CAP5: Five-way protection system
Cambridge Audio has developed a proprietary protection system to ensure reliability and long life of its amplifiers. This protection system comprises five main protection methods:
1. DC detection
Indicator – Unit has switched off during operation, protection LED constantly flashes in single bursts.
Description – CAP5 offers loudspeaker protection if the output of the amplifier goes to a high constant voltage (DC). This is a rare fault, although detecting it could just save those expensive loudspeakers.
Remedy – Due to the necessary sensitivity of the DC protection circuit, hard clipping of the amplifier may cause DC protection to be triggered. If this fault occurs please switch the unit off, power up again and check operation with a reduced volume level. If the DC fault occurs again please contact your dealer for service.
2. Over temperature detection
Indicator – Unit has switched off during operation, protection LED constantly flashes in bursts of two.
Description – CAP5 includes temperature detection which constantly monitors the heat generated by the output transistors. If the monitored temperature reaches a high level (suitably within the limits of the output devices) the amplifier will automatically switch into a fault mode. If the loudspeaker impedance is low, the temperature of the amplifier may rise faster as the amplifier is working harder. If the amplifier is mounted in a cabinet or the ventilation slots are obstructed, the over-temperature detection may activate/reactivate after a short listening time.
Remedy – The unit is not damaged, although it should be left for 15 minutes to cool down before being switched out of Standby.
3. Overvoltage/overcurrent detection
Indicator – Unit has switched off during operation, protection LED constantly flashes in bursts of three.
Description – CAP5 offers V/I protection by constantly monitoring the output transistors to keep them working inside their Safe Operating Area (SOA). The SOA is a set of limits given by the output transistor manufacturer to ensure reliability. V/I also protects the amplifier against short-circuits on the speaker terminals during use.
Remedy – The amplifier is being used outside its performance envelope. Reduce the volume. Also check to see if there is a short- or partial short- circuit between the loudspeaker terminals.
Note: If the indication remains the same and multiple loudspeakers are being used on each loudspeaker output, then please remove a pair and retry. If too many loudspeakers are connected to any amplifier, causing the load resistance to drop too low, the amplifier will be overdriven. CAP5 will detect this situation. If the indication remains the same with only one set of loudspeakers connected, there may be a fault with one or both of the loudspeakers.
4. Short-circuit detection
Indicator – As the unit attempts to come out of Standby mode, the protection LED flashes in bursts of four.
Description – During power up from Standby, CAP5 performs a check on the loudspeaker terminals to see if a short across the terminals has been accidentally introduced. If the resistance measured across the loudspeaker terminals is too low, the unit will remain in Standby mode until the fault has been removed and power up is re-attempted.
Remedy – User-related fault. There may be a short-circuit between the loudspeaker terminals. Check all loudspeaker connections before attempting to switch the unit out of Standby.
azur 651A
5. Intelligent clipping detection | ENGLISH |
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Indicator – Volume is nudged down automatically. | |
Description – CAP5 has the ability to detect when the amplifier starts to clip or overdrive at its output, which can damage loudspeakers and degrade the sound. Clipping distortion is caused at high volume levels when the output signal briefly goes outside the maximum voltage that the amplifier can provide, causing the tops of the signal to flatten off. When CAP5 detects clipping, the volume will be automatically nudged down until CAP5 detects an undistorted output.
The clipping detection is disabled by default. However, to enable the clipping detection, hold down the Standby/On button during power up (whilst switching on the unit at the rear panel power switch). The unit will indicate this by flashing the protection LED for several seconds.
Custom installation (C.I.) use
The 651A feature a Control Bus input/output that allow un-modulated remote control commands (positive logic, TTL level) to be received electrically by the unit and looped to another unit if desired. These control commands are typically generated by custom installation (multi-room) systems or remote IR receiver systems. The Control Bus sockets are colour-coded orange.
An IR Emitter Input is also provided that allows modulated IR remote control commands to be received electrically by the unit. Commands on this input operate the unit only and are not looped out demodulated on the Control Bus Output.
In addition the units feature 'direct' IR/Control codes as well as toggle codes for some of their features to simplify programming custom installation systems. Special direct On/Off and Mute commands can be accessed on the supplied remote control for teaching into C.I. systems as follows:
1.Press and hold the Standby button. The remote first generates its standby (toggle) command. Keep holding the button down and after 12 seconds an amplifier “On” command will be generated. If the button is held down for a further 12 seconds, an amplifier “Off” command is generated.
2.Press and hold the Mute button. The remote first generates its mute (toggle) command. Keep holding the button down and after 12 seconds a “Mute On” command will be generated. If the button is held down for a further 12 seconds, a “Mute Off” command is generated.
A full code table for this product is available on the Cambridge Audio website at www.cambridge-audio.com.
