINK 5mm LED’S 

 TECHNICAL SPECIFICATIONS

 INTENSITY 1000--1500mcd

 FORWARD VOLTAGE 3.0—3.6v

 FORWARD CURRENT 20m/a

 DOMI WAVELENGTH nm

 HOUSING WATER CLEAR

 VIEWING ANGLE 20 degrees

 RESISTORS SUPPLIED FOR USE ON 12 VOLTS UNLESS OTHERWISE REQUESTED FREE OF CHARGE*_

 

Sure, but get them in 3mm instead of 5.


----------



## Beefy

Finished construction tonight, powered on and everything checks out OK. No tubes in yet, but the power supply is putting out 27V and both DB bias have been set to their minimum value of about ~35mV. You might just be able to make out the blue tube LEDs through the flash.






 Its late now so I'll pop some tubes in tomorrow, test it with audio and get started on the casework. But I'm certainly optimistic at this point..... I can just hear the relay click at the very least. Thanks for all the help to this point folks - especially tomb!


----------



## fault151

Quote:


  Originally Posted by *MrMajestic2* /img/forum/go_quote.gif 
_Sure, but get them in 3mm instead of 5._

 

ok thank you


----------



## tomb

Quote:


  Originally Posted by *Beefy* /img/forum/go_quote.gif 
_Finished construction tonight, powered on and everything checks out OK. No tubes in yet, but the power supply is putting out 27V and both DB bias have been set to their minimum value of about ~35mV. You might just be able to make out the blue tube LEDs through the flash.

 <IMG]http://img356.imageshack.us/img356/428/mhm3pl2.jpg[/IMG>

 Its late now so I'll pop some tubes in tomorrow, test it with audio and get started on the casework. But I'm certainly optimistic at this point..... I can just hear the relay click at the very least. Thanks for all the help to this point folks - especially tomb! 
	

	
	
		
		

		
		
	


	


_

 

Nice work, Beefy! That was quick!


----------



## Beefy

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_That was quick!_

 

Once I get started, I just don't know when to stop 
	

	
	
		
		

		
		
	


	




 And along those lines, I just popped in some tubes despite my tiredness. How bright is the heater supposed to glow? It seems a LOT brighter than I expected.

 Perhaps I should double check the heater voltage. Are there any convenient test points for that?


----------



## Gaso

Quote:


  Originally Posted by *Beefy* /img/forum/go_quote.gif 
_Once I get started, I just don't know when to stop 
	

	
	
		
		

		
		
	


	




 And along those lines, I just popped in some tubes despite my tiredness. How bright is the heater supposed to glow? It seems a LOT brighter than I expected.

 Perhaps I should double check the heater voltage. Are there any convenient test points for that?_

 

Hi Beefy,

 Please refer to http://www.diyforums.org/MAX/setup/biaspts.jpg. Measure across Gnd and L TUBE or R TUBE bias points. In your case you should have around 13.5 VDC. 

 If you install by the silk screen, the tube heater voltage trimmers seem to work "backwards" compared to other trimmers. So fully clockwise = fully open. You might want to check the voltage ASAP.


----------



## tomb

The heaters are tied in series directly across V+ and Gnd - except for the heater resistor inbetween. They can stand a pretty wide range - from a low of 10V to 15.9V, if memory serves - the data sheets are under the Millett Tubes section on the MAX website. So, unless you're running more than 30V, or less than ~24V with the heater resistor installed, not to worry.
	

	
	
		
		

		
		
	


	




 So, in effect, the adjustment for the heaters is V+ and sizing the heater resistor.
	

	
	
		
		

		
		
	


	




 I was going to say, though - you lit the tubes with tube LED's, didn't you? They're supposed to be bright.
	

	
	
		
		

		
		
	


	




 The only thing you should see from the heaters is a small vertical rod in the center of the tubes. Normally, you can see that at top (unless you have top getters, then the getter flash hides it) - it glows bright orange, but is quite dim on its own.


----------



## Beefy

Quote:


  Originally Posted by *Gaso* /img/forum/go_quote.gif 
_ Measure across Gnd and L TUBE or R TUBE bias points. In your case you should have around 13.5 VDC._

 

Oh, the bias is fine. I read the initial check up many, many times, and every BIAS point was checked within seconds of powering on 
	

	
	
		
		

		
			





  Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_I was going to say, though - you lit the tubes with tube LED's, didn't you? They're supposed to be bright.
	

	
	
		
		

		
		
	


	




 The only thing you should see from the heaters is a small vertical rod in the center of the tubes. Normally, you can see that at top (unless you have top getters, then the getter flash hides it) - it glows bright orange, but is quite dim on its own._

 

Yes, they are lit with LEDs and they are very bright, but it is the vertical rod that I can also see glowing orange. The latter is just a lot brighter than I expected, thats all!


----------



## tomb

Quote:


  Originally Posted by *Beefy* /img/forum/go_quote.gif 
_<snip>Yes, they are lit with LEDs and they are very bright, but it is the vertical rod that I can also see glowing orange. The latter is just a lot brighter than I expected, thats all! 
	

	
	
		
		

		
		
	


	


_

 

Well, the very top tip of the vertical rod almost turns yellow it glows so hot. Even so, about all it can do is light up the tube tip without LEDs present. If you've got the proper V+ voltage and you used a 10-30 ohm heater resistor, it's probably fine.


----------



## Beefy

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Well, the very top tip of the vertical rod almost turns yellow it glows so hot. Even so, about all it can do is light up the tube tip without LEDs present._

 

That is exactly what I'm getting. In other news, it makes sound that isn't crappy! 
	

	
	
		
		

		
		
	


	




 I've got the DB at 90mV and running my sacrificial KSC-75 at the upper end of comfortable (which is actually pretty quiet for me). Tubes and Vreg h/sink are nice and warm, DB h/sink barely noticeable - benefits of the 1.5" sinks I guess.

 I'll let it run like this while I have breakfast......


----------



## Beefy

For the benefit of everyone, everywhere.......

 If you use an adhesive heat sick mounting kit, don't get isopropanol/flux-remover on them when you clean off the flux. It spreads adhesive all over the damn PCB, and is a massive pain to clean off.


----------



## amphead

Congrats Beefy! Another Max Lives!   

 I have no doubt that you have successfully built the Max based on your observations. Yes the heaters are quite warm on the Max. The only thing to be cautious about, is overbiasing the output transistors. We are waiting for your thorough report of the listening evaluation.


----------



## Beefy

Yep, she's definitely working. Currently powering my KSC-75 at 1/3 on the volume dial, and loud enough to hear through almost my entire apartment. All I have to do is wire up the test points, shorten the volume pot a touch and fit the power input and switch.

 Pics!


----------



## fault151

Beefy;4131815 said:
			
		

> Yep, she's definitely working. Currently powering my KSC-75 at 1/3 on the volume dial, and loud enough to hear through almost my entire apartment. All I have to do is wire up the test points, shorten the volume pot a touch and fit the power input and switch.
> 
> Pics!
> 
> Looking very nice!


----------



## Phil Townsend

Has anyone used 12AE6A made by a company called CEI Electron Tube.

 I dont think CEI built the tubes. 
 the getter is side mounted. 
 The Name, CEI is printed on the the tube and it looks like it could rub off.
 The 12AE6A is also printed.
 Additionally the 12AE6A is etched into the tube.

 I hope they are OK tubes since I got 12 of the from Ed at the Black Hole in Los Alamos. Cheap 50 cents each. Last of his stock on those.

 Phil


----------



## BoilermakerFan

Quote:


  Originally Posted by *Phil Townsend* /img/forum/go_quote.gif 
_Has anyone used 12AE6A made by a company called CEI Electron Tube.

 I dont think CEI built the tubes. 
 the getter is side mounted. 
 The Name, CEI is printed on the the tube and it looks like it could rub off.
 The 12AE6A is also printed.
 Additionally the 12AE6A is etched into the tube.

 I hope they are OK tubes since I got 12 of the from Ed at the Black Hole in Los Alamos. Cheap 50 cents each. Last of his stock on those.

 Phil_

 

I know Tom is working on a tube description and clarification page. There were only (3) manufacturers of these tubes, GE, RCA, and Sylvania. GE tubes have the tube number etched in white in the glass with dots under the lettering. The dots might be hard to see though. RCA put their tube designation in a squished rectangle. Sylvania etched their tube designation into the glass with a dark font. But, I have a 12AE6A tube in a Sylvania box labeled as Sylvania on the tube but the tube designation etched in GE's fashion with etched dots...


----------



## Phil Townsend

The letters are dark...So I guess they are Sylvania


----------



## tomb

Quote:


  Originally Posted by *Phil Townsend* /img/forum/go_quote.gif 
_The letters are dark...So I guess they are Sylvania_

 

I have some CEI's, but they're GE's: they have the etched designation and the white dots. It sound like yours are those. 
	

	
	
		
		

		
		
	


	




 Brian is correct. Although, there is actually a 4th mfr (Tung-Sol), but that still means that any "off-brand" was made by one of the Big Three/Four.


----------



## Beefy

I've basically finished the max aside from cleaning up the wiring, and have put it through its paces with my Audio Technica ATH-AD900 on my old Sony DVD player (will hook it up to a better source very soon). Here are my thoughts......

 My first set of tubes were some 12FK6, burnt in for about 8 hours. I agree that the 12FK6 tubes sound nice and airy. I agree that they lack bass and punch. I'll try my other set of 12FK6 later today.

 The 12AE6A have been in for about 5 hours and I'm listening to them now. They get back a lot of punch but are slightly veiled compared to the 12FK6 - though this has improved since the tubes first went in, so maybe the tubes need more time. Even so, I think I prefer these to the 12FK6.

 Comparing the 12AE6A Max to my M^3 (OPA627BP in L/R, AD8610 in GND, variable gain 2-12) is interesting. The Max is ever so slightly warmer and smoother, with the M^3 being more neutral and detailed (I get even more detail out of the M^3 with AD8610 all round). Treble is good on both, and both are sibilant on music that I know to be sibilant; the M^3 moreso, which I take as the M^3 having slightly better treble extension than the 12AE6A tubes (but this could still be a detail thing). Soundstage is excellent on both, with the M^3 having a tiny bit more front/back depth.

 Both amps are capable of driving my KSC-75 as mini speakers (the poor little buggers!) to ridiculous volume levels. No lack of power in either amp. But the most interesting thing in my comparison is that the M^3 maintains more of its punch at very low volume levels (even at a gain of only 2), whereas the Max needs a little bit more volume before things really get rocking. I really think the tubes like to be worked hard, whereas the OPAMPs are less picky.

 Lastly, the Max is definitely sexier - I can understand the emotive draw of tubes! The PCB symmetry is nice and all the big caps look very imposing. The M^3 is more understated and clinical looking.

 So that's my $0.02. At the end of the day, I am VERY happy with the Max, considering it cost half what the M^3 and S11 combo cost me. It will probably serve duty on the Rec monitor of my HT amp, for mixed TV, DVD and Xbox360 usage while the M^3 will specifically do CD duties. And I'm *definitely* selling my Corda Arietta! 
	

	
	
		
		

		
		
	


	




 [EDIT] Just thought I'd add specs for key positions at this point....
 CR1 - 4x 1000µF Nichicon UPW
 CA4/5 - 4x1800µF Nichicon UPW
 CA2 - 1000µF Nichicon Muse ES
 CA7 - 470µF Nichicon Muse ES
 CA3/6/9 - 0.22µF Wima MKP10
 CA8 - 0.18µF Sprague Vitamin Q
 QB8/9 - 2SC3422/2SA1359
 RB14 - 10ohm KOA
 PS set at 27V
 Tube bias set at 13.5V (hot)
 DB bias at 110-115mV, and within 1mV B1-B2
 DC offset <1mV


----------



## tomb

Thanks much for sharing your experiences and thoughts with the MAX, Beefy!


----------



## Beefy

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Thanks much for sharing your experiences and thoughts with the MAX, Beefy!_

 

No problems..... couldn't have done it without you and Beezar! 
	

	
	
		
		

		
		
	


	




 Just to add to my post above, my 12AE6A definitely need more time to burn in. I've had to shift the tube bias down by well over half a volt in the last 2 hours of quiescent use.....


----------



## amphead

Quote:


 It will probably serve duty on the Rec monitor of my HT amp, for mixed TV, DVD and Xbox360 usage 
 

Interesting application, thanks for the review.


----------



## Phil Townsend

When I go to set the various bias voltages should there be a load on the output?
 ie: Do I plug in a set of headphones...cheap ones just in case?
 Phil


----------



## tomb

Quote:


  Originally Posted by *Phil Townsend* /img/forum/go_quote.gif 
_When I go to set the various bias voltages should there be a load on the output?
 ie: Do I plug in a set of headphones...cheap ones just in case?
 Phil_

 

No. You don't need a headphone load to adjust any of the bias voltages.

 Since you mentioned a pair of cheap headphones, though - it's always a good idea to have a pair to plug in for the very first time on a newly built amp. Better yet, just quickly check for offset at the heaphone jack before plugging something in. Wait until the relay closes, though, or you'll get zero voltage and zero sound. Offset should be on the order of 1mV or less.


----------



## BoilermakerFan

I have a question for everyone. 

 I have (3) MAX boards and (5) BJT combos for the DBs. I'm installing these in a NABU enclosures so I have plenty of room. I want to use quick connectors so I can build up the three boards with different DBs and swap them in to my console easily for comparison testing. I know Phoenix Contact makes the connectors I need for the terminal blocks, but what can I use for the volume pot wires and RCA jacks? My volume pot will not be board mounted for any of my builds. I am willing to give up a little SQ for convenience, but once I pick the combo I like for each console, I will remove the quick connector and solder all connections to the boards. 

 This setup will allow me to compare a few different cap/BJT or MOSFET combos that haven't seen built or discussed, but I want to minimize resoldering the boards as much as I can.


----------



## tomb

Quote:


  Originally Posted by *BoilermakerFan* /img/forum/go_quote.gif 
_I have a question for everyone. 

 I have (3) MAX boards and (5) BJT combos for the DBs. I'm installing these in a NABU enclosures so I have plenty of room. I want to use quick connectors so I can build up the three boards with different DBs and swap them in to my console easily for comparison testing. I know Phoenix Contact makes the connectors I need for the terminal blocks, but what can I use for the volume pot wires and RCA jacks? My volume pot will not be board mounted for any of my builds. I am willing to give up a little SQ for convenience, but once I pick the combo I like for each console, I will remove the quick connector and solder all connections to the boards. 

 This setup will allow me to compare a few different cap/BJT or MOSFET combos that haven't seen built or discussed, but I want to minimize resoldering the boards as much as I can._

 

I have some pics from a user who simply used two Molex strips. The pin spread on the RK27's is 5mm. I believe that means you could use some 0.1"/2.54mm Molex's at 5 pins. You'd simply use every other pin for a total of 3 (two pins would remain blank - giving you a spacing of ~5.08mm, close enough. 
	

	
	
		
		

		
		
	


	




 ). You could solder in the 5-pin male headers at the respective two rows of pot pads on the board, after trimming every other pin from the bottom.

 I don't have the pics right now - I'll try to post them tonight. It looks pretty simple.


----------



## n_maher

Tom,

 It might also be pretty easy to use terminal blocks like the ones that amb recommends for the sigma power supplies. Have a look at Mouser Part #: 651-1729131 which seems like it'd be a drop in fit for the RK27 position. I've often thought about using them but haven't used an RK27 in a while. 
	

	
	
		
		

		
		
	


	




 If folks want more options have a look at page 1442 of Mouser's online catalog for a variety of shapes and configurations.


----------



## Phil Townsend

If you want the worlds best connectors...There is only one...LEMO
 and Mouser has them...Love them Lemos...
 Swiss made
 Push Pull
 Waterproof
 airproof
 low mass for small sigs.
 Gold silver copper contacts
 2 pin thur 48 pins
 etc
 etc
 etc
 Check them out!

 I use them instead of the RCA


----------



## BoilermakerFan

Thanks guys, I'll check them all out. That's why I posted my question here, I knew you guys could point me in the right direction...


----------



## MrMajestic2

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_I have some pics from a user who simply used two Molex strips. The pin spread on the RK27's is 5mm. I believe that means you could use some 0.1"/2.54mm Molex's at 5 pins. You'd simply use every other pin for a total of 3 (two pins would remain blank - giving you a spacing of ~5.08mm, close enough. 
	

	
	
		
		

		
		
	


	




 ). You could solder in the 5-pin male headers at the respective two rows of pot pads on the board, after trimming every other pin from the bottom.

 I don't have the pics right now - I'll try to post them tonight. It looks pretty simple._

 

Might have been my build:






 Very easy to do, and the Alps pot fits right on top of it also for testing.


----------



## Phil Townsend

Adjusting the bias for DB... for the first power up.

 RB12 is a 2k 20 turn pot and by adjusting it fully clockwise the ohm meter reads around 2k...
 So when I bump the power switch (off-on-off) The voltage across RB10 or RB11 will be very small. (test points TB1 or TB2 and TA2)

 DO I Have this all correct?
 I,m about to put the spurs to my MAX and since transistors have a zero sense of humor I waana be sure I've got it.


----------



## tomb

Quote:


  Originally Posted by *Phil Townsend* /img/forum/go_quote.gif 
_Adjusting the bias for DB... for the first power up.

 RB12 is a 2k 20 turn pot and by adjusting it fully clockwise the ohm meter reads around 2k...
 So when I bump the power switch (off-on-off) The voltage across RB10 or RB11 will be very small. (test points TB1 or TB2 and TA2)

 DO I Have this all correct?
 I,m about to put the spurs to my MAX and since transistors have a zero sense of humor I waana be sure I've got it._

 

Sounds right.
	

	
	
		
		

		
		
	


	




 Assuming everything's connected properly, you're not going to burn them up in the matter of seconds that it takes you to make your measurements. You will have some minimum current, though - anywhere around 25mV to 45mV might be what you measure in this condition.

 If they're in that range or close, then go ahead and set your V+ and get the tubes biased. You should be able to get V+ exact. However, don't worry if the tubes are rolling around 10-15VDC for the time being. You can always go back and get them adjusted later - they will change anyway as they burn in.


----------



## tomb

Quote:


  Originally Posted by *MrMajestic2* /img/forum/go_quote.gif 
_Might have been my build:

 <IMG]http://i5.photobucket.com/albums/y196/Boombastix/02240025.jpg[/IMG>

 Very easy to do, and the Alps pot fits right on top of it also for testing._

 

Actually, it was someone who sent me some pics very recently, but yours is close enough.


----------



## Beefy

Quote:


  Originally Posted by *MrMajestic2* /img/forum/go_quote.gif 
_Might have been my build:_

 

Swanky. VERY swanky.

 I almost wish I had gone for a larger case now. Having enough room to wire so cleanly would have been nice.

 Have you considered a stepped attenuator to replace that Alps pot? It seems a shame to have those Black Gates without one!


----------



## pinkfloyd4ever

hey tomb, I'm gonna bring up something we already discussed...setting the PS voltage. It seems like my regulator's heat sink is running alot cooler than normal (like cooler than the outer 2 output BJTs, when it's usually hotter than the 2 in the middle), so I checked the PS voltage and it was way lower than the 27.0v I'd checked it at about 10 minutes earlier, like around 26.8v. Now about 15 minutes later it's at 26.5. When I try to turn it back up to 27 it just kinda jumps around, indicating that the regulator isn't regulating, correct? What is going on? The point at which the ps voltage wouldn't go up anymore used to be like 28v back when I built it, and over the last few weeks it seems to be steadily dropping. Is something wrong with my regulator, or is my wallwart going bad already? It's this Triad model WAU24-750 I used to get about 24.85V ac at the terminal blocks, and now I'm reading as low as 24.2 at times. From our discussion before this leads me to believe that I need a wallwart with higher current output, but don't most people who use BJTs use one of similar specs?


----------



## tomb

Quote:


  Originally Posted by *pinkfloyd4ever* /img/forum/go_quote.gif 
_hey tomb, I'm gonna bring up something we already discussed...setting the PS voltage. It seems like my regulator's heat sink is running alot cooler than normal, so I checked the PS voltage and it was way lower than the 27.0v I'd checked it at about 10 minutes earlier, like around 26.8v. Now about 15 minutes later it's at 26.5. When I try to turn it back up to 27 it just kinda jumps around, indicating that the regulator isn't regulating, correct? What is going on? The point at which the ps voltage wouldn't go up anymore used to be like 28v back when I built it, and over the last few weeks it seems to be steadily dropping. Is something wrong with my regulator, or is my wallwart going bad already? It's this Triad model WAU24-750 I used to get about 24.85V ac at the terminal blocks, and now I'm reading as low as 24.2 at times. From our discussion before this leads me to believe that I need a wallwart with higher current output, but don't most people who use BJTs use one of similar specs?_

 

I'd say you have your condition diagnosed pretty well.

 As for the reasons, I'd suspect the wall voltage. That's kind of what I was getting at ages ago in a post that I sort of butchered. The gist of it was supposed to be that we're close to the limit with a 24VAC walwart to run at 27VDC. So, several things can happen to lose a half-volt or so - unfortunately, that's noticeable. The line voltage can easily change according to season.

 Other things that could cause it:
Your bias has gone up on the DB's.
One or more of the PS smoothing caps has a solder joint that's worked loose.
You covered the case, or did something else to cut down on ventilation. With BJT's, this would result in a higher temperature and might result in a higher current draw.


 EDIT: Before I end up butchering another post - yes, the supply is totally, linear regulated. However, as Pinkfloyd4ever is finding out, the LM317 has to have a few volts of over-voltage or else it drops out of regulation. Dropping 10V from the wall socket could be enough to lose a half volt or so at the MAX. IOW -> 120 :: 24 becomes 110 :: 22.


----------



## pinkfloyd4ever

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_The line voltage can easily change according to season.

 Other things that could cause it:
Your bias has gone up on the DB's.
One or more of the PS smoothing caps has a solder joint that's worked loose.
You covered the case, or did something else to cut down on ventilation. With BJT's, this would result in a higher temperature and might result in a higher current draw.
_

 

I'm thinking it's probably the change in my house's line voltage, cause I just checked it and it's 117.2 volts, and every other time I remember checking it it's been right around 120. I checked the bias of the DBs, and I've never had the cover on my amp (too lazy to drill all those holes, plus I love being able to see the inside of it). What are the PS smoothing caps, the little yellow ones b/t the 4 diodes behind the 'sink? I don't know why one of the solder joints would have come loose, but I guess it's worth checking...although I just remembered that I stressed one lead of one of em (if they are the PS smoothing caps) a little too much and cracked the casing when I was soldering them. 
	

	
	
		
		

		
		
	


	




Maybe I'll get a new one of those with my next mouser order.


----------



## tomb

Brian,

 Here is the pic I was talking about this morning. I could be wrong, but it seems like this would make it much easier to keep track of six separate wires.







 This is from Minh Luc's MAXes. He built a couple of excellent examples - one with BG's-VitQ's and one with ES's-K42's:










 I love those yellow LED's - gonna have to try those next!


----------



## tomb

Quote:


  Originally Posted by *pinkfloyd4ever* /img/forum/go_quote.gif 
_I'm thinking it's probably the change in my house's line voltage, cause I just checked it and it's 117.2 volts, and every other time I remember checking it it's been right around 120. I checked the bias of the DBs, and I've never had the cover on my amp (too lazy to drill all those holes, plus I love being able to see the inside of it). What are the PS smoothing caps, the little yellow ones b/t the 4 diodes behind the 'sink? I don't know why one of the solder joints would have come loose, but I guess it's worth checking...although I just remembered that I stressed one lead of one of em (if they are the PS smoothing caps) a little too much and cracked the casing when I was soldering them. Maybe I'll get a new one of those with my next mouser order._

 

Nah - the PS smoothing caps are the four big electrolytics. They help to keep the voltage at its highest after rectification.

 Yes - I agree about your line voltage. It could be enough to make a difference. Still, if you have your DB's cranked up, you could back off a bit. Overall performance is probably better with the higher voltage than another 10-20ma of Class A bias.


----------



## Beefy

I've noticed some interesting behaviour on my Max......

 Firstly, power supply. At idle it is 27V completely stable, while at load with music it raises a touch and oscillates slowly between 27.1-27.2V. Is this normal behaviour?

 Secondly, I thought that a good way to match the tube bias exactly would be to set the left tube at 13.5V ground-TA2L, then set TA2L-TA2R to zero volts using a DC MV scale and the right trimpot. It works well initially, but again, I notice some slow oscillation of about 0-25mV between the two points. Now this may be related to small power supply oscillations, but it may also be something different. Any insight?


----------



## Beefy

Quote:


  Originally Posted by *pinkfloyd4ever* /img/forum/go_quote.gif 
_ I used to get about 24.85V ac at the terminal blocks, and now I'm reading as low as 24.2 at times._

 

Just had a thought..... what do you get as the _unloaded_ AC voltage out of the wallwart? This might be a better determinant of your wallwart's health.

 For comparison, I get ~28V AC unloaded.


----------



## tomb

Quote:


  Originally Posted by *Beefy* /img/forum/go_quote.gif 
_I've noticed some interesting behaviour on my Max......

 Firstly, power supply. At idle it is 27V completely stable, while at load with music it raises a touch and oscillates slowly between 27.1-27.2V. Is this normal behaviour?

 Secondly, I thought that a good way to match the tube bias exactly would be to set the left tube at 13.5V ground-TA2L, then set TA2L-TA2R to zero volts using a DC MV scale and the right trimpot. It works well initially, but again, I notice some slow oscillation of about 0-25mV between the two points. Now this may be related to small power supply oscillations, but it may also be something different. Any insight?_

 

On the first one, it may be that you're experiencing a similar issue as pinkfloyd4ever. It could be that the voltage difference is right on the edge for the LM317. Now, why it goes up slightly - would you be perhaps using high-impedance phones? They put less of a current load on the buffers - even compared to idling without a load. If the LM317 is on the edge of regulation, it's conceivable that it could vary slightly upward. Just a guess, of course.

 On the second one - I'm not sure the tubes are even capable of maintaining a bias within 25mV - within a tenth of a volt, maybe, but to be honest, I've never measured them with that kind of resolution. They seem too much like mules to ever toe the line that closely.


----------



## Beefy

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_would you be perhaps using high-impedance phones?_

 

No, 32 ohm Audio Technica phones.

  Quote:


 On the first one, it may be that you're experiencing a similar issue as pinkfloyd4ever. It could be that the voltage difference is right on the edge for the LM317. 
 

I doubt that is the case, because the heatsink gets quite warm, so Vreg is obviously burning a fair bit of power to achieve regulation. Nevertheless, maybe I should drop it down to 26V and see if the behaviour changes.

 Of course, it might also be the case that it is oscillating between 27.149-27.151V, and the DMM rounding to four significant figures makes it seem worse. In any case, I'm not particularly concerned because the amp sounds great - just interesting behaviour, that's all


----------



## pinkfloyd4ever

Quote:


  Originally Posted by *Beefy* /img/forum/go_quote.gif 
_N
 Of course, it might also be the case that it is oscillating between 27.149-27.151V, and the DMM rounding to four significant figures makes it seem worse_

 

damn dude I don't find that unusual at all, I think you can expect that much drift from this PS, you have to get up into several hundreds of dollar power supplies to get less I'd think

 my unloaded voltage is about 27.9v, used to be a little higher, but again I think it's cause of my house's line voltage


----------



## fault151

Hi guys my hook up wire arrived today, its 24AWG. My immediate impressions is it looks a bit on the thin side???

 Will it still be ok for use a hook up?


----------



## tomb

Quote:


  Originally Posted by *fault151* /img/forum/go_quote.gif 
_Hi guys my hook up wire arrived today, its 24AWG. My immediate impressions is it looks a bit on the thin side???

 Will it still be ok for use a hook up?_

 

24AWG is good for headphone cable, but 22AWG is all I've ever used for hookup. The 24ga may still be fine if you don't run it too far.


----------



## nysulli

24 awg is good for a few amps, anything past 2 amps though i'd go with something bigger, or just double up on the 24 awg


----------



## fault151

Quote:


  Originally Posted by *nysulli* /img/forum/go_quote.gif 
_just double up on the 24 awg_

 

Yeh thats what i was thinking. Its pretty good stuff, just looks a little thin. Iv compared it to my 22awg shielded cable and there isnt a huge difference, although its obviously thicker. I'll just use it anyway then. Cheers guys.


----------



## BoilermakerFan

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Brian,

 Here is the pic I was talking about this morning. I could be wrong, but it seems like this would make it much easier to keep track of six separate wires.

 This is from Minh Luc's MAXes. He built a couple of excellent examples - one with BG's-VitQ's and one with ES's-K42's:

 I love those yellow LED's - gonna have to try those next!_

 

Thanks Tom. Didn't spend anytime online last night, my allergies have been killing me and the meds knock me out. 
	

	
	
		
		

		
		
	


	




 I have yellow-orange and yellow-green LEDs to try. Not bi-color, just their wavelength is in-between the two standard colors. I'm only going to be tube lighting one of my amps though. The other two will be buried in consoles, so there is no point to drilling out the tube sockets. LEDtronics has some pretty neat color selections too. I have a few other potential projects in the works that require a lot of LEDs, so the minimum quantity requirements won't be a problem for me, so I might pick up a few more unique colors.


----------



## BoilermakerFan

Does anyone make 3" heat sinks that will fit the MAX boards? All I have seen is 2-1/2" or less in Mouser's catalog. I don't even want the solder post style as I would prefer to have threaded heat sinks with screws. 

 My wife is pushing to get this console finished. 
	

	
	
		
		

		
		
	


	




 So I "had" to order the TPA Darwin Source Selector kits and the SKA OptiVol kits today. I actually opted to order one of the OptiVols as an assembled and tested unit so I know one will at least work as it should. I'll be ordering the gainclone amp kits from audiosector.com at the end of the week. 

 The gainclones need about 300VA at 24VAC and I was planning to use a 100VA 24VAC torroid for the MAX, but would it be ok to power both from the same torroid? Each component has it's own rectifier/regulator, but how much headroom should I allow for the gainclone amps if they get a little thirsty? Would 400VA be enough, should I just step up to 500VA, or keep them on separate trafos?


----------



## amphead

It seems that separate xformers, allows you the most versatility, while a combined/central xformer may or may not be cheaper. I'm leaning towards separate, however this is your call BMF.


----------



## tomb

Quote:


  Originally Posted by *BoilermakerFan* /img/forum/go_quote.gif 
_Does anyone make 3" heat sinks that will fit the MAX boards? All I have seen is 2-1/2" or less in Mouser's catalog. I don't even want the solder post style as I would prefer to have threaded heat sinks with screws. 

 My wife is pushing to get this console finished. 
	

	
	
		
		

		
		
	


	




 So I "had" to order the TPA Darwin Source Selector kits and the SKA OptiVol kits today. I actually opted to order one of the OptiVols as an assembled and tested unit so I know one will at least work as it should. I'll be ordering the gainclone amp kits from audiosector.com at the end of the week. 

 The gainclones need about 300VA at 24VAC and I was planning to use a 100VA 24VAC torroid for the MAX, but would it be ok to power both from the same torroid? Each component has it's own rectifier/regulator, but how much headroom should I allow for the gainclone amps if they get a little thirsty? Would 400VA be enough, should I just step up to 500VA, or keep them on separate trafos?_

 

I agree with Amphead on the transformers. You could still combine them all with the same power lead, so it wouldn't get too cumbersome.

 As for the heat sinks, I think we are stuck with 2-1/2" maximum. I did some research last night and that appears to be the limit of the offerings from both Aavid and Wakefield. Both of their catalogs are a little much to go through in one sitting, but Allied's Catalog Page 748 shows the pertinent Aavid line pretty clearly:
https://www.alliedelec.com/Catalog/p...df&pageNum=748

 The "531 ..." series are what are used on the MAX for the output transistors.


 EDIT: Note that the Gold Chromate finish is not ROHS-compatible. Get 'em while you can.


----------



## BoilermakerFan

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_EDIT: Note that the Gold Chromate finish is not ROHS-compatible. Get 'em while you can. 
	

	
	
		
		

		
			









_

 

How did you know I was eye'ing those? I'll be grabbing the gold screw mount 2-1/2" Aavid for the DBs and the larger 2-1/2" Wakefield for the LM338T. Would the 2-1/2" Aavid gold heatsink work for the LM338T also? They are rated for 9W so I think it should be fine. Although, Purdue colors are Black & Gold, so maybe I'll just stick with the black Wakefield for the LM338. 
	

	
	
		
		

		
		
	


	




 I'm going to keep them on separate transformers. I just don't want the amps sucking all the juice and dropping the voltage down on the MAX board. I have little DIN rail mounted terminal blocks and IEC circuit breakers, so I can get pretty crazy with the power supply wiring if I wanted too, but I'll just use the terminal blocks to make it easy. I might be putting the PSUs in a separate chassis too so I can install a couple of isolation trafos I pulled from bad UPS units.


----------



## bperboy

Quote:


  Originally Posted by *BoilermakerFan* /img/forum/go_quote.gif 
_Although, Purdue colors are Black & Gold, so maybe I'll just stick with the black Wakefield for the LM338. 
	

	
	
		
		

		
		
	


	


_

 

Uh oh.... I'll be going to Rose-Hulman in the fall; when I was at the bookstore last summer, I saw a tshirt that said "Friends don't let friends go to Purdue"!


----------



## BoilermakerFan

Quote:


  Originally Posted by *bperboy* /img/forum/go_quote.gif 
_Uh oh.... I'll be going to Rose-Hulman in the fall; when I was at the bookstore last summer, I saw a tshirt that said "Friends don't let friends go to Purdue"! 
	

	
	
		
		

		
		
	


	


_

 

LOL! Rose is a very good school, but it wasn't co-ed when I started college. They came after me and offered a little scholarship, but I had additional priorities besides an education, so I went to Purdue instead. I forget when Rose went co-ed, but it was in the mid-to-late '90's. I actually ended up switching over to the School of Technology (now College of Technology) at Purdue and dropped Chem. E. when I realized Purdue's engineering was all theoretical paper-pushing. The Industrial Technology program at Purdue was lots of hands-on lab work and perfect for me. I still use at least 80% of my degree 12 years later. Not many Purdue engineers I know can say that. I am becoming more interested in pursuing a Masters in applied mathematics though, with a heavy focus on algorithms.


----------



## pinkfloyd4ever

Quote:


  Originally Posted by *BoilermakerFan* /img/forum/go_quote.gif 
_So I "had" to order the TPA Darwin Source Selector kits and the SKA OptiVol kits today. I actually opted to order one of the OptiVols as an assembled and tested unit so I know one will at least work as it should._

 

what are you powering your Optivols with? I've been thinking about ordering one for my Max but I don't know what to power it with(and desoldering the Alps that's in there now does NOT look like fun). Anyway, for those who don't know, the optivol requires a +/- 15vdc supply, but uses only 13 mA

 EDIT: does the optivol have its LEDs & LDRs encapsulated in something light-proof? If not that's gonna be another hurdle since my Max is topless and of course it also has tube lights which would mess with the LDRs obviously


----------



## djbob

I'd like to start by sending a *BIG* thanks to TomB for his professionalism, dedication, guidance and wonderful support of a great project. Of course, many thanks also go to Colin for a fantastic design and his generosity in sharing the Max with us. This was a fun build and I learned alot. Thank you Gentlemen! I look forward to building more of your designs.

 As for my Max, well....It is simply Fantastic. I basically chose Boutique build #2 and it sounds wonderful. I now know what the "slam" is that TomB writes about. I'm currently running 12FK6's. I've tested with Senn HD25s, AKG 240s, and AD-A700. All of them sound incredible. I've also tested with different sources and my favorite so far is my Alien Dac with Muse ES's on output. 

 I'm in the process of building a custom case to house the Max/Alien together. I used to build custom furniture and have some skills as a PC case modder, so I hope to produce a case that will compliment this great Amp.

 Since I'd rather spend money on Audio equip.(not photo) please excuse the low quality of these shots:






[/url][/IMG]






[/url][/IMG]

 Once again, Thank you Colin and TomB.


----------



## BoilermakerFan

Quote:


  Originally Posted by *pinkfloyd4ever* /img/forum/go_quote.gif 
_what are you powering your Optivols with? I've been thinking about ordering one for my Max but I don't know what to power it with(and desoldering the Alps that's in there now does NOT look like fun). Anyway, for those who don't know, the optivol requires a +/- 15vdc supply, but uses only 13 mA

 EDIT: does the optivol have its LEDs & LDRs encapsulated in something light-proof? If not that's gonna be another hurdle since my Max is topless and of course it also has tube lights which would mess with the LDRs obviously_

 

I was planning on using either a wall wart or dropping the 18VDC in my NABU case down to 15VDC. I have an email into Greg to see which is the best way to power it. Worst case scenario, I'll have to build a little dual rail PSU. Looking at his picture on the site, the LDR are encapsuated, but they are also polarized to eliminate ambient light "noise" so the open case won't be an issue. 

 EDIT: There is an on-board resistor (2.2K for +/-15VDC) so you should be able to change the resistor to a higher value for a higher or lower incoming voltage. I don't see why we couldn't use the center LED points from the MAX board since they are at 24VDC without the resistor for the LED. I'll just have to talk to Greg and confirm the new value of the R4 resistor on the OptiVol board. From Greg in the SKA forum: "They're very dynamic... you only need 1 for stereo but a good source of reg DC ~ 30V @ 15mA+." So it looks like the resistor value will drop slightly. 

 Between the MAX board, a phono stage, Darwin, OptiVol, and gainclone amps, I'm going to need 3x24V, 2x15V, and 1x8.5V secondaries on the PSU trafos. I'll need at least two more secondary voltages if I add a DAC in the future too. 
	

	
	
		
		

		
		
	


	




 I'll be calling Victoria Magnetics for the toroids as soon as I hear back from Greg at SKA and I know which way I have to go to feed the OptiVol.


----------



## BoilermakerFan

Greg replied about the supply voltage for the OptiVol:

 "The OptiVol is set up to run on 30V DC floating. That can mean +30V or +/-15V. However, internally it is powered from a 5V6 zener through a dropping resistor, so it can be set to run from +18V easily simply by changing the resistor. I can probably supply the changed value if I know the supply. It is a simple calculation. The unit draws about 12 mA so R = ( Vs - 5.6)/ 0.012 . For +24V it would be 1.5K, use a 0.6W or higher resistor."

 I know tomb posted the info earlier, but I have forgotten, is the center LED mount on the MAX board seeing 24VDC or 27VDC if the resistor is left out and jumpered? This center "tap" would be a great way for those interested to power the OptiVol, but realize it may not attenuate low enough on the MAX with 12AE6A tubes and high sensitivity headphones without bumping up the output resistors on the OptiVol. I'm planning to use mine on my console with the 12FK6 tubes feeding the gainclone amps and old console speakers and will order a pair of 30K resistors to drop the output more if it's needed. The kit's current supplied resistors allow for a max attenuation of -54dB and it would be -55dB with the 30K resistors.


----------



## tomb

Quote:


  Originally Posted by *djbob* /img/forum/go_quote.gif 
_I'd like to start by sending a *BIG* thanks to TomB for his professionalism, dedication, guidance and wonderful support of a great project. Of course, many thanks also go to Colin for a fantastic design and his generosity in sharing the Max with us. This was a fun build and I learned alot. Thank you Gentlemen! I look forward to building more of your designs.

 As for my Max, well....It is simply Fantastic. I basically chose Boutique build #2 and it sounds wonderful. I now know what the "slam" is that TomB writes about. I'm currently running 12FK6's. I've tested with Senn HD25s, AKG 240s, and AD-A700. All of them sound incredible. I've also tested with different sources and my favorite so far is my Alien Dac with Muse ES's on output. 

 I'm in the process of building a custom case to house the Max/Alien together. I used to build custom furniture and have some skills as a PC case modder, so I hope to produce a case that will compliment this great Amp.

 Since I'd rather spend money on Audio equip.(not photo) please excuse the low quality of these shots:

 EDIT:




 Camera quality looks fine to me!
 END EDIT

 Once again, Thank you Colin and TomB._

 

Wow - thanks for the kind words, djbob! Your build looks perfect - glad you enjoy the MAX and the SLAM.


----------



## tomb

Quote:


  Originally Posted by *BoilermakerFan* /img/forum/go_quote.gif 
_Greg replied about the supply voltage for the OptiVol:

 "The OptiVol is set up to run on 30V DC floating. That can mean +30V or +/-15V. However, internally it is powered from a 5V6 zener through a dropping resistor, so it can be set to run from +18V easily simply by changing the resistor. I can probably supply the changed value if I know the supply. It is a simple calculation. The unit draws about 12 mA so R = ( Vs - 5.6)/ 0.012 . For +24V it would be 1.5K, use a 0.6W or higher resistor."

 I know tomb posted the info earlier, but I have forgotten, is the center LED mount on the MAX board seeing 24VDC or 27VDC if the resistor is left out and jumpered? This center "tap" would be a great way for those interested to power the OptiVol, but realize it may not attenuate low enough on the MAX with 12AE6A tubes and high sensitivity headphones without bumping up the output resistors on the OptiVol. I'm planning to use mine on my console with the 12FK6 tubes feeding the gainclone amps and old console speakers and will order a pair of 30K resistors to drop the output more if it's needed. The kit's current supplied resistors allow for a max attenuation of -54dB and it would be -55dB with the 30K resistors._

 

We went through this earlier in some of the discussions with Fran about the OptiVol, but I forget what we came up with.

 Yes, each LED pad on the MAX will see the full V+ voltage, whatever you have that set at. For 27VDC and using Greg's equation above, you'd have:
 (27-5.6)/0.012 = 1783ohms.
 Maybe you should send him a note and ask which would be better - 1.5K or 2K. 2K is what we use for the LED's anyway.


----------



## pinkfloyd4ever

Quote:


  Originally Posted by *BoilermakerFan* /img/forum/go_quote.gif 
_Greg replied about the supply voltage for the OptiVol:

 "The OptiVol is set up to run on 30V DC floating. That can mean +30V or +/-15V. However, internally it is powered from a 5V6 zener through a dropping resistor, so it can be set to run from +18V easily simply by changing the resistor. I can probably supply the changed value if I know the supply. It is a simple calculation. The unit draws about 12 mA so R = ( Vs - 5.6)/ 0.012 . For +24V it would be 1.5K, use a 0.6W or higher resistor."_

 

what exactly is the difference between +30V and +/-15V ?


----------



## Beefy

Quote:


  Originally Posted by *pinkfloyd4ever* /img/forum/go_quote.gif 
_what exactly is the difference between +30V and +/-15V ?_

 

Essentially nothing. Both provide 30V potential difference between + and -.

 But a ±15V would normally have a ground at zero volts sitting right in the middle of the +15V and -15V. It gives you more flexibility, because you have can 15V and 30V supplies for different parts of the circuit.


----------



## amphead

Congrats Djbob! Another Max Lives!   

 Very happy to find your satisfaction with the Max.

 Good point Beefy, on the voltage source. Edit:Of course we don't use +/- 15 volts on the Max board.


----------



## BoilermakerFan

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_We went through this earlier in some of the discussions with Fran about the OptiVol, but I forget what we came up with.

 Yes, each LED pad on the MAX will see the full V+ voltage, whatever you have that set at. For 27VDC and using Greg's equation above, you'd have:
 (27-5.6)/0.012 = 1783ohms.
 Maybe you should send him a note and ask which would be better - 1.5K or 2K. 2K is what we use for the LED's anyway._

 

I was going to use a 1.69K or 1.82K from Mouser:

 71-RN65D-F-1.69K or 71-RN65D-F-1.82K and they actually have them in stock.

 I emailed Greg about which value he thought was better to use. 

 Thanks Tom. 

 Note: To all, I'm not trying to imply this OptiVol is a better volume attenuator for the MAX. For my build it will be more convenient because I need to run the volume pot 18" away from the MAX board and the pot in the OptiVol is not in the signal path so induced noise will not be an issue, but I do plan to braid the connecting wires for extra caution. I know others were interested in it too when the discussion took the thread off topic, so I'm sharing the information on how to make it work if anyone else would like to try it. However, on a "standard" MAX build, in the standard Hoffman enclosure, I think the ALPS Blue pot is a lot easier to install and cheaper too.


----------



## BoilermakerFan

Quote:


  Originally Posted by *pinkfloyd4ever* /img/forum/go_quote.gif 
_what exactly is the difference between +30V and +/-15V ?_

 

Greg emailed me back with this information for those interested:

 "By floating 30V, I meant that there is no connection to signal ground on the powered circuitry of the OptiVol, only the signal side i.e In / Out / G.

 Also the OptiVol is fully ground planed to either signal ground or chassis whichever is convenient, to minimise stray field interference."

 And, FWIW, Greg is substituting a 1.8K resistor for my kits, so the 1.82K resistor from Mouser would be the better choice for 27V at the LED pad assuming the PSU is adjusted to 27VDC and the tubes are biased to 13.5VDC.


----------



## soloz2

So after trying numerous combinations of LED/resiters I've come to the solution that the white LED's I originally purchased for a Max build just are bad.

 So, can anyone suggest a good source for white LEDs?


----------



## tomb

Quote:


  Originally Posted by *soloz2* /img/forum/go_quote.gif 
_So after trying numerous combinations of LED/resiters I've come to the solution that the white LED's I originally purchased for a Max build just are bad.

 So, can anyone suggest a good source for white LEDs?_

 

Some of the guys have tried this seller and claim great success:

100 MEGA WHITE LED 3mm 14000mcd Free S/H - eBay (item 140226473570 end time May-21-08 01:02:03 PDT)

 I've been thinking about purchasing a bunch of different colors from him for Beezar. I was curious about the exact wavelength on some of them and he replied very quickly.


----------



## BoilermakerFan

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Some of the guys have tried this seller and claim great success:

100 MEGA WHITE LED 3mm 14000mcd Free S/H - eBay (item 140226473570 end time May-21-08 01:02:03 PDT)

 I've been thinking about purchasing a bunch of different colors from him for Beezar. I was curious about the exact wavelength on some of them and he replied very quickly._

 

Those are going to be intensely bright since they are typically used as flashlight "bulbs" in sets of 3. If your looking for a very bright LED, they'll do the job. I have just one in little LED flashlight and I held the flashlight up to the bottom of my 12FM6 tube and the lower third is bright, bright white, but it doesn't really carry through the tube like the red LED in the same flashlight does. The wavelength is just too focused.


----------



## soloz2

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Some of the guys have tried this seller and claim great success:

100 MEGA WHITE LED 3mm 14000mcd Free S/H - eBay (item 140226473570 end time May-21-08 01:02:03 PDT)

 I've been thinking about purchasing a bunch of different colors from him for Beezar. I was curious about the exact wavelength on some of them and he replied very quickly._

 

unfortunately that's where I got these white LEDs from


----------



## tomb

Quote:


  Originally Posted by *soloz2* /img/forum/go_quote.gif 
_unfortunately that's where I got these white LEDs from 
	

	
	
		
		

		
		
	


	


_

 

Oops. Any chance you exposed them to some over-voltage/current? I've burned some out back when I had the resistors sized for 1.2K on the MAX BOM. I fooled around with trying to get to 30V early in the prototyping stage and they burned out not too much later than that. I get the impression that they'll last forever if you put a decent safety factor in there, but if they get exposed to too much even for a short time, that may burn them out.

 Or ... maybe that ebay seller is not as good as the guys think.


----------



## BoilermakerFan

Quote:


  Originally Posted by *soloz2* /img/forum/go_quote.gif 
_unfortunately that's where I got these white LEDs from 
	

	
	
		
		

		
		
	


	


_

 

LEDtronics.com has white LEDs, but their online ordering has minimum quantities and elevated prices. A friend of mine orders from LEDtronics direct in large quantities for work projects and he's the one who pointed me in their direction for another project (LED specialty lighting) of mine.

 Here are their NY Distributors though, plus WESCO is their national distributor, so their should be a WESCO in Buffalo, NY. You'll have better luck with the MRO distributors who should sell you 10 or less.


 Beyond Components, LLC OEM & MRO
 14 Jet View Drive
 Rochester, NY 14624
 P: (585) 328-1880
 P: Toll-Free (800) 971-4242
 F: (585) 328-1886
 E-mail: sales@beyondc.com 
 Website: Beyond Components : To the Other Side of Ordinary

 Just in Time Electronics OEM & MRO
 1 Maxwell St.
 E Rockaway, NY 11518
 P: (516) 599-8705
 P: Toll-Free (800) 922-5878
 F: (516) 599-2647
 E-mail: jitsales@optonline.net

 Masline Electronics OEM
 511 Clinton Ave. South
 Rochester, NY 14620
 P: (716) 546-5373
 P: Toll-Free (800) 627-5463
 F: (716) 546-2004
 E-mail: glenn@masline.com
 Website: Masline Electronics, Inc. - Home 

 McMaster- Carr Supply Co. MRO



 And for you Tom:

 Beyond Components, LLC OEM & MRO
 231 Arnold Mill Road, Suite 500
 Woodstock, GA 30188
 P: (678) 494-2020
 P: Toll-Free (800) 971-4242
 F: (678) 494-2259
 E-mail: sales@beyondc.com
 Website: Beyond Components : To the Other Side of Ordinary 

 McMaster- Carr Supply Co. MRO
 6100 Fulton Industrial Blvd. 
 Atlanta, GA 30336-2852
 P: (404) 346-7000
 F: (404) 349-9091
 E-mail: atl.sales@mcmaster.com
 Website: McMaster-Carr


----------



## BoilermakerFan

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Oops. Any chance you exposed them to some over-voltage/current? I've burned some out back when I had the resistors sized for 1.2K on the MAX BOM. I fooled around with trying to get to 30V early in the prototyping stage and they burned out not too much later than that. I get the impression that they'll last forever if you put a decent safety factor in there, but if they get exposed to too much even for a short time, that may burn them out.

 Or ... maybe that ebay seller is not as good as the guys think. 
	

	
	
		
		

		
		
	


	


_

 

I think it's more likely that he ships bulk, untested LEDs. The white LEDs have a very high fall out rate so it's entirely possible to receive 10 or 25 bad ones in a single lot if they weren't tested before shipment.


----------



## soloz2

thanks for the help guys. 

 Yeah, I originally used the original BOM 1.2k resisters, the LEDs didn't see a voltage drop even w/ the LED and resister in the circuit. I tried diferent 1.2k resisters, and then popped in some 2k ones.

 I got a pack of 10 or so and have only been able to get 1 of the LEDs to work.

 well I went through the entire pack again today and was able to get 2 more to work. I threw out all the non-working ones, but now I have this max finished, just needs to be put int he case. it's been ready to go for like a month and a half save for the damn LEDs.


----------



## pinkfloyd4ever

Super Bright LEDs - LEDs


----------



## tomb

Quote:


  Originally Posted by *soloz2* /img/forum/go_quote.gif 
_thanks for the help guys. 

 Yeah, I originally used the original BOM 1.2k resisters, the LEDs didn't see a voltage drop even w/ the LED and resister in the circuit. I tried diferent 1.2k resisters, and then popped in some 2k ones.

 I got a pack of 10 or so and have only been able to get 1 of the LEDs to work.

 well I went through the entire pack again today and was able to get 2 more to work. I threw out all the non-working ones, but now I have this max finished, just needs to be put int he case. it's been ready to go for like a month and a half save for the damn LEDs._

 

Well, with your experience and the comments from Boilermakerfan, I've changed my mind about that ebay seller. It's a bit surprising because in the thread I started about finding a replacement for LSDiodes.com, several mentioned great experience with this guy. 

 That kind of reliability out of a pack of 10 is ridiculous. So, maybe pinkfloyd4ever's Super Bright LEDs is a much better choice.


----------



## BoilermakerFan

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Well, with your experience and the comments from Boilermakerfan, I've changed my mind about that ebay seller. It's a bit surprising because in the thread I started about finding a replacement for LSDiodes.com, several mentioned great experience with this guy. 

 That kind of reliability out of a pack of 10 is ridiculous. So, maybe pinkfloyd4ever's Super Bright LEDs is a much better choice._

 

I really think it is the white LEDs, not red, green, blue, orange, etc. I worked for a electrical industrial controls manufacturer a few years ago and we were trying to launch the LED replacement bulbs for panel lights. The customers wanted white and we could never qualify any white LEDs at the time because none would have less than 50% failure within 100 hours. All the other available colors had MTBF of over 100,000 hours. 

 I would also be leery of the new pink LEDs for the time being and only purchase tested LEDs. 

 For stock purposes, try calling those two local distributors of LEDtronics too, I think their prices may be better than the web site.

 EDIT: pinkfloyd4ever, thanks for that link! They have great prices on BA9 bayonet mounted 4-LED replacement bulbs. I need a few for my MAX builds to go into 22mm panel light mounts. $3 each is a steal!


----------



## tomb

Any experience with UV LEDs? Those are the ones that I burned out in referring to some of the posts awhile back. They were LSDiodes, but as I stated then - it seemed to me that I had overexposed them to too much voltage/current. I have one in an Alien DAC at much reduced current/voltage and it's lasted a good long while and is still going.

 To be honest, I haven't tried a white LED, but was considering it for one of the JFET-MOSFET builds I've got in the queue.


----------



## BoilermakerFan

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Any experience with UV LEDs? Those are the ones that I burned out in referring to some of the posts awhile back. They were LSDiodes, but as I stated then - it seemed to me that I had overexposed them to too much voltage/current. I have one in an Alien DAC at much reduced current/voltage and it's lasted a good long while and is still going.

 To be honest, I haven't tried a white LED, but was considering it for one of the JFET-MOSFET builds I've got in the queue._

 

I haven't because they really do elevate your exposure to both A & B rays and LEDs are so intense you can do a lot of damage to your retinas before you even realize it. I won't even use them in my LED houseplant lights because I can't keep my kids away from them.

 I'm really intrigued by the new pink LEDs though, but unfortunately they are only 5mm right now.


----------



## Thomas_K

Anyone buy a kit from Jeff lately? (Glassjaraudio)
 I bought and paid for a kit on April 1st, but nothing has arrived yet.
 Granted i live in Norway, so shipping usually takes a while. But over a month is too long. From the US standard mail usually takes 10-12 days.
 I asked Jeff on the 23rd, and he told me to just wait a little longer. Now he is not answering my e-mails.
 I initially got a tracking number, but the Norwegian Postal service has no record of any package entering the country with that number. 
 Nor any package in my name. Any ideas on what i can do?


----------



## tomb

Quote:


  Originally Posted by *Thomas_K* /img/forum/go_quote.gif 
_Anyone buy a kit from Jeff lately? (Glassjaraudio)
 I bought and paid for a kit on April 1st, but nothing has arrived yet.
 Granted i live in Norway, so shipping usually takes a while. But over a month is too long. From the US standard mail usually takes 10-12 days.
 I asked Jeff on the 23rd, and he told me to just wait a little longer. Now he is not answering my e-mails.
 I initially got a tracking number, but the Norwegian Postal service has no record of any package entering the country with that number. 
 Nor any package in my name. Any ideas on what i can do?_

 

Jeff's a good guy - I'm sure he'll respond eventually. Apparently, he must be trying to catch up on his stock after taking a break to do his taxes a couple of weeks ago.

 If you refer to some of the posts in the Alien DAC thread, he's having to wait on some Mouser orders. The headphone jack could be causing a problem, too - there appears to be a worldwide shortage from Neutrik right now on the NMJ6HCD2. Mouser says they'll have more in on the 15th, but everyone else is about 10-12 weeks behind that.

 Hopefully, he'll respond to you shortly and explain something similar to that, I'm guessing.


----------



## tomb

Quote:


  Originally Posted by *BoilermakerFan* /img/forum/go_quote.gif 
_I haven't because they really do elevate your exposure to both A & B rays and LEDs are so intense you can do a lot of damage to your retinas before you even realize it. I won't even use them in my LED houseplant lights because I can't keep my kids away from them.

 I'm really intrigued by the new pink LEDs though, but unfortunately they are only 5mm right now._

 

Yes, I've sort of read the same thing in different places. I doubt that I'll use any again, too - was just curious if you had an opinion.


----------



## tomb

We need to give a round of thanks to Bperboy! He represented Team Millett MAX at the Can Jam 08 by displaying his MOSFET MAX at the show! 
	

	
	
		
		

		
			








 He and I traded a few PMs about the JFET-MOSFET mod, so I'm curious as to whether he got those installed before the show. Regardless, he mentioned that he got a lot of good comments on his MAX. 
	

	
	
		
		

		
		
	


	





 EDIT: Head-Fi user Asr's pics:


----------



## BoilermakerFan

Thanks Bperboy!


----------



## bperboy

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_We need to give a round of thanks to Bperboy! He represented Team Millett MAX at the Can Jam 08 by displaying his MOSFET MAX at the show! 
	

	
	
		
		

		
		
	


	







 He and I traded a few PMs about the JFET-MOSFET mod, so I'm curious as to whether he got those installed before the show. Regardless, he mentioned that he got a lot of good comments on his MAX. 
	

	
	
		
		

		
		
	


	





 EDIT: Head-Fi user Asr's pics:_

 

Thanks guys!!! I was indeed the only Max there, and the only other Millett Hybrids there was The Monkey's Headroom Millett Hybrid and N_Maher's Starving Student Millett... I figured there would've been a few more, but oh well. 
	

	
	
		
		

		
		
	


	




 As to the JFET-MOSFET mod, I did make the change a few weeks ago, and it works out perfectly. It may have seemed a bit clearer to me, but then again, I don't have the most golden ears in the world.. maybe more like copper! 
	

	
	
		
		

		
		
	


	




 The Max certainly made my HD580s sing at the meet, as well as the several pairs of K701s that I tried, and even a pair of Grado HF-1s!


----------



## TimJo

Quote:


  Originally Posted by *pinkfloyd4ever* /img/forum/go_quote.gif 
_Super Bright LEDs - LEDs_

 

FWIW, I have had great luck with them as well. My favorites are their 605nm orange leds (3200 mcd). I have them in my 'Can't Miss #2' build and it gives the tubes a more natural looking glow like they have some serious high temp heating elements in them.


----------



## Thomas_K

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Jeff's a good guy - I'm sure he'll respond eventually. Apparently, he must be trying to catch up on his stock after taking a break to do his taxes a couple of weeks ago.

 If you refer to some of the posts in the Alien DAC thread, he's having to wait on some Mouser orders. The headphone jack could be causing a problem, too - there appears to be a worldwide shortage from Neutrik right now on the NMJ6HCD2. Mouser says they'll have more in on the 15th, but everyone else is about 10-12 weeks behind that.

 Hopefully, he'll respond to you shortly and explain something similar to that, I'm guessing._

 

Thanks *tomb*. I sure hope i hear something soon.
 He seems like a good guy. Which is why i ordered from him in the first place.
 I guess I'll just have to have a little more patience.


----------



## ericj

I've accumulated a lot of 12ae6a. By "a lot" i mean "way more than i will ever need". A bunch of 12fm6 as well. 

 I have about half a dozen tubes that i have only one of. Yeah, the internal construction varies that much. 

 I know these tubes got harder to find in the last year, and i know some sources started refusing to try and match them. 

 So, is there anyone following this thread who has an oddball tube that they wish they had a pair for? I'm selling. 

 I have: 

 GE 12ae6a that exactly matches one offered in an ebay store right now qty1. Halo getter on the top. Construction looks like RCA to me. 

 DuMont 12ae6 clear-top. I can't find any specifications that say what the difference is between 12ae6 and 12ae6a. Halo getter on the side. Construction looks like RCA to me. 

 DuMont 12ae6a with D-getter on the top. Construction again looks like RCA. 

 CBS (sylvania) clear-top 12ae6a with squareish D-getter on the side. Triple mica - the outer plates (diodes?) are crimped to a tiny round mica piece on the top. 

 Edit: I found another 12fm6. RCA, square getter on top. 

 I also have some tubes with identical internal construction and mismatched labels. You could always wash off the paint!

 I have an RCA clear-top 12FM6 and United Electron 12FM6 that look precisely the same. 

 I have a Sylvania triple-mica clear-top 12ae6a and a DuMont 12ae6a that looks precisely the same internally. 

 If you twist my arm, i could also sell you an unused max board, a pair of sockets, and some nichicon muse kz output caps. I'd thought about building a bjt max to go with my mosfet max, but i'm more interested in other designs these days and i doubt I'll get around to it.


----------



## BoilermakerFan

Quote:


  Originally Posted by *ericj* /img/forum/go_quote.gif 
_I've accumulated a lot of 12ae6a. By "a lot" i mean "way more than i will ever need". A bunch of 12fm6 as well. 

 I have about half a dozen tubes that i have only one of. Yeah, the internal construction varies that much. 

 I know these tubes got harder to find in the last year, and i know some sources started refusing to try and match them. 

 So, is there anyone following this thread who has an oddball tube that they wish they had a pair for? I'm selling. 

 I have: 

 GE 12ae6a that exactly matches one offered in an ebay store right now qty1. Halo getter on the top. Construction looks like RCA to me. 

 DuMont 12ae6 clear-top. I can't find any specifications that say what the difference is between 12ae6 and 12ae6a. Halo getter on the side. Construction looks like RCA to me. 

 DuMont 12ae6a with D-getter on the top. Construction again looks like RCA. 

 CBS (sylvania) clear-top 12ae6a with squareish D-getter on the side. Triple mica - the outer plates (diodes?) are crimped to a tiny round mica piece on the top. 

 I also have some tubes with identical internal construction and mismatched labels. You could always wash off the paint!

 I have an RCA clear-top 12FM6 and United Electron 12FM6 that look precisely the same. 

 I have a Sylvania triple-mica clear-top 12ae6a and a DuMont 12ae6a that looks precisely the same internally. 

 If you twist my arm, i could also sell you an unused max board, a pair of sockets, and some nichicon muse kz output caps. I'd thought about building a bjt max to go with my mosfet max, but i'm more interested in other designs these days and i doubt I'll get around to it._

 

I have an odd-man out 12FM6 that was the last one in stock at Radio Daze so I'd love to have a match for it. Send me a PM with your email and I'll be able to send you pics for a match if at all possible. I'd also be interested in the KZ caps...


----------



## amphead

Congrats Bperboy on representing TEAM MAX at CanJam08!

 I think I know what thats like. I had alot of great reactions at Mayberry on Acid.


----------



## jamess71

Sorry to beat a dead horse, After reading a billion posts 
	

	
	
		
		

		
		
	


	




 I'm still not sure on the concensus for the output resistors. I know it is very build specific. I am finishing up Can't Miss Build #1 and I use Denons and Beyer/ 80' s so I would like some gain reduction if it's possible without any loss in SQ. Are the Rikens the only way to go with say 100R ? Would there be any loss in detail with the Rikens? Thnaks again

 James
 _________


----------



## tomb

Quote:


  Originally Posted by *jamess71* /img/forum/go_quote.gif 
_Sorry to beat a dead horse, After reading a billion posts 
	

	
	
		
		

		
		
	


	




 I'm still not sure on the concensus for the output resistors. I know it is very build specific. I am finishing up Can't Miss Build #1 and I use Denons and Beyer/ 80' s so I would like some gain reduction if it's possible without any loss in SQ. Are the Rikens the only way to go with say 100R ? Would there be any loss in detail with the Rikens? Thnaks again

 James
 __________

 

The primary method of adjusting gain is by changing the tube type. If the 12FK6's with their lower gain is still too much, then the right resistance in RB14 may help.

 Best dynamics and detail are without, but 10 ohms may tame the tizziness enough to sound better than without.

 When you get up into the 47-100 ohms range, then the quality of the resistor means a great deal. Stackpoles and Kiwames are very close, IMHO, with Kiwames having more detail and sweetened highs. Stackpoles are rich, but probably fall off just a tad in the highs.

 I can't tell you much about the Rikens, except that Slowpogo thinks that they are noticeably better than Kiwames. These days, the Stackpoles and Kiwames can be had for a few dimes each at the right store 
	

	
	
		
		

		
		
	


	







, but Rikens are $2.70 - $4.50 each, plus shipping. That would temper my selection, but you're really the only one that can say whether they're worth the extra expense.


----------



## soloz2

Well now that I've got my second build done (took a while due to being busy with other projects) I'm going to start compiling parts for my 3rd build.

 Can anyone recommend a good stepped attenuator? I'd rather not spend a small fortune on the part, but I don't want something cheap either.

 I'm also considering a hifi2000 enclosure, but shipping costs for one case brings the total to more than I'd like. Anyone else interested in splitting shipping? Maybe if 2-3 more people want to order we could work something out. Of course, it would be easiest if we all lived somewhat close to each other...


----------



## n_maher

Quote:


  Originally Posted by *soloz2* /img/forum/go_quote.gif 
_I'm also considering a hifi2000 enclosure, but shipping costs for one case brings the total to more than I'd like. Anyone else interested in splitting shipping? Maybe if 2-3 more people want to order we could work something out. Of course, it would be easiest if we all lived somewhat close to each other..._

 

Someone posted a link recently to a US company that imports a limited number of the Hifi2000 chassis. I can't find it right now and can't remember the name but that might be worth looking into.


----------



## Ferrari

I think I know who that was 
	

	
	
		
		

		
		
	


	




 .


----------



## n_maher

Quote:


  Originally Posted by *Ferrari* /img/forum/go_quote.gif 
_I think I know who that was 
	

	
	
		
		

		
		
	


	




 ._

 

Thanks (again)!!!


----------



## soloz2

Quote:


  Originally Posted by *n_maher* /img/forum/go_quote.gif 
_Someone posted a link recently to a US company that imports a limited number of the Hifi2000 chassis. I can't find it right now and can't remember the name but that might be worth looking into._

 

 Quote:


  Originally Posted by *Ferrari* /img/forum/go_quote.gif 
_I think I know who that was 
	

	
	
		
		

		
		
	


	




 ._

 

that's going to be tight height wise. Tis a shame they don't have the 80mm high version. A single GX283 is $103.70 direct, the DS2480.18 from Teko, is shorter and is 74.39 plus shipping. The difference is $28 for a shorter case that would likely make the build more difficult since I find the Hammond enclosure a bit tight height wise.


----------



## tomb

Quote:


  Originally Posted by *soloz2* /img/forum/go_quote.gif 
_<snip>Can anyone recommend a good stepped attenuator? I'd rather not spend a small fortune on the part, but I don't want something cheap either.</snip>_

 

I forgot to mention that vixr used a Goldpoint stepped attenuator recently. I can't remember whether it was on one of his MAXes or his Bijou. I like the look of the Goldpoints, so would probably choose one myself. DACT has been a standard for a long time, too.

 There's the OptiVol that Fran has championed. Then there's the Joshua digital attenuator offered by Twisted Pear.

 On a different note - it took awhile, but I finally have a decent enough stock of good o-rings to offer for sale as tube rings. They should appear in 2-3 days on beezar.


----------



## BoilermakerFan

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_I forgot to mention that vixr used a Goldpoint stepped attenuator recently. I can't remember whether it was on one of his MAXes or his Bijou. I like the look of the Goldpoints, so would probably choose one myself. DACT has been a standard for a long time, too.

 There's the OptiVol that Fran has championed. Then there's the Joshua digital attenuator offered by Twisted Pear.

 On a different note - it took awhile, but I finally have a decent enough stock of good o-rings to offer for sale as tube rings. They should appear in 2-3 days on beezar._

 

Greg is working on my OptiVols and they should be shipping at the end of the week. But, my MAX boards are still naked, so it will be a few weeks before I can comment on it's actual sound. For the money, it was just too hard to pass up. If anyone else goes to order a kit, be sure to tell Greg what your MAX PSU is setup for and he'll include the correct resistors. The recommended default voltage for the MAX is 27VDC, so that is what will be present at the center LED pad on the board.

 The TPA Joshua Tree is being redesigned and hasn't been re-released yet. All the old boards are gone. I planned to order the JT with my Darwin kit... Now I'm just waiting for the JT to be re-released. 

 The Goldpoint is pretty pricey too. Peter Daniels posted a pic of his stepped attenuator stuffed with Caddock resistors!


----------



## soloz2

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_I forgot to mention that vixr used a Goldpoint stepped attenuator recently. I can't remember whether it was on one of his MAXes or his Bijou. I like the look of the Goldpoints, so would probably choose one myself. DACT has been a standard for a long time, too.

 There's the OptiVol that Fran has championed. Then there's the Joshua digital attenuator offered by Twisted Pear.

 On a different note - it took awhile, but I finally have a decent enough stock of good o-rings to offer for sale as tube rings. They should appear in 2-3 days on beezar._

 

I was originally going to get the joshua tree, but since it's OOS and I'm not sure when the new version will be available that kinda kills it for me.
 I was looking at the Gold points earlier today. The miniv looks to be pretty decent and at a decent price (although I like the JT price better)

 The OptiVol looks very tempting... especially at the price... I might have to look more into it.


----------



## pinkfloyd4ever

Quote:


  Originally Posted by *amphead* /img/forum/go_quote.gif 
_Congrats Bperboy on representing TEAM MAX at CanJam08!

 I think I know what thats like. I had alot of great reactions at Mayberry on Acid. _

 

i just can't believe he was the ONLY one there reppin' the mhm


----------



## dsavitsk

Quote:


  Originally Posted by *soloz2* /img/forum/go_quote.gif 
_Can anyone recommend a good stepped attenuator? I'd rather not spend a small fortune on the part, but I don't want something cheap either._

 

Don't know if these are too "cheap" but they work really well.

Stepped Attenuator potentiometer ladder volume control - eBay (item 130220471976 end time May-13-08 00:51:46 PDT)


----------



## amphead

Quote:


 i just can't believe he was the ONLY one there reppin' the mhm 
 

Who else brought one? 

 Nice looking attenuator Dsavitsk! Had not seen that upscale one.


----------



## jamess71

Quote:


  Originally Posted by *dsavitsk* /img/forum/go_quote.gif 
_Don't know if these are too "cheap" but they work really well.

Stepped Attenuator potentiometer ladder volume control - eBay (item 130220471976 end time May-13-08 00:51:46 PDT)_

 

Hmm not bad for $30. I think I might try it out. Would this be noticibly better than an alps pot? I know one thing for sure it looks cool. 
	

	
	
		
		

		
		
	


	




 James


----------



## pabbi1

They are noticeably better, but I have had mixed results out of the HK dealers (ymmv) - some great, some absolute crap (wrong r values, bad solder, and a one completely dead). The Taiwan dealers have been steller the 4 times purchased from them.

 That said, there is nothing like the Goldpoints, which is just wrong for the Max...


----------



## soloz2

That's my concern as well. I'd rather spend $100 more to have something I knew would be a marked improvement over the Alps I have ready to go in.

 Has anyone compared the ebay or optivol to say a goldpoint or DACT attenuator?


----------



## soloz2

Quote:


  Originally Posted by *pabbi1* /img/forum/go_quote.gif 
_
 That said, there is nothing like the Goldpoints, which is just wrong for the Max... 
	

	
	
		
		

		
		
	


	


_

 

Just curious what exactly you mean by this.


----------



## pabbi1

Quote:


  Originally Posted by *soloz2* /img/forum/go_quote.gif 
_Just curious what exactly you mean by this._

 

Spending as much on the attenuator(s) as the whole balance of the amp parts, when the amp _may_ not justify it seems wrong to me. The Goldpoints were a no brainer for the Blue Hawaii ($400ish for a pair, balanced), but not sure it would really help the Max over one of the Taiwan attenuators.

 The (good) Taiwan stereo attenuator went on my first Millett, and it was good, but after having mixed results in other builds (m³, BH) with the cheap attenuators, the RK27 was plenty good for my current design goals. 

 I don't stress every time I listen to my rig thinking, Damn, shoulda gotten the stepped attenuators... in fact, don't notice at all.


----------



## pinkfloyd4ever

Quote:


  Originally Posted by *amphead* /img/forum/go_quote.gif 
_Who else brought one? _

 

ahhaha nice. What config did you have there?


----------



## BoilermakerFan

Quote:


  Originally Posted by *soloz2* /img/forum/go_quote.gif 
_That's my concern as well. I'd rather spend $100 more to have something I knew would be a marked improvement over the Alps I have ready to go in.

 Has anyone compared the ebay or optivol to say a goldpoint or DACT attenuator?_

 

I'll be building one with an ALPS, one with an OptiVol, and one with a TPA Joshua Tree when the new boards are released. I don't expect to hear profound or audible differences though. 

 IMHO, I would wait for the new JT since it will support I2P communication with a Matrox Orbital VFD or LED display as well as the use of optical encoders for the attenuation signal. I just want the JT for it's support of the display and I2P. The chip will support other programed features too, so I'm going to see if I can grab the MP3 data off the USB input before it goes into the DAC and display the track info on the display along with the volume info. That would be pretty dang cool for my desktop MHM amp and it wuld be a huge benefit to me on my console builds since I can eliminate the need for a CD player completely.


----------



## soloz2

Quote:


  Originally Posted by *pabbi1* /img/forum/go_quote.gif 
_Spending as much on the attenuator(s) as the whole balance of the amp parts, when the amp _may_ not justify it seems wrong to me. The Goldpoints were a no brainer for the Blue Hawaii ($400ish for a pair, balanced), but not sure it would really help the Max over one of the Taiwan attenuators.

 The (good) Taiwan stereo attenuator went on my first Millett, and it was good, but after having mixed results in other builds (m³, BH) with the cheap attenuators, the RK27 was plenty good for my current design goals. 

 I don't stress every time I listen to my rig thinking, Damn, shoulda gotten the stepped attenuators... in fact, don't notice at all._

 

Thanks, that's what I was looking for in an answer. I've been coming to the same conclusion myself. I'm interested in trying the JT from twisted pear, but if the new version won't be out soon I'm not going to wait, but what has really sparked my interest is the optivol. The price is very reasonable and I haven't read anything bad (but then again there isn't a lot out there)


----------



## soloz2

Quote:


  Originally Posted by *BoilermakerFan* /img/forum/go_quote.gif 
_I'll be building one with an ALPS, one with an OptiVol, and one with a TPA Joshua Tree when the new boards are released. I don't expect to hear profound or audible differences though. 

 IMHO, I would wait for the new JT since it will support I2P communication with a Matrox Orbital VFD or LED display as well as the use of optical encoders for the attenuation signal. I just want the JT for it's support of the display and I2P. The chip will support other programed features too, so I'm going to see if I can grab the MP3 data off the USB input before it goes into the DAC and display the track info on the display along with the volume info. That would be pretty dang cool for my desktop MHM amp and it wuld be a huge benefit to me on my console builds since I can eliminate the need for a CD player completely._

 

missed your post before my last post...

 do you have any experience with the optivol yet? do you have it now, or will you be ordering it soon?


----------



## BoilermakerFan

Quote:


  Originally Posted by *soloz2* /img/forum/go_quote.gif 
_missed your post before my last post...

 do you have any experience with the optivol yet? do you have it now, or will you be ordering it soon?_

 

I have ordered them. I ordered one assembled & tested and one kit. Greg matches the LDRs into pairs, but I wanted one A&T unit to make sure it would work. I haven't received them yet, but I know Greg had the 1.8K input resistors in stock to setup the OptiVol for 27VDC input voltage. I suspect I will receive an email from Greg shortly letting me know they are on their way to the States. 

 If you have questions, you can jump onto his site and email him. I think his pre-sale support has been great.


----------



## Phil Townsend

It's alive and doing it's job...
 Biased up nicely and I
 Managed to not let the smoke out!



 I've set the bias at 67mv...I'll run it up later...wanna check the heat on the sinks first.

 I used Black Gates at all positions...
 For the CR4,5, L&R I installed 1470 mikes at each of the 4 positions (1000 +470)
 I bypassed the CR4,5 with NP BG .47 mikes
 I had to install the 1000 mike ones on the bottom of the board.
 The Power supply has 4000 mikes of BG at CR1a,b,c,d
 Also nonpolar BG at CR5 1 mike.

 Cree zero recovereries at DR1 A,B,C,D I love these guys...No spikes!

 NP 470 BG at CA7, L& R bypassed with .1Mundorfs...First pass on the Mundorfs... I'll adjust up or down as the amp comes around.

 NP BG at CA2 with a NP BG .47 at CA9

 I used the Audio Note resistors at RB1 LR and Mills ww (2.2 ohms) at RB 10& 11.

 The pot has some noise as it moves but I have an extra DACT to slide in some day.

 Thats about it...

 So Far it sounds real good...But BG's need 200 - 400 hours to really get up to snuff.

 O, I built a killer box to stuff everything into...

 Photos Later

 Phil
 Santa Fe


----------



## jamess71

Quote:


  Originally Posted by *Phil Townsend* /img/forum/go_quote.gif 
_It's alive and doing it's job...
 Biased up nicely and I
 Managed to not let the smoke out!



 I've set the bias at 67mv...I'll run it up later...wanna check the heat on the sinks first.

 I used Black Gates at all positions...
 For the CR4,5, L&R I installed 1470 mikes at each of the 4 positions (1000 +470)
 I bypassed the CR4,5 with NP BG .47 mikes
 I had to install the 1000 mike ones on the bottom of the board.
 The Power supply has 4000 mikes of BG at CR1a,b,c,d
 Also nonpolar BG at CR5 1 mike.

 Cree zero recovereries at DR1 A,B,C,D I love these guys...No spikes!

 NP 470 BG at CA7, L& R bypassed with .1Mundorfs...First pass on the Mundorfs... I'll adjust up or down as the amp comes around.

 NP BG at CA2 with a NP BG .47 at CA9

 I used the Audio Note resistors at RB1 LR and Mills ww (2.2 ohms) at RB 10& 11.

 The pot has some noise as it moves but I have an extra DACT to slide in some day.

 Thats about it...

 So Far it sounds real good...But BG's need 200 - 400 hours to really get up to snuff.

 O, I built a killer box to stuff everything into...

 Photos Later

 Phil
 Santa Fe_

 

Wow Phil thats gotta be one expensive Millet. 
	

	
	
		
		

		
			





 I'm sure it will sound Awesome after some burn in. Welcome to Head-Fi


----------



## jamess71

Quick question, what temperature do you guys set your soldering iron at for components on the board?


----------



## Phil Townsend

I build tube amps for a few folks and always seem to have various parts about...So not to expensive since most of the BG I bought 4 or 5 years ago...

 Phil
 Santa Fe


----------



## amphead

Phil, thats got to be near the top of the heap, if not at the top for components. We will be eagerly awaiting your sonic evaluations.  What phones?


----------



## tomb

Sounds great, Phil - can't wait to see the pics.

 I seriously doubt the pot as a source for the scratching, though - if it's an RK27. It's most likely the tubes. Black Gates especially are so quieting that the scratchiness happens more often. I forget what the explanation was - Negatron was the one that first explained it - but it has something to do with a not-quite-right ground connection throught the pins on the tubes.

 Try switching or replacing the tubes - I bet you'll notice a difference, even if the scratchiness doesn't go away. I flushed out an RK27 with enough flux cleaner once to almost remove all the lube for the shaft. It didn't do a thing - replaced the tube and it went away completely. The lube didn't come back, though.


----------



## ericj

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Black Gates especially are so quieting that the scratchiness happens more often._

 

You know I've seen the signal/noise ratio claims for the Black Gate caps - claimed to be less than the thermal noise that a theoretically ideal capacitor would introduce - but a claim that a capacitor actually _induces quietness_?! That's something!


----------



## Beefy

Quote:


  Originally Posted by *Phil Townsend* /img/forum/go_quote.gif 
_I used Black Gates at all positions..._

 

Sounds nice..... but don't the humble and inexpensive Panasonic FC/FM or Nichicon HE/PW have better leakage and ripple specs, and thus are far better for the power supply caps?


----------



## Phil Townsend

The Alps pot is good...I have had a similar problem with my old Stax SRM 1/MK2 Solid State Earspeaker Driver...
 All worked fine with the Stax unit until one fine day I did a cap swap...Yea, BGs. The darn Alps pot got some noise...Put in a new one a 10k I think, Yep the noise was still there. Finally I installed a 10k DACT...(Tight Fit) no noise but I could hear the contacts making before breaking...Oh Well...

 There is no noise on the Max if the pot is set and what noise there is is quite small.


----------



## Phil Townsend

Max in a Box


----------



## tomb

Quote:


  Originally Posted by *ericj* /img/forum/go_quote.gif 
_You know I've seen the signal/noise ratio claims for the Black Gate caps - claimed to be less than the thermal noise that a theoretically ideal capacitor would introduce - but a claim that a capacitor actually induces quietness?! That's something!_

 

Ya'll make fun of my description if you want, but it's fact as far as I'm concerned. I have never had an ES MAX exhibit scratchiness when adjusting volume. Yet, every single MAX with Black Gates does it. I think I've built enough of them to claim it as a trend. If you're very careful with the tubes and get a really good set, or if I remember correctly, you change over to the 12FK6's, you can make the scratchiness go away.

 Call it the speed of the Black Gates and the fact that the tubes can't keep up with the gain change. Maybe that will sound better.

 Dadgummit - my ears are still ringing from a Radiohead concert tonight. I probably shouldn't be posting.

 EDIT: To be specific, the Black Gates have much higher quieting/lower distortion at high frequencies. There's a bunch of graphs somewhere that demonstrate this, but 'nuff said. (Phil may have used the BG's everywhere, but my experience is referencing their standard use in the signal path.) Anyway, Phil suggested the same effect.


----------



## tomb

Nice job on the case, Phil! What's that doo-hickey on the bottom with that curl?

 The knob is cute and those are some mighty big BGs around that PS heat sink.


----------



## ruZZ.il

Hey really cool case! I really like that kind of style.

 meanwhile.... I'm engaged!


----------



## tomb

Quote:


  Originally Posted by *ruZZ.il* /img/forum/go_quote.gif 
_Hey really cool case! I really like that kind of style.

 meanwhile.... I'm engaged! 
	

	
	
		
		

		
		
	


	


_

 

Wow! Congratulations! I figured it was some life-changing event to keep you away the last month or so.


----------



## fault151

Hi guys, Can i use a 100k pot on the millet amp? I have just bust one of the pins off my 50k pot.


----------



## n_maher

The 100k pot should work just fine.


----------



## fault151

is there any difference in sound/performance?

 It wont be louder when i turn it will it?


----------



## amphead

Theoretically 50K will be better sounding, but my guess is you can't tell the difference enough to matter. 100K is often used with all-tube amps. Although I'm using 50K on my all-tube amp, just because I already had a 50K RK27. 

 Congrats RuZZ.il!
 I wondered where you were lurking.


----------



## fault151

Ok cheers for your help.


----------



## TimJo

Quote:


  Originally Posted by *ruZZ.il* /img/forum/go_quote.gif 
_meanwhile.... I'm engaged! 
	

	
	
		
		

		
			



_

 

Congratulations ruZZ.il!! 

 I hope your other half understands this hobby.


----------



## fault151

Hi guys, i'm trying to wire my leds to the board, Which out of the connections is the positive and negative?

 Iv attached the board layout and i've circled the led i'm referring to in pink. 

Board layout


----------



## MrMajestic2

Quote:


  Originally Posted by *fault151* /img/forum/go_quote.gif 
_Hi guys, i'm trying to wire my leds to the board, Which out of the connections is the positive and negative?

 Iv attached the board layout and i've circled the led i'm referring to in pink. 

Board layout_

 

The side where the text LEDC is, thats the negative the other one is positive.


----------



## tomb

Quote:


  Originally Posted by *fault151* /img/forum/go_quote.gif 
_Hi guys, i'm trying to wire my leds to the board, Which out of the connections is the positive and negative?

 Iv attached the board layout and i've circled the led i'm referring to in pink. 

Board layout_

 

Yeah, the silkscreening got a little tight in there. However, just look at the image you referenced: the trace is the dead giveaway. In the area of the ground plane, all the traces are positive (that's the purplish-brown thick line that connects to the LED pad on the right.). All of the negative pads in the ground plane area will have the four-point connection to the ground plane for ease of soldering.


 EDIT: too slow on the post again ...


----------



## fault151

Ok cheers guys! I'll get wiring now. 

 God i always manage to get a fast response on this thread, it's great!


----------



## adfinni

Quote:


  Originally Posted by *ruZZ.il* /img/forum/go_quote.gif 
_Hey really cool case! I really like that kind of style.

 meanwhile.... I'm engaged! 
	

	
	
		
		

		
		
	


	


_

 

Congrats 
	

	
	
		
		

		
		
	


	




 meanwhile, powered on the MAX + HF1 combo for the first time in a month or so and boy does it sound better than ever. Put goldfrapp 'supernature' on and am away in another world with alisons voice echoing around 
	

	
	
		
		

		
		
	


	




 Still haven't got any internal pics of mine, as it is such a PITA to take apart, but All I can say is that Black gate NXs really are sensational !!!

 On another note plugged in my ksc-75s the other day, and the MAX made them sound far far far far better than they really should sound. Especially good in css for those times when you need to position people through walls with 'audio-wall-hax'


----------



## tomb

Quote:


  Originally Posted by *adfinni* /img/forum/go_quote.gif 
_Congrats 
	

	
	
		
		

		
		
	


	




 meanwhile, powered on the MAX + HF1 combo for the first time in a month or so and boy does it sound better than ever. Put goldfrapp 'supernature' on and am away in another world with alisons voice echoing around 
	

	
	
		
		

		
		
	


	




 Still haven't got any internal pics of mine, as it is such a PITA to take apart, but All I can say is that Black gate NXs really are sensational !!!

 On another note plugged in my ksc-75s the other day, and the MAX made them sound far far far far better than they really sound. Especially good in css for those times when you need to position people through walls with 'audio-wall-hax' 
	

	
	
		
		

		
		
	


	





_

 

Yep, the BG's are hard to beat. VitQ's combined with the ES's can get pretty close, though. After testing numerous combinations, I think we've hit the sweet spot with that one. I listen to mine with KSC75's most of the time. They're just so convenient, sound great, and you don't have to worry about knocking them around a bit (or a lot). That said, the best pairing I've ever tried with the MAX is with the Grado HF-1's. It sounds as if you like that, too.

 How are your "roll bars" doing? I've noticed much better heat transfer with mine. There's quite a bit of radiation inside the case from the heat sinks to the case lid. With the roll bars, it dissipates quite a bit of the heat. 'Course, if I remember correctly, you left quite a bit of an opening behind your power supply.


----------



## ericj

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Ya'll make fun of my description if you want, but it's fact as far as I'm concerned. I have never had an ES MAX exhibit scratchiness when adjusting volume. Yet, every single MAX with Black Gates does it. I think I've built enough of them to claim it as a trend._

 

Maybe that's the transcendent electron transfer you're hearing.


----------



## Phil Townsend

O.K. I have set the tube bias many times... I've set it at 13.45 volts. (the DB is set to 84.5 left and right. My voltage is set for 26.95.

 The question is the Max has been running for 4 days.
 I shut it down at night.
 I turn it on in the AM and let it get hot.(2 or 3 hours)
 I measure the tube bias...it never remains at 13.45 on the left or right.
 Typically it will show 14.7 on the right and 12.7 on the left. These setting will vary but they never remain where I set it... Drift, yes and lots of it.

 So Rhettret, whatever shall I do? (Gone with the wind)
 And so Rhett replies " Frankly My dear I don't give a damn"

 But I do ask...What ever shall I do?


----------



## tomb

Quote:


  Originally Posted by *Phil Townsend* /img/forum/go_quote.gif 
_O.K. I have set the tube bias many times... I've set it at 13.45 volts. (the DB is set to 84.5 left and right. My voltage is set for 26.95.

 The question is the Max has been running for 4 days.
 I shut it down at night.
 I turn it on in the AM and let it get hot.(2 or 3 hours)
 I measure the tube bias...it never remains at 13.45 on the left or right.
 Typically it will show 14.7 on the right and 12.7 on the left. These setting will vary but they never remain where I set it... Drift, yes and lots of it.

 So Rhettret, whatever shall I do? (Gone with the wind)
 And so Rhett replies " Frankly My dear I don't give a damn"

 But I do ask...What ever shall I do?_

 

You probably shouldn't set final tube bias for a couple of hours - they will tend to drift for the first couple of hours. So if you set the bias as soon as you turn it on, you'll never have the correct setting.

 The left seems reasonable. The other tube is a bit unusual that it's going up when the other one is going down. Plus, it's quite a bit more than the other one. Seriously though, 1/4 - 1/2 volt is as good as you're ever going to get, most likely, but even broken-in tubes would prefer to have a final bias after about 2 hours. Then the 1/4 to 1/2 should be fairly consistent, but will be off in the beginning, rather than at the end. They should remain within a 1/4V or so from 4 to 8 hrs running time, but there again, I've never tracked it religously.

 EDIT: Four days should be enough to break-in most any Millett tube, so I don't think that's causing any of this - although it might have for the first couple of days. If it's worse than I what I described above, and you've run them for 4 days+, then it could be some bad tubes - getter flash too worn, would be a guess.


----------



## Phil Townsend

OK

 I have set the bias after at least 3=4 hours and and hour or so before shut down...

 Think I;ll try some new tubes...
 Thank You


----------



## Snicewicz

Well I am doing a final project in physics and It has to be a presentation to the class about electricity. It has to do with circuits, diodes, resistors, transistors and so on. 

 I was thinking that it would be cool to build a Millet Max and explain how certain parts of it work to do certain things. 

 Just curious I know it costs about what 160 dollars in materials, but how long usually does it take to build one, in hours?

 Also would I be able to do the explanations with the millet max like I want to?

 Thanks


----------



## Beefy

Quote:


  Originally Posted by *Phil Townsend* /img/forum/go_quote.gif 
_I have set the bias after at least 3=4 hours and and hour or so before shut down...

 Think I;ll try some new tubes..._

 

In my limited experience (6 tubes), it only takes 2-6 hours of total use for the tubes to stabilise. Anything after that time period is in the order of less than half a volt, and seems to be related mostly to temperature. On cold starts, tube bias starts high and drops, hitting a minimum inside an hour.


----------



## BoilermakerFan

Quote:


  Originally Posted by *Snicewicz* /img/forum/go_quote.gif 
_Well I am doing a final project in physics and It has to be a presentation to the class about electricity. It has to do with circuits, diodes, resistors, transistors and so on. 

 I was thinking that it would be cool to build a Millet Max and explain how certain parts of it work to do certain things. 

 Just curious I know it costs about what 160 dollars in materials, but how long usually does it take to build one, in hours?

 Also would I be able to do the explanations with the millet max like I want to?

 Thanks_

 

Yes, but you might have to explain to your classmates what the glass bottles in the middle do.


----------



## tomb

Quote:


  Originally Posted by *Beefy* /img/forum/go_quote.gif 
_In my limited experience (6 tubes), it only takes 2-6 hours of total use for the tubes to stabilise. Anything after that time period is in the order of less than half a volt, and seems to be related mostly to temperature. On cold starts, tube bias starts high and drops, hitting a minimum inside an hour._

 

You may have hit a lucky streak with those tubes.


----------



## Beefy

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_You may have hit a lucky streak with those tubes.
	

	
	
		
		

		
		
	


	


_

 

I'd like to think that a magical fairy just gave me good ones, considering I'm such a nice guy


----------



## tomb

Quote:


  Originally Posted by *Beefy* /img/forum/go_quote.gif 
_I'd like to think that a magical fairy just gave me good ones, considering I'm such a nice guy 
	

	
	
		
		

		
		
	


	


_

 

Uh oh. I think you just called me the Magical Millett Tube Fairy.


----------



## fault151

Hi guys, anyone know where i can get and board stand offs for the millet amp? Im using a box from hifi 2000. I could do with some sort of way to mount the board to the case but for it to be detachable. They only need to be 1.5cm or something similar.

 Looked on ebay, couldn't find anything suitable.


----------



## tomb

Quote:


  Originally Posted by *fault151* /img/forum/go_quote.gif 
_Hi guys, anyone know where i can get and board stand offs for the millet amp? Im using a box from hifi 2000. I could do with some sort of way to mount the board to the case but for it to be detachable. They only need to be 1.5cm or something similar.

 Looked on ebay, couldn't find anything suitable._

 

Standoffs are a hardware item, although they're not too common in a neighborhood hardware store. The holes in the MAX board are sized for #4. Typically, 4-40 screws are used. You can do a good job with just a set of 4-40 screws and some nylon spacers - probably 3/8" would do if you add a flat washer or two. Put the screws in from the bottom with the nuts on top of the board - it will make a pretty good substitute for true standoffs and everything should be available at the local hardware store - although #4 gets a bit small for many.

 Other than that - the standard vendors apply, but you can add Grainger and McMaster-Carr to Mouser, DigiKey, Jameco, Newark, Allied Elec, etc. - probably Farnell or RS Components in your area?


----------



## fault151

Ok cheers, ill give rs components a try. 

 Yeh i was just thinking of doing something very similar to what you suggested. I think the nylon spacers would be my best bet. Cheers.


----------



## MrMajestic2

Quote:


  Originally Posted by *fault151* /img/forum/go_quote.gif 
_Hi guys, anyone know where i can get and board stand offs for the millet amp? Im using a box from hifi 2000. I could do with some sort of way to mount the board to the case but for it to be detachable. They only need to be 1.5cm or something similar.

 Looked on ebay, couldn't find anything suitable._

 

Check Farnell.co.uk.


----------



## adfinni

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Yep, the BG's are hard to beat. VitQ's combined with the ES's can get pretty close, though. After testing numerous combinations, I think we've hit the sweet spot with that one. I listen to mine with KSC75's most of the time. They're just so convenient, sound great, and you don't have to worry about knocking them around a bit (or a lot). That said, the best pairing I've ever tried with the MAX is with the Grado HF-1's. It sounds as if you like that, too.

 How are your "roll bars" doing? I've noticed much better heat transfer with mine. There's quite a bit of radiation inside the case from the heat sinks to the case lid. With the roll bars, it dissipates quite a bit of the heat. 'Course, if I remember correctly, you left quite a bit of an opening behind your power supply._

 

My 75s have a loose connection in the left earcup, now I have an excuse to recable 
	

	
	
		
		

		
		
	


	




 The roll bars are great and have definately stopped me from sideswiping the tops of the tubes and causing any damage, so in that case very worthwhile.

 I haven't felt them for a while once the amp is running, but I do rmemeber them heating up a bit. The space at the back near the PSU is great, but it makes me realise how hot things are in there as during normal usage the PSU heatsink is too hot to touch after a few seconds. Biased @ 27V.

 Il eventualy open it up and put in a couple more caps I forgot to put in when I was first rushing to get it up and running, then will get some pics and more impressions posted. Finding time atm is hard with all this sunshine we are having over here. 25 degrees today, and been like that for the last 10 days, god bless global warming


----------



## BoilermakerFan

Quote:


  Originally Posted by *fault151* /img/forum/go_quote.gif 
_Ok cheers, ill give rs components a try. 

 Yeh i was just thinking of doing something very similar to what you suggested. I think the nylon spacers would be my best bet. Cheers._

 

I have a bunch from PC building too. Let me take an inventory this weekend to see how many I have left after mounting all my boards and I can drop some in the post to you. Do you want five or ten?

 You have my email, so just send me your address.


----------



## fault151

Ive just been told about a local electronics shop near by that i didnt know existed. i'll have a look in there and see what they have, if i can't find anything i'll let you know. Thanks for your help!!!!
	

	
	
		
		

		
		
	


	




 I just need 5.


----------



## Phil Townsend

Yep...The new 12AE6A's bias up real nice and and seem to stay put.
 Thank You
 Phil


----------



## regal

I understand that the load my DAC sees of my Max is 50 kOhm which is determined by the alps pot. Does this vary depending on what position I have the volume set too?


----------



## tomb

Quote:


  Originally Posted by *regal* /img/forum/go_quote.gif 
_I understand that the load my DAC sees of my Max is 50 kOhm which is determined by the alps pot. Does this vary depending on what position I have the volume set too?_

 

No, I don't think so. A pot is a voltage divider. The signal either goes through the rest of the circuit or to ground, depending on the position of the knob. However, I think that means anything connected before it will still see a total of 50K ohms.


----------



## tomb

FYI - the Neutrik NMJ6HCD2 headphone jack is back in stock at Mouser. I should have them at Beezar.com soon, too.


----------



## tomb

Another update:

 The United States Postal Service has changed their rate structures again (5/12/2008), including the API's that people use to run webstores. I'm working on it, but please send me an e-mail if any of you have issues with the shipping prices/options on beezar.com. This might apply to other businesses you shop at, so please keep it in mind if you see something strange.

 Thanks.


 EDIT: Fixed now - gotta love the Post Office.


----------



## ruZZ.il

Thanks guys! 
	

	
	
		
		

		
		
	


	



 Though I must be forward with you all, that combination process is not what's taking up the majority of my time (we're only planing on next summer, got time). Most of my energy is depleted in classes, leaving me feeling pretty doped by the end of the day. I wonder who can guess what we're studying now  Hopefully it'll be able to benefit us all someday 
	

	
	
		
		

		
		
	


	



 Regarding my lady, she's totally cool with this hobby 
	

	
	
		
		

		
		
	


	




 she's been rocking away with her mini^3 and vibes for a while now.. Anyway, once I re-charge, I'm bound to be back


----------



## Snicewicz

I am getting excited for this already. Going to see if I can take this on during the summer after I build my starving student version. 

 Im working my way up the ladder...


----------



## tomb

Quote:


  Originally Posted by *Snicewicz* /img/forum/go_quote.gif 
_I am getting excited for this already. Going to see if I can take this on during the summer after I build my starving student version. 

 Im working my way up the ladder..._

 

Good! We should have most of the non-standard parts for you at beezar. I haven't done that for the Starving Student, but am thinking about it.


----------



## soloz2

question for those who have used Alien DACs, figured I'd ask here since it's pertentant to my next max build.

 I'm wondering if anyone knows if an Alien DAC would be better than my Auzen Prelude (opa627 op-amps). I'll have more than enough room in my next build and I have a few boards so I was considering throwing one in.


----------



## tomb

Quote:


  Originally Posted by *soloz2* /img/forum/go_quote.gif 
_question for those who have used Alien DACs, figured I'd ask here since it's pertentant to my next max build.

 I'm wondering if anyone knows if an Alien DAC would be better than my Auzen Prelude (opa627 op-amps). I'll have more than enough room in my next build and I have a few boards so I was considering throwing one in._

 

I really love the Alien DAC and think that it's entirely appropriate for the MAX, but it doesn't test as well as many commercial DACs, the Auzen Prelude sound card included. Looking at the RMAA for the Auzen on techgage.com, it runs -118dBA noise and dynamic range, with 0.0001% THD. It sounds like they were complaining about some of that and the frequency response - suggesting there were driver issues - but all the figures are better than the Alien.

 That said, one of the reasons I think the Alien is so appropriate for the MAX is that the reaction is similar to the MAX - it may not test as well as many competitive devices, but the listening is superior in many cases. For instance, the Alien doesn't test nearly as well as an M-Audio Transit that I have, but the Alien sounds much, much better - IMO.

 I'd suggest that you try to get a listen of the Alien and decide for yourself. There may be someone who's listened to both that will post in the meantime, but you may have better luck posting the question somewhere in the Head-Fi Equipment section.


----------



## amphead

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_I really love the Alien DAC and think that it's entirely appropriate for the MAX, but it doesn't test as well as many commercial DACs, the Auzen Prelude sound card included. Looking at the RMAA for the Auzen on techgage.com, it runs -118dBA noise and dynamic range, with 0.0001% THD. It sounds like they were complaining about some of that and the frequency response - suggesting there were driver issues - but all the figures are better than the Alien.

 That said, one of the reasons I think the Alien is so appropriate for the MAX is that the reaction is similar to the MAX - it may not test as well as many competitive devices, but the listening is superior in many cases. For instance, the Alien doesn't test nearly as well as an M-Audio Transit that I have, but the Alien sounds much, much better - IMO.

 I'd suggest that you try to get a listen of the Alien and decide for yourself. There may be someone who's listened to both that will post in the meantime, but you may have better luck posting the question somewhere in the Head-Fi Equipment section.
	

	
	
		
		

		
		
	


	


_

 

You guys with the Alien DACs keep tempting me to build one, because I rely on whatever DAC is in the latest Sony Walkman Mp3 player. It's very nice with some eq, but Alien DAC and the MAX, would be a nice way to go.  Are these boards being baked in the cookie oven for SMD?  It would be my first excursion into SMT. Edit: I know what you mean Tom, sometimes the specifications from an engineering white paper, don't necessarily translate into what we perceive with our ears, as being more musical.


----------



## tomb

Quote:


  Originally Posted by *amphead* /img/forum/go_quote.gif 
_You guys with the Alien DACs keep tempting me to build one, because I rely on whatever DAC is in the latest Sony Walkman Mp3 player. It's very nice with some eq, but Alien DAC and the MAX, would be a nice way to go.  Are these boards being baked in the cookie oven for SMD?  It would be my first excursion into SMT. Edit: I know what you mean Tom, sometimes the specifications from an engineering white paper, don't necessarily translate into what we perceive with our ears, as being more musical._

 

Jeff Rossel sells the Alien DAC in kits - with the option of having the PCM chip pre-soldered. The rest is easy enough if you've ever fooled with SOIC-8 opamps or Steinchen's Millett DB board - that's how several of us cut our teeth on SMD resistors. Tangent's tutorial video on soldering SMD is indispensible, too. Good tweezers - I mean a nice, professional pair - something like $7-$10 worth - will help a lot. I like the kind with curved tips. They just seem to work with how my hands like to grip things and place them. One of those flux pens also helps - the stuff is so sticky it almost glues the parts in place so that you can solder them. 
	

	
	
		
		

		
		
	


	




 I've read in some posts lately that maybe Jeff is having trouble getting the regulator chips that are needed, so I don't know the latest status on availability.


----------



## slowpogo

I know you've spoken some about the Alien DAC's sound already tomb, but how do you think it compares to a typical consumer CD player/DVD player? Is it at least better than what you might hear coming out of a $100 Sony DVD player?


----------



## tomb

Quote:


  Originally Posted by *slowpogo* /img/forum/go_quote.gif 
_I know you've spoken some about the Alien DAC's sound already tomb, but how do you think it compares to a typical consumer CD player/DVD player? Is it at least better than what you might hear coming out of a $100 Sony DVD player?_

 

... more detail by miles. With BG's, it's quite superior to the stock Sony SCD-CE595, for instance. Some of the guys say it sounds even better with a couple of boutique film caps on the output, but I haven't tried that, yet - sort of. I do have an Alien using ES electrolytics on the output and they're bypassed with Sonicap GEN II's - that one is superior, too, but just a tad below the BG Aliens.

 It has a bit of background hiss when directly compared to a quality CD player - on the order of -90dB vs. -100dB. Most will never notice it unless you make direct comparisons and you're searching for it - also high-efficiency cans or IEMs. However, I know how sensitive your ears are though, so thought it worth mentioning.

 I still recommend one for everybody and they are perfect for many MAXes.


----------



## Daveze

A little update to my Max, I replaced the Vishay's that Jeff has for the RB14L/R with a pair of 100 Ohm Kiwames (yes Tom, those same ones I bought quite a while ago). I'm not going to try and quantify the change, just going to say that it sounds even nicer now.

 I really enjoy this amp.


----------



## tomb

Tube dampers are now available at beezar.com:















 Note that these will also fit the 19J6's on the Starving Student Millett.
	

	
	
		
		

		
		
	


	




 The Neutrik NMJ6HCD2 headphone jack is also available, but as I mentioned previously, Mouser has them in stock now, too. Hopefully beezar will provide an alternative if they run out again or if it helps save some shipping.


----------



## soloz2

tomb, know when you'll have more 2SC2238 in stock?


----------



## tomb

Quote:


  Originally Posted by *soloz2* /img/forum/go_quote.gif 
_tomb, know when you'll have more 2SC2238 in stock?_

 

Don't hold your breath.
	

	
	
		
		

		
			





 I had another episode this week of MCMinone sending me a bunch of CDIL brand 2SC2238's. They have something like 110 of them on order - about 3/4 of that are for me and beezar.

 Nothing's definite, though. I call up from time to time to check on the status of my outstanding order. When I did that this past week, the guy told me they had 30 in stock - I said, "Send them." Turns out, they were the same CDIL's that I had returned a couple of months ago. 
	

	
	
		
		

		
		
	


	




 I will keep suggesting the 2SC2344/2SA1011's - they are very, very close.


----------



## soloz2

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Don't hold your breath.
	

	
	
		
		

		
		
	


	




 I had another episode this week of MCMinone sending me a bunch of CDIL brand 2SC2238's. They have something like 110 of them on order - about 3/4 of that are for me and beezar.

 Nothing's definite, though. I call up from time to time to check on the status of my outstanding order. When I did that this past week, the guy told me they had 30 in stock - I said, "Send them." Turns out, they were the same CDIL's that I had returned a couple of months ago. 
	

	
	
		
		

		
		
	


	




 I will keep suggesting the 2SC2344/2SA1011's - they are very, very close._

 

I've been using the 2sc3422/2sa1359 with Muse ES, but think I'm going with some Blackgates for my next build. So the 2SC2344/2SA1011's are about the same with Blackgates?


----------



## tomb

Quote:


  Originally Posted by *soloz2* /img/forum/go_quote.gif 
_I've been using the 2sc3422/2sa1359 with Muse ES, but think I'm going with some Blackgates for my next build. So the 2SC2344/2SA1011's are about the same with Blackgates?_

 

Yep - they seem just as detailed with an excellent low end and midrange. Overall, they're somewhat laid back and neutral with just a tad brightness - but they give up nothing in the low end and midrange.

 Eokboy just installed a set on a PPAV2 - he seems to like them:
http://www.head-fi.org/forums/4206697-post7.html


----------



## agutt

Hey All, 

 I am building my first millet, which is my firs project using AC current. Other than this I have only built speakers. I am doing the diamond buffer, along with the VitaminQ tweak. I have just a few questions...

 When jumping resistors for the Diamond Buffer, what type of wire should be used?

 I have seen on some finished models "handle like" looking things on the top of the cases around the tubes. What are these, and where do I get them because the look awesome?

 I have a "newer" version of the PCB, and there are two extra terminal block mounts next to the Volume knob, and the 1/4" out. What are they for???? They were not on my parts list?????

 Any of you seasoned builders have any advice for me?


 Thanks a bunch. An apologies if this has already been posted. I have combed through the pages on this thread, but there are far too many for me to look through them all.

 Cheers

 Agutt


----------



## tomb

Quote:


  Originally Posted by *agutt* /img/forum/go_quote.gif 
_Hey All, 

 I am building my first millet, which is my firs project using AC current. Other than this I have only built speakers. I am doing the diamond buffer, along with the VitaminQ tweak. I have just a few questions..._

 

Congrats - you'll love it.
  Quote:


 When jumping resistors for the Diamond Buffer, what type of wire should be used? 
 

Use the same hard wire leads that you snip off of the resistors when you solder them into the board. You'll have plenty to pick from in no time.
	

	
	
		
		

		
		
	


	



  Quote:


 I have seen on some finished models "handle like" looking things on the top of the cases around the tubes. What are these, and where do I get them because the look awesome? 
 

They're called cabinet wire-pulls. IOW, a cabinet or drawer handle. The brushed-chrome versions can be found in almost every Home Depot or Lowes. I've included a dimensioned drawing for locating and drilling these into the top plate on the MAX website at Construction -> Drawings and Templates The link to the exact file is here: http://www.diyforums.org/MAX/constru...e-rollbars.pdf
  Quote:


 I have a "newer" version of the PCB, and there are two extra terminal block mounts next to the Volume knob, and the 1/4" out. What are they for???? They were not on my parts list????? 
 

The newly revised BOM - on 4/16/2008 - includes a note on these and in the BOM: MAX BOM. They are simply optional terminal blocks if you want to use them, but are not necessary. It depends on what you want to do.

 At the headphone jack, they make an easy connection to an additional headphone jack. Or, since the headphone jack is switched, a terminal block at that position is the perfect way to wire a set of pre-amp out jacks. The pre-amp out jacks would be hot unless a set of headphones were plugged in.

 The additional terminal block at the volume pot simply offers a second point of signal input that bypasses the traces in the board. For instance, I've just about finished the design for putting an Alien DAC under the board. However, there's no room for the signal input terminal block in the back. So, I will run the L,R,G wires from the connections at the back plate underneath the board and connect to the terminal block at the volume pot installed upside down beneath the board.

 They just give you many more options of wiring up the MAX, depending on what you need.
  Quote:


 Any of you seasoned builders have any advice for me? 
 

Everything's pretty straightforward if you follow the MAX website. Be sure you read all the sections in the "Tweaks" area. Also, be sure you read everything about biasing the buffers at Setup and Biasing. Most of the adjustments are not critical, but that doesn't apply to the diamond buffer - you need to be cautious, adjust a little bit at a time, measure, wait, measure, then adjust again.

 BTW - if you're using the brown sausage Vishay-Dale resistors, be sure you install them with the number rating up. If you get one misplaced, it's almost impossible to measure them when installed into the board, due to the paralleling. That rating designation may be the only way to confirm they're the right part if you run into trouble. Be careful and take your time when installing the parts for the diamond buffer - there's a lot of little parts and it gets easy to mix them up. Quote:


 

 Thanks a bunch. An apologies if this has already been posted. I have combed through the pages on this thread, but there are far too many for me to look through them all.

 Cheers

 Agutt 
 

Good luck - we're here to help!!


----------



## agutt

Thanks Tomb!

 Much appreciated!

 So I am running audio out of my digi002 (A pro-tools hardware interface) which allows me to use their D/A converters. So if I wanted to use that as a second RCA input, I just wire some RCA plugs to that terminal block and it is just the same as the one in the back?

 and also where is a good place to get a nice pan pot knob? I have seen some nice looking silver machined ones

 Thanks again!


----------



## ruZZ.il

Quote:


  Originally Posted by *agutt* /img/forum/go_quote.gif 
_ ... So if I wanted to use that as a second RCA input, I just wire some RCA plugs to that terminal block and it is just the same as the one in the back?..._

 

The input by the POT is a parallel of the input at the back, so its not quiet a second RCA input* but rather another first one  Its there for convenience. if you want multiple inputs, there are mechanical input selection dials/knobs or things like a digital input selection board, even one designed by a user here(if you're really interested, we'll find it)..

 There are even some decent knobs at mouser, but you'll find a plethora of recommendations if you search the forum, and even this thread.
 (like here or here. Allot of the ones you may have seen here are from PartsPipe(on ebay))

 -R

*[size=xx-small](ie, don't connect one sources output directly to another sources output. not even a left and right binding mono kind of thing, unless you use some resistors and stuff yada yada, but generally, don't)[/size]


----------



## BoilermakerFan

I wanted to post a few teaser shots of my upcoming MAX build...

 The case is the NABU recommended by Pabbi. The PSU side will be reworked or gutted to fit a custom torroid trafo with multiple taps of various voltages.

 You guys should recognize the MAX board, the rest of the cardboard templates are locators for the other other PCBs that will be installed. The Darwin input selector board is at the far right, but it will be mounted vertically, not flat, to allow for better wire routing. 

 This is the first of three similar builds, but each will be a little different.

 On to the pics, but these are it until it's finished 
	

	
	
		
		

		
		
	


	




 :


----------



## soloz2

BoilermakerFan, what torrid do you plan to use? I've been looking into adding a USB DAC and source selector to my next Max build as well, but have been leaning towards a USB powered USB DAC to avoid needing a second power supply, or a large torrid. I'm interested in your approach to the matter.


----------



## BoilermakerFan

Quote:


  Originally Posted by *soloz2* /img/forum/go_quote.gif 
_BoilermakerFan, what torrid do you plan to use? I've been looking into adding a USB DAC and source selector to my next Max build as well, but have been leaning towards a USB powered USB DAC to avoid needing a second power supply, or a large torrid. I'm interested in your approach to the matter._

 

A custom wound torroid from the guys in GA (Victoria Magnetics). 100VA at 24VAC for the MAX, 300VA at 22VACx2 or 26VACx2, 100VA at 15VACx2, and 50VA at 8.5VAC. 

 I won't be using a USB DAC in this build, but my second will have a NOS USB DAC that requires several different AC supply voltages. 

 The third build will be really crazy and will need more power and additional voltages, but it will be installed in two separate NABU cases to keep things cleaner.

 - BMF


----------



## BoilermakerFan

Hey guys, if you're only planning to build in an Alien DAC, it's powered by the USB so a custom torroid isn't required.

 The Darwin Source Selector (60mA draw) or SKA OptiVol (18mA draw) can be powered from the MAX board center LED tap if you use of the new 40VA or 50VA wall warts from Beezar.com and keep the bias on the BJTs at a reasonable level (required with the 1-1/2" heat sinks). 

 I have few components that will be drawing a fair amount of power from time to time, but most are lower power. I'm giving the MAX 100VA just to make sure it has a lot of headroom because I'll be running much higher bias levels on 2-1/2" heatsinks and I'm powering the Darwin and OptiVol from the 27VDC center LED tap, but I have the option of using the rectifier/regulator board from the NABU to produce about an amp of 5VDC too, which might come in handy for some other discrete-based projects. 
	

	
	
		
		

		
		
	


	




 Just trying to help keep your costs down, or at least allow you guys to spend the money on boutique parts that will make a much bigger impact on the sound. 
	

	
	
		
		

		
		
	


	




 - BMF


----------



## agutt

Quote:


  Originally Posted by *ruZZ.il* /img/forum/go_quote.gif 
_The input by the POT is a parallel of the input at the back, so its not quiet a second RCA input* but rather another first one  Its there for convenience. if you want multiple inputs, there are mechanical input selection dials/knobs or things like a digital input selection board, even one designed by a user here(if you're really interested, we'll find it)..

 There are even some decent knobs at mouser, but you'll find a plethora of recommendations if you search the forum, and even this thread.
 (like here or here. Allot of the ones you may have seen here are from PartsPipe(on ebay))

 -R

*[size=xx-small](ie, don't connect one sources output directly to another sources output. not even a left and right binding mono kind of thing, unless you use some resistors and stuff yada yada, but generally, don't)[/size]_

 

Thanks for the help, I found a very nice knob. I am interested in that selection switch. Basically I am looking to have 2-3 RCA Inputs with a switch, feed in to the inputs of my Millet. I have no idea what kind of switch I would need to get. I have been looking around in the forums, but couldn't come up with much. Any help would be great!

 -A


----------



## soloz2

well the enclosure I plan to use is 12"x12"x3" so I don't have loads of room.

 I'm already planning to pull power for an OptiVol from the center LED tap.

 I'd like to include a USB DAC, but due to wanting to keep costs down and while I have entertained just going all-out and getting a multi-tap torrid so I could get a better DAC that would likely double or triple the parts I have left to purchase.
 This has lead me to the conclusion that a USB powered USB DAC would likely be the way to go. I already have an Alien DAC board and parts are not too expensive so I could easily add a boutique Alien DAC.
 I was also looking at rotary selector switches to be able to switch 3 inputs and 1-2 outputs (inputs: DAC, analog from soundcard, extra) (outputs: Max, output for DAC)

 I already have a Triad 24vac 1000mA walwart I was planning on using, which should be enough for the Max and OptiVol.
 However, were I to choose a Darwin I'd probably need to get one of the larger walwarts from Beezar. How would it work to draw multiple taps from the same location?


----------



## BoilermakerFan

Quote:


  Originally Posted by *soloz2* /img/forum/go_quote.gif 
_well the enclosure I plan to use is 12"x12"x3" so I don't have loads of room.

 I'm already planning to pull power for an OptiVol from the center LED tap.

 I'd like to include a USB DAC, but due to wanting to keep costs down and while I have entertained just going all-out and getting a multi-tap torrid so I could get a better DAC that would likely double or triple the parts I have left to purchase.
 This has lead me to the conclusion that a USB powered USB DAC would likely be the way to go. I already have an Alien DAC board and parts are not too expensive so I could easily add a boutique Alien DAC.
 I was also looking at rotary selector switches to be able to switch 3 inputs and 1-2 outputs (inputs: DAC, analog from soundcard, extra) (outputs: Max, output for DAC)

 I already have a Triad 24vac 1000mA walwart I was planning on using, which should be enough for the Max and OptiVol.
 However, were I to choose a Darwin I'd probably need to get one of the larger walwarts from Beezar. How would it work to draw multiple taps from the same location?_

 

If you are going to use an Alien DAC, why would you want to use the analog output from your soundcard? Unless you have a higher end 24/96 or 24/192 soundcard, I wouldn't bother with the analog outs from the card. You can just use the USB to send the digital signal from your PC to the DAC. That would allow you to use a simple DPDT toggle switch for the inputs and the same for the outputs, much easier, and much cheaper. The Triad will be plenty of power for the MAX and OptiVol if your using BJTs or MOSFETS at the recommended bias levels. The Darwin would be overkill for your application since it supports 6 inputs and 2 outputs standard, or can be reconfigured to 7-in and 1-out. I have a TT, CDP, iPod, XM, FM Tuner, and PC sources so I needed the Darwin for this first build. My second will just be a DAC and TT, so I'll just use DPDTs.


----------



## soloz2

Quote:


  Originally Posted by *BoilermakerFan* /img/forum/go_quote.gif 
_If you are going to use an Alien DAC, why would you want to use the analog output from your soundcard? Unless you have a higher end 24/96 or 24/192 soundcard, I wouldn't bother with the analog outs from the card. You can just use the USB to send the digital signal from your PC to the DAC. That would allow you to use a simple DPDT toggle switch for the inputs and the same for the outputs, much easier, and much cheaper. The Triad will be plenty of power for the MAX and OptiVol if your using BJTs or MOSFETS at the recommended bias levels. The Darwin would be overkill for your application since it supports 6 inputs and 2 outputs standard, or can be reconfigured to 7-in and 1-out. I have a TT, CDP, iPod, XM, FM Tuner, and PC sources so I needed the Darwin for this first build. My second will just be a DAC and TT, so I'll just use DPDTs._

 

I want to be able to use the analog out from my soundcard for gaming/video. I have an Auzen X-Fi Prelude, so I'd only use the USB DAC for music.

 I know the Darwin would be a bit overkill, but I've been looking at prices for some nice rotary switches at about $40 for the ones I'm looking at the Darwin does seem nice as it will allow me to have shorter signal paths.


----------



## BoilermakerFan

Quote:


  Originally Posted by *soloz2* /img/forum/go_quote.gif 
_I want to be able to use the analog out from my soundcard for gaming/video. I have an Auzen X-Fi Prelude, so I'd only use the USB DAC for music.

 I know the Darwin would be a bit overkill, but I've been looking at prices for some nice rotary switches at about $40 for the ones I'm looking at the Darwin does seem nice as it will allow me to have shorter signal paths._

 

Gotcha, the X-Fi supports the EAX sound effects through 2-channel headphones if you use the analog outputs...

 Yep, the best feature of the Darwin is that the selector switches aren't in the signal path.


----------



## soloz2

Quote:


  Originally Posted by *BoilermakerFan* /img/forum/go_quote.gif 
_Gotcha, the X-Fi supports the EAX sound effects through 2-channel headphones if you use the analog outputs...

 Yep, the best feature of the Darwin is that the selector switches aren't in the signal path._

 

If I'm looking at the control wiring diagram correctly, if I decide to only have 1 output I can just use the one rotary selector and only worry about switching the input correct?


----------



## ruZZ.il

Quote:


  Originally Posted by *agutt* /img/forum/go_quote.gif 
_.. I am interested in that selection switch. Basically I am looking to have 2-3 RCA Inputs with a switch, feed in to the inputs of my Millet. .._

 

You seem to be here at the right time, and in the midst of a relating conversation  I'm not sure how much DIY experience you have, but one of the rotary selection switches may be the simplest to figure out... though the digital ones, following instructions, cant be too hard..


----------



## BoilermakerFan

Quote:


  Originally Posted by *soloz2* /img/forum/go_quote.gif 
_If I'm looking at the control wiring diagram correctly, if I decide to only have 1 output I can just use the one rotary selector and only worry about switching the input correct?_

 

Yes, you should be able to do that, but I haven't looked at mine close enough to tell you which wires need to be jumpered together. I actually "cheated" and ordered the balanced kit so I need to order another set of Alpha rotary switches and different multi-conductor cables to make two separate SE boards. I'll have to look more closely at it, but I probably already have the cables in my "project" box.


----------



## tomb

User c0nsumer built that digital input switch for his MAX, but he hasn't posted for a long time and I'm not sure he ever finished programming it. It might be worth sending him an e-mail, though:
Audio Input Switch - nuxx.net


----------



## BoilermakerFan

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_User c0nsumer built that digital input switch for his MAX, but he hasn't posted for a long time and I'm not sure he ever finished programming it. It might be worth sending him an e-mail, though:
Audio Input Switch - nuxx.net




_

 

Programming! 
	

	
	
		
		

		
		
	


	




 The Darwin is just good ol' relays for input switching. 

 Soloz, the Darwin can be jumpered for a single output right at the board, but you'll need to modify your ribbon cable or make your own twisted pairs and solder directly to the PCB which is a little tight, but would be easy enough with a smaller tip on the soldering iron. I'm definitely going to use multi-conductor cable or make my own twisted pairs and Lintz braid them to run to the selector switches. If you want to hardwire everything, you would be better off just buying the PCBs and the rest of the components from Mouser or Digi-Key. That's why I ordered the Balance kit instead of two Se kits.

 - BMF


----------



## tomb

Quote:


  Originally Posted by *BoilermakerFan* /img/forum/go_quote.gif 
_Programming! 
	

	
	
		
		

		
		
	


	




 The Darwin is just good ol' relays for input switching.</snip>_

 

Yes, well, I'm not promoting it, but there were several who seemed interested in it at the time.

 There's also a similar version, I think, from that guy on ebay that sells DIY PCB boards ... DIY Gene or something like that.


----------



## BoilermakerFan

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Yes, well, I'm not promoting it, but there were several who seemed interested in it at the time.

 There's also a similar version, I think, from that guy on ebay that sells DIY PCB boards ... DIY Gene or something like that._

 

The programmable version would be great in combination with other I2P communication parts such as the soon to be released TPA Joshua Tree Attenuator and it's compatibility with VFD displays. But for just source switching as a stand alone device, it's overkill - "not that there is anything wrong with that, Seinfeld."

 Let's just say this "might" be part of my plan for my second MAX build for my office. 
	

	
	
		
		

		
		
	


	




 - BMF


----------



## pinkfloyd4ever

I think the darwin is programmed too, it just comes preprogrammed from brian & russ so the user doesn't really have to do any programming


----------



## BoilermakerFan

Quote:


  Originally Posted by *pinkfloyd4ever* /img/forum/go_quote.gif 
_I think the darwin is programmed too, it just comes preprogrammed from brian & russ so the user doesn't really have to do any programming_

 

The Darwin is strictly a relay-based I/O switch with resistors and diodes to prevent pops and back-feeds/cross-feeds. 

 Their Joshua Tree however, is a relay-based, programmed attenuator.


----------



## DrizzitT

So...

 I'm planning on ordering parts to build a Millet Max today (pending parts approval of my co-projectee). Ordering seems more or less straight forwards off the BOM until QB9 L/R and QB8 L/R. In the BOM there's two NPN/PNP transistor options given, but both are calculated into the final price. I looked at the schematic and there's only 1 transistor in each required location... I assume we only need one of the choices? (ie, not both the MJE AND the BD?). I plan on utilizing some of the more expensive transistors, but I just want to make sure I'm not missing any of the parts after I order them.


----------



## fault151

Hi guys, just wanted to ask a quick question, i seem to be getting a lot of hum and interference through my millet. Could it be to do with grounding? Does it need to be grounded? When i touch the volume knob i can here more hum. Its a bit annoying because im sure its something that happened just recently. 

 Any ideas???

 Thank you


----------



## MrMajestic2

Quote:


  Originally Posted by *fault151* /img/forum/go_quote.gif 
_Hi guys, just wanted to ask a quick question, i seem to be getting a lot of hum and interference through my millet. Could it be to do with grounding? Does it need to be grounded? When i touch the volume knob i can here more hum. Its a bit annoying because im sure its something that happened just recently. 

 Any ideas???

 Thank you_

 

Grounding the pot should fix it.


----------



## tomb

Quote:


  Originally Posted by *MrMajestic2* /img/forum/go_quote.gif 
_Grounding the pot should fix it._

 

Good suggestion. However - if it doesn't, check the signal ground on the pinput terminal block. I've some isolated cases where the solder didn't wick through to the top - where the connection to the ground plane is. If the signal ground is not properly grounded, it'll play a racket almost constantly.


----------



## fault151

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Good suggestion. However - if it doesn't, check the signal ground on the pinput terminal block. I've some isolated cases where the solder didn't wick through to the top - where the connection to the ground plane is. If the signal ground is not properly grounded, it'll play a racket almost constantly._

 

cheers for your replies. i am getting a constant noise. I'll try the pot first and see how it goes. I'll do it at the weekend so bare with me. I'll let you know if i manage to solve it. Thanks guys!!!


----------



## rhester

I need some help. Messing around with the casing last nite on my Mosfet max and seem to have done some damage that I can't find. I get 28V in but getting 25.3V to TA2R adn TA2L and can't adjust that at all. LEDs are all on but apparently no voltage to the tubes as they never heat up. Any ideas where to start troubleshotting?


----------



## tomb

Quote:


  Originally Posted by *rhester* /img/forum/go_quote.gif 
_I need some help. Messing around with the casing last nite on my Mosfet max and seem to have done some damage that I can't find. I get 28V in but getting 25.3V to TA2R adn TA2L and can't adjust that at all. LEDs are all on but apparently no voltage to the tubes as they never heat up. Any ideas where to start troubleshotting?_

 

Maybe R1 broke loose? Measure voltage across R1 and see what you get. The LEDs are powered separately right off the PS, so if they light it doesn't mean anything. However, if the heaters on the tubes don't light, then you'll never be able to bias them. Somewhere you lost continuity with the in-series heater circuit between the two tubes. The only thing that's connected into that trace is R1.


----------



## BoilermakerFan

Well guys, after a few phone calls and emails, I still haven't heard back from Victoria Magnetics, but the email doesn't bounce back either. It's not looking good. 
	

	
	
		
		

		
		
	


	




 So I may have to track down another custom trafo manufacturer or go to separate units for even more $$$. I'm not quite ready to start winding my own transformers... yet, but I'm starting the research. 

 Have a great weekend everyone!


----------



## ruZZ.il

Quote:


  Originally Posted by *BoilermakerFan* /img/forum/go_quote.gif 
_... yet, but I'm starting the research. 

 Have a great weekend everyone!_

 












 Thanks, you too!


----------



## amphead

If you start winding your own xformers. Wind some toroids, as they can be mounted closer to the other components. Have a nice weekend!


----------



## BoilermakerFan

Thanks guys! Cracked open (and finished) a bottle of Dogfish Head "Chateau Jiahu" so the weekend is officially started! 

 Spun a little vinyl on the Pro-Ject TT tonight through the Kenwood receiver. Wifey wants to see some progress on the amp build now, so hopefully I can get some time in the garage with a soldering iron this extended weekend.


----------



## pinkfloyd4ever

Quote:


  Originally Posted by *BoilermakerFan* /img/forum/go_quote.gif 
_Wifey wants to see some progress on the amp build now_

 

you sir are a lucky man


----------



## tomb

Quote:


  Originally Posted by *pinkfloyd4ever* /img/forum/go_quote.gif 
_you sir are a lucky man_

 

I'm not so sure about that. It sounds like she's pushed him and his soldering iron out to the garage.


----------



## BoilermakerFan

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_I'm not so sure about that. It sounds like she's pushed him and his soldering iron out to the garage. 
	

	
	
		
		

		
		
	


	


_

 

It's not that bad. The beer fridges and dart board are out in the garage too. Had a nice little stereo system out there, but my daughter's CD player broke so it was moved into her room. No tunes in the garage until I get these amps built!

 I need to build my vent hood and new work bench, then I can move into the basement... BUT, the beer fridge will still be out in the garage. Too many projects, I just want to get my first two builds done (although the second one is waiting on MOSFETS from a certain online supplier that supports this thread... 
	

	
	
		
		

		
		
	


	




 ).


----------



## tomb

Arrggh - what a blatant hint.


----------



## agutt

Hey all,

 So as i continue to assemble my Millett MAX, I have come across another question. I am using white LEDS to illuminate the tubes. I would also like to use a white LED on the front panel, but I am having trouble finding a white led that has a 60 MCD output. Does it matter what kind of LED I use? Or can I use the same LED that I used on the tubes for the panel LED??

 Thanks!


----------



## Beefy

Quote:


  Originally Posted by *agutt* /img/forum/go_quote.gif 
_Or can I use the same LED that I used on the tubes for the panel LED??_

 

You can use the same LED, but you will have to use a much higher resistance at RA5C. Think 10kohms instead of 2kohms at RA5L/R.

 However, consider that LEDs you will use for the tubes have a very narrow viewing angle. Not the best for a front panel, where you want a wide viewing angle.


----------



## tomb

Get some Testor's DullCoat from Walmart in the toy model section. It will give the LED a diffuse coating and improve that angle issue.


----------



## Beefy

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Get some Testor's DullCoat from Walmart in the toy model section. It will give the LED a diffuse coating and improve that angle issue._

 

HEH! What a great idea!


----------



## BoilermakerFan

Hey guys, Greg at SKA emailed me to let me know the PCBs for the OptiVols are in. Mine are shipping tomorrow. I've been waiting over a week for a kit from Canada, so who knows how long it will take these to show up for Australia, but I ordered one assembled and tested, and one kit. I'll post a pic of the assembled and tested one, but it's not going to be used in my first build, it's going in the second build, the special MOSFET-MAX.


----------



## agutt

Thanks for the LED help! The build should be done by next week, so I'll put pics up asap...


----------



## agutt

I have found a White LED at radioshack that has a 20mA rating, which is the same as the LED on the BOM. So I should have no problems with this one correct?

 The MCD is rated at 1100, and the "Typical Voltage" is 3.6V

 I would like to avoid having to swap out my resistors since I have soldered them in already...

 Clearly my understanding of this in terms of electronics is poor...any explanation would be a great help!


----------



## Beefy

Quote:


  Originally Posted by *agutt* /img/forum/go_quote.gif 
_I have found a White LED at radioshack that has a 20mA rating, which is the same as the LED on the BOM. So I should have no problems with this one correct?_

 

It will work fine. It will just be very, very bright behind the default 2kohm resistor.

 As a comparison, I have a 300mcd diffused blue LED on my Max front panel behind a 10kohm resistor. This is borderline too bright for me......


----------



## agutt

I am going to try the dull coat, and if that is to bright, Ill swap the resistor.

 Thanks Beefy


----------



## tomb

Quote:


  Originally Posted by *agutt* /img/forum/go_quote.gif 
_I have found a White LED at radioshack that has a 20mA rating, which is the same as the LED on the BOM. So I should have no problems with this one correct?

 The MCD is rated at 1100, and the "Typical Voltage" is 3.6V

 I would like to avoid having to swap out my resistors since I have soldered them in already...

 Clearly my understanding of this in terms of electronics is poor...any explanation would be a great help!_

 

The LED positions on the MAX are fed with V+ voltage, whatever you've set for that. Most use the recommended 27VDC. The LED and the LED resistor are in series, so they will share that full voltage. Meanwhile, whatever current flows through them will be the same for both. Ohm's Law establishes this relationship as V = I*R. So, if V is 27VDC, then we can establish "I" by choosing the correct value for R. If we were sizing it for the full current rating of the LED you mention above (it's typical), then we'd use 0.02A (20ma) for "I". Then R = 27VDC/0.02, or 1350 ohms.

 Now, we don't really want to set a resistor for exactly that amount, because we can't be too sure of the rest of the components. If that 20ma is an absolute rating and our resistor is 5% low, then more current will flow and the LED might burn out pretty quickly.

 That said, there is another factor to consider and that is the power handling ability of the resistor. Power = I^2 * R. For the values we just arrived at, Power = (0.02^2) * 1350, or 0.54W. Unfortunately, resistor power ratings go in fractional increments like 1/8, 1/4, 1/2, and 1W. So, for 0.54W, we'd need to use a 1W resistor. Even then, if anything was the slightest bit off, the LED would still burn out.

 Luckily, the brightness curve for an LED is not really proportional. I don't know what it is exactly, but experience seems to indicate you can probably get at least 3/4 of the maximum brightness rating at 1/2 current. If we use 10ma up there as the current - so as to assume a decent safety factor on burning out the LED - then R = 27VDC/0.01A = 2700 ohms.

 That's an odd resistor size, so let's pick a 2K resistor and see how that works. I = V/R, so I = 27VDC/2000 = 13.5ma. Hmm not too bad - still a decent safety factor, but with a standard-issue, common resistor size. If we check the power equation, then P = (0.0135^2) * 2000, or P = 0.365W. That's a bit more than 1/4W, but plenty below 1/2W to allow for a decent safety factor.

 Hence, we chose 2K - 1/2W resistors for the LED positions.

 You can follow the same logic by setting a higher resistor for a super-bright LED in order to knock down the brightness to something reasonable for a panel LED. Let's say we used the 10K resistor. Then we have I = 27/10000, or I = 2.7ma. Checking for power, we'd have P = (0.0027^2) * 10,000, or P = 0.073W. Power should have a much higher safety factor (extreme failure could result in flames), so even though a 1/10W resistor might work, a 1/4W would probably be better.

 Hope that clears up some of your question.


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## agutt

tomb...you are the man. Thankyou!


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## agutt

OK so I did some math...

 Since my LED runs at 1100MCD I want to run this at about 10%.

 which would mean 2mA. Plug that into the math...

 P=IR 27=.002*R
 R=13500 ohms... again an odd resistor size so I will jump to either 15K or 10K

 For 15K I get...

 I=V/R
 I=27/15000
 I=1.8 mA (close to my desired 2mA)

 Therefore:

 P=(I^2)R
 P=(.0018^2)15000
 P=.048W

 Now this value is well under 1/8 W, BUt at radio shack I cannot find a 1/8W resistor at 15K. Will this work if I use a 1/4W or 1/2W at 15K???

 (If I go for the 10K which I might, It will be very easy to find a resistor, but will be brighter than what I desire)


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## agutt

Also this resistor be getting very hot because of such a huge difference correct?


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## ruZZ.il

agutt:

 No worries with using a higher power rating. Power ratings ~ Max power. Its 'kind' of like saying "this resistor can be heated up to 100 degrees" so heating it up to 70 is fine, and getting one that can go up to 200 is redundant but in this case, harmless and even desirable. 

 Regarding the heat, the lower the current the less heat it will actually produce and the higher the resistor, the lower the current.

 As you've seen, P=(I^2)R and and V=IR (I=V/R) you could substitute the second into the first and get P=(V^2)/R and since V is pretty much constant, P is directly proportionate to 1/R 
 Also, the actual power calculations here give you more margin than you think, since the actual voltage is actually [(V+) - Vled ]~(27-3.6).
 The current can be more accurately calculated with that voltage (Vled can be more accurately obtained from the LED specs per a given current).. but since you dont need such exact values, and its easy to stay within the margins, if you have a ratshack around, it may not hurt to buy one of those cheap resistor assortment packs and play around with it.. 

 -R


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## tomb

Quote:


  Originally Posted by *agutt* /img/forum/go_quote.gif 
_Also this resistor be getting very hot because of such a huge difference correct?_

 

No. Power is what's dissipated from the resistor. Looking at the equation, Power is proportional to the square of the current. Therefore, very tiny current - not much power. Even if the rating of the resistor gets very big, it's not enough to overcome the effect of squaring the current.

 Your calculations show P = 0.048W. That's not quite 50 millwatts. A 1/2W resistor dissipates the same as 500 millwatts.

 BTW, the board will easily accept up to 1/2W resistors for the LED positions. There's no difference in these ranges if the resistor has a higher power rating - as long as it fits in the board.


 EDIT: Uh-oh: dual post again. 
	

	
	
		
		

		
		
	


	




 EDIT2: Umm ... as an ME (meaning this is one of the few things I understand around here), I'm not sure I agree with that analogy, ruZZ.il. The resistor will burn at the same temperature in either case. The difference is that one will take much more power before it reaches that same temperature.
	

	
	
		
		

		
		
	


	




 Still, thanks for the post!


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## slowpogo

I may have missed it, but has anyone had the chance yet to do a direct comparison between the JFET Max and the Mosfet version with the amb mod?


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## ruZZ.il

Fair enough, though it was just 'kind of', anyway.. if I'd gotten into heat dissipation, you'd have beat me to it !


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## agutt

Thanks guys! it helped alot!


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## soloz2

just an FYI, I went to pick up another power jack from RS today and after going to two different stores and only finding the new version, which won't work nearly as well decided to get one to see if the mounting hole was at least the same size, which it isn't. Even if it was it would have to be isolated as it's metal and the ground would ground to the case.

 so the BOM should probably be updated and people encouraged to buy the ones from Mouser.

 here's the new RS version:
RadioShack.com - Cables, Parts & Connectors: Connectors & connectivity: DC power connectors: Size M Panel-mount Coaxial DC Power Jack


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## Beefy

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_So, if V is 27VDC, then we can establish "I" by choosing the correct value for R. If we were sizing it for the full current rating of the LED you mention above (it's typical), then we'd use 0.02A (20ma) for "I". Then R = 27VDC/0.02, or 1350 ohms._

 

Just for my own clarity...... do we have to take the forward voltage of the LED into account? Lets say it is 3V, then we use 24V in the equation, for 1200ohms?


----------



## tomb

Quote:


  Originally Posted by *Beefy* /img/forum/go_quote.gif 
_Just for my own clarity...... do we have to take the forward voltage of the LED into account? Lets say it is 3V, then we use 24V in the equation, for 1200ohms?_

 

Yes - technically, you are correct. However, the exact voltage across the LED is not known for every case (typically it varies depending on the LED color). The direction of the effect of the LED is to lower voltage across the resistor, thereby reducing current. So it adds an additional safety factor that can be ignored in sizing the resistor. That's my own judgment call, though, by trying to pick a resistor size with reasonable certainty that it will work for everyone.

 Someone else may want to calculate it more closely and look up the exact voltage drop of their particular LED and correct the exact voltage across the resistor accordingly.


----------



## Beefy

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_That's my own judgment call, though, by trying to pick a resistor size with reasonable certainty that it will work for everyone._

 

Yeah, that's fine. Just double-checking for my own builds


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## srserl

I'm done populating the board except for the heat sink assemblies (yay)! I need to order the mounting kits, and I noticed that I almost have enough parts to build another max. Maybe try the mosfet max this time, but not sure...what are the pros and cons of the mosfet vs the bjt version? Is there an estimated timeframe for the new Mosfet Max web site?
 Meanwhile, I have the case work to do for the current Max, and I also have the Millet starving student to listen to while I work.
 Life is good!

 Scott


----------



## tomb

Quote:


  Originally Posted by *srserl* /img/forum/go_quote.gif 
_I'm done populating the board except for the heat sink assemblies (yay)! I need to order the mounting kits, and I noticed that I almost have enough parts to build another max. Maybe try the mosfet max this time, but not sure...what are the pros and cons of the mosfet vs the bjt version? Is there an estimated timeframe for the new Mosfet Max web site?
 Meanwhile, I have the case work to do for the current Max, and I also have the Millet starving student to listen to while I work.
 Life is good!

 Scott_

 

Glad to hear it!

 About the MOSFET-MAX: I am still working on it and hope to have it done in the next week or two, at the most.

 The pros and cons are probably equivalent to the differences between an M3 and a PPAV2.

 The cons with MOSFETs are relatively easy: heat. They have to be biased much higher to obtain equivalent performance to the BJT. In the MAX, that means special considerations to the case. The easiest solution is to mount the board in the bottom slot of the standard Hammond (to make room for taller sinks), but that puts the tubes almost below the lid and lowers the pot and headphone jack below the centerline. It also pretty much precludes running the tip jack wiring underneath because there's no room under the board for the tip jacks themselves.

 I'm going to try some special things to use the 1" sinks for the MOSFETs in at least one version, but haven't had the chance. Unfortunately, this is the busiest time of the year for me: both at home and at work. So, I'm still behind.


----------



## rhester

If you use the next size Hammond enclosure 1455H2201 you can still have the tip jacks included in the solution. It also makes it easy to add an Alien in the case. The MOSFETs are nice (my working version has the ES caps and VitaQs bypasing) with great low end extension, detail and thump (especially with the ES). The highs are a little different. I think they are more present sounding or up front than the BJTs, but have a little edge to them (especially conmpared to the BGs in the BJT builds). But I did dedcide to keep the MOSFET build and sell the BG BJT build, if that tells you anything.


----------



## Beefy

Quote:


  Originally Posted by *rhester* /img/forum/go_quote.gif 
_If you use the next size Hammond enclosure 1455H2201_

 

1455*T*2201 perhaps? 
	

	
	
		
		

		
		
	


	




  Quote:


 The MOSFETs are nice (my working version has the ES caps and VitaQs bypasing) with great low end extension, detail and thump (especially with the ES). The highs are a little different. I think they are more present sounding or up front than the BJTs, but have a little edge to them (especially conmpared to the BGs in the BJT builds) 
 

That is almost exactly how I would describe the difference between my M^3 and the Max. The M^3 has a bit more slam at the low end, and a little more sizzle at the top end. Fairly similar through the middle.


----------



## tomb

Quote:


  Originally Posted by *Beefy* /img/forum/go_quote.gif 
_<snip>That is almost exactly how I would describe the difference between my M^3 and the Max. The M^3 has a bit more slam at the low end, and a little more sizzle at the top end. Fairly similar through the middle._

 

Well, thanks for that comparison, Beefy. I tend to shy away from direct comparisons these days - the MAX and the size of this thread have made us a bit of a target in certain circles.
	

	
	
		
		

		
		
	


	




 Nevertheless, that's high praise, regardless - I know how much you love your M3.


----------



## Beefy

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_I tend to shy away from direct comparisons these days - the MAX and the size of this thread have made us a bit of a target in certain circles.
	

	
	
		
		

		
		
	


	


_

 

Its a shame that you have to do that. Good comparisons are the best way for everyone to learn and make their designs better.

  Quote:


 Nevertheless, that's high praise, regardless - I know how much you love your M3.
	

	
	
		
		

		
		
	


	



 

Oi, I love *both* of my DIY amps! 
	

	
	
		
		

		
		
	


	




 I must say, I had more fun building my Max though. Partly because I knew a lot more than before starting my M^3, partly because picking boutique parts is much more interesting, and partly because the integration made casework a breeze. The Max certainly gets more comments with visitors too - there's just something about tubes......


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## Iniamyen

I just got my order from beezar and let me say wow. It was packed, organized and labeled really well. I figure it can't hurt to have another recommendation even if it's from a newb 
	

	
	
		
		

		
		
	


	




 As I'm waiting for my other parts from mouser/digikey (damn ups 
	

	
	
		
		

		
		
	


	




) I guess the best thing to do is ask more questions to further avoid screwing things up when I start:

 -I'm still a little confused about the heatsink assembly. I got the mounting kit from Beezar, the one that says it doesn't need thermal grease. However it seems as though everyone mentions using it. I have some arctic silver back from when I built my computer - would this work?

 -I want to make sure I have the correct order down for the biasing step: Make sure DB bias is at minimum voltages, THEN bias PS, THEN bias tubes, THEN bias DB's. Can the DB's be damaged from sitting at their minimums? I assume the answer is no but I want to make sure.

 -Grounding: I'm not sure what all is tied to case ground, or if I need to take precautions with the power supply. I notice that the power socket is isolated (so V+ and V- aren't tied to the case), but some of the notes about the RCA jacks used say that the MAX is negatively grounded. Can I tie the virtual ground to the case? Or will this cause problems? I'd rather not blindly assemble and then fry something.

 Thanks!!!


----------



## slowpogo

Quote:


  Originally Posted by *Iniamyen* /img/forum/go_quote.gif 
_-I'm still a little confused about the heatsink assembly. I got the mounting kit from Beezar, the one that says it doesn't need thermal grease. However it seems as though everyone mentions using it. I have some arctic silver back from when I built my computer - would this work?_

 

No, you don't need grease. The kit comes with a "thermal pad" that goes between the transistor and the heat sink; this serves the same function as the grease, that of heat transfer.


----------



## Iniamyen

Quote:


  Originally Posted by *slowpogo* /img/forum/go_quote.gif 
_No, you don't need grease. The kit comes with a "thermal pad" that goes between the transistor and the heat sink; this serves the same function as the grease, that of heat transfer._

 

That's my initial impression; however, mention is made of certain pad materials that you want to use grease for. I guess for this one you don't.

 I'm probably just thinking about this too hard.


----------



## slowpogo

Quote:


  Originally Posted by *Iniamyen* /img/forum/go_quote.gif 
_That's my initial impression; however, mention is made of certain pad materials that you want to use grease for. I guess for this one you don't._

 

I didn't get my kits from Beezar, but I'm also using Bergquist thermal pads, and didn't use any grease. They are biased to 110 for a few months now so, so far so good.


----------



## srserl

Thanks for the info Tom and rhester. I still have plenty of time before I start my second one, so no hurry. I placed a mouser order today and included all items I might need for a mosfet max if that's what I decide to build. I read somewhere on the Millet Max site about using a small value resistor on the output...has anyone tried that on a mosfet max to see if it tames the highs a bit?
 I plan to build a wood case for my next one, so I ordered the 1.5" heatsinks since there are no size restrictions for me. I also ordered a large heatsink that I will probably mount on the back of the case to help out. I'll place slots in the bottom and the back, plus the heatsink on the back.

 Scott


----------



## tomb

Quote:


  Originally Posted by *Iniamyen* /img/forum/go_quote.gif 
_I just got my order from beezar and let me say wow. It was packed, organized and labeled really well. I figure it can't hurt to have another recommendation even if it's from a newb 
	

	
	
		
		

		
		
	


	


_

 

Thanks for that kind remark.
	

	
	
		
		

		
		
	


	







  Quote:


 As I'm waiting for my other parts from mouser/digikey (damn ups 
	

	
	
		
		

		
		
	


	




) I guess the best thing to do is ask more questions to further avoid screwing things up when I start:

 -I'm still a little confused about the heatsink assembly. I got the mounting kit from Beezar, the one that says it doesn't need thermal grease. However it seems as though everyone mentions using it. I have some arctic silver back from when I built my computer - would this work? 
 

The other guys have answered this well. I'm pretty sure using grease will hurt the Bergquist pads, too.

  Quote:


 -I want to make sure I have the correct order down for the biasing step: Make sure DB bias is at minimum voltages, THEN bias PS, THEN bias tubes, THEN bias DB's. Can the DB's be damaged from sitting at their minimums? I assume the answer is no but I want to make sure. 
 

Yep - sounds like a plan, and No - the DB's can't be damaged if everything is hooked up correctly and they're idling at low bias (<50mV).

  Quote:


 -Grounding: I'm not sure what all is tied to case ground, or if I need to take precautions with the power supply. I notice that the power socket is isolated (so V+ and V- aren't tied to the case), but some of the notes about the RCA jacks used say that the MAX is negatively grounded. Can I tie the virtual ground to the case? Or will this cause problems? I'd rather not blindly assemble and then fry something.p 
 

Yes, the MAX and every Millett before it are negatively grounded. The difference is the MAX has a high-power/performance linear-regulated power supply _on the board_. That means the power input is AC - there is no V+ and V- at the power socket, in other words - it's 24VAC. You don't want that AC touching the case, because the negative DC power further down on the board can come into contact with the case very easily - either on-purpose or by accident. For instance, the recommended Beezar RCA jacks are not insulated/isolated. Their ground (same as the board's negative) touches the case.

 Another way to look at it is to look at the board itself: there is no ground plane in the back where there's AC. Technically, the 24VAC runs only from the terminal block to the string of rectifiers on the very back of the board. It's DC after that, but still carries ripple until going through the power caps and the regulator. The filtered, fully-linear-regulated DC power makes its final connection to the ground plane at CR5 (also RR2 and DR1). Quote:


 Thanks!!! 
 

You're welcome!


----------



## ruZZ.il

Regarding biasing the DBs:
 As has been recommended before, I suggest making sure they're actually biased to their minimum at first power up, and if not, shut down and make the change right away. It has happened (<cough cough>) that I powered up my first max with the BJTs at max and they didn't last too long 
 So, measure their bias first at least, then get the other voltages in the ball park, then get the BJTs.. is what I'd do..


----------



## MasiveMunkey

I just finished casing my millett maxed and I was wondering if the holes in the top (for heat) are necessary? 

 I'm not too good at case work so I'm sort of hesitant to drill 20+ holes in the top of the case if I don't absolutely have to.

 Also, which type of tube gives the best detail? I already have a set of the three different types, but haven't had a chance to compare each against each other.


----------



## BoilermakerFan

Quote:


  Originally Posted by *MasiveMunkey* /img/forum/go_quote.gif 
_I just finished casing my millett maxed and I was wondering if the holes in the top (for heat) are necessary? 

 I'm not too good at case work so I'm sort of hesitant to drill 20+ holes in the top of the case if I don't absolutely have to.

 Also, which type of tube gives the best detail? I already have a set of the three different types, but haven't had a chance to compare each against each other._

 

You can use a hole saw or punch to make one big hole over the area and cover it on the inside with screen. Several others have done that.

 The 12FK6 tubes are said to have the most detail. The 12AE6s have the most punch. The 12FM6 tubes fall in the middle and are the hardest to find. 

 Which caps did you use?


----------



## MasiveMunkey

Hmm... I don't remember I put them in such a long time ago. 

 So heat vents are necessary? My amp does feel kind of hot...


----------



## soloz2

Quote:


  Originally Posted by *MasiveMunkey* /img/forum/go_quote.gif 
_Hmm... I don't remember I put them in such a long time ago. 

 So heat vents are necessary? My amp does feel kind of hot..._

 

you could always run it topless...

 edit: on a more constructive note I have some nice wire mesh if you're in need


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## Iniamyen

Quote:


  Originally Posted by *MasiveMunkey* /img/forum/go_quote.gif 
_I just finished casing my millett maxed and I was wondering if the holes in the top (for heat) are necessary? 

 I'm not too good at case work so I'm sort of hesitant to drill 20+ holes in the top of the case if I don't absolutely have to.

 Also, which type of tube gives the best detail? I already have a set of the three different types, but haven't had a chance to compare each against each other._

 

I was thinking about this as well. If you're worried about drilling a lot of holes in the sense that they might not line up perfectly and look nice, you could always drill fewer larger holes. I was also thinking that you could drill holes in the side of the case (above the board level), and that convection would draw cooler air in from these, and you might only need one or two holes in each location. I don't know if anyone has done this.


----------



## BoilermakerFan

Quote:


  Originally Posted by *soloz2* /img/forum/go_quote.gif 
_you could always run it topless...

 edit: on a more constructive note I have some nice wire mesh if you're in need_

 

I'm interested in it. Send me a PM with the size of the pieces you have left. Did you ever use JB Weld to install it in your MAX? FWIW, I'll be in Buffalo, NY the week of June 23 too.

  Quote:


  Originally Posted by *Iniamyen* /img/forum/go_quote.gif 
_I was thinking about this as well. If you're worried about drilling a lot of holes in the sense that they might not line up perfectly and look nice, you could always drill fewer larger holes. I was also thinking that you could drill holes in the side of the case (above the board level), and that convection would draw cooler air in from these, and you might only need one or two holes in each location. I don't know if anyone has done this._

 

You still need to vent the top with enough area to enable the convection to occur. Side holes may help, but I think the side holes will be harder to drill nicely than the top holes. I might try holes at the rear to allow more convection flow around the voltage regulator. It also depends on high you biased your BJTs or MOSFETS. If you have the BJTs biased lower around 30mA then you could get away with less holes, but I still think it would be easier for you guyts to buy a Uni-Bit that goes up to 3/4" and make a few 3/4" holes over the DB and V-Reg heatsinks and use black or silver window screen on the inside to keep fingers and small bits out.


----------



## soloz2

Quote:


  Originally Posted by *BoilermakerFan* /img/forum/go_quote.gif 
_I'm interested in it. Send me a PM with the size of the pieces you have left. Did you ever use JB Weld to install it in your MAX? FWIW, I'll be in Buffalo, NY the week of June 23 too.

_

 

I have some modders mesh from a PC case mod I did a couple years ago... I have almost 1'x2' of that and then I have almost 2'x2' of some wire mesh I bought to use on Grados, and well You don't need a lot for Grado screens


----------



## slowpogo

Quote:


  Originally Posted by *BoilermakerFan* /img/forum/go_quote.gif 
_I'm interested in it. Send me a PM with the size of the pieces you have left. Did you ever use JB Weld to install it in your MAX?_

 

I used JB Qwik to secure my mesh. It worked great. I cut some plywood into the right size, wrapped it in wax paper, then used that as a "weight distribution plate". I put a big 30lb barbell on top of the wood, on top of the mesh w/ jb. The mesh ended up totally flat and secure.


----------



## BoilermakerFan

Quote:


  Originally Posted by *soloz2* /img/forum/go_quote.gif 
_I have some modders mesh from a PC case mod I did a couple years ago... I have almost 1'x2' of that and then I have almost 2'x2' of some wire mesh I bought to use on Grados, and well You don't need a lot for Grado screens 
	

	
	
		
		

		
		
	


	


_

 

I sent you a PM.


----------



## tomb

Quote:


  Originally Posted by *MasiveMunkey* /img/forum/go_quote.gif 
_I just finished casing my millett maxed and I was wondering if the holes in the top (for heat) are necessary? 

 I'm not too good at case work so I'm sort of hesitant to drill 20+ holes in the top of the case if I don't absolutely have to.

 Also, which type of tube gives the best detail? I already have a set of the three different types, but haven't had a chance to compare each against each other._

 

As others have said, topless is fine - many builders have left it at that.

 However, three things remove all fear from me:
 1. a stepped drill bit,
 2. the MAX website drilling templates, and 
 3. use of a spring-loaded center punch.

 In my situation, the template is used mainly as a guide for the spring-loaded punch. Secondarily, the template (when glued down with rubber cement) provides protection to the case finish from any errant metal chips (there are a lot of those). The punch removes any possibility that the drill bit walks. Use of the center punch will allow the use of a hand power drill - as shown in the construction section of the MAX website. You onlly have to eyeball the end of the drill bit with the center-punched indentation - it automatically "walks" to the indentation. Finally, a stepped drill bit ensures that the metal is cut, not ripped. Don't ever try to drill a hole in thin aluminum in one cut with a bit sized for the full size of the hole.

 All that said, I can understand why one would be reluctant with the finish at the size of that case lid. Personally, I would never attempt it without a glued-down drill template that covers the entire surface. There's just too much metal spraying around - even if you vacuum it up after every hole.
	

	
	
		
		

		
		
	


	




 After the first prototype, I use a Delta tabletop drill press with a Harbor Freight 4" indexing drill vise. The indexer only cost about $30 on sale. It's the smallest one they make, but just barely fits within the vertical travel of the small Delta drill press. (It won't fit on one of the cheaper Harbor Freight table top drill presses.) The holes go very quickly with one of those, but it's only time that it saves - not whether the holes are centered correctly and the finish is undamaged - the drilling template and the center hole punch do that. The drill press does result in finer cut holes - the edges are sharper and look more like a machine cut.

 As for the tube holes, there's just nothing like one of those Greenlee punches. Be careful that you are certain of the final hole size, though, if you purchase one. Many of them are made for conduit, which are referenced by ID. The OD can be many fractions of an inch larger. For instance, a "3/4-inch conduit punch" cuts an OD (hole size) of well over 1 inch.


----------



## soloz2

putting together my BOM for my 3rd Max build. the first two were Muse ES/k42 builds. I was happy with the amps, but feel a bit less slam would be desirable so the next build will be blackgates.

 Now of course CA2 will be 1000uf 25v NX
 CA7 will be 680uf 35v NX
 CA8 will likely be vitQ, but I have a case of k42's... so I haven't decided yet...
 CA9 will be jumpered

 now for the questions:
 CA3/CA6 I have both Wilmas and k42's. I'll have enough room to tombstone the k42's so that isn't an issue, which would be better?

 CA4/CA5, the original BOM called for 470uf 35v, the updated calls for 1000uf 35v.
 first question, is there any sonic benefit to using 1000uf, or is it cosmetic?
 second question, would there be any benefit to populating these positions with Blackgate NX caps?
 Finally, if it wouldn't be worth populating the positions with Blackgate NX, I do have some Muse ES 470uf 35v caps that I could use


----------



## tomb

Quote:


  Originally Posted by *soloz2* /img/forum/go_quote.gif 
_putting together my BOM for my 3rd Max build. the first two were Muse ES/k42 builds. I was happy with the amps, but feel a bit less slam would be desirable so the next build will be blackgates.

 Now of course CA2 will be 1000uf 25v NX
 CA7 will be 680uf 35v NX
 CA8 will likely be vitQ, but I have a case of k42's... so I haven't decided yet...
 CA9 will be jumpered_

 

This will kill my sales of K42's
	

	
	
		
		

		
		
	


	




, but there's no question the VitQ's are better. I would go with the 0.22uf's, though, simply because the capacitance rating of the Black Gates are higher than the typical 470uf. Otherwise, for ES's at 470uf I would use the 0.18uf VitQ's.

 Another option is the NX HiQ 0.47uf 50V - they will work well at CA9, too, but you are correct not to put the VitQ's back there.
  Quote:


 now for the questions:
 CA3/CA6 I have both Wilmas and k42's. I'll have enough room to tombstone the k42's so that isn't an issue, which would be better? 
 

Wima's, period - sound is not an issue here and the Wima's are unbeatable in these locations, IMHO.
  Quote:


 CA4/CA5, the original BOM called for 470uf 35v, the updated calls for 1000uf 35v.
 first question, is there any sonic benefit to using 1000uf, or is it cosmetic? 
 

No - getting rid of the tremendous slam will be accomplished by the BG's at CA2 and CA7 (in return for more detail), but you will noticeably lose bass with 470uf's at CA4/5. There is a lot of current to handle after the PS and CA4/CA5 take care of practically all of it.
  Quote:


 second question, would there be any benefit to populating these positions with Blackgate NX caps? 
 

Panasonic FM's are almost unparalled in their ESR/ripple. That said, sonic improvements might be noticeable with BG FK's (just a guess). I have heard that their ESR is even lower (you'll never find the data published, though), but it will be an expensive experiment.
	

