Lil' Erebus is an inexpensive and great sounding Eurorack synth voice incl. Midi and Echo effect. It's not the world's most temperature stabile VCO but it has a lots of potential and a brilliant price/performance ratio. It's a no-brainer. The DIY kit is complex but no special parts or techniques needed, basically very easy.

• Incl. Midi via 3,5mm connector (adapter included)
  
• Echo effect on board
• VCF with Resonance
• 2 OSC Waveforms - Saw & Pulse
• LFO - Triangle & Square
• 16 Patch Points
• Width: 42HP

Building instructions can be found here. For calibration watch this video.  DIY level: medium.

Micrón is a full synthesizer voice in 8 HP including VCO, VCF, EG and Overdrive! This thing is insane!

VCO: 7 octaves, Hard Sync, Suboctave, Saw/PWM, FM modulation, Temperature compensated.

VCF with autoscillation, and cutoff cv attenuator.

E.G.: Fast fixed attack, release 80ms to 1s, connected by default to the attenuator of the Cutoff CV and VCA. And it’s automatically disconnected when an envelope or modulation is connected to the VCA jack or the filter CV.

Width: 8 HP, Current Draw: + 51mA / – 41mA  (+/-12v)

Here is a demo video. Building instructions and calibration video can be found here.

DIY level: medium.

The OBF is a simple yet useful LFO capable of producing a variety of waveforms with a frequency range of 40 Hz to over 40 seconds per cycle. Using the "Skew" control, Saw, Triangle, Ramp, and PWM are easily attainable, while a pulse set to the OBF's sync input resets the LFO to -5V, the low point in its cycle. It's a full DIY kit.
Width: 4 HP, Current Draw: +13mA / – 13mA   (+/- 12v)

Building instructions, demo and calibration video can be found here.

DIY level: easy.

Pro Out is a line output module with VUmeter and balanced outs

Converts syntheziser level signals to balanced and professional line level (+4dBu, 6.3mm), and also at the consumer line level(-10dBv, stereo 3,5mm) in which it’s possible to connect your headphones.

2 Chanels with VUmeter per channel.
When the led marked as 0dB turns on, all line outputs are at their standard level.
The Vumeter can operate in bar or dot mode. Dot mode allows much lower consumption.
Width: 6HP, depth: 40mm, power consumption: BAR: 140mA with all leds on / DOT : 28mA

Building instructions, demo and calibration video can be found here and here is a demo video.

DIY level: medium

Dual Velocity Voltage Controlled Amplifier

The VVCA is an analog dual linear VCA can be used for audio and CV signals. The VVCA features two individual VCA’s. Each VCA behaves just like any other normal VCA when there is no cable connected to the velocity input. The velocity input offers velocity control over the CV input level, which means: The output level can be controlled by CV and Velocity.
Width: 4HP, power consumption: +12V (15mA), -12V (15mA), 5V (10mA)

Building instructions can be found here. DIY kit includes all parts.

DIY level: easy

Full DIY kit for a seven-band Eurorack Graphic EQ inspired by the classic Boss GE-7 pedal

A compact and high quality seven band graphic equaliser for Eurorack. Inspired by the Boss GE-7 pedal, but with pristine low-noise circuitry and a much broader frequency range. Push the faders up and to the left to boost, down and to the right to cut. Works great in feedback loops or as a tone control for individual voices. The kit comes with silver alu panel.

Building instructions can be found here. DIY level: super easy.

Chord Organ is a new firmware for the Music Thing Modular Radio Music module. It gives the module a completely different function. Instead of playing samples from the SD card, it synthesises chords. This is the full Chord Organ kit with dedicated Chord Organ silver alu panel and black button.

Note: you need to purchase a MicroSD card and a Micro-B USB Cable elsewhere to set up this module. The Micro-B cables are the smallest type shipped with Kindles and many Android phones. You also need a card reader to write files to the SD card, many laptops and desktops already have them built in now. The very cheap $2 MicroSD cards are not worth the trouble they will cause you, buy genuine SanDisk or Kingston branded MicroSD cards from Amazon or elsewhere. 32Gb maximum… that’s 108 hours of lossless audio in 16bit 44.1khz. Total file limit per card is 1200 files.

