Very strange but here is the history.
Picked up the 750x to run through my Ampeg 8X10. Everything works great for half a dozen practices with the amp in an 8 space rack (with fans) set next to the amp. We purposely did not set the rack on the cabinet to avoid vibration to the amp. We play our first gig and due to space constraints, we set the amp rack on top of the cabinet. All works fine until the last few songs when I switch to my drop D bass and I hear some rumbling, farting sound coming out of the speakers.
Three days after the gig we set up for practice with the amp on top of the cabinet again. As I'm warming up, I play a descending line ending on the E string and as I hit the E, the rig starts the farting rumbling thing again and cuts down to about 1/3 power. ***?
I hit the speaker switch, check all connections, check my bass and then turn the speakers back on....same thing. Maybe it's the pedal board. Run straight into the amp...same thing.
We are thinking the problem is a loose component on the circuit board caused by the vibration from the cabinet or maybe a bad connection in the speaker cabinet.
Anyone else have any suggestions regarding where to start running down the problem?
