VAC Musicbloc Master 300 iQ Setup guide

TheVACMaster300 iQMusicbloc™
Mono/Dual Stereo Beam PowerAmplifier
Operation&MaintenanceInformation
ValveAmplificationCompany
Manualissued01/26/2023
Valve Amplification Company,Inc. 2172 10th Street Sarasota,FL34237 Phone [phone] FAX[phone]

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CAUTION-SAFETYNOTICE
THEAMPLIFIERANDPOWERSUPPLY CONTAINNOUSERSERVICEABLEPARTS.DONOT REMOVETHEBOTTOM
PLATESORCHASSISCOVERS. LETHALVOLTAGESAREPRESENTWITHINTHECHASSIS.DONOT OPERATETHE
UNITSIFTHEYAREWET.
VACUUMTUBESBECOME HOT ENOUGHTO CAUSESERIOUSBURNS.NEVERTOUCH ATUBEWHENTHEUNIT
ISON. ITMAYTAKESEVERALMINUTESFOR THETUBESTO COOLDOWN AFTER THEUNITISSWITCHEDOFF. IT
ISSTRONGLY RECOMMENDEDTHATTHETUBECOVERSBELEFTINPLACEATALL TIMES.
THETUBECOVERSWILL BECOMEHOT INNORMALOPERATION. DONOT SETORSPRAYANYTHINGONTHEM.
Never touchatubeiftheglass isbroken.Theinternalstructurescarry highvoltageandcouldpresent aserious,
possibly lethalshock. Ifatubebreaks, unplug theamplifier andwait30 minutes, thenremovethetube.
Keepflammable objectsawayfrom theamplifier.
DONOT LEAVETHEAMPLIFIER UNATTENDEDINOPERATION.
THEAMPLIFIER IS HEAVY. ITISADVISABLETO HAVEASSISTANCEINUNPACKING,MOVING,ANDSETTINGUP.
BESURETO USEPROPER LIFTINGTECHNIQUESTO AVOIDBACKSTRAINANDINJURY.
BECERTAINTO INSTALL ITINASECURELOCATIONFROM WHICH ITCAN NOT FALL ORTIPOVER. IFNECESSARY,
SECURETHEAMPLIFIER TO THEWALL TO PREVENTTIPOVER.

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INDEX
Introduction
Installation
Connectiondiagrams
Operation
IlluminatedLogo
Installing NewTubes
OperationoftheVAC iQCircuit
Care OfChassis
Tips andAdvice
Fuses
AWordAbout TubesinGeneral
Output Tubes
LowLevel Tubes
Grounding
Tuning YourSystem
Specifications
Footnotes
Warranty&RegistrationForm

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INTRODUCTION
TheVACMaster 300 isauniquepower amplifier,andoneofthemretpowerfulanddetailedinVAC’s history.
Featuringanewfully balanceddirect-coupledinput &driver circuits,extremely fastandvividsoundisachieved.
Thisamplifier featuresVAC’s patented*iQContinuousAutomaticStable Bias System. Thisrevolutionary invention
istheonly approachcapable ofkeepingthetrueunderlyingidle point ofeachoutput tubeunvaryingandsteady
atall times.Thisleads toanuniquely stable operatingpoint andanunvarying relationshipbetweentheoutput
tubesandthespeakers. Theresultismore detail,control,andnuance,fromthetiniestwhisper totheloudest
crescendo.
TheMusicbloc™designiscapable ofbeingoperatedas amonoamplifier oras adual-mono(stereo)amplifier.
Thechassisismachinedfromthickaluminum, finishedinacombinationofhandpolishedmetallicbasecoat/clear
coatandhightemperature powder coatpaint.
TheMaster 300 isdesignednottothelatestfadbut tosubstance,forthehighestpossible soundquality.Time
spent familiarizing yourselfwith thismanualwill bewell rewarded.
*TheVACiQContinuousAutomaticBias technologyisprotectedbyU.S.Patent 8,749,310;worldwidepatents
pending.

