REDBACK A 4270 Paging PA Amplifier User Manual

REDBACK A 4270 Paging PA Amplifier

Product Information

• The A4270 is a 125 watt four-zone paging PA amplifier
• The A4280 is a 250 watt four-zone paging PA amplifier
• Optional extras include the A4488 four-zone paging console, A4373 remote volume module, A2280B remote volume wall plate, and A4376 rack mount ears
• All products are 100% developed, designed, and assembled in Australia
• Redback offers local support and feedback, with industry-leading 10-year warranties on almost every Australian-made public address product

Product Usage Instructions

1. Read the user manual carefully prior to installation
2. Install and connect the amplifier and any optional extras according to the instructions provided
3. Use the front panel controls to adjust the output volume of inputs 1-4:
   • 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.
   • BGM Output Select: Use this control to select the background music output.
   • Status Indicators: These indicators show the status of various amplifier functions, including VOX sensitivity, local music input signal, overload protection, and more.
   • Master Volume: Use this control to adjust the overall output volume of the amplifier.
   • Bass and Treble: Use these controls to adjust the bass and treble levels of the output.
   • Outputs 1-4: These outputs are used to connect speakers to the amplifier, with each output corresponding to a specific zone.
   • Normal Mic and Paging Mode: Use these controls to select the microphone input mode (normal or paging).
   • 1/2 Power Active: This indicator shows when the amplifier is operating at half power.
   • Mic BGM Active: This indicator shows when the microphone and background music inputs are active.
   • Evac Tones Active: This indicator shows when evacuation tones are active.
   • Over Temp Protect: These indicators show when the amplifier is overheating and has entered protection mode.
   • Over Peak Fault: This indicator shows when the amplifier has reached its peak output and has entered fault mode.
   • 24V On Load Limit DC: These indicators show the status of the amplifier’s power supply.
4. If any issues arise with the amplifier, refer to the user manual for troubleshooting steps or contact Redback for local servicing.

• A 4270 125 WATT FOUR ZONE PAGING PA AMPLIFIER
• A 4280 250 WATT FOUR ZONE PAGING PA AMPLIFIER

Optional Extras

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.
• You may be surprised to learn that Redback 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 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 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 centres or automated push button options.
• It’s not only the assembly team at Redback 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 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 & 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.

OVERVIEW

The Redback® A 4270 125 Watt and A 4280 250 Watt 4 Zone paging amplifiers are specifically designed for multi-zone applications. Based on the popular Redback® A 4377 and A 4387 amplifier series, these amplifiers have three inputs that can be configured for either microphone or line level. The addition of zone paging is made possible by connecting Redback® A 4488 paging consoles to the amplifier. The amplifiers have a main 100V speaker output plus as additional four separate 100V output speaker loads, each of which has provision for background music that can be overridden by the A 4488 paging microphones. The Redback® A 4270 conservatively delivers 125W RMS power, while the A 4280 delivers 250W RMS. Frequency response 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 flexibility for a wide scope of applications such as factories, workshops, mine sites, sports clubs and office buildings. The amplifiers 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 configured internally to 70V line or low impedance (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 amplifier also utilizes a half power mode which enables the amplifier to continue to run at a reduced output level if it is being overdriven. Tape output sockets are provided for recording purposes or feeding into additional power amplifiers. Remote volume available when A 4373 Digital volume control module fitted internally and external A 2280B wall plate or 1KΩ potentiometer is connected. MP3 based Alert and Evacuation tones along with chime tones and voice-over messages are built standard functions of the amplifiers.

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 fitted and external A 2280B wall plate)
• Rack Mountable (suits 19 inch racks) with optional A 4376 rack ears

FRONT PANEL CONTROLS

Figure 1 shows the layout of the front panel.

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 amplifier 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 amplifier 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 amplifier is being powered from the 24V input.

9. Fault Indicator
   This led indicates when the amplifier 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 amplifier. 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 amplifier is overheating. The output will be disconnected until the amplifier is once again cool enough to operate. If thie LED is orange the amplifier has gone into half-power mode. This mode lets the amplifier continue to run at a lower output rather than shutdown completely. This mode might be initiated from the amplifier 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.

REAR PANEL CONNECTIONS

1. 100V Out (Main) Output Connections
   This is the main output of the amplifier and is for connection of speakers fitted with a 100V line transformer.
   Always ensure that the total load of the speakers does not exceed the rated output of the amplifier 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 fire indicator board, break glass alarm etc.
   All tones are MP3 based files 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 files 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 fitted 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 amplifier 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 amplifier and an M205 7.5Amp for the A 4280 250 Watt amplifier.

AUDIO CONNECTIONS

The amplifier 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 figure 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 amplifier.

MIc XLR wiring Configuration

1. Earth/Shield
2. Signal Hot
3. Signal Cold

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.

POWER SUPPLY

The amplifier 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 confirm the capacity of the DC power supply used.

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, first disconnect power from the unit and then remove the lid. The location of the DIP switches is shown in figure 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.

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 trim pots located on the front of the amplifier (see figure 1).

REMOTE VOLUME (Optional)

• It is possible to control the master volume with the addition of the A 4373 Digital Remote volume board and a 1k potentiometer (or A 2280B wall plate) tied across the terminals labeled “Optional Plugin” on the rear of the amplifier.
• The plugin board is fitted inside the amplifier in the location shown in Figure 4.

NOTE: Take special care with the orientation of the board and remove power from the amplifier before fitting.

About 70V & 100V Line Speaker Systems

Wiring speakers in parallel for 70/100V line:W here 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 efiects 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 Q 2003 or similar impedance meter.

