Just bought my self a Asus GTX 970 and happily installed it.
Everything worked fine but I couldn’t get audio from the HDMI port to my receiver.
The only option I had was stereo and no sound from my speakers.
My previous card was an Asus 650 Ti Boost and it had no problems with 5.1 surround audio to my receiver. Actually there where the option of either sending it to the Display port or the HDMI port.
I also was using the latest 346.22 Nvidia driver from “xorg crack pushers” team.
So I was scratching my head for half a day until I remembered that there were some updates for Nvidia in the latest Linux kernels.
I checked the kernel version on my system and it was 3.13 on Ubuntu 14.04 LTS.
At kernel.org I found the latest kernel to be 18.1 and packages could be downloaded from http://kernel.ubuntu.com/~kernel-ppa/mainline/v3.18.1-vivid
The new kernel was easy to install just follow the instructions at http://linuxg.net/how-to-install-kernel-3-18-1-on-ubuntu-15-04-ubuntu-14-10-ubuntu-14-04-and-derivatives
After a reboot was I able to set-up audio to use the HDMI port again.