After enabling nVidia web driver for Sierra 10.12.2, you need to enable audio over HDMI or DP so that you can enjoy digital sound direct to your receiver.
Follow the simple instruction from :
https://www.tonymacx86.com/threads/clover-hdmi-audio-for-nvidia-amd-cards-easy-way.145399/
NOTE:
It is important to remove previous AppleHDA kext settings in Clover
Also, volume control does not work for audio over HDMI. Just use the volume control from your receiver.