5.3 Cooling
The amplifier uses a forced-air cooling system with
air flow from front to rear, maintaining a low operating
temperature within defined limits. Front-to-rear air-
flow is preferred as cooler air is present at the front in
nearly all applications. (This allows higher continuous
power levels without encountering thermal problems.)
Never attempt to reverse the airflow. The amplifier
modules require a pressure chamber between the
fans and heatsink, and this effect functions only in
one direction.
Make sure that there is an adequate air supply in front
of the amplifier, and that the rear of the amplifier has
sufficient space to allow the exhaust to escape. If
the amplifier is rack-mounted, do not use covers or
doors on the front or rear of the rack.
Should a heat sink overheat, the temperature
sensing circuits will mute the overheating channel.
If the power supply overheats, another sensing
circuit will mute all output channels until the power
supply cools to safe operating temperature. An early
warning before shut down will be indicated on the
front-panel LEDs, and a warning will be sent through
the NomadLink network.
Always make sure that the dust-filters behind the
detachable front-panel are clean to ensure maximum
possible airflow.
If the amplifier malfunctions due to dirty
dust filters, any required repairs are not
covered by the warranty.
5.4 Operating voltage
The label placed to the right of the mains
cable on the rear of the amplifier indicates the
AC mains voltage for which the amplifier is wired
and approved: 115 V or 230 V. Connect the power
cable only to the AC source type referred to on the
label. The warranty will not cover damage caused by
connecting to an incorrect type of AC mains.
Lab.gruppen switch mode amplifiers use primary
switching. Because the mains power is rectified
directly in front of the transformer, the amplifier is
insensitive to mains frequency. It may be connected
to 50 or 60Hz sources, and actually will operate on
line frequencies from DC to 400 Hz.
If the power plug mounted at the factory is not
appropriate for your country, it can be removed and
the proper connector wired in its place as follows:
BLACK or BROWN LIVE
WHITE or BLUE NEUTRAL
GREEN or GREEN/YELLOW EARTH(GROUND)
If you are not 100% confident of your
competence to replace the mains plug, engage
qualified personnel to do the job.
Once a suitable AC supply is connected, the
amplifier can be turned on using the front-panel
power switch. The amplifier then goes through a
soft-start sequence as it self-checks its circuits. The
fans will blow at high speed before dropping to idle,
and the “power” LED will illuminate.
Inrush power is controlled and limited during “soft-
start”, enabling multiple amplifiers to be powered up
simultaneously.
5.5 Grounding
There is no ground lift switch or terminal on the
FP+ Series amplifiers. The signal ground is always
floating, via a resistor, to chassis and therefore the
grounding system is automatic.
In the interests of safety, never disconnect the earth
(ground) pin on the AC power cord.
Use balanced input connections to avoid hum and
interference.
INsTALLATION 5
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