I had this problem at first with the same card, but fidgeting around with the settings in OSX>Sys>Audio and different settings in FCP + a couple of restarts, suddenly rendered not-digitally distorted audio in the whole system. I have no idea what I did, but it hasn’t returned to the screaming state again.
…unfortunately only to uncover a different problem… When not working in FCP, system audio is now clipping when reaching approx 90% of headroom (as in most music these days).
Lowering internal volumefaders (iTunes, QTplayer etc) by approx 10% corrects problem, but as there is no masterfader, this is a real repetitive pain. It seems to be a BlackMagic driver problem.
bjorn :: bareForm