Peavey 80304543, Operating Manual

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internal fans must have a source of air that is not preheated by other equipment. If cool, 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. As the amplifier heat
sinks heat up, the automatic thermal sensing circuitry will increase the fan speed. Depending upon signal conditions and amp
loading, the fan speed may increase to a maximum value, or it may decrease to a minimum value. This situation is quite normal.
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 INSTALLATION
In most low- to medium-power applications, the CS
® 500A 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
® 500A will have severe cooling problems, even at low power levels. Again, inadvertent short circuit or
sustained overloaded usage could also cause temporary thermal shutdown.
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
™ 500A is rated at 250 W RMS
per channel into 2 ohms. The bridge mode ratings are 500 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.
Often sound technicians use bridge mode operation to drive sound distribution systems in very large public address applications.
Unfortunately, due to power levels involved, the CS
®
500A power amplifier can only supply about 45 V RMS in bridge mode, and
therefore cannot successfully drive 70-volt systems directly without using expensive matching transformers.
DDT ™
Peavey’s patented DDT ™ compression system enables the sound technician to maximize the performance of the amplifier/speaker
combination by preventing the power amp from running out of headroom (clipping). This system is activated by unique circuitry that
senses signal conditions that might overload the amplifier. The circuitry will reduce the amplifier’s gain whenever 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 ® 500A 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 system enabled.
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