I just bought an used Apogee Duet for my brand new MacBook Pro. I have installed it with updated software from Apogees webpage and the restarted the Mac. When I connect it and play a song from iTunes I can see, that something is happening on the panel meters of the Duet and the meters in Maestro. But no sound comes out through the headphones. I have chosen the Duet for output and input in both Maestro and the system preferences of the Mac. Still nothing is heard. Anybody know what the probelm might be? Thanks.