Redback A 4270 User manual

www.redbackaudio.com.au Redback® Proudly Made In Australia 1
Redback® A 4270/80 Four Zone Paging PA Amplier
User manual revision number: 1.2 23/09/2021
Operating Manual
A 4270 125 WATT FOUR ZONE PAGING PA AMPLIFIER
A 4280 250 WATT FOUR ZONE PAGING PA AMPLIFIER
IMPORTANT NOTE:
Please read these instructions carefully from front to back prior to installation.
They include important setup instructions.
Failure to follow these instructions may prevent the unit from working as designed.
Redback® Proudly Made In Australia
Distributed by Altronic Distributors Pty. Ltd.
Phone: [phone] Fax: [phone] Internet: www.altronics.com.au
Optional Extras
A 2280B
Remote Volume Wall Plate
A 4373
Remote Volume Module
A 4376
Rack Mount Ears
A 4488
Four Zone Paging Console

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Redback® A 4270/80 Four Zone Paging PA Amplier
REDBACK is a registered trademark of Altronic Distributors Pty Ltd
You may be surprised to learn that Altronics is still manufacturing hundreds of product lines right here in Australia. We
have resisted the move offshore by offering our customers better quality products with innovations to save them time and
money.
Our Balcatta production facility manufactures/assembles:
Redback public address products
One-shot speaker & grill combinations
Zip-Rack 19 inch rack frame products
We strive to support local suppliers wherever possible in our supply chain, helping to support Australia’s manufacturing
industry.
Redback Audio Products
100% developed, designed & assembled in Australia.
Since 1976 we have been manufacturing Redback ampliers in Perth, Western Australia. 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. We believe there is signicant added value for customers when purchasing an Australian made
Redback amplier or PA product.
Local support & feedback.
Our best product features come as a direct result of feedback from our customers, and when you call us, you speak to a
real person - no recorded messages, call centres or automated push button options.
It’s not only the assembly team at Altronics who are employed as a direct result of your purchase, but hundreds more at
local companies used in the supply chain.
Industry leading 10 year warranty.
There’s a reason we have the industry leading DECADE warranty. It’s because of a long tried and tested history of bullet-
proof reliability. We’ve heard PA contractors tell us they still see the original Redford amplier still in service in schools.
We offer this comprehensive parts & labour warranty on almost every Australian Made Redback public address product.
This offers both installers and end users peace of mind that they will receive prompt local servicing in the rare event of any
problems.
Published by Altronic Distributors
© 2021 Altronic Distributors

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Redback® A 4270/80 Four Zone Paging PA Amplier
1.0 OVERVIEW
The Redback®A 4270 125 Watt and A 4280 250 Watt 4 Zone paging ampliers are specically designed for multi zone
applications. Based on the popular Redback®A 4377 and A 4387 amplier series, these ampliers have three inputs
which can be congured for either microphone or line level. The addition of zone paging is made possible by connecting
Redback®A 4488 paging consoles to the amplier. The ampliers have a main 100V speaker output plus as additional
four separate 100V output speaker loads, each of which has provision for background music which can be overriddden by
the A 4488 paging microphones.
The Redback®A 4270 conservatively delivers 125W RMS power, while the A 4280 delivers 250W RMS. Frequency re-
sponse extends from 50Hz to 15kHz ±3dB at a total harmonic distortion (THD) of less than 0.5% @ 1kHz.
Vox muting is provided on inputs one and two, which, when activated, automatically mutes the other inputs. Bass and
treble controls and phantom powering capability enable unparalleled exibility for a wide scope of applications such as
factories, workshops, mine sites, sports clubs and ofce buildings.
The ampliers operate from 240V AC mains or 24V DC permitting battery backup operation during mains power failure.
The output comes standard suitable for a 100V line load, but this can be congured internally to 70V line or low imped-
ance (4 - 16Ω) loads.
Thermal overload, overcurrent and overload protection circuitry and fuses on both AC and DC provide excellent fault
condition protection and robust performance. The amplier also utilises a half power mode which enables the amplier to
continue to run at a reduced output level if it is being over driven.
Tape output sockets are provided for recording purposes or feeding into additional power ampliers.
Remote volume available when A 4373 Digital volume control module tted internally and external A 2280B wall plate or
1KΩ potentiometer connected.
MP3 based Alert and Evacuation tones along with chime tones and voice over message are built standard functions of the
ampliers.
2.0 FEATURES
• 3 Balanced microphone inputs / 3 Aux inputs / 1 Music input
• Robust design incorporating latest Mosfet technology
• Very Low noise and distortion
• 100V Main Output standard with optional 70V and 4-16Ω outputs
• 100V Outputs 1- 4
• Zone paging (via optional Redback®A 4488 paging consoles)
• Background music (BGM) selectable to Outputs 1-4
• MP3 based Alert/Evac tones with MP3 voice over message for emergency tones
• 240V AC or 24V DC operation
• VOX muting on inputs 1 and 2 (Switch selectable internally)
• Adjustable VOX level sensitivities
• Bass and Treble controls
• Tape Output
• Phantom power on microphone inputs (DIP switch selectable internally)
• Multi stage thermally cued fan cooling
• Output Peak Limited
• Thermal Overload protected
• Signal Presence Indicator
• Half power mode when overdriven
• Fault Indicators
• 24V DC Power Status Indicator
• Optional remote volume (With A 4373 Digital volume control module tted and external A 2280B wall plate)
• Rack Mountable (suits 19 inch racks) with optional A 4376 rack ears

