When I turn the threshold below more than halfway I get a crazy high pitched sounding feedback. The strange thing is when the threshold is halfway or above it works and it doesn't seem to be affecting my overall tone to much. It is only when I put it below halfway. I am new to rack effects especially this so idk if it is one of the buttons. I am unfamiliar with some of the buttons on it like the "filtering tracking" and the "out and in" right next to it. On the back there are also three buttons that say "GND LIFT" that I also do not know what they do. If anyone has any experience with this and could help I would really appreciate it.