Adcom Stereo Amplifier GFA7807 User Manual

OWNER’S MANUAL  
GFA-7805  
& GFA-7807  
Multi-channel High-Current Power Amplifiers  
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TABLE OF CONTENTS  
WELCOME ........................................ 2  
SAFETY INFORMATION ...........................4  
DESCRIPTION OF UNIT  
GFA-7805 FEATURES ..............................5  
GFA-7807 FEATURES ..............................5  
WARRANTY INFORMATION .........................5  
INSTALLATION & HOOKUP  
UNPACKING THE GFA-7805/7807 .................. 6  
INSTALLING THE GFA-7805/7807 .................. 6  
OPERATION  
FRONT AND REAR PANEL DIAGRAMS ................7  
DESCRIPTION OF UNIT: REAR PANEL ............... 8  
DESCRIPTION OF UNIT: FRONT PANEL ............ 8-9  
CONNECTIONS DIAGRAM .........................10  
CONNECTING THE GFA-7805/7807 ................11  
TROUBLESHOOTING  
RESOLVING PROBLEMS ...........................12  
CARING FOR YOUR GFA-7805/7807 ............... 13  
SERVICE INFORMATION .......................... 13  
GFA-7805 SPECIFICATIONS ....................... 14  
GFA-7807 SPECIFICATIONS ....................... 15  
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THE FOLLOWING PRECAUTIONS AND SAFETY INSTRUCTIONS  
ARE REQUIREMENTS OF UL AND CSA SAFETY REGULATIONS  
Warning: To reduce the risk of fire or electric shock, do  
not expose this unit to rain or moisture.  
ATTENTION  
POUR PREVENIR LES CHOCS ELECTRIQUES NE PAS UTILISER CETTE FICHE  
POLARISEE AVEC UN PROLONGATEUR, UNE PRISE CE COURANT OU UNE  
AUTRE SORTIE CE COURANT, SAUF SI LES LAMES PEUVENT ETRE INSEREES  
A FOND SANS EN LAISSER AUCUNE PARTIE A DECOUVERT.  
CAUTION  
CAUTION  
RISK OF ELECTRIC SHOCK  
DO NOT OPEN  
TO PREVENT ELECTRIC SHOCK DO NOT USE THIS POLARIZED PLUG WITH  
AN EXTENSION CORD, RECEPTACLE OR OTHER OUTLET UNLESS THE  
BLADES CAN BE FULLY INSERTED TO PREVENT BLADE EXPOSURE.  
The graphic symbol of a lightning flash with an  
arrow point within a triangle signifies that there  
is dangerous voltage within the unit and it poses  
a hazard to anyone removing the cover to gain  
access to the interior of the unit. OnIy qualified  
service personnel should make any such attempt.  
CAUTION POWER LINES  
Any outdoor antenna must be located away from all power lines.  
OUTDOOR ANTENNA GROUNDING  
If an outside antenna is connected to your tuner or tuner/preamplifier,  
be sure the antenna system is grounded so as to provide some protection  
against voltage surges and built-up static charges. Section 810 of the  
National Electrical Code, ANSI/NFPA No. 701984, provides information  
with respect to proper grounding of the mast and supporting structure,  
grounding of the lead-in wire to an antenna discharge unit, size of  
grounding conductors, location of antenna discharge unit, connection to  
grounding electrodes, and requirements for the grounding electrode.  
The graphic symbol of an exclamation point within  
an equilateral triangle warns a user of the device  
that it is necessary to refer to the instruction manual  
and its warnings for proper operation of the unit.  
Donotplacethisunitonanunstablecart, stand, tripod,  
bracket, or table. The unit may fall, causing serious  
injury to a child or adult, and serious damage to the  
unit. Use only with a cart, stand, tripod, bracket, or  
table recommended by the manufacturer or sold with  
the unit. Any mounting of the device should follow the  
manufacturer’sinstructions, andshoulduseamounting  
accessory recommended by the manufacturer.  
a. Use No.10 AWG (5.3 mm2) copper, No.8 AWG (8.4 mm2) aluminum, No.17  
AWG (1.0 mm2) copper clad steel or bronze wire, or larger, as a ground wire.  
b. Secure antenna lead-in and ground wires to house with stand-off  
insulators spaced from 46 feet (1.221.83 m) apart.  
