# New Millett Hybrid MiniMAX (what happened to this thread?)



## m0b1liz3

A thread seems to have disappeared about a new millet max design that is smaller than the last. Anyone know where it went?


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## MASantos

maybe you can find some info on the millett max thread?


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## ruZZ.il

The thread was removed (by the big boss in management), but we will not give up!!!(DIY FOR THE PEOPLE!)

 The MiniMAX prototype boards have been ordered, and building will start up soon I guess. You can view more info here.


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## m0b1liz3

Yeah, I just wondered how small the boards actually are. I will feel a little silly if I could have fit one into my mini millet starving student case!


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## tomb

Quote:


  Originally Posted by *ruZZ.il* /img/forum/go_quote.gif 
_The thread was removed (by the big boss in management), but we will not give up!!!(DIY FOR THE PEOPLE!)

 The MiniMAX prototype boards have been ordered, and building will start up soon I guess. You can view more info here._

 

Yes, it's too bad, but I respect the wishes of the man in charge. Thanks for that link, btw.

 I am still looking for 2 more volunteers to help us build the prototypes. PM me for information if you are interested.


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## tomb

Sorry - all the MiniMAX prototype boards are now taken. Hopefully, someone will start a build thread when they arrive. (Someone has volunteered to do that, too.)


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## MrMajestic2

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Sorry - all the MiniMAX prototype boards are now taken. Hopefully, someone will start a build thread when they arrive. (Someone has volunteered to do that, too.)_

 

Nooooo, I missed it


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## MASantos

I've seen in the link provided that the PS has been redesigned and improved.

 What exactly was changed and improved?


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## Ferrari

Yes I would love to know it too.
 As far as I can see, that PS circuit (just like the old MH max) is lifted straight from Tangent's STEP/TREAD PS, with an added ground plane which is connected to the star-ground via a narrow strip (very SOHA II alike 
	

	
	
		
		

		
		
	


	




).


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## tomb

Quote:


  Originally Posted by *Ferrari* /img/forum/go_quote.gif 
_Yes I would love to know it too.
 As far as I can see, that PS circuit (just like the old MH max) is lifted straight from Tangent's STEP/TREAD PS, with an added ground plane which is connected to the star-ground via a narrow strip (very SOHA II alike 
	

	
	
		
		

		
		
	


	




)._

 

Well, since none of us saw the SOHA II board for months, we know it didn't come from there, did it?

 As for "lifting", the linear regulated schematic design comes from National Semi's own data sheet regarding the LM317. The layout is totally different from Tangent's STEPS and is derived from the original MAX and the original MAX prototype. Tangent himself has stated that the circuit is not proprietary and is in the data sheet. You would know that if you did your research, Ferrari.

 I am sorry that I sent you a PM once suggesting that it was unfair to compare the MAX to the Bijou. You were a valuable contributor to the Millett MAX at the time, often offering technical support to builders in the thread. I felt it was a bit unfair for you to do that while stating publicly that you felt the Bijou sounded better in a direct comparison. So I sent you a note. The Millett family has never intended to compete directly with high voltage, pure tube amps. You seemed to understand the comparison with a B22 was unfair, but couldn't understand that one.

 Ever since, your attitude has been shameful and sometimes vulgar. Your accusatory tone is not appreciated in the least.


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## tomb

Quote:


  Originally Posted by *MASantos* /img/forum/go_quote.gif 
_I've seen in the link provided that the PS has been redesigned and improved.

 What exactly was changed and improved?_

 

Colin and I literally did hours and hours of testing. We found that nothing over the existing MAX PS has as much effect as changing the grounding scheme. That's kind of hard to prove out for certain until you make another board. That's why we're prototyping - otherwise it would've been an updated layout and we would've run off production boards from the outset.

 Some of this is explained in the DIYForums thread, but suffice to say that the output tantalum, common to other off-board power supplies of this nature, is redundant in the MiniMAX configuration. The ESR of that cap is swamped by in the bank of electrolytics and film caps right after the PS in the Millett circuit itself. Instead, a resistance in the positive feed from the PS to the Millett circuit controls both the PS output impedance and the level of PS noise (ripple). Our tests have indicated it could be as low as ~0.027mVAC or as high as ~0.097mVAC. (Either value is outstanding for a PS mounted on the same board as the amp and with direct AC traces.)

 This is not unusual and is one of the reasons that the Millett MAX has somewhat been blazing a trail with a linear-regulated PS board-mtd on the same board as the amp circuit. In many power supply scenarios, there is some distance with corresponding resistance/inductance in the connecting wire/cabling between the amp and the PS. It's possible that the wiring impedance in offboard regulator setups helps to dampen the resonance caused by the regulator output impedance and ultra low ESR of the cap bank in the amplifier it typically serves. In the MAX, that connection is a short trace of less than 1/4". We have been able to control the PS noise in the MAX by removing the ground plane under the PS completely. For instance, the original MAX protoypes had line hum and ripple that were reduced below the level of audibility. This strategy has worked well - the regular MAX's power supply is rock-stable. Bass is impressive, as almost any MAX builder can attest.

 However, Cetoole has felt that the power supply noise could still be incrementally improved by using an improved grounding scheme along with the right combination of components. Cetoole's MiniMAX layout is the result of our testing in that regard. (Also with the help of Tangent's LNMP.) 

 The tradeoff is in regulator output impedance vs. ripple. As the ripple is reduced by adding series resistance, the output impedance is increased. This has the effect of losing some stability under a varying load. (Note that all of our testing is under the constant load of a 50ma-biased MAX with tubes lit.) What happens is that the ripple climbs slightly when a varying music signal is applied, and it can vary up and down by a few hundred uVAC. This has the effect of slightly softening the bass. However, the effect is very negligible and can be difficult to detect without direct measurements.

 Bottom line, there is an optimum series resistance, given the grounding scheme, that's somewhere between 1 ohm and perhaps milli or micro ohms (a long jumper). The optimum will result in the lowest noise, while still maintaining rock-hard stability under a varying signal.

 EDIT: The first MAXes and MiniMAXes that I had modded for low-noise were demonstrated at the Atlanta Mini Meet back on July 5th. You might check that thread for some listening impressions.


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## FallenAngel

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Bottom line, there is an optimum series resistance, given the grounding scheme, that's somewhere between 1 ohm and perhaps milli or micro ohms (a long jumper). The optimum will result in the lowest noise, while still maintaining rock-hard stability under a varying signal._

 

So a 0R47 resistor that I have lying around from Beta22 build would work perfectly right?


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## tomb

Quote:


  Originally Posted by *FallenAngel* /img/forum/go_quote.gif 
_So a 0R47 resistor that I have lying around from Beta22 build would work perfectly right? 
	

	
	
		
		

		
		
	


	


_

 

It's possible.


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## tomb

Since some accusations have been thrown out, perhaps a bit more insight into the long history of these changes is warranted.

 Note the photo below. Sans arrow, this is the same photo that has been posted on the DIYForums MiniMAX page _since February 24th_. (bottom right photo link on that page)






 The arrow is pointing to an 1/8" cut that I dug out of the top of the board and through the ground plane. That cut, with a few zigs and zags, goes all the way in front of the PS section, and continues on to the other side of the board. The ground plane in the PS is completey separated from the ground plane in the amp circuit. Underneath, however, is a small jumper in the center that connects the two ground planes through the pins of the component parts above.

 Further, the suggested ground plane cut had been drawn out by cetoole in his post made _over a year ago_ - back on March 13, 2007: DIYForums.org :: View topic - New Millett Hybrid Layout
 In that post, you may note that cetoole had left a small portion in the middle uncut. I modified it slightly on my actual build by making the cut continuous and simply adding a jumper between the two ground planes.

 The board in the pic above and the layout in the link is from the very first set of Millett Hybrid Maxed prototype boards that were ordered and received back on February 22, 2007. It's just that it took some of us awhile to get around to doing the surgery on the old boards.
	

	
	
		
		

		
		
	


	




 I was the first one to actually case it up in the Lansing case and posted pics back in February of this year, but the board is one of those that arrived in Feb, 2007. I felt like I noticed a difference with the Mini, but it was only recently that I built Tangent's LNMP (posted in the Pics of Your Builds thread early last week). Whereupon, we confirmed the outstandingly low noise of this grounding scheme (and continued testing almost constantly between then and the announcement of the MiniMAX).

 I trust that's sufficient proof of the heritage of the MiniMAX design by cetoole (using Pete Millett's legacy, of course!). So let's get back to DIY-ing.


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## tomb

I've posted the layout, schematic, and BOM on the MiniMAX home page. Hold down the -Ctrl- key while re-freshing if your browser has the old page cached.

 I'll fancy up the website to match the MAX's site as time goes on.


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## ruZZ.il

just took a quick look, so other than component sizes/values, etc, the circuit design differences are basically half the power caps, no tantalum, added series resistor after PS? otherwise it seems pretty much the same MAX goodness in half the size. nice. I'm possibly missing anything, anything?


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## pabbi1

Well, I am in on this - not because I need an(y) additional amp(s), or don't have enough to do, but rather to support the continuing DIY efforts of these exceptional designs. And the exceptional efforts of those who make this possible.

 Too bad commercial realities make this such a conflict. But, we DIY will _never_ buy commercial amps, and, to the extent it is felt that this curbs sales of other products is, at best, misguided. Easy enough for DIY to be blamed if sales start to slip amongst the commercial builders, I guess. 

 Perhaps it is at the margin that the superior design of these products now so tempts the usual buyer to do this that is the real threat, rather than believe more people overall will now have an amp.

 My opinion only.


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## vixr

what pabbi1 said...


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## tomb

Quote:


  Originally Posted by *ruZZ.il* /img/forum/go_quote.gif 
_just took a quick look, so other than component sizes/values, etc, the circuit design differences are basically half the power caps, no tantalum, added series resistor after PS? otherwise it seems pretty much the same MAX goodness in half the size. nice. I'm possibly missing anything, anything?_

 

Yes. The primary differences are in the PS grounding scheme, the overall layout with much shorter traces, but most importantly - our proposed high-level of integration with a pre-machined case.

 Also, the output coupling film caps have much more room. It'll be nice to install a couple of Vitamin Q's horizontally - just as any other component.

 Necessarily, there will be fairly rigid requirements on the panel-mounted parts, but we'll make certain that the availability is high. The rear power switch is probably the critical thing - most everything else is the same. (That's a smaller knob that I used from Partspipe, too.)


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## ruZZ.il

I'll probably skip the case for now and wait for a machined one(hopefully). I probably wouldn't get the case done till way after its available anyway...

 Also, would those be the .22 or 0.18 VQs?


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## tomb

Quote:


  Originally Posted by *ruZZ.il* /img/forum/go_quote.gif 
_I'll probably skip the case for now and wait for a machined one(hopefully). I probably wouldn't get the case done till way after its available anyway...

 Also, would those be the .22 or 0.18 VQs?_

 

0.18uf's - can't have everything.
	

	
	
		
		

		
			





 It's a tight squeeze as it is. However, the 0.22uf's should have a very short knee if you want to do that.

 Yeah, I can see this is probably going to work out with no one casing theirs until the machined version is ready. I have a lot of work to do.


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## tomb

Oops - first mistake! A user over on DIYForums pointed out that I left a 1-1/2" sink in for the PS on the BOM.

 It's fixed, now - can't have anything over an inch with this case.


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## cetoole

Quote:


  Originally Posted by *ruZZ.il* /img/forum/go_quote.gif 
_I'll probably skip the case for now and wait for a machined one(hopefully). I probably wouldn't get the case done till way after its available anyway..._

 

Yeah, same for me. I love the prospect of a DIY project with no casework involved.


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## TimJo

Quote:


  Originally Posted by *cetoole* /img/forum/go_quote.gif 
_Yeah, same for me. I love the prospect of a DIY project with no casework involved._

 

I hear that, especially after chipping the perfect paint job on my Bottle Head Seduction last night, and then messing it up even more trying to touch up the paint. 
	

	
	
		
		

		
		
	


	




 Oh well, it's the sound that matters, not the looks, right?


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## tomb

Found another mistake - updated the BOM to use the Schottky MBR360 _axial_ rectifiers. These should enable us to center mount the tip jacks.


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## pabbi1

Quote:


  Originally Posted by *cetoole* /img/forum/go_quote.gif 
_Yeah, same for me. I love the prospect of a DIY project with no casework involved._

 

x³

 That is the essence of what I think sets this apart.


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## rds

Quote:


 That is the essence of what I think sets this apart. 
 

Also, it's awesome. I love the compact design.


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## soloz2

Quote:


  Originally Posted by *cetoole* /img/forum/go_quote.gif 
_Yeah, same for me. I love the prospect of a DIY project with no casework involved._

 

I'm sold!


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## TimJo

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_I've posted the layout, schematic, and BOM on the MiniMAX home page._

 

A couple things I noticed reviewing the preliminary BOM and the schematic.

 1.) CM2 appears to have been removed from the circuit, but it still shows up on the BOM.

 2.) The labels for RB13 and RB14 appear to have been swapped on the MiniMax as compared to the regular Max, so the BOM should be updated to reflect this. (Or maybe you'll want to revise the schematic and the silk screen on the production run for consistency's sake?)

 3.) CM3 now specifies a 470μf capacitor, which is a change from the 330μf on the Max. Is this correct?

 Otherwise, things look good to me. I plan to put in an order with Mouser and Digi-Key tomorrow.


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## tomb

Quote:


  Originally Posted by *TimJo* /img/forum/go_quote.gif 
_A couple things I noticed reviewing the preliminary BOM and the schematic.

 1.) CM2 appears to have been removed from the circuit, but it still shows up on the BOM.

 2.) The labels for RB13 and RB14 appear to have been swapped on the MiniMax as compared to the regular Max, so the BOM should be updated to reflect this. (Or maybe you'll want to revise the schematic and the silk screen on the production run for consistency's sake?)

 3.) CM3 now specifies a 470μf capacitor, which is a change from the 330μf on the Max. Is this correct?

 Otherwise, things look good to me. I plan to put in an order with Mouser and Digi-Key tomorrow._

 

CM3 is correct. It's a bit more safety factor than is probably needed under normal circumstances - resulting in something like a 45 second delay (from memory w/o a stopwatch). However, there are various scenarios - testing, setup, kids with itchy trigger fingers - where turning the amp on and off within a minute or so will result in less than half the delay time. With the 330uf capacitor, cutting that delay time in half gets into the danger zone.

 I hope this increased delay doesn't irritate some folks, but the tubes aren't at their best before several minutes/half-hour, anyway. BTW, I've used 470uf on every productoin MAX I've built. Note that this is also tied to RM2 at 1MegaOhm. If you adjust RM2, then CM3 must change as well to result in the same RC product. So, we're really recommending an RC product of RM2 and CM3 of 470ohms-farads. 

 CM2 is a good catch - we'll have to get an explanation from Colin on that one. He's probably decided that it's redundant.

 Likewise, the RB13/RB14 swap - a good catch. My guess is that we'd need to correct the silkscreen on the production board. That would keep things consistent with the regular MAX. Again, we'll see what Colin suggests.


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## cetoole

Tom is right, CM2 was omitted because I felt it wasnt actually necessary, and RB13 and RB14 were swapped because I only added the resistors labeled on the miniMax boards as RB14 at the very last minute, and didnt even think about the consistency issue with the regular Max board. Sorry about this guys, it is already corrected for the final board.


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## TimJo

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_CM3 is correct._

 

Cool. Along those lines then, when I was putting together my orders for parts, I noticed the Digi-Key part # for CM3 needs to be updated to 493-1286-ND to reflect that change.

 It looks like Digi-Key dropped their requirements for a minimum order (didn't know that had happened) so I am going to use the Panasonic FM's on my build (plus the Murata trimpots, which I prefer). I'm going with 1800μf for CA4 & CA5 unless you think 1200μf is a better choice.


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## tomb

Quote:


  Originally Posted by *TimJo* /img/forum/go_quote.gif 
_Cool. Along those lines then, when I was putting together my orders for parts, I noticed the Digi-Key part # for CM3 needs to be updated to 493-1286-ND to reflect that change.

 It looks like Digi-Key dropped their requirements for a minimum order (didn't know that had happened) so I am going to use the Panasonic FM's on my build (plus the Murata trimpots, which I prefer). I'm going with 1800μf for CA4 & CA5 unless you think 1200μf is a better choice._

 

The 1800uf's are an excellent choice.

 I've updated the BOM according to your comments and Colin's.


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## tomb

The proto boards are here!!





 These will ship to the prototypers tomorrow ... stay tuned.


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## MusicMtnMonkey

Any guesses on when production boards for the mini max would be ready?

 I'm just a newbie diy type. If the Mini Max is "lower voltage" like some of the other Millett designs, it sounds like another good project? Not sure I really want to mess with point to point to do the starving student version. It seems attractive to have a more compact head amp than the max??

 I wouldn't want to mess with prototyping since I wouldn't know if I made a bad solder, had a bad part, or there was a problem with circuit design... However, I'd be a great "test subject" to see if beginners could easily assemble the project after all the prototyping is completed


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## FallenAngel

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_The proto boards are here!!

 These will ship to the prototypers tomorrow ... stay tuned. 
	

	
	
		
		

		
		
	


	


_

 

That is pure awesomeness!


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## bperboy

How about the MiniMax as a preamplifier?


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## ruZZ.il

As far as I understand, its functionally identical to the MAX, so, yes.


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## cetoole

ruZZ.il is right, it is functionally the same, and has the same output terminal block which is disconnected when headphones are plugged into the onboard headphone jack. The only issue, and I know you can get around it, is finding a place for the new output jacks.


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## TimJo

My board just arrived in the mail. I guess I know what I'll be doing this weekend...


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## cetoole

Quote:


  Originally Posted by *TimJo* /img/forum/go_quote.gif 
_My board just arrived in the mail. I guess I know what I'll be doing this weekend... 
	

	
	
		
		

		
		
	


	


_

 

Sweet TimJo! I havnt actually seen one of the real boards yet; I guess USPS had a minor hickup, as I usually get 1-2 days transit time to/from tomb. Cant wait to see your build.


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## bperboy

So we have to get the prototypes up and running, then get a final board put out, as well as getting the custom enclosures fabricated? Is there any sort of a timetable for this? I haven't built anything in awhile, but I think I may build one or two of these!


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## ruZZ.il

ooh boards! 
	

	
	
		
		

		
		
	


	




 I want to build mine already too. Unfortunately I wont be able to till just before mid September.. I'll be on vacation 
	

	
	
		
		

		
		
	


	




 driving up your west coast. I probably wont want to come back home too soon, I need some time off, but at least I'll have something to look forward to. 
 I was hoping this wouldn't hinder the prototyping any bit, but I'll be willing to try out any suggested changes anyone may find necessary.. miniMAX 0.2, of sorts. Though I suspect 0.1 will pretty much be 1.0 anyway(kudos)! I'll hopefully have time to make some measurements by that time too


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## tomb

The MiniMAX case design is finished and the drawings were submitted to Lansing for a quote this past Friday. I'll post an update when I hear back from them. However, preliminary feedback still indicates a walk-away price of ~$30 per case, if we can Group Buy at least 100. Here's what the drawings look like:
















 For those that may be interested, a more detailed look can be seen at DIYForums.

 At least one prototyper has populated a board - this one belongs to Max Hester (hope he doesn't mind my posting it):


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## Beefy

Looks great. I might build one of these just to use up all the spare parts from my last Max build


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## bperboy

Tom, count me in for 2 of everything... More tubes can never be a bad thing!


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## lordvader

If a groupbuy goes ahead for the cases, would shipping costs be prohibitively expensive for overseas diyers (Australia springs to mind 
	

	
	
		
		

		
		
	


	




 )?


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## tomb

Quote:


  Originally Posted by *lordvader* /img/forum/go_quote.gif 
_If a groupbuy goes ahead for the cases, would shipping costs be prohibitively expensive for overseas diyers (Australia springs to mind 
	

	
	
		
		

		
		
	


	




 )?_

 

It could get expensive for international shipping. Whether it's "prohibitively expensive" or not, I don't know - it will depend on the country and the shipping weight of the case. (Maybe it will be a lot lighter with all those cooling slots.
	

	
	
		
		

		
		
	


	




 )

 The problem with USPS international rates is that services that include insurance and delivery confirmation can get pretty expensive. On the other hand, First Class International is quite economical, but we'd have no recourse if the shipment was lost. People might not be willing to take the risk.


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## FallenAngel

Case looks great, I can't wait to grab one.

 As for international shipping; from personal experience, I have shipped USPS First Class (and CanadaPost AirMail for that matter) 6 times in the past to Australia, never any problems - usually takes about 1-2 weeks to arrive, never longer.


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## lordvader

Well if the groupbuy includes the miscellaneous hardware, such as knobs, sockets, as well as the pcbs (obviously), then even with shipping, the price might work out quite well for the "foreign" diyer 
	

	
	
		
		

		
		
	


	




 Of course, once you start buying tubes, caps, resistors ...

 You know what, count me in if it goes ahead ! I've finsihed my latest poweramp project, and just know I'll be suffering from withdrawals in a few months time


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## tomb

I have been mulling over starting to carry kits, but it will be a pretty big investment. I have to see how a lot of other things go before I can do that.

 On the other hand, there might be an opportunity to have an Australia-organized shipment - similar to what they did for the SSMH, but someone in Australia will need to volunteer for that.

 Up until a couple of weeks ago, I agreed with FallenAngel's assessment of the US Post Office. Then one guy in Ontario never received his Vitamin Q's from Beezar and Max Hester never got his first MiniMAX prototype board. Max is only 50 miles from me, so that was really bad!
	

	
	
		
		

		
		
	


	




 I sent both of them new ones, as evidenced by Max's pic up there.

 However, there's not much of a way that I can order a new batch of 100 cases with associated mfg costs, etc., if we lose a few in shipping. I'll definitely try to get extra, but we won't know if that's possible until Lansing gives us a price. Anyway, that's sort of why I've been thinking Priority-Mail-only for these cases - I'm sort of gun-shy on the USPS right now. Optional shipping choices might be something we should discuss when/if a Group Buy occurs.


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## Daveze

I'm definitely in for at least one case. I'd happily pay a premium for not having to frig about with the casework...


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## patton713MW

Yep, I'll take a case. (amillett from diyforums.com)


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## FallenAngel

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_I have been mulling over starting to carry kits, but it will be a pretty big investment. I have to see how a lot of other things go before I can do that.

 On the other hand, there might be an opportunity to have an Australia-organized shipment - similar to what they did for the SSMH, but someone in Australia will need to volunteer for that.

 Up until a couple of weeks ago, I agreed with FallenAngel's assessment of the US Post Office. Then one guy in Ontario never received his Vitamin Q's from Beezar and Max Hester never got his first MiniMAX prototype board. Max is only 50 miles from me, so that was really bad!
	

	
	
		
		

		
		
	


	




 I sent both of them new ones, as evidenced by Max's pic up there.

 However, there's not much of a way that I can order a new batch of 100 cases with associated mfg costs, etc., if we lose a few in shipping. I'll definitely try to get extra, but we won't know if that's possible until Lansing gives us a price. Anyway, that's sort of why I've been thinking Priority-Mail-only for these cases - I'm sort of gun-shy on the USPS right now. Optional shipping choices might be something we should discuss when/if a Group Buy occurs._

 

I highly recommend Priority Mail with Delivery Confirmation for all shipments, cost is usually only a couple of dollars more than First Class and Delivery Confirmation is $0.65


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## penger

Case looks awesome! Looks like a fun project too.


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## tomb

Well, I should've known the pricing was too good to be true. I've asked for a clarification, but the initial quote looks more than double what I was told in our preliminary conversations. Case price is what I thought - only about $15 per case. Tooling and setup are what they told me, too. However, they're charging the same tooling and setup costs for the silkscreening in addition to the machining. Plus, they are charging individually for machining each case besides the tooling and setup - that's a significant change. Per part machining is trivial for the front and back plate, but looks very expensive for the body. That makes sense according to the design, but nevertheless, they indicated that the number of holes would not effect price - that there were only per-surface charges. Again, I've asked for clarifications and explanations. I could be interpreting the quotes incorrectly.

 I've also asked for options that will reduce the cost if I am interpreting correctly - it's not organized like most quotes I've seen.

 Please stay tuned ... I'll keep the situation updated.


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## Beefy

If it is too expensive, I'd blow off the silk screening first thing. It doesn't really add much......


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## bperboy

In any case, we all appreciate the work you're doing... and for what it's worth, I rather like the silkscreening... makes it look quite professional!


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## tomb

Blowing off the top silkscreen is a no-brainer. We're not going to pay that premium for what little was on the top.

 The machining costs they're charging for the case is the big hit, though, because they're charging on a per-case basis. That is counter to every conversation I've had with them - doesn't mean they'll change that, though. What it does mean, is perhaps we may simplify the slots on the bottom and perhaps the slots on the sides may go away.

 My MiniMAX proto doesn't heat up appreciably for 3-4 hours with just a few 1/4" holes on the bottom and the _very_ flat rubber stoppers that Lansing uses (small air clearance). {EDIT: My original board in the one in my avatar pic doesn't have any cooling holes in the board, either.} So, the side slots would be nice, but I don't think they're really necessary.

 Obviously, if simplifying to slots just in one direction, one set, etc., will save money, that will be the first step.

 I'll continue to let you all know when I know. Thanks for staying tuned ...


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## Beefy

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_My MiniMAX proto doesn't heat up appreciably for 3-4 hours with just a few 1/4" holes on the bottom_

 

How much airflow actually comes up through the bottom holes with the PCB in the way?

 If I could only have one, I would be inclined to drop the bottom holes and simplify the sides. It is easy to drill the bottom yourself, because nobody sees it. And the open sides will let tube lighting shine out as well..... 
	

	
	
		
		

		
		
	


	




 [EDIT] I suppose the PCB support on the bottom of the case might still be an issue for some


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## ruZZ.il

Drilling the bottom wouldn't be too hard, but it's worthwhile for almost everyone to have holes at the bottom since the board has holes around the heat sinks and stuff for airflow. it would be a pity not to let them work. So it may be worthwhile to leave them anyway.. I'm easy though


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## Beefy

Quote:


  Originally Posted by *ruZZ.il* /img/forum/go_quote.gif 
_but it's worthwhile for almost everyone to have holes at the bottom since the board has holes around the heat sinks and stuff for airflow. it would be a pity not to let them work._

 

Ah, I see now. They aren't on the regular Max, and I didn't notice their addition on the new board photos


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## tomb

Yep - as ruZZ.il says, the bottom holes are more important in this situation. Colin and I had tried to prepare for some "deductive alternates." The side slots were only a recent afterthought. We thought they'd be nice if we could make them work, but maybe not at the cost.


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## FallenAngel

Yay, it's making music! 
	

	
	
		
		

		
		
	


	




 I didn't say "done" because I need to add the Wima PSU bypass caps but it runs fine without them and sounds pretty darn good. Can't wait for the case.


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## tomb

Quote:


  Originally Posted by *FallenAngel* /img/forum/go_quote.gif 
_Yay, it's making music! 
	

	
	
		
		

		
		
	


	




 I didn't say "done" because I need to add the Wima PSU bypass caps but it runs fine without them and sounds pretty darn good. Can't wait for the case.



_

 

Whoa - that was quick! You were just talking about starting it yesterday evening.

 Went for the BG's right away, huh?


----------



## FallenAngel

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Whoa - that was quick! You were just talking about starting it yesterday evening.

 Went for the BG's right away, huh?_

 

Hmm... started about a week ago, but tonight was too busy, check out my Melos mods thread to see what I've been up to tonight. 
	

	
	
		
		

		
		
	


	




 Going for some much deserved sleep, can't even look at the SOHA that has a few new parts waiting.


----------



## WilCox

TomB,

 Any updates on the availabilty of the PCB or the case? How are the prototypes working?


----------



## tomb

Quote:


  Originally Posted by *WilCox* /img/forum/go_quote.gif 
_TomB,

 Any updates on the availabilty of the PCB or the case? How are the prototypes working? 
	

	
	
		
		

		
		
	


	


_

 

We've had two complete the prototypes, but Colin is waiting for me to build mine because I have the LNMP. That will give us the final readings for the power supply noise quieting.

 Despite the various and sundry things that I've been doing the last few weeks - like moving two daughters back to college
	

	
	
		
		

		
		
	


	




 - I've been steadily busy on the case design. Lansing and I have been exchanging e-mails and revised case drawings on almost a daily basis.

 The result is that it appears the fully machined case, including bottom and side cooling slots, with silkscreened front and rear plates, will run about $50 per case (down from $75!!), assuming we can get 100 interested in a Group Buy. I have been waiting to "pretty up" the drawings and perhaps construct a rendering to better market what a prospective MiniMAX builder will get. $50 is still a healthy chunk (that's all up - case included, and initial shipping to me), so I want to present it in the right light (without getting another post deleted, too).
	

	
	
		
		

		
		
	


	







 Something else I've been busy on: transferring/updating DIYForums.org. You will soon see an updated version under new ownership and management. 
	

	
	
		
		

		
		
	


	







 *

 * Credit where credit's due: The transfer of ownership was a Nate Maher Special Initiative.


----------



## JamesL

Will you be offering the boards seperate from the case? 
 I'm always up for a new project, but I like building something that is more unique. 
 Exactly how big is this new board? I'm guessing something like 120^2 from the original 160^2?


----------



## tomb

Quote:


  Originally Posted by *JamesL* /img/forum/go_quote.gif 
_Will you be offering the boards seperate from the case? 
 I'm always up for a new project, but I like building something that is more unique. 
 Exactly how big is this new board? I'm guessing something like 120^2 from the original 160^2?_

 

About 5 inches wide by 6 inches long. With the MiniMAX, though, the real uniqueness is the tight integration with the case and quite a bit of volume-savings. The case is only about 1-1/2" tall. Yes, beezar will offer the boards for separate purchase, along with other parts. During the group buy, of course, you can ask me to time the order for the board with the group buy shipment for the case. My hope is to have some extra cases for sale at beezar as well, but due to the cost, this will be limited.


----------



## ruZZ.il

I just got home, and am supposed to start getting that third proto built! 
	

	
	
		
		

		
		
	


	




 BUT.... my luggage isn't here yet. yippeee... I'm skrewed till further notice..


----------



## WilCox

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Despite the various and sundry things that I've been doing the last few weeks - like moving two daughters back to college
	

	
	
		
		

		
		
	


	




 - I've been steadily busy on the case design. Lansing and I have been exchanging e-mails and revised case drawings on almost a daily basis.

 Something else I've been busy on: transferring/updating DIYForums.org. You will soon see an updated version under new ownership and management. 
	

	
	
		
		

		
		
	


	







 *

 * Credit where credit's due: The transfer of ownership was a Nate Maher Special Initiative.
	

	
	
		
		

		
		
	


	


_

 

Wow! You've been quite busy! I'm looking forward to building the MiniMAX. Thanks for all your hard work on behalf of the Head-Fi DIY crowd!


----------



## royewest

I wish you the best of luck with your diyforums.org project, tomb, but navigating to that url this evening makes you hope you have your virus protection sw updated and set to max protection....


----------



## tomb

Quote:


  Originally Posted by *royewest* /img/forum/go_quote.gif 
_I wish you the best of luck with your diyforums.org project, tomb, but navigating to that url this evening makes you hope you have your virus protection sw updated and set to max protection...._

 

There's a domain ownership move taking place - it should be back up shortly.

 EDIT: Back up and running under new ownership (paid for through proceeds from beezar.com)!


----------



## FallenAngel

Any updates on the Lansing cases for this amp? Mine has been sitting uncased for a little bit and I'd love to get my hands on one of those cool looking custom cases for it.

 As for the price, it does seem quite high for a case, perhaps without a silkscreen it would be cheaper?


----------



## tomb

Quote:


  Originally Posted by *FallenAngel* /img/forum/go_quote.gif 
_Any updates on the Lansing cases for this amp? Mine has been sitting uncased for a little bit and I'd love to get my hands on one of those cool looking custom cases for it.

 As for the price, it does seem quite high for a case, perhaps without a silkscreen it would be cheaper?_

 

Now wait a minute!!! 
	

	
	
		
		

		
			





 The price for two end panels on the teeny-tiny Mini3 case is $40(!) and now the entire MiniMAX case - with machined & anodized cooling slots top, bottom, both sides, machined front and rear panel, silkscreening on both ends - at $50 is "quite high for a case?"

 Please ... I'm juggling many things at once, here. We are close to holding the Group Buy. I just need to finish my own MiniMAX and do a bit of extra drawing. The price is worked out and everything has been confirmed with Lansing. So all we need is interest enough for 100.


----------



## ruZZ.il

x (1 or 2) for sure =)


----------



## FallenAngel

Didn't mean to discourage your generous efforts Tom, you know I'll be in for the case for my MiniMAX; I was just thinking that $50 for a case is a "quite higher" than what I usually spend. 
	

	
	
		
		

		
		
	


	




 As for the Mini^3 panels - definitely made for a select crowd. I'm just so much more utilitarian


----------



## tomb

Quote:


  Originally Posted by *FallenAngel* /img/forum/go_quote.gif 
_Didn't mean to discourage your generous efforts Tom, you know I'll be in for the case for my MiniMAX; I was just thinking that $50 for a case is a "quite higher" than what I usually spend. 
	

	
	
		
		

		
		
	


	




 As for the Mini^3 panels - definitely made for a select crowd. I'm just so much more utilitarian 
	

	
	
		
		

		
		
	


	


_

 

No problem - I didn't mean to snap. It's just that I worked for weeks going back and forth with Lansing to get the price down to where it is now. It's not going any further unless we delete the side slots. That might save us $5 a case and IMSO (InMyStrongOpinon), that would be a foolish savings. We need as much cooling as we can get.

 Other things were done - it took several days for me to drag it out of Lansing that they were going to charge us $300 for a special key-way punch for the power switch hole. The heck with that - we both agreed to just drill a small hole there, instead.

 The overall slots were reduced by making them slightly larger, then decreasing in number. The bottom was simply reproduced from the top - no extra slots all along the bottom anymore. This is reasonable; there is only a very small perimeter space between desktop and the bottom of the case. So, more slots would be wasted beyond the cross-sectional area of the clearance from the desktop.

 The side slots were cut down to one row only and then only in line with the sinks.

 Finally, it turns out that Lansing could not do "voided" silkscreened text. IOW, for a black case, I had proposed using white shaded areas on the back with the natural finish of the case showing through to form the words, "AUDIO INPUT," "TUBE BIAS," and "POWER." However, Lansing explained that wouldn't work - they'd have to print back over the white with black lettering. Unfortunately, that causes an extra tooling and setup charge. So, the black-shaded rectangles have been removed in favor of outlines, only.

 So, here is the latest and greatest, and the agreed-upon, priced-out design with Lansing. I need to finish my MiniMAX and do some LNMP testing. Once we do that and it checks out, then I'll order the production boards and set about having a couple of Group Buys for the cases:














 These are linked to the actual, plotted PDF's. So, you can right-click and download the genuine drawing.
	

	
	
		
		

		
		
	


	




 I'm also working on a rendering that will help us market the Group Buy a little better than just these drawings.


----------



## pabbi1

Simply outstanding - whatever we are paying you, it isn't enough.


----------



## n_maher

oh heck, i need another hybrid like i need a hole in the head, but I'm in whenever you get things rolling Tom. That's just outstanding.


----------



## bperboy

I'll be in for two!!!


----------



## Beefy

I wonder if a Mini-MOSFET-Max is possible with the level of ventilation in that case? Any thoughts?


----------



## Alcaudon

Wow! 
	

	
	
		
		

		
		
	


	




 I was planning a DIY wooden case for this, but looking at the results (and the very affordable price 
	

	
	
		
		

		
		
	


	




) I think I'll be in for 1 (maybe 2). Great work as usual, Tom!!!!

 Are they going to be black or clear?


----------



## tomb

Quote:


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

	
	
		
		

		
		
	


	




 I was planning a DIY wooden case for this, but looking at the results (and the very affordable price 
	

	
	
		
		

		
		
	


	




) I think I'll be in for 1 (maybe 2). Great work as usual, Tom!!!!

 Are they going to be black or clear?_

 

Thanks. Lansing has said we can mix the buy between silver or black, but I need to confirm the tooling and setup charges. They quoted both separately, so I suspect that if we wanted a mix, that tooling & setup would be X2.

 If we get 200, that means we could mix. That's because the tooling and setup charges are trivial when spread across 100 units. Otherwise, we may have to limit it to one or the other. I'll find out, report back, and also try to summarize the cost breakdown and let you guys help me decide how to structure the Group Buy.
	

	
	
		
		

		
		
	


	




  Quote:


  Originally Posted by *Beefy* 
_I wonder if a Mini-MOSFET-Max is possible with the level of ventilation in that case? Any thoughts?
	

	
	
		
		

		
		
	


	


_

 

We think so, if the bias is held to 80ma. However, it would definitely be an "advanced" build. As such, we are not going to recommend it as an "official" option - at least until we gain more experience with the case design.


----------



## soloz2

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_





_

 

Can't we make it go to 11?


----------



## Beefy

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_We think so, if the bias is held to 80ma. However, it would definitely be an "advanced" build. As such, we are not going to recommend it as an "official" option - at least until we gain more experience with the case design.
	

	
	
		
		

		
		
	


	


_

 

That sounds like a challenge, tomb. But first I need to investigate how much it would cost me to get hold of a full complement of Black Gates


----------



## ruZZ.il

Status update: I've lost my epoxy


----------



## tomb

Quote:


  Originally Posted by *ruZZ.il* /img/forum/go_quote.gif 
_Status update: I've lost my epoxy _

 

Why epoxy?


----------



## ruZZ.il

well, I had to glue the tube socket sides back together cause they're about next to go in 
	

	
	
		
		

		
		
	


	




 'had' to, cause I found the epoxy


----------



## tomb

Quote:


  Originally Posted by *ruZZ.il* /img/forum/go_quote.gif 
_well, I had to glue the tube socket sides back together cause they're about next to go in 
	

	
	
		
		

		
			





 'had' to, cause I found the epoxy 
	

	
	
		
		

		
		
	


	


_

 

Oh yeah - duh! I forgot about that!


----------



## ruZZ.il

a miniMAX lives! 
	

	
	
		
		

		
		
	


	




 After some head scratching, wondering why my measurements made no sense, I jumpered RB8/9, biased it all up perfectly, and enjoyed the music 
	

	
	
		
		

		
		
	


	




 I didn't really have the time to build this just yet, but did it anyway 
	

	
	
		
		

		
		
	


	




 I'll get around to impressions and measurements next week and maybe some photos during the w.end. Other than a dead LED and a lifted pad trying to get it out, it's a perfect little MAX, but those can be fixed. There were hardly a handful of details I came across that need to get sorted out for the production board, mostly just silk screening adjustments and synchronizing the BOM and the board. The effort that was put into this shows. Thank you Pete, Thank you Colin, thank you Tom!


----------



## amphead

That's awesome Russ! Let us know how it sounds.


----------



## ruZZ.il

well my very first brief impression was kinda groggy but when the tubes had been on for a bit and I'd upped the bias even to just 41ma over 30, things are already smoother, better bass, but still lacking some detail that I expect to crack in. Its a can't miss #1 sans the vit Qs (I'll stick them in a little later, with some tubing) so I'm pretty familiar with what its going to sound like, with already promising outcome 
	

	
	
		
		

		
		
	


	




 Was cool meeting you Ron!


----------



## ruZZ.il

Still need to fix the LED and add the Vit Q. bypasses..


----------



## tomb

Quote:


  Originally Posted by *ruZZ.il* /img/forum/go_quote.gif 
_




 Still need to fix the LED and add the Vit Q. bypasses.._

 

Let's put our heads together on installing the VitQ's. Things are much tighter than Colin and I had counted on. Max Hester had problems with the VitQ
 s first, but now I'm having the same issue. I've built mine except for putting the VitQ's in there and boy, is it tight. The pads aren't exactly far enough apart to allow a good kneeling position, either (the top of the cap is too high). I noted in Max's Mini, he kneeled them on one end and then nestled the lead on the high side inbetween the fins on the middle sinks. That's probably not a good idea for the long-term without some teflon tubing protection, but I was hoping we could make it without.

 I tried the 0.22uf K42's and they're too fat to fit between the back of the pot and the front of the right channel CA7 cap. So, it's the VitQ's somehow or back to Wima's.

 I'm thinking if we add some extra pads to the outside, that may give us enough room to kneel the VitQ's without the lead on the other end hitting the middle sinks.

 Tell us what you think when you try it.


----------



## Beefy

Quote:


  Originally Posted by *ruZZ.il* /img/forum/go_quote.gif 
_Still need to fix the LED and add the Vit Q. bypasses.._

 

Looking fantastic! 
	

	
	
		
		

		
		
	


	




 *

 I'm currently building up a Mouser BOM for one, maybe two of these babies. I'm thinking both will be Blackgate/VitQ builds, with one being an experimental MOSFET build, the other BJT. I'm using my previous BOM as a template, but coming up with a couple of inconsistencies. Any advice from tomb or other prototype builders would be appreciated, as I'd like to get some other goodies for my Buffalo DAC in the next couple of weeks.

 Oh, and sincere apologies if these have already been answered. I'm a bit too frazzled right now to go through the thread and actually absorb any of it.....

 CR5 has been deleted?
 CM2 has been deleted?
 CM3 is now 470µF? This controls the delay, so I assume that 330µF is still OK?
 Any word yet on RR4? I'm happy to buy multiple options now and install later.
 Part number for the tip jacks?
 RCA jacks will definitely be available at Beezar?
 The Mini MAX output stage seems to be a 100% complete translation of the regular MAX. So can I assume that the MOSFET output stage will translate 100% as well? That if I follow the MOSFET max BOM, I shouldn't be missing any parts?

 I think that is all for now. Cheers everyone! 
	

	
	
		
		

		
		
	


	




 *

 [EDIT]
  Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_That's probably not a good idea for the long-term without some teflon tubing protection, but I was hoping we could make it without._

 

Is it too hot there on the heatsink to just use heatshrink?


----------



## ruZZ.il

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_....he kneeled them on one end and then nestled the lead on the high side inbetween the fins on the middle sinks. ....some teflon tubing protection...._

 

Thats pretty much what I was thinking of doing. I was waiting till I got back home where I have some teflon tubing..

 The left side is less of an issue, since it can just lay on top of the headphone jack, perpendicular to it.. this would mean having a longer signal path.. most likely negligible.

 I was going for the kneeling with teflon on both sides for symmetry.. mosltly visual.

 ....It may just have to be that way. 
 I can think of other, less viable methods though:

 1. Laying the output electrolytics down and placing the vit Q's above them, perpendicular to them, in between the heat sinks. (this actually doesnt sound too bad... maybe you can try it out if you haven't soldered those in yet)

 2. adjusting the layout drastically, pushing the ccs aside, the electrolytics back, and positioning the vit Q between the heat sinks.. BZZZZT.


----------



## tomb

OK - I've got a creative bend that allows the VitQ to kneel to the outside without the end nipple getting too close to the outside sink. I actually moved the outside lead to the next closest middle pad, not the one on the outside. With a Z-bend that wraps around and under the end of the cap, that lets it sit on the board without the bend at the nipple touching the outside sink. It works the same for the middle sink, but that one is easy to see (high side of the cap). Plus, it's under 1".

 We have a solution - I'll draw up a template when I get a chance. It's just a single Z-bend underneath on the outside.

 Beefy - I'll have to answer some of that post tomorrow, when I get a chance (in about 7 hours). It's already past my bedtime on a work night.
	

	
	
		
		

		
		
	


	




 For now, though:


> Quote:
> 
> 
> CR5 has been deleted?
> ...


----------



## Beefy

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Beefy - I'll have to answer some of that post tomorrow, when I get a chance (in about 7 hours). It's already past my bedtime on a work night.
	

	
	
		
		

		
		
	


	




 For now, though:_

 

That pretty much answers everything - love your work 
	

	
	
		
		

		
		
	


	




  Quote:


 Yes, that should be correct. You can always punt and purchase a Lansing with a tall top. That would let you use taller sinks. Taller Lansings are available in the "C" style, but they're 2.5" tall. We won't be machining that style/size, though. 
 

I am still aiming for your pre-machined case with 1" heatsinks and MOSFETS. Realistically, I think that this combo will be better cooled than most regular MAXes in unventilated Hammond enclosures. I won't be able to open the MOSFETs right up, but I think it will still be a good option over any BJT combo.

 But there is only way for me to find out - by actually building it - and I plan to do exactly that


----------



## tomb

Quote:


  Originally Posted by *Beefy* /img/forum/go_quote.gif 
_That pretty much answers everything - love your work 
	

	
	
		
		

		
		
	


	






 I am still aiming for your pre-machined case with 1" heatsinks and MOSFETS. Realistically, I think that this combo will be better cooled than most regular MAXes in unventilated Hammond enclosures. I won't be able to open the MOSFETs right up, but I think it will still be a good option over any BJT combo.

 But there is only way for me to find out - by actually building it - and I plan to do exactly that 
	

	
	
		
		

		
		
	


	


_

 

Tip Jacks are Mouser #530-105-0801-1. (The part # will vary, depending on what color you pick.)

 Also, don't forget that we're using axial Schottky's - the MBR360 - for the rectifiers in the back. This is important, because the tip jack and rear panel layout won't work with TO-220-style rectifiers. It's really a tight fit on the proto board. If you don't bend those leads as close to the package as possible and as close to 90 degrees as possible, they won't fit in. Colin has said he's loosened up the holes and lead spacing a bit on the production design, I believe.


----------



## Beefy

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Tip Jacks are Mouser #530-105-0801-1.

 Also, don't forget that we're using axial Schottky's_

 

I already had the rectifiers covered, but good call.

 So my BOM is pretty much complete now, and I'll place my Mouser order in a few days. Still need to decide how I'm going to get hold of some Black Gates though. There are *none* in Australia


----------



## tomb

Quote:


  Originally Posted by *ruZZ.il* /img/forum/go_quote.gif 
_




 Still need to fix the LED and add the Vit Q. bypasses.._

 

I meant to say this looks great, Russ! Did you have trouble getting those MBR360's in? I had to work at it for awhile, but got them in and flush.

 You guys using all these Black Gates are making me feel substandard with my ES's.


----------



## ruZZ.il

Thanks! 
	

	
	
		
		

		
		
	


	




 The diodes were a bit of a tight fit, but I wouldn't really say they're a problem.. just an extra few minutes. I put the diode on the table, push and bend. It gets the leads pretty close to how they have to be. just a few small adjustments after that and they fit in with a little push. I pre-snipped too so once the bends were right it just fit in and stayed in, so soldering was easy. my fingers hurt just a little from the bending though 

 I must say, Mario Kart wii sounds fantastic through this amp!


----------



## Beefy

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_You guys using all these Black Gates are making me feel substandard with my ES's.
	

	
	
		
		

		
		
	


	


_

 

You know what? I say screw Black Gates. There are none in Australia at all, and I'm not paying $53 per amp plus shipping from Michael Percy 
	

	
	
		
		

		
		
	


	




 That money could buy me a LOT of beer, and various other substances that will allow me to enjoy the music even more. ES's will do juuuuuuuust fine!


----------



## tomb

Finished my MiniMAX (click for bigger pics):























 For you prototypers out there, a jumper at RR4 results in about 0.215mVAC ripple. So, a jumper _is not_ the optimum component to put in there. Right now, I have the old Millett Hybrid Polyfuse (RXEF050) in there - it has an R of about 1.5ohms - and the ripple went down to *0.038mVAC*! That is under a load, given the tube heaters and buffer bias at somewhere between 250 -300ma. Under music the ripple varies some, but not enough to be detrimental. In fact, it sounds much, much better than the jumper.

 I'll be doing additional testing with different resistances the rest of the weekend and try to find an optimum value/device to put in RR4, but for now, I'm convinced we have a winner in the design. I've got some ideas on some minor changes for cooling that I'll be discussing with Colin, but most likely, the first run of production boards will be ordered Monday.

 Heat is a bit of an issue with the middle sinks and the PS sink, but not outside of what's acceptable. At 27VDC and 50 ma bias in the buffers, I'm measuring the following when equilibrium is reached after about an hour or so:
 Outside sinks - 33 deg.C. (91.4 deg.F.)
 Center sinks - 43 deg.C. (109.4 deg.F.)
 PS sink - 45 deg.C. (113 deg.F.)
 The center sinks feel quite hot to the touch, but as you can see, this is not much more than the metal on a car during a hot sunny day.


----------



## patton713MW

Looks gorgeous! I really like the Vit-Q orientation!


----------



## FallenAngel

Awesome. Any news from Lansing?


----------



## tomb

Quote:


  Originally Posted by *FallenAngel* /img/forum/go_quote.gif 
_Awesome. Any news from Lansing? 
	

	
	
		
		

		
		
	


	


_

 

They're just waiting for me to give them the word ... and the money.
	

	
	
		
		

		
		
	


	




 Hopefully, I can organize the group buys this weekend. I have a couple more posts to do to help everyone visualize the case, but here's a teaser:


----------



## FallenAngel

Don't do that to me at work Tom! I'm drooling over the notepad in front of me!

 Yay! Group-buy, group-buy!

 Hell, I'll build another amp just so I can have 2 of those cases.


----------



## bperboy

OMGOMGOMGOMGOMG SEXY!!!! I was planning on building two.. those look so good I might have to do three!


----------



## patton713MW

Wow!! I already know what I'm doing with mine: Super bright LED in the center of the case so that all of those grill openings glow! That will look so hot!

 EDIT - Would there be any issues with running several LEDs in parallel from LEDC?


----------



## Beefy

I don't think I will even care how they sound...... that case is a work of art


----------



## m0b1liz3

Will it also be available in Black?


----------



## tomb

Quote:


  Originally Posted by *m0b1liz3* /img/forum/go_quote.gif 
_Will it also be available in Black?_

 

Yes. It's just that AutoCAD (translated = operator error) is having trouble rendering in black and mapping white text to the endplates.
	

	
	
		
		

		
		
	


	




 Lansing doesn't care about that, of course.


----------



## tomb

Quote:


  Originally Posted by *patton713MW* /img/forum/go_quote.gif 
_Wow!! I already know what I'm doing with mine: Super bright LED in the center of the case so that all of those grill openings glow! That will look so hot!

 EDIT - Would there be any issues with running several LEDs in parallel from LEDC?_

 

I would test it first with a breadboard - or a bunch of alligator clips and wire. There's a variance in some of these LEDs and they may not all glow equally (at least when I've tried it). Plus, you could quickly end up with a huge power resistor to handle all the current - 4 or 5 LEDs at 10ma a piece and you'd have some real power usage. That's the same as the bias on the transistors - and they have 1" extruded heat sinks.


----------



## tomb

Black -










 Also, this is something SPECIAL
	

	
	
		
		

		
		
	


	




, if your Adobe Acrobat Reader version is up-to-date, try clicking on the image in the following files. You should be able to spin, twist, zoom in and out - all in real time:







 [size=xx-small](These are linked to PDF's - either click to load Adobe Acrobat in your browser, or right-click and download the PDF to call up in Adobe Acrobat.)[/size]

 Watch for the Group Buys shortly ...


----------



## bperboy

Tom = Awesome.


----------



## Beefy

Ooooooh, 3D-tastic!


----------



## tomb

Based on the prototype builds, here's the updated layout and schematic (click for larger files):








 Here are some of the issues found out by the prototypers and how they've been addressed:

1. Axial Schottky's too difficult to fit into the rectifier positions.
 I believe the holes have been made a bit bigger, but a very tight bend allows them to fit without issue.

 In addition, we are changing the ceramic discs to axial ceramics. This should get that back end squared away with a really low profile.

2. PS trimmer operates backwards from previous MAXes.
 The silkscreen for the PS trimmer has been turned around.

3. LED resistors are too large for the pads.
 The traces are really tight on the MiniMAX, as you prototypers can attest. There isn't any room to make these pads larger. However, we have adjusted the BOM for an inexpensive 1W metal film that will fit the pads. I have yet to look for the same alternative at DigiKey, but will followup with that when I can. Also, cetoole won't like me saying this, but kneeling 1/2W carbon films works just fine.
	

	
	
		
		

		
		
	


	




4. The 0.018uf VitQ's won't fit easily between the front heat sinks.
 We knew this was tight from the beginning, but I thought perhaps they would fit horizontally. Unfortunately, those stupid VitaminQ nipples get in the way. We want everyone to be able to fit these in without resorting to expensive teflon tubing or the hassle of heat shrink. A creative Z-bend worked on mine to allow the cap to kneel to one side without touching any of the sinks. However, cetoole put some additional pads further out toward the sinks that should make this task easier.

 I will draw up a detail and post it on the website, as was done for the regular MAX, that will show how to bend the leads to make these fit - without touching the heat sinks and remaining below 1" height.

5. The heat sink temperatures are ~10 degrees higher on the PS sink and the middle two sinks, compared to the outboard sinks.
 The silkscreen pattern used in Eagle is slightly off from the actual extruded heat sink footprint. This resulted in some of the cooling holes actually being blocked.

 Cetoole and I worked to increase the number of holes where possible and to move them further out toward the tips of the heat sink fins for better cooling. We don't anticipate any issues with the machined case design (Group Buys in progress), but we still want the option for a manually drilled case as with the original MAX. Either a CT1 or DT1 Lansing case will work and are economical, but using simple drilled cooling holes will not be as efficient as the machined slots on the Group Buy case. So, hopefully the extra cooling holes in the board will benefit a manually drilled case.

 Of course, the original prototype was a manually drilled Lansing CT1 (has been featured on the temporary MiniMAX website page for several months), but the vinyl covering with that case option makes things pretty toasty. A manually drilled Lansing DT1 case should be completely analogous to the original MAX. I will provide drawings and drilling templates on the website for these manual options as well.

6. The LNMP tests resulted in two changes to the Power Supply in order to reduce ripple close to the target values (<0.060mVAC). 
 The result is a measured ripple/noise in the neighborhood of 0.038 to 0.54 mVAC, depending on components and line voltage. These two changes are:

 RR4 is now PF1, a polyfuse - part #RXEF050. This polyfuse was original Millett Hybrid and revMH Millett Hybrid equipment. The resistance is anywhere from about 1.5 to 0.5 ohms, decreasing with higher current rating. This works perfectly for our purposes and results in the very low ripple noted above. In addition, _the polyfuse will serve to protect the buffers_ - separate from the PS fuse, which actually serves to protect the walwart to a large extent.

 Note that the part# is for a 1/2A rated polyfuse. This has been tested (historically, too) and works fine for BJT buffers. Those who are willing to try a MOSFET-MiniMAX may need to adjust this rating upward, however. Again, we are not really recommending a MOSFET version except for experimentation by advanced builders.

 CR4 will most likely change to an electrolytic. This will reduce the ripple by about ~0.010mVAC (one of the reasons I cited a _range_ above). An added benefit is that an electrolytic is low cost compared to a tantalum. A 100uf 35V will be the recommendation.

 One final note - a DIP-16 or two DIP-8 sockets are pretty convenient for plugging in the relay. However, be sure to snip the leads that are not used - there are not pads for all 16 positions of a socket. Also, if you don't snip these very close to the plasic socket frame, you'll end up with a very tall relay installation that may interfere with using a center front-panel LED bezel.


----------



## digger945

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Finished my MiniMAX (click for bigger pics):_

 





 Grooooovyyyyy Tom. So group buy stuffs are not far behind, eh?


----------



## tomb

Quote:


  Originally Posted by *digger945* /img/forum/go_quote.gif 
_<IMG]http://www.diyforums.org/MiniMAX/gallery/TomB/MiniMAX7-560x420.jpg[/IMG>

 Grooooovyyyyy Tom. So group buy stuffs are not far behind, eh?_

 

The Group Buy for the case is going on right now. Boards will be available directly from beezar in 3-4 wks, perhaps sooner.


----------



## digger945

Most excellent! 
 Just put my name in the hat for a silver one.
 Thanks a bunch Tom.


----------



## JamesL

oh crud..
 This thing threw me off for a good second.
Soundstage reviews the MiniMax

 I didn't realize there was another miniMax =P


----------



## tomb

Quote:


  Originally Posted by *JamesL* /img/forum/go_quote.gif 
_oh crud..
 This thing threw me off for a good second.
Soundstage reviews the MiniMax

 I didn't realize there was another miniMax =P_

 

Well, strictly speaking, "MiniMAX" is only shorthand for us. The official name is "Millett Hybrid MiniMAX."


----------



## rhester

Put the resettable fuse in mine last nite, along with .22 Wima's in the CA1 positions. Definitely more detail n the soundstage (more black background) now, and nice punch with the ES's in the boutique spots. Can't wait for the cases.


----------



## tomb

Quote:


  Originally Posted by *rhester* /img/forum/go_quote.gif 
_Put the resettable fuse in mine last nite, along with .22 Wima's in the CA1 positions. Definitely more detail n the soundstage (more black background) now, and nice punch with the ES's in the boutique spots. Can't wait for the cases._

 

Yay, Max (Hester, not the amp)! It's great to read when someone else can tell the difference from the results of our testing!!


----------



## Thermofreak

will this minimax macth well with low impedance headphones? like audio technica or akg?


----------



## Daveze

My MilletMAX does beautiful things to my Grado's...the biggest (IMO) difference between my Millet and the Mini is that I'm running rather high bias (80mA with BJT's), which the Mini won't be capable of (happy to see someone prove that wrong with the custom case...)


----------



## WilCox

Quote:


  Originally Posted by *Thermofreak* /img/forum/go_quote.gif 
_will this minimax macth well with low impedance headphones? like audio technica or akg?_

 

I've built two of the Millett Hybrid Maxed for my ATH-1000 and ATH-5000 and they bring out the best of these phones. I suggest using NX Black Gates (680uf 35V) bypassed with Sprague Vitamin Q's (paper-in-oil, 0.18uf 100V) for the output caps to get the best out of your Audio Technicas when building your Mini.


----------



## tomb

FYI - boards were ordered last Friday. Ship date should be on the 15th.


----------



## GeWa

In that case, hold one for me!

 Regards


----------



## tomb

Anymore interest in the custom-machined case? We have a ways to go yet to hit the minimum.

 Thanks for the interest so far. Please understand that this GB is completely non-profit (as is required for DIY Group Buys). There will be no markup on the cases in the GB (no guarantees later on 
	

	
	
		
		

		
		
	


	




 )


----------



## Beefy

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Anymore interest in the custom-machined case? We have a ways to go yet to hit the minimum._

 

Unless I am completely nuts, which is a distinct possibility, I haven't seen a link posted anywhere on Head-Fi. So a lot of people might not be fully aware of it yet.

 Perhaps a post in the Group Buy forum here on Head-Fi, which you can link from this thread?


----------



## DaMnEd

You are nuts! (j/k)

http://www.head-fi.org/forums/f6/min...up-buy-368133/





 However, it was not directly linked on this thread and probably should have been.

 So...:

  Quote:


  Originally Posted by *FallenAngel* /img/forum/go_quote.gif 
_Just wanted to give a heads-up, the group buy for MiniMAX case is held at Headwize and DIYForums

 The cases look absolutely wonderful and come in both Black and Silver. We need to reach a minimum of 100 cases, so come on by, grab a case or two and build one hell of an amp!_

 

Maybe *tomb* can make a post here with images *and the links to the group threads "abroad".* Something more official looking 
	

	
	
		
		

		
		
	


	




.


----------



## Beefy

Quote:


  Originally Posted by *DaMnEd* /img/forum/go_quote.gif 
_You are nuts! (j/k)

http://www.head-fi.org/forums/f6/min...up-buy-368133/






 However, it was not directly linked on this thread and probably should have been._

 

Yeah, I missed that...... haven't had the time to browse outside my subscription page, and expected the link to be posted here in this thread.

 In any case, I'm already in for two and would love for the minimum buy to be hit. I'm definitely up for some solder slinging, but the casework can go jump in a lake!


----------



## ishtob

I'm interested in a board too, can you hold one for me?


----------



## tomb

Quote:


  Originally Posted by *ishtob* /img/forum/go_quote.gif 
_I'm interested in a board too, can you hold one for me?_

 

Boards will ship to me on the 15th. They'll be available at the regular outlet for Millett MAX parts.

 Thanks for the comments and interest in the MiniMAX case, guys. However, I can't make an official post about it (take a look at the title and the first post in this thread). I'm sorry, but that's the environment that Colin and I work in - and it's not limited to just this forum, either. If I had drawn a sketch on the back of a napkin, nobody would care. As it is, some must think we're Sony.
	

	
	
		
		

		
		
	


	




 AFAIK, the rest of you can post whatever, however.


----------



## DaMnEd

*Millett Hybrid MiniMAX Custom Machined Enclosure*

*Group-Buy

*

*tomb* has kick-started a group buy for a fantastic custom machined enclosure what will allow unparallel integration for anyone building a MiniMAX. The case is based on the Lansing DT1 enclosure, but altered to include tube holes, cooling slots on top, bottom, and both sides, with punched and silkscreened endplates.

*Renderings*


*










*

*Case design drawings (Links below, requires Adobe Acrobat Reader):*
http://www.diyforums.org/MiniMAX/cas...-M001-Rev3.pdf
http://www.diyforums.org/MiniMAX/cas...-M002-Rev3.pdf
http://www.diyforums.org/MiniMAX/cas...-M003-Rev3.pdf
http://www.diyforums.org/MiniMAX/cas...-M004-Rev3.pdf

*3D renderings (Links below, requires adobe Acrobat Reader latest version):*
http://www.diyforums.org/MiniMAX/cas...-M005-Rev4.pdf
http://www.diyforums.org/MiniMAX/cas...-M006-Rev1.pdf



 [size=medium]*Price (estimate): $55 (Black or Silver)*[/size]



*The Group Buy goal is 100 cases, 51 already in, please joi[size=x-small]n![/size][size=x-small] Group Buy ending at 11:59PM Saturday, October 18, 2008[/size]*

*More details and information on how take part in this Group-Buy can be found at **Headwize** and **DIYForums** where the Group-Buys are held.*


----------



## alwayshungry

Has anyone tried HD650s with the Minimax? I'm looking for a project to build and the prefinished case is drawing me to this. Thanks.


----------



## WilCox

Quote:


  Originally Posted by *alwayshungry* /img/forum/go_quote.gif 
_Has anyone tried HD650s with the Minimax? I'm looking for a project to build and the prefinished case is drawing me to this. Thanks._

 

Check out this thread: http://www.head-fi.org/forums/f6/new...ed-amp-233941/

 Since the MiniMax is a repackaging of the Millett Hybrid Maxed into a more compact format, the info in this thread regarding the HD650s should apply. I have two Maxes and they are awsome with the Senns!


----------



## tomb

I've added a line that tracks the estimated cost of the case in the Group Buys, depending on the number we have pledged so far.

 These are the costs that add into the overall price:
Tooling and Setup Charges
 ........This price is a total and is fixed, regardless of the number of cases. However, the greater the number of cases, the more this cost is reduced per case.
Unfinished Case Price
 ........ We receive almost a 1/3 discount on the regular price per case. The amount of discount varies with the number we buy, with the discount increasing as the quantity increases (up to 250).
Machining the extruded tube (body), punching and silkscreening the endplates
 ........ This is the greatest cost per case, and does not change per case, regardless of how many we order.
Shipping
 ........ This must be taken into account. There is a shipping cost _to_ me, then _from_ me _to_ the purchaser.

 Currently the price is $58.89 per case at 46 cases, without including shipping costs. I haven't counted the silver vs. black ratio, either. The silkscreen charges for each color is a $50 minimum. This works out to about 31 cases of each before incurring an additional charge.


----------



## DaMnEd

Very nice *tomb*, it's good to have that updated figure as numbers change!


----------



## Beefy

To any Australians watching this thread, I would like to draw your attention to this:

http://www.head-fi.org/forums/f42/ic...x-kits-371437/


----------



## Beefy

Hi tomb,

 Don't want to pull you off task too much, but I was wondering whether you can shed some further light on part numbers for things that have changed but not been updated in the official BOM? Just trying to make my possible Aussie group-buy BOM as accurate as possible......

  Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_In addition, we are changing the ceramic discs to axial ceramics.
 *
3. LED resistors are too large for the pads.
 The traces are really tight on the MiniMAX, as you prototypers can attest. There isn't any room to make these pads larger. However, we have adjusted the BOM for an inexpensive 1W metal film that will fit the pads.
 *
 CR4 will most likely change to an electrolytic.... A 100uf 35V will be the recommendation._

 

For CR4, I have specced up a Nichicon UPW which is a tidy 6.3x11mm and only $0.32...... but there doesn't seem to be a Panasonic FM alternative. They have a 68µF 35V at 6.3x11.2mm, or a 150µF 35V at 8x11.5mm which I feel may be too big. What do you think?

 Cheers!


----------



## tomb

Quote:


  Originally Posted by *Beefy* /img/forum/go_quote.gif 
_Hi tomb,

 Don't want to pull you off task too much, but I was wondering whether you can shed some further light on part numbers for things that have changed but not been updated in the official BOM? Just trying to make my possible Aussie group-buy BOM as accurate as possible......



 For CR4, I have specced up a Nichicon UPW which is a tidy 6.3x11mm and only $0.32...... but there doesn't seem to be a Panasonic FM alternative. They have a 68µF 35V at 6.3x11.2mm, or a 150µF 35V at 8x11.5mm which I feel may be too big. What do you think?

 Cheers! 
	

	
	
		
		

		
		
	


	


_

 

Good choice. Yes - you're correct. As a matter of fact, I've tried the 100uf 50V FM and it was too big (8mm dia). I have a 68uf 35V on order (FM from DigiKey), but as you can probably tell, they're out of stock and on order. It needs to be 6 (6.3) mm dia or less.


----------



## Beefy

Sorry to keep bugging you tomb....... 
	

	
	
		
		

		
		
	


	




 How is this for CR3? 147-75-101-RC
 Same specs as the ceramic disc but axial, and only 2.5x4mm.

 And for RA5? PR01000102001JR500
 This is 2.5x8.5mm, compared to the previously specced resistor at 3.5x10mm.

 Cheers!


----------



## tomb

Quote:


  Originally Posted by *Beefy* /img/forum/go_quote.gif 
_Sorry to keep bugging you tomb....... 
	

	
	
		
		

		
		
	


	




 How is this for CR3? 147-75-101-RC
 Same specs as the ceramic disc but axial, and only 2.5x4mm.

 And for RA5? PR01000102001JR500
 This is 2.5x8.5mm, compared to the previously specced resistor at 3.5x10mm.

 Cheers! 
	

	
	
		
		

		
		
	


	


_

 

Hmm ... looks like I haven't uploaded the latest changes to the BOM. I'll do that now. In the meantime, Colin had already selected Mouser part #581-SA102A101JAR for CR3A/B/C/D.

 As for the resistors - sure. They're only powering the LED's. Whatever will fit (same size as a V-D RN55) and is at least 1/2W. Power should be (0.0135^2) * 2000 = 0.37W at 27V. To tell the truth, I will probably continue to use 1/2W carbon films and kneel them, but don't tell Colin I said that.


----------



## Beefy

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_In the meantime, Colin had already selected Mouser part #581-SA102A101JAR for CR3A/B/C/D._

 

Cheaper and higher rated than what I picked! *thumbs up*


----------



## digger945

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Currently the price is $58.89 per case at 46 cases, without including shipping costs. I haven't counted the silver vs. black ratio, either. The silkscreen charges for each color is a $50 minimum. This works out to about 31 cases of each before incurring an additional charge._

 

So if we don't hit 100 cases ordered, can we still order them at that price ($58.89), provided everyone agrees?
 What if we wanted to order just one case outside of the group buy(down the road sometime)?


----------



## tomb

Quote:


  Originally Posted by *digger945* /img/forum/go_quote.gif 
_So if we don't hit 100 cases ordered, can we still order them at that price ($58.89), provided everyone agrees?
 What if we wanted to order just one case outside of the group buy(down the road sometime)?_

 

Unfortunately, I had to revise the price slightly upward since that first estimate. However, it's probably less than that now for a black one. Yes, as far as I'm concerned, we'll purchase the manufacturing run with what we have, regardless.

 As for buying them later on - I'll be ordering as many as beezar can afford, but the Group Buy is probably a once-in-lifetime event. Think about it - the 50 some odd we have right now will total over $3000. From what I've been hearing in the financial world, I can't get a loan to buy more than that, either. Further, to buy a single case once the Group Buy is over and done with will cost a minimum of about $1000 for tooling and setup.

 So, yes - beezar will have a _very_ few after the Group Buy, but they'll be as scarce as Grado HF-1's and will most likely be priced accordingly.


----------



## Beefy

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Yes, as far as I'm concerned, we'll purchase the manufacturing run with what we have, regardless._

 

That is great news 
	

	
	
		
		

		
		
	


	




  Quote:


 So, yes - beezar will have a _very_ few after the Group Buy, but they'll be as scarce as Grado HF-1's and will most likely be priced accordingly.
	

	
	
		
		

		
		
	


	



 

1. Buy Mini MAX cases.
 2. ???
 3. Profit!





 Oh, another silly little question...... what is the approx gap between the PCB and the group buy case? Just wondering what size standoff I should buy.
 [EDIT] Looks like about 4mm from the drawing?


----------



## digger945

^I'm not 100% sure, but I think that these cases have grooves that accept the miniMAX pcb, the pcb being made to some kinda "standard" size.


----------



## Beefy

Quote:


  Originally Posted by *digger945* /img/forum/go_quote.gif 
_^I'm not 100% sure, but I think that these cases have grooves that accept the miniMAX pcb, the pcb being made to some kinda "standard" size._

 

I mean 'height'. As in how far from the _bottom_ of the case to the bottom of the PCB.


----------



## digger945

Lansing DT enclosure
 Actually there are four slots, scroll down to page 5. I think we are using the DT1 which translates to:
 D=family/style
 T=140.4mm width
 1=38.6mm height
 Not at all like the one in Tom's miniMAX link in his sig.


----------



## Beefy

Quote:


  Originally Posted by *digger945* /img/forum/go_quote.gif 
_Lansing DT enclosure
 Actually there are four slots, scroll down to page 5._

 

Yeah, I'm in that PDF now.

 The PCB has to go in the lowest slot, which is 5.72mm from the bottom/outside of the case. I can't seem to see the thickness of the case though, to work out the exact standoff height required.


----------



## digger945

Here is a link to the post with the pdf files that show some assembled drawings. The links below the pics are the ones I was looking at.
 I actually like these better.
	

	
	
		
		

		
		
	


	




 How are you guys doin with the BantamDAC group buy? I really want to build the Bantam.


----------



## Beefy

Quote:


  Originally Posted by *digger945* /img/forum/go_quote.gif 
_Here is a link to the post with the pdf files that show some assembled drawings. The links below the pics are the ones I was looking at.
 I actually like these better.
	

	
	
		
		

		
		
	


	


_

 

That is the PDF that I measured the approx 4mm from, but it is pretty hard to get an exact measurement from a printed PDF - even with a scale bar.


----------



## tomb

Quote:


  Originally Posted by *Beefy* /img/forum/go_quote.gif 
_That is the PDF that I measured the approx 4mm from, but it is pretty hard to get an exact measurement from a printed PDF - even with a scale bar._

 

There are 8 slots and the bottom of the bottom slot (therefore, the bottom of the PCB), is 0.155" from the inside bottom surface of the case:






 P.S. The MiniMAX PCB will reside in the bottom slot.


----------



## Beefy

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_the bottom of the bottom slot (therefore, the bottom of the PCB), is 0.155" from the inside bottom surface of the case:_

 

At 3.937mm I wasn't far off! Thanks, as always 
	

	
	
		
		

		
		
	


	




 And Mouser part numbers for metric standoffs:
http://www.mouser.com/Search/Product...-FM1251-2545-A
http://www.mouser.com/Search/Product...-FM1301-3005-A

 The first one is an M2.5 thread, which from memory is the same as PC hard disk screws......

 [EDIT] OOOOPS, PC screws are imperial. Back to the drawing board......[/EDIT]


----------



## Daveze

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_So, yes - beezar will have a very few after the Group Buy, but they'll be as scarce as Grado HF-1's and will most likely be priced accordingly.
	

	
	
		
		

		
		
	


	


_

 

Hmm...MiniMAX cases as an investment option...novel.

 If only the Aussie dollar would crawl out of the hole its found itself in...


----------



## patton713MW

Wow, I'm glad I'll be in on the group buy! Talk about a limited production run! Plus, I'm getting a Silver, which will be even more rare!


----------



## Beefy

Just wanted to re-direct Australian folk to my non-for-profit Aussie group buy for Mini Max parts: http://www.head-fi.org/forums/f42/fs...x-kits-371437/

 We will be getting Mouser for the bulk of gear, but will also have a Digikey order Pansonic FM power caps and a Sonic Craft order for Black Gate coupling caps.

 If you want to make yourself a truly special Mini Max build, then I doubt Aussie builders will find a more cost effective way of doing it!


----------



## tomb

Thanks to Beefy for doing this great favor for the Australian MiniMAX interest.
	

	
	
		
		

		
		
	


	




 Also, I wanted to give another gentle reminder that the Group Buy for the cases ends tomorrow night at Midnight EDST (more or less). I spoke with Lansing today and confirmed the details that we had worked out and also some boring stuff like how they would ship them to me, how to pay, etc. So, we're all set, pretty much.

 ----------------------------------------------------------------------
 As for the MiniMAX board itself, I wanted to discuss a bit about how much effort Colin and I did on lowering the ripple/noise in the power supply. It was lot of work, but we're proud of it.
	

	
	
		
		

		
		
	


	




 Tangent lists his tests on his excellent Power Supply Tests page on his website. On that page you'll find that the following results of power supplies and ripple:

 STEPS ... 0.058mVAC (RMS)
 TREAD ... 0.060mVAC (RMS).

 Those readings are under a constant load condition of 240ma and were pretty much state-of-the-art for headphone hi-fi until the Sigma22 and the Young-Jung Super-Regulator.

 The MiniMAX prototype sitting on my coffee table measures *0.056mVAC *(RMS). This is with a Fluke and Tangent's LNMP and with a zero self-noise test (shorted probes register 0.000). My calcs estimate that the sitting load of a MiniMAX adjusted to 50ma bias in the buffers and running 27VDC from the power supply is running a constant load of approx. 280 to 300ma. This is with the PS connected to the amp circuit with the RXEF050 polyfuse (RR4).

 I had mentioned to Beefy that Colin had recommended the use of an electrolytic in CR4 instead of a tantalum to further lower ripple/noise. Our early testing indicated that such a swap would lower the ripple/noise by another 10uVAC. Sure enough, after measuring the above, I swapped out the CR4 tantalum with an electrolytic - 100uf 35V. The loaded ripple/noise now measures *0.046mVAC*. (Keep in mind that the 100uf 35V electrolytic is really too big - probably a 68uf 35V or similar is needed. The one I put in is sandwiched against the film cap and in direct contact with the heat sink fins.) This will be the recommended build (with a smaller size electrolytic).

 Finally, just a little history - our initial testing for RR4 (now PF1) tried out everything from a 2.2R resistor to a jumper (plus some small inductors, too). With the jumper, ripple/noise was in the 0.1mVAC to 0.2mVAC range, not very good. With a 1R resistor, ripple was measured as low as 0.038mVAC. However, there is a dynamic component to this tweaking: the ripple under a dynamic load (music playing with heaphones connected) ranges much higher with the 1R resistor than with lower values. The polyfuse is approximately 0.5R and gave the 0.056mVAC listed above and the dynamic ripple had much less ripple/noise. Plus, it has the added advantage of perhaps protecting the buffers, which the PS buss fuse never did. That's how we arrived at using the polyfuse.
	

	
	
		
		

		
		
	


	




 This tantalum-to-electrolytic change has been in the MiniMAX BOM for awhile, btw, but Mouser had incorrectly listed their 100uf 35V UPW cap as 6.3mm diameter - it's 8mm, which is too big. So, I adjusted the BOM for a smaller cap. This will allow a bit of clearance from the heat sink fins. Also note the change from RR4 to the PF1 polyfuse as mentioned above - that change has been in place for quite awhile now.


----------



## GeWa

I guess a Panasonic FC would be OK for CR4.

 Regards


----------



## Beefy

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_but Mouser had incorrectly listed their 100uf 35V UPW cap as 6.3mm diameter - it's 8mm, which is too big._

 

*blows raspberry* I knew I should have checked the data sheet. The FM are back in stock at Digikey thankfully... Digi-Key - P12926-ND (Panasonic - ECG - EEU-FM1V680)

  Quote:


 Thanks to Beefy for doing this great favor for the Australian MiniMAX interest. 
 

With the inability to combine Beezar shipping with the cases, some of the benefit is gone, unfortunately 
	

	
	
		
		

		
			





 But I understand the reasoning. Maybe I should leave the Beezar parts to individuals and just do the Mouser, Digikey and Sonic Craft as the group buy items? I'll sleep on it......


----------



## tomb

Quote:


  Originally Posted by *Beefy* /img/forum/go_quote.gif 
_*blows raspberry* I knew I should have checked the data sheet. The FM are back in stock at Digikey thankfully... Digi-Key - P12926-ND (Panasonic - ECG - EEU-FM1V680)



 With the inability to combine Beezar shipping with the cases, some of the benefit is gone, unfortunately 
	

	
	
		
		

		
		
	


	




 But I understand the reasoning. Maybe I should leave the Beezar parts to individuals and just do the Mouser, Digikey and Sonic Craft as the group buy items? I'll sleep on it......_

 

Yeah, I just received the 100uf 35V UPW from Mouser two days ago. I was a bit surprised when I opened it up to put it in the MiniMAX.

 YGPM.


----------



## Beefy

So it seems that a guy from my work has just bought a regular MAX PCB, and I have offered to add the parts he requires to my Mouser and Digikey orders.

 Instead of doing a whole new BOM I am hoping to just add an extra multiple of my current group buy kits, minus any Mini parts I don't require, plus any parts still required for the regular MAX. So the changes would be:

 Remove RR4/PF1?
 Add back CR5?
 Add back CM2?
 Can I keep the new axials at DR1?
 Can I keep the new axials at CR3?
 Can I keep the new 68µF 35V electrolytic at CR4?

 Importantly, is there anything else I have forgotten about?

 [EDIT]
 Back to the old power switch.
 I suppose he needs a Hammond case.
 [/EDIT]

 Cheers!


----------



## tomb

Quote:


  Originally Posted by *Beefy* /img/forum/go_quote.gif 
_So it seems that a guy from my work has just bought a regular MAX PCB, and I have offered to add the parts he requires to my Mouser and Digikey orders.

 Instead of doing a whole new BOM I am hoping to just add an extra multiple of my current group buy kits, minus any Mini parts I don't require, plus any parts still required for the regular MAX. So the changes would be:

 Remove RR4/PF1?_

 

Without doing board surgery, there is no place for this part.{quote]
 Add back CR5?[/quote]Same as above, without board surgery, this part is must be installed. Quote:


 Add back CM2? 
 

optional Quote:


 Can I keep the new axials at DR1? 
 

No. The holes are not setup for the axial Schotty's. Quote:


 Can I keep the new axials at CR3? 
 

yes Quote:


 Can I keep the new 68µF 35V electrolytic at CR4? 
 

Yes, this would probably help slightly. Quote:


 
 Importantly, is there anything else I have forgotten about? 
 

I don't think so. Quote:


 
 [EDIT]
 Back to the old power switch. 
 

Yes. Quote:


 I suppose he needs a Hammond case. 
 

Yes. Quote:


 [/EDIT]

 Cheers!


----------



## Beefy

Thanks for that tomb. I will make the changes to his BOM, and *finally* place all of my parts orders in the next day or so!


----------



## bperboy

Is the BOM on the MiniMax page fully updated? I'm getting ready to order two sets of parts, and I want to make sure I don't need to make any corrections.


----------



## tomb

Quote:


  Originally Posted by *bperboy* /img/forum/go_quote.gif 
_Is the BOM on the MiniMax page fully updated? I'm getting ready to order two sets of parts, and I want to make sure I don't need to make any corrections._

 

It should be, but I've been very busy of late, so no guarantees.
	

	
	
		
		

		
		
	


	




 Seriously, if the small, _less than_ 100uf electrolytic is listed for CR4, and a PF1 is listed instead of RR4, then that should be the latest and greatest.


----------



## ishtob

are the boards here ?! i got in the case group buy but can't seem to find the board for the minimax anywhere


----------



## DaMnEd

Quoting *tomb*:
  Quote:


 ** PCB's will be available for sale (at the usual Millett MAX outlet) on Friday, 10/24/2008.

 * Due to the requirement of shipping the cases via Priority Mail and International Priority Mail, combined shipping is not possible. (Your cost for shipping a boards/parts order at the same rates would be very expensive.)*

 A word of explanation -
 The MiniMAX cases must be shipped via Priority Mail and International Priority Mail. This is prudent, since there is no way of replacing a MiniMAX case lost in shipment. On the other hand, an order for boards and parts can be replaced. If I were to ship the boards and parts at the same rates required for the cases, it would cost you a monumental amount. As many of you have experienced, I can ship boards and parts at very economical First Class rates.

 Finally, the MiniMAX is a refined design. It has gone through the prototyping stage with extensive testing and obviously has a long heritage in the Millett Hybrid and Millett MAX designs. Therefore, we do not anticipate any changes with the MiniMAX BOM. I will also work on updating the MiniMAX website to the same standards as the MAX, MOSFET-MAX and BantamDAC shortly. 
 

PCBs released on my birthday 
	

	
	
		
		

		
		
	


	




!


----------



## tomb




----------



## Beefy

GAH! Its blue! 
	

	
	
		
		

		
		
	


	




 My order finger is twitchy..... Bring it on, Beezar!


----------



## tomb

Quote:


  Originally Posted by *Beefy* /img/forum/go_quote.gif 
_GAH! Its blue! 
	

	
	
		
		

		
		
	


	




 My order finger is twitchy..... Bring it on, Beezar!_

 

Maybe Wednesday evening on Beezar - because unfortunately, I have to go out of town for a couple of days anyway.


----------



## digger945

Indeed!


----------



## Beefy

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Maybe Wednesday evening on Beezar - because unfortunately, I have to go out of town for a couple of days anyway.
	

	
	
		
		

		
		
	


	


_

 

Look forward to it. My cart is loaded with everything else I need for _five and a half_ Max builds......


----------



## lordvader

NIIIIIIIICE !!!!!!!!

 (blue PCBs kick ass !!!!!)


----------



## JamesL

woah.. it's bluee


----------



## FallenAngel

I feel so left out 
	

	
	
		
		

		
			





 I have the green prototype one, but hey I got to listen to it before there rest, suckers


----------



## lordvader

... yeah, but blue PCBs sound better !!!


----------



## White Mike

Oh no, won't the (lovely) blue PCB clash with the green Nichicon ES's?


----------



## Beefy

Quote:


  Originally Posted by *White Mike* /img/forum/go_quote.gif 
_Oh no, won't the (lovely) blue PCB clash with the green Nichicon ES's? 
	

	
	
		
		

		
		
	


	


_

 

Perhaps. But it is going to look juuuuuuust fine with Black Gates


----------



## patton713MW

Quote:


  Originally Posted by *White Mike* /img/forum/go_quote.gif 
_Oh no, won't the (lovely) blue PCB clash with the green Nichicon ES's? 
	

	
	
		
		

		
		
	


	


_

 

Yeah, but the silver VitQs will all but make up for that


----------



## DaMnEd

MiniMAX PCB now avaiable @ Beezar.com





!


----------



## rhester

Does anybody know where BG can still be sourced from, especially the 470uF 35V NX? I found 1000uF, not in 16V but 25V with same footprint.


----------



## n_maher

I believe that Parts Connexion has one of the larger stocks. If they don't have it you probably won't find it but could also try Micheal Percy or Sonic Craft.


----------



## ruZZ.il

I recently got some from sonic craft.


----------



## Beefy

Quote:


  Originally Posted by *rhester* /img/forum/go_quote.gif 
_Does anybody know where BG can still be sourced from, especially the 470uF 35V NX? I found 1000uF, not in 16V but 25V with same footprint._

 

I bought *five sets* of Black Gates for Mini Maxes from Sonic Craft. You can go for the NX 1000µF 25V for CA2 and the NX *680*µF 35V for CA7.

 Michael Percy also claims to have stock of the same caps, but my emails to him kept getting bounced for some reason. Parts Connexion also has the NX 680µF 35V, but not the 1000µF


----------



## White Mike

Yeah, Sonic Craft and Percy are definitely the places to go.

 Though I don't think I'll be doing much O.S. buying until the Aussie dollar improves!


----------



## Beefy

Yeah, it makes things difficult. I was lucky - I bought all my parts on Wednesday at 0.67 but it is now down below 0.62


----------



## soloz2

I've been getting my BG's from Michael Percy.


----------



## Beefy

My group buy parts have started arriving. Black Gates today, Mouser tomorrow, Digikey should come Wednesday. I'm excited!


----------



## tomb

Wow - that's a lot of Black Gate NX's!

 Notice that BG is off a bit on their height of the 680uf 35V. It's more like ~23mm instead of 25.


----------



## TzeYang

HOLY **** I WET MY PANTS


----------



## Beefy

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Wow - that's a lot of Black Gate NX's!

 Notice that BG is off a bit on their height of the 680uf 35V. It's more like ~23mm instead of 25.
	

	
	
		
		

		
		
	


	


_

 

They're both ~1mm on either side of the spec 
	

	
	
		
		

		
		
	


	




  Quote:


  Originally Posted by *TzeYang* /img/forum/go_quote.gif 
_HOLY **** I WET MY PANTS_

 

*chuckle* Does this mean I'm cool now?


----------



## Daveze

Can I be cool too?


----------



## bperboy

No. 


 Build a MiniMax and then maybe I'll reconsider.


----------



## Beefy

Quote:


  Originally Posted by *bperboy* /img/forum/go_quote.gif 
_Build a MiniMax and then maybe I'll reconsider. 
	

	
	
		
		

		
		
	


	


_

 

Eight of those caps belong to Daveze


----------



## bperboy

Quote:


  Originally Posted by *Beefy* /img/forum/go_quote.gif 
_Eight of those caps belong to Daveze 
	

	
	
		
		

		
		
	


	


_

 

Oh snap. 
	

	
	
		
		

		
		
	


	




 I just got showed up.. my Muse ESs can't compete


----------



## tomb

The manufacturing order for the cases was turned into Lansing today. They will ship to me on 12/8/2008.


----------



## Beefy

Hmmmm, here's hoping that they arrive before Christmas for us poor international folk


----------



## soloz2

Quote:


  Originally Posted by *Beefy* /img/forum/go_quote.gif 
_Hmmmm, here's hoping that they arrive before Christmas for us poor international folk 
	

	
	
		
		

		
		
	


	


_

 

already Christmas at my place


----------



## Beefy

Quote:


  Originally Posted by *soloz2* /img/forum/go_quote.gif 
_already Christmas at my place_

 

Nice!


----------



## tomb

Gosh - it's raining Black Gates around here.


----------



## DaMnEd

Hope the wind pushes those clouds over here!


----------



## bperboy

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_The manufacturing order for the cases was turned into Lansing today. They will ship to me on 12/8/2008._

 

So we should expect them before Xmas, at least here the US? I'm planning on giving one away as a gift...


----------



## cetoole

Time to break up the rain of Black Gates..
	

	
	
		
		

		
		
	


	







 Note: caps not for minimax, and unfortunately, I wont have time to start work on either project until maybe turkey or winter break. Only thing that arrived today that I can get any immediate use out of is a set of MB Quart 400 headphones.


----------



## Beefy

Quote:


  Originally Posted by *cetoole* /img/forum/go_quote.gif 
_Time to break up the rain of Black Gates..
	

	
	
		
		

		
			



_

 

HAH! 
	

	
	
		
		

		
		
	


	




 What are they? Motor run caps for a tube amp?


----------



## DaMnEd

Are those beer cans in disguise? 
	

	
	
		
		

		
		
	


	




 Jesus!


----------



## n_maher

Quote:


  Originally Posted by *DaMnEd* /img/forum/go_quote.gif 
_Are those beer cans in disguise? 
	

	
	
		
		

		
		
	


	




 Jesus!_

 

_I like big caps and I can not lie..._


----------



## bperboy

Ahh, menace menace menace menace!


----------



## Beefy

Quote:


  Originally Posted by *n_maher* /img/forum/go_quote.gif 
_I like big caps and I can not lie..._

 

Ah _crap_. I can't get Sir Mix-A-Lot out of my head now


----------



## cetoole

Quote:


  Originally Posted by *Beefy* /img/forum/go_quote.gif 
_HAH! 
	

	
	
		
		

		
		
	


	




 What are they? Motor run caps for a tube amp?_

 

Yup, that is 10x 100uf 370VAC motor run caps (Metallized Polypropylene in Oil), for the power supply of the power amp I am planning. Triode strapped 6688-300B.

 DaMnEd: They are almost exactly the size of a 12oz beer can.

 Nate: You are a menacing inspiration to us all. I might have some circular hole cutting tech questions for you in a couple months, when I get down to building.


----------



## n_maher

Quote:


  Originally Posted by *cetoole* /img/forum/go_quote.gif 
_Nate: You are a menacing inspiration to us all. I might have some circular hole cutting tech questions for you in a couple months, when I get down to building._

 

Bring on the circle cutting questions, I've been refining my craft. 
	

	
	
		
		

		
		
	


	














 I've become such a sucker for huge iron.


----------



## rds

Has anyone built the Millet Max with Muse ES in CA2, and Vitamin Q bypassed Black Gates in CA7?
 ...seems like that might be good.


----------



## tomb

Quote:


  Originally Posted by *rds* /img/forum/go_quote.gif 
_Has anyone built the Millet Max with Muse ES in CA2, and Vitamin Q bypassed Black Gates in CA7?
 ...seems like that might be good._

 

WilCox used the ES's at CA2 and Black Gates at CA7. Whether he used VitQ's at the output bypass, I can't remember. Regardless, what you suggest might be an interesting combination to try.


----------



## WilCox

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_WilCox used the ES's at CA2 and Black Gates at CA7. Whether he used VitQ's at the output bypass, I can't remember. Regardless, what you suggest might be an interesting combination to try.
	

	
	
		
		

		
		
	


	


_

 













 I actually prefer the ES's at CA2 over the Black Gates -- more bass slam for my ATH-W5000 and W1000. My last build used the Super E-Cap configuration for the Black Gates which seemed to give a minor improvement in overall transparency and bass extension. Will have to go back to a single Black Gate plus VitaQ for my Mini builds due to lack of space. Also going to do one Mini with Black Gates at CA2.


----------



## Beefy

And so it begins...... 
	

	
	
		
		

		
		
	


	









 All very low profile parts have been fitted. Small signal transistors and trimmers will go in tomorrow, tube sockets and caps probably Wednesday.

 tomb wasn't joking when he said that the axial Schottky diodes were difficult to fit. They are also pretty difficult to solder due to their bulk, and the solder doesn't wick through the holes as the leads are so big. Continuity checks out fine though, so I'm not going to try to solder the top of the board.

 Strangely, I had my first ever dud Vishay Dale today. The 10.2 ohm resistor at RB3R checked out OK before installation, but half the pinkish casing split away on soldering. Resistance was still fine, but thankfully I had some spares to swap it out.

 So how is everyone else going with theirs????


----------



## tomb

Quote:


  Originally Posted by *Beefy* /img/forum/go_quote.gif 
_<snip>
 Strangely, I had my first ever dud Vishay Dale today. The 10.2 ohm resistor at RB3R checked out OK before installation, but half the pinkish casing split away on soldering. Resistance was still fine, but thankfully I had some spares to swap it out.

 So how is everyone else going with theirs????_

 

Looks great so far. 
	

	
	
		
		

		
		
	


	




 Yes, I've had a couple V-D's break apart on me, but it's usually because I was doing something stupid like grabbing them with a pair of pliers.
	

	
	
		
		

		
		
	


	




 However, that's why Colin and I quit using the red PRP resistors. Their quality control on the epoxy coating is horrible - half of them are weird-shaped blobs, etc., and break quite easily. As you've noticed, it's not very common with V-D's, thank goodness.


----------



## Beefy

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Looks great so far. 
	

	
	
		
		

		
		
	


	


_

 

My horrible photography skills mask the fact that it isn't really up to my usual standard. Nothing is as flush or as meticulously straight as I normally strive for. I'm not sure if I'm too tired and thus careless, or just excited to be working on something new


----------



## bperboy

I worked on my two boards for a few hours yesterday... made a good start, but am missing some things in my mouser order.. the BOM XLS download file was different than it is now when I placed my order.. Tomb, i'll be emailing you with a few questions later today...


----------



## Beefy

I'm a little confused by the orientation of the trimmers.

 RA1 and RB12 seems to match up to the layout and the silkscreen, and photos of Mini Max prototype builds.

 But RR3 is different. The silkscreen and the layout are different from the prototypes - it has rotated 180 degress. Has something changed here?


----------



## Beefy

More progress......







 Every low profile part except for RR3, the tube sockets and CM3 are now installed. RA5C will go in later when I decide what I want to do with LEDC.

 Aside from the confusion with the trimmers, everything has gone quite smoothly. I did mangle a PF1 trying to straighten the legs to mount it flush, so I wouldn't recommend others doing that...... thankfully, I bought a spare!


----------



## DaMnEd

Looking good!


----------



## lordvader

RR3 seems to be just a variable resistor, so it probably wouldn't matter which way its orientated, you'll just be spinning in the "other" direction ...

 Unless its initial value is important, in which case you'll be testing with either a dead short or max resistance (though RR2 looks like a "safety net" for that scenario ...)

 Another question, since the rectifier is using schottky diodes, is it really necessary to bypass them ?


----------



## Beefy

Quote:


  Originally Posted by *lordvader* /img/forum/go_quote.gif 
_RR3 seems to be just a variable resistor, so it probably wouldn't matter which way its orientated, you'll just be spinning in the "other" direction ..._

 

I tend to agree, but if there is a 'right' way, then I'm happy to hold off for an official response 
	

	
	
		
		

		
		
	


	




  Quote:


 Another question, since the rectifier is using schottky diodes, is it really necessary to bypass them ? 
 

I've read quite a few arguments about this, and the take-home message I get is that even if there is no benefit, it doesn't hurt. And for the sake of 40 cents, I'm happy to put them in


----------



## Beefy

YAY MAX!






 Everything is installed except the VitQ's at CA8, and all initial sanity checks are good. A happy 27.0V from V+ to GND, tube bias trimmers work properly, and 34/36mV quiescent through the buffers at the minimum setting. The relay is switching after ~30 seconds of power input.

 Far too early for listening impressions, but I believe that I have built the first working, non-prototype Mini Max 
	

	
	
		
		

		
		
	


	




 [EDIT] You might notice that QB9L is mounted a little strangely. The Aavid mounting kits I bought contained screws that were too long for the two middle heatsinks. A couple of washers 'pulled' the end of the screw sufficiently out of the way.


----------



## DaMnEd

CONGRATULATIONS! 
	

	
	
		
		

		
		
	


	




 2SC2238/2SA968?


----------



## Beefy

Yep. It is essentially a Can't Miss #1


----------



## bperboy

Is anyone planning on not installing LEDs in their MiniMax? I've had LSDiodes in my previous Max, but I'm thinking of just leaving those out..


----------



## DaMnEd

Quote:


  Originally Posted by *Beefy* /img/forum/go_quote.gif 
_Yep. It is essentially a Can't Miss #1_

 

Nice, I plan on building one just like yours, looking forward to your impressions!


----------



## Beefy

Quote:


  Originally Posted by *bperboy* /img/forum/go_quote.gif 
_Is anyone planning on not installing LEDs in their MiniMax? I've had LSDiodes in my previous Max, but I'm thinking of just leaving those out.._

 

Put them in, but leave out the resistors. Someone might prefer the bling when it comes to resale, and it is impossible to get the LEDs in later.


----------



## bperboy

Quote:


  Originally Posted by *Beefy* /img/forum/go_quote.gif 
_Put them in, but leave out the resistors. Someone might prefer the bling when it comes to resale, and it is impossible to get the LEDs in later._

 

That's not a bad idea at all.. what PN did you get for yours? I've got to make another order pretty soon with some stuff I didn't order the first time..


----------



## Beefy

All biased up to 100mV, or about 45mA, per channel no worries. Time to power down now, and get some much needed sleep


----------



## Beefy

Quote:


  Originally Posted by *bperboy* /img/forum/go_quote.gif 
_That's not a bad idea at all.. what PN did you get for yours? I've got to make another order pretty soon with some stuff I didn't order the first time.._

 

I got the red ones that I used in this Max from eBay.

 In my previous 'regular' Max, I used these but they are quite pricey.

 I also tried these previously...... and while they are not very bright, the colour is virtually identical to that of the heater, so it looks like the heater does all the illumination. Might be good if you want something subtle.


----------



## tomb

Quote:


  Originally Posted by *Beefy* /img/forum/go_quote.gif 
_Put them in, but leave out the resistors. Someone might prefer the bling when it comes to resale, and it is impossible to get the LEDs in later._

 

Not at all - it's quite easy to drop the LED's through the center hole in the tube sockets and install them later on. This is assuming, of course, that you drilled out the tube sockets. The LED's wouldn't be much use for tube lighting if that wasn't done.

 About RR3 - yes, I talked Colin into turning it around. It makes little difference except for which way you turn the screw - but RR3 in the MiniMAX prototype was reversed from all of the MAX boards that came before it. Plus, it looked a little weird having the epoxy-fill side of the trimmer facing forward.

 The other change from the MiniMAX proto boards:
 1. Blue. 
	

	
	
		
		

		
		
	


	



 2. The pads around CA8 have increased to the available space between the sinks.
 3. The cooling holes around all of the heat sinks have increased in number and have been moved out toward the edges of the fins, where possible. This may look a bit strange in some spots, but the traces below really dictated where the holes could go.


----------



## Beefy

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Not at all - it's quite easy to drop the LED's through the center hole in the tube sockets and install them later on. This is assuming, of course, that you drilled out the tube sockets._

 

Hmmmm, I tried this on my first Max, and none of those Lumex LEDs quite fit through the holes. These eBay jobbies I have now are the same.

 [EDIT] Everything still checks out fine in the bright light of day. My 'cold start' E12 delay with a 1M resistor and 470µF Panasonic FM cap is 38 seconds. Less than 1mV recorded from ground to output left or right.


----------



## tomb

Hmm ... well, sorry to hear that about the Lumex LED's, but maybe they have extra-wide flanges. I measure 4.1mm dia for the hole in the sockets that Beezar sells. The LSDiodes stock I still have remaining slide through without touching anything.


----------



## Beefy

And here is my little baby playing music from an iPod line out into sacrificial Koss KSC-75...












 Still far too early for in-depth impressions, but there is certainly nothing offensive that I have noticed yet.


----------



## rhester

I have finished my MiniMAX (second production run built, I belive). It is basically a Can't Miss Build #1 with BG bypassed with .18 VitaQ, PRP resistors, 47Ohm KIame in RB14 (socketed so can try differnt values), with 2238/968 transistors. Playing thru the 701s now and can't wait for the first few hundred hours are done to see what this thing will really sound like.

 Will post some pics later. Thanks Tom and Colin.


----------



## Beefy

Quote:


  Originally Posted by *rhester* /img/forum/go_quote.gif 
_I have finished my MiniMAX (second production run built, I belive). It is basically a Can't Miss Build #1 with BG bypassed with .18 VitaQ, PRP resistors, 47Ohm KIame in RB14 (socketed so can try differnt values), with 2238/968 transistors._

 

Nice! I've had a listen to mine from my Buffalo DAC and AD900's. It sounds sweet...... _real sweet_. But there is a fair bit of background noise with my super-sensitive AD900's (hopefully casing will reduce this), and even with FK6's there is only about 20-30 degrees of play on the volume knob before it is too loud. I definitely think I will drop in some 10 ohm resistors on mine, just like my regular Max build. But......

  Quote:


 Playing thru the 701s now 
 

...... you won't need any output resistors with those. They are very hard to drive anyway. 

  Quote:


 Will post some pics later. Thanks Tom and Colin. 
 

Look forward to them!


----------



## WilCox

Quote:


  Originally Posted by *rhester* /img/forum/go_quote.gif 
_I have finished my MiniMAX (second production run built, I belive). It is basically a Can't Miss Build #1 with BG bypassed with .18 VitaQ, PRP resistors, 47Ohm KIame in RB14 (socketed so can try differnt values), with 2238/968 transistors._

 

rhester,

 Congratulations on a successful build! Could you please give some information about the sockets you used for RB14. I'd like to try the same thing.

 Thanks!


----------



## cetoole

Quote:


  Originally Posted by *rhester* /img/forum/go_quote.gif 
_I have finished my MiniMAX (second production run built, I belive). It is basically a Can't Miss Build #1 with BG bypassed with .18 VitaQ, PRP resistors, 47Ohm KIame in RB14 (socketed so can try differnt values), with 2238/968 transistors. Playing thru the 701s now and can't wait for the first few hundred hours are done to see what this thing will really sound like.

 Will post some pics later. Thanks Tom and Colin._

 

Thank you, and Beefy too. AFAIK, you two are the first to finish up minimax builds on production PCBs, so knowing that it works just fine really lets me breath easier.


----------



## ruZZ.il

dude, even your prototypes work perfectly! 
	

	
	
		
		

		
		
	


	




 I know any change brings in chance of error.. but you had this one under control. rzpkt.


----------



## tomb

Ditto on the thanks, Beefy and Max! Those are great build pics, too, Beefy. Any trouble with the VitQ's? It looks from here that the extra holes Colin provided at CA8 helped.


----------



## bperboy

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Ditto on the thanks, Beefy and Max! Those are great build pics, too, Beefy. Any trouble with the VitQ's? It looks from here that the extra holes Colin provided at CA8 helped._

 

I don't have pics yet, but 0.18uF VitQs can fit completely horizontal with a little tugging...


----------



## Beefy

Quote:


  Originally Posted by *bperboy* /img/forum/go_quote.gif 
_I don't have pics yet, but 0.18uF VitQs can fit completely horizontal with a little tugging..._

 

I thought about that and I really don't think that is a good idea. It leaves the nipples in VERY close proximity to the heatsinks, and I wouldn't trust any heat shrink or similar to reliably cover them.

 I bent the leads on mine to fit like the following pic. Very crude and not to scale, but I think it gives a good idea of how you can 'offset' the lower end and keep both ends of the cap well away from the heatsinks.


----------



## bperboy

Well, it's a little too late for that now, as they're already in there and trimmed..


----------



## tomb

Quote:


  Originally Posted by *Beefy* /img/forum/go_quote.gif 
_I thought about that and I really don't think that is a good idea. It leaves the nipples in VERY close proximity to the heatsinks, and I wouldn't trust any heat shrink or similar to reliably cover them._

 

Agreed. The VitQ nipples should _not_ be poking inbetween the fins of the heat sinks. We thought perhaps in the early stages of the MiniMAX development that the 0.18uf VitQ's would fit horizontally with clearance, but the nipples get in the way (no comments on that, please 
	

	
	
		
		

		
		
	


	




 ).

 Beefy's bend as shown is a good one and one that I would recommend. Once making sure you've bent the leads as close to the nipple as absolutely possible, it might still be possible to put them kneeling by pulling the leads through from the bottom. That may make it fairly easy. You only have to be careful not to let even the corner of the cap sit above the height of the heat sinks.

 I had considered at one point to remove the leads and use SPC wire like we did on the K42's at one point. However, the VitaminQ leads appear to be solid copper underneath the surface tinning. I don't think we want to give those up.
	

	
	
		
		

		
		
	


	




 Plus, the solid leads provide quite a bit of stability for the kneeling position. As long as that bottom end is pulled flush against the board, they are quite robust in a position like Beefy's.

 On the MiniMAX proto, the bends had to be a bit more creative than that, so the new wider holes look like they simplified things quite a bit.
	

	
	
		
		

		
		
	


	





 EDIT: bperboy, I didn't see your last post while I was typing this. PM me and maybe there's something we can work if you're unhappy about how you installed the VitQ's. This is my fault for not having the website ready. I've been traveling too much lately, unfortunately.


----------



## digger945

That amp looks obscene, Beefy
	

	
	
		
		

		
		
	


	



 Did you say you ordered those Black Gates from Sonic Craft? That's fast shipping, I gotta check them out.


----------



## tomb

By the way ... what's being left unsaid of the reason for mounting the Vitamin Q's in the way we've described:

 I've had exposed nipples on K42's and Vitamin Q's arc to an anodized Hammond case - the same material as the heat sinks. So, it's the proximity to the conductive source that's the issue and whether the thickness and quality of the anodizing is enough to prevent arcing. I don't think it is in many instances.

 As a matter of fact, the anodizing on many of these heat sinks is scratched off right at the fins - most consider the center section with the transistor as the important part to insulate, so they're not even protected in packaging and shipping from the mfr. However, we have a different situation with the VitQ's on the MiniMAX board and so the fins' insulating quality comes into play if we nudge a VitQ nipple in there.

 Anyway, that's why it's probably not a good idea to let the nipples get inbetween the fins.


----------



## tomb

One other question came up from a user - the knob. This has been mentioned before, but is probably lost in this thread somewhere. The custom-machined Lansing case is setup for a ~1" diameter knob. Specifically, the silkscreened dial indicators are on a 1-1/16" diameter circle. The actual knob I use/will use is a Partspipe 24mm aluminum knob (24 x 25mm). This is slightly smaller than the 30mm knob used on the regular MAX. Partspipe has some excellent choices here:

 Black - PKG2, 24x25 SOLID Aluminum Black CD VOLUME TONE KNOB - eBay (item 300142226235 end time Nov-07-08 17:49:25 PST)

 Silver - PKG2, 24x25 SOLID Aluminum Silver CD VOLUME TONE KNOB - eBay (item 290267386624 end time Nov-11-08 17:07:39 PST)

 Gold - 2pcs 24x25 SOLID ALLOY GOLD CD VOLUME TONE KNOBS KNOB - eBay (item 300265944855 end time Nov-11-08 20:33:37 PST)

 Any of those are great choices, although the black and silver are probably more appropriate for the black and silver MiniMAX cases. They all come with set-screws and are solid. You have to be careful, because some of the ones Partspipe sells have plastic inserts and are press-fits. At any rate, the ones referenced are also priced as good as you will find any quality knob, IMHO. I think they are fibbing when they claim "machined." To me, they appear to be sintered. Nevertheless, they are hefty and solid and good enough for many us.


----------



## sandbasser

Greetings -

 I"m starting to get my orders together for the parts for my MiniMAX. I'm wondering about the LED. I see it spec'd in the BOM but I don't see where it is supposed to mount in the Lansing case. What am I missing???

 Thanks,


----------



## JamesL

Two LEDS are for the tubes, and the third one is at the center, to light up the case or to use as a front panel indicator.

 You'll likely have to drill one out yourself if you want a front panel LED. 
 I believe the consensus is that the tube lights/LEDS are perfectly suitable for a power indicator, and a front panel hole was left out in customized case.


----------



## sandbasser

Quote:


  Originally Posted by *JamesL* /img/forum/go_quote.gif 
_Two LEDS are for the tubes, and the third one is at the center, to light up the case or to use as a front panel indicator.

 You'll likely have to drill one out yourself if you want a front panel LED. 
 I believe the consensus is that the tube lights/LEDS are perfectly suitable for a power indicator, and a front panel hole was left out in customized case._

 

I think the tube LEDs will provide plenty of 'bling'; so, if I don't want to use the panel LED can I just leave it out (and its corresponding RLED)???

 Thanks,


----------



## tomb

Quote:


  Originally Posted by *sandbasser* /img/forum/go_quote.gif 
_I think the tube LEDs will provide plenty of 'bling'; so, if I don't want to use the panel LED can I just leave it out (and its corresponding RLED)???

 Thanks,_

 

Yes.


----------



## Beefy

Quote:


  Originally Posted by *digger945* /img/forum/go_quote.gif 
_That amp looks obscene, Beefy
	

	
	
		
		

		
		
	


	



 Did you say you ordered those Black Gates from Sonic Craft? That's fast shipping, I gotta check them out._

 

Thanks! 
	

	
	
		
		

		
		
	


	




 Yes, I ordered from Sonic Craft. I received them 9 days after ordering which is pretty fantastic for just Priority Mail.

  Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_The actual knob I use/will use is a Partspipe 24mm aluminum knob (24 x 25mm). This is slightly smaller than the 30mm knob used on the regular MAX._

 

Hmmmm, I was thinking that the 30mm knobs would be good, but luckily I have both sizes spare from last time I ordered


----------



## Beefy

I had a bit of a play around regarding the hiss issue I mentioned a little earlier......

 Without tubes in, the output buffer alone is dead silent with my AD900. Tubes in there is the slight noise, confirmed with 3 different sets of tubes. The noise is not volume dependent over the first half rotation, but then gets louder in the second half. I get the exact same phenomenon with my older regular Max but it is barely noticeable - presumably due to the output resistors in that build.

 Interestingly, the noise is much greater while the tube bias is very high on warmup, and drops off as as the tube bias drops down past 18-19V.

 Overall, its not really a problem (my sinus-problems-related tinnitus is louder than the hiss anyway), and I will reduce the effects with output resistors. It might be a good excuse for me to buy some harder to drive phones though......


----------



## tomb

Quote:


  Originally Posted by *Beefy* /img/forum/go_quote.gif 
_I had a bit of a play around regarding the hiss issue I mentioned a little earlier......

 Without tubes in, the output buffer alone is dead silent with my AD900. Tubes in there is the slight noise, confirmed with 3 different sets of tubes. The noise is not volume dependent over the first half rotation, but then gets louder in the second half. I get the exact same phenomenon with my older regular Max but it is barely noticeable - presumably due to the output resistors in that build._

 

Yep. We've recommended at least 10ohm output resistors from the very beginning to tame some of the tube noise. As you've experienced, however, it all depends on the headphones. IMHO, no one will ever hear anything with Sennheisers, Grados, AKG's, Koss, etc.

  Quote:


 Interestingly, the noise is much greater while the tube bias is very high on warmup, and drops off as as the tube bias drops down past 18-19V. 
 

Yes, of course! The high tube bias is a sign that the tubes haven't even warmed up yet - all sorts of bad noises, harshness, etc. may occur. They'll probably still drop a volt or so even after an hour. Most of us half-deaf types can get good listening in a few minutes, though.
	

	
	
		
		

		
		
	


	




  Quote:


 Overall, its not really a problem (my sinus-problems-related tinnitus is louder than the hiss anyway), and I will reduce the effects with output resistors. It might be a good excuse for me to buy some harder to drive phones though...... 
	

	
	
		
		

		
		
	


	



 

The MAX is really setup to be a current monster. Voltage differential is good enough to drive 300ohm phones, but lower impedances and lower efficiency really let the amp shine. I still prefer my HD580's over almost anything, with KSC75s/PX100s a pretty close second - especially at work, but that's MHO, YMMV.

 BTW, I don't think you've had that thing long enough to have those Black Gates break in.


----------



## Beefy

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Yep. We've recommended at least 10ohm output resistors from the very beginning to tame some of the tube noise. As you've experienced, however, it all depends on the headphones._

 

I've got both 10 and 47ohm KOA resistors from Beezar stashed away somewhere, so maybe I should investigate whether I can get something locally to socket them for the second build. I plan on using one of these to replace my 2Move at work, and hopefully with some ESW9 which are just as sensitive as the AD900. I would really like to get the balance right between noise and dynamics.

  Quote:


 BTW, I don't think you've had that thing long enough to have those Black Gates break in. 
 

Only 243 hrs, 54 mins to go


----------



## tomb

Quote:


  Originally Posted by *Beefy* /img/forum/go_quote.gif 
_I've got both 10 and 47ohm KOA resistors from Beezar stashed away somewhere, so maybe I should investigate whether I can get something locally to socket them for the second build. I plan on using one of these to replace my 2Move at work, and hopefully with some ESW9 which are just as sensitive as the AD900. I would really like to get the balance right between noise and dynamics._

 

I've tried an ESW7 on a MAX at a meet and I didn't notice any issues, but sometimes a meet is not the quietest place to listen.

 Let me ask another question - have you been using tubes that are well-broken in? If new, the situation is the same as a tube that's not warmed up - only worse.

 Also, I hesitate to recommend this, but there will be some quieting - especially at frequencies <1K - if you stick some film caps in there at CA9. The VitQ's I tried lowered the bass slightly, but there was less noise with a RMAA test below about 1K, if memory serves. Something else may work without doing that. I'm just guessing, but a pair of Wima's may not have any effect on the frequency response of the BG's, but could tame some of that hiss. It's worth a try and they're easy enough to take out if it hurts the bass.

 This is another exagerrated effect that exists with BG's perhaps, but not other caps. My BG Maxes have always been noisier - most definitely more detailed - but with scratching on the pot, etc. However, I just haven't done enough testing with the BG's (they are pretty expensive, you know) as with ES's. You are actually trailblazing with the MiniMAX and BG's.

  Quote:


 Only 243 hrs, 54 mins to go


----------



## Beefy

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Let me ask another question - have you been using tubes that are well-broken in? If new, the situation is the same as a tube that's not warmed up - only worse._

 

A mixture of old and new. All sound the same.

  Quote:


 Also, I hesitate to recommend this, but there will be some quieting - especially at frequencies <1K - if you stick some film caps in there at CA9. 
 

Interesting. What I'll do is make up the second one over the next couple of weeks, try some various combinations of output resistors and CA9 caps and report back with the results. I have both 0.22µF Wima and 0.18/0.22µF VitQ spare (though I doubt either of the VitQ will fit).

 Mind you, this is all probably making a mountain out of a molehill. It isn't nearly _that_ bad......


----------



## Beefy

I'm looking for something to socket the output resistors, and came across this and this. Am I looking at the right sort of thing?


----------



## tomb

Quote:


  Originally Posted by *Beefy* /img/forum/go_quote.gif 
_I'm looking for something to socket the output resistors, and came across this and this. Am I looking at the right sort of thing?_

 

Technically, yes ... practically, NO.

 In my experience, socket strips are horribly unstable when used in a one-per-pad basis. They're a little bit better if you keep the strip all together and snip the leads off of the ones inbetween that are not used. The resistors we use are huge in comparison to most of these things, which are meant to hold small pins on an IC. You need as much framework and supporting material around _and between_ the socket pins as you can get.

 The best scenario, IMHO, is to find a DIP socket that's long enough, cut off one side, snip the leads in the middle that aren't used, and use that instead.


----------



## Beefy

Check!


----------



## tomb

Due to some going back and forth with Lansing over approving their shop drawings for the case, the delivery has been pushed back to 12/15/2008.


----------



## n_maher

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_The best scenario, IMHO, is to find a DIP socket that's long enough, cut off one side, snip the leads in the middle that aren't used, and use that instead.
	

	
	
		
		

		
		
	


	


_

 

Just one word of caution, if you do this (snip the leads) make sure you cut them short enough so that they are nowhere near the surface of the pcb. Otherwise there's a chance that over time they could wear through the solder mask and short to anything that is below them.


----------



## bperboy

Haven't tried sound yet, but one of my MiniMaxes is running at 27VDC, 13.5VDC tube bias, and ~53mVDC BJT bias... looking good! 
	

	
	
		
		

		
			





 Tom, what would be a good BJT bias to shoot for once the cases arrive?


----------



## cetoole

Quote:


  Originally Posted by *bperboy* /img/forum/go_quote.gif 
_Haven't tried sound yet, but one of my MiniMaxes is running at 27VDC, 13.5VDC tube bias, and ~53mVDC BJT bias... looking good! 
	

	
	
		
		

		
		
	


	


_

 

Pics or it didnt happen!
	

	
	
		
		

		
		
	


	




 Hmm, gotta figure out a way to make my Max to drive my new Stax SR404 I bought today from Headroom. I dont think 12ae6a tubes will have sufficient gain, though they do nicely for my orthos. Nate, I guess when you reinstated your policy of "No stats in '08", you forced them upon me.


----------



## tomb

Quote:


  Originally Posted by *bperboy* /img/forum/go_quote.gif 
_<snip>
 Tom, what would be a good BJT bias to shoot for once the cases arrive?_

 

50ma/110mV - that's the typical standard. The cooling slots in the case might be good for more than that, but we'll have to see.


----------



## n_maher

Quote:


  Originally Posted by *cetoole* /img/forum/go_quote.gif 
_Nate, I guess when you reinstated your policy of "No stats in '08", you forced them upon me._

 

Indeed, I saw the add within a few minutes of Jorge posting it and had a hard time not calling, but ultimately sanity won over lust.


----------



## Beefy

Quote:


  Originally Posted by *n_maher* /img/forum/go_quote.gif 
_Just one word of caution, if you do this (snip the leads) make sure you cut them short enough so that they are nowhere near the surface of the pcb. Otherwise there's a chance that over time they could wear through the solder mask and short to anything that is below them._

 

Good point. I might even try to drill the entire pin out......


----------



## rhester

Here's a few pics of my naked mini (I can't wait for the case for this thing):


----------



## Beefy

Those red PRP resistors look great 
	

	
	
		
		

		
		
	


	




 Hmmm, you jumpered the heater resistor? I thought that was pretty important for tube life at the default 27V......


----------



## tomb

Quote:


  Originally Posted by *Beefy* /img/forum/go_quote.gif 
_Good point. I might even try to drill the entire pin out......_

 

I think you'll find that if you use a pair of flush cutters above the actual pin, the metal socket body crushes/clips easy enough to be out of the way. Besides what Nate said, you won't be able to actually push the pins that remain as far as they should go into the pads. If you don't do this, the result will be an unstable socket again (no longer superior to other methods). 
	

	
	
		
		

		
		
	


	




  Quote:


 Hmmm, you jumpered the heater resistor? I thought that was pretty important for tube life at the default 27V...... 
 

I recommend at least 10ohms for the heater resistor. This brings the voltage on the heaters closer to the "standard" 12.6VDC per heater and also provides a good safety factor over the widest possible PS voltage range. Technically, however, the heaters absolute limits are 15.9VDC each (and not below 10VDC).
	

	
	
		
		

		
		
	


	




 Great pics, Max!!
	

	
	
		
		

		
		
	


	




 You and Beefy (and Bperboy if he comes up with pics
	

	
	
		
		

		
		
	


	




 )are putting the rest of us to shame!


----------



## cetoole

Hey Max, way to take that (wait for it) MiniMax to the Max! 
	

	
	
		
		

		
		
	


	




  Quote:


  Originally Posted by *Beefy* /img/forum/go_quote.gif 
_Those red PRP resistors look great 
	

	
	
		
		

		
		
	


	




 Hmmm, you jumpered the heater resistor? I thought that was pretty important for tube life at the default 27V......_

 

They do look great, and I used them once on a BG/MOSFET Max build because of that, but man, never again. They are really annoying to work with, IMO. I think Tom said this earlier, but the red outer covering is really weak on them at least compared to other resistors I have used like the VD RN55, and has a tendency to break off, even under finger pressure.

 I wouldnt say the heater resistor is very important for tube life, but I would expect it to be shorter with the tube heater running at 13.5v, though probably not too much shorter.

  Quote:


  Originally Posted by *n_maher* /img/forum/go_quote.gif 
_Indeed, I saw the add within a few minutes of Jorge posting it and had a hard time not calling, but ultimately sanity won over lust. 
	

	
	
		
		

		
		
	


	


_

 

Oh, a wise guy, eh? What is that crack about sanity supposed to mean?
	

	
	
		
		

		
		
	


	




 I just happened to see the ad, sent headroom sales an email, then crashed. I dont even usually browse anything outside of the DIY sections and the big Ortho thread, but somehow stumbled across that post. I was just exhausted last night, and actually forgot about it until I got a reply from Jorge today while at work, informing me that I was the first respondent, and asking me to give him a call to actually place the order. First time I have dealt with Headroom, and they were very pleasant to talk with on the phone.


----------



## bperboy

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_<snip>
 Great pics, Max!!
	

	
	
		
		

		
		
	


	




 You and Beefy (and Bperboy if he comes up with pics
	

	
	
		
		

		
		
	


	




 )are putting the rest of us to shame!_

 

Ahhh! If only I didn't have finals next week! Hopefully I'll be able to snap some pics today or tomorrow...


----------



## gspence2000

I am new to the audiophile headphone scene, and am building a Millett Hybrid MiniMax as my first headphone amp. I'd like some advice regarding headphone selection. I live in rural Vermont and have no opportunity to audition headphones. In lieu of this, I have been reading all I can on the forums. I'd like to know how the Millett amps affect the sound, and whether that should influence my choice of headphones.

 I am zeroing in on the Sennheiser 600/650's, but am having a last-minute thoughts about the Sennheiser 595's.

 My music tastes are varied: 30% classical, 30% hard-bop jazz, 40% electronica.

 My questions:
 1) Does the Millett Max/MiniMax impart a warmth that compliments the 595's, making them more neutral? (I realize selection of tubes provides some play here)
 2) Would the 650's be extra warm/laid back with the Millett?
 3) Should I just give up on the one-size-fits-all approach and also get a cheap pair of Grado's for the electronica?

 I want something sweet for classical but don't want to suck the life out of the other musical styles that I enjoy.

 Thanks in advance!


----------



## digger945

Do you have a budget?
 Other than classical, is there another genre you enjoy?
 Does it matter to you, new or used from Head-Fi?


----------



## gspence2000

Quote:


  Originally Posted by *digger945* /img/forum/go_quote.gif 
_Do you have a budget?
 Other than classical, is there another genre you enjoy?
 Does it matter to you, new or used from Head-Fi?_

 

Classical, jazz and electronica are my main interests. Acoustic guitar and female vocals are important to me.

 My budget is $300 and I would be most interested in used equipment (that's why I put the HD 650's on my list--they would be way out of my price range otherwise
	

	
	
		
		

		
		
	


	




).


----------



## DaMnEd

With the Sennheiser 595's I wouldn't bother with an amp at all, no significant benefit imho. With the 650's an amp is a must.


