Watts are watts, whether ss or tube. How loud an amp can play without objectionable distortion (to the ear) is related to how gracefully it overloads. Tube amps are better in this in that they use less negative feedback. If the same excessive feedback was applied to a tube amp as typically used in ss designs, the overload characteristics would be just as bad if the amp was dc-coupled and far worse if ac coupled as most tube amps are. Fortunately, engineers have not been able to apply large amounts of negative feedback in tube amps because phase anomalies in the output transformer won't allow it.
Of course, lower amounts of negative feedback results in higher output impedance of the amp, resulting in measurement specs gurus freaking out.
David Berning
Of course, lower amounts of negative feedback results in higher output impedance of the amp, resulting in measurement specs gurus freaking out.
David Berning