Read all the safety and operating instructions before connecting or using  
this unit.  
c. Mount antenna discharge unit as close as possible to where lead-in enters  
house.  
Retain this notice and the owner’s manual for future reference.  
All warnings on the unit and in its operating instructions should be adhered to.  
All operating and use instructions should be followed.  
d. Use jumper wire not smaller than No.6 AWG (13.3 mm2) copper, or the  
equivalent, when a separate antenna grounding electrode is used. See NEC  
Section 810-21 (j).  
EXAMPLE OF ANTENNA GROUNDING AS PER NATIONAL ELECTRICAL CODE  
INSTRUCTIONS CONTAINED INARTICLE 810. RADIOAND TELEVISION EQUIPMENT.  
Do not use this unit near water. For example, near a bathtub, washbowl,  
kitchen sink, laundry tub, in a wet basement, or near a swimming pool.  
power lines  
The unit should be installed so that its location or position does not interfere  
with its proper ventilation. For example, it should not be situated on a  
bed, sofa, rug, or similar surface that may block the ventilation openings;  
or placed in a built-in installation, such as bookcase or cabinet, that may  
impede the flow of air through its ventilation openings.  
ground clamp  
service entrance  
conductors  
standoff  
insulators, b  
The unit should be situated away from heat sources such as radiators, heat  
registers, stoves, or other devices (including amplifiers) that produce heat.  
mast  
The unit should be connected to a power supply outlet only of the voltage  
and frequency marked on its rear panel.  
antenna  
lead-in wire  
service  
The power supply cord should be routed so that it is not likely to be walked  
on or pinched, especially near the plug, convenience receptacles, or where  
the cord exits from the unit.  
entrance  
equipment  
ground wire, a,b  
antenna  
ground clamps  
discharge  
unit, c  
Clean unit only as recommended in its instruction manual.  
to external antenna  
terminals of radio receiver  
The power supply cord of the unit should be unplugged from the wall outlet  
when it is to be unused for a long period of time.  
power service grounding  
electrode system  
(e.g. interior metal water pipe)  
ground wire, a,b  
ground clamps  
Care should be taken so that objects do not fall, and liquids are not spilled,  
into the enclosure through any openings.  
bonding jumper, d  
optional antenna grounding  
electrode driven 8 feet (2.44 M) into  
the earth if required by local codes.  
This unit should be serviced by qualified service personnel when:  
A. The power cord or the plug has been damaged; or  
B. Objects have fallen, or liquid has been spilled, into the unit; or  
C. The unit has been exposed to rain, or liquids of any kind; or  
D. The unit does not appear to operate normally, or exhibits a marked  
change in performance; or  
NOTE TO CATV SYSTEM INSTALLER  
This reminder is provided to call the CATV system installer’s attention to  
Article 82022 of the National Electrical Code that provides guidelines for  
proper grounding and, in particular, specifies that the cable ground shall  
be connected to the grounding system of the building, as close to the  
point of cable entry as practical.  
E. The device has been dropped, or the enclosure damaged.  
DO NOT ATTEMPT SERVICING OF THIS UNIT YOURSELF.  
REFER SERVICING TO QUALIFIED SERVICE PERSONNEL.  
