Questions re:  GaNfet technology vs other designs.

No, my statement is absolutely correct @atmasphere . Read my words carefully. "MAINLY" comes from a non-flat frequency response. That is especially true of most tube amplifiers such as the high output impedance of your own OTL amplifiers. The interaction of that output impedance with a speakers impedance will totally dominate any potential distortion profile your amps may have. Ditto for things like D’Agostino amplifiers. The effect is pronounced because the largest change in speaker impedance curves occurs where the equal loudness lines for the Fletcher Munson curves are close. Most amps have their lowest distortion here and hence not affected.

Tube amps due to typically low feedback would be expected to have mainly compressive distortion which tends to reduce perceived volume, however as we know, even the ability to detect low volumes of distortion, is not great so having much impact to coloration of the tone is questionable and certainly not exceeding the effects of impedance on frequency response in real world implementations.  Contrary to your technically correct comment I have seen you make about feedback levels and high frequency THD, I don’t think you have a lot of evidence to support it based on a multitude of full bandwidth distortion measurements by the likes of Stereophile and ASR showing most amplifiers, "no feedback" or otherwise having low distortion out to 20KHz, even going back some time on Stereophile. You have made claims of very low distortion being audible in other posts, but I can find no evidence provided to support those claims. I am quite certain there is no evidence to support a claim of tonal differences based on these very low distortion levels out to 20KHz. The compressive/expansive effects of distortion in audio electronics would pale compared to what happens intentionally or unintentionally in the recording process (and speakers at reasonable levels).

Keep in mind I am not discounting that distortion can impact perceived tonality, and the nature of the distortion, compressive or expansive will impact that change in perception. I am saying that at the practical levels of distortion, unless the amplifier is very high in distortion, the impact will be significant less than impedance effects and between a lot of amplifiers the distortion is low enough that it will have 0 impact on tonality.

@charles1dad , I would not be so quick to jump on the bandwagon.

@snapsc, have we all forgotten the Carver challenge already? https://www.stereophile.com/content/carver-challenge  -- Bob, took one of his SS amps, a rather run of the mill one, and in 4 days, made it sound exactly what was assumed to be a tube coupled tube amplifier. His goal was to match the transfer functions, or specifically the input to output relationship with a real load, which in laymans terms the frequency response (magnitude and phase) measured at the speaker terminals. Once he did that, they sounded the same. Did he perhaps add in some distortion on his amp to match the other amp? Potentially. He of course did not detail the changes, but the vast majority of the nulling requirement would be to match the frequency response at the terminals of the speaker. That is how you make two amps sound effectively the same. If you drive the amps into clipping, all bets are off. There is no indication that was done in the Carver Challenge, but a comment indicates he had to add lots of impedance at low frequencies to match what was happening on the two amps (drop it from 500 watts to <100 watts).

Too bad carver couldn't do this in production models, plus the two amps would probably still sound different with different speakers.

Presumably there is better measurement equipment today which would allow the "fine tuning" of the various amps I mentioned in a fashion that might? allow them to sound very similar??

@invalid ,

I quote,

No matter what speakers we used, every "difference" we thought we had isolated turned out to be there, in equal quantity, when we swapped amplifiers.

He probably could have and maybe just did most of his work with a resistive load adding in a set of speakers for verification. He wasn't going to give away all his secrets.

He did do things with his production models, but it would be good to question what are real sound difference, what is voicing, and what is marketing.