Oppo 203 SPDIF Digital Coax output

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

I plan on trying my 2019 Shield pro via usb soon to a dac I just picked up but as it stands for now I use my oppo 203 via coax set to LPCM to take advantage of high res files up to 24/192hz, will it send that via bitstream as well? that may be the difference as I also have my Oppo running hdmi to my Marantz 8805 and switching between the two sound different enough to tell apart with the dac using it's balanced outs to the 8805.

Thanks folks. Working with Oppo tech support. Something is awry, but a full power cycle seems to have changed something as well.

Please follow through with an update ...

@jdub39, to address the idea of 'streamer' (which to use), both players are very good and both are centered in a AV use capacity as opposed to
UHD Audio.
Streaming development is fluid and evolving.
Shield development has shown less emphasis on Audio Playback which may change.
Oppo dropped the UDP line ... !

Shield with a Linear PS could be good performer (not that it is not already) ... and then with an OS upgrade could be better ...
 
UDP-203 User Manual pg. 57 - S/PDIF Output / Bitstream shows:

" Bitstream (default) – Passes audio as compressed bit-stream format to the receiver/amplifier. Choose this setting if your receiver/amplifier is capable of decoding Dolby Digital and/or DTS.".  

Showing 'compressed bit-stream format'.
 

Limited insight from Oppo at as now. They insist the player shouldn't be doing what it's doing. I insist otherwise. Stalemate.

Meantime here is info from GeForce Forum on Shield ...

Audio pass-through vs local decoding

Shield can pass-through of all the mainstream codecs, but is not licensed to locally decode nor transcode of them. If the Shield detects that the device it is plugged into has the ability to handle the codec being used, the unaltered audio feed will be passed forward to be decoded out there. If it does not, Shield will simply fall back to basic decoding, and output a PCM 16bit stereo signal. In order to check the decoding formats ready to be passed forward by the Shield, go to Settings/About/Status/HDMI/Audio mode.

 

From <https://www.nvidia.com/en-us/geforce/forums/discover/297989/-

guide-audio-pass-through-hdmi-arc-physical-setup-settings/>