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GFA-7805 FEATURES  
• Precision-matched devices used throughout the signal path  
• 112,000 µF of power supply-filter capacitance to optimize transient response  
• Independent power supplies for each channel  
• Fewer gain stages improve signal reproduction accuracy  
• Custom toroidal power transformer provides better regulation and greater peak current capability  
• Independent thermal-overload and distortion LEDs for all 5 channels  
• High quality, gold-plated 5-way binding posts  
• Balanced XLR inputs  
• High quality, gold-plated RCA jacks  
• Large independent internal heatsinks for greater cooling capability of output devices  
• Convenient 12V DC power ON/OFF triggering  
• Heavy gauge, anodized aluminum front panel  
• Powder-coated, baked chassis and top cover for greater durability  
• Cooling vents for greater efficiency and cooler operation while driving low impedance loads  
• Forced convection temperature sensitive cooling  
GFA-7807 FEATURES  
• Precision-matched devices used throughout the signal path  
• 156,800 µF of power supply-filter capacitance to optimize transient response  
• Independent power supplies for each channel  
• Fewer gain stages improve signal reproduction accuracy  
• Custom toroidal power transformer provides better regulation and greater peak current capability  
• Independent thermal-overload and distortion LEDs for all 7 channels  
• High quality, gold plated 5-way binding posts  
• Balanced XLR inputs  
• High quality, gold-plated RCA jacks  
• Large independent, internal heatsinks for greater cooling capability of output devices  
• Heavy gauge, anodized aluminum front panel  
• Powder-coated, baked chassis and top cover for greater durability  
• Cooling vents for greater efficiency and cooler operation while driving low impedance loads  
• Forced convection temperature sensitive cooling  
ADCOM PROTECTION PLAN (USA Only)  
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, or if the ADCOM Warranty Card is not  
included in the carton, 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. Always retain your  
original sales receipt as a proof of purchase.  
5
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INTRODUCTION  
Congratulations on your decision to purchase the GFA-7805 or GFA-7807 multichannel power amplifier. The GFA-7805 and  
GFA-7807 have been designed to be high performance and musically accurate in a configuration specifically designed  
to integrate with any audio pre-amplifier. You have made a wise choice that will reward you for years to come with  
exceptionally accurate and musical sound reproduction. To realize the full potential of your new amplifier, and before  
making any connections to it, please read these operating and installation instructions thoroughly.  
UNPACKING THE GFA-7805/7807  
Before your new ADCOM amplifier 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-7805/07, 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.  
INSTALLING THE GFA-7805/7807  
During normal home operation the internal heatsinks of the GFA-7805/7807 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-7805/7807 should be kept away from external sources of heat such as radiators and hot-air ducts. The  
GFA-7805/7807 should never be placed with other heat-producing components in a cabinet or enclosure lacking free air  
flow. 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-7805/7807. 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-7805/7807, but the free flow of air through the ventilating slots in the amplifier may  
be partially obstructed.  
If you observe these recommendations, the GFA-7805/7807 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, panels and around the ventilating slots should be all that is required.  
The optimal performance of your new GFA-7805/7807 will ultimately depend on the care with which you make the  
connections between the amplifier, pre-amplifier, surround sound decoder 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 Inputs and Outputs section of CONNECTING THE GFA-7805/7807.  
6
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( )  
1
( )  
3
( )  
4
GFA-7807 REAR PANEL  
( )  
2
( )  
5
GFA-7807 FRONT PANEL  
LF  
C
RF  
RS  
RB  
LB  
LS  
distortion alert  
>
>
G
F
A
thermal protection  
7807  
( ) ( )  
( ) ( )  
6
7
8
9
(1) Input Jacks  
(4) AC Fuse  
(7) Power LED  
(2) Output Binding Posts  
(3) I2V DC Trigger  
(5) AC Power Cord  
(6) On/Off Switch  
(8) Thermal Protection LEDs  
(9) Distortion Alert LEDs  
7
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is an overload within the GFA-7805/7807. If your fuse  
fails please contact your dealer or ADCOM directly for a  
replacement or servicing.  
DESCRIPTION OF UNIT: REAR PANEL  
(1) Inputs  
The GFA-7805 and GFA 7807 have both balanced and unbal-  
anced inputs for each channel. The unbalanced connection  
is made via the gold plated RCA jack and the balanced con-  
nection is made via the XLR input connection. Each channel  
also has a switch which selects the type of input for each  
channel. Make sure the switch is in the appropriate posi-  
tion for the type of connection you have choosen. For best  
performance, always use high quality interconnects. Your  
ADCOM dealer can help select the best cable for your needs.  
(5) AC Power Cord  
The AC cord provides power to operate all the GFA-  
7805/7807’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 panel of the GFA-7805/7807.  
DESCRIPTION OF UNIT: FRONT PANEL  
(2) Outputs  
(6) On/Off Switch  
The GFA-7805’s and GFA-7807’s connections to the  
loudspeakers are made through high-grade, 5-way,  
gold-plated binding post terminals. There are two  
terminals for each speaker, which are colored RED for the  
positive (+) output and BLACK for the negative (-) output.  
