As the user of a solid-state preamp and vacuum tube amps, I have a different take on this. Since this is the reference system for my audio company, Virtual Image, I chose this particular solid-state preamp because, other than a slight leanness, it is extremely neutral, as a reference should be (the fact that I was able to eliminate that leanness later is icing on the cake). Solid-state amps, with their high damping factors, tend to offer overdamped bass--dry and unnatural-sounding, IMO. An extreme example of this was a friend who had Klipsch Cornwalls and drove them with a Crown DC-300A ss amp (known in the 70s for its high damping factor). We thought the speakers had no bass, but the problem was that the Crown amp was telling the 15" woofer to stop before it could overcome inertia and get all that mass to move! He bought a used tube amp, and, voila! Low frequencies!
It's an unfortunate dilemma of life and physics that a low output impedance is necessary to eliminate frequency response variations, but that it strangles the bass via overdamping. You have to accept the compromise that works best for you in this regard. As for me, I'll take slightly underdamped over slightly overdamped anytime (until perfect bass becomes an option). Obviously, some tube amps are waaayy underdamped, and I find this as unacceptable as solid-state bass. As a learning example all you need to do is go to a live concert, pay careful attention to the bass, go home, listen to a live LP or CD of similar music on your stereo, and cry. BTW, once you become aware of the overdamped-bass problem, you realize it's not just a problem in the bass, but in all frequency ranges.
--Al
