Adcom GFA-7300 User's Manual

Adcom GFA-7300 User's Manual
ADCOM
GFA-7400
&
GFA-7300
High Current
5-Channel
Power Amplifiers
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 electric shock, do not expose
this unit to rain or moisture.
RISK OF ELECTRIC SHOCK
DO NOT OPEN
>
AVIS. RISQUE DE CHOC ELECTRIQUE-NE PAS OUVRIR
The graphic symbol of a lightning flash with an arrow
point within a tnangle signifies that there 1s dangerous
voltage within the unit and it poses a hazard to anyone
removing the cover to gain 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 tnangle 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, tnpod, 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 urut 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 1s not likely to be walked
on or pinched, especially near the plug, convenience receptacles, or where
the cord exits from the unit
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
The power cord or the plug has been damaged, or
Objects have fallen, or hquid has been spilled, into the unit, or
The unit has been exposed to rain, or liquids of any kind, or
The unit does not appear to operate normally, or exhibits a
marked change in performance, or
The device has been dropped, or the enclosure damaged
m vou»
DO NOT ATTEMPT SERVICING OF THIS UNIT YOURSELF.
REFER SERVICING TO QUALIFIED SERVICE PERSONNEL.
ATTENTION
POUR PREVENIR LES CHOCS ELECTRIQUES NE PAS UTILISER
CETTE FICHE POLARISEE AVEC UN PROLONGATEUR, UNE PRISE
DE COURANT OU UNE AUTRE SORTIE DE COURANT, SAUF SI LES
LAMES PEUVENT ETRE INSEREES A FOND SANS EN LAISSER AU-
CUNE PARTIE A DECOUVERT
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
POWER LINES
Any outdoor antenna must be located away from all power lines.
OUTDOOR ANTENNA GROUNDING
If an outside antenna 1s 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 1s 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
N
GROUND CLAMP NN, \
~~ STANDOFF
SERVICE ENTRANCE
GONDUCTORS
INSULATORS, b
ao
|
e MAST
nN
SERVICE [ ANTENNA
ENTRANCE LEAD-IN WIRE
EQUIPMENT
ANTENNA
DISCHARGE
UNIT, ¢
TO EXTERNAL ANTENNA
TERMINALS OF RADIO RECEIVER
POWER SERVICE GROUNDING >
ELECTRODE SYSTEM | GROUND WIRE, a,b
(e g interior metal water pipe) \
GROUND CLAMPS
BONDING JUMPER, d
OPTIONAL ANTENNA GROUNDING
ELECTRODE DRIVEN B FEET (2 44 M) INTO
THE EARTH IF REQUIRED BY LOCAL
CODES SEE NEC SECTION 810-21 (f)
NOTE TO CATV SYSTEM INSTALLER
This reminder is provided to call the CATV system nstaller'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
TABLE OF CONTENTS
SAFETY INFORMATION coo, 1
INTRODUCTION
WARRANTY INFORMATION ......................mnvveeocenenen nene 2
DESCRIPTION OF UNIT
FEATURES GFA-7400...................e.e..eesvenercccncenreer ee, 3
FEATURES GFA-7300..............._reeeereeresiccrceccerenrneneeneeneecenee. 3
INSTALLATION 8: HOOKUP
UNPACKING THE GFA-7400/7300................ee.eemenenencacccenen 4
PLACING THE GFA-7400/7300 0.00 4
QUICK CONNECTION ................eeeeneenmainen rene eracaeren eee 5
CONNECTION DIAGRAM …......…..….......rcecrerissssarsorencern er nues 6
INPUTS AND OUTPUTS circ 7
CARING FOR YOUR GFA-7400/7300 ................e....eeem meme... 8
OPERATION
INPUTS AND OUTPUTS ….........………rrsseassanerrenrene en sensecerrennees 9
FUSES AND AC SUPPLY ooo, 10-11
LED DISPLAYS coir 12-13
TROUBLESHOOTING
RESOLVING PROBLEMS ....................enemiinciaceoreoren eee. 14-15
SERVICE INFORMATION ..................rmreecarrerionenenenneneeos 16
SPECIFICATIONS seereere eee, 17-18
INTRODUCTION
Congratulations on your decision to purchase the GFA-7400 or GFA-7300 5-channel power
amplifier. The GFA-7400 and GFA-7300 have been designed to be high performance and
musically accurate in a configuration specifically designed to integrate with any home theater
processor. 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.
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.
