Blaupunkt Velocity V250 Owner's Manual page 6

Controlled Amplifiers) &
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 feed-
through gain of a circuit from a remote location.
controls the signal flow through a circuit, much like a simple water flow valve.
SIGNAL INWTS
VCA OPERATION I-
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 (RM-1) 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
6
ELECTRICAL PIN-OUTS
It operates much like an external "hand" that
-40
-100
-100 -80 -60. -40 -20 ode
VCA TRANSFER FUNCTION
ELECTRICAL PINOUT
LIMITING
CONTROL
VOLTAGE