Tangential fun fact: amps have a fixed gain, because it's hard to make a variable gain without distortion [1]. The volume knob doesn't control amplification, in fact it controls an attenuation stage, because it's easier to make variable attenuation with low distortion.

[1] that's why there were so many different "classes" of amps, they're all making different tradeoffs about how they're doing the amplification.