I was just idly wondering about that. We use all these subjective phrases, about tone, but it ought to be possible to objectively compare one amp to another and see how they treat the signal differently... Do you folks in the design side of the industry do that yet? Obviously a frequency response chart is pretty easy and well established, but it seems to me there must be much more, especially if you dial in distortion. Would one input a pure tone or perhaps tone and harmonics, and with fourier analysis see how the balance and levels of harmonics changes when the signal goes through the amp? Would that give you a repeatable method for measuring the effects of distortion etc? Would changes to the signal envelope be significant? I suppose they must be if you consider compression of the signal... What other things might there be that affect the tone? I can see this getting very complicated to do rather easily. Is it more practical just to rely on the well attuned ear?