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GAINBASSTREBLEVOLUME

125B · 4 knobs

Aion FX

SigmaVintage Drive

Based on the Cornish ST-2

Category
Overdrive· Boost / Drive
Controls
Gain · Bass · Treble · Volume
Difficulty
Intermediate
Price
$12.50in stock

From the vendor

An adaptation of the Colorsound Overdriver, originally designed for David Gilmour as part of his custom integrated effect board.

The Sigma Vintage Drive is adapted from the Pete Cornish ST-2, traced by Aion FX in 2020.

Cornish pedals are best known for being extremely expensive. There are two reasons for this. First, the build quality and reliability is unmatched. Second, the mysterious nature of them, partially due to the fact that the circuit is obscured and partially because of the A-list of clients such as David Gilmour, Brian May and Pete Townshend.

Pete Cornish originally designed the ST-2 for David Gilmour as part of his custom integrated pedalboard. It was later released as a standalone product in 2007. Other owners include Keith Urban and John Shanks. Lou Reed had one as well.

The ST-2 had long been suspected to be based on the Colorsound Overdriver, given the description, control layout and the first customer (Gilmour is a known enthusiast of the Overdriver). However, it’s never been confirmed.

After tracing it, it’s clear that the ST-2 is definitely based on the Overdriver, but with a few twists. First, it’s double-buffered, the same as the G-2. Second, several values have been changed throughout the circuit and so the overall voicing will be different—it’s not a direct clone. Lastly, an op-amp gain stage has been added to the end to increase the available volume. The original Overdriver could get loud, but the ST-2 can get even louder!

The Sigma is a faithful reproduction of the ST-2 circuit, but with one major addition: an internal slide switch allowing the pedal to be used in true-bypass mode instead of buffered bypass. As with the Klon KTR, the buffered mode is “almost always better”, but with this feature, you can determine for yourself.

Schematic

The schematic is in the vendor's build document, page 7. Open the build document. No KiCad fragment has been drawn for this circuit yet.

Parts list 87 rows

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RefValueNormalizedTypeNotes
Resistors 45
R110M10MMetal film resistor, 1/4W
R21k1kMetal film resistor, 1/4W
R3120k120kMetal film resistor, 1/4W
R4120k120kMetal film resistor, 1/4W
R5200k200kMetal film resistor, 1/4W
R67k57.5kMetal film resistor, 1/4W
R710k10kMetal film resistor, 1/4W
R851R51Metal film resistor, 1/4W
R91M1MMetal film resistor, 1/4W
R101k1kMetal film resistor, 1/4W
R11120k120kMetal film resistor, 1/4W
R12120k120kMetal film resistor, 1/4W
R13200k200kMetal film resistor, 1/4W
R147k57.5kMetal film resistor, 1/4W
R155k65.6kMetal film resistor, 1/4W
R16120k120kMetal film resistor, 1/4W
R1718k18kMetal film resistor, 1/4W
R18150k150kMetal film resistor, 1/4W
R191k1kMetal film resistor, 1/4W
R20680R680Metal film resistor, 1/4W
R211k81.8kMetal film resistor, 1/4W
R2212k12kMetal film resistor, 1/4W
R234k74.7kMetal film resistor, 1/4W
R244k74.7kMetal film resistor, 1/4W
R255k15.1kMetal film resistor, 1/4W
R2639k39kMetal film resistor, 1/4W
R275k65.6kMetal film resistor, 1/4W
R28150k150kMetal film resistor, 1/4W
R2933k33kMetal film resistor, 1/4W
R301k81.8kMetal film resistor, 1/4W
R31330R330Metal film resistor, 1/4W
R3210k10kMetal film resistor, 1/4W
R335k15.1kMetal film resistor, 1/4W
R3410R10Metal film resistor, 1/4W
R3515k15kMetal film resistor, 1/4W
R3610k10kMetal film resistor, 1/4W
R3791R91Metal film resistor, 1/4W
R3891R91Metal film resistor, 1/4W
R3951k51kMetal film resistor, 1/4W
R40100R100Metal film resistor, 1/4W
R4151R51Metal film resistor, 1/4W
R4251R51Metal film resistor, 1/4W
R4310k10kMetal film resistor, 1/4W
R4410k10kMetal film resistor, 1/4W
LEDR4k74.7kMetal film resistor, 1/4W
Capacitors 26
C1100n100nFilm capacitor, 7.2 x 2.5mm
C24.7uF4.7uElectrolytic capacitor, 4mm
C31n1nFilm capacitor, 7.2 x 2.5mm
C422uF22uElectrolytic capacitor, 5mm
C5100n100nFilm capacitor, 7.2 x 2.5mm
C61n1nFilm capacitor, 7.2 x 2.5mm
C74.7uF4.7uElectrolytic capacitor, 4mm
C8220n220nFilm capacitor, 7.2 x 2.5mm
C922uF22uElectrolytic capacitor, 5mm
C10220pF220pMLCC capacitor, NP0/C0G
C1122uF22uElectrolytic capacitor, 5mm
C1210uF10uElectrolytic capacitor, 5mm
C13100n100nFilm capacitor, 7.2 x 2.5mm
C1410n10nFilm capacitor, 7.2 x 2.5mm
C1510n10nFilm capacitor, 7.2 x 2.5mm
C16100n100nFilm capacitor, 7.2 x 2.5mm
C1710uF10uElectrolytic capacitor, 5mm
C18100uF100uElectrolytic capacitor, 6.3mm
C194.7uF4.7uElectrolytic capacitor, 4mm
C20220pF220pMLCC capacitor, NP0/C0G
C2122uF22uElectrolytic capacitor, 5mm
C22220uF220uElectrolytic capacitor, 6.3mmPower supply filter capacitor.
C23100uF100uElectrolytic capacitor, 6.3mmPower supply filter capacitor.
C24220uF220uElectrolytic capacitor, 6.3mmPower supply filter capacitor.
C2522uF22uElectrolytic capacitor, 5mmReference voltage filter capacitor.
C26100n100nMLCC capacitor, X7RPower supply filter capacitor.
Diodes 1
D11N58171N5817Schottky diode, DO-41
Transistors 5
Q1BC549CBC549CBJT transistor, NPN, TO-92
Q2BC549CBC549CBJT transistor, NPN, TO-92
Q3BC549CBC549CBJT transistor, NPN, TO-92
Q4BC549CBC549CBJT transistor, NPN, TO-92
Q5BC549CBC549CBJT transistor, NPN, TO-92
ICs 1
IC1TL071TL071Operational amplifier, DIP8
Potentiometers 3
DRIVE50kCC50k16mm right-angle PCB mount pot
BASS100kBB100k16mm right-angle PCB mount pot
VOL.10kAA10k16mm right-angle PCB mount pot
Switches 1
FSW3PDT3PDTStomp switch, 3PDT
Jacks & sockets 4
IC1-SDIP-8 socketDIP-8 SOCKETIC socket, DIP-8
IN1/4" mono1/4" MONO1/4" phone jack, closed frameSwitchcraft 111X or equivalent.
OUT1/4" mono1/4" MONO1/4" phone jack, closed frameSwitchcraft 111X or equivalent.
DC2.1mm2.1MMDC jack, 2.1mm panel mountMouser 163-4302-E or equivalent.
Hardware 1
ENC125B125BEnclosure, die-cast aluminumCan also use a Hammond 1590N1.