----------



## gspence2000

DaMnEd, I see from your sig that you use HD-650s and Grado RS-80s with your MiniMAX. Do you switch between them based on the type of music you are listening to?


----------



## DaMnEd

The Grados are more of a portable rig, when home the 650 are used pretty much very time, the Grados have comfort issues and I can't use them for hours and hours unfortunately.

 But the Grados are rock kings, they render electric guitar like no other imho, but I do not listen to rock all that much.


----------



## gspence2000

Thanks DaMnEd. That's good info.


----------



## gspence2000

Anyone else have an opinion? Does the MillettMax color the sound, and would using the MillettMax affect your choice in headphones? Are there phones that especially complement the MillettMax?


----------



## soloz2

HD595's will benefit from an amp, but the HD600's would be my pick. Amazing match with a Max IMHO


----------



## Beefy

Quote:


  Originally Posted by *gspence2000* /img/forum/go_quote.gif 
_Anyone else have an opinion? Does the MillettMax color the sound, and would using the MillettMax affect your choice in headphones? Are there phones that especially complement the MillettMax?_

 

These questions are all pretty arbritrary. Colour the sound compared to _what_?

 In any case, if somebody gave me a pair of HD595, I'd give them to someone else......


----------



## Gross

Quote:


  Originally Posted by *Beefy* /img/forum/go_quote.gif 
_In any case, if somebody gave me a pair of HD595, I'd give them to someone else......_

 


 lol 
	

	
	
		
		

		
			





 (Me too...)

 And sticking with the thread, My build is probably 75% done, just waiting for a few things to show up. Sure looks impressive with everything on the board all 1" tall.

 Oh yeah, and my MillettMAX rocked the socks off my RS-1s, so I'd say get Grados.


----------



## tomb

Quote:


  Originally Posted by *Gross* /img/forum/go_quote.gif 
_lol 
	

	
	
		
		

		
		
	


	




 (Me too...)

 And sticking with the thread, My build is probably 75% done, just waiting for a few things to show up. Sure looks impressive with everything on the board all 1" tall.

 Oh yeah, and my MillettMAX rocked the socks off my RS-1s, so I'd say get Grados._

 

Gee ... those aren't Grados being held in an ... ahem ... interesting way in your avatar.
	

	
	
		
		

		
		
	


	










 BTW, I still like my HD580's best overall with the MAX and KSC-75's a close second, but I run with many different phones on the MAX and like them all: HD600's, HD580's, HD25-1 II's, Koss PortaPro's, Koss KSC-75's, Grado SR225's, Sony V6's, etc. The AKG K701's do very well with the MAX, too - I'm saving up for a pair of those or the K702's (if they ever drop in price). I don't have them anymore because my head is too big for them
	

	
	
		
		

		
		
	


	




, but the K81DJ's are a good match, too. Equation Audio RP-21's are great, too, and very cheap - I would highly recommend BigAmish's simple mods for those - a really surprisingly nice-sounding pair of headphones for basically $100.


----------



## cetoole

For headphones, my current favorites are the planar magnetics, best exemplified by the Yamaha Orthodynamaics and Fostex RP series. Of the standard dynamics, my favorites are the Sennheiser HD580/600 line, even over the HD650. I am definitely not a grado kind of guy, though I have never heard the RS-1.


----------



## bperboy

I'm with TomB on this one.. HD580s all the way. They are the only high-end pair of headphones I've ever owned, and they sound magnificent! I do want to get some k701s as well, but although I seem to be able to justify building two MiniMaxes, I can't bring myself to buy a new pair of cans...


----------



## gspence2000

Thanks all for the replies. HD 580s or 600s it is!


----------



## ruZZ.il

I still love my ultrasones 
	

	
	
		
		

		
		
	


	




 Though, I don't recall giving 580s a serious listen...


----------



## Gross

I have a pair of K-501s and I guess they are OK, but at work I mostly use my HD-600s. I own several KSC-75s as well, as bang for the buck they are awesome. And I don't even know the cans the cans are on in my avatar


----------



## Beefy

I bought some DIP sockets today.... seems that 6 pins is the perfect spacing for the RB14 position. However, the leads on the KOA resistors I bought from Beezar don't fit the sockets 
	

	
	
		
		

		
		
	


	




 All too hard; I think I will just drop in the 47R that I have and hope for the best


----------



## jamess71

Quote:


  Originally Posted by *Beefy* /img/forum/go_quote.gif 
_I bought some DIP sockets today.... seems that 6 pins is the perfect spacing for the RB14 position. However, the leads on the KOA resistors I bought from Beezar don't fit the sockets 
	

	
	
		
		

		
		
	


	




 All too hard; I think I will just drop in the 47R that I have and hope for the best 
	

	
	
		
		

		
		
	


	


_

 

Just a heads up Beefy, I tried the 47 Ohm kiwame's and there was a noticeable change in sound quality on my max. The 10 ohm worked just fine to clean up the very minor noise that I had. I'm using it with Denon AH-D2000 and they are are only 32 ohms. Damn near silent.


----------



## Beefy

Quote:


  Originally Posted by *jamess71* /img/forum/go_quote.gif 
_Just a heads up Beefy, I tried the 47 Ohm kiwame's and there was a noticeable change in sound quality on my max. The 10 ohm worked just fine to clean up the very minor noise that I had. I'm using it with Denon AH-D2000 and they are are only 32 ohms. Damn near silent._

 

Thanks for that James.

 I have bought some second hand ESW9 that should arrive late next week, so perhaps I will give them a test with my 10R'ed regular Max before I commit to anything on the new build.

 It might be the case that I have to source 22R as a happy medium......


----------



## tomb

Quote:


  Originally Posted by *Beefy* /img/forum/go_quote.gif 
_Thanks for that James.

 I have bought some second hand ESW9 that should arrive late next week, so perhaps I will give them a test with my 10R'ed regular Max before I commit to anything on the new build.

 It might be the case that I have to source 22R as a happy medium......_

 

Sorry the sockets didn't work for you, Beefy. I could swear I've used them before with the 2W resistors, but maybe not. Max Hester had sockets for his Kiwame's in his recent pics a few posts back. Maybe he can share his experience with us.

 YGPM.


----------



## Beefy

That's fine, my good man 
	

	
	
		
		

		
		
	


	




 I could sort of jam them in there so they would make contact, but they were no where near secure enough. It could very well be the sockets I bought as well.....

 In any case, I have ordered some 2W Kiwame from a UK outfit, and will soon have 10, 22, 33 and 47R to try. I should also have plenty of spares if any Australian builder needs any


----------



## rhester

Mine were sip sockets from Mouser (3M .100" Board Mount 10P 1ROW STRT SOCKET). They work fine but separating them, as they come in a connected strip, is a royal PITA. I intend to use it to find the right combo and then go permanent. Right now, the 47s with 12ae6 still have plenty of gain. I want to try the 100 and see how much more they tame the hi end.


----------



## rds

Is it considered important to transistor match with this amp?


----------



## Beefy

Quote:


  Originally Posted by *rds* /img/forum/go_quote.gif 
_Is it considered important to transistor match with this amp?_

 

MAX Construction explains transistor matching. Essentially, it is most important to match the CCS transistors at QA1 and QA2.


----------



## tomb

Quote:


  Originally Posted by *Beefy* /img/forum/go_quote.gif 
_MAX Construction explains transistor matching. Essentially, it is most important to match the CCS transistors at QA1 and QA2._

 

Yes, this is correct.

 However ... after doing several hundred sets of the matched transistors myself, I would _highly_ recommend that you go through the procedure. It's not critical to get them very close, except reasonably close for QB2 and QB3, perhaps.

 If memory serves, most of the 2N5087's I've purchased and tested for Beezar run mostly from 350 - 450 HFE, while 2N5088's run mostly from 400 HFE to 500HFE. So, there will often be differences of at least 50 - 100 HFE between the 5087's and 5088's. However, it's fairly easy to get the 5087's within about 10 HFE of each other and the 5088's the same.

 Yet, I have seen some 5087's and 5088's range all the way up to 700 and higher HFE. That's a huge difference. It doesn't happen all that often - perhaps 1 out of every 20 or 30, but I can't predict what would happen if one of those transistors were placed in the buffer with the more normal-rated ones. Most of the transistors in the diamond buffer are self-correcting. Also, there is obviously the trimmers' ability to balance the buffers from Left to Right.

 The one place this isn't possible is with QB2 and QB3. If those aren't _reasonably_ matched, you'll see a difference in bias from one side of the buffer to the other. You'll get differences of perhaps more than 10ma from TB1L to TB2L (or TB1R to TB2R in the Right channel). A difference there is not adjustable and cannot be compensated except for swapping out the transistors.

 Saying that, a _reasonable _matching is not on the order of 10HFE for QB2 and QB3, since they are complementary (5087 and 5088). So, 50 - 100 HFE is probably still acceptable. It's just whether you're unlucky enough to get one of those 700 HFE's in there with a 350 or lower. Then it may be too much of a difference to be self-correcting and you'll see significant differences in the test points within the same channel.

 I hope that doesn't confuse everyone - the big thing is to sort through the transistors, measure HFE, and just try to make sure the big offenders are weeded out.


----------



## ruZZ.il




----------



## digger945

Quote:


  Originally Posted by *jamess71* /img/forum/go_quote.gif 
_ I'm using it with Denon AH-D2000 and they are are only 32 ohms..._

 

I am pretty sure all Denons are 25Ω impedance, should it matter for your calculations.
 I know of none lower
	

	
	
		
		

		
		
	


	




.


----------



## digger945

I was just wondering Tom, if you use any peculiar methods for testing or matching your transistors. Do you believe that the warmth from holding the part between your fingers can throw the measurements off to a degree, or is this just something that has no effect at all.
 Just wondering and thanks so much for post #306, much appreciated
	

	
	
		
		

		
		
	


	




.


----------



## tomb

Quote:


  Originally Posted by *digger945* /img/forum/go_quote.gif 
_I was just wondering Tom, if you use any peculiar methods for testing or matching your transistors. Do you believe that the warmth from holding the part between your fingers can throw the measurements off to a degree, or is this just something that has no effect at all.
 Just wondering and thanks so much for post #306, much appreciated
	

	
	
		
		

		
		
	


	




._

 

Ha! 
	

	
	
		
		

		
		
	


	




 I don't think it's the warmth in your fingers so much as the battery level in the DMM. You will get different readings when you first turn on the DMM than you will 1/2 hour later. In most cases, though, the transistor will settle within a few seconds.

 However - I do so many of them, I don't leave them connected for more than about a second. It's counter-productive to do so. _Matching_ is the key, not an absolute measurement. So as long as you are consistent, everything will be fine. As stated earlier, though - you can probably get them as far apart as 50 HFE and be OK. It's the really outrageous ones you need to weed out.

 Just an FYI, but those input JFETs on a MOSFET-MAX are an entirely different matter.


----------



## JamesL

Is there a reason why most of the ouput caps recommended here are bipolar caps?
 BG NX, Muse ES..
 Would cerafines, Muse KZ, silmic II's, work just as well here?


----------



## tomb

Quote:


  Originally Posted by *JamesL* /img/forum/go_quote.gif 
_Is there a reason why most of the ouput caps recommended here are bipolar caps?
 BG NX, Muse ES..
 Would cerafines, Muse KZ, silmic II's, work just as well here?_

 

Cerafines are excellent if you can find them. KZ's and Silmic's are way too tall to fit in the MiniMAX case - everything is limited to 1" height, remember.


----------



## JamesL

I see
 I wonder if the 1000uF FG's or 220uF KZ's would be any better than the ES, considering I'll be paying the same price regardless.
 After all, the Millet SS uses 160uF stock without much noticeable effect w/ grados.


----------



## bperboy

Quote:


  Originally Posted by *JamesL* /img/forum/go_quote.gif 
_I see
 I wonder if the 1000uF FG's or 220uF KZ's would be any better than the ES, considering I'll be paying the same price regardless.
 After all, the Millet SS uses 160uF stock without much noticeable effect w/ grados._

 

Well, I do know the SS is not the same design as the Minimax, and has quite different design specifications...


----------



## tomb

Quote:


  Originally Posted by *JamesL* /img/forum/go_quote.gif 
_I see
 I wonder if the 1000uF FG's or 220uF KZ's would be any better than the ES, considering I'll be paying the same price regardless.
 After all, the Millet SS uses 160uF stock without much noticeable effect w/ grados._

 

ES's are better than FG's, so I don't see the point.

 As for the rest, do not go below the recommended values at CA2 and CA7. The Millett MAX is _not_ the SSMH. It doesn't even use the same tube circuit, much less the tubes, the power supply, the full-scale diamond buffer, the relay, etc. There is little similarity except the shared name of its benefactor and the general classification as a hybrid.


----------



## JamesL

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_ES's are better than FG's, so I don't see the point.

 As for the rest, do not go below the recommended values at CA2 and CA7. The Millett MAX is not the SSMH. It doesn't even use the same tube circuit, much less the tubes, the power supply, the full-scale diamond buffer, the relay, etc. There is little similarity except the shared name of its benefactor and the general classification as a hybrid._

 

Hmm.. I see.
 I do know that the SS is completely different in design from the regular millet, but I thought the specifications for the output coupling caps should be the same in all/most DC coupled headphone amplifier(voltage rating aside).


----------



## jamess71

Quote:


  Originally Posted by *digger945* /img/forum/go_quote.gif 
_I am pretty sure all Denons are 25Ω impedance, should it matter for your calculations.
 I know of none lower
	

	
	
		
		

		
			





._

 

Your absolutely right digger, Don't know why I had the 32 number in my head. Dooh


----------



## tomb

Quote:


  Originally Posted by *JamesL* /img/forum/go_quote.gif 
_Hmm.. I see.
 I do know that the SS is completely different in design from the regular millet, but I thought the specifications for the output coupling caps should be the same in all/most DC coupled headphone amplifier(voltage rating aside)._

 

It is - at least for the output coupling caps. However, no one is using caps as small as you suggested in the SSMH - 470uf quickly became the standard for the SSMH on the output (for the rail caps, too, but that's a different story). The revMH Millett Hybrid used this value almost from the beginning and has been documented for years on DIYForums.org.

 Just a simple calculation for the -3dB level of 220uf and 32ohm phones yields 22Hz - this means the actual roll off begins at somewhere around 300Hz, with response down 0.25dB at 100Hz! That is not very good performance for a high fidelity amplifier, which should be ruler-flat all the way through the audio spectrum.

 There are other things that affect the bass frequency response in the MAX/MiniMAX - the cathode bypass cap being one, the size of the rail caps are another. The revMH Millett Hybrid had a better response than the original used in Pete's Audio Express article. The reason was the use of 470uf caps on the output.

 The MAX improved on that response further still, with the use of a 1000uf cap at the cathode bypass - C2. (This doesn't even exist on the SSMH.) A very experienced tube designer who frequents this forum has recommended a minimum of 1000uf for a cathode bypass to preserve bass response. It makes a difference.

 If we were to compare tests for the SSMH and the revMH Millett Hybrid -
 Pete's SSMH using 160uf caps:





 AMB's revMH Millett Hybrid, 12AE6 tubes, 13.5V bias, diamond buffer at 25ma, 33 ohm load (470uf from the comparison with C2 in the pics):





 With 330 ohm load (all else the same):





 Note that the scales on the revMH Millett Hybrid responses are much larger, despite the smaller size image. That's a drop of only 0.5dB for 33ohms and negligible for 330ohms. Whereas the SSMH is down -3dB at ~20Hz. We believe the MAX improved on the bass response a great deal. Having built four revMH Millett's, the comparison with several MAXes was easily noticeable with an increase in bass. We believe we've enhanced that even more with the MiniMAX low-noise power supply improvements.

 All this is not to criticize the SSMH or overly-hype the MAX. The two amps simply have different design goals: simplicity and starving students for one, a fully-loaded, high-performance low-voltage tube hybrid for the other. It's probably best not to mix the two, however.


----------



## JamesL

Thanks for the enlightenment tomb.

 I got confused when you said "The Millett MAX is not the SSMH"... in response to a 220uF output coupling cap.
 I thought you meant that different values behaved completely differently between the two circuits.

 I do know the extent of a 160uF at the output driving 32ohm grados. The dt880 and hd650's I use however both have a much higher impedance, so I thought I could exercise some leniency. 
 Regardless, I'll stick with your advice as it makes more sense having the amp built suitable for all ranges of headphones.


----------



## slowpogo

I actually have the original Max, not the mini but it seems most Max-related action is here these days...

 My Q is about cap life expectancy. For the last 6 months or so I have been leaving my Max on for most of the time. Every few days I'll turn it off for a while, but I use the amp so sporadically throughout the day I just got sick of turning it on/off, and I have so many tubes I don't worry about tube lifespan.

 BUT it recently occurred to me (doh) that caps also have a lifespan. I'm using the BG NX caps in both boutique positions...am I going to wear them out this way, or do they only get "used" when there's music going through them...when the amp is idle are they kind of not being used?

 Cause so far the amp probably has 2000+ hours of being on, much much less than that with music going through.


----------



## tomb

Quote:


  Originally Posted by *slowpogo* /img/forum/go_quote.gif 
_I actually have the original Max, not the mini but it seems most Max-related action is here these days...

 My Q is about cap life expectancy. For the last 6 months or so I have been leaving my Max on for most of the time. Every few days I'll turn it off for a while, but I use the amp so sporadically throughout the day I just got sick of turning it on/off, and I have so many tubes I don't worry about tube lifespan.

 BUT it recently occurred to me (doh) that caps also have a lifespan. I'm using the BG NX caps in both boutique positions...am I going to wear them out this way, or do they only get "used" when there's music going through them...when the amp is idle are they kind of not being used?

 Cause so far the amp probably has 2000+ hours of being on, much much less than that with music going through._

 

I thought you sold your MAX on ebay.
	

	
	
		
		

		
		
	


	




 You are correct to be concerned. A capacitor's life is proportional to temperature. That life is quoted with respect to the capacitor's temperature rating, either 85 deg.C or 105 deg.C. for most caps. Black Gates are probably 85 deg.C. caps - most boutiques are. At that rating, 2000hrs is probably maximum life. Now, 85 degrees C. is 151 deg. F. Chances are, you are nowhere close to that rating. The capacitor life increases significantly at lower temps.

 Still, there is a limit and you may be in the neighborhood.

 P.S. Temperature ratings are exposure, period - doesn't matter if music is going or not.


----------



## royewest

2000 hours is the maximum life for some capacitors??


----------



## Beefy

Quote:


  Originally Posted by *royewest* /img/forum/go_quote.gif 
_2000 hours is the maximum life for some capacitors??_

 

Sometimes as low as 1000 hours, even for very good quality caps. But keep in mind that it is specced as minimum lifetime, at maximum temperature, at the maximum voltage.

 Lifetime itself is usually stated as leakage current not exceeding a certain level. A good cap doesn't just explode, or completely fail, right on the lifetime figure.


----------



## Gross

Another MiniMAX lives! At least the LEDs light up. I will figure out if the rest of works tomorrow, but my ass is going to bed now.


----------



## Beefy

Tell your ass to post some pics in the morning


----------



## slowpogo

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Still, there is a limit and you may be in the neighborhood.

 P.S. Temperature ratings are exposure, period - doesn't matter if music is going or not._

 

That's what I was afraid of..darn it, now I'll be paranoid when I listen to it, searching for degradation of sound quality.

 Which I guess leads to another question....at some point in the next few months my paranoia will drive me to buy new caps. I did can't-miss-build #1 (exactly as listed but with doubled Vitamin Qs), but I'm not rich enough for new Black Gates and won't be any time soon. (I notice Parts Connexion doesn't even carry the 1000uf NX anymore)

 What would be the best drop-in replacement caps for that config out of the usual boutiques (Muses, Elna etc)?


----------



## tomb

Quote:


  Originally Posted by *slowpogo* /img/forum/go_quote.gif 
_That's what I was afraid of..darn it, now I'll be paranoid when I listen to it, searching for degradation of sound quality.

 Which I guess leads to another question....at some point in the next few months my paranoia will drive me to buy new caps. I did can't-miss-build #1 (exactly as listed but with doubled Vitamin Qs), but I'm not rich enough for new Black Gates and won't be any time soon. (I notice Parts Connexion doesn't even carry the 1000uf NX anymore)

 What would be the best drop-in replacement caps for that config out of the usual boutiques (Muses, Elna etc)?_

 

Elna Cerafines have always been considered the inexpensive alternative to Black Gates, but they're actually harder to get.
	

	
	
		
		

		
		
	


	




 There's a few every once in awhile on ebay and then there's a UK store that sells them, I believe. Not cheap, but still less than Black Gates, I think. The Cerafines have another advantage: no huge break-in overhead as with BG's.


----------



## slowpogo

Thanks for the quick responses tomb...one more Q. Does C7 absolutely have to be at least 35v, or is 25v OK? I ask because I found some Cerafines at a reasonable cost but they only have 25v and 50v for the 470uf, and the 50v is too big.

 Or, I could use the big caps if it were OK to install them at an angle, so that one lead was through the hole almost all the way and the other one (front-most) was lengthier...you know, kind of like tomb-stoning resistors, except these would be laying as close to flat as possible.


----------



## tomb

Quote:


  Originally Posted by *slowpogo* /img/forum/go_quote.gif 
_Thanks for the quick responses tomb...one more Q. Does C7 absolutely have to be at least 35v, or is 25v OK? I ask because I found some Cerafines at a reasonable cost but they only have 25v and 50v for the 470uf, and the 50v is too big.

 Or, I could use the big caps if it were OK to install them at an angle, so that one lead was through the hole almost all the way and the other one (front-most) was lengthier...you know, kind of like tomb-stoning resistors, except these would be laying as close to flat as possible._

 

There are these:
** SALE !! 470uF 35V ELNA CERAFINE Audio Capacitors NOS - eBay (item 280279759729 end time Nov-23-08 09:13:07 PST)

 I wouldn't use 25V - you'd be risking the same thing you are now. They'll see the 27V for a few seconds until the heaters come up on the tubes, I believe. Then they won't last as long as they should as a result. Plus, any failure and they may see it as well. I've seen people flipping over electrolytics and I've done it too, on occasion - but nothing as big as these.

 The best scenario would be that ebay link, I think. The price is quite reasonable if you compare them against BG's.


----------



## slowpogo

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_There are these:
** SALE !! 470uF 35V ELNA CERAFINE Audio Capacitors NOS - eBay (item 280279759729 end time Nov-23-08 09:13:07 PST)

 I wouldn't use 25V - you'd be risking the same thing you are now. They'll see the 27V for a few seconds until the heaters come up on the tubes, I believe. Then they won't last as long as they should as a result. Plus, any failure and they may see it as well. I've seen people flipping over electrolytics and I've done it too, on occasion - but nothing as big as these.

 The best scenario would be that ebay link, I think. The price is quite reasonable if you compare them against BG's._

 

Thanks for the link..I try to avoid ordering stuff from halfway around the world but it's definitely worth a shot in this situation. Hopefully it's still there on Friday/payday.

 IIRC CA9 is left empty with the Black Gates because they are already so good they don't need the bypassing in that spot. Would the same apply to Cerafines do you think, or should CA9 be populated?

 I have some .27 Vitamin Qs and .47 Black Gate FKs that have been laying around forever...would be happy to toss a pair of either in CA9 if it would help. I know that "blooming mid" caps are not good there but I'm not sure if that applies to the BGs and VitQs.


----------



## slowpogo

Excuse me while I pile on the questions... 
	

	
	
		
		

		
			





 I'm just curious if people have tried using different caps in CA2 and CA7...like Elnas in CA2 and Muse ES in CA7, or something like that. I don't remember ever reading an account of it.

 Does this violate some basic law, or is it just taking a risk that it will sound bad to mix caps that way?


----------



## tomb

Quote:


  Originally Posted by *slowpogo* /img/forum/go_quote.gif 
_Excuse me while I pile on the questions... 
	

	
	
		
		

		
		
	


	




 I'm just curious if people have tried using different caps in CA2 and CA7...like Elnas in CA2 and Muse ES in CA7, or something like that. I don't remember ever reading an account of it.

 Does this violate some basic law, or is it just taking a risk that it will sound bad to mix caps that way?_

 

Pardon me for replying 
	

	
	
		
		

		
		
	


	




, but Will Cox has done pretty much the same thing - ES at CA2 and Black Gates at CA7. It's probably a great way to optimize cost while preserving audio quality.

 The original kits that Jeff Rossel sold used Panasonic FM's at CA2 with KZ's up front. All reports are that they sounded great (of course, the KZ's were 35mm tall, so that presented some difficulty).


----------



## WilCox

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Pardon me for replying 
	

	
	
		
		

		
		
	


	




, but Will Cox has done pretty much the same thing - ES at CA2 and Black Gates at CA7._

 

I actually tried both the MUSE ES and Blackgates at CA2 and thought the ES gave better bass slam. However, as Tom points out, the Blackgates take a long time to burn in and I may not have given them a fair chance. I'll be looking into this a little deeper when I get around to building my MiniMAX.


----------



## tomb

For what it's worth, IMHO, the Black Gates will _never_ have the bass slam of Muse ES's - nothing does, really.
	

	
	
		
		

		
		
	


	




 However, the BG's definitely have better detail. I believe that ES's with the right bypass film cap can _approach_ the BG's detail. Like everything else, though, it's all a compromise.


----------



## Gross

Ok, here we go. I got a couple of pics, but you will have to excuse the camera. It is quite a few years old, and I had to actually use macro lenses to get this close, the cam has its limitations. I took my time with this guy, and I am pretty happy how it turned out. I still have not listened to it, I will get to twisting some pots right after this post.



















 If you click on the pic, you get a larger one. And if you click that pic, you get another larger one.
	

	
	
		
		

		
		
	


	




 Not to shabby if you ask me.


----------



## DaMnEd

Looks great. Very clean, congratulations!


----------



## Beefy

Quote:


  Originally Posted by *Gross* /img/forum/go_quote.gif 
_Not to shabby if you ask me._

 

Your soldering technique is impeccable - far superior to mine!


----------



## Gross

Quote:


  Originally Posted by *Beefy* /img/forum/go_quote.gif 
_Your soldering technique is impeccable - far superior to mine! 
	

	
	
		
		

		
		
	


	


_

 


 Thanks. My solderstation at home is a Edsyn 951SX Loner. Edsyn does not have as much popularity on head-fi as some of the other manufacturers, but I use a portable one at work, and they both work great.

 As far as the actual work, I stick the components through the holes, and then use masking tape to hold them in place. Then I flip the board over in my mighty handy Pana-Vise. I pre-trimmed the leads and just took my time. On pieces with 3 legs, solder the middle one first, flip it back over and make sure it is straight with the world, then get the other 2 legs.


----------



## digger945

Grossly obscene


----------



## Gross

Here are some action shots:













 Not only does it look good, it sounds great too. Not a single hiccup, worked great from the get go. 

 With the LEDs I picked up some ultra bright wide angle flat top guys, and discovered if I sanded the sides they emitted light sideways very well, and as long as I did not scuff up the flat top, it still shoots plenty straight up. Yeah, Anal, I know. But it kicks ass.

 I have the DBs biased up to 100mV right now, sounds great, and the sinks are just slightly warm to the touch. The cooling holes in the PCB make a big difference, as I recall my MilletMAX DBs getting much warmer, biased to the same level. How high have people been going with the 2238/968 combo? I am using the 12FK6 tubes, and I have RB14L/R jumpered. With my Grado RS-1s I still have plenty of pot travel using my BantamDAC as my source, and the PC volumes maxed.

 How many completed production MiniMAXs are alive now?

 Thanks to everyone who made this happen.


----------



## cetoole

Hey Gross, that looks great! Real good job on that soldering. Must be nice having loaners from work, goes the other way for me. My third soldering station is sitting on my desk there right now (laptop woes). So, it sounds good, but does it make those headphones in your avatar vibrate?


----------



## Gross

Quote:


  Originally Posted by *cetoole* /img/forum/go_quote.gif 
_Hey Gross, that looks great! Real good job on that soldering. Must be nice having loaners from work, goes the other way for me. My third soldering station is sitting on my desk there right now (laptop woes). So, it sounds good, but does it make those headphones in your avatar vibrate?
	

	
	
		
		

		
		
	


	


_

 

Only Myself and 1 other know that answer
	

	
	
		
		

		
		
	


	




 And as far as the irons, I am in the same boat as you. I liked my solderstation at home so much, I bought a portable version to take to work, instead of those cheap 25w Wellers we were using. We are nerds, aren't we?


----------



## slowpogo

Nice work Gross. I like the red LEDs; they make your Max look...dangerous. 
	

	
	
		
		

		
		
	


	




 Has anyone here tried the Muse FG caps? Those I have never heard about. I ask because in that line is a 1000uf 35v cap that is only 1" tall. I always listen with my K701s (62ohm) so that cap would create a much more ideal corner frequency than the usual 470uf caps or even the 680uf BGs.


----------



## sandbasser

Gross - An exceptional build!!!

 Query: are the VitQs the .18 or the .22 µf???

 My parts are starting to arrive, then I start my build; hope the case gets here before Christmas!!!


----------



## Gross

Thanks everyone. My VitQs are the .18µf. I have some .22µf here, and looking at them I don't think they would fit. Yes, I am patiently waiting for the cases too. I just remembered I ordered a black one, Now I am excited again


----------



## ruZZ.il

Quote:


  Originally Posted by *Gross* /img/forum/go_quote.gif 
_Ok, here we go. I got a couple of pics..._

 

Good stuff, dude! Not too shabby at all.
 Looks like I got myself some competition.. or I'm even beat


----------



## pinkfloyd4ever

Quote:


  Originally Posted by *Gross* /img/forum/go_quote.gif 
_How high have people been going with the 2238/968 combo? I am using the 12FK6 tubes, and I have RB14L/R jumpered. With my Grado RS-1s I still have plenty of pot travel using my BantamDAC as my source, and the PC volumes maxed._

 

I have a standard Millett Max with 12FK6s, 2238/968 BJTs, and RB14 jumpered, using an Alien as a source and comp volume maxed, and I also can't get past 9 or 10 o'clock on my volume knob with my MS1s. (I have the knob on there such that straight down, or 6 oclock, is the minimum volume)

 So I guess if it bothers you, try some KOA Speers (same thing as Kiwames) at RB14. Beezar has em, although Mouser has them in all values


----------



## tomb

Dang ... konked out on the sofa again and missed all this action (been working too much, lately). Nice job, Gross! Although, I have the same question that Colin does.


----------



## gspence2000

Quote:


  Originally Posted by *Gross* /img/forum/go_quote.gif 
_Here are some action shots:











_

 

Gross, what do you have installed in TB1L, TB1R that your multimeter probes are clipped onto?


----------



## tomb

Quote:


  Originally Posted by *gspence2000* /img/forum/go_quote.gif 
_Gross, what do you have installed in TB1L, TB1R that your multimeter probes are clipped onto?_

 

Test points loops are a fairly common item. Tangent includes them in this TREAD kits, among other places.

 However, Vixr came up with the best solution: he bent a spent lead into a wire loop and threaded the ends through the hole in a glass bead - like the kind they use to make kid's jewelery. Then he soldered the exposed ends into the hole with the glass bead as the "stop".


----------



## bperboy

Did he break off the bead, or leave it in there?


----------



## gspence2000

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Test points loops are a fairly common item. Tangent includes them in this TREAD kits, among other places.

 However, Vixr came up with the best solution: he bent a spent lead into a wire loop and threaded the ends through the hole in a glass bead - like the kind they use to make kid's jewelery. Then he soldered the exposed ends into the hole with the glass bead as the "stop".
	

	
	
		
		

		
		
	


	


_

 

That's a great idea, thanks tomb.


----------



## tomb

Quote:


  Originally Posted by *bperboy* /img/forum/go_quote.gif 
_Did he break off the bead, or leave it in there?_

 

Left it in there - looked great, too. After all, that's one of the bad things about the "real" test points - it's a little piece of thick rubber tubing that melts if you hold the soldering iron on it too long.
	

	
	
		
		

		
		
	


	




  Quote:


  Originally Posted by *gspence2000* 
_That's a great idea, thanks tomb._

 

Thank Vixr.
	

	
	
		
		

		
		
	


	




 He's the one that came up with it. He had some great pics of it, too - wish I could remember what thread it was in - might've even been the MAX thread.


----------



## tomb

Aha! here we are - it was on Headwize.

 Vixr's Do It Yourself Test Points:










 And the actual thread here: HeadWize: DIY Workshop > DIY test points...


----------



## gspence2000

That is brilliant. Thanks for finding the pics.


----------



## Gross

Quote:


  Originally Posted by *ruZZ.il* /img/forum/go_quote.gif 
_Looks like I got myself some competition.. or I'm even beat 
_

 

Thanks, but just cuz I kick a lot of ass, does not mean you aren't still awesome.

 And to the rest of you, You guys know how to make a nerd blush. Thanks!

 And Tomb answered all the other questions, I just had a small meter clip on the board, works great.


----------



## slowpogo

Has anyone experimented with using 2200uf for CA4/5? Is there any benefit to this?

 I know the recommendation of 1800uf is meant to keep the caps no more than an inch tall...but I see digikey has some Pana FC caps that are 2200uf, 25v and still only 18x25.

 Sorry if this has been discussed ad nauseum, but I don't remember seeing those last spring when I was first building so I'm curious...now that I find myself back in Max Land.


----------



## Beefy

Quote:


  Originally Posted by *slowpogo* /img/forum/go_quote.gif 
_but I see digikey has some Pana FC caps that are 2200uf, 25v and still only 18x25._

 

*25*V? Too low rated. It really needs to be 35V.

 *

 I got my Kiwame output resistors yesterday, and installed 22R in my MiniMax today. Definite improvement over just jumpered, but doesn't really reduce the noise compared to my 10R regular Max. Though I suspect that proper casework and wiring will improve the MiniMax further......


----------



## tomb

Quote:


  Originally Posted by *slowpogo* /img/forum/go_quote.gif 
_Has anyone experimented with using 2200uf for CA4/5? Is there any benefit to this?

 I know the recommendation of 1800uf is meant to keep the caps no more than an inch tall...but I see digikey has some Pana FC caps that are 2200uf, 25v and still only 18x25.

 Sorry if this has been discussed ad nauseum, but I don't remember seeing those last spring when I was first building so I'm curious...now that I find myself back in Max Land._

 

Beefy is correct; the voltage is too low in case of failure. However, you should compare ratings:

*FM 1800uf 35V - 0.014ohms 3820ma ripple*
FC 2200uf 25V - 0.028ohms 2400ma ripple.

 Even if you go to FC's highest rated cap _at 35V_, -

FC 3900uf 35V - 0.014ohms 3735ma ripple,

 only then is the impedance as low as the 1800uf FM, but ripple is still not as good. Of course, the FC is 18 x 40mm high at that rating, to boot. You'll find that Nichicon UPW's are very similar to Panasonic FC's. So quite simply, _there is nothing as good as a Panasonic FM for the MAX_ in these positions and in the power supply.


----------



## WilCox

Quote:


  Originally Posted by *slowpogo* /img/forum/go_quote.gif 
_Has anyone experimented with using 2200uf for CA4/5? Is there any benefit to this?

 I know the recommendation of 1800uf is meant to keep the caps no more than an inch tall...but I see digikey has some Pana FC caps that are 2200uf, 25v and still only 18x25.

 Sorry if this has been discussed ad nauseum, but I don't remember seeing those last spring when I was first building so I'm curious...now that I find myself back in Max Land._

 

If you still want to try 2200uf, here are the ones that will fit from Mouser:

Nichicon Low Impedance Radial Electrolytic
 2200uf 35V 105C
 Mfg P/N: UPW1V222MHD6
 Mouser Cat. No.: 647-UPW1V222MHD6

 There is also a 1200uf that will fit at CR1:

Nichicon Low Impedance Radial Electrolytic
 1200uf 50V 105C
 Mfg P/N: UPW1H122MHD6
 Mouser Cat. No.: 647-UPW1H122MHD6

 As Tom mentions, the ripple rating of the UPW's is not as good as the FM's so you will have to decide what trade offs you want to make. Note that I have found the UPW's to work very well, in spite of the ratings.


----------



## slowpogo

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Beefy is correct; the voltage is too low in case of failure. However, you should compare ratings:

*FM 1800uf 35V - 0.014ohms 3820ma ripple*
FC 2200uf 25V - 0.028ohms 2400ma ripple.

 Even if you go to FC's highest rated cap at 35V, -

FC 3900uf 35V - 0.014ohms 3735ma ripple,

 only then is the impedance as low as the 1800uf FM, but ripple is still not as good. Of course, the FC is 18 x 40mm high at that rating, to boot. You'll find that Nichicon UPW's are very similar to Panasonic FC's. So quite simply, there is nothing as good as a Panasonic FM for the MAX in these positions and in the power supply._

 

Sorry, that was actually a typo, I meant *35v*. There's a 2200uf 35v FC cap that's only an inch tall. But, I see your point.

 Still I may try it in one of the positions, CA5 maybe since people seem to not mind or notice the worse ratings...and after checking I see the 31.5mm versions of the 2200uf, which have better ratings, will still fit in my case. I guess I'm just in a soldering mood lately


----------



## slowpogo

For anyone interested...I did just what I described above. I put the 2200uf 35v FC caps (31.5mm) in CA5.

 Although the ratings of that cap are a little worse than the FMs, I notice only good changes (pretty subtle). The sound seems to have slightly more foundation, not thicker really but more solid somehow. And the bass is a tiny bit improved -- that change *could* be my imagination because it's quite subtle but I seem to notice a bit more fatness and oomph.

 I wouldn't expect or encourage anyone to do this because it's a very small change, but FWIW I did it and like it.


----------



## tomb

Quote:


  Originally Posted by *slowpogo* /img/forum/go_quote.gif 
_For anyone interested...I did just what I described above. I put the 2200uf 35v FC caps (31.5mm) in CA5.

 Although the ratings of that cap are a little worse than the FMs, I notice only good changes (pretty subtle). The sound seems to have slightly more foundation, not thicker really but more solid somehow. And the bass is a tiny bit improved -- that change *could* be my imagination because it's quite subtle but I seem to notice a bit more fatness and oomph.

 I wouldn't expect or encourage anyone to do this because it's a very small change, but FWIW I did it and like it._

 

Well, don't minimize your accomplishment. At the very least, you've proven that they're a complete equivalent, perhaps slightly better. So, those caps can be added to the list of possible options with known success for the MAX.


----------



## Beefy

Almost finished my second Mini Max, and thought I'd post a photo of how I bent and heatshrinked the leads on the VitQ's......






 Clearance from the heatsinks on both sides is very good, there is very little exposed metal that can make contact with stray multimeter leads, and the only bit that sticks above the height of the heatsinks is the tape around the outside of the cap.


----------



## tomb

Outstanding, Beefy! I hope you don't mind my using several of your pics for the MiniMAX website. I had been working hard on it before the computers in our household went haywire lately.
	

	
	
		
		

		
		
	


	




 I've got a new one almost built, though, so maybe I'll be productive soon.


----------



## Beefy

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Outstanding, Beefy! I hope you don't mind my using several of your pics for the MiniMAX website. I had been working hard on it before the computers in our household went haywire lately.
	

	
	
		
		

		
		
	


	




 I've got a new one almost built, though, so maybe I'll be productive soon.
	

	
	
		
		

		
		
	


	


_

 

No probs at all. I've taken better construction photos of this second one as well..... with tripod, no flash. You're welcome to any of them.

 Oh, and a quick question. Where would be the safest and most convenient place to measure pre-regulator DC voltage? I'm getting 27VAC loaded at the terminal block, but I don't trust my meter's AC reading. Though if the pre-reg voltage measures high as well, I might increase the regulated voltage a bit to decrease heat production on the Vreg.


----------



## tomb

Quote:


  Originally Posted by *Beefy* /img/forum/go_quote.gif 
_No probs at all. I've taken better construction photos of this second one as well..... with tripod, no flash. You're welcome to any of them._

 

I'll take anything you can give me.
	

	
	
		
		

		
		
	


	




 Quote:


 
 Oh, and a quick question. Where would be the safest and most convenient place to measure pre-regulator DC voltage? I'm getting 27VAC loaded at the terminal block, but I don't trust my meter's AC reading. Though if the pre-reg voltage measures high as well, I might increase the regulated voltage a bit to decrease heat production on the Vreg. 
 

The traces leading from the outside axial Schottkys to CR1A and CR1B are rectified postive (+). So, I would put a probe on one of the legs of those outside Schottkys - the legs closest to the PS heat sink. GND, of course, can be measured from anywhere on the board.


----------



## Beefy

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_The traces leading from the outside axial Schottkys to CR1A and CR1B are rectified postive (+). So, I would put a probe on one of the legs of those outside Schottkys - the legs closest to the PS heat sink. GND, of course, can be measured from anywhere on the board._

 

Cheers for that....... next time I wont be so lazy, and will look at the board and work it out for myself 
	

	
	
		
		

		
		
	


	




 I'm measuring 33.1VDC, so increasing the regulated voltage to 28V will still give me 5V headroom for regulation and drop heat production a tad.

 When I've de-fluxed this new build, I'll take some glamour shots and send you some thumbnails. Just let me know which ones you want and at what resolution and filesize, and I'll either host or email them depending on size.


----------



## Beefy

These BG's still need 5324566 hrs burn-in, and I'm not sure these 12FK6 tubes are fully cooked yet.... but WOW.... no concern for bass quantity or quality with BG's in CA2 and Wima's in CA9.

 No concern for dynamics with 33R Kiwame in RB14 either, at least with my sacrificial KSC-75.


----------



## rds

I'm doing some very similar builds and I was planning to use 10R in RB14.
 Is 33R more appropriate for black gates or something?


----------



## Beefy

Quote:


  Originally Posted by *rds* /img/forum/go_quote.gif 
_Is 33R more appropriate for black gates or something?_

 

I will be predominantly using my Max with Audio Technica ESW9's, which are extremely sensitive. My first Mini Max was originally jumpered and was very noisy with these phones. With 10R in my regular Max, I can hear a touch of tube noise even with music playing. Switching in 22R to my first Mini Max was a slight improvement over this; you really need very quiet bits in the music to hear it. My second Mini Max build with 33R initially seems much better, but it also has Wimas in CA9, which tomb suggested may help reduce tube noise.

 [EDIT] Oh, the other thing, ridiculously low travel on the volume knob with the ESW9 when RB14 was jumpered or with 10R.

 I'll do some in-depth comparisons, burn in things some more, play with different tubes, etc, and come up with some final conclusions in a few days. But if you have anything less sensitive than ESW9, 10R or jumpered should be fine. I would personally lean away from jumpering though, if only to help protect the output stage from shorts.


----------



## bperboy

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Outstanding, Beefy! I hope you don't mind my using several of your pics for the MiniMAX website. I had been working hard on it before the computers in our household went haywire lately.
	

	
	
		
		

		
		
	


	




 I've got a new one almost built, though, so maybe I'll be productive soon.
	

	
	
		
		

		
		
	


	


_

 

Hopefully early next week I'll have some pics of both of my Minimaxes... although you'll probably only need to use one, as they'll be identical builds.


----------



## Beefy

*Beefy throws down the Gauntlet*


----------



## digger945

^^^^OK, now your being obscene LOL
	

	
	
		
		

		
		
	


	




 Two balanced thumbs UP


----------



## bperboy

Beefy, just you wait... I'll call your two Minimaxes and raise you a BantamDAC... on monday afternoon!


----------



## Daveze

Oh, you bad Beefy, you bad.

 I had 4 days back at home: populated the resistors and some diodes for both of my kits. Home again on the 13th for about 2-3 hours then on holidays at the beach. Hopefully I can finish the boards off before the cases arrive.

 I was thinking of just building these for kicks and flogging them off but I'm listing dangerously towards balancing my Grado's.

 Beefy, am I correct in thinking you're doing a test of Wima's vs unpopulated in CA9 position? Any thoughts? Oh, and I just noticed the different output resistors.


----------



## Beefy

Quote:


  Originally Posted by *Daveze* /img/forum/go_quote.gif 
_I had 4 days back at home: populated the resistors and some diodes for both of my kits._

 

Nothing missing yet? Thank christ! 
	

	
	
		
		

		
			





  Quote:


 I was thinking of just building these for kicks and flogging them off but I'm listing dangerously towards balancing my Grado's. 
 

Interesting idea, but I suspect you will seriously need to tame the gain. I've got four of each of 10, 22 and 47 ohm KOA/Kiwame if you need them.

  Quote:


 Beefy, am I correct in thinking you're doing a test of Wima's vs unpopulated in CA9 position? Any thoughts? Oh, and I just noticed the different output resistors. 
 

That was the intention, though the different output resistors won't make it a perfect comparison.

 But this 'comparison' is actually amusing in a way, in that I had no freakin' idea that I had bought so many spare parts for my first regular Max. I mean seriously...... what sane person buys four extra Wima caps? It worked out well for me though!


----------



## Daveze

Nothing missing. Though stupid brain made the hands put RM2 in RM1's spot. I removed it at the expense of the resistor, so I'll need to duck down to Jaycar for a substitute. Unless I have one spare from my Jisbos builds...

 I'd forgotten about the gain a little. I have enough trouble taming the output of the DAC-301, I use the tiniest little crack of volume control on my current MAX...I'm hoping the balanced outputs are a little tamer.


----------



## Beefy

Quote:


  Originally Posted by *Daveze* /img/forum/go_quote.gif 
_Nothing missing. Though stupid brain made the hands put RM2 in RM1's spot. I removed it at the expense of the resistor, so I'll need to duck down to Jaycar for a substitute. Unless I have one spare from my Jisbos builds..._

 

I do have spare Vishay Dales for pretty much every position if you need them. But considering it is just in the relay and outside the signal path, it is probably easier to do the Jaycar run.

  Quote:


 I'd forgotten about the gain a little. I have enough trouble taming the output of the DAC-301, I use the tiniest little crack of volume control on my current MAX...I'm hoping the balanced outputs are a little tamer. 
 

They're here if you need them. Let me know early though, because I might throw any you don't want into Lordvader's kit.


----------



## Daveze

Its cool, I'll pick them up myself. I need a few more items from Beezar so I'll get them in that swoop I think.


----------



## Beefy

Quote:


  Originally Posted by *Daveze* /img/forum/go_quote.gif 
_Its cool, I'll pick them up myself. I need a few more items from Beezar so I'll get them in that swoop I think._

 

Check.

 I actually managed to break two tube sockets this time round 
	

	
	
		
		

		
		
	


	



 But spares from last time saved me from having to make an extra order


----------



## jamess71

Ha I'm in the same boat Beefy. My last MMH boutique was the first amp I sourced all the parts myself. I have lots of spare parts too. The MMM should be a fun build. When are the cases due to arrive?


----------



## tomb

Quote:


  Originally Posted by *jamess71* /img/forum/go_quote.gif 
_Ha I'm in the same boat Beefy. My last MMH boutique was the first amp I sourced all the parts myself. I have lots of spare parts too. The MMM should be a fun build. When are the cases due to arrive?_

 

The cases are scheduled to ship to me on Dec. 15th.

 I talked to Lansing a week ago and the endplates had all been punched and sent off to anodizing. So, I assume they're in the midst of machining the tube(case body).


----------



## Beefy

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_The cases are scheduled to ship to me on Dec. 15th._

 

Rockin' 
	

	
	
		
		

		
		
	


	




 I sent you a couple of emails with pics to tomb@beezar.com.... did you receive them?


----------



## bperboy

My MiniMax that I biased successfully a few weeks ago does in fact play music! Not sure about the sound signature yet.. think burn-in needs to happen, possibly with the VitQs... but it still plays! w00t!


----------



## tomb

Quote:


  Originally Posted by *Beefy* /img/forum/go_quote.gif 
_Rockin' 
	

	
	
		
		

		
		
	


	




 I sent you a couple of emails with pics to tomb@beezar.com.... did you receive them?_

 

Yes - thanks, much!! Unfortunately, my outgoing e-mail on that PC is still messed up - as bperboy can also attest to. I replied, but it didn't go through - haven't had time to go another route, yet.


----------



## Beefy

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Yes - thanks, much!! Unfortunately, my outgoing e-mail on that PC is still messed up - as bperboy can also attest to. I replied, but it didn't go through - haven't had time to go another route, yet._

 

No probs! I'm in no rush obviously, but spam filters these days often get a bit testy with zip attachments, so thought I'd check


----------



## slowpogo

I ended up replacing my prematurely aged Black Gates with a combination that was not often talked about IIRC - SilmicII in CA2 and Cerafine in CA7.

 Wow, does it sound great. They definitely don't have the pinpoint detailed accuracy of the BGs, but they more than make up for it in other ways. With the Black Gates I often found myself admiring the sound, thinking, "Gee, that's detailed!" more than I was actually involved with and enjoying the music.

 With this new combo I immediately found myself connecting with the music much more. The sound has a warmth to it that I enjoy...maybe not warmth so much as not as clinically cool as the BGs. The highs are a touch less sparkling, but the midrange and timbre reproduction are palpable and so musical. The caps cost me about $20 total with shipping and I'm surprised to say I really think they sound better than the Black Gates overall.

 Also got some new tubes, 12AE6 Sylvania-made - my first pair of those and they are excellent.

 I know the Silmics benefit from burn-in, but even without that (and the tubes are still only hours old too) it feels like I have a new amp, one I like better than before. Happy happy ...


----------



## bperboy

Slowpogo, are you running your MiniMax naked right now like I think most of us are? I'm hesitant to really do any listening in my dorm, as I don't like having wires coming off in all directions with the amp just sitting on my desk.


----------



## TimJo

Quote:


  Originally Posted by *slowpogo* /img/forum/go_quote.gif 
_
 Also got some new tubes, 12AE6 Sylvania-made - my first pair of those and they are excellent.
_

 

Those are my favorites as well...


----------



## tomb

Quote:


  Originally Posted by *bperboy* /img/forum/go_quote.gif 
_Slowpogo, are you running your MiniMax naked right now like I think most of us are? I'm hesitant to really do any listening in my dorm, as I don't like having wires coming off in all directions with the amp just sitting on my desk._

 

I've had mine just on standoffs sitting on the coffee table for months, now. The heat sinks and board are a pretty robust combination as long as you support that middle hole with a standoff, too. Tubes should always be considered fragile, of course. 

 That very first MiniMAX - the one with the "CT1" Lansing case (pictured on the web site) - occupies a place on my desk at work.


----------



## bperboy

Tom, is there going to be a hole in the custom cases for a middle standoff, or are we just going to have to have it bolted from one end only?


----------



## Beefy

Quote:


  Originally Posted by *bperboy* /img/forum/go_quote.gif 
_Tom, is there going to be a hole in the custom cases for a middle standoff, or are we just going to have to have it bolted from one end only?_

 

I'm pretty sure that there is a hole in the case to screw in the standoff.

 I bought 4mm M2.5 female standoffs for the kits i put together. The plan was to use a small M2.5 screw to hold to the board before it slots into the case, another from the bottom once its in there. Hopefully it works out correctly once the cases arrive......


----------



## rds

Ah crap I didn't order the standoffs.

 They are not specified in the BOM by the way.


----------



## tomb

Yes, there is a "center" hole in the bottom of the tube (case body) that lines up with the center hole in the board.


----------



## bperboy

Quote:


  Originally Posted by *rds* /img/forum/go_quote.gif 
_Ah crap I didn't order the standoffs.

 They are not specified in the BOM by the way._

 

I don't think the standoffs I already have are going to be the right size, so I'll likely just use a couple of extra nuts. Should work just as well.


----------



## aphexii

Would the MiniMAX fit well in any other the other enclosures that Lansing offers? What about any of the Hammond enclosures?

 I was originally planning to build a MAX, but after seeing the PCB will be OOS for another month or so, figured I might try the MiniMAX out instead 
	

	
	
		
		

		
		
	


	




 My reason for asking about a different case is that I'd like to build a lexan top for it and the recommended enclosure doesn't seem like it would work well for it as the top doesn't seem to be a separate piece.


----------



## tomb

Quote:


  Originally Posted by *aphexii* /img/forum/go_quote.gif 
_Would the MiniMAX fit well in any other the other enclosures that Lansing offers? What about any of the Hammond enclosures?

 I was originally planning to build a MAX, but after seeing the PCB will be OOS for another month or so, figured I might try the MiniMAX out instead 
	

	
	
		
		

		
		
	


	




 My reason for asking about a different case is that I'd like to build a lexan top for it and the recommended enclosure doesn't seem like it would work well for it as the top doesn't seem to be a separate piece._

 

Lansing makes an "ET1" case with a removable lid that's the same size as the DT1 that we're custom machining. They also have the CT1, which is what I used to construct the original MiniMAX proto. It's a bit smaller in height, but otherwise the same, too.

 We selected the one-piece extruded tube style for machining the MiniMAX case because the "ET1" style's top lid (or bottom, if you prefer) doesn't have the Hammond-style Z-bend that allows the lid to be flush with the tops of the sides. It's a straight plate, so by sliding into the top slot, it sits about 1/16" below the tops of the sides. That won't affect you at all if you're using your own lid, though.

 More info is here: Lansing Instrument Enclosures Product Index

 They're quite nice to work with - ordering cases from them is not unlike simply ordering from Mouser or DigiKey, except that you have to do it old-style: call them up on their toll-free telephone line.


----------



## aphexii

Excellent, thanks for the info!

 One more question (if I may). Is there an alternative to 
 CR21uF 63V Box cap1DigiKey478-3367-ND

 Its the only part on my whole digikey order thats OOS


----------



## gspence2000

Tom,

 The miniMax BOM lists RR1 as 120 ohm 1/4W, but the Mouser part indicated is 1/8W. Also, RR2 is listed as 1/2W but the Mouser part is 1/4W. 

 Will that be a problem?


----------



## Beefy

Quote:


  Originally Posted by *gspence2000* /img/forum/go_quote.gif 
_Tom,

 The miniMax BOM lists RR1 as 120 ohm 1/4W, but the Mouser part indicated is 1/8W. Also, RR2 is listed as 1/2W but the Mouser part is 1/4W. 

 Will that be a problem?_

 

I asked that question when I built my regular Max, and others have asked it too 
	

	
	
		
		

		
		
	


	




 No, it is not a problem. The story is that the Vishay Dale resistors are military spec, and generally good for twice their rated value.


----------



## tomb

Quote:


  Originally Posted by *Beefy* /img/forum/go_quote.gif 
_I asked that question when I built my regular Max, and others have asked it too 
	

	
	
		
		

		
		
	


	




 No, it is not a problem. The story is that the Vishay Dale resistors are military spec, and generally good for twice their rated value._

 

Exactly correct.
	

	
	
		
		

		
		
	


	







  Quote:


  Originally Posted by *aphexii* /img/forum/go_quote.gif 
_Excellent, thanks for the info!

 One more question (if I may). Is there an alternative to 
 CR21uF 63V Box cap1DigiKey478-3367-ND

 Its the only part on my whole digikey order thats OOS 
	

	
	
		
		

		
		
	


	


_

 

Any 1uf 63V film cap with 5mm lead spacing will do, although an MKT-series is probably best. Try this one:
http://search.digikey.com/scripts/Dk...me=495-2470-ND


----------



## aphexii

Thanks! Looking forward to this build!


----------



## aphexii

I noticed this on Beezar.com's page for the MiniMAX PCB,

  Quote:


 The real difference with the MiniMAX vs. the MAX is that the MiniMAX board is slightly smaller, but with significantly less volume. 
 

Just for clarification, this is speaking to volume as it relates to its physical dimensions, not audible volume. Correct?


----------



## tomb

Quote:


  Originally Posted by *aphexii* /img/forum/go_quote.gif 
_I noticed this on Beezar.com's page for the MiniMAX PCB,



 Just for clarification, this is speaking to volume as it relates to its physical dimensions, not audible volume. Correct? 
	

	
	
		
		

		
		
	


	


_

 

Yes.
	

	
	
		
		

		
		
	


	







 Volume as in cubic inches, cubic feet, cubic meters, etc.


----------



## aphexii

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Yes.
	

	
	
		
		

		
			








 Volume as in cubic inches, cubic feet, cubic meters, etc.
	

	
	
		
		

		
		
	


	





_

 

lol, just wanted to make sure 
	

	
	
		
		

		
		
	


	







 haha

 I've built 4 fairly straightforward amps thus far, 3 Joshatdot CMOY's and a Mini^3. This will be my first desktop amp so I'm looking forward to it.

 I've read through the whole thread and I'm starting to comprehend a little of what everyone is saying, but is there a good resource to go to to learn about all the different resistors, caps, etc and how they all work together? Why some people decide to leave certain parts off? I guess just general stuff so I can wrap my head around what I'm actually doing and what each part does.

 Also, does the original MAX site serve as a good resource for the MiniMAX? (Similar build, just smaller?)


----------



## Beefy

Quote:


  Originally Posted by *aphexii* /img/forum/go_quote.gif 
_Also, does the original MAX site serve as a good resource for the MiniMAX?_

 

Yep. The 'tweaks' section for the original Max is a great reference to work out part selections for the Mini. Follow the BOM for most parts and any of the can't Miss Builds for the boutique choices, and, well, you can't miss! 
	

	
	
		
		

		
		
	


	




 Oh, but keep in mind that the 0.22µF VitQ's won't fit on the Mini Max. The 0.18µF VitQ is clearly the best option.


----------



## rds

Tomb - have you calculated what height standoff we need for the custom cases?
 I can't calculate it because I don't know which slot the board is intended to slide into.


----------



## Beefy

Quote:


  Originally Posted by *rds* /img/forum/go_quote.gif 
_Tomb - have you calculated what height standoff we need for the custom cases?
 I can't calculate it because I don't know which slot the board is intended to slide into._

 

Answer here: http://www.head-fi.org/forums/4856681-post159.html

 Bottom slot, so 0.155" or 3.973mm. I bought 4mm standoffs, female, M2.5 thread - hopefully they work out!


----------



## rds

OK, thanks.
 Is the M2.5 equivalent to the 4-40? Ie can we use 4-40 screws with the M2.5 standoffs?


----------



## JamesL

nvm


----------



## Beefy

Quote:


  Originally Posted by *rds* /img/forum/go_quote.gif 
_OK, thanks.
 Is the M2.5 equivalent to the 4-40? Ie can we use 4-40 screws with the M2.5 standoffs?_

 

Don't think so. You'll need perfectly matched screws and standoffs.


----------



## aphexii

Quote:


  Originally Posted by *Beefy* /img/forum/go_quote.gif 
_Yep. The 'tweaks' section for the original Max is a great reference to work out part selections for the Mini. Follow the BOM for most parts and any of the can't Miss Builds for the boutique choices, and, well, you can't miss! 
	

	
	
		
		

		
		
	


	




 Oh, but keep in mind that the 0.22µF VitQ's won't fit on the Mini Max. The 0.18µF VitQ is clearly the best option._

 

Awesome, thanks!


----------



## rds

Beefy could you link to the specific screws you choose for the standoffs (I assume they're from Mouser)?
 2mm of thread on either end is not much to work with. I'd imagine we want 4mm screws then...


----------



## FallenAngel

I greatly recommend just buying hardware on eBay - I bought LOTS of things from this store, REALLY AMAZING prices.


----------



## Beefy

Quote:


  Originally Posted by *rds* /img/forum/go_quote.gif 
_Beefy could you link to the specific screws you choose for the standoffs (I assume they're from Mouser)?
 2mm of thread on either end is not much to work with. I'd imagine we want 4mm screws then..._

 

I 'borrowed' a pile of various sized M2.5 screws from the engineering workshop in the department my lady friend works at. So no link I can supply, sorry


----------



## tomb

Quote:


  Originally Posted by *rds* /img/forum/go_quote.gif 
_Beefy could you link to the specific screws you choose for the standoffs (I assume they're from Mouser)?
 2mm of thread on either end is not much to work with. I'd imagine we want 4mm screws then..._

 

There's nothing wrong with threading a 3/8" - 1/2" screw all the way through the standoff - or use a spacer/combination of washers, instead. It can be a little tricky sliding the board into place without knocking off the washers with the screw partially in place, but it can be done. A nut on top of the board for the exposed screw finishes it up.


----------



## cetoole

Quote:


  Originally Posted by *FallenAngel* /img/forum/go_quote.gif 
_I greatly recommend just buying hardware on eBay - I bought LOTS of things from this store, REALLY AMAZING prices._

 

I can second that recommendation, I got a pile of good stuff there as well. Especially the standoffs are priced quite reasonably, as these things are pretty ridiculous at some stores.


----------



## JamesL

I've been getting all my hardware from Mouser lately. 
 This one looks like it'd work.
M3 4mm, Male/Female Hex
 Or you could also use a unthreaded one, and just use a ~8mm(length) screw + hex nut.

 The prices are usually cheaper than your local hardware store, and they usually have almost everything I need.


----------



## Beefy

Has anyone else bought and tried any 12FM6 from Beezar?

 I grabbed a pair, and one of them is crazy microphonic so I probably won't try and use them long term. But I was struck by how attractive they look in the amp. Because the horizontal 'dividers' are really translucent, you get MUCH better tube illumination......


----------



## slowpogo

I have seen pics of some recent builds w/ Black Gates, that use Wimas in CA9 rather than leaving it blank.

 Just curious if I missed something, back when I built mine it was recommended to leave that blank with BGs.

 Is the new recommendation to use Wimas or are people just experimenting? I may be trying some FK series in CA2, so I'd appreciate any new insight on bypassing BGs.


----------



## Beefy

I've been experimenting. IMHO, it really doesn't make much difference to sound quality or tube noise.

 But then I'm not one to sit and listen for hours just to determine minute and subtle difference...... in most cases, it is either offensive or OK.


----------



## pinkfloyd4ever

Quote:


  Originally Posted by *Beefy* /img/forum/go_quote.gif 
_Has anyone else bought and tried any 12FM6 from Beezar?

 I grabbed a pair, and one of them is crazy microphonic so I probably won't try and use them long term._

 

microphonics are really just the luck of the draw, doesn't mean the tube is otherwise bad or likely to fail soon. Search the original Max thread for 'dampers'. There are some silicon rings people have used for dampers that work quite well. Beezar actually sells them too, but you can probably find them locally and not pay (and wait) for shipping to Australia. I believe they work best if you use 2 per tube and position them right at the mica 'dividers'


----------



## rds

I have a big box of 12fm6s - I hope I'm lucky.

 Beefy - that avatar was really censored?! 
 By the way, was that a screen shot from Dogma?


----------



## Beefy

Quote:


  Originally Posted by *pinkfloyd4ever* /img/forum/go_quote.gif 
_microphonics are really just the luck of the draw, doesn't mean the tube is otherwise bad or likely to fail soon. Search the original Max thread for 'dampers'. There are some silicon rings people have used for dampers that work quite well. Beezar actually sells them too, but you can probably find them locally and not pay (and wait) for shipping to Australia. I believe they work best if you use 2 per tube and position them right at the mica 'dividers'_

 

Yes, I was tempted to buy some from Beezar with my last order, but didn't. Though I doubt they would help in this case anyway. After just touching the volume knob, it rings for several seconds... let alone any serious vibrations.

 My post was more directed at the attractiveness of the tubes anyway 
	

	
	
		
		

		
			




 I think they are Tung Sol construction?

  Quote:


  Originally Posted by *rds* /img/forum/go_quote.gif 
_I have a big box of 12fm6s - I hope I'm lucky.

 Beefy - that avatar was really censored?! 
 By the way, was that a screen shot from Dogma?_

 

Let us know how they go! 
	

	
	
		
		

		
		
	


	




 In answer to your questions, yes and yes.


----------



## tomb

pinkfloyd4ever is correct. Microphonics are the luck of the draw. There's no way to test for it except for putting one in an amp. Thankfully, the incidence of microphonic tubes is not very high, but it may be 1 in 20 or 30. One such as you describe is probably a little more scarce than that, even. By all means, if you received one from Beezar, please return it and I'll send you another. My supplier will replace the bad ones for me, as well.


----------



## Beefy

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_By all means, if you received one from Beezar, please return it and I'll send you another. My supplier will replace the bad ones for me, as well._

 

Pffft, more trouble than it is worth 
	

	
	
		
		

		
		
	


	




 I'm probably exaggerating the effect a fair bit as well, considering I'm doing my noise comparisons with IEMs rather than full-size cans.....


----------



## TimJo

Quote:


  Originally Posted by *Beefy* /img/forum/go_quote.gif 
_
 Has anyone else bought and tried any 12FM6 from Beezar?
_

 

Well, I have one of my amps set up for 12FM6's (not from Beezar though) and I like the sound with my 701's. The amp is actually modified a bit, with a higher current in the CCS and a higher operating point. I described this in the original Max thread back in August. Here is the post New Millett Hybrid Maxed Amp - Page 532

 I'm pretty sure that I'm the only one to have tried this, and I have no way of testing distortion, so there really is no way to know if it is an improvement or not. Nonetheless, when I want to listen to music with my 701's, it's the amp I use - one of the advantages of having multiple Maxes.


----------



## Beefy

Quote:


  Originally Posted by *slowpogo* /img/forum/go_quote.gif 
_Is the new recommendation to use Wimas or are people just experimenting? I may be trying some FK series in CA2, so I'd appreciate any new insight on bypassing BGs._

 

I've done some further testing on bypass caps at CA9......

 I found a combination of four 12FK6 tubes that gave me almost the exact same amount of background tube noise out of both channels of my 10R RB14 regular Max, and my Mini Max with 22R RB14 that had CA9 empty. So I powered everything down, populated CA9 on the Mini with Wima caps, and the noise was still pretty much exactly the same.

 And what I said before stands, in that I couldn't notice any difference in sound quality between two BG Mini Maxes with and without CA9 filled. So at the very least, and considering my crappy hearing, it isn't totally disastrous to include it.

 I must say though, the boards do look prettier with it there!


----------



## tomb

Quote:


  Originally Posted by *Beefy* /img/forum/go_quote.gif 
_I've done some further testing on bypass caps at CA9......

 I found a combination of four 12FK6 tubes that gave me almost the exact same amount of background tube noise out of both channels of my 10R RB14 regular Max, and my Mini Max with 22R RB14 that had CA9 empty. So I powered everything down, populated CA9 on the Mini with Wima caps, and the noise was still pretty much exactly the same.

 And what I said before stands, in that I couldn't notice any difference in sound quality between two BG Mini Maxes with and without CA9 filled. So at the very least, and considering my crappy hearing, it isn't totally disastrous to include it.

 I must say though, the boards do look prettier with it there! 
	

	
	
		
		

		
		
	


	


_

 

Well, it's nice that you did this research. In previous testing I noted a quieting of about 2-3 dB from about 1K down on RMAA with caps at CA9 versus not, but - that doesn't mean it was audible.

 Some of my anecdotal experience has also seemed to indicate that Wima caps on Black Gates are ignored. I think ruZZ.il discovered the same with Soniccap Gen II's, as well, which we were using early-on in the MAX development. On the other hand, VitQ's seem to have a smoothing effect on Black Gates, but VitQ's will also kill the bass back there at CA9, too.

 There's another cap I'm going to experiment with - the Roedersteins that I've been recommending for the Bantam. They also make an MKP cap that is at the level of quality of the Wima (maybe better?). Certainly, the Roederstein on the Bantam is blazingly fast. That's what it takes to keep up with Black Gates and some of us suspect that's why many bypass caps are simply ignored by the BG's.

 EDIT: Unfortunately, the Roedersteins are green and will clash quite a bit with the MiniMAX board.


----------



## rds

Just got to have a look at my order from Beezar today.
 The attention to detail and care taken in packaging is really amazing. Just absolutely first class in every way. 
 The mini max boards look fantastic too. I hope I will have a chance to get one built tomorrow.
 Somehow I had it in my mind that the board was larger. It is surprisingly small and the layout is excellent.
 Great stuff. This really makes me feel all warm and fuzzy about the diy community.


----------



## tomb

Quote:


  Originally Posted by *rds* /img/forum/go_quote.gif 
_Just got to have a look at my order from Beezar today.
 The attention to detail and care taken in packaging is really amazing. Just absolutely first class in every way. 
 The mini max boards look fantastic too. I hope I will have a chance to get one built tomorrow.
 Somehow I had it in my mind that the board was larger. It is surprisingly small and the layout is excellent.
 Great stuff. This really makes me feel all warm and fuzzy about the diy community._

 

Many thanks for those kind comments!

 Yes, cetoole has really achieved a tremendous level of refinement in the board design for the MiniMAX. If I do say so myself - it looks right, it goes together right, and it sounds right.
	

	
	
		
		

		
		
	


	




 I'm still working on the MiniMAX website and hope to have most of it up soon. This was a timely comment though, because I've just gone through writing much of the history of the MiniMAX. It reminded me that there was a heckuva lot of work that went behind the design of this board, too. I made mince-meat out of the PCB of at least one built MAX while we tried to solve the low-noise issue of the power supply. It included building Tangent's LNMP and trying countless different scenarios - at Colin's direction - until we came up with the present design and parts selection. I hope you enjoy the changes as much as the rest of us have.
	

	
	
		
		

		
		
	


	




 BTW, Lansing and I have been having conversations - the cases have all been paid for, finished, and I believe they were shipped on Friday. I expect to have confirmation of that on Monday, but they were that close when I spoke to them Thursday evening.
	

	
	
		
		

		
		
	


	





 P.S. Turns out that there was quite a bit of coordination that had to occur for Paypal to transfer payment(s) of that size (note that I said "s" as in plural
	

	
	
		
		

		
		
	


	




 )


----------



## rds

I've been matching 5088s and 5087s for the MiniMax and I noticed an interesting pattern.

 For the 5088s I bought them on a single reel of 100. I found that the hFE was normally distributed around 460 with a standard deviation of 15. There were no outliers.

 For the 5087 I bought them as a package of 100 singles (with formed leads). Here the distribution seemed trimodal with peaks at 570, 500, and 440. There were some values as low as 330 and as high as 660. 

 So my (tentative) conclusion is buying reels should give you a much tighter distribution and would definitely be a good choice if you don't plan to match. In my case with the 5088s in the absolute worst case I would have had a difference of 40 between two transistors.

 Anyways, I'll definitely be buying reels from now on.

 EDIT: These are Fairchild brand from Mouser


----------



## gspence2000

I was just sorting NPNs this evening. They were packaged together in a reel. I used nine paper cups to "bucketize" them to groups of 10 hFE. The other day I did the PNPs, which were loose. I remember seeing three clusters. I didn't record the standard deviation, but I used 26 cups.


----------



## rds

The big brother isn't all that much bigger.


----------



## tomb

Nice!

 Another MiniMAX lives!!


----------



## aphexii

About to place my order with Beezar, didn't see it in the BOM, but was curious how many 'HiQ Heat Sink Mounting Kit' I would need? Five?


----------



## gspence2000

Quote:


  Originally Posted by *aphexii* /img/forum/go_quote.gif 
_About to place my order with Beezar, didn't see it in the BOM, but was curious how many 'HiQ Heat Sink Mounting Kit' I would need? Five?_

 

You need four without shoulder washer ($1.00 ea) and one with shoulder washer ($1.25)


----------



## tomb

Quote:


  Originally Posted by *gspence2000* /img/forum/go_quote.gif 
_You need four without shoulder washer ($1.00 ea) and one with shoulder washer ($1.25)_

 

Depends on the output transistors. The 2SC2344/2SA1011 and the 2SC2238/2SA968, or MOSFETs (not recommended on the MiniMAX) are all TO-220 case and will use shoulder washers. "5" is the magic number, though. Many people forget about the LM317 on the heat sink in the power supply.


----------



## FallenAngel

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Depends on the output transistors. The 2SC2344/2SA1011 and the 2SC2238/2SA968, or MOSFETs (not recommended on the MiniMAX) are all TO-220 case and will use shoulder washers. "5" is the magic number, though. Many people forget about the LM317 on the heat sink in the power supply._

 

Ah, but do you really need shoulder washers for those? They're not touching anything or each other.


----------



## tomb

Quote:


  Originally Posted by *FallenAngel* /img/forum/go_quote.gif 
_Ah, but do you really need shoulder washers for those? They're not touching anything or each other. 
	

	
	
		
		

		
		
	


	


_

 

Well, yes - they will be touching the heat sinks, for sure.
	

	
	
		
		

		
		
	


	




 The anodizing on those things is not always the best. Plus, the screw will be in direct contact with the transistor's metal tab. This means potential shorts to ground are possible with the case, or with an adjusting wand or screwdriver. Chances are that nothing will happen, but it's just good practice to use them with metal-tabbed transistors, IMHO.


----------



## DaMnEd

Any news from Lansing *tomb*?


----------



## tomb

Quote:


  Originally Posted by *DaMnEd* /img/forum/go_quote.gif 
_Any news from Lansing *tomb*? 
	

	
	
		
		

		
		
	


	


_

 

yes


----------



## bperboy

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_yes_

 

Argh.. you're killin me!


----------



## tomb

Quote:


  Originally Posted by *bperboy* /img/forum/go_quote.gif 
_Argh.. you're killin me! 
	

	
	
		
		

		
		
	


	


_

 

I'll post more detail (and pics) tonight, but it's all great news.


----------



## aphexii

Argh, Well that sucks. Looks like the shopping cart on Beezar has a really short time out. I had the window open for about 3 hours, came back to add in the Mounting Kits and my cart was emptied 
	

	
	
		
		

		
		
	


	




 I'm used to the Digikey cart, it can last for days as long as I don't delete my cookies...


----------



## DaMnEd

Next time just log-in/out, the shopping cart is saved this way.


----------



## bperboy

That sounds very promising!! Early Xmas presents!


----------



## Beefy

Quote:


  Originally Posted by *aphexii* /img/forum/go_quote.gif 
_Argh, Well that sucks. Looks like the shopping cart on Beezar has a really short time out. I had the window open for about 3 hours, came back to add in the Mounting Kits and my cart was emptied 
	

	
	
		
		

		
		
	


	




 I'm used to the Digikey cart, it can last for days as long as I don't delete my cookies..._

 

If you're logged in on Beezar when you make your cart, it should be saved.

  Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_I'll post more detail (and pics) tonight, but it's all great news.
	

	
	
		
		

		
		
	


	


_

 

Huzzah!


----------



## aphexii

Quote:


  Originally Posted by *Beefy* /img/forum/go_quote.gif 
_If you're logged in on Beezar when you make your cart, it should be saved.



 Huzzah! 
	

	
	
		
		

		
		
	


	


_

 

Hmmm, maybe its an issue with the site then cause my cart just disappeared again before I even finished adding everything, and i'm logged in


----------



## tomb

(click for bigger pics)
 Black ...



 Silver ...



 My daughters call these the Totem Pole Men ...



 Back ...
















 A few notes -
 1. The side slots on the silver cases are slanted in the opposite direction of the approved shop drawings. This does not impact their functionality in any way and I will ship them along with the rest. Regardless, Lansing has agreed to refund $15 for each silver case that was purchased. As soon as their refund hits my Paypal account, I will start refunding the same amount to each of you for any silver case that was purchased. IOW, the silver cases are discounted to each of you by $15.

 2. The front plate has always been a challenge for Millett builders because both the headphone jack and pot are soldered to the board. This leaves little room for error adjustment. The holes for the pot and the jack are absolutely perfectly sized and perfectly spaced _horizontally_. However, depending on how flush you are able to solder the headphone jack and the pot to the PCB, you may need to whittle about 30 thousandths (about 1/32") from the top half of the holes.

 This is due to several things, not the least of which is the variance in individual soldering, as already mentioned, but also because the PCB has a natural dip in the middle (use a tight-fitting center post), but also because the Lansing cases have a slight bulge outward on the top side.

 All of this is relatively trivial and both pot and jack nuts will more than cover the fit difference - I only mention it because we don't want anyone torquing their RK27 to fit the plate. It's very easy to line up the holes on the pot, headphone jack, and the case screw holes and simply tighten everything down. It will work and they will fit, but I can't guarantee the condition of your pot afterward. So please - take the time to use an X-acto knife (the aluminum can be cut with a knife) or similar and try to get those holes worked into a slightly loose fit.

 3. Shipping will start Friday. Unfortunately, I've had to work late every night this week, and I don't expect tomorrow night to be any different. However, beginning Friday, I will be off for the entire holidays and will devote all my attention to getting these shipped. My goal will be to get them all shipped by the end of the weekend, but it may run into Monday - so, please be patient.

 Thanks! I'll repeat this post on DIYForums.org and in the Group Buy on Headwize.


----------



## FallenAngel

WOW! Those are really beautiful! Let me be the first to pose the rude question, so are there extras?


----------



## aphexii

WOW! Those look fantastic!


----------



## aphexii

Another random question from aphex 
	

	
	
		
		

		
		
	


	




 What color LED's do you guys think I should use on both the tube and LEDC. I still plan to try my best to make a lexan top for the enclosure so I want something snazzy.

 I'm a big fan of white LED's, so I'm thinking maybe white LED's for the tubes and purple for the LEDC ? Maybe the reverse?


----------



## rhester

Woo hoo, being just up the hiway I should get my soon. Can't wait to mate this great lil amp with a sexy case. My office desk is going to love me.


----------



## pinkfloyd4ever

oh man, I'd seen the renderings and drawings, but those are damn sexy...too bad I didn't have money to get one at the time of the Group buy. But as I've quickly learned in this hobby, you can't get in on em all unless you have alot of spare time and money (i.e. are retired), so I think I'll cope. To those who did get one though, enjoy em


----------



## Beefy

That is simply _outstanding_. Whatever we're paying you tomb, it isn't enough. And a cheaper price on the silver ones? Icing on the cake! 
	

	
	
		
		

		
		
	


	




 You know, of the two I built I had intended to sell one. But with them looking like that...... I don't know how I'm going to be able to part with one!


----------



## PhaedrusX

simply stunning...

 i'm glad Lansing didn't pre-mount those really low profile feet that they use on their C-Series cases.

 curious though, did Lansing include any other rubber feet, or will we have to order those from elsewhere?


----------



## rds

I haven't seen quite this procedure described here.
 As I'll be sending some of these out to be shipped into the wide world I wanted these installed in a way that it was virtually impossible for the cap leads to contact the heatsinks.
 With this bend the short lead would have to actually be ripped out of the board (or cap) for the long lead to contact the heatsink.


----------



## Daveze

If you want to be doubly sure, you can throw a small length of heatshrink around the long lead.


----------



## Beefy

This is how I did it:






 If you bend the other lead as well the whole cap is 'offset' towards the outer heatsink, allowing the caps to sit lower while still avoiding the inner heatsink. The heatshrink tubing over the leads seals the deal. [EDIT] GAH, beaten on the heatshrink comment! 
	

	
	
		
		

		
		
	


	




 PS, rds - it looks like I will be accepting that job offer in Vancouver. Might see you in a few months


----------



## rds

Quote:


 If you want to be doubly sure, you can throw a small length of heatshrink around the long lead. 
 

I think you're missing the mechanics of that setup. The short lead _must_ lengthen for the high end of the cap to move downwards (toward the board). So heat shrink is not redundant so much as pointless.

 Beefy - You chose wisely. 
 ...but don't call me for weed. Just cause I live here doesn't mean I have a grow op under my bed.


----------



## tomb

Quote:


  Originally Posted by *PhaedrusX* /img/forum/go_quote.gif 
_simply stunning...

 i'm glad Lansing didn't pre-mount those really low profile feet that they use on their C-Series cases.

 curious though, did Lansing include any other rubber feet, or will we have to order those from elsewhere?_

 

Excellent question! I'll be supplying four bumpers per case that I'm purchasing from Grainger. Lansing had some in that size, but they charge a fortune for them. The Grainger ones (3M #SJ5018) are not quite as low profile as Lansing's - more like a 1/4", but it's important to give you something. Do not just rest the case on a horizontal surface with no feet. It's important that the cooling slots on the bottom have room to pick up air. 3/8" would be best if you want to purchase your own.


----------



## tomb

Quote:


  Originally Posted by *rds* /img/forum/go_quote.gif 
_I haven't seen quite this procedure described here.
 As I'll be sending some of these out to be shipped into the wide world I wanted these installed in a way that it was virtually impossible for the cap leads to contact the heatsinks.
 With this bend the short lead would have to actually be ripped out of the board (or cap) for the long lead to contact the heatsink.









_

 

Actually, I really appreciated Beefy's pics of the way he bent his Vitamin Q's, but hadn't really seen how it matches up with the board. I'm sure it works fine either way. However, the way rds has done them in these pics is exactly how I do them - heat shrink is superfluous, but it doesn't hurt anything, either.

 There are two keys to this, and actually it's detailed quite well on the MAX websites with this drawing I made up:





 The only difference being is that the long lead doesn't have to travel as far backwards on the MiniMAX PCB to find a pad on the board.

 There are two essential keys to this:
 1. The short lead is left "straight" and is locked into the board by virtue of the tension of the short lead and the edge of the Vitamin Q resting on the board. Pull the lead through until the edge of the VitQ is pressed hard against the board. This side of the VitQ will not move if you do this.
 2. The long lead must be bent down sharply and back around the edge of the cap. After that, the angle you form with the lead relative to the pad nearest the heat sink (or the next pad over as rds has used) will dicate both the cap's height and its clearance from the heat sink. With the 0.18uf 100V VitQ's, it is very easy to have the end nipple of the VitQ about 1/16" (or more) clear from the edge of the heat sink fins and still have the highest point on the cap at 1" height.

 Done this way, you'll find that the caps are locked in solid - they aren't going to move.

 Please don't use the K42 mounting method that replaces the leads. For one, even the 0.18uf VitQ's are too tall for the MiniMAX in a vertical position. More importantly, though, the VitQ leads are tinned, _solid copper_ and that's good stuff.
	

	
	
		
		

		
		
	


	




 Many thanks to both Beefy and rds!


----------



## Beefy

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Actually, I really appreciated Beefy's pics of the way he bent his Vitamin Q's, but hadn't really seen how it matches up with the board. I'm sure it works fine either way._

 

I've got a brand spanking new DSLR and lens that I'm just itching to try out. I'll grab a couple of macro shots specifically of the VitQ's _in situ_ for you.


----------



## aphexii

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Depends on the output transistors. The 2SC2344/2SA1011 and the 2SC2238/2SA968, or MOSFETs (not recommended on the MiniMAX) are all TO-220 case and will use shoulder washers. "5" is the magic number, though. Many people forget about the LM317 on the heat sink in the power supply._

 

So if I'm just using the standard, 

 2N5087 PNP small signal
 2N5088 NPN small signal
 MJE243 NPN power transistor
 BD137 NPN power transistor
 MJE253 PNP power transistor
 BD138 PNP power transistor

 I would need 4 w/o shoulder washers, 1 with?


----------



## TimJo

Wow Tom, the cases look great! 

 Thanks for putting in so much time and effort to make these happen. It really shows...


----------



## tomb

Quote:


  Originally Posted by *aphexii* /img/forum/go_quote.gif 
_So if I'm just using the standard, 

 2N5087 PNP small signal
 2N5088 NPN small signal
 MJE243 NPN power transistor
 BD137 NPN power transistor
 MJE253 PNP power transistor
 BD138 PNP power transistor

 I would need 4 w/o shoulder washers, 1 with?_

 

That's a little confusing. You only need two pairs of complementary output transistors. So, it's either 2 sets of MJE243/253 OR 2 sets of BD137/138, NOT both. 

 Other than that, you are correct.


----------



## aphexii

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_That's a little confusing. You only need two pairs of complementary output transistors. So, it's either 2 sets of MJE243/253 OR 2 sets of BD137/138, NOT both. 

 Other than that, you are correct._

 

Ahhh, lol... Learning as I go I suppose 
	

	
	
		
		

		
		
	


	




 Thanks! Placing my order in a few!


----------



## aphexii

Got all my orders in! Can't wait till everything arrives! 

 I ended up buying quite an array of LED's, i'll mix and match till I find the color combo I like. 

 On a side note, I know the BOM calls for 3mm LED's under the tubes, but will 5mm fit as well? I assume they should as there seems to be a bit of clearance when they are mounted flush against the PCB.

 My Hakko 936 should be arriving right around the same time as well!


----------



## rds

Quote:


 On a side note, I know the BOM calls for 3mm LED's under the tubes, but will 5mm fit as well? I assume they should as there seems to be a bit of clearance when they are mounted flush against the PCB. 
 

The LED must be able to fit partially inside the tube socket and 5mm are too big for the diameter of the tube socket, so they won't work.


----------



## Beefy

VitQ _in situ_






 I *seriously* need to dust my desk, or put this thing in a box until the cases arrive


----------



## bperboy

Quote:


  Originally Posted by *Beefy* /img/forum/go_quote.gif 
_... or put this thing in a box until the cases arrive 
	

	
	
		
		

		
		
	


	


_

 

Won't be long now!


----------



## tomb

Quote:


  Originally Posted by *rds* /img/forum/go_quote.gif 
_The LED must be able to fit partially inside the tube socket and 5mm are too big for the diameter of the tube socket, so they won't work._

 

Not only that, but I could swear that there's not enough room for a 5mm under an installed tube socket. It's the main reason that LED holes were put in the board on the revMH Millett Hybrid - so that the LED could be installed from the bottom of the board - with the flange on the back side. That left enough room for the socket above.


----------



## tomb

Quote:


  Originally Posted by *Beefy* /img/forum/go_quote.gif 
_VitQ in situ






 I *seriously* need to dust my desk, or put this thing in a box until the cases arrive 
	

	
	
		
		

		
		
	


	


_

 

Good pic.


----------



## Bismar

I'm about to build my own minimax but am however stuck.

 I've ordered some Blackgates, but have just realized that 2SC2238/2SA968 are no longer in stock.

 I was wondering if anyone have used the 2SC2344/2SA1011 as a replacement for 2SC2238/2SA968 in conjunction with the blackgates and 0.22uf vitq's at CA8.

 If you have could you please share your experiences?

 Thanks,
 Bismar


----------



## digger945

5x 2SC2238 +5X 2SA968 TOSHIBA Pwr AMP Transistor TO-220 on ebay, I think I may have bought some parts from this guy before
	

	
	
		
		

		
		
	


	




(ALLPARTSPIPE).


----------



## Bismar

Quote:


  Originally Posted by *digger945* /img/forum/go_quote.gif 
_5x 2SC2238 +5X 2SA968 TOSHIBA Pwr AMP Transistor TO-220 on ebay, I think I may have bought some parts from this guy before
	

	
	
		
		

		
		
	


	




(ALLPARTSPIPE)._

 

Apparently in page 300 and something of the 500 and something page max thread, they are said to be fake


----------



## rds

Quote:


 Apparently in page 300 and something of the 500 and something page max thread, they are said to be fake 
 

yeah, there are a lot of fakes floating around. I would recommend getting the 2344/1011 from Tom - he is very meticulous about what he sells.
 Also I can say from personal experience that those transistors sound very good. Maybe even preferable to the 2238/968 depending on what kind of sound you like.


----------



## Bismar

Fair enough.

 What do you think would be best for contemporary, classical and opera?


----------



## digger945

^I don't want to complicate your build, but you should at least consider sockets for your transistors so you can swop in the future. I haven't used them yet, but I have some on order from Mouser.


----------



## Bismar

Just got a reply back from the ebay seller, he reckons they are genuine.

 Is there any telltale signs of the fakes ones other then the words CDIL? 

 Could always buy it and if its fake lodge a paypal complaint for my money back.


----------



## slowpogo

Quote:


  Originally Posted by *Bismar* /img/forum/go_quote.gif 
_Just got a reply back from the ebay seller, he reckons they are genuine.

 Is there any telltale signs of the fakes ones other then the words CDIL? 

 Could always buy it and if its fake lodge a paypal complaint for my money back._

 

Two things here...I have seen several bad stories about that seller. One of the stories, a guy got something that was proven definitively to be fake (an opamp I think).

 And secondly, I wouldn't put much stock in his assertion that they are genuine. I'm not saying you should assume he's lying, but it just doesn't mean much. Maybe they are fake and he honestly doesn't know it, or maybe they're fake and he knows it.

 I say this because even major vendors have been duped on transistors. I ordered the same transistor set for my Max, from RS Components UK, and they assured me they were genuine Toshiba. Then they wrote me back a few days later and said, sorry, they are actually generics.

 not trying to burst your balloon but as the above poster said, use sockets if you decide to try them..


----------



## Bismar

Right, so again back to my original qus.

 "I was wondering if anyone have used the 2SC2344/2SA1011 as a replacement for 2SC2238/2SA968 in conjunction with the blackgates and 0.22uf vitq's at CA8."


----------



## PhaedrusX

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_...I'll be supplying four bumpers per case that I'm purchasing from Grainger..._

 

that's great, tomb...always one step ahead of the curve, it seems.

 here's another one i can't quite see clearly around the bend:

 can anyone explain why MOSFETs are not being recommended for the MiniMAX? is it simply due to the limitations of the 1" heat sinks, or is there something else going on here, as well?


----------



## Beefy

Quote:


  Originally Posted by *PhaedrusX* /img/forum/go_quote.gif 
_can anyone explain why MOSFETs are not being recommended for the MiniMAX? is it simply due to the limitations of the 1" heat sinks, or is there something else going on here, as well?_

 

As I understand it, that's pretty much it. The MOSFETs do best with a lot of quiescent current and the 1" sinks aren't ideal. You would also need a higher rated part at PF1, which comes in different resistance values.

 I was originally going to do experiment with a MOSFET mini anyway, but decided against it to simplify my group buy for parts. Plus I didn't want to experiment on expensive Black Gate builds.


----------



## PhaedrusX

Quote:


  Originally Posted by *Beefy* /img/forum/go_quote.gif 
_As I understand it, that's pretty much it. The MOSFETs do best with a lot of quiescent current and the 1" sinks aren't ideal. You would also need a higher rated part at PF1, which comes in different resistance values.

 I was originally going to do experiment with a MOSFET mini anyway, but decided against it to simplify my group buy for parts. Plus I didn't want to experiment on expensive Black Gate builds._

 

thanks Beefy.

 curiously though, the MOSFET-MAX page mentions using 1" sinks with "special mods," but i couldn't find what mods were being referred to.

 i think amb also mentioned that 80-90mA should be possible with the shorter sinks, which made me wonder whether other issues were involved.

 i'm just wondering if this is more a matter of healthy caution being exercised here, or whether it really is going to be more trouble than it is worth.


----------



## Beefy

Quote:


  Originally Posted by *PhaedrusX* /img/forum/go_quote.gif 
_i'm just wondering if this is more a matter of healthy caution being exercised here, or whether it really is going to be more trouble than it is worth._

 

Healthy caution. With BJTs at 50mA, the heat density of the Mini Max is considerably higher than the regular Max. The caps in particular feel warmer. I personally wouldn't feel comfortable with things any hotter - even if it was still within spec. But for my DIY stuff I will always value safety and reliability over a very small percentage of performance.


----------



## gspence2000

Quote:


  Originally Posted by *Bismar* /img/forum/go_quote.gif 
_Right, so again back to my original qus.

 "I was wondering if anyone have used the 2SC2344/2SA1011 as a replacement for 2SC2238/2SA968 in conjunction with the blackgates and 0.22uf vitq's at CA8."_

 

I am building a "Can't Miss #1" but with the 2SC2344/2SA1011 this weekend. Note that the smaller 0.18uf VitaminQ's are needed to fit in the miniMax.

 I won't be able to give you listening impressions any time soon, but I just wanted to chime in and say that you are not the only one looking at this combo.


----------



## rhester

Woo hoo, got my case in today and just buttoned it up and threw the headphones on. Great looking case, very professional. Thanks Tom.

 Pics up soon.


----------



## tomb

Quote:


  Originally Posted by *rhester* /img/forum/go_quote.gif 
_Woo hoo, got my case in today and just buttoned it up and threw the headphones on. Great looking case, very professional. Thanks Tom.

 Pics up soon._

 

Wow, MAX - that was quick! I'm glad to hear the Post Office didn't give this package to one of your neighbors.
	

	
	
		
		

		
			








 Can't wait for the pics!


----------



## gspence2000

I just finished building my miniMax and powered it up for biasing and testing--with bad results.
	

	
	
		
		

		
		
	


	




 I am looking for help.

 This is basically a "Can't Miss #1" arrangement, but with 2SC2344/2SA1011's and VitQ .18uf's.

 I turned all the trimpots 25 turns clockwise before powering up.

 With my multimeter probes on the left DB Bias measurement points (Tb1L and TA2L), I get 0.0 or 0.1 mV.
	

	
	
		
		

		
		
	


	




 Same result on the right side. The heat sinks on Q8/Q9 stay cold (though I kept it powered on only very briefly). I was expecting something in the 20-40mv range, not 0.0. I did try to adjust the RB12L, RB12R trimpots, but they had no effect.

 I then checked power supply voltage, and all is well. I quickly trimmed it to about 27V. The three LED's are lit.

 I then checked the Tube Bias, and I got 8.5V on both the left and right channels. Adjusting the RA1L, RA1R trimpots has absolutely no effect on the tube bias. The value did float around just a tiny bit though (normal for tubes I guess).

 Here is a picture for inspection:




 I don't know what to do next. All advice is appreciated!


----------



## gspence2000

Quote:


  Originally Posted by *gspence2000* /img/forum/go_quote.gif 
_I just finished building my miniMax and powered it up for biasing and testing--with bad results.
	

	
	
		
		

		
		
	


	




 I am looking for help.

 This is basically a "Can't Miss #1" arrangement, but with 2SC2344/2SA1011's and VitQ .18uf's.

 I turned all the trimpots 25 turns clockwise before powering up.

 With my multimeter probes on the left DB Bias measurement points (Tb1L and TA2L), I get 0.0 or 0.1 mV.
	

	
	
		
		

		
		
	


	




 Same result on the right side. The heat sinks on Q8/Q9 stay cold (though I kept it powered on only very briefly). I was expecting something in the 20-40mv range, not 0.0. I did try to adjust the RB12L, RB12R trimpots, but they had no effect.

 I then checked power supply voltage, and all is well. I quickly trimmed it to about 27V. The three LED's are lit.

 I then checked the Tube Bias, and I got 8.5V on both the left and right channels. Adjusting the RA1L, RA1R trimpots has absolutely no effect on the tube bias. The value did float around just a tiny bit though (normal for tubes I guess).

 Here is a picture for inspection:




 I don't know what to do next. All advice is appreciated!_

 

I just took a good hard look at the picture I just posted, and noticed that RB8L/R and RB9L/R should be jumpered, not open. 
	

	
	
		
		

		
		
	


	




 I will go do that right now!


----------



## tomb

Quote:


  Originally Posted by *gspence2000* /img/forum/go_quote.gif 
_I just took a good hard look at the picture I just posted, and noticed that RB8L/R and RB9L/R should be jumpered, not open. 
	

	
	
		
		

		
		
	


	




 I will go do that right now!_

 

Yep, I think that would do it. It's a good pic once blown up on ImageShack. I don't see anything else amiss for right now. It looks like you've done a great job putting it together.


----------



## gspence2000

Hot damn! That did the trick. I'm getting 20mv on both sides now. Well, back to work!

 Thanks for taking a look TomB.


----------



## ruZZ.il

Good pic indeed. Welcome to the MAX


----------



## gspence2000

Something is still not working. 
	

	
	
		
		

		
		
	


	




 The DB bias won't go any higher than 19mv. With the trimpots set 25 turns clockwise, the left channel is 17.7mv and the right channel is 18.3mv. Turning the left trimpot 10 turns counterclockwise only goes up to 19.2mv and 10 turns on the right side yields only 18.3mv.

 The tube bias, which was giving 8.5v before I added the missing jumpers, now gives 0.7v on either side. 

 Any ideas?


----------



## tomb

Quote:


  Originally Posted by *gspence2000* /img/forum/go_quote.gif 
_Something is still not working. 
	

	
	
		
		

		
		
	


	




 The DB bias won't go any higher than 19mv. With the trimpots set 25 turns clockwise, the left channel is 17.7mv and the right channel is 18.3mv. Turning the left trimpot 10 turns counterclockwise only goes up to 19.2mv and 10 turns on the right side yields only 18.3mv.

 The tube bias, which was giving 8.5v before I added the missing jumpers, now gives 0.7v on either side. 

 Any ideas?
	

	
	
		
		

		
		
	


	


_

 

Sounds normal for the DB's. You haven't turned far enough. Try another 10 turns and see if you get more of a reaction (probably before you hit 20). Be careful, though - when you see it move, go slow. You'll eventually reach a point where 1/4 to 1/2 turn may mean 10mV.

 The same thing happens with the tubes - remember that the range is there for three different sets of tubes. You may have to try 20 turns and then the entire adjustment is in the last 5. I can't tell you how many, because to tell the truth, I've never cranked the trimmers down before starting. A bump on and off should be all you need to tell. However, there's nothing wrong with being cautious - as long as it doesn't lead you to think there's something wrong because you haven't turned the trimmers enough.

 Just keep an eye on them - make one turn at a time, then wait. When you see them move 10mV at a time, slow down to 1/2 turn, etc., etc.


----------



## gspence2000

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Sounds normal for the DB's. You haven't turned far enough. Try another 10 turns and see if you get more of a reaction (probably before you hit 20). Be careful, though - when you see it move, go slow. You'll eventually reach a point where 1/4 to 1/2 turn may mean 10mV.

 The same thing happens with the tubes - remember that the range is there for three different sets of tubes. You may have to try 20 turns and then the entire adjustment is in the last 5. I can't tell you how many, because to tell the truth, I've never cranked the trimmers down before starting. A bump on and off should be all you need to tell. However, there's nothing wrong with being cautious - as long as it doesn't lead you to think there's something wrong because you haven't turned the trimmers enough.

 Just keep an eye on them - make one turn at a time, then wait. When you see them move 10mV at a time, slow down to 1/2 turn, etc., etc._

 

I can't bias the DB or tubes no matter how much I turn the trimpots.
	

	
	
		
		

		
		
	


	




 The tube bias trimpots are the kind that click. Going from clicking on the clockwise end, all the way to clicking on the counterclockwise end, makes no difference--.7v all the way around.

 The db bias gives _very strange results_. Starting at the most-clockwise position, in increments of five counterclockwise turns:

 Left channel: 17.8, 18.2, 15.8, 2.7
 Right channel: 17.0, 17.6, 17.8, 13.2, 3.8

 It rises briefly, then it reverses and falls sharply.

 The tubes and VREG are slightly warm, but the other sinks are cold.

 Any ideas?


----------



## Beefy

You forgot to populate RA9!


----------



## rds

lol


----------



## gspence2000

Quote:


  Originally Posted by *Beefy* /img/forum/go_quote.gif 
_You forgot to populate RA9!_

 

Immediately after posting that picture I incorrectly said that I needed to jumper RB8L/R and RB9L/R. I meant to say _RA9L/R_ and RB9L/R; I installed those right away after discovering them. I have been having the problems adjusting DB and tube gain since then.


----------



## tomb

Good catch, guys!!

 EDIT: Oops - are you saying that you populated RA9L and RA9R, then you also jumpered RB8/9?

 Maybe you should give us another pic that's updated. Sounds like a lot of guys are ready to look.


----------



## Beefy

Quote:


  Originally Posted by *gspence2000* /img/forum/go_quote.gif 
_Immediately after posting that picture I incorrectly said that I needed to jumper RB8L/R and RB9L/R. I meant to say RA9L/R and RB9L/R_

 

Just to check...... RA9L/R should NOT be jumpered. It should have a 10k ohm resistor in there......


----------



## rhester

Here are some pics. You'll are in for a treat when you get your packages from the USPS. 

 Happy Holidays to all, especially TomB and cetoole.


----------



## cetoole

Holy crap Max, that looks great. I cant believe how quickly you got that case. Nice BantamHockeyPuckDAC in the background too.


----------



## bperboy

OMGOMGOMGOMGOMGBOWDOWNINWONDEROMGOMGOMG!!!!!!!!!!! !!












 Prays for USPS to deliver before christmas!!


----------



## tomb

Quote:


  Originally Posted by *cetoole* /img/forum/go_quote.gif 
_Holy crap Max, that looks great. I cant believe how quickly you got that case. Nice BantamHockeyPuckDAC in the background too._

 

X10 That's the first one - even beat you and me to a cased-up one.
	

	
	
		
		

		
		
	


	




 Yeah, USPS really set a record. Max is what - 50 miles from me? Still, his shipped about 4 PM yesterday and he got it this morning. That's less than 24 hours during Christmas peak. Unbelievable.


----------



## rds

Wow that looks awesome!


----------



## cetoole

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_X10 That's the first one - even beat you and me to a cased-up one.
	

	
	
		
		

		
		
	


	




 Yeah, USPS really set a record. Max is what - 50 miles from me? Still, his shipped about 4 PM yesterday and he got it this morning. That's less than 24 hours during Christmas peak. Unbelievable._

 

Lots of people are gonna beat me to having a cased up minimax. All I have done with the PCBs so far is look at them and say "oh cool, they are blue".


----------



## tomb

Quote:


  Originally Posted by *cetoole* /img/forum/go_quote.gif 
_Lots of people are gonna beat me to having a cased up minimax. All I have done with the PCBs so far is look at them and say "oh cool, they are blue"._

 

Well, yeah - but you keep cranking out the designs - that sure counts.
	

	
	
		
		

		
			








 I still can't get over how quick he got that case and put it together. Wow.


----------



## bperboy

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Well, yeah - but you keep cranking out the designs - that sure counts.
	

	
	
		
		

		
		
	


	







 I still can't get over how quick he got that case and put it together. Wow._

 

Did his get mailed on friday? Since mine got mailed this morning, I'm hoping for a tuesday delivery.. we'll see though.


----------



## Beefy

That _does_ look great 
	

	
	
		
		

		
		
	


	




 Gotta say though, I'm glad I got one of each colour as I have a sneaking suspicion I will prefer the silver. It is going to clash with my black y1 DACs though!


----------



## rhester

All I can say is that I really appreciate all you 2 have done for the DIY crowd. A year ago I couldn't solder a simple connection, now I can make professional looking and , more importantly, professional sounding amps and dacs.

 I raise a glass to both of you.


----------



## gspence2000

Quote:


  Originally Posted by *Beefy* /img/forum/go_quote.gif 
_Just to check...... RA9L/R should NOT be jumpered. It should have a 10k ohm resistor in there......_

 

Beefy, you get the prize!
	

	
	
		
		

		
		
	


	




 That was the problem exactly.

 In my horror in finding the unpopulated parts, I jumpered all four parts when I should have jumpered two and populated the other two with resistors.

 Somehow last night at 2am I got confused with all the notes I had scribbled on my printed copy of the BOM and I wrote "SKIP" on the parts bag containing those resistors.

 Thanks all for your help!

 Tube bias is now set and I am creeping up on the DB bias. Time for a glass of scotch.


----------



## Beefy

Quote:


  Originally Posted by *gspence2000* /img/forum/go_quote.gif 
_Beefy, you get the prize!
	

	
	
		
		

		
		
	


	




 That was the problem exactly._

 

Let me beat Tom to it...... another Max lives!


----------



## Bismar

Quote:


  Originally Posted by *gspence2000* /img/forum/go_quote.gif 
_Beefy, you get the prize!
	

	
	
		
		

		
		
	


	




 That was the problem exactly.

 In my horror in finding the unpopulated parts, I jumpered all four parts when I should have jumpered two and populated the other two with resistors.

 Somehow last night at 2am I got confused with all the notes I had scribbled on my printed copy of the BOM and I wrote "SKIP" on the parts bag containing those resistors.

 Thanks all for your help!

 Tube bias is now set and I am creeping up on the DB bias. Time for a glass of scotch._

 

Cool, tell us what you think of the 2SA2344/2SA1011 when your done.


----------



## tomb

Quote:


  Originally Posted by *Beefy* /img/forum/go_quote.gif 
_Let me beat Tom to it...... another Max lives! 
	

	
	
		
		

		
		
	


	


_

 

Ya beat me to it on both counts - good job! ... and thank goodness gspence2000 has his MiniMAX working!


----------



## gspence2000

Everything is working perfectly!
	

	
	
		
		

		
		
	


	




 It sounds great already; I can't wait for the tubes to burn in. And just in time for the new cases, which look beautiful by the way!
	

	
	
		
		

		
		
	


	




 Thanks again to everyone for their help, especially tomb and cetoole.


----------



## Bismar

Been reading up boutique caps, and was wondering if i could use a pair of 1000uF 25V and 470uF 35V ELNA Silmic II caps instead of Black Gates for the "Can't Miss Max build 1". 

 Are the voltages and capacitance suitable?

 According to some sites they are superior and at a fraction of the cost.


----------



## tomb

Quote:


  Originally Posted by *Bismar* /img/forum/go_quote.gif 
_Been reading up boutique caps, and was wondering if i could use a pair of 1000uF 25V and 470uF 35V ELNA Silmic II caps instead of Black Gates for the "Can't Miss Max build 1". 

 Are the voltages and capacitance suitable?

 According to some sites they are superior and at a fraction of the cost._

 

"Can't Miss" doesn't mean "Can't Build Any Other."
	

	
	
		
		

		
		
	


	







 Yes, those voltages are suitable. Finding them is a bit different. The 470uf Silmic's in 35V are quite scarce - if they exist at all - at least in my searches. The 50V version is easier to get, but waaaaay too tall for the MiniMAX (height is a hard-limit at 1"/25mm). You can probably go as low as 10V on the CA2 cap, but again, you will be limited by what you can find.

 EDIT: The 1000uf 25V Elna Silmic is also 36mm tall - it won't work in the MiniMAX with the Lansing case.


----------



## Bismar

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_"Can't Miss" doesn't mean "Can't Build Any Other."
	

	
	
		
		

		
		
	


	







 Yes, those voltages are suitable. Finding them is a bit different. The 470uf Silmic's in 35V are quite scarce - if they exist at all - at least in my searches. The 50V version is easier to get, but waaaaay too tall for the MiniMAX (height is a hard-limit at 1"/25mm). You can probably go as low as 10V on the CA2 cap, but again, you will be limited by what you can find.

 EDIT: The 1000uf 25V Elna Silmic is also 36mm tall - it won't work in the MiniMAX with the Lansing case._

 

The 470 uF 25V are 25mm high, will they be suitable?

 And how exactly will higher or lower voltages affect the amp?

 And as for CA9 i'm guessing if i go along this path i'll need to try it with and without wimas?

 Or is the reason that its left blank due to the transistors and not the black gates.


----------



## TimJo

Quote:


  Originally Posted by *rhester* /img/forum/go_quote.gif 
_
 Here are some pics. You'll are in for a treat when you get your packages from the USPS. 

 Happy Holidays to all, especially TomB and cetoole.
_

 

Wow Max, that really looks sharp. I can't wait for mine mine arrive this week.

 Thanks again Tom and Colin for making this happen...


----------



## tomb

Quote:


  Originally Posted by *Bismar* /img/forum/go_quote.gif 
_The 470 uF 25V are 25mm high, will they be suitable?_

 

That's a lower voltage than we recommend. I know there's a user who's trying it right now, but he has to assume the risk. You see, beyond just the safety factor in the voltage rating, it decreases with heat as well. The MAX/MiniMAX is a hot box up front between the heat sinks - and that's right where that cap goes.

 While there is no doubt that the Elna Silmic is a great-sounding cap, you may be missing the point behind the Millett design and bypassing electrolytics with film caps. The film cap will carry most of the sound - only the lower frequencies will be handled by the electrolytic.* Down there, it's pretty difficult to distinguish sound characteristics. Plus, many electrolytics are pretty good down in the low frequencies, anyway. Certainly, the Nichicon Muse ES is as good as it gets in mid-bass and low-bass, IMHO.

 However, the point is that you could even use quality power caps (UPW's, UHE's, FC's and FM's) and with the film bypasses it will result in great sound.

  Quote:


 And how exactly will higher or lower voltages affect the amp? 
 

They don't affect the amp per se, although higher voltage rating caps will probably have lower ESR and ripple ratings. The voltage ratings tell you whether the cap will survive in that circuit - or how long it will survive in months, weeks, or hours. 

  Quote:


 And as for CA9 i'm guessing if i go along this path i'll need to try it with and without wimas?

 Or is the reason that its left blank due to the transistors and not the black gates. 
 

The one exception is Black Gates. What really happens is that the Black Gates are so fast that the film cap has no effect - either in the circuit or out. This is a little less applicable at the output position - that sound is right at the entrance to your headphones and even the smallest difference is noticeable.

 Again, we have extensively tested the combinations listed and have gathered many reports from previous builders before we put up those "Can't Miss" recommendations. However, there's no reason you can't mix and match - but going off the reservation with a lower voltage rating on the cap is a bit further than I would condone under this circumstance.

Pardon the digression - 
 Something that continues to fascinate me - and please forgive me - I'm not trying to focus on your comments per se, but the fascination with selecting so many different things on the MAX/MiniMAX ... Yes, it has an effect and it's all great fun. However, I see so many customers simply order one pair of tubes or one pair of tubes for each type for their MAX/MiniMAX.

 The fact is that the tubes have the single greatest effect on sound of the amp. They also have the greatest variance in quality and sound of any component you could buy for the amp. To see customer after customer just simply order two and only two - every time - is frustrating.

 I'm probably guilty of causing that to some degree. I always assume that folks will go through a tube selection to find the pair that works best for them. When that is the starting point, then transistor selection, capacitor selection, etc., - all these things become important. However, if you haven't done that primary requirement of making certain you have a good pair of tubes - the rest is inconsequential.

 Don't get me wrong - this has nothing to do with whether the tubes are "good" or not. Some people like certain opamps, others hate the ones that some like. With tubes, they can all be tested but it won't tell you as much as popping one into your amp. At that point, a little critical listening and swapping different ones in and out can tell you a lot.

 I'm writing the MiniMAX website tube section right now. So, I'm going to change some of the text to reflect this. Hopefully, that will help.
 - End digression -


 EDIT: * Admittedly, this is largely anectodal. If you strictly run the frequency cutoff equation, you'll find the frequencies in the high midrange to low-high frequencies. Nevertheless, I believe the combination is more effected at mid to high frequencies with the film cap. Cap bypassing is sort of voodoo-arts, anyway. Unless you've tried certain combinations, there's no predicting the effect.


----------



## Beefy

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_The fact is that the tubes have the single greatest effect on sound of the amp. They also have the greatest variance in quality and sound of any component you could buy for the amp. To see customer after customer just simply order two and only two - every time - is frustrating.

 I'm probably guilty of causing that to some degree. I always assume that folks will go through a tube selection to find the pair that works best for them. When that is the starting point, then transistor selection, capacitor selection, etc., - all these things become important. However, if you haven't done that primary requirement of making certain you have a good pair of tubes - the rest is inconsequential._

 

Just to relay a little bit of my own experiences with tubes in various Maxes......

 12AE6 is too high a gain for any of my sensitive phones. I barely have to touch the volume knob to reach uncomfortable listening levels. That leaves me with 12FK6. I've tried..... 4, I think? different pairs of 12FK6 tubes. Constructed by RCA, Sylvania, and one other I can't quite recall this early in the morning.

 Aside from the Sylvania ones having ever so slighty higher noise floor, I can't tell the difference between them. Maybe my hearing sucks, maybe I'm not listening hard enough, maybe they were all really good tubes, maybe there isn't any difference.

 I do see your point about making sure you have 'good' tubes though. That one FM6 I had was a bit funny all round, and it would be a shame to judge the amp based on that......


----------



## rds

Quote:


 That one FM6 I had was a bit funny all round, and it would be a shame to judge the amp based on that...... 
 

You asked a while ago if I would comment on my 12FM6s when I got around to trying them.
 I've tried 3 pairs so far and all 6 tubes are extremely quiet. I have to actually tap the tube or amp to hear any microphonics. I haven't done enough listening yet to compare the 3 types of Mini Max tubes, but I also find the gain of the 12AE6 to be very high even for my 701s. I never get the volume even close to 12 o'clock with those tubes.


----------



## slowpogo

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_That's a lower voltage than we recommend. I know there's a user who's trying it right now, but he has to assume the risk._

 

That's probably me you're referring to ... by my measurements, the voltage hits about 23.4v for 5 seconds, then drops down to 13.5. I see why it's a "risk" but if the cap will spend like 99.9% of its life at slightly more than half its voltage rating, and the other .1% doesn't even exceed it, it seems quite safe by my reasoning.

 But I understand why the official specs are designed to make things as safe as possible; if my caps should die a weird death I won't whine to anyone.


----------



## TimJo

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_The fact is that the tubes have the single greatest effect on sound of the amp. They also have the greatest variance in quality and sound of any component you could buy for the amp. 
_

 

I tend to agree with this as well. I have multiple Maxes, a big collection of tubes. For the Max I use everyday with my Beyer 880's, I finally settled on a pair of Sylvania 12AE6A tubes with square side getter's. For whatever reason, this pair sounds the best with the 880's and I have been using them daily now for over 6 months. On the other hand, for my 701's, I use a different Max with a pair of GE 12FM6 tubes with square top getter's, because again after a bunch of tube rolling, this pair sounded the best.

 Here's a picture, dust and all...


----------



## tomb

Quote:


  Originally Posted by *slowpogo* /img/forum/go_quote.gif 
_That's probably me you're referring to ... by my measurements, the voltage hits about 23.4v for 5 seconds, then drops down to 13.5. I see why it's a "risk" but if the cap will spend like 99.9% of its life at slightly more than half its voltage rating, and the other .1% doesn't even exceed it, it seems quite safe by my reasoning.

 But I understand why the official specs are designed to make things as safe as possible; if my caps should die a weird death I won't whine to anyone._

 

I think the concern is the failure mode - just as it is with many of the semi-conductor amp designs around here. IOW, how much voltage does a cap see if another cap fails and they both span the power supply rails? In the case of the MAX/MiniMAX, I'd wonder what happens to that voltage at the output if a tube fails. I'm not certain, but I suspect the voltage would rack to almost the same as the PS voltage on both caps. Just so long as you are aware of the risk ...

  Quote:


  Originally Posted by *TimJo* 
_I tend to agree with this as well. I have multiple Maxes, a big collection of tubes. For the Max I use everyday with my Beyer 880's, I finally settled on a pair of Sylvania 12AE6A tubes with square side getter's. For whatever reason, this pair sounds the best with the 880's and I have been using them daily now for over 6 months. On the other hand, for my 701's, I use a different Max with a pair of GE 12FM6 tubes with square top getter's, because again after a bunch of tube rolling, this pair sounded the best.

 Here's a picture, dust and all..._

 

Yep - good anectodal experience to add to everyone's knowledge. Beefy related a different experience. That's probably the case with everyone - that each would find their own particular combination of tubes and headphones.


----------



## Bismar

So let me get this straight, when ordering from Beezar, i should get multiples of each tubes as they all perform differently?

 Or is there another shop that i can get tubes from?


----------



## gspence2000

Quote:


  Originally Posted by *rhester* /img/forum/go_quote.gif 
_Here are some pics. You'll are in for a treat when you get your packages from the USPS. _

 

Rhester,

 As you are the first to use the new cases, I'm curious if you used a 4mm standoff in the middle of the board, and if so, was that a good fit?

 I was thinking of starting with a longer standoff and doing a little fit-and-trim work with my bench grinder to make sure there is no stress on the board.


----------



## tomb

Quote:


  Originally Posted by *Bismar* /img/forum/go_quote.gif 
_So let me get this straight, when ordering from Beezar, i should get multiples of each tubes as they all perform differently?

 Or is there another shop that i can get tubes from?_

 

That's a bit of an overstatement based on the discussion that took place. Sorry if that opinion frustrates you, but of course - you are welcome to purchase your tubes anywhere you like. I don't have a particular lock on special tubes, but I have acquired a modest stock of Millett tubes lately.

 What we discussed is probably true for any tube in the business. Study this hobby for long - especially tubes - and you'll find reams of discussion at this and other forums about "gray plate RCA's" or "black plate GE's" or Telefunkens with the special markings, etc., etc. There's a reason people like The Tube Depot hand out business cards that identify themselves as a "Tone Consultant."


 EDIT: Maybe it would help you to think of a tube as an analog musical instrument. Every piano, violin, guitar, etc. can all play the same notes (well, most of them) at the same frequency. Yet, the quality of tone they produce can differ greatly. Some musicians may prefer one type of tone, others prefer another. Sometimes it comes down to the type of music that they play or even the venue.

 There's a famous guitarist who works almost exclusively for Hollywood. I heard him interviewed on NPR once, I believe. (This is the guy that played guitar for Steely Dan when they first began: Think "Reelin' In The Years.") He told of regularly driving a van to a set that was full of hundreds of guitars. It was because he was never quite sure what type of sound a particular movie or TV show was trying to achieve and had to be prepared.


----------



## Bismar

Thanks for the reply tomb, but for the tubes you sell, are they all likely to be around the same or should i purchase say 4 of each to see which sounds the best.

 As for buying tubes elsewhere, how would you know which are compatible? Isn't the Millet Max special in the sense that it requires less voltage then conventional tube amps?

 Thanks, once again for your patience


----------



## Beefy

Quote:


  Originally Posted by *Bismar* /img/forum/go_quote.gif 
_Thanks for the reply tomb, but for the tubes you sell, are they all likely to be around the same or should i purchase say 4 of each to see which sounds the best._

 

What phones are you going to be using the amp with?

  Quote:


 As for buying tubes elsewhere, how would you know which are compatible? Isn't the Millet Max special in the sense that it requires less voltage then conventional tube amps? 
 

Just look for 12FK6, 12FM6, 12AE6 or 12AE6A.

 There are a couple of Aussie tube shops that advertise 12FK6 and 12AE6, but they are VERY expensive.


----------



## Bismar

I plan to grab the K702.


----------



## Beefy

Quote:


  Originally Posted by *Bismar* /img/forum/go_quote.gif 
_I plan to grab the K702._

 

If it were me, I would just grab four 12AE6(A) for those.


----------



## Bismar

Cool, how about a AD700 or Super fi 3 studio?

 Probably won't use them when i get the k702's and they probably won't make much of a difference with a good amp, but still i would like to know.


----------



## Bismar

Quote:


  Originally Posted by *Beefy* /img/forum/go_quote.gif 
_If it were me, I would just grab four 12AE6(A) for those._

 

O and where would you get the 12AE6A from? Beezar doesn't stock them afaik.


----------



## rds

Quote:


 If it were me, I would just grab four 12AE6(A) for those. 
 

I would say 12FM6 too as they tend to have a little more bass which is a nice fit for the 701s.
 ...and when not get the 12FK6 while you're at it 
	

	
	
		
		

		
		
	


	




 ?


----------



## Beefy

Quote:


  Originally Posted by *Bismar* /img/forum/go_quote.gif 
_Cool, how about a AD700_

 

12FK6 for those

  Quote:


 or Super fi 3 studio? 
 

Far too sensitive for this amp.


----------



## tomb

Quote:


  Originally Posted by *Bismar* /img/forum/go_quote.gif 
_O and where would you get the 12AE6A from? Beezar doesn't stock them afaik._

 

Probably more than half of the 12AE6's I sell are "A's". I just refuse to make the distinction on the label - it confuses me too much. If anyone can explain what the difference is, please do - because I've never seen a difference in performance, per se.

 At any rate, I do match tube construction and mfr, so whether they're A's or not, bought in pairs, the tubes will be the same.


----------



## Bismar

Alright cool, so after all that i still should buy 4 tubes of every type at Beezar 
	

	
	
		
		

		
			





 Thanks for clearing it up though


----------



## Gross

Got my case today! Looks great. I can't quite use it yet though, as it has been sitting outside all day, which makes it about 8 degrees F. South Dakota kicks ass.


----------



## rds

Quote:


 Alright cool, so after all that i still should buy 4 tubes of every type at Beezar

 Thanks for clearing it up though 
 

Yeah, that sounds like a good idea.
 It might seem a little pricey, but when you consider what people usually pay on tubes for a tube amp it's actually quite cheap relatively speaking.


----------



## sandbasser

First and foremost!!! I received my GB case today!!! It's beautiful. 

 Now a question: what are you guys using for "Tip Jacks"??? BOM still shows TBD. A Mouse P/N would be appreciated.

 Now, got to get started on the build.


----------



## rds

Quote:


 Now a question: what are you guys using for "Tip Jacks"??? BOM still shows TBD. A Mouse P/N would be appreciated. 
 


 105-0801-001

 105-0802-001

 105-0803-001


----------



## gspence2000

Quote:


  Originally Posted by *sandbasser* /img/forum/go_quote.gif 
_First and foremost!!! I received my GB case today!!! It's beautiful. 

 Now a question: what are you guys using for "Tip Jacks"??? BOM still shows TBD. A Mouse P/N would be appreciated.

 Now, got to get started on the build._

 

I used 530-105-0803-1


----------



## cetoole

I got my cases today, and they look awesome. Thanks Tom.


----------



## tomb

Quote:


  Originally Posted by *rds* /img/forum/go_quote.gif 
_105-0801-001

 105-0802-001

 105-0803-001_

 

Yep - I will update the BOM for these values. Red is Right tube bias, White is Left tube bias and Black is Ground - exactly what I use, although sometimes I'll use gray for Ground because I bought a whole bunch on closeout once.
	

	
	
		
		

		
		
	


	




  Quote:


  Originally Posted by *cetoole* /img/forum/go_quote.gif 
_I got my cases today, and they look awesome. Thanks Tom._

 

Thanks - a great case for a great pcb design, right?


----------



## rds

I noticed quite a few people here are using an R1, so I assume you guys are running "high voltage". I'm interested in what voltages you are using.


----------



## Beefy

Quote:


  Originally Posted by *rds* /img/forum/go_quote.gif 
_I noticed quite a few people here are using an R1, so I assume you guys are running "high voltage". I'm interested in what voltages you are using._

 

28V with 10R in R1 over here.

 I'm thinking of putting some of my spare 22R Kiwame in there to drop the voltage a touch more and decrease heat output.


----------



## rds

Quote:


 I'm thinking of putting some of my spare 22R Kiwame in there to drop the voltage a touch more and decrease heat output. 
 

