/DCOM
details you can hear
G FA-7000
High Current THX®
5-Channel
Power Amplifier
LUCASFILM
THX
OWNER’S MANUAL
THE FOLLOWING PRECAUTIONS AND SAFETY INSTRUCTIONS
ARE REQUIREMENTS OF UL AND CSA SAFETY REGULATIONS
Warning: To reduce the risk of fire or eiectric shock, do not expose
this unit to rain or moisture.
CAUTION
A
RISK OF ELECTRIC SHOCK
DO NOT OPEN
'f
AVIS: RISQUE DE CHOC ELECTRIQUE-NE PAS OUVRIR
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 gam access to the interior of the
unit Only qualified service personnel should make
any such attempt.
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
Do not place this unit on an unstable cart, 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 man
ufacturer’s instructions, and should use a mounting ac
cessory recommended by the manufacturer
Read all the safety and operating instructions before connecting or using
this unit
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
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
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
The unit should be situated away from heat sources such as radiators, heat
registers, stoves, or other devices (including amplifiers) that produce heat
The unit should be connected to a power-supply outlet only of the voltage
and frequency marked on its rear panel
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
ATTENTION
POUR PRÉVENIR LES CHOCS ÉLECTRIQUES NE PAS UTILISER
CETTE FICHE POLARISÉE AVEC UN PROLONGATEUR, UNE PRISE
DE COURANT OU UNE AUTRE SORTIE DE COURANT, SAUF SI LES
LAMES PEUVENT ÊTRE INSÉRÉES À FOND SANS EN LAISSER AU
CUNE PARTIE À DÉCOUVERT
CAUTION
TO PREVENT ELECTRIC SHOCK DO NOT USE THIS POLARIZED PLUG
WITH AN EXTENSION CORD, RECEPTACLE OR OTHER OUTLET UN
LESS THE BLADES CAN BE FULLY INSERTED TO PREVENT BLADE
EXPOSURE
CAUTION
Any outdoor antenna must be located away from all power lines.
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. 70-1984, 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.
a. Use No.10 AWG (5.3 mm=^) copper. No.8 AWG (8 4 mm^) aluminum,
No.17 AWG (1 0 mm“) 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 4-6 feet (1.22-1.83 m) apart.
c Mount antenna discharge unit as close as possible to where lead-in
enters house
d. Use jumper wire not smaller than No.6 AWG (13.3 mm“) 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 IN ARTICLE 810 - RADIO AND TELEVISION EQUIPMENT
POWER LINES
STANDOFF
INSULATORS, b
ANTENNA
LEAD-IN WIRE
Clean unit only as recommended in its instruction manual
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
Care should be taken so that objects do not fall, and liquids are not spilled,
into the enclosure through any openings
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 ram, or liquids of any kind, or
D The unit does not appear to operate normally, or exhibits a
marked change in performance, or
E The device has been dropped, or the enclosure damaged
DO NOT ATTEMPT SERVICING OF THIS UNIT YOURSELF.
REFER SERVICING TO QUALIFIED SERVICE PERSONNEL.
TO EXTERNAL ANTENNA
POWER SERVICE GROUNDING
ELECTRODE SYSTEM
(e g interior metal water pipe)
BONDING JUMPER, d
OPTIONAL ANTENNA GROUNDING
ELECTRODE DRIVEN 8 FEET (2 44 M) INTO
THE EARTH IF REQUIRED BY LOCAL
CODES SEE NEC SECTION 810-21 (f)
TERMINALS OF RADIO RECEIVER
GROUND WIRE, a.b
GROUND CLAMPS
NOTE TO CATV SYSTEM INSTALLER
This reminder is provided to call the CATV system installer’s attention to
Article 820-22 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
GFA-7000 FEATURES
Precision-matched devices used throughout the signal path.
120,000 pF of power supply-filter capacitance for greater reserve capacity.
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.
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.
