3.4 STEREO STRAPPING
Two channels of program material do not
necessarily constitute a stereo program. A stereo
program is one where the two channels are
recorded and/or mixed to create the illusion
of a sir)gle, unified "panorama" of sound. The
stability of the psychoacoustic "image'' of each
sound source within the stereo program depends
upon·its ability to maintain a specific phase and
amplitude relationship from left to right channel.
If two independent compressors are used to
process the stereo program, a loud sound occurring
in one channel will cause a gain reduction only in
that channel. This gain reduction would cause the
perceived image of any sound spread between the
two channels to move toward the side which had
not been compressed, because the spread signal
would be momentarily softer in the compressed
channel. This can be avoided by linking the two
compressors in such a way that both channels
receive the same amount of compression - an
amount equal to the maximum ''needed'' by
either channel at that moment. On the 160X,
this is accomplished by means of the
STRAPPING jacks; a cable between these
jacks permits the RMS detectors of both -units
to "talk" to one another - but only when one
of the units' SLAVE buttons is depressed. Each
compressor then senses the incoming signal
level, which is compared to the threshold set on
the master (the unit whose SLAVE button is
not depressed). If the comprealon Is ;equired by
either channel, both channels are a,bject to
compression - the same amount of it - so the
stereo image remains stable.
When compressing a stereo program with a pair
of 160Xs, only the master unit controls need be
adjusted.
12
3.5 METER CALIBRATION
The INPUT/OUTPUT LEVEL DISPLAY in thr
160X is factory.calibrated to indicate "O" when
the signal level is +4 dBm (1.23 V) at either the
input or output of the 180X, depending on the
DISPLAY function switch position. (The
METER CALIBRATION control does not affect
the -GAIN CHANGE LEDs.) ·.
To recalibrate the LEVEL DISPLAY, depress
the DISPLAY button to meter the INPUT LEVEL,
and feed a 1 kHz signal at the selected nominal
operating level (the level desired for a ''O dB"
meter indication) to the 180X's SIGNAL INPUT.
Then adjust the rear panel METER CALIBRA-
TION control until the meter indicates ''O dB."
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