Is there actually a difference?

+1 Mickeyb

The blind test participants were a thoughtful looking group. 🤠

Interesting results from that test. My wife and I have four different systems in our house, and we certainly don't agree on what sounds "better". When I have a friend over to listen to the main system, more often than not there is disagreement over which sounds better, and for what reasons. People do hear things, and listen for things, differently.

I have two SS amps in my system that I swap back and forth. Perhaps not a fair comparison but one is a Threshold S200 I use for serious music listening and the other is a Parasound Zamp V3 which is used for casual listening and tv. The Zamp is very well reviewed and is considered to punch way above it's pay grade. That said...the Threshold destroys it in every category and I'm sure I could pick it out 100% of the time in a blind test. 

I recently picked up a set of Acoustic Zen Hologram II speaker cables and I can hear a very nice improvement while connected to the Threshold. I cannot hear any difference while connected to the Parasound. 

Like I said probably not a fair comparison, swap the Zamp out with JC1s or JC5s and I'm sure the differences wouldn't be so stark. My point is of course there are differences, class A alone puts a SS amp in another category. I want to try a tube amp next :)

Back  when I was young many years ago I could here all sorts of differences between amps. In the pre-nineties days the big amps often didn’t sound near as good as the low wattage four output transistor 60 watt class!
In those times interstate coupling caps were common and caused degradation. Around 2K many companies had adopted direct coupled designs with dc servos on the outputs. All at once amps sounded much cleaner, even the big amps were much improved. (Yes I know I’m oversimplifying!)
In recent years I found out about level matching amplifiers (within .003 volts) from Van Alstine. (Wish I’d known sooner.) Using his methodology, most modern amplifiers I’ve compared sound very similar in the mid frequencies. I think due variances in output impedance and how an amp interacts with a speaker’s modulus of impedance there are audible differences mainly in the frequency extremes.
 I think those who hear dramatic differences in amp sound are using a speaker with a difficult load. I’m not surprised when Alan Shaw has no winners of the Harbeth Challenge. Those speakers are such an easy load. I suspect any reasonably good modern amplifier would sound almost identical! Good discussion.