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Redback® A 4270/80 Four Zone Paging PA Amplier
3.0 FRONT PANEL CONTROLS
Figure 1 shows the layout of the front panel.
Fig 1
1 Inputs 1-4 volume controls
Use these controls to adjust the output volume of inputs 1-4 (volume 3 is used to adjust the volume of input 4 the
music input.
2 Master volume Control
Use this control to adjust the master volume.
3 Protect Indicator
This LED indicates when the amplier module has an internal circuitry fault.
4 BGM Output Select Switches
Use these switches to select which zones are to receive the background music.
5 Status Indicators
Normal Mode: Indicates that the amplier is operating in normal mode (i.e. no paging or Evac tones active).
Mic Paging Active: Indicates when an A 4488 paging mic console is in use.
Mic BGM Active: Indicates when the BGM input on the rear of an A 4488 paging console is active.
Evac Tones Active: Indicates when the Alert or Evac tones are active.
6 Power Switch
Use this to turn the unit on.
7 On Indicator
This led indicates the unit has power.
8 24V DC Indicator
This LED indicates when the amplier is being powered from the 24V input.
9 Fault Indicator
This led indicates when the amplier has a fault.
10 Peak Limit Indicator
This LED indicates when the input signal is clipping.
11 OverLoad Indicator
This LED indicates when the output is drawing too much current from the amplier. The output will be
disconnected until the current draw is reduced.
12 OverTemp/ Half Power Indicator
When this LED is red it indicates when the amplier is overheating. The output will be disconnected until the
amplier is once again cool enough to operate. If thie LED is orange the amplier has gone into half power mode.
This mode lets the amplier continue to run at a lower output rather than shutdown completely. This mode might
be initiated from the amplier being overdriven or overloaded.
13 Bass and Treble Controls
Use these controls to adjust the bass and treble.
14 Signal Presence Indicator
This LED indicates when an input signal is present.
15 Music Input
Use this input to connect a portable music player. This input over-rides the rear input 3 and is adjusted via the
volume 3 pot.
16 Vox level controls
Use these controls to adjust the vox sensitivities of inputs 1-2.
Model : A 4270
125W Public Address Amplier
24V
Signal Protect
DC
Over
Load
Power
Local Music
Input
Treble
Bass
On
Master Volume
Volume 1 Volume 2 Volume 3
_
0
+
Present
VOX 1
Sens. VOX 2
Sens.
Fault
Limit
Over Temp
Peak
16
1 2
13
3 6
78910111415
0
2
46
8
10 0
2
46
8
10 0
2
46
8
10 0
2
46
8
10
_
0
+
1/2 Power
Out 1
BGM Output Select
Out 2 Out 3 Out 4
Status Indicators
Mic
BGM
Active
Mic
Paging
Active
Evac
Tones
Active
Normal
Mode
12
4 5