	
	
		
		

		
		
	


	



  Quote:


 Finally, if it wouldn't be worth populating the positions with Blackgate NX, I do have some Muse ES 470uf 35v caps that I could use 
 

No - 1000uf is best, more than that - I have used 1800uf's on every build except the MiniMAX, where they were 1200uf's.


----------



## soloz2

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_This will kill my sales of K42's
	

	
	
		
		

		
		
	


	




, but there's no question the VitQ's are better. I would go with the 0.22uf's, though, simply because the capacitance rating of the Black Gates are higher than the typical 470uf. Otherwise, for ES's at 470uf I would use the 0.18uf VitQ's.

 Another option is the NX HiQ 0.47uf 50V - they will work well at CA9, too, but you are correct not to put the VitQ's back there._

 

the price for vit q's is about the same as the NX HiQ's anyone tried both?

  Quote:


 No - getting rid of the tremendous slam will be accomplished by the BG's at CA2 and CA7 (in return for more detail), but you will noticeably lose bass with 470uf's at CA4/5. There is a lot of current to handle after the PS and CA4/CA5 take care of practically all of it.
 Panasonic FM's are almost unparalled in their ESR/ripple. That said, sonic improvements might be noticeable with BG FK's (just a guess). I have heard that their ESR is even lower (you'll never find the data published, though), but it will be an expensive experiment.
	

	
	
		
		

		
		
	


	



 No - 1000uf is best, more than that - I have used 1800uf's on every build except the MiniMAX, where they were 1200uf's. 
 

hmm... well I guess Panasonic FM it is. $100 is a bit more than I'd like to spend


----------



## MrMajestic2

Quote:


  Originally Posted by *soloz2* /img/forum/go_quote.gif 
_the price for vit q's is about the same as the NX HiQ's anyone tried both?_

 

Yes, and I preferred VitQs.


----------



## Beefy

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Panasonic FM's are almost unparalled in their ESR/ripple._

 

This got me thinking, and looking at spec sheets.

 The Panasonic FM really are specced the best of the common used caps. I ordered from Mouser instead of Digikey, so no FM for me..... but I'm trying to remember why I bought Nichicon UPW instead of UHE. The UHE are better specced for both ESR and ripple, cheaper, and longer life!


----------



## JamesL

Does anybody know how the 1.5" TO-220 heatsinks fit inside a 1u case, with the pcb and standoffs?

 The beta22 and M3 boards are designed to utilize these hs' too, and standard 1u cases open up a bunch of possibilities.


----------



## BoilermakerFan

Quote:


  Originally Posted by *JamesL* /img/forum/go_quote.gif 
_Does anybody know how the 1.5" TO-220 heatsinks fit inside a 1u case, with the pcb and standoffs?

 The beta22 and M3 boards are designed to utilize these hs' too, and standard 1u cases open up a bunch of possibilities._

 

Isn't a 1u case 1-1/2" high (or technically 1.7" on the outside)? No chance of fitting a 1-1/2" heatsink on the board in anything smaller than a 2u case. Also, I believe true 1u, 2u, etc. are 19" wide to fit the standard racks.


----------



## JamesL

Ah, is it 1.7 on the outside?

 All I found was, 1 rack unit = 1.75", so I thought maybe I could fit it in if I shaved off about a eighth or quarter inch off the top of the heatsinks.

 Yes, rack chassis' are 19" wide, but many times, the sides are manufactured to meet the rack mount standards, and width/depth are just flat panels, so custom size chassis' can be manufactured easily (such as.. context engineering, or lansing enclosures) 
 Also, half-rack's are 9.5" wide, which is a much lesser used standard.
 I think headamp uses 1u tall cases for most of their amps, and RSA uses 1u tall chassis' for a lot of their non-portables.


----------



## BoilermakerFan

Quote:


  Originally Posted by *JamesL* /img/forum/go_quote.gif 
_Ah, is it 1.7 on the outside?

 All I found was, 1 rack unit = 1.75", so I thought maybe I could fit it in if I shaved off about a eighth or quarter inch off the top of the heatsinks.

 Yes, rack chassis' are 19" wide, but many times, the sides are manufactured to meet the rack mount standards, and width/depth are just flat panels, so custom size chassis' can be manufactured easily (such as.. context engineering, or lansing enclosures) 
 Also, half-rack's are 9.5" wide, which is a much lesser used standard._

 

For the money, you would be hard pressed to find a nicer, cheaper case than the NABU case Pabbi linked me to pages ago. They are 19" wide with a PSU isolated from the main compartment and the plastic front bezel can be removed and used for a template for a wood, aluminum or other new front bezel. Interior height is over 3-1/4" so even 2-1/2" heatsinks fit. The teaser pics I posted a few pages back show the MAX board laid out with room for other hardware boards including the OptiVol and Darwin source selector. There is still room for a large DAC such as a NOS DAC, Buffalo DAC, or even a phono stage and a DAC. 

 I think mine were $15 or so a piece since I bought five. Shipping was $30 for all five.


----------



## tomb

Quote:


  Originally Posted by *Beefy* /img/forum/go_quote.gif 
_This got me thinking, and looking at spec sheets.

 The Panasonic FM really are specced the best of the common used caps. I ordered from Mouser instead of Digikey, so no FM for me..... but I'm trying to remember why I bought Nichicon UPW instead of UHE. The UHE are better specced for both ESR and ripple, cheaper, and longer life! 
	

	
	
		
		

		
		
	


	


_

 

Yep - compared to UPW's, but UHE's are funny - they're not consistently that way throughout the line. Some sizes are worse. I think many don't look to UHE's because of that inconsistency, whereas UPW's seem to duplicate Panasonic FC's exactly (if my memory is correct).


----------



## soloz2

I know this has been posted before so I beg forgiveness as I can't seem to find the post.

 what size output caps would I want in an Alien feeding to a Max.


----------



## tomb

Quote:


  Originally Posted by *soloz2* /img/forum/go_quote.gif 
_I know this has been posted before so I beg forgiveness as I can't seem to find the post.

 what size output caps would I want in an Alien feeding to a Max._

 

As usual, we should refer to Dsavitsk's excellent reference on coupling caps:
Notes on Output Coupling Caps

 About four paragraphs down, he has a little table that displays rules of thumb for coupling cap ratings with input impedances of an amp. That input impedance is usually set by the pot. In the MAX, it's 50K. He is pretty conservative with his rule-of-thumb calcs (2 Hz), so probably 0.47uf to 1uf would be OK.

 The way many boutique film cap sizes seem to run, 0.47uf is still manageable, whereas 1uf is starting to get unreasonable in size and cost. That depends a lot on which cap you select, so YMMV. As Dsavitsk states, "... sometimes, when on a budget, it is worth having a higher 3db point in exchange for better signal integrity."

 EDIT: Most Alien DAC builds with electrolytics use 47uf Black Gates or Elna RFS, so this is never even an issue (100 times the value mentioned above). There is a high-quality HiQ NX Black Gate at 47uf 6.3V. That sort of sets the choice, because there are no other "HiQ" selections in voltage ratings close to that.

 However, I'm assuming you're looking at the optimum _film cap_ size without using electrolytics at all. That's usually the best choice if one is looking for a semi-permanent, integrated connection to an amp.


----------



## Iniamyen

I noticed that the silkscreen for RR3 results in a counterclockwise-turn to higher resistance (rather than the others which are clockwise.)

 Based on the pinout of a trimpot it seems to me like the orientation doesn't matter but I initially panicked when I turned everything clockwise and RR3 ohmed out to zero!


----------



## I-Love-Music

I've been keeping an eye on these for my main rig project. Looks awesome!


----------



## tomb

Quote:


  Originally Posted by *Iniamyen* /img/forum/go_quote.gif 
_I noticed that the silkscreen for RR3 results in a counterclockwise-turn to higher resistance (rather than the others which are clockwise.)

 Based on the pinout of a trimpot it seems to me like the orientation doesn't matter but I initially panicked when I turned everything clockwise and RR3 ohmed out to zero!_

 

No, it doesn't matter. It's important to get the tube trimmers reversed from one another, though - so you can turn them both in the same direction for adjusting tube bias.


----------



## soloz2

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_As usual, we should refer to Dsavitsk's excellent reference on coupling caps:
Notes on Output Coupling Caps

 About four paragraphs down, he has a little table that displays rules of thumb for coupling cap ratings with input impedances of an amp. That input impedance is usually set by the pot. In the MAX, it's 50K. He is pretty conservative with his rule-of-thumb calcs (2 Hz), so probably 0.47uf to 1uf would be OK.

 The way many boutique film cap sizes seem to run, 0.47uf is still manageable, whereas 1uf is starting to get unreasonable in size and cost. That depends a lot on which cap you select, so YMMV. As Dsavitsk states, "... sometimes, when on a budget, it is worth having a higher 3db point in exchange for better signal integrity."

 EDIT: Most Alien DAC builds with electrolytics use 47uf Black Gates or Elna RFS, so this is never even an issue (100 times the value mentioned above). There is a high-quality HiQ NX Black Gate at 47uf 6.3V. That sort of sets the choice, because there are no other "HiQ" selections in voltage ratings close to that.

 However, I'm assuming you're looking at the optimum film cap size without using electrolytics at all. That's usually the best choice if one is looking for a semi-permanent, integrated connection to an amp._

 

thanks, that's what I was looking for and just not seemingly able to find.

 I believe the OptiVol has an input impedance of 27k So I probably should be looking for around the 1uf mark. This could get quite expensive for a 'budget' DAC. I may look into bypassing a blackgate nx or Muse ES here.


----------



## rockcod

I found myself turning on and off the Max quite rapidly, thus defeating the purpose of the delay since CM3 doesn't have a chance to fully discharge. I am thinking about putting a bleeder resistor across RM2 and CM3 to quickly discharge CM3.

 Comments?


----------



## Iniamyen

Quote:


  Originally Posted by *rockcod* /img/forum/go_quote.gif 
_I found myself turning on and off the Max quite rapidly, thus defeating the purpose of the delay since CM3 doesn't have a chance to fully discharge. I am thinking about putting a bleeder resistor across RM2 and CM3 to quickly discharge CM3.

 Comments?_

 

As I understand it, the delay is for headphone protection and isn't there to purposefully protect any amp components. So if you're switching it on and off rapidly, then you must be still biasing things and wouldn't have your headphones plugged in yet - right?


----------



## rockcod

Quote:


  Originally Posted by *Iniamyen* /img/forum/go_quote.gif 
_As I understand it, the delay is for headphone protection and isn't there to purposefully protect any amp components. So if you're switching it on and off rapidly, then you must be still biasing things and wouldn't have your headphones plugged in yet - right?_

 

Your understanding is correct: the delay circuit provides turn-on/off delay muting functionality to protect the headphones only.

 But I am not biasing the Max (it's been done long ago) and the 'phones are plugged in.

 The problem here is w/o allowing enough time to discharge CM3 between power cycles, the delay circuit simply doesn't work as intended.


----------



## tomb

Quote:


  Originally Posted by *rockcod* /img/forum/go_quote.gif 
_Your understanding is correct: the delay circuit provides turn-on/off delay muting functionality to protect the headphones only.

 But I am not biasing the Max (it's been done long ago) and the 'phones are plugged in.

 The problem here is w/o allowing enough time to discharge CM3 between power cycles, the delay circuit simply doesn't work as intended._

 

No offense, but the delay circuit _does_ work as intended. If you discharged CM3 faster with a different-sized resistor in the circuit (it's currently 1M), then it would charge much faster and not provide a delay. Perhaps you could switch out one resistor for the other, but then we're talking about another relay/switch to protect the relay.

 I have had this happen frequently due to a lot of the testing I've done, but it goes from about 45 seconds down to about 20seconds, still offering adequate protection. Another reason why this does that for me is that I use 470uf for CM3 instead of the recommended 330uf. It doesn't matter to me that the turn-on is longer for normal listening: the tubes aren't really ready for quite a bit longer time than that (30 min?).

 Like Iniamyen, though, I'm curious as to why you're bumping your MAX on and off this quickly if you're not doing some sort of adjustment/testing.


----------



## rockcod

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_No offense, but the delay circuit does work as intended. If you discharged CM3 faster with a different-sized resistor in the circuit (it's currently 1M), then it would charge much faster and not provide a delay. Perhaps you could switch out one resistor for the other, but then we're talking about another relay/switch to protect the relay.

 I have had this happen frequently due to a lot of the testing I've done, but it goes from about 45 seconds down to about 20seconds, still offering adequate protection. Another reason why this does that for me is that I use 470uf for CM3 instead of the recommended 330uf. It doesn't matter to me that the turn-on is longer for normal listening: the tubes aren't really ready for quite a bit longer time than that (30 min?).

 Like Iniamyen, though, I'm curious as to why you're bumping your MAX on and off this quickly if you're not doing some sort of adjustment/testing._

 

It's quite OK, I don't take it offensively at all.

 I have the same settings as yours (1M and 470uf). I am satified w/ the inital turn on which takes 45 seconds for the relay to kick in so I want to leave the value for RM2 at 1M. But if "I" turn it off and then on immediately, this delay will be shortened considerably because CM3 still holds residual charge. This is why I am contemplating the bleeder resistor.

 As for why I am bumping my Max on and off -- it's not me, but my 11-year old


----------



## tomb

Quote:


  Originally Posted by *rockcod* /img/forum/go_quote.gif 
_<snip>
 As for why I am bumping my Max on and off -- it's not me, but my 11-year old
	

	
	
		
		

		
		
	


	


_

 

Oops. Colin didn't anticipate child protection features.


----------



## rockcod

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Oops. Colin didn't anticipate child protection features.
	

	
	
		
		

		
		
	


	


_

 

Probably will be incorporated in the next version?


----------



## ruZZ.il

While scoping out the output (behind the relay) a while ago I noticed the seemingly dangerous effect quiet clearly, and noticed that when the tubes are already hot, the phenomenon occurs with a shorter time delay after turn on. 

 This is just a speculation, but I think the 'noise' is caused by electrons filling up the space just around the anode and that this happens just as the thermal energy(heat) reaches the work function (amount of energy needed for the electron to escape the pull of the surrounding materials protons), and a bunch of other things I speculate too vaguely may happen then too. Now, when heating up the anode from room temperature, the time it takes to get hot enough for this to happen is longer than when the anode is already still hot from a recent toggle off.. so, you actually need shorter protection anyway.

 Don't take my word for any of this though, I'm still an uncertified anything 

 Just a few snapshots, left for your interpretation: (I didn't log any data, and the pics were far from concise. was just messing around)


----------



## BoilermakerFan

Quote:


  Originally Posted by *rockcod* /img/forum/go_quote.gif 
_Probably will be incorporated in the next version?
	

	
	
		
		

		
		
	


	


_

 

Yes, but will utilize an RFID proximity sensor and will require the implant of a RF chip in the top of your hand between the index and middle fingers. The new switch will incorporate a static discharge protection feature that can only be disabled by the correct RFID chip canceling the protection feature. Your 11 year old or anyone else will quickly learn not to touch Daddy's MAX! 
	

	
	
		
		

		
		
	


	




 In all seriousness, is your son cycling the power when you are there listening to your amp, or is he doing it at other times? You could change the power switch to be a keyed switch, but then it's a PITA for you.


----------



## Beefy

Quote:


  Originally Posted by *rockcod* /img/forum/go_quote.gif 
_As for why I am bumping my Max on and off -- it's not me, but my 11-year old
	

	
	
		
		

		
		
	


	


_

 

Boilermakerfan already hinted at it..... but if I were you, I'd invest in one of these: http://www.nkkswitches.com/pdf/CKM_CKL.pdf


----------



## BoilermakerFan

Quote:


  Originally Posted by *Beefy* /img/forum/go_quote.gif 
_Boilermakerfan already hinted at it..... but if I were you, I'd invest in one of these: http://www.nkkswitches.com/pdf/CKM_CKL.pdf



_

 

Oooo. I like the 19mm tubular key version. I need that for another project. Thanks Beefy. That would also give the MAX a very unique look, but it would be out of site most of the time. I think I'll use the tubular key switch on my desktop amp and put it right in front!

 Oh, and don't forget to use security bolts to hold the case together, or that kid could just grab a screwdriver or allen wrench to open the case and bypass the switch!


----------



## Beefy

Quote:


  Originally Posted by *BoilermakerFan* /img/forum/go_quote.gif 
_That would also give the MAX a very unique look, but it would be out of site most of the time. I think I'll use the tubular key switch on my desktop amp and put it right in front!_

 

Yeah, absolutely, mount it right there at the front! 
	

	
	
		
		

		
		
	


	




 BTW, you can probably find even nicer ones. That was just the first one I looked at from Mouser when searching for 'key lock switch'.

 [EDIT] Yeah, it looks like Omron might have some nice ones as well; the Mouser catalogue page is here: http://www.mouser.com/catalog/634/1632.pdf
 They can get pricey though! 
	

	
	
		
		

		
		
	


	



 [EDIT 2] You could even get one of the momentary key lock switches and use it for this The &epsilon;24 Power Switch Driver Circuit. It would be like firing up the car!


----------



## rockcod

Quote:


  Originally Posted by *BoilermakerFan* /img/forum/go_quote.gif 
_Yes, but will utilize an RFID proximity sensor and will require the implant of a RF chip in the top of your hand between the index and middle fingers. The new switch will incorporate a static discharge protection feature that can only be disabled by the correct RFID chip canceling the protection feature. Your 11 year old or anyone else will quickly learn not to touch Daddy's MAX! 
	

	
	
		
		

		
		
	


	




 In all seriousness, is your son cycling the power when you are there listening to your amp, or is he doing it at other times? You could change the power switch to be a keyed switch, but then it's a PITA for you._

 

RFID seems to be a good idea
	

	
	
		
		

		
		
	


	




 We share the Max as I want him to be interested in this hobby as well. For this reason, a keyed switch would be too discouraging


----------



## BoilermakerFan

Quote:


  Originally Posted by *rockcod* /img/forum/go_quote.gif 
_RFID seems to be a good idea
	

	
	
		
		

		
		
	


	




 We share the Max as I want him to be interested in this hobby as well. For this reason, a keyed switch would be too discouraging
	

	
	
		
		

		
		
	


	


_

 

Well, based on his itchy trigger finger, I'm glad to hear you're not introducing him to firearms yet. 
	

	
	
		
		

		
		
	


	




 I'm sure you could build a second relay timer circuit for the power switch that would actually latch it out if he cycles the power too quickly. I would have suggested latching it in, but that's a safety issue. Was he cycling the power because he wasn't hearing music right away when he turned it on? 

 I have a 9yo daughter and she's really into music too, she loves our vinyl, but she knows not to touch it. Unfortunately, my 2yo son don't listen to "No" very well, so I'll have to incorporate hidden magnetic latches into the top of the console cover to keep him from opening the top when albums are playing. We've already had a close call with a Beach Boys monophonic record!


----------



## tomb

I like that tube-bomb avatar.


----------



## jamess71

Quick question, finishing up another MMax and wondering if I need to tie the ground plain on the pcb to the case? In my first max I used a screw through the bottom of the case to the center tap. On this on I'm using a plastic standoff. 

 THnaks
 James


----------



## rockcod

Quote:


  Originally Posted by *BoilermakerFan* /img/forum/go_quote.gif 
_Well, based on his itchy trigger finger, I'm glad to hear you're not introducing him to firearms yet. 
	

	
	
		
		

		
		
	


	




 I'm sure you could build a second relay timer circuit for the power switch that would actually latch it out if he cycles the power too quickly. I would have suggested latching it in, but that's a safety issue. Was he cycling the power because he wasn't hearing music right away when he turned it on? 

 I have a 9yo daughter and she's really into music too, she loves our vinyl, but she knows not to touch it. Unfortunately, my 2yo son don't listen to "No" very well, so I'll have to incorporate hidden magnetic latches into the top of the console cover to keep him from opening the top when albums are playing. We've already had a close call with a Beach Boys monophonic record!_

 

A second relay maybe the answer.

 He is simply a happy-trigger type... for that, no firearm introduction


----------



## BoilermakerFan

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_I like that tube-bomb avatar. 
	

	
	
		
		

		
		
	


	


_

 

Thanks. I love the band that used it for their cover art too. Dave Grohl is a guitar tube amp aficionado, but I haven't spent the time to figure out which tube they used for the pic. I just edited it a bit and shrunk it down to fit! I have the concert t-shirt with the tube-bomb on it too. 
	

	
	
		
		

		
		
	


	




 If you get the chance to catch this tour, do it! It is one of the best concerts I've been to in a long time!


----------



## tomb

Quote:


  Originally Posted by *jamess71* /img/forum/go_quote.gif 
_Quick question, finishing up another MMax and wondering if I need to tie the ground plain on the pcb to the case? In my first max I used a screw through the bottom of the case to the center tap. On this on I'm using a plastic standoff. 

 THnaks
 James_

 

The primary connection to the case is probably through the ground connections on the RCA jacks. Other places where the PCB is grounded to the case are at the pot (the shaft/nut and ground wire) and the headphone jack (the threaded ferrule).

 I use a nylon nut on most of mine for that center screw - adjusting washers so that the nut gives the board a little tension. I've not noticed any ill effects from a lack of grounding.


----------



## jamess71

THanks Tomb. Now its out to Home Depot to find a drill press .

 James


----------



## amphead

Which drill press did you end up with?


----------



## soloz2

I'm considering putting an Opus in the same case as my next Max build instead of the Alien or Opus USB module... but what would be the best way to power everything?


----------



## pabbi1

Quote:


  Originally Posted by *soloz2* /img/forum/go_quote.gif 
_I'm considering putting an Opus in the same case as my next Max build instead of the Alien or Opus USB module... but what would be the best way to power everything?_

 

Toroids... like this perhaps. This was the Antek version I used for the Millets, and used the toroid from Twisted Pear for the OPUS.


----------



## agutt

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_The primary connection to the case is probably through the ground connections on the RCA jacks. Other places where the PCB is grounded to the case are at the pot (the shaft/nut and ground wire) and the headphone jack (the threaded ferrule)._

 

My front panels are made of wood. Do I need to run a ground to the case somehow?


----------



## tomb

Quote:


  Originally Posted by *agutt* /img/forum/go_quote.gif 
_My front panels are made of wood. Do I need to run a ground to the case somehow?_

 

Well, it might help if you connect that center screw to the case - with appropriate spacers, that is. That said, Colin put a huge ground plane on the MAX and if you don't notice a problem, it's probably fine. We've had several people build MAXes with wooden front and back endplates. I haven't heard of an issue with grounding that I can recall.

 I had an instance where I had soldered and re-soldered the input terminal block on my testbed MAX so much that it had ripped out the center plating on the ground pad. _That_ caused a problem. The only connection to ground is on the top side of the board. Without the through-hole plating, there was also insufficient wicking to the top side. The result was that the signal ground was not grounded. Loud, buzzing distortion was the result. I soldered a small jumper from the center pin on the terminal block underneath the board to the closest negative pin. That totally fixed it.

 I don't know why I related that story except to indicate that if you have a grounding issue, it will be pretty obvious, I think.


----------



## BoilermakerFan

My OptiVol and OptiVol kit showed up today from SKA. 
	

	
	
		
		

		
			





 I have to figure out how to mount the board for my remote application using some sort of plastic PCB clip. I'll have to browse the Mouser catalog tonight. An assembled unit will be mounted to the front faceplate and the threaded nut for the Alpha pot will hold it in place. 

 From the center of the pot shaft to the bottom of the PCB is about 20mm, but I would allow for 25mm just to make sure it's not shorted on the bottom of the case or MAX PCB. It will be a minimum of 15mm from the back side of the face plate to the back edge of the PCB for it's mounting "depth" into the enclosure, but again, I'd leave an extra 5mm to cover your short circuits... I won't be using the standard Hoffman enclosures, so you'll have to do the math to determine if the OptiVol will work with the standard short case, or will require the deeper case. The beauty of simplicity of this isolated volume attenuator is amazing.


----------



## soloz2

Quote:


  Originally Posted by *pabbi1* /img/forum/go_quote.gif 
_Toroids... like this perhaps. This was the Antek version I used for the Millets, and used the toroid from Twisted Pear for the OPUS._

 

I'm sorry, I should have been more clear. Yes, I was looking at Toroids and at wallwarts trying to decide what would be best. Everything will have a regulated power supply, I'm just looking for the best price/performance source. I wasn't sure how much current I'd need though. The one you linked looks like it'll probably do well though.
 I'm wondering if I'll notice any ill effects since I'd have to mount the toroid a couple inches away from the amp...


 My OptiVol kit showed up today too! 
	

	
	
		
		

		
		
	


	




 The knob I have has a set screw so I'm going to have to figure out something though...


----------



## BoilermakerFan

Quote:


  Originally Posted by *soloz2* /img/forum/go_quote.gif 
_I'm sorry, I should have been more clear. Yes, I was looking at Toroids and at wallwarts trying to decide what would be best. Everything will have a regulated power supply, I'm just looking for the best price/performance source. I wasn't sure how much current I'd need though. The one you linked looks like it'll probably do well though.
 I'm wondering if I'll notice any ill effects since I'd have to mount the toroid a couple inches away from the amp...


 My OptiVol kit showed up today too! 
	

	
	
		
		

		
		
	


	




 The knob I have has a set screw so I'm going to have to figure out something though..._

 

Which case do you have? You can buy steel covers for the toroid and it will be enough shielding. 100VA will be plenty for MAX, Darwin, and OptiVol, but check TPA's site for the Opus. The cleaner, more stable the PS, the cleaner and better the DAC works.


----------



## soloz2

Quote:


  Originally Posted by *BoilermakerFan* /img/forum/go_quote.gif 
_Which case do you have? You can buy steel covers for the toroid and it will be enough shielding. 100VA will be plenty for MAX, Darwin, and OptiVol, but check TPA's site for the Opus. The cleaner, more stable the PS, the cleaner and better the DAC works._

 

well I think 100va will be enough even if I add the Opus. the Toroids TPA sells are only 15va and supposedly one should work for an Opus so I should be good. I had previously figured that 50va would be enough for the Max, Darwin and OptiVol (1000ma for Max, 16ma for OptiVol, 60ma for Dawrin)

 That's all true. I think I'm just going to splurge and pre-order an Opus... then I have to wait


----------



## BoilermakerFan

Quote:


  Originally Posted by *soloz2* /img/forum/go_quote.gif 
_well I think 100va will be enough even if I add the Opus. the Toroids TPA sells are only 15va and supposedly one should work for an Opus so I should be good. I had previously figured that 50va would be enough for the Max, Darwin and OptiVol (1000ma for Max, 16ma for OptiVol, 60ma for Dawrin)

 That's all true. I think I'm just going to splurge and pre-order an Opus... then I have to wait 
	

	
	
		
		

		
		
	


	


_

 

I didn't realize the Opus only needed 15VA. What about the Buffalo DAC, it's SPDIF and USB our of the box with passive I/V and only like $30-$40 more than the comparable Opus. I think the Buffalo will be in stock before the Opus. 

 I'm patiently waiting for their revised Joshua Tree... The wait is killing me!


----------



## Iniamyen

Well, I got everything wired up, and I can kick it on and everything lights up nicely. The DB's even give ~30 mV biases so I can leave it on. However, the PS voltage seems to be stuck at around ~30.4 VDC (which I'm assuming is the regulated value.) No matter how much I adjust RR3 (clicks in either direction), the voltage doesn't budge.

 Any ideas before I post some pics? 
	

	
	
		
		

		
		
	


	




 TIA!

 EDIT: I also noticed that the tube biases are really high (20 V and climbing) so I don't want to leave it on very long.


----------



## Iniamyen

New problem:

 I figured out one of the pins on the regulator wasn't tacked down yet (d'oh!) so it's now fully situated.

 Now when I kick it on, no lights light up anymore, but I get a trimmable voltage that I can adjust between 1.3V and 1.4V. Any ideas?


----------



## tomb

Quote:


  Originally Posted by *Iniamyen* /img/forum/go_quote.gif 
_New problem:

 I figured out one of the pins on the regulator wasn't tacked down yet (d'oh!) so it's now fully situated.

 Now when I kick it on, no lights light up anymore, but I get a trimmable voltage that I can adjust between 1.3V and 1.4V. Any ideas?_

 

Check to see if you soldered CR5 in backwards - CR4, too.


----------



## Iniamyen

CR4 and CR5 look oriented correctly. I tried to get a close up picture but they're pretty well hidden haha.


----------



## tomb

Quote:


  Originally Posted by *Iniamyen* /img/forum/go_quote.gif 
_CR4 and CR5 look oriented correctly. I tried to get a close up picture but they're pretty well hidden haha._

 

Their polarity is critical. There should be a tiny red "+" on the yellow blob on the positive side. If not, there's no way to tell once they're soldered in. You'd have to remove them and turn them around to make sure.

 Before you go that far, what do you measure in AC Volts at the input terminal block? DC Volts into the regulator? You can measure this with one probe in "Gnd" and by touching one at the front pin on CR3A or CR3D, or the front pin on DR1A or DR1D.


----------



## Iniamyen

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Their polarity is critical. There should be a tiny red "+" on the yellow blob on the positive side. If not, there's no way to tell once they're soldered in. You'd have to remove them and turn them around to make sure.

 Before you go that far, what do you measure in AC Volts at the input terminal block? DC Volts into the regulator? You can measure this with one probe in "Gnd" and by touching one at the front pin on CR3A or CR3D, or the front pin on DR1A or DR1D._

 

I can see the markings on CR5 even though it's soldered in. There are similar markings on CR4 so I deduced that it was correct without actually seeing the "+". The marking is a line pointing to the + terminal like this:

 _______
 |
 |
 |
 |
 +

 Also I just found what may be a bad resistor in RR1. It should be 120, but it says 121K on the resistor, and Ohm's to 3K and slowly climbing.

 I'll double check the rest of the resistors in the morning when I'm less likely to make another dumb mistake. Maybe I can find a cheap 120ohm at Fry's or ratshack so I don't have to wait another week 
	

	
	
		
		

		
			





 I'll post back when I get this corrected and it hopefully fires right up!

 Thanks!


----------



## soloz2

Quote:


  Originally Posted by *BoilermakerFan* /img/forum/go_quote.gif 
_I didn't realize the Opus only needed 15VA. What about the Buffalo DAC, it's SPDIF and USB our of the box with passive I/V and only like $30-$40 more than the comparable Opus. I think the Buffalo will be in stock before the Opus. 

 I'm patiently waiting for their revised Joshua Tree... The wait is killing me!_

 

I don't think the Opus or Buffalo draw a lot of current. It seems to be the output stages that draw more. But without reading all the pages in the Opus thread I can't be sure and I've sent several emails to TPA over the course of a few weeks and haven't received a response yet so...
 The Buffalo will end up being around $80 more. The buffalo and LCDPS runs about $190, where the Opus, USB module and LCDPS runs $185. I think the Opus will be good enough for the Max, and I'm already spending more than $$160 more than intended. I'd like to keep the overage as little as possible right now. 
 I'm not even entirely sure how often I'll use the USB in as I have a good sound card right now anyway. and for the time being I don't have another digital source in my office.


----------



## tomb

Quote:


  Originally Posted by *Iniamyen* /img/forum/go_quote.gif 
_I can see the markings on CR5 even though it's soldered in. There are similar markings on CR4 so I deduced that it was correct without actually seeing the "+". The marking is a line pointing to the + terminal like this:

 _______
 |
 |
 |
 |
 +

 Also I just found what may be a bad resistor in RR1. It should be 120, but it says 121K on the resistor, and Ohm's to 3K and slowly climbing.

 I'll double check the rest of the resistors in the morning when I'm less likely to make another dumb mistake. Maybe I can find a cheap 120ohm at Fry's or ratshack so I don't have to wait another week 
	

	
	
		
		

		
		
	


	




 I'll post back when I get this corrected and it hopefully fires right up!

 Thanks!_

 

Yep - the wrong value at RR1 would do it. 
	

	
	
		
		

		
		
	


	




 Be careful checking the rest of them. You need to visually inspect the rating, if you can. Measuring will be inconclusive for many of them because they are in parallel with other resistors in the circuit.


----------



## BoilermakerFan

OK guys, Off Topic, but I had to share...

 The street a few blocks over has a huge yard sale every year. This year we were out at 7:00am right at the start. Spied a set of speakers, but didn't want to lug them around so I stopped on the way back and they were still there.

 Marantz HD-55 speakers for $5 for the pair. Tweeters looked great, and the mids/woofers looked too, so what the heck. Figured the L-Pads might be toasted and that's why he was selling them as "broken". Took them home and fired them up. One non-working tweeter and one non-working mid on the other. But when I pushed on the L-Pads, the two drivers in question worked! So I now have a pair of circa 1976/77 Marantz speakers for $5. 
	

	
	
		
		

		
		
	


	




 They need new cabinets, but my wife loved their sound, so they will be integrated into new enclosures that fit into the console I'm refurbishing. 

 Ok, thanks for listening and now back to our regularly scheduled program.


----------



## UglyJoe

Hey guys, I'm putting in a Mouser order for my Max and the recommended CM1 cap (47uF, 25 V electrolytic) is on backorder. Will this https://www.mouser.com/Search/Produc...47-UVZ1E470MDD work as a replacement? (I think so. The only thing that is different that I see is the length, and I think that the length reported for the recommended part is incorrect anyway.)


----------



## Beefy

Quote:


  Originally Posted by *UglyJoe* /img/forum/go_quote.gif 
_Will this https://www.mouser.com/Search/Produc...47-UVZ1E470MDD work as a replacement?_

 

Seems fine. This is the cap I used UPW1E470MDD because I went for the UPW series throughout.


----------



## bperboy

Guys, I'm getting kinda antsy, I want to build another Max! 
	

	
	
		
		

		
		
	


	




 But I think I should get some K701s first to go along with my HD580s.. what do you guys think I should do?


----------



## Beefy

Quote:


  Originally Posted by *bperboy* /img/forum/go_quote.gif 
_what do you guys think I should do?_

 

Finish your σ22 
	

	
	
		
		

		
		
	


	




 I'm not sure what Max you have now....... but why not wait just a touch until the MOSFET Max site is finalised, and build yourself a MOSFET Max with BlackGates?


----------



## bperboy

Quote:


  Originally Posted by *Beefy* /img/forum/go_quote.gif 
_Finish your σ22 
	

	
	
		
		

		
		
	


	




 I'm not sure what Max you have now....... but why not wait just a touch until the MOSFET Max site is finalised, and build yourself a MOSFET Max with BlackGates?_

 

Heh, the o22 is working again, but I'm waiting for my amp boards to get back... hopefully it will all come together! 

 I've got a Mosfet Max right now, actually the first attempted mosfet max, so its gettin up there in age! If I do end up building another, it'll be mosfets, but with boutique caps.. although I think buying a new pair of headphones would be a better investment right now. I've only ever owned the HD580s as a pair of full-size cans; I've always ended up upgrading the hardware behind them, so maybe a new reference would be good.


----------



## Beefy

Quote:


  Originally Posted by *bperboy* /img/forum/go_quote.gif 
_I've got a Mosfet Max right now, actually the first attempted mosfet max, so its gettin up there in age! If I do end up building another, it'll be mosfets, but with boutique caps.._

 

Ah, of course, I remember now! 
	

	
	
		
		

		
		
	


	




 Yeah, I think that the new changes for the MOSFET buffer, along with nice caps, will be a really nice piece of kit.

  Quote:


 although I think buying a new pair of headphones would be a better investment right now 
 

Yeah, I'm at the same point in my 'career'. I really enjoy doing the DIY stuff to pass the time, but really need other gear in order to have more fun with the music.


----------



## tomb

Quote:


  Originally Posted by *UglyJoe* /img/forum/go_quote.gif 
_Hey guys, I'm putting in a Mouser order for my Max and the recommended CM1 cap (47uF, 25 V electrolytic) is on backorder. Will this https://www.mouser.com/Search/Produc...47-UVZ1E470MDD work as a replacement? (I think so. The only thing that is different that I see is the length, and I think that the length reported for the recommended part is incorrect anyway.)_

 

The delay relay electrolytics are not critical. Just make sure they're 105 deg.C. because they're up there near the middle two sinks, which can get pretty warm. Other than that, any cap will do. I use Xicon's which are 8 cents each at Mouser: 140-HTRL25V47-RC. Unfortunately, they're back ordered on those, too. To tell the truth, though, I get mine locally in little 25-packs at GA Audio Lab.

 The Nichicon UVZ is just fine, though:
UVZ1E470MDD

 That one's 22 cents. The e12 and the original prototype BOM used a 22uf 25V radial tantalum, but those are very expensive ($2+), so Colin changed it. The 47uf electrolytic tested fine, so we stuck with it.


 EDIT: There's nothing wrong with the UPW that you and Beefy discussed, either - just wanted you to know that you have a wide choice with CM1 and CM3.


----------



## Cankin

do you guys think the MOSFET Max is a better option for low-impedance headphone than MH Max because of the higher current output?


----------



## Beefy

Quote:


  Originally Posted by *Cankin* /img/forum/go_quote.gif 
_do you guys think the MOSFET Max is a better option for low-impedance headphone than MH Max because of the higher current output?_

 

All other factors equal, I don't think that a MOSFET Max is going to be _that_ much better than a BJT Max. Seriously, with low impedance phones this amp WILL deafen you before it drops out of Class A - even with FK6 tubes - regardless of the output stage.

 That being said, I haven't yet seen many opinions of the MOSFET Max with AMB's suggested alterations. I'm really interested to see how it works out!


----------



## FallenAngel

Quote:


  Originally Posted by *Cankin* /img/forum/go_quote.gif 
_do you guys think the MOSFET Max is a better option for low-impedance headphone than MH Max because of the higher current output?_

 

Don't worry about current output ability, both will supply more than enough current for any headphone. Just remember, MOSFETs sound warmer than BJT and that's the main difference in sound.


----------



## bperboy

Quote:


  Originally Posted by *Beefy* /img/forum/go_quote.gif 
_All other factors equal, I don't think that a MOSFET Max is going to be that much better than a BJT Max. Seriously, with low impedance phones this amp WILL deafen you before it drops out of Class A - even with FK6 tubes - regardless of the output stage.

 That being said, I haven't yet seen many opinions of the MOSFET Max with AMB's suggested alterations. I'm really interested to see how it works out!_

 

I have made the alterations to the MOSFET stage, but I couldn't really tell you that I heard any differences... If I had two versions to compare, I might be able to do that, but all I could tell you is that both of them worked correctly.


----------



## tomb

rhester claimed recently in another thread that the MOSFET-MAX (JFET-mod) had better clarity on the high end than the BJT versions he'd built.

 Colin just built one recently, so maybe he can share his experiences, too. I'm about 40% finished with a new website for one and should have a couple building shortly, I hope.


----------



## Beefy

Quote:


  Originally Posted by *bperboy* /img/forum/go_quote.gif 
_I have made the alterations to the MOSFET stage, but I couldn't really tell you that I heard any differences... If I had two versions to compare, I might be able to do that, but all I could tell you is that both of them worked correctly._

 

Fair enough then. Have you considered just adding BlackGates to your current Max? Hell of a lot cheaper than a whole new build! 
	

	
	
		
		

		
			





 Oh, and looking at the photos on diyforums (though these are probably old now), putting the bigger caps at CA4/5?


----------



## bperboy

Quote:


  Originally Posted by *Beefy* /img/forum/go_quote.gif 
_Fair enough then. Have you considered just adding BlackGates to your current Max? Hell of a lot cheaper than a whole new build! 
	

	
	
		
		

		
		
	


	




 Oh, and looking at the photos on diyforums (though these are probably old now), putting the bigger caps at CA4/5?_

 

Not really, as I've already got Muse ES caps in there.. if I were to make any upgrades like that, I'd probably just do a new one; then I could make the casework a bit better and mount the board so the pot and jack are at the midline of the case.


----------



## bperboy

So when's that MOSFET site going up Tom?


----------



## soloz2

I have all the parts necessary to populate my next max (save for boutique caps, I'll be using BG and VitQ) but have been considering the Mosfet Max...

 if the Mosfet version has better highs, I'm in... just need a BOM and a little direction!


----------



## jamess71

Quote:


  Originally Posted by *amphead* /img/forum/go_quote.gif 
_Which drill press did you end up with?_

 

Delayed response amphead, been real busy with work. 

 None yet. Any recomendations for a budget drill press? I'll be mainly just using it for diy cases. I didn't realize the varieties and price ranges of these things. Ouch

 THnaks
 James


----------



## BoilermakerFan

I don't think one version is necessarily better than the other in a hands down fashion. There are about 10 different BJTs to choose from for the DBs that affect the sound and only one set of MOSFETs. The MOSFETs have to be biased higher in order to sound great, it's not that they are more powerful per say. Most of the BJTs recommended for the MAX were all used in 5W/ch amps...

 I have 7 sets of BJTs to try and 4 of them haven't been used on anyone's MAX to my knowledge yet. At least nobody has posted builds with them yet...

 I will build a MOSFET MAX to hear the differences, but I'm not at all convinced one is better than the other.

 James,

 I don't think you can go wrong with one of the Delta 10" or 12" benchtop drill presses and they are under $200 at HD.


----------



## BoilermakerFan

Quote:


  Originally Posted by *soloz2* /img/forum/go_quote.gif 
_I have all the parts necessary to populate my next max (save for boutique caps, I'll be using BG and VitQ) but have been considering the Mosfet Max...

 if the Mosfet version has better highs, I'm in... just need a BOM and a little direction! 
	

	
	
		
		

		
		
	


	


_

 

I have the revised BOM, PM me your email for the pics you requested and I'll forward the revised BOM to you as well.


----------



## tomb

Quote:


  Originally Posted by *BoilermakerFan* /img/forum/go_quote.gif 
_I don't think one version is necessarily better than the other in a hands down fashion. There are about 10 different BJTs to choose from for the DBs that affect the sound and only one set of MOSFETs. The MOSFETs have to be biased higher in order to sound great, it's not that they are more powerful per say. Most of the BJTs recommended for the MAX were all used in 5W/ch amps...

 I have 7 sets of BJTs to try and 4 of them haven't been used on anyone's MAX to my knowledge yet. At least nobody has posted builds with them yet...

 I will build a MOSFET MAX to hear the differences, but I'm not at all convinced one is better than the other._

 

Yes, I would agree with that. Differences will probably be subtle, but it will be interesting to find out for sure.
	

	
	
		
		

		
		
	


	




  Quote:


 James,

 I don't think you can go wrong with one of the Delta 10" or 12" benchtop drill presses and they are under $200 at HD. 
 

Agreed. Although, the Home Depot has stopped carrying the Delta's in our area - they offer Ryobi's, instead. Whereas if you go up to a floor-standing model, then Ridgid, I think.

 Lowes still carries the Delta tabletop model - that's what I have. The small 3" indexing vise ($30-$40) at Harbor Freight will just fit. That thing makes short work of drilling lots of holes on the same fixture - just one setup - very nice. However, the small cheapie drill presses they sell at HF and Pep Boys, etc., aren't big enough to take an attachment like that.

  Quote:


 I have the revised BOM, PM me your email for the pics you requested and I'll forward the revised BOM to you as well. 
 

Releasing privileged information are we?
	

	
	
		
		

		
		
	


	







 Seriously, I will send it if you don't. I'm just a bit embarassed that I don't have the JFETs and MOSFETs setup for sale at Beezar, yet, while the BOM specifies that as source. So, take that into consideration.


----------



## BoilermakerFan

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Yes, I would agree with that. Differences will probably be subtle, but it will be interesting to find out for sure. 
	

	
	
		
		

		
		
	


	


_

 

I discussed the one pair that I had a concern about with our friend and he said it wouldn't be a problem with the 2-1/2" heatsinks, so I'm going to order enough of them to allow me to sort them for higher beta values... 

  Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_I'm just a bit embarassed that I don't have the JFETs and MOSFETs setup for sale at Beezar, yet, while the BOM specifies that as source. So, take that into consideration. 
	

	
	
		
		

		
		
	


	


_

 

I was going to edit the BOM and put "Harass tomb to get them in stock at Beezar.com" in that field.


----------



## patton713MW

How would the cost of a MOSFET build compare to that of a BJT build?


----------



## BoilermakerFan

Quote:


  Originally Posted by *patton713MW* /img/forum/go_quote.gif 
_How would the cost of a MOSFET build compare to that of a BJT build?_

 

If I remember correctly, about $35-$50 more for matched MOSFETs than BJTs based on budgetary pricing from Beezar.com for the MOSFETs, with all other components being similar, i.e., the same boutique caps. If your really watching costs, the BJTs can be built on the smaller 1-1/2" heatsinks were the MOSFETs need 2" heatsinks.


----------



## tomb

That sounds good, except the BJT MAX is built around 1" sinks. The MOSFET-MAX can go up to about 150ma with 1-1/2" sinks, depending on how the case is ventilated. A well-ventilated case should be able to support 90ma bias with just 1" sinks, but that's something I'll be testing.


----------



## patton713MW

hmm... interesting. So that would bring the total build cost up to ~$180-$200? If as you say it's not that drastic of a difference in sound, i'd probably just stick to the BJTs. I'm paring it up with my DT880, is there any specific BJT combo that you could say sounds better with these phones? Any experience there?


----------



## soloz2

Quote:


  Originally Posted by *patton713MW* /img/forum/go_quote.gif 
_hmm... interesting. So that would bring the total build cost up to ~$180-$200? If as you say it's not that drastic of a difference in sound, i'd probably just stick to the BJTs. I'm paring it up with my DT880, is there any specific BJT combo that you could say sounds better with these phones? Any experience there?_

 

Ha-Ha! I haven't built one for that yet! Even simple changes make the price higher.


----------



## amphead

2SC3422/2SA1359 are my favorite BJTs for bass response.


----------



## patton713MW

Good, that fits what I'm looking at. I've decided to do Build #2. 

 I think I might pick up a pair of 12AE6 and a pair of 12FK6 just so I can hear them both and compare. Which tubes do you prefer?


----------



## MasiveMunkey

Quote:


  Originally Posted by *patton713MW* /img/forum/go_quote.gif 
_Good, that fits what I'm looking at. I've decided to do Build #2. 

 I think I might pick up a pair of 12AE6 and a pair of 12FK6 just so I can hear them both and compare. Which tubes do you prefer?_

 

I have DT880s as well and I prefer the 12AE6 tubes over the 12FK6s since the 12AE6s add more bass, which goes well with the DT880s. I haven't listened to my 12FM6 tubes yet, so no opinion on those.


----------



## jamess71

Thanks guys. I was in sears yesterday for an air conditioner and they had the 12" tabletop drill press on sale $40 dollars off. So I got the craftsman for $78. I think it will make my life a whole lot easier for my case work. Can' t go wrong with that price either. I'll let you know tomorrow after I case up my boutique max tonight. 
	

	
	
		
		

		
			





 James


----------



## tomb

Quote:


  Originally Posted by *patton713MW* /img/forum/go_quote.gif 
_Good, that fits what I'm looking at. I've decided to do Build #2. 

 I think I might pick up a pair of 12AE6 and a pair of 12FK6 just so I can hear them both and compare. Which tubes do you prefer?_

 

Ya'll please note that I have again revised the MAX Boutique page:

Millett Hybrid MAX Boutique

 We referenced it earlier, but I am officially proclaiming genuine Vitamin Q's as superior to K42's. After living with these things for quite awhile now, I tend to agree with Dsavitsk's reviews on both of them - perhaps not as much with the K42's, but 100% with the VitQ's:
Notes On Output Coupling Capacitors

 As with the JFET-mod to the MOSFET-MAX, I'd just as soon people not build something unless it has the latest/best we've found. That's also considering economics, too. IMHO, there just isn't a better buy in capacitors than spending ~$3 on a genuine Vitamin Q.


----------



## patton713MW

Quote:


  Originally Posted by *MasiveMunkey* /img/forum/go_quote.gif 
_I have DT880s as well and I prefer the 12AE6 tubes over the 12FK6s *since the 12AE6s add more bass, which goes well with the DT880s*._

 

Those were my thoughts exactly when I read the description on beezar.com. Haha, glad to see my logic and reasoning are still is based in some reality! 
	

	
	
		
		

		
		
	


	




 I know that the 12AE6 have a higher gain (14), how does that gain pair up with the DT880? How much of the volume pot range do you use?
  Quote:


  Originally Posted by *tomb* 
_I am officially proclaiming genuine Vitamin Q's as superior to K42's._

 

Good! I was wrestling that choice over in my mind last night, and its good to hear a firmer response on them other than "they're about the same". I think I might actually be getting parts narrowed down! 
	

	
	
		
		

		
		
	


	




 What are some good choices for the volume knob? I'm ordering from Mouser.com. The shaft size is 6mm?


----------



## tomb

Quote:


  Originally Posted by *patton713MW* /img/forum/go_quote.gif 
_Those were my thoughts exactly when I read the description on beezar.com. Haha, glad to see my logic and reasoning are still is based in some reality! 
	

	
	
		
		

		
		
	


	




 I know that the 12AE6 have a higher gain (14), how does that gain pair up with the DT880? How much of the volume pot range do you use?</snip>_

 

Gain is not quite up to 14 for a 12AE6 in the actual circuit, perhaps 12-1/2 with a 330ohm load, but down to 7-1/2 with 32ohms. It varies with the impedance of the load.

 Just so that you're not disappointed, I suspect that there are few of us who use much more than 1/2 of the volume travel. I think some builders have reported that 100 ohm output resistors attenuates things enough that it's in the same range as their other amps. That comes with a penalty in dynamics and detail - even using great resistors like Kiwame's. So, others of us like as little output resistance as possible, even if that means 1/4 turn on the volume for ear-splitting levels.

 Luckily, the ALPS RK27 is able to take that in stride with very good quieting and fantastic channel tracking down to almost zero.

 Or, you can always change to a 12FK6. Bass is not lacking in those, either, with low-impedance phones.


----------



## tomb

Quote:


  Originally Posted by *patton713MW* /img/forum/go_quote.gif 
_<snip>What are some good choices for the volume knob? I'm ordering from Mouser.com. The shaft size is 6mm?_

 

Yes, the ALPS RK27 is 6mm. Many of us use the knobs from Partspipe on e-bay (hongkongsuperseller). They are pretty much made for RK27's. The inside of the knob is counter-bored pretty deep so that the shaft almost fits without trimming. If we were using thicker case endplates than the Hammond's, I think they would fit without trimming. As it is, it's not much you have to cut off using these:

 Black -
2,30x22 Aluminum Hi-Fi CD VOLUME TONE CONTROL KNOB,B - eBay (item 300230353492 end time Jun-09-08 20:41:57 PDT)

 Silver -
2, 30x22 Aluminum Dimple Hi-Fi CD VOLUME Pointer KNOB - eBay (item 300230883058 end time Jun-11-08 16:34:04 PDT)

 These are great knobs - all I ever use on a full-size MAX. Plus, the ebay-er is dependable and shipping times are reasonable, considering the distance. $9.99 for two, including shipping.


----------



## patton713MW

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Just so that you're not disappointed, I suspect that there are few of us who use much more than 1/2 of the volume travel. I think some builders have reported that 100 ohm output resistors attenuates things enough that it's in the same range as their other amps. That comes with a penalty in dynamics and detail - even using great resistors like Kiwame's. So, others of us like as little output resistance as possible, even if that means 1/4 turn on the volume for ear-splitting levels._

 

I want to avoid output resistors, so I can live with limited volume travel. I have the 250 ohm DT880, so I assume that would give a gain around 12ish?
  Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Or, you can always change to a 12FK6. Bass is not lacking in those, either, with low-impedance phones._

 

Then would you say that it would be worth it to buy a pair of each instead of selecting one or the other?


----------



## patton713MW

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_<snip>Silver -
2, 30x22 Aluminum Dimple Hi-Fi CD VOLUME Pointer KNOB - eBay (item 300230883058 end time Jun-11-08 16:34:04 PDT)_

 

Wow, thats a great looking knob! Aluminum, beefy, smooth. Thanks!


----------



## tomb

Quote:


  Originally Posted by *patton713MW* /img/forum/go_quote.gif 
_Then would you say that it would be worth it to buy a pair of each instead of selecting one or the other?_

 

Chances are at 250ohm, you'd want the 12AE6's. Yet, NOS tubes can be fairly random. I've always bought extra in the hopes of rolling in that special pair that sound better than all the others. Changes like that are mitigated somewhat by the powerful SS buffers in the MAX, but you can't tell what you like until you hear it.


----------



## Takaji

Guys, I'm trying to find a 3mm LED for the MAX that is bright (around 5500 mcd as the BOM suggests). Can anyone give me some Mouser part numbers? I'm interested in light blue, blue, ultraviolet, aqua green...

 As well, I'm using the 2SC2238/2SA968 power transistor set in my build, and I've noted that the 2SC2238 has a reversed pinout. Does this mean that on the QB9L/R I mount the transistor on the outer pad (pad facing outwards with the thick white line silkscreened on it) or the inner pad (pad facing inwards closest to RB8L/R, RB10L/R)?

 Thanks a lot!


----------



## BoilermakerFan

Quote:


  Originally Posted by *Takaji* /img/forum/go_quote.gif 
_Guys, I'm trying to find a 3mm LED for the MAX that is bright (around 5500 mcd as the BOM suggests). Can anyone give me some Mouser part numbers? I'm interested in light blue, blue, ultraviolet, aqua green...

 As well, I'm using the 2SC2238/2SA968 power transistor set in my build, and I've noted that the 2SC2238 has a reversed pinout. Does this mean that on the QB9L/R I mount the transistor on the outer pad (pad facing outwards with the thick white line silkscreened on it) or the inner pad (pad facing inwards closest to RB8L/R, RB10L/R)?

 Thanks a lot!_

 

Uh oh, reverse pinout. You better send those transistors to me and I'll send you different ones to replace them. 
	

	
	
		
		

		
		
	


	




Millett Hybrid MAX BJT Transistors

 A picture is worth a 1,000 words, so check out the great pic on the MAX website...


----------



## MrMajestic2

Quote:


  Originally Posted by *Takaji* /img/forum/go_quote.gif 
_Guys, I'm trying to find a 3mm LED for the MAX that is bright (around 5500 mcd as the BOM suggests). Can anyone give me some Mouser part numbers? I'm interested in light blue, blue, ultraviolet, aqua green..._

 

Im pretty sure I have a couple of ultrabright blue ones that I never used in my Max builds. They are from LSDiodes and 5500mcd. They will blind you for a while 
	

	
	
		
		

		
			





 Drop me a PM if you want them. Otherwise these guys seem to have a good selection:
Alan Parekh Electronic Projects Online Store


----------



## Takaji

Quote:


  Originally Posted by *BoilermakerFan* /img/forum/go_quote.gif 
_Uh oh, reverse pinout. You better send those transistors to me and I'll send you different ones to replace them. 
	

	
	
		
		

		
		
	


	




Millett Hybrid MAX BJT Transistors

 A picture is worth a 1,000 words, so check out the great pic on the MAX website..._

 

Ahhh yes, of course!! I don't know how I missed that image. Thank you so much.


----------



## Takaji

Quote:


  Originally Posted by *MrMajestic2* /img/forum/go_quote.gif 
_Im pretty sure I have a couple of ultrabright blue ones that I never used in my Max builds. They are from LSDiodes and 5500mcd. They will blind you for a while 
	

	
	
		
		

		
		
	


	




 Drop me a PM if you want them. Otherwise these guys seem to have a good selection:
Alan Parekh Electronic Projects Online Store_

 

No way, this store is right in my city it seems!
 Thanks so much MrMajestic for recommending this place and your offer!


----------



## djbob

I was getting ready to order parts for my 2nd Max build and realized that Hi-Temp Radial Electrolytic Capacitors 25V 47uF 105C (for CM1) at Mouser are on backorder. Can anyone tell me of a suitable replacement for this cap? Could I use the 33uf with no adverse effects? I'd really hate to have to wait or order just this part from another supplier.


 Edit: Also, the Radial Tantalum Capacitors, Bulk Packaging 35V 10uF 10% (CR4) are backordered, so I also need to know a suitable substitute for this as well.

 Thanks


----------



## BoilermakerFan

Quote:


  Originally Posted by *djbob* /img/forum/go_quote.gif 
_I was getting ready to order parts for my 2nd Max build and realized that Hi-Temp Radial Electrolytic Capacitors 25V 47uF 105C (for CM1) at Mouser are on backorder. Can anyone tell me of a suitable replacement for this cap? Could I use the 33uf with no adverse effects? I'd really hate to have to wait or order just this part from another supplier.

 Thanks
	

	
	
		
		

		
		
	


	


_

 

You can split the BOM pretty easily between Digi-Key and Mouser. I'd just order the recommended V-D RD55 resistors from Mouser, and the caps from Digi-Key along with the Hoffman case to hit the minimum order requirements. Plus you can order Silmic II or Panasonic FC caps from Digi-Key if you want to try something different from the Muse ES without stepping all the way up to BGs.

 Also, just make sure you populate both orders at the same time in case you come across other items on back-order at either company. I had to wait about 3 weeks for a transistor to come in from Mouser because I waited 3 days after I already placed my Digi-Key order...


----------



## tomb

Quote:


  Originally Posted by *djbob* /img/forum/go_quote.gif 
_I was getting ready to order parts for my 2nd Max build and realized that Hi-Temp Radial Electrolytic Capacitors 25V 47uF 105C (for CM1) at Mouser are on backorder. Can anyone tell me of a suitable replacement for this cap? Could I use the 33uf with no adverse effects? I'd really hate to have to wait or order just this part from another supplier._

 

Boilermakerfan has a good suggestion - it's an excuse to use DigiKey for those wonderful Panasonic FM's for CR1's, CA4's and CA5's.

 Or, you can check the post #4918 where we just answered this a few pages back:
New Millett Hybrid MAX - Post #4918

 The quality of the electrolytics in the relay-delay are not critical. You can use any brand, almost. I use Xicons, although Mouser is out of those right now, too - but the Nichicon UVZ's will work just fine, too. Or, you can even use a 22uf 25V radial tantalum, but those are kind of expensive.

  Quote:


 Edit: Also, the Radial Tantalum Capacitors, Bulk Packaging 35V 10uF 10% (CR4) are backordered, so I also need to know a suitable substitute for this as well.

 Thanks
	

	
	
		
		

		
		
	


	



 

Any other radial tantalum with the same ratings should work. Even differing lead spacing can be bent to fit. However, this one by Kemet should be an equal replacement:
T350G106K035AT


----------



## soloz2

I was just going to suggest ordering from Digikey so you could get some Panasonic FM's but looks like I got beat to the punch line!




 so... when's the Mosfet Max site going to be up?


----------



## tomb

Quote:


  Originally Posted by *soloz2* /img/forum/go_quote.gif 
_<snip>so... when's the Mosfet Max site going to be up?_

 

I hate to over-commit, but maybe a week or two?


----------



## Beefy

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_I hate to over-commit, but maybe a week or two?_

 

You do realise that in exactly 14 days and 1 minute, there will be a constant stream of posts asking you why it hasn't been done yet..........


----------



## tomb

Quote:


  Originally Posted by *Beefy* /img/forum/go_quote.gif 
_You do realise that in exactly 14 days and 1 minute, there will be a constant stream of posts asking you why it hasn't been done yet.......... 
	

	
	
		
		

		
		
	


	


_

 

Looks like I'm already getting them.


----------



## bperboy

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Looks like I'm already getting them. 
	

	
	
		
		

		
		
	


	





_

 

Stream, stream, stream, where's our website?!


----------



## BoilermakerFan

Quote:


  Originally Posted by *bperboy* /img/forum/go_quote.gif 
_Stream, stream, stream, where's our website?! 
	

	
	
		
		

		
		
	


	





_

 

LOL! You have already built a MOSFET-MAX.


----------



## cetoole

Few pics of a MOSFET Max I recently finished:


----------



## rds

That's really nice!
 What paint did you use for the case?


----------



## tomb

Great job, Colin! 
	

	
	
		
		

		
		
	


	




 So, you biased 10ohm Kiwame output resistors directly to the MOSFETs?


----------



## cetoole

Tom, 5 ohm actually, and I changed the values for the JFET source resistors as well.

 Paint is 2 coats of self etching primer, followed by two of Rustoleum Hammered Black. For the headphone jack and LED bezel, it is primer+flat black.


----------



## Beefy

What are those bright red resistors? I've seen them used on a few DIY builds......

 Oh, googling TC50 is my friend - they are from PRP, correct?


----------



## tomb

Quote:


  Originally Posted by *Beefy* /img/forum/go_quote.gif 
_What are those bright red resistors? I've seen them used on a few DIY builds......

 Oh, googling TC50 is my friend - they are from PRP, correct?_

 

Yep - at Soniccraft, PartsConX and Handmade is starting to carry them, too, I believe. They go very nicely with Colin's Black Gate NX's.
	

	
	
		
		

		
			





 Colin - so did you go without CR5 entirely, or was that an interim pic? I recognize the Polystyrenes, but are those FG's in CR4 and CR5?


----------



## pinkfloyd4ever

Quote:


  Originally Posted by *cetoole* /img/forum/go_quote.gif 
_Paint is 2 coats of self etching primer, followed by two of Rustoleum Hammered Black._

 

DAAAAAAAMMMNNNNN that's an awesome finish there Colin. You get my vote for coolest hammond case yet. This rustoleum hammered finish paint does that by itself?


----------



## cetoole

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Yep - at Soniccraft, PartsConX and Handmade is starting to carry them, too, I believe. They go very nicely with Colin's Black Gate NX's.
	

	
	
		
		

		
		
	


	


_

 

Red LEDs all around too.
  Quote:


 Colin - so did you go without CR5 entirely, or was that an interim pic? I recognize the Polystyrenes, but are those FG's in CR4 and CR5? 
 

Yup, Nope, Yup, though I ended up removing them, Yup
  Quote:


  Originally Posted by *pinkfloyd4ever* /img/forum/go_quote.gif 
_DAAAAAAAMMMNNNNN that's an awesome finish there Colin. You get my vote for coolest hammond case yet. This rustoleum hammered finish paint does that by itself?_

 

Thanks Mr. Floyd, I like it. That is how hammered black paint dries, though the texture is dependent on how far away the spray can is from what you are painting and how thick you put the paint on. I have used it on two Millett Max amps now, and both look a bit different (other isnt completely reassembled yet, I took it apart to paint the case, so pics will come soon enough).


----------



## BoilermakerFan

Colin

 Is that a Nobel volume pot?


----------



## cetoole

Quote:


  Originally Posted by *BoilermakerFan* /img/forum/go_quote.gif 
_Colin

 Is that a Nobel volume pot?_

 

Of course, 10kohm. These pots are great (especially when you happen across a $2 each deal). I use them on almost all of my projects.


----------



## BoilermakerFan

Quote:


  Originally Posted by *cetoole* /img/forum/go_quote.gif 
_Of course, 10kohm. These pots are great (especially when you happen across a $2 each deal). I use them on almost all of my projects._

 

Most of us aren't that lucky...


----------



## cetoole

Quote:


  Originally Posted by *BoilermakerFan* /img/forum/go_quote.gif 
_Most of us aren't that lucky..._

 

Yeah, The Electronics Goldmine has an 8 audio pot grab bag for $2, that used to contain one Nobel pot per bag. I bought 10.


----------



## amphead

Colin, that's the Gothic Max!  Matching Darth Beyers optional. Nice effect, with red leds. Maybe some Bacardi black and Coke over ice to celebrate!


----------



## m0b1liz3

Has anyone added a bass extender to a MH to improve it's low end?


----------



## Beefy

Quote:


  Originally Posted by *m0b1liz3* /img/forum/go_quote.gif 
_Has anyone added a bass extender to a MH to improve it's low end?_

 

This amp needs _more_ low end? 
	

	
	
		
		

		
		
	


	




 What parts are you using? There are a number of options that are apparently optimal for good bass slam...... Muse ES at CA2 and CA7, Wima or blank at CA9, 2SC3422/2SA1359 output transistors, 12AE6(A) tubes......


----------



## m0b1liz3

Oops, might have been thinking of the starving student version.


----------



## UglyJoe

Question about the power transistors. I'm building a BG Max with the VitQ bypasses, and unfortunately the suggested 2238/968 BJT's aren't available right now. TomB suggested to use the 2344/1011 transistors as a replacement, and I am fine with that, however I wanted to take the opportunity and ask what others thought as well. I'm willing to trade some detail for a little extra bass, but only SMALL amounts of detail. I want something that the BG's will make worthwhile.

 Anythoughts? Also, I noticed that the lead time on arival of new 2238s at MCMinone is like 17 days now. Is it worth it just to wait and go with the tried and true? Or is there a good possibility that that lead time might be incorrect and the wait might be longer anyway?

 Thanks guys.


----------



## soloz2

Quote:


  Originally Posted by *UglyJoe* /img/forum/go_quote.gif 
_Question about the power transistors. I'm building a BG Max with the VitQ bypasses, and unfortunately the suggested 2238/968 BJT's aren't available right now. TomB suggested to use the 2344/1011 transistors as a replacement, and I am fine with that, however I wanted to take the opportunity and ask what others thought as well. I'm willing to trade some detail for a little extra bass, but only SMALL amounts of detail. I want something that the BG's will make worthwhile.

 Anythoughts? Also, I noticed that the lead time on arival of new 2238s at MCMinone is like 17 days now. Is it worth it just to wait and go with the tried and true? Or is there a good possibility that that lead time might be incorrect and the wait might be longer anyway?

 Thanks guys._

 


 I'm in the same situation. I'm leaning towards mosfets...


----------



## BoilermakerFan

Quote:


  Originally Posted by *UglyJoe* /img/forum/go_quote.gif 
_Question about the power transistors. I'm building a BG Max with the VitQ bypasses, and unfortunately the suggested 2238/968 BJT's aren't available right now. TomB suggested to use the 2344/1011 transistors as a replacement, and I am fine with that, however I wanted to take the opportunity and ask what others thought as well. I'm willing to trade some detail for a little extra bass, but only SMALL amounts of detail. I want something that the BG's will make worthwhile.

 Anythoughts? Also, I noticed that the lead time on arival of new 2238s at MCMinone is like 17 days now. Is it worth it just to wait and go with the tried and true? Or is there a good possibility that that lead time might be incorrect and the wait might be longer anyway?

 Thanks guys._

 

Are you using the Hoffman enclosure in the BOM? Is this your first build? 

 If this is your first build, I might suggest saving the BGs and using the Muse ES/Vit Qs with the 2344/1011s. You'll get 90% of the BG/2238 combo and have a lot less invested in the MAX. BUT, you'll have a great MAX to enjoy now instead of having to wait. 

 The problem Tom has had with the 2238s is actually receiving genuine 2238s. Even if they come into stock, there is no guarantee they will be genuine 2238s. 

 There are a few other BJTs that have not been tested and one set that needs to be re-evaluated in the MAX since Steinchen's web site comments were based on open-air transistors at very low bias levels. If you can be patient for a few more weeks, there may be some very good news coming forward. I personally have 4 different sets of "untested" BJTs on the way and I will make sure Tom receives the same sets from me for his comparison as well. I can't speak for Tom, but I know he is busy so we may not be able to report back within 4 weeks.

 Edit: So with the 5 sets I already have, and the 4 on the way, I'll have a "few" to choose from.


----------



## tomb

To echo Boilermakerfan, I have had a standing order with MCMinone for six months. They've attempted delivery of 2SC2238's twice during that period, but they were stamped and made by CDIL. Needless to say, they've moved that expected date so many times I can't count it anymore.

 I don't blame them, really. At least they stand behind the fact that they _want_ to sell only genuine Toshiba 2SC2238's. Counterfeits are rampant on ebay and elsewhere and many of the other reputable transistor dealers (BDent) have stopped trying to carry them altogether. The plain fact is that I suspect most of us may never see genuine Toshiba 2SC2238's again.


----------



## UglyJoe

Considering that waiting appears not be an option then, what is my best "other" option. Again, I understand that the 2344/1011 are a good replacement for the 2238/968; are they the only pair that makes sense with BG caps now, or does anyone else have another option that they like, that might have slightly less detail but something else going for it?


----------



## Iniamyen

Well, I'm having some issues desoldering one of the panel LED holes, and I still haven't done any casework, but it works (and beautifully I might add!!)

 I'm using the can't miss build #4 setup (WIMA + Muse ES + 3422/1359) with the 12AE6 tubes and I'm definitely loving the sound. Very smooth presentation, nice midrange, and nice punch to the bass. Definitely less harsh than my PIMETA with AD8610's with some music.

 Thanks for all the help! I'll *definitely* be building more of these for friends/family/myself so it's safe to say you guys have gained another fan for life!






















 EDIT: And holy crap that Vreg heatsink gets hot !


----------



## BoilermakerFan

Quote:


  Originally Posted by *UglyJoe* /img/forum/go_quote.gif 
_Considering that waiting appears not be an option then, what is my best "other" option. Again, I understand that the 2344/1011 are a good replacement for the 2238/968; are they the only pair that makes sense with BG caps now, or does anyone else have another option that they like, that might have slightly less detail but something else going for it?_

 

Well, I'll assume it's your first MAX, so you do not have a baseline to compare too. If a Porsche GT is 95% of a Ferrari Enzo, but you can't buy/drive/ or ride in an Enzo, are you going to be disappointed you had to "settle" owning and driving a Porsche GT? 
	

	
	
		
		

		
		
	


	




 You could use the BGs/VitQs with the 2344/1011s and enjoy the best "other" known/proven option at this time. Once Tom and I have had a chance to do listening comparisons of the 4 other sets, then we can report our findings to everyone and make recommendations. Tom's will probably be based on using them with 1" or 1-1/2" heatsinks and BGs or Muse ES caps. Mine will be based on using a different case with 2-1/2" heatsinks so I can run a lot higher bias current with Muse ES, Silmic IIs, and/or Cerafines. I will probably start with Muse ES caps since I have (3) sets of them from Beezar and they are easily sourced from there so I try to keep a known baseline and only change the DB transistors. If we find a set that we both really like head and shoulders above the current offerings, then you could swap out the 2344/1011s for this new set. 

 But perhaps you should let us know what type of music you primarily enjoy and what headphones you have or plan to purchase. That may change everyone's recommendations for you.


----------



## UglyJoe

Thanks, Boilermakerfan. I am not trying to be rude or ignore you, in case that is how it's coming across.

 Yes, this is my first Max (I've had 2 boards since the original group buy and simply haven't stuffed them yet). The reason I waited so long is because I wanted to build the BG version... maybe it's silly, but I hate to have spent all this time waiting to get the cash to build a BG Max and then not do it because the recommended transistor pair isn't available anymore.

 As far as musical tastes I like everything, but mostly listen to rock. I have a set of sr125's, and my next plan of purchase is either HD650s or K701s, if I can get a listen to them sometimes soon. I want something else to contrast the in-your-face grado sound, with a bigger soundstage, and the K701 seems to fit that bill; plus I seem to remember that the k701 pairs nicely with a Max.

 As far as what I like to get out of sound, detail is obviously extremely important. I don't mean to make it sound like I'm willing to completely sacrifice detail for bass... on the contrary, I'd be extremely disappointed with booming sloppy bass and no detail. However, I understand that the 2238/968 pair is sensational at detail and maybe not so strong in the bass, and that the 2344/1011 pair is like the toshibas, only not as good. My question was only if I had to lose a little of the detail of the 2238/968 pair already, if there might not be another pair with a little less detail but better payoff in bass or some other aspect than the 2344/1011 pair.


 EDIT: More than likely I'll order the 2344/1011 pair, as that seems to be the default BG build recommendation now that the 2238 is disappeared; I just wanted to get anyone else's thoughts on other possibilities that might work as well or better.


----------



## Beefy

Quote:


  Originally Posted by *UglyJoe* /img/forum/go_quote.gif 
_EDIT: More than likely I'll order the 2344/1011 pair, as that seems to be the default BG build recommendation now that the 2238 is disappeared; I just wanted to get anyone else's thoughts on other possibilities that might work as well or better._

 

I really suspect that the new MOSFET Max will become the de-facto pairing with Black Gates, based on AMB's simulations. Wait just a week or two, and tomb will hopefully have the MOSFET site up and post some comparative listening impressions.

 (And no, this IS NOT meant as a hurry up to tomb! 
	

	
	
		
		

		
		
	


	




 )


----------



## BoilermakerFan

Quote:


  Originally Posted by *UglyJoe* /img/forum/go_quote.gif 
_Thanks, Boilermakerfan. I am not trying to be rude or ignore you, in case that is how it's coming across.

 Yes, this is my first Max (I've had 2 boards since the original group buy and simply haven't stuffed them yet). The reason I waited so long is because I wanted to build the BG version... maybe it's silly, but I hate to have spent all this time waiting to get the cash to build a BG Max and then not do it because the recommended transistor pair isn't available anymore.

 As far as musical tastes I like everything, but mostly listen to rock. I have a set of sr125's, and my next plan of purchase is either HD650s or K701s, if I can get a listen to them sometimes soon. I want something else to contrast the in-your-face grado sound, with a bigger soundstage, and the K701 seems to fit that bill; plus I seem to remember that the k701 pairs nicely with a Max.

 As far as what I like to get out of sound, detail is obviously extremely important. I don't mean to make it sound like I'm willing to completely sacrifice detail for bass... on the contrary, I'd be extremely disappointed with booming sloppy bass and no detail. However, I understand that the 2238/968 pair is sensational at detail and maybe not so strong in the bass, and that the 2344/1011 pair is like the toshibas, only not as good. My question was only if I had to lose a little of the detail of the 2238/968 pair already, if there might not be another pair with a little less detail but better payoff in bass or some other aspect than the 2344/1011 pair.


 EDIT: More than likely I'll order the 2344/1011 pair, as that seems to be the default BG build recommendation now that the 2238 is disappeared; I just wanted to get anyone else's thoughts on other possibilities that might work as well or better._

 

It didn't come off that way. But if you have two boards and those cans, then I why don't you save the BGs for a MOSFET build and use the Muse ES caps/VitQs with the 2344/1011s and 12FK6 tubes? Personally, I think that setup would rock with the Grados since the Muse ES are bass caps and the VitQs keep the highs. The resolution and detail with the 12FK6 tubes is better too. Then build the MOSFET with the BGs and 12AE6A tubes for the K701s or K702s when they are finally released. 

 I'm planning to buy K601s now, then K702s when they hit the streets...


----------



## bhjazz

Quote:


  Originally Posted by *Iniamyen* /img/forum/go_quote.gif 
_I'm using the can't miss build #4 setup (WIMA + Muse ES + 3422/1359) with the 12AE6 tubes and I'm definitely loving the sound. Very smooth presentation, nice midrange, and nice punch to the bass. 

 Thanks for all the help! I'll *definitely* be building more of these for friends/family/myself so it's safe to say you guys have gained another fan for life!_

 

Beautiful build, Iniamyen. Nice work! 

 BTW: where is this "can't miss build" description you speak of? I have a max board waiting and I'd like to rough out my options. Thanks!

 Also, since you are near Seattle, you're in for a treat. There is a Head-Fi meet in Seattle on June 21. We'd love to meet you! Here is the thread if you want to browse. 

http://www.head-fi.org/forums/f24/ju...eattle-311361/

 Welcome to Head-Fi!


----------



## Beefy

Quote:


  Originally Posted by *bhjazz* /img/forum/go_quote.gif 
_BTW: where is this "can't miss build" description you speak of? I have a max board waiting and I'd like to rough out my options. Thanks!_

 

Millett Hybrid MAX Boutique

 I built #2.


----------



## tomb

Quote:


  Originally Posted by *Beefy* /img/forum/go_quote.gif 
_I really suspect that the new MOSFET Max will become the de-facto pairing with Black Gates, based on AMB's simulations. Wait just a week or two, and tomb will hopefully have the MOSFET site up and post some comparative listening impressions.

 (And no, this IS NOT meant as a hurry up to tomb! 
	

	
	
		
		

		
		
	


	




 )_

 

I didn't take it as one. Nevertheless, I suspect what else you state is probably the case. 
	

	
	
		
		

		
		
	


	




 Boilermakerfan - 
 Please don't take this in any way as discouragement.
	

	
	
		
		

		
		
	


	







 While I agree in principle that there _may_ be a _slight_ chance that we can discover a diamond in the rough with some of the other less-known transistors, I wouldn't get your hopes up too high.

 All of the recommended transistors and even their replacements are very well known to some, especially Steinchen. Note that his reviews were developed from a wide range of his experience in building just about every major solid-state DIY headphone amp ever designed. It's possible that we could find another transistor pair to be preferrable. So far, however, I've tried almost all of them and haven't found any of them to deviate very much from Steinchen's stated sound characteristics. 

 I would suggest, like you did, that perhaps UglyJoe try the 2SC2344/2SA1011 pair. Those are about 90-95% of the Toshibas. Plus, it's not an impossible job to change them out for another set sometime in the future.


----------



## Iniamyen

Quote:


  Originally Posted by *bhjazz* /img/forum/go_quote.gif 
_Beautiful build, Iniamyen. Nice work! 

 BTW: where is this "can't miss build" description you speak of? I have a max board waiting and I'd like to rough out my options. Thanks!

 Also, since you are near Seattle, you're in for a treat. There is a Head-Fi meet in Seattle on June 21. We'd love to meet you! Here is the thread if you want to browse. 

http://www.head-fi.org/forums/f24/ju...eattle-311361/

 Welcome to Head-Fi!_

 

Thanks for the link! I'm glad I posted this, cause otherwise I wouldn't have known about it. It sounds like a pretty big deal


----------



## amphead

Great work Iniamyen! Those white leds are a nice touch. Hope you are enjoying the sound.


----------



## BoilermakerFan

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_I didn't take it as one. Nevertheless, I suspect what else you state is probably the case. 
	

	
	
		
		

		
		
	


	




 Boilermakerfan - 
 Please don't take this in any way as discouragement.
	

	
	
		
		

		
		
	


	







 While I agree in principle that there may be a slight chance that we can discover a diamond in the rough with some of the other less-known transistors, I wouldn't get your hopes up too high._

 

I'm optimistic, and stubborn, so it definitely won't be taken as discouragement. 

 In order to facilitate swapping transistors, could I use these on the PCB?
310-13-164-41-001000

 My thought is to mount the transistors to the heatsinks on the correct sides for their pinouts with the Thermasil pads and then "plug" them into these socket strips for evaluation. The socket spacing is within the range for the BJTs and I'm switching to screw-mounted heatsinks so they will have support. I'll go through about $10 in Thermasil pads, but hey, that's 2 beers at a bar or just over 2 gallons of premium fuel. 
	

	
	
		
		

		
		
	


	




 My question is, how far could I push the bias before the pin and socket mounting would be a concern? Would 100mA really be pushing it or do you think that would be fine (heatsink size is not the concern, only the socket junction with the BJT)? 

 This would allow me to populate (3) MAX boards, one each with Muse ES, Silmic II, and Cerafine caps, all bypassed with VitQs running 12FK6 tubes initially. Then I can swap the BJTs between the boards, bias, and listen. Then I would repeat with 12AE6A tubes. The only variable I can't keep constant in these tests would be variations between the tubes on the different boards, until I narrow down the preferred BJTs with each set of caps, then swap tubes around to make sure it's the BJT/cap combo and not just golden tubes. 

 I think this is as easy and reliable as I can make it.


----------



## tomb

Quote:


  Originally Posted by *BoilermakerFan* /img/forum/go_quote.gif 
_I'm optimistic, and stubborn, so it definitely won't be taken as discouragement. 

 In order to facilitate swapping transistors, could I use these on the PCB?
310-13-164-41-001000</snip>_

 

I'm not too fond of Mil-Max sockets when they're not supported by additional cross-members as in DIP-sockets. They're not very stable, as anyone who's tried to use them as resistor sockets can attest. One is usually better off chopping up a DIP-socket, instead.

 I don't think Mouser has them, but DigiKey has a Molex-type socket made specifically for TO-220 transistors. I had some discussions with Colin early-on about this, but decided to build separate MAXes for each transistor type, anyway.
	

	
	
		
		

		
		
	


	




 Here's a pic:




 That's a Molex #10-18-2031, DigiKey part #WM2551-ND. Datasheet drawing here.

 The disadvantage I believe, is that you need some side clearance to manuever the transistor into the socket. So, the middle two sinks may be an issue for the inside transistor. Plus, you have to trim the legs so that their height is correct for the heat sink mount with the added length of the socket. That makes them useless for regular soldering. There's no reason why you can't solder on some spent leads if you decide to mount them permanently, however.

 P.S. The rest of your strategy sounds good.


----------



## soloz2

Quote:


  Originally Posted by *BoilermakerFan* /img/forum/go_quote.gif 
_ I'll go through about $10 in Thermasil pads, but hey, that's 2 beers at a bar or just over 2 gallons of premium fuel. 
	

	
	
		
		

		
			



_

 

hell that's 2 gallons of regular here... and I drive just under 60 miles a day round trip to work... I need a tiny car...


 Anyway, back on topic. BoilerMakerFan, you've almost got me convinced to try some of the new transistors, but I'm still leaning towards a mosfet build. If I still had Gradoes, or had a pair of RS1's (saving up) then I'd probably make a different decision.


----------



## UglyJoe

Quote:


  Originally Posted by *Beefy* /img/forum/go_quote.gif 
_I really suspect that the new MOSFET Max will become the de-facto pairing with Black Gates, based on AMB's simulations. Wait just a week or two, and tomb will hopefully have the MOSFET site up and post some comparative listening impressions.

 (And no, this IS NOT meant as a hurry up to tomb! 
	

	
	
		
		

		
		
	


	




 )_

 

 Quote:


  Originally Posted by *BoilermakerFan* /img/forum/go_quote.gif 
_It didn't come off that way. But if you have two boards and those cans, then I why don't you save the BGs for a MOSFET build and use the Muse ES caps/VitQs with the 2344/1011s and 12FK6 tubes? Personally, I think that setup would rock with the Grados since the Muse ES are bass caps and the VitQs keep the highs. The resolution and detail with the 12FK6 tubes is better too. Then build the MOSFET with the BGs and 12AE6A tubes for the K701s or K702s when they are finally released. 

 I'm planning to buy K601s now, then K702s when they hit the streets..._

 

Someone needs to catch me up on the MOSFET Max. When I was in the loop a couple of months ago it seemed to me that the BJT Max was outperforming, in most peoples opinions, the MOSFET version. However, there has been a lot of talk in the last few pages of the thread about a new MOSFET Max website and things like AMB's simulations, which I haven't come across yet. What's changed and what modifications have happened on the MOSFET side that seem to have everyone pumped about building the MOSFET version?

 BTW, thanks both of you. I'm strongly considering building the BG with MOSFETS when that option is available. I've already got the BGs for the BJT build, but I could just spend an extra $8 at Beezar to get the ESs and wait for the MOSFET version with my BGs. If anyone could point me out to previous discussion on the MOSFET Max and AMB's simulations and whatnot that has everyone excited, please do so.... 500 pages of thread is simply to long for me to look through to find it, and searching MOSFETS in the thread is close to useless as many times as they have been mentioned.


----------



## bperboy

Soloz2, sorry to take this OT, but is your PM box full?


----------



## soloz2

Quote:


  Originally Posted by *bperboy* /img/forum/go_quote.gif 
_Soloz2, sorry to take this OT, but is your PM box full?_

 

I got back to you. Just been busy.


----------



## BoilermakerFan

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_I'm not too fond of Mil-Max sockets when they're not supported by additional cross-members as in DIP-sockets. They're not very stable, as anyone who's tried to use them as resistor sockets can attest. One is usually better off chopping up a DIP-socket, instead.

 I don't think Mouser has them, but DigiKey has a Molex-type socket made specifically for TO-220 transistors. I had some discussions with Colin early-on about this, but decided to build separate MAXes for each transistor type, anyway.
	

	
	
		
		

		
		
	


	




 Here's a pic:




 That's a Molex #10-18-2031, DigiKey part #WM2551-ND. Datasheet drawing here.

 The disadvantage I believe, is that you need some side clearance to manuever the transistor into the socket. So, the middle two sinks may be an issue for the inside transistor. Plus, you have to trim the legs so that their height is correct for the heat sink mount with the added length of the socket. That makes them useless for regular soldering. There's no reason why you can't solder on some spent leads if you decide to mount them permanently, however.

 P.S. The rest of your strategy sounds good.
	

	
	
		
		

		
		
	


	


_

 

I would solder those into the boards, then use the screw-mounted sinks so I can mount the BJTs to the sinks, then plug in the combo into that socket. The screws would support the sinks...


----------



## tomb

Quote:


  Originally Posted by *UglyJoe* /img/forum/go_quote.gif 
_<snip>If anyone could point me out to previous discussion on the MOSFET Max and AMB's simulations and whatnot that has everyone excited, please do so.... 500 pages of thread is simply to long for me to look through to find it, and searching MOSFETS in the thread is close to useless as many times as they have been mentioned._

 

Without revealing too much from the new site still under development ... or dredging up some not-too-kind remarks about tubes from _non-believers_ ... this link will give you the essence of the conversion:

Millett Hybrid MAXed JFET-MOSFETmod

 Essentially, the original MOSFET buffer placed a bit of a capacitive load on the output of the tube, due to the charge capacitance of MOSFETs. Along with the input impedance of the buffer, this formed a filter that rolled off the highs slightly in the original version. The JFETs provide a very high impedance load to the tube and as Amb says, the high frequency roll-off is pushed well into the ultrasonic region.


----------



## Ferrari

The whole dicussion and the first implementation and evaluation of AMB's modification in January this year can be read at page 308-310 of this thread, uncensored.


----------



## procalli2007

Hi,

 Im trying to price up the BOM but as Im in the UK and only have a little electronics experience Im having problem making up a list.

 I am using farnell as the shipping cost is the cheapest.

 So I was wondering if anyone in the UK has already ordered the parts from farnell if they would be kind enough to paste a list here. 

 Also are there any parts which I should buy when I order the PCB from beezar.com?


 Thanks


----------



## tomb

We've had several Head-Fiers from the UK build Millett MAXes. User "adfinni' comes to mind as someone who posted just recently. You might try sending him a PM. He lives in London. I apologize if I forgot someone else who's posted lately. There are several in the beezar.com database, but there's not always a connection to a Head-Fi username.


----------



## BoilermakerFan

Quote:


  Originally Posted by *procalli2007* /img/forum/go_quote.gif 
_Hi,

 Im trying to price up the BOM but as Im in the UK and only have a little electronics experience Im having problem making up a list.

 I am using farnell as the shipping cost is the cheapest.

 So I was wondering if anyone in the UK has already ordered the parts from farnell if they would be kind enough to paste a list here. 

 Also are there any parts which I should buy when I order the PCB from beezar.com?


 Thanks_

 

I'm a little biased (rim shot), but I would definitely order as much from beezar.com as you can. The ALPS pot, the transistors, RCA jacks, Muse ES and VitQ caps, tubes, ceramic sockets, transistor mounting kits etc. Really, almost everything that Beezar sells you will need, so why not support the man that supports us?


----------



## procalli2007

Quote:


  Originally Posted by *BoilermakerFan* /img/forum/go_quote.gif 
_I'm a little biased (rim shot), but I would definitely order as much from beezar.com as you can. The ALPS pot, the transistors, RCA jacks, Muse ES and VitQ caps, tubes, ceramic sockets, transistor mounting kits etc. Really, almost everything that Beezar sells you will need, so why not support the man that supports us?_

 

I will probably do that but problem is I will have to do multiple orders as customs charges over £18.


----------



## adamus

the last 4 orders from the us i have been charged nothing from customs. Its pretty random


----------



## DrizzitT

So I just started populating my board with the resistors/diodes and noticed something...

 RR1 and RR2 are supposed to be 1/4 and 1/2 Watt resistors respectively, but the linked part is 1/8 and 1/4 Watt respectively. Are the 1/8, 1/4 watt ones acceptable or do we need the 1/4 and 1/2 Watt ones?


----------



## tomb

Quote:


  Originally Posted by *DrizzitT* /img/forum/go_quote.gif 
_So I just started populating my board with the resistors/diodes and noticed something...

 RR1 and RR2 are supposed to be 1/4 and 1/2 Watt resistors respectively, but the linked part is 1/8 and 1/4 Watt respectively. Are the 1/8, 1/4 watt ones acceptable or do we need the 1/4 and 1/2 Watt ones?_

 

Not to worry - everything's fine. 
	

	
	
		
		

		
		
	


	







 This is typical of mil-spec Vishay-Dale resistors, which everyone likes to use. They are mil-spec'd at one-half of the commercial power rating. RN55's will take 1/4W in stride and RN60's handle 1/2W continuously (both will probably handle even more than that).


----------



## procalli2007

Quote:


  Originally Posted by *BoilermakerFan* /img/forum/go_quote.gif 
_I'm a little biased (rim shot), but I would definitely order as much from beezar.com as you can. The ALPS pot, the transistors, RCA jacks, Muse ES and VitQ caps, tubes, ceramic sockets, transistor mounting kits etc. Really, almost everything that Beezar sells you will need, so why not support the man that supports us?_

 

I have made the first order with the pcb and transistors. Now Im going to make a second order but dont really understand fully the different parts.

 I will be ordering a pot, jack and 2 tube sockets but need a no nonsense list on which other parts are essential for a first build. I especially like the look of the green caps. Anyone willing to list which part and how many so I can complete an order.

 I will be usng it with either a hd 595 or a hd600.

 Thanks for any help.


----------



## Beefy

Quote:


  Originally Posted by *procalli2007* /img/forum/go_quote.gif 
_I will be ordering a pot, jack and 2 tube sockets but need a no nonsense list on which other parts are essential for a first build. I especially like the look of the green caps. Anyone willing to list which part and how many so I can complete an order._

 

That is what the BOM is for: MAX BOM

 Buy everything from Mouser or Digikey, except for what you can get at Beezar.


----------



## soloz2

Quote:


  Originally Posted by *procalli2007* /img/forum/go_quote.gif 
_I have made the first order with the pcb and transistors. Now Im going to make a second order but dont really understand fully the different parts.

 I will be ordering a pot, jack and 2 tube sockets but need a no nonsense list on which other parts are essential for a first build. I especially like the look of the green caps. Anyone willing to list which part and how many so I can complete an order.

 I will be usng it with either a hd 595 or a hd600.

 Thanks for any help._

 

the green caps are Nichicon Muse ES


----------



## BoilermakerFan

My transistor order shipped today! 

 Completing my Mouser and Digi-Key orders tonight.

 And, drum roll please... I finally decided to order a pair of AKG K601s for my first set of full-size headphones.


----------



## bperboy

Quote:


  Originally Posted by *BoilermakerFan* /img/forum/go_quote.gif 
_My transistor order shipped today! 

 Completing my Mouser and Digi-Key orders tonight.

 And, drum roll please... I finally decided to order a pair of AKG K601s for my first set of full-size headphones. 




_

 

You will let me know how they are! I've been seriously thinking about getting some akgs, either k501 or k701, but maybe k601 are very nice too!


----------



## BoilermakerFan

Quote:


  Originally Posted by *bperboy* /img/forum/go_quote.gif 
_You will let me know how they are! I've been seriously thinking about getting some akgs, either k501 or k701, but maybe k601 are very nice too!_

 

I sure will, but I only have my Denon C-700 canal phones to compare them too. Based on all the opinions and reviews of the K601s vs. K701s, I decided to start with the 601s. My plan is to recable them after they are broken in. I also need to order the 701 ear pads. Once the K702s are released, I'll probably wait for ALO to offer them with the Vampire Wire, then I'll add those to the stable. My next set of cans will be SR80s to serve as practice for mods and recable before I order SR225s. Then I'll round out the collection with a set of Denon D2000s, AT's, and Ultrasone HFI-780s. I just had to spend a lot of time deciding which pair to order first...


----------



## bperboy

Quote:


  Originally Posted by *BoilermakerFan* /img/forum/go_quote.gif 
_I sure will, but I only have my Denon C-700 canal phones to compare them too. Based on all the opinions and reviews of the K601s vs. K701s, I decided to start with the 601s. My plan is to recable them after they are broken in. I also need to order the 701 ear pads. Once the K702s are released, I'll probably wait for ALO to offer them with the Vampire Wire, then I'll add those to the stable. My next set of cans will be SR80s to serve as practice for mods and recable before I order SR225s. Then I'll round out the collection with a set of Denon D2000s, AT's, and Ultrasone HFI-780s. I just had to spend a lot of time deciding which pair to order first..._

 

Ugh, me = envious!


----------



## amphead

BMF, how much did you pay for K601? You might be able to pick up K701 for 10% more.


----------



## bperboy

Oh, by the way, is Evansville close to Terre Haute? I'll be at school in the fall, and if you're getting all of those cans, we'll have to have a nice mini-meet!


----------



## BoilermakerFan

Quote:


  Originally Posted by *amphead* /img/forum/go_quote.gif 
_BMF, how much did you pay for K601? You might be able to pick up K701 for 10% more._

 

Quoted $181.15 from NSL, but they are Special Order, Non-Stock. I have to call in the order tomorrow. The K701s are now up to $258.88. I missed the chance to grab them for $215 three months ago. Luckily, the K601s are down almost $35 from 3 months ago. 
	

	
	
		
		

		
		
	


	




 I actually don't want the K701s, I want the slightly different sound sig of the K601s. NSL has the K702s listed on their site due to arrive late Aug. 2008. According to NSL, the K702s come without the storage cradle and have a removable cable with a black headband. I'll wait and see, but that makes recabling easier, but then the two channels have unequal length wires. I prefer the black headband too, but I've also heard the K702s are supposed to be more comfortable, but sound the same...


  Quote:


  Originally Posted by *bperboy* /img/forum/go_quote.gif 
_Oh, by the way, is Evansville close to Terre Haute? I'll be at school in the fall, and if you're getting all of those cans, we'll have to have a nice mini-meet!_

 

Don't be envious. That is just my plan. I didn't say they would be ordered within the next 6 months. Hopefully within the next 18 months though! 
	

	
	
		
		

		
		
	


	




 I may have to order the Ultrasones next however, since NSL has them for $161. BUT, I have a _LOT_ of other gear I need to fund and build first. After the three MAXs, I need two build two phono stages; a 47 Labs Flatfish CD Transport clone (hardware in hand, just need upgrade caps and chassis); a SPDIF DAC; a USB DAC; a phono to USB ADC; I have to re-wire, re-cap, and re-resistor a 1957 mono Magnavox console; and the biggest project of all of them is an Aikido Octal headphone/ preamp to feed a LM3875 gainclone amp (or SKA 100W amp) with SKA 225W sub amp and SubXo. Speakers will be full range FE127 in Fonken GR enclosures and SDX7s for the subs all housed in a custom designed and built Art Deco retro console! Well, ok, the console is going to take a _long_ time, so I'll probably add some more headphones scattered throughout the other projects. I know this is the wrong site, but my family is more of a "jam the stereo speakers together" kind of family than a "all head off to listen to headphones" kind of family. 

 Now to answer your question. Evansville is 2 hours south of TH and is the mid-point of our trip up to West Lafayette when we go up to visit my Mother-In-Law who still works at Purdue, so usually we just pass through as quickly as we can. However, if you influence enough peeps up there and setup a mini-meet, send me a PM and I'll see if I can bring up a couple of MAX-based amps, 47 Labs Flatfish CD Transport Clone, DAC, and my K601s and hopefully HFI-780s.


----------



## WilCox

Just stumbled on this thread! Not sure how I missed it earlier!

 I just finished my MAX. I was looking for an amp that would do justice to my ATH-W5000 and the MAX sure does the trick. The mid-range is just gorgeous, the highs extended and the bass articulate and deep -- much better than my Lehmann or PreHead.

 Thanks to TomB for his help in getting my MAX up and running and for offering a one-stop-shop for all the hard-to-find parts.

 Now it's time to build another!


----------



## jonjon0nline

I cannot wait to build this! I should be ordering parts for mine some time next week


----------



## amphead

Congrats WilCox!

 Yep, the Max is an awesome piece of kit!


----------



## tomb

Quote:


  Originally Posted by *WilCox* /img/forum/go_quote.gif 
_Just stumbled on this thread! Not sure how I missed it earlier!

 I just finished my MAX. I was looking for an amp that would do justice to my ATH-W5000 and the MAX sure does the trick. The mid-range is just gorgeous, the highs extended and the bass articulate and deep -- much better than my Lehmann or PreHead.

 Thanks to TomB for his help in getting my MAX up and running and for offering a one-stop-shop for all the hard-to-find parts.

 Now it's time to build another!







_

 

Another MAX lives!!
	

	
	
		
		

		
		
	


	







 Wow - I knew your work was immaculate from the pics of your board in our e-mails, but had not seen it finished. That casework is just gorgeous!!


 P.S. Yeah, this thread gets a bit more traffic than DIYForums.org. 
	

	
	
		
		

		
		
	


	




 I always check the other site, though - but I may miss a day or two as I did in your case the first time around. Sure glad the end result was this great!!

 Thanks for keeping an eye on the thread as always, Amphead!! Good luck on finding that Bijou-buzz - it's got to be frustrating, but I'm sure you'll get it eventually.


----------



## WilCox

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Another MAX lives!!
	

	
	
		
		

		
		
	


	







 Wow - I knew your work was immaculate from the pics of your board in our e-mails, but had not seen it finished. That casework is just gorgeous!!


 P.S. Yeah, this thread gets a bit more traffic than DIYForums.org. 
	

	
	
		
		

		
		
	


	




 I always check the other site, though - but I may miss a day or two as I did in your case the first time around. Sure glad the end result was this great!!

 Thanks for keeping an eye on the thread as always, Amphead!! Good luck on finding that Bijou-buzz - it's got to be frustrating, but I'm sure you'll get it eventually._

 

Thanks for the kind words. I couldn't be more pleased. I must admit that this is first dynamic headphone system that matches (maybe betters) my STAX SRS-4040II system. The MAX kicks the ATH-W5000 over the top!


----------



## soloz2

well after over a month, several emails and even a phone call Par-metal still hasn't come through for me... I'm about ready to cut my losses and order a different enclosure 
	

	
	
		
		

		
		
	


	




. I just filed with paypal...


----------



## bperboy

Quote:


  Originally Posted by *soloz2* /img/forum/go_quote.gif 
_well after over a month, several emails and even a phone call Par-metal still hasn't come through for me... I'm about ready to cut my losses and order a different enclosure 
	

	
	
		
		

		
			





. I just filed with paypal..._

 

Hmm, I just ordered a nice 16x16x4 20 series by phone and it came within a week... how did you order your case?


----------



## soloz2

Quote:


  Originally Posted by *bperboy* /img/forum/go_quote.gif 
_Hmm, I just ordered a nice 16x16x4 20 series by phone and it came within a week... how did you order your case?_

 

I made the mistake of ordering from their ebay store... they sent silver instead of black, said they'd get a black one out right away then nothing... I emailed and no response, emailed again, then called to which was told they'd send a black one out right away. That was a week ago and NJ to NY shipping only takes 3 days max


----------



## bperboy

Quote:


  Originally Posted by *soloz2* /img/forum/go_quote.gif 
_I made the mistake of ordering from their ebay store... they sent silver instead of black, said they'd get a black one out right away then nothing... I emailed and no response, emailed again, then called to which was told they'd send a black one out right away. That was a week ago and NJ to NY shipping only takes 3 days max_

 

That's unfortunate... luckily I've had good luck the two times I've ordered, but both times, I've used the phone.


----------



## BoilermakerFan

Quote:


  Originally Posted by *soloz2* /img/forum/go_quote.gif 
_I made the mistake of ordering from their ebay store... they sent silver instead of black, said they'd get a black one out right away then nothing... I emailed and no response, emailed again, then called to which was told they'd send a black one out right away. That was a week ago and NJ to NY shipping only takes 3 days max_

 

So do you at least still have the silver one? It's a metal case correct? A body shop that specializes in motorcycles could easily paint it custom for you and the silver base will really make any color "pop." Of course, as an old school PC case modder, it should be within your reach too. Two words: Ghost Flames.


----------



## soloz2

Quote:


  Originally Posted by *BoilermakerFan* /img/forum/go_quote.gif 
_So do you at least still have the silver one? It's a metal case correct? A body shop that specializes in motorcycles could easily paint it custom for you and the silver base will really make any color "pop." Of course, as an old school PC case modder, it should be within your reach too. Two words: Ghost Flames. 
	

	
	
		
		

		
		
	


	


_

 

well painting is an option, however since before bidding and paying it was agreed that I would get a black enclosure I feel as if I should get a black enclosure.


----------



## BoilermakerFan

Quote:


  Originally Posted by *soloz2* /img/forum/go_quote.gif 
_well painting is an option, however since before bidding and paying it was agreed that I would get a black enclosure I feel as if I should get a black enclosure._

 

Fair enough, but worst case, at least you have an enclosure and you weren't completely e-Screwed. 





 I had a package show up today with 40 transistors inside! 
	

	
	
		
		

		
		
	


	




 Placed my Mouser and Digi-Key orders for the remaining bits to populate my third board along with other parts for a phono stage. Now I just need to order a few more bits from Handmade, Antek, and some Mogami wire then I'll be ready to rock-and-roll. 

 The only thing I really have left to decide is what type of umbilical cord to use to connect the PSU chassis to the signal chassis. I'll have four to six dual secondary transformers: (2) 15VAC, (2) 22VAC, and (2) 25VAC so I'm not sure what the best way to bring in the hot leads and ground into the signal chassis. Any recommendations? 

 Headphones get ordered tomorrow.


----------



## Beefy

Quote:


  Originally Posted by *BoilermakerFan* /img/forum/go_quote.gif 
_I'll have four to six dual secondary transformers: (2) 15VAC, (2) 22VAC, and (2) 25VAC so I'm not sure what the best way to bring in the hot leads and ground into the signal chassis. Any recommendations?_

 

A 3 and a 6 connector Amphenol Ecomate, perhaps?
http://www.mouser.com/catalog/634/1260.pdf

 If you need more, then two 6's..... but you would have to make VERY sure you don't get them mixed up!


----------



## BoilermakerFan

Quote:


  Originally Posted by *Beefy* /img/forum/go_quote.gif 
_A 3 and a 6 connector Amphenol Ecomate, perhaps?
http://www.mouser.com/catalog/634/1260.pdf

 If you need more, then two 6's..... but you would have to make VERY sure you don't get them mixed up!_

 

Hmmm... Not a bad idea. Much cheaper than the LEMO. I can use two of the 3 conductor for my big 22V draws and use one male panel and one female panel receptacle on the signal amp and use the opposite receptacles on the PSU. I'd do the same for 6 conductor umbilicals. That way there is only one way they can be hooked up, but I'll have two identical umbilical cables for each. Just need to track down good Belden 3+G and 6+G cable. The 3 conductor will even work for my higher voltage tube amp stuff too!


----------



## Beefy

Quote:


  Originally Posted by *BoilermakerFan* /img/forum/go_quote.gif 
_Just need to track down good Belden 3+G and 6+G cable. The 3 conductor will even work for my higher voltage tube amp stuff too! 
	

	
	
		
		

		
		
	


	


_

 

I wouldn't connect the grounds from power supply to amp. The benefit of separate chassis is that they are _separate_, and you can greatly reduce the possibility of ground loops. Connect amp grounds to your source only.... mind you, I'm not sure how this would work with your source in the same chassis. Hopefully it establishes its own ground somewhere in there.

 Also, there really isn't any need for anything other than standard hookup wire IMHO, so long as it is sufficient gauge for the current draw. Cover it in techflex and you're good to go.

 [EDIT] Another thing...... ideally, you would have a socket on the PSU case, plug on the PSU side of the cable, socket on the amp side of the cable, and a plug on the amp case. This way, you can never have live wires exposed. See my MMM here: http://www.head-fi.org/forums/4255177-post3285.html third pic shows you what I mean. However, you could possibly switch one of the cable around so that you have a plug on the PSU case. This non-symmetrical setup would mean that you could never get the umbilicals hooked up incorrectly. It is all a matter of what you think is more dangerous - live wires at a plug, or accidentally hooking things up wrong.

 Lastly, you could also consider Neutrik Speakon which comes in 2, 4 and 8 pin configs. However, I wouldn't use them for AC wiring - DC only! They aren't rated as high as the Amphenol.


----------



## BoilermakerFan

OK, one more question.

 Where can I find Elna Cerafine caps for CA2 and CA7? Handmade only has the small value Cerafines. 

 I did order Panasonic FC series for CA2 and CA7 to compare them with Muse ES, Silmic II, and Muse KZ. I'd like to add Cerafines to the list if I can find a source.

 Thanks.


----------



## BoilermakerFan

Quote:


  Originally Posted by *Beefy* /img/forum/go_quote.gif 
_I wouldn't connect the grounds from power supply to amp. The benefit of separate chassis is that they are separate, and you can greatly reduce the possibility of ground loops. Connect amp grounds to your source only.... mind you, I'm not sure how this would work with your source in the same chassis. Hopefully it establishes its own ground somewhere in there.

 Also, there really isn't any need for anything other than standard hookup wire IMHO, so long as it is sufficient gauge for the current draw. Cover it in techflex and you're good to go.

 [EDIT] Another thing...... ideally, you would have a socket on the PSU case, plug on the PSU side of the cable, socket on the amp side of the cable, and a plug on the amp case. This way, you can never have live wires exposed. See my MMM here: http://www.head-fi.org/forums/4255177-post3285.html third pic shows you what I mean. However, you could possibly switch one of the cable around so that you have a plug on the PSU case. This non-symmetrical setup would mean that you could never get the umbilicals hooked up incorrectly. It is all a matter of what you think is more dangerous - live wires at a plug, or accidentally hooking things up wrong.

 Lastly, you could also consider Neutrik Speakon which comes in 2, 4 and 8 pin configs. However, I wouldn't use them for AC wiring - DC only! They aren't rated as high as the Amphenol._

 

I was looking at the exposed pins issue. I'm not sure how to address it since I may need more than 3 pins at the 16A rating. I know the 22V is off a 300VA transformer, so that is a potential for over 13A ignoring efficiency and losses. Really, it would only need to be disconnected for servicing the PSU chassis. I have to stack the integrated amp on top of the PSU chassis, so I can have strain relief hardwired umbilicals out of the PSU and just match up the umbilicals to the corresponding receptacles on the amp. I need to look for another connector that was a 4-wire I found years ago with the option to have each of the 4 pins keyed differently so they couldn't be hooked up wrong. Worst case, I can make the Amphenol connectors work since the amp and PSU will be off limits inside the console.


----------



## Beefy

Quote:


  Originally Posted by *BoilermakerFan* /img/forum/go_quote.gif 
_I know the 22V is off a 300VA transformer_

 

Ooooh, yeah, I'd forgotten that you had such a huge transformer....... good luck with that!


----------



## pinkfloyd4ever

Quote:


  Originally Posted by *BoilermakerFan* /img/forum/go_quote.gif 
_OK, one more question.

 Where can I find Elna Cerafine caps for CA2 and CA7? Handmade only has the small value Cerafines. 

 I did order Panasonic FC series for CA2 and CA7 to compare them with Muse ES, Silmic II, and Muse KZ. I'd like to add Cerafines to the list if I can find a source.

 Thanks._

 

I believe Cerafines were discontinued and Silmics are their successors

 not that it's impossible to find them still, but it'll be harder than finding ESs, silmics, or KZs


----------



## BoilermakerFan

Quote:


  Originally Posted by *pinkfloyd4ever* /img/forum/go_quote.gif 
_I believe Cerafines were discontinued and Silmics are their successors

 not that it's impossible to find them still, but it'll be harder than finding ESs, silmics, or KZs_

 

I found them, or at least the correct capacities, but at higher voltages than the BOM at Welborne for $24/set. I'm on the bubble now, since That is about 50% of a set of BGs...


----------



## Alcaudon

Quote:


  Originally Posted by *BoilermakerFan* /img/forum/go_quote.gif 
_OK, one more question.

 Where can I find Elna Cerafine caps for CA2 and CA7? Handmade only has the small value Cerafines. 

 Thanks._

 

Try here: * a u d i o - c u b e *

 Quite expensive, though


----------



## BoilermakerFan

Quote:


  Originally Posted by *Alcaudon* /img/forum/go_quote.gif 
_Try here:  a u d i o - c u b e 

 Quite expensive, though 
	

	
	
		
		

		
			



_

 

Yes, for the cost to buy those and ship them with a weak US Dollar, I could buy Black Gates.


----------



## BoilermakerFan

Quote:


  Originally Posted by *BoilermakerFan* /img/forum/go_quote.gif 
_JW

 Can you post up the part numbers and source of the wire loop test points you use on your MAX (TB1L, TB2L, etc)? I like those a lot and for my builds they would be just as easy as test jacks at the back of the amp with less work. 
	

	
	
		
		

		
		
	


	




 Thanks._

 

 Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_This is a typical red one at Mouser:
534-5005. John may have used bigger ones, though.


 EDIT: Yeah, looks like he used the ones with longer wire loops:
534-5010_

 



 Arrrgggghhhh! 
	

	
	
		
		

		
		
	


	




 I knew I forgot something else to add to my Mouser order! 

 Oh well, I also forgot to order additional selector switches for my Darwin kit since I ordered the balanced kit to be cheap, I mean economical because I knew I wasn't going to use a lot of the "extra" bits like the ribbon cable and Molex connectors they include. Speaking of which, I'm planning to order a third Darwin PCB only and use Nais relays and V-D RN55 resistors on it. I need more stand-offs and a means to mount the OptiVol board too. I've realized it never truly ends, does it?

 Tom,

 I have a little anti-static bag taped up in bubble wrap for you. I just need to head to the USPS to get a box and postage, so you should see it Mon. or Tues. 

 - BMF


----------



## tomb

Quote:


  Originally Posted by *BoilermakerFan* /img/forum/go_quote.gif 
_<snip>

 Tom,

 I have a little anti-static bag taped up in bubble wrap for you. I just need to head to the USPS to get a box and postage, so you should see it Mon. or Tues. 

 - BMF_

 

Ooh - that sounds nice! Thank you!


----------



## BoilermakerFan

Well, I just couldn't do it. I couldn't go through all the processes I'm going through and NOT have a set of Cerafine caps to try out too. Plus I needed a couple of the smaller ones for the CD transport. So, a $28 order later, 8 caps are on their way. I also ordered my balance of the needed Cerafines from Handmade along with Silmic IIs and Muse KZ for CA2/CA7. 

 Has anyone used Silver Mica .22uF caps for CA3/CA6 or CA8/CA9? I also ordered (4) Solen PPE .22uF caps to try as bypass caps, but I'm not sure which EL caps to pair them with. Leaning towards the Silmic IIs, but I'll have to listen 
	

	
	
		
		

		
		
	


	




 to them and try them with the Muse ES and KZ too. 

 Finally, what the heck is a 16.9C77 cap? I'm guessing it's a ceramic cap, but a search on Mouser and Digi-Key returned zero results. I need one to replace a different cap on my JVC EZ-31 CD transport. 

 Need to order my Mogami wire for hook-up and headphones from Performance Audio. There are several different Mogami choices that I could use for the internal hook-up wire for the different applications. I noticed PA has Neutrik NP3TB-R and NP3TB-B 1/4" headphone jacks for $4.85 each, almost $3 cheaper than Mouser.


----------



## tomb

Quote:


  Originally Posted by *BoilermakerFan* /img/forum/go_quote.gif 
_Well, I just couldn't do it. I couldn't go through all the processes I'm going through and NOT have a set of Cerafine caps to try out too. Plus I needed a couple of the smaller ones for the CD transport. So, a $28 order later, 8 caps are on their way. I also ordered my balance of the needed Cerafines from Handmade along with Silmic IIs and Muse KZ for CA2/CA7._

 

$28 for 8 caps is still a long way from the cost of Black Gate NX's.
	

	
	
		
		

		
		
	


	



  Quote:


 Has anyone used Silver Mica .22uF caps for CA3/CA6 or CA8/CA9? I also ordered (4) Solen PPE .22uF caps to try as bypass caps, but I'm not sure which EL caps to pair them with. Leaning towards the Silmic IIs, but I'll have to listen 
	

	
	
		
		

		
		
	


	




 to them and try them with the Muse ES and KZ too. 
 

I don't know about the Silver Mica's, although you hear them mentioned a lot in reference to tube amps. As for the Solens, there are many better caps available, sorry to say. Vitamin Q's are certain to be superior. About the only thing better might be some Mundorf Silver Oils, Sonicap Platinums, or Jupiters, IMHO. (The MAX is too hot for Jupiters, btw.) 
  Quote:


 Finally, what the heck is a 16.9C77 cap? I'm guessing it's a ceramic cap, but a search on Mouser and Digi-Key returned zero results. I need one to replace a different cap on my JVC EZ-31 CD transport. 
 

can't help you with that one ... 
  Quote:


 Need to order my Mogami wire for hook-up and headphones from Performance Audio. There are several different Mogami choices that I could use for the internal hook-up wire for the different applications. I noticed PA has Neutrik NP3TB-R and NP3TB-B 1/4" headphone jacks for $4.85 each, almost $3 cheaper than Mouser. 
 

A lot of people like that Mogami Neglex 2534 for headphone wiring, but it won't be as nice as 22 ga. teflon for regular hookup wire, IMHO. The hassle with soldering PVC-insulation will be there with the Mogami. I've not done anything as long as you will no doubt have, but have had great luck Litz braiding the 22ga teflon with two ground wires.


----------



## soloz2

$28? I've got 4 blackgate NX caps that cost about that waiting to go into a Max


----------



## BoilermakerFan

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_<snip>
 I don't know about the Silver Mica's, although you hear them mentioned a lot in reference to tube amps. As for the Solens, there are many better caps available, sorry to say. Vitamin Q's are certain to be superior. About the only thing better might be some Mundorf Silver Oils, Sonicap Platinums, or Jupiters, IMHO. (The MAX is too hot for Jupiters, btw.)_

 

Yes, I read the reviews pages on the Solens, so it was $6 that won't be used on the amp. I'm going to order Jensen copper foil caps instead. I'll try the Silver Mica in place of the Wima's, but I think they will be a little tight to fit in.

 EDIT: I canceled the Solens...

  Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_<snip>A lot of people like that Mogami Neglex 2534 for headphone wiring, but it won't be as nice as 22 ga. teflon for regular hookup wire, IMHO. The hassle with soldering PVC-insulation will be there with the Mogami. I've not done anything as long as you will no doubt have, but have had great luck Litz braiding the 22ga teflon with two ground wires._

 

Yes, I'm planning to use some of the W2534 and W2893 for the AKGs. I also need the W3162 for the Darwin selector switch. But I forgot to add the 22ga assortment at Handmade, so I might see if I can cancel the Solen caps and add the wire...

 EDIT: Handmade canceled my first order so I could add the wire. So, I did not re-order the Solens and ordered (8) of the Silver Mica 220pF caps instead. I also ordered a ton of 22ga. wire, as well as some STP and Teflon Cat5 for my remote OptiVol and Darwin selector switches. Best part was, it took my order over $150, so I received the discount and it was like getting the Silver Mica caps for free! 

  Quote:


  Originally Posted by *soloz2* /img/forum/go_quote.gif 
_$28? I've got 4 blackgate NX caps that cost about that waiting to go into a Max_

 

They aren't that cheap now. The four caps for the MAX were $24, but I think they will be awesome with Jensen copper foil bypass caps.


----------



## pabbi1

Quote:


  Originally Posted by *BoilermakerFan* /img/forum/go_quote.gif 
_They aren't that cheap now. The four caps for the MAX were $24, but I think they will be awesome with Jensen copper foil bypass caps._

 



 Jensen copper foil... 
	

	
	
		
		

		
		
	


	




 Holy cow - now that is a no expense spared combo. I couldn't even do that in the Bijou - but, was sorely tempted.

 Now of you had said Mundorf Silver/Gold, that would be lifetime acheivement - or Darwin Award candidate action.


----------



## BoilermakerFan

Quote:


  Originally Posted by *pabbi1* /img/forum/go_quote.gif 
_Jensen copper foil... 
	

	
	
		
		

		
		
	


	




 Holy cow - now that is a no expense spared combo. I couldn't even do that in the Bijou - but, was sorely tempted.

 Now of you had said Mundorf Silver/Gold, that would be lifetime acheivement - or Darwin Award candidate action._

 

The Jensen Copper Foil Paper In Oil Signal Capacitors are $22-$27ea for .22uF caps! 
	

	
	
		
		

		
		
	


	




 And they are huge! 35mm long and 25mm diameter. 

 I'll be waiting a bit before I try those, but I do think they could take the Cerafine caps over the top with the 2238/968 BJTs or the MOSFETs. I'll have to reserve that build for my dedicated headphone amp. No sense in putting those in a console. 

 I am very tempted to add the BGs and be done, but I just won't be able to take advantage of them with their burn-in/time-loss properties. I just can't bring myself to leave a MAX amp powered up 4 days a week when I'm not even home. The biggest decision will be which way to go on the DBs. 

 I will show that MAX build respect and put it in a custom painted, FPE front paneled NABU too. I already have the idea of what i's going to look like in my head. 
	

	
	
		
		

		
		
	


	




 Beefy, I noticed you are using a filtered IEC power socket on your PSU for the MMM. Does it really help or is an isolation toroid enough in most cases?


----------



## BoilermakerFan

Tom

 Can you send me a PM with the Thermasil pads you use? The ones I ordered are the right size, but they do not have the hole for the mounting screw. I think I can make these work if I use an X-acto blade to cut out the hole using a BJT as the template. What do you think? 

 Thanks.


----------



## Beefy

Quote:


  Originally Posted by *BoilermakerFan* /img/forum/go_quote.gif 
_Beefy, I noticed you are using a filtered IEC power socket on your PSU for the MMM. Does it really help or is an isolation toroid enough in most cases?_

 

It makes me feel better, so yes, it helps 
	

	
	
		
		

		
		
	


	




 AMB has noted that the filter doesn't do much for the σ22/11. So, it was more a matter of pure excess than anything else. I did it because I could fit it in....... _just_...... but it also helps that it is a very nice quality switch, double fused, with faston connectors, all in one tidy unit......

 I bought it locally instead of from Mouser, but here it the part: FN 284-6-06

 They don't stock that particular one, but you can get the single filter ones (FN283) as well as any number of other models.


----------



## tomb

Quote:


  Originally Posted by *BoilermakerFan* /img/forum/go_quote.gif 
_Tom

 Can you send me a PM with the Thermasil pads you use? The ones I ordered are the right size, but they do not have the hole for the mounting screw. I think I can make these work if I use an X-acto blade to cut out the hole using a BJT as the template. What do you think? 

 Thanks._

 

I'd use an ice pick, if you have one. Just stick one on the heat sink over the hole and poke a hole through the pad. It shouldn't be an issue as long as you don't shred the pad.
	

	
	
		
		

		
		
	


	




 They're actually not Avid Thermasil, they're Bergquist Hi-Flow 115-AC. YGPM.


----------



## bperboy

When using the Max as a preamp before a power amp for speakers, would one simply turn the volume to max and connect the output of the millett to the input of the power amp? My power amp will have a volume control on it as well...


----------



## tomb

Quote:


  Originally Posted by *bperboy* /img/forum/go_quote.gif 
_When using the Max as a preamp before a power amp for speakers, would one simply turn the volume to max and connect the output of the millett to the input of the power amp? My power amp will have a volume control on it as well..._

 

Volume control is in the pre-amp. Most amps don't have a volume control, unless they're an integrated amp - in which case, the "integrated" means it has a pre-amp. Could that be the case?


----------



## BoilermakerFan

Quote:


  Originally Posted by *bperboy* /img/forum/go_quote.gif 
_When using the Max as a preamp before a power amp for speakers, would one simply turn the volume to max and connect the output of the millett to the input of the power amp? My power amp will have a volume control on it as well..._

 

 Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Volume control is in the pre-amp. Most amps don't have a volume control, unless they're an integrated amp - in which case, the "integrated" means it has a pre-amp. Could that be the case?_

 

Unless you have a custom built built amp with a potentiometer on the input to the amp, then Tom is correct and it's an integrated amp. The preamp and amp are integrated into one unit. The preamp does volume control and input selection. 

 If you already have the RCA outputs wired off the terminal block next to the headphone jack, then you could try feeding the signal from the MAX to your integrated amp, but I would only turn the volume up to "comfortable loud listening" level on the MAX. See how the speakers sound with the integrated amp turned up about 1/3 to no more than 1/2 way up. Then you can turn the MAX up a little more until it starts to have audible distortion, then back the MAX down a little. That would be a "rule of them" upper limit of output control for the MAX, then just use your integrated amp's volume pot. 

 That's assuming you didn't want to rip into the integrated amp and rewire it. 
	

	
	
		
		

		
		
	


	




 (I've been eyeing my old Kenwood integrated, but it was the first major purchase I made in HS and it still works great, so it stays intact until something finally gives up the ghost) The above will also let you bring the MAX to friends dorm rooms or apartments at R-H to introduce speaker guys to the tube sound...


----------



## bperboy

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Volume control is in the pre-amp. Most amps don't have a volume control, unless they're an integrated amp - in which case, the "integrated" means it has a pre-amp. Could that be the case?_

 

Well, this is an amp that I'm building... I'm not really sure if I want to use a preamp all the time, but I wanted to know for when I try it. Thanks!


----------



## BoilermakerFan

Quote:


  Originally Posted by *bperboy* /img/forum/go_quote.gif 
_Well, this is an amp that I'm building... I'm not really sure if I want to use a preamp all the time, but I wanted to know for when I try it. Thanks! 
	

	
	
		
		

		
		
	


	


_

 

Are you planning to switch sources by swapping RCA or XLR jacks all the time? 

 I'll drop you a PM...


----------



## bperboy

Quote:


  Originally Posted by *BoilermakerFan* /img/forum/go_quote.gif 
_Are you planning to switch sources by swapping RCA or XLR jacks all the time? 

 I'll drop you a PM..._

 

Well, this isn't certain at all, and I'm going to try it out with a 1/4" to RCA cable and see if I like it..


----------



## fakeplasticpete

Hey all...

 Just wanted to share my excitement. After many, many months of being distracted by work/life/laziness/etc., I finally got my MHMax built, biased and working!

 It's a standard vanilla build off the BOM, and it's just biased down to the starting specs, but it is *GOOD!!*

 Thanks to tomb, colin and everyone on the boards for making this possible!

 -pete


----------



## soloz2

quick question, on a MOSFET build I'm assuming RB14 is still optional? jumper is preferred, or is there a benefit to having a small 10-22ohm resister in that position.


----------



## bperboy

Quote:


  Originally Posted by *soloz2* /img/forum/go_quote.gif 
_quick question, on a MOSFET build I'm assuming RB14 is still optional? jumper is preferred, or is there a benefit to having a small 10-22ohm resister in that position._

 

I've got mine jumpered at the moment... doesn't hurt anything; limits the volume range a bit though...


----------



## soloz2

Now, would it be better to use 100ohm resisters for RB8 and RB9 and install a 220pF cap in CB8, or to use 121ohm for RB8 and 75ohm for RB9?

 by limits the volume range do you mean that you only have limited use of your volume pot's range?


----------



## bperboy

Quote:


  Originally Posted by *soloz2* /img/forum/go_quote.gif 
_by limits the volume range do you mean that you only have limited use of your volume pot's range?_

 

Correct sir! It's okay though, the RK27 has good enough tracking so it's not a big deal. My Mini^3 on the other hand... not so good tracking!


----------



## tomb

Quote:


  Originally Posted by *soloz2* /img/forum/go_quote.gif 
_Now, would it be better to use 100ohm resisters for RB8 and RB9 and install a 220pF cap in CB8, or to use 121ohm for RB8 and 75ohm for RB9?

 by limits the volume range do you mean that you only have limited use of your volume pot's range?_

 

If you're asking for personal preference, I'd choose keeping the resistors all the same at 100ohms, then use the cap at the N-channel MOSFETs.

 Bperboy answered the other one.


----------



## BoilermakerFan

Pics of the MAX board with 2-1/2" DB heatsinks and 2" V-Reg heatsink:














 I'm a little partial to the Black and Gold color scheme too!


----------



## Iniamyen

I just got it cased up "for good" so I thought I would show the obligatory in-the-dark pic


----------



## tomb

Quote:


  Originally Posted by *BoilermakerFan* /img/forum/go_quote.gif 
_Pics of the MAX board with 2-1/2" DB heatsinks and 2" V-Reg heatsink:

 <IMG]http://i142.photobucket.com/albums/r114/BoilermakerFan/IMG_1425.jpg[/IMG>
 <IMG]http://i142.photobucket.com/albums/r114/BoilermakerFan/IMG_1426.jpg[/IMG>
 I'm a little partial to the Black and Gold color scheme too! 
	

	
	
		
		

		
		
	


	


_

 

Uh-oh - you got those gold heat sinks. As for the color scheme, I think we know where that comes from.
	

	
	
		
		

		
		
	


	




  Quote:


  Originally Posted by *Inaimyen* 
_I just got it cased up "for good" so I thought I would show the obligatory in-the-dark pic._

 

Great job!


----------



## BoilermakerFan

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Uh-oh - you got those gold heat sinks. As for the color scheme, I think we know where that comes from.
	

	
	
		
		

		
		
	


	


_

 

Yes, I read somewhere that gold bling radiates more heat to provide a better cool factor. 
	

	
	
		
		

		
		
	


	




 LOL!

 And I ordered 14 of them. I almost went for 20-25, but decided to wait and pick up more after I saw them...


----------



## Beefy

I've got a question about chassis punches used for the tube holes on a MAX.

 Looking at the photos on the main MAX website, it seems that tomb uses this punch: Greenlee Products - Greenlee A Textron Company but this one isn't available from Mouser.

 Is this standard (ie, non 'Slug Buster') one an acceptable substitute? 730BB-1 / Greenlee Products - Greenlee A Textron Company
 The replacement die is the same part number, and the catalog seems to indicate that the 1" is the actual hole diameter....

 Also, just to confirm how these punches work. You drill a pilot hole, put the draw stud through the hole, screw down and line up the punch with your markings, then screw/drive the punch through the panel with a socket wrench......?


----------



## BoilermakerFan

Quote:


  Originally Posted by *Beefy* /img/forum/go_quote.gif 
_
 Also, just to confirm how these punches work. You drill a pilot hole, put the draw stud through the hole, screw down and line up the punch with your markings, then screw/drive the punch through the panel with a socket wrench......?_

 

A pneumatic ratchet works much faster! 
	

	
	
		
		

		
		
	


	




 I actually prefer the Uni-Bit stepper bits as there is no panel distortion with a Uni-Bit.


----------



## Beefy

Quote:


  Originally Posted by *BoilermakerFan* /img/forum/go_quote.gif 
_I actually prefer the Uni-Bit stepper bits as there is no panel distortion with a Uni-Bit._

 

That would be OK if I had access to a drill press. I'm not using a hand drill with one of those......


----------



## BoilermakerFan

Quote:


  Originally Posted by *Beefy* /img/forum/go_quote.gif 
_That would be OK if I had access to a drill press. I'm not using a hand drill with one of those......_

 







 Start with the smallest Uni-Bit to setup the pilot hole, then go to the bigger bit. It's fast and easy with hand drill, corded or cordless... I use a cordless most of the time for up to 7/8" (22mm) holes.


----------



## Beefy

Quote:


  Originally Posted by *BoilermakerFan* /img/forum/go_quote.gif 
_





 Start with the smallest Uni-Bit to setup the pilot hole, then go to the bigger bit. It's fast and easy with hand drill, corded or cordless... I use a cordless most of the time for up to 7/8" (22mm) holes._

 

Nup, not me. No bigger than ~13mm without a drill press. Otherwise you get poor alignment and it is just plain dangerous.


----------



## adamus

I just used one with the cheapest crappiest drill ($10), it created perfect holes, aligned to within 1mm. Its all in the pilot, after that it will align itself.


----------



## tomb

Quote:


  Originally Posted by *adamus* /img/forum/go_quote.gif 
_I just used one with the cheapest crappiest drill ($10), it created perfect holes, aligned to within 1mm. Its all in the pilot, after that it will align itself._

 

Yep - agreed. I did the entire first MAX prototype using the drilling templates, a spring-loaded center punch, unibit, and _hand-held power drill_ just to illustrate that it could easily be done:
MAX Casework Part 2 - Top Plate
 The hole-entry edges are cleaner with a drill press, but that's about the only difference. The hand-held power drill is _a lot_ quicker, too.

 As for the large holes, I would stop at about 3/4", but only because that's the limit of the Harbor Freight stepped bits I use. After that, it's pretty easy to whittle slivers from the edges of the hole with a strong knife. At least on the endplates, that's sufficient for 1" holes as long as there's a bit of a washer/edge to cover the hole edge. The top plate needs a punch for the tube holes, though. I suppose one could whittle those, too, but the aluminum is a lot thicker.


----------



## Beefy

I'll have a search around locally, and see what I can find.

 I might see if I can raid my the workshop where my g/f works too..... they have some very sexy tools and machines, but no time for my stuff unfortunately


----------



## tomb

Quote:


  Originally Posted by *Beefy* /img/forum/go_quote.gif 
_I've got a question about chassis punches used for the tube holes on a MAX.

 Looking at the photos on the main MAX website, it seems that tomb uses this punch: Greenlee Products - Greenlee A Textron Company but this one isn't available from Mouser.

 Is this standard (ie, non 'Slug Buster') one an acceptable substitute? 730BB-1 / Greenlee Products - Greenlee A Textron Company
 The replacement die is the same part number, and the catalog seems to indicate that the 1" is the actual hole diameter....

 Also, just to confirm how these punches work. You drill a pilot hole, put the draw stud through the hole, screw down and line up the punch with your markings, then screw/drive the punch through the panel with a socket wrench......?_

 

Beefy,

 I didn't see this original post that you had made. Yes - I've checked that Greenlee punch and it will work perfectly. The actual Greenlee PDF catalog is more help than their website. You can download it from this link:
http://www.greenlee.com/cat_docs/Holemaking_07.pdf
 Page 44 has the 730BB-1 listed and it confirms that the actual hole is 1.00 inch (25.4mm). That will enable you to also use the hole (tube) bushings from Mouser that are shown on the MAX website here:
MAX Drawings & Templates (at the bottom of the page).

 I actually used a version that Greenlee calls a "Slug Buster," but I'm sure that one will work great. The important thing is to not go cheap if you want one of these things. I've tried the Harbor Freight versions and they're horrible. The punch and draw-stud are all-important. If the threads are not held to a close tolerance (as in the Harbor Freight versions), then the punch will go sideways on you under pressure and start trying to cut at or outside of the perimeter of the die. Needless to say, the die is also hardened steel. So when that happens, everything is screwed up and the hole is ruined.

 The Greenlee's thread tolerance and wearability is top-notch. The punch, die, and draw-stud do not deviate from a straight line and work as slick as goose grease. 
	

	
	
		
		

		
		
	


	




 Your estimate of the operation is also correct. The hole needs to be 3/8" on most of these, but I always over-drill the hole. You've got plenty to work with and a little more lets you line up the punch perfectly with the circle on the drilling template - being careful not to tear through the paper while you're doing that, or it _will_ scratch the top plate (the punch, not the die). The 3/8" pilot hole is a bit tough to get dead-center w/o a drill press, so a little wiggle room helps as long as you have a good 1" diameter circle drawn for line-up.


----------



## Beefy

Thanks tomb! 
	

	
	
		
		

		
		
	


	




 If I can't get hold of anything locally, I'll grab one of the 1" punches. I might invest in a 7/8" one as well - it will do nicely for both the Amphenol Ecomate panel receptacles and the big Neutrik RCA jacks that I like.......


----------



## adamus

why not use a larger step drill - nice clean centred holes? 1 drill bit could do everything you wanter.


----------



## procalli2007

Hi, any uk max owners could point me int he direction of a suitable power supply/wall wart for the max? Ive looked on ebay but dont really know whats best.

 thanks


----------



## ruZZ.il

Quote:


  Originally Posted by *procalli2007* /img/forum/go_quote.gif 
_Hi, any uk max owners could point me int he direction of a suitable power supply/wall wart for the max? Ive looked on ebay but dont really know whats best.

 thanks_

 


L55BR@Maplin(uk). 240/24v 1.5A AC/AC Mains Power Supply (FOR ~240v AC GRID VOLTAGE! (typically outside US)). 

 You may find cheaper, but this will work perfectly. It's what I use.

 (Make sure you choose the L55BR).


----------



## procalli2007

thanks for the quick reply


----------



## Beefy

Quote:


  Originally Posted by *adamus* /img/forum/go_quote.gif 
_why not use a larger step drill - nice clean centred holes? 1 drill bit could do everything you wanter._

 

Because it is impossible to get a single step bit that covers all the hole sizes, I don't like hand drilling anything larger than half an inch and I think I will get superior results from a punch.


----------



## procalli2007

Has anyone bought the millet max cd off beezar.com and if so what do you think of the quality of videos ? Would it make the building process easier and are they detailed?


----------



## BoilermakerFan

Quote:


  Originally Posted by *procalli2007* /img/forum/go_quote.gif 
_Has anyone bought the millet max cd off beezar.com and if so what do you think of the quality of videos ? Would it make the building process easier and are they detailed?_

 

I have. I was happy with the videos, but I watched them a long time ago and plan on watching them again when I go to bias my amps. For me the main reason for buying the CD was to get the website content that I can view offline when I'm traveling and sitting in an airport.


----------



## pinkfloyd4ever

could someone direct me to a post detailing the sonic differences between the 3 Millett tube types? I know the Max site talks about the differences between brands, but not much about the sonic differences (other than gain). I know I've seen it on here before so I searched but I was hoping someone could tell me offhand where to find it, cause I don't really want to look thru all 894 search results


----------



## tomb

Quote:


  Originally Posted by *pinkfloyd4ever* /img/forum/go_quote.gif 
_could someone direct me to a post detailing the sonic differences between the 3 Millett tube types? I know the Max site talks about the differences between brands, but not much about the sonic differences (other than gain). I know I've seen it on here before so I searched but I was hoping someone could tell me offhand where to find it, cause I don't really want to look thru all 894 search results_

 

The general consensus through the years with most Millett builders is as follows:

*12AE6/A:* Most punch, best bass, highs are good with the best tubes, highest gain 
*12FM6:* Inbetween qualities of the other two, including gain
*12FK6:* Best high-end detail, may lack some punch and soundstage with high-impedance phones, lowest gain

 I'm going to have to revise that tube section on brands. It was done from memory and experience with the revMH Millett Hybrid. I was always looking for more punch with the revMH, but the MAX doesn't seem to have an issue with any tube in that regard (given the type differences above). Plus, I've had an opportunity to be exposed to many, many more tubes now. All of this is complicated even more because of the incestuous re-branding that went on with all of these tubes. In the end when it comes to brand, I think it's important to match construction in tube pairs, but it's often a roll of the dice each time as to the real performance of the tubes. That's not really different than anything else in the world of NOS tubes, though.


----------



## akione

Hmmm ....... well, I've decided to build a MMax, at last. 
	

	
	
		
		

		
		
	


	




 I think it's time I found out what it's all about. 
	

	
	
		
		

		
		
	


	




 (Tomb: you got mail - problem with order)


----------



## tomb

Quote:


  Originally Posted by *akione* /img/forum/go_quote.gif 
_Hmmm ....... well, I've decided to build a MMax, at last. 
	

	
	
		
		

		
		
	


	




 I think it's time I found out what it's all about. 
	

	
	
		
		

		
		
	


	




 (Tomb: you got mail - problem with order)_

 

Thanks! No problem - you've got a couple of e-mails coming.


----------



## mik000000

I am installing the 1359/3422 transistors and am not clear on the orientation. When bolting to the heat sinks, the lettering is away from the heat sink?


----------



## pinkfloyd4ever

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_The general consensus through the years with most Millett builders is as follows:

*12AE6/A:* Most punch, best bass, highs are good with the best tubes, highest gain 
*12FM6:* Inbetween qualities of the other two, including gain
*12FK6:* Best high-end detail, may lack some punch and soundstage with high-impedance phones, lowest gain_

 

ahh thanks, stellar as usual tomb


----------



## IcantHearU

Quote:


  Originally Posted by *mik000000* /img/forum/go_quote.gif 
_I am installing the 1359/3422 transistors and am not clear on the orientation. When bolting to the heat sinks, the lettering is away from the heat sink?_

 

Yes- and see this for heatsink/transistor orientation (on tomb's MAX site)

http://www.diyforums.org/MAX/bjt/BJTpositions.jpg


----------



## hazamatic

When hooking up the wires to the power terminal block, is there a negative and positive? 

 i.e. There are 3 terminals on the power terminal block. Is the middle one for negative or positive? Does it even matter? 

 Also, my walwart came with bare wires, one red and one black. I'm going to assume red is positive and black is negative, would that be correct? 

 Thanks!

 Sorry if this question has already been asked and answer


----------



## WilCox

Quote:


  Originally Posted by *hazamatic* /img/forum/go_quote.gif 
_When hooking up the wires to the power terminal block, is there a negative and positive? 

 i.e. There are 3 terminals on the power terminal block. Is the middle one for negative or positive? Does it even matter? 

 Also, my walwart came with bare wires, one red and one black. I'm going to assume red is positive and black is negative, would that be correct? 

 Thanks!

 Sorry if this question has already been asked and answer 
	

	
	
		
		

		
		
	


	


_

 

The specified wall wart is AC so there there is no concern for polarity. Terminals 1 and 2 are the connections you should use if you did not install a fuse. Terminals 2 and 3 are the ones you should use if you did install a fuse.


----------



## hazamatic

Yep I have an AC walwart. I didn't think it mattered which way you connect it. I just wanted to make sure


----------



## hazamatic

Ok I just finished my first MAX.

 Turned RB12 clockwise till I heard a click. 
 Plugged into the power and turned it on. 
 Straight away realised I forgot to put the tubes in. 
 Turned it off and put the tubes in.
 Turned it back on. 
 Measured the voltage across TB2 left and GND. 
 22V!! (not mV). Turned it off.
 Back on, measured TB2 right, samething ~22V. Turn off.

 Then I notice even when it is off, I'm still measuring ~1V at TB2 (same thing at TB1). I unplugged the walwart, and samething, still 1V. 

 Any one know what's going on? Is my multimeter screwed? It measures resistance perfectly....


----------



## Beefy

Quote:


  Originally Posted by *hazamatic* /img/forum/go_quote.gif 
_Measured the voltage across TB2 left and GND........ Any one know what's going on?_

 

Yes, you're measuring it wrong. According the the MAX setup procedure here MAX Setup and Bias Settings you should be measuring between TB and *TA* - NOT GND.

 I suggest you read the setup procedure through again VERY thoroughly.


----------



## UglyJoe

Hey guys, I'm finishing up my build tonight, and I'm a little confused about the heat sink mounting kits. The kits from Beezar have two flat washers, but the mounting instructions on the Max site only shows one. Is the second just a spare, or should it be used somewhere?

 Thanks


----------



## hazamatic

Quote:


  Originally Posted by *Beefy* /img/forum/go_quote.gif 
_Yes, you're measuring it wrong. According the the MAX setup procedure here MAX Setup and Bias Settings you should be measuring between TB and *TA* - NOT GND.

 I suggest you read the setup procedure through again VERY thoroughly._

 

Thanks Beefy! It works great now. I was looking at that same page but for some reason I missed that very important information lol


----------



## hazamatic

Quote:


  Originally Posted by *UglyJoe* /img/forum/go_quote.gif 
_Hey guys, I'm finishing up my build tonight, and I'm a little confused about the heat sink mounting kits. The kits from Beezar have two flat washers, but the mounting instructions on the Max site only shows one. Is the second just a spare, or should it be used somewhere?

 Thanks_

 

You use both washers. One for the side with the transistor and one for the side without. 

 Oh and you should probably tighten them before you install them. I left them a little loose and then I found it very difficult to tighten them unless you have a the proper tiny tools.


----------



## UglyJoe

Quote:


  Originally Posted by *hazamatic* /img/forum/go_quote.gif 
_You use both washers. One for the side with the transistor and one for the side without. 

 Oh and you should probably tighten them before you install them. I left them a little loose and then I found it very difficult to tighten them unless you have a the proper tiny tools._

 

So it goes:

 Screw --> shoulder washer --> flat washer --> transistor hole --> thermasil pad --> heatsink --> flat washer --> lock washer --> nut?


----------



## tomb

Quote:


  Originally Posted by *UglyJoe* /img/forum/go_quote.gif 
_So it goes:

 Screw --> shoulder washer --> flat washer --> transistor hole --> thermasil pad --> heatsink --> flat washer --> lock washer --> nut?_

 

Screw -->* flat washer --> shoulder washer -->* transistor hole --> thermasil pad --> heatsink --> flat washer --> lock washer --> nut.

 There's also this:
MAX Heat Sink Mounting

 You don't want to torque down a screw against a plastic shoulder washer - even a quality, glass-filled phenolic one.
	

	
	
		
		

		
			





 One of those socket-head cap screws will slice right through it.


----------



## UglyJoe

yay, good to hear from you tomb. Got my kit today, obv. 
	

	
	
		
		

		
		
	


	




 Thanks.

 Okay, that makes sense... there isn't a second washer on the Max website pic, so I couldn't figure out what the deal was. Also, I should be able to swap the screw/nut position right? Might make it easier with one of the middle sinks to tighten down after soldering to the board.


----------



## tomb

Quote:


  Originally Posted by *UglyJoe* /img/forum/go_quote.gif 
_yay, good to hear from you tomb. Got my kit today, obv. 
	

	
	
		
		

		
		
	


	




 Thanks.

 Okay, that makes sense... there isn't a second washer on the Max website pic, so I couldn't figure out what the deal was. Also, I should be able to swap the screw/nut position right? Might make it easier with one of the middle sinks to tighten down after soldering to the board._

 

Yeah, the pic is from the standard Avid catalog. However, I referenced the extra flat washer in the 2nd paragraph. To drive the point home, however, I added an additional note awhile ago toward the bottom of the page - about the Beezar kits.

 Yes - to your second question. Whatever makes it most convenient to you. Those middle sinks can be tough, but one advantage of the socket-head cap screws is that you can grab the head with a pair of needlenose pliers. That makes things easier, giving you tightening on both ends in tight spaces.


----------



## UglyJoe

shame on me for relying on pictures instead of reading... I don't usually do that...


----------



## UglyJoe

guys, i'm measuring apprx. 23 V for the tube bias regardless of where the trimmer is set. Any ideas? Pics tomorrow if no ideas


----------



## tomb

Quote:


  Originally Posted by *UglyJoe* /img/forum/go_quote.gif 
_guys, i'm measuring apprx. 23 V for the tube bias regardless of where the trimmer is set. Any ideas? Pics tomorrow if no ideas_

 

A not un-common mistake is forgetting to put in the heater resistor, R1. Without that resistor, or a lead soldered in its place, the heater circuit will be broken. No heaters - then no tube current, no bias, no music, etc.


----------



## UglyJoe

heater resistor is in place, though, and the top of the tubes sart glowing yellow, so they have power

 PSU dialed right into 27 V, and when I checked the DB's they were at 45mV or so.


----------



## tomb

Quote:


  Originally Posted by *UglyJoe* /img/forum/go_quote.gif 
_heater resistor is in place, though, and the top of the tubes sart glowing yellow, so they have power

 PSU dialed right into 27 V, and when I checked the DB's they were at 45mV or so._

 

OK, then it's possible that you haven't turned the trimmers far enough. They are not proportional with the tubes. Because of the ability to use 3 different types of tubes with different gains, the trimmers have a wide range, but are not active in the same range for every tube. You may have to turn 15 turns with little or no effect, while having adjustment in the final 5 turns. Every tube is a bit different, though, so I can't predict where that range may be for your situation.

 I'm wondering a bit about your color description, though - all mine glow a hot orange (not yellow) at the top of the cathode rod. Regardless, if that's the case, then the tubes are operating OK. The only other possibility besides not turning the trimmers enough is that your resistors or transistors in the CCS are mixed up. The CCS only uses 2N5087's - there are no 2N5088's in the CCS.


----------



## mik000000

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Can you measure voltage across the DM2 diode? That's the one that sits across the rails feeding the relay coil. Mine is a little bit more than 10VDC. If you don't have something close to 12VDC there, the relay coil will not shut.

 If you do have ~10VDC there, and you still can't get sound, then something's wrong with the relay._

 

I seem to be having the same problem as rhester. I have finished the max and all the test voltages are correct but no sound. when I connect to rb14 and ground i get sound, but nothing through the delay circuit. 
 All the solder joints appear to be fine. I measured the voltage across dm2 and am reading 0.
 Any suggestions?


----------



## tomb

Quote:


  Originally Posted by *mik000000* /img/forum/go_quote.gif 
_I seem to be having the same problem as rhester. I have finished the max and all the test voltages are correct but no sound. when I connect to rb14 and ground i get sound, but nothing through the delay circuit. 
 All the solder joints appear to be fine. I measured the voltage across dm2 and am reading 0.
 Any suggestions?_

 

Yes - a pic of your relay circuit section.

 A somewhat common mistake is to install the BD139 backwards.


----------



## UglyJoe

tomb,

 I actually got mine to work fine last night. I turned the trimmers full the other way, and it was fine. I thought I had already done that and still measured the 23 volts, but I either measured 2.3 or just had a brainfart. Anyway, everything is tuned in and ready to go.

 I started with 12ae6 tubes while making sure the board was okay... I'm going to pop in the 12FK6's when I get home today and go through the bias section again.

 The only thing I notice is that when I put my finger on top of the alps pot while listening the right channel goes out. A slight shaking of the board makes it come back in. I think this means a bad joint somewhere, and I'll trace it through when I get home tonight (I'm gonna bet one of the joints on the pot or the output plug were bad... I should have gone to my bigger tip and higher temps for those).


----------



## mik000000

here are the pics:





[/url][/IMG]

 and:






[/url][/IMG]


----------



## tomb

Quote:


  Originally Posted by *mik000000* /img/forum/go_quote.gif 
_here are the pics:
 <snip>
 and:
 <snip>_

 

OK - CM1 looks too big to be a 47uf cap. 47uf is just about the maximum - a tantalum is used on the actual e12 and our MAX prototypes. It needs to fire quickly to keep CM3 charged. I can't tell from your pics whether you have the correct RM1 and DM1 and whether they're oriented correctly. The BD139 looks fine, but did you use a Darlington transistor for QM2? You cannot use a 2N5088 here, it will not support the current. Finally, is it possible you mixed up DM1 and DM2? They look alike, but are totally different.

 I'd check again whether you've installed the correct parts in the correct orientation - especially those that were mentioned.


----------



## mik000000

I have rechecked the parts. QM2 is a MPAS14 and oriented with the silk screen on the board. 
 CM1 is a 47uf 25v electrolytic. and the positive is to the front of the board.
 RM1 is a 3.32k per the markings on the resisttor, but when measured I get 35R. RM2 is a 1m resistor per the markings, but when I measure I get 722 R

 I cannot tell about DM1 and DM2. There are no markings visible and they do look alike. 

 Unless you have any better suggestions, I will replace DM1 and DM2?


----------



## tomb

Quote:


  Originally Posted by *mik000000* /img/forum/go_quote.gif 
_I have rechecked the parts. QM2 is a MPAS14 and oriented with the silk screen on the board. 
 CM1 is a 47uf 25v electrolytic. and the positive is to the front of the board.
 RM1 is a 3.32k per the markings on the resisttor, but when measured I get 35R. RM2 is a 1m resistor per the markings, but when I measure I get 722 R

 I cannot tell about DM1 and DM2. There are no markings visible and they do look alike. 

 Unless you have any better suggestions, I will replace DM1 and DM2?_

 

If you are sure about the other parts, then yes. I can't think of anything else if the parts are correct - unless something has burned out, but that's unlikely at the currents in the relay circuit unless you have something soldered in backwards. The 1N4148 (DM2) should have the numbers printed around its circumference. The zener diode (DM1) does not. Besides checking for whether DM1 and DM2 have been switched, be sure to inspect the orientation on DM1 and whether DM1 and RM1 have been switched with each other.

 BTW, you seldom can measure resistor values once they're soldered into a circuit - too many things in parallel with them.


----------



## mik000000

Thank Tom. I know what I am doing tonight. I will try the diodes as I have spares and let you know. thanks again for the help


----------



## UglyJoe

Count another one in the living column, tomb.

 Got everything going today. Had a bad joint on one of the relay pins, reflowing fixed the channel going out problem. Currently burning in and slightly adjusting biases every hour or so.

 I want to send out a huge thank you to Colin for designing such a beautiful project, with so many cool feature built right in; thanks to Tom as well for the brutal undertaking of maintaining one of if not the best website for a DIY project I have seen, and then on top of that sourcing and giving us a place to get those hard to find parts with ease; and, of course, thanks to Mr. Millet for the original design way back when, and being so generous in giving us a template to push as far as the DIY community can.

 EDIT: Alison Krauss and Union Station LIVE is eating my life on this amp tonight... sound... is... phenomenal... and BGs haven't even come anywhere near burning in yet.


----------



## tomb

Thanks much for such kind words! It's nice to hear that you've got everything solved. Another MAX lives! 
	

	
	
		
		

		
			








 P.S. Post 'em if ya got 'em.


----------



## UglyJoe

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Thanks much for such kind words! It's nice to hear that you've got everything solved. Another MAX lives! 
	

	
	
		
		

		
		
	


	







 P.S. Post 'em if ya got 'em._

 

When I get it cased up I'll post. Right now it's just sitting in the main enclosure. BTW, I'm getting a slight hum and popping when I touch the ALPS shaft. Normal?

 I wish I had taken pics while putting it together... the Panavise circuit board holder came in uber handy and it almost looked professional! Well... sorta..


----------



## tomb

Quote:


  Originally Posted by *UglyJoe* /img/forum/go_quote.gif 
_When I get it cased up I'll post. Right now it's just sitting in the main enclosure. BTW, I'm getting a slight hum and popping when I touch the ALPS shaft. Normal?</snip>_

 

No, not normal. Did you solder in the grounding wire? That fixes it, unless something else is wrong. If so, you may need to reflow the ground connection at the signal input terminal block. If that thing doesn't wick properly, you may not get a good connection to the ground plane on top. That will cause a lot of pops, etc.


----------



## UglyJoe

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_No, not normal. Did you solder in the grounding wire? That fixes it, unless something else is wrong. If so, you may need to reflow the ground connection at the signal input terminal block. If that thing doesn't wick properly, you may not get a good connection to the ground plane on top. That will cause a lot of pops, etc._

 

What grounding wire? I assume it's to ground the alps chassis to the board, but I don't see one on any of the website pics...


 EDIT: Nevermind, got it.


----------



## Beefy

Quote:


  Originally Posted by *UglyJoe* /img/forum/go_quote.gif 
_BTW, I'm getting a slight hum and popping when I touch the ALPS shaft. Normal?_

 

Yes. Assuming you have a front panel that is electrically conductive, the pot shaft will be grounded when it is all cased up and this issue will disappear.

 If your front panel is not conductive, you will need to add an grounding wire. Just undo the top screw on the pot a little, wrap some thin hookup wire around it, then re-tighten the screw. There is a GND point just behind the pot that you can solder the wire into.


----------



## UglyJoe

Do you solder straight to the screw on the back of the alps, or does it come out and twist down on the wire?

 EDIT: Ninja'd


----------



## UglyJoe

Bah... I don't have a hex key that will fit this screw.

 So, when I use the aluminum front plate and the whole case is grounded via the RCA inputs to IG at the back plate, I shouldn't even have to worry about this right? Should be okay for a few days ungrounded while I work on the plates?


----------



## Beefy

Quote:


  Originally Posted by *UglyJoe* /img/forum/go_quote.gif 
_or does it come out and twist down on the wire?_

 

Yes, that one 
	

	
	
		
		

		
		
	


	




 Oh, and sorry..... I actually replied directly to your post without seeing tomb's 
	

	
	
		
		

		
		
	


	



 The popping is normal in the respect that if the pot isn't grounded, you will get popping. But it should be grounded and thus you shouldn't get popping.


----------



## tomb

Quote:


  Originally Posted by *UglyJoe* /img/forum/go_quote.gif 
_Bah... I don't have a hex key that will fit this screw.

 So, when I use the aluminum front plate and the whole case is grounded via the RCA inputs to IG at the back plate, I shouldn't even have to worry about this right? Should be okay for a few days ungrounded while I work on the plates?_

 

There's a small pad on the board in the back of the pot. Simply solder a short wire from there to the back screw on the ALPS. The screw is a Philips - nothing exotic. Just unscrew it enough to wrap the end of the wire around it, and screw it back in.


----------



## UglyJoe

Quote:


  Originally Posted by *Beefy* /img/forum/go_quote.gif 
_Yes, that one 
	

	
	
		
		

		
		
	


	




 Oh, and sorry..... I actually replied directly to your post without seeing tomb's 
	

	
	
		
		

		
		
	


	



 The popping is normal in the respect that if the pot isn't grounded, you will get popping. But it should be grounded and thus you shouldn't get popping._

 

But it's okay to leave as is till I get my panels done?


----------



## UglyJoe

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_There's a small pad on the board in the back of the pot. Simply solder a short wire from there to the back screw on the ALPS. The screw is a Philips - nothing exotic. Just unscrew it enough to wrap the end of the wire around it, and screw it back in._

 

Phillips? Sure doesn't look like one... but my eyes are crap, so...


----------



## Beefy

Quote:


  Originally Posted by *UglyJoe* /img/forum/go_quote.gif 
_But it's okay to leave as is till I get my panels done?_

 

Easier to do it now. And even if your front panel is conductive, it is more reliable to actually wire it in considering the GND point is right there.

  Quote:


  Originally Posted by *UglyJoe* /img/forum/go_quote.gif 
_Phillips? Sure doesn't look like one... but my eyes are crap, so..._

 

Yes, it is a tiny Phillips head.


----------



## UglyJoe

Well, that was easy. Funny how the right tool always makes things exponentially easier.


 EDIT: This amp is fantastic.

 EDIT2: Does it need a headphone load to burn in the caps? I don't see why it would.....


----------



## mik000000

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_If you are sure about the other parts, then yes. I can't think of anything else if the parts are correct - unless something has burned out, but that's unlikely at the currents in the relay circuit unless you have something soldered in backwards. The 1N4148 (DM2) should have the numbers printed around its circumference. The zener diode (DM1) does not. Besides checking for whether DM1 and DM2 have been switched, be sure to inspect the orientation on DM1 and whether DM1 and RM1 have been switched with each other.

 BTW, you seldom can measure resistor values once they're soldered into a circuit - too many things in parallel with them._

 

I replaced dm1 and dm2 and cm1 for good measure and still nothing. in an earlier post you said there should be 10v+ across dm2 and i have 0v. Does that tell us anything?


----------



## Beefy

Quote:


  Originally Posted by *UglyJoe* /img/forum/go_quote.gif 
_EDIT2: Does it need a headphone load to burn in the caps? I don't see why it would....._

 

Give up the idea of burning it in. Just _listen_ to it!


----------



## UglyJoe

Quote:


  Originally Posted by *Beefy* /img/forum/go_quote.gif 
_Give up the idea of burning it in. Just listen to it!_

 

Oh I am... I'm just going to also let it burn in whilst away, see.


----------



## tomb

Quote:


  Originally Posted by *mik000000* /img/forum/go_quote.gif 
_I replaced dm1 and dm2 and cm1 for good measure and still nothing. in an earlier post you said there should be 10v+ across dm2 and i have 0v. Does that tell us anything?_

 

0V confirms that your relay is not energized. At this point, I'd say that means either QM1 is bad, QM2 is bad, or both. Are you sure that's an MPSA14 you've got in there for QM2? That's the critical part. The BD139 is there to dissipate heat, more or less.

 What's the voltage across DM1? Across RM1?

 I hate to tell you, but I've got to turn in for the night - I'll take it up in the morning and see if you did anything else.


----------



## suneohair

Can someone tell me what enclosure is used here:

Millett MAX Gallery


----------



## mik000000

The good news is, it does seem that the problem is not with the relay, as I was not looking forward to removing that. The better news is I checked my parts box and I have a spare for both qm1 and qm2.
 I have measured the voltages as:
 DM1 11.6v
 RM1 15v

 And unfortunately, I have to head to work to pay for this hobby. Will try again later


----------



## MrMajestic2

Quote:


  Originally Posted by *suneohair* /img/forum/go_quote.gif 
_Can someone tell me what enclosure is used here:

Millett MAX Gallery_

 


 Its made by ATI in Thailand, dont remember the model. Unfortunetly they are no longer in business.


----------



## regal

Has anyone built a Max with a Amb's discrete power supply? One big advantage of low V tubes is the ability to have an ultra clean power supply for cheap. I always wondered what a tube would sound like with microvolt ripple.


----------



## suneohair

Quote:


  Originally Posted by *MrMajestic2* /img/forum/go_quote.gif 
_Its made by ATI in Thailand, dont remember the model. Unfortunetly they are no longer in business._

 

That sucks, I really liked the look of that one. Are there any others that are similar? There is the DigiKey HM903-ND, which is ok. Any recommendations would be awesome!


----------



## mik000000

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_0V confirms that your relay is not energized. At this point, I'd say that means either QM1 is bad, QM2 is bad, or both. Are you sure that's an MPSA14 you've got in there for QM2? That's the critical part. The BD139 is there to dissipate heat, more or less.

 What's the voltage across DM1? Across RM1?

 I hate to tell you, but I've got to turn in for the night - I'll take it up in the morning and see if you did anything else.
	

	
	
		
		

		
		
	


	


_

 

IT'S ALIVE!!!

 It was the BD139. And of course it was the last one i replaced. But it is producing glorious sound now. I need to reassemble it in the chassis and take some time to relax and listen and enjoy.

 thanks for the help Tom..as always


----------



## tomb

Quote:


  Originally Posted by *mik000000* /img/forum/go_quote.gif 
_IT'S ALIVE!!!

 It was the BD139. And of course it was the last one i replaced. But it is producing glorious sound now. I need to reassemble it in the chassis and take some time to relax and listen and enjoy.

 thanks for the help Tom..as always_

 

Thanks, but you did the work - I was just sitting here guessing.
	

	
	
		
		

		
		
	


	




 The important thing is that you got it working - yay!!