For my amp I was going to use the same resistor and have the PS at 30V.
 I doubt a couple volts will do much, but why not? Also it will decrease the Vreg heat which is currently generating the most heat on my amp (other than the tubes).


----------



## tomb

Quote:


  Originally Posted by *rds* /img/forum/go_quote.gif 
_For my amp I was going to use the same resistor and have the PS at 30V.
 I doubt a couple volts will do much, but why not? Also it will decrease the Vreg heat which is currently generating the most heat on my amp (other than the tubes)._

 

It's not going to reduce the Vreg heat, but using the Kiwame is OK - a bit expensive, but OK.

 The Vreg runs hot to the touch, but the temp should be well within the tolerance of the LM317 - assuming a normal, unregulated Class II 24VAC walwart.

 Keep in mind that the very-low-noise power supply on the MiniMAX has been tuned to 27VDC. In the earlier MAX, we were pretty flexible with the voltage recommendations. However, all of our testing for the PS on the MiniMAX was at 27VDC. I can't guarantee performance at a higher voltage. That's because the voltage drop across the LM317 will be less at the higher voltage. The LM317 is quieter with bigger voltage drops - up to 5V - that's about what results after rectification, then regulation down to 27VDC.


 P.S. Just a further note about the heater resistor - at 27VDC, 10 ohms (the BOM recommendation) results in 12.7V on the heaters, almost exactly the manufacturer's primary recommendation for the heater voltages (12.6V).


----------



## rds

Quote:


 P.S. Just a further note about the heater resistor - at 27VDC, 10 ohms (the BOM recommendation) results in 12.7V on the heaters, almost exactly the manufacturer's primary recommendation for the heater voltages (12.6V). 
 

Oh, I see. I thought the resistor was only intended for voltages closer to 30V. So for 27V I should be using a 10 ohm R1 rather than jumpering it?

 EDIT - I didn't mean Kiwames reduce the Vreg heat, but just that the Vreg won't need to drop as much voltage. But seeing as you did all the testing for 27V I think I'll keep mine there.


----------



## tomb

Quote:


  Originally Posted by *rds* /img/forum/go_quote.gif 
_Oh, I see. I thought the resistor was only intended for voltages closer to 30V. So for 27V I should be using a 10 ohm R1 rather than jumpering it?_

 

Optimum is probably the correct term - the heaters can tolerate anything between 10V and 15.9V (with a decent safety factor away from that margin). However, 12.6VDC is optimum. Lower voltages willl hamper performance, whereas higher voltages will decrease the life of the tube.


----------



## rds

Quote:


 Optimum is probably the correct term - the heaters can tolerate anything between 10V and 15.9V (with a decent safety factor away from that margin). However, 12.6VDC is optimum. Lower voltages willl hamper performance, whereas higher voltages will decrease the life of the tube. 
 

I wonder if a bit higher heater voltage will benefit performance while not reducing the tube life too much?
 For example having R1 jumpered with 27V PS. This should result in about 14V on the heater. 
 Maybe this would be a reasonable compromise considering the cooling abilities of the custom cases?

 EDIT - I mean 13.5V on the heater with 27V PS


----------



## gspence2000

TomB, what is the benefit of higher voltage, at least in terms of the Millett Hybrid Maxed? The Heater Resistor page on the Maxed web site says only _"higher plate voltages usually translate to higher performance"_. What does that mean? Why were people experimenting with 30V?


----------



## FallenAngel

Quote:


  Originally Posted by *gspence2000* /img/forum/go_quote.gif 
_TomB, what is the benefit of higher voltage, at least in terms of the Millett Hybrid Maxed? The Heater Resistor page on the Maxed web site says only "higher plate voltages usually translate to higher performance". What does that mean? Why were people experimenting with 30V?_

 

As with all amps, higher input voltage means higher voltage swing.


----------



## ruZZ.il

True, the higher voltage will increase the clipping threshold, which the signal probably doesn't get to much with 'normal' volumes, if at all. Though I wonder if it has much effect on slew rate, and would even go as far as guessing that at normal levels, the benefit would be from that..


----------



## tomb

Holy Crap! Head-Fi lost about 5 paragraphs in my post - DANG! Let me try again!

 Generally speaking, most tubes benefit from higher plate voltages. The Millett tubes are no different.

 As for heater voltages, the idea is to regulate the voltage as close as possible to recommended heater voltage as defined by the tube's data sheet. Lower voltages may increase heater life, but the flow of electrons, and therefore the output of the tube, is diminished. Higher voltages will decrease the life of the heater with little increased benefit.

 There is an outright TYPO that rds point out to me on the MAX website on the Heater Resistor page. This may be confusing matters. AFAIK, there is no axiom that a tube is more linear with higher heater voltage.

 As for plate voltage, that's a different matter. In fact, Pete Millet - in his AudioXpress article on the original Millett Hybrid - went as high as 19V bias and preferred the sound from the tubes because of the lower distortion. However, at biases that high - still with a 27VDC power supply - the voltage swing is very small. That may be why Pete makes the statement on his Starving Student web page that the Millett Hybrid clips in 1 or 2 Vrms. That's not really the case if bias is set at 1/2 the power supply.

 AMB's tests on the revMH Millett Hybrid show that:
 (http://www.ibiblio.org/tkan/audio/millett.html)
 "(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"

 He references tests on the other Millett tubes with similar results, but reduced according to their lower gains.

 Keep in mind that the Millett Hybrid has evolved through the revMH Millett Hybrid, the Millett Hybrid with Diamond Buffer boards, the MAX, and now the MiniMAX. Each has had progressively more complex and higher-performance circuits, especially in the buffers. That leads to an emphasis on maximizing voltage swing to take full advantage of the buffers.
*Accordingly, please remember that for the MiniMAX, we recommend 27VDC for the power supply and tube bias at 13.5VDC.*

 However, for those of you are wont to experiment, pushing the bias up to 19-20V may yield some interesting results. We have at least one MAX builder that I know of who's done this - TimJo. Maybe he'll see this and give us some more insight. Keep in mind, however, this is only experimental and not recommended - maybe something interesting with which to fool around.


----------



## tomb

BTW, all the MiniMAX cases have shipped.
	

	
	
		
		

		
		
	


	










 Now maybe I can enjoy those HF-1's for awhile!
	

	
	
		
		

		
		
	


	





 P.S. I am still waiting for the Silver case credit to hit my Paypal account. I called Lansing yesterday about it, because I received their official credit receipt in the mail yesterday. Lansing's bank is apparently taking their sweet time. I'll stay on top of it and refund everyone who ordered Silver as soon as the money hits my account.


----------



## tomb

The refund from Lansing hit my Paypal account. Refunds have been sent out to everyone who ordered a silver case.


----------



## Beefy

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_The refund from Lansing hit my Paypal account. Refunds have been sent out to everyone who ordered a silver case._

 

Got it...... thanks!


----------



## cetoole

Quote:


  Originally Posted by *Beefy* /img/forum/go_quote.gif 
_Got it...... thanks! 
	

	
	
		
		

		
		
	


	


_

 

x2, thanks a bunch Tom. The case was worth it at $55, but so much nicer at $40.


----------



## ruZZ.il

woohoo I'm going to have mine tomorrow! 
	

	
	
		
		

		
		
	


	




 Will only case it up after the w.end though.
 Anyway, happy holidays to all !


----------



## ruZZ.il

dumdedumdedum..... <click click>


----------



## bperboy

So, after the DB Bias is set, the only thing that would affect it is if I change the supply voltage? I.e. changing tubes and then tube bias shouldn't affect the DB bias? I ask because I received my cases (thanks Tom, they look wonderful!!!), and I'm going to set my DB Bias at 100mV, and then leave it (is that voltage okay?), and the only thing I'll do after that is roll tubes.

 Bperboy


----------



## tomb

Quote:


  Originally Posted by *bperboy* /img/forum/go_quote.gif 
_So, after the DB Bias is set, the only thing that would affect it is if I change the supply voltage? I.e. changing tubes and then tube bias shouldn't affect the DB bias? I ask because I received my cases (thanks Tom, they look wonderful!!!), and I'm going to set my DB Bias at 100mV, and then leave it (is that voltage okay?), and the only thing I'll do after that is roll tubes.

 Bperboy_

 

V+ is the only thing that affects DB bias, AFAIK. In any event, tubes and tube bias do not. Even then, you're converting the voltage across the 2.2 ohm DB output resistors to calculate the bias current - current is what we're actually setting to bias the DB's.

 I would set them at 110mV to give you 50ma bias - that's the MiniMAX standard we've set. You should get plenty of cooling with the custom case design.


----------



## bperboy

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_V+ is the only thing that affects DB bias, AFAIK. In any event, tubes and tube bias do not. Even then, you're converting the voltage across the 2.2 ohm DB output resistors to calculate the bias current - current is what we're actually setting to bias the DB's.

 I would set them at 110mV to give you 50ma bias - that's the MiniMAX standard we've set. You should get plenty of cooling with the custom case design.
	

	
	
		
		

		
		
	


	


_

 

Ach!! just finished closing up the case.. alrighty, I'll take care of that for the 2nd Minimax. Great project btw.. 
	

	
	
		
		

		
		
	


	







 Hope you're enjoying the HF-1s Tom!


----------



## alwayshungry

I've been putting together my miniMAX and I have a couple of questions.

 (1) What type of standoffs is everybody using for the PCB?

 (2) For the transistors on QB8L/R and QB9L/R I'm using option (C) and the BOM says to note reverse pinout. How does this affect the way I mount them to the board? Also does this have to do with which set of 3 solder points I use (since there are 2 sets for each transistor).


----------



## DaMnEd

Quote:


  Originally Posted by *alwayshungry* /img/forum/go_quote.gif 
_(2) For the transistors on QB8L/R and QB9L/R I'm using option (C) and the BOM says to note reverse pinout. How does this affect the way I mount them to the board? Also does this have to do with which set of 3 solder points I use (since there are 2 sets for each transistor)._

 

Millett Hybrid MAX BJT Transistors (MAX website but for this purpose same applies as far as mounting/solder side/points is concerned)


----------



## gspence2000

I just got home from holiday travels last night, and my case was waiting in the mailbox. I was up until 2am putting it together and listening to it. It's beautiful and sounds great with 12AE6 tubes!
	

	
	
		
		

		
			





 For those who haven't built their miniMax yet, don't forget to trim the post on the audio pot before soldering it onto the board. I forgot to do so and now it will be difficult to saw it off without putting strain on it.
	

	
	
		
		

		
		
	


	




 I used Mouser WP7104SEDorange LEDs to light the tubes and they look just right. The orange tubes go really well with the blue center LED.

 Now I can rock out at work all day


----------



## bperboy

Quote:


  Originally Posted by *gspence2000* /img/forum/go_quote.gif 
_For those who haven't built their miniMax yet, don't forget to trim the post on the audio pot before soldering it onto the board. I forgot to do so and now it will be difficult to saw it off without putting strain on it.
	

	
	
		
		

		
		
	


	


_

 

I forgot as well, but I always forget.. I don't mind much, so I probably won't trim the shafts.


----------



## tomb

The MiniMAX website is now finished and live:

MiniMAX

 Tonight and tomorrow, I'll be revamping the DIYForums.org home page, as well - no point in having a bunch of MiniMAX case renderings when we have the real thing, now.

 I'll add a Gallery to the MiniMAX site if more of you guys start posting some pics - hint, hint.
	

	
	
		
		

		
		
	


	





 P.S. Some people don't like to use the Dremel's cutoff wheel for cutting the pot shaft, but it works quite well if you're careful. It puts minimal pressure on the pot - I always wait until the board is cased up before cutting the shaft, anyway - can't tell for sure how long it needs to be before then.

 When you cut, wrap the entire case in a baggie or some other plastic, taped at the shaft. That should keep things protected from all the metal dust that'll go flying when you rev up that cutting wheel.


----------



## bperboy

Tom, I promise, I can get up some cell phone pics by maybe wednesday, but in two weeks, I can use my nice DSLR to get some sweet pics of a silver and black minimax.


----------



## tomb

Wait for your DSLR - we want the best for the website.


----------



## DaMnEd

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_The MiniMAX website is now finished and live:

MiniMAX

 Tonight and tomorrow, I'll be revamping the DIYForums.org home page, as well - no point in having a bunch of MiniMAX case renderings when we have the real thing, now.

 I'll add a Gallery to the MiniMAX site if more of you guys start posting some pics - hint, hint.
	

	
	
		
		

		
		
	


	


_

 

I had the opportunity to view the website in detail yesterday and congratulate the team, but I feel I must also do so publicly.

 This has to be the most comprehensive yet detailed website for a DIY project I've seen, bar none. Very easy to go through, accessible to the newbies like myself yet the technical details are not lost. Love all the visual aids, exceptional technical drawings!

 Amazing website, awesome custom case, Beezar's amazing customer service, what more could one ask... just perfect! 
	

	
	
		
		

		
		
	


	




 I will make sure to take a couple of decent shots as the project goes along!

 A big thank you for you both, Colin and Tom for this project!


----------



## bperboy

DaMnEd, a big QFT! Tom and Colin have done a wonderful job!


----------



## Apthenes

Quote:


  Originally Posted by *FallenAngel* /img/forum/go_quote.gif 
_Yay, it's making music! 
	

	
	
		
		

		
		
	


	




 I didn't say "done" because I need to add the Wima PSU bypass caps but it runs fine without them and sounds pretty darn good. Can't wait for the case.



_

 


 Impressive ! How big is it going to be once cased ? Any idea ?


----------



## Bismar

Have to say great work tomb, your dedication to the DIY community is amazing.

 Btw on the heater resistor page, you have a small typo on the 8th word from the end.


----------



## tomb

Quote:


  Originally Posted by *Bismar* /img/forum/go_quote.gif 
_Have to say great work tomb, your dedication to the DIY community is amazing.

 Btw on the heater resistor page, you have a small typo on the 8th word from the end._

 

Thanks - "lose" is now "close".


----------



## WilCox

After two MAX's and one MiniMAX with BlackGates and VitaQ's, I thought I'd try the ES/K42 combo. Despite rumors to the contrary, the K42 fits just fine. Still not sure if I like the sound though. More punch, for sure, but it sounds coarse compared to the BlackGate/VitaQ combo. I'll give it more time and see if it (or me) settles into the groove.


----------



## soloz2

I just opened up my package from beezar just now and I must admit the cases look fantastic! It's just a shame I don't have the $$ to populate the boards now. I had planned to have two boards populated before the enclosures came too... boy to things not always work out as planned...


----------



## Beefy

All you lucky buggers with your cases....... curse you, international shipping!


----------



## tomb

Quote:


  Originally Posted by *WilCox* /img/forum/go_quote.gif 
_After two MAX's and one MiniMAX with BlackGates and VitaQ's, I thought I'd try the ES/K42 combo. Despite rumors to the contrary, the K42 fits just fine. Still not sure if I like the sound though. More punch, for sure, but it sounds coarse compared to the BlackGate/VitaQ combo. I'll give it more time and see if it (or me) settles into the groove. 
	

	
	
		
		

		
		
	


	




 <IMG]http://www.head-fi.org/forums/members/wilcox-albums-millett-max-picture1647-mini-board.jpg[/IMG>
 <IMG]http://www.head-fi.org/forums/members/wilcox-albums-millett-max-picture1649-mini-k42.jpg[/IMG>_

 

Yep, the K42's are not going to sound as good as the VitaminQ's. I think you will be pleasantly surprised if you change those out to VitQ's, however. The ES/VitQ/2SC3422/2SA1359 is my personal favorite. I've built more MAXes/MiniMAXes with that configuration than any other.

 That said, I think the K42's are an improvement over the Wima's in the output position, so it depends on what it's compared against.

 What I really want to know, though, is how you fit those 0.22uf K42's in there between the CA7 cap and the pot/headphone jack. I didn't think there was anyway to get one of those slid in behind the pot, for sure.


----------



## lordvader

Quote:


  Originally Posted by *Beefy* /img/forum/go_quote.gif 
_All you lucky buggers with your cases....... curse you, international shipping! 
	

	
	
		
		

		
			









_

 

Seconded !!!!

 *sits patiently*


----------



## Gross

Well, I have mine all cased up now, looks great. I will throw up a pic tomorrow. What are people using for the audio hook up inside the amp? Do we need to worry about picking up noise routing wire past the psu and the outputs and whatnot? I just used some nice shielded 'Star-Quad' mic wire that I took from work. A bit beefier than I wanted, but it for sure works. 

 Also, anyone attempted to straighten out the slight crown in the case? 

 Oh yeah, and I may have mentioned this in the past, but with the barrier strip installed in the audio input spot, it covers the silk screen on the board. Sorry if I am beating a dead horse with that one. 

 All in all, It looks great and sounds great. I had my RS-1s plugged into my RA-1 Clone while I cased up my MiniMAX, and what a nice upgrade it was to get to listen to my MAX again. 

 Thanks Team MiniMAX.


 Edit:

 Whoa! Only 3 years and I already have 200 Posts! I will be catching up to the rest of you in no time.


----------



## Bismar

Just a quick question, is there any disadvantage in having the millet minimax in a plastic case as opposed to a metal case?

 I'm thinking of building my own out of acrylic.


----------



## WilCox

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Yep, the K42's are not going to sound as good as the VitaminQ's. I think you will be pleasantly surprised if you change those out to VitQ's, however. The ES/VitQ/2SC3422/2SA1359 is my personal favorite. I've built more MAXes/MiniMAXes with that configuration than any other._

 

Since this build uses the 3422/1359 combo, I think I'll swap out the K42's for the VitaQ's as you suggest. My MAX with the BlackGate/VitaQ/3422/1359 combo and is one of my favorites as well.

  Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_What I really want to know, though, is how you fit those 0.22uf K42's in there between the CA7 cap and the pot/headphone jack. I didn't think there was anyway to get one of those slid in behind the pot, for sure.
	

	
	
		
		

		
		
	


	


_

 

The 0.22uf K42 dropped right into both positions without any problem at all. There's not a lot of extra room, but I didn't have to use any force at all as the clearance is adequate. Since this is the only pair of K42's I have, I'm not sure how much variability there is on their dimensions from part-to-part.


----------



## Beefy

Quote:


  Originally Posted by *WilCox* /img/forum/go_quote.gif 
_The 0.22uf K42 dropped right into both positions without any problem at all. There's not a lot of extra room, but I didn't have to use any force at all as the clearance is adequate. Since this is the only pair of K42's I have, I'm not sure how much variability there is on their dimensions from part-to-part._

 

Odd. On my builds, the 0.18µF VitQ at CA8R is touching both the volume pot and the electrolytic at CA7R...... I've always assumed from pictures that the K42 are much 'fatter'.


----------



## bperboy

Quote:


  Originally Posted by *Gross* /img/forum/go_quote.gif 
_What are people using for the audio hook up inside the amp? Do we need to worry about picking up noise routing wire past the psu and the outputs and whatnot? I just used some nice shielded 'Star-Quad' mic wire that I took from work. A bit beefier than I wanted, but it for sure works._

 

I just used plain ole 22 ga. solid copper hookup wire from ratshack. I've used Star-Quad before, but honestly, I don't know that there would be a huge difference. 

  Quote:


 Also, anyone attempted to straighten out the slight crown in the case? 
 

Nope, but I did notice that. Once it's all screwed up, the crown isn't really noticeable, though, my silver case did have some scratches on the top.. probably from machining. It's a bit disappointing, but not entirely unexpected.

  Quote:


 Oh yeah, and I may have mentioned this in the past, but with the barrier strip installed in the audio input spot, it covers the silk screen on the board. Sorry if I am beating a dead horse with that one. 
 

Just check the Layout pic on the MiniMAX site. No big deal.


----------



## tomb

Just to be prudent, I would run two ground wires and Litz braid the signal wiring leading to the pot input terminal block. It's a very short length, easy to do, and might remove some potential interference whether you really hear it or not.

 Colin was pushing me to carry some shielded Mogami or similar and sell it in one foot lengths at Beezar. I'm not sure yet whether I can do it or not - carrying the cases on a regular basis is my big concern at the moment.


----------



## bperboy

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_...carrying the cases on a regular basis is my big concern at the moment._

 

Tom, since Lansing has now done a fairly large run of these cases, is there setup and tooling issues with producing more? I think that when AMB Labs carries the FPE panels for the Mini3, it doesn't cost as much, because everything's been setup already.


----------



## tomb

Quote:


  Originally Posted by *bperboy* /img/forum/go_quote.gif 
_Tom, since Lansing has now done a fairly large run of these cases, is there setup and tooling issues with producing more? I think that when AMB Labs carries the FPE panels for the Mini3, it doesn't cost as much, because everything's been setup already._

 

It's true there won't be tooling costs. However, there are manufacturing setup costs each and every time. Add to that the fact that we got a low volume discount the first time, and that I still have packaging and shipping costs, it's not much different. Heck, don't know if you guys noticed - but I even forgot to charge you all the Paypal fee.
	

	
	
		
		

		
		
	


	




 Plus, you have to count on the fact that I have to stock these - with no guarantee how many will sell, or when. Add in the long lead time to produce them, and it means I'm out of pocket several hundreds to a thousand dollars each time I will order. Because of the long lead time, it's not manageable to take pre-orders on a constant basis (at least not manageable by me).

 I'm debating how much they'll sell for right now and have discussed it with Colin, of course. We will be fair about it and not charge too much over cost - but if I don't make a bit of money from each one, there's no way to accumulate enough funds to order another batch - probably 10 at a time, perhaps. Do that two or three times, and it's real money in anybody's book. The only way to cover that is by making a profit each time. Even that's misleading, because the profit has to go back into ordering more stock.

 Sorry - I'm not purposely trying to poormouth myself and Beezar. I just hope you all don't have any misplaced expectations about the costs that are involved. I think if you compare the Lansing MiniMAX cases to what you'd get for the same thing done at FPE, it would probably cost 3-4 times as much (no, I'm not going to charge anywhere near that).


----------



## Bismar

So did anyone have any thoughts on my earlier question regarding the disadvantages of a plastic case over metal?

 I'm asking as i'm concerned that i would get a significant amount of audible noise due to EMR.


----------



## tomb

Quote:


  Originally Posted by *Bismar* /img/forum/go_quote.gif 
_So did anyone have any thoughts on my earlier question regarding the disadvantages of a plastic case over metal?

 I'm asking as i'm concerned that i would get a significant amount of audible noise due to EMR._

 

The MAX's ground plane is pretty big. I'm not sure any of us have had any audible noise just running from the bare board. So, a plastic case should not make much difference.

 That said, be sure you use two ground wires and Litz-braid your signal input wiring to the pot. It will run fine as a bare board, but casing one up tends to cram everything together. If anything is going to pick up interference and cause noise issues, it will the signal wiring to the pot.


----------



## Bismar

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_The MAX's ground plane is pretty big. I'm not sure any of us have had any audible noise just running from the bare board. So, a plastic case should not make much difference.

 That said, be sure you use two ground wires and Litz-braid your signal input wiring to the pot. It will run fine as a bare board, but casing one up tends to cram everything together. If anything is going to pick up interference and cause noise issues, it will the signal wiring to the pot._

 

Thanks tomb, by that do you mean 1 ground wire from each of the rca jacks or two wires that are connected to both?

 Also which is the ground terminal on the RCA jacks? The inner terminal or the outer one with the detachable ring.


----------



## Beefy

Quote:


  Originally Posted by *Bismar* /img/forum/go_quote.gif 
_Also which is the ground terminal on the RCA jacks? The inner terminal or the outer one with the detachable ring._

 

The outer ring is the ground.


----------



## tomb

Quote:


  Originally Posted by *Bismar* /img/forum/go_quote.gif 
_Thanks tomb, by that do you mean 1 ground wire from each of the rca jacks or two wires that are connected to both?_

 

One wire connected to each, or two wires connected to both.
	

	
	
		
		

		
		
	


	




 Seriously, I solder the ring tabs together and then solder two wires to the ring tab joint.


----------



## Bismar

Cool. Sorry about all the newb questions 
	

	
	
		
		

		
		
	


	




 Also just received my package from Beezar!

 Wow, i know everyone says tomb's packaging is fantastic, but wow, i've never seen so much bubble wrap before 

 You could quite literally shoot a bullet into the package and not hit anything but bubble wrap 
	

	
	
		
		

		
		
	


	




 But yeah, is nice to know that all my screws and silicone rubber o rings are safe from even the most destructive couriers in the world


----------



## Beefy

Cases arrived today 
	

	
	
		
		

		
			





 My silver one was missing the screws, but I was planning on using Beezar-bought socket head screws anyway. Will the holes tap just like the regular Hammond cases?


----------



## tomb

Quote:


  Originally Posted by *Beefy* /img/forum/go_quote.gif 
_Cases arrived today 
	

	
	
		
		

		
		
	


	




 My silver one was missing the screws, but I was planning on using Beezar-bought socket head screws anyway. Will the holes tap just like the regular Hammond cases?_

 

Cr*p!! Are you missing the rubber feet, too? They should be together with the screws in a little ziplock on the side of the box.

 I can't apologize enough if I forgot that - they'll be in the mail tomorrow morning.

 EDIT: The Lansing uses 4-40 screws. 6-32's are too big. I'll send you some socket head screws, too, though.


----------



## lordvader

Quote:


  Originally Posted by *Beefy* /img/forum/go_quote.gif 
_Cases arrived today 
	

	
	
		
		

		
		
	


	


_


----------



## Beefy

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Cr*p!! Are you missing the rubber feet, too? They should be together with the screws in a little ziplock on the side of the box.

 I can't apologize enough if I forgot that - they'll be in the mail tomorrow morning.

 EDIT: The Lansing uses 4-40 screws. 6-32's are too big. I'll send you some socket head screws, too, though.
	

	
	
		
		

		
		
	


	


_

 

Yeah, the whole pack was missing, unfortunately. Let me know how much it costs to send and I'll PayPal you the money. I've still got the case refund sitting in my account! 
	

	
	
		
		

		
		
	


	




  Quote:


  Originally Posted by *lordvader* /img/forum/go_quote.gif 
_



_

 

And a bill is coming your way 
	

	
	
		
		

		
		
	


	




 Should be able to send it Friday. Will email with details.


----------



## WilCox

Quote:


  Originally Posted by *Beefy* /img/forum/go_quote.gif 
_Odd. On my builds, the 0.18µF VitQ at CA8R is touching both the volume pot and the electrolytic at CA7R...... I've always assumed from pictures that the K42 are much 'fatter'._

 

Actually, the K42 0.22uf are only slightly "fatter" than the VitaQ 0.18uf. It's the shorter length of the K42 that makes them appear fatter. Here's what I measured from two samples of each:

Cap Type --- Diameter -- Length
 VitaQ 0.18uf -- 0.425" --- 1.230"
 K42 0.22uf ---- 0.435" --- 0.900"

 These are nominal dimensions -- no gauge R&R and standard deviation was not calculated. 
	

	
	
		
		

		
		
	


	




 In any event, I switched out the K42's for the VitaQ's and the sound is now more liquid, smoother and less harsh -- much better! Thanks TomB!


----------



## Beefy

Quote:


  Originally Posted by *bperboy* /img/forum/go_quote.gif 
_Nope, but I did notice that. Once it's all screwed up, the crown isn't really noticeable, though, my silver case did have some scratches on the top.. probably from machining. It's a bit disappointing, but not entirely unexpected._

 

Yeah, the 'body' of the cases aren't perfect, but still in better nick than any Hammond I've ever had. The silkscreened panels, however, are immaculate. Very happy! 
	

	
	
		
		

		
		
	


	




  Quote:


  Originally Posted by *WilCox* /img/forum/go_quote.gif 
_Actually, the K42 0.22uf are only slightly "fatter" than the VitaQ 0.18uf._

 

There ya go then


----------



## bperboy

Quote:


  Originally Posted by *Beefy* /img/forum/go_quote.gif 
_Yeah, the 'body' of the cases aren't perfect, but still in better nick than any Hammond I've ever had. The silkscreened panels, however, are immaculate. Very happy! 
	

	
	
		
		

		
		
	


	


_

 

True that!


----------



## tomb

Quote:


  Originally Posted by *Beefy* /img/forum/go_quote.gif 
_ Quote:


  Originally Posted by *WilCox* 
Actually, the K42 0.22uf are only slightly "fatter" than the VitaQ 0.18uf.

 

There ya go then 
	

	
	
		
		

		
		
	


	


_

 

Fooled me, too - but I tried to drop one in there when building the prototype board and it wouldn't fit.


----------



## Beefy

For the ground test point, is there any good reason why you could/should not just wire it directly to signal ground?

 They are directly connected through the ground plane anyway, and it would mean one less wire under the PCB......


----------



## tomb

Quote:


  Originally Posted by *Beefy* /img/forum/go_quote.gif 
_For the ground test point, is there any good reason why you could/should not just wire it directly to signal ground?

 They are directly connected through the ground plane anyway, and it would mean one less wire under the PCB......_

 

True, but it's going a ways to prove a theorem. It may have less reliability and add to the problems if you're trouble-shooting.

 The "GND" test point on the board is contiguous with the ground plane. The only thing that would sever that connection is if the board broke (not likely). However, the signal ground is connected through the terminal block, which depends on the tightness of the screw and the condition of the wire lead tip.


----------



## Beefy

A couple of quick hand-held, no flash pics - best I can do in a rush, before heading out for NYE. Will whip out the tripod tomorrow if I manage to avoid a hangover......
 [EDIT] Updated pics here.

 Quick comments:

 Litz braided 22AWG silver teflon wire from Navships is not particularly flexible. Make sure you have the length right so that you don't have extra cable bulk.

 I had to cut the tip jacks so that they didn't make contact with VREG H/S.

 4mm standoffs are perfect.

 It is very hard to get wire <20AWG to fit in the tabs on the power switch. I just used the same 22AWG stuff I used for signal wiring instead.


----------



## ShinyFalcon

Whew, the MiniMAX looks beautiful... and surprisingly small too! I hope it won't be a difficult project. To me it doesn't really seem that difficult, just a lot of parts to work with...

 I think I notice a 1/4" jack in the BOM. Is there a substitute for a mini jack? Or should I start recabling my headphones with 1/4" plugs, or use those mini->1/4" adapters?


----------



## tomb

Looks great, Beefy!

 All I ever use is 22ga, even on the power wiring. I was hoping the tip jacks wouldn't be that close, but it is a very compact package. Things may be a bit too close, depending on how the leads are soldered in.


  Quote:


  Originally Posted by *ShinyFalcon* /img/forum/go_quote.gif 
_Whew, the MiniMAX looks beautiful... and surprisingly small too! I hope it won't be a difficult project. To me it doesn't really seem that difficult, just a lot of parts to work with...

 I think I notice a 1/4" jack in the BOM. Is there a substitute for a mini jack? Or should I start recabling my headphones with 1/4" plugs, or use those mini->1/4" adapters?_

 

There's a terminal block next to the headphone jack, so you could fit in a mini-jack if you really wanted one. However, I'm not sure anyone is going to want to drill those custom Lansing endplates.


----------



## Bismar

Quote:


  Originally Posted by *Beefy* /img/forum/go_quote.gif 
_*Beefy throws down the Gauntlet*




_

 

Btw, i noticed something curious in Beefy's build photo as i wanted to get a photo of a complete build for my own upcoming build.

 Hopefully Beefy or someone could clear it up.

 What and where exactly is the wire beside the volume pot going to from the ground hole.

 Couldn't find any information about it on the new Minimax site or anything i've read so far.

 Any info would be great.

 Thanks


----------



## tomb

Quote:


  Originally Posted by *Bismar* /img/forum/go_quote.gif 
_Btw, i noticed something curious in Beefy's build photo as i wanted to get a photo of a complete build for my own upcoming build.

 Hopefully Beefy or someone could clear it up.

 What and where exactly is the wire beside the volume pot going to from the ground hole.

 Couldn't find any information about it on the new Minimax site or anything i've read so far.

 Any info would be great.

 Thanks_

 

It's a ground wire for the pot ... it's attached to one of the back screws of the RK27. You loosen one of the screws, loop the wire around it, screw it back in, and then solder the other end of the wire into the ground hole on the board.

 It's standard treatment for an Alps RK27, mostly because of the plastic body. Sometimes we forget that may not be common knowledge among new folk. 
	

	
	
		
		

		
		
	


	




 EDIT: Many times, you'll get hum when touching the pot/volume knob if this procedure is not done.


----------



## Bismar

Cool thanks, that information might be useful on the Minimax site 
	

	
	
		
		

		
			





 It will most likely get lost in this thread.

 Also i got another beginners question. Which of the terminals in the AC terminal block are used? They all seem to have paths running from them but the 2.1mm power jack only has two sockets afaik.

 Thanks,
 Bismar


----------



## fordgtlover

Similar to the Millett Max, you use connections 1 & 2 if you don't want to use a power fuse, otherwise use connections 2 & 3 for fused power. Connection 1 being closest to the edge of the board.


----------



## gspence2000

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_It's a ground wire for the pot ... it's attached to one of the back screws of the RK27. You loosen one of the screws, loop the wire around it, screw it back in, and then solder the other end of the wire into the ground hole on the board.

 It's standard treatment for an Alps RK27, mostly because of the plastic body. Sometimes we forget that may not be common knowledge among new folk. 
	

	
	
		
		

		
		
	


	




 EDIT: Many times, you'll get hum when touching the pot/volume knob if this procedure is not done._

 

That is very good information! I was getting quite a hum when I put my hand on the dial--less so after I cased it up though.

 Here are my suggestions to improve the MiniMAX web site:

 -add a note about grounding the pot,
 -add the 4mm standoff to the BOM,
 -maybe add a few part suggestions for the tube LED's (perhaps in the photo gallery you could put the LED part number in the caption if you know it),
 -discuss trimming the length of the post on the pot,
 -note that the tip jacks will need trimming,
 -specify that the power be connected through the fuse (the two screws on the right),
 -add a note about braiding the inputs and the two ground wires,
 -add a note about the two types of output transistor packages and when the shoulder washer is needed,
 -put a link on the construction page that points to the illustration at the bottom of the Diamond Buffer page, to clarify the orientation of the output transistors,
 -clarify that the R1 resistor is to be used in all cases (currently the impression is that it is only to be used if you are playing with high-voltage),
 -clarify that the initial setting of the voltage and tube gain trimpots is not critical and will not kill your amp when you first turn it on.

 That's all that I can think of--not to be critical though, I think the web site is very good!


----------



## Bismar

Thanks for clearing that up fordgt 
	

	
	
		
		

		
		
	


	




 If your after LEDs, i recommend hktaiyuen an ebay seller, extremely cheap LEDs and bright too for the price.


----------



## rds

gspence2000 I think these are good suggestions, but what do you mean 
  Quote:


 -add a note about braiding the inputs and the two ground wires, 
 

?

 If you are using 3 wires then a braid is probably best, but with 4 wires I'd say 2 separate twisted pairs is the way to go.


----------



## gspence2000

Quote:


  Originally Posted by *rds* /img/forum/go_quote.gif 
_gspence2000 I think these are good suggestions, but what do you mean 
 ?

 If you are using 3 wires then a braid is probably best, but with 4 wires I'd say 2 separate twisted pairs is the way to go._

 

I was referring to TomB's recommendation on braiding on this post.

 Myself, I just did a three-wire braid. It's all cased up now and I think I'll just leave it.


----------



## tomb

Actually, braiding three wires (only one ground) will _increase_ crosstalk. The second ground wire is needed to cancel the interference signals in the twist. The 4-wire Litz braid will also have much less crosstalk than two separate leads twisted. This makes sense if you think about it, because there's no way you can guarantee a separation distance between the two separate twisted leads.


 EDIT: this is a good tutorial on it -
http://www.chimeralabs.com/diy_braid.html

 I don't subscribe to his opinions on solid vs. flex (mainly because flex still stays separated within its own bundle), but the rest of it is probably OK. Dsavitsk is the one who corrected me long ago for braiding 3-wires from the output of an Alien DAC.
	

	
	
		
		

		
		
	


	




 Keep in mind that none of this probably matters on very short lengths, but the input wiring on the MiniMAX necessarily travels the entire length of the board.


----------



## gspence2000

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Actually, braiding three wires (only one ground) will increase crosstalk. The second ground wire is needed to cancel the interference signals in the twist. The 4-wire Litz braid will also have much less crosstalk than two separate leads twisted. This makes sense if you think about it, because there's no way you can guarantee a separation distance between the two separate twisted leads._

 

I guess I will re-do it then. I need to open up the case to put in the standoff (when my next Mouser order arrives) anyways. There is a 4-wire Litz braiding tutorial here.


----------



## rds

Quote:


 The 4-wire Litz braid will also have much less crosstalk than two separate leads twisted. This makes sense if you think about it, because there's no way you can guarantee a separation distance between the two separate twisted leads. 
 

I'm surprised to hear that. After all the idea of 2 separate twisted pairs is that they can actually be separated by an arbitrary distance. With a braid the 2 signal wires are separated by a few millimeters. Since induced current is directly proportional to the distance between 2 wires I would expect much greater crosstalk with a braid.
 I don't know what you mean by not being able to guarantee a separation distance. It seems to me that you can guarantee the distance by the physical placement of the 2 pairs.

 Also, the concept of twisted pairs is to have a return path for the lead wire as close to it as possible so that noise induced in the signal path is minimized. 
 I still don't know why people think it's a good idea to braid 2 signal wires together. That just increases the separation distance between each lead and return as well as decreasing the distance between the leads. Or in other words decreases immunity to while increasing crosstalk (as far as I can see anyways).


----------



## tomb

Quote:


  Originally Posted by *rds* /img/forum/go_quote.gif 
_I'm surprised to hear that. After all the idea of 2 separate twisted pairs is that they can actually be separated by an arbitrary distance. With a braid the 2 signal wires are separated by a few millimeters. Since induced current is directly proportional to the distance between 2 wires I would expect much greater crosstalk with a braid.
 I don't know what you mean by not being able to guarantee a separation distance. It seems to me that you can guarantee the distance by the physical placement of the 2 pairs._

 

All I meant was that you can't guarantee what happens when you button the case up - unless you are planning on installing guides along the entire length of the board. At that point, braiding is much easier, anyway.

  Quote:


 Also, the concept of twisted pairs is to have a return path for the lead wire as close to it as possible so that noise induced in the signal path is minimized. 
 I still don't know why people think it's a good idea to braid 2 signal wires together. That just increases the separation distance between each lead and return as well as decreasing the distance between the leads. Or in other words decreases immunity to while increasing crosstalk (as far as I can see anyways). 
 

I don't pretend to understand the total mechanics of Litz braiding - just that there's no benefit to two twisted pairs - as long as they are separated.


----------



## ruZZ.il

A problem (I imagine) with 2 separated pairs is that the ground is common to both of the signals, so lets say the left/ground pair has a left signal, but a (R and L) return signal, so that return signal would induce interference from the right channel on the left channel, and visa versa.
 The advantage of having the ground, left and right all in one braid is that the interference cancels each other out cause the net current is zero. As to why a 4 pair braid is better than a 3 pair..I don't recall the sense I once made of it, If I even did.. maybe symmetry or something, I donno.. 

 It would probably make more sense to have 2 separate pairs on, say, a balanced system. 

 BTW, THE CASES ARE COOL ! 
	

	
	
		
		

		
		
	


	




 I got mine last thursday, all the way to Israel with a friend, that got them in time thanks to Tom's thriftiness. THANKS TOM! 
	

	
	
		
		

		
		
	


	




 Now, I just need the time to box up. My RCA jacks need a bit of a bigger hole, and, well, I'm too busy studying. hmpf.


----------



## Bismar

Question, for the output resistors do the koa kiwame's make a big deal of difference as compared to the vishays? If so where can i get them from?

 Also what wattage do i need to be looking at for the output resistor.


----------



## Beefy

Quote:


  Originally Posted by *Bismar* /img/forum/go_quote.gif 
_Question, for the output resistors do the koa kiwame's make a big deal of difference as compared to the vishays? If so where can i get them from?_

 

I've got 2W Kiwame in 10R, 22R, 33R, 47R and 100R that I may be able to spare, just for the cost of postage. You would probably want 10R or 22R for your K701.

 I'll get back to you in a little while after somebody else gets back to me about them.


----------



## Bismar

Cool Beefy, let me know how it goes as soon as the other person gets back to you.


----------



## Beefy

Updated pics:





















 The last pic is my first deliberate attempt at bokeh


----------



## fordgtlover

Nice job. The silver looks great.


----------



## slowpogo

Quote:


  Originally Posted by *Bismar* /img/forum/go_quote.gif 
_Question, for the output resistors do the koa kiwame's make a big deal of difference as compared to the vishays? If so where can i get them from?

 Also what wattage do i need to be looking at for the output resistor._

 

I don't know why but nobody ever talks about Rikens for the output resistors (except me), however I really thought they sounded better than Kiwame. I used 15ohm resistors and tried both; the Kiwames reduced some high-end harshness but at the expense of adding a warm, hazy quality to all of the sound. I can see why they are popular in tube guitar amps, because they noticeably emphasize the "tubey-ness" of the sound.

 I guess some people like that, but I really preferred the Rikens, which tame the harshness but still keep things crisp, don't add any veil and give just the slightest bit of sweetness. It's not as noticeable at 15ohms but in other projects, I've found they also seem to open up the soundstage compared to metal film. They are not available at Beezar which may put them off people's radar, but if you're ever ordering anything from Parts Connexion grab a couple at about $2 each, it's well worth it IMO.


----------



## tomb

Quote:


  Originally Posted by *Beefy* /img/forum/go_quote.gif 
_Updated pics:






















 The last pic is my first deliberate attempt at bokeh 
	

	
	
		
		

		
		
	


	


_

 

Wow! Nice pics, Beefy! I especially like the last one. You should post a couple of these in the "Pics of Your Builds Thread", too. They will get more exposure that way.
	

	
	
		
		

		
		
	


	




 There are some people who just look at that thread and nothing else in this forum section. I saw someone ask, "What is the MiniMAX case?" in the SSMH thread, so maybe these will help.
	

	
	
		
		

		
		
	


	




 Bismar -
 About resistors - beezar has the Kiwame's (also some Stackpoles). However, you can also purchase them at Mouser. They are listed under "KOA SP2". Both types are 2W size, but you don't need that rating necessarily on the MiniMAX in the actual RB14L/R positions. It's just a convenient size for boutiques - it allows for easier removal and swap out if you're trying several.
	

	
	
		
		

		
		
	


	




 SlowPogo mentions the Rikens - everything I've heard about them confirms what he says, but as noted - you will pay a price for them. You might use the Kiwame's/Stackpoles to determine what ohms you prefer, then swap them out with a pair of Rikens once you know. That would save quite a bit of money from trying several pairs of Rikens, instead.

 There are also the Caddock resistors. These are shaped like the TO-220 output resistors. We had a MAX builder once build a MAX with nothing but the Caddock resistors in every position. He said it made a difference, but he was shooting for an extreme build - very interesting, but not something I'd recommend on a regular basis. Still, the Caddocks may be a realistic alternative for RB14L/R.

 Looks like PartsConnexion also has a new resistor - "Takman". These may be worth trying at RB14 as well.

 Another thing to consider is that the buffer output resistors may also benefit from a boutique replacement. As opposed to RB14L/R, 2W are _required_ at the buffer outputs (RB10L/R, RB11/LR). They must be 2.2 ohm as listed on the BOM. Chances are, trying this will not have as much effect if you use something in RB14L/R. Jumpering RB14L/R is probably the way to go if you start using boutiques at RB10 and RB11. We have also had one MAX builder recommend the Mills Wirewound as the best thing to use at RB10 and RB11.

 Except for Kiwames or Stackpoles at RB14, all of these other alternatives listed will cost you $$$ instead of a few dimes. Finally, be careful about the Kiwames - even some Head-Fi sponsors still think they should sell for $2 a piece.


----------



## tomb

I understand there's been some difficulty in finding the MiniMAX power switch internationally. Mouser has exorbitant shipping costs and Radio Shack is not available everywhere in the world.

 Of course, the idea is that the case is pre-drilled for all of the parts. This makes finding the real thing or a suitable replacement important. Because of that, I will do my best to keep them in stock at Beezar and they are listed now.

 Also, there's been quite a bit of discussion about the center hole standoff. A group of washers, a group of washers with a 4-40 nut on top, a spacer, a standoff, etc - all of these will work with a 3/8" - 1/2" long 4-40 screw. However, I haven't tried it personally yet (except the washers/nut on the early prototype in my 
 avatar), but it appears to me that a 1/8", 4-40 standoff - plus a flat washer - may be the simplest solution. The distance needed is 4mm or 5/32". Standoff's are not readily available everywhere in 5/32", only 1/8" (too small) or 3/16" (too big). A washer(s) can make up the difference.


----------



## omegamajor

Beefy: What color LED's (part #?) did you use under the tubes?


----------



## Beefy

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Wow! Nice pics, Beefy! I especially like the last one. You should post a couple of these in the "Pics of Your Builds Thread", too. They will get more exposure that way.
	

	
	
		
		

		
		
	


	




 There are some people who just look at that thread and nothing else in this forum section. I saw someone ask, "What is the MiniMAX case?" in the SSMH thread, so maybe these will help.
	

	
	
		
		

		
		
	


	


_

 

Will post that now. If you want any of these for the official site, just let me know 
	

	
	
		
		

		
		
	


	




  Quote:


 Bismar -
 About resistors - beezar has the Kiwame's (also some Stackpoles). However, you can also purchase them at Mouser. They are listed under "KOA SP2". Both types are 2W size, but you don't need that rating necessarily on the MiniMAX in the actual RB14L/R positions. It's just a convenient size for boutiques - it allows for easier removal and swap out if you're trying several.
	

	
	
		
		

		
		
	


	



 

I'll just send Bismar some spare 10R KOA that I bought from Beezar. It should be a good compromise for his hard to drive K701 and very sensitive AD700.

  Quote:


  Originally Posted by *omegamajor* /img/forum/go_quote.gif 
_Beefy: What color LED's (part #?) did you use under the tubes?_

 

They are from eBay seller eylane.

 My auction was exactly like this or this.


----------



## Bismar

Quote:


  Originally Posted by *Beefy* /img/forum/go_quote.gif 
_Will post that now. If you want any of these for the official site, just let me know 
	

	
	
		
		

		
		
	


	






 I'll just send Bismar some spare 10R KOA that I bought from Beezar. It should be a good compromise for his hard to drive K701 and very sensitive AD700.



 They are from eBay seller eylane.

 My auction was exactly like this or this._

 

Cool, Beefy thanks. As soon as you know if you can spare any of the other resistors, send me a pm and ill drop you some cash through paypal or DD.

 Also on the topic of the k701's, i haven't gotten them yet (waiting on payday).

 Just wondering do you guys think this is legitimate? 

NEW AKG K702 Reference Headphones K 702 headphone - eBay (item 260330222100 end time Jan-08-09 21:35:19 PST)

 Cheers,
 Bismar


----------



## Bismar

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Wow! Nice pics, Beefy! I especially like the last one. You should post a couple of these in the "Pics of Your Builds Thread", too. They will get more exposure that way.
	

	
	
		
		

		
		
	


	




 There are some people who just look at that thread and nothing else in this forum section. I saw someone ask, "What is the MiniMAX case?" in the SSMH thread, so maybe these will help.
	

	
	
		
		

		
		
	


	




 Bismar -
 About resistors - beezar has the Kiwame's (also some Stackpoles). However, you can also purchase them at Mouser. They are listed under "KOA SP2". Both types are 2W size, but you don't need that rating necessarily on the MiniMAX in the actual RB14L/R positions. It's just a convenient size for boutiques - it allows for easier removal and swap out if you're trying several.
	

	
	
		
		

		
		
	


	




 SlowPogo mentions the Rikens - everything I've heard about them confirms what he says, but as noted - you will pay a price for them. You might use the Kiwame's/Stackpoles to determine what ohms you prefer, then swap them out with a pair of Rikens once you know. That would save quite a bit of money from trying several pairs of Rikens, instead.

 There are also the Caddock resistors. These are shaped like the TO-220 output resistors. We had a MAX builder once build a MAX with nothing but the Caddock resistors in every position. He said it made a difference, but he was shooting for an extreme build - very interesting, but not something I'd recommend on a regular basis. Still, the Caddocks may be a realistic alternative for RB14L/R.

 Looks like PartsConnexion also has a new resistor - "Takman". These may be worth trying at RB14 as well.

 Another thing to consider is that the buffer output resistors may also benefit from a boutique replacement. As opposed to RB14L/R, 2W are required at the buffer outputs (RB10L/R, RB11/LR). They must be 2.2 ohm as listed on the BOM. Chances are, trying this will not have as much effect if you use something in RB14L/R. Jumpering RB14L/R is probably the way to go if you start using boutiques at RB10 and RB11. We have also had one MAX builder recommend the Mills Wirewound as the best thing to use at RB10 and RB11.

 Except for Kiwames or Stackpoles at RB14, all of these other alternatives listed will cost you $$$ instead of a few dimes. Finally, be careful about the Kiwames - even some Head-Fi sponsors still think they should sell for $2 a piece.
	

	
	
		
		

		
		
	


	





_

 

As far as i can tell, the only 2.2 ohm resistors that PCX stocks is by Mills. Have you heard anything about them? They are as expensive as the rikens.


----------



## tomb

Quote:


  Originally Posted by *Bismar* /img/forum/go_quote.gif 
_As far as i can tell, the only 2.2 ohm resistors that PCX stocks is by Mills. Have you heard anything about them? They are as expensive as the rikens._

 

The Mills were mentioned in that post you quoted.
	

	
	
		
		

		
		
	


	




 EDIT: BTW, Northern Sound and Light gave me a quote of $258.39 on Saturday for the K702 - good for 15 days, they said.


----------



## Bismar

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_The Mills were mentioned in that post you quoted.
	

	
	
		
		

		
		
	


	




 EDIT: BTW, Northern Sound and Light gave me a quote of $258.39 on Saturday for the K702 - good for 15 days, they said.
	

	
	
		
		

		
		
	


	


_

 

Whoops, speed reading is bad 
	

	
	
		
		

		
		
	


	




 And doh! 

 Thats a great price but they don't ship outside the states


----------



## bperboy

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_The Mills were mentioned in that post you quoted.
	

	
	
		
		

		
		
	


	




 EDIT: BTW, Northern Sound and Light gave me a quote of $258.39 on Saturday for the K702 - good for 15 days, they said.
	

	
	
		
		

		
		
	


	


_

 

Tom, I was planning on getting some K701s, but with a price that low, I suppose there's no real reason not to get the K702s. Same sound, but the blue look is a little lower-key than iPod white.


----------



## digger945

^Yea I just came from Norther Sound and Light and they have demo 701's for like $248, but hey with 702's at that price....
 I got a quote for Ultrasone Pro900's just a minute ago for $344. Way cool price if you ask me.


----------



## tomb

Quote:


  Originally Posted by *bperboy* /img/forum/go_quote.gif 
_Tom, I was planning on getting some K701s, but with a price that low, I suppose there's no real reason not to get the K702s. Same sound, but the blue look is a little lower-key than iPod white._

 

Yeah - never could stand that white myself, either. However, I was just checking for the heck of it. Those HF-1's have my new-headphone-itch satisfied for quite some time.


----------



## rds

I was wondering where the optimum voltage of 12.6V comes from for the heater voltage?


----------



## tomb

Quote:


  Originally Posted by *rds* /img/forum/go_quote.gif 
_I was wondering where the optimum voltage of 12.6V comes from for the heater voltage?_

 

The tube data sheets. They're on the MiniMAX website under the Millett Tubes section.
	

	
	
		
		

		
		
	


	




 12.6V is a very common heater voltage for tubes - the "12" in the tube designation is another signal.


----------



## alwayshungry

Hey Guys,
 I got my miniMAX board put together and biased but I get no audio.

 The left and right DB biases are set to 90mV, the left and right tube biases are set to 13.5V and the power supply voltage is set to 27V.

 All 3 LEDs light up as well as the filaments on the tubes. Any ideas? Thanks in advance.


----------



## tomb

Quote:


  Originally Posted by *alwayshungry* /img/forum/go_quote.gif 
_Hey Guys,
 I got my miniMAX board put together and biased but I get no audio.

 The left and right DB biases are set to 90mV, the left and right tube biases are set to 13.5V and the power supply voltage is set to 27V.

 All 3 LEDs light up as well as the filaments on the tubes. Any ideas? Thanks in advance.



_

 

If everything biases correctly, but you get no sound: look to the relay circuit.

 Your pic is a little fuzzy, but it looks like you may have the BD139 backwards. Refer to the diagram at the very bottom of the MiniMAX page here: Millett Hybrid MiniMAX Relay-Delay

 EDIT: Just to be clear, you should hear a little "click" come from the relay itself about 30 seconds to 1 minute after firing up the amp. If the amp has been on a short while previously, then the time will be shorter. If you don't hear that "click", that's the problem, and like I guessed - it looks like the BD139 may be in backwards.

 Not to worry - when other people have done this, it's not damaged. Just turn it around and re-install it.


----------



## Beefy

Problems like that can be in the relay. Power down, leave it a minute, then turn back on. Can you hear the relay trip after 30-45 seconds?

 [EDIT] How do you do that, tomb?!?


----------



## cetoole

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Yeah - never could stand that white myself, either. However, I was just checking for the heck of it. Those HF-1's have my new-headphone-itch satisfied for quite some time.
	

	
	
		
		

		
		
	


	


_

 

Glad some people here have an itch which can be sated. Up to ~10 new headphones in the past 5 months here. 
	

	
	
		
		

		
		
	


	




  Quote:


  Originally Posted by *alwayshungry* /img/forum/go_quote.gif 
_Hey Guys,
 I got my miniMAX board put together and biased but I get no audio.

 The left and right DB biases are set to 90mV, the left and right tube biases are set to 13.5V and the power supply voltage is set to 27V.

 All 3 LEDs light up as well as the filaments on the tubes. Any ideas? Thanks in advance.



_

 

In before Tom!

 Gonna guess that you have QM1 in backwards, the big TO126 transistor in the muting circuit. Everything else looks good, though fuzzy.

 edit: Ah crud, not in before Tom, or Beefy even. Doh!


----------



## Beefy

Quote:


  Originally Posted by *cetoole* /img/forum/go_quote.gif 
_or Beefy even._

 

What's that supposed to mean?!?


----------



## tomb

Wow - how's that for support?


----------



## cetoole

Quote:


  Originally Posted by *Beefy* /img/forum/go_quote.gif 
_What's that supposed to mean?!? 
	

	
	
		
		

		
		
	


	


_

 

Supposed to mean that neither of your posts were there when I started, and yours raced all the way around the world to beat mine, though I guess it is possible that my bits travel further, as they dont even stay on planet.


----------



## alwayshungry

Damn you guys are amazing. I flipped QM1 around and now it works. Thanks Colin, Tom and Beefy.


----------



## sandbasser

Hi Guys - 

 I'm going to start putting my MiniMAX together this weekend. I have a question: I'm considering using sockets for the power transistors (QB8&9); upside would be ease of changing transistors to see which sound better to me - what would the downside be, if any??? And, should I socket all 8 positions???

 Thanks,


----------



## tomb

Quote:


  Originally Posted by *sandbasser* /img/forum/go_quote.gif 
_Hi Guys - 

 I'm going to start putting my MiniMAX together this weekend. I have a question: I'm considering using sockets for the power transistors (QB8&9); upside would be ease of changing transistors to see which sound better to me - what would the downside be, if any??? And, should I socket all 8 positions???

 Thanks,_

 

Downsides?
You have to "saw" off the pins shorter than you need for soldering. This means a permanent installation is impossible with the same transistors.
Some thermal pads/insulators - such as the Bergquist that many of us use - are not really re-usable. So, you're probably down to using a Mica insulator and messing with grease if you make more than one change.
There is a high current and high frequency connection at the inputs to the transistors. For instance, a socket is probably not a good idea at all with MOSFETs and may induce oscillation. That's probably unlikely with the BJT's, but still - be aware that performance "may" not be the same. I've not tested the difference, nor am I aware that anyone else has - just that there's that opinion out there.
The biggest advantage with sockets is to keep you from having to solder the connection and then try to de-solder it. However, it may be that the act of bolting the transistor to the heat sink - with all of its associated mounting hardware, thermal conductor/electric insulator/grease, etc. - is the real trouble, not the soldering/de-soldering.

 Upsides?
You get to try all the different options without soldering.


----------



## slowpogo

I just noticed that I have R1 populated in my Max! Not just noticed - I've looked at it 1000 times - but I was just skimming the BOM and realized it's optional and meant to drop the heater voltage. It was part of my Glass Jar kit so I just automatically put it in I guess, having missed that it was optional. Mine is either 10 or 20 ohm; can't tell if the first band is supposed to be red or brown.

 Anyway, I don't use "high supply voltages," just the normal 24v Triad wall wart, and the power on the Max set at 27v.

 So how might that resistor be affecting things? Does it mean I have to turn my tube trimpots higher than I should to get 13.5v, because the resistor is limiting the voltage that gets to them?


----------



## tomb

Quote:


  Originally Posted by *slowpogo* /img/forum/go_quote.gif 
_I just noticed that I have R1 populated in my Max! Not just noticed - I've looked at it 1000 times - but I was just skimming the BOM and realized it's optional and meant to drop the heater voltage. It was part of my Glass Jar kit so I just automatically put it in I guess, having missed that it was optional. Mine is either 10 or 20 ohm; can't tell if the first band is supposed to be red or brown.

 Anyway, I don't use "high supply voltages," just the normal 24v Triad wall wart, and the power on the Max set at 27v.

 So how might that resistor be affecting things? Does it mean I have to turn my tube trimpots higher than I should to get 13.5v, because the resistor is limiting the voltage that gets to them?_

 

No. If the resistor is 10 ohms and you have your power supply set at 27V, then all is well. Not to worry.

 To be sure, read this page (newly revised) on the MiniMAX website:
MiniMAX Tube Heaters Resistor


----------



## Bismar

Just got my digikey order in (thanks fordgtlover) and noticed that i made a mistake.

 I didn't check if the digikey part was the same part as the mouser in the Minimax bom, and have thus got Panasonic caps for the CA3, CA6, CA9.

 Luckily, i have 4 Wima's form Beezar.

 This however means 2 of the caps need to be the panasonic ones. Which should i stick them in? Or are they all equal in terms of audio grades.


----------



## Beefy

Quote:


  Originally Posted by *Bismar* /img/forum/go_quote.gif 
_Luckily, i have 4 Wima's form Beezar.

 This however means 2 of the caps need to be the panasonic ones. Which should i stick them in? Or are they all equal in terms of audio grades._

 

If it were me, I would leave CA9 empty for now. Then get two more Wima caps for that position at a later date.


----------



## cetoole

If you got the Panasonic ECQ-P, which I have in my own personal build, they are actually quite good caps. Much lower voltage than the Wimas, for the same size, but this is because they are actually film/foil polypropylene, instead of metallized. I would go ahead and use them, but find some position where you have the same in the left and the right. If you are concerned about them maybe not being as good sounding as the Wimas (not gonna comment on this subject), stick them in CA3L/R. It is isolated there from the tubes by a CCS, and a strong RC filter from the output buffer, so should have the least impact.


----------



## Bismar

Quote:


  Originally Posted by *Beefy* /img/forum/go_quote.gif 
_If it were me, I would leave CA9 empty for now. Then get two more Wima caps for that position at a later date._

 

Heh, that Panasonics are that bad eh 

 I'm in no rush anyway, still waiting on mouser parts to come and from some store in europe who still haven't processed my order after 7 days of payment!


----------



## Beefy

Quote:


  Originally Posted by *cetoole* /img/forum/go_quote.gif 
_If you are concerned about them maybe not being as good sounding as the Wimas (not gonna comment on this subject)_

 

That wouldn't worry me...... but that red colour? Phwoar! Gotta have that! 
	

	
	
		
		

		
			





  Quote:


  Originally Posted by *Bismar* /img/forum/go_quote.gif 
_Heh, that Panasonics are that bad eh _

 

No, not at all. But for the sake of a few bucks, go for the bling!


----------



## Bismar

Quote:


  Originally Posted by *cetoole* /img/forum/go_quote.gif 
_If you got the Panasonic ECQ-P, which I have in my own personal build, they are actually quite good caps. Much lower voltage than the Wimas, for the same size, but this is because they are actually film/foil polypropylene, instead of metallized. I would go ahead and use them, but find some position where you have the same in the left and the right. If you are concerned about them maybe not being as good sounding as the Wimas (not gonna comment on this subject), stick them in CA3L/R. It is isolated there from the tubes by a CCS, and a strong RC filter from the output buffer, so should have the least impact._

 

Ok, cool.

 Will do!


----------



## cetoole

Yeah, the ECQ-P caps are quite excellent, so it is a crying shame they are being phased out. Of course, I am listening to the absolute best sound I have ever had in my house right now, and only using a lowly Koss E/90 amp.


----------



## fordgtlover

I'll throw in another vote for the ECQ-P caps. I have taken to them of late. If I had used them in my original Millett Max, I suspect that I would not have had the need to chase down an alternative to WIMAs for CA8, which led to the use of the K42 caps and then evolved into the use of the Vit Qs.

 Bismar, if you want to sell the Panasonics, I'll buy them off you. I would love to try them in the CA8 position on the Millett Max.


----------



## alwayshungry

post deleted


----------



## tomb

If our experience with the BantamDAC is any indication, then the Roederstein MKP's might have great potential, too. I've bought a set to try with a MiniMAX:
https://www.mouser.com/Search/Produc...-MKP1840422254

 Note that Mouser's printed catalog page is incorrect for these (they show 18mm lead spacing) - their size and lead spacing is identical to the Wima.

 Both the Wima and especially the Roedersteins have prominent mention in Humble Homemade HiFi's cap reviews:
Humble Homemade Hifi
 He actually reviews the MKP1837, but it appears that the MKP1841's at Mouser are the same thing, just in bigger sizes.


----------



## WilCox

Thought I would post a picture of my two MiniMAXs and thank Colin and Tom again for making this possible!


----------



## patton713MW

Beautiful, WilCox! Thanks for posting your amps!


----------



## cetoole

It is more than enough thanks seeing your builds there WilCox. It looks like you have some mighty fine headphones to use with them, hope you enjoy. The only thing I dont like about my newest headphones is they dont work (or even plug into) my own Max.


----------



## GeWa

My silver custom case arrived today 
	

	
	
		
		

		
		
	


	



 Thanks Tom for this incredible service!

 Regards


----------



## onyu

my black and silver case arrived today
 they are beautiful!


----------



## tomb

Wow - very nice! Like Colin said, it looks like you've got some really nice gear to go with them - IC's, too.
	

	
	
		
		

		
		
	


	



  Quote:


  Originally Posted by *WilCox* /img/forum/go_quote.gif 
_Thought I would post a picture of my two MiniMAXs and thank Colin and Tom again for making this possible!




_


----------



## WilCox

Quote:


  Originally Posted by *cetoole* /img/forum/go_quote.gif 
_It is more than enough thanks seeing your builds there WilCox. It looks like you have some mighty fine headphones to use with them, hope you enjoy. The only thing I dont like about my newest headphones is they dont work (or even plug into) my own Max._

 






 Well, maybe its time to design an amp for Jeklins and Stax! 
	

	
	
		
		

		
		
	


	




 There are a few of us out here who would love a good DIY electrostat amp. 

  Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Wow - very nice! Like Colin said, it looks like you've got some really nice gear to go with them - IC's, too.
	

	
	
		
		

		
		
	


	


_

 

The cases are really great! I am most impressed with the performance of these little guys -- transparent, warm and dynamic. My SR-007s haven't had much play time since I got the Minis fired up.


----------



## sandbasser

Quote:


  Originally Posted by *WilCox* /img/forum/go_quote.gif 
_Thought I would post a picture of my two MiniMAXs and thank Colin and Tom again for making this possible!




_

 

Wilcox -

 Beautiful... Where did you get the KNOBs??? They appear from the pictures to match the cases perfectly.


----------



## DaMnEd

Quote:


  Originally Posted by *sandbasser* /img/forum/go_quote.gif 
_Wilcox -

 Beautiful... Where did you get the KNOBs??? They appear from the pictures to match the cases perfectly._

 

99% sure they are from PARTSPIPE, 24x25.

 I have two on my way, one black, one gold (I asked for this mix instead of 2x same color).


----------



## WilCox

Quote:


  Originally Posted by *sandbasser* /img/forum/go_quote.gif 
_Wilcox -

 Beautiful... Where did you get the KNOBs??? They appear from the pictures to match the cases perfectly._

 

As DaMnEd suggests, PartsPipe is probably the best way to go. However, these are Audio Note knobs from Parts Connexion. They are very heavy brass with a plated finish and fairly expensive at $22.95 a pop, but they sure look nice. 
	

	
	
		
		

		
			





http://www.partsconnexion.com/catalo...sandknobs.html

 Also, the Audio Note knobs are made for a 6mm shaft and fit snuggly onto the Alps pot. I think the Parts Pipe knobs are 1/4" which would make them slightly oversize -- not a big deal.


----------



## DaMnEd

That 1%..... I better not buy the lottery, ever. 

 The amps look great 
	

	
	
		
		

		
		
	


	




! And I really like the photo composition, very nice..


----------



## aphexii

Anyone here using the 71-RN65D-F-22.1 (from the BOM) on the RB14?

 Seems to be a bit big for the spot, think I should just jumper it at first and see how it sounds?


----------



## DaMnEd

Quote:


  Originally Posted by *aphexii* /img/forum/go_quote.gif 
_Anyone here using the 71-RN65D-F-22.1 (from the BOM) on the RB14?

 Seems to be a bit big for the spot, think I should just jumper it at first and see how it sounds?_

 

Millett Hybrid MiniMAX Boutique (Scroll down to the "Output Resistors" section)

 Jumper it, if you find you have high-end harshness or tube noise latter on, or maybe want to tweak the gain, buy some Kiwame/Stackpole and install them.


----------



## aphexii

Quote:


  Originally Posted by *DaMnEd* /img/forum/go_quote.gif 
_Millett Hybrid MiniMAX Boutique (Scroll down to the "Output Resistors" section)

 Jumper it, if you find you have high-end harshness or tube noise latter on, or maybe want to tweak the gain, buy some Kiwame/Stackpole and install them._

 

Awesome, thanks!


 On a side note, any recommendations on where I might be able to get some sockets for the LED's?

 I'm not 100% sure on the color combo I want to go for and if I socket them it should make swapping quite a bit easier.


----------



## DaMnEd

I may be wrong but I think the clearance is to little to install sockets, then again... maybe tom can get you a definitive answer.


----------



## tomb

For LED sockets, there's this:
http://www.vcclite.com/TempDocuments...talog_Page.pdf
 Mouser carries them, but only on special order and 400 minimum. They're really designed for large, LED-video screen mfrs. Like DaMnEd said, though, I doubt that there's enough room below the sockets.

 The best way I've found to install/replace the LEDs is to be sure to mount them at the surface height of the tube sockets. This way, their light is directed up through the tubes, anyway. You should be able to melt the solder connection from the bottom side of the board and push them out with a spent lead or similar. Re-installing may be a bit more difficult, but should be possible if you make a solder blob to cover both holes, then melt it while pushing the LED in place from the top side.

 Of course, if you're lucky, you'll have both holes clear. I don't think that's likely, though, and getting some de-soldering braid under the tube socket to clean the holes is also difficult on a built board.


 BTW, the PartsPipe knobs we've been recommending are 6mm shaft size - there is no play on an Alps RK27:

 Black and Silver, 24 x 25mm:
2, 24x25 PREAMP DIY Aluminum Black CD VOLUME TONE KNOB - eBay (item 300284465234 end time Jan-09-09 18:13:09 PST)
PKG2, 24x25 SOLID Aluminum Silver CD VOLUME TONE KNOB - eBay (item 290267386624 end time Jan-10-09 17:07:39 PST)

 Black and Silver, 30 x 22mm:
2,30x22 Aluminum Hi-Fi CD VOLUME TONE CONTROL KNOB,B - eBay (item 290267404632 end time Jan-10-09 18:41:05 PST)
2, 30x22 Aluminum Dimple Hi-Fi CD VOLUME Pointer KNOB - eBay (item 300280385678 end time Jan-10-09 18:41:23 PST)

 I thought perhaps the 30mm were a bit big, but I've seen them used already and they look fine. I always used the 30mm on the regular MAX. Measure the tick marks on your case - it's based on a 1" diameter circle - and decide for yourself, though.


----------



## Beefy

I have both 24x25 and 30x22 knobs from Partspipe in my box of tricks, and tried both on my build. I actually preferred the 30x22 - it is better proportioned IMHO


----------



## tomb

Quote:


  Originally Posted by *Beefy* /img/forum/go_quote.gif 
_I have both 24x25 and 30x22 knobs from Partspipe in my box of tricks, and tried both on my build. I actually preferred the 30x22 - it is better proportioned IMHO 
	

	
	
		
		

		
		
	


	


_

 

I thought that was you.
	

	
	
		
		

		
		
	


	




 I didn't have time to check it, though, after searching for LED sockets.


----------



## cetoole

Quote:


  Originally Posted by *WilCox* /img/forum/go_quote.gif 
_





 Well, maybe its time to design an amp for Jeklins and Stax! 
	

	
	
		
		

		
		
	


	




 There are a few of us out here who would love a good DIY electrostat amp._

 

My Jecklins are dynamic, but my ESP/950 and SR404 do need something nice.


----------



## aphexii

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_For LED sockets, there's this:
http://www.vcclite.com/TempDocuments...talog_Page.pdf
 Mouser carries them, but only on special order and 400 minimum. They're really designed for large, LED-video screen mfrs. Like DaMnEd said, though, I doubt that there's enough room below the sockets.

 The best way I've found to install/replace the LEDs is to be sure to mount them at the surface height of the tube sockets. This way, their light is directed up through the tubes, anyway. You should be able to melt the solder connection from the bottom side of the board and push them out with a spent lead or similar. Re-installing may be a bit more difficult, but should be possible if you make a solder blob to cover both holes, then melt it while pushing the LED in place from the top side.

 Of course, if you're lucky, you'll have both holes clear. I don't think that's likely, though, and getting some de-soldering braid under the tube socket to clean the holes is also difficult on a built board._

 

Thanks for the link. I'm gonna see what I can do to find some other low kinda socket that might work, I'm sure they are hard to find though. With the tube socket in place, I do have a surprisingly good amount of room, so if I can get a lamp socket that basically goes nearly up to the ceramic of the tube socket, sliding the LED in through the center hole shouldn't be too bad as the 3mm fits through without a problem.

 As for the center LED, I think anything would work. 

 Thanks again, i'll keep ya posted if I come across anything.


----------



## ruZZ.il

I'm wondering if a jumper could be made to work.. I'm even sure that they would with a little fiddling..


----------



## aphexii

Actually, I think I may have found a solution - breaking down a dip socket. The led locks in place perfectly and it only adds about 2mm in height off the board.

 As soon as I get this broken down properly, i'll take pics


----------



## aphexii

Sorry for the crappy pics, sold my DSLR a few months back so I'm relegated to my wife's digicam with the worst macro on the face of the earth 
	

	
	
		
		

		
		
	


	




 Still need to double check fitment, but I could also remove the pins themselves and just solder them in directly if this doesn't work.

 EDIT: Looks like fitment is perfect, plenty of room for the socket over top and the led can just slide right in


----------



## Bismar

That's a great idea apexhii, stealing that for my upcoming build


----------



## tomb

Yes - very nice, Aphexii!


----------



## aphexii

Thanks guys! All soldered in and ready to go!


----------



## DaMnEd

Looking great!


----------



## aphexii

When you guys measured HFE with the Harbor Freight DMM, did you have to bend the pins on the PNP Transistors to fit in the meter?

 It seems the pins are bent the opposite way for the 5087 PNP for measurement. I'm also noticing my 5087 measurements (with the pins bent to fit) are showing in the 600-630 range, seems a bit high, no?


----------



## aphexii

Ahh, never mind, they are staggered but need to be in a straight line for both the meter and the board, no worries.

 My 5087 are really all over the board, much more so than the 5088. Out of twenty five 5087 I ended up with;

 520: 2
 522: 1
 528: 4
 540: 2
 555: 3
 578: 1
 588: 2
 600: 2
 605: 2
 609: 2
 615: 1
 620: 2
 627: 1

 In hindsight I really should have bought more as the BOM said, I figured 25 would be enough. 
	

	
	
		
		

		
		
	


	




 Think I can proceed from here or should I order more? I have a decent amount in the 520-540 range (9) and the 600-620 range (9), but is that too great a difference?


----------



## rds

Quote:


 Think I can proceed from here or should I order more? 
 

It depends how anal you want to be. I think the more engineering minded here would say using the closet group of 4 and 6 will be perfectly fine.

 EDIT - I'd suggest the 4 528 and 2 540 for qb2, qb4, and qb6 L/R. Then the 2 605 and 2 609 for qa1, qa2 L/R. Those are actually very close groups.


----------



## lordvader

Well my box of goodies has arrived (thanks Beefy !!!!), but I'm stuck at work, NOT putting this thing together !!!!

 AAAAARRRRGHHH


----------



## Beefy

Quote:


  Originally Posted by *lordvader* /img/forum/go_quote.gif 
_Well my box of goodies has arrived (thanks Beefy !!!!), but I'm stuck at work, NOT putting this thing together !!!!

 AAAAARRRRGHHH_

 

Your excitement will be tempered when you discover that your Black Gates have been replaced by painted candy.

 But then again, maybe you _really_ like candy?


----------



## aphexii

Quote:


  Originally Posted by *rds* /img/forum/go_quote.gif 
_It depends how anal you want to be. I think the more engineering minded here would say using the closet group of 4 and 6 will be perfectly fine.

 EDIT - I'd suggest the 4 528 and 2 540 for qb2, qb4, and qb6 L/R. Then the 2 605 and 2 609 for qa1, qa2 L/R. Those are actually very close groups._

 

I'm quite the antithesis of anal, so I guess i'm good to go, lol, thanks! 
	

	
	
		
		

		
		
	


	




 I assume I wouldn't be able to hear a difference of 12 (between the 528 and 540)

 As for the 5088, I ended up with 6 from 448-455 and 5 right at 475, so I think i'll just use the 448-455 group for QB3/5/7.


----------



## Bismar

Quote:


  Originally Posted by *Beefy* /img/forum/go_quote.gif 
_Your excitement will be tempered when you discover that your Black Gates have been replaced by painted candy.

 But then again, maybe you really like candy?_

 

Speaking of stuff from Beefy, i got my resistors, thanks very much for them !

 Now to wait on stuff from germany, and mouser...


----------



## Beefy

Quote:


  Originally Posted by *Bismar* /img/forum/go_quote.gif 
_Speaking of stuff from Beefy, i got my resistors, thanks very much for them !_

 

The silly bird at the post office forgot to charge me the postage for it, so no worries at all


----------



## tomb

Quote:


  Originally Posted by *aphexii* /img/forum/go_quote.gif 
_I'm quite the antithesis of anal, so I guess i'm good to go, lol, thanks! 
	

	
	
		
		

		
		
	


	




 I assume I wouldn't be able to hear a difference of 12 (between the 528 and 540)

 As for the 5088, I ended up with 6 from 448-455 and 5 right at 475, so I think i'll just use the 448-455 group for QB3/5/7._

 

rds is perfectly correct. I only match them in groups of about 10 HFE. I label cups at increments of 10 - 440, 450, 460, etc. Then 5 below or 5 above go in the same cup. You need to be flexible, though. As you've seen at least with the 5087's, you might get 50 out of 100 that are dead on at 375. No point in calling them 370 or 380 when they're that consistent at 375.

 Again, I do them that close because I'm selling them and do hundreds at a time. However, for the typical DIY build, the idea is that you separate out the 600's from those that are 450, etc., etc.

 Keep in mind that one of the nice things about a diamond buffer is that it tends to self-correct with these differences. However, the CCS's should probably be as close as you can get them. You may not need to make the Left CCS match the Right CCS, though, if you run short on transistors that are closely matched.


----------



## Beefy

I cased up my second Mini Max, so here are the last photos I will post of them - I promise! 
	

	
	
		
		

		
		
	


	




 Black with 24x25mm knob:





 Black with 30x22mm knob - much better IMHO:





 Re-shoot of silver from the same perpective. The vents go the wrong way - oh noes! 
	

	
	
		
		

		
		
	


	








 And a little bit of sibling rivalry to finish:


----------



## Bismar

Nice work! Can't say i like the look of the mismatched knobs though.

 How about some pictures in the dark?


----------



## Beefy

Quote:


  Originally Posted by *Bismar* /img/forum/go_quote.gif 
_Nice work! Can't say i like the look of the mismatched knobs though._

 

Pfffft, all black or all silver is boring 
	

	
	
		
		

		
			





  Quote:


 How about some pictures in the dark? 
 

If I was to take any more pictures of amps in the dark, my lady friend would kick me out of the house


----------



## WilCox

Quote:


  Originally Posted by *Beefy* /img/forum/go_quote.gif 
_I cased up my second Mini Max, so here are the last photos I will post of them - I promise! 
	

	
	
		
		

		
		
	


	


_

 

Very nice! I like the big knobs!


----------



## Bismar

Got a question, for RA8 and RA9, am i to understand it for both 12FK6 and 12FM6 jumpered would be best?

 And for 12AE6 1k & 10k ohms would be the best?


----------



## Beefy

Quote:


  Originally Posted by *Bismar* /img/forum/go_quote.gif 
_Got a question, for RA8 and RA9, am i to understand it for both 12FK6 and 12FM6 jumpered would be best?

 And for 12AE6 1k & 10k ohms would be the best?_

 

Wait, what? 
	

	
	
		
		

		
		
	


	




 RA8 and RA9 are the resistors for the tube CCS. They should be populated regardless of what tube you intend to use.

 Either use 1/10kohm or 1.13/11.3kohm for RA8/RA9 respectively.


----------



## tomb

Quote:


  Originally Posted by *Bismar* /img/forum/go_quote.gif 
_Got a question, for RA8 and RA9, am i to understand it for both 12FK6 and 12FM6 jumpered would be best?

 And for 12AE6 1k & 10k ohms would be the best?_

 

Whoops!! NO WAY!

 It sounds like you may be confusing the CCS resistors with the output resistors. RA8 and RA9 should be populated in every single case. Else, you'll never get the tubes to run. There are some variations in the values of RA8 and RA9 that can be used to give you different ratios, but unless you are thoroughly versed on tube theory and tube performance, I'd advise that you leave these alone. Details about the CCS (Constant Current Supply _for the tubes_) can be found here:
Millett Hybrid MiniMAX CCS

 For best results, and the best parts availability - *use 1K for RA8L/R and 10K for RA9L/R. This is a valid statement for every MAX - MAX, MOSFET-MAX, and MiniMAX.*

 Now that we have that covered
	

	
	
		
		

		
		
	


	




, there is one place on the board where you may want to adjust resistor values versus jumpering them: RB14L/R. These are the output resistors - the last thing in the circuit before the connection to the headphone. Depending on the values you may select, the results may go from full dynamics (jumpered) to less noise (10 to 68ohms?) to gain attenuation (100 to 150ohms).

 Note that there are also two other resistor positions that should be jumpered in every case when building a BJT output buffer (as opposed to a MOSFET buffer, which is not recommended for the MiniMAX): RB8L/R and RB9L/R.

 EDIT: I typed too much (as usual) and Beefy beat me to it.
	

	
	
		
		

		
		
	


	




 Also, as Beefy says, 1.13K and 11.3K are just as good, but not priced as cheap. Plus, going 1K/10K gives you commonality with the other 1K resistors on the board.


----------



## Beefy

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Now that we have that covered
	

	
	
		
		

		
		
	


	




, there is one place on the board where you may want to adjust resistor values versus jumpering them: RB14L/R. These are the output resistors - the last thing in the circuit before the connection to the headphone. Depending on the values you may select, the results may go from full dynamics (jumpered) to less noise (10 to 68ohms?) to gain attenuation (100 to 150ohms)._

 

I gave Bismar some 10R and 33R Kiwame. I was indirectly suggesting he use 10R in order to provide the best balance between his existing Audio Technica AD700 (super sensitive) and his future AKG K702.


----------



## Bismar

Whoops, i was looking at pictures of builds online and got confused by the RB8/9 ones, my bad! 
	

	
	
		
		

		
		
	


	




 Thanks for clearing that up.


----------



## tomb

Quote:


  Originally Posted by *Beefy* /img/forum/go_quote.gif 
_I gave Bismar some 10R and 33R Kiwame. I was indirectly suggesting he use 10R in order to provide the best balance between his existing Audio Technica AD700 (super sensitive) and his future AKG K702._

 

Sounds good to me.
	

	
	
		
		

		
		
	


	




 You've tested those combos more than anyone else, probably.

 We had another user jumper the resistors in the CCS, though, so I thought more emphasis was needed (and you beat me to it, anyway
	

	
	
		
		

		
		
	


	




 ).

 Colin could've given each resistor a different number - that would've perhaps prevented some of this confusion - but I think the lettering/numbering methodology he used is the best in the long run. It keeps things organized from Left to Right and with the primary sections of the amp - Power Supply (RR), Tube Circuit (RA), Buffer (RB), and Delay Relay (RM). This is also pretty much consistent with the other parts, too.


----------



## Beefy

Quote:


  Originally Posted by *Bismar* /img/forum/go_quote.gif 
_Whoops, i was looking at pictures of builds online and got confused by the RB8/9 ones, my bad! 
	

	
	
		
		

		
		
	


	




 Thanks for clearing that up._

 

Go to bed! 2:40AM is far too late/early to be soldering!


----------



## Bismar

Quote:


  Originally Posted by *Beefy* /img/forum/go_quote.gif 
_Go to bed! 2:40AM is far too late/early to be soldering! 
	

	
	
		
		

		
		
	


	


_

 

Haha  Just triple checking that all the parts i have so far are correct.


----------



## gspence2000

It's hard to see the indicator mark on the black knob, so I'd like to paint it. I was thinking of using automotive touch-up paint, and masking it carefully. Anyone have a better idea? Do they make nail polish in opaque white?


----------



## aphexii

Stupid question but why does the hFE change when I'm retesting these transistors? They are all off by 10-15 from where they were yesterday.

 Granted, I guess it doesn't matter since they are all off by the same amount, but i'm curious as to what causes it? Environmental factors?


----------



## slowpogo

I believe those small transistors are sensitive to humidity. Even if you had tested them only two hours later, they probably would have been different already.

 I ended up retesting mine a couple times over an evening and weeded out a few that seemed to drift a lot, but it's probably not necessary to do that.


----------



## tomb

Quote:


  Originally Posted by *aphexii* /img/forum/go_quote.gif 
_Stupid question but why does the hFE change when I'm retesting these transistors? They are all off by 10-15 from where they were yesterday.

 Granted, I guess it doesn't matter since they are all off by the same amount, but i'm curious as to what causes it? Environmental factors?_

 

The battery load of the DMM. The battery peaks when you first turn it on, then stabilizes at some lower level for the bulk of the testing you did previously. Leave it on awhile and then start testing them. They should stabilize at close to what they were before.
	

	
	
		
		

		
		
	


	




 In any event, as you recognized - it's not absolute numbers that really matter, but the differences from each other.

 EDIT: Slowpogo is correct, too, although I think it may be temperature, not humidity - but IMHO, "drift" is not the phenomenon you were asking about - they were all consistent from what you said, just different than before.


----------



## aphexii

DAMN!!!!!!! I dunno what happened, but one of my RB12's snapped off while soldering (think i put a bit too much pressure when trying to align it)

 I have a local electronics store that will probably sell one, but its more than likely an NTE brand (90% of what they well is NTE). Think it would be ok if I swapped both RB12's for NTE models?


----------



## aphexii

Well i just called, I don't think they knew what I was asking for, she said it was $11


----------



## cetoole

Tom is right, transistor beta is very temperature sensitive, and the heat from how you handle them while measuring, as well as how long you measure them will cause changes in the results, because your hand heats the parts and they heat themselves while being tested. Fun times, eh?


----------



## pinkfloyd4ever

Ok so I'm doing some tube rolling between different brands of the same type. Is it a bad idea to do this with the amp on, and just turn down the volume? I'm guessing I already know the answer to this, but just checking


----------



## cetoole

Pinkie, I think you already know the answer to that question*. 
	

	
	
		
		

		
		
	


	




*(Seriously, dont try it)


----------



## linuxworks

Quote:


  Originally Posted by *Beefy* /img/forum/go_quote.gif 
_Your excitement will be tempered when you discover that your Black Gates have been replaced by painted candy.

 But then again, maybe you really like candy?_

 

as long as you run the candy in its linear region, it will be fine.

 (ha!)


----------



## aphexii

Which direction to the trimpots go in? They look backwards for some reason in the pic on the minimax site compared to the silkscreened image...

 Am i just reading the silkscreen wrong?


----------



## rds

Quote:


 Which direction to the trimpots go in? 
 

The trimpots in your image are all correct orientation

 Very nice soldering by the way.


----------



## aphexii

Thanks, one other question... Is the BOM missing a terminal block? It only shows two on the BOM, but there seems to be three in the pic...


----------



## Beefy

Quote:


  Originally Posted by *rds* /img/forum/go_quote.gif 
_Very nice soldering by the way._

 

Oi! That is a pic of my Mini Max, taken from the official site! 
	

	
	
		
		

		
		
	


	




  Quote:


  Originally Posted by *aphexii* /img/forum/go_quote.gif 
_Thanks, one other question... Is the BOM missing a terminal block? It only shows two on the BOM, but there seems to be three in the pic..._

 

You only strictly need two...... the one at the power input, and one immediately next to the volume pot. There is room for a third next to the headphone jack, but is only required if you want a second headphone out or preamp out, or if you want your board to look 100% complete


----------



## aphexii

Quote:


  Originally Posted by *Beefy* /img/forum/go_quote.gif 
_Oi! That is a pic of my Mini Max, taken from the official site! 
	

	
	
		
		

		
		
	


	






 You only strictly need two...... the one at the power input, and one immediately next to the volume pot. There is room for a third next to the headphone jack, but is only required if you want a second headphone out or preamp out, or if you want your board to look 100% complete 
	

	
	
		
		

		
		
	


	


_

 

Awesome thanks! And yes, I wish my soldering was that good


----------



## Beefy

Quote:


  Originally Posted by *aphexii* /img/forum/go_quote.gif 
_Awesome thanks! And yes, I wish my soldering was that good 
	

	
	
		
		

		
		
	


	





_

 

Soldering technique really doesn't come into it much... at least not on the top side of the board 
	

	
	
		
		

		
		
	


	




 It is taking the time to bend the leads well, soldering one leg of the component and adjusting if necessary before you solder the next leg.


----------



## patton713MW

With CR3A-D, is there any functional difference between the axial or disc capacitors listed in the BoM?


----------



## linuxworks

Quote:


  Originally Posted by *Beefy* /img/forum/go_quote.gif 
_Soldering technique really doesn't come into it much... at least not on the top side of the board 
	

	
	
		
		

		
		
	


	




 It is taking the time to bend the leads well, soldering one leg of the component and adjusting if necessary before you solder the next leg._

 

100% this.

 get part anchored and then check for 'prettiness'. its a must-have for SMD but it also adds a 'looks good' touch to thru-hole, as well.

 I never defluxed before a month or two ago but I now do it. that ALSO helps with cosmetics and sometimes with the circuit, itself.


----------



## Beefy

Quote:


  Originally Posted by *patton713MW* /img/forum/go_quote.gif 
_With CR3A-D, is there any functional difference between the axial or disc capacitors listed in the BoM?_

 

No functional difference. Axial is preferred though because it keeps everything low profile at the back there, which is pretty important because of the close proximity of the tip jacks.

 *

 Man, I've gotta turn off instant email notification for this thread 
	

	
	
		
		

		
		
	


	




  Quote:


  Originally Posted by *linuxworks* /img/forum/go_quote.gif 
_I never defluxed before a month or two ago but I now do it. that ALSO helps with cosmetics and sometimes with the circuit, itself._

 

Yeah, essential for the pretty photos


----------



## aphexii

Hrmph. So I soldered in the first tube socket and tried to insert the tube to test it out, I didn't want to push all that hard but it really didn't seem to want to go in....


----------



## tomb

Quote:


  Originally Posted by *aphexii* /img/forum/go_quote.gif 
_Hrmph. So I soldered in the first tube socket and tried to insert the tube to test it out, I didn't want to push all that hard but it really didn't seem to want to go in...._

 

Push a little harder.
	

	
	
		
		

		
			





 These aren't delicate solid state parts. That said, however, it's why we recommend filling all the voids in the tube pin holes with solder. It's also why we state that the center of the board must be supported. There's a heckuva lot of stress put on those sockets and the board when plugging and unplugging tubes.

 If you drilled out the socket pins and epoxied the socket halves to use the tube LED's (you must have with your LED sockets), then they will be extra-tough the first time you use them. You might even want to use an old tube, if you have one. That way, you can apply more force without worrying about the tube (use a cloth to grip the tube).

 When doing the tube LED-thing, it's inevitable that some epoxy gets on the pins on the inside when you glue the socket halves back together. Not to worry - the first couple of times you plug and un-plug a tube, it will break the epoxy off of the pins, but not the ceramic. Things will get a little easier after that.


----------



## aphexii

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Push a little harder.
	

	
	
		
		

		
		
	


	




 These aren't delicate solid state parts. That said, however, it's why we recommend filling all the voids in the tube pin holes with solder. It's also why we state that the center of the board must be supported. There's a heckuva lot of stress put on those sockets and the board when plugging and unplugging tubes.

 If you drilled out the socket pins and epoxied the socket halves to use the tube LED's (you must have with your LED sockets), then they will be extra-tough the first time you use them. You might even want to use an old tube, if you have one. That way, you can apply more force without worrying about the tube (use a cloth to grip the tube).

 When doing the tube LED-thing, it's inevitable that some epoxy gets on the pins on the inside when you glue the socket halves back together. Not to worry - the first couple of times you plug and un-plug a tube, it will break the epoxy off of the pins, but not the ceramic. Things will get a little easier after that.
	

	
	
		
		

		
		
	


	


_

 


 Gotcha. Yea, mine were drilled and epoxied so I'll wait till i have it all ready to go before I start pushing like hell 
	

	
	
		
		

		
		
	


	




 BTW, thanks to all of you guys for answering all my Q's as I've gone along. I really do appreciate it....

 And on that note, another question.

 I'm having a tough time figuring out which way QM1 should go in, any suggestions?


----------



## DaMnEd

Quote:


  Originally Posted by *aphexii* /img/forum/go_quote.gif 
_I'm having a tough time figuring out which way QM1 should go in, any suggestions?_

 

Millett Hybrid MiniMAX Relay-Delay

 Bottom of the page


----------



## aphexii

Quote:


  Originally Posted by *DaMnEd* /img/forum/go_quote.gif 
_Millett Hybrid MiniMAX Relay-Delay

 Bottom of the page 
	

	
	
		
		

		
		
	


	


_

 

You would think, having graduated from law school a few years ago, I would be a wee bit more of an attentive reader 
	

	
	
		
		

		
		
	


	




 Guess not 
	

	
	
		
		

		
		
	


	




 lol, thanks!


----------



## aphexii

Am I nuts (or maybe thinking of another build), or are we supposed to do something to the RK27 before soldering it to the board?


----------



## DaMnEd

I believe you are supposed to trim the metal tab on the pot.


----------



## ruZZ.il

really?


----------



## rds

Quote:


 really? 
 

no


----------



## DaMnEd

I did a little search regarding this since I remember something (was not exactly sure what ) being done to the pot, came up with this: http://www.head-fi.org/forums/f6/new...im#post5207997


----------



## Beefy

You can still do it after you solder the pot in. You just have to make sure you hold the shaft very firmly with pliers so that any vibration/movement from the saw blade doesn't translate straight through to the pot itself.

 I actually trimmed both of my pots after the amp was fully cased.


----------



## tomb

Quote:


  Originally Posted by *Beefy* /img/forum/go_quote.gif 
_You can still do it after you solder the pot in. You just have to make sure you hold the shaft very firmly with pliers so that any vibration/movement from the saw blade doesn't translate straight through to the pot itself.

 I actually trimmed both of my pots after the amp was fully cased._

 

Also, be sure you "baggie" the amp before doing this, so none of those nasty metal shavings/powder get inside and do damage.

 I still prefer the Dremel to do this but you have to be very careful. The problem is that the pot shaft is such a soft metal that the cutting wheel will load up quickly with melted metal on it's surface. When that happens, it will bind and the Dremel's rpms will send it shooting off the shaft in either direction.

 About the locator tab on the pot - rds is correct. That's the little hole to the left of the pot shaft hole on the front plate. It's up to you whether you trim the post on the pot, though, or slightly enlarge the hole in case it doesn't line up perfectly. As noted early on when the cases came in, there will be some variation in how your own soldering has located the headphone jack and pot in terms of the relative heights, frontplate holes vs. pot/jack.


----------



## aphexii

Ahhh, ok, so the only part that needs to be trimmed from the pot is that small metal tab next to the shaft?


----------



## linuxworks

Quote:


  Originally Posted by *Beefy* /img/forum/go_quote.gif 
_
 I actually trimmed both of my pots after the amp was fully cased._

 

(horror)

 are you serious??

 aren't you worried about stress on the part?

 lately I've been taking the pots, brand new, then wrapping some shipping clear plastic tape (just stuff I had lying around the house) around all the parts that would matter except the metal shaft. THEN clamp the shaft in a vise and hacksaw that off. hopefully the pot won't go thru physical stress that much, that way.

 then unwrap the tape and the pot should be good go to. or maybe file or sand the rough edge down before removing the tape.

 seriously - even high end pots are not meant to be 'sawed on' while in place!!


----------



## linuxworks

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Also, be sure you "baggie" the amp before doing this, so none of those nasty metal shavings/powder get inside and do damage._

 

that was my use of clear packing tape 
	

	
	
		
		

		
		
	


	




 after I hacksawed a few pots and noticed that lotsa metal filings were all over the place, I later adopted the practice of wrapping things before sawing or painting or even some kinds of cleaning.

 just like autobody guys that use lots of masking tape when painting, think the same idea here


----------



## aphexii

I'm confused, are you guys trimming the shaft itself, or the little nipple next to it? (Wow, that sounds bad 
	

	
	
		
		

		
		
	


	




)


----------



## aphexii

WOW, can I get the first official 'He's an Idiot' of the thread? 
	

	
	
		
		

		
			





 How can I get in between those front heatsinks to tighten the screw? 
	

	
	
		
		

		
		
	


	




 Somehow tightening it before I soldered on the second one didn't cross my mind...lol


----------



## tomb

Not to worry - that's the advantage to using the socket head screws.
	

	
	
		
		

		
		
	


	




 A pair of needle-nose pliers is easily able to grip the head. Same for the nut on the other one. It's how I do the final tightening every time.

 If you don't have one of those - go back to Harbor Freight - they sell small long-nose, smooth-face needle-nose pliers for $1.99 or less:
Harbor Freight Tools - Quality Tools at the Lowest Prices


 P.S. Lookin' good so far!!


----------



## TimJo

Quote:


  Originally Posted by *linuxworks* /img/forum/go_quote.gif 
_clamp the shaft in a vise and hacksaw that off. hopefully the pot won't go thru physical stress that much, that way._

 

This is the best way to do it, if you have a vise.

 When I was a Manufacturing Engineer where we were having to do this in a production environment, we had jigs set up which held the various pots and motors, always supported by the shaft. This way, all of the force is transmitted through the shaft into the vise or clamp, and no load is transmitted into the bearings. The only difference in the production environment is that we were using a Bridgeport mill as opposed to a hacksaw or Dremel tool. But the idea is the same. With these Alps pots, the shaft material is so soft, I've been able to simply use a hacksaw blade itself just held in my hand, as opposed to a saw.


----------



## linuxworks

Quote:


  Originally Posted by *aphexii* /img/forum/go_quote.gif 
_I'm confused, are you guys trimming the shaft itself, or the little nipple next to it? (Wow, that sounds bad 
	

	
	
		
		

		
		
	


	




)_

 

on another forum, that might be 'sigfile material' (LOL!)


----------



## tomb

Quote:


  Originally Posted by *aphexii* /img/forum/go_quote.gif 
_I'm confused, are you guys trimming the shaft itself, or the little nipple next to it? (Wow, that sounds bad 
	

	
	
		
		

		
		
	


	




)_

 

Go back to the previous page and read the last paragraph in Post #746:
http://www.head-fi.org/forums/5269053-post746.html

 I'd try the fit first, before deciding if you want to cut it. You also need to compare this with the diameter of your knob or you may have an ugly hole showing on your front plate. If you do cut it (least likely, IMHO), the metal is so soft that your flush cutters can nip it off.


----------



## cetoole

Quote:


  Originally Posted by *linuxworks* /img/forum/go_quote.gif 
_(horror)

 are you serious??

 aren't you worried about stress on the part?

 lately I've been taking the pots, brand new, then wrapping some shipping clear plastic tape (just stuff I had lying around the house) around all the parts that would matter except the metal shaft. THEN clamp the shaft in a vise and hacksaw that off. hopefully the pot won't go thru physical stress that much, that way.

 then unwrap the tape and the pot should be good go to. or maybe file or sand the rough edge down before removing the tape.

 seriously - even high end pots are not meant to be 'sawed on' while in place!!_

 

I have to admit, I have trimmed the shaft on every single build I have done after it is completely installed, using a dremel. No problems yet, and it is just easier for me to judge how much I need to remove.


----------



## linuxworks

a dremel puts a lot less stress on the part than a hacksaw 
	

	
	
		
		

		
		
	


	




 I suppose if you are gentle enough with the grinder, the tool does the work instead of the toole...

 (sorry. could not be helped) 
	

	
	
		
		

		
		
	


	




 I know I'd slip and that grinder wheel would hit my case work. I don't trust myself THAT much!


----------



## tomb

Quote:


  Originally Posted by *cetoole* /img/forum/go_quote.gif 
_I have to admit, I have trimmed the shaft on every single build I have done after it is completely installed, using a dremel. No problems yet, and it is just easier for me to judge how much I need to remove._

 

Agreed. As long as you baggie everything up and watch out for loading the cutoff wheel.

 There's very little chance of the Dremel going anywhere near your case. the wheel is perpendicular to the pot shaft. That puts it parallel to the case front. When and if it binds, it's going off in the direction of the wheel spin - nowhere near the case. Still, you can make mince-meat of the shaft if you're not careful.

 EDIT: We're also not talking about a "grinder" per se, it's a cutoff wheel. It slices a 1/32" cut right across the pot shaft just like a knife through a stick of butter (slightly melted butter, at that).


----------



## Beefy

Quote:


  Originally Posted by *linuxworks* /img/forum/go_quote.gif 
_(horror)

 are you serious??

 aren't you worried about stress on the part?_

 

Entirely serious, and not worried. 32TPI hacksaw blade, big set of pliers holding the shaft, and saw slowly letting the blade do the work.


----------



## linuxworks

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_There's very little chance of the Dremel going anywhere near your case._

 

you haven't seen me with power tools. bwahahaha!






  Quote:


 EDIT: We're also not talking about a "grinder" per se, it's a cutoff wheel. It slices a 1/32" cut right across the pot shaft just like a knife through a stick of butter (slightly melted butter, at that). 
 

I have a dremel and I know the sand-discs you guys are talking about. I used to break those regularly and they went flying all over the place. one chip will likely hit MY case and ding it. I know myself too well. I just don't think its, in general, the way that people should trim their pot shafts. once is ok as a 'doh!' moment but not to PLAN to saw it off in-place. just seems wrong to me if you had a heads-up beforehand and knew you'd have to do some sawing before you finished the project.


----------



## cetoole

Linux, I think you are thinking of a different cutoff wheel than I use, the ones which are paper thin and fracture so easily are not recommended, for that exact reason, you are as likely to end up with a chunk of the wheel embedded in your eye or the case. No, the wheels I like are fiberglass reinforced cutoff wheels, which you can see here. These are 2-3x the thickness, and quite sturdy.


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## linuxworks

fiberglass wheels???

 wow. that's new to me!

 you say they don't break off and fly, seeking eyes? 
	

	
	
		
		

		
		
	


	




 that changes a lot!

 are they flexible and do they 'give' while in use?

 this is the stuff I was using, years ago:

http://www.amazon.com/Dremel-409-36P...ef=pd_sim_hi_1

 dangerous nasty things. hated them!!


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## tomb

Real men use the original cut-off wheels and don't break them.
	

	
	
		
		

		
		
	


	




 I change them out when they get to be the diameter of a dime or less.


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## linuxworks

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Real men use the original cut-off wheels and don't break them.
	

	
	
		
		

		
		
	


	




 I change them out when they get to be the diameter of a dime or less.
	

	
	
		
		

		
		
	


	


_

 

otoh, you can get a better feel for how much DIY the person has done by counting the broken brown wheel chips on the workbench table (LOL).

 I tend to break drills, easily, too, even when using my desktop drillpress.

 gimme a break - I just learned to walk and chew gum 2 years ago


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## cetoole

I have not broken a fiberglass wheel, and I have broken the original cutoff wheels plenty of times. I still always wear safety goggles though when doing any of this sort of work, but you accidentally torque the original wheels, you are looking at an imminent warp core breach, and it seems sometimes even when you dont do this. The fiberglass wheels do not give or flex, they are just much, much sturdier.

 Never broken a drill bit that I can remember. I have broken router bits while abusing them in a dremel, and even broken/burned out a dremel.


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## linuxworks

a local store was selling re-tipped or sharpened drill bits. maybe that has something to do with it? 
	

	
	
		
		

		
			





 even when I used brand new proper bits, there was wobble and sometimes a bit of etch would catch the bit and it would snap off. this is with a $99 sears tabletop general purpose press - not a fine precise thing by any means but the only thing common and cheap that sort of does the job.


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## cetoole

I think I have the same drill press as you, the cheapest or second cheapest of the Sears desktop models.


----------



## linuxworks

this is what I use:






 I have a harbor freight (I think it was) x-y table clamped to the base. that came in handy for drilling DIP socket holes. if only I could connect motors to the 2 x-y knobs and have my pc control this...


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## cetoole

Yup, that sure looks like it, except I dont have the X-Y table. PC control would be a fun project though, especially if you added a third axis.


----------



## linuxworks

I bought the xy table for my macro photo work (!) but now its finding a new life on the drillpress.

 even if I could just automate one of the knobs to move in .1 increments for DIP pin holes. THAT would be a neat trick. I could line up the x and have it shoot-off 8 or 10 pins in a row, perfectly spaced.

 its nice to dream..


----------



## aphexii

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Go back to the previous page and read the last paragraph in Post #746:
http://www.head-fi.org/forums/5269053-post746.html

 I'd try the fit first, before deciding if you want to cut it. You also need to compare this with the diameter of your knob or you may have an ugly hole showing on your front plate. If you do cut it (least likely, IMHO), the metal is so soft that your flush cutters can nip it off._

 

lol, even after re-reading that twice, I am still confused. It seems you guys are cutting both the shaft (for reasons I don't fully grasp) and the nipple (possibly - if needed to fit in the case)?


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## cetoole

We cut the shaft so the knob fits nice and close to the body of the case, and the nipple sometimes so the pot fits better in the case.


----------



## aphexii

Quote:


  Originally Posted by *cetoole* /img/forum/go_quote.gif 
_We cut the shaft so the knob fits nice and close to the body of the case, and the nipple sometimes so the pot fits better in the case._

 

ahhhhhhh, ok, gotcha. Thanks guys!


----------



## aphexii

Ok, i've think I've reached the point in my build where I need to order a case 
	

	
	
		
		

		
		
	


	




 Gonna work out the specifics as to exactly which case will work best with the Lexan top, but I'm leaning towards the ET1B6B-B1B2. Need to double check all the figures to make sure i'm getting the right size.


----------



## aphexii

How do I go about wiring up the power button, power socket, RCA sockets? Any tips?


----------



## Beefy

Quote:


  Originally Posted by *aphexii* /img/forum/go_quote.gif 
_How do I go about wiring up the power button, power socket, RCA sockets? Any tips?_

 

Give me a couple of hours, and I will have you covered......


----------



## tomb

Quote:


  Originally Posted by *aphexii* /img/forum/go_quote.gif 
_How do I go about wiring up the power button, power socket, RCA sockets? Any tips?_

 

It's easier to wire them up after you've attached them to the endplate. This is because all you need is a small jumper from one pin on the power jack to one pin on the power switch. Then you run the other wire from the power jack and the other wire from the switch to the terminal block (two wires).

 Be very careful when soldering the switch. The switch has a plastic body (as do many similar switches). Apply heat too long to the tabs and they will melt right through the plastic. The power jack is similar, being plastic, too.

 The RCA jacks are easiest if you solder the tabs of two ground rings together - but you have to make sure you get the spacing right. Then solder the ground wires (two recommended) to the tabs.

 The tip jacks are similar - they're plastic, so be careful of the heat.

 It always helps to tin the ends of the leads, first. Then typically, it only takes a small application of heat and they're soldered.

 EDIT: Sounds like from your posts that you're not going with the custom Lansing case. Take these hints with the understanding that they're made in the context of using the custom case.


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## aphexii

Thanks guys. Any recs on a temporary solution for setting DB and making sure everything is ok? I likely won't have the case ready for about a month or so as all the tools for drilling/etc are at my dads.


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## cetoole

Just use the holes provided and screw standoffs in all of them, so it can sit on a table. Careful you dont short anything.


----------



## Beefy

I promised my group buy participant lordvader that I would do this over the weekend, but time got the better of me. So now is the perfect thing to force me to do it... 
	

	
	
		
		

		
		
	


	




 I basically agree with everything tomb said. I start with the power switch, then the RCAs, then the tip jacks. Before connecting the tip jacks I connect the power and RCA just to make sure that the physical positioning of the wire to the tip jacks is correct before soldering them in.

 I use heatshrink to make the back panel joints more physically sturdy, and to help electrically isolate them. This also makes my 'small jumper' a lot bigger, because with very small lengths of wire the heat from soldering shrinks the heatshrink prematurely.

 One thing you have to be very careful of with the custom case is that the sharp edges on the ventilation slots do not strip your signal wires. Mine have a few small chunks taken out of the Teflon insulation...... not enough to expose bare wire in my builds, but it could be a problem.

 And pics. The signal wiring could probably be a touch shorter...... maybe half a braid less?


----------



## Bismar

Nice, any reason why the test point cables are so long and not runned from the top?


----------



## Beefy

They are long so that if I ever have to separate the back panel from the amp board, I can hopefully do it without cutting the wires.

 They are run underneath for cleanliness. Also, if the amp is ever out of the case, the test points can be measured on the top of the board without having wires in the way.


----------



## aphexii

Hrmph. So i turned the RB12's down till they clicked, quickly turn the amp on and off, my right one shows 15mv then fairly quickly drops to 0 (while the power is still on), my left one shoots to 64mv and holds. Also, LEDC came on the first time, but hasn't come on since. 

 Any ideas?


----------



## tomb

Nice pics, Beefy! More that I can use on the MiniMAX website and do that wiring page that GeoffSpence wanted.



  Quote:


  Originally Posted by *aphexii* /img/forum/go_quote.gif 
_Hrmph. So i turned the RB12's down till they clicked, quickly turn the amp on and off, my right one shows 15mv then fairly quickly drops to 0 (while the power is still on), my left one shoots to 64mv and holds. Also, LEDC came on the first time, but hasn't come on since. 

 Any ideas?_

 

The 15mV sounds like you were reading residual offset while the caps were still charging. Most likely, though, you will read anywhere from 20-40mV because you can't turn the current down to zero in the JFET biasing loop. The 64mV seems too high to me if the trimmers are turned down and as stated, the other should not go down to zero.

 How about the rest of the readings - V+ and Gnd, TA2L and TA2R? By the way, exactly which points were you reading when you measured the 15 and 64mV? Can you give us a more organized list of what you've measured?

 Unfortunately I'm on my way to bed, so I'll have to catch up with this in the morning. Don't worry - we'll figure it out. I halfway expect to look at in the morning and find that someone else has solved it for you.


----------



## aphexii

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Nice pics, Beefy! More that I can use on the MiniMAX website and do that wiring page that GeoffSpence wanted.





 The 15mV sounds like you were reading residual offset while the caps were still charging. Most likely, though, you will read anywhere from 20-40mV because you can't turn the current down to zero in the JFET biasing loop. The 64mV seems too high to me if the trimmers are turned down and as stated, the other should not go down to zero.

 How about the rest of the readings - V+ and Gnd, TA2L and TA2R? By the way, exactly which points were you reading when you measured the 15 and 64mV? Can you give us a more organized list of what you've measured?

 Unfortunately I'm on my way to bed, so I'll have to catch up with this in the morning. Don't worry - we'll figure it out. I halfway expect to look at in the morning and find that someone else has solved it for you.
	

	
	
		
		

		
		
	


	


_

 


 WOW! I'm a freaking IDIOT! I was measuring TB2L and TB1L at the same time, and TB1R and TB1L at the same time, hahahah, man I need to not do that stuff before I go to bed!

 TB1L/R - 12mv
 TB2L/R - 11mv

 V+/GND - 28v
 TA2L/GND - 24v
 TA2R/GNS - 13v


----------



## tomb

Quote:


  Originally Posted by *aphexii* /img/forum/go_quote.gif 
_WOW! I'm a freaking IDIOT! I was measuring TB2L and TB1L at the same time, and TB1R and TB1L at the same time, hahahah, man I need to not do that stuff before I go to bed!

 TB1L/R - 12mv
 TB2L/R - 11mv

 V+/GND - 28v
 TA2L/GND - 24v
 TA2R/GNS - 13v_

 

Except for biasing the Left tube (TA2L/GND), the rest of that looks OK - assuming you have the trimmers turned down on the buffer. We are actually recommending 27V at the power supply (V+/GND), though - just to eke out that last bit of noise reduction. The LM317 has a higher signal-to-noise ratio as the voltage difference becomes greater - up to 5V. So, the more you turn down the voltage (to 27VDC), the quieter the amp will be.


----------



## aphexii

Cool, thanks. 

 Well I got the PS down to 27V, but when I go back and retest the TB1L/R and TB2L/R its now showing 20V (not mV but V). When I pop the meter out of auto ranging, it shows OL for the mV reading.


----------



## aphexii

I'm throughly confused - Just tried testing with my Harbor Freight DMM as well, showing 20v


----------



## tomb

Quote:


  Originally Posted by *aphexii* /img/forum/go_quote.gif 
_I'm throughly confused - Just tried testing with my Harbor Freight DMM as well, showing 20v 
	

	
	
		
		

		
		
	


	


_

 

OK, we're still having to assume a bunch here. Study this page on the MiniMAX website:
MiniMAX Setup and Bias Settings

 At the top is a board photo identifying the test points. At the bottom of the page are tables that tell which points are referenced with which points. Be sure that you have a clear understanding of which two points you're trying to measure.


 For PS Voltage: *V+* with *GND*
 For tube bias: *TA2L/R* with *GND*
 For the buffers: Left Channel -*TB1L with TA2L* _or_ *TB2L with TA2L*
 and: Right Channel - *TB1R with TA2R *_or_ *TB2R with TA2R*.

 It does not matter in the case of the buffers whether you use TB1 or TB2 - just don't use them both at the same time - that's meaningless. There will be slight differences between TB1 or TB2 measured with respect to TA2, but they should be trivial. In fact, the difference in the two test points measured with respect to TA2 actually shows you how well your buffer is balanced in that channel - transistor and resistor matching, IOW. Other than that, I pick the high one and use that to measure bias. That way, I'm always aware of the danger point.

 Now, be sure of what you measure ... then come back to us and tell us specifically which two points you've measured and what you get.


----------



## sandbasser

I'm not sure why the TP leads are "UNDER" the board in user beefy's pix in post 780. Any comments??? Neatness? Keep them away from Hot Tubes??? Otherwise??? Sorry, I"m pretty much of a noobie to DIY.


----------



## tomb

Quote:


  Originally Posted by *sandbasser* /img/forum/go_quote.gif 
_I'm not sure why the TP leads are "UNDER" the board in user beefy's pix in post 780. Any comments??? Neatness? Keep them away from Hot Tubes??? Otherwise??? Sorry, I"m pretty much of a noobie to DIY._

 

All of the above.
	

	
	
		
		

		
		
	


	




 Be aware that things are very tight under the MiniMAX board in the Lansing case. However, running the TipJack leads under the board has been the standard practice since the original MAX (although the tip jacks themselves were actually located under the board level). I also ran them underneath on the early MiniMAX proto, I believe.

 You don't want the stray wires touching a heat sink, the tubes, blocking cooling holes, or worse - getting in the way of a trimmer. We've got plenty of wires above board, though, especially the input wiring to the volume pot terminal block. So, I wouldn't call it a hard-and-fast rule. After all, there are cooling holes to block on the bottom, too.


----------



## aphexii

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_OK, we're still having to assume a bunch here. Study this page on the MiniMAX website:
MiniMAX Setup and Bias Settings

 At the top is a board photo identifying the test points. At the bottom of the page are tables that tell which points are referenced with which points. Be sure that you have a clear understanding of which two points you're trying to measure.


 For PS Voltage: *V+* with *GND*
 For tube bias: *TA2L/R* with *GND*
 For the buffers: Left Channel -*TB1L with TA2L* or *TB2L with TA2L*
 and: Right Channel - *TB1R with TA2R *or *TB2R with TA2R*.

 It does not matter in the case of the buffers whether you use TB1 or TB2 - just don't use them both at the same time - that's meaningless. There will be slight differences between TB1 or TB2 measured with respect to TA2, but they should be trivial. In fact, the difference in the two test points measured with respect to TA2 actually shows you how well your buffer is balanced in that channel - transistor and resistor matching, IOW. Other than that, I pick the high one and use that to measure bias. That way, I'm always aware of the danger point.

 Now, be sure of what you measure ... then come back to us and tell us specifically which two points you've measured and what you get.
	

	
	
		
		

		
		
	


	








_

 


 AHHH! Ok, thats where I got confused. 

 Sorry about that, i'll make sure to specify what i'm measuring from here on out... Thanks for the clarification!


----------



## aphexii

Ok, double checking everything with the correct points, I'm not sure what's going wrong here. 

 For PS Voltage: V+ with GND
*27V*

 For tube bias: TA2L/R with GND
*23.5V* (TA2L)
*3.17V* (TA2R)

 For the buffers: Left Channel TB1L with TA2L
*32mv*

 and: Right Channel - TB1R with TA2R
*0 mv* (it goes to 3mv, then quickly drops to 0, with the power still on)

 Not sure how to best proceed.


----------



## rds




----------



## Beefy

Nice! I'm very envious of your white background for photos


----------



## gspence2000

Quote:


  Originally Posted by *rds* /img/forum/go_quote.gif 
_
















_

 

*awesome* pictures. Great product shots.


----------



## Lil' Knight

Look very neat 
	

	
	
		
		

		
		
	


	



 I'd love to have this on my desk


----------



## linuxworks

Quote:


  Originally Posted by *gspence2000* /img/forum/go_quote.gif 
_*awesome* pictures. Great product shots._

 

seconded - those came out great!


----------



## tomb

Quote:


  Originally Posted by *aphexii* /img/forum/go_quote.gif 
_Ok, double checking everything with the correct points, I'm not sure what's going wrong here. 

 For PS Voltage: V+ with GND
*27V*

 For tube bias: TA2L/R with GND
*23.5V* (TA2L)
*3.17V* (TA2R)

 For the buffers: Left Channel TB1L with TA2L
*32mv*

 and: Right Channel - TB1R with TA2R
*0 mv* (it goes to 3mv, then quickly drops to 0, with the power still on)

 Not sure how to best proceed._

 

OK - it looks like there may be a problem, but let's not panic yet.
	

	
	
		
		

		
		
	


	




 First thing - just for curiosity and to simplify things: those currents on the buffer are not going to cause any damage. So, let's eliminate the tubes as an issue. Neither one are at the bias point - can you turn the trimmers so that they approach the bias point of 13.5V? Proceed carefully, but remember - on a typical 25-turn trimmer, you may have to turn 15-20 turns before you start to see movement. Then the entire adjustment may be in 3 or 4 turns.

 Working ahead here, assuming you can get that done, we probably need a well-detailed pic of your board. There's really only one reason if it won't bias properly - a part is out of place, period.


----------



## tomb

Quote:


  Originally Posted by *rds* /img/forum/go_quote.gif 
_















_

 

Simply gorgeous! Can I use these on the MiniMAX website?


----------



## rds

Quote:


 Can I use these on the MiniMAX website? 
 

Of course, and thanks everyone for the comments.


----------



## aphexii

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_OK - it looks like there may be a problem, but let's not panic yet.
	

	
	
		
		

		
		
	


	




 First thing - just for curiosity and to simplify things: those currents on the buffer are not going to cause any damage. So, let's eliminate the tubes as an issue. Neither one are at the bias point - can you turn the trimmers so that they approach the bias point of 13.5V? Proceed carefully, but remember - on a typical 25-turn trimmer, you may have to turn 15-20 turns before you start to see movement. Then the entire adjustment may be in 3 or 4 turns.

 Working ahead here, assuming you can get that done, we probably need a well-detailed pic of your board. There's really only one reason if it won't bias properly - a part is out of place, period._

 

I was able to get the TA2L/GND down to 13.5v and the TA2R/GND up to 12v, but don't seem to be able to get it to move any higher.

 One thing I did notice while I was biasing, the heatsinks in the right buffer got very hot, the left ones were cool to the touch. The amp was on for about 2-3 minutes. The right is reading now, but something is still amiss.

 TA2L/TB2L - 33mv
 TA2R/TB2R - .9v 
	

	
	
		
		

		
		
	


	




 UPDATE: Here are the pics (I apologize for the poor quality, wish I still had my DSLR) I think it might be the RB12R trimpot, I mounted it backwards at first, desoldered it, then resoldered it but had some trouble getting it through properly. Its in there now, but crooked as you can tell. Would a short there cause my problem? If so, would anything else be damaged?


----------



## linuxworks

Quote:


  Originally Posted by *rds* /img/forum/go_quote.gif 
_Of course, and thanks everyone for the comments._

 

I gotta ask:

 iso 800?

 f22??

 is that right? (that's what exif says.)

 tell me these weren't handheld shots... 
	

	
	
		
		

		
		
	


	




 (edit: you had flash on. so I guess they were handheld? still, iso800? very odd to use such a high iso!)


----------



## rds

Quote:


 I gotta ask:

 iso 800?

 f22??

 is that right? (that's what exif says.)

 tell me these weren't handheld shots...

 (edit: you had flash on. so I guess they were handheld? still, iso800? very odd to use such a high iso!) 
 

The camera was handheld on a stack of books.
 iso800's the best.


----------



## aphexii

Added pics to my post above, please see the update.


----------



## cetoole

Nice pics, QB3R and QB2R are in backwards.


----------



## aphexii

Quote:


  Originally Posted by *cetoole* /img/forum/go_quote.gif 
_Nice pics, QB3R and QB2R are in backwards._

 

Well i'll be damned, how the heck did I miss that?! 
	

	
	
		
		

		
		
	


	




 I guess when you stare at something so long, you don't even notice things like that. Thanks a ton, i'll reverse them now and post back what happens.

 EDIT: ooooo, its flipped from the other side of the board. I think I just layed them all down at once and soldered the row. Darn!


----------



## aphexii

Would having those 2N5087_J18Z transistors in backwards cause any harm to them?


----------



## tomb

Quote:


  Originally Posted by *aphexii* /img/forum/go_quote.gif 
_Would having those 2N5087_J18Z transistors in backwards cause any harm to them?_

 

Both Q2 and Q3 are backwards. That means you have both 2N5087's and 2N5088's that are backwards. The signal transistors don't see much voltage, but on the other hand, I've never seen a TO-92 transistor survive a soldered-in backwards connection. It's best to replace all four of them.


----------



## rds

Here's my method for evening out the case lighting. I used a 900 ohm 1 watt resistor which results in about 10mA to each LED and 0.8 watts total power dissipation, at 27V.
 The little 3 LED configuration is actually very sturdy. Even if it were to be shorted it's no big deal - it would just be 27V through 900 ohms to ground rather than 26V through 900 ohms to ground.
 (no fancy camera today 
	

	
	
		
		

		
		
	


	




 )





 ...the blue is much deeper than it appears in the photo and the case lighting is far more orange. Damn canon powershot.


----------



## Beefy

Bling bling bling! 
	

	
	
		
		

		
			





 I just went with a single LED behind a 10k ohm resistor, pointed at the VREG H/S. Your multi-colour effect is nice though.


----------



## Bismar

Forgive my lack of knowledge in electronics, but if your only getting 10 mA before the LED's and have 3 LED's in parallel wouldn't that result in only 3 mA each? Aren’t these LED's rated at 20 mA?


----------



## rds

Quote:


 Forgive my lack of knowledge in electronics, but if your only getting 10 mA before the LED's and have 3 LED's in parallel wouldn't that result in only 3 mA each? Aren’t these LED's rated at 20 mA? 
 

Yeah, that writing is bizarre. I have no idea why I put the word 'before' there... it doesn't even make grammatical sense. What I meant to write is that each LED gets about 10mA.
 27V/900 ohm results in 30mA. That is divided fairly evenly between 3 of the same LEDs.

 The thing that you need to be careful about is not exceeding the power rating of your resistor. I also left that resistor a mm above the board to minimize thermal contact (not that you really need to).


----------



## Bismar

Cool that makes more sense know, i was afraid that whatever rudimentary knowledge i had just fled out the window


----------



## lordvader

Hey all.
 Quick question about reassembling the tube sockets after removing the center pin.

 Should I put epoxy on both halves (possibly glugging op the holes), or just the bottom part with the gold pins ?


----------



## Beefy

Quote:


  Originally Posted by *lordvader* /img/forum/go_quote.gif 
_Hey all.
 Quick question about reassembling the tube sockets after removing the center pin.