Home THX® standard DB-25 connector to simplify installation
Made in the USA
TABLE OF CONTENTS
INTRODUCTION
WHAT IS HOME THX®?........................................................2
WARRANTY INFORMATION.................................................2
DESCRIPTION OF UNIT
REAR PANEL.........................................................................3
FRONT PANEL
INSTALLATION & HOOKUP
UNPACKING THE GFA-7000
PLACING THE GFA-7000......................................................7
QUICK CONNECTION DIAGRAM
CONNECTING THE GFA-7000..............................................9
CARING FOR YOUR GFA-7000
TROUBLESHOOTING
RESOLVING PROBLEMS...................................................11
SERVICE INFORMATION
SPECIFICATIONS
......................................................................
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..........................................
...................................................
...............................................................
5
7
8
10
12
13
Thx . THX®, and Home THX® are registered trademarks of Lucasfilm Ltd
Dolby ProLogic® and Dolby AC-3® are registered trademarks of Dolby Laboratories Licensing Corp
INTRODUCTION
Congratulations on your decision to purchase the GFA-7000, Home THX® certified, 5channel power amplifier. Not only is the GFA-7000 certified for Home THX® systems, but it
will also integrate with any other home theater system, such as Dolby ProLogic® or Dolby
AC-3®, 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 make any connections to it.
WHAT IS HOME THX® ?
Home THX® is the system developed by Lucasfilm Ltd. to maximize the accuracy of film
soundtracks in a home environment. It is important as soundtracks and their related special
effects become a greater and greater part of the whole film viewing and listening experience.
In order for a component to display the Home THX® system mark, it has to conform to the
strict series of standards that were investigated and defined during the 1980's by Tom Holman
of Lucasfilm Ltd. A home theater surround system utilizing Home THX® certified components
throughout, will give the most accurate re-creation of the original sound tracks put on the film in
the creative “dubbing stage” by its director, conductor and sound designer. Approved Home
THX® components insure all the necessary improvements to deliver the intended effects of a
film in home theater sound reproduction. The benefits are:
• Clearer dialog
• Precise front-stage sound localization
• Expanded depth of the sound field
• Extended and smooth frequency response
• Wider dynamic range
• Smoother sound transition among channels
The Adcom GFA-7000 amplifier is designed not only to meet these standards, but to
exceed them and deliver the most accurate reproduction of Home THX®-encoded films.
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, 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.
DESCRIPTION OF UNIT
O RR, LR, R, C, L Inputs
The audio inputs for the GFA-7000 are through high-quality, gold-plated RCA jacks to
minimize high-frequency losses, noise, etc. They will accept standard RCA-type plugs, one for
each of the five channels; Left (L), Center (C), Right (R), Left Rear (LR), and Right Rear (RR).
To insure that the performance designed into the GFA-7000 is preserved, you should use the
highest quality audio cables possible. There are many cables which are Home THX® certified,
color-coded and specifically designed for this application. Your Adcom dealer can help select
the best cable for your needs. (See CONNECTING THE GFA-7000 for more information).
O RR, LR, R, C, L Outputs
The GFA-7000’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 binding posts will accept a variety of connector types; the most secure and prevalent
of these is the “U”-type spade connectors (at least 0.25” wide and maximum width of 0.57”),.
The terminal will also accept bare wire (up to AWG10) and “banana” type plugs (single or dual).
Pin connectors are not recommended for use with Home THX® equipment. (See CONNECTING
THE GFA-7000 for more information).
O DB-25 Multichannel Audio Input Connector
Input connections may be made with the optional DB-25 computer-type connector, which
is a Home THX® certified option when your Home THX® controller is provided with a similar
output connector. Using this type of connecting cable would override the need to use the RCAtype inputs (O). This mode of connection retains the same high level of signal transfer,
simplifies the job significantly and insures automatic, correct connections to all channels.
O AC Fuse
The AC Fuse protects the electronic circuits of the GFA-7000. This fuse, normally, will
blow only if there is an overload within the GFA-7000. It may, however, blow if the amplifier
attempts to deliver very high power into very low-impedance loudspeakers. In either case, BE
SURE TO REPLACE THE AC Fuse ONLY WITH AN EXACT REPLACEMENT FUSE. The
proper fuse values are:
Fuse Rating BUSS® Littlefuse®
For 115 volt operation
For 230 volt operation
Before attempting to replace a blown fuse, be certain to unplug the AC Power Cord from the AC
wall outlet to prevent possible electrical shock.
