[PaulFolbrecht]

Ok.  I would like to start a thread to discuss the merits of SET vs. PP.  Maybe this is a good idea and maybe it isn't.  Well, many of you probably know all there is to know already, but I don't.

I have used only PP tube amps and have thus-far loved their sound, in relation to SS - there was no going back for me.  Recently I became interested in SET, higher-power SET (845s), for I don't want to limit myself severly on speakers.  I have a used Dared VP-845 coming as an experiment, so soon I'll be able to finally hear SET sound in my system.

Of course I have heard so many times how their "presence" and realism can't be touched by PP, or anything else.  Of course many others argue that's not the case.  A few things have come to my attention recently:

1) PP amps with no/little neg. feedback tend to have EXACTLY the same high-impedence problems as SETs.  I used to think this was a big problem of SETs, and then I learned that my beloved AES Six Pacs have an OI >2ohm!  It apparantly DOES NOT MATTER, not in my system anyway.

2) There have been tests done with 2nd-order harmonic distortion demonstrating that it DOES produce a "pleasing sound".  In other words, intentional distortion, removed in a double-blind test, causes listeners to report a *degradation* of sound quality.  I have heard this but am not sure it's true.

3) The ear happens to produce TONS of low-order HD on it's own, in patterns that mimic SET amps - thus the argument that their distortion is "natural" and hardly noticed beyond the ear's own, anyway.  (I read that a 200Hz signal at 94dB produces >30% 2nd order HD!!!)

4) Loudspeakers also produce predominantly 2nd-order HD and, since it is usually out-of-phase with what the amp produces, the distortion *cancels* more than it adds at most freqs, LOWERING the total distortion of the system!  If this is true, that's pretty remarkable.

I think it could be very enlightening for those with more information on those topics or other technical matters related to SE vs. PP to share what they have.  At least, I am certainly very interested to hear it.

[PaulFolbrecht]

I can't $#!^% believe nobody's touching this.

[Wind Chaser]

Paul,

Here's a link that should get you going...http://www.vaughnaudio.com/tech-papers.html

John

[Jon L]

I can't $#!^% believe nobody's touching this.

It's just that this topic has been beaten to death many, many times.  Do a search here or Audio asylum to reveal a mountain of arguments.  

These days, one can assemble both a fabulous system or a crappy system around any of the amp topologies, tube, SS, SET, PP, even class-D/T, so what can I say?  Whether YOU will prefer one over others will depend entirely on your tastes, your sytem/room, and your skill in setting up your system.

[PaulFolbrecht]

John - Good reading, but certainly heavily in favor of SET...

Jon - Touche.  All true, of course.  I'm just interested in the theoretical arguments.  I find it interesting.  No doubt that both can sound great.

Then we get to pleasure vs. realism, that the arguments that many make that SET enjoyment is the former at the expense of the latter.  I use to think the "euphonic distortion" argument was nonsense, and I think I have changed my thinking on that.

Also on "simplist is best" mentality.  The simplest circuit we can get away with while minimizing distortion and frequency response and phase anamolies is best...

I find it interesting that the Six Pacs that I own & love almost have one foot in the SET camp by employing zero global neg. feedback.  Fairly rare in PP designs!  

All of the SET amps I look at, when measured objectively, put out very large amount of HD even at really low power levels AT LOW IMPEDENCES.  I suppose I can't have my cake (keep my excellent Gallo Ref 3s) and eat it too.  I'm talking over 1% TDH at 4W from an 845 amp into 4 ohms.  Same amp doesn't get about 1% till north of 10 watts into an 8ohm load...

So, maybe all that's unrealistic is SETs, even the highest-power models, without specially-designed speakers.

But I am really looking for more information on the whole euphonic distortion argument.  How many tests have been done?  Is it really demonstratable that it's pleasing and that THAT'S the biggest reason or at least one reason that some peope favor SET.....

[jon_010101]

Paul,

Here's a link that should get you going...http://www.vaughnaudio.com/tech-papers.html

John

I was really impressed by the Vaughn Audio papers... clear and honest description of the "problem" of SET vs. PP.

From a purely technical perspective, I favor push-pull, but with a triode output stage.  Listening-wise, however, I think there are some pretty awful SET amps and pretty awful push-pulls out there.  Simply too many variables to generalize.

[jon_010101]

Also on "simplist is best" mentality.  The simplest circuit we can get away with while minimizing distortion and frequency response and phase anamolies is best...

