Redback A 4372 User manual

Redback® A 4372 2 x 125 Watt Power Amplier
www.redbackaudio.com.au
Operating Manual
A 4372 2 x 125 Watt Power Amplier
Redback® Proudly Made In Australia
OVERVIEW
The Redback 2 x 125W power amplier is ideal for installations requiring high power zone ampliers. Ideally suited for use
in shopping centres, pedestrian precincts, public transport facilities and convention centres.
FEATURES
• Robust design incorporating latest Mosfet technology
• Very Low noise and distortion
• 100V outputs
• 240V AC or 24V DC operation
• Multi stage thermally cued fan cooling
• Output Peak Limited
• Thermal Overload protected
• Signal Presence Indicators
• Fault Indicators
• Power Status Indicators
• Rack Mountable (suits 19 inch racks)
POWER SUPPLY
The amplier operates on 230V AC or 24V DC primarily for battery backup operation. 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.
AUDIO CONNECTIONS
Audio input is via 3 pin XLR sockets on the rear of the amplier. These are 500mV line level balanced signal which are
normally fed from a mixer panel. Pinout details are printed on the rear of the amplier. Balanced Line Out XLR sockets are
also provided on the rear of the amplifer for passing the audio signal on to more slave ampliers if required. The
amplier output level controls are also rear mounted to prevent tampering or accidental adjustment.
User manual revision number: 1.0 10/02/2018

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Redback® A 4372 2 x 125 Watt Power Amplier
SPEAKER CONNECTIONS
Speakers fitted with 100V line transformers may be connected to the corresponding 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 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 is required. Listed below are the impedance at certain loads of speakers fitted with 70V
and 100V line transformers. The A 4372 Amplifier has two 125W 100V outputs. For a total load of 125 watts using 100V
line transformer fitted speakers the impedance of the speaker load should be 80Ω.
Fig 1. A 4372 front panel.
Channel 1 and 2 Indicators are identical in their functionality.
1,10 Signal Presence Indicator
This LED indicates when an input signal is present to this channel.
2,11 Peak Limit Indicator
This LED indicates when the input signal is clipping on this channel.
3,12 Over Current Limit Indicator
This LED indicates when the output module is drawing too much current from the amplier. The output module
will be disconnected until the current draw is reduced.
4,13 Over Temp Indicator
This LED indicates when the amplier module is overheating. The output will be disconnected until the amplier
module is once again cool enough to operate.
5,14 Protect Indicator
This LED indicates when the amplier module has an internal circuitry fault.
6,15 Half Power Indicator
This LED indicates when the amplier module is in Half Power mode. This can be caused when the amplier
module is being over driven or overloaded. Half Power Mode lets the amplier module continue to run without
shutting down, but with a slightly reduced power output.
7,16 24V DC Indicator
This LED indicates when the amplier channel is being powered from the 24V input.
8,17 Mains Indicator
This LED indicates when the amplier is being powered from the mains (230V AC).
9,18 On Indicator
This LED indicates the amplier channel has power.
19 Power Switch
Use this to turn the unit on.
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 effects 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 2001 or similar impedance meter.
About 70V & 100V Line Speaker SystemsLoad 70V 100V
0.5W 9.4kΩ 20kΩ
0.66W 7.12kΩ 15kΩ
1W 4.7kΩ 10kΩ
1.25W 3.76kΩ 8kΩ
2W 2.35kΩ 5kΩ
2.5W 1.88kΩ 4kΩ
3W 1.56kΩ 3.3kΩ
5W 940Ω 2kΩ
7.5W 626Ω 1.3kΩ
10W 470Ω 1kΩ
15W 313Ω 666Ω
20W 235Ω 500Ω
30W 156Ω 333Ω
40W 117Ω 250Ω
60W 78Ω 166Ω
100W 47Ω 100Ω
125W 37Ω 80Ω
250W 19Ω 40Ω
500W 9.4Ω 20Ω
191 2 3 4 5 6 7 8 9 101112 13 14 15 16 17 18
Mains On
Power
24V
Power Status
Signal Status
Present
Fault Status
Over
Limit Temp
Peak Protect
DC
Half
Power
Over
Current
Mains On
24V
Power Status
Signal Status
Present
Fault Status
Over
Limit Temp
Peak Protect
DC
Half
Power
Over
Current
Channel 2Channel 1
Model : A 4372
2 x 125W Public Address Amplier

