Next Page. Page 2 This service manual is intended to assist trained and qualified technical personnel in verifying the performance of, adjusting, and repairing the ADCOM GFA amplifier. The procedures described here are not intended for persons unfamiliar with the appropriate safety and test procedures. The version can usually be distinguished by external inspection. The convertible version has a detachable line cord. Internally, their are two differences. Page 7 V to V 1. Unplug the amplifier and remove the top cover.
Locate the connecting block mounted next to the power switch. The Inputs 1 and Outputs 2 are grouped in three 3 sections on the rear panel and are labeled L left , C center and R rear. As a rule of thumb, red is always Right , and either black or white is Left. If you have a three-connector RCA cable, there may be a yellow connector as well. This should be used for the Center channel.
The cable should have low capacitance, preferably not more than pF for each segment of the cable. Your Adcom Dealer can help you choose a set of cables that will work best for you. In connecting the amplifier to the loudspeaker, it is vital to maintain proper polarity positive to positive, negative to negative.
There are various ways to connect the speaker wire to the Output 2 terminals. The first and most popular is the "banana plug". It has a "springy", large contact area for stable performance, and is easily inserted and removed. You may also use the "spade" connector which should have a maximum width of 0. The spade connector has the largest area of contact for a low-resistance connection and can be made very secure. You may also use bare wires or pin connectors to connect to the Output 2 terminal by unscrewing the insulated head of the binding-post terminal and exposing the hole through the gold-plated post.
Bare wire up to AWG10 or pin connectors up to 0. Simple hand-tightening of the insulated head will securely connect the wire to the terminal. Finger pressure is all that is required. You should not use pliers or other tools which could damage or over-tighten the binding-post assembly.
It is very important to use the correct size of wire in order to avoid unnecessary loss of amplifier power in the cable, reduction of amplifier damping factor and other undesirable conditions. Specifications require the use of at least AWG16, stranded, copper cable. Recommended capacitance of the speaker wire should be less than or equal to 50pF per foot.
If longer runs are needed, it is best to consult with your Adcom Dealer to maximize the performance of your system under your exact listening conditions. All loudspeakers having a nominal impedance down to 4 ohms can be connect to and driven by the GFA The amplifier can drive these low-impedance speakers at more than adequate power levels with no difficulty.
It should be noted here that many loudspeaker systems which are nominally rated at 4 ohms drop in impedance, in some parts of their frequency range, to as low as 2 ohms and sometimes less. You will not experience difficulties even with these very low impedance loads unless you demand excessively high volumes levels from your system. In most applications, you can drive two or more sets of loudspeakers.
You should note, however, that when loudspeakers are wired in parallel, the impedance presented to the amplifier is lower than the nominal impedance of each loudspeaker. In other words, if you parallel two sets of 8-ohm loudspeakers, the resultant impedance presented to the amplifier will be 4 ohms. If 8-ohm and 4-ohm loudspeakers are paralleled, the resultant impedance will be approximately 2. In this last situation, depending upon the lowest impedance of the nominally 4-ohm speakers, and if excessive power demands are placed upon the amplifier, you may trigger the Thermal Protection on the amplifier or trigger the internal protection devices.
For convenient switching of multiple sets of speakers with impedance protection for the amplifier, you should consider the use of an ADCOM speaker selector. When turning a system of separate components on or off, there is a proper sequence to insure that no transient surges appear at your loudspeakers. If you own a vacuum-tube preamp, then follow the turn-on wait time according to its manufacturer.
After that, you may turn off the rest of the system. 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.
If the front panel, top or sides become dusty or fingerprinted, they can be cleaned with a soft lint-free cloth, slightly dampened with a very mild detergent solution or glass cleaner. Use the chart below to solve common situations that don't require professional attention.
Any problems not covered here should be brought to the attention of your Adcom Dealer or Adcom Customer Service Department. A special note on "hum": When there is a low-volume "hum" audible throughout your speakers, even with the main volume turned all the way down, you have a common phenomenon known as a "ground loop". A ground loop is basically a difference in ground voltages between two or more components which are connected electrically and which creates multiple current paths where there must only be one.
This difference in potential creates a 60Hz low-level sound approximately a low A , that appears to "hum", hence the name. It can be caused by adding new components to your system, but that does not imply there is anything electrically wrong with any new component.
Generally, the cause is the Cable-TV incoming signal line. This new incoming line may add an additional ground at a different potential from the AC line ground of your other equipment. Problem with source unit CD, tape, etc. Note 1 : Cable TV systems can sometimes contribute to ground-loop problems which cause "hum". To determine if your cable system is the contributing factor, disconnect the Cable-TV incoming signal line round, 75W at the wall, or the first component to which the cable is connected to i.
To purchase GFA spares or accessories, please contact the company via their website or visit an authorised retailer. Gallery Requests Search. Reviewed Jun 28th, by guest I own a lot of hi fi gear life long hobby. Submitted by rickwb on August 16th, Again, my thanks for a great site. Submitted by cmuto on January 21st, Submitted by JaS on January 21st, User login Login. Create new account Request new password. Latest Comments Re Re: Need Assistance Re: Pm
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