Eurorack Schematics

The following Eurorack schematics represent our personal (non-professional, non-expert) explorations into synth DIY. Many of these designs borrow heavily on the work of others (credited where due). Most are based on common analog and solid state components–no coding necessary. None of these designs were reviewed by anyone with the slightest hint of an electrical engineering degree.

Below you’ll find oscillators of varying degrees of musical usefulness; effects that accentuate or destroy your sound; utilities that expand your routing and wave-shaping options. As with any schematic found on the internet, exercise caution when building. Test the build before plugging it into your case. If you find mistakes in the schematic, or you have recommendations for improving the design, feel free to contact us and let us know.

Browse by Module Type

1V/Oct (1) 555 (2) Aggro (5) Clock (1) Distortion (2) Effect (10) Filter (1) FM (4) LFO (3) Modulation (7) Oscillator (4) Reverb (1) Signal routing (2) Utility (2)

Thunderdome

Two sounds enter. One sound leaves. That’s the basic concept of this module. Built around a DG419 analog switch, the Thunderdome uses an internal square-wave oscillator to switch between two input signals at audio rate, producing sounds ranging from atonal and metallic, to rhythmic and musical.

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Ambivalence Drive

Make up your mind, already. Ambivalence Drive is here to help. Ambivalence Drive uses control voltage to switch between two input signals, routing to a single output. Use the toggle to choose between a constant 5v reference or a variable voltage set with the Voltage Range knob.

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Destructo Disc

Named after the Mighty Krillin’s unstoppable sawblade of doom, the Destructo Disc is a sawtooth oscillator gone mad. Two waveshapers and an array of 555-based saw-width modulators transform a basic sawtooth waveform into a vast array of aggro sounds.

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Wocka

This module is a little fuzzy. Bears are fuzzy. My favorite bear is Fozzie the Bear. Fozzie sounds like fuzzy. Fozzie likes to tell bad jokes and celebrate his bad jokes with his trademark saying “Wocka wocka wocka”.

And that’s why this module is call Wocka.

Borrowing heavily from a circuit attributed to the mysterious “R. Lockhart Jr.”, this diode/transistor-based fuzz distortion is a wave destroyer.

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Inferno

How far down does the inferno go? Well… Ours isn’t as deep as Dante’s, but seven levels is still pretty deep.

Inferno is a frequency divider that creates square wave outputs at 1, 2, 3, 4, 5, 6 and 7 octaves below the original input signal.

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Sprung!

Sprung! is the result of several failed attempts to track down a decent schematic to drive a Mod™ 8EB2C1B spring reverb tank. This design incorporates overdrive and feedback circuits, to provide a very basic module to drive this specific tank.

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Adverb

Adverb is a stereo reverb with individual control over depth and mix for each stereo channel. Mono or stereo input (mono input normalizes to both channels).

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Lil’ Verb

Lil’ Verb is a mono reverb module with dual outputs, and feedback control over both outputs.

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Wah Baby

Based on a classic wah pedal design, fitted for Eurorack. Includes CV control over the effect switchable between an external CV source or an internal LFO.

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SSSCM

The next time someone tells you math isn’t magical, introduce them to the Single Sideband-Suppressing Carrier Modulator–or SSSCM for short.

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Forked

Conceptually based on the DivKid/Instruo Ochd (but with four LFOs instead of eight–get it?), Forked is a free-roaming modulation workhorse, with triangle and square outputs. One rate knob sets the general speed for each LFO, all of which run independently and asynchronously from one another. 

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Steptone & Son

Steptone & Son is based on the Stepped-tone Generator designed by Forrest M. Mims III. Also known as the Atari Punk Console, this is a classic DIY noise-maker comprised of two 555 timer-based square oscillators. Our version adds some new features to make it more flexible for use in modular systems.

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4Square

4Square is a nasty little box of fun built around a 4093 quad NAND Schmitt Trigger circuit. Four independent square-wave oscillators pinging off of one another to create complex sounds–metallic FM sounds, stepped square waves, classic video game bleeps and bloops.

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faceplate design for the D/MOD DIY Eurorack module

D/MOD

D/MOD is a vicious modulation effect that uses a CD4046 to generate frequencies to modulate an input signal. Effect knob controls how much of the output signal is fed back to the input stage of the circuit. Bias knob and CV input control the reference voltage for the CD4046, creating really harsh, distorted modulation effects.

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Faceplate of St. Filth DIY Eurorack module

St. Filth

Borrowed almost entirely from the Synthrotek DIRT filter, St. Filth ups the ante on lack of hygiene and social graces. A few experimental tweaks have been made to the original design, including: a mode switch to alternate between AC-coupled and DC-coupled inputs; amplified input signal, CV over the resonance; buffered output; LED to monitor filthiness.

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Voltage Kaiju

Voltage Kaiju is an enormous multi-use utility cobbled together from bits and pieces of ideas and schematics available online. There are two distinct stages: an LFO with triangle or square output, and dual voltage offset/scalers.

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Rock Throbster

Rock Throbster is, primarily, a tremolo effect. But it’s also a lot more. Internal LFO, with selectable square and triangle waveforms, provides the backbone for classic tremolo sounds. Push the LFO up into the audio range to achieve audio-rate AM effects. But, the real fun comes from the resonant distortion…

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