Allen&Heath GR8A - Manual (Page 8)

8 GR8A U SER G UIDE
REMOTE STANDBY 9-pin D-type female connector can be wired to
external switches to remotely mute individual channels. Any combination
of channels can be muted at the same time. Putting a channel into
standby mutes its output driver stage. To mute a channel simply switch its
connector pin to the common (+15V) pin. Do not connect the common pin
to any other equipment. The front panel STANDBY indicator lights to warn
that the channel is muted. Use shielded cable for long cable runs.
SIGNAL OUTPUTS These are the amplifier outputs that connect to the
speaker terminals. Each has a 2-way Phoenix type pluggable screw
terminal connector. Mating plugs are provided with the unit. Use suitable
gauge speaker wire, ensure reliable connections and observe the correct
polarity according to the legend printed above the connector. The
following connections are typical.
OUTPUT MODE switches The GR8A amplifier outputs can operate non-
bridged (independently) or be bridged in pairs according to the setting of
the tamperproof underpanel mode switches. Press the switch to 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 indicator lights
to show the pair of channels is bridged. If you are using remote standby
switching for the bridged pair make sure you switch them both together.
TRANSFORMER OPTION The high quality GR8X transformer option is
available separately from Allen & Heath to convert the amplifier outputs to
drive 70V or 100V speaker lines. Alternatively, any standard 70V or 100V
line transformer of suitable power rating and quality to match the amplifier
may be used.
To avoid damage to the amplifier make sure you do not
connect a combined speaker impedance of less than 4 ohms in
single mode, or less than 8 ohms in bridge mode.
To avoid damage to the speakers do not drive the amplifier
into clipping or feed it with a previously clipped signal.
Do not use bridge mode when using the amplifier with a 70V
or 100V line transformer.
NORMAL 70V or 100V TRANSFORMER OPTION BRIDGED