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Redback® A 4270/80 Four Zone Paging PA Amplier
4.0 REAR PANEL CONNECTIONS
Figure 2 shows the layout of the rear panel.
Fig 2
1 100V Out (Main) Output Connections
This is the main output of the amplier and is for connection of speakers tted with a 100V line transformer.
Always ensure that the total load of the speakers does not exceed the rated output of the amplier i.e. 80Ω
minimum at 100V for 125W and 40Ω minimum at 100V for 250 Watts. Otherwise either the DC or mains fuse
could blow or the fault led to activate and the amp will shut down. Always be careful to avoid short circuits and
connection to the wrong terminals.
2 100V Out (Out1 - Out4) Output Connections
These 100V line outputs are for zones which can be paged when the optional A 4488 paging microphones are
connected. Background music can be piped to these outputs via the front switches.
3 Connections for A 4488 Paging Consoles
These RJ45 ports are for connection of the optional A 4488 paging consoles.
4 Alert/Evacuation Tone Generator with Voice Over Message
Use these contacts to trigger the chime tones, the alert tone, the evacuation tone and to cancel any
of the tones once triggered. All tones & cancel function are operated by a closing contact to ground.
This could be triggered via a building re indicator board, break glass alarm etc.
All tones are MP3 based les and are stored on the supplied Micro SD card.
(Refer to section 15.0 for more details).
5 DIP Switches
These switches provide various functions (refer to section 17.0).
6 Micro SD Card
This is used to store the MP3 les used for the Alert, Evac and Chime tones and also the Voice over messages.
(Refer to section 15.0 for more details).
7 Inputs 1-3
These inputs can be either a balanced XLR input with sensitivities of 500mV or dual RCA line inputs with a 1V
input sensitivity. The line input dual RCA connectors are internally mixed to produce a mono input signal.
8 Tape Out
Dual RCA’s provided for recording purposes. This is a line level output.
9 Optional Plugin
This connection is to be used when the optional A 4373 Digital Volume Board if tted inside the amplifer. This
provides remote volume when used in conjunction with a 1K potentiometer wired to these terminals.
10 24VDC IN
Battery Backup: Provision has been provided to run the amplier from a suitably rated 24V battery system in the
event of a mains failure. Using appropriately rated cable, connect the battery to the “24V DC In” terminals.
Observe correct polarity when connecting. (see Fig 5 for more details)
11 DC Resettable fuses
This fuse protect the internal power supply. If the fuse is tripped it is easily reset by pressing the small button on
the fuse.
12 240V AC power socket (Australian standard)
Connects to 240V AC mains power with the included IEC lead. The internal fuse is an M205 5Amp for the
A 4270 125 Watt amplier and an M205 7.5Amp for the A 4280 250 Watt amplier.
78
12
9
10
11
3 4 56
12
240V AC @ 50Hz
RISK OF ELECTRIC SHOCK
OPEN BY QUALIFIED
PERSONNEL ONLY !
CAUTION
Tape Out Line 1 Mic 3 Mic 2 Mic 1
12
3
1 • Shield
2 • Hot
3 • Cold
MIc XLR
wiring
Conguration
Line 2
Line 3
L
R
L
R
L
R
Output
125W
Fuse
5 Amp
7.5 Amp
250W
AC Fuse (M 205)
DC FuseOutput
125W 10 Amp
20 Amp
250W
Resettable
DC Fuse
L
R
Optional
Plugin
- +
+_
24V
DC IN
Made in Australia by
Altronic Distributors Pty Ltd
www.redbackaudio.com.au
CH1
COM
CAN
EV
100V OUT
(MAIN)
- +
+_
AL
CH2
OUT4
(100V)
OUT3
(100V)
OUT2
(100V)
OUT1
(100V)
Evac
Volume
V/Over
Volume
Chime
Volume
DIP
Switches
To Paging
Console 1
To Paging
Console 2
(16GB
Maximum)
Micro SD Card
Output Triggers
Levels
+_+_+_+_
1 2 3 4
2 1
3
2 1
3
2 1
3

