Peavey CS 800S Manuel D'utilisation page 9

Inadequate cooling due to preheated air, a reduction of air flow caused by blockage of the amplifier's inlet/outlet ports, or severely
overloading the amp may cause the amplifier's thermal sensing system to temporarily shut down that particular channel. This will be
indicated by the channel power LED on the front panel ceasing to illuminate. Depending upon available cooling air, operation will be
restored to that channel relatively quickly, and the power LED will then be illuminated. 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,
steps should be taken to provide a cooler environment for all the amplifiers. As a general rule, electronic equipment in a cooler
environment will have a longer and more useful service life.
STUDIO AND HOME INSTALLATION
In most low- to medium-power applications, the CS 800S can be mounted in any configuration. It is desirable that, if at all possible,
the unit be located at the top of an equipment stack. This will prevent possible overheating of any sensitive equipment by the hot air
rising from the power amplifier. As a general rule, most home and studio requirements will never cause maximum high speed fan
operation. If it does, however, this may indicate that you have not taken the necessary steps to provide adequate cooling. Remember,
closed up in a cabinet, the CS 800S will have severe cooling problems, even at low power levels. Again, inadvertent short circuit or
sustained overloaded usage could also cause temporary thermal shutdown. Most home wiring and electrical circuits are only 15
amps. Two CS 800S amplifiers could cause a power panel 15 amp circuit breaker to trip if a severe overload occurs.
BRIDGE MODE
The bridge mode on stereo amplifiers is often misunderstood as to its actual operation and usage. In basic terms, when a two-
channel amplifier is operated in bridge mode, it is converted into a single channel unit with a power rating equal to the sum of both
channels' power ratings, at a load rating of twice that of the single channel rating. In this case, the CS 800S is rated at 600 W RMS
per channel into 2 ohms. The bridge mode ratings are 1,200 W RMS into 4 ohms (minimum load). The bridge mode operation is
accomplished by placing the mode switch into the bridge position, connecting the load between the red binding posts of each
channel, and then using channel A as the input channel. All channel B input functions are defeated.
Another application for bridge mode operation is to drive sound distribution systems in very large public address applications. In this
mode, the CS ® 800X 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 domestic applications where
large numbers of relatively small loudspeakers are used for background music and paging. Such systems require the use of 70-volt
transformers at each loudspeaker. Another common use for the bridge mode is in subwoofer applications where very high output
power levels are required to reproduce extremely low frequencies. Such enclosures usually contain two or four loudspeakers to
handle the high power levels involved. For bridge mode usage, the enclosure impedance must be 4 or 8 ohms. Never below 4 ohms!
Also make sure the enclosure can handle 1,200 watts reliably.
DDT ™
Peavey's patented DDT ™ compression system enables the sound man to maximize the performance of the amplifier/speaker
combination by preventing the power amp from running out of headroom (clipping). This compression system is activated by a unique
circuit that senses signal conditions that might overload the amplifier and reduce the amplifier's gain when clipping is imminent. The
threshold of compression is clipping itself and no specific threshold control is used. This technique effectively utilizes every precious
watt available for the power amplifier to reproduce the signal while at the same time minimizes clipping and distortion, and thus
significantly reduces the potential of loudspeaker degradation and damage. The DDT system is an automatic, hands-off approach to
the problem of power amplifier clipping.
Since the CS 800S power amplifier uses a circuit breaker for over-current protection, the DDT compression system plays even a more
important role in the continuous performance by preventing each channel from clipping and overloading. Continuous operation at
clipping can cause the circuit breaker to trip, but with the DDT activated this problem is minimized. For this reason, you should always
have the DDT compression system enabled.
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