Soundcard and stereo receiver "hum" ?
September 18, 2004 9:51 AM   Subscribe

I have my soundcard plugged into my stereo receiver and there's a "hum" that I can't seem to get rid of. My receiver is otherwise fine: no humming at all with anything else that's plugged into it. I'm using a Sound Blaster Live! with the latest drivers and patches, Windows200, and a cheapo Radio Shack cable (1/8" stereo -> RCA). Tweaking my windows mixer settings doesn't seem to help anything (with my windows master volume turned down I still get the hum). What steps should I follow to attempt to fix this? Will a better cable help? Could it be a software issue? Do I need to buy a new soundcard? If so, which one?
posted by TurkishGolds to Computers & Internet (10 answers total)
Do you get the hum if you plug your soundcard into something else, preferably something battery powered like a Walkman? If not, then you probably have a ground loop. Try plugging both the stereo and computer into the same outlet (although a stereo purist would blanche at this suggestion due to the noise being injected into the stereo power supply by the computer). This is a common problem in home theater and places that sell that stuff may have some advice and perhaps some gadgets to help you.
posted by caddis at 10:10 AM on September 18, 2004

I get the same when I plug my soundcard into my TV...
posted by ascullion at 10:14 AM on September 18, 2004

If it is a ground loop (very likely) you need an isolation transformer. If you're wanting to use this professionally, you'll want to go spend $100+ for a "Hum Eliminator" at a professional storel. That being said, if you were doing this professionally, you'd be using balanced equipment. :-D

You can use an isolation transformer meant for car audio, to eliminate engine noise and thumps from subwoofers. These cost about $10 and work "okay" with most audio frequencies, although they aren't perfect. Let's put it this way... when I was doing a ghetto job of setting up the college's club I used these all over and things went smoothly.
posted by shepd at 10:50 AM on September 18, 2004

Response by poster: So I ran the power for both my computer and stereo out of the same outlet and there was no difference whatsoever. There's an "impedance" switch on the back of my stereo (4 ohms or 8 ohms) -- playing with that also makes no difference whatsoever. Where can I buy an impedance transformer? I'm having trouble finding one online.
posted by TurkishGolds at 2:33 PM on September 18, 2004

Response by poster: Also, there's no optical output.
posted by TurkishGolds at 2:34 PM on September 18, 2004

TG, you need an "isolation transformer", in "You've got questions, we have blank stares" speak, that is a "Ground Loop Isolator". Let's see what I can find...

Here's one that looks good, but I don't like those extra unnecessary wires...

This is *exactly* what you want (Catalog #: 270-054).
posted by shepd at 3:43 PM on September 18, 2004

Response by poster: Thanks shepd and everyone else. I got the one you pointed out at Radio Shack and now everything is perfect.
posted by TurkishGolds at 5:10 PM on September 18, 2004

You can get an optical-output add-on for the SB Live
posted by delmoi at 7:31 PM on September 18, 2004

Thanks shepd and everyone else. I got the one you pointed out at Radio Shack and now everything is perfect.

Now that is an AskMeta success, and quick too. Good job shepd.
posted by caddis at 8:03 PM on September 18, 2004

You're all quite welcome. :-D
posted by shepd at 10:59 PM on September 18, 2004

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