Hi Pro Ac Fan
Seems to me, the ideal amplifier would completely disappear in your sound system, adding nothing, subtracting nothing and changing nothing except the power of the signal from the source. I don't think True Harmonic Distortion is the only value which bears on this quest. In other words, 2 amps of different design each with a value for THD approaching zero may still sound different. Why?
Maybe because amps are very complicated electronic devices with many components, the totality of their elements and design result in subtly different outputs - not necessarily of a sine wave, or test tone, but in the context of a complex, dynamic piece of music.
I've been testing a few amps to determine what to do with them - a Yamaha M80 beast, a Kenwood KA9100 which I pulled out of my HT system, and an Onkyo M504 which I now use to drive the front towers in the big HT system.
I really like them all, but each has a subtly unique sonic signature. That means, that, at best, only one of them disappears, and more probably than not, none of them achieve that standard of amplifier perfection.
Now, as to the difference between these solid state beauties and a nice Single End Triode tube amp, aside from the obvious difference of having an order or two of magnitude less power output, the tube amp sounds subtly different at similar listening levels. It's hard to describe, but here's my take on it - the mids are sweeter, fuller, more sonorous. The highs are more open, airy and ... well, sweeter. The big Onk, and Yammie beastie, on the other hand, hit much harder, have much more punch - the highs also sparkle, but it just sounds a bit different, not quite as sweet. Even though they have more punch, the mids are not as lush, or smooth, or something.
That's not to say that I don't really like my solid state amps. It's just to say, there're differences among the solid state amps, and then as a group, between these sand amps, on the one hand, and my one SET fire bottle amp, on the other hand.
For kicking back and listening to music, I just prefer the tubie - I find music more relaxing with the tubie. I also love what the big sandies do to music, and enjoy their efforts as well, maybe they're more exciting than the tubie, also pleasant BUT, when Roberta Flack, or Loreena McKennett, or Norma Jones is playing on the tubie, it sounds very much like a live performance, subtly more realistic an illusion of being there than I get from the sandies. Just my take.
