GFA-5200
High Current
Power Amplifier
OWNER'S MANUAL
Congratulations on your decision to purchase the GFA-5200 Stereo Power Amplifier. You have made a wise choice that will reward you with exceptionally accurate and musical sound reproduction for years to come. To realize the full potential of your new amplifier, please read these operating and installation instructions thoroughly before attempting to connect it.
ADCOM offers the enclosed valuable Limited Warranty. Please read the details on the Warranty Card carefully to understand the extent of the protection offered by the Warranty, its reasonable limitations, and what you should do in order to obtain its benefits. Be sure to verify that the serial number printed on the rear panel matches the serial number on the outer carton. If any number is altered or missing, you should notify us immediately in order to ensure that you have received a genuine ADCOM product which has not been opened, mishandled, or tampered with in any way.
Before your new GFA-5200 left our factory, it was carefully inspected for physical imperfections and tested for all electrical parameters as a routine part of ADCOM's systematic quality control. This, along with full operational and mechanical testing, should ensure a product flawless in both appearance and performance. After you have unpacked the GFA-5200, inspect it for physical damage. Save the shipping carton and all packing material as they are intended to reduce the possibility of transportation damage, should the amplifier ever need to be shipped again. In the unlikely event damage has occurred, notify your dealer immediately and request the name of the carrier so a written claim to cover shipping damages can be initiated. THE RIGHT TO A CLAIM AGAINST A PUBLIC CARRIER CAN BE FORFEITED IF THE CARRIER IS NOT NOTIFIED PROMPTLY IN WRITING AND IF THE SHIPPING CARTON AND PACKING MATERIALS ARE NOT AVAILABLE FOR INSPECTION BY THE CARRIER. SAVE ALL PACKING MATERIALS UNTIL THE CLAIM HAS BEEN SETTLED.
During normal home operation the internal heatsinks of the GFA-5200 may become warm. However, there are instances during high-level playback into low impedances when the heatsinks will become much warmer than usual. To ensure the amplifier's long-term, trouble-free operation it is necessary to provide adequate ventilation for the heatsinks. Therefore, the GFA-5200 should be kept away from external sources of heat such as radiators and hot-air ducts. The GFA-5200 should never be placed with other heat-producing components in a cabinet or enclosure lacking free air flow.
If you require that the GFA-5200 be mounted in an enclosed cabinet, it is recommended that the rear panel of the cabinet be provided with ventilation openings at the top and bottom to allow air to circulate freely in the cabinet. The top and bottom panel of the amplifier's chassis have been provided with vents to allow the necessary cooling of the internal components. It is imperative that these vents are not obstructed in any way.
We recommend that you do not stack other components on top of the GFA-5200. This is particularly important If your system includes low-impedance loudspeakers which are difficult to drive, or if you will consistently demand high volume levels from the amplifier and speaker system, Not only will heat generated by the amplifier affect the performance of equipment stacked on top of the GFA-5200, but the free flow of air through the ventilating slots in the amplifier may be partially obstructed.
If you observe these recommendations, the GFA-5200 will perform reliably in any reasonable environment. You should also pay attention to such normal considerations as protection from excessive dust and moisture. Occasional vacuuming of accumulated dust on the chassis, heatsinks, panels and around the ventilating slots should be all that is required.
The optimal performance of your new GFA-5200 will ultimately depend on the care with which you make the connections between the amplifier, preamplifier and the loudspeakers. All input and output signal connections should be made only with high-quality, low-loss, low-capacitance cables following the recommendations in the following relevant sections.
L INPUT / R INPUT (1)
The audio inputs to the GFA-5200 are through two high quality, gold plated RCA jacks to minimize high-frequency losses, noise. etc. They will accept standard RCA-type plugs, one for each channel, Left (L) and Right (R), usually supplied at the ends of interconnecting cables. To ensure that the performance designed into the GFA-5200 is realized, you should use the highest quality cables feasible. Whatever cable you finally select, it should have low capacitance. This is particularly important if you use a long run between the preamplifier and amplifier. Generally speaking, a cable with a capacitance of less than 100 pF will work best.
The load impedance which the GFA-5200 inputs present to the source preamplifier or tuner-preamplifier is 49.9k ohms. This load impedance results in minimal amplifier noise when used with a source component of low output impedance such as an ADCOM preamplifier or tuner/preamplifier.
