SET the best?

Speaking in very broad, generalized, terms, I tend to find pushpull amps to have a "tighter" more punchy sound than SET amps.  But, too much of that quality and the sound seems a bit artificial or "mechanical" and less natural than the more relaxed sound of good SET amps.  For me, for example, KT88 pushpull amps tend to be particularly likely to sound too punchy and mechanical for my taste, but, as with everything in audio, there are always exceptions. 

I like MANY pushpull amps (this would include OTL amps), while I also like SET amps.  It is never as simple as saying one type is better than another.  Right now, I favor my pushpull 349 tube amp over my SET amp (the SET amp costs considerably more), but, in some respects I still do prefer the SET amp--although the bass is less powerful and tight, it sounds more subtly "musical" (the quality of the bass changes with the music and sounds less "same" and "mechanical" as my pushpull 349 amp).  Both sound harmonically saturated, deliver an expansive and immersive soundstage, and sound relaxed and natural while still being very lively sounding; the pushpull 349 just delivers a little bit more of these qualities.  

Speaking in very broad, generalized, terms, I tend to find pushpull amps to have a "tighter" more punchy sound than SET amps.  But, too much of that quality and the sound seems a bit artificial or "mechanical" and less natural than the more relaxed sound of good SET amps.  For me, for example, KT88 pushpull amps tend to be particularly likely to sound too punchy and mechanical for my taste, but, as with everything in audio, there are always exceptions. 

I agree- I tend to see punchy bass as a coloration, since you never seem to run into it in live events. I've played in orchestras, jazz and folk ensembles, rock bands and just not encountered it. I think its the product of an overdamped speaker to a certain degree but I don't think that's all of it.

The distortion signature is what is at play here IMO. Most pentode-based amps employ a bit of feedback, but since they really don't have enough, they have an obvious distortion signature (the amplifier's 'sonic signature'). Some of that includes harmonics of bass fundamental tones, generated by the feedback itself. The ear is interpreting them as 'punchy' (and yes, this happens with many solid state amps too). IMO/IME the way around this is to make sure the amp is as linear as possible, so much so that it will sound reasonably decent with no feedback at all. Only then do you apply the feedback- and then it should be used to control gain more than anything else. With a pentode-based amp I suspect this would mean that the output section is wired Ultra-Linear.

But many pentode output stages really aren't that linear and need the feedback to linearize them. That is a bad move IMO. You can't get rid of all the distortion and if you start with a high distortion amp, the feedback will cause it to have a less musical distortion signature overall when you're done. Amps that have zero feedback have a different distortion signature that tends to favor the lower ordered harmonics which will mask the presence of the higher orders. But if you have no feedback you also have a much more limited range of speakers that are practical with the amp. For more on this see

The Power Paradigm Vs the Voltage Paradigm

Hey Plinko, The artifacts are phase shifts. The square wave stays good, its relative position is slightly different compared to where it should be.

I'm quite amazed at the diversity of the answers and the strong conviction behind the opinions. I'm on the side of keeping an open mind, as there are always surprises and it's so easy to run into the "I stand corrected" scenario. When going for recommendations, they all come through subjective filters. Just like asking about steaks: the answer depends whether you ask a meat lover or a vegan....

When people report loving something it comes from hearing a properly set up system with that topology. Negative opinions on the other hand come from lack of experience. Do not place much value on those (regardless of what architecture is being dissed.) Just remember: audio is not a perfect science, every topology has its flaws and compromises. When the ad says that one major flaw has been corrected, it can only be done through introducing a compromise somewhere else. In most cases the manufacturers are keenly aware of the shortcomings, but they don't want to rub it in our faces. (Product will not sell.) 

All being said - solid state easier to find for show and crowd-pleasing, and SET for meditation and contemplation.

Just stay focused with your purpose: do not buy a horse to sing, and do not get a bird to pull your wagon. Enjoy diversity.

@realworldaudio  Thanks for the laugh. So which definition of Plinko should I assume? 😊

+1 to this as well as so many of your posts.

larryi2,703 posts 11-29-2021 12:01pm Speaking in very broad, generalized, terms, I tend to find pushpull amps to have a "tighter" more punchy sound than SET amps. But, too much of that quality and the sound seems a bit artificial or "mechanical" and less natural than the more relaxed sound of good SET amps. For me, for example, KT88 pushpull amps tend to be particularly likely to sound too punchy

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Yes the Defy’s 12 KT88 tubes in certain recordings that offer a punding bass line is wayyy too much low hz’s for my 10x15 room. Grates my nerves,e ven at low vol. Mundorf supreme caps both in the W18Excdel and Defy7’s coupling caps, Now with dual FR and eliminated 1 W18, runninga single with a 20 uf Mundorf Supreme,, I know the bass will be explosive when I retube the Defy in Janurary. At 100watts, per channel, its not a good match for higher sens FR. But it will have to work, as thats my current amplifier. Luckily I listen only to CM, so might keep the W18 in, as most CM is recorded with mics distant from kettle drums and cello sections. But for hard driving music, + big PP amp, extra large room is a must to endure the pounding low range. I just uploaded a new video with the single W18 Dual FR and tweeter. results were good. Details open up, but lose some of that laid back linear magic, but gain in dynamics. I prefer duals vs a single FR. SETs are more laid back, the music flows witha natural grace and charm. While PP amps, as Larry correctly points out has this **driving* energy, again which some may prefer. Bottom line as I hear the 2 amps, with PP just about any speaker will work. Although both my techs mentioned over and over ,,,and over,, **You realize you have the wrong speaker for the Defy,,don’t You??...** I politely disagreed.

The Seas Thors with the Defy was a stunning experience,,

that is you like xovers and low efficiency,,and lastly have no issues with a middwoofer carrying mids up to the 2k+ hz region and a dome tweeter going as low to pick up where the midwoofer left off. I’ve not heard the king of all SETs a 845 big power tube. Thats a ways off, and have big expectations. Givena choice of Jadis new KT170 or a 845, no contest, 845 will dedliver a sound field full of nuances that will leave Jadis KT170 behind in the dust. I think the era of big PP power amps is slowly riding off into the sunset. SET’s star is arising in the eastern horizon.

China manufacturers are making SET’s at a more reasonable price with stunning designs. Once you hear a SET, PP amplification has lost some of its sheen. .