Speaker Hum (Grounding PC)

[RDennis]

I have built a PC just for playing music. When I built the machine at home, everything sounded fine. No "Humming".
Now I have connected the AUDIO OUT to a mixer and large amp. Now I get the "Hum".

My question is this...
In the old days, stereo components sometimes needed to be grounded to each other to eleminate the "hum".
Turntables were especially bad when connecting to the amp. Back then, we would just run a ground wire from the chassis of the Turntable to the chassis of the amp and the "hum" was gone.

Could I try this with the PC? Is the circuitry in the PC too delicate for this? Can I run a simple ground wire from the PC chassis to the amp chassis?

Thanks,
Rick

 

[Grill]

RDennis,
I don't know about the grounding part of your question but I can tell you what made my humming go away when I attached new Altec Lansing speakers to my system. All I needed to do was move the amplifier and my sub-woofer away from my PC and give it its own power source. I don't have the speakers power sharing the same surge protector as the PC. This eliminated the hum on my system. Hope this helps.
Grill

 

[snafupen]

better shielded cables may also help with the hum. many times when you run power cables too close to audio wires, the electricity will produce interference otherwise known as "hum"

 

[RDennis]

Thanks guys...
Here's what I've found. I have a power conditioner that I have the amp and mixer plugged into when I plug the PC into the power conditioner, all of the hum goes away, however, the PC needs to be located 60 feet from the Sound System, so I need to do some electrical wiring to allow myself a PC circuit that comes from the Conditioner. I would just throw down a 30 amp drop cord but that would just be in the way most of the time, so I'll do some wiring.
Just wanted you all to know that I found the problem.
Thanks for the help and suggestions.

Rick

 

[mrbean]

RE: Speaker Hum

This thread is a bit old, but I thought I'd shed some light on the subject.

RDennis, your initial suspicions seem correct. If you are using the standard analog out from your PC audio card (usually 1/8" to RCA), a 60 hz hum can be introduced. This is in fact caused by a ground loop between the computer and stereo.

A ground loop is defined on the Radio Shack web site as "An unwanted current that flows in a conductor between two points that are at different potentials. It usually occurs in a device that is connected to several AC devices (such as an equalizer or a piece of test equipment), creating an AC "hum". In video devices, this can appear as a bar rolling from top to bottom; in audio devices, it appears as an audible hum. It can be eliminated by connected [sic] all audio/video equipment to the same ground, or by using GLI's (Ground Loop Isolators). "

For more info, see this link: http://www.smr-home-theatre.org/Ground-Loops/

Obviously your solution cured this problem, but it didn't work for me. If you sort out all the electrical issues then the problem will go away. I didn't have the inclination or the patience, however.

That left me with two other options:
1) Use an optical digital output. Using a coax may not alleviate this issue, at least from what I have heard.
2) Purchase an audio isolation transformer, aka ground loop isolator. You can get one for about $15 @ Radioshack - part # 270-054. You can find it here: http://www.radioshack.com/product.a..._name=CTLG_007_002_004_000&product_id=270-054

If you are very particular about audio quality, then option 1 is probably the best solution. I'm using solution 2 as I have an older amp w/o digital inputs, and the audio is good as far as I'm concerned. It is possible for a group loop isolator to degrade sound quality however.

Cheers -