HP EliteDesk 800 G1 - DisplayPort to HDMI Audio

I've been fighting for several days to get the audio working from a HP EliteDesk 800 G1 SFF device into my Panasonic TV using a DisplayPort to HDMI Cable.  The PC is running Windows 10 build 10586.   I tried lots of things, including BIOS patches, various driver builds from MS and Intel, but all to no avail.

However, I have managed to get it working, by changing the Default Format for output to FM Radio Quality, down from DVD or CD in the Advanced TV Properties.   I'm not sure if this is a TV or PC/Driver problem, but I suspect its the latter as I had the same problem with another TV,  but the cable works on a Surface Pro 3 Mini-DP to DP to HDMI adapter, so I think this is PC related.

Hopefully this helps someone else out.