2
GFA-7400 FEATURES
e Precision-matched devices used throughout the signal path.
e 100,000 pF of power supply-filter capacitance for greater reserve capacity.
e Independent power supplies for each channel.
e Fewer gain stages improve signal reproduction accuracy.
e Custom toroidal power transformer provides better regulation and greater peak
current capability.
e Independent thermal-overload and distortion LEDs for all 5 channels.
e High quality, gold-plated 5-way binding posts.
e High quality, gold-plated RCA jacks.
e Large independent internal heatsinks for greater cooling capability of output
devices.
e Convenient 12 VDC power ON/OFF triggering.
e Heavy gauge, anodized aluminum front panel.
e Powder-coated, baked chassis and top cover for greater durability.
e Cooling vents for greater efficiency and cooler operation while driving low
impedance loads.
e Made in the USA
GFA-7300 FEATURES
e Precision-matched devices used throughout the signal path.
e 47,000 uF of power supply-filter capacitance for greater reserve capacity.
e Independent power supplies for each channel.
e Fewer gain stages improve signal reproduction accuracy.
e Custom toroidal power transformer provides better regulation and greater peak
current capability.
e Independent thermal-overload and distortion LEDs for all 5 channels.
e High quality, gold plated binding posts.
High quality, gold-plated RCA jacks.
e Large independent, internal heatsinks for greater cooling capability of output
devices.
¢ Heavy gauge, anodized aluminum front panel.
e Powder-coated, baked chassis and top cover for greater durability.
e Cooling vents for greater efficiency and cooler operation while driving low
impedance loads.
INSTALLATION & HOOKUP
UNPACKING THE GFA-7500 and GFA-7300
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-7400/7300,
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-7400/7300 -
During normal home operation the internal heatsinks of the GFA-7400/7300 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 amplifiers long-term, trouble-free
operation it is necessary to provide adequate ventilation for the heatsinks. Therefore, the GFA-
7400/7300 should be kept away from external sources of heat such as radiators and hot-air
ducts. The GFA-7400/7300 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-7400/7300.
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-7400/7300, but the free flow of air through the ventilating
slots in the amplifier may be partially obstructed.
If you observe these recommendations, the GFA-7400/7300 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-7400/7300 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-7400/7300.
Center Channel speaker —
Surround Processor a
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Front a - . f ас Front
Speaker Speaker
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| Surround Left Surround Right
| В- и —
Listening/Viewing position
NOTE! Product shown is for reference only, The GFA-7400 and GFA-7300 differ in
appearance but have the same basic configuration.
CONNECTING THE GFA-7400/7300
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 as follows:
GFA-7300 GFA-7400
RR (Right Rear) ..................eeeeee.eme.—.... Surround Right (SR)
LR (Left Rear)......................eeemceeeneeno Surround Left (SL)
FR (Front Right)... Front Right (FR)
C (Center)..…..….........….….….….….….…cerccccercacccreenes Center (C)
FL (Front Left). ooo Er Front Left (FL)
Oinputs:
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 rer FL (Front Left)
Red eer nee. FR (Front Right)
Green O C (Center)
White with Blue Stripe —..................... LR (Left Rear) / (Surround Left)
White with Red Stripe —................ RR (Right Rear) / (Surround Right)
Oodutputs:
NOTE:
The GFA-7400/7300 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
When connecting the amplifier to the loudspeaker, it is vital to maintain proper polarity
(positive to positive, negative to negative). On the GFA-7400/7300, 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 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 - ~— ee
an opening width of no less than 0.25” mac087 0.25" mn
(see diagram on right). A
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 vou 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 50pF per foot.
This insures high frequencies will not be rolled-off.
It is suggested that for all the channels follow this chart for speaker lengths and wire gauges.
up to 24 feet ......................e..eseriver AWG16
up to 36 feet ...............................emen—.. AWG14
up to 58 feet..........................e..eíserveeo 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.
7
All loudspeakers having a nominal impedance down to 4 ohms can be connected to and
driven by the GFA-7400/7300. 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.
It is not recommended that you run additional sets of speakers to the GFA-7400/7300. 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 good sonic
integrity while giving you the flexibility to add speakers throughout your house.
CARING FOR YOUR GFA-7400/7300
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-7400/7300.
DESCRIPTION OF UNIT
REAR PANEL
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NOTE! Product shown is GFA-7400, GFA-7300 is similar.
