Since your demonstration doesn't depend on listening, why not explain your procedure so we can either try it at home or poke holes in it, or both?
To demonstrate, here are the conditions and the test equipment.
For the test equipment, you'll need:
1. A DAW, of your choice at 44.1kHz, feeding a D/A converter.
2. A DSD recorder, or even better, a DSD workstation (you'll need that later)
3. A Common clock, at 44.1kHz (seems like we're stuck with that, but it'll do)
4. A DSD workstation, that will allow you to invert and compare files
For the control part of the test:
1. Play a stereo WAV file out of the D/A converter and record it into the DSD Recorder (or DSD Workstation).
2. Play the exact same stereo WAV file out of the D/A converter, and again, record it into the DSD Recorder (or DSD Workstation)
3. Line up these two files in the DSD Workstation (inverting one of them) and create a null. You should be left with the sum of two passes of residual noise
*** for anyone attempting to perform the same test by downconverting the DSD files to PCM in order to compare, you will notice that you can't get a perfect null. This is because the 44.1kHz external clock feeding the DSD recorder does NOT always refer to the exact same sample position - at DSD128 there are obviously 128 sample for every clock cycle)
4. Do not proceed until you can create an audio null with the control test.
5. Open up a complex mix session on your source DAW, that hopefully employs lots of live, random elements - reverbs with long decay, delays, modulation effects, etc...
6. Play this mix session out of your source DAW and record it into the DSD recorder, while simultaneously recording the output that feeds the D/A converter to a LPCM WAV File.
7. Play the WAV file that was captured in the source DAW out of the D/A converters (at exactly the same level) and record it into the DSD Recorder (or DSD Workstation).
8. Again, play the WAV file that was captured in the source DAW out of the D/A converters (at exactly the same level) and record it into the DSD Recorder (or DSD Workstation).
9. You now have three stereo DSD files for the test. #1 is the mix session running 'live' feeding the D/A converter, and #2 and #3 are both playback passes of the mix, captured as LPCM in the source DAW.
10. Create a null, using pass #2 and pass #3. (you've done this before)
11. Now, attempt to create a null, using pass #1, and report your findings to the group!