I recently purchased a markbass ta501 used from a tb'er. I've used it for about 2 months without problems. The only other noise i heard from my bass was the whirring of the fan, which didn't bother me. However, one day i plugged in my bass and all of a sudden the volume was dead. It was at a barely audible volume and there was a very loud buzz as I was playing. WHY is this? Is there a problem with my amp?