Chord organ now tracks 1v/Oct if you use the latest software downloaded here! http://polyfather.com/chord_organ

Building instructions can be found here. DIY level: easy.

This is a full kit which includes every single component to build a Radio Music module right down to the Teensy microprocessor board, the knobs, rack screws and power cable. Silver alu panel and red button.

Note: you need to purchase a MicroSD card and a Micro-B USB Cable elsewhere to set up this module. The Micro-B cables are the smallest type shipped with Kindles and many Android phones. You also need a card reader to write files to the SD card, many laptops and desktops already have them built in now. The very cheap $2 MicroSD cards are not worth the trouble they will cause you, buy genuine SanDisk or Kingston branded MicroSD cards from Amazon or elsewhere. 32Gb maximum… that’s 108 hours of lossless audio in 16bit 44.1khz. Total file limit per card is 1200 files.

Download the latest software here – http://polyfather.com/radio_music

Building instructions can be found here. DIY level: easy.

VCO-1 is an analogue VCO (oszillator) for the modular Eurorack system. From spring 2017 it can be complemented by VCO-1 Expander, which adds many functions like Sync, lin. FM, Wave Morphing, LFO etc. VCO-1 is temperature stable and provides a clean 1V/oct tracking over minimum 5 octaves. Will be a powerful combination!!!

Controls: Tuning (Coarse) ca. 20Hz - 20kHz, Tuning (Fine) ca. 8 half tones, Pulsewidthmodulation (PW). Connectors: 1V/oct input for CV-controlled pitch, PWM input for CV-controlled pulsewidth, Pulse audio output, Saw audio output. Power consumption: +12V: 25mA -12V: 20mA. Width: 10 HP, depth 40mm. This kit has all the necessary parts to build, including front panel and power cable. Building instructions, more infos and demos can be found here. Additional info: Unlike most DIY manufacturers, we produce our panels and circuit boards in germany. We also only use quality materials and durable parts. We hope that our customers appreciate and support that, even if it will cost you and us some extra €. The frontpanel was designed by Hannes Pasqualini / Papernoise.

DIY level: medium. The VCO-1 DIY kit can be built by medium experienced DIYers in about 2-4h. After finishing it, the 1V/oct tracking has to be adjusted, what might need some experience.

The Robaux SWT16 is a 16-track Eurorack trigger sequencer with up to 16 steps per track. Programmable like a classic TR machine, the SWT16 can be used not only for triggering drum sounds, but also for Envelopes, S‘n‘Hs or resetting LFOs. The SWT16 is polymetric - each track can have a different length, from 1 to 16 steps. Even more complex rhythms succeed with the individual clock divider per track.

The SWT16 has an intuitive user interface. All operation is via the illuminated 4x4 keypad. From the main screen, you can access the 16 different modes of the sequencer. The buttons adapt to the selected mode. With the back button, you can quickly return to the main screen. Each track has its own trigger output. In addition, the triggers are also sent via MIDI notes (requires an adapter).

Building instructions can be found here. DIY level: medium.

The LRMSMSLR brings the power of mid/side processing to the world of Eurorack. Mid/side processing is a powerful tool often utilised in mastering studios; it takes a stereo signal and separates it into the mid and side elements, allowing you to independently process them and then recombine them into a stereo signal.

DivKid made a good video about it to demo the creative possibilities! And there is a Muffwiggler thread.

Used creatively this allows a sound designer to do anything from using two filters with differing responses on a stereo signal without having to perfectly match them for a balanced stereo response, to using a VCA to modulate the stereo width at audio rates to add harmonics to a stereo signal, to techniques which haven't even been invented yet. The outputs are DC coupled so the LRMSMSLR can be used to get a sum and difference from two CV signals to create complex dynamic CV signals from plain old LFOs and envelopes.

