VCA-MC Series
Amplifier Accessories
page 8
Operation Manual
5. Align a supplied barrier plug with the corresponding pins in the VCA-MC4A or
VCA-MC8 module. Attach the cable to the plug as follows:
Connect twisted-pair HOT lead to the VCA channel terminal(s) you want to control.
Connect twisted-pair COLD lead to the +10V terminal.
Connect cable shield to the GND terminal.
The pin labeled GND on the VCA module is connected directly to the internal ground of the
amplifier.
NOTE: Do not connect this pin to any ground or extend it for any other
purpose.
In the VCAP wall-mount panel, do not connect the ground pin to the VCAP metal panel or
its junction box.
3.2 Wiring Your Own Potentiometer
You may use your own linear-taper potentiometer to control the VCA-MC module. We rec-
ommend using a 5 k ohm potentiometer; however, values up to 100 k ohms are acceptable.
A potentiometer near 100 k ohms may require an RFI bypass capacitor.
Wire the potentiometer as shown in Figure 3.2. Connect one end-terminal of the pot to the
power-supply ground and VCA ground; connect the other end-terminal to +10 VDC, and
connect the wiper to the VCA control input of your choice (VCA1, VCA2, and so on).
3.3 Wiring to an External Variable DC Voltage Source
The VCA-MC
control input
is the pin labeled VCA1, VCA2, and so on. It is possible to drive
the control input from an external voltage source such as a Crestron control system. Con-
nect a variable voltage source (0-10 VDC) between the ground pin and control input on the
MC-VCA module. No build-out resistance is required. DO NOT connect to the +10V pin.
The voltage range of the control input is 0 TO 10 VDC. If this range is
exceeded, proper operation is not guaranteed and damage may result to the
VCA card or amplifier.
It is not recommended to draw more than 20mA from the 10V supply. (20mA is approxi-
mately equivalent to having a 5 k ohm potentiometer connected to each channel of an 8-
channel amplifier. Crown-supplied VCAP panels are equipped with 5 k ohm potentiome-
ters). The 10V supply will survive a direct short.
Figure 3.2 Wiring Your Own Potentiometer
Summary of Contents for 1-VCAP
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