Adcom GFA-7707 User Manual
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HIGH CURRENT, MULTI-CHANNEL
POWER AMPLIFIERS
GFA-7705/07 Features
• Precision-matched devices used throughout the signal path.
• 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.
• ADCOM-Universal pre-prepped chassis and internal power supplies for easy in-field upgradeabiiity
from 5 to 7 channel configuration.
• Independent thermal-overload and distortion LEDs for ail 5 (to 7) channels.
• S.A.F.E.® Circuit: Self Annealing Fuse Equipped-automatic reset protection circuit in the event of
speaker or speaker wire dead-short.
• 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.
. Convenient 12 VDC power ON/OFF triggering.
• Heavy gauge, anodized aluminum front panel.
• Coolir^ vents for greater efficiency and cooler operation while driving low impedance loads.
Table of Contents
Introduction
Warranty Information....................................................................................................................4
Description of Unit— 20-Amp Device Notification............................................4
Rear Panel................................................................................................................................... 5
Front Panel.................................................................................................................................. 7
Installation & Hookup
Unpacking the GFA-7705/07........................................................................................................
Placement of the GFA-7705/07......................................................................................................9
Quick Connection Diagram.......................................................................................................... 10
Connecting the GFA-7705/07........................................................................................................ 11
Caring for your GFA-7705/07......................................................................................................... 12
Troubleshooting
Resolving Problems.....................................................................................................................13
Service Information...................................................................................................................... 14
Specifications.............................................................................................................................. 15
9
introduction
Congratulations on your decision to purchase the GFA-7705/07 multi-channel power amplifier. The GFA-7705/
07 integrates very well with any other home theater system, such as Dolby ProLogic™ or Dolby Digital™. You
have made a wise choice that vdll 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.
ADCOM Protection Plan (NORTH AMERICA 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
The GFA-7705/07 is a 20-Amp Device.
The GFA-7705/07 is high-power, high-current, wide-bandwidth design employing ADCOM’s Fast Analog Transform
(F.A.T.) circuitry with direct-coupled Power Rig output stages. All channels are completely monaural from
transformer secondaries through the output stages.
In order for this product to achieve its actual rated power output on all channels and to avoid repeatedly
throwing/popping the related electrical service panel circuit breaker, it is critical that the amplifier be
professionally installed on a 20-Amp household AC circuit and outlet, preferably dedicated but at minimum one
not shared with other large current-draw appliances or devices.
Common 15-Amp household circuits are easily and inexpensively converted to 20 Amp configuration by any high-
voltage licensed electrician.
For this reason, the GFA-7705/07 ships Factory-equipped vrith a hard wired, 20-Amp Plug on the AC Power Cord.
WARNING: DO NOT DEFEAT THE 20-AMP PLUG OR HARDWIRED AC POWER CORD TO EAAPLOY EITHER A 15 AMP
OUTLET OR “AUDIOPHILE” TYPE DETACHABLE POWER CORD.
DOING SO WILL VOID PRODUCT WARRANTY. MAY DAAAAGE THE PRODUCT AND PLACE THE USER AT EXTREME RISKOF
INJURY OR DEATH.
(3a) (3b) (4)
Rear Panel
Inputs (1)
The audio inputs for the GFA-7705 and 7707 are through high-quality, gold-plated RCA jacks to minimize highfrequency losses, rw)ise, etc. They will accept standard RCA-type plugs, one for each of the five channels; Front L
(Left), Center, Front R (Right), Surround L (Left), and Surround R (Right). To insure that the performance designed
into the GFA-7705/07 is preserved, you should use the highest quality, shielded 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-7705/07 for more information.)
Inputs (1b)
Chassis knock-out for future expansion channel-card input jack (GFA-7705 only).
Outputs (2)
The GFA-7705/07’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).
(See CONNECTING THE GFA-7705/07 for more information.)
Outputs (2b)
Chassis knock-out for future expansion channel-card output binding posts (GFA-7705 only).
WARNING
THERE ARE NO USER-SERVICEABLE PARTS OR FUSES INSIDE THE GFA-7705/07. In the event that the
amplifier’s rear-panel circuit breaker fails to reset (opens again v/hen power applied to unit and unit
turned on) you must refer the amplifier to ADCOM Factory Service or ADCOM Authorized Service Center.
Do not open the amplifier nor remove the topcover-Hazardous and Potentially Lethal Voltage Present
and Warranty may be voided.
12VDC Triggering (3a)
ADCOM has provided the installer the ability to control the OFF/ON function of the GFA-7705/07 by a
12Volt DC output jack on the rear of certain 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 wnth ADCOM and other brand pre-amplifiers. Although 12VDC is
optimal, the circuit will operate from approx. 5 to 30VDC. Center conductor (tip) is positive (+).
AC Circuit Breaker (3b)
The 15-Amp AC Breaker protects the electronic circuits of the GFA-7705/07. Normally, this breaker vdll
open only if there is an overload or a component failure within the GFA-7705/07.
If the Power LED (7) does not glow, it may be an indication that the AC Breaker has blown. If you are
using the 12VDC Triggering feature (above) it may be possible that there is no trigger voltage present or
a problem exists 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. If the problem is caus^ 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.
AC Power Cord (4)
The AC cord provides power to operate all the GFA-7705/07’s circuits. The GFA-7705/07 is a very high
power amplifier and as such must be directly connected to the wall outlet or an appropriate (noncurrent limiting) surge protector or AC line conditioner of 20-Amp service capability.
NOTE: As previously described on Page 4, the attached plug is a 20-Amp fitting which, in order for the
amplifier to deliver its rated power output, should not be defeated in order to accomodate standard
15-amp household vrall outlets.
Please consult vdth your dealer and/or licensed electrician for conversion of a 15 amp outlet and panel
circuit to a 20 amp circuit.
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