Originally Posted by Kentuckytech
Sorry for the delayed response, i've been out of town. I don't think its a ground loop problem. I grounded the processor and it didn't make any difference. The hum is very low and i only hear it when i turn off the processor, never when it is on. The funny thing is i can unplug the rca cables long enough for the sub's amps to auto power off and plug the cable back up and it won't turn the sub amps back on until i power up the processor again, i'm stumped?????
It clearly is a grounding problem. With XLR's most of us do not have similar problems, except for one thing. If you use cable, I assume you are coming out of that via HDMI into the prepro. If not (i.e., component video/audio), it may be coming from there, and you need a "ground trap" in front of the cable box. First, disconnect that from the prepro and see what happens. Satellite or HDMI connections from cable should not cause the issue, only RCA's.
Unless it still happens with no inputs connected to the prepro, check other input connections to the prepro one at a time. Also, I doubt it will do any good, but try reversing the unbalanced RCA connection cable to the sub. You might also try running a piece of zip cord between prepro and sub chassis to chassis. You might also try sub and prepro from the same electrical outlet or, as a last resort, "lifting" the AC ground for the sub, if it's 3-prong, with a "cheater" plug.
Actually, the true last resort is get a new sub, preferably one with XLR input.
Careful. Don't electrocute yourself.