Replace the AC Fuse 0A7/y 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.
If the Power LED (O) does not glow, it may be an indication that the AC fuse has blown. If
you are not sure, or the amplifier displays other symptoms, please consult the RESOLVING
PROBLEMS section on page 11. To remove the fuse-holder cap, you will need a %” standard
flat-blade screwdriver. Place the screwdriver in the recessed slot in the cap. Turn the cap Vb-
turn counter-clockwise (to the 10:30 position), until the cap pops out towards you. Grasp the
cap with your fingers and pull it completely out. The fuse is inserted in the back of the cap;
gently pull it free. Since the fuse has a ceramic body, you cannot visually examine the fuse
element, it is therefore suggested that you replace it with an identical substitute or bring the fuse
to your Adcom dealer so they may check its integrity. To replace the fuse, insert it in the back
of the fuse-holder cap. Place the cap into the fuse-holder with the arrow Vs -turn to the left of
center (10:30 position). Place the screwdriver in the recessed slot, gently press in and turn Vsturn clockwise (to the 12 o’clock position)
....
15 Amp 250 Volt
....
8 Amp 250 Volt
...............
.................
WARNING
ABC-15/250V
AGC-8/250V
...........
.............
(SAG) 314015/250V
(3AG) 312008/250V
O AC Power Cord
The AC cord provides power to operate all the GFA-7000’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-7000.
The GFA-7000’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
insure minimal hum from the system, do not defeat the polarity insuring 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 AC outlet unless the blades can be fully inserted to prevent blade
exposure.
FRONT PANEL
0 On/Off Switch
The On/Off Switch controls power to the power transformer and circuits of the GFA-7000.
Whenever the GFA-7000 is energized the Power LED (O) will glow. To turn the GFA-7000 on,
press the push-button. It will remain in the “engaged” position while the unit is energized. To
turn the GFA-7000 off, press the push-button in and release and it will move to the
“disengaged” position.
O Power LED
This LED will glow whenever the On/Off Switch (©) is turned on and the GFA-7000 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 LED (©) glows, that amplifier channel will not produce sound even though
the Power LED may still glow. When the GFA-7000 is turned off, the Power LED will take some
time to fade out completely. It may take up to 30 seconds to fully extinguish.
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 (O) 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.
o 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 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, othenvise it may cause the Thermal
Protection to be activated or, in extreme cases, damage your loudspeakers.
o Thermal Protection LEDs
The GFA-7000 is 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 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 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
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-7000 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 loadimpedance condition which may be causing activation of this circuitry.
(0) will remain on and the amplifier will still be energized. Once the temperature of
INSTALLATION & HOOKUP
UNPACKING THE GFA-7000
Before your new GFA-7000 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 GFA7000, 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.
PLACING THE GFA-7000
During normal home operation the internal heatsinks of the GFA-7000 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-7000 should be kept away from external sources of heat such as radiators and hot-air
ducts. The GFA-7000 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-7000. 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-7000, but the free flow of air through the ventilating slots in the
amplifier may be partially obstructed.
If you observe these recommendations, the GFA-7000 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-7000 will ultimately depend on the care with
which you make the connections between the amplifier, preamplifier, 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-7000.
QUICK CONNECTIONS
For those of you who are in a hurry to hook up your amplifier into your system, we have
included this quick-connection section. The wiring is straight forward and expeditious if you use
the proper cables and follow this diagram exactly. If you have any difficulties or questions,
please refer to the appropriate section of this manual for complete descriptions and instructions.
WARNING
Whenever connections to or from the GFA-7000 are being made, be certain that the AC
On/Off Switch (O) of the amplifier is in the OFF position, the AC Power Cord (6) of the
amplifier is disconnected from the AC wall outlet and that all associated components
are turned off.