----------



## soloz2

well I received another package today. Sat I got one from Tom and one from Amb. This one was from Brian Donegan 
	

	
	
		
		

		
		
	


	




 I haven't opened it yet, but I know there's a Darwin, Opus and USB module in there...

 Now I just have a few odds and ends to order from Mouser including a push button switch and a few last minute changes as I decided to build a MOSFET MAX.

 I also placed an order with Cardas today and added several pairs of RCA jacks 
	

	
	
		
		

		
		
	


	




 After that I just need to straighten out the whole Parmetal mess (still haven't gotten anywhere...) order a toroid to power everything and a few odds and ends.


----------



## amphead

Congrats mik000000! Another Max Lives   

 I remember that exact feeling, with the music taking me away as only the Max can. Edit: Stay tuned, the Starving Millett coming to a theatre near you.


----------



## sokece

I'm planning to build MAX this long weekend. I ordered parts from Mouser, Digikey, Beezer and I did not aware that I need to order more for 2N5087 and 2N5088. Basically, I did not order enough 2N5087 or 2N5088.

 I read the article from MAX Construction and suggest to match the transistors but the phrase "Matching the JFETs and BJT output transistors has limited usefulness" is unclear to me. 

 I'm going with BJT route. Is it important to match transistor PNP and NPN? if not what is the side effect?


----------



## tomb

Quote:


  Originally Posted by *sokece* /img/forum/go_quote.gif 
_I'm planning to build MAX this long weekend. I ordered parts from Mouser, Digikey, Beezer and I did not aware that I need to order more for 2N5087 and 2N5088. Basically, I did not order enough 2N5087 or 2N5088.

 I read the article from MAX Construction and suggest to match the transistors but the phrase "Matching the JFETs and BJT output transistors has limited usefulness" is unclear to me. 

 I'm going with BJT route. Is it important to match transistor PNP and NPN? if not what is the side effect?_

 

I'm sorry you forgot the 2N5087/2N5088's. They are so cheap that people often buy them and match them themselves. So, I didn't think anything of it when processing your order.

 Again, the construction article details how to match transistors with a very cheap multimeter from Harbor Freight. It's not so much that matching closely is important, as it is to reject those ones that are 100+ HFE away from the others. I match all those that I sell within ~10HFE, but variances of up to 20 or 30 are probably nothing to worry about. There are a few in a batch of 50, for instance, that might have an HFE of 500 - while all the rest are around 350. So, you'd definitely want to reject those high ones.

 The statement "Matching the JFETs and BJT output transistors has limited usefulness" means two things:

 1. JFET - the "BJT MAX" (also the MOSFET MAX in this area) uses a single JFET per channel to set set the current bias through the buffer. Since the JFET loop is directly adjustable by the trimmer, it's a little redundant to match the Left channel JFET to the Right channel JFET.

 2. BJT output transistors - this part of the statement refers to the big TO-220 output transistors, only. Those are often so consistent that it's pointless to measure their HFE. I've never seen them vary by more than 2 to 4 HFE, in fact - most are less varied than that, even.

 That leaves all the 2N5087's and the 2N5088's. Yes, those should be matched - but are not too critical. It's probably more important to have the CCS transistors matched more than the others. Those are the 2N5087's at QA1L-QA2L and QA1R-QA2R.


----------



## UglyJoe

Well, I finished the front and back plates last night. Everything looks good. Still have to drill out the top plate and get a knob. Sounds fantastic.

 This is the first amp I have ever had with tubes in it, and I noticed something that I wanted to make sure was normal. The amp is very microphonic, in that after the amp is powered on and the relay kicks in, with no source playing, tapping the amp comes through magnified over the headphones. No hum or anything like that... it's kinda like hearing the thump through a stethoscope. Is this normal?


----------



## patton713MW

I know we've been talking a lot about cutting the holes for the tubes, and I want to throw another question in. Could a hole saw be used? I have seen hole saws in 3/4 in and 1 in sizes. I know that they are often used in PC case modding, why wouldn't they work for kind of case work?


----------



## BoilermakerFan

Quote:


  Originally Posted by *patton713MW* /img/forum/go_quote.gif 
_I know we've been talking a lot about cutting the holes for the tubes, and I want to throw another question in. Could a hole saw be used? I have seen hole saws in 3/4 in and 1 in sizes. I know that they are often used in PC case modding, why wouldn't they work for kind of case work?_

 

They will work, but you'll have a rougher end finish in the hole compared to a stepper drill bit or punch. They are also harder to control on a hand drill than a step bit. I only use hole saws for 80mm, 105, and 120mm case fans and I've never had one actually come out round in metal when drilled by hand.


----------



## tomb

Quote:


  Originally Posted by *UglyJoe* /img/forum/go_quote.gif 
_Well, I finished the front and back plates last night. Everything looks good. Still have to drill out the top plate and get a knob. Sounds fantastic.

 This is the first amp I have ever had with tubes in it, and I noticed something that I wanted to make sure was normal. The amp is very microphonic, in that after the amp is powered on and the relay kicks in, with no source playing, tapping the amp comes through magnified over the headphones. No hum or anything like that... it's kinda like hearing the thump through a stethoscope. Is this normal?_

 

Amps aren't microphonic - tubes are.
	

	
	
		
		

		
			





 You have a microphonic tube. It's impossible to predict this when the tube is sold, because a tube can test just fine if it's microphonic. You'll never know until music is played through it. In fact, it depends on how irritating it is as to whether you can live with it or not.

 Basically, there are three options of what to do about it:
 1. Replace the tube. Most dealers (including me) will replace a microphonic tube.
 2. Try some tube dampers. Depending on how bad the microphonics are, you can make an unacceptable tube bearable, or a slightly microphonic tube almost defect-free. Sometimes they respond, sometimes they don't, though.
 3. Live with it.


----------



## tomb

Quote:


  Originally Posted by *BoilermakerFan* /img/forum/go_quote.gif 
_They will work, but you'll have a rougher end finish in the hole compared to a stepper drill bit or punch. They are also harder to control on a hand drill than a step bit. I only use hole saws for 80mm, 105, and 120mm case fans and I've never had one actually come out round in metal when drilled by hand._

 

Agreed. You need a very high quality hole saw bit with a very robust drill press -plus good tooling to lock the part in place. Like BoilermakerFan, I have never been able to use one without it slipping.

 Hole punches are somewhat expensive, but worth every penny, IMHO. They are even sold on ebay and you can catch a good buy for one used. I'd stick with Greenlee, though. Cheaper punches are worse than the hole saws.
	

	
	
		
		

		
		
	


	




 A good one like Greenlee will make butter out of a Hammond case top. You may find that you want one for those Neutrik locking-type headphone jacks, too.

 Grainger, Mouser, Tube supply vendors, Home Depot, Lowes, and electrical supply houses carry them. Just be careful if you get one that's labeled for conduit - those are sized for the O.D. of the conduit, but labeled for the conduit's I.D. That can cause a rude surprise when you punch a hole.


----------



## UglyJoe

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Amps aren't microphonic - tubes are.
	

	
	
		
		

		
		
	


	




 You have a microphonic tube. It's impossible to predict this when the tube is sold, because a tube can test just fine if it's microphonic. You'll never know until music is played through it. In fact, it depends on how irritating it is as to whether you can live with it or not.

 Basically, there are three options of what to do about it:
 1. Replace the tube. Most dealers (including me) will replace a microphonic tube.
 2. Try some tube dampers. Depending on how bad the microphonics are, you can make an unacceptable tube bearable, or a slightly microphonic tube almost defect-free. Sometimes they respond, sometimes they don't, though.
 3. Live with it._

 

As long as the microphonics aren't symptomatic of a tube's lifetime being shorter I don't really care. I don't notice it at all with music playing, only when the source is off and I'm actually tapping the enclosure. Otherwise it sounds just fine and, like I said, as long as the tube should otherwise be normal I am cool with it.


----------



## tomb

Quote:


  Originally Posted by *UglyJoe* /img/forum/go_quote.gif 
_As long as the microphonics aren't symptomatic of a tube's lifetime being shorter I don't really care. I don't notice it at all with music playing, only when the source is off and I'm actually tapping the enclosure. Otherwise it sounds just fine and, like I said, as long as the tube should otherwise be normal I am cool with it._

 

Yep - a couple of my best performing tubes were slightly microphonic. It was no big deal. However, keep using tubes (of any sort - not just a Millett) and you may eventually find one that could be so bad it rings when you breathe on it. You can't live with those.


----------



## UglyJoe

Well, here is a pic, nearly done. Ordered a knob from the hong kong ebay store tonight.






 Right now using an iPod as source. Cable is a diy iMod cable with Black Gate caps in the doc, vampire wire, and vampire RCAs (gotta have my bling). Eventually going to diy mod my iPod when I get the balls up to do it. I'm also using an old DVD player as a source, especially for long overnight burn in periods. I probably have 80-100 hours on the amp now.

 I couldn't justify a center hole punch, so I had to use a big stepped bit, and I got pretty far off on the right tube, but it works. Other than that it's mostly exactly as I wanted. Very, very happy with it.


----------



## tomb

Nice job, UglyJoe! Another MAX lives!


----------



## tomb

Quote:


  Originally Posted by *regal* /img/forum/go_quote.gif 
_Has anyone built a Max with a Amb's discrete power supply? One big advantage of low V tubes is the ability to have an ultra clean power supply for cheap. I always wondered what a tube would sound like with microvolt ripple._

 

I didn't mean to ignore this question, regal. However, you didn't realize how timely this question was. We're not going in the direction of AMB's stuff, per se, but we have been taking a serious look at tweaking the power supply of the MAX. We've been doing a lot of work in this regard. I don't know that we'll get it down into the microVolt range, but it will definitely be a measureable improvement. Whatever we come up with will be easy to retrofit to existing boards, too. It's one of the reasons the MOSFET-MAX and MiniMAX have been delayed a bit. I hope to announce something more concrete in a week or two.


----------



## Gross

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_ It's one of the reasons the MOSFET-MAX and MiniMAX have been delayed a bit. I hope to announce something more concrete in a week or two.
	

	
	
		
		

		
		
	


	


_

 


 Really?... And just this afternoon I was going to start populating my MOSFET-MAX board. Looks like I will wait just a bit longer.


----------



## pabbi1

My first Millett with built with a STEPS, and never considered anything less at the time. This is a move in a good direction.


----------



## tomb

Quote:


  Originally Posted by *Gross* /img/forum/go_quote.gif 
_Really?... And just this afternoon I was going to start populating my MOSFET-MAX board. Looks like I will wait just a bit longer._

 

There are a few more things to test before we fully document things. Technically, the MOSFET-MAX and design are not "official" yet - that will happen when I make the website live. However, it's a very simple mod - nothing to stop you from populating your board, I would think.


----------



## Gross

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_There are a few more things to test before we fully document things. Technically, the MOSFET-MAX and design are not "official" yet - that will happen when I make the website live. However, it's a very simple mod - nothing to stop you from populating your board, I would think._

 


 Any clues as to which parts I should leave out for now?

 And as far as matching QA1L/R and QA2L/R, I have 4 that are within 35hFE, and was curious as to which should match closer, QA1L to QA1R, or QA1L to QA2L?

 Thanks!


----------



## tomb

Quote:


  Originally Posted by *Gross* /img/forum/go_quote.gif 
_Any clues as to which parts I should leave out for now?_

 

It may be as simple as _adding_ a single resistor, but that's all I have for now.
  Quote:


 And as far as matching QA1L/R and QA2L/R, I have 4 that are within 35hFE, and was curious as to which should match closer, QA1L to QA1R, or QA1L to QA2L?

 Thanks! 
 

QA1L should be matched with QA2L. There is no adjustment between QA1 and QA2 within the same channel, whereas the trimmers can compensate if QA1-2L are 450 HFE vs. QA1-2R at 300, for instance.

 That said, 35 HFE is probably not enough to worry about in either case *EDIT*- but it sounds like you may not have purchased enough transistors for a good spread.*end EDIT*


----------



## amphead

Nice work Uglyjoe! Another Max Lives!   

 Wondered what happened to you? You started soon enough.


----------



## UglyJoe

Yeah.... I got my boards in the original GB. It was murder sitting with these gorgeous Max boards on my desk looking at me for almost a year... seriously, they have eyes, they were looking at me... nice guys, we talked for hours sometimes....


----------



## ruZZ.il

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_....
 That said, 35 HFE is probably not enough to worry about in either case._

 


 You mean I have strips of folded masking tape stuck to my wall with a few handfulls of transistors bunched up on them for nothing?!?!.. I spent hours when it was cold, and then some when it was hot, for nothing?!?


----------



## tomb

Quote:


  Originally Posted by *ruZZ.il* /img/forum/go_quote.gif 
_You mean I have strips of folded masking tape stuck to my wall with a few handfulls of transistors bunched up on them for nothing?!?!.. I spent hours when it was cold, and then some when it was hot, for nothing?!? 
	

	
	
		
		

		
		
	


	













_

 

Too bad for you. 
	

	
	
		
		

		
		
	


	







 EDIT:
 Ulp. Seriously - my bad! I keep forgetting the CCS is NOT made up of complements!
	

	
	
		
		

		
		
	


	







 You should've roasted me on that one - yeah, he should be able to get close than 35 HFE.
	

	
	
		
		

		
		
	


	



 EndEDIT


----------



## ruZZ.il

nah no worries, I was just kidding 
	

	
	
		
		

		
		
	


	




 all the hard work was done for the 2/4/6 and 3/5/7 pairs anyway.. I think you covered all this somewhere back there....... 

 meanwhile, I'm writing exams soon on "semiconductors 2" and something like "analog elec", which is basically transistors and all their configs and methods of analysis (Pi, T, etc..) (not just basically). While I still don't see the max's whole flow of electrons flashing before me, I'm far less baffled by looking at it all
	

	
	
		
		

		
		
	


	




 Edit:
 ..but it's still all too much a mess in my head  I haven't fired up my solder iron in waaaay too long than whats good for me  need some fumes damnit. no more paper!!


----------



## amphead

Less theory..........more hands-on!


----------



## Gross

so, I am gathering I should be closer than 35... I think I am going to be ok, although I only ordered 10. I have 2 pairs that are within 10, since now I know L&R don't need to match.


----------



## tomb

Beezar received a _very_ small shipment of _genuine_ Toshiba 2SC2238's. I believe there are 6 left at the time of this posting.


----------



## BoilermakerFan

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Beezar received a very small shipment of genuine Toshiba 2SC2238's. I believe there are 6 left at the time of this posting._

 

And then there were 4...


----------



## pinkfloyd4ever

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Beezar received a very small shipment of genuine Toshiba 2SC2238's. I believe there are 6 left at the time of this posting._

 

*[size=medium]YESSSSS[/size]* make that 2 baby!!


----------



## tomb

And then there were none ... the 2SC2238's are now gone. (One other bought them, but didn't post about it.)

 Thanks, guys!


----------



## amphead

They are in for a treat!


----------



## soloz2




----------



## WilCox

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_And then there were none ... the 2SC2238's are now gone. (One other bought them, but didn't post about it.)

 Thanks, guys!
	

	
	
		
		

		
		
	


	


_

 

That was me! Just finishing up MAX #2 with 2SC3422/2SA1359 and Backgate Super E-Cap with VitaminQ at the output (another _great_ match for ATH-W5000/1000). When I saw the 2238's were available, I couldn't resist planning Max #3.


----------



## akione

Well, we have another one living .....


----------



## BoilermakerFan

Quote:


  Originally Posted by *soloz2* /img/forum/go_quote.gif 
_



_

 

I thought you were building a MOSFET version for your next MAX?

 I finally got around to calling NSL and they had to call AKG to confirm that the K601s are in stock and available. Still $181 so I ordered them and should have them in 2-3 weeks. I'm going to use them stock for a bit so I can hopefully fully appreciate the improvements with a new cable and the K701 velour earpads. After listening to Gross' K501s, I'm really looking forward to getting these cans on my head!


----------



## tomb

Quote:


  Originally Posted by *akione* /img/forum/go_quote.gif 
_Well, we have another one living ..... 
	

	
	
		
		

		
		
	


	


_

 

Nice job, akione! Another MAX lives!!


----------



## soloz2

Quote:


  Originally Posted by *BoilermakerFan* /img/forum/go_quote.gif 
_I thought you were building a MOSFET version for your next MAX?_

 

well that was just the backup plan, but looks like that's the plan that's sticking!


----------



## GeWa

OK, I still have some casework to do but as of today he's making music!! 
	

	
	
		
		

		
		
	


	



 For the moment the DB's are biased at 90mV. I'm using the 2SC2238/2SA968 combo.






 Regards


----------



## BoilermakerFan

Quote:


  Originally Posted by *GeWa* /img/forum/go_quote.gif 
_OK, I still have some casework to do but as of today he's making music!! 
	

	
	
		
		

		
		
	


	



 For the moment the DB's are biased at 90mV. I'm using the 2SC2238/2SA968 combo.






 Regards_

 

Nice build! It's off topic, but what is the awesome amp to the right of the MAX?


----------



## paul_lindemann

How is the amp for microphonics?


----------



## Alcaudon

Quote:


  Originally Posted by *BoilermakerFan* /img/forum/go_quote.gif 
_Nice build! It's off topic, but what is the awesome amp to the right of the MAX?_

 

X2!!!!


----------



## GeWa

@BoilermakerFan

 That's my first ever attempt in DIY amps, a parallel push-pull with KT66's wired in triode. Definitely not a headphone amp 
	

	
	
		
		

		
		
	


	









 @paul_lindeman

 Absolutely not microphonic, you can even tap the tubes and it's still dead silent.

 @Alcaudon

 What's an X2?
	

	
	
		
		

		
		
	


	




 Regards


----------



## fc911c

Very Nice, now that's a work of art.


  Quote:


  Originally Posted by *GeWa* /img/forum/go_quote.gif 
_@BoilermakerFan

 That's my first ever attempt in DIY amps, a parallel push-pull with KT66's wired in triode. Definitely not a headphone amp 
	

	
	
		
		

		
		
	


	









 @paul_lindeman

 Absolutely not microphonic, you can even tap the tubes and it's still dead silent.

 @Alcaudon

 What's an X2?
	

	
	
		
		

		
		
	


	




 Regards_


----------



## BoilermakerFan

Quote:


  Originally Posted by *GeWa* /img/forum/go_quote.gif 
_@BoilermakerFan

 That's my first ever attempt in DIY amps, a parallel push-pull with KT66's wired in triode. Definitely not a headphone amp 
	

	
	
		
		

		
		
	


	










 @Alcaudon

 What's an X2?
	

	
	
		
		

		
		
	


	




 Regards_

 

X2 = Time Two... He also wanted to see a bigger pic and find out what your KT66 amp was. I'll be sending you a PM with more questions about your KT66 amp. The chassis work is stellar!

 - BMF


----------



## Alcaudon

Quote:


  Originally Posted by *BoilermakerFan* /img/forum/go_quote.gif 
_X2 = Time Two... He also wanted to see a bigger pic and find out what your KT66 amp was. I'll be sending you a PM with more questions about your KT66 amp. The chassis work is stellar!
 - BMF_

 

That's it, thanks for the explanation bmf 
	

	
	
		
		

		
		
	


	




 Impressive work Gewa!!!! What are you connectig there??? Seems like it could power a Delorean for a time travel!!!


----------



## hazamatic

Hi all, recently finished my first millet max, but having a slight problem. Maybe some one here can give me some tips on what to check first 
	

	
	
		
		

		
		
	


	




 1.) I can hear a crackling sound coming from the right channel. The left channel is totally silent, only the right channel seems affected. The crackling is not there all the time, it seems to come and go randomly. For example, it might crackle for 2 secs, then become silent, then crackle again 30 secs later. Or it could go minutes without crackling, or it might crackle for minutes at a time. It's not a loud crackle...I can't really hear it when music is playing unless the music is very soft and quiet or if I really concentrate and try to hear it.

 2.) Might be related to problem 1, not sure. I'm having problems reading the DB bias on the right channel (same problem on both bias points). I place probes on the DB bias points, but the voltage flucates greatly. Sometimes I do get a steady reading, and I'm assuming this is the REAL voltage. When I got a steady reading I set it to 107. However, when the reading is not steady, it flucates from 30-107 (never over what I set it to when I got a stable reading). I can't tell what causes the reading to become stable or not, seems to happen all by itself without me touching the probes after they are placed (I may have breathed on them 
	

	
	
		
		

		
		
	


	




). In comprasion, the left channel gives me a constant steady reading, all the time, every time. 


 So far I've tried replacing the tubes but I get the samething happening. Anyone got any ideas?


----------



## tomb

Quote:


  Originally Posted by *hazamatic* /img/forum/go_quote.gif 
_Hi all, recently finished my first millet max, but having a slight problem. Maybe some one here can give me some tips on what to check first 
	

	
	
		
		

		
		
	


	




 1.) I can hear a crackling sound coming from the right channel. The left channel is totally silent, only the right channel seems affected. The crackling is not there all the time, it seems to come and go randomly. For example, it might crackle for 2 secs, then become silent, then crackle again 30 secs later. Or it could go minutes without crackling, or it might crackle for minutes at a time. It's not a loud crackle...I can't really hear it when music is playing unless the music is very soft and quiet or if I really concentrate and try to hear it.

 2.) Might be related to problem 1, not sure. I'm having problems reading the DB bias on the right channel (same problem on both bias points). I place probes on the DB bias points, but the voltage flucates greatly. Sometimes I do get a steady reading, and I'm assuming this is the REAL voltage. When I got a steady reading I set it to 107. However, when the reading is not steady, it flucates from 30-107 (never over what I set it to when I got a stable reading). I can't tell what causes the reading to become stable or not, seems to happen all by itself without me touching the probes after they are placed (I may have breathed on them 
	

	
	
		
		

		
		
	


	




). In comprasion, the left channel gives me a constant steady reading, all the time, every time. 


 So far I've tried replacing the tubes but I get the samething happening. Anyone got any ideas?_

 

I agree that the problem is in a transistor(s) somewhere. Crackling is usually solid-state in nature, I think. Your unsteady readings are simply confirming that.

 A good place to start is to measure the Voltage across each resistor in the buffers. Then by direct comparison with your good Left channel, we should be able to narrow the problem down. Eventually, we'll want to measure the voltage to ground of the resistors we may find out of the norm, but let's try this first:

 Measure voltages across:
 RB1L?..........RB1R?
 RB2L?..........RB2R?
 RB3L?..........RB3R?
 RB4L?..........RB4R?
 RB5L?..........RB5R?
 RB6L?..........RB6R?
 RB7L?..........RB7R?

 RB8 and RB9 should be jumpered and we know the voltage differences across RB10 and RB11 - that's your buffer's bias.

 If we're lucky, it may be something as simple as re-flowing the solder around some of the parts in your Right buffer.


----------



## soloz2

well I shipped the enclosure back to par metal. I'm still hoping things will work out as I haven't found a different enclosure apx 12"x12". It doesn't need to be quite as deep and can probably be up to 14" wide, but I don't want anything wider.

 Next I just need to figure out the best power source.
 If I had more room I would get two toroids, one for the Opus and one for the Max, but since I don't have a lot of room I'll have to just get one. I'm just not sure exactly how to wire it.

 Alltogether I need to power:
 Max
 OptiVol - will get power from Max main power LED position
 Darwin
 Opus (I have a LCDPS)


----------



## rockcod

Quote:


  Originally Posted by *soloz2* /img/forum/go_quote.gif 
_well I shipped the enclosure back to par metal. I'm still hoping things will work out as I haven't found a different enclosure apx 12"x12"._

 

Anything wrong with it?


----------



## bperboy

Quote:


  Originally Posted by *rockcod* /img/forum/go_quote.gif 
_Anything wrong with it?_

 

The colors I believe... IIRC Soloz was having some ordering issues with the ParMetal eBay store...


----------



## BoilermakerFan

Quote:


  Originally Posted by *soloz2* /img/forum/go_quote.gif 
_well I shipped the enclosure back to par metal. I'm still hoping things will work out as I haven't found a different enclosure apx 12"x12". It doesn't need to be quite as deep and can probably be up to 14" wide, but I don't want anything wider.

 Next I just need to figure out the best power source.
 If I had more room I would get two toroids, one for the Opus and one for the Max, but since I don't have a lot of room I'll have to just get one. I'm just not sure exactly how to wire it.

 Alltogether I need to power:
 Max
 OptiVol - will get power from Max main power LED position
 Darwin
 Opus (I have a LCDPS)_

 

What about using two or three Hoffman enclosures? Just stack them. One PSU, one DAC, one MAX with the Darwin and OptiVol. Just use the 8" deep boxes. 


 Too bad you couldn't squeeze the width to under 19". Then the NABU would work great. Plenty of room for two toroids, a 100VA and 50VA on the PSU side, and lots of room for the MAX, Darwin, OPUS, and OptiVol on the front panel (and provision for Joshua Tree and VFD on the front). There would still be room in there for a phono stage if you ever decide to really feed the analog addiction and get into vinyl. 

 My buddy's panel shop can waterjet cut front panels out of aluminum, but I really need ten or more peeps to go in on a group buy to cover the cost of programming so I need to figure out how "simple" to make the panel. I asked about laser etching and they can do that too, so I need CorelDraw to mock a nice panel font and labeling. Plus, I just found out he's a Head-Fi'er, but not an active poster. He has a custom ALO iPod cord for his car and the ALO dock for his house. I'm working on him and I'll give him one of my MAXes to demo. Though I suspect I won't get it back. 
	

	
	
		
		

		
			





 haven't decided which one he'll get, it will depend on my listening results of my BJT trials. 

 Unfortunately, I won't be able to make your deadline for the end of July meet on the custom front panel, I just don't have the time to lay it out in CAD. 

 - BMF


----------



## Daveze

I have a couple of quick questions:
 - Has anybody given consideration to a temperature operating point for the buffer, rather than directly considering the bias current? I've got a very open case (no top, front or back panels) and the larger heatsinks (not as large as BMF though...), so I've dialed in at 120mV, which has the centre heatsinks at 40C (104F). Its approaching a point where it is difficult to dial in the voltage precisely, so I wouldn't go much higher but I'm wondering if anybody has challenged their operating points based on temp.
 - A little while ago I changed from Panasonic/Wima to Nichicon/VitQ (.18uF). While it was nicer I was missing a bit of the low end punch that I thought the Panasonic/Wima combo had. Is it simply the change from .22 to .18, and hence, would going to the .22 VitQ bring back the slam. (I'm guessing not really...)
 - (Extension to the second question) Should I swap the MJE243/53 combo for the 2SC3422/SA1359 combo? I'm thinking it'll solve my question 2 issue, so I'm really after someone to twist my rubber arm...


----------



## Beefy

Quote:


  Originally Posted by *Daveze* /img/forum/go_quote.gif 
_ - A little while ago I changed from Panasonic/Wima to Nichicon/VitQ (.18uF). While it was nicer I was missing a bit of the low end punch that I thought the Panasonic/Wima combo had. Is it simply the change from .22 to .18, and hence, would going to the .22 VitQ bring back the slam. (I'm guessing not really...)_

 

From memory you had a Glass Jar kit? Thus, shouldn't you have had Muze KZ at CA7? So it would follow that you have replaced the Panasonic at CA2 and the Wima at CA9?

 According to tomb, the basic Wima is really the best choice at CA9 and anything else has the potential to kill the bass. Perhaps this is what you are hearing.

  Quote:


 - (Extension to the second question) Should I swap the MJE243/53 combo for the 2SC3422/SA1359 combo? I'm thinking it'll solve my question 2 issue, so I'm really after someone to twist my rubber arm... 
 

The problem may be in getting the old transistors out, and the new ones in. Might not be so easy with soldered heatsinks....... but if you think you can manage it, why not? You'll be pretty close to a Can't Miss #2......


----------



## Daveze

Ooh, I nearly provided all the necessary information for the post...except that I didn't.

 Glass Jar kit is correct, I'm referring to CA7 and CA8: the 470uF Muse UKZ's (you're correct, they're not Panasonics) but are now 470uf Muse ES's, and 0.22uF Wima's are now 0.18 VitQ's. I still have the Wima's in CA9 and CA2 should be the Panasonic. I'm not game to change CA2, I've previously tried to remove components that are joined to the ground plane and toasted the pads...now that my board is populated, I'd really rather not make that mistake.

 I've toasted and replaced my output transistors before (it is an [expletive] of a process), I think I was one of the first few that contributed towards learning what happened when you switch the N and P channel BJT's around...


----------



## BoilermakerFan

Quote:


  Originally Posted by *Daveze* /img/forum/go_quote.gif 
_Ooh, I nearly provided all the necessary information for the post...except that I didn't.

 Glass Jar kit is correct, I'm referring to CA7 and CA8: the 470uF Muse UKZ's (you're correct, they're not Panasonics) but are now 470uf Muse ES's, and 0.22uF Wima's are now 0.18 VitQ's. I still have the Wima's in CA9 and CA2 should be the Panasonic. I'm not game to change CA2, I've previously tried to remove components that are joined to the ground plane and toasted the pads...now that my board is populated, I'd really rather not make that mistake.

 I've toasted and replaced my output transistors before (it is an [expletive] of a process), I think I was one of the first few that contributed towards learning what happened when you switch the N and P channel BJT's around..._

 

The .18VitQs in CA8 should be fine with the Muse ES or KZ caps. I'm planning to use the .18 VitQs for builds in CA8, although I also have the .22 VitQs as back ups. Is the Panasonic in CA2 a FC or FM cap? 

 I'll let Tom weigh in on the temp question, but I think you would be ok at 40degC. You need to check the curves for your BJTs though. You just want enough bias current to get them into their most liner range. There are minimum currents needed, but some of the chips I have need alot more bias current to really get into their linear range.


----------



## Beefy

Quote:


  Originally Posted by *Daveze* /img/forum/go_quote.gif 
_Ooh, I nearly provided all the necessary information for the post...except that I didn't._

 

HEH! 
	

	
	
		
		

		
		
	


	




  Quote:


 Glass Jar kit is correct, I'm referring to CA7 and CA8: the 470uF Muse UKZ's (you're correct, they're not Panasonics) but are now 470uf Muse ES's, and 0.22uF Wima's are now 0.18 VitQ's. 
 

Odd. 'They' say that ES should give a better bass response than the KZ which excel at the highs...... but who 'they' are, and whether they are just blowing smoke or not, is another matter.

  Quote:


 I've toasted and replaced my output transistors before (it is an [expletive] of a process), I think I was one of the first few that contributed towards learning what happened when you switch the N and P channel BJT's around... 
 

Are you actually unhappy with how it sounds? If no, then I wouldn't bother. Too much effort for too little reward.

  Quote:


  Originally Posted by *BoilermakerFan* /img/forum/go_quote.gif 
_Is the Panasonic in CA2 a FC or FM cap?_

 

FC according to the BOM on Geocities.


----------



## tomb

Quote:


  Originally Posted by *Daveze* /img/forum/go_quote.gif 
_Ooh, I nearly provided all the necessary information for the post...except that I didn't.

 Glass Jar kit is correct, I'm referring to CA7 and CA8: the 470uF Muse UKZ's (you're correct, they're not Panasonics) but are now 470uf Muse ES's, and 0.22uF Wima's are now 0.18 VitQ's. I still have the Wima's in CA9 and CA2 should be the Panasonic. I'm not game to change CA2, I've previously tried to remove components that are joined to the ground plane and toasted the pads...now that my board is populated, I'd really rather not make that mistake.

 I've toasted and replaced my output transistors before (it is an [expletive] of a process), I think I was one of the first few that contributed towards learning what happened when you switch the N and P channel BJT's around..._

 

You shouldn't be experiencing any loss of bass with this combination. As Beefy and BMF have indicated, if you had put the VitQ's in CA9, I would expect a noticeable loss in bass, but not at CA8. There may be two reasons for this: 1) Since you mentioned the possibility, it may be that the caps don't have a complete connection through the pads. You might try re-flowing the solder a bit, 2) Sometimes the VitQ's are a bit like old NOS tubes (they are NOS, too, after all). They may require a few hours of run-in to return to their designed capacitance.

 All that said, the Wima's easily have the most bass resonance with the Muse ES's, but the VitQ's should hardly be far enough off to be easily noticeable. However, what you get in return is a simply sterling high end with sparkle, and a very luscious mid-range. Also, good bass is more or less assured by the right combination at CA2 and CA9, not necessarily at CA7 and CA8 (assuming CA7 is large enough to prevent bass filtering).

 EDIT: Quote:


  Originally Posted by *Beefy* 
_Odd. 'They' say that ES should give a better bass response than the KZ which excel at the highs...... but who 'they' are, and whether they are just blowing smoke or not, is another matter._

 

No smoke - ES's are the bass slam kings of electrolytics. Dsavitsk confirms this, among others.


----------



## Daveze

40degC is fine, its been chugging along nicely for the last month or so at that bias point. How do I read the curves? Which curves should I read?

 CA2 is the FC series cap.

 I should point out that its not like the amp lacks bass, its just not quite as intensive as it was before the swap, I don't want to undo the swap because other aspects of the sound are nicer. I'm just wondering if the difference in bass is due to the caps themselves or the values of the caps, which leads me to question whether I might be better served with a .22 VitQ...


----------



## tomb

Quote:


  Originally Posted by *Daveze* /img/forum/go_quote.gif 
_40degC is fine, its been chugging along nicely for the last month or so at that bias point. How do I read the curves? Which curves should I read?

 CA2 is the FC series cap.

 I should point out that its not like the amp lacks bass, its just not quite as intensive as it was before the swap, I don't want to undo the swap because other aspects of the sound are nicer. I'm just wondering if the difference in bass is due to the caps themselves or the values of the caps, which leads me to question whether I might be better served with a .22 VitQ..._

 

It's the value of CA7 that determines whether bass is cut from the size of the caps. As long as the parallel capacitance of CA7 and CA8 are >470uf, you're OK from that standpoint.

 Another thing to consider - the ES's will need some run-in, too. It shouldn't take more than a couple of hours to make a difference with them, though. Some people pooh-pooh run-in for electrolytics, but these are relatively big caps directly in the signal path. There will be some differences as they run-in.

 I can assure you that I have a MAX with ES's and 0.18uf VitQ's in front and the bass is staggering. I have them in CA2, also, which helps. You didn't start with them there, though, so I don't expect that would explain what you're noticing.

 EDIT: The MAX website has all the data sheets for the transistors used on the MAX. The BJT output transistor data sheets can be found at:
http://www.diyforums.org/MAX/MAXbjt.php

 There is an article written by Nelson Pass that demonstrates distortion continues to drop as Class A bias is increased. Diminishing returns occur as some point where increased heat outweighs the decreased distortion. Most builders of the original Millett Hybrid Diamond Buffers settled in at 25-30ma bias, but two sets of output transistors were paralleled, allowing 50-60ma total through the buffer. So, that's where we zero-in with our recommendations for the MAX. This bias current has also proved supportable with the recommended case and ventilation.

 If you leave the case open, and have taller heat sinks, you should be able to approach MOSFET biases up to 100ma or more. QB1L/R may be a limiting factor in this, but I'm not aware of anyone reaching a limit other than heat. 50 or 60 deg.C. is not alarming if you have those temps at the middle two sinks and the PS sink - those are usually the hottest.


----------



## akione

Quote:


  Originally Posted by *Daveze* /img/forum/go_quote.gif 
_........I should point out that its not like the amp lacks bass, its just not quite as intensive as it was before the swap, .........._

 

Perhaps the bass is tighter now ........ it's easy to be deceived 
	

	
	
		
		

		
		
	


	




 What do you think is wrong with the MJE's ? Or is it just curiosity ? 
	

	
	
		
		

		
		
	


	




 I'm actually curious myself about this. I built mine with ES's, 0.22 vitQ's and MJE's and it sounds fine. 
 But without a reference, I don't think it would be worth the effort changing anything, unless it's going 
 to be a huge change for the better. I suspect the differences would be subtle at best and not noticeable 
 without another amp to compare it to. If that's the case, then it's not worth doing any changes, IMO.


----------



## Daveze

That's what I had figured regarding the sizing, I was just wondering if there was a curious interaction that the differently sized CA8 might introduce.

 In terms of run-in: if they're not run-in now, they'll never run-in. I listen to at least an album every evening, perhaps 2 or 3 for weekends, and they've been installed for the last 2 months or so. I generally avoid making snap opinions on things, so I've given it some thought before asking the question.

 I've seen the datasheets before too but as I said, I just don't really know what I'm looking for. At the moment I just increase the voltage every so often and keep an eye on the temperature for a while after doing so.


----------



## tomb

Quote:


  Originally Posted by *Daveze* /img/forum/go_quote.gif 
_That's what I had figured regarding the sizing, I was just wondering if there was a curious interaction that the differently sized CA8 might introduce.

 In terms of run-in: if they're not run-in now, they'll never run-in. I listen to at least an album every evening, perhaps 2 or 3 for weekends, and they've been installed for the last 2 months or so. I generally avoid making snap opinions on things, so I've given it some thought before asking the question._

 

OK - well you thoroughly put the run-in question to bed.
	

	
	
		
		

		
		
	


	




 It's possible that you don't like the tradeoffs involved with the VitQ's.

 As was suggested before, you can probably recover some of that bass by putting the 1000uf ES's in at CA2. It didn't sound like you wanted to do that, though. I would seriously doubt that 0.22uf VitQ's would make any difference - only if the 0.18uf's you have are bad. That's a little unlikely, too - or things would sound bad, probably not equally in both channels, either.

 Certain tubes might give you better bass slam, too.

  Quote:


 I've seen the datasheets before too but as I said, I just don't really know what I'm looking for. At the moment I just increase the voltage every so often and keep an eye on the temperature for a while after doing so. 
 

I can't answer this one off the top of my head and it's way past my bedtime.
	

	
	
		
		

		
		
	


	




 I'll try to look at it tomorrow and/or ask Colin for a good explanation of what to look for in the transistor curves.


----------



## Beefy

Daveze - you're an Aussie but not from Perth, right?

 If you are from Perth, I might be inclined to let you have a listen to my Max for the price of a beer. I've also got a spare set of ES 1000µF as alts for CA2 and VitQ 0.22µF as alts for CA8, which would cost you another beer.

 Hell, I think I even have some 2344/1011 transistors that I will probably never use, unless I build (and they will work in) a Stacker........


----------



## hazamatic

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_I agree that the problem is in a transistor(s) somewhere. Crackling is usually solid-state in nature, I think. Your unsteady readings are simply confirming that.

 A good place to start is to measure the Voltage across each resistor in the buffers. Then by direct comparison with your good Left channel, we should be able to narrow the problem down. Eventually, we'll want to measure the voltage to ground of the resistors we may find out of the norm, but let's try this first:

 Measure voltages across:
 RB1L?..........RB1R?
 RB2L?..........RB2R?
 RB3L?..........RB3R?
 RB4L?..........RB4R?
 RB5L?..........RB5R?
 RB6L?..........RB6R?
 RB7L?..........RB7R?

 RB8 and RB9 should be jumpered and we know the voltage differences across RB10 and RB11 - that's your buffer's bias.

 If we're lucky, it may be something as simple as re-flowing the solder around some of the parts in your Right buffer._

 

Thanks tomb, I'll give this a shot when I get some more free time


----------



## Daveze

Mmm, beer...

 You're correct, I'm a Brisbanian, which makes it quite a long hope to try out your Max. I think I'd be paying more attention to the M3 though, it seems to be that amp that I'd like but never really going to get around to building...

 I'll see what it takes to get the temp to 50degC (that's approximately where a lot of Nelson's amps operate at) and provide some feedback. I've got spare MJE's and I have the 3422/1359's on hand, so if I toast the current set, its just the inconvenience of needing to install them rather than wanting.


----------



## ruZZ.il

Switching out the MJE was... well, to say the least, like getting a new amp.
 Kind of like taking a veil off from over your head.
 There was no need to go back and A/B to see if I was fooling myself or not, it was rather profound.


----------



## akione

Quote:


  Originally Posted by *ruZZ.il* /img/forum/go_quote.gif 
_Switching out the MJE was... well, to say the least, like getting a new amp.
 Kind of like taking a veil off from over your head.
 There was no need to go back and A/B to see if I was fooling myself or not, it was rather profound._

 

Excellent! That's the kind of thing I was looking for. 
 If you only swapped the transistors, then it looks like it's going to be worth doing. 
 So often it seems that several items are different between the builds, so the evidence doesn't seem quite so convincing.
 I think I might try it for myself, now. Thanks.


----------



## Daveze

I think that's my rubber arm twisted...


----------



## Daveze

So I wound out the trimmers a little...

 After nearly an hour of slowly bringing up the bias, I'm sitting at 176mV (80mA) for each channel, which is sitting at basically 50degC for the hottest point of the centre heatsinks. For the kids at home: its very tough to get it to sit on the voltage, the trimmers get super-duper sensitive. If you haven't been following the story the whole time, I have the larger heatsinks with an open chassis, you might toast your pretty BJT's trying this with the shorter sinks trapped inside the case...

 Listening impressions? Well, I think its a bit clearer, more detail in the high-mids through highs. I wouldn't say its night and day though but to some it might be. A worthwhile exercise in systematically challenging what I understood to be the limits.

 I'm away for the remainder of the week, so I won't get around to doing anything further for at least a week. If I keep bringing the bias up, am I likely to blow something more than just the output BJT's? I don't mind if they let go, because I've got a small stash of MJE's handy and the 3422/1359 combo to put in, but if I cook some of the small signalers I'll be mighty disappointed because that was quite an un-fun experience last time...


----------



## tomb

Quote:


  Originally Posted by *Daveze* /img/forum/go_quote.gif 
_So I wound out the trimmers a little...

 After nearly an hour of slowly bringing up the bias, I'm sitting at 176mV (80mA) for each channel, which is sitting at basically 50degC for the hottest point of the centre heatsinks. For the kids at home: its very tough to get it to sit on the voltage, the trimmers get super-duper sensitive. If you haven't been following the story the whole time, I have the larger heatsinks with an open chassis, you might toast your pretty BJT's trying this with the shorter sinks trapped inside the case...

 Listening impressions? Well, I think its a bit clearer, more detail in the high-mids through highs. I wouldn't say its night and day though but to some it might be. A worthwhile exercise in systematically challenging what I understood to be the limits.

 I'm away for the remainder of the week, so I won't get around to doing anything further for at least a week. If I keep bringing the bias up, am I likely to blow something more than just the output BJT's? I don't mind if they let go, because I've got a small stash of MJE's handy and the 3422/1359 combo to put in, but if I cook some of the small signalers I'll be mighty disappointed because that was quite an un-fun experience last time..._

 

The PN4392 is probably the only one to worry about. I don't think it's a problem, though, now that we're using a current multiplier in the circuit instead of a unity-current mirror. QB1L/R are actually the hottest parts on the board in my first prototype, but the buffer circuit was not setup as a current multiplier, so the JFETs saw a lot more of the actual bias current.

 The LM317 should shut itself down if it gets too hot. It's fairly reliable from a thermal protection perspective.

 It's interesting to hear that you've pushed the BJT's that far. My guess is that their own instability is coming into play with those trimmers. That's the problem with BJTs - they tend toward a thermal runaway. Without active cooling, they probably reach a point where the current/temperature is like dropping off a cliff. The heat sinks help tremendously. The old Millett Hybrid Diamond Buffers would get squirrelly at a lot lower current - no heat sinks. 3.3 ohm resistors were the safe selection for those, but that cut down on the actual bias current.


----------



## sokece

I finally finish my Millet Max project. Everything works fine, except I get confuse biasing the tube. I'm not sure if I tune the tube bias correctly. 
 If I turn the volume up the tube voltage is going up and if turn the volume down the tube voltage is going down. I set the volume in the middle and then I tune the tube voltage.

 Is this suppose to be like this or did I do something wrong?


----------



## tomb

Quote:


  Originally Posted by *sokece* /img/forum/go_quote.gif 
_I finally finish my Millet Max project. Everything works fine, except I get confuse biasing the tube. I'm not sure if I tune the tube bias correctly. 
 If I turn the volume up the tube voltage is going up and if turn the volume down the tube voltage is going down. I set the volume in the middle and then I tune the tube voltage.

 Is this suppose to be like this or did I do something wrong?_

 

Yes, I believe you may be doing/have done something wrong. Tube bias is independent of the volume control.

 Questions:
 1. What points were you measuring (as labeled on the board)?
 2. What are your measurements of the tube bias?
 3. What is your voltage set (V+)?
 4. What is your buffer bias setting and measurement?


----------



## sokece

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Yes, I believe you may be doing/have done something wrong. Tube bias is independent of the volume control.

 Questions:
 1. What points were you measuring (as labeled on the board)?
 2. What are your measurements of the tube bias?
 3. What is your voltage set (V+)?
 4. What is your buffer bias setting and measurement?_

 


 1. TA2L/R and GND
 2. 13 - 14V
 3. 27V
 4. 110 mv


----------



## tomb

Quote:


  Originally Posted by *sokece* /img/forum/go_quote.gif 
_1. TA2L/R and GND
 2. 13 - 14V
 3. 27V
 4. 110 mv_

 

That all looks great. I'm not sure I understand what the problem is - how much is the tube bias varying? If it's from 13 to 14V ... shoot - a sneeze on the tubes will cause it to vary that much. If you're anywhere in that 13 to 14 Volt range with both of the tubes, forget about being more precise and start listening to the music. 
	

	
	
		
		

		
		
	


	




 You can adjust final bias by listening: adjusting the bias on one of the tubes until you hear the music centered between left and right in your headphones.

 I often refer to the tubes as mules - they act very similar: tending to go in one direction after you've pointed them there, while it takes quite a bit to make them go the other way. Sometimes, they'll just balk and sit, not moving at all. On the other hand, you might leave them in one place only to come back later and find that they've moved.

 Welcome to tubes, iow.


----------



## sokece

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Yes, I believe you may be doing/have done something wrong. Tube bias is independent of the volume control.

 Questions:
 1. What points were you measuring (as labeled on the board)?
 2. What are your measurements of the tube bias?
 3. What is your voltage set (V+)?
 4. What is your buffer bias setting and measurement?_

 

I switch with a different set. I bought 2AE6A and 2FK6 from you. I try the other set and It does not change the tube voltage any more. I guess the 2AE6A tubes were bad. I hope I can get an exchange.

 Since I have bad 2AE6A tubes, I cannot compare the sound between 2AE6A and 2FK6. Which model do you think better for K701?


----------



## tomb

Quote:


  Originally Posted by *sokece* /img/forum/go_quote.gif 
_I switch with a different set. I bought 2AE6A and 2FK6 from you. I try the other set and It does not change the tube voltage any more. I guess the 2AE6A tubes were bad. I hope I can get an exchange.

 Since I have bad 2AE6A tubes, I cannot compare the sound between 2AE6A and 2FK6. Which model do you think better for K701?_

 

Of course, you are welcome to exchange them. However, I'm still wondering if something else is wrong. The 12AE6A tubes have much higher gain than the 12FK6's. So, if the problem is there, it may just be that it showed up more with the 12AE6's. It seems very unlikely that both tubes would've been bad in that same way.

 You haven't told us how much they varied when you moved the volume control. Are we talking tenths of a volt or less?

 EDIT: I'm going to have to take this back up in the morning.


----------



## sokece

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Of course, you are welcome to exchange them. However, I'm still wondering if something else is wrong. The 12AE6A tubes have much higher gain than the 12FK6's. So, if the problem is there, it may just be that it showed up more with the 12AE6's. It seems very unlikely that both tubes would've been bad in that same way.

 You haven't told us how much they varied when you moved the volume control. Are we talking tenths of a volt or less?

 EDIT: I'm going to have to take this back up in the morning.
	

	
	
		
		

		
		
	


	


_

 


 let say, I set the volume control in the middle and tube voltage to 13.5 V. If I turn the volume all the way down, the tube voltage goes down to 12+V. If I turn volume all way up it goes 14+V. I can hear weird sound when I pause the music source and turn the volume control too fast. 

 I had the project done about 4 days ago. I have been listening from the amp since then. Yesterday, I noticed the tube voltage went up / down if I turn the volume control. I try with 2FK6 the weird noise gone. Using 2FK6, the tube voltage is consistent to 13.5V.


----------



## akione

Quote:


  Originally Posted by *sokece* /img/forum/go_quote.gif 
_let say, I set the volume control in the middle and tube voltage to 13.5 V. If I turn the volume all the way down, the tube voltage goes down to 12+V. If I turn volume all way up it goes 14+V. I can hear weird sound when I pause the music source and turn the volume control too fast._

 

It might be worth trying with a different source. It sounds like your present source is very low - I can't imagine getting the volume control anywhere near 1/2 way with either set of valves. Mine is barely off 0 with 12AE6's and HD580's.


----------



## tomb

Quote:


  Originally Posted by *sokece* /img/forum/go_quote.gif 
_let say, I set the volume control in the middle and tube voltage to 13.5 V. If I turn the volume all the way down, the tube voltage goes down to 12+V. If I turn volume all way up it goes 14+V. I can hear weird sound when I pause the music source and turn the volume control too fast. 

 I had the project done about 4 days ago. I have been listening from the amp since then. Yesterday, I noticed the tube voltage went up / down if I turn the volume control. I try with 2FK6 the weird noise gone. Using 2FK6, the tube voltage is consistent to 13.5V._

 

I kind of agree with akione on this one, but in a different way. With a very strong source (2VAC RMS?), a 12AE6 tube will most likely start clipping at the power rails where you're turning the volume knob (starting at halfway?). That may cause the effects you describe.

 Clipping is easy enough to estimate in this case: with a gain of ~12 and a source at 2VAC, the tube will want to swing 12 x 2 VAC, or 24V in either direction. The power supply only supports a maximum swing of +or- 13.5V if the power supply is set at 27VDC. However, the reality is something a bit less - there are losses in the circuit and the rail-to-rail swing is probably something less than +or- 13.5 - maybe closer to 12.5 or so, I think. At any rate, it's quite possible that you approach clipping to the rails at 1/2 volume knob travel. The CCS may not register a valid voltage when that starts happening.

 The weird noise that you describe is another function of the high gain, but not usually noticed by most people - it depends on the capacitors you've used. I've remarked before in this thread that Black Gates are so fast that the high gain of a 12AE6 tube can't keep up with quick volume changes - a brief scratchiness or distorted noise occurs with a quick volume change. It quickly goes away - almost to the point of suspecting a dirty volume pot, but the volume pot is OK with 12FK6's, or if you switch tubes, the scratchiness may follow the tube. This hasn't been an issue with ES caps, but seems to occur on every Black Gate version I've built.

 Another thing to consider is that tubes can vary in their gain - some are stronger than others. You may have happened on a particularly strong pair of 12AE6's that may have more gain than most (that's good, really - unless you start turning the volume up too far). This may exacerbate the situation and cause the effects you describe, even if you haven't used Black Gates.

 I would set your bias without your source connected and with the volume control set to zero. Adjust it for 13.5VDC at that point, only. Then see if you get good sound as a result, and whether you ever end up turning the volume knob past halfway while listening. As akione states, you've been in a region of the volume control that no one ventures with 12AE6's.
	

	
	
		
		

		
			





 Anyway, I would try that. Regardless, I will cheerfully exchange the tubes if you want to do that. That would also allow me to confirm whether those 12AE6's are really anything unusual.


----------



## soloz2

Quote:


  Originally Posted by *BoilermakerFan* /img/forum/go_quote.gif 
_What about using two or three Hoffman enclosures? Just stack them. One PSU, one DAC, one MAX with the Darwin and OptiVol. Just use the 8" deep boxes. 


 - BMF_

 

do you have a part number? I took a brief look on the site the and really only saw commercial enclosures.


----------



## tomb

Quote:


  Originally Posted by *soloz2* /img/forum/go_quote.gif 
_do you have a part number? I took a brief look on the site the and really only saw commercial enclosures._

 

I think he means Hammond, not Hoffman.


----------



## sokece

Quote:


  Originally Posted by *akione* /img/forum/go_quote.gif 
_It might be worth trying with a different source. It sounds like your present source is very low - I can't imagine getting the volume control anywhere near 1/2 way with either set of valves. Mine is barely off 0 with 12AE6's and HD580's._

 

I'm not sure what do you mean by "present source is very low". The primary reason I build the amp, I want more gain to drive my K701. My Millet Max amp get the source from iAudio X5 line out. I can plug the the source directly to the headphone's plug in X5 but I don't think that is the best way to go. I would rather use the line out as my source. As you know, the line out is very flat, natural and low power.


----------



## sokece

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_I kind of agree with akione on this one, but in a different way. With a very strong source (2VAC RMS?), a 12AE6 tube will most likely start clipping at the power rails where you're turning the volume knob (starting at halfway?). That may cause the effects you describe.

 Clipping is easy enough to estimate in this case: with a gain of ~12 and a source at 2VAC, the tube will want to swing 12 x 2 VAC, or 24V in either direction. The power supply only supports a maximum swing of +or- 13.5V if the power supply is set at 27VDC. However, the reality is something a bit less - there are losses in the circuit and the rail-to-rail swing is probably something less than +or- 13.5 - maybe closer to 12.5 or so, I think. At any rate, it's quite possible that you approach clipping to the rails at 1/2 volume knob travel. The CCS may not register a valid voltage when that starts happening.

 The weird noise that you describe is another function of the high gain, but not usually noticed by most people - it depends on the capacitors you've used. I've remarked before in this thread that Black Gates are so fast that the high gain of a 12AE6 tube can't keep up with quick volume changes - a brief scratchiness or distorted noise occurs with a quick volume change. It quickly goes away - almost to the point of suspecting a dirty volume pot, but the volume pot is OK with 12FK6's, or if you switch tubes, the scratchiness may follow the tube. This hasn't been an issue with ES caps, but seems to occur on every Black Gate version I've built.

 Another thing to consider is that tubes can vary in their gain - some are stronger than others. You may have happened on a particularly strong pair of 12AE6's that may have more gain than most (that's good, really - unless you start turning the volume up too far). This may exacerbate the situation and cause the effects you describe, even if you haven't used Black Gates.

 I would set your bias without your source connected and with the volume control set to zero. Adjust it for 13.5VDC at that point, only. Then see if you get good sound as a result, and whether you ever end up turning the volume knob past halfway while listening. As akione states, you've been in a region of the volume control that no one ventures with 12AE6's.
	

	
	
		
		

		
		
	


	




 Anyway, I would try that. Regardless, I will cheerfully exchange the tubes if you want to do that. That would also allow me to confirm whether those 12AE6's are really anything unusual. 
	

	
	
		
		

		
		
	


	





_

 


 I build "Can't Miss MAX Build #2" MAX. I already tried lower the volume all the way down and set the tube voltage to 13.5V. It is louder compare to the 13.5V with volume in the middle. 

 As the volume goes up the tube voltage goes up, I thought the amp was design like that (I'm noobs here 
	

	
	
		
		

		
		
	


	




 ). I dig through the information on the net and no one mentions anything about that. It is little strange and It gets me confuse in the first place. To be honest with you, those 2AE6A are not bad at all even sound better than 2FK6. It may just the 2AE6A has more gain than 2FK6. 

 So in this case, do you think I have a good build and the tube 2AE6As behave differently? or I still have some problem somewhere.


----------



## BoilermakerFan

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_I think he means Hammond, not Hoffman.
	

	
	
		
		

		
		
	


	


_

 

Hammond, Hoffman, whatever, they're all electrical enclosures to me. 
	

	
	
		
		

		
		
	


	




 Tom was correct, I did mean the Hammond enclosures, just the longer version of the default recommendation on MHM BOM.


----------



## tomb

Quote:


  Originally Posted by *sokece* /img/forum/go_quote.gif 
_I build "Can't Miss MAX Build #2" MAX. I already tried lower the volume all the way down and set the tube voltage to 13.5V. It is louder compare to the 13.5V with volume in the middle. 

 As the volume goes up the tube voltage goes up, I thought the amp was design like that (I'm noobs here 
	

	
	
		
		

		
		
	


	




 ). I dig through the information on the net and no one mentions anything about that. It is little strange and It gets me confuse in the first place. To be honest with you, those 2AE6A are not bad at all even sound better than 2FK6. It may just the 2AE6A has more gain than 2FK6. 

 So in this case, do you think I have a good build and the tube 2AE6As behave differently? or I still have some problem somewhere._

 

Sokece,

 We all learn something every day from this wonderful community and I have learned something new tonight. There is nothing wrong with your 12AE6's (BTW, have you got a "1" on your keyboard?
	

	
	
		
		

		
		
	


	




 ).

 I've tried it repeatedly on my MAXes and it does the same thing. I can't explain it completely, except to say that it's something similar to what many experienced on the SOHA. When a builder tried to bias without some of the critical components on the board, strange readings would result. What's happening is that the pot represents an input load on the grid, I believe. When you adjust the volume pot toward full on, it shorts the input to the grid and it loses the differential bias from the cathode. My guess is that the large gain has something to do with it, and is why the 12FK6 is able to tolerate the same action with seemingly no reaction.

 What you're also doing by biasing the tube at some intermediate point is applying a forced attenuation on the signal prior to amplification by the tube. This has the effect of reducing volume somewhat, but it also severely reduces your volume travel. A better way to do it is something that Dsavitsk has recommended on occasion and what some have done with the Starving Student Millett - placing resistors in series with the L and R input to the pot.

 At any rate - there is nothing wrong with your MAX and nothing wrong with your 12AE6's. I will probably file this incident away for posterity and include the recommendation that the volume knob must be set at 0 for biasing the tubes.


 P.S. As you've already noticed, the 12AE6's will probably give you better impact with your K701's.


----------



## soloz2

would there be any issues with placing a max w/ a toroid psu underneath an LCD? I have a 22" monitor and if I put the amp under the monitor I could use a Nabu...


----------



## BoilermakerFan

Quote:


  Originally Posted by *soloz2* /img/forum/go_quote.gif 
_would there be any issues with placing a max w/ a toroid psu underneath an LCD? I have a 22" monitor and if I put the amp under the monitor I could use a Nabu..._

 

Only heat issues. The top of the NABU is strong enough and the steel will shield any magnetic fields since you do not need to ventilate the PSU side. I would plan on making a raised support shelf for the display to leave at least 1" of space to let the heat out of the NABU chassis. The main issue is the big change in the ergonomics of your display since it would be at least 4-1/2" higher than it is now. So I guess it would really depend on how big your display base is and how you want to orient the MAX board in the NABU, but most of the heat from the MAX will still be centered in the NABU chassis. Did you keep enough modder's mesh for larger openings in the top?

 I'm fortunate in that I have a computer credenza and there is a shelf centered over my monitor were I will put my desktop MAX. I'm also planning to add a dedicated 20A receptacle circuit behind the desk so my MAX doesn't share the A/C outlets or circuit with my PCs to help keep noise out of the line.


----------



## soloz2

Quote:


  Originally Posted by *BoilermakerFan* /img/forum/go_quote.gif 
_Only heat issues. The top of the NABU is strong enough and the steel will shield any magnetic fields since you do not need to ventilate the PSU side. I would plan on making a raised support shelf for the display to leave at least 1" of space to let the heat out of the NABU chassis. The main issue is the big change in the ergonomics of your display since it would be at least 4-1/2" higher than it is now. So I guess it would really depend on how big your display base is and how you want to orient the MAX board in the NABU, but most of the heat from the MAX will still be centered in the NABU chassis. Did you keep enough modder's mesh for larger openings in the top?

 I'm fortunate in that I have a computer credenza and there is a shelf centered over my monitor were I will put my desktop MAX. I'm also planning to add a dedicated 20A receptacle circuit behind the desk so my MAX doesn't share the A/C outlets or circuit with my PCs to help keep noise out of the line._

 

the amp will not be supporting the monitor. this is what I have:
Newegg.com - HP w2207h Black 22" 5ms HDMI Widescreen LCD Monitor 300 cd/m2 1000:1 Built in Speakers - LCD Monitors
 As you can see the fully adjustable stand just has a nice wide platform and then goes back so I could potentially put the amp underneath the monitor and it wouldn't have to support any weight.


----------



## BoilermakerFan

Quote:


  Originally Posted by *soloz2* /img/forum/go_quote.gif 
_the amp will not be supporting the monitor. this is what I have:
Newegg.com - HP w2207h Black 22" 5ms HDMI Widescreen LCD Monitor 300 cd/m2 1000:1 Built in Speakers - LCD Monitors
 As you can see the fully adjustable stand just has a nice wide platform and then goes back so I could potentially put the amp underneath the monitor and it wouldn't have to support any weight._

 

That's a nice base on the LCD, so you might have to make new feet (or buy isolation cone feet) for the NABU just to clear the height of the LCD base, but as long as you leave enough clearance over the top of the case before the bottom of the LCD I think it would be ok. The bottom of the LCD would be warm, but I don't think you have enough heat to do any long term damage. PC LCDs are used in some pretty hot industrial environments. I would use a filtered fused IEC power input for the NABU just to make sure no PC PSU noise comes in to the MAX, but it's only about $15 more than the non-filtered input so that's a cheaper way to protect the MAX if you don't already have everything to wire in a dedicated 20A wall receptacle. 

 Beefy, please post up the part numbers of your filtered IEC power input and fuse drawer that you used on the M^3.

 You can order a 100VA and a couple of 50 VA toroids from AnTek. Plus in the NABU you can run 2-1/2" heatsinks on the DBs and 2" heatsink on the V-Reg, but I would switch to screw mount versions to make sure they have enough support. I plan to mount mine with 1" machine screws.

 - BMF


----------



## soloz2

Quote:


  Originally Posted by *BoilermakerFan* /img/forum/go_quote.gif 
_That's a nice base on the LCD, so you might have to make new feet (or buy isolation cone feet) for the NABU just to clear the height of the LCD base, but as long as you leave enough clearance over the top of the case before the bottom of the LCD I think it would be ok. The bottom of the LCD would be warm, but I don't think you have enough heat to do any long term damage. PC LCDs are used in some pretty hot industrial environments. I would use a filtered fused IEC power input for the NABU just to make sure no PC PSU noise comes in to the MAX, but it's only about $15 more than the non-filtered input so that's a cheaper way to protect the MAX if you don't already have everything to wire in a dedicated 20A wall receptacle. 

 Beefy, please post up the part numbers of your filtered IEC power input and fuse drawer that you used on the M^3.

 You can order a 100VA and a couple of 50 VA toroids from AnTek. Plus in the NABU you can run 2-1/2" heatsinks on the DBs and 2" heatsink on the V-Reg, but I would switch to screw mount versions to make sure they have enough support. I plan to mount mine with 1" machine screws.

 - BMF_

 

that was my thought... I think I want to find a different vendor for the toroids though... isn't antek the same as parmetal?


----------



## Beefy

Quote:


  Originally Posted by *BoilermakerFan* /img/forum/go_quote.gif 
_Beefy, please post up the part numbers of your filtered IEC power input and fuse drawer that you used on the M^3._

 

It is a Schaffner FN 284. They are available in different shapes and ratings; datasheet here http://www.schaffner.com/components/...0%20e%2013.pdf


----------



## BoilermakerFan

Quote:


  Originally Posted by *soloz2* /img/forum/go_quote.gif 
_that was my thought... I think I want to find a different vendor for the toroids though... isn't antek the same as parmetal?_

 

I guess they are, Brian posted in the DIY cases thread. Parts Connextion has toroids.


----------



## MrMajestic2

Quote:


  Originally Posted by *Beefy* /img/forum/go_quote.gif 
_It is a Schaffner FN 284. They are available in different shapes and ratings; datasheet here http://www.schaffner.com/components/...0%20e%2013.pdf_

 

For some reason these are really expensive here in Sweden. Where did you get yours? Mouser seems to be non-stocked on them.


----------



## Beefy

Quote:


  Originally Posted by *MrMajestic2* /img/forum/go_quote.gif 
_For some reason these are really expensive here in Sweden. Where did you get yours?_

 

They were both quite expensive unfortunately, but I think the price is worth it for an integrated unit like that. I got the FN 284 at RS Components. I've also got a FN 286 for my upcoming Buffalo build, which I bought from Farnell.

  Quote:


 Mouser seems to be non-stocked on them. 
 

Mouser does have stock of the FN 283 which is the exact same unit, but with only a single fuse - FN283


----------



## MrMajestic2

Quote:


  Originally Posted by *Beefy* /img/forum/go_quote.gif 
_They were both quite expensive unfortunately, but I think the price is worth it for an integrated unit like that. I got the FN 284 at RS Components. I've also got a FN 286 for my upcoming Buffalo build, which I bought from Farnell.

 Mouser does have stock of the FN 283 which is the exact same unit, but with only a single fuse - FN283_

 

Great, thanks a lot. The Schaffners cost almost $100 over here, so Mouser is cheap


----------



## BoilermakerFan

Quote:


  Originally Posted by *MrMajestic2* /img/forum/go_quote.gif 
_For some reason these are really expensive here in Sweden. Where did you get yours? Mouser seems to be non-stocked on them._

 

Digi-Key has a similar one (10A dual fuse) from Shurter in stock for US$27:
Digi-Key - 486-1303-ND (Schurter Inc - DD12.9121.111)

 The fuse drawer is US$3.46.


----------



## Beefy

Quote:


  Originally Posted by *BoilermakerFan* /img/forum/go_quote.gif 
_Digi-Key has a similar one (dual fuse) from Shurter in stock for US$27:_

 

Yeah, I was looking at the Schurter as well but they were even more expensive locally 
	

	
	
		
		

		
		
	


	




  Quote:


  Originally Posted by *MrMajestic2* /img/forum/go_quote.gif 
_The Schaffners cost almost $100 over here, so Mouser is cheap 
	

	
	
		
		

		
		
	


	


_

 

Holy crap!


----------



## BoilermakerFan

I'm going to order the Schurter one from Digi-Key because I need to order a fuse drawer for my other Schurter since the web site was incorrect when it said that it included the fuse drawer. I also need an OPA627BP, a crystal for my CD transport mods, and a few other small bits I keep forgetting to order, like the test point loops.


----------



## soloz2

idk... I'm tempted to give parmetal another go since everyone else seems to have had good luck. Maybe if I call I can get a good transaction... idk.

 I was looking at partsexpress for toroids. they seem to have good prices.


----------



## bperboy

Quote:


  Originally Posted by *soloz2* /img/forum/go_quote.gif 
_idk... I'm tempted to give parmetal another go since everyone else seems to have had good luck. Maybe if I call I can get a good transaction... idk.

 I was looking at partsexpress for toroids. they seem to have good prices._

 

Yep, definitely call, and you will probably have good luck! But YMMV!


----------



## Scy

Hello everybody. Got my max wired and cased up a couple days ago. I must say I really like this amp, a lot. Thanks for everyone involved, and especially TomB for his support for the community and for supplying the parts.
 The aluminium ends of the case were made by FPE (Schaeffer AG) and the elm wood sides by a local carpenter.

 Took some photos today, so here goes:












 Some more pics at my flickr


----------



## pinkfloyd4ever

WOOWWW VERY NICE, Scy! That's one hell of a first post. I love that case


----------



## tomb

Quote:


  Originally Posted by *pinkfloyd4ever* /img/forum/go_quote.gif 
_WOOWWW VERY NICE, Scy! That's one hell of a first post. I love that case_

 

Ditto(!) and Wow!! Another MAX is living large!


----------



## fc911c

WOW outstanding, really looks high end. Now I want a case like that for mine.

 Frank


----------



## WilCox

Quote:


  Originally Posted by *Scy* /img/forum/go_quote.gif 
_Hello everybody. Got my max wired and cased up a couple days ago. I must say I really like this amp, a lot. Thanks for everyone involved, and especially TomB for his support for the community and for supplying the parts._

 

Fantastic job! One of the best (if not _THE_ best) I've seen.

 Happy listening.


----------



## Ech0

Simply stunning work Scy! You certainly did the MMax proud.

 Ech0


----------



## BoilermakerFan

Great work Scy. You guys keep raising the bar for casework before I've even had a chance to get started on mine!


----------



## MrMajestic2

Very nice scy, that one will be hard to top.


----------



## TimJo

That looks really great. Very classy casework, fitting for the quality of the sound the Max creates.

 That looks like a Can't Miss #2, correct?

 BTW, welcome to Head-Fi...


----------



## Scy

Thanks for the nice comments! 
	

	
	
		
		

		
			





  Quote:


  Originally Posted by *TimJo* /img/forum/go_quote.gif 
_
 That looks like a Can't Miss #2, correct?
_

 

That's correct.
 Muses and wimas in other positions + 0.18uf VitQ's as the output coupling caps.
 The diamond buffers are 2SC3422/2SA1359, biased up to 110mV atm.


----------



## GeWa

Sent you a PM Scy.

 Regards


----------



## digger945

Scy, that's not a case, it's a work of ART!


----------



## Listen2this1

That case is Purely Amazing, great design and craftmanship.


----------



## soloz2

I'm looking at this filtered power inlet. 
DD12.9121.111
 I believe it will work, but I've never used one of these before so I'd just like to make sure before placing an order. Plus, the fuse drawer is separate... what one do I need?


----------



## ruZZ.il

Assuming your toroid is, say, 30VA, you'd need around 30VA with over head, so, in the states, that's at least 120v*I=30, or I=30/120=0.25A. Since they're all in the range of a handful of amps, that's not your concern. as for the poles and stuff.. I dunno. great help I am ha? 
	

	
	
		
		

		
		
	


	




 Edit: I'm guessing 1 fuse is probably enough, and more than most people around here have.. though most wall warts probably have some sort of self burn out thing anyway..


----------



## soloz2

Quote:


  Originally Posted by *ruZZ.il* /img/forum/go_quote.gif 
_Assuming your toroid is, say, 30VA, you'd need around 30VA with over head, so, in the states, that's at least 120v*I=30, or I=30/120=0.25A. Since they're all in the range of a handful of amps, that's not your concern. as for the poles and stuff.. I dunno. great help I am ha? 
	

	
	
		
		

		
		
	


	




 Edit: I'm guessing 1 fuse is probably enough, and more than most people around here have.. though most wall warts probably have some sort of self burn out thing anyway.._

 

no, I was referring to the actual fuse drawer that you have to purchase separately.

 I have a 100va toriod for my Max and a 20va toroid for my Opus. I may add an IVY stage later, so that would likely be another 20va toroid. 

 I'm thinking a 3a quick blow fuse will be good. Give me enough overhead for inrush current, but not too high so as not to protect the electronics. Maybe my thinking is flawed though?
 Maybe I should go a little higher as I'm building a mosfet max?

 I wasn't sure about the actual fuse drawer. I think 4301.1405
 this is the one I need though, can anyone confirm this?


----------



## TimJo

Quote:


  Originally Posted by *soloz2* /img/forum/go_quote.gif 
_I'm looking at this filtered power inlet. 
DD12.9121.111
 I believe it will work, but I've never used one of these before so I'd just like to make sure before placing an order. Plus, the fuse drawer is separate... what one do I need?_

 

I've never ordered one of these before, but it looks like the one you called out doesn't have a fuse drawer. It looks to me like the 693.KE10.xxxx.xxx series are the ones with fuse drawers. The one you called out looks to me like it just has a switch and an EMC filter.


----------



## soloz2

Quote:


  Originally Posted by *TimJo* /img/forum/go_quote.gif 
_I've never ordered one of these before, but it looks like the one you called out doesn't have a fuse drawer. It looks to me like the 693.KE10.xxxx.xxx series are the ones with fuse drawers. The one you called out looks to me like it just has a switch and an EMC filter._

 

It says it has a fuse drawer that has to be purchased separately
http://www.schurterinc.com/pdf/english/typ_DD12.pdf


 edit: would it be worth the extra few $$ to get the medical grade filter?


----------



## BoilermakerFan

Quote:


  Originally Posted by *soloz2* /img/forum/go_quote.gif 
_It says it has a fuse drawer that has to be purchased separately
http://www.schurterinc.com/pdf/english/typ_DD12.pdf


 edit: would it be worth the extra few $$ to get the medical grade filter?_

 

General Purpose is fine. Order one withe the 2 pole fuse and order a standard or finger safe 2 pole fuse drawer. Then both the hot and neutral legs are fused in case you ever plug into a circuit that has it's polarity reversed. AC devises will work fine, but if the neutral was fused it just takes longer for the fuse to blow or it may never blow if there was a ground fault on an inversed circuit (i.e., your hot was fused, but the outlet was wired wrong so the fuse is actually on the neutral). Fuse both legs and start with a 2A slow blow, use a 3A slow blow if the 2A pops too often to be a problem. Fast blow fuses will probably blow when you power up the MAX just because of the in rush on the tubes. 

 The links I posted a few pages back were for a 2 pole fused drawer general purpose filter and 2 pole finger safe fuse drawer IIRC. It might have been a standard fuse drawer, but the part numbers will work together and the inlet is rated for 10A, so it will handle the load.


----------



## TimJo

Quote:


  Originally Posted by *soloz2* /img/forum/go_quote.gif 
_It says it has a fuse drawer that has to be purchased separately
http://www.schurterinc.com/pdf/english/typ_DD12.pdf_

 

Your right, sorry about that soloz2. Too many numbers and I think I got cross-eyed.
	

	
	
		
		

		
		
	


	




 It looks like BoilermakerFan has it figured out...


----------



## sokece

Quote:


  Originally Posted by *Scy* /img/forum/go_quote.gif 
_Hello everybody. Got my max wired and cased up a couple days ago. I must say I really like this amp, a lot. Thanks for everyone involved, and especially TomB for his support for the community and for supplying the parts.
 The aluminium ends of the case were made by FPE (Schaeffer AG) and the elm wood sides by a local carpenter.

 Took some photos today, so here goes:












 Some more pics at my flickr_

 

Really nice case. 
 Do you mind tell us how much you spend for the case?


----------



## DrizzitT

Another Millett Max (build 2) lives! I'm not much of an audiophile (built for cost of mats for a friend + soldering experience), but it does sound good.

 One problem though... I got both the 12FK6 and the 12AE6 from beezar.com. The 12AE6's all work fine, one of the 12FK6's hums. The humming gets worse when my hand gets closer and when I tap the tube, I don't "hear" the tap like all the other tubes. Switched channels and the same problem, only on the other side. Is this a tube problem or circuit problem? I'm guessing tubes due to the consistency of the problem over channels but this is my first foray into tubes so...


----------



## amphead

Beautiful Scy! That front panel is just so nice. congrats! Another Max Lives!


----------



## Daveze

Scy, I like the idea of the huge heatsink on the regulator...mine's running pretty darn hot (52-55 degC) and I imagine anyone with MOSFETs must be in a similar spot. 

 For anyone interested in mine, I think I've chickened out on swapping my output transistors. I was thinking about it the other night and I remembered just how much of a pain of a job it was the first time. I might change my mind when I get home though...

 On the plus side, it has been operating really happily at 176mA for a while now. Its a little bit sensitive to surrounding temps though, when its nice and chilly (I dunno 15-18 degC) it sits happily at about 49-50 deg C but it does get up to ~52 degC on the warmer days (mid 20's). After the fiddling required to get it to measure 176mV, it does sit very comfortably there, no variation. I was thinking of upping it to say 90-100mA (298mV and 220mV) but seeing the sensitivity to surrounding temps has scared me off a bit, particularly because I'll forget when we come back into summer and it gets properly hot.

 Tom, I'll make a mental note to check the temp on the PN4392 when I get home.


----------



## tomb

Quote:


  Originally Posted by *DrizzitT* /img/forum/go_quote.gif 
_Another Millett Max (build 2) lives! I'm not much of an audiophile (built for cost of mats for a friend + soldering experience), but it does sound good.

 One problem though... I got both the 12FK6 and the 12AE6 from beezar.com. The 12AE6's all work fine, one of the 12FK6's hums. The humming gets worse when my hand gets closer and when I tap the tube, I don't "hear" the tap like all the other tubes. Switched channels and the same problem, only on the other side. Is this a tube problem or circuit problem? I'm guessing tubes due to the consistency of the problem over channels but this is my first foray into tubes so..._

 

It's possible that it's a grounding problem through the pins (bad connection). That's usually the case if your hand causes a reaction, I think. You might try going over the pins with a cotton swab and some alcohol. I do that for all that I sell, but it's possible I missed one. There's also the possibility that the poor connection is inside the tube.

 Regardless, if you can't get it to work to your satisfaction, please return it and I'll replace it, no charge.
	

	
	
		
		

		
			





  Quote:


  Originally Posted by *Daveze* 
_Tom, I'll make a mental note to check the temp on the PN4392 when I get home._

 

It's probably OK since we changed to the current multiplier in the diamond buffer, but still - that's the other critical part to worry about getting hot (besides the LM317 and the output transistors). There are a few resistors that could get pretty toasty (heater resistor, voltage adjust resistor on the LM317, and the output transistor power resistors), but they should all be sized at almost twice the needed rating.


----------



## BoilermakerFan

Quote:


  Originally Posted by *DrizzitT* /img/forum/go_quote.gif 
_
 One problem though... <snip> Switched channels and the same problem, only on the other side. <snip>..._

 

Since the problem follows the tube, and doesn't stay in the same channel, I don't think he has a grounding problem. Plus the AE6As are fine, so it's bad tube. Just swap out the tube with Tom.


----------



## soloz2

I have to get ready for work now, but I've spent the last hour and a half going through parts to see what I really need and already have for my current Max build. I just needed a few parts
 I'm getting 
 a push button switch
 filtered IEC input
 2" heatsinks instead of the 1.5" ones I currently have 
	

	
	
		
		

		
		
	


	



 and I missed needing CB8 so I grabbed a couple of those.
 I just need to pick out some fuses and then I'm all set, but that will likely have to be tonight 
	

	
	
		
		

		
		
	


	




 good thing I get orders practically next day!


----------



## tomb

Quote:


  Originally Posted by *BoilermakerFan* /img/forum/go_quote.gif 
_Since the problem follows the tube, and doesn't stay in the same channel, I don't think he has a grounding problem. Plus the AE6As are fine, so it's bad tube. Just swap out the tube with Tom._

 

Yep - I worded it poorly, but grounding the tube through the pin connections is what I was talking about, not really "grounding" in the sense we normally talk about. Sometimes the pins themselves can get a hairline crack at the entry point into the tube, too. In either case, as you say, it would follow the tube, though.


----------



## Scy

Quote:


  Originally Posted by *sokece* /img/forum/go_quote.gif 
_Really nice case. 
 Do you mind tell us how much you spend for the case?_

 

As you might have guessed, it's not exactly a bargain.
 Most of the price is for the parts from fpe.
 For the front- and back panels and the acrylic cover, the overall cost was around 90€ including 19% tax and shipping.
 The wooden parts cost 25€
 then there is the sheet of metal at the bottom, some screws and bolts and the feet for the case. Haven't really thought the cost for those, but it was nothing much I suppose.


----------



## srserl

Scy, your amp looks stunning! I really like the contrast of old-school look of the wood and tubes with the high tech look of the plexiglass (and components), heatsinks, and front panel.
 Definitely one of the best looking amps I have seen.

 Scott


----------



## Daveze

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_It's probably OK since we changed to the current multiplier in the diamond buffer, but still - that's the other critical part to worry about getting hot (besides the LM317 and the output transistors). There are a few resistors that could get pretty toasty (heater resistor, voltage adjust resistor on the LM317, and the output transistor power resistors), but they should all be sized at almost twice the needed rating._

 

For your interest, the PN4392 hardly breaks a sweat. All the guys around the LM317 do get hot though, some I imagine will be because of the current but I think the proximity to the LM317 heatsink (currently 55 degC) has a bit to do with it. Also, I only have the 1" heatsink on the LM317, which is quite nearsighted of me.

 The rectifier diodes are also getting a bit warm too.


----------



## DrizzitT

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Yep - I worded it poorly, but grounding the tube through the pin connections is what I was talking about, not really "grounding" in the sense we normally talk about. Sometimes the pins themselves can get a hairline crack at the entry point into the tube, too. In either case, as you say, it would follow the tube, though.
	

	
	
		
		

		
		
	


	





_

 

Hm. I'll give the tube cleaning a try later this week, and if it doesn't work, I'll contact you, tomb, regarding the swapping of tubes. 

 Also, a question. What gauge wire is being used for casing the power terminal/switches/3.5mm/RCA jacks? I'm thinking of buying some "better" (non-EE hookup wire) wire but am not very familiar with gauge sizes (I'm assuming they aren't quite the same as speaker wire). I currently have 30 gauge, but that looks a bit too thin for this purpose... Probably going to buy from the ebay site listed on the diyMod page. Also, I assume hook-up wire is sufficient for the test points (ie, crappy wire won't affect the overall system). Thanks for the help guys!


----------



## ruZZ.il

Quote:


  Originally Posted by *DrizzitT* /img/forum/go_quote.gif 
_Hm. I'll give the tube cleaning a try later this week, and if it doesn't work, I'll contact you, tomb, regarding the swapping of tubes. 

 Also, a question. What gauge wire is being used for casing the power terminal/switches/3.5mm/RCA jacks? I'm thinking of buying some "better" (non-EE hookup wire) wire but am not very familiar with gauge sizes (I'm assuming they aren't quite the same as speaker wire). I currently have 30 gauge, but that looks a bit too thin for this purpose... Probably going to buy from the ebay site listed on the diyMod page. Also, I assume hook-up wire is sufficient for the test points (ie, crappy wire won't affect the overall system). Thanks for the help guys!_

 

I think 22awg is probably your best all round bet for that kind of stuff. 24awg would be sufficient too, and is what I've used for some headphone re-cabling with great results, so it'll be good for short internal runs. it'll probably be good for all the internal wiring.. JohnsWireShop is where we got a lot of wire from around here, and probably who you were referring to. He doesn't have much 22awg in right now, but if you took what he had, you'd still be able to strip that pair and use the bits. If you only need a foot or 2, I'll gladly send you some, though it'll take a little while to get there.. just let me know. Also, IIRC, he may have gone on vacation for a little while, promising to come back with a bunch of re-stock. It may be worth sending him a message before ordering.
 Again, if you don't mind waiting about 2 weeks, I'll send you a little variety pack enough for a build or 2..


----------



## tomb

What a wonderful offer, ruZZ.il! Yes, I am in complete agreement, to0: 22ga teflon SPC is a great way to go - all I ever use.

 You have a great suggestion to drop John a note. He's back from his vacation(?) now, apparently, but doesn't have much 22ga except those two twisted pairs last time I looked. I'm getting very low myself and hope that he has more soon.


 EDIT: I sent navships (John) a note asking about more 22ga. I'll let you all know what he says.


----------



## tomb

Wow - that was pretty quick! See reply below from John of John's Wire Shop on ebay:

  Quote:


 *Hi, I just got in a lot of 22ga wire. I was hoping to get this listed in my store much sooner, I will start listing these today as soon as I take the pictures of the wire. Some of the colors that I have in 22ga are, white, black, blue, green, gray, red, white/gray/red, white/red/violet, white/blue/orange, white/brown/black, plus many more colors with strips. John 


 - navships*


----------



## soloz2

I'm wondering if anyone can help me out. I just realized that I don't have enough standoffs to mount my Max. I hope to bring it to the Toronto meet on Saturday, I should be receiving all the other parts I need and the enclosure and toroids tomorrow or Friday, but I'm short some standoffs to mount the Max board in the enclosure, I don't think I have enough time to order some.

 Does anyone have some standoffs? I'll need 5 or so. I'd be more than happy to send some funds via PP


----------



## tomb

Quote:


  Originally Posted by *soloz2* /img/forum/go_quote.gif 
_I'm wondering if anyone can help me out. I just realized that I don't have enough standoffs to mount my Max. I hope to bring it to the Toronto meet on Saturday, I should be receiving all the other parts I need and the enclosure and toroids tomorrow or Friday, but I'm short some standoffs to mount the Max board in the enclosure, I don't think I have enough time to order some.

 Does anyone have some standoffs? I'll need 5 or so. I'd be more than happy to send some funds via PP_

 

I can probably spare that many that are either 3/8" or 1/2" - I forget which I have. The mail is going to be pushing it to get it to you in time, though. I may be able to get them in the mail to you this afternoon, but I can't guarantee that for certain - it may be tomorrow morning.

 PM me with your address if you're interested. I'm sure I have it somewhere, but that would save me the time from looking it up.


----------



## BoilermakerFan

Also, if Tom can't help you out, couldn't you use PC standoffs in a pinch? I think even Best Buy sells them now. Lowe's will have the small 4-40 pan head screws and cap nuts to secure it temporarily if Tom's don't make it in time. 

 Worst case, I know Lowe's has nylon spacers that will accept 4-40 screws so you could temp it in that way with a pan head sheet metal screw, nylon spacer, and cap nut. Might require a trip into Buffalo to hit a Lowe's, but Lowe's has a much better small hardware selection than the big orange box store.


----------



## soloz2

Quote:


  Originally Posted by *BoilermakerFan* /img/forum/go_quote.gif 
_Also, if Tom can't help you out, couldn't you use PC standoffs in a pinch? I think even Best Buy sells them now. Lowe's will have the small 4-40 pan head screws and cap nuts to secure it temporarily if Tom's don't make it in time. 

 Worst case, I know Lowe's has nylon spacers that will accept 4-40 screws so you could temp it in that way with a pan head sheet metal screw, nylon spacer, and cap nut. Might require a trip into Buffalo to hit a Lowe's, but Lowe's has a much better small hardware selection than the big orange box store._

 

nearest lowes is an hour away... 
	

	
	
		
		

		
			





 Tom mailed me some. Thanks for the suggestion. 
 I thought of PC standoffs, but I don't think I have 5, as I've used them in a couple builds already... lol


----------



## BoilermakerFan

Quote:


  Originally Posted by *soloz2* /img/forum/go_quote.gif 
_nearest lowes is an hour away... 
	

	
	
		
		

		
		
	


	




 Tom mailed me some. Thanks for the suggestion. 
 I thought of PC standoffs, but I don't think I have 5, as I've used them in a couple builds already... lol 
	

	
	
		
		

		
		
	


	


_

 

Yes, but tomorrow is Thursday, so that means the free concert in downtown Buffalo! Wings at Gabrielle's Gate and a couple of rum & Cokes at the Croc Bar before you head to the show! I can even tell you who it is tomorrow, it's the Gin Blossoms. So, uh, well depending on your music preference... At least you'll have great wings and your parts! But Thurs., Aug. 7 is Zappa Plays Zappa which would be really cool to see for free.


----------



## soloz2

Quote:


  Originally Posted by *BoilermakerFan* /img/forum/go_quote.gif 
_Yes, but tomorrow is Thursday, so that means the free concert in downtown Buffalo! Wings at Gabrielle's Gate and a couple of rum & Cokes at the Croc Bar before you head to the show! I can even tell you who it is tomorrow, it's the Gin Blossoms. So, uh, well depending on your music preference... At least you'll have great wings and your parts! But Thurs., Aug. 7 is Zappa Plays Zappa which would be really cool to see for free._

 

how did I not know this?!?!


----------



## BoilermakerFan

Quote:


  Originally Posted by *soloz2* /img/forum/go_quote.gif 
_how did I not know this?!?!_

 

I'll tell you offline! 
	

	
	
		
		

		
		
	


	




 I'll email you the link too. With all my traveling, I try to keep up on the live music scenes for all the major cities I visit.


----------



## DrizzitT

Quote:


  Originally Posted by *ruZZ.il* /img/forum/go_quote.gif 
_ If you only need a foot or 2, I'll gladly send you some, though it'll take a little while to get there.. just let me know. Also, IIRC, he may have gone on vacation for a little while, promising to come back with a bunch of re-stock. It may be worth sending him a message before ordering.
 Again, if you don't mind waiting about 2 weeks, I'll send you a little variety pack enough for a build or 2.._

 

Wow Ruzz, Thanks for the offer. I think I'll pass though as it'll be pretty easy for me to get some 22 gauge wire from John's Wire Shop. Thanks for the offer and the help though!


----------



## soloz2

well I have some good news... and some not so good news...

 First order of news, the good news!
 - My Par-Metal order arrived, a day early! They got it right this time, black enclosure, silver (clear) faceplate. I also got my two toroids. However, this is also part of the not so good news...
 And now for the not so good news.
 - Par-Metal didn't get this order flawless... I had ordered the divider so I would have a separate psu section. Order is missing this part completely.
 - I purchased 2" heatsinks because I knew I'd have room, and they fit fine with my estimate standoffs (borrowed) but the tubes are about 1/8" too long. This means I need to shave off the standoffs, find shorter ones or use longer ones and let the tubes stick out a little bit. This would also necessitate going down to 1.5" heatsinks.


----------



## BoilermakerFan

Quote:


  Originally Posted by *soloz2* /img/forum/go_quote.gif 
_well I have some good news... and some not so good news...

 First order of news, the good news!
 - My Par-Metal order arrived, a day early! They got it right this time, black enclosure, silver (clear) faceplate. I also got my two toroids. However, this is also part of the not so good news...
 And now for the not so good news.
 - Par-Metal didn't get this order flawless... I had ordered the divider so I would have a separate psu section. Order is missing this part completely.
 - I purchased 2" heatsinks because I knew I'd have room, and they fit fine with my estimate standoffs (borrowed) but the tubes are about 1/8" too long. This means I need to shave off the standoffs, find shorter ones or use longer ones and let the tubes stick out a little bit. This would also necessitate going down to 1.5" heatsinks._

 

That sucks about the divider. I assume it can be added after the fact? 

 Shave down the standoffs, keep the 2" sinks and keep the tubes covered, or use a glass dome or lense to cover the small of tube sticking out...


----------



## soloz2

what's the best way to shave down the standoffs? or is there a place where I could buy shorter ones?


----------



## tomb

Quote:


  Originally Posted by *soloz2* /img/forum/go_quote.gif 
_what's the best way to shave down the standoffs? or is there a place where I could buy shorter ones?_

 

You can get 4-40 threaded standoffs as short as 1/4" - at any location that sells standoffs, more or less. If you're talking spacers, you can make it shorter than that. Of course, a very thin spacer is a washer.
	

	
	
		
		

		
		
	


	




 If you have the 4-40 screws, you can stack thin washers to get whatever space you need. Put the screw head on the bottom of the case and use a washer, lock washer, and nut on top of the board. Then spacing is only limited by the number of washers you have and the length of your screws.


----------



## soloz2

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_You can get 4-40 threaded standoffs as short as 1/4" - at any location that sells standoffs, more or less. If you're talking spacers, you can make it shorter than that. Of course, a very thin spacer is a washer.
	

	
	
		
		

		
		
	


	




 If you have the 4-40 screws, you can stack thin washers to get whatever space you need. Put the screw head on the bottom of the case and use a washer, lock washer, and nut on top of the board. Then spacing is only limited by the number of washers you have and the length of your screws.
	

	
	
		
		

		
		
	


	


_

 

yeah, that's what I figured... just haven't found a good place yet. I went to Home Depot today and picked up some 4-40 machine screws, but they didn't have any spacers, lock washers or flat washers...


----------



## tomb

Quote:


  Originally Posted by *soloz2* /img/forum/go_quote.gif 
_yeah, that's what I figured... just haven't found a good place yet. I went to Home Depot today and picked up some 4-40 machine screws, but they didn't have any spacers, lock washers or flat washers..._

 

You'll have better luck finding 4-40 hardware at an Ace Hardware, not Home Depot or Lowes. There are better places, of course, but if your town/area is big enough for a Home Depot, there's usually an Ace Hardware around somewhere, too.


----------



## soloz2

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_You'll have better luck finding 4-40 hardware at an Ace Hardware, not Home Depot or Lowes. There are better places, of course, but if your town/area is big enough for a Home Depot, there's usually an Ace Hardware around somewhere, too._

 

I live in a town that still has a 'general' store lol. I haven't found any Ace hardware stores where I would typically go shopping, but I did just look at their website and found one that's about 15-20 min from where I work so maybe I'll stop in one day on my lunch hour.


----------



## BoilermakerFan

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_You'll have better luck finding 4-40 hardware at an Ace Hardware, not Home Depot or Lowes. There are better places, of course, but if your town/area is big enough for a Home Depot, there's usually an Ace Hardware around somewhere, too._

 

It must be hit or miss then because our Lowes has a great selection of SS 4-40 and metric hardware. Our HD stinks for hardware though. Industrial or wholesale distributors like Fastenal are also good for small SAE or metric hardware. I've had to use them for a 50mm and 75mm long 3mm bolt before.


----------



## pinkfloyd4ever

Quote:


  Originally Posted by *BoilermakerFan* /img/forum/go_quote.gif 
_Industrial or wholesale distributors like Fastenal are also good for small SAE or metric hardware. I've had to use them for a 50mm and 75mm long 3mm bolt before._

 

YESSS why have I not been there yet?!?! I have one about a mile from my house
	

	
	
		
		

		
		
	


	







 p.s. what were u using bolts that size on?


----------



## BoilermakerFan

Quote:


  Originally Posted by *pinkfloyd4ever* /img/forum/go_quote.gif 
_p.s. what were u using bolts that size on?_

 

A R/C electric 4x4 rock crawler on a custom CF chassis. I have more hobbies than most people have loose pennies in a jar. LOL!


----------



## tomb

Information regarding the MiniMAX DIY design may always be found at DIYforums.org. I've asked that one of the volunteers post a build thread when the prototypes come in.


----------



## soloz2

I'm looking for knob suggestions... I think I'd like a large volume knob somewhere around 40mm in diameter, and then a smaller knob for source selection, maybe around 30mm.

 Here's the catch. I want them to be the same style/or complement each other well. Also, the volume pot is a small push style on the OptiVol. I can wedge something in there to use a set screw knob if I have to. Then, the shaft for the source selector is a D style 1/4" so it's a little larger.

 I'm having difficulty finding something that will look good and work well for both.

 I like this:
48x22 SOLID Aluminum VALVE TUBE AMPLIFIER EFFECT KNOB - eBay (item 300244651646 end time Jul-31-08 03:32:37 PDT)
 I'm contemplating these:
28x28 SOLID SILVER STOVE TOP VOLUME TUNE DIY AMP KNOB - eBay (item 290239901872 end time Aug-18-08 00:05:55 PDT)
 but so far the best matching pair I've found is the ebony wood ones here:
Audio Catalog
 (wife said she didn't like the way these look)

 enclosure will be black with silver (natural aluminum) faceplate.


----------



## digger945

Quote:


  Originally Posted by *pinkfloyd4ever* /img/forum/go_quote.gif 
_YESSS why have I not been there yet?!?! I have one about a mile from my house
	

	
	
		
		

		
			






_

 

Seriously guy, you gotta check out Fastenal. It's like nut-bolt-tool heaven. Did I mention TOOLS


----------



## BoilermakerFan

Quote:


  Originally Posted by *soloz2* /img/forum/go_quote.gif 
_I'm looking for knob suggestions... I think I'd like a large volume knob somewhere around 40mm in diameter, and then a smaller knob for source selection, maybe around 30mm.

 Here's the catch. I want them to be the same style/or complement each other well. Also, the volume pot is a small push style on the OptiVol. I can wedge something in there to use a set screw knob if I have to. Then, the shaft for the source selector is a D style 1/4" so it's a little larger.

 I'm having difficulty finding something that will look good and work well for both.

 I like this:
48x22 SOLID Aluminum VALVE TUBE AMPLIFIER EFFECT KNOB - eBay (item 300244651646 end time Jul-31-08 03:32:37 PDT)
 I'm contemplating these:
28x28 SOLID SILVER STOVE TOP VOLUME TUNE DIY AMP KNOB - eBay (item 290239901872 end time Aug-18-08 00:05:55 PDT)
 but so far the best matching pair I've found is the ebony wood ones here:
Audio Catalog
 (wife said she didn't like the way these look)

 enclosure will be black with silver (natural aluminum) faceplate._

 

You can use a different potentiometer for the OptiVol too, but it just adds more cost. The OptiVol has a much smaller shaft diameter than an ALPS or my Darwin selector. A set screw style knob will work if you get a longer set screw, but it won't be a truly circular rotation, it will be slightly elliptical. The eBay seller has some cool vintage style knobs too, IIRC.


----------



## soloz2

I'm game for using a different pot, anyone have a suggestion for a good mono pot?


----------



## BoilermakerFan

Quote:


  Originally Posted by *soloz2* /img/forum/go_quote.gif 
_I'm game for using a different pot, anyone have a suggestion for a good mono pot?_

 

That's the great thing about the OptiVol, it doesn't have to be a great pot, but I believe it is 100K correct? I forget and I don't have mine handy. Worst case, you could use an ALPS or Noble 100K stereo pot and just use the rear points. I'd heat shrink the front set just to CYA against any shorts.

 Did you not like the knobs on DIYEnclosure's site?


----------



## Daveze

Well, don't I feel like an absolute ass.

 Not much to do for a Tuesday...why don't we bite the bullet and swap to the 3422/1359 combo? I'll tell you why that's a dumb idea: because you lift the centre pad for QB9R, that's why. In one swoop of retardedness I took a really nice sounding amp and turned it into a green card with bits soldered onto it.

 I'd successfully removed the transistors and was in the process of cleaning the holes when the centre pads gave a bit more resistance...applying a little more consistent heat I smelt that dreaded smell (I've done this before...at the beginning of the MAX build, I just bought a new board) and lo and behold the pad has lifted at the sides. The exact reason I was wary of removing C2R/L, I've fallen foul of here.

 I'm just really sad now.


----------



## tomb

Quote:


  Originally Posted by *Daveze* /img/forum/go_quote.gif 
_Well, don't I feel like an absolute ass.

 Not much to do for a Tuesday...why don't we bite the bullet and swap to the 3422/1359 combo? I'll tell you why that's a dumb idea: because you lift the centre pad for QB9R, that's why. In one swoop of retardedness I took a really nice sounding amp and turned it into a green card with bits soldered onto it.

 I'd successfully removed the transistors and was in the process of cleaning the holes when the centre pads gave a bit more resistance...applying a little more consistent heat I smelt that dreaded smell (I've done this before...at the beginning of the MAX build, I just bought a new board) and lo and behold the pad has lifted at the sides. The exact reason I was wary of removing C2R/L, I've fallen foul of here.

 I'm just really sad now._

 

Lifted pads can be repaired? You can just solder short jumpers from the transistor pins to the pads on the other side of the heat sink.


----------



## Daveze

I know but its so friggin fiddly (because stupid Josh soldered the heatsinks to the board) that I really really can't be stuffed tonight...I'm liable to break something. Out of frustration.

 I'm actually thinking of running the leads diagonally underneath the heatsink to the Mosfet pads...if the leads have enough length. Thats for the QB9L/R, I haven't cleaned the pad for QB9L because its going to go the way of its R brother.


----------



## TimJo

Well, I just finished building another Max last night. It is another Can't Miss #2 because it seems to be the perfect match for my Beyers. It will now become my main amp in the living room, and the one that it is replacing will become a test bed for playing around with trying out different operating points specifically for 12FM6 tubes.

 I let it burn-in over night and here are a couple of not so good pictures from this morning. I still need to finish drilling the lid and the power supply connection, but nonetheless it sounds great!


----------



## tomb

Quote:


  Originally Posted by *TimJo* /img/forum/go_quote.gif 
_Well, I just finished building another Max last night. It is another Can't Miss #2 because it seems to be the perfect match for my Beyers. It will now become my main amp in the living room, and the one that it is replacing will become a test bed for playing around with trying out different operating points specifically for 12FM6 tubes.

 I let it burn-in over night and here are a couple of not so good pictures from this morning. I still need to finish drilling the lid and the power supply connection, but nonetheless it sounds great!_

 

Another MAX is livin' large!!
	

	
	
		
		

		
		
	


	







 I love those battleship-gun Vitamin Q's.
	

	
	
		
		

		
		
	


	





 P.S. That's a neat looking turntable. What are using for an RIAA preamp?


----------



## TimJo

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Another MAX is livin' large!!
	

	
	
		
		

		
		
	


	







 I love those battleship-gun Vitamin Q's.
	

	
	
		
		

		
		
	


	





 P.S. That's a neat looking turntable. What are using for an RIAA preamp?_

 

Thanks. I have a Linn Linto pre-amp that is paired with the Benz cartridge. 

 I'm also building a Bottle Head Seduction phono stage right now that will go with my Pro-Ject turntable in the office. Just like headphone amps, you can't have too many turntables.


----------



## BoilermakerFan

Quote:


  Originally Posted by *TimJo* /img/forum/go_quote.gif 
_Thanks. I have a Linn Linto pre-amp that is paired with the Benz cartridge. 

 I'm also building a Bottle Head Seduction phono stage right now that will go with my Pro-Ject turntable in the office. Just like headphone amps, you can't have too many turntables. 
	

	
	
		
		

		
		
	


	


_

 

Nice TT TimJo. Did you also happen to notice that John released an Aikido phono stage kit? I think I'm going to order the PCB and tubes, but wait a bit before I fund it's build. I have an old Pro-Ject 1.2 TT and I'm building a OPA627-based phono stage from a design posted by Peter Daniels on DIYaudio. The wifey won't let me step up to something like the VPI Scout at this time. She mentioned something about college tuition for the kids...


----------



## BoilermakerFan

My AKG K601s are scheduled for delivery on Tuesday. I can't wait! 
	

	
	
		
		

		
		
	


	




 <- Except mine will be black...


----------



## Daveze

After a little bit of fiddling I got the 3422/1359's into place. They really are a world apart from the MJE's...

 The low-end punch that I thought had gone is back again with a vengeance, I'd hate to hear them substituted into a straight GJA kit build. It'd melt your face off.

 I'm up to 140mV (~64mA) and sitting at ~45 degC, which is a pretty good point for the moment. I don't quite remember how I described the difference last time but its...clearer...more nice with the higher bias. I'll aim to get back up to 176mV (80mA) tomorrow night. On that note, can someone provide an explanation for my observation: when I blow on the heatsinks the current increases. Blowing should drop the temperature (better heat transfer with moving air) but I thought BJT's were such that the higher the temperature the more they conducted? I think this is back to knowing how to read the transistor curves, which as I mentioned last time are a mystery to me.


----------



## tomb

Quote:


  Originally Posted by *Daveze* /img/forum/go_quote.gif 
_After a little bit of fiddling I got the 3422/1359's into place. They really are a world apart from the MJE's...

 The low-end punch that I thought had gone is back again with a vengeance, I'd hate to hear them substituted into a straight GJA kit build. It'd melt your face off.

 I'm up to 140mV (~64mA) and sitting at ~45 degC, which is a pretty good point for the moment. I don't quite remember how I described the difference last time but its...clearer...more nice with the higher bias. I'll aim to get back up to 176mV (80mA) tomorrow night. On that note, can someone provide an explanation for my observation: when I blow on the heatsinks the current increases. Blowing should drop the temperature (better heat transfer with moving air) but I thought BJT's were such that the higher the temperature the more they conducted? I think this is back to knowing how to read the transistor curves, which as I mentioned last time are a mystery to me._

 

Glad to hear you like the 3422's. After trying most of the transistors we recommend, they are still my personal favorites.

 As for the current increasing when you blow on the transistors - all things being equal, transistors will support more power dissipation with better cooling (positive temperature coefficient). It may seem counter-intuitive, but the fact that current increases when you cool the sinks is exactly correct. Otherwise, you wouldn't be able to increase bias with bigger heat sinks.

 The case of MOSFETs is that when cooling is not so good, current drops, lowering the power dissipation (power capability) of the device. The difference being that you want the MOSFETs to dissipate power/run with a lot of current, or they are not within their optimum performance region. That still means you need big sinks, because Power = Heat = I x V, so to increase power, you need to increase current, so the sinks have to be bigger (assuming voltage is constant in our applications).

 The difference is what happens to the device when current is too high, or thermal dissipation is not sufficient. BJT's suffer a trait known as thermal runaway. The real danger in thermal runaway with BJT's is something called _secondary breakdown_. It's way above my head and is a phenomenon that's probably been the subject of many a Doctorate dissertation. Here's a good link that explains some of it from Sanyo:
Quality and Reliability Handbook ver.3


----------



## tomb

Just a word for some of you who may be wondering about the regular MAX in face of the MiniMAX: the regular MAX is not going away. Yes, we are trying some improvements in the power supply of the MiniMAX, but the primary motivation for the MiniMAX will be the custom-machined enclosure. The idea is to get the amp into the simplest, pre-packaged casing solution possible.

 Because of that, the MiniMAX may be limited in its flexibility. I would not recommend it for MOSFETs, for instance (there are always exceptions, I suppose). Plus, the 1" height restriction is absolute in the Mini - again, because of the custom-machined enclosure. That limits boutique electrolytic selections to only the Muse ES or the BG NX. If the power improvements prove out with the Mini, they'll be incorporated into the regular MAX, but this change will be incremental and may not occur for a few months.

 So, the MAX will continue to be supported, offering some features and flexibility that perhaps the MiniMAX does not. We think that both designs offer distinct choices in building a low-voltage tube hybrid of the Millett Hybrid heritage.


----------



## Daveze

Thanks, I can definitely understand why they're your favourites, they're very nice. Normally I go to sleep listening to an album of jazz or something, it was quite tough last night, spent the whole time just listening and loving the details...

 Thanks also for the explanation. Its a little early in the morning for the Sanyo link but I'll chew it over later in the day when I'm a little more mentally dexterous.

 I love my MAX!


----------



## BoilermakerFan

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Just a word for some of you who may be wondering about the regular MAX in face of the MiniMAX: the regular MAX is not going away. Yes, we are trying some improvements in the power supply of the MiniMAX, but the primary motivation for the MiniMAX will be the custom-machined enclosure. The idea is to get the amp into the simplest, pre-packaged casing solution possible.

 Because of that, the MiniMAX may be limited in its flexibility. I would not recommend it for MOSFETs, for instance (there are always exceptions, I suppose). Plus, the 1" height restriction is absolute in the Mini - again, because of the custom-machined enclosure. That limits boutique electrolytic selections to only the Muse ES or the BG NX. If the power improvements prove out with the Mini, they'll be incorporated into the regular MAX, but this change will be incremental and may not occur for a few months.

 So, the MAX will continue to be supported, offering some features and flexibility that perhaps the MiniMAX does not. We think that both designs offer distinct choices in building a low-voltage tube hybrid of the Millett Hybrid heritage._

 

I know there was demand for it's development, but those limitations are pretty "big" to me, but I guess I'll need to call my desktop MAX a MegaMAX or MegaMOSFET-MAX if I decide to go with the alternate silicone. 

 Have you had a chance to try any of the other BJTs I sent you? I know your busy with other related projects, but I was just curious. I've been sidelined by home improvement projects. Latest one was ripping out carpet from the kitchen and replacing it with vinyl tiles. But we all know that if the wife is happy, then we get more time in the lab so I'm hoping to get a kitchen pass in the next few weeks. I'm envious of the guys who have the time to crank out a MAX in a weekend. Man I wish I had that much free time! Soon I'll just have to go 
	

	
	
		
		

		
			





 and disappear for while!


----------



## tomb

FYI, Beezar.com received a new shipment of genuine, Toshiba 2SC2238's yesterday. There are many more coming in a few days, too.


----------



## BoilermakerFan

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_FYI, Beezar.com received a new shipment of genuine, Toshiba 2SC2238's yesterday. There are many more coming in a few days, too. 
	

	
	
		
		

		
		
	


	





_

 

Glad to hear they are finally starting to trickle in. LMK when the next shipment comes in, I could go for a second set for a portable amp application. 

 My K601s arrived yesterday so now I have strong motivation to get a MAX built up. I'm just using my crappy Audigy 2 ZS external headphone jack to burn in the cans with a pink noise track looped in Foobar2000. I did listen to Foo Fighters, Beck, Frank Zappa, Jewel, RHCP, Frank Sinatra, and Natasha Bedingfield (at 320kbs or FLAC) on the cans last night straight out of the box. I really like these cans and I can't wait for the magic once they hit 200 to 400 hours! Tonight I'll listen again after 20 hours of pink noise...

 Now I just can't decide whether to build the first MAX with the 2238s/Muse ES/VitQs or 2238s/Cerafines/VitQs. The first was intended for the console, but I'll eventually use it in my desktop amp and swap in a MAX with 3422s/Muse ES/VitQs for the console to get more slam out of the console with a 1"/4"/8" 3-way speaker setup. I'll use the transistor sockets on the first board too, so I can swap transistor pairs easily.


----------



## tomb

Quote:


  Originally Posted by *BoilermakerFan* /img/forum/go_quote.gif 
_Glad to hear they are finally starting to trickle in. LMK when the next shipment comes in, I could go for a second set for a portable amp application. 

 My K601s arrived yesterday so now I have strong motivation to get a MAX built up. I'm just using my crappy Audigy 2 ZS external headphone jack to burn in the cans with a pink noise track looped in Foobar2000. I did listen to Foo Fighters, Beck, Frank Zappa, Jewel, RHCP, Frank Sinatra, and Natasha Bedingfield (at 320kbs or FLAC) on the cans last night straight out of the box. I really like these cans and I can't wait for the magic once they hit 200 to 400 hours! Tonight I'll listen again after 20 hours of pink noise...

 Now I just can't decide whether to build the first MAX with the 2238s/Muse ES/VitQs or 2238s/Cerafines/VitQs. The first was intended for the console, but I'll eventually use it in my desktop amp and swap in a MAX with 3422s/Muse ES/VitQs for the console to get more slam out of the console with a 1"/4"/8" 3-way speaker setup. I'll use the transistor sockets on the first board too, so I can swap transistor pairs easily._

 

Yep, at the time of this posting, there's still about 2 dozen 2SC2238's left. I lack a few of having that many 2SA968's - mostly because people have been buying them in the hopes of finding the 2238's elsewhere - but more are coming with the other 2SC2238's (about 6 dozen) that are due in at the end of the week (est.).

 I was shocked when I found the package waiting on the porch for me late Monday. I'd only had them ordered since February.
	

	
	
		
		

		
		
	


	




 When I opened the package and saw that they checked out, I promptly got on the phone and ordered all the rest that they currently had in stock. Those are the ones mentioned above that are already on the way.

 Those are all excellent combinations that you mentioned for the MAX, by the way. IMHO, ES's with VitQ's come very close to Black Gate quality. On the other hand from what I've heard, the Cerafines are already at that point. It's just that in the sizes the MAX needs, they're harder to get than the 2SC2238's.


----------



## BoilermakerFan

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_<snip>
 Those are all excellent combinations that you mentioned for the MAX, by the way. IMHO, ES's with VitQ's come very close to Black Gate quality. On the other hand from what I've heard, the Cerafines are already at that point. It's just that in the sizes the MAX needs, they're harder to get than the 2SC2238's.
	

	
	
		
		

		
		
	


	


_

 

Really? They were easy to find, just a little more expensive than I expected, but still half the cost of BG NXs. Legitimate 2238s however, have been very hard to find, or maybe I'm just content enough to wait for a legitimate 2238 from a great reseller. 
	

	
	
		
		

		
		
	


	




 Thanks for the opinion Tom. I think I will use the Cerafines in the socketed DB MAX then. If I hear a potential DB combo that is just lacking a little low end, then I'll flip it to the third board in a dedicated build with my second set of Muse ES caps. I wish there was an easy way to socket the caps for easy swapping of those too.


----------



## TimJo

As an experiment, I modified the CCS on my first Max to see if there is a better operating point for the 12FM6 tubes. 

 I installed 681R/6K81 resistors in RA8/RA9 which yields a 0.95ma current source. With this CCS, I have the tubes biased at 20v for an operating point that seems better matched for 12FM6 plate characteristics.

 I've been listening to this '12FM6' Max all week and overall I'd say it is an improvement when compared to the 12FM6's at the 0.56ma/13.5v operating point. There is a lot more detail to my ears, and possibly less distortion (but this is purely subjective since I don't have any test equipment to make an analytical measurement of the difference in distortion). With the bias at 20v, there is the potential for clipping at high volume, but I never drive my headphones at high enough volume to get there (as far as I know - again I wish I had a scope). It has crossed my mind that further mods could be made to bump the transformer to 28v so there would be more headroom for the higher operating point, but I'm not sure it is really required.

 I terms of sound, this tube seems to be a better fit for my 701's rather than my Beyers. The sound signature is more recessed, and kind of 'laid back' when compared to the 12AE6A's, which might explain why I like the combination with the 701's better. This does make me wonder if there is a different set of BJT's that would match the FM's better than the 3422/1359 pair I have in this amp. I may play around with that in the future - maybe the 2238/968 pair would be better suited...

 Overall, I probably still prefer the 12AE6A's, but it is nice to have options. 
	

	
	
		
		

		
		
	


	







 One thing I'd like to add: This experiment was based on comments Pete Millett made in his original article  Build a Low-Voltage Tube Hybrid Headphone/Line Amp. I'd encourage anyone who hasn't already read this, to do so. It is good to know where the design of the Max originated from, and to thank Pete for giving it away to the community.


----------



## akione

You might consider the 'standard' MJE243/253 as an alternative.

 I was curious (and sceptical) about the transistors' effect on the sound, so I did some experimenting. 
 I made a rig from 4 Jisbos, 2 with MJE's and 2 with 2238/968. I made it so that they were all powered 
 at the same time and by using a relay on the outputs, I could switch on-the-fly between them, 
 without any time delay.

 Perhaps unsurprisingly, they are much closer than some people would have you believe. 
	

	
	
		
		

		
		
	


	




 In fact, when I let someone else try it without knowing which he was listening too, he said the switch 
 was ' a reality switch for the percussion' . I listened for myself and had to agree with him. 
 The surprising thing was, it was the MJE's that we both thought were more 'real' .

 Of course, this was in Jisbos, not the MMax. There are also some mods I would
 like to try before making any definite conclusions, but I would certainly say at 
 this 'preliminary' stage, that the MJE's could well be a better option for some people.

 YMMV, of course.


----------



## tomb

That's some great experimentation, guys!!

 TimJo,
 With your permmission, I'd like to add your writeup to the MAX website as a "Tweak." It would be really nice if you could sketch up a graph marking the bias/CCS points of interest, hint, hint.
	

	
	
		
		

		
		
	


	




 Something rudimentary would be fine - I could "pretty it up" for website quality.

 Yes, you are absolutely correct that Pete did some perhaps "weird" tube biasing in his original AudioXpress article, at least as compared to the consensus biasing we've followed for the past few years. It's neat that you carried that a little further. 
	

	
	
		
		

		
		
	


	







 Akione,
 Great contribution and thanks for posting that info! The MJE's are the default listed on the MAX BOM and I believe that's what Jeff Rossel ships with his kits. They are a fine choice for output transistors.

 Just MHO, but there may be differences from the JISBOS to the MAX because of the MAX's output capacitors. There are definitely a couple of transistor selections that have better percussion than the 2SC2238's - one reason the 2SC3422's are my personal favorite. However, the 2SC2238's just seem to push more detail through the caps. They do this at very little detriment to the rest of the frequency spectrum.

 Similarly, Black Gate NX's pass the most detail as output couplers on the MAX. This is one reason that we recommend the 2SC2238 as the optimum choice for Black Gates NX's. The combination can sound very solid-state like and can be sound-competitive with a SS amp, IMHO, while having a tube "flavoring."

 However, there is no other combination that can compete with the bass slam of Muse ES's and the 2SC3422's, IMHO.
	

	
	
		
		

		
		
	


	




 As you say, YMMV! Thanks for that report and for the experimentation! It can be surprising how different output transistors can affect the sound signature in an amp with zero-feedback. That means there are a lot of choices to suit different preferences, and it can be a lot of fun trying out the different options.


----------



## akione

Hi Tom,

 Yes, I agree, using them in the Jisbos isn't really a definitve statement on how they might sound in a Max 
	

	
	
		
		

		
		
	


	



 - hence my delay in posting about this before now. 

 I've also found them to be quite sensitve to 'available power', which is why I want to do some more experiments. 
 I need to get a more suitable transformer, so I can give them a bit more juice - powering 2 is no problem, but 4 
 at the same time is a bit much for the little supply I knocked up for the test. 
	

	
	
		
		

		
		
	


	




 Maybe I should order some 3422's, too .......


----------



## manaox2

Any thoughts on this?

 CA2: Nichicon Muse ES, 1000uf 16V
 CA7: Nichicon Muse ES, 470uf 35V
 CA8: Vitamin Q's, 0.18uf (0.22uf) 100V
 CA9: Wima (and elsewhere)
 2SC2238/2SA968 BJT Diamond Buffer


----------



## TimJo

Quote:


  Originally Posted by *akione* /img/forum/go_quote.gif 
_
 You might consider the 'standard' MJE243/253 as an alternative.

 ...it was the MJE's that we both thought were more 'real' .
_

 

Interesting experiment akione, maybe I'll check those out. It does make some sense that the tube stage is going to have a more noticeable effect on the sound signature than the output buffer.


----------



## BoilermakerFan

Quote:


  Originally Posted by *manaox2* /img/forum/go_quote.gif 
_Any thoughts on this?

 CA2: Nichicon Muse ES, 1000uf 16V
 CA7: Nichicon Muse ES, 470uf 35V
 CA8: Vitamin Q's, 0.18uf (0.22uf) 100V
 CA9: Wima (and elsewhere)
 2SC2238/2SA968 BJT Diamond Buffer_

 

It should be a nice build and one that I am planning to try. The other caps that I plan to try with the 2238s/968s are Cerafines and Silmic IIs.


----------



## soloz2

I haven't gotten the chance to really look into this, but I'm only getting .5v at the LED position. I jumpered R5L/C/R so I should be reading 27v


----------



## tomb

Quote:


  Originally Posted by *soloz2* /img/forum/go_quote.gif 
_I haven't gotten the chance to really look into this, but I'm only getting .5v at the LED position. I jumpered R5L/C/R so I should be reading 27v_

 

Yes, that's correct - you should be reading whatever is set for V+ if you've jumpered those positions.


----------



## pinkfloyd4ever

I'm building a Max with 2SC3422/2SA1359 BJT pairs, Blackgates, and Vitamin Qs at CA8. Is there a consensus that, with Blackgates, CA9 is best left blank rather than putting Vitamin Qs there?


----------



## tomb

Quote:


  Originally Posted by *pinkfloyd4ever* /img/forum/go_quote.gif 
_I'm building a Max with 2SC3422/2SA1359 BJT pairs, Blackgates, and Vitamin Qs at CA8. Is there a consensus that, with Blackgates, CA9 is best left blank rather than putting Vitamin Qs there?_

 

IMHO, VitQ's in that position will cut the bass. Most anything else is superfluous; the Black Gates are so fast that none of the usual suspects have any effect (Wimas, etc.).

 However, according to some of my tests with RMAA, there is some additional noise quieting possible if you can find a cap that will work in that position without cutting the bass. I would suggest the Black Gate HiQ NX 0.47uf 50V tiny electrolytics in that position. There are a few MAX builders who've had good luck with those. I would suggest them in the front, too, but the VitQ's are still best up there, IMHO.

 EDIT: Note that I haven't tried this combination myself, yet, but I intend to on the next MAX with Black Gates.


----------



## pinkfloyd4ever

cool thanks tom!!


----------



## GeWa

My amp is also finished now. A standard Hammond case but with a perforated stainless steel top. This way I'm keeping the hard working BJT's satisfied by giving them enough cool air.
















 Regards


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## tomb

Another MAX lives!!
	

	
	
		
		

		
		
	


	







 Nice job, GeWa!


----------



## soloz2

well I figured as much, but a simple fix with my voltage problem... didn't have a good ground 
	

	
	
		
		

		
		
	


	




 got power to my OptiVol and was finally able to turn it on and give it a listen
	

	
	
		
		

		
		
	


	




 Just preliminary listening with a PS1 as source. Sounds damn fine 
	

	
	
		
		

		
		
	


	




 I've got the Dan in Real Life soundtrack in at the moment.


 So I'll say it now.... Another Max Lives!


----------



## BoilermakerFan

Quote:


  Originally Posted by *soloz2* /img/forum/go_quote.gif 
_well I figured as much, but a simple fix with my voltage problem... didn't have a good ground 
	

	
	
		
		

		
		
	


	




 got power to my OptiVol and was finally able to turn it on and give it a listen
	

	
	
		
		

		
		
	


	




 Just preliminary listening with a PS1 as source. Sounds damn fine 
	

	
	
		
		

		
		
	


	




 I've got the Dan in Real Life soundtrack in at the moment.


 So I'll say it now.... Another Max Lives!_

 

Good deal! Now, this one is a MOSFET-MAX correct? And how does the OptiVol "sound" compared to the ALPS? Are you getting enough attenuation with the stock resistors for the OptiVol? Every 3K increase on the resistors is 2dB IIRC... Yes, I have (2) OptiVols for my MAXes, but I figured I'd ask the questions for everyone else and mine won't realistically be finished for at least another 6 weeks...


----------



## soloz2

Quote:


  Originally Posted by *BoilermakerFan* /img/forum/go_quote.gif 
_Good deal! Now, this one is a MOSFET-MAX correct? And how does the OptiVol "sound" compared to the ALPS? Are you getting enough attenuation with the stock resistors for the OptiVol? Every 3K increase on the resistors is 2dB IIRC... Yes, I have (2) OptiVols for my MAXes, but I figured I'd ask the questions for everyone else and mine won't realistically be finished for at least another 6 weeks..._

 

Yes, MOSFET version.

 I could use maybe a little more attenuation, but it's not bad as is.

 It's hard to compare to Alps, as the previous Maxs I've built were ES/K42/BJC 
	

	
	
		
		

		
		
	


	




 This one is a Blackgate/Vit-Q/MOSFET So far so good though.


 I picked up a couple PS1's a while ago and I have one in the living room and just pulled out the second to listen and it keeps skipping... I'll have to add it to my list of things to look at/upgrade/fix lol

 Yeah, don't even have an hour on this amp yet so no real comments on sound yet. It's not lacking bass, but doesn't have the slam my previous builds had... but that's good as far as I'm concerned. I'm not a huge bass head! the highs and mids already sound great


----------



## BoilermakerFan

Quote:


  Originally Posted by *soloz2* /img/forum/go_quote.gif 
_Yes, MOSFET version.

 I could use maybe a little more attenuation, but it's not bad as is.

 It's hard to compare to Alps, as the previous Maxs I've built were ES/K42/BJC 
	

	
	
		
		

		
		
	


	




 This one is a Blackgate/Vit-Q/MOSFET So far so good though.


 I picked up a couple PS1's a while ago and I have one in the living room and just pulled out the second to listen and it keeps skipping... I'll have to add it to my list of things to look at/upgrade/fix lol

 Yeah, don't even have an hour on this amp yet so no real comments on sound yet. It's not lacking bass, but doesn't have the slam my previous builds had... but that's good as far as I'm concerned. I'm not a huge bass head! the highs and mids already sound great 
	

	
	
		
		

		
		
	


	


_

 

Don't the BGs need 4,000,000 hours of burn in time?


----------



## soloz2

Quote:


  Originally Posted by *BoilermakerFan* /img/forum/go_quote.gif 
_Don't the BGs need 4,000,000 hours of burn in time? 
	

	
	
		
		

		
		
	


	


_

 

something like that...


----------



## BoilermakerFan

Quote:


  Originally Posted by *soloz2* /img/forum/go_quote.gif 
_something like that...
	

	
	
		
		

		
		
	


	


_

 

Yep, what's five decimal places between friends, right? 
	

	
	
		
		

		
		
	


	





 EDIT: Wait a minute... Where are the pics?


----------



## tomb

Quote:


  Originally Posted by *soloz2* /img/forum/go_quote.gif 
_Yes, MOSFET version.

 I could use maybe a little more attenuation, but it's not bad as is.

 It's hard to compare to Alps, as the previous Maxs I've built were ES/K42/BJC 
	

	
	
		
		

		
		
	


	




 This one is a Blackgate/Vit-Q/MOSFET So far so good though.


 I picked up a couple PS1's a while ago and I have one in the living room and just pulled out the second to listen and it keeps skipping... I'll have to add it to my list of things to look at/upgrade/fix lol

 Yeah, don't even have an hour on this amp yet so no real comments on sound yet. It's not lacking bass, but doesn't have the slam my previous builds had... but that's good as far as I'm concerned. I'm not a huge bass head! the highs and mids already sound great 
	

	
	
		
		

		
		
	


	


_

 

I don't think Black Gates take _quite_ as long as many imply. Although, there is no doubt in my mind that a break-in is necessary.

 It's usually taken about 2 weeks of perhaps 4hrs daily, maybe 6-8hrs on Sat/Sun. I'm a bit surprised that you say the highs are already good. That's the bellweather with me. I can detect some "fuzziness" up till about 2 wks. Then the highs get very smooth. Bass slam takes a little longer, but it will never equal the ES's.

 Returning them to "broken-in" condition doesn't take that long - perhaps a day or so if the amp has gone un-used for a couple of weeks - an hour or so if only a few days.

 This is variable according to size, too. The above applies to the 1000uf and 680uf BG's used in the MAX. The teeny ones used in an Alien DAC may only take a few hours to come in.

 At least, that's been my experience. Despite that, I'm sure someone somewhere will say that improvement continues up to 200hrs, 1000hrs, or 4,000,000 hrs.


----------



## digger945

Any quick answers for a Diamond Buffer with the Left channel warm and working and the Right channel cold and no sound. I have cked voltage, ground, output resistors, all solder joints, input resistors. Next is the transistors, just wondering if someone had a quick fix.
 I should add that this has worked good a couple of times, and seems to want to make sound in the right channel just as you unplug it from the wall. 24.2 volts from the supply, and all measurements are taken from the DB board itself. I have about 5mA bias on the Left side, 0 on the Right, and I checked the bias trimmer pot also. Both sides seem to match up pretty good when measured unpowered.


----------



## digger945

BC550, BC560, 2N5485, 2SC2238, 2SA968.
 This is the best sounding amp I have owned yet, what little I have listened to it.
 All pins on the buffer board look perfect and align perfect.


----------



## tomb

Are the Q3's in there some place? I can't see anything wrong with the rest of the part orientation, assuming reverse pinouts on the BC's and 2SC2238/2SA968's.


----------



## digger945

Yes, 550's, with the flat side facing the center of the board, I have listened to this amp before, and it sounded way too good for anything to be wrong, that's why I am puzzled that now I have no sound on the right only.


----------



## digger945

Do you remember the Millett auction for Krmathis's Beta22 build?


----------



## digger945

I don't mean to be a thread hog, I just love this awesome amp and how great it sounds. I will eventually get her goin', it's probably a component failure anyway.
 Hey how can I get in on the Mini Max group buy with the Lansing case.
	

	
	
		
		

		
		
	


	




???
 I really like the "mini max" avatar, thats a phat knob!


----------



## tomb

Quote:


  Originally Posted by *digger945* /img/forum/go_quote.gif 
_I don't mean to be a thread hog, I just love this awesome amp and how great it sounds. I will eventually get her goin', it's probably a component failure anyway.
 Hey how can I get in on the Mini Max group buy with the Lansing case.
	

	
	
		
		

		
		
	


	




???
 I really like the "mini max" avatar, thats a phat knob!
	

	
	
		
		

		
		
	


	


_

 

OK - flat side facing the center of the board sounds right for the Q3's. What about a pic of the bottom? Is it possible you've lost the V+ connection or Gnd for the bad channel? The pins were all hand-fabricated on that board. Depending on how one did it, they may not be the most stable things around.

 The MiniMAX Group Buy for the case will be announced in several forums when it's ready (I'm still fighting with the drawings). We're still waiting for some of the prototype boards to be delivered, though. In one case, it's been 5 days and counting for less than a hundred miles. That sounds a bit bad, even for the US Post Office.


----------



## digger945

All of my voltage and current measurements were with the board in the amp and powered up. The pins seem ok to me, and I get the same measurements for both left and right, only difference is right has no bias current no matter what the pot is adjusted to. Currently I have it adjusted the same as the left, about 1.27k, measurements for that taken out of the amp of course. 
 I will take another look tomorrow.
 Hey thanks for the info on the new mini max, that's gonna be a sharp amp for sure.
 Thank you for your help, tomb, and good luck with the upcoming board build for Krmathis's Beta. I can't wait to read how he likes it.
 BTW, when I first heard this hybrid, my jaw hit the desk, I could not believe the detail and space.


----------



## tomb

Quote:


  Originally Posted by *digger945* /img/forum/go_quote.gif 
_All of my voltage and current measurements were with the board in the amp and powered up. The pins seem ok to me, and I get the same measurements for both left and right, only difference is right has no bias current no matter what the pot is adjusted to. Currently I have it adjusted the same as the left, about 1.27k, measurements for that taken out of the amp of course. 
 I will take another look tomorrow.
 Hey thanks for the info on the new mini max, that's gonna be a sharp amp for sure.
 Thank you for your help, tomb, and good luck with the upcoming board build for Krmathis's Beta. I can't wait to read how he likes it._

 

OK - I'd start with the JFET, first. No JFET, no current ... plus, they are static sensitive. Just a guess. I once soldered a whole bank of transistors on one side of the DB board in reverse. It started to smell pretty quickly when powered up, though. I replaced them all and it worked like a champ. So, lots of things can go wrong but still be fixed.


----------



## digger945

Hey thanks, that's what I needed, just a little nudge in the right direction. Can't wait to hear a MAX or the new miniMAX. I will look for updates here and on DIY.
 Thanks again tomb.


----------



## soloz2

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_I don't think Black Gates take quite as long as many imply. Although, there is no doubt in my mind that a break-in is necessary.

 It's usually taken about 2 weeks of perhaps 4hrs daily, maybe 6-8hrs on Sat/Sun. I'm a bit surprised that you say the highs are already good. That's the bellweather with me. I can detect some "fuzziness" up till about 2 wks. Then the highs get very smooth. Bass slam takes a little longer, but it will never equal the ES's.

 Returning them to "broken-in" condition doesn't take that long - perhaps a day or so if the amp has gone un-used for a couple of weeks - an hour or so if only a few days.

 This is variable according to size, too. The above applies to the 1000uf and 680uf BG's used in the MAX. The teeny ones used in an Alien DAC may only take a few hours to come in.

 At least, that's been my experience. Despite that, I'm sure someone somewhere will say that improvement continues up to 200hrs, 1000hrs, or 4,000,000 hrs. 
	

	
	
		
		

		
		
	


	


_

 

Let me clarify this a bit... I've been without a good desktop headphone amp for over a month now and haven't even touched my HD580's in almost as long, all my listening has been done via speakers, so putting my HD580's back on my head and listening to that familiar Max sound (different yet similar) brought a smile to my face.

 I was also listening to a CD that I have yet to sit down and listen to on my main sytem and on a PS1 that I never even plugged in before... so when I say 'good' I mean good for an amp that has less than 10 hours and still needs more biasing... I'll hook my good CDP up to it before I'm through


----------



## digger945

Problem solved, ground on right tube bias pot. Sounds great now (heaven).
 Someone tell me how much more gooder the MAX sounds, please.

 ......and another Hybrid LIVES!!!!!!


----------



## tomb

Quote:


  Originally Posted by *digger945* /img/forum/go_quote.gif 
_Problem solved, ground on right tube bias pot. Sounds great now (heaven).
 Someone tell me how much more gooder the MAX sounds, please.

 ......and another Hybrid LIVES!!!!!!_

 

revMH Millett Hybrid, to be exact - thanks to Drew, Nate, and Steinchen.
	

	
	
		
		

		
		
	


	




 The MAX compared to the revMH? Similar, but add earthquake bass ... plus, add great features like an integrated PS (only requires a 24VAC wall adapter) and a headphone-protective delay circuit. 
	

	
	
		
		

		
		
	


	




 Glad you solved your problem!!


----------



## digger945

I'm not gonna pretend like I know what I'm doin, just kept comparing it to the left, cuz I knew it was working. 24 volts on the right tube output and 12 on the left. Fix the ground bias and pulled it down to 12, got lucky really.


 I simply cannot believe the space that is created by this little amp, I gotta do the miniMAX now for sure. You gotta full blown Millett fan here buddy.

 I need to give thanks to GeWa for building and testing this amp before he shipped it to me.
 THANK YOU GeWa!!!


----------



## tomb

Quote:


  Originally Posted by *digger945* /img/forum/go_quote.gif 
_I'm not gonna pretend like I know what I'm doin, just kept comparing it to the left, cuz I knew it was working. 24 volts on the right tube output and 12 on the left. Fix the ground bias and pulled it down to 12, got lucky really._

 

There's a lot of us that don't know what we're doing, but with some logical deductions, a meter, and some perseverance - surprisingly, a lot of us can figure out what's wrong.
	

	
	
		
		

		
		
	


	







 You did a great job and it sounds like you knew exactly what to do - namely, giving it a try!!

  Quote:


 I simply cannot believe the space that is created by this little amp, I gotta do the miniMAX now for sure. You gotta full blown Millett fan here buddy.

 I need to give thanks to GeWa for building and testing this amp before he shipped it to me.
 THANK YOU GeWa!!! 
 

Glad to hear it! Sorry that some of us (me) have been slow on getting this thing going. I hope we'll see some build pics in a few more days from somebody.
	

	
	
		
		

		
		
	


	




 Meanwhile, I'm making a bit more progress with the case design drawings - got four of 'em so far (but they're little - 11 x 17's).


----------



## mb3k

I'm back!
 ...but uh oh, 536 pages of MHM madness to read?
 Tomb, I've been reading the max website and saw that AMB has introduced a JFET-mod MOSFET-MAX but I can't find the webpage/site that describes the modification.

 Ive also seen that CA4 and CA5 have been changed from 470u to over 1000u. 

 Anything else I'm missing?
 Wow it's been a while.. I want to get my MHM built!


----------



## tomb

Quote:


  Originally Posted by *mb3k* /img/forum/go_quote.gif 
_I'm back!
 ...but uh oh, 536 pages of MHM madness to read?
 Tomb, I've been reading the max website and saw that AMB has introduced a JFET-mod MOSFET-MAX but I can't find the webpage/site that describes the modification.

 Ive also seen that CA4 and CA5 have been changed from 470u to over 1000u. 

 Anything else I'm missing?
 Wow it's been a while.. I want to get my MHM built! 
	

	
	
		
		

		
			



_

 

Nice to have you back! I'll try to get the pages I have uploaded and online tomorrow sometime. I've got about 75% of the MOSFET-MAX site built - should be enough for someone of your capability.
	

	
	
		
		

		
		
	


	




 Yeah, we're recommending the high capacitance for various reasons. (Check the MiniMAX thread for further details.) Panasonic FM 1800uf 35V would be the best bet. They're only a few dimes more than the smaller caps and offer much lower impedance and higher ripple rejection than the UPW's. UPW has a 2200uf that's only 25mm high if you must order them from Mouser.


----------



## tomb

The Millett Hybrid MOSFET-MAX website is now online:
MOSFET-MAX

 Please be patient - I'll add more stuff when I get a chance.


----------



## Beefy

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_The Millett Hybrid MOSFET-MAX website is now online:
MOSFET-MAX

 Please be patient - I'll add more stuff when I get a chance.
	

	
	
		
		

		
		
	


	


_

 

It seems to be broken for Firefox 3 
	

	
	
		
		

		
		
	


	




 [EDIT] Yep, the site is borked for Firefox 3.01. Works fine in IE7 though.


----------



## bperboy

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_The Millett Hybrid MOSFET-MAX website is now online:
MOSFET-MAX

 Please be patient - I'll add more stuff when I get a chance.
	

	
	
		
		

		
		
	


	


_

 

Nice!! I like the color scheme! It seems to fit the MOSFET Max very nicely. Wait a minute... what month is this? March?


----------



## tomb

Quote:


  Originally Posted by *Beefy* /img/forum/go_quote.gif 
_It seems to be broken for Firefox 3 
	

	
	
		
		

		
		
	


	




 [EDIT] Yep, the site is borked for Firefox 3.01. Works fine in IE7 though._

 

Hmm ... I'll check into it.

  Quote:


  Originally Posted by *bperboy* 
_Nice!! I like the color scheme! It seems to fit the MOSFET Max very nicely. Wait a minute... what month is this? March?_

 

I'm assuming you mean the "Last changed by Date" on some of the pages? Yeah, I've been working on it for awhile.
	

	
	
		
		

		
		
	


	




 EDIT: Looks fixed now for Firefox 3 ...


----------



## mb3k

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Hmm ... I'll check into it.

 I'm assuming you mean the "Last changed by Date" on some of the pages? Yeah, I've been working on it for awhile.
	

	
	
		
		

		
		
	


	




 EDIT: Looks fixed now for Firefox 3 ..._

 

Thanks Tom, looking great as always. 
	

	
	
		
		

		
		
	


	



 Wow, that's not too bad at all, just a couple of changes.


----------



## amphead

Mosfet Max site looks awesome! I like the golden theme.


----------



## BoilermakerFan

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Hmm ... I'll check into it.
 <snip> 
 EDIT: Looks fixed now for Firefox 3 ..._

 

Ah, thanks Tom. IE is short for Internet Evil... Friends don't let Friends surf with IE...


----------



## tomb

Boilermakerfan has been bugging me about this for quite awhile.
	

	
	
		
		

		
		
	


	




 Sorry it took so long, but MOSFETs and JFETs for the MOSFET-MAX are now available at beezar.


----------



## BoilermakerFan

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Boilermakerfan has been bugging me about this for quite awhile.
	

	
	
		
		

		
		
	


	




 Sorry it took so long, but MOSFETs and JFETs for the MOSFET-MAX are now available at beezar._

 








 Wow! It's like Christmas in July, except in August... LOL! Thanks Tom.


----------



## joe_seattle

Does anyone have a sense of what the improvement would be going from the Millett Staving Student Hybrid Amp to the Millett Hybrid Maxed Amp? Would it be, say, as much as going from the Grado SR60 to the SR225?

 And has anyone had a chance to compare the Darkvoice 336i to the Millett Max?


----------



## tomb

Quote:


  Originally Posted by *joe_seattle* /img/forum/go_quote.gif 
_Does anyone have a sense of what the improvement would be going from the Millett Staving Student Hybrid Amp to the Millett Hybrid Maxed Amp?_

 

Yes, and I posted it in your "Best DIY Amp for HD600" thread. Quote:


 Would it be, say, as much as going from the Grado SR60 to the SR225? 
 

That's a pretty good analogy, but there are built-in features that apply to the MAX that don't exist on the SSMH - delay relay for headphone protection, close integration with a case design, ability to use three different tubes (each with different gain), ability to use dozens of different output transistors - including MOSFETs, no power supply issues (any 24VAC walwart at 750ma or greater will work). Finally, you'll find that the MAX possesses some of the deepest, strongest bass slam in its price range, as well. Again, this is no criticism against the SSMH - there's simply a big difference in price/features/sound. Each has its niche in the tube hybrid area.

 Have you looked at the website - http://www.diyforums.org/MAX?

  Quote:


 And has anyone had a chance to compare the Darkvoice 336i to the Millett Max? 
 

I think if you follow the links I provided in your original post, you'll have plenty of comparisons that will allow you to deduce the direct comparison with a Darkvoice.


----------



## slowpogo

I haven't been here much lately, so forgive me for asking, has the MOSFET-Max website launched?


----------



## MrMajestic2

Quote:


  Originally Posted by *slowpogo* /img/forum/go_quote.gif 
_I haven't been here much lately, so forgive me for asking, has the MOSFET-Max website launched?_

 

MOSFET-MAX Overview


----------



## tomb

Quote:


  Originally Posted by *slowpogo* /img/forum/go_quote.gif 
_I haven't been here much lately, so forgive me for asking, has the MOSFET-Max website launched?_

 

FYI, your MAX figures prominently with a pic on the MOSFET-MAX website, as does MrMajestic2's.

 There are some features I hope to add in the future, but I'm a bit busy right now with other things.


----------



## slowpogo

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_FYI, your MAX figures prominently with a pic on the MOSFET-MAX website, as does MrMajestic2's_

 

Awesome! That was a nice little cap to my day to see that.


----------



## tomb

I've updated the case templates for the MOSFET-MAX. The new templates incorporate 1-1/2" heat sinks and placement of the board in the bottom Hammond slot. This is the default choice for the MOSFET-MAX.

 I haven't directly tested the backplate layout yet, so be forewarned if you happen to try it first.
	

	
	
		
		

		
		
	


	




 I'll try to build one up when I get a chance.


----------



## digger945

Listening to some Pink Floyd with the revMH Hybrid, Great Gig in the Sky. The depth and detail is astonishing for me. Any better than this and I will need a box of Puffs. Good stuff.


----------



## manaox2

I was excited. Finally finished doing everything but my casework on my millett, but I plug in the DC adapter from TRIAD and test it to find it not working. 
	

	
	
		
		

		
		
	


	




 What a downer. Beezar has three orders from me currently. I'm tempted to wire up my toroid a little early. 
	

	
	
		
		

		
		
	


	




 EDIT: Wired up my toroid. Had all my biases all the way down. LEDs lit up bright orange. Bad news is that the resistor at RB2L started smoking.... expected something to go wrong. I remember this being a problem for others. I'm searching the thread now.

 Think I may have found a short on the middle pin of the transistor at QB9L. 
	

	
	
		
		

		
		
	


	




 Do I have to replace them all?


----------



## tomb

Quote:


  Originally Posted by *manaox2* /img/forum/go_quote.gif 
_I was excited. Finally finished doing everything but my casework on my millett, but I plug in the DC adapter from TRIAD and test it to find it not working. 
	

	
	
		
		

		
		
	


	




 What a downer. Beezar has three orders from me currently. I'm tempted to wire up my toroid a little early. 
	

	
	
		
		

		
		
	


	




 EDIT: Wired up my toroid. Had all my biases all the way down. LEDs lit up bright orange. Bad news is that the resistor at RB2L started smoking.... expected something to go wrong. I remember this being a problem for others. I'm searching the thread now.

 Think I may have found a short on the middle pin of the transistor at QB9L. 
	

	
	
		
		

		
		
	


	




 Do I have to replace them all?_

 

I think a pic or two might be in order. I'm wondering if you swapped the output transistors, perhaps.

 Also "_DC_ adapter?" I hope not.
	

	
	
		
		

		
		
	


	




 However, if it was AC, and you had something swapped/shorted on the board, it's possible it burned out the secondary fuse in the TRIAD adapter.

 Do this while taking some pics - look at the board from the rear and try to see if you can match up the correct parts on a one-to-one basis with the schematic on the MAX website. Don't cheat - make sure you have the parts in their correct locations.
	

	
	
		
		

		
		
	


	




 EDIT: It's the buffer parts - the ones with a "B" that need checking, I think.


----------



## GeWa

@digger945

 Did you already had the time to case-up the Millett?

 Regards


----------



## manaox2

Here are enough pictures I think:

manaox2/millett RB2L burn - Photobucket - Video and Image Hosting

 I'm going to check the places now. The reason the "AC" adapter burned out was because I connected the live to ground I think. Should have double checked that somehow. Thanks for the help!


----------



## tomb

Quote:


  Originally Posted by *manaox2* /img/forum/go_quote.gif 
_Here are enough pictures I think:

manaox2/millett RB2L burn - Photobucket - Video and Image Hosting

 I'm going to check the places now. The reason the "AC" adapter burned out was because I connected the live to ground I think. Should have double checked that somehow. Thanks for the help!_

 

Wow - pretty comprehensive set of pics. They took me awhile to download.

 Unfortunately, I don't see anything that's discernable in the pics that would've led to this problem. However, I can't see the details on the resistors and the transistors, so can't tell whether they're in the correct positions.

 Here's a few things I've noticed that you might check:

 1. You are most likely correct that QB9L has a short. It appears to have a blob of solder connecting the middle lead to one of the other traces - this shows up in your "Picture022.jpg" and "Picture024.jpg". I can't tell if it's a blob of solder or perhaps a damaged trace, which sort of leads to the next point.

 2. Try to clean the board a bit better. Depending on the flux you're using, it could be enough to cause a short, especially if the solder is mixed in a bit. That may be what's going on with QB9L, but it's a bit hard to tell. Try some 91% rubbing alcohol from Walmart - it's 80 or 90 cents a quart - pretty cheap. A board the size of the MAX may take a toothbrush and 10-12 rinses, depending on how much flux you used. Towel it off with a paper towel at first - that will get a lot of the flux off while the alcohol has it dissolved.

 3. The jumpers on the fuse may be causing some confusion. They're not needed. Use of terminals 1 and 2 (refer to the MAX layout)will bypass the fuse completely. Use terminals 1 and 3 to use the fuse.

 4. Keep RB2L unpopulated and see if you can bias the right channel OK. If so, then make voltage measurements of each resistor lead to ground and record them for the left and right channel. Post them here and we may be able to diagnose the problem - that's assuming that the apparent short at QB9L is not the problem. In any event, you can check the unpopulated pads at RB2L for voltage without burning up another resistor. RB2L is only 10 ohms, probably as little as 3 volts will burn it up (1W). However, I suspect that it saw the full voltage across the buffer (13.5V) and fried pretty quickly.

 Your board looks pretty good except for the things mentioned above. Nice placement, nothing much crooked - a good job. If we can solve this, you should have a great amp to enjoy.


----------



## amphead

Yeah Manaox2, TomB certainly has nailed down the way to check it by removing RB2L. If it still blows a fuse then there is a short to the ground plane most likely in that vicinity.


----------



## tomb

Quote:


  Originally Posted by *amphead* /img/forum/go_quote.gif 
_Yeah Manaox2, TomB certainly has nailed down the way to check it by removing RB2L. If it still blows a fuse then there is a short to the ground plane most likely in that vicinity._

 

Amphead, do you recall where that defective ground short was that you found for Pabbi? Wasn't his RB2L burning up as well?


----------



## manaox2

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Here's a few things I've noticed that you might check:_

 

Thanks for the advice. RB2L ruptured at a small point along the side, but no burning or browning of the resistor. I've got some 100% alcohol to clean the board with and then check the voltages. I'm also worried I flowed on solder to the the ground plane somewhere, I'm going to check around for that as well. I'll get back later tonight with some measurements. Thanks again for the advice!


----------



## digger945

Quote:


  Originally Posted by *GeWa* /img/forum/go_quote.gif 
_@digger945

 Did you already had the time to case-up the Millett?

 Regards_

 

I am working on it now, just ordered some purple LED's to go under the tube sockets and a volume knob. I still listen to it every day, it is my new #1 amp now. I will submit pics when I have it completed, for sure.
 EDIT: ....and a bigger heat sink for the PS. BTW GeWa, what kind of PS is that, it has a huge cap on it?


----------



## manaox2

well, more smoke today. I cleaned up the board and cleared the solder that flowed into empty holes. I plugged it in to take some measurements and everything was fine for three or so minutes. Then came a plume of thick smoke that ended as quick as it came. I promptly unplugged it, and noticed that QB8L was very very toasty especially compared to the other trannies. 

 I'm not sure where the smoke came from. I did manage to measure the voltage from ground to RB2L. A whopping 21.45v. Way higher then expected. I need some more ideas while I'm ohming out the board, it sounds like I have a good amount of work ahead of me.


----------



## digger945

manaox, did you figure out anything new?


----------



## manaox2

Quote:


  Originally Posted by *digger945* /img/forum/go_quote.gif 
_manaox, did you figure out anything new?_

 

Good timing.


----------



## digger945

If I was playin horseshoes, that would be a point
	

	
	
		
		

		
			




 Maybe Tom will be on soon, did you see anything fried really good?
 Unfortunately I am not that familiar with the MAX, but can you pin it down to just one channel, left or right? If you can get one channel working then you got a reference to probe the other, maybe see where the difference is.


----------



## tomb

Good advice, digger. Manaox, I'd definitely check the leads and traces around QB8L and QB9L for a board defect. Either that, or the transistors are swapped. QB8L (outside) should be a 2SC2238 and QB9L (center) should be a 2SA968.


----------



## digger945

What's the status on the MiniMAX Tom? Boards and/or kits.


----------



## manaox2

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Good advice, digger. Manaox, I'd definitely check the leads and traces around QB8L and QB9L for a board defect. Either that, or the transistors are swapped. QB8L (outside) should be a 2SC2238 and QB9L (center) should be a 2SA968._

 

Tom, you are very good at this. And that was good advice digger, I was trying that when I smoked the board a second time. Tom gets bingo, the transistors were swapped. 
	

	
	
		
		

		
		
	


	




 They are surely toasted by the time I desolder them now, I'll have to replace them with another transistor combo I have on hand. I'm red faced, but thanks so much for the help and lets hope this fixes things.


----------



## tomb

Quote:


  Originally Posted by *manaox2* /img/forum/go_quote.gif 
_Tom, you are very good at this. And that was good advice digger, I was trying that when I smoked the board a second time. Tom gets bingo, the transistors were swapped. 
	

	
	
		
		

		
		
	


	




 They are surely toasted by the time I desolder them now, I'll have to replace them with another transistor combo I have on hand. I'm red faced, but thanks so much for the help and lets hope this fixes things._

 

No need to be red-faced. It's happened many times. Let's just cross our fingers and hope that fixes it.
	

	
	
		
		

		
		
	


	




 They should be a snap to remove - just make a solder blob just large enough to cover all three pins and they should drop out. One user suggested tying a little string through the mounting tab hole and pulling on it while holding the solder to the pins.

 Continue to leave RB2L out, just in case - until you can confirm nothing smokes and voltages look OK.


----------



## tomb

Quote:


  Originally Posted by *digger945* /img/forum/go_quote.gif 
_What's the status on the MiniMAX Tom? Boards and/or kits._

 

Board protos are still being built - I hope to have mine done this weekend. The custom case price just about blew us out of the water, but we have a plan to reduce costs significantly. Bottom line, however, the case price may be about $50 each, not $35, but we'll continue to try to get the price down.


----------



## manaox2

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_No need to be red-faced. It's happened many times. Let's just cross our fingers and hope that fixes it.
	

	
	
		
		

		
		
	


	




 They should be a snap to remove - just make a solder blob just large enough to cover all three pins and they should drop out. One user suggested tying a little string through the mounting tab hole and pulling on it while holding the solder to the pins.

 Continue to leave RB2L out, just in case - until you can confirm nothing smokes and voltages look OK._

 

Your methods sounded better then the way I did it (destroyed them), but it wasn't that hard. I'll keep that in mind next time. I should have a working amp by tomorrow evening if this was the major malfunction. 
	

	
	
		
		

		
		
	


	




 Can't wait to have an amp again...


----------



## digger945

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Board protos are still being built - I hope to have mine done this weekend. The custom case price just about blew us out of the water, but we have a plan to reduce costs significantly. Bottom line, however, the case price may be about $50 each, not $35, but we'll continue to try to get the price down._

 

So you will offer a case, no matter the price? Will it include that phat volume knob? I still can't believe this Hybrid, is it the combo 968/2238 output trannys? Love this little amp.


----------



## FallenAngel

Case looks a little on the expensive side, hope we can bring the price down to something similar to or a bit more expensive than a Hammond. I'm also hoping to have this project done this weekend.


----------



## bperboy

Quote:


  Originally Posted by *FallenAngel* /img/forum/go_quote.gif 
_Case looks a little on the expensive side, hope we can bring the price down to something similar to or a bit more expensive than a Hammond. I'm also hoping to have this project done this weekend. 
	

	
	
		
		

		
		
	


	


_

 

I was looking forward to gettin this thing built tonight!


----------



## FallenAngel

Quote:


  Originally Posted by *bperboy* /img/forum/go_quote.gif 
_I was looking forward to gettin this thing built tonight! 
	

	
	
		
		

		
		
	


	


_

 

Race ya 
	

	
	
		
		

		
		
	


	




 Mine will just be missing the Wima 0.1uF PSU bypass caps, the rest arrived today. I'm also thinking of how I'm possibly going to fit 0.22uF VitaminQ caps in that case. How tall is it exactly?


----------



## tomb

Quote:


  Originally Posted by *digger945* /img/forum/go_quote.gif 
_So you will offer a case, no matter the price? Will it include that phat volume knob? I still can't believe this Hybrid, is it the combo 968/2238 output trannys? Love this little amp._

 

Yes, assuming we can get 100 cases sold in a Group Buy. Of course, the more we get, the lower the price.

 The "phat volume knob" is purchased from ebay store "Partspipe", run by ebay user "hongkongsuperseller." I don't plan on selling them, because they're easy enough to get from him.


----------



## manaox2

Ok, results are: before I repopulated RB2L, I tested the board with the new transistors. No smoke that I saw, I was able to quickly check the bias settings and managed to get the power supply to 27v and the L tube bias to be 13.49 and the right down to 13.89... so I said good enough, set the biases all back to minimum, repopulated RB2L and then turned on. Thought I might have saw a few wafts of smoke, but nothing I could feel got too hot except the tubes getting rather warm. My biases said otherwise:

 Gound to TB2L: 0.272V
 Gound to TA2L: 0.272V
 Ground to TB1L: 0.272V
 Ground to TA2R: 22.80V
 Ground to TB2R: 22.77V
 Ground to TB1R: 22.78V

 Neither channel could be adjusted. The power supply could, but that doesn't look good.


----------



## tomb

Quote:


  Originally Posted by *manaox2* /img/forum/go_quote.gif 
_Ok, results are: before I repopulated RB2L, I tested the board with the new transistors. No smoke that I saw, I was able to quickly check the bias settings and managed to get the power supply to 27v and the L tube bias to be 13.49 and the right down to 13.89... so I said good enough, set the biases all back to minimum, repopulated RB2L and then turned on. Thought I might have saw a few wafts of smoke, but nothing I could feel got too hot except the tubes getting rather warm. My biases said otherwise:

 Gound to TB2L: 0.272V
 Gound to TA2L: 0.272V
 Ground to TB1L: 0.272V
 Ground to TA2R: 22.80V
 Ground to TB2R: 22.77V
 Ground to TB1R: 22.78V

 Neither channel could be adjusted. The power supply could, but that doesn't look good. 
	

	
	
		
		

		
		
	


	


_

 

Remember that when biasing the buffer, we're trying to measure milliVolts. We only measured to Ground in the buffers when we were troubleshooting. Bias in the buffers is set by measuring the milliVolts across the RB10 and RB11 power resistors.

 We do that by measuring, in milliVolts, TA2L to TB1L (or TB2L - they're the ~same) for the Left channel and TA2R to TB1R (or TB2R) for the Right channel.

 Not sure what you've done by "setting the biases back to minimum." You should leave the tubes biased and the voltage set to 27. The buffer trimmers, on the other hand, should be screwed in clockwise about 20 turns, or when they click - whichever comes first.

 Once you've done that, kick the power back on and take a quick measurement of TA1L to TB1L (or TB2L). Turn it off and record the milliVolts that you read. Turn it back on and do the same for TA1R to TB1R (or TB2R). Turn it back off. Look at the voltage readings that you wrote down. Are they somewhere in the range of 25 to 50mV (0.025 to 0.050V on your meter)? If so, you're on the right track. You want to get to 110mV per channel (0.110V on your meter) eventually - VERY SLOWLY.

 Refer to this page and study it again before doing any of this:
MAX Setup and Bias Settings

 Also click on the link in the middle of that page for "Click here for a blow-by-blow detail on biasing the DB's. " That will help you some, too. Also study that layout photo (click to make it bigger) to be sure that you know the bias points mentioned above and how to measure them. If anything is still wrong, you don't want to be fiddling about trying to figure out which point is which while your transistors/resistors are cooking again.

 Good luck!


----------



## manaox2

Power supply is fine when biased. The DB Bias is 0mv both sides. I can only bias the right tube. 
	

	
	
		
		

		
		
	


	




 The transisters still do not get warm at all after 5 minutes. Sure that I have a problem somewhere, can't find any shorts with the meter when ohming it out.


----------



## tomb

Quote:


  Originally Posted by *manaox2* /img/forum/go_quote.gif 
_Power supply is fine when biased. The DB Bias is 0mv both sides. I can only bias the right tube. 
	

	
	
		
		

		
			





 The transisters still do not get warm at all after 5 minutes. Sure that I have a problem somewhere, can't find any shorts with the meter when ohming it out._

 

Well, this is depressing - especially after you discovered that the output transistors were swapped.

 I'm a little stumped though, if you are actually measuring 0mV. You can't even measure 0mV when the power is cut off. There's enough residual current in the caps to show a few mV even when the power is off. Did you go over my post and the web page on the MAX website? Are you sure that you're measuring the correct bias points?

 If so, maybe we should try some pics again. However, you need to use something with a macro lens and try to get photos clear enough that we can read the resistor designations.

 Short of that, we need to have you check all of those parts again. Make yourself a list of all the buffer parts and write them down as you check them. Don't cheat.


----------



## manaox2

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_If so, maybe we should try some pics again. However, you need to use something with a macro lens and try to get photos clear enough that we can read the resistor designations.

 Short of that, we need to have you check all of those parts again. Make yourself a list of all the buffer parts and write them down as you check them. Don't cheat. 
	

	
	
		
		

		
		
	


	


_

 

I've checked and rechecked again now, both DB stick to 0mv. 
	

	
	
		
		

		
		
	


	




 New pics are up with supermacro at the link:

manaox2/millett RB2L burn - Photobucket - Video and Image Hosting

 I'll get around to checking all the parts again by Saturday when I have time again. Thanks Tom.


----------



## Beefy

I don't know nearly enough about the design to assist your problem with this build...... but I do have a suggestion to help you for future builds.

 When you bend the leads ready to mount a resistor or diode, do it so that you can read the label on the part - particularly for the VD resistors that don't use colour bands. It makes your life a lot easier when it comes to troubleshooting

 Cheers!


----------



## tomb

Quote:


  Originally Posted by *manaox2* /img/forum/go_quote.gif 
_I've checked and rechecked again now, both DB stick to 0mv. 
	

	
	
		
		

		
		
	


	




 New pics are up with supermacro at the link:

manaox2/millett RB2L burn - Photobucket - Video and Image Hosting

 I'll get around to checking all the parts again by Saturday when I have time again. Thanks Tom._

 

OMG. If those are 3422's/1359's, they're on the wrong side of the heat sinks.


----------



## manaox2

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_OMG. If those are 3422's/1359's, they're on the wrong side of the heat sinks.
	

	
	
		
		

		
		
	


	


_

 

Where are some directions for the boutique transistors? If there is a way, I may mess this up again it seems.


----------



## Daveze

Millett Hybrid MAX BJT Transistors

 Ouch...been there, done that, got the scars to prove it.


----------



## tomb

More to the point of Daveze's link, this is the fundamental reference for the different BJT's:


----------



## manaox2

New transistors are fixed in their proper positions finally and the right channel is currently working it seems. Right DB Bias is currently at 39 mv. 

