# Pete Millett's Menace



## n_maher

I'm going to create a thread for this amp since it is my intention at the end of the build to publish the schematic and any relevant details so that anyone who's crazy enough can build this amp. As of right now the amp is in working condition and headed to Florida for the party that will be CanJam. First, a little backstory...

_A Brief History of The Meance_

 So really this started years ago, but if I tell the story that way it won't make a bit of sense to anyone other than myself. And I did say brief history and I swear I'll try to keep it that way. 

 This really got going in late December of this past year when I got a message from a friend (who shall remain nameless) that they had an abandoned project that I might be interested in picking up. The basic gist of the project was that they had taken the Van Waarde project along with the Wheatfield HA-2 design and started to improve upon the general concept. Most notably this involved paralleling the output tubes and increasing the output coupling capacitance to the point where driving low-impedance headphones would be possible. The original HA-2 was technically able to do this but not all that well in my opinion. So me being the unabashed Pete Millett fan that I am and a former HA-2 owner jumped all over it. Quick note - both the Van Waarde and the HA-2 schematic are out there if you know where to look, the Waarde is at Headwize (linked above) and owners of the HA-2 know where to find its schematic. I believe that Headroom still owns the HA-2 design and as such I won't be publishing that schematic, only my revised version. Now the revised design that started this mess had been taken to the proof of concept level but in such a way that things like the power supply still needed figuring. So while I won't be using much of what was done as a part of that project I do owe my friend a huge debt of gratitude in terms of motivation and inspiration, without that initial push I'm sure that this would have never happened. 

 Now I'm no designer, I never have been and I never will be since there just aren't enough hours in the day and honestly I'm completely comfortable leaving that up to other folks. I love building this stuff but typically my interest dies off quickly after that point. To a degree that had to change for this project since there was still much work to be done. So I started doing some basic math along with consulting with a few folks about the power supply. It was initially my hope to simply re-use the existing HA-2 tube-rectified design and tweak it as needed. This was quickly abandoned after seeing that the existing PS design was pretty much tapped in terms of current capacity. It was at this point that I decided to call in the big guns and see if I couldn't enlist the help of the guy who was really responsible for all this. I've communicated off and on with Pete Millett for the past few years, mostly as a result of my dealings with the Low Voltage Hybrid project as well as dealing with the issues that my original HA-2 had. Like I said, I'm a hug Pete fan the guy gives tirelessly to this hobby and I can't wait to shake his hand next week, I'm getting side-tracked, back to the story. But Pete's a busy guy and I didn't really expect to have him launch into it the way that he did but it'd be safe to say that this project may well have died without his help. He continues to be a integral part of the design process and I can't say thanks enough so, thanks Pete! I started talking power supply design with Pete and we quickly came up with a couple of concepts and I elected to go with what seemed to be the simplest from a parts perspective (fewer transformers and bits that I was used to working with). I also elected to have the amplification side of the equation be essentially a tweaked HA-2 that will run parallel output tubes, larger output coupling capacitors and modified heater supplies. This should help some of the issues that the original HA-2 suffered from which were some PS hum and output impedance that wasn't really all that suited for driving Grados.

 So I sketched up schematics and sent them to Pete and what followed was some back and forth that culminated with some rather large parts orders in late March but I didn't get around to actually starting the build until April 10th. Nothing like leaving myself plenty of time to get it ready for CanJam. 
	

	
	
		
		

		
			





 I think I'll stop here and leave the details to later on in the process but hopefully that paints at least a little bit of a picture as to where this came from and where it's headed. As I said in the beginning it's my full intention to publish the schematics that Pete and I came up with when I get back from CanJam. The versions that I have uploaded right now have a few minor errors in them and I'd rather not steer someone in the wrong direction.

 Here area a few pictures from during construction, all told I think I've got about 14 days/nights of on and off work into the amp. Maybe 40hrs or so, it's pretty hard to tell really as I'm sure if someone had large chunks of time rather than a hour here and there it could be done more quickly.













































 Finally, here are two shots from testing the amp last night.











 I'm going to hold off on internal wiring shots until I can update pictures since there are substantial changes from what i had before. I've posted one on this site already but since this is intended to be the source for good information about the amp I don't want to cause confusion. 

 I also can't offer much in the way of listening impression since I've spent a grand total of 2hrs listening to the amp, only one of which was after the final modifications. What I have heard so far offers great promise and the root of the design is sound so I have little doubt that the amp will perform up to my expectations, which are quite high. 
	

	
	
		
		

		
		
	


	





 So that's it, the introduction of The Menace. Once again I have to say a huge thanks to Pete Millett who's advice and help throughout this project was simply invaluable.


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## n_maher

WARNING: The following schematics depicts a project that involves working with high voltages. Use of this schematic is permitted with the understanding that if you're not careful, this thing can kill you. Not only are you working with line voltages but the HV (B+) supply has a lot more current capacity than your typical tube project and should be treated with a great deal of respect. Getting hit by ~300V is no fun, assuming you live to tell the tale. That said with proper respect and care there's nothing exceptionally complex about this amp or power supply.

 WARNING2: There may still be errors in the schematic (please see note below) and please feel free to tell me if you see any. Pete was kind enough to digitize my hand-drawn version and we've caught one mistake already. So please, just post or shoot me a PM, nobody's perfect and you won't hurt my feelings one bit. 
	

	
	
		
		

		
		
	


	




 Schematic (updated 5/20)

*Amp*
*Important Correction* - in the original schematic C3 is NOT CORRECT! It should be the same cap used at the C4 position (10uF/400V). You will probably have a very bad day if you use a 50V cap at this position. I've updated the image file but the old one may stay in your browser's cache for a while. If you're still seeing a 220uF cap at C3 you're seeing the old file.





*PS*





 I'll be putting together some other thoughts and comments on the build at some point in the near future (hopefully) but there are a couple items of note to start:

 Rectifier tubes: this PS can run on any of the following - 5AR4s, 5R4s, or 5U4s. Depending on the tube that you get you may exceed the peak current capacity of the tubes and see some arcing at startup. I haven't had this issue with any of the tubes but for both the 5AR4 and 5R4 we are at or near the peak. The issue with the 5U4 is that they stress the 5V winding of the BFT more than they should be. Pete and I spoke with the trafo manufacturer who essentially said that if we weren't exceeding the total VA for the trafo we should be fine. This was one of the reasons that we selected this transformer, it's absurdly overbuilt and I like that. I've run the amp for more than 5hrs straight with 5U4s in there and the trafo gets barely warm to the touch. My preference right now is to run 5AR4s since they offer a nice slow warm up of the B+ which is easier on the tubes in the amplifier section.

 B+: we're running the HV section of the transformer pretty hard as well, but again, the man'f was consulted and the advice was similar to the filament section. Also, B+ will vary depending on the rectifier tube choice that you make, I haven't taken measurements with all 3 but I do know that I get an acceptably high B+ regardless of choice. 

 General Comment: clearly there are lots of alternate configurations that can be chosen depending on what your end goal is. What is presented here is simply one example of a working configuration that has, to my ears anyway, produced great results.

 more later....


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## n_maher

reserved for updates2


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## pabbi1

Having followed the HA family tree (Millett Hybrid, HA-1 and HA-2 (my long-time love)) this is uber interesting. Just wonder if it will sound better than the HA-2 on Senns as well?

