CAP4
Cambridge Audio has developed a proprietary protection system to ensure reliability and a long life for its amplifiers and the speakers they are connected to. This protection system comprises of four main protection methods:
1. DC detection
Indication - Unit switches off during operation. The front panel speaker A/B white LED’s flash in unison with the red LED in the following sequence, one quick flash with long pause between flashes. Read below for more information.
Description – CAP4 offers loudspeaker protection if the output of the amplifier goes to a high constant voltage (DC) because of some internal fault. 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, extremely hard clipping of the amplifier may cause DC protection to be triggered. If this fault occurs, please contact your dealer for service.
2. Over temperature detection
Indication - Unit switches off during operation. The front panel speaker A/B white LED’s flash in unison with the red LED in the following sequence, two quick flashes with long pause between flashes. Read below for more information.
Description - Over temperature is caused by a combination of high listening levels and low impedance speakers. CAP4 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. The unit should ideally be left for 15 minutes in this state to cool down adequately. If the unit has not fully cooled down then the temperature may reach the limit soon after the amplifier is powered up. 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 internal temperature of the output transistors has reached the over temperature limit. Leave the unit for 15 minutes to cool down before pressing the Standby button to resume normal operation.
3. Overvoltage/Overcurrent(V/I) detection
Indication - Unit switches off during operation. The front panel speaker A/B white LED’s flash in unison with the red LED in following sequence, three quick flashes with long pause between flashes. Read below for more information.
Description – CAP4 offers V/I (voltage/current) 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. The V/I protection has been incorporated within the amplifier circuitry to provide a fast response to temporary overload conditions. When the V/I protection is triggered the unit will continue to operate but distortion may be heard as the unit protects the output transistors.
Remedy - Reduce the volume. If distortion is still present, check the speaker connections and ratings.
4. Intelligent clipping detection
Indication - Volume is reduced automatically.
Description – CAP4 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 attempts to go outside the maximum voltage that the amplifier can provide, causing the tops of the signal to flatten off. When CAP4 detects clipping the volume will be automatically reduced down until CAP4 detects an un-distorted output.
Note: The clipping detection is disabled by default. The clipping detection can be enabled in the Setup Menu, by following the steps in this FAQ.
If CAP4 is persisting, it is also advisable to check the specifications of your speakers to ensure that they are compatible with the EXA100. Both amplifiers can be used with speakers with an impedance of between 4 and 8 Ohms.
If your connected speakers fall outside of these specifications, then this could also be a reason The EXA100 outputs 100W RMS into 8 Ohms and 155W RMS into 4 Ohms, for CAP4 protection being activated.