Bosch LBB 1914/10 - User Manual

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Communications Systems | LBB 190x/10 and LBB 191x/10 Plena Mixer Amplifiers

The Plena mixer amplifier is a versatile, high-performance

unit with four mono microphone inputs and a music input.

It fulfills a wide variety of public address requirements at

a surprisingly low cost.

Functions

All input channels have a phantom power supply to

provide power to condenser microphones and selectable

speech filters for improved intelligibility. Input channels 3

and 4 can also be switched to line sensitivity. Separate

music inputs are available with their own input selector

and volume control.

Input channel 1 can take priority over all other

microphone and music inputs. Contact closure on the 5-

pin DIN connector, or if the signal level on channel 1

exceeds a predefined value (VOX) will activate priority. A

2-tone chime can be configured to precede a priority

announcement. A telephone or emergency input with VOX

activation and its own preset volume control overrides all

other input.

Loop through input and output connections enable

external sound processing equipment, such as an

equalizer or the Plena feedback suppressor, to be

connected between the preamplifier and the power

amplifier stages. An LED VU-meter monitors the master

output. The unit also has a tape output channel.

The Plena mixer amplifiers come in a range of maximum

output power. This power is directly available on 70 V and

100 V constant voltage connections and on a low

impedance connection for an 8 ohm load. Moreover, the

amplifiers have a separate 70 V / 100 V call-only output

channel for addressing areas where only priority

announcements are required, and a 70 V / 100 V mix-only

output channel for areas where no priority

announcements should be heard. The call-only output can

also be used for 3-wire remote, volume control override.

For more output power than the built-in power stage can

deliver, additional Plena power amplifiers can be

connected to the balanced line output in a loop-through

arrangement.

The LBB 1914/10 offers the same functionality as the

LBB 1912/10 but also has two front-panel switches to

direct the amplifier output to two separate zones. This is

useful when certain announcements or background music

should not be heard in part of a building. Priority calls,

however, are always routed to both zones.

LBB 190x/10 and LBB 191x/10 Plena

Mixer Amplifiers

▶

Range of single and dual zone mixer amplifiers from

30 W to 120 W

▶

Four low-noise balanced inputs for microphone or line

▶

Selectable priority & VOX switching on microphone

input 1

▶

Optional 2-tone chime to precede announcements

▶

VOX activated emergency override

▶

Outputs for normal, call-only and mix-only zones

▶

Choice of CD, tuner or auxiliary music inputs

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Bosch LBB 1914/10 Specifications

General

Number of Channels	2
Frequency Response	50 Hz - 20 kHz
Damping Factor	>100
Input Impedance	10 kΩ
Input Sensitivity	100 mV
Mains Voltage	100 - 240 V AC, 50/60 Hz
Power Consumption	30 W
Signal-to-Noise Ratio	> 70 dB
Outputs	2 x speaker terminals
Total Harmonic Distortion	< 0.5 %
Output Impedance	4 Ω
Power Supply	100 - 240 V AC, 50/60 Hz