Subaru 2004 Legacy Owner's Manual page 230

Power switch and volume/bass/treble/fader/
balance control (ON/VOL)
The dial (1) is used for both power (ON/OFF) and vol-
ume control. The radio is turned ON and OFF by push-
ing the dial and the volume is controlled by turning the
dial.
This dial is used for bass/treble controls when the
"BASS/TREB" button (8) is in the depressed position.
It is also used for fader/balance controls when the
"FAD/BAL" button (6) is in the depressed position.
Audio
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