Thank you PolarNettles - I worked this out last night, you are right - my understanding of the technology was incorrect. I assumed all output would go via the Windows High Def Audio and it was...

I have an Onkyo TX-NR646 Amplifier connected to my PC via the DVI port on my Video Card. My video card is a Nvidia GeForce GTX 1050 Ti. Its a great amp and I want to use it's hardware encoding...