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COMPRESSIONBLENDVOLUME

125B · 3 knobs

Aion FX

OceanidOptical Compressor

Based on the Cornish OC-1

Category
Compressor
Controls
Compression · Blend · Volume
Difficulty
Intermediate
Price
$12.50in stock

From the vendor

Pete Cornish's original optical compressor design features a clean blend and a complex side-chain for envelope detection along with his legendary input buffer.

The Oceanid Optical Compressor is adapted from the Pete Cornish OC-1 Optical Compressor, originally released in 2014 and traced by Aion FX in 2019.

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 and Brian May. The OC-1 in particular names Paul McCartney as an owner.

The OC-1 is an original circuit, and it bears the marks of careful design, without any clear comparisons to anything else out there. It uses the LDR-to-ground method of volume reduction as seen in early optical limiter circuits like the LA2A, but the methods of generating the LED control voltage from the envelope are unique, and the clean-blend circuit is a little more complex than what you normally see.

The Oceanid is a faithful reproduction of the OC-1 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 8. Open the build document. No KiCad fragment has been drawn for this circuit yet.

Parts list 95 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
R101M1MMetal film resistor, 1/4W
R1110k10kMetal film resistor, 1/4W
R1210k10kMetal film resistor, 1/4W
R1310k10kMetal film resistor, 1/4W
R141M1MMetal film resistor, 1/4W
R158k28.2kMetal film resistor, 1/4W
R1691R91Metal film resistor, 1/4W
R1710k10kMetal film resistor, 1/4W
R1810k10kMetal film resistor, 1/4W
R1951k51kMetal film resistor, 1/4W
R2018k18kMetal film resistor, 1/4W
R2110k10kMetal film resistor, 1/4W
R2291R91Metal film resistor, 1/4W
R231M1MMetal film resistor, 1/4W
R242k22.2kMetal film resistor, 1/4W
R2530k30kMetal film resistor, 1/4W
R2691k91kMetal film resistor, 1/4W
R2710k10kMetal film resistor, 1/4W
R2891k91kMetal film resistor, 1/4W
R29100k100kMetal film resistor, 1/4W
R30100R100Metal film resistor, 1/4W
R311k1kMetal film resistor, 1/4W
R3215k15kMetal film resistor, 1/4W
R3310k10kMetal film resistor, 1/4W
R34100k100kMetal film resistor, 1/4W
R3547k47kMetal film resistor, 1/4W
R363k33.3kMetal film resistor, 1/4W
R371k1kMetal film resistor, 1/4W
R3891R91Metal film resistor, 1/4W
R3951k51kMetal film resistor, 1/4W
R40100R100Metal film resistor, 1/4W
R418k28.2kMetal film resistor, 1/4W
R4210k10kMetal film resistor, 1/4W
R43100R100Metal film resistor, 1/4W
R44100R100Metal film resistor, 1/4W
LEDR10k10kMetal film resistor, 1/4WLED current-limiting resistor. Adjust value to change LED brightness.
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
C62.2uF2.2uElectrolytic capacitor, 4mm
C7470pF470pMLCC capacitor, NP0/C0G
C822uF22uElectrolytic capacitor, 5mm
C9100n100nFilm capacitor, 7.2 x 2.5mm
C104.7uF4.7uElectrolytic capacitor, 4mm
C11220pF220pMLCC capacitor, NP0/C0G
C12470n470nFilm capacitor, 7.2 x 3mm
C13220pF220pMLCC capacitor, NP0/C0G
C14470n470nFilm capacitor, 7.2 x 3mm
C1522uF22uElectrolytic capacitor, 5mm
C16100n100nFilm capacitor, 7.2 x 2.5mm
C172.2uF2.2uElectrolytic capacitor, 4mm
C18150pF150pMLCC capacitor, NP0/C0G
C1922uF22uElectrolytic capacitor, 5mm
C204.7uF4.7uElectrolytic capacitor, 4mm
C21100n100nMLCC capacitor, X7RPower supply filter capacitor.
C22100uF100uElectrolytic capacitor, 6.3mmPower supply filter capacitor.
C2347uF47uElectrolytic capacitor, 5mmVoltage reference filter capacitor.
C24220uF220uElectrolytic capacitor, 6.3mmPower supply filter capacitor.
C25220n220nMLCC capacitor, X7RPower supply filter capacitor.
C26220uF220uElectrolytic capacitor, 6.3mmPower supply filter capacitor.
Diodes 4
D11N58171N5817Schottky diode, DO-41
D21N9141N914Fast-switching diode, DO-35
D31N9141N914Fast-switching diode, DO-35
Z1LM4040-5.0LM4040-5.0Voltage reference, TO-92Full part number is LM4040CIZ-5.0. See build notes for more info.
Transistors 2
Q1BC549CBC549CBJT transistor, NPN, TO-92Can use 2N5088 (rotate 180 degrees).
Q2BC550CBC550CBJT transistor, NPN, TO-92Can use 2N5088 (rotate 180 degrees).
ICs 4
IC1TL072TL072Operational amplifier, DIP8
IC2TL072TL072Operational amplifier, DIP8
IC3LM358NLM358NOperational amplifier, DIP8
IC4LM358NLM358NOperational amplifier, DIP8
Opto 1
VACT.NSL-32NSL-32Vactrol/opto-isolator, NSL-32Make sure this is installed correctly. See build notes.
Potentiometers 3
COMP.10kCC10k16mm right-angle PCB mount pot
BLEND25kBB25k16mm right-angle PCB mount pot
VOL.100kAA100k16mm right-angle PCB mount pot
Trimmers 1
BIAS20k20kTrimmer, 10%, 1/4”Bourns 3362P or equivalent
Switches 1
FSW3PDT3PDTStomp switch, 3PDTAvailable from Aion FX.
Jacks & sockets 7
IC1-SDIP-8 socketDIP-8 SOCKETIC socket, DIP-8
IC2-SDIP-8 socketDIP-8 SOCKETIC socket, DIP-8
IC3-SDIP-8 socketDIP-8 SOCKETIC socket, DIP-8
IC4-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 mountLumberg NEB/J 21 C or equivalent.
Hardware 1
ENC125B125BEnclosure, die-cast aluminumCan also use a Hammond 1590N1.