I just purchased the 12 channel Behringer 1202 usb output mixer to use for recording my drum set. I'm using GarageBand as the input as I do the the EQ and FX settings directly on the mixer. The issue is that every time I open up GarageBand I have to change my input/output preferences to the built in input/outputs and then plug in the mixer, click use once it detects the mixer, and then change output back to built in for it to pick up any sound. Is there any reason that I am unable to use the mixer when it's already plugged through usb before opening GarageBand?