LRMSMSLR has two four inputs and four outputs in the following order:
Left & Right signal in 
/ Mid & Side signal out 
/ Mid & Side signal in 
/ Left & Right signal out
The Mid out is half-normalled to the Mid in, as is the Side out to the Side in. This means Left and Right in and out can be patched in, passing the stereo signal through unaltered to the Left and Right outs until the Mid and Side inputs are patched in. This allows you to AB any processing by simply pulling out the jacks on the MS inputs.
The LRMSMSLR uses high quality low noise opamps throughout for studio quality sound.

Full DIY Kit. Manual can be found here. DIY level: easy.

Descent is an analogue dual envelope generator. It provides 2 independent voltage controlled decay EGs. The envelopes can be switched between triggered or gated (sustain) mode. The first trigger input is normalized to the second one and each channel provides a LED to visualize the envelope signal. The shape of the envelope can be adjusted between lin/exp with a trimmer on the back of the PCB. Decay times are adjustable between a few ms up to several seconds. It comes as a complete kit with all needed parts to build it. That includes a multi colour aluminum frontpanel, high quality jacks and smooth 9mm metal pots.

• Current draw: +12V 70mA | -12V 30mA
• Width: 6HP
• Depth: 40mm
• CV input voltage: +/-5V
• CV output voltage: 0-8V.

Building instructions can be found here. DIY level: easy, medium.

The TubeOhm SMR4P is a 10HP Eurorack Multimode VCF that combines the best features from two different filter circuits. The SMR4P design features the warm sound of the SMR4MkII filter alongside the 15 various filter shapes of the 4-Pole Mission VCF. This makes SMR4P a powerful ‘Swiss Army Knife’ filter, that can be switched between different filter types and slopes depending on your current need. This design also has some extra creative features, such as voltage-controlled switching between filter types, VC Cutoff Modulation, internal FM and a built-in VCA.

• Lowpass Modes: 6 + 12 + 18 + 24dB
• Hipass Modes: 6 + 12 + 18dB
• Bandpass Modes: 6 + 12dB
• Other Modes: HP2LP, HP3LP,Notch,Phaser, Notch+LP1, Phaser+LP1
• Current draw: 50 mA on + 12V, 30 mA  on -12V
• Width: 10HP
• Depth: 55mm
• Freq. Range: 20Hz - 22kHz

Building instructions can be found here. DIY level: advanced.

An essential tool for DIYers! Test 3 is a tool for measuring voltages and currents in your Eurorack system. This means that just a single circuit board or module can now replace a convoluted test setup with multiple multimeters, custom cables etc. Two push buttons allow you to cycle the value shown on the LED display between three measurements (voltage, current and stored peak current) of the three power rails. The peak currents continually update in the background on all rails, making it ideal for quickly getting maximum current figures. Apart from measuring the current draw of a single module, Test 3 also supports testing power supplies and cables, measuring an entire system (up to 1 A of current on each rail), troubleshooting DIY modules, powering a skiff or breadboard from a larger system...

• Width: 8 HP
• Current draw: +12: 35 mA

DIY level: easy. Building instructions can be found here.

The Time Wizard got a bag full of arcane time-warping tricks. All his magical feats are based on 6 dividers with selectable division factors and 4 switches providing 81 routing variations. This module's occult powers have been harnessed to easily clock and reset other sequencers with odd time signatures, provide weird clock division/multiplication ratios, and create complex poly-rhythms.

• Sextuple clock divider divided in two sections A and B
• Dedicated potentiometer acting on the division factor for each divider
• Clock multiplying and weird div / mult ratio abilities for the first section, first section incoming clock can be multiplied by 3 or 4, allowing to get easily triplets from a 16th clock or mult / div association as x4 / 7
• Independant clocking or divider association abilities for the second section, so B5 and B6 can get their clock in internaly from B4. For example, associating B4 = /7 and B5 = /16 provide a hit at each clock begining of 4 bars with a 7/4 time signature
• Auto-reset available for the first section or the whole module, the autoreset is provided by B6
• Additional logic functions for divider A2 : A2 output can provide the following functions : A2 AND B5 or A2 OR A3
• Jumper on the back for Trigger or Gate selection for B5 and B6
• User replaceable firmware chip
• 8hp / 22mm deep
• Power consumption: 20mA @ +12V

DIY level: medium/easy. Building instructions can be found on our info page.

