LBB 1920/00 Plena Universal Pre-Amplifier

- Four universal low-noise input channels for microphone or line
- Separate tone control, speech filter and direct output per channel
- Selectable blocking, serial and mixing priorities
- Multifunctional inter-connection point
- Priority and emergency relay outputs
- Master volume control

The Plena Pre-Amplifier is a high-performance, versatile four input channel mono mixer pre-amplifier, capable of fulfilling a wide variety of public address requirements.

Functions
All input channels provide a choice of a balanced 3-pin XLR connector for microphone or line level (selectable), a balanced 5-pin DIN-connector for microphone or line level with priority contact, or a line level stereo cinch-connector, converted to mono. Microphone inputs have a phantom power supply. Each input channel has its own volume and tone control, a selectable speech filter to reduce the bass content of the speech signal for improved intelligibility, and a balanced direct output on XLR after the channel controls. Three priority modes are available for the input channels. In the blocking mode the input channel that is activated first gets priority over all other input channels. In the serial mode input channel 1 has priority over channels 2, 3 and 4, channel 2 has priority over channels 3 and 4, and channel 3 has priority over channel 4. Each of the input channels can be mixed to the master output, irrespective of priority, by separately setting that channel to the mixing mode.

Balanced XLR interconnection input and output are provided in combination with an insertion/cascade selector. In insertion mode an external sound processing device, e.g. an equalizer, can be connected between these connections. In the cascade mode, multiple LBB1920/00 pre-amplifiers can be cascaded to increase the number of input channels to 8, 12, or even more. Internally the interconnection input can be switched as an emergency input with a signal level detector (VOX). If an emergency audio signal is detected, this input overrules all other inputs and even bypasses the master volume control. The emergency input has its own internal volume preset.

In order to get a message through (although the local volume may be set to a low volume level for e.g. background music), override relay contacts are provided for overriding local loudspeaker volume controls. Upon closing one of the input channel priority contacts, this relay will be activated. For the emergency input another VOX activated relay is provided to trigger external equipment or for local volume control override. An overload protected 24 VDC output is available to supply power to external relays, so no additional external power supply is required.