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Redback® A 4270/80 Four Zone Paging PA Amplier
5.0 AUDIO CONNECTIONS
The amplier has three balanced XLR audio inputs, three dual RCA line inputs which are internally
mixed to create mono signals and a front mounted Music Input for portable devices. This input when
connected, over-rides the rear channel 3 audio sources and is adjusted via the volume 3 level control.
A VOX function is also included which when enabled will allow input 1 to mute inputs 2 and 3, or
input 2 to mute input 3. The VOX circuitry is selected by internal switches as shown in gure 5. The
VOX1 switch when set to ON will allow input 1 to mute inputs 2 & 3. The VOX2 switch when set to ON
will allow input 2 to mute input 3. The VOX sensitivity is adjusted by the trimpots located on the front
of the amplier.
Fig 3 shows a typical install where the A 4270 has a balanced microphone connected to input 1 and
a Line level source connected to input 2. If the VOX1 switch is set to “ON”, the microphone will VOX
mute the CD player connected to input 2.
Fig 3
6.0 POWER SUPPLY
The amplier operates on 230V AC or primarily for battery backup operation a 24V DC supply. Ensure power is switched
OFF at the front panel before connecting either mains power to the IEC socket or 24V DC to the screw terminal input. As
high currents may be drawn when operating from a 24V DC supply conrm the capacity of the DC power supply used.
7.0 PHANTOM POWER
All three microphone inputs have DIP switch selectable phantom power. When enabled 15V DC will be connected to the
Hot and Cold pins of the corresponding XLR. To access the DIP switches, rst disconnect power from the unit and then
remove the lid. The location of the DIP switches is shown in gure 4.
The Phantom power DIP switch settings are:
DIP 1 enables the phantom power to the XLR connector on input 1.
DIP 2 enables the phantom power to the XLR connector on input 2.
DIP 3 enables the phantom power to the XLR connector on input 3.
DIP 4 is not used.
8.0 VOX MUTING
Vox muting is provided on inputs one and two, which, when activated, automatically mutes the other inputs.
The VOX1 switch when set to ON will allow input 1 to mute inputs 2 & 3. The VOX2 switch when set to ON will allow
input 2 to mute input 3.
The VOX sensitivity is adjusted by the trimpots located on the front of the amplier (see gure 1).
Speakers tted with
100V line transformers.
CD
REDBACK
240V AC @ 50Hz
RISK OF ELECTRIC SHOCK
OPEN BY QUALIFIED
PERSONNEL ONLY !
CAUTION
Tape Out Line 1 Mic 3 Mic 2 Mic 1
12
3
1 • Shield
2 • Hot
3 • Cold
MIc XLR
wiring
Conguration
Line 2
Line 3
L
R
L
R
L
R
Output
125W
Fuse
5 Amp
7.5 Amp
250W
AC Fuse (M 205)
DC FuseOutput
125W 10 Amp
20 Amp
250W
Resettable
DC Fuse
L
R
Optional
Plugin
- +
+_
24V
DC IN
Made in Australia by
Altronic Distributors Pty Ltd
www.redbackaudio.com.au
CH1
COM
CAN
EV
100V OUT
(MAIN)
- +
+_
AL
CH2
OUT4
(100V)
OUT3
(100V)
OUT2
(100V)
OUT1
(100V)
Evac
Volume
V/Over
Volume
Chime
Volume
DIP
Switches
To Paging
Console 1
To Paging
Console 2
(16GB
Maximum)
Micro SD Card
Output Triggers
Levels
+_+_+_+_
1 2 3 4
2 1
3
2 1
3
2 1
3
12
3
1 • Earth/Shield
2 • Signal Hot
3 • Signal Cold
MIc XLR
wiring
Conguration

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Redback® A 4270/80 Four Zone Paging PA Amplier
9.0 REMOTE VOLUME (Optional)
It is possible to control the master volume with the addition of the A 4373 Digital Remote volume board and a 1kΩ
potentiometer (or Altronics A 2280B wall plate) tted across the terminals labelled “Optional Plugin” on the rear of the
amplier. The plugin board is tted inside the amplier in the location shown in gure 4.
NOTE: Take special care with the orientation of the board and remove power from the amplier before tting.
Fig 4
Fig 5
PHANTOM POWER
DIP SWITCHES
1=MIC1
2=MIC2
3=MIC3
VOX1 VOX2
ON
OFF
ON
OFF
EARTH
LIFT
SWITCH
EARTH
LIFT
PLUGIN
PLUGIN
i
Wiring speakers in parallel for 70/100V line:Where several speakers are to
be used at one time, on one circuit, it becomes necessary to use speakers tted
with line-matching transformers. This is to overcome the eects of connecting
speakers in parallel and cable losses. The amplier generally has an output
voltage of 100 volts (70 volts is typically used in North America, however
operation is similar). In this conguration the total wattage load on the amplier
is derived from adding all the line transformer primary tap ratings together. For
example, 70 one watt speakers will have a total speaker load of 70 watts. Or
alternatively, it is conceivable to connect 100 one watt speakers to a 100 watt,
100 volt line amplier.
Measuring 70/100V Line Speaker Impedance:To measure amplier system
load, you must use an impedance meter in order to measure the ac resistance
of the connected speaker network. Impedance cannot be measured with a
standard multimeter, as this measures the dc resistance. Use the Altronics
Q 2003 or similar impedance meter.
About 70V & 100V Line Speaker SystemsLoad 70V 100V
0.5W 9.4kΩ 20k Ω
0.66W 7.12kΩ 15k Ω
1W 4.7kΩ 10k Ω
1.25W 3.76kΩ 8k Ω
2W 2.35kΩ 5k Ω
2.5W 1.88kΩ 4k Ω
3W 1.56kΩ 3.3k Ω
5W 940Ω 2k Ω
7.5W 626Ω 1.3k Ω
10W 470Ω 1k Ω
15W 313Ω 666 Ω
20W 235Ω 500 Ω
30W 156Ω 333 Ω
40W 117Ω 250 Ω
60W 78Ω 166 Ω
100W 47Ω 100 Ω
125W 37Ω 80 Ω
250W 19Ω 40 Ω
500W 9.4Ω 20 Ω

