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Old 10-22-2018, 02:09 PM
skrell skrell is offline
Join Date: Nov 2008
Posts: 21
Default Ground hum from my Mbox 3

Hello good people.

I've just set up my studio in my new apartment, and discovered to my dismay that there is a hum coming from the speakers connected to my Mbox. The noise intensifies when the computer is working under a bigger load. Any tips to how I can combat this noise?

The sound can be heard here.

Will a pair of shielded xlr <-> jack cables do it? Or should I try changing to a higher quality USB cable between the Mbox and the PC?
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Old 10-22-2018, 05:13 PM
Darryl Ramm Darryl Ramm is offline
Join Date: Nov 2010
Location: USA
Posts: 12,825
Default Re: Ground hum from my Mbox 3

This is with no inputs live on the interface? Remove all input cables, mic leads, guitar cables etc. from the interface.

USB cable is unlikely to make much difference. You leave out any useful info like the exact monitors and cable wiring used today. You have a pile of troubleshooting to do. All the usual ground loop and interference type troubleshooting to do that you can find discussed many times on DUC, in books on audio engineering or all over the web.

Start with gain staging the monitors and interface, if you dime many low-mid range monitor volume you will hear pretty horrible noise. Now is the time to do a quick pink noise level calibration.

Then look at the quality of the ground at the PC. Unplug and power off the monitors. Do you hear the same noise on headphones? You should be running balanced signals cabling into the monitors, assuming they have balanced inputs. Check with a multimeter that the cable is wired as it should be. If the monitors have grounded power leads try them in the same outlet as the PC and then do the opposite: try them on a different breaker circuit if possible. Try turning off the PC monitor and florescent or LED lights nearby. Move any electrical devices turn off all electrical devices on the same breaker circuit, or whole house etc. to try to isolate sourced of noise. Try different and longer USB cable with the interface moved away from the computer (that is not to say a more expensive/Fancy USB cable is any better, just looking for a faulty cable).

Any balanced audio cable should have a shield, the quality there can vary. And things like routing the cables away (or at 90 degrees across) other cables may help. And in some cases to bypass a ground loop you may deliberately break the shield...

Last edited by Darryl Ramm; 10-22-2018 at 05:41 PM.
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