Bosch Plena Power Amplifier LB1935 - User Manual

Communications Systems | LBB 1930/20 Plena Power Amplifier
The LBB 1930/20 is a powerful 120 W power amplifier in a
2U high 19” case for rack mounting or tabletop use. LEDs
on the front panel show the status of the amplifier:
power, audio output level, and supervised functions. This
high-performance unit fulfills a wide range of public
address requirements at a surprisingly low cost.
Functions
Dependability
The amplifier is protected against overload and short
circuits. A temperature-controlled fan ensures high
reliability at high output levels and low acoustic noise at
lower output levels. An overheat protection circuit
switches off the power stage and activates an LED on the
front panel, if the internal temperature reaches a critical
limit due to poor ventilation or overload.
The unit operates both on mains power and on a 24 V
battery power supply for emergency back up, with
automatic switchover.
For emergency and evacuation use, the following
functions are monitored: mains presence, battery present,
pilot tone presence, amplifier operation. Front panel LEDs
indicate the status of supervised functions. The LEDs of
pilot tone supervision and battery status can be switched
off for general public address use. Failsafe (normally
energized) relays are provided for each supervised
function. These relays are always active regardless of the
switches on the rear panel.
Input
The system has two balanced inputs with priority control,
each with a loop-through facility. This makes it easy to
connect remote systems that require priority control. An
additional 100 V line input is provided to connect the
amplifier to a 100 V loudspeaker line to provide more
power to remote locations.
Gain or level control is located on the rear of the unit to
avoid accidental setting change. A meter with LED-bar
shows the output level.
Output
The amplifier has 70 V and 100 V outputs for constant
voltage loudspeaker systems, and a low impedance output
for 8 ohm loudspeaker loads.
The LBB 1930/20 has two separate priority controlled 100
V outputs for zones that only need announcements made
via the priority input, and for zones that will not receive
announcements made via the priority input.
Controls and indicators
Front
•
Meter (LED's for -20, -6, 0 dB and Power ON)
•
Battery operation indicator
•
Overheat indicator
LBB 1930/20 Plena Power Amplifier
▶
120 W power amplifier in a compact housing
▶
70 V / 100 V and 8 ohm outputs
▶
Dual inputs with priority switching
▶
100 V input for slave operation on 100 V speaker line
▶
Temperature controlled forced front to back
ventilation, directly stackable.
▶
Mains, battery back-up and pilot tone supervision
▶
EN 54‑16 and EN 60849 compliant
www.boschsecurity.com

Bosch Plena Power Amplifier LB1935 Specifications

General

Brand	Bosch
Model	Plena Power Amplifier LB1935
Category	Amplifier
Language	English

Summary

Introduction

Manual Purpose and Scope

Defines the goal and scope of the Installation and User Instructions.

Digital Document Information

States availability of instructions in PDF format with hyperlinks.

Intended Audience and Related Docs

Identifies users and lists related documentation for the Plena system.

Alert and Sign Conventions

Explains alert types (Note, Caution, Warning, Danger) and safety signs.

System Overview

Plena Product Range Overview

Overview of the Plena system as a family of elements for PA solutions.

Amplifiers

Plena Amplifier Range Introduction

Introduces the Plena Power Amplifier series and their shared features.

Front Panel Controls and Indicators

Details the indicators and controls found on the amplifier's front panel.

Rear Panel Connectors and Indicators

Details the connectors and indicators found on the amplifier's rear panel.

Internal Fuse Settings for Voltage Output

Explains how to select output voltage (70 V or 100 V) using internal fuses.

Installation and Mounting Options

Covers suitability for table-top and 19-inch rack-mounting installations.

Connecting Back-up Power Supply

Instructions for connecting a 24 Vdc back-up power supply for emergency use.

Line Input and Loopthrough Connections

Describes connecting line inputs and using loopthrough for cascading amplifiers.

Priority Input and Control Terminal Usage

Explains priority input connection and control terminals for zoning and muting.

100 V Slave Input Connection

Details connecting the amplifier to an existing 100 V loudspeaker line.

Constant Voltage Loudspeaker Connections

How to connect 100 V and 70 V constant voltage loudspeakers.

Low Impedance Loudspeaker Connections

How to connect 8 Ohm low impedance loudspeakers.

Mains Power Connection

Instructions for connecting the amplifier to the mains power supply.

Supervision

Input Pilot Tone Supervision

Supervises pre-amplifier, connections, and amplifier function via pilot tone.

Battery Supervision

Monitors the availability and status of the back-up power supply.

Mains Supply Supervision

Supervises the availability of the main power supply.

Operation

Amplifier Power On and Off

Instructions for powering the amplifier on and off using the rear switch.

Technical Data: Electrical, Performance, Inputs

Details electrical, performance, input, and environmental specifications.

Technical Data: Outputs, General, Dimensions

Covers loudspeaker outputs, general EMC, acoustic noise, dimensions, and weight.

Power Consumption Details

Provides detailed power consumption figures for various operating conditions.