A USB mic is not a 1394 source. 1394 is specifically firewire devices (cameras and decks). I don't know what the procedure would be for inputting voice into the avid from a usb device. But if you're on a mac you could use garage band (or one of many free audio recorders including quicktime) to record the vo and then just import the AIFF. Same thing applies for a pc, but I don't off hand know what free or built in recording utilities are available.