Adcom GFA-7705 User Manual

Distortion Alert LEDs (7)
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 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 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 vour
loudspeakers.
Thermal Protection LEDs (8a)
The GFA-7705/07 is provided with both a thermal protection circuit and a current overload circuit
which will shut down the individual amplifier's channels if its heatsink temperature reaches 85° C or the
amplifier’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 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 (7) 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-7705/07 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 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.
S.A.F.E.® Protection Circuit (8b)
Self-Annealing Fuse Equipped: Instead of blowing internal protection rail fuses in the event of a dead-
short to either a loudspeaker or speaker cable leads, the GFA-7705/07 will enter into a self-protect
SAFE mode.
If the output of any channel of the amplifier becomes shorted the protection circuit will trip and
the individual Thermal Protection LED for that channel will light. The Protection LED will blink
approximately every 5 seconds as the circuit will attempt to reset; if the short has been corrected the
amplifier 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 amplifier power is
switched off.
8

Adcom GFA-7705 Specifications

Power

power rating into 8 ohms	200 Watts continuous average power per channel
power rating into 4 ohms	300 Watts continuous average power per channel
power consumption idle 7 channel	120W

Audio Performance

frequency response at 1 watt into 8 ohms	+0, -0.22dB
power bandwidth	3 Hz to 130kHz
dynamic headroom into 4 ohms	1.90 dB

Electrical Specifications

input sensitivity for 1 watt output	0.1 volts
input sensitivity for 200 watts output	1.40 volts
damping factor (20Hz to 20kHz)	800

Dimensions and Weight

chassis dimensions	8.5” (216mm) x 17” (432mm) x 17.5” (444.5mm)
maximum dimensions	9 3/8” (238mm) x 17” (432mm) x 18.5” (470mm)
unit weight GFA-7707	35.5 kg