BuildYourOwnFuzzFace

GuitarPedalWorkshop

HistoryofDistortedGuitar•  Earlydistor?on:mechanical– Firstcommercialexample:Rocket881951

– Speakerabuse:LinkWrayRumble1958

ATrendSeLngFault•  1961MartyRobbinsDon’tWorry– Blownchannelonconsole– Becomesabigcrossoverhit– Everyoneasksfor“thatsound”

•  MaestroFuzz-Tone•  EngineerGlenSnoddyreverseengineersbadchannel•  GibsonsellsSnoddy’sdesignasMaestroFuzz-Tonein1962

Afewmore…•  1964:TheKinksYouReallyGotMe– DaveDaviescutsslitsinhisspeaker

•  1965:RollingStones(ICan’tGetNo)Sa=sfac=on– KeithRichardsusedMaestroFuzz-Tone

1966:TheArbiterFuzzFace

•  DesignedbyIvorArbiterinLondonasasimpler,lowerbudgetMaestro.

•  UsedGermaniumtransistors•  Notwosoundedthesameun?ltheswitchtosilicontransistors– Temperaturesensi?ve– Widecomponentvariances

•  CurrentsiliconversionsoldbyDunlop

JimiHendrix

TheFuzzFaceCircuit

OriginalGePNPFuzzFace

OriginalPNPFuzzFace

•  Germaniumtransistors– Temperaturesensi?ve– Leaky– “Soaer”sound(somesaymoretube-like)– Widegainvariancewithonemodel

•  Posi?vegroundcircuit– Nopowerinput…baderyonly– NPNGetransistorsrareandexpensive

InputStage

•  Commonemideramplifier–  Baseisinput,collectorout–  Emideriscommontoboth–  C1isaDCblockingcap–  R1setscollectorcurrent–  Inputimpedanceisbetween5-8K

•  Closetoaverageguitarimpedanceofabout10K•  VariesbasedonfuzzpotseLng

– Gainshouldbe49dB,butlimitedbyfeedbacknetworktoabout18dB

OutputStage•  Alsoacommonemideramp

•  Differencefrominputisthefeedbackstage

•  Outputimpedanceisabout500Ohms– Notideal

FeedbackNetwork

•  Desensi?zesgain&makesitconstant

•  Reducesnoise(rejectsunwantedsignals)

•  Affectsinputimpedance

FeedbackNetwork

•  Fuzzatminimum– Largeamountofsignalfedbacktoinput,reducinggainwithafeedbackloop

•  Turnupfuzz– Gainincreasesassignalisshuntedtoground

Whatdoesthesignallooklike?

OursiliconNPNFuzzFace

OursiliconNPNFuzzFace•  Nega?veground•  2N3903transistors– Good“allaround”fuzz–  Cantryothertransistors,andasymmetricalgains

•  SlightlydifferentR2value(330vs.470)•  SlightlydifferentC2value(22uFvs.20uF)•  BoardmountedPots–  Trydifferentvaluesforvolumepottogetdifferenttonalranges(potandC3actasRChigh-passfilter)

•  3PDTtruebypassswitch–  CanaddanLEDifyouwant

Construc?on

Tips•  Wiresshouldbeabout4incheseach•  Tinyourwires•  Mountthepotslast•  Youdon’thavetousethe3PDTswitchun?lyou’rereadytomounteverythinginacase

•  Sincethisisnegground,youcanputaDCjackinyourcaseandpowerfromapedalboard

•  Potsare16mmshaaifyouwanttoaddknobs•  Payaden?ontotransistoroutlineonboardtogetthepinoutcorrect

Whyastereoinputjack?

•  Commoninguitarpedals•  Tipissignal•  Ringandsleeveactasaswitchthatonlyallowsthebaderytodrainwheninputisplugged

•  Connectnegbaderyterminaltoringorsleeve•  Connectremainingterminalonjack(ringorsleeveyoudidn’tuse)tonegterminalonPCB

3PDTTrueBypass

•  Inbypasstheinputandoutputjack?psaredirectlyconnected

•  LED:don’tforgetresistors!

Let’sBuildIt!

FinalThoughts

•  Experimentwiththiscircuit•  hdp://diystompboxes.com•  Severalgoodsuppliersofpedalspecificcomponents:– SmallBearElectronics– BitchesLoveMySwitches– RussianGetransistorsoneBay– Mouser,Digikeyforcommonstuff