Open the FireWire Audio Console. If you plan to record optical S/PDIF, set the optical in and out options to TOSLink. If you are recording coax (RCA) S/PDIF make sure optical is set to ADAT or None, not TOSLink.

When you're ready to record in via S/PDIF set the clock source to in your host app to "S/PDIF" and make sure the S/PDIF device you're recording from is on "INTERNAL" clock. Make sure the Sample Rate on the 828 also matches the Sample Rate of the S/PDIF source. When you are done recording a S/PDIF signal, your clock source should be set to Internal for playback. When playing to a S/PDIF destination, your clock source should be on internal or any other valid Clock Source, and the S/PDIF device receiving the S/PDIF should be clocking to S/PDIF.