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I've got my PC plugged into my Panasonic 47WX49, and my cable into my Panny. When I use my PC, my speakers hum nicely unless I unplug the 1/8" audio cable that goes to my TV, OR if I unplug the cable from the TV. I also hear it in the TV speakers when tuned to the Computer input, but not on any of the other inputs.


So I've figured out that the problem is the cable. At least I think. There is a grounding wire connected to my cable hook-up outside, but I can't tell if it is actually grounded. The ONLY other thing I can think of is that the cable runs up the side of my house, outside, and next to the 240V incoming power line. I guess that could be it.


Well, I just spent 10 minutes moving the cable line around so it wouldn't run along side it, but past it perpendicularly. I still get the hum. Any ideas?

I'd love to get rid of the hum, but it only goes away when I unplug the cable from the TV when I'm using my computer as the source.


Peter
 

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This hum has to do with the cable being properly grounded and your computer being properly grounded through the third pin on the power plug, and the fact that if you make a schematic of all of the ground connections, you will come up with a shape that could be called a loop. A ground loop, to be exact.


The way to get rid of the hum is to break the loop. That's why disconnecting the cable or the 1/8" plug kills the hum.


Several companies have 75 ohm male - female ground interruptors made specifically to solve this problem. I have seen them for around $10 ( www.calrad.com; email them for a dealer in your area), although the Hi Fi company McIntosh has them for something like $60. Or was it $120?


What I do not know about these devices is whether they will cause a problem with digital cable or with two-way cable. Call your cable company and ask if they use a return path. This will take about ten calls to get to someone who has a clue what you are asking about.


In fact, here's a challenge -- call the cable company and tell them that you need the ground isolated on the cable inside the house. If you can find someone who understands the issue, and they have a solution, it will likely cost you very little!
 

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I have the same problem with my cable connection, but it is only an issue when it is raining, and for several days following.
 
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