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. 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 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 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 LEDbar 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 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.Controls and indicators Front •Meter (LED's for -20, -6, 0 dB and Power ON) •Battery operation indicator •Overheat indicator •Air inlet for forced air cooling Back •Level control input 1 •Level control input 2 •Power button •Mains switch Interconnections Back •Priority line input 1 (XLR/balanced) •Line loop-through 1 (XLR/balanced) •Program line input 2 (XLR/balanced) •Line loop-through 2 (XLR/balanced) •Priority controlled loudspeaker output terminals •24 VDC power supply terminal •Three loudspeaker direct output terminals •Two 100 V slave input terminals •Input 2 enable control terminal •Input 1 priority control terminal •Earth connection screw •Mains socket Certifications and approvals Safetyacc. to EN 60065 Immunityacc. to EN 50130‑4 Emissionacc. to EN 55103‑1 Emergencyacc. to EN 54‑16 / EN 60849 RegionCertification EuropeCE CPD PolandCNBOP Parts included QuantityComponent 1LBB 1938/20 Plena Power Amplifier 1Power cord 1Set of 19" mounting brackets 1Installation and User Instructions Technical specifications Electrical Mains power supply Voltage230 VAC, ±10%, 50/60 Hz Inrush current19 A Max power consumption2200 VA Battery power supply Voltage24 VDC +15% / -15% Current max30 A Performance Output power (rms/maximum)480 W / 720 W Power reduction on backup power-1 dB Frequency response50 Hz to 20 kHz (+1/‑3 dB @ ‑10 dB ref. rated output) Distortion<1% @ rated output power, 1 kHz S/N (flat at max volume)>90 dB Line inputs2 x Connector3-pin XLR, balanced Sensitivity1 V Impedance20 kohm CMRR>25 dB (50 Hz to 20 kHz) Gain40 dB 100 V input ConnectorScrew, unbalanced Sensitivity100 V Impedance330 kohm Line loop-through output2 x Connector3-pin XLR Nominal level1 V ImpedanceDirect connection to line input Loudspeaker outputs3 x ConnectorScrew, floating Direct output100 V, 70 V, 8 ohm Priority only (from input 1)100V or 70 V internally selectable Music (non-priority) only100V or 70 V internally selectable Power consumption Mains operation Max power990 W-3dB715 W-6dB510 W Pilot tone*110 W Idle25 W 24 VDC operation Max power32 A (770 W) 2 | LBB 1938/20 Plena Power Amplifier3 | LBB 1938/20 Plena Power Amplifier-3 dB 26 A (625 W)-6 dB 18 A (430 W) Pilot tone* 3.8 A (91 W) Idle 0.7 A (17 W) * 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 Approx. 25 kg Mounting Standalone, 19”rack Color Charcoal Environmental Operating temperature-10 ºC to +55 ºC (14 ºF to +131 ºF) Storage temperature-40 ºC to +70 ºC (-40 ºF to +158 ºF) Relative humidity <95% Acoustic noise level of fan Ordering information <48 dB SPL @ 1 m (max output) LBB 1938/20 Plena Power Amplifier 480 W power amplifier in a 3U high 19”case for rack