Triton AX Pro Buzzing - Can't tell if from Motherboard or Decoder

[Coollok100]

Bit complicated to explain my setup, but I have an optical audio out coming out from my computer, leading to the Dolby Decoder box (came with headphones), which then my headphones are plugged into. The trouble I've been having is I can hear an audible buzzing sound coming from my headphones (not that loud, but annoying) and I have no way of telling if it is coming from the on-board sound from my motherboard, or the decoder box. Any help would be appreciated.

[xToFxREAPER]

Bit complicated to explain my setup, but I have an optical audio out coming out from my computer, leading to the Dolby Decoder box (came with headphones), which then my headphones are plugged into. The trouble I've been having is I can hear an audible buzzing sound coming from my headphones (not that loud, but annoying) and I have no way of telling if it is coming from the on-board sound from my motherboard, or the decoder box. Any help would be appreciated.

ive had that headset, there isnt really any way to know unless you have another audio source you can test it with such as a console or naything that will output off optical for that matter. It could also be "dirty" power so to speak going through the usb as my friend had that issue, basically interference which cant really be changed

[Coollok100]

I shouldn't be getting any dirty power off the USB, as that is only plugged in for the mic, and whether it is plugged in or not the sound remains. As the unit is powered by AC, is it possible dirty power could be coming from there, and is it possible to resolve it? As far as I know I don't have anything else that'll output optical unfortunately.

[t0wer]

 It wont be caused by the onboard optical, as its a a digital signal with no electrical connection.

[ShearMe]

Could be caused by the USB power - even just a data connection between my PC and my DAC transferred nasty static over.