Would You Rather Own A Good SET Amp, Or A Great Push Pull Amp?

So if you listen mainly listen to (an amplified) rock or electronic music, push-pull would be fine. But if you want to fully enjoy an acoustic music, you will do that better with a set amplifier.

But, with proper speakers and a quality build, SET amps deliver a very "pure" sound that can be quite seductive.  While bass tends to be not as tight and punchy as that of a good pushpull amp, the bass has its own positive attributes--it has natural and subtle differences of tone while pushpull bass is much tighter and punchy at the cost of sounding a touch "mechanical" (sameness).  I have no disagreement with someone finding the balance of attributes favoring SET amps.

I can't describe better my experience with SET and push-pull amps. I personally prefer a natural bass of a SET than a push pull punchy bass. My set amplifier has a very high distortion (THD) but it sounds clearer than my push-pull and solid state amplifiers with much less THD. The comment made by Ralph somehow explains this phenomenon. 

It surprises me that the THD is still a major parameter for measuring the sound quality. It is quite irrelevant to the quality of the sound as we perceive it. Even the formula by which it is calculated doesn't look relevant. I guess the engineers were unable to develop  a more adequate parameter for measuring the sound quality so far. I suggest this is the only reason why THD still remains a standard. 

@atmasphere (Ralph), ​My judgment comes not from a particular knowledge of electronics but from the practice, from my (humble) experience of using and auditioning audio equipment. Hence, it can be subjective. Since your judgment is clearly  based on your extended knowledge of electronics, it should be objective. But, as you have also mentioned in a number of different threads, measurement and theory do not necessarily correctly reflect how the sound is actually reproduced. Much depends on the models the measurement parameters are derived from (they can be misleading). A good example of that is the formula for the THD, as you likely agreed. In the light of your comments in this and the other threats, a more truthful parameter would take into account how an amplifier performs on high harmonics and how low harmonics mask the distortion in high harmonics, and not only at 1khz. It is not impossible to construct such a formula and create a new parameter, call it an Overall Distortion Measure (ODM) or whatever, amean for all tested frequencies or for each frequency range separately. Electronic engineers like you, could surely contribute to this.  

My comment that you call "at least misleading" comes from the earlier cited observations by @larryi  , which completely coincide with my experience using the PP and SET amps, though of different power (I comment just a bit later about my perception regarding amplifiers of different power). Based on your comments, these comparative observations may not be correct because of different power capacities that SET and PP amps typically have. Suggesting that the above observations are correct (see my note below), a simple implication is that a SET amp should manage better with the reproduction of acoustic music (that includes classical music, most of jazz and unplugged rock performances) since it does that in the "purest possible" way at a reasonable volume level. At the same time, for instance, there is no "natural" base in an amplified rock music and a tight and punchy bass can be more pleasing, just as an example. Regarding your note, although the bass energy in a symphony can be about the same as in rock, the base is still natural (acoustic) in any kind of classical music. 

Regarding the power differences in SET and PP amps that you addressed, I personally, very rarely raise the volume of my 5.5W SET amp more than 1/4 and my normal listening level is below that on any kind of music including rock or symphonic or music (and my Thiel CS 6 speakers are not sensible at all, they are at 87). In general, on all amplifiers I have and had in the past, I try to keep a similar volume level, at least below 1/2 even if for rock, independently of the speakers I use. To me, the distortion raises too much above a reasonable volume level,  independently  from how powerful the amp is; that is to say, on e.g., 1/4th volume level, I do not perceive too much louder the music played on my 600 watts SS amp than on the 5.5 watts SET amp on the same volume level. To my perception, independently of the power an amp has, there is more or less the same threshold level above which the distortion is notable, a reason why I don't care too much about the power in watts. 

Actually I've said quite the opposite, although decades ago we could hear things we couldn't measure. Those days are gone as measurement technology has vastly improved. Apparently the education of what the measurements mean is still lacking.  

@atmasphere ,  My memory could have failed in this issue. Though you agree that THD does not reflect the sound quality, are there other important parameters based on which we can judge about the SQ without the audition? 

If you have clean power you will find yourself naturally and easily playing the system at higher volume levels because the artificial 'loudness cues' generated by the electronics are vastly reduced. 

If you are really intent on using an SET, you would do yourself quite a favor by using a speaker of greater efficiency!

The loudness can be subjective. I was just auditioning a cassette  deck on two different cassettes on my 50 watts PP amp  with EL 84 output tubes. The first cassette is not "loudly recorded", so I had to rise the volume up to almost 1/2 of the max power. This was an optimal level since rising higher the volume did not really result in a louder coherent reproduction. The other cassette is recorder louder, so that I had to drop the volume at about 1/4 to get the same loudness as on the first cassette. Rising the volume higher had the same affect as with the first cassette at the level 1/2.  A natural implication here is that the distortion did not actually come from the amplifier:  The sound itself becomes "distorted" if it is higher than an acceptable (in this case, for me) level. So, it looks like a completely acoustic (non-electronic) matter. 

I played my 5.5 W SET amp (EL34 tubes) alternatively with 91db and 87db speakers. Honestly, I noted only a slight difference, much less than i normally note between two different CDs recorded at slightly different loudness levels. And the SQ with the large (less sensible) Thiel speakers is much better. 

I would love to audition a non-SET SS amp with the same clarity as my SET amp (at this point, I am a bit skeptical).

Yes- I mentioned some prior, such as understanding the harmonic spectrum created by the amp. IMO that is more important than the THD. 

@atmasphere ,  it would be interesting to detail this point: which are these important parameters that more realistically reflect the real performance of an amplifier, or are they still to be developed? 

I am about to change my earlier  point of view that engineering is a purely applied science. I share the concern by @invalid . I think that before we talk about the amplification, we need to understand how the music performance in question was recorded. That is to say, two things are to be distinguished and seen  separately: Which kind of music we are talking about and how it was recorded (with a single microphone or each instrument separately etc.) , and then how the recorded music is reproduced by some amplifier. I think that the second issue should be discussed based on the analysis of the first one. So suppose for now that we have a "perfect" amplifier of your choice and see how its reproduction is affected by a particular kind of music and by how this music was recorded. 

I suggest that an inherently loud music (e.g., rock) is easier and more natural to reproduce loudly than an inherently non-loud music (e.g., jazz). If we force the amp to play an inherently non-loud music loudly, you may unavoidably get some distortion, regardless of how the amp is built.  By the way, among the two cassettes mentioned in my  previous post, the first one was jazz and the second one was rock music (such an analysis would understandably make less sense for CDs, i.e., it should be an analog source).