by Robin Vincent | 5,0 / 5,0 | Approximate reading time: 2 Minutes
Bastl Instruments Kastle Synthesizer

Bastl Instruments' Kastle  ·  Source:

Bastl Instruments Kastle

Bastl Instruments Kastle  ·  Source:


Here’s a crazy little thing. A lo-fi, pocket sized, battery-run synthesizer that can make beeping noises or modulate your other gear into spasm. It’s called Kastle and looks a lot like an electronics student project.


Kastle the concept

Kastle is two things: it’s a synth but it’s also an open source DIY project that hopes to spawn a whole range of products. It runs on two Attiny 85 chips that can be programmed with an Arduino. One chip is dedicated to sound generation and the other to modulation.

Kastle the synth

The synth version combines a complex oscillator and LFO with a stepped waveform generator. I confess that I find the website description is a little bit confusing. But there’s an oscillator that makes noises that you can change the pith and timbre of and also the waveshape. There’s another oscillator that seems to be referred to as a pulse OSC that’s probably also the LFO – but can be combined with the first oscillator to thicken the sound. Synthesis is achieved with Phase Modulation, Phase Distortion or Track and Hold Modulation. In phase modulation Kastle has two operators, a carrier and a modulator or simple FM-type sound generation. Phase distortion, made famous by Casio, syncs together two ramped oscillators. Track and Hold basically uses one oscillator to mess with the other one. So there’s definitely two things going on – at least!

I think it’s best not to dwell on the specifications and enjoy the way it can screw with itself via patching. The manual encourages you to do the following:

Connect OSC PULSE to the BIT IN to create varying random patterns.
Connect OSC PULSE to any of the OSC inputs to see what happens.
Connect any LFO signal to the MODE pin to change the synthesis mode on the go.
Connect OSC PULSE to the LFO RST pin to create chaotic modulation waveforms.


In the box

It comes with 10 mini patch cables (and a sticker) to get you plugging things into itself. They also encourage you to connect it to larger modular setups for some surprising and interesting results. Checkout the video below. It starts off a bit crappy but it really begins to grow on me as I see how much it messes up other gear.

So, it’s a hand-made DIY project synth that sounds weird, fits in your pocket and looks like a lot of fun to play with. They are knocking them out for $79 or $65 if you want to build it yourself. As it can be reprogrammed there’s the possibility of new features in the future and I wonder what other Kastle boxes could emerge. That makes it quite a cool little box of noises. One for the Christmas list I think.

More information is available on the Bastl Instrument’s website.

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Bastl Instruments Kastle Synthesizer

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