Kofi Annan in: "Push and Pull with Me"

[Kofi Annan]

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

[arnoldc]

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 The 10Y for vocals, and the 300B for anything colored (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!

[danFrank]

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

[Kofi Annan]

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

[arnoldc]

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

[Andrewbee]

Kofi,

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.

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

[Kofi Annan]

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

[arnoldc]

Angela Instruments sells ceramic "top caps" for the 807. That's what I used on my 807 amp, and yes Alexandar is a very helpful guy. Gave me lots of hand on the "other side" of the fence, i.e., Tetrode

[Sheldon]

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]

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.