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Old 16th August 2005, 01:24 AM   #1
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Default Kofi Annan in: "Push and Pull with Me"

So, being on the verge of completing Kuei's phono preamplifier (just fried a resistor, so I'm awaiting some new ones) and not being one to want to wait long periods between projects, I wanted to start soliciting recommendations for a new amplifier.

I have a Bottlehead Kit SET 2A3, which I like a lot, but having never heard a push pull tube amp in my short, sweet life, I thought I'd try to build one of those thingees. And so, the questions begin...

I would like to try my hand at a simple, but nice sounding push-pull amplifier. I like the "fewer parts" concept, but I could be compelled to choose a more complex design were it to yield a better sonic result. It looks like KT88s and EL84s are popular valves for push-pull design, but I'm not sure where to begin looking for a simple, relatively cheap (could spend a few bucks for the right design) tube amp design.

Now here's where you come in. You're familiar with the drill by now, so this part probably doesn't need further explanation. You recommend things for me to try. I ask stupid questions. You respond thoughfully. I don't get it and ask you to clarify, displaying a level of ignorance you previously thought impossible. You clarify and begin to lose patience. I claim to get it, I try it, it doesn't work, I post another question. You respond....

Ad nauseum until the project is finished, I get a divorce or I run out of money. And beleive me, I would have been divorced already if that were a real option. Clearly, Mrs. Annan is in for the long haul.

So... help a brother out, will ya buddy?

Yours in relentless ignorance and enduring gratitude,
Kofi
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Old 16th August 2005, 02:10 AM   #2
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Default Re: Kofi Annan in: "Push and Pull with Me"

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Originally posted by Kofi Annan
Kofi Annan in: "Push and Pull with Me"
Idunno... I'd kinda rather not...



Got any 6V6s on hand? EL84? ECL82/6BM8? Any will make a fine 5-15W class A or AB PP amp.

Tim

P.S. SY and your simulpostings again!
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Old 16th August 2005, 02:10 AM   #3
SY is offline SY  United States
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Keep it simple; you've got enough worries staying out of jail right now. If you don't need scads of power (10W is enough), I'd recommend a simple, classic circuit like Morgan Jones's Bevois Valley (in "Valve Amplifiers"), with push-pull EL84. It's neither exotic nor expensive, but solidly engineered. At a higher power level, I'd look at cloning the Eico HF87, 35W with push-pull EL34.
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Old 16th August 2005, 03:08 AM   #4
Sheldon is offline Sheldon  United States
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Here's another one using commonly available stuff, low part count, even an off the shelf chassis. Pictures too.

http://www.electra-print.com/EL84PSA_2.html

And Jack at Electra-print is willing to chat if you give him a call.
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Old 16th August 2005, 04:32 AM   #5
amperex is offline amperex  United States
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Push-pull 6V6 (or 7C5) triode connected. Do a google search on 'poinzie's audio page'. Killer little 6V6 amp. Drive the amp direct from a source with the 5965 or change the 5965 to a 6SN7 and use a preamp for superior sonics.

Use older Sylvania 6V6GT or believe it the newer GE 6V6GTA (excellent). Stay away from metal 6V6 as they do not sound good.
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Old 16th August 2005, 06:47 AM   #6
PRR is offline PRR  United States
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> never heard a push pull tube amp in my short, sweet life

You gotta live with a Williamson for a few years. This and its simpler kin were THE hi-fi once upon a time. They had POWER.

A real Williamson (Heath had a nearly-right Williamson) is a good amp. But it will make you appreciate the SET 2A3 too.

If what you really want is a more powerful less-sweet SET 2A3, build a push-pull 2A3. If you also decline feedback, and use cathode-bias, you only need a twin-triode (volt-amp, cathodyne) driver. If you use more than 8 resistors, you over-did it.
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Old 16th August 2005, 11:21 AM   #7
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Quote:
Got any 6V6s on hand? EL84? ECL82/6BM8? Any will make a fine 5-15W class A or AB PP amp.
Nnnnnope! But I have cash and credit, which can be exchanged for goods and services.

Quote:
If you don't need scads of power (10W is enough), I'd recommend a simple, classic circuit like Morgan Jones's Bevois Valley (in "Valve Amplifiers"), with push-pull EL84. It's neither exotic nor expensive, but solidly engineered.
Yeah! I was looking at that one. I like the design, so I'm glad to hear that its got some good reviews. That's on the short list.

Quote:
Here's another one using commonly available stuff, low part count, even an off the shelf chassis. Pictures too.

http://www.electra-print.com/EL84PSA_2.html

And Jack at Electra-print is willing to chat if you give him a call.
Oooohhh... low parts, lotsa pretty pictures and a contact number. Tough to beat. Has Jack ever stopped anyone from crying before?

Quote:
Push-pull 6V6 (or 7C5) triode connected. Do a google search on 'poinzie's audio page'. Killer little 6V6 amp. Drive the amp direct from a source with the 5965 or change the 5965 to a 6SN7 and use a preamp for superior sonics.

Use older Sylvania 6V6GT or believe it the newer GE 6V6GTA (excellent). Stay away from metal 6V6 as they do not sound good.
More great advice. I'll check out what Poinzie has to offer.

Quote:
You gotta live with a Williamson for a few years. This and its simpler kin were THE hi-fi once upon a time. They had POWER.

A real Williamson (Heath had a nearly-right Williamson) is a good amp. But it will make you appreciate the SET 2A3 too.

If what you really want is a more powerful less-sweet SET 2A3, build a push-pull 2A3. If you also decline feedback, and use cathode-bias, you only need a twin-triode (volt-amp, cathodyne) driver. If you use more than 8 resistors, you over-did it.
I have looked at the Williamson design quite a bit, but I'm thinking I need a simpler design. I like the idea of declining feedback and using few resistors, though.

What about a KT88 design? Are the EL84s and 6V6s just better?

Kofi
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Old 16th August 2005, 11:44 AM   #8
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KT88 will for sure get you more power. But they're 6dB more expensive than EL34 for 3dB more power (that doesn't include extra iron expenses). 3dB more power is BARELY discernable.
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Old 16th August 2005, 01:26 PM   #9
jlsem is offline jlsem  United States
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Quote:
You gotta live with a Williamson for a few years. This and its simpler kin were THE hi-fi once upon a time. They had POWER.
The original Williamson is excellent, but for today's cd players you don't need all that gain in the first stage. I'd replace the first 6SN7 with an input/phase-splitting/step-up transformer which simplifies the circuit even more.

John
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Old 16th August 2005, 02:48 PM   #10
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Kofi,

Sounds like the amp in this thread would be right up your alley:

Cathode Feedback from Secondary for PP Amp

Yves and Gingertube's amp has received thumbs up from quite a few people. I've been thinking about incorporating Thorsten's phono stage directly into it for a full function integrated amp. Built with Hammond iron it'd be really reasonable, cost wise.

BTW, love your posts here and love your work at the UN, can you swing it so I can get a ride in one of those mega-cool black helicopters?

That'd be sweet.

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