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Description of Unit:
Front Panel
[ 1 ] On/Standby/Vacation
This LED monitors the status of operation
of the amplifier. The LED will glow
amber whenever the rear panel Power/
Vacation switch is in the OFF (powered
down with only minimal circuitry
energized) or AUTO position (amplifier
is in the standby mode). When powered
up (from AUTO) using the 3-30V AC/DC
triggering or signal sensing feature, the
LED will change to red, changing back
to amber when there is no longer signal
present or the 3-30V AC/DC triggering
is not energized. The LED will glow red
whenever the rear panel power switch
is in the ON and the GFA-6006/6002 is
energized.
The Power LED indicates that there is
AC voltage being fed to the amplifier,
but it does not signify that the entire
amplifier's circuits are in operation.
1
If, for example, one of the Thermal
Protection LEDs glows, that amplifier
channel
will
not
produce
even though the Power LED may
still glow. Additionally, the internal
power transformer is provided with a
thermostat which will interrupt power
into the transformer if its temperature
exceeds 125°C. This high temperature
will seldom, if ever, be encountered
unless the amplifier is subjected to
abnormal conditions, such as operation
into loads of less than 3 ohms at very
high listening levels. If the AC Fuse has
not failed, the Power LED is out, and the
Thermal Protection LED does not glow,
8
| ADCOM GFA-6006/02 Owner's Manual
this would indicate that the thermostat
within the transformer has opened.
Once
the
temperature
transformer decreases to a normal
level, the thermostat will reset itself
automatically and normal operation
will resume. If you are to avoid
continually tripping the thermostat in
the transformer, you must reduce the
sound level demands, correct the load
impedance of the loudspeakers, or both.
[ 2 ] Thermal Protection
The GFA-6002/6006 are 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 in 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
2
at those levels. If any amplifier channel's
output through the loudspeaker(s) ceases
sound
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 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 channels of
amplification in the GFA-6002/6006 is
an indication that the amplifier has
been over-driven or that the load the
loudspeakers are presenting to the
amplifier is unreasonably low. If you
within
the
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.
[ 3 ] Distortion Alert
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
amplifier is driving. Sometimes, when
the amplifier is in use, the LEDs may
occasionally flicker during high volume
listening, particularly if you are driving
3
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 over driving the amplifier 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.
the
loudspeakers
which
the
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