1.0 GENERAL DESCRIPTION
The ALM771 Audio Level Master is an audio level controller
designed to maintain consistent audio program output levels over a wide
range of input levels. The unit is designed to be used at cable
television head-end installations, connected between the audio output
of a satellite receiver - ad insert switch and the inputs of TV and FM
channel modulators. It can also be used in any application where there
is a need for high quality automatic level control.
The ALM771 can be connected in pairs to handle stereo program
material. Simply connect one wire between two ALM771 and the control
functions will track together to provide professional stereo automatic
level control.
dB-linear control characteristics allow smooth gain control over a
30 dB range. Program input levels can vary plus or minus 15 dB while
the output level remains constant. An elegant Voltage Controlled
Amplifier (VCA) design provides very low noise and distortion. Program-
dependent release time assure that gain is controlled without the usual
compressor artifacts common to less sophisticated designs, such as
"ducking", a sudden drop in average overall level after a loud
transient, such as the sound of gunfire in a movie. Noise rush-up
during pauses in program audio is eliminated by a noise gate circuit
that prevents a gain increase when the input audio level drops.
A three color LED display allows for easy set-up and monitoring of
the input audio level. This display can be easily observed from a
distance. The ALM771 is a high performance audio controller that is
transparent in its operation. It has no "sound" of its own, but
automatically produces an output that sounds as if the input level is
being correctly set manually, even with widely varying input levels.
2.0 INSTALLATION
Remove the ALM771 from its packaging material and select a place
in your rack for mounting. There is a standard mounting bracket
provided with each unit. Simply bolt the unit into the rear rack rail
near the modulator to be controlled.
3.0 CONNECTION AND SETUP
Audio connections to the unit are made to a removable connector
block at the rear of the unit. For ease of connection, unplug the
connector block, connect wiring, and plug block back into unit. Connect
wiring by inserting stripped wires into the appropriate holes in block,
and secure by tightening the screws on top. PUSH FIRMLY ON THE
CONNECTOR BLOCK TO SNAP IT INTO PLACE.
From a BALANCED output source to ALM771 input:
Refer to the connector block drawing on the next page.
SOURCE TIP or HI - to input T
SOURCE RING or LO - to input R
ALM771.ISB PAGE 2 OF 4