Whenever connections to or from the GFA-5200 are being made, be certain that the AC on/off switch of the amplifier is in the off position, the AC cord of the amplifier is disconnected from the AC wall outlet and that all associated components are turned off.
To preserve the correct stereophonic effects, please be certain to connect the left output of the preamplifier or tuner-preamplifier to the RCA jack on the GFA-5200 labeled L INPUT and the right output of the source component to the R INPUT jack.
L OUTPUT / R OUTPUT (2)
The GFA-5200's connection to the loudspeakers are made through two high quality, five-way, gold-plated binding posts located on the rear panel. These terminals will accommodate either bare wire, tinned wire, terminal pins, spade lugs or banana plugs, both single and dual. These output terminals are color coded RED and BLACK to indicate polarity. To ensure correct stereo phasing, you must connect the RED output terminal (labeled "+") to the loudspeaker INPUT terminal color coded RED (or labeled POSITIVE, "+", POS, 8 OHMS or 4 OHMS). The BLACK binding post terminal on the amplifier (labeled "-") should be connected to the loudspeaker INPUT terminal color coded BLACK (or labeled NEGATIVE, "-", NEG, C, COMMON, G, or GROUND).
The R OUTPUT should be connected to the right channel loudspeaker, as you face the pair of loudspeakers, and the L OUTPUT to the left channel loudspeaker.
In order to ensure that connections to the loudspeakers are correct, you must be able to identify each wire conductor of the loudspeaker cables at both ends of the cables. This is relatively easy to do since most loudspeaker cables consist of two parallel, stranded conductors in a flexible insulation, with a coding system for wire identification. Sometimes there is a colored "tracer" wrapped around one of the conductors; some cables have one of the conductors colored silver and the other copper; some have a "ridge" molded on the insulation of one of the conductors, while others are imprinted with "+" and/or "-" markings.
Generally speaking, when making connections to the loudspeakers from the amplifier it is very important to use the correct type and size of wire in order to avoid unnecessary loss of amplifier power in the cable, reduction of amplifier damping factor and other undesirable conditions. For runs up to twelve feet, ordinary "zip" or lamp cord, made up of 18AWG stranded wire and available in a variety of insulation colors may be used. For runs up to forty feet, 16AWG stranded wire should be used as a minimum to prevent power losses. For lengths over forty feet and not exceeding sixty feet, use at least 14AWG stranded wire. Runs exceeding sixty feet require the use of heavier conductors such as 12AWG.
There are several different ways to connect the wiring to the R OUTPUT and L OUTPUT. The methods used will depend on the specific type of connectors supplied with the loudspeakers, the speaker cables, etc. As a matter of course, we prefer to use banana plugs because it is generally the most secure method of connection. Also, the springs of the banana plugs create a self-cleaning action which ensures the best contact between the binding posts and the connectors themselves. There are "sockets" provided in the center of the binding posts' studs which permit secure seating of the banana plugs. Before inserting the banana plug into the binding post, ensure the binding post is securely hand tightened in a clockwise direction.
Additionally, when connecting the cables to the amplifier and loudspeakers, it is important that you "tin" the wires with good quality electronic solder in order to minimize contact resistance. Tinning prevents the buildup of surface compounds which can form on copper wire and increase its contact resistance.
If you prefer to use other methods of connection, unscrew the insulated head of the binding post until the hole in the binding post stud is accessible. You can then insert the bare or tinned wire, or terminal pin, through the hole. You can also use the many variety of spade lugs available by simply placing the tines of the spade lug onto the binding post stud. Turn the insulated head of the binding post clockwise until the wire or connector is firmly secured. Finger pressure is sufficient and you should not use pliers or other tools which could damage or over tighten the binding post assembly. The binding post has been designed in such a way that finger pressure is all that is required to cause a "pinching" action among the different metal surfaces to ensure proper connection.
All loudspeakers having a nominal impedance down to 4 ohms can be connected to, and driven by, the GFA-5200. The amplifier can drive these low impedances 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 below 2 ohms. You should not experience difficulties even with these very low-impedance loads unless you demand excessively high volume levels from the system.
