Grimm Audio MP1 Assembly instructions

Please read this manual before operating the unit!

TPInLB

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Table of Contents
Introduction 4
ImportantSafetyInstructions 5
1.Operation 7
2.Modifyingfactorysettings 8
3.Specifications 12
4.Appendix1,Microphonevoltageslist 13
5.GrimmAudioLimitedWaranty 15

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Introduction
ThankyouforchoosingtheGrimmAudioMP1powersupplyfortubecondensor
microphones.TheMP1iseminentlyfittobeusedwithmoderntubemicrophones,
butithasbeenespeciallydesignedtoreplacethetraditional(usuallypassive)power
suppliesthatorginallycamewiththenowuniqueandverycostlytubemicrophones
fromthefiftiesandsixties.Contrarytowhatmanybelieve,theseoldpowersupplies
canbeimprovedupon,bothwithregardtostability,noiselevelandlastbutnot
leastsoundquality.Andthisisnotjustbecausetheelectrolyticsintheoldsup-
pliestendtodryout,andcarboncompositeresistorshaveshotupinvalueorgone
noisy:evenifthesehavebeenreplacedwithmoderngoodqualitycomponents,the
classicalsupplyisstillnomatchfortheMP1.

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Important Safety Instructions
Grimm Audio gaat er van uit dat u deze Engelstalige tekst volledig begrijpt. Als u hier moeite
mee heeft dient u contact op te nemen met Grimm Audio. Op verzoek sturen wij u een vertaling
toe.
Grimm Audio nimmt an, dass Sie diesen Englischen Text völlig verstehen. Wenn notwendig,
nehmen Sie bitte Kontakt auf mit Grimm Audio. Auf Wünsch wird Ihnen eine Übersetzung zu-
geschickt.
Grimm Audio suppose que le lecteur comprend parfaitement le texte en Anglais ci-dessous. En
cas de doute s.v.p. contacter Grimm Audio. Si necessaire, on pourra vous envoyer une traduc-
tion.
Grimm Audio da por supuesto que el texto en versión Inglesa no ofrece ninguna duda de in-
terpretación y se entiende integramente. Si este no fuese su caso rogamos contacte con Grimm
Audio quien, a petición, se encargaría de enviarle la correspondiente traducción.
Please follow these precautions when using this product:
1.Readtheseinstructions.
2.Keeptheseinstructions.
3.Heedallwarnings.
4.Followallinstructions.
5.Dangerousvoltageisinsidethisapparatus.Openingisonlyallowedbyqualified
servicepersonnel.
6.Verifylinevoltagebeforeuse.
7.Donotdefeatthesafetypurposeofthepolarizedorgrounding-typeplug.A
polarizedplughastwobladeswithonewiderthantheother.Agrounding-typeplug
hastwobladesandathirdgroundingprong.Thewidebladeorthethirdprongare
providedforyoursafety.Whentheprovidedplugdoesnotfitintoyouroutlet,con-
sultanelectricianforreplacementoftheobsoleteoutlet.
8.Protectthepowercordfrombeingwalkedonorpinched,particularlyatplugs,
conveniencereceptables,andthepointwheretheyexitfromtheapparatus.
9.Unplugthisapparatusduringlightningstormsorwhenunusedforlongperiods
oftime.

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10.Donotusethisapparatusnearwater.
11.Donotusethisapparatusoutside.
12.Donotexposetheapparatustodrippingorsplashing.Donotplaceobjects
filledwithliquids(flowervases,drinkcans,coffeecups,etc)ontheapparatus.
13.Cleanonlywithadry,soft,non-fluffycloth.Donotsprayanyliquidcleaneronto
thecabinet,asthismayleadtodangerousshocks.Donotsprayanyliquidcleaner
ontothefaceplate,asthismaydamagethefrontpanel.
14.Installinaccordancewiththemanufacturer’sinstructions.
15.Donotinstallnearanyheatsourcessuchasradiators,heatregisters,stoves,or
otherapparatus(includingamplifiers)thatproduceheat.Avoidexposuretodirect
sunlight.
16.Useonlyattachmentsoraccessoriesspecifiedbythemanufacturer.
17.Useonlywithacart,stand,bracket,ortabledesignedforusewithprofessional
audioormusicequipment.Inanyinstallation,makesurethatinjuryordamagewill
notresultfromcablespullingontheapparatusanditsmounting.Ifacartisused,
useprecautionwhenmovingthecart/apparatuscombinationtoavoidinjuryfrom
tip-over.
18.Thisunitrunsslightlywarmwhenoperatednormally.Operateinanormalventi-
latedarea.Ifthisproductwillbeinstalledinarack,makecertainthereissufficient
airmovementwithintherack.
19.Referallservicingtoqualifiedservicepersonnel.Servicingisrequiredwhenthe
apparatushasbeendamagedinanyway,suchaswhenthepower-supplycordor
plugisdamaged,liquidhasbeenspilledorobjectshavefallenintotheapparatus,
theapparatushasbeenexposedtorainormoisture,doesnotoperatenormally,or
hasbeendropped.
20.WARNING: Toreducetheriskoffireorelectricshock,donotexposethisappa-
ratustorainormoisture.

