My cell phone has been causing issues with all my amps lately, it even does it in the truck with the stereo I have in there. It even affects my monitor so I have to set it aside far enough away that it doesn't cause interference. With my amps I have tried changing amps, tubes, guitars, cords and cables and it doesn't seem to change anything. I just have to turn it off or put it in a different room while I play. I think it just boils down to the fact that I need a new phone. Mine has been around the block. It is about 5 years old and has been dropped numerous times from 3 stories up as well as just kind of abused in general in a construction site environement. The problem is it won't die. I like the ruggedness of it but would like some of the more modern features. Unfortunately the newer phones couldn't withstand the torture I subject my phone to. So for now I am stuck until they make something more rugged. That's fine with me though because I don't like answering the phone while I am playing or on the computer anyway, much less when I am driving.