I have a Ampeg SVP Pro that makes a loud popping/cracking noise while I play. It only seems to do it during the first 30 min or so. I do let the tubes warm up for around 5 min before adding any volume, but my guitarist turns on his Mesa triple rec and just starts whaling noise free immediately and his amp has pre and power tubes. The noise seems to be mainly in the highs as I can almost eliminate it by turning off my tweeter and rolling off the treble a bit. Adjusting the gain or drive does not seem to have an effect either. I had a preamp tube go bad in a SWR head once, but it was a constant hissing and crackling, this is an intermittent problem that does seem to vanish after a bit of playing time. All my connections seem tight as well. I don't want to have to replace the tubes if they don't need it as I don't have a lot of cash at the moment. I don't know exactly what tubes are in it now, I'll check tonight at practice and post it later. Any assistance would help greatly. My setup is connected as follows: bass to preamp input, preamp output to BBE input, BBE output to power amp in.