 The bad news is that left channel is still stuck at the odd 0mV for DB. The left tube bias is also at 0v. 
	

	
	
		
		

		
		
	


	




 At least I'm moving forward now I think.


----------



## amphead

Manaox2, one way to fix this problem is to use right to left mirroring of the readings, on the board. If the board was fully functioning, the readings would be roughly the same between right and left channels. Starting from the power supply and moving toward the tubes then db's.


----------



## manaox2

Quote:


  Originally Posted by *amphead* /img/forum/go_quote.gif 
_Manaox2, one way to fix this problem is to use right to left mirroring of the readings, on the board. If the board was fully functioning, the readings would be roughly the same between right and left channels. Starting from the power supply and moving toward the tubes then db's._

 

I'm new to this method of trouble shooting. I also don't want to short anything. Can you give me some advice on how I use the multimeter to mirror test while the board is on properly?

 Also, I have biased up my right DB bias up to 61mv and now my left tube bias has gone to 11mv... dunno why.


----------



## tomb

Quote:


  Originally Posted by *manaox2* /img/forum/go_quote.gif 
_I'm new to this method of trouble shooting. I also don't want to short anything. Can you give me some advice on how I use the multimeter to mirror test while the board is on properly?

 Also, I have biased up my right DB bias up to 61mv and now my left tube bias has gone to 11mv... dunno why._

 

I believe all Amphead is saying is that now that you've got a good Right channel in the buffer, start comparing the measurement differences with the bad channel.

 I agree with his suggestion, but he may not be up on how long we've been working this. So, I think for the time being that you can stick with measuring the buffer and perhaps the CCS in each channel. If you still have something swapped in that Left channel, it will load the tube and CCS such that you won't be able to bias either the buffer or the tube on that Left channel. IOW, you've got something swapped/wrong in that Left channel.

 An easy way to compare is to use your multimeter to measure the voltage differences across each resistor in the buffer. By comparing the Right (good) channel with the readings on the Left (bad) channel, we may be able to narrow down to the bad part(s).

 That said, you need to do this in an organized manner. List out the different resistors and write down the readings for both channels. Here's a list to go by:

 RA2R .V?..... RA2L.V?
 RA8R ......... RA8L
 RA9R ......... RA9L
 RB1R ......... RB1L
 RB2R ......... RB2L
 RB3R ......... RB3L
 RB4R ......... RB4L
 RB5R ......... RB5L
 RB6R ......... RB6L
 RB7R ......... RB7L
 RB8R ......... RB8L --> These should be jumpers!!
 RB9R ......... RB9L --> These should be jumpers!!
 RB10R .mV.. RB10L --> Measure mV here!
 RB11R .mV.. RB11L --> Measure mV here!
 RB12R ....... RB12L --> These are the trimmers, don't measure for the time being.
 RB13R ....... RB13L

 Try recording the readings for all of those and let's see what we come up with.


----------



## manaox2

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Try recording the readings for all of those and let's see what we come up with. 
	

	
	
		
		

		
		
	


	





_

 


 Away we go:
  Code:


```
[left]RA2R: 2.081VRA2L: 2.630V RA8R: 0.653VRA8L: 0.664V RA9R: 23.54VRA9L: 23.06V RB1R: 1mVRB1L: 590mV RB2R: 28mVRB2L: 35mV RB3R: 30mVRB3L: 7mV RB4R: 281mVRB4L: 339mV RB5R: 296mVRB5L: 129mV RB6R: 301mVRB6L: 333mV RB7R: 301mVRB7L: 203mV RB8R: 0mV RB8L: 0mV --> These should be jumpers!! RB9R: 0mV RB9L: 0mV --> These should be jumpers!! RB10R: 40mVRB10L: 0mV --> Measure mV here! RB11R: 40mVRB11L: 0mV --> Measure mV here! RB12R: xxRB12L: xx --> These are the trimmers, don't measure for the time being. RB13R: 137mVRB13L: 151mV[/left]
```


----------



## tomb

Quote:


  Originally Posted by *manaox2* /img/forum/go_quote.gif 
_Away we go:
  Code:



		Code:
	

[left]RA2R: 2.081VRA2L: 2.630V RA8R: 0.653VRA8L: 0.664V RA9R: 23.54VRA9L: 23.06V RB1R: 1mVRB1L: 590mV RB2R: 28mVRB2L: 35mV RB3R: 30mVRB3L: 7mV RB4R: 281mVRB4L: 339mV RB5R: 296mVRB5L: 129mV RB6R: 301mVRB6L: 333mV RB7R: 301mVRB7L: 203mV RB8R: 0mV RB8L: 0mV --> These should be jumpers!! RB9R: 0mV RB9L: 0mV --> These should be jumpers!! RB10R: 40mVRB10L: 0mV --> Measure mV here! RB11R: 40mVRB11L: 0mV --> Measure mV here! RB12R: xxRB12L: xx --> These are the trimmers, don't measure for the time being. RB13R: 137mVRB13L: 151mV[/left]


_

 

OK - take a close look at QB2L and QB3L - see if they're switched. I always keep track by thinking - odd-numbered transistor, even-numbered part #. So, 2N5087's go on even-numbered parts, such as QB2. 2N5088's go on odd-numbered parts, such as QB3.

 Also take a close look at QB8L and QB9L. The 2SC3422 goes at QB8L (outside heat sink) and the 2SA1359 goes at QB9L (inside heat sink).

 What appears to be happening is an asymmetric current is set up at the signal-input transistors, QB2L and QB3L. That could be because they're swapped, or the output transistors are swapped, or it could even be because RB2L or RB3L are the wrong sizes.


----------



## manaox2

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_OK - take a close look at QB2L and QB3L - see if they're switched. I always keep track by thinking - odd-numbered transistor, even-numbered part #. So, 2N5087's go on even-numbered parts, such as QB2. 2N5088's go on odd-numbered parts, such as QB3.

 Also take a close look at QB8L and QB9L. The 2SC3422 goes at QB8L (outside heat sink) and the 2SA1359 goes at QB9L (inside heat sink).

 What appears to be happening is an asymmetric current is set up at the signal-input transistors, QB2L and QB3L. That could be because they're swapped, or the output transistors are swapped, or it could even be because RB2L or RB3L are the wrong sizes._

 

It might have something to do with the small burnt hole on the front of QB3L. 
	

	
	
		
		

		
		
	


	




 It was a bit hidden by QB2L. I don't know what to do about the matching of that transistor now. I'll check to see what extras I have close.

 EDIT: With the burned out transistor replaced, still no change. All of the transistors are proper or seem to be. Any other problem that might be in relation to the burned RB2L and QB3L transistor?


----------



## tomb

Quote:


  Originally Posted by *manaox2* /img/forum/go_quote.gif 
_It might have something to do with the small burnt hole on the front of QB3L. 
	

	
	
		
		

		
		
	


	




 It was a bit hidden by QB2L. I don't know what to do about the matching of that transistor now. I'll check to see what extras I have close.

 EDIT: With the burned out transistor replaced, still no change. All of the transistors are proper or seem to be. Any other problem that might be in relation to the burned RB2L and QB3L transistor?_

 

 Quote:


  Originally Posted by *tomb* 
_Also take a close look at QB8L and QB9L. The 2SC3422 goes at QB8L (outside heat sink) and the 2SA1359 goes at QB9L (inside heat sink).

 What appears to be happening is an asymmetric current is set up at the signal-input transistors, QB2L and QB3L. That could be because they're swapped, or the output transistors are swapped, or it could even be because RB2L or RB3L are the wrong sizes._

 

You quoted the other possibilities I mentioned. Some thoughts:
 1. A transistor doesn't have to be visibly burned to be bad.
 2. Have you really confirmed that the big output transistors are in the correct locations? You might take them out. If you have a meter that can measure HFE, you can check them that way. The power output transistors you're using should be pretty consistent at 240 HFE.
 3. If you have to remove the resistors to check them, then do so. Measuring is indeterminate in the circuit - there are too many other resistances in parallel to them. If you didn't solder them where you can see the designation, take them out to confirm the ratings. Start with RB2L and RB3L as mentioned.


----------



## manaox2

Big output transistors are in their correct positions. Would I have to remove all of the large transistors to check their Hfe if the right channel works? I'm going to check the resistors before I go on with the transistors and risk having to remove and find six more matched.


----------



## tomb

Quote:


  Originally Posted by *manaox2* /img/forum/go_quote.gif 
_Big output transistors are in their correct positions. Would I have to remove all of the large transistors to check their Hfe if the right channel works? I'm going to check the resistors before I go on with the transistors and risk having to remove and find six more matched._

 

Please don't mess with the channel that's working.


----------



## manaox2

Another max lives! 
	

	
	
		
		

		
		
	


	




 Both channels can be biases now successfully. It was a bad QB2L as well, you caught that dead on. Thanks for all the help, I was cutting it to the wire on time to get this done. I owe you a beer, probably more for the great help. 
	

	
	
		
		

		
		
	


	




 Have a great Holiday!


----------



## tomb

Quote:


  Originally Posted by *manaox2* /img/forum/go_quote.gif 
_Another max lives! 
	

	
	
		
		

		
		
	


	




 Both channels can be biases now successfully. It was a bad QB2L as well, you caught that dead on. Thanks for all the help, I was cutting it to the wire on time to get this done. I owe you a beer, probably more for the great help. 
	

	
	
		
		

		
		
	


	




 Have a great Holiday!_

 

Thank goodness!! You don't owe me anything, though. I owe you for not giving up! I'm sure it was frustrating, but all the trouble becomes nothing more than a nuisance if you get it all working in the end.

 Congrats! Another MAX lives!


----------



## amphead

Thats great news Manaox2! Another Max Lives!   

 Let us know how it sounds. I think you are in for a treat.


----------



## manaox2

Quote:


  Originally Posted by *amphead* /img/forum/go_quote.gif 
_Thats great news Manaox2! Another Max Lives!   

 Let us know how it sounds. I think you are in for a treat._

 

Well, I tested it Wednesday after finally getting around to getting it successfully biased to 90mv on the DB. I recieved no sound out to the headphones however. So, today I made a cable out of a cheap RCA to mini for my input instead that I could test to see if it worked. 
	

	
	
		
		

		
		
	


	




 no go, so therefore I assumed it was the amp. 

 I removed the fuse bypasses that was said to not be needed and now no power, but I can fix that at the very least by rebypassing it if necessary. I'm more concerned on why I do not get sound out of my headphone jack. I need to ground the pot, but I thought I should still be able to hear something. 
	

	
	
		
		

		
		
	


	




 I jumped the gun on it working it seems.


----------



## tomb

Quote:


  Originally Posted by *manaox2* /img/forum/go_quote.gif 
_Well, I tested it Wednesday after finally getting around to getting it successfully biased to 90mv on the DB. I recieved no sound out to the headphones however. So, today I made a cable out of a cheap RCA to mini for my input instead that I could test to see if it worked. 
	

	
	
		
		

		
		
	


	




 no go, so therefore I assumed it was the amp. 

 I removed the fuse bypasses that was said to not be needed and now no power, but I can fix that at the very least by rebypassing it if necessary. I'm more concerned on why I do not get sound out of my headphone jack. I need to ground the pot, but I thought I should still be able to hear something. 
	

	
	
		
		

		
		
	


	




 I jumped the gun on it working it seems._

 

The problem may be in your relay delay. Here's some things to check:

 1. Do you hear the relay fire? It should be a noticeable click after 30 - 45 seconds.
 2. If you have some alligator jumpers, try hooking them to the RB14 output resistors (or jumpers if you didn't install them). Wait until the tubes warm up and the capacitors are fully charged - about 30 seconds. Hook the other ends to a headphone plug. Do you get music?
 3. Pics of your relay-delay section? Installing the BD139 or the zener diode backwards seem to be the mistakes made for people who've had trouble in that area.


----------



## manaox2

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_The problem may be in your relay delay. Here's some things to check:

 1. Do you hear the relay fire? It should be a noticeable click after 30 - 45 seconds.
 2. If you have some alligator jumpers, try hooking them to the RB14 output resistors (or jumpers if you didn't install them). Wait until the tubes warm up and the capacitors are fully charged - about 30 seconds. Hook the other ends to a headphone plug. Do you get music?
 3. Pics of your relay-delay section? Installing the BD139 or the zener diode backwards seem to be the mistakes made for people who've had trouble in that area._

 

Top:
IMGP2228.jpg - Image - Photobucket - Video and Image Hosting
 Bottom:
IMGP2230.jpg - Image - Photobucket - Video and Image Hosting

 I think thats the section you want. If not, I'm pretty sure you can see everything else fairly well in the other pictures in that folder on photobucket.

 I tried listening to each of the RB14 positions (not with alligator clips, I just snipped off the jack from some cheap earbuds to use) and heard nothing. I also hear no click.


----------



## cetoole

In before Tom B. 
	

	
	
		
		

		
		
	


	




 QM1 is installed backwards.


----------



## tomb

Quote:


  Originally Posted by *manaox2* /img/forum/go_quote.gif 
_Top:
IMGP2228.jpg - Image - Photobucket - Video and Image Hosting
 Bottom:
IMGP2230.jpg - Image - Photobucket - Video and Image Hosting

 I think thats the section you want. If not, I'm pretty sure you can see everything else fairly well in the other pictures in that folder on photobucket.

 I tried listening to each of the RB14 positions (not with alligator clips, I just snipped off the jack from some cheap earbuds to use) and heard nothing. I also hear no click. 
	

	
	
		
		

		
		
	


	


_

 

Did you attach the middle wire from the cheap earbuds to a ground point somewhere on the board? If not, a complete circuit wouldn't be formed to produce the signal. It's more or less impossible to have bias readings correct throughout the board and not have music with a functioning source. The only thing that should cause this is a non-functioning delay-relay at the headphone jack. However, you should always hear a signal from a direct connection to the RB14 resistors and to Ground. So, I suspect that you didn't connect the ground wire from those earbuds.

 I'll let you know if I see anything in the pics.


 EDIT: Your BD-139 is absolutely installed BACKWARDS. Take a look at the bottom of the e12 relay page on the MAX website:
Millett Hybrid MAX e12 Delay


----------



## amphead

Good call Cetoole, TomB! Let's see how it sounds.


----------



## tomb

Looks like a bunch of us were posting at the same time!


----------



## manaox2

Well, that did it. 
	

	
	
		
		

		
		
	


	




 I heard the amp for the first time, an event I've been wishing for for the last 6 months... 
	

	
	
		
		

		
		
	


	




 Can't wait for it to burn in a little. 
	

	
	
		
		

		
		
	


	




 Thanks again!


----------



## Daveze

Congrats, especially after all the hard work.


----------



## manaox2

Quote:


  Originally Posted by *Daveze* /img/forum/go_quote.gif 
_Congrats, especially after all the hard work._

 

Thanks, it sounds very good already from just a 1st gen shuffle!


----------



## Daveze

My first audition was an Iriver H20 as the source into my junky-junk IEM's (they'd almost be worthy...if they had the inserts). It sounded great even then. Its even nicer again with my DAC-301 and my Grado's. Unfortunately I'm still at work, I can think of a fantastic way the rest of the afternoon...


----------



## Superpong

This discussion thred is so huge. I believe that someone may ask these questions already. 

 - Has anyone tried Nichicon MUSE (The black body, not the green one) for CA7? or Has anyone tried Jupiter as a by-pass cap? Just want to hear some comments or personal experiences.


----------



## tomb

Quote:


  Originally Posted by *Superpong* /img/forum/go_quote.gif 
_This discussion thred is so huge. I believe that someone may ask these questions already. 

 - Has anyone tried Nichicon MUSE (The black body, not the green one) for CA7? or Has anyone tried Jupiter as a by-pass cap? Just want to hear some comments or personal experiences._

 

The Nichicon MUSE KZ's were standard for CA7 in Jeff Rossel's MAX kits. I see he's selling the capacitors separately now, so I don't know if he's selling MAX kits anymore. Of course, the KZ's can also be obtained at Handmade Electronics and Michael Percy.

 The only issue with the KZ's is that they're giants. You must put the PCB in the bottom slot of the Hammond case to have enough clearance. For that reason, the KZ's are probably a good choice to use with the MOSFET-MAX, since the default recommendation is to use 1-1/2" heat sinks. That gives plenty of room for the KZ's. I'd put them in at CA2 as well.

 As for Jupiters, unfortunately the high heat developed by the MAX from the Power Supply, the high-Class A bias in the output stage, and even proximity to the tubes - make the _Jupiters a very bad choice_ for the MAX. The manufacturer states that they should never be exposed to temperatures more than 110 deg. F. A typical MAX heat sink probably runs to 122 deg., maybe higher in a closed up case (even with ventilation).

 I believe I read recently where Dsavitsk's "L'espressivo Plus" failed the Jupiter capacitors that he had used. The caps were installed away from the tubes, underneath a completely perforated top plate. Plus, the power supply (heat producer) was in a separate cabinet altogether. It's a shame, because I pretty much believe Dsavitsk's Notes on Output Coupling Capacitors almost 100% (especially after he improved his initial bad review on the K42's - they are better caps than he originally described, IMHO*). He describes the Jupiters as some of the best film caps available, period. Unfortunately, they are not for the MAX.


 * I have to say that I've been listening to the MiniMAX almost every day lately at work. It has a couple of 0.1uf K42's on the output (Wima's at the tubes), simply because nothing else would fit in the original prototype (not the current prototype). They sound very, very good - lots of punchy bass, and highs that are extended enough to approach "tizziness." This is the amp in my avatar - it also uses the 2SC2344/2SA1011 Sanyo transistors.


----------



## BoilermakerFan

Well, I was going to try to get this posted up over the weekend, but ah well, all you married with family guys know how that goes! 

 So I have my K601s here and no decent amp to play them on but I have (3) MAX boards, several sets of caps and TEN sets of potential diamond buffers. 

 Brian D. at TPA confirmed that I can use one Darwin to switch my source and sole pair of headphones between the 3 different MAXes. So that will allow me to do side by side listening comparisons on the fly. Now for the detailed plan:

 I am going to temporarily mount all three MAXes on the top of one of my NABU chassis. I am going to layout and drill the top of the NABU so I can access the machine screws that will be holding my heatsinks in place from the bottom of the NABU without having to dismount the boards. I will be using the transistor sockets at all positions on the MAX boards so reverse pin out DBs aren't a problem. I'll use unthreaded spacers for the screws and heatsinks so they will be very stable and solidly mounted. All DB transistors are being mounted in sets to 2-1/2" tall heatsinks so I can crank up the bias on a few key chips to really get them into their sweet spots based on the curves. Each set of DBs will be moved between the three different boards and listened to a few different bias levels to get a feel for the sound of each cap/DB/bias level combo. Yes, 40 heatsinks and forty transistors, this isn't a cheap trial and I only have 12 heatsinks at the moment (but that's enough to get started!)... Volume will initially be controlled by ALPS pots since I have three of them, but after I boil down my favorite combos, I will take the time to wire in the OptiVol for a final side by side comparison. (If I can easily pull the signal from all three boards through one volume attenuator, then it will be the OptiVol, but I haven't checked into that closely yet.) MAX Board ONE will have Cerafine caps with VitQ.18 bypass caps and JFETs for the matched pairs so I can use the MOSFET DBs with it in it's final intended build. MAX Board TWO will have Muse ES bypassed with .18 Vit Qs. MAX Board THREE is up in the air, but I'm leaning towards the Panasonic FC caps since several builders I really respect use them as their standard cap when they don't use BGs. These will also use .18 Vit Q bypass caps. I also have Silmic II and Muse KZ caps on hand, but I don't intend to swap those in unless I just really like the sound of the Cerafine caps over everything else with every DB combo, then the FCs will be swapped out for Silmics and the ESs out for the KZs. BUT I don't see that happening anytime soon. 

 So the bypass caps will stay .18 Vit Qs across the board for now since they are low cost and generally the default recommendation. I have .22 K42s, Wimas, and Vit Qs too in case I run into a disagreeable combo. Oh, all tubes will be FK6 initially since I have 3 pairs of RCA tubes that are all similar. Once things are boiled down or I see a trend of very bright highs and no bass across all boards with a DB combo, then I'll try a set of AE6A tubes. 

 My sources will be my Pro-Ject 1.2 TT with Grado Green cartridge and an assortment of vinyl from monophonic Beach Boys to the Foo Fighters on 180gram vinyl! I'll be building a very simple OPA627 phono stage that has received great reviews on diyAudio for the initial phono stage, but I have parts and plans to build 3 other phono stages in the future. The other source will be my Sony A816 DAP straight from it's headphone jack via mini-to-RCA cable because I have my music as 320kps or lossless and I listen to the Sony every week for hours on end, so I know how the files sound on my Denon C700s and Shure E2Gs. One good source, one ok source. My 47 Labs Flatfish clone and DAC won't be finished for some time so I won't have a great source for a while, but the Grado Green cartridge might upgraded to a Gold sooner than later, as well as the addition of a set of Ultrasone HFI-780s since my B-Day is approaching in October. 
	

	
	
		
		

		
			





 So, on to the initial 3 DB combos:
 The 2238s/968s, the MOSFETs, and either the Toshiba 2SA1930/2SC5171 or Sanyo 2SB1274/2SD1913 - leaning towards the Toshibas since they are on the same price level as the 2238s if not a hair more expensive and the curves look to great potential with higher bias levels.

 The remaining contenders:
 2SA1011/2SC2344
 2SA1358/2SC3421
 2SA1359/2SC3422
 2SB649A/2SD669A
 2SB507/2SD313
 2SA699/2SC1226 - Note, these are discontinued and being salvaged off an old Garrard integrated receiver, but they fall into the 5W range like the others and the curves are decent. Why not? 

 If any of you guys want to weigh in on which of the following four sets should be the first to go in 2SA1930/2SC5171, 2SB1274/2SD1913, 2SB649A/2SD669A, or 2SB507/2SD313; post up your opinions! If side by side comparisons have been done to death between the MOSFETs and 2238/968s, then maybe I'll start with two previously untested BJT combos. I'll let you guys have some say in what starts off the competition, I mean comparisons...

 Phwew! Long post. Now I know how tomb must feel sometimes! 
	

	
	
		
		

		
		
	


	




 - BMF


----------



## TzeYang

hai guys.

 I'm not building the millett hybrid max, but i have a question regarding the 12AE6, 12FK6 tube. 

 Pin 5 and 6 are the internal diodes right? I don't need the diodes so instead of grounding them can i just leave them open instead?

 Thanks.


----------



## joneeboi

What happened to the diyforums.org website? I wanted to look at the MAX schematic, but now the whole website has disappeared.


----------



## tomb

Quote:


  Originally Posted by *joneeboi* /img/forum/go_quote.gif 
_What happened to the diyforums.org website? I wanted to look at the MAX schematic, but now the whole website has disappeared._

 

There's a domain ownership move taking place. It should be back up after awhile.

 EDIT: Back up under new ownership (paid for through proceeds from beezar.com)!!


----------



## amphead

That's awesome TomB! Quite an event for the DIY community!


----------



## tomb

Quote:


  Originally Posted by *amphead* /img/forum/go_quote.gif 
_That's awesome TomB! Quite an event for the DIY community! _

 

Credit where credit's due: Nate Maher is responsible for coordinating the sale from Drew. I owe Nate a big sales commission, but he's holding me hostage for what that payment might be.
	

	
	
		
		

		
		
	


	







 Yes, I hope we can grow it in the near future - but not to compete with Head-Fi or others - it will stay mostly focused on the straight DIY-projects that you've all already seen: Millett, Colin Toole, and hopefully Dsavitsk will be adding some stuff soon. Maybe we can talk Nate into doing some web pages for the Menace, too, if the other forum doesn't have first claim.


----------



## jamess71

Thats Awesome tomB. Looking forward to things to come.


----------



## n_maher

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Credit where credit's due: Nate Maher is responsible for coordinating the sale from Drew. I owe Nate a big sales commission, but he's holding me hostage for what that payment might be.
	

	
	
		
		

		
		
	


	





_

 

Considering how little I did I continue to say nothing is in order. 
	

	
	
		
		

		
		
	


	




  Quote:


 Maybe we can talk Nate into doing some web pages for the Menace, too, if the other forum doesn't have first claim.
	

	
	
		
		

		
		
	


	



 

There is a writeup planned and for sure that information can be made available to DIYForums.


----------



## WilCox

I finished my second MAX over a month ago, but hadn't had time to upload the pictures and post. This one has a pair of Black Gates at the output in a "Super-E" configuration. The Vitamin-Q mounts on the bottom.

 There seems to be slight improvement in bass articiulation with this configuration and will theoretically, at least, provide less phase shift at the bottom octave with my Audio Technica phones.

 Thanks again Tom and Colin (and Pete) for a great amp!


----------



## tomb

WOW! Very cool!


----------



## digger945

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Thank goodness!! You don't owe me anything, though. I owe you for not giving up! I'm sure it was frustrating, but all the trouble becomes nothing more than a nuisance if you get it all working in the end.

 Congrats! Another MAX lives!
	

	
	
		
		

		
		
	


	





_

 


 If Tom wont take a beer, this tarheel will!! Good to see you got it goin'. Does it sound good or what?


----------



## Daveze

Wilcox, very tidy build. Pardon my ignorance but how is the Super-E configuration achieved?


----------



## WilCox

Quote:


  Originally Posted by *Daveze* /img/forum/go_quote.gif 
_Wilcox, very tidy build. Pardon my ignorance but how is the Super-E configuration achieved?_

 

It's just two Black Gate non-polars in parallel, making sure that one is reversed relative to the other so that inductance artifacts are cancelled. Here is a paper describing the Super E-Cap:

black gate super e-cap

 I'm not sure how much snake-oil we have here, but in any case, you get twice the capacitance which lowers the cut-off frequency.


----------



## BoilermakerFan

Quote:


  Originally Posted by *WilCox* /img/forum/go_quote.gif 
_It's just two Black Gate non-polars in parallel, making sure that one is reversed relative to the other so that inductance artifacts are cancelled. Here is a paper describing the Super E-Cap:

black gate super e-cap

 I'm not sure how much snake-oil we have here, but in any case, you get twice the capacitance which lowers the cut-off frequency. 
	

	
	
		
		

		
		
	


	


_

 

Which DB combo did you use, the 2SC3422/2SA1359 or the 2SC3421/2SA1358?


----------



## tomb

Quote:


  Originally Posted by *BoilermakerFan* /img/forum/go_quote.gif 
_Well, I was going to try to get this posted up over the weekend, but ah well, all you married with family guys know how that goes!_

 

Yes to that - and it seems not to get any easier as they get older, either. It's a blessed thing to bear, though - although not so conducive to building prototypes lately.
	

	
	
		
		

		
		
	


	




  Quote:


 So I have my K601s here and no decent amp to play them on but I have (3) MAX boards, several sets of caps and TEN sets of potential diamond buffers. 

 Brian D. at TPA confirmed that I can use one Darwin to switch my source and sole pair of headphones between the 3 different MAXes. So that will allow me to do side by side listening comparisons on the fly. Now for the detailed plan:

 I am going to temporarily mount all three MAXes on the top of one of my NABU chassis. I am going to layout and drill the top of the NABU so I can access the machine screws that will be holding my heatsinks in place from the bottom of the NABU without having to dismount the boards. I will be using the transistor sockets at all positions on the MAX boards so reverse pin out DBs aren't a problem. I'll use unthreaded spacers for the screws and heatsinks so they will be very stable and solidly mounted. All DB transistors are being mounted in sets to 2-1/2" tall heatsinks so I can crank up the bias on a few key chips to really get them into their sweet spots based on the curves. Each set of DBs will be moved between the three different boards and listened to a few different bias levels to get a feel for the sound of each cap/DB/bias level combo. Yes, 40 heatsinks and forty transistors, this isn't a cheap trial and I only have 12 heatsinks at the moment (but that's enough to get started!)... Volume will initially be controlled by ALPS pots since I have three of them, but after I boil down my favorite combos, I will take the time to wire in the OptiVol for a final side by side comparison. (If I can easily pull the signal from all three boards through one volume attenuator, then it will be the OptiVol, but I haven't checked into that closely yet.) MAX Board ONE will have Cerafine caps with VitQ.18 bypass caps and JFETs for the matched pairs so I can use the MOSFET DBs with it in it's final intended build. MAX Board TWO will have Muse ES bypassed with .18 Vit Qs. MAX Board THREE is up in the air, but I'm leaning towards the Panasonic FC caps since several builders I really respect use them as their standard cap when they don't use BGs. These will also use .18 Vit Q bypass caps. I also have Silmic II and Muse KZ caps on hand, but I don't intend to swap those in unless I just really like the sound of the Cerafine caps over everything else with every DB combo, then the FCs will be swapped out for Silmics and the ESs out for the KZs. BUT I don't see that happening anytime soon. 
 

If it were me, I'd use the KZ's or the Silmic's - assuming you're already going to try the ES's and Black Gates and you have no height issues. FC's are nice caps, and decent sounding for quality "power" caps, but not up to the standards of a true boutique. I've remarked about this before, but FC's benefit from a guitar-amp-recapping reputation at DIYAudio and other places. That's not the same thing as a true signal cap application such as at the MAX's CA7.

 I recently built the SSMH with FC's all around, too, and while the sound of that little amp is beyond impressive at the cost, it's easy to tell that the FC's are imparting their own signature to the sound. The difference from something like a Black Gate or Cerafine is quite obvious.

 The Millett Hybrid tradition has been to use the film bypasses and this mitigates the effect of even a power-quality electrolytic in a signal path. However, it stands to reason that you'd be better off starting with the KZ's or Silmics, IMHO.

  Quote:


 So the bypass caps will stay .18 Vit Qs across the board for now since they are low cost and generally the default recommendation. I have .22 K42s, Wimas, and Vit Qs too in case I run into a disagreeable combo. Oh, all tubes will be FK6 initially since I have 3 pairs of RCA tubes that are all similar. Once things are boiled down or I see a trend of very bright highs and no bass across all boards with a DB combo, then I'll try a set of AE6A tubes. 
 

Be sure to keep the Wima's at all positions other than the output bypasses. Try the K42's if you have a mind - I noted lately that they are a still a worthy option and can really enhance the bass slam, while having extended highs. They passed out of favor for awhile after Dsavitsk included them in his excellent Notes on Coupling Capacitors web page - making me wonder where we had gone wrong!? I noticed that he's revised his review upward, though, and recent listening on my part confirms this re-assessment. 

  Quote:


 My sources will be my Pro-Ject 1.2 TT with Grado Green cartridge and an assortment of vinyl from monophonic Beach Boys to the Foo Fighters on 180gram vinyl! I'll be building a very simple OPA627 phono stage that has received great reviews on diyAudio for the initial phono stage, but I have parts and plans to build 3 other phono stages in the future. The other source will be my Sony A816 DAP straight from it's headphone jack via mini-to-RCA cable because I have my music as 320kps or lossless and I listen to the Sony every week for hours on end, so I know how the files sound on my Denon C700s and Shure E2Gs. One good source, one ok source. My 47 Labs Flatfish clone and DAC won't be finished for some time so I won't have a great source for a while, but the Grado Green cartridge might upgraded to a Gold sooner than later, as well as the addition of a set of Ultrasone HFI-780s since my B-Day is approaching in October. 
	

	
	
		
		

		
		
	


	



 

A DAC - even an Alien or the soon-to-come BantamDAC - with FLAC files will be best in the long run, IMHO. One thing about the MAX was that I was able to tell the shortcomings in mp3 files almost immediately. 

  Quote:


 So, on to the initial 3 DB combos:
 The 2238s/968s, the MOSFETs, and either the Toshiba 2SA1930/2SC5171 or Sanyo 2SB1274/2SD1913 - leaning towards the Toshibas since they are on the same price level as the 2238s if not a hair more expensive and the curves look to great potential with higher bias levels.

 The remaining contenders:
 2SA1011/2SC2344
 2SA1358/2SC3421
 2SA1359/2SC3422
 2SB649A/2SD669A
 2SB507/2SD313
 2SA699/2SC1226 - Note, these are discontinued and being salvaged off an old Garrard integrated receiver, but they fall into the 5W range like the others and the curves are decent. Why not? 
 

Again, just MHO, but the greatest range in sound and effect would be to build your first three with the following pairs:

 2SC2238/2SA968
 2SC3422/2SA1359
 2SC3421/2SA1358

 At least with those, you will get a fairly wide spread of different sound signatures and at the same time be assured that the quality of listening is up to a Millett MAX standard. Roll in the 2SC2344/2SA1011's if you want to save the 2SC2238/2SA968's for something special - the differences are very subtle, at best, between those two pairs.

 Also, don't hesitate to roll in a pair of 12AE6's right away. You might want to settle on your "best" pair of tubes, first. They have as much or more of an effect than anything else in the amp. The only reason I've implied otherwise in the past is that rolling the tubes in and out is "easy" and "assumed."

 Look for 12FK6's that have punch or 12AE6's that have extended highs - those are your primary differences. You may find that some 12FK6's are very extended in the highs, but somewhat "soft" in dynamics - much like the difference between a BUF634 output buffer vs. a discrete output buffer. 12AE6's on the other hand, will have dynamics that bounce the headphones off of your head, but it may take some searching to find a pair that have highs that are as extended as a 12FK6 - but it is possible - they are out there! 

  Quote:


 If any of you guys want to weigh in on which of the following four sets should be the first to go in 2SA1930/2SC5171, 2SB1274/2SD1913, 2SB649A/2SD669A, or 2SB507/2SD313; post up your opinions! If side by side comparisons have been done to death between the MOSFETs and 2238/968s, then maybe I'll start with two previously untested BJT combos. I'll let you guys have some say in what starts off the competition, I mean comparisons...

 Phwew! Long post. Now I know how tomb must feel sometimes! 
	

	
	
		
		

		
		
	


	




 - BMF 
 

Good luck!


----------



## WilCox

Quote:


  Originally Posted by *BoilermakerFan* /img/forum/go_quote.gif 
_Which DB combo did you use, the 2SC3422/2SA1359 or the 2SC3421/2SA1358?_

 

This build uses the 2SC3422/2SA1359 combo which seems to work out well. My first build was with the 2SC3421/2SA1358 since I was looking for more bass slam out of my ATH-W5000 and W1000. However, with the 2SC3422/2SA1359 and Black Gate Super E-Cap, I seem to get the added treble clarity while retaining the bass slam.

 My next build, likely the Mini, will be with 2SC2238/2SA968.


----------



## Daveze

Wilcox, thanks for that info. I was at work and had seen that website but didn't seem to be able to wade through the marketing...guff. Your distilled summary is exactly what I was after. I'm wondering just how unique their manufacturing is though, I'd be quite surprised if an automated cap-making-machine introduced much variation...must investigate more.


----------



## BoilermakerFan

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_ If it were me, I'd use the KZ's or the Silmic's - assuming you're already going to try the ES's and Black Gates and you have no height issues. FC's are nice caps, and decent sounding for quality "power" caps, but not up to the standards of a true boutique. I've remarked about this before, but FC's benefit from a guitar-amp-recapping reputation at DIYAudio and other places. That's not the same thing as a true signal cap application such as at the MAX's CA7. 

 I recently built the SSMH with FC's all around, too, and while the sound of that little amp is beyond impressive at the cost, it's easy to tell that the FC's are imparting their own signature to the sound. The difference from something like a Black Gate or Cerafine is quite obvious.

 The Millett Hybrid tradition has been to use the film bypasses and this mitigates the effect of even a power-quality electrolytic in a signal path. However, it stands to reason that you'd be better off starting with the KZ's or Silmics, IMHO._

 

OK, thanks Tom, I have the room, hence the 2-1/2" heatsinks, so I'll use the KZs since their described sound signature is different than the ESs and Cerafines. Aren't the Silmic IIs close to the sound signature of the Cerafines, just not quite as nice? Edit: Now I think I need to order Cerafines for my gainclone too! 

  Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Be sure to keep the Wima's at all positions other than the output bypasses. Try the K42's if you have a mind - I noted lately that they are a still a worthy option and can really enhance the bass slam, while having extended highs. They passed out of favor for awhile after Dsavitsk included them in his excellent Notes on Coupling Capacitors web page - making me wonder where we had gone wrong!? I noticed that he's revised his review upward, though, and recent listening on my part confirms this re-assessment._

 

To clarify, I was planning to keep Wima's at all the other .22uF positions, I would only roll in the others into the bypass positions if I heard a distinct issue with one of the boards with the .18 Vit Qs not getting along with the Cerafines or KZs (we know they play well with the ES caps). I don't expect it to happen, but I have them. Eventually I may roll in the K42s to replace Wimas in the other positions, but that's another set of evaluations and I have other stuff I'd rather build...

  Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_A DAC - even an Alien or the soon-to-come BantamDAC - with FLAC files will be best in the long run, IMHO. One thing about the MAX was that I was able to tell the shortcomings in mp3 files almost immediately._

 

Oh, I agree, but I want to see if any of the combos is more forgiving of lesser sources while still sounding good since some peeps might want to build a MAX to get into headphones before they start working on upgrading the rest of their sources and/or cans. I'm waiting on a BantamDAC. 
	

	
	
		
		

		
		
	


	




 I have a CD transport and I'll be building a NOS DAC along the lines of Dsavitsk's design with the ability to bring in USB FLAC files or the SPDIF signal from my transport. I just don't have the time to get it finished before I build the MAX, Darwin, phono stage, and the gainclone amp for the console. 

  Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Again, just MHO, but the greatest range in sound and effect would be to build your first three with the following pairs:

 2SC2238/2SA968
 2SC3422/2SA1359
 2SC3421/2SA1358

 At least with those, you will get a fairly wide spread of different sound signatures and at the same time be assured that the quality of listening is up to a Millett MAX standard. Roll in the 2SC2344/2SA1011's if you want to save the 2SC2238/2SA968's for something special - the differences are very subtle, at best, between those two pairs._

 

All of those will be tested, I just wanted to start with the 2238/968 and either the MOSFETs, or two of the untested BJT DBs since nobody else has built a MAX with them. For my evaluation to have any value, I have to listen to all of them to be able to say what works best and what isn't worth the trouble. I'm now leaning towards the two untested 649A/669A and 1274/1913 combos for the initial testing, but the heatsinks and sockets for the rest of the boards will be here before I get the boards fully populated, so it's not a huge deal. I will probably use hex head cap screws to mount the sinks so I can swap out the DBs even faster and safer. 

  Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_ Also, don't hesitate to roll in a pair of 12AE6's right away. You might want to settle on your "best" pair of tubes, first. They have as much or more of an effect than anything else in the amp. The only reason I've implied otherwise in the past is that rolling the tubes in and out is "easy" and "assumed."

 Look for 12FK6's that have punch or 12AE6's that have extended highs - those are your primary differences. You may find that some 12FK6's are very extended in the highs, but somewhat "soft" in dynamics - much like the difference between a BUF634 output buffer vs. a discrete output buffer. 12AE6's on the other hand, will have dynamics that bounce the headphones off of your head, but it may take some searching to find a pair that have highs that are as extended as a 12FK6 - but it is possible - they are out there!_

 

I'll roll in the 12AE6s too, I was just going to start with 12FK6s since I will need to use the FK6s with my gainclone amps for the console in order to keep the gain down a bit to work better with the gainclone's gain of 32. I planned to use AE6s or FM6s for my stand alone desktop MAX. All of the DB combos will be evaluated on all of the boards with all of the tubes. By my calculations with 3 boards, 10 sets of DBs, and at least 11 pairs of tubes I have 330 variations to test and that's before I start to cherry pick my favorite individual tubes on one set of 
	

	
	
		
		

		
		
	


	




. I plan on taking very good notes so I can narrow down the combos for further listening with HFI-780s and the other tweaks such as JFET vs. BJT for the small signal caps and K42s instead of Wimas. A lot of listening, but some of it will be done while I'm building other stuff like the phono stages, DACs, and refurbishing my older Magnavox 6V6GT tubed mono console. 

  Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Good luck!_

 

Thanks, and thank you for the feedback.


----------



## manaox2

Quote:


  Originally Posted by *digger945* /img/forum/go_quote.gif 
_If Tom wont take a beer, this tarheel will!! Good to see you got it goin' Does it sound good or what?
	

	
	
		
		

		
		
	


	


_

 

It sounds greater by the second. Changes during warm-up and the tubes settling aside, It'll make me shed a tear any day now from just the shuffle it seems! If I get that ballsie for my Opus I have populated already, I will have a source that at least will compare to the iMod I sold to afford it. Glad that I finally have a real headphone amplifier again for my favorite phones. 

 So surprise, I also originally bought the parts for three of these beasts also with a NABU case... 
	

	
	
		
		

		
		
	


	




 As soon as I put the funds aside and get the attenuator for the real project, we will see what I learned from the experience. Pabbi1 should see a brother amp hopefully coming in the new year (if that darn updated Joshua tree attenuator gets released at least!).

 BTW, that crazy blackgate super-E with Vit-Q bypass up there really gets the geek in me drooling! Wondering if I can afford to get eight of those sweet blackgates now.


----------



## digger945

manaox, 
 I wanna know if your eyes water when you get the Opus feedin' the Max.

 Yea that's the only reason I didn't go home (Asheville) this year, cuz I bought way too many diy stuffs and goodies


----------



## pabbi1

Quote:


  Originally Posted by *manaox2* /img/forum/go_quote.gif 
_ So surprise, I also originally bought the parts for three of these beasts also with a NABU case... 
	

	
	
		
		

		
		
	


	




 As soon as I put the funds aside and get the attenuator for the real project, we will see what I learned from the experience. Pabbi1 should see a brother amp hopefully coming in the new year (if that darn updated Joshua tree attenuator gets released at least!)._

 

Oh, and Sam, I happen to have an unused Ballsie board.. 

 3 sets of boards? Hmmmm... but, this does bring up a question: Has anyone else built a balanced Maxx? Not necessarily with a DAC, but, certainly, I can't be the only one so far... and the most FUN amp I have ever had.

 I have already built a WAY badder brother for Maxxie... they are far different animals, 350v vs 28v. No end to the madness...


----------



## BoilermakerFan

Quote:


  Originally Posted by *manaox2* /img/forum/go_quote.gif 
_<snip> (if that darn updated Joshua tree attenuator gets released at least!).<snip> 

 BTW, that crazy blackgate super-E with Vit-Q bypass up there really gets the geek in me drooling! Wondering if I can afford to get eight of those sweet blackgates now._

 

I'm waiting for the JT too for my destop MAX in the NABU. I'll definitely be incorporating the VFD! 

 There may be a lower cost way to duplicate the concept with other non-polarized caps... Maybe it would work, but worst case you just have more coupling capacity as WilCox said.

  Quote:


  Originally Posted by *pabbi1* /img/forum/go_quote.gif 
_<snip>

 3 sets of boards? Hmmmm... but, this does bring up a question: Has anyone else built a balanced Maxx? Not necessarily with a DAC, but, certainly, I can't be the only one so far... and the most FUN amp I have ever had.
 <snip>_

 

The thought has occurred to me. Greg at SKA even said that a 100K ALPS Blue Velvet could be used to operate two OptiVols for a lower cost way to implement stereo volume control since he could tweak the output resistors on the OptiVols to better match them than trying to match 8 sets of LDRs. They ALPS Blue Velvets two channels track close enough to work. So maybe I have done a little more than think about it. But my TT is SE and I haven't done the homework to find a SE to Balanced phono stage. 

 I just figured I would build two stereo Octal Aikido boards into a balanced headphone amp if I was going to go balanced, but there is a significant price difference between that and a balanced MAX. 

 Three MAXes would make a really nice preamp feeding (6) LM3875 based gainclones (one bridged and paralleled for much higher output power to the subs) for home theater applications too! A motorized encoder driven JT would handle the volume attenuation. 

 - BMF


----------



## rockcod

I am stumbled. I initially installed LM338 as VREG, rectifiers are HFA08TB60 HEXFREDs. Voltage measured across V+ and GND is 17.8V and keeps dropping, MOSFET bias is overloaded (beyond the mV range) and QB9s get hot quickly (even smoke after 10 seconds) and so does VREG. Then I changed VREG to LM317, voltage measured across V+ and GND is now 13.4V and keeps dropping quickly, VREG gets hot (it's dropping too much voltage), but QB9s remain normal. Adjusting RR3 doesn't do anything.

 I've replaced DR1 & DR2, CR2, CR4, & CR5, checked RR1 & RR2. I don't think it is the problem with the HEXFREDs as they are used in my other builds, besides, voltage across CR1 is normal at 27.8V.

 Any insight?

 Edit: Ok, found the problem -- I mistakenly used 10K instead of 1K in RB2s & RB3s. I guess I shouldn't be listening to music while soldering -- it is too distracting


----------



## RubberDuk

Just dropping by to mention I bought a MAX built by a fellow head-fier and I'm in love. That is all. Carry on.


----------



## amphead

Happy to hear that you are enjoying your Max RubberDuk! They were well designed and should last at least 50 years or more! So you should have some listening pleasure for quite awhile. Once they are dialed in they just keep on ticking like a Timex watch, but sound like a Rolex Submariner!  Edit: good that you found that Rockcod! Should be an easy fix from there.


----------



## tomb

Quote:


  Originally Posted by *rockcod* /img/forum/go_quote.gif 
_I am stumbled. I initially installed LM338 as VREG, rectifiers are HFA08TB60 HEXFREDs. Voltage measured across V+ and GND is 17.8V and keeps dropping, MOSFET bias is overloaded (beyond the mV range) and QB9s get hot quickly (even smoke after 10 seconds) and so does VREG. Then I changed VREG to LM317, voltage measured across V+ and GND is now 13.4V and keeps dropping quickly, VREG gets hot (it's dropping too much voltage), but QB9s remain normal. Adjusting RR3 doesn't do anything.

 I've replaced DR1 & DR2, CR2, CR4, & CR5, checked RR1 & RR2. I don't think it is the problem with the HEXFREDs as they are used in my other builds, besides, voltage across CR1 is normal at 27.8V.

 Any insight?

 Edit: Ok, found the problem -- I mistakenly used 10K instead of 1K in RB2s & RB3s. I guess I shouldn't be listening to music while soldering -- it is too distracting _

 

Glad to hear you found your problem so quickly!


----------



## ruZZ.il

Quote:


  Originally Posted by *rockcod* /img/forum/go_quote.gif 
_......
 Edit: Ok, found the problem --
 ...._

 

its the fumes man! I bet cause you solder so fast that you get a steady stream of them and by then 1, 10, same thing  

 good stuff on finding it so quickly though! you recover well from fumes


----------



## manaox2

Quote:


  Originally Posted by *digger945* /img/forum/go_quote.gif 
_manaox, 
 I wanna know if your eyes water when you get the Opus feedin' the Max.

 Yea that's the only reason I didn't go home (Asheville) this year, cuz I bought way too many diy stuffs and goodies
	

	
	
		
		

		
			












_

 

I wish I could do that! I do have a populated OPUS, but no ballsie. TPA is out of stock of them too. Have to wait for more funds anyway... so no biggie.

 My max has really started settling in now. It generally takes about 5 hours for it to really settle though it seems with my voltage meter still, though my tubes have well over 50 hours. It sounds really great after its been on about two hours, but even I can notice some soft clipping before that.

 The weirdest thing is that things don't sound like they are located properly in the right earphone. I listen to a lot of holophonic stuff (3D aural recording for headphones) and the right side is kind of collapsed. Things that should sound directly behind me sound off to the left corner of the back end and not the middle, regardless of the three sources (granted that they were pretty low end) I've tried. The right side sounds moved to the back end as well. Now something may be wrong with my HD650s which I will test with some different phones later (not the UE11, don't worry about that), but does anyone else have any ideas on something that could cause this with the amp build? 

 Its like the front right quarter area of headspace is being almost completely bypassed which I thought might be fixed by burn-in. With binaural or holophonically recorded tracks, it feels like I have had my right ear relocated closer to the back of my head. 
	

	
	
		
		

		
		
	


	




 Its a very interesting yet fatiguing effect that has me constantly wanting to twist my head around to focus on the source of the sound on the right (and with headphones attached to my head, of course that doesn't work). 

 I replaced some of the transisters in the left channal when I repaired my mistakes, but things actually sound in their proper places there. So unless its one of those things where the brain interprets audio cues on the left side and they aren't projected properly to connect with the right side noises, I am not sure why the never touched matched transistors would be causing this. At least I can say this is interesting and could be a variety of thing such as source, cable, amp, headphones, hearing, or just brain damage.  I rule out the source and cable just because of them working with other things perfectly fine and my brain or hearing isn't affected without the headphones. That leaves either the headphones or amp. If its actually my amp and I obviously suspect it is, it is a very odd occurence to me.


----------



## tomb

Try swapping the tubes and see if the issue follows the tubes.

 What you describe is somewhat typical for a tube that's either not quite up to the snuff of the other one, or one where the bias has fallen off. Bias on the tubes will continue to drop for 2-3 hours on a typical 12AE6, but more than likely, they will not drop the same. The result is that after a couple of hours your soundfield will seem a bit mis-matched.

 Sometimes this effect can occur with a difference in the tenths of a volt. In those cases, you're often better off just listening to your headphones while you make a fine bias adjustment. If that doesn't fix it, then it's a bothersome mis-match in the tubes.

 They take some fiddling ... welcome to tubes.


----------



## jamess71

Quote:


  Originally Posted by *RubberDuk* /img/forum/go_quote.gif 
_Just dropping by to mention I bought a MAX built by a fellow head-fier and I'm in love. That is all. Carry on. 
	

	
	
		
		

		
		
	


	


_

 

Hey RubberDuk, I am so happy to hear that. Enjoy....... 
	

	
	
		
		

		
		
	


	




 James


----------



## fc911c

Hi

 how do I measure the heater voltage to the tube?

 Thanks
 Frank


----------



## tomb

Quote:


  Originally Posted by *fc911c* /img/forum/go_quote.gif 
_Hi

 how do I measure the heater voltage to the tube?

 Thanks
 Frank_

 

Right lead of R1 to V+ is the heater voltage for the Right tube.

 Left lead of R1 to Gnd is the heater voltage for the Left tube.

 Alternatively, you can measure the voltage drop across R1, subtract from the value of V+, and divide by two.


----------



## fc911c

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Right lead of R1 to V+ is the heater voltage for the Right tube.

 Left lead of R1 to Gnd is the heater voltage for the Left tube.

 Alternatively, you can measure the voltage drop across R1, subtract from the value of V+, and divide by two.
	

	
	
		
		

		
		
	


	


_

 

ok thanks Tom

 I have 12.7 on both sides on one of my Millet amps and 12.6 and 12.9 on the other board. How come the differance in voltage on the second one?

 BTW I am running 29v

 thanks
 Frank


----------



## tomb

Quote:


  Originally Posted by *fc911c* /img/forum/go_quote.gif 
_ok thanks Tom

 I have 12.7 on both sides on one of my Millet amps and 12.6 and 12.9 on the other board. How come the differance in voltage on the second one?

 BTW I am running 29v

 thanks
 Frank_

 

Just guessing, of course, but I'd chalk the difference up to the variance in the tubes. The heaters will draw what they need to draw, but there may be slight variances (although I can't remember seeing a difference that big). Swap them with each other and see if the voltage difference follows. If not, then you may have a mis-matched part somewhere else on the board.


----------



## fc911c

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Just guessing, of course, but I'd chalk the difference up to the variance in the tubes. The heaters will draw what they need to draw, but there may be slight variances (although I can't remember seeing a difference that big). Swap them with each other and see if the voltage difference follows. If not, then you may have a mis-matched part somewhere else on the board._

 

Hi Tom

 you guessed right it moved with the tube. At least I know it wasn't something I did. 
	

	
	
		
		

		
		
	


	




 Maybe it will settle down after the tube burns in for a while.

 Frank


----------



## acold7dusta

another soundless Millet...

 some things to note: 

 Sound does come out of RB14L/R

 Everything has been biased: @85mV on BD137/8, 27VDC across board, 13.5VDC per tube bias

 QM1 is in the correct orientation (wording facing the front of case)

 Tubes light up and get warm

 I do not hear any audible clicking from the relay.

 transistor heatsinks get a tad warm, but not uncomfortablly hot like stated on the website


 Any tips/things i can try? I have a camera that can take decent macros if that will help.

 Thanks in advanced!


----------



## ruZZ.il

Quote:


  Originally Posted by *acold7dusta* /img/forum/go_quote.gif 
_





 another soundless Millet...

 ....

 Sound does come out of RB14L/R
 ....._

 

[size=xx-small]
 Check the Relay. does it click after a few seconds?..[/size] it could be the E-12 delay circuit. check out all the parts there for values, orientation, shorts, cold solder joints, etc. pics would be good if you don't find anything and of that region specifically.


----------



## tomb

Quote:


  Originally Posted by *ruZZ.il* /img/forum/go_quote.gif 
_[size=xx-small]
 Check the Relay. does it click after a few seconds?..[/size] it could be the E-12 delay circuit. check out all the parts there for values, orientation, shorts, cold solder joints, etc. pics would be good if you don't find anything and of that region specifically._

 

Yes - Russ is correct - it has to be in the relay circuit: sound from RB14L/R proves it.

 Get us some pics as soon as you can. In the meantime, since you seem certain the BD139 is oriented correctly, check these:

 - DM1, zener diode, backwards
 - Not using a Darlington transistor for QM2 (MPSA14)


----------



## acold7dusta

Here's some orientation shots:











 and my soldering joints:





 Rest of the album:
acold7dusta/headphone amp - Page 1 - Photobucket - Video and Image Hosting

 I'll get a shot of the DM1 in a bit.


----------



## acold7dusta

I just noticed that I am using a MPSA14 transistor for QM2... but thats what the bill of materials calls for


----------



## MrMajestic2

Quote:


  Originally Posted by *acold7dusta* /img/forum/go_quote.gif 
_Here's some orientation shots:

http://i169.photobucket.com/albums/u...p/IMG_1069.jpg

http://i169.photobucket.com/albums/u...p/IMG_1067.jpg

 and my soldering joints:
http://i169.photobucket.com/albums/u...p/IMG_1065.jpg

 Rest of the album:
acold7dusta/headphone amp - Page 1 - Photobucket - Video and Image Hosting

 I'll get a shot of the DM1 in a bit._

 


 I would reflow the solder joints. Some look poorly filled.


----------



## tomb

Just to make sure - have you left the amp on for more than a minute or two? It may take up to 90 seconds or longer before a relay will trip. That can seem so long it may appear as if it's not going to work.

 Your parts look OK, except as you mention, we can't see DM1 in those shots.

 MrMajestic2's suggestion is a good one. It looks like you may not have complete connection on some of those joints.


----------



## TimJo

Quote:


  Originally Posted by *acold7dusta* /img/forum/go_quote.gif 
_
 I'll get a shot of the DM1 in a bit._

 

Just make sure the dark band is towards the pot.

 I can't see anything obvious. You probably should follow MrMajestic's advice and reflow the joints and see if something changes...

 Edit: Looks like Tom posted at the same time. At least we are in agreement...


----------



## acold7dusta

soldering iron is heating up, so ill be reflowing solder shortly

 tomb, 
 why can't an MPSA14 be used for QM2? It's exactly what was listed in the BOM.


----------



## MrMajestic2

Quote:


  Originally Posted by *acold7dusta* /img/forum/go_quote.gif 
_tomb, 
 why can't an MPSA14 be used for QM2? It's exactly what was listed in the BOM._

 

He meant that one of the problems could be that you are NOT using an MPSA14 for QM2. You are using one, so that not the problem


----------



## acold7dusta

reflowed the solder across the whole board: (sorry about my unsteady arm)






 much better connections, but still no sound. 

 Is there any way i can test to see if QM2, QM1, DM1, DM2, and the relay are all working properly?


----------



## tomb

Reflow the connections from the top, too. The only connection to Ground is through the ground plane on top. (Well, there's through-hole plating, but it's not a good idea to depend on that.) DM1 looks like it's not even connected to the ground plane in one of your pics up there.

 You can measure the voltage to Ground of the following parts, but wait for 2-3 minutes before doing it, to be sure that you have given the relay enough time to close.

 Refer to this schematic:





 It's pretty difficult to measure around the legs of the transistors, so let's measure the resistors and the diodes. Put one probe in a "GND" connection on the board (anywhere - the further away, the better), then use the other probe to measure the following:

 RM1 - each leg
 DM1 - each leg (note which side has the black stripe)
 RM2 - each leg
 DM2 - each leg (note which side has the black stripe)
 RA4L/R - each leg

 Come back and tell us what you get.


----------



## acold7dusta

thanks alot for this feedback!

 Tom,

 RM1-leg 1=25.6v
 leg 2=2.2v
 DM1- leg 1= 0v assuming this is a problem...
 leg 2 (black stripe)= 2.21v 
 RM2-leg 1=1.22v
 leg 2= 1.63v
 DM2- leg 1= .6v
 leg 2 (black stripe) = 1.62v
 RA4L- 12.8v (assuming it can be measured from TA2L/R)
 RA4R- 12.8v


----------



## tomb

Quote:


  Originally Posted by *acold7dusta* /img/forum/go_quote.gif 
_thanks alot for this feedback!

 Tom,

 RM1-leg 1=25.6v_

 

This is essentially V+.
  Quote:


 leg 2=2.2v 
 

This is the remaining voltage after current flow through RM1. EDIT: This is the problem! You should have 10-12Volts right here. It's probably a Mouser/keyboard error. I bet RM1 is 332K instead of the 3.32K that's required!. 
  Quote:


 DM1- leg 1= 0v assuming this is a problem... 
 

Nope. This leg of DM1 is tied to Ground. You should get 0V.
  Quote:


 leg 2 (black stripe)= 2.21v 
 

This leg is back to the same point as the leg 2 of RM1 (~2.2V)
  Quote:


 RM2-leg 1=1.22v 
 

I can't tell which is which here, but this is the problem, combined with leg 2.
  Quote:


 leg 2= 1.63v 
 

Either this leg or leg 1 of RM2 should be 10-12Volts.
  Quote:


 DM2- leg 1= .6v 
 

There should be more voltage here.
  Quote:


 leg 2 (black stripe) = 1.62v 
 

If this is the high side of DM2, it should be 10-12Volts.
  Quote:


 RA4L- 12.8v (assuming it can be measured from TA2L/R)
 RA4R- 12.8v 
 

These aren't really in the delay circuit. They are charging the output caps at 1/2 the supply voltage per channel. So, they are more or less perfect.

 EDIT: The problem appears to be that maybe you substituted a 332K resistor for RM1 instead of 3.32K. Those upper legs of RM2 and DM2 should be seeing 10-12 Volts.


----------



## acold7dusta

hmm i guess ill reflow the solder again on QM2, but it doesnt look promising. Otherwise ill get an order in with mouser tomarrow. Thanks for the help/support again. I really appreciate it


----------



## tomb

Quote:


  Originally Posted by *acold7dusta* /img/forum/go_quote.gif 
_hmm i guess ill reflow the solder again on QM2, but it doesnt look promising. Otherwise ill get an order in with mouser tomarrow. Thanks for the help/support again. I really appreciate it_

 

Actually, I made the wrong conclusion. Going over it again and comparing to one of mine, you should have 10-12Volts right there at the end of RM1/DM1.

 Looks like you put in a 332K resistor instead of a 3.32K resistor? There's way too much voltage drop after RM1.


----------



## acold7dusta

Great catch Tom. I took my ohmmeter and got 3.32K on RM2, and 987K on RM1. Simple enough to swap to resistors. Thanks for the walkthrough, I should've checked that stuff day one...



 ...and it lives!

 thanks alot guys!


----------



## tomb

Quote:


  Originally Posted by *acold7dusta* /img/forum/go_quote.gif 
_Great catch Tom. I took my ohmmeter and got 3.32K on RM2, and 987K on RM1. Simple enough to swap to resistors. Thanks for the walkthrough, I should've checked that stuff day one...



 ...and it lives!

 thanks alot guys!_

 

Glad to hear it!!


----------



## amphead

acold7dusta, good job! Another Max Lives!   

 Let us know how it sounds.


----------



## acold7dusta

sounds great! i love how it sounds-smooth highs, great bass extension and very "airy" sound. Once I complete my LOD for my zune, drill my top panel and wire up my front LED ill be all set!


----------



## Migroo

CAD printouts?

 hi guys - can anyone point me to where i might download the cad cutouts for the MAX faceplates and casework? i've had a look on the max website and the cad printouts are mentioned but I can't find a download link!

 thanks


----------



## tomb

Quote:


  Originally Posted by *Migroo* /img/forum/go_quote.gif 
_CAD printouts?

 hi guys - can anyone point me to where i might download the cad cutouts for the MAX faceplates and casework? i've had a look on the max website and the cad printouts are mentioned but I can't find a download link!

 thanks_

 

Under Construction -> Drawings & Templates

 There are many files to pick from.


----------



## Migroo

Thanks tomb!

 Hopefully i'll get chance to use the pillar drill at work tomorrow!


----------



## manaox2

Over the last three days, my MHMax has been acting up. The power has become uncontrollable with spikes and randomly reaching voltages well about 29v steadily which affects my DB bias also. I'm worried about it and surprised that my power adapter even obtain that kind of voltage. My trimmer can turn it down once it climbs, but it still spikes and drops randomly over a range of 15mv. It started this a little after I decided to change tubes after it appeared I might have a bum one recently. Maybe I wrecked something.


----------



## ruZZ.il

how frequent is it?
 Try remove the tubes and measure the voltage.. see it it's stable.
 do you have a standoff in the center of the board to keep it from flexing while changing tubes?. Maybe take a look and make sure everything looks good underneath. check around the trimmer too. Is it more stable at some voltage settings than others?
 maybe lower your DB bias for a little while while you check things out..


----------



## manaox2

Quote:


  Originally Posted by *ruZZ.il* /img/forum/go_quote.gif 
_how frequent is it?
 Try remove the tubes and measure the voltage.. see it it's stable.
 do you have a standoff in the center of the board to keep it from flexing while changing tubes?. Maybe take a look and make sure everything looks good underneath. check around the trimmer too. Is it more stable at some voltage settings than others?
 maybe lower your DB bias for a little while while you check things out.._

 

I don't have a center mounted standoff in place yet. Everything looks fine underneath and sometimes its stable, but eventually (within 12 hours) it goes back to doing this. The trimmer seems like it isn't mounted quite flush and might be getting a bit of a wiggle. Perhaps I will de/resolder it.


----------



## tomb

Quote:


  Originally Posted by *manaox2* /img/forum/go_quote.gif 
_I don't have a center mounted standoff in place yet. Everything looks fine underneath and sometimes its stable, but eventually (within 12 hours) it goes back to doing this. The trimmer seems like it isn't mounted quite flush and might be getting a bit of a wiggle. Perhaps I will de/resolder it._

 

I would suspect the trimmer, too. However, the root of the problem is most likely exactly what Russ said: no center post. Plugging and unplugging the tubes without the center of the board supported can wreak havoc with the board, breaking cold solder joints or worse - tearing traces.

 I'd replace the trimmer if you can and go over the bottom of the board with your soldering iron to make sure you have good hot solder joints. Then put a center post in! It's pretty easy - all you need is a standoff, a screw, and enough washers to adjust the spacing so that the standoff just barely touches the desktop/case bottom.


----------



## amphead

Did you try reflowing solder on the bottom of the board? Could be that there is an intermittent cold solder joint aggravated by the board flexing, as others have mentioned.


----------



## manaox2

Quote:


  Originally Posted by *amphead* /img/forum/go_quote.gif 
_Did you try reflowing solder on the bottom of the board? Could be that there is an intermittent cold solder joint aggravated by the board flexing, as others have mentioned._

 

I'm fairly certain that is the problem, its too bad I am not near my soldering station this week. 
	

	
	
		
		

		
		
	


	




 I will be settled into my new location in about a month, I will be getting my first paycheck from my new job after graduating college tomorrow.


----------



## ruZZ.il

Congrats! 
	

	
	
		
		

		
		
	


	




 Keep us updated!


----------



## amphead

Awesome, that certainly is fantastic news!


----------



## aaronylee

Hello everyone!

 I finally found the time in medical school to give this a shot. I bought the board with the first group buy a few years ago. I hope it hasn't changed since then...

 I had a quick question that I wasn't sure had been asked before or not. Is it necessary to have the LEDs populated under the tube amps? I tried to read the schematic and it looked like it might not affect it, but I wasn't sure. 

 Thanks everyone!


----------



## FallenAngel

Quote:


  Originally Posted by *aaronylee* /img/forum/go_quote.gif 
_Hello everyone!

 I finally found the time in medical school to give this a shot. I bought the board with the first group buy a few years ago. I hope it hasn't changed since then...

 I had a quick question that I wasn't sure had been asked before or not. Is it necessary to have the LEDs populated under the tube amps? I tried to read the schematic and it looked like it might not affect it, but I wasn't sure. 

 Thanks everyone!_

 

Purely cosmetic.


----------



## pinkfloyd4ever

I suppose you're right BMF

 (i know there's quotation code, I find the italics hard to read)
*" * 
 A couple of recommendations: I would order your trimpots (RA1L/R, RB12L/R, RR3) and big 1000uf electrolytic caps (CA4L/R, CA5L/R, CR1A/B/C/D) from Digikey, because they have Murata trimpots and Panasonic FM caps, which are significantly better than the Mouser alternatives. For the big electrolytics, I'd just order 10 of the 50V since it's cheaper than ordering 4 of the 50V's and 4 of the 35V's (10 because it's cheaper than buying the 8 actually needed). I'd also get CR3A/B/C/D from Digikey. I was told by a career EE (now a project manager) that they're higher quality than the ones listed from Mouser.

 Mouser is cheaper without cutting corners on just about everything else, however I'd get the small transistor set (they come matched, which saves alot of hassle, trust me!), output transistors, heatsink mounting kits, tubes, pot, RCA jacks, tube sockets, Vitamin Q's (optional, but most would def recommend them) and power brick (don't forget the cord, it's sold separately) from Beezar. Beezar is a good place to get the Muse ES electrolytics if you want them rather than Blackgates for CA7 & CA9, read up on that on the Max site.* "*

 ..and on a related note BMF
	

	
	
		
		

		
		
	


	




, my best-friend-from-college's best friend from high school is the tight end for Purdue, Jerry Wasikowski


----------



## BoilermakerFan

Quote:


  Originally Posted by *pinkfloyd4ever* /img/forum/go_quote.gif 
_[nevermind]_

 

I think you should put some of that info back in the post, especially the component recommendations simply because it's a little daunting to go through 
 550 pages if your newer to the MAX and it was good advice...

 I read the original post in my Gmail alert email.


----------



## rhester

Who has tried the OptiVol with the Max? I am wanting to try one but don't know where to pull power from. Any help without reading way too many pages.


----------



## pinkfloyd4ever

Head-Fi: Covering Headphones, Earphones and Portable Audio - Search Results soloz2 and BoilerMakerFan have, and I believe they got the power from the center LED pads


----------



## BoilermakerFan

Quote:


  Originally Posted by *rhester* /img/forum/go_quote.gif 
_Who has tried the OptiVol with the Max? I am wanting to try one but don't know where to pull power from. Any help without reading way too many pages._

 

I have the OptiVols for the MAXes, but I haven't cased any of mine up or had a chance to get my 3 boards populated. If the tube LEDs and LED resistor positions are jumpered then there will be 27VDC at the center tap. You will need to tell Greg at SKA that your OptiVol is for a MAX with 0-27VDC so he can provide the correct resistors for the power to the OptiVol. 

 Maybe Tom or somebody else can confirm what voltage would be present at the center LED position if the tube LEDs are used. I don't want to assume it is 27VDC if all the LEDs are wired in series. 

 I know a couple of the guys used them with their 24V Aikido builds and I plan to use an OptiVol on my 24V Aikido as well as the MAXes, so I need to order two more kits. FWIW, the potentiometer on the OptiVol is 100K Log, not 50K Log, but I forgot to ask Greg what happens if a 50K is used in the circuit...


----------



## soloz2

Yep, I've got a Max with an OptiVol and I highly recommend it! great attenuator for the money. Just let Greg know that you plan to use it with a Max (27v) and he'll help you out. I just received a second over the weekend for a second Max.

 If you jumper the RLEDs (R5 if I remember correct...) then you get 27v.


----------



## BoilermakerFan

Hey guys, just wanted to let you know that the US dollar has gotten stronger against the OZ dollar so the OptiVol kits are now ~$17.50 shipped. Greg also made some improvements to the design so the LED is now constant powered and it has a little more attenuation range. 

 My wife is putting me under the gun to have the DR console refurb'ed by Thanksgiving since we're hosting this year. That means I won't be able to fully complete my DB comparisons until after T-day. I'm setting up the MAX in this build so I can easily remove it to complete my testing. 

 I also now have a pair of Yamaha YH-3 orthodynamic headphones to test with in addition to my K601s.


----------



## BoilermakerFan

Oh, if anyone does decide to order an OptiVol or kit, be sure to let greg know it's going on a MH MAX with a 0-27VDC power source so he can include or use the correct resistors.


----------



## pinkfloyd4ever

Quote:


  Originally Posted by *BoilermakerFan* /img/forum/go_quote.gif 
_Hey guys, just wanted to let you know that the US dollar has gotten stronger against the OZ dollar so the OptiVol kits are now ~$17.50 shipped. Greg also made some improvements to the design so the LED is now constant powered and it has a little more attenuation range._

 

NIIIICEEE, I'm gonna use one on my speaker amp build...guess I need to get my sh!t together and figure out which one so I know what voltage to tell him i'll be using when I order
 anyone know if a gainclone kit from audiosector or chipamp.com can power an optivol? I would guess that it would work, but has anyone here done it?


----------



## BoilermakerFan

Quote:


  Originally Posted by *pinkfloyd4ever* /img/forum/go_quote.gif 
_NIIIICEEE, I'm gonna use one on my speaker amp build...guess I need to get my sh!t together and figure out which one so I know what voltage to tell him i'll be using when I order
 anyone know if a gainclone kit from audiosector or chipamp.com can power an optivol? I would guess that it would work, but has anyone here done it?_

 

I have Peter's Premium GC amp kit for my console refurb. I'll be using a 300VA toroid to feed the two mono PSUs. I'm using my MAX as the preamp to power the OptiVol. You can either make your own small PSU with a PCB from Greg or determine the voltage you plan to use for your GC and let Greg know that output from the gainclone PSUs. I'll be using 22VAC secondary which translates to 35VDC, IIRC, but you might want to confirm with Peter via email. Both Greg (SKA) and Peter (AudioSector) have been a great help over the months as this project has progressed. 

 What I really like about the OptiVol is the factthat the pot isn't in the signal path, so you can remotely mount I away from the OptiVol PCB and keep the actual signal paths as short as possible. 

 Off topic, but I've also been working with Greg to use two OptiVols controlled by one 50K ALPS pot for a balanced setup. There are a couple of components that might need to be tweaked to get the correct attenuation range, but it should work well enough to allow me to build a balanced attenuator for about $50. 
	

	
	
		
		

		
			





 Does it track as well as stepped attenuator? No, but it's continuously variable and 20% the cost too so I can deal with small tracking errors in the ALPS pot. A single gang 50K pot could also be used with the component changes, but Greg includes the 100K pots so it kind of a moot point outside of the balanced setup.


----------



## manaox2

Quote:


  Originally Posted by *BoilermakerFan* /img/forum/go_quote.gif 
_Oh, if anyone does decide to order an OptiVol or kit, be sure to let greg know it's going on a MH MAX with a 0-27VDC power source so he can include or use the correct resistors._

 

Good news! I guess since the JT Attenuator is taking the better part of a year at least to be released I'm going to have to go that route soon.


----------



## BoilermakerFan

Man, I had nice reply all typed up and it didn't post up, I received a page load error instead. 

 So long post cut short... The JT with AC1 will cost more than the MAX itself. Now if the goal is to use the additional flexibility and power of the AC1 and VFD to display other info such as artist and track title or run other firmware tweaks like cross feed (if possible) than I can see the value, but for just volume attenuation, I can't see how the standard ALPS or OptiVol would be lacking much behind the JT.


----------



## manaox2

Quote:


  Originally Posted by *BoilermakerFan* /img/forum/go_quote.gif 
_Man, I had nice reply all typed up and it didn't post up, I received a page load error instead. 

 So long post cut short... The JT with AC1 will cost more than the MAX itself. Now if the goal is to use the additional flexibility and power of the AC1 and VFD to display other info such as artist and track title or run other firmware tweaks like cross feed (if possible) than I can see the value, but for just volume attenuation, I can't see how the standard ALPS or OptiVol would be lacking much behind the JT._

 

I'm making a balanced boutique millett max with an internal OPUS DAC. 
	

	
	
		
		

		
		
	


	




 I have a millett max with an ALPs too, they seem to be a good value for it.


----------



## pinkfloyd4ever

holy crap, why didn't anyone tell me touching 2 of the metal tabs of the rectifier diodes together is a bad idea?
	

	
	
		
		

		
		
	


	




 I'm just surprised I haven't heard of anyone else doing it. For those who are wondering exactly what happens, its similar to what happens when shorting a lead-acid battery, although I wouldn't recommend doing that either....not that I've ever done it
	

	
	
		
		

		
		
	


	




 Anyway, this actually happened last night. I've been using it for a few periods of a couple hours today and everything seems ok, and measures the same as before, but is there a chance I messed anything up?


----------



## cetoole

It has been done, Pinkie, though obviously, never by me.
	

	
	
		
		

		
		
	


	




 It turns out also to be a bad idea to accidentally touch one of the diode tabs to the uninsulated portion of the AC input jack, though again, something I would never do.
	

	
	
		
		

		
		
	


	




 Finally, licking the tabs of the rectifiers while on is a REALLY bad idea. I really never tried this one though.
	

	
	
		
		

		
		
	


	




 I would just monitor it for a bit, and if everything remains the same, I would be hopeful that you got away with it this time.

 So, any guesses why we moved to recommending axial rectifier diodes for the minimax? The ones we specify for that though dont fit the regular max board, yet.


----------



## pinkfloyd4ever

Quote:


  Originally Posted by *cetoole* /img/forum/go_quote.gif 
_Finally, licking the tabs of the rectifiers while on is a REALLY bad idea._

 

LMAO, I guess I'm not the only one then, Colin


----------



## manaox2

Quote:


  Originally Posted by *cetoole* /img/forum/go_quote.gif 
_Finally, licking the tabs of the rectifiers while on is a REALLY bad idea. I really never tried this one though.
	

	
	
		
		

		
		
	


	


_

 

I thought of that when looking at your avatar.


----------



## BoilermakerFan

Small progress today, I finished matching my small signal transistors at lunch. I ended up with a total spread of 20 points on one BJT combo, a 17 point spread on the other BJT combo, and 6 point spread across all transistors for the MOSFET-MAX. All the CCS transistors are identically matched quads. 
	

	
	
		
		

		
		
	


	




 I am very, very tempted to order a MiniMAX board for the MOSFET-MAX for the better ground plane, but my concern is the closer spacing of components with my relatively high bias currents. I will be implementing the other changes to my MAX boards as mods, so the big difference will be the ground plane. 

 We're hosting Thanksgiving this year, so I have a few other pressing projects to complete before next week, so building will FINALLY commence the weekend after when all the company is gone. Or I might just 
	

	
	
		
		

		
		
	


	




 for a while in the basement, but I suspect the smell of solder will give me away... LOL!


----------



## tomb

Quote:


  Originally Posted by *BoilermakerFan* /img/forum/go_quote.gif 
_Small progress today, I finished matching my small signal transistors at lunch. I ended up with a total spread of 20 points on one BJT combo, a 17 point spread on the other BJT combo, and 6 point spread across all transistors for the MOSFET-MAX. All the CCS transistors are identically matched quads. 
	

	
	
		
		

		
		
	


	




 I am very, very tempted to order a MiniMAX board for the MOSFET-MAX for the better ground plane, but my concern is the closer spacing of components with my relatively high bias currents. I will be implementing the other changes to my MAX boards as mods, so the big difference will be the ground plane. 

 We're hosting Thanksgiving this year, so I have a few other pressing projects to complete before next week, so building will FINALLY commence the weekend after when all the company is gone. Or I might just 
	

	
	
		
		

		
		
	


	




 for a while in the basement, but I suspect the smell of solder will give me away... LOL!_

 

The regular MAX board is still the preferred choice for a MOSFET-MAX.


----------



## BoilermakerFan

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_The regular MAX board is still the preferred choice for a MOSFET-MAX.
	

	
	
		
		

		
			



_

 

Thanks Tom. I was concerned about the extra heat since I'll be running about 3 times the bias current.


----------



## amphead

Still enjoying my Millett Max thoroughly, when I get the time. Sounds like you will be building another one soon BMF.  The Mojo thread makes the front page again!


----------



## tomb

Quote:


  Originally Posted by *amphead* /img/forum/go_quote.gif 
_Still enjoying my Millett Max thoroughly, when I get the time. Sounds like you will be building another one soon BMF.  The Mojo thread makes the front page again!_

 

Yes, thanks - and a V1.2 PCB is in the works.


----------



## BoilermakerFan

Quote:


  Originally Posted by *amphead* /img/forum/go_quote.gif 
_Still enjoying my Millett Max thoroughly, when I get the time. Sounds like you will be building another one soon BMF.  The Mojo thread makes the front page again!_

 

I have two BJT units in the works and a MOSFET-MAX, but the MOSFET is going to hold out for the V1.2 board. 

 Just went and visited my favorite local body shop for an estimate on my car (wife induced damage) and he said he can paint the yellow zinc plated NABU chassis with no problems. So when the car goes in, there _might_ be a couple of chassis in the trunk too.


----------



## slowpogo

I have a question about the Muse ES caps. On the Max Boutique page (and many places in this thread), it is said that they have amazing deep bass slam. But it is also said on that page that they can "approach Black Gates for detail and neutrality."

 I would think those statements are somewhat mutually exclusive. Deep bass with good slam, I would say the caps are bass-heavy, not neutral. What am I missing?


----------



## BoilermakerFan

Quote:


  Originally Posted by *slowpogo* /img/forum/go_quote.gif 
_I have a question about the Muse ES caps. On the Max Boutique page (and many places in this thread), it is said that they have amazing deep bass slam. But it is also said on that page that they can "approach Black Gates for detail and neutrality."

 I would think those statements are somewhat mutually exclusive. Deep bass with good slam, I would say the caps are bass-heavy, not neutral. What am I missing?_

 

I don't think it is mutually exclusive. The Muse ES caps have the ability to provide tremendous bass slam when paired with certain tubes, BJT DB buffers and the VitQ bypass caps. When the same caps are used with the 2238/968 pairs and FK6 tubes, then you 'll see a little less bass slam, but the reward is the detail and neutrality approaching the BG NXs. Once I get my two BJT boards populated, one will have Muse ES caps, the other will have Silmic IIs. The third board was designated to be a MOSFET build, but I'm waiting for the V1.2 board for it. It will be built with Cerafine caps. All three builds will use the VitQ .18s for by-pass duty. 

 I'll be able to swap 11 pairs of BJTs in and out and I have 3 MOSFET pairs in addition to the 11 BJTs for MOSFET-MAX so I will be able to closely audition many cap/DB combos. Unfortunately, I didn't think to double up a few of the more popular combos so I could do side-by-side, real-time swaps. I will be able to swap between the two BJT amps in real-time using the same source and same headphones and when I find a combo I really like, I'll swap the DBs to the other board and listen again. Eventually I'll boil down my favorite combo for the two BJT boards and I'll order duplicates if it ends up being one single DB set, but I doubt that will happen since tubes will also play a factor, so I suspect I'll have a favorite tube/Db combo for the Muse caps that is different than the Cerafines or Silmic IIs. Oh, I forgot, I have the Muse KZs and another cap combo too, so I may use the KZs instead of the Silmics since the Silmics are supposed to be so close to the Cerafines.


----------



## tomb

BMF is correct for the most part. However, the context of saying that is relative to the bypass film cap. The ES's have tremendous bass slam - no doubt. However, they are also a very transparent cap - more so than BG's, for instance (MHO). So, there is potential for a great system if paired with an optimum film cap. When paired with Wima's or even more so - the Russian K42's - bass slam is tremendous. However, VitQ's bring out enormous detail. At the same time, VitQ's cut the bass response to a certain degree.

 So, it's the combination of caps that I was commenting on. With many bypass caps, the ES's live up to their reputation of bass slam. With VitQ's, IMHO, the detail is such that they compete well with Black Gates. This is because while the combo still lacks a small amount of detail compared to the BG's, the greater transparency gives them an added edge.

 Anyway, none of this is contradictory - it's just that the combinations yield sometime unique results.


----------



## slowpogo

I decided to measure the voltage across CA7 when my Max is turned on. It starts low and slowly climbs to 23.4v, stays there several seconds and then falls down to the 13.5v bias level. I did this a few times and it was the same on both caps.

 So if I wanted I could try some 25v caps in CA7 (like the Muse KZ), and unless the amp malfunctions they will be fine, correct?

 And if the amp does malfunction what is the worst that can happen? They will see 27v and wear out very quickly, or worse than that? There doesn't seem to be much risk, esp. with the Muses being not expensive at all.


----------



## cetoole

Honestly, you could probably get away with it just fine, and I have done the same measurements. Neither Tom or I will suggest doing so though (think I am safe putting these words in that particular horse's mouth).


----------



## slowpogo

Well, based on that idea I threw the 1000uf Black Gates I used to have in CA2 into CA7. I currently have some BG FK series in CA2. (I have been experiencing some kind of cap-rolling mania lately -- seriously, sometimes I question whether DIY is healthy for me!)

 Sounds great! Basically like the 680uf Black Gates, but the bass is a little deeper, which you would expect with the lower corner frequency. I also have always had doubled-up Vitamin Qs bypassing CA7 (0.44uf) so that probably helps with the extra capacitance.

 So there's an idea for y'all...it will never be officially endorsed, but go ahead and get 4 of the 1000uf 25v Black Gate NX caps for CA2 and CA7. It will be just as good as "can't miss build #1" but with deeper, liquid bass.


----------



## slowpogo

Well, based on that idea I threw the 1000uf Black Gates I used to have in CA2 into CA7. I currently have some BG FK series in CA2. (I have been experiencing some kind of cap-rolling mania lately -- seriously, sometimes I question whether DIY is healthy for me!)

 Sounds great! Basically like the 680uf Black Gates, but the bass is a little deeper, which you would expect with the lower corner frequency. I also have always had doubled-up Vitamin Qs bypassing CA7 (0.44uf) so that probably helps with the extra capacitance.

 So there's an idea for y'all...it will never be officially endorsed, but go ahead and get 4 of the 1000uf 25v Black Gate NX caps for CA2 and CA7. It will be just as good as "can't miss build #1" but with deeper, liquid bass.


----------



## cetoole

Quote:


  Originally Posted by *slowpogo* /img/forum/go_quote.gif 
_Well, based on that idea I threw the 1000uf Black Gates I used to have in CA2 into CA7. I currently have some BG FK series in CA2. (I have been experiencing some kind of cap-rolling mania lately -- seriously, sometimes I question whether DIY is healthy for me!)

 Sounds great! Basically like the 680uf Black Gates, but the bass is a little deeper, which you would expect with the lower corner frequency. I also have always had doubled-up Vitamin Qs bypassing CA7 (0.44uf) so that probably helps with the extra capacitance.

 So there's an idea for y'all...it will never be officially endorsed, but go ahead and get 4 of the 1000uf 25v Black Gate NX caps for CA2 and CA7. It will be just as good as "can't miss build #1" but with deeper, liquid bass._

 

Glad it worked out for you. The only real concern is possibly in an error state, and then long term longevity. BTW, you know there is a 1500uf 16v BG NX which is the same size as the ones you are using, and would be suitable for cathode bypass.


----------



## slowpogo

Quote:


  Originally Posted by *cetoole* /img/forum/go_quote.gif 
_Glad it worked out for you. The only real concern is possibly in an error state, and then long term longevity. BTW, you know there is a 1500uf 16v BG NX which is the same size as the ones you are using, and would be suitable for cathode bypass._

 

I think the cap you speak of is actually 10v - still usable? And I'm guessing the main benefit there would be more bass?

 I'll probably stick with the FK's there...plenty of bass as it is, and the FK has a more direct, airy sound that acts as good "preparation" for the more rich NX at the output. Using NX for both, I found the sound to be very dynamic and detailed but lacking impact and bite. Percussion sounded a bit too polite for example.


----------



## cetoole

Eh, yeah, you are right, it is 10v. Still usable though, it would have to be a really weird problem to get anywhere near that voltage on the cathode.


----------



## soloz2

for those using a Max to drive k701's what bias have you set the diamond buffers to?

 I've got a Can't miss #1 with GE style side ring 12AE6 tubes that will be primarily used with k701's, but I don't have any k701's on hand to tweak the amp. I would imagine higher bias would probably be better, but around 85-90mV seems to sound pretty good with my Senns.


----------



## cetoole

I have K701, and while they definitely are not my favorite cans, even of my dynamics, they can certainly be driven just fine with normal bias levels. I run my amp a bit hotter than normal, but 50mA is just fine.


----------



## Dan55

Hi all,

 I've been working on this build for a few weeks now, following the excellent instructions at diyforums. I plugged in my board last night and was pleased that nothing exploded (as happened during my attempt at an amp-6) but dismayed that nothing worked either. The tube lights don't illuminate, and I have no voltage between v+ and gnd. 

 I wired the kubiconn jack according to the pictures in the wiring and assembly section of diyforums, as near as I can tell (I'm using a three-position terminal block and left the positions nearest the non-existent fuse empty). Anyone have any thoughts? Thanks.


----------



## TimJo

Can you post some pictures?


----------



## ruZZ.il

Yep. Pics would help. Also measurements.
 Measure AC at the input. Is PF1 present? Check the orientation of the diodes.. eh.. 2 many things.. pics.. pics.. try get a nice close up, specially the power supply area, top and bottom.


----------



## Dan55

Thanks for the replies! I'll try to post some pics when I get back to my board in a few days. Being out of town, I was just wondering if there was some common wiring problem that could be easily fixed (I was assuming that no electricity was getting to the amp). 

 Is there any way to ensure that I'm connecting the correct lugs on the jack to the correct terminals (something similar to using a multimeter and interconnect to determine which lug on a stereo jack corresponds to left/right/ground? I obviously know very little about electronics but have completed a few projects by browsing these pages. Thanks again.


----------



## tomb

Quote:


  Originally Posted by *Dan55* /img/forum/go_quote.gif 
_Thanks for the replies! I'll try to post some pics when I get back to my board in a few days. Being out of town, I was just wondering if there was some common wiring problem that could be easily fixed (I was assuming that no electricity was getting to the amp). 

 Is there any way to ensure that I'm connecting the correct lugs on the jack to the correct terminals (something similar to using a multimeter and interconnect to determine which lug on a stereo jack corresponds to left/right/ground? I obviously know very little about electronics but have completed a few projects by browsing these pages. Thanks again._

 

You should be able to measure the voltage at V+ and GND. That's just the voltage coming off the linear-regulated power supply and should tell you at least that your power is good and hooked up OK.

 As for the rest, a common mistake is not to populate or jumper R1 - the heater resistor. If that position is left open, it would do just what you've noticed: no power to the tubes, no buffer current, nada. The PS should still measure good voltage (at V+ and GND), though - probably anywhere from 25 to 29VDC, depending on the position of the trimmer.


----------



## Dan55

Thanks Tomb. I have R1 populated with the resistor specified on the BOM. I've attached some pictures (I think). Hope they are helpful. 

 As for measurements, I'm still getting nothing between v+ and gnd. With my multimeter set to 200v AC I'm getting a reading of 1 at both terminal blocks with the positive end and .7 with the negative end (I have no idea what this means).


----------



## cetoole

Dan, two of your rectifier diodes are in backwards (the left ones as seen in your first picture). You need to line the tab on them up with the thick markings on the silkscreen.


----------



## Dan55

Quote:


  Originally Posted by *cetoole* /img/forum/go_quote.gif 
_Dan, two of your rectifier diodes are in backwards (the left ones as seen in your first picture). You need to line the tab on them up with the thick markings on the silkscreen._

 

Thanks cetoole! I haven't had much luck removing the diodes, but hopefully the amp is salvageable. It's good to know what went wrong.


----------



## cetoole

Quote:


  Originally Posted by *Dan55* /img/forum/go_quote.gif 
_Thanks cetoole! I haven't had much luck removing the diodes, but hopefully the amp is salvageable. It's good to know what went wrong._

 

It might be easiest (I know it is for me) to flood the area with solder, so as to bridge the two diode legs, and then heat them both at the same time and pull the diode out. Careful, because the tab will get very hot. If you have spares, and it wouldnt be a bad idea to just do this, but cut the legs off and remove them by heating and pulling separately.


----------



## Dan55

Quote:


  Originally Posted by *cetoole* /img/forum/go_quote.gif 
_It might be easiest (I know it is for me) to flood the area with solder, so as to bridge the two diode legs, and then heat them both at the same time and pull the diode out. Careful, because the tab will get very hot. If you have spares, and it wouldnt be a bad idea to just do this, but cut the legs off and remove them by heating and pulling separately._

 

Thanks for your help. I used the second method mostly by accident (in my haste I broke one of the diode legs). I just put in another order to Mouser, so I'm sure I'll be back soon with some more questions.


----------



## slowpogo

I'm wondering if anyone's noticed the expensive 12AE6 tubes being sold on ebay, advertised as "Millett Hybrid upgrade tubes." They're selling for $24-48 for a pair!

 The only thing that might ever tempt me to buy some is that he's selling Westinghouse and Tung-Sol tubes, which I haven't heard and am very curious about. However, I don't know if they're really Westinghouse-made or actually GE/RCA whatever.

 Also he has some Sylvanias built to "low-noise GTE specifications." Is this just snake oil, or does anyone know what that means?


----------



## tomb

Quote:


  Originally Posted by *slowpogo* /img/forum/go_quote.gif 
_I'm wondering if anyone's noticed the expensive 12AE6 tubes being sold on ebay, advertised as "Millett Hybrid upgrade tubes." They're selling for $24-48 for a pair!

 The only thing that might ever tempt me to buy some is that he's selling Westinghouse and Tung-Sol tubes, which I haven't heard and am very curious about. However, I don't know if they're really Westinghouse-made or actually GE/RCA whatever.

 Also he has some Sylvanias built to "low-noise GTE specifications." Is this just snake oil, or does anyone know what that means?_

 

It's mostly snake oil, as far as I can see. However, the matching service is useful if he's doing that, but I would expect to see $5 per pair for the matching service - or something like that. That would be closer to the going rate. $24 to $48 is ... well, no comment. It's flattering that he specifically mentions the MAX, but not if he prices things like that.

 AFAIK, Westinghouse did not make Millett tubes: GE, RCA, Tung-Sol, and Sylvania, that's it. I have quite a few Westinghouse's and they're a mix like everyone else's.


----------



## amphead

Yeah, it's flattering indeed, and most purchasers read this thread so "good luck" for his marketing technique.


----------



## TimJo

Quote:


  Originally Posted by *slowpogo* /img/forum/go_quote.gif 
_Also he has some Sylvanias built to "low-noise GTE specifications." Is this just snake oil, or does anyone know what that means?_

 

This seems like snake oil to me. GTE was the parent company for Sylvania during the 60's and based on what this says, General Telephone acquired Sylvania to take advantage of _their_ technology.

_In 1959 General Telephone and Sylvania Electric Products merged, and the parent's name was changed to General Telephone & Electronics Corporation (GT&E). The merger gave Sylvania - a leader in such industries as lighting, television and radio, and chemistry and metallurgy - the needed capital to expand. For General Telephone, the merger meant the added benefit of Sylvania's extensive research and development capabilities in the field of electronics._

 If a telephone company acquired Sylvania, doesn't it seem funny that they would be creating the specifications for a vacuum tube that was used in car radios, something they have no prior experience or interest in?


----------



## slowpogo

I'm curious about "double bypassing." What about bypassing a Cerafine with both a Vitamin Q and a 0.47 Black Gate NX? Would this yield the benefits of both bypass caps, or would it just be a crapshoot? I know it would introduce more "phase distortion" in theory, but is this something you could actually hear or just measure?


----------



## Dan55

Quote:


  Originally Posted by *cetoole* /img/forum/go_quote.gif 
_Dan, two of your rectifier diodes are in backwards (the left ones as seen in your first picture). You need to line the tab on them up with the thick markings on the silkscreen._

 

Hi all,

 I switched the rectifier diodes per cetoole's advice but am still getting no response from the amp (0 dcv between gnd and v+). I was just wondering if anything else was obviously out of place or if there was something else I should try.

 Thanks!
 Dan


----------



## fran

1. Are you getting absolutely 0v or are you getting a tiny few millivolts like you do when you turn on your DMM with the leads not touching anything? ie have you a dead short between + and GND?

 2. Also you don't have the onboard fuse installed, but have you installed the jumpers to get around this?

 3. Can you measure the AC where it enters the millet board so that you know you have power that far?


 Fran


----------



## cetoole

OK, I have a guess, and it isnt good, but here goes: when you had DR1D in backwards, that effectively shorted the wallwart's output, and probably blew an internal protection fuse, which means that wallwart is now basically toast. Let us do some measurements though, and if you can, please dig up another source of AC voltage you can use to make sure your meter is working properly. Basically, I would like you to unplug the wallwart from the Max, and try and measure the AC voltage on the output with no load, then do the same with another AC wallwart which is known good.


----------



## Dan55

Thanks for the responses! I'm starting to feel rather silly, as I clearly have no idea what is going on here. I should probably start by saying that I did get some life out of the amp while taking measurements with a different wallwart. At the risk of ruining the amp, I plugged in a wallwart with input AC 120v and output of *DC* 12V. The LEDs turned on and I read about 12v between v+ and gnd. I have never understood where the conversion between AC and DC occurs in the power supply; can I use an AC-DC wallwart?

 Regarding the Triad specified on the BOM, I took some measurements using my radioshack multimeter (I never thought I would use it for anything but the construction of a CMOY). The lowest setting is AC 200v, and I read about .6 both at the terminals on the board and by just touching a probe to the end of the wallwart without plugging it in. This again confounds me, as the output should be only 24VAC.


----------



## fran

OK, you really need to feed this with 24V AC, not DC. Also feeding it with 12VDC won't give you the readings you want.

 Plug in the AC wallwart to your wall socket. Set your multimeter to volts AC at whatever setting is closest to 24V. Measure the voltage at the jack at the end of the wallwarts cable. What do you get there?


 Fran


----------



## tomb

"At the risk of ruining the amp, ..."

 Careful here - you're close to doing just that.
	

	
	
		
		

		
			





 Go plugging in things that are not designed for the amp and expect disastrous results.

 Listen to Colin and Fran and do what they say before you try plugging in a totally alien power supply again. No harm can be done to the amp if you make certain to measure the walwart by itself and report back first.


----------



## Dan55

Sorry for the confusion; I meant to say that if I measure just the jack without plugging it into the amp, I get a reading of 0.6V. This is with the multimeter set to 200V. It jumps from .1 to .6 when I touch the jack with one of the probes.

 I knew I was asking for trouble by plugging in the AC-DC wallwart; I'll try to refrain from working with such equipment at 2:00 am.


----------



## ruZZ.il

Sounds like a dead transformer. Maybe fixable, maybe not, but I'm not sure I'd get into it. As for sticking in foreign power sources, I'd show more caution, but for now I doubt you've actually done any damage with the 12vDC you stuck in. I wouldn't sweat that. Now that you've re-orientated your input diodes, I'd go about getting another 24vAC source and trying again.


----------



## cetoole

Quote:


  Originally Posted by *ruZZ.il* /img/forum/go_quote.gif 
_Sounds like a dead transformer. Maybe fixable, maybe not, but I'm not sure I'd get into it. As for sticking in foreign power sources, I'd show more caution, but for now I doubt you've actually done any damage with the 12vDC you stuck in. I wouldn't sweat that. Now that you've re-orientated your input diodes, I'd go about getting another 24vAC source and trying again._

 

Probably not, as DC will just pass through the rectifiers and regulator, as that will be unable to regulate so act just like a small resistor. That said, I agree with Beefy that it isnt a good idea to do this. Sounds like you need a new 24vac wallwart.


----------



## Dan55

Okay. I'll pick up a new wallwart and try to learn something about electronics in the meantime. Thanks very much for all your help.


----------



## slowpogo

I think I've reached the end of my recent tube-rolling mental illness. Here's what I ended up with:

 CA2: Black Gate FK 1000uf 16v
 CA7: Black Gate NX 680uf 35v
 CA8: Vitamin Q 0.18uf
 CA9: Mundorf Silver/Oil 0.33uf

 The Mundorfs are big but actually fit fine, if you don't mind the transistor trimpots being obscured. You can always pull the caps back a little if you need to.

 Those suckers are $32 each, and though I cringed as I ordered them (as I said, it must be a mental illness of sorts), I don't regret it at all...they're worth it, and very obviously better than Vitamin Qs in that spot. I've read a bunch of "capacitor shootout" articles and the Mundorf Silver/Oil seemed to be a favorite of everyone, most thinking they were even better than the more expensive Silver/Gold.

 Really nice...much more 3d, better detail and separation, a balanced but sweet and musical sound that makes me want to stop analyzing and keep listening.

 Anyone looking to splurge, I really doubt you wouldn't like them or think they weren't a big step up from the Vitamin Q's.

 The FK's work great in CA2; they are a little dry but have a faster, more direct sound, while the NX's seem slightly distant and polite to me. But the small-value Vitamin Q did the perfect thing, added just a touch of high-end sparkle and midrange richness to the FK. I did not notice any negative effect on the bass, it still sounds deep, fat and tight.


----------



## soloz2

Quote:


  Originally Posted by *slowpogo* /img/forum/go_quote.gif 
_I think I've reached the end of my recent tube-rolling mental illness. Here's what I ended up with:

 CA2: Black Gate FK 1000uf 16v
 CA7: Black Gate NX 680uf 35v
 CA8: Vitamin Q 0.18uf
 CA9: Mundorf Silver/Oil 0.33uf

 The Mundorfs are big but actually fit fine, if you don't mind the transistor trimpots being obscured. You can always pull the caps back a little if you need to.

 Those suckers are $32 each, and though I cringed as I ordered them (as I said, it must be a mental illness of sorts), I don't regret it at all...they're worth it, and very obviously better than Vitamin Qs in that spot. I've read a bunch of "capacitor shootout" articles and the Mundorf Silver/Oil seemed to be a favorite of everyone, most thinking they were even better than the more expensive Silver/Gold.

 Really nice...much more 3d, better detail and separation, a balanced but sweet and musical sound that makes me want to stop analyzing and keep listening.

 Anyone looking to splurge, I really doubt you wouldn't like them or think they weren't a big step up from the Vitamin Q's.

 The FK's work great in CA2; they are a little dry but have a faster, more direct sound, while the NX's seem slightly distant and polite to me. But the small-value Vitamin Q did the perfect thing, added just a touch of high-end sparkle and midrange richness to the FK. I did not notice any negative effect on the bass, it still sounds deep, fat and tight._

 

did you try a Blackgate NX in CA2 and leaving CA9 blank?


----------



## slowpogo

Quote:


  Originally Posted by *soloz2* /img/forum/go_quote.gif 
_did you try a Blackgate NX in CA2 and leaving CA9 blank?_

 

Yes, that's what I originally had (can't miss build #1). The FK/Vitamin Q is not really "better," just more direct and more to my liking.


----------



## Forte

This "Stay tuned for the MAX pcb V1.2 - available in a few weeks!" has been on the Beezar website for a while.

 Any news on when the new boards will be available and what improvements are there being made to them?


----------



## Daveze

Rumor is that it picks up some of the power supply and layout improvements from the MiniMAX. I'm not too sure beyond that.


----------



## Bismar

Not quite a rumor, see here for tombs comments on a thread.

http://www.head-fi.org/forums/5082613-post16.html


----------



## Daveze

I knew...I was just playing it cool


----------



## johnwmclean

First post here in this thread, I’m planning on building one of these. What’s news with getting a board? Where can I get one?


----------



## tomb

We're working on the new version of the Millett Hybrid MAX as we speak.

 The new V1.2 of the "regular" MAX PCB will incorporate the same power supply as the MiniMAX.

 In addition, there will be provision for onboard mounting and wiring of a BantamDAC. An onboard relay will be used to provide convenient switching between "normal" RCA inputs and the BantamDAC.

 The technical issues are that we are going in the other direction as some with the relay and headphone relay - toward a lower parts count with commonality between the two relays. We've confirmed that the relay and smaller parts count will work in both positions, but as with anything new, there are a couple of kinks we still need to work out.

 When that's done, we should be ordering more boards and will have them in stock at Beezar - Jeff Rossell will have them, too.


----------



## Beefy

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_In addition, there will be provision for onboard mounting and wiring of a BantamDAC. An onboard relay will be used to provide convenient switching between "normal" RCA inputs and the BantamDAC._

 

Sweet!


----------



## Dr Evil Dan

Maybe a noob question: Are the BOMs updated for new versions of the boards? It seems like 1.2 will be bringing some big changes.


----------



## tomb

Quote:


  Originally Posted by *Dr Evil Dan* /img/forum/go_quote.gif 
_Maybe a noob question: Are the BOMs updated for new versions of the boards? It seems like 1.2 will be bringing some big changes._

 

Kind of jumping the gun aren't we?
	

	
	
		
		

		
		
	


	







 When the board is ready, we'll update the BOM.


----------



## BoilermakerFan

Quote:


  Originally Posted by *Dr Evil Dan* /img/forum/go_quote.gif 
_Maybe a noob question: Are the BOMs updated for new versions of the boards? It seems like 1.2 will be bringing some big changes._

 

Tom and Colin are really good about those details. I suspect the revised v1.2 BOMs will be updated once the final component requires are determined and the boards are ready for sale.

 Edit: Man, Tom must have a faster connection than I do... Ha ha ha...


----------



## BoilermakerFan

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Kind of jumping the gun aren't we?
	

	
	
		
		

		
		
	


	







 When the board is ready, we'll update the BOM.
	

	
	
		
		

		
		
	


	


_

 

But what if we want to order parts on assumptions, maybes, and secret information?


----------



## soloz2

I know all the recent fuss has been in the MiniMax thread, but I thought I'd post something more here 
	

	
	
		
		

		
		
	


	









 Can't Miss #1 with OptiVol, pre-out and room for future additions.


----------



## tomb

Quote:


  Originally Posted by *soloz2* /img/forum/go_quote.gif 
_I know all the recent fuss has been in the MiniMax thread, but I thought I'd post something more here 
	

	
	
		
		

		
		
	


	









 Can't Miss #1 with OptiVol, pre-out and room for future additions._

 

Very nice! How did you do that power switch?

 Also - did you do those Grado's? They look fantastic.


----------



## pinkfloyd4ever

I was wondering about the Grados too...they look like Headfiled HF-1's maybe?


----------



## Forte

Quote:


  Originally Posted by *soloz2* /img/forum/go_quote.gif 
_I know all the recent fuss has been in the MiniMax thread, but I thought I'd post something more here 
	

	
	
		
		

		
		
	


	




 Can't Miss #1 with OptiVol, pre-out and room for future additions._

 

Looks Great...

 X2 for more info on power switch.

 Would also like to know what case you used and can we get a look inside?


----------



## BoilermakerFan

Quote:


  Originally Posted by *soloz2* /img/forum/go_quote.gif 
_I know all the recent fuss has been in the MiniMax thread, but I thought I'd post something more here 
	

	
	
		
		

		
		
	


	





 Can't Miss #1 with OptiVol, pre-out and room for future additions._

 

Looks great man! How do you like the OptiVol versus the ALPS in your other MAX? Did you bump up the output resistors to around 50K to get more attenuation range? 


 I will be building my two BJT MAXes, but the MOSFET-MAX is waiting for the v1.2 PCB. I have way too much time matching parts for the MOSFET build to not wait for the improved board since I need the integrated BantamDAC at the PC. The last remaining pieces that were on backorder forever from Mouser finaly showed up last week too.


----------



## soloz2

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Very nice! How did you do that power switch?

 Also - did you do those Grado's? They look fantastic.
	

	
	
		
		

		
			



_

 

Thanks! It's a latching switch so it does everything, worth the extra few $$ IMHO 
	

	
	
		
		

		
		
	


	




 Yes, well partially. Aura actually made the cups. They are rosewood. They were a little bit of a learning experience for him as they were the 2nd cups he made and I pretty much told him to do whatever he thought was best. I installed them and put the screens in. There is some room for improvement cosmetically, but they sound good. 

  Quote:


  Originally Posted by *pinkfloyd4ever* /img/forum/go_quote.gif 
_I was wondering about the Grados too...they look like Headfiled HF-1's maybe?_

 

Nope, SR225's. I still need to replace the stock cable and headband though... just haven't had time. I do have a nice leather band and they'll most likely get Cardas 
	

	
	
		
		

		
		
	


	




  Quote:


  Originally Posted by *Forte* /img/forum/go_quote.gif 
_Looks Great...

 X2 for more info on power switch.

 Would also like to know what case you used and can we get a look inside?_

 

I might be persuaded to pull the top off for a pic. The enclosure is a Parmetal 20 series 12"x12"x3" I got a custom back panel that is essentially the same as the front, just without the overhang.

  Quote:


  Originally Posted by *BoilermakerFan* /img/forum/go_quote.gif 
_Looks great man! How do you like the OptiVol versus the ALPS in your other MAX? Did you bump up the output resistors to around 50K to get more attenuation range? 


 I will be building my two BJT MAXes, but the MOSFET-MAX is waiting for the v1.2 PCB. I have way too much time matching parts for the MOSFET build to not wait for the improved board since I need the integrated BantamDAC at the PC. The last remaining pieces that were on backorder forever from Mouser finaly showed up last week too._

 

I really like the OptiVol. it seems to lower the noise floor and is very smooth.
 I did change the resistors in mine, I forget what I used though...


----------



## tomb

Here's the current layout from cetoole for MAX V1.2:






 It will change slightly from this layout. The relays will both be 24V relays. Use of a 78L24 regulator (TO-92) allows deletion of the zener-resistor-BD139 regulator used on previous MAXes and the MiniMAX. Colin felt this was necessary because the back of the board is pretty cramped once the BantamDAC is mounted, and we'd rather have one relay type for the whole board. Tests have indicated that offset spikes both on turn-on (controlled by the delay) and turn-off are almost immeasureable. This is in stark contrast to the present relays which still spike on turn off - albeit harmlessly under load. Colin will most likely be updating the relay portion of the layout at the headphone position. We'll post that when available.

 This simplifies the potential parts count for both of the relays. We have a parts selection already worked out that provides 45 seconds delay from a cold start, with at least 30 seconds delay still retained upon a fast hot-start (turned off and then turned back on).

 The Bantam will reside in the rectangular area in back, with ~45 degree terminal blocks for both RCA inputs and an output-input connection from the Bantam. A single, two-position terminal block will allow controlling the relay switching (between RCA-input or Bantam-input) with a simple back-plate mounted SPST switch. Of course, there is no delay on the relay for the input switching.

 The board also uses the new low-noise power supply first premiered on the MiniMAX. It also provides cooling holes under all the heat sinks. Beyond that, it provides the same flexibility in part selection as the regular MAX. Although, we are probably going to try to steer everyone toward a MOSFET version on the MAX V1.2 and BJT versions on the MiniMAX. YMMV, of course.

 Here's the same layout showing how the BantamDAC will reside on the board:






 Comments are welcome, of course.


----------



## Beefy

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Comments are welcome, of course.
	

	
	
		
		

		
		
	


	


_

 

Only that I will be really keen to see how everything fits on the back panel of the default Hammond case. Otherwise, looks really great!


----------



## tomb

Quote:


  Originally Posted by *Beefy* /img/forum/go_quote.gif 
_Only that I will be really keen to see how everything fits on the back panel of the default Hammond case. Otherwise, looks really great! 
	

	
	
		
		

		
		
	


	


_

 

Well, we're only adding a Type B USB jack and a 1/4" hole for a toggle switch. There's gracious plenty room for that on the MAX-size case.


----------



## srserl

If I ever build another mosfet max, I will probably look into a case that is longer front to back. I had trouble with the tip jacks sticking into the case too far, so I spaced the back plate out by putting a 2.5mm abs plastic plate between the case and bezel, then another small piece of 2.5mm abs between the tip jacks and the back plate. This also gave a little more room for the power jack which fit before the mod, but now has plenty of clearance.

 Scott


----------



## Bismar

Nice, why's there 3 input terminals? Also won't the Bantam get in the way of wires going into the top two input blocks?

 Sooo when can we expect to see a symmetrical version


----------



## Beefy

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Well, we're only adding a Type B USB jack and a 1/4" hole for a toggle switch. There's gracious plenty room for that on the MAX-size case._

 

More from the height of the Bantam module, getting close to the tip jacks and input wiring.

  Quote:


  Originally Posted by *srserl* /img/forum/go_quote.gif 
_If I ever build another mosfet max, I will probably look into a case that is longer front to back. I had trouble with the tip jacks sticking into the case too far, so I spaced the back plate out by putting a 2.5mm abs plastic plate between the case and bezel, then another small piece of 2.5mm abs between the tip jacks and the back plate. This also gave a little more room for the power jack which fit before the mod, but now has plenty of clearance._

 

Before building my Mini Maxes, I toyed with the idea of doing a MOSFET Max in a Hammond 1455T2201. Exactly the same case, with an extra 5cm length. It would leave room at the back for all the wiring...... and perhaps even room at the front for a stepped attenuator 
	

	
	
		
		

		
		
	


	




  Quote:


  Originally Posted by *Bismar* /img/forum/go_quote.gif 
_Nice, why's there 3 input terminals? Also won't the Bantam get in the way of wires going into the top two input blocks?_

 

Input from Bantam, input from RCA jacks, input for relay switch, optional front input like on the Mini Max (this front one looks like it is not switched by the relay).

 And tomb did specifically say 45 degree terminal blocks. Looks like it will be OK, so long as you can get the jacks in a sensible spot.


----------



## tomb

Quote:


  Originally Posted by *Bismar* /img/forum/go_quote.gif 
_Nice, why's there 3 input terminals?_

 

I'm going to assume you mean the terminal block by the pot as the "3rd" input terminal. There's nothing saying you have to install a block there, but it does give extra flexibility at no penalty to the board layout.
  Quote:


 Also won't the Bantam get in the way of wires going into the top two input blocks? 
 

No. The tallest thing in the way of the RCA leads would be the Bantam's C7 cap, and that's well away from the terminal blocks. Remember also, that this isn't the MiniMAX. The case is 2" tall and the board will have at least 30-35mm free and clear above it. The Bantam's C7 is only 12.5mm high.

 Also, as mentioned above - the terminal blocks we're proposing are 145 degree terminal blocks - the wiring enters as much from above as it does from the side:





  Quote:


 Sooo when can we expect to see a symmetrical version  
 

I'm not sure I understand this one. Cetoole's layouts are eminently symmetrical. This one is different in the back to make room for the Bantam.

 Notice that the board is carried the entire length of the Hammond-style case. The notch is there to make RCA preamp outputs or speaker terminals easier, since they coulf be fed from the terminal block pads underneath at the headphone jack. Or, the notch could be used for tip jacks fed through to the bottom. This is all because there won't be any clearance from the back plate if the bezels are not used. That said, remember that if the board is placed in the 3rd slot, all the tip jacks can be mounted beneath the level of the board, anyway.

 It may help to refer to the MAX website to refresh our memory on how the MAX is put together in the Hammond case.
	

	
	
		
		

		
		
	


	





 EDIT: Beefy beat me to it. Of course, I think the regular style Hammond will work fine (or another I have in mind for a surprise), but there's no reason you can't go all the way to a "T" size case, too.

 EDIT2: Sorry - I guess it's the 1455T_*2201*_, as opposed to the 1455T*1601*, the MAX standard.

 Believe me, though, the Bantam will even fit under the board in the third slot if the C7 cap is turned horizontal. As noted, we're going to push this as the MOSFET option, anyway, since that's not very realistic for the MiniMAX. The PCB would then be located near the bottom of the case, giving almost 1-3/4" high and 6" wide of back plate to work with. There's plenty of room back there, IMHO.


----------



## Beefy

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_No. The tallest thing in the way of the RCA leads would be the Bantam's C7 cap, and that's well away from the terminal blocks. Remember also, that this isn't the MiniMAX. The case is 2" tall and the board will have at least 30-35mm free and clear above it. The Bantam's C7 is only 12.5mm high._

 

Check!


----------



## BoilermakerFan

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Here's the current layout from cetoole for MAX V1.2:



 It will change slightly from this layout. The relays will both be 24V relays. Use of a 78L24 regulator (TO-92) allows deletion of the zener-resistor-BD139 regulator used on previous MAXes and the MiniMAX. Colin felt this was necessary because the back of the board is pretty cramped once the BantamDAC is mounted, and we'd rather have one relay type for the whole board. Tests have indicated that offset spikes both on turn-on (controlled by the delay) and turn-off are almost immeasureable. This is in stark contrast to the present relays which still spike on turn off - albeit harmlessly under load. Colin will most likely be updating the relay portion of the layout at the headphone position. We'll post that when available.

 This simplifies the potential parts count for both of the relays. We have a parts selection already worked out that provides 45 seconds delay from a cold start, with at least 30 seconds delay still retained upon a fast hot-start (turned off and then turned back on).

 The Bantam will reside in the rectangular area in back, with ~45 degree terminal blocks for both RCA inputs and an output-input connection from the Bantam. A single, two-position terminal block will allow controlling the relay switching (between RCA-input or Bantam-input) with a simple back-plate mounted SPST switch. Of course, there is no delay on the relay for the input switching.

 The board also uses the new low-noise power supply first premiered on the MiniMAX. It also provides cooling holes under all the heat sinks. Beyond that, it provides the same flexibility in part selection as the regular MAX. Although, we are probably going to try to steer everyone toward a MOSFET version on the MAX V1.2 and BJT versions on the MiniMAX. YMMV, of course.

 Here's the same layout showing how the BantamDAC will reside on the board:


 Comments are welcome, of course.
	

	
	
		
		

		
		
	


	


_

 

Hmmm... I challenge Colin to design a RIAA corrected phono input stage that fits in the same dimensional area as the BantamDAC! Height is open for me, I have plenty of room. 
	

	
	
		
		

		
		
	


	




 Tom, just put me down for one of the new boards when they're ready. 

 Have you had a chance to demo any of the other BJTs in the DBs yet? I've been a little out of the loop so I might have missed a post. I think you need to roll some DBs and compare them only with the Yamaha orthodynamic headphones. I'm way behind in my builds or I would share my thoughts.


----------



## slowpogo

The new board looks great. I see the PS now only uses two electrolytics; are these still the 1000uf 50v, just fewer of them?

 Also, while I'm mentioning the power supply...what are people's opinions on using boutique caps in the Max PS? I ask because I'm considering swapping two of my four 1000uf FM caps for 470uf Cerafines. Since only two caps are required to start with I thought it a safe experiment.


----------



## Beefy

Quote:


  Originally Posted by *slowpogo* /img/forum/go_quote.gif 
_Also, while I'm mentioning the power supply...what are people's opinions on using boutique caps in the Max PS? I ask because I'm considering swapping two of my four 1000uf FM caps for 470uf Cerafines._

 

Honestly? Pointless, waste of money, and probably detrimental to performance.


----------



## slowpogo

Quote:


  Originally Posted by *Beefy* /img/forum/go_quote.gif 
_Honestly? Pointless, waste of money, and probably detrimental to performance._

 

OK, noted. But there seem to be many who think boutiques in the power supply are good. I know that upgrading the PS caps on my 1212m with some old Black Gates I had made a nice difference.


----------



## Beefy

Quote:


  Originally Posted by *slowpogo* /img/forum/go_quote.gif 
_OK, noted. But there seem to be many who think boutiques in the power supply are good._

 

A lot of people believe in Astrology.


----------



## bperboy

Quote:


  Originally Posted by *Beefy* /img/forum/go_quote.gif 
_A lot of people believe in Astrology._

 

... and Scientology.


----------



## slowpogo

Quote:


  Originally Posted by *Beefy* /img/forum/go_quote.gif 
_A lot of people believe in Astrology._

 







 So this is one of _those_ topics...OK. I thought it was pretty accepted that the quality of the power supply, and thus the components used in it will affect sound quality.


----------



## Beefy

Quote:


  Originally Posted by *slowpogo* /img/forum/go_quote.gif 
_





 So this is one of those topics...OK._

 

Yes, it is definitely one of those topics. Obviously output coupling caps affect sound quality. I can see how local power decoupling caps caps might affect sound quality. But we are talking about pre-regulator reservoir caps here - I just don't see it.

  Quote:


 I thought it was pretty accepted that the quality of the power supply, and thus the components used in it will affect sound quality. 
 

Exactly right. In the _power supply_, you should use quality _power supply_ caps. For pre-regulator reservoir caps you want them as large as practical (without appearing like a dead short while they charge) and very low ESR. The caps you propose using are neither of these things.

 In my honest opinion, using them is a waste of money, and any 'audible' difference will likely be all in your mind.


----------



## slowpogo

Quote:


  Originally Posted by *Beefy* /img/forum/go_quote.gif 
_But we are talking about pre-regulator reservoir caps here - I just don't see it._

 

Back when I was building my first Pimeta, it seemed most everyone thought it a good idea to use boutiques for the four electrolytic positions. IIRC there were a few people saying, "Anything more than FMs is a waste" but their voices were drowned out. I think people typically use boutiques in the PS section of the PPA also.

 Are those spots also "pre-regulator reservoir caps"? I'm not trying to argue, just trying to understand why this concept that was lodged in my head early on is false. I don't remember the details but I do recall explanations from some about why boutiques would help the sound in these positions.


----------



## Beefy

Quote:


  Originally Posted by *slowpogo* /img/forum/go_quote.gif 
_IIRC there were a few people saying, "Anything more than FMs is a waste" but their voices were drowned out._

 

That doesn't mean that they were wrong 
	

	
	
		
		

		
		
	


	




  Quote:


 Are those spots also "pre-regulator reservoir caps"? 
 

No. The four electrolytic caps at C2/C3 in the Pimeta are analogous to CA4/5 in the Max, not the pre-regulator caps at CR1.

 In the Pimeta C2/C3 are almost directly connected to the power inputs of the OPAMPs, and it is feasible that a poor cap choice there could alter the sound of the amp. Though I am still very skeptical that boutique caps would offer a significant audible advantage over a quality power supply cap like a Panasonic FM.


----------



## tomb

Beefy is correct, but this subject is a bit clouded by a couple things - 

 1. The Elna Cerafines have apparently been an acceptable substitute for power caps for a long time. It may be that they are unique in that regard, but I don't know for sure. As slowpogo references, Tangent actually sold the Elna Cerafines through his Parts shop as the rail caps for the PIMETA.

 2. There is a school of thought that the signal voltage for all amps ultimately comes from the power supply. In that sense, boutique caps offer an advantage by providing "audio quality" voltage from the very beginning of the circuit - the power supply.

 I suspect that as time went on, the DIY headphone amplifier community gained more knowledge and a sense of which type of cap was important where. After a time, it seemed clear that with amplifiers of quality power supplies and quality circuit designs, the sense grew that power caps were selected for power cap ratings. In that aspect, power caps will have ratings superior to most boutiques (ESR and ripple). (There may be a few exceptions.) I could be wrong about the history of things, but it's just my sense from standing on the outside and trying to catch up to speed a couple of years ago.


----------



## slowpogo

I removed the caps at CA4 to try something else there...the solder in the holes was really gunked up so it took awhile to get the holes clean.

 I put the other caps in, and did not solder them, just bent the leads.

 Once I reconnected the amp, things were weird. There is a buzz dead center, and when I play music it sounds distant and reverberated and only plays in the center. There is no bass to speak of. And vocals sound like they have a weird flange or phaser effect on them, but only the vocals seem to go beyond dead center, they seem "wider."

 I made sure all the connections were good. I checked that the pads are still connected and not lifted. Everything I can think of seems fine with the multimeter.

 Is it possible that something got fried, like maybe the transistors at QA1-2? I was careful, like I always am to not apply heat too long to any one spot and switch between the left/right sides.


----------



## slowpogo

A-HA! It wasn't even the amp, but the cable running to the sound card. Somehow the ground wire connection broke on the RCA plugs. Fixed it, all is well.


----------



## pinkfloyd4ever

ok so I built a Max that was originally for jgonino, but he disappeared, so I sold it to someone else on the FS forums. A few days after he received it, the buyer PMs me saying something's wrong, it smells like something burning and one channel isn't working. He sends it back to me, I get it today and open it up before powering it up. The big resistors (RB10 & RB11) on the right buffer look weird (the bands that were red before are now brown). So I put my DMM probes in the buffer tip jacks and fire it up. The bias voltage shoots up to 8 volts, climbs gradually to 10 in the next few seconds. The two suspect resistors start glowing orange(!) and the heatsinks of the right output BJTs get hot VERY fast. So obviously I need to replace RB10 & RB11, as well as the output BJTs on the left channel. I'm guessing what caused this is that I had the top off for the 200+ hours I burned it in, and for some reason didn't think to rebias the BJTs after I put the cover on before shipped it.
	

	
	
		
		

		
		
	


	




 (duh) Feel free to point & laugh or otherwise insult me. Anyway, should I also replace all the small transistors in the buffer?


----------



## Beefy

Bugger, eh 
	

	
	
		
		

		
		
	


	




 I can't offer specific advice about what needs replacing...... but I can suggest that when you fire it up to test it for the first time, do it without tubes in.


----------



## cetoole

Nope, no pointing or laughing from this quadrant, thermal runaway isnt a funny matter (assuming that is what happened). Now, what was the buffer bias before you closed it up? I have to admit I never checked on my own, and am actually running a bit over the default recommendation, and have had no issues, so I wonder if something else could be going on, such as shipping damage. 

 If it was me, I would replace all the transistors in that channel while I have it apart, but again, that is just me. PM or email me if you need any of the parts, I probably have piles of them all just laying around.


----------



## pinkfloyd4ever

Quote:


  Originally Posted by *Beefy* /img/forum/go_quote.gif 
_but I can suggest that when you fire it up to test it for the first time, do it without tubes in._

 

really, why's that? Running it without tubes in won't damage it? I thought the tubes were pretty robust anyway.

  Quote:


  Originally Posted by *cetoole* /img/forum/go_quote.gif 
_ Now, what was the buffer bias before you closed it up?_

 

 I had it at 110 mV (I always measure between TB1 and TB2, so 220mV as I read it)


----------



## Beefy

Quote:


  Originally Posted by *pinkfloyd4ever* /img/forum/go_quote.gif 
_really, why's that? Running it without tubes in won't damage it? I thought the tubes were pretty robust anyway._

 

Not for the sake of the tubes. But rather it is my understanding that it is more difficult to damage to buffer without the tubes in there.


----------



## tomb

Quote:


  Originally Posted by *pinkfloyd4ever* /img/forum/go_quote.gif 
_really, why's that? Running it without tubes in won't damage it? I thought the tubes were pretty robust anyway.

 I had it at 110 mV (I always measure between TB1 and TB2, so 220mV as I read it)_

 

Well, that could be your problem. Measuring between TB1 and TB2 only gives you an indication of the imbalance between the complementary output portions of the buffer in the same channel. Depending on how good the matching is with transistors and resistors, you could have a ~2mv to 10mv difference at a true bias of 110mv. If you've adjusted that difference for 220mv, you could possibly have _several hundred_ milliamps of bias on the buffer.

 The only true way to measure the actual bias on a buffer channel is to measure just one of those points referenced to TA2.


----------



## cetoole

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Well, that could be your problem. Measuring between TB1 and TB2 only gives you an indication of the imbalance between the complementary output portions of the buffer in the same channel. Depending on how good the matching is with transistors and resistors, you could have a ~2mv to 10mv difference at a true bias of 110mv. If you've adjusted that difference for 220mv, you could possibly have several hundred milliamps of bias on the buffer.

 The only true way to measure the actual bias on a buffer channel is to measure just one of those points referenced to TA2.
	

	
	
		
		

		
		
	


	


_

 

Yes, this is kind of my guess too. In theory, they should be just about even, but if you accidentally get transistors which are too mismatched, you can certainly get a large difference. Its kind of rare, but it happens. Of course, we could still be barking up the wrong tree and it be a result of some external damage or something. I am surprised though that your fuse didnt blow or the internal protection in the wallwart trip.


----------



## pinkfloyd4ever

Well it doesn't have the fuse, though I'm probably gonna add that now. I had the guy that bought it check the wallwart before he sent the amp, so I know it's still good. And I guess I shouldn't have said I _always_ check between TB1 & TB2. I'd actually check between TA1 and a TB point almost as often, and it was always 109-111. I'd just use the measurement between TB1 and TB2 to fine tune it (but maybe that's not even what I was doing?)


----------



## rds

To burn up a 2W 2.2 ohm resistor you'll need huge current. I don't see how accidentally biasing a little high is going to make that happen.
 It seems there must be something else going on here. Maybe check the resistors at the base...


----------



## tomb

pics ...


----------



## nocturnalsheet

anybody did any review/comparisons on the sound differences between say different brands of the same tube(12ae6a,12fm6, 12fk6)?

 cant seem to find any info. gotten a millet, thinking of reading up on tubes before i take the plunge.

 thanks for the help

 regards.


----------



## tomb

Quote:


  Originally Posted by *nocturnalsheet* /img/forum/go_quote.gif 
_anybody did any review/comparisons on the sound differences between say different brands of the same tube(12ae6a,12fm6, 12fk6)?

 cant seem to find any info. gotten a millet, thinking of reading up on tubes before i take the plunge.

 thanks for the help

 regards._

 

I've sort of given up trying to assign sound qualities per brand.
	

	
	
		
		

		
			





 First of all, the brands were freely mixed from one mfr to another. Even so, I've found great sounding tubes from each of the manufacturers - Tung Sol, GE, RCA, and Sylvania. What distinguishes one from the other is the level of clear highs that are available.

 Sylvania generally built the best structure in the tubes - all of them have a channel going across the plates at the top mica spacer. None of the other mfrs used that construction. At the same time, that doesn't necessarily guarantee the best sound.

 Generally speaking (very generally) ... and this is per MFR, not painted-on "brand": 
*RCA -* very good overall neutral sound, sort of clear, but slightly soft highs - similar to the BUF634 sound of a PIMETA, if you've heard that. They are very forgiving for almost any recording.
*GE -* lots of prat, great bass impact and powerful punch, great mids, not as good in the highs as an overall average compared to the others.
*Tung Sol -* very similar to the RCA's, very neutral, but with "sweeter" extended highs, compared to the RCA's soft highs.
*Sylvania -* similar to the others - if you find a good one, the highs are very revealing, which can be good or bad, depending on the recording.

 All that said, there is much more difference in the sound from type to type: 12AE6 compared to 12FM6 and 12FK6. The 12AE6 has the most impact and is the most dynamic. I would recommend them for high impedance phones in every case.
 12FK6 has the best highs and detail, but impact can be lacking except on low impedance phones.
 12FM6 is in the middle of the other two.

 Despite all of this, you'd be better off deciding on which tube type and making sure you have a decent match in construction and output. As noted, the brand name means nothing.

 Hope that helps ...


----------



## nocturnalsheet

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_I've sort of given up trying to assign sound qualities per brand.
	

	
	
		
		

		
		
	


	




 First of all, the brands were freely mixed from one mfr to another. Even so, I've found great sounding tubes from each of the manufacturers - Tung Sol, GE, RCA, and Sylvania. What distinguishes one from the other is the level of clear highs that are available.

 Sylvania generally built the best structure in the tubes - all of them have a channel going across the plates at the top mica spacer. None of the other mfrs used that construction. At the same time, that doesn't necessarily guarantee the best sound.

 Generally speaking (very generally) ... and this is per MFR, not painted-on "brand": 
*RCA -* very good overall neutral sound, sort of clear, but slightly soft highs - similar to the BUF634 sound of a PIMETA, if you've heard that. They are very forgiving for almost any recording.
*GE -* lots of prat, great bass impact and powerful punch, great mids, not as good in the highs as an overall average compared to the others.
*Tung Sol -* very similar to the RCA's, very neutral, but with "sweeter" extended highs, compared to the RCA's soft highs.
*Sylvania -* similar to the others - if you find a good one, the highs are very revealing, which can be good or bad, depending on the recording.

 All that said, there is much more difference in the sound from type to type: 12AE6 compared to 12FM6 and 12FK6. The 12AE6 has the most impact and is the most dynamic. I would recommend them for high impedance phones in every case.
 12FK6 has the best highs and detail, but impact can be lacking except on low impedance phones.
 12FM6 is in the middle of the other two.

 Despite all of this, you'd be better off deciding on which tube type and making sure you have a decent match in construction and output. As noted, the brand name means nothing.

 Hope that helps ..._

 

hi tomb,

 thanks for the insightful post. guess i will be trying out different brands of 12ae6a tubes as i am using the hd580 with it. tung sol tubes sounds interesting(that is if i can get my hands on some)

 regards.


----------



## pinkfloyd4ever

HOkay, finally got around to taking some pics...















 Edit: I soldered on some fuse clips, and the 1 amp slow blow fuse I had blew pretty quick after i switching it on, def in less than 3 seconds


----------



## cetoole

Wow, you can really see the scorching. I would just replace all the transistors in that section and at least RB10/11. Maybe see if you can measure the other resistors, but I would imagine they are all fine. Is that more scorching around the fuse, or just flux? Also, I see you have test points for the buffer bias. Any chance someone ever shorted the buffer bias points?


----------



## pinkfloyd4ever

that's just flux around the fuse clips. I actually didn't clean the flux after soldering the wires for the test points. But ya, it definitely looks like the solder joints at RB10/11 had been melted from the heat of the resistors(obviously, if they start glowing bright orange shortly after power-on)...maybe a little on the joints immediately adjacent too

 This one shows it a little more clearly


----------



## tomb

I'm like Colin - I would suspect something in the wiring and the case - especially if it happened after you put the lid back on. Maybe the VitQ's are contacting the case lid - or some wiring is getting jammed into the endplate/lid/case fastening points?

 I had a nasty scare once where I discovered that I had one of the tipjack wires get stuck in the bottom slot where one of the endplate screws went in. I ended up screwing the screw through the wire's insulation and shorted it out. It could've been real nasty had I let it go for awhile.

 I don't see anything wrong in the pics unless the VitQ's have moved and have their leads touching something. It almost appears as if the back lead on one the VitQ's either contacted the nearby test point or the RB10 resistor lead, but it could be the angle of the photo. There's also an exposed lead on the RCA jack? Could that have contacted something?


----------



## pinkfloyd4ever

Quote:


  Originally Posted by *cetoole* /img/forum/go_quote.gif 
_Any chance someone ever shorted the buffer bias points?_

 

could that happen if you had the DMM probes in the tip jacks and were to switch thru the different modes on the centech DMM (with both the amp and meter turned on)? If so, that may be it. I didn't even think to warn him against that. I did have him checking the tube bias

  Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_I'm like Colin - I would suspect something in the wiring and the case - especially if it happened after you put the lid back on. Maybe the VitQ's are contacting the case lid - or some wiring is getting jammed into the endplate/lid/case fastening points?_

 

 Yaa I was kind of afraid of that when I saw the way a couple of the wires looked as if they had been pinched or kinked. Even if it wasn't that, I prob should have put heat shrink over the exposed metal ends of the tip jacks and shorten a couple of those wires. I don't think it was the VitQs touching the case, as they're well below the top, plus if any part of them were to touch the case it'd just be the tape and the outside metal shell, not the lead

  Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_I don't see anything wrong in the pics unless the VitQ's have moved and have their leads touching something. It almost appears as if the back lead on one the VitQ's either contacted the nearby test point or the RB10 resistor lead, but it could be the angle of the photo._

 

nah, the leads would almost have to have been strained to the point of breaking before it touched anything metal that it shouldn't be touching. And ya, that's just a bad angle on the pic. 

  Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_There's also an exposed lead on the RCA jack? Could that have contacted something?_

 

hmm I doubt it at the place you're talking about...but when I got the amp back, the input ground and one of the channels' + wires were loose from the terminal block. I assumed this was from the return shipping, but if it happened on the first shipping (to the buyer) and they shorted could this have caused it? Although I guess if this had been the case, neither channel would have been working upon arrival, which definitely wasn't the case..
	

	
	
		
		

		
		
	


	




 anyway, I guess I know what I need to know what to do to fix the damage (and hopefully prevent it from happening again), regardless of what caused it. The two small transistors between the Wimas are in the amp section right? Should I replace those too?


----------



## tomb

Quote:


  Originally Posted by *pinkfloyd4ever* /img/forum/go_quote.gif 
_<snip>

 anyway, I guess I know what I need to know what to do to fix the damage (and hopefully prevent it from happening again), regardless of what caused it. The two small transistors between the Wimas are in the amp section right? Should I replace those too?_

 

No - they're the CCS's for the tubes. I doubt seriously they were damaged - they just don't see that much current.

 Also, I don't think there's much he could do with the meter, unless he was sticking the probes where they weren't supposed to go.
	

	
	
		
		

		
		
	


	




 If it was working before you buttoned it up, most likely it was a case-wire-crushing incident.


----------



## slowpogo

I'm wondering about adding a plexi top plate to the standard Hammond case.

 It wouldn't be too hard with Front Panel Express...the 2mm thick plexi should still slide in the panel slot. Still, I'd prefer to have a "screw down" top that I could remove without taking off the end plates.

 Anyone have an idea how to accomplish this? I have an idea of gluing some kind of screw receptacle into the slots, one at each corner area, that would stick out 1/4" or so and allow you to screw a plate down.

 I just don't know where I could find such a part (basically a small bracket with a screw hole on one end). Maybe there's a simple way to make this part? Any ideas appreciated.


----------



## tomb

Quote:


  Originally Posted by *slowpogo* /img/forum/go_quote.gif 
_I'm wondering about adding a plexi top plate to the standard Hammond case.

 It wouldn't be too hard with Front Panel Express...the 2mm thick plexi should still slide in the panel slot. Still, I'd prefer to have a "screw down" top that I could remove without taking off the end plates.

 Anyone have an idea how to accomplish this? I have an idea of gluing some kind of screw receptacle into the slots, one at each corner area, that would stick out 1/4" or so and allow you to screw a plate down.

 I just don't know where I could find such a part (basically a small bracket with a screw hole on one end). Maybe there's a simple way to make this part? Any ideas appreciated._

 

I hope it's more than 2mm thick.
	

	
	
		
		

		
		
	


	




 EDIT: Never mind - 2mm will be fine - don't know what I was thinking.
	

	
	
		
		

		
		
	


	




 As for a screw down top plate, I don't know. The problem is that the top slot in the Hammond is not the most stable thing to attach to, unless you do it along the entire length. Amb does most of his cases this way, I think - by attaching the screw posts to the acrylic, then there are tab(s) that slide into the case slots (I think). However, I don't think the assembly would be stable if you unscrewed the mounts from the top plate - they would just fall out of the slot.

 It might be worth sending him a PM or e-mail and asking him how he does it, though.


----------



## tomb

cetoole has finished the design on the MAX V1.2:






 Here's the schematic, too (click for a larger image):





 Of course, the primary changes are the incorporation of the superior MiniMAX power supply, and room for the BantamDAC on board. Switching between BantamDAC and "normal" RCA inputs will be controlled with a back panel SPST switch (2-position terminal block) that throws a 24V relay. Since the 24V relay was required because of the limited space back there, we also incorporated it into the headphone delay-relay.

 Surprise, surprise! With fewer parts and higher voltage, the headphone relay-delay works better than ever. We have sized and tested the parts selection for a Cold-Start delay time of 45 seconds, but the Hot-Start time is still ~30 seconds. Transients on cutoff - if they are there - are too fast to measure with my Fluke. This is an improvement over the existing design and other delay-relays, which throw a few volts of transient offset upon shutoff. Normally, this is trivial with a connected load and only noticeable when measured in a zero-load condition. However, this new circuit appears to have no offset on shut-off at all, load or not. This is of course, a nice benefit to the new circuit, besides the commonality of relays and fewer parts. I have been living with the new relay circuit on a MiniMAX for a few weeks now with no ill effects whatsoever - as stated it works _better_.

 As mentioned to some other people on different occasions, there's little to do to improve the existing MiniMAX with BJT's - this design is not going to do any better, and the MiniMAX package with the custom case is unbeatable. However, the regular MAX board always allowed for 1-1/2" sinks and parts, so MOSFETs should work well. Accordingly, we are going to steer the focus for the MAX V1.2 in that direction of MOSFETs, but of course, it can always be built with BJT buffers, too.

 A request for quote on prototypes has been sent. I don't know if we'll need volunteers, yet. The board is pretty well proven and we've proven the new relay circuits, too. If anything, a proto build will only be necessary to prove out the fit with the case and the BantamDAC hookup. We'll keep you updated.


----------



## BoilermakerFan

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_cetoole has finished the design on the MAX V1.2:


 Of course, the primary changes are the incorporation of the superior MiniMAX power supply, and room for the BantamDAC on board. Switching between BantamDAC and "normal" RCA inputs will be controlled with a back panel SPST switch (2-position terminal block) that throws a 24V relay. Since the 24V relay was required because of the limited space back there, we also incorporated it into the headphone delay-relay.

 Surprise, surprise! With fewer parts and higher voltage, the headphone relay-delay works better than ever. We have sized and tested the parts selection for a Cold-Start delay time of 45 seconds, but the Hot-Start time is still ~30 seconds. Transients on cutoff - if they are there - are too fast to measure with my Fluke. This is an improvement over the existing design and other delay-relays, which throw a few volts of transient offset upon shutoff. Normally, this is trivial with a connected load and only noticeable when measured in a zero-load condition. However, this new circuit appears to have no offset on shut-off at all, load or not. This is of course, a nice benefit to the new circuit, besides the commonality of relays and fewer parts. I have been living with the new relay circuit on a MiniMAX for a few weeks now with no ill effects whatsoever - as stated it works better.

 As mentioned to some other people on different occasions, there's little to do to improve the existing MiniMAX with BJT's - this design is not going to do any better, and the MiniMAX package with the custom case is unbeatable. However, the regular MAX board always allowed for 1-1/2" sinks and parts, so MOSFETs should work well. Accordingly, we are going to steer the focus for the MAX V1.2 in that direction of MOSFETs, but of course, it can always be built with BJT buffers, too.

 A request for quote on prototypes has been sent. I don't know if we'll need volunteers, yet. The board is pretty well proven and we've proven the new relay circuits, too. If anything, a proto build will only be necessary to prove out the fit with the case and the BantamDAC hookup. We'll keep you updated.
	

	
	
		
		

		
		
	


	


_

 

Yeah! Just let me know when they are ready for sale and put me down for two. I need one for my MOSFET-MAX and I'm so far behind, I'll go ahead and build my BJT integrated amp with the new board and mount the phono stage where the BantamDAC would be for my console. 

 I have 3 of the current style boards, so I will be building one of those up with BJTs and and probably the Muse ES caps then I can listen to it with the other two and see how much of a difference I can hear. 

 Also, if anyone wants a current style board, I'll let two of them go for $5 each plus the USPS Priority Mail charges.


----------



## tomb

BMF - drop me a PM if you get no takers. I'll buy them from you.


----------



## BoilermakerFan

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_BMF - drop me a PM if you get no takers. I'll buy them from you.
	

	
	
		
		

		
		
	


	


_

 

Thanks Tom. I'll let you know, but I figure I'd try to help peeps on a tight budget. The $15 savings basically covers a wall wart PSU. Need to formally post them in the for sale forum too.


----------



## abcheng

Hey guys, I bought the PCBs a while and never got around to build them until now. I'm currently ordering parts to build my 
 Millett Maxed Amp, but I have a question about the heatsinks listed on the BOM.

 Aavid #531002B02500G (1"h.) 4 
 Aavid #531002B02500G (1-1/2"h.) 4 

 There are two types of heatsinks listed, and the difference I see is in height. I purchase one or the other, but not both right?


----------



## cetoole

Quote:


  Originally Posted by *abcheng* /img/forum/go_quote.gif 
_Hey guys, I bought the PCBs a while and never got around to build them until now. I'm currently ordering parts to build my 
 Millett Maxed Amp, but I have a question about the heatsinks listed on the BOM.

 Aavid #531002B02500G (1"h.) 4 
 Aavid #531002B02500G (1-1/2"h.) 4 

 There are two types of heatsinks listed, and the difference I see is in height. I purchase one or the other, but not both right?_

 

Yup, and which one depends on what you want to be able to bias to, and will effect how you case it.


----------



## MASantos

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_cetoole has finished the design on the MAX V1.2:

 Of course, the primary changes are the incorporation of the superior MiniMAX power supply, and room for the BantamDAC on board. Switching between BantamDAC and "normal" RCA inputs will be controlled with a back panel SPST switch (2-position terminal block) that throws a 24V relay. Since the 24V relay was required because of the limited space back there, we also incorporated it into the headphone delay-relay.
_

 

You say a back panel SPST. I guess this is kind of a dumb question, but can it be wired to the front panel right?

  Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Surprise, surprise! With fewer parts and higher voltage, the headphone relay-delay works better than ever. We have sized and tested the parts selection for a Cold-Start delay time of 45 seconds, but the Hot-Start time is still ~30 seconds. Transients on cutoff - if they are there - are too fast to measure with my Fluke. This is an improvement over the existing design and other delay-relays, which throw a few volts of transient offset upon shutoff. Normally, this is trivial with a connected load and only noticeable when measured in a zero-load condition. However, this new circuit appears to have no offset on shut-off at all, load or not. This is of course, a nice benefit to the new circuit, besides the commonality of relays and fewer parts. I have been living with the new relay circuit on a MiniMAX for a few weeks now with no ill effects whatsoever - as stated it works better._

 

Now, will v1.3 have a sigma11??? 
	

	
	
		
		

		
		
	


	











 Seriously now, I could imagine a balanced Millett MAX board with sigma11 power supply, board pads for stepped attenuator, onboard connectors and so on... 
	

	
	
		
		

		
		
	


	




 the ultimate Millett Hibrid!


----------



## tomb

Quote:


  Originally Posted by *MASantos* /img/forum/go_quote.gif 
_You say a back panel SPST. I guess this is kind of a dumb question, but can it be wired to the front panel right?_

 

If you want to run the leads that far, of course. That's another reason the board is slotted in the back - besides the fact that it takes up the entire length of the Hammond case, now.


  Quote:


 Now, will v1.3 have a sigma11??? 
	

	
	
		
		

		
		
	


	











 Seriously now, I could imagine a balanced Millett MAX board with sigma11 power supply, board pads for stepped attenuator, onboard connectors and so on... 
	

	
	
		
		

		
		
	


	




 the ultimate Millett Hibrid! 
 

Talk to Pabbi1. His is pretty close to that.


----------



## MASantos

Thanks tomb!


----------



## nocturnalsheet

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_I've sort of given up trying to assign sound qualities per brand.
	

	
	
		
		

		
		
	


	




 First of all, the brands were freely mixed from one mfr to another. Even so, I've found great sounding tubes from each of the manufacturers - Tung Sol, GE, RCA, and Sylvania. What distinguishes one from the other is the level of clear highs that are available.

 Sylvania generally built the best structure in the tubes - all of them have a channel going across the plates at the top mica spacer. None of the other mfrs used that construction. At the same time, that doesn't necessarily guarantee the best sound.

 Generally speaking (very generally) ... and this is per MFR, not painted-on "brand": 
*RCA -* very good overall neutral sound, sort of clear, but slightly soft highs - similar to the BUF634 sound of a PIMETA, if you've heard that. They are very forgiving for almost any recording.
*GE -* lots of prat, great bass impact and powerful punch, great mids, not as good in the highs as an overall average compared to the others.
*Tung Sol -* very similar to the RCA's, very neutral, but with "sweeter" extended highs, compared to the RCA's soft highs.
*Sylvania -* similar to the others - if you find a good one, the highs are very revealing, which can be good or bad, depending on the recording.

 All that said, there is much more difference in the sound from type to type: 12AE6 compared to 12FM6 and 12FK6. The 12AE6 has the most impact and is the most dynamic. I would recommend them for high impedance phones in every case.
 12FK6 has the best highs and detail, but impact can be lacking except on low impedance phones.
 12FM6 is in the middle of the other two.

 Despite all of this, you'd be better off deciding on which tube type and making sure you have a decent match in construction and output. As noted, the brand name means nothing.

 Hope that helps ..._

 

Hi Tomb, 

 currently tried a few tubes and currently my configuration is RCA 12AE6A with Slyvania 12AE6A. 

 thinking of finding few more tubes to try again. 

 btw how do i tell from observation who is the MFR of the different tubes? 

 thanks.


----------



## tomb

Quote:


  Originally Posted by *nocturnalsheet* /img/forum/go_quote.gif 
_Hi Tomb, 

 currently tried a few tubes and currently my configuration is RCA 12AE6A with Slyvania 12AE6A. 

 thinking of finding few more tubes to try again. 

 btw how do i tell from observation who is the MFR of the different tubes? 

 thanks._

 

Believe it or not, it's pretty simple, really. There were four manufacturers of Millett tubes:

*RCA -* tell-tale sign is the presence of a dark-gray, etched tube designation on the side near the top of the tube. The designation ("12AE6", "12FK6", etc.) is bordered by an octagon whose sides have been shortened to fit the text. I often refer to it as a "squished octagon." Note that sometimes this feature may be highly worn and almost invisible. It's often a process of deductive elmination - if the other tell-tale signs are not there, then keep looking for the presence of the squished octagon, no matter how light. If you can't find one, or you find a tube designation etched on the side near the top of the tube - without an octagon or any other border - then it's Tung-Sol.

*GE -* Pretty easy for these. GE used white etching on the sides of the tube. This etching is often large, perhaps covering 1/2 the space of the visible side of a tube. The tube designation is accompanied by a series of white dots beneath. "Size" in this context means the total space of the tube designation text and the dots that are below. The white lettering itself is about twice the size of an RCA or Tung-Sol designation. The dots - about 3 to 5 total, on a couple of rows - are about 1/16" in diameter or slightly smaller.

 The lower gain tubes by GE - 12FK6's for instance - also have a very unique appearance. GE stamped one-piece "J" plates with a contiguous outside lip. All the other mfrs would trim the plates on one end, although there are some with better finishes than others on the trimmed edge. However, only GE used the stamped "J" with an outside-bordering lip.

 GE's also were the only ones to use "rings" for getters in some of their tubes (not all). These can be side rings - welded sideways to one of the plates at mid-height, or on a rod at the very top - "halo" fashion. These "rings" are more like a thick washer than any sort of bent or curved wire and are much smaller than RCA-style halo getters - around 1/4" diameter or slightly larger. 

*Sylvania -* Very easy to spot these, too. Sylvania actually built their tubes differently than anyone else. Sylvania uses an upside-down channel as additional support at the top of the plates and the top mica spacer. This channel is 90 degrees relative to the parallel plates as you look down at the top of the tube. Every other mfr just used a clear disc at the top of the plates. Sylvania has the clear disc, too, but no one else has this supporting channel that rests on the top mica spacer. Note that the clear disc (1/4" - 3/8" dia) is often not present at all in the other mfrs - the plates are sometimes free-floating at top except for the top mica spacer.

 Also, many Sylvanias have a _vertical_ side square getter. No other mfr used side getters except that they were welded to one of the plates sideways (which may be the predominant getter for all tube types). The Sylvanias that used these have a supporting vertical rod and the getter is welded in the middle - as if the getter was going up top but never made it. 

*Tung-Sol -* When you've elminated every other possibility, the chances are the tube is Tung-Sol. The most predominant feature is the _lack of_ features of any of the tubes' mfrs above, along with a tube designation etching at the top of the tube sides - dark gray and without a border. Some Tung-Sol tubes have tube tips that are rounded and "bobbed," instead of pulled up into a pointy tip.

 Beyond this, except for the GE "J" plates in their 12FK6's, the mfrs shared plate types with each other to a large degree. There are some that I've only seen on RCA and vice-versa, but the distinguishing feature is not worth mentioning, since often the finish may be the only thing unique, not the shape.

 An unfortunate fact is that even after all of this, I've come across tubes that have both a squished octagon tube designator and white etching with dots.
	

	
	
		
		

		
		
	


	




 I guess this can be explained by GE's on and off ownership of RCA as a subsidiary. Hope this helps you.


----------



## tomb

Quote:


  Originally Posted by *nocturnalsheet* /img/forum/go_quote.gif 
_Hi Tomb, 

 currently tried a few tubes and currently my configuration is RCA 12AE6A with Slyvania 12AE6A. 

 thinking of finding few more tubes to try again. 

 btw how do i tell from observation who is the MFR of the different tubes? 

 thanks._

 

You mean I wrote all of that this morning and you didn't care to check back?


----------



## nocturnalsheet

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_You mean I wrote all of that this morning and you didn't care to check back?
	

	
	
		
		

		
		
	


	





_

 

Hey Tomb,

 I did check back, thanks for your inputs, really appreciate it.

 different timezones we are in you know. 
	

	
	
		
		

		
		
	


	




 i shall wait for the tubes to arrive and try to figure out who are the manufacturers.


----------



## tomb

Proto boards have arrived! I'm going to build one and if works out, production boards will be ordered immediately. Thought you might like to see how they turned out (click for full size pics):


----------



## Beefy

Nice! I like the little extra touches, like the silkscreen label for the fuse / no fuse......


----------



## ruZZ.il

The board has really evolved nicely. I'm not sure when I'll get to check one out though.. I've already got a few MAXs 
	

	
	
		
		

		
		
	


	




 Though, no mosfet one yet, and it'll probably stay nice and cool with those holes. They really keep the miniMAX cool.. hmmm..


----------



## abcheng

Quote:


  Originally Posted by *cetoole* /img/forum/go_quote.gif 
_Yup, and which one depends on what you want to be able to bias to, and will effect how you case it._

 

Thanks for the reply. Will the 1.5" heat sinks fit in the Hammond case in the BOM?

 Does anyone have any of these parts available?

 RB12L/R 2K ohm Trimmer Pot - Mouser doesn't have any in stock right now. 

 as well as:

 Tube LED's, 3mm ultra-high, 5500 mcd - Blue

 I can only seem to find 3600mcd LEDs on Mouser. Is 3600mcd bright enough, or should go with 5500mcd LEDs instead?

  Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Proto boards have arrived! I'm going to build one and if works out, production boards will be ordered immediately. Thought you might like to see how they turned out (click for full size pics):_

 

Wow, the proto boards of the new version are out when I'm about to build the original version of the Millett Max ? I may have to wait until the boards for the new version of the Millett Max are available.


----------



## BoilermakerFan

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Proto boards have arrived! I'm going to build one and if works out, production boards will be ordered immediately. Thought you might like to see how they turned out (click for full size pics):_

 

They look great! With those cooling holes and 2-1/2" 'sinks, I should be able to go for 600mA bias current! 
	

	
	
		
		

		
			






 J/K


 Edit: I noticed a typo on the board! Shouldn't the upper right corner read BantamPHONO? It's ok, I have a sharpie, so I'll fix mine, no need to hold up the order on my account.


----------



## TheEKey

Hello everyone,

 I'm new to DIY headphone amp and MHM is my second project.

 Anyway, I have a weird problem that I'm not able to debug. Please help.


 My built with no case yet






 It works generally 
	

	
	
		
		

		
		
	


	




 The problem I have is sort of weird. To sum up, it works when I use 3.5mm plug but it fails when I use 6.45mm plug.

 When I use 3.5mm plug, it rocks~! I love what I have.

 When I use 6.45mm plug, it sounds like this:
 1) Midrange tilts largely (about 90% to the left channel)
 2) Midrange becomes weak, grainy and sometimes sounds like sparkle.
 3) Stage becomes so wide in a strange way. Imagine it's a concert hall, speakers are hung at the 4 corners of the hall. I feel like sitting right next to the far left speaker and very far to the main performing stage.
 4) Midrange is delayed (like heavily feedbacked).
 5) Low is still heavy and clear but somehow over-amplified.

 I have read some interesting posts on this topic. Does it sound like what c0nsumer faced when he's building his?


 First trial GOOD with 3.5mm jack like this.





 Second trial BAD with 6.45mm jack like this.





 So I figured, maybe there's a problem with the jack. So I tried using 3.5mm plugs when touched the 6.45mm jack with the correct left, right and ground. Surprisingly, it was GOOD.





 I started to get confused and thought that maybe i got bad luck and installed a bad jack. So I tried this: 6.45mm into a Neutrik. I wired it the appropriate right, left and ground "holes". The result, another surprise, it was BAD





 Then I tried this. 6.45mm to a Neutrik wired to the original jack on board.
 Result: BAD





 I thought: hey, I got it. It must be the 6.45mm jack itself turned sour..... so I tried same combinations on some other generic jack
 Results were all BAD





 I have no idea how to tackle this problem anymore. Need you guys' help. 

 For references, it introduces hiss when I touched the "upcap" vol knob. Not sure if this is related.





 Closeup on different corners of the top of the board.

















 Bottom view of the board.





 I sucked at soldering. So I left some traces. Don't know if they cause problem. But let's take a look.





 But everything's fine when I used 3.5mm.

 So where should I start to do? Did I burn some transistors when I do the soldering? If you guys wanna have any closer look of the amp, let me know. I'm more than happy to post.

 Note that I have done the biasing following the procedures on the original Maxed pages.

 I think I need Dr. House here........

 Cheer,

 TheEKey


----------



## MrMajestic2

My first thought would be that the ground is not making contact when you have headphones plugged into the Neutrik jack. Maybe something is wrong with the jack on the inside. If transistors were blown then the 3.5mm jack would have the same issue.


----------



## tomb

First of all, thanks for all the photos. It will make trouble-shooting this a lot easier!

 The first thing I noticed is that perhaps you're wiring up the 3.5mm jack wrong in the first place. If I'm not mistaken, the longest lug coming off of the 3.5mm jack is Ground. You have the blue wire connected to that. Yet, you're connecting the blue wire to the Left channel (OL).

 Things can get mixed up quickly like this - it may even be that you have the inputs crossed, too, so that if you cross the outputs, maybe it sounds correct.

 In any event - there's no way - let me repeat - NO WAY - the headphone jack can be wired up incorrectly (it's soldered directly to the pads!). Secondly, I doubt seriously that there's anything wrong with the jack. You can easily check this by measuring zero resistance from the contacts on top to the PCB pads at left. If you get zero ohms from the OL pad to the top contact on the jack, then OR to the middle contact, and OG to the bottom contact, the only way that jack can fail is if the contacts don't move and rise up when you insert the plug. I bet you can see them pop up when you insert a plug, though. If that happens, then contact is made, period.

 So, check your input wiring - make absolutely certain you're connecting Ground to IG, Left to IL, and Right to IR. Note! They are not in the same positions from Input to Output at the headphone jack. Jacks use the outer ring as Ground, so the contact/PCB pad on the outside closest to the plug is Ground. Whereas, ground is shared in the middle between RCA jacks at back, so the Input Ground is in the middle.*

 Let us know what you find after you check these things out. Good luck!
	

	
	
		
		

		
		
	


	





 *EDIT: What I mean by this is that typcially we solder RCA jacks' ground tabs together in the middle. So, you end up with three leads coming off of the RCA jacks, with Ground in the middle.


----------



## n_maher

The RK27 also needs to be grounded, doesn't it?


----------



## MrMajestic2

Tomb is spot on I think. Its probably the input wiring. 3.5mm jack is definitely wired incorrectly when examining the photos. It will sound right because of input wiring being wrong. Not many moving parts in the Neutrik jack to break


----------



## tomb

Quote:


  Originally Posted by *n_maher* /img/forum/go_quote.gif 
_The RK27 also needs to be grounded, doesn't it?_

 

Yep - this is correct, too. You will get the noise when touching the pot shaft until you run a ground wire from the PCB pad to one of the screws on the back of the volume pot.


----------



## tomb

Quote:


  Originally Posted by *MrMajestic2* /img/forum/go_quote.gif 
_Tomb is spot on I think. Its probably the input wiring. 3.5mm jack is definitely wired incorrectly when examining the photos. It will sound right because of input wiring being wrong. Not many moving parts in the Neutrik jack to break 
	

	
	
		
		

		
		
	


	


_

 

Thanks for the help! Hope those tubes get to you soon!


----------



## MrMajestic2

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Thanks for the help! Hope those tubes get to you soon!
	

	
	
		
		

		
		
	


	


_

 

Thanks, I'll let you know when they get here


----------



## n_maher

I'd also encourge the OP to cut the legs on that regulator before they get bent even more and short something. That'll cause a real problem!


----------



## soloz2

well my max has decided to only give me hum now... not really sure what happened.

 about a week and a half ago I got around to wiring up the Opus and Darwin. They were to be powered from a separate toroid and one of tpa's dual psu boards. Wired everything up and the power LED didn't work any longer neither did the LED on my OptiVol. I didn't get a chance to look until today and still no dice. I unwired everything, and still doesn't work. At first I thought the hum was coming from the darwin but when I unhooked it and ran the input direct to the max still hum. 
	

	
	
		
		

		
		
	


	




 Now to figure out what's causing the problem and how much needs to be replaced. Just frustrating because nothing works now.


----------



## tomb

Quote:


  Originally Posted by *soloz2* /img/forum/go_quote.gif 
_well my max has decided to only give me hum now... not really sure what happened.

 about a week and a half ago I got around to wiring up the Opus and Darwin. They were to be powered from a separate toroid and one of tpa's dual psu boards. Wired everything up and the power LED didn't work any longer neither did the LED on my OptiVol. I didn't get a chance to look until today and still no dice. I unwired everything, and still doesn't work. At first I thought the hum was coming from the darwin but when I unhooked it and ran the input direct to the max still hum. 
	

	
	
		
		

		
		
	


	




 Now to figure out what's causing the problem and how much needs to be replaced. Just frustrating because nothing works now._

 

Start measuring some voltages for us and maybe we can help you figure it out. For instance, do you get power out of the toroid? What about V+ and Gnd on the board? etc., etc.