© Inputs
The audio inputs for the GFA-7400/7300 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; Front Left, Center, Right Front, Left Rear, and Right Rear. To insure
that the performance designed into the GFA-7500 is preserved, you should use the highest
quality audio cables possible. There are many cables which are color-coded and specifically
designed for this application. Your Adcom dealer can help select the best cable for your needs.
(See CONNECTING THE GFA-7400/7400 for more information).
© Outputs
The GFA-7400'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 GFA-7300's connections to the loudspeakers are basically similar; there are two
terminals for each speaker, which are colored RED for the positive (+) output and BLACK for the
negative (-) output. The high-grade gold-plated binding post terminals on the GFA-7300 are
however, different. These connectors easily accept stripped bare wires or pins. To use spade lugs
it is necessary to remove the black molded plastic guide block that fits over the binding posts. To
remove, take out the two screws at the top and bottom of guide block. Store the guide block and
screws for future use.
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). (See
CONNECTING THE GFA-7400/7300 for more information).
© 12VDC Triggering. (GFA-7400 Only)
The GFA-7400 and GFA-7300 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-7400 by a 12Volt DC output jack on the rear of certain ADCOM pre-amplifiers and tuner pre-
amplifiers. When using this feature the front panel Power Switch must be left in the in “on”
position. To connect you will need a monaural mini phone plug to monaural mini phone plug cable
of appropriate length (not included) to reach from the rear panel of the amplifier to the rear panel
of the pre-amplifier. Contact your dealer for information on using this feature with ADCOM and
other brand pre-amplifiers. Although 12VDC is optimal the circuit will operate from approx. 5 to
30VDC, not to exceed 250mv. Center conductor (tip) is positive (+).
© AC Fuse
The AC Fuse protects the electronic circuits of the GFA-7400/7300. This fuse, normally, will
fail only if there is an overload within the GFA-7400/7300. It may, however, fail 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:
GFA-7400:
Fuse Rating BUSS® Littelfuse®
For 115 volt operation ....... 15 Amp 250 Volt .............. ABC-15/250V.......... (3AB) 314015/250V
For 230 volt operation........ 8 Amp 250 Volt .............. AGC-8/250V ........... (3AG) 312008/250V
GFA-7300: Fuse Rating BUSS® Littelfuse®
For 115 volt operation ....... T8 Amp 250 Volt .............. MDL-8A/250V ......... (3AG) 313008/250V
For 230 volt operation ........ T4 Amp 250 Volt .............. MDL-4A/250V ......... (BAG) 313004/250V
WARNING
Before attempting to replace a failed fuse, be certain to unplug the AC Power 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.
If the Power LED (@) does not glow, it may be an indication that the AC fuse has blown. If
you are using the 12VDC Triggering feature (GFA-7400 Only) it may be possible that there is a
problem with that connection. To determine if the problem is caused by a malfunction in the
12VDC system, remove the small plug inserted into the 12VDC Triggering jack. Press the front
panel power switch to turn off the amp, and immediately re-press the power switch. Ifthe problem
is caused by the 12VDC triggering circuit the amp will turn on and the LED will glow. DO NOT
attempt repair of the 12VDC system. If you are not sure, or the amplifier displays other symptoms,
please consult the RESOLVING PROBLEMS section on page 13.
10
Fuse replacement GFA-7400:
To remove the fuse-holder cap, you will need a %4" standard flat-blade screwdriver. Place the
screwdriver in the recessed slot in the cap. Turn the cap */s-turn counter-clockwise, 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. Place the screwdriver in the recessed slot, gently press in and
turn /s-turn clockwise.
Fuse replacement GFA-7300:
To remove the fuse-holder cap, you will need a #2 Philips type screwdriver. Place the screwdriver
in the recessed slot in the cap. Turn the cap counter-clockwise, 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.
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.. Place the screwdriver in the recessed slot, gently press in and turn clockwise until
fully inserted, being careful not to over-tighten.
© AC Power Cord
The AC cord provides power to operate all the GFA-7400 and 7300'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-7400/7300.
The GFA-7400 and 7300'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.
11
FRONT PANEL
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NOTE! Product shown is the GFA-7400. The GFA-7300 is similar in appearance.
O On/Off Switch
The On/Off Switch controls power to the power transformer and circuits of the GFA-
7400/7300. Whenever the GFA-7400/7300 is energized the Power LED (6) will glow. To turn
the GFA-7400/7300 on, press the push-button. It will remain in the “engaged” position while the
unit is energized. To turn the GFA-7400/7300 off, press the push-button in and release and it will
move to the “disengaged” position.
