Bosch F.01U.024.957 Datasheet
Communications Systems | LBB 1935/20 Plena Power Amplifier
LBB 1935/20 Plena Power Amplifier
240 W power amplifier in a 2U high housing
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70 V / 100 V and 8 ohm outputs
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Dual inputs with priority switching
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100 V input for slave operation on 100 V speaker line
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Temperature controlled forced front to back
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ventilation, directly stackable
Mains, battery back-up, and pilot tone supervision
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TÜV certified according to IEC 60849
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The LBB 1935/20 is a powerful 240 W power amplifier in a
2U 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 highperformance unit fulfills a wide range of public address
requirements at a surprisingly low cost.
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.
The unit operates both on mains power and on a 24 V
battery power supply for emergency back up, with
automatic switchover.
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 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.
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 LBB 1935/20 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 receive
announcements made via the priority input.
Controls and indicators
Front
Meter (LED's for -20, -6, 0 dB and Power ON)
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Battery operation indicator
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Overheat indicator
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2 | LBB 1935/20 Plena Power Amplifier
Back
Level control input 1
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Level control input 2
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Power button
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Mains switch
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Interconnections
Back
Priority line input 1 (XLR/balanced)
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Line loop-through 1 (XLR/balanced)
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Program line input 2 (XLR/balanced)
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Line loop-through 2 (XLR/balanced)
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Priority controlled loudspeaker output terminals
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24 VDC power supply terminal
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Three loudspeaker direct output terminals
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Two 100 V slave input terminals
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Input 2 enable control terminal
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Input 1 priority control terminal
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Earth connection screw
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Mains socket
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Certifications and Approvals
Region Certification
Europe CE
Safety acc. to EN 60065
Immunity acc. to EN 55103-2
Emission acc. to EN 55103-1
EVAC (TÜV certified) acc. to IEC 60849
Parts Included
Quantity Component
1 LBB 1935/20 Plena Power Amplifier
1 Power cord
1 Set of 19" mounting brackets
1 Installation and User Instructions
1 Cable with XLR connector
Technical Specifications
Electrical
Mains power supply
Voltage 230 VAC, ±10%, 50/60 Hz
Inrush current 9 A
Max power consumption 760 VA
Battery power supply
Voltage 24 VDC +15% / -15%
Current max 11 A
IEC 60849
Mains power supply
Performance
Output power (rms/maximum) 240 / 360 W
Power reduction on backup pow-er-1 dB
Frequency response 50 Hz to 20 kHz (+1 / ‑3 dB at ‑10 dB ref.
rated output)
Distortion <1% at rated output power, 1 kHz
S/N (flat at max volume) >90 dB
Line inputs 2 x
Connector 3-pin XLR, balanced
Sensitivity 1 V
Impedance 20 kohm
CMRR >25 dB (50 Hz to 20 kHz)
Gain 40 dB
100 V input
Connector Screw, unbalanced
Sensitivity 100 V
Impedance 330 kohm
Line loop-through output 2 x
Connector 3-pin XLR
Nominal level 1 V
Impedance Direct connection to line input
Loudspeaker outputs 3 x
Connector Screw, floating
Direct output 100 V, 70 V, 8 ohm
Priority only (from input 1) 100 V or 70 V internally selectable
Music (non-priority) only 100 V or 70 V internally selectable
Power consumption
Mains operation
Max power 451 W
-3dB 340 W
-6dB 244 W
Pilot tone* 55 W
Idle 16 W
24 V operation
Max power 12.1 A (290 W)
-3 dB 11.4 A (274 W)
-6 dB 8.1 A (194 W)
Pilot tone* 1.7 A (41 W)
Idle 0.3 A (7 W)
* 20 kHz -20dB with maximum loudspeaker load
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