Just purchased a new Commander Plus. I find that it has quite the ground hum when using the balanced outputs to American Audio powered speakers. The hum remains if I disconnect all inputs, lift the ground on the incoming power and isolate the unit from the equipment rack. I bought this unit as a quieter replacement to a ****** EM-460, but have found it to be quite a bit noisier due to the grounding issues.
Has anyone else had similar issues?
Another strange note (which makes this ground hum demon hard to find and destroy): the hum disappears when using unbalanced outputs, when running the balanced inputs through a nice SR mixer, when running the mixer through a new AA V5000 amplifier. The hum is strongest (comprimises ~ half of the total amp output) when running balanced through an older V3000 (slightly quiets to ~10% of total amp output when V3000 ground is lifted), quieter (but present) when running through Crest CA and LT power amps (completely disappears when ground is lifted).
We tested other (non-commander & consequently non-grounded) AA mixers out of the box with no ground hum (all other variables held constant). When we got a second new Commander Plus, It had the same hum.
I would rather not lift the ground on all my power amplifiers (safety issues), I would rather not run unbalanced (I have ~200 foot runs at times). I would rather not buy another mixer (this one is new - I like the features of individual channel metering and dual XLR mic inputs on the face, etc). I would rather not send the unit in for repair since:
It is new; we also tested another new unit that had the same issue - I think it is a general design flaw
The last time I had an American Audio unit serviced it took 2-3 months to get it back in usable condition (it also had an intermittent/hard to isolate problem; but was happy to receive a working unit after all was said and done)
What are my options?
Thanks in advance.
Original Post