 And, I will throw the B word out - will this drive me back to SE? 

 Looks like a P2P even I could love.


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## ericj

We call it the van Waarde amp, but Dr. van Waarde attributes the original design to Rudy van Stratum. 

 OTOH, I guess for the purposes of this thread, we can keep calling it a van Waarde.

 It looks like you're paralleling both sides of a 6080 per channel. I have seen small speaker amps like that. 

 So, this seems like big overkill. Am i not understanding the amp?


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## tomb

Amazing work, Nate!!


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## n_maher

Quote:


  Originally Posted by *ericj* /img/forum/go_quote.gif 
_We call it the van Waarde amp, but Dr. van Waarde attributes the original design to Rudy van Stratum. 

 OTOH, I guess for the purposes of this thread, we can keep calling it a van Waarde._

 

Well, regardless of what we call it I think it's important to give credit where credit is due so your information is appreciated. But really, this all probably goes back a lot further than that so I hope no offense will be taken by those who paved the way.

  Quote:


 It looks like you're paralleling both sides of a 6080 per channel. I have seen small speaker amps like that. 
 

That is correct, the output tubes are run in parallel.

  Quote:


 So, this seems like big overkill. Am i not understanding the amp? 
 

Overkill might be a strong word in the same sense that the beta22 is overkill. 

 The basic premise here was to take the Wheatfield HA-2 model and do some things to improve upon it that simply couldn't be done in the commercial realm. For example, the power supply weighs nearly 50lbs by itself. No commercial man'f is ever going to want to deal with that! So were all of the changes strictly required, of course not, but where would be the fun in stopping there. The parallel tubes and increased output coupling capacitance on the other hand allow the amp to be much better suited to driving low impedance headphones like my HF-1s. So to me those were required. Also, I wanted to retain as much of the original amps characteristics so I made choices based on that requirement that are clearly unnecessary for anyone but me.

 I'm not trying to claim that what is presented here is either the most efficient or cost effective way of achieving a given goal. Just an approach that I chose based on my ideas and priorities. If only one of these gets built (mine) that's fine by me, maybe someone else will look at and find inspiration to do something different. The idea is just to share.


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## n_maher

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Amazing work, Nate!!
	

	
	
		
		

		
		
	


	





_

 

Thanks Tom, as you well know these tend to be a labor of love.


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## amphead

Thanks Nate, for bringing such a promising design to the table. And thanks Pete for continuing to improve designs for the DIY community!


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## pmillett

Quote:


  Originally Posted by *ericj* /img/forum/go_quote.gif 
_So, this seems like big overkill. Am i not understanding the amp?_

 

Hey, if you don't like overkill, go for a (practical and perfectly "adequate") opamp-in-a-box!






 Besides, it can double as a beverage warmer.

 I really think this thread needs to be titled "Nate Maher's Menace". Nate did all the work. I only helped because Nate promised to pick up my beer tab at CanJam. He doesn't know what he signed himself up for 
	

	
	
		
		

		
		
	


	




 Or maybe call it Maher's Menace...

 ...Maher's Millett Menace...

 ...Menacing Maher's Millett...

 ...Maher's Mega-Massive Menace...

 Pete


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## dsavitsk

Quote:


  Originally Posted by *ericj* /img/forum/go_quote.gif 
_So, this seems like big overkill. Am i not understanding the amp?_

 

Z out is defined by 1/Gm. Gm on the 6080 (7000 umho) is not that high which means Z out is high. Paralleling the sides halves it. Even with one, there is still plenty of current to drive low Z phones to be very loud, but even with a bunch of sides in parallel, damping factor is still not very good. 

 If you want to use a cathode follower to dive phones, (and I think there are better ways to drive low Z phones, but you probably already knew that that was my opinion) and you are willing to parallel sides, a 6922 or a 6H30 seems like the better choice. 6080's need a ton of heater current and a ton of plate current, and while they also thus have a ton of output power so they can afford to be really inefficient, a few parallel 6922 sides also has plenty of current and a lower Z out as well.

 Here is a nice primer: http://www.tubecad.com/2005/June/blog0049.htm

 You'll notice that a 6as7/6080 can output 1.63W into a 32 ohm load, while the single 6922 can only muster 25mW. But, you can double this for parallel sides, (3W v. 1/2 watt) and, more importantly, if you put 25mW through your Grados, you will lose your hearing. I measured mine, and at normal listening levels, I was at 3mW. 5mW hurt.

 More important, in my experience, is that damping factor matters more for these low Z phones. Damping factor, which is the ability of the amplifier to control the speaker, is the ratio of speaker Z over Z out from the amplifier. I think with Grados you want at least 5 in an ideal situation. That means a Z out of about 6, which means 24 total 6as7's for 32 ohm phones. Obviously that's just silly, but it illustrates the point that this is an inelegant brute force method not really appropriate for low Z phones. The old truism that Grados need current and Senns need voltage is basically true. Ironically, while there is a history of 6080's in headphone amps, I don't think they are actually a very good choice for either.


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## Pars

Quote:


  Originally Posted by *pmillett* /img/forum/go_quote.gif 
_<snip>

 I really think this thread needs to be titled "Nate Maher's Menace". Nate did all the work. I only helped because Nate promised to pick up my beer tab at CanJam. He doesn't know what he signed himself up for 
	

	
	
		
		

		
		
	


	




 Or maybe call it Maher's Menace...

 ...Maher's Millett Menace...

 ...Menacing Maher's Millett...

 ...Maher's Mega-Massive Menace...

 Pete_

 

How about Maher's Menacing Bar Tab


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## holland

Sweet looking amp. I can't wait to hear more details about it (won't be at canjam).

 For some reason, I keep thinking AM/PM...NM/PM...PM/NM...Those damned am/pm commercials.

 "AM/PM. Too much good stuff."


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## grawk

Aniston's Revenge?


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## ericj

Quote:


  Originally Posted by *dsavitsk* /img/forum/go_quote.gif 
_If you want to use a cathode follower to dive phones, (and I think there are better ways to drive low Z phones, but you probably already knew that that was my opinion) and you are willing to parallel sides, a 6922 or a 6H30 seems like the better choice._

 

Or two sides of a 6N6P, for example. 

  Quote:


  Originally Posted by *dsavitsk* /img/forum/go_quote.gif 
_More important, in my experience, is that damping factor matters more for these low Z phones. Damping factor, which is the ability of the amplifier to control the speaker, is the ratio of speaker Z over Z out from the amplifier. I think with Grados you want at least 5 in an ideal situation. That means a Z out of about 6, which means 24 total 6as7's for 32 ohm phones. Obviously that's just silly, but it illustrates the point that this is an inelegant brute force method not really appropriate for low Z phones. The old truism that Grados need current and Senns need voltage is basically true. Ironically, while there is a history of 6080's in headphone amps, I don't think they are actually a very good choice for either._

 

You have a point about the damping factor i suppose.

