ceithir

Manual

Size
Width: 58hp
Depth: 27mm

Power
+12: 410mA
-12: 390mA

Features
Quad stereo mixing VCA 
Morphable filter modes 
Stereo enhancement
Internal LFO modulation 
Optimised Oscillator mode 
Pingable resonance
Multiple limiter types

Description
The culmination of years of filter experimentation at Instruō, ceithir is a quad state-variable filter and resonator system that expands upon the sonic architecture first introduced in the I-ō47. Each of its four analogue filter cores can operate independently as a traditional state-variable filter, a resonant sine waveform oscillator, or a precision pitch-trackable resonator, offering low pass, band pass, high pass, notch, and morphable responses alongside extensive CV control. Integrated waveshaping and soft-limiting circuits allow ceithir to move effortlessly from subtle harmonic enhancement to aggressive resonant saturation, while dedicated strike inputs transform each filter into a playable percussive voice.

Far beyond a conventional filter bank, ceithir is designed as an animated stereo sound environment. Advanced Morph and Width controls generate immersive spatial movement through phase manipulation by all-pass filtering, while four internally routed trianglewave LFOs create evolving modulation networks capable of continuously reshaping frequency, resonance, stereo enhancement, and timbre. With parameter linking, global frequency control, and integrated master stereo routing options, ceithir delivers the unmistakably musical character of Instruō filters on an entirely new scale.