Hi there, I have been getting this noise coming from my Asus Xonar Essence STX. It comes out of my headset when I plug it in the Analog output of the sound card. Before you have a listen I suggest you turn your volume down a bit.
This ONLY happens with the Analog output, I am currently using the SPDIF output to my astro mixamp (which sucks).
I have latest drivers installed.