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1. Operation
Upondelivery,anMP1isfactorysettothetypicalsupplyvoltagesofyourmicro-
phonemodel.ThismicrophonetypeisindicatedatthebackoftheMP1.Ifthe
microphonefeaturesremotecontrolofitspolarpattern,thiscanbecontrolledwith
theoptionalknobonthefrontpaneloftheMP1.Thereisamulti-pinXLRcablecon-
nectorsuppliedwiththeMP1.Youwillneedtoattachthisconnectortoyourown
microphonecable(orletyourdealerdothat).Forwiringdata,refertothe‘specifica-
tions’chapterofthismanual.Pleasemakesureyoudoublecheckifyousoldered
therightwiretotherightXLRpin,yourmicrophonecangetdamagedifyoufailto
doso!
Ingeneral,weadvisetofirstconnectallcablesandthenturnontheMP1.Bydoing
sooneavoidspotentialdamagetotheconnectors’plating.Itisgoodtoknowthat
duetocharacteristicsofour‘shuntregulator’circuitrythepeakcurrentislimited,
whichwilllengthenyourmicrophones’tubelife.
TheMP1isdeliveredwithadetachablefoot.Thiscanberemovedbygentlytwist-
ingthefootcounterclockwise.Withoutfeet,twoMP1’scanbeconnectedtogether
toformastereo1U19”unit.AnMP1generatessomeheat.Whenusingastereoset
ofMP1’sina19”rack,itisadvisedtokeeponefreerackspacebelowandaboveto
provideoptimalcooling.
Technology
TheMP1featuresaspeciallydesigneddiscreteshunthigh-voltageregulatorfed
fromacurrentsourcetomaximisesuppressionfrommainsinducedanomalies.It
alsooffersverylownoise(typ.-96dBVor16uV20-20.000Hzunweighted).More
importantly,thisshuntsupplysoundsmorenaturalthanthemorecommonlyused
modernseriesregulators,duetotheabsenseofelectrolyticcapacitorsattheout-
put.
Itwouldhavebeenquickandeasytorelyonindustrystandardvoltageregulators
fortheheatersupply.However,inquiteafewclassicalmicstheheatervoltageis
alsousedtobiasthegridoftheamplifyingtubeinthemicrophone,implicating
anopengatewayfromheatersupplytothesensitiveinputofthemic’samplifying
stage.Wethereforechosetodesignacleanandultralownoisediscretevoltage
regulatorfortheheatersupplyaswell.Itfeaturesaverylowdrifttoensurethe
heatervoltagealwaysremainswithinspecs.
Boththehigh-voltageandtheheatersupplieshaveanextra‘crowbar’protection
circuitthatwillswitchonincaseoneofthesuppliesbreaksdown.Thisisanextra
lineofdefencetoprotectthevaluabletubeinyourmicrophone.

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2. Modifiying factory settings
YourMP1isfactorysettothesupplyvoltagesofthemicrophonespecifiedinyour
order.IncaseyouneedtoadjusttheMP1tothesupplyvoltagesofadifferent
microphone,therearevariousinternalsettingstofacilitatethis.Wehavetowarn
youhoweverthatselectingawrongvoltagewillveryprobablyleadtodamageof
the(sometimesveryexpensive)tube.Sounlessyouareanexperiencedengineeror
likelivingdangerously,wedonotadvisetochangethefactoryvoltagesettings!In
anycaseGrimmAudiocannotacceptliabilityfordamagetomicrophones.Forthose
peoplethatstillwanttochangetheinternalsettings,pleasereadthefollowingin-
structionscarefully.
Inappendix1alistcanbefoundofknownmicrophonetypeswiththeirfactory
advicedsupplyvoltages.Shouldyourmicrophonenotbelisted,pleaseconsultthe
originalmanufacturer.PleasealsocheckthisMP1manualonGrimmAudio’sweb-
site,itmighthavehadanupdateofthemicrophonelist.Threepresethighvolt-
ageareavailablefromtheMP1:120,145and210V.Thesearesetinternallyusing
jumpersandnotbyexternalcontrols,toavoidcostlymistakeswhileamicrophone
isconnected.Atrimpotallowssome(+/-8%)adjustmentofthesevoltages.TheHT
supplyisinherentlyshort-circuitproofasitisashuntsupply.Asanextrasafetya
“crowbarcircuit”willshutdownthecurrentsourceincasetheoutputvoltageex-
ceedsthenominalvaluebymorethan12%duetomalfunctioning.However,Grimm
Audiocannotacceptliabilityincaseofdamagetomicrophonesshouldeventhe
protectioncircuitfail.
Fortheheatervoltagetwopresetvaluesareavailable:6.0and3.9V.Thesevalues
arechoseninconjunctiontowhatisprescribedformostclassicalmicrophones.
Theytooaresetbyinternaljumpers.Athirdjumperpositionenablesatrimpotand
allowstheheatervoltagetobesetatanydesiredvaluebetween3.6and7.0V.In
addition,theoutputpolaritycanbereversedassomemicsrequirenegativeheater
voltage.Noiseisverylow:typ.<-120dBV(<1uV),animprovementofatleast
30dBoverindustrystandardvoltageregulators.Theoutputisshort-circuitproof,
thecurrentlimitsat0.5A.Asanextrasafetyacrowbarcircuithasbeenaddedto
protectthemicagainstunforseenfailuresshouldtheheatervoltageexceedthe
nominalvalueby10%(incaseofthevariableheatervoltagesettingasecondtrim-
potallowstheusertosetanappropriatethreshold).However,GrimmAudiocannot
acceptliabilityincaseofdamagetomicrophonesshouldeventheprotectioncircuit
fail.
Check the voltages output of your MP1
HowtheMP1isset,caneasilybemeasuredfromtheoutside:abluetestsocket
allowsthemeasurementoftheheatervoltage,aredsocketgivesaccestotheHT
dividedbij10(forsafetyreasons);ablacksocketpovidesagroundreference.These

