How can I have two monitors and a a/v receiver for sound connected to my pc?

[TechnologyHatesMeButILoveIt]

The optical port on either the motherbaord of a/v receiver is bad, so sound crackles and goes out. So the simple solution seemed to be to just use a HDMI for sound, but I have no idea how to get it to work. And my home theater is a 7.1 channel, so using an older method would ruin the sound. I might as well keep using my monitor's sound if I can't use a cable that supports 7.1

Right now I have two monitors, one 1080p, and then my main is 4k. The 1080p is connected via HDMI, and the 4k is DP. My GPU has three DP ports, and only 1 HDMI. My motherboard does have a HDMI though, but I can't get my second monitor to work with it or my a/v receiver.
So really I have one HDMI. My receiver doesn't have a dp port, its four years old.

I can't figure out why the HDMI does not work on my motherboard. And even if I could get it to work, how would I prevent it from just turning my TV into a monitor? Because that is what happens when I connect the GPU's HDMI to one of my a/v receiver's HDMI inputs.

I have a brand new: GIGABYTE LGA1151 Intel Z170 ATX DDR4 Motherboards (GA-Z170X-UD3 Ultra)
And a new: Gigabyte GeForce GTX GV-N1080G1 GAMING-8GD Video Graphics Cards

It's frustrating that they don't work... I've already replaced too many brand new MSI parts, and had hoped Gigabyte worked better.

 

[americanaudiophile]

You can try using an HDMI audio extractor in between the PC and the 1080p HDMI monitor. That will give you an optical audio output for the receiver.
https/www.amazon.com/AV-Access-Extractor-Converter-Amplifier/dp/B01IHBG458

 

[Karadjgne]

I have 2x monitors, onkyo a/v with 5.1 surround and pc speakers + sub. None of which are connected via hdmi for audio. Use the motherboard audio, not the gpu. It uses the Windows sound settings to differentiate between outputs. Mostly I use the pc speakers (better fill than the monitor) but when the wife/mother-in-law isn't home I'll flip the Realtek software on and change the output to the a/v and shake the house. Motherboard audio has come a very long way since the days of the 486 class boards when a SoundBlaster 16 was an absolute must have card.