9
automatically and normal operation will resume. If you
are to avoid tripping the thermostat in the transformer
continually, you must reduce the sound level demands,
correct the load impedance of the loudspeakers, or both.
(8) Thermal Protection LEDs
The GFA-7805/7807 are provided with a thermal protection
circuit which will shut down the individual ampliers
if its heatsink temperature reaches 85°C. The Thermal
Protection LEDs will light whenever the thermal protection
circuit in its respective channel has been triggered and the
amplier is inoperative. The thermal protection circuitry
will typically be triggered by very high power demands
into impedances much lower than the amplier is capable
of driving at those levels. If any amplier channel’s
output through the loudspeaker(s) ceases abruptly, and
its Thermal Protection LED glows, you will know that its
heatsink temperature has become unacceptably high
and the circuitry is protecting the amplication devices.
Please note that the Power LED (7) will remain on and the
amplier will still be energized. Once the temperature
of the heatsink(s) drops to a safe operating level, that
amplier will automatically resume operation.
Activation of the Thermal Protection circuitry in any
of the ampliers in the GFA-7805/7807 is an indication
that the amplier has been over-driven or that the
load the loudspeakers are presenting to the amplier
is unreasonably low. If you wish to prevent recurrent
activation of the thermal protection circuitry, you must
reduce the volume-level demands or correct the load
impedance condition which may be causing activation of
this circuitry.
(9) Distortion Alert LEDs
The Distortion Alert circuit is a unique ADCOM distortion
detection system which reads all forms of non-linear
distortion such as THD, IM, slew-induced, “clipping,” etc.
The Distortion Alert LEDs will light when distortion reaches
approximately 1% regardless of impedance, voltage/
current phase angle or the reactance of the loudspeakers
which the amplier is driving. Sometimes, when the
amplier is in use, the LEDs may occasionally icker
during high volume listening, particularly if you are driving
low impedances. This ickering is no cause for concern.
The LEDs are simply warning you that the amplier is
approaching its maximum power output into the particular
loudspeakers you are using. If, however, the Distortion
Alert LEDs glow brightly or are illuminated most of the
time during playback, you are over driving the amplier
and should turn down your volume control to reduce
the listening level, otherwise it may cause the Thermal
Protection to be activated or, in extreme cases, damage
your loudspeakers.
