I have recently upgraded to the DAC/AMP SMSL SD-793II which is connected to my Asus Xonar DX via SPDIF. I am very happy with the sound in general, but since the optical out on my soundcard shares its port with the microphone, I am forced to connect my front panel header to my soundcard and use my microphone this way.
The issue I'm facing now though is that I'm getting a very annoying buzz through my microphone which is unbearable. I've tried to figure out why and where it comes from, and the conclusion is that my DAC interfering in some way. If I touch the metal casing of my DAC the buzzing is getting louder, if I touch a metal part on my PC tower however, makes the buzz go almost completely away. Another thing I should add is that I tried to attach an external microphone to my headphones almost a bit like in this picture: http://i.imgur.com/AEGWV4S.jpg
If I unplug the mic and just leave the cable in the port I am still getting a buzzing sound - when I just plug the microphone directly into the port without any extension cable the buzz is completely gone.
There's a couple of people on the internet that have a similar problem with their front panel ports that cause ground loop or something and suggest shielding the cables, but since I'm not really adept with that kind of stuff I'm unsure wether or not this is gonna solve my problems.
Are there any things I could try or has someone else had the same issue and got theirs sorted out in some way?