A 4037 • Phase5 40W 3 Input 100V Public Address Amplifier

A 3 input 40W 100V line output PA amplifier designed for medium sized background audio and paging announcement installations. Compatible with A4573 alert/evac/chime board and remote digital volume control (with A 4373).

SKU: A 4037 Categories: , , ,
Designed to meet the requirements of medium sized professional public address installations, delivering an output power of 40W, 60W and 100W RMS respectively.Frequency response extends from 60Hz to 15kHz at a total harmonic distortion (THD) of less than 0.5%. Features include, VOX muting, three balanced XLR microphone inputs, three line RCA inputs, bass and treble controls, enabling a diversity of installation applications, including schools, public halls, workshops and sporting complexes. Inbuilt VOX muting allows input 1 (mic or line) to mute inputs 2-3 and input 2 (mic or line) to mute input 3. 

Powered from 240V AC mains or 24V DC permitting battery backup operation during mains power failure. Output is 100V line only. All units feature thermal overload shutdown to protect the amplifier if a speaker fault condition develops.  

A 4573 Alert/evac option board: When fitted, generates pre chime, bell, alert and evacuation tones.  The alert tone can function continuously, or switch to evac tone after a preset time delay (adjustable 30 seconds to 4.5 minutes).  Simply connects to the  amplifier internally via the cable provided.

A 4373 Digital remote volume option board: When fitted and used in conjunction with A 2280B wallplate to provide remote volume level adjustment. Ideal for situations where the amplifier is located in a remote rack. 

Key Features:

  • 3 balanced microphone inputs
  •  Phantom power on mic inputs
  • 3 line inputs
  • 19” rack mount kit included
  • VOX muting
  • Tape output RCA sockets
  • Bass and treble tone controls
  • 100V line output
  • 240V AC or 24V DC operation
  • Built in short circuit protection
  • 10 year warranty
  • Optional evac module available
  • Optional remote volume module
  • Australian designed & assembled


Developed, designed & assembled in Australia.
Since 1976 Redback PA products have been manufactured in Perth, Western Australia by Altronics. With over 40 years experience in the commercial audio industry, we offer consultants, installers and end users reliable products of high build quality with local product support.


Backed by an industry leading 10 Year Manufacturer Warranty.
Our Redback products have a long tried and tested history of bulletproof reliability. Altronics offers a 10 Year Warranty on all Australian Made Redback products. Our local in-house service department has all the know how to answer technical queries and provide timely service.

Power Output: 40 watts RMS
Distortion: < 0.5% @ 1kHz
Signal to Noise Ratio: Typically 75dB below rated output. All inputs.

Frequency Response
Mic inputs: 50Hz – 10kHz, -3dB
Line inputs: 60Hz – 15kHz, -3dB
Output line: 100V

Input Sensitivity
Mic 1-3: 3mV
Line inputs 1-3: 300mV

Output Connectors
Speakers: Screw terminals

Input Connectors
Mic 1-3: 3 pin XLR balanced
Line inputs 1-3: RCA stereo socket
24V DC power: Screw terminals
240V AC power: IEC power connector
VOX Muting: 60dB below rated output
Remote volume: Screw terminals

Mic inputs: Volume
Line inputs: Volume
Bass: ±10dB @ 100Hz
Treble: ±13dB @ 10kHz
Power: On/off switch
Indicators: Power, Overload

Power supply: 240V AC or 24V DC
Current Draw: 220mA Standby, 3A Full @ 24V DC
Protection: 1A AC fuse and 4A DC fuse

Weight: ≈7.1 kg
Dimensions: ≈423W x 225D x 88H mm
Colour: Black

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