Peavey CS 1800G - Manual (Page 7)

INSTALLATION AND CONNECTION
The Peavey CS
commercial series power amplifier is designed for durability in commercial installations and the
quality of performance required in studio and home applications. The unit is a standard rack-mount configuration,
high and is cooled by automatic two-speed internal fans. All of the input and output connections are on the back
panel. The front panel contains LED indicators for power and DDT activation, sensitivity controls,
and a mains power switch.
INDUSTRIAL AND COMMERCIAL INSTALLATIONS
For commercial and other installations, where sustained high power operation is required, the CS 1
should be
mounted in a standard rack. It is not necessary to leave rack space between each amplifier in the stack, since the fan
pulls air in from the rear and exhausts the hot air out of the front. However, an adequate COOL air supply must be
provided for the amplifier when rack-mounted. The internal fan must have a source of air that is not preheated by other
equipment. The amplifier will start up in “Low Speed” fan operation, and will normally stay at low speed operation
unless sustained high power operating levels occur. Then as the amplifier’s “Heat Sinks” heat up, the automatic thermal
sensing circuitry will cause high speed operation to occur. Depending on signal conditions and amp loading, high speed
fan operation may continue or it may cycle continuously between high and low. This situation is quite normal.
If cooling is inadequate due to preheated air, or a reduction of air flow occurs due to blockage of the amplifier inlet/
outlet ports, or if the amplifier is severely overloaded or short circuited, then the amplifier thermal sensing system may
cause temporary shutdown of that particular channel. This is indicated by the channel power LED on the front panel
ceasing to illuminate. Depending on available cooling air, operation should be restored in that channel relatively
quickly, and the power LED will be illuminated. In any event, corrective action should be taken to determine the cause
of the thermal shutdown. If the amplifier is not severely overloaded or shorted, and air flow is normal in and out of the
unit, then steps should be taken to provide a cooler environment for all the amplifiers. As a general rule, the cooler
electronic equipment is operated, the longer its useful service life.
BRIDGE MODE
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 into a single channel unit with a Power Rating
equal to the sum of both channel’s power ratings, and at a Load Rating of twice that of the single channel rating. In this
case, the CS
is rated at 900 W RMS per channel into 2 ohms. Thus, the Bridge Rating is 1800 W RMS into
4 ohms (minimum load). Bridge mode operation is accomplished by placing the mode switch in the “BRIDGE”
position, connecting the load between the RED binding posts of each channel, and using channel A as the input chan-
nel. All the channel B functions as an input are defeated and they serve no purpose in Bridge mode.
A popular application for Bridge mode operation is to drive sound distribution systems in large public address applica-
tions. In this mode, the CS 1800G power amplifier can actually drive 70 volt systems directly without using expensive
matching transformers. The real advantage of such an approach is primarily cost.
70 volt distribution systems are very common in applications where rather large numbers of relatively small loudspeak-
ers are used for background music and paging. Such systems require the use of 70 volt transformers at each loud-
speaker. Another common use for the Bridge mode is in subwoofer applications where very high power levels are
required to adequately reproduce the extreme low frequencies. Such enclosures usually contain 2 or 4 loudspeakers to
handle the power levels involved. For Bridge mode usage, the enclosure impedance must be 4 or 8 ohms; never below
4 ohms! Also make sure that the enclosure can handle 1800 watts reliably.
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