With the indulgence of the readers of this forum. I'd like to make a few subjective comments about the sound of DSD vs PCM.
I now suspect most, or maybe all, of the edgy, flat, and tonally impaired "PCM" sound is the result of the wrong choice of electronics for the I/V converter and active lowpass filter. Nearly all opamps, and many transistor circuits (like the Marantz/Philips HDAM circuits), are too slow for PCM - by a factor of 100 or more. The slewing interval is very short, which means that it hardly shows at all in a long-duration FFT measurement. But it impairs Nyquist reconstruction of the waveform, and the departure from ideal reconstruction is greatest at high frequencies.
DSD, by contrast, has a spread spectrum in the 1~10MHz region, which results in very different IM products down in the audio band. In effect, all it does is raise the noise floor, instead of create a myriad of sum-and-difference tones.
What's behind this half-baked hypothesis? Well, what I hear from DACs with current-output ladder converters and non-slewing analog electronics is a sound a lot like professional-grade DSD. What underlined this was a direct comparison, using the same tracks, of a DSD track, recorded at a very high quality level, played with two very different converters:
The first was the Invicta, which is a pretty decent ESS 9018-based DAC (and designed in close collaboration with the ESS team) with direct DSD playback. It might not be in the exalted class of the Playback Designs, but it's not that far off, either.
The second method was a lot clunkier and at first blush, most of us would expect a lot worse sound. Pure Music converted the 128fs DSD track to 24/88.2, which went to the PCM-1704-based Monarchy through the Resonessence Concero USB -> S/PDIF bridge. Based on the signal path, I expected pretty funky sound.
But ... in practice, both sounded about equally good. Neither sounded like "PCM", and the sound quality was actually excellent from both. In some ways, the Monarchy was better ... more spacious, more open, which is a good quality for symphonic material. The Invicta was a bit more "focused" and a bit more in-your-face, but certainly not obnoxious. Both were some of the best digital I've ever heard, from any system.
The Invicta and certainly the Monarchy are probably one or two steps below the "ultimate" DSD and PCM converters. Everyone mentions the Playback Designs as one of the best DSD machines out there. I have not heard the Phasure NOS1 or the TotalDAC, but these seem to be the pinnacle of ladder conversion technology, and both are free of the usual analog slew-limiting problems of conventional PCM DACs.
All three are unfortunately far out of my price range, so I won't be buying a Playback Designs, Phasure NOS1, or TotalDAC any time soon. (Sigh!) But I will encourage David Robinson to audition them in his MBL-based system, and try the same comparison that I've done in my own more modest system.