background image

GR8A

 

U

SER 

G

UIDE

 

Front Panel Controls 

 

POWER switch

   Turns the amplifier on or off. 

 I

  = on, 

 0

  = off.  

 

TEMP indicator

   Shows the status of the amplifier temperature 

management system: 

Green  Low temperature   

Amplifier on, cooling fan stopped 

Amber  Medium temperature 

Cooling fan running at slow speed 

Red 

High temperature  

Cooling fan running at fast speed 

 

SIG indicators

   Each channel has a 3-colour indicator to monitor the 

output signal level: 

Green  Signal present 

Turns on at 140mW into a 4 ohm speaker. 

Amber  Medium level 

Turns on at 10 watts into a 4 ohm speaker. 

Red 

Signal peak 

Turns on just before clipping 

 

STANDBY indicators

   Each channel has a red indicator that lights when 

it is in standby mode with its output stage muted.  All channels are held in 
standby mode for a few seconds when you switch the unit on.  This 
prevents thumps in the speakers while the power rails stabilise.  Selected 
channels can be put into standby mode using the rear panel REMOTE 
STANDBY connector switching facility. 

 

BRIDGE MODE indicators

   Each pair of channels has a green indicator 

that lights when it is configured for bridged operation using the rear panel 
OUTPUT MODE switches. 

 

LEVEL controls

   Each channel has a rotary control 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 level setting is required.  Simply set the level, pull off 
the knob and push in the blanking plug.  The level can be adjusted without 
refitting the knob by pulling out the plug and using a small slotted 
screwdriver to turn the control shaft. 

 

MONITOR switch

   8 Position switch to select one of the 8 amplifier 

outputs as the monitor source for headphones or local speaker.  This lets 
you check the selected amplifier from its speaker terminals attenuated 
through a series resistor to match the sensitivity of the headphones. 

 

PHONES socket

   Plug in headphones to listen to the selected monitor 

source.  This is a TRS jack socket wired for standard stereo headphones.  
The selected channel is monitored in mono. 

 

SENS switch

   Adjusts the monitor output to match the sensitivity of the 

connected headphones.  This is an underpanel tamperproof switch to 
prevent accidental operation.  Use a pen or similar pointed object to 
change its setting.  The output level is increased when the switch is in its 
pressed position. 

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 ...

Reviews: