Allen&Heath GR8A - Manual (Page 10)

10 GR8A U SER G UIDE
OPERATION
Switching On
Connect all input and output cables to the unit, ensure it is correctly
installed as described previously and that the input and bridge mode
switches are set as required. Make sure the mains voltage setting is
correct and the mains switch in the ‘0’ off position. Start with all level
controls set minimum. Ensure that all equipment connected to the
amplifier is turned on. Switch the unit on by pressing the mains switch to
its ‘I’ position. The TEMP indicator lights, changing from amber to green
after a few seconds. The fan runs briefly during this time. The STANDBY
indicators illuminate for a few seconds and then go out. This shows that
the outputs are muted while the unit powers up and stabilises.
To avoid loud thumps or damage to your speakers always turn
amplifiers on last and off first.
Setting the Level Controls
It is typical to set the amplifier level controls to maximum and adjust the
volume using the preceding mixer or other equipment controls. This is fine
if the equipment gain structure is correctly set and the preceding
equipment operating level matches the sensitivity of the amplifier. If this is
not the case you can use the 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
the output signal level. This is off when there is no signal, green for low
levels, amber for normal levels and red as the signal approaches clipping.
It is very important not to operate the amplifier with the meter
led showing red for more than a brief instant, for example on music
peaks, as this may result in damage to the loudspeaker as the
amplifier clips the music signal. It is also important not to send the
amplifier an already clipped signal as this may also damage the
loudspeaker.
Channel Monitoring
Use headphones or a small speaker to monitor the amplifier output
signals. Select the channel you wish to listen to using the front panel
rotary switch. The signal is sourced from the speaker terminals so that
you can check the signal as it is routed to the speaker.
Fan Cooling
It is normal for the amplifier to run hot when it is working hard. The fan
switches from off to slow to fast depending on internal temperature. The
TEMP indicator lights green, amber or red accordingly.