Ok, so I've been having a problem with my amp, and I'll try to describe it the best I can. When playing, my amp will start to make this annoying, low frequency hum. It isn't that noticeable while playing, but when I stop, all you hear is "hmmmmmmmmmmmmmmmmm." I can then give the amp a little bump, and it will stop. It may come back, or it may not. I've checked all of my tubes, and they are all in their sockets properly. Does anyone have any idea what might be causing this?