REDBACK A 4275C Phase5 125W 100V Public Address Mixer Amplifier User Guide
- June 9, 2024
- redback
Table of Contents
Product Guide
A 4275C Phase5® 125W 100V Public Address Mixer Amplifier
Overview
Designed in conjunction with Australia’s leading PA professionals to cater for
the needs of multi-source installations. This redesigned unit offers the
ability to monitor amplifier status via the colour LCD screen, plus custom
labelling of inputs. The A 2711 optional USB & SD card module provides music
playback when fitted.
Engineered for professional PA installations, the A 4275C delivers 125W RMS
power. Frequency response extends from 50Hz to 15kHz ±3dB at a total harmonic
distortion (THD) of less than 0.5% @ 1kHz. Voice/Vox muting, including three
levels of input priority, bass and treble controls and phantom powering
capability enable unparalleled flexibility for a wide scope of applications
such as schools, shopping centres, workshops, mine sites and office buildings.
Operates from 240V AC mains or 24V DC permitting battery backup operation
during mains power failure. Output can be 100V line, 70V line or low impedance
(4 – 16Ω) loads.
LCD status readout.
Indicates input and output levels, amplifier status; including heatsink
temperature, overload and over current conditions. 240V AC or 24V DC
operation. Also allows custom labelling of input sources via USB keyboard.
Flexible input configuration.
Each input can be configured for either balanced microphone or line use. A dip
switch is supplied for each input providing the following features:
- Phantom power on/off
- Mic or line
- 100mV or 1V
- Vox muting on/off (priority)
Three levels of priority.
Priority selection is by a dip switch on the rear panel: Input 1 over 2-6,
input 2 over 3-6 and input 3 over 4-6.
Protection & Limiting
In the event of an overload, the output current is limited by the internal
circuitry, thus reducing the output voltage at the speaker terminals. Input
limiting restricts the output to 110V regardless of input level. This
prevents dangerously high voltages from damaging the loudspeaker. The circuit
includes thermal overload shutdown, over current and overload protection plus
fuses on both AC and DC supply rails.
Key Features
Australian made
10 year manufacturer warranty with local product support
VU meter on LCD screen
Output peak limited
Multi-stage thermally cued fan cooling
2U 19” rack mount
Record out terminals
Remote volume facility
Optional alert, evac & chime tone generator (A 4573)
Vox activated 24V DC output
6 inputs with 3 pin XLR or 2 x RCA sockets
Phantom powering available on all inputs
Three levels of priority
Option for mic/line to operate vox muting on inputs 1 to 3
Push to talk (PTT) terminals on rear panel
Bass and treble tone controls
Power amp line out connector
Terminals for 100V line, 70V line and 4 – 16Ω loads
240V AC or 24V DC power operation
Thermal & fuse overload protection
Built in short circuit protection
300mA trickle charge facility for 24V DC batteries
Master volume can be configured as pre or post line out
About Redback® Public Address Amplifiers
Redback® amplifiers are proudly designed, engineered and manufactured in
Australia.
Each unit is covered by a comprehensive 10 year parts and labour warranty.
Redback® offers rock solid reliability from over 45 years experience in the
commercial sound industry. Redback® offer locally available servicing and
parts, plus the ability to offer feedback direct to the manufacturer.
Rear Panel
| 1 | 240V AC input |
|---|---|
| 2 | 100V/70/4-16Ω line terminals |
| 3 | 10A DC resettable blade fuse |
| 4 | 24V DC input terminal |
| 5 | 24V DC battery charge link terminal |
| 6 | RJ45 Interface port |
| 7 | a. Remote Volume Control Contacts |
b. PTT Contacts
c. Power Fail Contacts
d. 24V DC Switched Output
8| Tape Out RCA
9| Send / Return RCA
10| Preamp XLR Output
11| Input 1 DIP Switch Selections
12| Input 1 Balanced 3 Pin XLR
13| Input 1 Line Stereo RCA
Specifications
Electrical
| Power output: | 125 Watts RMS |
|---|---|
| Distortion: | < 0.5% @ 1kHz |
| Output line: | 100V, 70V or 4-16Ω |
Signal to noise ratio (Limiting by-passed)
Mic inputs:| Typically 75dB below rated output.
Line inputs:| Typically 81dB below rated output.
Line output:| 600Ω balanced, 0dBV
Mic input frequency response:| 50Hz – 12kHz, -3dB
Line input frequency response:| 50Hz – 15kHz, -3dB
Input sensitivity:| 100mV-1V (line), 3mV balanced (mic)
Power supply:| 240V AC or 24V DC
Current draw:| 350mA standby, 8A full load @ 24V DC
240V AC power:| IEC power connector
24V DC power:| Screw terminal
Protection:| 5A AC, 10A DC fuses
Vox muting:| 60dB below rated output
LED indicators:| Power, fault, all other indicators on LCD
Controls
| Master Volume: | Controls all output level |
|---|---|
| Line Inputs: | Volume |
| Bass: | ±10dB @ 100Hz |
| Treble: | ±10dB @ 10kHz |
| Power: | On/Off switch |
Mechanical
| Dimensions: | 483W x 380D x 88H mm (410D inc. handles) |
|---|---|
| Weight: | ≈14.5kg |
Optional Add Ons
| A 2711 | MP3 USB/SD Audio Module |
|---|---|
| A 4573 | Alert/Evac Tone Module |
| A 2280B | Remote Volume Wall plate |
Connections
| Inputs | Mic 1-6 | Line 1-6 | Send/Return |
|---|---|---|---|
| 3 pin XLR female (balanced) | Stereo RCA | RCA sockets | |
| Outputs | Speakers | Tape Out | Preamp Out |
| Screw terminals for 100V line, 70V line and 8-16Ω | Mixed mono Dual RCA | ||
| sockets | 3 pin XLR male (balanced), RCA socket |
Notes: We do not recommend using this amplifier with a combination of low
impedance and 100V line speakers.
**Architect Specifications
**
A 4275C
The amplifier shall have a power output of 125 Watts RMS. The unit shall have
6 inputs. All inputs shall consist of one balanced XLR microphone input and
dual RCA line input. In addition, a local music input shall have a 3.5mm
stereo line unbalanced input. Frequency response shall be 50Hz – 12 kHz (-3dB)
for microphone inputs and 50Hz – 15 kHz (- 3dB) for line inputs.
The unit shall have separate volume controls for each microphone / line input
and tone controls providing 10dB cut or boost at 100Hz and 10dB cut or boost
at 10kHz.
The unit shall operate from 240V AC or 24V DC with a LED indicator, and be
fuse protected. The unit shall have overload protection via DC fuses.
The amplifier shall be capable of delivering full power of 100V RMS into a 333
ohm (125W) inductive load with less than 0.5% distortion measured at 1 kHz and
with system hum and noise typically -75dB with all volume controls at minimum.
The speaker outputs shall be 100V and 4-16 ohms provided via screw terminals.
Tape output shall be provided via dual RCA sockets. Internal muting shall be
provided by the VOX muting circuit. Muting should be configurable so that
input 1 shall over-ride inputs 2, 3 and local music or input 2 shall override
input 3 and local music.
Amplifier status readout shall be provided via front panel LCD readout. The
amplifier shall be housed in a high quality 2RU metal chassis suitable for
rack mounting. The amplifier shall be a REDBACK PHASE 5 model A 4275C.
Internet:www.redbackaudio.com.au
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