Simultaneous digital passthrough via HDMI and optical

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2

I don’t think you can (the Setup settings specify digital passthrough for either one or the other)

You could use “splitters” if both devices have the same input

eg. if both (DAC & AVR) have SPDIF (Toslink) then use a splitter (use Passthrough for Optical) and use the HDMI for Video Only

or if both have HDMI (For Video and Audio) then use a spiltter (use Passthrough for HDMI)