Railroad Car PA Amplifier
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OP98X Description
- Ambient noise sensing automatic level adjusting PA amplifier
- Meets all needs for long-term performance in public transportation
- PA systems
- Drives multiple loudspeakers over wide acoustical, electrical,
- mechanical and environmental conditions
- 120 watt audio output
- 70 volt system and 8 ohm
- 4 logic controlled output zones
- Over 2500 Installed on NYC MTA
Built and tested for metropolitan subway cars, the OP980 meets all rigorous needs for long term performance in all transit public address systems. The amplifier is capable of driving multiple loudspeakers with precision and safety over the wide acoustical, electrical, mechanical, and environmental conditions of a subway car.
There are four output zones to permit addressing the passenger compartment, the trainman cabins, and the left or right exterior speakers, or any combination. With 120 watts of power available, the amplifier is conservatively utilized in applications requiring up to 36 distributed loudspeakers In addition to providing unequalled fidelity and utility, the amplifier has a unique circuit that automatically adjusts the volume level relative to the background noise in the train car. This ensures intelligible messages during peak subway usage while providing moderate levels when there are few riders.
Over a thousand OP980 PA Amplifiers are in current use. In service since 2004 with zero failures in service.
OP98X Specifications
Audio
- Power output: 120 wattsMax, 60 watts nominal
- Frequency Response: 100 Hz - 10 kHz +- 1 dB
- Distortion: THD is 0.5 % or less
- Background Noise: 7 millivolts (A-weighted) or 80 dB down
- Output Level - No level change vs. DC over the operating voltage range
Input stage
- Transformer coupled - dc blocked - 10 kohm input impedance
- Audio input voltage - 0.3 to 5 Vac, potentiometer set up
- Active high pass filter 100 Hz or 300 Hz (for horn speakers)
- TVS diode protection for any input signal above 10 Vac
Power Amplifier Stage
- Class B - Biased at cut off - 50 ma quiescent
- Transformer coupled - 70 volt and low impedance
- Output limited to 120 watts regardless of DC power
- Short circuit protection - turns off for too low load
- Four output zones - any or all may be ON
- Output levels - Zone 1 is 70 volts - Zone 2, 3, or 4 can be 70V or direct
Automatic Level Adjusting
- Uses the loudspeakers as microphones to sense ambient noise
- Gain stays latched during announcements
- Listening range can be adjusted from 50 to 80 dB noise SPL
- Sensitivity can be set up for up to 20 dB gain change.
- Control Inputs
- PTT for zones 1,2,3,4
- Automatic level enabl
- Activate by pull to common
- Input impedance 10K ohms
Electrical
- DC Power - 18 volts to 64 volts DC
- Current - 0.05 Amperes quiescent
- - 5 amperes @ 60 watts audio output
- - 10 amperes at 120 watts audio output
- Filtering - Inductor, 5 kW TVS at 65 volts, 5700 uF
- RF field or radiation - Non existent
- Spike protection - Fully protected for 3000 volt 150 Joules
- Ground Isolation - 2,000V, circuit to metal chassis ground
Mechanical
- Aluminum case with integral heat sink
- Case Size: 4.75" x 6.5" x 10.5"
- Mounting: four holes on 8" X 5" centers on a 8.5" X 11" plate8
- Weight: 11 lbs
- Connectors - Input/output/control/power - AMP Mini 24 pin
- Ground - 1/4 inch stud with nut and washers.
- Construction
- IPC -610 Assembly
- ISO 9002 Process
Environmental
- Temperature Range - -30 to + 80 degrees Celsius
- Humidity - 99 percent, non-condensing
- Vibration - 2 G's continuously, 8 G's for 20 ms
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