REDBACK A4370A 125 Watt Power Amplifier User Manual

: June 11, 2024
: redback

Table of Contents

REDBACK A4370A 125 Watt Power Amplifier
FEATURES
POWER SUPPLY
AUDIO CONNECTIONS
SPEAKER CONNECTIONS
TROUBLESHOOTING
SPECIFICATIONS
Warranty
References
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REDBACK A4370A 125 Watt Power Amplifier

REDBACK-A4370A-125-Watt-Power-Amplifier-product
OVERVIEW

These Redback 125W and 250W power amplifiers are ideal for installations requiring high-power zone amplifiers. Ideally suited for shopping centers, pedestrian precincts, public transport facilities, and convention centers.

FEATURES

Robust design incorporating the 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 amplifier 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) High currents may be drawn when operating from a 24V DC supply to confirm the capacity of the DC power supply used.

AUDIO CONNECTIONS

Audio input is via a 3-pin XLR socket on the amplifier’s rear. This is a 1V line-level balanced signal which is normally fed from a mixer panel. Pinout details are printed on the rear of the amplifier. A balanced Line Out XLR socket is also provided on the rear of the amplifier for passing the audio signal on to more slave amplifiers if required. The amplifier output level control is also rear-mounted to prevent tampering or accidental adjustment (see Fig 2 for more details).

SPEAKER CONNECTIONS

Speakers with a total impedance of 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 amplifier. 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 ancillary 24V devices (see Fig 2 for more details). The output has a maximum current draw of 1 amp. If more than 1 amp is drawn from the output, internal poly switches will disconnect the output. These will reset once the current draw is reduced.

REDBACK-A4370A-125-Watt-Power-Amplifier-fig-1

TROUBLESHOOTING

If the REDBACK Phase 4 amplifier fails to deliver the rated performance, check the following.

No Power, No Lights
Make sure the amplifier power switch is on. Make sure the mains power switch is on at the wall. Check the mains and DC fuse. Replace with only the correct type and rating. Overrated fuses will invalidate the 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 the signal LED on the front panel is lit to indicate there is a 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.
The amplifier Keeps on Cutting In & Out
Make sure that there is adequate ventilation around the amplifier. 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 24V DC Out connector is wired correctly.

Fig 2 shows a typical install where the A 4370A amplifiers are used as slave amplifiers with the audio output from the mixer amplifier passed through each slave amplifier. REDBACK-A4370A-125-Watt-Power-Amplifier-
fig-2

SPECIFICATIONS

Power output:	A 4370A – 125 W RMS, A 4380A – 250W
Distortion:	< 0.5%, @ 1kHz
Frequency respons	50Hz – 15kHz, -3dB
Output line:	100V, 70V, or 4 – 160
Signal to noise ratio:	(peak limiting by-passed) > 90 dB
Line output:	6000 balanced, 0dBV, 3 pin XLR
Speaker connection:	Screw terminals

24V DC output:

Inputs:

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 amplifiers in Perth, Western Australia. With over 40 years of 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 a significant added value for customers when purchasing an Australian-made Redback amplifier 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 centers, 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.

Warranty

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 bulletproof reliability. We’ve heard PA contractors tell us they still see the original Redford amplifier still in service in schools. We offer this comprehensive parts & labor 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.