I've got an iXR, it's been great so far. I'm trying to hook up some monitors to it and they're not outputting the sound from the mic. I can see the sound from the mic in apps on the computer. (MacBook) I can play music from the computer and hear it on the monitors. But nothing from the mic comes out the monitors. I've fiddled with the input/device mix knob and it doesn't change anything. What could I be doing wrong?