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mode. Remember, the 4-ohm minimum load must be connected between the red binding posts. If
individual loads were connected to each output (as in normal stereo applications) when the
bridge mode is selected. Channel A would supply a normal in-phase signal to its respective load,
but Channel B would supply an abnormal out-of-phase signal to its respective load, and both of
these signals would contain Channel A source material (Channel B source material, if present,
would be defeated). This is a potentially dangerous situation, especially if the individual
chan--
nels are being used to supply high and low signals in a typical biamp configuration. Obviously,
the speaker components on Channel B would no longer be supplied their
intended
signal but an
out-of-phase version of the Channel A signal, which could easily destroy the
associated
IOLK-
speaker components. To help prevent this, whenever the bridge mode is selected, the standby
(“0”)
LED and the LED array itself on Channel B is defeated (off), just as if
there
was some kind
of a fault condition present on Channel B. This provides a positive indication that the CS
1000X
is no longer in the stereo mode.
TRANSFORMER
CHANNEL
B
INPUTS
AND SENSITIVITY
CONTROL ARE DEFEATED
CONNECT LOAD
BETWEEN RED
BINDING POSTS
7OVIlOOV
LINE
RANSFORMER
X-OVER
INPUT SENSITIVITY CONTROLS
0
PATCH PANEL (BRIDGE MODE) WITH JUMPERS
The input sensitivity rating of a power amplifier is
,he
RMS voltage level required at the
input
to
produce full-rated power into the rated load at the output. This voltage then becomes the level at
which the associated mixer must operate in order to drive the amplifier to full output. The
CS 1200X sensitivity controls are calibrated in decibel volts values rather than RMS voltage
(usually listed in typical mixer specs), and as such are more useful, since most contemporary
mixers employ LED arrays to indicate mixer output levels and are calibrated in decibel volts.
Knowing the power amplifier sensitivity rating in decibel volts will allow the mixer operator to
know the status of the power amplifier by noting which LED on the mixer is peaking. Obviously,
the LED labeled the same or closest to the sensitivity rating of the power amplifier will indicate
full power output of the system. Operation at levels above this rating will cause the power ampli-
fier to clip (produce distortion) unless the associated amplifier has a compressor/limiter to mini-
mize this distortion. Such a system, called DDT (U.S. Patent
#4,3
l&053), is included in the CS
1200X,
and the advantages should be obvious. Without DDT, the sound engineer must “ride
gain” on the mixer or employ an outboard limiter in order to prevent amp clipping. With DDT
the sound man can relax more and enjoy the “ride.”
For maximum mixer headroom (which in
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