The fast route to safety
PLENA Public Address and Voice Alarm System
PLENA voice alarm components
LBB1935/20 PLENA 240 W Power Amplifier
240 W power amplifier in a 2U housing for the PLENA system: 70 V / 100 V and 8 ohm outputs, dual inputs with priority switching, 100 V input for slave use.
- 240 W Output
- 70 V / 100 V and 8 Ohm
- Dual Inputs Priority Switching
The fast route to safety
PLENA Public Address and Voice Alarm System
PLENA voice alarm components
LBB1935/20 PLENA 240 W Power Amplifier
240 W power amplifier in a 2U housing for the PLENA system: 70 V / 100 V and 8 ohm outputs, dual inputs with priority switching, 100 V input for slave use.
- 240 W Output
- 70 V / 100 V and 8 Ohm
- Dual Inputs Priority Switching
BOSCH · PLENA VOICE ALARM
Bosch LBB1935/20 Front Panel
Select Zoom to inspect the amplifier’s front-panel labels.
BOSCH · PLENA VOICE ALARM
Bosch LBB1935/20 Front Panel
Select Zoom to inspect the amplifier’s front-panel labels.
Key specs
- Rated output: 240 W RMS
- Speaker outputs: 70 V / 100 V / 8 Ω
- Audio inputs: 2 balanced XLR inputs with priority switching
- Expansion input: 100 V loudspeaker line input
- Backup power: 24 V DC with automatic switchover
- Certification: EN 54-16
Bosch LBB1935/20 Technical Specifications
The Bosch LBB1935/20 is a 240 W RMS PLENA power amplifier with two balanced inputs, priority switching, and loudspeaker outputs for 70 V, 100 V, and 8 Ω systems.
Electrical
| Specification | Value |
|---|---|
| Mains supply | 230 V AC, ±10%, 50/60 Hz |
| Mains inrush current | 9 A |
| Maximum apparent power | 760 VA |
| Backup supply voltage | 24 V DC, ±15% |
| Battery supply maximum current | 11 A, as listed under Battery Power Supply |
| Backup switchover | Automatic when mains power fails |
Amplifier Performance
| Specification | Value |
|---|---|
| Rated output power | 240 W RMS |
| Maximum output power | 360 W |
| Output reduction on backup power | −1 dB |
| Frequency response | 50 Hz to 20 kHz (+1/−3 dB at −10 dB relative to rated output) |
| Distortion | <1% at rated output power, 1 kHz |
| Signal-to-noise ratio | >90 dB at maximum volume, flat |
Audio Inputs
| Specification | Value |
|---|---|
| Balanced line inputs | 2 × 3-pin XLR |
| Input assignment | Input 1 for priority audio, Input 2 for programme audio |
| Line input sensitivity | 1 V |
| Line input impedance | 20 kΩ |
| Line input common-mode rejection | >25 dB from 50 Hz to 20 kHz |
| Line input gain | 40 dB |
| 100 V line input | Unbalanced screw terminals for connection to a 100 V loudspeaker line |
| 100 V input sensitivity | 100 V |
| 100 V input impedance | 330 kΩ |
Audio Outputs
| Specification | Value |
|---|---|
| Line loop-through outputs | 2 × 3-pin XLR, directly connected to the respective line inputs |
| Loop-through nominal level | 1 V |
| Loudspeaker outputs | 3 output groups with floating screw terminals |
| Direct loudspeaker output | 100 V, 70 V, or 8 Ω |
| Priority-only output | Carries priority audio from Input 1. Internally selectable for 100 V or 70 V. |
| Non-priority output | Carries programme audio. Internally selectable for 100 V or 70 V. |
Controls, Supervision and Protection
| Specification | Value |
|---|---|
| Rear-panel control terminals | Input 1 priority control and Input 2 enable |
| Rear-panel level adjustment | Separate level controls for Inputs 1 and 2 |
| Front-panel output meter | LEDs at −20 dB, −6 dB, and 0 dB |
| Front-panel status indicators | Power, pilot tone, battery, mains, and overheat |
| Supervised functions | Mains supply, backup battery, pilot tone, and amplifier operation |
| Fault signalling | Normally energized fail-safe relays |
| Amplifier protection | Overload, short circuit, and thermal shutdown |
| Cooling | Temperature-controlled fan |
Power Consumption
| Specification | Value |
|---|---|
| AC operation, maximum | 451 W |
| AC operation at −3 dB / −6 dB | 340 W / 244 W |
| AC operation with pilot tone / idle | 55 W / 16 W |
| 24 V DC operation, maximum | 12.1 A (290 W), as listed under Power Consumption |
| 24 V DC operation at −3 dB / −6 dB | 11.4 A (274 W) / 8.1 A (194 W) |
| 24 V DC operation with pilot tone / idle | 1.7 A (41 W) / 0.3 A (7 W) |
| Pilot-tone test condition | 20 kHz at −20 dB with maximum loudspeaker load |
Mechanical
| Specification | Value |
|---|---|
| Dimensions (H × W × D) | 100 × 430 × 270 mm, including feet |
| Mounting | 19-inch rack or tabletop |
| Rack height | 2U |
| Weight | Approx. 12.5 kg |
| Colour | Charcoal |
Environmental
| Specification | Value |
|---|---|
| Operating temperature | −10 °C to +55 °C |
| Storage and transport temperature | −40 °C to +70 °C |
| Relative humidity | <95% |
| Fan noise | <48 dB SPL at 1 m at maximum output |
Standards
| Specification | Value |
|---|---|
| Voice alarm certification | EN 54-16 |
| Safety | EN 60065 |
| Immunity | EN 50130-4 |
| Emissions | EN 55103-1 |
Questions & answers
Know before you buy
Quick answers about the LBB1935/20, and how it compares.
What is the Bosch LBB1935/20?
The Bosch LBB1935/20 is a 240 W RMS PLENA power amplifier for public address and voice alarm systems. It provides loudspeaker power for announcements, evacuation messages, and background music.
Which loudspeakers can I connect to the Bosch LBB1935/20?
The amplifier supports 70 V and 100 V constant-voltage loudspeaker systems, as well as 8 Ω low-impedance loudspeaker loads. The output must match the loudspeaker system.
Can the Bosch LBB1935/20 work with the PLENA LBB1990/00 controller?
Yes. Bosch’s PLENA manual shows the LBB1935/20 paired with the LBB1990/00 for two-channel operation. In that setup, background music can continue in zones that are not receiving an announcement.
Can an announcement override background music on this amplifier?
Yes. The LBB1935/20 has two balanced audio inputs with priority switching. When Input 1 is activated as the priority input, its announcement can take precedence over programmed audio on Input 2.
Will the Bosch LBB1935/20 keep working during a power outage?
Yes, when a suitable external 24 V DC backup supply is connected. The amplifier switches to backup power automatically if mains power fails.
Can the Bosch LBB1935/20 add power to an existing 100 V loudspeaker system?
Yes. Its dedicated 100 V line input accepts audio from an existing 100 V loudspeaker line. The amplifier can then power a separate loudspeaker load in another area.
Who is the authorized Bosch distributor in Pakistan?
ESCO (Electronic Security Company) is an authorized Bosch distributor in Pakistan. Contact ESCO to check the current Bosch LBB1935/20 price and availability or request a project quotation.