[The following is a rather long explanation - but I need help diagnosing a problem] I have a Hartke 5000 that I run in biamp mode with an Avatar 15 and an Avatar 2x10. The other night, after an hour or so of playing, a loud crackling like sound starting coming from my 2x10 cabinet. Fearing that I blew the speakers, I immediately checked them, but the simple push test revealed nothing. I next hooked up the Hartke to a polytone 2x8 & 1x15 cabinet and I still had some crackling sounds, but less. I also tried switching speaker cables to no avail, as well as bass cable and bass. When I switched heads to a Polytone Pro, it seemed to stop, so I figured my amp had something loose inside. A close inspection inside the amp revealed nothing. So I thought I'd have to take the amp in to a pro. However, the next night we had rehearsal, and not only did my amp crackle, so did the PA and one guitar amp and all were on the same extension. Moving the guitar amp to another plug removed the problem from that amp. So my next test was to change the multi-outlet strip - but this didn't work either. So I plugged into a different wall outlet, but still it crackled. Finally, I tried a third outlet and it appeared to be OK. Unfortunately, the crackle isn't constant and I may not have tested long enough at the new outlet. To sum it up, my questions are: Can this really be a problem with the house wiring for one circuit? Or am I fooling myself, and there really is something wrong with either the amp or the speakers? Are some amps more susceptible to such interference? And if they are, can they pass along the crackling to other items in the same circuit? Thanks for any assistance.