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jrebman 28th February 2009 08:13 PM

Need PS schematic for Musical Machine
I've decided to build Poins' Musical Machine amp, but a slightly modified version with 6sn7 driver and Pimm CCS. I also intend to build the amp as a pair of monoblocks and am looking for a very good, preferrably tube rectified, LC power supply design that would be sufficient for one channel. I will use film caps (no electrolytics) and want something that is robust, clean, and very quiet. I'd also more than likely have custom PTs made for the project so as to simplify things for the 4 different voltages needed.

If anybody could help, it would be much appreciated.

I'm blind so can't work with schematics very effectively, nor tools such as PSUD II, and would like to find something a little simpler than the design posted with the schematic on Poins' web site.

This amp will be a labor of love, so I am looking for quality and performance as opposed to on the cheap.



aardvarkash10 28th February 2009 09:04 PM

And I thought I was brave and dedicated! I'm no help Jim, but big respect to you for getting into this project - I'll bet you hear a whole lot more than I can! Regards

Eli Duttman 28th February 2009 09:29 PM


6SN7s in the LTP will give you a stage gain of approx. 5. That's WAY too little :( Poinz switched from the 5965 to the 6GK5, in part, because a mu in the 40s proved marginal.

As for your vacuum rectified B+ supply, the 6BY5 dual damper feeding an ARRL approved LCLC filter should prove highly satisfactory. IMO, you should use a high quality 'lytic in the 1st LC section. That cap. is not in the signal path and there is no good reason for failing to realize the space and cost savings a 'lytic provides.

jrebman 28th February 2009 09:42 PM


Thanks, but aside from the trouble of dealing with schematics, and as long as I have a good written description of the circuit, it's generally not too difficult. I had 20+ years of experience working on electronics before I lost my sight 19 years ago, so I'm sure that helps a lot. I'm learning to dislike PC boards though :-).

Eli, well, I see no mention of changing from the 5965 so I suspect that the web site is way, way out of date. I'm also not exactly sure what an ARRL approved supply is. I know what ARRL is, but that's about it.

I'm kind of cautious whenit comes to damper diodes when it comes to full duty cycle power supplies. I know people rave about them and some of their advantages seem appealing, but they were never designed for continuous duty use, but rather intermittent, pulsed power supplies, and it makes me wonder how long the will actually hold up in a power amp.

Hopefully Poins will chime in here. I sent him a couple of emails this week but have not heard back yet.



kevinkr 28th February 2009 10:18 PM

6BY5 has proved quite reliable in applications in excess of 100mA continuous in a number of friends 45 based stereo amplifiers, and in my headphone amplifier over a good number of years. IMO They seem to outlast current production 5AR4 in similar applications and the Sylvania and GE types I have used have given me no trouble at all, not something I can say for anything other than a Mullard or Tele 5AR4...

boywonder 1st March 2009 03:51 AM

Poindexter's 6GK5 version is shown in posts 6&7 of this thread, one with a mono tube rectified B+ and one with SS rectified stereo B+

I am in the final stages of breadboarding this design; presently installing a startup B+ delay due to SS rectification. Poinz has been very helpful answering my newbie questions although it usually takes him a few days.

jrebman 1st March 2009 04:07 PM


Thanks -- for some reason that post did not show up in my search, but that looks like what I'm after.



jrebman 1st March 2009 04:13 PM

Umm, didn't see anything about the musical machine on that link -- just the el34 amp.

-- Jim

jrebman 1st March 2009 05:12 PM

I guess that I need to make it a bit more clear -- I am wanting to build the 6v6 triode PP amp that has been known as the Musical Machine, not the el34/6l6 amp.



boywonder 1st March 2009 06:18 PM

Got it.

The 6GK5 version of Poindexter's Music machine is in post #2 of this thread, and the (SS) power supply is in post #27.

It appears that it would be fairly straightforward to downsize Poindexter's tube rectified PS for the mono 6V6 version. I have quite a number of PSUD models of both the SS and 5AR4 supplies modeled, so I'll give it a crack and post the results if you have your transformer voltage and secondary impedance handy.

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