• WARNING: Tube/Valve amplifiers use potentially LETHAL HIGH VOLTAGES.
    Building, troubleshooting and testing of these amplifiers should only be
    performed by someone who is thoroughly familiar with
    the safety precautions around high voltages.

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
 

SY

diyAudio Moderator Emeritus
2002-10-24 10:19 pm
Chicagoland
www.SYclotron.com
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.
 

amperex

Member
2005-02-20 1:42 pm
MI
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.
 

PRR

Member
Paid Member
2003-06-12 7:04 pm
Maine USA
> 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.
 
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.

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.

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?

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.

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
 

jlsem

Member
2003-06-17 1:12 am
Dallas,TX
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
 

BHD

diyAudio Member
2004-06-07 8:25 pm
Brooklyn Park, MN
Kofi,

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

http://www.diyaudio.com/forums/showthread.php?s=&threadid=57411

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.

:cool:
 
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.

Yeah, but they look cool. Alriiiight, FINE! I'll stay away from 'em for the sake of Frugaphilia.

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

http://www.diyaudio.com/forums/show...&threadid=57411

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.

I'm reviewing this thread now. Well, not right now, but you know...

OK-- so I had a pretty interesting afternoon. I was looking at the EL84 PP schematic that Sheldon forwarded and I decided to give Jack at Electraprint a call to discuss the prices on his OPTs. Well, I got quite a bit of information in the 30 minutes he spent talking to me about tube amps.

I talked to him about the EL84 P-P and he thought that I might hear too much notch distortion on my Fostex 206Es (~97dB SPL). Actually, I think he said that the more sensitive the speaker, the more likely it will be that I hear the distortion innate to a push-pull amp, but I read it as "you may hear distortion".

I asked if he thought that SETs had a distinct advantage over PP and he did not hesitiate to advise that he thought it did. He described the SET sound as more "freewheelin'" and said given a choice, he'd build a(n) SET.

Now I know I'm deeply in the realm of opinion here and I'm likely to cause some serious arguments by posting this. Just understand that I want to build an amp that will please my ears and I REALLY LIKE my SET 2A3 monoblocks.

So... gimme some for and against PP vs. SET that I can use. Don't forget to present pure opinion as bona fide fact and crush all those who oppose you with extreme prejudice. Assail the unbelievers as ignorant ogres without a shred of decency and pollute the general discourse with the type of slander and bile normally reserved for a rival political opponent in a third world election.

And have fun!

So, I could conceivably go with a single-ended 300b design. That would certainly fuel my power lust. But if the PP EL84 will do it all with the same low distortion...

Oh and by the way, NO MORE HELICOPTER RIDES!!! The Feds are all over it. I don't know who told you about the rides, but I don't know nothing about it and I never heard of you anyways.

So: PP or SET?

See? Frustrating dealing with my posts, ain't it?

Kofi
 
Kofi, here's my story...

When I learned building a tube amp, I went for a 2A3 myself. I can say "I fell in love" with it, and has driven an Infinity @ 89dB for about a year. Although I also owned a PP amp (Anthem Amp-1) I tend to listen to the 2A3 more.

When I built a 45, I knew I have to get more sensitive speakers, so I got a medium sensitivity vintage Altec speakers coupled with Oxford horns, this gave me lots of listening pleasure even with full classical music.

My third amp is a switchable 10Y/50/300B amp, many thanks to Thorsten for educating me, which gives a different flavor. Believe it or not, I like the 50 for rock :D The 10Y for vocals, and the 300B for anything colored :D (to my ears, ok)

In between, I've been borrowing PP amps like the PrimaLuna Prologue One (which sounded good in it's own right), some Japanese made EL34, some China made, a couple of Vintage, but I still go back to SET.

I follow this thread because, it is also to my interest what you'll be ending up with given your 2A3 preference.

Cheers!
 
Make a push-pull 2a3 amp. No pentode/tetrode (EL34, KT88, 6L6, EL84, etc.) amp will beat it for sound quality, period! No Feedback, too. You will need good output transformers though. If you are happy with your SET 2A3 amp, then big power output isn't too big a concern for you. Depending on how you design the driver stage, you will get 8-15 watts output with a pair of 2A3 tubes.
Daniel
 
In between, I've been borrowing PP amps like the PrimaLuna Prologue One (which sounded good in it's own right), some Japanese made EL34, some China made, a couple of Vintage, but I still go back to SET.

Yeah. That's kinda where Jack was going with this. Thanks for the input.

Make a push-pull 2a3 amp. No pentode/tetrode (EL34, KT88, 6L6, EL84, etc.) amp will beat it for sound quality, period! No Feedback, too. You will need good output transformers though. If you are happy with your SET 2A3 amp, then big power output isn't too big a concern for you. Depending on how you design the driver stage, you will get 8-15 watts output with a pair of 2A3 tubes.

