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Copyright © NAGRAVISION S.A. 2005-2009
April 28, 2009
10 ARES-ML GAIN AND LEVEL STRUCTURE.
The input of the ARES-ML has 3 principal stages: The analogue microphone pre-amplifier “front end”,
the PGA (Programmable Gain Amplifier) and the DGA (Digital Gain Adjustment).
Different adjustments are available at all three stages. Only one, the “recording level” is readily
accessible from the front panel by the user (using the left/right keys).
The microphone pre-amplifier stage has two selectable sensitivity settings which correspond to a
typical dynamic microphone (34 dB) and the NAGRA microphone (19 dB); this selection is made in
the “Screwdriver” menu in the “Input device manager”.
Dynamic microphone sensitivity is low and needs more gain than a condenser or Electret
microphone. So, if a dynamic microphone is used, 34 dB gain is needed, and if a condenser
microphone such as the NAGRA one, or any other external condenser microphone (such as the
SONY ECM MS907 Stereo microphone) then 19dB gain should be selected. The correct selection of
this gain will avoid the saturation of the PGA and DGA stages.
In the Codec section of the machine the first stage is equipped with a PGA adjustable gain setting
allowing the modulometer to be calibrated to give an accurate indication of SPL (Sound Pressure
Level). This setting is available in 3 dB steps and is also found in the Screwdriver menu and allows a
range of 24 dB variation. This value is factory set to 9 dB for the NAGRA microphone and 6 dB for an
external dynamic microphone such as a Sennheiser MD21.
Finally, the MAIN RECORD LEVEL is the actual level that should be used to adjust the recording
level during operation of the machine and is accessible using the Left and Right keys without any
need for going into the menus. This task is achieved by the DGA, and the range of adjustment allows
0dB Full Scale to be displayed on the modulometer for 84 dB to 144 dB SPL. The normal range of
acceptable input levels ranges from 84 dB to 110dB SPL. The range from 110dB to 144 dB SPL will
not allow 0 dB to be indicated on the modulometer without risk of saturation of the codec.
84 dB is the usual setting for an interview in a quiet environment. 110 dB allows the recording of
somebody shouting at a distance of about 40 cm from the microphone.
The zone from 110 to 144 allows the user to make a fade out or to record with headroom (by
recording below the 0dB point on the modulometer).