When I am playing the spider valve 212 it seems fine until i change the amp model or channel, then the volume jumps like full blast but as soon as i turn the channel volume one way or the other it goes back to normal until i try to change the amp model again. The amp is ten years old but has been parked and not played in a dust free climate controlled environment for 7 years. Amp was played very little and is like new condition. Was working fine until the day I parked it. I have a smaller amp which I used the headphone jack and plugged into the power amp in on the 212 to see if the tube would perform ok. This seems to work as it bypasses the 212s modeling and effects. All the inner amp parts look very clean. Any ideas?