User manual

AGC CALIBRATION AND SETUP (FM and ST / WEB versions) ENG
Page 40
21 AGC CALIBRATION AND SETUP (FM and ST / WEB versions)
21.1 AGC SPEED
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 modified:
0 AGC Speed: sets the signal compensation speed
1 AGC Mode: sets the maximum amplification level (MaxG), correction pause time (Hold) and the freeze
threshold (GATE)
DEFAULT SCREEN
INPUT CALIBRATION menu
AGC Speed
The AGC speed value is expressed in dB/sec - i.e. the number of dB amplified or attenuated in one second.
The AGC operates at its full speed value only when the input signal level is less than - 3dB and greater than 3 dB
compared to the internal 0 dB reference level. Within this interval, the AGC speed is reduced to one quarter of the set
value, as high compression and high amplification speed on the whole band can engender unpleasant pumping effects.
For example, with AGC speed = + 5 dB, an input signal of - 15 dBm will be amplified to - 5 dBm in exactly two seconds
(the approach to the 0 threshold is slower, as explained).
High AGC Speed values obviously make it possible to quickly recover strong level differences, but they can also lead to
unpleasant ‘pumping’ effects.
We suggest using medium speed levels of around 2 to 3 dB, and especially that you concentrate on the audio sources
connected to the processor, to obtain the most even sound possible.
AGC Speed acts on both the digital and analog inputs
and sets the compensation speed of the input channel signal level
variation.
21.2 AGC MODE
The AGC Mode menu mainly serves to regulate the maximum level gain recoverable by the AGC (MaxGain) and its
intervention time (with reference to the interval –3 to 3 dB within which the AGC works at one quarter of the user-set
speed).
DEFAULT SCREEN
INPUT CALIBRATION menu
AGC Mode
The Hold parameter allows you to define the time the AGC system has to wait before intervening when the signal varies.
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.
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.