So over the past couple weeks my 2x12 6505 has been acting up. It sounds just as good as it always has when I'm actually playing, but sometimes when I'm not playing I'll notice a weird kinda rhythmic tapping/clicking, almost like someone was winding a clock, coming through the speakers. Sometimes it's fast and almost kinda sounds like a fart with a tiny bit of reverb (not trying to be funny... this .... is really pissing me off) and sometimes it's slow. When it happens I can play quietly and the sound is still there, but everything else sounds like it always has. When I play loud with my OD on it's still there, but the sound of the actual guitar is enough to drown it out. Once again, with the OD on everything sounds normal except for the mysterious clicking. And it only happens intermittently, and flicking the amp to stand by for about 10 seconds and then turning it back on again fixes the problem but after about 10 minutes of playing it comes back. I've done some research online and all I can think of is that it could be a bad preamp tube, however I can't find anyone else who's had the exact same problem so I'm afraid it could be something less simple and more costly. If it helps the only thing I have going into the 6505 is a fulltone OCD out front used as a boost and a Boss GE-7 in the effects loop. I have 3 shows over the next 10 days and need to get this sorted out ASAP so any (fast) responses are GREATLY appreciated.