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INSTALLATION
01) Theamplifier isquiteheavy.Consider thelocationcarefully,and useappropriatehelpinlifting, etc., so
as toavoidinjury. Ensure thatitwill nottipover inyouruse;ifthere isariskofthis, especially dueto
children, takeall necessary steps tosecure theamplifier toawall.
002) Install thevacuumtubes.Eachtubeoritsboxhas a“V”number,whichcorresponds tothelabelsonthe
topplateoftheamplifier;theseindicatewhere eachtubeshouldbeinstalled.
Fiteachtubeintothematching socket.
Wheninserting andremoving tubes, handle them bytheir bases, notbytheir glass bulbs.
Notethatthere isalocatorridgeonthetubes’ center poststhatindicatesproper alignment.
03) Placethetopventilationgrill inplace. Itrestsonthefourbuttonmagnetsattachedtothesiderails.
04) Setthebackpanel switchtoBalanced(forusewith balancedsourcesonXLRconnector) orSingle-
ended(viaRCAconnector) as desired.Balancedinput ispreferred.Note:ifoperatinginthemono
modewith RCAinputs, usetheupper (“left”) RCAinput.
05) Setthethree Mono/Stereoswitchestothedesiredmodeofoperation.
06) Install theinput cablesinthebackpanel jacksthatcorresponds totheswitchsettingsselectedabove.
07) Connectthespeaker cables;theblackleadgoesto“-“or“Ground”.Theredleadgoesto“+” or
“Positive”. There are binding postpairsforleft andright instereooperation, andanother formono.
08) Connect12 volttrigger input cablesintotheappropriatesocketsonthebackpanel ifdesired;either will
slavetheoff/onfunctiontotheexternalconnection.
09) Provideadequateventilation-allowatleastsix inchesaboveandthree inchestoeachside,andfront
andback.
10) Donotplaceinacompletely enclosedcabinet.
11) Donotoperateonanysurfacethatmight blockair flow.
12) Thechassisandglass will becomehotinnormaluse.
13) Thepower supply mayproduceasmall mechanicalhum;therefore avoidplacingthesystemonany
surfacethatcouldactas asoundingboard,oratanylocationintheroomthatcorresponds toa
resonanceatyourlocalpower frequency(50 Hzor60 Hz).
14) Donotallowthechassistotouchanymetalparts,suchas theframeofanequipment rack. Thismight

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createaparallel groundpath thatcoulddegradethesoundofyoursystem. Notethatexternalgrounding
systemsmight degradeperformance.
15) Connectthepower cordtothepower sourceindicatedontherearpanel (will beeither 100,120,220,
or240 voltsAC).Voltageconversionsmustbedoneatthefactory ofbyanauthorizedVACimporter.
16) Avoidpower conditionersorpower cablesthatfloatthegroundpin.Thisisanunsafepractice,and
couldresultindamagetoyoursystem andlethalshock.
17) Maximumpower requirement isapproximately 1000 watts.Paycloseattentiontopower quality,andbe
aware thatdifferent power cords canalter thesound.
NOTE:Donotremoveandconnectinput cablesorspeaker cableswhile isamplifier isrunning. Doingsorisks
damagetoyourloudspeakersortheamplifier.
NOTE:Donotoperatetheamplifier without loudspeakersorloadresistorsattached.
NOTE:Donotoperatewithout theventilationgrill inplace.
NOTE:Takecare tokeepeveryone,especially childrenandpets,frombeingable toreachandtouchthetubes,
whichbecomeextremely hotandcouldcauseseriousinjury.
NOTE:Never touchatubeiftheglass isbroken.Theinternalstructurescarry highvoltageandcouldpresent a
serious,possibly lethalshock.Ifatubebreaks,unplugtheamplifier andwait30 minutes,thenremovethe
tube.
NOTE:Keepflammable objectsawayfrom theamplifier.
REMINDER: Donotremoveandconnectinput cablesorspeaker cableswhile isamplifier isrunning. Doing
sorisksdamagetoyourloudspeakersortheamplifier.
REMINDER: Donotoperatetheamplifier without aloudspeaker orloadresistorattached.
REMINDER: ProvideadequateventilationFailure todosomayshortentheamplifier’s life,andmayresultin
tubefailures.

