Peavey CS 800x4 Protection Features, Distortion Detection Technique DDT Limiting, Short Circuit

Protection Features

The CS® 800x4 amplifier incorporates several circuits to protect both itself and loudspeakers under virtually any situation. Peavey has made this amplifier as foolproof as possible by making it immune to short and open circuits, mismatched loads, DC voltage and overheating. If a channel goes into the DDT™ gain reduction mode, the DDT LED illuminates. The speaker load remains connected, but clipping percentage or output power is instantly reduced. When a problem occurs that causes a channel to go into a protection mode, the PWR (Power) LED for that channel will turn off. DC voltage on the output, excessive subsonic frequencies, or thermal overload will cause the channel’s output relay to disconnect the speaker load until the problem is corrected or the amplifier cools down.

Distortion Detection Technique (DDT) Limiting

Any time a channel is driven into hard, continuous clipping, the DDT circuit will automatically reduce the channel gain to a level just slightly into clipping, guarding the speakers against the damaging, high-power, continuous square waves that may be produced. Situations that may activate the DDT circuit include uncontrolled feedback, oscillations, an improper equipment setting or malfunction upstream from the amplifier. Normal program transients will not trigger DDT; only steady, excessive clipping will cause the DDT LED to illuminate.

LFC Impedance Sensing

The CS 800x4 amplifier features innovative circuitry for safe operation into any load. When an amplifier senses a load that overstresses the output stage, the Load Fault Correction circuit adjusts the channel gain to a safe level. Extreme load fault under high power levels will cause the signal to be muted for the associated channel. This method of output stage protection is far more effective than the standard limiting found on conventional power amplifiers. The LFC circuit is sonically transparent in normal use and unobtrusive when activated.

Thermal Protection

The internal fan will keep the amplifier operating well within its intended temperature range under all normal conditions. If the heat sink temperature reaches 85°C, which may indicate an obstructed air supply, the channels will protect themselves by disconnecting their load and shutting down until the heat sink has cooled. During this time, the PWR LED will go out, the DDT LED will stay lit and the cooling fan will continue operating at high speed.

Short Circuit

If an output is shorted, the LFC and thermal circuits will automatically protect the amplifier. The LFC circuit senses the short circuit as an extremely stressful load condition and attenuates the signal, protecting the channel’s output transistors from over current stress. If the short circuit remains, the amplifier will eventually thermally protect itself by opening both channel speaker relays, disconnecting the loads until the heat sink cools down.

DC Voltage Protection

If an amplifier channel detects DC voltage or subsonic frequencies at its output terminals, its speaker relay opens and disconnects the load to prevent speaker damage.

Turn-On/Turn-Off Protection

Upon powering-up, the amplifier mutes the input signals and stays in Protect mode with the speaker connect relays open for approximately four seconds. This allows the internal power supplies to charge and the amplifier to stabilize. After the relays engage, the signals slowly increase the muted signals to their normal level. Also, when power is removed, the input signals are muted so that no thumps or pops are heard.

13