It's been a while. After installing my PAS3-Z kit everything was good till now. After my pre-amp has been on for a few minutes (probably just long enough to warm up) static like noise starts on both channels. I think it is somehow linked to the power supply but I can't seem to pin it down. I can sometimes get it to stop temporarily by lowering the volume all the way down and tapping or wiggeling the 12X4 tube. I had a spare 12X4 tube so I tried replacing it just to see what happened, and I get the same results with the new tube.