User`s guide

Headphone Output level
To change Duet’s headphone output level (i.e the listening level of connected headphones):
1) Push the Multi-function Controller Knob until the
headphone icon is lit on the Duet’s display
2) Turn the controller knob to the desired listening level.
Phones
The controller knob operates in parallel with Maestro’s
headphone control.
Adjusting Input & Output Levels - Apogee Duet Quick Start Guide
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