Monitors Buzzing when virus USB connected

[chrisjadescorpion]

hey

loving my virus ti polar. making some nice dnb sounds.
i am getting a horrible buzz in my monitors though. yamaha hs80m's.
my interface is an apogee duet (unbalanced outs maybe?)

i trouble shooted my setup and noticed that the problem starts when the virus ti is connected via usb to my 2011 macbook pro.
when i disconnect the usb - the noise immediately stopped.
possible causes? my first guess would be the virus psu.
my second guess would be the lack of balanced signal from the duet.
this is the email i got from access:

Dear Christopher,
Thank you for your email. This pretty much sounds like a grounding issue with your system. Is this noise on all outputs as soon as USB gets plugged in and are all outs not showing this once USB is unplugged? If that is the case, then it must be a grounding issue with the current setup. Make sure you're using a power conditioner or try changing around your power cabling to see if this makes a difference.

Best wishes,
Jörg Hüttner

ANY HELP WILL BE REPAID WItH SMILEY FACEs.