Ok, the title of this thread is "Absolute best source?
Let's clean the 0's and 1's out of our ears and be a little more objective:
IMHO, the absolute best SOURCES, are, in order of best sound:
1. Analog studio 16 or 32 track master tape played back on a modded Scully studio tape deck - As close as one can ever get to the original source.
2. Pristine vinyl played on a good turntable like the Michell Orbe or SME30II; and this source is
2. The analog broadcast of the BBC Proms played back on an updated Leak Troughline tuner or an American Public Radio Station live studio broadcast played back on on a McIntosh MR71 or MR74, or Accuphase T100 (refurbished and aligned, of course).
3. Any of the really well-recorded Redbook CD's with HDCD encoding played back on a Philips (or Marantz) CD-80 CD (this had the super expensive and Philips best transport ever made) feeding an Adcom GDA-700 DAC with HDCD decoding.
4. Same as 3. above, without an HDCD disc.
IMO, SACD an DVD-Audio sound no better than a properly-mastered Redbook CD with or without HDCD encoding, but to my ears, the HDCD's always sound better.
As always, YMMV, of course. But remember, not all of the world is digital.