Drrsutliff, I really appreciate your logical and sensible approach. The answer to your first question is yes, I have the ST optical cable connected between the DCC2 and CDSD as indicated. To your second question, I have used 3 different cables. Your last question is where things seem to get weird. Since my last writing I have figured out that with all connections made exactly as instructed, the only way I can get sound at all is with the back INT/EXT switch on the CDSD set to INT, which is not consistent with the instructions. However, on the front of the DCC2 there is a button to select Internal or External Clock. With the back switch set to INT on the CDSD I can toggle between Internal or External Clock on the DCC2. When I toggle between the two there is a slight delay while it changes. This seems to indicate to me that there is a change going on, and if I believe what the lighted button is telling me it's switching between Internal and External Clocks. I can't honestly tell you that I can hear a difference between the two settings, not with the limited exposure so far.
Regarding EMM documentation, I can say that what I can find all seems to be the same as for Pre-SE units as for SE units. I don't know if there was a change and not well documented but I do know the only way I can get sound is how I've described. I'm going to try and get to the bottom of this with EMM but from what I've read elsewhere that may be easier said than done.
Thanks again for the help!