OK, I'm not trying to convince Craig as I can't properly ABX my gear, but for any other interested bystanders who will accept a lesser standard of "proof"...
I dusted off my old NAD521i, test track Nitin Sawhey "Tides". Co-ax out from NAD into Au51 DAC. Result, muddy all-round. No separation/layering of instruments, extension of soundstage outside speakers, looser, muddy bass, cymbals don't shimmer and decay like they should.
Then CD into a £20 USB DVD drive-->iTunes on the Macmini-->Art Legato USB converter-->same coax lead into same DAC. Result, no comparision, you'd be deaf not to tell the difference and everything missing above is back. For a laugh, I then played the track on Spotify. On a casual listen I can't tell the difference from the CD i.e. even Spotify through the Mini/Legato killed the CD transport into the same DAC.
Maybe there's something wrong with my DAC :rofl: