My question is, of course aside from the obvious matching with the speakers, what in the amplifier design would lead to a difference in sonic character between the 4 and 8 ohm taps?
what happened here was you were asking the amp for more power, and being kt88's, they are capable of more power...
if you want some math, we can do that....
the drawback here could be higher distortions, but if that was a 3rd harmonic, then better for the bass....
if you did that to an el84 amp, then things might have been different....the el84 would have clipped sooner than a kt88...
What would happen if I used the 4 ohm tap to drive an 8 ohm speaker?
then the amp will be loafing around and delivering less power...
distortion will be lower, but then for tube amps, that is usually
not an issue as long as you can not hear it....
lastly, for solid state amps, this speaker matching is not such a big
issue, ss amps have output impedances below an ohm, see the damping factor specs for ss amp....
tube amps have much higher output impedances, (lower damping factors...) the 4 8 and 16 ohm taps in a tube amp is not the output impedance of that tube amp, they are OPT secondary taps for
connecting speakers....