SSM-2120 Analog, SSM-2120 Datasheet - Page 6

• Manufacturer Part Number: SSM-2120
• Description: (SSM-2122) Dynamic Range Processors/Dual VCA
• Manufacturer: Analog

In the noise gate, downward expander and compressor/limiter
applications, this potentiometer will establish the onset of the
control action. The sensitivity of the control action depends on
the value of R
For a positive unipolar control output add two diodes as shown
in Figure 7a. This is useful in compressor/limiter applications.
Figure 7b shows a typical response.
Bipolar control outputs can be realized by adding a resistor from
the op amp output to V+. This is useful in compandor circuits
SSM2120/SSM2122
MONO
MONO
OR R
OR R
MONO – R
STEREO – R
MONO – R
STEREO – R
L
L
Figure 9. Control Circuit for Stereo Compressor/Limiter with Noise Gating and Input/Output Curve
T
R
R
R
R
.
IN
IN
IN
IN
IN
IN
IN
IN
= 10k
= 10k
= 20k
= 20k
MONO
OR R
REC IN
REC
L
R
IN
LL
Figure 7. Compressor/Limiter Control Circuit and Typical Response
2V
2V
a. Control Circuit
Figure 8. Compandor Control Circuit and Typical Curves
FIGURE 6
FIGURE 7
C
|I
|I
C
THRESHOLD COM.
THRESHOLD EXP.
AV
AV
IN
I N
a. Control Circuit
a. Control Circuit
|
|
LOG AV
LOG AV
V+
V–
V+
V–
1.5M
1.5M
200
200
THRESH
V–
THRESH
THRESHOLD
1k
1k
CONTROL
GAIN
V
V
R
R
T
T
T
–V
T
+V
39k
C
C
39k
V+
V+
–6–
V–
V–
CON
CON
OUT
R
R
as shown in Figure 8a, with its response in Figure 8b. The value
of the resistor R
control amplifier.
STEREO COMPRESSOR/LIMITER
The two control circuits of Figures 6 and 7 can be used in
conjunction to produce composite control voltages. Figures 9a
and 9b show this type of circuit and transfer function for a
stereo compressor/limiter which also acts as a downward
expander for noise gating. The output noise in the absence of a
PV
PV
OUT
R
CON
200
200
TO –V
TO +V
OR –V
PV
b. Input/Output Curve
C
C
C
will determine the maximum output from the
THRESHOLD
EXPANSION
Curve
b. Typical Compressor/Limiter Control
b. Typical Compandor Control Curves
+
+
–
–
*
V
IN
– dB
*UPPER LIMIT CAN BE FIXED BY
VALUE OF PULL UP RESISTOR (R
CONNECTED TO POSITIVE SUPPLY
V
T
<
COMPRESSION
THRESHOLD
0
*
V
V
V
IN
T
IN
=
– dB
– dB
BE ESTABLISHED BY
VALUES OF R
0
R
LOWER LIMITS CAN
*
LL
THRESHOLD
, RESPECTIVELY
V
T
*UPPER AND
>
0
PV
*
PV
AND
)
REV. C