User’s Manual
9 17
11. Protection Systems
In addition to the usual protection consisting of
fuses, these products are complete of different
protection devices in order to safeguard them
from possible risks of damage. Protection
conditions are signalled by the fact that the PROT
(6) signalling lamp located on the front panel of
the equipment will light (Short Circuit excluded),
the unit will stop working and only the fan will
continue to run.
11.1. Power Output Short Circuit
Applying a lower loading impedance than the
rated value means requiring the equipment to
supply a power higher than it can do on a
continuous basis.
In order to avoid this problem, the units are
equipped with a circuit protecting them against
overloads that protects automatically.
The protection circuit will be tripped immediately
on the amplifier if any of the following cases
occurs:
•
Short circuit on one of the loudspeaker
outputs.
•
Loading impedance less
than 50%
of the
rated value.
•
power required of the loudspeaker system
connected to the constant-voltage lines higher
than the power that the amplifier is able to
deliver.
Overload conditions are signalled by the fact that
the unit doesn’t supply any amplified signal at the
power output.
The equipment will resume normal operation after
a power cycle as soon as the cause of the
overload has been eliminated.
11.2. Turn On / Turn Off Delay
A mute circuit with relay, with a delayed starting
up and immediate power turning off, has been
inserted in order to avoid the switch-on/turn-off
transients that may cause damage to the
loudspeakers.
11.3. Power Unit Over Temperature
The thermal protection is of the self-resetting type,
and is tripped when the equipment reaches an
excessively high temperature.
This may be due, for example, to the fact that the
ambient temperature is too high or to the
insufficient ventilation of the rack cabinet.
The equipment will resume normal operation as
soon as the cause of the temperature overload
has been eliminated.
11.4. Power Supply Over Voltage
The A.C. voltage is monitored; if its value does not
fall within the correct running range (over voltage)
the supply will be automatically blocked. The
amplifier will restart when the main supply voltage
is under the maximum running voltage.
11.5. Power Supply Soft Start
The units are provided with a soft-start system to
reduce the inrush current when switched on. This
feature is particularly useful in multiple devices
installations.
12. Advanced Functions
12.1. Noise Gate
A Noise Gate circuit has been inserted for each
input channel in order to minimize the background
noise on the output when no signal is applied at
the input. The channel opening threshold could be
adjusted through the controls (1) located on the
front panel of the equipment. The Fig6 shows
available internal setting for the noise gate circuit.
12.2. Remote
The remote master volume level control for each
output channel is available if the C656-RJ Remote
control optional cards is used. The figure Fig6.
shows
the
C656-RJ
insertion
operation.
Connection with the female RJ45 socket (26)
must be via shielded cable without section
limitations for distances up to 150 mt.
The figure
Fig5. shows the connections to these sockets.
An
external pot (10K) can be connected for remote
master volume level control for each output
channel or a switch for the mute control. The
external pot is governed by the master level of the
amplifier allowing the installer to set the volume,
then lock the amplifier in a rack, leaving the user
with just a master volume control that cannot go
beyond the level set on the master control.
C10K
MAX
MIN
NC=ON
NO=OFF
SHIELD
PRIORITY
1 2 3 4 5 6 7 8
1
2
3
4
5
6
7
8
GND= 2,4,8
VCA MASTER 1= 7
VCA MASTER 2= 1
PRIORITY= 5
Fig5. Remote Socket Pin-out
