Redback A 4370A User manual

www.redbackaudio.com.au Redback® Proudly Made In Australia 1
Redback® 125/250Watt Power Ampliers
Operating Manual
A 4370A 125 Watt Power Amplier
A 4380A 250 Watt Power Amplier
OVERVIEW
These Redback 125W and 250W power ampliers are 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
• 70V, 100V and 4-16Ω outputs
• 240V AC or 24V DC operation
• 24V DC @ 1 Amp output for external devices
• 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. (see Fig 2
for more details) 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 a 3 pin XLR socket on the rear of the amplier. This is a 500mV line level balanced signal which is
normally fed from a mixer panel. Pinout details are printed on the rear of the amplier. A balanced Line Out XLR socket is
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 control is also rear mounted to prevent tampering or accidental adjustment (see Fig 2 for more
details).
User manual revision number: 1.0 24/02/2020

www.redbackaudio.com.auRedback® Proudly Made In Australia
2
Redback® 125/250Watt Power Ampliers
SPEAKER CONNECTIONS
Speakers with a total impedance or 4-16Ω may be connected to the terminals marked 4-16Ω on the rear of the amplifier.
Speakers fitted with line transformers (either 70V or 100V) 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. Fig 1 lists the impedance at certain loads of
speakers fitted with 70V and 100V line transformers. So for a total load of 250 watts using 100V line transformer fitted
speakers the impedance of the speaker load should be 40Ω.
24V DC OUTPUT
A constant 24V output terminal has been provided to power ancilliary 24V devices (see Fig 2 for more details). The ouput
has a maximum current draw of 1 amp. If more than 1 amp is drawn from the output, internal polyswitches will
disconnect the output. These will reset once the current draw is reduced.
Fig 1
TROUBLE SHOOTING
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 will invalidate warranty.
Distorted Output
Check that the speaker type is correct for the output that you are using (ie. 4-16Ω, 70V or 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.
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 fitted
with line-matching transformers. This is to overcome the effects of connecting
speakers in parallel and cable losses. The amplifier generally has an output
voltage of 100 volts (70 volts is typically used in North America, however
operation is similar). In this configuration the total wattage load on the amplifier
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 amplifier.
Measuring 70/100V Line Speaker Impedance: To measure amplifier 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 Systems
Load 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

