User manual

AGC CALIBRATION AND SETUP (TV version) ENG
Page 42
22 AGC CALIBRATION AND SETUP (TV version)
22.1 OPERATIVE PRINCIPLES
On the contrary of Radio broadcasting, the Tv audio broadcasting needs at the same time a good uniformity of the sound
levels between different programs or contributions and the respect of original audio level of the program being processed
(e.g. dialogs, sound effects of environment scenes, ‘silence’ passages of classical music and movies, etc). The
processor implements therefore a powerful audio Gain Control based on two operating ranges :
If the level of input signal is less than the Gate Level (settable
trough menu), the processor doesn’t operate.
- When the input signal level ranges between Gate level
and Floor Level the processor implements an Automatic
Gain Control, with Agc speed settable between 0.2 and 6
dB/sec (but standard values are the lowest ones: 0.2 ; 0.4
dB/sec). In this range the original sound levels are mostly
preserved and the processor interventions (as indicated
by the low Agc values) are reduced to a minimum.
- When the input signal level ranges between Floor level and the maximum admitted Level (0 dB by default), the
processor implements an Automatic Gain Control, with Agc speed settable between 0 and 6 dB/sec (but standard
values are the intermediate ones: 3 ÷4 dB/sec). In this range the processor interventions are frequent (as indicated
by the high Agc values), in order to keep an optimal and uniform output sound level.
Depending on the kind of the broadcast program (e.g. News, Movie, music, etc) you can set both the Floor and the Gate
levels: the first must to be set in correspondence of the transition between weak and strong level of incoming audio
signal; the second in correspondence of the lowest level to process. That range splitting is necessary because an high
compression and amplification speed, on the whole band, can engender unpleasant pumping effects.
You can find a Recommended Setting Table
on the last page of this manual.
22.2 GATE LEVEL
The Gate Level parameter shows the threshold level under which the AGC system is frozen, and does not amplify the
signal.
While operating without the signal, the display visualises the AGC GATED status
.
The Gate Level can be varied from –40 to – 26 dBu with 2.0 dBu steps and it must be set depending on the kind of the
broadcast program (e.g. News, Movie, music, etc) in correspondence of the lowest level to process.
You can find a Recommended Setting Table on the last page of this manual.
22.3 FLOOR LEVEL
The Floor Level parameter shows the threshold level under which the AGC system operates in Floor AGC mode and
over which it operates in Work AGC mode.
This Level must be set in correspondence of the transition between weak and high level of input audio signal, depending
on the kind of the broadcast program (e.g. News, Movie, music, etc). Its level can be varied from –24 to – 6 dBu with 2.0
dBu steps.
When the input signal level ranges between Gate level and Floor Level the processor implements an Automatic Gain
Control, with Agc speed settable between 0.2 and 6 dB/sec (but standard values are the lowest ones: 0.2 ; 0.4 dB/sec).
The Floor/Gate thresholds splitting is necessary because an high compression and amplification speed, on the whole
band, can engender unpleasant pumping effects. You can see a Recommended Setting Table
on the last page of this
manual.