PS the 1650AR also had R2R Multibit converters as well.
If your wondering what DXD is here a snippet from Stereophile.
"The only reason to use DSD is that you get a smaller file, because DXD is better. No disc can hold a DXD album. This is why no one knows about it, because it has to be downloaded. Most of the guys who produce SACDs do so from DXD files. I know this for a fact, because I probably sold them the converter they are using.
There are thousands of recordings in DXD out there—probably half the SACDs out there were recorded in DXD on a Pyramix system—but no one has heard them in the DXD format. Yet, it was not until I experienced DXD that I was no longer able to hear the signal as a digital reproduction. In contrast, DXD is calm and warm, with a deep, resonant and well defined stereo perspective. So much so that it evokes memories of the heady days of analog."