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Appendix
Appendix
Expander
An expander is another form of automatic level control. By attenuating the sig-
nal 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 parame-
ter. The trigger signal is determined using the KEY IN parameter.
Ratio controls the amount of expansion—the change in output signal level rela-
tive 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 unaf-
fected.
Out Gain sets the expander’s output signal level.
Knee sets the transition of the signal at the threshold. With a hard knee, the tran-
sition 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.
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)
5 ms to 42.3 sec
*1
, 6 ms to 46.0 sec
*2
, 8 ms to 63.4 sec
*3
(160 points)
*1. These values are obtained when the sampling frequency is 48kHz.
*2. These values are obtained when the sampling frequency is 44.1 kHz.
*3. These values are obtained when the sampling frequency is 32 kHz
-70
-60
-50
-40
-30
-20
-10
0
+10
+20
-70
-60
-50
-40
-30
-20
-10
0
+10
+20
Input Level
Output Level
dB
dB
Threshold = -10dB
Knee = hard
Expansion ratio = 2:1
-70
-60
-50
-40
-30
-20
-10
0
+10
+20
-70
-60
-50
-40
-30
-20
-10
0
+10
+20
Input Level
Output Level
dB
dB
Threshold = -20dB
Knee = knee5
Expansion ratio = 2:1
