Open Kalimba
A DIY tine synth in the spirit of the Korg Phase8: tuned steel tines, plucked and sustained by electromagnetic drive coils, built one voice at a time.
Korg’s Phase8 is a beautiful idea: an acoustic synthesizer where each voice is a real vibrating steel resonator, excited and sustained by an electromagnet and played like an instrument. It’s also expensive. The Open Kalimba is my attempt to build the same kind of instrument from shop stock, and to document it well enough that someone else could too.
The design
Each voice is a steel tine clamped at one end, with a hand-wound coil and a small neodymium bias magnet underneath it. The coil picks up the tine’s vibration; a feedback loop drives it back, so a note can ring as long as you like or decay naturally. The plan is to build it as eight-note modules, so two modules make a sixteen-key instrument.
- Tines are cut from 0.031 in high-carbon steel feeler-gauge stock, half an inch wide. Before cutting, I clamp uncut strips at different free lengths and pluck-test the pitch.
- Coils are wound on bobbins turned from Delrin around a quarter-inch steel core, using fine magnet wire. That’s what the coil winder is for.
- Magnets are 6 × 3 mm N50 discs.
- Mounting is a toe clamp on a plywood base, with a threaded center pole through each coil.
Where it stands
I’m building a single-voice test rig first, to get the electronics and the sustain loop right before multiplying anything by sixteen. The clamp block is an acrylic stand-in for now; a steel bar is on order to replace it.
I’ve also been studying the 1970s Fender Rhodes. A Rhodes note is a struck tine coupled to a heavy tone bar, essentially an asymmetric tuning fork. That points to a better design than a tine in a massive steel block: a cantilevered tone bar resting on felt pegs. Once the steel-block baseline works, that’s the next thing to try. It’s also the idea behind the gong ageng.
Still undecided: which scale the keys should be in, and whether the brains end up on a Raspberry Pi Pico or an ESP32-S3.