Mad Bean Pedals Zygote User manual

1
http://www.madbeanpedals.compresents
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zy yg go ot te e
FX TYPE:FUZZ
PCBartwork m 2010madbeanpedals
Releasedate:12.10.10
REVISED:03.24.11
TheZygoteisan“allinone”fuzz.ItallowsyoutobuildseveraltypesofFuzzFacecircuitsononeboard,with
aslittleastwocontrols,anduptofivecontrolsandtwoswitches.Additionally,youcanbuildeitherpositive
groundPNPornegativegroundNPN.
ThedesignincorporateselementsfromboththeFulltone’69and’70pedalaswellassomeothermods.You
canchoosetobuildeitheroneusingtheinstructionsbelow,ormakeahybridofthetwo.Additionalcontrolswill
addtotheoverallflexibilityofthecircuit,althoughyoumayfindtheTweakknobalittleredundantinsome
settings(ifusingtheB/Mswitch).
Thecontrolsareasfollows
STRAIN:Turningthiscontrolupreducestheamountofoverallfuzz(similartotheBiascontrolonthe’69).This
isdonebyaddinga50kpotinserieswiththeinputofthecircuit.Thismayalsobeusefulindialingdownthe
inputfromahumbucker.
DRAIN:Turningthiscontrolupreducesthevoltagetothecircuit(voltagesag)fromthenominal9vbyusinga
5kpotinserieswiththevoltagesupply.Atmax,itwillreducethevoltagetoaround5.5v.
FUZZ:Theoverallfuzzamount.
TWEAK:WorksinconjunctionwiththeB/Mswitch.InBoostmode,thiscontroladdsoutputsimilartothe
“Contour”knobona’69.InMidsmodeitreducesoutputsimilartothe“Mids”controlonthe’70.
VOL:Overalloutput.
B/M(Boost/Mids):Thiseitherputsa1kpotinserieswitha220RresistorforBoost,ora1kpotinserieswith
a220Randinparallelwithanadditional1kresistorforMids.
FAT:Thisswitchallowsyoutoselecttwodifferentinputcapstocontrolthebassfeedingintothecircuit.The
secondcap(2u2orother)isaddedinparallelwiththefirsttoincreasetheoverallvalue.
Parts
· XiconorSpragueaxialelectrolyticcaps,16v
· Malloryaxialfilmcaps,orsimilar
· Xiconcarbonfilmorcarboncompresistors,¼W
· 16mmAlphapots
· MatchedpairofPNPtransistors(Hfeof~70onQ1and~120onQ2)

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R1 1M Q1,Q2 PNPGE
R2 100k
R3 33k D1 1n4001
R4 220R
R5 1k FAT SPST
R6 220R B/M SPST
R7 1M
T1 25k
C1 10pF
C2 2u2 TWEAK 1kB
C3 68n* VOL 500kA
C4 10pF STRAIN 50kB
C5 22uF FUZZ 1kB
C6 10n** DRAIN 5kB
C7 47uF
TransistorsResistors
Trimmers
Pots
Caps
Diodes
Switch
*68nissuggestedforC3,butlowervalueswillproducemore
dramaticdifferenceswiththe“Fat”switch.Youcouldeasilygo
downto22n.
**C6is100ninthe’70version.

3
PNP–PositiveGround(“69”)

4
NPN–NegativeGround(“70”)

5
2.06”Wx1.89”H(includingborders)
B
Bi ia as si in ng gt th he ez zy yg go ot te e
UsingyourDMM,adjustT1untilyougetapproximately+/4.5v(dependingonwhetherornotyouare
doingpos.orneg.ground)readingonthecollectorofQ2.TheZygoteissetuptoprovideaverywide
rangeforbiasing.NotethatifyouorderPNPtransistorsfromSmallbear,Stevetypicallysendsalongthe
valuestocorrectlybiasthatparticularset.Youcansubinthevaluesheindicates,ifyoulike.Ifyoustill
wanttousethetrimpot,adjustitsothattheresistanceonthepot+the220Rinserieswithitaddsupto
thevalueheindicatesforthecollectorofQ2

