here - DorkbotPDX

BuildYourOwnFuzzFace
GuitarPedalWorkshop
HistoryofDistortedGuitar
•  Earlydistor?on:mechanical
–  Firstcommercialexample:Rocket881951
–  Speakerabuse:LinkWrayRumble1958
ATrendSeLngFault
•  1961MartyRobbinsDon’tWorry
–  Blownchannelonconsole
–  Becomesabigcrossoverhit
–  Everyoneasksfor“thatsound”
•  MaestroFuzz-Tone
•  EngineerGlenSnoddyreverseengineersbadchannel
•  GibsonsellsSnoddy’sdesignasMaestroFuzz-Tonein
1962
Afewmore…
•  1964:TheKinksYouReallyGotMe
–  DaveDaviescutsslitsinhisspeaker
•  1965:RollingStones(ICan’tGetNo)
Sa=sfac=on
–  KeithRichardsusedMaestroFuzz-Tone
1966:TheArbiterFuzzFace
•  DesignedbyIvorArbiterinLondonasa
simpler,lowerbudgetMaestro.
•  UsedGermaniumtransistors
•  Notwosoundedthesameun?ltheswitchto
silicontransistors
–  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,butlimitedbyfeedbacknetwork
toabout18dB
OutputStage
•  Alsoacommonemider
amp
•  Differencefrominputis
thefeedbackstage
•  Outputimpedanceis
about500Ohms
–  Notideal
FeedbackNetwork
•  Desensi?zesgain&makesit
constant
•  Reducesnoise(rejects
unwantedsignals)
•  Affectsinputimpedance
FeedbackNetwork
•  Fuzzatminimum
–  Largeamountofsignalfedbacktoinput,reducing
gainwithafeedbackloop
•  Turnupfuzz
–  Gainincreasesassignalisshuntedtoground
Whatdoesthesignallooklike?
OursiliconNPNFuzzFace
OursiliconNPNFuzzFace
•  Nega?veground
•  2N3903transistors
–  Good“allaround”fuzz
–  Cantryothertransistors,andasymmetricalgains
•  SlightlydifferentR2value(330vs.470)
•  SlightlydifferentC2value(22uFvs.20uF)
•  BoardmountedPots
–  Trydifferentvaluesforvolumepottogetdifferent
tonalranges(potandC3actasRChigh-passfilter)
•  3PDTtruebypassswitch
–  CanaddanLEDifyouwant
Construc?on
Tips
Wiresshouldbeabout4incheseach
Tinyourwires
Mountthepotslast
Youdon’thavetousethe3PDTswitchun?l
you’rereadytomounteverythinginacase
•  Sincethisisnegground,youcanputaDCjackin
yourcaseandpowerfromapedalboard
•  Potsare16mmshaaifyouwanttoaddknobs
•  Payaden?ontotransistoroutlineonboardto
getthepinoutcorrect
• 
• 
• 
• 
Whyastereoinputjack?
•  Commoninguitarpedals
•  Tipissignal
•  Ringandsleeveactasaswitchthatonly
allowsthebaderytodrainwheninputis
plugged
•  Connectnegbaderyterminaltoringorsleeve
•  Connectremainingterminalonjack(ringor
sleeveyoudidn’tuse)tonegterminalonPCB
3PDTTrueBypass
•  Inbypasstheinputandoutputjack?psare
directlyconnected
•  LED:don’tforgetresistors!
Let’sBuildIt!
FinalThoughts
•  Experimentwiththiscircuit
•  hdp://diystompboxes.com
•  Severalgoodsuppliersofpedalspecific
components:
–  SmallBearElectronics
–  BitchesLoveMySwitches
–  RussianGetransistorsoneBay
–  Mouser,Digikeyforcommonstuff