A new ground type HUM noise has started recently. it's not extremely loud, but it's there.
With no mic or anything plugged in the input, I just plug the output, the hum is there. I've tried a ground lift just to see, still there.
This is with both N72's alternatively .
Now what is bizarre is, if I go past a certain output level, the HUM can disappear.
With my "output Level fader" on the SCA at 0, hum is always there, at every gain step, but when I raise my gain to the 6th position, and raise the "output level fader" on full, the hum suddenly disappears. The hum will be there on all previous gain position regardless of "output level fader" position.
If I raise the gain to 7th notch, hum starts up again but if I lower the output level fader a bit, I can get it to disappear again in a certain position. I can do this with every gain position after by lowering the "output level fader" to a certain point and get it to disappear.
This happens with both N72 cards, so i'm assuming the problem comes from the Power Supply itself and not my N72's. I doubt that they both developed this problem at the same time
What could be the problem? or defective part that I should look at, if you can guide me to troubleshoot this problem.
The rack has never been moved around either, this just developed with time.
I'm thinking maybe an old Cap? Would you know around which one with this type of behavior ? I'm looking for guidance here
Thanks