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B
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ThereareafewkeydifferencesinbuildingeitherthepositivegroundPNPandnegativeground
NPN.IfbuildingthePNP,youshouldfollowthelayoutdiagramonpg.2.Youwillneedtoconnect
yourbatterysupplysothattheblack(negative)wiregoestothe9vpadontheboard,andthered
wire(positive)goestoground(typicallythisisdonebyconnectingittotheringofaTRSinput
jack).Eventhoughthissetupusesonlyabatterytopowertheeffect,thebatterywillonlybein
usewhenajackispluggedintotheinputjack.Oncethejackisunpluggedthebattery
disconnects.
IfyouhaveneverusedPNPgermaniumtransistorsbefore,IHIGHLYrecommendyoubya
matchedsetfromSmallBear.Thesearealreadytestedforleakageandhavetheappropriate
gainsforQ1andQ2.Steveoffersseveralsetstochoosefrom.
Ifyouwanttouseapowersupply,youcandothefollowing
· UseaPSliketheVoodooLabsPedalPowerwhichcansupplynegativeandpositive
ground.Itcandothisbecauseeach9voutputisisolated.Youcanpurchasea2.1mm
cablewhichhastheneg/poswiresflippedormakeyourown.Ifyouareusingadifferent
supply,makesurethattheoutputsareisolatedoryouwillkillyourboardandpossibly
yourpowersupply.
· Byadedicatedwallwartthathasa2.1mmpositivetipplug.Youcangettheseoff
Mouser,althoughtheyaregenerallyunregulatedandputoutcloserto13v.
· UseaRoadRageboard.Thisisprobablythebestsolutionbecauseyoucansetituplike
anegativegroundpowersupply,buttheRRboardflipsthepowerto9vinternally.This
meansyoucanusethesamePS/plugsasyourregularnegativegroundeffects,provided
youwireeverythingproperly,anditwillcostaboutthesameasbuyingadedicatedwall
wart.Idonotrecommendusingabatteryinthissituation.Seethewiringdiagrambelow
whichillustrateshowtodothisproperly.
ToconvertthislayouttouseNPNandnegativeground,dothefollowing
· Reversethedirectionofallelectrolyticcaps
· ReversethedirectionofD1
· Hook+9vtothe9vpadontheboard.TheGNDpadhookstoground,asyouwouldany
othernegativegroundeffect.
FortheNPNversion,therearemanytypesoftransistorsyoucanuse.Isuggesteitherthe
2SC1815orBC108.Bothofthesewereusedinthe“70”pedalatdifferenttimes.Again,check
SmallBeartoseewhatStevehastooffer.YoucanalsouseNPNgermaniumtransistors,
althoughthesealotmoreexpensive.Plainoldsiliconworksreallywellhere,soIwouldn’tworry
toomuchaboutthat.
NOTE:PNPtransistors,thelittlemetaltabsthatstickoutfromthehousingalmostalwaysindicate
theEmitterofthetransistor.Sometransistorsmayhaveareddot,andthesecanindicate
Collectorinafewcases.Whileyouprobablywillnotdamagethetransistorbyputtingitin
backwards(I’veneverhadthishappen),trytofigureoutwhichiswhichbeforepluggingitin.
Alsonotethatthepinoutof2SC1815ismostlikelydifferentthanthetypicalEBC(typicalisEC
B).Consultadatasheetbeforeusingthistype,asitmayrequireyoutotwisttheleadsaroundto
plugintothecorrectspotsonyourtransistorsockets(yes…usesockets).

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9
REVSION:YOUNEEDTOADDC4ONTHEROADRAGETOMAKETHISWORK!!
ThisproductisintendedforDIYuseonly.Commercialuse,includingthesaleofPCBs,
kitsorpedalsutilizingthisinformation,isstrictlyprohibited.