Math & Rythm! Two outputs and five different rhythmic flavors multiply by a load of “algo-rhythmic” processing to result in a practically infinite number of polyrhythms. That’s the fundamental formula that produces the Knight's Gallop principle : a dual trigger generator providing sequences according to tables and modes.

• Dual Output Trigger Generator
• Variable length sequences (up to 16 steps)
• Length and Pulse amount potentiometers and CV inputs
• Shift + & shift - buttons allowing to shift the sequence forward and backward
• Main (MN) mode providing a lot of utlity modes for the second output : reset, no shift, invert and reverse
• Compute (CP) mode calculating associated sequences for the second output delivering very musical polyrythm
• Random (RD) mode adding randomness on the sequence feeding the second output, 4 amounts of randomness determined by the sub mode
• Dual (DL) mode allowing to set the two outputs seperatly
• Record (RC) mode turning the Knight's Gallop into a “play your sequence on the buttons and record it” module
• Five different kind of tables for five different rythmic flavours : Classic Euclidean (CE), Revised Euclidean (RE), Erdos Deep (ED), Divide Integer (DI) & Divided sequences (DS)
• User replaceable firmware chip
• 8hp / 25mm deep
• Power consumption: 22mA @ +12V

DIY level: medium. Building instructions can be found on our info page.

Basicaly, the Bishop's Miscellany is a dual stepped CV/Gate Recorder. It records two CV’s and two Gates on steps a bit like an analog shift register but with a lot more. First, plug in your CV/Gate keyboard, your MIDI interface, your ribbon, your joystick or your favorite CV/Gate controller and record a sequence. If you are too lazy to play something, you can even use the internal random generator to feed the inputs. Then, play the sequence and mangle it, it's that easy!

• Dual Stepped CV / Gate Recorder
• Variable length sequences (up to 32 steps)
• Shift parameter scanning differents segments in your original sequence.
• AB switch allowing to record two different 32 steps sequences.
• Random value generator very handly to create random loops or to play sequences randomly
• Cut funtion hacking the gate out 1 for more dynamic phrases
• CV inputs for Length and Shift functions • Gate inputs for all the switch functions (Record, AB, Cut and Random)
• 12hp / 22mm deep
• Power consumption: 25mA @ +12V

DIY level: medium/easy. Building instructions can be found on our info page.

Penrose is a very nice CV quantizer DIY kit for the eurorack format. It takes an incoming continuous CV voltage and converts it to the nearest note in a scale. Active notes can be selected with the 12 buttons. You can use it to tune the output of your analog sequencer, as a semi random melody generator, for fast chiptune arpeggios and much more. It comes as a complete kit with all needed parts to build it. That includes a multi colour aluminum frontpanel, high quality jacks and illuminated bi-color push buttons. The project is open source, so the schematic and source code is available.

Specs:

• Current draw: +12V 60mA | -12V 2.5mA

• Width: 6HP Depth: 40mm

• CV input voltage: 0-10V
CV
• Output voltage: 0-10V

Building instructions, more infos and demos can be found here.

DIY level: easy/medium.

Mal-2 is a random signal generator mainly intended as CV modulation source. It has 2 modes of operation to provide you with smooth random goodness. Imagine Eris herself lends you a third hand to keep your patches interesting. 1) In the first mode the CHANGE knob morphs from a cubic interpolated (sine like shaped) random signal to a random walk function that could make a wallstreet broker delirious with joy. 2) In the second mode the CHANGE knob sets the self similarity. On the minimum setting the signal is completely random. On the maximum setting the random sequence is locked to a repeating, identical 8 step sequence. In between the sequence seamlessly morphs to new shapes over time. This gives you a random CV where you can shape the bounds in which the chaos unfolds and goes far beyond a slew limited white noise.

Specs:

•     6 HP
•     12 bit CV output
•     through hole components DIY kit
•     Random gate output
•     CV inputs with attenuverter for both knobs
•     super slow cycles times up to lower audio range
•     +12V 60mA | -12V 5mA

Building instructions, more infos and demos can be found here.

