User guide

13
TECHNICALGLOSSARY
ENGLISH ENGLISH
Balancedandunbalanced
Finalstage
Impedance(Z)
Ground
Mixer
Pre-amplifier
Ground
Aconnectionisbalancedwhenthesignaliscarriedbytwoconductors(hot
andcold)andascreeningbraid.Thehotpinhasthejobofcarryingthein-
phasesignal,whilethecoldonecarriesthesamesignal,butoutofphase.
Thismethodenablestomaketransmittedsignalsimmuneto
electromagneticinterferenceevenoverlonglines,thankstothefactthat
whenthetwosignalsreachthereceivingdevice,theyarealgebraically
subtractedonefromtheother,producinganewsignalwithtwicethe
amplitudeandeliminatingtheinterferencealongitspath.
(outputstage)
Anelectroniccircuitwhichconvertslowpowersignalstohighpower
signalswithsufficientcurrenttomovethecoilsandthereforetheconesof
aloudspeaker.
RepresentstheresistanceofferedtoACbyanelectriccircuit.Itis
measuredinOhmsandasopposedtotheresistance,takesinto
considerationthecircuit'sinductivecomponents(coils)andcapacitive
components(condensers).Audiosignals'inputandoutputcircuitsare
dividedintolowimpedance(withaZoflessthan5kOhms,suchas
microphonesandloudspeakers)andhighimpedance(whenZismore
than10kOhms,asisthecasewithelectronicinstruments,CDplayersand
taperecorders).Whenconnectingdifferentunits,itisnecessarytotryto
keepOUTandINimpedancessimilar.
Electricalreferencepointforasignaltravellingroundacircuitoralonga
cable.Thegroundgenerallyhasavalueofzerovoltsandiscarriedby
audiocablesbymeansofametalsheathwhichalsohasthefunctionof
screeningthesignal(i.e.protectingitfromexternalelectromagnetic
interference.
Anactiveelectroniccircuitabletomixtwoormoreaudiosignalstogether.
Amixercanalsofeatureaudioeffects,mixingthemwiththeoriginal
signals.
Thisisanactiveelectroniccircuitwhichhandleslowpowersignals.The
unit'sfunctionsare:handlingtheincomingandoutgoingaudiosignals
(excludingspeakerenclosures),volumeandequalization.
Theground(orearth)inanelectricaldeviceisrepresentedbythephysical
connectionofthemetalpartsexposedtotheuserandacableinthepower
plug(themiddlepin).Bymeansofthemainspowersupply,theground
cable(normallyrecognizableforitsyellow/greencolour)isconnectedtoa
metalpolehammeredintotheground,ofteninthebasementofthe
buildingitself.
Theaimofthegroundsystemistodisperseinthegroundanycurrent
whichintheeventoffaultscouldelectrocuteauserwhentouchingthe
metalpartsoftheunitinquestion.Thedispersionofenergyissometimes
alsousedtoeliminateanyaudiohum,whichcanbeachievedbymeansof
acapacitiveconnectionbetweenthesignalgroundandtheamplifier
ground,orevenaphysicalconnection.
THD
TIM
Toneburst
WattsRMS
TotalHarmonicDistortion.Thisvalueindicatestherelationshipbetween
theeffectivevalueofthespuriousharmonicsgeneratedbythesystemin
questionandtheeffectivevalueofthefundamentalsinewaveusedinthe
test.THDisnormallyexpressedasapercentage.
Transientintermodulation.Measurementofintermodulationdistortion
duringthemostcriticalmomentsofanamplifier'soperation:powerful
transientswhichmustreleasehighenergyinaveryshortperiodare
generated.
Themeasurementscarriedoutinlaboratoriestotestamplifiers'power
don'ttakeintoconsiderationtheconstantelectricalvariationswhicha
complexaudiosignalcanhavethroughtime.Nowadayspoweris
expressedinpeakWatts(asfarastheresponseofanoutputstagewith
extremelybrieftransientsstatesisconcerned),musicalWatts(which
indicatethehypotheticalpoweronastablesinusoidalsignal)andRMS
Watts(whichmeasuretherealpower,butreferredtoastablerepetitive
complexsignal).ThemeasurementtechniquewithToneBurstsignalsis
extremelysignificantasitcyclicallyrecreatesthepossibledynamicrange
whichanormalaudiosignalcanhavethroughtime.Thissystemensuresa
controlofthequalityandcapacityoftheoutputtransistorsandaboveallof
thepowersupplycontainedintheamplifierbeingtested.
Thisisameasurementwhichexpressestheeffectivevalueofthepower,
i.e.therealamountofpowerwhichasystemisabletodeliver.RMS(Root
MeanSquare)isthemathematicalmethodusedtocalculatetheeffective
power:thesquarerootofthemean(average)ofthesumofthesquaresof
theharmonicscontainedinthespectrum.TheRMSWattsareexactlyhalf
themusicalWattsandaneighththepeak/peakWatts.