$1395.00 per ea

Quantity Price
ea $1,395.00
2+ $1,255.00
per ea
All prices shown are (inc. GST)


Manufactured in Australia to stringent engineering criteria, the Phase 4 amplifier series exhibit quite remarkable performance and outstanding reliability. Over 2 years in design and development, the evolution of Phase 4 included extensive consultation and input from pro sound contractors and installers across the country. The host of features incorporated commend this amplifier series to the most demanding of pro sound and industrial PA system applications. Redback Phase 4 amplifiers incorporate on demand multi-staged thermally cued fan forced cooling.

The output power stage is thermally monitored enabling automatic operation of a long life computer style cooling fan to "off", "low" or "high" air flow through a specially designed tunnel heatsink. In quiescent or ordinary cycle paging mode the fan is inoperative. Over temperature sensing is employed to shut down the amplifier in extreme over heat conditions, eg extreme over load and /or over drive misuse. Reā€“start is automatic once normal temperatures are attained. Output peak limiting.

The output voltage is limited to 105V maximum RMS voltage irrespective of load impedance to prevent damage to speaker load. Standard 100V line PA amplifiers can deliver up to 180 volts or more under conditions of high drive and very light loading. This output over voltage can quickly destroy any loudspeakers connected.


  • 2 X 125W amplifiers in a single chassis
  • Multi-stage thermally cued cooling
  • LED bargraph VU meter
  • Input signal presence indicator
  • Output peak limited
  • 2U 19" rack mount
  • 3 pin XLR input, 3 pin XLR loop out
  • Level control rear mounted
  • 100V, 70V and 4 - 16 Ohm outputs
  • Thermal and overload protection
  • 240V AC, or 24V DC operation
  • 300mA 24V battery trickle charge

100% 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. Read more about our Australian Made products

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. Read more about our industry leading warranty.

Information & Downloads


  • Power Output: 2 x 125 Watts RMS
  • Distortion: < 0.5%, @ 1kHz
  • Frequency Response: 50Hz - 15kHz, -3dB
  • Speaker Outputs: 100V, 70V, or 4 - 16 Ohm
  • Sensitivity: 500mV balanced
  • Signal to Noise Ratio:(Peak Limiting By-Passed) > 90 dB
  • Line Output: 600 Ohm balanced, 0dBV
  • Output Connectors
  • Speakers: Screw Terminals
  • Line Out: 3 pin XLR
  • Trickle Charge: Screw Terminals
  • Input Connectors
  • Inputs: 3 pin XLR balanced
  • 24V DC Power: Screw Terminals
  • 240V AC Power: IEC Chassis Socket
  • Controls
  • Master: Volume (on rear panel)
  • Power: On/Off Switch
  • Indicators: Power, Fault, VU Meter, Signal Present, Output Peak Limiting
  • Power Supply: 240V AC or 24V DC (nominal)
  • Protection: 7.5A AC Fuse and 2 x 10A DC Fuses
  • Dimensions: 483W x 407D (Including Handles) x 88H
  • Weight: 18kg
  • *Specifications subject to change without notice
    • *Specifications are subject to change without notice.

Warranty & Returns


We offer 12 months warranty on this product from its date of purchase. This is available from Altronics stores, online purchases or Altronics resellers. In accordance with our full warranty terms we will repair, replace or refund if goods you have purchased from us are defective.


Not withstanding our warranty policy, if you are dissatisfied with our goods or service you may return the goods within 14 days of our despatch date. Simply contact us for a return authorisation number and we will refund your purchase in full, less transport costs on receipt of goods. All returned goods must be in as sold condition including all packaging, instructions, invoices etc.