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Redback® A 4270/80 Four Zone Paging PA Amplier
10.0 SPEAKER CONNECTIONS
Speakers fitted with 100V line transformers may be connected to the output terminals on the rear of the amplifer. Always
ensure the total load of the fitted speakers does not exceed the rated output of the amplifier (ie 125 watts for the A 4270
and 250 watts for the A 4280 amplifier) otherwise damage may result. When fitting speakers with line transformers the
impedance of the load cannot be measured using a standard multimeter. An impedance meter (such as the Altronics
Q 2003) is required. Fig 5 lists the impedance at certain loads of speakers fitted with 70V and 100V line transformers. So
for a total load of 125 watts using 100V line transformer fitted speakers, the impedance of the speaker load should be
80Ω.
Fig 6 shows a typical install where the A 4270 has all ve outputs connected to 100V line speakers and two Redback®
A 4488 Paging consoles connected to the RJ45 ports.
NOTE: The total load of all speakers must not exceed the total load rating of the amplier.
Audio from the amplier is output to the main 100V Out terminals and is not affected by the A 4488 paging consoles.
The audio from the amplier can also be piped to any of the 100V zone outputs 1- 4 and used as background music
to that zone. This is achieved by pressing the “BGM Output Select” switches on the front of the amplier. If paging is
required to these zones then the Redback®A 4488 paging consoles can be connected as shown. The paging consoles
provide paging to all four output zones and will override the background music to those zones (refer to section 13.0 for
more details).
Fig 6
RJ45 cabling conguration (586A ‘Straight through’)
The A 4488 paging consoles are connected to the amplier using “pin to pin” conguration RJ45 data cabling as shown
in g 7. When installing ensure all connections are veried with a LAN cable tester before switching any system
component on.
Failure to follow the correct wiring conguration may result in damage to system components.
and will Void the warranty.
Fig 7
240V AC @ 50Hz
RISK OF ELECTRIC SHOCK
OPEN BY QUALIFIED
PERSONNEL ONLY !
CAUTION
Tape Out Line 1 Mic 3 Mic 2 Mic 1
12
3
1 • Shield
2 • Hot
3 • Cold
MIc XLR
wiring
Conguration
Line 2
Line 3
L
R
L
R
L
R
Output
125W
Fuse
5 Amp
7.5 Amp
250W
AC Fuse (M 205)
DC FuseOutput
125W 10 Amp
20 Amp
250W
Resettable
DC Fuse
L
R
Optional
Plugin
- +
+_
24V
DC IN
Made in Australia by
Altronic Distributors Pty Ltd
www.redbackaudio.com.au
CH1
COM
CAN
EV
(MAIN)
- +
+_
AL
CH2
Evac
Volume
V/Over
Volume
Chime
Volume
DIP
Switches
To Paging
Console 1
To Paging
Console 2
(16GB
Maximum)
Micro SD Card
Output Triggers
Levels
+_+_+_+_
1 2 3 4
2 1
3
2 1
3
2 1
3
4 Zone Communicator
System Busy
Page
Lock On
All Call Cancel
A 4488
4 Zone Communicator
System Busy
Page
Lock On
All Call Cancel
A 4488
CAT5e cable
Max 300M
Speakers tted with
100V line transformers.
Main 100V Out
100V
Out 4
100V
Out 3
100V
Out 2
100V
Out 1
The total speaker load must not exceed
the rated output of the amplier.
A 4270 - 125 Watts
A 4280 - 250 Watts
568A
1 RX+
2 RX-
3 TX +
4
5
6 TX-
7
8
StraightThrough
(both ends)
Pins Face Upwards
1 TX+
2 TX-
3 RX +
4
5
6 RX-
7
8

