Crown Audio CH Series, CL Series operation manual Model CL4 Circuit Block Diagram

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CH and CL Series Power Amplifiers

5 Principles of Operation

The signal next enters the main amplifier error amp where it is mixed with a small portion of the output voltage and current in such a way as to control the amplifier’s overall output perfor- mance.

Following the error amp is the modulator stage where the audio signal is compared to an extremely accurate 250-kHz triangle waveform. Comparators output a Pulse Width Modulated (PWM) string of pulses at 250 kHz that vary in width depending on the level of the input sig- nal. These strings of pulses, one for the posi- tive side and one for the negative side, are connected to the output stage via optocouplers.

The signals from the optos are then passed to gate drivers that amplify the pulses to the level required to drive output devices. The driven

output devices are now able to produce PWM pulses that have an output voltage from the negative high-voltage rail (–Vcc) to the positive high-voltage rail (+Vcc). This output voltage is always the same (2 * Vcc) but the width of the pulses is still dependent on the level of the input signal. The positive and negative output PWM pulses then pass through inductors and are summed together. Summing the output sig- nals through inductors reconstructs the audio signal, amplified to the desired level. There is a small amount of ripple on the output that is at double the switching frequency (500 kHz).

The amplified audio signal is then passed through an output filter that removes the resid- ual ripple voltage.

Protection for the output devices is performed by a very precise pulse-by-pulse current limiter circuit that operates each time the output devices switch. The current limiting is “flat” meaning that, regardless of the output voltage, the output current always limits at a certain value.

The turn-on delay circuitry functions to keep the modulators turned off (which keeps the out- puts from switching) until all supplies are up and stable.

Thermal probes monitor Heatsink tempera- tures and power transformer temperature. As the temperatures rise, the probes send a pro- portional voltage to the fan control circuit and the Thermal Limit Control (TLC) circuit. The fan

Figure 5.4 Model CL4 Circuit Block Diagram

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Operation Manual

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Contents CH and CL Series Some models may be exported under the name AmcronImportant Safety Instructions Use only with a cart, stand, tripod, bracket, orEuropean Representatives Name and Address Safety StandardCrown International, Inc EMC StandardsTable of Contents Welcome FeaturesHow to Use This Manual Setup Unpack Your Amplifier Install Your AmplifierReinstall no-touch cover to maintain safety Choose Input Wire and ConnectorsChoose Output Wire and Connectors Switch Settings Model CH4 Models CH1 and CH2Models CH1 & CH2 140V Bridge Mode Wire Your System Models CH1 & CH2 Stereo ModeRefer to .5 for output connector pin assign- ments Inputs Connect input wiring to Channel Model CH4 Stereo ModeModel CH4 Bridge Mode Models CL1 & CL2 Bridge Mode Models CL1 & CL2 StereoInputs Connect input wiring to CH1 Model CL4 Stereo ModeModel CL4 Bridge Mode Screw terminal All Models How to Parallel the Inputs in Stereo ModeStartup Procedure Connect to AC MainsPrecautions OperationCH and CL Series Front Panel Controls and Indicators Operation Speed Fan-On-Demand Controls IndicatorsIf the amplifier output stage stops operating Advanced Features Options SST-4632 SST-4622SST-3632 Fault Monitoring Location of Fault JackPrecision Detented Level Controls Attenuation in dBPrinciples of Operation CH1, CH2, CL1 and CL2Power Indicator LED is driven from the low-voltage supply Models CL1 & CL2 Circuit Block DiagramCH4 and CL4 Audio Signal Path Model CH4 Circuit Block DiagramModel CL4 Circuit Block Diagram Power Supply Operation Flashing TroubleshootingAmplifier output wires have developed a short circuit Specifications 120V/60 Hz Units, Bridge mono modeOhms 275W KHz at rated THD Ohms 560WOhms 450W 600WModel CL1 & CL2 CH and CL Series Power Amplifiers Models CH4 & CL4 Damping Factor Typical Output Impedance AC Power Draw Thermal Dissipation Following equation is used to calculate thermal dissipationAC Power Draw Thermal Dissipation AC Power Draw Thermal Dissipation CL2 Service Warranty 12/01Worldwide Except USA & Canada Fax Mo/day/yrThis page Intentionally Left Blank ‰ Personal/Consumer ‰ Business/Corporate ModelIndividual or Business Name Phone # Fax #