Hi there. Recently picked up a second-hand Ampeg SVP-Pro. Gigged it for the first time last night, sounded great. At tonight's gig however, there was a loud buzz coming from the XLR out. It wasn't coming out of the jack out. Tried changing cables, changing channels on the desk (all the same as the previous night to begin with) to no avail. The buzzing even kept going when the unit was powered off, until the XLR was disconnected.
When I got back tonight, I tried plugging it into my desk at home and it seemed to work fine.
The only thing I can think of that would cause this is a grounding difference, since the unit has no ground lift option (I think?). Does anyone have any idea of what might have caused this? If it keeps happening, it's going to be a serious problem.
Also, although the unit has 2 jack outs, it seems as though plugging one in cuts the other off (that's what I ended up doing; taking a jack into the desk but it cut out the sound from my cab). Is that normal? I can't see the point in having 2 of them in that case.