Hey Everyone, Bought my Shuttle 6.0 back in October, and I continue to have a peculiar problem that I was not able to find advice on anywhere else in the forums. If there are other threads that address this specific issue, please link them. My bass has passive pickups, and from what I can tell a very low output. Therefore, I usually am just trying to get as much volume from my cab as possible. I've experimented with different amounts of gain/volume on the preamp paired with different amounts of master volume. Sometimes when I have everything turned up pretty high, this results in the amp letting out a horrific high pitched noise with the protect light coming on. Turning the gain and/or volume down makes it stop. It always happens as I'm working with/facing the amp, which could just be a coincidence since it takes place when I'm turning things up. Could this be feedback that I am experiencing, or is the unit malfunctioning? Has anyone heard of/experienced this before?