What bit depth and sampling rate is the ADC outputting?

Can you supply a reference to the model of ADC?

From what I can read in the manual: Analog to Digital Audio Converter
This Analog to Digital Audio Converter is designed for either home or professional audio switching. It converts the analogue stereo audio signal from R/L input to Coaxial and Toslink outputs simultaneously. The output digital audio signal is 2-channel uncompressed PCM (Linear Pulse Code Modulation) with a sampling rate at 48 KHz. This Converter is small in size and quite easy to install.

It works when I connect it to my Amp to test it, but is not detected on the Sonos Ray,

Thank you for your help, really struggling here, I even tried taking the optical output from the Amp to the Sonos and it also does not work.

Thanks

It looks like it ought to work. Have you tried manually starting play from the TV input on the Ray, using the Browse (source) menu?

I have tried again a few times and the same result. The output from the ADC worked through my amp perfectly but it will not play through the Sonos. If I take an optical output from another device like the DVD playing a CD to the Sonos directly it does work. So the ADC is working, the Sonos is working, it just seems there is some reason why the Sonos will not detect or read the signal from the ADC.

About the only thing that occurs to me is that the ADC output's jitter could be more than Sonos is happy with. Can you lay your hands on another ADC to test with?