SSM-2120 Analog, SSM-2120 Datasheet - Page 11

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

REV. C
FADER AUTOMATION
The SSM2120 can be used in fader automation systems to serve
two channels. The inverting control port is connected through
an attenuator to the VCA control voltage source. The noninverting
control port is connected to a control circuit (such as Figure 6)
which senses the input signal level to the VCA. Above the
threshold voltage, which can be set quite low (for example
–60 dBV), the VCA operates at its programmed gain. Below
this threshold the VCA will downward expand at a rate deter-
mined by the +V
time constant in the 10 ms to 25 ms range, the modulation of
the VCA standing noise floor (–80 dB at unity-gain), can be
kept inaudibly low.
C
control port attenuator. By keeping the release
SIG
SIG
OUT 1
–V
IN 1
C1
Figure 16. SSM2122 Basic Connection (Control Ports at 0 V)
50k
*
36k
V–
V+
36k
10pF
TL082
1/2
47
2000pF
V+
220k
200
200
0.1µF
150k
–15V
1
2
3
4
5
6
7
8
SSM2122
–11–
*
OPTIONAL CONTROL FEEDTHROUGH TRIM
The SSM2300 8-channel multiplexed sample-and-hold IC
makes an excellent controller for VCAs in automation systems.
Figure 16 shows the basic connection for the SSM2122 operating
as a unity-gain VCA with its noninverting control ports grounded
and access to the inverting control ports. This is typical for fader
automation applications. Since this device is a pinout option of
the SSM2120, the VCAs will behave exactly as described
earlier in the VCA section.
The SSM2122 can also be used with two or more op amps to
implement complex voltage-controlled filter functions. Biquad
and state-variable two-pole filters offering low pass, bandpass
and high pass outputs can be realized. Higher order filters can
also be formed by connecting two or more such stages in series.
16
15
14
13
12
11
10
9
0.1µF
220k
200
200
+15V
TL082
47
2000pF
1/2
36k
10pF
36k
V–
V+
50k
SSM2120/SSM2122
*
SIG
–V
SIG
C2
OUT 2
IN 2