I’ve gone thru Ted Smith’s videos and posts about how DSD “is” the “analog” signal and all one really needs to do is LP filter. That’s a very simple interpretation; please correct me as needed!
I was going thru the HiFiEngine’s schematics and serv. manuals and ran across the Arcam Black Box “Delta” series of DACs.
And comparing to the master digital chip list on:
https://www.dutchaudioclassics.nl/the_complete_d_a_dac_converter_list
That list has the wrong chipset for the Black Box 500 DAC. Going thru various Black Box schematics, Arcam did what I believe Ted suggests. The TDA1307 is a rare and unique DF, made by Philips, and used various Philips / Marantz products. The 1307 got little attention because the PMD100 chip with HDCD was attn-grabbing rock star in the mid/late 1990s. The TDA1307 interpolator converts I2S (PCM) to Bitstream (“DSD”). And then Arcam follows that with their own, custom “Bitstream digital to analog converter (DAC)” which may be what Ted had in mind. Not sure. The schematics for the Black Box 500 are readily avail at the usual places. Have a look!