Hummmmmmmmmmmmmmmmmmmmmmm

2002-09-21 02:52:58

 
I was referred to this site.  I am glad I found it.  Finally some people who know audio hardware and music.

I got this small problem.  When I play mp3 music through my stereo amplifier there is an annoying AC hum. Tthe PC is plugged into the aux input through a good 6 meter cable made for PC to stereo use and only that input has the hum.  Tuner, tape in, phono are quiet.  There is also a constant hum on the small PC speakers.

The stereo (its old but sounds pretty good otherwise)  has a two wire power cord, the PC has a three wire cord (hot, neutral and ground).  The only way to eliminate the hum is to plug the PC into the wall socket through a two wire adaptor plug,  isolating the PC from ground.  Running a wire from the PC chassis to the stereo chassis has little or no effect. Running my PC ungrounded doesn't sound like a good idea and it really isn't a fix.

I can't figure out if I have a bad sound card (Creative SB Live), a bad PC power supply, a bad situation in the house wiring- some kind of ground loop  or what.  Anybody got any ideas?  Any thoughts on additional troubleshooting?  I know that tracking hum on even simple systems can be a nightmare.
Richard

Hummmmmmmmmmmmmmmmmmmmmmm

Reply #1 – 2002-09-21 10:57:05

This page might help: http://documents.epanorama.net/documents/g...loop/index.html

Hummmmmmmmmmmmmmmmmmmmmmm

Reply #2 – 2002-09-21 12:14:08

In the above website, this pages describes your problem : http://documents.epanorama.net/documents/g...me_solving.html
(Beware of the nasty ad popup in this page : I don't know where it links to, but the "close" buttons are fake, don't click them. It'll disappear after about one minute.)

The problem would come from the antenna of your receiver.
They advise antenna or audio insulators. I don't know them, but there is also another kind of audio insulator : wiring the computer - receiver cable as a "twinax" instead of a coax. It might solve the problem.

This is done using a cable with two cores and one shield, like a cheap stereo cable with left and right channels in the same shield. But you'll have to use one per channel : one of the cores will be the chanel, the other will be wired as if it was the shield, and the shield will be connected only at one end of the cable. At the other end (usually the receiver end), it must not touch anything, it must be left unplugged.
This way, there can be no current flowing through it and causing hum.