 In my own use, I have no senns or grados. Well, I have senns, but px100 and hd25sp are portables and don't count. 

 i seem to have a lot of 600-ohm cans, which just need a lot of gain or as you say voltage, and orthos, which need unusually high gain for their relatively low impedance - 150 ohms at the most - and thus seem to need both more than average voltage and more than average current. A damped-flat Yamaha HP-1 at 150 ohms needs slightly more gain than a 600-ohm K240-M or DT990 for the same SPL. 

 And yeah, I'm building an amp with a 6080 too, but mostly just out of curiosity.


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## dsavitsk

Quote:


  Originally Posted by *ericj* /img/forum/go_quote.gif 
_And yeah, I'm building an amp with a 6080 too, but mostly just out of curiosity._

 

In general, I think that if tubes are in the amp, that transformer coupling is a good plan. The lower the impedance of the transformer, all other things being equal, the better it will perform. The 6080 has such a low rp that you can use a low impedance transformer. So, it could be used to good effect in that regard. Though at that point, I'd use a 45 or a 2A3


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## pmillett

Quote:


  Originally Posted by *dsavitsk* /img/forum/go_quote.gif 
_In general, I think that if tubes are in the amp, that transformer coupling is a good plan. The lower the impedance of the transformer, all other things being equal, the better it will perform. The 6080 has such a low rp that you can use a low impedance transformer. So, it could be used to good effect in that regard. Though at that point, I'd use a 45 or a 2A3 
	

	
	
		
		

		
		
	


	


_

 

Transformer coupling is wonderful. But wonderful transformers are expensive...

 Pete


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## ericj

Quote:


  Originally Posted by *pmillett* /img/forum/go_quote.gif 
_Transformer coupling is wonderful. But wonderful transformers are expensive...

 Pete_

 

Not to mention, what impedance should the transformer secondary have? A man with four pair of good headphones could have one with 24-ohm impedance (a denon for example) and one with 600-ohm impedance, and another at 200 ohms and another at 400 ohms . . . .


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## nikongod

very nice work nate. i like the layout a lot, and cant wait to see the inner-bits of the amp.


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## dsavitsk

Quote:


  Originally Posted by *pmillett* /img/forum/go_quote.gif 
_Transformer coupling is wonderful. But wonderful transformers are expensive..._

 

Yeah, I guess, but compared to a 50lb power supply? For the money people spend on amps around here, a $100, or even $200 pair of OPTs isn't really that bad. And, even a $40 pair of power toroids can do wonderful things.

  Quote:


  Originally Posted by *ericj* /img/forum/go_quote.gif 
_Not to mention, what impedance should the transformer secondary have? A man with four pair of good headphones could have one with 24-ohm impedance (a denon for example) and one with 600-ohm impedance, and another at 200 ohms and another at 400 ohms . . . ._

 

Sowter has a good solution for this. They use 4 equal secondaries that can be combined in various parallel and series connections for multiple impedances. You can also just push them up higher so long as the induction is sufficient -- it usually is with parafeed. So long as gain is sufficient, you end up with lower distortion this way.

 Anyhow, I apologize for derailing the thread, so I'll leave it alone.


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## amphead

Quote:


 They use 4 equal secondaries that can be combined in various parallel and series connections for multiple impedances. 
 

Hmmm..... hadn't thought of that way to get impedance/load matching. Very Nice.


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## n_maher

Quote:


  Originally Posted by *dsavitsk* /img/forum/go_quote.gif 
_Yeah, I guess, but compared to a 50lb power supply?_

 

Well, the problem is that it's kind of hard to eliminate the 50lb beast if you want to be able to run the amp at the current levels that I did and keep it tube rectified. The B+ needed to supply almost .4A of current at ~300V and there are three different heater supplies: 5V for the rectifiers, 6.3V for the input and 6.3V @10A for the output tubes.

  Quote:


 Anyhow, I apologize for derailing the thread, so I'll leave it alone. 
 

Actually, I think that the discussion is great. The design is a platform, not a directive so exploring options are a welcome addition. At one point I was actually considering a transformer coupled version but decided to stick w/ my original plan of a hot-rodded HA-2. I can't wait to hear Pete's new TTVJ trafo coupled design at CanJam.

  Quote:


  Originally Posted by *nikongod* /img/forum/go_quote.gif 
_very nice work nate. i like the layout a lot, and cant wait to see the inner-bits of the amp._

 

Thanks Ari, the layout was largely dictated by function, not form ironically enough. The PS layout is darn near a schematic in the way that it's put together. For the amp I knew certain things, like wanting to keep the heater wiring as far away from the signal path as possible, so I chose to have the heater wiring come into the chassis on the opposite side of the rear panel. For the amp I also went as far as doing CAD drawings of the layout and a wiring diagram to try and head off any potential problems. Those efforts paid huge dividends in the form of much less thought having to go into the wiring when I got down to business. And in truth the circuit is pretty straight forward and simple (low parts count) compared to a lot of the SS stuff that I've worked on.


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## ericj

Quote:


  Originally Posted by *n_maher* /img/forum/go_quote.gif 
_Well, the problem is that it's kind of hard to eliminate the 50lb beast if you want to be able to run the amp at the current levels that I did and keep it tube rectified. The B+ needed to supply almost .4A of current at ~300V and there are three different heater supplies: 5V for the rectifiers, 6.3V for the input and 6.3V @10A for the output tubes._

 

eh? 10 amps? 2.5 amps per 6080 iirc.


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## mrarroyo

Do not understand any of the technical stuff! 
	

	
	
		
		

		
		
	


	




 But if the amp sounds half as good as it looks it will be a killer. Nice work!


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## n_maher

Quote:


  Originally Posted by *ericj* /img/forum/go_quote.gif 
_eh? 10 amps? 2.5 amps per 6080 iirc._

 

I thought that I'd mentioned before but I just looked and I didn't - the amp was designed to be able to run at least 7 output tube options: 6AS7, 6080, 5998, 7236, 6528, 6336, 421A and I'm sure many others that I haven't found yet. The heater requirements range from a low of 2.4A (per tube) all the way up to 5A. I'm working through all the substitutes listed in Duncan's TDSL but for the 6080 alone there are more than 10 alternative tubes listed so I'm sure my wallet will give up long before I run out of tubes to try.


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## dsavitsk

Quote:


  Originally Posted by *n_maher* /img/forum/go_quote.gif 
_Actually, I think that the discussion is great._

 

Okay, then I'll say more 
	

	
	
		
		

		
		
	


	





  Quote:


  Originally Posted by *n_maher* /img/forum/go_quote.gif 
_Well, the problem is that it's kind of hard to eliminate the 50lb beast if you want to be able to run the amp at the current levels that I did and keep it tube rectified. The B+ needed to supply almost .4A of current at ~300V and there are three different heater supplies: 5V for the rectifiers, 6.3V for the input and 6.3V @10A for the output tubes._

 

So, I guess the point I was trying to make is that there are 2 main ways to lower the output impedance (assuming no solid state buffers). One is to use brute force -- a stack of cathode followers, or something similar -- the other is to use impedance matching via a transformer. With the transformer, you wouldn't need the huge volume of tubes, and thus would save the expense of a huge power supply. A single 6H30 will power almost any phones to extreme volumes, for example.

  Quote:


  Originally Posted by *n_maher* /img/forum/go_quote.gif 
_I can't wait to hear Pete's new TTVJ trafo coupled design at CanJam._

 

I didn't know such a thing existed. I'm curious to see how Pete designed it.


