I get an unpleasant buzzing out of my amp when I'm not playing. It... Decreases when I deepen my bass's tone knob, Increases as my bass's volume goes up, except when it hits max volume, where the buz reduces, Increases as my amps high and medium high setting increases, cuts off when i touch (pull up, push down, hold) any one of my strings. This buzzing is variable in volume, as to the time and the conditions mentioned above. The most confusing part is the last symptom I mentioned; muting any string. Does anyone have a clue as to what the problem could be.