The On/Off Switch controls power to the power  
transformer and circuits of the GFA-7805/7807. Whenever  
the GFA-7805/7807 is energized the Power LED (7)  
will glow. To turn the GFA-7805/7807 on, press the  
push-button. It will remain in the “engaged” position while  
the unit is energized. To turn the GFA-7805/7807 off, press  
the push-button in and release and it will move to the  
“disengaged” position.  
The binding posts will accept a variety of connector types.  
The most secure and prevalent of these is the “U”-type  
spade connectors (at least 0.25wide 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. It  
may take up to 30 seconds to fully extinguish.  
(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.  
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.  
(4) AC Fuse  
The AC Fuse protects the electronic circuits of the GFA-  
Once the temperature within the transformer decreases  
to a normal level, the thermostat will reset itself  
7805/7807. This fuse, normally, will fail only if there  
8
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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. 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.  
(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. 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 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-7805/7807 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.  
9
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WARNING  
WHENEVER CONNECTIONS TO OR FROM  
THE GFA-7805 & GFA-7807 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 OFF.  
Right Back  
Left Back  
Left Surround  
LS LB RB RS RF C LF  
12VDC trigger  
unbalanced input  
unbalanced input  
unbalanced input  
unbalanced input  
unbalanced input  
unbalanced input  
unbalanced input  
input select  
input select  
input select  
input select  
input select  
input select  
input select  
balanced input  
balanced input  
balanced input  
balanced input  
balanced input  
balanced input  
balanced input  
output  
output  
output  
output  
output  
output  
output  
AC fuse  
15ABC 250V  
WARNING: To reduce the risk of fire or electric shock,  
do not expose this appliance to rain or moisture.  
serial number  
CAUTION  
ATTENTION: Pour ev` iter tout risque de feu ou choc el` ectrique,  
ne pas exposer cet appareil a` la pluie ou a` l'humidite.`  
RISK OF ELECTRIC SHOCK  
DO NOT OPEN  
Model:GFA-7807 Power Amplifier  
Powerconsumption (max): XXXX  
AVIS: Risque de choc el` ectrique- ne pas ouvrir.  
W
Left Front  
Center  
Right Surround  
Right Front  
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CONNECTING THE GFA-7805/7807 TO YOUR SPEAKERS  
When connecting the amplifier to the loudspeaker, it is vital to maintain proper polarity (positive to positive, negative  
to negative). On the GFA-7805/7807, the positive terminal is color coded RED and labeled “+,” and the negative is color  
coded BLACK and labeled “-”. The positive terminal on the speaker will be color coded RED, or will be labeled “+,” “pos,”  
“positive,” “8 ohms” or “4 ohms.” The negative terminal on the speaker will be color coded BLACK, or will be labeled “-,”  
“neg,” “negative,” “C,” “Common,” “G,” or “ground.”  
We recommend that your speaker cables be terminated with “U” type spade connectors. These will give the most contact  
area insuring long-term reliability. The spade connector should have a maximum width of 0.57 inches and an opening  
width of no less than 0.25".  
To properly connect the speaker cable to the binding posts, 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 posts have 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.  
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. Sound audio engineering practice suggests the  
use of at least AWG16, stranded, copper cable. Recommended capacitance of the speaker wire should not exceed 5OpF  
per foot. This insures high frequencies will not be rolled off.  
All loudspeakers having a nominal impedance down to 4 ohms can be connected to and driven by the GFA-7805/7807.  
The amplifier can drive these low-impedance speakers at more than adequate power levels with no difficulty. It should  
be noted 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.  
We do not recommend that you run additional sets of speakers to the GFA-7805/7807. If you choose to add remote  
speakers in another room, we strongly suggest that a switching system to disconnect the non-home-theater speakers be  
incorporated when the surround sound (home theater) mode is in operation. A device such as the ADCOM GFS-3 or GFS-6  
speaker selector is recommended. A Speaker Selector enables you to maintain good sonic integrity while giving you the  
flexibility to add speakers throughout your house.  
