Hi, hi have a MBP 13'' Core 2 Duo. I've tried this method plugging in my guitar through the combined analog audio port and selecting audio input on the preferences, and then used an usb headphones to monitoring my play. It works but with horrible latency and sound, is there a way to improve this latency?? Maybe trying the other usb port on the mbp for the usb headphones?? Thanks and sorry for my english.