Bosch Appliances Stereo Amplifier LBB 1938 20 User Manual

Communications Systems | LBB 1938/20 Plena Power Amplifier  
LBB 1938/20 Plena Power Amplifier  
u 480 W power amplifier in a 3U high 19”housing  
u EN 54‑16 certified and EN 60849 compliant  
u 70 V / 100 V and 8 ohm outputs  
u Dual inputs with priority switching  
u 100 V input for slave operation on 100 V speaker  
line  
The LBB 1938/20 is a powerful 480 W power amplifier  
in a 3U 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.  
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.  
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.  
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 unit operates both on mains power and on a 24 V  
battery power supply for emergency back up, with  
automatic switchover.  
The LBB 1938/20 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 get any announcements made via  
the priority input.  
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  
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3 | LBB 1938/20 Plena Power Amplifier  
-3 dB  
26 A (625 W)  
18 A (430 W)  
3.8 A (91 W)  
0.7 A (17 W)  
-6 dB  
Pilot tone*  
Idle  
* 20 kHz -20dB with maximum loudspeaker load  
Mechanical  
Dimensions (H x W x D)  
145 x 430 x 370 mm  
(19" wide, 3U high, with feet)  
Weight  
Mounting  
Color  
Approx. 25 kg  
Standalone, 19”rack  
Charcoal  
Environmental  
Operating temperature  
Storage temperature  
-10 ºC to +55 ºC (14 ºF to +131 ºF)  
-40 ºC to +70 ºC (-40 ºF to  
+158 ºF)  
Relative humidity  
<95%  
Acoustic noise level of fan  
<48 dB SPL @ 1 m (max output)  
Ordering information  
LBB 1938/20 Plena Power Amplifier  
480 W power amplifier in a 3U high 19”case for rack  
mounting or tabletop use.  
Order number LBB1938/20  
Represented by:  
Americas:  
Europe, Middle East, Africa:  
Bosch Security Systems B.V.  
P.O. Box 80002  
5617 BA Eindhoven, The Netherlands  
Phone: + 31 40 2577 284  
Fax: +31 40 2577 330  
Asia-Pacific:  
Robert Bosch (SEA) Pte Ltd, Security  
Systems  
11 Bishan Street 21  
Singapore 573943  
Phone: +65 6571 2808  
Fax: +65 6571 2699  
China:  
America Latina:  
Bosch Security Systems, Inc.  
12000 Portland Avenue South  
Burnsville MN 55337, USA  
Phone: +1-800-392-3497  
Fax: +1-800-955-6831  
Bosch (Shanghai) Security Systems Ltd. Robert Bosch Ltda Security Systems Division  
201 Building, No. 333 Fuquan Road  
North IBP  
Changning District, Shanghai  
200335 China  
Phone +86 21 22181111  
Fax: +86 21 22182398  
Via Anhanguera, Km 98  
CEP 13065-900  
Campinas, Sao Paulo, Brazil  
Phone: +55 19 2103 2860  
Fax: +55 19 2103 2862  
© Bosch Security Systems 2012 | Data subject to change without notice  
1889273995 | en, V2, 24. Nov 2012  
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