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Summary of Contents for Adcom GFA-555MS
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Page 1: Power Amplifier
HIGH CURRENT POWER AMPLIFIER GFA-555ms The contents of this manual are subject to change. Please check our website www.adcom.com www.adcom-usa.com for the most current version. Copyright © 2011 Adcom LLC... - Page 2 Please read thoroughly these operating instructions for the GFA-555ms before connecting or attempting to operate it. The installation and operation of the GFA-555ms are described in the following pages. We sincerely hope you will value and enjoy the considerable attention we have given its design and construction.
- Page 3 To achieve the above, eight sets of specially selected TO-3-type, metal-cased bipolar output transistors are used in the GFA-555ms in a triple-Darlington configuration of its driver and output stages. The safe operating area of these transistors, along with their circuit topology, insures very efficient power delivery to reactive loads, regardless of the phase angle of voltage and current.
- Page 4 If any number is altered or missing, you should notify us immediately in order to insure that you have received a genuine ADCOM product which has not been opened, mishandled or tampered with in any way.
- Page 5 GFA-555ms, but the free flow of air through the ventilating slots provided in the chassis of the amplifier may be partially obstructed. If you require that the GFA-555ms be...
- Page 6 To insure that the performance designed into the GFA-555ms is preserved, you should use the highest quality plugs and cable as are feasible. There are many cables which are designed specifically for these applications and your ADCOM dealer can be of help in selecting the best cable for your application.
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Page 7: Stereo/Bridged Mono Input/Output
COMMON, G, or GROUND). NOTE The GFA-555ms is polarity correct; that is, it does not invert "phase". Any positive-going signal at its inputs will appear as a positive-going signal at its outputs. The RIGHT STEREO OUTPUT should be connected to the right-channel loudspeaker, as you face the pair of loudspeakers, and the LEFT STEREO OUTPUT to the left-channel loudspeaker. - Page 8 and not exceeding 60 feet, useAWG14stranded wire only. Runs exceeding 60 feet require the use of heavier conductors such asAWG12stranded wire. If you find it difficult to obtain the correct-size wire for your specific connecting length, you can parallel two runs of the next smaller gauge of wire to keep wire resistance at a minimum.
- Page 9 All loudspeaker systems having a nominal impedance down to 2 ohms can be connected to, and driven by, the GFA-555ms. The GFA-555ms can drive these low impedances at more than adequate power levels with no difficulty. It should be noted here that many loudspeaker systems which are rated, nominally, at 4 ohms drop in impedance, in some parts of their frequency range, to as low as 2 ohms (and some others to even less than 2 ohms).
- Page 10 INPUT jack should be removed since the right-channel input portion of the amplifier is inoperative. Only a single loudspeaker is to be connected to the GFA-555ms when in the bridged mono mode. Please note that connections made to the loudspeaker from the GFA-555ms, when used in the bridged mono mode, are different from those made when the amplifier is used in the stereo mode.
- Page 11 4 ohms. It is not recommended that the GFA-555ms be used in the bridged mono mode into loudspeakers, or multiple loudspeaker loads, which drop in value substantially below 4 ohms. Otherwise, you may trigger the THERMAL PROTECTION 0 or blow one of the DC RAIL FUSES e.
- Page 12 The GFA-555ms has a massive power supply which remains charged for up to FIVE MINUTES after the amplifier is turned off and the POWER LED ceases to glow. It also remains energized when the POWER.
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Page 13: Ac Line Cord
The AC cord is a 3-conductor, heavy-duty cable supplied with a heavy-duty, molded 3-prong AC plug. It provides the power to operate all the GFA-555ms's circuits. Its plug should be inserted in a standard, 120V/60Hz outlet with a minimum capacity of 15amperes and should have a dedicated branch circuit. -
Page 14: Ac Line Fuses
(POWER LED does not glow), a failed electronic component or other internal malfunction must be suspected. Make no further attempts at fuse replacement or operation of the amplifier. Refer the problem to competent ADCOM-authorized service personnel. -
Page 15: Ac On/Off Switch
The AC ON/OFF switch controls power to the power transformer and circuits of the GFA-555ms. Whenever the GFA-555ms is energized, the red POWER LED will glow. Push the top of the rocker switch to energize the GFA-555ms. Push the bottom of the rocker switch to turn the unit off. - Page 16 PROTECTION to be activated or, in extreme cases, damage your loudspeakers. THERMAL PROTECTION LED The GFA-555ms is provided with a thermal protection circuit which will shut down the amplifier if the temperature of either heatsinks reaches 85°C. The THERMAL PROTECTION LED will light whenever the thermal protection circuit on either channel, or both channels, has been triggered and the amplifier is inoperative.
- Page 17 EXTREME CASES, UNDERTAKE ALL THREE. CARING FOR YOUR GFA-555ms Great care has been taken by ADCOM to assure 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 of heavy-gauge steel, both painted and baked.
- Page 18 When calling or writing about your GFA-555ms, be sure to note and refer to its model and serial numbers as well as the date of purchase and the ADCOM authorized dealer from whom it was purchased. In the event the unit must be returned for service, you will be instructed as to the proper procedure when you call or write.
- Page 19 GFA-555ms SPECIFICATIONS Power Rating (To FTC Requirements) 125 watts continuous average power into 8 ohms at any frequency between 20Hz and 20kHz with both channels driven at less than 0.04% THD. 200 watts continuous average power into 4 ohms at any frequency between 20Hz and 20kHz with both channels driven at less than 0.05% THD.—...
- Page 20 IM Distortion, Bridged (CCIF, Any Combination from 4kHz to 20kHz) ≦0.005% 400 watts into 8 ohms THD + Noise at 400 Watts into 8 Ohms, Bridged 20Hz 0.004% 1kHz 0.004% 10kHz 0.020% 20kHz 0.050% Frequency Response @ 1 Watt into 8 Ohms 10Hz to 20kHz +0.
- Page 21 No part of this manual may be reproduced or electronically transmitted without the express written consent of Adcom LLC. Adcom LLC shale not be liable for any errors contained herein or for any damages arising out of or related to this document or the information contained herein, even if Adcom LLC has been advised of the possibility of such damages.
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