----------



## soloz2

V+ to gnd is 27v, that's as far as I got. so the toroid isn't the problem neither is the power supply of the Max. So, either something where the OptiVol isn't getting good power I suppose could be the source of the hum, or a problem with the OptiVol itself, or the problem is something else on the max. 

 I'm going to look at the OptiVol first since the LED doesn't light up and the power LED doesn't light up, and they're both tied in together so removing one or the other may shed some light...


----------



## soloz2

figured it out. I was overcomplecating things. Since I've tapped the power from the Max I installed a distribution block to feed both the power LED and OptiVol, but when I tested voltages I just tested power and ground from the screws and got 27v so I moved on, but I didn't test power at the OptiVol or power LED :duh:

 Well, I must have snagged the positive leads when I was working before because they came loose and a few crimp terminal just solved the problem. 


 And the moral of the story is that sometimes the simplest answer is the best answer... now I get to put everything back together! 
	

	
	
		
		

		
		
	


	




 Also a little bit of TF2 does wonders!


----------



## TheEKey

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_First of all, thanks for all the photos. It will make trouble-shooting this a lot easier!

 The first thing I noticed is that perhaps you're wiring up the 3.5mm jack wrong in the first place. If I'm not mistaken, the longest lug coming off of the 3.5mm jack is Ground. You have the blue wire connected to that. Yet, you're connecting the blue wire to the Left channel (OL).

 Things can get mixed up quickly like this - it may even be that you have the inputs crossed, too,_

 

Thanks for the tips. I will try and get back~!
 Finger crossed 
	

	
	
		
		

		
		
	


	




 TheEKey


----------



## TheEKey

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_First of all, thanks for all the photos. It will make trouble-shooting this a lot easier!

 The first thing I noticed is that perhaps you're wiring up the 3.5mm jack wrong in the first place. If I'm not mistaken, the longest lug coming off of the 3.5mm jack is Ground. You have the blue wire connected to that. Yet, you're connecting the blue wire to the Left channel (OL).

 Things can get mixed up quickly like this - it may even be that you have the inputs crossed, too_

 

Thank you, TomB. I mismatched the L/R/G for sure. Now it's fixed. Enjoying it for couple hours~!
 Start to feel the itch to play around with the output caps. Need some vitamin and volka...

 BTW, any DIYer's ever tried to build a switch for different output caps for MHM? Do you think it's worth bothering or just better stay single-minded?

 TheEKey


----------



## tomb

Quote:


  Originally Posted by *TheEKey* /img/forum/go_quote.gif 
_Thank you, TomB. I mismatched the L/R/G for sure. Now it's fixed. Enjoying it for couple hours~!
 Start to feel the itch to play around with the output caps. Need some vitamin and volka...

 BTW, any DIYer's ever tried to build a switch for different output caps for MHM? Do you think it's worth bothering or just better stay single-minded?

 TheEKey_

 

Glad to hear you got it working!

 As far as a switch for the output caps, I'm not sure that would be a good idea. Even if it were just switching the bypass caps, the momentary charges and discharges might bleed through the switch with arcing. This could expose your headphones to transient spikes or worse. I've just not seen it done, maybe for the same reason that most don't socket capacitors, either.

 I've switched the output resistors before and that works well if you want to try to that - switching between 10 ohms and 100 ohms, jumpers and 47 ohms, or something like that. This can easily be accomplished with a DPDT switch.

 If you're really interested in the best output cap, IMHO you won't find anything better than a 196- or 96-series VitaminQ at the prices we have. Beyond that, you're talking $tens of dollars to get noticeable improvements with Mundorfs and the like, IMHO. We did a lot of experimentation early on with the MAX regarding the output caps.


----------



## TheEKey

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Glad to hear you got it working!

 As far as a switch for the output caps, I'm not sure that would be a good idea. Even if it were just switching the bypass caps, the momentary charges and discharges might bleed through the switch with arcing. This could expose your headphones to transient spikes or worse. I've just not seen it done, ...._

 

Yea. Feels awesome to get rid of some sticky bugs. Especially this one was particularly easy to do.

 I'm done with the output resistors during the building and settled with jump.

 For the output caps, I really think the default Muse ES provides too much bass. Looking for more muscial and vocal caps. I should try the VitaminQ. 

 TheEKey


----------



## tomb

Quote:


  Originally Posted by *TheEKey* /img/forum/go_quote.gif 
_Yea. Feels awesome to get rid of some sticky bugs. Especially this one was particularly easy to do.

 I'm done with the output resistors during the building and settled with jump.

 For the output caps, I really think the default Muse ES provides too much bass. Looking for more muscial and vocal caps. I should try the VitaminQ. 

 TheEKey_

 

Well, remember that the MAX's sound is a combination of many factors. It's true that the ES's provide a lot of bass, but they are very transparent as well. Much of that bass can come from the tubes - especially 12AE6's, although it still depends on the particular pair of tubes. I don't know what you have in there (I'll have to look at your pics again), but you may find the high end changes a lot with 12FM6's or 12FK6's.

 The VitQ's will also definitely make a difference. It's been stated many times, but I think the combination of ES's bypassed by VitQ's comes very close to the detail of Black Gates.


----------



## BoilermakerFan

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Well, remember that the MAX's sound is a combination of many factors. It's true that the ES's provide a lot of bass, but they are very transparent as well. Much of that bass can come from the tubes - especially 12AE6's, although it still depends on the particular pair of tubes. I don't know what you have in there (I'll have to look at your pics again), but you may find the high end changes a lot with 12FM6's or 12FK6's.

 The VitQ's will also definitely make a difference. It's been stated many times, but I think the combination of ES's bypassed by VitQ's comes very close to the detail of Black Gates.
	

	
	
		
		

		
		
	


	


_

 

And let's not forget the subtle or not-so-subtle differences the DBs make too. 

 TheEKey, I think I would roll a few different tube sets in and out with the ESs bypassed with VitQs. Then decide if you still think there is too much bass even with 12FK6 tubes. I don't recall seeing which DBs you're using, but you might try a different set of DBs too before rolling Cerafine, Muse KZ, or Silmic II caps into your MHM. I have a buddy who really likes forward, bright highs and less bass. He loves SR-325i over the RS-1s and also loves his Markl modded Denon D2000s. His tastes are different than mine, but I'd build his MHM with 12FK6 tubes, KZ caps and VitQ bypass caps. I forget the recommended DB combo right now, but it leans to the high with a more clinical sound...


----------



## TheEKey

Quote:


 The VitQ's will also definitely make a difference. It's been stated many times, but I think the combination of ES's bypassed by VitQ's comes very close to the detail of Black Gates.
 __________________
 TomB 
 

 Quote:


  Originally Posted by *BoilermakerFan* /img/forum/go_quote.gif 
_And let's not forget the subtle or not-so-subtle differences the DBs make too. _

 

Currently I use 12FM6. Is this considered heavy bass? Will it contribute the most of the responses.

 I would definitely like to try out more tubes. 

 First of all, I'll try out as many as combinations shown in the Max Boutique. Hope that I will hit the right one.

 For DB, I think I will leave it to the next MHM ( I'm amazed that Bantam DAC is included in the MHM 1.2 board) 

 Cheer~!

 TheEKey


----------



## tomb

Quote:


  Originally Posted by *TheEKey* /img/forum/go_quote.gif 
_Currently I use 12FM6. Is this considered heavy bass? Will it contribute the most of the responses.

 I would definitely like to try out more tubes. 

 First of all, I'll try out as many as combinations shown in the Max Boutique. Hope that I will hit the right one.

 For DB, I think I will leave it to the next MHM ( I'm amazed that Bantam DAC is included in the MHM 1.2 board) 

 Cheer~!

 TheEKey_

 

No, 12FM6's are not bass-heavy. I'd suggest those VitQ's as the first thing you try, then.


----------



## Dan55

Quote:


  Originally Posted by *cetoole* /img/forum/go_quote.gif 
_OK, I have a guess, and it isnt good, but here goes: when you had DR1D in backwards, that effectively shorted the wallwart's output, and probably blew an internal protection fuse, which means that wallwart is now basically toast. Let us do some measurements though, and if you can, please dig up another source of AC voltage you can use to make sure your meter is working properly. Basically, I would like you to unplug the wallwart from the Max, and try and measure the AC voltage on the output with no load, then do the same with another AC wallwart which is known good._

 

I finally picked up a new AC wallwart, and the Max is working beautifully (I think). Thanks for all the help!


----------



## cetoole

Quote:


  Originally Posted by *Dan55* /img/forum/go_quote.gif 
_I finally picked up a new AC wallwart, and the Max is working beautifully (I think). Thanks for all the help!_

 

Awesome! Great to have some closure on that, and glad that Another Max Lives!


----------



## amphead

Another Max Lives!    All is right with the world again.


----------



## rbx

First of all let me thank you for this thread, which inspired me to buy the Millett Hybrid Maxed kit from glass jar audio and following to build this great amp about 6 months ago (first DIY amp build 
	

	
	
		
		

		
		
	


	




 ): 
















 Unfortunately since some time the left channel started to hiss and then slightly hum/crack from time to time (ca. 10-20 sec.) I changed the cd-player with another one in order to eliminate the fault in cd-player - the problem persisted. Eventually the slight hiss/hum/crack was there even when I turn off the cd-player - slight hiss/hum/crack in the left channel from time to time. Setup is standard - 27V supply voltage, 13,5V tube voltage, 110mV on the output stage. 220V to 110V adapter before the power supply. 

 I'll be grateful if you could help me to determine the source of the problem, in case you know/have had similar problems. Please keep in mind my somehow limited electric circuit schematics understanding skills 
	

	
	
		
		

		
		
	


	




.


----------



## BoilermakerFan

Quote:


  Originally Posted by *rbx* /img/forum/go_quote.gif 
_First of all let me thank you for this thread, which inspired me to buy the Millett Hybrid Maxed kit from glass jar audio and following to build this great amp about 6 months ago (first DIY amp build 
	

	
	
		
		

		
		
	


	




 ): 

 Unfortunately since some time the left channel started to hiss and then slightly hum/crack from time to time (ca. 10-20 sec.) I changed the cd-player with another one in order to eliminate the fault in cd-player - the problem persisted. Eventually the slight hiss/hum/crack was there even when I turn off the cd-player - slight hiss/hum/crack in the left channel from time to time. Setup is standard - 27V supply voltage, 13,5V tube voltage, 110mV on the output stage. 220V to 110V adapter before the power supply. 

 I'll be grateful if you could help me to determine the source of the problem, in case you know/have had similar problems. Please keep in mind my somehow limited electric circuit schematics understanding skills 
	

	
	
		
		

		
		
	


	




._

 

Did you swap the tubes left and right to eliminate the possibility of a failing tube? If you swap and the problem follows the tube to the right channel, then you just need a new tube.


----------



## rbx

@BoilermakerFan: Thank you for the suggestion, just tried it, but the hum stays on the left side, alas it is not the tube. The noise resembles something like a AM tuner noise between the stations, and its level is independent from the volume level.


----------



## tomb

Quote:


  Originally Posted by *rbx* /img/forum/go_quote.gif 
_@BoilermakerFan: Thank you for the suggestion, just tried it, but the hum stays on the left side, alas it is not the tube. The noise resembles something like a AM tuner noise between the stations, and its level is independent from the volume level._

 

It could be a loose input wire connection. I had a recent scare on mine and checked everything, only to discover that the stupid little 3.5mm jack on my BantamDAC was starting its expected routine of losing continuity. Rotate the plug about an 1/8th turn - everything's OK. Rotate it back, and huge hum and noise on the left channel. -Sigh- I'm going to learn not to use those things one day.
	

	
	
		
		

		
		
	


	




 Check your terminal block wiring and make certain that the lead in wires haven't worked loose, oxidized, or been crushed into nothingness (my particular problem from repeatedly tightening the terminal block screws).


----------



## rbx

@tomb: Thank you for the advice. At the first glance the terminal connections seem fine, and the hum appears as well without any interconnects put in. I'll nevertheless check them thoroughly again and resolder the RCA jacks and ground to be sure for a cold joint.


----------



## amphead

You could try reflowing solder at all of your critical points, being cautious not to get solder bridges to the ground plane from the top. Good Luck!


----------



## Mr.Unknown

people,
 i realize that 70% of Millett max í of tangentsoft,. Psu is step, Buffer is of M^3, only input stage is new.
 I can't find millett tube in my country(12AE6- 12FM6...) so can i design input stage with another tube such as 12AU7 or 12AX7 ,.....
 Please help me, thank.


----------



## Mr.Unknown

people,
 i realize that 70% of Millett max í of tangentsoft,. Psu is step, Buffer is of PPAv2(mistaken), only input stage is new.
 I can't find millett tube in my country(12AE6- 12FM6...) so can i design input stage with another tube such as 12AU7 or 12AX7 ,.....
 Please help me, thank.


----------



## tomb

Quote:


  Originally Posted by *Mr.Unknown* /img/forum/go_quote.gif 
_people,
 i realize that 70% of Millett max í of tangentsoft,. Psu is step,_

 

Nope. The power supply has been totally re-designed, based loosely on the LM317 datasheet. So, it's not really similar anymore. Besides, even Tangent allowed that the design was his PCB layout - not the circuit. The circuit has always been a derivative of the LM317 datasheet. Only now, the power supply has been greatly enhanced. It includes specific measures that work only for the MAX to achieve a very competitive low-noise output - developed through our own exhaustive trial and error experimentation.
	

	
	
		
		

		
			




  Quote:


 Buffer is of M^3, only input stage is new. 
 

This is totally incorrect, too. The MAX's buffer was _never_ based on the M3, even with the MOSFET option. It traces its lineage most directly back to Steinchen's implementation of the diamond buffer for the Millett Hybrid. Before that, it was implemented in any number of places, most notably by PPL in the second version of the PPA. However, the diamond buffer is fairly common in its basic circuit and can probably be traced back to some of Walt Jung's designs. The MOSFET version of the diamond buffer has a few extra wrinkles that AMB helped develop, but even then - not based on the M3.

 The input stage is pure Pete Millett and has not changed (except a slightly different cetoole-designed-CCS) since his original publication in AudioXpress magazine.
  Quote:


 I can't find millett tube in my country(12AE6- 12FM6...) so can i design input stage with another tube such as 12AU7 or 12AX7 ,.....
 Please help me, thank. 
 

Sorry. Those two tubes you mention are not even close. However, it's not like Millett tubes are scarce. Except for the 12FM6, you can find Millett tubes at just about _every_ vendor who sells tubes, including e-bay, beezar.com, and many overseas outlets.


----------



## nocturnalsheet

Hi guys, need some help/advice on my millet. i was playing around with tube rolling the past 2 days and was about to case back my millet when i noticed this(see pictures). 

 it look burned out and i have no idea what that is suppose to be or do. (i bought the millet and didnt build it myself so i have no clue on the schematics involved)

 i didnt dare to turn on my millet after discovering this but my millet was working fine and my headphones werent damaged prior to my discovery. 
















 is the problem serious? 
 how does it affect the whole circuitry? 
 should i refrain from using the millet until the part is replaced? 
 what could be the cause of this?

 thanks. your help is very much appreciated.


----------



## soloz2

that's just RLED. see if the power LED (and tube LEDs) light up if you flip on the power. It likely needs to be replaced.


----------



## tomb

Soloz2 is correct, but that resistor looks woefully undersized. The Panel LED shouldn't be pulling that much amperage, but if it was sized with the rest, it would be 10-15ma. At least a 1/2W resistor is needed. Those are usually twice the physical size of the one in the photo.

 EDIT: The tube LED resistors look adequate size, but someone may have assumed that the panel LED wouldn't pull as much and sized it for the same ohms, but less power. If so, it would still pull the same milliamps and burn out.


----------



## nocturnalsheet

Quote:


  Originally Posted by *soloz2* /img/forum/go_quote.gif 
_that's just RLED. see if the power LED (and tube LEDs) light up if you flip on the power. It likely needs to be replaced._

 

 Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Soloz2 is correct, but that resistor looks woefully undersized. The Panel LED shouldn't be pulling that much amperage, but if it was sized with the rest, it would be 10-15ma. At least a 1/2W resistor is needed. Those are usually twice the physical size of the one in the photo.

 EDIT: The tube LED resistors look adequate size, but someone may have assumed that the panel LED wouldn't pull as much and sized it for the same ohms, but less power. If so, it would still pull the same milliamps and burn out._

 


 thanks for the fast replies.

 tried powering on and both the power led and tube led lights up. 
	

	
	
		
		

		
		
	


	




 is there any danger to my millet if i continue to use it with the burned resistor?

 what is the part that i should get to replace it?

 thanks for the help.


----------



## soloz2

this is the part from the BOM:
293-2K-RC

 But you can source a 2kohm 1/2w resister elsewhere


----------



## tomb

Quote:


  Originally Posted by *nocturnalsheet* /img/forum/go_quote.gif 
_thanks for the fast replies.

 tried powering on and both the power led and tube led lights up. 
	

	
	
		
		

		
		
	


	


_

 

That may be true, but it's probably hanging by a thread. You can count on it failing soon, most likely.

  Quote:


 is there any danger to my millet if i continue to use it with the burned resistor? 
 

No.

  Quote:


 what is the part that i should get to replace it? 
 

Soloz2 gave you a good link.

  Quote:


 thanks for the help. 
 

One other thing - I don't like seeing the center support not used. That's the open hole in the middle. It should be attached to the bottom of the case with a standoff such that the board doesn't flex at all when plugging and unplugging tubes. I guess if you never do any tube-rolling, it'll be fine, but otherwise - something else to work on to keep another failure from occurring that would be much more serious.

 Another option is to simply install a screw long enough to touch the bottom of the case. IOW, you'd use a nut to fasten it to the board, but if it was long enough to touch bottom, then it would provide the needed support at least in one direction.


----------



## nocturnalsheet

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_That may be true, but it's probably hanging by a thread. You can count on it failing soon, most likely.

 No.

 Soloz2 gave you a good link.

 One other thing - I don't like seeing the center support not used. That's the open hole in the middle. It should be attached to the bottom of the case with a standoff such that the board doesn't flex at all when plugging and unplugging tubes. I guess if you never do any tube-rolling, it'll be fine, but otherwise - something else to work on to keep another failure from occurring that would be much more serious.

 Another option is to simply install a screw long enough to touch the bottom of the case. IOW, you'd use a nut to fasten it to the board, but if it was long enough to touch bottom, then it would provide the needed support at least in one direction._

 

thanks for the advice tomb, in the process of rectifying my millet and sourcing the resistor locally.

 @Soloz2 thanks for the link, allowed me to know what exact part to get.


----------



## smegger

Finally getting round to finishing my millet which i started over a year ago!!! 
	

	
	
		
		

		
		
	


	










 Been out of the loop in thinking about what i was going to do with it, 
 i have realised i am really awkward because i ordered a little toroid with it instead of the wall wart. I ant really see any problems as a wall wart is just a little transformer aint it!

 i just want to check that the amp will run ok with this before i go ahead and order my face plates from font panel express.

 Cant wait to finally get this finished and see what my k601s will sound like with proper power!

 here is a photo the toriod, my board and the general layout of the casing i am thinking about
















 Thanks for the help in advance guys!

 Wana get this build finished finally!


----------



## tomb

It looks OK from here! Be sure you wire the secondaries of that toroid in parallel - Black and Orange (0V) should be wired together as one lead, then Red and Yellow (25VAC) should be wired together to form the second lead. This will give you 25VAC at 1.2A.

 I'd still try to connect it up temporarily and make certain everything works before purchasing the expensive panels. There always a chance the tubes can pick up the interference from the toroid in one position or another. Most likely, it will be fine, but you never know ... hate to spend all that money and then decide the toroid works better in the back or something.


----------



## smegger

was thinking that about the parallel, school physics coming back to me!

 i think ill give the wire up a go tomorrow. and give the thing a listen.

 Would i need to fuse the board or will the fuse in the power supply be enough?

 any idea what fuse i would need for either of these??

 cheers tomb


----------



## BoilermakerFan

If there is any way you can fab or source a cover or at least isolate the toroid, it will help.

 FWIW, a few others are already using 50VA or 100VA toroids with no issues. I'll be using a 100VA in a NABU where it is isolated from the MAX board.


----------



## tomb

Quote:


  Originally Posted by *smegger* /img/forum/go_quote.gif 
_was thinking that about the parallel, school physics coming back to me!

 i think ill give the wire up a go tomorrow. and give the thing a listen.

 Would i need to fuse the board or will the fuse in the power supply be enough?

 any idea what fuse i would need?

 cheers tomb_

 

A 1A slo-blo would probably do the trick. With a raw transformer, it's a good idea to use the fuse on the board. The fuse on the line side will protect the primary, but there's nothing to protect the secondaries unless you use the fuse on the board.


----------



## BoilermakerFan

Are your taxes done yet Tom? 
	

	
	
		
		

		
			





 Just finished mine today...


----------



## smegger

Problems 
	

	
	
		
		

		
		
	


	













 think i left my amp on too long the first run!!! didnt see the bit about turning down Rb12 L/R

 now been checking the values getting 28/9mV on the left chanel

 getting like 600+mV on the right one! this is way to high! 

 What is likely to have broken? trimmer or have i fried the right channel? 

 can i check this?

 no burning smell or anything one had the amp on like for a minute tops the first time.


----------



## tomb

Quote:


  Originally Posted by *smegger* /img/forum/go_quote.gif 
_Problems 
	

	
	
		
		

		
		
	


	













 think i left my amp on too long the first run!!! didnt see the bit about turning down Rb12 L/R

 now been checking the values getting 28/9mV on the left chanel_

 

I hope you mean 28mV, which essentially means the RB12L trimmer is turned all the way down right now. Leave it for now so that you can use this channel as your reference for "what's right."

  Quote:


 getting like 600+mV on the right one! this is way to high! 
 

Yep - that's too high. However, are you saying it's this high with the trimmer turned all the way down or is this what you measured without adjustment? 

  Quote:


 What is likely to have broken? trimmer or have i fried the right channel? 
 

It takes quite a few minutes to really smoke one. Most likely, you've got a part out of place. Go over VERY carefully the parts you have in the right channel buffer compared to the left's. Make certain you have the same resistors in the same positions and the same TO-92 transistors (e.g., 2n5088's in the right place vs. 2n5087's in the right place). Check to make certain that you didn't swap the output transistors from the positions on the left channel. Refer to this diagram on the MAX website for proper location of the output transistors:





 Also refer to the buffer biasing setup page on the MAX website:
MAX Setup and Bias Settings

 What about the tubes, voltage adjust, volume control position, etc? Were these measurements made with the tubes in - were they biased? What was the voltage? Was the volume knob turned down to zero? You must have the volume down when you bias. You should kick the power on and off to make these measurements until you solve the buffer bias problem. Still, one of these things may be your problem. 

 By the way, is there any chance you used MOSFETs? I noticed in your pics that you went with the taller heat sinks. The layout pic above and setup reference will not apply with MOSFETs - we'll have to look at the MOSFET-MAX website, instead.

  Quote:


 can i check this?

 no burning smell or anything one had the amp on like for a minute tops the first time. 
 

Yes, you can check this. It may take some effort, but we usually solve these things.


----------



## smegger

had a quick check, def not mosfets,

 tubes in volume down when i did the test, 

 both trimmers turned down fully down as per the website got 28mV in the left and like 600mV in the right

 i checked the resistance of the trimmer pots by using my multimeter and the outer two pins on the pots and tried to check adjustment by taking different reading while turning the screws and the left one gives different valuse as expected however the right one doesn't seem to change?

 could this be the problem???

 il have a more detailed check over the components now.


 EDIT

 Just set the Power Supply to 27v

 getting 28.7mV on the left channel


 getting 700+mV on right channel

 Tube bias wasnt set for this

 EDIT 2

 just noticed QB1R is in the wrong way round correcting now

 EDIT 3

 WOOO Getting the right numbers now to drive to my student flat to get my K601s!

 thanks TOMB!


----------



## tomb

Quote:


  Originally Posted by *smegger* /img/forum/go_quote.gif 
_<snip>

 EDIT 2

 just noticed QB1R is in the wrong way round correcting now

 EDIT 3

 WOOO Getting the right numbers now to drive to my student flat to get my K601s!

 thanks TOMB!_

 

Way to go!! You did it, though!

 How's the xfmr? Any hum with it to the side like that? If not, order those panels, now!!


----------



## smegger

Cant hear any thing out of the ordinary in normal listening, any way to isolate it just to be sure?

 Also my k601s now sounds awesome! who ever said these had no bass!

 Really enjoying the first sounds out of my amp!


----------



## tomb

Quote:


  Originally Posted by *smegger* /img/forum/go_quote.gif 
_Cant hear any thing out of the ordinary in normal listening, any way to isolate it just to be sure?

 Also my k601s now sounds awesome! who ever said these had no bass!

 Really enjoying the first sounds out of my amp!_

 

Well, the K601's are pretty revealing. So if you don't hear anything, chances are things are fine. I'm no expert in such things, but what seems to be certain is that you need to use steel in order to block any potential hum. Some have encased the entire toroid in a steel box. Others have put a steel divider in the case between the toroid and AC and the rest of the amp. Keep in mind, though, that many people use toroids bare (they are naturally less noisy) - just as you had it in your mock-up layout - and never have an issue.

 I only mentioned it to urge a bit of caution before you spent all the $$ on the panels. As I said, if you don't hear it - I'm sure everything is fine.


----------



## Takaji

Finally I'm done university for the year, and I can start again on finishing up my MAX build. I've been mulling over ideas in my head for an enclosure, and I had a post saved from the forums of a nice case, but I can't remember what brand the case is... is anybody familiar with this? It's Ferrari's build.






 More photos at the link here.

 Thanks!


----------



## johnwmclean

Quote:


  Originally Posted by *Takaji* /img/forum/go_quote.gif 
_Finally I'm done university for the year, and I can start again on finishing up my MAX build. I've been mulling over ideas in my head for an enclosure, and I had a post saved from the forums of a nice case, but I can't remember what brand the case is... is anybody familiar with this? It's Ferrari's build._

 

Looks like one of these DACT enclosures:

DACT Enclosure - Soundlabs Group


----------



## soloz2

hifi2000
modushop.biz

 upon closer inspection it's an ATI (or something like that) case but they went out of business if I recall correctly


----------



## Takaji

IMO ATI Research had the nicest enclosures available. It's a real shame they're out of business. The other cases seem too rectilinear...

 Thanks for the help in identifying it, though. I'm still not sure what I'm gonna choose for an enclosure, but I'm looking at modushop.biz more closely now.


----------



## mrarroyo

Any of you looking for boards? I ask because I have three (3) new boards I never got around building.


----------



## WilCox

TomB and Colin,

 Did you guys try adding a Polyfuse in series with DR3 in the V1 MAX board? I know the ground configuration was a big contributor in lowering the noise floor of the MiniMAX (and upcomming V2 MAX), but I was just wondering if adding PF1 to my V1 MAX would be a measureable improvement.


----------



## WilCox

Quote:


  Originally Posted by *WilCox* /img/forum/go_quote.gif 
_TomB and Colin,

 Did you guys try adding a Polyfuse in series with DR3 in the V1 MAX board? I know the ground configuration was a big contributor in lowering the noise floor of the MiniMAX (and upcomming V2 MAX), but I was just wondering if adding PF1 to my V1 MAX would be a measureable improvement._

 

Nevermind! I just looked at the board layout of the V1 MAX and realized that there would be a lot of traces and ground planes that would need to be cut to make this work.


----------



## BoilermakerFan

Quote:


  Originally Posted by *WilCox* /img/forum/go_quote.gif 
_Nevermind! I just looked at the board layout of the V1 MAX and realized that there would be a lot of traces and ground planes that would need to be cut to make this work. 
	

	
	
		
		

		
			



_

 

I plan to add a polyfuse, but I can't remember what points it spans and which trace gets cut...


----------



## WilCox

Quote:


  Originally Posted by *BoilermakerFan* /img/forum/go_quote.gif 
_I plan to add a polyfuse, but I can't remember what points it spans and which trace gets cut..._

 

Actually, it may not be so bad! CR5 may not be needed and may be able to be removed. Then the anode of DR3 can be relocated to the + pad where CR5 was. Then cut the trace after the CR5 + pad before it joins the power buss and insert the Polyfuse there. Colin and Tom should confirm if that would work and (assuming they have tried it) that it makes any difference.


----------



## Beefy

tomb suggested a procedure to me to convert the V1 to V2, but it is quite involved and not for the faint hearted......

 If it were me, I would either wait for V2 to build a new one. Or build a second if I already had one!


----------



## tomb

Quote:


  Originally Posted by *Beefy* /img/forum/go_quote.gif 
_tomb suggested a procedure to me to convert the V1 to V2, but it is quite involved and not for the faint hearted......

 If it were me, I would either wait for V2 to build a new one. Or build a second if I already had one! 
	

	
	
		
		

		
		
	


	


_

 

V2 is definitely looking up. The board is populated and the relays appear to work fine, although I haven't tested it with the Bantam, yet. The headphone relay is interesting - Colin has gone toward less parts, not more. Part of that philosophy dictated a change to 24V relays and the use of a 78L24 regulator instead of the zener diode/resistor combination. We had to rework the delays at the higher voltage, so you'll see a requirement for a 2M resistor. Either that, or it was upsizing to 1000uf caps or more. We didn't want to do that. Anyway, it works great - as a matter of fact, the offset that's always appeared on turn-off is completely gone. Most headphone delay circuits exhibit a brief excursion of a few volts under zero load, a bit less with a headphone connected. Even under zero load with this one, it's immeasureable on my Fluke. The parts selection we worked out will give you 45 seconds from a cold start, but at least 20-30 seconds on a quick re-start.

 The power supply measures *45uV noise* with the LNMP, so the MiniMAX power supply is a success for the MAX V2! This is also with 2x2000uf in the PS and 4x3300uf caps for CA4/5. I used a 0.75A polyfuse. I built it with MOSFETS, that's the reason for all the current bling.
	

	
	
		
		

		
		
	


	




 Right now, I'm not happy with the sound of the MOSFETs, though. The JFET-mod is not up to the quality of the MiniMAX sound with BJT's. With 1-1/2" sinks, I have it biased up to 150ma, but it runs a little hot on the middle sinks.
	

	
	
		
		

		
		
	


	




 I've tried dropping the bias down to 120ma, but it sounds noticeably worse - a hard, etched sound. One of the things Colin suggested is that the gate capacitance on the Z24/Z34's is too much for the tubes and this style of buffer. We talked about a lot of different things, though. Still in the next few days, I'm going to change those out to the IRF510/9510's and some Zetex's for the input JFETs. We'll see if that makes a difference.

 I'll post some pics when I get a chance. I've been covered up with doing other stuff lately.


----------



## Beefy

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_This is also with 2x2000uf in the PS and 4x3300uf caps for CA4/5. I used a 0.75A polyfuse. I built it with MOSFETS, that's the reason for all the current bling.
	

	
	
		
		

		
		
	


	


_

 

Bling indeed! Those must be pretty tall caps to fit?

  Quote:


 Right now, I'm not happy with the sound of the MOSFETs, though. 
 

How is it different from the old MOSFET Max that everyone seems to love......


----------



## tomb

Quote:


  Originally Posted by *Beefy* /img/forum/go_quote.gif 
_Bling indeed! Those must be pretty tall caps to fit?_

 

They're all ~35mm.
  Quote:


 How is it different from the old MOSFET Max that everyone seems to love...... 
	

	
	
		
		

		
		
	


	



 

It shouldn't be - except that it has a cleaner power supply. Now either the MAX's old power supply muddied things up a bit so that the hard edges were softened out or it's been that way all along and no one had built enough of the BJT's to be familiar with the comparison. That's the only thing I can figure - because everything else works perfectly.

 I ran it for quite awhile - some of this may be due to the KZ's I was using for output caps. Those obviously have a break-in: a lot less time than Black Gates, but the changes are striking. Many people talk in terms of the KZ's having a hard edge or "etching" to their sound, also. So maybe it's confluence of "etch", I don't know, but I ordered some Silmic's to replace them. That's the first thing I will try.


----------



## Beefy

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Now either the MAX's old power supply muddied things up a bit so that the hard edges were softened out or it's been that way all along and no one had built enough of the BJT's to be familiar with the comparison._

 

I do know that sacd_lover has had quite the assortment of Maxes, and raves the most about his MOSFET Max. It might be interesting to see what configuration he has in his amps.

  Quote:


 I ran it for quite awhile - some of this may be due to the KZ's I was using for output caps. Those obviously have a break-in: a lot less time than Black Gates, but the changes are striking. Many people talk in terms of the KZ's having a hard edge or "etching" to their sound, also. So maybe it's confluence of "etch", I don't know, but I ordered some Silmic's to replace them. That's the first thing I will try. 
 

If it were me, I would go with old-familiar. In your case, stick some Muse ES in there for some more direct comparisons to the combo you enjoy the most, and have the most experience with.


----------



## soloz2

Hmm... I've built several BJT versions and one MOSFET version and didn't notice the problems you're describing


----------



## BoilermakerFan

Quote:


  Originally Posted by *Beefy* /img/forum/go_quote.gif 
_If it were me, I would go with old-familiar. In your case, stick some Muse ES in there for some more direct comparisons to the combo you enjoy the most, and have the most experience with._

 

I second that Tom! But you already knew that... 
	

	
	
		
		

		
		
	


	




 Seriously though. Can you swap in the ES caps while you wait for the Silmics to show up? I think the KZs are causes at least half of your pain. I can send you my set of Cerafines and BC transistors too if you wish. 

 I have to prep all 5 of my NABU lower chassis for paint this week. My car was hit by my neighbor and my preferred shop is a direct bill with his insurance company. So I get to use my preferred shop and he has to buy Audi Brilliant Black Metallic paint anyways... So my lower chassis will all be sprayed Brilliant Black metallic instead of the satin since it will be $20 for all five this way. 
	

	
	
		
		

		
		
	


	




 Perf' ing the bottoms of the two V1.2 MHM chassis to line up with the new board cooling holes and adding holes in the bottom at the heatsink mounts to make my swaps faster too. The Aikido 24V will be prepped and painted along with 2 chassis for PSUs on the consoles. I'm going to try to get one top prepped with Om cut into the top to be backed by mesh for the cooling and two other will have blue agave plant silhouettes cut into them for the other two, but they won't be painted black...

 My buddy also dropped off one of the most amazing pieces of figured walnut I have seen in a long time. It's old growth harvested off a customer's private farm and milled locally. Wow! Only finish it will get is carved lettering and an oiled finish. Going to be one awesome face plate for one of my amps. I have enough of the walnut to also make feet and use as detail in the maple knobs for it. Only cost me 
	

	
	
		
		

		
		
	


	




 for the wood too. I suspect my buddy who gave the wood will eventually become the owner of my third MHM and a set of SFI orthos I build for him, but we'll see. He's a vintage guitar player so I'll have to get with Colin on how to mod (if necessary) the input to accept an electric guitar source as one of the two inputs beside the BantamDAC.


----------



## tomb

Thanks, guys! I already have a pair of Silmics and will put those in first (got them at CA2 already). It may just be the KZ's, but I have my doubts that they really sound that bad on their own.
	

	
	
		
		

		
		
	


	




 When I described the problem to Colin, of the things he suggested might be causing the issue, one was that it might be a symptom of too much gate capacitance in the MOSFETs. Turns out, the IRF510/9510's are way down in the capacitance values compared to other MOSFETs. Maybe that's why Pete used them on the Starving Student. We'll see what does what, though.

 It will have to wait a few days longer, unfortunately - I'm fighting with a couple of Starving Students that need to have the production boards and casing design vetted.

 EDIT: Sounds like some outstanding casework you have going there, BMF! Looking forward to seeing them!


----------



## kugino

both mouser and digikey are out of the CA4 and CA5 caps (1800uF 35V)...they won't be shipping until later this summer!! so, can someone recommend a replacement for these caps? thanks.


----------



## tomb

Quote:


  Originally Posted by *kugino* /img/forum/go_quote.gif 
_both mouser and digikey are out of the CA4 and CA5 caps (1800uF 35V)...they won't be shipping until later this summer!! so, can someone recommend a replacement for these caps? thanks._

 

Mouser has 91 of the UPW's in 1800uf 35V:
UPW1V182MHD6. These are slightly smaller than the 2200uf UPW's, but definitely in the ball park. They have 384 of the 2200uf 35V:
http://www.mouser.com/Search/Product...vfdOEj8hrJQ%3d
 They also have a Nichicon UHD, which looks to be the best choice for ESR and ripple, very close to the Panasonic FM at 1800uf 35V, same physical size:
http://www.mouser.com/Search/Product...5QXNp7Ln7Ok%3d

 Also, the 1000uf 50V Panasonic FM's at DigiKey are very close to the same ratings of ESR and ripple - exact same physical size.


----------



## kugino

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Mouser has 91 of the UPW's in 1800uf 35V:
UPW1V182MHD6. These are slightly smaller than the 2200uf UPW's, but definitely in the ball park. They have 384 of the 2200uf 35V:
UPW1V222MHD6
 They also have a Nichicon UHD, which looks to be the best choice for ESR and ripple, very close to the Panasonic FM at 1800uf 35V, same physical size:
UHD1V182MHD

 Also, the 1000uf 50V Panasonic FM's at DigiKey are very close to the same ratings of ESR and ripple - exact same physical size._

 

thanks, tom. of these, which do you think would work/sound the best?


----------



## tomb

Quote:


  Originally Posted by *kugino* /img/forum/go_quote.gif 
_thanks, tom. of these, which do you think would work/sound the best?_

 

For MAX or MiniMAX? I'm getting my threads mixed up these days. Those suggestions are for a MiniMAX where the height is restricted to 1" (25mm).

 If you're building a MAX and can go as much as 1-1/2" height, then a whole range of other caps can be used. I put 3300uf 35V Panasonic FC's on the V1.2 prototype MAX.


----------



## Beefy

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_I put 3300uf 35V Panasonic FC's on the V1.2 prototype MAX._

 

It just clicked...... I'm guessing you don't have to worry about turn off thump with the new relay system?


----------



## tomb

Quote:


  Originally Posted by *Beefy* /img/forum/go_quote.gif 
_It just clicked...... I'm guessing you don't have to worry about turn off thump with the new relay system?_

 

I'll check it again tonight to be sure, but with 1800uf's there's no measureable offset (thump) at turn off. I've been using the circuit on a MiniMAX for some months now and tried measuring it every which way, with no results. It's a slight click that's heard as opposed to a small whoosh or thump as before.
	

	
	
		
		

		
			





 You're correct to question whether my maxxed out capacitors on this MOSFET-MAX made a difference, but I'll let you know for sure.

 All I had until a few days ago were some 1/2A slo-blo fuses and it went through those like a soldering iron melting solder.
	

	
	
		
		

		
		
	


	




 I finally bypassed the fuse to get it biased and have been running it like that since.


----------



## Beefy

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_All I had until a few days ago were some 1/2A slo-blo fuses and it went through those like a soldering iron melting solder.
	

	
	
		
		

		
		
	


	


_

 

How hot does Vreg get?


----------



## tomb

Quote:


  Originally Posted by *Beefy* /img/forum/go_quote.gif 
_How hot does Vreg get? 
	

	
	
		
		

		
		
	


	


_

 

Vreg stays fine at 150ma bias - no more than about 45deg.C. The weak point is the MOSFET that ends up between the two middle heat sinks. It's at about 60deg.C., while the other one is at about 50deg.C. The outer MOSFETs are about the same as the Vreg. Because of the positive temperature coefficient, the bias may drop when I case it up. So I'm setting it up with tip jacks on all bias points just as I did the very first MAX prototype. That should give us some better info.


----------



## kugino

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_For MAX or MiniMAX? I'm getting my threads mixed up these days. Those suggestions are for a MiniMAX where the height is restricted to 1" (25mm).

 If you're building a MAX and can go as much as 1-1/2" height, then a whole range of other caps can be used. I put 3300uf 35V Panasonic FC's on the V1.2 prototype MAX._

 

tom, i'm building a MAX...i'm not sure what version board i have, though, as it was given to me by a friend. i'll go with the 2200uf caps just to be safe...thanks again.


----------



## BoilermakerFan

Quote:


  Originally Posted by *kugino* /img/forum/go_quote.gif 
_tom, i'm building a MAX...i'm not sure what version board i have, though, as it was given to me by a friend. i'll go with the 2200uf caps just to be safe...thanks again._

 

If it's a MHM board from Beezar, it's a version 1.0. Tom has the only V1.2 PCB right now, much to my dismay and repeated offers. 
	

	
	
		
		

		
		
	


	




  Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_EDIT: Sounds like some outstanding casework you have going there, BMF! Looking forward to seeing them!_

 

Thanks Tom. I finally succeeded in getting the V1.2 drawing to print out to the correct scale so I can locate all the screw and vent holes I need to drill in the bottom before paint. Also need to add a few more holes in the back for RCA and the IEC cutout. Decided to try to get one top prepped for paint too, but I need to see if he'll leave it without clear coat for me to do a little pin striping on the top after it's painted. Then I'll bring it back for clear and cure. It will definitely be one of a kind and hoping to match the level of work set by MrMajestic's so long ago.


----------



## Listen2this1

Does it hurt anything if I run two set of headphones at one time. One pair is Grado 325i's (32Ω) and the other pair is D7000's (25Ω)? I know the combo will be a really low load for the Max.


----------



## tomb

Quote:


  Originally Posted by *Listen2this1* /img/forum/go_quote.gif 
_Does it hurt anything if I run two set of headphones at one time. One pair is Grado 325i's (32Ω) and the other pair is D7000's (25Ω)? I know the combo will be a really low load for the Max._

 

No, I doubt it. The real issue would be with sound if those impedances were more of a mismatch - Sennheisers with Grados, for instance. The combined impedance of what you mentioned is 14 ohms - I doubt seriously that the MAX will have any trouble with that.


----------



## Listen2this1

Well I will give it a shot.


----------



## tomb

Quote:


  Originally Posted by *Listen2this1* /img/forum/go_quote.gif 
_Well I will give it a shot._

 

The last time cetoole and I discussed it, he's pretty much been using his MAX to drive a couple of desktop speakers (8ohm). That's mostly because he's into all sorts of electrostatics these days
	

	
	
		
		

		
		
	


	




, but he still uses the MAX for his orthos, too. At any rate, 8 ohms is fine for a MAX (within reason, of course - it's still a headphone amp).


----------



## BoilermakerFan

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_The last time cetoole and I discussed it, he's pretty much been using his MAX exclusively to drive a couple of desktop speakers (8ohm). That's mostly because he's into all sorts of electrostatics these days
	

	
	
		
		

		
		
	


	




, but he still uses the MAX for his orthos, too. At any rate, 8 ohms is fine for a MAX.
	

	
	
		
		

		
		
	


	


_

 

He has a couple MB Quart dynamics in the heard and he'll be demo'ing RS-1s and ESW9s shortly...


----------



## tomb

I posted this in another thread, but it really belongs here. It's just that they were talking about the MOSFET-MAX. At any rate, a good report - it was the KZ's!

 Just an update on the MOSFET-MAX V1.2 - I came to the conclusion that I hate Muse KZ caps. I replaced the KZ's on the outputs today with a pair of Silmic's at 1000uf 35V (big caps, but there was room!). It sounds wonderful.
	

	
	
		
		

		
		
	


	




 I even backed it down from 150ma bias in the buffer down to 125ma. It still sounds wonderful.
	

	
	
		
		

		
		
	


	




 Next up is testing the BantamDAC on the board with the switching relay, but I've got to do some more building first. The Starving Student PCB version blew out another one of my BantamDACs.


----------



## BoilermakerFan

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_I posted this in another thread, but it really belongs here. It's just that they were talking about the MOSFET-MAX. At any rate, a good report - it was the KZ's!

 Just an update on the MOSFET-MAX V1.2 - I came to the conclusion that I hate Muse KZ caps. I replaced the KZ's on the outputs today with a pair of Silmic's at 1000uf 35V (big caps, but there was room!). It sounds wonderful.
	

	
	
		
		

		
		
	


	




 I even backed it down from 150ma bias in the buffer down to 125ma. It still sounds wonderful.
	

	
	
		
		

		
		
	


	




 Next up is testing the BantamDAC on the board with the switching relay, but I've got to do some more building first. The Starving Student PCB version blew out another one of my BantamDACs.
	

	
	
		
		

		
		
	


	


_

 

 Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_ One of the things Colin suggested is that the gate capacitance on the Z24/Z34's is too much for the tubes and this style of buffer. We talked about a lot of different things, though. Still in the next few days, I'm going to change those out to the IRF510/9510's and some Zetex's for the input JFETs. We'll see if that makes a difference._

 

That is great news! Especially since I've been planning to use my Cerafines for my MOSFET-MAX with the IRF510/9510 DBs. Still planning to swap in the Zetexes? 

 Oh, and Starving Students don't need DACs, they need food! You might as well build a few extra BantamDACs while your at it.


----------



## Jrossel

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_
 Just an update on the MOSFET-MAX V1.2 - I came to the conclusion that I hate Muse KZ caps. I replaced the KZ's on the outputs today with a pair of Silmic's at 1000uf 35V (big caps, but there was room!). It sounds wonderful.
	

	
	
		
		

		
		
	


	




 I even backed it down from 150ma bias in the buffer down to 125ma. It still sounds wonderful.
	

	
	
		
		

		
		
	


	


_

 

I will make a note on the KZs for my kit BOM. Were they 1000 uF as well?
 Lots of people asking about MAX kits. Are we getting close to a release?

 Your proto board looks pretty cool.

 JR


----------



## soloz2

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_I posted this in another thread, but it really belongs here. It's just that they were talking about the MOSFET-MAX. At any rate, a good report - it was the KZ's!

 Just an update on the MOSFET-MAX V1.2 - I came to the conclusion that I hate Muse KZ caps. I replaced the KZ's on the outputs today with a pair of Silmic's at 1000uf 35V (big caps, but there was room!). It sounds wonderful.
	

	
	
		
		

		
		
	


	




 I even backed it down from 150ma bias in the buffer down to 125ma. It still sounds wonderful.
	

	
	
		
		

		
		
	


	




 Next up is testing the BantamDAC on the board with the switching relay, but I've got to do some more building first. The Starving Student PCB version blew out another one of my BantamDACs.
	

	
	
		
		

		
		
	


	







_

 


 glad to hear it! I'm still struggling to believe that there could be a better 'budget' DIY amp than my current MOSFET Max!


----------



## tomb

Quote:


  Originally Posted by *Jrossel* /img/forum/go_quote.gif 
_I will make a note on the KZs for my kit BOM. Were they 1000 uF as well?
 Lots of people asking about MAX kits. Are we getting close to a release?

 Your proto board looks pretty cool.

 JR_

 

Thanks, Jeff! Sorry about the comments on the KZ's. I just never tried them before, believe it or not.
	

	
	
		
		

		
		
	


	




 There must be some bad combination that results from their "hard etched sound" that combines badly with Millett tubes - or perhaps the VitQ's that we use for output bypasses. The MOSFETs definitely contribute to this, because they do seem very fast.

 To be specific, no on the 1000uf - the KZ's I tried were 470uf 50V. Keep in mind this is only in the CA7 positions - the direct output couplers. Sound quality means everything at that spot. To sum up again, I used the following:

 PS - 2 x 2000uf 50V Panasonic FC
 CA4/CA5 Decouplers - 3300uf 35V Panasonic FC
 CA2 - 1000uf 25V Elna RFS Silmic II
 CA7 - 1000uf 35V Elna RFS Silmic II
 Wima MKP10 bypasses all around, except 0.22uf 100V 196P-series Sprague VitaminQ at CA8

 MOSFETS are Z24/9Z34 with Toshiba JFETs 2SJ74 and 2SK170 at Q2/Q3 buffer signal input positions.

 Thanks for the comments on the board! Yes, we are getting very close. The PS tests just as good as the MiniMAX, the sound is great with the combo I'm using now. The only thing left is to test the BantamDAC mounting and the input-relay switching. I'll try to get to it this weekend, but you know how things go - I've got the Starving Student I've got to release for sale on Beezar, too.


----------



## Beefy

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Just an update on the MOSFET-MAX V1.2 - I came to the conclusion that I hate Muse KZ caps. I replaced the KZ's on the outputs today with a pair of Silmic's at 1000uf 35V (big caps, but there was room!). It sounds wonderful.
	

	
	
		
		

		
			





 I even backed it down from 150ma bias in the buffer down to 125ma. It still sounds wonderful.
	

	
	
		
		

		
		
	


	


_

 

What did I tell ya, eh?


----------



## BoilermakerFan

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Thanks, Jeff! Sorry about the comments on the KZ's. I just never tried them before, believe it or not.
	

	
	
		
		

		
		
	


	




 There must be some bad combination that results from their "hard etched sound" that combines badly with Millett tubes - or perhaps the VitQ's that we use for output bypasses. The MOSFETs definitely contribute to this, because they do seem very fast.

 To be specific, no on the 1000uf - the KZ's I tried were 470uf 50V. Keep in mind this is only in the CA7 positions - the direct output couplers. Sound quality means everything at that spot. To sum up again, I used the following:

 PS - 2 x 2000uf 50V Panasonic FC
 CA4/CA5 Decouplers - 3300uf 35V Panasonic FC
 CA2 - 1000uf 25V Elna RFS Silmic II
 CA7 - 1000uf 35V Elna RFS Silmic II
 Wima MKP10 bypasses all around, except 0.22uf 100V 196P-series Sprague VitaminQ at CA8

 MOSFETS are Z24/9Z34 with Toshiba JFETs 2SJ74 and 2SK170 at Q2/Q3 buffer signal input positions.

 Thanks for the comments on the board! Yes, we are getting very close. The PS tests just as good as the MiniMAX, the sound is great with the combo I'm using now. The only thing left is to test the BantamDAC mounting and the input-relay switching. I'll try to get to it this weekend, but you know how things go - I've got the Starving Student I've got to release for sale on Beezar, too.
	

	
	
		
		

		
		
	


	


_

 

Now socket the DB transistor positions, add 3/8" spacers under the sinks and screw mount them! Then you can swap DBs till your hearts content like I plan to do! Might have to invest in permanent voltage meters for the bias current test points too. 
	

	
	
		
		

		
		
	


	




 Off to eBay...

 Laying out the chassis for the new V1.2 boards in the NABUs. My top cover art will allow both tubes to be visible or have clearance if I need it. Tom, how tall are your tube top tips measured from the top of the PCB? Just want to make sure I have the height I need to allow me to put screening in the chassis to cover the openings.


----------



## tomb

Quote:


  Originally Posted by *BoilermakerFan* /img/forum/go_quote.gif 
_Now socket the DB transistor positions, add 3/8" spacers under the sinks and screw mount them! Then you can swap DBs till your hearts content like I plan to do! Might have to invest in permanent voltage meters for the bias current test points too. 
	

	
	
		
		

		
		
	


	




 Off to eBay...

 Laying out the chassis for the new V1.2 boards in the NABUs. My top cover art will allow both tubes to be visible or have clearance if I need it. Tom, how tall are your tube top tips measured from the top of the PCB? Just want to make sure I have the height I need to allow me to put screening in the chassis to cover the openings._

 

Standard tube height from the base is 1-7/8", but there's the socket height to consider - probably about 5/8". So, I'd say approx. 2-1/2" ... this will vary according to the tubes, but should be about maximum.


----------



## TimJo

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_The Starving Student PCB version blew out another one of my BantamDACs.
	

	
	
		
		

		
		
	


	


_

 






 What happened?


----------



## BoilermakerFan

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Standard tube height from the base is 1-7/8", but there's the socket height to consider - probably about 5/8". So, I'd say approx. 2-1/2" ... this will vary according to the tubes, but should be about maximum._

 

Thanks. I saw the tube drawing, but wasn't sure of the maximum height installed with the sockets.


----------



## tomb

Quote:


  Originally Posted by *TimJo* /img/forum/go_quote.gif 
_





 What happened?_

 

Talk to Ludoo.
	

	
	
		
		

		
		
	


	




 It's a common recurring problem, unfortunately. There is something in the grounded cathode/MOSFETs on the SSMH that cause a voltage/ground issue to develop on the RCA inputs. It's enough to fry an Alien/BantamDAC under the right scenario. This time, the DAC had been plugged in to the USB for hours - so the DAC's output caps were plenty charged. The SSMH was on, because some of us suspected the offset occurred on power up (PS "stuttering"). I think I missed the socket on one channel and accidentally touched the center pin to the outside of the RCA jacks on the SSMH (negative ground). That was enough - that channel is dead.

 I'd talk about the suspicions of what causes it more, but it should probably be discussed in the SSMH thread, not here. Before anyone asks, let me say I've not had issue one with MAX/MiniMAX and Bantams/Aliens - nor have I heard of an issue, either.


----------



## tomb

Success!! The MOSFET-MAX V1.2 prototype now lives with an onboard BantamDAC and operating switching relay between the DAC and RCA inputs. The operation is seamless, no switching noise, nada - it works flawlessly
 !
	

	
	
		
		

		
		
	


	




 Today I spent some time building another BantamDAC and hooking it up to check the final feature in the MAX V1.2 PCB - the onboard Bantam with relay switching between RCA inputs and the Bantam. Pics below.









 Note the Bantam with output leads plugged into a 6p terminal block (2x3's in this case). The three leads on the right are from RCA jacks. The 2p terminal block is connected to a DPDT switch. I haven't populated the LED because I'm going to use the other two poles on the switch to activate the LED when the switch is thrown. This will all be wired to the front panel.
	

	
	
		
		

		
		
	


	




 Cetoole has some tweaks we've discussed to add to the board, but we're essentially ready to go to production.


----------



## zkool448

Congrats tomb 
	

	
	
		
		

		
		
	


	




 What sets this MAX V1.2 apart to me is the built-in DAC feature - a nice, convenient option IMO.

_[size=xx-small]* Let me know when you're fully done with that proto board, I'd be happy to take that off your hands[/size]_


----------



## tomb

Quote:


  Originally Posted by *zkool448* /img/forum/go_quote.gif 
_Congrats tomb 
	

	
	
		
		

		
		
	


	




 What sets this MAX V1.2 apart to me is the built-in DAC feature - a nice, convenient option IMO.

[size=xx-small]* Let me know when you're fully done with that proto board, I'd be happy to take that off your hands[/size]





_

 

Thanks! It's been a long time coming (more of that one-man band thing and too much to do). I can't wait to case it up. The MOSFET buffer is really something else with the Elna Silmic caps, too.
	

	
	
		
		

		
		
	


	




 EDIT: I suppose my HF-1's will be passe', soon.


----------



## BoilermakerFan

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Success!! The MOSFET-MAX V1.2 prototype now lives with an onboard BantamDAC and operating switching relay between the DAC and RCA inputs. The operation is seamless, no switching noise, nada - it works flawlessly
 !
	

	
	
		
		

		
		
	


	




 Today I spent some time building another BantamDAC and hooking it up to check the final feature in the MAX V1.2 PCB - the onboard Bantam with relay switching between RCA inputs and the Bantam. Pics below.









 Note the Bantam with output leads plugged into a 6p terminal block (2x3's in this case). The three leads on the right are from RCA jacks. The 2p terminal block is connected to a DPDT switch. I haven't populated the LED because I'm going to use the other two poles on the switch to activate the LED when the switch is thrown. This will all be wired to the front panel.
	

	
	
		
		

		
		
	


	




 Cetoole has some tweaks we've discussed to add to the board, but we're essentially ready to go to production.
	

	
	
		
		

		
		
	


	


_

 

Woohoo! Can you do us a huge favor for those of us who have full parts count for V1.0 MAXes that are waiting for the V1.2 release? When it's in production, can you do a small BOM for only the new or changed parts calling out exactly what has changed and what new parts we'll need to order for the V1.2 build? 

 It's nice to see I can use my Darwin I/O control and bypass a DPDT, although I did drill holes in the rear for them in two chassis as a precaution. 

 I have pics of my V1.0 board mocked up in it's NABU chassis that will be my console amp so it also has the AudioSector Gainclone boards in it. With 1/4" PCB standoffs and 3/8" spacers between the PCB and 2-1/2" DB heatsinks, I still have 1/4" of clearance between the top of the DB heatsink and the chassis top! So it's a full 3" of available clearance from the top of the PCB! Tubes and everything else will remain safely under cover. 
	

	
	
		
		

		
		
	


	




 I have pics, but need to upload them to photobucket...

  Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Thanks! It's been a long time coming (more of that one-man band thing and too much to do). I can't wait to case it up. The MOSFET buffer is really something else with the Elna Silmic caps, too.
	

	
	
		
		

		
		
	


	




 EDIT: I suppose my HF-1's will be passe', soon.
	

	
	
		
		

		
		
	


	


_

 

Why do you say that? They look great next to the V1.2 MAX. I have Silmics and Cerafines, but was planning to use the Cerafines in my MOSFET-MAX. Muse ESs are going in V1.0 with the console amp. Maybe my V1.2 BJT MAX needs the Silmics?

 You might be able to talk me into prepping a NABU case for you too (but I'll need to order more...). 
	

	
	
		
		

		
		
	


	




 I have the layout pretty standardized now (including access to the DB heatsink mounting screws from below to allow fast swaps of DB with socketed boards). I also figured out how to maximize utility and aesthetics by reusing or cutting out the existing holes in the chassis so only the old TO-3 V-reg holes are visible if they aren't used (using mine for the Darwin and phono stage regs so they're closed). 

 OT, but the Aikido 24V was much more challenging to prep since it's so much bigger. Almost as many cooling holes in that PCB as the new MAX too!


----------



## tomb

Quote:


  Originally Posted by *BoilermakerFan* /img/forum/go_quote.gif 
_Woohoo! Can you do us a huge favor for those of us who have full parts count for V1.0 MAXes that are waiting for the V1.2 release? When it's in production, can you do a small BOM for only the new or changed parts calling out exactly what has changed and what new parts we'll need to order for the V1.2 build?_

 

Yep - I'll work on it! 

 <snip>

  Quote:


 Why do you say that? They look great next to the V1.2 MAX. 
 

The new Grado HF-2 is being sold to Head-Fi members as we speak (at TTVJ) and will be unveiled at CanJam. 

  Quote:


 I have Silmics and Cerafines, but was planning to use the Cerafines in my MOSFET-MAX. Muse ESs are going in V1.0 with the console amp. Maybe my V1.2 BJT MAX needs the Silmics? 
 

Cerafines are probably just as good, although I still haven't had the pleasure.
	

	
	
		
		

		
		
	


	




 ES's will always be the first choice for 1" heights and the MiniMAX.

  Quote:


 You might be able to talk me into prepping a NABU case for you too (but I'll need to order more...). 
	

	
	
		
		

		
		
	


	




 I have the layout pretty standardized now (including access to the DB heatsink mounting screws from below to allow fast swaps of DB with socketed boards). I also figured out how to maximize utility and aesthetics by reusing or cutting out the existing holes in the chassis so only the old TO-3 V-reg holes are visible if they aren't used (using mine for the Darwin and phono stage regs so they're closed). 

 OT, but the Aikido 24V was much more challenging to prep since it's so much bigger. Almost as many cooling holes in that PCB as the new MAX too! 
 

The production version will have even larger holes under the center sinks - that's one of the tweaks we're making.


----------



## GRUN

hi TomB

 I finished building my miniMAX few weeks ago.

 I feel MAX sound is warm and bouncing!
 It looks like the sound of RS-1 if it compares it.
 This is just my favorite sound. thanks!


----------



## BoilermakerFan

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Yep - I'll work on it! 

 <snip>


 The new Grado HF-2 is being sold to Head-Fi members as we speak (at TTVJ) and will be unveiled at CanJam. 

 Cerafines are probably just as good, although I still haven't had the pleasure.
	

	
	
		
		

		
		
	


	




 ES's will always be the first choice for 1" heights and the MiniMAX.

 The production version will have even larger holes under the center sinks - that's one of the tweaks we're making.
	

	
	
		
		

		
		
	


	


_

 

Uh oh, must resist pre-order...

 Well, the Cerafines are definitely going in my MOSFET-MAX, and since the KZs have been "difficult" in the MAX, I'll probably use the Silmics in the V1.2 BJT. I need the bass punch of the ES for my console as I'll have no EQ in it.

 I should have enough air flow with the holes I have drilled, plus the big 5/16" holes under the DB mounting screws...


----------



## BoilermakerFan

Pics of the mock up of the V1.0 BJT build as promised...

 Below you can see the location of the gainclone amp boards at the rear with their corresponding PSU cards still attached to the front. That's the Darwin I/O selector to the far right. I need a smaller PCB card for my phono stage to fit it in between the MAX and Darwin. The little bits outside the case to the left with the red center leads are my vintage, salvaged Garrard mid-fi BJT pairs that will demo'd in the MAX just to hear them. Holes across the front from left to right are, 3/4" for power, four original holes above the center line for LEDs mounted to a PCB which is being repopulated (and stealthed behind the wood front), two hoes for 1/4" jacks, two holes for the Darwin selector switches, and the ALPS pot. The rectangular hole next to the gainclone is the hole for an L-Con USB jack. This chassis has been my guinea pig metal. It's going in the console, to be buried in the guts and out of sight later so some parts will be removed or only installed temporarily. The IEC power input will not be used and instead PowerCon will feed in the 24Vac from a separate chassis housing the toroid. 








 Trying to show the 1/4" of clearance to the top, even with the 2-1/2" heat sinks sitting on 3/8" spacers. I still need to drill a couple of wiring holes in the divider once I know all of the sizes and quantity. 








 A bigger side view, the double gang ALPS will be replaced with a single since the OptiVols only need a single gang to control both channels. 









 After all the metal work is done on the 5 chassis, they'll be sent out for blasting, then head over to the body shop for paint in either black or navy blue. Then I'll label everything on the back with dry transfer lettering before dropping the chassis off again for 3 coats of clear at the body shop. The tops are going receive designs cut in the tops before being blasted and painted.


----------



## tomb

Gotta love those gold heat sinks.
	

	
	
		
		

		
		
	


	




 Looks like quite an ambitious project you have - it'll be neat seeing it finished!


----------



## BoilermakerFan

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Gotta love those gold heat sinks.
	

	
	
		
		

		
			





 Looks like quite an ambitious project you have - it'll be neat seeing it finished!_

 

Hmmm, what school's colors are Black & Gold? 
	

	
	
		
		

		
		
	


	




 And this is just one of the four amps I'm building, though they will all be similar though the Darwin's wiring in the Aikido will be more complicated as I'll use it to change caps and inputs/outputs and it will have a standalone BantamDAC for USB, and eventually a separate DAC for the Shigaclone CD transport. 

 I can't wait to get them finished too!


----------



## kugino

boilermakerfan, those are some awesome heatsinks! look forward to seeing the finished product.

 just biased my maxed about an hour ago, which was built using mostly leftover parts...one of my 12AE6 tubes was busted so tom's sending me another pair. had to take the 12FK6 from my minimax in the office to bias this guy. so far, sounds pretty great out of the opus feeding the rs1 
	

	
	
		
		

		
		
	


	




...case will be done one of these days...


----------



## soloz2

I know there was some discussion about this before, but I cant seem to find it with the search tool.

 A couple people inquired on using the Max as a low-powered speaker amp. Did anyone ever try this?


----------



## Forte

Quote:


  Originally Posted by *soloz2* /img/forum/go_quote.gif 
_I know there was some discussion about this before, but I cant seem to find it with the search tool.

 A couple people inquired on using the Max as a low-powered speaker amp. Did anyone ever try this?_

 

It has been asked a few times IIRC, here is one I bookmarked. http://www.head-fi.org/forums/4123219-post4584.html


----------



## soloz2

thanks, that's what I remembered as well. I just couldn't remember if a zobel network or anything like that was recommended.


----------



## BoilermakerFan

There are a couple of other tweaks, but I don't have access to them ATM. 

 Bigger heat sinks will always help too. 

 I'll be running mine out to SpeakOn 2 pole connectors on the rear panels of at least two amps and I might build the third the same way.


----------



## soloz2

I was thinking that when the updated board comes out I might build a new one, and then I'd either sell my current Maxed board or I thought maybe it might make a killer computer system that could drive some small speakers or headphones. 
 It already has 2" heatsinks


----------



## BoilermakerFan

The V1.2 board will only improve the performance.

 So as not to confuse this thread, I'll send you more info off line tomorrow when I get back home and have all the info in front of me.


----------



## aaronylee

Hey everyone,

 I could use some help troubleshooting. I just built the Millet Hybrid Max and I was trying to bias the tubes and ran into some trouble.

 I followed the instructions on the site for biasing and was able to get the DBs at 93mV and the power supply at 27VDC. When I measured the tubes I noticed that they were sitting at around 23VDC with the trimmers all the way down (I heard the click on both sides) I don't understand how I'm suppose to get them down to 18.5VDC! I wonder if theres something wrong with my wiring...

 I then threw caution to the wind and hooked up my DT880s and a CD player. When I started listening I noticed that the volume was really low even when I turned up the volume all the way... It's kind of doing the opposite of what I expected an amp to do...

 Also there's intermittent crackles and pops. 

 Any help would be greatly appreciated!

 Thanks!


----------



## tomb

Quote:


  Originally Posted by *aaronylee* /img/forum/go_quote.gif 
_Hey everyone,

 I could use some help troubleshooting. I just built the Millet Hybrid Max and I was trying to bias the tubes and ran into some trouble.

 I followed the instructions on the site for biasing and was able to get the DBs at 93mV and the power supply at 27VDC. When I measured the tubes I noticed that they were sitting at around 23VDC with the trimmers all the way down (I heard the click on both sides) I don't understand how I'm suppose to get them down to 18.5VDC! I wonder if theres something wrong with my wiring...

 I then threw caution to the wind and hooked up my DT880s and a CD player. When I started listening I noticed that the volume was really low even when I turned up the volume all the way... It's kind of doing the opposite of what I expected an amp to do...

 Also there's intermittent crackles and pops. 

 Any help would be greatly appreciated!

 Thanks!_

 

First, try turning the trimmers the other way.
	

	
	
		
		

		
		
	


	




 There's no "correct" direction per se, it all depends on the tubes and where they bias out.

 Second, bias them for 13.5VDC, not 18.5.

 Let us know how that turns out.


----------



## aaronylee

WOW it actually works! Another Millet is born!

 Thanks so much TomB! That totally cleared everything up! Now I just need to let it burn in =)


----------



## tomb

Quote:


  Originally Posted by *aaronylee* /img/forum/go_quote.gif 
_WOW it actually works! Another Millet is born!

 Thanks so much TomB! That totally cleared everything up! Now I just need to let it burn in =)_

 

It doesn't count without pics.
	

	
	
		
		

		
		
	


	










 Seriously, glad you got it working!


----------



## Forte

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Success!! The MOSFET-MAX V1.2 prototype now lives with an onboard BantamDAC and operating switching relay between the DAC and RCA inputs. 

 Today I spent some time building another BantamDAC and hooking it up to check the final feature in the MAX V1.2 PCB - the onboard Bantam with relay switching between RCA inputs and the Bantam. Pics below.

 Cetoole has some tweaks we've discussed to add to the board, but we're essentially ready to go to production._

 


 tomb - Any updates on where the V1.2 boards are at and when they will be ready?


----------



## tomb

Quote:


  Originally Posted by *Forte* /img/forum/go_quote.gif 
_tomb - Any updates on where the V1.2 boards are at and when they will be ready?_

 

New prototypes were ordered on Friday. They should ship to me this Friday. There's two, smaller relays in the back as opposed to the single one of before. That way, the input signals from two sources should be completely isolated. I'm working on the BOM right now and should be able to put the proto together quickly. We just want to make sure before I spend $$hundreds on a production run.
	

	
	
		
		

		
		
	


	




 P.S. I have a volunteer who's going to build a 2nd prototype, too. I'll let him identify himself if he wants.


----------



## BoilermakerFan

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_New prototypes were ordered on Friday. They should ship to me this Friday. There's two, smaller relays in the back as opposed to the single one of before. That way, the input signals from two sources should be completely isolated. I'm working on the BOM right now and should be able to put the proto together quickly. We just want to make sure before I spend $$hundreds on a production run.
	

	
	
		
		

		
		
	


	




 P.S. I have a volunteer who's going to build a 2nd prototype, too. I'll let him identify himself if he wants.
	

	
	
		
		

		
		
	


	


_

 

I think the diehards already know who it is.


----------



## soloz2

Quote:


  Originally Posted by *BoilermakerFan* /img/forum/go_quote.gif 
_I think the diehards already know who it is._

 

speaking of which... I might need to 'borrow' it


----------



## BoilermakerFan

Quote:


  Originally Posted by *soloz2* /img/forum/go_quote.gif 
_speaking of which... I might need to 'borrow' it 
	

	
	
		
		

		
		
	


	


_

 

Heh heh. It's not a gift, I'm paying the prototype price for it, but the wait was killing me and I'll be building this one as a BJT since Tom built his as a MOSFET. It will be built with Silmic II/VitQ caps or Muse ES. kind of on the fence right now... It will be socketed for all of the DB experiments too. So it's going to be a real workhorse.

 It will actually be my "spare" amp once the MOSFET-MAX is done, but it's still getting the full custom NABU chassis treatment, BantamDAC, OptiVol, 100VA toroid, etc. Then she'll head out to San Fran to spend a little time with rythmndevil and his photography studio before heading back here to go to my dad's along with my K240DFs. 

 I'm also starting my V1.0 MHM which is my preamp for my old Silvertone console. It's not V1.2 worthy and no need for a BantamDAC so the V1.0 is perfect for it.


----------



## soloz2

I've had a miniMax board from the beginning... finally got one built over the weekend and I'm listening right now. Pretty damn good IMHO. If the Max 1.2 is slightly better... I'll have to build a fully tweaked MOSFET to replace my current v1 MOSFET Max.


----------



## BoilermakerFan

Quote:


  Originally Posted by *soloz2* /img/forum/go_quote.gif 
_I've had a miniMax board from the beginning... finally got one built over the weekend and I'm listening right now. Pretty damn good IMHO. If the Max 1.2 is slightly better... I'll have to build a fully tweaked MOSFET to replace my current v1 MOSFET Max._

 

I'll help you with the parts spec. since you can run the bigger heatsinks you can crank up the bias. Just pull your BGs off the V1.0. 
	

	
	
		
		

		
		
	


	




 OT, but I'll check for those 6AU6 tubes for you too.


----------



## jdkJake

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_New prototypes were ordered on Friday. They should ship to me this Friday. There's two, smaller relays in the back as opposed to the single one of before. That way, the input signals from two sources should be completely isolated. I'm working on the BOM right now and should be able to put the proto together quickly. We just want to make sure before I spend $$hundreds on a production run.
	

	
	
		
		

		
		
	


	




 P.S. I have a volunteer who's going to build a 2nd prototype, too. I'll let him identify himself if he wants.
	

	
	
		
		

		
		
	


	


_

 

That is great news TomB!

 The end of summer is approaching and I will finally be able to return to my garage-based workshop and build a project or two.

 My miniMAX needs a mate and the MOSFET MAX looks mighty attractive!

 Keep us in the loop....

 jk


----------



## BoilermakerFan

Quote:


  Originally Posted by *jdkJake* /img/forum/go_quote.gif 
_That is great news TomB!

 The end of summer is approaching and I will finally be able to return to my garage-based workshop and build a project or two.

 My miniMAX needs a mate and the MOSFET MAX looks mighty attractive!

 Keep us in the loop....

 jk_

 

We will. I can't wait to build my MOSFET-MAX on a production board to go with my BJT prototype...


----------



## tomb

Here's the latest prototype that should ship from the PCB mfr today:


----------



## Beefy

God dammit. Why do I feel the urge to build another one of these things?!?


----------



## BoilermakerFan

Quote:


  Originally Posted by *Beefy* /img/forum/go_quote.gif 
_God dammit. Why do I feel the urge to build another one of these things?!? 
	

	
	
		
		

		
		
	


	


_

 

Because this one will go to 11!


----------



## JamesL

I'm not sure if this has been addressed before, but will beezar be stocking any of the other transistors again? 2SC3422/2SA1359 or 2SC2238/2SA968
 MCM seems to have at least one of each pair backordered or discontinued.



 Also, is it common for the lansing cases to have a slightly bulged top?
 I tried clamps and heavy weights to try make the top of the case flush with the panel, but with no luck.
 I was hoping that I'd have better luck if I purchased another one.


----------



## wolf18t

Sorry if this already been asked but is the new board can be use for MOSFET buffer or BJT?


----------



## BoilermakerFan

Quote:


  Originally Posted by *JamesL* /img/forum/go_quote.gif 
_I'm not sure if this has been addressed before, but will beezar be stocking any of the other transistors again? 2SC3422/2SA1359 or 2SC2238/2SA968
 MCM seems to have at least one of each pair backordered or discontinued.



 Also, is it common for the lansing cases to have a slightly bulged top?
 I tried clamps and heavy weights to try make the top of the case flush with the panel, but with no luck.
 I was hoping that I'd have better luck if I purchased another one.



_

 

Can't help you on the MiniScminny, as bigger is better for heatsinks, IMHO... 
	

	
	
		
		

		
		
	


	




 The 2SC2238/2SA968s are very hard to find as geniume Toshibas. When Tom can get genuine Toshibas, he does, but they usually are limited to 8-10 sets and they sell out within 48 hours. 

 I know I have at least one set of the 3422/1359s. Let me check if I have 2 sets. I'll need them to audition in my build, but I do not plan to keep them as I have have the 2238/968s for my BJT build.


  Quote:


  Originally Posted by *wolf18t* /img/forum/go_quote.gif 
_Sorry if this already been asked but is the new board can be use for MOSFET buffer or BJT?_

 

It can be built as either DB, but the BOM for each is a little different. You can run BJT buffers on a board built for MOSFETs, but not the other way around, so if your not sure which you would like, build it as a MOSFET and socket the DBs. However, you will need a new case as the sockets add 3/8" height to the transistors and heatsinks. All of my builds are going to be socketed, so stand by for pics of the forthcoming V1.2 prototype...


----------



## soloz2

I placed an order from MCM at the beginning of the month for the miniMax I just built hoping to get a set of genuine 2SC2238/2SA968 transistors. The 2SC2238 were Toshiba, however the 2SA968 were not... luckily (not sure how it happened) I had a spare pair of Toshiba 2SA968 and was able to make a set.


----------



## tomb

Quote:


  Originally Posted by *JamesL* /img/forum/go_quote.gif 
_I'm not sure if this has been addressed before, but will beezar be stocking any of the other transistors again? 2SC3422/2SA1359 or 2SC2238/2SA968
 MCM seems to have at least one of each pair backordered or discontinued._

 

BMF has described this pretty well, but let me give you the specifics.

 It pains me to report that the 2SC3422/2SA1359 has very suddenly attained the status of _*more-than-rare*_. What complicates this is that this Toshiba pair came in two versions - high gain ("Y" version) and low gain ("O") version. The gain versions were marked on the transistor, as it turns out. Up till now, every transistor pair I've supplied for 2SC3422/2SA1359 has been the high gain versions. Unfortunately, the last shipment I received was in GREEN, and they were all marked "O". Try as I could, from several different vendors and my own exhaustive exploration, the high gain versions have disappeared. As with most of these complementary transistors, it may be that you can find a few of the NPN versions, but the PNP's are almost impossible. Of course, with a diamond buffer, you need both. One without the other is useless. Moreover, one with high gain and one with low gain is just as useless.

 Similarly, 2SC2238 can be found in places, but not 2SA968's - at least genuine ones. The last shipment I got were "K" versions, which I believe mean Korea. I'm probably going to sell them that way - with full disclosure, but so far - there are not even clones or copies for the 2SC3422/2SA1359's. I'm afraid they may have been a unique/singular discovery by Steinchen and while the standard was taken up by the rest of us to follow on, it wasn't enough to maintain the supply.


  Quote:


 Also, is it common for the lansing cases to have a slightly bulged top?
 I tried clamps and heavy weights to try make the top of the case flush with the panel, but with no luck.
 I was hoping that I'd have better luck if I purchased another one.




 

Sorry about that, but yes - they all seem to have that slight bulge. If you're like me and several other folks, just bend it back down. The case seems to be pretty tough. I doubt seriously that you're in any danger of buckling or anything. Standing on it might be a reasonable option, too. I tend to push the front plate up slightly within its tolerance so that the bulge is disguised.

 What can I say? Hammond cases are so warped sometimes it almost takes a pry-bar to get the top plate to slide into the slot. Beyond that, I speak from direct experience now - custom Hammond jobs are machined _after_ anodizing. At least Lansing waits until the machining is done to make it look right.
	

	
	
		
		

		
		
	


	




 Sometimes I think us DIY-er's are way too picky, though.
	

	
	
		
		

		
		
	


	







 I mean, what would it take you to try to duplicate that slot pattern - even with a decent mill it would be a feat, unless it was CNC? I'm just happy that we have several vendors to pick from and they'll work with us a little bit.

 Heck, a couple of years ago in this community, the opportunity to get a pre-machined case for a DIY design was a flat-out impossibility. It's funny how a couple of designs and group buys have changed the standards for everyone.
	

	
	
		
		

		
		
	


	




 Sorry - guess I'm venting a little bit ...


----------



## tomb

Quote:


  Originally Posted by *wolf18t* /img/forum/go_quote.gif 
_Sorry if this already been asked but is the new board can be use for MOSFET buffer or BJT?_

 

I'll be honest here. The MiniMAX is as good as it gets for BJT's. Since it's as small as it can get in a through-hole PCB, that also means it's optimized - smallest trace length and all of that. At the same time, the MiniMAX is more or less specifically designed with the custom Beezar/Lansing case in mind. That case will only tolerate 1" high components, which are too short for the minimum heat sink requirements of MOSFETs.

 Can the Millett MAX be built with BJT's? YES.
 Can the MiniMAX be built with MOSFETs? NO.

 So, MiniMAX = BJT. Millett Hybrid MAX = MOSFETs. At least, that's the way I look at it.


----------



## BoilermakerFan

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_BMF has described this pretty well, but let me give you the specifics.

 It pains me to report that the 2SC3422/2SA1359 has very suddenly attained the status of *more-than-rare*. What complicates this is that this Toshiba pair came in two versions - high gain ("Y" version) and low gain ("O") version. The gain versions were marked on the transistor, as it turns out. Up till now, every transistor pair I've supplied for 2SC3422/2SA1359 has been the high gain versions. Unfortunately, the last shipment I received was in GREEN, and they were all marked "O". Try as I could, from several different vendors and my own exhaustive exploration, the high gain versions have disappeared. As with most of these complementary transistors, it may be that you can find a few of the NPN versions, but the PNP's are almost impossible. Of course, with a diamond buffer, you need both. One without the other is useless. Moreover, one with high gain and one with low gain is just as useless.

 Similarly, 2SC2238 can be found in places, but not 2SA968's - at least genuine ones. The last shipment I got were "K" versions, which I believe mean Korea. I'm probably going to sell them that way - with full disclosure, but so far - there are not even clones or copies for the 2SC3422/2SA1359's. I'm afraid they may have been a unique/singular discovery by Steinchen and while the standard was taken up by the rest of us to follow on, it wasn't enough to maintain the supply._

 

Whoah! So ordering DBs like crazy almost two years ago is actually paying off now? Cool. 

 Want to try some of my other DB combos? Or do you just want to wait for my notes and try a few that rise to the top? IIRC, I had at least 5 that have never been tried in a MHM and 3 were never tested by Steinchen. 




  Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_<snip>

 Sometimes I think us DIY-er's are way too picky, though.
	

	
	
		
		

		
			








 I mean, what would it take you to try to duplicate that slot pattern - even with a decent mill it would be a feat, unless it was CNC? I'm just happy that we have several vendors to pick from and they'll work with us a little bit.

 Heck, a couple of years ago in this community, the opportunity to get a pre-machined case for a DIY design was a flat-out impossibility. It's funny how a couple of designs and group buys have changed the standards for everyone.
	

	
	
		
		

		
		
	


	




 Sorry - guess I'm venting a little bit ..._

 

So, what do I get if I duplicate that slot pattern by hand in a steel lid? 
	

	
	
		
		

		
		
	


	




 I have a Uni-Bit and a nibbler. Those two tools, a scribe, a set of triangles, and a metal straight edge are all you need. Oh and time. There is a reason why there have not been any additional or finished pics of my chassis yet. The Aikido is getting the OM symbol cut out in the top and the MHMs are getting an Agave plant in the top. 

 I am that picky so I'm cutting out my patterns with a nibbler, or rather nibblers. Wore out one already, need to buy a nice one with replaceable blades from Eastwood. 

 I think the bottom of the Aikido chassis has over 200 holes. The MAXI-MOSFET-MAX FWA will have about 150 maybe more if I integrate a CDP into the top. 

 After the holes are drilled, punched or cut out, it gets wire brushed, then abrasive blasted before heading to the auto body shop for two days. Then back to me for dry transfer lettering and pin striping, then back to the shop for clear coat and bake. And that is just the steel chassis. My amps will have wood fronts with stealthed LEDs and hand carved lettering (or custom dry transfer), wood/brass feet, and custom knobs. 


 Team WAY Over The Top FTW!


----------



## BoilermakerFan

Ordering the new bits I need for the prototype tonight from Mouser.


----------



## tomb

V1.2.1 of the new MAX PCB _[size=xx-small](click for bigger pics)[/size]_ :


----------



## BoilermakerFan

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_V1.2.1 of the new MAX PCB [size=xx-small](click for bigger pics)[/size] :_

 

Booyah! My Mouser orders shipped yesterday via USPS. Can't wait!


----------



## dean0

I already have MiniMax Amp, what is the difference between MiniMax and Maxed versions, apart from the incorpirated DAC
 dean0


----------



## BoilermakerFan

Quote:


  Originally Posted by *dean0* /img/forum/go_quote.gif 
_I already have MiniMax Amp, what is the difference between MiniMax and Maxed versions, apart from the incorpirated DAC
 dean0_

 

Tom answered this one page back, but:

  Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_I'll be honest here. The MiniMAX is as good as it gets for BJT's. Since it's as small as it can get in a through-hole PCB, that also means it's optimized - smallest trace length and all of that. At the same time, the MiniMAX is more or less specifically designed with the custom Beezar/Lansing case in mind. That case will only tolerate 1" high components, which are too short for the minimum heat sink requirements of MOSFETs.

 Can the Millett MAX be built with BJT's? YES.
 Can the MiniMAX be built with MOSFETs? NO.

 So, MiniMAX = BJT. Millett Hybrid MAX = MOSFETs. At least, that's the way I look at it.
	

	
	
		
		

		
		
	


	


_

 

That said, the heatsink limitations are only if you are using the stock cases recommended in the BOMs for the smallest footprint possible. Use a larger chassis and heatsink height limitations can be eliminated. I use the NABU surplus chassis which will clear 2-1/2" heatsinks, the largest available in the footprints for the MAX boards. Bigger heatsinks mean that you can run higher bias currents with less chance of thermal run away or thermal shutdown depending on whether it's a BJT or MOSFET.


----------



## tomb

BMF is absolutely correct. However, I'll add a little more specific to the argument. The MOSFET-MAX is an absolute GRADO-MONSTER. That may apply to other low-impedance phones as well, but since Grado's are probably the best in that mix, I'll leave it at that. The speed, detail, and bass that's literally pumped through Grados with a MOSFET-MAX is simply amazing. I can't imagine a better amp for them, IMHO - of course.

 All that said, at higher impedances these differences begin to become moot. Does a BJT MiniMAX supply a high-impedance Sennheiser just as well as a MOSFET-MAX? Yes - maybe a bit better, more musical, IOW. Does the MiniMAX do a great job with Grados - especially compared to other amps in the same class? Absolutely.

 It's just that in direct comparison with Grados, the MOSFET-MAX is hands-down superior.


----------



## soloz2

idk... I'd take my MOSFET Max over a BJC Max for my HD580's... but I plan on building a similarly configured miniMax so we shall see...


----------



## BoilermakerFan

Muaaahaaaahhaaaaahaaaahhhhhh!

 My cans will bring all of the MAX builds to their knees! Heck, my Yamaha HP-1s are rated for 3 watts! Then there are my Kenwood KH-82s which need a lot of current to get going but clip if the signal gain is too high...

 Oh yeah, I have a couple of those Grados Tom mentioned. I'll have to go find which Rubbermaid tote I put them in. 
	

	
	
		
		

		
		
	


	




 Though I really need to sell the 325s to fund a DAC build. 

 Soloz2, have you tried the IRF510/9510 MOSFETs yet? Also, I think there are a couple of BJTs that can sound really, really good, but I'm planning to through 14 sets of BJTs through the prototype and I have 3 sets of MOSFETS for the production board build.


----------



## soloz2

Quote:


  Originally Posted by *BoilermakerFan* /img/forum/go_quote.gif 
_Muaaahaaaahhaaaaahaaaahhhhhh!
 Soloz2, have you tried the IRF510/9510 MOSFETs yet? Also, I think there are a couple of BJTs that can sound really, really good, but I'm planning to through 14 sets of BJTs through the prototype and I have 3 sets of MOSFETS for the production board build._

 

no, only the standard pair.


----------



## JamesL

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_
 It pains me to report that the 2SC3422/2SA1359 has very suddenly attained the status of *more-than-rare*. 
 Similarly, 2SC2238 can be found in places, but not 2SA968's - at least genuine ones._

 

Ah, that's too bad. How would you rate the bd138 and mje253 pairs compared to the two "boutique" pairs available at beezar? I'm skeptical that the output transistors will define the sound of the amp to a large degree, but from what I'm reading from the descriptions, it seems the default recommendations get closer to a more balanced, neutral sound.
  Quote:


 Sorry about that, but yes - they all seem to have that slight bulge. 
 

Don't be sorry. It doesn't bother me that much, and even if it did, it wouldn't be your fault. I'm just happy that someone put in the effort and time to get quality, professionally milled chassis' to diy'ers.


----------



## Beefy

Quote:


  Originally Posted by *JamesL* /img/forum/go_quote.gif 
_I'm skeptical that the output transistors will define the sound of the amp to a large degree..._

 

Compared to many other audiophool tweaks, this one might be fairly well grounded in reality. There is no global negative feedback in the Millet Max, so different output transistors could potentially have significant effects on the sound.

 Practically, I haven't compared any. I prefer to build and listen


----------



## BoilermakerFan

Quote:


  Originally Posted by *JamesL* /img/forum/go_quote.gif 
_Ah, that's too bad. How would you rate the bd138 and mje253 pairs compared to the two "boutique" pairs available at beezar? I'm skeptical that the output transistors will define the sound of the amp to a large degree, but from what I'm reading from the descriptions, it seems the default recommendations get closer to a more balanced, neutral sound.

 <snip>_

 

I did not order the default DBs for my comparisons, but the cost to try a set of "boutique" DBs is so low, $12 a set on the high end, why not try them. They are in the signal path so they will sculpt the sound signature just as the tubes and caps do. All three work together in concert. The sound is only as good as the weakest link. Tom experienced pains and horrible sound quality with KZ caps on his last MOSFET proto build. Sound quality restored when Silmic IIs were swapped in. A cap might have amore pronounced effect than the DB or may not...

 If you really want to get into it on paper, look at the data sheets, see the distortion figures, the slew rates, and look at the curves. Each will have it's sweet spot for bias current and the slew rate directly effects how fast the MAX can respond to transients and you will hear the differences, as long as you have cans that can react and respond fast enough to make those differences audible. This is where orthodynamics shine. My headphones really will put the MAXes to the test. They are extremely power hungry and extremely fast so small differences in the amp will become exponentially easier to hear, _amplified_ if you will... 
	

	
	
		
		

		
		
	


	





 EDIT: Good to see you back in the MHM thread Beefy!


----------



## tomb

Quote:


  Originally Posted by *JamesL* /img/forum/go_quote.gif 
_Ah, that's too bad. How would you rate the bd138 and mje253 pairs compared to the two "boutique" pairs available at beezar? I'm skeptical that the output transistors will define the sound of the amp to a large degree, but from what I'm reading from the descriptions, it seems the default recommendations get closer to a more balanced, neutral sound._

 

I'd lean toward the BD137/138's at this point. They've got a much higher bandwidth than the MJE's.

 Beefy is correct ... without feedback, the output transistors are on their own to respond and have a significant effect on sound signature - not as great as the tubes, but more than the other components in the amp.


----------



## jdkJake

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_V1.2.1 of the new MAX PCB ..._

 

TomB,

 Realizing there are some fairly major part changes, are you going to be releasing an updated BOM for the entire project or just the delta changes to the existing BOM?

 Thanks!

 jk


----------



## jdkJake

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_BMF is absolutely correct. However, I'll add a little more specific to the argument. The MOSFET-MAX is an absolute GRADO-MONSTER. That may apply to other low-impedance phones as well, but since Grado's are probably the best in that mix, I'll leave it at that. The speed, detail, and bass that's literally pumped through Grados with a MOSFET-MAX is simply amazing. I can't imagine a better amp for them, IMHO - of course.

 All that said, at higher impedances these differences begin to become moot. Does a BJT MiniMAX supply a high-impedance Sennheiser just as well as a MOSFET-MAX? Yes - maybe a bit better, more musical, IOW. Does the MiniMAX do a great job with Grados - especially compared to other amps in the same class? Absolutely.

 It's just that in direct comparison with Grados, the MOSFET-MAX is hands-down superior._

 

Great to hear TomB. I love the miniMax with the HD650's. I REALLY want a full-time millett for the Grados. This should fit the bill nicely.

 Any time frame estimates on the release of the new boards?

 Thanks

 jk


----------



## BoilermakerFan

Quote:


  Originally Posted by *jdkJake* /img/forum/go_quote.gif 
_TomB,

 Realizing there are some fairly major part changes, are you going to be releasing an updated BOM for the entire project or just the delta changes to the existing BOM?

 Thanks!

 jk_

 

There will be a revised BOM. Tom sent it to me so I could order the parts I needed. I sent Tom one minor suggested change this evening. Not really a change to the BOM, just clarification.


  Quote:


  Originally Posted by *jdkJake* /img/forum/go_quote.gif 
_Great to hear TomB. I love the miniMax with the HD650's. I REALLY want a full-time millett for the Grados. This should fit the bill nicely.

 Any time frame estimates on the release of the new boards?

 Thanks

 jk_

 

Tom has his prototype board and mine arrived from Tom today. My new parts from Mouser arrived today too, but of course I have to head out of town until Thursday for a job interview. Oh well. Will build this weekend and wire in two sources to test the input switching since I do not have a BantamDAC yet. I might be able to fit a phono stage in the same area, though it will be tight as the normal stage takes up roughly 2-1/2" square.


----------



## tomb

Quote:


  Originally Posted by *jdkJake* /img/forum/go_quote.gif 
_TomB,

 Realizing there are some fairly major part changes, are you going to be releasing an updated BOM for the entire project or just the delta changes to the existing BOM?

 Thanks!

 jk_

 

As BMF said, I've revised a BOM for him so that he could order parts. However, your question makes me think that perhaps I should just make a BOM that highlights the changes. That way, both the existing MAX/MiniMAX and MOSFET-MAX BOM's would still apply.

 Essentially, there are three major changes that distinguish the MAX V1.2a board from old:

*1. Power Supply -* exactly the same as the MiniMAX. Although, you have the option to use 1-1/2" sinks, which means you can use two 2000uf 50V electrolytics.
*2. Headphone Relay -* cetoole has gone to 24VDC relays throughout. This is combined with a 78L24 voltage regulator that replaces the resistor/zener diode combination used in competing relay circuits. The result is that parts count is reduced and interestingly - relay transients at the headphone jack are reduced to being immeasureable. Many relay-delay circuits have a few full volts of transient at the point of shutoff, depending on the headphone load. This transient is not enough to cause any harm, but still - it can be measured even with a $9.99 DMM. The 24V relay snaps so fast that I can't measure anything. I've used this arrangement on a modified MiniMAX for the past year and can attest to its reliability. 
*3. Signal Input Section -* Lastly, this is the most significant change with the MAX V1.2a board. As many of you have seen before, the PCB allows for a BantamDAC to be mounted directly to the board, with relay switching between the Bantam as a source or normal RCA input jacks.

 The previous prototype I built performed flawlessly with this switching arrangement. However, it used only one relay and so depended on the dB quieting that existed between the contacts in the relay itself to control cross-talk between the two competing sources. Unfortunately, if both sources were "live", there was audible bleed-through of the signal. (Absolutely nothing was wrong with it if the other source was switched off, however.)

 For this proto, cetoole has designed a couple of mini-relays that will independently switch the two sources. Further, he has designed in some resistors that will "short" the un-used signal source when not in use, to further remove any possibility of crosstalk above the SN ratio of the amp itself.

 One last thing - we've been playing around with the idea of using the IRF510 (used on the Starving Student) and its complement, the IRF9510, as the MOSFETs to make up the MOSFET diamond buffer. Further, cetoole has identified some Xetex FETs that will replace the SK-type Toshibas that were always in short supply. Both the MOSFETs and input FETs have lower gate capacitances than have been previously used, which should allow better performance at lower Class A biases. I have been running the prototype almost every day for the last several months at 125ma bias - even had it up to 150ma bias for short periods, with no ill effects. However, lower biases noticeably affected the sound quality, IMHO. Still, I haven't cased it up yet, so who knows if that bias can be maintained? The new MOSFETs and FETs should alleviate some of this and again - looking forward to trying the combination out.


----------



## BoilermakerFan

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_<snip>
*2. Headphone Relay -* cetoole has gone to 24VDC relays throughout. This is combined with a 78L24 voltage regulator that replaces the resistor/zener diode combination used in competing relay circuits. <snip>_

 

Ah dammit, I missed that change on the BOM... Crap. I also realized I ordered IRF510_s_PBF instead of the IRF510PBFs so I have 2 surface mount 510s instead of TO-220s. 
	

	
	
		
		

		
			














 EDIT: _Third_ Mouser order in five will be placed today...


----------



## tomb

Quote:


  Originally Posted by *BoilermakerFan* /img/forum/go_quote.gif 
_Ah dammit, I missed that change on the BOM... Crap. I also realized I ordered IRF510sPBF instead of the IRF510PBFs so I have 2 surface mount 510s instead of TO-220s. 
	

	
	
		
		

		
		
	


	













 EDIT: Third Mouser order in five will be placed today..._

 

Be sure you catch the fact that the electrolytics in the relay-delay circuit are now rated for 35V, too.


----------



## Daveze

I'd nearly convinced myself that I was finished with the MilletMAX, wasn't interested in V1.2 and that it was time to move onto an M3 or some other amp...

 Tom, you suck.


----------



## Beefy

Quote:


  Originally Posted by *Daveze* /img/forum/go_quote.gif 
_I'd nearly convinced myself that I was finished with the MilletMAX, wasn't interested in V1.2 and that it was time to move onto an M3 or some other amp...

 Tom, you suck._

 






 I was thinking along those exact same lines for a while, but have decided to go on a slightly different tangent. It seems I will probably end up building _two_ M3's before you have built your first......


----------



## tomb

Quote:


  Originally Posted by *Daveze* /img/forum/go_quote.gif 
_I'd nearly convinced myself that I was finished with the MilletMAX, wasn't interested in V1.2 and that it was time to move onto an M3 or some other amp...

 Tom, you suck._


----------



## BoilermakerFan

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Be sure you catch the fact that the electrolytics in the relay-delay circuit are now rated for 35V, too.
	

	
	
		
		

		
		
	


	


_

 

Thanks Tom. I think I have 35V caps already, but CYA so I'l order new ones to be sure. Just miffed that I missed it. Managed to order fricken (9) PF1s of different values as I had a saved project and ordered it too. Missed the fact that it had .90A up to 1.5A values of the poly fuses on it since I'm modding my old V1.0 board and not really sure what value PF I'll need for my LM338 and much higher bias currents. 


 Have the part numbers for the Xetex FETs from Mouser too? Might as well add those.  


 You know I'm a huge proponent of the IRF510/9510s and had planned to use those even before the SS was out... Definitely recommend them or the IRF610/9610 for guys that want a little brighter treble.


----------



## Daveze

Quote:


  Originally Posted by *Beefy* /img/forum/go_quote.gif 
_





 I was thinking along those exact same lines for a while, but have decided to go on a slightly different tangent. It seems I will probably end up building two M3's before you have built your first...... 
	

	
	
		
		

		
		
	


	


_

 

Another one? That's just being greedy.

 What's the reason I should use to convince myself to build one?


----------



## BoilermakerFan

Quote:


  Originally Posted by *Daveze* /img/forum/go_quote.gif 
_Another one? That's just being greedy.

 What's the reason I should use to convince myself to build one?_

 

A MOSFET-MAX? New ground plane for lower noise, new input switching, and new 510/9510 DB for a faster amp with awesome SQ. Add an OptiVol and take the potentiometer out of the signal path too.


----------



## Daveze

Actually I was referring to an M3...the MOSFET-MAX has been a given since Tom announced those reasons.


----------



## tomb

Quote:


  Originally Posted by *BoilermakerFan* /img/forum/go_quote.gif 
_Thanks Tom. I think I have 35V caps already, but CYA so I'l order new ones to be sure. Just miffed that I missed it. Managed to order fricken (9) PF1s of different values as I had a saved project and ordered it too. Missed the fact that it had .90A up to 1.5A values of the poly fuses on it since I'm modding my old V1.0 board and not really sure what value PF I'll need for my LM338 and much higher bias currents._

 

I went with 0.75A and it's worked fine for up to 150ma bias - would probably go higher, too. 

  Quote:


 Have the part numbers for the Xetex FETs from Mouser too? Might as well add those.  
 

QB2L/R - ZVP3306A (P-channel MOSFET)
 QB3L/R - ZVN3306A (N-channel MOSFET)

 I bought ten each - remember that they must be matched according to current.
 EDIT: Also remember that they are reversed compared to the silkscreen on the PCB - the silkscreen still follows the BJT version for QB2 and QB3.

  Quote:


 You know I'm a huge proponent of the IRF510/9510s and had planned to use those even before the SS was out... Definitely recommend them or the IRF610/9610 for guys that want a little brighter treble. 
 

Yes - it was your idea first to start looking at those. I hope those and the Zetex's (misspelled it earlier) work out.


----------



## Beefy

Quote:


  Originally Posted by *Daveze* /img/forum/go_quote.gif 
_Another one? That's just being greedy._

 

In all fairness, they will be in just a single case...... 
	

	
	
		
		

		
		
	


	




  Quote:


 What's the reason I should use to convince myself to build one? 
 

Variety is the spice of life!


----------



## BoilermakerFan

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_I went with 0.75A and it's worked fine for up to 150ma bias - would probably go higher, too. 


 QB2L/R - ZVP3306A (P-channel MOSFET)
 QB3L/R - ZVN3306A (N-channel MOSFET)

 I bought ten each - remember that they must be matched according to current.

 Yes - it was your idea first to start looking at those. I hope those and the Zetex's (misspelled it earlier) work out._

 

I'll start with a PF1 of 1.1A on the MOSFET and .90A on the BJTs, but I have up to 1.5A which will trip at 5A so the LM338 gets protected too. 

 How well have the Zetexes matched up? I may order 20 or 30 of each... We'll see how much I have to pad my order to avoid the fees. I need knobs for the console refurb, so those are about $15 total that I'll just order now to get it out of the way too. 

 Well, you know the Toshibas and the IRF510s play nice. If the Zetexes darken the sound, then it can be recouped with IRF610s... My plan was to pair the 510s with FM12 tubes and the 610s with the AE6 tubes for initial listening. For guys that like crazy bright sound, FK6 tubes and 610s should pretty well fit the bill. 
	

	
	
		
		

		
		
	


	




 And believe it or not, I know a member who would really enjoy that sound with BG caps.


 EDIT: Missed parts and Zetex ordered. Only went with 10 each too as they are a little pricey. I'd recommend others just wait and ordered matched sets from Tom if they prove out to be worthy of replacing the Toshibas. $12 for 10 pieces of each to narrow down to 2 pairs of matched FETS is a little steep. That said, if they do match well and I can get another set or two out of mine, then I might sell them off to recoup the money if I don't use them on another build like a portable amp.


----------



## BoilermakerFan

Everything arrived, but I did not get started over the weekend as planned. I had better offers for night time activities. 
	

	
	
		
		

		
			





 Starting the builds, a V1.0 and V1.2, both as BJT buffers. The roll call for testing DB pairs as it stands right now is:

 2238/968
 3422/1359
 2344/1011
 3421/1358
 649A/669A
 5171/1930
 1226/690 (Obsolete - salvaged from Mid-Fi Garrard integrated receiver)
 1913/1274
 507/313

 I've managed to misplace a few previously untested DB pairs, and a couple of well recognized boutique sets are also AWOL for now. 

 I'm using BC546C/556C small signal transistors, so I have 3 packs of the standard transistors matched by Tom up for sale if anyone needs them. I'll entertain equal value trades for caps, LEDs, etc.


----------



## BoilermakerFan

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_I went with 0.75A and it's worked fine for up to 150ma bias - would probably go higher, too. 


 QB2L/R - ZVP3306A (P-channel MOSFET)
 QB3L/R - ZVN3306A (N-channel MOSFET)

 I bought ten each - remember that they must be matched according to current.
 EDIT: Also remember that they are reversed compared to the silkscreen on the PCB - the silkscreen still follows the BJT version for QB2 and QB3.

 Yes - it was your idea first to start looking at those. I hope those and the Zetex's (misspelled it earlier) work out._

 

OK, now I'm showing that I'm still a newbie, but can I use my el-Cheapo Harbor Freight meter to match the Zetex? How does the DGS pins of the MOSFET correspond to the EBC pins on a BJT transistor? I'm assuming the meter is low power so they wouldn't toast, but I'm also not willing to risk it. 

 Tom, I'll send you my N and P channel numbers for my 10 to compare to yours and see if we might be able to match up any extremes we have in out limited samples.


----------



## luvdunhill

Quote:


  Originally Posted by *BoilermakerFan* /img/forum/go_quote.gif 
_OK, now I'm showing that I'm still a newbie, but can I use my el-Cheapo Harbor Freight meter to match the Zetex? How does the DGS pins of the MOSFET correspond to the EBC pins on a BJT transistor? I'm assuming the meter is low power so they wouldn't toast, but I'm also not willing to risk it. 

 Tom, I'll send you my N and P channel numbers for my 10 to compare to yours and see if we might be able to match up any extremes we have in out limited samples._

 

nope, you'll need a power supply and a resistor to measure the MOSFET Vgs. Check out AMB's site on how to match MOSFETs. I would argue the term match by current, but I understand what you're trying to get at.

 The Zetex are good transistors, I have a bunch of them myself.


----------



## BoilermakerFan

Quote:


  Originally Posted by *luvdunhill* /img/forum/go_quote.gif 
_nope, you'll need a power supply and a resistor to measure the MOSFET Vgs. Check out AMB's site on how to match MOSFETs. I would argue the term match by current, but I understand what you're trying to get at.

 The Zetex are good transistors, I have a bunch of them myself._

 

Thanks. A similar circuit is also in Jones' book on building valve amps, but I thought it was for DMMs without HFE. 

 I may just keep the BC546C/BC556Cs as I have sets that are matched insanely close (every pair/quad are within 10. One full set is within 8 for the whole amp and most pairs are exact matches within the capabilities and error of my DMM) and I'm building the V1.2 prototype as a BJT, I'd save the Zetexes for the official MOSFET-MAX build.


----------



## tomb

Quote:


  Originally Posted by *BoilermakerFan* /img/forum/go_quote.gif 
_Thanks. A similar circuit is also in Jones' book on building valve amps, but I thought it was for DMMs without HFE. 

 I may just keep the BC546C/BC556Cs as I have sets that are matched insanely close (every pair/quad are within 10. One full set is within 8 for the whole amp and most pairs are exact matches within the capabilities and error of my DMM) and I'm building the V1.2 prototype as a BJT, I'd save the Zetexes for the official MOSFET-MAX build._

 

Technically, it's matching for I[size=xx-small]DSS[/size]. This is done by measuring current in the circuit shown below, which puts the JFET into saturation at its I[size=xx-small]DSS[/size]:





 An easy modification to the circuit shown above is to substitute a 100R resistor for the ammeter and then simply read voltage across the resistor with your DMM and convert to current. I have a little breadboard set up to do this. It's a bit more difficult than matching for HFE on BJT's, but it goes fairly quickly once you have everything set up.


----------



## luvdunhill

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Technically, it's matching for I[size=xx-small]DSS[/size]_

 

The ZVP3306A/ZVN3306A are MOSFETs, and as such you want to use a setup like this:






 Ideally, the voltage and resistor will set the test jig as close to how the devices will be operating in the target circuit.

 You'll want to match to around 100mV difference at a bare minimum, but 10mV is possible with a standard hand held DMM. If you're looking for any more resolution than that, you'll need a nice bench meter. The difficult lies in controlling the temperature, as this will be the largest source of error in your measurements. Either mount them to a large block of aluminum or use an enclosure of sorts if your target current is small enough to run the device with free air heatsinking. I use a thermocouple to ensure the measurements are taken plus or minus a few degrees Celsius.

 In fact, there is a better way to match MOSFETs that involves using a current limiting bench supply and another adjustable supply between the gate and source, but it's a bit more complicated.


----------



## Pars

Quote:


  Originally Posted by *luvdunhill* /img/forum/go_quote.gif 
_<snip>
 In fact, there is a better way to match MOSFETs that involves using a current limiting bench supply and another adjustable supply between the gate and source, but it's a bit more complicated._

 

Have you got a pointer to this method? Thanks.


----------



## luvdunhill

Quote:


  Originally Posted by *Pars* /img/forum/go_quote.gif 
_Have you got a pointer to this method? Thanks._

 

Can't say there is a reference. At the time I was matching $10 MOSFETs and wanted to get them very close and discovered a way that is more accurate, but a bigger PITA. More accurate meaning that the matching process exactly duplicates the operating point in the circuit. This is the key really, and as I said the temperature of the device is the hardest element to control. Then again, my target current was around 2A. You really need a current limiting supply and a something to bias the device and adjust until you are drawing the desired current, then measure and record Vgs. You can use a 9v battery and a pot if you don't have another bench supply. Also you should model the target junction temperature. In my case this was 60C, and once this was met I took down the Vgs reading.


----------



## BoilermakerFan

Quote:


  Originally Posted by *luvdunhill* /img/forum/go_quote.gif 
_The ZVP3306A/ZVN3306A are MOSFETs, and as such you want to use a setup like this:






 Ideally, the voltage and resistor will set the test jig as close to how the devices will be operating in the target circuit.

 You'll want to match to around 100mV difference at a bare minimum, but 10mV is possible with a standard hand held DMM. If you're looking for any more resolution than that, you'll need a nice bench meter. The difficult lies in controlling the temperature, as this will be the largest source of error in your measurements. Either mount them to a large block of aluminum or use an enclosure of sorts if your target current is small enough to run the device with free air heatsinking. I use a thermocouple to ensure the measurements are taken plus or minus a few degrees Celsius.

 In fact, there is a better way to match MOSFETs that involves using a current limiting bench supply and another adjustable supply between the gate and source, but it's a bit more complicated._

 

Will the MOSFET test circuit also for JFETs or is Tom's JFET diagram required? I was going to protoboad the circuit with a potentiometer for the resistor to allow adjustment, use TO-220 and TO-92 transistor sockets in parallel, then and use a DPDT so I can flip a switch to do N-channel or P-channel with either TO-220 or TO-92 FETs. I could proto both on the same board with another DPDT in the center, but one is just easier than two...

 My Sears DMM is acting up and the display only works when the case is fully opened which means it's warped and loses contact when it's tightened down on the sides. Picking up a Amprobe 37XR-A as a replacement later today...


----------



## luvdunhill

Quote:


  Originally Posted by *BoilermakerFan* /img/forum/go_quote.gif 
_Will the MOSFET test circuit also for JFETs or is Tom's JFET diagram required?_

 

First, I don't really know if JFETs are used in the MOSFET-MAX to be honest, I was just answering your question about how to match MOSFETs. So, I'll leave that question to Tom

 But the answer the above, I wouldn't recommend it. The resistor in the MOSFET matching jig needs to be able to dissipate a good amount of heat, depending on the matching current. Notice that AMB suggests a 5W resistor in the above diagram.


----------



## tomb

Quote:


  Originally Posted by *luvdunhill* /img/forum/go_quote.gif 
_First, I don't really know if JFETs are used in the MOSFET-MAX to be honest, I was just answering your question about how to match MOSFETs. So, I'll leave that question to Tom

 But the answer the above, I wouldn't recommend it. The resistor in the MOSFET matching jig needs to be able to dissipate a good amount of heat, depending on the matching current. Notice that AMB suggests a 5W resistor in the above diagram._

 

It's plenty for the currents used in the Xetex's and Toshiba SK's - and even PN4392's and 2N5486's. The Toshiba SK's average 7-10ma. That's 0.01W - plenty for a measly 'ole RN55. The PN4392's and 2N5486's are less than half as much.

*No one said anything about matching the power MOSFETs. * Even AMB says that's unnecessary and nowhere in the history of everything Millett MAX/MOSFET MAX/MiniMAX have we ever recommended matching anything of a power output nature. MOSFETs should be tested, which can be done holding the two probes of a DMM in your hand along with the MOSFET - nothing else.
	

	
	
		
		

		
		
	


	







 P.S. They're all FETs, whether MOS or J, they're still being used for the same purpose (as a JFET) - the first diagrams I posted should work fine.


----------



## BoilermakerFan

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_It's plenty for the currents used in the Xetex's and Toshiba SK's - and even PN4392's and 2N5486's. The Toshiba SK's average 7-10ma. That's 0.01W - plenty for a measly 'ole RN55. The PN4392's and 2N5486's are less than half as much.

*No one said anything about matching the power MOSFETs. * Even AMB says that's unnecessary and nowhere in the history of everything Millett MAX/MOSFET MAX/MiniMAX have we ever recommended matching anything of a power output nature. MOSFETs should be tested, which can be done holding the two probes of a DMM in your hand along with the MOSFET - nothing else.
	

	
	
		
		

		
		
	


	







 P.S. They're all FETs, whether MOS or J - the first diagrams I posted will work fine. In the signal input positions of a Diamond Buffer (QB2 and QB3), the I[size=xx-small]DSS[/size] is all you're interested in matching._

 

Thanks guys. I'll build one of them and test my FETs...

 Picked up my new meter today too. Local, family-owned electronics shop even knocked $5 off the price!

Amprobe® Test Tools


----------



## tomb

Quote:


  Originally Posted by *BoilermakerFan* /img/forum/go_quote.gif 
_Thanks guys. I'll build one of them and test my FETs...

 Picked up my new meter today too. Local, family-owned electronics shop even knocked $5 off the price!

Amprobe® Test Tools_

 

The Xetex's test out at 65-70ma. So, you might want to use an RN60, instead. That's 1/2W, but even an RN55 would probably be OK - you don't leave the FETs stuck in there for very long.
	

	
	
		
		

		
		
	


	




 In light of that, a 1000R resistor might be a better choice - these do seem to move more current than the others I mentioned.


----------



## BoilermakerFan

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_The Xetex's test out at 65-70ma. So, you might want to use an RN60, instead. That's 1/2W, but even an RN55 would probably be OK - you don't leave the FETs stuck in there for very long.
	

	
	
		
		

		
		
	


	




 In light of that, a 1000R resistor might be a better choice - these do seem to move more current than the others I mentioned._

 

RN55 are actually 1/2W, just derated to 1/4 for MIL-SPEC, but I have RN60s for other projects and a couple 2W Caddocks.


----------



## tomb

Quote:


  Originally Posted by *BoilermakerFan* /img/forum/go_quote.gif 
_RN55 are actually 1/2W, just derated to 1/4 for MIL-SPEC, but I have RN60s for other projects and a couple 2W Caddocks._

 

Actuall, it's 1/8 to 1/4 for RN55's and 1/4 to 1/2 for RN60's. Still - there's no reason you would want to leave these in the circuit that long anyway. It's quite similar to matching BJT's or even resistors - consistency in comparison is what's important, not absolute measurement. Pop the FET in the circuit, take a reading, then pull it out and pop the next one in, etc., etc.


----------



## luvdunhill

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_P.S. They're all FETs, whether MOS or J, they're still being used for the same purpose (as a JFET) - the first diagrams I posted should work fine._

 

Perhaps this is more appropriate in another thread, but...

 When the GS junction is shorted on a JFET, the device *saturates*. When this happens on a MOSFET, it is *off*. Again, they are not equivalent and you aren't testing anything if you test a MOSFET this way.


----------



## bhjazz

Whoa...crap. I forgot I still have boards for this. Yikes! Gotta get going!


----------



## tomb

Quote:


  Originally Posted by *luvdunhill* /img/forum/go_quote.gif 
_Perhaps this is more appropriate in another thread, but...

 When the GS junction is shorted on a JFET, the device *saturates*. When this happens on a MOSFET, it is *off*. Again, they are not equivalent and you aren't testing anything if you test a MOSFET this way._

 

Ah, OK - understood. I was led to believe they would work as a JFET. Then perhaps they aren't appropriate in this application and we should just stick with the SK/SJ's.


----------



## tomb

Let me make this clear since I confused things quite a bit in the last few posts: Luvdunhill is correct about the Zetex MOSFETs and the testing circuit he explained. There is a nice article by Nelson Pass that explains this further:
http://www.passdiy.com/pdf/mos.pdf

 In it, you will find similar schematics to the one Luvdunhill provided and an in-depth explanation for testing MOSFETs. (Ironically, Pass states at one point that perhaps "matched parts is the best approach doesn't always hold up.") The Zetex's are also specifically mentioned.

 I apologize for causing confusion over this.


----------



## BoilermakerFan

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Let me make this clear since I confused things quite a bit in the last few posts: Luvdunhill is correct about the Zetex MOSFETs and the testing circuit he explained. There is a nice article by Nelson Pass that explains this further:
http://www.passdiy.com/pdf/mos.pdf

 In it, you will find similar schematics to the one Luvdunhill provided and an in-depth explanation for testing MOSFETs. (Ironically, Pass states at one point that perhaps "matched parts is the best approach doesn't always hold up.") The Zetex's are also specifically mentioned.

 I apologize for causing confusion over this.
	

	
	
		
		

		
		
	


	


_

 

No worries Tom, I wasn't confused. I was planning to keep my prototype the BC546C/C556C for small signal and try the Zetex on my MOSFET-MAX on a production board. Seriously considering TO-92 sockets for that build so I can easily swap small signal transistors though...

 I think the fact that the MAX can be built so many ways may confuse a few peeps, but that flexibility is what drew me to the MAX in the first place. The support of the MAX community is just the icing on a really big cupcake!


----------



## luvdunhill

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Ah, OK - understood. I was led to believe they would 
 work as a JFET_

 

Perhaps what you mean to say is depletion mode MOSFETs behave similar to a JFET in that an electric field is used to deplete the channel of current carriers. However, these devices are enhancement MOSFETs, and work a bit differently. As you said, there really isn't any reason to match devices in this circuit, as the output devices aren't paralleled. Furthermore, if you're looking to pick a complimentary pair from your matching efforts, good luck. Complimentary MOSFETs (with the very, very rare exception) are sorta up there with unicorns and pink ponies.


----------



## tomb

Quote:


  Originally Posted by *luvdunhill* /img/forum/go_quote.gif 
_Perhaps what you mean to say is depletion mode MOSFETs behave similar to a JFET in that an electric field is used to deplete the channel of current carriers. However, these devices are enhancement MOSFETs, and work a bit differently. As you said, there really isn't any reason to match devices in this circuit, as the output devices aren't paralleled. Furthermore, if you're looking to pick a complimentary pair from your matching efforts, good luck. Complimentary MOSFETs (with the very, very rare exception) are sorta up there with unicorns and pink ponies._

 

Now you're confusing me further. There are plenty of both paralleled and complimentary devices in the MAX's diamond MOSFET buffers. The real question about matching is whether the juice is worth the squeeze. For output devices, this is almost always not the case. However, at the sensitive location of the paralleled/complementary signal input pair - matching usually makes a big difference. This is because while the individual channels can be biased independently, the complementary halves of each buffer channel cannot. Offset at the signal input pair is magnified the most. Unfortunately, the procedure discussed on the last page or two makes me think we'd still be better off with the low-noise Toshiba's, despite their supposed scarcity. At least the effort of finding matches is much less severe and totally repeatable.


----------



## luvdunhill

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Now you're confusing me further._

 

Wait, you want to substitute the Zetex MOSFETs for the input JFETs? Er, why would you expect that to work? I think everyone in this thread is confused 
	

	
	
		
		

		
		
	


	




 I'll just let you guys work it out, or PM me if I can help.


----------



## tomb

Quote:


  Originally Posted by *luvdunhill* /img/forum/go_quote.gif 
_Wait, you want to substitute the Zetex MOSFETs for the input JFETs? Er, why would you expect that to work?_

 

I was told that they might be good replacements for the Toshiba 2SJ74/2SK170 JFETs that were specified by AMB for the JFET-mod MOSFET-MAX, which pretty much forms the basis of the MOSFET-MAX. They substitute for QB2L/R and QB3L/R in the diamond buffer circuit, which were formerly BJT's in the BJT-version of the diamond buffer. The result is that they provide both low-noise, small signal capability along with super-high input impedance. The gate capacitance of the output MOSFETs creates a low-pass filter with the input impedance of "normal" BJT's to cause a high-frequency roll-off. AMB's JFET-mod solves this, but there is an issue with the minimum bias currents/resulting voltage at QB2L/R and QB3L/R that may be less than optimium. I was told the Zetex's may be a better fit there.

 We are proposing to change the complementary output MOSFETs for similar reasons - lower gate capacitance - to the IRF510/9510's, which are the same as used on the SSMH (IRF510).


----------



## BoilermakerFan

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_I was told that they might be good replacements for the Toshiba 2SJ74/2SK170 JFETs that were specified by AMB for the JFET-mod MOSFET-MAX, which pretty much forms the basis of the MOSFET-MAX. They substitute for QB2L/R and QB3L/R in the diamond buffer circuit, which were formerly BJT's in the BJT-version of the diamond buffer. The result is that they provide both low-noise, small signal capability along with super-high input impedance. The gate capacitance of the output MOSFETs creates a low-pass filter with the input impedance of "normal" BJT's to cause a high-frequency roll-off. AMB's JFET-mod solves this, but there is an issue with the minimum bias currents/resulting voltage at QB2L/R and QB3L/R that may be less than optimium. I was told the Zetex's may be a better fit there.

 We are proposing to change the complementary output MOSFETs for similar reasons - lower gate capacitance - to the IRF510/9510's, which are the same as used on the SSMH (IRF510)._

 

Whoah, whoah, whoah...

 Why don't we just switch to the LSK170s then? I'll check and see if they have the SJ74s...


----------



## luvdunhill

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_I was told that they might be good replacements for the Toshiba 2SJ74/2SK170 JFETs that were specified by AMB for the JFET-mod MOSFET-MAX, which pretty much forms the basis of the MOSFET-MAX._

 

oh ok, I wouldn't guess that would work so well, or require some sort of (undesirable) compensation. I guess you'll find out. Funny, all the hits on google for "MOSFET diamond buffer" are MAX related


----------



## tomb

Quote:


  Originally Posted by *luvdunhill* /img/forum/go_quote.gif 
_oh ok, I wouldn't guess that would work so well, or require some sort of (undesirable) compensation. I guess you'll find out. Funny, all the hits on google for "MOSFET diamond buffer" are MAX related 
	

	
	
		
		

		
		
	


	


_

 

MOSFET-MAX website
 EDIT: I'm not aware that anyone else has actually built one (a MOSFET diamond buffer), except us - much less used it as a primary design for a headphone amp.
	

	
	
		
		

		
		
	


	




 The Toshiba JFETs work great, btw and have served quite well as the basis for the MOSFET-MAX. However, there are issues - not the least of which that they are no longer made and quite scarce. That said, Beezar.com sells them and so does AMB Labs.


----------



## BoilermakerFan

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_I was told that they might be good replacements for the Toshiba 2SJ74/2SK170 JFETs that were specified by AMB for the JFET-mod MOSFET-MAX, which pretty much forms the basis of the MOSFET-MAX. They substitute for QB2L/R and QB3L/R in the diamond buffer circuit, which were formerly BJT's in the BJT-version of the diamond buffer. The result is that they provide both low-noise, small signal capability along with super-high input impedance. The gate capacitance of the output MOSFETs creates a low-pass filter with the input impedance of "normal" BJT's to cause a high-frequency roll-off. AMB's JFET-mod solves this, but there is an issue with the minimum bias currents/resulting voltage at QB2L/R and QB3L/R that may be less than optimium. I was told the Zetex's may be a better fit there.

 We are proposing to change the complementary output MOSFETs for similar reasons - lower gate capacitance - to the IRF510/9510's, which are the same as used on the SSMH (IRF510)._

 

No 2SJ74 equivalent from Linear Systems...

 Are the BC546C/BC556C or the low noise equivalents "normal" BJTs?


----------



## tomb

Quote:


  Originally Posted by *BoilermakerFan* /img/forum/go_quote.gif 
_No 2SJ74 equivalent from Linear Systems...

 Are the BC546C/BC556C or the low noise equivalents "normal" BJTs?_

 

In the case of the MAX/MOSFET-MAX/MiniMAX, "normal" BJT's are 2N5087 and 2N5088.


----------



## BoilermakerFan

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_In the case of the MAX/MOSFET-MAX/MiniMAX, "normal" BJT's are 2N5087 and 2N5088.
	

	
	
		
		

		
		
	


	


_

 

So I'm wondering if the BC's have a higher input impedance to minimize or prevent the high freq. roll-off or do BJTs inherently have low input impedance? I did not see the input impedance in the data sheets for the Fairchild parts I have, they only listed capacitance.


----------



## tomb

Quote:


  Originally Posted by *BoilermakerFan* /img/forum/go_quote.gif 
_So I'm wondering if the BC's have a higher input impedance to minimize or prevent the high freq. roll-off or do BJTs inherently have low input impedance? I did not see the input impedance in the data sheets for the Fairchild parts I have, they only listed capacitance._

 

BC's are only a different brand of BJT's - none of which have as high an input impedance as the Toshiba JFETs (1 nano-amp at 30V = 3 x 10^10 ohms). The Zetex's are about 20 times less than that (1.5 x 10^9). However, from what I've found - BJT's range from about 5 to 25 KOhms (1.5 x 10^4).


 EDIT: Keep in mind that we're talking input impedance here because of the gate capacitance of the output MOSFETs. BJT input with BJT output = good.


----------



## seroxatmad

Hi

 I have finally started populating my millett max!

 The BOM i initally used had 470uf for CA4 and CA5. Will it be worth desoldering and replacing with the 1000uF in the latest BOM.

 The 470uF i used are rated 63V wereas the 1000uF are 35V. Is 35V enough of a safety margin?

 Cheers

 John


----------



## tomb

Quote:


  Originally Posted by *seroxatmad* /img/forum/go_quote.gif 
_Hi

 I have finally started populating my millett max!

 The BOM i initally used had 470uf for CA4 and CA5. Will it be worth desoldering and replacing with the 1000uF in the latest BOM.

 The 470uF i used are rated 63V wereas the 1000uF are 35V. Is 35V enough of a safety margin?

 Cheers

 John_

 

Actually, 1000uf is a minimum. Most of us started using 1800uf's - both Panasonic FM's and Nichicon KW's are available in 1800uf 35V and 25mm high. (Note that you'll have to use the search for Mouser - it's not a size that's listed in their catalog.) If you already had 1000uf's, probably not a big difference, but the MAX will benefit from the higher capacitance over 470uf's.

 63V is OK, but you won't even be able to get Panasonic FM's in that voltage. 35V is all you need, though. Nothing on the board after the PS area can go over 30V. The rectified voltage may go between 35-40V, so we specify 50V electrolytics in the power supply (CR1A,B,C,D).


----------



## seroxatmad

They are Panasonic FC's as in the UK are easier to source via RS.

 Farnell list the FM's but always seem to out of stock 
	

	
	
		
		

		
		
	


	




 Thanks

 John

 P.S Will a 0.6W be ok for RR2?


----------



## tomb

Quote:


  Originally Posted by *seroxatmad* /img/forum/go_quote.gif 
_They are Panasonic FC's as in the UK are easier to source via RS.

 Farnell list the FM's but always seem to out of stock 
	

	
	
		
		

		
		
	


	




 Thanks

 John

 P.S Will a 0.6W be ok for RR2?_

 

Yes.


----------



## seroxatmad

Quote:


 Will a 0.6W be ok for RR2? 
 

Sorry I meant a 0.4W

 Cheers

 John


----------



## tomb

Quote:


  Originally Posted by *seroxatmad* /img/forum/go_quote.gif 
_Sorry I meant a 0.4W

 Cheers

 John_

 

Most likely.


----------



## seroxatmad

I am using a Meter with hFE to match my 2N5087G/2N5088G transistors.

 They are all around gain of 100 out. Should I order more as a larger sample, I have 50 of each.

 I ordered them from farnell UK but the 2N5088G came from newark USA via farnell and the 2N5087G's from Farnell UK supplied in completely differing packages.

 Cheers

 John


----------



## tomb

Quote:


  Originally Posted by *seroxatmad* /img/forum/go_quote.gif 
_I am using a Meter with hFE to match my 2N5087G/2N5088G transistors.

 They are all around gain of 100 out. Should I order more as a larger sample, I have 50 of each.

 I ordered them from farnell UK but the 2N5088G came from newark USA via farnell and the 2N5087G's from Farnell UK supplied in completely differing packages.

 Cheers

 John_

 

You should be able to match the 2N5087's with the 2N5087's within about 10-20HFE. Similarly, you should be able to match the 2N5088's with the 2N5088's - within about 10-20 HFE. However, they may be as much as 100 or more off, 2N5087's from 2N5088's. One probably needs a very large sample from the same place (ideally) to get the two different transistors close to each other. That's OK. Try to get them as close as you can, but you're not going to see them equal except under very large sample sizes, and even then - a very small minority.


----------



## Marzie

hey, just a quick q. I powered on my millett today after sitting on the shelf for a few months and getting moved around a bit. the sound is now fading in and out, I get heavy, loud response on music only, then the vocals will sound like they are in the background, then come to the forground, almost like oscillation, any thoughts? I just rebiased the tubes and that didnt do anything. This is on rca outputs at the back, Im about to go check the headphone out.


----------



## tomb

Quote:


  Originally Posted by *Marzie* /img/forum/go_quote.gif 
_hey, just a quick q. I powered on my millett today after sitting on the shelf for a few months and getting moved around a bit. the sound is now fading in and out, I get heavy, loud response on music only, then the vocals will sound like they are in the background, then come to the forground, almost like oscillation, any thoughts? I just rebiased the tubes and that didnt do anything. This is on rca outputs at the back, Im about to go check the headphone out._

 

If the tube bias is stable, chances are the tubes aren't the issue.

 Is it possible something came loose in the amp? Sometimes those RCA inputs can wriggle free from the terminal blocks and cause all sorts of weird symptoms.


----------



## TheKisho

Anyone know the progress on the Millett Hybrid MAXed version 1.2 of the PCBs? I've been researching the Millett Hybrid MAXed for a while [for a future DIY project]. I've noticed that the Millett Hybrid MAXed version 1.2 has been 'coming soon' for a while now, and I wanted to see what improvements it has over the previous versions.


 P.S. I know it's probably been mentioned before on this thread but it's just so long to check the whole thing.


----------



## Marzie

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_If the tube bias is stable, chances are the tubes aren't the issue.

 Is it possible something came loose in the amp? Sometimes those RCA inputs can wriggle free from the terminal blocks and cause all sorts of weird symptoms._

 

No I found the problem. It was a problem with the way I had my receiver set up. I have the tape outputs on the reciever going into the Millett and then to the tape inputs. Then I turn one of my input sources to play out the tape outputs and the speakers play the tape inputs. Well I had 5 ch. set up on that particular input (from my pc) so it picks and chooses what parts of the signal it wants to send out each particular channel. I just turned it to 2 ch. stereo and no more problem! Thanks!


----------



## TheKisho

Quick Reply fail. Duplicate post.


----------



## TheKisho

Quick Reply fail. Duplicate post.


----------



## tomb

Quote:


  Originally Posted by *TheKisho* /img/forum/go_quote.gif 
_Anyone know the progress on the Millett Hybrid MAXed version 1.2 of the PCBs? I've been researching the Millett Hybrid MAXed for a while [for a future DIY project]. I've noticed that the Millett Hybrid MAXed version 1.2 has been 'coming soon' for a while now, and I wanted to see what improvements it has over the previous versions.


 P.S. I know it's probably been mentioned before on this thread but it's just so long to check the whole thing._

 

The MAX V1.2.1 PCB was pictured about 3-4 pages back in this post:
http://www.head-fi.org/forums/f6/new...ml#post5969335

 There are some posts after that describing the new features. Essentially, there are two relays used for independent control of the onboard BantamDAC (or GrubDAC now, too, I guess) or RCA inputs. The headphone relay has been greatly improved as well. Cetoole went to a 24V relay and a small 24V regulator. That greatly simplifies the circuit (less parts) and results in immeasureable spikes at turn-off, which is the first time I've seen that in a headphone relay circuit. There's usually always a momentary spike of a few volts or so - not on this one.

 The power supply incorporates the full features of the well-developed MiniMAX power supply, providing high current and voltage to the rest of the amp at less than 0.040 mVrms AC, a truly outstanding spec. This performance has been validated using even larger caps (2000uf 50V) and a higher current PolyFuse connection to the amp circuit (0.75A rating) on the MAX V1.2.

 Cooling holes have been enlarged and optimized throughout the board for high-current MOSFET Diamond Buffer operation. I've been running the earlier prototype for months at 125ma DB bias with no problems at all. Of course, when using MOSFETs the heat sinks should be 1-1/2" tall. A small disadvantage, but those taller sinks come with some advantages in return - larger caps can be used - 1000uf 35V Elna RFS Silmics at CA2 and CA7. Plus, I believe we can fit some 0.47uf VitaminQ's up front as well, or at least parallel some of the smaller ones - there's enough room. (I have the 0.22uf's in the first proto right now.)

 EDIT: Now, if I can only find time to build it.


----------



## TheKisho

That looks awesome. I can't wait to build one. Will it cost the same or similar to the latest released Maxed to build?


----------



## BoilermakerFan

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_EDIT: Now, if I can only find time to build it.
	

	
	
		
		

		
		
	


	


_

 

[size=x-large]*AMEN!*[/size]

 Mine is still unpopulated as well. I was unemployed and had the time, but no money. Now I'm back to work and have no time. Actually I've quite sick and crashing out at 9:00pm with the kids. Had 3 pairs of headphones in the house for mods too, so those took priority since I trade my services for other stuff like cables and web site development. Down to three more cans in the cue and one Stax energizer box before I can dive into the MAX builds full tilt again.


----------



## tomb

I'm going to be out of the country again (at least off the mainland) for the next week, too. So there's another week that's going to go by without building it.
	

	
	
		
		

		
		
	


	




 Maybe next weekend ...


----------



## BoilermakerFan

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_I'm going to be out of the country again (at least off the mainland) for the next week, too. So there's another week that's going to go by without building it.
	

	
	
		
		

		
		
	


	




 Maybe next weekend ..._

 

But Hawaii isn't such a bad place to be for a week. Or PR for that matter.


----------



## tomb

Quote:


  Originally Posted by *BoilermakerFan* /img/forum/go_quote.gif 
_But Hawaii isn't such a bad place to be for a week. Or PR for that matter._

 

It's PR - as long as they haven't shut the island down because of the smoke from the burning oil terminals.


----------



## acvtre

I'm a noob in audio DIY, so far I've built only a cmoy and a pimeta V2 (not completed), but it seems to me that this amp is not too much difficult to populate, isn't it? Or is it only an impression of mine? can you roll the tubes?

 P.S.:How much does it heat up?


----------



## acvtre

Double post.


----------



## tomb

Quote:


  Originally Posted by *acvtre* /img/forum/go_quote.gif 
_I'm a noob in audio DIY, so far I've built only a cmoy and a pimeta V2 (not completed), but it seems to me that this amp is not too much difficult to populate, isn't it? Or is it only an impression of mine? can you roll the tubes?

 P.S.:How much does it heat up?_

 

In the case of the MiniMAX (another thread), the set bias and the custom-machined case combine to control the heat. It can probably be adjusted to a much higher bias with little ill effect, but we tried to be conservative and chose the best combination for BJT Diamond Buffers and 1" high heat sinks (50ma bias).

 However, this is a difficult question for the Millett MAX because there's so much flexibility. It can be built exactly like the MiniMAX, but good casework is still needed to ensure adequate cooling. Applied properly, there is very little heat rejected from the case.

 The MOSFET-MAX is a different story. MOSFETs like to run hot with a higher current bias and the MAX will allow 1-1/2" tall heat sinks, if desired. However, the higher the bias the better it sounds, IMHO. I've gone as high as 150ma current bias, but finally settled at 125ma. That's very hot on the center heat sinks, but there's been no indication of failure after several months of running. It's not cased yet, so that may make a difference. However, with the negative temperature coefficient of MOSFETs, it may actually run cooler cased up. I don't know for sure yet, though, so will have to defer to those more experienced in building the MOSFET version.

 Hope that helps ...


----------



## acvtre

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_In the case of the MiniMAX (another thread), the set bias and the custom-machined case combine to control the heat. It can probably be adjusted to a much higher bias with little ill effect, but we tried to be conservative and chose the best combination for BJT Diamond Buffers and 1" high heat sinks (50ma bias).

 However, this is a difficult question for the Millett MAX because there's so much flexibility. It can be built exactly like the MiniMAX, but good casework is still needed to ensure adequate cooling. Applied properly, there is very little heat rejected from the case.

 The MOSFET-MAX is a different story. MOSFETs like to run hot with a higher current bias and the MAX will allow 1-1/2" tall heat sinks, if desired. However, the higher the bias the better it sounds, IMHO. I've gone as high as 150ma current bias, but finally settled at 125ma. That's very hot on the center heat sinks, but there's been no indication of failure after several months of running. It's not cased yet, so that may make a difference. However, with the negative temperature coefficient of MOSFETs, it may actually run cooler cased up. I don't know for sure yet, though, so will have to defer to those more experienced in building the MOSFET version.

 Hope that helps ..._

 

Of course that helps, and about the difficulty and the rolling?
 The SSMH it's obviously easy beacuse there's the guide and the project in itself is really easy. But the MM is really really interesting because of the STEP, and Bantam DAC space included.
 I guess the MM Mosfet is the best.


----------



## Daveze

The difficulty is moderate, with those two builds under your belt, you should be alright. 

 Tubing rolling is an option, limited sensibly to 12AE6, 12FM6 and 12FK6. You also have very worthwhile transistor rolling, and caps too.

 I think it was Tom that summarised that it depends on your cans as to whether the Mini or the big max is better. The mosfet version eats low impedance cans but for high impedance, the mini works better. I can't really comment because I haven't built the mosfet yet...but I do have a very high bias BJT (old MM boards) that is rather pleasant.


----------



## Daveze

Double post...


----------



## acvtre

Quote:


  Originally Posted by *Daveze* /img/forum/go_quote.gif 
_The difficulty is moderate, with those two builds under your belt, you should be alright. 

 Tubing rolling is an option, limited sensibly to 12AE6, 12FM6 and 12FK6. You also have very worthwhile transistor rolling, and caps too.

 I think it was Tom that summarised that it depends on your cans as to whether the Mini or the big max is better. The mosfet version eats low impedance cans but for high impedance, the mini works better. I can't really comment because I haven't built the mosfet yet...but I do have a very high bias BJT (old MM boards) that is rather pleasant._

 

So what you all say is that the mini it's better I think, because if you have a low impedance can you can add impedance with an adapter but if you have high impedance you cannot take off impedance.


----------



## Daveze

Ah, sorry, I think I wasn't clear. The Mosfet Max is best for low impedance, Mini Max is best for high impedance. I'm not much for 'impedance adaptors', I think you're better off matching phones to circuits but YMMV. I find its just an excuse to build more amps and buy more phones...


----------



## acvtre

Quote:


  Originally Posted by *Daveze* /img/forum/go_quote.gif 
_Ah, sorry, I think I wasn't clear. The Mosfet Max is best for low impedance, Mini Max is best for high impedance. I'm not much for 'impedance adaptors', I think you're better off matching phones to circuits but YMMV. I find its just an excuse to build more amps and buy more phones..._

 

Ah this could be a problem, since I've got an AKG k240, so 55ohm, but I'm going to buy senn hd595, so 300ohm.
 What would you suggest to build? I was for MM mosfet. What kind of transistors do you suggest to roll? the classical op627 and other similar?


----------



## Daveze

Hmm, tough. I'd say go with the mini, If you're anything like me you'll love the custom case. 

 I think you need to get up to speed with the new boards: opamps (OPA627, etc) are out, discrete buffers are in. Indulgence.


----------



## acvtre

Quote:


  Originally Posted by *Daveze* /img/forum/go_quote.gif 
_Hmm, tough. I'd say go with the mini, If you're anything like me you'll love the custom case. 

 I think you need to get up to speed with the new boards: opamps (OPA627, etc) are out, discrete buffers are in. Indulgence._

 

Actually I would prefer a complete kit with pcb and other stuff needed and also the case ready. I think I have to wait beezar.com


----------



## Beefy

Quote:


  Originally Posted by *Daveze* /img/forum/go_quote.gif 
_Ah, sorry, I think I wasn't clear. The Mosfet Max is best for low impedance, Mini Max is best for high impedance._

 

I see what you are saying, but in all fairness...... if you are dropping out of Class A with BJT's at 50mA with *any* impedance phones, there is a good chance you have just deafened yourself.


----------



## acvtre

Quote:


  Originally Posted by *Beefy* /img/forum/go_quote.gif 
_I see what you are saying, but in all fairness...... if you are dropping out of Class A with BJT's at 50mA with *any* impedance phones, there is a good chance you have just deafened yourself._

 

So you say minimax and MM are equal, in the sens that you don't have to bother about the impedance?


----------



## Beefy

Impedance is something you shouldn't ever worry about in the real world. There are very few scenarios where it is actually important.


----------



## acvtre

Quote:


  Originally Posted by *Beefy* /img/forum/go_quote.gif 
_Impedance is something you shouldn't ever worry about in the real world. There are very few scenarios where it is actually important._

 

Great, so since the MM is bigger, this means easier to populate, I think I'll go for the MM mosfet and hopefully also the Bantam DAC. Good choice?


----------



## tomb

Quote:


  Originally Posted by *acvtre* /img/forum/go_quote.gif 
_Great, so since the MM is bigger, this means easier to populate, I think I'll go for the MM mosfet and hopefully also the Bantam DAC. Good choice?_

 

I think what Beefy is saying is that to distinguish between the designs is splitting hairs to a certain extent. Although, the MOSFET-MAX can power some desktop speakers fairly well - I wouldn't recommend that for the MiniMAX.

 Ultimately, the MOSFET-MAX is a more "advanced" build: temperatures are hotter, options are more numerous, so therefore, you need to make intelligent choices, etc. The MiniMAX is the better choice starting out, most likely.


----------



## Beefy

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_I think what Beefy is saying is that to distinguish between the designs is splitting hairs to a certain extent._

 

That one


----------



## acvtre

Ok, now the problem is, beezar sells only the minimax PCB or also the kit as for the SSMH?

 EDIT:
 omg but it's terribly expensive. Absolutely impossible, ok now the choice is...the millet hybrid maxed or the SSMH? the others are really too much expensive.


----------



## tomb

Quote:


  Originally Posted by *acvtre* /img/forum/go_quote.gif 
_Ok, now the problem is, beezar sells only the minimax PCB or also the kit as for the SSMH?

 EDIT:
 omg but it's terribly expensive. Absolutely impossible, ok now the choice is...the millet hybrid maxed or the SSMH? the others are really too much expensive._

 

The custom case on the MiniMAX is only $40 more than the case you'd need on the MAX. Many spend that for a couple of two-inch long endplates from FPE.
	

	
	
		
		

		
		
	


	




 That's the only thing you'll save over the MAX. Plus, the MAX will have a more expensive parts set due to the number of relays included (3 as opposed to 1 on the MiniMAX).

 No doubt, the Starving Student is less expensive ... but as I've said before, proportionally so, I think.


----------



## acvtre

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_The custom case on the MiniMAX is only $40 more than the case you'd need on the MAX. Many spend that for a couple of two-inch long endplates from FPE.
	

	
	
		
		

		
		
	


	




 That's the only thing you'll save over the MAX. Plus, the MAX will have a more expensive parts set due to the number of relays included (3 as opposed to 1 on the MiniMAX).

 No doubt, the Starving Student is less expensive ... but as I've said before, proportionally so, I think.
	

	
	
		
		

		
		
	


	


_

 

Ok, maybe there's something that I don't understand because the BOM on DIYforum.org says that I would spend over 230$ for the mini and 150$ for the max, so the difference is not of only 40$. Consider that the stuff in europe is not as cheap as in USa. In addition, I don't know why, the maxed it seems to me to be easier, maybe it's only an impression.
 Actually I don't know what to do, I'm going crazy. Actually, I can't see or understand a reason to spend more money for the minimax, the only problem for the maxed would be the casework for me. *My real intention is to simply populate the PCB, that's all.*
 Nobody sells a kit with all the needed stuff?


----------



## tomb

Quote:


  Originally Posted by *acvtre* /img/forum/go_quote.gif 
_Ok, maybe there's something that I don't understand because the BOM on DIYforum.org says that I would spend over 230$ for the mini and 150$ for the max, so the difference is not of only 40$. Consider that the stuff in europe is not as cheap as in USa. In addition, I don't know why, the maxed it seems to me to be easier, maybe it's only an impression.
 Actually I don't know what to do, I'm going crazy. Actually, I can't see or understand a reason to spend more money for the minimax, the only problem for the maxed would be the casework for me. *My real intention is to simply populate the PCB, that's all.*
 Nobody sells a kit with all the needed stuff?_

 

First - yes, I sell kits for the MiniMAX, but it's not "official." (maybe that just changed 
	

	
	
		
		

		
		
	


	




 )

 Second - if your "... real intention is to simply populate the PCB, that's all.", then you'll never have a working amp. We're proud that the MAX/MiniMAX family has as much or more onboard components than probably any other DIY PCB design - pot, headphone jack, power supply, etc. However, that's still a far cry from being able to complete a working amp. There are switches, power jacks, tip jacks, RCA jacks, wiring, knob, etc. All of these are needed to get a working amp in order.

 Third - yeah, there are differences in the BOM of the MAX and MiniMAX. Both amps evolved over time. The MAX was first and although the BOM was very complete for most of amps of the time period it came out, there are many more components listed in the MiniMAX BOM. The MiniMAX BOM is the BOM for a complete kit, period. There are tip jacks, RCA jacks, a machined knob, more expensive capacitors, the 12FM6 tubes (rarer and more $$), and even a DMM and trimmer adjustment tool. These add up to ~$30 in extras. Combined with the $40 difference for the MiniMAX case, that's approximately the same for the MAX - it would be the same for the same parts, iow.

 Now - anymore questions about pricing ... please address them to me in a PM or e-mail. I suggest that you study these designs further before you turn this into a window shopping discussion again. No offense, but that's not what these threads are about.


----------



## acvtre

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_...cut...
 Now - anymore questions about pricing ... please address them to me in a PM or e-mail. I suggest that you study these designs further before you turn this into a window shopping discussion again. No offense, but that's not what these threads are about.
	

	
	
		
		

		
		
	


	





_

 

So sorry, that wasn't my intention.
 However with "My real intention is to simply populate the PCB, that's all" I mean that I just wanna completly build the amp and don't take technical decisions because I can't, unfortunately. 
	

	
	
		
		

		
		
	


	



 About the third point: basically you say that the hybrid maxed is older and the minimax newer and better. So it's better if I chose between the MM mosfet, not the hybrid maxed, and the minimax, is that right?

 Big noob question: what is the tube bias? (right, ground, left) what is supposed to plug in there?


----------



## tomb

Quote:


  Originally Posted by *acvtre* /img/forum/go_quote.gif 
_So sorry, that wasn't my intention._

 

No problem. It's just that much talk of pricing and selling will get me banned as a Member-Of-the-Trade. We have to respect the rules that Jude and the Mods set if we want to participate in Head-Fi.
	

	
	
		
		

		
		
	


	




 Quote:


 However with "My real intention is to simply populate the PCB, that's all" I mean that I just wanna completly build the amp and don't take technical decisions because I can't, unfortunately. 
	

	
	
		
		

		
		
	


	



 

I understand, but it should be a learning experience. Have you read and understood the MAX/MiniMAX websites? That should be the first step. Quote:


 About the third point: basically you say that the hybrid maxed is older and the minimax newer and better. So it's better if I chose between the MM mosfet, not the hybrid maxed, and the minimax, is that right? 
 

No one said "better." Assuming we get the new MAX V1.2 PCB in production (It's not available right now, so some of these questions are moot.), the same parts = the same performance.

 The MiniMAX was designed later. The purpose being to cram as many through-hole parts into as small a PCB space as we could, and design what we think is the best custom-case offering available. Along the way, we also addressed the original MAX power supply and improved it on the MiniMAX so that it has major-league quieting and ripple performance. The whole thing ties up into a neat little package that many have enjoyed building.

 When the MAX V1.2 board is ready, it will have more features (like a board-mounted Bantam or Grub DAC), but still, equal parts = equal performance. The one distinguishing difference is that the MAX will allow the use of MOSFETs. You see, MOSFETs require a certain minimum of current bias to operate correctly (and to even turn on). That current bias is high enough to need 1-1/2" heat sinks. That size heat sink will not fit in the MiniMAX. So, if you want to use MOSFETs, the MAX is the only option.
  Quote:


 Big noob question: what is the tube bias? (right, ground, left) what is supposed to plug in there? 
 

A DMM plugs into the tip jacks so that you can measure bias. Bias on a vacuum tube determines the center point of the zero voltage reference for the music signal. The tubes work on positive voltage being supplied to the tube. However, music needs both negative and positive voltage to create a music signal (a sine wave that fluctuates between negative and positive).

 The way we do this on a tube is to elevate a bias point for the grid so that there is a voltage difference above and below the music signal as it exits the tube. The Millett Hybrid/MAX/MiniMAX works on a 24-27VDC power supply. So, we set the tube bias at 13.5VDC if the power supply is set at 27VDC. That centers the music signal at 13.5VDC and allows the tube to amplify the music signal from +13.5V (27VDC) to -13.5V (0VDC).

 In the case of the Millett Hybrid/MAX/MiniMAX family, there are three tubes that can be used - 12AE6, 12FM6, and 12FK6. Each tube will have an entirely different adjustment to set that tube bias. In fact, each tube within the same type will have a different adjustment on the trimmers to set that 13.5V bias. So, we provide the tip jacks in the design so that these changes can be easily made at any time. After all, tube rolling is one the more fun things about tubes. You don't want to have to take the case apart every time you change a tube.

 Hope that makes a little sense. It's complicated, I know - more reading will help.


----------



## BoilermakerFan

Decided to do my V1.2 proto as a MOSFET-MAX. Checking to make sure I have all the parts and transistors I need before I start building.

 EDIT: V1.0 kit is sold...


----------



## tomb

Good news! I finally finished building the MAX V1.2a prototype:




 New V1.2a on left, older V1.2 prototype on the right.

 The need for the new prototype was determined by cetoole after I discovered that the original with only one source relay had some bleed-through between the two sourcing channels. The new V1.2a uses two, very small relays - one each dedicated to each source. Switching is again through a simple SPST switch (although I only had DPDT's on each proto - figured I'd splice in the Bantam's LED with the other contacts
	

	
	
		
		

		
			





 ).








 Here's a closeup of the source input area in the back. The Bantam is clearly shown. What's interesting is the use of the punch-down blocks. Colin found these and decided to use them because things continue to get tighter back there and the punch-down blocks offered similar capability to the standard terminal blocks, but are both thinner and taller, allowing adequate clearance from the Bantam both horizontally and vertically.

 You can see the two tiny relays. They're fired with a single 0.1uf X7R cap and powered with a 78L24 regulator.




 I'll live with it for a few days to make sure everything's OK, then production PCB's will be ordered shortly thereafter.


----------



## BoilermakerFan

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_What's interesting is the use of the punch-down blocks. Colin found these and decided to use them because things continue to get tighter back there and the punch-down blocks offered similar capability to the standard terminal blocks, but are both thinner and taller, allowing adequate clearance from the Bantam both horizontally and vertically._

 

Colin, eh? 
	

	
	
		
		

		
		
	


	




 Have you tested it with the GrubDAC yet?

 Did you used the IRF510/9510s again? 


 I found a chassis alternative for the new V1.2 board too. It's not as pretty as the Hammond, but it wide enough to fit a 50-80VA shielded and potted toroid (at least a SumR will fit) next to the V1.2 board and you can run 2-1/2" heat sinks since it's 4-1/8" tall. Better tube protection, but you'll have to window it to see the tubes... Plenty of room for a OptiVol or even Joshua Tree if you're creative with the mounting. 

 I'll take pics tomorrow and post up the info.


----------



## tomb

Quote:


  Originally Posted by *BoilermakerFan* /img/forum/go_quote.gif 
_Colin, eh? 
	

	
	
		
		

		
		
	


	




 Have you tested it with the GrubDAC yet?_

 

No, not yet, but I have some parts on order to build a couple. Quote:


 
 Did you used the IRF510/9510s again? 
 

No, I stuck with the standard Z24/Z34's. I didn't want to change anything except to test out the new relay section. It's been too long without MAX PCB's, so I didn't want to confuse the prototyping. Besides, I suspect that after comparing specs the Z24/Z34 may be the better MOSFETs, anyway. Quote:


 

 I found a chassis alternative for the new V1.2 board too. It's not as pretty as the Hammond, but it wide enough to fit a 50-80VA shielded and potted toroid (at least a SumR will fit) next to the V1.2 board and you can run 2-1/2" heat sinks since it's 4-1/8" tall. Better tube protection, but you'll have to window it to see the tubes... Plenty of room for a OptiVol or even Joshua Tree if you're creative with the mounting. 

 I'll take pics tomorrow and post up the info. 
 

Sounds good.


----------



## BoilermakerFan

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_No, I stuck with the standard Z24/Z34's. I didn't want to change anything except to test out the new relay section. It's been too long without MAX PCB's, so I didn't want to confuse the prototyping. Besides, I suspect that after comparing specs the Z24/Z34 may be the better MOSFETs, anyway._

 

On the curves? The 510/9510 need a little more bias to hit their sweet spot, IIRC, but their gate capacitance was much lower. 

 I've been side-tracked by work, life, and commissioned builds, but I still intend to build mine with the .18VitQs, Silmic IIs, BC546C/BC556C, and 510/9510s initially. Tubes will be the FM6s. I'll roll in all the other buffers including the Z24/Z34 and I'll use it to feed my gainclone as well as cans so I can see if a few DBs rise to the top. I may be pushing as much as 300mA bias on a couple DB sets. 

 If you can send a GrubDAC my way for testing/audition, that would be greatly appreciated.


----------



## tomb

Quote:


  Originally Posted by *BoilermakerFan* /img/forum/go_quote.gif 
_On the curves? The 510/9510 need a little more bias to hit their sweet spot, IIRC, but their gate capacitance was much lower. </snip>_

 

It's true that the gate capacitance is lower, but I'm not sure that's in effect once they are biased sufficiently. On the other hand, the ON resistance is much lower on the Z24/Z34's, plus they are marketed as 3rd generation MOSFETs, whereas the 510/9510's are 2nd generation.

 EDIT: But what do I really know? I just didn't want a change that I had to suspect along with testing the other stuff.


----------



## BoilermakerFan

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_It's true that the gate capacitance is lower, but I'm not sure that's in effect once they are biased sufficiently. On the other hand, the ON resistance is much lower on the Z24/Z34's, plus they are marketed as 3rd generation MOSFETs, whereas the 510/9510's are 2nd generation._

 

Now for the million dollar question...

 Do they sound better? Can you hear any difference? 

 I'll do auditions of both myself, but I figured I'd be the first to ask you since I can be the second one to hear it if I hurry this weekend.


----------



## tomb

Quote:


  Originally Posted by *BoilermakerFan* /img/forum/go_quote.gif 
_Now for the million dollar question...

 Do they sound better? Can you hear any difference? 

 I'll do auditions of both myself, but I figured I'd be the first to ask you since I can be the second one to hear it if I hurry this weekend._

 

See this quote:
  Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_EDIT: But what do I really know? I just didn't want a change that I had to suspect along with testing the other stuff.
	

	
	
		
		

		
		
	


	


_

 

Besides, I haven't used anything but the Z24/Z34's yet - those were on the 1st proto, too. Hence, "didn't want a change ... along with testing the other stuff."


----------



## BoilermakerFan

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Besides, I haven't used anything but the Z24/Z34's yet - those were on the 1st proto, too. Hence, "didn't want a change ... along with testing the other stuff."
	

	
	
		
		

		
		
	


	


_

 

Ah, I thought you did use the 510/9510s when you had the KZs in the first proto. I thought you only changed out the KZs for Silmics. 

 Hmmm... How hard would it be to wire Silmic IIs and Muse ES caps through switches to flip/flop between both, taking the caps off the board? I'd just label the switch "Bass Boost."


----------



## tomb

Quote:


  Originally Posted by *BoilermakerFan* /img/forum/go_quote.gif 
_Ah, I thought you did use the 510/9510s when you had the KZs in the first proto. I thought you only changed out the KZs for Silmics._

 

No, you came up with the idea to use 510/9510's after I built it, if I remember correctly. In any event, Z24/Z34's is all I've used so far. Those KZ's had to go quickly, though - yuck. 
  Quote:


 Hmmm... How hard would it be to wire Silmic IIs and Muse ES caps through switches to flip/flop between both, taking the caps off the board? I'd just label the switch "Bass Boost." 
 

It's not needed.
	

	
	
		
		

		
		
	


	




 Seriously, even as much as I love ES caps, I'd use the Elna's all the time if they weren't so d*mn huge.
	

	
	
		
		

		
		
	


	




 That's not an issue in a MOSFET-MAX with 1-1/2" sinks. They're as good as Black Gate NX's, except that they're cheap, available from a mass parts supplier (DigiKey), there's no ridiculously long break-ins (maybe a few days), and the bass is right there almost from the start. The _only_ bad trait is their size - very nice caps, at least in a MAX.


----------



## stang

I really want to buy one of these for my future Grado's now 
	

	
	
		
		

		
		
	


	




 I am not the DIY type of...kid...
	

	
	
		
		

		
		
	


	




 Just gotta hope someone dislikes their 220V one haha


----------



## tomb

Quote:


  Originally Posted by *stang* /img/forum/go_quote.gif 
_I really want to buy one of these for my future Grado's now 
	

	
	
		
		

		
		
	


	




 I am not the DIY type of...kid...
	

	
	
		
		

		
		
	


	




 Just gotta hope someone dislikes their 220V one haha 
	

	
	
		
		

		
		
	


	


_

 

The MOSFET-MAX is definitely a Grado-driver. It does wonderfully with an AKG K701, too - the amount of bass it will pump through a K701 is surprising.


----------



## stang

Yeah they sound good too. Oh, too many to choose from 
	

	
	
		
		

		
		
	


	




. Well I supposed I should actually BUY the Grado's first then save up haha. RS-1's here I come. I think I will skip the HF-2. As good as they are supposed to be, I think my ALO-780 will compliment the RS-1 better than the HF-2, as they are more different from each other. I got $500usd to spend anyway, should be pretty easy to get a used RS-1 classic for that 
	

	
	
		
		

		
		
	


	




 If the RS-1 I am looking at sell, I think I might just buy that EAR MAX + HD that's here in Australia and save for a pair of RS-1.


----------



## BoogieWoogie

Just to know if I get a 110v version can I use it in europe with a converter ?


----------



## stang

Delete.


----------



## BoilermakerFan

Quote:


  Originally Posted by *BoogieWoogie* /img/forum/go_quote.gif 
_Just to know if I get a 110v version can I use it in europe with a converter ?_

 

The MHM uses a wall wart by default, 25VA to 40VA @ 24Vac. So if you build it according to the BOM, it doesn't matter as long as the wall wart plug is compatible with the MHM's power jack. You will just need a new wall wart compatible with Europe's wall receptacles. 

 If you want to build it in a larger enclosure you can use a 30VA-40VA 120/240 toroid which will allow you to run larger heatsinks and bump up the bias currents a bit to put more load on the transformer. But fair warning, the potential current with a 30VA toroid is 1.25A and goes up to 1.6A with a 40VA supply but the default LM317T is only rated for 1.5A. 

 If you decide to use a toroid instead of a wall wart, you can use a 30VA 120/240 toroid and buy a filtered/fused IEC inlet that has the 120/240 switch built into the receptacle. Then you would just need a compatible IEC power cord for the country's receptacles.


----------



## Beefy

*no longer relevant*


----------



## BoilermakerFan

Corrected original post.


----------



## Beefy

Well stock is actually 24VA, according to the BOM.

 And it isn't to make me happy, just an observation


----------



## Beefy

*double post*


----------



## BoilermakerFan

Quote:


  Originally Posted by *Beefy* /img/forum/go_quote.gif 
_Well stock is actually 24VA, according to the BOM.

 And it isn't to make me happy, just an observation 
	

	
	
		
		

		
		
	


	


_

 

Just giving you a hard time. My wall warts from Beezar are all 40VA or 50VA... 

 But it was a good catch. I forgot I'm in the MHM thread and I have made a lot of BOM changes to my build to support the high currents I will be running.


----------



## BoogieWoogie

What ??Sorry I dint get a word I'm not familiarize with electric terms and I'm not a DYT.
 Its this amp

 Would  something this work ? Or I only would need this plug converter to europe format, I recall its 220V in Europe


----------



## BoogieWoogie

double post..


----------



## BoilermakerFan

Quote:


  Originally Posted by *BoogieWoogie* /img/forum/go_quote.gif 
_What ??Sorry I dint get a word I'm not familiarize with electric terms and I'm not a DYT.
 Its this amp

 Would  something this work ? Or I only would need this plug converter to europa format _

 

That's a Mini-MAX, it only has 1" heat sinks so you cannot push very high bias currents so even a 40VA wall wart is overkill. All you need is a 25-30VA wall wart with an output of 24Vac. Most have screw terminals so you can attach the wire that is terminated in te correct plug for the jack on the back of the Mini-MAX.