In most applications, you can drive two or more sets of loudspeakers. You should note, however, that when loudspeakers are run in parallel, the impedance presented to the amplifier is lower than the nominal impedance of each loudspeaker. In other words, if you parallel two 8-ohm sets of 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 2.6 ohms. In this last situation, depending upon the lowest impedance of the nominally 4 ohm speakers, and if excessive power demands are placed on the amplifier, you may trigger the THERMAL PROTECTION LED on the amplifier (see its respective section for more information). For convenient switching of multiple sets of speakers with impedance protection for the amplifier, you should consider the use of an ADCOM speaker selector. These are available from your local ADCOM dealer.
The GFA-5200 is "polarity correct" and does not invert phase. That is, any positive going signal at its input will appear as a positive going signal at its output.
AC LINE CORD (3)
The AC cord provides power to operate all the GFA-5200's circuits. Its plug can be connected to a standard wall outlet provided the outlet supplies a voltage compatible with the POWER requirements printed on the rear of the GFA-5200.
The GFA-5200's power cord is supplied with a "polarized" AC plug as required by UL/CSA standards and the National Electrical Code. To minimize the risk of electrical shock and to ensure minimal hum from the system, do not defeat the polarity ensuring feature of the plug (one wide blade and one narrow blade). To prevent electrical shock, do not use this polarized plug with an extension cord or other outlet unless the blades can be fully inserted to prevent blade exposure.
AC FUSE (4)
The AC FUSE protects the electronic circuits of the GFA-5200. This fuse will normally blow only if there is an overload within the GFA-5200. For continued protection of the electronic circuits the fuse should be replaced only with a fuse of the same type and value as printed on the rear panel of the amplifier.
If turning on the amplifier does not cause the POWER LED 6 to glow, this may indicate that the AC FUSE is blown. Unplug the AC LINE CORD 3 from the AC wall outlet and turn the ON/OFF SWITCH 5 off and check the fuse. If the fuse is blown, replace it only with one of the same type and value as printed on the rear panel of the amplifier. If, after replacing the fuse, it blows immediately upon turning on the amplifier (POWER LED 6 does not glow), a failed electronic component or other internal problem must be suspected. Make no further attempts at fuse replacement or operation of the amplifier. Refer the problem to competent ADCOM-authorized service personnel.
To remove a blown or suspect fuse from its holder, use only a # 2 Phillips screwdriver to prevent damage to the fuse holder. Simply press lightly on the fuse holder cap and turn counterclockwise. The cap will pop out after a quarter turn. Once a new fuse has been installed in the fuse holder cap, insert it into the fuse holder body and press lightly while turning the cap clockwise until it is firmly seated. Be certain not to cause cross threading of the fuse holder body and cap to prevent damage to the fuse holder. DO NOT FORCE THE FUSE HOLDER CAP INTO THE THREADS.
Before attempting to check or replace a blown fuse, be certain to unplug the AC line cord from the AC wall outlet to prevent possible electrical shock.
Replace the AC FUSE only with one identical in type and rating as printed on the rear panel. DO NOT USE ANY SUBSTITUTE FUSES WITH DIFFERENT RATINGS OR VALUES. Failure to observe this precaution may cause serious damage to the amplifier circuits, MAY CREATE A FIRE HAZARD, AND MAY VOID THE WARRANTY.
ON/OFF SWITCH (5)
The ON/OFF SWITCH controls power to the power transformer and circuits of the GFA-5200. Whenever the GFA-5200 is energized the POWER LED will glow. To turn the GFA-5200 on, press the push button. It will remain in the "engaged" position while the unit is energized. To turn the GFA-5200 off, press the push button again and it will move to the "disengaged" position.
POWER LED (6)
This LED will glow whenever the ON/OFF SWITCH 5 is turned on and the GFA-5200 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, the THERMAL PROTECTION LED glows, the amplifier 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 125ºC. 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 is not blown, the POWER LED is out, and the THERMAL PROTECTION LED 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 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.
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 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 overdriving 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.
THERMAL PROTECTION LEDs (8)
The GFA-5200 is provided with a thermal protection circuit which will shut down the amplifier if either heatsink's temperature reaches 85ºC. The THERMAL PROTECTION LEDs will light whenever the thermal protection circuit 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 either amplifier channel's output through the loudspeaker(s) ceases abruptly, and one or both the THERMAL PROTECTION LEDs glow, 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 6 will remain on and the amplifier will still be energized. Once the temperature of the heatsink(s) drops to a safe operating level, the amplifier will automatically resume operation.
