Adcom GFA-6002, GFA-6006 Distortion Alert, Description of Unit Front Panel, Thermal Protection

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.

this would indicate that the thermostat within the transformer has opened.

Once the temperature within the 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

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.

[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 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

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If, for example, one of the Thermal Protection LEDs glows, that amplifier channel will not produce sound 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,

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 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

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.