Azden FMX-DSLR Operating Manual page 6

Using the AGC ON/OFF Feature
The Auto Gain Control (AGC) in the camera will vary the amount of gain depending upon the input signal level. During quiet
moments, the AGC will increase the gain, which will also increase the amount of hiss from the camera preamplifiers. The AGC
ON/OFF feature, when it is set to the OFF position, will trick the camera's AGC in order to disable the wild swings of the AGC. It
activates an inaudible tone of 20kHz to the left channel that prevents the AGC from increasing the gain to its maximum level.
This reduces the hiss that normally occurs when the camera is recording audio during quiet moments. This inaudible tone is
recorded by the camera but can be easily filtered out if necessary. You can still use the left channel for recording normal audio
at the same time that AGC switch is in the OFF position.
The camera's audio level meter may indicate some audio when there is no apparent sound with the AGC switch in the OFF posi-
tion. This is because the audio level meter is sensing the 20kHz inaudible tone and you should not be concerned about.
You may also want to record audio only on the right channel and leave the left channel unused for the AGC control signal if this
tone presents a problem. In this case, you should set the OUTPUT Mode Selector (○ 7 ) to ST for stereo to keep the AGC signal
separated from the record signal.
It is important that you do a test recording and play back the audio to see if it is acceptable.
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