Solid State vs. Tubes - What if Transistors came first?

Peter Walker (Quad) did a study comparing the sound of his own amps (Quad II and 303) tubes vs. transistors. He used RTR dubs of master tapes and presumably Quad ESL's. The two amps are well matched power-wise. It was a very thorough listening comparison using a written scoring system. He and his panelists could not distinguish between the two, until driven into clipping. It was a blind test - the amps were labeled A and B. The music chosen was various selections presumably from Decca and EMI masters. This is the most thorough test comparing tubes and SS that I am aware of! The listening panelists were recording professionals and musicians. Peter Walker's conclusion was that all well-designed amps operated below clipping will sound the same. I will point out that this was not your typical "get together in a basement with your buddies for a few hours swapping cables between two amps". It was a carefully planned and set up experiment (matched levels) - now forgotten and unaware of by today's hobbyists. 

The listening panel used a statistically-based scoring system. They did not know the identity of the amps under test - only that they were amp A and amp B. Musical selections (RTR tape) were kept short and varied to minimize listening fatigue. So there you have it. As thorough a test of two high quality amps as possible to do, under controlled conditions!

The conclusion from this is that either topology (tube or SS) can be made to achieve identical sonic quality!