 Should I put epoxy on both halves (possibly glugging op the holes), or just the bottom part with the gold pins ?_

 

I use 5 minute Araldite on mine, only applied to the top half. I mix it up with a toothpick, and apply a dab in every large section between the holes. I keep it held together tightly with thumb and index finger of one hand, and regularly move the pins with my other hand to make sure they don't stick. I've never had anything block the sockets.

 When that is dry, I apply a good dose around the outside. From memory, I threw in a completed tube socket for you?


----------



## lordvader

Yup, there's a completed one there 
	

	
	
		
		

		
		
	


	



 (obviously, I won't take it apart for reference !)

 Thanks, I'll give it a shot on the weekend, and hopefully the thing will be singing !!!!


----------



## aphexii

Thanks a MILLION for all the help everybody! Everything is soldered back in (the correct direction this time) and the numbers are coming out great.

 Yea! Thanks again!


----------



## Bismar

ITS ALIVEEEE !! 
	

	
	
		
		

		
		
	


	



















 2nd ever DIY project, and it works straight off the bat (*cough* whoever said a CMOY is the first step  ) Currently burning it in for an hour at 90 mV then to make it a 110 mV. 
	

	
	
		
		

		
		
	


	




 Have to say, never soldered anything for this long before. The entire thing amp from start to finish took me some 7 and a half hours 0_o, and I'm not even done biasing it yet! How long do most of you guys take?

 Anyway this amp builds a little different then most, just to point out the highlights.

 - Elna Silmic II caps on CA2 and CA7
 - Panasonic Film Caps on CA3 and CA6 (didn't have enough WIMA's)
 - Panasonic Resistors (Just umm a recommendation to anyone using the Digikey bom, these don't fit flush at all on the board, they suffer the same nipple problems as the Vit Q)
 - 0.22uF Vit Q's on CA8
 - Awesome resistor mounting on RA14

 Don't ask me how it sounds like yet  Don't really have anything to compare it against except a Corda 2 Move.

 Also, do i put bigger resistor values in RA14 if i wanted to increase the amount of turns in the ALPS pot to get it to a normal listening volume?

 Finally, thanks to everyone who made this possible for me, just to name a few 
	

	
	
		
		

		
		
	


	



 - tomb - answering all the many many silly questions i had
 - cetoole - as above 
 - Beefy - questions, and inadvertently introducing me to the DIY world by his thread at headphonic

 Now to build a case for it!


----------



## gspence2000

Quote:


  Originally Posted by *Bismar* /img/forum/go_quote.gif 
_ITS ALIVEEEE !! 
	

	
	
		
		

		
		
	


	




ImageShack - Image Hosting :: 90740053ga9.jpg

ImageShack - Image Hosting :: 21564423lz3.jpg

ImageShack - Image Hosting :: 68210778al3.jpg

 2nd ever DIY project, and it works straight off the bat (*cough* whoever said a CMOY is the first step  ) Currently burning it in for an hour at 90 mV then to make it a 110 mV. 
	

	
	
		
		

		
		
	


	




 Have to say, never soldered anything for this long before. The entire thing amp from start to finish took me some 7 and a half hours 0_o, and I'm not even done biasing it yet! How long do most of you guys take?

 Anyway this amp builds a little different then most, just to point out the highlights.

 - Elna Silmic II caps on CA2 and CA7
 - Panasonic Film Caps on CA3 and CA6 (didn't have enough WIMA's)
 - Panasonic Resistors (Just umm a recommendation to anyone using the Digikey bom, these don't fit flush at all on the board, they suffer the same nipple problems as the Vit Q)
 - 0.22uF Vit Q's on CA8
 - Awesome resistor mounting on RA14

 Don't ask me how it sounds like yet  Don't really have anything to compare it against except a Corda 2 Move.

 Also, do i put bigger resistor values in RA14 if i wanted to increase the amount of turns in the ALPS pot to get it to a normal listening volume?

 Finally, thanks to everyone who made this possible for me, just to name a few 
	

	
	
		
		

		
		
	


	



 - tomb - answering all the many many silly questions i had
 - cetoole - as above 
 - Beefy - questions, and inadvertently introducing me to the DIY world by his thread at headphonic_

 

Looks great! It took me a few rounds of photos and questions on the forum to get my build mistakes diagnosed and fixed. 
	

	
	
		
		

		
		
	


	




 What are you going to do for a case with those big VitQ's sticking out?


----------



## Bismar

The Elna's are actually way taller then the Vit Q's and much more then 1", which doesn't matter to me as i am planning to build my own case out of acrylic (verry special acrylic ). 

 I'll post pics when i start on construction of the case.


----------



## gspence2000

Quote:


  Originally Posted by *Bismar* /img/forum/go_quote.gif 
_The Elna's are actually way taller then the Vit Q's and much more then 1", which doesn't matter to me as i am planning to build my own case out of acrylic (verry special acrylic ). 

 I'll post pics when i start on construction of the case._

 

Oh, that's right. I forgot that you were the one making the acrylic case.


----------



## tomb

Quote:


  Originally Posted by *gspence2000* /img/forum/go_quote.gif 
_Looks great! It took me a few rounds of photos and questions on the forum to get my build mistakes diagnosed and fixed. 
	

	
	
		
		

		
		
	


	




 What are you going to do for a case with those big VitQ's sticking out?_

 

It's not just the VitQ's - those Elna Silmics are 35mm tall.
	

	
	
		
		

		
		
	


	




 Nice job, Bismar!

 About the output resistors - many of us find the amp better detailed without anything there but a jumper. However, you have to learn to live with the fact that the volume knob is adjusted in the first 1/4 turn for almost everything but the most inefficient phones. There again, some of us don't have an issue with that - and thankfully, the tracking on the RK27 is so nice that it's not an issue.

 So - just be aware ... as you increase the value of those output resistors, it will start to take the edge off the detail pretty quickly. The Kiwame's are very good at keeping things "sweet", however, so YMMV. Either that - or just buy some Ortho's and you won't have any trouble with too little volume knob travel.
	

	
	
		
		

		
		
	


	











 EDIT: Oops - I was a little late about mentioning the height of the Elna's, I see.


----------



## aphexii

Beautiful job Bismar! If you don't mind me asking, where did you get the 3mm Purple LED's?

 I ran across these for $0.50 - 3mm Purple/UV LED - FrozenCPU.com


----------



## Bismar

Got them from a ebay seller, could be hktaiyuen or someone else. Was about $8 + shipping for 100 of those UV leds. 

 He also sells other LEDs which are of superb quality too.


----------



## Bismar

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_It's not just the VitQ's - those Elna Silmics are 35mm tall.
	

	
	
		
		

		
			





 Nice job, Bismar!

 About the output resistors - many of us find the amp better detailed without anything there but a jumper. However, you have to learn to live with the fact that the volume knob is adjusted in the first 1/4 turn for almost everything but the most inefficient phones. There again, some of us don't have an issue with that - and thankfully, the tracking on the RK27 is so nice that it's not an issue.

 So - just be aware ... as you increase the value of those output resistors, it will start to take the edge off the detail pretty quickly. The Kiwame's are very good at keeping things "sweet", however, so YMMV. Either that - or just buy some Ortho's and you won't have any trouble with too little volume knob travel.
	

	
	
		
		

		
		
	


	











 EDIT: Oops - I was a little late about mentioning the height of the Elna's, I see._

 

Cool thanks, i'll try different combinations and see which suits me best.

 Also how low can the alps pot go before getting distortions?


----------



## tomb

Quote:


  Originally Posted by *Bismar* /img/forum/go_quote.gif 
_Cool thanks, i'll try different combinations and see which suits me best.

 Also how low can the alps pot go before getting distortions?_

 

It won't distort.

 You know, maybe it's time to remind everyone about the ALPS RK27 pot. Here lately, there've been a lot of posts about wanting something better than just the "lowly-old" ALPS - or some suggestions that we're limiting the board design by using the ALPS mounted to the board.
	

	
	
		
		

		
		
	


	




 The fact is, there are few - if any - volume pots that you can install that works better than the ALPS RK27. Tangent did some extensive tests on tracking with stereo volume pots quite awhile ago. The ALPS RK27 stood up better than all the others he tested it against: Notes on Audio Attenuators The only exception might be the DACT, but you can see that maybe it's a little weird at the low end, IMHO.

 Here's a comparison of the log-graphs he produced by measuring tracking on the pots - it's in an Excel file that you can download from him, but I extracted the charts for you:

























 EDIT:Look for the separation between yellow and blue lines at any point in the graphs. That tells you the channel tracking. On the EVJ, it's clearly audible at low positions, for instance. the other tool he used was an approximate curve fit of the measured data - I guess it might be viewed as an approximation of the "controlability" of the volume attenuation. Large steps or irregular curves can result in distateful volume differences at certain positions of the knob-travel. Read his article, though, you may glean a different interpretation than that.


----------



## bperboy

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_It won't distort.

 ...._

 

In other words, listen to TomB and just use the Blue Velvet.. I really doubt you'll hear an improvement with any other part, without spending more than the cost of the entire amp.


----------



## tomb

BTW, thanks to some recommendations by Pete Millett and Nate Maher, plus some additional help from Jim Cross at vacuumtubesinc.com, Beezar.com is now setup to test and match tubes. I also have a new shipment coming in of 12FM6 tubes, so hopefully it will be a long while before we run out of those. 12AE6's are still fairly easy to obtain, with 12FK6's getting harder all the time, IMHO. 12FM6's of course, have been unobtanium for a couple of years, except at Beezar.


----------



## soloz2

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_BTW, thanks to some recommendations by Pete Millett and Nate Maher, plus some additional help from Jim Cross at vacuumtubesinc.com, Beezar.com is now setup to test and match tubes. I also have a new shipment coming in of 12FM6 tubes, so hopefully it will be a long while before we run out of those. 12AE6's are still fairly easy to obtain, with 12FK6's getting harder all the time, IMHO. 12FM6's of course, have been unobtanium for a couple of years, except at Beezar.
	

	
	
		
		

		
		
	


	


_

 

not true... I've got some 12FM6's sitting on my desk right now that I didn't get from beezar. I picked them up probably 8-9 months ago


----------



## tomb

Quote:


  Originally Posted by *soloz2* /img/forum/go_quote.gif 
_not true... I've got some 12FM6's sitting on my desk right now that I didn't get from beezar. I picked them up probably 8-9 months ago 
	

	
	
		
		

		
		
	


	


_

 

Well, yes - like a Grandfather's attic, it's always possible to discover a treasure somewhere ... and they do pop up from time to time. There's one or two on ebay right now ... one or two.


----------



## soloz2

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Well, yes - like a Grandfather's attic, it's always possible to discover a treasure somewhere ... and they do pop up from time to time. There's one or two on ebay right now ... one or two.
	

	
	
		
		

		
		
	


	


_

 

I didn't say I had a treasure trove... just that there were 'some' sitting on my desk. Basically I have a pair. lol



 I haven't had the time or funds to populate my miniMax boards just yet, but I've got a Max that was a fairly interesting build that will be done this weekend. It's going to look stellar as well


----------



## Beefy

Quote:


  Originally Posted by *Bismar* /img/forum/go_quote.gif 
_ITS ALIVEEEE !! 
	

	
	
		
		

		
		
	


	


_

 

That's great Bismar. The first non-Mini Mini Max! 
	

	
	
		
		

		
		
	


	




  Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_About the output resistors - many of us find the amp better detailed without anything there but a jumper. However, you have to learn to live with the fact that the volume knob is adjusted in the first 1/4 turn for almost everything but the most inefficient phones. There again, some of us don't have an issue with that - and thankfully, the tracking on the RK27 is so nice that it's not an issue.

 So - just be aware ... as you increase the value of those output resistors, it will start to take the edge off the detail pretty quickly. The Kiwame's are very good at keeping things "sweet", however, so YMMV. Either that - or just buy some Ortho's and you won't have any trouble with too little volume knob travel.
	

	
	
		
		

		
		
	


	








_

 

As discussed before, Bismar is currently using VERY sensitive ATH-AD700. Jumpered, and tube noise is very distracting even when music is playing, and travel on the volume pot is virtually non-existant...... about half an hour on the clock scale. Even with 10R in my regular Max, you only get about an hour volume play. 22-33R is where noise drops to inaudible levels, and 33R is what I sent to Bismar. In terms of sound quality differences between these resistors and similarly sensitive phones, I could never notice any problems - aside from the negative effects of the noise.

 Looks like they are socketed though. I believe he is also buying some K701 which I also gave him some 10R for, or he can jumper then.


----------



## aphexii

So I finally got the RCA's temporarily hooked up... THIS SOUNDS PHENOMENAL!!!!! Exactly what I was hoping it would sound like, thank you guys so much!!! 
	

	
	
		
		

		
		
	


	










 One quick Q though, for some reason my right channel is much more microphonic than the left. Even very very light taps on the left tube produce microphonics through the right channel. 

 Could this be because its not cased up yet?


----------



## Bismar

Quote:


  Originally Posted by *Beefy* /img/forum/go_quote.gif 
_That's great Bismar. The first non-Mini Mini Max! 
	

	
	
		
		

		
		
	


	






 As discussed before, Bismar is currently using VERY sensitive ATH-AD700. Jumpered, and tube noise is very distracting even when music is playing, and travel on the volume pot is virtually non-existant...... about half an hour on the clock scale. Even with 10R in my regular Max, you only get about an hour volume play. 22-33R is where noise drops to inaudible levels, and 33R is what I sent to Bismar. In terms of sound quality differences between these resistors and similarly sensitive phones, I could never notice any problems - aside from the negative effects of the noise.

 Looks like they are socketed though. I believe he is also buying some K701 which I also gave him some 10R for, or he can jumper then._

 

Yep, i'm kinda waiting for the aus dollar to hit 0.71 US again :/ So should have bought it last week 
	

	
	
		
		

		
		
	


	




 Just out of curiosity, how long is it recommended to run these amps for at max? I notice the tubes get pretty hot.

 Also is there a maximum current that one can draw from LEDC? I plan to have quite a few LEDS in the future in parallel, pretty much as soon as i get a higher wattage resistor.

 Also no one did answer my previous question, how many hours did most of you guys take to build the Minimax.


----------



## aphexii

Quote:


  Originally Posted by *Bismar* /img/forum/go_quote.gif 
_Also no one did answer my previous question, how many hours did most of you guys take to build the Minimax._

 

I was going slow through mine, usually had a Netflix Instant Movie on throughout most of the build. I stopped and started, a few hours here and there over a few days. I'd say I probably put in 8-9 hours total.


----------



## Beefy

Quote:


  Originally Posted by *Bismar* /img/forum/go_quote.gif 
_Just out of curiosity, how long is it recommended to run these amps for at max? I notice the tubes get pretty hot._

 

Heat production shouldn't really change with volume. Class A, baby. But yes, the whole amp DOES get hot. If you've used all recommended parts with are rated to a minimum of 85 degrees Celsius, you should be A-O-K.

 But still, I wouldn't run it on 'Max' just for the sake of it. It can't be good for your phones......

  Quote:


 Also no one did answer my previous question, how many hours did most of you guys take to build the Minimax. 
 

Excluding the tube sockets? Maybe 4-5 hours? Plus casing it all up.


----------



## cetoole

I have phones that the Max cranked to the max is just fine on, and it is too quiet any lower (Pioneer SE-700, some orthos are close). Heck, it wont even run my 'stats at all, even maxed out! My amp doesnt mind at all though, all that happens is I dont get quite enough volume.


----------



## rds

Quote:


 One quick Q though, for some reason my right channel is much more microphonic than the left. Even very very light taps on the left tube produce microphonics through the right channel.

 Could this be because its not cased up yet? 
 

Unfortunately, it means one tube is more microphonic. Casing it won't change that at all.
 The only solution (if you need a solution) is a new tube to replace the one on the right.


----------



## patton713MW

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_BTW, thanks to some recommendations by Pete Millett and Nate Maher, plus some additional help from Jim Cross at vacuumtubesinc.com, Beezar.com is now setup to test and match tubes. I also have a new shipment coming in of 12FM6 tubes, so hopefully it will be a long while before we run out of those. 12AE6's are still fairly easy to obtain, with 12FK6's getting harder all the time, IMHO. 12FM6's of course, have been unobtanium for a couple of years, except at Beezar.
	

	
	
		
		

		
		
	


	


_

 

Would you still recommend that we buy more than one pair of a specific tube if the matching will improve?


----------



## aphexii

Quote:


  Originally Posted by *rds* /img/forum/go_quote.gif 
_Unfortunately, it means one tube is more microphonic. Casing it won't change that at all.
 The only solution (if you need a solution) is a new tube to replace the one on the right._

 

Dang, your right. I just swapped it with the other tube and now the left is super microphonic


----------



## Bismar

So i never did get an answer, is there a maximum current in which i can draw from LEDC? I'm looking to put in quite a few LEDs.


----------



## ruZZ.il

Not much problem in paralleling LEDs there, just make sure the resistor (RA5C) you use is rated accordingly. What type of LEDs do you plan to use, and how many? cause their current adds up, which will result in more heat on the regulator. I doubt a handful would be a problem.. but I cant see how evil your smirk is when you say 'quiet a few'  If you give us some details as to what you're thinking.. we can be.. more precise 
	

	
	
		
		

		
		
	


	




 (accordingly: P=V*I, so you'd look at the LED datasheet and see typical forward voltage(Vf) and current(If), so for the resistor, make sure that for n LEDs, choose a resistor with a power rating larger than P=V*I=[(V+)-Vf]*(n*If). 'If' is also set by R, so make sure to choose R ~ [(V+)-Vf]/(n*If). You may not want LEDs at their typical brightness, so calculate R with a the desired current in mind. This is all limited by how much heat your regulator can dissipate.. again, a handful or 2 will be OK)


----------



## soloz2

Quote:


  Originally Posted by *Bismar* /img/forum/go_quote.gif 
_So i never did get an answer, is there a maximum current in which i can draw from LEDC? I'm looking to put in quite a few LEDs._

 

I've powered an OptiVol and power LED at the same time. You should be fine. Any more than that and I would probably recommend building a small separate psu.


----------



## Bismar

I understand the theory behind the resistors, just not sure if the amp can power say about 6 LED's rated at 20 mA each. So a 120 mA in total pretty much.


----------



## tomb

Quote:


  Originally Posted by *Bismar* /img/forum/go_quote.gif 
_I understand the theory behind the resistors, just not sure if the amp can power say about 6 LED's rated at 20 mA each. So a 120 mA in total pretty much._

 

I'm not certain about soloz's setup - he may be using one of the monster walwarts. If not, then as he says, you may be fine.

 However - IMHO, you'd probably be better off using one of the monster walwarts we recommended for the regular MAX (especially the MOSFET-MAX) - 40 to 50 VA. The MiniMAX probably has something like a 350ma draw at 50ma buffer bias, but the high capacitive load will draw at least half again over that - probably 500-600 ma on startup. That's why we recommend the 750ma walwart in the standard configuration. 

 ruZZ.il is absolutely correct, too - you will need to give careful consideration to the resistor. Even if you size the current at half that amount (what I'd do - 10ma each is very safe and hardly any diminishment in brightness - might let you keep the regular walwart, too), that's what - 40ma at the center resistor - assuming you use 10ma each for the tubes? That's at least a 2W resistor (675 ohms) - but it should probably be more. If you go with 20ma, that's almost a 5W resistor (333 ohms) to handle 80ma (assuming 20ma ea at the tubes). That means an aluminum heat-sinked resistor and there's not enough room on the board for that.


  Quote:


  Originally Posted by *patton713MW* 
_Would you still recommend that we buy more than one pair of a specific tube if the matching will improve?_

 

No - if you choose the matching service, I'd say that's much less important than before. That's one of the reasons I decided to start doing it. Despite my opinions, people still continue to just order a pair of each tube type. That's fine, but I'd rather give them the best scenario if everyone's going to do that.

 Buying multiple tubes is still a consideration because there are differences between tube brands and construction. Distortion may vary and response to bass vs. mids vs. highs. As always, please make a note on the order form at Beezar and I'll try to do the best I can to fulfill the request.
	

	
	
		
		

		
		
	


	






 NOTE: that resistor sizing above is assuming the center resistor only, with 4 LED's at your 10ma (675ohms) or 20ma (333 ohms) sizing. Also, wattage is rated at 2X for safety - a normal safety factor consideration for sizing resistors.


----------



## soloz2

Sorry, I should have specified that I am using a Toroid. I know overkill 
	

	
	
		
		

		
		
	


	




 I can let you know how a wallwart works with a similar setup later tonight or tomorrow when I get the casework done (90% there) and power it up.


----------



## Bismar

Hmm, i'm actually a little confused about how you limit current to LED's. From what i can understand your dumping 27 V into the resistor to allow only 40 mA to pass, which i assume is connected in series to a parallel bank of LED's. But wouldn't this result in a voltage drop of 0 at the LED's?


----------



## rds

Quote:


 But wouldn't this result in a voltage drop of 0 at the LED's? 
 

LEDs generally drop about 0.7V across them. With voltages as high as 27V we usually just ignore that and assume all the voltage drops across the resistor - it doesn't change the current calculation significantly.


----------



## Bismar

I'm a little confused, according to wikipedia Red LEDs start at 2.7 V and go up to 3.5 or so for Ultra Bright Whites or UV's.


----------



## tomb

Quote:


  Originally Posted by *Bismar* /img/forum/go_quote.gif 
_I'm a little confused, according to wikipedia Red LEDs start at 2.7 V and go up to 3.5 or so for Ultra Bright Whites or UV's._

 

Yes and their current varies, too. There are lots of different LED's. However, rds's statement is still correct: it's negligible in the face of 27V and the drop through the resistor.


----------



## Bismar

Mmm, sorry i'm just trying to understand the concepts behind it. If all of the 27 volts is going to the resistor to set a current of 40mA, where would you get say 3.5v to power the LED's? 

 And if you do take that 3.5 volts into account, wouldn't the correct resistor be 588 ohms?


----------



## lordvader

Done and done !

 My minimax and I are rockin' out right now !

 More detailed analysis to follow, I've currently got the default tubes in, which have way too much gain for my k601s. Gonna do a swap a bit later


----------



## Beefy

Quote:


  Originally Posted by *lordvader* /img/forum/go_quote.gif 
_Done and done !

 My minimax and I are rockin' out right now !_

 

Pics, or it didn't happen!


----------



## ruZZ.il

DIODES- Think of them as smart, varying resistors. So in the case here, there is still a voltage divider over 2 resistors, (a resistor and a diode). but what's the resistance of the diode? well, that depends on the voltage thats applied to it. It's usually enough to discuss a simplified model of diodes, and enough in this case. 

 Imagine a power source (V) a resistor (R), and a diode (D) all hooked up in series. 

 So, lets say a negative voltage is applied (V), the resistance of the diode becomes VERY large therefor almost no current can pass through the circuit. As the voltage increases (gets closer to zero), the resistance drops but proportional somehow to the voltage, so still, very little current passes through (usually negligible, and is even considered an open circuit).

 As the voltage becomes positive, the resistance of the diode slowly drops even more, but now the current slowly starts to increase (but still very small), until the voltage is approximately a certain value(depends on the type) ('around' Vf - the forward voltage of a diode). this is the point where the current through the diode actually starts to become significant, and the diode is considered as 'open' but still acts as a resistor!. The resistance of the diode is whatever is required so that the voltage drop on the diode is Vf, and it stays pretty close to Vf as the source voltage increases!. from here on, as the source voltage increases, the current will increase significantly, but the resistance of the diode is still that so that the voltage across it is Vf. The remaining source voltage is dropped on the resistor (R).

 So, lets say a source of 27v is applied to a resistor and a diode. Lets assume the diode is 'open', therefor the voltage across it is Vf (we'll assume Vf=4v, a typical-ish voltage for a LED). With a resistor(R) of 2K ohms, what is the resistance of the diode? We know that the voltage drop on it is 4v, so the voltage drop on the resistor is (27-4)v=23V, therefor the current through the resistor(R) is 23v/2k=11.5mA. The resistance of the diode? well, Rd=Vf/I, so Rd=4v/11.5ma= 347 ohm.

 Lets look at a different scenario:

 V=27v, R=1K, Vf=4v
 so, Vr=(27-4)=23v, Ir=23/1000=23mA. 
 so the resistance of the diode is: Rd=Vf/I=4V/23ma=174 ohm.

 (Now we've seen how the resistor(R) controls the current through the diode 
	

	
	
		
		

		
		
	


	




 )

 So the diode basically varies in whatever way is necessary so that the voltage drop is around Vf.

 Since it behaves this way, we don't actually need to know the resistance of the diode. We can just assume that the voltage drop is around Vf, and the current can be calculated by the remaining voltage divided by the resistor (R) [ so, I= (V-Vf)/R ] 


 The physics behind it all are actually a bit different, its not really about resistance, its all about conductivity, so what controls what isn't quiet like I mentioned above, but behaviorally - more or less. Unless one has actually sat through, or read through, a class on semiconductors, one's unlikely to, and not expected to actually know any of this though.. so no worries if you don't actually get it all (I can't even say that I do either) 


 I hope I've cleared up more than confused 
	

	
	
		
		

		
		
	


	




 Also, a quick browse through the wikipedia entries may help some more, specifically Diode Modeling. even just looking at some pics


----------



## Scy

Here's mine.

 I guess it's a bit silly to do custom panels for a case that is already custom made. But then again, why the hell not.
	

	
	
		
		

		
			




 I wanted to try some custom engravings with the FPE, so I created the line drawing and the custom text engravings in the front panel.
 I also added a source selector and some extra inputs. 
 Turned out pretty good, I think.


----------



## gspence2000

Quote:


  Originally Posted by *Scy* /img/forum/go_quote.gif 
_Here's mine.

 I guess it's a bit silly to do custom panels for a case that is already custom made. But then again, why the hell not.
	

	
	
		
		

		
		
	


	



 I wanted to try some custom engravings with the FPE, so I created the line drawing and the custom text engravings in the front panel.
 I also added a source selector and some extra inputs. 
 Turned out pretty good, I think._

 

Wow! Beautiful work. Very impressive.
	

	
	
		
		

		
		
	


	




 Those extra features must have been a tight fit.


----------



## Scy

Thanks!

 There's quite a nice amount of space back there thanks to the low profile components. With a little work you could almost put a bantam dac in there. 
	

	
	
		
		

		
		
	


	



 I used a small grayhill rotary switch at the front, it still has some space around it but it's quite well stuffed in there.


----------



## Logistic

Nice work! What did you use for the casing of your bantam dac? Is it a Hammond enclosure?


----------



## Scy

Quote:


  Originally Posted by *Logistic* /img/forum/go_quote.gif 
_Nice work! What did you use for the casing of your bantam dac? Is it a Hammond enclosure?_

 

Thanks!
 It's some case from the 1455 series. I just cut it shorter and made the panels from a sheet of acrylic.


----------



## ruZZ.il

wow. nice! 
	

	
	
		
		

		
		
	


	




 snap some shots of the inside when you crack it open next time if you can.. would like to see how it all squeezed in.


----------



## Beefy

Quote:


  Originally Posted by *Scy* /img/forum/go_quote.gif 
_Here's mine.

 I guess it's a bit silly to do custom panels for a case that is already custom made. But then again, why the hell not.
	

	
	
		
		

		
		
	


	


_

 

Looks great! 
	

	
	
		
		

		
		
	


	




 But I too would love to see how you shoe-horned that all in without blocking any ventilation......


----------



## linuxworks

scy, beautiful work, there!

 you have given me some ideas.... 
	

	
	
		
		

		
		
	


	




 also, how much did FPE charge for your front panel?


----------



## WilCox

Quote:


  Originally Posted by *Scy* /img/forum/go_quote.gif 
_Here's mine._

 

Fantastic workmanship! What a great looking amp! Did FPE do the rear panel as well?


----------



## rds

I went with blue case lighting and orange tubes for my MiniMAX which I think suits the blue pcb and red/orange components.
 Also, the color temperatures make sense to me - hot tubes and a cool pcb 
	

	
	
		
		

		
		
	


	









 ...can you tell I like complementary colors?


----------



## tomb

Quote:


  Originally Posted by *Scy* /img/forum/go_quote.gif 
_Here's mine.

 I guess it's a bit silly to do custom panels for a case that is already custom made. But then again, why the hell not.
	

	
	
		
		

		
		
	


	



 I wanted to try some custom engravings with the FPE, so I created the line drawing and the custom text engravings in the front panel.
 I also added a source selector and some extra inputs. 
 Turned out pretty good, I think._

 

Yes, it did!
	

	
	
		
		

		
		
	


	







 Very cool - I love the pics of your BantamDAC with those clear-acrylic panels, too.

  Quote:


  Originally Posted by *rds* /img/forum/go_quote.gif 
_I went with blue case lighting and orange tubes for my MiniMAX which I think suits the blue pcb and red/orange components.
 Also, the color temperatures make sense to me - hot tubes and a cool pcb 
	

	
	
		
		

		
		
	


	





 ...can you tell I like complementary colors?_

 

Beautiful work, as always!


----------



## patton713MW

Quote:


  Originally Posted by *rds* /img/forum/go_quote.gif 
_I went with blue case lighting and orange tubes for my MiniMAX which I think suits the blue pcb and red/orange components.
 Also, the color temperatures make sense to me - hot tubes and a cool pcb 
	

	
	
		
		

		
		
	


	




 ...can you tell I like complementary colors?_

 

I couldn't decide between blue or orange for my future build, I think you just answered my question!


----------



## lordvader

Figured I may finally add a proper impression of the MiniMax, well, as good an impression I may make after listening for 2 days 
	

	
	
		
		

		
		
	


	




 My current "reference" amp is a DoZ headphone amp (Rod Elliots P70). That was my first amp, and is one I know inside out 
	

	
	
		
		

		
		
	


	




 Oh, and I'm using AKG K601s !

 Moving to this, my first tube amp, gave a different sound, almost a new type of sparkle, or air, that I hadn't heard before. I'm currently using the 12FK6 tubes, and the mids and highs are sublime, though perhaps verging on bright (acoustic sounds AMAZING !!!!). At the moment though, I am running the simplest signal path, meaning no output resistors, and the output cap (BG type N) is unbypassed (my DoZ also as unbypassed BG caps on the output).

 I'll let it play on a bit longer before I start tweaking, but it is a truly engrossing experience. The plan was to use the MiniMAX at work, while working, but I've found myself just sitting there listening to music, not getting much done at all !

 Bass isn't as strong as my DoZ, but that's to be expected with the tube choice (the 12AE6s had way too much gain), but it still kicks and has impact, and spent this entire afternoon listening to Liquid Tension Experiment (which has awesome drums, bass, guitar, etc !).

 Sorry, no pics, only have a film camera !


----------



## tomb

Quote:


  Originally Posted by *lordvader* /img/forum/go_quote.gif 
_Figured I may finally add a proper impression of the MiniMax, well, as good an impression I may make after listening for 2 days 
	

	
	
		
		

		
		
	


	




 My current "reference" amp is a DoZ headphone amp (Rod Elliots P70). That was my first amp, and is one I know inside out 
	

	
	
		
		

		
		
	


	




 Oh, and I'm using AKG K601s !

 Moving to this, my first tube amp, gave a different sound, almost a new type of sparkle, or air, that I hadn't heard before. I'm currently using the 12FK6 tubes, and the mids and highs are sublime, though perhaps verging on bright (acoustic sounds AMAZING !!!!). At the moment though, I am running the simplest signal path, meaning no output resistors, and the output cap (BG type N) is unbypassed (my DoZ also as unbypassed BG caps on the output).

 I'll let it play on a bit longer before I start tweaking, but it is a truly engrossing experience. The plan was to use the MiniMAX at work, while working, but I've found myself just sitting there listening to music, not getting much done at all !

 Bass isn't as strong as my DoZ, but that's to be expected with the tube choice (the 12AE6s had way too much gain), but it still kicks and has impact, and spent this entire afternoon listening to Liquid Tension Experiment (which has awesome drums, bass, guitar, etc !).

 Sorry, no pics, only have a film camera !_

 

Cool! Glad you're enjoying it!

 That bass should come in a week or two - that's one of the traits of the Black Gates. Detail is fantastic, but they take forever to break-in - bass is the last thing to come in.


----------



## Daveze

Phew, I've only just started using my Blackgate + 3422/1359 combo and was feeling a tad disheartened at the lack of bass (compared to my thoroughly burnt in Muse + 3422/1359 combo). I've just wired up the test points, so tomorrow I'll start some tube rolling.


----------



## tomb

Quote:


  Originally Posted by *Daveze* /img/forum/go_quote.gif 
_Phew, I've only just started using my Blackgate + 3422/1359 combo and was feeling a tad disheartened at the lack of bass (compared to my thoroughly burnt in Muse + 3422/1359 combo). I've just wired up the test points, so tomorrow I'll start some tube rolling._

 

Yep. The Black Gates will never equal the bass slam of the Muse ES, but they will get pretty close ... eventually.


----------



## Beefy

lordvader and Daveze: I'm so glad to know that my kits ended up good hands! 
	

	
	
		
		

		
		
	


	



 [size=xx-small](and that I didn't fudge them up for either of you!)[/size]

  Quote:


  Originally Posted by *lordvader* /img/forum/go_quote.gif 
_and the output cap (BG type N) is *unbypassed* (my DoZ also as unbypassed BG caps on the output)._

 

*Gasp* Blasphemy! You've got some VitQ's in your package...... pop those in lickedy split! 
	

	
	
		
		

		
		
	


	




  Quote:


  Originally Posted by *Daveze* /img/forum/go_quote.gif 
_so tomorrow I'll start some tube rolling._

 

I just bought up this blokes last 6 12FK6 tubes. Normally I wouldn't be bothered, but sitting at home writing grants is *boring*......


----------



## aphexii

Are these specs for the recommended Lansing enclosure correct?

 Style = Single Tube (D)
 Width = 5.53" (T)
 Height = 1.52" (1)
 Length = 6.00" (60)
 Color = Clear Anodize (A)

 06 (Extended Metal Panel - 4 Hole)
 A1 - Clear Anodize Pan Head Silver (3/8")


----------



## tomb

Quote:


  Originally Posted by *aphexii* /img/forum/go_quote.gif 
_Are these specs for the recommended Lansing enclosure correct?

 Style = Single Tube (D)
 Width = 5.53" (T)
 Height = 1.52" (1)
 Length = 6.00" (60)
 Color = Clear Anodize (A)

 06 (Extended Metal Panel - 4 Hole)
 A1 - Clear Anodize Pan Head Silver (3/8")_

 

Yes.


----------



## aphexii

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Yes._

 

Thanks!

 I'm looking at the *ET1K6X-K1B2*. I think I have it right, gonna call them to confirm.

 Style = Removable Top (E)
 Width = 5.53" (T)
 Height = 1.52" (1)
 Color = Black Anodize (K)
 Length = 6.00" (6)
 Top = None (X)
 Bezel = Black Anodize (K1) - ?? Not Sure ??
 Screws = Anodize Pan Head B Black - 3/8" - (B2)


----------



## omegamajor

I just recently finished building my miniMAX and have one small issue with it. There is a low level hum, almost inaudible. It becomes louder when I put my hand over the tubes. It goes away, however, if I touch any part of the case (including the volume knob and audio inputs, since they are all connected). This hum occurs even without audio inputs connected and no matter where the volume knob is at. The case is definitely grounded to the DC ground plane through the mount in the middle of the board. I have also grounded the potentiometer.

 I only just noticed this now and I'm sitting at work. I don't recall noticing it at home but I will check again tonight. It could just be that we have something extremely noisy around here that I'm not aware of. I should also note that I do not hear the hum on my SS, which I have here as well.

 Ideas or suggestions? Thanks!


----------



## adamus

I'd put money on it being a grounding issue.


----------



## omegamajor

Quote:


  Originally Posted by *adamus* /img/forum/go_quote.gif 
_I'd put money on it being a grounding issue._

 

I suspect so as well, yet I cannot think of where/what it could be. I built mine just like most other people have, so the electrical contact points to the case are the same (volume pot, audio inputs and standoff screw). I can't help but think that the RCA jacks should be isolated from the case, but so many others have built them using the ones from tomb that I doubt those as the cause.

 As a test I connected a wire to earth ground (from a power outlet) and touched the case but it had no effect.

 I'm hoping it's just a noise issue in the office somewhere.


----------



## tomb

Quote:


  Originally Posted by *omegamajor* /img/forum/go_quote.gif 
_I suspect so as well, yet I cannot think of where/what it could be. I built mine just like most other people have, so the electrical contact points to the case are the same (volume pot, audio inputs and standoff screw). I can't help but think that the RCA jacks should be isolated from the case, but so many others have built them using the ones from tomb that I doubt those as the cause.

 As a test I connected a wire to earth ground (from a power outlet) and touched the case but it had no effect.

 I'm hoping it's just a noise issue in the office somewhere._

 

Actually, one of the best ground connections occurs at the RCA jacks. There are other places as well, though - and you mentioned the center standoff. However, keep in mind that all of the MiniMAX cases were anodized _after_ machining. So, unless you scrape away the finish where the jacks or a screw contact the holes, the amp is not grounded to the case.

 I'd suspect the pot first, but you state that you installed the ground wire to the board.

 There are other possibilities, though:
 1. Bad tubes - see if things change if you switch,
 2. Bad connections at the tubes - bent pins, bad socket (maybe glue in the wrong place if you drilled them out and glued them back together, or
 3. A metal power input jack or the power input jack (or power switch) somehow making a connection to the case. The power input is AC - it's possible that the case will pick up hum if the power input jack (and switch) are not completely isolated.
 4. Bad soldering on the center pin of the input terminal block - I've had this happen on a couple of prototypes that were "well used." The ground plane is on the top of the MiniMAX board, but we solder underneath. If for some reason the solder did not make contact through the hole plating or wick sufficiently to the top side, then the ground connection is not there. In which case, you can try to solder a jumper from the terminal block center pin to a convenient ground spot on the board somewhere and see if that helps things.


 EDIT: As you say, it could be the location. I've never had an issue with a MAX or MiniMAX board and ground-related hum, even without the case (but I have had the issue with an uncased SSMH). The ground plane is fairly extensive on the MAX/MiniMAX. It's usually a bad connection somewhere, not grounding the pot, or bad tubes.


----------



## omegamajor

I'm beginning to suspect a tube. I pulled the case off and can still hear the hum, perhaps a little louder than with the case on. It goes away whenever I touch anything that is connected to DC ground (tops of electrolytics, headphone ground, volume ground, etc). This implies that my body is changing the capacitance of the ground plane in some manner. I have also disconnected the inputs as a test and the hum remained.

 tomb: To address your third and fourth points, I am using a plastic power jack, not a metal one, and I made sure that all my ground solder joints are good.

 Does turning the amp on without any tubes installed provide any useful information in determining the tubes as a source of hum? What about just one tube installed? I tried both no tubes and with one tube or the other and heard nothing. The hum is only present with both tubes installed.


----------



## digger945

What kinda PS are you using major?


----------



## omegamajor

Quote:


  Originally Posted by *digger945* /img/forum/go_quote.gif 
_What kinda PS are you using major?_

 

The one that tomb sells on his website.


----------



## lordvader

Quote:


  Originally Posted by *Beefy* /img/forum/go_quote.gif 
_*Gasp* Blasphemy! You've got some VitQ's in your package...... pop those in lickedy split! 
	

	
	
		
		

		
		
	


	


_

 

The plan was/is to enjoy the amp without those for a while, and then chuck them in !
 Every DIY project I've done, I've gone all out, so haven't "enjoyed" the upgrade process !


----------



## omegamajor

So I got home and tried my other tubes. It's still there, but just barely. I plugged it into my BantamDAC and viola! The hum was gone. I guess the DAC alters the ground capacitance enough that it takes care of the hum. At this point I'm not going to worry about it. It's barely audible if it is there and the DAC has grounded it out.


----------



## cetoole

Sounds like a ground loop to me. What source had you been using before, and how was it powered?


----------



## omegamajor

Quote:


  Originally Posted by *cetoole* /img/forum/go_quote.gif 
_Sounds like a ground loop to me. What source had you been using before, and how was it powered?_

 

It's not a ground loop issue with the source. The hum exists even if both inputs are grounded. It's gotta be something internal to the amp. I still suspect the tubes because the hum was a bit more subdued with my other pair, but still present. Also, waving my hand over the tubes caused it to get louder. My intuition is telling me it's something with either the filament(s) or the fact that the diode portion of the tubes is grounded. Why are the diodes grounded anyway?


----------



## Daveze

Where is your amp located? I was getting some strange huming and odd sounds while it was close to my desktop computer. Moved it to the other side of the desk and she's dead quiet.


----------



## omegamajor

Quote:


  Originally Posted by *Daveze* /img/forum/go_quote.gif 
_Where is your amp located? I was getting some strange huming and odd sounds while it was close to my desktop computer. Moved it to the other side of the desk and she's dead quiet._

 

Thanks for the suggestion but I've already eliminated that as a possibility.


----------



## tomb

Quote:


  Originally Posted by *omegamajor* /img/forum/go_quote.gif 
_It's not a ground loop issue with the source. The hum exists even if both inputs are grounded. It's gotta be something internal to the amp. I still suspect the tubes because the hum was a bit more subdued with my other pair, but still present. Also, waving my hand over the tubes caused it to get louder. My intuition is telling me it's something with either the filament(s) or the fact that the diode portion of the tubes is grounded. Why are the diodes grounded anyway?_

 

The diodes have been grounded ever since the original Audio Xpress magazine article for the Millett Hybrid - that's Pete Millett's original design. One side of the diodes is the tube cathode. If they weren't tied off to ground, they might be creating a competing voltage potential and interfering with the tube bias (I think 
	

	
	
		
		

		
			





 ).

 In any event, I sort of doubt that both sets of tubes are causing hum - it's just not that common. Often it may only be one tube - not two sets of pairs. If the sockets are not completey grounded, or there is a bad connection between some of the tube pins and the socket pins, that might cause what you're noticing, perhaps. Although, I haven't heard of this happening except in the case of a single tube being bad and causing hum.

 What are the readings on your MiniMAX? Voltage setting, tube and buffer bias, etc?

 How did you run your input wiring?

 Maybe the walwart is bad?

 Got some pics? Maybe someone will spot something.


----------



## rds

Has anyone place with the CCS for 12FM6 tubes? I have socketed ra8 and ra9 for this purpose.
 From the datasheet it looks like the 12FM6 is better suited to a CCS in the 90mA range (rather than stock 58mA).

 Also, have people been pushing BJT bias with the custom cases? It seems these would be able to ventilate for bias in excess of 60mA. I haven't tried it myself yet. Right now I'm using 55mA (or 120mV).


----------



## omegamajor

Quote:


 If the sockets are not completey grounded, or there is a bad connection between some of the tube pins and the socket pins, that might cause what you're noticing, perhaps. 
 

The pins on the tubes appear to be making good contact, especially given how many times I've inserted and removed them.

  Quote:


 What are the readings on your MiniMAX? Voltage setting, tube and buffer bias, etc? 
 

The power supply is right at 27.0VDC. Tubes are at ~13.5V (still drifting around a tiny bit). Buffers are at 100mV and are perfectly balanced (thanks to your prematched parts).

  Quote:


 How did you run your input wiring? 
 

I did a 4 wire braid and ran it along the very outside edge right next to the case wall. Even so, the hum still exists with the input wiring disconnected from the screw terminals.

  Quote:


 Maybe the walwart is bad? 
 

It's possible I suppose.

  Quote:


 Got some pics? Maybe someone will spot something. 
 

I'll see about getting some pics up later. I have looked over everything multiple times and it all looks just fine.

 The loudness of the hum changed when I was swapping tubes around, which says to me that something isn't right with the tubes or they induce something else upon the circuit.

 I'm almost tempted to start snipping some pins off my second set of tubes so that I can start tracking down where this may be originating from. The first thing I would want to do is to connect only the heaters of the tubes and nothing else.


----------



## cetoole

Quote:


  Originally Posted by *rds* /img/forum/go_quote.gif 
_Has anyone place with the CCS for 12FM6 tubes? I have socketed ra8 and ra9 for this purpose.
 From the datasheet it looks like the 12FM6 is better suited to a CCS in the 90mA range (rather than stock 58mA)._

 

Methinks you are about 2 orders of magnitude too high, should be more like 0.9mA. Havnt played with it though.


----------



## Beefy

Quote:


  Originally Posted by *rds* /img/forum/go_quote.gif 
_Also, have people been pushing BJT bias with the custom cases? It seems these would be able to ventilate for bias in excess of 60mA. I haven't tried it myself yet. Right now I'm using 55mA (or 120mV)._

 

I tested the internal temperature of my Mini Max the other day..... ambient temp in excess of 50 degrees celsius, and Vreg H/S up to 65.

 Not quite as hot as my regular Max, but I wouldn't crank it higher than 50mA if it were me.


----------



## Daveze

Thats a fairly impressive ambient though. One of mine is currently on work rig duty, currently doing 50mA but I might take in the temp probes and see how much I can comfortably get out of it.


----------



## cetoole

I think beefy means 50°C inside the case, not inside his room. At least I hope, as we dont want our beefy well done.


----------



## rds

Quote:


 Methinks you are about 2 orders of magnitude too high, should be more like 0.9mA. Havnt played with it though. 
 

hah, yeah. 90mA might take it out of the linear region


----------



## Daveze

Quote:


  Originally Posted by *cetoole* /img/forum/go_quote.gif 
_I think beefy means 50°C inside the case, not inside his room. At least I hope, as we dont want our beefy well done._

 

Touche. Engage brain then type...


----------



## Beefy

Quote:


  Originally Posted by *cetoole* /img/forum/go_quote.gif 
_I think beefy means 50°C inside the case, not inside his room. At least I hope, as we dont want our beefy well done._

 

HEH, yes, that is right. 50-55 degrees 'floating' inside the case depending on proximity to heatsinks. Buffer heatsinks are 55-60 degrees, VREG 60-65. Tubes are hotter than this, but I can't get a reliable reading with the probe I have.

 Room temperature was approx 25 degrees...... so roughly a 30-40 degree delta at 28V supply and 50mA quiescent current.


----------



## soloz2

Quote:


  Originally Posted by *Bismar* /img/forum/go_quote.gif 
_So i never did get an answer, is there a maximum current in which i can draw from LEDC? I'm looking to put in quite a few LEDs._

 

 Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_I'm not certain about soloz's setup - he may be using one of the monster walwarts. If not, then as he says, you may be fine.

 However - IMHO, you'd probably be better off using one of the monster walwarts we recommended for the regular MAX (especially the MOSFET-MAX) - 40 to 50 VA. The MiniMAX probably has something like a 350ma draw at 50ma buffer bias, but the high capacitive load will draw at least half again over that - probably 500-600 ma on startup. That's why we recommend the 750ma walwart in the standard configuration. _

 

 Quote:


  Originally Posted by *soloz2* /img/forum/go_quote.gif 
_Sorry, I should have specified that I am using a Toroid. I know overkill 
	

	
	
		
		

		
		
	


	




 I can let you know how a wallwart works with a similar setup later tonight or tomorrow when I get the casework done (90% there) and power it up._

 

Just an update.

 In my personal max I have a toroid so powering the extras is a non-issue.

 However, I can say with that a 1a wallwart will power a regular Max with BJC's biased to 95mv and an Optivol. There is also LEDs under the tubes and a power LED.

 I've only used a 750ma wallwart on one Max build so far, the rest have all been 1000ma. The cost increase is negligible. The current Max I probably would have gone higher still, but the owner plans to switch to a toroid in the near future anyway.


----------



## tomb

Quote:


  Originally Posted by *Beefy* /img/forum/go_quote.gif 
_HEH, yes, that is right. 50-55 degrees 'floating' inside the case depending on proximity to heatsinks. Buffer heatsinks are 55-60 degrees, VREG 60-65. Tubes are hotter than this, but I can't get a reliable reading with the probe I have.

 Room temperature was approx 25 degrees...... so roughly a 30-40 degree delta at 28V supply and 50mA quiescent current._

 

Last time I measured it (in the original prototype), it seemed the plastic on the transistors and the LM317 were 50-60deg.C and 55-65deg.C, respectively. So, I'm kind of surprised that the ambient in the case is that high. That said, it's still only about 130 deg.F., which can be the temperature of someone's attic on a hot day (or car seats in a parked car). So, the components can withstand much more.

 I think the real limiting factor is the CA2 and CA7 caps. Being "boutique" electrolytics, I think they are the most susceptible to high temps. However, even the ES's and Black Gate NX's are rated for 85 deg.C. constant temp and the temps are well away from that.


----------



## Beefy

My Vreg has always been hotter than that...... the wallwarts I buy put out over 25VAC loaded, and up to 34VDC pre-regulator which is a fair bit of heat loss on Vreg. That is why I bumped my regulated voltages to 28VDC.

 And yeah, CA2 an CA7 were always the biggest concern for me. I just checked the VitQ specs, and the 96P are apparently good to 125 which is good.


----------



## aphexii

AHHH! I can't decide. About to order my case from Lansing and I don't know if I want Silver or Black.

 If I went with silver, I could do the clear lexan 1/16" top which is easily sourced. While the black (i think) would look better with a smoked lexan top, but 1/16" thick smoked lexan/acrylic seems to be quite hard to find. The black clase with a perfectly clear top might look a little odd.


----------



## tomb

Quote:


  Originally Posted by *aphexii* /img/forum/go_quote.gif 
_AHHH! I can't decide. About to order my case from Lansing and I don't know if I want Silver or Black.

 If I went with silver, I could do the clear lexan 1/16" top which is easily sourced. While the black (i think) would look better with a smoked lexan top, but 1/16" thick smoked lexan/acrylic seems to be quite hard to find. The black clase with a perfectly clear top might look a little odd._

 

Amb does all of his amps in black with a clear top. I'm not so sure it looks bad.
	

	
	
		
		

		
			





 Here's his revMH Millett Hybrid:


----------



## aphexii

Ooooo. I hadn't seen that before. SEXY! 

 Thanks!


----------



## tomb

I finally came up with a standard Center Standoff Kit for the MiniMAX Beezar/Lansing custom-machined cases:

 They consist of two metric M3x0.5 screws - one 5mm long and one 4mm long, a 4mm aluminum hex standoff with the same threads, and washers. I'm suggesting that a lock washer and flat washer be used with the longer screw on top of the PCB. This is the screw that will be inaccessible when the case is buttoned up, so hopefully the lock washer will keep it locked. The 4mm long screw will then be used with a single flat washer on the bottom of the case.

 These are available on Beezar now, but will be supplied with all Beezar/Lansing cases in the future (along with the rubber feet and case screws).


----------



## THE_SOURCE41

Hello,

 So I just ordered the Parts to start a MiniMAX and I was just wondering where I can get an already machined case for it?

 Sam


----------



## THE_SOURCE41

This is also my first DIY amp so I was just wondering what type of Solder do you think works best for building an amp?

 Sam


----------



## rds

Quote:


 This is also my first DIY amp so I was just wondering what type of Solder do you think works best for building an amp? 
 

All the questions you have have probably been answered (many times).
 As far as I know, machined cases are not available at the moment. But you're best checking with Tomb on that one.

http://www.head-fi.org/forums/f6/iro...oolkit-404999/


----------



## aphexii

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_I finally came up with a standard Center Standoff Kit for the MiniMAX Beezar/Lansing custom-machined cases:

 They consist of two metric M3x0.5 screws - one 5mm long and one 4mm long, a 4mm aluminum hex standoff with the same threads, and washers. I'm suggesting that a lock washer and flat washer be used with the longer screw on top of the PCB. This is the screw that will be inaccessible when the case is buttoned up, so hopefully the lock washer will keep it locked. The 4mm long screw will then be used with a single flat washer on the bottom of the case.

 These are available on Beezar now, but will be supplied with all Beezar/Lansing cases in the future (along with the rubber feet and case screws)._

 

Sweet, Thanks!


----------



## Scy

Quote:


  Originally Posted by *ruZZ.il* /img/forum/go_quote.gif 
_wow. nice! 
	

	
	
		
		

		
		
	


	




 snap some shots of the inside when you crack it open next time if you can.. would like to see how it all squeezed in._

 

 Quote:


  Originally Posted by *Beefy* /img/forum/go_quote.gif 
_Looks great! 
	

	
	
		
		

		
		
	


	




 But I too would love to see how you shoe-horned that all in without blocking any ventilation...... 
	

	
	
		
		

		
		
	


	


_

 

I removed the front panel to work on it a bit. Here's a couple pictures, don't know if they will tell you much. 
 Putting the front panel back on is a bit of a struggle, hopefully I don't have to do that too often. The back panel is a piece of cake.
 Can't say about the ventilation, maybe I better just not to worry about it 
	

	
	
		
		

		
		
	


	




 ...for too much at least 
	

	
	
		
		

		
		
	


	









 And one without the case.



  Quote:


  Originally Posted by *linuxworks* /img/forum/go_quote.gif 
_scy, beautiful work, there!

 you have given me some ideas.... 
	

	
	
		
		

		
		
	


	




 also, how much did FPE charge for your front panel?_

 

Thanks, glad to hear that. 
 The front panel was about 40€ (including the 19% tax). A bit pricey perhaps, but then again not having the ability to create such thing myself, it's not too bad. 
 +the quality is great and the production time short.
  Quote:


  Originally Posted by *WilCox* /img/forum/go_quote.gif 
_Fantastic workmanship! What a great looking amp! Did FPE do the rear panel as well?_

 

Yes, it's from pfe. It's made from thinner material and has no color fill-ins and such, so the cost is about the half of the front panel.


----------



## Beefy

Good stuff


----------



## adn6244

Hi All,

 I noticed CA7 recommeded is alsways 35V but 1000uf is ranging from 16-25V depending on the brands selected.

 CA2: Nichicon Muse ES, 1000uf 16V, Black Gate NX 1000uf 25V
 CA7: Nichicon Muse ES, 470uf 35V, Black Gate NX 680uf 35V 

 I found the following caps in the local store :
 1. nichicon fine gold 1000uf 25V and 470uf 25V
 2. nichicon muse fx 1000uf 25V and Silmic 470uf 35V

 Can I used either one of the above combination on CA2 & CA7? Or if I need to split them to get the better results, please help.

 appreciate your advice please.


----------



## Beefy

Quote:


  Originally Posted by *adn6244* /img/forum/go_quote.gif 
_1. nichicon fine gold 1000uf 25V and 470uf 25V
 2. nichicon muse fx 1000uf 25V and Silmic 470uf 35V

 Can I used either one of the above combination on CA2 & CA7?_

 

For CA7, 25V is probably too low rated. I believe that the 35V Silmic are too tall for the default case. Not sure about the options for CA2.

 But if you are having trouble finding caps, why not just get Muse ES from Beezar?


----------



## adn6244

thanks beefy. i only need CA2 & CA7 components and ordering only these 2 parts will be expensive in terms of shipping. But credit should go to beezar...the way tomb packaged the components for shippinng is amazing!!

 can you elaborate why rating is low but the recommended blackgate for CA2 is also 25V. don't get me wrong, I am still confused how to calculate the voltage range in the circuit design. 

 the silmic i found is within the 1" height so there is no problem in terms of physical fit.


----------



## Beefy

Quote:


  Originally Posted by *adn6244* /img/forum/go_quote.gif 
_can you elaborate why rating is low but the recommended blackgate for CA2 is also 25V. don't get me wrong, I am still confused how to calculate the voltage range in the circuit design._

 

Alright, lets just go back to square one, and confirm exactly what the minimum specs are that we need for both positions, from the official BOM.
 CA2: 1000µF, 16V
 CA7: 470µF, 35V

 So 25V BlackGates are fine at CA2, but not CA7. From your selections:
 Nichicon Fine Gold 1000µF 25V are OK for CA2, but not CA7.
 Nichicon Fine Gold 470µF 25V are no good for either position.
 Nichicon Muse FX 1000µF 25V are OK for CA2, but not CA7. The FX have been replaced by 'FW' series, and the Fine Gold are apparently better anyway, so avoid these.

  Quote:


 the silmic i found is within the 1" height so there is no problem in terms of physical fit. 
 

Right you are. My mistake. These would probably be good for CA7.


----------



## tomb

CA2 is the cathode bias capacitor on the tube. It shunts the circuit from the backside of the tube and is not even in the circuit unless the music wave exceeds the bias differential relative to the supply voltage. As such, it sees very little voltage - much less than 10V, for instance. When you see some caps selected at 25V, it's because that's the most readily available cap in that brand and at the capacity needed (1000uf). As with any capacitor, there's no penalty for selecting a higher voltage rating - except a higher price and a larger cap (larger may not fit).

 CA7 is directly in the circuit - every bit of the signal passes through that cap. The two CA7 caps split the supply voltage and sit at 13.5VDC. However, good practice says we size the caps to take the full potential voltage of the circuit in case of failure. If one of the CA7 caps fail, the other CA7 will see the full supply voltage on the other side - 27V. Hence, we rate those capacitors at 35V (25V is too small).


----------



## aphexii

So I snagged a killer deal on three NOS 12FM6 tubes on eBay the other day, and they just arrived. I figured it wouldn't be bad to have some backups, and at $5 shipped for all three, I just couldn't pass it up.

 How would I go about matching the tubes up? (or seeing if they match at all). Not exactly sure what I'm looking for I suppose.

 Any help would be greatly appreciated!


----------



## Beefy

Quote:


  Originally Posted by *Beefy* /img/forum/go_quote.gif 
_I just bought up this blokes last 6 12FK6 tubes. Normally I wouldn't be bothered, but sitting at home writing grants is *boring*...... 
	

	
	
		
		

		
			



_

 

I finally managed to pick these tubes up from the post office today.









 I've never seen photos of top getters on 12FK6 tubes before, only 12AE6? But here are six of them......

 The three in the first pic are all Philips MiniWatt (USA), the second pic are Mullard and AVW and claim to be made in Australia. The date on one of the Mullard boxes is 15/10/64...... always amazes me that these things are over a decade older than I am


----------



## tomb

Quote:


  Originally Posted by *aphexii* /img/forum/go_quote.gif 
_So I snagged a killer deal on three NOS 12FM6 tubes on eBay the other day, and they just arrived. I figured it wouldn't be bad to have some backups, and at $5 shipped for all three, I just couldn't pass it up.

 How would I go about matching the tubes up? (or seeing if they match at all). Not exactly sure what I'm looking for I suppose.

 Any help would be greatly appreciated!_

 

A tube tester.

 Short of that, you can try to match the construction at least. There's no guarantee that they're actually Tung-Sol, but usually the tubes of the manufacturers that made them were theirs, but not always. Balancing the tubes is easy with the bias, but if they are mis-matched on output, you'll notice that one ear in your headphones seems more dynamic than the other. You can still try to match them by ear that way.

 EDIT: I've listened to these so long now, my ears have begun to easily tell the difference in mismatched tubes. It's seldom that the mistmatch is great, though - the differences are most often very subtle. Every once in awhile, though, the differences are so great that mismatch is easily heard.


----------



## tomb

Quote:


  Originally Posted by *Beefy* /img/forum/go_quote.gif 
_I finally managed to pick these tubes up from the post office today.









 I've never seen photos of top getters on 12FK6 tubes before, only 12AE6? But here are six of them......

 The three in the first pic are all Philips MiniWatt (USA), the second pic are Mullard and AVW and claim to be made in Australia. The date on one of the Mullard boxes is 15/10/64...... always amazes me that these things are over a decade older than I am 
	

	
	
		
		

		
		
	


	


_

 

Wow - you've made a real find with the ones on the right. I've never seen getters and top spacers such as the ones you have on the right. I'd guess that they may really be made in Australia, perhaps. Another mfr to add to the big four, perhaps.
	

	
	
		
		

		
		
	


	




 The ones on the left are GE's with top halo getters and "J" plates.
	

	
	
		
		

		
		
	


	




 The white etching and dots on the glass are tell-tale. Also, no one else made "J" plates like that - flat with a lipped edge all around. Top halo getters are also rare with 12FK6's - only GE's did that, AFAIK.


----------



## Beefy

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Wow - you've made a real find with the ones on the right. I've never seen getters and top spacers such as the ones you have on the right. I'd guess that they may really be made in Australia, perhaps. Another mfr to add to the big four, perhaps.
	

	
	
		
		

		
		
	


	


_

 

FWIW, all three of these have the 12FK6 in a 'flattened octagon' like the webpage says is common for RCA tubes.


----------



## tomb

Quote:


  Originally Posted by *Beefy* /img/forum/go_quote.gif 
_FWIW, all three of these have the 12FK6 in a 'flattened octagon' like the webpage says is common for RCA tubes._

 

That's true - RCA's always are marked with an etched, squished octagon, but it doesn't quite look like an RCA octagon. Theirs is thinner than that, but I'd have to look and compare them up close to tell for sure.

 One thing's for certain - RCA never used top spacers like that. I've never seen any like that on any Millett tubes - or the getters. Those getters are giant rings - never seen any like that anywhere near that size.

 The plates, the grid housing, and the glass look typical, though, but those weren't limited to one mfr. Maybe RCA sold many of the components, but assembly was done by someone else in Australia.


----------



## Beefy

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Maybe RCA sold many of the components, but assembly was done by someone else in Australia.
	

	
	
		
		

		
		
	


	


_

 

In any case, nothing blew up on any of them in initial testing


----------



## bperboy

Okay, long story short, my minimax got yanked off my desk.. tube broken. 
	

	
	
		
		

		
		
	


	




 I've replaced the 12AE6As with a pair of 12FK6s, but I'm having some voltage reading issues. Here's the rundown.

 PSU: now reads about 14v, down from 27v

 TubeL: -2V at minimum bias. (always stays negative)
 TubeR: 0V at minimum bias (biases up correctly)

 BufferL: about -2V (turned off immediately, but maybe transistors are fried?)
 BufferR: 90mV (biases relatively normally)

 Looks like my left channel is the problem. Anything specific I should be testing for?


----------



## tomb

Quote:


  Originally Posted by *bperboy* /img/forum/go_quote.gif 
_Okay, long story short, my minimax got yanked off my desk.. tube broken. 
	

	
	
		
		

		
		
	


	




 I've replaced the 12AE6As with a pair of 12FK6s, but I'm having some voltage reading issues. Here's the rundown.

 PSU: now reads about 14v, down from 27v

 TubeL: -2V at minimum bias. (always stays negative)
 TubeR: 0V at minimum bias (biases up correctly)

 BufferL: about -2V (turned off immediately, but maybe transistors are fried?)
 BufferR: 90mV (biases relatively normally)

 Looks like my left channel is the problem. Anything specific I should be testing for?_

 

Sorry to hear about it. Obviously, something else got broken. I'd go over the entire board and collection of parts very carefully. Also look for traces on the bottom of the board that may have separated from their pads.


----------



## bperboy

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Sorry to hear about it. Obviously, something else got broken. I'd go over the entire board and collection of parts very carefully. Also look for traces on the bottom of the board that may have separated from their pads._

 

Remind me not to do anything requiring intelligence in the morning. The ground test point is in the middle. Not the right. D'oh.


----------



## pinkfloyd4ever

Quote:


  Originally Posted by *Beefy* /img/forum/go_quote.gif 
_I've never seen photos of top getters on 12FK6 tubes before, only 12AE6? But here are six of them......_

 

FWIW I've actually been listening to my Max with a pair of top getter 12FK6's for pretty much all of the year or so since I finished my max...guess I got lucky. They're RCA branded but made by GE. They came in a fairly new looking box, with their newer modern RCA logo as opposed to the older circle logo. The tabs of the box tops have a "(4-69)" printed on them, so I assume that's the manufacture date. I got them in from vacuumtubes.net in October '07 if anyone cares (not that I have any clue if they have any more like em)

 Of course, I've never seen any like those on the bottom (hell I've only really seen the 20 or so Millett tubes in my own stash in person.) If even tom has never seen any like em, they MUST be rare. He's been collecting Millett tubes since before yours in the Mullard boxes were even made!


----------



## adn6244

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_CA2 is the cathode bias capacitor on the tube. It shunts the circuit from the backside of the tube and is not even in the circuit unless the music wave exceeds the bias differential relative to the supply voltage. As such, it sees very little voltage - much less than 10V, for instance. When you see some caps selected at 25V, it's because that's the most readily available cap in that brand and at the capacity needed (1000uf). As with any capacitor, there's no penalty for selecting a higher voltage rating - except a higher price and a larger cap (larger may not fit).

 CA7 is directly in the circuit - every bit of the signal passes through that cap. The two CA7 caps split the supply voltage and sit at 13.5VDC. However, good practice says we size the caps to take the full potential voltage of the circuit in case of failure. If one of the CA7 caps fail, the other CA7 will see the full supply voltage on the other side - 27V. Hence, we rate those capacitors at 35V (25V is too small)._

 

Thanks tomb. I made a mistake the silmic is only 25v so I guess I need to place another order with beezar really soon!


----------



## tomb

Quote:


  Originally Posted by *adn6244* /img/forum/go_quote.gif 
_Thanks tomb. I made a mistake the silmic is only 25v so I guess I need to place another order with beezar really soon!_

 

OK - I was afraid of that, because I've looked at Silmic's before to try them on the MiniMAX, but they just don't make anything that will fit.

 There are a couple of guys on e-bay who sell the Cerafines at 470uf 35V. Those are 25mm tall if you're interested - kind of expensive if you include shipping ($3-$5 per cap w/o shipping if memory serves), but still less than Black Gates.


 EDIT: Well, shoot - he must've sold them all. There's some 50V on ebay, but those are way too big. Oh well - guess they had to run out of them at some point.


----------



## n_maher

Test fit of panels and initial setup complete. Other than 1 RTFM moment during construction things went without a hitch. Great job on the board and case guys!


----------



## Lil' Knight

Very nice, Nate!

 I wonder when the 1.2 board comes out? I'm thinking of getting one to use with my SE phones, so tempting


----------



## tomb

Great job, Nate! Glad to see everything turned out OK in the end.


----------



## tomb

Quote:


  Originally Posted by *Lil' Knight* /img/forum/go_quote.gif 
_Very nice, Nate!

 I wonder when the 1.2 board comes out? I'm thinking of getting one to use with my SE phones, so tempting 
	

	
	
		
		

		
		
	


	


_

 

I'm afraid we waited too long and now cetoole's schoolwork is getting the way. I'm sure he'll finish it up first chance he gets.

 BTW, the regular MAX will always be more flexible, but the MiniMAX makes a nicer package. Except for the flexibility of parts, the only real difference is that flexibility (1-1/2" heat sinks) will allow the regular MAX to use MOSFETs. Except for that, the MiniMAX gives up nothing and adds the cool packaging.


----------



## oneplustwo

Anyone have any suggestions for a volume knob? I just realized there wasn't one on the BOM so I'm looking for suggestions. Or is there a DIY knob I can try to make on my own? (My CMoy had a friggin' $5 knob which seems kinda ridiculous given the cost of the rest of the parts.)


----------



## tomb

Quote:


  Originally Posted by *oneplustwo* /img/forum/go_quote.gif 
_Anyone have any suggestions for a volume knob? I just realized there wasn't one on the BOM so I'm looking for suggestions._

 

Really? It's right there on the BOM under "MISC:"
 "Volume Knob, e-bay Partspipe" 

 Originally, I had suggested the 24 x 25mm knob, but everyone seems to think the 30mm x 22mm knob used on the regular MAX looks best.

 Whichever, they're usually about $9.95 for two, shipping included. I think the case deserves at least this much.


----------



## GeWa

My MiniMax board was laying here finished for quit some time now and yesterday I finally had the time (and courage) to fire it up. I first dialed in the power supply voltage and after that the tube bias, no problems so far. I than started to try to set the bias for the DB's and because my meter stayed at 0,0V, after several turns, I became a little worried. After powering down the whole thing and checking the board I came to the conclusion that I soldered my transistors in the wrong location. 
	

	
	
		
		

		
		
	


	



 Now I have to desolder them and also the heatsinks to get deicent access to the screws. I HATE THIS PART OF DIY.

 Regards


----------



## tomb

Quote:


  Originally Posted by *GeWa* /img/forum/go_quote.gif 
_My MiniMax board was laying here finished for quit some time now and yesterday I finally had the time (and courage) to fire it up. I first dialed in the power supply voltage and after that the tube bias, no problems so far. I than started to try to set the bias for the DB's and because my meter stayed at 0,0V, after several turns, I became a little worried. After powering down the whole thing and checking the board I came to the conclusion that I soldered my transistors in the wrong location. 
	

	
	
		
		

		
		
	


	



 Now I have to desolder them and also the heatsinks to get deicent access to the screws. I HATE THIS PART OF DIY.

 Regards_

 

Goodness! I would try some needlenose pliers before I considered un-soldering the heat sinks. If you go back with some socket head screws, it's easy to tighten them by holding on the head sideways with some needlenose pliers.

 You may find it's easier to destruct the board than it is to remove soldered-on heat sinks!

 n_maher just a recent similar experience with his, and I guarantee he didn't remove the heat sinks.


----------



## cetoole

Actually, removing the heatsinks isnt too bad. I have done it a few times, on a Max once and on a M3. Of course, I cut the transistor legs first, then wiggled it out.


----------



## ruZZ.il

As Tom suggests, you probably don't need to remove those heat-sinks.

 There shouldn't be too much problem getting the screws open. May be a little tricky depending on how you installed them, but I'm pretty sure you'll be able to get at it.

 Once you've got those screws out, though, I suggest looping something through the transistors hole, like some wire, or string. Put a *little slack on it while you melt a large blob of solder on the solder points, and get your iron at a good angle to get contact with all 3 pads at the same time. The transistor should elegantly slide out if done right. Don't pull too tight, or you may mess up some pads. 

 Getting them back in is a little trickier. If you have some solder wick, or a pump, and manage to clean up the holes nicely, it'll be a breeze. Just get the transistor in the right way, screw it in nice and tight, then solder... if you cant clean the holes too well, you'll be doing a somewhat reverse process of getting them out, which.. isn't as sympathetic.


----------



## pinkfloyd4ever

Quote:


  Originally Posted by *ruZZ.il* /img/forum/go_quote.gif 
_Once you've got those screws out, though, I suggest looping something through the transistors hole, like some wire, or string. Put a *little slack on it while you melt a large blob of solder on the solder points, and get your iron at a good angle to get contact with all 3 pads at the same time. The transistor should elegantly slide out if done right. Don't pull too tight, or you may mess up some pads._

 

 oooo ya a great trick!
 I've heard of this before but kinda had forgotten about it. Glad it came up now, as I'm about to remove the whole buffer of one channel on a standard Max. Anyone got any adaptations of this that work well with TO-92 packages? I was thinking of looping some fishing line around twice (once on each side of the middle lead), but i dunno if the line would melt thru before I could get the the solder joints of all 3 leads melted....hmmm


----------



## cetoole

Not necessarily the right way to do things, but what I do is flood all the pins with solder so I can heat them all at the same time, then pull while heating. For the TO92 parts, I would just cut them off and replace. Removing pins one at a time is very easy, and I feel more comfortable using new parts, especially when they cost what, $0.03 each?


----------



## GeWa

Thanks for the suggestions and making it look easy. I removed the screws with a pair of needle pliers without to much problems. I never tighten those things to hard anyway. I than succeeded in removing the transistors with a good blob of solder on the tip trying to heat up the three pins at once. Bit of a hassle and a blister on my fingertip but I got them all of without ruining my board. Transistors didn't survived the surgery though!
 Will leave the rest for tomorrow 
	

	
	
		
		

		
		
	


	




 Regards


----------



## ruZZ.il

Quote:


  Originally Posted by *pinkfloyd4ever* /img/forum/go_quote.gif 
_ Anyone got any adaptations of this that work well with TO-92 packages?_

 

Works well with just a little wire.. I use that solid core telephone wire.. have loads of it. scooby doo we used to call it, I still do.

 Colin: I'd just snip them too when I have loads lying around.. any by now, I usually do 
	

	
	
		
		

		
		
	


	




 But I've been at times when I don't, and getting specific ones to here sometimes takes ages...


 GeWa: Glad you're making progress. You sure they're busted ? They're pretty resilient buggers.. sometimes..


----------



## tomb

Quote:


  Originally Posted by *ruZZ.il* /img/forum/go_quote.gif 
_<snip>

 GeWa: Glad you're making progress. You sure they're busted ? They're pretty resilient buggers.. sometimes.._

 

Agreed. Those output transistors can often survive being soldered in backwards. I'd stick them in the HFE socket of a DMM. If they register OK, then put 'em back in.


----------



## aphexii

So as it turns out, there is a local Acrylic shop very close to home who happens to stock the exact 1/16" acrylic I need for the top panel of my ET1 case. 

 I went ahead and converted the PDF of the custom design from the MiniMAX site into an Adobe Illustrator file for him and he's gonna work on fabbing the tops for me sometime in the next few days. He said he should be able to do all the custom vents as well. 

 I did have to make some slight adjustments to the file as the original top is 5.528" wide and the ET1 top needs to be 5.295" wide so it can slide into the case. I adjusted all the measurements and everything seems to be spot on. 

 Really exited to see how this comes out!


----------



## aphexii

Here are some pics of the tubes I picked up on eBay, anyone able to tell how closely matched up they are?


----------



## Beefy

The construction looks virtually identical to me. Other than that... unless you have a tube tester, use your ears!


----------



## slowpogo

Maybe you knew this already, but just FYI, those are actually GE tubes, not Tung Sol (because of the "frost etched" dots and text).


----------



## tomb

Yep. Slowpogo is correct - those are definitely GE tubes.

 The plates are certainly identical. However, all I can see of the getters is a side-square getter on the middle one - can't see the others - but there's no indication that they would be any different. The tubes appear to be identical in every other respect.


----------



## tomb

I don't know if this is OK by the rules, but since I'm not making a penny from it (well, maybe a couple$ for the PCB), I'll post it anyway. Besides, it's a Head-Fi sponsor. Whiplash Audio is selling the MiniMAX:
Mini Millett Max Tube Amp


----------



## Beefy

The MOT mafia will be knocking on your door in no time


----------



## tomb

At the request of many builders, a small supply of MiniMAX cases (very limited) are available now at Beezar. More will be made if these are taken, but the lead time is about a month, if memory serves.


----------



## Bismar

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_At the request of many builders, a small supply of MiniMAX cases (very limited) are available now at Beezar. More will be made if these are taken, but the lead time is about a month, if memory serves.
	

	
	
		
		

		
		
	


	


_

 

Excellent value as always tomb! It's amazing how you can get them made so cheap. If only my not so Mini Minimax as Beefy calls it will fit into one of those.... Ahh o well, slowly making progress with my own enclosure.

 Just out of curiosity though why can't the cases be combined with other beezar products? Would make shipping a hell of a lot cheaper for international peeps.


----------



## tomb

Quote:


  Originally Posted by *Bismar* /img/forum/go_quote.gif 
_Excellent value as always tomb! It's amazing how you can get them made so cheap. If only my not so Mini Minimax as Beefy calls it will fit into one of those.... Ahh o well, slowly making progress with my own enclosure.

 Just out of curiosity though why can't the cases be combined with other beezar products? Would make shipping a hell of a lot cheaper for international peeps._

 

Not really. In many cases, someone can order a "regular" order with 1st Class Int'l shipping plus the Priority Mail of the MiniMAX case for cheaper than the combined order using Priority Mail. I've sold several of the cases with combined shipping and the charges and/or refunds are ridiculously small, combined with a ridiculously difficult calculation.

 MiniMAX cases will be shipped separately via Priority Mail or Priority Mail International, with insurance and delivery confirmation.

*NOTE: There is no issue with combined shipping of the cases themselves (multiple cases). I hope I didn't create that confusion.*


----------



## tomb

deleted


----------



## aphexii

Hmmm, so i'm working on my front panel from FPE and trying to decide if I should stick with the 1.5mm thick to keep it as thin as the stock panel, or if I should bump up the thickness to 3-4mm.


----------



## MrMajestic2

Quote:


  Originally Posted by *aphexii* /img/forum/go_quote.gif 
_Hmmm, so i'm working on my front panel from FPE and trying to decide if I should stick with the 1.5mm thick to keep it as thin as the stock panel, or if I should bump up the thickness to 3-4mm._

 

I have used 4mm on all my FPE front panels and it looks much nicer than 1.5mm.


----------



## aphexii

Quote:


  Originally Posted by *MrMajestic2* /img/forum/go_quote.gif 
_I have used 4mm on all my FPE front panels and it looks much nicer than 1.5mm._

 

After pouring over as many FPE pics as I can find, I think I have to agree.

 Thanks!


----------



## tomb

Sorry, but I've had to change the policy back to my original basis: _MiniMAX cases are shipped separately via Priority Mail._ PM/e-mail me if you want an explanation, but I've tried the other way with a few folks and it's not going to work.


----------



## aphexii

Acrylic shop hit a slight delay, should have the acrylic top panel in hand by tomorrow afternoon. I'm still working out the 4mm thick front panel for the black ET1 lansing case.

 I'm torn between going for a raw aluminum finish with no-fill text (silver on silver) or black anodized with black fill (black on black), with a matching partspipe knob. I like things to be subtle. Not sure which would look better with the acrylic top and black case. I was pretty sure I was set on black anodized, but since the anodizing is done before cutting the edges all come out silver. 

 I think I'll snap some pics once I have the acrylic panel in hand and make some mock ups in PS.


----------



## aphexii

Acrylic Panel is here! Even at 1/16" its a tiny tiny bit too thick for the ET1 case, so I had to shave down the edges a bit to slide it in. Need to do a tiny bit more work on it, but its very close to a perfect fit now.


----------



## patton713MW

Just to throw it out there, the screwdriver method to pull the tube socket pin worked great for me. My sockets have the thick bottom. I inserted a fine flat-head screwdriver into the notch, and carefully twisting it was able to open the gap to ~1mm. Then I used a larger flat-head, and lifted the pin from the bottom of socket. It worked great!


----------



## patton713MW

Quote:


  Originally Posted by *aphexii* /img/forum/go_quote.gif 
_Acrylic Panel is here! Even at 1/16" its a tiny tiny bit too thick for the ET1 case, so I had to shave down the edges a bit to slide it in. Need to do a tiny bit more work on it, but its very close to a perfect fit now._

 

Very nice!


----------



## linuxworks

acrylic case was GREAT!

 very well executed.


----------



## aphexii

Thanks guys! Working on the photoshop mockups to see if it would look better with a raw aluminum (silver) faceplate or black anodized.


----------



## tomb

Very nice, aphexii!!


----------



## oneplustwo

loving mine...





 I built it using the "can't miss" boutique bits but it still needs a knob. but now I'm thinking about selling it to fund a B22. stupid upgrade-itis!


----------



## ruZZ.il

I've actually started to understand the schematics of the beta22 so I think my time to build one is nearing too 
	

	
	
		
		

		
		
	


	




 I can't sell my max though. specially the mini. It's still so wonderful to listen to and so easy to whip out and take to another room or something.. I dunno, I guess I've been so busy lately though, that I'm hardly in a hurry to do anything right now ;(


----------



## oneplustwo

That's a good point... I would hate to sell the minimax. But I have a feeling it would be scarcely used if the B22 is as good as everyone says it is.


----------



## patton713MW

I can't say for sure as I haven't heard either yet, but I would think that one doesn't necessarily replace the other. SS sound with the B22, and tube sound with the Millett. Anyone with more experience have any thoughts?


----------



## tomb

Quote:


  Originally Posted by *oneplustwo* /img/forum/go_quote.gif 
_That's a good point... I would hate to sell the minimax. But I have a feeling it would be scarcely used if the B22 is as good as everyone says it is._

 

Why? Seems astounding enough to see you mention the two in the same paragraph - the B22 only costs about 5 times as much.


----------



## aphexii

Finished up with the mock faceplates. I think i'm leaning black but time will tell which I end up ordering. The Silver is a bit off in color as I didn't have a silver knob so I had to fake it for an approximation, and the black would likely get black on black text (though no in-fill is a possibility as well)

 What do you guys think?


----------



## cetoole

The only real issue with FPE, besides cost, is that they cut panels from preanodized stock, so if you get black, the edges will still be raw aluminum. It is less noticeable with clear anodize, so that is something to think about. The only way I know of to get around this is to either send in your own metal or anodize it yourself.


----------



## aphexii

Quote:


  Originally Posted by *cetoole* /img/forum/go_quote.gif 
_The only real issue with FPE, besides cost, is that they cut panels from preanodized stock, so if you get black, the edges will still be raw aluminum. It is less noticeable with clear anodize, so that is something to think about. The only way I know of to get around this is to either send in your own metal or anodize it yourself._

 

Yea, I'm kinda annoyed they don't have the option to anodize it after they make the cut. All the previous models i've seen look good with the black anodize, but I worry it might clash too much with a black front, 4mm silver edges and a clear acrylic top. Going ALL silver on the front might make it look a bit cleaner.

 How difficult is it to anodize yourself?


----------



## cetoole

DIY anodize involves acid and electricity, so more dangerous and difficult the deeper you want the anodize layer (so depending how durable you want it). I have never tried it, probably never will. There are companies who can probably do it for you, though of course, doing this will leave you with only one color on the faceplate. You would have to redo any infilling. Best bet would be to send them preanodized stock of the correct size.


----------



## tomb

If you want to mess with acid baths and lethal DC rectifier currents, then DIY-anodizing might be a good choice. Otherwise, I'd leave it alone.
	

	
	
		
		

		
			





Aluminum Anodizing at home - DIY aluminium Anodising

 We used to use sulfuric anodizing a lot at Lockheed, but it was not for the faint-hearted. They also invented a resin-coating finish that's used on alloy wheels these days, from what I understand.


----------



## aphexii

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_If you want to mess with acid baths and lethal DC rectifier currents, then DIY-anodizing might be a good choice. Otherwise, I'd leave it alone.
	

	
	
		
		

		
		
	


	




Aluminum Anodizing at home - DIY aluminium Anodising

 We used to use sulfuric anodizing a lot at Lockheed, but it was not for the faint-hearted. They also invented a resin-coating finish that's used on alloy wheels these days, from what I understand.
	

	
	
		
		

		
		
	


	


_

 

What's a good DIY project if the chance of death isn't involved?


----------



## linuxworks

Quote:


  Originally Posted by *aphexii* /img/forum/go_quote.gif 
_What's a good DIY project if the chance of death isn't involved? 
	

	
	
		
		

		
		
	


	


_

 

such has been said about deep-frying turkeys.

 it sounds good, in theory; but I would not want to do it at home!


----------



## linuxworks

question about the heatsinks and the solder posts, on them.

 is it *really* necessary that the heatsinks be soldered? as long as they rest squarely on the pcboard and the leads to the transistors are well soldered - and if the screw holds tight enough on the to-220 tab, then why is that not good enough? the leads from the to-220's go straight down and so they pretty much ensure the HS isn't going anywhere.

 I hate the thought of having to unsolder them. perhaps I'll tack-solder them lightly but I'm not sure its such a great idea to douse the holes with solder...

 I'm curious why the solder heatsinks were spec'd instead of screw ones? or did I miss the place that talked about the option to choose either? I simply ordered from mouser based on the BOM and didn't really give much thought to the solder-post vs screw type.

 the ones with the posts in them, do they come out, easily? maybe I can convert the mouser ones I got into being screw-style if I remove those force-fit solder posts?


----------



## rds

Quote:


 I hate the thought of having to unsolder them. perhaps I'll tack-solder them lightly but I'm not sure its such a great idea to douse the holes with solder... 
 

I tack my heatsinks in place like this:










 It takes the strain off the to220 part, but the heatsink is still easily removable.
 Just heat up that ribbon of solder and use a solder pump to suck it away.

 Also, that solder tack is surprising strong. Chances are you'd crack the board before breaking that joint.


----------



## linuxworks

cool. sounds like a plan.

 I was going to do it just like you did.

 still, I think if I was paying attention, I would have ordered the screw style instead. solder type is more for automated wave-soldering machines, isn't it? diy is not quite the same and so screws would have been a better choice for the 'oops' that often happen on a one-off assembly we do at home.


----------



## rds

Can you link to these screw style ones? I don't think I've seen them before.


----------



## linuxworks

the ones that amb spec's for his b22 are screw-type (as I call it). you either use metal screws or you tap threads in the existing holes. but there are no solder posts on those.

 (I'm doing a b22 build almost at the same time as the minimax)


----------



## tomb

Quote:


  Originally Posted by *linuxworks* /img/forum/go_quote.gif 
_cool. sounds like a plan.

 I was going to do it just like you did.

 still, I think if I was paying attention, I would have ordered the screw style instead. solder type is more for automated wave-soldering machines, isn't it? diy is not quite the same and so screws would have been a better choice for the 'oops' that often happen on a one-off assembly we do at home._

 

Is everything supposed to be for wave-soldering?
	

	
	
		
		

		
		
	


	







 I don't think so. Yes, pinned heat sinks are difficult to remove ... but then again, they're not supposed to be removed, anyway. There are issues with tapped heat sinks, too. The pinned heat sinks were chosen on purpose and have served well for _several hundred_ MAXes and MiniMAXes. However, it's DIY and you're welcome to choose the parts you wish at any time, of course.
	

	
	
		
		

		
		
	


	




 EDIT: If you go back far enough in the history, the M3 was purposely chosen for pinned heat sinks, too - the non-pinned heat sinks were considered an issue in the early days. Pinned sinks are simpler, require less skill to install properly, are more plentiful, and cheaper.

 rds's method seems a simple solution if you're afraid of soldering the heat sinks in permanently.


----------



## linuxworks

I'm curious, what is the drawback with the screw type?

 is it the need for tapping or that tapping could be off-center?

 I don't have taps/dies but a strong screw seems to be all I need to start some threads, as long as the screw is stronger than the heatsink material. or use sheet metal screws, maybe.

 I realize that normally you don't have to remove them once you install them, but what if you blow a part that needs replacing? it just seems from a serviceability POV, the more things you can easily and non-destructively remove - the better.

 at the least, I would suggest a note in the bom to give the user a choice. it really is worth mentioning and giving alternate part #'s for the screw type.


----------



## linuxworks

has anyone tried these things? they are called 'slow color change leds':






 on ebay, you search for 'slow color change led' and this comes up.

 I have one in a usb xmas tree gadget; it cycles between R,G,B and shades between them. slow transition (hence the 'slow color change' name).

 I'm thinking of trying it under the tube sockets. is that going too far? 
	

	
	
		
		

		
		
	


	







 I did place an order so I'll find out anyway. apparently the controllers and 3 separate led's are in the led casing so you only supply 3v or so to them and they cycle on their own between the various colors. kinda neat in a bling kinda way


----------



## aphexii

Interesting, very curious to see how those come out... The only thing that might annoy me is if they change at different speeds so the colors don't match up. 

 On a side note, is the technology built directly into the LED itself? Or does it use a separate controller to handle the color change?


----------



## aphexii

Almost forgot to mention. Turns out there is a local anodizing shop about 5 minutes from my house. He can do a black anodize for $4.75, but has a minimum order of $125 
	

	
	
		
		

		
		
	


	




 I asked if he could just maybe throw mine in with someone elses order when they needed a black anodize and he said no.

 So it looks like I'm back to FPE only, silver or black.


----------



## linuxworks

I broke a led off my usb xmas tree (lol) and its JUST a single led with 'guts' inside. I'll take a photo later on. you can see the 3 led 'bases' and the controller chip (I think) inside.

 its JUST 2 wires and you have no control over timing. most likely they each will have a mind of their own. it may not be what people want..

 I might go back to using discrete leds or 4wire leds (3 colors but no 'chip'). that way I really can parallel the 2 leds and have the colors be 100% in sync. problem then is to find a simple/cheap outboard controller to PWM control the voltages (3 of them) to the leds and create a nice pattern 
	

	
	
		
		

		
		
	


	




 I've seen PIC chip circuits do this but its more effort than I'm onboard for.


----------



## aphexii

So i'm tossing around the idea of making an acrylic sandwich of the faceplate. 

 Anodized Aluminum with the Logo and Volume Knob cut out ---> Brushed/Frosted acrylic in the middle ---> solid piece of aluminum on the back with holes cut for the LED's to shine though.

 Ideally, the strategically placed LED's would light up the Acrylic from the back, and the holes on the front would allow it to glow from behind. Primarily through the logo and around the volume knob.


----------



## tomb

Quote:


  Originally Posted by *aphexii* /img/forum/go_quote.gif 
_So i'm tossing around the idea of making an acrylic sandwich of the faceplate. 

 Anodized Aluminum with the Logo and Volume Knob cut out ---> Brushed/Frosted acrylic in the middle ---> solid piece of aluminum on the back with holes cut for the LED's to shine though.

 Ideally, the strategically placed LED's would light up the Acrylic from the back, and the holes on the front would allow it to glow from behind. Primarily through the logo and around the volume knob._

 

Talk to MrMajestic2 ... been there, done that:


----------



## Forte

Quote:


  Originally Posted by *linuxworks* /img/forum/go_quote.gif 
_has anyone tried these things? they are called 'slow color change leds':






 on ebay, you search for 'slow color change led' and this comes up.

 I'm thinking of trying it under the tube sockets. is that going too far? 
	

	
	
		
		

		
		
	


	






_

 


 There was a neat build a few years ago the builder called the Disco MINT. http://www.head-fi.org/forums/f6/dis...warning-85534/
 Not used to light tubes but may give you an idea of what to expect.

 As to the question of too far? One of the local electronics stores here has 7 Colour LED's, maybe your not going far enough!
	

	
	
		
		

		
		
	


	



 (5mm only though, might be difficult to fit)


----------



## patton713MW

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Nice pics, Beefy! More that I can use on the MiniMAX website and do that wiring page that GeoffSpence wanted._

 

Tom, are there any plans to make this page? I just wired everything up in my MiniMAX, but needed to search for Beefy's pictures to figure out how to get it all wired up. And the only reason I knew to search for his pictures is because I've followed this whole thread. Someone new to the MiniMAX would probably benefit from wiring directions on the build website.

 BTW - My MiniMAX is fully assembled! I'm going to bias it in the morning, it's way too late and my eyes are pretty bugged out. Hopefully, another MiniMAX will live! 
	

	
	
		
		

		
		
	


	




 EDIT - R1 is optional, right? Am I correct that it needs to be jumpered if not used?


----------



## ruZZ.il

which wiring? it's not too dissimilar than the MAX.

 R1 is optional, and should be jumpered if not used. It should bring about a slight improvement in the power supply, but I haven't scoped it out so cant say what. I've still got mine jumpered, and already have the part! I've just been.. pretty busy this semester. Fortunately, it'll have been my most intense one throughout my degree, and I'm half way through exams already, so almost there! 
	

	
	
		
		

		
		
	


	




 I'll hopefully get back into the game after it all.. but I'll be getting married in august 
	

	
	
		
		

		
		
	


	




 so, we'll see...


----------



## tomb

Quote:


  Originally Posted by *patton713MW* /img/forum/go_quote.gif 
_Tom, are there any plans to make this page? I just wired everything up in my MiniMAX, but needed to search for Beefy's pictures to figure out how to get it all wired up. And the only reason I knew to search for his pictures is because I've followed this whole thread. Someone new to the MiniMAX would probably benefit from wiring directions on the build website._

 

I'm sorry, Andrew. Between running beezar, getting the MAX V1.2 proto going, and launching the SSMH PCB (working on the website, now), I'm spread pretty thin lately.

 Yes - by all means - my intent is to add a "Wiring and Assembly" page. It'll get done when it gets done, though.
	

	
	
		
		

		
		
	


	



  Quote:


 BTW - My MiniMAX is fully assembled! I'm going to bias it in the morning, it's way too late and my eyes are pretty bugged out. Hopefully, another MiniMAX will live! 
	

	
	
		
		

		
		
	


	



 

Pics or it doesn't count!!
	

	
	
		
		

		
		
	


	



  Quote:


 EDIT - R1 is optional, right? Am I correct that it needs to be jumpered if not used? 
 

You are better off with R1 than without, but a jumper will let you run fine indefinitely. I say that because 10ohms at 27VDC will put the heater voltage at its optimum value for tube performance and longevity.


----------



## MASantos

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_I'm sorry, Andrew. Between running beezar, getting the MAX V1.2 proto going, and launching the SSMH PCB (working on the website, now), I'm spread pretty thin lately.
_

 

[threadjack] 
	

	
	
		
		

		
		
	


	




 SSMH? 

 [/threadjack]


----------



## tomb

Quote:


  Originally Posted by *MASantos* /img/forum/go_quote.gif 
_








 [threadjack] 
	

	
	
		
		

		
		
	


	




 SSMH? 

 [/threadjack]_

 

At least I'm an equal-opportunity thread-jacker. I mention the MAX and MiniMAX regularly over in the SSMH thread.


----------



## ruZZ.il

how's the tube availability for that? I picked up some tube sockets for a SS, but never got around to looking for tubes much. they weren't readily available at the time..


----------



## patton713MW

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_I'm sorry, Andrew. Between running beezar, getting the MAX V1.2 proto going, and launching the SSMH PCB (working on the website, now), I'm spread pretty thin lately.

 Yes - by all means - my intent is to add a "Wiring and Assembly" page. It'll get done when it gets done, though.
	

	
	
		
		

		
		
	


	


_

 

No worries, I understand that there is a lot on your plate. Maybe for the time being you could just add a link at the end of the construction page to Beefy's post?

  Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Pics or it doesn't count!!
	

	
	
		
		

		
		
	


	


_

 

Will post them when it's alive! 
	

	
	
		
		

		
		
	


	




 I've been taking pictures throughout the whole process if you want them, though I can't guarantee that they'll be as pretty as Beefy's or LinuxWorks'.


----------



## tomb

Quote:


  Originally Posted by *ruZZ.il* /img/forum/go_quote.gif 
_how's the tube availability for that? I picked up some tube sockets for a SS, but never got around to looking for tubes much. they weren't readily available at the time.._

 

YGPM


----------



## patton713MW

ARG!! I got a bad wallwart! 
	

	
	
		
		

		
		
	


	




 Of all the things to be bad, it had to be that! *sigh* Well, let's see how fast Mouser can ship a wallwart...

 These will have to hold you all over until I can post some live shots:


----------



## tomb

Nice work! Looks great!!
	

	
	
		
		

		
		
	


	




 Sorry to hear about the walwart, though.


----------



## oneplustwo

Hey Tom,

 Any hints on how to get the silicone thingys on the tubes? I'm afraid of breaking them... seems like a really tight fit.


----------



## Beefy

Just a total shot in the dark here, as I've never used them......

 Silicone rubber softens a touch on heating. Perhaps drop them in some almost boiling water, let them sit for a bit, then scoop them out and quickly slide them onto the tubes.


----------



## aphexii

Quote:


  Originally Posted by *Beefy* /img/forum/go_quote.gif 
_Just a total shot in the dark here, as I've never used them......

 Silicone rubber softens a touch on heating. Perhaps drop them in some almost boiling water, let them sit for a bit, then scoop them out and quickly slide them onto the tubes._

 

I'm thinking maybe to try rolling it on like a condom...


----------



## Beefy

Quote:


  Originally Posted by *aphexii* /img/forum/go_quote.gif 
_I'm thinking maybe to try rolling it on like a condom... 
	

	
	
		
		

		
			



_

 

Maybe you need to lube the tube, like...... something...... that needs lubing......?


----------



## Beefy

Quote:


  Originally Posted by *patton713MW* /img/forum/go_quote.gif 
_These will have to hold you all over until I can post some live shots:_

 

While I think about it......

 For the Mini Max I am selling (same one I posted photos of the wiring), I opened it back up and put heatshrink over the entire length of the input signal wiring. That tidies it up a bit, and protects the wire from damage from any sharp edges on the ventilation slots.


----------



## Daveze

The slots combined with the ventilation are very good at fraying up the input signal wires. I used a length of the Fibreglass sleeving stuff (Vidaflex) that I've had in my scraps box for a while. Its not quite long enough but it does the job and looks quite reasonable.


----------



## linuxworks

my build, in living color-

 an intermediate stage:






 the final thing, all lit up and ready to go:






 I ended up using 2 superbright red point-source LEDs under the tube sockets (not the small LEDs but the larger standard size) and I also used a slow-color change LED as the center non-tube light. this worked out perfectly as the tube lites are fixed-red and the center one cycles between colors in a low-key kind of way.

 sound is great! I really like it so far and its only been working for a few hours, now.

 I almost fried my output transistors. I had them all soldered in and ready to go - then I saw this:






 I had them all swapped!

 see, tom; THIS is why I'm glad I didn't solder in those heatsinks! 
	

	
	
		
		

		
		
	


	




 I *thought* I had picked the right transistor places for the to220 parts but that handy diagram caught me in time and saved me a LOT of hair pulling!

 so, thanks to checking and triple checking, it worked fine on the first build. took a good 8 hours (all day today) to build.

 this was a fun build. I would recommend it for people who want something a bit different from the usual solid state stuff


----------



## Beefy

Quote:


  Originally Posted by *Daveze* /img/forum/go_quote.gif 
_The slots combined with the ventilation are very good at fraying up the input signal wires. I used a length of the Fibreglass sleeving stuff (Vidaflex) that I've had in my scraps box for a while. Its not quite long enough but it does the job and looks quite reasonable._

 

Yeah, that would be better than heatshrink for both abrasion and temperature resistance.

 How are you liking your amps with a bit more time on them?

  Quote:


  Originally Posted by *linuxworks* /img/forum/go_quote.gif 
_my build, in living color-_

 

Beautiful photos as always. The tube LEDs are insanely bright!

 What parts are you using at the typical boutique positions?


----------



## linuxworks

nothing at all boutique. not even the 'wed wimas' (lol).

 I ordered pretty much purely from the BOM and got the parts from digikey and mouser (about half and half). I started using the more expensive vishays (the smaller blue ones) but I didn't get enough of them so I moved to 'brown vishays' for the center section of the board 
	

	
	
		
		

		
		
	


	




 I do have a vit-Q in the proper places. they were cheap (and strange looking) enough that I bought into that one


----------



## linuxworks

oh, and for the 'rubber parts' (lol), I just stretched it a few times using some pliers until I broke it in a bit. after that it was easy to just slip on the tube.

 ...no lube needed


----------



## rds

The Panasonic film caps you used are technically better than the Wimas in an audiophile sense (ie foil and film rather than metalized film).


----------



## Daveze

Quote:


  Originally Posted by *Beefy* /img/forum/go_quote.gif 
_Yeah, that would be better than heatshrink for both abrasion and temperature resistance.

 How are you liking your amps with a bit more time on them?_

 

That's the other reason I went for it, its very abrasion resistant. I've only finished the one, I assume it still sounds very fine. It took a few days but eventually it really started to shine. I'm out at site at the moment and the amp is in my desk at work, so I suppose I'm going to go through the same process when I return. Coupled with the y1, its a little 'shrill' so I might take Mister X's advice and remove the film bypass.

 The other still needs output transistors installed and panel wiring completed...


----------



## Beefy

Quote:


  Originally Posted by *Daveze* /img/forum/go_quote.gif 
_Coupled with the y1, its a little 'shrill' so I might take Mister X's advice and remove the film bypass._

 

I can imagine it might be with the low-mid Grados...... you still have SR-80 and SR-225 from a bit of searching?

 The combo does sing oh-so-sweet with the more mellow ESW9 though


----------



## Daveze

Its actually with a pair of Sextetts, they replace my 240s as my work 'phones. They sound really good with the big MAX at home but then again, I listen a bit louder a home than i do at work.

 I really like semi-open for work so that I can hear people coming/talking. I was considering something like the ATH-AD900s or similar for a while but figured I should give the Sextetts a proper listen.


----------



## GeWa

Quote:


 I had them all swapped!

 see, tom; THIS is why I'm glad I didn't solder in those heatsinks! 
	

	
	
		
		

		
		
	


	




 I *thought* I had picked the right transistor places for the to220 parts but that handy diagram caught me in time and saved me a LOT of hair pulling! 
 

Had the same problem but I already "did soldered" the heatsinks in! It took me a while to change the output transistors but in the end I managed to do a successful job if i may say so myself. Everything is dialed in now and ready to go in the casing.

 Regards


----------



## oneplustwo

linuxworks - thanks for the tip. I just ended up stretching them with my fingers and rolling them inside out a couple times and then they slipped over without too much force.


----------



## tomb

Quote:


  Originally Posted by *Daveze* /img/forum/go_quote.gif 
_That's the other reason I went for it, its very abrasion resistant. I've only finished the one, I assume it still sounds very fine. It took a few days but eventually it really started to shine. I'm out at site at the moment and the amp is in my desk at work, so I suppose I'm going to go through the same process when I return. Coupled with the y1, its a little 'shrill' so I might take Mister X's advice and remove the film bypass.

 The other still needs output transistors installed and panel wiring completed..._

 

At 600ohms and a fairly low sensitivity, it could be that the Sextets may be too much for the MiniMAX to push. There are only a few phones I'd put in that category, and the Sextets may be one of them. I'd never try it without zero output resistors (jumpers) and only 12AE6's. It could be that your regular MAX is setup this way, but maybe you did the MiniMAX differently.

 Let me know if you want some especially high output 12AE6's - I may be able to provide you with some if you still have problems with this.
	

	
	
		
		

		
		
	


	




 EDIT: I'm suggesting this carefully, because the MAX/MiniMAX are capable of some whopping current, but they're limited in voltage swing to 1/2 the power supply. For instance, there's no issue at all in using a MiniMAX with Orthos - Colin has sent me a couple and I have the new Fostex T50RP's, too. They all sound great - his Yamaha's are the best things I've heard from mids to highs (still prefer my great HF-1's overall, though). Still, 600 ohms is mighty difficult for any headphone amp, period.


----------



## soloz2

my Max could probably drive them! I haven't tried sextets, but I'm confident 
	

	
	
		
		

		
		
	


	




 (MOSFET output stage with a nice big toroid)


----------



## tomb

Quote:


  Originally Posted by *soloz2* /img/forum/go_quote.gif 
_my Max could probably drive them! I haven't tried sextets, but I'm confident 
	

	
	
		
		

		
			





 (MOSFET output stage with a nice big toroid)_

 

Yes, of course - and with taller heat sinks and higher bias, the MiniMAX may be able to do the same thing, but the case is the thing and 1" is the limit.
	

	
	
		
		

		
		
	


	




 I'm wondering if Daveze is the fellow who super-biased his BJT's on the regular MAX. There was someone who did that - put over 100ma on the BJT's, I think, but I can't remember who exactly.


----------



## soloz2

it wasn't me. and yeah, I do have 2" sinks on my Max


----------



## Daveze

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Yes, of course - and with taller heat sinks and higher bias, the MiniMAX may be able to do the same thing, but the case is the thing and 1" is the limit.
	

	
	
		
		

		
		
	


	




 I'm wondering if Daveze is the fellow who super-biased his BJT's on the regular MAX. There was someone who did that - put over 100ma on the BJT's, I think, but I can't remember who exactly._

 

Guilty. Not quite 100 mA, only up to 80 mA. You do raise a good point though, I might try some more tube rolling and see what I come up with. One reason I went with two Mini's was that I was loosely considering a balanced rig, maybe I've come across a good reason to try it.


----------



## tomb

Quote:


  Originally Posted by *Daveze* /img/forum/go_quote.gif 
_Guilty. Not quite 100 mA, only up to 80 mA. You do raise a good point though, I might try some more tube rolling and see what I come up with. One reason I went with two Mini's was that I was loosely considering a balanced rig, maybe I've come across a good reason to try it._

 

Weren't you asking about going higher than that at one point, though? Still, I wasn't too far off.
	

	
	
		
		

		
		
	


	




 Extra current will help some on the big MAXes, but not on the MiniMAX. However, with that high impedance, the best you can do is get some high output 12AE6's and make sure you don't use any output resistors. In that regard, the MiniMAX should be equal to the task, I would think.

 Your idea of balancing would solve it all, probably - more current available and twice the voltage gain.


----------



## Daveze

I was considering going higher but after changing the transistors twice already, I really didn't feel like going through the grief of a third change in the event of transistor failure. At that point they were running ~50 degC, which is a nice point to leave them.

 Now I just need a small balanced DAC. My DAC-301 would be up to the task but needs a case. Is there a fancy way to make two y1 into a balanced arrangement?


----------



## patton713MW

I noticed that the top of my Lansing case is slightly bowed outward. Have any of you noticed this on your cases? What did you do to flatten it? I've tried bending it by hand, but it doesn't seem to want to flatten out.


----------



## linuxworks

"use a bigger hammer"






 I just pressed on mine, leaning on it, until it flexed flat. be careful, though - and it really may not be worth risking, to be honest. minor flaw - and sometimes when I try to fix minor things, I make it even worse..


----------



## tomb

Quote:


  Originally Posted by *patton713MW* /img/forum/go_quote.gif 
_I noticed that the top of my Lansing case is slightly bowed outward. Have any of you noticed this on your cases? What did you do to flatten it? I've tried bending it by hand, but it doesn't seem to want to flatten out._

 

They're all like that. You can actually offset the endplates slightly to account for the difference. Just whittle an extra sliver or two off the bottom of the pot-shaft and headphone-jack holes.


----------



## cetoole

Quote:


  Originally Posted by *Daveze* /img/forum/go_quote.gif 
_Is there a fancy way to make two y1 into a balanced arrangement?_

 

No, the only thing you could do if you needed balanced out of a y1 was add a phase splitter of some sort, or maybe a transformer.


----------



## linuxworks

this is a fun little amp. I'm really glad I jumped in on the GB and got the machined case. that made ALL the diff.

 I used to be into ham radio (1970's timeframe) and this 2 tube unit reminds me a lot of stuff I used to use back then. it was a neat time for electronics and DIY back then, too..

 so far I've left the buffers at 90 and have not pushed to (120?) yet. am I missing much by leaving it so low? I don't feel a lot of heat off the case and I kind of like it that way..


----------



## tomb

Quote:


  Originally Posted by *linuxworks* /img/forum/go_quote.gif 
_this is a fun little amp. I'm really glad I jumped in on the GB and got the machined case. that made ALL the diff.

 I used to be into ham radio (1970's timeframe) and this 2 tube unit reminds me a lot of stuff I used to use back then. it was a neat time for electronics and DIY back then, too..

 so far I've left the buffers at 90 and have not pushed to (120?) yet. am I missing much by leaving it so low? I don't feel a lot of heat off the case and I kind of like it that way.._

 

You should be able to get 110mV (50ma) without any issue, probably a bit further, if you want to push it. However, 110mv (50ma) is our official recommendation.
	

	
	
		
		

		
		
	


	




 90mV is only a little more than the PPA and CKKIII get without any heat sinks.


----------



## Beefy

Quote:


  Originally Posted by *cetoole* /img/forum/go_quote.gif 
_No, the only thing you could do if you needed balanced out of a y1 was add a phase splitter of some sort, or maybe a transformer._

 

See, I've been thinking about this, and there is theoretically a better way if you do have two y1.

 With ASIO4ALL and Foobar, you are able to map the music channels to whatever ASIO device you like. If you had a plugin that was capable of generating a perfect inverse signal to your music in real time, you may be able to send left + and left - to one device, then right + and right - to a separate device.

 Completely theoretical of course, and the plugin doesn't appear to exist.


----------



## rds

You could use an Opus DAC. It will be cheaper than two y1s and uses a better DAC chip.

  Quote:


  Originally Posted by *Daveze* /img/forum/go_quote.gif 
_Is there a fancy way to make two y1 into a balanced arrangement?_


----------



## Beefy

He already has the y1's


----------



## linuxworks

Quote:


  Originally Posted by *Beefy* /img/forum/go_quote.gif 
_
 Completely theoretical of course, and the plugin doesn't appear to exist._

 

have you tried rot13?

 (kidding!)


----------



## Daveze

Beefy nailed it: an Opus is about one [Opus price] more expensive than two y1's...
	

	
	
		
		

		
			





 I think the real option is to try my DAC-301 in balanced mode, then look into a Twisted Pear design...Buffalo32 would be nice if I could just keep track on the availability.


----------



## Beefy

Quote:


  Originally Posted by *Daveze* /img/forum/go_quote.gif 
_Buffalo32 would be nice if I could just keep track on the availability._

 

I am subscribed to their news announcements


----------



## linuxworks

more color photos


----------



## Caribou679

WoW! Looks grand!! Well done!!

 How does the "Tube Bias" connections works?

 regards


----------



## linuxworks

the short answer: find the total voltage in your unit (27v normally) and divide in half, then set the bias to that midpoint (13.5v in my case). measure from center post (ground) to left and then center post to right.

 I think you have to check this ever so often, based on the tube aging (?) and also when you CHANGE or swap-out tubes. (is that correct?)


----------



## tomb

Quote:


  Originally Posted by *linuxworks* /img/forum/go_quote.gif 
_the short answer: find the total voltage in your unit (27v normally) and divide in half, then set the bias to that midpoint (13.5v in my case). measure from center post (ground) to left and then center post to right.

 I think you have to check this ever so often, based on the tube aging (?) and also when you CHANGE or swap-out tubes. (is that correct?)_

 

Ice Creammmm!!
	

	
	
		
		

		
		
	


	










 That LED is cool.
	

	
	
		
		

		
		
	


	




 You're right, though - those tube sockets are sitting high in the saddle.
	

	
	
		
		

		
		
	


	




 What you'll find is that the Millett tubes will take a couple of hours to settle. So even with broken in tubes, it might be best to set the bias for 14V or so. That way, they'll probably hit 13.5 after a couple of hours and stay there the rest of the day. This is highly variable, though, and seems to be more prevalent for 12AE6's than 12FK6's. 12FK6's will tend to settle out very quickly and stay there. I think it has to do with how much amplification the plate is putting out - the more there is, the more it has a chance to move around a bit.

 Yes, you should always check the bias when you change tubes - even if they're tubes of the same type.


----------



## linuxworks

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_ You're right, though - those tube sockets are sitting high in the saddle.
	

	
	
		
		

		
		
	


	


_

 

well, if your socket falls off the saddle, you need to tell it to get right back on it again or it will be afraid for life.


----------



## linuxworks

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Ice Creammmm!!
	

	
	
		
		

		
		
	


	










 That LED is cool.
	

	
	
		
		

		
		
	


	


_

 

'cherry garcia', anyone?


----------



## patton713MW

Another MiniMAX lives!!


----------



## tomb

Quote:


  Originally Posted by *patton713MW* /img/forum/go_quote.gif 
_Another MiniMAX lives!! 
	

	
	
		
		

		
		
	


	


_

 

Way to go, Andrew! Glad to hear it worked out well for you, but knowing the care you were taking, I didn't doubt the result.

 I hope Mouser gave you your money back for that walwart.


----------



## patton713MW

I'm about to hit them up for it. Question: What volume do I bias the tubes at? I had them dialed in, then went to check them a bit later, and was surprised to see that they changed a lot at a different volume setting.

 EDIT - Interestingly, the left tube varies much more than the right:
 Bias Voltage, from Min volume to Max volume:

 w/ 12AE6 tubes
 Left: 13.27V - 14.92V
 Right: 13.43V - 14.17V

 EDIT2 - Even more interesting, the bias voltage doesn't change at all with the 12FM6.


----------



## tomb

Quote:


  Originally Posted by *patton713MW* /img/forum/go_quote.gif 
_I'm about to hit them up for it. Question: What volume do I bias the tubes at? I had them dialed in, then went to check them a bit later, and was surprised to see that they changed a lot at a different volume setting.

 EDIT - Interestingly, the left tube varies much more than the right:
 Bias Voltage, from Min volume to Max volume:

 w/ 12AE6 tubes
 Left: 13.27V - 14.92V
 Right: 13.43V - 14.17V

 EDIT2 - Even more interesting, the bias voltage doesn't change at all with the 12FM6._

 

Yes, you'll see some strange readings if you attempt to bias at anything other than Volume Knob = 0.

 The 12AE6 has such high gain that it will overdrive the buffer at maximum volume under no load - one tube may go almost to zero while the other tube goes to 27V. It's not a condition where the amp is expected to operate - at all. The other tubes will have a lesser effect as you've noticed.

 Keep in mind that your bias will tend to drift for the first few hours or so - and much more on new tubes than ones that have been well-broken-in. Because of the high gain of the 12AE6, it's always going to be finicky with bias - very mule-like - whereas the 12FK6's are often set once and they stay.


----------



## patton713MW

Thanks, that's really helpful information! I just called up Mouser, and they are going to refund me for the wallwart, and I don't have to send them the bad one. Cool!

 This amp sounds like happy!


----------



## patton713MW

Live pictures!






 Originally, I went with orange tube LEDs, and a blue LED1. However, after casing it up, I decided that I didn't really like the orange tubes. Maybe if the case were black; the orange glass of the tube just didn't jive with the silver case. Luckily, I socketed the tube LEDs, so I just wiggled them out, and dropped in some blues. Then I wired up 3 orange LEDs in series for LED1, and I think it looks great. I definitely stole the idea from rds, so thanks for the inspiration! I really like how he used the 3 LEDs to even out the lighting around the case. I decided to wire them in series vs parallel, but otherwise I used his same idea.






 Here it is with the blue tubes and orange case lighting. One thing that I love about the blue tubes is that it allows you to see the orange glow of the tube heater. With the orange LEDs, you can't even tell that there is a heater. The orange heater glow looks great with the blue tube glow.


----------



## tomb

Great work! Great pics, too!

 Yeah, I put amber tube lights in my prototype MiniMAX and I don't like them. I'll change them some day.


----------



## Beefy

Nice and clean part positioning patton713MW. I can see all of the resistor values in your photos!


----------



## tomb

Quote:


  Originally Posted by *Beefy* /img/forum/go_quote.gif 
_Nice and clean part positioning patton713MW. I can see all of the resistor values in your photos! 
	

	
	
		
		

		
		
	


	


_

 

Yes, agreed - AFAIK, it's his first build. He has been patiently waiting/participating every once in awhile for months at DIYForums.org, while we were going through prototyping and getting the case group buy processed.

 He chastised me, though, for not having the Wiring & Assembly page done. He went searching through the thread looking for your wiring pics to get it finished.


----------



## patton713MW

Quote:


  Originally Posted by *Beefy* /img/forum/go_quote.gif 
_Nice and clean part positioning patton713MW. I can see all of the resistor values in your photos! 
	

	
	
		
		

		
		
	


	


_

 

Thanks! I'm quite the perfectionist when I want to be. 
	

	
	
		
		

		
		
	


	




 I have built several CMoys in the past, but this is my first major build. It was a lot of fun!

  Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Yes, agreed - AFAIK, it's his first build. He has been patiently waiting/participating every once in awhile for months at DIYForums.org, while we were going through prototyping and getting the case group buy processed._

 

Truth be told, I had to wait because it took a while for the funds to amass (college student, I'm sure you all understand). In the end though, I'm really glad that I waited. It gave me the chance to study the design well, and see what kind of tweaks others implemented. IE: rds' case lighting. Also, by the time I went to order, Tom had the equipment to do tube matching, which financially allowed me to get a pair of all three types. So it all worked out in the end, and I'm left with an amazing sounding and looking amp!

 Speaking of the different tubes, I spent a few hours today auditioning each pair. My feelings are pretty much inline with the general consensus. I settled on the 12AE6, because of its punchy, solid bass. My DT880s have always been a bit lean on the bass, so the 12AE6 puts the "fun" back in them. Also, it sounds very balanced with male vocals. It is ever so slightly recessed on female vocals, but not enough to drive me to another tube. This tube is just more fun.

 The 12FM6 has decent bass, though it is not as impactful as the 12AE6. Of the three, it portrayed female vocals the best, though the male vocals seem like they are missing something. It sounds like the very center of the voice is slightly recessed. Mids seem pronounced, though well articulated.

 The 12FK6 did well with male vocals, but female vocals were overbearing. This alone was enough to cause me to not use the 12FK6. Also, the bass is subdued. Otherwise, they sound good.

 I also experimented with RB14 values. In the end, I decided on 10Ω Stackpoles. Honestly, I can't articulate the difference in sound quality between jumpered and resistors in place. I decided to go with them because listening with the jumpers was slightly fatiguing after a while, and the 10Ω resistors eliminated the fatigue. Perhaps the resistors eliminated some slight harshness that caused the fatigue. 

 So, it's now all cased up and happy! I should get the volume knob tomorrow, and it'll be complete!


----------



## lordvader

OK !
 Pics finally !

 A friend at work brought in his camera, and took some happy snaps of my MiniMax and k601s !

 The pics are here (some are quite large !).

amp


----------



## Beefy

That's awesome, lordvader. Glad it all worked out well for you!


----------



## tomb

Wow! Awesome pics, lordvader! You guys should go take a look - here's a sample:


----------



## lordvader

Thanks guys 
	

	
	
		
		

		
		
	


	




 Massive props to the dude who took the photos !
 If I took them, the film will still be in the camera 6 months from now


----------



## patton713MW

I've noticed that the heater on the right tube glows brighter than the heater on the left tube. Is this anything that I should be concerned about?


----------



## pinkfloyd4ever

Are your tubes of identical construction? If so I wouldn't worry about it as long as they're biased close to the same voltage--but as Tom always says, final bias fine-tuning should be done with your ears

 off topic, but I'm guessing you go to CMSU? Where are you from? Just wondering for future reference in case we ever get another meet together here in StL. You ever been to one of EZKCdude's meets? They're alot bigger & better than the one we managed to put together here back in June '07.


----------



## tomb

Quote:


  Originally Posted by *patton713MW* /img/forum/go_quote.gif 
_I've noticed that the heater on the right tube glows brighter than the heater on the left tube. Is this anything that I should be concerned about?_

 

As pinkfloyd4ever suggests - by itself, a brighter heater in one tube means nothing. You should've been sent matched construction and matched performance tubes. As long as they sound the same, not to worry.

 However mistakes are sometimes made, so if there's an issue - let me know and we'll address it.


----------



## patton713MW

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_As pinkfloyd4ever suggests - by itself, a brighter heater in one tube means nothing. You should've been sent matched construction and matched performance tubes. As long as they sound the same, not to worry.

 However mistakes are sometimes made, so if there's an issue - let me know and we'll address it.
	

	
	
		
		

		
		
	


	


_

 

No problems with tube matching, you did a great job. They look and sound the same, and they are biased equally. I was just curious if perhaps something was wrong with my setup, or heater resistor perhaps.

 Out of curiosity, are there detrimental side effects of having the tube bias low or high? Obviously I try to keep them right on 13.5, however the voltages will vary over the period of several hours, depending on how long it has been on. Should I just set it when I'm sure it's well warmed up, and forget about it?

  Quote:


  Originally Posted by *pinkfloyd4ever* /img/forum/go_quote.gif 
_off topic, but I'm guessing you go to CMSU? Where are you from? Just wondering for future reference in case we ever get another meet together here in StL. You ever been to one of EZKCdude's meets? They're alot bigger & better than the one we managed to put together here back in June '07._

 

Yep, I'm going to school at UCM (was CMSU, they changed the name on me...). I'm from St. Louis though. I'd love to meet up with some other headfiers and broaden my horizons. Better leave my wallet at home though...


----------



## tomb

Quote:


  Originally Posted by *patton713MW* /img/forum/go_quote.gif 
_No problems with tube matching, you did a great job. They look and sound the same, and they are biased equally. I was just curious if perhaps something was wrong with my setup, or heater resistor perhaps.

 Out of curiosity, are there detrimental side effects of having the tube bias low or high? Obviously I try to keep them right on 13.5, however the voltages will vary over the period of several hours, depending on how long it has been on. Should I just set it when I'm sure it's well warmed up, and forget about it?_

 

Now you've done it. You've asked one of "those" questions.
	

	
	
		
		

		
		
	


	







 Personally, I set them when I'm certain they're warmed up. Alternatively, well broken-in tubes seem to gradually drop in bias over a few hours, so I tend to set them at 13.75 or something like that - then forget about it. Keep in mind that with new tubes, they may need checking every couple of hours or so for a day or two.

 In actuality with a 27VDC power supply, setting the tube bias at 13.5V will allow for the maximum voltage swing in either direction (+or- 13.5V). This results in the maximum power setting for the amp and gives the buffers the highest peaks without clipping.

 However ... the tubes generally respond in a more linear fashion the higher the plate voltages go. IOW, the tubes may sound "better" with less distortion at 18 or 20V. However, higher bias settings leave little or nothing for voltage swing at the buffers. So, it's a Catch 22 - the tubes may sound "sweeter" but their tendency to clip goes way up. You'll see if you read Pete Millett's original Millett Hybrid article (Audio Xpress) that he experimented with high biases on the tubes - but you can also see his clipping waveform photos.

 Again, I set them for 13.5V (or allow a little for warmup) and forget it.


----------



## ruZZ.il

so, someone using solely lower impedance cans, outputting lower amplitude voltage swings anyway, may as well bias a little higher anyway?


----------



## patton713MW

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Now you've done it. You've asked one of "those" questions.
	

	
	
		
		

		
		
	


	





_

 

Mua ha ha... 
	

	
	
		
		

		
		
	


	




  Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_However ... the tubes generally respond in a more linear fashion the higher the plate voltages go. IOW, the tubes may sound "better" with less distortion at 18 or 20V. However, higher bias settings leave little or nothing for voltage swing at the buffers. So, it's a Catch 22 - the tubes may sound "sweeter" but their tendency to clip goes way up. You'll see if you read Pete Millett's original Millett Hybrid article (Audio Xpress) that he experimented with high biases on the tubes - but you can also see his clipping waveform photos._

 

Is this why some experiment with higher V+, to raise the tube plate voltages while maintaining buffer clipping levels?

  Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Personally, I set them when I'm certain they're warmed up. Alternatively, well broken-in tubes seem to gradually drop in bias over a few hours, so I tend to set them at 13.75 or something like that - then forget about it. Keep in mind that with new tubes, they may need checking every couple of hours or so for a day or two... Again, I set them for 13.5V (or allow a little for warmup) and forget it._

 

I've let my amp run constantly since last Friday, so I feel like the tubes are getting broken-in. The 12AE6s have MUCH less voltage swing (than what was mentioned before) from zero volume to listening volume, usually less than 0.1 V. About the voltage change from warming up: I decided to keep track of that last night. I biased the amp at 13.5 V (it had been on all day), and then turned it off and let the tubes cool. Then, I turned it back on, and measured the bias. This is what I got on the left tube:

 1 min = 14.70 V
 5 min = 14.35 V
 20 min = 13.93 V
 30 min = 13.68 V
 40 min = 13.65 V

 This morning, I checked again, and it was at 13.4 V. So, I re-biased both tubes to 13.50 V, and I'll probably just leave it there. It's interesting though how gradually the voltages drop after letting the tubes cool. I'll test it again after a week or so to see if additional break in time has changed anything.

