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GR8A

 

U

SER 

G

UIDE

 

 

Rear Panel Controls and Connectors 

 

MAINS INPUT

      The 

GR8A

 AC mains voltage setting is factory wired 

according to country of order.  An IEC power lead with moulded plug 
suitable for your mains outlet is supplied with the unit. 

 

Check that the mains voltage marked on the rear panel 

matches your local supply.

 

 

Read and heed all the warnings printed on the rear panel and 

at the start of this user guide.

 

 

BATTERY INPUT

   An emergency back-up supply such as battery or UPS 

is a common requirement for public announcement installations.  The 

GR8A

 has a 4way Phoenix type pluggable screw terminal input to connect 

two 24V DC batteries for back-up power in the event of a loss of mains 
supply.  Use heavy gauge wire and observe the correct polarity according 
to the legend printed above the connector.  A mating connector is provided 
with the unit. 

 

SIGNAL INPUTS

   Each channel has a 3-pin female XLR chassis socket 

input.  These are electronically balanced and wired pin 2 = hot.  Input 
sensitivity is +4dBu for rated power output.  Good quality 2 core screened 
signal cable should be used for these inputs to avoid signal degradation or 
interference pickup over long cable runs.  Use balanced connections 
where possible. 

 

INPUT MODE switches

   Three tamperproof underpanel switches 

configure the inputs to allow different combinations of common input 
sourcing.  Use these when you have one or two sources feeding several 
channels.  This eliminates the need for custom multi-plug input cables. 

8 Independent 

No common sourcing 

4 way mono 

Input 1 to channels 1–4.  5-8 independent 

8 way mono 

Input 1 to channels 1–8 

2 way stereo 

Input 1 (L), 2 (R) to channels 1/2, 3/4 

4 way stereo 

Input 1 (L), 2 (R) to channels 1/2, 3/4, 5/6, 7/8 

 

MONITOR

   TRS output with tip = signal, ring and sleeve = ground.  

Follows the source selected on the front panel MONITOR switch to feed a 
small local loudspeaker or monitoring system as an alternative to the 
headphones.  The speaker voltage is reduced through a series resistor to 
prevent overload.  Further attenuation may be needed if this output is to 
feed an external amplifier or other line level equipment input. 

Summary of Contents for GR8A

Page 1: ...8 Channel Amplifier GR8A USER GUIDE Publication AP4298 ...

Page 2: ... of performance and reliability for which this equipment has been designed and manufactured read this User Guide before operating In the event of a failure notify and return the defective unit to ALLEN HEATH or its authorised agent as soon as possible for repair under warranty subject to the following conditions Conditions Of Warranty The equipment has been installed and operated in accordance wit...

Page 3: ... remove this connection CONTENTS Warranty 2 Safety Warnings 3 Welcome to the Allen Heath GR8A 4 General Precautions 4 Specifications 5 Front Panel Controls 6 Rear Panel Controls and Connectors 7 Installation 9 Operation 10 Block Diagram 11 SAFETY WARNING Mains electricity is dangerous and can kill Mains voltage is present within the GR8A Do not remove the top cover There are no user serviceable pa...

Page 4: ... Remote output standby control per channel Service And Technical Support Under normal operating conditions the GR8A does not require user maintenance or calibration apart from occasional vacuuming of the air intake filter should it become ingrained with dust To avoid damage to internal components by mishandling and or misconnection service work should be referred only to technically competent pers...

Page 5: ... into 8 ohms Peak transient power Unbridged 130W into 4 ohms Bridged 250W into 8 ohms Slew rate 10V uS Frequency response 20Hz to 20kHz 0 0 5dB Total Harmonic Distortion 6W into 8 ohms 1kHz 0 03 Signal to noise ratio Relative to 60W into 4 ohms 100dB Stand by Separate control per channel Control Switch common 15V to channel pin Attenuation 80dB Inter channel Crosstalk relative to 60W into 4 ohms 1...

Page 6: ...ontrol that adjusts its level from fully off to maximum sensitivity In bridged mode the odd numbered channel control sets the overall level and the even numbered control is not used Use the level controls to match the amplifiers to the connected source equipment set maximum volume allowed or adjust the balance between different outputs Blanking plugs are provided for situations where tamper proof ...

Page 7: ...d and wired pin 2 hot Input sensitivity is 4dBu for rated power output Good quality 2 core screened signal cable should be used for these inputs to avoid signal degradation or interference pickup over long cable runs Use balanced connections where possible INPUT MODE switches Three tamperproof underpanel switches configure the inputs to allow different combinations of common input sourcing Use the...

Page 8: ...o select bridge mode using a pen or similar pointed object This configures two amplifiers to work together into one speaker Use bridge mode when you need a lot more amplifier power to drive a single speaker BRIDGE MODE Use the odd numbered channel input and controls The even numbered input is disabled You should blank off the unused level controls using the plugs provided The front panel BRIDGE in...

Page 9: ...nd screened cables for the inputs If you have problems with ground loops lift the screen connection at one end of the input cables or operate the source equipment ground lift switches Use adequately rated speaker wire for the outputs Input cables may be run together but outputs should be separated to avoid interaction between the amplifiers Route all input and output cables away from mains compute...

Page 10: ...amplifier level controls to correct the signal matching These controls can also be used to preset the maximum volume allowed for each output or to balance the volume between different outputs Remove the knobs and fit the blanking plugs provided with the unit if you wish to lock the controls and make them tamperproof Metering A 3 colour signal meter indicator is provided for each channel to monitor...

Page 11: ...GR8A USER GUIDE 11 BLOCK DIAGRAM ...

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