I had a similar issue that turned out to be a combination of a bad DSP board in my pre/pro, and issue of compatibility requiring a firmware udpate. The compatibility issue was with a new Digital Cable set top box input to the dsp.
You may want to try to isolate it to either the pre-pro, amps, or inputs. It always helps me to have some spare equip around for this purpose.
You may want to try to isolate it to either the pre-pro, amps, or inputs. It always helps me to have some spare equip around for this purpose.