Power Supply For Korg Volca

For the last post of 2018, I wanted to write about the making of a small power supply for 4 Korg Volca.

Power supply inside

A Korg Volca can be powered by batteries or by a dedicated power supply : the Korg KA-350.  Not only is that power supply expensive compared to the affordable Volca, but it is over-dimensioned and you end up using one per box.
Moreover, Korg uses a slightly different connector than most 9V guitar pedals power supplies and the polarity is reversed (positive inside).  They correspond to the EIAJ-02 japanese standard.  Size is 4.0 x 1.7mm.

Power plug assembly in progress

There are some solutions out there, like alternative power supplies, adapters, daisy chain cables, etc.  Nevertheless, I couldn't resist to make my own power supply.

Bob screws the cables

This is a classical dual regulated power supply.    I used a design from the excellent Sonelec website.  You'll find the layout below.

The transformer is a 220V to 2x 12V transformer.  Bridge rectifiers are DB205.  Regulators are LM317.  The power plugs are PP-014 from CUI.  The enclosure is a 137x97x67mm ABS Polycarbonate Power Supply Case.

Splices

I bought the 5 connectors from Mouser and the plastic enclosure from Banzai Music.  All the other parts are leftovers from previous projects : I usually buy a little more each time to cover losses, destruction or to simply fill my drawers just in case...

Each one of the two outputs of the power supply is split in two with splices and a bit of heat shrink tube.

The transformer is only rated for 12 VA, which means 500 mA per output.  Volca are reported to draw about 80mA. This means a total of 160 mA per output.  That's enough safety margin for me.



That's it.  Let the fun begins.

Circuit and layout

Sequencer

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.