..In subwoofers,(32,000 watt Peaveys),a low end hum is present, but not always, the dimming panel when ltg. is 60% or lower adds to distortion in subwoofers at a midrange tone. The dimming panel doesn't seem to be the cause of the hum, yet it adds a higher tone of distortion.
I think you mean 3ea 2000w subs I hope! Anyway, apparently you are not a sound guy and your terms like "low end hum","adds to distortion in subwoofers" and "adds a higher tone of distortion" means very little. And what the heck is a LV and HV rack?
At any rate it sounds like there is a power quality problem probably caused by the lighting controls and possibly other systems in the building. Maybe grounding issues and low level wiring issues also. Isolated grounds were probably a waste of time.
This is going to be a tough situation to troubleshoot. I would start by shutting down the lighting system and see if that helps. It should never have been fed from the same panel. An isolated power system might be the solution. I can't understand why a competant sound contractor would not be able to get to the bottom of this.
-Hal