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## dsavitsk

Quote:


  Originally Posted by *n_maher* /img/forum/go_quote.gif 
_I can't wait to hear Pete's new TTVJ trafo coupled design at CanJam._

 

Is it this one? TTVJ Millett 307A Headphone Amplifier [TTVJ Millett 307A] - $5,995.00 : TTVJ, Todd The Vinyl Junkie

 That would explain why everyone is sold out of 307A's right now. It took me forever to track some down recently.


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## n_maher

Quote:


  Originally Posted by *dsavitsk* /img/forum/go_quote.gif 
_Okay, then I'll say more 
	

	
	
		
		

		
		
	


	


_

 

Please do, as I said I'm no designer and contributed very little to this project from a design perspective. About all I designed was the heater biasing setup, which is really nothing more than a series of voltage dividers. I was rather happy that it actually worked. 
	

	
	
		
		

		
		
	


	




  Quote:


 I didn't know such a thing existed. I'm curious to see how Pete designed it. 
 

The TTVJ Millett 307A Headphone Amp.


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## vcoheda

Quote:


  Originally Posted by *dsavitsk* /img/forum/go_quote.gif 
_Is it this one? TTVJ Millett 307A Headphone Amplifier [TTVJ Millett 307A] - $5,995.00 : TTVJ, Todd The Vinyl Junkie

 That would explain why everyone is sold out of 307A's right now. It took me forever to track some down recently._

 

wow!

 that amp looks pretty cool. 6K though.


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## nikongod

I like OTL amps. pete's comment on good transformers having a good price is very true, but i agree with davistk's point of transformers doing cool things.

 i still think the amp looks pimp, and if nate REALLY wants transformers they can always be run parafeed in a their own little case like moth used to do. its a nice project for a rainy day.


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## pmillett

Quote:


  Originally Posted by *dsavitsk* /img/forum/go_quote.gif 
_ A single 6H30 will power almost any phones to extreme volumes, for example._

 

True... I built an amp using a single 6H30pi and a Sowter 9351. It sounded very nice. But it had two issues: The Miller capacitance of a 6H30p is high, so you need a fairly low-Z source to drive it. And the 9351 costs 91 GBP each - given today's worthless dollar, that's $360 worth of OPTs, plus shipping from England.

 Pete


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## pabbi1

I was exposed to a schematic using 6H30 on psu and 6H30pi on the amp sections (sorry, not literate enough to know which 'stage') but it requires 6 Lundahl transforners at around $1k for the Sweedish iron, unless I was confused about the trannies required for the balanced build.

 Still considering this, some day.

dsavitsk: Something like this?

 This from the same guy loosely associated with the Raven project.


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## dsavitsk

Quote:


  Originally Posted by *pmillett* /img/forum/go_quote.gif 
_True... I built an amp using a single 6H30pi and a Sowter 9351. It sounded very nice. But it had two issues: The Miller capacitance of a 6H30p is high, so you need a fairly low-Z source to drive it. And the 9351 costs 91 GBP each - given today's worthless dollar, that's $360 worth of OPTs, plus shipping from England.

 Pete_

 


 That's a lot. I got a pair of 1W parafeed 5K:32 transformers from electra-print for under $100. I also got a pair of nickel lams to swap into those, also for $100, which means $200 for Nickel parafeed transformers. Or, $200 for Intact Audio's nickel AVC's which can be used as an OPT (I am working on a version right now with 71a's). Or, my single feed 5K:32 electra-prints gapped at 35mA weren't more than $150 or so.

 Lundahl has the LL1930 which will work for differential or single ended parafeed at about $120 or so. The Hammond 119DA is decent at $60, though they were more decent when they cost $30 for the pair last year. A pair of power toroids can be had for about $40 and can sound surprisingly good.

 Check out my L'espressivo project for more: 
Background and ramblings
Actual build instructions

Or my shunt regulated single feed amp

  Quote:


  Originally Posted by *pabbi1* /img/forum/go_quote.gif 
_
dsavitsk: Something like this?_

 

Yeah, but you can get away with way cheaper iron.

 Here's the Balanced L'espressivo, which would run you about $180 or so.


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## Voltron

Quote:


  Originally Posted by *pmillett* /img/forum/go_quote.gif 
_Hey, if you don't like overkill, go for a (practical and perfectly "adequate") opamp-in-a-box!






 Besides, it can double as a beverage warmer.

 I really think this thread needs to be titled "Nate Maher's Menace". Nate did all the work. I only helped because Nate promised to pick up my beer tab at CanJam. He doesn't know what he signed himself up for 
	

	
	
		
		

		
		
	


	




 Or maybe call it Maher's Menace...

 ...Maher's Millett Menace...

 ...Menacing Maher's Millett...

 ...Maher's Mega-Massive Menace...

 Pete_

 

One vote for Maher's Menacing Millett. Too bad Nate's going to need a second mortgage to cover that bar tab! Talk about menacing.


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## fierce_freak

dsavitsk, I've been very interested in both the L'espressivo and the S^3 amps you've put together for quite awhile. I'm looking at putting together a high-end tube amp in the near future, but perhaps I'll start out with a balanced L'espressivo to start (I've never heard a transformer coupled amp, only OTL).

 I've been thinking of going more along the line that Nate has gone, though, as all the top tube amps that are easy to get impressions on are, for the most part, overbuilt OTL amps (Wheatfield, Zana Deux, Singlepowers).


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## n_maher

Quote:


  Originally Posted by *Voltron* /img/forum/go_quote.gif 
_One vote for Maher's Menacing Millett. Too bad Nate's going to need a second mortgage to cover that bar tab! Talk about menacing. 
	

	
	
		
		

		
		
	


	








_

 

Al, my plan is to get him started drinking whisky and only later remind him that I agreed to pick up the *beer tab.* As my West Coast lawyer I may need backup on this...


----------



## Voltron

Quote:


  Originally Posted by *n_maher* /img/forum/go_quote.gif 
_Al, my plan is to get him started drinking whisky and only later remind him that I agreed to pick up the *beer tab.* As my West Coast lawyer I may need backup on this... 
	

	
	
		
		

		
		
	


	


_

 

Given that your East Coast counsel is a ball of nerves and and will be rather distracted, I will gladly step in and practice law outside my jurisdiction to back you up on this one. Only problem I foresee is that Pete has been reading this thread, so we had better scrub our posts.


----------



## naamanf

Quote:


  Originally Posted by *n_maher* /img/forum/go_quote.gif 
_I'm going to create a thread for this amp since it is my intention at the end of the build to publish the schematic and any relevant details so that anyone who's crazy enough can build this amp._

 

Well we have already established I'm crazy......


----------



## dsavitsk

Quote:


  Originally Posted by *n_maher* /img/forum/go_quote.gif 
_Al, my plan is to get him started drinking whisky and only later remind him that I agreed to pick up the *beer tab.*_

 

TV : Are you stuck in a deadend job?
 Homer : May be.
 TV : Are you sitting on your couch in front of the tv ...
 Homer : What's it to you?
 TV : Are you on to your 3rd beer of the evening?
 Homer : Does whiskey count as beer?


