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Noisy USB ground on main computer


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#1 jonuk76

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Posted 03 January 2016 - 07:41 AM

I recently got an external USB DAC and some good quality desktop speakers, but have been having some issues with noise. Both low pitched "hum" and high pitched digital noise which corresponds to disk activity, things redrawing on screen and even mouse movements.  It's very annoying... I'm lead to believe this problem is down to a ground loop.

 

From my testing, I believe the issue is somewhere in the PC itself.  I've gone as far as disconnecting all external items (all USB and display cables) just in case one of those is the cause, but got no improvement.

 

I have tried switching over the DAC to an old backup desktop (self built) - no problem

I have tried switching it over to an Apple Macbook - no problem

 

But if I plug it back into the computer I want to use it with, immediately the noise returns.

 

I've checked all internal connections, replaced power lead, but all with no improvement.

 

The specs are as follows:

 

Corsair 200R Case

i5-4670K CPU

Gigabyte Z97X-Gaming 3 motherboard

Radeon R9-270

16Gb DDR3-1866

256 Gb Sandisk Ultra+ SSD

2 Tb & 1 Tb additional drives

XFX 650XTR PSU

Arcam rPAC DAC

M-Audio BX5 D2 speakers

 

So my question is any ideas on how to solve an issue like this?

 

Thanks

 

EDIT - sorry this should really be in hardware - it's not a software problem!


Edited by jonuk76, 03 January 2016 - 08:31 AM.

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#2 technonymous

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Posted 03 January 2016 - 08:29 AM

Hi there jonuk76,

 

My question would be is there any wiif devices plugged into the DAC? Is the DAC plugged into the front of the case? Typically the front case panels are absolutely horrible when it comes to audio. The wires from the front panel are typically not shielded very good. They run through the desktop to the motherboard and pickup everything along the way. You want to split those USB wires as much as possible zip tie them up out of the way from other wires. Or get some larger wire that you can butcher and use. Rewire the USB connector by pulling the pins out and milk the wires through the larger wire shielding. A cable coax line might work good. Some panels in the front are metal and have a poor ground to the larger case chassis, due to paint etc. Maybe taking a dremel cut tool and knocking a little paint off there where the screws go in or change the screws from painted black ones to cleaner metal ones. Just throwing some ideas out there. Switch the DAC to the back usb ports that are directly mounted. They are better filtered.



#3 jonuk76

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Posted 05 January 2016 - 06:14 AM

Hi, thanks for the suggestions.  The DAC has either been connected to a rear USB port, or as part of my experiments, through a powered hub.  I think I have got to the bottom of it anyway - a bad RCA interconnect from the DAC to the speakers seems to be the main cause.  The ground connection on one channel was broken.  A different cable yields a much better sound with much less noise.  The idea of cleaning up the earths in the case is a good one though.  This case is painted inside and out, and also uses black screws, for example to attach the motherboard to the chassis, so possibly that could be worth looking at.

 

Thanks again :)


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#4 technonymous

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Posted 05 January 2016 - 08:50 PM

Hi, thanks for the suggestions.  The DAC has either been connected to a rear USB port, or as part of my experiments, through a powered hub.  I think I have got to the bottom of it anyway - a bad RCA interconnect from the DAC to the speakers seems to be the main cause.  The ground connection on one channel was broken.  A different cable yields a much better sound with much less noise.  The idea of cleaning up the earths in the case is a good one though.  This case is painted inside and out, and also uses black screws, for example to attach the motherboard to the chassis, so possibly that could be worth looking at.

 

Thanks again :)

No problem. I get this issue a lot :)






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