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are2mmsocketssomultimetertestpinsfitdirectly.Pleasecheckthesevoltages
beforeconnectingthemicrophone.Markthattheheatervoltagewillmeasureap-
proximately0.1Vhigheratthissocketthanindicatedabove.Thisisonpurposeto
compensateforcablevoltageloss.
Tominimizetheriskofaccidentaldamagetomicrophonesequipedwith3.9V
tubesbypluggingtheseintoa6VMP1supply,GrimmAudiohasdecidedtodeliver
its3.9VversionwithanXLR6socketandthe6VversionwithanXLR7socket.The
factorysetvoltageisindicatedontheback.Ofcourse,ifauserchoosestochange
theinternalvoltagesettings,theXLRpincountnolongergivestherightindication!
Thisisoneofthereasonswedisencouragethechangeoffactorysettings.
TheMP1featuresarotaryswitchtoallowachoiceofpolarpatternonmicrophones
equippedwithsucharemotecontrolinput.ThecorrespondingpinontheXLR6or
XLR7microphoneconnectorcanbevariedbetween0Vandthe120or145HTvolt-
agesorbetween0VandHT+40V,dependingontheinternaljumpersetting.For
example:ifHTissetto120V,itcanbevariedbetween0and120Vor0and160
V.(The40Vover-voltageisnotavailableatthe210Vsettingastherearenomicro-
phonesthatrequirethat).
Changing the internal settings
OpeninguptheMP1andchangingitsinternalpresetsortrimmingsisbestlefttoa
trainedtechnician.Whenswitchedon,therearepotentiallydangerousvoltagesas
highas300Vinside.GrimmAudiocannotacceptanyresponsabilityfordamages
toeitherpersons,ortheMP1itself,ortoanymicrophoneconnectedbyunwittingly
chosenvoltagesorpolarities.
BeforeopeningtheMP1,switchoffthemainspowerandremovethepowercord.
Alsoremoveanyaudiocables.Wait30secondstoallowtheHTontheelectrolyt-
icstoreachasafevalue(<40V).Removethe2screwsfromonesideofthecover
aswellasthe2screwoppositeofthemontheotherside.Carefullyslidethecover
backwards,awayfromthewoodenfront.Theelectronicswillthenbecomevisible.
Anoverviewofsettingandtrimpotsofthepcbisgiveninfig.1onthenextpage.
High Tension (HT) settings
Jumpers7to10settheHT(highvoltagetothemicrophone)to120,145or210V.
Thejunperontheleft-handrowsetsthevoltage,thejumperontheright-handrow
setsthecrowbarprotection.Theyshouldalwaysbechangedinpairs:bothinthe
120Vposition,orbothinthe145Vposition,orbothinthe210Vposition.Failure
todosomayshuttheMP1down,orincriminatecorrectprotectionagainstover-
voltage.

10
Inaddition,J4mustbesettotheupperpositionwhen210VHTischosen.(Failure
todosowillstilloutput210Vbuttheshuntsupplywillnotbeabletofunctionop-
timally,possiblydegradingsoundquality).
ChoosethelowerpositionforJ4ifyouwantawiderrangeof0-160Vavailablefor
polarpatterncontrolinthe120VHTcase.Thiswillalsoworkforthe145VHT,
resultingina0-184Vvariablevoltage,althoughnomicrophoneisknowntousthat
needsthissetting.
ThetrimpotallowssomeadjustmentoftheHToutputvoltage.Thecrowbarprotec-
tionthresholdsremainfixed.Trimmingtheoutputvoltageclosetothetreshold
valuesisnotrecommendedasthisincreasestheriskofill-triggeredshutdown.
ToresetacrowbaractionitsufficestoswitchoftheMP1,waitafewsecondsand
switchonagain.
Heater Voltage Settings
Thejumperssettingtheheatervoltagearelocatedtotherightinfig.1.
FirsttakealookatthetwojumpersJ2&J3intheright-handtopcorner.Theyset
theheatervoltage’soutputpolarity:||ispositive.Changetheirorientationby90
degrees:==isnegative.Checkwiththered(plus)probeofthemultimeterinserted
intothebluetestsocket(nomicconnectedyet!).
 Fig1.VoltageadjustmentjumpersinsidetheMP1.