# Large hum/buzz coming from audio!!



## Muffy7 (Apr 13, 2005)

Hi Everyone.

I have a panasonic home theatre system. It's decent, very nice to the mediocre ear. Anyway, i use my computer to play dvd's, and music, and all that jazz. So what i did, is i took an RCA to 1/8'' wire and hooked up my sound system to the sound card in my computer. Any time the volume is turned up, a hum goes up with it. Its consistent with the volume. I tried unplugging my computer's power from the wall, and left it dead. I plugged in the wire, turned it up, and it is still there! So i think that throws out electrical interference? 
The weird thing, is that when i plug the same wire into my mp3 player, there is not the slightest hum at all! So i know the wire and the sound system are fine. I have a pci creative sound card (sound blaster live! 24 bit *old*) and the onboard Realtek one. I tried plugging it into both. Still the same result!

So it have to me some sort of an interference from the computer, but i can't for the life of me figure it out!

please help!

- Kevin


p.s. i thought about using an external sound card hooked up through usb (xmod for example) because if my mp3 player works... than that would have too. Well, please help me!


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## cwwozniak (Nov 29, 2005)

Muffy7 said:


> I tried unplugging my computer's power from the wall, and left it dead. I plugged in the wire, turned it up, and it is still there! So i think that throws out electrical interference?


Did you also unplug the AC power for any other devices, like a printer or monitor, that are connected to the PC? The chassis of the PC could have still been connected to power ground through the monitor or printer cable.


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## kiwiguy (Aug 17, 2003)

Or the PC is connected too a router which is connected to cable or DSL etc.

What you have is an earth loop, arising from a connection to ground within the system that is different to that of the audio amp.


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## cwwozniak (Nov 29, 2005)

kiwiguy said:


> What you have is an earth loop, arising from a connection to ground within the system that is different to that of the audio amp.


And something like this *may* help break that loop:

http://www.radioshack.com/sm-see-all-needs-and-wants--pi-2062214.html

This one from Radio Shack even includes a 1/8 inch stereo plug adapter.


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## cwwozniak (Nov 29, 2005)

Muffy7 said:


> I have a pci creative sound card (sound blaster live! 24 bit *old*) and the onboard Realtek one.
> 
> p.s. i thought about using an external sound card hooked up through usb (xmod for example) because if my mp3 player works... than that would have too. Well, please help me!


A new audio card or an external audio box might still have the same ground loop / hum issues. The output grounds would probably still be connected to the computer's chassis.

Some other options if you do go with a sound card upgrade ...

Is the audio setup for your home theater simple stereo or do you have multi-channel surround sound? If your audio system has an optical or coaxial S/PDIF input, you might want to consider getting an internal card or or external box with a matching S/PDIF output. An optical connection would eliminate any possible ground loops. Not sure what the distance limits are for S/PDIF.


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## Muffy7 (Apr 13, 2005)

It's been awhile since i posted this.. but for everyone to know i figured it out!

What happened was that my cable was split between my modem and my dvd player, which somehow made a large hum. After i unplugged it from the dvd player, it was completely gone!


:]

thanks for the help too.


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