Q: I swear my guitar amp sounds different to me every day when I turn it on, and I never change the settings. Is there some technical reason or problem that could cause this?

A: There are several things that could make your amp sound different to you, including AC wall power variations and fluctuations and the humidity - both its effect on sound traveling through the air and on a paper speaker cone. Your guitar's tone may also vary slightly due to humidity changes, aging strings, and so on.

But the biggest thing is probably your changing perception - everything from your mood to what you have been hearing/listening to prior to turning on your amp may affect how you perceive the tone. Plus, your hearing can vary from day to day, depending on a number of factors, including subtle ear fatigue.

There's not much you can do about these variables, although it's not a bad idea to put your amp on a voltage regulator/AC filter, and you could try to strictly control the humidity in the room, though this isn't easy.