I’m not sure that you can do what you describe. If I understand correctly, you’re trying to use the ADAT in on the MR816 to feed digital audio to and play it back via the MR816’s analog out’s. Dont think you can route this way inside the MR.
I use the MR regularly as an analog/mic pre in, with ADAT out’s running to an RME Multiface or Digiface (the unit moves back and forth between my mobile rig and studio DAW.
I wanted to do exactly this so I could use the MR816 to create mjultiple headphone mixes when I was doing location recording’s (use an ADAT out from my RME Digiface, go into the MR and route different digital mixes to several analog stereo pairs on the MR816, come out of them to headphone amps for the musicians). Went into the MR’s mixer and searched long and hard but could find no way to route it.
It looks to me as though the MR has an ADAT in but signals coming in to it are simply passed through to the firewire interface.
If someone does know of a way to do this (route inputs to the MR816’s ADAT in to the MR’s analog out’s) I would love to know how to do it.