Okay, I've managed to reduce the ground loop to the cable inlet. I think it also may be related to the socket that the TV/ VCR/ cable box are connected to. However, the socket is on the same circuit as the socket I use to hook up the Audio equipment. I do know that the primary problem is the cable. What can I do? Do I need to have the cable company come out? Is there any DIY that I can try?

You need a cable isolation transformer. There was a link somewhere for them. I think RadioShack also makes them.

You can try (in order of increasing price and effectiveness)

RadioShack RF Interference Filter 15-579
Xantech 63400 Ground Breaker
Jensen Transformers Cable TV RF Isolator VRD-1FF

But I would have the cable company come out and make sure you cable feed is hooked up properly. The experts will hopefully correct me if I am wrong, but I believe that they are supposed to tie the cable ground to the same ground as the electrical system. Or something like that.

I'm going to throw my two cents in here, even though I don't know that much about ground loops.

When I got my 950/770 combo, I had a loud hum coming from the center channel. I talked to Scott and he told me how to isolate it. I finally figured it was what you have, the cable outlet. He gave me some fixes for that, but they didn't work. I would eliminate the humm, but also the cable feed. Finally, on a wild try, I bought another, what I would call, inexpensive ($40)surge protector. I plugged it into its own recepticle and plugged the amp into it. All the other equipment is on another surge protector plugged into the adjacent recepticle. Guess what? No more hum. Dead silence. I can't tell you why this worked. Theoretically, they're on the same circuit, I think. But, it might be worth a try before you start putting big bucks into this.
Ron

I have an isolation loop for the CATV line in my power conditioning unit. Does the same thing.

I also had good luck with the Xantech 63400 Ellen has linked to.


[This message has been edited by Kevin C Brown (edited June 23, 2003).]

Here's another one that's pretty cheap:

http://mcm.newark.com/NewarkWebCommerce/...0&QText=33-6925

If you have a couple 75ohm/300ohm matching (i.e. "balun")transformers in your junk box here's something to try: Hook the 300ohm ends of two transformers together, back to back in other words. Then insert this assembly into your cable feed line using the 75ohm ends. This works, I've done it and it can be a quick, cheap and dirty way of troubleshooting the problem before spending any money on a fancy-schmancy isolation transformer. (I wouldn't recommend it as a permanent fix though.) Good Luck!

I actually used the 75-300-75 ohm (or reverse, can't remember!) kludge fix for a while Did work fine though!

I would just be careful using the cable isolation transformer...I used the Xantech and it would not let me get any of the digital channels on that TV - only the analog ones. Once the isolator was removed I got my digital channels back. Now I bought a Belkin pureAV surge protector with sat/cable line protection, and this resolved the ground loop problem by grounding the cable line to the electrical system.

Yes, that is a concern. It's a matter of bandwidth for the transformer used. Jensen (in the previous link) makes a model that is compatible with digital cable. It is expensive which is why I suggested trying the cheap and dirty kludge before plunking down the cash.

If you try the cheapy method, not just any balun works. If you sort through your drawer of these things you need one that is isolating, i.e. it should exhibit a couple of mega-ohms between the connectors. You need a volt-ohm meter to sort them out. Most are only 50 ohms or less, and will not work.

Check out
www.smr-home-theatre.org/Ground-Loops