Cap5 - Fiveway Protection System - Cambridge Audio AZUR 851A User Manual

CAP5 - Fiveway protection system

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. Note: Due to the required sensitivity of the CAP5
system, it is possible that mains power disturbances can falsely trigger
CAP5 in extreme situations. This protection system comprises of five
main protection methods:
1. DC detection
Indication - Unit has switched off during operation, display flashes
"DC ERROR". Press the INFO input select button for a brief on-screen
description and remedy, or read below for more information.
Mode
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,
extremely hard clipping of the amplifier may cause DC protection to be
triggered. If this fault occurs press the RESET input select button, then
press the Standby/On button to 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
Indication - Unit has switched off during operation, display flashes
"OVER TEMP". Press the INFO input select button for a brief on-screen
description and remedy, or read below for more information.
Mode
Description - Over temperature is caused by a combination of high
listening levels and low impedance speakers. 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 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. Press the RESET
input select button and leave the unit for 15 minutes to cool down before
pressing the Standby button to resume normal operation.
3. Overvoltage/overcurrent detection
Description - CAP5 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.
12
4. Short circuit detection
Indication - Unit has not come out of Standby, display flashes "SPKR
SHORT". Press the INFO input select button for a brief on-screen
description and remedy, or read below for more information.
Mode
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 (display flashes "SPKR CHECK"). If the
resistance measured across the loudspeaker terminals is too low the
unit will stay in Standby mode until the fault has been removed and
Power up is re-attempted (display flashes "SPKR SHORT").
Volume
Remedy - User related fault. There may be a short circuit between the
loudspeaker terminals. Press the RESET input select button and check
all loudspeaker connections before attempting to switch the unit out of
Standby (display will flash "SPKR CHECK" then "SPKR OK" when short
circuit fixed).
It is possible to disable the short circuit detection feature by pressing the
SHORT DT button to off when in the 851A System Configure menu, but
it is not recommended. This would only be required if the loudspeakers
have very low DC resistance.
5. Intelligent clipping detection
Indication - Volume is reduced automatically, "CLIPPING" appears on the
front panel display.
Mode
Description - CAP5 has the ability to detect when the amplifier starts
to clip or overdrive at its output, which can damage loudspeakers, and
Volume
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 CAP5 detects clipping the volume will be automatically reduced
down until CAP5 detects an undistorted output.
It is possible to disable the clipping detection feature by pressing the
CLIP DT button to off when in the 851A System Configure menu.
Note: Disabling the clipping detection is not advised as this feature has
been added deliberately to protect the amplifier and loudspeakers.
Volume
Volume