I know there are quite a few threads out there on this topic, however I wanted to get people's opinions on my specific system setup and the possible causes.

I have a Yamaha RXV-1800 receiver, Bell ExpressVu HD Box and PS3 (just listing my 3 pronged plug items). I bought a subwoofer and built a DIY box including an amp with a 3 pronged plug. At first everything sounded great, but a week or so down the road I developed a hum in the system (from the sub).

I've tried attaching a ground loop isolator, plugging the sub amp into a 2 prong plug and have yet to try hooking up an external device (such as an iPod) to see if the problem persists.

This problem is driving me MAD, as the sub sounds amazing when in use. The only resolution I can think of at this point is to replace my RCA cable running from the subwoofer to receiver. It is quite a long cable, but could something as simple as this be my problem?

Any insight would be appreciated.

Thanks in advance,
Phil

Yes, your sub cable could be causing a hum, as well as the power outlet the sub is plugged into. Try plugging the sub into the same outlets as the rest of the system, use an extension cord if needed and see if that helps. I would also try another sub cable just in case yours has a poor connector on it. Maybe move the sub right next to your receiver and try both items at once. One more question, does the hum stop when you unplug the satelite box and its input cable from everything?

I haven't tried disconnecting the satellite box, however I've heard that co-ax cables could be the problem. If it is, are there any solutions?

where exactly did you try putting an isolator?

I put the isolator between the receiver and sub.

and that did nothing to reduce the hum?

does the sub hum by itself with nothing (line leveL) connected to it?

I put the isolator between the receiver and sub.

Near the sub or the Avr?

The isolator DID reduce the hum significantly, however it was still there. And no, the sub does not hum with nothing connected. It also does not hum when I connect an external source (such as an ipod to it).

I connected the isolator nearer to the sub, not the receiver.

Thank you all for the help, but after playing with the system for a while, buying a new higher quality sub cable and re-routing my run, I was able to get rid of the hum. I believe it was coming from my incoming satellite cables.