Adcom GFA-555 Pro - Bridged Mode and Protection; Bridged Mono Hook Up; Amplifier Protection Circuits

BRIDGED (MONO) HOOK UP
The ADCOM GFA-555 PRO amplifier can be used as an extremely powerful monaural amplifier
without the use of any additional accessories or modifications.
p For mono operation, the Stereo/Bridged switch on the rear panel should be placed in the Bridged position.
In the Bridged mode only a single input cable is used. The input cable to the GFA-555 should be plugged into the
Right Channel input only. The Right Channel input signal attenuator will function should amplifier matching be
necessary.
When connecting a single speaker to the GFA-555 in bridged operation, the Positive lead from the speaker
should be connected to the Right Channel Positive (Red) output terminal on the GFA-555. The Negative lead from
the speaker should be connected to the Left Channel Positive (Red) output terminal. Remember that when
connecting the speaker wires, you should maintain proper phasing to obtain maximum bass response and coherent
sound quality.
SECTION 4
AMPLIFIER PROTECTION CIRCUIT
Your GFA-555 power amplifier is equipped with externally mounted circuit breakers. These Breakers are
designed to provide overload protection for the amplifier. There are two circuit breakers for each channel mounted
on the front panel for easy access. If any of the circuit breakers should trip, a button in the center of the breaker will
pop out. Before resetting the breaker be sure to turn the power switch off, lower the input signal level and check for
short circuits. To reset the circuit breaker simply depress the button that has popped out. If the breaker trips again
immediately; ‘recheck all connections for shorts and allow several seconds to elapse before attempting to reset the
breaker again. UNDER NO CIRCUMSTANCES SHOULD THE BREAKER BUTTON BE DEPRESSED AND
HELD IN. If any of the breakers cannot be successfully reset after checking all connections, please refer to Section 8.
Thermal cutoffs are also employed to protect the amplifier under high temperature conditions. Should
any of the thermal cutoffs activate, Turn off the amplifier, reduce the input signal level and make sure that the
amplifier has adequate ventilation. Allow several minutes for the thermostat to reset before resuming normal
operation.
It should be noted that any time the circuit breakers trip, it is an indication that the amplifier is either
encountering a short circuit or being over-driven. Check all input and output connections for loose wires and short
circuits. The input signal level should be reduced either through the use of the input signal attenuators on the
GFA-555 or at the mixing console main output or volume control. The most common cause of Thermal shut-down
is improper ventilation of the amplifier. Please refer to Section 2 for proper installation instructions.
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