IN & OUT SETTINGS (FM VERSION) ENG
Page 27
12.1.3 CHOOSING THE PROPER AGC OPERATION
One of the most important processor function is the Automatic Gain Control (AGC) system, which
compensates for variations in the input level to keep the signal at 0 dB.
The following parameters regulate the AGC function and may be edited:
- AGC Mode: acts on both the digital and analog inputs sets the maximum amplification level applied to the
input signal by the AGC (MaxG) and the correction waiting time (Hold)
- AGC Speed: acts on both the digital and analog inputs and sets the compensation speed of the input
channel signal level variation.
AGC Mode parameter mainly serves to regulate the maximum level gain recoverable by the AGC (MaxGain) and
its intervention time (Hold). Hold = 0 means that the system reacts instantly to any source signal variations, while
Hold = 2 means that you must wait two seconds before the automatic level compensation process begins.
For instance, setting MaxGain = 12 means that maximum amplification is +12dB: thus a -12dB signal can be
compensated to 0, while a -15dB signal will reach a maximum of -3dB.
F.i., if AGC Speed is set as 2 dB/sec and the input signal drops down of 6 dB, the compensation trip will be
completely reached after 3 seconds if Hold time is 0 sec (6/2) and after 6 seconds (3 + 6/2) if Hold time is 3
seconds.
We suggest setting a medium MaxGain
value (no more than +12 dB, keeping in mind that this value may already
be enough to alter level ratios between different musical passages, as in the case of classical music), and Hold =
0 if the music flow is discontinuous and immediate AGC intervention is required, or a higher Hold value (3 or 4
seconds) if any silent breaks may occur during the broadcast (pauses in speech, line changeover between
studios, etc.).
Falcon 15 menu provides 5 fixed combinations of MaxGain and Hold parameters (i.e. those parameters may
not be selected or edited individually, but only within preset combinations).
Mode 0 Hold=0Sec MaxG=+08dB
Mode 1 Hold=1Sec MaxG=+10dB
Mode 2 Hold=0Sec MaxG=+12dB
Mode 3 Hold=2Sec MaxG=+12dB
Mode 4 Hold=3Sec MaxG=+15dB
Mode 5 Hold=3Sec MaxG=+20dB
Mode 6 Hold=0Sec MaxG=+15dB
Mode 7 Hold=0Sec MaxG=+20dB
The AGC speed indicates the number of dB by which the input level may be increased or decreased in one
second.
For example, with AGC speed = + 5 dB, an input signal of – 15 dB will be reduced to – 5 dB in exactly two
seconds***
***the approach to the 0 threshold is slower, as AGC works at 1/4 of the user-set speed within the interval –3 to + 3 dB
centered on 0 dB reference level
High AGC Speed values obviously make it possible to quickly recover strong level differences, but they can also
lead to unpleasant 'pumping' effects.