Zoom H4n Pro Operation Manual page 46

Make recording settings for the built-in mics and external input jacks.
Use either MIC or INPUT 1 and 2 as the stereo input source.
Connecting an external microphone
sets input automatically
or
INPUT 1 and 2 recording levels
can be set independently.
Recording functions:
P.071
INPUT 1/2 LEVEL LINK
045
or
at once
1
or
* Selection is
possible when
stopped, recording or
Selected
in recording standby.
buttons light
2
Use both MIC and INPUT 1 and 2 as stereo inputs.
Connecting an external microphone
sets input automatically
1
2
On the 4CH mode top screen, if you
press a REC LEVEL button, "REC
LEVEL TARGET" appears. Select
the input and adjust it.