Problem with RCA audio cables connected at the same time as the PC - AVS Forum
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Old 04-30-2013, 01:48 PM - Thread Starter
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I have a 2.1 speaker system. It has a mini jack cable that plugs into the computer, and the two red and white RCA inputs, and a mini jack input.

I have my PS3 connected to the red and white RCA inputs, and don't have any problems with that. While that is connected, I can have the PC connected with the 1-way mini jack cable without any problems with the audio. The problem is, when I connect the RCA cables from the cable box into a RCA to mini jack adapter and plug that into the mini jack input, there is a buzz or humming sound. I tried unplugging the PS3 audio cables and plugging in the cable box RCA's directly, but the same problem happened, so it isn't a problem with the RCA to mini jack Y adapter. If I disconnect the PC audio while the cable box is connected via either directly or through the adapter, then the noise problem stops. Same thing if I disconnect the cable box audio while the PC audio is connected.

So there is a problem for some reason with having the PC and the cable box audio connected at the same time. The RCA cables are new.
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Old 04-30-2013, 02:11 PM
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Your description suggests that your cable tv's grounding is not the same as the grounding of the pc. One possible fix would be to get an in-line isolation transformer for the incoming cable tv's coax. Something like this: http://www.amazon.com/Dayton-Audio-VIT-1-Isolation-Transformer/dp/B0002KR2RM

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Old 04-30-2013, 03:23 PM - Thread Starter
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I didn't have this problem when I had the cable box connected to different speakers, but when I connected the cable box to the same speaker system that my PC is connected to at this time, I have that problem. What does the grounding of the power have to do with the audio?

Also, what is the point of your user name and avatar?
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Old 05-01-2013, 11:34 AM
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You have hum. It's likely 120Hz. That means it's a power issue, and a very common one, especially since it comes and goes depending on what components are connected in different ways. Sounds to me as if the PC and cable box are the source of the loop. Radio Shack sells an isolator for $20...

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