whether plugged into my QSC or my carvin's power amp (effects loop) my new ampeg SVP-pro buzzes. The one think I actually like about my carvin is that it's silent. The ampeg buzzes as long as it's on, even if the volumes off. The buzz stops when I switch the unit off, however. The bass doesn't matter, plugged in or unplugged, it's the same buzz. The buzz is goes up when the poweramp attentuation goes down- the only factor that affects the amount of buzz- and boy does it affect it! Wide open, the buzz is unbeably loud. With the control on about 1/4 there's a bearable, yet still easily audible buzz. It does this at every output I've put it through, and in different buildings. What seems to be the problem? Thanks!