We suggest that you follow this chart below for maximum speaker lengths and minimum wire gauges. If longer runs are  
needed, we recomend that you consult with your ADCOM Dealer to maximize the performance of your system for your  
exact conditions.  
up to 24 feet AWGI6  
up to 36 feet AWGI4  
up to 58 feet AWGI2  
11  
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RESOLVING PROBLEMS  
Use the chart below to solve common situations that don’t require professional attention. If the steps stated in POSSIBLE  
SOLUTION do not resolve your problem, then please contact your ADCOM Dealer or call the ADCOM Customer Service  
Department. Any problems not covered here should be brought to the attention of your ADCOM Dealer or ADCOM  
Customer Service Department.  
SYMPTOM  
POSSIBLE REASON  
POSSIBLE SOLUTION  
Power LED does not  
AC Power Cord(s) not plugged in.  
Plug in AC Power Cord(s).  
glow. No sound  
AC Fuse(s) failed.  
Replace AC Fuse(s).  
Transformer thermal protection engaged.  
I2V DC triggering malfunctioning.  
Wait until unit cools down. It will reset.  
Reset power switch manually. Check  
connection of 12V DC trigger at source.  
Make sure whole system is on.  
Verify all connections on rear of amp.  
Power LED glows,  
but no sound  
Preamp or source unit is not on.  
Connections in rear of amp are loose.  
One channel not  
producing sound  
INPUT(s) or OUTPUT(s) connector  
disconnected or loose.  
Verify both connections on that channel.  
Speaker disconnected.  
Verify connection at speaker.  
Internal protection engaged.  
Bring to Dealer or Service Center.  
If Cable TV is present (see Note 1).  
If Cable TV is not present (see Note 2).  
Try different source (tuner, tape, etc.)  
and/or different RCA cable.  
Hum from all speakers  
at any volume  
Ground loop (difference in ground voltages  
between components).  
Hum from all speakers  
(hum goes up or  
down with volume)  
Hum from the amplifier  
itself  
Problem with source unit (CD, tape, etc.),  
or RCA cable connecting that source unit  
to the preamp.  
Some major appliance, dimmer, halogen or  
fluorescent light is creating interference.  
Make sure all appliances, dimmers and  
suspect lights are off.  
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 potentials creates a 60Hz low-level sound  
(approximately a low A), that seems to “hum.”  
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. With the advent of audio/video and home theater systems, the problem has become  
commonplace. Generally, the cause is the Cable-TV incoming signal line. This new incoming line may add an additional  
ground at a different potential to the AC line ground of your other equipment (refer to Note I and 2, to troubleshoot  
a hum problem).  
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, 75Ω) at the wall, or the first  
component the cable is connected to (i.e. the cable box, or VCR). If the hum is no longer present, you must insert a “75Ω  
Ground Loop Isolator” before reconnecting the line. You should check with your ADCOM Dealer to obtain one. If the “75Ω  
Ground Loop Isolator” works only partially or not at all, then please read Note 2 to complete the troubleshooting procedure.  
Note 2: Make sure that the power amplifier is at least 6” from the Preamp and/or Processor. Usually putting another  
component between them is sufficient to minimize the hum. If this does not reduce the hum, turn the system off and  
disconnect all Inputs from the amplifier. If the hum still persists, then your Dealer or Service Center must examine the  
amplifier. If the hum disappears, try another set of RCA cables. 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  
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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. 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 directly onto the GFA-7805/7807.  
SERVICING  
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 inquires to:  
Phone, Fax or Email inquires to:  
ADCOM Service  
8551 East Anderson Drive, Suite 105  
Scottsdale, Arizona 85255 USA  
Voice: (480) 607-2277  
Fax: (480) 348-9876  
Monday through Friday  
9:00 AM to 5:00 PM MST  
For Fax inquires, please include a return Fax number for the reply. When calling or writing about your GFA-7805/7807, 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 any communications to us, please include a daytime phone number where we may reach you. 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. UNDER NO CIRCUMSTANCES SHOULD YOUR UNIT BE SHIPPED TO OUR FACTORY WITHOUT PRIOR  
AUTHORIZATION, OR PACKED IN OTHER THAN ITS ORIGINAL CARTON AND FILLERS.  