 I don't know if any of this matters to you all, or if it is something that you already know, I just find it interesting.


----------



## tomb

Quote:


  Originally Posted by *ruZZ.il* /img/forum/go_quote.gif 
_so, someone using solely lower impedance cans, outputting lower amplitude voltage swings anyway, may as well bias a little higher anyway? 
	

	
	
		
		

		
		
	


	


_

 

Could be.
	

	
	
		
		

		
		
	


	




 However, I'd definitely call this an advanced experiment. The basic Millett circuit has been built for several years now. IMHO, one is better off by changing tubes and tube types than fiddling with a bias other than 13.5V. Still, the flexibility is there and it's easy to try out. I believe TimJo has experimented with this using 12FM6 tubes quite a bit and prefers a bias up around 15V, if I remember correctly.

  Quote:


  Originally Posted by *patton713MW* /img/forum/go_quote.gif 
_Mua ha ha... 
	

	
	
		
		

		
		
	


	





 Is this why some experiment with higher V+, to raise the tube plate voltages while maintaining buffer clipping levels?_

 

Yes. As you guessed, at least when raising the V+, you compensate for the potential clipping otherwise.

 Again, I'd like to caution folks - the MiniMAX was built with specific settings in mind and for a very specific case
	

	
	
		
		

		
		
	


	




. Deviate from that too much, and I can't guarantee that performance will be as good. Raising the power supply voltage above 27VDC is problemmatic without an especially powerful walwart or a separate trannie. There is the potential that ripple will rise after we went to such great lengths to reduce it significantly. Better to leave this kind of experimentation to the regular MAX, I think.

  Quote:


 I've let my amp run constantly since last Friday, so I feel like the tubes are getting broken-in. The 12AE6s have MUCH less voltage swing (than what was mentioned before) from zero volume to listening volume, usually less than 0.1 V. About the voltage change from warming up: I decided to keep track of that last night. I biased the amp at 13.5 V (it had been on all day), and then turned it off and let the tubes cool. Then, I turned it back on, and measured the bias. This is what I got on the left tube:

 1 min = 14.70 V
 5 min = 14.35 V
 20 min = 13.93 V
 30 min = 13.68 V
 40 min = 13.65 V

 This morning, I checked again, and it was at 13.4 V. So, I re-biased both tubes to 13.50 V, and I'll probably just leave it there. It's interesting though how gradually the voltages drop after letting the tubes cool. I'll test it again after a week or so to see if additional break in time has changed anything.

 I don't know if any of this matters to you all, or if it is something that you already know, I just find it interesting. 
	

	
	
		
		

		
		
	


	



 

Yep - as I've mentioned often, this will happen as the tubes gradually break-in. Even so, you'll probably note that kind of difference for the life of the tubes. They're not really "in a groove" before the first hour or two.


----------



## TheEKey

Sorry. post under the wrong topic. 

http://www.head-fi.org/forums/f6/new...ml#post5467283

 I post it back to the Millett Hybrid MAXed topic.


----------



## tomb

Quote:


  Originally Posted by *TheEKey* /img/forum/go_quote.gif 
_Sorry. post under the wrong topic. 

http://www.head-fi.org/forums/f6/new...ml#post5467283

 I post it back to the Millett Hybrid MAXed topic._

 

No problem! Check your wiring - I posted about it in the thread.


----------



## Bismar

Well this is odd, both my tube led's died at EXACTLY the same time.

 Any idea why this might be?

 Replacing them works right away. So at least no permanent damage was done to the more important parts of the amp(Phew!)

 Edit:

 Now that i think about it, i could have sworn since the time i built the amp till the death of the leds, they have been gradually getting dimmer, as the new ones seem much brighter. But then i did have them sitting higher this time. Hmm...


----------



## tomb

Quote:


  Originally Posted by *Bismar* /img/forum/go_quote.gif 
_Well this is odd, both my tube led's died at EXACTLY the same time.

 Any idea why this might be?

 Replacing them works right away. So at least no permanent damage was done to the more important parts of the amp(Phew!)

 Edit:

 Now that i think about it, i could have sworn since the time i built the amp till the death of the leds, they have been gradually getting dimmer, as the new ones seem much brighter. But then i did have them sitting higher this time. Hmm..._

 

LEDs are an electronic commodity. There are some out there that don't even light the first time out.
	

	
	
		
		

		
		
	


	




 Quality LEDs should last indefinitely, though, if you've used the resistor sizes we've spec'd. Go all the way up to 20ma on an LED and you may find it will burn out in no time.


----------



## Beefy

Quote:


  Originally Posted by *Bismar* /img/forum/go_quote.gif 
_Well this is odd, both my tube led's died at EXACTLY the same time.

 Any idea why this might be?_

 

As tomb said. All you might have had was the tiniest little voltage spike to push them over the edge.

  Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Quality LEDs should last indefinitely, though, if you've used the resistor sizes we've spec'd. Go all the way up to 20ma on an LED and you may find it will burn out in no time._

 

In my regular Max I pushed the LEDs to 20mA no worries. Of course, they were Lumex and rated to 30mA continuous, 100mA spike......


----------



## THE_SOURCE41

I am just putting in the wima film caps into my pcb and i am wondering if I should put them in ca9 L/R. I am using black gates in ca 7 and ca 2. if i dont put these in do i leave it blank or do I jump them?

 sam


----------



## pinkfloyd4ever

leave it blank. CA9 is just bypassing CA2, which means they're in parallel, so no jumpering of the CA9 pads is necessary


----------



## tomb

Quote:


  Originally Posted by *pinkfloyd4ever* /img/forum/go_quote.gif 
_leave it blank. CA9 is just bypassing CA2, which means they're in parallel, so no jumpering of the CA9 pads is necessary_

 

Correct. More than that, though, capacitors block DC voltage. Put a jumper in instead of a capacitor, and you've created a dead short.
	

	
	
		
		

		
		
	


	




 You should always leave them blank if there are pads where capacitors should go, but you decide not to use them.


----------



## THE_SOURCE41

Ok thanks! I was just wondering.


----------



## THE_SOURCE41

Oh and another question.
 When looking at the picture on the millet website there look to be 3 Terminal Block 3pos 5mm but in the BOM there is only a requirement of 2. Am I missing something?


----------



## tomb

Quote:


  Originally Posted by *THE_SOURCE41* /img/forum/go_quote.gif 
_Oh and another question.
 When looking at the picture on the millet website there look to be 3 Terminal Block 3pos 5mm but in the BOM there is only a requirement of 2. Am I missing something?_

 

The 3-pos terminal block by the headphone jack is entirely optional. There is no facility for it with the MiniMAX custom case. However, the option is there if you want to drill a hole on the frontplate for a 3.5mm headphone jack or, run leads to the rear plate for preamp-out RCA jacks (also requiring more holes to be drilled). Of course, either option is trivial if you're using your own case. So, it's up to you - but that's why it's not listed as a required part on the BOM.


----------



## THE_SOURCE41

Ok thanks. thats the one I left blank so I am in good shape.

 Sam


----------



## Mr.Unknown

people,
 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 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._

 

I addressed this in the other thread, however ... Sorry, but except for the 12FM6, it's not like Millett tubes are scarce - they're not! You should be able to find them at almost any vendor who sells tubes - including e-bay, beezar.com, etc. - including many overseas outlets (I've purchased Millett tubes from international vendors myself from time to time).

 BTW, 12AU7 or 12AX7 are not even close. Millett tubes come from a special category of tubes known as "space-charge" tubes. The 6GM8 is probably the most famous in audiophile terms, but most of them were specifically designed for 12V on both the plates and heaters.


----------



## linuxworks

I was told that these tubes (this style) was popular in a thing called 'all american 5':

All American Five - Wikipedia, the free encyclopedia

 some history for you


----------



## tomb

Quote:


  Originally Posted by *linuxworks* /img/forum/go_quote.gif 
_I was told that these tubes (this style) was popular in a thing called 'all american 5':

All American Five - Wikipedia, the free encyclopedia

 some history for you 
	

	
	
		
		

		
			



_

 

Um ... thanks for the link, but I don't think space-charge tubes were used in the All American Five. That's pretty much a defacto-standardized tube radio configuration that used "normal" high-voltage tubes. There were some low-voltage conversions, but none used the truly low-voltage space charge tubes developed by Tung-Sol for use in car radios without a "vibrator" (watch the comments on that!
	

	
	
		
		

		
		
	


	




 ).

 Here's one of the best links on space-charge tubes that I'm aware of and one that I included in the tube sections on the MAX/MiniMAX websites:
Space Charge and Other Low-Voltage Tubes

 You'll note that all of the Millett tubes are listed and so is Pete Millett's original Millett Hybrid article.


----------



## linuxworks

I do not know tubes very well (lol). but what I've found in searching is this:

AA5 History

 then search on '12FK6' (search the text using browser search function).

 they say:
*
 ALL AMERICAN FIVE - TUBE COMPLEMENT (list by John Reinicke)

 CONVERTER IF AMP DETECTOR/ AUDIO RECTIFIER YEAR 1st Audio OUTPUT*

 12GA6 12EA6 12FM6 mid to late 50's
 12AD6 12AC6 12AJ6 12V B+ tubes for
 12AG6 12AF6 12FK6 car radios, same
 12FA6 12BL6 12AE6 pinouts as their
 12EG6 12DZ6 12FT6 AA5 counterparts


 and this '1st audio' seems to have an entry for the fk6 tube.

 so, I don't know - maybe its possible that under certain designs, this AA5 used the 12fk6 tube? (that's just one I have on my MM, I realize there are other choices).


----------



## tomb

Quote:


  Originally Posted by *linuxworks* /img/forum/go_quote.gif 
_I do not know tubes very well (lol). but what I've found in searching is this:

AA5 History

 then search on '12FK6' (search the text using browser search function).

 they say:
*
 ALL AMERICAN FIVE - TUBE COMPLEMENT (list by John Reinicke)

 CONVERTER IF AMP DETECTOR/ AUDIO RECTIFIER YEAR 1st Audio OUTPUT*

 12GA6 12EA6 12FM6 mid to late 50's
 12AD6 12AC6 12AJ6 12V B+ tubes for
 12AG6 12AF6 12FK6 car radios, same
 12FA6 12BL6 12AE6 pinouts as their
 12EG6 12DZ6 12FT6 AA5 counterparts


 and this '1st audio' seems to have an entry for the fk6 tube.

 so, I don't know - maybe its possible that under certain designs, this AA5 used the 12fk6 tube? (that's just one I have on my MM, I realize there are other choices)._

 

Well, I think the operative term is "car radio," which is only a small subset of the very lengthy history of the AA5, but OK - point taken.


----------



## Frihed89

I posted this by mistake on the starving student thread.

 Perhaps this question has been asked before, but this is a long thread.

 Where can I order an adapter? I am in Denmark: 230VAC/50hz with Schuko plugs. Can anyone give me a part number to an adapter?

 Is there anything tied to the AC frequency?

 Thanks.


----------



## ruZZ.il

you mean something like this?

[size=medium]L55BR[/size]@Maplin(uk). 240/24v 1.5A AC/AC Mains Power Supply (FOR ~240v AC GRID VOLTAGE! (typically outside US)).

 I'm not quiet sure if maplin will get that to denmark. maybe someone else knows something from farnell or something..


----------



## tomb

I can't help you beyond what ruZZ.il's posted, but I can confirm that we have many international MiniMAX builders who use 50Hz. It's all rectified in the power supply, anyway, so there's no issue with the different frequency - as long as you use a proper AC walwart.


----------



## Frihed89

Thanks. The 1.5A was what i really needed. I have a multi-multi adapter 100-230V - 2A on the input side and 15-24V -4.5A max on the output. Would that work. It's made by Targus. No paperwork.

 And thanks to you too Tom.


----------



## MrMajestic2

Quote:


  Originally Posted by *Frihed89* /img/forum/go_quote.gif 
_Thanks. The 1.5A was what i really needed. I have a multi-multi adapter 100-230V - 2A on the input side and 15-24V -4.5A max on the output. Would that work. It's made by Targus. No paperwork.

 And thanks to you too Tom._

 

That´s most likely DC so it wont work.


----------



## eitel

Quote:


  Originally Posted by *Frihed89* /img/forum/go_quote.gif 
_I posted this by mistake on the starving student thread.

 Perhaps this question has been asked before, but this is a long thread.

 Where can I order an adapter? I am in Denmark: 230VAC/50hz with Schuko plugs. Can anyone give me a part number to an adapter?

 Is there anything tied to the AC frequency?

 Thanks._

 

I will use part no. 56-298-60 from ELFA for my Minimax. 230VAC in, 23.3V and 860mA out.


----------



## Frihed89

Quote:


  Originally Posted by *eitel* /img/forum/go_quote.gif 
_I will use part no. 56-298-60 from ELFA for my Minimax. 230VAC in, 23.3V and 860mA out._

 


 OK and tanks.


----------



## gspence2000

Has anyone noticed harsh sibilance from the 12AE6 tubes?

 First, my setup: MiniMax is driving a pair of Senn HD 580s. The audio source is an AMB Y1 DAC connected to my PC's X-Fi card. I have EAX set to "ampitheater", CMSS-3d and Crystalizer turned all the way up. Just kidding--all the X-Fi nonsense is disabled.
	

	
	
		
		

		
		
	


	




 I've been using 12AE6 tubes with my MiniMax for a couple of months now, and have been happy with them except that sometimes vocals have a harsh "sss" sound. I figured that some of the recordings were less-than-optimal.

 Today I was listening to U2's new album and track two "Moment of Surrender" was so full of harsh sibilance that I couldn't stand it.

 I switched to the 12FK6 tubes and the nasty sibilance is gone.

 Have any of you had this kind of experience with the 12AE6 tubes?


----------



## linuxworks

I use the fk6 tubes (only, so far) and one thing I did notice is that the sib. is LESS with this amp/combo than with most of my other SS amps. could be my imagination but one of the things I like about the MM is that its more mellow than SS. but again, I've only tried that one set of tubes so far.


----------



## tomb

I agree with linuxworks. Dating all the way back to the original revMH Millett Hybrid, sibilance is the last thing I've every heard with these things.

 Moreover, if anything, highs are more accentuated with 12FK6's than they are with 12AE6's. Very generally speaking, 12AE6's have more punch, 12FK6's have more highs, with 12FM6's inbetween. That's very general, though, and it's quite possible to get a pair of 12AE6's that sound as good as 12FK6's in the highs. The best thing to say is that tubes vary, period.

 All that said, I'd suspect your source, to be honest. You may have been kidding about all that stuff, but the truth is, something similar may be going on in the background. Try just running it directly from the Gamma DAC connected to USB - bypass that X-Fi thing altogether.


----------



## Beefy

I'm running a y1 through USB into my Mini Max with 12FK6 and listening right now. Phones are ATH-ESW9. Not even a hint of sibilance...... unless it was there on the original recording.

 What output caps do you have on the y1? Might be a factor.


----------



## gspence2000

Bypassing the X-Fi and using the y1 as a USB sound card sounds the same to me. I am still finding that for at least a few "problem" recordings, my 12AE6 tubes present harsh sibilance. The 12FK6 tubes seem to mellow it out. 

 As the 12FK6 tubes are giving me plenty of bass I am happy to stick with them for a while. One of my 12AE6 tubes was pretty microphonic anyways so I just needed an excuse to roll the tubes.

 Most of the music that I listen to during the day is streaming from the Rhapsody music service. Perhaps their streaming audio format is partially to blame.


----------



## tomb

Quote:


  Originally Posted by *gspence2000* /img/forum/go_quote.gif 
_Bypassing the X-Fi and using the y1 as a USB sound card sounds the same to me. I am still finding that for at least a few "problem" recordings, my 12AE6 tubes present harsh sibilance. The 12FK6 tubes seem to mellow it out. 

 As the 12FK6 tubes are giving me plenty of bass I am happy to stick with them for a while. One of my 12AE6 tubes was pretty microphonic anyways so I just needed an excuse to roll the tubes.

 Most of the music that I listen to during the day is streaming from the Rhapsody music service. Perhaps their streaming audio format is partially to blame._

 

Tubes are not free of distortion. It's just that it's often considered "good" distortion. So if there's an artifact in the particular music source, it's conceivable that tubes can superimpose harmonics over certain frequencies to give a bad result. Sibilance as a result is not very common with tubes, though, which is why we suspect something in your source. Most likely whatever phenomenon is causing it is exacerbated by the high-gain 12AE6's.

 Again, just to remove the idea that bad tubes are causing this - I'd try a totally independent, virgin source, if you have one. FLAC files with a USB DAC are preferred in every case with a MAX/MiniMAX, IMHO.


----------



## pinkfloyd4ever

Quote:


  Originally Posted by *gspence2000* /img/forum/go_quote.gif 
_Most of the music that I listen to during the day is streaming from the Rhapsody music service. Perhaps their streaming audio format is partially to blame._

 

my guess is that using Rhapsody as your source is probably your biggest problem. Virtually all streaming music (rhapsody, XM, sirius, anything else you can think of) is crapified in one way or another, despite the smoke the proprietors' marketing departments like to blow up your @ss about "crystal clear streaming digital....."


----------



## aphexii

Hmmm, trying to figure out with my dad how were going to drill the power switch hole. We used the stock switch which calls for a .402" hole, which unfortunately doesn't seem to have an easy fraction equivalent for a drill bit. (Though having a 402/1000 drill but would be the utmost of cool)

 3/8 is a hair too small and 1/2 is a hair too big. 7/16 is close, but a smidgen too big (though once locked down I guess it should hold fine).

 Think we should just go for 7/16?

 I tossed around the idea of maybe scrapping the back power switch and getting a vandal switch for the front (and add the hole to my FPE panel when I order), but then I run into issues of routing power up front in such a tiny case and very little room for the switch itself.


----------



## WilCox

Quote:


  Originally Posted by *aphexii* /img/forum/go_quote.gif 
_3/8 is a hair too small and 1/2 is a hair too big. 7/16 is close, but a smidgen too big (though once locked down I guess it should hold fine)._

 

This will make a perfect size hole if you drill first to 3/8":

Ace - Ace Tree: Tools: Hand Tools: Taps & Dies: Tap / Die Accessories: General® Repairman'S Reamer (130)


----------



## tomb

Wilcox has a great idea. You can also use the 3/8" drill and whittle a little bit more out. The 7/16" is definitely too big. I used the 3/8" on the original prototype for the MiniMAX, then reamed it out a bit with a simple pocket knife. Note that if you use the square-version of the switch, it includes a locating tab to keep the switch square. You can kind of smash the tab in so that it'll never move - you don't really have to go to the trouble of cutting a keyway:





 P.S. You're correct that the switch is small and doesn't take up much depth. We searched for quite awhile to find a switch that satisfied those requirements.


----------



## THE_SOURCE41

I am biasing the dbs and am wondering where do you look for the measurments? is it the ground to tb2l or tb1l or tb1r 2r? or is it only between 1 and 2


----------



## Uncle Bob

I notice on the beezar website that only the black enclosure is listed

 Is this the end of the silver version or is there going to be another batch ordered?


----------



## tomb

Quote:


  Originally Posted by *Uncle Bob* /img/forum/go_quote.gif 
_I notice on the beezar website that only the black enclosure is listed

 Is this the end of the silver version or is there going to be another batch ordered?_

 

Afraid so. I've ordered a new batch of black, but the demand for silver is so small I can't afford the quantity needed to get the cost down.
	

	
	
		
		

		
		
	


	




 I may offer them as a special order only, but they'll be pricy. Besides the demand being less, I've had some complaints about Lansing's finish. Technically, they're not "silver" but "clear." Because of that, none of the fabrication marks from the extrusion and handling are covered up - they show right through. The first thing people notice are the streaks. I don't think that's objectionable, necessarily, but it's another reason that the demand is low, which makes the cost high. The result is that it's just not worth it, IMHO.


----------



## Uncle Bob

shame, but thanks for the quick reply.


----------



## patton713MW

Sweet, that just means that my silver case is even more "limited edition"!


----------



## THE_SOURCE41

Ok I found out what I was doing wrong with the biasing but now i have another problem. I have 27v for the power supply

 23v at both tubes.

 and nothing at the DBs even with playing around with the trim pots.

 I have no idea what is wrong.

 Sam


----------



## tomb

Quote:


  Originally Posted by *THE_SOURCE41* /img/forum/go_quote.gif 
_Ok I found out what I was doing wrong with the biasing but now i have another problem. I have 27v for the power supply

 23v at both tubes.

 and nothing at the DBs even with playing around with the trim pots.

 I have no idea what is wrong.

 Sam_

 

pics ...


----------



## THE_SOURCE41

Ok I got the tubes to be biased at 13.5

 But I am still getting nothing at the DBs.

 Here are some pictures

http://i193.photobucket.com/albums/z...6/DSC00179.jpg
http://i193.photobucket.com/albums/z...6/DSC00180.jpg
http://i193.photobucket.com/albums/z...6/DSC00181.jpg
http://i193.photobucket.com/albums/z...6/DSC00182.jpg
http://i193.photobucket.com/albums/z...6/DSC00183.jpg


 Thanks for the help!

 Sam


----------



## tomb

Quote:


  Originally Posted by *THE_SOURCE41* /img/forum/go_quote.gif 
_Ok I got the tubes to be biased at 13.5

 But I am still getting nothing at the DBs.

 Here are some pictures

http://i193.photobucket.com/albums/z...6/DSC00179.jpg
http://i193.photobucket.com/albums/z...6/DSC00180.jpg
http://i193.photobucket.com/albums/z...6/DSC00181.jpg
http://i193.photobucket.com/albums/z...6/DSC00182.jpg
http://i193.photobucket.com/albums/z...6/DSC00183.jpg


 Thanks for the help!

 Sam_

 

What output transistors are those? If they're 2SC3422/2SA1359 or 2SC3421/2SA1358, they're in backwards. They should go on the right side of the heat sinks as you're looking at the board from the headphone jack and volume pot.

 Unscrew them from the heat sinks, then make a solder blob big enough to cover all three pins on the bottom of the board. Each transistor should fall out when you do that. If not, try to tie a little string, piece of tape, etc. to the transistor and pull down while you're heating the blob on the bottom of the board with your soldering iron. You don't really have to clean them up - just switch them into the pads on the other sides of the heat sinks and solder them in.

 For the time being, don't worry about the heat pads if you don't have any extra. They'll cool enough for the time being just being bolted directly to the heat sinks. You can go back later and add the pads by bending the transistors back slightly to make enough room to get in there - probably should put the pads back before you case it up.

 Let us know if those are the transistors and work on switching them around when you get a chance. It's not that difficult, so don't give up. I didn't see anything else wrong for the time being.
	

	
	
		
		

		
		
	


	





 P.S. Chances are they're OK - it takes a lot to burn those things up.


----------



## THE_SOURCE41

Ok ya they are in the wrong place. Thanks for the help. I will get those turned around.


----------



## ssoaos

Hi, I have noise issue with my Minimax and hope someone has seen it and could help. 

 I just finished building the Minimax and put in Tom's custom case. After two days the bias is stabilized. But there is a audible ground hum. It is not related to volume level. 
 1. The pot is grounded. 
 2. When I touch the case, the noise is gone. 
 3. I swapped the tube(They are 12AE6s from Beezar), the noise is lowered. 
 4. I thought it was ground loop, so I took the board out from the case, the noise was still there. 
 5. I disconnected the RCAs from the board, but it did not help. 
 6. If I touch any electrolytic cap, the noise it gone. 
 Any suggestion would be appreciated.

 Stanley


----------



## Beefy

Is the amp actually hooked up to a source? Is the incoming ground wiring properly connected?


----------



## ssoaos

Hi, No source. I started by disconnected the source. Took the board out from the case with back panel connected. The disconnected the RCA. 

 Stanley


----------



## ssoaos

Hi Beefy, I just tried with only one tube installed. I noise goes away. It does not matter which channel.


----------



## cetoole

Sorry to say, that doesnt actually help you any. With either tube out, the heaters on both wont light, so the tubes dont function and buffers dont bias. How about you post some pics here? It sounds to me like a grounding issue.


----------



## Beefy

Try connecting it to a source and listening to it, rather than just sitting it on a desk and burning it in


----------



## ssoaos

Thank you Colin and Beefy,
 Tom reminded me if I pulled out one tube, the series supply to the filament was broken and so my other channel is obviously quiet. Silly me! I did more tests last night by swapping the tube and the noise followed the tube to that channel, so Tom believes it is the tube and he is sending me a replacement to try. I did resoldered the whole board so the chance of having a cold solder is probably zero. I disconnect the input wire and the only wires to the board are the two AC wires. 
 Any suggestion is appreciated. 
 Thank you all!
 Stanley


----------



## oneplustwo

Hey folks,

 Just wanted to share some brief impressions of how my minimax compares to the active ground beta 22 I just built.

 In short, the mini holds its own quite well! If I was to quantify SQ where my receiver headphone jack is 70, the mini max would rate at about a 91, and the beta would be a 97.

 There's definitely more "color" in the minimax due to the tubes but I find the power and detail available is very good. This is in contrast to the beta where the sound is more clean/analytical for lack of a better word, but the power is awesome! Transient response seems instantaneous and even the softer sections are detailed and clear.

 Is it worth the added cost? There is no right answer, obviously, but I didn't spend that much more on the beta than the mini since I went super cheap on the case work. So the price comparison for me isn't really apples to apples. For what it's worth, I'm glad I built the beta and love the quirky result. 

 Should I keep both? I'm not really that excited about selling the mini even though I told myself I would to justify the cost of the beta. For the moment, I'll keep them both. But after a few months, if I find I'm not listening to the mini any more I may sell it. I hate selling stuff I made though...


----------



## tomb

Quote:


  Originally Posted by *oneplustwo* /img/forum/go_quote.gif 
_Hey folks,

 Just wanted to share some brief impressions of how my minimax compares to the active ground beta 22 I just built.

 In short, the mini holds its own quite well! If I was to quantify SQ where my receiver headphone jack is 70, the mini max would rate at about a 91, and the beta would be a 97.

 There's definitely more "color" in the minimax due to the tubes but I find the power and detail available is very good. This is in contrast to the beta where the sound is more clean/analytical for lack of a better word, but the power is awesome! Transient response seems instantaneous and even the softer sections are detailed and clear.

 Is it worth the added cost? There is no right answer, obviously, but I didn't spend that much more on the beta than the mini since I went super cheap on the case work. So the price comparison for me isn't really apples to apples. For what it's worth, I'm glad I built the beta and love the quirky result. 

 Should I keep both? I'm not really that excited about selling the mini even though I told myself I would to justify the cost of the beta. For the moment, I'll keep them both. But after a few months, if I find I'm not listening to the mini any more I may sell it. I hate selling stuff I made though..._

 

I never thought I'd see someone compare the MiniMAX to the B22, but thanks for the report.
	

	
	
		
		

		
		
	


	




 If anything, it confirms the thoughts that we've had: the changes to the power supply, the parts selection, the board layout, etc - it's pretty much as good as it gets when coming to the BJT version of a MAX/Millett Hybrid. When you factor in the case - despite the higher cost over a run-of-the-mill Hammond/Lansing - the result is even more satisfying.


----------



## THE_SOURCE41

I have life and sound in my amp! I just want to say thank you to tomb and everyone who has helped me with this. 
 I will post pics once it is enclosed and completely set up.

 Sam


----------



## Beefy

Quote:


  Originally Posted by *oneplustwo* /img/forum/go_quote.gif 
_Just wanted to share some brief impressions of how my minimax compares to the active ground beta 22 I just built.

 In short, the mini holds its own quite well! If I was to quantify SQ where my receiver headphone jack is 70, the mini max would rate at about a 91, and the beta would be a 97._

 

I think that sometimes people forget how little 'real' difference there is between well designed amps. Sure, if you sit a couple of amps you are familiar with side by side, listen to tracks you have listened to for years, in an ideal environment with a complete lack of distractions...... then the potential for differences is there.

 But when I am just kicking back and listening to the _music_, that really doesn't matter to me. I still maintain that my MMM is a better amp than any of the Maxes that I have built; that doesn't take away from the fact that I thoroughly enjoyed building and listening to every one of those amps.


----------



## oneplustwo

Agreed! Now that you mention it, I am curious how the MMM sounds having built the mini3 and the beta now. I'll have to use all my will power to NOT find out for myself.


----------



## tomb

Quote:


  Originally Posted by *THE_SOURCE41* /img/forum/go_quote.gif 
_I have life and sound in my amp! I just want to say thank you to tomb and everyone who has helped me with this. 
 I will post pics once it is enclosed and completely set up.

 Sam_

 

Glad to hear it! ... and thank you for not giving up.
	

	
	
		
		

		
		
	


	




 We've had one or two that did that when they realized a mistake with the output transistors. Hopefully, it wasn't that hard for you. Bring on the pics!!


----------



## aphexii

Just curious, what gauge wire are you guys using for your hookups? I have 18 or 20 gauge stranded in there right now but its a bit less flexible than I would prefer and have been thinking of maybe picking up some thinner wire.


----------



## TimJo

Quite a few of us use the 22 ga. Navships silver/teflon wire...

http://www.head-fi.org/forums/f6/hoo...dation-404921/


----------



## linuxworks

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Glad to hear it! ... and thank you for not giving up.
	

	
	
		
		

		
			





 We've had one or two that did that when they realized a mistake with the output transistors._

 

raises hand, embarrassingly 
	

	
	
		
		

		
		
	


	




 I soldered in all 4 transistors in the wrong 'mirror image' holes but fortunately found my mistake BEFORE applying power. I have a good desoldering gun (hakko) so it was not hard to fix but man, that would have bummed me out had I not caught it before power-up time.

 check check and visually check again.

 I do think that to make things more user goof-proof, the extra set of holes should not really be there and people should just get the right parts as long as they're not *impossible* or overly expensive.

 that was the only gotcha in my build.


----------



## patton713MW

Quote:


  Originally Posted by *aphexii* /img/forum/go_quote.gif 
_Just curious, what gauge wire are you guys using for your hookups?_

 

22 gauge from Navships, just like TimJo said.


----------



## tomb

Quote:


  Originally Posted by *linuxworks* /img/forum/go_quote.gif 
_raises hand, embarrassingly 
	

	
	
		
		

		
		
	


	




 I soldered in all 4 transistors in the wrong 'mirror image' holes but fortunately found my mistake BEFORE applying power. I have a good desoldering gun (hakko) so it was not hard to fix but man, that would have bummed me out had I not caught it before power-up time.

 check check and visually check again.

 I do think that to make things more user goof-proof, the extra set of holes should not really be there and people should just get the right parts as long as they're not *impossible* or overly expensive.

 that was the only gotcha in my build._

 

I suspect almost as many builds were made with the 2SC2344/2SA1011's as opposed to the 2SC3422/2SA1359's. Those transistor pairs go on opposite sides from each other. So, the extra holes are needed.
	

	
	
		
		

		
		
	


	




 Also - we've been surprised since the start of the MAX/MiniMAX builds when people have messed up, because it appears that reversed output transistors are OK every time. Get the TO-92s mixed up and in the first instant of applied power they're fried, but the TO-220's take quite a bit to blow. I guess they _melt_ easier than they _short_ out, because mistakes in over-biasing have burned up more than have the incidents of soldering them in backwards.
	

	
	
		
		

		
		
	


	







 P.S. Glad you recovered, too.


----------



## aphexii

Quote:


  Originally Posted by *patton713MW* /img/forum/go_quote.gif 
_22 gauge from Navships, just like TimJo said._

 

Thanks guys, i'll place an order tonight!


----------



## tomb

Quote:


  Originally Posted by *aphexii* /img/forum/go_quote.gif 
_Thanks guys, i'll place an order tonight!_

 

Yep - John at John's Silver Teflon Wire Shop (navships) is a good guy. Last time, we started a thread for him and it gave him some of the biggest business he's ever had.

 Study his selections though, and pay attention to the total diameter and insulation thickness. Look at all the other 22 ga to make sure you're getting the thinnest stuff. Some of his wire has got some really thick insulation on it (it can be good for certain things, but just be sure you're aware of the difference). Likewise, stay away from the Kapton stuff.


----------



## patton713MW

What's the difference between the Kapton and the other silver/copper?


----------



## tomb

Quote:


  Originally Posted by *patton713MW* /img/forum/go_quote.gif 
_What's the difference between the Kapton and the other silver/copper?_

 

From what I remember, Kapton makes the wire stiff as all h*ll and it also has abrasion problems from what I've read. It's just more trouble than needed for our stuff. Stick with the normal teflon-spc.


----------



## eitel

Hi guys,

 I am almost done building my minimax, but could need some help figuring out a noise issue.

 When I touch/tap the volume knob, chassis or pretty much anything on the amp, the tap itself is amplified through one of the audio channels. When I switch the tubes around the tapping ends up in the other channel. Could this the result of a bad tube?

 I also noticed that if I bias the tubes(12FM6) at 13.5V and then switch them around, the bias is 11 and 17 volts. Is this normal?

 Any help is appreciated.


----------



## rds

Quote:


  Originally Posted by *eitel* /img/forum/go_quote.gif 
_Hi guys,

 I am almost done building my minimax, but could need some help figuring out a noise issue.

 When I touch/tap the volume knob, chassis or pretty much anything on the amp, the tap itself is amplified through one of the audio channels. When I switch the tubes around the tapping ends up in the other channel. Could this the result of a bad tube?

 I also noticed that if I bias the tubes(12FM6) at 13.5V and then switch them around, the bias is 11 and 17 volts. Is this normal?

 Any help is appreciated._

 

The tap issue is what people mean when they say a tube is "microphonic". The tube itself is picking up the vibration and turning it into electrical noise. The solution is to replace the tube.

 The bias thing is normal too. That is the reason we bias the tubes to begin with (if that makes sense).


----------



## tomb

Quote:


  Originally Posted by *eitel* /img/forum/go_quote.gif 
_Hi guys,

 I am almost done building my minimax, but could need some help figuring out a noise issue.

 When I touch/tap the volume knob, chassis or pretty much anything on the amp, the tap itself is amplified through one of the audio channels. When I switch the tubes around the tapping ends up in the other channel. Could this the result of a bad tube?

 I also noticed that if I bias the tubes(12FM6) at 13.5V and then switch them around, the bias is 11 and 17 volts. Is this normal?

 Any help is appreciated._

 

Yes, rds is absolutely correct.

 If I've supplied the tube in question, please let me know - I'll send you another. All my tubes are tested, but microphonics is not something that shows up in a tester - you have to plug them in an amp, first.

 As rds says, every tube will have a slightly different bias point. That's why we have the tube bias adjustment in the first place.


----------



## eitel

Quote:


  Originally Posted by *rds* /img/forum/go_quote.gif 
_The tap issue is what people mean when they say a tube is "microphonic". The tube itself is picking up the vibration and turning it into electrical noise. The solution is to replace the tube._

 

That makes sense. Thanks a lot.

  Quote:


  Originally Posted by *rds* /img/forum/go_quote.gif 
_The bias thing is normal too. That is the reason we bias the tubes to begin with (if that makes sense)._

 

What I meant to ask was if it is normal for the bias point to be that much different for a matched pair of tubes. But based on your and Tom's answer I guess it is


----------



## tomb

Quote:


  Originally Posted by *eitel* /img/forum/go_quote.gif 
_<snip>What I meant to ask was if it is normal for the bias point to be that much different for a matched pair of tubes. But based on your and Tom's answer I guess it is 
	

	
	
		
		

		
		
	


	


_

 

Think of it as two people - one shorter than the other, but both of them can jump the same amount. Their jumping "output" is the same, but they start from a different level. Put a step stool under the shorter person so that they start at the same height, then their jumps will reach the same level. Tube bias adds the step stool.

 There's also some compensation going on in the circuit, too. Even if the two tubes were perfectly matched in bias, there may be subtle differences in the two CCS's, slightly different resistors/trimmers in the circuit, etc.

 Or, I may have just messed up and the tubes aren't really matched (assuming I supplied them).


----------



## ssoaos

hi, a few days ago I reported some noise issues from my new MiniMax. Some of you jumped right in to help. After talking to Tom he sent me a new 12AE6 to replace the noisy side and the problem was solved. 

 I wanted to thank you all and Tom's offer.

 Regards,
 Stanley


----------



## ruZZ.il

ENJOY!


----------



## THE_SOURCE41

Quote:


 Glad to hear it! ... and thank you for not giving up. We've had one or two that did that when they realized a mistake with the output transistors. Hopefully, it wasn't that hard for you. Bring on the pics!! 
 

I will be posting pics as soon as i get back home. I am on spring break in london for the rest of the week.


----------



## Gradofan2

Where can I find the power output for various impedance loads for the MiniMax?

 I'd like to confirm it has enough power to drive both my low and high impedance phones to loud volumes without noise at about 12 O'clock on the POT.


----------



## WilCox

Quote:


  Originally Posted by *Gradofan2* /img/forum/go_quote.gif 
_Where can I find the power output for various impedance loads for the MiniMax?

 I'd like to confirm it has enough power to drive both my low and high impedance phones to loud volumes without noise at about 12 O'clock on the POT._

 

I don't have the specs you're looking for, but maybe Tom or Colin have that handy.

 What I can tell you that the MiniMax has plenty of gain for both my low impedance (Grado RS2, ATH-W5000) and high impedance (Senn HD650) phones, never needing to go past 12 o-clock with any of the three different gain tubes. I cannot hear any hiss or hum at full volume (as long as I disconnect my DAC which is not nearly as quiet as the amp!

 Hope that helps a bit.


----------



## tomb

Quote:


  Originally Posted by *Gradofan2* /img/forum/go_quote.gif 
_Where can I find the power output for various impedance loads for the MiniMax?

 I'd like to confirm it has enough power to drive both my low and high impedance phones to loud volumes without noise at about 12 O'clock on the POT._

 

With respect, I think we're confusing a couple of terms here. Whether the MiniMAX has enough power to drive your Senns and Grados with authority (it does) has _zero_ to do with the position of the volume knob. The position of the volume knob is dictated by _gain._

 With 12AE6 tubes, you probably will never get past the 9 o'clock position before excruciating volume is achieved with your Grados. With 12FM6 tubes, you can probably get to 12 o'clock. With 12FK6 tubes, perhaps 2 o'clock. The gains differ on these tubes: 14 for 12AE6, 10 for 12FM6 and 7 for 12FK6. The actual bias and supply voltage result in a bit less gain than the book values on these tubes, but the difference is consistent.

 With the MiniMAX, the diamond buffer is so powerful that the tubes will _always_ clip well before the buffer ever runs out of power. So, conceivably, the use of 12FK6 tubes may forestall clipping for the majority of the volume travel. However, they don't have enough voltage swing to really drive Senns with authority - 12AE6's are needed for that. 12FM6's are more or less in the middle.

 All that said, the MiniMAX is probably better at low impedance phones than high ones. I think it pairs with Grados better than any other phones. However, it can drive Senns to a very nice sound as well. As for noise - well, I think the MiniMAX is extremely quiet as tubes and Milletts go, especially with the new low-noise power supply on the MiniMAX. Tubes are not going to be as quiest as solid-state amps, however, but you should never hear hum - more like some tizziness in the highs or a bit of hiss with very low-impedance/high sensitivty phones (not Grados) and this can be tweaked out, depending on how it's built - and it does not happen in most circumstances.

 As for power data, it's something I've got on the "do list", but haven't got 'round to it yet. You really need a scope to make the determination for the clipping point of the tubes to make this accurate (power is measured just below that). The only phones I've heard of the MAX having trouble with are some particularly inefficient 600 ohm phones. They will drive orthos with authority, which are just about the hardest-to-drive headphones around without being super-high impedance.


----------



## Gradofan2

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_With respect, I think we're confusing a couple of terms here. Whether the MiniMAX has enough power to drive your Senns and Grados with authority (it does) has zero to do with the position of the volume knob. The position of the volume knob is dictated by gain.

 With 12AE6 tubes, you probably will never get past the 9 o'clock position before excruciating volume is achieved with your Grados. With 12FM6 tubes, you can probably get to 12 o'clock. With 12FK6 tubes, perhaps 2 o'clock. The gains differ on these tubes: 14 for 12AE6, 10 for 12FM6 and 7 for 12FK6. The actual bias and supply voltage result in a bit less gain than the book values on these tubes, but the difference is consistent.

 With the MiniMAX, the diamond buffer is so powerful that the tubes will always clip well before the buffer ever runs out of power. So, conceivably, the use of 12FK6 tubes may forestall clipping for the majority of the volume travel. However, they don't have enough voltage swing to really drive Senns with authority - 12AE6's are needed for that. 12FM6's are more or less in the middle.

 All that said, the MiniMAX is probably better at low impedance phones than high ones. I think it pairs with Grados better than any other phones. However, it can drive Senns to a very nice sound as well. As for noise - well, I think the MiniMAX is extremely quiet as tubes and Milletts go, especially with the new low-noise power supply on the MiniMAX. Tubes are not going to be as quiest as solid-state amps, however, but you should never hear hum - more like some tizziness in the highs or a bit of hiss with very low-impedance/high sensitivty phones (not Grados) and this can be tweaked out, depending on how it's built - and it does not happen in most circumstances.

 As for power data, it's something I've got on the "do list", but haven't got 'round to it yet. You really need a scope to make the determination for the clipping point of the tubes to make this accurate (power is measured just below that). The only phones I've heard of the MAX having trouble with are some particularly inefficient 600 ohm phones. They will drive orthos with authority, which are just about the hardest-to-drive headphones around without being super-high impedance._

 

OK... thanks...

 So... then... do you think the MiniMax can provide enough voltage to control Senns really well... if... I use the 12AE6? 

 Also... SACD Lover... just reported he prefers the sound of the Millett Hybrid Mosfet Max to the sound of the MiniMax - he thinks its richer and more robust with his Grados. 

 I don't know what the diffrences in the construction are... though I suspect the Mosfet Max has a more robust power supply, and perhaps larger caps. 

 Anyway... perhaps you know?

 I guess I've developed an interest as a result of SACD Lover's posts, and because his reference standard is pretty high (Extreme). 

 I had an earlier Millett Hybrid Head (Shellbook), which was OK with Grados, but lacked enough voltage / power to drive Senns really well. 

 With it, I preferred the 12AE6 tubes, because of their gain / dynamics.

 I also prefer a very dynamic, powerful sound. I didn't get that out of the Hybrid Head.

 So... this is you??? http://diyforums.org/MOSFET-MAX/MOSFET-MAXcontacts.php (Tom Blanchard - MAX Webmaster)? 

 And... is Drew Dunn still involved? I just emailed him with some questions. I've still got his Maxi Moy - which is one of the best amps, I've tried - and... I've tried some good ones.


----------



## Beefy

Quote:


  Originally Posted by *Gradofan2* /img/forum/go_quote.gif 
_Also... SACD Lover... just reported he prefers the sound of the Millett Hybrid Mosfet Max to the sound of the MiniMax - he thinks its richer and more robust with his Grados._

 

I don't believe that SACD lover has ever heard a Mini Max. It is quite new, and has been improved over the board for regular/MOSFET Maxes.

  Quote:


 though I suspect the Mosfet Max has a more robust power supply, and perhaps larger caps. 
 

Poppycock. The Mini Max has a better power supply than any MOSFET Max has - that was the biggest improvement with the new Mini Max. A new board will be available with the same improvements for the regular/MOSFET Max soon.

 As for larger caps? That is just silly.

  Quote:


 And... is Drew Dunn still involved? 
 

I don't believe so. tomb and cetoole are the people behind the updated Millett Hybrids.


----------



## tomb

Quote:


  Originally Posted by *Beefy* /img/forum/go_quote.gif 
_ Quote:


 And... is Drew Dunn still involved? 
 

I don't believe so. tomb and cetoole are the people behind the updated Millett Hybrids._

 

Allow me to knock down this question quickly, because Jude has asked me the same question a couple of times in the past.
	

	
	
		
		

		
		
	


	




 I purchased the former Millett Hybrid site and forum from Drew Dunn. He has no affiliation with cetoole, myself, or the business that gave me an MOT-status.

 It seems to me that some of these questions are better suited for a PM or an e-mail, not the general Head-Fi forum. If you have specific questions about the MiniMAX, that's fine to ask them here.


----------



## gspence2000

Quote:


  Originally Posted by *gspence2000* /img/forum/go_quote.gif 
_Has anyone noticed harsh sibilance from the 12AE6 tubes?

 First, my setup: MiniMax is driving a pair of Senn HD 580s. The audio source is an AMB Y1 DAC connected to my PC's X-Fi card. I have EAX set to "ampitheater", CMSS-3d and Crystalizer turned all the way up. Just kidding--all the X-Fi nonsense is disabled.
	

	
	
		
		

		
		
	


	




 I've been using 12AE6 tubes with my MiniMax for a couple of months now, and have been happy with them except that sometimes vocals have a harsh "sss" sound. I figured that some of the recordings were less-than-optimal.

 Today I was listening to U2's new album and track two "Moment of Surrender" was so full of harsh sibilance that I couldn't stand it.

 I switched to the 12FK6 tubes and the nasty sibilance is gone.

 Have any of you had this kind of experience with the 12AE6 tubes?_

 

An update to the sibilance issue I reported a few weeks ago. The tracks that were exhibiting sibilance problems were streaming audio from the Rhapsody music service. I have since compared those tracks to FLAC encodings and I can confirm that Rhapsody is the source of the problem. Most of Rhapsody's streaming music is of very good quality, but there are a few exceptions.

 I am now back to the 12AE6's but I enjoyed listening to the FK's for a couple of weeks.

 If anyone else subscribes to Rhapsody, I'd be interested to know if you hear the problem on track 2 of U2's new album.


----------



## aphexii

lol, didn't think about the different screw holes on the plates before drilling the backplate using the template for the standard lansing case (mine has 2 screw holes in the middle, not 4 in the corners). I get it all soldered up and ready to mount, only to realize the square power button blocks the screw 
	

	
	
		
		

		
		
	


	




 Gonna swing by a local electronics shop to find a mini throw switch, the smaller round shape should give me enough clearance for the screw (I hope).


----------



## linuxworks

I have zero complaints about gain level or 'drive' with my minimax and senn hd580/650.

 I use the fk6 tubes (right now).

 if there's a lack of gain or 'drive' then I must be deaf since things sound 'just fine' to me with my phones and this amp.


----------



## gspence2000

Quote:


  Originally Posted by *linuxworks* /img/forum/go_quote.gif 
_I have zero complaints about gain level or 'drive' with my minimax and senn hd580/650.

 I use the fk6 tubes (right now).

 if there's a lack of gain or 'drive' then I must be deaf since things sound 'just fine' to me with my phones and this amp._

 

I concur, 12FK6's with my HD580's sounds great to me.


----------



## tomb

Quote:


  Originally Posted by *linuxworks* /img/forum/go_quote.gif 
_I have zero complaints about gain level or 'drive' with my minimax and senn hd580/650.

 I use the fk6 tubes (right now).

 if there's a lack of gain or 'drive' then I must be deaf since things sound 'just fine' to me with my phones and this amp._

 

 Quote:


  Originally Posted by *gspence2000* 
_I concur, 12FK6's with my HD580's sounds great to me._

 

Glad to hear it! However, I would encourage you both to try 12AE6's with high-impedance phones when you can. There's more to it than just gain. In fact, you may not like the lack of volume travel that can occur with the 12AE6, even with high-impedance phones. There is a difference in dynamics, though, because the 12AE6 can swing more volts. So, I'm just suggesting that you try a pair (if you haven't) ... you may like the difference.


----------



## Gradofan2

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Allow me to knock down this question quickly, because Jude has asked me the same question a couple of times in the past.
	

	
	
		
		

		
		
	


	




 I purchased the former Millett Hybrid site and forum from Drew Dunn. He has no affiliation with cetoole, myself, or the business that gave me an MOT-status.

 It seems to me that some of these questions are better suited for a PM or an e-mail, not the general Head-Fi forum. If you have specific questions about the MiniMAX, that's fine to ask them here.
	

	
	
		
		

		
		
	


	


_

 

Here ya go... 

 This is why... I had that question.

MOSFET-MAX Contacts

 I bought a couple of his amps about 3 years ago.


----------



## tomb

Quote:


  Originally Posted by *Gradofan2* /img/forum/go_quote.gif 
_Here ya go... 

 This is why... I had that question.

MOSFET-MAX Contacts

 I bought a couple of his amps about 3 years ago._

 

Thanks for pointing that out - it's now corrected - on the original MAX website, too.


----------



## aphexii

An odd issue cropped up last night, trying to troubleshoot what's going on.

 The amp was stable last week when I checked;

 V+/GND - 27V
 TA2L/GND - 13.2V
 TA2R/GNS - 13.5V
 TA2L/TB2L - 90mV
 TA2R/TB2R - 90mV

 Last night while listening with the amp back in my custom case for about 20-30 minutes, the amp shut off. Turned it off and back on, it stayed in for 5-10 seconds, the turned back off. Killed the power and pulled the amp out of the case and noticed the left side was easily 10x as hot as the right, insanely hot.

 Grabbed my meter and here is what everything was testing at after the shutdown last night;

 V+/GND - 27V
 TA2L/GND - 9.35V
 TA2R/GNS - 15V
 TA2L/TB2L - .300V
 TA2R/TB2R - 90mV

 Did something die on me?


----------



## tomb

Quote:


  Originally Posted by *aphexii* /img/forum/go_quote.gif 
_An odd issue cropped up last night, trying to troubleshoot what's going on.

 The amp was stable last week when I checked;

 V+/GND - 27V
 TA2L/GND - 13.2V
 TA2R/GNS - 13.5V
 TA2L/TB2L - 90mV
 TA2R/TB2R - 90mV

 Last night while listening with the amp back in my custom case for about 20-30 minutes, the amp shut off. Turned it off and back on, it stayed in for 5-10 seconds, the turned back off. Killed the power and pulled the amp out of the case and noticed the left side was easily 10x as hot as the right, insanely hot.

 Grabbed my meter and here is what everything was testing at after the shutdown last night;

 V+/GND - 27V
 TA2L/GND - 9.35V
 TA2R/GNS - 15V
 TA2L/TB2L - .300V
 TA2R/TB2R - 90mV

 Did something die on me?_

 

It sounds like a short developed somewhere. Most likely, the polyfuse is opening on high current - that's what causes the shutdown. When you turn it off and let it cool, then the polyfuse resets, allowing you to turn it on again.

 Inspection is the first course of action - take the board out and see if you spot any damage or a situation where the wiring got chafed and blew something. Then focus on measuring the buffers - try to measure the voltage drop across the resistors and compare them to the good (right) side.


----------



## aphexii

Thanks for the quick reply Tom!

 Everything looks fine afaik, nothing charred or melted. Resistors on the left side all seem to check out fine with my DMM. 

 Anything else I can check?


----------



## tomb

Quote:


  Originally Posted by *aphexii* /img/forum/go_quote.gif 
_Thanks for the quick reply Tom!

 Everything looks fine afaik, nothing charred or melted. Resistors on the left side all seem to check out fine with my DMM. 

 Anything else I can check?_

 

Hmm ... well, just to make sure - I was suggesting to read the _voltage drop_ across the resistors _with power-on_. Realizing, of course, that you may have to do that in stages if the amp will only stay for short periods of time. The idea is to try and pinpoint where in the circuit that things are different. There will be a difference somewhere other than the DB test points (maybe).

 Other things to look for, but possible unlikely, are the tubes. Try switching the two tubes with each other and see if that changes things. Also check the measurements on the CCS resistors - again, check for voltage drop on those resistors with the power on, comparing the bad side with the good side. Finally, if you are unable to find the issue yourself, you might try a good photograph of top and bottom of the board - maybe we'll see something.

 From what you describe, it sure sounds like something shorted. From your first post, you mention "with the amp _back_ in my custom case for about 20-30 minutes ..." It sounds like it was out of the case, but then you put it back in the case and it only took 20-30 minutes to notice the problem. Sorry to say this, but if that interpretation of events is correct, that's a classic symptom of a case shorting issue. It happens a lot - board runs fine by itself, but case it up and all sorts of problems appear. Something is touching somewhere that shouldn't. Sometimes the contact is so miniscule it may take heat and a bit of thermal expansion to show up - 20 to 30 minutes, then poof.


----------



## aphexii

lol, well it was unlikely but it was indeed a bad tube 
	

	
	
		
		

		
		
	


	




 I pulled the tube out and noticed two pins stayed behind in the socket. Pulled them out with some tweezers, grabbed my other set of 12FK6's and its working PERFECT again, numbers are spot on.

 Thanks a million for the help! Would have never thought a tube could go bad like that. Maybe a clue, but I did notice the left tube seemed to make a slight ping/settling noise about two weeks ago while I was listening. Thought it was just settling in or something.

 Anyway, glad it was something so simple and not my soldering 
	

	
	
		
		

		
		
	


	




 Thanks again!


----------



## cetoole

Bad tubes sure can be a pain, but at least it was something which turned out to be easy to fix. Did you notice if the getter on the bad tube had turned white?


----------



## tomb

Quote:


  Originally Posted by *aphexii* /img/forum/go_quote.gif 
_lol, well it was unlikely but it was indeed a bad tube 
	

	
	
		
		

		
		
	


	




 I pulled the tube out and noticed two pins stayed behind in the socket. Pulled them out with some tweezers, grabbed my other set of 12FK6's and its working PERFECT again, numbers are spot on.

 Thanks a million for the help! Would have never thought a tube could go bad like that. Maybe a clue, but I did notice the left tube seemed to make a slight ping/settling noise about two weeks ago while I was listening. Thought it was just settling in or something.

 Anyway, glad it was something so simple and not my soldering 
	

	
	
		
		

		
		
	


	




 Thanks again!_

 

As cetoole said, thank goodness it was just a tube.
	

	
	
		
		

		
		
	


	




 That was the plan, of course - guess as many things as I can think of and one of them is bound to be right.
	

	
	
		
		

		
		
	


	










 Seriously though, there are common problems with tubes, but an outright failure is not one of them. Further, a tube failure resulting in an over-heated buffer has never happened, AFAIK - this may be a first.

 It's also nice to know that the polyfuse is doing more than stabilizing the power supply output. For the first time, I think - we have confirmation that it will save the buffers.


----------



## aphexii

Just curious, want to make sure my LED's didn't cause the problem as its the only thing I have that's really different about my build (other than the plexiglass, but I don't suspect a problem lies there). 

 Since i have the LED's socketed (as I posted earlier in the thread), i used three 3mm White LED's in the LEDC with the default BOM resistor, 2K ohm 1W, at RA5C. The LED's are rated 3.2-3.4V, 13000mcd, though I'm not sure how accurate the millicandela rating is as they were an 'eBay special' from Hong Kong.

 Other than dimming the LED's by using 3 in place of 1, could doing this have caused this issue?


----------



## tomb

Hmm ... don't think that would've caused anything. The resistor essentially sets the current - 13.5ma, assuming 27VDC supply voltage with the 2K resistor. The three LED's would simply divide that current three ways. You kind of answered your own question about the LEDs, though. Given the same resistor, chances are that just one of those white LEDs by itself would've been a lot brighter than the three together.


----------



## aphexii

Well crap, the problem is back again. Swapped tubes L to R and the tubes work fine in the other side, so its gotta be something else (or something with the socket?). I never let it get to the point of overheating, I just noticed it got hot right away so I pulled out the DMM and it was back up to .300+ V on the left side.

 The only thing I changed today was I swapped the tube LED for another color, which required pulling the tube out and then putting it back in.

 Should I test the TA2L/TB2L without a tube on that side and see what the readings are? Would that help diagnose the problem?

 EDIT: Ok, well I did a quick test without the tubes in. TA2L/TB2L was still at .300 V and TA2R/TB2R was still at 90mV.


----------



## aphexii

And now it seems to be working again. LOL, I officially don't get it.

 Turned the amp on without the tubes and started checking the voltage drops across the resistors. The DMM was showing .300 V for the TA2L/TB2R and the heatsinks on the left were blazing hot within a minute. 

 As I'm busy testing, I feel the sinks and they feel noticably cooler. I check TA2L/TB2L and its now showing 90 mV again. Roughly 3-4 minutes had passed since I turned the amp on, it never moved. 

 So apparently there must be a short somewhere, but why does it seem to come and go? Its now been holding steady at 90mV for almost 15 minutes.


----------



## tomb

Quote:


  Originally Posted by *aphexii* /img/forum/go_quote.gif 
_And now it seems to be working again. LOL, I officially don't get it.

 Turned the amp on without the tubes and started checking the voltage drops across the resistors. The DMM was showing .300 V for the TA2L/TB2R and the heatsinks on the left were blazing hot within a minute. 

 As I'm busy testing, I feel the sinks and they feel noticably cooler. I check TA2L/TB2L and its now showing 90 mV again. Roughly 3-4 minutes had passed since I turned the amp on, it never moved. 

 So apparently there must be a short somewhere, but why does it seem to come and go? Its now been holding steady at 90mV for almost 15 minutes._

 

Two possibilities that might be worth looking into:
 1. There's a short in those LED sockets. You might try giving us some pics again of that area, but I guess it may be difficult with the tube sockets above.
 2. There's some metal somewhere inside the tube sockets that is shorting out - maybe leftovers from the bad tube when it lost the pins?

 Also, there's still the possibility that the case is touching somewhere and that all the fiddling with the tubes may be a coincidence. As mentioned before, it can be the tiniest thing - a bit of wire chafing, a trace on the board that's scraping the case, etc.

 Just guesses, of course - but maybe it will help.


----------



## aphexii

Ok, so I definitely have an issue with something shorting while in the case, as everything seemed to be working great until I threw it back in the case again and voila, the problem is back.

 I dont have anything to measure the CCS while its in the case, but the left side got blazing hot again within 1-2 minutes of the amp being on. When I shine a light into the case nothing seems to be touching, but I did notice that since the plexiglass top is a bit too wide, it causes the center of the metal bottom to bow up ever so slightly. I wonder if some contact might be made in the center, which would in turn short the left side, but as far as I can see, nothing is making contact.


----------



## tomb

Quote:


  Originally Posted by *aphexii* /img/forum/go_quote.gif 
_Ok, so I definitely have an issue with something shorting while in the case, as everything seemed to be working great until I threw it back in the case again and voila, the problem is back.

 I dont have anything to measure the CCS while its in the case, but the left side got blazing hot again within 1-2 minutes of the amp being on. When I shine a light into the case nothing seems to be touching, but I did notice that since the plexiglass top is a bit too wide, it causes the center of the metal bottom to bow up ever so slightly. I wonder if some contact might be made in the center, which would in turn short the left side, but as far as I can see, nothing is making contact._

 

Unfortunately, this is something you're going to have to solve yourself. There's little that we can do but offer some suggestions on things to check. Pics are probably useless in this case - if you can take a pic that shows the contact, then you've seen it.
	

	
	
		
		

		
		
	


	




 1. Check out the slots. These, too, will make harder contact on the edges of the board if the case is bowed up slightly. The thing to focus on with this is whether the slot edges have cut into the green mask and are touching a live trace.
 2. Check the tip jack leads. Because of the slack we normally put in these, it's easier than it should be to get the leads jammed into one of the slots where it chafes between the slot and the board or the backplate. I had one once bend into the slot where one of the backplate screws screw in. Everything was fine until I tightened the screw, which was cutting into the wire lead.
 3. Try to slide the board in without the endplates - look horizontally through the case to see if there's any contact. Again, I'd focus on whether the case slots have cut into a trace somewhere.
 4. It's possible - but not too likely - that the clearance is so close to the coupling caps' pads that they are arcing to the case. This will happen because the coupling caps are not grounded directly in the circuit, but will short if an exposed lead/pad is held close enough to a grounded contact surface. If all else fails, try some electrical tape across the pads on the bottom of the board for the CA7 and CA8 caps. (Note that you should see some burn marks somewhere if this is really happening.)

 Good luck!


----------



## aphexii

No problem, well I definitely appreciate the help you've given thus far. These are things I would have never thought of.

 Well I seem to be isolating the problem a bit more, and "may" have a clue based on your first point above. Here's a step by step, testing along the way after each step.

 1) I removed the plexiglass to reduce the bow, still shorting
 2) Removed the plates, still shorting, tried a higher slot on the case to make sure it wasn't making contact with the bottom, still shorting
 3) Took the amp out of the case completely and laid it on a non-conductive surface, still shorting
 4) Detached the Output Wires, still shorting
 5) Removed the Center LED, still shorting

 After all of this, I tested the right side, showed normal. Went back to the left and voila, the left is working fine again. Once the left shorts out, does testing the right somehow change/discharge something in the left?

 On close inspection of the edges of the board, there does indeed appear to be some blue mask that has been scraped ever so slightly on the left side (close to the standoff hole in the front left corner), I see a bit of the silver/gold below where the scrape is. The right has a faint scuff in the same location, but it doesn't seem nearly as pronounced (though even the left seems slight). Think this could be the problem spot? And if so, what could I use to cover it?

 EDIT: So I added them each, back, one at at a time while the amp was in the case. No short. As soon as I added the new tubes, it shorts. I test the right side, then the left, left shows it has a short. I remove the tubes, test the left and its still shorting. Test the right, then the left, left is fine. 
	

	
	
		
		

		
		
	


	




 EDIT #2: My steps above no longer work, I can't get the left side to return to normal now. Gonna grab the soldering wick tomorrow morning and clean up some areas that might be a little close.


----------



## tomb

Quote:


  Originally Posted by *aphexii* /img/forum/go_quote.gif 
_No problem, well I definitely appreciate the help you've given thus far. These are things I would have never thought of.

 Well I seem to be isolating the problem a bit more, and "may" have a clue based on your first point above. Here's a step by step, testing along the way after each step.

 1) I removed the plexiglass to reduce the bow, still shorting
 2) Removed the plates, still shorting, tried a higher slot on the case to make sure it wasn't making contact with the bottom, still shorting
 3) Took the amp out of the case completely and laid it on a non-conductive surface, still shorting
 4) Detached the Output Wires, still shorting
 5) Removed the Center LED, still shorting

 After all of this, I tested the right side, showed normal. Went back to the left and voila, the left is working fine again. Once the left shorts out, does testing the right somehow change/discharge something in the left?_

 

I don't know.
	

	
	
		
		

		
		
	


	




 Reading through your steps 1 - 5 above, I'm almost suspecting a wiring issue.

  Quote:


 On close inspection of the edges of the board, there does indeed appear to be some blue mask that has been scraped ever so slightly on the left side (close to the standoff hole in the front left corner), I see a bit of the silver/gold below where the scrape is. The right has a faint scuff in the same location, but it doesn't seem nearly as pronounced (though even the left seems slight). Think this could be the problem spot? And if so, what could I use to cover it? 
 

Scrapes and copper showing by themselves are not necessarily an issue. Remember that the entire top surface of the board is the ground plane. It's a _good_ thing if that comes into contact with the case slots. It's the traces underneath that are fed from the positive supply (with one exception on top). If one of those is scraped and touches the slots, then a short may result.

  Quote:


 EDIT: So I added them each, back, one at at a time while the amp was in the case. No short. As soon as I added the new tubes, it shorts. I test the right side, then the left, left shows it has a short. I remove the tubes, test the left and its still shorting. Test the right, then the left, left is fine. 
	

	
	
		
		

		
		
	


	



 

This is the devil in the details with trying to find an intermittent short. I suspect that the _force_ involved with plugging in/pulling out the tubes is what forces the contact somewhere. I still suspect something in your wiring. I don't think we can blame the case if you are able to create the shorting without the case.
	

	
	
		
		

		
		
	


	




  Quote:


 EDIT #2: My steps above no longer work, I can't get the left side to return to normal now. Gonna grab the soldering wick tomorrow morning and clean up some areas that might be a little close. 
 

I sort of doubt it's the board at this point, wither, but I could be wrong. Inspect every bit of the wiring and their contact points. One question - are you using a center post on the board through all of this? That can certainly cause the board to flex more than it should. Although, that should result in intermittent circuit continuity if a trace was broken/cracked, not an intermittent short. 

 What about your VitQ's? Is it possible one of the leads is contacting a heat sink and that possibly the force of the tubes is somehow causing a shaking (assuming the VitQ's are somewhat loose) or a bending that's forcing the nipples/leads to contact the heat sinks? There may only be a small spot on the heat sinks where the anodizing has worn off to cause this. Any place else you may have an exposed lead/jumper is a worthy candidate for checking, too.

 At this point, since the case is probably not the issue, perhaps some pics would help - taken when you have shorting, if possible.


----------



## kugino

i need some help with DB biasing...

 i just finished building the mini max...didn't get any readings while trying to bias the tubes, then realized i had forgotten to jumper RB8/RB9. jumpered them and got a reading for the tubes, biased them to 13.5 (still fluctuating). voltage is steady at 27V. 

 then, went to the DB biasing...and i get ZERO readout on the MM. a quick power on/power off has a residual of a few mV, but nothing large. i turned the trimmers 15 turns but no increase, so i turned them back down. i checked the power transistors to make sure i had the right ones in the right sockets, and they check alright. i have 2SC3422 in QB8L/R and 2SA1359 in QB9L/R. 

 any thoughts? right now i have a pair of 12FK6 tubes in there...i thought this might be a trouble-free build, but i guess not. any help would be much appreciated.

 update: okay, after poking around this thread, methinks the power transistors are in the wrong direction. if you have the front of the board facing you, the pins are currently in the left-hand slots. i believe for the 2SC3422/2SA1359 pair, the pins have to be in the right-hand slots. correct?


----------



## tomb

Quote:


  Originally Posted by *kugino* /img/forum/go_quote.gif 
_i need some help with DB biasing...

 i just finished building the mini max...didn't get any readings while trying to bias the tubes, then realized i had forgotten to jumper RB8/RB9. jumpered them and got a reading for the tubes, biased them to 13.5 (still fluctuating). voltage is steady at 27V. 

 then, went to the DB biasing...and i get ZERO readout on the MM. a quick power on/power off has a residual of a few mV, but nothing large. i turned the trimmers 15 turns but no increase, so i turned them back down. i checked the power transistors to make sure i had the right ones in the right sockets, and they check alright. i have 2SC3422 in QB8L/R and 2SA1359 in QB9L/R. 

 any thoughts? right now i have a pair of 12FK6 tubes in there...i thought this might be a trouble-free build, but i guess not. any help would be much appreciated.

 update: okay, after poking around this thread, methinks the power transistors are in the wrong direction. if you have the front of the board facing you, the pins are currently in the left-hand slots. i believe for the 2SC3422/2SA1359 pair, the pins have to be in the right-hand slots. correct?_

 

Yes. See pic below from the Output Stage -> BJT Diamond Buffer page of the MiniMAX website:






 Not to worry - there hasn't been an instance yet where the output transistors have not survived a backwards mounting.
	

	
	
		
		

		
		
	


	




 Melt a solder blob on the backside of the board for each transistor - large enough to cover all three pins. If they don't drop right out when the blob is melted, then tie a string through the mounting hole and pull with one hand while you're melting the solder with the other.

 Don't worry about replacing the Bergquist pads right now. The 2SC3422/2SA1359 are inherently insulated because they're plastic bodied. The heat transfer efficiency loss won't be bad enough in the short term. When you get more pads, you can remove the mounting hardware again, bend the transistors back slightly, and slip a pad in place. Or, just use some grease.
	

	
	
		
		

		
		
	


	




 It think they'll be fine for the short term, though.

 Let us know how you fare.


----------



## kugino

tom, thanks for the info. i finally got all the transistors removed and replaced (pain in the arse!) and was able to get most of the hardware back on. i've biased the tubes (13.5V) and the DB bias on both sides now stands at about 100mV. 

 however, i cannot get any sound out of the headphone jack. i've tried to make sure the source, rca cables, and headphones are okay, and they're fine. any ideas about what could be the problem? i removed that ouput terminal block next to the headphone jack, but that shouldn't be the problem, should it? 

 here's a pic:


----------



## gspence2000

Quote:


  Originally Posted by *kugino* /img/forum/go_quote.gif 
_tom, thanks for the info. i finally got all the transistors removed and replaced (pain in the arse!) and was able to get most of the hardware back on. i've biased the tubes (13.5V) and the DB bias on both sides now stands at about 100mV. 

 however, i cannot get any sound out of the headphone jack. i've tried to make sure the source, rca cables, and headphones are okay, and they're fine. any ideas about what could be the problem? i removed that ouput terminal block next to the headphone jack, but that shouldn't be the problem, should it? _

 

The relay-delay circuit comes to mind as a possible source of your problem. Verify that the relay is closing.

 Edit: check that QM1 is oriented correctly.


----------



## tomb

Quote:


  Originally Posted by *kugino* /img/forum/go_quote.gif 
_tom, thanks for the info. i finally got all the transistors removed and replaced (pain in the arse!) and was able to get most of the hardware back on. i've biased the tubes (13.5V) and the DB bias on both sides now stands at about 100mV. 

 however, i cannot get any sound out of the headphone jack. i've tried to make sure the source, rca cables, and headphones are okay, and they're fine. any ideas about what could be the problem? i removed that ouput terminal block next to the headphone jack, but that shouldn't be the problem, should it? 

 here's a pic:




_

 

Well, it sounds like you have everything biased up properly (you can safely take the buffer to 110mV, at least). In that case, the only thing that can cause this is a problem with the headphone relay-delay circuit. I can see from your pic that the BD139 appears to be mounted correctly - that's usually the most common mistake. The other one is using something other than the MPSA14 Darlingtion transistor for QM2. If that's just another one of the 2N5087's or 2N5088's, it'll never close the relay.

 There are a couple of things to check first - can you jumper the Left and Right headphone connections to the end lead on RB14L and RB14R? If you get music, then you know it's the headphone relay circuit. Once confirming that, you might take a closeup photo of just the relay-delay section and let us take another look - can't see too much from this pic.


 P.S. I hope you're planning on shortening that wire. It's a tight squeeze into the MiniMAX case.
	

	
	
		
		

		
		
	


	







 Also - just in case, remember it'll take up to 45 seconds or more to fire the relay from a cold start.


----------



## kugino

sure enough, jumpering the headphone L/R to RB14L/R produces sound. this is the best pic with my iphone...i can fire up the SLR if necessary.

 i'm using the MPSA14 at QM2...i have a couple of 10ohm Koas at RB14L/R. other than that, everything is straight from the BOM, and DM1/DM2 look to be in the right configuration.


----------



## kugino

Quote:


  Originally Posted by *gspence2000* /img/forum/go_quote.gif 
_The relay-delay circuit comes to mind as a possible source of your problem. Verify that the relay is closing.

 Edit: check that QM1 is oriented correctly._

 

i'm looking at QM1 now...the part no. is facing the front. is that the correct orientation?


----------



## tomb

Quote:


  Originally Posted by *kugino* /img/forum/go_quote.gif 
_i'm looking at QM1 now...the part no. is facing the front. is that the correct orientation?_

 

Yes. Check the diodes. Make certain that you didn't get the zener diode mixed up with the 1N4148 and vice-versa. If all of that checks out, then try re-flowing the solder on the backside, especially around the MPSA14.

 Also, study this schematic:





 See if you can read 12V across DM1.

 If all of that fails, you maybe should replace the QM2.

 EDIT: OK - you said you checked DM1 and DM2. Still, doesn't hurt to check again. This has to be something simple. If you have all the right parts in the right place, then either the soldering isn't good, or one of the parts is bad.


----------



## kugino

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Yes. Check the diodes. Make certain that you didn't get the zener diode mixed up with the 1N4148 and vice-versa. If all of that checks out, then try re-flowing the solder on the backside, especially around the MPSA14.

 Also, study this schematic:





 See if you can read 12V across DM1.

 If all of that fails, you maybe should replace the QM2.

 EDIT: OK - you said you checked DM1 and DM2. Still, doesn't hurt to check again. This has to be something simple. If you have all the right parts in the right place, then either the soldering isn't good, or one of the parts is bad.
	

	
	
		
		

		
		
	


	


_

 

i re-soldered a bunch of the leads and checked all the wiring. hooked everything up and voila, music! it's now in the case (terminal tips were a tight fit...will need to fix the wiring one of these days) and i need to take a break for a bit. excellent fun, though...

 thanks tom and others who have been very helpful. now to enjoy the music for awhile...


----------



## tomb

Quote:


  Originally Posted by *kugino* /img/forum/go_quote.gif 
_i re-soldered a bunch of the leads and checked all the wiring. hooked everything up and voila, music! it's now in the case (terminal tips were a tight fit...will need to fix the wiring one of these days) and i need to take a break for a bit. excellent fun, though...

 thanks tom and others who have been very helpful. now to enjoy the music for awhile... 
	

	
	
		
		

		
		
	


	


_

 

Excellent!! Give us some pics of the finished product when you can!


----------



## kugino

here's a completed pic of my amp, sitting in my office, happy and glowy


----------



## tomb

Another MiniMAX lives!!


----------



## Mizu

Could you tell what are the main difference between the mini and the starving student amp ? Are they using the same tube types ? And is this a relatively easy second project ?

 Thanks

 Nevermind, just found the website !


----------



## tomb

Quote:


  Originally Posted by *Mizu* /img/forum/go_quote.gif 
_Could you tell what are the main difference between the mini and the starving student amp ? Are they using the same tube types ? And is this a relatively easy second project ?

 Thanks

 Nevermind, just found the website !_

 

Speaking of the website, I just put the final touches on a very detailed "Wiring & Assembly" page I've been working on the last few weeks and added it to the website (in the Construction pages).


----------



## soloz2

looks good too!


----------



## r_aquarii

when is the full kit available?


----------



## tomb

Quote:


  Originally Posted by *r_aquarii* /img/forum/go_quote.gif 
_when is the full kit available?_

 

Hopefully, late June or early July. DigiKey is out of the Panasonic FM's in 1800uf 35V. I'd rather supply the kits with those caps than another type.


----------



## rds

ooh, a complete kit? That's very cool


----------



## tomb

Quote:


  Originally Posted by *rds* /img/forum/go_quote.gif 
_ooh, a complete kit? That's very cool 
	

	
	
		
		

		
		
	


	


_

 

Yep - now that there are more cases in stock, I thought perhaps that would be the best deal. Plus, it will allow me to control the parts selection, which I think is important. Of course, the PCB's and cases are available separately, too.


----------



## individual6891

Sorry Tom, just to keep everything back to this thread instead of the other one " Computer as source"!! Once the Max has been updated with the ground plane, whats the main differences between this and the miniMax? Also will it be safe to use the 24VAC 0.4A that I mentioned before on the MiniMax? It'll have to be a lower bias I presume? Also will the next revision of this have Bantam support?


----------



## tomb

Quote:


  Originally Posted by *individual6891* /img/forum/go_quote.gif 
_Sorry Tom, just to keep everything back to this thread instead of the other one " Computer as source"!! Once the Max has been updated with the ground plane, whats the main differences between this and the miniMax?_

 

The primary difference is the size of the board - allowing a bit more flexibility, including MOSFETs - and the onboard BantamDAC with input relay switching.

 BTW - there's a lot more involved than just that ground plane to get that noise/ripple as low as we did. It took a lot of painstaking measurements and trial and error experiments, based on Colin Toole's recommendations and constant supervision.
	

	
	
		
		

		
		
	


	



  Quote:


 Also will it be safe to use the 24VAC 0.4A that I mentioned before on the MiniMax? 
 

You can try it, but I'd rather that you stuck with the 0.75A minimum recommendation. The issue is not one of the amperage, but the over-voltage that results from a lightly loaded walwart - we want that over-voltage. It needs to supply about 34-35V after rectification, in order to support the recommended 27VDC on the board with full regulation. Less voltage (a more loaded walwart, iow) and you'll have to turn the 27VDC down on the board or accept that the power supply will not perform to that 45uV noise/ripple (it will be higher).
  Quote:


 It'll have to be a lower bias I presume? 
 

The MiniMAX runs with 50ma bias in the BJT diamond buffer. You can probably eke out 60ma on one, but that's all. The 1" heat sinks that allow the compact Beezar/Lansing custom-machined case won't reject anymore heat than that.

 Not to worry - the MiniMAX is as good as it gets with BJT's. The MAX V1.2 will have no advantage in that regard - only the added convenience of the onboard BantamDAC. However, the MAX V1.2 will support bigger heat sinks, thus the MOSFETs are an option at their much greater bias current.

  Quote:


 Also will the next revision of this have Bantam support? 
 

Not with the MiniMAX - there will be no revisions for it. As stated above, the MiniMAX is as good as it gets with BJT diamond buffers. It's also as small as anyone can make it and still use through-hole parts. Of course, SMD would be no advantage with all those heat sinks. So in effect, the MiniMAX is as small as can be made, period - and still keep all the performance features.


----------



## Beefy

So now that I am in Canada, I need to buy a new power supply for my MiniMax. I was looking at this one at Newark:
TRIAD MAGNETICS|WAU24-1000|External Plug-In Power Supply | Newark Canada
 Looking at the image linked in the spec sheet, it seems to come terminated with the correct connector at 2.1mm ID, 5.5mm OD:
http://triadmagnetics.com/CatalogGraphics/Wpi-ta.gif

 So unless I am missing something, this should just be buy and plug in, no mess, no fuss......?


----------



## tomb

Quote:


  Originally Posted by *Beefy* /img/forum/go_quote.gif 
_So now that I am in Canada, I need to buy a new power supply for my MiniMax. I was looking at this one at Newark:
TRIAD MAGNETICS|WAU24-1000|External Plug-In Power Supply | Newark Canada
 Looking at the image linked in the spec sheet, it seems to come terminated with the correct connector at 2.1mm ID, 5.5mm OD:
http://triadmagnetics.com/CatalogGraphics/Wpi-ta.gif

 So unless I am missing something, this should just be buy and plug in, no mess, no fuss......?_

 

Yes, but actually - you'll be fine with this one:
TRIAD MAGNETICS|WAU24-750|External Plug-In Power Supply | Newark Canada
 This one will cost a little less and 750ma is all you need for a MiniMAX.


----------



## Beefy

Less current? PFFFT! I was actually seriously considering the 1.8A model!


----------



## tomb

Quote:


  Originally Posted by *Beefy* /img/forum/go_quote.gif 
_Less current? PFFFT! I was actually seriously considering the 1.8A model! 
	

	
	
		
		

		
		
	


	


_

 

Save that one for the MOSFET-MAX.


----------



## tomb

Just an FYI, but I've updated the MiniMAX BOM to reflect the upcoming kit parts selection. The BOM is now complete and contains all parts required to build a MiniMAX, including the knob and recommended boutique parts selection. Plus, the prices have been updated to reflect the latest Mouser pricing.


----------



## BobMcN

Any update on a launch date or pricing for the complete kit direct from Beezar?


----------



## tomb

Hmm ... can't post that here, but I will say that it's _slightly_ less than the total shown on the BOM. End of the month is my hopeful time frame, but we'll see.


----------



## ecclesand

I have a question....when rolling tubes, one of the tube jacks (or whatever it's called) makes a crunching noise. I'm being gentle when I rock the tubes in and out. Is this a problem? It only does it on one side...


----------



## tomb

Quote:


  Originally Posted by *ecclesand* /img/forum/go_quote.gif 
_I have a question....when rolling tubes, one of the tube jacks (or whatever it's called) makes a crunching noise. I'm being gentle when I rock the tubes in and out. Is this a problem? It only does it on one side..._

 

Sockets ... It could be a piece of glue, a piece of a broken tube pin, etc. You might turn the amp over (careful that anything not soldered down is removed) and try patting it a few times and see if that dislodges anything from the tube socket (tubes removed, of course!).

 If that all checks out, don't worry about it.


----------



## ecclesand

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Sockets ... It could be a piece of glue, a piece of a broken tube pin, etc. You might turn the amp over (careful that anything not soldered down is removed) and try patting it a few times and see if that dislodges anything from the tube socket (tubes removed, of course!).

 If that all checks out, don't worry about it.
	

	
	
		
		

		
		
	


	


_

 

Thanks, Tom...nothing came out. I just wanted to make sure I wasn't breaking the ceramic tube socket.


----------



## THE_SOURCE41

Hey I haven't been on in awhile because of time restraints but I have finally gotten time to work on and totally finish my Millett Minimax and I just have a question about biasing. I have gotten my DBs perfectly biased at 110mV and the power supply is pretty much constant at 27V after it warms up. The question I have is how long till the Tubes will remain constant. I have set them up and they remain constant then change. I then turn the amp off wait for it to cool down and then turn it on again. I wait for it to heat up again but the tubes voltage will have changed and then I bias it and get it constant and repeat cycle. How long should it be before I get a good constant reading?

 thanks 
 Sam


----------



## Beefy

Bias it to 13.5V about an hour after it has turned on. Forget about it for now, and listen to music.

 In about a week, bias it to 13.5V about an hour after it has turned on. Forget about it forever, and listen to music.


----------



## THE_SOURCE41

Thanks very much Beefy


----------



## tomb

Beefy is correct. Another method is what I've been doing lately - just bias them to 14 or 14.5V soon after you turn it on. They'll stablize at 13.5V after about an hour.

 Or, try biasing them at 15VDC, period. If you're not using some super-high-impedance cans, the reduction in voltage swing won't hurt much and the tubes will sound a lot better.


----------



## soloz2

powered up the minimax I built yesterday and it's a goodin


----------



## tomb

Quote:


  Originally Posted by *soloz2* /img/forum/go_quote.gif 
_powered up the minimax I built yesterday and it's a goodin 
	

	
	
		
		

		
		
	


	


_

 

Sounds great, but it doesn't count without pics!


----------



## gspence2000

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Beefy is correct. Another method is what I've been doing lately - just bias them to 14 or 14.5V soon after you turn it on. They'll stablize at 13.5V after about an hour.

 Or, try biasing them at 15VDC, period. If you're not using some super-high-impedance cans, the reduction in voltage swing won't hurt much and the tubes will sound a lot better.
	

	
	
		
		

		
		
	


	


_

 

Aw, now you've got me confused again. I thought that voltage swing was where it's at. Are you saying that the tubes are in their "sweet spot" at 15VDC--more linear or something? 

 Also, won't this shorten the tube life (not that these things are at all expensive as tubes go)?

 I'll try biasing to 15VDC today and see if I can hear a difference.


----------



## tomb

Quote:


  Originally Posted by *gspence2000* /img/forum/go_quote.gif 
_Aw, now you've got me confused again. I thought that voltage swing was where it's at. Are you saying that the tubes are in their "sweet spot" at 15VDC--more linear or something?_

 

Yes, possibly. Quote:


 
 Also, won't this shorten the tube life (not that these things are at all expensive as tubes go)? 
 

No - the plates are rated for 30V, max. Quote:


 
 I'll try biasing to 15VDC today and see if I can hear a difference. 
 

Yep - best way to tell - try it out.


----------



## Beefy

Quote:


  Originally Posted by *gspence2000* /img/forum/go_quote.gif 
_I thought that voltage swing was where it's at._

 

Voltage swing seems to be the tech-spec FOTM right now. Sure it can be important for high impedance phones, but a volt or two one way or the other isn't going to make a heck of a lot of difference...... unless you specifically enjoy tinnitus?


----------



## soloz2

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Sounds great, but it doesn't count without pics!
	

	
	
		
		

		
		
	


	





_

 

Just a couple from before I wired it up


----------



## 118716

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Sounds great, but it doesn't count without pics!
	

	
	
		
		

		
		
	


	





_

 

I'll be sure to post plenty when it gets to me


----------



## adn6244

i need help...my tube bias one channel can be adjusted to 13.5mv but one channel stays at around 21.5mv and refuse to move no matter how many close wise or anti close wise turns on the trimmer.

 anything wrong with the trimmer or tubes?

 one thing i noticed is that the tube socket for this channel does not have a tight grip to the tube...could this be the reason?


----------



## tomb

Quote:


  Originally Posted by *adn6244* /img/forum/go_quote.gif 
_i need help...my tube bias one channel can be adjusted to 13.5mv but one channel stays at around 21.5mv and refuse to move no matter how many close wise or anti close wise turns on the trimmer.

 anything wrong with the trimmer or tubes?

 one thing i noticed is that the tube socket for this channel does not have a tight grip to the tube...could this be the reason?_

 

Yes, it could very well have something to do with it. If the pins to the heaters aren't making contact, it won't light. If the pin to the plate is not making contact, you won't be able to bias. Gently bend the pins on the tube outward slightly and see if that makes a big difference.


----------



## adn6244

Hi Tomb,
 thanks for your reply. I use a tiny screw driver to retension the socket and now the tubes are firmly in and i can see the centre part lighted up in orange. I adjusted the PS voltage to 27V.

 interesting findings :
 PS Voltage: V+ with GND = 27V

 Now both the 2 tube bias: TA2L/R with GND = around 24.1V to 24.2V
 Buffers: Left/Right Channel = 24.1V to 24.2V (The last time I checked was 44mv and I did not adjust the trimmer after that)

 Did I just fry something? sigh.....


----------



## tomb

Quote:


  Originally Posted by *adn6244* /img/forum/go_quote.gif 
_Hi Tomb,
 thanks for your reply. I use a tiny screw driver to retension the socket and now the tubes are firmly in and i can see the centre part lighted up in orange. I adjusted the PS voltage to 27V.

 interesting findings :
 PS Voltage: V+ with GND = 27V

 Now both the 2 tube bias: TA2L/R with GND = around 24.1V to 24.2V
 Buffers: Left/Right Channel = 24.1V to 24.2V (The last time I checked was 44mv and I did not adjust the trimmer after that)

 Did I just fry something? sigh....._

 

Be sure you're referencing the correct points. The Buffers _are not _referenced to Ground. You must measure TA2L/R to TB2L/R (or TA2L/R to TB1L/R). Also - at 44mV, the output transistors are just barely switched on (if they are at all). You need to get them up to 90-110mV.

 As for the tubes, remember that you may have to turn 15 turns or more on a 20 turn trimmer to see an effect, depending on where the bias shakes out. This is because the trimmers are sized to be able to bias three totally different tubes and their gains.

 When it comes to the tubes - if you have power, and the cathodes are lit, these are the only explanations:
 1. You haven't turned the trimmers enough.
 2. The trimmers are bad.
 3. You've got bad connections in the socket.

 #3 is highly unlikely if the tubes are lit.
 #2 can be easily checked - measure the resistance on the trimmer leads under the board. Turn them about 5 turns, then measure again. If you get different values, the trimmers are working.
 #1 is the easiest, but be careful if you don't have clutched trimmers such as the Murata's. Bourns will snap if you turn them beyond the click warning. I believe Vishay's have a clutch that will allow them to over-turn, but I'm not sure.

 EDIT: I should add that bad tubes are always a possibility, but again - if the cathodes are lit, this is fairly unlikely also. Two tubes being bad are very unlikely, so switching them is an easy way to confirm.


----------



## adn6244

What i read from the setup page :
 "Both DB channels should average below 50mV or thereabouts, but this depends on the JFET variance. I've seen some with minimum voltage of 25mV and some with a minimum voltage of over 40mV. If the bias voltage is much higher than 50mV, turn the amp off until you figure out whether the trimmers are operating correctly. Once you confirm that the bias voltage is safe, then leave the amp on and proceed with setting up the power supply voltage and tube bias settings, first."

 I started to ensure DB bias is below 50mV and proceed to adj the PS bias. I got the 27V for PS and now stuck with Tube bias.

 I am sure I got the DB bias ref point correct. I have a feeling I may have snap the Bourns as I went past the click warning twice. I'll double check again later.

 Thanks for your prompt reply, really appreciate it. Will update you later if I am able to resolve it...thanks again.


----------



## tomb

Quote:


  Originally Posted by *adn6244* /img/forum/go_quote.gif 
_What i read from the setup page :
 "Both DB channels should average below 50mV or thereabouts, but this depends on the JFET variance. I've seen some with minimum voltage of 25mV and some with a minimum voltage of over 40mV. If the bias voltage is much higher than 50mV, turn the amp off until you figure out whether the trimmers are operating correctly. Once you confirm that the bias voltage is safe, then leave the amp on and proceed with setting up the power supply voltage and tube bias settings, first."

 I started to ensure DB bias is below 50mV and proceed to adj the PS bias. I got the 27V for PS and now stuck with Tube bias.

 I am sure I got the DB bias ref point correct. I have a feeling I may have snap the Bourns as I went past the click warning twice. I'll double check again later.

 Thanks for your prompt reply, really appreciate it. Will update you later if I am able to resolve it...thanks again._

 

OK, I didn't understand that you were still going through the initial setup procedure.

 Check those trimmers with your DMM - it should be easy to verify if they're OK.


----------



## adn6244

my apologies for not making myself clear...sleepy after staring at the bright blue led for too long 
	

	
	
		
		

		
			





 went to test the amp again after a good sleep...guess what...all readings are ok except one channel - most likely snap the trimmer. will check the trimmer later today.

 thanks tomb for your prompt advice.


----------



## JamesL

Is anybody else having trouble sourcing isolated 2.1 jacks from mouser?
 The one on the BOM is obsolete, and this one is out of stock. I know mouser stocked another one, but I can't find it. iirc, it was only rated for something like 20v anyways.


----------



## tomb

Quote:


  Originally Posted by *JamesL* /img/forum/go_quote.gif 
_Is anybody else having trouble sourcing isolated 2.1 jacks from mouser?
 The one on the BOM is obsolete, and this one is out of stock. I know mouser stocked another one, but I can't find it. iirc, it was only rated for something like 20v anyways._

 

It was rated for 0.5A at 12/24V. Unfortunately, you're correct on the rest. Mouser put us in a hard place by running out of these before a ROHS version was ready. The only alternative I've found is an "outie" availalble at Jameco -
Jameco Electronics Interconnects: VARIOUS: DPJ-021A-R


----------



## JamesL

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_It was rated for 0.5A at 12/24V. Unfortunately, you're correct on the rest. Mouser put us in a hard place by running out of these before a ROHS version was ready. The only alternative I've found is an "outie" availalble at Jameco -
Jameco Electronics Interconnects: VARIOUS: DPJ-021A-R_

 

Oh yeah.. that kind of sucks. 
 Anyways, I just ordered a temporary plastic jack until they get the new ones in stock.


----------



## oneplustwo

Hey folks... got a setup question.

 I got the DB's down to practically zero. The PS voltage is set to 27V. But I can't get the tubes to bias correctly. One is fixed at 27V, the other is fixed at zero. Nothing happens to either regardless of trimmer position. The LED lights up fine and the tubes start to glow orange after a minute or so.


----------



## tomb

Quote:


  Originally Posted by *oneplustwo* /img/forum/go_quote.gif 
_Hey folks... got a setup question.

 I got the DB's down to practically zero. The PS voltage is set to 27V. But I can't get the tubes to bias correctly. One is fixed at 27V, the other is fixed at zero. Nothing happens to either regardless of trimmer position. The LED lights up fine and the tubes start to glow orange after a minute or so._

 

I'm sorry you're having trouble with this. Unfortunately, you should not be able to get the DB's down to zero under any circumstance. Same for a tube at zero - it shouldn't happen. I think we need to see some pics and see if we can spot what's wrong.


----------



## oneplustwo

Here you go:






















 Hope that helps. Sorry for the noisy pictures. I was trying to get the lens stopped down enough for some reasonable DOF.


----------



## tomb

OK, I don't see anything in particular, but then the photos aren't detailed enough for me to see the part #'s. Still, I don't see anything obviously out of place or deleted.

 Tell us exactly what measurement you get when you state the "DB's are near zero." Can you adjust both for more than ~60mVDC? You should be able to bias them up to about 70-80mVDC without any issue of over-heating. Go slow and only about a half-turn at a time once you get them above 50-60mV.

 Also, for the tubes - have you racked the trimmers through all their turns in both directions? As I told you earlier, it's quite possible that the tube adjustment can be the last 5 turns out of 20+ turns on the trimmers. You've got 27VDC in the PS, so nothing's wrong there. The tubes are not a complicated circuit - if they're lit, there's very little that can be wrong.

 One thing to check is to be certain that you used 2N5087's for the CCS's (some people have mistakenly used 2N5088's there). Those are the little pairs of transistors between the WIMA caps on the sides of the tubes. Also, make certain that you have a 1K and 10K resistor there, too. That little circuit - along with the trimmers - determines the bias on the tubes.

 P.S. It does appear that you have very little wicking on the top side of the PCB. That kind of implies some possible soldering issues. I don't want to make that call right now, though, but keep in mind that re-flowing some solder everywhere might help if we can't figure anything else out.

 P.S.#2 - I've got to get to bed right now, but I'll take a look first thing in the morning ...


----------



## rds

Looks like all 4 of your BJTs are in backwards (ie you need to rotate the heatsinks 180 degrees.
 See here: Millett Hybrid MiniMAX BJT Transistors


----------



## tomb

Quote:


  Originally Posted by *rds* /img/forum/go_quote.gif 
_Looks like all 4 of your BJTs are in backwards (ie you need to rotate the heatsinks 180 degrees.
 See here: Millett Hybrid MiniMAX BJT Transistors_

 

Good catch, Ryan! You're more up on what one of these are supposed to look like right now than anybody else!
	

	
	
		
		

		
		
	


	




 I think you're just suggesting to rotate the heat sinks for purposes of illustration, though.
	

	
	
		
		

		
		
	


	




 I'd remove the transistors and re-install them on the other side of the sinks. (Trying to get those heat sinks out can be tough, if not impossible.) Make a solder blob big enough to cover all three pins on the bottom of the board for each transistor. While heating each blob, they may just fall right out. If not, you can tie a loop of string or thread around the transistor and yank on it while the solder is melted. Don't worry about a thermal pad/insulator if you don't have replacements - those are plastic-bodied BJT's and should be OK without them (unless those are MJE's). This will get you going pretty quickly in the right direction.


----------



## oneplustwo

Ah! That's right. That's what I get for just looking at the photos and not reading thoroughly enough. You would think this being my second one that things would go more smoothly. Chalk it up to arrogance. I'll swap them tonight and hopefully everything goes smoothly from there. Thanks folks!


----------



## tomb

Quote:


  Originally Posted by *oneplustwo* /img/forum/go_quote.gif 
_Ah! That's right. That's what I get for just looking at the photos and not reading thoroughly enough. You would think this being my second one that things would go more smoothly. Chalk it up to arrogance. I'll swap them tonight and hopefully everything goes smoothly from there. Thanks folks!_

 

No problem! I've almost done it a couple of times. That, combined with my looking constantly at a MOSFET-MAX the last few months that has them on the left side of the heat sinks - it's easy to get them mixed up.

 Let us know how it goes!


----------



## linuxworks

Quote:


  Originally Posted by *rds* /img/forum/go_quote.gif 
_Looks like all 4 of your BJTs are in backwards (ie you need to rotate the heatsinks 180 degrees.
 See here: Millett Hybrid MiniMAX BJT Transistors_

 

I put all the driver trans in backwards, myself, first time thru! 
	

	
	
		
		

		
		
	


	




 fortunately, I found this before I applied power. but I did have to unsolder them all.

 easy mistake to make. don't feel bad


----------



## rds

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_You're more up on what one of these are supposed to look like right now than anybody else!
	

	
	
		
		

		
			



_

 

Yes, the landscape of the MiniMAX has become very familiar, like the neighborhood where I grew up ...


----------



## sandbasser

The recent direction of this thread brings up a question - at least to me... Is there any point in socketing the BJTs??? It could make rolling easier and eliminate any possible worries about solder if installed backwards. 

 Personally, I'm big on putting things in backward. Right now I'm waiting for a 5K pot from Mouser - I soldered one in backwards and then I broke one off one of the legs when trying to remove it


----------



## tomb

Quote:


  Originally Posted by *sandbasser* /img/forum/go_quote.gif 
_The recent direction of this thread brings up a question - at least to me... Is there any point in socketing the BJTs??? It could make rolling easier and eliminate any possible worries about solder if installed backwards._

 

Yes, there are TO-220 sockets available - even TO-92 ones. However, you have to snip the leads fairly short to make them work. Also, it's more of a roll-in and snap down motion to plug them in from what I understand. With the close proximity nature of the MiniMAX, there may not be enough room to do that right next to some of the heat sinks. That said, I believe BoilerMakerFan is going to use some output sockets on some of his builds. Perhaps he can add some insight to this. 
  Quote:


 Personally, I'm big on putting things in backward. 
 

Quote of the year right there!! 
	

	
	
		
		

		
		
	


	










 We need to save that one for posterity.
	

	
	
		
		

		
		
	


	



  Quote:


 Right now I'm waiting for a 5K pot from Mouser right now - I soldered one it backwards and then I broke one off one of the legs 
	

	
	
		
		

		
		
	


	



 

Yes, as you and the rest of us have often found out, precision cermit trimmers are not made to be removed and re-installed reliably. Install them correctly the first time, and you never, ever have an issue. Otherwise ... Keep in mind, however, there's no great problem in installing them backwards - simply get used to turning the adjustment screw the other way. If you were using the MiniMAX custom case, however, that requires more care, because the trimmer screws must line up with the pre-machined holes.


----------



## oneplustwo

Just a quick update... got the parts resoldered and everything works just fine now. Listening to it right now through my Grados and gamma 1 and kind of regret that I sold my first one and that this one is going out the door tomorrow! Finishing my balanced B22 (someday) will probably help me move on though. Thanks again for the help folks!


----------



## tomb

Quote:


  Originally Posted by *oneplustwo* /img/forum/go_quote.gif 
_Just a quick update... got the parts resoldered and everything works just fine now. Listening to it right now through my Grados and gamma 1 and kind of regret that I sold my first one and that this one is going out the door tomorrow! Finishing my balanced B22 (someday) will probably help me move on though. Thanks again for the help folks!_

 

Nice going! Give us some pics!


----------



## oneplustwo

It looks like any other minimax with the black enclosure. One question... one of the tubes seems to glow brighter than the other. Not a huge difference but noticeable to me. Is that normal?


----------



## tomb

Quote:


  Originally Posted by *oneplustwo* /img/forum/go_quote.gif 
_It looks like any other minimax with the black enclosure. One question... one of the tubes seems to glow brighter than the other. Not a huge difference but noticeable to me. Is that normal?_

 

Yes, there can be quite a variation in the brightness of the cathode. It doesn't mean that it translates into differences of the tubes at all - there's no correlation.


----------



## linuxworks

Quote:


  Originally Posted by *sandbasser* /img/forum/go_quote.gif 
_The recent direction of this thread brings up a question - at least to me... Is there any point in socketing the BJTs??? It could make rolling easier and eliminate any possible worries about solder if installed backwards. _

 

on the high current driver transistors, that would not be a good design choice. sockets aren't the best for things like that. do they even make to220 pin sockets? never saw anything like that.

 I remember the old days (to3) sockets. but not seen to220 sockets.

 (whatever happened to to3 transistors? how come to220 took over?)


----------



## sandbasser

Quote:


  Originally Posted by *linuxworks* /img/forum/go_quote.gif 
_... do they even make to220 pin sockets?_

 

I found some... at Mouser: 10-18-2031 Molex IC & Component Sockets

 Sorry no picture on Mouser... I'll try to take one.


----------



## tomb

Quote:


  Originally Posted by *sandbasser* /img/forum/go_quote.gif 
_I found some... at Mouser: 10-18-2031 Molex IC & Component Sockets

 Sorry no picture on Mouser... I'll try to take one._

 

Yep - they exist. Thanks for looking them up.


----------



## JamesL

This projects been delayed for quite a long time, but I finally got my board last week.

 Do the regulator/transistors need insulators? i put the heatsinks in to get a feel for the case height, and it seems that the chance of the heatsinks shorting against the top of the case is almost non-existent.


 edit:
 edited out the first question; I found my answer on diyforums


----------



## tomb

Quote:


  Originally Posted by *JamesL* /img/forum/go_quote.gif 
_This projects been delayed for quite a long time, but I finally got my board last week.

 Do the regulator/transistors need insulators? i put the heatsinks in to get a feel for the case height, and it seems that the chance of the heatsinks shorting against the top of the case is almost non-existent.


 edit:
 edited out the first question; I found my answer on diyforums_

 

Technically, no. However, the MiniMAX is something you may be sticking DMM probes into quite often. Those can make contact even if the case doesn't. Also, not every heat sink has perfect anodizing. So, using insulators are pennies to be safe.


----------



## Daveze

This may be obvious but you don't need insulators where the transistors are fully enclosed. I'm supposed to be quite smart but I didn't pick that the first time


----------



## 118716

I've had my MiniMAX for about two weeks now, Soloz2 did a fantastic job of building it for me, I promised that I'd post a pic 
	

	
	
		
		

		
		
	


	









 It really does sound sublime with my HD600 and I couldn't be happier


----------



## linuxworks

Quote:


  Originally Posted by *sandbasser* /img/forum/go_quote.gif 
_I found some... at Mouser: 10-18-2031 Molex IC & Component Sockets_

 

couldn't you have posted this BEFORE I placed my mouser order, this week?

 lol! 
	

	
	
		
		

		
		
	


	




 next one, for sure. looks interesting. I wonder if there is capacitance or resistance issues to care about with those?

 if they can carry good current (to220's are final drivers, quite often) then I'll start using them. me hates unsoldering power tab transistors. me hates it mucho.


----------



## sandbasser

Quote:


  Originally Posted by *linuxworks* /img/forum/go_quote.gif 
_couldn't you have posted this BEFORE I placed my mouser order, this week?

 lol! 
	

	
	
		
		

		
			





 next one, for sure. looks interesting. I wonder if there is capacitance or resistance issues to care about with those?

 if they can carry good current (to220's are final drivers, quite often) then I'll start using them. me hates unsoldering power tab transistors. me hates it mucho._

 

Linuxworks -

 I decided not to use them... After dry-fitting them I found that they are fairly tall and the heat sinks for the MM barely clear them.

 PM me your address and I'll mail you some. To try.

 Regards,


----------



## sandbasser

Wow!!! I finally finished my MiniMAX. It's a long story... It's been a heck of a year...

 Listening to it now. Trying 12FM6 tubes first. They sound very good. 

 I'm using 2SC2344/2SA1011 BJTs. Everything else right off the TomBs BOM. (I haven't got a decent knob yet. I'll put a temp on and take some pix for posting later this week.)

 I was very worried about biasing the DBs; but it was easy-peasy (I read and re-read the instructions several times). Then a few seconds to adjust the PS Voltage and tube bias. Then shut it down and hooked up my MP3 player (a Sansa Fuse) and phones (I have tried my Grado RS80s, MS1s and Denon AH-D950s - the Denons sound best to my old ears). Waiting for the delay timer the first time seemed like an eternity. 

 Now I'm enjoying some mellow Francis Albert Sinatra. Ahhhh...


----------



## tomb

Another MiniMAX lives! Got some pics?


----------



## BobMcN

Finished my MiniMAX this past weekend, so I can finally join the club! It's got about 30 hours of burn in on it right now and has opened up very nicely. I'm using 12AE6 tubes with my HD-600's, and have the 2SC3422 / 2S1359 transistors. 

 No need for any pictures since it looks just like any other one on Beezar.

 Thanks Tom for some clarifications on the adjustments and all your help.

 Bob


----------



## acvtre

Hi guys, I need this comparison if anyone knows something about both. 
 A guy can build me the CTH for 250$ and the kit for the minimax costs about 220$ and I have to build it on my own (which could be a great pleasure).
 What do you suggest? Is there an enormous difference between these two amps?


----------



## tomb

Quote:


  Originally Posted by *acvtre* /img/forum/go_quote.gif 
_Hi guys, I need this comparison if anyone knows something about both. 
 A guy can build me the CTH for 250$ and the kit for the minimax costs about 220$ and I have to build it on my own (which could be a great pleasure).
 What do you suggest? Is there an enormous difference between these two amps?_

 

Go for the CTH. There's no way we'll be able to walk you through building a MiniMAX and have you be satisfied for a $30 price difference. You either want to do DIY or not.


----------



## Daveze

Its not really an apples to apples comparison. Its really whether you want to DIY. Do you have other builds under your belt or experience soldering? If not, I'd suggest your eat your extra $30 making a little CMOY before embarking on the MiniMAX.


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## acvtre

Actually I love the DIY but I have to do more practice. I built a cmoy and a pimeta V2 so far (almost finished). The minimax doesn't seem to be so difficult to built and there is a good giude on DIYforums.org.
 But do you know if there is a big SQ difference between these two?

 P.S.: do you have any book to suggest about the audio and DIY?


----------



## tomb

Quote:


  Originally Posted by *acvtre* /img/forum/go_quote.gif 
_Actually I love the DIY but I have to do more practice. I built a cmoy and a pimeta V2 so far (almost finished). The minimax doesn't seem to be so difficult to built and there is a good giude on DIYforums.org.
 But do you know if there is a big SQ difference between these two?

 P.S.: do you have any book to suggest about the audio and DIY?_

 

Those that know me can tell you I absolutely despise these questions in the DIY section. I don't want to turn the DIY-support thread for the MiniMAX into a "who likes what best" thread. That's just inviting a furball of comments going back and forth that have nothing to do with building this amp design.

 IMHO, it's in poor taste to come into a DIY amp's support thread and ask comparisons of this amp against other DIY amps. We are all just as proud of the individual designs we support. So in my mind, it's analogous to coming into someone's home and asking whose daughters you would prefer for a date - ours or the neighbors'. No good will come of it.
	

	
	
		
		

		
		
	


	




 The amplifier section on Head-Fi is the proper place to ask such questions. I'm not about to offer up review links for other DIY designs in this thread, but here are some starters on the MiniMAX and the MAX (built with BJT output buffers, they're both pretty much the same - but the MiniMAX will hold the edge with the new power supply). Note that many of these are comparisons against commercial amps, which is OK in my book because we don't compete on the same level as with other DIY amps:

http://www.head-fi.org/forums/f5/ini...inimax-427611/
http://www.head-fi.org/forums/f5/mil...ht=Millett+MAX
http://www.head-fi.org/forums/f5/mil...ssions-429181/
http://www.head-fi.org/forums/f5/min...ht=Bada+review
http://www.head-fi.org/forums/f5/mil...ht=Millett+MAX
http://www.head-fi.org/forums/f5/mil...ht=Millett+MAX

 (Note that the MiniMAX is currently sold pre-built at Whiplash Audio here. You might use that price as the proper value comparison against the DIY kit version.)

 Maybe the CTH guys can help you with some review links in their thread.


----------



## acvtre

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_So in my mind, it's analogous to coming into someone's home and asking whose daughters you would prefer for a date - ours or the neighbors'. No good will come of it.
	

	
	
		
		

		
		
	


	


_

 

Ahahahahah, really funny. ROTFL 
	

	
	
		
		

		
		
	


	



 Ok, understood the message, so sorry again, I have to pay more attention.
 However, thanks for the links. Now I'm sure, I wanna build a minimax!!!!


----------



## cfcubed

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Maybe the CTH guys can help you with some review links in their thread.
	

	
	
		
		

		
		
	


	


_

 

Guess you could call me a CTH guy & I'd just suggest using Search (e.g. terms: *cth* with adjectives like *bass amazing* etc.). There is also some older feedback on the main CTH site and the place you get it.

 Agree w/Tom - perhaps the Headphone Amps forum is more appropriate for gleaning opinions... And that's what they will be, opinions, and everyone has his/her own. I think ideally one would visit meets to help form their own opinions, or if $$$ allows have their own stable of toys


----------



## sandbasser

Questions and observations about MiniMAX...

 I've noticed that my MiniMAX doesn't get particularly hot - is this normal??? does it depend on the BJTs used??? Does it indicate that the heat sink bolts need to be tighter???

 OTOH - the power adapter (a Triad from the BOM) gets pretty warm - is this normal???

 My MiniMAX has now been running about 40 hours and it sounds quite nice.

 Finally, is there anything in particular I can do to 'train' my ears to be more discerning??? I read a lot of opinions on this (and other forums) - but in some cases it's truly hard to hear any other than very large differences in sounds. (not just MiniMAX - also - SSH Kit and 3 other builds I've done.

 Thanks,


----------



## Daveze

Can you expand on 'particularly hot'? Its not dependent on the BJTs but on the bias point you are at. Mine isn't 'particularly hot' on the outside either and I don't have my thermometer here (at work) so I can't provide any better indication either. I know that Beefy once did some measurements and was basically at the comfortable temperature limit for the 110mV/50mA bias. 

 I also find the transformer is a bit hotter, particularly the littler one.

 What 'phones are you using? Personally, I try to avoid being too 'discerning', in favor of just listening to the music. I tend to classify things in terms of how much I like it, how enjoyable or comfortable it is to listen to. To become more discerning you need to focus on the details and for me that means I stop listening to the music.


----------



## tomb

I agree with Daveze - we need more specific data to render a judgment for you. The cooling slots in the custom Beezar-Lansing case perform quite well. However, the heat is directly dependent on the Diamond Buffer bias as Daveze says. You should crank it up to 110mV (50ma) if you haven't already - performance is increased up to that point and the case/heat sinks can more than handle it.

 Yes, the Triad power supply may get hot - but again, relative to what? If there is a way you can measure the temperature, we can discuss it from a common point of reference. I doubt that it's in danger of overloading, though. If you're using the 750ma walwart, it's at least twice the rating needed.


----------



## sandbasser

Hi Guys -

 The MiniMAX Case temp is ~ 100F directly above the LM317, ~ 87F above the BJTs. I have NOT really measured the temp of the heatsinks themselves... I'm trying to avoid taking everything apart unless it's absolutely necessary 
	

	
	
		
		

		
		
	


	




 and it's tough to get a reliable reading shooting the laser in the vent holes.

 Initial setting of the bias was 50ma... I have NOT rechecked it yet - the amp has significantly less than 100 hours on it. The Triad wallwart (a 750ma unit) is ~ 102F. Room temp is ~ 72F. (I have a MicroTemp Laser Thermometer.)

 I guess those temps are probably OK... But, the reason I asked is that I'm wondering if the tightness of the heat sink screws matter. I didn't tighten them real tight when I installed them. Does tightness have any effect on temp???

 Daveze -

 Thanks for the comments on listening... I am definitely enjoying listening. I currently have a set of Denon AH-D950s, Grado SR-80s and Allesandro (Grado) MS-1s (with full MS-1000 conversion). I'm in the market for a better set of phones. I'm going to go out this weekend and try some. Recommendations anyone??? (great sounding phones for MiniMAX)

 Thanks,


----------



## tomb

Quote:


  Originally Posted by *sandbasser* /img/forum/go_quote.gif 
_Hi Guys -

 The MiniMAX Case temp is ~ 100F directly above the LM317, ~ 87F above the BJTs. I have NOT really measured the temp of the heatsinks themselves... I'm trying to avoid taking everything apart unless it's absolutely necessary 
	

	
	
		
		

		
			





 and it's tough to get a reliable reading shooting the laser in the vent holes.

 Initial setting of the bias was 50ma... I have NOT rechecked it yet - the amp has significantly less than 100 hours on it. The Triad wallwart (a 750ma unit) is ~ 102F. Room temp is ~ 72F. (I have a MicroTemp Laser Thermometer.)

 I guess those temps are probably OK... But, the reason I asked is that I'm wondering if the tightness of the heat sink screws matter. I didn't tighten them real tight when I installed them. Does tightness have any effect on temp???

 Daveve -

 Thanks for the comments on listening... I am definitely enjoying listening. I currently have a set of Denon AH-D950s, Grado SR-80s and Allesandro (Grado) MS-1s (with full MS-1000 conversion). I'm in the market for a better set of phones. I'm going to go out this weekend and try some. Recommendations anyone??? (great sounding phones for MiniMAX)

 Thanks,_

 

Actually, the heat sinks need to be tight up to the point of cutting into the Bergquist pads - which doesn't take much. As long as you have a snug fit and the lock washer is compressed, the Bergquist "flowable" substance should take care of the rest.

 Just as you say, those temps seem quite alright to me. One thing to check - the volume knob should get warm (assuming you're using a metal one) to the touch after the amp has been on for 3-4 hours. This varies considerably with room temps, though. During the summer next to a bright window the knob may get warm within 1 hour, but takes a lot longer at 72 deg. and less without external influence (sun through a window).


----------



## tomb

About the listening ... if you can get your hands on a recording of Chesky's Demonstration Disc, that can get you started with telling the differences in sound quality. Better yet is the Focal JM Lab Tools CD - it has specific frequency tones all the way down to 20Hz and up to 20KHz. Playing that through a MiniMAX with different headphones and comparing to some other amps (no names!) can be an ear-opening experience.
	

	
	
		
		

		
		
	


	




 Also, it may sound silly to some, but a pair of KSC-75's are just unbelievable with a MiniMAX. I think they are better than many of the lower level Grado's - at least with a good amp like the MiniMAX. Another great suggestion - other than Grados and you're already on that path - are the Sennheiser HD25-1's. The MiniMAX does well with both the HD580 and HD600, too, but those are probably more expensive. On the other hand, I've seen some places lately that sell the HD25-1 minus accessories for ~$100. That's a steal.


----------



## sandbasser

TomB -

 Thanks for the information on discs and suggestions on phones.


----------



## acvtre

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_...Better yet is the Focal JM Lab Tools CD - it has specific frequency tones all the way down to 20Hz and up to 20KHz. Playing that through a MiniMAX with different headphones and comparing to some other amps (no names!) can be an ear-opening experience.
	

	
	
		
		

		
		
	


	




..._

 

That's cool, where can I find it?


----------



## acvtre

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_...Better yet is the Focal JM Lab Tools CD - it has specific frequency tones all the way down to 20Hz and up to 20KHz. Playing that through a MiniMAX with different headphones and comparing to some other amps (no names!) can be an ear-opening experience.
	

	
	
		
		

		
		
	


	




..._

 

That's cool, where can I find it? I'm not going to buy a rapidshare account for sure.


----------



## tomb

Yeah, it looks like rapidshare may be the only place to get it. Just Google "JM Lab Focal Tools CD." You'll get a bunch of responses, but they all go to rapidshare. Still, it looks like it's free, but be sure to check for viruses, etc. I got mine through the News Groups on GigaNews (alt.binaries.sounds.lossless). Maybe I shouldn't have said that, but I don't think Focal's selling it, anyway - can't find it anywhere on their website. There's my confession, though.


----------



## ujamerstand

I've just finished building my minimax. Tuned it to the recommended settings. All I can say is... wow, this stuff is really good! The distortions and clipping I would get before I hooked the amp up all but disappeared. In addition, the amp revealed details that I did not noticed before. Except for some minor flaws like microphonics from one tube, and some scratching noise when I turn the knob, (which is barely noticeable when the music is on) It made my listening experience much more enjoyable! Thanks for making it possible tomb, you really made my day!


----------



## sandbasser

I don't know how this compares with the 'JM Lab Focal Tools CD'; but the Bink downloads are certainly easier to get 
	

	
	
		
		

		
		
	


	




 Here's a linky.

Michael Knowles: Extras


----------



## tomb

Quote:


  Originally Posted by *ujamerstand* /img/forum/go_quote.gif 
_I've just finished building my minimax. Tuned it to the recommended settings. All I can say is... wow, this stuff is really good! The distortions and clipping I would get before I hooked the amp up all but disappeared. In addition, the amp revealed details that I did not noticed before. Except for some minor flaws like microphonics from one tube, and some scratching noise when I turn the knob, (which is barely noticeable when the music is on) It made my listening experience much more enjoyable! Thanks for making it possible tomb, you really made my day!_

 

Glad to hear it!

 About the microphonics - if it's one of my tubes, I'll replace it, of course. Microphonics is something that a tube tester can't check.

 About the scratchiness in the volume knob - this is an artifact of the tubes and Millett circuit. Some tubes do it, some don't. Just a guess, but I think the distortion is a reaction in the tube grid/plates to the increased signal. Black Gates on the output seem to exaggerrate the condition, too. My guess is that the BG's are so fast, the tubes can't keep up when the volume knob is adjusted quickly. Most of the time, this only happens with the high-gain 12AE6's, but I'm not sure if that holds in every case.

 I once ruined an RK27 by flushing it with alcohol (it removed all the shaft grease) in an attempt to remove the scratchiness. It didn't work. That MAX had Black Gates and every one I've built since with BG's has had a similar phenomenon, although it can happen sometimes with ES's, too. Unlike the conventional wisdom with other pots and amps, however - *I can guarantee you it's not the Alps pot!!
	

	
	
		
		

		
		
	


	


*


----------



## tomb

Quote:


  Originally Posted by *sandbasser* /img/forum/go_quote.gif 
_I don't know how this compares with the 'JM Lab Focal Tools CD'; but the Bink downloads are certainly easier to get 
	

	
	
		
		

		
		
	


	




 Here's a linky.

Michael Knowles: Extras_

 

Ah - very good! Yes - I bet those will work well. As I said before, it's very interesting comparing a MAX/MiniMAX and headphones with others on those 50Hz tones and below.


----------



## ujamerstand

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_About the scratchiness in the volume knob - this is an artifact of the tubes and Millett circuit. _

 

The scratchiness actually disappeared, I'm guessing the problem corrected itself after the tubes have been used after a while. The microphonics only occurs on one side, and since the amp doesn't move around, it doesn't really bother me all that much. Perhaps later I'd get a second set of a tubes just to play with.


----------



## Firestorm252

hiya.
 Long time lurker, first time poster so apologies if my first post is about a problem 
	

	
	
		
		

		
		
	


	




 Finished getting mine put together (after a long on-off building process).
 Started getting everything setup and biased and found my right tube bias isn't budging from 23.5V, but after some testing I found my RA1R trimmer is bad. I've got everything else zeroed in except for that value, also the DB's were set to <40mv first thing when I applied power.

 I'm off on a tangent from my real problem. The right channel isn't working, but the weird part is that when I apply audio only to the right channel and turn it up there _is_ audio. It's just full of static and extremely quiet, as in I hear it at 50% volume or higher when left channel is already too loud at the 9 o'clock position. Flipped the 12FM6 tubes and same effect and also tested with a pair of 12AE6 tubes and same.

 I read another user, adn6244, had an issue with the bad tube bias trimmer, but I don't believe they had an issue with that channel being faulty. And as I understand the circuit, a high tube bias shouldn't have such an effect on the sound unless I'm misreading it which is very much a possibility.

 Also, after letting it run while zeroing in the DB bias I noticed that the QB8R heatsink is dead cold compared to everything else. 

 Current knowns:
All components are in the proper places and orientation
Checked and reflowed all solder joints
Left channel is fine, right channel is not.
QB8R (2SC2344) heatsink remains dead cold.

 I'm inclined to say that QB8R is bad or that it's not receiving enough signal. Are there any ways to check for a bad NPN transistor or whether a component behind it is bad? Am I going down the wrong troubleshooting path somewhere?

 Thanks for any help ahead of time. It may be a bit before I can reply as I'm squeezing some more troubleshooting in between university capstone projects and tests.


----------



## tomb

Quote:


  Originally Posted by *Firestorm252* /img/forum/go_quote.gif 
_hiya.
 Long time lurker, first time poster so apologies if my first post is about a problem 
	

	
	
		
		

		
		
	


	




 Finished getting mine put together (after a long on-off building process).
 Started getting everything setup and biased and found my right tube bias isn't budging from 23.5V, but after some testing I found my RA1R trimmer is bad. I've got everything else zeroed in except for that value, also the DB's were set to <40mv first thing when I applied power.

 I'm off on a tangent from my real problem. The right channel isn't working, but the weird part is that when I apply audio only to the right channel and turn it up there is audio. It's just full of static and extremely quiet, as in I hear it at 50% volume or higher when left channel is already too loud at the 9 o'clock position. Flipped the 12FM6 tubes and same effect and also tested with a pair of 12AE6 tubes and same.

 I read another user, adn6244, had an issue with the bad tube bias trimmer, but I don't believe they had an issue with that channel being faulty. And as I understand the circuit, a high tube bias shouldn't have such an effect on the sound unless I'm misreading it which is very much a possibility.

 Also, after letting it run while zeroing in the DB bias I noticed that the QB8R heatsink is dead cold compared to everything else. 

 Current knowns:
All components are in the proper places and orientation
Checked and reflowed all solder joints
Left channel is fine, right channel is not.
QB8R (2SC2344) heatsink remains dead cold.

 I'm inclined to say that QB8R is bad or that it's not receiving enough signal. Are there any ways to check for a bad NPN transistor or whether a component behind it is bad? Am I going down the wrong troubleshooting path somewhere?

 Thanks for any help ahead of time. It may be a bit before I can reply as I'm squeezing some more troubleshooting in between university capstone projects and tests._

 

I'm a bit confused. Why would you expect perfect sound out of the right channel if you can't get the tube to bias? Essentially, that means the signal is getting either zero or very little amplification. Hence, low to no volume, staticky and noisy sound. Actually, that confirms that the right tube may be OK - you just can't get it biased. Replace the trimmer (if you're absolutely certain it's bad) and then get the tube biased.

 As for QB8R running cold, it depends on where you've set the DB bias. If you only checked to make sure that it's <40mv while attempting this troubleshooting, it's quite possible that it's not biased at all (IOW, "OFF"). That means it's not going to develop any heat without a music signal. In that area of bias voltage/current, there's very little difference between ON and OFF with the transistor's current bias.

 You know the buffer isn't going to burn up at this point, so get the tube biased and go from there. Attempting to listen to sound in the meantime is going to send you off on a tangent - as you noticed.

 BTW, re-check the trimmer. Some tubes may bias in only the last five turns of a trimmer. If you've purchased the Murata or Vishay trimmers, they've got a clutch mechanism that prevents damage from over-turning. So unless you melted the heck out of it, chances are it's still good. Many people will come to the conclusion that the tube and/or trimer may be bad when it's just that they haven't really turned it 20-25 turns, which is what it may take for some tubes.