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 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 80 .

Fig 6 shows a typical install where the A 4270 has all five 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 amplifier.

Audio from the amplifier is output to the main 100V Out terminals and is not affected by the A 4488 paging consoles. The audio from the amplifier 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 amplifier. 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).

RJ45 cabling configuration (586A ‘Straight through’)

The A 4488 paging consoles are connected to the amplifier using “pin to pin” configuration RJ45 data cabling as shown in fig 7. When installing ensure all connections are verified with a LAN cable tester before switching any system component on.

Failure to follow the correct wiring configuration may result in damage to system components. and will Void the warranty.

A 4488 CONNECTIONS

Figure 8 shows the layout of the rear panel.

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 amplifier.

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.

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 amplifier.

• IMPORTANT NOTE
  Ensure power is switched off when adjusting DIP switches.

• New settings will be effective when power is switched back on.

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 illuminate 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 finished. The selected zones’ LED’s will flash for a few seconds after paging has finished. While these LED’s are still flashing 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 amplifier front panel switches.

BACKGROUND MUSIC (REAR OF A 4488 PAGING CONSOLE)

Background music to the four output zones is primarily fed from the audio output of the amplifier 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, first 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 flash 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.

Connecting an audio source to the BGM input

ALERT, EVACUATION and CHIME MP3 FILES and ALERT and EVAC VOICE OVER MESSAGES

The supplied MIcro SD card houses all the MP3 audio files used for the output tones. These files are stored in five separate folders (see figure 5) and relate to the corresponding output. e.g. the Alert folder houses the MP3 file to be played when the Alert mode is triggered.
These files can be any length and bit rate, but must be in MP3 format (they cannot be Wav files or AAC files).

Note 1: MP3 files should have the following specifications for optimum performance. 128kbps, 44.1kHz, 32bit, VBR or CBR, Stereo (even better as mono).
Note 2: only one MP3 file can be in each folder

There is also a folder labelled “#LIBRARY# which contains a host of sample MP3 files. The “Voice” folder contains the MP3 audio files played as the Alert and Evacuation messages. There are separate folders for both the Alert and Evacuation messages as shown in figure 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 file is present in the relevant folder. If the voice over message is not required leave the folder empty.

INSTALLING MP3 FILES

• You will first need to remove power from the amplifier 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 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 figure 12.

Open the Removable Disk and you should get a window that looks like figure 13.

• The contents of the SD Card include a Library folder of sample MP3 files and five folders for the MP3 files associated with the various triggers.
• There should be default MP3 files included in each folder. These will need to be replaced with your own MP3 files.
• Open the folder in which you want to install an MP3 (in our case its the Alert folder) and you should see an MP3 file which is named Alert.MP3 as shown in figure 14.

This MP3 file needs to be deleted and replaced by the MP3 file you want to play when you activate the Alert mode. The MP3 file name is not important. But it is important that there is only one MP3 file in the Alert folder. Check the properties of the MP3 file.

NOTE the new MP3 file cannot be “Read only”.

• To check this, right click on the MP3 file and scroll down and select Properties, you will get a window that looks like figure 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 amplifier is OFF
  and insert the SD card into the slot in the rear; it will click when fully inserted. The amplifier is ready to use.

DIP SWITCH SETTINGS

These switches affect the alert/evac triggers on the rear of the amplifier.

• 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.

FIRMWARE UPDATE

It is possible to update the firmware for this unit by downloading updated versions from redbackaudio.com.au.

To perform an update, follow these steps.

1. Download the Zip file from the website.
2. Remove the SD card from the amplifier and insert it into your PC. (Follow the steps on page 11 to open the SD card).
3. Extract the contents of the Zip file to the root folder of the SD Card.
4. Rename the extracted .BIN file 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 amplifier.
7. Turn the amplifier ON. The unit will check the SD card and if an update is required the amplifier will perform the update automatically.

TROUBLESHOOTING

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

No Power, No Lights
Make sure amplifier 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. Overrated fuses with invalidated 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.

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.

Unit will not play MP3 files.
Make sure all MP3 files are not “Read Only”. See page 13
MP3 files should have the following specifications for optimum performance. 128kbps, 44.1kHz, 32bit, VBR or
CBR, Stereo (even better as mono).

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, over-temp, 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

Specifications 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 authorization number. Please ensure you have all the relevant documentation on hand. We do not accept unauthorized returns. Proof of purchase is required so please retain your invoice.

RELATED PRODUCTS

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Redback® A4390A 500W Power Amplifier
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The Redback A 4395A is a 500 Watt Mixer amplifier for installations requiring a high power zone amplifier. The amplifier has two audio inputs, with input 1 either a balanced XLR input or dual RCA line input, and input 2 a dual RCA. There is also a music input on the front of the amplifier for connection of portable devices. This input when connected, over-rides the rear input 2 audio source and is adjusted via the volume 2 level control.

Redback® A4275B 125W MIxer Amplifier, A4285B 250W MIxer Amplifier These Redback 125W and 250W mixer amplifiers are ideal for applications that require up to six inputs. Featuring six mic/line inputs with four levels of VOX priority, an LCD interface and a minimum and maximum Master Volume Over-ride. It also includes a 24V switched output via PTT microphone (not supplied) and a USB keyboard interface for labelling of inputs and installer contact details. A music Input on front panel overrides input 6 and the unit includes remote volume control (via optional A 2280B wall plate) and a 300mA Backup Battery charging terminal.

www.redbackaudio.com.au

References

• redbackaudio.com - Crazy Domains

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