----------



## tomb

Just stick with the BOM (which I'll update soon, btw). You need something that provides 24VAC output (not negotiable) with at least a 1A current capability. You can actually go higher with the current, but not lower.

 (Pay no attention to this section if you're not an experienced DIY-er.
	

	
	
		
		

		
		
	


	




 )
 Honestly, I haven't found over-voltage to be that much of an issue - perhaps a volt or two once the walwart is even lightly loaded, as opposed to no load.

 In any event, the PS heat sink will handle it. The limiting point of heat is the center two DB sinks, not the PS sink.





 EDIT: If it's a MiniMAX, BMF is correct (well, only 0.75A is required) - that's a less current intensive amp than a MOSFET-MAX - two different animals.


----------



## BoilermakerFan

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Just stick with the BOM (which I'll update soon, btw). You need something that provides 24VAC output (not negotiable) with at least a 1A current capability. You can actually go higher with the current, but not lower.

 (Pay no attention to this section if you're not an experienced DIY-er.
	

	
	
		
		

		
		
	


	




 )
 Honestly, I haven't found over-voltage to be that much of an issue - perhaps a volt or two once the walwart is even lightly loaded, as opposed to no load.

 In any event, the PS heat sink will handle it. The limiting point of heat is the center two DB sinks, not the PS sink.





 EDIT: If it's a MiniMAX, BMF is correct (well, only 0.75A is required) - that's a less current intensive amp than a MOSFET-MAX - two different animals.
	

	
	
		
		

		
		
	


	


_

 

Venting the bottom of the enclosure under the middle DB and V-Reg heat sinks should really help cooling with the vent holes in the new PCB too. 

 I went back and seriously edited my original post Tom. Stepping up to big boy bias levels required 6 BOM changes and my build is too far deviated from the normal BOM, so I don't want to confuse new builders.

 The main point of my original post is that there are some nice options if a builder wants dual voltage compatibility and is willing to give up the beautiful Hammond enclosure for a larger one that can accept a switchable 120/240V IEC power inlet and use a dual primary toroid.


----------



## BoogieWoogie

Could you link me something from amazon or ebay that will do the job ?


----------



## Beefy

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Honestly, I haven't found over-voltage to be that much of an issue - perhaps a volt or two once the walwart is even lightly loaded, as opposed to no load._

 

I've used three different 24VA wallwarts in Australia and Canada, and not one of them has ever been under 27VAC with tubes hot and music playing. Maybe my line voltage is just always high......


----------



## Beefy

Quote:


  Originally Posted by *BoogieWoogie* /img/forum/go_quote.gif 
_Could you link me something from amazon or ebay that will do the job ?_

 

Well this is the one I ended up with (but Nexxtech branded), because I bought it before I had my Canadian credit card: Enercell*™ Switchable 18/24V/1A AC Power Adapter - RadioShack.com


----------



## BoilermakerFan

Quote:


  Originally Posted by *Beefy* /img/forum/go_quote.gif 
_I've used three different 24VA wallwarts in Australia and Canada, and not one of them has ever been under 27VAC with tubes hot and music playing. Maybe my line voltage is just always high......_

 

High line voltage is far more common than low voltage nowadays in most parts of the US. Utilities figured out they can deliver a lot more billable power (or meet increasing demand) to residences and industry without having to upgrade much of their infrastructure if they bump up the line voltages. So the HV and MV lines were all bumped 5%-10% and this trickles down to as much as 5% on the 240V lines in the US residential grid. I'm fortunate in that my local grid is tied to a university campus so my line voltage stays pretty much 120V-121V.


----------



## BoogieWoogie

Quote:


  Originally Posted by *Beefy* /img/forum/go_quote.gif 
_Well this is the one I ended up with (but Nexxtech branded), because I bought it before I had my Canadian credit card: Enercell*™ Switchable 18/24V/1A AC Power Adapter - RadioShack.com_

 

So if I connect that to a 220v corrent it can deal with it ?


----------



## Beefy

Quote:


  Originally Posted by *BoogieWoogie* /img/forum/go_quote.gif 
_So if I connect that to a 220v corrent it can deal with it ?_

 

Ah crap, no, I forgot the whole point of this was to find something for 230V input.


----------



## Beefy

I can't find anything on eBay. Your best bet is to look at local electronic stores that sell security equipment. 24VAC output at 1 amp is a VERY common option for powering security cameras and controllers.


----------



## BoogieWoogie

Actually its 220v but as the seller states it comes with Triad wallcharger so I think I will only need this converter or am I wrong ?


----------



## Beefy

Trust me, just find something locally. It will be easier, cheaper, and much more likely to get you exactly what you need.


----------



## BoogieWoogie

Quote:


  Originally Posted by *Beefy* /img/forum/go_quote.gif 
_Trust me, just find something locally. It will be easier, cheaper, and much more likely to get you exactly what you need._

 

Yes I pretend to do that but I need to know what I'm looking for, so the step down 220v to 120v like that in my link is the only thing I need ?


----------



## Beefy

If you buy something locally, you won't need the step down transformer.

 Just look around at your local electronics shops for a 220V input, 24VAC at 1 amp output wallwart. You *will* be able to find something, because they are a very common item for security systems.


----------



## Beefy

*double post*

 Godammnit, what is up with the forums today?!?!


----------



## BoilermakerFan

Quote:


  Originally Posted by *BoogieWoogie* /img/forum/go_quote.gif 
_Actually its 220v but as the seller states it comes with Triad wallcharger so I think I will only need this converter or am I wrong ?_

 

Skip the converter. They just add noise and as Beefy stated, you only need a 230Vac local wall wart that puts out 24Vac @ 1A. 

 Locally, all you have to ask for is a 24Vac, 1amp wall wart power supply or power transformer. Since you're calling locally, the shop will sell you the correctly plugged 230Vac unit. Then you will only need the loose cable than goes from the wall wart to the amp. If the amp you buy comes with the US wall wart, you can reuse the cord from that wall wart on your locally sourced one. Worst case, you have to buy a new cord from Tom's Beezar.com web shop for a Mini-MAX, Millett Hybrid MAX, or the new V1.2 MOSFET-MAX. 

 Note: This all assuming you are looking to power a MAX amp.


----------



## BoogieWoogie

Quote:


  Originally Posted by *BoilermakerFan* /img/forum/go_quote.gif 
_Skip the converter. They just add noise and as Beefy stated, you only need a 230Vac local wall wart that puts out 24Vac @ 1A. 

 Locally, all you have to ask for is a 24Vac, 1amp wall wart power supply or power transformer. Since you're calling locally, the shop will sell you the correctly plugged 230Vac unit. Then you will only need the loose cable than goes from the wall wart to the amp. If the amp you buy comes with the US wall wart, you can reuse the cord from that wall wart on your locally sourced one. Worst case, you have to buy a new cord from Tom's Beezar.com web shop for a Mini-MAX, Millett Hybrid MAX, or the new V1.2 MOSFET-MAX. 

 Note: This all assuming you are looking to power a MAX amp._

 

Its the Minimax , by reusing you mean cut ? The wall wart in europe doesn't come with the same cord ?

 Bleh so much trouble.. Maybe would be better buy a european version amp


----------



## tomb

Quote:


  Originally Posted by *BoogieWoogie* /img/forum/go_quote.gif 
_Its the Minimax , by reusing you mean cut ? The wall wart in europe doesn't come with the same cord ?

 Bleh so much trouble.. Maybe would be better buy a european version amp
	

	
	
		
		

		
		
	


	


_

 

There are numerous MiniMAX owners and builders in Europe. None of them have had any trouble finding a walwart with the correct rating and connector.
	

	
	
		
		

		
		
	


	




 EDIT: This one at Farnell should work perfectly:
http://uk.farnell.com/multicomp/t240...Ntt=24VAC750ma


----------



## Beefy

I found that at Farnell as well, and it is great as the connector is the correct size. But I still reckon something could be had cheaper - IF the effort was made to look at a local store......


----------



## BoogieWoogie

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_There are numerous MiniMAX owners and builders in Europe. None of them have had any trouble finding a walwart with the correct rating and connector.
	

	
	
		
		

		
		
	


	


_

 

Does it need to be exactly 24v 1000ma ?

 found this one I think its this , for50$ ...


----------



## Beefy

Quote:


  Originally Posted by *BoogieWoogie* /img/forum/go_quote.gif 
_Does it need to be exactly 24v 1000ma?_

 

No, 750mA minimum, as high as 2A and you should be OK.

 But it HAS to be AC, and I can't tell from that page whether that adapter is AC or DC.


----------



## BoogieWoogie

Quote:


  Originally Posted by *Beefy* /img/forum/go_quote.gif 
_No, 750mA minimum, as high as 2A and you should be OK.

 But it HAS to be AC, and I can't tell from that page whether that adapter is AC or DC._

 

But the voltage has to be exactly 24v ? 
 The most common are the 12v ones .. Dont seems to find 24 besides that one.


----------



## Beefy

Yes, it has to be 24V


----------



## BoogieWoogie

has to be 12v ? din't you mean could be. 
 As for the input type how its called the Minimax one?


----------



## Beefy

Quote:


  Originally Posted by *BoogieWoogie* /img/forum/go_quote.gif 
_has to be 12v ? din't you mean could be._

 

Sorry, has to be 24V. I'm typing faster than I'm thinking today.

  Quote:


 As for the input type how its called the Minimax one? 
 

Eh? I don't know what you mean.


----------



## BoogieWoogie

Quote:


  Originally Posted by *Beefy* /img/forum/go_quote.gif 
_Sorry, has to be 24V. I'm typing faster than I'm thinking today.



 Eh? I don't know what you mean._

 

The cable entrance.


----------



## Beefy

The cable entrance is the same on ALL of the Maxes as far as I know. The one Tomb linked from Farnell was perfect.


----------



## BoogieWoogie

Finally! I think this is it

Transformador 700mA- 24V saida - MTK

 input tension - AC 220V
 output tension – 24V
 intensity - 700mA

 for 10€ must be it I only hope is the same cable entrace of the miniMax


----------



## tomb

Quote:


  Originally Posted by *BoogieWoogie* /img/forum/go_quote.gif 
_Finally! I think this is it

Transformador 700mA- 24V saida - MTK

 input tension - AC 220V
 output tension – 24V
 intensity - 700mA

 for 10€ must be it I only hope is the same cable entrace of the miniMax_

 

You need to look somewhere else. They don't even have the category. The one you just picked is a DC walwart - it has cooling slots and that's tell-tale for DC.

 Did you not try the Farnell link I posted? That one was perfect.


----------



## BoogieWoogie

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_You need to look somewhere else. They don't even have the category. The one you just picked is a DC walwart - it has cooling slots and that's tell-tale for DC.

 Did you not try the Farnell link I posted? That one was perfect._

 

Yes I have cheked but is to much expensive 23€+shipping costs, my country certainly has one too just have to find it.

 Camon lol ..

 This is MUST work does it ?. It is on AC->AC this is what I need right.

 input: 220VAC
 output: 24VAC 1000mA
 DC cable 5.5x2.5x11mm - Right size ?


----------



## tomb

Quote:


  Originally Posted by *BoogieWoogie* /img/forum/go_quote.gif 
_Yes I have cheked but is to much expensive 23€+shipping costs, my country certainly has one too just have to find it.

 Camon lol ..

 This is MUST work does it ?. It is on AC->AC this is what I need right.

 input: 220VAC
 output: 24VAC 1000mA
 DC cable 5.5x *2.5* x11mm - Right size ?_

 

Sorry - the 2.5 is the problem. That's the diameter of the plug - it needs to be 2.1mm. You may be able to change out the socket on the MiniMAX, but it seems unbelievable that you can't find the right one in your country.

 How about security systems? One of the most common sources in this country are walwarts that are used to supply security systems. They get around the electrical licensing requirements by using 24VAC walwarts because they can run lengthy wiring with voltages that don't approach licensing requirements. Just a thought ...

 Is there a Farnell in your country? Maybe the price is cheaper than the one in the UK that I referenced.


----------



## BoogieWoogie

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Sorry - the 2.5 is the problem. That's the diameter of the plug - it needs to be 2.1mm. You may be able to change out the socket on the MiniMAX, but it seems unbelievable that you can't find the right one in your country.

 How about security systems? One of the most common sources in this country are walwarts that are used to supply security systems. They get around the electrical licensing requirements by using 24VAC walwarts because they can run lengthy wiring with voltages that don't approach licensing requirements. Just a thought ...

 Is there a Farnell in your country? Maybe the price is cheaper than the one in the UK that I referenced.
	

	
	
		
		

		
		
	


	


_

 

I did an search and actually it seems to exist Farnell Portugal  I have never eared about this store.
 Edit: Its on spain and Origin country from the same you linked is GB United Kindom I guess I will have to pay the shipping costs too..


----------



## jdkJake

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Good news! I finally finished building the MAX V1.2a prototype:

 I'll live with it for a few days to make sure everything's OK, then production PCB's will be ordered shortly thereafter.
	

	
	
		
		

		
		
	


	


_

 

YEAH!!!

 Great news Tom. I am so looking forward to this build I cannot tell you.

 Keep us in the loop!

 jk


----------



## tomb

Quote:


  Originally Posted by *jdkJake* /img/forum/go_quote.gif 
_YEAH!!!

 Great news Tom. I am so looking forward to this build I cannot tell you.

 Keep us in the loop!

 jk_

 

Production PCB's are on their way. They'll probably be available in the first or second week in February.


----------



## tomb

Production PCB's are here!


----------



## Beefy

Ooooh, that's purty!


----------



## soloz2

Looks great! I'll have to look a bit closer when I'm back on my PC though.


----------



## ujamerstand

Nice! You can even switch between the bantamDAC and some other source! Is it in the same foot print as the minimax?


----------



## tomb

Quote:


  Originally Posted by *ujamerstand* /img/forum/go_quote.gif 
_Nice! You can even switch between the bantamDAC and some other source! Is it in the same foot print as the minimax?_

 

Um ... no - the MiniMAX is about 1/3 smaller - no room for a BantamDAC or GrubDAC on one of those.


----------



## ujamerstand

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Um ... no - the MiniMAX is about 1/3 smaller - no room for a BantamDAC or GrubDAC on one of those.
	

	
	
		
		

		
		
	


	


_

 

Ah, okay. I just assumed because the layout looked familiar.


----------



## tomb

Quote:


  Originally Posted by *ujamerstand* /img/forum/go_quote.gif 
_Ah, okay. I just assumed because the layout looked familiar._

 

Yep. The history is that the MAX came first - a splendid design from cetoole that was a "MAXimum" upgrade from the old Millett Hybrid. Literally hundreds of MAXes were built over the last few years.

 The MiniMAX was a return to one of the original MAX prototypes that started out with a smaller board sized for the Lansing case. I talked cetoole into re-designing that PCB so that we could offer a smaller version of the original MAX that used a Lansing case (my avatar is the first working prototype of the MiniMAX). While we were at it, we designed the custom-machined and silkscreened Beezar/Lansing case that people have become familiar with as the MiniMAX. Finally, we did extensive testing/re-design to get the onboard power supply to a level of DIY-competitiveness with regard to ripple and noise.

 By that time, the MAX PCB was obsolete. So cetoole started on an updated design, using the MiniMAX power supply design and making use of the extra room afforded by the larger MAX PCB to implement an onboard BantamDAC (now includes the GrubDAC, too). It's taken awhile, but we went through a couple of iterations to solve the input sourcing relay arrangement. What you see above is the final production version that will go on sale at Beezar shortly.

 We see the MiniMAX continuing because of the excellent case and refined total package that it represents. Plus, using BJT's as the output diamond buffer - it's as good as it can get (the MAX can do no better with BJT's). However, the larger MAX board allows the use of a Hammond 1455T1601 case, which can accomodate 1-1/2" heat sinks. This is enough for the high-bias needed for MOSFETs in the diamond buffer. So, MiniMAX - custom case and BJT diamond buffer and MAX - onboard Bantam/GrubDAC and MOSFET diamond buffer. At least, that's the way we'll be recommending the choice between the two.
	

	
	
		
		

		
		
	


	




 Hopefully that gives you some of the history if you weren't familiar with it. Of course, you can read all of this and more on the History pages of the MAX, MOSFET-MAX, and MiniMAX websites.


----------



## soloz2

No, it's larger than the miniMax.


----------



## Lou Erickson

I was just wondering about this! It looks like a perfect headphone amp for the office. If I can find a case big enough to wedge a hard drive and little USB hub into as well, it'll be perfect. One USB cable to work's computer, let it play music through the DAC in the box... Mmm.

 Very shiny, Tom!

 Now, all I have to do is get a couple of these OTHER projects done first.


----------



## BoilermakerFan

Quote:


  Originally Posted by *Lou Erickson* /img/forum/go_quote.gif 
_I was just wondering about this! It looks like a perfect headphone amp for the office. If I can find a case big enough to wedge a hard drive and little USB hub into as well, it'll be perfect. One USB cable to work's computer, let it play music through the DAC in the box... Mmm.

 Very shiny, Tom!

 Now, all I have to do is get a couple of these OTHER projects done first._

 

There are USB hubs that are small enough to fit in the extended Hammond case and there are other cases with similar sized footprints that are taller so they will easily accommodate a USB hub. Add a 16-32Gig thumb drive with FLAC files and you're set.


----------



## tomb

I've updated the BOM to include the new parts required for the V1.2 PCB (now on sale). Note that the PS is almost identical to the MiniMAX, but a different parts selection is used for a couple of items to support the higher current of MOSFETs (our recommended diamond buffer for the MAX as opposed to BJT's on the MiniMAX).

 BOM on the MOSFET-MAX website:
MOSFET-MAX BOM
 (The MOSFET-MAX website will become the primary reference for the V1.2 PCB.)

 Also, please note that the relay-delay circuit has been updated to use a 24V regulator and 24V relay, doing away with the old Zener diode, resistor, and one of the electrolytics. This simplifies the circuit allowing for more reliability and better performance. Transient voltage offset on turn-off is almost non-existent, while the parts have been sized to provide ~45 seconds at turn-on from a cold start. Note also the use of suppressor diodes on the relay-delay and the relay input switching. These will provide better long-term protection of the relay contacts than the old 1N4148's.

 I haven't cased one up yet, but bias at 125ma has been steady for months (also on the older proto) with little sign of over-heating on the naked PCB's.

 I haven't updated the DigiKey section of the BOM yet, but the Elna RFS Silmic II - 1000uf 16V at CA2, and 1000uf 35V at CA7 are what we're recommending for the signal path. These caps are available at DigiKey and elsewhere and sound every bit as good as Black Gates to me. Use of one at CA2 seems to provide as much bass as an ES, too - just sterling audio caps all the way around, it seems. KZ's at Mouser are a distant alternate.


----------



## jdkJake

Great news Tom!

 Besides the Elna RFS, any other recommendations that deviate from the BOM?

 Also, are there any plans on updating the casework templates or will the old versions still work with the updated artwork?

 jk


----------



## tomb

Quote:


  Originally Posted by *jdkJake* /img/forum/go_quote.gif 
_Great news Tom!

 Besides the Elna RFS, any other recommendations that deviate from the BOM?

 Also, are there any plans on updating the casework templates or will the old versions still work with the updated artwork?

 jk_

 

No, but really - the entire BOM for the MOSFET-MAX is a bit of a deviation from a BJT MAX - taller caps, JFET-input, MOSFETs on the output, higher current PF1. Then there's the entire relay switching in back and the updated relay-delay circuit - but all of that is on the BOM. Also, the punch-down block in back is very new and unique to the MAX series. We had to use that because of the lack of space back there, but the desire to maintain some sort of terminal block-like capability (as opposed to MOLEX pins).

 As for the case, the templates should be very close. I'll have to check because the spacing is slightly different with the sinks up front. Plus, there's the need for the USB connector in back (a square hole).

 I had planned on tying the Bantam/GrubDAC LED into a switch up front: one LED for USB connection (red) and another for USB connection and switch to onboard DAC source (green). This can be done with a simple DPDT up front.

 And actually ... the plans are to use speaker binding posts in the back as an option - tied into the headphone jack up front (one of the reasons that large slot is in the back - to allow the wiring to come up from below. Those items will need to be detailed in the drawing templates as well, but that should be a simple change I'll take care of very soon.


----------



## tomb

By the way - I remembered that I do have the templates for the case already laid out. As I said, the changes are not very many. I just have to post them. So, I'll do that this weekend.

 Also - just a point of interest, but I specifically requested gold flush on the pads instead of leaded - in keeping with the MOSFET-MAX color scheme. However, Imagineering told me that gold was only good for 6-8 months. So, that's why the new PCB is red and _silver_ instead of red and gold. The expiration on leaded pads is in years, not months.


----------



## MASantos

Tomb, why the "notch" on the back of the board near the power supply section? Space for an IEC connector?


----------



## BoilermakerFan

Quote:


  Originally Posted by *MASantos* /img/forum/go_quote.gif 
_Tomb, why the "notch" on the back of the board near the power supply section? Space for an IEC connector?_

 

 Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_And actually ... the plans are to use speaker binding posts in the back as an option - tied into the headphone jack up front (one of the reasons that large slot is in the back - to allow the wiring to come up from below. Those items will need to be detailed in the drawing templates as well, but that should be a simple change I'll take care of very soon.
	

	
	
		
		

		
		
	


	


_

 

The notch is to clear speaker binding posts in the stock Hammond chassis.


----------



## tomb

The notch is also there for using a Box Enclosure case, which uses no bezels. (I've had a couple of special color Box enclosures for a MAX for two years now and haven't used them.) Since the length of board = length of case, without the notch there would be no room for any wiring underneath - tip jacks, speaker binding posts, or anything else.


----------



## amphead

Great to see the Max going strong with the new rev. Kudos Tom/Colin!


----------



## MASantos

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_The notch is also there for using a Box Enclosure case, which uses no bezels. (I've had a couple of special color Box enclosures for a MAX for two years now and haven't used them.) Since the length of board = length of case, without the notch there would be no room for any wiring underneath - tip jacks, speaker binding posts, or anything else._

 

Speakers? How much power can this new MAX deliver?


----------



## tomb

Quote:


  Originally Posted by *MASantos* /img/forum/go_quote.gif 
_Speakers? How much power can this new MAX deliver?_

 

Should be similar to a basic M3, but will be limited by the heat sinks. It should be superior to the Starving Student doing this, too, and dsavitsk successfully ran small speakers with that. It's not enough for something big, but certainly for some desktop flea speakers or similar. To be honest, I haven't tried it yet myself, but I'm looking forward to it. Cetoole uses his as the primary source for a pair of desktop speakers - for a couple of years now, I believe. That was just the BJT version, though. The MOSFET version is more capable.


----------



## BoilermakerFan

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Should be similar to a basic M3, but will be limited by the heat sinks. It should be superior to the Starving Student doing this, too, and dsavitsk successfully ran small speakers with that. It's not enough for something big, but certainly for some desktop flea speakers or similar. To be honest, I haven't tried it yet myself, but I'm looking forward to it. Cetoole uses his as the primary source for a pair of desktop speakers - for a couple of years now, I believe. That was just the BJT version, though. The MOSFET version is more capable._

 

On the 2-1/2" heatsinks biased around 250mA with a bigger supply, PF, and upgraded LM338 V-Reg, it was calculated to be right around 1W. At 250mA bias, the DBs are dissipating almost 7W and that was really "MAXing" out the biggest heat sinks available. 

 I forget where the critical bias level is, over 180mA-190mA IIRC, but at a point over 150mA, the stock 5087/5088 small signal transistors will leave their linear range or simply see too much current. I don't have time to search through hundreds of emails to find the exact value, but just know that you can't keep cranking up the bias even if you run the 338T, larger PF, and 2-1/2" sinks.


----------



## hedmaster

Hi guys, I bought a Millet Max second hand and need some help. The inputs in the back are not the usual RCAs, rather it is 1/4" phone plug. 

 How much will this degrade the sound, if any? Also, there are no holes for biasing. Is that a big deal? According to the builder (have to look up for name), this amp was built about 2 yrs ago. 

 Would upgrading the power supply to the one on Beezar help with sound quality as well? 

 I plan on taking some pics of the amp, so that I can get some pointers on some potential improvements, and to get a basic understanding of the build. ie whether or not any boutique items were used or not. 

 I believe the tubes are the originals (12AE6s). I plan on replacing them. That means that I should buy one of those biasing tools and bias it to match the new tubes, right?

 Also, do you lose much low end punch with the 12FM6 vs the AE6? What do you gain, higher resolution on the top end, or ?

 Thanks for any help you can give me, 
 Matt


----------



## tomb

Quote:


  Originally Posted by *hedmaster* /img/forum/go_quote.gif 
_Hi guys, I bought a Millet Max second hand and need some help. The inputs in the back are not the usual RCAs, rather it is 1/4" phone plug. 

 How much will this degrade the sound, if any?_

 

It won't, but it's not very convienient.
  Quote:


 Also, there are no holes for biasing. Is that a big deal? According to the builder (have to look up for name), this amp was built about 2 yrs ago. 
 

It just means you have to take the back plate off and slide out the lid to get to the adjustments. the only one you really need to worry about is the tube bias.

 EDIT: But you have to have a DMM to measure the bias while you're adjusting.
	

	
	
		
		

		
			




  Quote:


 
 Would upgrading the power supply to the one on Beezar help with sound quality as well? 
 

No, the only power supplies on Beezar are high-current Class II 24VAC walwarts. Sound quality is unaffected unless your present walwart is under-rated. 
  Quote:


 I plan on taking some pics of the amp, so that I can get some pointers on some potential improvements, and to get a basic understanding of the build. ie whether or not any boutique items were used or not. 

 I believe the tubes are the originals (12AE6s). I plan on replacing them. That means that I should buy one of those biasing tools and bias it to match the new tubes, right? 
 

A small screwdriver will work fine as long as you don't touch anything else but the adjusting screws. Refer to this page on the MAX website for details:
MAX Setup and Bias Settings
  Quote:


 Also, do you lose much low end punch with the 12FM6 vs the AE6? What do you gain, higher resolution on the top end, or ? 
 

No, you probably won't notice it unless going all the way to a 12FK6. The 12FK6 is generally regarded as having a bit more resolution on the top end, while the 12AE6 has more punch. The 12FM6 is kind've a combination of both. The primary reason for switching tubes is gain. While the 12AE6 has a lot of low-end punch, its high gain may be way too much for many headphones. The 12FK6 has the least gain and the 12FM6 is inbetween.

 Note that _*any*_ change in tubes will require re-biasing. The sound quality will be directly affected if you don't do this.
	

	
	
		
		

		
		
	


	




 It's a very simple procedure, though.
  Quote:


 Thanks for any help you can give me, 
 Matt 
 

Anytime ...


----------



## redfish-bluefish

I thought I would finally say hi, as I have lurked on and off since 2005 
	

	
	
		
		

		
		
	


	




 This seemed like the best place to do it, as I have really been thinking hard on building one of Millett Max amps. I built a cmoy back in '05 and then went Lo-fi with my electronics (obsessed with building guitar pedals). At any rate, I am back on my headphones kick and wanted to ask a couple of related questions as I research the various options on the Milletts.

 First, I see a lot of posts where people talk about this or that matching well with Grados. When this statement is made, are they speaking of the entire Grado lineup (if I remember correctly, they are all the same or similar impedance) or only the high-end. I ask because of my second question...

 A few pages back on the thread I read that Grados would pair very well with the MOSFET build, so this is the direction I am thinking of going. Does this sound reasonable for a pair of SR 80's?

 Thanks!
 1,2
 red-blue


----------



## tomb

Quote:


  Originally Posted by *redfish-bluefish* /img/forum/go_quote.gif 
_I thought I would finally say hi, as I have lurked on and off since 2005 
	

	
	
		
		

		
		
	


	




 This seemed like the best place to do it, as I have really been thinking hard on building one of Millett Max amps. I built a cmoy back in '05 and then went Lo-fi with my electronics (obsessed with building guitar pedals). At any rate, I am back on my headphones kick and wanted to ask a couple of related questions as I research the various options on the Milletts.

 First, I see a lot of posts where people talk about this or that matching well with Grados. When this statement is made, are they speaking of the entire Grado lineup (if I remember correctly, they are all the same or similar impedance) or only the high-end. I ask because of my second question..._

 

When you see those statements, they're referring to the fact that the diamond buffers in the MAX/MiniMAX/MOSFET-MAX are able to supply high currents to low impedance phones such as Grados. Further, the tubes used in the gain stage give that well-rounded, warm and lush midrange that seems to "tame" the natural hotnesss and sometimes harshness of Grados. I think this applies to the entire line, but of course, as you move up in Grados, the bass gets stronger, there's less harshness, and everything gets smoother (generally). Note that the high currents also apply to K701/K702's as well. A MOSFET-MAX can supply more than enough current to elicit very strong bass from K701/K702's. The Class A bias on a MOSFET-MAX approaches 2W (not all of that is available to the headphones, though).

 One caveat to that is that if you're ever thinking of using high-impedance phones, the MOSFET-MAX will do fine, but the BJT versions may have an advantage. There's a turn-on voltage that the MOSFETs need to burn to operate. This means there's not as much voltage swing available as there is with BJT's. Grados and AKG's will never miss that, though.
  Quote:


 
 A few pages back on the thread I read that Grados would pair very well with the MOSFET build, so this is the direction I am thinking of going. Does this sound reasonable for a pair of SR 80's? 
 

I think so. I have 3 Grado's myself - HF-2's, HF-1's, and SR-225's. I've owned a pair of SR-80's in the past, too. You will not want for power if using these with a MOSFET-MAX.

 Also, on a slightly different note, remember that one of the nice things about the MAX lineup is that even though they use tubes, they are all low voltage - nothing over 24-27V. That's re-assuring when you're first starting out in DIY. Quote:


 
 Thanks!
 1,2
 red-blue 
 

Welcome to the posting on Head-Fi! I hope you enjoy it.


----------



## redfish-bluefish

Thanks, Tomb. You Sir, are an enabler! I was waffling on this a little, but now I think I'll be scraping the cash together to do the build. Maybe I'll sell something. MOSFET it shall be. I think I should build for what I have now (I don't have much!) and collect for the future in the future.

 And yes, it has not been lost on me that this will be a GREAT intro to tubes. I've only built one other tube circuit, even lower voltage than this, believe it or not.

 After I have some time to poke around and generate questions as I attempt to answer others, I'll be tossing them out here.
 Thanks!


----------



## tomb

Quote:


  Originally Posted by *redfish-bluefish* /img/forum/go_quote.gif 
_Thanks, Tomb. You Sir, are an enabler! I was waffling on this a little, but now I think I'll be scraping the cash together to do the build. Maybe I'll sell something. MOSFET it shall be. I think I should build for what I have now (I don't have much!) and collect for the future in the future.

 And yes, it has not been lost on me that this will be a GREAT intro to tubes. I've only built one other tube circuit, even lower voltage than this, believe it or not.

 After I have some time to poke around and generate questions as I attempt to answer others, I'll be tossing them out here.
 Thanks!_

 

Good deal! We'll be here when you come back for more questions.


----------



## Beefy

Quote:


  Originally Posted by *redfish-bluefish* /img/forum/go_quote.gif 
_Thanks, Tomb. You Sir, are an enabler! I was waffling on this a little, but now I think I'll be scraping the cash together to do the build. Maybe I'll sell something. MOSFET it shall be. I think I should build for what I have now (I don't have much!) and collect for the future in the future._

 

Depending on your confidence, skills and funds, you may still be better off going with a BJT MiniMax. Beezar sells a full kit, including a gorgeous pre-machined case.


----------



## radicalrev

Guys, bought a pair of tubes from Beezar. One of tubes lights up brighter than the other, is it normal for this? Will there be an unbalanced sound? I tried listening to it and couldn't hear any difference, but still curious.


----------



## Beefy

The heater brightness is often _apparently_ different, depending on the geometry of the glass. If you can't hear any difference, I certainly wouldn't worry.


----------



## redfish-bluefish

Quote:


  Originally Posted by *Beefy* /img/forum/go_quote.gif 
_Depending on your confidence, skills and funds, you may still be better off going with a BJT MiniMax. Beezar sells a full kit, including a gorgeous pre-machined case._

 

That might be an option. tomb made a good sell for the MOSFET build. I've no doubt that I wouldn't go wrong with any of them, but what are your thoughts on why the BJT MiniMax might be a better option?

 Thanks,
 1,2
 red-blue


----------



## BoilermakerFan

Quote:


  Originally Posted by *redfish-bluefish* /img/forum/go_quote.gif 
_That might be an option. tomb made a good sell for the MOSFET build. I've no doubt that I wouldn't go wrong with any of them, but what are your thoughts on why the BJT MiniMax might be a better option?

 Thanks,
 1,2
 red-blue_

 

Because it's a full kit with all the machining/drilling on the case done for you. If you build a MOSFET-MAX, it has to go in a bigger chassis like the spec'ed Hammond and you have to mark and drill all the holes as well as order the parts from a few different places.


----------



## tomb

These guys are right. If you're just starting out, the MiniMAX kit is the way to go with MAXes. With the experience you learn, you can easily tackle a MOSFET-MAX later on.
	

	
	
		
		

		
		
	


	




 One caveat to that is that I expect Glass Jar Audio to offer new kits for the MAX soon. Jeff indicated to me that he'd like to carry the new PCB as the MOSFET-MAX. He may still be accumulating all of the parts, though, because his listing still says out-of-stock. Maybe he'll be ready by the time you build a MiniMAX kit?


----------



## Beefy

Quote:


  Originally Posted by *redfish-bluefish* /img/forum/go_quote.gif 
_I've no doubt that I wouldn't go wrong with any of them, but what are your thoughts on why the BJT MiniMax might be a better option?_

 

Only because it comes as a really nice kit, with everything in it. Great way to get back into DIY with less risk


----------



## regal

I just tried these 2SC3421/1358's from Beezar.com and these are fantastic with Grado's. Much better than the ebay 2238/968's they replaced. I really recommend giving these a try. Thanks Tomb for suggesting these as I would have written them off based on Steinchen's ratings.


----------



## Beefy

Quote:


  Originally Posted by *regal* /img/forum/go_quote.gif 
_Much better than the ebay 2238/968's they replaced._

 

Reputable seller? Otherwise, good chance they were fake.


----------



## MASantos

Going back to the powering speakers topic, what would be needed to enable the mosfet max to deliver around 5-10W? 

 I guess bigger heatsinks, higher voltage for the output stage? I would love to see a hibrid power amp, a MH meets B22 sort of thing!


----------



## tomb

Quote:


  Originally Posted by *MASantos* /img/forum/go_quote.gif 
_Going back to the powering speakers topic, what would be needed to enable the mosfet max to deliver around 5-10W? 

 I guess bigger heatsinks, higher voltage for the output stage? I would love to see a hibrid power amp, a MH meets B22 sort of thing! 
	

	
	
		
		

		
		
	


	


_

 

You might ask BoilerMakerFan. He and cetoole have had extensive conversations on applying a MAX to power speakers.


----------



## Beefy

Quote:


  Originally Posted by *MASantos* /img/forum/go_quote.gif 
_Going back to the powering speakers topic, what would be needed to enable the mosfet max to deliver around 5-10W? 

 I guess bigger heatsinks, higher voltage for the output stage? I would love to see a hibrid power amp, a MH meets B22 sort of thing! 
	

	
	
		
		

		
		
	


	


_

 

 Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_You might ask BoilerMakerFan. He and cetoole have had extensive conversations on applying a MAX to power speakers._

 

My simple answer would be to go balanced


----------



## MASantos

Quote:


  Originally Posted by *Beefy* /img/forum/go_quote.gif 
_My simple answer would be to go balanced 
	

	
	
		
		

		
		
	


	


_

 

That would double it quite easily! Add a sigma22 bipassing the millettmax power supply, off board heatsinks and quite easily reach 3W. But then then the parts cost would probably allow for a better design, specific for low power speakers!


----------



## BoilermakerFan

The MHM and MOSFET-MAX wasn't designed to be a speaker amp or built as balanced. If you want that much power you're better off with a different design. For the cost of a balanced MHM you can build a F5 which will do 25W Class A. Another $200 in PS mods and the F5 is suitable for headphone use with extremely low noise and ripple that only improves it's speaker performance. I just can't recommend a balance MHM when there are better options in the $400-$600 price range, especially for a dual role of headphones and speakers. 

 The MOSFET-MAX is capable of delivering about 2W to speakers as it is and with 92dB or better efficient speakers, it will be enough for "normal" listening levels and near field monitor applications. The tweaks I pursued where to raise the bias levels over 150mA (perhaps pushing to 225mA, but that really approaches the safe upper limit of 7W dissipation on a 2-1/2" heat sink and it better have lots of ventilation for good air flow). The higher bias just keels the amp in Class A longer when driving speakers. I am not changing the voltage, it stays 24Vac and a LM338 is capable of handling 5A so the PS is fine with that change. The polyfuse needs to be bumped up to 1.35A as a starting point, but it may need to go up to nearly 2A if you are really driving inefficient speakers and really putting a high demand on the PS. My speakers are 93dB/W and 97dB/W. IIRC, Colin's speakers are 91 or 92dB/W. 

 There are several tweaks that need to be done to the BOM, but if you're still interested, drop me a PM with your email addy and I'll detail the changes. In order to avoid confusion, I'm not going to post in this thread.


----------



## redfish-bluefish

Quote:


  Originally Posted by *BoilermakerFan* /img/forum/go_quote.gif 
_Because it's a full kit with all the machining/drilling on the case done for you. If you build a MOSFET-MAX, it has to go in a bigger chassis like the spec'ed Hammond and you have to mark and drill all the holes as well as order the parts from a few different places._

 

Gotcha.

 I'll keep that in mind in making decisions, but I do have some experience with and tools for layouts, drilling etc. You are, of course, right about ordering--I've made enough mistakes on Mouser orders to know that if you don't truly know what you are looking for/at, you run a high risk of screw up. Actually, even if you do know!

 I guess that I have really been approaching this from more of a "what do I want sonically" standpoint. I have a lot of confidence, but am humble enough to recognize that my electronics experience is in a totally different genre.

 I very much appreciate the input.
 Thanks!
 1,2
 red-blue


----------



## funch

Since the supply of the specified Wima cap's has dried up, does anyone here know of
 either an alternate source, or a suitable replacement?


----------



## Lil' Knight

Last time I checked, Beezar still has the Wimas.


----------



## funch

Nope! They're gone too. I've got several .18uF Vitamin Q's, but it seems as though
 I read somewhere that using boutique cap's in CA3/6/9 wasn't a good idea.


----------



## tomb

Quote:


  Originally Posted by *funch* /img/forum/go_quote.gif 
_Nope! They're gone too. I've got several .18uF Vitamin Q's, but it seems as though
 I read somewhere that using boutique cap's in CA3/6/9 wasn't a good idea._

 

I've got some more right now, but unfortunately I'm out of town until next weekend. If you can wait until then, I've have them re-listed.

 I had zero'd the stock on the Wima caps so there would be enough for MiniMAX kit orders - until I received more of them.


----------



## funch

Shoulda' known 'the man' had it covered. No big rush on my part. I just noticed that
 Mouser shows their next delivery is the end of June, so I went looking for a replacement.
 Not much out there as a decent replacement. BTW, would .18 or .22 Sprague's work in
 CA3/6/9?


----------



## tomb

Quote:


  Originally Posted by *funch* /img/forum/go_quote.gif 
_Shoulda' known 'the man' had it covered. No big rush on my part. I just noticed that
 Mouser shows their next delivery is the end of June, so I went looking for a replacement.
 Not much out there as a decent replacement. BTW, would .18 or .22 Sprague's work in
 CA3/6/9?_

 

I would recommend staying with the Wima's, if you can wait. VitQ's make no difference at CA3 and CA6 (a waste) and they'll actually cut some of the bass at CA9.


----------



## Beefy

Is there still a Panasonic alternative from Digikey?


----------



## BoilermakerFan

Quote:


  Originally Posted by *Beefy* /img/forum/go_quote.gif 
_Is there still a Panasonic alternative from Digikey?_

 

I was just going to recommend them. Panny makes a yellow box cap, but I forget the family now. Unfortunately, the great PE caps from Panasonic were discontinued. I grabbed 20 or so pieces of .18uF and .22uF with a few others. The Vishay box caps are decent too.


----------



## tomb

Quote:


  Originally Posted by *BoilermakerFan* /img/forum/go_quote.gif 
_I was just going to recommend them. Panny makes a yellow box cap, but I forget the family now. Unfortunately, the great PE caps from Panasonic were discontinued. I grabbed 20 or so pieces of .18uF and .22uF with a few others. The Vishay box caps are decent too._

 

The Vishay-Roederstein MKP's (polypropylene) I thought showed great promise after the MKT's we use on the BantamDAC. However, I've tried them:





 ... and they're not as good as Wima's.
	

	
	
		
		

		
			





 I should have the Wima's listed on Friday.


----------



## funch

I have a question about the value of CA8 in the MOSFET-Max.
  I have some .18uF Vitamin Q's and was wondering if they would
  work well, or should I stick with the .22uF value?


----------



## BoilermakerFan

Quote: 





funch said:


> I have a question about the value of CA8 in the MOSFET-Max.
> I have some .18uF Vitamin Q's and was wondering if they would
> work well, or should I stick with the .22uF value?


 

 General opinion is that the .18s sound better, especially with the Silmic II caps.


----------



## funch

Thanks. I'm planning on using the Silmic's, and you
  just saved me 5 bucks.


----------



## tomb

I can't tell the difference in sound between the 0.18uf and 0.22uf VitQ's.  I use the 0.22uf's on the MAX/MOSFET-MAX PCB simply because the board is bigger and they'll fit.  They're both 196P/96P series VitQ's, so they're the best Vitamin Q types you can get.
   
  The differences are that the 96P series uses something called "inserted tab" construction, while the 196P uses "extended foil" construction.  Supposedly, there's no difference in performance between the two except that the "inserted tab" construction is smaller than the "extended foil" construction for the same ratings.  Both caps are rated for 125 deg. C. operation.  Other "P" types such as 91P or 191P are 85 deg.C. rated caps.  "Vitamin Q" oil is used for all four series.
   
  Sprague series such as 118P or 121P, etc. are not "Vitamin Q's."  AFAIK, only the 91P/191P and 96P/196P are truly Vitamin Q's.


----------



## jdkJake

Started my MOSFET build today. Been a while since I built anything, but, it came back pretty quick. Kind of like riding a bike. Getting used to soldering with glasses has been the biggest struggle. It is hell getting old!! 

 Anyway, going through my parts I noticed I might have an off-sized cap for CR4. The recommended mouser was out when I ordered and I went with the digikey part. The recommended mouser part is 82pf while the recommended digikey is 10pf. I have limited knowledge of power supply design, so, I put it out to ya'all. Will I be okay of should I really go for 82pf (or even 100pf) which I can get locally.

 Thanks!


 jk


----------



## tomb

Quote: 





jdkjake said:


> Started my MOSFET build today. Been a while since I built anything, but, it came back pretty quick. Kind of like riding a bike. Getting used to soldering with glasses has been the biggest struggle. It is hell getting old!!
> 
> Anyway, going through my parts I noticed I might have an off-sized cap for CR4. The recommended mouser was out when I ordered and I went with the digikey part. The recommended mouser part is 82pf while the recommended digikey is 10pf. I have limited knowledge of power supply design, so, I put it out to ya'all. Will I be okay of should I really go for 82pf (or even 100pf) which I can get locally.
> 
> ...


 

 That's "uf" not "pf", but it's a good question because the DigiKey part is a tantalum and we don't want that.  Use this one from DigiKey: http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&name=P10293-ND
   
  It's a Panasonic FC at 82uf 35V - same as the Mouser selection.  I'll correct that on the BOM when I get a chance.


----------



## jdkJake

Quote: 





tomb said:


> That's "uf" not "pf", but it's a good question because the DigiKey part is a tantalum and we don't want that.  Use this one from DigiKey: http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&name=P10293-ND
> 
> It's a Panasonic FC at 82uf 35V - same as the Mouser selection.  I'll correct that on the BOM when I get a chance.


 
   
  Thanks for the clarification Tom. I need to pay more attention as I type. Did I mention the new glasses?  
   
  One more question, is there a consensus on CA4/CA5? I have Panasonic FM's at 1800uf but can easily order FC's 2200uf or 3300uf since I have to re-order the part for CR4. Which do you think make the difference? The quality of the part (assuming FM has better ESR, ripple, etc...) or the reserve capacity (which, the FC has in spades at either rating)?
   
  jk


----------



## jdkJake

Quote: 





tomb said:


> That's "uf" not "pf", but it's a good question because the DigiKey part is a tantalum and we don't want that.  Use this one from DigiKey: http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&name=P10293-ND
> 
> It's a Panasonic FC at 82uf 35V - same as the Mouser selection.  I'll correct that on the BOM when I get a chance.


 
   
  Another FYI, the digikey reference at CM3 also needs to be updated as it points to a 330uf part.
   
  I think P12415-ND is the correct reference (although there is a FC series part that will work as well).
   
  jk


----------



## tomb

Quote: 





jdkjake said:


> Another FYI, the digikey reference at CM3 also needs to be updated as it points to a 330uf part.
> 
> I think P12415-ND is the correct reference (although there is a FC series part that will work as well).
> 
> jk


 

 CM3 should be as cheap as you can find.  There's no reason to use a sterling FM there.
   
  Don't use the DigiKey portion of the BOM - it's not been vetted and to the best of my recollection, DigiKey doesn't have all the necessary parts, anyway (although the Silmics are most highly recommended).  Notice that the "Input Control" section is completely blank for DigiKey.  I'll look into it when I get a chance, but using the DigiKey section might be risky.  The Mouser side is correct.
   
  Quote: 





> One more question, is there a consensus on CA4/CA5? I have Panasonic FM's at 1800uf but can easily order FC's 2200uf or 3300uf since I have to re-order the part for CR4. Which do you think make the difference? The quality of the part (assuming FM has better ESR, ripple, etc...) or the reserve capacity (which, the FC has in spades at either rating)?


 
   
   I like the UHE's at Mouser.  Otherwise, use the larger FC's.  I used 3300uf's on the first proto, but didn't like them as well as the UHE's.  I believe the Panasonic FM at 1800uf (the standard on the MiniMAX) is out of stock right now, anyway.


----------



## jdkJake

Okay, but, I already have a set of the 1800uf FM's. Is there a big enough of a difference to warrant moving up to 2200uf?

 jk


----------



## tomb

Quote: 





jdkjake said:


> Okay, but, I already have a set of the 1800uf FM's. Is there a big enough of a difference to warrant moving up to 2200uf?
> 
> jk


 


 Nah - the FM's are great.  I'm sure they'll be fine.


----------



## jdkJake

Great. Thanks Tom.

 One more question on the BOM. The value for R1 is stated to be 10 ohm 1W while the parts links are 2W parts. I know a 2W will always work, but will a 1W suffice?


 jk


----------



## jdkJake

Missed it by THAT much!
   
  Oh well. A couple part set backs, but, overall, things are moving along pretty good. Made a lot of progress over the weekend. Now I just need to wait on a few more parts that I mis-ordered and I can finish up the PCB build.
   
  Lesson learned: Triple and even quad check the BOM before hitting "purchase". I swear I wasn't drunk when I put my orders together, but, you would never know it from the mistakes. I ordered only one of a key resister pair (RA8) and half a fuse holder (DOH!). Who the heck orders half a fuse holder! Gees. Also mis-sized and mis-typed the cap for CR4. Anyway, once I get those parts, I should be able to finish it up quickly. The soldering skills have returned to full strength, so, at least I got that going for me. Fun stuff though. Been a while since I built up a PCB and I must say it was a most enjoyable way to spend a few hours.
   
  Here is a quick vanity shot of where I stand. I have not mounted the power supply regulator until I get CR4 placed. It looks to be tight. 
   
   

   
  Full "boutique" cap and output resister load out.
   
  jk
   
  BTW: Turns out I must have the golden touch for tube sockets. Those puppies split apart like nobodies business using just a flat blade screw driver. A couple drops of gel-style super glue and I was good to go. Whole process took a few minutes at best. Very cool.
   
  EDIT: Oh yeah, this is the MOSFET build with the version 1.2 PCB. Suppose I should have mentioned that!


----------



## tomb

Looks great, jk!!


----------



## jdkJake

Thanks Tom, your help has been invaluable, both directly and indirectly (via this thread). Both are a wealth of information.

 I cannot wait to fire this bad boy up. In the meantime, I guess I will have to rely on my miniMAX to tide me over! . I have a particularly nice set of 12AE6 in there (sylvania construction, side getter) that has me captivated. You never know when you will find a particularly good set of millett tubes! 

 But that is a topic for another thread...

 jk

 BTW: any comment on R1 being 1W vice 2W?


----------



## tomb

Quote: 





jdkjake said:


> </snip>
> BTW: any comment on R1 being 1W vice 2W?


 


 For safety's sake, if R1 is 30 ohms, then 2W is necessary.  If R1 is 10 ohms (typical), then only 1/2W is needed.  We sized the wattage in case someone used the larger value.  So, if you select 10 ohms, then you can easily use a 1W resistor if you want.


----------



## tomb

Just an FYI, but I've updated all the drawings and templates on the MOSFET-MAX website:
http://www.diyforums.org/MOSFET-MAX/MOSFET-MAXtemplate.php


----------



## funch

Methinks there be something screwy with the PDF file for the top drilling template.
   
  I can't seem to get it to print correctly. (Of course, the methinks part is where I usually foul up!)


----------



## tomb

Quote: 





funch said:


> Methinks there be something screwy with the PDF file for the top drilling template.
> 
> I can't seem to get it to print correctly. (Of course, the methinks part is where I usually foul up!)


 
  Try the 8.5 x 14 version if you can't get that one to work - they should be the same thing, only the 8.5 x 14 hasn't been cropped into two smaller versions.
   
  I'll take a look at it tonight and see if there's some issue with it.


----------



## jdkJake

tomb said:


> For safety's sake, if R1 is 30 ohms, then 2W is necessary.  If R1 is 10 ohms (typical), then only 1/2W is needed.  We sized the wattage in case someone used the larger value.  So, if you select 10 ohms, then you can easily use a 1W resistor if you want.







 Okay, great. I happen to have a 1W part. 

 Thanks!

 jk


----------



## jdkJake

Quote: 





tomb said:


> Try the 8.5 x 14 version if you can't get that one to work - they should be the same thing, only the 8.5 x 14 hasn't been cropped into two smaller versions.
> 
> I'll take a look at it tonight and see if there's some issue with it.


 
   
  Do you have a Mac? 
   
  If so, try turning "auto-rotate" off when you print it. It should align after that point.
   
  I am having troubles with the endplate. I will let you know when I figure that one out.
   
  jk


----------



## funch

No Mac. PC. The PDF file for the top plate comes up very
  different from the others, and I can't find a way to print it
  out at a scale of 1:1.


----------



## tomb

Guys - I'll have this fixed tonight.  I apologize, but I see the problem now.  They're very over-sized.  I actually cropped the 8.5x14 file using Photoshop and it blew the scale.  I need to re-plot them both directly from the CAD file.
   
  In the meantime, what I said a few posts back is correct - the 8.5 x 14 file is scaled correctly.  That's the "Combined templates ..." line just above the "Additional Info" section.  Keep in mind that if you print it to an 8.5 x 11 sheet, you'll need to be certain that Adobe Acrobat doesn't scale it automatically to the smaller sheet size (it must crop part of the image).


----------



## funch

Got it! Just printed it out with the 8 x 14 file. It's just a teensie bit undersized (probably printer error).
  I'll try it again when the other file is fixed and report back. Thanks.


----------



## jdkJake

Quote: 





funch said:


> Got it! Just printed it out with the 8 x 14 file. It's just a teensie bit undersized (probably printer error).
> I'll try it again when the other file is fixed and report back. Thanks.


 
   
  I think there is also a problem with the 8x14 version. The scale between the top plate and the endplates differ by 1/16 of an inch. When printed on the same sheet of paper (either 8x14 or 8x11 cropped) the scale for the top plate appears to be dead on while the end plate is 1/16 short.
   
  I think we are best to wait for Tom to repost.
   
  jk


----------



## tomb

Hmm ... I just measured the 8.5 x 14 here at work and the graphic scales are dead-on, top and bottom.  Maybe there's some printer stretching going on?
   
  Still, when I get the separate ones posted that sort of error should be minimal as opposed to a 14" print.


----------



## funch

I just checked the measuring scale for the 8 x 14 against the end-plate-only drawing that I had already printed
  and they're the same, so I'm sure that it's my printer . My analog calipers read  99.5mm on the 100mm line, so
  allowing for, uh, caliper error, they're probably close enough for gum'ent work.


----------



## tomb

OK - I've uploaded new PDF's of the top&bottom plates drawing and of the endplates drawing.  See if those will work now.  I don't see anything wrong on my end, but then again - I thought that before.


----------



## jdkJake

tomb said:


> OK - I've uploaded new PDF's of the top&bottom plates drawing and of the endplates drawing.  See if those will work now.  I don't see anything wrong on my end, but then again - I thought that before.







 Thanks Tom,

 I will give them a go and let you know. Funny thing about the last 8x14 was that while the scale for the endplates was short by a 1/16, the actual templates were just fine. Go figure. Probably some wild streching/compressing going on in preview. You know that adobe stuff just hates the Mac. 

 jk


----------



## jdkJake

She lives!!
   
  Some pics during check out and verification of operation. Perfect! Works as designed. no problems with the build. (Take a bow Tom and Collin!)
   

   
  I received the last of the needed (mis-ordered) parts and put power to her tonight. Biased to 27V/14.5V/265mv (power/tube/db).
   
  Added a pair of tasty 12FK6 (sylvania construction, side getter -- LOVE that sylvania construction!!)
   

   
  Letting her burn in while we be jammin!
   

   
  Since this is a test configuration, I just hooked up the iPod (line out) and a pair of SR225.
   
  So, how does it sound?
   
  Well, remember, still breaking it in. Not boxed up nor cabled properly, but, so far, WONDERFUL!
   
  When TomB says this is a Grado monster, he is NOT kidding. Even with just an iPod as a source, this thing is a BEAST!! Whereas the miniMAX can drive low impedance headphones, this thing takes control and does not let go! By far the best sound I have heard with my SR225. Smooth, powerful, detailed. Did I mention the bass? Control and authority are the words that come to mind. Cannot wait to hear the HF-2's and a decent source. If this gets better, then I am truly fortunate. 
   
  Now to box her up. More to come....
   
  jk


----------



## funch

Jake - Looking fabulous. Can't wait to see it cased.
   
  tomb - Measurements on my end are spot on. Also, I see you've gone back to
  the previous design for the back endplate. Oops! Nevermind. I see the one I
  printed out a couple of days ago probably was for the regular, or Mini max. The
  board is on the third slot. My bad!


----------



## jdkJake

Quote: 





funch said:


> Jake - Looking fabulous. Can't wait to see it cased.
> 
> tomb - Measurements on my end are spot on. Also, I see you've gone back to
> the previous design for the back endplate. Oops! Nevermind. I see the one I
> ...


 
   
   
  Thanks funch.
   
  I am actually completed with the casework. I am going for a pretty much standard design and was able to use the templates from the previous files without much issue. So, sorry TomB, but, I was not able to verify the new templates as I was able to make the last set work for me. BTW, the rubber cement trick TomB has on the Millett MAXed site works great (http://www.diyforums.org/MAX/MAXcasework.php). It really speeds things along and insures good accuracy.
   
  The drill work went *okay*. It was probably the toughest part mainly due to my drill press being in my garage and the summer fully-arrived in Florida. Hot as hell from here on out, but, I sucked it up, sweat it out and got the work done. As for the actual work, in the end, the center punch technique did not work as well as me just trusting in the drill press to be consistent. Certainly much faster with all the holes that need to be drilled. Using the templates while site checking the holes for accuracy worked far better than some I agonized over with the center punch. No matter, the drill work is finished and it looks fine. Not perfect, but fine nonetheless.
   
  I put the entire box together to verify all the placements. It is tight in the back. Especially by the big power supply caps. The final test point (TB2L) comes quite close and needed to be slightly bent at the crimp point to clear properly. Although it was probably fine as it was shrink wrapped, I wanted to be certain and reduce strain on either part. While it is nice to have the ground jack centered in the case, you might consider shifting everything over slightly to give you more room on the last test point (TB2L). The tabs on the power jack are also close to the power supply caps, but, they do clear, so, everything is good from that standpoint. I bent down the unused spade to get it completely out of the way. Of course everything is shrink wrapped for safety.
   
  While everything fit well, I was ultimately not quite satisfied with the overall look of the top plate. I chose a black anodized case and while the drill holes were fairly clean, they are not quite perfect and let the raw aluminum color come through too much. It just looked a bit amatuer. So, I went ahead and sprayed both the top and front plate with a light coat of satin black paint. That really cleans things up and makes the overall look more polished. The plates are still drying, so, I will post a picture tomorrow once everything is dry and I can bolt it back together.
   
  One tip that I think may have already been mentioned, drill the calibration holes prior to the tube holes. One of them is REALLY close to the tube hole and doing it after the fact makes it difficult to get a good hole. Oh, also make sure you ground your Pot. I forgot and was getting ground loop hum/buzz when touching the volume control. I fixed that today using the guidelines on the miniMAX site (http://www.diyforums.org/MiniMAX/MiniMAXwiring.php). It is really tight to do with the heatsinks in place, but, it can be done with a little bit of patience. Cleared everything right up. There is a ground pad on the board located for just this purpose. I am surprised I missed it during assembly.
   
  Anyway, still sounds great! Still just using the iPod as a source until I fully bolt it up. I did sneak a listen with the HF-2's though. Very, very nice. I think some more burn in and a better source is in order before I comment further. 
   
  jk


----------



## jdkJake

All dressed up and ready for the party!!
   
  Now she looks as good as she sounds.
   

   
  Now to add a GrubDac and make that front panel selector switch functional!
   
  Thanks to Tom (TomB) and Collin (cetoole) as well as all the folks who contributed to this thread. A great build and an even better final product!
   
  jk


----------



## jdkJake

Re: The new templates.
   
  TomB, I printed out the latest set of templates and they are perfect (at least on my Mac and printer).
   
  The scale issue seems to be completely resolved.
   
  jk


----------



## funch

Looking good, Jake! The Goldpoint knob really looks great on the amp.


----------



## jdkJake

Thanks funch, 

 The Goldpoint knobs are expensive, but, really, really nice. Plus they are true 6mm-compatible knobs, which, is really nice. 

 jk


----------



## jdkJake

Good eye BTW, 

 jk


----------



## BoilermakerFan

Quote: 





jdkjake said:


> Thanks funch,
> 
> The Goldpoint knobs are expensive, but, really, really nice. Plus they are true 6mm-compatible knobs, which, is really nice.
> 
> jk


 

 Bah!  $15 each isn't expensive, Justin's $50 each knobs, now those are expensive!


----------



## H22

Wow, that amp looks great!
   
  I have built a minimax as a gift, with plans to build one for myself later. I have yet t get around to doing it, but I think i will do a mosfetmax instead.
  I have been to the mosftetmax web page, and downloaded the BOM, what i am wondering is if anyone has used mouser or digikey to create a "project" ?
  If a project is created and made public, then all one needs to do is enter the project name and the order is automatically generated, saves a bunch of time typing in part numbers!
   
  I apologise if this has already been covered on this thread, but 402 pages is more thani have time to tackle!
   
  If not I will try to get one done.
   
  cool amp!
  Joe


----------



## jdkJake

Quote: 





h22 said:


> Wow, that amp looks great!
> 
> I have built a minimax as a gift, with plans to build one for myself later. I have yet t get around to doing it, but I think i will do a mosfetmax instead.
> I have been to the mosftetmax web page, and downloaded the BOM, what i am wondering is if anyone has used mouser or digikey to create a "project" ?
> ...


 

 Thanks!!
   
  I did not create a project as I did not get all the parts from a single vendor. While I ordered the majority from Mouser, I also got key components from Digikey (mostly Elma and Panasonic caps) and I ordered as much as possible from Beezar (gotta show the love to Beezar for making this even possible). Heck, I even got a couple parts from Rat Shack (relay cap and 10ohm heater resister) when I screwed up my Mouser order.
   
  Of all the threads on the new version PCB (v1.2), I have not seen anyone advertise a project available. Sorry.
   
  jk


----------



## tomb

Colin got me the newest schematic and it's been updated on the website:
MOSFET-MAX Schematic


----------



## TBomb06

Holy cow...it is unbelievable how this project has grown since I last visited it. I think I was one of the first few (relatively speaking) to build the original revision of the Max, and I sort of stopped keeping up with this thread once I got mine working, and I haven't really thought about it until recently because I've been really happy with it. Now I come back, and my last post in this thread was almost 3 years and 350 pages ago, and things have changed quite a bit! So awesome to see that the hard work that was put into this project continues to be fruitful today.
   
  If it's not too much of an inconvenience, I'd rather not have to read back through the past 3 years of this thread, so could someone help me out on the major changes of the latest revision of the Max? I know there is an on board DAC now, as well as some other tweaks. My major concern is if there is anything about my current "Rev 1" build that I can change to reflect the current state of the Max. Here's the rundown of my non-mosfet build right now:
   
  QB8/QB9 - 2SC3422/2SA1359 Power Transistors
   
  CA2L/R - 1000uF Nichicon Muse ES
   
  CA7L/R - 470uF Nichicon Muse ES
   
  CA4L/R, CA5L/R - 470uF Nichicon basic caps
   
  I'm running 12AE6 tubes at the moment, and I have Grado SR225's. I listen mostly to rock and I like the bass to slam 
   
  From the looks of the current BOM, I should probably upgrade the CA4/CA5 caps, but is there anything else I should be on the lookout for? Thanks in advance for the answers, I'm sure some of you guys will be able to take me to school again


----------



## BoilermakerFan

Quote: 





tbomb06 said:


> Holy cow...it is unbelievable how this project has grown since I last visited it. I think I was one of the first few (relatively speaking) to build the original revision of the Max, and I sort of stopped keeping up with this thread once I got mine working, and I haven't really thought about it until recently because I've been really happy with it. Now I come back, and my last post in this thread was almost 3 years and 350 pages ago, and things have changed quite a bit! So awesome to see that the hard work that was put into this project continues to be fruitful today.
> 
> If it's not too much of an inconvenience, I'd rather not have to read back through the past 3 years of this thread, so could someone help me out on the major changes of the latest revision of the Max? I know there is an on board DAC now, as well as some other tweaks. My major concern is if there is anything about my current "Rev 1" build that I can change to reflect the current state of the Max. Here's the rundown of my non-mosfet build right now:
> 
> ...


 

 If you're chomping at the bit to upgrade, then seek out Toshiba 2238/968s for Q8/Q9 and swap in VitQs for the bypass caps. Then you can always try Silmic II caps as well.


----------



## jdkJake

From my reading, the biggest change is to the power supply. Not sure you can do much in that area without the new circuit.
   
  I'm sure someone else will chime in.
   
  jk


----------



## TBomb06

Quote: 





boilermakerfan said:


> If you're chomping at the bit to upgrade, then seek out Toshiba 2238/968s for Q8/Q9 and swap in VitQs for the bypass caps. Then you can always try Silmic II caps as well.


 

 What is the benefit of the 2238/968 combo over the 3422/1359s I have? I'm really just curious...I've been out of the loop for so long...


----------



## BoilermakerFan

Quote: 





tbomb06 said:


> What is the benefit of the 2238/968 combo over the 3422/1359s I have? I'm really just curious...I've been out of the loop for so long...


 

 From Steinchen's site for the 2238/968s:
   
  "neutral and balanced sound, tight bass. detailed and clear highs without being bright, easy to listen to
excellent choice but note reversed pinout!"
   
I'll add that the 2238/968 has less bass emphasis but overall better control and a more refined sound.  Better detail resolution or retrieval if your cans can relay that detail.  That's a matter of opinion with Grados. 
   
   
WRT to the PS, you could mod it and it involves cutting a trace to accommodate the polyfuse, the tantalum caps were scrapped too.  It will lower the noise floor, but how much rework do you want to do?  Swap out the tantalum caps with small electrolytics and that will be an improvement.


----------



## TBomb06

Yeah, I don't want to do a ton of rework. It's a real pain to have to switch out a lot of parts, especially the small ones. I'm going to change out the CA4/5 caps from the 470uF to the 1800uF recommended in the new BOM, and change out the CA8 bypass caps to the .18uF VitaminQs, and probably leave it at that. My Max sounds pretty dang good to me as it is, and if I'm going to put a ton of work into it, I'm just going to build a Mosfet Max from scratch and be done with it


----------



## BoilermakerFan

Quote: 





tbomb06 said:


> Yeah, I don't want to do a ton of rework. It's a real pain to have to switch out a lot of parts, especially the small ones. I'm going to change out the CA4/5 caps from the 470uF to the 1800uF recommended in the new BOM, and change out the CA8 bypass caps to the .18uF VitaminQs, and probably leave it at that. My Max sounds pretty dang good to me as it is, and if I'm going to put a ton of work into it, I'm just going to build a Mosfet Max from scratch and be done with it


 

 That sounds like a great plan.  If I was building from scratch and had 2238/968s I'd probably use them in a different amp, a power amp at higher voltage with big heatsinks so they can really flex their muscles and deliver 10-15W each.  Parallel a set at 15W each for 30W/ch amp, then use a resistor network to protect the headphones and run off the speaker terminals.  Oh wait, I do have the 2238/968s.  Now to find that schematic...


----------



## tomb

Quote: 





tbomb06 said:


> Yeah, I don't want to do a ton of rework. It's a real pain to have to switch out a lot of parts, especially the small ones. I'm going to change out the CA4/5 caps from the 470uF to the 1800uF recommended in the new BOM, and change out the CA8 bypass caps to the .18uF VitaminQs, and probably leave it at that. My Max sounds pretty dang good to me as it is, and if I'm going to put a ton of work into it, I'm just going to build a Mosfet Max from scratch and be done with it


 

 Those sound like reasonable mods to make, if you're really into modding.  The power supply makes the most difference, however.  In the extensive testing that cetoole and I made, though, the biggest difference in the PS was made through an improved ground plane under the PS.  That's kind of hard to put back once the PCB is made without it.
	

	
	
		
		

		
		
	


	



   
  The original Millett MAX PCB removed the ground plane from under the PS section to remove some audible ripple and hum in the production MAXes.  However, it left the PS with a performance in the 1-2mV range of ripple.  That's a respectable performance and comparable to an Elpac regulated power supply, but not something we were satisfied with as time went on.
   
  Meanwhile, I had finished off one of the very first Millett MAX prototype PCB's - actually a forerunner to the MiniMAX (the very first MAX prototype PCB's were MiniMAX-sized).  When finished with a proposed cut in the ground plane around the PS (very difficult surgery on the PCB), it had a ripple that measured around 0.06 - 0.07mV: a performance that equaled a STEPS or TREAD.
   
  That set us on a path of extensive testing to 1) find out the best design for a new MiniMAX PCB (the current one that's been such a success), and 2) find out if the existing MAX PCB's could be sufficiently modded to result in similar performance in the PS.  As things turned out, the bulk of the solution lay in a very small resistance connection between the PS and the amp circuit.  You see, even a TREAD or STEPS usually has wire leads that connect it to an amp.  Those wire leads provide enough of a "buffer" of resistance to keep the LM317 from oscillating, thereby causing the ripple.
   
  In the original MAX production PCB's, the connection between PS and amp circuit is a very short, almost zero resistance connection, with a huge bank of capacitors that immediately follow (CA4/CA5 and the Wima bypasses).  Those capacitors are needed in the zero feedback, single-ended circuit to help sink the return ground signal from a pair of headphones, while at the same time helping to supply the current load to the tube heaters and diamond buffer Class A bias.  Anyway, much to our surprise, regardless of the modding - we could not lower the ripple below about 0.2mV. on an existing MAX production PCB.  Conclusion? The ground plane was needed under the PS.
   
  That's why the MiniMAX PCB has a different power supply design and the same design was incorporated into the MAX V1.2 PCB as well.  Further testing and tweaking with electrolytics vs tantalums - as BMF stated - lowered the final ripple to around 0.045mV, a truly outstanding performance.
   
  This history is chronicled in detail on the MiniMAX website -
http://www.diyforums.org/MiniMAX/MiniMAXhistory3.php


----------



## TBomb06

Quote: 





tomb said:


> Those sound like reasonable mods to make, if you're really into modding.  The power supply makes the most difference, however.  In the extensive testing that cetoole and I made, though, the biggest difference in the PS was made through an improved ground plane under the PS.  That's kind of hard to put back once the PCB is made without it.
> 
> 
> 
> ...


 

 Thanks for the info, Tom! I had a feeling you would chime in, since you guided me through building this amp the first time around  I also should have known that you would have been determined to take what was already quite good and perfect it  So would there be anything I could change to the PS that would be worthwhile? Possibly changing the tantalum caps to equivalent value electrolytics? I'd rather do what I can while I'm making changes so that I don't have to take everything out of the case again...


----------



## tomb

Quote: 





tbomb06 said:


> Thanks for the info, Tom! I had a feeling you would chime in, since you guided me through building this amp the first time around  I also should have known that you would have been determined to take what was already quite good and perfect it  So would there be anything I could change to the PS that would be worthwhile? Possibly changing the tantalum caps to equivalent value electrolytics? I'd rather do what I can while I'm making changes so that I don't have to take everything out of the case again...


 
  Here's the details on converting the original Millett Hybrid MAX PCB to the MiniMAX/MAX V1.2 power supply:
   
  First - a partial pic of the original layout.  What you want to cut is the blue trace from C5's "+" pad to the horizontal pink trace it feeds into.  All of this is on the bottom of the PCB, of course.  The trace is all the same, it's just that in the pic, the blue trace turns pink as it goes under the red ground plane.  So, you want to remove it from the C5 "+" pad up to the "T" joint where it goes horizontal across the width of the board.




   
  Next, this pic shows the extent of the work. Essentially, the only part to be added is PF1 - a 0.5A polyfuse, something like the one on the MiniMAX BOM - RXE50, or something like that. C5 is deleted, but the existing DR3 must be connected ahead of the polyfuse and so must be twisted from it's original position and soldered to the C5 "+" pad.




   
  This should give you a ripple performance of about 0.2mVAC, not as good as a MiniMAX or MAX V1.2 PCB, but almost a magnitude better than the original design.  (As stated before, you need the ground plane under the PS to get any better performance, as in a _new_ V1.2 PCB.
	

	
	
		
		

		
		
	


	




 )


----------



## TBomb06

Awesome info Tom, thanks for taking the time to put that together! So then, should I replace the CR4 10uF 35V tantalum with an equivalent sized electrolytic such as this or should I get the 82uF 35V specified in the new BOM? The modification doesn't seem like a terribly difficult undertaking, and if it makes a big difference I'm sure it's worth doing before I box this thing up for good. If I get the itch to do something else I'll just suck it up and build a Mosfet Max


----------



## tomb

Quote: 





tbomb06 said:


> Awesome info Tom, thanks for taking the time to put that together! So then, should I replace the CR4 10uF 35V tantalum with an equivalent sized electrolytic such as this or should I get the 82uF 35V specified in the new BOM? The modification doesn't seem like a terribly difficult undertaking, and if it makes a big difference I'm sure it's worth doing before I box this thing up for good. If I get the itch to do something else I'll just suck it up and build a Mosfet Max


 

 Yeah, I forgot - CR4 should be the 82uf 35V electrolytic.  Tantalums are much stronger than electrolytics on the uf scale.  So an electrolytic about 10 times the rating of the 10uf tantalum would be about right.  I think when I selected the electrolytic for CR4, it turned out that 100uf wasn't available or else the line spacing was wrong.  82uf is close enough.


----------



## TBomb06

Ok, I got all my parts in and I'm getting ready to make the aforementioned changes. The only thing I have any concern about now is the actual cutting of the trace from CR5+ to the horizontal trace. Is it necessary to actually remove a chunk of the trace, or will a couple of good cuts across the trace (as in, two parallel cuts) do the trick?


----------



## tomb

Quote: 





tbomb06 said:


> Ok, I got all my parts in and I'm getting ready to make the aforementioned changes. The only thing I have any concern about now is the actual cutting of the trace from CR5+ to the horizontal trace. Is it necessary to actually remove a chunk of the trace, or will a couple of good cuts across the trace (as in, two parallel cuts) do the trick?


 

 You'll find that when you're trying to cut a trace in PCB, it's often quite difficult to tell whether there are tiny imbedded pieces that are still making the connection.  I think it's best to clean out an entire channel.  A good X-acto knife and some patience will result in a good job.


----------



## jdkJake

Wow, do my ears hurt! I don't think the body was meant to take as much Grado listening as I have been doing over the past few weeks. Those bowls are brutal on the outer ear!





 Man this amp sounds good with Grado's! I knew the HF-2 would sound good, but, I was completely caught off guard at how well the sr225 sounds. I was originally *this* close to dumping my 225's as I could never get them to the point of being truly listenable for an extended period of time. This amp has changed that thought completely. This kind of performance makes you understand what the fuss is all about with Grados. While far from accurate, they are a fun listen and really get you into the music. Now I might have to pick up a pair of RS-1's and see how far this can go. Damn you TomB!! 





 Anyway, I am seriously considering building another one. Use all the same parts in terms of caps, resistors, etc. This time though, build it with BJT's and see if the ability to use larger parts can produce something that might even surpass the minimax in terms of sound quality. My minimax sounds wonderful with the HD650 Maybe I can take them a bit farther using the new board.





 My question would be, which BJT's to use? I know some of the toshiba parts are rarer than rare, does anyone know a potential source for something like a 2238/968 combo? BoilermakerFan, where did you source your set (if you do not mind me asking)?





 jk


----------



## TBomb06

So, I just finished making the changes I had in store for my Max. Hoooooly crap. I don't know if it's just in my head, but it sounds (even more) freakin' amazing now! 
	

	
	
		
		

		
		
	


	



   
  It took me a couple of hours to replace the CA4L/R, CA5L/R, CA8L/R, and CR4 caps, along with modifying the power supply. It took a long time to get the polyfuse soldered in, particularly with the DR1 lead attached to the same point. I wound up putting one leg of the polyfuse through the hole, then soldering the leg of DR1 to the top of the board and the leg of the polyfuse. Getting the other leg of the polyfuse in was tricky because they're so thin it kept bending off to one side or the other. Cutting the trace under the board wasn't too bad, it just took a little patience.
   
  Anyway, thanks for the advice guys, I really do appreciate it! Now I just need to get my front panel in and get the case finished up and I'll be done with this one...


----------



## tomb

Quote: 





tbomb06 said:


> So, I just finished making the changes I had in store for my Max. Hoooooly crap. I don't know if it's just in my head, but it sounds (even more) freakin' amazing now!
> 
> 
> 
> ...


 

 Glad to hear it made a noticeable improvement.  It kind of lets you know how important it is to have a very clean power supply feeding an amplifier.


----------



## Antistase

My second MMax is playing. Still breaking in but I tend to reckon I like it better enough than my old one. Of course I can't make a direct comparison as I used different resistors,  boutique caps caps and bjt in this one.
  One of the first impressions is  that the 12FM6s play significantly better in this version. 
  Also, strangely, with this board I don't get any hum touching the naked pot even without grounding it.
   
  As usual I run then amp rather high at 30V, 19V tube bias and 130mv bjt bias.
   
  I need to case it and then build a grub. I'm probably not paying attention but I couldn't find instructions to connect it to the MM 1.2 board. 
  Also are drilling templates available for using the bottom slot of the standard case ( as I'm using 1" heat sinks) and with the USB hole? Not a big issue to work this out, as the pain is the top plate, but in case they are already available it would make the job quicker.
   
  A


----------



## jdkJake

Looks great! 

 All of the templates are on the MOSFET-MAX site. Don't pay attention to the thumbnails, the downloads are correct. They have the USB location on the back panel. As for the bottom, I just repeated the top pattern. It lines up well with the vent holes in the board.

 Did you build BJTs or MOSFETs?

 jk


----------



## Antistase

I used BJT. I've never found a mosfet amplifier I like. My M3 included. And, as the MM uses more or less the same buffer as the M3 I decided to stick with BJT. I have to state that I'm a committed thermionic amp estimator and builder but  can't find any subjective ground backing the claim mosfets sound more like triodes than SS (because supposed 2nd harmonic distortion dominance).
   
  This time I used the 2344/101 whilst my other MM uses 2238/968. I also, this time, splashed on prp and mills resistors.
  Like Thomas says the 2234 gives amazing drumming. I will wait to see if the lower frequencies will get more body as I'm super spoiled with my old MM on K42Y+2239/968. I used tapped heat sink this time to make power BJTs replacement less painful.
   
  This MM makes my Beyer DT48S Nagra, and my self too, extremely happy.
   
   
  Cheers,
  A


----------



## Aalelan

First time Amp builder here and I have started with the MOSFET MAX.  After some woes of following the Digikey BOM (didn't see that post soon enough  ) The last of my parts should be here on July 7th.  I cant wait!!  Here is a shot of what I have got so far and a link to my gallery for the process..
   
http://www.aalelan.com/gallery3/index.php/Projects/Millett-Hybrid-MOSFET-MAX


----------



## Aalelan

First time Amp builder here and I have started with the MOSFET MAX.  After some woes of following the Digikey BOM (didn't see that post soon enough  ) The last of my parts should be here on July 7th.  I cant wait!!  Here is a shot of what I have got so far and a link to my gallery for the process..
   
http://www.aalelan.com/gallery3/index.php/Projects/Millett-Hybrid-MOSFET-MAX


----------



## Aalelan

First time Amp builder here and I have started with the MOSFET MAX.  After some woes of following the Digikey BOM (didn't see that post soon enough  ) The last of my parts should be here on July 7th.  I cant wait!!  Here is a shot of what I have got so far and a link to my gallery for the process..
   
http://www.aalelan.com/gallery3/index.php/Projects/Millett-Hybrid-MOSFET-MAX


----------



## Aalelan

First time Amp builder here and I have started with the MOSFET MAX.  After some woes of following the Digikey BOM (didn't see that post soon enough  ) The last of my parts should be here on July 7th.  I cant wait!!  Here is a shot of what I have got so far and a link to my gallery for the process..
   
  http://www.aalelan.com/gallery3/index.php/Projects/Millett-Hybrid-MOSFET-MAX
   

   
  http://www.aalelan.com/gallery3/index.php/Projects/Millett-Hybrid-MOSFET-MAX
   
  First time Amp builder here and I have started with the MOSFET MAX.  After some woes of following the Digikey BOM (didn't see that post soon enough  ) The last of my parts should be here on July 7th.  I cant wait!!  Here is a shot of what I have got so far and a link to my gallery for the process..
   
  http://www.aalelan.com/gallery3/index.php/Projects/Millett-Hybrid-MOSFET-MAX
   
  First time Amp builder here and I have started with the MOSFET MAX.  After some woes of following the Digikey BOM (didn't see that post soon enough  ) The last of my parts should be here on July 7th.  I cant wait!!  Here is a shot of what I have got so far and a link to my gallery for the process..
   
  http://www.aalelan.com/gallery3/index.php/Projects/Millett-Hybrid-MOSFET-MAX


----------



## jdkJake

Looks like you are making good progress. One question, are you sure you want to jumper R1? What voltage do you intend to run at? I know it is marked as "optional" on the BOM, but, IMHO, it is not. You can always pick up a 10ohm, 1 watt from Rat Shack.

 See: http://www.diyforums.org/MOSFET-MAX/MOSFET-MAXheaterResistor.php

 You also might want to have a couple of resisters ready for RB14 as well. I know they are in the output path, but, you might need them to clean up the signal a bit. 

 Good luck and the remaining build!

 jk


----------



## jdkJake

"This time I used the 2344/101 whilst my other MM uses 2238/968. I also, this time, splashed on prp and mills resistors."




 Sounds very interesting. You will have to tell me what you think of the new combo after it gets a few hours on it. I still have a curiosity to build one with the 2238/968 combo, but, they seem to be made of "unobtainium". My mini has the 2234/101 combo, so, nothing probably gained by a max version of that build.



 jk


----------



## Aalelan

I have a 10Ohm 1/2 watt that I can put in, I just jumped it out to start with, oh and I plan to just run at 27v..   I dont have anything for RB14 but that should not be hard to pick up..   There is an actual electronics store down the road, not a radio shack but real honest to goodness store.. Carries odd stuff and a little $$ but has saved me in a pinch a few times..


----------



## jdkJake

aalelan said:


> I have a 10Ohm 1/2 watt that I can put in, I just jumped it out to start with, oh and I plan to just run at 27v..   I dont have anything for RB14 but that should not be hard to pick up..   There is an actual electronics store down the road, not a radio shack but real honest to goodness store.. Carries odd stuff and a little $$ but has saved me in a pinch a few times..







 You are a lucky fellow. All of ours have closed up.

 I think you also need to check your JFET mounting. I think you have them in backwards. The artwork should not be followed for those parts.

 See: http://www.diyforums.org/MOSFET-MAX/MOSFET-MAXmosfets.php

 jk


----------



## jdkJake

aalelan said:


> I have a 10Ohm 1/2 watt that I can put in, I just jumped it out to start with, oh and I plan to just run at 27v..   I dont have anything for RB14 but that should not be hard to pick up..   There is an actual electronics store down the road, not a radio shack but real honest to goodness store.. Carries odd stuff and a little $$ but has saved me in a pinch a few times..







 BTW, you should really consider installing R1 if you want to run at 27v. I would hate to see you damage your tubes over such a small part change.

 jk


----------



## jdkJake

aalelan said:


> I have a 10Ohm 1/2 watt that I can put in, I just jumped it out to start with, oh and I plan to just run at 27v..   I dont have anything for RB14 but that should not be hard to pick up..   There is an actual electronics store down the road, not a radio shack but real honest to goodness store.. Carries odd stuff and a little $$ but has saved me in a pinch a few times..







 One last item, since RB14 is in the signal path, a lot of folks use "boutique" parts. Just be careful not to just slap in any old resistor. It might hurt more than it helps.

 jk


----------



## tomb

The RB14 resistors _are required_.  Unlike a BJT version, the MOSFETs will oscillate without them.  They won't overheat and blow up or anything - but it won't sound as good as it should - there will be ringing, etc. and harsh higher frequencies.
   
  jdkjake is also correct - if those are JFETs at QB2 and QB3, they should be installed backwards relative to the silkscreen.


----------



## jdkJake

Quote: 





> Originally Posted by *Aalelan* /img/forum/go_quote.gif
> 
> Here is a shot of what I have got so far and a link to my gallery for the process..
> 
> ...


 
   
  Took a quick look at the build gallery. Did you re-order a new cap for CR4? The digikey part (tantalum) is incorrect, it needs to be an electrolytic. I made the same mistake initially. I think that cap can be as big as 100uf 35V and still work fine. Perhaps TomB can verify.
   
  jk


----------



## tomb

Verifed.
	

	
	
		
		

		
			




   
  I'm sorry guys - I will fix that DigiKey section first chance I get.  There's just not enough time these days, it seems.


----------



## Aalelan

JK,
  Yeah, I am lucky, its not the best store but it has things..  Thanks for catching My JFET error, iron is heating up now..
 Also while the iron is hot I'm going to put in the R1 10Ohm I have  .  I'm still reading through the 400+ pages of this post so I'm learning as I go 
   
  As for RB14L/R I was gonig by the current BOM where Tom said jumper out unless you are having noise issues or desire greater gain reduction.. so I was starting without them..  Looks like I might need to see if my local shop has some, I didnt order them. 
   
  Man you guys post faster than I can type..  No, I didnt realize that CR4 was wrong till today..  I have powered it up to make the LEDs come on.. what is the downfall to keeping it tantalum ?
   
  Tomb,
   
  Dont worry about time, it seems you put some much blood sweat and tears into this project and site, I cant even imagiane!!  Oh and I just orderd my GrubDAC today, thanks again for answering my standoff question email..


----------



## Aalelan

ok, my de-soldering skills, well lets just say they are bad  I may need to reorder those JFETs 
   
  EDIT:
  Yep, I pulled a leg off one of the J74's   Just emailed Tom to see if he can add to my order I put in this morning for my GrubDAC Kit..  I sure hope so, I'd really like to have this thing going by next weekend to start burning it in


----------



## jdkJake

aalelan said:


> ok, my de-soldering skills, well lets just say they are bad  I may need to reorder those JFETs







 Did you use braid or a pump? I am partial to braid, but, lot's of folks like the pump. Using a little bit of flux to speed things up can help as well. In general, I find it easiest to suck up as much as possible before trying to pull the part clear from the board. It can be tough with transistors, especially since they are so heat sensitive. I use alligator heatsinks when I put them in as well as when I pull them. They are cheap and work well to protect the part. 

 You can order some high quality resistors from beezar that work great at RB14. They stock multiple sizes, I used the 22R that TomB used on his build. Sounds wonderful. Unfortunately, looks like you might have to reorder JFETs, so, at least you can get them all in one shot.

 BTW, be careful powering up a partially populated board. All kinds of bad things can happen depending upon which parts are still missing. I would not recommend doing that in the future.

 jk


----------



## tomb

Quote: 





antistase said:


> I used BJT. I've never found a mosfet amplifier I like. My M3 included. And, as the MM uses more or less the same buffer as the M3 I decided to stick with BJT. I have to state that I'm a committed thermionic amp estimator and builder but  can't find any subjective ground backing the claim mosfets sound more like triodes than SS (because supposed 2nd harmonic distortion dominance).
> 
> This time I used the 2344/101 whilst my other MM uses 2238/968. I also, this time, splashed on prp and mills resistors.
> Like Thomas says the 2234 gives amazing drumming. I will wait to see if the lower frequencies will get more body as I'm super spoiled with my old MM on K42Y+2239/968. I used tapped heat sink this time to make power BJTs replacement less painful.
> ...


 


 Oops - I didn't see all of these posts before - been busy with those grubDAC kits!
   
  Again, I have to apologize - but there's no particular instructions (yet) for connecting the Bantam or grubDAC to the PCB.  The punch down blocks should be clear for two sets of L/R/G input connections - use one set for RCA inputs and one set for the onboard DAC.  The two-position terminal block is there for a SPDT switch.  I can't remember which is which, but connect the switch and the DAC/RCA inputs to different sources and it's easy enough to tell which one goes to which switch position.  You can also use a DPDT switch instead, and wire the LED on the onboard DAC to the front panel.  I did that with the MOSFET-MAX V1.2 I was showing at CanJam.  A red LED indicated that USB was connected, while throwing the switch to activate the onboard DAC input lit a green LED, instead.
   
  I'll detail all this stuff on the website when I get a chance.


----------



## TBomb06

Quote: 





jdkjake said:


> Did you use braid or a pump? I am partial to braid, but, lot's of folks like the pump. Using a little bit of flux to speed things up can help as well. In general, I find it easiest to suck up as much as possible before trying to pull the part clear from the board. It can be tough with transistors, especially since they are so heat sensitive. I use alligator heatsinks when I put them in as well as when I pull them. They are cheap and work well to protect the part.
> 
> You can order some high quality resistors from beezar that work great at RB14. They stock multiple sizes, I used the 22R that TomB used on his build. Sounds wonderful. Unfortunately, looks like you might have to reorder JFETs, so, at least you can get them all in one shot.
> 
> ...


 
   
   
  So, I've been running my Max for a couple of years without R1 or RB14 installed, but after reading some more recent posts, I've decided to install them both. For RB14 I ordered some Kiwame 22R resistors, but for R1, I can just use any old 10 ohm resistor, right?
   
  I'm interested to see if I will notice any loss of impact or signal degradation with the RB14 resistors in place. I listen to Grados, so it will be nice to have a little bit of a reduction in the output, especially since I like the 12AE6 tubes with the higher gain, but I don't want to lose any of that awesome slam


----------



## Aalelan

Quote: 





jdkjake said:


> Did you use braid or a pump? I am partial to braid, but, lot's of folks like the pump. Using a little bit of flux to speed things up can help as well. In general, I find it easiest to suck up as much as possible before trying to pull the part clear from the board. It can be tough with transistors, especially since they are so heat sensitive. I use alligator heatsinks when I put them in as well as when I pull them. They are cheap and work well to protect the part.
> 
> You can order some high quality resistors from beezar that work great at RB14. They stock multiple sizes, I used the 22R that TomB used on his build. Sounds wonderful. Unfortunately, looks like you might have to reorder JFETs, so, at least you can get them all in one shot.
> 
> ...


 

 Well I used some braid but it was just not in the cards for me that day I think.. I have a pump now to, I never used one but I was at the shack looking at knobs and such and got one..
   
  For now I don't have / didn't order any nice resistors for RB14,  I have some carbon ones I will put in till I make another mouser-key order 
	

	
	
		
		

		
		
	


	




.
   
  I will be carefull, I had seen other pics of powered on boards and didn't think twice about doing on my not finished one for some reason!  How about running a done board without tubes, what would that do if anything, besides not make any sound


----------



## jdkJake

tbomb06 said:


> So, I've been running my Max for a couple of years without R1 or RB14 installed, but after reading some more recent posts, I've decided to install them both. For RB14 I ordered some Kiwame 22R resistors, but for R1, I can just use any old 10 ohm resistor, right?
> 
> I'm interested to see if I will notice any loss of impact or signal degradation with the RB14 resistors in place. I listen to Grados, so it will be nice to have a little bit of a reduction in the output, especially since I like the 12AE6 tubes with the higher gain, but I don't want to lose any of that awesome slam







 Do you have a BJT build or a MOSFET build? Also, what voltage are you running at? 24V or greater?

 As I understand it, R1 only comes into play if you are running over 24V. Reference:

 http://www.diyforums.org/MOSFET-MAX/MOSFET-MAXheaterResistor.php

 You will need at least a 1/2 watt resistor or greater if using 10ohm at that position.

 As for RB14, I doubt you will hear any noticeable attenuation until that value starts to approach 100R or greater. The 22R is there to help keep the MOSFET's from oscillating ( provided you have a MOSFET build ).

 jk


----------



## jdkJake

aalelan said:


> Well I used some braid but it was just not in the cards for me that day I think.. I have a pump now to, I never used one but I was at the shack looking at knobs and such and got one..
> 
> For now I don't have / didn't order any nice resistors for RB14,  I have some carbon ones I will put in till I make another mouser-key order
> 
> ...







 As far as I know, it should do no harm. The main key on first power up is to insure the bias on the MOSFET/BJT is set as low as possible until you have a chance to set it. With the current parts and artwork, this is fully clockwise on the RB12 pots.

 jk


----------



## tomb

Quote: 





tbomb06 said:


> So, I've been running my Max for a couple of years without R1 or RB14 installed, but after reading some more recent posts, I've decided to install them both. For RB14 I ordered some Kiwame 22R resistors, but for R1, I can just use any old 10 ohm resistor, right?
> 
> I'm interested to see if I will notice any loss of impact or signal degradation with the RB14 resistors in place. I listen to Grados, so it will be nice to have a little bit of a reduction in the output, especially since I like the 12AE6 tubes with the higher gain, but I don't want to lose any of that awesome slam


 

 I prefer nothing but jumpers (or sometimes 10R) at RB14 with a BJT MAX.  Please note that my statement about RB14 resistors being _required_ has to do with a MOSFET-MAX, only.  As I stated, the MOSFETs will oscillate - the 2.2 power resistors ((RB10/RB11) are not enough to keep the MOSFETs stable.
   
  You don't have any MOSFETs in a BJT MAX - two different animals.


----------



## BoilermakerFan

Quote: 





jdkjake said:


> My question would be, which BJT's to use? I know some of the toshiba parts are rarer than rare, does anyone know a potential source for something like a 2238/968 combo? BoilermakerFan, where did you source your set (if you do not mind me asking)?
> 
> 
> jk


 
   
  Sorry for th elate reply, but I was out for the last week on a fantastic family vacation...
   
  I have a couple of sets I acquired from Tom over the span of 2 years.  I have a couple more, but I can't yet confirm if they are genuine Toshibas.
   
  My plan is to roll them into the new MOSFET-MAX to see how they sound against the IRF24/34s and IRF540/9540s.  AMB used BJTs on his old MOSFET-MAX and really liked how they sounded, so I'll try it and see though I do plan to eventually use for pairs for a nice little hybrid 35w/ch amp in the future.


----------



## TBomb06

Quote: 





tomb said:


> I prefer nothing but jumpers (or sometimes 10R) at RB14 with a BJT MAX.  Please note that my statement about RB14 resistors being _required_ has to do with a MOSFET-MAX, only.  As I stated, the MOSFETs will oscillate - the 2.2 power resistors ((RB10/RB11) are not enough to keep the MOSFETs stable.
> 
> You don't have any MOSFETs in a BJT MAX - two different animals.


 

 Right, I realize the difference between the two configurations  I just wasn't sure as to the need for the RB14 resistors. So, if they are only used to keep the MOSFETs from oscillating, what is the point of putting 10R resistors there on the BJT build if they don't offer any attenuation? Also, since I'm only running 27V at the power supply, is it necessary for me to use R1 either? Perhaps I took all of those suggestions out of context...


----------



## tomb

Quote: 





tbomb06 said:


> Right, I realize the difference between the two configurations  I just wasn't sure as to the need for the RB14 resistors. So, if they are only used to keep the MOSFETs from oscillating, what is the point of putting 10R resistors there on the BJT build if they don't offer any attenuation? Also, since I'm only running 27V at the power supply, is it necessary for me to use R1 either? Perhaps I took all of those suggestions out of context...


 
  10R resistors do provide some quieting.  Trouble is, they will also cut some of the detail.  It's a balancing act.
	

	
	
		
		

		
		
	


	




  It can also help lower the cutoff frequency a bit on lower impedance phones such as Grado's or Denons.  On the other hand, the MOSFETs in a MOSFET-MAX are running such high currents that the output resistors don't seem to impact the detail, but my ears can detect ringing with only jumpers on a MOSFET-MAX (oscillation).
   
  R1 at 10ohms is optimum when running 27VDC.  This is explained here:
http://www.diyforums.org/MAX/MAXheaterResistor.php
  There is a similar page on the MOSFET-MAX and MiniMAX websites, too.  The heaters like to run at their rated voltage - 12.6V.  Lower than that, and you get reduced performance.  Higher than that, and you get reduced life.  Without the resistor at 27V, each heater is seeing 13.5V.


----------



## Aalelan

OK, I have it all build except for the replacement JFETs for the ones I killed, They are on there way..   Oh and RB14L/R are just carbon for now till I put in another order for stuff..


----------



## TBomb06

Quote: 





tomb said:


> 10R resistors do provide some quieting.  Trouble is, they will also cut some of the detail.  It's a balancing act.
> 
> 
> 
> ...


 
   
  Okie doke. I'll definitely put in the 10ohm R1, and then try out the 10Rs for RB14. I'll hang on to the 22Rs I got for when I inevitably end up building a MOSFET Max  I just haaaadd to come back here and see what's been going on that I've missed out on...


----------



## tomb

Quote: 





aalelan said:


> OK, I have it all build except for the replacement JFETs for the ones I killed, They are on there way..   Oh and RB14L/R are just carbon for now till I put in another order for stuff..


 

 Looks like you've done a great job!  You did a great job on cleaning up the JFET holes, too!


----------



## Aalelan

Quote: 





tomb said:


> Quote:
> 
> 
> Originally Posted by *Listen2this1* /img/forum/go_quote.gif
> ...


 

 I know this is an old thread but it begs the question that has been in the back of my head..  If I wanted to drive some external speakers how do I do the math to figure out what will work?  I'm still a little confused on the whole Ohm math and what the Max MOSFET can do..
   
  I know its a headphone amp but I can think of a few situations where here at work on the weekends I would not want to be tied to my headset.


----------



## BoilermakerFan

Quote: 





aalelan said:


> I know this is an old thread but it begs the question that has been in the back of my head..  If I wanted to drive some external speakers how do I do the math to figure out what will work?  I'm still a little confused on the whole Ohm math and what the Max MOSFET can do..
> 
> I know its a headphone amp but I can think of a few situations where here at work on the weekends I would not want to be tied to my headset.


 
   
  We've covered it briefly, but the MOSFET-MAX will do over 2W into 8R.  So any speaker with a sensitivity of 91dB or greater should sound fine near field.
   
  There are ways to get more power through the MAX, but you really need to run 2-1/2" heat sinks on the V-reg and DBs.  If your willing to swap over to a new chassis, then you can have some higher power fun.
   
  I forget the exact bias level, but at some point over 80mA or so the small signal transistors leave their optimal points on the curve and need to swapped out to BC446C/BC546Cs that can handle the higher current.  The V-reg needs to go from a 317 to a 338, and the poly fuse needs a bump.  Depending on how high you bias, then the transformer may need a little bump too.  I haven't tried it on my MOSFET-MAX yet, but on my Liquid Gold, IRF540s biased out at 215mA at 55degC on 2-1/2" heat sinks.  They should be able to run at a similar bias and temp point in the MAX though.  It really doesn't change the peak power output significantly, just keeps the amp in Class A a lot longer and lets the amp pass more current when necessary. 
   
  I'd also be a little gun shy on trying to push BJTs much higher than stock when driving speakers too.  There shouldn't be any problems stock, but cranking up the bias on a modded amp and then driving speakers always opens that little door of risk to thermal run away.


----------



## Aalelan

Ok, this may not be the right thread but its related...  I got my parts in for my GrubDAC tonight and put it all together.  How does one go about debugging issues??  I plug it into the USB and the laptop does not see any new hardware, nor will the LED light up.  I have gone over it with a magnifying glass and I dont see anything..
   
  The only odd thing is I had one SMD cap left with nowhere to put it, but I think it might have been an error on Tom's kit.. the bag said among the other spots C5, but C5 is one of the three big thru hole caps..
   
  Can someone point me in the right direction?
   
   
  EDIT:
  Oh yeah!!! Its alive!!  well still not the Grub


----------



## jdkJake

Quote: 





aalelan said:


> EDIT:
> Oh yeah!!! Its alive!!  well still not the Grub


 
   
  Great news Aalelan (well, the MAX part anyway)!
   
  Now to case it up! Keep the pictures coming.
   
  jk


----------



## tomb

Quote: 





aalelan said:


> Ok, this may not be the right thread but its related...  I got my parts in for my GrubDAC tonight and put it all together.  How does one go about debugging issues??  I plug it into the USB and the laptop does not see any new hardware, nor will the LED light up.  I have gone over it with a magnifying glass and I dont see anything..
> 
> The only odd thing is I had one SMD cap left with nowhere to put it, but I think it might have been an error on Tom's kit.. the bag said among the other spots C5, but C5 is one of the three big thru hole caps.. </snip>


 

 You need to post this in the GrubDAC thread so that cobaltmute can see it and offer support.  Offhand, the first thing I'd suggest is to see if you can measure 3.3VDC at the 3.3V test point (referenced to Gnd).
   
  P.S. I hope that doesn't mean I packed an extra SMD cap in everyone's order, but it's possible.


----------



## Aalelan

Dangit   turns out it might have worked before farting around with it, its looking like Windows 7 does not like it and thats all I have here at the house.. brought home and old crappy laptop from work and booom! recognized it..  
   
  Man I get trigger happy, I better go hook it up and make sure sounds come out of it now.  Just ask Tomb about me being took quick to do things 
   
  EDIT..
   
  Yep and the GrubDAC sounds AWSOME!!!  Just need to figure out my Windows 7 support issue


----------



## funch

Quote: 





aalelan said:


> Dangit   turns out it might have worked before farting around with it, its looking like Windows 7 does not like it and thats all I have here at the house.. brought home and old crappy laptop from work and booom! recognized it..
> 
> Man I get trigger happy, I better go hook it up and make sure sounds come out of it now.  Just ask Tomb about me being took quick to do things


 


 Gee, I thought that I was the only one to do the knee-jerk thing.
	

	
	
		
		

		
		
	


	




 Can't count how many times I've had to drop back and punt after jumping to
  a wrong conclusion.


----------



## tomb

Quote: 





aalelan said:


> Dangit   turns out it might have worked before farting around with it, its looking like Windows 7 does not like it and thats all I have here at the house.. brought home and old crappy laptop from work and booom! recognized it..
> 
> Man I get trigger happy, I better go hook it up and make sure sounds come out of it now.  Just ask Tomb about me being took quick to do things
> 
> ...


 
   
  I don't think Windows 7 the issue - the grubDAC works first time, every time on my Windows 7 PC.


----------



## Aalelan

Quote: 





tomb said:


> I don't think Windows 7 the issue - the grubDAC works first time, every time on my Windows 7 PC.


 

 Yeah, I figured it out alittle bit ago...  I guess there was a problem on my first try as it had shutdown the USB HUB in my laptop, the device was stopped (oops)  restarted the USB hub host service and bam! there was the grub...  Been Playing some Led Zepp FLAC's through it and its rock'n!!!
   
  Thanks for all your help Tom!!  I know I have pestered the poo out of you the last few weeks


----------



## jdkJake

Forgot I had these on the camera.
   
  Some "night" shots. This was before I painted the top, so, the vent holes are not black. Still, pretty cool. The blue really lets you see the heater filament.
   

   

   

   
   
  jk


----------



## Aalelan

GrubDAC all mounted, Just need to figure out how I want to case it up 
   
  PS running at 27v  Tube Bias is 13.5V  and MOSFET bias is at 180mv
   

   
  One of many Night shots I took the other night, saw JK put his up and figured i would share one too


----------



## jdkJake

So what do you think of the sound of your new combo?

 What phones are you using?

 jk


----------



## Aalelan

I love it!!  as for phones, I don't have a good pair yet/anymore  I used a set of Bose comfort quite 2 on it and it was amazing!!  
   
  Suggestions on a sub $200 set that would go well with the MAX?


----------



## jdkJake

Wow, that's a loaded question! 

 There is a whole forum dedicated to answering it as well.

 Personally, I built this version to act as my main amp for Grado's. In that regard, I am extremely pleased. That being said, Grado's have a very distinct sound and opinions on that sound are all over the board. Suffice to say, I like them, particularly on this amp which really brings them to life.

 I haven't really hooked up my HD650's as I do not want to change out the tubes yet. Just lazy I guess. That and I am really enjoying my grads right now. I am sure I will get to the HD650's sooner or later and let you know what I think.

 jk


----------



## jdkJake

BTW, if you do want to try out the Grado sound, the SR60 is a good place to start at a low price. You can always work your way up the chain if you like their sound (as finances and desire allow).
   
  There are also a lot of them available in the used forum at varying prices and condition.
   
  jk


----------



## tomb

Grados are wonderful with the MOSFET-MAX.  Of course, you haven't really heard an AKG K701 until you've heard one with a MOSFET-MAX.  I am fully admitting my bias, of course.


----------



## jdkJake

tomb said:


> Grados are wonderful with the MOSFET-MAX.  Of course, you haven't really heard an AKG K701 until you've heard one with a MOSFET-MAX.  I am fully admitting my bias, of course.







 That's an interesting combination. Everyone complains how the 701/702 is light in bass. I suspect the MOSFET-MAX would help that situation considerably. 

 I might have to try that combination. Just have to find a pair of 701's.


 jk


----------



## MASantos

I drive my pair of 701's with the revH millett hybrid with the discrete diamond buffer, the predecessor of the the Millett MAX, and it really makes the 701 shine! I thinking of building a MAX to improve the 701's even more! I don't think you can go wrong with one of these!


----------



## jdkJake

Interesting. The 701/702 are pretty fairly priced right now.

 TomB/MASantos, what tubes are you running your K701's with?

 MASantos, what BJT pair did you go with?

 jk


----------



## BoilermakerFan

I'd throw K601s and vintage K401s on the list as well.  K401s were my favorite of the 401, 601, 701.  Just not a fan of the more peaked highs on the 701s.  The 12AE6 tubes can help that, but I thought the 401s had the best sound sig.  Only reason I sold them is because my SR-Lambdas had the same sound sig, but much faster transient response though they were a little brighter than the K401s but not peaky or overly analytical like the 701s.


----------



## MASantos

The Bjt's are the MJE243 and 253, and I'm running FK's, but I never really did extensive tube rolling though.


----------



## TBomb06

Well, I had a feeling this would end up happening, but I ordered the parts for a MOSFET Max today . After reading how awesome the MOSFET version is with Grados, I figured I might as well go ahead and do it and get it over with. I'll probably end up casing up the BJT version I have (which sounds pretty awesome as it is) and giving it to my dad to use with the SR-60's I bought him a couple of years ago. I'm pumped to get all my parts in and start building...I've already been through my spare parts from my last build and matched my transistors  I can't wait to hear how this thing will sound!


----------



## jdkJake

Excellent.

 I most interested to hear what you think of the new PCB as well as the MOSFETs.

 I suspect you will not be disappointed!

 jk


----------



## TBomb06

Quote: 





jdkjake said:


> Excellent.
> 
> I most interested to hear what you think of the new PCB as well as the MOSFETs.
> 
> ...


 

 I suspect I will not be either 
   
  I do have a question regarding the input switching. Is the 2 position terminal for wiring up a selector switch to choose between the 2 sources? Is that the only way to select between the 2 sources? I don't really know that I'll ever use more than one source at a time, but I decided to go ahead and build it up with the capability just in case.
   
*EDIT: Nevermind, found the answer to that one.*
   
  Also, on the BOM it lists 6 2N5087 for QB4L/R and QB6L/R, and 6 2N5088 for QB5L/R and QB7L/R. From looking at the schematic and the layout, there are only 4 of each that I see. Did I miss something? 
   
  Oh, and on the MOSFET Max sit, it says QB2 and QB3 should be reversed compared to the silk screen on the board. Is that due to the different type of transistor used for the MOSFET version compared to the BJT?
   
*EDIT: Found the answer to that one too.*
   
  Ok...I think that's it for now...


----------



## jdkJake

Looks like you figured most of it out.

 I currently have the selector "open" which defaults to a single input. I believe it is the right-most input when facing the front of the amp. The selector is a simple shorting circuit, so, it is easy to implement as required. Just as easy for single input is attaching to the terminal block by the alps. 

 I never noticed the mismatch in the number of small transistors. I just bought and used the matched set from beezar and never paid any mind to it. I will have to re-check when I get home (currently on the road). Interesting observation though.

 jk


----------



## TBomb06

Cool, thanks for the input. One other question has to do with the upsized CA7 caps. I used the Muse ES's in my first amp, and loved the sound. Unfortunately, they don't make the 1000uF ES's in anything bigger than a 25V (I know I might could get by using this if I had to). What has everyone been using for the 1000uF 35V cap? I've thought about using the Elna Silmic II but I don't know anything about how it would sound. Would the Muse KZs be comparable to the ES? I'll be using Vitamin-Qs for the CA7 bypass caps. I'm still planning to use the ESs for CA2.


----------



## Aalelan

Speaking of CA7,  I read that this is the biggest spot affect for bass.  Could one use Nichicon HE 2200uf in this spot, if so would you have to make any tweaks downstream?
   
  I could not sleep last night and was just thinking, I'm still learning and may ask crazy things sometimes.


----------



## tomb

Quote: 





tbomb06 said:


> Cool, thanks for the input. One other question has to do with the upsized CA7 caps. I used the Muse ES's in my first amp, and loved the sound. Unfortunately, they don't make the 1000uF ES's in anything bigger than a 25V (I know I might could get by using this if I had to). What has everyone been using for the 1000uF 35V cap? I've thought about using the Elna Silmic II but I don't know anything about how it would sound. Would the Muse KZs be comparable to the ES? I'll be using Vitamin-Qs for the CA7 bypass caps. I'm still planning to use the ESs for CA2.


 

 If you're building a MOSFET-MAX, you're already using 1-1/2" tall heat sinks and locating the PCB in the bottom slot of the recommended Hammond case.  This allows you to alleviate the only issue with Elna RFS Silmic II's: their very-large size.  IMHO, there's no reason to use anything else than an Elna RFS Silmic II, as long as the rating is sufficient _and there's sufficient room_.  They are as good as Black Gate NX's without the break-in and the high cost (now add rarity!).  What's not to like?
   
  Use the 1000uf Elna RFS Silmic II at 16V, 25V, or 35V for CA2 L/R - all available and stocked at DigiKey.  Use the 1000uf Elna RFS Silmic II at 35V for CA7 L/R.  Handmade Electronics also stocks some of those sizes.
   
  Stay away from KZ's - their natural "etchiness" combines badly with the detail of the MOSFET diamond buffer and borders on constant sibilance. (I speak from experience. 
	

	
	
		
		

		
		
	


	




)


----------



## tomb

Quote: 





aalelan said:


> Speaking of CA7,  I read that this is the biggest spot affect for bass.  Could one use Nichicon HE 2200uf in this spot, if so would you have to make any tweaks downstream?
> 
> I could not sleep last night and was just thinking, I'm still learning and may ask crazy things sometimes.


 
  Actually, the CA2 and CA9 position have the most to do with _preserving_ bass from the basic input signal/source.  It's a question of keeping all there is, or taking some away.  This can happen with the wrong bypass cap at CA9 (don't use Vitamin Q's, there, for instance), or if CA2 is too small (<1000uf).  Either the ES 1000uf 16V or the Elna RFS Silmic II at 1000uf and one of the voltage ratings listed in the previous post is best.  For CA9, you should just use Wima MKP10's.
   
  As far as bass at CA7, it's strictly controlled by the RC-circuit cutoff frequency formed with CA7, RB14, and the impedance of the headphones.  1000uf should take care of everything down to 4 ohms, assuming you use a 22R at RB14.


----------



## Aalelan

Quote: 





tomb said:


> Actually, the CA2 and CA9 position have the most to do with _preserving_ bass from the basic input signal/source.  It's a question of keeping all there is, or taking some away.  This can happen with the wrong bypass cap at CA9 (don't use Vitamin Q's, there, for instance), or if CA2 is too small (<1000uf).  Either the ES 1000uf 16V or the Elna RFS Silmic II at 1000uf and one of the voltage ratings listed in the previous post is best.  For CA9, you should just use Wima MKP10's.
> 
> As far as bass at CA7, it's strictly controlled by the RC-circuit cutoff frequency formed with CA7, RB14, and the impedance of the headphones.  1000uf should take care of everything down to 4 ohms, assuming you use a 22R at RB14.


 

 Thanks Tomb,  I guess I got confused when i was reading last night.  I do have Wima MKP10's in CA9 but used a Panasonic FM 1000uf in CA2.  Maybe I will look into getting a better option for CA2 then.  Looks like digikey has the Elna in stock [size=small]604-1111-ND[/size]
   
  Now that I have it all working I'm play mode to see what changes what


----------



## tomb

Quote: 





aalelan said:


> Thanks Tomb,  I guess I got confused when i was reading last night.  I do have Wima MKP10's in CA9 but used a Panasonic FM 1000uf in CA2.  Maybe I will look into getting a better option for CA2 then.  Looks like digikey has the Elna in stock [size=small]604-1111-ND[/size]
> 
> Now that I have it all working I'm play mode to see what changes what


 

 Yeah, that's the perfect cap to use at CA2 for the MOSFET-MAX.  However, please note that once you're using 1000uf at CA2 anyway - the changes to a true boutique cap will be subtle back there, at best.  The most noticeable changes are at CA7.  Still, it's probably worth the investment if you're looking to incorporate the best tweaks.
   
  Focus on tubes, too, if you can - that's where the biggest changes are made, once you have the proper caps in the proper positions.  There's a huge variance in the quality of Millett-type tubes.  The quality can't be tested on a tube tester, either, so it's more of a pot-luck, tube-rolling type of thing, even though all the tubes you might be trying are the same designation, for instance.


----------



## TBomb06

Quote: 





tomb said:


> If you're building a MOSFET-MAX, you're already using 1-1/2" tall heat sinks and locating the PCB in the bottom slot of the recommended Hammond case.  This allows you to alleviate the only issue with Elna RFS Silmic II's: their very-large size.  IMHO, there's no reason to use anything else than an Elna RFS Silmic II, as long as the rating is sufficient _and there's sufficient room_.  They are as good as Black Gate NX's without the break-in and the high cost (now add rarity!).  What's not to like?
> 
> Use the 1000uf Elna RFS Silmic II at 16V, 25V, or 35V for CA2 L/R - all available and stocked at DigiKey.  Use the 1000uf Elna RFS Silmic II at 35V for CA7 L/R.  Handmade Electronics also stocks some of those sizes.
> 
> ...


 

 Thanks for the information, Tom! Just to make sure, are there any drawbacks to using a cap rated at a higher voltage than recommended? For instance, if I use a 1000uF 50V cap at CA2 and CA7, will there be any negative consequences?


----------



## Aalelan

I have gotten lost on what a good bias point is for the MAX-MOSFET  Running the PS at 27v  and tubes at 13.5v  what should I do the FET's at?  I'm currently running at 180mv..
   
  Thanks!


----------



## funch

Another MOSFET lives!
   




   




   




   




   




   




   




   




   
  This shot shows the interference between the back PS cap (2200uF/35V) and the test point. I simply
  loosened the cap and bent the tip of the point a bit.
   




   




   
  Tube LED's are the violet ones from Beezar. They look nice with the top off, but don't really show up
  when it's all buttoned up. I may change them to red. Power LED is the color-change also from Beezar.


----------



## tomb

Quote: 





aalelan said:


> I have gotten lost on what a good bias point is for the MAX-MOSFET  Running the PS at 27v  and tubes at 13.5v  what should I do the FET's at?  I'm currently running at 180mv..
> 
> Thanks!


 

 You should boost them up to 275mV, if you can stand the heat.  Unlike the BJT's, the MOSFETs will get better and better, the more current you feed them.  I regularly run mine at 125ma (~275mV)


----------



## tomb

Quote: 





funch said:


> Another MOSFET lives!


 


 Nice job, funch!!  Great casework!
   
  Another MOSFET-MAX lives!


----------



## jdkJake

tomb said:


> Focus on tubes, too, if you can - that's where the biggest changes are made, once you have the proper caps in the proper positions.  There's a huge variance in the quality of Millett-type tubes.  The quality can't be tested on a tube tester, either, so it's more of a pot-luck, tube-rolling type of thing, even though all the tubes you might be trying are the same designation, for instance.







 This is REALLY good advice. I was surprised at how much tubes vary the sound. I guess it is the mechanical nature of their construction. I have had two sets of tubes, seemingly identical, perform completely differently. Also, learn how to spot microphonic tubes. TomB taught me how to recognize that condition (whereas part of the tube internal touches the glass and starts to "ring") and how to tolerate it, attempt to fix it or chuck it. In the pictures I show above, the left tube, marked RAYTHEON is slightly microphonic. Not enough to make a difference, but, microphonic nonetheless. The right tube is completely fine. Welcome to the wonderful world of tubes!  am I getting rid of that tube? Nope. Sounds great at the volume I listen too.

 jk


----------



## jdkJake

tomb said:


> You should boost them up to 275mV, if you can stand the heat.  Unlike the BJT's, the MOSFETs will get better and better, the more current you feed them.  I regularly run mine at 125ma (~275mV)







 I run mine at 120ma (~265mV).

 Crank those puppies up! Put them to work!


 jk


----------



## jdkJake

YEAH Funch!

 I have been waiting for this post for a while now, you have been suspiciously quiet! 

 Looks great! You drill work is superb. Far superior to mine!

 So, what do you think? Enquiring minds want to know. 

 Details, details please.

 jk


----------



## funch

tomb - Thanks for the nice words.
   
  Jake - Thanks. The drill work took FOREVER, but was worth it. To get the holes as accurate as possible,
   
  I placed the template on each panel and used a spring loaded punch to dimple it. Then I used my pin vise with
   
  a small bit just to start and dimple the hole. After that, I went back with the largest bit that would fit in the
   
  pin vise to enlarge the dimple. That way the bit for the final drilling won't wander, and will put the hole in the
   
  exact correct location. BTW, I used the drill press for the final drilling. I still botched the two rear holes over
   
  the PS heat sink, but you have to do a second look to see it. The final step was to used a hand countersink
   
  tool to clean up each hole.
   




   
  Impressions to come later.


----------



## jdkJake

You even drilled the right tube bushing!!

 Your the man Funch. Awesome attention to detail. 

 jk


----------



## Aalelan

Looks Great Funch!!!  I need to make up my mind how I want to do my casework for mine..
   
  OK, OK... I have taken a baby step up I moved them to 220mv, I will scoot them up a little at a time over the next few days.
   
  I'm trying to talk a guy at work in to getting a set of AGK K701's so I can try them out on this!  I think he kinda wants to, its just going to take a few nudges 
   
  This is just like when I rebuilt my Corvette, every time I look at it I think "well I could do this....."  what have I got myself into!?!?
   
  AA


----------



## funch

Quote: 





jdkjake said:


> You even drilled the right tube bushing!!
> 
> Your the man Funch. Awesome attention to detail.
> 
> jk


 


 Actually, it's called being terminally anal!  I did try to run it up and down
   
  the drill bit on the press, and tried to file it, but it's too tough, so I had to
   
  use an Xacto knife to carve it away.


----------



## Aalelan

Scratching head here..  Playing around here at my desk and I figured I would check my voltages.. my FET bias had droped about 12mv from last night so I tweaked it up again..  then I checked my tubes, left was at 16v!! and the right was at 14v..  I got the right back down to 13.5 but the left will not go down at all for some reason..  I checked the PS output and it was at 24!?!  so I check the AC side of things and the wall wart is only putting out 22.8v  where it was running at almost 27V loaded up.  The most I can get out of the PS adjusting the 1K is 25.4v
   
  Everything seems to be going whacky on me, any ideas??
   
  EDIT: just to note the wall wart is the 50va one from Beezar, so it should be plenty hefty enough.
   
  AA


----------



## tomb

Quote: 





aalelan said:


> Scratching head here..  Playing around here at my desk and I figured I would check my voltages.. my FET bias had droped about 12mv from last night so I tweaked it up again..  then I checked my tubes, left was at 16v!! and the right was at 14v..  I got the right back down to 13.5 but the left will not go down at all for some reason..  I checked the PS output and it was at 24!?!  so I check the AC side of things and the wall wart is only putting out 22.8v  where it was running at almost 27V loaded up.  The most I can get out of the PS adjusting the 1K is 25.4v
> 
> Everything seems to be going whacky on me, any ideas??
> 
> ...


 


 The tubes may very well change bias as they break-in.  That's not unusual.  As far as the left one not going down, that doesn't sound normal.  However, the biggest issue may just be your line voltage.  Is it possible that your area has some scheduled brown-outs?  This is the time of the year for those things - or just power sags, period.  It would explain a lot.
   
  Try checking it later tonight and see if things have calmed back down.


----------



## Aalelan

Quote: 





tomb said:


> The tubes may very well change bias as they break-in.  That's not unusual.  As far as the left one not going down, that doesn't sound normal.  However, the biggest issue may just be your line voltage.  Is it possible that your area has some scheduled brown-outs?  This is the time of the year for those things - or just power sags, period.  It would explain a lot.
> 
> Try checking it later tonight and see if things have calmed back down.


 
  Ok, partial answer and more questions   
   
  I moved up to my office where that circuit is know to be on the verge of overloaded all the time..  The wall voltage there is 108VAC, down the bedroom and living room I get 120VAC.. Move the Wall wart and voltage comes out ok..
   
  So for the questions:
   
  1)  how much can the MAX 1.2 PS bump up the voltage?  is that why I could not adjust up past ~25 when I was only getting 23 from the wall wart?
   
  2) So how about that left tube?  I know they take time to break in and they seem to always read high before they warm up..  but they had been fairly stable the last few days (right at 13.5 - 13.6)..  what would cause just that left tube to shoot up so high and not come down?  I have not got it below 15v even with the trimmer all the way in 
   
  3)  I cant seem to remember now, started talking the wife mid post and lost it


----------



## tomb

Quote: 





aalelan said:


> Ok, partial answer and more questions
> 
> I moved up to my office where that circuit is know to be on the verge of overloaded all the time..  The wall voltage there is 108VAC, down the bedroom and living room I get 120VAC.. Move the Wall wart and voltage comes out ok..
> 
> ...


   
  The PS regulator "floats" by regulating to a voltage difference. It's that difference that's regulated, not the specific value of the output voltage. This works fine in most instances because we're really only interested in removing the noise to provide high-quality audio. All of the major headphone audio linear-regulation schemes work this way. It only becomes a problem when we have something like the MAX/MiniMAX with several specific voltages that need to be set.

 Actually, there's only one specific voltage: V+. The tubes are simply biased at 1/2 of that, whatever that is. In any event, the 27VDC recommendation for V+ is based on the walwart supplying at least 24VAC to the terminal block _under load_. You can actually push it to 28 - 28.5VDC before you lose regulation ability under the best of conditions, but that's why we dropped it back to 27VDC for most scenarios.  Frankly, I've been a bit surprised at a couple of instances lately where there are problems in meeting this voltage.  As mentioned earlier, I suspect that there's some brownouts occuring during the peak of the summer season and that's raising this issue to the forefront.  Just as likely - as you mention - may be a localized circuit that turns out to be heavily loaded.  I would not want to plug one of my MAXes or MiniMAXes into the circuit that feeds my color laser printer, for instance.
	

	
	
		
		

		
			






> 2) So how about that left tube?  I know they take time to break in and they seem to always read high before they warm up..  but they had been fairly stable the last few days (right at 13.5 - 13.6)..  what would cause just that left tube to shoot up so high and not come down?  I have not got it below 15v even with the trimmer all the way in


 
 Again, the bias is directly related to the V+ voltage.  If that changes, then the bias changes.  The changes should be consistent between the tubes, though - but this is not always the case, unfortunately.
   
  Have you tried turning the trimmer the other way? Sometimes the bias changes direction on the trimmer, depending on which side of the resistance the bias has altered. If that doesn't work, then it may be one of those infrequent (thankfully) occasions where the tube went bad. Let me know and I'll replace it if it was a Beezar tube.
   


> 3)  I cant seem to remember now, started talking the wife mid post and lost it


----------



## Aalelan

Tomb,
   
  That left tube is still acting up YGPM..


----------



## TBomb06

Well, I got my MOSFET Max built today and I'm listening to it now. My experience building my first BJT Max helped me out a lot this time around, as everything fired up perfectly and worked right out of the box, which was a relief. Once I get this one all cased up I'll post some photos, and once it's broken in I'll do a comparison to my BJT build and see how much difference I can hear with the MOSFETs. I know those red boards sure are pretty...I'm thinking I'll have to do a lexan top so I can show off the beautifully designed circuit board.
   
  Thanks for all the help guys, I appreciate you making my life easier


----------



## Nakattack

Hey guys, I'm having problems with a MAX I received on loan today. I power the amp up, and one of the channels doesn't work, but if I switch the amp off and play with the tubes I can change which side receives a signal. Any ideas on how to fix this?


----------



## Aalelan

Quote: 





nakattack said:


> Hey guys, I'm having problems with a MAX I received on loan today. I power the amp up, and one of the channels doesn't work, but if I switch the amp off and play with the tubes I can change which side receives a signal. Any ideas on how to fix this?


 
   
  Well if play with the tubes means you swap sides with them, I would say it sounds like you have a dead tube.  Also the fact that you can get it to switch would lead me to believe that none of the solid state parts are dead/damaged.
   
  Not what you wanted to hear I bet but thats my opinion on whats happening..
   
  AA


----------



## tomb

A tube that's not biased will also act like a dead tube.  Does the tube glow?  Look for an orange glow near the top in the center of the tube.  If it glows, it's probably OK - at least it would produce some sort of signal if it were biased correctly.


----------



## funch

Aw crud!  I was listening last night, and all had been well for about an hour or so. Suddenly, the sound distorted, the volume dropped, and 'click',
  everything went dead. The distortion sounded like the situation when you power an amp down with the music still playing and after a few seconds
  the PS caps run out of reserve, the sound distorts, and the music stops. I'm visiting out of town right now, so don't have access to my meter so
  I won't  be  able to troubleshoot 'till Monday. BTW, it happened in both channels simultaneously. Any thoughts?


----------



## jdkJake

funch said:


> Aw crud!  I was listening last night, and all had been well for about an hour or so. Suddenly, the sound distorted, the volume dropped, and 'click',
> 
> 
> everything went dead. The distortion sounded like the situation when you power an amp down with the music still playing and after a few seconds
> ...







 Check the fuse?

 Did you use a fuse?


----------



## funch

Fuse still intact. LED's still light. No fireworks/smoke.


----------



## Nakattack

Quote: 





aalelan said:


> Well if play with the tubes means you swap sides with them, I would say it sounds like you have a dead tube.  Also the fact that you can get it to switch would lead me to believe that none of the solid state parts are dead/damaged.
> 
> Not what you wanted to hear I bet but thats my opinion on whats happening..
> 
> AA


 

 I wasn't swapping them, just wiggling them around a little bit. I managed to fix it by wiggling them, I think the tube sockets are loose? I'm scared to move it now, just incase a tube moves and I lose another channel. So far it sounds good, but the only real improvement I've heard over the headamp of my Maverick D1 is a little more bass punch. I'll have to do a critical listening sesh soon, and maybe some better RCA's.


----------



## rarebear

Is this still the AMP to build ?
  If yes or no where can I get the info I need to buy and build the kit..
   
  Thanks Much


----------



## Aalelan

Quote: 





rarebear said:


> Is this still the AMP to build ?
> If yes or no where can I get the info I need to buy and build the kit..
> 
> Thanks Much


 

 Not so much a kit but  you can get the board here http://beezar.com/  and the build of materials are here http://www.diyforums.org/MOSFET-MAX/MOSFET-MAXbom.php
   
  I suggest going with the mouser side of the BOM as there are still a few "errors" on the Digikey side..   This is a great amp to build I had a blast doing it and it sounds great!  IMHO if you have any kind of soldering skills at all and can read you can do this with some patients.  Just take it slow and easy..
   
  AA


----------



## rarebear

Thanks Very Much,
  I have some skills  
  I think I'll give it a try, I just wanted to make sure it was not out of date...


----------



## Aalelan

Quote: 





rarebear said:


> Thanks Very Much,
> I have some skills
> I think I'll give it a try, I just wanted to make sure it was not out of date...


 

 Still very much up to date... I just build mine a few weeks ago and I think the version 1.2 board just came out this year..
   
  AA


----------



## rarebear

I ordered the board 
   
  What OUTPUT STAGE should I use???
   
   
  Also are there any step by step pictorials ???
   
  I need a little more help than I am finding @DYI
   
  I have seen some good ones on other stuff and I am a metal worker and electronics is not my strong suite..
   
  If there is not one I would like to make one as I have some graphics and web design skills better 
  In the 80s I made a lot of the hardware parts for the Global Positioning Satellite and Aegis Radar Systems..
  I even worked at Keystone Camera and over seen the operation of the wave solder machine but that dosen't help me stuff the board with correct parts 
   
  Any help greatly appreciated


----------



## tomb

Quote: 





rarebear said:


> I ordered the board
> 
> What OUTPUT STAGE should I use???
> 
> ...


 


http://www.diyforums.org/MAX
http://www.diyforums.org/MOSFET-MAX


----------



## TBomb06

Quote: 





rarebear said:


> I ordered the board
> 
> What OUTPUT STAGE should I use???
> 
> ...


 

 As Tom mentioned, the DIY Forums have a couple of very thorough guides for both the BJT and MOSFET Max boards. Thanks to the effort of the Max team, you can build a Max pretty easily just by following the bill of materials and the silkscreen on the board. The "regular" Max site has some helpful information about the actual populating of the board, and the MOSFET Max site has some valuable info about certain tweaks made to the new 1.2 MOSFET version of the amp. I'd suggest reading through both of those sites, as well as the current bill of material to get an idea for what you're in for. You can also search through this thread (using the "Search this thread" button) if you have any particular questions. Or you can just ask, and I'm sure someone will be happy to answer you. I've built both the first production version of the BJT Max and the latest version MOSFET Max, and they both sound pretty dang good. The MOSFET version runs a little hotter and requires the taller heat sinks, so part of the decision depends on how you want to case the amp up. Anyway, check out the sites that Tom put together, there's a ton of valuable information there, and in this thread. Happy building!


----------



## rarebear

[size=10pt]I have checked the pages and don’t see a guide or how to, am I missing something some place ????[/size]
  [size=10pt]I am unsure what to order as I see some things are optional but can't find why or where there is a note on options...[/size]
   
  [size=10pt][size=10pt]Before ordering I should have found a better GUIDE [/size][size=10pt]L[/size][/size]


----------



## TBomb06

Quote: 





rarebear said:


> [size=10pt]I have checked the pages and don’t see a guide or how to, am I missing something some place ????[/size]
> [size=10pt]I am unsure what to order as I see some things are optional but can't find why or where there is a note on options...[/size]
> 
> [size=10pt][size=10pt]Before ordering I should have found a better GUIDE [/size][size=10pt]L[/size][/size]


 
   
   
  Ok, well, this is a pretty good walk-through of the build process for the PCB itself:
   
  http://diyforums.org/MAX/MAXconstruction.php
   
  That, along with some common sense, will get you pretty far.
   
  Are you going to build a BJT Max or MOSFET Max? If you're building the MOSFET version, use the Mouser section of this BOM:
   
  http://diyforums.org/MOSFET-MAX/MOSFET-MAXbom.php
   
  For some of the miscellaneous parts you will need to order from Beezar.com or AMB's shop, or source them yourself from other places such as Parts Connexion or Handmade Electronics.
   
  I can't see how you could still have too many questions about how to get started after reading through those two links. This project has been going on for over 3 years now, and is very well documented by the guys who created the Max, so give those resources a thorough reading before you complain about needing a "better guide".


----------



## rarebear

I have been reading the link below.....
http://www.diyforums.org/MOSFET-MAX/MOSFET-MAXoverview.php
   
  I thought this link  http://diyforums.org/MAX/MAXconstruction.php was a different build ???
   
  I was reading the quote below and was stumped as to what option to pick..
  As well notes on order list had a few options and notes to reference that I could not find on the order page...
   
   
  Quote: 





> *NOTE: You must decide which output stage to use - either BJT Diamond Buffer or MOSFET Diamond Buffer. You cannot build both. Please refer to the original *


 
   Pretty much everything after that was like saying blah blah blah to me...
  After reading it all twice I never did see discripton of what was different, that a layman could understand or the writer gave there opinion what to choose...  Let me say I am disbaled due to a failed back surgery and also suffer from depression and it is very hard for me to read things I understand let a lone things I dont 
  I do not mean to inslute in any way as I have my own website and often what I write gets lost from my mind to my fingers to the page...  I am in way over my head what I am reading and just dont find in the navagiation bar links of the link I was sent the info I need.......
   
  I'll check the other link you posted and maybe it will make sense...


----------



## TBomb06

The first link you posted is for the current version of the Max PCB, which is 1.2, the one you ordered from Beezar.com. The board itself can be populated with one of two output stages, the BJT version or MOSFET version, although the general opinion is that if you are populating the larger 1.2 board, build it as a MOSFET version, and if you want to build a BJT version, get the MiniMax kit from Beezar. This might be a better option for you because, as far as I know, it includes pretty much every thing you need and the transistor matching is done for you, it even includes a very nice machined case. This will help a lot in ordering/managing/sorting parts, which in itself can be a pretty big project. I know you've already ordered a 1.2 board, but if you get in touch with Tom "TomB" he might be able to figure something out for you if you wanted to switch to a MiniMax kit. I don't mean to put words in his mouth, though, and he may or may not be able to do anything for you. I hope that helps.


----------



## jdkJake

Rarebear, I have to agree with Tbomb06, the miniMax kit might be a better match as it includes all you need to build the amp, including the casework. 

 That being said, it will not help you bias/setup the amp properly. For that, you will have to be able to read and comprehend the various pages on the miniMax site if you want any chance at a successful build.

 Perhaps you should reconsider the build. You can buy a pre-built miniMax from Whiplash Audio (a site sponsor). There will be no surprises going that route.

 Just a thought.


----------



## rarebear

Well I can read, I just can't stay focused longed (say 30 mins max)
   
  Last year I took a online class on how to repair a 25 jewel watch, this year looks like building some electronics I hope...
   
  I'll try some more reading 
   
  Case work is my strong suite

   
  PS: Thanks T Bomb for telling which option to use 
   
  Quote: 





> general opinion is that if you are populating the larger 1.2 board, build it as a MOSFET version


 
   
   
  You can see some pics of how I made the case @facebook
http://www.facebook.com/album.php?id=1642539189&aid=2024851&s=20&hash=3541bc47752af4de9c7c017f06ac4b67#!/album.php?id=1642539189&aid=2024851&s=0&hash=46bc8b2b0525d40e260977874f219fc0


----------



## TBomb06

You're definitely welcome. The Max will probably be a bit of a challenge for you, I know the first one I built wasn't without its fair share of problems. My advice would be to try and break the web sites down into sections, and try to digest them a piece at a time before moving on to the next. Also, have a good plan in place before you start building to avoid any issues that might pop up during the build process. It might look something like this:
   
  1. Determine your build's bill of materials. I'll run you through the optional/commented sections to the best of my knowledge.
   
  a. Decide on boutique caps (Vit Q's from Beezar, Elna Silmic II's from Handmade, etc.)
   
  For example, on my build, I chose to use .22uF Vitamin Q caps from Beezar for my CA8L/R positions, and 1000uF Elna Silmic II's for CA2L/R and CA7L/R. The other film caps are all Wima's like on the standard BoM.
   
  b. Buy and match the 2N5087 and 5088 small transistors. As the comment in the BoM states, you'll want to buy at least 50 of them, and a cheap meter from Harbor Freight that lets you measure the HFE of the transistors to match them closely. This is documented on the Max site as well.
   
  c. R1 10ohm 1W heater resistor. Install this one, don't consider it to be optional.
   
  d. Choose what color LEDs you want to use - Beezar.com has several to choose from.
   
  e. If you want to use an on-board fuse, you'll need to plan accordingly and order the fuse clips and a 5x20mm 1A slo-blo fuse. Install a 3 position terminal block for the power so you can wire it to either use the fuse or bypass it if you wish.
   
  Everything else is basically just an alternate part number, except for the heatsinks. Just get the 1.5" heatsinks otherwise you will have to run the MOSFETs at reduced current levels, which is not ideal. Stick to Mouser for most of your parts, get what you can from Beezar.com, and you might have to order your larger boutique caps from elsewhere if you wish to use them. I'd go ahead and get 5 of the heatsink mounting kits from Beezar for the VREG and your MOSFETs while you're at it. It won't hurt to order one or two extras of all your parts, especially the less expensive ones, in case one gets damaged for some reason or another.
   
  2. Organize your parts as they come in. A HUGE benefit is to use the "custom part number" feature of Mouser's cart so that as you add an item to your cart, you can verify that it is what the BoM calls for, and then name it for the Part ID that it has on the BoM (So you'd type in "RA1L/R" for the 5K Ohm Trim Pot).
   
  3. Plan ahead, and think about how the build will go. Arrange your parts by height, so you won't miss a small part that has be snuck in between some taller parts. If you want to go ahead and do the case work beforehand, go for it, or you can wait until you know you have a working amp.
   
  4. If you want to remove the pin that holds the tube sockets together so the LEDs can shine into the tubes better, do that and use some epoxy to glue them back together the day before you plan to start building the board.
   
  5. Populate the board, and check to make sure the proper parts are going in the proper places as you go. Again, the silkscreen on the board tells you the name of every part on the board, and how it should be positioned. You just have to make sure it's the right part. The more thorough you are, the more likely you are to have you board fire right up when you turn it on, and not catch on fire 
   
  6. Check everything again after you're done. Make sure you don't have any empty places on the board, make sure you don't have any parts installed backwards (other than the QB2/3 transistors, which is explained on the Max site). Check for any solder bridges or leads you missed. Clean up the bottom of the board to remove excess flux. Make sure your DB trimmers are turned all the way down before you fire it up.
   
  7. Temporarily wire up your power and turn it on. Observe for signs of smoke . Immediately check your DB voltage to make sure you aren't running too much through the buffers (in case you didn't get the trimmers turned down properly). If your DB voltage is nice and low (or 0) then go ahead and set your power supply voltage to 27VDC, then set your left and right tube bias to 13.5VDC each, then get to work on your DB voltage till you get it to around 175mv/80ma. Check to make sure nothing's getting overly hot. The heat sinks will get rather warm, but make sure no other parts are too hot or anything.
   
  8. Turn off the amp. Put it in the case, hook everything up, start listening, and gradually raise the bias for the DB up to 275mv/125ma.
   
  Again, all of this is outlined pretty well on the Max website and some of it is just from personal experience. I'm sure others more knowledgeable than I am can chime in with their own advice


----------



## rarebear

Well I read the Millet History then the Max History page to find the JFET-MOSFET is the latest version...
  I wish it was blog style and I would have been done with the first sentence 
   
  I am back to where I left off, ordering parts and find NO ORDER INFO once again..........
   
  I'm still looking to find  
   Quote: 





> What's needed ...  Basic construction and* parts selection is covered in detail within these web pages*


 
   
  This is the statement that made me place the order.. Do I need to read other versions website to find what parts to order for this one??
   
*Why is there not a simple list of the latest version parts to buy?*
  If thats it, where does it discribe what Optional is?
   
  Late and Time to Sleep before I go crazy....
  Thanks Again


----------



## Beefy

Quote: 





> Originally Posted by *rarebear* /img/forum/go_quote.gif
> 
> *Why is there not a simple list of the latest version parts to buy?*


 


 If you don't know what a BOM is, or are too ADD to find this this or this, then step away from the soldering iron right now and buy a commercial product.


----------



## Aalelan

Anybody have a best method for removing a heatsink from a board?  I have an idea I want to do for both heat and asthetics,  I have ordered 2" heat sinks to replace the PS and the two center MOSFETs.  I want them to stick up out of the top like the tubes will,  I'm going to leave the outer two at 1.5" as they do not get that warm and I just wanted the sinks standing up in the center dividing the tubes kinda..
   
  Thanks!
  AA


----------



## Beefy

Quote: 





aalelan said:


> Anybody have a best method for removing a heatsink from a board?


 


 Only to not solder them in the first place. I wish you good luck, sir!


----------



## Aalelan

Well my new sinks will be in Tomorrow..  I'll let you know how it goes and take a new picture..


----------



## TBomb06

Nevermind.


----------



## rarebear

If the text Optional was a Hot Link to the info I needed to understand this Materials List it would be awesome but its NOT.........
   
  So can someone PLEASE  show me where this is without insluting me or my disabilities ??????
   

   
   
  Thank You
   
  PS: I forgot to add just above the red arrow RA9 L/R 11.3 OHM there is no qty listed.. I am unsure of how many to buy here also.........


----------



## tomb

If you look closely, there's an RA8L/R and RA9L/R just above where you've so graciously pointed.  One might take that to mean there are two choices for RA8 and RA9 and the optional choice is highlighted, with the resulting different CCS current listed.  The fact that the quantities are only included for the optional choice indicates that it is actually the default.
   
  On the other hand, you could follow the advice that some have been trying to give you and buy a commercial amp, instead.  At the very least, you should acquaint yourself with a CMoy and come back to this when you have a bit more experience.
   
  Your order hasn't shipped yet.  Let me know if you want to cancel and I'll cheerfully refund your money.


----------



## tomb

Quote: 





aalelan said:


> Anybody have a best method for removing a heatsink from a board?  I have an idea I want to do for both heat and asthetics,  I have ordered 2" heat sinks to replace the PS and the two center MOSFETs.  I want them to stick up out of the top like the tubes will,  I'm going to leave the outer two at 1.5" as they do not get that warm and I just wanted the sinks standing up in the center dividing the tubes kinda..
> 
> Thanks!
> AA


 

 You know, MOSFETs almost love running hot.  I have months of burn-in on two MOSFET-MAXes and those MOSFETs on the center sinks have not given out.  Plus, the fact that MOSFETs have a positive temperature coeffiicent means that they'll probably run cooler when it's cased up.


----------



## rarebear

In your first parapraph you post the word CHOICE three times............
   
  As I asked before:
  Where do I find the Text  on where to make these CHOICES ???
   
  I'll ask one last time for the fouth or fifth time.......
  Pictures seemed to fail, let me try again...
   
  Where do I find the text that explains what the options are ?  I am sure you have not choosen a clear winner since you list two and seem to love to have a CHOICE for the buyers to make, where do I educate myself about the CHOICES to be made on the materials list so I can place an order???
   
  Thank You Yet Again........


----------



## TBomb06

Nevermind.


----------



## cobaltmute

Did you look at the tweaks page:
http://diyforums.org/MOSFET-MAX/MOSFET-MAXccs.php
   
  An option is a tweak...


----------



## rarebear

Thank You! Cobalt,
   
  I would not have thought to look at the Twweks page till I was almost done building the board.....


----------



## TBomb06

Nevermind.


----------



## rarebear

Yes Sir I am Ridiclous...........
   
  When I ask a question several times and its not answered and I am told I have A.D.D. I am at least able to stay focoused and answer a simple question.......
   
  You say on the webpage the cost is trival so why not just list to buy both? I guess you did but not to me...
  I seen it as a Option and had to Choose one or the other.........
   
  List parts as Alteranive Parts in your Construction Page (when you get around to making one for this version)
  You can also add  text above and below the order page and not just export a execl spread sheet with badly formated CSS on top (it dosent scale well) I maybe ridiclous at electronics but not at many things like web and graphics design..   I will still treat you with respect and not call you names because of my short comings..
   
  Thanks so much for those who tried to help...


----------



## tomb

Quote:


rarebear said:


> Yes Sir I am Ridiclous...........
> 
> When I ask a question several times and its not answered and I am told I have A.D.D. I am at least able to stay focoused and answer a simple question.......
> 
> ...


 

 Your attitude is not conducive to receiving help - at all.  Good luck with the amp, but my offer still stands: just let me know and I'll cancel the order and cheerfully refund your money.
   
  As for the sorry web design on the BOM, I guess you didn't notice the two other options you had available (oh, sorry for that word "option," again) for accessing the BOM - both in pure Excel and PDF form.  Thanks for your comments, too, by the way.  Glad to know that all my work on websites is so appreciated.
   
  Mods - I think you can delete several of the previous posts and increase the value of this thread immensely.


----------



## Beefy

Quote: 





rarebear said:


> Thank You! Cobalt,
> 
> I would not have thought to look at the Twweks page till I was almost done building the board.....


 


 Now where is my facepalm gif collection......
   
  Your problem is your complete and utter lack of patience. The _correct_ way to undertake a DIY project is to do ALL of the reading FIRST, THEN ask questions, THEN start building.


----------



## TBomb06

Nevermind.


----------



## rarebear

T Bomb and all you are all correct......
   
  I should have read the site top to bottom first........
   
  I am new to this site and doing DIY Electronics and need to read the site before trying to order PERIOD.
   
  Just like TomB thinks his site is great ( I do appreciate his efforts) I thought it would be as easy as ordering some parts and solding them together like someone said.........
   
  For what ever the reason I could figuer what parts to order..
  I was told several dozen times to just make a CHOICE... To make that choice I did think I had to read every page even the tweaks page to find ordering indo.. I wanted to gather all parts in front of me and not read the history of who designed this and who improvered that..... You all what the shout out and I am sure they are  deserved but with my first project not on my list of need to know right now...
   
  To me a tweak is what you do to a hand gernade pin before you put it in your pocket or something you do after a build or during to make it sound better, not where you find pre-order info.....
   
  TomB,
  I downloaded the excel file and it there are none of the popup notes in Excel 2010 I guess you might have used an older version.......... I guess the link that is broken to Tweaks->MAX Boutique sections might have saved me asking all these ridiclous questions..........
   
   
  My Applogies I get frustrated and have always had little paitents.. My Father always told me I was Russian not Hungarian.......  My Appoligies Once Agian
   
  PS: I did not mean to inslute Toms webpage by pointing out theformating of the CSS was bad .... If you look at the screen shot I posted you see Blue Numbers all over and on top of text and numbers....... That is not Correctly formated I call that bad and not good formating........ I have ADD and rediclous and and the word bad is an inslute????????   I'm guessing its not me at this point now........


----------



## rarebear

Just send me the Refund    
TomB  see the MODs have edited out your inslut sir...........


----------



## tomb

Quote: 





rarebear said:


> Just send me the Refund
> TomB  see the MODs have edited out your inslut sir...........


 

 Sorry, but there's nothing of mine that's been edited out - insult or otherwise.
   
  Best of luck with you in your endeavors, Johnny.  Try to calm down in the future and maybe you'll have better success.  Your order is cancelled and refunded.


----------



## funch

WOW!! I head out of town for a few days, and miss all the 'fun'. tomb, you have the patience of
  the proverbial saint. Anyway.....
   
  I got back home today, plugged in my amp, made all the measurements. Nothing out of whack,
  so I plug in some music and ..... everything is fine. ?????   Must'a been bad juju. If anything else
  screwy happens, I'll report back, otherwise .... 
	

	
	
		
		

		
			





.


----------



## jdkJake

Well, one things for sure. This thread is far from boring.

 Funch, you might want to check your relay circuit. Perhaps the relay triggered for some reason and cut off the output.


----------



## rarebear

To anyone looking to build this AMP here is my advise........
   
  Don't bother asking any questions as the MAX Team they will not answer your direct questions only point you to a website......
  They do have plenty of time to call you names and belittle you but none to answer a simple question......
   
  They take time to answer questions they think you will ask next but again not the one you asked.......
   
  If you think they have spent a good amount of time making the website easy to follow like a technical manual you'll be wrong..
  Iin fact the currect model is missing any construction pictures as well as the construction page the older model has......... I guess the team is busy working on building this page and has no time to answer a single question to me.. I would have been happy to take the needed photos, edit them and build the page for them but they would rather call me names instead of help a friend.........
   
  So my advise is if you think you may need help building this unit look elsewhere as I found no friends here.....


----------



## Beefy

Quote: 





rarebear said:


> To anyone looking to build this AMP here is my advise........
> 
> Don't bother asking any questions as the MAX Team they will not answer your direct questions only point you to a website......


 


 You're missing the point. You want everything handed to you on a platter, before you have done any reading or research yourself because of your own admitted failings of attention span. EVERY DIY project talked about on Head-Fi will be met with the same scorn of impatience that we have placed on you. It is called DI*Y* for a reason.
   
  Tom is one of the nicest and most helpful guys in the entire community. The fact that you have managed to annoy even his good nature speaks volume about you, not about him.


----------



## jdkJake

Rarebear,



 I think folks are more than willing to help, but, it is a two way process. Please understand, we may have similar frustrations with the feedback we receive from you as well. Legitimately, most folks here are truly committed to helping you make a successful build as long as you can demonstrate a reasonable level of competence and comprehension of the product and the build process. The last thing anyone wants to see is for you to fail miserably because of a misunderstanding of the product and processes. 



 Remember, this is not a commercial product, rather , the fruits of a committed group of individuals to share a project with the community. The level of available documentation is unprecedented for this type of endeavor. Of the other DIY projects, only the AMB projects enjoy such a complete and passionate level of support. The level of commitment of TomB to this product is extraordinary. Please remember, he has a day job and does this out of a desire to learn and share this learning with others. The web sites, while not perfect, are more than adequate to answer most if not all of your questions satisfactorily if you take the time to carefully review the content. The other best place for information is this thread. I realize it is long, but, most if not all questions are addressed as well as a plethora of build options. It is kind of a "right of passage" to read and review the thread before attempting the build. The version 1.2 product is new and while very mature, is still going through the optimization process. So, relevant questions can and will be answered quickly and courteously if you remain patient with the process and temper your expectations from the responses. At least that has been my experience and I have successfully built the product to meet my personal expectations.  



 As Beefy stated above, the Y part of DIY cannot be understated. Ultimately, you will be responsible for the final product, good or bad.


----------



## BoilermakerFan

Quote:  





> I have ADD ........


 

 I'll see your ADD and raise you an H with added Hyperactivity.  ADD is not an excuse for your behavior or attitude, unless you referring to a condition other than Attention Deficit Disorder.  Cut way back on the sugar, high fructose corn syrup, and red number five food coloring.  Add Omega 3, 6, and 9 oils to your diet.  You'll fell better, your temper will calm down and your ADD will be less of a Disorder and more of a Gift.  I write that from personal experience so it is not an attack or insult.

  
  Quote: 





rarebear said:


> To anyone looking to build this AMP here is my advise........
> 
> Don't bother asking any questions as the MAX Team they will not answer your direct questions only point you to a website......
> They do have plenty of time to call you names and belittle you but none to answer a simple question......
> ...


 
   
  How do you expect to make friends when you pull out a dagger or a sword and charge into the DIY crowd? 
   
  If you want to experience the MAX amp and work into DIY slowly, buy a complete amp from Whiplash Audio.  I suspect Whiplash would be willing to build one with the Silmic II and Vit Q caps, then you can roll the tubes and poke around under the hood.  Lurk more, troll less.  For your first personal build, start with an amp or other component that has a lower parts count and a more rigid BOM. A gain clone amp kit comes to mind as an easy first build that yields nice sounding results.  Not a headphone amp per say, but and easier build than a MOSFET-MAX for a first-timer.


----------



## rarebear

Jake,
  My point is not to drag this on but you end in saying questions will answered quickly and courteously ...
   
  I did not have a build question, while trying to order parts after buying the board I was very confused and only got more confused when told to just make a CHOICE.....
   
  It seems that you cant get an question answered other than read the website it has everything you need......
_I read where I thought I would find what I was looking for and more_ but the info I needed was elsewhere...
   
  After the second time I was being insluted for asking what page the info I needed was on I was done..... Period
   
  So I find your statemant falus and completly unture..
  The only info you will get is what you said.. The webpage has all the info you need...
   
  I was trying to order parts and NO ONE would answer a smiple question.... 
   
  I do know enough that one of these units you can no longer get parts for or they are hard to get my hurry was I feared buying the board and not being able to buy the parts listed... Thats why I was in a hurry and I sure you will tell this is not the case with these parts but I dont know that and just wanted to place an order but I guess everyone is to smart here to answer a dumb noobs question........
   
  I have my own website rexmill.com and dont make a dime from it or the classes I give for FREE I even pay for lunch becasue I love learning and helping people.. Here you have to ask the right question and everyone is to busy calling people names instead of helping Tom improve his website...
   
  This all I have to say, I'll have have this amp in my house as I will just remind me of my blood boiling yesterday......


----------



## Beefy

Quote: 





> Originally Posted by *rarebear* /img/forum/go_quote.gif
> 
> I was trying to order parts and NO ONE would answer a smiple question....


 


 *sigh* You are still missing the point. Order parts AFTER you have done the required reading.


----------



## rarebear

Beffy
  You are not even reading my post if you are you seem to not understand what you read sir
   
  I explained what I was in a hurry to buy parts but that when over your head......
   
  You keep adding I have ADD or a attention problem which is not true at all....
   
  I can only read for short times because of back pain...
  Not ADD or an attention problem................
   
  Maybe Tom should just sell built amps because anyone that askes a question your only answers are either read the website or buy one built  Answering a question is of the question.. Do you all think your too smart to answer dumb questions I guess? I am not wothly of having a question answered? I get it.......


----------



## Beefy

Quote: 





> Originally Posted by *rarebear* /img/forum/go_quote.gif
> 
> I explained what I was in a hurry to buy parts but that when over your head......


 


 Nothing went over my head, and I understand the situation completely. You are impatient, and have too short an attention span to read all of the material before ordering. When you weren't handed everything on a platter, you flipped your lid.
   
  Slow down. Stop being in a hurry. Read everything first. Then order.
   
   
  Quote: 





> I am not wothly of having a question answered? I get it.......


 
   
  No, you are not worthy. Not until you bother to do the required reading. Everybody else manages to put in the effort to do that, so what do you think makes you so special that you don't have to?


----------



## TBomb06

Nevermind.


----------



## jdkJake

Rarebear, 

 Well, I am sorry your experience has not been favorable as mine has been exactly the opposite; favorable and rewarding. The bill of materials is a starting point, a suggestion for a journey. Not a bible, nor a mandate. Your statements remind me of a some-what famous song:

 "freedom of choice is what you got, freedom from choice is what you want"

 I wish I could say something that would help resolve this apparent conflict, but, I am apparently not eloquent enough. Perhaps in time, you can give it another chance. With the possible exception of the tubes, there are no parts that can not be replaced by equal substitutes with a resulting tweak in supporting elements. So, do not worry about hurrying though the process. Take your time to get it right in the first place. I personally spent many months preparing for my build and putting in place my desired configuration. It was part of the process and at least half of the fun. Nothing worth doing is quick or easy, or at least that has been my experience. 

 In the future, I am personally more than willing to help as long as you can show some level of due diligence on your part before proceeding with the process of procuring parts and starting the build process. Believe it or not, most of your questions were answered quickly and correctly; you just did not like the answers. There is not much that can be done about that from our end. In the end, some, but not all, of the answers were a diplomatic way of stating you might be in over your head and should probably consider a build that presents far few options for customization. Perhaps a kit whereas everything is provided without the need for an open-ended BOM. Beezar offers just such a kit for the miniMAX which would make your HD600's sing. Whether or not Tom would sell you that kit after these proceedings is another matter.

 In any case, I will not be commenting on this further, good luck to you in future endeavors.


----------



## rarebear

My Applogies to All  Tom and formost the Mods here who I am making there job harder..........
   
  I was unclear as to what to order, my friends.....
   
   
  MY HOPE was to order parts and lay them out in front of me and them start the build have visual refferences in front of me....... This is how I wanted to start the project..............
   
   
  I asked a few times, I even made a screenshot to illustrate what I was confused about....
   
  I will not bring back up what happened after but I wish you all well.......
   
  I will spend my time learning to read a schematic, order parts on my own even drill my own PCBs  made in my metal and wood shop I have in the garage...Do it all on my own seems to be what I have to do.......
   
  Enjoy and Be Well......


----------



## TBomb06

Nevermind.


----------



## n_maher

I think this vein of discussion has gone long enough. Let's move on, shall we?


----------



## TBomb06

Righto, moving right along. Here are some images of my recently built MOSFET Max as it sits right now. I might do some more casework later if I can come up with a design that I like, but for now the wife says I've spent enough time working on this thing


----------



## tomb

Very nice, TBomb06!!  Another MOSFET-MAX lives.


----------



## jdkJake

Sweet TBomb06.
   
  Looks like a custom front panel. Give us a "full-frontal" please! I want to be able to read the lettering.  
   
  Hellofa knob as well. No chance of accidental slippage with that baby. Is it lighted?


----------



## TBomb06

Thanks guys!
  
  Quote: 





jdkjake said:


> Sweet TBomb06.
> 
> Looks like a custom front panel. Give us a "full-frontal" please! I want to be able to read the lettering.
> 
> Hellofa knob as well. No chance of accidental slippage with that baby. Is it lighted?


 

 Haha yeah, it is a big knob. It was silver, but I painted it black (not a perfect finish, but good enough for me) and I drilled it for the LED and wired it to the center LED position on the board. It just says "Millett MAX" in the top left, then "Tube/Solid State Headphone Amplifier" in the bottom left, "Headphones" and "Volume" under the respective areas, although the knob is so big you can't really see where it says "Volume" unless you're looking from beneath the amp  That's ok though, I know it's a volume knob  I'll try and get some more pictures up later!


----------



## funch

TBomb06 - nice job. Hope you're enjoying yours as much as I am mine. I've been listening with
  a pair of Grado 325is's, and am happy to report that what is said about the synergy with the
  MOSFET-Max is true. The amp tames the aggressive brightness of the Grados, while still letting
  the good stuff (clarity/dynamics) come through.
   
  Well, it appears that my earlier report of my amp quitting was a bit premature. When it happened,
  I was using my diyMod with an LOD cable and cap box that I had just built. Turns out that the
  problem was with the LOD not latching properly in the iPod, causing a loose connection.


----------



## rarebear

Is there any room to back the board back from the front of case?
  I was thinking I would have make a knob that the knob locking screw was on a small shoulder and was locked to shaft from the inside and you dont see the screw hole in the knob?
   
  Looks like the board fits the case like a glove..
  I guess it was designed to fit it and not much room for any mods?
   
  I had plans on the knob I wuld have made to place a small drill spot and fill with paint and lay out a few other drill spots around as dial as a volume sale some think you can try...
   
  IE: make a graphic in photoshop with layout holes and print it
  Then use rubbing glue or tape to hold it to face plate and center punch holes form shaft loaction and have dots say ever 30º to mark volume level then center puch and drill shallow spots...


----------



## BoilermakerFan

There is an ~8" deep version of the Hammond case.  The stock BOM chassis is approximately 6" deep.  I don't have the part number, you'll have to look it up on Mouser by inputting the stock number then backing out to the catalog page to find the extended version's part number.


----------



## rarebear

There are also vinyl graphic makers that use a plotter (large computer printer) with a cutting blade to make vinyl graphics.. These are cheap like maybe a a buck each, when you make a sheet full of many opposed to one..  They are like the custom graphics you see on car windows the last few years here in the south not sure if they are all over the USA
   
  You can visit Sawmillcreek.com they have a grapic or engraving done with a Craftsman bench type or full blown Shop Bot like my friend Steve has..
*Engravers Forum *cnc engravers
*Sign Design and Fabrication*  Plotters
   
  Dozens of guys that do this as a hobby and PT Job if any one is looking for engraving or to fancy up your face


----------



## jdkJake

Quote: 





funch said:


> Well, it appears that my earlier report of my amp quitting was a bit premature. When it happened,
> I was using my diyMod with an LOD cable and cap box that I had just built. Turns out that the
> problem was with the LOD not latching properly in the iPod, causing a loose connection.


 

 That's actually GREAT news funch. Glad to hear it was something so trivial. 
   
  I agree with your Grado comments, although I do not have the 325, it does wonders for the 225 and HF-2.
   
  Things have calmed down enough on the home front so that it looks to be a grubdac weekend! Hope to have a fully "tricked out" MOSFET-MAX by Monday.


----------



## jdkJake

Quote: 





boilermakerfan said:


> There is an ~8" deep version of the Hammond case.  The stock BOM chassis is approximately 6" deep.  I don't have the part number, you'll have to look it up on Mouser by inputting the stock number then backing out to the catalog page to find the extended version's part number.


