Tag Archives: DIY

Circuit Abbey Euro-Duino

euroduino_panelEurorack and Arduino. What common may be between a huge analogue rack and a brains for a toy robot? Perhaps it is openness of the both platforms and broad variety of existing solutions based on them. Nowadays it is not something outstanding to use a digital controller inside analog module, but Arduino also is respected for its simple and user-friendly development tools, allowing to create a device doing random tasks for minimum time and money. A couple of years ago Arduino chips had took their place in Eurorack modules. 4ms, Flame use AVR controllers in their products and Soundmachines specifically used Arduino to develop their Robotto and had published an SDK for it.

And now appeared modules that are intended to be programmed by owners. The first one was utility-module Expert Sleepers Disting ($175), based on PIC32MX uC, then Circuit Abbey Euro-Duino ($145), based on Arduino as it comes from the name. The price for the DIY kit of this module is just $95 and it has lots of fun within! So, let’s take a closer look at the module.
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ESI Gigaport HD DC-Coupling Mod

There is number of DAW-sequencer plug-ins that can work with control voltages. For example:  Expert Sleepers Silent Way and M.O.T.U. Volta. Also, any specific CV source can be made with SynthEdit, SynthMaker, Pure Data, Max/MSP etc. In order to output CV to a hardware, an audio-interface with DC-coupled analog outputs is required. (Audio-interface should work correctly with direct current) Most of today’s audio-interfaces have protecting HP filters, placed right before analog outputs. These filters let only alternating current to be passed trough (outputs are AC-coupled) and also provide good dynamic range. Few old professional interfaces (MOTU 828 and others) has DC-coupled outputs. Also, Expert Sleepers has the whole range of specialized audio-interfaces and DACs with DC-coupled outputs. These are good interfaces, but a bit expensive.

The ESI Gigaport HD is known as inexpensive, multichannel 24/96-ready USB audio-interface. Out of the box this interface has AC-coupled outputs but circuit can be easily modified to support CV.

ESI Gigaport HD DC-Coupling: CapacitorsThere is eight electrolytic capacitors inside the device: C36, C41, C46…C71 (marked red). All we have to do is to short capacitor’s terminals together. The first option is to solder a jumper wires around each cap. The second option is to insert switches that could toggle DC- or AC-coupling for individual outputs.
ESI Gigaport HD DC-Coupling: Schematic

Finally we got an interface that supports both CV and audio.

Measured specifications

  • Channel number: 8
  • Amplitude: 6v p-p max. (−3…+3 volts)
  • Maximal positive sample value (32767 или 8388607) inverts (Version 3 drivers)!
  • Channel DC cross-talk: <0.03% (<146dB)

Use carefully! Unprotected inputs/outputs are sensitive to low-impedance current sources. Inaccurate connection may cause damage to interface or degrade it’s specs.

L-1 modules

l-1_logoBelarusian electronics designer Alexey Laman manufactures Eurorack modules under L-1 trademark. His modules are highlighted both by himself and by community members as top-quality modules comparable to Cwejman products. The Company is founded in 2012. Today’s model range includes several dynamic effects (compressor, VCA, mixers), VCF and even vocoder! Modules can be purchased as fully-assembled units or as DIY-kits. In this review I’m going to introduce three L-1 modules at once: 2180VCF, Quad VCA/Mixer and Tube VCA. Continue reading

AVR Synth 16

avrsynth_picLast time I was telling about one Elby Designs module. So, let’s continue the Australian equipment subject with interesting product manufactured under same brand; AVR Synth. This is the virtual analog synthesizer working on AVR-family microcontroller. The firmware of this synthesizer is written in Assembly language. The code is open-source and schematic is also open. I’m going to tell about the original, 16-bit version and about few forks of this project.

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Microtonal Synthesizer

Russian musician-experimentalist Alex Pleninger has been working on this instrument for about a year. The synthesizer consists of three identical blocks. Each of them is based on digital synthesis core. Each core uses two ARM microprocessors. The blocks are controlled with three sensor keyboards: two with 25 keys and one with 50 keys. Capacitive sensors provide only touch sensivity. The scale of each of three blocks can be programmed via control panels. Scale is expressed as index and radicand of the root which determines number of pitches in the octave. Also, the coefficient of the frequency multiplication applied by each successive degree can be manually entered. All of this data is displayed on OLED displays. The instrument also has transpose switch and buttons to select attack and release time. Three sustain pedals can be connected. The interesting detail is that the synthesizer has no MIDI ports at all. (Pleninger is well-known for his hostility to MIDI)
The device is custom-made for one of the famous recording studios.

MFOS Eight Stage Phase Shifter

phase_shifter_3Music From Outer Space is probably most famous Synth-DIY website. It’s author, Ray Wilson has developed huge amount of various modules and can offer wide variety of DIY-kits: module PCBs, noise generators, complete modular synths and even vocoder. Today I’m gonna tell about Eight Stage Phase Shifter module which Eurorack version I had pleasure to build recently.

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Thonk Turing Machine


Sorry, but English version of this review is unavailable due to significant size of text to be translated.

You can read about this great module suite here.

This is a fragment of 3-voice part made with Turing Machine and recorded to single track.

Wob-Wob Fader

Wob-Wob Fader is simple CV-source controlled by fader. The feature here is that maximal voltage is reached in the middle position. This controller make it possible to easy perform sweeps widely used in modern music. similar technique is used with vinyl disks. This module has one Wob-fader and one fader with selectable mode.

UPDATE: Values of R2 and R3 can be changed to 4.7K to obtain more expressive sweep.

Creative Commons license
This circuit is published under Creative Commons «Attribution-NonCommercial-NoDerivs» 3.0 license.
Any use beyond this license must be discussed with author.