8
Distortion Alert LEDs (8)
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.
Thermal Protection LEDs (9)
The GFA-7700 is provided with both a thermal protection circuit and a current overload circuit which
will shut down the individual amplier’s channels if its heatsink temperature reaches 85°C or the
amplier’s outputs are shorted. The Thermal Protection LEDs will light when either of these protection
circuits are on 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. If the output of any channel of the amplier becomes shorted
the protection circuit will trip and the Thermal Protection LED for that channel will light. After
approximately 5 seconds the unit will attempt to reset, if the short has been corrected the amplier
will resume proper operation. If the short is still present the channel will cycle off again. The cycling of
the protection circuit will continue until the short is corrected or the amplier power is switched off.
Activation of the Thermal Protection circuitry in any of the ampliers in the GFA-7700 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.
