Gakken SX-150 Synth Kit

The Gakken SX-150 analog synth kit, distributed by Make, came in stock again recently and so I ordered one. Here’s the finished article:
Gakken SX-150 synth

This is a nice kit for anyone starting out making, it simply screws together (no soldering needed). The SX-150 is played with a stylus with a continuous contact strip, there are no individual contacts tuned to notes, unlike the Stylophone. This makes it hard to play notes, but is good for sliding pitch effects. However, because it has a small but fully analog synthesis circuit, it can still make usable sounds. Make have published a hack to allow it to be controlled by MIDI which should make it usable for playing notes and sequencing.

The instructions for the SX-150 describe the principles behind the analog synthesis circuits so it’s potentially a good starting point for creating analog synth circuits or maybe even hacking the SX-150 itself. One hack could be to add more synthesis controls such as LFO depth and resonance level, amongst others.

Gakken SX-150 circuit board top
SX-150 PCB front, the controls and synth circuit capacitors are mounted here.

Gakken SX-150 circuit board bottom
SX-150 PCB back, most of the synth circuit components are surface mounted here.

The kit comes with a chronicle of synthesis which includes a section on hacking projects. I guess it would help if you can read Japanese… although a few ideas can be got just from the images.

Gakken SX-150 synthesizer chronicle
Gakken Synthesizer Chronicle

Gakken SX-150 synth box
SX-150 Box

Meeblip DIY Kit Build

My Meeblip DIY kit is now built and making noise!
Meeblip synth kit

The hardware of the Meeblip is perhaps about as simple as a digital synth could possibly be: a microcontroller (with a good number of switches and knobs connected it), a MIDI interface to get notes in, a digital-to-analog convertor, and just enough audio circuitry to get sounds out. All the subtractive synthesis is done in the microcontroller, so it sounds like a simple soft-synth plugin. Except of course it lives in its own hardware, where the audio output circuit seems to add a bit of pleasing grunge to the sound.

Reflex Audio/CDM are steadily developing new versions of the Meeblip. The circuit board of this one is revision 1.31 SE which has some changes to previous versions: it’s now red, has a power switch, there is no USB power, and the connectors are mounted on the bottom to make positioning a front panel easier. There’s no case with the DIY kit (the quick build kit has a case), although there’s the option of the new SE case becoming available at the end of August, or even a home brew case…

The build instructions are easy to follow, although they are yet to be fully updated for the 1.31 SE board. So if you have a go at building this revision, one gotcha is that in order to check the power (step 3), all the power supply components need to be soldered in first, including the power diode, regulator and new power switch. One other thing to note is that the Meeblip needs a good low-noise external power supply, otherwise it can get some hum on the audio.

MeeBlip Hackable Synth

Meeblip open source synth

The MeeBlip is an open source hardware digital synth that was designed by James Grahame of Reflex Audio in collaboration with Peter Kirn of Create Digital Music.

The MeeBlip is designed to be hackable – easily modified to change the way it works. The MeeBlip seems like a good starting point for developing my own hardware synth projects so I ordered a kit to build with a view to doing some hacking…

Building The WOM

At the Beam Festival in June I joined a group of people in building one of Tom Bug’s brilliant Workshop Oscillator Machines in one of the workshop sessions.

Building the Bugbrand WOM (Workshop Oscillator Machine)

Even though the WOM is a simple design it can make some complex and sometimes chaotic sounds. It includes some circuit bending tricks including ‘power starvation’. This causes the part of the circuit that creates the basic elements of the sound, the oscillators, to enter unexpected cycling patterns when they struggle to work as normal as their power is gradually sucked away. With power starvation switched on – just a slight twist of one of the WOMs controls… a completely new sound is created. Playing the WOM is noisy harsh unpredictable fun.

Bugbrand WOM (Workshop Oscillator Machine)

The contacts at the bottom of the WOM look a bit like a deranged piano keyboard. They’re actually electrical contacts which you touch to become part of the circuit to bend its function.