Hate to say it, but the circuits with the lowest measured distortion, best phase response, and frequency response are probably going to be push-pull and have a bit of feedback.

You are correct... One argument as to why people like SET is that the distortion is 2nd order, which is musically-satisfying, and therefore easily ignored.  A proper push-pull amp has minimal measurable 2nd order distortion, but struggles to eliminate the less-appealing 3rd harmonic.  So, comparing them directly, the one with more 2nd order distortion will sound more natural, colorful, etc.  Of course, it is also lower fidelity in the truest sense.

I'd argue that the real advantages of SET only become apparent is when the amp is operated well-below the point at which it begins to significantly distort.  Hence, with very efficient speakers.  Of course, those efficient super-speakers have their own peculiar distortions, so it becomes unclear how much is actually gained.  

Anyways, there are too many variables... so I'm going to duck out of this thread before any pissing matches arise!

[WEEZ]

Be careful....even too much 2nd order can sound bad...

If you hear an amplifier that makes an alto saxaphone sound like a kazoo, you'll know what I'm talking about......
 
 

WEEZ

[Bob Reynolds]

But I am really looking for more information on the whole euphonic distortion argument. How many tests have been done? Is it really demonstratable that it's pleasing and that THAT'S the biggest reason or at least one reason that some peope favor SET.....

Paul,

This may address your question: "Euphonic Distortion: Naughty but Nice?" http://stereophile.com/reference/406howard/

The concluding paragraph ends with:

"Unless and until somebody comes up with a "magic" pattern of nonlinearity that truly enhances sound quality, I will believe euphonic distortion to be a fantasy. The only "good" nonlinear distortion is that of a nature and amplitude such that the human ear cannot detect it. "

-- Bob

P.S, You may find some interesting information regarding SET on the Pass Labs web site. Nelson Pass builds electronics with the simple is better philosophy. Being a physicist, his gear measures well, but also sounds excellent as well. I think he still has a picture of one of his DIY amps that used light bulbs.

[PaulFolbrecht]

I just posted this on the Yahoo SET forum:


Gentlemen,

The last 20 minutes of my life has been the first 20 minutes listening to a SET amp and I do believe it will be far from my last.

Don't know if I mentioned, but I'd ordered a used Dared VP-845 on agon as an experiment and possibly for a 2nd system (I'd really prefer monos for the main system).

Anyway, it's really true.  I don't know what it is, but I've just not heard (recorded) music quite like this before.  "Immediacy" - yes, that does a nice job of summing it up.  Just a you-are-there *palpability*.

Since I'd discovered tubes, and especially 0-negative-feedback triode amps, I've found it nigh impossible to just quit listening to music when I'm at home.  I think I may have found that next, even higher plane.

Seriously... this is %#!@%# scary.  And I'm driving my FAR from crazy-efficient Gallo Ref 3s with an amp that puts out MAYBE 10W/ch before THD rises to definitely-audible levels.  Nuts.

In the last few days, I've done a ton of reading on the theory of single-ended vs. push-pull, and my biases had switched the OTHER way - I had been seriously leaning towards PP as generally superior.  It had become plausible to me that the large amount of 2nd-order harmonic distortion generated by all SETs was responsible for the "euphonic" qualities touted by its afficianados.

However, after listening, I believe there's no way that can be the case for one reason: soundstaging.  What I've got in front of me right now is the largest and most well-defined soundstage I've ever heard, and there's just no tootin' way any kind of *distortion* could result in that *happening by chance*.  This is where the realism is coming from.

I guess, then, I have to fall back on the technical explanations offered by the SET crowd (am I one of them now??):

1) Getting rid of even-ordered harmonics but leaving odd-ordered sounds WORSE (despite lowering THD) because the natural distorion produced by the ear has a decaying succession of both even and odd products.

2) 2nd-order HD generated by the amp may actually be CANCELED OUT by the speakers which normally produce their own 2OHD out-of-phase with the amps.

3) The amount of 2nd-order HD produced by SETs - while large - is actually not terribly significant compared to the amount that the ear itself produces.  (A 200hz tone at 94dB produces 2OHD in the ear of over THIRTY PERCENT!!!)

4) The very simple signal path of SETs (no phase splitter, etc) really DOES help.

5) Crossover distortion produced by push-pull amps, although (?) apparantly unmeasurable, really does exist and really does have a significant affect on signal integrity that destroys soundstaging and realism.

