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My Ground Loop / Speaker Hum Story

post #1 of 2
Thread Starter 
Here's a brief story about how I fixed a ground loop issue last weekend.

After adding a Buttkicker amp to my system, I started to get a pretty serious hum from my LRC speakers that couldn't be solved by moving cables around. After moving cables around, I didn't hear any change to the hum. So I then unplugged the coax (Charter Digital Cable) from the wall and the hum went away. Armed with that evidence, I suspected that ground loop was being caused by the cable line.

After reading recommendations on several threads here, I purchased the Jensen VRD-1FF and installed it on the line. Voila! The hum disappeared. However, my lower network cable channels (ABC, Fox, NBC) disappeared. Those channels showed no signal on my TiVo. The Jensen instructions provided several recommendations for getting lost channels back and I followed all of their steps (like making sure the cable end was even with the connector, making sure that the wire wasn't barbed, screwing the connector and not the VRD-1FF, making sure the unused cables were all capped, etc.). Unfortunately none of those suggestions fixed the problem with the missing channels.

I bought a second VRD-1FF thinking the first one was faulty. Same problem. I should have done this first, but I then decided to go outside and check the ground cable from the cable line to the house ground. The cable ground was connected to a metal water heater open drain pipe exiting my garage. After reading some more threads here, I came to the conclusion that the problem was being caused because the cable ground was not connected to the house ground. So I called out a Charter technician and and I asked him connect the cable ground to the house ground. However, after he connected the cable ground to the house ground, with the VRD-1FF removed, I still had the same hum problem. The cable guy then re-did all of the connectors inside and out to make sure they were all perfect. I still had the noise. Then I told the technician that I thought that weak signal strength for those channels might be the issue and asked if he could install an amplifier to test that theory. He then installed an amplifier at the point where the the cable enters my house. It was a 10 port device (don't know the name) that was powered from the inside via one of my unused cable ports. With the amplifier in place, and with the VRD-1FF inline, the hum was gone and I was able to receive all channels.

The technician would have not gone through all of these steps if I didn't press him to do it. He was very nice but he was definitely in a troubleshooting area in which he had no experience. However, armed with the knowledge I've gained here, I was able to guide him to a solution.

Although I would have preferred to solve the ground loop problem without that VRD-1FF, I'm thankful that it's working as I fully realize I could have spent many, many more house chasing this kind of issue.

I hope someone else is able to glean some troubleshooting nuggets from this story and have a bit easier job fixing their own speaker hum / ground loop problem
post #2 of 2
Nice job, there is a sticky on hum , this story is worth putting there
http://www.avsforum.com/t/322698/hum-faq
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