----------



## pmillett

Quote:


  Originally Posted by *Voltron* /img/forum/go_quote.gif 
_Given that your East Coast counsel is a ball of nerves and and will be rather distracted, I will gladly step in and practice law outside my jurisdiction to back you up on this one. Only problem I foresee is that Pete has been reading this thread, so we had better scrub our posts. 
	

	
	
		
		

		
		
	


	


_

 

Wait... you owe me beer too, don't you? I sense a conflict of interest...

 Pete


----------



## amphead

Dsavitsk, how about 119DA and the Bijou?


----------



## pabbi1

Quote:


  Originally Posted by *pmillett* /img/forum/go_quote.gif 
_Wait... you owe me beer too, don't you? I sense a conflict of interest...

 Pete_

 

Truth be told, and in a perfect world, half the DIY board owes you (more than) a beer... I'm sure my tab is at five or six, just based on your designs I have enjoyed / built.


----------



## dsavitsk

Quote:


  Originally Posted by *amphead* /img/forum/go_quote.gif 
_Dsavitsk, how about 119DA and the Bijou?_

 

One answer is that I think the Amveco toroids actually sound better for less money. Or, the Lundahl LL1930's also sound better for about $40 extra (these use mu metal rather than amorphous cores and lack the shielding of the other Lundahls which is why they are less expensive. They are still quite good, and probably the best deal in the Lundahl line.) If you have the Hammonds, use them, but otherwise they probably aren't the best deal in the price range.

 By the way, here's a post on how to pick your power toroid for output use: HeadWize: View Post [DIY Workshop > Less-pressivo: High performance, low cost, all tube, headphone amp]

 The other answer is that the Bijou is not really the ideal platform for transformer coupling. It will work, but the amp uses various features to obtain a low Z out, and my sense is that using those features is an either or with transformers. That is, transformers allow you to build much simpler circuits that use many less components -- less tubes, less capacitors, etc. The trade off, of course, is that you have to spend the extra money on the transformer. But, doing both in the same amp is probably not the best idea from a design perspective as I think it probably compromises both designs. That is to say, I don't think adding a pair of OPTs is going to bring much to the table.

 I like to joke about the original L'espressivo being so cheap to build, but honestly, the only reason it ever becomes expensive is if you start adding expensive parts -- the parts list remains pretty constant.


----------



## amphead

Ok, the only reason I brought that up was Lo Z phones(K701) and NFB removed. The lower the impedance load, the closer to a shorted output. Just too large of a current demand that might be tamed with a matched OPT. Nates design here looks good. The Native Menace.


----------



## n_maher

Quote:


  Originally Posted by *amphead* /img/forum/go_quote.gif 
_Nate's implementation of Pete's design here looks good._

 

FIFY


----------



## amphead

ISC


----------



## swt61

Quote:


  Originally Posted by *grawk* /img/forum/go_quote.gif 
_Aniston's Revenge?_

 

Not sure how obscure that reference is to many here, but I just about spit my drink out!


----------



## grawk

It can't be THAT obscure, can it?


----------



## nikongod

hi dsavitsk

 i was looking at the less-pressivo thread over at headwize, and that amp looks sweet. I like original design too, but too much money 
	

	
	
		
		

		
		
	


	




 i was curious with the balanced schematic why you put the cap between the halves of the transformer with no ground connection rather than at both ends with the centers grounded. it is still parafeed, and no current flows in the primary, but why drop the safety feature of having the transformer grounded?


----------



## dsavitsk

Quote:


  Originally Posted by *nikongod* /img/forum/go_quote.gif 
_i was curious with the balanced schematic why you put the cap between the halves of the transformer with no ground connection rather than at both ends with the centers grounded. it is still parafeed, and no current flows in the primary, but why drop the safety feature of having the transformer grounded?_

 


 So, two issues. The first is what it means to be balanced, and the second is the parafeed part. For my own personal safety, I don't believe in using balanced phones that have no connection to ground, especially with high voltage amplifiers. OPTs are inherently going to give out a balanced signal, but I always ground one side of the secondary. So, when I say balanced, I really mean that the amp is balanced throughout, but not on the output necessarily. If you really want to do balanced phones, I'd connect another wire to ground the body of the phones.

 For the parafeed part, any high voltage amp (for dynamic phones) is going to have something between you and the high voltage. With OTL and most single ended parafeed, it is a capacitor -- parafeed (though not the original Espressivo) having a transformer too. With single feed designs, the primary of the transformer sits at a high voltage with the secondary grounded. With the balanced design, like the single feed design, the transformer acts as the block. 

 Your suggestion essentially puts a secondary safety measure in place. The down side is that, as drawn, the signal path includes 2 tubes, 1 transformer, and one cap. Your suggestion would add a second cap plus the biasing mechanism which would need to be bypassed with a cap (or LED) which would impact in the sound quality. But, being aware of these issues and knowing what stands behind you and oblivion, is important. I happen to trust transformers more than caps to block voltage.


----------



## funch

Question for Nate. Where did you get those nifty tranny mounting isolators?


----------



## n_maher

Those are from McMaster Carr - I'll grab part numbers and post them later since you're not the first to ask. 
	

	
	
		
		

		
		
	


	




 If you want to look in the mean time I believe that they are listed under vibration isolating grommets or something like that.


----------



## n_maher

The Blue ones are part no:9311K139. Based on that you should be able to find the range that they carry, which is how I found the black ones.


----------



## philodox

Wow, look what I miss when I leave for a few days. Sounds like a great project Nate... can't see the pics right now unforunately, but I'm gonna try to get to a internet cafe or something to have a look. Can't wait to hear this at CanJam!


----------



## philodox

Well, I'm at home now and stealing internet from someone in my building. WOW! That is what I call a power supply! You never cease to amaze Nate... I can't wait to hear this beast.


----------



## swt61

Quote:


  Originally Posted by *philodox* /img/forum/go_quote.gif 
_when I leave for a few days._

 

A few days!? 
	

	
	
		
		

		
		
	


	




 We had the national guard working with the Canadian authorities trying to locate your body. 
	

	
	
		
		

		
		
	


	




 Good to see your OK!


----------



## pabbi1

OK, long time, no update - any impressions, specifically from CanJam? How is she to live with, Nate?

 Still looking for the BOM, and build details... pretty please?


----------



## pukka

This post brought a big smile on my face... 

 Back in 2002 I took Pete's design and started doing rounds and rounds of PSU design testing and tube/components permutations and started harrasing everyone around, including Pete (who kindly explained the design and suggested things to try) 
	

	
	
		
		

		
		
	


	




 The fact is my final setup is still over a woodboard, never cased it up as I thought it was overkill and wanted to test other amp designs, as everyone told me WCF were a very constrained design in terms of improvement.

 In short the beefiest and more expensive section of the amp was the PSU, its design had the most impact on final sound. I end up with tube rectified (5C3S) to a double LCLC stage with plenty capacitance (900uF). Used a seperate transformer for 6.3VAC heating. B+ was around 210VDC.

 I tried tons of input and output tubes, including paralleling sections, the final tube chosen for input was a 6H30P-DR, and the output a 5998.

