10
VACiQ ContinuousAutomaticBiasSystem
In engineering,theabbreviation “Iq”denotesthequiescentcurrentof avacuumtube,also known asthe
idlecurrentorbiaspoint.Forbestperformance,theIq mustbesetand maintained precisely,even asthe
amplifierwarmsup,thepowerlinevaries,thetubesdrift,and regardless of whetheryou'replayingthe
musicsoftlyorloudly.
No systemhasbeen ableto do this. Until now.
Theresultof 17 yearsof research,theVACiQBiasControlSystemisthefirstand onlysystemableto
monitorcontinuouslythetruebiaspointof each outputtubeand hold itpreciselyatthedesired value,
thusensuringoptimalperformanceatall times. Itactuallyoutperformsmanualsystemsbecauseitcan
correctfortheheatingeffectsthatoccurwhen reproducingloud passagesof music.TheVACcircuitboth
MONITORSand CONTROLS,continuously,in realtime.
Theresultingperformancedifferenceisonethatyou can easilyhear.And notonlydoesitsound better, it
radicallyreducestherateof tubefailures,and isself-diagnosing.
Operation
In operation,theiQcircuitmonitorsand maintainsthecorrectbiasadjustmentfortheKT88 outputtubes
atall times,regardless of themusicplaying.
TheiQsystemcontainstwo othercomponentsthatinformyou of tubecondition and protecttheamplifier;
theoperation of thesetwo circuitsisindicated bythebicolorLEDs.
If an LEDilluminatesGREEN,thisisan indication thattheassociated tubeisbecomingweak.In a
conventionalamplifier, you would haveadvanced thebiascontrolwell clockwiseforthistube.No
immediateaction isrequired;simplyreplacethisKT88 with afresh onewhen timepermits,and the
amplifierwill makethebestof theweaktubeuntil then.
An LEDwill illuminateRED if an outputtubedrawsexcessivecurrent,i.e.,if a‘run away’occurs. Becauseof
thestabilizingaction of theauto biascircuit,thisismostlikelyto occurif somethinginsidethetubehas
physicallybroken.TheiQsystemdetectsthefaultwithin afraction of asecond and shutsdown themain
powersupply,thuspreventinganydamage;all of thishappenslongbeforethefusecan react.Switch
poweroff,and replaceand discard theindicated tubeafteritcoolsdown.
See thecharton thenextpage.