Well that's about it for now.  So far everything I've listened to sounds great, although I do think the bass is a bit looser than I'm use to.  I can live with that.  I don't have my bi-amping amp (on the Gallo's 2nd voicecoils) turned on yet cause I wanted to see what the amp could do on it's own.

BTW, this Dared is an absolute BEAST.  It weights like 80 lb!!  I nearly hurt myself getting it on my rack and I am a little worried the glass shelf will shatter in the middle of the night and kill my Shanling CDP on the shelf below and the Rotel HT processor below that.  I hope not.

Talk to y'll later.

Paul

[jon_010101]

The last 20 minutes of my life has been the first 20 minutes listening to a SET amp and I do believe it will be far from my last.

Don't know if I mentioned, but I'd ordered a used Dared VP-845 on agon as an experiment and possibly for a 2nd system (I'd really prefer monos for the main system).

So what amps were you using before these?

[PaulFolbrecht]

AES Six Pacs (all triode, 0 neg feedack PP).  They are great amps.  They are the best tube amps I've heard before the 845.  What they offer, the SET offers more of.

[SET Man]

Gentlemen,

The last 20 minutes of my life has been the first 20 minutes listening to a SET amp and I do believe it will be far from my last. ...

Hi,

   Ahhh.... PP vs. SE question, the never ending question.

   I see that you just bought a SET amp. Congratulation!   As a guy who called himself "SET Man" I want to welcome you to the world of Single Ended Triode! The oldest form of amplication... hard to believe it isn't it?

   Now you have heard it for yoursleve what SET is all about I think you could give this PP vs. SE a rest. I'm not a technical person. But... If it is all about measurement than I will just  go out and get a $200 reciever... and  you know what it got remote too!
 
 But SET is not for everyone ( very big room or with low-ef speaker, music type and etc)  So, for some PP and SS will be answer.... there are some advantage and disadvantage with PP and SS. So, choose what you think best for you.

 And lately there are so many SET amp coming on the market. Not all are created equal so shop wisely.

  Of cause if SET work for you (room and speaker) than you will be rewarded with every nuances, intimate, and purity of the sound.

    Anyway, now just relax, enjoy the music and forget about the gears, and measurements stuffs.

Take care,
Buddy

PS
If you have small to medium room... you might want to try to get rid of those xover in the speaker... you know hi-ef Single Driver  Speaker  

[jon_010101]

AES Six Pacs (all triode, 0 neg feedack PP).  They are great amps.  They are the best tube amps I've heard before the 845.  What they offer, the SET offers more of.

Very nice... both the Six Pacs and the Dareds seem to offer great performance.  I'd be curious what you'll think of the Six Pacs after a few weeks of listening to 845's.  Mebbe you won't be able to go back, or perhaps you'll find advantages of PP that you overlooked before.  I feel like one of the biggest bonuses of SET is that sounds can "appear" instantly... that leading-edge transient seems so well defined.  PP rarely have that sense of instant-on speed when an instrument starts playing.  I think this might be due to the transformer being already magnetized in SET by the DC field from the tube's bias current.  Less energy wasted in fidgeting the magnetic field around in the core.

Congrats on the amps... makes me want to try some high power SET in my own system .

[PaulFolbrecht]

Well, the plan is to sell the Pacs, if I definitely like SET better (sniff)..

[PaulFolbrecht]

Has anybody ever heard of "Kailin"??

http://cgi.audiogon.com/cgi-bin/auc.pl?ampstube&1149642730&auc&3&4&

[Steve]

Hi Paul,

     The only things I might add are:

1) The IM distortion is 3-4 times the HD, at low signal levels.

2) SET damping is different than PP damping if one examines the entire cycle, depending on which class the PP amp is operated at.

Hope this helps and enjoy your new amps, Paul.  

[PaulFolbrecht]

Steve,

SET: Are ya fer it or agin' it?  I can't tell. :-}

Wait - you're a dealer.  You must favor SET and push-pull. ;-}

[Steve]

Which ever you like is all that counts Paul.

Tubes rule in my book!

Enjoy.  

[boead]

Hey Paul,

If you like the sound of the Dared VP-845 and your Gallo.

You need to try a Decware Select and a pair of Ed, hornshoppe, horns or another efficient speaker.

Years ago now I picked up a very used Decware Select on Audiogon and a pair of Klipsch RB5’s (96db 1w/1m) and was mostly blown away. I’ve made lots of changes and improvements since but the Select amp is still with me (although it’s Vaughn modified).

Remember; “if the first watt sucks, why continue?”