CONNECTING THE GFA-7000
Remember, that the Left and Right designations are as you are sitting down in your
listening/viewing area. On the rear panel, the inputs and outputs are grouped in 5 bracketed
sets, one for each channel. They are abbreviated as indicated;
RR
.......................................
LR
..........................................
R
..................................................
C
................................................
L
.....................................................
Right Rear
Left Rear
Right
Center
Left
Oinputs:
To preserve the correct effects, be certain to connect the RCA cables to the proper RCA-
input connector. If the cables are color coded, then use this sequence for the connections:
Blue..........................................................Left(L)
Red
.......................................................
Right(R)
Green..................................................Center(C)
White with Blue Stripe.................................Left Rear(LR)
White with Red Stripe...............................Right Rear(RR)
Home THX® certified RCA cables will have directional arrows printed on the side of each
cable. Make certain that these arrows are pointed towards the GFA-7000. The recommended
maximum RCA cable capacitance should be less than or equal to 30pF per foot when
measured between the two conductors, and less than or equal to 50pF per foot when measured
between one conductor and the shield.
With the DB-25 computer-type Multichannel input connector(O), there is no need to worry
about color coding or properly connecting the RCA plugs, as this is done in One connector with
one cable. The DB-25 can easily transfer all five channels from the output of the Home THX®
processor unit to the input of the GFA-7000 amplifier. There can be no errors with the DB-25, it
is shaped so that it can only be connected in the proper direction. Contact your dealer to locate
a THX® DB-25 signal cable.
OOutputs:
NOTE:
The GFA-7000 is “polarity correct”. That is it does not invert phase from input to output. Any
positive signals at its inputs will appear as a positive signal at its outputs
In connecting the amplifier to the loudspeaker, it is vital to maintain proper polarity (positive
to positive, negative to negative). On the GFA-7000, 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”.
It is recommended by the Home THX® standards 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”
max 0 57” 0 25" min
_i
_____
___
(see diagram on right).
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-tiqhten the bindingpost assembly. The binding posts, haye 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 ayoid unnecessary loss of
amplifier power in the cable, reduction of amplifier damping factor and other undesirable
conditions. Home THX® specifications require the use of at least AWG16, stranded, copper
cable. Recommended capacitance of the speaker wire should not exceed 50pF per foot. This
insures high frequencies will not be rolled-off.
It is suggested that the three front channels follow this chart for speaker lengths and wire
gauges. These recommendations are standardized Home THX® performance specifications.
up to 24 feet
up to 36 feet
up to 58 feet
.........................................
.........................................
.........................................
AWG16
AWG14
AWG12
Generally, for the two rear surround channels, longer runs of cable are needed, but since
less program material is being transmitted through the cable, longer runs are acceptable:
up to 48 feet
up to 72 feet
up to 116 feet
.........................................
.........................................
.........................................
AWG16
AWG14
AWG12
If longer runs are needed, it is best to consult with your Adcom Dealer to maximize the
performance of your system with your exact conditions.
All loudspeakers haying a nominal impedance down to 4 ohms can be connected to and
driven by the GFA-7000. 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.
It is not recommended that you run additional sets of speakers on any or all of the
amplifiers in the GFA-7000 in order to insure the integrity of a Home THX® system. If you
choose to add remote speakers in another room, it is strongly suggested 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, GFS-4 or
GFS-6 Speaker Selector is strongly recommended. A Speaker Selector enables you to maintain
Home THX® integrity while giving you the flexibility to add speakers throughout your house.
CARING FOR YOUR GFA-7000
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-7000.
10
TROUBLESHOOTING
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.
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”, 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. 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 Note1 and 2 below to
troubleshoot a hum problem).
SYMPTOM POSSIBLE REASON POSSIBLE SOLUTION
Power LED does not
glow No sound
Power LED glows,
but no sound
One channel not
producing sound
Hum from all speakers
at any volume
Hum from all speakers
(hum goes up or
down with volume)
Hum from the amplifier
Itself
AC Power Cord(O) not plugged in. Plug in AC Power Cord(O).
AC Fuse(O) blown. Replace AC Fuse(O).
