OPTIMOD-PC
OPERATION
3-19
to the look-ahead limiter to prevent strong high frequency energy from triggering
audible gain pumping or ducking. The high frequency limiting action in the five-
band compressor also helps prevent this artifact.
LOOK-AHEAD LIMITER:
The
L
OOK
-A
HEAD
L
IMITER
preset is a Two-Band preset that
turns off the stereo enhancer, AGC, equalizer, and two-band compressor so that you
can use the processing as fast look-ahead protection limiter.
This preset’s
L
ESS
-M
ORE
control is set to 1.0.
With this setting, there is unity gain
from the input to the output of the audio processing block, which does not include
the Processor Mixer. Even though the gain is unity through the processing block,
you can still use the Processor Mixer to adjust the I/O gain according to your re-
quirements.
When
L
ESS
-M
ORE
= 1, the threshold of the look-ahead limiter is the same as the
Processor Mixer’s output clipping level. This means that there can be no look-ahead
limiter gain reduction because the Processor Mixer will clip before any gain reduc-
tion could occur. Functionally,
L
ESS
-M
ORE
= 1 bypasses the processing.
This is equivalent to setting the input, threshold, and make-up gain con-
trols of a studio-style protection limiter to “0 dB.”
To produce look-ahead limiter gain reduction, turn up the
L
ESS
-M
ORE
control. Each
step of the
L
ESS
-M
ORE
control increases the drive level to the look-ahead limiter by
1 dB and increases the input/output gain by 1 dB for signals below the limiter
threshold. At
L
ESS
-M
ORE
=
10
, the processor’s gain below threshold has increased to
9 dB and the input headroom (the difference between the processor mixer clipping
level and the look-ahead limiter threshold) is also 9 dB.
Instead of adjusting
L
ESS
-M
ORE
, you could adjust the
F
INAL
L
IMIT
D
RIVE
control (which
what
L
ESS
-M
ORE
actually does). The
F
INAL
L
IMIT
D
RIVE
control allows you to achieve
up to 12 dB of look-ahead limiting.
Do not set the
F
INAL
L
IMIT
D
RIVE
control below “0” with this preset; doing
so will compromise system headroom.
Adjusting the
L
ESS
-M
ORE
or
F
INAL
L
IMIT
D
RIVE
controls is equivalent to si-
multaneously decreasing the threshold and increasing the make-up gain
in a protection limiter having threshold and output make-up gain con-
trols.
When the output level controls in the I/O Mixer are set to their maximum values, the
FACTORY PROGRAMMING PRESETS (PROTECTION; AGC)
Preset Names
Source Preset
Normal Less-More
AGC+FLAT LIMITER
AGC+FLAT LIMITER
5.0
AGC+50us LIMITER
AGC+50us LIMITER
5.0
AGC+75us LIMITER
AGC+75us LIMITER
5.0
LOOK-AHEAD LIMITER
LOOK-AHEAD LIMITER
1.0
Table 3-1: Protection and AGC Presets
