No one has mentioned the output impedance of tubed amps vs. that of SS amps. The higher impedance typically found in tube amps makes them more load dependent, and can introduce audible variations in system response based on the speaker’s reactance. In my opinion this phenomenon accounts for much of the mystique around system synergy. It is said the McIntosh MC275 has an unusually low output impedance and therefore sounds more “solid state” than other tube amps.
