IN / OUT SETTINGS (ST version) | ENG | |
14.1.3 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
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
High AGC Speed values obviously make it possible to quickly recover strong level differences, but they can also lead to unpleasant 'pumping' effects.
Page 43