 Also - to be perfectly honest, the output transistors are some of the more robust pieces on the board. People can install them backwards and power them up for quite awhile before discovering their mistake - then still have the transistors survive and everything be OK after turning the transistors around. I'm not at all saying you've put QB8R in backwards - only that those things are very seldom damaged/go bad.

 I can't say for certain that's what's going on, but check some of these things I mentioned and come back and tell us what you found.


----------



## Firestorm252

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_I'm a bit confused. Why would you expect perfect sound out of the right channel if you can't get the tube to bias? Essentially, that means the signal is getting either zero or very little amplification. Hence, low to no volume, staticky and noisy sound. Actually, that confirms that the right tube may be OK - you just can't get it biased. Replace the trimmer (if you're absolutely certain it's bad) and then get the tube biased.

 As for QB8R running cold, it depends on where you've set the DB bias. If you only checked to make sure that it's <40mv while attempting this troubleshooting, it's quite possible that it's not biased at all (IOW, "OFF"). That means it's not going to develop any heat without a music signal. In that area of bias voltage/current, there's very little difference between ON and OFF with the transistor's current bias.

 You know the buffer isn't going to burn up at this point, so get the tube biased and go from there. Attempting to listen to sound in the meantime is going to send you off on a tangent - as you noticed.

 BTW, re-check the trimmer. Some tubes may bias in only the last five turns of a trimmer. If you've purchased the Murata or Vishay trimmers, they've got a clutch mechanism that prevents damage from over-turning. So unless you melted the heck out of it, chances are it's still good. Many people will come to the conclusion that the tube and/or trimer may be bad when it's just that they haven't really turned it 20-25 turns, which is what it may take for some tubes.

 Also - to be perfectly honest, the output transistors are some of the more robust pieces on the board. People can install them backwards and power them up for quite awhile before discovering their mistake - then still have the transistors survive and everything be OK after turning the transistors around. I'm not at all saying you've put QB8R in backwards - only that those things are very seldom damaged/go bad.

 I can't say for certain that's what's going on, but check some of these things I mentioned and come back and tell us what you found.
	

	
	
		
		

		
		
	


	


_

 

ah, thanks for the clarification 
 I'm completely new to tubes, so I assumed the bias would not be along the same path as signal and would not cause the issue. Assumed, without checking the schematic, that the bias would be hitting the heater and just causing it to run hotter. 




 I guess I've some more reading to do on how they work 
	

	
	
		
		

		
		
	


	




 As for the trimmer, I believe it is bad. I removed it, tested it, turned it 15x one way measured, reset, and turned 15x the other way. got no change in value at all. But I'll give it another go with 20+ turns when I get back from campus in a day or so.

 As for the heatsink, I turned up the bias to ~80-90mv on each channel and left it for a bit to heat before I made the temperature observation on QB8R.

 Thanks for the help


----------



## tomb

OK - sounds like you did adequate testing on the trimmer. Also, if you ran the bias up to 80 - 90mV, then you definitely should've gotten heat from QB8R.

 Sounds like we need some pics.


----------



## Firestorm252

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_OK - sounds like you did adequate testing on the trimmer. Also, if you ran the bias up to 80 - 90mV, then you definitely should've gotten heat from QB8R.

 Sounds like we need some pics.
	

	
	
		
		

		
			



_

 

Just got home from work and here's some old photos and mock-up photos, pre-wiring, pre-biasing and pre-taking the trimmer off. I upped them to the forum galleries so they resized automatically and are pretty messy. If you would like the raw 10MP shots I can up them someplace.

 Notes: 
yes, I know that's definitely not a shoulder washer on QB9L. Forgot to account for the LM317, so I used what I had available: motherboard paper washers.
The Bergquist pad for the LM317 folded over as I handled the heatsink, I went ahead and folded the rest.





















 I'll try to get some new photos taken particularly an "above" shot, an underside shot, and shots with the rest of the BJT DB in view, but I'm currently having issues with my camera. 

 Unfortunately this hobby of mine is getting pushed to the wayside as finals week is just two weeks away, so I've not had time to work on it. If I make any headway/troubleshooting progress I'll be sure to post. But I will be ordering a new set of trimmers, 2-3 just to be sure and a Hammond 1455T1601 (I plan to mount using standoffs)


----------



## tomb

Looks like excellent workmanship from here!
	

	
	
		
		

		
		
	


	




 Let's hope it was all that trimmer!


----------



## BoxOPwn

Does anyone know where I could buy a *stock* Lansing DT1 case?


----------



## tomb

Quote:


  Originally Posted by *BoxOPwn* /img/forum/go_quote.gif 
_Does anyone know where I could buy a *stock* Lansing DT1 case?_

 

Umm ... have you tried Lansing?


----------



## ShinyFalcon

MiniMAX Drawings & Templates

 I believe you can order direct from Lansing enclosures, but will have to call or email them.

http://www.lansing-enclosures.com/ma...pak_prices.pdf


----------



## BoxOPwn

I knew you could order direct, but was hoping that was not the only option.


----------



## BlingBlingDr

Got my miniMAX kit from beezar last week and I am getting everything ready to start cracking on this thing next Thursday. Given the small size of the board, will a Weller ST3 .125" X 0.750" ST Series Screwdriver Tip on my iron cause any problems, i.e. be too large?

 Thanks!


----------



## tomb

Quote:


  Originally Posted by *BlingBlingDr* /img/forum/go_quote.gif 
_Got my miniMAX kit from beezar last week and I am getting everything ready to start cracking on this thing next Thursday. Given the small size of the board, will a Weller ST3 .125" X 0.750" ST Series Screwdriver Tip on my iron cause any problems, i.e. be too large?

 Thanks!_

 

Yes - I think you'd do better with a much smaller tip. I use the standard that comes with the Hakko 936 - it's 0.063" (1.6mm chisel). I'm not saying you need one that small necessarily, but it's certainly within the average needed for projects around here.


----------



## BlingBlingDr

Thanks! Just a few more days of class, 20 pages of writing, wisdom teeth extraction, and a final exam before my journey begins. MiniMAX ahoy!


----------



## Firestorm252

Back to report.
 Got the new trimmers and tested them _before_ I stuck them in this time. My luck, I got another bad one out of the 5 I ordered 
	

	
	
		
		

		
		
	


	




 Anyway, it's working great now. Got it setup and biased over the course of an hour or so Friday night. Tube bias still seems to be fluctuating a tiny bit, is that normal for tubes?

 Overall sounds great; heard that one of the drummers in_ Blueman Group - What is Rock? [live]_ was slightly off in the beginning and a guitar part I've never been quite able to pick out cleanly in _Nobuo Uematsu's - Otherworld_. I remember at 1AM debating sleep or continue listening 
	

	
	
		
		

		
		
	


	




 Thanks for the help. I was debating whether to redo an entire channel's DB til tomb corrected me on how RA1R was influencing the circuit.

 Now I just need to get the casework done over the holidays and some better headphones in the future... mmm how my starving college student wallet cringes


----------



## tomb

Quote:


  Originally Posted by *Firestorm252* /img/forum/go_quote.gif 
_Back to report.
 Got the new trimmers and tested them before I stuck them in this time. My luck, I got another bad one out of the 5 I ordered 
	

	
	
		
		

		
		
	


	




 Anyway, it's working great now. Got it setup and biased over the course of an hour or so Friday night. Tube bias still seems to be fluctuating a tiny bit, is that normal for tubes?

 Overall sounds great; heard that one of the drummers in Blueman Group - What is Rock? [live] was slightly off in the beginning and a guitar part I've never been quite able to pick out cleanly in Nobuo Uematsu's - Otherworld. I remember at 1AM debating sleep or continue listening 
	

	
	
		
		

		
		
	


	




 Thanks for the help. I was debating whether to redo an entire channel's DB til tomb corrected me on how RA1R was influencing the circuit.

 Now I just need to get the casework done over the holidays and some better headphones in the future... mmm how my starving college student wallet cringes_

 

So glad to hear you got it working!

 Yeah, tubes are sort of like mules - you go one way, they go the other. The bias will hunt, too, especially early on. You should notice, however, that the bias will drop by about 0.1 to 0.2 per hour for about 2-3 hrs - after that, they should be pretty solid. If I'm shooting for 13.5, I usually adjust to 13.7 - 13.8 when the amp is first turned on (well, after 15 minutes or so - not immediatedly after throwing the switch). That usually works out over several hours. However, if the tubes have not been broken in, they'll drop more than that after a couple of hours - perhaps as much as a volt - but that should stop after a day or two when they're broken in.

 You'll also find that you can never get them accurate - 13.4, 13.6, etc. That tendency to drop over the first couple of hours means I always set them high, though. Seriously, though, things are not that precise with the tubes - anything from 13 to 15 will sound pretty good.

 If you're noticing more of a drop than that over a few hours and after a few days, it's possible the tubes are bad.


----------



## H22

Got Home 3 days ago and what was on my doorstep? 
 A big-ol-box-o-minimax goodness!

 So I took it to work with my iron and during the day in my spare time ( i work out in the oil patch ) i started assebling it, against my better judgement (more on that later).

 I purchaced the complete kit with the black gate option, And I was very impressed with the packaging, Top notch.

 I also liked how most of the parts were in little labled bags, saved a bunch of time! One thing that was missing was the RB1 (1k) resistors, all those parts and missing 2 little resistors
	

	
	
		
		

		
		
	


	




. Not a big deal, considering how many parts are included I can understand how they might get overlooked. 

 As I said earlier, I assembled it in spurts in my spare time, so inevitably i mad a couple of mistakes, first and foremost i didnt do enough digging for info when it came time to mount the big dimond buffer transistors. My kit came with the smaller 2SC3422 and 2SA1359 units, and as I was just looking at the pics for a guide i installed them in the wrong location
	

	
	
		
		

		
		
	


	




 . Now remounting the outer two will not be all that hard, however the inner two will be a bear. As I mounted them in the upper hole of the heatsink, there is plenty of lead left on them to just clip them off near the PCB and mount them in the lower hole of the heatsink. But getting clippers into the center two with the black gates in place is all but impossible. I may have to de-sodier the caps to get enough access to do it. I could try to de-soldier the trasistors, but this will heat them up so much i am worried it will destroy them.... 

 And another small oversite was I went ahead and installed CA9 (WIMA's) but I notice that it is recomended to leave these unpopulated if the black gates are used in CA7? So should I remove them????

 I went ahead and ordered a new set of transistors just in case I damage the ones I have, and I asked for a couple of 1K resistors to boot.


 GREAT KIT!!! WELL DONE!, If I had to make any recomendations though it would be a link(s) on the construction page to the various build options (i.e. the transistors/caps etc) just cause I remember whem building it I was following the instructions on the breezar site link, and it didnt say anything about the different mounting positions, I found that the next day when I was on the minimax page..... Again, My bad ,but the easier the info is to find the less idiots like me will be likelly to mess it up
	

	
	
		
		

		
		
	


	




 Joe


----------



## tomb

Quote:


  Originally Posted by *H22* /img/forum/go_quote.gif 
_Got Home 3 days ago and what was on my doorstep? 
 A big-ol-box-o-minimax goodness!

 So I took it to work with my iron and during the day in my spare time ( i work out in the oil patch ) i started assebling it, against my better judgement (more on that later).

 I purchaced the complete kit with the black gate option, And I was very impressed with the packaging, Top notch.

 I also liked how most of the parts were in little labled bags, saved a bunch of time! One thing that was missing was the RB1 (1k) resistors, all those parts and missing 2 little resistors
	

	
	
		
		

		
		
	


	




. Not a big deal, considering how many parts are included I can understand how they might get overlooked._

 

Arrggh! I've been chasing you for a couple of hours - both with posts on DIYForums.org, a PM, and an e-mail:

 Sorry about the resistors - PM me with your real name and I'll drop a couple in the mail to you.
  Quote:


 As I said earlier, I assembled it in spurts in my spare time, so inevitably i mad a couple of mistakes, first and foremost i didnt do enough digging for info when it came time to mount the big dimond buffer transistors. My kit came with the smaller 2SC3422 and 2SA1359 units, and as I was just looking at the pics for a guide i installed them in the wrong location
	

	
	
		
		

		
		
	


	




 . Now remounting the outer two will not be all that hard, however the inner two will be a bear. As I mounted them in the upper hole of the heatsink, there is plenty of lead left on them to just clip them off near the PCB and mount them in the lower hole of the heatsink. But getting clippers into the center two with the black gates in place is all but impossible. I may have to de-sodier the caps to get enough access to do it. I could try to de-soldier the trasistors, but this will heat them up so much i am worried it will destroy them.... 
 

You should not have to cut the leads. Unbolt the transistor from the heat sink, tie a string through the transistor hole. Make a solder blob on the bottom of the board large enough to cover all three pins and stay melted - then pull on the string. Each transistor should drop right out doing that. Be careful with those things - there may never be anymore of that kind again!

 Please don't cut the leads and mount them on the lower heat sink holes - they're run much hotter doing that. Follow the procedure above; it works easier than it reads.
	

	
	
		
		

		
		
	


	



  Quote:


 And another small oversite was I went ahead and installed CA9 (WIMA's) but I notice that it is recomended to leave these unpopulated if the black gates are used in CA7? So should I remove them???? 
 

CA9 is the bypass for CA2. CA2 is a Muse ES 1000uf 16V and using Wima's at CA9 are perfect. the Black Gates are only at CA7 and the bypass for them is CA8, which is where you install those two 0.18uf Vitamin Q's.

  Quote:


 I went ahead and ordered a new set of transistors just in case I damage the ones I have, and I asked for a couple of 1K resistors to boot. 
 

OK - NOW I know who you are!!
	

	
	
		
		

		
		
	


	




  Quote:


 GREAT KIT!!! WELL DONE!, If I had to make any recomendations though it would be a link(s) on the construction page to the various build options (i.e. the transistors/caps etc) just cause I remember whem building it I was following the instructions on the breezar site link, and it didnt say anything about the different mounting positions, I found that the next day when I was on the minimax page..... Again, My bad ,but the easier the info is to find the less idiots like me will be likelly to mess it up
	

	
	
		
		

		
		
	


	




 Joe 
 

Thanks for the kind comments. I'll add the link as you suggest.


----------



## H22

Quote:


 Arrggh! I've been chasing you for a couple of hours - both with posts on DIYForums.org, a PM, and an e-mail: 
 

Sorry bout that, the DIYforum looked a bit less used than this one, so i posted here as well.......

 Thanks Tomb, I will try as you suggested to remove the transistors tonight, then its set-up and listen time ( I will substitute a pair of standard 1K resistors for now till the others show up ) .


----------



## tomb

Quote:


  Originally Posted by *H22* /img/forum/go_quote.gif 
_Sorry bout that, the DIYforum looked a bit less used than this one ... </snip>_

 

Ha! That's a bit of an understatement.
	

	
	
		
		

		
		
	


	




 At least it still operates.


----------



## THE_SOURCE41

Hello
 This is more of a question for tomb but does beezar ship internationally?

 Thanks


----------



## tomb

Quote:


  Originally Posted by *THE_SOURCE41* /img/forum/go_quote.gif 
_Hello
 This is more of a question for tomb but does beezar ship internationally?

 Thanks_

 

Of course. Keep in mind that certain high-ticket items require Priority Mail International. That's the minimum USPS shipment service that allows insurance on international shipments.


----------



## ecclesand

Can the minimax drive 600ohm loads well? Specifically, does the minimax have enough power to properly drive a Beyer DT990 600 Ohms?


----------



## tomb

Quote:


  Originally Posted by *ecclesand* /img/forum/go_quote.gif 
_Can the minimax drive 600ohm loads well? Specifically, does the minimax have enough power to properly drive a Beyer DT990 600 Ohms?_

 

Honestly, I'd have to say it's pushing the MiniMAX's limit to use a 600 ohm load. At best, there's a 13.5V swing, which should be plenty adequate with 12AE6 tubes (high gain choice). However, not lacking the direct experience myself, I have known a couple of other MAX/MiniMAX builders who have had some problems with those cans. Who knows? It may be that they were trying it with 12FK6's and/or 150 ohm output resistors, but I don't know that for sure.

 I guess all of that's a qualified "maybe."
	

	
	
		
		

		
			





 Note that there are many DIY amps that may have trouble with the 600 ohm DT990's. I recall that was usually Morsel's threshold that caused concern with some designs and finally neglecting that was one of the reasons Amb took the Mini3 from a _troubled_ 2 x 9V battery source to a _successful _single 9V battery source and finally released the design for production. Morsel and her 600 ohm cans were out of the picture at that point.


----------



## ecclesand

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Honestly, I'd have to say it's pushing the MiniMAX's limit to use a 600 ohm load. At best, there's a 13.5V swing, which should be plenty adequate with 12AE6 tubes (high gain choice). However, not lacking the direct experience myself, I have known a couple of other MAX/MiniMAX builders who have had some problems with those cans. Who knows? It may be that they were trying it with 12FK6's and/or 150 ohm output resistors, but I don't know that for sure.

 I guess all of that's a qualified "maybe."
	

	
	
		
		

		
		
	


	




 Note that there are many DIY amps that may have trouble with the 600 ohm DT990's. I recall that was usually Morsel's threshold that caused concern with some designs and finally neglecting that was one of the reasons Amb took the Mini3 from a troubled 2 x 9V battery source to a successful single 9V battery source and finally released the design for production. Morsel and her 600 ohm cans were out of the picture at that point.
	

	
	
		
		

		
		
	


	


_

 

Thanks for the info, Tom. I'm running a DT990 600ohm thru my Whiplash Audio Minimax with a set of Sylvania 12AE6 tubes and it sounds very good to my ears. I am unable to move the volume past the 11am mark without hurting my ears. I asked because I did some reading and found that perhaps they can sound even better with a more powerful tube amp. Decisions....decisions.


----------



## tomb

Quote:


  Originally Posted by *ecclesand* /img/forum/go_quote.gif 
_Thanks for the info, Tom. I'm running a DT990 600ohm thru my Whiplash Audio Minimax with a set of Sylvania 12AE6 tubes and it sounds very good to my ears. I am unable to move the volume past the 11am mark without hurting my ears. I asked because I did some reading and found that perhaps they can sound even better with a more powerful tube amp. Decisions....decisions.
	

	
	
		
		

		
		
	


	


_

 

Sounds like it's handling it well, then. As I said, the anecdotal reports may have had some extenuating circumstances, but I haven't had any direct experience - so was afraid to make a more definitive statement.


----------



## BoxOPwn

Are there any Hammond enclosures that will fit the minimax?


----------



## tomb

Quote:


  Originally Posted by *BoxOPwn* /img/forum/go_quote.gif 
_Are there any Hammond enclosures that will fit the minimax?_

 

Sorry, not without ordering a larger case than necessary and bolting the MiniMAX PCB to the bottom of the case.

 Lansing is really quite reasonable with direct orders.
	

	
	
		
		

		
		
	


	




 Otherwise, I may have some separate cases on sale after the first of the year.


----------



## BoxOPwn

Also, is there a recommended replacement for the power jack which has become obsolete. I found this one, 163-R123B-E, but i'm not sure if it will work.


----------



## tomb

Quote:


  Originally Posted by *BoxOPwn* /img/forum/go_quote.gif 
_Also, is there a recommended replacement for the power jack which has become obsolete. I found this one, 163-R123B-E, but i'm not sure if it will work._

 

Nope - that's not it. They simply replaced the other one with an ROHS version. If you click on the link in the MiniMAX BOM, the Mouser page has a reference to the new ROHS version:
163-4302-E


----------



## BoxOPwn

Thanks, you are very helpful.


----------



## BlingBlingDr

I've begun prep work on my MiniMAX and I am crossing my fingers for a huge snow storm in NYC so I can lock myself up all weekend without feeling guilty. I would like to use my MiniMAX as a preamp for an Onkyo stereo reciever and a set of Klipsh Promedia speakers with a Zero DAC as the source (in addition to using it with my Grado 80s). I have been reading the original MAX thread for ideas. I am building the beezar kit, and my understanding is that space is at a premium in the case. Maybe I can mount two RCA jacks on the left-hand side of the case with the signal coming from the board's output to the headphone jacks? Any ideas or suggestions would be highly appreciated.

 PS - As I drilled out the center pin from one of the tube sockets, the bit seized and spun the socket out of the vise. It flew across the room and some of the pins are bent out of shape 
	

	
	
		
		

		
		
	


	




. Am I risking mechanical failure down the line if I don't replace the socket and instead try to "massage" it into the board?

 Thanks!!


----------



## tomb

Quote:


  Originally Posted by *BlingBlingDr* /img/forum/go_quote.gif 
_I've begun prep work on my MiniMAX and I am crossing my fingers for a huge snow storm in NYC so I can lock myself up all weekend without feeling guilty. I would like to use my MiniMAX as a preamp for an Onkyo stereo reciever and a set of Klipsh Promedia speakers with a Zero DAC as the source (in addition to using it with my Grado 80s). I have been reading the original MAX thread for ideas. I am building the beezar kit, and my understanding is that space is at a premium in the case. Maybe I can mount two RCA jacks on the left-hand side of the case with the signal coming from the board's output to the headphone jacks? Any ideas or suggestions would be highly appreciated._

 

Installing a terminal block next to the headphone jack is the easiest way to set it up for a pre-amp. Run leads from the terminal block to a pair of output RCA jacks on the rear. The case was not designed for this and I'm not sure how you fit two extra RCA jacks on the back plate and not have it look bad. Plus, you're liable to tear up the silkscreening when you clamp it to drill the needed holes anyway:





 That said, it can certainly be done. Head-Fi user "Scy" used the Beezar/Lansing custom case extrusion, but went to FPE for his own different design of back plate and front plate -














 As you can see, many more RCA jacks can be fit in with a little work and preparation.
	

	
	
		
		

		
		
	


	




  Quote:


 PS - As I drilled out the center pin from one of the tube sockets, the bit seized and spun the socket out of the vise. It flew across the room and some of the pins are bent out of shape 
	

	
	
		
		

		
		
	


	




. Am I risking mechanical failure down the line if I don't replace the socket and instead try to "massage" it into the board?

 Thanks!! 
 

The pins will be fine if you bend them back. You need to bend them out to properly solder them to the PCB, anyway. Refer to this sequence for the Starving Student's PCB tube sockets (Step #7.). It's perfectly applicable to any PCB tube socket on a PCB:
SSMH Construction - PCB Part 2


 EDIT: Sorry - I just now noticed that I duplicated one of those pics. It's fixed, now.


----------



## BlingBlingDr

Thanks!


----------



## BlingBlingDr

Things seem to be going smoothly with my build. Thanks for the feedback. I am a bit confused about the trim pots. Based on the schematics, ->3, I have placed them backwards. When I look at previous builds, the pots trim pots are placed as I have them in the picture. Should I be concerned or reposition them?


----------



## Beefy

It doesn't actually matter which way they go. You might just end up turning them in counter-intuitive directions to get the right settings.

 In any case, this photo on the MiniMax website is from my build, and AFAIK, everything is oriented correctly, so yours is all good.

 [EDIT] Ooooh, but for the machined case, you couldn't adjust the tube trimmers. This would be a problem. But yours is indeed all good.


----------



## tomb

Quote:


  Originally Posted by *BlingBlingDr* /img/forum/go_quote.gif 
_Things seem to be going smoothly with my build. Thanks for the feedback. I am a bit confused about the trim pots. Based on the schematics, ->3, I have placed them backwards. When I look at previous builds, the pots trim pots are placed as I have them in the picture. Should I be concerned or reposition them?
	

	
	
		
		

		
			



_

 

Yes, Beefy is correct. The only critical trim pots are for the tubes, because as he says - the trimmer screws must be accessible from the holes in the case top. However, not to worry - you've installed them just as everyone does.

 P.S. Strictly speaking, the orientation on the schematic may not be correct, but all of the trimmers are interchangeable in their orientation. Most important though, the schematic is rarely used as a reference for physical locations. The board silkscreen is the best reference for that and that appears to be what you've followed.
	

	
	
		
		

		
		
	


	




 EDIT: Looks like great workmanship so far!


----------



## BlingBlingDr

And it sings 
	

	
	
		
		

		
		
	


	




. Thanks a bunch to everyone who posted their pics, trials, and tribulations. Special thanks to TomB and Beefy for their lightning fast responses to my questions.


----------



## tomb

Quote:


  Originally Posted by *BlingBlingDr* /img/forum/go_quote.gif 
_And it sings 
	

	
	
		
		

		
		
	


	




. Thanks a bunch to everyone who posted their pics, trials, and tribulations. Special thanks to TomB and Beefy for their lightning fast responses to my questions._

 

That's great news! Congrats! Give us a pic when it's cased up, too.


----------



## BlingBlingDr

Here she is all cased up and ready to go


----------



## tomb

Looks great! A MiniMAX kit lives!


----------



## H22

Thanks to Tomb, just finnished mine ( after a minor error I made mounting the transistors ). 
 Didn't have much time to listen to it before I gave it away *sigh*.
 Spent Christmas morning with it constantly adjusting the tube bias at My brothers house, He and his wife were blown away by the sound (think i may have to build them one now....). Ten I travelled 3 hours to My fathers house and let My step mother listen to it for about an hour before i told here it was her gift. 
 It was a huge success, everyone in the house would pop in a CD and just sit and listen, every once in a while there eyes would pop open and they would mouth "WOW", or they would stop the music, take off the phones and tell me they heard something they had never heard before. 

 Wonderfull little amp, great kit. 

 I did notice that the bass was a bit lean at first, but after 8-10 hours of use it started coming in nicely. the sound stage also seemed to widen quite a bit. 

 Now I HAVE to build one for myself. Also thinking of using it as a pre-amp for a gainclone to power a set of mid sized/bookshelf speakers. 

 Joe


----------



## tomb

Quote:


  Originally Posted by *H22* /img/forum/go_quote.gif 
_Thanks to Tomb, just finnished mine ( after a minor error I made mounting the transistors ). 
 Didn't have much time to listen to it before I gave it away *sigh*.
 Spent Christmas morning with it constantly adjusting the tube bias at My brothers house, He and his wife were blown away by the sound (think i may have to build them one now....). Ten I travelled 3 hours to My fathers house and let My step mother listen to it for about an hour before i told here it was her gift. 
 It was a huge success, everyone in the house would pop in a CD and just sit and listen, every once in a while there eyes would pop open and they would mouth "WOW", or they would stop the music, take off the phones and tell me they heard something they had never heard before. 

 Wonderfull little amp, great kit. 

 I did notice that the bass was a bit lean at first, but after 8-10 hours of use it started coming in nicely. the sound stage also seemed to widen quite a bit. 

 Now I HAVE to build one for myself. Also thinking of using it as a pre-amp for a gainclone to power a set of mid sized/bookshelf speakers. 

 Joe_

 

Thank you for such nice comments! Glad to hear you got those transistors worked out!

 As for the lean bass at start, you ordered the Black Gates upgrade. Unfortunately, that's a fact of life with Black Gates - long break-ins. This subject is argued endlessly around here, but there are a few things that definitely require break-in, some of them quite lengthy. Black Gates take about a week of average running for the best bass. Most other audio caps in the signal path only take a few hours. Other caps' break-in is best described as starting out cloudy, with an unnatural bass warmth. Then as they break-in, the unnatural warmth goes away and the cloudy turns to transparent.

 With BG's, they start out a bit "fuzzy" then get more transparent and detailed as time goes on. However, the bass is the last thing to come in. That's about the only time the MiniMAX can be described as being lean on bass.
	

	
	
		
		

		
		
	


	







 Thanks again for the very kind comments.


----------



## H22

Quote:


 As for the lean bass at start, you ordered the Black Gates upgrade. Unfortunately, that's a fact of life with Black Gates - long break-ins. This subject is argued endlessly around here, but there are a few things that definitely require break-in, some of them quite lengthy. Black Gates take about a week of average running for the best bass. Most other audio caps in the signal path only take a few hours. Other caps' break-in is best described as starting out cloudy, with an unnatural bass warmth. Then as they break-in, the unnatural warmth goes away and the cloudy turns to transparent. 
 

Well thats good to hear. I had just assumed that this was the case ( caps requiring burn in ) but I was a *bit* woried at first when It seemed light in the bass . That makes me wish that I had longer to play with it! 

 I just have to build one for myself now, but I am thinking I will opt for the mosfet vesion and possibly set it up to also power a small set of desktop sized speakers, just a bit conserned there about heat dissapation. Looking at the case I don't think it would be too hard to mount some small computer fans ( tiny guys, about 2" square and .5" thick ) to bolw through the bottom of the case. Just have to mount taller feet on the case. I am not wanting huge power here, just something to use on a night stand. if this would work the only down side would be possibly damaging a set of phones by not turning the volume down. 
 But I guess to make it worthwhile I need to find a set of 2-3 inch drivers that are efficient enough to sound good with the amp.


----------



## tomb

Quote:


  Originally Posted by *H22* /img/forum/go_quote.gif 
_Well thats good to hear. I had just assumed that this was the case ( caps requiring burn in ) but I was a *bit* woried at first when It seemed light in the bass . That makes me wish that I had longer to play with it! 

 I just have to build one for myself now, but I am thinking I will opt for the mosfet vesion and possibly set it up to also power a small set of desktop sized speakers, just a bit conserned there about heat dissapation. Looking at the case I don't think it would be too hard to mount some small computer fans ( tiny guys, about 2" square and .5" thick ) to bolw through the bottom of the case. Just have to mount taller feet on the case. I am not wanting huge power here, just something to use on a night stand. if this would work the only down side would be possibly damaging a set of phones by not turning the volume down. 
 But I guess to make it worthwhile I need to find a set of 2-3 inch drivers that are efficient enough to sound good with the amp._

 

The MiniMAX can power a couple of flea speakers already. You should give it a try.

 As for MOSFETs, we really reserved that for the regular MAX (still working on V1.2a). Even if you provided fans, there are other issues involved with going to MOSFETs in the small MiniMAX case. You need about 80ma minimum bias for proper MOSFET operation, but that's more than 50% higher than the recommended bias limit on the MiniMAX. I'm not sure it's a situation with ventilation and the case slots as much as it is the thermal inertia provided by the heat sinks. That much bias really needs 1-1/2" sinks to keep from falling off the cliff into thermal runaway. Your fans may keep it cool in a steady-state condition, but any little upset - especially when making bias adjustments in the first place - could be enough to fry the MOSFETs.

 The other factor is that with the MAX and 1-1/2" sinks, the sound seems to improve noticeably the higher one goes with the bias. 80-90ma is not enough to wring out the best performance with the MOSFETs, IMHO - more like 120-150ma. I've been running the first MAX V1.2 prototype at 125ma for months now and it sounds good. I had it set at 150ma for a short while, but felt it was too much for the center two sinks. I still haven't tried to case it up yet, so who knows if that much bias (125ma) can still be supported? That's one of the things yet to be developed in the MAX V1.2 prototyping.


----------



## Beefy

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_That much bias really needs 1-1/2" sinks to keep from falling off the cliff into thermal runaway._

 

MOSFETs have a negative tempco. Not to say you couldn't still manage to fry them with too high a bias......


----------



## tomb

Quote:


  Originally Posted by *Beefy* /img/forum/go_quote.gif 
_MOSFETs have a negative tempco. Not to say you couldn't still manage to fry them with too high a bias......_

 

Technically you're correct about the negative temperature coefficient, but the more I learn about MOSFETs, the more I find that's not worth much. Heat is heat, eventually any substance will reach a breakdown point. More - there are specific references to thermal runaway for MOSFETs in the literature:
Power MOSFET Thermal Runaway
Power MOSFET Thermal Runaway-Severns example
Interactive Power Electronics Seminar (iPES) - Thermal Runaway of a MOSFET

  Quote:


 "Like many others, I used to list immunity to thermal runaway as one of the advantages of power MOSFETs over bipolar transistors. Then I read Rudy Severns application note and discovered otherwise." 
 

 - referenced in the links above.


----------



## H22

Quote:


 As for MOSFETs, we really reserved that for the regular MAX (still working on V1.2a). Even if you provided fans, there are other issues involved with going to MOSFETs in the small MiniMAX case. You need about 80ma minimum bias for proper MOSFET operation, but that's more than 50% higher than the recommended bias limit on the MiniMAX. I'm not sure it's a situation with ventilation and the case slots as much as it is the thermal inertia provided by the heat sinks. That much bias really needs 1-1/2" sinks to keep from falling off the cliff into thermal runaway. Your fans may keep it cool in a steady-state condition, but any little upset - especially when making bias adjustments in the first place - could be enough to fry the MOSFETs.

 The other factor is that with the MAX and 1-1/2" sinks, the sound seems to improve noticeably the higher one goes with the bias. 80-90ma is not enough to wring out the best performance with the MOSFETs, IMHO - more like 120-150ma. I've been running the first MAX V1.2 prototype at 125ma for months now and it sounds good. I had it set at 150ma for a short while, but felt it was too much for the center two sinks. I still haven't tried to case it up yet, so who knows if that much bias (125ma) can still be supported? That's one of the things yet to be developed in the MAX V1.2 prototyping. 
 

well thats very usefull advice. Sounds like the best way to implement it would be either the standard "MAX" or "MINIMAX" in a completelly separate enclosure, As I have read that remote mounting the transistors is a bad idea, possibly mounting them under the board on a large (PCB sized) heatsink would be a good plan, while not ideal for airflow (fins would be pointed down) the huge amount of thermal mass might make up for it?

 While I know a gainclone is a far cheeper and simpler route to a small power amp, I like the tubes! and I am not ready just yet to jump into a full bore all tube power amp. As I said, im just looking to power a set of 2"~4" drivers at a moderate level, and I think a modified "MAX" would be a fun project.
 If I were to use a large heatsink as the "bottom" of the enclosure, and use the 3amp PS regulator and requisite powersuply, would I be safe to assume that 20W per channel is acheivable?
 If the PS circuit is pushed to ~2.5 amps @ 27v, that is ~65 watts, given the tube heater/bias current draw that should stilll be enough power left over for what I want.
 Plus it would save all the fuss of using fans.


----------



## Oberst Oswald

Fast question... RB8L/R & RB9L/R do these get jumped when using Black Gates or are the jumpers only for a MOSFET version? I'm building the Beezar kit. The BOM says.... "NOT USED - For MOSFET ONLY - jumper out". Thx


----------



## tomb

Quote:


  Originally Posted by *Oberst Oswald* /img/forum/go_quote.gif 
_Fast question... RB8L/R & RB9L/R do these get jumped when using Black Gates or are the jumpers only for a MOSFET version? I'm building the Beezar kit. The BOM says.... "NOT USED - For MOSFET ONLY - jumper out". Thx_

 

That's correct. The use of Black Gates has nothing to do with it - only whether the diamond buffer uses BJT's or MOSFETs. All MiniMAXes use BJT's, so RB8L/R and RB9L/R are jumpered out.
	

	
	
		
		

		
		
	


	




 P.S. It's also summarized here:
http://www.diyforums.org/MiniMAX/MiniMAXbjt.php


----------



## Oberst Oswald

Have a problem... DB Bias. I turned the pots clockwise until I heard the click and took a reading: 1.7mV. Seemed safe so I set the power supply voltage to 27v. Set Tube Bias to Left 13.57, Right 13.63. All is well...so I thought When back to adjust the DB Bias to 110mV but I could not get the pots to adjust properly to get the mV climbing. Smelled smoke and shut of fast. Too late...think I burned out the QB1R transistor because now the board lights up for a few seconds and than slowly dims off. Now I can buy new transistors etc but I don't know whats wrong with why I can't get the pots to adjust. I have a good camera but I don't know how to post pictures to show you my build. Pretty sure I did a good job building it and triple+ checked everything but I'm hopelessly lost now on where the problem is and what I need to do or buy to repair it. Thanks in advance for all help.


----------



## tomb

Quote:


  Originally Posted by *Oberst Oswald* /img/forum/go_quote.gif 
_Have a problem... DB Bias. I turned the pots clockwise until I heard the click and took a reading: 1.7mV. Seemed safe so I set the power supply voltage to 27v. Set Tube Bias to Left 13.57, Right 13.63. All is well...so I thought When back to adjust the DB Bias to 110mV but I could not get the pots to adjust properly to get the mV climbing. Smelled smoke and shut of fast. Too late...think I burned out the QB1R transistor because now the board lights up for a few seconds and than slowly dims off. Now I can buy new transistors etc but I don't know whats wrong with why I can't get the pots to adjust. I have a good camera but I don't know how to post pictures to show you my build. Pretty sure I did a good job building it and triple+ checked everything but I'm hopelessly lost now on where the problem is and what I need to do or buy to repair it. Thanks in advance for all help._

 

We need to see the pics. From what you describe, it's not anything with how you were performing the setup. Moreover - QB1 is not really in the "critical path" of the buffer - it only sets the current bias. Other parts in the buffer will fry long before it does if something is wrong. Instead, I suspect some parts are out of place in the buffer.

 Head-Fi has its own photo posting system - try that. Or, you can e-mail them to me at Beezar and I'll post them.


----------



## tomb

Just an FYI if any others were following this, but Oberst Oswald and I discovered his problem offline and he is working on it.


----------



## WyldRage

I build one, but I am having troubles with biasing.

 The LEDs lit up, the tubes were heating up and the power supply is at 27 VDC. When I first plugged it in, the left side tube was at 500 mV and the right side 200 mV. The DB were less than 5 mV. 

 Now, turning it on/off has no effect. The mesures (except power) are slowly decreasing, measuring LT 250 mV and RT 11 mV about 2 hours since I started it. I repeat: turning it on or off has NO effect on the measures.

 Since this is my first project, I have no idea what's wrong. 

 Here are pics:


----------



## tomb

Quote:


  Originally Posted by *WyldRage* /img/forum/go_quote.gif 
_I build one, but I am having troubles with biasing.

 The LEDs lit up, the tubes were heating up and the power supply is at 27 VDC. When I first plugged it in, the left side tube was at 500 mV and the right side 200 mV. The DB were less than 5 mV. 

 Now, turning it on/off has no effect. The mesures (except power) are slowly decreasing, measuring LT 250 mV and RT 11 mV about 2 hours since I started it. I repeat: turning it on or off has NO effect on the measures.

 Since this is my first project, I have no idea what's wrong. 

 Here are pics:







_

 

You must install jumpers at RB8L/R and RB9L/R. Refer to this page:
Millett Hybrid MiniMAX BJT Transistors

 "Jumpered out" means you install and solder a spent resistor lead into the pads at each position. There must be a zero-ohm connection across those pads for the amp to work.


----------



## WyldRage

Cheers, must have missed that.

 It's done! Haven't listened toit yet though.


----------



## tomb

Quote:


  Originally Posted by *WyldRage* /img/forum/go_quote.gif 
_Cheers, must have missed that.

 It's done! Haven't listened toit yet though._

 

So, have you listened to it now?
	

	
	
		
		

		
		
	


	




 Keep in mind that those Black Gates will take awhile to break-in.


----------



## WyldRage

I like them. They've got good bass and good definition. I had decided to build one for a future pair of headphone (Audeze LCD-2) and all I've got right now are Senn IE8. I like them, but the amp is a bit wasted on these.

 Absolutely love the glow.


----------



## tomb

Quote:


  Originally Posted by *WyldRage* /img/forum/go_quote.gif 
_I like them. They've got good bass and good definition. I had decided to build one for a future pair of headphone (Audeze LCD-2) and all I've got right now are Senn IE8. I like them, but the amp is a bit wasted on these.

 Absolutely love the glow. 
	

	
	
		
		

		
		
	


	


_

 

That's great to hear! BTW, the MiniMAX and MAX do very well with Orthos.


----------



## iamthecheese

Sheeee lives!

 I started my kit from Beezar yesterday and spend my day off today sucking down solder fumes.
 Surprisingly enough to me it turned on first try and stayed powered for about a minute before I turned it off. No smoking anything on it 
	

	
	
		
		

		
		
	


	




 Haven't checked the HP out yet...I'm off to go check voltages and bias everything


----------



## tomb

Quote:


  Originally Posted by *iamthecheese* /img/forum/go_quote.gif 
_Sheeee lives!

 I started my kit from Beezar yesterday and spend my day off today sucking down solder fumes.
 Surprisingly enough to me it turned on first try and stayed powered for about a minute before I turned it off. No smoking anything on it 
	

	
	
		
		

		
		
	


	




 Haven't checked the HP out yet...I'm off to go check voltages and bias everything 
	

	
	
		
		

		
		
	


	


_

 

Great to hear! Be sure to let us know how the rest of it goes!
	

	
	
		
		

		
		
	


	




 EDIT: I assume that means it went OK without the fuse.


----------



## iamthecheese

Ok... So I wired the RCA jacks to see if I could get sound. I didn't 
	

	
	
		
		

		
		
	


	




 . So i go to check voltages...PSU is I get set to 27.0 V and as I'm going to check the DB I notice only 1 heatsink is hot and the rest are cool. If your look at the front of the amp the far left heatsink is the only one that is hot, the other 3 are cool.

 Help please?


----------



## tomb

Quote:


  Originally Posted by *iamthecheese* /img/forum/go_quote.gif 
_Ok... So I wired the RCA jacks to see if I could get sound. I didn't 
	

	
	
		
		

		
		
	


	




 . So i go to check voltages...PSU is I get set to 27.0 V and as I'm going to check the DB I notice only 1 heatsink is hot and the rest are cool. If your look at the front of the amp the far left heatsink is the only one that is hot, the other 3 are cool.

 Help please?_

 

You need to give us some logical, organized measurements. Study this page carefully and work calmly through the PS voltage setting to the tube bias, and then to the DB bias for adjustment and measurement:
http://www.diyforums.org/MiniMAX/MiniMAXsetup.php

 Then come back and tell us what you've adjusted and what the specific measurements are. Remember - if you turned down the DB trimmers as recommended, the transistors are OFF. They won't develop heat. However, there are enough mismatches in some of the currents to perhaps let heat develop in one or two even if you have them turned down.

 So, please go back - be methodical, logical, and in sequence adjust, measure, then tell us what you've got.
	

	
	
		
		

		
		
	


	




 EDIT: Sorry - forgot the link.


----------



## iamthecheese

Here are my measurements after turning RB12l/r 4 times counter clockwise and RA1l/r 10 times counter clockwise.

 v+ to ground = 27.0 V

 TA2l to ground = 2.4v
 TA2r to ground = 0.5v

 TB1l with Ta2l = 0.49v
 tb2l with ta2l = 0.49v
 tb1r with ta2r = 0.0 v
 tb2r with ta2r = 0.0 v

 Same heating problem.


----------



## tomb

Quote:


  Originally Posted by *iamthecheese* /img/forum/go_quote.gif 
_Here are my measurements after turning RB12l/r 4 times counter clockwise and RA1l/r 10 times counter clockwise.

 v+ to ground = 27.0 V

 TA2l to ground = 2.4v
 TA2r to ground = 0.5v

 TB1l with Ta2l = 0.49v
 tb2l with ta2l = 0.49v
 tb1r with ta2r = 0.0 v
 tb2r with ta2r = 0.0 v

 Same heating problem._

 

OK - if you've truly measured 0.49V on TB1L-TA1L and TB2L-TA2L, then that's dangerous. That's 490mV or about 220ma. *Turn that trimmer down NOW! * *Clockwise is DOWN for the buffers*, not counter-clockwise!!!

 Once you do that, leave the buffer alone. Try to see if you can bias the tubes first. Note that the trimmers will go 25 turns, so you've got quite a bit more to adjust. Sometimes the tubes may bias only in the last 5 turns out of 25. Keep a watch on the meter - turn until you can see the voltage change. You can't burn up anything with the tube bias.
	

	
	
		
		

		
		
	


	




 Also - when you go back to the buffer, note that you should have your meter set to read in *mili*-Volts, not Volts.


 EDIT: There's an additional link on that same page that may help you further, here:
http://www.diyforums.org/MiniMAX/setup/DB-Bias.htm (it's a pop-up window on that page).


----------



## iamthecheese

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_OK - if you've truly measured 0.49V on TB1L-TA1L and TB2L-TA2L, then that's dangerous. That's 490mV or about 220ma. *Turn that trimmer down NOW! * *Clockwise is DOWN for the buffers*, not counter-clockwise!!!

 Once you do that, leave the buffer alone. Try to see if you can bias the tubes first. Note that the trimmers will go 25 turns, so you've got quite a bit more to adjust. Sometimes the tubes may bias only in the last 5 turns out of 25. Keep a watch on the meter - turn until you can see the voltage change. You can't burn up anything with the tube bias.
	

	
	
		
		

		
			





 Also - when you go back to the buffer, note that you should have your meter set to read in *mili*-Volts, not Volts.


 EDIT: There's an additional link on that same page that may help you further, here:
MiniMAX Setup - DB Bias (it's a pop-up window on that page)._

 


 Well I turned the DB trimmers down all the way and turned the amp on. They now read 444mv and 440 mv :O :O so I went and shut if off and didn't even read the tube voltages.... but the other two still reading 0(I turned that one all the way off too).

 I'm confused. Should I take a picture of the amp? I'm pretty sure everything should be in correctly. I checked twice before I soldered anything and the jumpers are in rb8l/r and rb8l/r.


----------



## tomb

Quote:


  Originally Posted by *iamthecheese* /img/forum/go_quote.gif 
_Well I turned the DB trimmers down all the way and turned the amp on. They now read 444mv and 440 mv :O :O so I went and shut if off and didn't even read the tube voltages.... but the other two still reading 0(I turned that one all the way off too).

 I'm confused. Should I take a picture of the amp? I'm pretty sure everything should be in correctly. I checked twice before I soldered anything and the jumpers are in rb8l/r and rb8l/r._

 

Did you understand that you need to turn the DB trimmers CLOCKWISE to turn them DOWN? You were turning them the other way in the other posts.

 If that's not the case, then yes - we need pics.


----------



## iamthecheese

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Did you understand that you need to turn the DB trimmers CLOCKWISE to turn them DOWN? You were turning them the other way in the other posts.

 If that's not the case, then yes - we need pics.
	

	
	
		
		

		
		
	


	


_

 

yep. im sure i turned them clockwise...even pulled up the windows clock to check 
	

	
	
		
		

		
		
	


	




...ill take pics tomorrow...off to bed now


----------



## tomb

Quote:


  Originally Posted by *iamthecheese* /img/forum/go_quote.gif 
_yep. im sure i turned them clockwise...even pulled up the windows clock to check 
	

	
	
		
		

		
		
	


	




...ill take pics tomorrow...off to bed now_

 

OK - I'll check back in the morning.


----------



## iamthecheese

I'll post a link since its a 2 mb image.
 heres a link to the image:
http://img109.imageshack.us/img109/7273/img3122h.jpg


----------



## tomb

Quote:


  Originally Posted by *iamthecheese* /img/forum/go_quote.gif 
_I'll post a link since its a 2 mb image.
 heres a link to the image:
http://img109.imageshack.us/img109/7273/img3122h.jpg_

 

OK, I don't mean to be critical, but I went to a great deal of trouble to include notes in the kits about turning the resistors so that their ratings were showing. There are many in the pic that I can't confirm visually because the ratings are not showing.
	

	
	
		
		

		
		
	


	




 Maybe I forgot the notes along with the fuse & clips?

 What happens is that once resistors are populated in a PCB, there are often too many parallel connections to make a direct resistance measurement that makes any sense. So, if we can't see the ratings (on V-D resistors), there's no other way to confirm their proper rating short of taking them out.

 Off hand, though, I don't see any easily-detected mistakes. I'll keep looking, but let me ask this -

 1. Based on the pic, you need to turn the DB trimmers clockwise - have you turned them at least 10-20 turns in that direction?
 2. Your measurements have been a little non-standard with Volts vs. mV. Are you certain you're measuring on the right scale? For instance, 44mV would make perfect sense, whereas 440mV will burn the buffer up.

 Let's make certain you're measuring the proper quantities. You need to have your meter (the one that came with the kit) set to the "2000m" selection under "DCV". The results should be read as "###", with "###" as the reading in mV. If you are only reading two "#", as in "##" then you're OK - you are actually at tens of milliVolts. If you're reading "###" and the first "#" is greater than 1, then you're in danger.

 Let's try those two things and re-measure TA2L to TB1L (or TB2L) and TA2R to TB1R (or TB2R).

 EDIT: You were correct - I'm getting mixed up with the MOSFET-MAXes I have in front of me. It appears the trimmers are correctly oriented.


----------



## tomb

Don't worry - installing the trimmers backwards means nothing to the operation of the amp. It's just that it affects which way you turn them in our conversation!


----------



## Oberst Oswald

Quote:


  Originally Posted by *Oberst Oswald* /img/forum/go_quote.gif 
_Have a problem... DB Bias. I turned the pots clockwise until I heard the click and took a reading: 1.7mV. Seemed safe so I set the power supply voltage to 27v. Set Tube Bias to Left 13.57, Right 13.63. All is well...so I thought When back to adjust the DB Bias to 110mV but I could not get the pots to adjust properly to get the mV climbing. Smelled smoke and shut of fast. Too late...think I burned out the QB1R transistor because now the board lights up for a few seconds and than slowly dims off. Now I can buy new transistors etc but I don't know whats wrong with why I can't get the pots to adjust. I have a good camera but I don't know how to post pictures to show you my build. Pretty sure I did a good job building it and triple+ checked everything but I'm hopelessly lost now on where the problem is and what I need to do or buy to repair it. Thanks in advance for all help._

 


 The MAX is completed and sounding great with my D-7000's. The problem I had was that I installed the 2SA3422 & 2SA1359 power transistors on the wrong side of the heat sinks. Tomb quickly seen that and advised me on an easy way to switch them... blob solder & string. After testing to see if they were still good (they were) I've put them in correctly. Left side worked fine but only had slight static on the right & could not adjust DB or tube voltage. Tomb sent me new PN4392, 2N5087 & 2N5088 transistors and I changed QB1R first (this was the smoker). No cigar. Had a fun time changing the rest. After testing the hFE it turned out the QB2R was also bad. 

 Some tips to others who might have to replace transistors. Waxed dental floss works good as the string- it is stiff & strong. After desoldering a #60 drill bit with a pin vise work fine to clear the holes.

 I can't say enough on how helpful & patient tomb was on solving my problem. The man and his kit are both 1st class...

 Now let's see if I can post a picture. It's big picture that I hope resized properly...


----------



## BriFi

I recently finished up my MiniMAX build, so I thought I'd drop by this thread and post a few pictures:











 I received the kit last Thursday evening and spent the entire evening putting it together. Total build time was about six hours from opening the box to having it all cased up, with a break for dinner. tomb really does an excellent job putting these kits together. I wanted an amp to keep on my desk at work but haven't had a lot of time lately to spec out and order a bunch of parts, so the kit was a great way for me to put together an amp quickly and still have it be a DIY project.

 This is my first foray into the world of tubes. I obviously can't form any final opinions until I have a few more hours of operation (particularly on the Black Gates) but let's just say I like what I hear so far


----------



## tomb

Thank you both for the very kind comments!
	

	
	
		
		

		
		
	


	







 P.S. The pics are great, too. I hope to see yours cased up, too, Oberst!


----------



## iamthecheese

Well Originally i put some resistors in the wrong spots, the amp turned on but I couldn't get it biased correctly. I spent this morning with some desoldering braid fixing all of that and now the amp still wont produce sound, but it turns on. Also, now all the voltages of the tubes, DB and power supply are correct...any ideas?

 Edit: Fixed that. Now I'm having other less severe issues.


----------



## tomb

Quote:


  Originally Posted by *iamthecheese* /img/forum/go_quote.gif 
_Well Originally i put some resistors in the wrong spots, the amp turned on but I couldn't get it biased correctly. I spent this morning with some desoldering braid fixing all of that and now the amp still wont produce sound, but it turns on. Also, now all the voltages of the tubes, DB and power supply are correct...any ideas?_

 

In case anyone is watching this thread, I just wanted to say that iamthecheese and I have been trading a few dozen e-mails tracing down his problems. We're still working on it and hopefully we'll have good results to report sometime soon.


----------



## BoogieWoogie

FInally received my minimax !
 The previously owner already had setup it but he is from US. 
 So now do I need to setup anything on its ready to go ?


----------



## tomb

Quote:


  Originally Posted by *BoogieWoogie* /img/forum/go_quote.gif 
_FInally received my minimax !
 The previously owner already had setup it but he is from US. 
 So now do I need to setup anything on its ready to go ?_

 

Wow - that's a loaded question.
	

	
	
		
		

		
		
	


	







 1. Do you have the correct power? The amp must be supplied with 24VAC - it can't be DC. Plus, it must have at least a 750ma rating.
 2. Did the previous owner tell you which tube went where? Most likely, it wasn't shipped with the tubes plugged into the amp. There's a 99.9% (empirical guess) probabability that the left and right tubes are not biased to the same setting. So, you should probably be prepared to adjust the tube bias.

 Other than that, it shouldn't require any adjustment/preparation.


----------



## BoogieWoogie

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Wow - that's a loaded question.
	

	
	
		
		

		
		
	


	







 1. Do you have the correct power? The amp must be supplied with 24VAC - it can't be DC. Plus, it must have at least a 750ma rating.
 2. Did the previous owner tell you which tube went where? Most likely, it wasn't shipped with the tubes plugged into the amp. There's a 99.9% (empirical guess) probabability that the left and right tubes are not biased to the same setting. So, you should probably be prepared to adjust the tube bias.

 Other than that, it shouldn't require any adjustment/preparation._

 

1- Luckily my home town electronic store had a 24vac ac-ac 1A with the same output size =D

 2. You mean one tube is configured for the left and other to the right ? No he dint tell me I just plugged them without knowing would make any difference. 
 Dam what now 
	

	
	
		
		

		
		
	


	




 I have no idea how to configure this, how do I check the voltage with the voltmeter ? (yeah don't laugh)


----------



## the_equalizer

Quote:


  Originally Posted by *BoogieWoogie* /img/forum/go_quote.gif 
_<snip> 
 Dam what now 
	

	
	
		
		

		
			





 I have no idea how to configure this, how do I check the voltage with the voltmeter ? (yeah don't laugh)_

 

This seems like a nice tutorial on multimeter use. 

 After that you'd want to go to the setup section in the MiniMax website to see how to bias the tubes.

 cheers!


----------



## Beefy

Quote:


  Originally Posted by *BoogieWoogie* /img/forum/go_quote.gif 
_1- Luckily my home town electronic store had a 24vac ac-ac 1A with the same output size =D_

 

Didn't I tell you? 
	

	
	
		
		

		
		
	


	




  Quote:


 2. You mean one tube is configured for the left and other to the right ? No he dint tell me I just plugged them without knowing would make any difference. 
 Dam what now 
	

	
	
		
		

		
		
	


	




 I have no idea how to configure this, how do I check the voltage with the voltmeter ? (yeah don't laugh) 
 

Don't worry, it won't break anything if the tubes aren't properly biased. Absolute worst case scenario, you get slightly higher distortion in one channel, or one channel clips earlier than the other at very high volumes.

 the_equalizer's advice is good. But don't obsess over it.


----------



## BoogieWoogie

Quote:


  Originally Posted by *Beefy* /img/forum/go_quote.gif 
_Didn't I tell you? 
	

	
	
		
		

		
		
	


	






 Don't worry, it won't break anything if the tubes aren't properly biased. Absolute worst case scenario, you get slightly higher distortion in one channel, or one channel clips earlier than the other at very high volumes.

 the_equalizer's advice is good. But don't obsess over it._

 

You sure ? I though it would fry the amp then I'm going to give it a listen immediately !


----------



## Beefy

So long as the power going in is 24VAC, and nothing broke during shipping, there isn't anything that should fry. Fire it up!


----------



## BoogieWoogie

I just tested the multimeter and its 25.5v coming from the transformer no biggy ?


----------



## Beefy

Nup, that's fine, so long as it is AC.


----------



## tomb

Beefy is correct in everything he's told you.

 However, don't get upset if the sound is horrible in one channel or another - or even missing. Sometimes the bias can be that different. Either swap the tubes around or realize that all it takes is a turn of a screw while you are measuring with your meter at the tip jacks in back. Very simple stuff, but if the bias is way off, you may think the amp is broken. It would be a shame to jump to conclusions - so please keep that in mind.


----------



## BoogieWoogie

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Beefy is correct in everything he's told you.

 However, don't get upset if the sound is horrible in one channel or another - or even missing. Sometimes the bias can be that different. Either swap the tubes around or realize that all it takes is a turn of a screw while you are measuring with your meter at the tip jacks in back. Very simple stuff, but if the bias is way off, you may think the amp is broken. It would be a shame to jump to conclusions - so please keep that in mind.
	

	
	
		
		

		
		
	


	


_

 

I checked with the previous owner and he said the 2 have the same bias setup and after 50hours playing he checked and were no changes.

 Well it sounds terrible but because I have plug it to my first cheapest dvd I got when they came out, still waiting for the dac...


----------



## wierddemon

I have a Millet Hybrid Max that I got second hand about a week ago. This is my first time with tubes and so I know very little. When I was attempting to bias the tubes I noticed that they were close to 21mV each when (if I have been reading correctly) they should be at 13.5mV each since the power supply is at 27mV. Given that the tubes were biased incorrectly (to my understanding), I wanted to check to make sure the DB biasing was done correctly. How do I do this and what should the voltage be set to for the left and right DB?


----------



## tomb

Quote:


  Originally Posted by *wierddemon* /img/forum/go_quote.gif 
_I have a Millet Hybrid Max that I got second hand about a week ago. This is my first time with tubes and so I know very little. When I was attempting to bias the tubes I noticed that they were close to 21mV each when (if I have been reading correctly) they should be at 13.5mV each since the power supply is at 27mV. Given that the tubes were biased incorrectly (to my understanding), I wanted to check to make sure the DB biasing was done correctly. How do I do this and what should the voltage be set to for the left and right DB?_

 

I would recommend that you not mess with the DB's. No offense, but if you have trouble keeping mV straight from V, you could fry the amp in no time.
	

	
	
		
		

		
		
	


	




 Seriously (not that the above was a total joke), practice a little more taking readings, swapping tubes and adjusting the tubes until you are completely confident what you are reading and how the changes occur relative to adjusting the trimmers.


----------



## moonboy403

On my MiniMax, there's a little bit of hissing with my JH13 Pro even with the lowest gain tube and regardless of volume level even with the 12FK6 tubes. 

 1) Is it safe to assume that the gain of the MiniMax is still too high for the JH13? 
 2) Is there any way to lower the gain further?

 Thanks.


----------



## gspence2000

Sounds like the pot needs grounding. See this post.


----------



## moonboy403

Quote:


  Originally Posted by *gspence2000* /img/forum/go_quote.gif 
_Sounds like the pot needs grounding. See this post._

 

I'm not getting any hum, just plain hiss as the JH13 is pretty sensitive at 119db @ 1mw and 28 ohms. 

 With the use of an impedance adapter solved this problem but if I could, I would rather mod the MiniMax so I wouldn't have to use the impedance adapter which IMO degrades the SQ a bit.


----------



## tomb

Quote:


  Originally Posted by *moonboy403* /img/forum/go_quote.gif 
_I'm not getting any hum, just plain hiss as the JH13 is pretty sensitive at 119db @ 1mw and 28 ohms. 

 With the use of an impedance adapter solved this problem but if I could, I would rather mod the MiniMax so I wouldn't have to use the impedance adapter which IMO degrades the SQ a bit._

 

Yes, there are some low impedance/high efficiency phones that may exhibit hiss. You control this with the output resistors - anything from a jumper to 100ohms. Most find 10 or 22 ohms are enough, but there are exceptions that may need more output resistance. I think Beefy used much higher values for some AT headphones, but I'm not exactly sure what they were.


----------



## Beefy

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Yes, there are some low impedance/high efficiency phones that may exhibit hiss. You control this with the output resistors - anything from a jumper to 100ohms. Most find 10 or 22 ohms are enough, but there are exceptions that may need more output resistance. I think Beefy used much higher values for some AT headphones, but I'm not exactly sure what they were._

 

I used 33 ohm output resistors for 32 ohms AT-ESW9s. Works great as a balance between noise/gain reduction and damping for these sensitive phones.

 But in all honesty, as much as I love the MiniMax I don't think that it is even remotely suitable for IEMs. Too high a gain, too high a noise floor. Even higher resistances or impedance adapters might help with IEMs, but your damping factor will drop off a cliff.

  Quote:


  Originally Posted by *gspence2000* /img/forum/go_quote.gif 
_Sounds like the pot needs grounding. See this post._

 

No, I really doubt that is all it is.


----------



## moonboy403

Quote:


  Originally Posted by *Beefy* /img/forum/go_quote.gif 
_I used 33 ohm output resistors for 32 ohms AT-ESW9s. Works great as a balance between noise/gain reduction and damping for these sensitive phones.

 But in all honesty, as much as I love the MiniMax I don't think that it is even remotely suitable for IEMs. Too high a gain, too high a noise floor. Even higher resistances or impedance adapters might help with IEMs, but your damping factor will drop off a cliff.



 No, I really doubt that is all it is._

 

I'm using a UE impedance adapter which is said to be around 100 ohms. All hiss and noise are eliminated. While SQ degraded a bit, I still think my JH13 sounds very good the MiniMax. 

 Beefy, seeing that you have the Superfi 5, can you test it out on your MiniMax to see if there's any hiss? Also, are there any specific brand of output resistors I should be looking at? A link to which resistors I should be buying would be nice (so I only have to them to cart and buy them). 
	

	
	
		
		

		
			





 The reason why I wanna keep the MiniMax is because of its capability in driving wide range of headphones. I already have a speaker amp dedicated to the K1000, so if I buy a portable amp for the JH13, I'll have to buy yet another amp for my other headpones. 

 Thanks


----------



## Beefy

Quote:


  Originally Posted by *moonboy403* /img/forum/go_quote.gif 
_Beefy, seeing that you have the Superfi 5, can you test it out on your MiniMax to see if there's any hiss?_

 

I previously have. I normally listen at fairly low volumes, and the noise floor was just too high to be able to enjoy it at all.

  Quote:


 The reason why I wanna keep the MiniMax is because of its capability in driving wide range of headphones. I already have a speaker amp dedicated to the K1000, so if I buy a portable amp for the JH13, I'll have to buy yet another amp for my other headpones. 
 

And it is worth keeping. But different/larger in-line resistors aren't going to be any better than the impedance adapter you are using now.

 Perhaps you could consider making yourself something in a cable adaptor at intermediate values between 33 and 100 ohm? The default boutique suggestion for the Max amps is Kiwame or KOA SPR2. Beezar still stocks 47R KOA which might be a good place to start.


----------



## iamthecheese

Well it turns out one of the ground pins on the volume pot wasn't making good contact. So after that was fixed everything works and sounds great.

 I'm gunna case it up after class today then post some pics!


----------



## wierddemon

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_I would recommend that you not mess with the DB's. No offense, but if you have trouble keeping mV straight from V, you could fry the amp in no time.
	

	
	
		
		

		
		
	


	




 Seriously (not that the above was a total joke), practice a little more taking readings, swapping tubes and adjusting the tubes until you are completely confident what you are reading and how the changes occur relative to adjusting the trimmers._

 

Hmmm... alright, I guess I'll just hope that the DB is set properly at this point.

 I get that I am in the DIY form and that everyone here is more advanced than me, but I did specifically say that I was just getting into this stuff and trying to learn.


----------



## tomb

Quote:


  Originally Posted by *wierddemon* /img/forum/go_quote.gif 
_Hmmm... alright, I guess I'll just hope that the DB is set properly at this point.

 I get that I am in the DIY form and that everyone here is more advanced than me, but I did specifically say that I was just getting into this stuff and trying to learn._

 

Yes, I sort of figured that. However, "learning" with the Class A bias on a Diamond Buffer is the sort of first lesson that can be painful (to your wallet) and destructive. We don't even recommend the MiniMAX as a first build, and only a second with some qualification.

 Build something - perhaps a CMoy, learn a little more about making meter readings and then perhaps BJT's and thermal runaway. Bias the tubes all you want - the amp is built with those adjustments in mind without having to take one apart. DB bias is different.

 I'm sorry if that's not taken as constructive advice, either, but I would never suggest to someone that they could take a MiniMAX apart and adjust the DB bias without having built it or without being a somewhat experienced DIY-er.


----------



## iamthecheese

First before I post the pics I just wanted to say that Thomas(tomb) of Beezar was an INCREDIBLE help and showed great patience with my build problems. There is NO way I could have gotten to where I am with the amp without him. 

 Now, pics as promised:
 Flash:



 No Flash(I love the LEDs under the tubes):


----------



## tomb

Thanks, iamthecheese - those are very kind comments. However, you deserve the bulk of the credit. There are many who would have given up long ago in the face of the great work and trouble-shooting that you did. Thanks for sticking with it and discovering the problem yourself in the end!!

 Pics look great!


----------



## tomb

See how mixed up this got me? Sorry - wrong thread!

 (EDIT: Starving Student kit sales w/o Priority Mail shipping)


----------



## phangtonpower

Just received the Minimax from whiplash, and couldn't be happier, but I have a question about biasing the power supply. I live in Japan and the voltage here is 100v. When I bias the amp with the tubes in it the highest I can get it is 23.9VDC. Seems kinda low, probably the low voltage here in Japan? When the tubes are out, I get about 26.9VDC, which seems closer to the recommended optimum VDC. So I guess my question is, should I be taking the readings with the tubes in or out?


----------



## rds

What do you mean by "biasing the power suppy"?

 Are you measuring voltage using the red, blue and white tip jacks on the back of the case? Which trimmer are you adjusting?

 To me it sounds like you're adjusting the tube bias, which should be at 13.5V (between red and black, and between blue and black) with the tubes in and warmed up.


----------



## phangtonpower

Sorry I didn't mean biasing, just setting the Power Supply. The probes are on GND and V+, and trimming it at RR3. I have the tubes biased at 12VDC since the PS is at 23.9VDC.


----------



## rds

Ok gotcha. To answer your question the reading you get with the tubes in is the "real" voltage under load. Although 24V isn't the "optimum" voltage, imo it is not something to worry about.

 The transformer you have is rated for (NA) 120V AC, so that is the cause of your lower regulated voltage. You could look for Japanese 24 VAC (750mA or higher) wallwart with a 2.1 x 5.5mm barrel plug connector. I don't know of any offhand, but I would imagine they are available from local electronic parts stores.


----------



## phangtonpower

Cool thanks. That's what I figured. Just wanted to clear that up.
 Nice build by the way 
	

	
	
		
		

		
		
	


	




 Edit: I live out in the country side, so it is a little difficult.


----------



## tomb

Quote:


  Originally Posted by *phangtonpower* /img/forum/go_quote.gif 
_Cool thanks. That's what I figured. Just wanted to clear that up.
 Nice build by the way 
	

	
	
		
		

		
		
	


	




 Edit: I live out in the country side, so it is a little difficult._

 

You might try going ahead and biasing the tubes up to 13 or 14 anyway - and see how they sound. 12FM6's especially like a bit higher voltage on the plates. Depending on the headphones and source, I doubt that you'll end up clipping - with popular music, anyway. I regularly bias my 12FM6's to 15V, but that's with 27VDC on the power supply.


----------



## phangtonpower

Thanks Tomb and RDS.

 Don't ask me how, but I found a 24V 2.08A transformer and have everything set perfect 
	

	
	
		
		

		
		
	


	




 Kinda new to biasing tubes, and was wondering what the advantage of having higher voltage on the tubes are if I listen at lower levels? Right now I have my amp in between 9 and 10, which is probably my average listening levels. Sometimes I'll crank to 12, but not often. I'm using 12AE6's biased to 14 with my HD650's. Source is a gamma y2. Is it to give headphones a higher voltage swing even at lower levels? Sorry for the Newb question


----------



## tomb

Quote:


  Originally Posted by *phangtonpower* /img/forum/go_quote.gif 
_Thanks Tomb and RDS.

 Don't ask me how, but I found a 24V 2.08A transformer and have everything set perfect 
	

	
	
		
		

		
			





 Kinda new to biasing tubes, and was wondering what the advantage of having higher voltage on the tubes are if I listen at lower levels? Right now I have my amp in between 9 and 10, which is probably my average listening levels. Sometimes I'll crank to 12, but not often. I'm using 12AE6's biased to 14 with my HD650's. Source is a gamma y2. Is it to give headphones a higher voltage swing even at lower levels? Sorry for the Newb question 
	

	
	
		
		

		
		
	


	


_

 

The voltage swing is only one component and as you mention, it probably doesn't have as much significance at lower volumes - for sure. What you have set for the 12AE6's and HD650's is probably best, though.

 However, for low impedance cans that use more current than voltage swing, you can gain possibly better results by upping the voltage and sacrificing a little voltage swing (as with 12FM6's and Grado's, for instance). The reasons are highly technical and someone such as cetoole or Dsavitsk would need to explain it thoroughly - I can't. Suffice to say that all things being equal, many tubes perform better (less distortion) with higher voltage on the plates (or B+ as it's sometimes referenced). This is true even with the low-voltage space-charge tubes used by the Millett Hybrid/MAX/MiniMAX. Pete Millett mentioned as much in his original Millett Hybrid magazine article in Audio Xpress magazine (what started it all!): 
http://www.diyforums.org/MAX/history/ax_hybrid.pdf

 Pete even went as high as a 19V bias!
	

	
	
		
		

		
		
	


	




 We don't normally recommend such extremes because we can't guarantee the headphones/source/etc. for all the many builders and users out there. Certainly, bias at 1/2 the supply voltage is the safest, most certain performance setting for all headphones - just saying that some experimentation may yield some interesting results. As stated, I've found that 15V bias works quite well for Grado's and AKG 701's using 12FM6 tubes. I haven't fooled with much else beyond that, though.


----------



## iamthecheese

Well I decided to take a gamble and change out the 22 ohm resistors near the relay for jumpers.
 So far I'd say its paid off...here's a couple of observations
 1. More detail(as expected)
 2. no noise when I pause the music until the pot gets up near 1 o clock. I have no problem with this because the 12 o clock position is near deafening. With winamp at a -4.0 db pre amp setting I still only listen between 9 and 10 actively and 8 when I'm working on school stuff.
 3. Easier to pick out bad recording and low bitrate mp3s now.

 Overall I'm really glad I did it, I enjoy the amp much more now and luckily there weren't any bad side effects.


----------



## tomb

Quote:


  Originally Posted by *iamthecheese* /img/forum/go_quote.gif 
_Well I decided to take a gamble and change out the 22 ohm resistors near the relay for jumpers.
 So far I'd say its paid off...here's a couple of observations
 1. More detail(as expected)
 2. no noise when I pause the music until the pot gets up near 1 o clock. I have no problem with this because the 12 o clock position is near deafening. With winamp at a -4.0 db pre amp setting I still only listen between 9 and 10 actively and 8 when I'm working on school stuff.
 3. Easier to pick out bad recording and low bitrate mp3s now.

 Overall I'm really glad I did it, I enjoy the amp much more now and luckily there weren't any bad side effects._

 

Yep. It's tough to recommend what's best, because what works for one doesn't work for others. It depends on your headphones and source. Some people can't stand to not be able to move the volume knob it's whole travel and have gone as far as 150ohms. I can't imagine it would sound very good that way. On the other hand, there are some with 25ohm AT's, Denons, or even IEM's that claim to hear hiss unless they put in 22 or 33R.

 I'm like you - for most mainstream headphones - Grado's, AKG's, Sennheisers - jumpers work best.


----------



## phangtonpower

Thanks for the reply Tomb. I'm sure I'll be bothering you guys some more in the future.


----------



## BoogieWoogie

I have this newbiw doubt , will it sound better after 30minutes being hotter or is just the same ?


----------



## tomb

Quote:


  Originally Posted by *BoogieWoogie* /img/forum/go_quote.gif 
_I have this newbiw doubt , will it sound better after 30minutes being hotter or is just the same ?_

 

I'm not sure I understand what "newbiw" means. Can you give us some more information? Back earlier in the thread you weren't even sure if the tubes were biased correctly. I find it almost impossible for _any_ two tubes to have the same bias setting, so I doubt the original owner knew what he was talking about when he told you that.

 If the bias is more than a couple of volts off, it can mean the difference between sounding great and sounding awful. You need to check the bias, tell us what it measures and go from there.


----------



## Beefy

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_I'm not sure I understand what "newbiw" means._

 

Typo for newbie!


----------



## tomb

Quote:


  Originally Posted by *Beefy* /img/forum/go_quote.gif 
_Typo for newbie! 
	

	
	
		
		

		
		
	


	


_

 

Right! I guess my brain wasn't working - shows how late I was up last night packing SSMH kit orders.


----------



## BoogieWoogie

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_I'm not sure I understand what "newbiw" means. Can you give us some more information? Back earlier in the thread you weren't even sure if the tubes were biased correctly. I find it almost impossible for any two tubes to have the same bias setting, so I doubt the original owner knew what he was talking about when he told you that.

 If the bias is more than a couple of volts off, it can mean the difference between sounding great and sounding awful. You need to check the bias, tell us what it measures and go from there._

 

What I wanted to know is if the tube amps like this should let be turned on some minutes before listening, and let it heat up.

 I already tested the minimax with an borrowed DacMagic and the sound was absolutely amazing I really loved and felt the warm sound from the tubes but with aliendac its basically the same sound from the laptop onboard, still think the bias setting isn't right ?

 I'm willing to try to check but I it seems a bit confusing.


----------



## tomb

Quote:


  Originally Posted by *BoogieWoogie* /img/forum/go_quote.gif 
_What I wanted to know is if the tube amps like this should let be turned on some minutes before listening, and let it heat up.

 I already tested the minimax with an borrowed DacMagic and the sound was absolutely amazing I really loved and felt the warm sound from the tubes but with aliendac its basically the same sound from the laptop onboard, still think the bias setting isn't right ?

 I'm willing to try to check but I it seems a bit confusing._

 

Well OK - at least you are being more descriptive here.
	

	
	
		
		

		
		
	


	




 It sounds to me that you just don't like the AlienDAC. An Alien/BantamDAC ordinarily sound much nicer, especially compared to an onboard laptop output, but it depends on the build, of course. If the Alien was built without regulation on the analog output and some-less-than-sterling output caps, it's conceivable that it wouldn't be much of an upgrade over a decent laptop output.

 Based on your clearer explanation this time, it doesn't sound like the MiniMAX.


 P.S. You do need to let it heat up for the best sound, but we're talking within the margins of very slight incremental improvement - perhaps 2 hours vs. the first 15 minutes, that sort of thing. I'd say if you gave it at least 10 minutes of warmup, the MiniMAX sound is pretty much 95% there. So, yeah - pick another source, I suppose.


----------



## BoogieWoogie

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Well OK - at least you are being more descriptive here.
	

	
	
		
		

		
		
	


	




 It sounds to me that you just don't like the AlienDAC. An Alien/BantamDAC ordinarily sound much nicer, especially compared to an onboard laptop output, but it depends on the build, of course. If the Alien was built without regulation on the analog output and some-less-than-sterling output caps, it's conceivable that it wouldn't be much of an upgrade over a decent laptop output.

 Based on your clearer explanation this time, it doesn't sound like the MiniMAX.


 P.S. You do need to let it heat up for the best sound, but we're talking within the margins of very slight incremental improvement - perhaps 2 hours vs. the first 15 minutes, that sort of thing. I'd say if you gave it at least 10 minutes of warmup, the MiniMAX sound is pretty much 95% there. So, yeah - pick another source, I suppose.
	

	
	
		
		

		
		
	


	


_

 

I dont know much about the aliendac is smaller than my finger it was build by MASantos I believe and my laptop is a recent Toshiba A500-14c 1100€. 

 The differences with the dacmagic was just like being in the dark and turning the lights on, there is no comparison so the aliendac isn't doing anything and yeah I'm thinking on going for a gamma 2 to go with the minimax , from what I have been said it used similar architecture of the DacMagic and DacMagic owners experienced the y2 to be better so I'm only hoping this to be truly a good combo.


----------



## the_equalizer

Hello to all,

 Looking for a better amplifier than my SSMH, a couple of weeks ago I decided to buy a Millet MiniMAX kit from beezar.com. Two days ago the wait came to an end as I received my kit. Yesterday I allocated the whole day to the build and, after a marathon 12-hour long building session, the amp fired up perfectly and sweet music came out of my K701's

 So, to the point of my message: to all of you guys involved in the development of this terrific little amp: my admiration, respect and thanks. From the nice and clean design of the two stages, to the beautifully compact and simmetrical board layout, through the quality of manufacture of said board, the work of prototyping the amp to improve the layout and desing, the neatness of the custom machined case, and the outstanding effort of gathering all the required component to make up the kits, setting up a page to sell them, the carefull work that goes into the packing of each order, writing all the documentation, man I could go on here for pages and pages, so I'll just restate what I said. My full admiration, respect and thanks to you all MiniMAX team.

 And last but not least, as to the sound of the amp... oh, finally my K701's sound like I had imagined: deep, precise bass; sweet treble: rich, liquid mids; fast transients and dynamics. 

 Again, as with the SSMH kit I put together some months ago, I look and listen to my new amp and can barely believe it was I who put the thing together.

 Thank you so much for a very entertaining and instructive build, and a remarkable amplifier.

 cheers!


----------



## tomb

Wow!! Thank you so much, equalizer. Those are very kind words and coming from you, mean quite a lot. You've made my day/week!
	

	
	
		
		

		
		
	


	







 I will be sure to tell cetoole to take a look at your post, too.

 BTW, new cases arrived from Lansing today so the MiniMAX kits are back in stock!


----------



## the_equalizer

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Wow!! Thank you so much, equalizer. Those are very kind words and coming from you, mean quite a lot. You've made my day/week!
	

	
	
		
		

		
		
	


	







 I will be sure to tell cetoole to take a look at your post, too.

 BTW, new cases arrived from Lansing today so the MiniMAX kits are back in stock!
	

	
	
		
		

		
		
	


	


_

 


 Well TomB, there's a saying in my country: "Honor to whom honor is due". 
	

	
	
		
		

		
		
	


	




 Without efforts such as this I would have simply put down any build more complex than a CMoy simply for the cost of getting all the different parts down here and what I dread most: casework 
	

	
	
		
		

		
		
	


	




 (I'm a software engineer, damn it! 
	

	
	
		
		

		
		
	


	




). So, again: thanks! 

 On a more technical aside I have a question for you MiniMAX experts. I live in a fairly warm place, currently temperatures hover around 75F/25C, but pretty soon we'll be reaching 86F/30C every day and starting in mid May, for some three weeks, we'll be hitting 100F/38C every day. 

 So, is it safe to bias the DB at 110mV ? For safety I set the bias at 90mV and currently the heatsinks barely get warm, but still I'm afraid that if I bias them for that top 50mA current, when the warm days come, the output DB's will melt! 

 Finally, I know you've probably seen hundreds of these but still... some pics 
	

	
	
		
		

		
		
	


	




 In the midst of populating the board





 The board loaded, clean and wired, ready for testing/setup





 First time switch on... it works !!





 After biasing, and testing, finally ready to rock! Ah, yes: no LED's, I like the natural tube glow, even if subdued.


----------



## tomb

Uh-oh. If you're implying with those temperatures that the amp will be exposed to that and not in an air-conditioned environment, then yes - the heat transfer will be affected by those temperatures. 90mv is prudent and will probably be OK in 86F temps, but I'd watch it closely. If the volume knob starts getting very hot (not just warm), you know the amp is cooking inside. Unfortunately, 100F temps will be even worse, so keep a very close eye on it if you run it in those kind of temperatures.
	

	
	
		
		

		
		
	


	




 I doubt that the transistors will be damaged in either case. Thermal runaways almost need an incorrect bias to really burn up - the heat sinks offer a lot of thermal inertia and prevent that as long as the bias is correctly adjusted, in spite of higher ambient temperatures.

 The real issue is how hot the electrolytic capacitors get and the kind of shortened life/sound degradation that may occur because they've been exposed to very high heat. This is particularly important for the ES caps because they're only 85C caps (the Panasonics are all 105C). I doubt that temps will reach 85C in any case, but shortened life and performance is affected before that.

 If you listen for an hour or so under those conditions, I doubt that any long-term issues will occur. However, it's not something where you'd want to leave the amp on for several hours unattended in those conditions.
	

	
	
		
		

		
		
	


	





 Nice handiwork in those pics, by the way!!


----------



## the_equalizer

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Uh-oh. If you're implying with those temperatures that the amp will be exposed to that and not in an air-conditioned environment, then yes - the heat transfer will be affected by those temperatures. 90mv is prudent and will probably be OK in 86F temps, but I'd watch it closely. If the volume knob starts getting very hot (not just warm), you know the amp is cooking inside. Unfortunately, 100F temps will be even worse, so keep a very close eye on it if you run it in those kind of temperatures.
	

	
	
		
		

		
			





 I doubt that the transistors will be damaged in either case. Thermal runaways almost need an incorrect bias to really burn up - the heat sinks offer a lot of thermal inertia and prevent that as long as the bias is correctly adjusted, in spite of higher ambient temperatures.

 The real issue is how hot the electrolytic capacitors get and the kind of shortened life/sound degradation that may occur because they've been exposed to very high heat. This is particularly important for the ES caps because they're only 85C caps (the Panasonics are all 105C). I doubt that temps will reach 85C in any case, but shortened life and performance is affected before that.

 If you listen for an hour or so under those conditions, I doubt that any long-term issues will occur. However, it's not something where you'd want to leave the amp on for several hours unattended in those conditions.
	

	
	
		
		

		
		
	


	





 Nice handiwork in those pics, by the way!!_

 


 Thanks TomB, note taken: I'll leave it biased as it is, at 90mV. 

 What's more, today I took the amp to my office and had it on all day, and it got hot. Not burning hot, as I can lay my hand on the case for as long as I like, but definitely not the barely warm temps it reached while running for an hour or two on the test bench the last two nights. 

 Thanks for the compliment, such a nice amplifier simply deserves, demands even, to be carefully built.

 cheers!


----------



## tomb

Ah-ha! I couldn't see that last pic earlier. Now I see you have SR225's hooked up to the MiniMAX. That's a very good combination!!

 Yes, there's no real issue with turning the amp on and off when you're not listening. Truly, 95% of the sound is there in the first 15 minutes and with the relay-delay, there's no issue with hitting the power switch as often as you think is prudent. I usually still turn the volume down every time - just as an added precaution. (I do that with SS amps, too - just prudent, it seems.)


----------



## BoogieWoogie

Finaly I have found the way to check the bias and its 16,50 to the Right and its 15,94 on the left ! 

 I checked in AC 2V mode in multimeter is this the right config ?


----------



## the_equalizer

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Ah-ha! I couldn't see that last pic earlier. Now I see you have SR225's hooked up to the MiniMAX. That's a very good combination!!

 Yes, there's no real issue with turning the amp on and off when you're not listening. Truly, 95% of the sound is there in the first 15 minutes and with the relay-delay, there's no issue with hitting the power switch as often as you think is prudent. I usually still turn the volume down every time - just as an added precaution. (I do that with SS amps, too - just prudent, it seems.)_

 

It most certainly is a great combination, I was just enyoing Queen's "A night at the Opera" and boy, Brian May's guitar work sounds sooooo good.

 Indeed, one of my main reasons to switch from the "Starving Student" Hybrid to the MiniMAX was the relay-delay circuit (turn-on/off thumps both annoy and worry me). The circuit works perfectly and now I have great sound *AND* peace of mind.

 cheers!


----------



## the_equalizer

Quote:


  Originally Posted by *BoogieWoogie* /img/forum/go_quote.gif 
_Finaly I have found the way to check the bias and its 16,50 to the Right and its 15,94 on the left ! 

 I checked in AC 2V mode in multimeter is this the right config ?_

 

Are you sure that was the range? The measurements make sense, but the range doesn't. Tube bias in the MiniMAX is measured in a DC range of at least 20 V so... DC 20V

 cheers!


----------



## BoogieWoogie

Quote:


  Originally Posted by *the_equalizer* /img/forum/go_quote.gif 
_Are you sure that was the range? The measurements make sense, but the range doesn't. Tube bias in the MiniMAX is measured in a DC range of at least 20 V so... DC 20V

 cheers!_

 

My bad it was set to 20v.

 Edit. Got it in the 13,5 and finally it sounds good and I can feel the warm sound ! you were right tomb


----------



## the_equalizer

Boy this amp does not cease to amaze me. Last night I tried it with my Etymotic ER-6i IEM's, and it is so silent! I had to turn the knob up to 11 o'clock to start noticing hiss. No music playing of course, with the ER-6i that volume on the MiniMAX would have literally blown my (inner) ears out.

 Besides the silence it was my impression that the amp lent more impact to the somewhat lean bass in the ER-6i's. Fantastic!

 cheers!


----------



## tomb

That's great to hear! I keep wanting to buy a pair of the old Altec-Lansing IM716's and was wondering how they'd do.


----------



## the_equalizer

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_That's great to hear! I keep wanting to buy a pair of the old Altec-Lansing IM716's and was wondering how they'd do._

 

I'd say they'd do great, considering that my amp has jumpers in the RB14 positions (making it more prone to hiss with sensitive cans, as I understand).

 cheers!


----------



## Oberst Oswald

Finally figured out how to post pictures (except for size). Here's my MiniMax that is used for gaming mostly.









 MiniMax for gaming, Starving Student for the iPod & the Travagan's Red for the STAX (game with them when the house dragon isn't home)... wondering what should I build next? Yup, got the bug & I'm drunk with success on my SSMH working nicely on the 1st click of the switch. Been thinking about 3 channel Beta 22 or the Bijue tube amp (sp?) since Glass Jar Audio has semi kits for sale. I don't need any more amps but I just want to build something and might as well go to the top end so I can be hopefully cured.


----------



## the_equalizer

Quote:


  Originally Posted by *Oberst Oswald* /img/forum/go_quote.gif 
_Finally figured out how to post pictures (except for size). Here's my MiniMax that is used for gaming mostly.
 <snip>

 MiniMax for gaming, Starving Student for the iPod & the Travagan's Red for the STAX (game with them when the house dragon isn't home)... wondering what should I build next? Yup, got the bug & I'm drunk with success on my SSMH working nicely on the 1st click of the switch. Been thinking about 3 channel Beta 22 or the Bijue tube amp (sp?) since Glass Jar Audio has semi kits for sale. I don't need any more amps but I just want to build something and might as well go to the top end so I can be hopefully cured._

 

Cool setup you have there! Saw your Millett "Starving Student" pics too and those look great too.

 While I think a B22 seems like a truly fun build and I'd definitely go for it if I were you, I have to say that I don't think one can be cured of the DIY bug. I've been DIYing audio stuff for the last 18 years (electric guitar stuff mostly, headphone stuff only for the last 6 months) and I must tell you that I don't feel anywhere near to "cured" !!
	

	
	
		
		

		
		
	


	




 cheers!


----------



## hembergler

So my package from Beezar arrived two days ago. Yesterday I was sick, so I stayed home from school and possibly turned in the most productive sick day of all time 
	

	
	
		
		

		
		
	


	




 I spent nearly ten hours working on it (hey, I'm uh... thorough!), but another MiniMAX lives! 

 Here's an obligatory photo, although they all start to look the same after a while 
	

	
	
		
		

		
		
	


	




 (sorry for the poor quality, I took it with my cellphone because I was too excited to case it up to bother grabbing my actual camera (and don't worry, I cleaned up some of the wiring since this photo))






 I must say that it sounds absolutely wonderful. I snagged an AKG K271 a few days ago just so I could have a decent dynamic headphone to listen to it with, and oh my! I can't stop listening! Someone stop me!

 Now for my two beginner mistakes: 
 - I probably should have drilled out the tube sockets and mounted the color-changing LED higher, since on the whole it's rather dim. At the same time, I don't always want my room filled with LED lighting, so maybe the subtlety is for the better.
 - I don't think I soldered the tube sockets in sufficiently. I thought I did a very good job of filling in the connections with copious amounts of solder in the midst, but it seems that the tubes are slightly wobbly now that it's cased up. I might have to redo those joints going forward.

 Regardless, on the whole I'm very proud that I managed to churn out sound the first time I connected my headphones. 
	

	
	
		
		

		
		
	


	




 And of course, many many many many thanks to TomB's efforts in organizing his wonderful kits. My jaw dropped when I saw how well packed and laid out it was. There's no way I would have pieced it all together without it. I still don't understand everything that I put together, but it was a big step for me in the DIY world. Soon enough I'll be cranking through those BOMs myself, but for now, thanks so much TomB, your efforts are greatly appreciated.


----------



## tomb

Gosh.
	

	
	
		
		

		
		
	


	




 Thank you so much for those wonderful comments. I'm so glad you enjoyed the kit and the MiniMAX!


----------



## MASantos

Quote:


  Originally Posted by *Oberst Oswald* /img/forum/go_quote.gif 
_
 MiniMax for gaming, Starving Student for the iPod & the Travagan's Red for the STAX (game with them when the house dragon isn't home)... wondering what should I build next? Yup, got the bug & I'm drunk with success on my SSMH working nicely on the 1st click of the switch. Been thinking about 3 channel Beta 22 or the Bijue tube amp (sp?) since Glass Jar Audio has semi kits for sale. I don't need any more amps but I just want to build something and might as well go to the top end so I can be hopefully cured._

 

A bit of topic, but is that a submarine game? What is it?


----------



## Oberst Oswald

The game in the picture is "Silent Hunter 3" (with the Gray Wolf mod installed) which you can get on Steam. You play as the Germans during WWII. 

 "Silent Hunter 4" allows you to play as the Americans fighting the Japanese in the Pacific. This also can be bought on Steam.


----------



## iamthecheese

Just a random thought...Is there something better than a wallwart the minimax can use...kinda like an M3 can use a STEPS or a TREAD?


----------



## PScal

The MiniMax has an onboard regulated power supply. The wallwart is only a transformer that steps the voltage down to 24vac.


----------



## tomb

Quote:


  Originally Posted by *iamthecheese* /img/forum/go_quote.gif 
_Just a random thought...Is there something better than a wallwart the minimax can use...kinda like an M3 can use a STEPS or a TREAD?_

 

Yes - what PScal said. The power supply on the MiniMAX is actually a modification of the STEPS, which itself was a modification of the standard LM317 application notes. The difference being that the MiniMAX was specifically tuned even further to achieve somewhere around a ~45uV ripple, when measured at the V+ and Gnd points, which essentially is the point of separation between the amp and the power supply.

 Just think of the walwart as the transformer in the power supply circuit - that's all it is.


----------



## iamthecheese

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Yes - what PScal said. The power supply on the MiniMAX is actually a modification of the STEPS, which itself was a modification of the standard LM317 application notes. The difference being that the MiniMAX was specifically tuned even further to achieve somewhere around a ~45uV ripple, when measured at the V+ and Gnd points, which essentially is the point of separation between the amp and the power supply.

 Just think of the walwart as the transformer in the power supply circuit - that's all it is.
	

	
	
		
		

		
		
	


	


_

 

I was kinda of hoping to get rid of the wallwart...maybe a psu that would use a standard 110v cord like computer PSUs just to free up space on my UPS(its full and I have to keep switching around plugs).

 Is it even realistic to have an external transformer that would be in a lansing case with the same length and width to put under the minimax?
 Or would it mostly be a waste of time?


----------



## tomb

Quote:


  Originally Posted by *iamthecheese* /img/forum/go_quote.gif 
_I was kinda of hoping to get rid of the wallwart...maybe a psu that would use a standard 110v cord like computer PSUs just to free up space on my UPS(its full and I have to keep switching around plugs).

 Is it even realistic to have an external transformer that would be in a lansing case with the same length and width to put under the minimax?
 Or would it mostly be a waste of time?_

 

You're kidding, right?
	

	
	
		
		

		
		
	


	







 The MiniMAX and its case is as small as things can get without going to SMD!! No, there is no room whatsoever for a transformer.

 Frankly, the walwart is a _feature_ - not a detriment. There's an entirely different level of skill and accepted danger when dealing with a DIY-ed transformer using line voltage inside a case. Plus, there is assurance that things are always quieter with the transformer outside of the case. I used to build my own walwarts for many designs just for that very reason - to keep from having to worry about transformer noise inside the case.

 There are plenty of extension cords or adapters that can be used to physically get the walwart off of your UPS outlet tree. I often do the same with my outlet strips. Any drugstore or grocery store can probably fix you up.


----------



## BoogieWoogie

I had the minimax bias at 17v 16v each tube then I tested it with a dac and the sound was great but I changed after to 13,4v and dint turn on until my dac came, now that it came the sound is to much distorted and metalic feeling, I changed back to 17 just to check and this effect was lessier. Is the my multimeter defected or is something wrong with minimax ?


----------



## tomb

Quote:


  Originally Posted by *BoogieWoogie* /img/forum/go_quote.gif 
_I had the minimax bias at 17v 16v each tube then I tested it with a dac and the sound was great but I changed after to 13,4v and dint turn on until my dac came, now that it came the sound is to much distorted and metalic feeling, I changed back to 17 just to check and this effect was lessier. Is the my multimeter defected or is something wrong with minimax ?_

 

I'm not sure I understand all of that, but if you're asking if a higher bias could make the tubes sound better - yes, that's entirely possible.

 However, you need to be careful that final biases are based on a warmed up amp. Bias will drop over the first hour or two. So, if you set it to 13.5 in the first few minutes, it may very well drop to 12 or less several minutes later. That could definitely sound bad. Or, your 17 or 16V bias (which is it?) could have dropped to 14 or 13.5, which means it might have been where it should've been.
	

	
	
		
		

		
		
	


	




 Also, tubes will change over time as the getter burns out remaining gases that may be in the tubes from sitting on the shelf for the last 50 years. So, a recheck is always in order if you want the very best sound.


----------



## BoogieWoogie

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_I'm not sure I understand all of that, but if you're asking if a higher bias could make the tubes sound better - yes, that's entirely possible.

 However, you need to be careful that final biases are based on a warmed up amp. Bias will drop over the first hour or two. So, if you set it to 13.5 in the first few minutes, it may very well drop to 12 or less several minutes later. That could definitely sound bad. Or, your 17 or 16V bias (which is it?) could have dropped to 14 or 13.5, which means it might have been where it should've been.
	

	
	
		
		

		
		
	


	




 Also, tubes will change over time as the getter burns out remaining gases that may be in the tubes from sitting on the shelf for the last 50 years. So, a recheck is always in order if you want the very best sound._

 

I don't think thats it ,Its been 3 hours on and I just checked its 13,50 13,68 , whats the max bias recommend so I can tune it be hear ?


----------



## tomb

Quote:


  Originally Posted by *BoogieWoogie* /img/forum/go_quote.gif 
_I don't think thats it ,Its been 3 hours on and I just checked its 13,50 13,68 , whats the max bias recommend so I can tune it be hear ?_

 

1/2 the supply voltage, as measured and set at V+ and Gnd. However, if it sounds better to you with your particular tubes and setup to adjust the bias to 16 or 17, then do so.


----------



## tomb

I finally got around to posting a bunch of pics of the different MiniMAX builds out there. Surprisingly, even with a custom case there are some variations.
	

	
	
		
		

		
		
	


	




MiniMAX Photo Gallery


----------



## the_equalizer

Great! I enjoy galleries a lot. Thanks TomB !

 cheers!


----------



## tomb

Quote:


  Originally Posted by *the_equalizer* /img/forum/go_quote.gif 
_Great! I enjoy galleries a lot. Thanks TomB !

 cheers!_

 

Thanks! Now that you mention it, though, I didn't have the latest pics - including yours.
	

	
	
		
		

		
		
	


	




 That's now been remedied.


----------



## timmyGCSE

how long do you reckon the latest round of kits will be in stock tom? I'll probably be looking to order a kit beginning of may.
 Also whats the shipping cost to the UK like?

 and with the wallwart..can I just use a UK equivelent that gives the same output? or just use a travel adapter..


----------



## tomb

Quote:


  Originally Posted by *timmyGCSE* /img/forum/go_quote.gif 
_how long do you reckon the latest round of kits will be in stock tom? I'll probably be looking to order a kit beginning of may._

 

Beezar attempts to keep the MiniMAX kit in stock at all times. Quote:


 Also whats the shipping cost to the UK like?

 and with the wallwart..can I just use a UK equivelent that gives the same output? or just use a travel adapter.. 
 

There are answers to both these questions, but I'm afraid you need to send me a PM or e-mail. It's not exactly proper to be conducting business in the thread (I'll get banned.).


----------



## timmyGCSE

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Beezar attempts to keep the MiniMAX kit in stock at all times.There are answers to both these questions, but I'm afraid you need to send me a PM or e-mail. It's not exactly proper to be conducting business in the thread (I'll get banned.).
	

	
	
		
		

		
		
	


	





_

 

ok cool sounds good

 and 
	

	
	
		
		

		
		
	


	




 yes of course..thats two bad suggestions in one day *slaps forehead*


----------



## rbarth

Hello everybody. This is my first question on this forum to complete my first MiniMAX purchased from Beezer: When using the Toshiba 2SC3422/2SA1359 output transistors, how do you create a jumper connection for RB8L/R and RB9L/R? Is this just a piece of wire? If so, what gauge and what kind (solid, stranded) should I use? Thanks in advance for any answers to this.


----------



## Beefy

Just use the cut off leg of a resistor.


----------



## rbarth

Quote:


  Originally Posted by *Beefy* /img/forum/go_quote.gif 
_Just use the cut off leg of a resistor._

 

Many thanks for your quick reply. Back to work!


----------



## BlingBlingDr

Hey. Is there a difference between these two ways of soldering the VitQs in terms of performance? Is either one better than the other?

 Notice how the longer lead is soldered through a different hole in each one.


----------



## soloz2

no, difference.


----------



## BlingBlingDr

Excellent.


----------



## tomb

Quote:


  Originally Posted by *BlingBlingDr* /img/forum/go_quote.gif 
_Hey. Is there a difference between these two ways of soldering the VitQs in terms of performance? Is either one better than the other?

 Notice how the longer lead is soldered through a different hole in each one._

 

No, there is no difference in terms of performance. However, I prefer the arrangement in the 2nd pic (not saying it's right or wrong, though). It may be preferrable to get as much of the lead as far away from the heat sink as possible. These things will arc under certain conditions. If there is a portion of the heat sink where the anodization has worn off and if the insulation between transistor and heat sink is not optimum, then it may be possible for the Vitamin Q to arc from those leads over to the heat sink.

 Granted, that's a lot of "if's", but I have seen the older Russian K42's arc against the top of the case if they weren't insulated. Of course, in that instance the case was grounded and the heat sinks aren't. So, the chances are probably very slim. If you can use one of the closer in pads - do so. If it's a hassle to do that, chances are you'll still be fine.


----------



## radicalrev

Just got my Minimax from a Head-Fi member a couple of days ago. The minimax doesn't have the tube light (led) and was wondering if I could still add them? 

 Any DIYer in the Los Angeles area care to help me?


----------



## tomb

Quote:


  Originally Posted by *radicalrev* /img/forum/go_quote.gif 
_Just got my Minimax from a Head-Fi member a couple of days ago. The minimax doesn't have the tube light (led) and was wondering if I could still add them? 

 Any DIYer in the Los Angeles area care to help me? 
	

	
	
		
		

		
		
	


	


_

 

It's possible, but it may not be the easiest trick in the world.
	

	
	
		
		

		
		
	


	




 I'm assuming that the reason the LED's are not there is because the tube sockets weren't drilled. You see, the tube sockets have a center pin that completely fills the center of the socket where you would want to have the LED - or at least to shine the LED through. Normal procedure is to drill the center pins out, then glue the socket halves back together. (See reference in the SSMH build thread in my signature - the procedure is the same.) This becomes more difficult when the sockets are already soldered into the PCB, but it can be done.


----------



## rbarth

I'm having a lot of trouble soldering the Emerson Tip Jacks, mainly because I'm not sure what the orientation of my tinned wires should be in relation to the silver contacts that stick out from the rear of the jacks. Should my wires be wrapped around these contacts somehow? (If so, then I'm guessing they shouldn't be tinned.) Should they run parallel to the contacts? Or, should they be connected at a 90 degree angle somehow to the end of the contacts where there are those little nubs? The relevant connections shown on the MiniMAX site are covered with heat shrink, so I can't see what went on there. I'm just not getting this....


----------



## tomb

Quote:


  Originally Posted by *rbarth* /img/forum/go_quote.gif 
_I'm having a lot of trouble soldering the Emerson Tip Jacks, mainly because I'm not sure what the orientation of my tinned wires should be in relation to the silver contacts that stick out from the rear of the jacks. Should my wires be wrapped around these contacts somehow? (If so, then I'm guessing they shouldn't be tinned.) Should they run parallel to the contacts? Or, should they be connected at a 90 degree angle somehow to the end of the contacts where there are those little nubs? The relevant connections shown on the MiniMAX site are covered with heat shrink, so I can't see what went on there. I'm just not getting this...._

 

Generally, you should have about one to two turns of the wire wrapped around the tip jack contact. Orient this so that the continuation of the wire lead ends up on the bottom of the tip jack contact and is pointed down. This will keep you from having to bend the entire assembly down by hand (and perhaps cracking the solder joint) to clear the PS heat sink.

 The solder joint should run the span of the bare lead that's wrapped around the tip jack contact. That keeps the connection strong in the face of a lot of stress when you assemble/disassemble the back plate and case. Make sure you heat shrink each connection, though, because the leads are very close to the PS heat sink.


----------



## rbarth

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Generally, you should have about one to two turns of the wire wrapped around the tip jack contact. Orient this so that the continuation of the wire lead ends up on the bottom of the tip jack contact and is pointed down. This will keep you from having to bend the entire assembly down by hand (and perhaps cracking the solder joint) to clear the PS heat sink.

 The solder joint should run the span of the bare lead that's wrapped around the tip jack contact. That keeps the connection strong in the face of a lot of stress when you assemble/disassemble the back plate and case. Make sure you heat shrink each connection, though, because the leads are very close to the PS heat sink.
	

	
	
		
		

		
		
	


	


_

 

Thanks for your response, Tom. It was very clear and very, very helpful. I guess what threw me off was that I thought that, except for the volume pot ground wire, all wiring connections should be tinned prior to soldering. Clearly that's not the case with the tip jack connections.


----------



## tomb

Quote:


  Originally Posted by *rbarth* /img/forum/go_quote.gif 
_Thanks for your response, Tom. It was very clear and very, very helpful. I guess what threw me off was that I thought that, except for the volume pot ground wire, all wiring connections should be tinned prior to soldering. Clearly that's not the case with the tip jack connections._

 

Actually, I still tin them ... but lightly.
	

	
	
		
		

		
		
	


	




 Seriously, a small bit of tinning (very small) and multi-strand wire can behave like solid wire.

 If you use too much, though, it could get frustrating because it would be impossible to remove - you just have to cut the wire and try again. So, please - only do what makes you feel comfortable.


----------



## rbarth

Just finished my first MiniMAX, turned it on and no explosions (yet). BUT: Power supply voltage reads 30.3V and spinning the RR3 trimmer screw in either direction does not change this reading. Trimmers for the tubes and DB are working fine, I can lower and increase the voltages for them. What could be wrong? How do I diagnose/fix this problem?


----------



## tomb

Quote:


  Originally Posted by *rbarth* /img/forum/go_quote.gif 
_Just finished my first MiniMAX, turned it on and no explosions (yet). BUT: Power supply voltage reads 30.3V and spinning the RR3 trimmer screw in either direction does not change this reading. Trimmers for the tubes and DB are working fine, I can lower and increase the voltages for them. What could be wrong? How do I diagnose/fix this problem?_

 

See if you can measure a resistance difference in RR3 when you turn it (amp off!) - measure the two pins underneath the PCB that are not connected, turn the screw about a half dozen times in either direction and measure the pins afterward each time.

 If that seems to work, give us some pics of the PS section. Used to, this issue could've been a result of turning the small cap around in the PS, but we've changed the parts since that time, so I'm a bit unsure what it might be if the trimmer checks out. 30.3VDC is just about what you should get if there's no regulation whatsoever, so it could be the LM317, too.

 As I said, give us some pics if the trimmer checks out OK.


----------



## rbarth

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_See if you can measure a resistance difference in RR3 when you turn it (amp off!) - measure the two pins underneath the PCB that are not connected, turn the screw about a half dozen times in either direction and measure the pins afterward each time.

 If that seems to work, give us some pics of the PS section. Used to, this issue could've been a result of turning the small cap around in the PS, but we've changed the parts since that time, so I'm a bit unsure what it might be if the trimmer checks out. 30.3VDC is just about what you should get if there's no regulation whatsoever, so it could be the LM317, too.

 As I said, give us some pics if the trimmer checks out OK.
	

	
	
		
		

		
			



_

 

With the amp off and measuring from underneath the two pins of RR3 that are not connected, my resistance readings are the same no matter how much I turn the screw in either direction. The meter always stabilizes at 00.4 ohms. So, am I right in saying that this trimmer doesn't check out and needs to be replaced?


----------



## tomb

Quote:


  Originally Posted by *rbarth* /img/forum/go_quote.gif 
_With the amp off and measuring from underneath the two pins of RR3 that are not connected, my resistance readings are the same no matter how much I turn the screw in either direction. The meter always stabilizes at 00.4 ohms. So, am I right in saying that this trimmer doesn't check out and needs to be replaced?_

 

YES.

 YGPM.


----------



## rbarth

I replaced the RR3 and am still having the same problem: the voltage reading doesn't change when spinning the trimmer screw. The old trimmer gave a reading of 30.3 VDC, the new trimmer is giving me a 29.5 VDC reading, no matter what. I am a newbie, however I'm certain that I'm using my multimeter properly, that it's working OK and that I installed the RR3 properly. Also, since I was given a caution about how sensitive this part is to heat, I was very careful about that when soldering the new RR3 in. Attached are two pics of my board, a full shot and one that focuses on the power supply. What do I do next? Thanks.

 EDIT: Oh my goodness, the pics are terrible quality. Guess they were downsized because they are JPEG images. Sorry about that.


----------



## tomb

Quote:


  Originally Posted by *rbarth* /img/forum/go_quote.gif 
_I replaced the RR3 and am still having the same problem: the voltage reading doesn't change when spinning the trimmer screw. The old trimmer gave a reading of 30.3 VDC, the new trimmer is giving me a 29.5 VDC reading, no matter what. I am a newbie, however I'm certain that I'm using my multimeter properly, that it's working OK and that I installed the RR3 properly. Also, since I was given a caution about how sensitive this part is to heat, I was very careful about that when soldering the new RR3 in. Attached are two pics of my board, a full shot and one that focuses on the power supply. What do I do next? Thanks.

 EDIT: Oh my goodness, the pics are terrible quality. Guess they were downsized because they are JPEG images. Sorry about that._

 

Are you sure you've turned RR3 enough turns? 29.5 is almost exactly what you should get at maximum voltage. The LM317 will not allow any higher voltage, so it will seem as if turning the trimmer further in that direction will not work.

 However, turn the trimmer in the other direction and you should see that voltage go down. Which direction? I don't remember off hand, but the Murata trimmers have clutches that prevent damage if you turn too far. This may seem like a hassle, but you should attempt turning the trimmer at least 20 turns in one direction. If no response, then turn at least 20 turns in the other direction. You should see that voltage start to drop about 0.1V per turn or thereabouts when you hit the range.

 Let us know how that turns out. If unsuccessful, try again at the photos. We can't tell anything from those. See if you can use the macro setting on your camera and end up with a photo that just covers the heat sink area.


----------



## tomb

I just wanted to update anyone that was following rbarth's problems. We discovered offline that one of the PS diodes was reversed. Rbarth fixed that and is now enjoying a fully operating MiniMAX.


----------



## Amarphael

Hello all, 

 My newly aquired Minimax is giving me the same trouble as rbarth was having, But in my case the unresponsive trimmer is at the right tube bias, RA1R. I did the check that was suggested and resistance measures are the same regardless. I guess i should purchase a new trimmer? Can it be possible for this component to get faulty during transit or from repeated power on/offs?


----------



## tomb

Quote:


  Originally Posted by *Amarphael* /img/forum/go_quote.gif 
_Hello all, 

 My newly aquired Minimax is giving me the same trouble as rbarth was having, But in my case the unresponsive trimmer is at the right tube bias, RA1R. I did the check that was suggested and resistance measures are the same regardless. I guess i should purchase a new trimmer? Can it be possible for this component to get faulty during transit or from repeated power on/offs?_

 

No - it is not, but if it's a trimmer without a clutch, it's easily ruined by someone turning the screw too far past the audible clicks (signifying the end of travel).

 Note that IMHO, rbarth did not have a bad trimmer despite what he apparently measured. Replacing his trimmer had no effect. Instead, there was a reversed diode in the mix all along. To measure the trimmer's resistance, you have to select the correct two terminals on the bottom of the PCB to measure on the trimmer. Further, you need to be sure you turn it in both directions. If it does have a clutch, turns in the same direction at the end of its travel will register no change. Turn the screw the other way, and it should start varying.

 Many people think the tube trimmers have no effect, but they're just not turning them far enough. (Don't turn past a click, if you hear one, though.) You see, for the adjustment to work for 3 different tube types, each with differing gains, the trimmers need to have a very wide range of adjustment. This means that for a given tube type, it may only have a useful range of adjustment in the first or last 5 turns of the 25-turn trimmer.


----------



## Amarphael

My right bias is at 23.75V constantly, It didn't flinch one bit and I turned it a whole lot more than 25 turns in either direction, Until the the clicks showed up. Is this voltage rating maximal for the 12FM6? 

 Ichecked with the unconnected terminals as shown. 


][/url]


----------



## tomb

Quote:


  Originally Posted by *Amarphael* /img/forum/go_quote.gif 
_My right bias is at 23.75V constantly, It didn't flinch one bit and I turned it a whole lot more than 25 turns in either direction, Until the the clicks showed up. Is this voltage rating maximal for the 12FM6? 

 Ichecked with the unconnected terminals as shown. 


][/url]

_

 

Well, we need to know more information. First of all, if you're just checking for whether the trimmer is OK, you need to measure resistance - not volts, and the amp needs to be turned OFF. If you attempt to measure voltage, it's not going to tell you anything - the voltage won't change unless the tube is in, is lit, and is operating correctly. Did you have the tube in when you were making these voltage measurements?

 Let us know the complete picture of what you're doing:
 Amp on or off?
 Tube in or not, is it lit and warm?
 What are you measuring and from what and where?

 Again, turn the amp off and measure resistance only on those points in the pic you posted. Turn the trimmer about ten turns or so one direction and see if the resistance value changed. If not, then turn ten turns the other direction and see if the resistance value changed. That's the way you check to see if the trimmer is good - whether its resistance is changing when you turn the screw.

 Too many other things have to be right (mainly the tube) if you attempt to measure bias voltage with the amp on and the tube in. According to your complaint, the first thing we want to do is eliminate this suspicion that the trimmer is messed up (I seriously doubt it).


----------



## Amarphael

I apologize that i got you confused. I measured resistance alright 
	

	
	
		
		

		
		
	


	




 The amp was off, tubes in. The reading was constant on 4.865ohms on the RA1R, on the RA1L it was 1.8 something and went down when i did a few turns counterclockwise. 

 I'm also fairly sure that it couldn't have been damaged in transit (it's a passive component) so i think the fella i bought it from messed it up like this and didn't tell me about it. I also wonder how the DB Bias reached more than 200mV when i got it...


----------



## tomb

Quote:


  Originally Posted by *Amarphael* /img/forum/go_quote.gif 
_I apologize that i got you confused. I measured resistance alright 
	

	
	
		
		

		
		
	


	




 The amp was off, tubes in. The reading was constant on 4.865ohms on the RA1R, on the RA1L it was 1.8 something and went down when i did a few turns counterclockwise. 

 I'm also fairly sure that it couldn't have been damaged in transit (it's a passive component) so i think the fella i bought it from messed it up like this and didn't tell me about it. I also wonder how the DB Bias reached more than 200mV when i got it..._

 

OK - sounds like you did the right thing, then. I apologize for my confusion, too.
	

	
	
		
		

		
		
	


	




 I guess the trimmer is bad after all. Usually they're bad to begin with, or are damaged when soldered in the board. I don't ever specify or supply the kind of trimmers that can be damaged by turning them too far. However, if it's one of those with a clicking warning - then they can be easily damaged if someone did that.


----------



## dongringo

Hi everyone,

 Could you please check this out real quick and give me your opinion?

http://www.head-fi.org/forums/f6/did...inimax-482205/

 My brother screwed up our first DIY project and I would like to know if we should just scrap it. Also, if we do solder another cap in, how do we test to make sure it works? We're new at this obviously.

 Thanks for any info.


----------



## tomb

Quote:


  Originally Posted by *dongringo* /img/forum/go_quote.gif 
_Hi everyone,

 Could you please check this out real quick and give me your opinion?

http://www.head-fi.org/forums/f6/did...inimax-482205/

 My brother screwed up our first DIY project and I would like to know if we should just scrap it. Also, if we do solder another cap in, how do we test to make sure it works? We're new at this obviously.

 Thanks for any info._

 

I think the guys gave you some good answers in your other thread. Two things:
 1. Take the drill away from your brother.
	

	
	
		
		

		
		
	


	



 2. I wouldn't worry about doing anything more at this point. Just stick the leads of a new capacitor through the drilled holes and fill them with solder. Make certain that the solder touches both the leads and the solder pads on the back of the PCB. For the two pads close together, those are contacting the ground plane on top of the PCB. So, make sure you melt the solder well around the lead and both of those two pads - especially the inner one. The through-hole plating should be intact on the inner pad (it hasn't been drilled!!) and that should complete the electrical connection. The other drilled pad is connected to the trace on the bottom of the PCB and shouldn't be an issue when you fill that hole with solder on the bottom.


----------



## dongringo

Thanks Tom. Much appreciated. The drill has been confiscated.


----------



## thebasso

Hi everyone,

 I was wondering if someone could tell me what kind of wire to use for the final wiring. Also, does someone happen to have a diagram of the wiring or a pic? Any info would be greatly appreciated. I can't possibly go through 65,000 posts to find the answer.

 Thanks in advance.


----------



## tomb

Quote:


  Originally Posted by *thebasso* /img/forum/go_quote.gif 
_Hi everyone,

 I was wondering if someone could tell me what kind of wire to use for the final wiring. Also, does someone happen to have a diagram of the wiring or a pic? Any info would be greatly appreciated. I can't possibly go through 65,000 posts to find the answer.

 Thanks in advance._

 

Have you checked the MiniMAX website? There's a whole page on Wiring and Assembly, complete with detailed photos and wire size recommendations (I use 22ga from ebay's John's Silver Teflon Wire Shop for everything):
MiniMAX Wiring & Assembly


----------



## thebasso

Thanks Alot;

 I didn't see the wiring portion in miniMAX website.

 Thanks again.


----------



## thebasso

Hi DYI's
 After building my first my first DYI project and triple checking everything I managed to literally blow up my miniMAX. You win some you lose some.
 Anyway I still have the casing and volume knob and a few misc option parts.
 If you want them you can have them for free. Just give me $10 for postage.
 Crap that was an expensive screw up. I threw the rest down the hill.
 Let me know.

 Ken


----------



## dongringo

I concur with the above statement by thebasso, as I am his brother, and know how hard he worked on it. Even the tubes fried. What could have happened? At any rate, it doesn't matter now because it wasn't salvageable, and as a result, is in the woods at the bottom of the hill in who knows how many pieces.

 Any thoughts on what may have went wrong? I have a DIY project coming soon and this experience has me scared.


----------



## Beefy

Quote:


  Originally Posted by *dongringo* /img/forum/go_quote.gif 
_At any rate, it doesn't matter now because it wasn't salvageable, and as a result, is in the woods at the bottom of the hill in who knows how many pieces.

 Any thoughts on what may have went wrong? I have a DIY project coming soon and this experience has me scared._

 

How the flying fig are we supposed to even guess at that? Normally a good procedure for troubleshooting is to have the project handy to take readings or supply photos - not destroy it in a fit of stupid frustration.


----------



## thebasso

It wasn't stupid frustration. I BLEW the bloody thing up!


----------



## dongringo

Quote:


  Originally Posted by *Beefy* /img/forum/go_quote.gif 
_How the flying fig are we supposed to even guess at that? Normally a good procedure for troubleshooting is to have the project handy to take readings or supply photos - not destroy it in a fit of stupid frustration._

 

First of all, I don't appreciate the tone. Secondly, it was just a question. If you don't have any idea then don't answer the question. Thanks.


----------



## Beefy

Quote:


  Originally Posted by *dongringo* /img/forum/go_quote.gif 
_First of all, I don't appreciate the tone._

 

Don't care.

  Quote:


 Secondly, it was just a question. If you don't have any idea then don't answer the question. Thanks. 
 

I'd have plenty of ideas if it wasn't in the woods at the bottom of the hill in who knows how many pieces.


----------



## the_equalizer

Quote:


  Originally Posted by *thebasso* /img/forum/go_quote.gif 
_Hi DYI's
 After building my first my first DYI project and triple checking everything I managed to literally blow up my miniMAX. You win some you lose some.
 Anyway I still have the casing and volume knob and a few misc option parts.
 If you want them you can have them for free. Just give me $10 for postage.
 Crap that was an expensive screw up. I threw the rest down the hill.
 Let me know.

 Ken_

 

I'm sorry to hear things didn't work out well for you 
	

	
	
		
		

		
		
	


	




 ... I hope neither you nor your brother got hurt when the amp blew out. 

 My recommendation: don't give up, get past it and try it again maybe with a simpler circuit like a CMoy, an a47 or a "Starving Student" Hybrid.

 cheers!


----------



## dongringo

@ the_equalizer

 Thank you for your positive words of encouragement. 
	

	
	
		
		

		
		
	


	




 The kit I have coming should be much, much easier. It's just a Bottlehead Crack, all point to point. Should still be fun, even after this incident.


----------



## the_equalizer

Quote:


  Originally Posted by *dongringo* /img/forum/go_quote.gif 
_@ the_equalizer

 Thank you for your positive words of encouragement. 
	

	
	
		
		

		
		
	


	




 The kit I have coming should be much, much easier. It's just a Bottlehead Crack, all point to point. Should still be fun, even after this incident. 
	

	
	
		
		

		
		
	


	


_

 

Wow.. I've had my eyes on that kit for a long time. You need to be careful with that build, AFAIK it handles high voltages (unlike the MiniMAX) which are lethal. Take care and good luck with it.

 cheers!


----------



## thebasso

The MiniMax remaining has been given away. 

 @ the_equalizer - Thanks!


----------



## thebasso

.


----------



## dongringo

.


----------



## Beefy

Quote:


  Originally Posted by *dongringo* /img/forum/go_quote.gif 
_





 Thanks for the warning. Well, at least it comes with detailed instructions. 
	

	
	
		
		

		
		
	


	


_

 

And THESE aren't detailed instructions?!?

 I look forward to seeing you both on the news......


----------



## tomb

Quote:


  Originally Posted by *dongringo* /img/forum/go_quote.gif 
_@ the_equalizer

 Thank you for your positive words of encouragement. 
	

	
	
		
		

		
			





 The kit I have coming should be much, much easier. It's just a Bottlehead Crack, all point to point. Should still be fun, even after this incident. 
	

	
	
		
		

		
		
	


	


_

 

You should listen to these guys. We were all here ready to help in the blink of an eye. IMHO, after this incident a Bottlehead is a recipe for disaster. *You can kill yourself with the voltage in one of those.* If you think it will be easier than a manufactured PCB with paint-by-numbers silkscreen and a pre-machined custom case, I think you're sadly mistaken.

 AFAIK, you're one of two who've given up on a MiniMAX - after literally hundreds have been built. You guys need to back up and try to build a CMoy, learn not to drill out holes off center on PCB pads because you can't get the solder out, learn not to rip the leads out of electrolytic capacitors, and worst of all, learn not to blow up your amplifier kits in the woods and then come back here posting about building something lethal the next time.

 I'm sorry that this experience happened, but we were here to help, and as I noted in PM's and implied in e-mails, I've been known to repair a few myself. Help was easily available.


----------



## timmyGCSE

oh wow...erm..sorry to hear it didn't work out :-/ what a waste.
 I would just like to echo everyone elses sentiment on the lethal voltages...

 anyway, guys, dumb question - can one of you wonderful chaps give me a brief breakdown on MiniMAX vs SSMH. The reason being is I'm considering my next full size can purchase, and I think I'm pretty much settled on some D2000's, which will leave me with £200 spare. I could do something entirely different or I could go ahead and build a miniMAX, but is it worth it? sure I assume it will be better but why? and will I really notice the difference with D2000's? TIA


----------



## dongringo

For those of you who continue to post negative comments about my brother's miniMax build:

 CHILL OUT! He posted on this thread about it because he thought it was a funny experience. He threw it down the hill because he decided DIY just wasn't for him. He didn't want to bother with it any longer. Is there something so wrong with that?

 As far as I'm concerned, I know about the lethal voltages of the Bottlehead. I know it won't be easy as it will be MY first build. But I plan to take my own sweet time about it to make sure I get it right. 

 It just amazes me how sometimes on these threads one can't be funny and humble without getting attacked.

 Please guys, no more negativity.


----------



## the_equalizer

Quote:


  Originally Posted by *timmyGCSE* /img/forum/go_quote.gif 
_oh wow...erm..sorry to hear it didn't work out :-/ what a waste.
 I would just like to echo everyone elses sentiment on the lethal voltages...

 anyway, guys, dumb question - can one of you wonderful chaps give me a brief breakdown on MiniMAX vs SSMH. The reason being is I'm considering my next full size can purchase, and I think I'm pretty much settled on some D2000's, which will leave me with £200 spare. I could do something entirely different or I could go ahead and build a miniMAX, but is it worth it? sure I assume it will be better but why? and will I really notice the difference with D2000's? TIA_

 

TomB usually does not allow comparison posts. I'll send you a PM with my impressions on these two amps.


