Return to the Electronics Forum | Post a Follow-Up

 o
Electrical Hum

Posted by criticalmass (My Page) on
Sat, Sep 30, 06 at 8:02

I posted this message a few months ago, and wanted to try again, since I got only one response.

I watch movies on my computer. I have 2 S-video cables (connected with a coupler), and a 20 ft. 1/8" headphone cable (with a 1/8" - 2 RCA adapter) running from my computer to my DVD burner. I then have component video cables coming out of the DVD recorder going into the tv, and then fiber optic cable connecting the DVD recorder to my amplifier.

What happens is that when I watch a movie on my TV, I have to turn on my DVD recorder first (out of inputs on the TV), then turn on the amplifier. I get an electrical hum, which ranges from "mildly annoying" to "downright maddening" in the background. This probably means I'm turning up the amplifier too loud, but if I turn it down, you can't hear it.

Troubleshooting: When I unplug the headphone cable from my computer, the humming stops. If I plug it into a portable CD player, it's still gone, so therefore it must be coming from the computer. Another member suggested it could be the sound card, but mine is integrated on the motherboard, but how do I test or fix that? The computer is plugged into a surge/battery backup. Could that be it?

Thanks in advance!


Follow-Up Postings:

 o
RE: Electrical Hum

You might have better luck asking this in a computer forum.

If it was me I would just seperate the computer stuff from the tv stuff.


 o
RE: Electrical Hum

Plug another amplifier (even amplified speakers) into the computer and see if you hear the hum from that.

If yes, it could be the mainboard's onboard sound processor. Most of these are fairly mediocre and shielding is piddle-poor. Shifting cables around or moving other electrically noisy parts (which is to say "just about everything") around inside the computer chassis sometimes helps.

Have you muted all the sound card inputs you're not using?

If all else fails, disable the internal sound processor in the BIOS setup and fit a good quality PCI soundcard. Turtle Beach cards used to be good but I don't know whether they are any more. Maybe Yamaha? It's probably overkill but Echo (echoaudio.com) makes very nice pro-quality sound cards. I can't recommend M-audio; I bought their Audiophile 2496 card a few years back and have regretted it ever since.

If the hum goes away with a different amp, you may just have a ground loop. This is typically a buzzing sound with overtone components rather than a pure 60 Hz hum.

The classic ground loop solution is to fit ground lifters ("cheater" 3-pin to 2-pin adapters) to one or more of the devices (computer, DVD, amplifier).

Also try adding extra ground connections among the chassis, and/or lifting the shield ground at one end of each audio cable.

Getting rid of ground loop hum is often a maddening process of trial and error. Good luck.


 o Post a Follow-Up

Please Note: Only registered members are able to post messages to this forum.

    If you are a member, please log in.

    If you aren't yet a member, join now!


Return to the Electronics Forum

Information about Posting

  • You must be logged in to post a message. Once you are logged in, a posting window will appear at the bottom of the messages. If you are not a member, please register for an account.
  • Posting is a two-step process. Once you have composed your message, you will be taken to the preview page. You will then have a chance to review your post, make changes and upload photos.
  • After posting your message, you may need to refresh the forum page in order to see it.
  • Before posting copyrighted material, please read about Copyright and Fair Use.
  • We have a strict no-advertising policy!
  • If you would like to practice posting or uploading photos, please visit our Test forum.
  • If you need assistance, please Contact Us and we will be happy to help.


Learn more about in-text links on this page here