Bastl Instruments Kastle 1.5 Is Now Black, Powered By Micro-USB & Features 3 New Synthesis Modes

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That came unexpectedly now. Bastl Instruments released today a major upgrade of their excellent mini experimental Synthesizer Kastle. As a small introduction: “Kastle is a mini modular Synthesizer with a headphone output, 2 in/out ports for interfacing other gear and it runs on just 3 AA batteries. It is DIY friendly and ideal for beginners in modular synthesis, but it will add some quite unique functionality to any modular Synthesizer system. It delivers the fun of modular synthesis at a low cost and fits into your pocket so you can play it everywhere!”

Improved Design – Black Is The New Silver 

First of all, what is striking is the new look of the Kastle v.1.5, which now comes in a smooth black finish compared to its predecessor, as well as made of fiberglass and no longer in acrylic what made it more durable. The developers also added a second way to power the device. Batteries is no longer the main power system but also a standard micro USB jack that makes it possible to use without changing batteries. A good move from the developer that is especially interesting for musicians who use the Kastle daily on music stages.

3 Synthesizer Modes Are Not Enough 

It was already impressive to see what kind of Synth modes the little Kastle included in the first version. But as you know the Bastl crew, they have to cut out the hardware and take the thing to another level. They reworked in the Kastle v.1.5 the whole sound core and made the entire sound much better. The ranges and smoothness is significantly increased enhancing the palette of the possible sounds.

The new Kastle is now capable of using two sound generation engines running in parallel on the main output and on the secondary OSC output. That opens for sure an entire new sound world with this small experimental instrument. What is admirable here is how easy the developers have implemented this new engines. In large systems, you will certainly need more time to combine two synthesis types together. In the Kastle v.1.5, musicians can either use them separately or mix them together by simply connecting them with a patch cable.

The most exciting are certainly the 3 new synth modes: format synthesis, noise mode and tonal noise mode. The formant mode is inspired by the Helmholz Synthesizer – one of the first synths ever built by accessing different combinations of harmonics over fundamental – creating so called formants (vowels)

© Photo credits

The noise modes are basically a granular playback of the flash memory (where the program is stored) of the sound processing chip. That sounds like a typical Bastl Instruments instrument!  In other words it is a data player of a piece of computer code (that runs the sound core of the Kastle synth) that has very distinct sonic qualities on its own often referred to as “glitch” in aesthetic terms. However this mode is so purposeful that instead of talking about a mistake we should be talking about being true to what the true nature of Kastle truly is in very modernistic terms (it is a digital Synthesizer)

For a price of less than 100 €, the Kastle v.1 was already an absolute no-brainer for experimental musicians in 2017. Shortly before the end of the year, Bastl Instruments had done this again and almost developed this little Synthesizer into a must-have instrument for everyone. Bravo Bastl crew! 


  • 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

The new Bastl Instruments Kastle v.1.5 is now available in a build (80€) and DIY Kit version.

More information here: Bastl Instruments Kastle v.1.5 

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