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Peavey CS 1400/2000

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CS 1400/2000 Manual (pdf)

Operation

Operation Modes

Stereo Operation
For stereo (dual channel) operation, turn the amplifier OFF and set the mode select switches on the back panel to the out (extended) position. In this mode, both channels operate independently of each other, with their input attenuators controlling their respective levels. Thus, a signal at channel A’s input produces an amplified signal at channel A’s output, while a signal at channel B’s input produces an amplified signal at channel B’s output.

Bridged Mono Operation
Both amplifier channels can be bridged together to make a very powerful single-channel monaural amplifier. Use extreme caution when operating in the bridged mode; potentially lethal voltage may be present at the output terminals. To bridge the amplifier, depress the rear panel Bridge switch to the IN position. Direct the signal to channel A’s input and connect the speakers across the hot outputs (the "+" binding posts) of channels A and B. Only channel A’s input attenuator is active while in Bridge Mono mode.

Unlike the stereo mode, in which one side of each output is at ground, both sides are hot in bridged mode. Channel A’s side is the same polarity as its input with the minimum nominal load impedance being 4 ohms (equivalent to driving both channels at 2 ohms) in bridged mode. Driving bridged loads of less than 4 ohms will activate the DDT™ circuitry (see Indicators section), resulting in a loss of power, and may also cause a thermal (overheating) overload.

Switches & Controls

Front Panel

Rear Panel

AC Power Switch/Circuit Breaker (1)
The CS Series amplifiers feature a combination AC switch/circuit breaker on the front panel. If the switch shuts off during normal use, push it back to the ON position once. If the switch will not stay in the ON position, the amplifier needs servicing.

Input Attenuators (2)
Whenever possible, set the attenuators fully clockwise to maintain optimum system headroom. The input attenuator controls (one for channel A, one for channel B) located on the front panel attenuate signal level (decrease gain) for the respective amplifier channels in all modes.

Bridge Select Switch (3)
The rear panel Bridge Select switch determines if the amplifier is in stereo (two channels) or in Bridged Mono mode. Do not operate the Bridge Select switch with the amplifier powered on.

DDT™ Defeat Switch (4)
For normal operation, the DDT circuit should remain operational by leaving the DDT Defeat Switch in the extended position. This will prevent excessive distortion and potential speaker damage.

Indicators

CS Series amplifiers feature three front panel LED indicators per channel: PWR (power), SIG (signal) and DDT™ (Distortion Detection Technique). These LED indicators inform the user of each channel’s operating status and warn of possible abnormal conditions.

PWR LED (1)
The Power LED indicates that the channel is operational. It illuminates under normal operation and remains on even when the channel’s DDT circuit is activated.

SIG LED (2)
The Signal LED illuminates when its channel produces an output signal of greater than 1 volt RMS or 25 mV input with a 0 dB attenuation of the front panel knobs. This is useful in determining whether a signal is reaching and being amplified by the amplifier. If the Signal LED is illuminated but no sound is present, that means a signal is present at the amplifier but a problem may exist after the amplifier, such as in the cables or speakers.

DDT LED (3)
A channel’s DDT LED will illuminate at the onset of clipping. If the LEDs are flashing quickly and intermittently, the channel is just at the clip threshold, while a steady, bright glow means the amp is clip limiting, or reducing gain to prevent severely clipped waveforms from reaching the speakers.

Protection Features

The Peavey CS Series incorporates several circuits to protect the amplifier and speakers under virtually any situation. Peavey has made the amplifiers as foolproof as possible by making them 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 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 or excessive subsonic frequencies will cause the triac crowbar circuit to activate to protect the speakers. If the amplifier overheats, the signal will be removed from the channel that is at fault until the amplifier cools down, thus protecting the amplifier.

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
CS Series amplifiers feature 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 fans will keep the amplifier operating well within its intended temperature range under all normal conditions. If a channel’s heat sink temperature reaches 85°C (which may indicate an obstructed air supply), that channel will independently protect itself by muting its input signal and shut down until it has cooled. During this time, the PWR LED will go out and the cooling fans 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 channel will eventually thermally protect itself by muting the input signal.

DC Voltage Protection
If an amplifier channel detects DC voltage or subsonic frequencies at its output terminals, the output triac crowbar circuitry will activate immediately to prevent speaker damage.

Turn-On/Turn-Off Protection
Upon powering up, the amplifier stays in Protect mode, muting the input signal for approximately four seconds while the power supplies charge and stabilize. Also, when power is removed, the input signals are muted so that no thumps or pops are heard.

Speaker Protection

All loudspeakers have electrical, thermal and physical limits that must be observed to prevent damage or failure. Excessive power, low frequencies applied to high frequency drivers, severely clipped waveforms and DC voltage can all be fatal to cone and compression drivers. Peavey CS Series amplifiers automatically protect speakers from DC voltages and subsonic signals. If using an electronic crossover, be extremely careful that the low and mid bands are connected to the correct amplifiers and drivers and not to those designed for a higher frequency band. An amplifier’s clipping point is its maximum peak output power, and some of the higher powered Peavey CS Series amplifiers can deliver more power than many speakers can safely handle. Be sure the peak power capability of the amplifier is not excessive for your speaker system.

Fuses may also be used to limit power to speaker drivers, although as current-limiting rather than voltage-limiting devices, they are an imperfect solution, and as the weakest links, they only limit once before needing replacement. Some poor-quality fuses have a significant series resistance that could degrade the amplifier’s damping of the speaker’s motion and may even deteriorate the system’s sound quality. If you elect to use fuses, check with the speaker manufacturer to determine the proper current rating and time lag required.

Do not drive any low frequency speaker enclosure with frequencies lower than its own tuned frequency; the reduced acoustical damping could cause a ported speaker to bottom out even at moderate power. Consult the speaker system specifications to determine its frequency limits.