Ground Loop Hum & Cable Isolator

[Club1820]

So when I first set up my HT I had a terrible Ground Loop Hum. With the help of this forum I purchased the Jensen Isolator and all things were great. I connected the isolator directly to the cable outlet in the basement/HT and the hum was gone. I even "think" it improved the picture. (?)

So today I decided to connect the isolator to the incoming cable connection directly where it first enters the house. I connected the isolator to the incoming connection, then the other end of the isolator to the splitter. I figured I would continue to eliminate the hum and quite possibly improve the picture to all the connected sets.

Well, lo and behold - the hum was back again in the HT. Why?!?!? Can anyone explain this to me. I thought that the hum would have continued to be eliminated.

Thanks for any responses.

[Chris D]

Dunno, but you've got me interested. I'll watch this thread.

[PewterTA]

Most likely when you did that you elimated the hum from coming in from the cable company, but one of the other TVs/VCRs/etc that is connected to the line is causing a ground loop hum as well.

I'd remove each connection from all the other rooms and see if any one of those elimates the hum from the HT. If so, then you know it's something with whatever is connected on that portion of the line (ie TV/VCR/Cable Modem). Otherwise, if none of them remove the hum, remove the splitter from the line to the HT as it might be introducing noise into the line that the isolater got when connected at the HT point.

Basically need to get back to Cable company -> Isolator -> HT and start "expanding" from there to find your culprit.

I did the same as you and found out that my PC (which went from PC -> ethernet -> router -> ethernet -> cable modem -> coax -> splitter -> coax -> HT) was running through the line causing it, as soon as I disconnected my ethernet connection from my PC the ground loop disappeared. This was with my isolator on the first 'leg' of the connection just like you are doing. It took me some time to figure that out, but I finally go it... Funny thing was, I knew that my PC connected via any wire caused a ground loop hum with my Pre/Pro & Amp...just never thought it would go to all that length. ha ha.

So needless to say I put the isolator back on my HT leg and it works fine.