John:

This is the important one to me, which is from one of my earlier posts:

"Tube amps produce more harmonic distortion, but the type they produce is even order distortion, and is not as harsh-sounding as the odd order distortion transistors produce. Large amounts of even-order distortion (as high as 1-2%) produces little listening fatigue, and can even be relatively pleasant. On the other hand, small amounts of odd-order distortion (less than 0.5%) are audible, even by untrained ears, and make music harder to enjoy."