Transformer thermal protection engaged
Preamp or source unit is not on
Connections in rear of amp are loose. Verify all connections on rear of amp
INPUT(O) orOUTPUT(O) connector
disconnected or loose.
Speaker disconnected. Verify connection at speaker.
Internal protection engaged Bring to Dealer or Service Center
Ground loop (difference in ground voltages
between components).
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
Wait until unit cools down, it will reset.
Make sure whole system is on.
Verify both connections on that channel
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
Make sure all appliances, dimmers and
suspect lights are off
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, 75Q) 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 "750. Ground Loop Isolator” before reconnecting the line. You should check with your Adcom Dealer to
obtain one. If the “75Q 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.
11
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. Please have the following information readily at hand: the unit’s model and serial
numbers, and dealer from which it was bought. 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
Phone or Fax inquiries to:
Voice: 908-390-1130
Fax: 908-390-9152
Monday through Friday
9:00 AM to 5:00 PM Eastern Time
UNDER NO CIRCUMSTANCES SHOULD YOUR UNIT BE SHIPPED TO OUR
FACTORY WITHOUT PRIOR AUTHORIZATION, OR PACKED IN OTHER
THAN ITS ORIGINAL CARTON AND FILLERS.
For fax inquires, please include a return fax or voice number for the reply. When calling or
writing about your GFA-7000, 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. For warranty coverage, a copy of the original proof of purchase is
required. If you have no original copy, please contact your dealer to obtain a duplicate copy.
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.
12
GFA-7000 SPECIFICATIONS
Power Rating (To FTC Requirements)
130 watts continuous average power into 8 ohms at any frequency between 20Hz to 20kHz with all channels driven at less
than 0 05%THD
200 watts continuous average power into 4 ohms at any frequency between 20Hz to 20kHz with all channels driven at less
than 0.05% THD
IM Distortion (SMPTE)
1 watt to 130 watts into 8 ohms.
1 watt to 200 watts into 4 ohms.
IM Distortion (CCiF, Any Combination from 4kHz to 20kHz)
130 watts into 8 ohms......................................................................
200 watts into 4 ohms
THD + Noise at 130 watts into 8 ohms (Typical)
20Hz............................................................................
1kHz
........................................................................
10kHz....................................................................
20kHz
......................
THD + Noise at 200 watts into 4 ohms (Typical)
20Hz .
1kHz ..
10kHz.
20kHz
.................................................................
.............................
.....................
...................
..............................................
< 0 05%
< 0 05%
. <0 02%
. <0 02%
0.0075%
0 007%
0 015%
. 0.025%
0 015%
0 010%
0 022%
0 035%
Frequency Response @ 1 Watt into 8 ohms (10Hz to 20kHz)..
Power Bandwidth (-3dB) ............................................................
Dynamic Headroom into 4 ohms.
.......................
Signai to Noise Ratio, “A” Weighted (130 watts into 8 ohms)
Gain
.................................
....................................................................
input Sensitivity
for 1 Watt....
for 130 Watts.
Input Impedance
....................................................................................
Damping Factor (20Hz to 20kHz)...........................................................
Rise Time (5kHz, 90V, peak-to-peak square wave, 20% to 80%)
Power Consumption (Continuous, All Channels Driven)
Quiescent...................................................................................................
Maximum..............................................................................
130 watts into 8 ohms...............................................................................
Power (Available in 230VAC on special order)
Chassis Dimensions.............................................
Maximum Dimensions..
Weight
....................................................................
Weight, Packed
...........
.............
.............................................
7” (178mm) x 17” (432mm) x 13y4” (349mm)
Tit (187mm) x 17” (432mm) x 14W (378mm)
..................................................
... +0,-0 25dB
1 5Hzto100kHz
19dB
>115dB
29dB
0.1 volts
1 14 volts
50kQ
>800
2.7pS
, . 80VA
1440VA
1200VA
115VAC-50/60HZ
411b (18 6 kg)
. 46 lb. (21 3 kg)
JtXX)M
11 Elkins Road
East Brunswick, NJ 08816
USA
Tel: (908) 390-1130
Fax: (908) 390-9152
95DG11
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