No sound from Optical with zx9

I'm getting no sound output when I select optical in the settings.
I have it selected as RAW
Downmix switched on

Just getting no audio at all from my receiver (Arcam avr750)

At the bottom of the optical RAW option it has this tip:
"tip: if selecting RAW output for S/PDIF, turn ON the 'HD audio core playback' switch too"

I can't find that switch anywhere in the settings.

Any help or suggestions would be much appreciated!

Thanks

 

It's the next option down the list from SPDIF Audio.

 

Hi, thanks for the reply.
The next option down from SPDIF Audio on the list is the Downmix Audio settings. Which I've switched on.
Is that the same as 'HD audio core playback' switch?

 

You may need to update your firmware.

Be aware that while DTS-HD has a true DTS core, TrueHD doesn't have a core as such - it has an associated AC-3 track which you have to include if you remux to MKV say.

 

Thanks for the reply
My firmware is up to date. The files I'm trying to play are DTS-HD. The option you have highlighted there, I've switched both those to 'on'. Is that correct or should they be set to 'off'?
Is the Downmix option what is being refered to as the 'HD audio core playback' switch?

 

Yes, on is correct and yes, that's the downmix option referred to - only lossy codecs like AC-3 and DTS can be passed over optical, DTS-HD and TrueHD cannot.

 

So there's no other options I can try to maybe get the sound working out of optical?
This is not an issue that's come up in the past?

 

No - I don't use S/PDIF but when I've tested it, it's been fine...

 

I guess I have a faulty unit then.
Thanks for your help