»Ilse« is an elegantly minimal, but fully functional synthesizer in a 16 HP Eurorack module. The only thing you need to let it meow is a MIDI to CV converter (or another CV source) to trigger its frequency and gate inputs. Because it has such a low part count (only 2 opamps and 7 transistors) it is ideal for Eurorack beginners or entry-level DIY projects.
Ilse is designed as a low cost, easy to build, but still flexible and feature rich synthesizer. It works as a Eurorack module as well as standalone with two 9V batteries (not included).
Ilse is open source and inspired by Syntherjack’s single-chip synthesizer Totoro. Check out his website with nice explanations, e.g. on the filter (we use the same filter on Ilse). We extended the design for external voltage control on filter, oscillators and LFO. Schematics and layout can be found here: github.com/clwe/ILSE.
- two saw tooth oscillators
- brigded-T low pass filter with resonance switch
- triangle LFO with speed control, and routing to filter or oscillators
- simple mixer and detune for oscillators
- level control
- external filter input
- 1V/Oct input for oscillators
- Filter Cutoff (exponential)
- LFO Speed (linear, via pin header)
- Oscillator 2 detune (linear, via pin header)
You might as well just examine the schematics in the simulator and build your own synthesizer from it. It uses a neat trick to build the exponential converters directly into the saw tooth oscillators as you can see from the simulation below. Note that the tuning of the oscillators is not temperature compensated and will thus change with room temperature. We would not recommend using Ilse in a stage situation where reliable and exact pitches are important.
It features a simple voltage controllable low pass filter that you can modulate with the inbuilt LFO or an external source.
Ilse was designed for educational use and was used in an introduction to electronics course. For more details on the schematics see the course material.