Chair Audio - Ilse

Ilse is an elegantly minimal, yet fully functional synthesizer voice in a compact 10 HP Eurorack module. The only thing you need to let it meow is a CV source to trigger its 1V/Oct frequency input (or a MIDI to CV converter and a MIDI sequencer) . Because it has a low part count it is ideal for Eurorack beginners or entry-level DIY projects.

Ilse is named after a cat, living in the legendary “Villa” in Weimar, Germany. The “Villa” was a place where a community lived and came together. Many underground concerts and parties took place here before the house got sold, renovated, and the mayor moved in. We created the graphics on the aluminum face-plate in her memory. Ilse (the synth) makes great acid sounds, so it was only logical to illustrate a cat tripping. Turn the knobs to make her look around or roll her eyes.

Ilse is designed to be affordable, easy to build, yet flexible, and feature rich. It is a synthesizer voice for your Eurorack, but can even be driven without a rack using two 9V batteries (not included).

Ilse is fully open source (KiCad schematic and layout is available in a git repository) 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. Unlike Totoro, Ilse is designed around a unique oscillator design, which integrates the exponential conversion directly into the oscillator core. This results in an efficient circuitry saving you build time, parts and costs.

PCB and face-plate are manufactured in the EU.

Features:
Functions
• Two saw tooth oscillators
• Bridged-T low pass filter with resonance control
• Triangle LFO with speed control, and routing to filter and/or oscillators
• Simple mixer and detune for oscillators

Controls
• LFO Speed, Filter Modulation, Osc Modulation
• Filter Cutoff, Filter Resonance
• Tuning, Osc2 Detune
• Osc1/Osc2 (Filter in)
• Output volume

Input/Output
• 1V/Oct CV for oscillators (0-5V)
• Gate (0-5V)
• Filter cutoff (0-5V)
• External filter input
• Volume controlled output
• LFO Speed (linear, via solder pad on back, 0-8V)
• Oscillator 2 detune (linear, via via solder pad on back, 0-8V)

DIY-Kit-Type:
THT-Kit-1. This is a Do-It-Yourself kit, not an assembled module. The kit includes all parts to build the module. Only trough-hole parts to solder. Make sure to check the build guide before you buy. For build guide, more info, videos etc. please check the buttons below.