SOL
The problem with Spotify on Windows it can only write to the default audio device, that does not provide the most direct path to the DAC as the digital stream goes through the system mixer and may get resampled or otherwise altered. You will still benefit from a better DAC but overall the situation with Spotify is less than ideal on Windows.
There have been long standing requests from the community for Spotify to add ASIO or WASAPI exclusive mode support that were largely ignored.
https://community.spotify.com/t5/Live-Ideas/ASIO-Output-support/idi-p/19519
They kind of half-assed the sound device selection in the latest versions but afaik it is still not using the exclusive mode and was reported to be unreliable:
https://community.spotify.com/t5/Live-Ideas/Allow-user-to-select-default-sound-device/idi-p/5351
What can you do about it?
1.
Fidelify is a 3rd party Spotify client that supports WASAPI exclusive mode, but its stability and feature set is questionable (I haven't tried it).
2. Use Chromecast Audio through its optical output into your DAC. One caveat your DAC must be able to deal with incoming jitter as the CCA's optical output
has been found to be quite jittery. Another aspect the CCA is using 256kbps AAC stream vs. 320kbps OGG on desktop, but given AAC is a better compression algorithm the quality should be equivalent if not better.
3. JRiver media center comes with a virtual WDM driver that can intercept/route audio with minimal changes to the JRiver engine, and then out to a WASAPI/ASIO device. I use this, this is still not a true direct path to the DAC but a big improvement over the default Windows sound device IMO, but ymmv, etc.
4.
Virtual Audio Cable/ASIO Bridge out to an ASIO driver or maybe Asio4All, this is a similar concept to #3 but I've found it doesn't sound as good.
Huh? Spotify is 16 bits/44.1 kHz compressed. If you have Windows resample audio to 32/192kHz that ain't a good thing.