hum created when pc is connected to home theater system

[boostm3]

Ive been enjoying my Realtek ALC861 7.1 codec that came with my motherboard for a couple of years now, but Ive got a question about hum.

When I connect my set of Boston pc speakers which comprise two small speakers plus a powered subwoofer to the ALC861, all is well and things sound fine.

But, when I want to hear the music in my Media Player library stored on my pc on my home theater system, I connect the ALC861 to my available audio input rca connectors on my Sony home theater receiver and I get a hum mostly in the right channel which is loud enough to be annoying. It can be mitigated some by turning down the volume on my receiver and controlling the level by pc volume controls. My Sony receiver is a 5.1 channel receiver from their es line. To drive the front pair of Klipsch tower speakers, I have a Rotel preamp connected to a powerful Rotel amp. The Sony Receiver drives all the other speakers, with just the Mains being driven by the Rotel preamp + amp. The receiver connects to the preamp via its pre-outs into the latter’s aux in.

The hum is only generated when the ALC861 connects to the receiver. As I say, when it connects to the amplified Boston set of PC speakers and connected Subwoofer, I hear no hum.

Is this unavoidable? Would a better or more expensive pc sound card produce less noise? Any other ideas?

Thanks.

 

[10010011]

Sounds like you could have a floating ground.

Try running a separate wire from the case of the PC to the chassis of your receiver and see if that helps.

 

[boostm3]

Sounds like you could have a floating ground.

Try running a separate wire from the case of the PC to the chassis of your receiver and see if that helps.

I just ran a length of speaker wire from the pc chassis to a metal screw on the chassis of the receiver about 20 ft away, and sure enough, that took care of the hum.

Now, the problem is, as I say, the pc and receiver are about 20 ft away. Its very difficult for me to use a piece of wire like this as part of the permanent installation.. Is there any other way, now that we have isolated the issue, to get rid of it? Would purchasing ground isolaters or something like that to install on each of the two devices solve the problem? Any other ideas besides connecting the two chassis?

Thanks for the tips!

**** EDIT ****

Fixed it! I didnt have to stretch a wire 20 ft to join the chassis of the pc and the receiver. I found that all i needed to do was connect a screw on the pc chassis to a screw in the chassis of the cable modem right next to it! That cleaned it right up. I guess since the cable modem/router joins everything from the tv (which connects to the receiver) to the pc (and to the phones tooalthough I dont think that part was involved!), grounding the pc and the cablemodem/router did the trick..

Thanks again ...

 

[10010011]

I take it you already have a long patch cord connecting them?

Why not just wrap the extra ground wire around it or tie-wrap them together?

I do not use isolators as to me it's a band-aid approach.

You could also invest in a wireless audio device like a Linksys Music Bridge.

 

[boostm3]

In case you didnt read my resolution which I added on as an 'edit' to my last post:


**** EDIT ****

Fixed it! I didnt have to stretch a wire 20 ft to join the chassis of the pc and the receiver. I found that all i needed to do was connect a wire from a screw on the pc chassis to a screw in the chassis of the cable modem right next to it! That cleaned it right up. I guess since the cable modem/router joins everything from the tv (which connects to the receiver) to the pc (and to the phones too although I dont think that part was involved!), grounding the pc and the cablemodem/router did the trick..

Thanks again ...