Cap5 - Five Way Protection System - Cambridge Audio azur 540A Mode D'emploi

CAP5 - FIVE WAY PROTECTION SYSTEM

Cambridge Audio has developed a proprietary protection system to
ensure reliability and a long life to its amplifiers. This protection system
comprises of 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) 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,
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. 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
14 Azur integrated amplifier
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 - User related fault. The internal temperature of the output
transistors has reached the over temperature limit. 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 - The unit attempts to come out of Standby mode, the
protection LED 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. Many amplifier designers include V/I
limiting in the signal path which can degrade the signal by compressing
dynamics. The CAP5 system operates outside the signal path and when
triggered shuts down the amp rather than limits the size of the signal
passing through the amp (signal compression). V/I also protects the
amplifier against short circuits on the speaker terminals during use.
Remedy - The resistance on the loudspeaker terminals is too low. Check
to see if there is a 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 overheat. 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.