Tubes do timbre. Timbre is the quality of sound that lets us distinguish the same note(s) played on different instruments. It is this unique characteristic that defines the difference between say a French horn, cornet, trumpet and/or trombone playing the same note. It is all in the harmonics and wave front differences from the different tubing and bells for brass. Same for strings, woodwinds, all instruments, including human voice. The recording venue also has its unique timbre.
Piano is extremely challenging because there are so many constituent sounds making up the timbre. Think about the piano - keys, hammers, felt, unison strings, pedals, dampers, soundboard, frame and reflecting top, (grands), all contribute to the sound of the instrument. Tubes struggle with the piano, solid state tends to make all pianos sound like electronic keyboards. That is why human vocals and piano are great for critical differentiation when listening for amp attributes.
Negative feedback and switching distortion make it difficult for solid state devices to capture timbre. Now I may p!$$ off a few folks, but the more "sand" in tube amp circuitry makes tubes sound more like solid state. Overly regulated power and filament supplies can make tube amps sound more detailed, but, IMO, at the loss of timbre. A simple, Class A FET circuit can sound wonderful, but forget about all of the regulation and high power...it is all about the first watt whether tubes or SS.
It is this elegant simplicity that make BH kit so wonderful!!!
Cheers,
Geary
