Adcom GFA-565 User Manual Download Page 11

OUTPUT "+") should be connected to the loudspeaker input terminal color-coded RED (or 

labeled POSITIVE, "+", POS, 8 OHMS or 4 OHMS). The 

RIGHT RED 

output binding post 

terminal  on  the amplifier  (labeled BRIDGED MONO  OUTPUT  "-")  should  be  connected  to 

the BLACK loudspeaker terminal (or labeled NEG, "-", C, COM, COMMON, G, or GROUND). 

All  the  wiring  and  phasing  recommendations  in  the  section  RIGHT/LEFT  STEREO 

SPEAKER OUTPUT 8 apply to this connection as well. Please note that if you want to insure 

correct  stereo  phasing  with  optimal  bass  response,  you  must  observe  these  connections 

precisely. 

 

Although the GFA-565 can generate a substantially greater amount of power in the bridged 

mono mode than when it is in its normal stereo mode, it requires the use of loudspeakers the 

nominal impedance of which does not drop below 4 ohms. It is not recommended that the 

GFA-565  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.  Please  refer  to  the 

section  RIGHT/LEFT  STEREO  SPEAKER  OUTPUT  for  further  clarification.  A  little  known 

fact is that when any amplifier is operated in the bridged mode, the load is "split" between 

the  two  amplifiers  in  the  bridged  configuration.  Therefore,  an  8-ohm  loudspeaker  will  be 

seen by the amplifier as if it were a 4-ohm load; a 4-ohm loudspeaker load will be seen by 

the amplifier as a 2-ohm load.   

 

NOTE

 

If the connections described above are followed exactly, the GFA-565 will be polarity 

correct, that is, it will 

not 

invert "phase". Any positive-going signal at its input will appear 

as a positive-going signal at the loudspeaker. 

 

 

 

DC RAIL FUSES

 

The DC RAIL FUSES provide protection for the output stages and power supply in the event 

of excessive current demands from the amplifier, either long-term or short-term. 

 

If  the  amplifier  ceases  to  operate,  either  on  one  or  both  channels,  particularly  during 

high-level passages, or long-term high-volume playback, and the POWER LED glows while 

the THERMAL PROTECTION LED is out, the chances are that one or both of the DC RAIL 

FUSES on that channel, or both channels, are blown.   

 

Your  ADCOM  amplifier  is  designed  to  activate  its  protective  devices  reliably,  particularly 

Summary of Contents for GFA-565

Page 1: ...HIGH CURRENT POWER AMPLIFIER GFA 565 The contents of this manual are subject to change Please check our website www adcom com or www adcom usa com for the most current version Copyright 2011 Adcom LLC...

Page 2: ...can drive a very broad range of loudspeakers including those with very low impedances at sustained high power levels even when the impedances are highly reactive Great care was taken to insure that di...

Page 3: ...her efficiency was insured by using a toroidal design Additionally thermal and dynamic tracking of the bias for the triple Darlington driver and output stages is provided to insure that the amplifier...

Page 4: ...outer carton 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 wi...

Page 5: ...t only will the heat generated by the amplifier affect the performance of equipment stacked on top of the GFA 565 but the free flow of air through the ventilating slots provided in the chassis of the...

Page 6: ...lication Your ADCOM dealer can help select the best cable for your needs RIGHT LEFT INPUT Unbalanced The audio inputs to the GFA 565 are through two high quality gold plated brass RCA jacks using Tefl...

Page 7: ...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 Be certain when the GFA 565 is used in Its...

Page 8: ...hich you should observe in order to insure maximum performance from your amplifier It is most important that you make certain the wiring you have selected has as Iowa capacitance as possible All ampli...

Page 9: ...wer 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...

Page 10: ...inal of the loudspeaker to the negative terminal of the loudspeaker and vice versa Repeat the listening test with the mono signal to make sure you are correct in your initial evaluation If you can now...

Page 11: ...of the DC RAIL FUSES e Please refer to the section RIGHT LEFT STEREO SPEAKER OUTPUT for further clarification A little known fact is that when any amplifier is operated in the bridged mode the load i...

Page 12: ...d their time current blowing points have been carefully selected and thoroughly tested to deliver optimal performance while still accomplishing their protective functions Replace these fuses individua...

Page 13: ...ts Its plug should be inserted in a standard 120V 60Hz outlet with a minimum capacity of 15amperes and should have a dedicated branch circuit It is not recommended that you connect the GFA 565 into a...

Page 14: ...g on the amplifier 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 Refe...

Page 15: ...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 you have blown one or more of the DC RAIL FU...

Page 16: ...l to reduce the listening level demands or you may blow the DC RAIL FUSES cause the THERMAL PROTECTION to be activated or in extreme cases damage your loudspeakers THERMAL PROTECTION LED The GFA 565 i...

Page 17: ...ility The chassis top cover and rear panel are of heavy gauge steel both painted and baked If the front panel top or sides should become dusty or fingerprinted they can be cleaned with a soft Iintless...

Page 18: ...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 UNDER...

Page 19: ...05 THD 700 watts continuous average power into 8 ohms at any frequency between 20Hz and 20kHz at less than 0 1 THD bridged IM Distortion SMPTE 1 watt to 250 watts into 8 ohms 0 009 1 watt to 350 watts...

Page 20: ...10Hz to 20kHz 0 0 25dB Power Bandwidth 3dB 5 Hz to 100kHz Dynamic Headroom into 4 Ohms 2 5dB Signal to Noise Ratio A Weighted 250 watts into 8 ohms 110dB Gain 27 0dB Input Impedance 100 000 ohms Inpu...

Page 21: ...om logo are registered trademarks of Adcom LLC 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...

Page 22: ......

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