Hi Eric,
You should be using the audio outputs from the DeckLink Studio. If you use your computer’s onboard audio, then the audio will be off a difference hardware clock and you will get a/v sync issues.
As for your audio sounding “tin-like”, it’s best describe exactly how you’ve connected them, such as make model of the speakers, type of cables used etc.
regards
Kristian Lam
Blackmagic Design