Peavey CS 1200 User Manual

5 Care must be taken to never remove a crossover module or replace it with the GS-1200 power switch on. The complex circuitry
used in the crossover modules receives bipolar power through the socket, and removal or replacement could cause severe
transients which can destroy the loudspeaker system. Always turn theCS-1200off first. As an added feature, the bipolar power
for the crossover islands can be supplied from either channel of the CS-1200. Thus, if one channel should shut down for any
reason, the redundancy of the system will maintain operation of the crossovers.
6. The individual sensitivity controls on each channel play a very important role n the use of the crossover modules. As such, they
represent a signal loss when they are operated at another setting other than full clockwise (maximum sensitivity). Biamped
speaker systems usually require less signal level for the high frequency components because they are generally more efficient.
Consequently, a system balance can be achieved by reducing the high pass level. This is particularly important on non-Peavey
loudspeakers where the PL-500, PL-800 or PL-1200 crossover modules must be used. These modules are referred to as “no pad
and equalization” types. As such, there is no reduction in high pass level. Consequently, the pad must beaccomplished using the
high pass channel sensitivity control. The amount of pad required isalways the difference between theefficiency ratings of the
high and low speaker components. Whenever Peavey loudspeakers are operated using the special crossovers, the sensitivity
controls should be set at full clockwise settings (maximum sensitivity) to provide maximum system headroom since the correct
pad and equalization is already provided in the crossover module.
Bridge Mode (10) (12) (16)
The bridge mode on stereo amplifiers Is often misunderstood as to the actual operation and usage. In basic terms, when a two-channel
amplifier is operated in the bridge mode, it is converted to a single-channel unit with a power rating equal to the sum of both channels’
continuous power ratings, ata load rating of twice that of the single-channel ratings. For the CS-1200, the bridge ratingsare 1200 watts RMS
(continuous) into 8 ohms (minimum load). Bridge mode operation is accomplished by placing the mode switch (16) in the bridge position,
connecting the load betweenthe red b nding posts of each channel, and using Channel Aasthe input channel. All functions of Channel B as
an input are defeated. What actually happens from the technical standpoint is that Channel B is supplied an input signal which is equal in
level but is 180° out-of-phase from that of the Channel A input signal (i.e., when Channel A s signal is positive, Channel B’s signal is negative
and vise versa). Thus, the load (which is connected between the channels) sees the sum of the output voltages of both channels (which is
then twice that of the single channel), and this load must be 8 ohms or greater.
For the CS-1200, the selection of bridge mode should invoke the following interesting question: “Where would I needa 1200 watt, 8ohm
amplifier?” When you consider the fact thatthere are virtually no 8 ohm speaker components which can handle 1200 watts RMS (continuous)
safely, there are generally no practical applications for a bridged CS-1200 in simple sound systems. The real purpose is to drive sound
distribution systems in very large public address applications. In the bridge mode, the CS-1200 can supply 70 or 100 volts RMS directly
without matching transformers. 70 volt distribution systems are very common in domestic applications where large numbers of relatively
small loudspeakers are used for background music and paging. Such systems require the use ol 70 volt transformers at each loudspeaker.
100 volt systems are more common in export applications. Occasionally a large speaker array might require (or handle) 1200 watts RMS into
8 ohms directly. This then might be a practical application.
Diagram 4 shows the actual arrangement for the CS-1200 patch panel in the bridge mode. Notice the jumper plugs are inserted in the
transformer (10) and crossover (12) accessory sockets of Island A. These jumper plugs cause theXLR connector ol this island to be wired in
the unbalanced configuration (as in Diagram 1) and complete the connection to the parallel bridge power amp input jacks (formerly Channel
A power amp input). Th^Channel A sensitivity control now determines the sensitivity of the bridge mode amplifier. The Channel B power
amp input jacks anc sensitivity control have been deleted since they serve no purpose in this mode and are actually electronically removed
from tho circuit. Both sets of parallel V" output phone jacks have been deleted on the diagram since these also are normally not used in the
bridge mode. Remember, the 8 ohm minimum load must bo connected between the red binding posts. If individual 4 ohm 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 be the Channel A source material (Channel B source material, if present, would be defeated). This is a very dangerous situation,
especially if the individual channels are being used to supply high and lew signals in the typical biamp configuration. Obviously, the speaker
components on Channel B would no longer be supplied their intended signal but rather an out-of-phase version of the Channel A signal,
which could destroy the associated loudspeaker components. To minimize the possibility of this happening on the CS-1200, v/henever the
bridge mode is selected, thestandby (“0”) LED and the LED array itself on Channel B is defeated (off), just as if there wasa fault condition on
Channel B. This provides a positive indication that the CS-1200 is no longer in the stereo mode.
Often technicians fall into what we call “the bridge syndrome.” This is designing a system for bridge mode operation when indeed they
really don’t need it. A typical example is where two 4 ohm speaker enclosures are wired in series, creating an 8 ohm load, and this load is then
driven in bridge mode. In this case, a CS-1200 would deliver 600 watts RMS to each enclosure (a total of 1200 watts for both). A much better
approach is to use the CS-1200 in the stereo mode and then connect one 4 ohm speaker enclosure to each channel of the CS-1200 and

Peavey CS 1200 Specifications

General

Channels	2
Signal to Noise Ratio	> 100 dB
Input Impedance	20k ohms balanced, 10k ohms unbalanced
Weight	35 lbs
Dimensions	3.5" H x 19" W x 15.25" D