(Voltage
Controlled Amplifiers)
ELECTRICAL PIN-OUTS
Used in Professional Audio for some years, but totally new to the car audio world, is a remote
control gain devices called a “VCA”. This is a small integrated circuit that can control the
through gain of a circuit from a remote location.
It operates much like an external “hand” that
controls the signal flow through a circuit, much like a simple water flow valve.
CONTROL VOLTAGE
SIGNAL
VCA OPERATION
-40
LIMITING
-100
-100 -80
-40
CONTROL
VOLTAGE
VCA TRANSFER FUNCTION
Many people want to have a remote control for a high power amplifier in order to control the
loudness of a subwoofer amplifier independently of the radio. Remote mounting of an input gain
control would be a major problem with most car audio amplifiers because of the likely noise
intrusion into the signal path.
With a VCA circuit on the input of an amplifier, the gain can be controlled remotely but is done
with moderate level DC voltages (O-1 5 volts) that are insensitive to noise (noise is an AC voltage).
Using the optional Blaupunkt remote control
you simply plug the remote into the amp to
control the overall gain. For people wanting to interface with highly custom installations, you can
use an RJ-11 telephone jack and variable resistor to achieve similar results using the circuit below,
This is
recommended for very experienced Blaupunkt installation centers for it may void the
warranty of the amplifier otherwise.
l
-
REMOTE GAIN CONTROL
ELECTRICAL
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