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OPERATION
Thepower switchisonthefront panel.
Soundwill beginapproximately 60 seconds after turnon.
Aswith all highfidelityproducts, thesoundcharacteristicoftheVAC changessomewhatas itwarmsup.We
adviseagainstleavingtheequipment onatall timesforsafetyreasons,andbecauseoftheattendant acceleration
ofoutput tubewearandpower consumption.Lifeoftheoutput tubesaverages3,000 to8,000 hours.Forbest
tubelife, turntheamplifier off whenyouare notlistening.
AnytimethattheVACPower Amplifier has notbeenusedforafewweeksthesoundmaybedifferent.Thisis
alsonormalforhighresolutionaudioequipment.Optimumsoundshouldreturnafter afewhoursofoperation,
preferably with anaudiosignal.
PleasenotethatalthoughyourVAC System has beenrun for48 hoursatthefactory, thebreak-intimeofhigh
resolutionaudioequipment isinfuriatingly long. TheMaster 300'ssoundwill continuetoseasonforapproximately
200 hours.Theearly soundoftheamplifier will beless extended,dynamic,andcoherent.Thenthesoundwill
improvenoticeably,followedbyaperiodofdarker sound,finally givingwaytothedesiredmusicality.Patience
isavirtue.
Alsobeaware thatmanycomponentsdisplaytheneedforanewbreakinperiodafter beingtransportedin
unheatedcargoaircraft.
ILLUMINATEDLOGO
Theilluminationofthefront VAC logomayturnedonoroff viatheswitchonthefront panel.

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INSTALLINGNEWTUBES
First, see theSAFETYNOTICEearlier inthemanual.
Output tubesare typeKT88.Replacement output tubesshouldbepurchasedfromVAC. Itisdesirable thattubes
beinmatchedoctets,andbeclosetothe"bogey"valuesforthemajorparameters.Makecertainthateachtube
fitsfirmly initssocket.
ALL POWERMUSTBEOFF.Removethetopgrill andtheoldtubesafter they havecooleddown(TUBESBECOME
HOT ENOUGHTO CAUSESERIOUSBURNSWHENINOPERATIONANDMAYTAKESEVERALMINUTESTO COOL
DOWN).Install thenewtubesfirmly andfully inthesockets,observingthatthetubewill only fitintothesocket
inoneorientation, determinedbytheplastic“keyway” inthecenter ofthebase. Donotuseexcessiveforce.
Replacethetoprods before operating theamplifier.
ThepatentedVACiQsystemwill adjustthebias settingsforthetubesautomatically.Thefront panel indicators
will letyouknowifthere isaproblem with anyoftheKT88 tubes.
Aslight violetglowinthetubeisnotcauseforconcern.
Thesmall tubesare type6SN7GTB. They shouldbematchedsection-to-sectionandtoeachother,andbeclose
to“bogey” values-thisisparticularly important fortheVAC direct-coupledcircuits.
Intheevent thattrouble isencounteredcheckconnectionsand/ortry another tube.Stopiftheproblempersists
andconsultwith yourdealer orVAC.
Forfurther information, refer toTips &Advice:TubesinGeneralandTips &Advice:Output Tubes.

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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.

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IQSystem Indicators
GREEN=WEAKTUBE, REPLACEATYOURCONVENIENCE
RED=DEFECTIVETUBE, REPLACE, DO NOTUSEAGAIN!

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CAREOFCHASSIS
VAC chassisare machinedaluminum forsuperiorelectromagneticperformance. Themainchassisandthe
fasciaare finishedinanacryliclacquer, similartofineautomobile;similarcare mustbetakeninwiping or
cleaning. THEAMPMUSTBESWITCHEDOFF ANDUNPLUGGED, andatnotimemayanycleaning materialbe
allowedtogetintothetubesocketsorjacks.

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TIPS&ADVICESECTION
Tips:Fuses
Youramplifier isdesignedtouse“slowblow”typefuses. Theseare containedinthefusedrawer builtinto
thepower receptacle.
Inthefusedrawer are twofuses. Theonefurthersinistheactivefuse. Theonenearer totheoutsideisa
spare.
Thefuseratingsare labeledonthebackofthepower supply. Becertaintouseonly thefuserating
applicable toyourlocalac supply voltage.
With ahighpower amplifier, there canbeanappreciable surgeofcurrent forafewmilliseconds when
power isswitchedon. Over time, thiscanfatigueafuseandcauseittofail attheinstant thatpower is
applied. Thismaybeconsiderednormal.

