A 4033B • 30W 3 Input 100V PA Amplifier (Rack Mount Version)

The rack mount version of our A 4031B 30W amplifier, possibly the most popular PA amplifier ever sold in Australia! This 30W model is the mainstay of the small & medium PA install range, offering both 100V line and low impedance outputs. Suits a wide scope of installation applications, including schools, public halls, workshops and sporting complexes.

SKU: A 4033B Categories: ,

This PA amplifier has been designed to meet the requirements of small to medium sized professional public address installations. Frequency response extends from 40Hz to 10kHz at a total harmonic distortion (THD) of less than 0.5%. Features such as push to talk (PTT) auxiliary muting, three combined balanced line microphone / stereo line inputs, tape out, and separate bass and treble controls give this amplifier a wide scope of installation applications, including schools, public halls, workshops and sporting complexes. Output may be 100V line or low impedance (8 – 16Ω) speaker loads. This unit features thermal overload shutdown, over current and short circuit protection.

Vox muting: The VOX circuit allows telephone paging via line input one or two (selectable internally). When paging via the telephone, all other line inputs are muted (ie. background music). Features variable sensitivity and time delay settings.

Key Features:

  • Push to talk (PTT) muting on microphone 1
  • 3 balanced microphone inputs
  • Built in VOX muting circuit
  • 3 stereo line inputs
  • Bass and treble tone controls
  • Tape output
  • Output terminals for 100V line and 8 – 16Ω loads
  • 240V AC operation
  • Built in short circuit protection
  • Thermal shutdown circuit protection
  • 19″ rack mountable (ears included)


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.

Distortion: < 0.5% @ 1kHz
Output line: 100V or 8 – 16Ω
Signal to Noise Ratio:
All volume controls min, typically 72dB below rated output. All inputs display same S/N ratio
Frequency Response:
Mic: 52Hz – 10kHz, -3dB
Line: 40Hz – 10kHz, -3dB
Input Sensitivity:
Mic 1: 2.6mV balanced or 3.2mV unbalanced
Mic 2: 2.6mV balanced
Mic 3: 2.6mV balanced
Line inputs: 150mV
Volume 1: Controls mic 1 / line 1
Volume 2: Controls mic 2 / line 2
Volume 3: Controls mic 3 / line 3
Bass: ±10dB @ 100Hz
Treble: ±13dB @ 10kHz
Power: On/off switch
Output Connectors
Speakers: Screw terminals
Tape out: RCA sockets
Muting: PTT via microphone, switch contacts or internal VOX muting. -79dB below rated output
Input Connectors
Mic 1: 5 pin DIN balanced or 3 pin XLR balanced or 6.35mm jack unbalanced
Mics 2 & 3: 3 pin XLR balanced
Line inputs: RCA stereo socket, bridged mono
240V AC power: IEC power connector
Power supply: 240V AC
Indicators: Power
Fuse protection: 1A AC, 1.5A x 2 DC internal
Size: 483W x 220D x 88H mm
Weight: 6.9g
Colour: Black
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