From Soundstage review by Marc Mickelson:
Of perhaps greater importance than how the D-70 is connected to the rest of your system is how you connect the D-70 to the P-70. I'm not just talking here about your choice of coaxial or AES/EBU digital cable, but rather about the combo's AES-3 connectivity. This requires that you use two AES/EBU cables and a separate BNC-terminated clock-link cable to slave the DAC to the transport. This configuration not only enables the DAC to convert the 176.4kHz sampling frequency from the transport, it also maximizes the DAC's rejection of jitter, which only improves its sound.
So I don't get too far off on a tangent here, this is by far the best-sounding way to hear the Esoteric combination, which means that you have to use the two pieces together to hear both at their best. Yes, I did listen to them separately, and they sound very good on their own, but when used together and linked in the way I describe above, their sound is far superior than it is when they are linked with a single digital cable -- or to other DACs and transports. Given this, everything you read below regarding the sonics of the P-70 and D-70 applies to using the combo with AES-3 and word-sync connections.
Bottom line: with the AES-3 connectivity option available in the P70 (and its matching D70 DAC), you need to use the P70 with a DAC that allows for this design feature to be implemented. Beyond the D70, I don't know of any other DAC that has this feature. This in no way invalidates its usage as a transport with a simple single cable connection, I simply think it is a bit expensive to purchase this unit without intending to use all its design features that maximizes its performance. Therefore don't but it if you are not willing to buy the D70 at some point.