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 WILL NOT BE ACCEPTED  
UNDER ANY CIRCUMSTANCES.  
13  
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GFA-7805 SPECIFICATIONS  
Power Rating (To EIA/CEA-490-A Requirements)  
300 Watts continuous average power per channel into 8 ohms at any frequency between 20Hz and 20kHz with all  
channels driven at less than 1.00% THD.  
450 Watts continuous average power per channel into 4 ohms at any frequency between 20Hz and 20khz with all  
channels driven at less than 1.00% THD.  
THD + Noise at 300 watts into 8 Ohms (Typical)  
20Hz. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0.012%  
1kHz. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0.135%  
10kHz. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0.12%  
20kHz. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0.12%  
THD + Noise at 450 watts into 4 Ohms (Typical)  
20Hz. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0.3%  
1 kHz. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0.3%  
10kHz. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0.27%  
20kHz. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0.1%  
Frequency Response @ 1 Watt into 8 Ohms  
10Hz to 20kHz. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . +0, -0.25dB  
Power Bandwidth (-3d B). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3Hz to 130kHz  
Dynamic Headroom Into 4 Ohms. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0.96 dB  
Signal to Noise Ratio, “A” Weighted  
300 watts into 8 ohms. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ≥ 112dB  
Gain. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29.67dB  
Input Sensitivity  
for 1 Watt output. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0.1 volts  
for 300 Watts output. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.61 volts  
Input Impedance  
Unbalanced. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 500K ohms  
Balanced. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10K ohms  
Damping Factor  
1k. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . > 500  
General  
Power (available in 230VAC by special order). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 120VAC—50/6OHz  
Chassis Dimension. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 193/4” (501.65mm) x 17” (432mm) x 83/4” (222.25mm)  
Maximum Dimensions. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 203/4” (527.05mm) x 17” (432mm) x 91/2” (241.3mm)  
Weight. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 88 lbs. (40kg)  
Weight, Packed. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 138.6 lbs. (63kg)  
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GFA-7807 SPECIFICATIONS  
Power Rating (To EIA/CEA-490-A Requirements)  
300 Watts continuous average power per channel into 8 ohms at any frequency between 20Hz and 20kHz with all  
channels driven at less than 1.00% THD.  
450 Watts continuous average power per channel into 4 ohms at any frequency between 20Hz and 20khz with all  
channels driven at less than 1.00% THD.  
THD + Noise at 300 watts into 8 Ohms (Typical)  
20Hz. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0.012%  
1kHz. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0.135%  
10kHz. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0.12%  
20kHz. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0.12%  
THD + Noise at 450 watts into 4 Ohms (Typical)  
20Hz. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0.3%  
1 kHz. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0.3%  
10kHz. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0.27%  
20kHz. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0.1%  
Frequency Response @ 1 Watt into 8 Ohms  
10Hz to 20kHz. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . +0, -0.25dB  
Power Bandwidth (-3d B). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3Hz to 130kHz  
Dynamic Headroom Into 4 Ohms. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0.96 dB  
Signal to Noise Ratio, “A” Weighted  
300 watts into 8 ohms. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ≥ 112dB  
Gain. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29.67dB  
Input Sensitivity  
for 1 Watt output. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0.1 volts  
for 300 Watts output. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.61 volts  
Input Impedance  
Unbalanced. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 500K ohms  
Balanced. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10K ohms  
Damping Factor  
1k. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . > 500  
General  
Power (available in 230VAC by special order). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 120VAC—50/6OHz  
Chassis Dimension. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 193/4” (501.65mm) x 17” (432mm) x 83/4” (222.25mm)  
Maximum Dimensions. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 203/4” (527.05mm) x 17” (432mm) x 91/2” (241.3mm)  
Weight. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 118.8 lbs. (54kg)  
Weight, Packed. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 169.4 lbs. (77kg)  
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ADCOM  
A division of Klein Technology Group, LLC  
8551 East Anderson Drive, Suite 105  
Scottsdale, Arizona 85255  
Voice: (480) 607-2277  
Fax: (480) 348-9876  
GFA7805_07_manual_v1  
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