Lab.gruppen LAB 300 - Manual (Page 4)

Please refer to diagram on page 3
1. Speaker
connector
This type of speaker connector may be unfamiliar to
some users. A full description is found in the
operation section. (See page 6).
2. AC line cord (See page 5).
3. Clip limiter switch
Turns the clip limiter on and off. (See page 8).
4. Input
jack
Alternative to using input XLR or for linking inputs
with other amplifiers. (See page 5).
5. Input signal XLR (See page 5).
6. Phase reverse switch for channel B
For reversing the input signal phase of channel B to
allow bridged operation. (See page 7).
7. Link
switch
Allows a single input to drive both channels
simultaneously. (See page 6).
8. Gain select switch
Allows amplifier gain to be switched between 23dB
and its normal gain at 0.775mV input sensitivity.
(See page 7).
Installation
1. Mounting
The amplifier is one rack unit high (1U) and will
mount in a standard EIA 19 inch rack. Amplifiers
may be stacked directly on top of each other. There
is no need for spacing between units. If it is the
intention to fill a rack with amplifiers, we
recommend racking is started from the bottom of
the rack. It is also recommended that rear supports
are used for amplifiers mounted in the middle of the
rack, especially if used as part of a portable system.
2. Cooling
Should a heat sink get too hot, its sensing circuit
will mute the hot channel. If the power supply
overheats, another sensing circuit will mute both
output channels, until it cools down to a safe
operation temperature.
Make sure that there is adequate air supply in the
rack and that the space at the rear allows the
exhaust to escape.
For fixed installations with a central cooling
system, usually found in fixed installations with a
dedicated rack room, it may be necessary to
calculate the maximum heat emission. Refer to
Power consumption on page 5.
3. Operating voltage
A label just below the mains cable on the rear of
the amplifier indicates the AC mains voltage, for
which the amplifier is wired. Connect the power
cable only to the AC source referred to on the label.
The warranty will not cover damage caused by
connecting to the wrong type of AC mains.
For converting a 230 volt amplifier to 115 volt or
vice-versa, see Appendix A.
The amplifier is supplied with an approved European
AC line connector. If this connector is not
appropriate for your country, it can be cut off and
wired to a suitable connector in the following way :
BROWN LIVE
BLUE
NEUTRAL
GREEN/YELLOW EARTH
Once the AC connector is connected to a suitable AC
supply, the amplifier can be started with the AC
actuator.
4. Grounding
There is no ground lift switch or terminal on this
amplifier. The signal ground is always floating via a
resistor to chassis and the grounding system is
automatic. If a potential above 0.6V presents itself
between signal ground and chassis ground, a short
circuit is introduced between the two, thereby
enabling electrical protection. If a unit in the system
is faulty, its mains fuse will blow, due to this
automatic ground system.
If however you wish to tie the signal ground to
chassis, connect the XLR-connector’s shell lug to
pin 1. In the interest of safety never disconnect the
earth pin on the AC cord.
For all units that are EMC approved (radio
interference), there is an AC mains filter. This filter
needs the chassis ground for reference, otherwise a
current loop is formed via the signal ground.
Use the balanced input to avoid hum and
interference.
5. Power consumption
There are three ways to determine the
power/current consumption of the amplifier:
First, the peak current draw at full output
power. Under this condition the power will trip the
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