User`s guide

Speaker Output level
To change Quartet’s speaker output level (i.e the listening level of connected speakers):
1) Press the speaker output Touchpad.
The ring around the selected icon will be brighter than the others after you select it.
2) Turn the controller knob to the desired listening level.
The controller knob operates in parallel with any software output controls on the Mac.
Operation - Apogee Quartet User’s Guide
Version 1, September 2012 19