 With that coupled to my K401 (120Ohm, 89dB sensitivity) sound was incredibly organic, plentiful of controlled bass and overly lush while having very good distortion figures and characteristics. I'm not a classic music listener but know how real instruments sound like, and strings and piano sound was incredible. I did some sims aided by Alex Cavalli but ended up using pots and fiding sweet bias spots by ear. 

 For inputs I tried Ecc88, 6SN7 both short and tall bottle, 6N1P and 6H30P-DR. Sound with the 6H30P-DR was clearly the best, sounding like an octal tube in terms of distortion characteristics but like a noval in terms of "definition" when biased in its sweet spot. 6N1P was second best but more analytical.

 For output I tried 3 different 6AS7 NOS tubes, a RCA 6080, svetlana NOS 6C13C, and TungSol 5998. Also 6H30P-DR. Tried paralleled sections, etc...

 A single 5998 came out as a winner probably due to its lower Zo as advised by Pete, followed by the 6C13S.

 The key there was to run it hot enough (original Waarde amp didn't sound quite right to me) and the kind of Rk resistors used.

 Of course the output caps were key, I tried tons of kinds and combinations and in the end I found the Solens to be the most neutral, there are non electrolityc caps today much better than the Solens... 

 In the end I discovered I needed a better source also but that got put on hold until recently I buillt a USB based DDDAC and tube DIY "sparked" back on me . I may give it another shot!

 Can't wait to see the final Menace design published!


----------



## holland

Quote:


  Originally Posted by *pabbi1* /img/forum/go_quote.gif 
_OK, long time, no update - any impressions, specifically from CanJam? How is she to live with, Nate?

 Still looking for the BOM, and build details... pretty please?_

 

Sorry to be a PITA, but x2 or x3 or x(n).


----------



## n_maher

Quote:


  Originally Posted by *pabbi1* /img/forum/go_quote.gif 
_OK, long time, no update - any impressions, specifically from CanJam? How is she to live with, Nate?_

 

Sorry, I've been busy trying to play catch-up after CanJam. I have a final version of the schematic that Pete did based on my hand-sketched ones, I need to do a final review of that and then I'll post it. Impressions from CanJam were all really positive and are scattered throughout the thread in the Meet Forum. For most of the meet it was running with a Sylvania Bad Boy on the input and Cetron 5998s on the output, this was a very nice combo and seemed to drive both Grados and Senns equally well. Since getting the amp home I've been running a CBS 5692 on the input and Tung Sol 421A's on the output and I've been loving every minute of that experience. I've added some additional heat sinking to the top panel of the amp and I think that has it running pretty reasonable surface temperatures. It's a little hard to measure with it in my rack so I may need to pull it again and run it in the open to make sure that further heat sinks aren't required. At CanJam it was running a pretty consistent 150F directly over the resistors and that dissipated pretty quickly as you moved away from that location.

  Quote:


 Still looking for the BOM, and build details... pretty please? 
 

It's going to be a bit before I get anything like that uploaded but I think you'll be able to see from the schematic that putting together a BOM is not all that difficult. Parts count really is pretty low and Pete included the grounding configuration that I used in the schematic. I do still have just a bit of ground hum to try and trouble shoot at some point but it is in audible for almost the full first half of the volume pot. With my source if you're running the volume half way up you are well into the mid 90's of db's, which is a LOT louder than I listen. Still, I'd like to get it even quieter if I can but that experimentation may have to wait a while. Also, I need to take some updated pictures of the internal wiring to post along with the schematic, that will help explain a lot of what I did I think. 

 Ok, I'll try and get motivated right now to at least review the schematic and also take the updated pictures. With a little luck I'll post up at least the pictures tonight.


----------



## n_maher

As promised, updated pictures...

 Pete is reviewing the final schematic along with the last few questions that I had. I've also managed to dial out the last bit of noise on the inputs. I've got a temporary fix in place and will be adding a permanent solution at some point that will involve a ground lift switch on the inputs. Bottom line, with it in place I'm more likely to hear the fridge running two rooms away through a closed door than I am to hear noise in the background of the amp. :dance:

 the amp guts






 amp top panel





 ps guts 





 ps top 





 I expect to have the schematic in the next couple of days and I'll post it up as soon as I do.

 Listening again tonight, but with different tubes. 5U4GB's/RCA 6SN7/Cetron 5998s - sounds outstanding good to me.


----------



## pabbi1

You are a gentleman, and a scholar, taught by a master. Can't wait.


----------



## naamanf

Very nice Nate! I think I will need to add this to my list of amps to make. 


 <-Adds Menace to list of amps to make. Looks at wallet and time available and cries.


----------



## n_maher

Quote:


  Originally Posted by *pabbi1* /img/forum/go_quote.gif 
_You are a gentleman, and a scholar, *taught by a master*. Can't wait._

 

One out of three ain't bad. 
	

	
	
		
		

		
		
	


	




  Quote:


  Originally Posted by *naamanf* /img/forum/go_quote.gif 
_Very nice Nate! I think I will need to add this to my list of amps to make. 


 <-Adds Menace to list of amps to make. Looks at wallet and time available and cries._

 

Just wait till you start buying tubes... first you'll realize that you need a tube tester if you're really going to buy tubes and feel good about it. Then you'll realize that, geez, ya know, it really makes sense to have backups for your favorite pairs. And wait, there's those exotic hard to find pairs. My wife caught site of my tube stash for the first time this weekend and it was not good. Between rectifiers, inputs and outputs I'd say I'm up around 50 now. 
	

	
	
		
		

		
		
	


	




 And of course, thanks for the kind words. I put more than just a little bit of thought into both the physical and circuit layout and how I wanted the chassis to come together. There was still a bit of luck in pulling it off as close to my original vision as I did but it wasn't entirely be accident.


----------



## naamanf

Thank god my wife understands this insanity. Or at least she puts up with it. There are a couple local stores that have a large NOS and used tube collection with a tester.


----------



## n_maher

WARNING: The following schematics depicts a project that involves working with high voltages. Use of this schematic is permitted with the understanding that if you're not careful, this thing can kill you. Not only are you working with line voltages but the HV (B+) supply has a lot more current capacity than your typical tube project and should be treated with a great deal of respect. Getting hit by ~300V is no fun, assuming you live to tell the tale. That said with proper respect and care there's nothing exceptionally complex about this amp or power supply.

*C3 Mistake*: the first posted version of the schematic had the incorrect value for C3. If C3 and C4 don't show the same value for you you're still seeing the old schematic and need to clear the old image out of your browser's cache.


 Schematic (updated 5/20)

*Amp*





*PS*





 More information contained in post #2 of this thread.


----------



## grawk

this is a heck of a gift to the community you guys are giving.


----------



## n_maher

It was always Pete and I's goal to publish the design for private use so I'm glad - now I'm just hoping there's someone else crazy enough to build it! Also, if there's someone really crazy I'll provide information about an alternate power supply configuration that uses damper diodes instead of the rectifier types shown here. This disadvantage to that PS is that it would require an additional filament supply but it has other advantages that are worth considering.


----------



## n_maher

One quick correction - C3 on the amp schematic is supposed to be the same 10uF/400V cap used for C4. Please don't anyone build this w/ a 50V cap, that'd be a bad thing!