Activation of the THERMAL PROTECTION circuitry in the GFA-5200 is an indication that the amplifier has been overdriven 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.
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. DO NOT SPRAY OR POUR LIQUIDS OF ANY KIND ON THE GFA-5200.
ADCOM has a Technical Service Department to answer questions pertinent to the installation and operation of your unit. In the event of difficulty, please contact us for prompt advice. If your problem cannot be resolved through our combined efforts, we may refer you to an authorized repair agency, or authorize return of the unit to our factory. To aid us in directing you to a convenient service center, it would be helpful if you indicate which major city is accessible to your home.
Please address mail inquiries to:
ADCOM Service Corporation
11 Elkins Road
East
Brunswick, NJ 08816 USA
Other inquiries to:
Telephone: 908-390-1130
Fax: 908-390-9152
Monday
through Friday
9:00 AM to 5:00 PM EST
For fax inquires, please include a return fax number for the reply. When calling or writing about your GFA-5200, be sure to note and refer to its serial number as well as the date of purchase and the dealer from whom it was purchased. In the event the unit must be returned to our factory for service, you will be instructed on the proper procedure when you call or write for a Return Authorization.
If the original shipping carton and its fillers have been lost, discarded, or damaged, a duplicate carton may be obtained from our Service Department for a nominal charge.
Always ship PREPAID VIA UNITED PARCEL SERVICE (UPS) OR OTHER APPROVED CARRIER. DO NOT SHIP VIA PARCEL POST, since the packing was not designed to withstand rough Parcel Post handling. FREIGHT COLLECT SHIPMENTS CAN NOT BE ACCEPTED UNDER ANY CIRCUMSTANCES.
UNDER NO CIRCUMSTANCES SHOULD YOUR UNIT BE SHIPPED TO OUR FACTORY WITHOUT PRIOR AUTHORIZATION, OR PACKED IN OTHER THAN ITS ORIGINAL CARTON AND FILLERS.
GFA-5200 SPECIFICATIONS
Power Rating (To FTC Requirements)
50 watts continuous average power into 8 ohms at any frequency: 20Hz and 20kHz with both channels driven at less than 0.18% THD
80 watts continuous average power into 4 ohms at any frequency: 20Hz and 20kHz with both channels driven at less than 0.18% THD
IM Distortion (SMPTE)
1 watt to 50 watts into 8 ohms..... < 0.07%
1 watt to 80 watts into 4 ohms..... < 0.07%
IM Distortion (CCIF, Any Combination from 4kHz to 20kHz)
50 watts into 8 ohms..... < 0.035%
80 watts into 4 ohms..... < 0.035%
THD + Noise at 50 watts into 8 ohms (Typical)
20Hz..... 0.018%
1kHz..... 0.02%
10kHz..... 0.07%
20kHz..... 0.14%
THD + Noise at 80 watts into 4 ohms (Typical)
20Hz..... 0.018%
1kHz..... 0.02%
10kHz..... 0.08%
20kHz..... 0.165%
Frequency Response @ 1 Watt into 8 ohms (10Hz to 20kHz)..... +0, -0.25dB
Power Bandwidth (-3dB)..... 3Hz to 130kHz
Dynamic Headroom into 4 ohms..... 2.2 dB
Signal to Noise Ratio, "A" Weighted (50 watts into 8 ohms)..... >98dB
Gain..... 29 dB
Input Sensitivity
for 1 Watt..... 0.1 volts
for 50 watts..... 0.71 volts
Input Impedance..... 49.9k ohms
Damping Factor (20Hz to 20kHz)..... >260
Rise Time (5kHz, 90V, peak-to-peak square wave, 20% to 80%)..... 1.1 µS
Power Consumption (Continuous, Both Channels Driven)
Quiescent..... 50VA
Maximum..... 600VA
50 watts into 8 ohms..... 325VA
80 watts into 4 ohms..... 480VA
Power (Available in 230VAC by special order)..... 115VAC - 50/60Hz
Chassis Dimensions..... 3" (72mm) x 17" (432mm) x 11 3/8" (289mm)
Maximum Dimensions..... 3 1/4" (83mm) x 17" (432mm) x 12 1/8" (308mm)
Weight..... 17 lbs. (7.7kg)
Weight, Packed..... 22 lbs. (10.0kg)