Questions re:  GaNfet technology vs other designs.

Try to listen to Atmasphere's class D monoblocks or any of the AGD models.  Currently (no pun intended) those are the best bets for what you're looking for.  The Orchard Ultra Stereo looks promising, but I can't speak to it directly.

Don't let yourself fall into the trap of "musical" / engaging. Mainly that comes from a non-flat frequency response

@theaudioamp This statement is incorrect. The ear converts distortion into tonality; actually the reason some amps sound musical and others do not is the distortion signature of the amp (often referred to by audiophiles as the 'sonic signature') rather than a frequency response error.

This is why you can measure two amps on the bench that are equally flat in frequency response but one will sound bright and the other doesn't. Higher ordered harmonics (the 5th and above) are perceived by the ear as harshness and brightness if they are not masked by lower ordered harmonics. This is a problem with most solid state amps made and why tubes are still around. But if the solid state amp has the right distortion spectra (lower orders dominating) it can sound as smooth and musical as a tube amp, yet will have nice flat frequency response.

@atmasphere 

Thanks for correcting the misinformation post (Although I'm sure it was well intended).

Charles

Ralph, is it possible then to get different technology amps...say OTL, ZOTL, Gan, Class A....to sound almost identical if you can get the distortion spectra for each very similar to each other?

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.