Bad day with my Ampeg SVT-CL 2001. During rehearsal, after some playing for around 10 minutes or so, the amp begins to crackle (all speakers). Tried some other cables but no improvement. The actual sound here: After setting the amp in stand-by mode and turning it on again, it begins to crackle for a while without playing something. Than it stops, but still crackles while playing. After setting the amp off completely, and turning on, first the sound is good. Then after a while crackles begin again . Not happy. The tubes are fairly new, around a month old. And the head always stays on its place. Does anyone know what could be wrong with it? I have no clue. Could it be a tube problem?