Bosch PRAESENSA Installation Manual page 92

92 en | Amplifier, 600W 8-channel | PRA-AD608
Loop (A to B)
A third loudspeaker connection topology is the so-called Class‑A loop, where the loudspeakers
are connected in a loop, starting at output A and ending at output B, with the end of the loop
being supervised with an end‑of‑line device.
In normal operation the loop is driven from output A only. In case of an interruption of the
loudspeaker line, this will result in the loudspeaker signal not arriving at output B and neither
at the end‑of‑line device. The disconnection of the end‑of‑line device will be detected at
output A, and as a result output B will be activated to drive the loop from the opposite side in
an attempt to reach all loudspeakers again. A loudspeaker line fault will be reported.
Follow the procedure below to connect the loudspeakers according to this scheme:
1.
2.
3.
Notice!
Unlike the 4‑channel amplifier, the outputs of the 8‑channel amplifier use 4‑pole connectors
without separate terminals for the end‑of‑line device.
Do not replace the 4‑pole plug by two 2‑pole plugs for outputs A and B separately, because
then it is possible that plug B gets disconnected from the amplifier, while the end‑of‑line
device remains connected to the loudspeaker line and no fault is being reported, until an
interruption occurs in the loop. Only then it will appear that the loudspeaker line after the
interruption cannot be driven from output B anymore. When the 4‑pole plug for outputs A and
B combined would get unplugged unintentionally, then both outputs A and B would be
disconnected together with the end-of-line device and a fault would be reported immediately.
2019.11 | V1.00 |
Connect all loudspeaker in parallel in a loop‑through fashion. Observe equal polarity for
all loudspeakers. Connect one side of the loudspeaker cable to output A, observing
polarity.
Connect the other side of the loudspeaker cable to output B. In this case maintaining the
correct polarity is especially important, as reversal on one end will short circuit the
amplifier channel, not immediately, but when output B is activated in case of interruption
of one conductor.
Connect an end‑of‑line device to output B, in parallel with the loudspeaker cable.
Installation manual
PRAESENSA
Bosch Security Systems B.V.