Oppo 203 SPDIF Digital Coax output


Question: Does the SPDIF digital coax audio output of the Oppo 203 send the input (HDMI) audio signal unaltered when bitstream is selected? If it's possible, what are the settings to use? My use case is 2-channel streaming music from an NVidia Shield Pro 2017 using the HDMI input of the Oppo, with the SPDIF digital out feeding an external DAC. I've tried various settings, and the telltale sign of alteration is when I change the speaker config (e.g., distance of front left speaker), it changes the sound on the digital coax out! Direct A/B comparison between the USB (both Stereo and high resolution stereo) out of the NVidia Shield and the SPDIF digital out also sound markedly different. Maybe it's some setting with the Shield, maybe it's some setting with the Oppo.

Somewhat related question: is there a difference in USB sound between the Shield 2017 vs. 2019?
jitenn
Page 57 of the User manual states that, setting allows a choice for upper 
sample rate limit for coax / optical ( S/PDIF ).
Bitstream is shown as the default setting.
The Shield Pro settings: (Advanced Sound Settings) One) Audio Output, Auto or USB (your case).
Two) USB Audio Mode, High Quality Stereo.
Having a 16GB Android TV Shield (updated / no HDR) the online user manual covers up to the latest Shield TV Pro (2019 at least) settings.
My use has been streaming to HD TV no external components (HDMI) and not having tried using Shield as a UHD Audio Streamer.
Something else for me to do ...
One thing you could try is to set up the Shield without the Oppo in the flow ... 
 

Thanks Rego. Yes, my settings are textbook correct. 

Oppo: Bitstream S/PDIF
Shield: (manual) toggle between HDMI and USB; USB always set to HQ stereo
Connections:
- Shield HDMI OUT to Oppo HDMI IN;
- Oppo S/PDIF OUT to DAC S/PDIF IN;
- Shield USB OUT to DAC USB IN;
- Oppo Analog OUT to Preamp IN;
- DAC Analog OUT to Preamp IN (separate input). That's partly why I can do an A/B test instantly on Oppo Analog OUT vs. Oppo  S/PDIF+DAC S/PDIF, and it sounds near identical (suggesting Oppo altering signal); but with Oppo S/PDIF+DAC vs. Shield USB+DAC sounds markedly different
- DAC Analog OUT to Preamp IN (separate input).
This connection uses the 203s DAC and should sound different from the sound of the external DAC (unless the 'sound' of both DACs is similar which is unlikely).

vs. Oppo S/PDIF+DAC S/PDIF
This connection does not use internal 203 DAC.

 Oppo S/PDIF+DAC vs. Shield USB+DAC
Oppo Analog OUT vs. Oppo S/PDIF+DAC S/PDIF, and it sounds near identical (suggesting Oppo altering signal)
This should sound very different as in Oppo vs. Shield above ... 203 Analog Out is using the internal 203 DAC.

I think you should separate the two players (UDP-203 and Shield) and isolate the settings for each.
Shield appears to not have suitable connections as a streamer without the internal DAC ... but does have a pass-through capability.

UDP-203 does DSD while Shield does not.

The quality of Cables alone could contribute to attributed differences.

As stated " sounds markedly different " ... please elaborate on the sound quality as to which is preferable.

If the goal is use Shield as a high quality Audio Streamer then isolating the settings for Pass Through is important.
 



 
On the off chance the OP is sending DSD files from the streamer to the Opposite over HDMI, the Opportunity won't output DSD over coax into a DAC, but will output them over HDMI