Class A Solid State Sound

I like talking tech but i don't think attributing a sound to a transistor is useful anymore. 

Pass tunes his amps for high second order distortion and his fans love it.

Thanks for the information about Pass XA, Erik. I also believe the entire design and voicing are what leads to sonic differences. However, even today, I find mosfet based output stages to generally present a smoother, potentially less objectionable sound...just my opinion.

I have not heard the amps you mention but I do generally seem to prefer amplifiers that use Bi-Polar output devices, such as Clayton's M300 monos.  One possibly meaningful comparison I have made was when I owned both the M300s and Lamm's M1.2 Reference amplifiers for an extended period of time (i.e., months).  I ended up keeping the Claytons and selling the Lamms but I cannot rule out that my preference may have been due to the difference in power between those amplifiers.