Mysterious Interference Hum?

[funkyaneurysm]

Hello all!

I have just bought a beautiful set of Logitech Z-560 4.1 speakers. I'm so happy with their crisp, percussive sound & RAW POWER.

EXCEPT FOR A BLOODY ANNOYING, CONSTANT INTERFERENCE HUM!

When plugged into my Soundblaster Live! 5.1 they pick up a shockingly annoying interferance hum - they're almost UNUSABLE!

If I unplug the jacks the hum almost dissapears. If I move them through the air around my case, the interference increases slightly as I get closer to my 2x 40gb HDD's.

I have tested the speakers with other devices away from my PC and no hum.

Bizzarely, the hum is not as bad if I run an extension cord from the other end of my house to the speaker system - the hum increases again when the speakers & PC are on the same powerpoint!!

This one has fooled me. Could it be a problem with my Soundcard? Perhaps it picks up interference from my HDD's? Are HDD's known to cause interference?

Do you have any ideas?
Thanks!

AMD 1.4G
256M RAM
GForce 2 Pro
2x 40G HDD
19" Philips 109P Monitor
Win ME (heh heh)
Logitech Cordless mouse

"Ok, is it plugged in ?"
"What do you mean 'IN?' "
"Oh... God...shoot me..."

 

[Guest]

The thing that confuses me about your problem is the fact that you say:

"Bizzarely, the hum is not as bad if I run an extension cord from the other end of my house to the speaker system - the hum increases again when the speakers & PC are on the same powerpoint!! "

This is the exact opposite of what I would expect, as the hum is almost always attributable to ground loop conditions which would seemingly be worse on a different circuit (I assume it is a different circuit, but that may be a bad assumption) and across an extension cord. BTW hum usually = 60/50Hz signal.

I would suggest more trial and error experimentation, that is always what works best for me for this particualar symptom.

 

[Crashman]

Hmmm, a hum, probably at 60Hz. This can be caused by not having the speakers pluged in all the way, or a line near the audio cable. If it's internal noise, it could be caused by the CD Audio cable, have you tried removing that to test it?

<font color=blue>You're posting in a forum with class. It may be third class, but it's still class!</font color=blue>

 

[4Ryan6]

Near by cell phone, or cordless phones can produce a hum in the Creative Soundcards, used to make mine go berserk, cell phone doesn't even have to be in the same room, just turned on. Switched to the Turtle Beach Santa Cruz and the problem disappeared. Ryan






Details, Details, Its all in the Details, If you need help, Don't leave out the Details.

 

[funkyaneurysm]

Thanks for your help guys. I've been too busy with work to even turn my speakers on lately, but had a chance this morning.
I discovered this;

I changed the powerboard & all power cables.
* No change. BIG HUMMM.

SO I played with the speaker & PC power cables & discovered this;

* When speakers NOT connected to PC & PC UNplugged from mains, no hum (well, der)

* When speakers Connected to PC & PC unplugged from mains, no hum

* When speakers NOT connected to PC (plugs lying on floor near PC) & PC Plugged into mains, SLIGHT HUM

* When speakers Connected to PC & PC Plugged into mains, BIG HUM! - The PC does not have to be powered on & running.

So I tested further with my other system, which is an AMD k6-400 with a Diamond MOnster Sound MX400 Sound card. I placed this system in the exact spot my system was.

* NO hum whatsoever in any situation. (WHa!? WTF?)

SO I brought my system back into the room and replaced the sound card with the Diamond from my old system.

* Exactly the same problem as in original situation. So supprisingly, I don't think the Creative product is at fault (IT DOES HAPPEN!)

NOw, as suggested, I have done some reading about ground loops. The logitech Z-560's don't have a ground plug. Waht would this mean?


BTW, I have tested with & without power to the monitor & it makes no diff.

So, as it doesn't matter if the PC is ON - only plugged into the mains - I am wondering now if this problem could be the powersupply? Could it not be grounded properly?



"Ok, is it plugged in ?"
"What do you mean 'IN?' "
"Oh... God...shoot me..."