this a 100 watt version with a quad of SED EL34s and 6 - 12ax7. In the higher gain channel it is picking up radio interference as well don't know if that could be related. Just wondering if a input jack on either the FX loop or front of the amp could be acting like a open circuit? The volume fluctuation is intermittant, the amp sounds like god for the most time just the loss in volume or volume boost at inoppurtune times with no real loss in tone either way. Would any of you have an idea how to go about troubleshooting this? Thanks in advance.