Doepfer A-122 24dB Lowpass (CEM)

24dB low pass filter based on a Curtis filter circuit which is known from many polyphonic 1980s synthesizers. It features voltage control of cutoff frequency and resonance; self-oscillation is possible, too.

The A-122 is buit around the integrated filter circuit CEM3379 by Curtis which has been in used in synthesizers like the Ensoniq units ESQ1 and SQ-80 or the Sequential Prophet 200. This IC's brothers, the CEM 3372 and 3378 were used in the Prophet VS, Akai VX600 as well in the Oberheim units Matrix-12 and Xpander. You can expect classic 80s sound from this module.

It is a low pass filter with a slope of -24dB per octave, voltage controlled cutoff frequency and resonance. Latter goes up till oscillation and generates a sine wave then.