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Redback® A 4270/80 Four Zone Paging PA Amplier
1 2 3 67
24VDC In Volume
Mic
Chime
Volume
1 2 3 4
1
2
PA System Chime On
SW PA System Chime O
Internal Chime On Internal Chime O
On O
DIP Switches 1-2 Settings
ON
1 2 3 4
BGM
Volume
BGM
Input
45
2 3 4
DIP Switches 2 - 4
Set the Paging
O O O
Console ID
ID
On O O
On On O
O On O
O O On
On O On
On On On
O On On
7
8
1
2
3
4
5
6
11.0 A 4488 CONNECTIONS
Figure 8 shows the layout of the rear panel.
Fig 8
1 24V DC connector
2.1mm DC jack (centre pin positive). A 24V DC plugpack may be required if the A 4488 is run more than 100m
from the amplier.
2 RJ45 connector
For connection back to the A 4270 or A 4280. Either port can be used.
3 DIP switch options
These switches set the pre-announcement chime and set the ID number.
4 BGM (Background Music) Input
The background music can be connected via a 3.5mm Stereo Jack.
5 BGM volume
Use this volume to adjust the background music level.
6 Chime volume
Use this volume to adjust the chime level.
7 Microphone volume
Use this volume to adjust the microphone level.
12.0 A 4488 DIP SWITCH SETTINGS
DIP switch 1 sets the pre-announcement chime on or off.
DIP switches 2-4 set the paging console ID number.
NOTE: The ID must be set to either ID1 or ID2 when using the
A 4488 with the A 4270 or A 4280 amplier.
IMPORTANT NOTE:
Ensure power is switched off when adjusting DIP switches.
New settings will be effective when power is switched back on.
Fig 9
Fig 9

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Redback® A 4270/80 Four Zone Paging PA Amplier
13.0 A 4488 GENERAL PAGING
To page to a zone select the desired zone/s by pressing the buttons 1- 4 or by pressing the “All Call” button if all zones
are desired. Make sure the switch is in the centre position before selecting the zones. The selected zones’ LED’s will illumi-
nate to indicate they have been pressed. Move the “Push to talk” switch down to the “Page” position and speak into the
microphone. Release the PTT switch when nished. The selected zones’ LED’s will ash for a few seconds after paging has
nished. While these LED’s are still ashing paging can be directed to these zones again by simply moving the PTT switch
back to the “Page” position.
If two paging consoles are connected to the system one console will be “Locked Out” when the other is in use.
Paging to the selected zones will override the background music to those zones, if the BGM was selected to be active by
the amplier front panel switches.
14.0 BACKGROUND MUSIC (REAR OF A 4488 PAGING CONSOLE)
Background music to the four output zones is primarily fed from the audio output of the amplier and selected by the
front panel switches. But the background music can also be fed from the rear of the A 4488 paging consoles.
This second method involves connecting an audio source (such as a mobile phone, tablet etc.) to the 3.5mm input jack on
the rear of the paging microphone as shown in Figure 10. This provides a local source of background music.
To activate the background music, rst make sure the Push to Talk (PTT) switch is in the centre position and then select
the zones to receive the background music. The selected zones LED indicators will ash to signify they have been selected.
Next move the PTT switch to the up position which is lablelled “Lock On”. While the switch is in this position and only this
position will the background music will be piped out to the zones selected.
The volume is adjusted by the BGM volume trimpot on the rear of the microphone.
If the PTT switch is moved to the “Page” position the background music will stop and paging will be active.
If the PTT switch is in the centre position the BGM and paging are not active.
If background music is required again to the same zones as previously selected, then all thats needed to initiate it again is
to move the PTT switch back to the “Lock On” position.
If the BGM is to be piped to different zones then it is only a matter of selecting the new zones, and then moving the PTT
switch to the “Lock On” position.
Fig 10
TO ACTIVATE THE BGM
MOVE THE SWITCH TO
THE “LOCK ON” POSITION
24VDC In
Volume
Mic
Chime
Volume
1 2 3 4
1
2
PASystem Chime On
SW PASystem Chime O
Internal Chime On Internal Chime O
On O
DIP Switches 1-2 Settings
ON
1 2 3 4
BGM
Volume
BGM
Input
REAR OF A 4488
ADJUST THE BACKGROUND
MUSIC VOLUME
BACKGROUND
MUSIC SOURCE
Connecting an audio source to the BGM input
4 Zone Communicator
System Busy
Page
BGM
All Call Cancel
A 4488

