Adcom THX GFA-7000 - Manual (Page 8)

o 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 1% regardless of impedance, voltage/current
phase angle or the reactance of the loudspeakers which the amplifier is driving. Sometimes,
when the amplifier is in use, the LEDs may occasionally flicker during high volume listening,
particularly if you are driving low impedances. This flickering is no cause for concern. The
LEDs are simply warning you that the amplifier 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 overdriving the amplifier and should
turn down your volume control to reduce the listening level, othenvise it may cause the Thermal
Protection to be activated or, in extreme cases, damage your loudspeakers.
o
Thermal Protection LEDs
The GFA-7000 is provided with a thermal protection circuit which will shut down the
individual amplifiers if its heatsink temperature reaches 85°C. The Thermal Protection LEDs will
light whenever the thermal protection circuit on its respective channel has been triggered and
the amplifier is inoperative. The thermal protection circuitry will typically be triggered by very
high power demands into impedances much lower than the amplifier is capable of driving at
those levels. If any amplifier 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 amplification devices. Please note that the
Power LED
(
0
)
will remain on and the amplifier will still be energized. Once the temperature of
the heatsink(s) drops to a safe operating level, that amplifier will automatically resume
operation.
Activation of the Thermal Protection circuitry in any of the amplifiers in the GFA-7000 is an
indication that the amplifier has been overdriven or that the load the loudspeakers are
presenting to the amplifier 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.