Monday, 12 February 2018


One of the simplest and cheapest CV/gate step sequencer is the Korg SQ-1.

Korg SQ-1 step sequencer

Powered via USB or batteries, the small machine is able to deliver one 16 steps or two 8 steps sequences in various of ways.

There are very few settings for CV out.  The SQ-1 can play linear, minor, major or chromatic scales with a 1V, 2V or 5V ranges (in V/Oct mode) or 8V range (in V/Hz mode).

Its biggest drawback is that there is no way to choose the root note of the scale.  So it's either C major/A minor (major mode) or C minor/Eb major (minor mode).   You'll have to transpose yourself by adding voltage (83 mV per semi-tone).  Good enough for fun, maybe not suitable for a full symphony.

Otherwise it's an enjoyable machine that I bought mostly for parameter automation.

I don't have a lot to control on the synth just yet.  But it's still possible to have some fun.

In action

Here above, the SQ-1 sequences Rings in sympathetic strings mode.  The sample and hold modules gives some randomness to the position parameter.  Odd output is untreated, while the even output is connected to the phaser.  So one every two notes is treated by the phaser and mixed a bit differently for a bit of variation.  Sequence evolution is me activating and deactivating the gates.  The SQ-1 has no pattern memory whatsoever.
All is synced to the tempo of the Korg Volca Beats, responsible for the basic drum pattern.
Additional effects : TAL DUB II for the delay, NI Guitar Rig as guitar amp simulation and Thomas Mundt LoudMax.

Sunday, 4 February 2018

The case

I finally made it.

I got a case for my modular synthesizer.

The finished case
Even though I had identified the necessary pieces of wood available at home, I dismissed my initial idea of having a full custom 8U wooden case.
I got inspired by this thread on Muff Wiggler to use a basic tool case to host my first modular synth. 

I reckon my initial idea of 2U 84HP utility panel would have taken me too much time.  So starting from an existing box seems a better idea.

As usual with me, I progressed step by step.

The box is a standard tool case from the local DIY store (Sencys from Brico). External dimensions are 46 x 33 x 15 cm.   This is great for hosting a 6U 84HP Eurorack modular synthesizer.
I'll keep the lid from now.

The Doepfer A100 DIY kit is perfect for the job : four rails, two bus boards, a power supply is all you need to start..

Checking everything is in place ...

I started by checking that everything could easily fit into the box.  And from there I evaluated what would be needed to mount the kit inside.

Apart from the box, I exclusively used pieces of woods already available in the house.  Mainly remnant from a 6mm thick MDF wood panel..

I decided to keep the foam inside.  I only had to tighten the corners and cut out the part where sides were recovering the bottom part.

I bought some 6mm x 6mm square nuts to fit in the rail, as the standard hexagonal ones have a tendency to rotate and block into the rail.  As I miscalculated my needs, I kept 4 hex nuts per rail, two on each end, for a total of 21 nuts per rail.  I reckon this will suffice.

The back of the structure is a bit more than 4 cm deep.  It gets to support the power supply placed vertically and can accommodate 2 8HP modules turned horizontally.  Not as good as the 2U utility panel I initially envisaged, but this will do.

For the bus boards, I decided to fix them from below an horizontal wood piece.  These slats were a bit thick.  The box is not very deep.  This way I keep a full 7 cm clear.  The bus boards are blocked by the foam.  And yes I checked if, by any chance, this would be conductive … which it is not, obviously.

The connection of the power supply to the 240V-15V AC transformer is done via an appropriated connector on the front panel to avoid piercing the box.  No trouble thanks to the parts I collected when I started to make guitar pedal kits.

A green LED connected between the -12V rail and the ground (with the help of a 1k resistor) indicates when the case is powered.

Both fit into a custom panel, drilled with some ventilation holes.

I made sure the power wires would stay nicely on the side and I double checked the connection with a voltmeter.

Before fixing inside the case
Finally, I secured the lot into the box thanks to four 5mm carriage bolts.

Finished.  It's time to add modules.