----------



## tomb

Quote:


  Originally Posted by *dongringo* /img/forum/go_quote.gif 
_For those of you who continue to post negative comments about my brother's miniMax build:

 CHILL OUT! He posted on this thread about it because he thought it was a funny experience. He threw it down the hill because he decided DIY just wasn't for him. He didn't want to bother with it any longer. Is there something so wrong with that?_

 

There's nothing wrong with what you do with your money and time in your own privacy. However, when you post about this nonense in a public thread about my product, it implies that other people will have trouble, will worry about support, will worry whether there are instructions (that one really got me
	

	
	
		
		

		
		
	


	




), etc., etc. Quote:


 
 As far as I'm concerned, I know about the lethal voltages of the Bottlehead. I know it won't be easy as it will be MY first build. But I plan to take my own sweet time about it to make sure I get it right. 
 

Your track record is not good. Again I say - build a CMoy and try to get a successful result before you tackle potentially lethal enterprises. Quote:


 
 It just amazes me how sometimes on these threads one can't be funny and humble without getting attacked.

 Please guys, no more negativity. 
	

	
	
		
		

		
		
	


	



 

No one interpreted it as funny and I still don't.


----------



## timmyGCSE

Quote:


  Originally Posted by *dongringo* /img/forum/go_quote.gif 
_For those of you who continue to post negative comments about my brother's miniMax build:

 CHILL OUT! He posted on this thread about it because he thought it was a funny experience. He threw it down the hill because he decided DIY just wasn't for him. He didn't want to bother with it any longer. Is there something so wrong with that?

 As far as I'm concerned, I know about the lethal voltages of the Bottlehead. I know it won't be easy as it will be MY first build. But I plan to take my own sweet time about it to make sure I get it right. 

 It just amazes me how sometimes on these threads one can't be funny and humble without getting attacked.

 Please guys, no more negativity. 
	

	
	
		
		

		
		
	


	


_

 

I guess you just have to kind of realise that alot of hard work, effort and contribution has gone into these projects - not in the least at the design stage, all the help TomB, equalizer and others give on a daily basis is enormous and very appreciated around these parts. As Tom said, your brother is only one of two people he is aware of who have given up on the project - says alot for the effort and help put in by these guys. And I guess instead of accepting help even if it seems like a lost cause and just throwing it down a hill is, to me, an insult to the guys and almost like all the advice was thrown back in their faces. If I had the same failure I would be gutted and even apologetic. Just think about how much *free time* is devoted to this project alone and then you might understand why some may feel upset 

  Quote:


  Originally Posted by *the_equalizer* /img/forum/go_quote.gif 
_TomB usually does not allow comparison posts. I'll send you a PM with my impressions on these two amps._

 

oops..ha I think this is gaffe number 3 I've made 
	

	
	
		
		

		
		
	


	




 but thankyou that would be most kind of you


----------



## dongringo

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_There's nothing wrong with what you do with your money and time in your own privacy. However, when you post about this nonense in a public thread about my product, it implies that other people will have trouble, will worry about support, will worry whether there are instructions (that one really got me
	

	
	
		
		

		
		
	


	




), etc., etc.Your track record is not good. Again I say - build a CMoy and try to get a successful result before you tackle potentially lethal enterprises.No one interpreted it as funny and I still don't.
	

	
	
		
		

		
		
	


	


_

 

Wow! You have no sense of humor. This is a public forum and there's nothing wrong with sharing experiences, good or bad. Nobody said anything about your product not being a good one or the apparent mistake on this build being YOUR fault. Things don't always work out. People react differently when things don't go right, such as COMICALLY throwing the project down the hill. If you can't imagine that as being funny, then I don't know what to say other than maybe you should relax a little.


----------



## timmyGCSE

Quote:


  Originally Posted by *dongringo* /img/forum/go_quote.gif 
_such as *COMICALLY* throwing the project down the hill. If you can't imagine that as being funny, then I don't know what to say other than maybe you should relax a little._

 

yes I can see how throwing a project I would actually love to build and am debating at the moment whether I can afford it is comical, and I'm sure Tom can see how a project he has spent hours and hours designing, producing and supporting, then being publically dissed (yes..you did..'at least this one has instructions' - what a complete idiotic comment) when really the problem is not with the kit but with the builder is comical 
	

	
	
		
		

		
		
	


	



 I tried a reasoning response above ^^ but clearly you are too arrogant or ignorant or both to understand. Good luck with your next project, and lets hope you don't need any help with it eh


----------



## phangtonpower

^I find what you guys have said pretty insulting, and I'm pretty chill with a nice cold beer in my hand
	

	
	
		
		

		
		
	


	



 If you can't see how it's not insulting, I think you need to relax.


----------



## dongringo

Quote:


  Originally Posted by *timmyGCSE* /img/forum/go_quote.gif 
_I guess you just have to kind of realise that alot of hard work, effort and contribution has gone into these projects - not in the least at the design stage, all the help TomB, equalizer and others give on a daily basis is enormous and very appreciated around these parts. As Tom said, your brother is only one of two people he is aware of who have given up on the project - says alot for the effort and help put in by these guys. And I guess instead of accepting help even if it seems like a lost cause and just throwing it down a hill is, to me, an insult to the guys and almost like all the advice was thrown back in their faces. If I had the same failure I would be gutted and even apologetic. Just think about how much *free time* is devoted to this project alone and then you might understand why some may feel upset_

 

I see what you're saying timmy. The thing is, my brother's experience wasn't meant to insult anyone. He just decided that DIY isn't for him and comically threw it down the hill to get it out of his life. This experience was taken way out of context. Maybe some people would have mourned the loss of the miniMax. Some may have done everything in their power to find the problem and try to fix it. My brother decided to just get rid of it. Nothing wrong with that. Things get so negative so fast on this forum sometimes it's crazy.


----------



## dongringo

Quote:


  Originally Posted by *timmyGCSE* /img/forum/go_quote.gif 
_yes I can see how throwing a project I would actually love to build and am debating at the moment whether I can afford it is comical, and I'm sure Tom can see how a project he has spent hours and hours designing, producing and supporting, then being publically dissed (yes..you did..'at least this one has instructions' - what a complete idiotic comment) when really the problem is not with the kit but with the builder is comical 
	

	
	
		
		

		
		
	


	



 I tried a reasoning response above ^^ but clearly you are too arrogant or ignorant or both to understand. Good luck with your next project, and lets hope you don't need any help with it eh_

 

Sheesh, you didn't even give me a chance to respond. 

 I agree about my comment about the instructions. I APOLOGIZE TO TOM for that comment. It wasn't meant to be an insult at the time. All I meant by it was that the miniMax instructions are designed for people who already have a knowledge of DIY. THERE IS NOTHING WRONG WITH THE MINIMAX INSTRUCTIONS. I meant no harm and I'm sorry if it caused any.


----------



## dongringo

PEACE!


----------



## thebasso

Sorry Tom;
 I didn't mean for it to be an insult, but a comical experience.
 You do have a high quality product, it was just beyond my abilities.
 I've never built any kind of electronics before.

 One thing though, my brother (dongringo) didn't build the miniMax. He was at work most of the time.


----------



## Yaka

began building this last night, first thing i did was drill the tube sockets, drilled through and when loosening my workbench vice socket fell and broke upon impact:/ dont suppose anyone in the uk sells em do they? would order from beezar but with uk flights grounded prolly be a while till i get em






 shots from my iphone 3g so excuse the quality


----------



## tomb

I'll send you a pair Monday, Yaka. Maybe the volcanic ash will be cleared up soon.


----------



## Coupe

Just ordered the MiniMAX. First build! *crosses fingers*

 Cheer to Tomb!


----------



## Yaka

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_I'll send you a pair Monday, Yaka. Maybe the volcanic ash will be cleared up soon.
	

	
	
		
		

		
		
	


	


_

 

cool thanks mate. shall have to be more careful in the future


----------



## MASantos

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_I'll send you a pair Monday, Yaka. Maybe the volcanic ash will be cleared up soon.
	

	
	
		
		

		
		
	


	


_

 

Some companies are hopeful about restarting partial flights tomorrow!

 I'm not getting on a plane other places in Europe until European Air Traffic control agencies and other aviation related agencies say it's safe! 

 Losing all engines during flight isn't something to kid about!


----------



## timmyGCSE

the first part:
24V AC/AC 1A ADAPTOR FOR LOW VOLTAGE FOUNTAIN PUMP NEW on eBay (end time 21-Apr-10 13:19:09 BST)

 has been purchased 
	

	
	
		
		

		
		
	


	




 ordering the rest from Tom/Beezar next week. Can't wait


----------



## the_equalizer

Quote:


  Originally Posted by *timmyGCSE* /img/forum/go_quote.gif 
_the first part:
24V AC/AC 1A ADAPTOR FOR LOW VOLTAGE FOUNTAIN PUMP NEW on eBay (end time 21-Apr-10 13:19:09 BST)

 has been purchased 
	

	
	
		
		

		
		
	


	




 ordering the rest from Tom/Beezar next week. Can't wait 
	

	
	
		
		

		
		
	


	


_

 

Hmmm... you *did* notice there's a *full* kit at Beezar, didn't you?

 cheers!


----------



## timmyGCSE

Quote:


  Originally Posted by *the_equalizer* /img/forum/go_quote.gif 
_Hmmm... you *did* notice there's a *full* kit at Beezar, didn't you?

 cheers!_

 

yes I did lol but the full kit at beezar includes a 110v to 24v power brick, unfortunately our wall sockets in the UK put out 230v AC so tomb has kindly done a revised BOM and invoice for me sans wallwart and I've purchased my own compatible one that does 230v AC to 24V AC


----------



## the_equalizer

Quote:


  Originally Posted by *timmyGCSE* /img/forum/go_quote.gif 
_yes I did lol but the full kit at beezar includes a 110v to 24v power brick, unfortunately our wall sockets in the UK put out 230v AC so tomb has kindly done a revised BOM and invoice for me sans wallwart and I've purchased my own compatible one that does 230v AC to 24V AC_

 

Ah! true, you need a proper wall-wart for the UK.. 
	

	
	
		
		

		
		
	


	





 cheers!


----------



## Yaka

ive got this one me self MULTICOMP|T2403AD|PSU, IN-LINE, 24VAC, 750MA | Farnell United Kingdom 

 i tend to stay away from ebay for these type of things when i ordered a replacement wall wart for my old camera of ebay 2 years ago lucky the mrs decided to investigate where the funny smell was coming from


----------



## Lil' Knight

Anyone knows where I could buy the Blackgates for the CA2 and CA7? Both SonicCraft and Percy Audio run out of stock those values.


----------



## tomb

Quote:


  Originally Posted by *Lil' Knight* /img/forum/go_quote.gif 
_Anyone knows where I could buy the Blackgates for the CA2 and CA7? Both SonicCraft and Percy Audio run out of stock those values._

 

It sounds better to just stick with the ES's at CA2. BG NX's will make a detectable difference at CA7 (the cap of choice was the NX 680uf 35V), but AFAIK, there are no retailers left that carry them. I even contacted some overseas sources with no luck. The ES's bypassed with Vitamin Q's come awfully close and are actually more transparent sounding, IMHO. The BG's may have more detail, but there's a bit of a silky-grained fog. Plus, there's the long break-in, too.


----------



## Lil' Knight

Thanks, Tom. I'd just go with the ES then.


----------



## Lil' Knight

Tom,

 I'm wondering if the Elna Cerafine 470uF/25v would be fine for the CA7? I can't find the 35V ones.

 EDIT: Hmmm, kind of confused here. Part Connexion has the Elna 470uf/35v but it's 35mm while the 25v is 25mm.


----------



## Beefy

Quote:


  Originally Posted by *Lil' Knight* /img/forum/go_quote.gif 
_Tom,

 I'm wondering if the Elna Cerafine 470uF/25v would be fine for the CA7? I can't find the 35V ones.

 EDIT: Hmmm, kind of confused here. Part Connexion has the Elna 470uf/35v but it's 35mm while the 25v is 25mm._

 

I believe that both the Elna Cerafine and Silmic in the correct rating are too big for the MiniMax case.

 In any case, I'm pretty sure that 25V is too low. If you have a tube failure, the cap will see the full regulated voltage of 27V.

 [EDIT] Actually, according to the datasheet on the PCX page, the Cerafine should be OK. Both Silmic and Silmic II are too big.


----------



## Lil' Knight

Ah, so the 25v is only 20mm and the 35v is 25mm. I should have checked the datasheet, rather than believe PCX. 
	

	
	
		
		

		
		
	


	




 Trying to find the 35v in the CONUS though, I really don't want to merely buy 2 caps and waiting for shipping from Canada.


----------



## tomb

The Elna Cerafine at 470uf 35V is only 25mm tall and would be an excellent cap at CA7 for the MiniMAX ... if you can find one. IMHO, however, it may be more difficult to find one of those than the BG NX.
	

	
	
		
		

		
		
	


	




 The Cerafines have been out of production much longer. I'm a little shocked to see them at PCX - grab them, if you can.


----------



## Lil' Knight

Yes, I ordered a couple of them, along with the Nichicon Fine Gold 1000uf.


----------



## Coupe

Well, Tomb is probably getting annoyed from all the e-mails, but the answers have been very helpful. This is my first DIY project and my first soldering project so don't laugh too hard.

 I broke one of the tube sockets so I'm waiting for a rush delivery from beezar. 
	

	
	
		
		

		
			





 Anyway, just gunna post up some pictures and can you guys tell me what you think?





 By couped at 2010-04-26





 By couped, shot with DSLR-A700 at 2010-04-26





 By couped, shot with DSLR-A700 at 2010-04-26





 By couped, shot with DSLR-A700 at 2010-04-26

 In that last picture if you can see the circle on the image. When I was cutting the excess off a solder i scratched the PCB and a little copper got exposed. Is this a problem? What should I use to fix it?

 Thank you for all your help and thanks again to Tomb and Cetoole for a great amp and great support!


----------



## tomb

Don't worry about the scratch - as long as the trace isn't damaged. I scratch them all the time. The blue mask is not there to provide insulation, only to help control where the solder goes.
	

	
	
		
		

		
		
	


	




 It looks OK, except:
 1. It could just be the lighting in the photos, but QB2R appears to be reversed.
 2. Don't forget to solder jumpers at RB8L/R and RB9L/R.


----------



## Coupe

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Don't worry about the scratch - as long as the trace isn't damaged. I scratch them all the time. The blue mask is not there to provide insulation, only to help control where the solder goes.
	

	
	
		
		

		
		
	


	




 It looks OK, except:
 1. It could just be the lighting in the photos, but QB2R appears to be reversed.
 2. Don't forget to solder jumpers at RB8L/R and RB9L/R._

 

Wow good eye tom it is reversed. 
	

	
	
		
		

		
		
	


	




 Speaking of those I had a question. You matched the HFE on the 87s. However, I thought I had to use all the 87s you sent (apparently I needed 6, but got 10). Anyway on one set I checked the HFE and paired a 440 set and installed on the left and right channel QB4. All the others 87s installed were 470s. Will this make a difference?

 PS. I ordered some parts from beezar early this morning, can you cancel order 1156? 1157 is the proper order. Thank you


----------



## tomb

Quote:


  Originally Posted by *Coupe* /img/forum/go_quote.gif 
_Wow good eye tom it is reversed. 
	

	
	
		
		

		
		
	


	




 Speaking of those I had a question. You matched the HFE on the 87s. However, I thought I had to use all the 87s you sent (apparently I needed 6, but got 10). Anyway on one set I checked the HFE and paired a 440 set and installed on the left and right channel QB4. All the others 87s installed were 470s. Will this make a difference?_

 

No, it won't make a difference per se, but I thought we went over this in e-mails. It sounds like you're forgeting the four CCS transistors - QA1L/R and QA2L/R. Those are the other four 2N5087's and are in the little bag marked "CCS." Maybe this link will help make it clearer:
Millett Hybrid MiniMAX CCS
 It's actually more critical that these be well-matched than the ones in the buffer; the performance of the tubes depend on it.

 As for the diamond buffer, there are six 2N5087's and six 2N5088's, no more, no less. The PN4392's - one per channel - are in there to set the current bias in the buffer. Quote:


 
 PS. I ordered some parts from beezar early this morning, can you cancel order 1156? 1157 is the proper order. Thank you 
 

I can't get to it while at my day job. Plus, you should send me a PM - it's not appropriate to discuss business orders within a forum thread. No harm, hopefully, I'm sure you weren't aware of the rules around here.


----------



## Coupe

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_No, it won't make a difference per se, but I thought we went over this in e-mails. It sounds like you're forgeting the four CCS transistors - QA1L/R and QA2L/R. Those are the other four 2N5087's and are in the little bag marked "CCS." Maybe this link will help make it clearer:
Millett Hybrid MiniMAX CCS
 It's actually more critical that these be well-matched than the ones in the buffer; the performance of the tubes depend on it.

 As for the diamond buffer, there are six 2N5087's and six 2N5088's, no more, no less. The PN4392's - one per channel - are in there to set the current bias in the buffer.I can't get to it while at my day job. Plus, you should send me a PM - it's not appropriate to discuss business orders within a forum thread. No harm, hopefully, I'm sure you weren't aware of the rules around here.
	

	
	
		
		

		
		
	


	


_

 

AHH I see. So the QA1 and 2 are the most important?

 Hrm well the 4 87s I have left are 445, 447, 465, 467. Damnit I messed up again. Would these be fine if I matched them L/R with similar HFE or should I just order matching ones from beezar?


----------



## tomb

Quote:


  Originally Posted by *Coupe* /img/forum/go_quote.gif 
_AHH I see. So the QA1 and 2 are the most important?

 Hrm well the 4 87s I have left are 445, 447, 465, 467. Damnit I messed up again. Would these be fine if I matched them L/R with similar HFE or should I just order matching ones from beezar?_

 

Those are all close enough. Put the 445 and 447 together on one channel, then the 465 and 467 on the other channel.

 Actually, it's really not that critical. What's important is that you not have something like a 300 or 500 in that mix.


----------



## Coupe

So close! 
	

	
	
		
		

		
		
	


	








 By couped at 2010-04-26


 BTW are vacuum tubes like halogen bulbs where you can't touch the glass with your bare finger?


----------



## tomb

Quote:


  Originally Posted by *Coupe* /img/forum/go_quote.gif 
_<snip>
 BTW are vacuum tubes like halogen bulbs where you can't touch the glass with your bare finger?_

 

No, but your bare fingers aren't going to feel very comfortable for long if the tube is on.


----------



## Lil' Knight

Another MiniMax lives 
	

	
	
		
		

		
		
	


	




 Makes sweet sound right at the first try. Thanks Tom for a wonderful amp. The build is very straight-forward. Pics later, gotta go class now.


----------



## the_equalizer

Quote:


  Originally Posted by *Lil' Knight* /img/forum/go_quote.gif 
_Another MiniMax lives 
	

	
	
		
		

		
		
	


	




 Makes sweet sound right at the first try. Thanks Tom for a wonderful amp. The build is very straight-forward. Pics later, gotta go class now._

 

Congratulations! It is a very nice amplifier. Enjoy!


----------



## Coupe

I am curious as to the trimmers. I gave the DB trims 20 turns till clicks and the other trimmers about 10 turns clockwise. Should I bring them all the way down so I don't burn something when I first fire it up?? I read the diyguide and I just want to verify things before the initial fire up.

 Since the amp won't fly. Need to verify!






 edit:

 So been verifying. What is the green rectangle by the voltage regulator and does direction matter?


----------



## Lil' Knight

Pics. Sorry for my messy desk.




































 The build has Elna Cerafine and Nichicon ES. I skip the output resistors for better dynamic. Each tube is biased at 14.5V at first and after 2 hours, it dropped to ~13.5V.

 Only minor problem is that when I used too much strength to push the tube socket down and broke the tube LED 
	

	
	
		
		

		
		
	


	




 Now only one side lights up. If anyone could help me desolder the tube socket and LED, please let me know. I really suck at desoldering stuffs.


----------



## Yaka

tube sockets are impossible to remove, i got my the sockets on my ss beta board wonky couldnt remove them. maybe my soldering skills are crap but im sure its hard


----------



## Beefy

Quote:


  Originally Posted by *Lil' Knight* /img/forum/go_quote.gif 
_If anyone could help me desolder the tube socket and LED, please let me know. I really suck at desoldering stuffs._

 

 Quote:


  Originally Posted by *Yaka* /img/forum/go_quote.gif 
_tube sockets are impossible to remove, i got my the sockets on my ss beta board wonky couldnt remove them. maybe my soldering skills are crap but im sure its hard_

 

I concur with yaka - removing the tube sockets will be all but impossible. A better strategy would be cut power to the second LED to make it look 'balanced' again.

 If you _really_ want the tubes illuminated, you could short both LEDs under the tubes and install a second set of LED directly series with RA5 L/R.


----------



## Lil' Knight

Argg, that sucks. Not a big problem because I only look at the amp on one angle. The feeling of something imperfect still on my head though


----------



## tomb

Quote:


  Originally Posted by *Lil' Knight* /img/forum/go_quote.gif 
_Argg, that sucks. Not a big problem because I only look at the amp on one angle. The feeling of something imperfect still on my head though 
	

	
	
		
		

		
		
	


	


_

 

The LED should fall right out of the center hole. Poke it through from the other side while making a solder blob big enough to cover both leads. It should fall right out. Clean the holes in the PCB and drop another right in. Yeah, it's not as easy as it sounds, but it's not as hard as some are suggesting.
	

	
	
		
		

		
		
	


	




 I've replaced them/changed colors all the time. The only real trick is getting the solder out of those little PCB holes. With practice, flux, and de-soldering braid, it can be done, though.
	

	
	
		
		

		
		
	


	




 Nice pics - you do good work, Lil' Knight. Could be that those RCA cables are a bit overwhelming.
	

	
	
		
		

		
		
	


	







 P.S. There should be no reason to even contemplate removing the sockets.


----------



## tomb

Quote:


  Originally Posted by *Coupe* /img/forum/go_quote.gif 
_





 I am curious as to the trimmers. I gave the DB trims 20 turns till clicks and the other trimmers about 10 turns clockwise. Should I bring them all the way down so I don't burn something when I first fire it up?? I read the diyguide and I just want to verify things before the initial fire up._

 

Quit messing with it. You might break the trimmers before you even get to use them.
	

	
	
		
		

		
		
	


	




 Quote:


 
 Since the amp won't fly. Need to verify!





 

I used to build and fly model airplanes, but somehow I don't think the airfoil is quite right on the MiniMAX.
	

	
	
		
		

		
		
	


	




 Quote:


 
 edit:

 So been verifying. What is the green rectangle by the voltage regulator and does direction matter? 
 

The green rectangle is a Vishay-Roederstein box film capacitor and no, orientation doesn't matter on one of those.


 P.S. BTW - your MiniMAX is looking good, too. Sockets should be on the way.


----------



## Beefy

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_The LED should fall right out of the center hole. Poke it through from the other side while making a solder blob big enough to cover both leads. It should fall right out._

 

Well yeah, if the LED does come out easily that is a far better option than removing the socket 
	

	
	
		
		

		
		
	


	




  Quote:


 Could be that those RCA cables are a bit overwhelming. 
 

Missed that..... oh dear......


----------



## tomb

Quote:


  Originally Posted by *Beefy* /img/forum/go_quote.gif 
_Well yeah, if the LED does come out easily that is a far better option than removing the socket 
	

	
	
		
		

		
		
	


	


_

 

Yep, it's close - but the LED's I package with the kit are small enough to fit through the center hole. Now, if there's some glue that's oozed out in the center of the socket when they were glued back together, that could make it a bit difficult. Still, better to drill out the bad LED and excess glue than remove the tube socket.
	

	
	
		
		

		
		
	


	



  Quote:


 

 Missed that..... oh dear...... 
	

	
	
		
		

		
		
	


	



 

Yep. Them's some strong cables on that UDAC (I think that's what that is.)


----------



## tomb

BTW, we're making fun of Lil' Knight's cables, but I want you all to know that he has resurrected the blown-up MiniMAX from a few pages back. Some of what you see is what was left from that incident. He bought the remains, contacted me for some parts and advice and has done a great job in bringing it back from the dead. Thanks, Lil' Knight! Another MiniMAX lives!


----------



## Lil' Knight

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Yep. Them's some strong cables on that UDAC (I think that's what that is.)
	

	
	
		
		

		
		
	


	


_

 

Haha 
	

	
	
		
		

		
		
	


	




 I know it looks huge but actually very soft. I can't find any RCA cables around to use.

 And yes, I got the remains from the unfortunate build of 'thebasso' and thanks to Tom's great help, finishing the build smoothly.


----------



## Beefy

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_but I want you all to know that he has resurrected the blown-up MiniMAX from a few pages back. Some of what you see is what was left from that incident. He bought the remains, contacted me for some parts and advice and has done a great job in bringing it back from the dead._

 

I'm curious...... what actually 'blew up' and, what caused it?


----------



## the_equalizer

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_BTW, we're making fun of Lil' Knight's cables, but I want you all to know that he has resurrected the blown-up MiniMAX from a few pages back. Some of what you see is what was left from that incident. He bought the remains, contacted me for some parts and advice and has done a great job in bringing it back from the dead. Thanks, Lil' Knight! Another MiniMAX lives!
	

	
	
		
		

		
		
	


	


_

 

 Quote:


  Originally Posted by *Lil' Knight* /img/forum/go_quote.gif 
_Haha 
	

	
	
		
		

		
		
	


	




 I know it looks huge but actually very soft. I can't find any RCA cables around to use.

 And yes, I got the remains from the unfortunate build of 'thebasso' and thanks to Tom's great help, finishing the build smoothly._

 

Wow! great work!


----------



## Lil' Knight

Now I'm wondering if anyone tried biasing the BD more than 110mV? How stable would the amp be if I go with 115 or 120mV?


----------



## the_equalizer

I'm no expert, as I've only built this amp once, but I think you don't want to go higher than 110mV (50mA bias current if I'm not mistaken) or the output transistors will get fried due to thermal runaway.


----------



## tomb

Actually, they'll take quite a bit more bias than that.
	

	
	
		
		

		
		
	


	




 120mV is only 54ma. I doubt that they'll break a sweat on that.

 When cetoole designed the amp and I setup the website for support, we had to settle on numbers that we felt were the best compromise between performance and reliability under all circumstances. 50ma was our arrived at, round number recommendation for DB bias.

 IMHO, you can probably exceed the 50ma recommendation by 10ma without much difficulty - as long as you are in ambient conditions of ~70-75 deg.F. However, there are some people who are in hotter conditions, leave their amp on all day, don't bother to install the feet on the bottom (there are intake slots on the bottom), run it on their bed (soft covers block ventilation), block the side vents with a coke on their desk, etc., etc.

 There's also the fact that the capacitors' life will be much reduced at higher temperature levels inside the amp. The boutique caps especially, are only 85 deg.C. caps. That's still very high and you should never even approach that temperature inside the amp and life/performance is reduced much below that.

 So, again - the 50ma (110mV) recommendation stands. However, if you are willing to fiddle, take responsibility for potential failures from getting too hot, etc. - as stated, you can probably boost that by 10ma without issue or 20ma if you're _very _careful. I would not run one at 80ma for any length of time whatsoever, however. YMMV, of course.

 Now the primary question - is performance enhanced beyond 50ma bias with BJT's? If it is, I couldn't tell.


----------



## Lil' Knight

I let the amp run straight for 8 hours with 160ohm load. To my surprise, the amp barely got warm, let alone hot. I can touch the case without any problem. I'll let it run a couple more days and try to pump the DB bias to 120mV to see how it does the job.


----------



## Beefy

Yeah, the case itself doesn't get hot...... but drop a temperature probe into the amp at the holes for the tube bias pots, and you might be surprised at the internal temperatures. The cathode bypass caps near there are right in the centre of two hot tubes, the regulator heatsink and the inside heatsinks of the buffer.

 I can't remember exactly what my temperatures were, but they were high enough that I didn't want to needlessly increase the heat output. And don't forget that a increases in current through the buffer also increases heat output at the regulator!


----------



## tomb

Quote:


  Originally Posted by *Beefy* /img/forum/go_quote.gif 
_<snip> And don't forget that a increases in current through the buffer also increases heat output at the regulator! 
	

	
	
		
		

		
		
	


	


_

 

Exactly. All the current has to run throught the regulator, too. EDIT: I can't remember where the crossover point is, but there is a point where current increases will result in more heat at the regulator than at the BJT's, I think.
	

	
	
		
		

		
		
	


	




 BTW, the buffer will run hotter feeding a pair of Grados than it will feeding a pair of Senns. Lower impedance, higher current.


----------



## Coupe

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Quit messing with it. You might break the trimmers before you even get to use them.
	

	
	
		
		

		
			





I used to build and fly model airplanes, but somehow I don't think the airfoil is quite right on the MiniMAX.
	

	
	
		
		

		
		
	


	




The green rectangle is a Vishay-Roederstein box film capacitor and no, orientation doesn't matter on one of those.


 P.S. BTW - your MiniMAX is looking good, too. Sockets should be on the way._

 

Alright Alright I'll stop! Ahh thx. BTW I just went to the HD and bought some stuff to keep me busy. I used the heat gun on the power receiver and it melted the inside plastic a little. 
	

	
	
		
		

		
		
	


	




 No worries though I checked resistance from that ground to the terminal blocks.

Picked this up and I was wondering if it would be good for wiring RCA to terminal block and BIAS to terminal block?


----------



## Lil' Knight

Just 'upgrade' the stock knob to my custom one. It's really a nice treat to turn the pot.


----------



## the_equalizer

Quote:


  Originally Posted by *Lil' Knight* /img/forum/go_quote.gif 
_Just 'upgrade' the stock knob to my custom one. It's really a nice treat to turn the pot.

 </snip>_

 

Gorgeous knob, simply gorgeous! enjoy your new amp!


----------



## Coupe

Almost done! and I'm scared!


----------



## tomb

Quote:


  Originally Posted by *Coupe* /img/forum/go_quote.gif 
_Almost done! and I'm scared!



_

 

Carefully read over the Setup and Biasing page here:
MiniMAX Setup and Bias Settings

 In particular, be sure to read the "Blow-by-blow" link above the settings table.


----------



## Lil' Knight

Quote:


  Originally Posted by *Coupe* /img/forum/go_quote.gif 
_Almost done! and I'm scared!



_

 

Make sure all the components are in the right place and I'd say you're 90% done.


----------



## Coupe




----------



## Coupe

Left the AMP on all night. Should that burn the caps and tubes in even with no music?

 Readjusted the tube bias this morning.

 I am absolutely amazed! The sound is so complete now! I love this sound stage!

 TY so much tomb and cetoole!


----------



## tomb

Quote:


  Originally Posted by *Coupe* /img/forum/go_quote.gif 
_Left the AMP on all night. Should that burn the caps and tubes in even with no music?

 Readjusted the tube bias this morning.

 I am absolutely amazed! The sound is so complete now! I love this sound stage!

 TY so much tomb and cetoole!



_

 

That's great to hear!!

 Just an FYI, but the caps that really need to break in are in the signal path and yes - you have to play music or something similar or they're not in use even if the amp is on.

 Still, it doesn't take that long - maybe a few hours, IMHO.

 When the tubes are lit, they're on, though - doesn't matter whether a signal is going through them.


----------



## MoxMonkey

finally getting around to building my minimax and despite everything I've read I'm still confused about just what to use for RB14

 I'll mainly be using this amp with my sr225s and vtg10's so I'm not sure if jumpering it would be best or if I should use either the 10r, 47r or 100r kiwame's I've got

 any advice is appreciated


----------



## tomb

Quote:


  Originally Posted by *MoxMonkey* /img/forum/go_quote.gif 
_finally getting around to building my minimax and despite everything I've read I'm still confused about just what to use for RB14

 I'll mainly be using this amp with my sr225s and vtg10's so I'm not sure if jumpering it would be best or if I should use either the 10r, 47r or 100r kiwame's I've got

 any advice is appreciated_

 

Use the 10R. That's the best all-around choice. Don't ever use anything as high as 47R or 100R if you're interested in performance. It will really cut back the detail.

 A couple of caveats are that some people have detected a bit of hiss when using very sensitive and very low impedance headphones (Audio Technicas, IEM's). Also, some people are real sticklers for being able to use the total volume knob adjustment. You won't be able to do that on the MiniMAX with Grados. Typically, all adjustment will be between 7 - 10 o'clock. With Senns, adjustment is usually between 7-12 o'clock, but this also depends on the tubes. The primary method for adjusting gain with the Millett Hybrid/MAX/MiniMAX is with the tube type. However, in those cases where changing tubes doesn't provide enough gain adjustment to suit, you can use up to 150R on the output - but it will come with a penalty in detail. You'll find that the Alps has no trouble with signal matching at very low positions of volume travel, so there's no reason to go to these measures unless you really prefer it that way.
	

	
	
		
		

		
		
	


	




 EDIT: Sorry, but I didn't know what VTG10's were until I looked them up. I'd still try the 10R's. If you have problems with those Audio-Technicas, then maybe you could change them to a higher resistance.


----------



## Beefy

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Use the 10R. That's the best all-around choice. Don't ever use anything as high as 47R or 100R if you're interested in performance. It will really cut back the detail.

 A couple of caveats are that some people have detected a bit of hiss when using very sensitive and very low impedance headphones (Audio Technicas, IEM's)._

 

To MoxMonkey: tomb is probably talking about me 
	

	
	
		
		

		
		
	


	



 My MiniMax is used exclusively with sensitive ATH-ESW9 (impedance 42 ohms) so I used 33R on the outputs...... still gives a damping factor of greater than 1, and tames the noise. With 10R, the background noise was just audible with music playing.

 But I absolutely agree that for Grados you want to aim lower than 33. If it were me, it would depend on which phone you use most...... 10 if you prefer the Grados, 22 if you prefer the W10VTG.


----------



## the_equalizer

I mostly use Grado's (85% of the time) with my MiniMAX and I set it up with jumpers. As TomB stated, the knob hovers around the 9 o'clock position without any channel mismatch problems. 

 I also use it with my ER-6i IEMs (15% of the time) and it works great too, even though the volume knob hovers around the 7 o'clock position with those. Very silent too, although you can hear the noise floor with these sensitive IEMs


----------



## Coupe

Ya think with the sig headphones I should jumper?

 O btw proof!


----------



## Lil' Knight

Yet another MiniMax lives! (
	

	
	
		
		

		
		
	


	




)
 I was not 100% happy with the last build and decided to build another one again. This time is exactly what I wanted. The tube LEDs are much, much better. Also, I decided to go with the stock configuration (Nichicon caps and 10R Kiwame resistors). To my surprise, the sound is a lot smoother than my last build (Elna Cerafine and no output resistors). I also pushed the BJT to 120mV. A little bit hotter and still sounding great.
















 BTW, Tom, did I remember correctly that you said that the RCA jacks are 'industry standard', 13mm space? I'm thinking of using the RCA couplers with my Pico DAC to have a minimal setup for my HD800.


----------



## MoxMonkey

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Use the 10R. That's the best all-around choice. Don't ever use anything as high as 47R or 100R if you're interested in performance. It will really cut back the detail.

 A couple of caveats are that some people have detected a bit of hiss when using very sensitive and very low impedance headphones (Audio Technicas, IEM's). Also, some people are real sticklers for being able to use the total volume knob adjustment. You won't be able to do that on the MiniMAX with Grados. Typically, all adjustment will be between 7 - 10 o'clock. With Senns, adjustment is usually between 7-12 o'clock, but this also depends on the tubes. The primary method for adjusting gain with the Millett Hybrid/MAX/MiniMAX is with the tube type. However, in those cases where changing tubes doesn't provide enough gain adjustment to suit, you can use up to 150R on the output - but it will come with a penalty in detail. You'll find that the Alps has no trouble with signal matching at very low positions of volume travel, so there's no reason to go to these measures unless you really prefer it that way.
	

	
	
		
		

		
			





 EDIT: Sorry, but I didn't know what VTG10's were until I looked them up. I'd still try the 10R's. If you have problems with those Audio-Technicas, then maybe you could change them to a higher resistance.
	

	
	
		
		

		
		
	


	


_

 


  Quote:


  Originally Posted by *Beefy* /img/forum/go_quote.gif 
_To MoxMonkey: tomb is probably talking about me 
	

	
	
		
		

		
		
	


	



 My MiniMax is used exclusively with sensitive ATH-ESW9 (impedance 42 ohms) so I used 33R on the outputs...... still gives a damping factor of greater than 1, and tames the noise. With 10R, the background noise was just audible with music playing.

 But I absolutely agree that for Grados you want to aim lower than 33. If it were me, it would depend on which phone you use most...... 10 if you prefer the Grados, 22 if you prefer the W10VTG._

 

thanks guys. I jumpered it for now gonna see how it sounds and then play around figure I have the time so why not. Now I'm assuming QM1 doesn't have a specific orientation (based off the silk screen on the pcb) but I just wanted to make sure before I put it in


----------



## Lil' Knight

The QM1 does have orientation. The silkscreen is hard to see but when you look carefully, the bigger tab faces the tubes and smaller one faces away from the tubes.


----------



## MoxMonkey

now that you mention it I can see the silkscreen showing it's orientation now as well lol chalk that one up to it being far too late


----------



## Lil' Knight

As I mentioned before, just pay attention putting the components correctly and you're 90% done. I really like Colin's designs, very straight forward.


----------



## MoxMonkey

yah for the most part the entire thing is paint by numbers just a few things that I don't know
   
  also same question regarding PF1 likely doesn't have orrientation but want to check before I blow it up if it does


----------



## Lil' Knight

The PF1 doesn't have orientation.


----------



## MoxMonkey

awesome, thanks yet again


----------



## Lil' Knight

You might pay attention to the DR1s. At first, I thought they all have the same orientations.


----------



## MoxMonkey

nah those I got based off the pics on diyforums...the stuff I asked about were things I couldn't make out in the pictures also pcb is stuffed just need to clean it and wire and bias it


----------



## Lil' Knight

The wiring is pretty easy. Just go ahead and let the amp sings


----------



## Lil' Knight

Anyone using the MiniMax in 230V? I'm bringing this amp along with me on the trip next week but still haven't figured out a good wallwart to use in 230V? Can a 115-230V converter work just fine?


----------



## tomb

Quote: 





lil' knight said:


> Anyone using the MiniMax in 230V? I'm bringing this amp along with me on the trip next week but still haven't figured out a good wallwart to use in 230V? Can a 115-230V converter work just fine?


 

 You should have no issues with a convertor, as long as the amperage rating is adequate.  The MiniMAX has been built in many foreign countries where convertors or 220V walwarts are used.


----------



## Lil' Knight

Thanks, Tom. Great to hear that.


----------



## MoxMonkey

finally got around to doing the last bit of wiring and pcb cleaning (ugh what a pain) and the initial bias setup and it works 
   
  now to just let it warm up to set the final bias and then we'll case it up


----------



## Lil' Knight

Great! Can't wait to see some pics.


----------



## MoxMonkey

what is the consensus on knob size from partspipe?  gotta get around to ordering one


----------



## ShinyFalcon

I ordered a 48mm solid aluminum knob off of them, which is the biggest they have from what I saw. It's a nice size. Anything smaller just feels weird to me.
   
  As for the MiniMAX, 48mm might be too big, so check and see how tall the panels are...


----------



## tomb

Be careful about Partspipe's knobs - I've ordered dozens over the last couple of years and their quality control is getting bad lately. I've had several that I had to re-tap because they weren't properly de-burred at the set-screw hole's interior opening.  Since that's right at the point of the shaft, it made the set screw useless until the threads were cleaned out and re-formed.
   
  In addition, I've received about a half-dozen that had two set screws installed, about 90 degrees apart.  That pretty much means there's no position of the knob where a set screw is not plainly visible (IOW - ugly).  I don't know yet if they did that because they messed up and over-sized the shaft hole or whether one set screw position is stripped, or what.  I haven't tried to return any yet and I'm not sure how to go about that with the distances and language issues involved.  So word to the wise - inspect what you receive carefully.
   
   
  P.S. The standard MAX knobs are 30mm.  That's used on the MIniMAX most often, too, but the Mini can easily use 24-25mm diameter with no issues.  Partspipe also has some very nice 24mm knobs, one of which is shown in my avatar (assuming their quality control is OK).  It might be a tad too long to be perfect on the production MiniMAX case, but it's not bad at all.  Note that a 48mm dia knob just might exceed the total height of the front panel from top to bottom.
	

	
	
		
		

		
			





  That's quite a bit too big.


----------



## Coupe

Still lovin the MiniMax!  
   
  Right now been using the FK6's.  They feel like the best combination. 
	

	
	
		
		

		
		
	


	



   
   Love the AE6 on first impression, but the bass distorted on high volumes. 
	

	
	
		
		

		
		
	


	



   
  Neways, just wanted to say thanks again for all the help.  Love current fig.


----------



## Calku

wrong thread


----------



## Za'afiel

pre-wired pcb

   
  Count one MiniMAX living in the Philippines  
	

	
	
		
		

		
		
	


	




 I'm not aware though if there are any other MAX family owners here.
   
  This is my first ever DIY build. I've had about three electronics classes back in high school and practiced soldering for a week before building this kit. That said, PCB assembly took me about eight hours, wiring, assembly, and biasing another two. Thankfully every part checked out, it's all good. Kiwame 10R used.
   
  They make the HF2s sing really well, and I've settled with the 12FK6 tubes.
   
  Sorry if this is a late upload tomb. The package arrived all in perfect condition. Parts were carefully bagged and properly labeled. The documentation included in the kit and all the online information was more than enough to guide me through the entire process of building this wonderful work of art. Kudos to tomb and cetoole, and to everyone involved in the MiniMAX project!
   
  For everyone's reference, I originally had the wallwart removed from the BOM, because the mains here is 220V 60Hz, and thought of just finding a 220V-24VAC transformer locally. However my initial search was futile, and eventually I got the BOM wallwart from Mouser separately, to be used with a converter instead. I got a 220-110 60W one. The MiniMAX came to life, I was able to bias the db's and tubes properly, however I could not get the VREG to get up to 27VDC at all.
   
  With tomb's help we were able to discover using multimeters, pictures, and the power of deduction that the suspect may be the converter. Without load, the wallwart (remember, it's connected to a 220-110 transformer) outputs a healthy 24~25VAC, but when measuring from the terminal block with the MiniMAX switched on, it drops to 22VAC. Measuring from Gnd and V+, it's 22VDC, and goes no higher. I tried using a larger transformer, a hundred-watt one, but it merely makes the VREG put out 24VDC, max. As such the tubes have been adjusted to receive only 12VDC each for now.
   
  I don't particularly like the look underneath my table (think two wallwarts, one straddling the other), so I will redouble my efforts to find a 220V-24VAC transformer, like phangtonpower did here. It's most likely going to be the exposed type, so I will also have to look for a nice case and appropriate plugs.
   
  cheers


----------



## Coupe

Been thinking about upgrading to high end phones like AKG K701 or K1000 and the DT 880 600 ohms or a BD Tesla


----------



## HiGHFLYiN9

Quote:  





> The LED should fall right out of the center hole. Poke it through from the other side while making a solder blob big enough to cover both leads. It should fall right out. Clean the holes in the PCB and drop another right in. Yeah, it's not as easy as it sounds, but it's not as hard as some are suggesting.
> 
> 
> 
> ...


 

 I actually pulled the LEDs out of mine as I'm going to try some diffused orange ones. I heated both leads at the same time while pulling from the other side with a pair of slim needle nose pliers. It took a little bit of effort but I got it


----------



## sandbasser

What tomb says is quite true...  it's definitely easier than it sounds to replace the tube LEDs. 
   
  Personally, I like the 'color change' LEDs that are on the beezar site.  But, I'll admit they might not be everybody's cup of tea.


----------



## ShinyFalcon

Hmm, I wonder if strobe LEDs exist...
	

	
	
		
		

		
		
	


	



   
  Beautiful pics!


----------



## Coupe

Quote: 





coupe said:


> Been thinking about upgrading to high end phones like AKG K701 or K1000 and the DT 880 600 ohms or a BD Tesla


 

 Can the Minimax handle these kinda cans?


----------



## jdkJake

Good question. It can certainly handle the 701



 As for the k1000 or 600ohm 880, that is another question. Certainly the 880 would benefit from the high gain of a 12AE6 and the tube bias set to allow maximum voltage swing (13.5). It might struggle at high volumes, but, I do not know of anyone with a pair.



 Perhaps someone who owns a pair can chime in.



 jk

 EDIT: OOPS, looks like the T1 is also 600 ohm. That might be a tough load at volume.


----------



## Lil' Knight

We did try the K1000 and DT880 (250ohm) with the MiniMAX last week and it actually did a good job driving both of them.


----------



## Coupe

I am getting more and more interested in swapping the present dt 990 250s for dt 990 600s.  Does anyone have experience on how well this amp can power 600 ohms?


----------



## drclaw

So I got my MiniMax all put together and was starting to do the biasing.  I did everything that was mentiond in the directions. when I tried to adjust the left db bias and the left tube, nothing happened.   Did I blow my transistors?  I'm not really sure what could be wrong.


----------



## jdkJake

What do you mean by "nothing happened"?
   
  What was the bias(es) before you tried to change it(them)? Did you rotate clockwise or counter clockwise? How many times in each direction?


----------



## tomb

jdkJake is correct - there are 25 turns in the trimmers that bias the tubes.  However, any one tube may run through its entire voltage adjustment in about 5 turns.  This is because the trimmers and the circuit is designed to accomodate three different types of tubes with entirely different gains and operating points.  So the adjustment is not necessarily that precise for any one tube type.  Depending on where the trimmer starts out, it can sometimes be a little difficult to find that adjustment point and it may seem like the tube is not reacting at all.  On the other hand, something else may be wrong.
   
  1. Does the tube glow (look for an orange glow at the top center of the tube) and get warm/hot?
  If not, then there may be something more wrong than the adjustment of the trimmer.
  2. Are you able to adjust the voltages to their correct setting elsewhere on the PCB, or are the tubes the first thing you've tried?
  3. Have you tried switching tubes?  If you can adjust one tube, take it out and try it in the other socket.  Similarly, if the one tube seems dead, if you plug it in the other socket, can you adjust it there?  This can be important in telling you whether the tube is bad or the circuit to the socket is somehow messed up.  If you can confirm one or the other, you're halfway there.


----------



## drclaw

Sorry for being rather unclear.  
   
  jkdJake, I have been trying to set the biases.  I turned the trimmer for the BJT DB completely closed (until it clicked a couple of times).
  I then powered it up and set the power supply voltage to 27V.   Then I moved on to set the tubes biases.  I got the right tubes set no problem.   I moved on the the left tube, and I get around 26.4V.  I know that this is incorrect.  It's supposed to be ~13.5V.  I switched the tubes. I get around 28.1V with the other tube, so I switched them back.   I then decided to try the DB biases.  I got the right perfect.  Then moved on to the left.  No reading.  My meter will occasionally flicker up to 2mV tops.  
   
  Thank you for the help guys!


----------



## ManBeard

Another MiniMax lives:
   
  (Sorry, crappy phone pics)
   

   
  Few build shots:
   

   

   
  Pretty much the stock config. Dialed the tube bias in at 14V and the DB's at 110mV. Also used 10R output resistors.
   
  Sounds great so far. I'm impressed with how well it drives the HE-5's.
   
  Thanks TomB for offering such a great kit.
   
  Cheers.


----------



## tomb

Thank you for the kind comment and you're welcome!  That's a great job and your phone pics look pretty d*mn good!


----------



## jdkJake

Quote: 





drclaw said:


> jkdJake, I have been trying to set the biases.  I turned the trimmer for the BJT DB completely closed (until it clicked a couple of times).
> I then powered it up and set the power supply voltage to 27V.   Then I moved on to set the tubes biases.  I got the right tubes set no problem.   I moved on the the left tube, and I get around 26.4V.  I know that this is incorrect.  It's supposed to be ~13.5V.  I switched the tubes. I get around 28.1V with the other tube, so I switched them back.   I then decided to try the DB biases.  I got the right perfect.  Then moved on to the left.  No reading.  My meter will occasionally flicker up to 2mV tops.


 

 How many times, and in what direction did you rotate the DB bias for the left side? 
   
  Did it measure no reading right away? Does it change at all going counter-clockwise or clockwise?


----------



## drclaw

I rotated the DB bias clockwise until it clicked a couple of times.  It was around 20 turns.  There was no reading from the first time on, and it doesn't change when I turn the trimmer either direction.    It will just sporadically jump to 2mV and then back down to 0.


----------



## QRomo

Just finished putting together my MiniMAX and everything seems to be working great. Thanks again to TomB for taking the time to offer such a great kit. Between that, the MiniMAX site, and this thread I got all the info I needed to make the whole process smooth as silk.
   
  That said, I've got a couple questions:
   

 I read the CCS tweaks page and it mentioned that the current is set with 12AE6 tubes in mind. How much does the CCS current setting affect the amp's performance, and how do you determine the optimum setting for a given tube (12FM6 and 12FK6)? I had a look at the tubes page to try to figure that out but was unsuccessful. I've gone with the default 1K and 10K in RA8 and RA9 that came with the kit for now, but I've installed SIP sockets so I can easily change them out if need be.
 While biasing the DBs, I noticed my bias voltages would float up and down from 110mV to 111mV without any change to the trimmers. I figured that was probably due to thermal fluctuations since when I blew on one of the heatsinks it caused the bias voltage to jump 2-3mV. It makes me wonder if my DBs are going to end up running at a different bias point once I've cased everything up, which I'd have to get creative to be able to measure. The board's currently out in the open on my workbench and near a window, which might be making the output transistors run cooler than normal. Does anyone have an idea how much I can expect the biases to change once in the case, if at all?  I figure +/- 5mV probably won't make too much of a difference one way or the other, but if it's much more than that I'm not sure.
   
  Also, a tip for anyone else building a MiniMAX. I found when I dry fit my 1/4" jack and pot as flush as possible to the board that the front panel wouldn't fit over them, probably due to manufacturing tolerances. So make sure to check for fit before you've soldered them into the board. My solution was to wiggle the jack a bit until I could get the front panel fit perfectly over both it and the pot, then leave the panel on while I soldered them (the panel fit is tight and will remain in place by itself). My jack ended up slightly raised on one side, but at least the panel now fits properly.


----------



## jdkJake

drclaw said:


> I rotated the DB bias clockwise until it clicked a couple of times.  It was around 20 turns.  There was no reading from the first time on, and it doesn't change when I turn the trimmer either direction.    It will just sporadically jump to 2mV and then back down to 0.







 Okay, so, now comes the fun part. Debugging. 

 IMO, the first thing you should do is do a quick visual check to be sure all components are on the board and nothing is missing. Also check the bottom side of the board to be sure you soldered all of the parts to the board. Also look for any possible cold solder joints.

 After that, you are going to need to move through the circuit and take some readings at various places on the board to isolate the part that is giving you your issue. This will take time and you need to be VERY careful probing a live board. You do not want to short anything out on accident. You basically need to follow the circuit on the left side and work your way through it. Since you have a mirror image on the right side that appears to be working, there will be some cases where you can reflect the measurements across each side and do a quick comparison. This will work in some, but not all cases as the circuits are loaded differently. But, it should help speed things up. 

 I will bust out the schematic later after work and see if we can find a couple of strategic places to check. Hopefully someone else will chime in as well.


----------



## jdkJake

BTW drclaw, if you can post a couple pictures, that would help as well. As least one of the top and one of the bottom of the board.
   
   
  When you do your inspection, be sure to check the orientation of all your transistors and polarized parts (caps, diodes, etc...) as well.


----------



## tomb

Quote: 





qromo said:


> Just finished putting together my MiniMAX and everything seems to be working great. Thanks again to TomB for taking the time to offer such a great kit. Between that, the MiniMAX site, and this thread I got all the info I needed to make the whole process smooth as silk.
> 
> That said, I've got a couple questions:
> 
> ...


 

 1. I'll see if I can ask Colin or Dsavitsk for an explanation on that one.  Basically, it has to do with picking the current where the tube curves are the straightest (most linear).  It can have a major effect on distortion in high-voltage tube circuits, but I'm not sure it has the same effect on the low voltage tubes.  Again, Colin made the determination early in the design that the change to the more prevalent size resistors and the small resulting change in the CCS current was worth it.  Not directly related, but performance is actually better with more voltage on the plates - 15V for the 12FM6, for instance.  I'm not sure any of that applies with the 12FK6's, though - they seem to be fairly tolerant of any setting, perhaps because of their low gain compared to the other two tube types.
   
  2. 2-3mV variance on a 110mV setting?  We should all be so lucky! 
	

	
	
		
		

		
			





  The cooling slots on the MiniMAX case are sufficient to keep the bias from floating too much.  In fact, the amp runs a bit cooler overall and is more stable in my experience.  Make certain you use the rubber feet on the bottom, though - it's important that the amp has sufficient airflow underneath.
   
  3. The front panel is designed for the headphone jack and pot at a completely flush-soldered condition.  However, that still leaves a lot of variance in where those levels end up in the great spattering of users out there and how they may solder (including me).  If I had it to do over again (it would require more design and tooling costs, which I can't afford right now.), I would probably make the holes larger so that some movement is tolerated.  After all, the three holes (1 for the HP jack, 2 for the pot) are pretty much covered up with much large diameter nuts/washers/knob.
   
  However, there seems to be enough play, when considering the slight bow in the PCB (that can be forced out through the attachment process) and also the fact that the case extrusion itself seems to have a bow in the top.  Several of us have carefully bent out some of that top bow in the extrusion by pressing down with a book on top, carefully standing on it, etc.  It seems pretty tough - you just want to make sure you don't put undo stress right on a machining point - that could locally deform the metal and ruin the case.


----------



## tomb

Quote: 





drclaw said:


> I rotated the DB bias clockwise until it clicked a couple of times.  It was around 20 turns.  There was no reading from the first time on, and it doesn't change when I turn the trimmer either direction.    It will just sporadically jump to 2mV and then back down to 0.


 

 We need pics -
   
  Questions -
   
  1. Tell us exactly which test points you're using
   
  2. Make certain you're adjusting the right trimmers.  I get them mixed up with the tube trimmers all the time.
  
  3. All other adjustments OK?
   
  4. Can you sense any heat coming from the DB's?
   
  5. Does it play music?
   
  We need pics ...


----------



## TimJo

Quote: 





qromo said:


> I read the CCS tweaks page and it mentioned that the current is set with 12AE6 tubes in mind. How much does the CCS current setting affect the amp's performance, and how do you determine the optimum setting for a given tube (12FM6 and 12FK6)? I had a look at the tubes page to try to figure that out but was unsuccessful. I've gone with the default 1K and 10K in RA8 and RA9 that came with the kit for now, but I've installed SIP sockets so I can easily change them out if need be.


 

  Quote: 





tomb said:


> 1. I'll see if I can ask Colin or Dsavitsk for an explanation on that one.  Basically, it has to do with picking the current where the tube curves are the straightest (most linear).  It can have a major effect on distortion in high-voltage tube circuits, but I'm not sure it has the same effect on the low voltage tubes.  Again, Colin made the determination early in the design that the change to the more prevalent size resistors and the small resulting change in the CCS current was worth it.  Not directly related, but performance is actually better with more voltage on the plates - 15V for the 12FM6, for instance.  I'm not sure any of that applies with the 12FK6's, though - they seem to be fairly tolerant of any setting, perhaps because of their low gain compared to the other two tube types.


   
  A while ago, I built a version of the original max board with an alternative operating point that I picked out for 12FM6's. I use it with my AKG 701's and _I think_ it sounds pretty good. I increased both the current and the plate voltage. I don't crank up the volume when I listen, so the higher plate voltage has never led to clipping that I am aware of. If you have the resistors socketed, then why not play around a bit using your ears as a judge. If memory serves, you just need to keep the ratio between the resistor pair as close to a 10 to 1 ratio as possible.


----------



## drclaw

Unfortunately I am out of town for the next week.  As soon as I get home though, I will take lots of pictures and we will get this sorted out!


----------



## QRomo

Quote: 





> Originally Posted by *tomb* /img/forum/go_quote.gif
> 
> 1. I'll see if I can ask Colin or Dsavitsk for an explanation on that one.  Basically, it has to do with picking the current where the tube curves are the straightest (most linear).  It can have a major effect on distortion in high-voltage tube circuits, but I'm not sure it has the same effect on the low voltage tubes.  Again, Colin made the determination early in the design that the change to the more prevalent size resistors and the small resulting change in the CCS current was worth it.  Not directly related, but performance is actually better with more voltage on the plates - 15V for the 12FM6, for instance.  I'm not sure any of that applies with the 12FK6's, though - they seem to be fairly tolerant of any setting, perhaps because of their low gain compared to the other two tube types.


 
   
  Interesting.  I've set the tube bias at the recommended 13.5V.  Perhaps I'll try increasing that and see how it sounds. As for the CCS current, I'd love to hear an explanation if you can get one.  I'll see what I can learn with my Google fu in the meantime.
   
  Quote: 





> Originally Posted by *tomb* /img/forum/go_quote.gif
> 
> 2. 2-3mV variance on a 110mV setting?  We should all be so lucky!
> 
> ...


 
   
  Ha! I guess I should count my lucky stars and leave well enough alone. I let the amp run overnight and both channels seem pretty steady at 110mV, so I'll leave it at that.
   
  Quote: 





> Originally Posted by *tomb* /img/forum/go_quote.gif
> 
> 
> 3. The front panel is designed for the headphone jack and pot at a completely flush-soldered condition.  However, that still leaves a lot of variance in where those levels end up in the great spattering of users out there and how they may solder (including me).  If I had it to do over again (it would require more design and tooling costs, which I can't afford right now.), I would probably make the holes larger so that some movement is tolerated.  After all, the three holes (1 for the HP jack, 2 for the pot) are pretty much covered up with much large diameter nuts/washers/knob.
> ...


 
   
  Yeah, I figured it wasn't a problem with the panel or PCB layout.  It was probably just the combination of my particular set of components.  Didn't occur to me that it might be a slight bow in the PCB, though soldering the jack and pot in with the panel fitted seems to have done the trick.
   
  Quote: 





> Originally Posted by *TimJo*
> 
> 
> 
> A while ago, I built a version of the original max board with an alternative operating point that I picked out for 12FM6's. I use it with my AKG 701's and _I think_ it sounds pretty good. I increased both the current and the plate voltage. I don't crank up the volume when I listen, so the higher plate voltage has never led to clipping that I am aware of. If you have the resistors socketed, then why not play around a bit using your ears as a judge. If memory serves, you just need to keep the ratio between the resistor pair as close to a 10 to 1 ratio as possible.


 
   
  I'd like to, but I don't have enough resistors on hand in the appropriate values at the moment. I'll have to order some with my next project and give it a go then.


----------



## tomb

From Pete Millett in the original Millett Hybrid article in AudioXpress magazine: 
  Quote: 





> [size=x-small][size=x-small][size=x-small]There’s nothing sacred about using [/size][/size][/size][size=x-small][size=x-small][size=x-small]0.56mA as the plate current—looking at [/size][/size][/size][size=x-small][size=x-small][size=x-small]the plate curves, I thought it looked like [/size][/size][/size][size=x-small][size=x-small][size=x-small]a good point to operate the 12AE6 tube.  [/size][/size][/size][size=x-small][size=x-small][size=x-small]I also tried a 1mA part, and got slightly [/size][/size][/size][size=x-small][size=x-small][size=x-small]higher distortion. You may want to try [/size][/size][/size][size=x-small][size=x-small][size=x-small]different currents, especially if you use [/size][/size][/size][size=x-small][size=x-small][size=x-small]tubes other than the ones I tried.[/size][/size][/size]


 
   Note that in the same article, Pete measure 0.5% output distortion with both the 12AE6 and 12FM6.


----------



## Caphead78

I am sure the answer to this is somewhere in this 107 page thread, and I apologize accordingly, but how doable is the minimax as a first-time DIY project? Is there something cheaper I should try first to get used to the build process?


----------



## tomb

Quote: 





caphead78 said:


> I am sure the answer to this is somewhere in this 107 page thread, and I apologize accordingly, but how doable is the minimax as a first-time DIY project? Is there something cheaper I should try first to get used to the build process?


 

 My standard recommendation is that everyone should build a CMoy, first:
http://www.tangentsoft.net/audio/cmoy-tutorial/
   
  There are quite a few who've built a MiniMAX as their first kit, but it's not been without some struggle in some cases.  I think the MiniMAX makes a great 2nd project, but probably not a 1st one.


----------



## drclaw

Sorry for the delay in getting the pics up.  Been out of town.  
   
  Here are the pics (sorry for the crappy quality, I'm no photographer).
   
   
  Top:
   
   

   
  I get sound out of the right channel.  Nothing out of the left channel.  
   
  Thanks for all of the help so far jdkJake and Tom!


----------



## Lil' Knight

Wow. Seriously, at least you should clean your PCB before doing any debugging. I suspect there's a short somewhere in the PCB.


----------



## jdkJake

Welcome back drclaw.



 I have to agree with lil'knight, if you do a quick clean of the board, it will be easier to see any error.



 Right off the bat, I see quite a few cold solder joints, but, it is hard to tell with all of the flux in the way. Go to your local drug store and pick up some 91% rubbing alcohol. A big bottle is like $1USD. Also pick up the cheapest nylon toothbrush they have. I bought this serious large pack of them for like $2USD. They are terrible quality for teeth, but, are really handy around the house for various cleaning chores. Carefully clean and scrub the back of the board. There are some further details on the miniMAX (and other max) sites. Then take another picture and send it off.



 Also, for the top of the board, if you can get a shot straight on and with more light, I think I would be much easier to see that all the various parts are installed correctly.

 EDIT: I meant 91% and not 97%, sorry!


----------



## drclaw

Ha I knew that was going to be the first thing said!  I cleaned off as much as I could.  
   
  Here are the pictures.  

   
   
  Top side:


----------



## tomb

QB2L and QB3L are reversed.  Look at the silkscreen.  They are actually supposed to be upside down compared to the same ones on the right side.  You've installed them in the same orientation on both channels.


----------



## drclaw

I de-soldered them, but when I got QB3L out, one of the leads fell off..


----------



## tomb

Quote: 





drclaw said:


> I de-soldered them, but when I got QB3L out, one of the leads fell off..


 


 PM me with your address - I'll send you a couple more.


----------



## MrDavis

I've been searching the threads and I think I found part of the answer. However, since I'm a noob at this, I want to ask anyway.
   
  Is the *12FK6* *a better tube for t**h**e *audiotechnica AD700 than the *12FM6? *
   
  Is there enough difference in the sound for me to try the *12FK6?*


----------



## Beefy

Trust me, you want as low gain as possible, so go for the 12FK6. And I would strongly recommend that you use 10 or 22R output resistors.


----------



## tomb

Quote: 





mrdavis said:


> I've been searching the threads and I think I found part of the answer. However, since I'm a noob at this, I want to ask anyway.
> 
> Is the *12FK6* *a better tube for t**h**e *audiotechnica AD700 than the *12FM6? *
> 
> Is there enough difference in the sound for me to try the *12FK6?*


 

 This is tubes ....!  There is always a reason to try a different tube.  Only you can tell if you like the difference ... but there will be a difference.


----------



## jdkJake

Quote: 





mrdavis said:


> I've been searching the threads and I think I found part of the answer. However, since I'm a noob at this, I want to ask anyway.
> 
> Is the *12FK6* *a better tube for t**h**e *audiotechnica AD700 than the *12FM6? *
> 
> Is there enough difference in the sound for me to try the *12FK6?*


 

 Yes, there can be a LOT of difference. 
   
  Give them all a shot, Millett tubes are a bargain!! Especially compared to some other more exotic tubes. I suggest you have at least one set of each (12AE6, 12FM6 and 12FK6) to try out. Different construction makes for different sonics as well. Collecting them can become quite the habit.
   
  Heck, rolling tubes is half the fun of a tube-based amp! Dig in and have some fun!


----------



## MrDavis

I have the 10R installed in my minimax.  I guess I'll order the 12FK6 and give it a try.


----------



## Coupe

Got the fk6 running dt990 600 ohms. The travel of the pot is much better and the sound is us just right


----------



## jdkJake

I think the 12FK6 is an under rated option for the millett series. Especially if you listen at low volumes. The gain is plenty for that type of listening and gives you a more useful range of the amp. It also puts the control further into the sweet spot of the pot. They also give up very little to nothing over the other tubes. Well, except for the occasional AE6, which, can be a pretty special tube if you get a good one.


----------



## drclaw

So I got the new transistors in and installed them (thanks a to Tom!!), but now a new problem has developed.  I was going back and checking the power supply's voltage and i had a measurement at around 25V.  Then it started to drop.  after a couple of seconds of free fall it hit 0.  The tubes stopped glowing, and I couldn't get a reading anywhere.  I checked everything, turned it off, stepped away for a couple of minutes, and then came back.   Tried it again.  It did the same thing.  I really have no clue what could be happening.


----------



## Beefy

Quote: 





drclaw said:


> So I got the new transistors in and installed them (thanks a to Tom!!), but now a new problem has developed.  I was going back and checking the power supply's voltage and i had a measurement at around 25V.  Then it started to drop.  after a couple of seconds of free fall it hit 0.  The tubes stopped glowing, and I couldn't get a reading anywhere.  I checked everything, turned it off, stepped away for a couple of minutes, and then came back.   Tried it again.  It did the same thing.  I really have no clue what could be happening.


 


 Fuse burnt out? Polyfuse tripped? Wallwart crapping out? Take some measurements before you panic.


----------



## tomb

Quote: 





beefy said:


> Fuse burnt out? *Polyfuse tripped?* Wallwart crapping out? Take some measurements before you panic.


 

 That's my guess.  If you still have some stuff messed up in the buffers and they drew way too much current, it could cause this scenario.  The polyfuse would react exactly with the symptoms you describe.
   
  As Beefy says, you need to start measuring things, especially the buffer.  If you were checking the power supply, did you check the buffer to verify a reasonable current bias first?  Can you tell if anything got hot?


----------



## BobSaysHi

Hey guys, I'm slowly reading through the max website (all the pages, it takes a while), and I am on the boutique pages and tweaks. How difficult would it be to build the amp first with the basic BOM, then later upgrade several parts to boutique? The website is quite helpful and I am slowly starting to understand the function of everything. 
   
  I have built my friend a cmoy, but I did not pick out the parts, I just put it together. I think I can put the MAX together all right, are the boutique parts worth the increase in price (esp. shipping) or should I order from one place. Is the K42Y-2 cap worth the price as an upgrade?
   
  I apologize if this has already been answered in this long thread, but I'd really like to know.


----------



## Lil' Knight

It's just the matter of desoldering and resoldering.
   
  I'm not sure if the K42Y would fit, you might want to low down the uf. The Vitamin Q caps are excellent and I don't see any reason to change them.


----------



## tomb

Yep.  We used and recommended the K42's for awhile, but the Vitamin Q's are just superior in every way.
   
  A few of the other things we discovered (apply to regular BJT MAX and the MiniMAX):

 Wima MKP10 caps are best as bypasses everywhere, except at CA8, where the Vitamin Q's are superior to everything but super-expensive film caps.
 Muse ES are superior at CA2, regardless of the caps used at CA7 (back when Black Gates were available, we tried using them at CA2, but the ES's are still better even if BG's are used at CA7).
 For 1" sinks (1" tallest parts) The Muse ES at 470uf 35V is the best choice for CA7 as long as Black Gates are gone.  The Muse Fine Gold at 1000uf 35V is only 1" tall and is a good choice for low impedance cans. 
 Don't be afraid to alter the tube bias - 15V sounds pretty good with 12FM6's and low impedance tubes.  It's probably best to keep the widest swing for high impedance phones and use bias at 1/2 the power supply voltage (V+ and Gnd).
 50ma bias works best for 1" high sinks, but you can push it 20-30ma, depending on the case cooling.
 Use 10R for R1 (best compromise for heater voltage when power supply is set for 27VDC).
 1800uf, 35V Panasonic FM at CA4-L/R and CA5-L/R and 1000uf 50V Panasonic FM at CR1-A,B.  The Nichicon UHD's have specs that are very, very close and I've been using them lately while Panasonic FM's are out of stock at DigiKey.
 I like the MiniMAX and BJT MAX best with jumpers on the output - no output resistors.  Note that this may result in a bit of bass loss with very low impedance headphones (fine with Grados, though) and the Muse FG CA7 option might be best if you're contemplating very low-impedance phones.
   
  A few of the things we discovered with the MOSFET-MAX:

 The MOSFETs sound better the higher the bias.  About 125ma is about maximum with 1-1/2" sinks.  They run very hot, but MOSFETs can take it.  Also, when casing up the temp will tend to drop due to the reverse heat coefficient of MOSFETs.
 If height is no object (use 1-1/2" sinks), Use the Elna RFS Silmic II's at CA2 and CA7 - they are as good as Black Gates at CA7 and as good as ES's at CA2.  You should be able to find 1000uf for both positions (16V, 25, 35 at CA2 and 35V at CA7).
 Stay away from the Muse KZ - their natural etchiness sound can bloom into full-blown sibilance with the MOSFETs on a MOSFET-MAX.
 Don't use a MOSFET-MAX without output resistors.  The MOSFETs oscillate slightly (ringing) at the output with just the 2.2ohm RB10 and RB11 resistors (no jumpers at RB14, iow).  I use 22R Kiwame's, but 10R may also work - haven't tried it yet, though.
 Cap choices for CA4-L/R and CA5-L/R are many.  Start with the Panasonics above as a minimum, but you can also use NIchicon UHE's up to 2000uf at CR1 and higher for CA4 and CA5 - just keep the height under 1-1/2".
   
  Just MHO, a MOSFET-MAX is superior with low-impedance Grados and especially K701's (you've never heard K701's unless you hear them through a MOSFET-MAX - MHO and I'm biased, obviously).  The MiniMAX is best all-around and for high-impedance cans and maybe a bit quieter due to the smaller size and resulting smaller trace lengths.
   
  I've used nothing but Alien DAC's, BantamDAC's and now the GrubDAC with my MAXes/MiniMAXes and the sound is quite nice.


----------



## BobSaysHi

wow tomb, thanks a lot! I'll look around for all those parts. 
   
  but I have to get some money first...
	

	
	
		
		

		
		
	


	



   
  I'll be back in a week after I sell some things...


----------



## drclaw

Well I did some poking around with my meter, and I was getting what I guess was the correct voltage throughout the power supply.  when I moved on to the amp and buffer I wasn't getting anything.  I wasn't able to pinpoint the exact problem part.


----------



## jdkJake

Did you measure across the polyfuse between the power supply and the amp?


----------



## tomb

Quote: 





drclaw said:


> Well I did some poking around with my meter, and I was getting what I guess was the correct voltage throughout the power supply.  when I moved on to the amp and buffer I wasn't getting anything.  I wasn't able to pinpoint the exact problem part.


 


 What jdkjake said.  Also - did you do anything besides change out QB2L and QB3L?  You said you were getting sound before from the right channel.  Can you give us a bigger/better pic of the area of the PCB from the tubes to the output buffer?
   
  You should also check all the resistors in the buffer with your DMM.  None of them are in parallel with anything, so your DMM should be able to confirm every value (except RB10/RB11, and we know what they are.  Make a list of the resistors and their values from the BOM and measure both of each from the left and right channel.  See if there are any differences and report back with your list and the results.
   
  Second, verify the transistors are in their correct positions - 2SC3422's on the outside sinks and 2SA1359's on the inside sinks.  All four output transistors should be on the right side of the sinks as you're looking from the front with the pot and headphone jack.  As for the little TO-92 transistors, there's a great key to keep in mind to see if they're installed in the proper places - even transistors go on the odd-numbered silkscreen and vice-versa.  For instance, QB2 is even, but uses a 2N5087 (odd).  QB3 is odd, but uses a 2N5088.  This is consistent throughout the buffer.  Bend the transistors sideways a bit so that you can see and verify the part label for each one.


----------



## drclaw

I think the problem is the polyfuse.  Going in it I measured ~28V.  Coming out I measured ~2V.   
   
  I didn't have time to take measurements of all the resistors before they stopped getting power.  There is a light click that occurs right before it shuts down.  Is that the polyfuse tripping? 
   
  The transistors are all on the right side of the sinks and in the right positions.  
   
   
   
  Thanks for all the help so far jdkJake and TomB.  I really appreciate it!


----------



## Beefy

Quote: 





drclaw said:


> I think the problem is the polyfuse.  Going in it I measured ~28V.  Coming out I measured ~2V.
> 
> I didn't have time to take measurements of all the resistors before they stopped getting power.  There is a light click that occurs right before it shuts down.  Is that the polyfuse tripping?
> 
> ...


 


 The physical click is the relay tripping. You have a short somewhere, or a trimpot turned way too high in the buffer. Does anything get hot before the voltage drops?
   
  From memory, if you pull the tubes (with the amp off of course!) your buffer current should be cut. Try this and see if the voltage still drops.


----------



## tomb

Quote: 





drclaw said:


> I think the problem is the polyfuse.  Going in it I measured ~28V.  Coming out I measured ~2V.
> 
> I didn't have time to take measurements of all the resistors before they stopped getting power.  There is a light click that occurs right before it shuts down.  Is that the polyfuse tripping?
> 
> ...


 

 1. You measure the resistors with the power OFF.
  2. It's the other transistors I'm really worried about - the TO-92's.
  3. As Beefy says, the click is the relay - there's nothing else on the board that has an electrical-mechanical action.  The polyfuse is not mechanical.  It simply increases resistance in response to load.  If its current rating is exceeded, it approaches infinite resistance, effectively turning the circuit off.  _The polyfuse can be nothing but a symptom, not a cause._
   
  You have a problem in the buffer, most likely, and these issues are almost always a part in the wrong spot.
   
  Tell us what you get when you measure resistance for the following (Power OFF):
  RB1L, RB1R
  RB2L, RB2R
  RB3L, RB3R
  RB4L, RB4R
  RB5L, RB5R
  RB6L, RB6R
  RB7L, RB7R


----------



## drclaw

Just measured the resistors.  Here's what I got:
  RB1L 974, RB1R  974
  RB2L 10,  RB2R 10
  RB3L 10, RB3R  10
  RB4L 98, RB4R 98
  RB5L 98, RB5R 98
  RB6L 216, RB6R 216
  RB7L 216, RB7R 216


----------



## tomb

Quote: 





drclaw said:


> Just measured the resistors.  Here's what I got:
> RB1L 974, RB1R  974
> RB2L 10,  RB2R 10
> RB3L 10, RB3R  10
> ...


 

 I forgot RB13, but since the rest of all of those are correct, it doesn't matter.
   
  What about the TO-92 transistors?  Have you confirmed that all of those are in the correct positions?


----------



## drclaw

Yes, all of the TO-92 transistors are in the correct place.  
   
  When I was checking the transistors I noticed a slightly melted spot on the 2k trimmer in RB12L.  It isn't very bad but maybe that is what is causing the problems?


----------



## Beefy

Have you tried firing it up without tubes?
  Have you checked to see if anything gets hot before the power dies?


----------



## drclaw

Yup.
   
  The transistor in QB9L gets crazy hot.  The others don't.


----------



## Beefy

Quote: 





drclaw said:


> Yup.
> 
> The transistor in QB9L gets crazy hot.  The others don't.


 


 Even with the tubes pulled?
   
  That means you've got a short somewhere near QB9L, or QB9L is internally shorted. Check the resistances across each pair of pins to gain some insight. Use the holes for the alternate transistor locations to make it easy. I can't confirm any readings though, as I don't have an amp in front of me......


----------



## tomb

It's hard to tell from the quality of your pics, but it almost looks like the solder blobs could be touching each other on one of the output transistors in the middle (QB9).  Is that possible?
   
  I also seem to detect some excess solder around the alternate holes for QB9L.  Did you perhaps have it soldered in the wrong side at first, then removed it and re-installed it?  Further - did you apply power when it was in that condition?  If the solder pads are not touching, maybe QB9 is burned out, reversed, etc.?


----------



## jdkJake

drclaw said:


> Yes, all of the TO-92 transistors are in the correct place.
> 
> 
> 
> ...







 Melted where? The enclosure?

 Can you verify RA7L is not shorting against the tube socket pin 7.

 Another picture, with as much light and focus as you can muster would go a long way to help.


----------



## drclaw

Quote: 





beefy said:


> Even with the tubes pulled?
> 
> That means you've got a short somewhere near QB9L, or QB9L is internally shorted. Check the resistances across each pair of pins to gain some insight. Use the holes for the alternate transistor locations to make it easy. I can't confirm any readings though, as I don't have an amp in front of me......


 
  No shorts at or near QB9L.  
  I checked the resistance.  On the right transistor, it would start at around 900 and work its way up until it got to too high for my meter.  On the left one, it would start at around 300 and work its way up.  

  
  Quote: 





tomb said:


> It's hard to tell from the quality of your pics, but it almost looks like the solder blobs could be touching each other on one of the output transistors in the middle (QB9).  Is that possible?
> 
> I also seem to detect some excess solder around the alternate holes for QB9L.  Did you perhaps have it soldered in the wrong side at first, then removed it and re-installed it?  Further - did you apply power when it was in that condition?  If the solder pads are not touching, maybe QB9 is burned out, reversed, etc.?


 

 The solder blobs aren't touching each other.  I checked.  
  The excess solder is there by accident.  The transistors haven't been moved out of their current locations.  


  
  Quote: 





jdkjake said:


> Melted where? The enclosure?
> 
> Can you verify RA7L is not shorting against the tube socket pin 7.
> 
> Another picture, with as much light and focus as you can muster would go a long way to help.


 

 Yeah, it's on the corner of the enclosure.
   
  RA7L is not shorting against the tube socket.


----------



## tomb

If you hit one of the trimmers with your soldering iron, I don't think it would cause these problems - melting a chunk of one of the trimmers and/or the Wima caps happens often with little ill effect.
   
  Jdkjake is right - we need better pics from you.  The reason is that the only thing that can cause this is a part out of place.  So, I know you've checked the important parts, but we're all missing something here.  I don't mean to re-state the obvious, but there's got to be a part messed up/mixed up on the PCB somewhere.


----------



## drclaw

Here is the new picture.


----------



## Beefy

Looks to me like your VitQ is shorting to the QB9L heatsink. Don't know if this is your problem though.
   
  And while I don't like to kick a guy when he's down...... it has to be said that your construction needs a LOT more attention to detail. Your resistor and capacitor mounting is just plain sloppy, and I don't want to know how many cold solder joints you have based on how the test points are connected.


----------



## tomb

At first I thought it was the camera angle, but what is going on with the CA7L Muse ES cap in the left channel?  It looks racked up against the trimmer and almost looks impossible to allow room for the QB2L and QB3L transistors.  Also, the VitQ is pushed way back too.

 Is it possible that VitQ lead is touching the heat sink and shorting out?  It doesn't take much for those things to start arcing.
 Is it possible the can of the ES cap is touching the leads of QB2L and QB3L and shorting out?
 Are the leads for QB2L and QB3L touching each other and shorting out because they're all squeezed by the cap pushing back?
   
  It just looks like something bad is going on in that area, but we can't see anything from the angle of the pic (a much better pic, btw!).
   
  EDIT: Looks like Beefy and I think alike and were posting at the same time!


----------



## jdkJake

Can you also post a picture from the other direction ( back to front)?

 This is a MUCH better picture to work with.


----------



## drclaw

If I had powered it up at the time of the previous photo, than yes, the VitQ would have shorted out with the heatsink.  It just got pushed over.  Same thing with the Muse ES cap at CA7L.  
   
  I know that some of my work is sloppy.  I'm still a pretty big newbie.  
  Practice makes perfect!  
	

	
	
		
		

		
		
	


	



   
   
   
  From back to front close up:

   
  Close up of the problem side:


----------



## tomb

You need to go over every transistor solder joint in that left channel very carefully.  Looking at QB2L, I can't believe the leads are not touching.  It appears that the transistor is bent sideways so far to the headphone jack side that the far edge of the transistor is over the center pad.  If the leads are bent sideways that far, chances are they're touching.  There's also a solder blob on QB3R that looks big enough to cover both pads.  Make certain you don't have any solder blobs touching other pads and inspect all of the transistor leads to ensure that you don't have anything touching.  Are the pads clean and leads secure on the heat sinked transistors?
   
  Can you get us similar pics of the bottom of the PCB?  I'm beginning to think it's some messy solder joint somewhere that's shorting out.  We can't confirm the transistors from these pics, but if you've double-checked that none are in the wrong place and you've already checked and measured the resistors, then that leaves a short somewhere as the issue - touching lead, solder blob out of place, etc.
   
   
  EDIT:  Just an FYI, but I'm afraid you're going to have problems casing it up unless you change the mounting of those Vitamin Q's - they appear to be too high toward the center.  You should refer to this detail from the MiniMAX website: 
	

	
	
		
		

		
			




   
  This image is a little ideal, but there's a scale PDF link below on that page (http://www.diyforums.org/MiniMAX/MiniMAXvitQ.php) that has it drawn exactly:
http://www.diyforums.org/MiniMAX/vitQ/VitQinstall.pdf
   
  The key is that I don't think you can get the height low enough (without shorting out the leads) unless that tall lead is bent slightly back under the VitQ and soldered into one of the interior holes - not the outside one.


----------



## QRomo

The MiniMAX is my first tube amp, so excuse my ignorance, but is there a lot of variation in how microphonic these Millet tubes are? The first set I tried were the 12FM6's that came with my kit and they picked up any vibration transmitted through the chassis. I figured it was just par for the course and it was really only a problem when I tapped the chassis or changed the volume (and only faintly on volume change), so it didn't bother me. However, I recently decided to give a couple 12AE6's a try and once I swapped them in I found them to be dead silent, even when I tap the tubes directly. Did I get a bit lucky with the 12AE6's or a bit unlucky with the 12FM6's?


----------



## jdkJake

Unlucky with the 12FM6's.
   
  Most Millett tubes I have are dead silent. I have a couple that are just slightly microphonic, but, they sound so good, I tolerate them nonetheless. If it is highly microphonic, I usually return them. In general, most tubes I have used are fine (and I have a serious Millett tube fetish going on!)
   
  Where did you get them? Most places will take them back and/or replace them if they are microphonic. It is something that cannot be tested except by listening.
   
  EDIT, just realized you got these from Beezar. Contact Tom, he will take them back and get you a new set. He is VERY good about that!


----------



## QRomo

Nah, no need to have Tom go to the trouble. They sound fine other than the microphonics, and since I'm not in the habit of routinely tapping my amp their slight flaw doesn't really bother me.


----------



## H0bbes

Hello guys, long time lurker first time poster 
	

	
	
		
		

		
		
	


	



   
  A huge thanks to tomb for his excellent service, communication throughout the buying process and packaging.
  Was really an enjoyable second diy project for me, here are some pics.
   
   
  The package


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  Nicely protected individual boxes
   


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  Individual boxes
   


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  Bubble wrapped individual boxes for further protection
   


Spoiler



 

   


   
  The sealed PCB nicely wrapped
   


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  Unwrapped and unpopulated PCB
   


Spoiler



 

   


   
   
  I then cleaned the PCB with alcohol swabs
   


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  Populated with resistors
   


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  Fully populated PCB front view
   


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  Fully populated PCB side view
   


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  Back plate and hook up wires
   


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  Input wires
   


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  Side view with tubes
   


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  Finally tube glows with star 
	

	
	
		
		

		
		
	


	



   


Spoiler


----------



## jdkJake

Sweet.

 Awesome pictures! Your photography skills are most excellent.

 Congrats and enjoy. What tubes are you using?


----------



## H0bbes

Thanks jdkJake 
   
  I'm using 12FM6s as recommended by tomb, regretted that I did not ordered any extra tubes to roll tho
   
  Btw, since you have both MOSFET MAX and the miniMAX, how do they compare? I'm already itching for a third diy project


----------



## drclaw

It's alive!!
   
  I went over any suspicious looking solder joints and redid the VitQs.  Powered it up and it has worked since!
   
  I reallly appreciate all of the help you guys have given me with this!   Thank you so much!!!
   
   




   
  (I'll post some pics later)


----------



## H0bbes

Grats drclaw 
	

	
	
		
		

		
		
	


	



   
  I'm sure you'll enjoy the fruits of your labor


----------



## tomb

Quote: 





drclaw said:


> It's alive!!
> 
> I went over any suspicious looking solder joints and redid the VitQs.  Powered it up and it has worked since!
> 
> ...


 
   
  Quote: 





h0bbes said:


> Grats drclaw
> 
> 
> 
> ...


 

 WOW - great news all the way around!  drclaw gets his fixed and H0bbes posts some great pics of his build, not to mention some very flattering pics of my shipment packing - thanks for that!!


----------



## jdkJake

Quote: 





drclaw said:


> It's alive!!
> 
> I went over any suspicious looking solder joints and redid the VitQs.  Powered it up and it has worked since!
> 
> ...


 
   
  That is great news drclaw. Enjoy!!


----------



## jdkJake

Quote: 





h0bbes said:


> Thanks jdkJake
> 
> I'm using 12FM6s as recommended by tomb, regretted that I did not ordered any extra tubes to roll tho
> 
> Btw, since you have both MOSFET MAX and the miniMAX, how do they compare? I'm already itching for a third diy project


 

 Good question, complicated answer. They actually sound a lot more different than I imagined they would. I am still listening to the MOSFET-MAX almost exclusively to form a valid opinion. So, these are just early impressions.
   
  For my Grados, the MOSFET rules. There is no comparison. I would reach for it each and every time. It really matches up with those phones. For the Senn HD650, too early to tell as I just started listening to them with the MOSFET-MAX. At first blush, it seems a bit "thicker" if that is a word for it. Smooth with lots and lots of bass, but, far warmer and not quite as dynamic as the miniMAX. Again, I need more time on it before I comment further, but, the miniMAX seems a better match for the HD650. At least with my miniMAX configuration.
   
  Now the complicated part. Not only are these two different amps in output buffers (MOSFETS vice 2SC2344/2SA1101 BJT's which report to have a brighter sound signature), I also have Black Gates at CA7. So, the entire output buffer is much different. The REALLY interesting thing to note is that I just discovered my miniMAX BJT's are under biased by a significant amount. While they are both exactly set to the same value, that value is 53mv, which is way under the suggested range. It has been that way since I got the amp. I only found this out this week when I pulled the board to check the transistors that were installed (I did not build it). 
   
  So, what does this mean? It means I need to up my miniMAX bias and give it a good listen again. Hard to believe, but, it might even get better. 
   
  The MOSFET-MAX is a great build of a great amp. I highly recommend it. It's nice to have the luxury of amps specifically targeted to a certain sound and headphone combo. What kind of phones are you using?


----------



## H0bbes

Quote: 





tomb said:


> Â
> 
> WOW - great news all the way around!  drclaw gets his fixed and H0bbes posts some great pics of his build, not to mention some very flattering pics of my shipment packing - thanks for that!!
> 
> ...


 


 Your welcome tomb 

  
  Quote: 





jdkjake said:


> Good question, complicated answer. They actually sound a lot more different than I imagined they would. I am still listening to the MOSFET-MAX almost exclusively to form a valid opinion. So, these are just early impressions.
> Â
> For my Grados, the MOSFET rules. There is no comparison. I would reach for it each and every time. It really matches up with those phones. For the Senn HD650, too early to tell as I just started listening to them with the MOSFET-MAX. At first blush, it seems a bit "thicker" if that is a word for it. Smooth with lots and lots of bass, but, far warmer and not quite as dynamic as the miniMAX. Again, I need more time on it before I comment further, but, the miniMAX seems a better match for the HD650. At least with my miniMAX configuration.
> Â
> ...


 

 Wow, thanks for the lengthy comparison post, jdkJake.
   
  So the MOSFETs version are more tube like than the BJTs?
  The reason why I asked is because based on my very short time with the miniMax (less than 20 hours or so), it sounded a little bright or perhaps not as tubey like sounding as I envisioned it to be.
  Perhaps I should let it burn in for a while more before forming an impression.
   
  My BJTs are biased at 115mv and I also found that by varying the tube bias voltage it changes the sound a little bit.
  With 13.5v dynamic range seems to be better and with 15v bass, details and imaging seems to be better but dynamic range suffers a little bit.
   
  I agree, having a certain amps to be paired with a certain headphones is close to being in headphone/audio nirvana. Having said that I'm trying to setup the minimax for my grados/alessandros headphones. That is why I have 1000uf Nichicon Fine Golds at CA7 and RB14 jumpered after consulting tomb.
   
  So it seems like I should get a MOSFET-MAX built, hopefully beezar.com will offer a MOSFET MAX kit when I'm ready to build one
  I really hate caseworks, and not ready to invest in casework tools yet.


----------



## jdkJake

Quote: 





h0bbes said:


> Â
> So the MOSFETs version are more tube like than the BJTs?
> The reason why I asked is because based on my very short time with the miniMax (less than 20 hours or so), it sounded a little bright or perhaps not as tubey like sounding as I envisioned it to be.
> Perhaps I should let it burn in for a while more before forming an impression.
> ...


 

 I have limited experience with all-tube-based headphone amps, so, I really cannot comment how the MOSFETs compare. I have read that is the case, but, do not have anything to back it up. The only all-tube designs I have heard were speaker amps. Certainly give it some more time. Especially the tubes. I have noticed that can take about a week or so to properly "wake up" after sleeping for so long on a shelf somewhere.
   
  I would be surprised if Beezar makes a MOSFET kit as it is intended to be an experimenters platform, but, you never know. Certainly it is not hard to obtain the parts as the BOM is pretty complete. If you can build the amp, the BOM should not present an issue. It is more juggling out of stock parts and/or parts only available from a few vendors. Just be sure to check it multiple times before pressing purchase. It can really save on extra shipping that way. Shipping is the penalty you pay for mistakes/ommisions, which, I have paid on multiple occasions.  
   
  The casework required is minimal, all you need is a drill and some rubber cement. The board is designed to fit in a standard case, you just need vent holes and jack holes. The MAX site goes into details on how it can be accomplished with a handheld drill. I even drilled the tube holes, but, I do have a drill press, vice and clamps available. Most of the tools can be rented for an afternoon if you really do not have them (including punch kits). The rubber cement is for the template method, which, works really quite well.
   
     http://www.diyforums.org/MAX/MAXcasework.php


----------



## Beefy

Beezar is unlikely to offer a kit, because of the casework. The pre-machined MiniMax case is what makes it such a great kit.


----------



## tomb

Quote: 





beefy said:


> Beezar is unlikely to offer a kit, because of the casework. The pre-machined MiniMax case is what makes it such a great kit.


 

 Well ... since you mentioned it, I'm wondering if developing a similar case for the MOSFET-MAX would be worthwhile, or whether it would kill the sales of the MiniMAX.  I keep thinking that there's room for both - MiniMAX for all-around and high-impedance and then MiniMAX as a Grado/K701 killer, but then I don't know for sure.  Any opinions?


----------



## Beefy

Quote: 





tomb said:


> Well ... since you mentioned it, I'm wondering if developing a similar case for the MOSFET-MAX would be worthwhile, or whether it would kill the sales of the MiniMAX.  I keep thinking that there's room for both - MiniMAX for all-around and high-impedance and then MiniMAX as a Grado/K701 killer, but then I don't know for sure.  Any opinions?


 


 I personally think it would split the MiniMax sales. And while there are differences between the two versions, they are mostly philosophical - as far as I'm concerned, both amps are great for both purposes.


----------



## jdkJake

Quote: 





tomb said:


> Well ... since you mentioned it, I'm wondering if developing a similar case for the MOSFET-MAX would be worthwhile, or whether it would kill the sales of the MiniMAX.  I keep thinking that there's room for both - MiniMAX for all-around and high-impedance and then MiniMAX as a Grado/K701 killer, but then I don't know for sure.  Any opinions?


 

 Interesting concept. The miniMAX case is quite nice. Wouldn't it kind of limit the build options? How would you handle the DAC option? Not sure everyone would be keen to add a DAC. But then, you never know, that might be the compelling feature that takes it over the top.
   
  No doubt it would takes sales from the miniMAX. Which would be undeserved as it is a FINE amp!


----------



## QRomo

Quote: 





tomb said:


> Well ... since you mentioned it, I'm wondering if developing a similar case for the MOSFET-MAX would be worthwhile, or whether it would kill the sales of the MiniMAX.  I keep thinking that there's room for both - MiniMAX for all-around and high-impedance and then MiniMAX as a Grado/K701 killer, but then I don't know for sure.  Any opinions?


 

 Good question! If a MOSFET-MAX kit were to become available, I think I'd eventually buy it just to compare with my MiniMAX. It would also be handy to have the GrubDAC integrated into the custom case. I know that would be a selling point for a lot of people.
   
  I'm not sure which I would have opted for if both kits were available when I got my MiniMAX. I'd have read up a lot more on the MOSFET-MAX to see which would suit my listening preferences better. I could see how the combo amp/DAC possibility of the MOSFET-MAX could make it the more popular of the two, though.


----------



## H0bbes

Quote: 





beefy said:


> Beezar is unlikely to offer a kit, because of the casework. The pre-machined MiniMax case is what makes it such a great kit.


 

 I agree, that is why I hope that Beezar could offer the MOSFET MAX kit and if dimensions of both PCBs arent too far apart, Beezar could unify one case for both built since 80-90% of the parts in the BOM list are similiar.
  In doing so, Beezar could offer amps for both low impedance and high impedance crowd while keeping the cost of stocking equivalent to or slightly higher than stocking for one model; hopefully in the long run it could hit a better volume thus achieving a better profit margin through MOQs/bulk purchase. Just a thought tho.
   
  Before deciding on the Minimax kit I was actually considering the M3 with Sigma11 PSU and I've actually emailed amb to enquire about payment/parts, however it turns out that i do not have time to work on a M3 and Sigma11 due to certain last minute changes in commitments (both work and family)
  Not to mention the time/cost needed for extra tools for the case work, the cost of shipping/lead time from 3-4 different vendors so in the end I settled for a kit like the Minimax from a single vendor thus saving time and money
   


  
  Quote: 





jdkjake said:


> I have limited experience with all-tube-based headphone amps, so, I really cannot comment how the MOSFETs compare. I have read that is the case, but, do not have anything to back it up. The only all-tube designs I have heard were speaker amps. Certainly give it some more time. Especially the tubes. I have noticed that can take about a week or so to properly "wake up" after sleeping for so long on a shelf somewhere.
> 
> I would be surprised if Beezar makes a MOSFET kit as it is intended to be an experimenters platform, but, you never know. Certainly it is not hard to obtain the parts as the BOM is pretty complete. If you can build the amp, the BOM should not present an issue. It is more juggling out of stock parts and/or parts only available from a few vendors. Just be sure to check it multiple times before pressing purchase. It can really save on extra shipping that way. Shipping is the penalty you pay for mistakes/ommisions, which, I have paid on multiple occasions.
> 
> ...


 
   
  Thanks for your effort tho 
 Yeah, guess i should give those tubes some time before forming an impression.
   
  Shipping is a problem for me, as I do not reside in the states; if i were to purchase parts from say 4 different vendors, the shipping cost alone will kill me and any cost benefit associated with DIY. 
   
  Unfortunately the country that i resides in does not have equipment rentals, i will have to borrow from friends or buy them outright and that too isnt in favor of DIY.
  However i could borrow a drill 
	

	
	
		
		

		
			





  and i do have some small vices/clamps so i might attempt a MOSFET Max built when time permits.(thanks for the link)


----------



## Beefy

Quote: 





h0bbes said:


> I agree, that is why I hope that Beezar could offer the MOSFET MAX kit and if dimensions of both PCBs arent too far apart, Beezar could unify one case for both built since 80-90% of the parts in the BOM list are similiar.


 


 Why would you want one case size? A key benefit of the MiniMax is so that it fits in as small a space as technically possible. That small size is too small for the higher heat output of the MOSFETs.
   
  Look, I know everyone loves kits for everything, but there really is a point where DIY becomes getting someone else to do it for you. The MiniMax kit is a brilliant kit that will happily power anything except some very difficult orthos and, obviously, Stax. If you want more from a DIY product, then DIY.


----------



## H0bbes

Quote: 





beefy said:


> Why would you want one case size? A key benefit of the MiniMax is so that it fits in as small a space as technically possible. That small size is too small for the higher heat output of the MOSFETs.
> 
> Look, I know everyone loves kits for everything, but there really is a point where DIY becomes getting someone else to do it for you. The MiniMax kit is a brilliant kit that will happily power anything except some very difficult orthos and, obviously, Stax. If you want more from a DIY product, then DIY.


 

 You are right in saying it defeats the purpose of the minimax to be space efficient, but i was trying to give a suggestion/seeing things in another perspective that IF you have all the materials to built 2 models and it cost you as much or a little bit extra to stock them why not offer 2 models.
   
  That suggestion was made in good faith and seeing that we do not have much online businesses catering for audio DIY like beezar.com, I would hope for it to be profitable and sustainable to continue to offer something for the DIY crowd.
  Perhaps i have misinterpreted your post but you seems to be very agitated with the suggestion. Also it doesnt mean that my idea reflects what everyone thinks, be all end all argument or it goes down well with tomb, at the end of the day its just an idea that came across me and my appologies if my idea agitates you.
   
  Now having said that, the DIY part, each and every one of us have a different definition of DIY; its a very ambiguous term. Perhaps you may think that by buying a kit and assembling it does not constitute as DIY and some one across the globe some where else thinks that by buying a drill to do up your casework doesnt constitute as DIY either because if you need to buy/borrow a drill you might as well have some one do it for you. See each one of us have got a very different definition of DIY and im not going to argue with you where that cut off point is.
   
  Never in my previous posts that I did implied or directly expressed that the Minimax kit is not a solid product or flawed; its a great product. But i was thinking now that i have attempted the minimax, and i'm itching/planning for a second project,and i really like tomb's service i was hoping he has another kit/product to offer as im not confident yet with caseworks to warrant an investment in  casework tools. That was when the idea came across me that perhaps someone somewhere would have the same thought as me and since the mosfet and the bjt maxs parts are quite similiar and if its not going to cost tomb any much extra why not offer it in a kit form as well.


----------



## Beefy

Quote: 





> Originally Posted by *H0bbes* /img/forum/go_quote.gif
> 
> That suggestion was made in good faith......
> 
> Never in my previous posts......


 


 Oh, man up and stop being so sensitive.
   
  Realistically, I suspect that very few people will build both a Mini- and MOSFET- Max. It will be either one or the other, and I personally see no problem with keeping the distinction as one being a safe kit, the other 'proper' DIY - purely for practical reasons of how they are built, and the ever-so-slight increased difficulty of the MOSFET version.
   
  And I think that part of the problem is the other distinction between the builds that has cropped up. Tom is 'classifying' them into two different categories based on performance, which is something I think is totally unnecessary. I can understand entirely why he does it though...... the typical Head-Fier demands this segmentation and stereotyping. I want an amp for low impedance phones, I want an amp for high impedance phones, people say this amp sounds best with 'X' therefore it is no good for 'Y'. Ridiculous.
   
  But I don't speak for Tom, so it is entirely up to him as to what he wants to stock. I just don't want to see him go to a whole heap of trouble designing and stocking a case for no good reason, or because of a vocal and/or lazy minority.


----------



## tomb

Beefy is correct in most of this, but he fails to mention the effort that it took to design and market that MiniMAX case.  It's easily the hardest thing I've done in DIY.  It also continues to be one of the largest investments in my small business to keep in stock.  Without the income from the kits, I'd never be able to afford to order more cases.  It's also why I steadfastly refuse to sell a kit without the case.  I have to order large manufacturing lots months in advance, then watch dozens of those cases sit in a box as my investment, hoping that they'll eventually sell during the next year.
   
  As for the MOSFET-MAX, it's true that I'm trying to distinguish the two as different amps.  First, because I think they truly are different in how they apply to headphones.  Beefy indicated it without coming out and saying it - the MOSFET-MAX has plenty of current to supply an ortho whereas a MiniMAX probably doesn't.  A MOSFET-MAX is also the best thing I've heard with a K701, my favorite pairing, as a matter of fact.  At the same time, the voltage swing sort of sucks compared to the MiniMAX.  Part of this is the turn-on voltage of the MOSFETs - they eat quite a bit of voltage just to operate as compared to BJT's.  So, there is truly a technical difference between the two amps.
   
  Second, if I don't emphasize the difference, and have any prospect of developing a custom case and kit for the MOSFET-MAX, then my huge investment in MiniMAX cases will go for naught - no one will be interested in those anymore if they think the amps are the same.
   
  Just an FYI, but a true custom case for the MOSFET-MAX won't happen overnight (if it does at all).  It's a huge effort and in the end, I may not be able to afford it anyway.


----------



## Beefy

Quote: 





tomb said:


> Beefy is correct in most of this, but he fails to mention the effort that it took to design and market that MiniMAX case.  It's easily the hardest thing I've done in DIY.


 

 And what an absolutely legendary effort it was - I can't imagine anything else coming close.
   
  I just wish there was some way I could justify keeping my own MiniMax


----------



## H0bbes

Quote: 





beefy said:


> Oh, man up and stop being so sensitive.
> 
> Realistically, I suspect that very few people will build both a Mini- and MOSFET- Max. It will be either one or the other, and I personally see no problem with keeping the distinction as one being a safe kit, the other 'proper' DIY - purely for practical reasons of how they are built, and the ever-so-slight increased difficulty of the MOSFET version.
> 
> ...


 

  
  Since its not my style to stooped to personal attacks I'll leave it as such 
   
  Hence my previous suggestion as a form of interest check if people would love to have a mosfetmax in a kit form as well, and tomb did posted that he too wonders if its worthwhile. In my books its not always either or, black or white, there's different shades of colors as well.
   
  Again as i said previously my suggestion was also based on profitability/in a business point of view; supply and demand.
  I also dont see anything wrong with people having or expressing their own opinions, at least it forms a basis of discussion.
  Now i've heard that some people thinks that Grado cans are overly bright for them and Senheiser cans are overly veiled for them, so I should never try or buy both headphones? That sounds even more ridiculous.
   
  Neither do i speak for him, like i said previously it was just an idea/interest check/a basis for discussion/suggestion and never did it crossed my mind that by giving an idea in this forum constitutes as being vocal or warrants any personal attacks. Perhaps I should redefine my definition of freedom of speech


----------



## Beefy

Quote: 





> Originally Posted by *H0bbes* /img/forum/go_quote.gif
> 
> Perhaps I should redefine my definition of freedom of speech


 


 You will do well on Head-Fi.


----------



## jdkJake

Quote: 





tomb said:


> As for the MOSFET-MAX, it's true that I'm trying to distinguish the two as different amps.  First, because I think they truly are different in how they apply to headphones.  Beefy indicated it without coming out and saying it - the MOSFET-MAX has plenty of current to supply an ortho whereas a MiniMAX probably doesn't.  A MOSFET-MAX is also the best thing I've heard with a K701, my favorite pairing, as a matter of fact.  At the same time, the voltage swing sort of sucks compared to the MiniMAX.  Part of this is the turn-on voltage of the MOSFETs - they eat quite a bit of voltage just to operate as compared to BJT's.  So, there is truly a technical difference between the two amps.


 

 Sorry Beefy, I have to agree with Tom on this one. As someone who has the luxury of owning both amps, sitting side-by-side, being feed from the same source, they are indeed different. They share a similar trait, but, different executions of that trait. 
   
  Now that does NOT mean either will not suffice on it's own, that is certainly not true. I could easily be happy with one or the other and just make tube swaps to change the character as desired. Even that is really not necessary, but, it does allow me to manipulate the gain to great effect. I do have to say though, at first blush, the BJT miniMAX seems to be the better all-around performer. The MOSFET version seems to be just a bit more specialized in it's sound. So, I think the miniMAX kit is the better decision in the long run.
   
  At the end of the day, I find it amazing Tom can justify the kits at all. I would suspect the audience for these products is fairly small. There is a lot of risk in what he is doing and I applaud him for taking that risk. I personally think one kit is plenty. The miniMAX serves the greatest audience and is one NICE piece of kit!


----------



## jdkJake

Quote: 





beefy said:


> I just wish there was some way I could justify keeping my own MiniMax


 

 Looks like you have become a dedicated Stax man.  
   
  One day I have to audition a pair of those. Then again, maybe I should just take my MAX's and run for the hills! This hobby is addictive and relentless at the same time.


----------



## Beefy

Quote: 





> Originally Posted by *jdkJake* /img/forum/go_quote.gif
> 
> Sorry Beefy, I have to agree with Tom on this one. As someone who has the luxury of owning both amps, sitting side-by-side, being feed from the same source, they are indeed different. They share a similar trait, but, different executions of that trait.


 

 Oh, I'm not saying they don't sound different - I'm pretty sure they do. I'm just pressing the point that the MiniMax should only be for high impedance and the MOSFET Max only for high current is pretty silly. But the nature of Head-Fi demands these stereotypes.

  
  Quote: 





			
				jdkJake said:
			
		

> Looks like you have become a dedicated Stax man.
> One day I have to audition a pair of those. Then again, maybe I should just take my MAX's and run for the hills! This hobby is addictive and relentless at the same time.


 

 No, not really dedicated Stax. In fact, I will probably not expand my Stax collection beyond the Exstata and SR-Lambda. But the MiniMax is sitting unused, and I really need a new DIY challenge. I don't know what that challenge is yet.
   
  Ironically enough, considering what I posted above, it will almost certainly have to be a kit with casework included. While I'm overseas I just don't have access to the tools and space that casework requires. Maybe a Bottlehead kit, with some severe modifications and upgrades......


----------



## crazeddaffy

So I started on my kit, but I'm really confused as to whether to use 10R or 22R.
  Also, for the diamond buffer is this correct way to mount the transistor:
  screw
  washer
  transistor mounted on top hole
  thermal tape - should i cut excess or fold it onto the other side?
  heatsink
  washer
  lock washer
  hex nut


----------



## tomb

Quote: 





crazeddaffy said:


> So I started on my kit, but I'm really confused as to whether to use 10R or 22R.
> Also, for the diamond buffer is this correct way to mount the transistor:
> screw
> washer
> ...


 

 Why not use a jumper?  That's one of your three choices, too.  If you use mainstream headphones, chances are you'll prefer the jumper or 10R.  If you have some very low impedance, super-efficient phones or even IEM's, then opt for the 22R.  The more resistance, the less detail in the music, but you will hear less tube noise or hiss (not really a common occurrence, IMHO, but some people hear this stuff).  So, you want to get away with as little as possible.  The MiniMAX will run just fine with only jumpers in those positions.  10R is the safe bet for most people, though.
   
  Yes, your heat sink sequence is correct.  Refer to this page on the MiniMAX website:
http://www.diyforums.org/MiniMAX/MiniMAXheatsink.php
  It's completely accurate except that in the case of the fully-plastic bodied transistors supplied with the kit, the shoulder washer is not necessary and is not supplied.
   
  Remember that the screw direction is arbitrary - only the position of the thermal tape inbetween the heat sink and the transistor is not.  Depending on the tools you use to tighten the assemblies, you may want to think about how you mount the two transistors on the center heat sinks.  A pair of needle nose pliers should be sufficient to grab nuts or socket-head screw heads if they end up in-between the two center heat sinks.  (The socket head cap screws' heads have sufficient surface area and knurling to allow easy manipulation with needle nose pliers.)
   
  As for the thermal tape/insulating pad, the long dimension should be at the bottom of the heat sink, not the top.  You can try to fold it over underneath, but the Bergquist pad is usually a bit wider than the slot in the heat sink, so this can turn into a mess if you do it that way.  The best scenario is to simply cut it to fit.  The slots in the heat sinks are actually intended to allow air flow beneath the transistor and through the heat sink/transistor leads.


----------



## crazeddaffy

Do I just use a piece of wire for the jumper?


----------



## tomb

Quote: 





crazeddaffy said:


> Do I just use a piece of wire for the jumper?


 

 Yep - just one of the trimmed leads from an installed resistor is all you need.  (Bend the ends so that they stick through the holes, of course.  Then solder in place just like it was any other part. 
	

	
	
		
		

		
			





)


----------



## crazeddaffy

Thank you. Also, is this scratch bad enough for me to have to get a new board?


----------



## jdkJake

Quote: 





crazeddaffy said:


> Thank you. Also, is this scratch bad enough for me to have to get a new board?


 
   
  I doubt it. What happened?


----------



## crazeddaffy

I was unsoldering with a braid, but it wouldn't come out so I yanked it out with pliers, which resulted in a careless scratch.


----------



## jdkJake

Well, at first glance, I think you are fine. How deep is the scratch?


----------



## crazeddaffy

Not deep at all. It's only exposing the metal.


----------



## jdkJake

The metal? You mean it has exposed the ground plane?

 Hmmm, should still be okay, but, might want to cover that to protect from an accidental short. Not quite sure what to use for that. Perhaps an epoxy? Some form of non-conducting filler should be fine.


----------



## jdkJake

Take a peek at this:



 http://www.circuitrework.com/guides/2-7.shtml




 A pretty cool site all around. A lot of good tips for repair and restoration.


----------



## BobSaysHi

I accidentally soldered the a resistor in the wrong spot and while I was desoldering it the plastic part of the resistor cracked and the metal below is exposed. I haven't gotten to see if it works as I am not finished, but how bad/dangerous is this?


----------



## jdkJake

Quote: 





bobsayshi said:


> I accidentally soldered the a resistor in the wrong spot and while I was desoldering it the plastic part of the resistor cracked and the metal below is exposed. I haven't gotten to see if it works as I am not finished, but how bad/dangerous is this?


 

 Toss it. Get another. That one is toast.
   
  Yet another offering to the DIY gods...


----------



## BobSaysHi

Quote: 





jdkjake said:


> Toss it. Get another. That one is toast.
> 
> Yet another offering to the DIY gods...


 

 Damn...
   
  I hate to pay shipping for one 1K ohm resistor, but I guess I have no choice. Thanks anyway


----------



## drclaw

You might want to check Radioshack first.


----------



## jdkJake

Drclaw is right. You might be able to get it locally.

 Where in Texas are you? Do you live near a frys? They will most certainly have it and probably a bit higher quality than ratshack. A decent electronics repair shop will have a resister that size as well.


----------



## tomb

I've sent him a PM.  He'll get his 1K resistor.


----------



## jdkJake

So, re-baised the BJT's on miniMAX this weekend. Recall they were under biased by a significant margin. I took them from about 59mv to 100mv.
   
  Been using them the last couple of days with the HD650's. Aural memory is tough, but, they sound better to me. Quite a bit more dynamic. Transients seem a bit crisper as well. That fabulous case is still cool, cool, cool. Amazing how efficiently it dissipates heat!


----------



## tomb

Quote: 





jdkjake said:


> So, re-baised the BJT's on miniMAX this weekend. Recall they were under biased by a significant margin. I took them from about 59mv to 100mv.
> 
> Been using them the last couple of days with the HD650's. Aural memory is tough, but, they sound better to me. Quite a bit more dynamic. Transients seem a bit crisper as well. That fabulous case is still cool, cool, cool. Amazing how efficiently it dissipates heat!


 

 Yep - 110mV is the standard recommendation.  So you've still got some room to go, if you want.


----------



## jdkJake

tomb said:


> Yep - 110mV is the standard recommendation.  So you've still got some room to go, if you want.






 Yeah, I wanted to run it like this for a week or so and see how it holds the setting. 

 Good stuff!


----------



## BobSaysHi

Hey guys, I have a problem. I completed my amp and started to bias the power supply voltage, and the amp lit up and my multimeter got a reading. So I biased it to 27 volts like the site recommended. The amp was on for about 5 seconds combined. After that I was going to bias the BJT and I turned the BJT trimmer down then. After I stuck the "probe" part of the multimeter in, the amp wouldn't turn on anymore. What could I have done while moving the multimeter to cause it to stop functioning?


----------



## tomb

Quote: 





bobsayshi said:


> Hey guys, I have a problem. I completed my amp and started to bias the power supply voltage, and the amp lit up and my multimeter got a reading. So I biased it to 27 volts like the site recommended. The amp was on for about 5 seconds combined. After that I was going to bias the BJT and I turned the BJT trimmer down then. After I stuck the "probe" part of the multimeter in, the amp wouldn't turn on anymore. What could I have done while moving the multimeter to cause it to stop functioning?


 

 Well, first - I would say that 5 seconds _may be_ too long to allow the amp to be on without checking the mV in the buffer, first - if the worst case existed and the trimmers were really out of range.  I think you'll find that there is a major warning on the top of the page on the MiniMAX website to "bump the amp on and off" just long enough to quickly check the mV in the buffer - before you go on to set anything else:
http://www.diyforums.org/MiniMAX/MiniMAXsetup.php .
   
  That said, you need to give us more detail about what happened and what is going on, now.  Was there something you touched with the multimeter that caused a spark and resulted in your suspicion of the multimeter?  Were you measuring the buffer with mV?  You can't measure with mA using the meter in this situation, or you'll cause a direct short.  Are you measuring with the probes in the proper positions - check the web page referenced above again, and the key plan shown there and below:




   
  What's the situation now?  Have you confirmed that the walwart is still producing voltage?  Is the fuse still OK?  Do the tubes light, etc., etc.?


----------



## BobSaysHi

It was late when I typed that. I think it has something to do withe the power supply wiring. I put the probes in the right spot, I think (like 95% sure). I'm going to resolder some things and if that doesn't work I'll take pictures and go really in depth about what happened. Also, there weren't any sparks and I did bump it to check the voltage, I would bump it and the multimeter would read, then I turned it off to change the trimmer, then I bumped it on again. The reason why I mentioned it is because everything worked fine. I walked away and when I came back to check the tube bias, it wouldn't turn on.


----------



## tomb

Quote: 





bobsayshi said:


> It was late when I typed that. I think it has something to do withe the power supply wiring. I put the probes in the right spot, I think (like 95% sure). I'm going to resolder some things and if that doesn't work I'll take pictures and go really in depth about what happened. Also, there weren't any sparks and I did bump it to check the voltage, I would bump it and the multimeter would read, then I turned it off to change the trimmer, then I bumped it on again. The reason why I mentioned it is because everything worked fine. I walked away and when I came back to check the tube bias, it wouldn't turn on.


 

 OK - then maybe you're right, perhaps the power wiring came undone.  Let us know what you find out.


----------



## BobSaysHi

I see, when I soldered my wires on I heated the power jack too much and melted the plastic/ bent the metal prong on top. I looked at the BOM and the power jack is no longer sold at mouser, and after a search it looks like all the ends are square. Is there a specific part that you would recommend?
   
   
  I'm going to go take a picture in a minute...


----------



## BobSaysHi

That's the best I can do with my iphone 3g's camera.
   
  edit: sometimes the pictures show up for me but not for everybody else. let me know if this is the case.


----------



## tomb

Well, you know for the power terminal, one lead is supposed to come from the switch and one lead from the power socket.  Then you run a short lead from the un-used lug on the switch to the unused "hot" lug (there are 3) on the power socket.  Take a look at this pic from the MiniMAX website (http://www.diyforums.org/MiniMAX/MiniMAXwiring.php):
   




   
  Use this for a new power connector:
http://www.mouser.com/ProductDetail/Kobiconn/163-4302-E/?qs=sGAEpiMZZMu2f9RNbWupYtIo6vLbBrLyp5YHgEJ%2fC6w%3d
  It's the same as the old one, just made with ROHS compliant materials.  Mouser has only 66,465 in stock, so you better hurry. 
	

	
	
		
		

		
		
	


	



   
  Or, you can let me send you one - but Mouser may be faster than me.


----------



## BobSaysHi

-double post-


----------



## BobSaysHi

Quote: 





tomb said:


> Well, you know for the power terminal, one lead is supposed to come from the switch and one lead from the power socket.  Then you run a short lead from the un-used lug on the switch to the unused "hot" lug (there are 3) on the power socket.  Take a look at this pic from the MiniMAX website (http://www.diyforums.org/MiniMAX/MiniMAXwiring.php):


 

 Yeah I used to have it set up like that, however I changed the wiring to make sure that it wasn't the switch causing the problems.


----------



## jdkJake

Quote: 





bobsayshi said:


> That's the best I can do with my iphone 3g's camera.
> 
> edit: sometimes the pictures show up for me but not for everybody else. let me know if this is the case.


 

 So, why did you use two wires for each connection?
   
  Have you checked the fuse? I suspect it has blown.


----------



## BobSaysHi

There are two wires for no other reason besides the fact that I have 50 feet of cable and not enough projects to use it on


----------



## BobSaysHi

I have a blown fuse. Well, what did I do wrong to cause it to "blow". 
   
  Hey Tomb, can I cancel my order? Beezar says it hasn't shipped yet and the power socket wasn't the problem.


----------



## jdkJake

Something called for more current than was available. I suspect you have/had a short somewhere on the board. Probably near the power supply section. I doubt anything down wind of the power supply would pull down a fuse, particularly a slo-blow. But, TomB will correct me if I am wrong.
   
  What size fuse where you using?


----------



## tomb

Quote: 





bobsayshi said:


> I have a blown fuse. Well, what did I do wrong to cause it to "blow".
> 
> Hey Tomb, can I cancel my order? Beezar says it hasn't shipped yet and the power socket wasn't the problem.


 
  Of course, I'll be happy to cancel your order - but it was for the tubes.  I was going to give you the power socket.
   
  Not so fast in any event, though.  If you blew the fuse, there's a reason.  The fuse protects the power supply.  As such, there's very little in the tube section or in the buffer that can hurt the fuse - it's all pretty much in the power supply.  So, I'm wondering if perhaps you soldered too long on the power socket and melted some of it in addition to the power switch.  That may be the source of your short, which is the most likely explanation for why the fuse blew.
   
  I can supply you with an extra fuse, too, but you should check that socket - make sure there's close to infinite resistance between the two lugs that are wired.  If not, then that means the power socket is shorted and needs to be replaced.  Still, it could be something else, but that's where I'd look first.


----------



## jdkJake

Quote: 





bobsayshi said:


> There are two wires for no other reason besides the fact that I have 50 feet of cable and not enough projects to use it on


 

 Ummm, okay. Whatever floats your boat.


----------



## BobSaysHi

Quote: 





tomb said:


> Not so fast in any event, though.  If you blew the fuse, there's a reason.  The fuse protects the power supply.  As such, there's very little in the tube section or in the buffer that can hurt the fuse - it's all pretty much in the power supply.  So, I'm wondering if perhaps you soldered too long on the power socket and melted some of it in addition to the power switch.  That may be the source of your short, which is the most likely explanation for why the fuse blew.
> 
> I can supply you with an extra fuse, too, but you should check that socket - make sure there's close to infinite resistance between the two lugs that are wired.  If not, then that means the power socket is shorted and needs to be replaced.  Still, it could be something else, but that's where I'd look first.


 

 Hmm, well how would I go about testing this? I have a basic idea on how to do this, but I don't want anything else to fry/break. Also I just looked and the vreg wasn't soldered on (oops). Could this have blown the fuse?


----------



## jdkJake

Quote: 





bobsayshi said:


> Hmm, well how would I go about testing this? I have a basic idea on how to do this, but I don't want anything else to fry/break. Also I just looked and the vreg wasn't soldered on (oops). Could this have blown the fuse?


 
   
  Seriously? Wow. Surprised it worked at all.
   
  Believe it or not, I don't think this is the source of your problem. I would still check that socket out for shorts.


----------



## jdkJake

Quote: 





bobsayshi said:


> Hmm, well how would I go about testing this? I have a basic idea on how to do this, but I don't want anything else to fry/break.


 

 Do you have a multimeter?


----------



## BobSaysHi

yeah I have a multimeter. And on the multimeter I see an "ohm" symbol. but from there I really don't want mess anything up by jumping to conclusions. Also the manual was NO help. 
   
  While soldering on the vreg (I had it ready to go, just forgot to solder) I noticed a joint wasn't shiny so I hit that, and after reflowing the solder on all my joints, they are all very shiny ( except for the larger ones which are only kinda shiny)
   
  On an unrelated note my lamp bulb EXPLODED while I was finishing up. It scared the crap outta me!


----------



## jdkJake

So the lights literally went out huh? Bad timing for sure.

 So, does your multimeter have separate probe jacks for measuring voltage vice resistance? Some of the less expensive ones are like that. What meter are you using? Show a quick pic.

 Did you clean the flux off your board before you fired it up?


----------



## BobSaysHi




----------



## jdkJake

Ah, the old Harbor Freight special! I have one of those in the kit bag as well. I bought it especially for the transistor tester. 
   
  So, on the bottom of the righthand side, there are three jacks. You want the black probe in the COM jack (or ground) and the red probe in the VΩmA jack as we are going to measure resistance, specified as Ω.
   
  First, POWER DOWN. Never measure resistance on a live circuit. In your case, unplug the power from the socket. You want to set the scale in the same range area as you have it in the picture (the settings for resistance or "Ω". You can stay 2000k and work your way down for more sensitivity. Leave the probes apart and notice a "1" or "I" in on the left hand side of the screen. This indicates an "open" or infinite resistance. Touch the two probes together and you should see a 0 (or close anyway) on the right hand side of the screen. This indicates a "short" or no resistance. Everything else in between these values is your measure. Sometimes, the scale setting is too big to display the actual number, just decrease the scale (counter-clockwise) until the appropriate number displays. If you measure infinite resistance, always work though all of the range settings to be sure, largest to smallest. I suggest you practice on a resistor or two to get the hang of it. 
   
  Remember, when you measure in an installed circuit, you are getting the total resistance between those points, so do not think you can always measure a resistor installed in a circuit and get the specified value. More likely, it is the true resistance at that point in the circuit.
   
  So, what TomB is having you do is to check for an "short" at the power socket. Ideally, these should be "open" or near/at infinite resistance. A small value (near zero or zero) means they are shorted and the plug is probably no good anymore.
   
  Hope this helps.


----------



## BobSaysHi

Thank you so much for your straight forward answers, esp. the part about no live circuit. That would've been bad 
	

	
	
		
		

		
		
	


	



   
  My plug is fine, it read 0.00and that's a good sign. The multimeter is a tricky tool to figure out if you have no experience. 
   
  I'm going to run up to radioshack tomorrow and pick up some fuses in the hopes that I will have this project wrapped up by the end of the week.
   