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Redback® A 4270/80 Four Zone Paging PA Amplier
15.0 ALERT, EVACUATION and CHIME MP3 FILES and ALERT and EVAC VOICE OVER MESSAGES
The supplied MIcro SD card houses all the MP3 audio les used for the output tones. These les are stored in ve separate
folders (see gure 5) and relate to the corresponding output. e.g. the Alert folder houses the MP3 le to be played when
the Alert mode is triggered.
These les can be any length and bit rate, but must be in MP3 format (they cannot be Wav les or AAC les).
Note 1: MP3 les should have the following specications for optimum performance. 128kbps, 44.1kHz, 32bit, VBR or CBR,
Stereo (even better as mono).
Note 2: only one MP3 le can be in each folder.
There is also a folder labelled “#LIBRARY# which contains a host of sample MP3 les.
The “Voice” folder contains the MP3 audio les played as the Alert and Evacuation messages. There are separate folders
for both the Alert and Evacuation messages as shown in gure 11.
The messages have to be recordered in MP3 format using any readily available PC software or other means, and then
transferred to these folders.
Activating the Voice Over Message:
Voice over messages become active when an MP3 le is present in the relevant folder. If the voice over message is not
required leave the folder empty.
Fig 11
16.0 INSTALLING MP3 FILES
You will rst need to remove power from the amplier then remove the Micro SD card from the rear of the unit.
To remove the Micro SD card push the card in and it will eject itself.
In order to access the program, the Micro SD card will need to be connected to a PC. You will need a PC or laptop equipped
with an Micro SD card reader to do this. If a Micro SD slot is not available then the Altronics D 0371A USB Memory Card
Reader or similar would be suitable (not supplied).
Step by step guide to installing an MP3 onto the Micro SD card with a Windows installed PC
Make sure the PC is on and card reader connected and correctly installed. Then insert the SD card into the reader.
Go to “My Computer” or “This PC” and open the SD card which is usually marked “Removable disk”.
In this case it is named “Removable disk (O:) as shown in gure 12.

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Redback® A 4270/80 Four Zone Paging PA Amplier
Fig 12
Open the Removable Disk and you should get a window that looks like gure 13.
Fig 13
The contents of the SD Card include a Library folder of sample MP3 les and ve folders for the MP3 les associated with
the various triggers.
There should be default MP3 les included in each folder. These will need to be replaced with your own MP3 les.
Open the folder in which you want to install an MP3 (in our case its the Alert folder) and you should see an MP3 le which
is named Alert.MP3 as shown in gure 14.

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Redback® A 4270/80 Four Zone Paging PA Amplier
Fig 14
This MP3 le needs to be deleted and replaced by the MP3 le you want to play when you activate the Alert mode. The
MP3 le name is not important. But it is important that there is only one MP3 le in the Alert folder.
Check the properties of the MP3 le.
NOTE the new MP3 le cannot be “Read only”.
To check this, right click on the MP3 le and scroll down and select Properties, you will get a window that looks like gure
15.
Make sure the “Read Only” box has no tick in it.
The new MP3 is now installed on the card. Repeat these steps for the other MP3 folders if you need to.
The card can be removed from the PC following windows safe card removal procedures. Make sure the amplier is OFF
and insert the SD card into the slot in the rear; it will click when fully inserted. The amplier is ready to use.
Fig 15