----------



## grawk

but capacitors make great firecrackers.

 ref. first take on the balanced mosfet


----------



## n_maher

Quote:


  Originally Posted by *grawk* /img/forum/go_quote.gif 
_but capacitors make great firecrackers.

 ref. first take on the balanced mosfet 
	

	
	
		
		

		
		
	


	


_

 

Except that this might make what happened in your PS look like childs play, instead of 2x the rated voltage we'd be looking at ~5x or more. I'm going to try hacking the jpg file this afternoon to see if I can fix it. It's been a bad Monday in the office though so for now the warning is the best that I can do!


----------



## Ferrari

Thanks for sharing the schematics with the DIY community. Looks good! 
	

	
	
		
		

		
		
	


	



 Dr. van Waarde amp concept is clearly visible: cathode follower (via grid stopper resistor), but with 2-halves of a 6AS7G in parallel, feeding by higher B+ voltage.


----------



## n_maher

I've updated the schematic to fix the C3 mistake - however it may require folks to clear their browser cache to see the correct image file. I did a direct replacement of the image file so that I didn't have to change links so the old image may show up for some folks for a while.


----------



## Skylab

I have to confess this looks like one helluva amp!


----------



## grawk

It sounds better than it looks, and I think it looks great.


----------



## nikongod

Many many thanks nate for posting up the PSU schematic. I am happy to see that an OTL tube amp that sounds as pimptastic as the reviews indicate can be built with such small value caps. You are an inspiration.


----------



## mrarroyo

Man, if I only had skills! 
	

	
	
		
		

		
			





 Thanks for posting the diagrams.


----------



## holland

Thanks for posting the details. This looks surprisingly easy to build, making it that much more accessible.

 It's too bad I blew my budget already or I'd move this up to #1 ahead of all my other half built stuff.


----------



## n_maher

Quote:


  Originally Posted by *holland* /img/forum/go_quote.gif 
_Thanks for posting the details. This looks surprisingly easy to build, making it that much more accessible.

 It's too bad I blew my budget already or I'd move this up to #1 ahead of all my other half built stuff._

 

Just remember that schematics can be deceptive and that the devil is in the details. Casework on this project not only requires a fair amount of time but tools as well. Assuming one were to use the same caps that I did you'd need to have a drill press and several different sizes of hole saws. I'd say I spent well over $100 just on tools to complete this build and the fasteners weren't cheap either. The raw parts cost that you'd get by looking at the schematic really only hints at the total build cost. All the same I'm working on a BOM with sources and prices, not sure when I'll get it done or posted though.


----------



## cetoole

Quote:


  Originally Posted by *n_maher* /img/forum/go_quote.gif 
_All the same I'm working on a BOM with sources and prices, not sure when I'll get it done or posted though._

 

Just dont let the wife see it!


----------



## holland

Quote:


  Originally Posted by *n_maher* /img/forum/go_quote.gif 
_Just remember that schematics can be deceptive and that the devil is in the details. Casework on this project not only requires a fair amount of time but tools as well. Assuming one were to use the same caps that I did you'd need to have a drill press and several different sizes of hole saws. I'd say I spent well over $100 just on tools to complete this build and the fasteners weren't cheap either. The raw parts cost that you'd get by looking at the schematic really only hints at the total build cost. All the same I'm working on a BOM with sources and prices, not sure when I'll get it done or posted though._

 

I absolutely agree with that, and the prices can vary wildly with it. I've done enough stuff in various hobbies to have seen that (guys can spend thousands of dollars on beautification alone).

 I think there are many alternatives to doing things, it's just a matter of how creative you want to be or how pretty you want to make it. Fortunately, I'm one of function over form and I'm not afraid to deviate from what amp builder XYZ uses. I'm also not one to show things externally, nor do I showcase, so that makes being cheap easy, but a 3RU or 4RU case may be necessary for this thing for internal mounting. That's $$$ by itself as well.

 I saw in a little dot thread that cut up soup cans painted black can be used as cap covers.


----------



## digger945

Is there anything all that special about the trafo's used, e-core/toroid and if I find a good buy on a trafo (surplus or used) that is rated for 110v and I happen to have say 125v at the wall socket, on a 3 to 1 winding that would equate to 45v difference. 
 Just wondering if and how you deal with that. I'm doin my own research, just thought I would get the ideas of experienced amp builders first.
 Thanks


----------



## jamess71

Looks sweet Nate. Excellent casework. When are we gonna have another meet so I can hear it?


----------



## n_maher

Quote:


  Originally Posted by *digger945* /img/forum/go_quote.gif 
_Is there anything all that special about the trafo's used_

 

The special thing from where I sit is that this amp requires a lot of current capacity (relative to other tube amps) on the HV winding. It takes a huge trafo to do that and it's not something you're likely to come across unless you're hunting in some pretty odd salvage yards. When Pete and I were looking for possible candidates there weren't many in the "affordable" bracket and the BFT isn't exactly cheap.

 And thanks James - Salty, drp and I have talked about something this fall maybe. But life is pretty complicated for all of us right now so it's been tough to try and pull anything together. But if there's a meet, I'll try and make it and schlep my 60lb boat anchor with me.


----------



## tosehee

Nice looking amp.

 A few questions..

 1. Where does this stand in terms of competitors like WA22, EC SE, DNA Sonnett, WA5LE, Bijou and such?
 2. I've never done any DIY in the past. How much would it cost to buildl this if commissioned to a builder?


----------



## n_maher

Ok, time to update this thread and have some more fun in the process.

 Earlier in the year I sold The Menace. Sad day, for sure, but one that ultimately became more and more necessary as my daughter started to take over more and more of the space that I formerly called audio-home. As I found myself now headphone ampless I started digging through drawers in my diy workshop looking to see if I had enough parts to build a power supply for my long out of service Millett Hybrid. What I found was that in typical fashion I'd acquired an insane degree of spare parts for the Menace. So with a little help from my friend nikongod we tweaked an existing design that used the same tube compliment but had a transformer coupled output and created what I named the MenaceTC Lite. Why Lite? Well, two reasons, one it weighs less than the original Menace due largely to the fact that it uses a SS power supply and two, the real MenaceTC is still sitting in 4 more boxes and is my "keep me sane this winter" project. 
	

	
	
		
		

		
		
	


	




 So while this amp won't take up permanent residence it seemed like a great warm-up for the bigger project and a good way to reduce the clutter.

 When I get a chance I'll try to finish up the Lite schematic and post it, it's a deceptively simple looking beast but is not without it's share of neat tricks and takes some careful attention to details to get it quite. Some highlights: a choke filtered power supply rather than the typical throw a huge cap in there style, it uses LEDs to bias the input tube along with some other trickery that Ari will have to explain involving some CCS's. But this is getting long, so without further adieu here she is in mostly finished garb. Some folks got a chance to hear this at the most recent NYC meet and the comments were mostly positive.

*
 Top Side*





*
 Wiring Overall*





*Custom Top Panel (by Cam-Expert)*





*Back Panel (prior to trafo cover)*


----------



## TimJo

Wow, looks great Nate. 

 Hats off to you and Ari. What kind of transistors are you using on those CCS's?


----------



## Skylab

Very cool! That seems like an amp that would have a lot of appeal - not everyone can handle a full Menace


----------



## n_maher

Quote:


  Originally Posted by *TimJo* /img/forum/go_quote.gif 
_Wow, looks great Nate. 

