Xonar Essence STX strange buzz with computer off.

[Vega]

I have a Asus Xonar Essence STX hooked up to a pair of AudioEngine A2's via Monster RCA cables and a 12" JBL Sub. When the computer is on, there is absolutely no noise from the speakers or sub. It is dead silent, such an awesome very low to no noise signal even with the volumes of all equipment at max.

The issue is when I turn the computer off, instantly the speakers and sub emit a annoying buzz/hiss/hum like you would typically see in a bad ground-loop. My question is, why would this noise only happen when the computer is OFF?

All of the equipment, the A2 speakers (2-prong power cord), Sub (2-prong power cord), and computer/monitors (all three prong), are plugged into the same UPS and single wall outlet.

What exactly changes in the ground/signal path from the Xonar Essence STX's RCA signal path to go from a dead silent super clear signal while the computer is on to such a noisy racket when the computer is off? It does not make much sense.

Anyone have any thoughts?

 

[thefluffy]

Well, I can point out one thing that changes in the signal path. When you power off the computer, the Xonar STX has a pair of relays that disables the output of the card. You can hear the clicking when you first power your computer on.The relay disconnects the card from the signal cable going out of it. I would lean towards it possibly being interference. Make sure all of your signal cables are not run near your A/C power cables. My second suggestion would be to buy some Coax audio cables off of monoprice. They are actually use the shielding as one of the conductors and should help fight off some interference. Plus they are cheap, like $3 for 6 ft!!!!

Daniel

 

[rive22]

I used to get the same thing and I've had a couple different cards in my box so we can scratch that idea. I also tried a USB soundcard and that was a nofix. The Essence card has that really nice EMI shield on it as well. I'm with you though it's incredibly annoying. I had the interference in my last build too with all completely different parts except the case, 2 drives, & an optical, but all recently new. And hooked up to a laptop the speakers didn't make any noise.

But get this, since I've done a little modding to my cooling and plugged off the back exhaust port on my case, bam the interference is gone. So it must be something from inside the case.

I hear that though my computer is in my bedroom and I would always forget about the annoying noise while using the speakers and then I'd go to try and sleep and remember the noise once I settled in and have to get up every time to shut my speakers off.