Good suggestion, but I'm thinking that for the price, I might be happier with a 300b SET. I'm becoming intrigued by the Direct Reactance Drive 300b project on the Electraprint site. I've read some great things about it.

Anyone else with any advice here? Anyone with direct experience with the 300b DRD circuit, above?

Kofi
 
Kofi,

I have a friend who owns a 300B DRD made by Jack Eliano himself that I was able to borrow. It is a very quiet amp and got some balls but it sounded too dry and analytical to me, but some people like it that way.

Here's a picture of that amp in the foreground, it's a HUGE mono blocks. The other pair of monoblocks is a TS Audio direct-coupled, and the ugly amp in the middle, is my first attempt to make a direct-coupled 2A3 :D

[IMGDEAD]http://img42.imageshack.us/img42/4056/img18408ry.th.jpg[/IMGDEAD]
 
Kofi,

Since you are after opinions I can't help you but the fact is you need a SE pentode / tetrode amp:devilr:

I recommended the RH 807 by Alex Kitic. Its here on this site and he also has a site.

Forget about all those wussy triode non-nfb amps. Walk on the wild side where you will have no friends in agreement but plenty music.

P.S.
Sorry about letting the cat out of the bad with the helicopter rides but I was so thrilled with the half dozen you gave me that I just could not stop talking about them!

Andrew
 
It is a very quiet amp and got some balls but it sounded too dry and analytical to me, but some people like it that way.

Good advice! I think I'll scratch it. Anyway, it would be waaaaay too expensive.

Since you are after opinions I can't help you but the fact is you need a SE pentode / tetrode amp

I recommended the RH 807 by Alex Kitic. Its here on this site and he also has a site.

Forget about all those wussy triode non-nfb amps. Walk on the wild side where you will have no friends in agreement but plenty music.

OK-- this I will look into. But what the hell do you do with the anode cap on the 807? Never seen one. Looks dangerous. Oooooh. Danger.

Sorry about letting the cat out of the bad with the helicopter rides

We never met. Say it.

Kofi
 
Hmm, given that you are satisfied with your present amp, it sounds like your motivation is really to try something different. In many circumstances that might be considered dangerous, sick, ill advised, etc.. But, hey, this is DIY, and there are certain similarities to the UN too (which is a pretty frightening thought). Soo, go with your hunch and make something a little different, and realize that it won't be the last, so don't agonize.

If you just want a little more power but still want SE, you could try Andrewbee's notion. Or you could still go PP and just use it when you want to crank things up (you won't hear any crossover distortion when it's loud). You still have the 2A3, or you could ... well you can see where this is going.

BTW, not everyone prefers SE. Some people like PP more than SE. Actually I wonder if the preference is more system (speaker) driven than amp driven. So you might want to consider different speaker types too. Are you sorry yet that you asked?

Sheldon
 

BHD

diyAudio Member
2004-06-07 8:25 pm
Brooklyn Park, MN
I talked to him about the EL84 P-P and he thought that I might hear too much notch distortion on my Fostex 206Es (~97dB SPL).

Well, since you know you like the sound of 2A3's, you could always build a class A push pull 2A3 amp. Since both tubes will be conducting all the time, there will be no "notch distortion". It's basically a pair of single ended amps out of phase, cancelling out the even order harmonic distortion. You get double the watts with much less distortion. Well, at least second order harmonic distortion, but you get more third...

And thus begins the debate on single ended versus push pull.

However, I really don't think that you'll hear "notch distortion" with high efficiency speakers. If PP amps are biased more than a watt or two into class A, the vast majority of the time the amps are operating that way and there is no "notch" to be heard. Notch distortion is more an issue with class B amps.

I think the only thing that makes class AB objectionable is the fact that during peaks, the ouput tubes start alternating between the two (or more) output tubes, turning on and off. When this happens, the damping factor of the amp (and its ability to control the loudspeaker) drops and you get a system that sounds fine at low volume, but the sound falls apart on loud passages. There isn't really any notch distortion, because there's a little bit of overlap when they "hand over" the signal to the other tube, but the change in the damping factor alters the sound to the negative, in my opinion.

OK-- this I will look into. But what the hell do you do with the anode cap on the 807? Never seen one. Looks dangerous. Oooooh. Danger.

Anode cap + curious rugrat = Exposed lethal voltages and dead rugrat.

This will result in Mrs. Annan turning stoolie and BAM! You're spending lots of time with Slobodan Milosovic in a small cell in the Hague.

Oh and by the way, NO MORE HELICOPTER RIDES!!! The Feds are all over it. I don't know who told you about the rides, but I don't know nothing about it and I never heard of you anyways.

I think it was Augusto Pinochet that told me... or maybe he just OFFERED me a ride. Anyway, mum's the word.

;)