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Redback® A 4270/80 Four Zone Paging PA Amplier
17.0 DIP SWITCH SETTINGS
These switches affect the alert/evac triggers on the rear of the amplier.
Switch 1: The Alert and Evac contacts can be set to either continuous or momentary operation.
In continuous mode the alert/evac tone will continue while the corresponding rear contact is triggered.
In momentary mode the alert/evac tone will continue to sound after a momentary trigger of the rear contact.
1 - OFF: continuous operation of alert/evac contacts
1 - ON: momentary operation of alert/evac contacts
Switches 2 - 4 Evacuation Timer Settings:
These switches control the time period before the unit switches from the alert, to the evac tone when the Alert is triggered
by the rear contact. This time period can be switched from 30 seconds to 180 seconds in 30 second increments.
Sw2 = OFF, Sw3 = ON, Sw4 = ON - Changeover = 30 Sec
Sw2 = ON, Sw3 = OFF, Sw4 = ON - Changeover = 60 Sec
Sw2 = OFF, Sw3 = OFF, Sw4 = ON - Changeover = 90 Sec
Sw2 = ON, Sw3 = ON, Sw4 = OFF - Changeover = 120 Sec
Sw2 = ON, Sw3 = OFF, Sw4 = OFF - Changeover = 150 Sec
Sw2 = OFF, Sw3 = OFF, Sw4 = OFF - Changeover = 180 Sec
Note: Setting all switches 2 - 4 to ON deactivates the switchover function.
18.0 FIRMWARE UPDATE
It is possible to update the rmware for this unit by downloading updated versions from www.altronics.com.au or
redbackaudio.com.au.
To perform an update, follow these steps.
1) Download the Zip le from the website.
2) Remove the SD card from the amplier and insert it into your PC. (Follow the steps on page 11 to open the SD card).
3) Extract the contents of the Zip le to the root folder of the SD Card.
4) Rename the extracted .BIN le to update.BIN.
5) Remove the SD card from the PC following windows safe card removal procedures.
6) With the power turned OFF, insert the SD card back into the amplier.
7) Turn the amplier ON. The unit will check the SD card and if an update is required the amplier will perform the update
automatically.
19.0 TROUBLESHOOTING
If the REDBACK Phase 4 amplier fails to deliver the rated performance, check the following:
No Power, No Lights
Make sure amplier power switch is on. Make sure mains power switch is on at the wall. Check the mains and DC fuse.
Replace with only the correct type and rating. Over rated fuses with invalidate warranty.
Distorted Output
Check that the speaker type is correct for the output that you are using (ie. 100V line). Check for any short circuits on the
speaker line.
Very Low Output Volume
Make sure that the input is the correct level (check for shorted connectors). Check for any short circuits on the speaker
line.
Check if signal LED on the front panel is lit to indicate there is signal. If it is not lit there is no signal present.
Continually Blows Fuses
Make sure that the speaker line is not shorted. Check speaker types, ratings and if on correct output.
Amplier Keeps on Cutting In & Out
Make sure that there is adequate ventilation around the amplier. Check the vent slots on the front,top and sides are not
covered or blocked and the fan on the rear is functioning correctly. Check also speaker types, ratings and for any short
circuits on the speaker line.

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Redback® A 4270/80 Four Zone Paging PA Amplier
Unit will not play MP3 les.
Make sure all MP3 les are not “Read Only”. See page 13
MP3 les should have the following specications for optimum performance. 128kbps, 44.1kHz, 32bit, VBR or
CBR, Stereo (even better as mono).
.
20.0 SPECIFICATIONS
POWER OUTPUTS
Power: .......................................... A 4377 -125 watts RMS
.........................................A 4387 - 250 watts RMS
Distortion:..................................................< 0.5%, @ 1kHz
Output line: ............................................................... 100V
FREQUENCY RESPONSE
Mic inputs :...........................................50Hz - 12kHz, -3dB
Line inputs: ...........................................50Hz - 15kHz, -3dB
MIC SENSITIVITY
Mic inputs: ................................................................. 3mV
Line inputs:.....................................................................1V
Music input: ............................................................500mV
SIGNAL TO NOISE RATIO
Mic inputs: .............................. > 75dB below rated output
LINE OUTPUT .................. 600Ω balanced, 0dB , 3 Pin XLR
OUTPUT CONNECTORS
Speakers: ...................................................Screw terminals
INPUT CONNECTORS
Inputs: .................................3 pin XLR balanced or 2 x RCA
24V DC power: ..........................................Screw terminals
240V AC power: ............................... IEC power connector
MUTING:..................... PTT via microphone switch contacts
........................................ VOX muting (inputs 1-2)
CONTROLS
Mic/Line/Music inputs: ............................................ Volume
Power: ...........................................................On/off switch
Indicators:......................Power, signal present, output peak
limiting, overtemp ,Overload Protect, Half Power, 24V DC
POWER SUPPLY: ................................240V AC or 24V DC
FUSE PROTECTION: ......................125W - 5A AC ,10A DC
...................250W - 7.5A AC ,20A DC
DIMENSIONS ...................................≈483W x 300D x 88H
* Specications subject to change without notice
All Australian made Redback products are covered by a 10 year warranty.
Should a product become faulty please contact us to obtain a return authorisation number. Please ensure you have all the
relevant documentation on hand. We do not accept unauthorised returns. Proof of purchase is required so please retain
your invoice.

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Redback® A 4270/80 Four Zone Paging PA Amplier
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