(Emergency!) Output sound from interface

2 Options:

1) Yes, you can simply connect from the headphone socket to the PA. You'll need to go from 1/8 to 2*RCA jacks. This has the benefit of being really straightforward and as it seems you are quite new to this, will cause least stress on the night. The snag is you must remember to silence all other noises your mac might make - sound effects, warning bleeps, key taps etc as these will all be broadcast and will annoy the audience, but especially the sound engineer.

2) You can certainly use your audio interface. I don't have that particular one but it has 10 outputs which are 1/4 jack. 2 of these should be L+R masters, probably 1+2. In system preferences, simply select sound->output->your interface. Then go into sound effects and make sure these are playing through the internal speakers. I suspect these are "balanced outputs" and is a solution less likely to cause havoc with electrical noise going through the PA although any sound engineer will know how to get round this one.

Incidentally, although your Mac won't crash, there's always the exception that proves the rule and I would burn everything to a CD AS WELL.

Have Fun

I had a FireWire 410 for a while, and it works just like doc james explained. However, the 410 has unbalanced line outs only. Still better than than the built-in sound, but make sure your cables are short and don't run near other electrical wiring. It was the lack of balanced outputs that made the 410 unusable for my setup, but I hear a lot of people are happy with it.

- Martin

Driver:
http://www.m-audio.com/index.php?do=support&tab=driver

Also, I carry a set of music on iPod (with charger etc) and a set of burned disks for backup.