@ Power LED
This LED will glow whenever the On/Off Switch (0) is turned on and the GFA-7400/7300 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-7400/7300 is turned off, the Power LED will take some
time to fade out completely. № 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 (0) has not failed,
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 tripping the
thermostat in the transformer continually, you must reduce the sound level demands, correct the
load impedance of the loudspeakers, or both.
12
O Thermal Protection LEDs
The GFA-7400/7300 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 (@) 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-7400/7300 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.
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, siew-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 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.
13
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.
SYMPTOM
Power LED does not
glow. No sound
POSSIBLE REASON
AC Power Cord(@) not plugged in.
AC Fuse(©@)failed.
Transformer thermal protection engaged
12VDC triggering malfunctioning
(GFA-7400 Only)
Preamp or source unit is not on.
Connections in rear of amp are loose.
POSSIBLE SOLUTION
Plug in AC Power Cord(@)
Replace AC Fuse(@).
Wait until unit cools down. it will reset.
Reset power switch manually Check
connection of 12VDC trigger at source
Make sure whole system 1s on.
Verify all connections on rear of amp
Power LED glows,
but no sound
One channel not
producing sound
INPUT(O) or QUTPUT(O) connector
disconnected or loose.
Speaker disconnected.
Internal protection engaged
Verify both connections on that channel
Verify connection at speaker.
Bring to Dealer or Service Center
Hum from all speakers
at any volume
Ground loop (difference in ground voltages
between components).
If Cable TV is present (see Note 1).
If Cable TV is not present (see Note 2).
Hum from all speakers
(hum goes up or
down with volume).
Problem with source unit (CD, tape, etc.),
or RCA cable connecting that source unit
to the preamp.
Try different source (tuner, tape, etc.)
and/or different RCA cable
Hum from the amplifier
itself
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”, 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 Note 1 and 2 on next page, to
troubleshoot a hum problem).
14
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 “75Q Ground Loop
Isolator” before reconnecting the line. You should check with your Adcom Dealer to obtain one. If
the “750 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.
15
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: Phone, Fax or E-mail inquiries to:
ADCOM Service Corporation Voice: 732-390-1130
11 Elkins Road Fax: 732-390-5657
East Brunswick, NJ 08816 Monday through Friday
9:00AM to 5:00PM EST
E-mail: [email protected]
New Location and Telephone Numbers as of Spring 1998
ADCOM Service Corporation Voice: 732-683-2356
10 Timber Lane Fax: 732-683-2358
Marlboro, NJ 07746
USA
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-7400/7300, 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.
16
GFA-7400 SPECIFICATIONS
Power Rating (To FTC Requirements)
100 watts continuous average power into 8 ohms at any frequency between 20Hz to 20kHz with all channels driven at
less than 0.075% THD
150 watts continuous average power into 4 ohms at any frequency between 20Hz to 20kHz with all channels driven at
less than 0.075% THD
IM Distortion (SMPTE)
1 watt to 100 watts into 8 ohms........................eesucmecrirmenerermear ere eE Teee ee ncereerrecereeererernarenercacerrererenrecenermee. < 0 075%
1 watt to 150 watts into 4 ohms.....................ereeeseiseurecerer neceser een en receccareroen renenenarrermencarerererereneremene.. < 0.075%
IM Distortion (CCIF, Any Combination from 4kHz to 20kHz)
100 watts into 8 ohms ...........e....eeserrrevermensrensareceeneneareracerecoeneneveneraneenearece arena nerare ener enanenenececence rare ne narenenereonreanene. < 0.025%
