Subwoofer humming issues

dane_peterson

So now that my home theater is complete, I don't want to set foot behind my TV stand. But unfortunately, I'm having some humming issues with my new sub.

The issue is twofold... when I turn on the sub amp, I get a mild 60hz hum. Then, when I turn on the receiver, this hum is amplified even louder. It's tolerable when only the amp is on, but not when I have my receiver turned on. When I remove the audio cable, the sound disipates significantly.

I'm currently using a Behringer EP1500 amp on bridged mode. I'm connecting the Sub out from my receiver w/ a decent analog RCA cable and RCA->1/4" adapter.

I've tried plugging the amp into the wall vs the Panamax and didn't yield any different results. I've heard mixed opinions about using a 2-prong power cable, which I do have available but yet to try. I'm just wondering if I'd notice improvements w/ a dedicated subwoofer cable, or if I should try an RCA->XLR adapter or what...

tonyb

Ground loop problems can be testy to find.Having that sub amp in bridged most likely isn't helping.You can try a cheap 2 buck cheater plug on that amp.Or if the back of your system looks like a bowl of spaghetti,then make sure none of the power cables are touching the I/C's.Then unplug one I/C at a time to see if it goes away.Cable boxes are usually the culprit.Could just be a bad I/C too.Start with straightening out the wires and get a cheater plug on the amp.I always try to cross my I/c's and power cables at right angles.

dane_peterson

So here's an interesting curveball...
I also discovered significant humming coming from my speakers when the sub cable is plugged in. Only happens when the cable is connected to both the AVR and amp... as soon as one end disconnects, the sound goes away. Thoughts?

Serendipity

Sounds like a ground loop to me.

tonyb

Try the cheater plug on the AVR.Definately a ground loop issue.Make sure none of the power cables come into contact with the I/C's.What changed in the system to create the hum?? Obviously it wasn't always humming.

dane_peterson

The latest:
I unscrewed my coax cable from the wall and the sound vanished. So it appears the coaxial cable is the culprite after all. Ran this through my Power Center, but still have some humming. Going to try to Ground Loop Isolator and see if that makes a difference.

Thanks for the help!

dpowell

One thing that worked for me since my sub is close to my amp was to loosen one of the screws on the sub amp, wrap a piece of picture hanging wire around it, tighten the screw and attach the other end of the wire to the grounding post on my AV receiver. Humming problem gone. Two prong adapter worked well for subs further away.

dane_peterson

Ended up fixing it with a Jensen RF Ground Isolator. Set me back a few bucks, but worth it in the end.