Bastl Instruments Kastle Synth

The Bastl Instruments Kastle Synth is a modular Lo-Fi Synth in pocket size. As such, it is ideally suited as an introduction to modular synthesis, but also adds unique functions to the advanced Modular System. In two Attiny 85 chips it combines a complex oscillator LFO and waveform generator. Thanks to battery operation, digital Lo-Fi sounds, melodic as well as noisy, soft, hard and drony sounds can be created on the go. The Mini Modular Synthesizer develops its full potential in conjunction with various modular devices.

Sound generation in the Kastle Synth

The oscillator section of the Bastl Kastle Synth has three parameters: Pitch, Timbre and Waveshape. All are equipped with control voltage and three different synthesis modes. Phase Distortion, Phase Modulation (FM) and Track & Hold Modulation are available as modes. Each mode uses two oscillators. The Waveshape knob can also be used to adjust the pulse width of the rectangular output of the main oscillator. There is a main and a rectangle Output that can be used independently or combined.
The voltage LFO controllable has a triangle and rectangular Output input and a reset input. A rungler-inspired stepped waveform Generator produces eight different voltages, either in random order or in eight- or 16-level repeating patterns. The playback of the pattern loops depends on how BIT IN is patched.

Bastl Instruments Kastle Project

The Kastle project Bastl Instruments is an open source DIY project based on two Attiny 85 chips that can be reprogrammed with Arduino (google: "programming Attiny 85 with Arduino"). One chip is used to generate sounds, while the second chip is dedicated to modulation. Various firmwares are available for the Attiny Chips.