150 watts into 4 ohms ...............e..enveeraneorreororerororaracerocarernenerrneraener res eecennereranarenarenenerenarineatererrerrenenemarimanerenaeenace < 0.025%
THD + Noise at 100 watts into 8 ohms (Typical)
20HZ ...........ererceneccanerarmenscacaceneecorcene nene ranenecararaCene rar Teneatacaenereeacaroaaooononenaninenenerenenineeearacarnonrere rv onecanceracararacaceracrenrs 0.012%
1KHZ ......e..erenerecccceereosrene encara rar armaneneceneoenencranecen ener eonenenanosronareuneceneneneenenenarer en eceneneeaceorederenereanreranenenrUrrteneccaneereen. 0.012%
TOKHZ .........e.arecacoceonerraracacararonecareneenanen encarece ener enennenenancomenenenoormecrcenenenENTErnerenererracocarenerenmenvererenanenTeretareracerarmomnreT.. 0.02%
20kHZ .............eeeeeeacareranarenorooncenacan PITRE PTOI PPPPPPPPPPP 0.025%
DOHZ voices esis erases tree es erase ner these sera bees ea anata Ere aera eee a RE Teen see a bea ae sees eek be baat sees he ARERR Eats ea esse arn Eee esses sn eas 0 025%
1KHZ ..nnneecerenerecararanec enana recen erenar een rrenerenerorrecarnecrnererioacarecenererareneen reno rerereeneo oro ermerTaneneranenrecerecarererererererrorrneneeTe.. 0 025%
TOKHZ ............…..…acossessenmrererereranasenerererenepanere caca snen te ne era renr ne ane ne re rem ea tete career 00e + anerrrnencecrnrcarterecaneneneoreenencaraces .0035%
721] y AS 0.045%
Frequency Response @ 1 Watt into 8 ohms (10Hz to 20kHz) ...........................e.e.mm.eeemiernenrere ree +0, -0.25dB
Power Bandwidth (-3dB) ...........................ee.xcecenezecerenrrennrener once eran enernenenieeene ninio nenceco rare ereneacacerenerenemencas 1.5Hz to 65kHz
Dynamic Headroom into 4 ohms...........................ecemeeereeeeeee eter sees ene e 2.5 dB
Signal to Noise Ratio, “A” Weighted (100 watts into 8 ohms)...................................--..... 200000000 anne > 110dB
Galin...........eerecoso roce errar araceraerorereernreraracerareeevocacerecccnarer Te rener e ArUEr toro rere Ne ranerenaranenavaranenivcere atera eninenonceeavarenenanecemecroaeenene. 29dB
Input Sensitivity
(E: R ER EREREKERENEKEKEREKRRENRERERERERAREERAKKEBARERERERERERRKREREEEKEEDOKEKKERERLULUERRREREEEEEUKEEREREEEKERELKERELUREKEAKRRELKUUG 0.1 volts
for 100 Waitts................e.ecoccccoreneainezee nee ene rererarernenerooonerrererecerecrTETEENE TRENT rEOereeeneonene rre nereneernemtareterenenenrererenerranenrenes 1.0 volts
Input Impedance ..........................-e.iereerrie eee reee Dee rneerrarreneceninoorecorecorererenereneravonrerene recerca roer recen. 50kQ
Damping Factor (20Hz to 20kHz)...........................eeeesrrerrerecerecrenenen eran er ne Re De eRnereerenar eenceeo e nencaoncerecarererereneremene 00 > 400
Rise Time (5kHz, 80V, peak-to-peak square wave, 20% to 80%) .....................—....mm.-m.emmmecie nene rene 4.515
Power Consumption (Continuous, All Channels Driven)
QUIESCEN O OS 96VA
Maximum ............—.eesererecoececenencere ee rernarnenenererereraoareoacacecocereereicaceranace never enana neon Dnerenenenemenencarcentereneacecarareceerenrernee. 1440VA
100 watts into 8 ohms ..................esereesrresenrrevererererenenercamenseree e erreneneane reee enenenenereneccecoceraneraraneramerimrenmenecertareree. 1165VA
Power (Available in 230VAC on special order) .….….….…..….….….....serseeneenençençennsnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnn 115VAC - 50/60Hz
Chassis Dimensions................e-.....eserererecacecere reee ee eneneraoe ercer renacer een rene. 5” (127mm) x 17” (432mm) x 14” (355.6mm)
Maximum Dimensions... emcees sess eee en 5%,” (146mm) x 17” (432mm) x 15” (381mm)
Weider EEE eter sashes e Reber Reena EEE Eee RL SEs 42 |b. (19.1 kg)
Weight, Packed ......................-....r.eeeir Deere eee ere nene erec nene ene entererenarerenererenerecneenenentaceneerereneneceetecos. 48 Ib. (22.8 kg)
All specifications are subject to change or improvement without notice. Dimensions and weights listed are approximate, actual
product may vary slightly.