DIY level: easy/medium.

The 2M is a dual three channel mixer in 6 HP with volume controls over all the inputs as well as the final output. As its design has been specially focused on audio applications, the input potentiometers are audio-taper type while the output ones are linear. Low distortion / high quality audio operational amplifiers have been selected in order to achieve clean audio mixing, but is also DC-coupled, so it can perform CV signal mixing as well. Great for a small system, allowing for submixes or even stereo mixing.

Specs:

• 6HP
• 38 mm depth
• Consumption: +/-12V 25mA

Building instructions can be found here.

DIY level: easy/medium.

The 8S is an 8 step sequencer in 8 HP with control over parameters of the sequence as reset, hold, random step and direction. It’s been designed to work with clock related signals like triggers or gates but any type of CV signals can be used at its inputs. The output signal path is completely analog and its range can be set as unipolar (0 to +5 volts) or bipolar (-5 to +5 volts) via jumper on the back.

Specs:

• 8HP
• 38 mm depth
• Consumption: +12V 55mA, -12V 10mA

Building instructions can be found here.

DIY level: easy/medium.

The 1F is a voltage controlled switch, intended to be ‘one friend’ for your sequencer. Its design has been specially focused on working with sequences, by giving them some randomness, applying transpositions or constant variation over time. For this, 0.1% tolerance resistors have been used to achieve exact unitary gains for precision summing of the v/oct signals. More detailed info on the demo video.

Specs:

• 4HP
• 38 mm depth
• Consumption: 15mA +12V; 10mA -12V

Building instructions can be found here.

DIY level: easy.

What and why the B.I.Y. idea? The B.I.Y. kits are designed to allow anyone to easily create professional quality, reliable versions of their favourite (or personally designed) guitar pedals at home. The circuit board requires no off-board wiring greatly reducing the potential for failure while vastly reducing build time. The board also features dedicated space for a voltage regulator, reverse-polarity protection, filtering capacitors, on/off indicator LED, and creating 1/2Vcc. 

We offer 4 different kits: Bazz Fuss (Fuzz), SHO Boost (Zvex Super Hard On clone), Cave Dweller Delay and Tube Screamer (Classic Distortion). They always contain the bare-bones B.I.Y. guitar pedal kit, a predrilled Eddystone aluminium enclosure, all the components, wire and ~5g high-grade solder plus components for the kit of your choice. Instructions can be found here.

DIY level: easy to medium.

The perfect solution for midifying small analogue synths or gadgets due to small dimensions: 17x12x4mm. The PCB itself comes assembled. Midi input, one pair of CV/Gate outputs, V/Oct scale only, stable scale over four octaves, MIDI-learn button and configuration via Sys-Ex. Made by Midi-Hardware.com. We also offer a full kit, including box and all you need to build a full standalone interface with a small budget. Power supply available separately here. Please check detailed info and instructions before you buy, they can be found here.

DIY level: easy. The PCB itself comes assembled, only a few cables to solder.

SOON AVAILABLE AGAIN! Our converter is a top solution for:

• any DIY project that needs clean and stable 9V like guitar pedals etc.,
• if you want to migrate your 9V projects into your Eurorack system or want to create a stable 9V source from your Eurorack,
• and generally all projects like Fuzz boxes, which suffer from bleed through caused by dirty switching supplies.

All that mess is cleaned up!

Our converter uses 12V (DC) -+20% on the input and generates a stabilized, very clean 9V +-1% of 150mA at the output side. It also is save against wrong polarity on the input, overpower save due a self resetting fuse. It works with all of our 12V DC power supplies.

DIY level: easy. The PCB itself is assembled, only a few cables to solder.

We developed this module to power modules like our TR-808 Kick or single Eurorack modules by a standard power supply. It uses 12V to 18V (DC) on the input and generates a symmetrical output of +/-12V (1W) at the output side. It also is save against wrong polarity on the input, overpower save due a self resetting fuse. It's a top solution for any DIY project that needs symmetrical power. A more powerful version is also planned. We also offer a power supply for it.

DIY level: easy. The PCB itself is assembled, only a few cables to solder.