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Tips:AWordAbout TubesinGeneral
Itistruethateachbrandoftubesounds different inaparticularhighresolutioncircuit. Thisisbecausenotwo
manufacturersmakeatubetypeinquitethesameway, andthecentraltendenciesoftheperformance
parameterswill differ slightly with eachmaker. Toemphasize thepoint, examinetheplatestructure ofany
two6SN7from different manufacturerswill probably findthatthey maynoteventhesameshapeandsize.
(Becarefulhere, as oftenatubeismadebyafirm other thanindicatedonitslabel. Intheheydayoftubesit
was commontocrossbrandbetweenmajorlabels, suchas GEandRCA. Todaymanylabelsdonot
manufacture their tubesatall, including GoldAeroandRAM.)
Thissonicvariabilitymayatfirstseem aliability, but further thought will revealthatitisanadvantage, justlike
theabilitytoadjustVTAonatonearm. Theowner ofatubeamplifier canselectthosetubeswhichsound
liketherealthing inhis/her specificsystem. Ofcourse, ifthemanufacturer youprefer israre youmaywant to
purchaseafewspare tubesforthefuture.
Howlong shouldtubeslast?Ithas long beenknowninprofessionalcircles(andprobably nowforgotten)
thatatubesuchas the12AX7will displaybetter performancecharacteristicsafter twoyears ofcontinual
operationthanwhenitwas new. Innormaluseitisnotunusualforalowlevel tubetolast5yearsorlonger.
Output tubesare another story, as they are continually providing significant amountsofcurrent. Here the
soundisyourbestguide. Certainly atubeshouldbereplacedwhenitsemissionissignificantly downorits
transconductanceissubstantially out ofspecification. Innormaluse, output tubeswill lastatleast2yearsand
perhaps more than5years.
Itisnormaltosee aslight violetglowinapower tubesuchas aKT88. However, avividvioletindicates
excess current flowthroughthetubeandshouldbeinvestigated.
VAC cantesttubesforconcernedcustomers.

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Tips:Output Tubes
YourVAC Amplifier usestheKT88 kinkless tetrode, with theGoldLion(Russia)versionprovided. Itisstrongly
recommendedthatreplacement tubesbepurchasedonly from VAC. If, however, youwant tocustomize
thesoundtoyourtastes, beaware thatas with interconnectsandspeaker cables, eachtubemanufacturer's
KT88 tends tohaveadistinctsound, as well as itsownreliabilityprofile.
Tips:LowLevel Tubes
TheVoltageAmplifier/PhaseSplitter anddriver tubesintheMaster are the6SN7GTB medium muoctaltwin
triode. Youramplifier isfittedwith thecurrent productionVAC Tested6SN7from Tung Sol(Russia). There are
dozensofversionsofthistubeavailable innewoldstock(NOS) from avarietyofsources. Itwouldbe
impossible tocharacterize them all.
Thematchesamong thefour6SN7GTB are criticaltotheMaster 300'sperformance. Therefore we
recommendthatreplacement tubesbeobtainedinsetsfrom VAC.

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Tips:AudioGrounding
Systemsincorporating single-endedinterconnectcables(“RCAcables”) are pronetoaproblem knownas
“groundlooping”, whichcanresultinextraneoushumsandbuzzesaudible throughtheloudspeaker. Ifthis
occursinyoursystem, youhavetoattempttominimize thegroundloop.
Tominimize thebuzz using thenormalRCAinput jack, there are severalsteps youcantake:
1) Usetheshortestinterconnectspossible.
2) Useinterconnectswith goodshielding properties.
3) Keeptheaudiocablesas closetogether as possible.
4) KeeptheAC cords awayfrom theaudiocables.
5) Try different groundsettingsonyourpreamplifier, ifithas them.
6) Theuseofcheater plugsisnotrecommendedandposesasafetyhazard.
7) Externalgrounding systemsmaydegradethesoundorcausemalfunctions.

