Hi Marc,
You’ll need to send video out via the DeckLink card in Logic Pro in order for the audio to go out as well. Make sure you select the DeckLink card as the video output device in Logic, then open a compatible Quicktime movie.
The good thing is that once you’ve got that working, you can close the movie window in Logic and audio playout will still continue.
Just like Final Cut, Logic has it’s own audio (and video) settings that overrides what’s in the system sound preferences.
regards
Kristian
Blackmagic Design