17
GFA-7300 SPECIFICATIONS
Power Rating (To FTC Requirements)
60 watts continuous average power into 8 ohms at any frequency between 20Hz to 20kHz with all channels driven at less
than 0.075% THD
90 watts continuous average power into 4 ohms at any frequency between 20Hz to 20kHz with all channels driven at less
than 0.075% THD
IM Distortion (SMPTE)
1 watt to 60 watts into 8 ohms.........................—.—.ereeeeeeeea e ene nee eee eee aire 00 < 0 07%
1 watt to 90 watts into 4 ONMS.…...……….…..………rrsrersrerescencensenenmennrenenererareenere cena оо, не < 0.07%
IM Distortion (CCIF, Any Combination from 4kHz to 20kHz)
60 watts into 8 ohms .......................eserverieceinen eee Dee nene eee eee eo arena e menea a avaro aL < 0 025%
90 watts into 4 ohms ...........................emmenen ie e Rene eee. arre e errar A arena e dies < 0.025%
2ОНа..... oi reece ete ete eee eee eee eee enone eee D оо ы. 0.0075%
A ны. . 0.007%
TOKHZ ce rrr estes ees ovate e rinrere marea ae meerieo LL. 0.015%
20KHZ ....... e nrerminnnnenninenes neeinene none enen cane nee reaa ere ere ere ees reteset ene eee ees e riendas a mios . … 0 025%
20Нг2. ............ e чоооаве aan ‚ .. 0.015%
TKHHZ nue воненнннннные ененннененненнннненненнненененененненененынененнннононенонотонотоносточеночануатанаоочевоавовоаноьвввававововое зачечые a 0.010%
LT E teres eee e esses eee sees eee A a ea …. 0022%
20kHZ ...........ececamacereracana en nens ne aan nene eee teen ner TaR arar eee reee KR on vena Les 0 035%
Frequency Response @ 1 Watt into 8 ohms (10Hz to 20kHz) ninas drena ae … +0, -0 25dB
Power Bandwidth (-3dB) ...............................e...e.eneerereena nene a les 1.5Hz to 100kHz
Dynamic Headroom into 4 ohms..........................-...=..1 EEE EEE a 1.9 dB
Signal to Noise Ratio, “A” Weighted (60 watts into 8 ohms).......... ................. ner den nea ae > 115dB
N pronesacaceraeneotocacrenenanenererenenonaea KERLEREREEREREEKEREEE REREEREEN REEKEREE eevee ereneoa …. . 29dB
Input Sensitivity
for | [email protected]…..…....…ocrreresrceseencerererenssncencencaseeranresnrnsa seu EEE RER EEE ERBE EEE A . 0 1 volts
for 60 Watts. ………. …....….……urcerrsrcsrenrersrrncens venrenrensanmaneramenerenaravenerarane evene areas à Aa ооо, 1.14 volts
input Impedance ... ...............…rcvararerasersrenerssanercenserrarecrararcens never ncererererarecesaneasensepenenerenaanae manner aan AE AAA A nieii. 50kQ2
Damping Factor (20Hz to 20KHz)..…............….....……..….….…ccsrerrererranes verrreneranersenranenrre vccaneransen aires À de A A mea mias > 800
Rise Time (SkHz, 90V, peak-to-peak square wave, 20% to 80%)... eee eo arerriaaa о mias ‚2 TuS
Power Consumption (Continuous, All Channels Driven)
QUIESCENt eee rere career este be sas shee see sesso se eee esse see ese ease essere conan ee A 80VA
Maximum..................erenmieiiee einer reee enineree cree re eee Deere rrreeraa cercare e eee eres meorenaaa errarero A e a ies 960VA
60 watts into 8 ONMS …..….….....……….….…………rvrrercrercerrereneenserscoracecaus BERTRAM a . …. . B40VA
Power (Available in 230VAC on special order) ....................ec.1..2. 0000000. eee EEE arre a eee À orties 115VAC - 50/60Hz
Chassis Dimensions............ rer RER RER EEE EEE EEE ero .. 4/7 (118mm) x 17” (432mm) x 14” (355 6mm)
Maximum Dimensions ………...…..…..….......…rsrserierersencensentsssenererensrenerenan a nen sara 5” (127mm) x 17” (432mm) x 14°/,” (375mm)
| TT ERRE ERREGER ARE a are 35 Ib. (15 9 kg)
Weight, Packed........ . ......................ieieicice reee er enero ener era roer ereer eco rearareraDa eereececea verrerorera ene reee emerreraas 40 Ib. (18.2 kg)
All specifications are subject to change or improvement without notice. Dimensions and weights listed are approximate, actuai
product may vary slightly.
18
11 Elkins Road
East Brunswick, NJ 08816
USA
Tel: 732-390-1130
Fax: 732-390-5657
Web: http://www.adcom.com
New Location and Telephone Numbers as of Spring 1998
ADCOM
10 Timber Lane
Marlboro, NJ 07746
USA
Tel: 732-683-2356
Fax: 732-683-2358
98KFTD01
PRINTED IN THE USA
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