www.redbackaudio.com.au Redback® Proudly Made In Australia 3
Redback® 125/250Watt Power Ampliers
Fig 2
Fig 2 shows a typical install where the A 4370A ampliers are used as slave ampliers with the audio output from the
mixer amplier passed through each slave amplier.
4 -16Ω70V
230V AC @ 50Hz
100V
A 4370
MODEL AC FUSE
5A
A 4380 7.5A
INPUT
24V DC
+
–
RISK OF ELECTRIC SHOCK
OPEN BY QUALIFIED
PERSONNEL ONLY !
CAUTION
OUTPUTS
+
–
+
–
+
–
+_
VOLUME
1
2
3
1 • Shield
2 • Hot
3 • Cold
LINE IN
0
2
46
8
10
21
3
LINE OUT
RESETTABLE
FUSE
Made in Australia by
Altronic Distributors Pty Ltd
www.altronics.com.au
24V DC
OUT
(1A Max)
2 1
3
2 1
3
4 -16Ω70V
230V AC @ 50Hz
100V
A 4370
MODEL AC FUSE
5A
A 4380 7.5A
INPUT
24V DC
+
–
RISK OF ELECTRIC SHOCK
OPEN BY QUALIFIED
PERSONNEL ONLY !
CAUTION
OUTPUTS
+
–
+
–
+
–
+_
VOLUME
1
2
3
1 • Shield
2 • Hot
3 • Cold
LINE IN
0
2
46
8
10
21
3
LINE OUT
RESETTABLE
FUSE
Made in Australia by
Altronic Distributors Pty Ltd
www.altronics.com.au
24V DC
OUT
(1A Max)
2 1
3
2 1
3
4 -16Ω70V
230V AC @ 50Hz
100V
A 4370
MODEL AC FUSE
5A
A 4380 7.5A
INPUT
24V DC
+
–
RISK OF ELECTRIC SHOCK
OPEN BY QUALIFIED
PERSONNEL ONLY !
CAUTION
OUTPUTS
+
–
+
–
+
–
+_
VOLUME
1
2
3
1 • Shield
2 • Hot
3 • Cold
LINE IN
0
2
46
8
10
21
3
LINE OUT
RESETTABLE
FUSE
Made in Australia by
Altronic Distributors Pty Ltd
www.altronics.com.au
24V DC
OUT
(1A Max)
2 1
3
2 1
3
4 -16Ω70V100V OUTPUTS L
R
24V DC IN
Balanced Mic
+_
PTT
(short to
activate)
Power Fail
(Contacts
close on
power fail)
SendReturn
Tape Out
Preamp Out
Link To Charge
Backup battery
Input 1Input 3 Input 2Input 4Input 5Input 6
ALERT - EVAC MODULE
Output Levels
Voice Chime Alert
Over & Evac EV COMCANCH
AL
Triggers
L
R
+
–
Rem. Vol
Connect
to 1KΩ Pot
+
–
+
–
+
–
Line
24V DC
Switched
Output
DIP 5
Interface
DIP 4
DIP 1
DIP 2DIP 3
Balanced Mic
Line
Balanced Mic
Line
Balanced Mic
Line
Balanced Mic
Line
Balanced Mic
Line
Balanced Line
L
R
L
R
L
R
L
R
L
R
2 1
3
2 1
3
2 1
3
2 1
3
2 1
3
2 1
3
2 1
3
1 2 3 4 5 6 7 8
1 2 3 4 1 2 3 4 1 2 3 4 1 2 3 4
230V AC @ 50Hz
www.altronics.com.au
RESETTABLE
DC FUSE
Made in Australia
by Altronic
Distributors
Pty Ltd
DIP 5
DIP 4
IMPORTANT NOTE
Ensure power is switched OFF when
adjusting DIP switches. New
settings will be eective when
power is switched back on.
DIP 3
SW ItemOnO
1
2
Input 6 Level 1V 100mV
3
Not USed
4Input 5 Level 1V 100mV
Not USed
1
2
3
4
DIP 2
SW ItemOnO
Input 4 Level 1V 100mV
Not USed
Input 3 Level 1V 100mV
Input 3 Priority OnO
*
DIP 1
SW ItemOnO
1
2
Input 2 Level 1V 100mV
3
Input 2 Priority OnO
4Input 1 Level 1V 100mV
Input 1 Priority OnO
*
*
SW ItemOnO
1
2
3
4Not Used
Not Used
Not Used
Not Used
DIP 4
DIP 1
DIP 2DIP 3
SW ItemOnO
Switched 24VDCOutOnO
Phantom Power Input 6 OnO
OnO
1
2
3
4Phantom Power Input 5
OnO
5Phantom Power Input 4
OnO
6Phantom Power Input 3
OnO
7Phantom Power Input 2
OnO
8Phantom Power Input 1
Preamp Out †Post
Pre
†Sets the Preamplier output to
Pre or Post Master.
DIP 5
Priority or VOX muting is only
functional on inputs 1-3. When
VOX is enabled on input 1 it will
override all other inputs includ-
ing the Alert/Evac Module. VOX
enabled on input 2 will override
inputs 3-6. VOX enabled on input
3 will override inputs 4-6.
If the Alert/Evac module is tted
it will override inputs 2-6.
*
Model 125W
5AAC Fuse
250W
7.5A
AC Fuse Ratings
RISK OF ELECTRIC SHOCK
OPEN BY QUALIFIED
PERSONNEL ONLY !
CAUTION
Speakers tted with
100V line transformers.
SLAVE AMPLIFIER
SLAVE AMPLIFIER
A 4370A AMPLIFIER
MIXER AMPLIFIER
+-

www.redbackaudio.com.auRedback® Proudly Made In Australia
4
Redback® 125/250Watt Power Ampliers
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 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
Australian Made Status
All Redback® house products made by Altronics will now be sporting the ofcial Australian Made logo. Since starting
manufacturing 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 40 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
*Specications subject to change without notice
SPECIFICATIONS Measurements referenced to 1kHz.
Power output: A 4370A - 125 W RMS, A 4380A - 250W
Distortion: < 0.5%, @ 1kHz
Frequency response:50Hz - 15kHz, -3dB
Output line: 100V, 70V, or 4 - 16Ω
Signal to noise ratio: (peak limiting by-passed) > 90 dB
Line output:600Ωbalanced, 0dBV, 3 pin XLR
Speaker connection:Screw terminals
Inputs: 3 pin XLR (500mV)
24V-30V dc power: Screw terminals
240V ac power: IEC power connector
Indicators: Mains, 24V DC, Power, Signal presence,
Over temp, Over current, Shut down, Peak limiting
Current Draw: A 4380A -250mA Standby, 17A Full @ 24V dc
Power supply: 240V ac or 24V dc (nominal)
Protection: A 4370A - 5A ac and 10A dc fuse
Dimensions: ≈483W x 340D x 88H
24V DC output: Screw terminals
Current Draw: A 4370A -250mA Standby, 8A Full @ 24V dc
A 4380A - 7.5A ac and 20A dc fuse
Input Impedance: ≈10KΩ