Sennheiser S1 DIGITAL Instruction Manual page 22

Using the S1 DIGITAL
The following switch positions apply to the left and right channel:
No treble boost
Adjusting the microphone sensitivity
The microphone sensitivity has been factory preset to 35 mV/Pa.
Use a slotted screwdriver to adjust the microphone sensitivity.
Treble boost –
step 1
Treble boost –
step 2
Treble boost –
step 3
S1 DIGITAL | 21