 
   
  The 8 inch deep version(s):
   
  http://www.mouser.com/Search/Refine.aspx?Keyword=546-1455T2201


----------



## BoilermakerFan

Quote: 





jdkjake said:


> The 8 inch deep version(s):
> 
> http://www.mouser.com/Search/Refine.aspx?Keyword=546-1455T2201


 
   
  Thanks, but I wasn't going to spoon feed him, I was going to make him be the *Y *in DIY.


----------



## rarebear

Here is image of a dial I was thinking of...
   

   
  I think the set screw holes would look better on the inside 
   
   
   
  You all are killing me with the kindness ...
   
   
  I have no plans of building any amps right at this moment..
  I am thinking about a Beta 22 but since SkyLab thinks its not a whole lot better than a Dark Voice and same price and no labor I just my buy Dark Voice amp but nothing in stone yet... 
   
  I may make a rack and some of those pointy brass feet for my equipment  that they use on high end amps? Is the purpose? Or is it just to get air space under the case or some other high tech reason?
   
  ENJOY


----------



## jdkJake

Quote: 





boilermakerfan said:


> Thanks, but I wasn't going to spoon feed him, I was going to make him be the *Y *in DIY.


 
   
  Point taken.
   
  Guess I am an old softy....


----------



## BoilermakerFan

Quote: 





rarebear said:


> Here is image of a dial I was thinking of...
> 
> 
> 
> ...


 
   
  A RK27 shaft will be long enough to accommodate that design.  It will work fine. 
   

 Skylab has auditioned more equipment than most guys can dream about, he's well respected, and a friend, so I respect his opinion though I haven't heard a Dark Voice.  The big point of contention with a B22 is that they go up in smoke so easily.  Even very experienced builders have had a B22 go up in smoke while commissioning a new build.  Even if you buy one already assembled and tested, there is a risk of damage occurring in shipping.  Then just forget to turn off the power to your B22 just once before unplugging your headphones and you'll never forget again as you'll be pulling bad parts off the boards, then chasing down the ones hiding after you think you have all the badly charred parts replaced.
   
  The cone feet concentrate the weight and make the amp or rack very stable and minimize vibration.  If the rack is designed correctly to distribute the weight properly, a 3-point tripod is a better base than 4-points, but if too much weight is on one side, it will tip over.  If your making  them, why not use bronze?  It's a much denser metal and less brittle than brass.


----------



## TBomb06

Well, one thing I can say after listening to my MOSFET Max for a few days is that it sounds just incredible with my SR225's. Slightly more bass than my BJT version (which was built with parts known for good bass), and the highs seem to be a little more pronounced than with my BJT version. This is just my take, and is definitely not scientific. I just know it sounds so good I have to stop myself from turning it up so loud that I end up damaging my ears . I love the way this amp sounds with my Grados for the music I listen to. Guitar riffs are right there in your face, the drums are so tight and clear, and the bass punches through really well. One other thought on the aesthetics of the amp...the BJT build with the 1" heat sinks and the Muse ES caps looks downright puny compared to this one with the 1.5" sinks and the big Silmic II caps. It looks like it means serious business, which I love. Great work Tom, Colin, and all the others who have helped make this project so awesome!


----------



## rarebear

I was looking at some systems and really liked the racks as I never seen one..
  They seem to be all square with a X shape I guess so there is lots of air around systems
   
  I just finished SkyLabs review of the Beta 22 and for the money almost you can buy a Dark Voice and not have build it.. Thanks for the info on the Betas burning..
   
  Oh what size is the shaft?


----------



## jdkJake

* sigh*



 Look up the part number from the BOM. There are multiple distributors. Their web sites will give you the exact dimensions.


----------



## the_equalizer

Quote: 





boilermakerfan said:


> SNIP
> 
> Then just forget to turn off the power to your B22 just once before unplugging your headphones and you'll never forget again as you'll be pulling bad parts off the boards, then chasing down the ones hiding after you think you have all the badly charred parts replaced.
> 
> SNIP


 

 Hmmm.. not good       I was thinking about building a B22, but if it requires such delicate treatment, I guess I'll pass for the time being.
   
  cheers!


----------



## BoilermakerFan

Quote: 





the_equalizer said:


> Hmmm.. not good       I was thinking about building a B22, but if it requires such delicate treatment, I guess I'll pass for the time being.
> 
> cheers!


 
  Dig into it, they might have come up with a fix, but I know of two B22s that went up in smoke at meets because cans were unplugged from powered up amps.  TBH, for the money, I think other amps can be built that would sound as good and deliver more power or they are cheaper to build for the same amount of power.  A PassDIY F5 comes to mind.  It will need resistors on the headphone jack to protect it from the shorts too, but it should be more robust than the B22.


----------



## rarebear

I need to finish a small lathe job and will have time to make some knobs next week..
   
  I have some 1 3/8" brass and was thinking of making a rare wood and antiqued brass knob or just something quick out of aluminum to get some opinions..
   
  I'll up up the shaft size but I guess its a 1/4"
   
  Anyone know if there are any designs styled like this I might use as a reference?


----------



## TBomb06

Quote: 





boilermakerfan said:


> Dig into it, they might have come up with a fix, but I know of two B22s that went up in smoke at meets because cans were unplugged from powered up amps.  TBH, for the money, I think other amps can be built that would sound as good and deliver more power or they are cheaper to build for the same amount of power.  A PassDIY F5 comes to mind.  It will need resistors on the headphone jack to protect it from the shorts too, but it should be more robust than the B22.


 

 I believe AMB said that as long as you turn the volume all the way down before you unplug them, it shouldn't be a big deal. I think it's a safe practice to turn the volume all the way down when you plug/unplug headphones on a powered up amp anyway. And it's only if you use a TRS jack,  not if you're using something like XLR.

  
  Quote: 





rarebear said:


> I'll up up the shaft size but I guess its a 1/4"


 

 Close. It's 6mm.


----------



## jdkJake

So, you know the old adage? Measure twice, cut once? Learned that one again today.
   
  I built my grubdac for my MOSFET-MAX today. The build went fine (documented on the grubdac thread). Works well, sounds good so far.
   
  When I went to install it into my MOSFET-MAX, I learned something, very, VERY important. While the BantamDac and GrubDac are the same size physically, the placement of the USB connector differs between the builds (DOH!). I had drilled my MOSFET-MAX panel to the template that matches the BantamDac, as such, the USB jack does not line up correctly. So, fair warning to everyone else, determine which DAC you want to include (if any) and cut appropriately.
   
  No bitterness, this is my mistake. I have not yet decided how to fix it. I am hoping for divine guidance or some inspiration. Feel free to jump in!   Normally, re-drilling the back panel would be no problem, but, I used those cheap-ass voltage monitoring jacks, which, are one time use. So, removing the back panel to re-drill is a royal pain as I will have to replace those jacks as well. I'll figure something out. Probably have to use a pig-tail though the existing hole. We shall see. Not optimum, but, it will work and avoid rework at this point. I want to live with the DAC for a while and see what I think of the sound as compared to my Keces and y1.
   
  Anyway, here is a shot of the test configuration (which I do not condone, open voltages and such).
   

   
  The front panel switch is set to switch the input and power up the DAC at the same time. The switch is in place of the L1 ferrite, which I actually had in line until the bead itself cracked under the physical stress. I ended up removing it for now until I can get a replacement. Not sure what the effect will be overall on the sound beyond lessing the total amount of noise reduction on the +5 input. I will fix it on my next mouser/digikey order (maybe).
   
  How does it sound? At first, the bass was WAY big and sounded out of balance. As the amp warmed up and the DAC got a bit of burn-in, that seemed to change. The bass is still big, but, the upper end is opening up. I need to listen to it more. I also need to get it off the netbook that is providing the signal and see how it sounds on the main rig. So far, it sounds like a Wolfsen. I am partial to Burr-Brown, so, time will tell. Got to love the packaging though! This AMP is ready for ANYTHING. Bring it on...


----------



## tomb

Well, I'll have to take credit for some of this mistake.  Obviously, the templates I've provided on the MOSFET-MAX website do not take the grubDAC into account, yet.  I thought they were in relatively the same position as the BantamDAC, just MiniUSB on one and USB-B on the other, but I guess you're saying it's not that simple.
	

	
	
		
		

		
			




   
  Colin is re-designing the BantamDAC for a Mini-USB and the same PCB planform as the grubDAC, so maybe that will simplify things in the future.  Sorry, I know that doesn't help you now.


----------



## BoilermakerFan

Use a cheap Harbor Freight nibbler tool and cut out a small rectangular area of the mistake and the area where the correct hole should be.  Head to your local hobby shop and buy a piece of 0.083" aluminum sheet.  Trim it at least 3/16" over size or more and carefully rough up the back, inside edge of the Hammond panel and the edge of the insert.  JB Weld it in place or better yet, use the Magnum Steel putty and clamp it in  place so the magnum Steel oozes out of both sides.  Filet or chamfer the inside edge of the cutout so it looks more finished and fold it over the back side of the insert.  If you do it correctly, you'll have a thin layer of Magnum Steel between the chassis and the fill plate, plus it over laps enough to bond on the edges of the Hammond back and the over lap locks it in place.  The Magnum Steel is strong.  I used it to encase the cracked oil drain on my cheap DeVilbiss "7HP" air compressor to keep it running for as long as I could.  That was in '04 or '05.  It's still going strong and has yet to crack further.  Air compressors are subject to extreme heat and cooling cycles and vibration, so if it holds a compressor block together, I think it will serve your needs well.


----------



## BoilermakerFan

You have one other option...
   
  Use said nibbler to cut out the back for a L-Conn USB B connector and mount it up.  Remove the miniUSB jack from the Grub and drop the leads into the PCB on the Grub.  You'll have to use the 8" deep chassis though so it will fit, but you can more than likely salvage the rear panel and connectors if you have at least 2" of play in the leads.  If you cut them short, SORRY!
   
  Here's my AudioSector NOS USB DAC in the 6" deep Hammon case for reference:


----------



## jdkJake

No worries TomB!
   
  It is always on the builder to double and triple check these things. Sleep well. I will figure it out. Worse comes to worse, I will just re-drill another back panel. I want to move some things around anyway and maybe add a bypass out to allow me to chain to another amp. 
   
  It is all good. Part of the adventure!


----------



## jdkJake

Thanks for the tips BoilermakerFan.
   
  I am leaning to a combo of the two approaches. In other words, remove the jack, wire to a panel mounted version. Clean up the back panel.
   
  I bought a second grubdac to build another switch box that would allow me to use it across multiple devices. I may just re-build that one for the MOSFET-MAX and re-purpose this one for the switch box (which I have yet to build). So, in any case, I should be good to go. They both need similar switch controls.
   
  Where did you source that L-Conn USB connector? 
   
   
  BTW, Nice work on the AudioSector. What do you think of the sound? I am always pining to try a NOS design.


----------



## tomb

"L-com" is the actual name:
http://www.l-com.com/productfamily.aspx?id=1393
   
  I've bought several of them, but never used them.  It's a great suggestion by BMF, but be forewarned: these things are about three times bigger than you think they are.


----------



## Aalelan

Well I have to say I noticed the USB thing before I cut, but when I made my own measurements I still got the hole in the wrong place   Far as I can tell with the default layout on the max site, you have to get it up almost touching the bottom RCA jack to make a nice square hole..  I think I will redo the back of mine sometime and change things up a little..  I have some scrap Al 1/8" plate laying around I can make end caps out of..
   
  Out of town for the weekend but I will post some pics of the cased up beast when I get home.. I just need to get my acrylic top part made and I will be done.   Then I will start doing more tweaks to it


----------



## BoilermakerFan

Quote: 





tomb said:


> "L-com" is the actual name:
> http://www.l-com.com/productfamily.aspx?id=1393
> 
> I've bought several of them, but never used them.  It's a great suggestion by BMF, but be forewarned: these things are about three times bigger than you think they are.


 
  Damn, somehow managed to insert a horizontal line and now I can't delete the person, so I'll work above it...
   

 L-Conn, L-Com, whatever.  
	

	
	
		
		

		
		
	


	




  I knew Tom would post a link.
   
  This is one that came through the Toole/tomb small group buy, to me by way of Mr. Toole.  It is big, but damn are they nice! 
   





  I only have 30-40 minutes of time on the AS NOS USB DAC.  The BGs are nowhere near burned it.  Even so, it is a sweet DAC.  It might measure with higher Jitter, but I sure as hell don't hear it.  Maybe I just like Wow and Flutter so my brain tunes it out.  Killer bass, just an enjoyable sound, but it was the last kit.  He only has a fully assembled unit left.  He's working on a balanced 24/192 NOS DACs right now.  Once it's up to his standard, he'll make the boards and I'll be receiving a Paypal invoice for a USB and SPDIF versions.    Then my systems are done.  Other than a custom TT and Pearl 2 phono stage, there isn't anything else I expect to add other than things already on the project list.  My DACs are covered with those new balanced units from AS.  Nice to see a light at the end of the tunnel and realize it's _not _a train.


----------



## jdkJake

Room with a view: Temp digs for the grubdac...
   
  So, I came up with a temporary mounting point for the grubdac. The trick is to "move uptown" and exploit the room the case supports. I am using a cable pigtail to provide the USB connection. Luckily, the case for the MOSFET-MAX is big enough to accommodate a variety of mounting options (and the grubdac is so incredibility small). This will suffice until I can evaluate the DAC and decide how I want to rectify the situation long term. Good stuff!!
   
  Some pics:


----------



## rarebear

Just noticed the USB cable on the Capistor?
   
  If you would like some sheet metal let me know , I have a few gauges of SS and some carbon steel if you want to try and make a bracket..
  I think I have some brass too...


----------



## jdkJake

Thanks, but this is just a temporary fix at best.

 I just want to be able to evaluate the part before I make any extensive changes to the casework.


----------



## Aalelan

Not really related to the MAX but,anyone have a good suggestion on a small speaker tube amp setup?  say ~5-10w per channel?
   
  Thanks!!
   
  AA


----------



## FallenAngel

http://pmillett.com/
  Quote: 





aalelan said:


> Not really related to the MAX but,anyone have a good suggestion on a small speaker tube amp setup?  say ~5-10w per channel?
> 
> Thanks!!
> 
> AA


----------



## BoilermakerFan

Quote: 





aalelan said:


> Not really related to the MAX but,anyone have a good suggestion on a small speaker tube amp setup?  say ~5-10w per channel?
> 
> Thanks!!
> 
> AA


 

 Buy - Decware Taboo or Mini Torii.  DIY - An Octode from AJ van Dorn.  I'm working on a 10W version.  As designed it's a 40W/ch amp, but I have 10W OPT iron that has the 8200R primary impedance needed for the design.  It was in AudioXpress and John Broskie wrote about it in TubeCAD.  Basically you get a SET sound with the speed and power of pentode P-P.  There are other great amp designs on diyAudio too.  The Red Light District and it's variations being a hugely popular amp.


----------



## Aalelan

OK, I have my Max MOSFET built and LOVE IT!!!  I have 4 Elna Silmic II coming in to do a recap of CA2 and CA7..  Soon as I get that in (hope tuesday night) and get the lexan top on I will post some new pics..
   
  I have a question though..  I'm pretty good a following instructions and building things, even things I don't really understand (like this amp  )  Can anyone reccomend a amps for dummies 101 kinda book/site that applies to tube amps and hybrids like this?  I want to better understand the stages and what affects what..
   
  Thanks guys!!
   
  AA


----------



## BoilermakerFan

Pete Millet's site that FA linked will have you buried in reading material for months.  Seriously.  Start there.  Also, start reading John Broskie's TubeCAD Journal.
   
  http://www.tubecad.com/


----------



## Aalelan

Thanks BoilermakerFan, I should have just started there earlier like you said for my other question..  well I know what my bedtime reading is going to be for a while 
   
  Thanks again!!!
   
  AA


----------



## BoilermakerFan

Quote: 





aalelan said:


> Thanks BoilermakerFan, I should have just started there earlier like you said for my other question..  well I know what my bedtime reading is going to be for a while
> 
> Thanks again!!!
> 
> AA


 

 I'll drop you a PM to keep this thread from going more OT.


----------



## funch

Here's how I'm setting up a Grub in my MOSFET-Max.
   
   




   
   
  I moved the Grub board over and drilled 2 new mounting holes.
   








   
   
  Spacers are two 4/40 flat washers per hole.
   
   












   
   
   
   
   
  As you can see, my RCA's use the unsulating washers, so that places the bottom one lower than normal.
   
  FWIW


----------



## jdkJake

Nice. Very clever!
   
  How the heck did you make that hole on the back panel for that mini-b jack??? 
   
  I gotta know how you did that.
   
  BTW, your grub is missing a few key parts.


----------



## funch

Missing parts? Whatdya mean? It works fine.  OK, I lied. Just thought the pix would be clearer without
  the cap's in the way.
   
  Here's how I did the hole. I put a piece of masking tape on the inside of the back panel, mounted the
  panel, then slid the board with the Grub mounted on it into the amp and against the tape to make an
  impression of where the jack would hit the panel. Then I drilled two 5/32' holes side by side, and used
  some small hobby files (Harbor Freight) and a lot of patience to shape the hole.
   
  BTW, the little bugger fired right up (after I installed the cap's).  I'm listening to it as I type, and it's sounding
  pretty good for no bigger than it is.
   
  More pix:
   
















   
  I've since done the tweak from the website by replacing the electrolytic cap's with 330uF FM's.


----------



## jdkJake

Ingenious! Thanks for sharing that technique. I like where you put the grub LED as well.

 Yeah, for the size and price, I am pretty impressed with the grub. I have a set of replacement panels in the house, so, I am going to go ahead and redo my back panel make everything fit properly. It would be nice if it were not the middle of summer. My garage shop has extremely limited summer hours.


----------



## tomb

Very nice, funch - exactly how it's supposed to work!


----------



## funch

Quote: 





jdkjake said:


> My garage shop has extremely limited summer hours.


 


      Tell me about it. I live in the Phoenix area. Who needs a sauna when I've got the garage! 
   
   
       tomb - Thanks for the nice word.


----------



## Aalelan

In my need to tinker and play I picked up a pair of 12AJ6 tubes (since they are compatible) and tried to use them tonight..  I turned my trimmers for the tube bias all the way down and install the tubes.. fire it up and sound!  I let it warm up for a little bit and start moving up the bias and set it at 13.5 (well at least on one side).  Here is the thing, as I turn up the volume the bias goes up and hits a point where it distorts out.. ( I also have a set of external mid size speakers jacked into the MAX)
   
  What is causing the bias to raise with the volume knob?  Do I have wonky tubes or what?
   
  Thanks for all your help, I'm still learning 
   
  AA


----------



## tomb

Quote: 





aalelan said:


> In my need to tinker and play I picked up a pair of 12AJ6 tubes (since they are compatible) and tried to use them tonight..  I turned my trimmers for the tube bias all the way down and install the tubes.. fire it up and sound!  I let it warm up for a little bit and start moving up the bias and set it at 13.5 (well at least on one side).  Here is the thing, as I turn up the volume the bias goes up and hits a point where it distorts out.. ( I also have a set of external mid size speakers jacked into the MAX)
> 
> What is causing the bias to raise with the volume knob?  Do I have wonky tubes or what?
> 
> ...


 

 "Compatible" is a huge stretch when it comes to the 12AJ6.  The pinouts, heater and plate voltages may be the same, but the similarity ends there.  The amplification factor is 55, almost four times the high gain of the 12AE6.  An amplification factor that high quickly outstrips the voltage supply in the buffer and all sorts of weird things happen.
   
  My guess is that you didn't check the other tube and would've found that as the bias rose on the one, it would proportionally drop on the other.  That's what will happen with a 12AE6 if you crank the volume knob up past three-quarters turn.  It's just that it happens almost immediately with the high gain of the 12AJ6
   
  I can't explain the actual phenomenon, but needless to say, the amp won't work with that tube.


----------



## Calku

I moved the right input to make room for the usb. Obviously that left an unsightly hole, but at least its on the backside. Unfortunately I don't have any replacments to remake the back panel. They are only sold in packs of 10, so the empty hole is here to stay. Next up is to replace the KZs with Elna Silmics at CA2 and CA7, and maybe buy a new camera.  I would post more pictures, but they all came out blurry and very crappy.


----------



## funch

Calku - I would say that mounting the RCA's as you did is the best solution if one
  was going to mount either DAC in the Max. I did what I did on mine because I had
  already mounted my RCA's.


----------



## jdkJake

Calku, how come you did not bring out any of the test points? How are you biasing the tubes?


----------



## Calku

Quote: 





jdkjake said:


> Calku, how come you did not bring out any of the test points? How are you biasing the tubes?


 


 I was too lazy and too anixous to get it done so I could listen to it.  Initially I biased the tube with the top off for a few days.  Once it was stable, I buttoned it up.  Since then, I've open it up a dozen times replacing caps, resistors, adding the grub, and fixing the grub a couple times.  So I always check the bias then, and it's been good.  I still have a few things I want to do before I call it complete, so I may add the test points to the list.


----------



## tomb

There was a time when _no one_ used tip jacks on the old Millett Hybrid.  A lot of people simply ran them with the top down (removed).  I'm afraid the Millett MAX set a new standard, but there's nothing wrong with running one old school.


----------



## jdkJake

I hear what you are saying, but, you gotta love the convenience of those tip jacks! 
   
  I guess I like to roll tubes too much for old school. Although, I seem to have calmed that vice a bit.


----------



## jdkJake

So, I am no funch, But I am not above stealing ideas from him!  
   
  It was cool enough to work in the garage this weekend thanks to endless rains. So, I was able to remake the panels for my MOSFET-MAX to fit the GrubDAC. It is now where it belongs:
   
   

   
   
  Nice and tight...
   

   
  So, here is where I steal the great installation idea funch had.  Of course, I do not have his superb patience and skill to make the USB hole perfect, but, it is good enough for jdkJake.  
   

   
  Imitation is the greatest form of flattery right? Thanks funch!! I love the form and function of this mounting. 
   
  I owe you a cold one (or two). Heck, I owe TomB, Collin and CobaltMute a couple of cold ones as well.
   
  Next CanJam maybe?


----------



## funch

Thanks, Jake, for the nice comments. Your amp looks great!  TBH, I don't think the planet could handle another 'me'.


----------



## tomb

Very nice, Jake!  That's the way it's supposed to work - great job!!


----------



## jdkJake

Okay, since I finally finished my updated switchbox, I figure it is time for a family portrait. 
   
  This is my mighty Millett setup (I know, should have cleaned up and dusted down the kids before taking the picture, oh well):
   

   

   
  As you can see, the Hammond enclosure is the theme de jour'. The top boxes are my DIY MOSFET-MAX and Whiplash MiniMAX. The bottom boxes are my DIY Gamma2 and DIY passive switchbox (take2).
   
  Take your pleasure. Two amps, two DACs, tubes tailored to service both high and low impedance phones as desired. Nice.
   
  Sounds even better than it looks!


----------



## funch

Oh, Lawdy I hate when I do dumb stuff!
   
  To this point, I've only used my MOSFET MAX with low-impedence cans (Grado 325 and Denon 2000). Tonight, I tried it
  with my HD600's since I sold the other two, and noticed some distortion. After a little research, I discovered that I installed
  QB2 and 3 backwards. Well, forward on the silkscreen, which is backward for the circuit. So, off goes another order to
  Beezar! Hope I didn't mess up anything else. It did sound great with the Grado's and Denon's, even with the oops though.
   
  BTW, nice stuff Jake!


----------



## jdkJake

Well that is certainly interesting. That ended up swapping the drain and source of the JFET. I am somewhat surprised it worked as well as it did. Current would generally flow from source to drain on the n-channel. Time to read up on JFETs to learn why that still worked.

 BTW: thanks!


----------



## tomb

Not sure I understand why either. 
	

	
	
		
		

		
			




   
  Those were great pics back there, btw - Jake!


----------



## funch

OK folks, I have good news and bad news.
   
  First, the bad. I discovered that I had also installed QB4L and QB6L backwards. Aaaaaaaaaaaaaaaaaaaaaaaaarrrrrrrrrrrrrrrrrrrrrrrrrrrgh!!!! 
  Now, I'm hearing this little voice: "Step away from the soldering iron!!"   Methinks my days (daze?) in DIY are numbered.
   
  Second, the good. I got those two switched around and installed the new QB2/3, and it's sounding wonderfull out of my HD600's. No more
  distortions. Now I'm waiting for the Denon 7000's I just bought to see how they sound.
   
  Amazing that the amp worked with all those goofs. I guess God does watch out for fools.


----------



## jdkJake

Wow, some crazy fortune there funch!

 But, at least it is all settled out and you are up and running. For that, I am very glad to hear.

 Since it worked, it makes me wonder how many other amps out in the wild might be built like that as well.


----------



## Lil' Knight

Quote: 





jdkjake said:


> Okay, since I finally finished my updated switchbox, I figure it is time for a family portrait.


 

 Looks great there.
   
  Do you have the part number of that Neutrik USB jack? The one on Neutrik's site makes me confused.


----------



## jdkJake

lil' knight said:


> Do you have the part number of that Neutrik USB jack? The one on Neutrik's site makes me confused.






 http://www.mouser.com/ProductDetail/Neutrik/NAUSB-W-B/?qs=sGAEpiMZZMvdqMP%2faZ%252bGClXWRDJ%252b0qCv

 They have a silver version as well.


----------



## Lil' Knight

Thanks.


----------



## funch

So... I'm thinking of venturing forth again and building a BJT Max and am looking for advice
  on output devices that would work best for HD600's.


----------



## jdkJake

How about:
   
  http://www.molex.com/pdm_docs/sd/010182031_sd.pdf
   




   
  Seriously, this should be good to see what people comes back with. 
   
  BTW, if you do decide to go the socket route, drop me a PM, I have some BJT's for you to try out that I would love to hear your opinion on.


----------



## funch

Like these? http://www.mouser.com/Search/ProductDetail.aspx?R=10-18-2031virtualkey53810000virtualkey538-10-18-2031
   
  That 's a great idea Jake. Thanks.


----------



## jdkJake

That be them.

Sachu used them on his EHHA Rev A. I thought it was great idea as well.


----------



## W-Moran3

Hello All,
  I’m very close to being able to test my first build (Millett Hybrid MOSFET-MAX V1.2).  Procuring all the parts has been an adventure and I think I put in 2 orders each to Mouser, Digi-Key, Beezar, Parts Express and 2 trips to Fry’s!  
  Mouser did not have VRM1 and VSR1 in a 24V Output Voltage version as in the BOM (Mouser [size=8pt]512-MC78L24ACP[/size]).  I was able to get the [size=8pt]MC78L15ACP[/size]  from Mouser which has an Output Voltage of 15V and a Max. Input Voltage of 35V  (vs. the 24V Output/ 40V Max. Input spec of the original).  I also tried the alternative Digi-Key part BD13916STU-ND, but it came in a TO-126 package (not the TO-92 package).
  Can I get up and running with the 15V Mouser part (512_MC78L15ACP) or should I wait and keep trying to track down something closer to the original Fairchild Semiconductor MC78L24ACP?  What are the implications of using the 15V part short-term and long-term?  I'm anxious to test out the build; but definitely do not want to trash all the work invested. Thanks in advance for any guidance.


----------



## jdkJake

Well, the design is for a 24V part. I would not attempt to use the 15V part.

You do not have to go with the fairchild version, there are other manufactures of that part. Mouser has the following in stock:

http://ca.mouser.com/ProductDetail/ON-Semiconductor/MC78L24ACPG/?qs=sGAEpiMZZMtUqDgmOWBjgFMGuATcbJe5B%252bkgjn21gvc%3d


----------



## tomb

Quote: 





w-moran3 said:


> Hello All,
> I’m very close to being able to test my first build (Millett Hybrid MOSFET-MAX V1.2).  Procuring all the parts has been an adventure and I think I put in 2 orders each to Mouser, Digi-Key, Beezar, Parts Express and 2 trips to Fry’s!
> Mouser did not have VRM1 and VSR1 in a 24V Output Voltage version as in the BOM (Mouser [size=8pt]512-MC78L24ACP[/size]).  I was able to get the [size=8pt]MC78L15ACP[/size]  from Mouser which has an Output Voltage of 15V and a Max. Input Voltage of 35V  (vs. the 24V Output/ 40V Max. Input spec of the original).  I also tried the alternative Digi-Key part BD13916STU-ND, but it came in a TO-126 package (not the TO-92 package).
> Can I get up and running with the 15V Mouser part (512_MC78L15ACP) or should I wait and keep trying to track down something closer to the original Fairchild Semiconductor MC78L24ACP?  What are the implications of using the 15V part short-term and long-term?  I'm anxious to test out the build; but definitely do not want to trash all the work invested. Thanks in advance for any guidance.


 


 Jake is correct about the relay voltage regulator.  It won't work at 15V - you need to select the 24V one.  Unfortunately, that's the peril in my making such specific BOM's that link directly to a single part: if that part is out-of-stock, it's not intuitive for someone new to the design about where to look.  The key part type in that Mouser Part # string is "78L24".  If you do a Mouser search for 78L24, you'll get a listing of over two dozen!  Just pick one that's a TO-92 configuration and is in stock at a reasonable quantity and price.  The one that Jake listed will work fine, or select this one as another choice:
http://ca.mouser.com/ProductDetail/STMicroelectronics/L78L24ACZ-AP/?qs=sGAEpiMZZMtGzcFJCuAvkS9iXjOH%252bb%2fQ
  (Jake's is cheaper.
	

	
	
		
		

		
		
	


	




)
   
  As for the BD-139, that's a total mistake which I will correct NOW.  I apologize for that.  The DigiKey portion of the BOM has not been vetted.  The design does not use a BD-139 anymore - either at the headphone relay or the input relays.  The BD-139 along with a Zener diode was the old design that AMB used in his E12 design.  With the MOSFET-MAX, all of that was replaced with the 78L24 voltage regulator, along with 24V relays (instead of 12V).  The parts collection is simpler, cheaper, and at the higher voltage, the spikes ordinarily seen with an E12 device on shutoff disappear.  It's an improvement all the way around.  It can even be implemented on the MiniMAX using the existing MiniMAX PCB (how I tested it prior to MAX V1.2 PCB production).


----------



## tomb

Here's a pic of the same circuit on the MiniMAX.  I used a DIP socket in case I had trouble and could easily change back to a 12V relay instead of the new 24V relay.  As you can see, the biggest thing that's required is to replace the BD139 with a TO-92 78L24.  The right hand pin goes to the ground pad of DM1 (DM1 and RM2 are deleted).  Unfortunately, both CM1 and CM3 (the electrolytics) need to be upgraded to 35V ratings - the standard issue with the MiniMAX won't work at the higher voltage.





 As stated, this removes the voltage spikes often seen at turnoff with previous delay circuits. Cetoole (his design) and I surmised that the higher voltage on the relay causes the contacts to close much faster and more forcefully than on the lower-voltage relays, reducing the potential for transients. There are upgraded diodes with transient suppression capability provided for on the MAX V1.2 PCB as well, but these are needed for the best longevity of the contacts, not to reduce the measurable transients at the headphone jack.


----------



## H22

excited.....


----------



## FallenAngel

You were right Tom, I put a pair of 5087 instead of 5088 on one of the channels, a few things screwy there, replaced the transistors and everything is working perfectly now.


----------



## tomb

Quote: 





fallenangel said:


> You were right Tom, I put a pair of 5087 instead of 5088 on one of the channels, a few things screwy there, replaced the transistors and everything is working perfectly now.


 

 Glad to hear you found the mistake!


----------



## tomb

Quote: 





h22 said:


> Just got the red board and a grub DAC in the mail today! thanks Tomb ,still waiting on mouser and handmade. May need to get different caps for CA4&5 as the ones i oreded from handmade are right at the minimum (1000uf).
> 
> Getting eited though, thanks Tomb!


 

 Well, you don't really need audiophile caps at CA4 and CA5 - those are power caps.  Panasonic FC's, Nichicon UPW's, or best choice - Nichicon UHE's are preferred.  Something 1800uf or bigger is preferred.


----------



## H22

Quote: 





tomb said:


> Quote:
> 
> 
> 
> ...


 

 That's kind of what i figured, I was hoping to use the good caps in all positions, but not a big deal, as these are not directly in the signal path i am not too worried about it, I made the mouser order, sans the large caps, and only realized i might need to make another order when i tried to get the larger value silmic's. Will put in an order for some UHE's tonight.


----------



## H22

Well, got the grub DAC put together, and pat of the Millett max. Still waiting on mouser & handmade, but so far looks good.


----------



## jdkJake

Are you building a MOSFET or BJT version?

If you are building MOSFET, you really need to review the following page as I fear you have some rework ahead of you:

 http://www.diyforums.org/MOSFET-MAX/MOSFET-MAXmosfets.php


----------



## tomb

Quote: 





jdkjake said:


> Are you building a MOSFET or BJT version?
> 
> If you are building MOSFET, you really need to review the following page as I fear you have some rework ahead of you:
> 
> http://www.diyforums.org/MOSFET-MAX/MOSFET-MAXmosfets.php


 

 Yes, if he's using the JFETs (2SJ74 and 2SK170), then he needs to turn QB2-L/R and QB3-L/R around backwards.


----------



## MrDavis

I'm glad I saw this, I think I would have made the same mistake.


----------



## H22

Quote: 





tomb said:


> Quote:
> 
> 
> 
> ...


 
  Hmmm, really, looks like someone did not read the directions carefully enough. Good catch guys and thanks for the heads up! I looked at the pic, but completely failed to notice the reversed orientation. Oh well, where is the fun in all of this if you don't get to use some wick once in a while. 

  
  The grub seems to be ok, all i have done so far is just plug it in but my laptop recognizes it. The caps from handmade arrived today, and my mouser order should be here tomorrow, so might be testing this over the weekend. I only hope that i can get  the resistors in the correct direction......
   
  Tomb, I just placed an order with beezar for a few more items, and I attempted to get some of the KOA resistors you offer, but they were out of stock. not a big deal, but i got to wondering if those "fancy" resistors really help the amp? would it be a worthwhile upgrade to use them in the signal path?


----------



## tomb

Quote: 





h22 said:


> Quote:
> 
> 
> 
> ...


 
  Hmm ... not quite sure what you're talking about with the Kiwame's, but you should probably shoot me a PM or an e-mail through Beezar.  We can't talk Beezar business on Head-Fi.


----------



## H22

Made some more progress, Mouser order arrived. I did make one mistake when I placed the order though, when I entered the part number for the 100 ohm resistors, a list of several resistors came up, thinking it was just a packaging differance i ordered the cheaper of the two, turns out i should have paid more attention, as they were 100k resistors rather than 100. So, another order went out. However the power supply seems to work fine.


----------



## H22

Well it works! Both the MOSFET max and the grub DAC seem to work just fine. I used elna silmic II 1000uf caps in the signal path, used the wima for C9, and the vitaminQ in the other bypass position. Initial impression was that the low end was not as strong as my minimax with black gates, nor was it as musical, it had an etchy-ness to the top end, and tended to be somewhat simblant. It has opened up and mellowed out a bi with some use, etchy-ness is mostly gone, and the low end is improving, but I still think it is not as fluid or musical as the BJT I built a while ago. I am listening through a set o M-50's. I am hoping it will continue to improve as it burns in, but I also think I might start looking at different bypass caps as well to smooth it out a bit more. Excellent kit and web support though. Thanks.


----------



## jdkJake

h22 said:


> AWell it works! Both the MOSFET max and the grub DAC seem to work just fine. I used elna silmic II 1000uf caps in the signal path, used the wima for C9, and the vitaminQ in the other bypass position. Initial impression was that the low end was not as strong as my minimax with black gates, nor was it as musical, it had an etchy-ness to the top end, and tended to be somewhat simblant. It has opened up and mellowed out a bi with some use, etchy-ness is mostly gone, and the low end is improving, but I still think it is not as fluid or musical as the BJT I built a while ago. I am listening through a set o M-50's. I am hoping it will continue to improve as it burns in, but I also think I might start looking at different bypass caps as well to smooth it out a bit more. Excellent kit and web support though. Thanks.





Interesting. My experience with the MOSFET MAX was that it had a much stronger low end response with my low impedance Grados than the miniMAX. What type of tubes are you using?


----------



## tomb

Quote: 





h22 said:


> Well it works! Both the MOSFET max and the grub DAC seem to work just fine. I used elna silmic II 1000uf caps in the signal path, used the wima for C9, and the vitaminQ in the other bypass position. Initial impression was that the low end was not as strong as my minimax with black gates, nor was it as musical, it had an etchy-ness to the top end, and tended to be somewhat simblant. It has opened up and mellowed out a bi with some use, etchy-ness is mostly gone, and the low end is improving, but I still think it is not as fluid or musical as the BJT I built a while ago. I am listening through a set o M-50's. I am hoping it will continue to improve as it burns in, but I also think I might start looking at different bypass caps as well to smooth it out a bit more. Excellent kit and web support though. Thanks.


 

 You've got to use at least 22R on the output resistors (RB14-L/R) or the MOSFETs will oscillate and contribute to that "etched" sound.  FYI, it's really horrible if you had used KZ's, but try the 22R's - they settle everything out just perfectly.  Unlike the MiniMAX, additional resistance on the output has little effect on detail, but the 22R is enough to tame the MOSFETs for excellent detailed, but smooth highs.  I've built several and the additional resistance on the output is key.  All of mine have Wima's at CA9, VitQ's at CA8, and Elna's at CA2 and CA7.  The Elna's should not require a long break-in period - maybe 24 hrs, that's it. 
   
  Note that the 1.15K for R8 and 11.5K for R9 is important, too.  I think I saw in the other thread you used 1.13K for R8.  R8 actually governs the CCS - R9 only needs to be at least 10X more resistance.  However, 1K results in a CCS current of 0.65.  1.13K results in 0.575, but 1.15K results in 0.565.  jdkjake may be correct in that 2% difference is not significant, but if you went with the older 1K/10K, it's a big difference.


----------



## jdkJake

Quote: 





tomb said:


> Note that the 1.15K for R8 and 11.5K for R9 is important, too.  I think I saw in the other thread you used 1.13K for R8.  R8 actually governs the CCS - R9 only needs to be at least 10X more resistance.  However, 1K results in a CCS current of 0.65.  1.13K results in 0.575, but 1.15K results in 0.565.  jdkjake may be correct in that 2% difference is not significant, but if you went with the older 1K/10K, it's a big difference.


 


  TomB,
   
  In your opinion, is it more critical to get closer to the design point of 0.565 than say a 1% resistor? Does the design spec for the CCS stay consistent over a wide set of tubes (say a 12FK6 vice 12AE6)?
   
  Thanks.


----------



## tomb

Quote: 





jdkjake said:


> Quote:
> 
> 
> 
> ...


 

 No ... because 0.560 is actually the original design point picked out by Pete Millett.  I've still picked a point (0.565) where the resistors are available at economical prices.  The real point is that there is a big difference in performance from the original 1K/10K combination that resulted in a 0.650 operating point.
   
  No - the CCS operating point is only a compromise among the tubes.  Each tube (12AE6, 12FM6, and 12FK6) will have its own optimum.  I don't know what that is, though - but I did test for the differences and the lower number works better with all three tubes.  There is a great possibility, though, that you might find an even better operating point with a given tube.  Even Pete said, "There's nothing sacred about using 0.56mA as the plate current - looking at the plate curves, I thought it looked like a good point to operate the 12AE6 tube."
   
  The original Millett Hybrid used a constant current diode to set the CCS.  However, Colin Toole's design of the MAX/MiniMAX/MOSFET-MAX uses a cascade transistor arrangement that allows us to change the resistors and alter the CCS currents.  Colin had always hoped that people would do some experimentation with the CCS.  Doing so has not been talked about much, but after I saw how much difference it made with Dsavitsk's new Torpedo (coming soon!), I decided to try it out and things worked out great.


----------



## H22

tomb said:


> You've got to use at least 22R on the output resistors (RB14-L/R) or the MOSFETs will oscillate and contribute to that "etched" sound.  FYI, it's really horrible if you had used KZ's, but try the 22R's - they settle everything out just perfectly.  Unlike the MiniMAX, additional resistance on the output has little effect on detail, but the 22R is enough to tame the MOSFETs for excellent detailed, but smooth highs.  I've built several and the additional resistance on the output is key.  All of mine have Wima's at CA9, VitQ's at CA8, and Elna's at CA2 and CA7.  The Elna's should not require a long break-in period - maybe 24 hrs, that's it.
> 
> Note that the 1.15K for R8 and 11.5K for R9 is important, too.  I think I saw in the other thread you used 1.13K for R8.  R8 actually governs the CCS - R9 only needs to be at least 10X more resistance.  However, 1K results in a CCS current of 0.65.  1.13K results in 0.575, but 1.15K results in 0.565.  jdkjake may be correct in that 2% difference is not significant, but if you went with the older 1K/10K, it's a big difference.





 


I'm pretty sure I used the 22R's for R14, I read that R14 was needed and not optional in the MOSFET version, so I used what was on the BOM. Same with the CCS resistors, I ordered extra 1k and 10k, just to have them, but I also ordered and used the 1.13k & 11.3k from the BOM after I read yor post on he minimax thread. I tried to order the 1.15/11.5 resistors, but mouser does not have them in the line that the others are, my thought was that the diff between 1.13 and 1.15 was just not a big enough difference to worry about.

For an update, it has improved greatly with about another 20 hours of burn in. It also seems to helpmif Iet it " warm up " for 10 min or so before I start listening. 
This amp is really starting to make me want to buy a better set of cans though, so I need to start looking at what would be a good can for me, initially the HD650's would seem like a good choice, but I'm a bit of a bass head, so I'm thinking another can might be better. 

Again, amp is sounding great, wish I had the mini here to compare them side by side, but thy will have to wait.


----------



## tomb

Quote: 





h22 said:


> I'm pretty sure I used the 22R's for R14, I read that R14 was needed and not optional in the MOSFET version, so I used what was on the BOM. Same with the CCS resistors, I ordered extra 1k and 10k, just to have them, but I also ordered and used the 1.13k & 11.3k from the BOM after I read yor post on he minimax thread. I tried to order the 1.15/11.5 resistors, but mouser does not have them in the line that the others are, my thought was that the diff between 1.13 and 1.15 was just not a big enough difference to worry about.For an update, it has improved greatly with about another 20 hours of burn in. It also seems to helpmif Iet it " warm up " for 10 min or so before I start listening. This amp is really starting to make me want to buy a better set of cans though, so I need to start looking at what would be a good can for me, initially the HD650's would seem like a good choice, but I'm a bit of a bass head, so I'm thinking another can might be better. Again, amp is sounding great, wish I had the mini here to compare them side by side, but thy will have to wait.


 

 OK - that all makes sense.  Yes, the Millett-type tubes take awhile to warm up.  I think tubes perform better when they're hot, but at the low voltage of the space-charge tubes, it takes longer.  I think best listening is definitely available within 15 minutes, perhaps sooner.
   
  As for a different pair of headphones, I would recommend the K701's or Grado HF-2's for the MOSFET-MAX.  Just MHO, of course.


----------



## Tacoboy

Where currently is the best place(s) to order parts for to build the Millett Hybrid Mosfet Max?


----------



## jdkJake

The BOM has part numbers for Mouser. I would start there.


----------



## Tacoboy

Quote: 





jdkjake said:


> The BOM has part numbers for Mouser. I would start there.


 

 BOM?
  Mouser?


----------



## MrDavis

BOM is Bill of Material.  A.K.A a parts list.  http://www.diyforums.org/MOSFET-MAX/MOSFET-MAXbom.php
   
  Mouser is a parts suppler.  http://www.mouser.com/
   
  The Mouser parts list on the BOM is more up to date. 
  
  Quote: 





tacoboy said:


> BOM?
> Mouser?


----------



## Beefy

Quote: 





tacoboy said:


> BOM?
> Mouser?


 

 Uh-oh......


----------



## W-Moran3

IT WORKS!!!
  I’m so pumped!!!!
  Hooked it up and queued the inaugural song last night.
   . . .
_Everything In It’s Right Place_ by Radiohead.
  1)      I’m a huge Radiohead fan
  2)      It’s the perfect title (if it works)
  3)      I’m a huge Radiohead fan
  4)      IT WORKED!
   
  Although I’m posting this after that first night, I’m still excited that it has been up and running without any problems.  My fabrication skills way outstrip my electrical skills and knowledge.  My previous EE project was one of those kits for a blinking Christmas tree ornament many years ago. So there’s hope to those that are on the fence with respect to starting a build.  I would like to give back to the community. Enclosed are some hits and misses during the project.  Thanks to TomB and jdkJake for their help!


----------



## jdkJake

Congrats on the build! Looks great!!
   
  The lessons-learned is a neat idea. What a great presentation of that material.
   
  I love, Love, LOVE the AutoCAD work! Very, very cool.
   
  Enjoy your amp. I know you will.


----------



## tomb

Holy cow!!  Saying, "a MOSFET-MAX lives 
	

	
	
		
		

		
		
	


	




" just doesn't seem to do that justice.  Very nice AutoCAD work, by the way ... very!!


----------



## HiGHFLYiN9

Quote: 





w-moran3 said:


> Although I’m posting this after that first night, I’m still excited that it has been up and running without any problems.  My fabrication skills way outstrip my electrical skills and knowledge.  My previous EE project was one of those kits for a blinking Christmas tree ornament many years ago. So there’s hope to those that are on the fence with respect to starting a build.  I would like to give back to the community. Enclosed are some hits and misses during the project.  Thanks to TomB and jdkJake for their help!


 
  Nice work and incredible documentation. You have enough there for a magazine article  The preliminary design would actually make a pretty cool looking amp too:


----------



## BobSaysHi




----------



## W-Moran3

[size=11pt]Thanks all, glad to contribute!  Since the build I purchased a set of AKG K702’s (influenced by comments in this thread).  I’ve been breaking them in through a combination of test tones and listening.  I’m enjoying the combination and listening to music very, very much.[/size]
	

	
	
		
		

		
			





[size=11pt]  Yesterday’s mail brought an order of caps.  I plan to upgrade to Elna’s and Nichicon’s in the big cap locations.  Also I’ve been reading through the V-DAC Mod thread.  A few more parts and I’ll be ready to tweak that component also.  Then I’m done . . .  Unless I fry something.  Then I’ll return to the Bantam DAC thread! [/size]
	

	
	
		
		

		
		
	


	


  (I still can’t believe I didn’t zap, cook, short, melt, blow up, flip, invert, wrong part something.  Hopefully the luck will continue.)


----------



## tomb

It gets really frustrating when someone sends me an e-mail with an invalid return address.  I've tried several times with this individual with various spellings and all the replies fail.  So, I'm posting here in the hopes that he'll see it.
   
  The question was what to do about the "MC78L24ACP" regulator being out of stock at Mouser.  I've posted this before, but there's a downside to the BOM's I do with specific links to specific parts.  If that part is out of stock, it may not seem obvious what to do.
   
  Search on Mouser for "*78L24*" and you'll get this:
[size=small]http://www.mouser.com/Search/Refine.aspx?Keyword=78L24[/size]
   
  The very first one in the list says they have 1,565 in stock at 74 cents each.  Further down, there's another one that says they have 5,977 in stock at only 54 cents each.  There are many more besides that.  Just be careful to get a TO-92 version, not something SMD.
	

	
	
		
		

		
		
	


	



   
  Hopefully, he'll see this.


----------



## tomb

Bump - still hope the guy sees this, because I can't get through to his e-mail.  Last try, though.


----------



## W-Moran3

If this is in reference to post # 6253.
  Your post #6255 and jdkJake's post #6254 answered my questions. I was able to order your recommendations from Mouser and the amp has been up and running great for awhile now  Thank you for your help and sorry if I left an open ended thread.


----------



## tomb

No worries.  The person in question got in touch with me.  This was something that happened within the last couple of days and it wasn't you W-Moran3.


----------



## eertelppa

The lessons learnt document is awesome! And yeah very nice auto-cad work.
   
  I think I am going to try and build a mosfet and use with my grados and mainly as an introduction to building amps. I was going to build a starving student, but pcb's are still available for this and the cost is not that much greater. I plan to build my own case and hopefully I can figure a way to mount the tubes higher so they are more visible.
   
  I have a lot of work ahead of me. Ordering from beezar and mouser so trying to get all the mouser stuff in order as I type.
   
  Thanks,
   
  Austin
   
  ps: I was thinking about going with telefunkens or bugle boy 12AU7 for the starving student. Anything similar for the 12AE6, 12AE6A, 12FM6, 12FK6 options out there?
  pps: Also any suggestions on extra stuff to buy or parts to spend a little extra on? I am ordering some extra resistors and for anything super cheap I have been ordering an extra. I think some people splurge on capacitors on some diy projects.


----------



## W-Moran3

Some things to think about to avoid extra shipping charges and trips to the store.  Some are mentioned outside of the BOM and they are easy to forget about while you are excitedly rushing to order all the electrical components.
    1)  Tube Bushings:  Mouser [size=8pt]Part #561-MP10012.[/size]








  2)  3.5mm Stereo Panel Mount Jack:  Parts Express - 090-317   [size=8pt]http://www.parts-express.com/pe/showdetl.cfm?Partnumber=090-317%20%20%20%20%20%20%20%20&FTR=090-317  [/size]For if you want a 2nd sized jack.





  3)  Gold RCA Jack, Chassis Mount:  Parts Express - 091-1120  [size=8pt]http://www.parts-express.com/pe/showdetl.cfm?Partnumber=091-1120%20%20%20%20%20%20%20&FTR=091-1120 [/size]
          There are many alternative manufacturers to check out if you want to.  You can spend way more ($$) than the ~$7 that these go for by looking at higher end products.





  4)  Cabinet Cone Spikes:  Parts Express 240-660  [size=8pt]http://www.parts-express.com/pe/showdetl.cfm?Partnumber=240-660&FTR=240-660  [/size]This is optional.





  5)  Tip Jacks – Insulated Standard Type: 2.00mm.  Digi-Key J320-ND Think about how you want to color code them.





  6)  Knobs:  I ordered 2 kinds so I could touch and feel them.  (I like them both)
          Digi-Key 226-4103-ND  -Mach. Alum. Instra. Knob - ML Model Soft Touch - Matte Black
  [size=8pt]



[/size]        Digi-Key 226-4002-ND  -Mach. Alum. Instra. Knob - OEJ Model - Matte Black
                                                                                                                                                                           
  Other Stuff To Think About
    7)  Hammond Case Color:  Make sure you order the color intended (aluminum or black).  BOM defaults to aluminum.
    8)  Heat Sink Mounting Kit (insulator & hardware).[size=8pt]  http://www.diyforums.org/MAX/MAXheatsink.php  [/size]Suggest getting a kit up front rather than assemble the individual pieces.
    9)  Wiring – I used standard wire to connect the RCA jacks to the ALPS pot.  You could get fancy here with material (Cu, Ag) and insulation types.
  10)  Hardware:  The build suggests some longer case screws for the Hammond case (need to extend threads with a tap). Also remember a PCB standoff solution for the center of the board.
   
  If you haven’t already, read TBomb06’s post #6146. It lists out a good plan to follow.  Good luck and have fun!


----------



## eertelppa

Like OMGawd!!!111!
   
  No but seriously thank you so much for posting. I was worried no one was going to and I told myself I was gonna order everything tonight so in hopes it will ship out tomorrow.
   
  I was planning on ordering from mouser and beezar. Yeah I am missing a lot of things....
   
   
  -I plan to make my own case
  -My checklist:
     -bom (currently at $100 mouser, ordered 1 or 2 extra of anything cheap <.50)
        -first need to double check cause there was like 50 things to order;
        -second need to confirm (if possible) about the 3 or 4 things i had to find alternatives for to make sure they are fine, I have them written down but of course on my desk at home
     -beezar
        -pcb
        -led thingys
        -caps
        -pot
        -mosfet parts
     -all spec
        -soder wick
        -slim nose pliers
        -tweezers
        -flush cutter
        -solder wire
     -tubes (need to see who all made 12AE6 in case I want somewhat fancier ones....I have the notes at home)
     -tube bushings
     -3.5mm stereo panel mount jack
     -gold rca jack
     -cone jacks (? need to research what these are)
     -tip jacks (? need to research what these are)
     -knobs (yeah definitely would like to order ones that I like the look of)
     -heat sink mounting kit (? need to research what this is)
     -wiring (need to see if mouser sells this)
   
  I think I read that post but am going double check. Thanks again for the reply and advice!
   
  Austin
   
  edit: Wow! I just read his post and printed it out. Seems like I was doing a lot of things similar to his suggestions already, which is comforting to know. It also has some really good suggestions and info on starting it up and testing and all that stuff I had no idea about.


----------



## MrDavis

Check out the BOM on the MiniMax and the Millett Max.  It won't take you long to figure out what is missing on the MOSFET MAX BOM.
   
  http://www.diyforums.org/MiniMAX/MiniMAXbom.php
   
  http://www.diyforums.org/MAX/MAXbom.php
   
  I'm almost done building my MOSFET MAX.  Just have to finish the wiring, set and biasing, and then put in its case...


----------



## eertelppa

Whew sometimes I hate being a perfectionist.
   
  Ok so it seems like I am currently about to order from mouser and beezar.
   
  -caps -- need to figure out the cap situation and remove the ones from mouser and get the elna ones from hndme.com.
  ---not sure if i need 2 - 1000uF 25v and 2 - 1000uF 50v or 4 - 1000uF 25V or 4 - 1000uF 50v
  ---buying vitq from beezar
  ---not sure about other caps CA3/4/5/6/9 (currently have ones from mouser in bom)
  -knobs -- one of two things i would order from digikey
  -tip jacks -- not sure what these are but would be the second thing to order from digikey
  -was able to find additional stuff either on beezar or mouser so would prefer not to use digikey for two items
  -cone spikes -- would be only part from parts connection so will hold off
  -heat sink kit -- got 5 of these
  -slo-blo -- added fuse
   
  so besides the caps, knobs (can prob find locally), tip jacks, and cone spikes (optional of course) it seems like I am good to go.
   
  If no replies in the morning I will just get the caps I think are correct (and not get the CA2L/R or CA7L/R from mouser) and order my stuff from hndme, beezar, and mouser in hopes it ships tomorrow.
   
   
  Thanks for all the great advice so far!
   
  Austin


----------



## jdkJake

Tip jacks:

http://www.diyforums.org/MAX/MAXcasework3.php

Suggest you go re-read the various MAX pages (both regular and MOSFET) at diyforums prior to finalizing your purchases and attempting the build.


----------



## jdkJake

Caps:

You need two (2) 1000uf 16V for CA2 (left and right)
You need two (2) 1000uf 35V for CA7 (left and right)
You need four (4) 1800uf 35V (minimum, you can go up to 2200uf if you like) for CA4 and CA5 (left and right).

Again, suggest you re-read the diyforum MAX sites again to get a better idea of the scope of the build as well as to capture the parts you appear to be overlooking.

Also, digikey stocks the Elma RFS line of capacitors if you wish to consolidate your order further and save on shipping.


----------



## eertelppa

Jake,
   
  First of all thank you for the response and advice.
   
  I need to get back to work so I will be quick, but spent the last hr or so reading through all the sections and correcting my items accordingly.
   
  I worded it incorrectly when I was talking about the caps, as I knew which ones I needed but was not seeing those at hndme.com and was curious if others would work.
   
  Now I have the correct ones:
  (2) 1000uf 16V for CA2 (left and right) - elna from digikey
 (2) 1000uf 35V for CA7 (left and right) - elna from digikey
  (4) 2200uf 35V - nichicon (had 8 in cart for some reason so changed to 4)
   
  Ordered the tip jacks per colors and amount as similar to build pictures. Ordered some wire from navships.
   
  Other than that I am fairly confident I did not miss anything. Thanks again for the help as to be honest I flipped through the website but must have always passed up the construction section which seemed to be the most beneficial. Will definately have it by my side during the build.
   
  Regards,
   
  Austin


----------



## ryssen

I cant on the schama how the 6,3 volts for the filamnts are made?
  Hoe is it made?


----------



## Beefy

Well they are 12V tubes for a start (*12*AE6, *12*FK6). So they are wired in-series directly off the 27V power supply, with resistor R1 dropping the voltage down to the correct value.
   
  On the schematic http://www.diyforums.org/MiniMAX/schematic/MiniMAXsch100.png follow V+ (27V) at pin 3 on VTR through pin 4 on VTR through R1, then pin 3 and 4 on VTL through to Ground.


----------



## ryssen

OK now I see it.thanks!


----------



## freethink

Hi, new to this thread (and amp building), and and am hoping to get some help with my Max build.  I finally got it all put together but when I power it up I only get 1.6V to V+.  I do have 36V going to the input on the vreg.  Adjusting RR3 doesn't seem to have much affect on the output voltage, but RR3 does seem to be working according to my meter.  Do you think I might have a bad regulator?  Is there any way to test it without removing it?  Being a newbie at this, I thought I'd seek the wisdom of the group before going through the trouble of replacing it. Any help is greatly appreciated.  I've put a lot of time into this thing up to this point, and it's a huge bummer to not have it working


----------



## funch

I had a similar problem with the heater supplies on my EHHA Rev. A kit from Glassjar. Turns out that I got non-adjustable reg's by mistake. FWIW


----------



## tomb

Quote: 





freethink said:


> Hi, new to this thread (and amp building), and and am hoping to get some help with my Max build.  I finally got it all put together but when I power it up I only get 1.6V to V+.  I do have 36V going to the input on the vreg.  Adjusting RR3 doesn't seem to have much affect on the output voltage, but RR3 does seem to be working according to my meter.  Do you think I might have a bad regulator?  Is there any way to test it without removing it?  Being a newbie at this, I thought I'd seek the wisdom of the group before going through the trouble of replacing it. Any help is greatly appreciated.  I've put a lot of time into this thing up to this point, and it's a huge bummer to not have it working


 

 Tell us what you're building exactly.  Is it the new MAX V1.2 PCB?
   
  If so, the only thing I can think of is that RR3 is bad.  With earlier MAXes that used tantalum capacitors in the power supply, if you got one of them backwards, it would do what you describe.  However, the new PCB doesn't use any tantalums.  You might check CR4 and be certain that you have the polarity correct.  The large stripe on the capacitor plastic wrap signifies the negative side.
   
  The only other thing that you can get backwards in that part of the circuit are the diodes, you might check them, too.
   
  Funch's input is most welcome, but I've never heard of a non-adjustable LM317.  As long as you purchased that as the regulator, I don't think that's the problem.


----------



## freethink

Quote: 





tomb said:


> Tell us what you're building exactly.  Is it the new MAX V1.2 PCB?
> 
> If so, the only thing I can think of is that RR3 is bad.  With earlier MAXes that used tantalum capacitors in the power supply, if you got one of them backwards, it would do what you describe.  However, the new PCB doesn't use any tantalums.  You might check CR4 and be certain that you have the polarity correct.  The large stripe on the capacitor plastic wrap signifies the negative side.
> 
> ...


 


  I'm building the Mosfet MAX V1.2.  I've checked CR4 as well as all 6 diodes and they all are aligned correctly.  RR3 may be bad but it seems like it's working.  I hooked my meter up to it and am getting a range of 1.0 ohm - .99K ohm.  Interestingly, if I bridge the output and adj on the LM317 the amp comes alive and I get ~31V at V+.  I've only done this for 1-2 seconds at a time because I'm worried about sending too much voltage.  I guess I'll try replacing RR3 to see if that does the trick.  Unfortunately I'll have to order one, so it will take a while.  If I wanted to do some troubleshooting with a fixed resister in place of RR3, what size would you suggest? (I'm using the 24VAC PS from the BOM)  Also, I'll try to take a picture of the PS circuit later tonight so I can get some additional eyes on it.  Thanks.


----------



## funch

Quote: 





tomb said:


> Funch's input is most welcome, but I've never heard of a non-adjustable LM317.  As long as you purchased that as the regulator, I don't think that's the problem.


 


 Oops! My bad. Mine was an LD1085. Helps if I know what I'm talking about. :-/


----------



## tomb

Quote: 





freethink said:


> I'm building the Mosfet MAX V1.2.  I've checked CR4 as well as all 6 diodes and they all are aligned correctly.  RR3 may be bad but it seems like it's working.  I hooked my meter up to it and am getting a range of 1.0 ohm - .99K ohm.  Interestingly, if I bridge the output and adj on the LM317 the amp comes alive and I get ~31V at V+.  I've only done this for 1-2 seconds at a time because I'm worried about sending too much voltage.  I guess I'll try replacing RR3 to see if that does the trick.  Unfortunately I'll have to order one, so it will take a while.  If I wanted to do some troubleshooting with a fixed resister in place of RR3, what size would you suggest? (I'm using the 24VAC PS from the BOM)  Also, I'll try to take a picture of the PS circuit later tonight so I can get some additional eyes on it.  Thanks.


 

 Well, it sounds like you tested the problem.  The trimmer must be OK if you can vary it from 1 to 1000 ohms.  The only thing I can think of is maybe you installed the regulator backwards?  Otherwise, it doesn't make sense unless the pads are so messed up on the trimmer that the regulator is not seeing the resistance changes.  A pic will help.


----------



## tomb

Quote: 





funch said:


> Oops! My bad. Mine was an LD1085. Helps if I know what I'm talking about. :-/


 

 No problem - thanks for trying to help.  He wasn't specific, so unless you were intimate with the design, there's no reason you would know that.  Anyway, the desire to help is what makes the Head-Fi community such a wonderful resource.


----------



## freethink

Quote: 





tomb said:


> Well, it sounds like you tested the problem.  The trimmer must be OK if you can vary it from 1 to 1000 ohms.  The only thing I can think of is maybe you installed the regulator backwards?  Otherwise, it doesn't make sense unless the pads are so messed up on the trimmer that the regulator is not seeing the resistance changes.  A pic will help.


 


  I'm pretty sure I've got the regulator aligned correctly.  It really seems like the regulator isn't working correctly.  I hooked my meter leads directly to the ADJ pin and to GND and can dial in a resistance range of 2.0-3.1K ohms.  Does that range sound about right? If it's not a bad regulator, I'm at a loss as to what else it could be considering the input voltage of 36V and the confirmed resistance on the ADJ pin.  Maybe the pics below will help....  I might just run to Frys and pick up another regulator. They carry a NTE 956 which from what I can tell is the same as the LM317??
   
  Thanks for all your help


----------



## freethink

Ok, I've done some more troubleshooting.  The issue seems to be with RR3 or something related to RR3.  If I remove RR3 from the circuit voltage slowly builds to 30V+ at v+.  As soon as I put RR3 back in place voltage drops to next to nothing.  It doesn't seem to matter where RR3 is set, just placing it on the board causes voltage to drop.  When I test RR3 with my meter just on a breadboard I can dial the resistance through the expected range just fine.  Also, just to make sure, I tested replacing RR3 with some fixed resisters that were within the range of RR3, and I get the same result, barely any voltage.  Ugg, this is so frustrating.  I just want to play with my amp 
   
  Update: I was able to get 27V from the PS by adding ~100K ohm of resistance in place of RR3 using a bunch of resisters I had laying around.  Hoping this info helps pinpoint the issue because I'm not sure what to do at this point to fix this.  I guess I either need to figure out what is wrong, or do a work around and replace RR2 with a higher resistance.  On the bright side I was able to set the biases and give it a listen, and it sounded AMAZING!  I can't wait to get this thing buttoned up


----------



## freethink

Ok, I'm a dumba$$....  On the BOM, the Mouser link for RR1 didn't resolve so I added the part on my own, and inadvertently added a 120K ohm instead of a 120 ohm.  Thankfully I stumbled across a LM317 calculator which helped me realize my problem.  I can't believe I did that, but I guess I'm glad I figured it out.  Rock and roll!!!


----------



## tomb

Quote: 





freethink said:


> Ok, I'm a dumba$$....  On the BOM, the Mouser link for RR1 didn't resolve so I added the part on my own, and inadvertently added a 120K ohm instead of a 120 ohm.  Thankfully I stumbled across a LM317 calculator which helped me realize my problem.  I can't believe I did that, but I guess I'm glad I figured it out.  Rock and roll!!!


 

 That's great news!  I apologize, though, because that's the peril of using direct links for parts on my BOM's.  If the part is out of stock, people tend to get lost instead of using a search on the description and/or checking the MAX websites for more detail.  Anyway - glad you solved the problem!


----------



## freethink

Quote: 





tomb said:


> That's great news!  I apologize, though, because that's the peril of using direct links for parts on my BOM's.  If the part is out of stock, people tend to get lost instead of using a search on the description and/or checking the MAX websites for more detail.  Anyway - glad you solved the problem!


 


  I actually did do a search on Mouser, but it was on the part #, not the description, and that's what got me in trouble.  When you search Mouser for 71-RN55D-F-121 the first 2 of 3 results are 120K ohm 
	

	
	
		
		

		
		
	


	




  Bottom line is I should have paid closer attention when ordering.  Thanks for all your help and for everything you do for all the diyforums projects!  I'm loving my MAX and grubdac combo!


----------



## Dan55

Hi all,
   
  I was hoping to get some help troubleshooting my Millett Max. It's been working beautifully for years now, but I recently started losing sound. It started with a buzzing through the 1/8'' jack, then I lost all sound through that jack, and now I don't seem to be getting anything from the 1/4'' jack either. All of the power measurements seem to be fine. I am measuring continuity from IG to OG but not from IL and IR to OL and OR; is this typical? Any suggestions as to where I can start poking around? Thanks so much for the great project and any assistance you can offer.
   
  Dan


----------



## tomb

Quote: 





dan55 said:


> Hi all,
> 
> I was hoping to get some help troubleshooting my Millett Max. It's been working beautifully for years now, but I recently started losing sound. It started with a buzzing through the 1/8'' jack, then I lost all sound through that jack, and now I don't seem to be getting anything from the 1/4'' jack either. All of the power measurements seem to be fine. I am measuring continuity from IG to OG but not from IL and IR to OL and OR; is this typical? Any suggestions as to where I can start poking around? Thanks so much for the great project and any assistance you can offer.
> 
> Dan


 

 You need to be more specific.  What power measurements are OK?  Have you checked the tube bias?  The issues with the 1/8" jack and loss of sound may just be a coincidence.  Unfortunately, the spring contacts in 1/8" jacks are so small that use over time will cause them to lose contact and start inermittently connecting or producing static.  Sorry to say it's a common problem and just something that we put up with (or learn to use 1/4" jacks).  The loss of sound through the 1/4" jack is something different, though.  You shouldn't lose that through bad contacts unless it was put through some serious abuse over a long period of time.  So, I suspect that something else is going on.
   
  If you've been switching tubes in and out over time, it's possible that the bias may be so far off that you wouldn't get any sound.  Then again, you may just have a wire loose in the signal path somewhere.  All the more reason to confirm those measurements and add tube bias and buffer bias to them.  You might double check the terminal blocks, too - those have a tendency to loosen over a period of time, depending on the type of wiring you used and how much torque you put on the screws.


----------



## Dan55

Thanks very much for the response, tomb. I'm measuring 27V for the power supply (V+ to ground), 13.5V for each tube bias (TA2L/R to ground), and 75mV for each DB bias (TB1L/R to TA2L/R). I think the problem is probably in the signal path somewhere, particularly the 1/8'' input jack I'm using that is connected to the back of the board. The initial buzzing I was getting was affected when I moved the wires from this jack to the board around a bit.  If I plug an interconnect into that jack, though, I'm still measuring continuity between the interconnect and the input pads at the front of the board, next to the pot. I'm not sure if this indicates that the input jack is okay.
   
  The output jacks are the only part of the amp that have seen heavy usage. I have not replaced the tubes and the source remains connected to the input jack.
   
  Sorry for the lack of specificity. I'm a bit stumped and posted hastily yesterday when I lost all output and had to start using my computer's audio jack! Please let me know if there are anymore measurements I can take to narrow down the problem.


----------



## tomb

Quote: 





dan55 said:


> Thanks very much for the response, tomb. I'm measuring 27V for the power supply (V+ to ground), 13.5V for each tube bias (TA2L/R to ground), and 75mV for each DB bias (TB1L/R to TA2L/R). I think the problem is probably in the signal path somewhere, particularly the 1/8'' input jack I'm using that is connected to the back of the board. The initial buzzing I was getting was affected when I moved the wires from this jack to the board around a bit.  If I plug an interconnect into that jack, though, I'm still measuring continuity between the interconnect and the input pads at the front of the board, next to the pot. I'm not sure if this indicates that the input jack is okay.
> 
> The output jacks are the only part of the amp that have seen heavy usage. I have not replaced the tubes and the source remains connected to the input jack.
> 
> Sorry for the lack of specificity. I'm a bit stumped and posted hastily yesterday when I lost all output and had to start using my computer's audio jack! Please let me know if there are anymore measurements I can take to narrow down the problem.


 

 OK - it sounds like there's an issue with this 1/8" jack you're using.  How about getting rid of that and connect some RCA jacks with new wire into the input terminal block?  If your only source connector is through an 1/8" mini-jack, then get a convertor patch cord.  It's pretty easy to find mini-to-RCA convertor patch cords at Walmart and other places.  Doing this would at least confirm there's nothing wrong with the MAX.


----------



## Dan55

Thanks so much for the help, tomb. The problem is indeed with the output on my DAC. I was using a second output on the DAC for another amp and it didn't occur to me that the output jack I was using on the DAC was just as likely to have gone as the input jack on the amp. I'll try troubleshooting the DAC for a while before bothering AMB with my newb questions.
   
  The amp remains flawless and sounds even better after having had to listen to my computer's audio for a few nights. Thanks again!


----------



## ryssen

I wonder what the sound difference beetwen mosfet and Bjt´s are.Anyone kompared the 2?


----------



## tomb

Quote: 





ryssen said:


> I wonder what the sound difference beetwen mosfet and Bjt´s are.Anyone kompared the 2?


 

 Well, sort of obviously ... I have built both and listened to both.  Fundamentally, with a high-impedance phone, the MiniMAX (or BJT MAX) is superior and probably has more headroom.  However, with low-impedance phones or small speakers, the MOSFET-MAX is superior.  I would define low-impedance as 32 ohm Grados and high-impedance as 300 ohm Sennheisers.  Between those two limits, it gets much more difficult to tell the difference.  Also, both will do pretty d*mn good with the other's optimum.  IOW, a MiniMAX (or BJT MAX) will still do pretty good with Grados, while a MOSFET-MAX will do OK with Sennheisers.  It's just that they're not necessarily optimum at that.
   
  The MiniMAX can deliver 50ma in Class A to a low-impedance load.  At the same time, the MOSFET-MAX can swing as much as 11.5V in either direction for a high-impedance load.  This is in the opposite direction of the optimums for both amps, yet both of these values exceed the limits of many solid-state amps (especially portables).
   
  The MOSFET-MAX is probably less successful with high-impedance than the MiniMAX is with low-impedance.  But there's not many things that can drive to low-impedance headphones with as much power and detail as a MOSFET-MAX.  Other MOSFET-output DIY headphone amps can deliver more power, perhaps. but not with a tube front-end, AFAIK.  The MOSFET-MAX has the potential of delivering almost 1.25W, if necessary, with certain settings.


----------



## ryssen

Thanks for the explantion,I will then build a BJT as I have the Sennheizer HD650.


----------



## chadbang

I'm just wondering if I'm imagining things (I don't think so) but I use my Millet Maxed (BJT) and work. It sounds okay for the first three hours of so, and then it sort of seems to "bloom" with bass and sounds warmer and fantastic. I've noticed this every day for two weeks. Anyone else have a similar experience. Is this amp just very slow to warm up? Cause when it does...wow. i'm in heaven.


----------



## tomb

Quote: 





chadbang said:


> I'm just wondering if I'm imagining things (I don't think so) but I use my Millet Maxed (BJT) and work. It sounds okay for the first three hours of so, and then it sort of seems to "bloom" with bass and sounds warmer and fantastic. I've noticed this every day for two weeks. Anyone else have a similar experience. Is this amp just very slow to warm up? Cause when it does...wow. i'm in heaven.


 
  A couple of things -
  1. Yes, for some reason - maybe that they're low-voltage tubes - the Millett-type tubes can take a long time to warm up for the best sound.  That said, I would say the peak is ordinarily an hour, not 3.  However, some tubes may vary longer than that, it all depends.
  2. You might check your tube bias during the period you describe - maybe once an hour.  You may find that the tubes "float" a bit in bias over a few hours and perhaps there's some sort of optimum bias point that results in the sound you enjoy.  I've seen some tubes continue to drop their bias by a few tenths of a volt for several hours.


----------



## ryssen

As I am building a Millet Max BJT I wonder how tall the heatsinks should be,and how many mA I should bias it to?


----------



## tomb

Quote: 





ryssen said:


> As I am building a Millet Max BJT I wonder how tall the heatsinks should be,and how many mA I should bias it to?


 

 Normal method with BJT's is to bias to 50ma (110mV on the test points) and use 1" tall heat sinks.  This is what we do on the MiniMAX.  However, I've had reports from one builder who claimed to notice a difference when biasing the BJT's to even higher currents on the regular MAX.  If you use 1-1/2" tall heat sinks, you could bias all the way up to 125ma, which is the recommended bias for a MOSFET-MAX.
   
  The MAX (as opposed to the MiniMAX) uses the Hammond 1455T1601 as the recommended case.  It will accomodate 1-1/2" heat sinks if you want to use them.  Don't forget to make the power supply heat sink 1-1/2", too.  It will draw much more current - in fact, there's a bias point where the heat of the power supply sink actually takes over as the hottest part on the PCB.  If you bias up that high, you also need to use a 1000ma walwart (WAU24-1000).  We depend on the higher current rating to give us those extra few volts to 27VDC at the V+ point on the PCB.  If you stay with the lower current rating walwart, there will be enough current most likely, but you'll lose a couple of volts to stay in regulation.  (When adjusting the power supply trimmer, notice the voltage point where you can't adjust any higher, then back off by at least 1 to 1.5V.  That's your maximum voltage to keep the power supply in regulation, as in _low noise_.  Typically, you should be able to get to 28-28.5VDC, then back off to 27VDC as the final setting.  If you turn the bias current up past 50ma and don't use a higher current walwart, you won't be able to get this much voltage.)
   
  Lastly, remember that BJT's will drive into thermal runaway if you're not careful.  They aren't as tolerant as MOSFETs at high currents and temperatures.  Those biases above should work with the taller heat sinks, but you need to be very careful that you don't push them higher while you're adjusting/setting things.  What will happen in thermal runaway is that as the BJT's heat up, they'll draw more current on their own.  If they draw more current, then they heat up even more, which makes them draw more current ... and if this continues, things get nasty pretty quick.
	

	
	
		
		

		
			





  Also remember to check the bias  with the case lid on (using more tip jacks on the back or some other method). BJT's will run hotter closed up (MOSFETs do the opposite).  So - always keep an eye on things, wait on the BJT's to heat up each time with small increases in bias current, and GO SLOW.
   
  Good luck!


----------



## ryssen

Is seems hard (Impossible) to find a WAU24-1000 för 220V that I have.I am going to use a 30VA torid,if that is allright? (I have to use a bigger case)


----------



## tomb

Quote: 





ryssen said:


> Is seems hard (Impossible) to find a WAU24-1000 för 220V that I have.I am going to use a 30VA torid,if that is allright? (I have to use a bigger case)


 

 Oops.  I didn't realize you were outside the US.  Sure - 30VA at 24VAC should be more than enough.


----------



## funch

Has anyone here tried the MOSFET Max with Thunderpants?


----------



## tomb

Quote: 





funch said:


> Has anyone here tried the MOSFET Max with Thunderpants?


 

 Not specifically with the actual Thunderpants, but remember cetoole designed it (the MOSFET-MAX).  He let me audition a couple of orthos with it (modded Yamaha's and modded older/retro Fostex) - not to mention that I owned the TR50rp's myself until Smeggy talked me into selling them to him (availability was low at the time and he needed the raw materials for his thunderpants).  The thing to remember is that depending on the tube and the bias setpoint (which can vary), you can swing up to 12V plus or minus at a minimum of 125ma (1.5W) - and that's just in Class A.


----------



## scootsit

Quick question. I'm just finishing up my Mosfet Max, and am starting on the casework. The diagrams are a little confusing to me. Should I be drilling out the top and bottom of the case or just the top? It would make sense that it be both so that air flows through the case, but hey, what do I know? Anyway, any help would be appreciated!
  Thanks!


----------



## scootsit

One more stupid question. On the Max 1.2 board, I've noticed that the silk screening for the trimpots have a little bit of a shape to one side. I assumed that went to the back of the trimpot. I understand that it won't matter as the trimpots are linear, but it will effect the way I turn the trimpots for adjustments. Is the side with the two "bumps" the back of the trimpot or the front?
  Thanks, yet again!


----------



## tomb

Quote: 





scootsit said:


> Quick question. I'm just finishing up my Mosfet Max, and am starting on the casework. The diagrams are a little confusing to me. Should I be drilling out the top and bottom of the case or just the top? It would make sense that it be both so that air flows through the case, but hey, what do I know? Anyway, any help would be appreciated!
> Thanks!


 

 You should drill both.  Make certain that you have rubber feet that allow the air to circulate from underneath.  It would be a waste to drill holes in the bottom and then lay it flat on a surface, covering the holes up.  There's a boundary layer in effect, too, so get rubber feet as tall as you can.
   
  If you're enterprising, there's no need to duplicate the drill pattern that's used on the top.  You can simply drill some 1/4" holes somewhat spread out on the bottom.  You should have more "free area" on the bottom than on the top, though, so get out your calculator and add up the circular area of the holes.  The top is based on 3/16" diameter holes, so - each 3/16" hole is 0.0276 sq.in.


----------



## tomb

Quote: 





scootsit said:


> One more stupid question. On the Max 1.2 board, I've noticed that the silk screening for the trimpots have a little bit of a shape to one side. I assumed that went to the back of the trimpot. I understand that it won't matter as the trimpots are linear, but it will effect the way I turn the trimpots for adjustments. Is the side with the two "bumps" the back of the trimpot or the front?
> Thanks, yet again!


 

 Yes, meaning the back of the trimmer is the side with the glue - not the writing.


----------



## scootsit

Tom, as always, thanks a ton!


----------



## scootsit

I'm glad I just re-read a few pages of this forum. I installed my QB2/3 backwards. Oh well, I had more I wanted to do anyway.
   
  So. Now, for my stupid question of the day: What are the pads labelled IS 1/2 for? They are in back by the input relays. I looked through a bunch of pictures and can't seem to find anyone using them.
   
  Also, why would you want to bypass the fuse on the power input? That's just out of curiosity.
   
  Thanks again!


----------



## jdkJake

Quote: 





scootsit said:


> So. Now, for my stupid question of the day: What are the pads labelled IS 1/2 for? They are in back by the input relays. I looked through a bunch of pictures and can't seem to find anyone using them.
> 
> Also, why would you want to bypass the fuse on the power input? That's just out of curiosity.


 


  IS 1/2 is where you can wire a switch for switching between the two separate inputs. A simple SPST switch can be used to switch between two input sources. As an example, here is how I switch between the RCA input jacks and an internally mounted GrubDAC:
   

   

   
   
  As for the fuse question, I would highly recommend using one, however, the board supports the option of not using one. Saves you a bit of money and complexity I suppose. IMHO, penny-wise, pound-foolish not to use one. Always highly recommended.


----------



## scootsit

Wait, I thought the relay circuit made the switch unnecessary.
   
  I am using the fuse, I was just curious why one would not want to.


----------



## tomb

Quote: 





scootsit said:


> Wait, I thought the relay circuit made the switch unnecessary.
> 
> I am using the fuse, I was just curious why one would not want to.


 

 A switch can potentially add noise through cross-talk in the contacts.  The relays do this as well, but it's controlled much better and with the right circuit, is well below the S/N ratio of the amp.  As far as the MAX V1.2 PCB is concerned, the switch is required.  You will never be able to switch to the RCA inputs if you don't use the switch and the relay scheme - unless, of course, you bypass the entire arrangement.
   
  As for the fuse - to be honest, I was against it in the beginning and that's why I suggested to cetoole that he keep the option of feeding power through either way.  I'm not aware of another amp that uses a fuse on the PCB when it's fed with a walwart power supply.  Fuses are absolutely needed if the amp is fed directly from wall power, but that's not the case with the MAX.  So it seemed to cause more problems than it helped in the early going.  I was a complete convert, though, because over the years, it's proven to be a good thing.  I thought it only protected the walwart, but experience has shown it protects the entire amp when builders have screwed the diamond buffer.


----------



## scootsit

Tom,
  With the newest board, the switch is necessary? I didn't realize that. I assume any SPST switch will work. Which set of contacts are used when the switch is opened/closed? Sorry for being such a drain, I'm just a little confused.
   
  Thanks as always for all of your help.


----------



## tomb

Quote: 





scootsit said:


> Tom,
> With the newest board, the switch is necessary? I didn't realize that. I assume any SPST switch will work. Which set of contacts are used when the switch is opened/closed? Sorry for being such a drain, I'm just a little confused.
> 
> Thanks as always for all of your help.


 

 If you populate the input relay-switching, the default (relays de-energized) is only one of the signal input punchdown blocks.  You can never change the input to the other punchdown block unless you throw the switch.  Something is needed to energize the relays to switch to the other input - that "something" is Switch S1.  There are only two terminals, so it can be any old SPST switch - as long as it isn't momentary - that would be quite irritating.
   
  I believe the left input punchdown block is the one that is in the circuit with the relays de-energized, but you can't really tell once it's wired in and if you've used a toggle like I did (no way to physically tell ON or OFF), so don't take that as gospel.  Maybe jdkJake knows which is which.  Here's my 2nd prototype (production PCB's are RED):
   
  



   
  EDIT: the two white wires curving around behind the heat sink are the wires to the two-position terminal block for Switch S1.  I used long wires on mine so I could mount the switch on the front plate.  It's easy to tell the output wires from the BantamDAC going to the left-hand input punchdown block.  The orange, purple and black wires come from a "test" pair of RCA jacks.  So, two input sources - one the onboard BantamDAC (could now be a GrubDAC or SkeletonDAC, too) and the other to a standard pair of RCA jacks, whichh could be connected to anything.
   
  The two mini-relays are energized in an either-or fashion by throwing the switch.  However, one of the relays is energized by default when the power is on to the amp.  The resistors are there to sink an un-used relay's output to ground, which cuts down on the cross-talk between the contacts.  Both are fed from a TO-92 linear regulator at 24VDC.  The jumper is there because cetoole (the designer) didn't want to break the groundplane above the signal traces.  There is also a suppressor diode that works better than the old 1N4148 to cut down on the potential arcing between relay contacts and will promote long-life in the relays.
   
  The relay circuit changes were also incorporated into the output relay-delay circuit for headphone protection.  The old Zener-diode and high-power transistor arrangement with its legacy in the e22 design is gone.  Instead, a single TO-92 linear regulator is used and the headphone relay is 24V.  This change significantly cut down on the transient voltage that many people see at cut-off.  (The time delay prevents headphones from seeing any transients on power on, but power off has always been a bit of an issue with headphone delay-relays.)


----------



## scootsit

Got it now. Thanks so much! One more (hopefully final) trip to radioshack!


----------



## funch

Yes, the input nearest the corner is the one activated with the switch 'off ' (de-energized).


----------



## scootsit

Thanks funch.
  Another Millet Mosfet will soon be living. I'll post pictures shortly! My casework is somewhat lacking, unfortunately. But, I can't wait to get this sucker going.


----------



## scootsit

I seem to be finding conflicting stories. Are the output resistors (RB14) necessary or not on the Mosfet Max?


----------



## funch

They can be jumpered, used to reduce gain, or tailor the sound.
   
  Check tomb's post #9, line 5 under the 'treble' heading in this thread:
http://www.head-fi.org/t/573516/bass-tweaks-for-the-marvelous-millett-hybrid-max


----------



## Beefy

Quote: 





funch said:


> They can be jumpered, used to reduce gain, or tailor the sound.


 

 I recall that they are absolutely required for the MOSFET Max in order to prevent oscillation.


----------



## scootsit

Thanks guys. The BOM said optional, but I recalled seeing elsewhere that they were mandatory.


----------



## tomb

Quote: 





scootsit said:


> Thanks guys. The BOM said optional, but I recalled seeing elsewhere that they were mandatory.


 

 Sorry, but Beefy is absolutely correct.  You need a minimum of 22R to keep the MOSFETs from oscillating.


----------



## scootsit

Can I see a picture of how you guys routed the wires for your biasing contacts?
  Thanks!
  -Scott


----------



## funch

Post #6110.  http://www.head-fi.org/t/233941/new-millett-hybrid-maxed-amp/6105
   
  Just run the wires straight back from the solder holes and bring them up through the notch in the back of the PCB.


----------



## tomb

Quote: 





scootsit said:


> Can I see a picture of how you guys routed the wires for your biasing contacts?
> Thanks!
> -Scott


 

 This is from the MAX website for the BJT MAX, but the wiring for metering the buffer bias would be no different:

  





   
  EDIT: Oops - looks like Funch and I were responding at the same time!


----------



## scootsit

Awesome, thanks guys. I searched, but I guess I didn't go far enough through the posts to find that. Last question, what do you recommend biasing the Mosfets to? I saw the range on the website of 176-264mV, and 220-275mV elsewhere. I've got it biased at 180mV to start, but what would be optimal, or is there a page explaining it similar to the one for tube bias?
  Thanks!


----------



## tomb

Quote: 





scootsit said:


> Awesome, thanks guys. I searched, but I guess I didn't go far enough through the posts to find that. Last question, what do you recommend biasing the Mosfets to? I saw the range on the website of 176-264mV, and 220-275mV elsewhere. I've got it biased at 180mV to start, but what would be optimal, or is there a page explaining it similar to the one for tube bias?
> Thanks!


 

http://www.diyforums.org/MOSFET-MAX/MOSFET-MAXsetup.php
   
  It says right in the table, 220-275mV (125ma is max, IMHO).


----------



## scootsit

I see that, and understand that. But, that's a 50mV range. What value in that range is recommended? What determines where in the range is best, etc?


----------



## scootsit

Sorry for all of the bone-headed questions. I've got it now. It's been a long week. Tomb, your patience is incredible and appreciated. Sorry again guys.
  Thanks!


----------



## ryssen

I the setup and Biasing the same for the Mini MAX and the Millet MAX?


----------



## scootsit

The bias points are the same. The values for the output buffer are not. Both are listed on the website:
  http://www.diyforums.org/MAX/MAXsetup.php
   
  If you are building the Mosfet, they have updated the Mosfet values a little further on the page TomB linked to above.


----------



## scootsit

I just biased my Mosfets. It's weird. In order to obtain 100mA, I need to get them to 282mV. It seems weird that they wouldn't be exactly the same as the values on the website. Any thoughts on what I did wrong?


----------



## tomb

Quote: 





scootsit said:


> I just biased my Mosfets. It's weird. In order to obtain 100mA, I need to get them to 282mV. It seems weird that they wouldn't be exactly the same as the values on the website. Any thoughts on what I did wrong?


 
  You can't read milliamps with your meter - not unless you broke the circuit to the MOSFETs somewhere and wired the meter in series with the MOSFETs.  It can't be done without screwing up the PCB.
   
  The whole point about biasing the buffer is that we're trying to achieve a certain value in current: about 125 milliamps.  The way we do that is to measure mV across one of the power resistors that are connecting the MOSFET pairs, which your meter can do quite easily without having to be placed into the circuit.  RB10 or RB11 is 2.2 ohms.  So, if you divide the measurement of millivolts by 2.2, you get the value of current in the circuit in milliamps.  Thus, to have 100ma bias in the buffer, you should adjust RB12 (the buffer trimmer in each channel) until you read 220mV (2.2 x 100ma, I = V/R).  So, right now you have 282mV/2.2 = 128ma. (That's pretty close to 125ma - I'd leave it there.
	

	
	
		
		

		
		
	


	




)
   
  By the way:

 for TB1R or TB2R with TA2R: TB1R with TA2R measures across RB11R, TB2R with TA2R measures across RB10R - take your pick for the Right channel.
 for TB1L or TB1R with TA2L: TB1L with TA2L measures across RB11L, TB1L with TA2L measures across RB10L - take your pick for the Left channel.
  If you try placing your probes across the leads of one of the resistors above, you'll be reading the same thing as those test points.
   
  Looks like I had the English screwed up on the webpage's table for this stuff, so I've corrected that.
   
  P.S. Anytime someone mentions measuring the current on a built PCB, they are more often than not talking about measuring the voltage across a resistor of known value.  The measurement in voltage divided by the resistor's ohm value is the current through that resistor.  Wiring a meter in series within the circuit is always the last choice for measuring current, because you can very easily blow up a meter if the current range setting is exceeded.


----------



## scootsit

TomB, let me reiterate my last posting - your patience and help is spectacular. Thanks so much. A Millett Mosfet lives and sounds INCREDIBLE! I couldn't have done it without your help! Thanks!


----------



## scootsit

Out of curiosity, I noticed you used a nylon nut to support the screw through the center hole. Is there any reason not to just let the case touch the screw and ground the case through that?


----------



## tomb

Quote: 





scootsit said:


> TomB, let me reiterate my last posting - your patience and help is spectacular. Thanks so much. A Millett Mosfet lives and sounds INCREDIBLE! I couldn't have done it without your help! Thanks!


 

 Great!  Another MOSFET-MAX lives!


----------



## tomb

Quote: 





scootsit said:


> Out of curiosity, I noticed you used a nylon nut to support the screw through the center hole. Is there any reason not to just let the case touch the screw and ground the case through that?


 

 It's only a spacer and nylon was just what I had on hand.
	

	
	
		
		

		
		
	


	



   
  Keep in mind, though, that you need more than just the screw and spacers of some type are absolutely recommended - even if it's just a stack of washers to make up the total space.  It's not grounding so much at the center standoff as much as structural support for the tubes.  The PCB will undergo a huge amount of flex - perhaps a damaging amount - if there's nothing to support the board when you plug and unplug the tubes.  Those sockets can be awfully tight sometimes.


----------



## jdkJake

scootsit said:


> TomB, let me reiterate my last posting - your patience and help is spectacular. Thanks so much. A Millett Mosfet lives and sounds INCREDIBLE! I couldn't have done it without your help! Thanks!




Pics?

It is not official without pics!


----------



## tomb

Quote: 





jdkjake said:


> Pics?
> It is not official without pics!


 

 Yeah, you're right.  I suppose I was jumping the gun because we've had a fairly lengthy discussion with scootsit.


----------



## scootsit

I will take some tonight. I'm still biasing the tubes/mosfets and finishing some last minute casework. My output caps are the KZ 100uF, so I had to use a grinding wheel to grind the top of the case down a little bit to make them fit better. I've been listening to it, but it's not quite pretty enough yet. A day or two more and I'll be ready to take some pictures.
   
  Regarding the screw, my PCB is bowed slightly (which is good, otherwise those caps would NEVER have fit). I used a screw, put a few washers and a nut under the head, and then a nut underneath. It just barely scrapes the bottom of the case when you push the board in/take it out. I'm tempted to put grommets right under the tubes, just to disperse the force a little better, but we'll see about that.


----------



## scootsit

I've been using these feet for audio stuff, and really like them, so I'll probably use them on this. They're exactly the same as the expensive audio-purposed ones, but are made for household use (hence being somewhere in the vicinity of 1/4th the price)
  http://www.amazon.com/Sorbothane-Hemisphere-Non-Skid-Adhesive-Durometer/dp/B003IMSIBA/ref=sr_1_3?ie=UTF8&qid=1329880811&sr=8-3


----------



## tomb

Quote: 





scootsit said:


> I've been using these feet for audio stuff, and really like them, so I'll probably use them on this. They're exactly the same as the expensive audio-purposed ones, but are made for household use (hence being somewhere in the vicinity of 1/4th the price)
> http://www.amazon.com/Sorbothane-Hemisphere-Non-Skid-Adhesive-Durometer/dp/B003IMSIBA/ref=sr_1_3?ie=UTF8&qid=1329880811&sr=8-3


 

 Those look great, although a bit expensive, I think.  When you case it up, it helps to have cooling slots in the bottom and tall feet will allow the air to come from underneath.


----------



## scootsit

They are cheap relative to IsoNodes, which are about twice the price for 8. They work really, really well. Anyway, I'm just about done. When I was biasing the power supply, my V+ lead slipped and shorted to the grounding plane, I want to clean off the char marks...


----------



## ModMax

What size is required for the screws to support the PCB in the center & four corners?


----------



## scootsit

4-40 or 3mil.


----------



## scootsit

Hey all, sorry for the delay, it's been a crazy week. I wanted to post pictures of my build.
   
  So, here's the board/view from above. I chose to route the biasing contacts above the board, instead of below because of how low in the case the Mosfet board sits.
  I actually got this as a kit from Glass Jar Audio, which I then modified with parts from Beezar.

   
  Here it is from the outside:

   
  I'm not 100% on those tube protectors. I'll probably spray paint them black, if I decide to keep them, I may just lose them, I haven't decided.
  I also need to cut the shaft on the pot just a little bit. Finally, in this picture, the back plate is not screwed on.
   
  I also intend to add a grubDAC. I built it, but bridged a bunch of contacts, which someone is helping me fix.
   
  Awesome build that yields an awesome amp! TomB is perhaps the most patient, helpful human being on the face of the planet, and I highly recommend that anyone interested give it a shot.


----------



## scootsit

TomB,
  I don't want to suggest that there is anything wrong with the website, but I think there are some minor tweaks to the Mosfet webpage which might make it a bit easier to use, if you'd be interested in hearing them, let me know.


----------



## tomb

Quote: 





scootsit said:


> TomB,
> I don't want to suggest that there is anything wrong with the website, but I think there are some minor tweaks to the Mosfet webpage which might make it a bit easier to use, if you'd be interested in hearing them, let me know.


 

 Yes, I know - the MOSFET-MAX website has been neglected.  There are a lot of things I wanted to put up there but just never had time.  I welcome your comments.  If you can PM me with a "Do-List," I'll do my best to get them up there.
   
  Many thanks for the kind words, by the way.
   
  Oh - I almost forgot: Another MOSFET-MAX lives!


----------



## jdkJake

Now, it is official! 

Nice job!


----------



## scootsit

Thanks, Jake.
  I'm really torn about whether or not to keep the tube protectors. Anyone have any thoughts?


----------



## scootsit

How long did it take for your tubes to burn in, guys? I'm going insane over here trying to bias. I keep thinking I've got it, then it changes on me. I think I've got about 15 hrs on them. Do they need more?
   
  -Edit-
  Nevermind, I found the answer to my questions.


----------



## scootsit

This left biasing is killing me. I leave it for hours, get it set to ~13.5. If I turn off the power and power it back on (I had to move it into a different room) after about 10 mins, the right tube is already settled to ~13.55, and within the hour, settles to 13.5. The left tube on the other hand will sometimes fall all the way to 12.5, or jump to 14.3. I think my left trimpot is bad, I just ordered a new one from mouser, so hopefully that takes care of it!


----------



## tomb

Quote: 





scootsit said:


> This left biasing is killing me. I leave it for hours, get it set to ~13.5. If I turn off the power and power it back on (I had to move it into a different room) after about 10 mins, the right tube is already settled to ~13.55, and within the hour, settles to 13.5. The left tube on the other hand will sometimes fall all the way to 12.5, or jump to 14.3. I think my left trimpot is bad, I just ordered a new one from mouser, so hopefully that takes care of it!


 

 It could very well be a bad tube.  Try swapping them and see if the problem follows the tube.


----------



## scootsit

Will do. I just placed an order with you last night. I might need to order a tube from you, did you ship it yet?


----------



## tomb

Nope - see your e-mail.


----------



## scootsit

I have a question. I was just doing some listening on my Millet Mosfet. I have been really enjoying it (even with one bad tube). Anyway, I was considering grounding my pot to the ground point next to it on the board and was evaluating if it was necessary (my case is already grounded through the center stand-off). I realized that when the volume is all the way up, there is a tiny bit of scratching in the left channel whenever I turn the knob. It sounds like a dirty pot, but this is a brand new RK27, which is sealed, so I doubt that. This is only audible at levels far above anything I would ever listen at and is very faint, so I'm not too concerned. But, I am curious as to why it would only be in one channel. I read that it could be the microphonics of the tubes, particularly since it was in the channel with the bad tube, I changed the tube and it remained. I wanted to switch to lower gain tubes, so I changed both tubes and now it has gone away. This is weird. I do notice a slight hum when I touch the pot so I need to ground it, but I cannot figure out the scratch I heard with the 12AE6As.


----------



## tomb

Quote: 





scootsit said:


> I have a question. I was just doing some listening on my Millet Mosfet. I have been really enjoying it (even with one bad tube). Anyway, I was considering grounding my pot to the ground point next to it on the board and was evaluating if it was necessary (my case is already grounded through the center stand-off). I realized that when the volume is all the way up, there is a tiny bit of scratching in the left channel whenever I turn the knob. It sounds like a dirty pot, but this is a brand new RK27, which is sealed, so I doubt that. This is only audible at levels far above anything I would ever listen at and is very faint, so I'm not too concerned. But, I am curious as to why it would only be in one channel. I read that it could be the microphonics of the tubes, particularly since it was in the channel with the bad tube, I changed the tube and it remained. I wanted to switch to lower gain tubes, so I changed both tubes and now it has gone away. This is weird. I do notice a slight hum when I touch the pot so I need to ground it, but I cannot figure out the scratch I heard with the 12AE6As.


 
  I have heard the scratchiness from time to time - but only when quickly moving the volume knob with certain tubes and capacitors (Black Gates).  As you say, _it's not the pot. _ There is some sort of phenomenon with the tubes that cause the scratchiness under certain scenarios.  Just an FYI, but running the volume knob to maximum with 12AE6's is like going through a black hole.  It's not normal, nor was it ever intended under regular circumstances.  I have seen the signal wave "flip" so that one channel is reversed from the other at high volume settings with 12AE6 tubes.  I suspect the gain outstrips the voltage available in the buffer at max volume without a load - weird things start to happen.  With a load connected (headphones), you will reach driver-blowing volumes much, much lower on the dial before you ever get to where the weird things happen.


----------



## scootsit

Oh, I was not concerned about it for listening purposes, just a weird phenomenon that I cannot explain. Thanks for the recommendation of the FK6s...they're like butta. No going back, and the dampeners seem to really make a difference. ANYWAY, I'll stop hijacking this thread with my non-sequiters and issues. Thanks a TON!


----------



## Beefy

DC from your source can also make the pot sound scratchy.


----------



## tomb

Quote: 





beefy said:


> DC from your source can also make the pot sound scratchy.


 

 Good thought, Beefy!  That would explain why it seems to be heard so seldom and seemingly only with high gain tubes.  Perhaps just a trickle of offset from a source could be enough to induce some scratchiness when racking the volume knob.


----------



## scootsit

Wow, do I feel like an idiot.
  I just searched through this whole thread and found that no matter what, tube bias may vary (once burned-in) by about 1/4V-1/2V. So, I've been driving myself NUTS, trying to get between 13.50 and 13.55V for nothing!
   
  I also was convinced that the Mosfet voltage was varying whenever I adjusted the tubes, and the tube bias varying whenever I adjusted the Mosfets. It only very recently occurred to me that if I removed the top every time to adjust either, that the subsequent cooling would cause all voltages to increase (to some extent) every time, which is exactly what happens. Oy. A few more hours to let everything settle in, and I may FINALLY be done with biasing!!!


----------



## tomb

Yep.  Tubes are often like mules.  They're hard to get going in a certain direction. Once they do, it may be difficult to pull them back.  As you've found, it's effort wasted trying to get the bias precise.


----------



## bruce108

Go easy guys, you're dealing with a techno-nullity.
   
  Question: what is the output current of the MiniMax with the diamond buffer set-up? (I appreciate it will vary with tubes.) I'm asking because, with FK6s, I find this amp a very, very good match with AKG K701s & I'd like to recommend it to people who ask for numbers. I'm asking here because I can't seem to find the figures on the DIY site.


----------



## tomb

Quote: 





bruce108 said:


> Go easy guys, you're dealing with a techno-nullity.
> 
> Question: what is the output current of the MiniMax with the diamond buffer set-up? (I appreciate it will vary with tubes.) I'm asking because, with FK6s, I find this amp a very, very good match with AKG K701s & I'd like to recommend it to people who ask for numbers. I'm asking here because I can't seem to find the figures on the DIY site.


 
  This is not as straightforward a question as it may seem.  The best way to put it is that the recommended setup will Class A bias the output transistors to 50 milliamps a piece.  So, that means at least that much current is available at the output before the transistors would go into a switching mode.  They'll supply much more than that if they enter a switching mode, but the sound quality may suffer.  That still means much higher transient currents may be available for music peaks (like bass thumps).  Beyond that, it's whatever the heat sinks and the walwart will put out before shutting down - or blowing the fuse.


----------



## bruce108

Thanks, Tom, that helps.


----------



## scootsit

Tomb,
  Some time ago, there was a discussion between you and dsavitsk (I think) about low impedance cans and you mentioned the output impedance of the millet mosfet. I found it once and now, no matter what I search, I cannot seem to find it! What is the output impedance of the millet mosfet?


----------



## tomb

Quote: 





scootsit said:


> Tomb,
> Some time ago, there was a discussion between you and dsavitsk (I think) about low impedance cans and you mentioned the output impedance of the millet mosfet. I found it once and now, no matter what I search, I cannot seem to find it! What is the output impedance of the millet mosfet?


 
  The output resistors would easily override any impedance at the buffer's output.  So, take that value (RB14) as the output impedance - 22R.
   
  The important focus of the discussion was that Dsavitsk and I do not necessarily agree with the drive to super-low output impedance in an amplifier.  It's one of the things that can cause Grado's to sound harsh, for instance.  Dsavitsk thinks it has to do with some headphones having a high inherent damping.  Apply such a headphone to an amp with very low output impedance and the result could be over-damping, which can lead to more distortion, not less.  That may be the key to why everyone seems to think Grado's need tube amps (inherently higher output impedance).  It has certainly proved out empirically for both of us.


----------



## Beefy

Quote: 





tomb said:


> The important focus of the discussion was that Dsavitsk and I do not necessarily agree with the drive to super-low output impedance in an amplifier.  It's one of the things that can cause Grado's to sound harsh, for instance.  Dsavitsk thinks it has to do with some headphones having a high inherent damping.  Apply such a headphone to an amp with very low output impedance and the result could be over-damping, which can lead to more distortion, not less.  That may be the key to why everyone seems to think Grado's need tube amps (inherently higher output impedance).  It has certainly proved out empirically for both of us.


 
   
  Indeed, and it is entirely dependent upon the phones. IMHO the low impedance Audio Technicas sound far better from a low output impedance amp. The bass gets all flabby if the output impedance is high.


----------



## scootsit

I remembered being really interested in the debate. I just couldn't find it. That's really interesting and I'm very curious now to build something with really low output impedance and hear the difference. Thanks for the answer, very interesting.
   
  I just picked up some cans with 4.4kohm impedance, there is actually audible sound out of the Millet, which is pretty impressive!


----------



## scootsit

In particular, this reminds me of the claims regarding the O2, and makes me really curious if those claims hold water given real-world, low-impedance cans. BUT, this thread is probably not the place for those considerations.


----------



## tomb

Quote: 





scootsit said:


> In particular, this reminds me of the claims regarding the O2, and makes me really curious if those claims hold water given real-world, low-impedance cans. BUT, this thread is probably not the place for those considerations.


 
  Well, one of the things I had confused for awhile was equating high inherent damping with low impedance phones.  A low impedance headphone does not necessarily mean high inherent damping (it just happens to be true for Grados).  However, high-impedance phones automatically mean that the damping factor will be higher for any amp: DF = Zload/Zout.  The real issue occurs with low impedance phones, which seem to be more prevalent today.  For 300 ohm headphones, the Zout of the amp is always very small compared to the headphones' Z, but at 32 ohms, small changes in Zout can have significant effects on the DF.


----------



## scootsit

I can imagine that it would depend on the sensitivity and the impedance.


----------



## ModMax

Regarding the Millett MOFSET-MAX amp, RA2L/R and RA4L/R call for a 1Kohm Metal Film Resistor.  Is this a requirement, or can a 10Kohm Metal Film Resistor be placed here?  What about a 1Kohm Carbon Film Resistor instead of Metal Film?


----------



## tomb

Quote: 





modmax said:


> Regarding the Millett MOFSET-MAX amp, RA2L/R and RA4L/R call for a 1Kohm Metal Film Resistor.  Is this a requirement, or can a 10Kohm Metal Film Resistor be placed here?  What about a 1Kohm Carbon Film Resistor instead of Metal Film?


 
  I answered this in your e-mail, but just in case someone else is interested in this post:
   
  RA2-L/R serves as the capacitance isolator in the voltage supply line (+) between the tube signal section and the output buffer.  The value is not that critical, but 10K is probably way too much - better to stick in the 1K range.
   
  RA4-L/R serves as the bleeder resistors for the output caps.  You can also assume that they serve to apply current to the output caps to charge them in case there's no load connected (headphones).  You could probably use the 10K here, but you might have to adjust the timing on the relay-delay.  Again, better to keep it at 1K to prevent having to change some of the other things on the amp that have been tested out and tweaked over the years.
   
  Bottom line, neither resistor is in the signal path, nor are they critical if they vary by 10-20% or more.  So, your 1K carbon will do fine.


----------



## preproman

+1


----------



## ModMax

My next step in building my MOSFET-MAX is installing the VitQ caps I picked up from Beezar (http://beezar.com/catalog/product_info.php?cPath=24&products_id=68).
   
  (1) My 1st question is:  Do the VitQ caps have a polarity?  I don't see any markings on the cap case nor have I been able to detect that either lead is connected to the cap case as suggested by other forums online.  Does it matter which direction they are installed?
   
  Also, on the subject of boutique components, my build is as follows:
   
  CA2/CA7 = Elna Silmic II 1000uF 35V
  CA8 = VitQ .22uF 100V
  CA9 = Wima .22uF 250V
   
  (2)  My 2nd question is:  Should I leave CA9 blank with my setup or go ahead and populate with the Wima cap?


----------



## scootsit

Quote: 





modmax said:


> My next step in building my MOSFET-MAX is installing the VitQ caps I picked up from Beezar (http://beezar.com/catalog/product_info.php?cPath=24&products_id=68).
> 
> (1) My 1st question is:  Do the VitQ caps have a polarity?  I don't see any markings on the cap case nor have I been able to detect that either lead is connected to the cap case as suggested by other forums online.  Does it matter which direction they are installed?
> 
> ...


 
   
  1) No.
   
  2) I think so, but Tomb would be better to answer that.


----------



## tomb

1) No.
  2) Yes - populate CA9 with the Wima.  The Elna's play well with the Wima's.  It's only with Black Gates at CA2 should you leave CA9 blank.  Also, don't try to put a boutique film cap back there, either - it will most likely end up cutting out some bass - that includes VitQ's as well.  Up front at CA8 VitQ's are the preferred choice (Sonicap Gen II's are good), but any other boutque film cap that will fit is appropriate, too.


----------



## ModMax

Many thanks, tomb and scootsit.


----------



## ModMax

The PCB assembly is done.  Now on to the casework.  For those who have finished the MOSFET-MAX, any tips/tweaks/tricks regarding the casework you can suggest?  For a little background, I am using the standard Hammond case from the BOM and plan to integrate the grubDAC onboard.


----------



## funch

When I did mine, I mounted two RCA jacks on the left side of the rear panel, one above the other. That caused interference with the Grub, so I would recommend
  that, if you're also installing RCA's, you mount them side by side above the Grub.


----------



## bwshockley

Hello Everyone,
  Very new to DIY Audio, just ordered some parts for a Hybrid Maxed Amp that I plan using at work.  I'll probably get most the little stuff before the PCB board gets here, but I'm taking the chance to organize my work bench.  I'll post some build shots as I move along, and I might have a few questions, but for now I'm just saying hello.
   
  A little background: I've got a master's in aerospace engineering, so I've had some past courses in electrical engineering and basic circuits.  I've had to break out the text book and freshen up a little.  I don't plan on making any deviations from the design, but the engineer in me is curious what each part of the amp does.
   
  I guess that's it for now.


----------



## scootsit

Quote: 





bwshockley said:


> Hello Everyone,
> Very new to DIY Audio, just ordered some parts for a Hybrid Maxed Amp that I plan using at work.  I'll probably get most the little stuff before the PCB board gets here, but I'm taking the chance to organize my work bench.  I'll post some build shots as I move along, and I might have a few questions, but for now I'm just saying hello.
> 
> A little background: I've got a master's in aerospace engineering, so I've had some past courses in electrical engineering and basic circuits.  I've had to break out the text book and freshen up a little.  I don't plan on making any deviations from the design, but the engineer in me is curious what each part of the amp does.
> ...


 

 Welcome! It's an awesome build. Definitely one of the most fun I have done (though not that many), and in the end, you really feel like you've accomplished something! Are you going BJT or Mosfet?


----------



## fc911c

What build do you guys recomend for the HD800, Mosfet, BJT's, Caps??
   
  Thanks


----------



## bwshockley

Quote: 





scootsit said:


> Welcome! It's an awesome build. Definitely one of the most fun I have done (though not that many), and in the end, you really feel like you've accomplished something! Are you going BJT or Mosfet?


 

 I was going with MOSFET.  However, I'm not knowledgeable enough to know which I should lean towards.  I don't have headphones for this yet.  I've been using cheap things that technically work, but will purchase a nice mid-range, closed-back, over-the-ear set for work.  Maybe the ATH-M50(s)?
   
  Any recommendations on either head phones or MOSFET v. BJT?


----------



## tomb

Quote: 





bwshockley said:


> I was going with MOSFET.  However, I'm not knowledgeable enough to know which I should lean towards.  I don't have headphones for this yet.  I've been using cheap things that technically work, but will purchase a nice mid-range, closed-back, over-the-ear set for work.  Maybe the ATH-M50(s)?
> 
> Any recommendations on either head phones or MOSFET v. BJT?


 
  Impedance of the ATH-M50 is 38 ohms.  If you stay with low-impedance phones, the MOSFET-MAX is absolutely the best bet.
   
  One thing you should try to do - order the Toshiba JFET's from http://www.bdent.com  I used to make up and sell a matched quad, but my supplier ran out of the 2SJ74's.  BDent has them at a reasonable price for someone building an amp, but they're way too expensive for me to re-sell that way.  You can read up on the AMB-JFET mod to the MOSFET-MAX here (near the bottom of the page):
http://www.diyforums.org/MOSFET-MAX/MOSFET-MAXhistory2.php
   
  Details on how to mount them are here:
http://www.diyforums.org/MOSFET-MAX/MOSFET-MAXmosfets.php
   
  These can make a huge difference in the response and linearity of the MOSFET version at QB2 and QB3.
   
  The MOSFET-MAX really shines with low-impedance phones, but will do a pretty good job with high-impedance, too.  The limitation is the tubes, but a a pair of 12AE6's will ensure enough voltage swing for the higher-impedance phones.  The key is that the Class A bias on the MOSFET output buffer is at least 125ma and can be pushed to 150ma or more (carefully).  If the phones will use it, it has the capability of supplying perhaps 1-1/2 Watts.   The BJT MiniMAX version is best all-around, but is really optimized for size, convenience, and the custom-machined case.  On the other hand, the full-sized V1.2 MAX PCB offers the flexibility of the onboard DAC and more flexibility with the cap sizes.   I usually steer people toward the MOSFET-MAX for low-impedance and toward the MiniMAX if they want to try all phones and are looking for a complete kit.


----------



## bwshockley

Quote: 





tomb said:


> Impedance of the ATH-M50 is 38 ohms.  If you stay with low-impedance phones, the MOSFET-MAX is absolutely the best bet.
> 
> One thing you should try to do - order the Toshiba JFET's from http://www.bdent.com  I used to make up and sell a matched quad, but my supplier ran out of the 2SJ74's.  BDent has them at a reasonable price for someone building an amp, but they're way too expensive for me to re-sell that way.  You can read up on the AMB-JFET mod to the MOSFET-MAX here (near the bottom of the page):
> http://www.diyforums.org/MOSFET-MAX/MOSFET-MAXhistory2.php
> ...


 
   
  I think I will stick with the MOSFET-MAX version right now, since that is the direction I have already set out on.  I ordered a matched quad set of the Toshiba 2SJ74BL & 2SK170BL from AMB.org and a pair of 12AE6's from you (I think), Tom, along with the v1.2 PCB and other recommended items.
   
  Thanks much for the response.  Getting very excited to start my first DIY AMP.


----------



## preproman

Can the Millett Hybrid MAXed be made into a Balanced configuration - two of everything?  If so will the double the voltage swing for the higher impedance phones - the HD800s specifically?
   
  Also - can you replace the caps with Black Gates or V-Caps?


----------



## tomb

Quote: 





preproman said:


> Can the Millett Hybrid MAXed be made into a Balanced configuration - two of everything?  If so will the double the voltage swing for the higher impedance phones - the HD800s specifically?
> 
> Also - can you replace the caps with Black Gates or V-Caps?


 
  Yes, Head-Fi user "Pabbi1" built one like that several years ago.  There is also no restriction on which brand of caps you use.
   
  EDIT: Corrected "Pabbi1" username.  Also, here is the link to his post of the "FrankenMAX" as he called his balanced version:
http://www.head-fi.org/t/233941/new-millett-hybrid-maxed-amp/2670#post_3518367
  Unfortunately, it looks like the pics are gone.


----------



## preproman

Quote: 





tomb said:


> Yes, Head-Fi user "Pabbi1" built one like that several years ago.  There is also no restriction on which brand of caps you use.
> 
> EDIT: Corrected "Pabbi1" username.  Also, here is the link to his post of the "FrankenMAX" as he called his balanced version:
> http://www.head-fi.org/t/233941/new-millett-hybrid-maxed-amp/2670#post_3518367
> Unfortunately, it looks like the pics are gone.


 
   
   
  Thanks,  yeah the pictures are gone.  I've bee trying to find some compressions of this AMP (balanced or unbalanced) Compared to some of the balanced chimerical amps like the Woo Wa22 and or any other amp it can be compared to.


----------



## preproman

Is a balanced MHM OTL or Transformer coupled?


----------



## tomb

Quote: 





preproman said:


> Is a balanced MHM OTL or Transformer coupled?


 
   
  Unless you count the walwart, there are no transformers in any of the Millett Hybrids - MAX, MiniMAX, MOSFET-MAX or even the Starving Student.


----------



## bwshockley

Speaking of the walwart power supply, I'm looking into alternatives.  I'm not a big fan of blocky, outlet hogging converters, convenient as they are.  I was looking into a different input source without by passing the the two 2200uf capacitor bank or voltage regulator.  I was wanting something that is pretty much self-contained and found the Mean Well EPS-35-36 (http://www.meanwell.com/search/eps-35/default.htm).  It has an adjustable output voltage of roughly 32 to 39 volts DC at 1A.  I'd simply replace everything forward of the power from CR1A on the board, tune it to roughly 33 volts and continue to use the built in voltage regulator to send 27VDC to the rest of the board.  The EPS-35-36 can be had for around $15 online from what I've been able to find.  They are 3" x 2" x 1".  Not exactly small, but not huge either.  Other than moving the bulk for the walwart to inside the amp case, can anyone see a reason this wouldn't work?


----------



## scootsit

Quote: 





bwshockley said:


> Speaking of the walwart power supply, I'm looking into alternatives.  I'm not a big fan of blocky, outlet hogging converters, convenient as they are.  I was looking into a different input source without by passing the the two 2200uf capacitor bank or voltage regulator.  I was wanting something that is pretty much self-contained and found the Mean Well EPS-35-36 (http://www.meanwell.com/search/eps-35/default.htm).  It has an adjustable output voltage of roughly 32 to 39 volts DC at 1A.  I'd simply replace everything forward of the power from CR1A on the board, tune it to roughly 33 volts and continue to use the built in voltage regulator to send 27VDC to the rest of the board.  The EPS-35-36 can be had for around $15 online from what I've been able to find.  They are 3" x 2" x 1".  Not exactly small, but not huge either.  Other than moving the bulk for the walwart to inside the amp case, can anyone see a reason this wouldn't work?


 

 Wouldn't moving the transformer into the case and that close to the tubes introduce noise?
  I did something pretty simple with a regular Millet (not the Max). I got a transformer from radioshack, and put it in a small, vented box. I then basically used a sigma25 (the draw of the Millett is lower than the Max), and boxed those separate from the amp itself. With the size of the input caps, you could probably just put a transformer in a small box that is still separate, but doesn't crowd the outlet, and have all of the regulators, etc on the main board. My thoughts, but I am far, far, far from an expert!


----------



## tomb

Quote: 





bwshockley said:


> Speaking of the walwart power supply, I'm looking into alternatives.  I'm not a big fan of blocky, outlet hogging converters, convenient as they are.  I was looking into a different input source without by passing the the two 2200uf capacitor bank or voltage regulator.  I was wanting something that is pretty much self-contained and found the Mean Well EPS-35-36 (http://www.meanwell.com/search/eps-35/default.htm).  It has an adjustable output voltage of roughly 32 to 39 volts DC at 1A.  I'd simply replace everything forward of the power from CR1A on the board, tune it to roughly 33 volts and continue to use the built in voltage regulator to send 27VDC to the rest of the board.  The EPS-35-36 can be had for around $15 online from what I've been able to find.  They are 3" x 2" x 1".  Not exactly small, but not huge either.  Other than moving the bulk for the walwart to inside the amp case, can anyone see a reason this wouldn't work?


 
  The only way you won't degrade performance with the MOSFET-MAX's onboard linear-regulated power supply is to use one of AMB's Sigma 11 power supplies.  The performance on the MAX/MiniMAX is about 45uV noise.  AMB's is down in the single digits of uV supposedly, but I kind of doubt that you would notice the difference with a tube/tube-hybrid amp (the tubes usually have more noise than that).  In any event, there is no commercial switching power supply that's going to meet those kind of specs.
   
  The Meanwell power supply you've sugested has 200mV ripple (noise).  That's absolutely atrocious for audio, IMHO.  It represents over 4000 times more noise than the MAX V1.2 PCB's onboard power supply (200 vs. 0.045).  It may even be audible (ripple hum) in certain situations, but the performance will be degraded well before that - fat, loose bass, and other artifacts.


----------



## KimLaroux

Quote: 





scootsit said:


> Wouldn't moving the transformer into the case and that close to the tubes introduce noise?


 
   
  It's not a transformer, it's a switching-mode-power-supply. Connect Main AC to one side, get DC on the other.
   
  Quote: 





bwshockley said:


> Speaking of the walwart power supply, I'm looking into alternatives.  I'm not a big fan of blocky, outlet hogging converters, convenient as they are.  I was looking into a different input source without by passing the the two 2200uf capacitor bank or voltage regulator.  I was wanting something that is pretty much self-contained and found the Mean Well EPS-35-36 (http://www.meanwell.com/search/eps-35/default.htm).  It has an adjustable output voltage of roughly 32 to 39 volts DC at 1A.  I'd simply replace everything forward of the power from CR1A on the board, tune it to roughly 33 volts and continue to use the built in voltage regulator to send 27VDC to the rest of the board.  The EPS-35-36 can be had for around $15 online from what I've been able to find.  They are 3" x 2" x 1".  Not exactly small, but not huge either.  Other than moving the bulk for the walwart to inside the amp case, can anyone see a reason this wouldn't work?


 
   
  The problem I see is electromagnetic interference radiating from the SMPS to the rest of the amplifier. These things are not the cleanest components around. The solution is to place a grounded shield between the SMPS and the rest of the amp. You can easily build one using sheet metal. It doesn't have to be air-tight, but is has to be grounded. Here's a picture as example. You can see the shield isolating the PSU in a corner of the enclosure.
   
  Edit: Sorry I did not see tomb's reply... tomb, I think bwshockley wants to replace the wall wart with a SMPS, while _keeping_ the amplifier's on-board linear regulator. The idea is to bypass the diode bridge, but keep everything else. I don't see that as a problem, especially since today's DC wall warts are SMPS anyways.


----------



## bwshockley

Quote: 





kimlaroux said:


> It's not a transformer, it's a switching-mode-power-supply. Connect Main AC to one side, get DC on the other.
> 
> 
> The problem I see is electromagnetic interference radiating from the SMPS to the rest of the amplifier. These things are not the cleanest components around. The solution is to place a grounded shield between the SMPS and the rest of the amp. You can easily build one using sheet metal. It doesn't have to be air-tight, but is has to be grounded. Here's a picture as example. You can see the shield isolating the PSU in a corner of the enclosure.
> ...


 

 Yes, my thought was to not bypass the voltage regulator on the board.  I wouldn't have expected the SMPS to provide cleaner juice than what was there.  I'd only bypass the diode bridge (not needed).  Tom, does this alleviate your concern?
   
  I had two concerns, the first being the EMI and the second heat.  This may not be worth it in the end.  I'd basically section my enclosure in two, isolating both air and EMI for the SMPS.  Ugh.  Maybe I'll build a big ole wireless charging station like the newest Nokia phones.  That's gotta put out a great deal of EMI.


----------



## preproman

Quote: 





bwshockley said:


> Yes, my thought was to not bypass the voltage regulator on the board.  I wouldn't have expected the SMPS to provide cleaner juice than what was there.  I'd only bypass the diode bridge (not needed).  Tom, does this alleviate your concern?
> 
> I had two concerns, the first being the EMI and the second heat.  This may not be worth it in the end.  I'd basically section my enclosure in two, isolating both air and EMI for the SMPS.  Ugh.  Maybe I'll build a big ole wireless charging station like the newest Nokia phones.  That's gotta put out a great deal of EMI.


 
   
   
  bwshockley,
   
  To your knowledge what kind of sound sig. are you trying to achieve with the MHM?  I'm interested in getting (YBM) to build me a balanced one and was wondering how they compare to other hybrid or pure tube amps that's out there as far as performance goes.  Any info or links to reviews of the MHM would be helpful.
   
  I'm just trying to find out what should I expect from this amp.
   
  Thanks


----------



## tomb

Quote: 





bwshockley said:


> Yes, my thought was to not bypass the voltage regulator on the board.  I wouldn't have expected the SMPS to provide cleaner juice than what was there.  I'd only bypass the diode bridge (not needed).  Tom, does this alleviate your concern?
> 
> I had two concerns, the first being the EMI and the second heat.  This may not be worth it in the end.  I'd basically section my enclosure in two, isolating both air and EMI for the SMPS.  Ugh.  Maybe I'll build a big ole wireless charging station like the newest Nokia phones.  That's gotta put out a great deal of EMI.


 
  Yes - I misunderstood and it does negate my post to a large degree.  If you're wanting to ensure something greater than the typical 27VDC setting for a MAX, I can understand that and perhaps this is a good way to go, especially if you don't want to change the voltage rating on the caps.  You would need something with a dependable voltage control to ensure that it doesn't approach 35VDC, the minimum rating on most of the caps.
   
  A couple of things to think about, though:

 If building the MOSFET-MAX, you could easily substitute with all 50V-rated caps and still meet the 35mm height allowance.  In that scenario, casing up a simple AC transformer might be an easier, cheaper option than fooling with a switching supply.
 The MAX power supply was tested and tweaked extensively for a 24VAC transformer or simple walwart (nothing more than a cased-up transformer with ready-made connectors).  Switching supplies have been known to throw out a whole lot of high-frequency noise that the MAX power supply may not be designed to filter out.


----------



## splaz

Is the only concern the plugpack taking up space ?

I do occasionaly see 24v AC transformers with a short mains lead, then a small plastic housing. Also slimline long ones in plastic or metal ones.

They are pretty ugly though, easiest would be to leave it behind a desk or on the floor floating around. If you wanted to re case them though it should be in theory as easy as chopping off and then re doing the plug. But you still have safety measures to consider. Metal chassis should be grounded or made of another material that is double insulated and it will need strain relief/abrasion protection on the mains cable entry. Not quite as difficult though as wiring it all internally. 

Ideally if you go that route, a metal cased transformer should help with shielding and you could more easily bond that to the chassis its going in.

There may be other safety concerns, those are just off the top of my head.

Lastly this is just advice given it may not be safe or legal in your country and should be carried out by someone competent and posessing any qualifications legally required.


----------



## bwshockley

Quote: 





tomb said:


> Yes - I misunderstood and it does negate my post to a large degree.  If you're wanting to ensure something greater than the typical 27VDC setting for a MAX, I can understand that and perhaps this is a good way to go, especially if you don't want to change the voltage rating on the caps.  You would need something with a dependable voltage control to ensure that it doesn't approach 35VDC, the minimum rating on most of the caps.
> 
> A couple of things to think about, though:
> 
> ...


 
   
  My reasoning behind the change is simply cosmetic in nature.  I'm not smart enough to go messing around with higher voltages.  I'd still tune the on board regulator to around 27VDC.  On your second note, that may be more of a concern.  I don't want to introduce any additional noise.  I'll stick with the walwart for now.
   
  preproman - Your question is beyond my knowledge.  I am just looking for an interesting project that provides an amp for some headphones.  I'm no audiophile and wouldn't have the capability to compare or contrast with other amps.  Sorry, maybe someone else can chime in with an answer?


----------



## bwshockley

Well, today was first power on for my MOSFET MAX.  The build was more difficult than my Millet P-P Engineer's Amplifier.  I guess because many of the components are smaller and closer together.  I made two mistakes while building, which I noticed immediately after I did them.  Both mistakes was installing a PNP/NPN transistor backwards.  The first time I thought to myself "Well, that was dumb, the silkscreen is right there to show you the way!"  The second time I just shook my head.  After making the switch TWICE, I was very very careful after that.
   
  I turned all the variable resistors full CW, crossed my fingers, and powered on.  LEDs glowed nicely, nothing popped and I quickly checked the MOSFET Bias'.  With them both reading zero, I adjusted the input voltage to 27.0VDC, adjusted each tube to 13.5VDC - going back and forth to let them "warm up" a bit and adjust to themselves.  Then I started adjusting the MOSFET bias.  At first I didn't think I was doing anything, even though I knew it'd be a jump from zero to something, but I unturned the resistor 15 full turns at least before it jumped to about 80mV.  I set each one at 240mV, rechecked my supply voltage and adjusted, checked the tubes again, adjusted, checked the MOSFETs.  Well, you get the idea.  After about 30 minutes everything seemed settled in for now.  Wasn't as hard as I thought it'd be.  I've got a few connectors coming in the next couple days, so that's as far as I get to go for now.  No actual listening!
   
  But, I did get some materials for my case ordered.  Mahogany and some Alder wood.  Think I'm going with the Alder for this one.
   
  Well, I tried adding some images to my post, but got errors.  I'll try again later.
   
  EDIT: Okay, here is a link to what should be an album here on head-fi.
   
http://www.head-fi.org/gallery/album/view/id/691846


----------



## tomb

Quote: 





bwshockley said:


> Well, today was first power on for my MOSFET MAX.  The build was more difficult than my Millet P-P Engineer's Amplifier.  I guess because many of the components are smaller and closer together.  I made two mistakes while building, which I noticed immediately after I did them.  Both mistakes was installing a PNP/NPN transistor backwards.  The first time I thought to myself "Well, that was dumb, the silkscreen is right there to show you the way!"  The second time I just shook my head.  After making the switch TWICE, I was very very careful after that.
> 
> I turned all the variable resistors full CW, crossed my fingers, and powered on.  LEDs glowed nicely, nothing popped and I quickly checked the MOSFET Bias'.  With them both reading zero, I adjusted the input voltage to 27.0VDC, adjusted each tube to 13.5VDC - going back and forth to let them "warm up" a bit and adjust to themselves.  Then I started adjusting the MOSFET bias.  At first I didn't think I was doing anything, even though I knew it'd be a jump from zero to something, but I unturned the resistor 15 full turns at least before it jumped to about 80mV.  I set each one at 240mV, rechecked my supply voltage and adjusted, checked the tubes again, adjusted, checked the MOSFETs.  Well, you get the idea.  After about 30 minutes everything seemed settled in for now.  Wasn't as hard as I thought it'd be.  I've got a few connectors coming in the next couple days, so that's as far as I get to go for now.  No actual listening!
> 
> ...


 
  Nice work!  The 2nd paragraph in your post describes exactly how firing up the amp should go.


----------



## bwshockley

Question on source selection.
   
  I've decided to go ahead and add in the skeleton DAC to my board.  I'm now reviewing my options for switching sources.  Of course, I could use a simple SPST attached at "IS".  However I was thinking about using the TRS headphone jack as the switch, such that the circuit at IS is normally closed when no analog input is used, selecting the DAC as the source and likewise, open when an plug is inserted into the jack, selecting the analog as the source.
   
  Does anyone have a recommendation for a 3.5mm or 1/4" stereo jack with a built in SPST or even SPDT switch rated at ~27vdc?  Specifically, I'd like something similar to schematic "C" shown here: http://en.wikipedia.org/wiki/TRS_connector#Configurations_and_schematic_symbols Notice the isolation of the switch and the audio connects.
   
  Anyone know of another option if my above fears are true? It'd sure be nice to just have the amp automatically switch sources based on either signal or a plug switch.


----------



## scootsit

Quote: 





bwshockley said:


> Question on source selection.
> 
> I've decided to go ahead and add in the skeleton DAC to my board.  I'm now reviewing my options for switching sources.  Of course, I could use a simple SPST attached at "IS".  However I was thinking about using the TRS headphone jack as the switch, such that the circuit at IS is normally closed when no analog input is used, selecting the DAC as the source and likewise, open when an plug is inserted into the jack, selecting the analog as the source.
> 
> ...


 

 The Max uses relays. I built one with a switched 1/4" plug on my original Millet hybrid, works great. I didn't use relays though, I just had the three channels going through the plug, then when a plug is inserted, they lift off and make contact with the plug. Also, on my Skeleton DAC, there's a tiny bit of noise, which is absent on the Grub. If you have the option, I'd recommend the Grub over the Skeleton.


----------



## tomb

Granted, the SkeletonDAC is not as detailed as the GrubDAC, but the GrubDAC is more expensive.  However, I've built several SkeletonDACs and know many other people who've built them, too - there should not be any "noise."  Outside of that, I agree with your recommendation - assuming someone wants to pay the difference in price.


----------



## scootsit

Quote: 





tomb said:


> Granted, the SkeletonDAC is not as detailed as the GrubDAC, but the GrubDAC is more expensive.  However, I've built several SkeletonDACs and know many other people who've built them, too - there should not be any "noise."  Outside of that, I agree with your recommendation - assuming someone wants to pay the difference in price.


 

 I guess noise is the wrong word. When I connect the SkeletonDAC to the Millett with 14x gain and crank it, there was a little bit of digital gunk for lack of a better word.  It was very faint, but sounded sort of like a 56k modem. Granted, it is 100% imperceptible unless you turned the knob to 11, may have been an issue with my build, but that was my experience. The grub may well have done the same thing, it is in a different amp at lower gain...so I probably should have left that content out.


----------



## bwshockley

Quote: 





tomb said:


> Granted, the SkeletonDAC is not as detailed as the GrubDAC, but the GrubDAC is more expensive.  However, I've built several SkeletonDACs and know many other people who've built them, too - there should not be any "noise."  Outside of that, I agree with your recommendation - assuming someone wants to pay the difference in price.


 

 Hey Tom, any chance you have or are getting more GrubDAC kits?  Or even just the PCB?


----------



## tomb

Quote: 





bwshockley said:


> Hey Tom, any chance you have or are getting more GrubDAC kits?  Or even just the PCB?


 
  Kits will be restocked probably by this weekend.  As for the PCB, there's plenty.  They've been in stock and available on the Beezar website for months ... and months.


----------



## bwshockley

Quote: 





tomb said:


> Kits will be restocked probably by this weekend.  As for the PCB, there's plenty.  They've been in stock and available on the Beezar website for months ... and months.


 
  Could I possibly switch out my Skeleton DAC for a Grub DAC and pay the difference?


----------



## bwshockley

I have another question that came to light last night.  When I first powered on and tuned my MOSFET-MAX I did not have my potentiometer installed, nor did I have any input or outputs installed.  Last night, I was messing around and forgot that I'd placed the pot on the board and I went to check my voltages across the tubes and it was much lower than the initial 13.5vdc.  At first I couldn't figure it out until I realized the pot was in.  Removing it (it was just pressed onto the board) and tubes went back to 13.5vdc.  Of course, turning the pot made a difference too.
   
  So, I guess to get to my point, should the 13.5vdc bias be without the pot, or with the pot at "full volume"?  Should the pot even be making a difference to that voltage or is there something wrong?
   
  Tonight I should have the last of my parts to at least test out the amp using actual input and headphones.


----------



## tomb

Quote: 





bwshockley said:


> Could I possibly switch out my Skeleton DAC for a Grub DAC and pay the difference?


 
  Yes, we will work it out.


----------



## tomb

Quote:


bwshockley said:


> I have another question that came to light last night.  When I first powered on and tuned my MOSFET-MAX I did not have my potentiometer installed, nor did I have any input or outputs installed.  Last night, I was messing around and forgot that I'd placed the pot on the board and I went to check my voltages across the tubes and it was much lower than the initial 13.5vdc.  At first I couldn't figure it out until I realized the pot was in.  Removing it (it was just pressed onto the board) and tubes went back to 13.5vdc.  Of course, turning the pot made a difference too.
> 
> So, I guess to get to my point, should the 13.5vdc bias be without the pot, or with the pot at "full volume"?  Should the pot even be making a difference to that voltage or is there something wrong?
> 
> Tonight I should have the last of my parts to at least test out the amp using actual input and headphones.


 
  This used to be a common question in the old days, at least about the volume part (volume setting for biasing tubes).
   
  What you have noticed is perfectly normal.  You've noticed that the pot has an impedance that the tubes can see.
	

	
	
		
		

		
			





  I can't remember anyone attempting to bias the tubes without the pot installed, but there's a first time for everything.  Regardless, *bias the tubes with the pot installed and the volume at zero*.


----------



## bwshockley

tomb said:


> Quote:
> ]
> This used to be a common question in the old days, at least about the volume part (volume setting for biasing tubes).
> 
> What you have noticed is perfectly normal.  You've noticed that the pot has an impedance that the tubes can see.   I can't remember anyone attempting to bias the tubes without the pot installed, but there's a first time for everything.  Regardless, *bias the tubes with the pot installed and the volume at zero*.




Thanks for all the help Tom. I have made the proper adjustments.

Also, tonight I final hear sound through the amp. Some Pink Floyd, Adele, and Foo Fighters. I'm not sure if I'm just biased, but it sounds great. The sound is interesting. This is too much fun!


----------



## primer

Damn it ................. I'm nearly finished populating the MAX and I just realised that I forget the LEDs.  sh#t  sh#t  sh#t


----------



## tomb

Quote: 





primer said:


> Damn it ................. I'm nearly finished populating the MAX and I just realised that I forget the LEDs.  sh#t  sh#t  sh#t


 
  If you drilled out the center pins from the tube sockets, it's not an issue.  You should be able to slip the LEDs right throug the socket to the PCB pads.


----------



## primer

Quote: 





tomb said:


> If you drilled out the center pins from the tube sockets, it's not an issue.  You should be able to slip the LEDs right throug the socket to the PCB pads.


 
   


 Thanks tomb, managed to desolder the sockets finally.


----------



## elctronn

Please can I use Mosfet Diamond Buffer with symmetrical supply?

  Please exist some replacement 2N5486? I can't get it.
   
  Thank You.


----------



## Avro_Arrow

You can use a PN4392 in place of the 2N5486


----------



## bwshockley

You can purchase a pair of 2N5486 from amb.org/shop for US $0.50 per pair.  Not sure if you are saying you can't find them or can't receive them, but AMB ships worldwide.


----------



## ModMax

Should the MOSFET-MAX PCB be grounded to the case?  I don't think so, but I want to be sure before moving forward.  Also, I read *somewhere* that it's best if the RCA jacks make contact with the rear panel.  Is this correct?  Thx.


----------



## scootsit

Quote: 





modmax said:


> Should the MOSFET-MAX PCB be grounded to the case?  I don't think so, but I want to be sure before moving forward.  Also, I read *somewhere* that it's best if the RCA jacks make contact with the rear panel.  Is this correct?  Thx.


 

 Having the case grounded helps block out radio noise. Allowing the RCAs to contact the metal grounds the case to the board, since the outside of the jack is the ground.


----------



## tomb

Quote: 





modmax said:


> Should the MOSFET-MAX PCB be grounded to the case?  I don't think so, but I want to be sure before moving forward.  Also, I read *somewhere* that it's best if the RCA jacks make contact with the rear panel.  Is this correct?  Thx.


 
  Scootsit has it correct.  Another path for grounding the PCB to the case is through the center standoff - you can scrape off some of the anodizing on the inside of the case so that the standoff makes good electrical contact.  All that said, the MAXes are all very resistant to hum and interference.  Outside of the errant cell phone, I haven't seen or heard of any issue.  We _know_ the onboard linear-regulated power supply is audiophile-quiet. 
   
  P.S. the headphone jack and the volume pot also provide potential ground paths for the case, but neither are as consistent as the two paths mentioned above.


----------



## ModMax

Asked tomb this same question by email, but thought I would post it here to in case it helps others or others can offer some advice.
   
  Does the following wiring diagram look correct for the MOSFET-MAX power socket to SPST switch and PCB with fuse?


----------



## scootsit

Quote: 





modmax said:


> Asked tomb this same question by email, but thought I would post it here to in case it helps others or others can offer some advice.
> 
> Does the following wiring diagram look correct for the MOSFET-MAX power socket to SPST switch and PCB with fuse?


 
  Yes. Tomb may want to chime in further.


----------



## ModMax

Or is this alternate wiring preferred so that no power is supplied to any circuits until the SPST switch is thrown?
   
  Diagram PDF attached


----------



## KimLaroux

Quote: 





modmax said:


> Or is this alternate wiring preferred so that no power is supplied to any circuits until the SPST switch is thrown?
> 
> Diagram PDF attached


 
   
  This circuit will not work. You need to connect AC-2 to the other side of the power supply. You need to "close" the circuit for current to flow. This circuit has no return path, so no current will flow even with the switch "on".
   
  There's plenty of information about wiring on the MAX website. I think this particular picture from the website describes well what you need to to:





   
  This is exactly what your first schematic showed. The polarity is irrelevant.


----------



## ModMax

Thanks Kim.  The pic is very helpful - thanks for including.
   
  I think in my first schematic though, I made a mistake.  I had the power socket GND pin left as unconnected, but the pic above shows this pin connected for return path.  I guess I am a bit confused on the socket - why are there 3 contacts on this socket?  Just an extra + lead?


----------



## scootsit

Quote: 





modmax said:


> Or is this alternate wiring preferred so that no power is supplied to any circuits until the SPST switch is thrown?
> 
> Diagram PDF attached


 

 I don't understand the question, as it currently is, no power is supplied until the switch is closed. That's how the switch works.


----------



## tomb

Quote: 





modmax said:


> Thanks Kim.  The pic is very helpful - thanks for including.
> 
> I think in my first schematic though, I made a mistake.  I had the power socket GND pin left as unconnected, but the pic above shows this pin connected for return path.  I guess I am a bit confused on the socket - why are there 3 contacts on this socket?  Just an extra + lead?


 
  That socket is totally typical as it comes with three pins.  It's meant to cut out a battery circuit if you plug in an AC Adapter.  The third pin is connected to the other non-center pin when no plug is connected.  Thus, you can run one lead of a DC battery circuit through the pins.  When the plug is inserted into the socket, the circuit to the battery would then be broken.  For our purposes, you just need the one pin that is "hot" when a plug is inserted, combined with the center pin.  I never remember for sure myself which is which.  I simply touch a DMM probe to the contact spring inside the socket and find out which pin has zero resistance by touching the other DMM probe.  Or, simply look at the photo above that Kim posted: center pin and far outside pin.
   
  I didn't comment on your schematic before because it made no sense without context.  Are you building a point-to-point MAX or MiniMAX?  If not, then the PCB's are being used.   In all the MAXes/MiniMAXes, the DC power supply is onboard the PCB.  So all outside connections - walwart, adapter socket, down to the terminal block - are all AC current with no polarity.  Note that you still need two AC connections from the wall and walwart, however.  You can't simply create one by "teeing off" of an existing AC lead.


----------



## scootsit

How do the Kiwame output resistors effect the sound? I got some laying around, and was thinking about swapping them into my Millet, but never got around to it. Does it really make an audible difference?


----------



## scootsit

Would a 12AU6 work as a drop in tube? I'm just curious, found about a gazillion on ebay really cheap, curious how they might sound.


----------



## tomb

Quote: 





scootsit said:


> Would a 12AU6 work as a drop in tube? I'm just curious, found about a gazillion on ebay really cheap, curious how they might sound.


 
  It might be a possibility for another amp design, but the 12AU6 is not a possibility as a drop-in replacement for the Millett Hybrid design.  Even discounting the fact that it's not a space-charge tube that runs with 12.6V as design-center plate voltage (the 12AU6 wants 250V!), the pinouts are critically different.  In the 12AE6, 12FM6, and 12FK6, the cathode is pin 2 and the plate is pin 7.  In the 12AU6, the cathode is pin 7 and the plate is pin 5.
   
  Not a good swap if you want to keep things from blowing up.


----------



## scootsit

Quote: 





tomb said:


> Quote:
> 
> 
> 
> ...


 

 I guess I should have actually taken the 30 seconds to read the pinout and more before asking. I just saw the same heater voltage/current and assumed...oops.


----------



## ModMax

So, I have finally powered-on my MOSFET-MAX for the 1st time and in the process of biasing.  Currently, my values are as follows:
   
  - Power Supply Voltage = 27.0 VDC
  - Tube Bias = ~13.5 VDC for both tubes
  - DB Bias = 0.0 mVDC for both L & R
   
  I am using matched 12FM6 tubes I purchased from Beezar.com.  They are new so I expect fluctuations in Tube bias for a bit until they are "broken in".
   
  My questions are:
  - Is it enough to break-in the tubes by turning on the amp and (1) leaving it on for hours, and (2) occasionally checking and adjusting the tube bias, and (3) leaving the DB bias at 0.0 mV, and (4) running no audio through the amp?  
  - How long is the typical break-in period for new tubes?
  - Is there a suggested or best method to break-in new tubes?
  - Should I wait for the tubes to break-in before adjusting DB bias since DB bias can have negative impact on transistor health?


----------



## tomb

Quote: 





modmax said:


> So, I have finally powered-on my MOSFET-MAX for the 1st time and in the process of biasing.  Currently, my values are as follows:
> 
> - Power Supply Voltage = 27.0 VDC
> - Tube Bias = ~13.5 VDC for both tubes
> ...


 
  Nothing is going to take more than a few hours to break-in.  However, until you put bias current to the DB, nothing is going to get "heat-soaked."  There is no advantage to not biasing the MOSFETs and getting that going.  "Negative Impact" is in years if your heat sinks are done properly.  MOSFETs _like_ to run hot.  I'm no expert on MOSFETs, but seems like I've heard and been told that they're not even linear in a non-biased state.
   
  Just keep in mind also that tubes are not perfect little solid-state devices.  I liken them to mules when it comes to biasing.  If you have them within a quarter volt, you're doing fine.  Also, if you're using 12FM6's, I would up the bias to 15V on the MOSFET-MAX.  You will lose very little voltage swing and the 12FM6's operate much better with a little more voltage.  You shouldn't miss the voltage swing on the MOSFET-MAX because the MOSFETs each up a couple of volts for biasing, anyway.


----------



## ModMax

Thanks, TomB.
   
  Can you recommend a sweet-spot value for the DB bias?  MOSFET bias setup states 220 - 275 mV.  Anywhere in that range you could recommend?


----------



## tomb

Quote: 





modmax said:


> Thanks, TomB.
> 
> Can you recommend a sweet-spot value for the DB bias?  MOSFET bias setup states 220 - 275 mV.  Anywhere in that range you could recommend?


 
  Depends on your case.  If you have plenty of cooling, go for the 275mV (125ma).  If not, then stay on the low end.  I think 150ma is too much for the PCB/heat sink design, even for a well-ventilated case.  It will sound noticeably worse if you go below ~90 ma (<200mV), though.


----------



## ModMax

I followed the case templates from the MOSFET-MAX site and the heatsinks are 1.5" and I bought the HiQ Heat Sink Mounting kits from Beezar.com.  Given this info, what would you recommend for a max DB bias?


----------



## tomb

Quote: 





modmax said:


> I followed the case templates from the MOSFET-MAX site and the heatsinks are 1.5" and I bought the HiQ Heat Sink Mounting kits from Beezar.com.  Given this info, what would you recommend for a max DB bias?


 
  What I said above.  There are heat sinks that are larger than the ones the PCB allows - some as large as an entire case or larger.  That's all I meant from that statement - that there's a physical limitation based on the PCB and case design that prevents you from biasing them further.


----------



## ModMax

First listen is not good.
   
  MOSFET-MAX setup:

 V+ = 27 VDC
 12FM6 Tubes = ~15 VDC
 MOSFET Bias = ~225 mV
   
  Audio chain:
  Foobar 2K (WASAPI: Speakers (USB Audio DAC)) --> grubDAC (internal) --> MOSFET-MAX --> Grado SR60
   
  I have both 1/4" and 1/8" jacks on my amp.   With both jacks, there is a humming / static sound and music sounds very tinny and faint.  This is with MOSFET-MAX volume @ 100%.  Also, strange thing, physically touching and moving the L/R/Gnd wires connecting the grubDAC and also the RCA inputs to the MOSFET-MAX changes the humming sound I hear during playback.
   
  I grounded the case to the MOSFET-MAX both through the RCA inputs and through the center standoff.  I also connected 2 ground wires from the grubDAC to the single ground input at SW2.  I also connected 2 ground wires, one from each RCA input, to the single ground input at SW1.
   
  Anybody have any ideas on what might be the problem?


----------



## ModMax

Wait just a minute....  okay, I flipped the input select switch and suddenly I hear my music - a lot of it and it sounds pretty damn good.
   
  Chain is still Foobar 2K (WASAPI: Speakers (USB Audio DAC)) --> grubDAC (internal) --> MOSFET-MAX --> Grado SR60.
   
  I am confused though.  This position of the input select toggle switch on my front panel breaks the connection between IS-1 and IS-2 on the MOSFET-MAX.  I thought breaking this connection would turn on SW1 (which my RCA jacks are connected).  But apparently IS-1 --> IS-2 break turns on SW2.  Does this sound correct?
   
  Also, with the front panel input select switch flipped to the position which connects IS-1 to IS-2, which turns on SW1, should I hear any sound coming from my grubDAC (connected to SW2)?  I do hear some sound which as I mentioned in my post above has a humming / static noise in the foreground and very faint sound of my music in the background.  And the humming / static sound is affected by touching and moving the L/R/Gnd wires coming from the RCA inputs and grubDAC L/R/G connections.
   
  Should I not have grounded the MOSFET-MAX PCB to the case bottom via center standoff and the rear panel via RCA jacks?
   
  Do I need to ground the volume pot to the PCB via the set screw on the top right corner of the volume pot and ground pad near the pot on the PCB?


----------



## tomb

Quote: 





modmax said:


> Wait just a minute....  okay, I flipped the input select switch and suddenly I hear my music - a lot of it and it sounds pretty damn good.
> 
> Chain is still Foobar 2K (WASAPI: Speakers (USB Audio DAC)) --> grubDAC (internal) --> MOSFET-MAX --> Grado SR60.
> 
> ...


 
  The switch energizes both relays.  However, the input connections to the pot go through the energized poles on SW1, but through the de-energized poles on SW2.  IOW, the input block closest to the right side of the PCB (looking from the front or volume pot) is connected with the relays de-energized or OFF.  The input block on the inside or left (when viewed from the front or volume pot) is connected when the relays are energized or ON.
   
  If you have a signal going through the GrubDAC at the same time you are connected to signal through the other input block, yes - you will hear some bleed-through.  The main reason this happens is that the volume travel/gain on the amp is really over 100% at 12 o'clock on the volume pot.  There is not a source nor headphone in existence that will require a volume setting much beyond this.  So, you are really into the >120dB regime if you are turning up the pot enough to hear the music bleed-through from the Grub.  Still, the input relays are for convienience, only - not to fully shut off any chance of _active_ signal between the two input blocks.  So, if you switch from one to the other and then listen for extended periods, I would go ahead and shut off the other music source.  This still gives you the convenience of not having to connect/disconnect RCA cables.. 
   
  Note that isolation for the relay contacts is about 95dB at 1MHz and increases exponentially at frequencies below that.  In the audible band, it should be well above 120dB.
   
  I'm not sure about hearing differences when you move the wires around.  That sounds like bad connections or at least, bad connections with the ground wires.
	

	
	
		
		

		
			




   
  Yes, you should ground everything you mentioned, but truthfully, you shouldn't notice an ill effect just with the bare PCB - except for the signal ground not making a good connection at the input blocks.  With that, you will definitely notice noise - sometimes very bad noise.
   
  The pot ground is simply an irritant issue, IMHO, although to be perfectly correct - it should be grounded.  9 times out of 10, the pot will ground itself through the shaft and the case endplate.  However, if it doesn't make this connection or you don't install the ground wire, then you will get some hum if you touch the volume knob (assuming you use a conductive knob).


----------



## ModMax

Any chance I should expect to hear some ground hum when the input selected is RCA but there is no source connected to the RCA jacks?


----------



## KimLaroux

Quote: 





tomb said:


> [...]
> 
> The pot ground is simply an irritant issue, IMHO, although to be perfectly correct - it should be grounded.  9 times out of 10, the pot will ground itself through the shaft and the case endplate.  However, if it doesn't make this connection or you don't install the ground wire, then you will get some hum if you touch the volume knob (assuming you use a conductive knob).


 
   
  I used a large plastic knob on my Starving Student, and every time I touched it the amp hummed. Grounding the shaft did the trick.
   
  In tube amps, you can make them hum just by passing your finger close to a wire, without even touching it. It can be really annoying when you try to debug a running amp.


----------



## ModMax

Can someone try an experiment where they set the input to their Millett to RCA without any source connected to the RCA and let me know if they hear any hum in their headphones? And if they do, at what % volume they begin to hear the hum?


----------



## Goobley

Whilst I don't have this amp, in my experience it's very rare for an amp with open RCA jacks to be silent.
   
  If you connect a source does the hum reduce in volume?
   
  If it does then I'd expect that it's completely normal behaviour. On my SS CKKIII (on which during one normally shorts the audio pads to ground during the setup process) with open RCA I get noticeable noise by 15% on the pot, if I have a decent source connected then it's silent until 75-80%.
   
  Should the RCA jacks be grounded to the case on this amp? (As far as I'm aware on most amps the RCA should be isolated with plastic washers from the case)
   
  Hope you get these issues sorted,
  Chris


----------



## scootsit

Quote: 





goobley said:


> Whilst I don't have this amp, in my experience it's very rare for an amp with open RCA jacks to be silent.
> 
> If you connect a source does the hum reduce in volume?
> 
> ...


 

 My millett, with the RCAs in use is pretty close to silent. Your RCAs should be grounded to the case (well, assuming your case is grounded elsewhere, it doesn't really matter). I use the plastic on the outside, as they are colored, and no plastic on the inside, fyi.


----------



## ModMax

Quote: 





goobley said:


> Whilst I don't have this amp, in my experience it's very rare for an amp with open RCA jacks to be silent.
> 
> If you connect a source does the hum reduce in volume?
> 
> ...


 
   
  Thanks Chris.  I will connect a source to my RCAs tomorrow after I get a cable and see if the hum is reduced.  I don't recall hearing any hum when listening with the grubDAC selected as input.
   
  Quote: 





scootsit said:


> My millett, with the RCAs in use is pretty close to silent. Your RCAs should be grounded to the case (well, assuming your case is grounded elsewhere, it doesn't really matter). I use the plastic on the outside, as they are colored, and no plastic on the inside, fyi.


 
   
  Thanks.  I did measure the RCA jacks to ground and found continuity for both RCA jacks (outer body) and PCB GND with a value of 0.2 Ohms.  With my 12FM6 tubes in the sockets, I measure 33 Ohms between V+ and GND, and approx. 1 kOhm between RCA L/R and GND.  I am using GND at the center standoff of the PCB.  I also made sure that I have continuity (0.2 Ohms) between the RCA jacks (outer body) and the screw head on the underside of my case that grounds the PCB's center standoff to the enclosure.  So my RCA jacks are grounded to the rear panel which in turn grounds the PCB to the rear panel.  The PCB is also grounded to the enclosure through the center standoff.
   
  I also use the color plastic washers on the outside of the rear panel for the RCA and no plastic on the inside.


----------



## scootsit

Quote: 





modmax said:


> Quote:
> 
> 
> 
> ...


 

 That all sounds about right. 0.2r is a tiny bit high, not really high, but perhaps a tad.
  I think your build is probably fine, and if you threw a source (even turned off) onto the RCAs, it'd be silent. Just make sure you've scraped off some anodizing wherever you ground your case, because the anodizing is non-conductive. If there is nothing around the RCAs in the holes, then that's a ground. Mine grounds there, and through the standoff, I basically dragged the board in an out a few times to scrape away some of the anodizing under the standoff.


----------



## KimLaroux

My cheap DMM shows 0.6 Ohms when I touch the leads together. Was this 0.2 Ohms measurement error-corrected? If not, then those 0.2 Ohms were probably just the impedance of the leads and the points of contact.
   
  From what I can understand, your enclosure is grounded at two places. This sounds like a ground loop, and could explain the hum you get.


----------



## scootsit

Quote: 





kimlaroux said:


> My cheap DMM shows 0.6 Ohms when I touch the leads together. Was this 0.2 Ohms measurement error-corrected? If not, then those 0.2 Ohms were probably just the impedance of the leads and the points of contact.
> 
> From what I can understand, your enclosure is grounded at two places. This sounds like a ground loop, and could explain the hum you get.


 

 It shouldn't be a problem, the signal isn't using the case as a grounding plane, it's really just a bit of shielding, as far as I know.
   
  When you connect a source to the RCAs, the hum will go away, it's no big deal, it happens any time you have RCAs without a source connected. If there is still hum with a source connected, that's different.


----------



## tomb

Quote: 





scootsit said:


> When you connect a source to the RCAs, the hum will go away, it's no big deal, it happens any time you have RCAs without a source connected. If there is still hum with a source connected, that's different.


 
*THIS ^*


----------



## ModMax

Quote: 





kimlaroux said:


> My cheap DMM shows 0.6 Ohms when I touch the leads together. Was this 0.2 Ohms measurement error-corrected? If not, then those 0.2 Ohms were probably just the impedance of the leads and the points of contact.
> 
> From what I can understand, your enclosure is grounded at two places. This sounds like a ground loop, and could explain the hum you get.


 
   
  My DMM shows 0.1 Ohm with just the leads contacting one another.


----------



## scootsit

Quote: 





modmax said:


> Quote:
> 
> 
> 
> ...


 

 Do you have a source with RCAs?
  Connect it and see if there is hum.
  You really don't need to play anything, just connect the cables, you can turn it on, too. Don't play anything. Basically, if it's really close to silent (I have a hunch it will be) under actual playing conditions, what does it matter if there's some RFI/noise when conditions are such (ie: nothing connected) that you cannot play anything?


----------



## ModMax

Is it recommended to set the volume of a source (iPod, laptop, etc..) to its maximum when connecting to an amp or dac/amp like the MOSFET-MAX?  I noticed that when I connect my grubDAC to my laptop, the laptop automatically sets its volume to max.


----------



## tomb

Quote: 





modmax said:


> Is it recommended to set the volume of a source (iPod, laptop, etc..) to its maximum when connecting to an amp or dac/amp like the MOSFET-MAX?  I noticed that when I connect my grubDAC to my laptop, the laptop automatically sets its volume to max.


 
  If you're using a digital line-out source (sound card or DAC on a PC), absolutely set the volume to maximum.  Otherwise, you get software interpolation in the signal which can degrade the quality.
   
  iPods are different, unless you have a line-out adapter.  The signal from an iPod headphone output is already amplified analog.  It's among the worst of sources that you can connect directly to an amp.  If you're using the iPod headphone jack, then adjust things so that they're stable and you're not driving the MOSFET-MAX into clipping.
   
  All other analog line-out sources have no volume adjustment, anyway - they follow IES/Phillips/Sony Redbook standards (hopefully, anyway).


----------



## ModMax

Quote: 





tomb said:


> If you're using a digital line-out source (sound card or DAC on a PC), absolutely set the volume to maximum.  Otherwise, you get software interpolation in the signal which can degrade the quality.
> 
> iPods are different, unless you have a line-out adapter.  The signal from an iPod headphone output is already amplified analog.  It's among the worst of sources that you can connect directly to an amp.  If you're using the iPod headphone jack, then adjust things so that they're stable and you're not driving the MOSFET-MAX into clipping.
> 
> All other analog line-out sources have no volume adjustment, anyway - they follow IES/Phillips/Sony Redbook standards (hopefully, anyway).


 
   
  So iPod dock to LOD adapter to MOSFET-MAX RCA = set iPod to max volume, correct?
   
  What about PC headphone out to MOSFET-MAX RCA?  What would you recommend in this case?


----------



## tomb

Quote: 





modmax said:


> So iPod dock to LOD adapter to MOSFET-MAX RCA = set iPod to max volume, correct?
> 
> What about PC headphone out to MOSFET-MAX RCA?  What would you recommend in this case?


 
  A PC headphone out is worse than an iPod headphone out, IMHO.  If you don't have a sound card with line out, then that's why you have the grubDAC - connect to the USB and forget about it.
   
  I don't have your equipment, though, and know nothing about the details of your setup.  Why don't you try it?  If it sounds like crap, then don't use it that way.


----------



## scootsit

An ipod with LOD, you cannot control the volume, it defaults to 1V rail-to-rail.


----------



## ModMax

Can anyone recommend a good source for a volume knob for the ALPS pot on the MOSFET-MAX?  I like the Kilo knobs, but all of their shaft lengths are only .510" which is too short for the ALPS pot shaft.


