I use the M13 with my Mesa Boogie Dual Rec, I was recording and I wanted to record some feedback for ambient noise tracks, so I switched on a delay and a reverb on the effects unit. For a second it was feeding back nicely, with the decay and mix controls turned up quite high on both effects, but it began to build and build, louder and louder (feedback loop?) until I had to hit the effects off. Instantly after my amp was noisy as hell, humming very loudly and making scratchy noises when I adjusted the knobs on the front of my amp. I hit the standby button off/on and there is a THUMP that is ridiculously loud coming from the speaker. I know for certain this isn't a speaker issue, it's either my amp (which has been sent in and diagnosed before when I experienced the same problem, they replaced my loaded power tube board because the screen capacitors were fried...but by what? After that it worked fine) or my effects pedal having some weird issue and loading my amp down when I use too much delay and reverb at the same time. On a timeline basis, there is a correlation because this never has happened before I owned the M13, and since I've had it this is the second time this has happened. When it does happen, it blows the loaded power tube board, the screen caps, the power tubes, and the diodes. Add to that the price for it to have the parts replaced at $100 an hour, the cost of parts, and the cost of shipping...it's a small fortune. I can't afford it this time, and I'm really frustrated. Ideas or suggestions? I'd be very greatful if a Line 6 tech employee would join in on this little discussion.