Bastl Instruments Kastle ARP Mini Melody Generating Synthesizer


Pocket-sized patchable synthbox with uncountable melodies to explore

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Kastle ARP is a unique modular melody generator based on a quantized sine wave oscillator with a digital waveshaper.

The pitch selection employs straightforward concepts to unleash surprising intricacy. The quantized oscillator ensures it is always in tune, and its pitch can be selected using the NOTE and CHORD inputs. The decay envelope adds variation by occasionally skipping pitches before retriggering. The timbre control allows you to blend between noble sine waves and 8-bit chip-tunes.

A melodic take on your beloved glitchbox

Kastle ARP features a versatile LFO section, inherited from the original Kastle Drum, that combines simplicity with complexity.

In boot-mode, you can easily access the root note and fine pitch tuning. Additionally, the bass output plays the root pitch of the current chord, enhancing the overall sound.

A simple must-have Synth for every Kastle-head

For maximum joy, try running your Kastle ARP through delay and reverb effects. By combining it with other Kastle synths, you can achieve unparalleled patch flexibility.


  • quantized-pitch sine wave oscillator
  • NOTE knob to browse thru 8 octaves
  • timbre xor waveshaper
  • CHORD CV input switches between 3 chords
  • CV controllable decay envelope generator
  • triggered pitch with “negative” decay to achieve melodic variation
  • BASS output with the root of the chord
  • boot mode to set a root note and fine-tune
  • voltage-controllable clock with square and triangle output
  • stepped voltage generator with random, 8-step, and 16-step loop modes
  • two I/O CV ports routable to any patch point
  • the main OUT capable of driving headphones
  • 3x AA battery operation or USB power, selectable by a switch
  • open source
  • durable black and silver PCB enclosure
  • comes with a pack of 10 patch cables
  • package doesn’t include batteries for environmental reasons

Dimensions: 70 x 60 x 50 mm

Power: 5V via Micro USB or 3x AA battery

Note: Kastle ARP may sound different when powered by AA batteries than when powered via USB due to the difference in voltages (5V on USB vs. 4.5V via AA batteries).

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Bastl Instruments Kastle ARP Mini Melody Generating Synthesizer