Behringer 1204
Information that I received from Behringer. If you toggle the red 2-tr/usb buttons, then it will fix the issue. Connect the USB connection from the mixer to your computer. You will need to select the 2TR/USB to CTRL ROOM button so that the computer output will be routed away from the main mix to the CTRL ROOM output. Do not press the 2TR/USB to MAIN button.
Behringer 1204usb Mixer
The XENYX 1204USB - 12-Input USB Audio Mixer from Behringer is a 12-input audio mixer with an integrated USB computer audio interface. It enables you to mix together and shape the sound of multiple audio signals, and route the audio to several outputs.
Behringer 1204 Usb Driver Download
You will want to connect the control room outputs to your power amp or powered speakers and control your monitoring level via the CTRL ROOM knob. You will be able to monitor through the speakers or the headphones. The USB interface built into the mixer is class compliant under Windows and uses core audio driver on a Mac.