----------



## scootsit

Quote: 





modmax said:


> Can anyone recommend a good source for a volume knob for the ALPS pot on the MOSFET-MAX?  I like the Kilo knobs, but all of their shaft lengths are only .510" which is too short for the ALPS pot shaft.


 

 Tomb suggests an ebay seller, where I got mine from. I actually still have one I may never use. His site is here: http://myworld.ebay.com/hongkongsuperseller/
   
  Radio Shack has some okay knobs, too.
   
  With that ebay seller, I did have to cut the shaft slightly, FYI.


----------



## ModMax

What tool did you use to cut the shaft?


----------



## scootsit

Quote: 





modmax said:


> What tool did you use to cut the shaft?


 

 A saw. A very small hand saw.


----------



## tomb

I use a Dremel cut-off disk (or however many it takes - they break often):

   
  It slices through like butter until you get about 3/4 of the way through the shaft.  By that time, the cut-off disk has loaded up a bit on the metal and may start to kick out of the cutting groove.  Stay with it and be patient and you'll have a fantastic cut in about 10 seconds.  One of those grinding stones that typically comes in a Dremel kit has a huge counter-sink that lets you finish up the pot shaft end nicely:

   
  It's a typical bit that looks like the above.  It actually has significant depression in the top (counter sink).  It's almost like a hole that's the same diameter as the pot shaft.  Use this bit by inserting the end of the pot shaft into the top depression of the Dremel bit (you should actually move the Dremel, not the pot shaft), and it smooths and rounds off the freshly cut shaft very nicely.
   
  A saw is OK, but at the risk of disagreeing a bit with scootsit, it may tend to put a bit more stress on the pot shaft.


----------



## ModMax

Has anyone had any luck with Kilo knobs on their Millett MAX builds with ALPS RK27 pot?
   
  The shaft length on the Kilo knobs is 0.510 inches, which would mean a pretty good trim (a little more than .25 inches) needed for the ALPS pot shaft to shorten it so the knob base sits close to flush against the case front panel.
   
  Specifically, I am considering this knob with a 6mm diameter shaft?
   
  Digikey Product Page:
http://www.digikey.com/product-detail/en/ML-90-3-6MM/226-3028-ND/305260
   
  Kilo Datasheet:
http://media.digikey.com/pdf/Data%20Sheets/Kilo%20International%20PDFs/ML%20Knobs.pdf
   
  Should I go for a .25 inch diameter shaft or will a 6 mm diameter shaft work fine? 
   
  Also, given the set screw is .285 inches from base of knob, and with the ALPS pot shaft trimmed to a lenght of approximately .510 inches, would the position of the set screw be an issue for securing the knob to the ALPS pot shaft securely, in your opinion(s)?


----------



## tomb

Quote: 





modmax said:


> Has anyone had any luck with Kilo knobs on their Millett MAX builds with ALPS RK27 pot?
> 
> The shaft length on the Kilo knobs is 0.510 inches, which would mean a pretty good trim (a little more than .25 inches) needed for the ALPS pot shaft to shorten it so the knob base sits close to flush against the case front panel.
> 
> ...


 
  All the knobs I use I get from PartsPipe on ebay - also know as HongKongSuperSeller.
   
  This is a PartsPipe knob,

  and this:

   
  Strictly speaking, the ALPS RK27 uses a 6mm shaft.  An English knob will have a wobble.
   
  Finally - JMHO, but never, ever cut the pot shaft based on calculated dimensions.  Assemble your amp, try the knob on for fit.  See how much space you have between the back of the knob and the front surface of the front plate.  Cut this much off of the pot shaft - no more.  You should still have enough play beyond the set-screw to provide some clearance so that the knob doesn't rub.
   
  I put my amps in a large freezer bag (or a kitchen garbage bag) with a small hole cut through the bottom for the shaft.  I put some masking tape around the base of the shaft where it pokes through the plastic bag for added safety.  Then I pull out the Moto-Tool and cut.  The bag protects everything from the aluminum dust.  Also, not only is your pot locked into the PCB, but the shaft nut provides additional stability and protection from torquing/bending the shaft when cutting.  There's no danger of that with a Dremel, but you could scar up other things without the baggie.


----------



## funch

(edit: looks like tomb beat me to the punch)
   
  The ALPS pot has a 6mm shaft.
   
  The way I trim a pot shaft to length is:
   
  1) Install the pot onto the front panel.
   
  2) Place the knob on the shaft.
   
  3) Measure the distance from the backside of the knob to the surface of the front panel in mm.
   
  4) Remove the knob and the pot from the panel.
   
  5) Measure from the end of the pot shaft to match the distance you measured in step 3 and mark a line on the shaft.
   
  6) Cut the pot shaft just slightly in front (toward the shaft end) of that line. Be sure the cut is flat, and not at an angle.
   
  7) Reinstall the pot to the front panel. Install the knob. If the knob is too far away from the panel, file the shaft down
      until the knob sits where you want it too. Then file the cut edge smooth.


----------



## KimLaroux

Talking about RK27 and knobs... The RK27 I got has a perfectly round shaft, like so:
   




  Yeah that's a totally random picture 
   
  Are these shafts meant to be used only with knobs that have screws? Or is it possible to mount a screw-less knob to this type of shaft?


----------



## tomb

The fact that there's a slot there implies a press-fit knob.  However, none of those type of knobs seem to fit the "quality" of the pot.  Further, unless the knob hole is perfectly matched to the shaft diameter, a slotted shaft causes even more wobble when the set-screw is tightened.  With the length of shaft that several of us have established as the Head-Fi DIY standard (RK27, 50K, 25mm shaft), most of the time the slotted portion is cut off, anyway.
	

	
	
		
		

		
			




   
  Just an FYI, but AFAIK - all the *50K* ALPS RK27's are a special manufacturing order (iow, high volume).  This is further complicated by the Japanese tsunami.  The ALPS factory was hit.


----------



## ModMax

Here is the shaft on my 50K ALPS RK27 pot.  25mm long shaft with a 14mm long slot.  After trimming, I still anticipate some of the slot will remain.


----------



## tomb

Quote: 





modmax said:


> Here is the shaft on my 50K ALPS RK27 pot.  25mm long shaft with a 14mm long slot.  After trimming, I still anticipate some of the slot will remain.


 
  I'm sorry.  You may think you have an ALPS RK27, but you don't.  There isn't a shaft like that anywhere in the data sheet for an RK27:
http://www.diyforums.org/Torpedo/template/RK271.pdf


----------



## ModMax

tomb said:


> I'm sorry.  You may think you have an ALPS RK27, but you don't.  There isn't a shaft like that anywhere in the data sheet for an RK27:
> http://www.diyforums.org/Torpedo/template/RK271.pdf




I'm pretty sure it's an ALPS RK27. Maybe because its old? Got it from a Millett kit from Glass Jar Audio back in 2008 or 2009.


----------



## KimLaroux

The RK27 in my Audio-gd NFB-12 also has a similar shaft. I doubt Audio-gd would be using knockoffs in their amplifiers...
   
  Maybe these were special bulk orders at Alps.


----------



## tomb

OK - here's the ALPS factory site itself - every RK27 they produce.  None have shafts like that:
http://www.alps.com/WebObjects/catalog.woa/E/HTML/Potentiometer/RotaryPotentiometers/RK271/RK271_list.html
  Even their "other varieties" pages doesn't show a knurled shaft option:
http://www.alps.com/WebObjects/catalog.woa/E/PDF/Potentiometer/MetalShaft/RK271/RK271_VARIETYOTHER.PDF
   
  There are a lot of knock-offs out there for ALPS RK27's - always have been.  Here are what I would suspect are fakes on ebay:
http://www.ebay.com/itm/Japan-ALPS-RK27-VOLUME-Potentiometer-Dual-20K-Knurled-/220918121214?pt=US_Amplifier_Parts_Components&hash=item336fbf02fe
http://www.ebay.com/itm/Japan-ALPS-RK27-VOLUME-potentiometer-Dual-100K-knurled-/320746881260?pt=US_Amplifier_Parts_Components&hash=item4aae0100ec
   
  I think the stepped type have been known to be fakes for years:
http://www.ebay.com/itm/ALPS-100K-AX2-Stereo-Audio-Potentiometer-Step-type-/320965528399?pt=US_Amplifier_Parts_Components&hash=item4abb094b4f
   
  This subject has come up before, too:
http://www.head-fi.org/t/512581/alps-rk27-ebay
http://www.head-fi.org/t/218942/alps-stepped-attenuators-pin-order
  This one goes back to 2002:
http://www.head-fi.org/t/11313/alps-potentiometers-for-a-good-price
   
  Just sayin ...


----------



## Lil' Knight

Pretty sure those RK27s with knurled shaft are fakes. I have a friend who runs an audio store and stocks those, admits he imported them from China and they are not the genuine ones.

The fact that Audio-Gd uses them doesn't say anything... the company itself locates in China.


----------



## scootsit

I've actually heard rumblings that some of the fakes are as good or better than the real ones. I mean, it makes sense that if you're going to make a pot, you make it resemble the top seller. I bought my Millett kit from glass jar and then modified it after. I have a smooth shaft, but it could well be a fake. I notice no channel imbalance, and there is the tiniest bit of scratchiness in one channel at very, very high volumes. I guess what I'm saying is, if it ain't broke don't fix it...


----------



## ModMax

Quote: 





tomb said:


> OK - here's the ALPS factory site itself - every RK27 they produce.  None have shafts like that:
> http://www.alps.com/WebObjects/catalog.woa/E/HTML/Potentiometer/RotaryPotentiometers/RK271/RK271_list.html
> Even their "other varieties" pages doesn't show a knurled shaft option:
> http://www.alps.com/WebObjects/catalog.woa/E/PDF/Potentiometer/MetalShaft/RK271/RK271_VARIETYOTHER.PDF
> ...


 
   
  Quote: 





lil' knight said:


> Pretty sure those RK27s with knurled shaft are fakes. I have a friend who runs an audio store and stocks those, admits he imported them from China and they are not the genuine ones.
> The fact that Audio-Gd uses them doesn't say anything... the company itself locates in China.


 
   
  Bummer.  Tom, do you have any RK27's in stock at Beezar?  I'll order if you do.  Shouldn't be too difficult to replace in my Millett.  Though it's not broke, I still would like to fix with a genuine part since I have already put so much into the kit to date.  Plus, cutting and fitting a knob to the solid, single-diameter shaft should be a bit easier than the knurled shaft.
   
  Wonder if Glass Jar Audio knows that the ALPS he was shipping were possible fakes?  I'll send Jeff a message to ask about this...


----------



## tomb

Quote: 





modmax said:


> Bummer.  Tom, do you have any RK27's in stock at Beezar?  I'll order if you do.  Shouldn't be too difficult to replace in my Millett.  Though it's not broke, I still would like to fix with a genuine part since I have already put so much into the kit to date.  Plus, cutting and fitting a knob to the solid, single-diameter shaft should be a bit easier than the knurled shaft.
> 
> Wonder if Glass Jar Audio knows that the ALPS he was shipping were possible fakes?  I'll send Jeff a message to ask about this...


 
  Yes, of course - I have plenty of the genuine article.
   
  I agree that you should send a note to Jeff.  I've even ordered from AMB and Tangent before when I've run out of stock.  You see, you have to order several hundred from ALPS to have the 50K ones manufactured - and it takes a couple of months, at least.  Last time they made me order twice as much as normal because their factory was hit by the tsunami.  Beezar's cash flow still hasn't recovered.
	

	
	
		
		

		
		
	


	



   
  So far as I know - only AMB, Tangent, Beezar, and Justin at Headamp sell the real thing at 50K.  (I think Justin's was a temporary over-stock situation for awhile, don't know if he's still selling them or not.)


----------



## KimLaroux

Wow that's scary... to think that Audio-gd would be using fakes in their products. At least their topology does not make the audio signal go trough the pot.
   
  The 50K I bought from parts connexion seems to be genuine. But these guys have been selling fake Hakko stations without knowing they were fake, so who knows...


----------



## ModMax

Quote: 





tomb said:


> OK - here's the ALPS factory site itself - every RK27 they produce.  None have shafts like that:
> http://www.alps.com/WebObjects/catalog.woa/E/HTML/Potentiometer/RotaryPotentiometers/RK271/RK271_list.html
> Even their "other varieties" pages doesn't show a knurled shaft option:
> http://www.alps.com/WebObjects/catalog.woa/E/PDF/Potentiometer/MetalShaft/RK271/RK271_VARIETYOTHER.PDF
> ...


 
   
   
  Here is another discussion online stating that ALPS says they've never made an RK27 pot with a knurled shaft.  
   
http://www.audiokarma.org/forums/showpost.php?p=4374867&postcount=3
   
   
  I just assumed since it came as a kit from a reputable online vendor, it must be genuine.  In any case, I have submitted an inquiry to ALPS to ask if my pot is genuine.  I have a feeling they will say it is not.


----------



## ModMax

Quote: 





tomb said:


> Yes, of course - I have plenty of the genuine article.
> 
> I agree that you should send a note to Jeff.  I've even ordered from AMB and Tangent before when I've run out of stock.  You see, you have to order several hundred from ALPS to have the 50K ones manufactured - and it takes a couple of months, at least.  Last time they made me order twice as much as normal because their factory was hit by the tsunami.  Beezar's cash flow still hasn't recovered.
> 
> ...


 
   
   
  Okay, I just submitted my Beezar order for a genuine ALPS RK27 pot and other goodies...  Thanks for pointing out my pot was not the genuine article before I went through the trouble of cutting the shaft and fitting the knob.


----------



## tomb

Quote: 





modmax said:


> Okay, I just submitted my Beezar order for a genuine ALPS RK27 pot and other goodies...  Thanks for pointing out my pot was not the genuine article before I went through the trouble of cutting the shaft and fitting the knob.


 
  No problem - I think we all were advising you on how to cut the pot shaft with the best intentions.  However, when you posted the pic of that shaft, it kind of negated all the conversation up to that point.
	

	
	
		
		

		
		
	


	



   
  Thanks for the order!


----------



## scootsit

Quote: 





tomb said:


> Quote:
> 
> 
> 
> ...


 

 I wish they made a pot with that shaft. I have a gazillion of those knobs from old stereos I've junked for parts for other old stereos.


----------



## Makiah S

Ok wow, I love this thread so far best of all [there is a priced out part's list at the very begining!]
   
  My next Question is does some one have the Schemtaics for this! As well as any updates to the now 3 year old Part's list! ^^ I think I can shell out and Extra $30 to build what sounds like a very awesome Millet hybrid.  Glad I found this ^^


----------



## scootsit

Quote: 





mshenay said:


> Ok wow, I love this thread so far best of all [there is a priced out part's list at the very begining!]
> 
> My next Question is does some one have the Schemtaics for this! As well as any updates to the now 3 year old Part's list! ^^ I think I can shell out and Extra $30 to build what sounds like a very awesome Millet hybrid.  Glad I found this ^^


 

 The Millet Mosfet Max is going to be closer to ~$200. All of the build info is here: http://www.diyforums.org/MOSFET-MAX/MOSFET-MAXoverview.php
   
  The Millett is not the same as the Millett Mosfet Max, they use entirely different buffers. The Millet Max is a production board, and for the Millet Minimax, there is a full kit (~$200). The Millett hybrid is not in production, and hasn't been in 20 years, you are just making the circuit on your own.


----------



## Makiah S

Quote: 





scootsit said:


> The Millet Mosfet Max is going to be closer to ~$200. All of the build info is here: http://www.diyforums.org/MOSFET-MAX/MOSFET-MAXoverview.php
> 
> The Millett is not the same as the Millett Mosfet Max, they use entirely different buffers. The Millet Max is a production board, and for the Millet Minimax, there is a full kit (~$200). The Millett hybrid is not in production, and hasn't been in 20 years, you are just making the circuit on your own.


 
  Sadly I found a Modded Indeed G3 for around $100... will it sound as nice as the Millet Max... no but for half the price and with all the Bravo V2 mods I was going to make already impliment or improved... it's a pot o gold to me! Non the less. I may still build this... seeing as it will b twice what I'm paying for the Indeed G3, plus if I like the G3 [seeing as it's an intro Tube Hybrid] it will make me more certian I need to build a Millet Max [seeing as if I don;t like tubes... I'm out $200 and coutnless hours] So i'ma try a good intro tube amp first!


----------



## scootsit

Good plan.


----------



## Makiah S

Quote: 





scootsit said:


> Good plan.


 
  I know right!


----------



## ModMax

One of my 12FM6 tubes won't behave - the bias is not consistent from day to day.
   
  Yesterday, after having my Millett on for about an hour, I checked the bias and found the tube bias for this particular tube at 15.75V.  I adjusted the trim pot and brought the bias down to about 15.10V.  Today, after having the amp on for about an hour and listening to a movie through it from my laptop, the tube is reading 14.64V!
   
  The other 12FM6 tube in my system is fairly consistent and ranges around 15V - 15.25V after a 30-60min warm up.
   
  Both tubes were matched by Beezar.
   
  The MOSFET biases are pretty consistent and typically are around 230mV after a 30-60min warm up.
   
   
  Any ideas as to why one of my 12FM6 tubes might be inconsistent?  Could it be due to the fake ALPS pot?


----------



## vixr

Quote: 





modmax said:


> One of my 12FM6 tubes won't behave - the bias is not consistent from day to day.
> 
> Yesterday, after having my Millett on for about an hour, I checked the bias and found the tube bias for this particular tube at 15.75V.  I adjusted the trim pot and brought the bias down to about 15.10V.  Today, after having the amp on for about an hour and listening to a movie through it from my laptop, the tube is reading 14.64V!
> 
> ...


 
  what about swapping the tubes between the original sockets and see if the problem follows the tube? at least that would eliminate any other issues...


----------



## tomb

Vixr has a good suggestion.
   
  Honestly, though, I'm wondering what's the deal with your tube that just varies between 15 - 15.25V. 
	

	
	
		
		

		
			




   
  My experience with most Millett tubes is what you describe for the one you're complaining about.
	

	
	
		
		

		
		
	


	




  If you check the bias after an hour, it's always dropped by about a 1/2 volt.  I regularly set my tube bias at 1/2 to 1 V higher when the amp is cold.


----------



## ModMax

tomb said:


> Vixr has a good suggestion.
> 
> Honestly, though, I'm wondering what's the deal with your tube that just varies between 15 - 15.25V.
> 
> My experience with most Millett tubes is what you describe for the one you're complaining about.   If you check the bias after an hour, it's always dropped by about a 1/2 volt.  I regularly set my tube bias at 1/2 to 1 V higher when the amp is cold.





I misspoke. My one "good" tube starts out at about 15.7V and usually settles between 15V-15.25V after about an hour. I will try setting tube bias to +1/2V higher when cold. If that doesn't help, then I will swap tubes to see if behavior follows tube or not.


----------



## tomb

Quote: 





modmax said:


> I misspoke. My one "good" tube starts out at about 15.7V and usually settles between 15V-15.25V after about an hour. I will try setting tube bias to +1/2V higher when cold. If that doesn't help, then I will swap tubes to see if behavior follows tube or not.


 
  OK - let me know if it's a Beezar tube, you decide it's bad, and I will replace it.


----------



## ModMax

In a stroke of bad luck, while removing the "fake" ALPS pot from my MOSFET-MAX build, I also removed one of the top-side PCB pads + corresponding via for one of the ALPS pot pins.  I have attached a pic below showing the through-hole PCB pad in question.  The bottom-side PCB pad is still there, though I don't know if it is making solid contact with the PCB trace any longer.  
   
  So here's my question:  After soldering the new "genuine" ALPS pot to the PCB, and if I don't measure continuity between the PCB trace and the ALPS pin in question, can I solder a 22AWG, silver plated copper wire between the ALPS pin and the pin on the 3 pin header which shares the same trace?  Will this affect performance negatively or should I be alright?
  I am unsure if AWG vs trace width and length makes a big difference here.


----------



## tomb

A resistor lead jumper on the bottom would suffice.  It's possible to do it on the top since the Alps sits a bit above the PCB surface and gives you access to the pins.  However, a soldering mask should never take the place of insulation, so if you do it on top, it should probably be an insulated hook-up wire.
   
  You're not going to notice any effect at all with such a short patch.


----------



## ModMax

Quote: 





tomb said:


> A resistor lead jumper on the bottom would suffice.  It's possible to do it on the top since the Alps sits a bit above the PCB surface and gives you access to the pins.  However, a soldering mask should never take the place of insulation, so if you do it on top, it should probably be an insulated hook-up wire.
> 
> You're not going to notice any effect at all with such a short patch.


 
   
   
  I lucked out afterall.  The through hole eyelet on the bottom side of the PCB still had a solid connection to the trace.  Thanks for the advice, Tom re: the resistor lead jump.
   
  By the way, does a new ALPS pot mean I should start over with the setup and biasing of the amp?


----------



## ModMax

Anyone have advice on recommended bias settings for each of the different Millett MOSFET-MAX tubes.  The MAX website recommends 13.5V for each tube given a 27V supply bias.
   
  In and earlier post to me, Tom recommended approx 15V for the 12FM6.
   
  What about the 12AE6 and 12FK6 tubes?  What's the recommended bias setting for each of these?


----------



## tomb

Quote: 





modmax said:


> Anyone have advice on recommended bias settings for each of the different Millett MOSFET-MAX tubes.  The MAX website recommends 13.5V for each tube given a 27V supply bias.
> 
> In and earlier post to me, Tom recommended approx 15V for the 12FM6.
> 
> What about the 12AE6 and 12FK6 tubes?  What's the recommended bias setting for each of these?


 
  Default is 13.5 only because that gives you the maximum voltage swing up and down, but anywhere between 13.5 and 15 is fine.  Why not experiment and see if it makes a difference to you?


----------



## scootsit

So is 15V for the FM the best?


----------



## tomb

Quote: 





scootsit said:


> So is 15V for the FM the best?


 
  Yes, I think so.


----------



## scootsit

Do you think so for all the Millett tubes? I'll try biasing mine higher soon!


----------



## tomb

Quote: 





scootsit said:


> Do you think so for all the Millett tubes? I'll try biasing mine higher soon!


 
  It's possible, but I'm not as certain as I am with the 12FM6's.  Plus, tube biasing on the Millett Hybrid series is not too far off from "adjusting" the volume knob.  It's something you should be checking on a regular basis and perhaps experimenting with a great deal.  JMHO ...


----------



## fmlfml

Is there any other diy balanced headphone amp except beta 22


----------



## tomb

Quote: 





fmlfml said:


> Is there any other diy balanced headphone amp except beta 22


 
  A B22 will only be balanced if you build it that way.  Same for the Millett MAX - Head-Fi user pabbi built one.  A balanced M3 has been built and sold many times - I believe Rockhopper onced offered them commercially.  There are plenty of other examples as well.


----------



## KimLaroux

As tomb said, any DIY amplifier can be built for balanced operation. basically, you just have to build a 4 channel amplifier, and bridge the outputs.
   
  The only limitation is you can't buy a full kit and turn it into a balanced amplifier. You'll need a custom enclosure around twice the size of the normal amp.


----------



## ModMax

My MOSFET-MAX is complete, pics below:
   
   
  1.  The innards.  Integrated grubDAC in upper left corner.  Also, VitQs (Beezar.com) and Elna Silmic II's as part of the build.  Most of the wiring is routed under the PCB.
   

   
   
  2.  Rear view.  Black=GND, Red=V+, Green=L/R Tube Bias, Blue=L/R MOSFET Bias.  RCAs (Beezar.com) and USB for grubDAC.  Square opening took a long while and was started with a 1/4" hole and squared off with a metal file.
   
   

   
  3.  Front View.  Center toggle for power, side toggle for input select (DAC vs RCA).  Both 1/4" and 1/8" TRS plug sockets.  Knob is KILO ML-90-3-6MM from
  DigiKey (Part #226-3028-ND).
   
   

   
   
  4.  Input select toggle.  Down (RED) for grubDAC, Up (GREEN) for RCA.
   
   

   

   
   
  Oh, and did I mention, it sounds amazing!!!  My ears have never been happier especially with my HE-400s.  Current setup:  V+=27 V, 12AE6 Tubes=14 V, MOSFETs=230 mV


----------



## dustinsterk

Quote: 





modmax said:


> My MOSFET-MAX is complete, pics below:
> 
> 
> 1.  The innards.  Integrated grubDAC in upper left corner.  Also, VitQs (Beezar.com) and Elna Silmic II's as part of the build.  Most of the wiring is routed under the PCB.
> ...


 
   
  Wow...look amazing!  Do you mind me asking what the total spend was?


----------



## ModMax

Quote: 





dustinsterk said:


> Wow...look amazing!  Do you mind me asking what the total spend was?


 
   
  Thanks!
   
  Not sure... I do plan on putting a final BOM together with all parts I used... I can get back to you then with some up-to-date pricing on the components for this build.


----------



## tomb

Quote: 





modmax said:


> Thanks!
> 
> Not sure... I do plan on putting a final BOM together with all parts I used... I can get back to you then with some up-to-date pricing on the components for this build.


 
  That's gorgeous!  Great job!!!


----------



## jdkJake

Nice work ModMax. 

I especially like the color-coded bias jacks.


----------



## scootsit

When you mentioned biasing the tubes to 15V, you leave the supply voltage at 27, right?


----------



## tomb

Quote: 





scootsit said:


> When you mentioned biasing the tubes to 15V, you leave the supply voltage at 27, right?


 
  Yes.  That seems to be the limit with a typical 24VAC walwart.  You might can get it up to 28V, but at some point, you push the voltage out of regulation and things end up a lot noisier.  This can depend a bit on your house's line voltage, too - is it 120V or close to 115 or 110V?  All of that led us to the decision to just tell everyone to set the power supply at 27VDC.  That takes care of 99% of the situations while guaranteeing that the regulation is still active.
   
  As for the tubes at 27VDC, the center point of the signal wave would theoretically still be at 13.5V.  So, biasing at 15V means you would lose the tops of the waves at 27-15V = 12V signals, instead of 13.5V signals.  All that means is that you may not be able to turn the volume up as loud without clipping.  Since with most headphones you never even get close to this point, biasing at 15V has a very small effect.  Yet, the tubes seem to run with less distortion at the higher voltage.


----------



## scootsit

Quote: 





tomb said:


> Quote:
> 
> 
> 
> ...


 

 Perfect. I've never even gotten to 12 o'clock on the volume. Thanks, Tomb.


----------



## tomb

Quote: 





scootsit said:


> Perfect. I've never even gotten to 12 o'clock on the volume. Thanks, Tomb.


 
  Keep in mind that this seems to work best with 12FM6 tubes.  I'm not sure 12AE6's and 12FK6's have as much advantage at the higher voltage.  It just seems to suit the 12FM6 the most.


----------



## ModMax

Maybe this has been addressed before, but here goes anyway:
   
  To avoid adjusting bias on the tubes, which seems to vary more than any other bias on my MAX, would it be possible to use a voltage regulator IC (possibly adjustable depending on tube in use) to provide a stable tube bias VDC?
   
  I am curious since I am not aware of commercial tube hybrid amps (Schiit, etc) requiring bias adjustments...


----------



## tomb

Quote: 





modmax said:


> Maybe this has been addressed before, but here goes anyway:
> 
> To avoid adjusting bias on the tubes, which seems to vary more than any other bias on my MAX, would it be possible to use a voltage regulator IC (possibly adjustable depending on tube in use) to provide a stable tube bias VDC?
> 
> I am curious since I am not aware of commercial tube hybrid amps (Schiit, etc) requiring bias adjustments...


 
  There's a catch: commercial tube hybrid amps (Schiit, etc.) do not use three completely different types of tubes.  And by different, I mean entirely different plate loadings.  They are designed for one tube, period.  Then everyone looks for all the other tubes that are functional equivalents and tries them for different sound characteristics (tube rolling).  Or, they go further and choose not-quite equivalent - but perhaps similar - tubes for even more differences in sound.  Bottom line, all the mfr has to do is simply choose one bias-setting resistor (assuming a similar circuit) and that's that.
   
  Secondly, think for a minute about the voltage difference in commercial amps and the Millett Hybrid circuit.  The Millett uses automobile radio tubes - tubes that were designed to be used where the maximum voltage on the plates was around 12V.  Say your bias on a Millett is 1 or 2 volts off of optimum.  That's 10 to 15% error in the bias setting - somewhat significant.  However, consider a commercial amp that doesn't use these DIY-friendly tubes (low-voltage, no killings or electrocutions involved): it uses 100, 200, maybe even 300V on the tube plates.  Granted, the tubes may vary somewhat proportionally in bias variance - but not completely.  The bias voltage errors from tube to tube then become scatter within those huge voltages.
   
  The Millett Hybrid and its variants - the revMH Millett Hybrid, the Millett Hybrid MAX, the Millett Hybrid MiniMAX, and the Millett Hybrid MOSFET-MAX, use three different tubes with different gain structures.  It's liking saying a commercial amp can take a 12AX7 and run the same with a 12AU7 (it can't).  That's why the bias is adjustable with trim pots.
   
  Now, it just so happens that the Millett-style space-charge tubes happen to vary quite a bit in their bias settings, even among the same tube types.  That's another reason for having the little trimmers.  I suppose you might say there's a price to be paid for not worrying about electrocution.
	

	
	
		
		

		
			




   
  That said, there is a dirty little secret that I will share, but not recommend: assuming you stick with the same tube type, you can probably set the bias once and get away with simply changing tubes out and never re-adjusting.  Yeah, it won't have the optimum voltage swing if the bias is off, but it will still play and sound pretty good.
	

	
	
		
		

		
		
	


	




  It won't if you take out a 12AE6 and replace it with a 12FK6, however.  The bias may be so far off that there isn't enough voltage swing to produce an output.  Hence, the adjustable-resistance trimmers. 
	

	
	
		
		

		
		
	


	



   
   
  P.S. The Starving Student Millett Hybrid does not fall under this category.  It's a completely different design than the original Millett Hybrid and its variants.  It uses high-voltage tubes at a medium voltage - and the circuit is designed for that one tube, only.


----------



## ModMax

Quote: 





tomb said:


> There's a catch: commercial tube hybrid amps (Schiit, etc.) do not use three completely different types of tubes.  And by different, I mean entirely different plate loadings.  They are designed for one tube, period.  Then everyone looks for all the other tubes that are functional equivalents and tries them for different sound characteristics (tube rolling).  Or, they go further and choose not-quite equivalent - but perhaps similar - tubes for even more differences in sound.  Bottom line, all the mfr has to do is simply choose one bias-setting resistor (assuming a similar circuit) and that's that.
> 
> Secondly, think for a minute about the voltage difference in commercial amps and the Millett Hybrid circuit.  The Millett uses automobile radio tubes - tubes that were designed to be used where the maximum voltage on the plates was around 12V.  Say your bias on a Millett is 1 or 2 volts off of optimum.  That's 10 to 15% error in the bias setting - somewhat significant.  However, consider a commercial amp that doesn't use these DIY-friendly tubes (low-voltage, no killings or electrocutions involved): it uses 100, 200, maybe even 300V on the tube plates.  Granted, the tubes may vary somewhat proportionally in bias variance - but not completely.  The bias voltage errors from tube to tube then become scatter within those huge voltages.
> 
> ...


 
   
   
  Thanks Tom. 
   
  Say I wanted my tube bias to be 14VDC for all tube types, 12AE6, 12FM6, and 12FK6.  Would it be possible to use a voltage regulator, or some other type of component, to dynamically adjust the bias to 14VDC independent of the tube type?
   
  Maybe this is not possible given the circuit topology of the MOSFET-MAX?


----------



## tomb

Quote: 





modmax said:


> Thanks Tom.
> 
> Say I wanted my tube bias to be 14VDC for all tube types, 12AE6, 12FM6, and 12FK6.  Would it be possible to use a voltage regulator, or some other type of component, to dynamically adjust the bias to 14VDC independent of the tube type?
> 
> Maybe this is not possible given the circuit topology of the MOSFET-MAX?


 
  Anything's possible, I suppose, but I suspect you're talking some pretty sophisticated electronics.  I doubt seriously the voltage regulator itself would be that widely tolerant - it would "drop out" of regulation pretty easily.  Some of the variances with the tubes can be as much as 10V from one type to the other.  Again, that's we have trimmers and measure. 
	

	
	
		
		

		
		
	


	




 
   
  Maybe someone else may have a better idea.


----------



## scootsit

Quote: 





tomb said:


> Quote:
> 
> 
> 
> ...


 

 I was actually thinking the same thing. My thought was that the current required would fry an aweful lot of regulators.


----------



## KimLaroux

Not to mention that the 14VDC is just the bias point on the plates. There's also AC audio signal at this point. If you simply place a voltage regulator in there, the regulator will filter out the audio signal.
   
  The only way to do this is to use a servo like in the CTH. But it gets complicated fast. You have to redesign the whole circuit at this point.


----------



## ModMax

Showing my MOSFET-MAX amp with HE-400 + AKG K271 at the Austin head-fi meetup tomorrow!  Can't wait...


----------



## tomb

Quote: 





modmax said:


> Showing my MOSFET-MAX amp with HE-400 + AKG K271 at the Austin head-fi meetup tomorrow!  Can't wait...


 
  Cool!  Post some pics when you can!


----------



## ModMax

Quote: 





tomb said:


> Cool!  Post some pics when you can!


 
   
  Austin head-fi meetup pics posted by member pabbi1 - my amps in one of those pics... 
	

	
	
		
		

		
		
	


	



   
  http://www.head-fi.org/g/a/747422/austin-march-2013


----------



## tdubl07

Hi guys, I'm gonna finish up my build tonight. I've read over all of the construction notes on the mini max site. I have a question. All the biasing for this thing, is this done with the case on? Seems to me it would have to be without the case to measure your db biasing and measure voltages off the pcb reference points? So in other words, do I adjust the trimmers for db biasing and power supply voltage with the case off and then do the tube biasing off of the rear bias posts after the case has been assembled? Edit, this is on a mini max if that matters.
   
  Thanks Trav


----------



## tomb

Quote: 





tdubl07 said:


> Hi guys, I'm gonna finish up my build tonight. I've read over all of the construction notes on the mini max site. I have a question. All the biasing for this thing, is this done with the case on? Seems to me it would have to be without the case to measure your db biasing and measure voltages off the pcb reference points? So in other words, do I adjust the trimmers for db biasing and power supply voltage with the case off and then do the tube biasing off of the rear bias posts after the case has been assembled? Edit, this is on a mini max if that matters.
> 
> Thanks Trav


 
  You are correct.  You can't reach the DB biasing points once it's cased up.  The idea is that the bias never changes - unless you're prepared to take it apart to re-adjust it to some new value.  On the other hand, every tube change needs to be checked for bias, thus the tip jacks in the rear and the little holes on top to poke a trimmer tool through.
   
  Keep in mind that with DB bias, you're not referencing to Ground.  All that's going to show is 27VDC (assuming you set the PS at the recommended voltage).  Instead, you are using the points that bridge the push-pull resistors - RB10-L/R and RB11-L/R.  There are two forward points for each channel, one for each resistor.  Really though, the resistors are not going to be different, but the two points are convenient because of the crowded area between the heat sinks and the output capacitors (CA7, CA8).  Simply pick which one's easiest to get to, then the other measuring point is that channel's tube bias point.  So, if you've wired up the backplate, but haven't totally assembled it, you'd put one DMM probe in the proper channel tip jack.  Then the other probe goes into one of the two forward test points between heat sinks.
   
  I've always recommended 110mV, which results in 50ma, but you can safely push it to 70ma with the MiniMAX custom case - it ventilates that well.  Be sure to use those tall square bumpers I supply, though, otherwise the intake slots on the bottom are covered up.


----------



## tdubl07

Awesome response. Thanks Tom. I'll post up results when i get get buttoned up. Thanks again


----------



## scootsit

Hey guys, have you heard that Intel recently developed a new MOSFET? The transistor is evidently the same as the one in the ivy bridge chips. It allows for 37% faster switching and 50% less power use. They're called tri-gate transistors. Any chance one could be popped into a Millett? More here: http://en.wikipedia.org/wiki/Multigate_device#Tri-gate_transistors
   
  Also, if they use that little power, wouldn't this be a great transistor for portable applications?
  (If the transistors themselves were commercially available, of course)
   
   
  Sorry for the way-off-topic-post


----------



## DudeMyCans

Scootsit. I'm not sure that's going to be any use in power applications, it looks to me that its not a discrete device so much as another way of packing more transistors into a memory chip.


----------



## scootsit

Quote: 





dudemycans said:


> Scootsit. I'm not sure that's going to be any use in power applications, it looks to me that its not a discrete device so much as another way of packing more transistors into a memory chip.


 

 I understand that, this was more theoretically speaking than in practice.
   
  I realize I was unclear in my statement.


----------



## DingoSmuggler

Quote: 





scootsit said:


> Hey guys, have you heard that Intel recently developed a new MOSFET? The transistor is evidently the same as the one in the ivy bridge chips. It allows for 37% faster switching and 50% less power use. They're called tri-gate transistors. Any chance one could be popped into a Millett? More here: http://en.wikipedia.org/wiki/Multigate_device#Tri-gate_transistors
> 
> Also, if they use that little power, wouldn't this be a great transistor for portable applications?
> (If the transistors themselves were commercially available, of course)
> ...


 
  digital circuits are concerned with getting a transistor fully on and fully off as quickly and efficiently as possible, linear amp circuits are concerned with the area in-between.
  A good switching mosfet doesn't mean a good linear mosfet.


----------



## tomb

Quote: 





dingosmuggler said:


> digital circuits are concerned with getting a transistor fully on and fully off as quickly and efficiently as possible, linear amp circuits are concerned with the area in-between.
> A good switching mosfet doesn't mean a good linear mosfet.


 
  Yeah, I don't have nearly the knowledge that you guys do about MOSFETs, but I was going to say ... everything we do is to keep the dang things from "switching" in the first place. 
	

	
	
		
		

		
			




   
  Still, I'm glad scootsit is keeping watch and asking interesting questions!
   
  Here's one that I have that I should've asked AMB but didn't:
  Why are the MOSFET complements in the M3 and B22 (and the MOSFET_MAX
	

	
	
		
		

		
		
	


	




) the Z24 and 9Z*3*4 .. instead of the Z24 and 9Z*2*4?


----------



## tdubl07

Finally got my mini max finished last night. But not before I realised I soldered the transistors on the wrong side of the heatsinks. Apparently the only part of the instructions i missed. That was fun unsoldering those :eek: Sounds great though now that it's done


----------



## KimLaroux

Quote: 





tomb said:


> ...
> Here's one that I have that I should've asked AMB but didn't:
> Why are the MOSFET complements in the M3 and B22 (and the MOSFET_MAX
> 
> ...


 
   
  I'd guess it has to do with those specs:.
   

 ​*IRFZ24*​*IRF9Z24*​*IRF9Z34*​RDSon (ohms)​0.07​0.28​0.14​Transconducatance​4.5​1.4​5.9​
   
  Which shows the 9Z34 matches better to the Z24 than the 9Z24 does.
   
  Though when you compare reaction times and pins capacitance, the 9Z34 is not a better match. But I think those specs can be compensated for in the circuit, while the ones in the table cannot.


----------



## tomb

Quote: 





kimlaroux said:


> I'd guess it has to do with those specs:.
> 
> 
> ​*IRFZ24*​*IRF9Z24*​*IRF9Z34*​RDSon (ohms)​0.07​0.28​0.14​Transconducatance​4.5​1.4​5.9​
> ...


 
  That's as good an explanation as any.  Yet, I'm not so sure that even BJT complements are that close to each other.  I would think reaction times are the most important.
   
  The capacitance differences are definitely compensated in the circuit.  We do the same thing in the MOSFET-MAX:

  A 220pF capictor is bridged across the Z24's.  Again, one would think that compensating in that way - or especially compensating for resistance/transconductance differences would be even easier ... but not reaction times.


----------



## tdubl07

Hi Guys, question on biasing the tubes on the mini max. If I set the tube bias after the amp has been on and listening to it for about 30 min I set the bias to 13.5 on each tube. If I turn it off for a while and then back on, the biases are up to 14.5-14.8 and then slowly settle unitl its warmed up. Is this correct procedure, or do you bias them when cold right after turning on the amp? Sorry if this is a dumb question but I'm new to the tube world


----------



## KimLaroux

Well reaction times are measured as the time it takes for the MOSFET to switch between 10% and 90% of the difference between Vgs and Vds:
   
   

   
  If you consider the times (td, tf) as independent, fixed values, then they create a slope that is dependent on the difference between Vds and Vgs. The higher the difference, the steeper the slope is. Since audio applications, especially headphones ones, don't need the full switching from 10% to 90%, you can cheat by raising the voltages and only using a part of the slope. This way you can match the slopes of different parts, even if their rise and fall times aren't the same.
   
  But then I'm unsure if the times are independent on the difference between the gate and the drain. The datasheets suggests so, anyways.
   
  In reality though, NFB should take care of all of this...
   
  Thinking about it... switching times are probably just not a concern here. We're talking about differences in the nanoseconds. Just to put that in perspective, one nanosecond is the cycle time of a 1 Ghz waveform...


----------



## tomb

Quote: 





kimlaroux said:


> Well reaction times are measured as the time it takes for the MOSFET to switch between 10% and 90% of the difference between Vgs and Vds:
> 
> 
> 
> ...


 
  Well, I think the Class A bias would take care of that, too - switching should be removed from the scenario altogether.


----------



## lmisner

Is ther a downside to bypassing RB14L/R or reducing it to 1 or 2R?


----------



## tomb

Quote: 





lmisner said:


> Is ther a downside to bypassing RB14L/R or reducing it to 1 or 2R?


 
  If you're not using MOSFETs, then no - I've often used nothing but jumpers at RB14.  However, I'm not sure the MOSFET-MAX is stable without about 22R on the output.  Now, I would encourage you to experiment if you're building a MOSFET-MAX.  It's pretty easy to confirm by listening for less bass - that's an indication the MOSFETs are oscillating.  It may be that a higher resistance is needed for RB10 and RB11 - perhaps a 3.3R or 4.7R might make the MOSFETs stable at their output, instead of hanging 22R resistors on the outside.


----------



## lmisner

Ok, thanks.  I have the mosfet version. Never did like the 22R, but figured it was there for protection or phase margin.  Guess I'll hook my scope up and see what I get when I lower the value.


----------



## thomaskuhn

I am surprised that this amp still has a very active forum going for it!  Well, I am finally having to fix something in my MAX that I have had since the first boards were printed.  I have used it ever since in my office.  Well, one thing that always drove me crazy was that I put the power switch "upside down." It always feels more natural to push in the top of a rocker switch to power on.  So I decided to, "ah, 1,2,3" Ill just undo the thumb screws, and flip it.  Well...  The power socket broke apart into about 4 pieces.  I looked on the BOM to get the part number, but notice that and updated BOM had a radio shack all metal socket that could be used. It was easier fro me to go to RS, vs ordering.   My concern is that the original  BOM Socket shows a very clear note... "Must be isolated from Case", but the RS part is all metal.
  
 I already have the RS part, so should I isolate it from the case, or will it work fine the way it is?
  
 Thanks,
  
 Tom


----------



## tomb

thomaskuhn said:


> I am surprised that this amp still has a very active forum going for it!  Well, I am finally having to fix something in my MAX that I have had since the first boards were printed.  I have used it ever since in my office.  Well, one thing that always drove me crazy was that I put the power switch "upside down." It always feels more natural to push in the top of a rocker switch to power on.  So I decided to, "ah, 1,2,3" Ill just undo the thumb screws, and flip it.  Well...  The power socket broke apart into about 4 pieces.  I looked on the BOM to get the part number, but notice that and updated BOM had a radio shack all metal socket that could be used. It was easier fro me to go to RS, vs ordering.   My concern is that the original  BOM Socket shows a very clear note... "Must be isolated from Case", but the RS part is all metal.
> 
> I already have the RS part, so should I isolate it from the case, or will it work fine the way it is?
> 
> ...


 
  
 You definitely need to isolate the power socket if it is metal.  The Millett MAX uses an AC power supply.  If it's not isolated from the case, your amp's ground will be infected with 60 Hz, possibly resulting in hum.


----------



## thomaskuhn

AH, that's right.  Now I remember the AC power supply.  Thanks!!


----------



## H22

Hello all, thought I would bump this thread with a quick update and a poll that might spark some discussion.
  
 It has been so busy at work for the last 8 months that I have not had a whole lot of time to listen to my MHMA, keep it at work on my desk. I however last night I stayed late to do some soldering work on a b22 kit so i figured it was only fitting to fire it up and listen while i breathed massive amounts of solder fumes.
  
 I was using my grub dac as the source. First thing I noticed was just terribly week bass and a very, very flat sound stage, perplexed I decided to take the headphones off and let it warm up for awhile as that tends to help.
 I put the cans bac on after 10 min or so and tried again. No, good, just sounded very flat and no "body" at all. 
  
 After some digging around I found that the wire connections at both the DAC output and amp input looked questionable. I also noticed a melted spot on the DAC output cap closest to the output wires where the iron had hit it and burned into the corner a bit.
  
 After fixing all three of these issues the amp was back to its old self, sounding great! Not sure which "fix" fixed it, don't care, just glad it was simple.
  
 Now for the big question.
  
 Now that this amp has been around awhile, and many have been built, I am wondering if there is a preferred cap set for C7 and C2? I initially built mine with Silmic II's for c2&7, bypassed by wima and VQ respectively.
 I swapped the silmics for MUSE some time ago, but I'm thinking of putting the silmics back in place.
  
 I notice Tomb recommends the green bipolar MUSE ES, I have some of these as well.
  
 So, what are you guys using? is there a favorite? is there any kind of consensus on what seems to be the "best"?
  
 I used the black gates years ago on a mini max build, those things were awesome, wish i could get another set  .


----------



## vixr

I ran the ES and Muse in all mine


----------



## tomb

IMHO, the Elna Silmic RFS II's are every bit as good as Black Gate NX's.  If you have the case height - and it appears that you do - use an Elna Silmic RFS II 1000uf at the cathode bypass and then another Elna Silmic RFS II 1000uf at the output.  The only difference being that you only need a 16V rating on the cathode bypass (the ones by the tubes), but you need a 35V rating at the output.
  
 The only disadvantage to Elna Silmic RFS II's are that they are GIANTs - probably bigger than any other cap you could use.  The Black Gate NX's were positively compact! - their primary redeeming virtue.  Their size puts the Elna's out of the realm of possibility with the MiniMAX and its custom enclosure, but if that's not a design constraint, then the Elna's are the way to go, period.
  
 It's more icing on the cake that you can buy them from "regular 'ol" DigiKey.
  
  
 P.S. Keep the Wima's back at the cathode bypass position.  "Boutique" caps there seem to kill the bass.  As a matter of fact, you can probably go without them with high-quality electrolytics (like the Elna's or BG's).
  
 Up front at the output, the film caps matter for sparkle - use something besides the Wima's, if you can: VitQ's, Sonicaps, Auricaps, Teflon or similar ...
  
  
 P.S.2. Vixr builds great stuff!  Not trying to contradict, but I built a lot of these and specifically tested all the caps.  Muse ES are best for bass and size, but they need bypasses to sound their best (the treble is not so hot by themselves).  I hate Muse KZ's, but maybe that's a personal opinion - very strident and "etchy" to my ears.  The Muse FG's are very, very close to an ideal "mellow" cap - does everything pretty good, but nothing very great.  The Elna's - like I said, as good as BG's, IMHO.
  
 Wima's are great in the back and around the power caps, but horrible up front - they tend to produce a similar sound to the KZ's up front: strident and etchy.  VitQ's are ideal up front, while Sonicap Gen II's add tons of sparkle.  I've tried the Roedersteins that were highly reviewed in other capacitor articles, but they fell way short of the Wima's overall.  I used to use the Russian K42's - they are pretty good when paired with ES's, but fall short otherwise.


----------



## vixr

for me the ES, Muse KZ and FK tubes had the best sound with the HD600, I also always use the corda cross 1 which has a very mellowing effect... With the AE tubes the sound was quite harsh. For film I used wima because my other fave orange drops just killed the bass


----------



## tomb

vixr said:


> for me the ES, Muse KZ and FK tubes had the best sound with the HD600, I also always use the corda cross 1 which has a very mellowing effect... With the AE tubes the sound was quite harsh. For film I used wima because my other fave orange drops just killed the bass


 
 Makes sense ... I normally ran the 12AE6's.


----------



## H22

wow, thanks for all the replies.
  
 I posted that last query right before i started soldering on a y1+y2 project (took a break from the  B22 as I am still waiting on parts for the power supply). 
  
 As I stated before, I initially had elnas in the amp in all positions. Right now I dont remember why i swapped them out, weather it was curiosity or if i was looking for a better sound (possibly due to the a fore mentioned wiring issues?)
  
 The "muze" caps i put in were the KZ units. For testing purposes I went ahead and swapped the output caps to the muze ES units. I was surprised to find that, even though these were half the uf rating of the KZ's (470 vs 1000) tha bass actually sounded better, and had much more impact to it 
	

	
	
		
		

		
		
	


	




, tomb's description of these is accurate for sure. I like them, the VQ's must be doing a good job because i was not wanting for high end either.  I will have to get my hand on a set of the Sonicap Gen II's tomb mentions, I would be interested in this pairing.
  
 think I will leave it s is for now and try to get more listening time on these caps. I still have the elna's, I think i will go ahead and put those back in the rear as i think i am inclined to agree with tomb, the KZ's may not be for me.
  
 while on this subject, I am fairly good at de-soldering, but its still a pain and tends to degrade the PCB pads over time, is there a good solution for putting sockets in place? I realize this would be a bad idea for a permanent install given the weight of the caps (especially the elnas...those suckers are heavy!) but for swapping to find a great combo it would be very useful.
  
 Thanks again guys.
  
 As a side note, once I Finnish the  B22 and Y2 (might be awhile if work picks up again...), my next project was going to be another tube/SS amp, I was thinking the EHHA rev A would be awesome, as people seem to love it. But i'm seriously thinking the torpedo will be my next amp. I already have a hybrid, and the B22 will be my second SS amp (PPA V2 being my beloved first, listening to it now), I have shied away from true tube amps due to the high voltage, but as great as the EHHA is reported to be, i already have a hybrid, and curiosity is killing me, I have never heard a true tube amp, and the torpedo is just too appealing to pass up.


----------



## H22

Tomb, I just looked up the Sonicap Gen II's, they don't appear to offer them in a .22uf rating, rather .15 and .33, what would you recommend?
  
 Joe


----------



## tomb

h22 said:


> Tomb, I just looked up the Sonicap Gen II's, they don't appear to offer them in a .22uf rating, rather .15 and .33, what would you recommend?
> 
> Joe


 
 0.33uf - what goes in the MiniMAX kits right now.


----------



## TBomb06

I realize this is a necro-post, but hopefully I might be able to get an answer to a pretty subjective question that's been on my mind lately as I have been struck with upgrade-itis for no apparent reason.
  
 Is there anything available commercially that compares to the quality or features of a well built Mosfet Max with nice caps (Elna Silmics, VitQs)? Not that I have any complaints with my Max, moreso just curious to know how much one would have to spend on a commercially available product to get something comparable to or better than the Max.


----------



## tomb

tbomb06 said:


> I realize this is a necro-post, but hopefully I might be able to get an answer to a pretty subjective question that's been on my mind lately as I have been struck with upgrade-itis for no apparent reason.
> 
> Is there anything available commercially that compares to the quality or features of a well built Mosfet Max with nice caps (Elna Silmics, VitQs)? Not that I have any complaints with my Max, moreso just curious to know how much one would have to spend on a commercially available product to get something comparable to or better than the Max.


 

 I can't help you much in comparing to commercial products.  The gap between DIY performance and commercial products is pretty wide (DIY+price is superior).  Yet, commercial products are going to be more refined (nicer casework) and have more features (more input/output connections, etc.).  However, Beezar products are proportional in performance with price.  If you look at the BOM for the MOSFET-MAX and its total cost and compare that to a Torpedo, you'll see that the Torpedo is more expensive.  There's a reason for that. 
	

	
	
		
		

		
		
	


	




  Beyond that, there are tube amps that exceed the quality of the Torpedo as well.
  
 That said, the MOSFET-MAX is in the same league as one of those super-powerful hybrid tube amps.  So if you're looking to power some typically inefficient orthos or speakers, then the MOSFET-MAX will win, hands-down.  However, if you're looking for the purest, most transparent sound with "normal" headphone loads, then there's the Torpedo and many other commercial alternatives as well.  You just have to be careful with tube amps in picking transformer-output vs. OTL's.  IMHO, transformer-output amps are miles ahead in transparency compared to the typical OTL tube amp with coupling capacitors (including most hybrids).
  
 Maybe that can give you some insight without my shilling too much.


----------



## TBomb06

tomb said:


> I can't help you much in comparing to commercial products.  The gap between DIY performance and commercial products is pretty wide (DIY+price is superior).  Yet, commercial products are going to be more refined (nicer casework) and have more features (more input/output connections, etc.).  However, Beezar products are proportional in performance with price.  If you look at the BOM for the MOSFET-MAX and its total cost and compare that to a Torpedo, you'll see that the Torpedo is more expensive.  There's a reason for that.
> 
> 
> 
> ...


 
  
 Haha ok, so, let me see if I'm picking up what you're putting down... If I wanted to "upgrade" from my MOSFET-MAX, considering I have some DIY capability, my money would be better spent going the Torpedo route. Or, I can rest soundly knowing that my Max is already pretty good and I really shouldn't worry myself with upgrading. Ehhhh?


----------



## tomb

tbomb06 said:


> tomb said:
> 
> 
> > I can't help you much in comparing to commercial products.  The gap between DIY performance and commercial products is pretty wide (DIY+price is superior).  Yet, commercial products are going to be more refined (nicer casework) and have more features (more input/output connections, etc.).  However, Beezar products are proportional in performance with price.  If you look at the BOM for the MOSFET-MAX and its total cost and compare that to a Torpedo, you'll see that the Torpedo is more expensive.  There's a reason for that.
> ...


 

 That's a pretty good statement, but I won't mislead you.  Can you get noticeably better sound if you spend more?  Yes, but the devil is in the details and it's not always a sure thing.  If you wanted to PM me, I could relate more of my opinion - just remember that it's just that: opinion.


----------



## TBomb06

tomb said:


> That's a pretty good statement, but I won't mislead you.  Can you get noticeably better sound if you spend more?  Yes, but the devil is in the details and it's not always a sure thing.  If you wanted to PM me, I could relate more of my opinion - just remember that it's just that: opinion.


 
 Thanks Tom. Sent you a PM


----------



## H22

Does anyone have FPE files for the MOSFET max? I would love to get some fancy faceplates and lid for mine.


----------



## tomb

h22 said:


> Does anyone have FPE files for the MOSFET max? I would love to get some fancy faceplates and lid for mine.


 

 I don't know, but the MOSFET-MAX website has plenty of drawings with graphic scales and dimensions: MOSFET-MAX Drawings & Templates.  I haven't personally messed with FPE (there's no business case at their prices*), but with the information on the MOSFET-MAX website, you should be able to come up with your own FPE design. 
	

	
	
		
		

		
		
	


	




 
  
  
 * Yes, I know AMB did this for the Mini3, but seriously - he could've done the entire case with laser-etching all around for almost the same price.


----------



## ModMax

I believe there is a problem with my Millett MOSFET-MAX after 2 years of excellent service.
  
 Every now and again, when listening to music/movies, with music/movies paused, or very quiet passages in music/movies, I will hear a buzzing or "bzzzzzt" sound on the left.  Today, I heard it again while watching a movie on my PC while the movie was paused.  I shutdown the movie to investigate as follows:
  
 Specs & Equipment:
 - HifiMan HE-400s
 - Power supply @ 27 V
 - Tube Bias at 14.0 - 14.1 V
 - Mosfet Bias at 275mV
 - Tubes 12AE6 (matched from Beezar)
  
 Boutiques:
 - CA2L/R Elna RFS Silmic II 1000uF, 35V (Handmade Electronics)
 - CA7L/R Elna RFS Silmic II 1000uF, 35V (Handmade Electronics)
 - CA8L/R VitQ 0.22uF 100V PIO Cap (Beezar)
  
 Debug steps so far:
  
 1.  I turned up the volume from min to max - I hear a buzzing from the left earcup between 2 o'clock and 4 o'clock.  Buzzing gets louder progressing from 2 to 4 o'clock then cuts out after 4 o'clock.  No buzzing from right earcup.
  
 Is it a bad driver in left earcup?
 2.  I swapped cable connections on the bottom of the HE-400 earcup terminals between left and right earcups.  Now I heard buzzing on right earcup.  No buzzing on left earcup.
  
 Is it a bad headphone cable?
 3.  I plugged in a pair of Grado SR-60 and some Shure IEMs and I hear buzzing from both only on left side.  No buzzing on right.
  
 Is it a bad tube?
 4.  I swapped left and right tubes.  Buzzing was still only in left earcup.  
  
 Is it a bad 1/4" Neutrik jack?
 5.  I plugged all headphones into the 1/8" jack and heard buzzing only in left earcup between 2 o'clock and 4 o'clock.
  
 Is it a bad integrated grubDAC?
 6.  Buzzing still audible with grubDAC USB disconnected and only in left earcup..
 7.  Switched over to RCA inputs and buzzing still audible only in left earcup.  Nothing plugged into RCA ports.
  
  
 Can someone help with further recommendations for debug to root cause this problem?  Or, better yet, does someone know what the problem is due to past experience?  :-D


----------



## tomb

Well, until I got to #4., I would've instantly said, "bad tube."  However, you have admirably performed the steps necessary to remove the most likely suspects.
  
 I hesitate to mention this, because in my time on Head-Fi I have not read of this happening.  However, relays are known to go bad after extended use and age.  Very often, if they are in the signal stage, a bad set of relay contacts can cause an awful buzz, depending on which channel's relay contacts go bad, first.
  
 If you read a lot of threads in AudioKarma's vintage sections, etc., you might see where this happens with some regularity with equipment using relays that are vintage.  I have a couple of Sony cassette decks where the relays are known to cause problems.  There is a huge, intermittent buzz that occurs - perhaps exaggerated by the huge amplification that takes place in a tape deck among signal, recording, and playback.  Bottom line, it's the relays and it is a known and documented condition.
  
 Again, I have not heard of this happening to any headphone relay-delay circuit on Head-Fi, but if you can maybe place some alligator clips leading to your headphone connections at the right place, you might confirm whether this is the case.  An ideal location would be on the right lead of RB14L before it feeds into RA4L and the relay, and the bottom lead of RB14R, before it feeds into RA4R.
  
 If the buzz still exists after checking your headphone response from these points (maybe you should use a cheap pair of headphones/earbuds), then it has to be a bad transistor in the buffer, most likely.  If the signal is clear when connecting to those points, then replace the relay.
  
 Let us know what you find ...


----------



## ModMax

Thanks, Tom, for the excellent (as usual) advice.  I have not yet given it a try but I will this week and will follow-up with my findings.
  
 On another note, I am having a case of upgrade-itis and I was wondering if my Millet MOSFET-MAX amp is capable of driving the Hifiman HE-500 headphones to their full potential?  I have seen a posting on 6moons that claims these headphone require 1W of power.
  
 Has anyone paired the HE-500 with the Millett MOSFET-MAX and if so, what are your impressions?


----------



## tomb

modmax said:


> Thanks, Tom, for the excellent (as usual) advice.  I have not yet given it a try but I will this week and will follow-up with my findings.
> 
> On another note, I am having a case of upgrade-itis and I was wondering if my Millet MOSFET-MAX amp is capable of driving the Hifiman HE-500 headphones to their full potential?  I have seen a posting on 6moons that claims these headphone require 1W of power.
> 
> Has anyone paired the HE-500 with the Millett MOSFET-MAX and if so, what are your impressions?


 

 Just crank up the bias if there's any doubt - it won't be an issue.  I've had it up to 150ma bias before - it can go higher than that if you can stand to run it hot.  The existing bias recommendation (125ma max) is very conservative.
  
 I've successfully driven modded vintage Fostex's and modded Yamaha's that were very, very inefficient - with a MOSFET-MAX.  The only thing you need to be concerned about are the center heat sinks.  One of those cheapo Extech meters with a thermocouple can help you check this.  You can even mod it to use a 30V power supply, depending on the caps you used.  Granted, that's quite a mod because it would require a transformer, but still ... the MOSFETs can take it.


----------



## ModMax

I have an integrated grubDAC within my MOSFET MAX enclosure with front panel switch to select between RCAs and grubDAC.
  
 I want to add output RCAs to the grubDAC so that I can use the grubDAC with other amps.  Can I just connect a couple RCAs to the grubDAC outputs which are also connected to the MOSFET MAX PCB, or do I need to put another switch in place to select between grubDAC driving MAX PCB vs RCAs?


----------



## FallenAngel

Wiring them in parallel is just fine.


----------



## schubert

*HELLPP!  *My beloved Mosfet Max is misbehaving.  One channel cut out, so I went looking for the problem.  (It turns out the problem had nothing to do with the amp!)  First I rechecked all the biases, which I hadn't done since I built it a couple of years ago.  They were all pretty high, so I reset the tube bias and then started reducing the mosfet bias in one channel and the whole thing went dark.  (At this point I noticed that my cat had chewed through the headphone cord.  Anyone want a free cat?)  Well, I figured the mosfets were fried because of overbiasing, and that a blown fuse made it go dark.  I replaced the mosfets, turned the biasing pots all the way down, and turned it on again - and blew another fuse.  The V+ was OK, still the same 27V.  Any ideas?  What should I look for?


----------



## tomb

schubert said:


> *HELLPP!  *My beloved Mosfet Max is misbehaving.  One channel cut out, so I went looking for the problem.  (It turns out the problem had nothing to do with the amp!)  First I rechecked all the biases, which I hadn't done since I built it a couple of years ago.  They were all pretty high, so I reset the tube bias and then started reducing the mosfet bias in one channel and the whole thing went dark.  (At this point I noticed that my cat had chewed through the headphone cord.  Anyone want a free cat?)  Well, I figured the mosfets were fried because of overbiasing, and that a blown fuse made it go dark.  I replaced the mosfets, turned the biasing pots all the way down, and turned it on again - and blew another fuse.  The V+ was OK, still the same 27V.  Any ideas?  What should I look for?


 

 1. Check the resistance in the biasing pots with the power turned off.  Ensure that they're being turned in the right direction.  A fully "closed" buffer trimmer on the MOSFET-MAX should measure 1K ohm with your DMM.  If it's a lot less, you may have over-biased the buffer.
 2. Check and re-check those mosfets.  Did you switch one from the other?  Are they mounted with the proper shoulder washer?
  
 The 9Z34's go on the inside heat sinks, the Z24's go on the outside heat sinks.  All the mosfets should be on the left side when facing the PCB from the volume pot/headphone jack.


----------



## schubert

There's no question that I overbiased - I had it set right at first, but the bias drifted significantly with time.  The mosfets are in correctly, for it worked ok for quite a while before this happened;  and they're shoulder-washered too.  Question - between which two pins on the biasing pots should there be 1000 ohms when "closed"?  I couldn't tell from the schematic.  I just turned them clockwise as it says in the guide.
  
 Anyhow, I think I'm on my way now - I found that QB1R/L were shorted, so I replaced them and this time the fuse didn't blow.


----------



## tomb

schubert said:


> There's no question that I overbiased - I had it set right at first, but the bias drifted significantly with time.  The mosfets are in correctly, for it worked ok for quite a while before this happened;  and they're shoulder-washered too.  Question - between which two pins on the biasing pots should there be 1000 ohms when "closed"?  I couldn't tell from the schematic.  I just turned them clockwise as it says in the guide.
> 
> Anyhow, I think I'm on my way now - I found that QB1R/L were shorted, so I replaced them and this time the fuse didn't blow.


 

 Well, for future reference, two of the pins are tied together on the trimmers.  So, you either read zero ohms or something else.  I would try to post a pic, but seriously, it's pretty easy to see the trace connecting two of the pins and as I said - if two of the pins measure zero ohms, then put one of the DMM probes on the unused pin. 
	

	
	
		
		

		
			




  
 If QB1R/L are shorted, that can really mess things up.
  
 Good luck in fixing it!


----------



## schubert

Well, duh - don't I feel stupid - I see what you mean now that I look more closely at the schematic.  Anyway, success - it's all put back together, well biased, and making beautiful music again.


----------



## kugino

does anyone here need parts for their millet hybrid builds? i have some leftover parts that someone could use...contact me if you're interested and i can tell you what i have.


----------



## ModMax

tomb said:


> Just crank up the bias if there's any doubt - it won't be an issue.  I've had it up to 150ma bias before - it can go higher than that if you can stand to run it hot.  The existing bias recommendation (125ma max) is very conservative.
> 
> I've successfully driven modded vintage Fostex's and modded Yamaha's that were very, very inefficient - with a MOSFET-MAX.  The only thing you need to be concerned about are the center heat sinks.  One of those cheapo Extech meters with a thermocouple can help you check this.  You can even mod it to use a 30V power supply, depending on the caps you used.  Granted, that's quite a mod because it would require a transformer, but still ... the MOSFETs can take it.


 
 Looks like the issue I have been having is the 1/4" Neutrik jack failing.  The additional 1/8" jack I have installed sounds nice and clear.
  
 Neutrik 1/4" has static.  I think I might have to stick with the 1/8" jack for a while.


----------



## kugino

modmax said:


> Looks like the issue I have been having is the 1/4" Neutrik jack failing.  The additional 1/8" jack I have installed sounds nice and clear.
> 
> Neutrik 1/4" has static.  I think I might have to stick with the 1/8" jack for a while.  The 1/4" Neutrik on Mouser is $1.46/each, but they want $8 shipping!


Yeah, shipping always gets you. Sorry, but I don't have a spare 1/4" jack in my spare parts bin. Hopefully you'll be able to find one...


----------



## tomb

The price plus 1st Class US domestic shipping might be cheaper at Beezar.  In no way do I try to compete with Mouser, though.


----------



## TBomb06

tomb said:


> Actually, the CA2 and CA9 position have the most to do with _preserving_ bass from the basic input signal/source.  It's a question of keeping all there is, or taking some away.  This can happen with the wrong bypass cap at CA9 (don't use Vitamin Q's, there, for instance), or if CA2 is too small (<1000uf).  Either the ES 1000uf 16V or the Elna RFS Silmic II at 1000uf and one of the voltage ratings listed in the previous post is best.  For CA9, you should just use Wima MKP10's.
> 
> As far as bass at CA7, it's strictly controlled by the RC-circuit cutoff frequency formed with CA7, RB14, and the impedance of the headphones.  1000uf should take care of everything down to 4 ohms, assuming you use a 22R at RB14.




Sorry to dig up a post from forever ago, but I was curious to know if there is any benefit to upsizing CA2 to 2200uf from 1000uf. I was considering throwing some 2200uf Silmic IIs in there (currently using 1000uf Silmic IIs) and possibly jumpering CA9 rather than using the Wimas, but I'm not sure if it will be an improvement or a degradation. Thoughts anyone?


----------



## tomb

tbomb06 said:


> tomb said:
> 
> 
> > Actually, the CA2 and CA9 position have the most to do with _preserving_ bass from the basic input signal/source.  It's a question of keeping all there is, or taking some away.  This can happen with the wrong bypass cap at CA9 (don't use Vitamin Q's, there, for instance), or if CA2 is too small (<1000uf).  Either the ES 1000uf 16V or the Elna RFS Silmic II at 1000uf and one of the voltage ratings listed in the previous post is best.  For CA9, you should just use Wima MKP10's.
> ...


 

 Since it's a question of _preserving_ the bass at the  cathode bypass position*, once you achieve that, increasing the cap size has no effect.  I don't know the math off the top of my head.  It depends on the actual voltage going through the circuit at the caps.  That's why many may oversize the cathode bypass cap at that position.  It may be 360uf, 470uf or 680uf, perhaps.  Putting 1000uf there ensures that there's plenty, regardless of the uncertainty on voltage.
  
 IOW, you might be able to reduce the cap size and still retain all of the bass.  Increasing it beyond 1000uf will have no effect.
  
 As for the bypass of the bypass (the Wimas), that's a different mode in play.  For instance, when using Black Gate NX's back there, it was found that no bypass worked best.  The ES's seem to work best with Wima's.  When I tried VitQ's back there, it seemed to kill the bass.
  
 There is no rhyme or reason to bypass caps.  What works, works.  Explaining it is a bit fruitless.  There may be many combinations that work or many that don't.  I experimented with the most common ones available to MiniMAX users and found the best combination that worked.  That's what makes up the BOM and the MiniMAX kits.  Beyond that, have at it - if you wish. 
	

	
	
		
		

		
			





 
  
 * Note that this is completely different than the CA7 position - the output capacitors.  There, the RC circuit formed with the headphone impedance dictates whether the high-pass filter formed allows bass down to 20Hz or below.  With low impedance phones, there may be some improvement with 1000uf caps instead of the 470uf supplied with the kits and in the BOM.  This difference is hard to judge, though, because the ES caps at 470uf have inherently better bass response than higher rated caps that may also fit: Nichicon FG's come to mind.  It's a hard choice between the FG 1000uf and the ES 470uf when 32ohm and below impedance phones are used.  In the case of Grados, I would opt for the ES's every time.  They sound better, produce bass better, and Grados tend to peak out at 50Hz instead of 20Hz, anyway.  The ES's will also sound better with anything above 32Hz.  32 ohms and below with other headphones may be a different story, but then you would be optimizing the amp for a specific set of headphones, most likely, which most people would consider limiting.


----------



## TBomb06

tomb said:


> Since it's a question of _preserving_ the bass at the  cathode bypass position*, once you achieve that, increasing the cap size has no effect.  I don't know the math off the top of my head.  It depends on the actual voltage going through the circuit at the caps.  That's why many may oversize the cathode bypass cap at that position.  It may be 360uf, 470uf or 680uf, perhaps.  Putting 1000uf there ensures that there's plenty, regardless of the uncertainty on voltage.
> 
> IOW, you might be able to reduce the cap size and still retain all of the bass.  Increasing it beyond 1000uf will have no effect.
> 
> ...


 
  
 Thanks Tom! My first MAX build was the original green board with BJT output buffers and Muse ES caps at CA2/CA7 as you described, later modified to include the PS improvements (you walked me through this years ago 
	

	
	
		
		

		
		
	


	




) and VitQs at CA8L/R. It sounded great with my Grado 225s. After the Mosfet MAX red boards came out, I built another one with the Mosfet buffers and used Silmic II caps (1000uf) at CA2/CA7, and VitQs at CA8. I need to go back and A/B my original with my mosfet version and see which I prefer, as I seem to recall the Muse ES version having more/better bass, but it could be my imagination.
  
 As I use this amp almost exclusively with my Grado 225s, you think the ES caps at 470uf with the mosfet build would have better synergy than the Silmic IIs at 1000uf in the CA7 position? I still have a few of the ES's laying around so it wouldn't be hard to switch them out...


----------



## tomb

tbomb06 said:


> tomb said:
> 
> 
> > Since it's a question of _preserving_ the bass at the  cathode bypass position*, once you achieve that, increasing the cap size has no effect.  I don't know the math off the top of my head.  It depends on the actual voltage going through the circuit at the caps.  That's why many may oversize the cathode bypass cap at that position.  It may be 360uf, 470uf or 680uf, perhaps.  Putting 1000uf there ensures that there's plenty, regardless of the uncertainty on voltage.
> ...


 

 Umm ... no.  My comparison was to what is available under the 1" tall MiniMAX hood with the custom-machined case.*  In that case (35V, 25mm height restriction), you only have the choice of Muse ES's, FG's and then non-audio-quality power caps (Nichicon UHE/UPW, Panasonic FM/FC, etc.).  In that scenario, the ES 470uf's are better than the FG 1000uf's (both 25mm tall), but it's close.  I come down on the side of the ES's.
  
 If you have no height restriction (usually the MOSFET-MAX), then Silmics at 1000uf are the way to go ... especially at CA7.  I personally think the Elna Silmic RFS II's are every bit as good as Black Gate NX's.  It's just that they're huge and won't fit into a lot places.
  
  
 * Maybe I misunderstood and thought the question was about the MiniMAX.


----------



## TBomb06

tomb said:


> Umm ... no.  My comparison was to what is available under the 1" tall MiniMAX hood with the custom-machined case.*  In that case (35V, 25mm height restriction), you only have the choice of Muse ES's, FG's and then non-audio-quality power caps (Nichicon UHE/UPW, Panasonic FM/FC, etc.).  In that scenario, the ES 470uf's are better than the FG 1000uf's (both 25mm tall), but it's close.  I come down on the side of the ES's.
> 
> If you have no height restriction (usually the MOSFET-MAX), then Silmics at 1000uf are the way to go ... especially at CA7.  I personally think the Elna Silmic RFS II's are every bit as good as Black Gate NX's.  It's just that they're huge and won't fit into a lot places.
> 
> ...


 
  
 Ah, thanks for clarifying! Yes, I am talking about the MOSFET-MAX with no height restrictions 
	

	
	
		
		

		
		
	


	




 Sounds like a case of "if it's not broke, don't break it 
	

	
	
		
		

		
		
	


	




" so I'll just keep rocking what I have. I'll probably still do an A/B with my BJT MAX with the Muse ES just to see how different it is. Since you seem to view the Silmic IIs very favorably, and previously recommended that the BG NXs sound great without the bypass cap at CA9, do you have any experience with the Silmics un-bypassed at CA9? Just curious if there would be any improvement without the Wimas there like you experienced with the Black Gates.


----------



## NuClear235

So what now?
I am finishing to order BOM.
I selected 
CA2 Silmic II 1000uF 35V
CA4,5 Panasonic 1800uF 35V
CA7 Silmic Ii 1000uF 35V
And
edit: CA8 still I dont know... VitaminQ or Sonicaps or none?

Is it for FET version.
I have big enclosure.


----------



## tomb

nuclear235 said:


> So what now?
> I am finishing to order BOM.
> I selected
> CA2 Silmic II 1000uF 35V
> ...


 

 I would go with the 0.22uf Vitamin Q's.  I don't recommend them most of the time because they won't fit into a MiniMAX.  You should use them at CA8, however - at the output of the amp.  CA9 is at the cathode bypass back at the tubes.  The Wima's are fine there, but you can leave them blank when using the Silmics.  You need very little voltage rating back there for CA2, so you can go with 25V or 16V if you can find the Silmics in that rating.


----------



## NuClear235

Yes, I mean CA8. (already edited)
 So at CA8 is Better VitaminQ than Sonicap ?
 So will be paralel CA7 Silmic II and CA8 VitaminQ?


----------



## tomb

Yes, marginally.  The reason the Sonicaps are used on the MIniMAX is because they fit.  The 0.18uf VitQ's that would fit are gone, so I started using the Sonicaps in the kits.  You don't have that problem on a MAX/MOSFET-MAX and the 0.22uf VitQ's will fit just fine.  You'd be fine with either one, though, it's a very marginal preference toward the VitQ's.
  
 Yes, they will be parallel to CA7.


----------



## TBomb06

At CA4 and CA5, which would be more beneficial, the higher capacitance and lower ripple current of the Nichicon UHE (2200uf, 3450mA) or the higher ripple current but lower capacitance of the Panasonic FM (1800uf, 3820mA)? Or something else with more than 2200uf and greater ripple current? Specifically in a MOSFET Max.
  
 Edit: After thinking about it more, it seems capacitance would be more beneficial than ripple current since CA4/CA5 are after the power supply rather than actually "in" the power supply. Correct?


----------



## tomb

tbomb06 said:


> At CA4 and CA5, which would be more beneficial, the higher capacitance and lower ripple current of the Nichicon UHE (2200uf, 3450mA) or the higher ripple current but lower capacitance of the Panasonic FM (1800uf, 3820mA)? Or something else with more than 2200uf and greater ripple current? Specifically in a MOSFET Max.
> 
> Edit: After thinking about it more, it seems capacitance would be more beneficial than ripple current since CA4/CA5 are after the power supply rather than actually "in" the power supply. Correct?


 

 I use UHE's in the MOSFET-MAX.  Even their 1800uf have better ripple current.  Like with a lot of this, they're just bigger/taller.


----------



## NuClear235

I am finishing my Max FET amp (red PCB). I would like do any improvement (tuning) of this nice amp. So I am thinking about improve pot. 
Change it to stepped ladder attenuator?
Or I found LDR optical attenuator used in some tube amps.
http://www.diyaudio.com/forums/analog-line-level/80194-lightspeed-attenuator-new-passive-preamp.html

Anybody use it?
The LDR has input inpedance only 5kohm. Will be it problem?
Any tip or idea?


----------



## tomb

nuclear235 said:


> I am finishing my Max FET amp (red PCB). I would like do any improvement (tuning) of this nice amp. So I am thinking about improve pot.
> Change it to stepped ladder attenuator?
> Or I found LDR optical attenuator used in some tube amps.
> http://www.diyaudio.com/forums/analog-line-level/80194-lightspeed-attenuator-new-passive-preamp.html
> ...


 
  
 This has been discussed extensively in this very thread.  Search in this thread for "OptiVol".


----------



## NuClear235

I finished MAX FET version. I am very dissapointed with sound. On oscilloscope is all right, but sound is flat, dead, with no instruments separation an almost no space. 
(I have MiniMax BJT and it has excellent sound with almost 3D space.)

Capacitors are ELNA Silmic II, Wima and VitaminQ.
Front FETs are original paired matched Toshiba original 2SK170BL and 2SJ4BL.

Only one thing I did other way - I bought Output FETs unpaired just in local shop.
Can be problem here?

I tried exchange Valve tubes betwen MiniMax and FET Max. No difference. The problem is in output buffer stage.
Any tip, please?


----------



## tomb

nuclear235 said:


> I finished MAX FET version. I am very dissapointed with sound. On oscilloscope is all right, but sound is flat, dead, with no instruments separation an almost no space.
> (I have MiniMax BJT and it has excellent sound with almost 3D space.)
> 
> Capacitors are ELNA Silmic II, Wima and VitaminQ.
> ...


 
  
  As I noted in our e-mails, I'm not sure where your problem is, but originally biasing the buffers to only 90mV might've been a start.  Perhaps it left you with a bad impression when the MOSFETs should've been biased about 3 times that or more.
	

	
	
		
		

		
		
	


	




  The MOSFET buffer with the JFET mod should be superior, though. Here's a pic of your amp:
  

  
 We can't tell a whole lot from that, unfortunately.  We need to know more about the output buffer and what you have supplying it:

Did you jumper out RB1-L/R?  These are standard on the MiniMAX and MAX, but are changed to jumpers only on the MOSFET-MAX.
What voltage do you have supplying the buffer?  You should have 27VDC coming from the power supply and it should be served with 24VAC at 1000ma.
Do you have at least 22R on the output resistors?  The buffer may oscillate if you don't.
Did you install the Toshiba JFETs in reverse to the silkscreen on the PCB?  This is detailed on this page: The Millett Hybrid MOSFET-MAXed Output Stage
Did you use the 2N5486 FETs at QB1-L/R?
Are RB12-L/R 1K trimmers?
RB4, RB5, RB6, RB7, RB8, RB9 - L/R are all 100R?
RB10, RB11 - L/R are 2.2R?
Is PF1 rated for 0.75A?  This could be choking down the power supply, if not.
What is the present bias on the tubes (and what type tubes?)?
What is the present bias on the buffer (mV and ma)?


----------



## NuClear235

Yes, did talk about it thru email. Thak You for all tips.I made this ask to forum, if anybody did not the same problem.
-jumper YES
-YES -27V at stabilied DC part (AC 24V/6A source)
-NO -rezistor 22R I have tampered (as in MiniMax) - I have 300 ohm headphones
-NO -I did it as it is printed on PCB  I will repair it
-YES 1k trimmers
-YES 100R VishayDale
-YES 2.2R
-YES PF1
-Tubes 12EA, bias 13,5V
-Buffer BIAS 230mV between TB1L and TB2L. Current I dont know.

So I will connect output rezistor 22R and rotate FETs...


----------



## tomb

nuclear235 said:


> Yes, did talk about it thru email. Thak You for all tips.I made this ask to forum, if anybody did not the same problem.
> -jumper YES
> -YES -27V at stabilied DC part (AC 24V/6A source)
> -NO -rezistor 22R I have tampered (as in MiniMax) - I have 300 ohm headphones
> ...


 
  
 That's your answer.  Note that it's possible they've been burned out, too.  Transistors can take a lot of abuse, but soldering them in backwards is often not recoverable.  The silkscreen is correct if 2N5087/88's are used, but the reversal is required if the Toshiba JFETs are installed.  There's no good method to show it two ways on the PCB silkscreen, so documenting it thoroughly on the MOSFET-MAX website was the choice.
  
 All of this is detailed here:
  





  
 Anyway, I hope the JFETs are OK and you notice an immediate difference.


----------



## NuClear235

I changet them. Amp plays, so I hope they are OK. Or bad will play too?
Sound stage is better and sound is not so boring. It is big step of improvement.
Thank You for detailed solution. It was mea culpa.

I changed tubes to 12FK6 - fo it is amp build. 12AE I have to MiniMax.
Buffer BIAS set to 250mV. Heatsinks are colder than I expected.
What still stay is that sound is like "speakers playing thru fat textil". So we said it our language-I dont know English equivalent. Highs are not crystal clear... BJT MiniMax still rulez with airy sound.


----------



## tomb

nuclear235 said:


> I changet them. Amp plays, so I hope they are OK. Or bad will play too?
> Sound stage is better and sound is not so boring. It is big step of improvement.
> Thank You for detailed solution. It was mea culpa.
> 
> ...


 
  
 Well, here's another language issue 
	

	
	
		
		

		
		
	


	




 :


> -NO -rezistor 22R I have tampered (as in MiniMax) - I have 300 ohm headphones


 
 I don't really understand what you're saying there.  If you have higher resistance at the output than 22R, that could be a reason you're missing the highs.  Stick with 22R - you might even try less, but I would hesitate to go below 10R.
  
 There is an issue using 12FK6 tubes with 300 ohm headphones, too.  The 12FK6 is the lowest gain tube available in the Millett Hybrid circuit.  There may not be enough voltage swing at that load impedance to properly run the headphones.  This is especially true with the MOSFET-MAX, because the MOSFETs eat up a couple of volts just to attain a turn-on state.  You may have noticed this when biasing.  Unlike BJT's which react to bias changes immediately, you can turn the trimmers quite a few turns (assuming they're set low in their range) before the MOSFETs even react with a higher current.
  
 You should put either 12FM6 or 12AE6 in there if you're using 300 ohm headphones.  That said, it may very well be that the MiniMAX is better with higher-impedance phones.  The MOSFET-MAX is really for low-impedance phones - especially like planars - or flea speakers.  It can really put out the current, but may suffer from lack of voltage swing with high impedance loads.
  
 EDIT: One example of this is several years ago, the two best competing DIY headphone amps were the PPA and the M3.  These two amps were very similar in all respects, except one was based on a BJT buffer, the other used MOSFETs.  Many people think to this day that the PPA was better with Senns with its discrete BJT output than the M3 with MOSFETs.  In any other area, the amps were equivalent or perhaps the nod went to the M3 with lower impedance loads.  So, it's a debate with a rich history, BJT's vs. MOSFETs.
  
 Finally, if the heat sinks are cool, crank it up.  You should be able to hit 150ma (330mV) if you really want to push it.  It may not maintain that when you case it up, but at least you would've tried all the variables.


----------



## NuClear235

I had RB14 replaced by 0R. Now I am trying 22R. Maybe lower volume and other sound signature changed.
I check my older headphones Koss Porta Pro (60 ohm) and Sennheiser HD570 (120 ohm).
They are more compatible, that is true.
Give more Bias to buffer is not improving sound quality at my amp. 
I check it again by oscilloscope - all is perfect.
Maybe I am not compatible with mosfet sound.  it still sounds like all instruments on one pile and covered by wool - as cheap headphone amp in mobile phone. Only bass is deep and dynamics is not bad too. I thought is problem in high-mids - they make space in recording.

Thank You for info about M3 and PPA.


----------



## tomb

nuclear235 said:


> I had RB14 replaced by 0R. Now I am trying 22R. Maybe lower volume and other sound signature changed.
> I check my older headphones Koss Porta Pro (60 ohm) and Sennheiser HD570 (120 ohm).
> They are more compatible, that is true.
> Give more Bias to buffer is not improving sound quality at my amp.
> ...


 
  
 The MOSFETs could be oscillating with 0R at RB14.
  
 That's probably true about more bias.  Current bias does hit a point of diminishing returns.  I just thought it was one more thing to try.
  
 That said, it could very well be your tubes, too.  They can make all the difference between transparency and not.


----------



## NuClear235

Sound is not perfect, but is powerful.
I connected it to my fullrange speakers Fostex and it plays.
Volume is enough for office listening, so probably I will get this amp to my office.
Or I am thinking about change buffer to BJT, I dont know yet...


----------



## tomb

Yep.  I knew it could drive speakers.
	

	
	
		
		

		
		
	


	




 You may need some bigger capacitors on the output to get full bass response, but it's usually a reasonable compromise in using the stock capacitor sizes because desktop speakers can't reproduce deep bass, anyway.


----------



## tomb

nuclear235 said:


> Sound is not perfect, but is powerful.
> I connected it to my fullrange speakers Fostex and it plays.
> Volume is enough for office listening, so probably I will get this amp to my office.
> Or I am thinking about change buffer to BJT, I dont know yet...


 
  
 Just waiting to hear your results after your e-mail expressing worry that _you haven't been biasing things correctly_.  Obviously if that's the case, it will directly affect the sound quality of the amp and any satisfaction with what you're hearing.  I've stated several times before, I believe the MOSFET-MAX - properly configured - has superior sound to the BJT version (MiniMAX).  Anyway, just to help others the complete instructions for biasing are here:
MOSFET-MAX Setup and Biasing


----------



## scottie4442

ok, I have tried looking everywhere, I am trying to build a mosfet max and need either a quad matched 2sj74/2sk170 or replacements, as I am going to build this in mosfet DB.  I have looked everywhere on google and ebay, the only place I can find them are from China and have read the warnings about the fakes from china.  Anyone have any ideas where I can get a quad match or what replacements I can use for these. thanks for any help


----------



## tomb

scottie4442 said:


> ok, I have tried looking everywhere, I am trying to build a mosfet max and need either a quad matched 2sj74/2sk170 or replacements, as I am going to build this in mosfet DB.  I have looked everywhere on google and ebay, the only place I can find them are from China and have read the warnings about the fakes from china.  Anyone have any ideas where I can get a quad match or what replacements I can use for these. thanks for any help


 
 Order them from bdent.com (B&D Enterprises, they're in New Jersey):
http://www.bdent.com/2sk170bl-2sj74bl-toshiba-audio-transistor.html


----------



## scottie4442

Thanks, I will try them. I want to setup my MOSFET max for my internet radio that I am building, just some flea speakers, for my desktop at work. I have seen that some people on here mention running the MOSFET max with 12aj6's but you would need high PS voltage, any idea where I could get a list of changes to run them?


----------



## tomb

scottie4442 said:


> Thanks, I will try them. I want to setup my MOSFET max for my internet radio that I am building, just some flea speakers, for my desktop at work. I have seen that some people on here mention running the MOSFET max with 12aj6's but you would need high PS voltage, any idea where I could get a list of changes to run them?


 
  
 Nope - the 12AJ6 is rated for 30V - same as the other Millett Hybrid tubes.  You should be able to pop them right in there and bias to 13.5V.
  
 Trouble is, the 12AJ6 is a unicorn.  I've never seen one anywhere, nor have I ever heard of anybody having one.


----------



## schubert

The Tube Store has them, or claims to have them, anyway.
http://www.thetubestore.com/Tubes/12A-Types/12AJ6


----------



## scottie4442

I have 14 of them and saw that they were supposedly compatible, I will try them out and post results, I also have 12ae6 and 12fm6 so I will try to compare them all.


----------



## tomb

schubert said:


> The Tube Store has them, or claims to have them, anyway.
> http://www.thetubestore.com/Tubes/12A-Types/12AJ6







scottie4442 said:


> I have 14 of them and saw that they were supposedly compatible, I will try them out and post results, I also have 12ae6 and 12fm6 so I will try to compare them all.




You guys are right and I was wrong.

I was going from memory and mixed it up with the 12FT6. That's the unicorn. I mentioned it on this page, but not on the other Millett Hybrid pages, for some reason - maybe because I thought there was no point in pursuing a unicorn:


> There is also the 12FT6 tube, with an amplification of 15, but I can find no one who can substantiate whether it actually existed.



http://diyforums.org/MiniMAX/MiniMAXtubes.php

The problem with the 12AJ6 is that the amplification factor is *55!* It's probably un-usable in a headphone amp. This is detailed here:
http://diyforums.org/MOSFET-MAX/MOSFET-MAXtubes.php


----------



## scottie4442

I know the 12aj6 are not good for headphone, but thought they might work well for small 8 ohm speakers. I am researching any changes that need to be made to the mosfet max so that these work, some people have said that they clip off at low volumes, not sure if this is after trying them or if they have looked at the specs and are making this call.


----------



## tomb

By all means, give them a try.

Clipping is the danger, though. With that kind of gain, you will quickly exceed the voltage available to the buffer.


----------



## scottie4442

I am researching how to get more voltage to the buffer circuit, especially with out hitting the tube with more voltage.


----------



## addseo1118

Nice to see your posts. Thanks for sharing here.


----------



## NuClear235

I have now big problem:
 When I am changing the volume with Alps pot so I hear SCRATCHING in sound.
 I tried:
 -change tubes (12AE to 12FK)
 -change pot (I thied 6 pots, different values too /5k/22k/50k/100k)
 problem still is it here!
  
 Did not have the same problem anybody here, please?


----------



## DingoSmuggler

nuclear235 said:


> I have now big problem:
> When I am changing the volume with Alps pot so I hear SCRATCHING in sound.
> I tried:
> -change tubes (12AE to 12FK)
> ...


 
 This sounds like there is DC current across the pot, which would be due to the DC-offset from your source.
 A film cap on each left & right input leads, before the pot will AC couple them, and should get rid of the scratching.
 2.2uF would be my preferred value for a 50k pot, but anything between 1uF and 10uF will do the trick.


----------



## NuClear235

It makes scratching sound  when is not connected at input any source...
 So where is DC voltage from ?


----------



## DingoSmuggler

nuclear235 said:


> It makes scratching sound  when is not connected at input any source...
> So where is DC voltage from ?


 
 Well I'm all out of ideas now. Good luck eliminating this gremlin.


----------



## NuClear235

When I insert capacitor after pot, so is problem gone. But is it another capacitor in signal way.


----------



## tomb

nuclear235 said:


> When I insert capacitor after pot, so is problem gone. But is it another capacitor in signal way.


 
  
 Yes, but as we discussed in e-mails, what is between the pot and the source? (Answer: nothing) Why would a capacitor after the pot stop the scratching?  If it's DC, then where is it coming from if not from the source?  You stated you didn't even have a source connected.  I suspect that may be the issue, but I can't explain why.


----------



## NuClear235

Solved: I bought new tubes and scratching is gone.


----------



## tomb

Glad to hear the new tubes solved it!


----------



## mik000000

i am sure this has been covered in this thread, but i cant find it.
  
 if i dont want to use a wallwart, all i need is a 24vac transformer to feed the max board directly? i understand i would be risking adding noise from the transformer.
 thanks


----------



## tomb

mik000000 said:


> i am sure this has been covered in this thread, but i cant find it.
> 
> if i dont want to use a wallwart, all i need is a 24vac transformer to feed the max board directly? i understand i would be risking adding noise from the transformer.
> thanks


 
 If you want to put the transformer in the same case, then yes - you run the risk of adding noise.
  
 If you simply purchase a 24VAC transformer, put it in a box, then use leads to connect it to the Millett MAX, then no - there is no difference from the walwart.
  
 P.S. It's quite possible that you can locate a 24VAC transformer within the same case as the MAX and have it just as noise-free, it's just that it becomes a trial and error procedure to find out what distance/position results in low-noise.


----------



## mik000000

thanks.
  
 i have an Amveco 62063 in my drawer which is 30vac (2 x 15v). will that be too much voltage?


----------



## tomb

mik000000 said:


> thanks.
> 
> i have an Amveco 62063 in my drawer which is 30vac (2 x 15v). will that be too much voltage?


 
 Could be.  Depending on the current rating of the transformer, you could get as much as 33-35VDC.  If you regulate that back down to the typical 27VDC used on a walwart-equipped MAX, you may not have enough heat sink to burn off that much voltage.  It would be pretty wasteful, anyway - better to let it run at the higher voltage.  The only issue you would have is with the voltage rating for many of the electrolytic capacitors on the PCB.  That's too close to the 35V electrolytic capacitor rating used for most of the caps.  You should change to capacitors with a 50V rating (next highest step after 35V) throughout the MAX.
  
 The tubes will like the higher voltage, though - and so will the rest of the amp.


----------



## JamesBr

tomb said:


> Could be.  Depending on the current rating of the transformer, you could get as much as 33-35VDC.  If you regulate that back down to the typical 27VDC used on a walwart-equipped MAX, you may not have enough heat sink to burn off that much voltage.  It would be pretty wasteful, anyway - better to let it run at the higher voltage.  The only issue you would have is with the voltage rating for many of the electrolytic capacitors on the PCB.  That's too close to the 35V electrolytic capacitor rating used for most of the caps.  You should change to capacitors with a 50V rating (next highest step after 35V) throughout the MAX.
> 
> The tubes will like the higher voltage, though - and so will the rest of the amp.


 
 +1, good explanation !


----------



## mrpoutyjeans

Hi, not sure if this thread is still active or if anyone is looking that could provide me with some guidance, but I'm kind of going crazy. My friend and I each purchased a MAX kit from glassjaraudio and built identically. His amp is just great!
  
 Mine, not so much.
  
It's constructed identically to the first, it powers on and holds a steady voltage across the V+ and G measuring points for ~10 seconds, then immediately the voltage plummets to almost nothing over the course of about 15-20 seconds. I've measured the voltage between the output leg (middle position) of the LM317T power supply regulator and common ground, and successfully tuned it to 27V. Still, each time I power the amp on it holds voltage up to 17-19V for a few seconds and then it drops to near zero. I've been able to watch the tube LED's light up fully on power on, stay fully lit for ~10 seconds, then start dimming in correlation with the power drop until they are barely lit.
 
I am at a complete loss as to why this is happening, and have swapped tubes and power supplies between the working amp and the broken one without solving the issue. My thinking is there's a bad part somewhere in the mix, but I am not sure where to start looking or how to diagnose a part failure such as this. I've gotten familiar with the relay-delay on the working amp (waiting 10-15 seconds after an input source is applied to start hearing any output), and my first thought was there may be fault after this relay opens up. The voltage holds steady at 17-19V for 10-15 seconds, then starts dropping violently until the current measured between V+ and GND is only between 1V and 2V. 
 
Any ideas? My hunch is a component somewhere along the way, but I am reluctant to start blindly replacing parts without a clue what is causing the failure. It's almost as though a component is causing the power supply to stop delivering full power, or maybe a capacitor is charging past its rated voltage and draining the PSU faster than it can recharge?
 
Another thing I've noticed is subsequent power-on's after a first failed attempt will result in the voltage drop occurring much quicker, with power building for only a few seconds before dropping to between 1V and 2V measured at V+ and GND.
 
Thanks,


----------



## tomb

mrpoutyjeans said:


> Hi, not sure if this thread is still active or if anyone is looking that could provide me with some guidance, but I'm kind of going crazy. My friend and I each purchased a MAX kit from glassjaraudio and built identically. His amp is just great!
> 
> Mine, not so much.
> 
> ...


 
  
 There are a number of things that can cause this, but I suspect the symptom you describe is the LM317 (VREG) shutting down due to high current.  I'm not sure the fact that turning it back on more quickly after it shuts down means anything except that the tube heaters don't take as long to warm up.  Thus, the high current shutdown occurs more quickly.
  
 A dead short would tend to be instantaneous, really, and would probably blow the fuse, too.  So, I'm wondering if you simply have the DB's biased too high.   Study this page: http://diyforums.org/MOSFET-MAX/MOSFET-MAXsetup.php and make certain that you are measuring the proper test points when you are biasing the MOSFETs.  The biggest mistake someone usually makes is referencing the bias measurement pads to Ground.  One probe should be on the tube bias point for that channel and then the other at TA2/L-R or TB2/L-R.  If you are really uncertain, you can simply place the probes across the leads of any of the power resistors (the big ones between the heat sinks).  You are measuring the same thing when you do that.  Or, you may not realize you are reading V on the meter when it should be mV.  There are probably other instances of mixing this up, too.
  
 Anyway - check that and see if it helps.
  
 If that checks out, start reviewing the resistors and transistors in the diamond buffer.  If you got some of those mixed up, it could cause an over-current situation.


----------



## ultraman31

mrpoutyjeans said:


> Hi, not sure if this thread is still active or if anyone is looking that could provide me with some guidance, but I'm kind of going crazy. My friend and I each purchased a MAX kit from glassjaraudio and built identically. His amp is just great!
> 
> Mine, not so much.
> 
> ...


 
  
 I'm also thinking about buying a kit from the glassjaraudio, and since you got one not too long ago, I guess you can answer some of the questions I have. The version of PCB is v1.2? Also, does the kit comes with the Mosfet or Diamond Buffer?


----------



## tomb

It's a diamond buffer in either case. The difference is whether the output devices are BJT transistors or MOSFETs.

MOSFETs can be Class A biased at much higher currents (with effect) than BJT transistors. On the other hand, BJT transistors preserve the voltage swing, whereas MOSFETs burn up a couple of volts before they can be biased into Class A.

As for the PCB, Jeff sells the V1.2 PCB that I happily supply him. There is no other at this point.


----------



## ultraman31

tomb said:


> It's a diamond buffer in either case. The difference is whether the output devices are BJT transistors or MOSFETs.
> 
> MOSFETs can be Class A biased at much higher currents (with effect) than BJT transistors. On the other hand, BJT transistors preserve the voltage swing, whereas MOSFETs burn up a couple of volts before they can be biased into Class A.
> 
> As for the PCB, Jeff sells the V1.2 PCB that I happily supply him. There is no other at this point.


 
  
 Thank you for clarification!


----------



## tomb

ultraman31 said:


> tomb said:
> 
> 
> > It's a diamond buffer in either case. The difference is whether the output devices are BJT transistors or MOSFETs.
> ...


 
  
 You're welcome!
  
 About which Jeff sells - pretty sure it's MOSFETs.  Although knowing Jeff, he might supply BJTs, instead - if you asked.  Keep in mind that changes some of the resistors, too, but as said - they're still both diamond buffers.


----------



## ultraman31

tomb said:


> You're welcome!
> 
> About which Jeff sells - pretty sure it's MOSFETs.  Although knowing Jeff, he might supply BJTs, instead - if you asked.  Keep in mind that changes some of the resistors, too, but as said - they're still both diamond buffers.


 
  
 I contacted him and he sent me a part list, and I ended up ordering one from him instead of searching internet for individual parts. Can't wait to start this project!!!


----------



## mrpoutyjeans

> I contacted him and he sent me a part list, and I ended up ordering one from him instead of searching internet for individual parts. Can't wait to start this project!!!


 
  
 Sorry for not replying sooner, but TomB is on top of it anyway!


----------



## FJJB

Hey guys! Im having a similar problem to *mrpoutyjeans. *When I turn on my amp it reads 17v with the trimmer all the way down, and after a few seconds it plummets to around 5v which is insane knowing that it should be 25-27v, and also the LEDs dim. The PS heatsink gets pretty hot and the left channel one gets warm but not hot, the others are ok to the touch. Something really bad must be going on... I jumpered the 2 if the resistors and the J1 plug. Am I missing something?
  
 Oh! and the fuse blew up.
  
 Thanks in advance!


----------



## mrpoutyjeans

fjjb said:


> Hey guys! Im having a similar problem to *mrpoutyjeans. *When I turn on my amp it reads 17v with the trimmer all the way down, and after a few seconds it plummets to around 5v which is insane knowing that it should be 25-27v, and also the LEDs dim. The PS heatsink gets pretty hot and the left channel one gets warm but not hot, the others are ok to the touch. Something really bad must be going on... I jumpered the 2 if the resistors and the J1 plug. Am I missing something?
> 
> Oh! and the fuse blew up.
> 
> Thanks in advance!


 
 I'm still having my issues too . Checked all my connections and resistors, everything should be good but no dice. We thought we traced it to a bad tube, but after ordering some more from Beezar, it's still not working. 
  
 I should have mentioned in my original post that my fuse also blew the first time I powered it up, but since replacing it has not.


----------



## tomb

Did anyone read my post up there - http://www.head-fi.org/t/233941/new-millett-hybrid-maxed-amp/6645#post_12367479 ?
  
 It didn't seem like anyone read it and certainly, no one specifically responded to it.  I can't respond to arrows shot in the dark and try to figure out where they came from.  Troubleshooting begins with an organized approach.  Tell me what is going wrong now and what about what I suggested in the post I referenced?  Have you confirmed that the bias is set properly?
  
 Might be time for some pics, too.


----------



## FJJB

Thanks *tomb* for the information. I must have skipped your post or something. Anyway, just found out what was going on. The problem was a mistake of mine when I soldered QB9R/L and QB8R/L transistors at random because they came in a single package and I thought that they were all the same. Maybe it happened because I had been working on the amp the whole day and the transistors were the last components to install, at least in my build because of the heatsinks, and after installing the power regulator the only things left to solder were the 4 DB transistors which were all in a single package, and I thought well they must be all the same; it was pretty late in the morning already so I was pretty tired and wanted to finish it already...). 
  
 Then I just desoldered two of them which were in the wrong position and swapped them. After that everything is fine and everything is running fine for a few hours now without any drop in voltage.
  
 Hope this helps anyone out there having the same issues as I had!
  
 The sound is incredible btw!


----------



## ultraman31

Third day of working on this amp... and here's the status.
  

  
 I put the trimmer pot backward, so I need to rotate them, but let me know if there's anything I've done incorrectly! 
  
 I have few questions for those who finished with this project.
 1. Is there any easier way to take out the metal piece on the tube socket?
 2. Standard drill is strong enough to put holes in the enclosure (it's Hammond 1455T1601) and is there any easier ways to put holes in it?


----------



## tomb

fjjb said:


> Thanks *tomb* for the information. I must have skipped your post or something. Anyway, just found out what was going on. The problem was a mistake of mine when I soldered QB9R/L and QB8R/L transistors at random because they came in a single package and I thought that they were all the same. Maybe it happened because I had been working on the amp the whole day and the transistors were the last components to install, at least in my build because of the heatsinks, and after installing the power regulator the only things left to solder were the 4 DB transistors which were all in a single package, and I thought well they must be all the same; it was pretty late in the morning already so I was pretty tired and wanted to finish it already...).
> 
> Then I just desoldered two of them which were in the wrong position and swapped them. After that everything is fine and everything is running fine for a few hours now without any drop in voltage.
> 
> ...


 
  
 Well, thanks for letting me know and glad you're enjoying it!
  
 I hope mrpoutyjeans has similar results - ready to help, if otherwise though.


----------



## tomb

ultraman31 said:


> Third day of working on this amp... and here's the status.
> 
> 
> 
> ...


 
  
 There is no bad effect at having the trimmer pots in backward.  It only means you turn the screw in the other direction.  Since we never specify the direction of the screw turning, it doesn't matter anyway.  Further - the tube trimmers are ambidextrous, anyway, meaning there is just as much chance that they have to be turned one way with one type of tube as the other way with another type of tube.
  
 1. You can try carefully prying the socket halves apart with a thin screwdriver blade.  I wouldn't really advise it - I typically break 1 out of 3 or 4 doing it that way.  Take a look at the SSMH PCB website on diyforums.org or the SSMH PCB build thread here on HeadFi (see my sig).  There is an extensive description and how-to on drilling out the socket centers.
  
 2. Standard drill bits should not be used on thin aluminum (including case thickness).  What you need to use is known as a stepped drill bit.  They are available at Harbor Freight pretty cheap:
http://www.harborfreight.com/titanium-nitride-coated-high-speed-steel-step-bit-set-3-pc-69087.html
  
 The one on the left in that link is actually the most useful for a Hammond 1455-series case.  The other two are for thinner and thicker material, respectively.  I demonstrated on the original Millett-MAX website on diyforums.org how to drill all the holes with a hand-held drill.  Admittedly, a drill press is a lot better, but you can get acceptable results if you use a center punch, a stepped drill bit, and perhaps the template system I describe in the Millett MAX website: http://www.diyforums.org/MAX/MAXcasework.php


----------



## Marzie

I'm having some issues with my older Max. I didn't used to have any problems, but I have made some changes, and I'm not sure which one is causing my problem.
  
 I'm hearing frequent static in my headphones. it is not consistent, sometimes it is very faint, sometimes it is loud, mostly loud. Sometimes it lasts for 1 or 2 seconds, stops for 1 or 2, comes back, stops, then stops for 20 seconds. Sometimes it gets really loud and goes for 5-10 seconds with no pause. I usually notice it when my music stops and I haven't started a new album. It is almost like a clicking/chattering sound. Sometimes, it actually is a steady click, like a click track.
  
 I thought it might be the source, but even with the source unplugged, I still hear it. I thought it might be the wall wart or power strip (it still might be.) It was on a power strip and I moved it to its own wall outlet, it got better for  few minutes, or an hour, but now its back.
  
 Earlier when it was really bad and fairly continuous, I was able to make it switch sides, or at least loudness in each side, by alternatively touching the top of CA2L and CA2R. I used to be able to induce or worsen it by jostling the audio cables, which made me think it was source, but same result with no source. Then I was able to do the same with the power cable, which led me to the PSU. Now I don't seem to be able to induce it at all.
  
 As for changes, I recently changed to a different set of tubes that I have had rolling around in a drawer at home for a few years (I'm exaggerating, they were in their boxes, secured, but quite neglected.) I think I used these tubes a few times before I de-casing my Max, I can't recall if the problem existed at that point.
  
 I was taking my max out of its case for testing in another project, and the crappy soldering on the RCA jacks broke free. When I re-cased, I soldered those better than they were at first (IMO.) Also, I think re soldered the power wiring, which I thought would have been a better connection. I replaced the ground wire with navships wire. I also changed over to using the fuse circuit.
  
 Other than being able to change the side of the static, I've tried touching a number of components (jacks, tops of caps, tops of heatsinks, etc) to see if it is a grounding issue. From my experience, that does not appear to be the case.
  
 I made sure all the voltages were good (I can't recall if I checked them right when I replaced the tubes) and they look fine.
  
 Please let me know if there is anything you can recommend. I have more tubes if you think that is the cause, but I don't want to go through the voltage checks again if I don't have to (I'll never get any work done if I'm fiddling with my amp all day!) 
	

	
	
		
		

		
			





 
  
  
 Thanks in advance!
 Mike


----------



## tomb

marzie said:


> I'm having some issues with my older Max. I didn't used to have any problems, but I have made some changes, and I'm not sure which one is causing my problem.
> 
> I'm hearing frequent static in my headphones. it is not consistent, sometimes it is very faint, sometimes it is loud, mostly loud. Sometimes it lasts for 1 or 2 seconds, stops for 1 or 2, comes back, stops, then stops for 20 seconds. Sometimes it gets really loud and goes for 5-10 seconds with no pause. I usually notice it when my music stops and I haven't started a new album. It is almost like a clicking/chattering sound. Sometimes, it actually is a steady click, like a click track.
> 
> ...


 
  
 Could be a ground loop, could be bad grounding, could be the tubes.
  

Ground loops are well documented.  I'm no expert, but you should be able to search and find many methods to remove it.  IMHO, I really haven't seen many cases that are really caused by ground loops, but it's something that should be considered.
Bad grounding at the signal input (RCA jacks).  You mention that you may have had bad soldering on the RCA jacks.  A bad ground connection on the RCA jacks will cause horrible noise on the output of the amp.  It could be intermittent, it could get strong and then get soft or go away.  Waving your hand may affect things if the overall amp has a grounding issue in the signal lines.
Like wise, it could simply be the tubes.  This is the easiest to fix and the easiest to check: replace the tubes.  Bad tubes can do all that you describe and can definitely react simply from waving your hand.  Another thing to check are the pins.  Sometimes, old tubes may have corroded pins (sometimes they can be downright green and crusted).  I try to metal-brush and alcohol treat every pin on tubes that I sell.  Still, the corrosion may be such that even if knocked off the immediate surface finish, storing them for a time may allow some of the corrosion to grow back.  So, check pins and make sure they have a good connection.  If that fails, then change the tubes.


----------



## ultraman31

tomb said:


> There is no bad effect at having the trimmer pots in backward.  It only means you turn the screw in the other direction.  Since we never specify the direction of the screw turning, it doesn't matter anyway.  Further - the tube trimmers are ambidextrous, anyway, meaning there is just as much chance that they have to be turned one way with one type of tube as the other way with another type of tube.
> 
> 1. You can try carefully prying the socket halves apart with a thin screwdriver blade.  I wouldn't really advise it - I typically break 1 out of 3 or 4 doing it that way.  Take a look at the SSMH PCB website on diyforums.org or the SSMH PCB build thread here on HeadFi (see my sig).  There is an extensive description and how-to on drilling out the socket centers.
> 
> ...


 
  
 I took out the trimmer pot and placed in correct alignment and I ordered the step drill bits so it should be in sometime next week. Meanwhile, I put all the parts in pcb and one question came up. For the RB1L/R, the BOM says "NA jumper out (for DB only)". I'm not really sure what jumper out means. Do I leave it alone or put any low impedance resister?


----------



## tomb

ultraman31 said:


> tomb said:
> 
> 
> > There is no bad effect at having the trimmer pots in backward.  It only means you turn the screw in the other direction.  Since we never specify the direction of the screw turning, it doesn't matter anyway.  Further - the tube trimmers are ambidextrous, anyway, meaning there is just as much chance that they have to be turned one way with one type of tube as the other way with another type of tube.
> ...


 
  
 Ah ... I need to change that.  Both MOSFET and BJT are Diamond Buffers (DB), it's just that one is MOSFET and one is BJT. 
	

	
	
		
		

		
		
	


	




  This is a better reference:
http://diyforums.org/MOSFET-MAX/MOSFET-MAXmosfets.php.
 It simply states at the top in the bullet-ed list: "*RB1L/R is jumpered out"*
  
 In electronics, a jumper is a device used to continue the electrical connection with no other affect.  IOW, you take a snipped off lead* from a resistor or diode and solder it in that position, just as if the solid wire was a resistor/capacitor/whatever.  It will have zero resistance, inductance, and capacitance and simply act as a continuation of the circuit traces on the PCB.  The reason this is done, pretty much in every case for a PCB, is to allow flexibility to do something else - if wanted.  In this case, the Millett MAX V1.2 PCB can be built either of two ways - 1) BJT Diamond Buffer, or 2) MOSFET Diamond Buffer.  In the case of the BJT Diamond Buffer, RB1-L/R is populated with 1K resistors and something else is jumpered out, instead.
  
 * Do not use a length of solder, a garbage bag twist tie, or some other useless piece of connector that I've seen others use over the years.
	

	
	
		
		

		
		
	


	




  If you continue in DIY, you should build yourself a little collection of snipped leads of various sizes and thicknesses just for the purpose of using them for jumpers.  It really only takes one DIY project of saving the spent leads in a little baggie (maybe a Mouser baggie to be really cheap) before you'll have more than you ever need in the future.


----------



## ultraman31

tomb said:


> There is no bad effect at having the trimmer pots in backward.  It only means you turn the screw in the other direction.  Since we never specify the direction of the screw turning, it doesn't matter anyway.  Further - the tube trimmers are ambidextrous, anyway, meaning there is just as much chance that they have to be turned one way with one type of tube as the other way with another type of tube.
> 
> 1. You can try carefully prying the socket halves apart with a thin screwdriver blade.  I wouldn't really advise it - I typically break 1 out of 3 or 4 doing it that way.  Take a look at the SSMH PCB website on diyforums.org or the SSMH PCB build thread here on HeadFi (see my sig).  There is an extensive description and how-to on drilling out the socket centers.
> 
> ...


 
  
 I went and tried with the drilling to take metal piece out from the tube socket and ended up cracking both sockets...  I looked for 12ae6 tube socket with the hole in the middle on internet and I found this (http://www.amazon.com/Cary-Bakelite-Vacuum-Socket-12ae6/dp/B00KSFBP8S/ref=sr_1_6?ie=UTF8&qid=1459031877&sr=8-6&keywords=12ae6+socket).


----------



## tomb

ultraman31 said:


> tomb said:
> 
> 
> > There is no bad effect at having the trimmer pots in backward.  It only means you turn the screw in the other direction.  Since we never specify the direction of the screw turning, it doesn't matter anyway.  Further - the tube trimmers are ambidextrous, anyway, meaning there is just as much chance that they have to be turned one way with one type of tube as the other way with another type of tube.
> ...


 

 Yeah, it takes a light touch and a drill press is really the best.
  
 Those sockets you found look OK.  Keep in mind that the pins may be at a different radius dimension than the ceramics, but maybe they're worth a shot!
  
 On the other hand, PM me your address and I'll drill the holes out of a couple of them and send them to you.


----------



## ultraman31

tomb said:


> Yeah, it takes a light touch and a drill press is really the best.
> 
> Those sockets you found look OK.  Keep in mind that the pins may be at a different radius dimension than the ceramics, but maybe they're worth a shot!
> 
> On the other hand, PM me your address and I'll drill the holes out of a couple of them and send them to you.


 
  
 Awesome! I'll send PM right now! Thank you!


----------



## FJJB

Hey guys! So recently after building my Mosfet Max I noticed that one of the tubes is getting more lit and slightly hotter than the other one. When I mean lit I mean the filament inside the tube. Is this normal? so far the sound is great and I have checked the tube bias and its all normal and if I switch the tubes the one that gets lit more still gets as lit as in the other socket (it all stays the same). However, there are times that I turn on the amp and both tubes will glow the same. I know this is not a amp breaking problem however I just want to know if this is normal so that one of my tubes doesnt die earlier than the other because of heat or something.


----------



## tomb

fjjb said:


> Hey guys! So recently after building my Mosfet Max I noticed that one of the tubes is getting more lit and slightly hotter than the other one. When I mean lit I mean the filament inside the tube. Is this normal? so far the sound is great and I have checked the tube bias and its all normal and if I switch the tubes the one that gets lit more still gets as lit as in the other socket (it all stays the same). However, there are times that I turn on the amp and both tubes will glow the same. I know this is not a amp breaking problem however I just want to know if this is normal so that one of my tubes doesnt die earlier than the other because of heat or something.




It could very well be an indication that the tube is going bad. Tubes are almost organic - no two are really indentical. There is nothing inherently wrong about one tube glowing more brightly than another.

However, you say you've noticed this one change its brightness. That probably means it's wearing out. Still, if it sounds OK, just enjoy it until it goes bad. It may yet have time remaining in the hundreds or thousands of hours.


----------



## FJJB

Thanks for the info Tomb. I may add that I just found that a tiny hair of wire from the right channel RCA was touching ground and I would at times lose the sound altogether. However after fixing this problem for some weird reason the tube (which was the one amplifying the right channel) that wasn't getting as lit as the other tube is now getting lit well. Who knows... maybe this short was drawing too much current as to make the tube lit well? or maybe im at a lucky streak of it getting lit all the way.
  
 Whatever it may be, it works, which is what matters and if the tube dies on me I have some replacement although they are the 12FM6 instead of the 12FK6 which im currently using (and honestly like more than the FMs).


----------



## tomb

fjjb said:


> Thanks for the info Tomb. I may add that I just found that a tiny hair of wire from the right channel RCA was touching ground and I would at times lose the sound altogether. However after fixing this problem for some weird reason the tube (which was the one amplifying the right channel) that wasn't getting as lit as the other tube is now getting lit well. Who knows... maybe this short was drawing too much current as to make the tube lit well? or maybe im at a lucky streak of it getting lit all the way.
> 
> Whatever it may be, it works, which is what matters and if the tube dies on me I have some replacement although they are the 12FM6 instead of the 12FK6 which im currently using (and honestly like more than the FMs).


 
  
 I'm glad that you found the problem!  Way to go!


----------



## FJJB

Hey again! I know I have been bothering for a while but another problem came up -___-. Is it normal to have a 120hz hum all the time? This hum is apparent when im at a very low gain, as well as if I crank the volume up all the way with or without a source connected. The volume is constant which kinda tells me that it bypasses the volume pot? Also I tested changing the tubes and detaching any ground (volume pot and RCA). Also I tested the source (DAC) and its clean. Even if I don't have any connection at all I would still hear it, and although with music its barely noticeable, when it gets pretty quite in the music or in video dialogues it gets distracting... I really don't bother with most amp hiss but this hum is quite distracting. Is this normal? could it be a filter capacitor gone bad?
  
 Thanks in advance.


----------



## tomb

fjjb said:


> Hey again! I know I have been bothering for a while but another problem came up -___-. Is it normal to have a 120hz hum all the time? This hum is apparent when im at a very low gain, as well as if I crank the volume up all the way with or without a source connected. The volume is constant which kinda tells me that it bypasses the volume pot? Also I tested changing the tubes and detaching any ground (volume pot and RCA). Also I tested the source (DAC) and its clean. Even if I don't have any connection at all I would still hear it, and although with music its barely noticeable, when it gets pretty quite in the music or in video dialogues it gets distracting... I really don't bother with most amp hiss but this hum is quite distracting. Is this normal? could it be a filter capacitor gone bad?
> 
> Thanks in advance.




You should never hear any ripple with a Millett MAX. The power supply noise is down in the 45 micro-volt range.

You definitely have a problem.


----------



## FJJB

So you think its the power supply stage which might be defective? I will try to swap most of the caps (although they look fine), some rectifiers and at the most extreme the ps lm317t. But this will have to wait until summer because I dont have any tools where I am right now.


----------



## tomb

fjjb said:


> So you think its the power supply stage which might be defective? I will try to swap most of the caps (although they look fine), some rectifiers and at the most extreme the ps lm317t. But this will have to wait until summer because I dont have any tools where I am right now.


 
  
 No, I'm not implying that at all.  The power supply is a superior design.  Swapping caps is not going to do anything, either, unless they're 30 years old or you bought something seriously cut-rate.
  
 The point I was trying to make is that if you built the power supply correctly, that is NOT the problem.  Look elsewhere.


----------



## ultraman31

So over two weeks of work (had to wait for parts), finally came to end (still not quite done yet), At first, there's really loud hum noise, but found out it was the grounding issue. Quick fix and then it sound amazing!! I'm waiting for the heat shrink and heat gun to wrap up the connection and it should be good to go! One thing I noticed is the left LED is blinking time to time. It doesn't affect the sound, so I think it might be faulty LED. Also, I would like to thank @tomb for all the help! Without his help, it would have been rather difficult project!!


----------



## ultraman31

Also, I just got the volume knob which I bought from ebay, but apparently, it's too loose... it has some screw but missing head, so no way to tighten it up. Can anyone recommend the volume knob? I don't want this to happen again...


----------



## FJJB

Just found where the 120hz hum was coming from! I just took some measurements to the power supply and although it was on the 27vdc I used a closer measurement on the DDM and it showed that it was at 27.4~ and so I lowered that value to 26.9vdc and the hum went away. I guess that the variable resistor was too open and wasn't attenuating much of the ripple coming from the PS. Hopefully this post will help future MMM builders troubleshoot a similar problem if ever encountered.


----------



## tomb

fjjb said:


> Just found where the 120hz hum was coming from! I just took some measurements to the power supply and although it was on the 27vdc I used a closer measurement on the DDM and it showed that it was at 27.4~ and so I lowered that value to 26.9vdc and the hum went away. I guess that the variable resistor was too open and wasn't attenuating much of the ripple coming from the PS. Hopefully this post will help future MMM builders troubleshoot a similar problem if ever encountered.



Yes - the LM317 has to "burn" some volts to provide regulation. Regulation is largely the mechanism that removes ripple.


----------



## FJJB

Good to know. Thanks again for helping out on the forums! Hopefully I won't have any problems as to bother again. Now some


----------



## tomb

fjjb said:


> Good to know. Thanks again for helping out on the forums! Hopefully I won't have any problems as to bother again. Now some


 

 Well, thanks, but I probably shouldn't have been so definite that it wasn't the power supply.  Maybe "properly setup" was implied, but not stated. 
	

	
	
		
		

		
		
	


	




  This has been a problem before, though, and I should add some notes on the website(s) about it.
  
 My typical method is to always adjust for the highest voltage I can get with the trimmer.  When you make a half-turn and the voltage no long changes, stop, then dial it back by a full 1.5V at least.  That usually ensures the LM317 is in the range where it is still regulating.  If this voltage is still higher than 27V, then dial it back to 27V.
  
 Anyway, I apologize for not mentioning this possibility as a reason for the hum/ripple you were hearing.


----------



## 3lectroD4ve

Hello,
 Will someone please point me to the JFET (2SJ74B, 2SK170B) matching procedure?
 Thanks


----------



## tomb

3lectrod4ve said:


> Hello,
> Will someone please point me to the JFET (2SJ74B, 2SK170B) matching procedure?
> Thanks




http://www.diamondstar.de/transistor_matching_jfet.html


----------



## 3lectroD4ve

Thanks!


----------



## 3lectroD4ve

Got it working tonight! A little hum but otherwise the sound is sweet.


----------



## tomb

3lectrod4ve said:


> Got it working tonight! A little hum but otherwise the sound is sweet.


 
  
 A Millett Max should NEVER hum.  Either you have bad tubes or your power supply is not operating correctly.  Turn the trimmer until the voltage no longer goes up.  Then turn it back down by at least 1.5V.  That will ensure that the LM317 is in a regulation mode and that it's not adjusted outside of its voltage capability.


----------



## tedk84

hello guys  im the new one, dennis, 32 from germany.

i think i made a mess out of my build  i accidently switched qb8l and qb9l, operated the build WITHOUT a fuse (... yeah, i know, i know). after two or three secs, i saw smoke, think it was near the left tube socket (having the volume pot directing towards me).
now i have the following readings:

v+ and gnd adjusted to 27v.
ta2rl and tb1 are 0v from the beginning,
ta2rl and tb2 have 10mV then slowly drop to zero. 
gnd to ta2l/r are near (edit this in later since im on a train atm).

Can you guys help me fix my build?
Thanks in advance

Dennis


----------



## tomb

tedk84 said:


> hello guys  im the new one, dennis, 32 from germany.
> 
> i think i made a mess out of my build  i accidently switched qb8l and qb9l, operated the build WITHOUT a fuse (... yeah, i know, i know). after two or three secs, i saw smoke, think it was near the left tube socket (having the volume pot directing towards me).
> now i have the following readings:
> ...




QB8 and QB9 are maybe strong enough to withstand being reversed. However, it sounds like you may have burned out one or more of the smaller, TO-92 transistors. Unfortunately, figuring out which transistors may be bad is a difficult thing once they're soldered into the circuit. You should probably replace all of them to be certain.

That may sound awful and it probably is from the amount of work required, but it's only a dollar or two in cost.


----------



## tedk84

tomb said:


> QB8 and QB9 are maybe strong enough to withstand being reversed. However, it sounds like you may have burned out one or more of the smaller, TO-92 transistors. Unfortunately, figuring out which transistors may be bad is a difficult thing once they're soldered into the circuit. You should probably replace all of them to be certain.
> 
> That may sound awful and it probably is from the amount of work required, but it's only a dollar or two in cost.


 
  
  
 Hey TomB,
  
 This is like the 5th edit... my thoughts wouldnt let me get any rest... i was triple- and quadchecking things... end of story - some smoke, but no damage actually. the amp works like a charm, i was just too cautious. after like 10 or 15 rounds, i was able to get 220mV between both TA2(R/L) and TB1/TB2. I then tested with a old headphone...
  
 Anyway, lessons learned... fuses are on the way 
 Thanks for your time and help!
  
 Dennis


----------



## tomb

tedk84 said:


> tomb said:
> 
> 
> > QB8 and QB9 are maybe strong enough to withstand being reversed. However, it sounds like you may have burned out one or more of the smaller, TO-92 transistors. Unfortunately, figuring out which transistors may be bad is a difficult thing once they're soldered into the circuit. You should probably replace all of them to be certain.
> ...


 
  
 Well, that's the best possible news!  Glad to hear it!


----------



## Blooze

Hey Tom! Long, long time no talk.

I'm in the process of getting rid of my big ole speaker rigs and going to headphones as my main squeeze. Gonna have a small set of bookshelves pushed by a pair of Pass ACA's and Aikido as the speaker rig. I happened to have ran across the original Max pcb that I think I got from Vixr. Any reason not to go ahead and populate this thing? I mean, I'd love to have an Ear, but the only way that's gonna happen is if I make a version of my own.

Anyway, glad to be back in the game.


----------



## tomb

blooze said:


> Hey Tom! Long, long time no talk.
> 
> I'm in the process of getting rid of my big ole speaker rigs and going to headphones as my main squeeze. Gonna have a small set of bookshelves pushed by a pair of Pass ACA's and Aikido as the speaker rig. I happened to have ran across the original Max pcb that I think I got from Vixr. Any reason not to go ahead and populate this thing? I mean, I'd love to have an Ear, but the only way that's gonna happen is if I make a version of my own.
> 
> Anyway, glad to be back in the game.


 

 Glad to hear from you!
  
 The original Millett Hybrid MAX is a classic.  Good luck in the build, but I'm sure you won't need it!


----------



## Blooze

Thanks. Gives me a good reason to build the Corda Crossfeed pcb I have too.


----------



## tedk84

NVM


----------



## Blooze

Quick question. Since I have the original V1 board I seem to recall being able to cut a trace, maybe to C5, to improve the PS noise floor. Am I recalling correctly?

Heck, I should probably get the V 1.2 pcb and put a DAC on it. Then buy a DAP to use with it, lol.

 Shoot, I still have an old unpopulated revMH and populated DB pcb for it I never made if I wanna really stretch back.


----------



## tomb

blooze said:


> Quick question. Since I have the original V1 board I seem to recall being able to cut a trace, maybe to C5, to improve the PS noise floor. Am I recalling correctly?
> 
> Heck, I should probably get the V 1.2 pcb and put a DAC on it. Then buy a DAP to use with it, lol.
> 
> Shoot, I still have an old unpopulated revMH and populated DB pcb for it I never made if I wanna really stretch back.


 
  
 You may be thinking of the original Millett Hybrid MAX prototype, which actually became the Mini-MAX.  As it turns out, a ground plane underneath the rectifiers and power supply caps (CR1-A,B,C,D) results in the quietest power supply - as long as there is a very small ground plane connection to the rest of the amplifier circuit.  In the MiniMAX, this was done with a small ground plane trace at RR3.  In the original Millett MAX prototype, which was sized the same as the MiniMAX, a ground plane existed all the way across the PCB.  It was found that this infected the amp with 60Hz hum.  The solution was to cut all the way across the ground plane so that the power supply ground plane was separated from the rest of the PCB, save for a small connection at resistor R3.
  
 That probably sounds very confusing.  The gist of it was that it was originally thought no ground plane at all under the power supply was the correct solution, because it removed the hum when the power supply was built off the board.  So, all original Millett Hybrid MAX boards were made without a ground plane under the power supply section.  However, that was not the _quietest _solution as we discovered later on with the Mini-MAX.  A ground plane is needed under the power supply portion of the board.  Unfortunately, it's kind of hard (impossible) to retrofit the PCB unless it was made that way.
  
 The Millett Hybrid MAX V1.2 incorporates a ground plane under the power supply and is connected with a small ground plane trace to the rest of the PCB near RR3.  This is the best solution for the quietest power supply performance.


----------



## Blooze

Found it. Post #6038.

http://www.head-fi.org/t/233941/new-millett-hybrid-maxed-amp/6030#post_6748727


----------



## tomb

blooze said:


> Found it. Post #6038.
> 
> http://www.head-fi.org/t/233941/new-millett-hybrid-maxed-amp/6030#post_6748727


 

 ​Dang!  I forgot about that.  Good find!
  
 You'll note, however, that it confirms what I said above.  It will be much better with this mod, but it still won't equal MiniMAX performance or the newer Millett MAX V1.2 PCB.  You need the ground plane under the LM317 and the CR1 caps.


----------



## Blooze

tomb said:


> ​Dang!  I forgot about that.  Good find!
> 
> You'll note, however, that it confirms what I said above.  It will be much better with this mod, but it still won't equal MiniMAX performance or the newer Millett MAX V1.2 PCB.  You need the ground plane under the LM317 and the CR1 caps.




Yup. I figured I have the board, might as well build it.


----------



## Marzie

Hi Tom!
  
 I posted a few months back about the MOSFET Max I am building and integrating with a Raspberry Pi. (Thread Here.) Anyway, I am still working on the case, however I finished getting the amp and Pi section built. I am having a major problem with noise however. I'm sure it has something to do with a ground loop, or I am missing something. I'm going to try and be as clear as possible, however I realize this is not a typical design. Below is a pic for reference.
  

  
  
 The 24 VAC wall wart goes to the terminal block in the lower right corner. From there, one side goes back to the AC input of the Max. The other goes to a 24VAC/5VDC "buck" converter. The 5VDC then goes into a small device called an ATXRaspi. That feeds the Pi with 5VDC, and allows you to use a momentary pushbutton to shut down or reboot the pi safely. I don't think that is (directly) causing my problem (see below.)
  
 I will spare you some of the details. Right now, the Main Pi is outputting on the RCA jacks to the Max. There is a lot of hum/noise on that input channel, and even some on the other input channel that has another source or nothing playing. Here are the steps/configurations I have done:
  
 First/desired configuration
 ATXRaspi feeding "Main" Pi - Pi feeding one input channel of amp via RCA jacks (currently using RCA jacks for testing, will be hard wired in final version)
 Result: Lots of hum on that channel, even some hum on the other channel.
  
 Tried other input channel of amp:
 Same result
  
 Tried using headphone out of Main Pi
 Same result
  
 Tried connecting the Main Pi to a seperate power source
 Hum was gone, but need to identify why
  
 Tried connecting (an)Other Pi to ATXRaspi to see if "buck" converter was inducing noise on the main power supply
 Left Main Pi connected to Max and playing while Other Pi was running
 No hum, other than some odd electrical noise when changing tracks in software, and occasional static when just sitting there, will need to track this down eventually but for now, not a major concern
  
 Tried putting headphones into Other Pi while it played music to see if noise followed the ATXRaspi
 Headphone out was perfectly clear, no noise
  
 Connected Other Pi (on ATXRaspi) to Max on one input, left Main Pi playing on other input
 Instant noise as soon as RCA jacks were connected, even on other channel with the Main Pi. The Main Pi only gained a little noise, but the Other Pi had a ton of noise.
  
 So, everything points to some type of ground loop issue. I am horrible at finding the cause of these issues and fixing them, so any help you can offer would be appreciated.
  
 One thing to note, I am using a wood case, and I know that affects it somehow, being that it is completely insulated.
  
 Anyway, I'm sure you can point me in the right direction. Thanks!
  
 Mike


----------



## tomb

> Tried connecting the Main Pi to a seperate power source
> Hum was gone, but need to identify why
> 
> *Tried connecting (an)Other Pi to ATXRaspi to see if "buck" converter was inducing noise on the main power supply*
> ...


 
  
 I'm not really understanding that bolded part, but the sentence above that is the key.  Especially suspicious is the "buck" converter.  Those devices are sometimes notorious for noise on the converted DC line.  Depending on how the wiring is setup to the ATXRaspi on the MAX board, it could be infecting the signal lines.  Notice how the ground plane is limited around the power supply on the MAX and only connected to the rest of the amplifier circuit with a small piece of ground plane in the center.  This is what makes the difference between whether the ground plane reduces noise versus increases it.  It came about after many months and prototype testing of the basic Millett Hybrid MAX and MiniMAX.  (And NO it was not copied - Colin Toole's ground plane design was independently developed with a little bit of my help, it pre-dated any of Cavalli's designs, and it is documented with its time reference on diyforums.org.)
  
 I'm no expert on ground loops, either, but I'm not sure a ground loop - in the traditional sense - is possible when the walwart is essentially ungrounded.  The two-wire AC output from the walwart has no ground reference.  The MAX board creates its own ground for the circuit, but this is completely isolated from the 24VAC inlet plug.  Even if you used a metal inlet plug, it would still be insulated by the wood.  So, I don't think a potential ground loop has anything to do with this.  Instead, I think the AC (or other power noise) is leaking back out of the buck converter's DC and somehow infecting the signal lines on the MAX, perhaps through the ATXRaspi?
  
 If I understand your description of tests, the first sentence in your quote above solved the problem.  I don't know if that implies the buck converter was still in the circuit, but I would work toward keeping the buck converter away from the circuit that supplies the MAX.  Your ingenuity in using the terminal block is commendable, but with the buck converter, it sounds like it created more problems than it solved.


----------



## Marzie

I'll explain the bolded part. I left the buck converter connected to the power circuit as before, but powered a different pi with it. I then hooked a wall wart up to the Pi that is supposed to go to the amp. When I connected the RCA of the Main pi to the amp, there was no noise, even with the buck converter still in the power supply circuit, just not powering the Main Pi. I then plugged my headphones into the other pi, the one that was connected to the buck converter. There was no noise on it. Then I connected the other pi to the amp. The hum came back. So it only occurs when ANY pi and the amp are connected to the same power circuit AND connected to each other. Each on their own is fine with the same power circuit. It's only when I try to connect one to the other that the ground issue surfaces.
  
 I could bring another power supply for the Pi into the amp enclosure, but I feel that would be a little silly. I could also (potentially) bring in 120 VAC and include separate internal/external (top of the enclosure) transformers for both the 5 VDC and the 24 VAC.Seems like a little overkill, but I really want to use this design. I might just say screw it and buy or make a nice enclosure for the pi that matches the amp enclosure. Just frustrating as this _should _work.
  
 I spent some time taking a bunch of voltage measurements. Some of them won't matter at all, as I'm sure they are effectively the same measurement. But maybe you can draw more from them than I can. If you need clarification, let me know, I was just jotting them down in a way that made sense to me. Maybe not so much to others.
  
 One thing I didn't try, and I don't know if it would be a good idea or not, was to connect the amp output ground to the star ground. Not sure what effect that would have, but I don't think it would be good.
  
 The biggest potential measurement issues that I see are:
  
*[color=rgba(0, 0, 0, 0.870588)]Voltage difference from pi output to amp star with music playing from phone and headphones connected to pi and amp (NOTE: Amp and Pi are NOT connected at this point)[/color][color=rgba(0, 0, 0, 0.870588)][/color]
 [color=rgba(0, 0, 0, 0.870588)]453-463 mV DC[/color][color=rgba(0, 0, 0, 0.870588)][/color]
 [color=rgba(0, 0, 0, 0.870588)][/color]
 [color=rgba(0, 0, 0, 0.870588)]Voltage difference from pi output to amp input with music playing from phone and headphones connected to pi and amp (NOTE: Amp and Pi are NOT connected at this point)[/color][color=rgba(0, 0, 0, 0.870588)][/color]
 [color=rgba(0, 0, 0, 0.870588)]453-463 [/color]**[color=rgba(0, 0, 0, 0.870588)]mV DC[/color]** *
  
*[color=rgba(0, 0, 0, 0.870588)]Voltage difference from amp input/phone output to amp OUTPUT ground with music playing, amp set to phone channel and headphones connected (NOTE: Amp and Pi are NOT connected at this point)[/color][color=rgba(0, 0, 0, 0.870588)][/color]
 [color=rgba(0, 0, 0, 0.870588)]0.2 [/color]**[color=rgba(0, 0, 0, 0.870588)]mV DC[/color]*
  
*[color=rgba(0, 0, 0, 0.870588)]Voltage difference from amp input/pi output to amp output ground with music playing, amp set to pi channel and headphones connected[/color][color=rgba(0, 0, 0, 0.870588)][/color]
 [color=rgba(0, 0, 0, 0.870588)]0.5 [/color]**[color=rgba(0, 0, 0, 0.870588)]mV DC[/color]*
  
*Measurements*
  
 [color=rgba(0, 0, 0, 0.870588)]NOTE: All STAR ground references tests were actually tested using ground reference test point, not the one in the center of the board. "Earth" is using the ground terminal of a wall outlet.[/color]
  
 [color=rgba(0, 0, 0, 0.870588)]All measurements in mV DC.[/color][color=rgba(0, 0, 0, 0.870588)][/color]
 [color=rgba(0, 0, 0, 0.870588)][/color]
 [color=rgba(0, 0, 0, 0.870588)]-0.3 mV DC to 1.2 in air, 0 when completely still[/color][color=rgba(0, 0, 0, 0.870588)][/color]
 [color=rgba(0, 0, 0, 0.870588)][/color]
*[color=rgba(0, 0, 0, 0.870588)]Amp[/color]*[color=rgba(0, 0, 0, 0.870588)][/color]
 [color=rgba(0, 0, 0, 0.870588)][/color]
 [color=rgba(0, 0, 0, 0.870588)]Voltage difference from star to earth[/color][color=rgba(0, 0, 0, 0.870588)][/color]
 [color=rgba(0, 0, 0, 0.870588)]15 - 20[/color][color=rgba(0, 0, 0, 0.870588)][/color]
 [color=rgba(0, 0, 0, 0.870588)][/color]
 [color=rgba(0, 0, 0, 0.870588)]Voltage difference from input to earth[/color][color=rgba(0, 0, 0, 0.870588)][/color]
 [color=rgba(0, 0, 0, 0.870588)]35 - 50[/color][color=rgba(0, 0, 0, 0.870588)][/color]
 [color=rgba(0, 0, 0, 0.870588)][/color]
 [color=rgba(0, 0, 0, 0.870588)]Voltage difference from star to earth with music playing from phone[/color][color=rgba(0, 0, 0, 0.870588)][/color]
 [color=rgba(0, 0, 0, 0.870588)]75 -85[/color][color=rgba(0, 0, 0, 0.870588)][/color]
 [color=rgba(0, 0, 0, 0.870588)][/color]
 [color=rgba(0, 0, 0, 0.870588)]Voltage difference from amp input/phone output to earth with music playing from phone[/color][color=rgba(0, 0, 0, 0.870588)][/color]
 [color=rgba(0, 0, 0, 0.870588)]75-85[/color][color=rgba(0, 0, 0, 0.870588)][/color]
 [color=rgba(0, 0, 0, 0.870588)][/color]
 [color=rgba(0, 0, 0, 0.870588)]Voltage difference from star to earth with music playing from phone and headphones connected [/color][color=rgba(0, 0, 0, 0.870588)][/color]
 [color=rgba(0, 0, 0, 0.870588)]75-80[/color][color=rgba(0, 0, 0, 0.870588)][/color]
 [color=rgba(0, 0, 0, 0.870588)][/color]
 [color=rgba(0, 0, 0, 0.870588)]Voltage difference from amp input/phone output to earth with music playing from phone and headphones connected[/color][color=rgba(0, 0, 0, 0.870588)][/color]
 [color=rgba(0, 0, 0, 0.870588)]75-80[/color][color=rgba(0, 0, 0, 0.870588)][/color]
 [color=rgba(0, 0, 0, 0.870588)][/color]
 [color=rgba(0, 0, 0, 0.870588)]Voltage difference from amp input/phone output to STAR with music playing amp set to phone channel and headphones connected[/color][color=rgba(0, 0, 0, 0.870588)][/color]
 [color=rgba(0, 0, 0, 0.870588)](NOTE: Amp and Pi are NOT connected at this point)[/color][color=rgba(0, 0, 0, 0.870588)][/color]
 [color=rgba(0, 0, 0, 0.870588)]0.1-0.4[/color][color=rgba(0, 0, 0, 0.870588)][/color]
 [color=rgba(0, 0, 0, 0.870588)][/color]
 [color=rgba(0, 0, 0, 0.870588)]Voltage difference from star to amp OUTPUT ground with music playing, amp set to phone channel and headphones connected, (NOTE: Amp and Pi are NOT connected at this point)[/color][color=rgba(0, 0, 0, 0.870588)][/color]
 [color=rgba(0, 0, 0, 0.870588)]0.1-0.2[/color][color=rgba(0, 0, 0, 0.870588)][/color]
 [color=rgba(0, 0, 0, 0.870588)][/color]
 [color=rgba(0, 0, 0, 0.870588)]Voltage difference from amp input/phone output to amp OUTPUT ground with music playing, amp set to phone channel and headphones connected (NOTE: Amp and Pi are NOT connected at this point)[/color][color=rgba(0, 0, 0, 0.870588)][/color]
 [color=rgba(0, 0, 0, 0.870588)]0.2[/color][color=rgba(0, 0, 0, 0.870588)][/color]
 [color=rgba(0, 0, 0, 0.870588)][/color]
 [color=rgba(0, 0, 0, 0.870588)]Voltage difference from earth to amp OUTPUT ground with music playing, amp set to phone channel and headphones connected (NOTE: Amp and Pi are NOT connected at this point)[/color][color=rgba(0, 0, 0, 0.870588)][/color]
 [color=rgba(0, 0, 0, 0.870588)]135-145[/color][color=rgba(0, 0, 0, 0.870588)][/color]
 [color=rgba(0, 0, 0, 0.870588)][/color]
*[color=rgba(0, 0, 0, 0.870588)]Pi[/color]*[color=rgba(0, 0, 0, 0.870588)][/color]
 [color=rgba(0, 0, 0, 0.870588)][/color]
 [color=rgba(0, 0, 0, 0.870588)]Voltage difference from output to earth[/color][color=rgba(0, 0, 0, 0.870588)][/color]
 [color=rgba(0, 0, 0, 0.870588)]73-80 (powered off)[/color][color=rgba(0, 0, 0, 0.870588)][/color]
 [color=rgba(0, 0, 0, 0.870588)][/color]
 [color=rgba(0, 0, 0, 0.870588)]Voltage difference from output to earth with music playing[/color][color=rgba(0, 0, 0, 0.870588)][/color]
 [color=rgba(0, 0, 0, 0.870588)]63-70[/color][color=rgba(0, 0, 0, 0.870588)][/color]
 [color=rgba(0, 0, 0, 0.870588)][/color]
 [color=rgba(0, 0, 0, 0.870588)]Voltage difference from output to earth with music playing and headphones connected [/color][color=rgba(0, 0, 0, 0.870588)][/color]
 [color=rgba(0, 0, 0, 0.870588)]80-90[/color][color=rgba(0, 0, 0, 0.870588)][/color]
 [color=rgba(0, 0, 0, 0.870588)][/color]
 [color=rgba(0, 0, 0, 0.870588)]Voltage difference from pi output to star with music playing from phone and headphones connected to pi and amp (NOTE: Amp and Pi are NOT connected at this point)[/color][color=rgba(0, 0, 0, 0.870588)][/color]
 [color=rgba(0, 0, 0, 0.870588)]453-463[/color][color=rgba(0, 0, 0, 0.870588)][/color]
 [color=rgba(0, 0, 0, 0.870588)][/color]
 [color=rgba(0, 0, 0, 0.870588)]Voltage difference from pi output to amp input with music playing from phone and headphones connected to pi and amp (NOTE: Amp and Pi are NOT connected at this point)[/color][color=rgba(0, 0, 0, 0.870588)][/color]
 [color=rgba(0, 0, 0, 0.870588)]453-463[/color][color=rgba(0, 0, 0, 0.870588)][/color]
 [color=rgba(0, 0, 0, 0.870588)][/color]
*[color=rgba(0, 0, 0, 0.870588)]Pi and Amp connected[/color]*[color=rgba(0, 0, 0, 0.870588)][/color]
 [color=rgba(0, 0, 0, 0.870588)][/color]
 [color=rgba(0, 0, 0, 0.870588)]Voltage difference from star to earth with music playing, amp set to pi channel and headphones connected[/color][color=rgba(0, 0, 0, 0.870588)][/color]
 [color=rgba(0, 0, 0, 0.870588)]73-80[/color][color=rgba(0, 0, 0, 0.870588)][/color]
 [color=rgba(0, 0, 0, 0.870588)][/color]
 [color=rgba(0, 0, 0, 0.870588)]Voltage difference from amp input/pi output to earth with music playing, amp set to pi channel and headphones connected[/color][color=rgba(0, 0, 0, 0.870588)][/color]
 [color=rgba(0, 0, 0, 0.870588)]75-83[/color][color=rgba(0, 0, 0, 0.870588)][/color]
 [color=rgba(0, 0, 0, 0.870588)][/color]
 [color=rgba(0, 0, 0, 0.870588)]Voltage difference from amp input/pi output to STAR with music playing amp set to pi channel and headphones connected[/color][color=rgba(0, 0, 0, 0.870588)][/color]
 [color=rgba(0, 0, 0, 0.870588)]0.6[/color][color=rgba(0, 0, 0, 0.870588)][/color]
 [color=rgba(0, 0, 0, 0.870588)][/color]
 [color=rgba(0, 0, 0, 0.870588)]Voltage difference from star to amp output ground with music playing, amp set to pi channel and headphones connected[/color][color=rgba(0, 0, 0, 0.870588)][/color]
 [color=rgba(0, 0, 0, 0.870588)]0.1[/color][color=rgba(0, 0, 0, 0.870588)][/color]
 [color=rgba(0, 0, 0, 0.870588)][/color]
 [color=rgba(0, 0, 0, 0.870588)]Voltage difference from amp input/pi output to amp output ground with music playing, amp set to pi channel and headphones connected[/color][color=rgba(0, 0, 0, 0.870588)][/color]
 [color=rgba(0, 0, 0, 0.870588)]0.5[/color][color=rgba(0, 0, 0, 0.870588)][/color]
 [color=rgba(0, 0, 0, 0.870588)][/color]
 [color=rgba(0, 0, 0, 0.870588)]Voltage difference from earth to amp output ground with music playing, amp set to pi channel and headphones connected[/color][color=rgba(0, 0, 0, 0.870588)][/color]
 [color=rgba(0, 0, 0, 0.870588)]95-102[/color][color=rgba(0, 0, 0, 0.870588)][/color]
 [color=rgba(0, 0, 0, 0.870588)][/color]
 [color=rgba(0, 0, 0, 0.870588)][/color]
 [color=rgba(0, 0, 0, 0.870588)]Sound quality effect when star ground connected to earth ground:[/color][color=rgba(0, 0, 0, 0.870588)][/color]
 [color=rgba(0, 0, 0, 0.870588)]None, still has hum[/color][color=rgba(0, 0, 0, 0.870588)][/color]
 [color=rgba(0, 0, 0, 0.870588)][/color]
 Sound quality effect when output ground connected to earth ground[color=rgba(0, 0, 0, 0.870588)][/color]
 None[color=rgba(0, 0, 0, 0.870588)], still has hum[/color][color=rgba(0, 0, 0, 0.870588)][/color]
 [color=rgba(0, 0, 0, 0.870588)][/color]
 [color=rgba(0, 0, 0, 0.870588)][/color]
 [color=rgba(0, 0, 0, 0.870588)][/color]


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## tomb

I don't know - I think this still proves that the buck converter is causing the issue.  Just because you could hear no hum through the Pi that you had connected to the buck converter, that doesn't mean it wasn't causing noise - because it wasn't amplified.   Once you connect the buck converter so that it's going through the MAX, you hear it.  "Hum" may be a relative term here, too.  Is it really 60Hz hum or is it something higher like 120Hz ripple or oscillation on some other frequency?  I've had an amp design that was causing a spike at 180Hz.  It sounded for all the world like ripple, but it was actually fast Schottkys oscillating as the rectifier.  Some snubber capacitors around the Schottkys removed the noise.
  
 There could be a lot of different types of noise coming from the buck converter.
  
 I am not sure your measurements mean anything.  Ground at the wall outlet (your "earth") is not connected to your project, because of the two wire AC output from the walwart.  Output ground on the amp, on the other hand, is referenced to the DC-negative ground plane on the MAX board, which is also not connected to your "earth."


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## scootsit

Hey tomb, I'm sorry, I can't seem to find the biasing ranges. I found the ones on diy forums, but I also recall that there was a tweak of increasing the tube biasing to about 15V and the mosfets closer to 285 or 290mV. Am I making this up? I just moved and my amp seems to be biased to the values I'm remembering. 

Thanks!


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## tomb

scootsit said:


> Hey tomb, I'm sorry, I can't seem to find the biasing ranges. I found the ones on diy forums, but I also recall that there was a tweak of increasing the tube biasing to about 15V and the mosfets closer to 285 or 290mV. Am I making this up? I just moved and my amp seems to be biased to the values I'm remembering.
> 
> Thanks!


 
  
 This page has all of the bias points for a MOSFET-MAX:
http://diyforums.org/MOSFET-MAX/MOSFET-MAXsetup.php
  
 It shows that the MOSFETs are biased around 220mV to 275mV.  However, that is a very conservative bias for the MOSFET-MAX.  If you are willing to keep an eye on the heat build-up, then yes - you can try to bias them even higher.  I think an increase to 150ma (330mV) is probably do-able under most circumstances.  Higher than that, you probably need to make sure the heat sinks have good ventilation.  If I remember correctly, there is definitely a difference in sound quality going from 80ma to 125ma.  I'm not sure I noticed much of a change beyond that, but it's been a long time.  Obviously, if the higher bias is not doing anything for you, then you would want to let the amp run cooler.
  
 The 15V tube bias I think is limited to the 12FM6 tubes, specifically.  I believe someone discovered a long way back that the tube curves for that tube are more optimum at 15V.


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## scootsit

I found that page, but couldn't figure out where I got the 15v bias. I'm using 12FK6 tubes, do I'm not sure why I biased so high. Thanks!


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## tomb

scootsit said:


> I found that page, but couldn't figure out where I got the 15v bias. I'm using 12FK6 tubes, do I'm not sure why I biased so high. Thanks!


 
  
 Yes - for the 12FK6 and 12AE6 tubes, the best bias is 13.5V.  This assumes that you have the power supply output adjusted to 27VDC.  So, that gives you an equal voltage swing up and down around 13.5V.
  
 The 12FM6 - as stated - seems to run better at 15V.  Although that gives you unequal voltage swing with a 27VDC power supply setting, there are really very few times one would use that entire swing.  So, it seems to work a bit better overall.  Obviously, if you could set the voltage supply to 30VDC, then it would work even better.  However, years of testing with very high current 24VAC walwarts (up to 2 Amps), 29VDC seems to be the absolute limit before the LM317 loses regulation (and thus, the PS gets noisy).  We settled on the conservative 27VDC setting recommendation to account for worldwide variances in line voltage and walwarts.
  
 You might be able to get 28-28.5VDC power supply voltage if you try, but you run the danger of losing LM317 regulation and making the amp noisy.  You can see this yourself by adjusting the PS trimmer.  Simply keep turning the voltage up until it stops increasing.  To be absolutely certain you haven't exceeded the regulation capability of the LM317, dial it back by about 2VDC.  The LM317 needs to burn about 1.5VDC to maintain regulation, so if you dial back 2V to be absolutely safe, it often ends up at 27.5 - 27VDC.
	

	
	
		
		

		
			




  
 The primary basis of the voltage increase from 24VAC to 27-29VDC is through rectification and cap smoothing.  While an over-abundance of current capability will buy you some more voltage, I think it's in the fractions of volts or less.  All that pretty much means you need to implement your own transformer if you want 30VDC on the PCB, or - accept a very slight chance of clipping on the positive side of the voltage swing from 15V to 27VDC.
  
 The discussions on the 12FM6 occurred only through forum posts, either in here somewhere or on diyforms.org back with the original revMH Millett Hybrid.  I can't remember who originally discovered the optimum tube curves for the 12FM6, but Pete Millett even mentioned higher biases to reduce tube distortion in his original Audio Xpress article:
_*"Build A Low-Voltage Tube Hybrid Headphone/Line Amp"*_
 Look at pages 28-29 (pages 9 and 12 of the PDF excerpt) for Pete's discussion on raising the bias to reduce the distortion, at the expense of lower output (less room before clipping).


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## ericj

I suck at drilling holes. Good thing my local maker space has an abrasive waterjet system.


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## tomb

Wow!  Your pattern matches the tube protectors, too - very cool.


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## ericj

tomb said:


> Wow!  Your pattern matches the tube protectors, too - very cool.


 
  
 Thanks. It's all cut out on the waterjet, from 1/16" aluminum. There's a spacer frame that slides into the rails. Did the front and back panels on the waterjet too, with some slight adjustments from the PDF drilling templates since i want a front switch, no external fuse, etc. 
  
 I think i spent $22 in cutting time (at $55/hr) doing this. Laser cut polycarbonate or wood laminate would be much, much cheaper and faster. But that makerspace is an hour away from me. 
  
 The holes for the trimpots are sized for the Vishay trimpot tweaker, though i have not tested to see if they are as precisely located as the tube holes are. This is of course the original Max board from 10 years ago. I think i was one of the first builders w/ the mosfet output. I need to update the circuit. 
  
 I think it actually runs cooler with the slit vents than with the drilled holes. And yeah, I did the center punch thing, and used a drill press, and it still came out looking very amateurish. 
  
 I still have another max board. Debating whether to build it out with sanyo power transistors.


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## Muamp

Hi ericj,
 
Quote:


> I suck at drilling holes. Good thing my local maker space has an abrasive waterjet system.



I guess 'maker space' is an organisation in USA. Do they have any outlets in the UK?
To cut aluminium like that is awesome.
 
David.


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## ericj

muamp said:


> Hi ericj,
> 
> Quote:
> 
> ...


 
  
 It's more a movement than an organization. 
  
 The basic idea is to have a place - a space - where people can access tools and supplies and share expertise to make physical things, do projects, etc. Most are run as not-for-profit organizations. Some have an emphasis on incubating new businesses that make products or software. 
  
 ProVolt is the maker space that is near me, in Provo UT. It was created out of the remains of Zeni Kinetic, which was a failed 3d printer manufacturer. So they have one working, not-very-good 3d printer, a whole lot of 3d printer filament some of which is defective, and a 2-axis abrasive waterjet system that was previously used to cut out the sheet metal parts for the 3d printers they manufactured. There are also a whole lot of hand tools, power tools, a vinyl cutter, and other stuff. 
  
 An abrasive waterjet works by mixing an abrasive (garnet sand usually) with extremely high pressure water through a diamond nozzle. They will cut damn near anything but an hour of cutting uses a $20 bag of garnet and a lot of electricity. 
  
 Here's a video of ProVolt's OMAX waterjet cutting titanium: 
  

  
 Anyway, in Salt Lake City, about an hour from me, there are two maker spaces (Make Salt Lake and 801 Labs) that have laser cutting systems. If i build another Max, I will probably get some bamboo ply and cut a very similar set of panels and rings with one of their systems.


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## ericj

And yeah, there are some makerspaces in the UK - http://www.nesta.org.uk/uk-makerspaces-data


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## Muamp

Thanks for the info ericj.
Even though I have a small CNC, I would love to have access to other tools, like the abrassive water jet cutters, also laser cutters, and I am now one of the few remaiming DIYers that still doesn't have a 3D printer.
I will check out if there are any maker-spaces near me.

Thanks,

David.


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## ericj

I know a lot of people who have 3d printers and don't use them. 
  
 Some of that has got to be because there are a lot of 3d printers that aren't very good. 
  
 i've bought 3d printed items that were pretty good. I've also seen a lot of 3d printed items that were pretty rough and barely useful. 
  
 The waterjet is the closest thing this makerspace has to an income stream. Every once in a while someone pays for something to be manufactured on it.


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## ultraman31

So, all of sudden, the left channel went blank... When I put the headphone jack into the insert just about 2/3, I hear the left channel, but it doesn't sound right... I'm suspecting it's the female insert....or any other thoughts on what could it be? I know I'm providing barely any info, but just wondering... I'll probably be able to check in about a month or so.


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## vixr

ultraman31 said:


> So, all of sudden, the left channel went blank... When I put the headphone jack into the insert just about 2/3, I hear the left channel, but it doesn't sound right... I'm suspecting it's the female insert....or any other thoughts on what could it be? I know I'm providing barely any info, but just wondering... I'll probably be able to check in about a month or so.


 
 some of my tubes are very old... its an easy place to start...swap them in the sockets.


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## ultraman31

I checked the tube by swapping, but still the same left channel.


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## tomb

ultraman31 said:


> I checked the tube by swapping, but still the same left channel.


 

 Unless you noticed a burning smell or an unusual amount of heat coming from the amp, my guess is a dodgy solder connection somewhere that came loose.


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## schubert

I don't know if anyone else has experienced this, but I've had long-term reliability problems with the Mosfet Max.  It's a great sounding amp but it has petered out on me twice now, both times because QB1R/L failed.  I biased it at the minimum recommended setting but it still got quite hot, so I thought maybe I might solve the problem by re-casing it and maybe adding a fan.  I couldn't find a case I liked, however, so instead I replaced the top of the existing case with a bit of expanded metal cut from an old file holder and made heat sinks for QB1R/L out of sheet aluminum, and glued them on using JBWeld.  It still gets pretty warm in there (50-55º, and the QB1 sinks approach 60º) but now the heat can escape and it looks cool, too.
 Original version:

  
 New version:


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## Marzie

I am having an issue with my Max, it's probably something dumb. It was working a few weeks ago. Since then, I have finished my enclosure and made a few wiring changes. I removed the hard wires for power and added terminal screws for power and output. I made a couple changes to the input wiring, but other than that, it should be the same. I plugged it in, when I threw the switch it blew a fuse. I thought I might have a short but + to - is like 470 k Ohm. Pictures attached.

EDITED: Formatting.


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## Marzie

Nevermind, somehow a fast blow fuse found it's way into the amp.

After almost a year and a half, I have my pi-max project working as I wanted. I have the ability to play my pi straight to my max, in the same enclosure. I can also play the pi to my stereo system un-amped, or the pi through the max to my stereo. Lastly, I can play content from anything else hooked up to my stereo either to the max with headphones, or feed it back to the stereo to my speakers.

I have some casework left to do, and I'm planning to add a small screen to the enclosure for the pi along with some buttons for playback.

Thanks to everyone for all your help. When it's done I'll post some pictures here and in the other thread I started for my build.


----------

