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Appendix
■ Expander
An expander is another form of automatic level control.
By attenuating the signal below the threshold, the
expander reduces low-level noise and effectively
increases the dynamic range of the recorded material.
Expander (EXP) parameters:
Threshold determines the level of input signal required to
trigger the expander. Signals above the threshold pass
through unaffected. Signals at and below the threshold
level are attenuated by the amount specified using the
Ratio parameter. The trigger signal is determined using
the KEY IN parameter.
Ratio controls the amount of expansion-the change in
output signal level relative to change in input signal
level. With a 1:2 ratio, for example, a 5 dB change in
input level (below the threshold) results in a 10 dB
change in output level. For a 1:5 ratio, a 2 dB change in
input level (below the threshold) results in a 10 dB
change in output level.
Attack controls how soon the signal is expanded once
the expander has been triggered. With a fast attack time,
the signal is expanded almost immediately. With a slow
attack time, the initial transient of a sound passes through
unaffected.
Out Gain sets the expander's output signal level.
Knee sets the transition of the signal at the threshold.
With a hard knee, the transition between unexpanded
and expanded signal is immediate. With the softest knee,
knee5, the transition starts before the signal reaches the
threshold and gradually ends above the threshold.
Release determines how soon the expander returns to its
normal gain once the trigger signal level drops below the
threshold.
■ Compander
A compander is a compressor-expander-a combination
of signal compression and expansion. The compander
attenuates the input signal above the threshold as well as
the level below the width. For very dynamic material,
this program allows you to retain the dynamic range
without having to be concerned with excessive output
signal levels and clipping.
CompanderH (CPH) and CompanderS (CPS) parameters:
Threshold determines the level of input signal required to
trigger the compander. Signals above the threshold pass
through unaffected. Signals at and below the threshold
level are attenuated by the amount specified using the
Ratio parameter. The trigger signal is determined using
the KEY IN parameter.
Ratio controls the amount of companding-the change in
output signal level relative to change in input signal
level. With a 2:1 ratio, for example, a 10 dB change in
input level (above the threshold) results in a 5 dB change
in output level. The hard compander (CPH) has a fixed
ratio of 5:1 for expansion and the soft compander (CPS)
has a fixed ratio of 1.5:1 for expansion.
Attack controls how soon the signal is companded once
the compander has been triggered. With a fast attack
time, the signal is companded almost immediately. With
a slow attack time, the initial transient of a sound passes
through unaffected.
Out Gain sets the compander's output signal level.
Width is used to determine the distance, in decibels,
between the expander and the compressor. With a width
of 90 dB, the expander is effectively switched off and the
compander is simply a compressor-limiter. With a
smaller width (30dB) and a high threshold (0dB), the
compander is an expander-compressor-limiter.
Release determines how soon the compander returns to
its normal gain once the trigger signal level drops below
the threshold.
Parameter Value
Threshold (dB)
–54 to 0 (55 points)
Ratio
1.0, 1.1, 1.3, 1.5, 1.7, 2.0, 2.5, 3.0, 3.5,
4.0, 5.0, 6.0, 8.0, 10, 20, ∞ (16 points)
Attack (ms) 0 to 120 (121 points)
Outgain (dB) 0 to +18 (36 points)
Knee hard,1,2,3,4,5 (6 points)
Release (ms) 6 ms to 46.1 sec (160 points)
Threshold = –10dB
Knee = knee5
–70
–60
–50
–40
–30
–20
–10
0
+10
+20
–70 –60 –50 –40 –30 –20 –10 0 +10 +20
dB
dB
Output Level
Input Level
Expansion ratio = 2:1
Parameter Value
Threshold (dB)
–54 to 0 (55 points)
Ratio
1.0, 1.1, 1.3, 1.5, 1.7, 2.0, 2.5, 3.0, 3.5,
4.0, 5.0, 6.0, 8.0, 10, 20 (15 points)
Attack (ms) 0 to 120 (121 points)
Outgain (dB) –18 to 0 (36 points)
Width (dB) 1 to 90 (90 points)
Release (ms) 6 ms to 46.1 sec (160 points)
Threshold
Width
–70
–60
–50
–40
–30
–20
–10
0
+10
+20
–70 –60 –50 –40 –30 –20 –10 0 +10 +20
dB
dB
Output Level
Input Level