How do I shield an audio cable in my computer case which I cannot take out and replace?

December 28, 2009 9:55 AM

How do I shield an audio cable in my computer case which I cannot take out and replace?

The cable running from my motherboard to the front headphone jack is unshielded, apparently. I constantly hear a high-pitched mosquito sound in my headphones, and static when my hard drive spins up.

What's a good DIY way to shield the cable? Foil tape? Some kind of mesh jacket? I can't replace it because that would require soldering knowledge, I think. However, I can unplug one end of the cable if needed.

posted by aliasless to Computers & Internet (6 answers total)

You can get braided copper shielding at a local electronics supply outfit. I'd talk to the guys there before making a purchase. If it's too expensive, aluminum foil should work too, though it isn't going to be pretty.

Remember that you're going to need to make sure the shield is grounded if it's going to be effective.
posted by valkyryn at 10:22 AM on December 28, 2009

Braided copper shielding will work well but keep in mind that one end of it will be grounded bare copper right next to the motherboard -- make sure to insulate it anywhere it gets near other electrical contacts or you're just asking for a short sometime in the future (eg, when you try to put the lid back on the case).

The easiest way to ground the shielding would be to cut a piece that's way too long and cut a long slit in it so you can push it up onto the audio cable with a long tail hanging free, then wedge that long tail under any screw on the case.
posted by range at 10:38 AM on December 28, 2009

Make sure you don's short anything out or, well, you will get rid of that high pitched noise. And all the others. An those annoying fans. You get my point.

You can probably also buy (or even make) a filter for you headphones and cut out the high frequency noise. All it takes is a small capacitor and resistor. The magic words here are low pass filter.
posted by Kid Charlemagne at 10:43 AM on December 28, 2009

I'm not an EE, but this sounds like the sort of thing that twisted pair is good at, and it avoids the risks of something shorting on the grounded shielding.
posted by Good Brain at 11:27 AM on December 28, 2009

You might want to strap some ferrite cores on the other cables that are causing the interference. If you know the sound comes from spinning up the hard drive it might be worth slapping a ferrite core on the hard drives power cable.
posted by chairface at 11:38 AM on December 28, 2009

You should also be prepared to accept that the EMI isn't being radiated through the cable but conducted such as through the power rails.
posted by Rhomboid at 4:27 AM on December 29, 2009