Btw - what thousand pound amplifiers have a several percent distortion?

Single-ended triode amps do - and they can cost a *lot* more than
that!

But what are we measuring? Valve "distotion" is viewed as a rosie glow.
Transistor x/over or switching distortion in a poorly designed (or
over-driven) solid state amp of only a few 10ths % is unbearable!

Not all distotions are created eaqual - but they are all deviations from the
"straight wire with gain" model of the "ideal" amp.

David