Amp noise can be caused by a number of things including a poorly grounded source of electricity, poorly shielded guitar cables and fluorescent lighting. Try changing these things one thing at a time to isolate the problem. Also modern high gain amps with cascading gain stages not only amplify your signal many times over but any trace noise also gets amplified. It’s the nature of the beast. Even active pickups, which are normally very noise free, can hum on a high gain amp. Normally the noise is only an issue while the amp is at idle and a good noise gate can cure hiss from a high gain amplifier. High gain amps also have a rather large electromagnetic field and they can cause a similar phenomenon to single coils in that the noise will come and go as the player’s position in relation to the amp changes. Once again this is the nature of the beast and a good noise gate can be a cure.