Microphone "robotic" sound issue

[tsjnsn]

OS: Win8
Motherboard: GIGABYTE|GA-990FXA-UD3 AM3+ R
Mic: Turtle Beach x12

So I have been having this problem for a while now (1 month). The microphone I use sounds robotic to the listener (sort of like feedback).  I am almost positive it is a driver problem, but I can't seem to fix it no matter what I try.

It seemed to have started when I installed Flash Media Live Encoder (which I have since gotten rid of).

Here's my troubleshooting so far:
1. I have used the mic on a different computer with no problems.
2. I have used the mic on a different operating system on the same computer with no problems.
3. I have swapped out the motherboard with a brand new one and am still having the issue.
4. I have installed the latest audio drivers for my motherboard and am still having the issue.

My last resort is to reinstall windows 8.

Any help would be much appreciated!

EDIT:
If this helps at all, the mic input shows activity all the time. Even when unplugged.

[Vezina]

Maybe it s some Windows 8 issue ,more and more show up every week.
Try some Windows 7 and see what happens.

[timmib]

Sounds to me like the mic input is feeding two lines.  Or, if the sounds are slightly out of sync could be a feedback loop.

In XP and Win7 the digital sound signals are processed to some degree through the kernel.  Just to keep this in mind if the following does not isolate the problem.

First, the mic input noise.  Leave the mic unplugged. Using your sound manager, mute the mic input.  Not gone?  Use the windows sound manager (multimedia device?)  to mute the mic input.  Not gone?  There's something else 'attached' to the mic input.  Pci board?   Don't know what audio video sw you've got installed.  Might look for a 'service' or run at start sw. 

Kim