I've got a technical issue with my Aggie AG500 and I was hoping one of you guys might know what the problem is before I take it in for repairs. I was practicing in the living room of my apartment at fairly low levels, keeping the volume knob around 8 o' clock. As I was playing, the amplifier kept incrementally getting quiter and quieter so I would have to keep turning up. I would actually hear it fall down in volume every minute or so. Now, I'm playing with the volume at 1 o' clock to get similar levels as it was 10 minutes ago at 8 o' clock! At the original level I was playing, it was shaking the floor, but now it's thin and just barely audible. To rule a couple of things out: I'm playing a passive bass (so it's not the battery), I played with several different cables, and plugged into several different outlets throughout the house. I can't seem to figure this one out, so I could really use somebodies help!!