User manual ADCOM GFA-780X

[. . . ] OWNER'S MANUAL GFA-7805 & GFA-7807 Multi-channel High-Current Power Amplifiers WELCOME Dear fellow ADCOM product owner, Welcome to the ADCOM family!For more than twenty years, ADCOM products have delivered excellent performance and value for customers around the world. Our products are designed by our experienced and demanding engineering team, built to the highest standards in our factory, and sold and serviced through dealers, custom installers, and other retailers whose primary goal is your complete satisfaction. We know you are anxious to hear your new amplifier in action, but please take a few minutes to read this owner's manual before connecting the amplifier to your system. [. . . ] There are two terminals for each speaker, which are colored RED for the positive (+) output and BLACK for the negative (-) output. The most secure and prevalent of these is the "U"-type spade connectors (at least 0. 25'' wide and maximum width of 0. 57"). The terminal will also accept bare wire (up to AWG1O) and "banana" type plugs (single or dual). (7) Power LED This LED will glow whenever the On/Off Switch (6) is turned on and the GFA-7805/7807 is energized. The Power LED indicates that there is AC voltage being fed to the amplifier, but it does not signify that all the amplifier's circuits are in operation. If, for example, one of the Thermal Protection LEDs (9) glows, that amplifier channel will not produce sound even though the Power LED may still glow. When the GFA-7805/7807 is turned off, the Power LED will take some time to fade out completely. 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, etc. If the AC Fuse (4) has not failed, the Power LED is out, and the Thermal Protection LED (9) does not glow, 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 (3) I2V DC Trigger The GFA-7805 and GFA-7807 are very high power amplifiers and as such must be directly connected to the wall outlet or an appropriate surge protector or AC line conditioner. It must never be connected to the `switched' outlets on the rear panel of a pre-amplifier. Usually this would mean that when you turn on/off your pre-amplifier you would have to turn on/off your power amplifier separately. We have, however, provided the ability to control the OFF/ON function of the GFA-7805/7807 by a l2V DC output jack on the rear of certain ADCOM pre-amplifiers. When using this feature the front panel Power Switch must be left in the in "on" position. To connect the preamplifier 12V DC output jack to the amplifier 12V DC jack, you will need a monaural mini phone plug to monaural mini phone plug cable. Contact your dealer for information on using this feature with ADCOM and other brand pre-amplifiers. (4) AC Fuse The AC Fuse protects the electronic circuits of the GFA7805/7807. This fuse, normally, will fail only if there 8 automatically and normal operation will resume. If you are to avoid tripping the thermostat in the transformer continually, you must reduce the sound level demands, correct the load impedance of the loudspeakers, or both. (9) 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 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. 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. (8) Thermal Protection LEDs The GFA-7805/7807 are provided with a thermal protection circuit which will shut down the individual amplifiers if its heatsink temperature reaches 85°C. [. . . ] Connect one RCA cable at a time to see if one specific cable is responsible. If any or all cables cause the hum to appear, then the preamp or processor should be evaluated for proper operation by your Dealer or Authorized Service Center. 12 CARING FOR YOUR GFA-7805/7807 Great care has been taken by ADCOM to ensure that your amplifier is as flawless in appearance as it is electronically. The front panel is a heavy-gauge, high-grade aluminum extrusion carefully finished and anodized for durability. The chassis, top cover and rear panel are heavy-gauge steel that has been powder coated and baked to ensure a lasting finish. [. . . ]