Just to explain the config - Babyface will be connected as normal to a PC via USB2.  2x analogue inputs, and 1xSPDIF input from a laptop soundcard, initially just 2x analogue outputs.  It would be great if when the PC is powered off and the Babyface under its own mains power, the unit would still pass audio from the SPDIF to the outputs, maintaining the last routing config used - can this be done?  Many thanks for any help.