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SPECIFICATIONS
TheVAC Master 300 has beendevelopedwith thecriticalearas themajorarbiter ofquality, with both
conventionalanduniquemeasurementsproviding insight andguidanceas necessary. Thelackofemphasis
onmeasurementsisduetothefactthatengineering'sarsenalofequipment andtechniquesdonotoperate
onthepatternrecognitionprincipalsthatcontrolhumanperceptionofsound.
Intheimmortalwords ofDaniel vonRecklinghausen, ifitmeasuresgoodandsounds bad, itisbad. Ifit
measuresbadandsounds good, you'vemeasuredthewrong things.
Forthoseconcernedwith testbenchperformance, thefollowing describestypicalmeasuredperformance
whenoperatedat120 VAC, 60 Hz.
• 160 watt/channel dualmonointo4ohms*;320 watt monointo4ohms*
•Frequencyresponse4Hzto75 kHz
•Power bandwidth 20 Hzto70 kHz
•Single-endedinput viaRCAjack, non-inverting
•Balancedinput viaXLR jack, non-inverting relativetopin2("pin2hot", traditionalEIA/RCA
broadcast/recording standard);ampisfully balancedinthismode
•12 volttrigger
•Illuminatedlogo;maybeswitchedoff
•8xKT88, 4x6SN7GTB
•Detachable power cord, standard15A IEC power receptacle
•Maybefactory configuredforoperationat100, 120, 220, or230/240 voltoperation
*Anextremely stiff power lineisrequiredtoachievetheseoutput powers. Exactoutput power will depend
uponthecharacteristicsoftheindividualtubesfittedandtheir condition**. Avariationof1dB inmaximum
output power mayoccurunder normalcircumstanceswith freshtubes.
** Traditionally, tubesare consideredtobeatendofusefullifewhenpower capabilityisreducedby3
dBW, but thismaynotnecessarily correlatewith subjectivesoundquality. ThegreeniQstatusLEDswill alert
youpriortothispoint.

WARRANTY
Your equipmentiswarranted for aperiod ofthirty(30) daysfromthe dateofpurchase.In addition,ifthe registration
formisreceived byVACalongwithacopyofyour sales receiptfromanauthorized VACdealer withinthisthirtydays,
the warrantywill beextended totwo (2) years (tubes excepted). Thiswarrantyapplies only tounitssoldinthe United
States ofAmericathroughauthorized VACdealers andoperated withinthe United States bythe originalpurchaser.It
covers factoryserviceand,withinthe continentalU.S., standard return shipping. For warrantyinformationoutside of
the U.S.contactthe importer ofVACequipmentfor your country.Unitssoldoutside ofthe U.S.shouldstill be
registered withVAC.Itisthe responsibilityofthe customer and/ordealer toensure suitabilityofthisequipmentfor
anyparticularapplication.
Your questions andcommentsare alwayswelcome.Contact:
ValveAmplificationCompany
2172 10th Street
Sarasota, FL34237
Telephone [phone] Fax[phone]
[e-mail]
_____________________________ Detach and mail totheaddress above assoon aspossible. ____________________________
Master300 RegistrationForm
Name ________________________________________________________________________
Address ________________________________________________________________________
________________________________________________________________________
Telephone _______/_______-_____________ e-mail __________________________________
Dealer name ________________________________City____________________________________
Salesperson ___________________ Purchase date____________SerialNumber ________________
How didyoufirstlearn ofVACproducts? ____________________________________________________
What other brands/modelsdidyouconsider? _________________________________________________
_____________________________________________________________________________________
What made youdecide onthe VAC? _______________________________________________________
_____________________________________________________________________________________
What else wouldyoulikeus toknow? _______________________________________________________
_____________________________________________________________________________________
_____________________________________________________________________________________
Optional:
What magazines do youreadregularly?________________________________________________________
What are your hobbies (besides fillinginwarrantycards)? _______________________________________
What are your favoritetypes ofmusic? ______________________________________________________
_____________________________________________________________________________________
On what format? (CD,LP,DVD,SACD,MP3,etc.) ______________________________________________