COTA

Multimode filter with soft clipping mode

This is a 10HP wide four pole multimode filter module capable of -24dB/octave low pass, -12dB/octave low pass and +/-6dB/octave bandpass outputs simultaneously. The filter core is based on four identical cascaded current controlled integrators. This is similar to the topology found on the filters in the SH series of monosynths as well as the CEM3320, IR3109 and SSM2040 filters of the classic polyphonics.

At high resonance, it's called 'feedback' here, the COTA VCF will oscillate well over the whole of the audio band with a clean sinewave. The module also features a feedback input which breaks the internal feedback path that controls the resonance. This means that additional modules can process the -24dB output before feeding it back into the COTA's feedback input. This allows a large variety of new timbres to be created. And it also allows for voltage controlled resonance by using a VCA module to go between the COTA's -24dB output and feedback input.

The module has two audio inputs, each with its own mini level control, which are mixed together before being sent to the filter core. The mixer can be operated in either 'clean' or 'soft clip' modes. Clean mode will simply mix the signals together and feed them cleanly into the filter core. Soft clip mode will gently limit the maximum voltage output of the mixer rounding off the top and the bottom peaks of the audio signal. In soft clip mode the asymmetry control allows you to force the mixer's output harder into the negative soft clipping zone distorting the audio in an interesting way.

www.oakleysound.com/COTA-e.htm