Anyone experience this? Makes crackling type noise all on its own, all channels, all modes, guitar plugged in or not, foot switch plugged in or not. Tried different speaker cab - nope, this is the combo, by the way. Turning each and every knob makes no difference (though this SOUNDS like a dirty pot'). It did seem to have an effect when I plugged a 1/4 jack into each of the speaker outputs. Coating with DeOxit didn't seem to make much difference. The noise is barely audible when playing but will drive a person crazy when not.