Hi all! I had a quick question on this unit. I use this with an Ampeg 410 8ohm cab. Its played approx 4 hours a week (mainly church). Last night, during service, it was cutting in and out of signal and was acting VERY sensitive to my bass, ie it was distorting and almost sounding like a blown speaker (we tested, and the cab is just fine, not blown at all). I am thinking its a tube issue, but wanted to see if anyone else here had experiences with these. We have tried a different bass, different cab, and its still doing it. One thing that concerns me, is it LOOKS like all of the tubes are lighting up, but I dont know if I can see them all. So my questions are: -How often do you change the tubes on your bass heads? -Does the fading in and out/distorting problem sound like something tubes would cause? Thanks a bunch!