I agree 1000% with Almarg; I'm no engineer but I'm quite sure that the main difference is that tube amps clip more softly and gradually than solid state. It's not so much a question of what different amps do when they're playing within their power range, but rather how they sound when pushed beyond it.
"tube watts" versus "solid state watts"
I'm sure you, like me, have seen it written more than once that brand X tube amplifier, rated at 30WPC, sounded more powerful / more authoritative than brand Y solid state amplifier, also rated at 30WPC. Or that brand Z tube amp, only rated at 15W, was comfortably able to drive brand A speakers, because those 15 were tube watts and therefore up to the job. Heck, I think I've even heard the phenomenon with my own ears.
My question is: is there any basis in electrical engineering for this effect? Can we say scientifically what's going on here?
My question is: is there any basis in electrical engineering for this effect? Can we say scientifically what's going on here?