PLENA power amplifier LBB1938/20 Architects’ and Engineers’ Specifications
PLENA power amplifier LBB1938/20 Architects’ and Engineers’ Specifications The power amplifier shall have a nominal output power of 480Watts RMS. It shall operate on 230VAC and shall have its source power supplied by a detachable IEC power cord. In addition the unit shall be capable of being directly powered by a 24Vdc source, such as storage batteries. It shall have an On/off button on the rear panel; to prevent inadvertent power down. Supervision shall be implemented for functioning of the amplifier, overheat, power supply (both mains and 24VDC back-up power) and pilot tone. Three relays shall be provided on the rear panel for each supervised function. The relays shall be normally energized (fail safe) and have three contacts each (normally open, common, normally closed). The supervised functions shall be indicated on the front panel with four LED’s: Pilot tone, Battery supply, Mains power and Overheat. If supervision is not necessary, it shall be possible to switch off the indicators on the front panel by switches next to the relay outputs (to prevent the fault indicators from lighting up continuously). The relays shall always function regardless of the settings of these switches. The pilot tone supervision shall monitor the presence of a 20kHz (± 20%) pilot tone. The pilot tone level input shall be between 50 – 150mV, typically 100mV -20dBV for input, and thus -20dB ref max power. The amplifier shall fit in an IEC 60849 compliant system. Pilot tone supervision shall be done after the power stage at the loudspeaker line connections, thus monitoring the correct functioning of the amplifier. The unit shall have 70V and 100V constant voltage outputs. It shall also have a low impedance output to drive an 8 Ohm load. Loudspeaker connections shall be on a terminal strip with safety insulation. The amplifier shall be protected against overload and short circuit. The unit shall have two balanced line level inputs with priority control, using 3-pin female XLR connectors and also have balanced line level loop through outputs, using 3-pin male XLR connectors, to facilitate easy connection of multiple power amplifiers. The unit shall have a 100V line input on a terminal strip to facilitate the power amplifier to be connected to 100V loudspeaker lines on remote locations. Additionally the amplifier shall have two separate priority controlled 100V outputs for zones that only need announcements made via the priority input, and for zones that will not get any announcements made via the priority input. The power amplifier shall have two (for both inputs) continuously variable rotary controls for setting its sensitivity at the rear side of the unit to avoid accidental setting change. A LED VU-meter shall allow for monitoring of the output level. The unit shall have an operating temperature range of –10 to +55C and shall have forced air cooling from front to back, with a built-in temperature controlled forced fan from front to back. The unit shall be 19”-wide and 3U-high. Brackets for 19”-mounting shall be included. The unit shall comply to EN55103-1 and EN55103-2 for EMC emission and immunity. The power amplifier shall be a Plena model LBB1938/20, manufactured by Bosch Security Systems. 922 141 50522 en 03-40 © 2003 Robert Bosch GmbH Data subject to change without notice.
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