It is a HUM. All by itself, in the low freq. range. The dimming panel adds to it when the low freq. hum has shown itself, the dimming panel adds a mid range hum on top of the low freq. hum.
The hum is not always there. It seems after time as equip. heats up then it MAY swow up. To me it seems that there is a piece of equip. that it causing resistance and creating this low end hum to start.
Now is it a 60Hz hum? Well it seems to be. But all the equip. uses 60Hz power obviously, so it would most likely be a 60Hz hum, electricians problem now.
Could a breaker heat up and cause a hum? Loose connection? Inductive reactance?
We are thinking of bringing in a generator to get a new source of power, shutting down the rest of the bldg.
Yet, this problem shows up 85% of the time, we have been there on occasion and it doesn't show.
Last time we killed main power panel breakers one at a time, no affect. when we shut down the power to the sound equip., the hum stopped after getting fired back up and did not return in the next 1 1/2 hours while we were there. I would have thought that the heat/resistance factor would have shown up shortly after reboot.
