Roland GO:MIXER PRO-X Owner's Manual page 9

(*1) The [HEADPHONE/SMARTPHONE OUT] knob adjusts
the overall volume that is recorded.
(*2) The sound distorts if you turn the knob up too high.
Adjust the knob so that the sound doesn't distort, and
raise the volume using the [HEADPHONE/SMARTPHONE
OUT] knob.
MEMO
To adjust the volume of the devices connected to
LINE IN 1 and LINE IN 2, use the volume controls of
those devices.
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