INTRODUCTION |
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Pleasereadthoroughlytheseoperatinginstructions | fortheGFA555msbeforeconnecting | ||
orattemptingtooperateit.Theinstallationando | perationoftheGFA555msaredescribedin | ||
thefollowingpages.Wesincerelyhopeyouwillval | ueandenjoytheconsiderableattention | ||
we have given its design and construction. This man | ual has been written to help you | ||
understand the correct operation of the GFA555ms. | Please read it carefully to fully | ||
comprehendallitsfeaturesandfunctionsandthere | byderivemaximumperformancefromits | ||
useinyoursystem.Itisagoodideatokeepthis | manualhandyforfuturereference. | ||
PREFACE |
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WARNING |
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TheGFA555msisaverypowerfulamplifiercapable |
| ofdeliveringverylargepeaksintolow | |
impedances, exceeding 80 amperes per channel. There | fore, be certain to exercise | ||
extreme cautionwhenmakingconnectionstoandfromtheamp | lifier. Always make certain | ||
that the amplifier is disconnected from the AC outlet, and its large filter capacitors
are discharged. Pleasenotethatthepowersupplycapacitorscanta kemorethan five
minutes todischarge . Failure to observe this precaution may result in damage to the loudspeakers and/or blowing of the amplifier's DC RAIL FUSES, conditions which are NOT covered by the warranty.
TheGFA555msamplifiercandriveaverybroadrang | eofloudspeakers. includingthose | ||
withverylowimpedances,atsustainedhighpowerl |
| evels,evenwhentheimpedancesare | |
highlyreactive.Greatcarewastakentoinsuretha |
| tdistortionintheamplifierwouldremain | |
extremely low, particularly when driving these high | ly reactive loads in which the phase | ||
anglesofthevoltageandthecurrentaresubstanti |
| allydifferent.Alittleknownfactisthat | |
amplifierswhichmeasureextremelywellonthetest | benchintoaresistiveloadmaynot | ||
developthesameamountofpowerintoaloudspeaker | .Dependingontheamplifier'sdesign, | ||
sometimesaslittleasonethirdofthepowerwhich |
| theamplifierdevelopsintoaresistoris | |
deliveredtoaspeakerload.Also,thedistortionl | evelmeasuredwhentheamplifierisdriving | ||
aresistiveloadisdegraded.insomecasesquites |
| ubstantially,whendrivingtheloudspeaker. | |
Itis,however,verydifficulttomeasuretheperfo | rmanceofanamplifierintoaloudspeaker. | ||
Onereasonwhythisinformationisnotwidelyknown | isbecauseduringsuchhighpower | ||
tests, destruction of the loudspeaker is often the | result. In order to determine the | ||
performance of the GFA555ms, ADCOM developed a "co | mputer model" of a "difficult" | ||
loudspeakerload.Acomputermodel"mimics"therea | ctanceoftheverydifficultspeakerand | ||
duplicatestheactualphaseanglesofthevoltagea |
| ndcurrentthroughouttheentireaudio | |
range. In this manner, highpower testing of amplif | ier parameters could be undertaken | ||
