I searched through a few threads & didn't find anything about this so forgive me if this is nothing new... I have the Hartke plugged into a 15" Ampeg Classic. After less than 30 seconds of turning it on there's like a White noise with random thumps coming through. Nothing too loud that disrupts normal play. And that's before I even plug in the bass. Plugging in the bass makes no difference on this mystery noise. It's almost as if the fan is being amplified or something. We've taken to calling it "the wave machine" like one of those ambient noise things people use to help fall asleep. I fiddled around with knobs to see if it was the tube, no change. But when I clicked the compressor to "on" there was a break in the noise when it 'clicked'. If I hold the compressor knob just at the 'click' (for lack of better term, that point where it's just about to turn on/off) the noise disappears. So I'm guessing it's somewhere in the wiring there? I have no idea about amp stuff, just wondering if anyone's had this experience or has any idea what to do about it.