Interference via ground affecting speakers - options?

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BassTek

Supreme [H]ardness
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Jul 13, 2002
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I have some interference and noise affecting my speakers after going with powered monitors (M-Audio Studiophile BX5a) run from from my X-Fi Titanium HD. At first I thought it was EMI from the video cards going over the the RCA cables but it turned out to be interference being dumped out of the computer ground and being picked up through the grounds in the speakers.

Basically the symptoms are every time I move my mouse I hear a faint buzz, and the noise increases as my video cards work harder. There is a lot of buzzing when playing a game. The noise is not picked up by my headphones. The noise is present even when the speakers are powered on and the RCA cables are not connected to the sound card. I was able to get rid of the noise by plugging the speakers into an extension cord and dragging it to an outlet that is on a different circuit (thus breaking the ground loop). When I did this computer audio was back to normal even with the RCA cables connected.

So I need to find a way to isolate/filter my computer to stop the interference. Has anyone else had this problem before?

I'm looking at getting either a Tripp-Lite Isobar DBS or Isobar Ultra. They advertise separate filter banks but I wonder how well they actually work. Both seem to be about the same board layout but the DBS has one extra filtering choke (although those could just be stock images:

http://www.amazon.com/Tripp-Lite-IS...ressor/dp/B0000511X0/ref=cm_cr_pr_product_top

or

http://www.amazon.com/Tripp-Lite-IS...3?s=electronics&ie=UTF8&qid=1327875019&sr=1-3

If anyone else has any suggestions please share.
 
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You do not have a ground loop, because the noise still exists when the audio cables are disconnected. (A ground loop occurs when 2 components create a circuit with 1 path along the signal lines & the return through the ground. You can test this by using a 3-prong AC adapter to lift the speakers' ground, since there can be no loop with an ungrounded component.) AFAIK, any power filter will connect all outlets to a common ground & should not be expected to fix a ground loop.

Your symptoms suggest that the PC is contaminating the AC line with noise, and isolated power filters might help. I can't recommend a specific product, however. What PSU do you have?
 
It might be your mb that is the issue and the one way to fix it is to get a differnt/beter mb. I have an old Asrock mb that causes that issue.
 
PSU is an Enermax Modu 82+ and motherboard is an Asus Rampage Extreme II. I think I might try the Isobar as my first solution, if the filtering doesn't work at least I have a heavy duty surge suppressor at the end of the day. I also have another PSU that I could swap in to see if that solves the issue.

If it's the motherboard and there isn't a way to solve it without replacement I might have to live with it for the next while. Can't really justify replacing an X58 motherboard this late in the game without going the full upgrade route and my CPU still handles everything I use it for well.
 
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