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Redback® A 4372 2 x 125 Watt Power Amplier
Fig 2. A 4372 rear panel.
Channel 1 and 2 outputs are identical in their functionality.
1,8 Line Input
This is a balanced XLR input with an input sensitivity of 500mV.
2,9 Line Output
This is a balanced XLR output for passing the audio output on to slave ampliers if required.
3,10 Channel volume control
Use this control to adjust the output volume of the channel.
4,11 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.
NOTE: 24V DC needs to connected to both of the 24V inputs. There is no internal connection between these
terminals.
5,12 DC Resettable fuses
These fuses protect the internal power supply. If the fuses are tripped they are easily reset by pressing the small
buttons on the fuses.
6,13 Output Connections
Speakers tted with a 100V line transformer may be connected to these terminals. 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.
Otherwise either the DC or mains fuse could blow or the fault led activate and the amp will shut down. Always
be careful to avoid short circuits and connection to the wrong terminals.
7 Mains Power Input
This is for connection to a 230VAC supply. The internal fuse is an M205 7.5Amp.
RISK OF ELECTRIC SHOCK
OPEN BY QUALIFIED
PERSONNEL ONLY !
CAUTION
0
2
46
8
10
230V AC @ 50Hz
(AC FUSE 7.5A M205)
INPUT
24V DC
+_
12
3
1 • Shield
2 • Hot
3 • Cold
21
3
RESETTABLE
FUSE
Made in Australia by
Altronic Distributors Pty Ltd
www.redbackaudio.com.au
VOLUME 1LINE OUT 1
LINE IN 1
CHANNEL 1
+_
100V
OUT 1
1 • Shield
2 • Hot
3 • Cold
21
3
RESETTABLE
FUSE
VOLUME 2LINE OUT 2
LINE IN 2
CHANNEL 2
+_
100V
OUT 2
INPUT
24V DC
+_
12
3
2 1
3
2 1
3
0
2
46
8
10
1 2 3
2 1
3
2 1
3
4 5 6 7 8 9 10 11 12 13
SPECIFICATIONS
POWER OUTPUTS
Power: ...................................................2 x 125 watts RMS
Distortion:..................................................< 0.5%, @ 1kHz
Output line: ............................................................... 100V
FREQUENCY RESPONSE
Mic inputs :...........................................50Hz - 12kHz, -3dB
MIC SENSITIVITY (3 Pin XLR) ............................... 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
24V DC power: ..........................................Screw terminals
240V AC power: ................................IEC power connector
CONTROLS
Mic inputs: .............................................................Volume
Power: ...........................................................On/off switch
Indicators:......................Power, signal present, output peak
limiting, overtemp ,current limit, Protect, Half Power, 24V
DC, Mains
POWER SUPPLY: ................................240V AC or 24V DC
FUSE PROTECTION: .........................7.5A AC , 2x 10A DC
DIMENSIONS ...................................≈483W x 410D x 88H
*Specications subject to change without notice

www.redbackaudio.com.auRedback® Proudly Made In Australia4
Redback® A 4372 2 x 125 Watt Power Amplier
TROUBLE SHOOTING
If the REDBACK Phase 5 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 will 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.
No Output From 24V DC
Make sure the the 24V DC Out connector is wired correctly.
REDBACK® is a registered trademark of Altronic Distributors Pty Ltd
Since 1976 Redback ampliers have been manufactured in Perth, Western Australia by Altronics. With over 35 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
Australian Made Status
All Redback house products made by Altronics will now be sporting the ofcial Australian Made logo. Since starting manu-
facturing of commercial audio equipment in the mid 70’s we have always taken pride in producing a quality local product.
The new adoption of the Australian Made logo will help us get the word out to local and export markets that our
products carry the ofcial compliance seal of the Australian Made campaign. We have always pushed our ‘local is better’
line in all of our marketing efforts, it’s always an added boost when you are backed up by a widely recognised and
respected icon.
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 -
that’s over 37 years of operation - and still going strong!
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.
Distributed by Altronic Distributors Pty. Ltd.
Phone: [phone] Fax: [phone] Internet: www.altronics.com.au