I have an Ampeg SVT-CL that has been giving me intermittent crackling/fuzzing/buzzing that seems to happen especially when I hit low notes, but can happen with high notes as well. I've gone through the following troubleshooting steps: Plug in pre-amp out of another amp (Ampeg B2R) into SVT's power amp in. No noise this way. The power amp section is probably good. Reflow solder in pre-amp board input jacks as one showed a crack. This helped quite a bit as this was contributing to the noise but it wasn't the only source. Instrument patch cable between pre-amp out and power amp in. Noise still present. Tapped on the various tubes with power on. Lots of crackling when tapping phase inverter tube. Replaced tube. Seemed to improve but still intermittently present. Could have just been corroded contacts that was contributing to the problem. Improved ground connection on pre-amp board pad that touches the back left stud (when facing amp). Again, seemed to help a bit but problem is still intermittently present. Changed pre-amp tubes one at a time. Noise still intermittently present. Put original pre-amp tubes back in. I noticed that the gain pot is pretty scratchy if I move it while there's a signal through the amp. I put a little Deoxit in there and rotated it a bunch. This is the last thing that I've done so far and it seems to have eliminated the problem although I haven't had the opportunity to test it long enough to confirm. Is it possible that a potentiometer can cause this issue while it is stationary? Thanks for reading.