EVGATech_LeeM
 
What happens if you switch to the Line-In input?

No sound at all. There's a "pop" when I turn on recording, but otherwise, no sound then.
The terrible noise in the mic port is connected to the video card power. Its all clear when PC is idle, but starting up any game gives this result.

As well, the rear channel also has terrible noise when gaming, most probably caused by videocard power. It even produces sound when mouse cursor is moved.

Tried isolating the sound card rear plate from the PC casing metal, no help for both mic noise and rear channel noise.
I can put up with mic noise by connecting it to the onboard sound card, but the rear channel is a problem. The extension card of Nu Audio pro is right next to the video card (they do touch each other) and I can't move it away. What can I do to increase shielding and lower the noise? 
Strange the other channels are just fine.

This noise is most probably coming from the PCIexpress connection, not from a bad shielding (which is most of the time pure placebo)
The best you can try is to put your card in another PCIex port, hoping it gets less noise, as a 1x PCIEx card can use ANY PCIEx port (even 16x, smaller fit in larger ones)
You can try to switch your card power connector for one which isn't connected to any other (direct powersuppy to card with no other feeding)
 
Only Evga can truly resolve this issue by reducing input noise coming from both PCIEx and power using filtering components on the card.
Perhaps on the next one?

I have done some tests on the electric noise in the mic and rear channel issue recently. Here is the result: The noise is only around when my headphones (5.1 physical ones, with 4 jacks) are connected to both the main and additional card. Its all clear if only the add. card is used (no front channel or mic). Its all fine with simple stereo headphones mode. But when I link both cards with my headphones, the current starts flowing between and noise appears. Its not specific to any special port, its just a factor of lower resistance path.
So, its some kind of a Ground Loop issue, may be connected with power unit or computer casing or generally bad grounding of the house.

Vivicector
I have done some tests on the electric noise in the mic and rear channel issue recently. Here is the result: The noise is only around when my headphones (5.1 physical ones, with 4 jacks) are connected to both the main and additional card. Its all clear if only the add. card is used (no front channel or mic). Its all fine with simple stereo headphones mode. But when I link both cards with my headphones, the current starts flowing between and noise appears. Its not specific to any special port, its just a factor of lower resistance path.
So, its some kind of a Ground Loop issue, may be connected with power unit or computer casing or generally bad grounding of the house.

I can see how that could create a ground loop issue.  Let me check with our team for solutions. 

EVGATech_LeeM
 
I can see how that could create a ground loop issue.  Let me check with our team for solutions. 

I am not sure it can be helped at all... What do you think, may be I can try connecting both main and additional cards bodies with a thick copper wire to to give the current an even easier way to flow?

Can I use Nahimic 3 extra software with Nu Audio? Or only the version integrated in drivers is compatible? 

Update: thick copper wire between the plates of both cards has not helped reduce the electric noise. Tried connecting the wire to different parts of the system, no effect.

This actually looks really cool