 Hats off to you and Ari. What kind of transistors are you using on those CCS's?_

 

10M45s and thanks, it came together better than I could have hoped really. I should also mention that cetoole helped me with some final wiring tweaks that really pushed the noise floor amazingly low. I've tried the amp with my Ety ER4Ps, there is some background noise but it's lower than the noise floor of most recordings and disappears once there is actual music playing. With any full-sized can that I've tried (both open and closed) I have to unplug the headphone jack to be sure that there's any noise. 

  Quote:


  Originally Posted by *Skylab* /img/forum/go_quote.gif 
_Very cool! That seems like an amp that would have a lot of appeal - not everyone can handle a full Menace 
	

	
	
		
		

		
		
	


	


_

 

Thanks man, while it weighs less and is less bulky compared to the original it's still rather beastly. I'd guess around 25lbs total so it seems I don't know how to build portables anymore.


----------



## Skylab

Quote:


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

 Thanks man, while it weighs less and is less bulky compared to the original it's still rather beastly. I'd guess around 25lbs total so it seems I don't know how to build portables anymore._

 

Well, good iron does carry some weight


----------



## fishski13

awesome job Nate. i love the G-10 epoxy glass and turrets. i used the same for my PS smoothing caps in my F5. any noise issues with the PEC pot?


----------



## diego

That's a really nice amp, congrats. Who made the output transformers? How does it sound compared to the menace? Specially since it has such a different topology.


----------



## n_maher

Quote:


  Originally Posted by *fishski13* /img/forum/go_quote.gif 
_awesome job Nate. i love the G-10 epoxy glass and turrets. i used the same for my PS smoothing caps in my F5. any noise issues with the PEC pot?_

 

Nope, no noise issues so far. And the turrets are a really great way to do secure PTP layouts, I'll be using them on everything now.

  Quote:


  Originally Posted by *diego* /img/forum/go_quote.gif 
_That's a really nice amp, congrats. Who made the output transformers? How does it sound compared to the menace? Specially since it has such a different topology._

 

The output transformers were made by Electraprint. As to how it might compare to the original, that's like asking me to compare my kids. 
	

	
	
		
		

		
			





 What I can say is that the original was somewhat hit or miss with low impedance headphones and the Lite is much better suited to this duty both in terms of output impedance and gain. Without a doubt the Lite sounds better with my HF-2s, I can't say whether or not that impression would hold true with other headphones.


----------



## johnwmclean

Nate, that’s a really lovely work - congrats, looking forward to the schematic.


----------



## fishski13

n_maher;6199603 said:
			
		

> And the turrets are a really great way to do secure PTP layouts, I'll be using them on everything now.QUOTE]
> 
> x2. my friend who builds guitar amps turned me on to turrets. it's a really cool/fun technique to use and build with as well.
> 
> all 3 of the PECs i've recently used do have some noise from time to time.


----------



## sandbasser

What are turrets???


----------



## n_maher

Quote:


  Originally Posted by *sandbasser* /img/forum/go_quote.gif 
_What are turrets???_

 

These little guys.

*Premounted on octal socket terminal boards*





 or

*Individual terminal posts*





 And fish that's a huge bummer about the PEC pots, I'm hoping my luck is better.


----------



## Coreyk78

The MenaceTC Lite seems like a really cool project, great work Nate!
 Are you planning to share the schematic? I think I already have a lot of the parts needed, I have a C-14X choke sitting in a box and an Antek 1T150 power transformer from an aborted project. I also have some NOS 6AS7 and 6SN7 tubes that I got for free from a friend at work who is into HAM radio stuff


----------



## fishski13

Quote:


  Originally Posted by *sandbasser* /img/forum/go_quote.gif 
_What are turrets???_

 

here's where i got mine: Boards and Board Making Parts


----------



## n_maher

Quote:


  Originally Posted by *Coreyk78* /img/forum/go_quote.gif 
_Are you planning to share the schematic?_

 

Yup, absolutely. I only have a rough hand-drawn version right now which does not include some essential information so I'd rather not post that. I'll try to put something together before the end of the year, feel free to remind me occasionally.


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## fishski13

Quote:


  Originally Posted by *n_maher* /img/forum/go_quote.gif 
_Yup, absolutely. I only have a rough hand-drawn version right now which does not include some essential information so I'd rather not post that. I'll try to put something together before the end of the year, feel free to remind me occasionally._

 

sweet!


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## TimJo

Quote:


  Originally Posted by *n_maher* /img/forum/go_quote.gif 
_Yup, absolutely. I only have a rough hand-drawn version right now which does not include some essential information so I'd rather not post that. I'll try to put something together before the end of the year, feel free to remind me occasionally._

 

That's exciting. Can't wait...


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## Coreyk78

Quote:


  Originally Posted by *n_maher* /img/forum/go_quote.gif 
_Yup, absolutely. I only have a rough hand-drawn version right now which does not include some essential information so I'd rather not post that. I'll try to put something together before the end of the year, feel free to remind me occasionally._

 

nudge nudge...


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## bidoux

Is it possible to know what connectors you used in The Menace OTL ? I think they are amphenol but I do not know which one exactly. Thanks for any answer.


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## n_maher

Yes, they were amphenol connectors, from the ecomate series IIRC.


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## bidoux

I bought these : DIN 3+PE MAL and DIN 3+PE FEM  . They are expensive but they look great and at least they won't be responsible of any failure the amp may have.


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## n3rdling

Oh cool, this thread got bumped up.   Right now I own the Menace, so if you need any pictures let me know bidoux.  I think you'll like it a lot! 
	

	
	
		
		

		
			




   
  Does anybody know things like the output impedance and output power of the amp?


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## bidoux

Thank you for your offer n3rdling, but n_maher already uploaded some pics of the amp so I hope it won't be necessary. 
	

	
	
		
		

		
		
	


	



   
  Actually, I am not building a clone of The Menace, the power supply for instance is very different (solid state and DC heater), I am not using the same input tube (ECC88). The similarities between my project and n_maher's are  :
   
  - OTL
  - relatively high output current (around 100mA I think)
  - parallel 6080 (6AS7)
   
  I have another question : in this picture (http://www.pbase.com/n_maher/image/96984139.jpg) how are the two caps attached to the chassis ? It seems that they are glued to it, but I'm not sure.


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## n3rdling

Very cool   
   
  Yes those are glued on.


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## Vingborg

n_maher said:


> It was always Pete and I's goal to publish the design for private use so I'm glad - now I'm just hoping there's someone else crazy enough to build it! Also, if there's someone really crazy I'll provide information about an alternate power supply configuration that uses damper diodes instead of the rectifier types shown here. This disadvantage to that PS is that it would require an additional filament supply but it has other advantages that are worth considering.


 
 Hello everyone 
  
 Pardon me for interupt in this "old" thread..
  
 Thank you for all these nice information about this exciting amp - It was actually Mr. Pete Millett himself who gave me the link to this thread, after I had made contact to him regarding a headamp for low impedance phones 
  
 But I would like to se the schematics for the alternate power supply with diodes - Is that possible? 
 I think that psu would be great for me 
  
 Best regards from 
 Vingborg
  in Denmark


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