Found some - here
Original source DXD, there's up to 11.2MHz DSD samples, then assorted formats down to 44/16 CD quality FLAC.
The DSD files are huge, ie >500MB for a 6 minute 5.6MHz DSD *.dff file, vs 25MB for a 44/16 FLAC.
The DAC software/drivers can "upsample" any PCM source to DSD, which is really a very pointless feature. However, although it's a bit of a fiddle to get native DSD playback, once set up it can be done with an auto setting, the DAC switches mode seamlessly, allowing (non blind if you're the one changing files of course) playback comparison at original format.