  These are the correct fuses right?:
http://www.radioshack.com/product/index.jsp?productId=2102747
   
  BTW: I really want to thank everybody for the patience and knowledge to help me finish this (hopefully)


----------



## tomb

Quote: 





bobsayshi said:


> Thank you so much for your straight forward answers, esp. the part about no live circuit. That would've been bad
> 
> 
> 
> ...


 


 No, those are not correct!  The MiniMAX uses a 5x20mm fuse size - those are 1-1/4".  This is what you should use:
http://www.radioshack.com/product/index.jsp?productId=2103770


----------



## jdkJake

bobsayshi said:


> Thank you so much for your straight forward answers, esp. the part about no live circuit. That would've been bad
> 
> 
> 
> ...







 I think you need to go back to what I wrote and reread it one more time.

 (HINT: what does a value of 0 represent?)

 BTW, be careful buying fuses. There are multiple types as well as sizes and ratings. Be sure you get the right part otherwise you defeat the purpose of the fuse. Remember, that fuse might have saved your amp.


----------



## BobSaysHi

Quote: 





> So, what TomB is having you do is to check for an "short" at the power socket. Ideally, these should be "open" or near/at infinite resistance. A small value (near zero or zero) means they are shorted and the plug is probably no good anymore.
> 
> Hope this helps.


 
  Well, dang.


----------



## tomb

Quote: 





jdkjake said:


> I think you need to go back to what I wrote and reread it one more time.
> 
> *(HINT: what does a value of 0 represent?)*


 

 Good catch - I missed that when looking up the correct fuse for him this morning.  I haven't had a chance to look since then - it's been one of those days ...


----------



## BobSaysHi

I think I've been unintentionally misleading you guys, sorry. 
	

	
	
		
		

		
		
	


	



   
  I forgot to take the plug out (from my power supply, it was off) and got a shorted 0.00 on my multimeter. but when I took the plug out i got infinite resistance (1) between the pegs. So the plug is in working order.
   
  I don't think I'll do any work till the 3 day weekend when I can focus entirely on my amp, and try not to mess any thing else up.
   
   
  Quote: 





tomb said:


> It's been one of those days ...


 
   
  It's been one of those weeks


----------



## jdkJake

Quote: 





bobsayshi said:


> I think I've been unintentionally misleading you guys, sorry.
> 
> 
> 
> ...


 

 We have all had weeks like those. That's what 3-day weekends are for!
   
  In any case, your response is also quite telling. You need to verify that you indeed got a short with the plug inserted. Did you measure 0 (or near 0) at each of the ranges of measurement? Did you rotate clockwise through all of the settings (200k through 200)?
   
  In any case. you should not be reading a direct short with that plug installed. There should be at least some resistance. While the plug is most likely fine, there is most likely a definite short early in the power input path. That is why the fuse blew. A direct short between power and ground dumped too much current through it, so, it blew. Do not put another fuse into the fuse holder until you isolate that short, otherwise, you will just blow another one.
   
  What kind of wall-wart are you using?
   
  Anyway, at least you have someplace to start.


----------



## BobSaysHi

Quote: 





jdkjake said:


> Anyway, at least you have someplace to start.


 

 ... I think I'll go take some pictures ...
   
  brb


----------



## BobSaysHi

OK, they say a picture is worth a thousand words, and I certainly hope that's true.
   
  To start off, I guess I failed to mention that I am using the kit from Beezar, which comes with a multimeter and its own power supply.
   
  My lamp exploded 
	

	
	
		
		

		
		
	


	




, so the lighting isn't very good, but it's the best I can do.
   
  EDIT: the wires aren't connected to anything.
   
  Here are the "probes" on the pegs with the plug out and then the multimeter:

   

   
  And here is the multimeter with the plug in:
  (btw I was born with three hands 
	

	
	
		
		

		
		
	


	




)
   

  lamp     ^
   
  and the ranges fluctuated from about ~3 to 8 on the lowest setting

   

  I am eagerly awaiting your response


----------



## tomb

Plug in means nothing.  You may be reading the resistance of the transformer coils in the walwart along with who knows what else.  It's a useless measurement.
   
  Plug out and a "1" on the meter means that the resistance has exceeded the limits of the 20,000K ohm band setting.  IOW, near infinite resistance, so the socket should be OK.
   
  EDIT: Can you get your light fixed and provide us with some better pics of the board?


----------



## BobSaysHi

Quote: 





tomb said:


> Plug in means nothing.  You may be reading the resistance of the transformer coils in the walwart along with who knows what else.  It's a useless measurement.
> 
> Plug out and a "1" on the meter means that the resistance has exceeded the limits of the 20,000K ohm band setting.  IOW, near infinite resistance, so the socket should be OK.
> 
> EDIT: Can you get your light fixed and provide us with some better pics of the board?


 

 I figured as much. I got my tubes today (shipped faster than I expected!) and am going to get some isopropyl (90-99%) alcohol to clean the back of the board (it got dirty on my table) and I'll try to take pics of anything that could've caused the problem. Although from what I see, it looks pretty good. I think my originally unsoldered vreg caused the short, because it was the only problem that was easily identifiable. Although I'm clearly not an expert.


----------



## jdkJake

Good to see you are getting the hang of the multimeter. I kinda of figured you would measure at least SOME resistance with the plug in. Like TomB said, the actual value means nothing unless it was a short (reading of 0) or an open (reading of "I" or infinite).
   
  I also agree with TomB, better pictures would help a lot. Do you have a friend with a better camera? No offense, but, those pictures you are posting really do not help much at all for looking at circuits and solder joints. Lots of light and lots of focus are your friends.
   
  Were you able to locate extra fuses of the correct size and rating? Have you verified all other parts have been properly soldered? Particularly in the power supply area? I hesitate to recommend you try another fuse with the recently soldered regulator until you have inspected that power supply area good for potential shorts. Also make sure you really clean the board good with the alcohol. It really helps a lot.


----------



## BobSaysHi

Quote: 





jdkjake said:


> I also agree with TomB, *better pictures would help a lot.* Do you have a friend with a better camera? No offense, but, those pictures you are posting really do not help much at all for looking at circuits and solder joints. Lots of light and lots of focus are your friends.
> 
> Were you able to locate extra fuses of the correct size and rating? Have you verified all other parts have been properly soldered? Particularly in the power supply area? I hesitate to recommend you try another fuse with the recently soldered regulator until you have inspected that power supply area good for potential shorts. Also make sure you *really clean the board good with the alcohol.* It really helps a lot.


 
   
  My dad is coming home friday and he owns a digital camera. I'm not sure about quality, I haven't seen any pictures on it in a long time, but hopefully the pictures will be in focus.
   
  I am scrubbing with alcohol right now. After dinner I'll scrub more. Can 90% isopropyl alcohol damage any components? 
   
  And lastly, I see bits of copper coming through where I desoldered. They are nowhere near the power supply and don't bridge or touch anything. should I put epoxy over these? I'd take a picture, but it'd be useless. It's about the width of the tip of a pencil.


----------



## jdkJake

Scrub and rinse a couple times and you should be good. When all the flux is gone, the joints are shiny, you are good. If you have a white film or stickiness, you need to scrub a little more. Firm, but, gentle.

 The alcohol should not hurt the parts. Particularly the passive components. Just be sure to let it dry before you attempt to power it up.

 Where did you desolder? Sounds like a bit too much heat and/or force. Did you lift a trace or a solder pad? Be sure to take a picture of that area.


----------



## BobSaysHi

Quote: 





jdkjake said:


> Scrub and rinse a couple times and you should be good. When all the flux is gone, the joints are shiny, you are good. If you have a *white film* or stickiness, you need to scrub a little more. Firm, but, gentle.
> 
> The alcohol should not hurt the parts. Particularly the passive components. Just be sure to let it dry before you attempt to power it up.
> 
> Where did you desolder? Sounds like a bit *too much heat* and/or force. Did you lift a trace or a solder pad? Be sure to take a picture of that area.


 
  I definitely have that white film, I'll scrub it good.
   
  It isn't actually on any of the traces and I didn't lift anything up (I think). It almost looks like burnt on flux, however it isn't coming off. I'll worry about it friday when I have a camera, and can show you the issue. 
   
  Thank you jdkJake and tomb for helping me through this. You guys must be so tired of me by now.
   
  It is killing me having this thing so close to completion, you have no idea.


----------



## tomb

I find it a good practice to use a paper towel.  The alcohol readily dissolves the flux, but it has nowhere to go unless you dab it up with something - or hold the PCB vertically and let it drain down into something.  For a board like the MiniMAX, it usually takes me at least a half-dozen rinses/scrubs/pats before the PCB gets shiny and loses the white coating (dissolved rosin).
   
  You're very safe if you confine your rinsing to the bottom of the PCB, but keep in mind that there are some parts that won't take kindly to the alcohol.  For instance, the volume pot can lose its grease, and the electrolytics are only moisture-resistant, they can't take immersion.
   
  I scratch my PCB's in some way or other all the time.  If the copper is showing, as long as it's not touching anything it shouldn't, it's not an issue.  After all, the blue mask is there to control solder creep, not to provide insulation.  Jake is correct about the traces - if you've got some of those lifted/damaged, you need to show us the situation, if you can.


----------



## jdkJake

Quote: 





bobsayshi said:


> It is killing me having this thing so close to completion, you have no idea.


 

 Oh, believe me, I think we understand just fine!


----------



## BobSaysHi

PICTURE TIME!!!  
	

	
	
		
		

		
		
	


	



   
  These pictures are huge, you have been warned. Be sure to open these in a new tab/window for the full effect.
   
  My workplace:
  btw, I really enjoyed this album while working.

   
  A bunch of pictures of the board:
   
  that weird looking stuff on this side has been cleaned off.

   

   

   

   

   
  I think everything is good to go, I just need the OK from you guys before I try again.


----------



## tomb

Well, I don't really see that any part is out of place, but there are quite a few cold solder joints.  In particular, I'm concerned about the tube sockets - at least on a long term basis.  It looks as if you were unable to poke the sockets' PCB pins all the way through the holes in the PCB.  The sockets depend on a mechanical connection as much as they do with solder.  So, be careful when plugging in the tubes and try not to put much stress on those joints.
   
  There are a couple of solder bridges on the tube trimmers' pins, but they're on the same trace, so no foul.
   
  Put the DMM probes in one of the DB's test point pairs and set the DMM to measure DC millivolts.  Put the tubes in, carefully connect the power and notice your reading on the DMM.  You should get a reading of something between 30-50mV, I believe.  Disconnect the power.  If the reading was greater than that, screw the trimmer down (clockwise) a couple of turns and try the power again.  Notice the reading.  If not low enough, disconnect the power and go another couple of turns on the trimmer.  Re-connect the power and notice the reading.  It should be decreasing from before.  Do this for both channels - always disconnecting the power in-between - until you get the readings in that range (or close to it).
   
  Once you've done that, you can rest easy that you're not going to burn up the buffer.  Re-connect the power, then adjust the power supply for 27VDC at V+ and Gnd, then adjust the tube biases for 13.5V each.  Notice that adjusting each of these is different than the buffer adjustments.  The power supply adjustment is very precise - several turns per volt, and you can easily control it to the tenth of a volt.  The tubes are just the opposite - voltages may be all over the place and you'll have to turn the trimmers and watch the meter just to tell which direction you should be turning.  The readings will fluctuate greatly and will seem very imprecise.  You may turn to 13.5V on one tube, then watch it keep going up or down without any input from you.  Turn it back, and it may keep going in the same direction for tenths of a volt without any input from you.  This is perfectly normal.  The tubes are more like mules than a precise electronic device - they'll hunt, float over several tenths of a volt, and they have backlash.  Just get them within a few tenths (higher is better than lower) and be satisfied that they don't vary too much.
   
  Once you've done all of that, go back to adjusting the buffers - start with a turn at a time, then gradually decrease to a half-turn then a quarter-turn as you get close.  Make the adjustment, then go to the other channel and do the same.  Usually, in the time it takes you to adjust the one channel, the other channel has heated up sufficiently with the new setting to be turned up again.  Alternate like this between channels until you get to about 90-100mV (40-45ma).  Let it run like that for quite some time - listen to music, etc., while checking the buffer bias occasionally (both channels).  If everything seems stable after a few hours, go ahead and boost the bias that final bit to 110mV (50ma).  You're done!


----------



## jdkJake

What TomB said. 

 Seriously, you might want to consider going back over a few of those cold solder joints before you case it up.


----------



## BobSaysHi

I was all ready to go, I read through the MAX setup and your post several times. After I was ready to go and had everything set up correctly, I plugged in the power, and my fuse blew. Hopefully radioshack is open on labor day. I didn't replace the power socket with the new one you sent me because I thought it was ok after testing it (it sill gives me a 1 on testing, sigh), however I don't see any other potential problems. And I was so looking forward to seeing the lights turn on.


----------



## tomb

Well, I still don't see anything that would cause a dead short.  Unless ... that mat looks like it has some solder blobs on it and it doesn't look like you're supporting the bare PCB with anything.  That might make it easy to short some of those solder connections underneath.  Still, it seems we'd see some burn marks if it was enough to blow the fuse.  Change that socket out and see if that makes a difference.  Next time, though, maybe place the PCB directly on the glass table top when you power it up - not the mat.


----------



## BobSaysHi

Quote: 





tomb said:


> Well, I still don't see anything that would cause a dead short.  *Unless ... that mat looks like it has some solder blobs on it and it doesn't look like you're supporting the bare PCB with anything.  That might make it easy to short some of those solder connections underneath.*  Still, it seems we'd see some burn marks if it was enough to blow the fuse.  Change that socket out and see if that makes a difference.  Next time, though, maybe place the PCB directly on the glass table top when you power it up - not the mat.


 

 I turned it on my desk touching nothing but glass, not on the matt with blobs of solder on it. I hopefully the power socket is the problem.


----------



## BobSaysHi

OK, so I just ran up to radioshack and bought more fuses. after changing the power socket the lights lit up!


----------



## BobSaysHi

I have a problem. I can turn the amp on, however it'll turn on for about half a second and turn off again. I've biased the db's and they got like a 20  (I think so at least, I cant be 100% sure because it turns off too soon) and I biased the power supply voltage already. No clue as to what the problem is.


----------



## jdkJake

Quote: 





bobsayshi said:


> I have a problem. I can turn the amp on, however it'll turn on for about half a second and turn off again. I've biased the db's and they got like a 20  (I think so at least, I cant be 100% sure because it turns off too soon) and I biased the power supply voltage already. No clue as to what the problem is.


 

 What do you mean by "turn off again"?  Are you turning it off or is it turning off by itself?


----------



## BobSaysHi

the leds slowly dim and then the whole thing turns off by itself


----------



## drclaw

Sounds exactly like the problem I had.  
  More than likely you have a short somewhere. Check all of the little transistors.  It is very easy to have a short between the leads.
  Also, go over every solder joint that doesn't look even close to perfect.  
   
  -John


----------



## jdkJake

Okay, that's the polyfuse doing it's job.

 As drclaw says, you need to hit those cold solder joints. Also take a closer look at the parts (particularly the transistors) around rb3l, rb5l, rb7l. From the pictures they might not be soldered. Or at least not fully.

 Take it easy with the paste flux. You should not need any to reflow those joints. If you do use it, use it sparingly.


----------



## tomb

One thing you can do to check: put one DMM probe on GND and use the other to touch to every solder joint that has a trace on it on the bottom of the PCB.  If you get zero resistance for any of those solder joints, that's your short.  (Do this with the power OFF.)
   
  Can you be more specific about the "20"?  Was it definitely reading in mV?  Or could it be something much higher?


----------



## BobSaysHi

Quote: 





tomb said:


> One thing you can do to check: put one DMM probe on GND and use the other to touch to every solder joint that has a trace on it on the bottom of the PCB.  If you get zero resistance for any of those solder joints, that's your short.  (Do this with the power OFF.)
> 
> Can you be more specific about the "20"?  Was it definitely reading in mV?  Or could it be something much higher?


 
  it was in mV, however the amp turns off too quickly to be completely sure of the reading. I screwed the trimmers all the way down. After I retouch my joints like you guys suggested I will measure the mV again.
   
  Thanks a lot guys!


----------



## BobSaysHi

I've had no luck. I have tested all the solder points for shorts, desoldered several areas, resoldered the entire board, all with no change. 
   
  Any ideas would be welcome


----------



## jdkJake

Quote: 





tomb said:


> One thing you can do to check: put one DMM probe on GND and use the other to touch to every solder joint that has a trace on it on the bottom of the PCB.  If you get zero resistance for any of those solder joints, that's your short.  (Do this with the power OFF.)


 

 I thought Tom's advice was excellent (see above).
   
  EDIT: Oops! just saw you did that. Before or after you resoldered?


----------



## BobSaysHi

Quote: 





jdkjake said:


> I thought Tom's advice was excellent (see above).
> 
> EDIT: Oops! just saw you did that. Before or after you resoldered?


 

 I tested all the solder joints before and after I desoldered and resoldered. I have been at this since 4:30, it is now 10. I don't think I missed any solder joints.


----------



## jdkJake

Okay. Well, probably best to take a break and pick it up tomorrow.
   
  You still have a short somewhere on the board. Just have to find it. I will take a look at your pictures again once I get back to my big screen.


----------



## BobSaysHi

Quote: 





jdkjake said:


> Okay. Well, probably best to take a break and pick it up tomorrow.
> 
> You still have a short somewhere on the board. Just have to find it. I will take a look at your pictures again once I get back to my big screen.


 

 OK, I'll keep trying tomorrow. My board looks much cleaner now, If I was you I wouldn't bother looking over it again. If I don't find anything tomorrow I will post newer pictures.


----------



## jdkJake

bobsayshi said:


> OK, I'll keep trying tomorrow. My board looks much cleaner now, If I was you I wouldn't bother looking over it again. If I don't find anything tomorrow I will post newer pictures.







 Okay. Standing by for new pics.

 You might want to scan the top components and be sure you do not have any leads touching. Perhaps a resistor touching a cap shell or heatsink or a cap shoved up against a heatsink. Also look at the pins of your transistors and be sure they are not shorting because of a solder blob.


----------



## BobSaysHi

I cant find a short. I've spent longer looking for a short than I did building the thing.
   
  Is it possible that I broke a part? Or perhaps put a cap in backwards? Or put anything in backwards? Does dog hair conduct electricity? If the trimmers are all the way down is it possible the amp could not turn on at all? Do the DIY gods hate me?
   
  Remember, the amp turns on for less than a second and then the leds dim and turn off. If you are still convinced there is a short I'm just going to put it on a shelf and leave it there.


----------



## jdkJake

Nah man, that's half the fun of DIY. Figuring out where you screwed up. 



 It's cool, it happens to everyone. If you must, step aside a day or two, but rest assured, we will figure it out.



 So, have you verified the orientation of all your polarized parts? How about all of your transistors? Can you measure the voltage across the polyfuse and let us know what it measures at?



 Most of all, where are the pictures you promised? You SAID there would be pictures!


----------



## BobSaysHi

It rained 7 inches overnight and my house flooded, I'll have a camera either tomorrow or friday. I have no more time to invest this week. It looks like I have to replace all the carpet in my house. If I sound frustrated about my amp its because of other things. 
   
  edit: It actually rained 8+ inches


----------



## jdkJake

Ouch. Sorry to hear that. 

 Worry about your house and family first. Everything else is secondary.

 We will be here when you are ready.


----------



## BobSaysHi

Quote: 





jdkjake said:


> Ouch. Sorry to hear that.
> 
> Worry about your house and family first. Everything else is secondary.
> 
> We will be here when you are ready.


 

 You guys on head-fi are the nicest people I've had the pleasure of talking to on the internet. Thank you and TomB for your patience. 
	

	
	
		
		

		
		
	


	



   
  I'll try and take pictures on friday, however if I get up to radioshack tomorrow, I will have pictures then.


----------



## tomb

Quote: 





bobsayshi said:


> I cant find a short. I've spent longer looking for a short than I did building the thing.
> 
> Is it possible that I broke a part? Or perhaps put a cap in backwards? Or put anything in backwards? Does dog hair conduct electricity? If the trimmers are all the way down is it possible the amp could not turn on at all? Do the DIY gods hate me?
> 
> Remember, the amp turns on for less than a second and then the leds dim and turn off. If you are still convinced there is a short I'm just going to put it on a shelf and leave it there.


 

 There is always the possibility that you turned the trimmers the wrong way, and it's reacting to too much current pushed through the buffer.
   
  In any event, I agree with Jake - it sounds like you have more important issues to resolve right now.  I hope the damage wasn't too bad, considering - good luck!


----------



## BobSaysHi

Quote: 





tomb said:


> There is always the possibility that you turned the trimmers the wrong way, and it's reacting to too much current pushed through the buffer.
> 
> In any event, I agree with Jake - it sounds like you have more important issues to resolve right now.  I hope the damage wasn't too bad, considering - good luck!


 

 The damage wasn't very bad, and my family finally has an excuse to get new carpet.
   
  The site said to turn the trimmers clockwise till they clicked and I made sure to do that. However, I might not have turned them down the very first time i turned it on (it's been a couple long weeks and i don't remember). Is there any way to check if they are damaged?


----------



## tomb

Quote: 





bobsayshi said:


> The damage wasn't very bad, and my family finally has an excuse to get new carpet.
> 
> The site said to turn the trimmers clockwise till they clicked and I made sure to do that. However, I might not have turned them down the very first time i turned it on (it's been a couple long weeks and i don't remember). Is there any way to check if they are damaged?


 

 Yes - using the ohms feature of your DMM.  Pick one pin of the two that are on the same trace for one probe of the DMM - then place the other probe on the single pin that's not on a trace.  You should be able to measure changes in resistance, depending on how you turn the screw.  All the way clockwise should be 2K on the buffer trimmers, for instance, while all the way counter-clockwise should be 0 ohms.  As long as you can measure changes in resistance from moving the trimmer a couple of turns, then they're OK.  There's no need to turn 25 turns just to see if they'll go to zero, iow.


----------



## FishHead

Well I did a search of the forum and could not find what I was looking for, so be kind if it is already out there.
   
  I am in the middle of soldering up my board and have come to the tube holders.  Now my PCB has a bow to it and I am looking for advice on whether to solder them flush with the board or to solder them so they are even and flat.  I am concerned if I take the even and flat route the tubes will be catywampus if the PCB gets straightened  during the install in the case.
   
  Thanks in Advance!


----------



## tomb

Quote: 





fishhead said:


> Well I did a search of the forum and could not find what I was looking for, so be kind if it is already out there.
> 
> I am in the middle of soldering up my board and have come to the tube holders.  Now my PCB has a bow to it and I am looking for advice on whether to solder them flush with the board or to solder them so they are even and flat.  I am concerned if I take the even and flat route the tubes will be catywampus if the PCB gets straightened  during the install in the case.
> 
> Thanks in Advance!


 

 The bow is minor and as you say, the case mounting will take it out.  IMHO, you should bend the tube socket pins out far enough that they just fail to fit into the holes in the PCB.  That way, the sockets have a force fit into the PCB.  You may even find that with some judicious pin-bending, you can actually adjust the fit so that they're completely flush at the start. 
	

	
	
		
		

		
		
	


	



   
  Put both sockets in this way, then flip the PCB over onto a board.  Press down firmly on the PCB while soldering each pin.  Do this by applying plenty of solder - the holes should be completely filled and the solder should wick up the pins on the top side of the PCB by 1/8 - 1/4".  (Remember that the tube socket joints are just as much mechanical as electrical, so they need a lot of the strength that comes from a well-soldered joint.)  While still holding the solder iron to the joint to keep the solder melted, release the solder in your free hand so that you apply force to the bottom of the PCB, forcing the socket flush to the PCB (it's upside down, remember).  Release the soldering iron while continuing to press down until the solder cools.  Do this alternating from one socket to the other, and from one pin on each socket to the opposite pin on each socket - like alternating lug nuts on a car tire/wheel - until you get all the pins soldered. 
   
  You can lift up the PCB periodically, turn it over, and check for socket level after soldering a pin on each socket, in turn.  If the sockets look out-of-level, then press down slightly in the opposite direction of the out-of-level when you go to solder another pair of pins.  Probably the best description I have of soldering tube sockets into a PCB is in the Build Thread for the Starving Student or on the Starving Student website here:
http://www.diyforums.org/SSMH/SSMHconstruct3.php
   
  The principles remain the same for any PCB tube socket and PCB.
	

	
	
		
		

		
		
	


	



   
   
  P.S. Don't over-obsess about this.  It's nice to have them straight and flush, but you'll find that most tube bases are far from it.  The tube pins can be slightly bent to overcome any out-of-level tube socket.


----------



## FishHead

Thanks for the link. That was what I was looking for.


----------



## FishHead

Finished but not Finished.
   
  v+ to Grnd:   26.5 vdc
   
  All screws turned clockwise until clicking.
  Ta2R to grnd:    20+ VDC  Final value not seen as power button mashed.  
  Ta2L to grnd:    20+ VDC  Final value not seen as power button mashed.
  Tb2R to grnd:    20+ VDC    "       "                                              "'
  Tb2L to grnd:    20 + VDC   "      "                                               "
   
  Pretty Leds light nicely.  No smoke.  No solder bridges seen.  No hot electronic smells (I mash the buttons when 20 VDC arrives).
   

   
   
  Thanks in advance.


----------



## tomb

Quote: 





fishhead said:


> Finished but not Finished.
> 
> v+ to Grnd:   26.5 vdc
> 
> ...


 

 Well, TA2R to GND and TA2L to GND set the tube bias.  Turning the RA5 trimmers all the way clockwise is not going to accomplish anything but increase your frustration when you try to bias the tubes.
   
  As for the Diamond Buffer bias, the measurement is TB2R to TA2R and TB2L to TA2L, not to GROUND.   All you're doing is repeating the measurement of the tube bias by measuring those test points to ground.  Please refer to this page to review what we're trying to bias:
http://www.diyforums.org/MiniMAX/MiniMAXsetup.php
   
  In the case of the buffer, all the test points provide is a measurement across the the RB10 and RB11 resistors.  Either one can be measured to set the bias.  All four resistors are 2.2 ohms.  So, if you measure in mV (you cannot measure milliAmps in this instance), you only need to divide by 2.2 to get the mA of bias through the circuit.  Again, though, you are not measuring to ground when biasing the buffer - only the voltage across the resistors connecting the complementary output transistors in the push-pull arrangement.
   
  So, please  and carefully - set your probes in TA2L and TB2L, turn the power on, note the mV reading, and turn the power off.  If it's less than about 40mV, then that's OK.  Set the probes in TA2R and TB2R and turn the power back on.  If it's less than about 40mV again, then turn the power off.  You're OK and need to turn your attention to biasing the tubes.  Refer to this page again:
http://www.diyforums.org/MiniMAX/MiniMAXsetup.php
   
   
  P.S. Nice stone table, btw.  Also, your work looks very good.  I'm sure once we verify the correct points to measure, you'll be able to get it up and running in no time.


----------



## FishHead

v+ to Grnd:   26.5 vdc

  

 All screws turned clockwise until clicking.

 Ta2R to grnd:    20+ VDC  Final value not seen as power button mashed.  

 Ta2L to grnd:    20+ VDC  Final value not seen as power button mashed.

 Tb2R to grnd:    20+ VDC    "       "                                              "'

 Tb2L to grnd:    20 + VDC   "      "    

  

 Ta2R to Tb2R:  36.4 mv

 Ta2L to Tb2L:  35.7 mv  

  

 I am glad you are smarter than I look.  

  

 We now return you to your regular programming.

 If this was a real emergency ....

 I would have gone and gotten a homebrew!


----------



## tomb

Quote: 





fishhead said:


> v+ to Grnd:   26.5 vdc
> 
> 
> 
> ...


 

 Yep - you look fine on those DB bias points.  You should be free and clear to bias the tubes, etc.  Let us know how it turns out!


----------



## FishHead

Currently 
   
  Ha, I said Currently:
   
  27 v+ to Ground
  23.48 ta2R to Ground
  23.49 ta2L to Ground
  110.1 mv         ta2R to tB2R
  110.1 mv         ta2L to tB2L
   
  No amount of turning RA1l or RA1r is moving the readings.  Temping though it is to attach a drill to the little blue BOURNS tool (a minute or so should prove something),  I would like to try something else first.  
   
  I am open for suggestions:  Oh, and I have had the amp on all day to stabilize temps.  No problems noted.  Amp is fairly cool.


----------



## jdkJake

Have you tried both directions? At least 20 or 30 turns?


----------



## tomb

Another question - are the tubes lit?  Do you see an orange glow in the middle rod of the tubes?  Depending on tube construction, it may only appear as a single point in the top of the rod or at the bottom where the pins are connected to the various internal tube pieces.
   
  Jake is also correct - if you confirm the questions above, then perhaps you haven't moved the trimmers enough.  If you screwed them all the way down clockwise, note that I mentioned earlier that this would only increase your frustration in trying to find the happy medium of the tube adjustment.  You may have to literally turn 20 turns or more in the counter-clockwise direction before you see a response in lowering the voltage.
   
  Check these things out and let us know ...


----------



## FishHead

Yep,  First clockwise until I though I heard a click then I just kept a going while watching the meter.  Nothing changed.
   
  Then I decided to see if anything would change at all. So I turned it the other direction say thirty times.  Nothing changed.
   
  That is when I had the impulse to hook up the electric drill and see what it would do.  Fortunately I fought that urge down.
   
  Since both L and R are doing the same thing I am guessing I did something in the Power supply area.  I am fighting the urge to poke around until cooler more experienced heads point me in the right direction.


----------



## FishHead

Hi Tomb,
   
  The tubes are beautiful.  All blue with a little orange tip glowing.  They are hot to the touch but not burning hot.  The two middle heat sinks are hot to the touch but not burning hot.  The two outside heat sinks are cool and the power supply heat sink is cooler than the tubes but hotter than the outside heat sink.


----------



## FishHead

Well I chucked up the bit and started toward the amp......
   
  Must have scared something loose because I turned it on and no voltage to the Right side.... Must lay of the beer after work.... Check the left side. 23.5 V.  
   
  Well if the right side changed I better check the Mv.    345 mv! dang WAY too much beer after work.  Turn it off.  Mash the power button and re adjust the mv.  110.  Nice
   
  Turn it off yada yada yada.  Adjust what moves.  yada yada.... look!  Now tube voltage goes down if I turn it counter clock wise.  Well what do you know.
   
  Dial everything in.  Come in and type this note and hope it is all good when I go back to check if it was just not a beer hallucination.  (I love spelling checkers)
   
  If you see a picture of a completed box next... all is well.


----------



## jdkJake

What are you using as your ground reference? What point on the board?
   
  EDIT: Hopefully, Never mind!


----------



## tomb

No offense, but I thought counter-clockwise on the tube trimmers was the only way to go ... you cranked them down all the way they'd go clockwise to start.  Based on your description, either you haven't turned them enough counter-clockwise, or you destroyed the RA1 trimmers.  That's because everything you've related so far sounds like *you've built everything correctly*.  So, we're dealing with a little anxiety and lack of patience perhaps?  Just kidding! 
	

	
	
		
		

		
		
	


	




  Let us know what you find when you exercise those tube bias trimmers some more ...  Meanwhile, I'm grabbing another Sierra Nevada Torpedo from the frig ... I'll check for your posts in another short while and hopefully you'll find music at the end of this trial ...


----------



## Beefy

Other consideration...... make sure your volume control is at zero to try and bias the tubes. I found that funky things happen to the bias if you accidentally have the volume up.


----------



## FishHead

Done and in Spec!  Thanks for the advice!
   
  110 mv all around
  13.5 v tubes
  27 v power.
  Now to see how it sounds.


----------



## tomb

Another MiniMAX lives!!


----------



## jdkJake

Sweet.

 That must have been some good beer!


----------



## FishHead

Its new home, breaking in some 701s.
   

   
  People who know me don't believe me when I say I built it.

 But then I explain the support network.
   
  And they still don't believe me...  as I said,  They know me.


----------



## tomb

Quote: 





fishhead said:


> Its new home, breaking in some 701s.
> 
> 
> 
> ...


 

 And we're glad we could help you look so professional in your handiwork. 
	

	
	
		
		

		
			




  It looks right at home on that desktop.


----------



## jdkJake

Looks great!
   
  I assume it sounds as good as it looks?


----------



## BobSaysHi

Hey guys, I'm back. I'm done fiddling with my amp. I simply have no idea what to do and where to look. I need a professional. 
   
  Is there anyone I can send it to to figure out whats wrong with it? Or could my local electronics shop fix it?


----------



## jdkJake

Giving up on her already, huh?

 Well, sorry to hear that. I was hoping we could walk you though it and get it up and running. However, I understand, you have to be willing to do it, or what is the point.

 Not sure who could fix it for you. I am in the middle of another project (actually two), so, I really cannot take it on right now. Maybe in a few weeks. I would love for you to hear what that great little amp is capable of.


----------



## ShinyFalcon

BobSaysHi, where in Texas are you located?


----------



## tomb

Quote: 





> Originally Posted by *jdkJake* /img/forum/go_quote.gif
> 
> Giving up on her already, huh?
> 
> ...


 
   
  Quote: 





shinyfalcon said:


> BobSaysHi, where in Texas are you located?


 


 Not to worry - we've found someone who's going to help BobSaysHi.


----------



## tomb

Quote: 





bobsayshi said:


> Hey guys, I'm back. I'm done fiddling with my amp. I simply have no idea what to do and where to look. I need a professional.
> 
> Is there anyone I can send it to to figure out whats wrong with it? Or could my local electronics shop fix it?


 

 Just a preliminary look, BobSaysHi, but you've got several resistors mixed up in the primary tube circuit and CCS sections.  That may be more than enough to cause the high-current drain.  I'll keep studying it and let you know the specifics when I find them.
   
  EDIT: It appears that the resistors are mixed up everywhere.  Just as a gentle reminder for future reference for everyone, item #3 in the MiniMAX notes included with each kit states the following: _"3. _[size=11pt]_... Despite what package the resistors are in, they may all be different.  Make certain you either measure them or you understand the exponential notation of the rating."_[/size]
   
  [size=11pt]To make this even clearer, I'm editing the MiniMAX Notes to read as follows:[/size]
_[size=11pt][size=medium]3. Please, please, please – install the V-D resistors (the little brown ones) so that the rating (the exponential numbers) is visible from the top of the board.  Despite what package the resistors are in, they may all be different values.  *You must select the correct value resistor and match it up with the correct designation on the PCB*.  Make certain you either measure them or you understand the exponential notation of the rating.  A 1K resistor will show “1001F.”  A 100R resistor will show “1000F.”  1M is “1004.”  The notation works by 100 multiplied by 10 to the power of the last number.  Smaller resistances such as 10R are shown as “10R2” (actually 10.2 ohms) or something similar.[/size][/size]_
   
  [size=11pt] This is going to take me awhile, BobSaysHi ... [/size]


----------



## BobSaysHi

Quote: 





tomb said:


> Just a preliminary look, BobSaysHi, but you've got several resistors mixed up in the primary tube circuit and CCS sections.  That may be more than enough to cause the high-current drain.  I'll keep studying it and let you know the specifics when I find them.
> 
> EDIT: It appears that the resistors are mixed up everywhere.  Just as a gentle reminder for future reference for everyone, item #3 in the MiniMAX notes included with each kit states the following: _"3. _[size=11pt]_... Despite what package the resistors are in, they may all be different.  Make certain you either measure them or you understand the exponential notation of the rating."_[/size]
> 
> ...


 
   
  Oh, well that would explain why it wasn't working. 
	

	
	
		
		

		
		
	


	



   
  That is definitely what I did wrong. I didn't think to check the values when they were in the packages. 
	

	
	
		
		

		
		
	


	



   
  I didn't make it easy for you either, and I apologize for that.


----------



## tomb

Quote: 





bobsayshi said:


> Oh, well that would explain why it wasn't working.
> 
> 
> 
> ...


 

 's all right - just give me time.
	

	
	
		
		

		
		
	


	



   
  P.S. Funny thing is ... I could've sworn we asked you to confirm the resistor values.


----------



## rayk

I finished building my miniMAX last night, and have taken some measurements - for some reason the tube bias won't budge from around 23V  no matter how much I turn the trimms.

 The power supply is biased to 27V, both DB are sitting at around 90mV. I'm using the 12FK6 tubes atm, I have some 12FM6s aswell which I haven't tried yet.
   
  Cheers!


----------



## tomb

Quote: 





rayk said:


> I finished building my miniMAX last night, and have taken some measurements - for some reason the tube bias won't budge from around 23V  no matter how much I turn the trimms.
> 
> The power supply is biased to 27V, both DB are sitting at around 90mV. I'm using the 12FK6 tubes atm, I have some 12FM6s aswell which I haven't tried yet.
> 
> Cheers!


 

 Some questions -
  1. Are the tubes lit?  Do they get warm?
  2. How many turns on the RA1 trimmers have you tried?  Note that those trimmers are picked for 3 types of tubes with widely varying gains.  That means for one tube type, you may have bias adjustment in the first 3 or 4 turns.  For a different tube type, it might be 3 or 4 turns somewhere in the middle of the 25-turn(!) trimmers.  For the third tube type (out of 12AE6, 12FK6, 12FM6), it might be the last 3 or 5 turns out 25.
   
  Granted, that's an exagerration to illustrate the example, but hopefully you get the point - don't give up on turning the trimmers.  it's somewhat difficult, but another thing you can check is the trimmers themselves.  Put a DMM probe on the un-traced pin of a trimmer on the bottom of the PCB, then place the other probe on one of the two pins that are on the trace.  Measure the resistance (all of this with the power off!), turn the trimmer 5 turns or more, then measure again.  If you see an obvious change in resistance, then they're OK.  Note that you may need to try turning in both directions when making this measurement if the trimmer happens to be at the end of its travel when you start.
   
  Try those things and then let us know what's going on.


----------



## rayk

Yep the tubes get warm and light up. I think I'm about 25 turns or so, so I will try checking the trimmers tonight. Haven't tested the amp for sound yet either  
	

	
	
		
		

		
		
	


	




 - I think it was on for a total of 30minutes, so not sure if the tubes are still breaking in (first time dealing with a tube amp) 
	

	
	
		
		

		
		
	


	



   
  Cheers Tom for quick reply!


----------



## tomb

Quote: 





rayk said:


> Yep the tubes get warm and light up. I think I'm about 25 turns or so, so I will try checking the trimmers tonight. Haven't tested the amp for sound yet either
> 
> 
> 
> ...


 

 Well, if the bias is at 23V, you're probably not going to get any sound.  Breaking in tubes may change the bias by a few volts, but not that much.  The tube part of the amplifier circuit is very simple, though, so my guess is that there's nothing bad wrong - especially if you already have the DB's biased to 90mV.  My guess is that you haven't turned the trimmers enough or in the right direction.


----------



## FishHead

I can feel your pain.  If you go back a page 118 you can see I experienced the same problem.   I metered the bias while turning the pot and I think that got me started turning it the right direction.
  Clockwise, Counter-clockwise...it is just all so confusing.  The meter knows best.  Two other bits of advice I received which may or may not help.  Have the volume turned all the way down and let the amp warm up a little.  I think I left mine on overnight w/ no inputs.
   
  I just checked and Counter-clockwise is reducing the bias voltage on mine.


----------



## rayk

Turns out ("snicker") I had o turn the trimmers counter clock wise. Got them around 13.5V, powersupply at 27V and DBs running at around 109mV.
   
  Posted the finished build in the other thread - http://www.head-fi.org/forum/thread/85561/post-pics-of-your-builds/7320#post_6975938
   
  Thank you for all the support Tom! And for making such a well put together kit 
	

	
	
		
		

		
			





!


----------



## tomb

Quote: 





rayk said:


> Turns out ("snicker") I had o turn the trimmers counter clock wise. Got them around 13.5V, powersupply at 27V and DBs running at around 109mV.
> 
> Posted the finished build in the other thread - http://www.head-fi.org/forum/thread/85561/post-pics-of-your-builds/7320#post_6975938
> 
> ...


 

 Yay!!  Way to go!


----------



## BlingBlingDr

I built one of these bad boys about a year ago and am in the market for a new pair of headphones.  Anyone match a pair of ATH-M50 headphones with a Minimax?  I have the Grado S80s, but the bass can be underwhelming. 
   
  Update: Went ahead an bought 'em.  Couldn't help myself.  I will let your know my impressions in comparison to the S80s.
   
  PS: When is Beezar gonna come out with another big project for me to sink my teeth/soldering iron into?


----------



## jdkJake

Quote: 





blingblingdr said:


> I built one of these bad boys about a year ago and am in the market for a new pair of headphones.  Anyone match a pair of ATH-M50 headphones with a Minimax?  I have the Grado S80s, but the bass can be underwhelming.
> 
> Update: Went ahead an bought 'em.  Couldn't help myself.  I will let your know my impressions in comparison to the S80s.
> 
> PS: When is Beezar gonna come out with another big project for me to sink my teeth/soldering iron into?


 

 Build a MOSFET-MAX and those Grado's will sing! You will not ever complain for lack of bass.


----------



## tomb

Quote:


			
				BlingBlingDr said:
			
		

> PS: When is Beezar gonna come out with another big project for me to sink my teeth/soldering iron into?


  Beezar is working on a big project and has been for a several months.
	

	
	
		
		

		
		
	


	




  Those of you that venture to that other forum (head-c*se) or have been to CanJam may be familiar with it.  It's had some growing pains, but the potential is enormous.  I'm hopeful that Dsavitsk and Beezar will have something to announce eventually that should interest a lot of people.  It's definitely unique and has not been something that's done in DIY on a large scale or kit basis up till now.  Just remember the name, "Torpedo."


----------



## jdkJake

And TomB isn't talking about an IPA from Chico CA!


----------



## BlingBlingDr

I am considering using my Minimax as a pre-amp. What should I take into consideration when doing this? I have read about output and input impedance considerations, but don't know exactly what I should be looking at. When it is time to build another headphone amp, I might modify my Minimax with RCA outs for use as a pre-amp. For the time being, I am just thinking of using the headphone out. Any thoughts? Thanks.


----------



## tomb

Quote: 





blingblingdr said:


> I am considering using my Minimax as a pre-amp. What should I take into consideration when doing this? I have read about output and input impedance considerations, but don't know exactly what I should be looking at. When it is time to build another headphone amp, I might modify my Minimax with RCA outs for use as a pre-amp. For the time being, I am just thinking of using the headphone out. Any thoughts? Thanks.


 

 Just keep the gain low.  The concern is that you can overdrive the inputs to a power amp.  12FK6 tubes might help in that regard.  There are several of us that have used the MAX/MiniMAX as a preamp.  It does well as long as you're careful about that gain.


----------



## tomb

Well, I'm embarassed at how long this took (why I don't offer it very often), but we now have music from BobSaysHi's MiniMAX:
    


   
  I'll be shipping it back to him tomorrow.  Meanwhile, the problem had to do with many resistors that were installed in the wrong places.  This has happened to new MiniMAX builders more than once.  I've since added some additional warning notes to the notes included with kits and also made notes on the resistor parts bags that they are not the same and the values must be checked before locating them on the PCB!
   
  P.S. Much to my chagrin, I actually swapped locations on the CCS resistors while fixing this.  I should've made myself some notes!


----------



## gspence2000

TomB, what is that object on the right side of the photo?  It doesn't look like a MiniMAX--can you tell us a little about it?


----------



## Beefy

That is the Torpedo. Been mentioned a few times......


----------



## BobSaysHi

Quote: 





tomb said:


> Well, I'm embarassed at how long this took (why I don't offer it very often), but we now have music from BobSaysHi's MiniMAX:
> 
> 
> 
> ...


----------



## jdkJake

BobSaysHi, you are a very fortunate individual.

 TomB, nice shot of the torpedo. Based upon what I have been reading, that project is progressing nicely. A very interesting design for sure.


----------



## tomb

Quote: 





jdkjake said:


> BobSaysHi, you are a very fortunate individual.
> 
> TomB, nice shot of the torpedo. Based upon what I have been reading, that project is progressing nicely. A very interesting design for sure.


 

 Yes - some early toothing pains, but it's consistently improving thanks to Dsavitsk's expertise and some really great prototype builders.  It's already suitably impressive and fixing to get better with the latest refinement, thanks to a suggestion from cetoole, of all people.


----------



## BobSaysHi

Hey guys, quick question about the tube bias.
   
  When I turn the amp on the bias is ~14.5 V. It takes about an hour to get down within good levels. This is normal right? Nothing for me to be concerned about?
   
  Also, this amp sounds absolutely awesome with my dt880s, and my new hd650s are coming today and I cant wait to hear them. Thanks tomb, for helping me out.


----------



## Beefy

That sounds all good, Bob.


----------



## BobSaysHi

I figured. I just like to be cautious.
   
  HD650s are here. Sounds fan-freaking-tastic.


----------



## tomb

Great to hear, Bob!  As Beefy confirmed, it takes about an hour or so before the bias quits dropping.  What you describe is *perfectly normal*.  Those 12AE6's make a good pairing with Sennheisers.


----------



## jdkJake

Quote:  





> Those 12AE6's make a good pairing with Sennheisers.


 


  Ain't that the truth!


----------



## nate911

Sorry if I'm reviving an older thread, but I just finished my Minimax (connected to a grubDAC)--sounds amazing!
  I had some problems drilling out the tube sockets but tomb helped me out (I ordered his kit).
  I had a fun time building this amp; thanks for a great kit and amp. Here are some pics:


----------



## tomb

Quote: 





nate911 said:


> Sorry if I'm reviving an older thread, but I just finished my Minimax (connected to a grubDAC)--sounds amazing!
> I had some problems drilling out the tube sockets but tomb helped me out (I ordered his kit).
> I had a fun time building this amp; thanks for a great kit and amp. Here are some pics:


 

 Nice work, Nate!  Those are great pics with the tube lighting, too!


----------



## jdkJake

nate911 said:


> Sorry if I'm reviving an older thread, but I just finished my Minimax (connected to a grubDAC)--sounds amazing!





Never feel you need to apologize for resurrecting a build thread with a new build.

It is always a great day when a new amp comes to life! Congrats!


----------



## nate911

Quote: 





> Originally Posted by *tomb* /img/forum/go_quote.gif
> 
> 
> Nice work, Nate!  Those are great pics with the tube lighting, too!


 

 Thanks! Yea I snapped some good pics, beautiful amp and case.
   

 Quote:


jdkjake said:


> Never feel you need to apologize for resurrecting a build thread with a new build.It is always a great day when a new amp comes to life! Congrats!


 

 Indeed, thanks!


----------



## FallenAngel

Getting a weird DB bias with my latest build - can't set DB bias on one channel lower than 135mV, while the other one I can set normally to 80mV.  I think the soldering job is fine, but I didn't match the transistors very well.
   
  Perhaps the PN4392 is burned, otherwise, the 2K trimpot inline with 100R is still too high...  Maybe the CSS transistors are poorly matched, but I wasn't expecting it to have such crazy results...


----------



## tomb

Quote: 





fallenangel said:


> Getting a weird DB bias with my latest build - can't set DB bias on one channel lower than 135mV, while the other one I can set normally to 80mV.  I think the soldering job is fine, but I didn't match the transistors very well.
> 
> Perhaps the PN4392 is burned, otherwise, the 2K trimpot inline with 100R is still too high...  Maybe the CSS transistors are poorly matched, but I wasn't expecting it to have such crazy results...


 

 You're correct.  Miss-matched transistors are not going to prevent you from turning down the bias below 135mV and the CCS transistors are not going to have an effect on this (unless they're 5088's or something really weird).  I suspect something else is going on - bad trimmer, bad PN4392 as you suggest (although that implies zero bias), or maybe you misplaced a resistor.  It should be easy to compare with the good channel, just be very methodical.  It's almost like proof-reading our own essay paper: it's really hard to see our own mistakes (assuming that's it, that is).  Let us know what you find.


----------



## tomb

BTW, I was planning on making a bigger announcement (with some SASE freebies from Beezar), but I've started supplying 1.15K and 11.5K resistors for the CCS (RA8 and RA9 - L/R).  It brings the CCS current down to 0.565ma and cuts the distortion in half.  IMHO, the difference is easily noticed in the listening.  I never thought that little bit of change (the original MiniMAX was 0.650ma) would make that much of a difference.  However, after working with Dsavitsk's Torpedo prototype over the last year, he's taught me that small changes in the CCS can have a big effect.  I've tested with RMAA extensively, before and after - with old CCS and new CCS currents, and the 1.15K/11.5K resistors make a real difference.\
   
   
  EDIT: Dang, I thought I clicked to edit the post above.  Oh, well ...


----------



## tomb

Oops!  I knew I shouldn't have posted that from memory!  The distortion on the MiniMAX is improved by about 1/3 (still audible, IMHO).  The MOSFET-MAX's distortion is the one that's cut in half.  Regardless, major improvements either way with either amp.  Of course, the optimum loads still apply - MiniMAX is best for all-around and high impedance and the MOSFET-MAX does best with low impedance.


----------



## MrDavis

Quote: 





tomb said:


> Oops!  I knew I shouldn't have posted that from memory!  The distortion on the MiniMAX is improved by about 1/3 (still audible, IMHO).  The MOSFET-MAX's distortion is the one that's cut in half.  Regardless, major improvements either way with either amp.  Of course, the optimum loads still apply - MiniMAX is best for all-around and high impedance and the MOSFET-MAX does best with low impedance.


 
   
  I'm still a noob at this, so I just want to make sure I'm ordering the correct resistors.
   
  1.15 KOhms
  http://www.mouser.com/Search/ProductDetail.aspx?R=RN55D1151FB14virtualkey61300000virtualkey71-RN55D1151F
   
  11.5 KOhms
  http://www.mouser.com/Search/ProductDetail.aspx?R=RN55D1152FB14virtualkey61300000virtualkey71-RN55D1152F


----------



## tomb

Quote: 





mrdavis said:


> Quote:
> 
> 
> 
> ...


 

 Yes - those are absolutely correct.  BTW, if you send Beezar an SASE - I'll send them to you for no extra charge.


----------



## slowpogo

Quote: 





tomb said:


> Yes - those are absolutely correct.  BTW, if you send Beezar an SASE - I'll send them to you for no extra charge.


 

 Would this change in the CCS resistors also help the older BJT Millett Max, which I have? If so, I might take you up on that (typically) kind offer.


----------



## MrDavis

Quote: 





tomb said:


> Quote:
> 
> 
> 
> ...


 
   
  I have to order a few more parts from you that I forgot to include in my last order.  I add it to the order notes section.  Thanks tomb.


----------



## H22

That is interesting, on my MOSFET max I used The 1.13 and 11.3, should be sorta close....


----------



## jdkJake

h22 said:


> AThat is interesting, on my MOSFET max I used The 1.13 and 11.3, should be sorta close....





Within 2%. I would not worry about it.

Depending upon the tolerance of the resistors you used, you might be there already.


----------



## Gotez

I just finished soldering my Millitt Minimax. However, when I tried to turn the amp on for biasing the fuse blew immediately. I have checked al parts and solder joints and I do not seem to have any shortages or parts mixed up. I did however turn all trimpots 20 turns clockwise. Could it be a problem that I also turned the power supply and tube bias trimmers down? Should I turn these back up?
   
  Thank you in advance, I’ll take some pictures when it is working (or when I need further help )


----------



## Beefy

Try firing it up without tubes in. That cuts out the heaters and the buffer current should be way down low.


----------



## Gotez

Thank you,
   
  I will try this. If this works next steps would be:
   
  Bias buffer
  Put tubes back
  Bias PS
  Bias Tubes
   
  right?


----------



## Gotez

It's Alive!!!!
   
  Changed the fuse for a 1.25A fuse and biased the buffer and tubes. Sound is delicious and very addicting.
   
  Many thanks to Beefy and of course Tomb. His service and help are outstanding!
   
  Will post pictures soon!


----------



## Gotez

Van Millitt MiniMax​
   
   

 

Van Millitt MiniMax​
   
  As promised!


----------



## TomForshaw

I'm about to start mine - can't wait!
   
  As I don't have a suitable AC supply (I'm in the UK), I'll be using a 32V 70W HP SMPS I managed to get for the bargain price of free - going to match transistors tomorrow and hopefully start the build this week. Very excited


----------



## FallenAngel

Uhm... that might not be a great idea...


----------



## TomForshaw

Could you elaborate? Voltage should be about the same 24V AC supply, so i'm planning to go into the regulator after the decoupling caps as per the schematic. Only change will be the rectifier section (DR1A jumpered, the rest unpopulated).


----------



## tomb

Quote: 





tomforshaw said:


> Could you elaborate? Voltage should be about the same 24V AC supply, so i'm planning to go into the regulator after the decoupling caps as per the schematic. Only change will be the rectifier section (DR1A jumpered, the rest unpopulated).


 

 I'm not saying you can't do it, but there are a lot of factors to consider that may affect the proper operation of the amp.  A lot of it depends on whether you plan to utilize all those volts, or whether you plan on trying to regulate down to 27VDC, the recommended setting for the PS on the MiniMAX.
   
If you plan on using the 32V - 
  You only need a couple of volts from the LM317 to keep the voltage in regulation.  However, there is a physical limitation on the tube heaters.  Anything over 30V supplied to the amp circuit will lower the life expectancy of the tubes.  You'll need to resize R1 - there is a tweak page on the MiniMAX website with a graph that will show you how to do this: http://www.diyforums.org/MiniMAX/MiniMAXheaterResistor.php
   
  Plus, I'm not sure how the LM317 circuit will react when fed from an SMPS.  It's quite possible that you'll be injecting a lot of high-frequency hash into the amplifier circuit that's not there with an unregulated, non-switching voltage source.  All of the filtering occurs before the LM317, so if you're bypassing all of that, it may adversely affect the sound quality of the amp. 
   
If you plan on regulating down to 27VDC -
  Linear regulation is superior for sound quality.  However, it's very wasteful from an energy perspective and things get hot fast.  The 1" tall heat sinks used in the MiniMAX may not be enough to knock down the voltage that far.  Since the custom case is only 1" tall, that's your limit with the heat sink - but it may not be enough.


----------



## TomForshaw

Thanks Tomb. I was planning on retaining the regulator - it sounds like the best way to go and a lot of thought seems to have gone into the design.
   
  I just measured the SMPS - it's 29.8V unloaded - I suppose that may change when it's driving something, but if it's around there that would reduce the work somewhat that the regulator has to do - and the heat that gets burned off in the case. Hopefully 3V of overhead will be enough for the regulator - sounds like it might be pushing it a bit, but that can be adjusted later if it's not happy. 
   
  Tempted to give it a try as it's what I've got on hand...
   
  I'll check the supply on an oscilloscope, but there seems to be plenty of supply decoupling - although I'm tempted to retain CR3B as well to help block out a bit more of the potential high frequency noise.


----------



## TomForshaw




----------



## tomb

Looks good so far!


----------



## TomForshaw

Thanks - I just wanted to congratulate on the quality of the kit and documentation by the way - it's truly excellent.
   
  I'm going to leave it where it is for today because I want to savour the build.


----------



## TomForshaw

Progress! Drilled out the tube sockets - was a bit scary but not as bad as I'd imagined. Glue them back together they seem to be fine. They haven't fallen apart yet...
   
  Sorry about the shoddy pictures...promise better ones when it's a bit lighter 
   

   

   

   

   
  ...done!
   
  I'm fairly sure that's everything, apart from the rectifiers of course. Hoping to get it tested over the weekend...
   
  Edit: Gratuitous tube shot...


----------



## Gotez

Clean up your desk 
   
  Why did you decide to add the rectifiers last?
   
  BTW: I would like to buy extra tubes for the Minimax, how important is it that they are matched? Few ebay seller provide matched tubes! I am testing the 12FK6 tubes now, and plan to try the 12FM6 tubes tonight.


----------



## TomForshaw

Haha it's got pretty hideous lately! Since I spilled about a million washers/lock nuts the mess seems to have defeated me...
   
  Not sure if you can see it but I'm not actually using the rectifiers - instead I'll be using a big SMPS from a printer which I found as the plug-in AC supply won't work over here. Instead you can see one of the positions is jumpered - I've added one of the little filter caps to try to tame any potential high frequency noise. My Dad has handily informed me that the ripple rejection of the 317 is still around 60dB at 50kHz (though I'm not sure what the switching frequency actually is) so I'm hoping the capacitors will do the rest. 
   
  I'm hoping to get it boxed up and biased over the weekend. Yay!


----------



## jdkJake

gotez said:


> I would like to buy extra tubes for the Minimax, how important is it that they are matched? Few ebay seller provide matched tubes! I am testing the 12FK6 tubes now, and plan to try the 12FM6 tubes tonight.




Without starting a religious war, matching is nice to have, but, probably not essential. IMO, it really depends more upon whether the tubes are of the same construction and same manufacturing lot. If you can get a matched set without spending a fortune then I would do it, otherwise I would not worry about it too much.

As for tubes, I generally prefer to stay away from eBay. Especially for millett tubes. Both Beezar (http://www.beezar.com/) and Radio Electric (http://www.vacuumtubes.net/) will sell you all the matched pairs you can handle at a fair price and stand behind the sale. I have dealt successfully with both and can recommend either.


----------



## Gotez

Quote: 





jdkjake said:


> Quote:
> 
> 
> 
> ...


 
   
  I have dealt with Beezar and I very content with the service. I have purchased two sets of valves there. I would however like to try different brands and makes. I will check Radio Electric. Thank you for the advice.


----------



## the_equalizer

So, a bit of a strange question... about a year ago, when I built my MiniMax, I just did not feel like cutting the pot's shaft to proper length. Now, it's starting to become irksome to see the knob kind of 'hanging in the air'.
   
  Is there a high risk of damaging the pot (or some other component. Maybe the relay?) if I use my Dremel to cut the shaft with the amp assembled  (I'd remove the tubes, of course) ?
   
  cheers!


----------



## MrDavis

Yes, it can be done.  The directions are right here: http://www.diyforums.org/MiniMAX/MiniMAXwiring.php
   
  Its on the bottom of the page.  Item #10 under Assembly.
  
  Quote: 





the_equalizer said:


> So, a bit of a strange question... about a year ago, when I built my MiniMax, I just did not feel like cutting the pot's shaft to proper length. Now, it's starting to become irksome to see the knob kind of 'hanging in the air'.
> 
> Is there a high risk of damaging the pot (or some other component. Maybe the relay?) if I use my Dremel to cut the shaft with the amp assembled  (I'd remove the tubes, of course) ?
> 
> cheers!


----------



## the_equalizer

Thanks for pointing that out! It's been so long since I read those directions that I didn't recall that fragment at all.
   
  cheers!


----------



## TomForshaw

Hooray! It's alive!
   
  Did the wiring on Friday - biased it today. I'll get some images up - but it sounds great.
   
  As in really, really fantastic! I'm blown away by how natural it sounds - it's astonishingly good. My favourite thing I've built.
   
  Also, there's no obvious problem using the DC supply - no noise or any nasties like that. I love it!


----------



## tomb

Quote: 





tomforshaw said:


> Hooray! It's alive!
> 
> Did the wiring on Friday - biased it today. I'll get some images up - but it sounds great.
> 
> ...


 

 Glad to hear it!  Looking forward to your pics!


----------



## TomForshaw

Running the tubes at 13.5V with the buffer voltages at 110mV (so 50mA?) and it's sounding fantastic 
   
  Had a bit of a scare when measuring the buffer as I misread the instructions and measured relative to ground rather than the correct reference point. I measured rather more than ~30mV...turned it off pretty quickly! Once I'd figured out where I was actually supposed to measure it from though they were both at 27mV.
   
  I was wondering, would it be possible to make the amp run as class AB with the buffers wound all the way back, or would I still need to burn my headphones and ruin my hearing to make it come out of class A? I'm not sure what the usual amount of power is when listening...
   
  The thing that really grabbed me is the extension at both ends - I was expecting a nice top end, but the bass is fantastic too. I'm using Alessandro MS1s and the bass really sounds great. The positioning is really something too - can't see me ever getting rid of it.
   
  It's a lovely sounding thing though. I wasn't expecting it to sound as noticeably better as it does (if that makes any sense...). Here it is playing with my DAC - seems like a great combination:
   

   

   
  As you may be able to see, I haven't put the nut into the headphone jack - it seems quite stiff and I'm reluctant to really go for it and wrench it down as the socket is plastic. Any other builders found it to put up a bit of a fight?


----------



## tomb

I'm not sure what's going on with your headphone jack.  Sometimes the front plate has to be tourqued on a bit, depending on the height at which you soldered the headphone jack and volume pot.  That's somewhat of a variable whereas the case screws do not vary at all.  If that's the situation, it could be torquing the headphone jack a bit, causing the inside threads to deform slightly, making the ferrule difficult to screw in.  Try loosening the front plate screws so that the front plate can wiggle a bit, then see if that makes it easier to screw in the ferrule.
   
  Everything else sounds normal from your description.  As for power/Class A/Class A/B, the whole point of most DIY headphone amps is to run them in Class A.  You get the best sound possible from the circuit, because the transistors never have to switch on to respond to a musical peak (they're always on), causing switching distortion.  The amount of Class A needed depends on the headphone load - but 50ma on the MiniMAX is what it's designed for, heat rejection-wise.  It's tough for commercial amps to utilize Class A because of energy standards or simply not wanting to make the investment in heat sinks and cooling.
   
  As for your headphones - they're only going to draw whatever power they need, not any more than that.


----------



## TomForshaw

Thanks Tomb.
   
  I was just inquisitive to see if I could hear a difference between class A and AB, but I guess it'd need to be insanely loud to get enough current flowing to pull it out of class A. I'll try loosening the panel a bit. It goes in a little way, just not all the way down - though it feels like it would if I gave it the beans with a spanner or something.


----------



## tomb

Quote: 





tomforshaw said:


> Thanks Tomb.
> 
> I was just inquisitive to see if I could hear a difference between class A and AB, but I guess it'd need to be insanely loud to get enough current flowing to pull it out of class A. I'll try loosening the panel a bit. It goes in a little way, just not all the way down - though it feels like it would if I gave it the beans with a spanner or something.


 

 Are you using the finishing washer?  That thing is thick and tapered - it's easy to recognize.  If you're trying to screw the ferrule in without it, I'm not sure the threads go that deep.  Just a thought ...


----------



## jdkJake

Nice build TomForshaw! 
   
  The miniMAX is a great little amp that continues to delight. I pulled mine out last night after a lengthy absence. I had forgotten how good it can sound. A fun night of listening for sure.
   
  Enjoy your amp, I know you will! 
	

	
	
		
		

		
			




   
   
  BTW: That tube picture turned out great. Nice shot!


----------



## Ikarios

Bringing this thread back up from the depths because I just received my MiniMAX and, like I've always suspected, it's one freakin' gorgeous piece of kit. TomB has really outdone himself on this one with the custom Lansing case (I know, I'm late to the party). I'll have to read through some of the the thread to get an idea of what biasing is all about, and how to go about swapping tubes if I need to.


----------



## the_equalizer

Have fun building the MiniMAX, Aflac. It's as fun to build as it is to listen to. I absolutely love mine!


----------



## Ikarios

Quote: 





the_equalizer said:


> Have fun building the MiniMAX, Aflac. It's as fun to build as it is to listen to. I absolutely love mine!


 

 I should mention that I bought mine used on the FS Forums, so it's pre-constructed... so I miss out on the building experience  I don't have time to solder at school anymore however and I don't have access to a decent iron at home anymore, so maybe it's for the best. I guess I won't have to deal with biasing (which looks somewhat complicated) so that's a plus.


----------



## jdkJake

Congrats on the purchase.
   
  Biasing the tubes is straightforward. You will have to most likely re-bias every time you roll a set of tubes. BTW, even biasing the BJT's is not too bad, you just have to remove the board from the case.
   
  I would suggest you at least verify the tube bias. The BJTs being out of bias is a bit more subtle. I bought mine pre-built as well (from Whiplash) and the BJT bias was quite a bit lower than optimal. Everything being "in spec" just brings out all it has too offer.


----------



## berserkir

Phew, finished my build. Thanks to TomB for great service & product.
  This one is with 1000&470 uF Silmics at soundpath and 0.22uF Vit-Q.


----------



## tomb

Another MiniMAX lives! 
	

	
	
		
		

		
		
	


	



   
  That's a very nice DIY-enclosure implementation.  You don't see that very often with a MiniMAX PCB, since the "normal" build uses the Beezar/Lansing custom case.


----------



## tomb

Just an FYI, but the MiniMAX is now laser-etched with a new design on the endplates:


  No more silkscreen that might rub or scrape off while you're DIY-ing all the wiring and connectors in the back.  The etching is absolutely permanent (and more detailed!)  The knob is very slightly smaller in diameter, too.  I think it makes for a neater package.


----------



## Yaka

do they just replace the old ones? and can we buy just the plates?


----------



## tomb

Quote: 





yaka said:


> do they just replace the old ones? and can we buy just the plates?


 
  Yes and No.  If there's some sort of demand for just new plates on existing MiniMAXes, I might consider selling them separately - after ordering another manufacturing run, anodizing them, and then having them laser-etched.  Naturally, that's quite a hurdle.  So, the intent is just that people who buy MiniMAX kits from now on will get the updated plates.  There are no extras.
   
  Cars have major style changes every few years, amps can too, can't they?


----------



## vixr

Quote: 





tomb said:


> Yes and No.  If there's some sort of demand for just new plates on existing MiniMAXes, I might consider selling them separately - after ordering another manufacturing run, anodizing them, and then having them laser-etched.  Naturally, that's quite a hurdle.  So, the intent is just that people who buy MiniMAX kits from now on will get the updated plates.  There are no extras.
> 
> Cars have major style changes every few years, amps can too, can't they?


 
  which just made my original un-built Mini a collectors item...


----------



## Za'afiel

Nice new panels there tomb. Looking forward to more refreshing updates on the MiniMAX.


----------



## lordearl

How does this amp sound with low impedance headphones?  I have a pair of KRK KNS8400 (36 ohms) which are just waiting to be paired with a hybrid amp......


----------



## tomb

Quote: 





lordearl said:


> How does this amp sound with low impedance headphones?  I have a pair of KRK KNS8400 (36 ohms) which are just waiting to be paired with a hybrid amp......


 
  Well, I can't tell you about those specific headphones, but the MiniMAX is designed to handle both low-impedance and high-impedance headphones.  It can pulse 50-75 ma Class A current (depending on bias setting) without sending the output transistors into a switching mode.  At the same time, the tubes and power supply give it a potential 13.5V swing in voltage to handle high-impedance.  I would recommend that you use 12FK6 tubes for low impedance, though (there are three total tube types that can be used with the MiniMAX).  The 12FK6's are the lowest gain tubes and that will allow more current for a given voltage with a low-impedance load.


----------



## mol

Hi, I have a MiniMax kit from Beezar.com that has been sitting in my stuff to do pile for a while.  In the meantime I was busy getting married and renovating an apartment to move into.  It's probably been sitting untouched for 3+ years.  Are the electrolytic caps still good to use or should I replace them?  Any other parts that might have limited shelf live?
  
  Thanks for any advice.


----------



## lordearl

Quote: 





tomb said:


> Well, I can't tell you about those specific headphones, but the MiniMAX is designed to handle both low-impedance and high-impedance headphones.


 
   
  I recall reading somewhere that the amp sounds great with Grado/Alessandro headphones - is there any model in particular?


----------



## tomb

Quote: 





lordearl said:


> I recall reading somewhere that the amp sounds great with Grado/Alessandro headphones - is there any model in particular?


 
  No - Grados have a fairly distinct family sound that's pretty consistent.  If it sounds good with one model, it should sound good with all of them.


----------



## lordearl

Quote: 





mol said:


> It's probably been sitting untouched for 3+ years.  Are the electrolytic caps still good to use or should I replace them?  Any other parts that might have limited shelf live?


 
   
  That should be fine I'd have thought (think about NOS capacitors and tubes, some have been laying around for over 50 years!!)


----------



## mol

Quote: 





lordearl said:


> That should be fine I'd have thought (think about NOS capacitors and tubes, some have been laying around for over 50 years!!)


 
   

 Thanks, I guess I will go ahead and build the amp.  I had heard of electrolytic caps going bad after being left on the shelf for a while, but was unsure how long was too long.


----------



## lordearl

tomb said:


> No - Grados have a fairly distinct family sound that's pretty consistent.  If it sounds good with one model, it should sound good with all of them.




Any other headphone recommendations for pairing with the minimax? I live in quite a remote area so will be ordering some headphones without listening. I tend to like a flat response with smooth treble.


----------



## tomb

Quote: 





lordearl said:


> Any other headphone recommendations for pairing with the minimax? I live in quite a remote area so will be ordering some headphones without listening. I tend to like a flat response with smooth treble.


 
  Well, the thing about the MiniMAX is that it does well with almost all headphones between 32 and 300 ohms.  It will even do a great job with the Sennheiser HD580/600/650.  For Grados, it has pretty decent current capability at low impedances with the 50-75ma Class A bias.  At the same time, if you adjust the tube bias for maximum voltage swing, you have + or - 13.5V available for high impedance phones.


----------



## the_equalizer

Hello everyone,
   
    My Mini-Max TRIAD 24v wall-wart power supply seems to be dead. The cable looks fine but there's no voltage coming out of it. I was wondering if someone has tried the Radio Shack Enercell 18/24 1A AC wall-wart. From the specs and simple manual I can't see why it would not work.  Any opinions on it?
   
  cheers!


----------



## Beefy

the_equalizer said:


> Hello everyone,
> 
> My Mini-Max TRIAD 24v wall-wart power supply seems to be dead. The cable looks fine but there's no voltage coming out of it. I was wondering if someone has tried the Radio Shack Enercell 18/24 1A AC wall-wart. From the specs and simple manual I can't see why it would not work.  Any opinions on it?
> 
> cheers!




Pretty sure that is the one I bought when I moved to Canada and it was fine. Just make sure you get the right size connecter and it will plug right in.


----------



## tintin220

I wonder if the MiniMAX would benefit at all from having some kind of isolated or dedicated power supply, such as the sigma11.


----------



## the_equalizer

Quote: 





beefy said:


> Pretty sure that is the one I bought when I moved to Canada and it was fine. Just make sure you get the right size connecter and it will plug right in.


 
   
  Great news, thanks!


----------



## Beefy

tintin220 said:


> I wonder if the MiniMAX would benefit at all from having some kind of isolated or dedicated power supply, such as the sigma11.




Not necessary. It has a linear regulated power supply on-board. The plug pack is just a convenient and safe way of getting the AC to the amp.


----------



## tintin220

Ah, thanks for the info, I just got my hands on one and I'm thinking of having it as my daily driver while I sell literally everything else I own.


----------



## the_equalizer

Wow, I must be having a REALLY strong bout of bad luck. I bought the Enercell 18/24 AC adapter and.... it's as dead as my TRIAD!!    Yeah, I suspected my VOM might be the problem but I checked with a second one  with the same result:  0V out of both AC acapters  
   
  I know this is only marginally related to the thread but I had to vent somewhere. 
   
  cheers!


----------



## tomb

Quote: 





tintin220 said:


> Ah, thanks for the info, I just got my hands on one and I'm thinking of having it as my daily driver while I sell literally everything else I own.


 
  Yep - what Beefy said.


----------



## tomb

Quote: 





the_equalizer said:


> Wow, I must be having a REALLY strong bout of bad luck. I bought the Enercell 18/24 AC adapter and.... it's as dead as my TRIAD!!    Yeah, I suspected my VOM might be the problem but I checked with a second one  with the same result:  0V out of both AC acapters
> 
> I know this is only marginally related to the thread but I had to vent somewhere.
> 
> cheers!


 
  I haven't had any trouble with the Triads in the states and have shipped a few hundred over the years. 
	

	
	
		
		

		
			




   
  That said, the fuse on the MiniMAX PCB will protect the secondary side of the adapter, but it won't do much for the primaries.  If there's an issue with the line voltage, shorting at the outlets, etc., it may burn up whatever is used as a fuse inside the walwart.  Unfortunately, many 24VAC adapters will have protection, but it's often non-resettable/non-replaceable.


----------



## scottie4442

Ok, trying to source out the parts to build my miniMax.  I got everything ready to order except QM2, Fairchild discontinued the mpsa14 and the replacements only have .5a continuous collector current, the fairchild has 1.2a continuous collector current.  Any ideas for a replacement for the mpsa14 that would work.  Thanks


----------



## tomb

Quote: 





scottie4442 said:


> Ok, trying to source out the parts to build my miniMax.  I got everything ready to order except QM2, Fairchild discontinued the mpsa14 and the replacements only have .5a continuous collector current, the fairchild has 1.2a continuous collector current.  Any ideas for a replacement for the mpsa14 that would work.  Thanks


 
  Allied Electronics has 181 in stock right now.  Or, shoot me a note if you're ordering stuff from Beezar.  I'll drop one in your order.


----------



## scottie4442

thanks, I will do that. I really appreciate the help.  I need to order several parts that you carry for the miniMax, much easier than trying to find all these special parts where ever.  Thanks for having beezar, it helps those of us that are tinkerers but want good quality equipment.  One of my friends compared you to the old Heathkit. (oh sorry about the PM to you and cetoole, it was before I read this post).


----------



## the_equalizer

tomb said:


> I haven't had any trouble with the Triads in the states and have shipped a few hundred over the years.
> 
> That said, the fuse on the MiniMAX PCB will protect the secondary side of the adapter, but it won't do much for the primaries.  If there's an issue with the line voltage, shorting at the outlets, etc., it may burn up whatever is used as a fuse inside the walwart.  Unfortunately, many 24VAC adapters will have protection, but it's often non-resettable/non-replaceable.




Well the TRIAD worked perfectly for almost three years. I'm a bit mistified as to how it died so suddenly. Anyway for those in need of using one of these RadioShack Enercell 18/24 VAC adapters, a couple of recommendations:

1.- The correct tip for the MiniMax is size 'M'
2.- Take a VOM to the store and test the adapter you buy... You might find it hard to believe but two of these bought in different RadioShack stores in towns 35 miles apart were both as dead as my TRIAD. What are the odds of that happening!? Finally the third adapter I got, after going back to the last RadioShack store and claiming my warranty, worked fine and has been working without a hitch..


----------



## scottie4442

Another MiniMax lives. Just got mine finished today and it sound AMAZING.


----------



## tomb

Wow - those must be white LED's under those tubes! 
	

	
	
		
		

		
		
	


	



   
  Nice work and congratulations!! 
	

	
	
		
		

		
		
	


	



   
  P.S. Hey - are those Black Gate NX's at CA2?


----------



## scottie4442

no, nichicons, the red is an Elna (think I spelled that right), I tired and Elna for ca2 but it was about 3mm too tall. I did use a Russian k42 .01 ohm for a bypass instead of a vitamin q, I had a few already. I wanted to try the white and they look really cool, I thought they might be good with the color changing led in the center position, but they are so bright that the drown out the color changer. I am colecting part for a SOHA II and a Bijou as my next two projects.


----------



## lordearl

An odd question given this is a headphone forum, but does the minimax have enough grunt to power a pair of small desktop 8 ohm speakers (90dB efficiency)? Probably only need a few watts at most, and I thought that using the high gain tube might be a perfect option.


----------



## tomb

Quote: 





lordearl said:


> An odd question given this is a headphone forum, but does the minimax have enough grunt to power a pair of small desktop 8 ohm speakers (90dB efficiency)? Probably only need a few watts at most, and I thought that using the high gain tube might be a perfect option.


 
  The MOSFET-MAX would be a better choice, but if you can turn the bias up on the MiniMAX, it may do OK.  It can probably stand 70-80ma without a big issue (we normally recommend 50ma).  Keep in mind that the -3dB bass cutoff with the normal MiniMAX 470uf output caps may be up to ~42 Hz.


----------



## zwack

I finished my build and decided to fire it up. I measured the DB bias first and these where almost 0 mV, which seemed a bit odd to me. When I measured the power supply voltage I noticed that it measures 1.4 Volts, no matter in which direction I turn the potentiometer (RR3). I verified that the input pin of the LM317 sees the rectified 34 Vdc. I verified that resistors RR1 (121R) and RR2 (2K) are not defective and have the correct values.Checked if the potentiometer is working. It does. All diodes in the voltage supply section are working too and placed in the right direction according to the silk screen.  
   
  Some more informations about my build: 
  In the diamond buffer section I'n using two pairs of 2SC2238/2SA968. As these have a reverse pinout I soldered them to the MOSFET locations according to the image here: http://diyforums.org/MiniMAX/MiniMAXbjt.php
  RB8L/R, RB9L/R are jumpered out, hope that I understood that well
   
  Double checked all other transistors and they're all in the right place. For QB1L/R I used J310's instead of PN4392's 
   
  I checked the polarity of all caps and they are all positioned the right way. 
   
  I'm using a way oversized torroid 24Vac (225VA) transformer. So surely not running out of power here. 
   
  Any ideas what might be wrong here?? I'm thinking that it could be a faulty LM317, but maybe anybody has experienced problem this before and knows how to solve it
   
   
   
  I have made to little posts here, so I'm not yet allowed to attach any images. Here's a link to a picture of the almost finished board. _Please notice that the LM317, tubes and _RB14L/R_ where not yet installed or jumered when I took this picture._
http://www.flickr.com/photos/mandarijnen/9306836728/sizes/o/in/photostream/


----------



## tomb

Quote: 





zwack said:


> I finished my build and decided to fire it up. I measured the DB bias first and these where almost 0 mV, which seemed a bit odd to me. When I measured the power supply voltage I noticed that it measures 1.4 Volts, no matter in which direction I turn the potentiometer (RR3). I verified that the input pin of the LM317 sees the rectified 34 Vdc. I verified that resistors RR1 (121R) and RR2 (2K) are not defective and have the correct values.Checked if the potentiometer is working. It does. All diodes in the voltage supply section are working too and placed in the right direction according to the silk screen.
> 
> Some more informations about my build:
> In the diamond buffer section I'n using two pairs of 2SC2238/2SA968. As these have a reverse pinout I soldered them to the MOSFET locations according to the image here: http://diyforums.org/MiniMAX/MiniMAXbjt.php
> ...


 
  I've seen it before, but it's usually a reversed part in the power supply.  I don't see that in your photograph (a damn good photo, btw!).
   
  I'm curious about something though, can you describe how you made the power connections to the power supply terminal block?  Did you use the terminals that would put the fuse in the circuit?  The other times I've seen this has been when there is a major short in the buffer, but the fuse usually blows.  Let us know how you have things connected.
   
  Also, it looks like you have the transistor mounting screws touching in the buffer's center heat sinks.  The shoulder washers should be isolating the screws from the transistors, but it's sort of like daring the thing to short when the screws are touching like that.
   
  Another time I've seen this has been when the resistor ratings are wrong.  Mouser will often show resistor selections for 120R, 12K, 120K, so forth from a single search for "120R".  So, it's easy for people to order the wrong thing sometimes.  If that RR1 resistor is off by a few magnitudes, you'll get very little to no voltage out of the power supply.  I can't see it the way you have it soldered in and from the angle of the photo.  I know you say you checked it, but it's sometimes easy to get the scales mixed up on a DMM, too.
   
  Just some guesses - best I can do with the info so far.


----------



## gspence2000

lordearl said:


> An odd question given this is a headphone forum, but does the minimax have enough grunt to power a pair of small desktop 8 ohm speakers (90dB efficiency)? Probably only need a few watts at most, and I thought that using the high gain tube might be a perfect option.




I use my MiniMAX with a pair of uFonken speakers featuring Fostex FF85WK drivers, which are 86 dB efficiency. This works will for me in a near-field setup (sitting at my computer). I had asked TomB about this before I tried it, and he advised me to watch that it didn't get too hot. I have not had any heat problems though. I use the high-gain tubes anyways because my main headphones are Sennheiser 580's.


----------



## zwack

> Originally Posted by *tomb* /img/forum/go_quote.gif
> 
> I've seen it before, but it's usually a reversed part in the power supply.  I don't see that in your photograph (a damn good photo, btw!).


 
  Thanks, it's shot with a 5 year old "Canon IXUS 860 IS". That little photo camera still amazes me. 
   
  
  


> I'm curious about something though, can you describe how you made the power connections to the power supply terminal block?  Did you use the terminals that would put the fuse in the circuit?  The other times I've seen this has been when there is a major short in the buffer, but the fuse usually blows.  Let us know how you have things connected.


 
  Here's the connection. It's putting the fuse in circuit.

   
   
   


> Also, it looks like you have the transistor mounting screws touching in the buffer's center heat sinks.  The shoulder washers should be isolating the screws from the transistors, but it's sort of like daring the thing to short when the screws are touching like that.


 
  Fixed that!

   
  


> Another time I've seen this has been when the resistor ratings are wrong.  Mouser will often show resistor selections for 120R, 12K, 120K, so forth from a single search for "120R".  So, it's easy for people to order the wrong thing sometimes.  If that RR1 resistor is off by a few magnitudes, you'll get very little to no voltage out of the power supply.  I can't see it the way you have it soldered in and from the angle of the photo.  I know you say you checked it, but it's sometimes easy to get the scales mixed up on a DMM, too.


 
   
 I had checked it, but guess what! I overlooked the letter "k" before the Ohm 
	

	
	
		
		

		
		
	


	




.  I had ordered some 121K resistors instead of 121R's. I could confirm it by checking the order details from my latest Mouser order. While I was at it I checked all other components I ordered as well. They are all the same (values) as per the BOM.  
 This is the little basterd. 

   
  
   


> Just some guesses - best I can do with the info so far.


 
  You did great! Thanks for that! Now to order some new 121R resistors before I can proceed to start testing the amp.


----------



## tomb

Quote: 





zwack said:


> Thanks, it's shot with a 5 year old "Canon IXUS 860 IS". That little photo camera still amazes me.
> 
> 
> 
> ...


 
  Ha!  I thought that might be the case about the resistor!  I wish Mouser would fix their searches from doing that.  I have a couple of hundred 221K resistors instead of 221R resistors because of the same thing. 
	

	
	
		
		

		
		
	


	




  Anyway, good news and look forward to you getting it working!! 
	

	
	
		
		

		
		
	


	



   
  P.S. Yes - great camera, but I suspect the operator had a lot more to do with it.


----------



## lordearl

Quote: 





gspence2000 said:


> I use my MiniMAX with a pair of uFonken speakers featuring Fostex FF85WK drivers, which are 86 dB efficiency. This works will for me in a near-field setup (sitting at my computer). I had asked TomB about this before I tried it, and he advised me to watch that it didn't get too hot. I have not had any heat problems though. I use the high-gain tubes anyways because my main headphones are Sennheiser 580's.


 
   
  Thanks GSPENCE - great news.
  Did you change the output capacitors in order to lower the bass frequency response?


----------



## zwack

I got it working now 
	

	
	
		
		

		
			



. Thanks again. DB and tubes are biased and it's now running at 27V. The only thing that doesn't work is the relay circuit. I did a quick search and came across another thread started by someone who had the same problem.
   
  I'll quote some of your (tomb) posts from that thread.
   


> Give us a voltage measurement across DM2 - the 1N4148 diode. It should be close to 12V. If it is, then yes - the relay is bad. I kind of doubt that, though.
> 
> By the way - I forgot that we couldn't see your resistors because of the way you turned them. Any way you can confirm the value of RM1 and RM2?


 
  I measured the voltage across DM2. It measures 3.3V instead of 12V. Something is obviously wrong here, but I can figure out what..
   
   


> 1. Measure the voltage at the point indicated on RM1 relative to GND:
> 
> 
> 
> ...


 
  It measures 27V, so full voltage going to the circuit.
   
   


> 2. Next, measure the voltage across two points indicated on DM1 as shown:
> 
> 
> 
> ...


 
  The voltage across DM1 is 11.5V. The Zener must be doing it's job.
   
   


> 3. Next, measure the voltage at either of the points indicated on DM2/RM2 relative to GND:
> 
> 
> 
> ...


 
  My DDM measures 10.9V. Should be enough to switch the relay, but for some reason the relay doesn't switch.
   
  Here is a image of my relay delay circuit (click to enlarge):

   
  As you can see I used the BD139 for QM1. I installed it per the directions on the Minimax relay-delay page. QM2 is not revealing itself on the photograph, but I can confirm it's a MPSA14. 
   
  The next photograph shows the values of the resistors and one can even read the text on the Zener (thanks to my camera and .. not to forget the operator 
	

	
	
		
		

		
		
	


	


). All values are as per the BOM. 

   
  I'm certainly not an engineer, but my best quesses are that the 1N4148 is working like it's supposed to be or... the relay might be faulty.
   
  Edit: forgot to mention that I waited for over a minute to start measuring.


----------



## tomb

You didn't show the bottom of the PCB.  It might be that you have some cold solder joints on the relay.  Can you try re-flowing the solder on the relay pins?  The first two next to DM2 might be the key (they're the coil connection).  Be careful of the heat, though, it may be just as likely that you could've burned out the relay coil in soldering it.  I think it may be the former rather than the latter, though.
   
  If you are measuring close to 12V across the leads of DM2 (you said 10.9V), then there's no reason the relay should not actuate.  That voltage will vary from very low to 12V, as the capacitors charge.  As long as you wait more than ~45 seconds, you should be measuring the steady-state voltage.  If the coil at the two pads next to DM2 are registering close to 12V and the solder joints are good, then the relay must be bad.
   
  According to the data sheet, the relay coil should actuate at about 8.4V _maximum_.  That means that it may actuate at an even lower voltage.  So, if you get 10.9V and you do not hear a "click" at about 45 seconds (cold start) or 30 seconds (hot start), then either the solder joints are bad or the relay is.
   
  P.S. Once you hear a click, that may not be all there is to it.  It could be the Left and Right signal contacts are not connecting into the circuit on the PCB.  One thing at a time, though ...


----------



## zwack

I just did a test with another 12V relay I have lying around. I put it on a breadboard, put a diode over the coil and connected the negative side to ground from the Minimax and the positive side to the 12V side of DM2 (Where the text "DM2" is printed onto the PCB). The relay actuated just fine. Than I connected the negative side to the other side of DM2 (just like the relay on the board) while keeping the positive side connected to the same point. Now the relay refused to actuate. It looks like the voltage difference is too small between the positive and negative sides of the relay's coils. 
   
  I can more or less confirm this when I measure the voltage over DM2 directly from power up. It starts to rise slow to 3.1V. Than it stops rising and stays there. 
  The voltage between the negative side of the coil and ground is 7V! This explains why the relay won't actuate. Now to find the source of this problem.
   
_ps. I have not checked for bad solder joints yet, but I do not think they are the source of the problem. To be sure I'll re-solder all components from the relay-delay circuit._


----------



## zwack

PROBLEM SOLVED! 
   
  After some time studying the relay-delay circuit, the only thing that I could come up with was that QM2 was not functioning like supposed to be. It was not going full open or something like that. That would also explain why the voltage difference between the negative side of the coil and ground was 7V. QM2 did not short it to ground. The MPSA14 (QM2) is now replaced by another one and the relay is working fine now. 
   
  I always get a bit anxious when things don't work, especially when I don't fully understand what's going within the circuits. Still leaning and determined to get there 
   
  Now to test the amp with some music. I will report on how it goes and eventually post some pics of the finished amp.


----------



## tomb

Quote: 





zwack said:


> PROBLEM SOLVED!
> 
> After some time studying the relay-delay circuit, the only thing that I could come up with was that QM2 was not functioning like supposed to be. It was not going full open or something like that. That would also explain why the voltage difference between the negative side of the coil and ground was 7V. QM2 did not short it to ground. The MPSA14 (QM2) is now replaced by another one and the relay is working fine now.
> 
> ...


 
  Way to go!  Glad to see you got it working!


----------



## zwack

And there is music! I temporary hooked it up to my computer using some old RCA connectors, just for testing. Sound is a bit thin, but that could well be coming from the computer's soundcard. When I finished the build I will be using my left-over Rega DAC in combination with my CD-pro transport. I have a good feeling that the Rega-CD-pro combination will sound better.
   
  I still have a question about the tubes:
   

 I'm currently using 12FM6 tubes. At the time I ordered them I was not aware of the tube matching service at Beezar. The ones I got are from Raytheon & Tung-Sol and rated 90 and 85  Whatever that stands for. On both boxes "RCA Side HS" written, assuming that they where produced in the same factory. Are the tubes close enough matched?


----------



## tomb

Quote: 





zwack said:


> And there is music! I temporary hooked it up to my computer using some old RCA connectors, just for testing. Sound is a bit thin, but that could well be coming from the computer's soundcard. When I finished the build I will be using my left-over Rega DAC in combination with my CD-pro transport. I have a good feeling that the Rega-CD-pro combination will sound better.
> 
> I still have a question about the tubes:
> 
> ...


 
  Probably.  "Millett" tubes were only made by four manufacturers: GE, RCA, Tung Sol, and Sylvania.  So, no matter what the original tube box says, or the painted-on tube label, it's one of those manufacturers that made it.
   
  As for the notations on the top of the Beezar tube boxes, I've always intended to document this thoroughly, but it's one of those things that you never quite get around to doing:
   
  Top Left - tube box or tube label mfr
  Top Right - tube tester reading
  Middle - tube designation
  Bottom Left - "real" mfr
  Bottom Middle - getter type
  Bottom Right - plate type (graphical representation)
   
  "RCA Side HS" - (I'm assuming this was on the bottom) means RCA was the mfr and the getters are Horse-Shoe type mounted on the side of the plates.
   
  Unfortunately, we need to state that you didn't order a kit.  Tubes are completely matched according to test, mfr, and construction with tubes that come with a kit.  I try to do my best if someone orders tubes separately and they don't pay for matching.  In the case of 12FM6's, those tubes are very scarce.  Beezar may represent the largest stock in the world right now, but that's still only about a hundred.  In your case, the painted-on labels for the tubes have little to do with the actual mfr.  Not seeing/remembering the boxes specifically at this point, it sounds like I gave you two RCA-manufactured tubes with identical construction that are 90 and 85 tested output.  That's within 10%, so they should be pretty good.
   
  Not to be outrageously self-serving, tubes are not like opamps.  Every one may sound different.  You are encouraged to buy as many as you like (not just from me) so that you can experience the differences.  You never know when you might find that golden tube that does everything just as you want it to.


----------



## zwack

Thanks a lot for the explanation. 
   
  After I became aware of the tube matching service I ordered two matched 12FK6 tubes along with some other stuff I still needed. These tubes are both rated at 75 and do come from the same manufacturer. I will try these after some time to get used to the 12FM6 tubes. This will make my ears more receptive for the differences between the different types of tubes. If it shows that I prefer the 12FM6 tubes over 12FK6's than I will surely order some more from you and make sure that I'll go for the matching service!
   
  I'd like to share that I'm very satisfied with the way you handle your orders and the support you give.


----------



## tomb

Quote: 





zwack said:


> Thanks a lot for the explanation.
> 
> After I became aware of the tube matching service I ordered two matched 12FK6 tubes along with some other stuff I still needed. These tubes are both rated at 75 and do come from the same manufacturer. I will try these after some time to get used to the 12FM6 tubes. This will make my ears more receptive for the differences between the different types of tubes. If it shows that I prefer the 12FM6 tubes over 12FK6's than I will surely order some more from you and make sure that I'll go for the matching service!
> 
> I'd like to share that I'm very satisfied with the way you handle your orders and the support you give.


 
  Thank you for the very nice comments!


----------



## zwack

Currently listening the the third album using the MiniMAX. I'm very pleased with it, but compared to the left channel the right channel is just a tiny bit louder. I'm using the 12FM6 tubes with are not matched (left: 85, right:90). Can the small volume offset be the result of the unmatched tubes? 

Ps. All transistors used are bought matched from Beezar.


----------



## Beefy

Could be the pot as well, could be wax in your ears.
   
  Run a 60Hz sine wave through your source/amp. Measure the AC voltage at the input, after the volume pot (try a few different volume levels), and at the outputs. Most multimeters will pick up 60Hz AC just fine, and this will tell you where any large channel imbalance might be.


----------



## tomb

Or, you could just swap the tubes from one channel to the other.


----------



## zwack

Quote: 





beefy said:


> Could be the pot as well, could be wax in your ears.
> 
> Run a 60Hz sine wave through your source/amp. Measure the AC voltage at the input, after the volume pot (try a few different volume levels), and at the outputs. Most multimeters will pick up 60Hz AC just fine, and this will tell you where any large channel imbalance might be.


 
  Definitely no wax in my ears. Reversing my headphone also reversed the louder channel 
	

	
	
		
		

		
		
	


	


. I ran a 60hz sine wave through the amp and this revealed that the AC measured (at the output) at the right channel was indeed higher. Measuring at the input before and after the pot revealed that the pot's channels are perfect in sync. Thanks for the advice. 
  Quote: 





tomb said:


> Or, you could just swap the tubes from one channel to the other.


 
  After the measurements I swapped the tubes and measured again. Now the difference was a lot smaller. Than I realized that I had to adjust the bias again. After adjusting the difference was still a lot smaller that with the tubes reversed. When listening the difference is now hardly noticeably.  
   
  Is it possible that the channel imbalance is caused by the diamond buffer stage, which is somewhat corrected by the unmatched tubes (or emphasized when reversed)??? Or maybe I'm just talking nonsense??  Is there a way to check my theory?


----------



## tomb

Quote: 





zwack said:


> Definitely no wax in my ears. Reversing my headphone also reversed the louder channel
> 
> 
> 
> ...


 
  No - tubes are imperfect devices.  People try to treat them like opamps, but it's sort of the difference between a horse and mule* (tubes).  You can actually compensate for differing tube outputs somewhat by adjusting the bias by ear.  Get both tubes as close as you can in measured bias, then pick one and turn the trimmer screw with your headphones on until you you're satisfied the sound is centered.
   
  Trouble with that is that the inherently stronger tube is still going to respond more strongly to music peaks.  You can't really hope for much more than a 1-2 dB difference.  They're always going to be slightly off, but you can get them close enough that you won't notice with the proper tubes.  Keep in mind that some Millett tubes will continue to drop in bias for 1-2 hours.  Plus, it's always possible that you haven't run these enough.  Bias may change radically with NOS tubes used for the first time in decades - they get little bits of gas in them from sitting so long and it takes some running in to burn out those bits.
   
  I think you've ordered some more, so perhaps out of a greater selection you'll get something closer to what you want.
	

	
	
		
		

		
		
	


	



   
   
  * Just a caveat to that - mules are often stronger and better than horses in many things, it's just that they don't automatically pop out of the chutes ready to run.  You have to adjust with them a bit, learn their traits, etc.  Once you do, you may find that they do many things better.  Well, anyway ... it's an analogy, nothing more.


----------



## zwack

All clear.
  I did order some new tubes indeed. 
	

	
	
		
		

		
			




   
  The bias of my tubes stops dropping after half an hour or so. They drop half a volt.
  Another thing I noticed is that the "louder" tube also sounds a bit more sparkling or better said: the other tube sounds like there is a curtain hanging between me and the sound. I hope that the new tubes, or a combinations of those old and new make both channels sound equally sparkling without the imbalance. I have a good feeling that this will be fixed. Still the amps sounds already very good. I'm very pleased with it!


----------



## zwack

Well I finished my build. It was a fun build and I'm very pleased with it. I published an article (complete with pictures) about it on my website:
   
  Here's the link: http://ce-designs.net/index.php/my-projects/headphone-amplifiers/articles-the-millett-hybrid-minimax
   
  please note that I still need to replace the current volume knob with a nice black knob  
   
  Thanks to all for the needed support!


----------



## tomb

Quote: 





zwack said:


> Well I finished my build. It was a fun build and I'm very pleased with it. I published an article (complete with pictures) about it on my website:
> 
> Here's the link: http://ce-designs.net/index.php/my-projects/headphone-amplifiers/articles-the-millett-hybrid-minimax
> 
> ...


 
  Thank you for such a nice review!  It's humbling to read the efforts and results of builders like you!
   
  BTW - I was able to find four of the tubes we spoke about in 12FM6 (RCA grey plates) and they'll be shipped out tomorrow.  Unfortunately, the 12FM6 has reached a point of scarcity that there's very little to pick from.  AFAIK, Beezar has the largest stock anywhere, and it's not much - perhaps about 150 at this point in time.
   
  Just a couple of comments -

 0.22uf Vitamin Q's are still in stock at Beezar, but they may not last long.  I have a few dozen, but no more.  The MiniMAX was originally based on the 0.18uf Vitamin Q's because they will fit on the PCB with the custom Beezar case, whereas the 0.22uf won't.  I still sell what I have remaining mainly for the MOSFET-MAX which doesn't have a custom case and leaves all options open.
 There is a revised headphone relay-delay that we (cetoole and I) applied to the MOSFET-MAX.  It uses a 24VDC regulator and relay, and deletes the zener diode altogether.  Testing was done on the MiniMAX, so it's very easy to retrofit.  The advantage is that the higher voltage regulator and relay actuate much quicker.  The turn on phase is almost devoid of transient spikes and the turn-off phase is so much quicker that transients are minimized in that regime as well.  I recently updated the MOSFET-MAX website with details of the new relay scheme (MOSFET-MAX Relay-Delay) and it shows a photo of a MiniMAX PCB with the parts and their mounting particulars:
   




   
  As can be seen in the photo above, the mods are fairly simple - the biggest change is the use of a 78L24 TO-92 regulator in place of the BD-139.  The middle lead of the 78L24 goes to the left pad at DM1.  DM1 and RM1 are deleted completely.  It would be best to use a transient suppressor in place of DM2, but it's not strictly necessary if you want to try it out.  Also, CM3 should be rated at 35V, but I've never experienced a failure with the standard MiniMAX caps as specified.  Replacing DM2 with an SA48C may promote a longer life for the relay and perhaps reduces the transients even more than the diode.  It's something fairly easy to try anyway.
   
   
  P.S. I socketed the relay as shown in the pic. You have to snip off some of the pins to make it work and even two DIP-8 sockets work as well (as shown in the pic).


----------



## zwack

> BTW - I was able to find four of the tubes we spoke about in 12FM6 (RCA grey plates) and they'll be shipped out tomorrow.  Unfortunately, the 12FM6 has reached a point of scarcity that there's very little to pick from.  AFAIK, Beezar has the largest stock anywhere, and it's not much - perhaps about 150 at this point in time.


 
   
  I just read that my tubes where shipped. Thanks for all the efforts to serve my request! Very much appreciated!
   
  Regarding the spikes. They're actually not that bad. Just a soft click when the relay is actuated. The click is a bit louder when the relay opens again, but certainly not that loud that it would damage the headphone.
   
  btw I corrected the text about the 22uf Vitamin Q's on my website


----------



## tomb

Quote: 





zwack said:


> I just read that my tubes where shipped. Thanks for all the efforts to serve my request! Very much appreciated!
> 
> Regarding the spikes. They're actually not that bad. Just a soft click when the relay is actuated. The click is a bit louder when the relay opens again, but certainly not that loud that it would damage the headphone.
> 
> btw I corrected the text about the 22uf Vitamin Q's on my website


 
  Many thanks - I hope the tubes work out!  If they don't, though, please let me know and I'll do what I can with the stock that I have!


----------



## zwack

I have a good feeling that the tubes will work out. 
  Next Friday a friend of mine is coming over to listen the amplifier. I will probably be building another MiniMAX if he really likes it!


----------



## lordearl

Is anyone using the Minimax with Beyerdynamic DT880s? I have the 600 ohm impedance version and plan to use jumpers at R8 & R9. Any feedback would be greatly appreciated as I am ok at soldering, but TERRIBLE at de-soldering.


----------



## tomb

Quote: 





lordearl said:


> Is anyone using the Minimax with Beyerdynamic DT880s? I have the 600 ohm impedance version and plan to use jumpers at R8 & R9. Any feedback would be greatly appreciated as I am ok at soldering, but TERRIBLE at de-soldering.


 
  Jumpers are good.  Also be sure you use the 12AE6 and adjust the tube bias for the greatest voltage swing, which is the 13.5V midpoint of a 27VDC setting at V+ and GND.


----------



## lordearl

Finally finished my build this afternoon, however there's a slight hitch - I keep getting 0mV when measuring TB1L (or TB1R) with reference to TA2L. This also happens with the right channel.
Everything else appears fine (volts in 27v, tube bias 13.5) and I can't have smoked the bd137, etc, as I've checked the orientation numerous times.

Any suggestions would be most helpful


----------



## tomb

lordearl said:


> Finally finished my build this afternoon, however there's a slight hitch - I keep getting 0mV when measuring TB1L (or TB1R) with reference to TA2L. This also happens with the right channel.
> Everything else appears fine (volts in 27v, tube bias 13.5) and I can't have smoked the bd137, etc, as I've checked the orientation numerous times.
> 
> Any suggestions would be most helpful


 
  
 Back up a minute and be very careful what you're typing or what you're measuring. 
	

	
	
		
		

		
		
	


	




  To bias the buffer, you need to measure mV between TB1L (or TB2L) with reference to TA2L.  That's for the left channel.  For the right channel, it's TB1R (or TB2R) with TA2R.
  
 If you want to be really simple about it, all those test points are doing is allowing you to measure the voltage across RB10L (or RB11L) for the left channel or RB10R (or RB11R) for the right channel.  You could just as easily pick one of those resistors and measure the voltage across the leads - that's the bias for that channel.  There are two sets of resistors - RB10 and RB11 for each channel, that's why there are two test point choices for each channel.  However, unless the transistors in the buffer are grossly unmatched, the bias is going to be pretty close between RB10 and RB11 for each channel.
  
 Anyway - see if that clears some things up for you and let us know.  On the other hand, if what you typed above is a typo, then try it again and let us know specifically what you're measuring.  You should be able to measure about 20-30mV even with the transistors un-biased.


----------



## lordearl

Thanks Tom, yes was a typo, however I was measuring the correct points, results are as follows;

TB2R-TA2R: 0.0mV
TB1R-TA2R: 0.0mV
Voltage across RB10R: 0.0mV
Voltage across RB11R: 0.0mV

The left side reads exactly the same.

The voltage is 27.1v DC and I set the bias on each tube to 13.5v.
After a minute or two the bias always goes to roughly the 16v mark on both tubes.
Also the LED (LEDC) keeps wildly changing color.

Does this help in narrowing down the issue?


----------



## tomb

lordearl said:


> Thanks Tom, yes was a typo, however I was measuring the correct points, results are as follows;
> 
> TB2R-TA2R: 0.0mV
> TB1R-TA2R: 0.0mV
> ...


 
  
 Well, the center "Color Change" LED is supposed to keep wildly changing color. 
	

	
	
		
		

		
		
	


	



  
 As for the rest, you've got something amiss in the buffer.  As I stated up there, you should be able to read 20-30mV even with the RB12 trimmers turned all the way down.
  
 Time for some pics.


----------



## lordearl

No worries - pics attached.  Hopefully the resolution is OK.
 By the way, sound is actually making it through the amp - it is highly attenuated (volume is less than the output of the source, even with the pot all the way up, and the sound is rather distorted in bursts).


----------



## tomb

lordearl said:


> No worries - pics attached.  Hopefully the resolution is OK.
> By the way, sound is actually making it through the amp - it is highly attenuated (volume is less than the output of the source, even with the pot all the way up, and the sound is rather distorted in bursts).


 
  
 I'm sorry to say that you have the output transistors soldered to the PCB on the wrong side of the heat sinks.  Look at the first page in the "Notes on the Millett Hybrid MiniMAX" document that was included in your kit. 
	

	
	
		
		

		
		
	


	



  
 Or here:

 Swap them out to the other side and let me know if things work after that.  If not, I'll send you some more transistors.


----------



## lordearl

Argh!
 And I was attempting to be so meticulous - two fundamental errors, putting the BD137 in the wrong spot, TWICE!
  
 How important is the matching?  I can try to source two BD137 from a local electronics store.
  
 Oddly enough, I have two pairs of BD139/BD140 already mounted to heatsinks here with me, will they work at all?


----------



## lordearl

The other option is of course to simply cut the traces on the PCB which are leading to where I've incorrectly soldered the BD137, then solder a jumper on the underside of the board to where the BD137 should have been soldered in the first instance.
  
 That is probably the easiest solution as I won't be using any other transistors besides the BD137/BD138, the desoldering is simply too perilous!


----------



## tomb

lordearl said:


> Argh!
> And I was attempting to be so meticulous - two fundamental errors, putting the BD137 in the wrong spot, TWICE!
> 
> How important is the matching?  I can try to source two BD137 from a local electronics store.
> ...


 
 The BD139/BD140 offer sub-standard performance in the MiniMAX circuit.  It has to do with the fact that there's no feedback.  Feedbacked transistors sound pretty much the same, but with no feedback, you get a lot of sonic differences.


----------



## tomb

lordearl said:


> The other option is of course to simply cut the traces on the PCB which are leading to where I've incorrectly soldered the BD137, then solder a jumper on the underside of the board to where the BD137 should have been soldered in the first instance.
> 
> That is probably the easiest solution as I won't be using any other transistors besides the BD137/BD138, the desoldering is simply too perilous!


 
  
 I would strongly recommend against this:
  
 1. Traces are not all that easy to cut - you'd have eight of them to do.  The board will end up pretty messed up by the time you get through with it.  It might not even be usable.
 2. To make matters worse, you have to engineer a crossover.  You can't simply solder some spent leads in a different direction - they have to cross over one another.
  
 The simplest answer is to remove the transistors.  You only need to make a blob of melted solder big enough to cover all three pins.  A lot of the time, the transistor will simply drop out of the board.  If not, you can tie a string or something similar through the mounting tab hole.  Pull on the string when you have the solder blob melted and it will come right out.
  
 You don't absolutely need the heat sink mounting pads in a case like this.  Yes, it's nice to start with them, but you could simply smear some Vaseline on the backs of the transistors and probably get 90% of the heat transfer effect.  For that matter, since the transistors are all plastic-bodied, you could mount them dry and get probably 75% of the heat transfer effect.  The differences may be even closer than that - I'm just guessing.
  
 Anyway - cutting traces on a PCB is the absolute last resort.  Never do it if you can help it.
	

	
	
		
		

		
			




  
  
 Edit: Changed a word that might be interpreted as vulgar by our international folk.


----------



## lordearl

OK, I may as well attempt the de-soldering of the BD137 initially, then buy some more if it doesn't work out.
 I'll turn the board upside down, tie a weight to the transistor, then de-solder using the blob technique - fingers x'd it will fall out.
  
 Is the transistor at risk of being damaged if I apply too much solder heat?


----------



## tomb

lordearl said:


> OK, I may as well attempt the de-soldering of the BD137 initially, then buy some more if it doesn't work out.
> I'll turn the board upside down, tie a weight to the transistor, then de-solder using the blob technique - fingers x'd it will fall out.
> 
> Is the transistor at risk of being damaged if I apply too much solder heat?


 
  
 They can withstand a lot of heat, but remember that all you're trying to do is melt the solder blob.  Once the transistor comes out, clean up the pads with de-soldering braid.  A dental pick can sometimes help clear out the holes.


----------



## lordearl

To quote an earlier post - "Another Minimax lives!!"
  
 Switched the transistors to their correct spots very easily - there's two holes on each heatsink, so I just clipped them out and then re-attached them to the lower hole in each heatsink, which meant no desoldering was even necessary!
  
 The sound is phenomenal, even without any burn-in time.  I'm using jumpers at the output, with 12AE6 and DT880 headphones....B E A U T I F U L !!!
  
 Will post more impressions as the burn-in continues, but for now - a *massive* thanks to Tom B for all his help, an absolute legend.


----------



## tomb

lordearl said:


> To quote an earlier post - "Another Minimax lives!!"
> 
> Switched the transistors to their correct spots very easily - there's two holes on each heatsink, so I just clipped them out and then re-attached them to the lower hole in each heatsink, which meant no desoldering was even necessary!
> 
> ...


 
  
 Thanks for the kind comments! 
	

	
	
		
		

		
		
	


	



  
 I'm glad you tried just using the jumpers.  I think the amp sounds best that way, but not many people are willing to try it for some reason.  The "noise" I reference in the parts kit might be a little hiss with very low-impedance, high-efficiency earbuds or IEM's, _but almost every solid state amp has the same issue in those cases_.  There are very few SS amps - especially opamp-based ones - that do not have some resistance on the output.
  
 For the great majority of headphones, though, no output resistance is ever needed on the MiniMAX.


----------



## lordearl

Agree - I've tried a number of SS, hybrid and full tube commercial offerings, and all my low impedance headphones (eg KRK KNS8400 @ 32 ohms) have a slight amount of hiss.  The minimax actually has VERY LITTLE detectable hiss, and on the 600 ohms DT880, silent as a grave!!


----------



## lordearl

Tom - a couple of quick questions if I may:
  

I'm about to build a small non-oversampling DAC which uses passive current-to-voltage converters in the form of a single resister per channel.  There is no filtering at the output, so I'm not sure on whether I need to implement some ultra-sonic frequency filtering in the chain before the Minimax.  Does the Minimax have any filtering of this nature?  If so, obviously I won't need to solder the capacitors into my DAC circuit.
What is the input impedance of the Minimax?


----------



## tomb

lordearl said:


> Tom - a couple of quick questions if I may:
> 
> 
> I'm about to build a small non-oversampling DAC which uses passive current-to-voltage converters in the form of a single resister per channel.  There is no filtering at the output, so I'm not sure on whether I need to implement some ultra-sonic frequency filtering in the chain before the Minimax.  Does the Minimax have any filtering of this nature?  If so, obviously I won't need to solder the capacitors into my DAC circuit.
> What is the input impedance of the Minimax?


 
 1. It doesn't really matter - the entire output of the MIniMAX is filtered with capacitors.  Whatever offset may exist, it's stopped at the output (and the relay-delay is there to ensure the caps are charged prior to a load switched in).  I also doubt that the tubes are going to do anything in the ultra-sonic regime.
  
 2. The input impedance is the impedance of the volume pot - 50K.


----------



## dentaku81

Has anyone tried a miniMax with Mad Dogs? Does it output enough power to drive them? I seem to remember reading that the amp output is about 0.8 watts at ~50 ohms which should be enough in theory. I would just like to hear from someone who has tried the combo.


----------



## tomb

dentaku81 said:


> Has anyone tried a miniMax with Mad Dogs? Does it output enough power to drive them? I seem to remember reading that the amp output is about 0.8 watts at ~50 ohms which should be enough in theory. I would just like to hear from someone who has tried the combo.


 
 I'm not sure it's that powerful, if that's what you think is really needed.  From my observations, ortho power requirements are wildly over-stated.
  
 In any event, the Class A current capability can probably be dialed up to 75ma with the 1" heat sinks and custom case.  That would equate to about 0.28W.  A MOSFET-MAX can be dialed up to 125ma bias, which should result in 0.78W with a 50 ohm load.


----------



## dentaku81

tomb said:


> I'm not sure it's that powerful, if that's what you think is really needed.  From my observations, ortho power requirements are wildly over-stated.
> 
> In any event, the Class A current capability can probably be dialed up to 75ma with the 1" heat sinks and custom case.  That would equate to about 0.28W.  A MOSFET-MAX can be dialed up to 125ma bias, which should result in 0.78W with a 50 ohm load.


 
 I asked Dan from Mr speakers what the power requirements were and he replied "at least 200mW at 50ohms", so it looks like the minimax with the custom case might work. Is the custom case the one that comes in the beezar kit?


----------



## tomb

dentaku81 said:


> I asked Dan from Mr speakers what the power requirements were and he replied "at least 200mW at 50ohms", so it looks like the minimax with the custom case might work. Is the custom case the one that comes in the beezar kit?


 
 That seems more reasonable for an ortho.  Yes - the custom case is the one that comes in the beezar kit.


----------



## dentaku81

tomb said:


> That seems more reasonable for an ortho.  Yes - the custom case is the one that comes in the beezar kit.


 
 Awesome, im currently building a cmoy to re-learn how to solder, but i will start on the minimax after that.


----------



## tomb

dentaku81 said:


> Awesome, im currently building a cmoy to re-learn how to solder, but i will start on the minimax after that.


 
 Sounds like a good plan.


----------



## wewewho77

Will HE500 and LCD2 sounds good with miniMax? Right now I paired them with EF5. Will miniMax gives a significant improvement over EF5? Thanks


----------



## tomb

wewewho77 said:


> Will HE500 and LCD2 sounds good with miniMax? Right now I paired them with EF5. Will miniMax gives a significant improvement over EF5? Thanks


 
 Typically, I don't like direct comparisons in the DIY forum section.  We're not really trying to compete against commercial products.
  
 What I will tell you - I know nothing about the EF-5 except photos, etc. - is that I am not a fan of single-tube stereo amplifiers.  In my years of testing and matching literally thousands of tubes, the incidence of dual-triode tubes where the triodes are matched is very low.  I'd say one in 20 or 30, probably.  If the triodes are unmatched, you can balance the channels, but the stronger triode will always pump more output with transients, etc.*
  
 * With two-tube amps using dual-triode tubes, the triodes of each tube are typically connected in parallel.  That averages the output.  You can have one tube measuring 120/80 and another at 105/95 - theoretically, they are matched because they each average to 100.  It exponentially increases your chances of matching the tubes' output in the amp.


----------



## wewewho77

Sorry tom I didn't mean disrespect to anybody here. I used to be sceptical about tubes for their noise issue, old technology etc. But I also realize that tubes has so many faithful fans out there. I thought there's must be something special about them. So I decided to buy this EF5 amplifier for my HE500. And then I finally can understand why so many people loooves the sound of tubes. And my EF5 is so small but sounds so nice to my ears. I wonder if a bigger tube amps will take my setup to a much higher level. I asked around and someone very experienced DIYer suggested to try SSMH or miniMax if I want to have a big step up from my current setup. He said these amps are a steal for their price. So I just want to know your opinion here guys. Maybe I just send you PM than ask in this thread about the comparison between them. I really appreciate your information. Thanks


----------



## tomb

wewewho77 said:


> Sorry tom I didn't mean disrespect to anybody here. I used to be sceptical about tubes for their noise issue, old technology etc. But I also realize that tubes has so many faithful fans out there. I thought there's must be something special about them. So I decided to buy this EF5 amplifier for my HE500. And then I finally can understand why so many people loooves the sound of tubes. And my EF5 is so small but sounds so nice to my ears. I wonder if a bigger tube amps will take my setup to a much higher level. I asked around and someone very experienced DIYer suggested to try SSMH or miniMax if I want to have a big step up from my current setup. He said these amps are a steal for their price. So I just want to know your opinion here guys. Maybe I just send you PM than ask in this thread about the comparison between them. I really appreciate your information. Thanks


 
 No disrespect was felt. 
	

	
	
		
		

		
		
	


	



  
 It's a perfectly natural question, but probably best asked in the Head-Fi Amplifier section.  No one's going to object to sound quality comparisons, there.  It's just that DIY - in my opinion - is about offering do-it-yourself designs and support.  (This is the MiniMAX support thread, for instance.)  We're not even trying to compete against each other with most designs.  Most of us, even if we're MOT's, are running on shoestring budgets and do this because of our love of the hobby.  Yes, I'd be untruthful if I didn't say economics plays a large part, but that's simply the reality of buying, selling, and the required investments to do that on a regular basis.
  
 Anyway - it's just my opinion and one I try to adhere to.  As I said, no one's going to object to you asking any sort of comparison question over in the Amplifier section.  Besides reviews, that's the almost the whole purpose of that section.
  
 There's a comparison review on Head-Fi, but I think he had some dud tubes, or else didn't re-bias with tube changes.
	

	
	
		
		

		
		
	


	




  The MiniMAX was also sold as a fully-built product by Whiplash Audio for awhile, too.  I believe there are several reviews of the Whiplash Audio MiniMAX on Head-Fi.  The MiniMAX has been around for quite awhile - just google "Millett Hybrid MiniMAX review" and you'll find a bunch - even some youtube videos like this one: http://www.youtube.com/watch?v=kQtTv1qI1Yc


----------



## Bismar

Hi all,
  
 I was wondering if I may have a hand in troubleshooting my MiniMax.
  
 It's been going strong for quite a couple of years now, but unfortunately as I did not use a case for it, dust gathered and the blue smoke escaped.
  
 At first i thought the problem was isolated around the burnt QM1 which I've replaced, found out DM1 was open circuit, so replaced that as well. Fuse was a gone as well. I've then verified that the relay now successfully trips and that both relay output coils are switching. TA2L- Gnd/ TA2R-Gnd and TA2L-TB1L/ TA2R-TB2R are biased still correctly.
  
 I'm not really where to go from here. Could anyone recommend any other pads i should be testing?
  
 Cheers,
 Bismar


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## tomb

bismar said:


> Hi all,
> 
> I was wondering if I may have a hand in troubleshooting my MiniMax.
> 
> ...


 
 Questions:

If those points are biased correctly, does that mean that the amp turns on, but you get no sound?
What is the voltage setting?
Are you using the proper adapter (24VAC)?
How about the tubes - have you tried swapping them out?
  
 I'm not sure I see the issue from your description.  If the bias points are correct and you can tell that the relay switches in, you should get sound unless the tubes are blown.  Maybe you have a shorted tube?  Just as a check, can you give us the exact readings from your bias points?


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## Bismar

tomb said:


> Questions:
> 
> If those points are biased correctly, does that mean that the amp turns on, but you get no sound?
> What is the voltage setting?
> ...


 
  
 tomb,
  
 Thanks very much for your help, you solved it! 
  
 Its been so long that one pair of tubes has blown I did not honestly think about even swapping them out. Turns out both my previous tubes must have blown in the short.
  
 Its such a huge difference being able to use this amp again!


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## tomb

bismar said:


> tomb,
> 
> Thanks very much for your help, you solved it!
> 
> ...


 
  
 Glad you got it fixed!


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## tomb

*MiniMAX Improved Relay-Delay*
  
 I've meant to document this for a long time, but an e-mail this weekend from a customer finally forced me to do it. 
	

	
	
		
		

		
		
	


	




  As some of you know, the MOSFET-MAX uses an updated relay-delay circuit.  This circuit uses 24VDC instead of a zener-induced 12VDC supply.  This is accomplished by using a 24VDC regulator - the 78L24 - to establish the voltage to the relay.  The relay, in turn, is a 24VDC rated relay.
  
 The result is that the entire relay circuit operates much, much faster.  There are no immediately measurable spikes in voltage on turn OFF, where as the existing circuit had quite a bit.  Turn OFF voltage spikes to the headphone output are caused by the charged capacitors on the PCB and minute arcing between the relay contacts.  You can measure this yourself by applying a DMM to the headphone output while turning the amp off.  The voltage is liable to spike to several whole-number volts before everything dies down.  There is very little to no spikes using the 24VDC relay circuit that cetoole designed for the MOSFET-MAX.
  
 So what?  Well, ... it's very easy to implement this into an existing MiniMAX.  You don't need the MOSFET-MAX PCB to do it.
  
 Here's the original circuit schematic for the relay-delay used on the original Millett Hybrid MAX and the current Millett Hybrid MiniMAX:




 And here's the updated version using 24VDC, the new regulator, and a 24VDC relay:




 This can be implemented as it stands on an existing MiniMAX PCB as shown in the photo below:
  



  
 Note that RM2 has been replaced with 2M.  I soldered together two 1M resistors in the pic above, since 2M resistors aren't that common in my toolbox.  Further, there is no DM1, RM1, or QM1 (BD139 transistor).  The 78L24 is soldered into the first two pads of QM1 with the middle leg (pin 2) stretched out to connect to GND at the left pad of DM1.  This is all that's needed to obtain the advantages of the new relay circuit and its improvements.
  
 Note that most Millett Hybrid MAXes, MiniMAXes, and MOSFET-MAXes are setup with 27VDC at the power supply adjustment.  This gives sufficient voltage headroom to allow the 78L24 to regulate at 24VDC.  Other amplifier designs that run right at 24VDC or less will probably not work.  JMHO, but I believe the higher voltage - not just the regulator - has a lot to do with speeding up the relay and cutting down on the voltage spikes.
  
 Anyway, I hope I've demonstrated that it's pretty easy to implement the new circuit in existing MAXes or MiniMAXes.


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## lordearl

Thanks Tom - but is it entirely necessary to do the mod?
  
 In my minimax, I notice a slight click on power on, and also the same at power off.  But it's not painful on the ears or anyway, so I never ever take my headphones out of the socket. Is that ok?


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## tomb

lordearl said:


> Thanks Tom - but is it entirely necessary to do the mod?
> 
> In my minimax, I notice a slight click on power on, and also the same at power off.  But it's not painful on the ears or anyway, so I never ever take my headphones out of the socket. Is that ok?


 

 No, it is not necessary to do the mod.  The existing relay-delay provides ample protection and I have never unplugged my headphones with a MiniMAX.  However, for those measurement freaks who've applied a DMM to the amp at power off, they may have noticed some voltage spikes that would make them uncomfortable.  These spikes on Turn OFF are not exclusive to the MiniMAX or _even a tube amp or hybrid_.  They exist in any amp with significant capacitor loading (almost anything with more than a CMoy's 2 x 220uf).  This relay is fast enough to stop most of those spikes.  It is an improvement, nothing more.
  
 BTW - I forgot to mention that the BOM should be followed from the MOSFET-MAX.  It also specifies a different electrolytic capacitor for CM3.  It should be a 470uf, 35V cap.  The CM3 normally specified for the MiniMAX (470uf 16V) will blow up at 24VDC.
  
 Again, this is only documented for those wishing for a measureable improvement - and especially for those attempting to implement their own relay-delay in other amp designs.  It has been discussed several times before in this thread and the Starving Student thread.  It's just that I never documented how simple it is to install in the MiniMAX.
  
  
 P.S. I might have converted to this relay circuit completely in future MiniMAX kits, but the future of the MiniMAX is in doubt.  I'm afraid the market has been saturated and sales have been non-existent lately.  When it comes time to manufacture more custom-machined cases to the tune of several thousands of dollars, it may just be the best business decision to not continue with it.


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## NuClear235

Thank You for still care and developing this project !
 Your support is great - photos, details ...
 Stay with us 
	

	
	
		
		

		
		
	


	



 Thanx a lot!

 edit: I just did it.


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