I switched the power cable with no luck and flipped ground lift and level switches with same issues. I still have the same problem with other amp (Roland power amp into PA system). One interesting thing is that none of the outputs on the back work, xlr and quarter inch, as well as the phones out on the front, but while it was messing up I ran a 1/4" cable from the "output to amp" on the front and it started working fine. It would be nice to be able to use one of the other outputs though so I could control the volume with the eleven rack itself and not the amp.