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Old 19th October 2004, 07:16 PM   #1
percy is offline percy  United States
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Default Recommendations needed for designs of PP pentode strapped as Triode

Ok, finally, after going back and forth I have decided what type of amp I want to build.

I would like to build a amplifier with Push-Pull output using a pentode in triode mode. I don't want to confine it to a particular tube complement but I am thinking EL34 or KT88. With 6N1P/6922/6DJ8 in the driver/input stages. This will be used at home for listening to a wide variety of music - if that fact matters.

The one I have found so far, and I like, is the PP-1C from vacuumstate.com, and ofcourse there is the Williamson. I not sure whether the PP1-C schematic on the website is just a symbolic circuit of a commerical product with the trade secrets removed or it is indeed an actual complete and working circuit. By the way anybody know what is the PP-2CS?

Any other good ones that I could consider ?

Thanks!
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Old 19th October 2004, 08:30 PM   #2
mcs is offline mcs  Denmark
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There's an "improved" Williamson here: http://stiftsbogtrykkeriet.dk/~mcs/Williamson/

It shouldn't be too hard to change the design to use 6N1Ps

Best regards,

Mikkel C. Simonsen
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Old 19th October 2004, 08:44 PM   #3
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Quote:
"improved" Williamson

Yes, but Percy seems to be looking for a good design.
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Old 19th October 2004, 08:56 PM   #4
percy is offline percy  United States
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Thanks. Interesting website you have Mikkel.
I will look at the improved design in detail and let you know if I have any questions.

There were a couple other Willys I found on the net too.

http://www.dc-daylight.ltd.uk/Valve-...pril-1947.html

http://www.xs4all.nl/~ideas/amps/


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Originally posted by analog_sa

Yes, but Percy seems to be looking for a good design.
Frank, what do you recommend ?
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Old 19th October 2004, 09:08 PM   #5
mcs is offline mcs  Denmark
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Quote:
Originally posted by analog_sa
Yes, but Percy seems to be looking for a good design.
So what's bad about the Williamson?

Best regards,

Mikkel C. Simonsen
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Old 19th October 2004, 09:11 PM   #6
Wodgy is offline Wodgy  United States
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The PP-2C schematic is proprietary but Allen Wright will probably share it with you if you email him. He's shared it with a number of people here and on AudioAsylum, on condition we don't redistribute it. It's basically a higher power version of the PP-1C, using the KT88, with some other modifications. I haven't built it yet, but I'm planning to. Brett here at DIYaudio has said some very nice things about it.

By the way, the AES Super Amp is another triode push-pull design you might be interested in. It's available in kit form, but is fairly expensive even then. One good thing about it is that because AES is a division of Cary, it has solid resale value.
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Old 19th October 2004, 09:32 PM   #7
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Quote:
So what's bad about the Williamson?

I sincerely doubt it was good even in its heyday. Especially if you are aware of what amps preceded it. It certainly was the amp which started the numbers competition and i personally blame it for several decades of bad sounding/ good measuring amps which followed.

What's bad about it? For one it doesn't sound very good although it's probably better than a lot of SS amps. I used to have a commercially built pair with all Partridge iron and i really spent time and effort trying to get it to sound good. Too much feedback, too many 6SN7 (mine had 6J5) and way too many stages.

What would i suggest? First of all establish if your speakers can play with a zero nfb amp. My current PP choice is a 2 stage amp: a driver stage, phase-splitting transformer and o/p stage.

PP1-C seems to be an excellent choice as well.

regards
peter
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Old 19th October 2004, 09:37 PM   #8
mcs is offline mcs  Denmark
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Just because Williamson used 20dBs of feedback you don't have to. The one I have (one of my many un-finished projects) sounds good to me. If sounds fine without any feedback also - and then it's sensitive enough for tape head signals (about 0.5mVrms)

Can an amp have too many 6SN7s?

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Old 19th October 2004, 09:52 PM   #9
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Can an amp have too many 6SN7s?
Depends on the listener. One is sometimes tolerable but repeating the same annoying tonal signature again and again can get very tiring. Which, to some extent, is true for any tube - even the good ones should be used not more than once in a system.
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Old 19th October 2004, 09:58 PM   #10
SY is offline SY  United States
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Just to give a contrary view, mine is 100% opposite of analog's. I've built Williamsons, and with a very few modifications (mostly twiddling the LF time constants), it's a very linear, very good-sounding amp. Morgan Jones did a very nice deconstruction of this design in "Valve Amplifiers", which I would strongly recommend you read.
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