Hey Peter
Sorry, I'm not a STP boffin nor a 5.1 guy , I don't have a lot of experience to offer in this regard, but not discounting your request for general purpose audio support, it does seems like this particular issue is with STP itself, rather than the MXO2. Case in point: if I add/open audio only clips in FCP then they play out through my MXO2 without issue because the v-out support is pervasive ... if STP is not doing this whilst advertising that it does (and switching active outputs dependent on the clip) then that seems a bit inconsistent and buggy. You've probably been down this road already. looking for a workable solution to the immediate problem within STP itself, perhaps you can create and thereafter add a dummy video track (slug) to your project? Might be worth digging for suggestions on the STP fora too, see if anyone else has figured something out already (if you haven' yet done so). I'd also strongly suggest dropping your feedback regarding inconsistent v-out support to the STP dev team over on the Apple feedback site:
http://www.apple.com/feedback/soundtrack.html
In the meantime, I'll also add my comments to Matrox regarding general purpose audio support.
Andy
