Peavey CS 1200X - Manual (Page 15)

normal intermittent applications, low-speed fan operation will provide adequate cooling. Since
the CS 1200X is a redundant two-channel amplifier, but only one fan is employed, the fan
circuitry is an independent system, separately fused internally. You will notice that the heat sink
components are divided horizontally. The lower half contains Channel A output transistors,
while the upper half belongs to Channel B. The fan provides equal cooling for both channels.
Each channel has separate built-in thermal sensors and fault logic circuitry. If one channel’s heat
sink reaches an operating temperature of its logic will cause high-speed fan operation
irrespective of the other channel’s operating temperature. In other words, either channel’s heating
will control the fan speed. Under normal continuous usage at full-rated power output into the
rated load, the thermal logic system will continuously monitor heat sink temperatures and will
automatically select the fan speed required to maintain safe operating limits for the power tran-
sistors.
HIGH TEMPERATURE LIMITS
Because of the very efficient design of the CS 1200X heat tunnel dissipation system, thermal
shutdown conditions will almost never occur unless there is truly an external fault. For con-
tinuous operation, the CS 1200X requires a source of cool air. As an added help in locating
mismatched or shorted speakers, the DDT active LED is a powerful tool. If this LED flashes
continuously at relatively low-output power levels (indicated by low-power readings on the LED
array), it is almost a sure sign that the amplifier loading impedance is too low in value, or that
there might be a short circuit. Remember, usually the power LED array should reach 100%
before the DDT system is activated on any particular channel. The CS 1200X also has a fail-safe
thermal mechanism built into the unit. If either channel’s thermal logic system should fail to
cause thermal shutdown in that channel or if the fan itself should fail, this fail-safe system will
shut down the entire amplifier, just as if you had turned off the power switch. This is
just one
more protection that Peavey has incorporated into this unique amplifier as a backup system. If
this should ever occur, immediately seek professional help at an authorized Peavey service
center.
PASSIVE CROSSOVER
The purpose of a traditional high-level passive crossover found inside most speaker systems is to
separate the low-frequency material from the program and feed it to the woofer (low-frequency
driver), and to separate the high-frequency material from the program and feed it to the tweeter
(high-frequency driver). This crossover is connected between a power amplifier and the speak-
ers, and, as its name implies, is made up entirely of passive components (no transistors or tubes).
Such a system is usually referred to as “full-range,” which simply means that the power amplifier
must handle the full range of frequencies. There are many good reasons for using a biamplified
professional system as opposed to a full-range system. One reason is that the biamp system will
provide more headroom with the same power amplifier complement than that of the full-range
system. The term headroom deserves some consideration. Program material (music or speech) is
made up of many different frequencies and their harmonics. Most music, especially contempo-
rary rock music, is bass-heavy. That is, the low-frequency material contains much more energy
than the high-frequency material. If both high- and low-frequency material, such as voice and
bass guitar, are present in a full-range system, the high-energy bass frequencies can
use up most
of the power available from the power amplifier, leaving little (or none) for the high frequencies.
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