I tried to post earlier but for some reason it didn't go through.
The DAC64 I'm now using (Ser. No. 5100) is actually my second, since we (the dealer, the Chord rep., and I) discovered a defect in the first one (Ser. No. 5063). Not to belabor the point, but I wonder if the "defect" was actually the "major design flaw", as mentioned by "reliable sources". To be brief, my first unit would not play at all---the sound was absolutely garbled--- with my Rotel RCD 950, and incorrectly on certain CDs with my CEC transport, although I had no (discernible) difficulty with my Sony DVD player. Go figure!
The unit I now have continues to perform flawlessly.
As for inputs: I've found the XLR input(using a BEL cable)to be the better of the two---XLR/RCA(using the supplied adapter)---available to me. (The optical output connector on the CEC is incompatible with the Chord input, so I haven't even tried to devise a method of using that inter-connection. Optical connections strike me as just so many unnecessary monkey-motions, going from electronics to optical on one end and vice versa on the other end. So why do it, unless there is a problem with electrical interference in the interconnection?)
Jim