Traveling light? Bastl has got you covered. We've managed to pack a lot of energy and soul into a tiny box named the Kastle.

The Bastl Kastle is a mini modular synthesizer you can play anywhere. It's powered by just 3 AA batteries or a regular micro USB charger, and it offers a headphone output and 2 in/out ports for interfacing with other gear, whether a keyboard, a groove box, or a Eurorack synth.

The device is DIY-friendly and ideal for beginners in synthesis, but it will also add unique functionality to any full-sized modular synthesizer system. It delivers the fun of modular at a low cost, and it fits into your pocket so you can play it anywhere.

As Sound on Sound’s Paul Nagle summarizes Kastle in his review: “It’s a stand-alone synth, a modulation source for your modular, and can live in your pocket ready to impress your friends. You’d have to be pretty hard-hearted to find no pleasure in it.”

Be an operator with a pocket calculator

The Kastle has a unique digital lo-fi sound, and it can be melodic, rhythmic, as well as very noisy and droning, soft or harsh. It was designed to be fun on its own, but it thrives best in an ecosystem of other modular gear.

The Kastle is an open-source DIY project that runs on two Attiny 85 chips which can be reprogrammed with an Arduino (just Google "programming Attiny 85 with Arduino"). One chip is dedicated to sound generation while the other handles modulation. Several firmware versions for the Attiny chips are available on GitHub.

Version 1.5 combines a complex oscillator and LFO with a stepped waveform generator.

The oscillator section has 3 sound parameters: PITCH, TIMBRE, and WAVESHAPE – all under voltage control, offering 6 different synthesis modes. It has a main output and a secondary waveform output. Both can be used independently or combined. The 3 synthesis modes available through the main output are: phase modulation, noise mode, and track & hold modulation. There are 3 more modes on the secondary OSC output: phase distortion, tonal noise mode, and formant synthesis. Each mode uses one or two oscillators. The PITCH parameter controls the main oscillator, the TIMBRE sets the PITCH of the modulating oscillator, and the WAVESHAPE depends on the synthesis mode.

The voltage-controllable LFO has triangle and square outputs and a reset input. The stepped waveform generator is inspired by the Rungler circuit by Rob Hordijk. It can produce 8 different voltages either in random order or in 8 or 16 step looping patterns depending on how the BIT IN is patched.

Features

• complex oscillator
• 3 synthesis modes on the main output: phase modulation, noise mode, track & hold modulation
• 3 more modes on the secondary OSC output: phase distortion, tonal noise mode, formant synthesis
• PITCH control with offset and CV input with attenuator
• TIMBRE control with offset and CV input with attenuator
• WAVESHAPE control with offset and CV input
• voltage controllable LFO with triangle and square outputs and reset input
• stepped voltage generator with random, 8-step, and 16-step loop mode
• 2 I/O CV ports that can be routed to any patch point
• the main output can drive headphones
• 3x AA battery operation or USB power selectable by a switch
• open source
• possibility of exchanging different LFO and OSC chips
• durable black & silver PCB enclosure

Tutorials

• Kastle v1.5 - new features & style
• Bastl Kastle 1.5 - Unboxing & Review
• Bastl Kastle v1.5 | Unboxing + Sound Demo & overview
• Bastl Kastles: LFO Sounds Part 1
• Bastl Kastles: LFO Sounds Part 2
• The random mini-synth family #87: Kastle with VCA - BASTL KASTLE TUTORIAL
• The random mini-synth family #15: Bastl Kastle Tutorial - dance
• Bastl’s Kastles - a larger context for the tiniest modular synths
• How To Patch Bastl Kastle 16 Step Sequence - Random Note
• How to Sync a Bastl Kastle with Pocket Operators - Easy, Quick and Detailed - with ONE cable
• How To Expand Bastl Kastle & Volca Modular Using A Breadboard
• Sync Tutorial - Volca Beats + Bastl Kastle | Funktuate
• Technical Excursion: Patching the Bastl Kastle 1.5 Synthesizer

What's in the box

• Kastle synth
• 10 patch cables
• user manual
• sticker
• for environmental reasons we are excluding the batteries from the package

Technical details

• dimensions: 70 x 60 x 50 mm
• power: 5V via Micro USB or 3x AA batteries
• FAQ

Downloads

• user manual pdf
• Japan (nihon) manual pdf
• press release pdf
• patch sheets G-drive pdf by Revok
   
• Free Kastle sample pack mega by Nocturnx