Accuphase DP-78 digital input

Does any one know if either through the RCA/optical inputs or if an input board option will allow the Accuphase DP-78 to accept a 24 bit digital input from an external digital source such as a computer. Literature is not clear.
The DP-78 plays 24/96, you'll need the option board for 192. I use the DAC with the Squeezebox Touch / EDO app, excellent sound!
Does the DP-78 accept 24/96 or does it upsample to 24? I'm assuming the same with the option board for 192. the DAC in the DP-78 is so good it would be ashame to not be able to use it to it's full potential.