Bosch Security Systems | 2006-11 | 9922 141 50751en
Plena Power Amplifier | Installation and User Instructions | Amplifiers en | 9
3 Amplifiers
3.1 Introduction
The Plena Power Amplifier range consists of four mono
amplifiers:
• 120 W LBB1930/20: 2 units high
• 240 W LBB1935/20: 2 units high
• 480 W LBB1938/20: 3 units high
• 1000 W PLN-1P1000: 3 units high.
In this manual all illustrations show either the LBB1938
power amplifier that is 3 units high or the LBB1935
power amplifier that is 2 units high. All connections are
the same between the different power amplifiers.
These power amplifiers have 70 V and 100 V constant
voltage outputs and a low impedance output for 8 Ohm
loudspeakers. Two inputs, priority and input 2 give
priority and controlled outputs. A 100 V slave input
gives connection to existing loudspeaker lines. The line
inputs are balanced and have a loopthrough facility.
The amplifiers have overload and short-circuit
protection. A temperature controlled fan and overheat
protection gives high reliability.
Battery operation with automatic switch-over from the
mains supply is available.
3.2 Controls, connectors and
indicators
3.2.1 Front panel connectors and
indicators
See figure 3.1 for an overview of the indicators:
1 VU meter - LED’s for 20, 6, 0 dB and power ON.
2 Pilot-Tone - Supervised function that monitors a
20kHz pilot tone.
3 Battery - Supervised function to indicate battery
operation.
4 Mains - Supervised function to indicate mains
supply.
5 Overheat - Supervised function to give warning of
overheating.
6 Air inlet - Cooling is made by a forced ventilation
from front to back. Amplifiers can be stacked on top
of each other. A supply of cool air from the front is
necessary.
figure 3.1: Front panel LBB1938/20
0dB
-6 dB
-20 dB
Battery OverheatMainsPilot-Tone
Status
Plena Booster Amplifier
1
3 4 52 6
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