The Doepfer A-121-2 Multi Mode Filter Modular Synthesizer is a voltage controlled multi-mode flter using a cut-off gradient of -12dB / octave. Four outputs are featured, each with unique characteristics – Low-Pass, Band-Pass, High-Pass & Notch (Band Reject). Filter effects occur at the frequency set by the cut-off, which can itself be set manually or manipulated via voltage control (for example an LFO or ADSR modulation filter). There are 2 CV inputs (control voltages are summed) and the Resonance can be adjusted all the way to self-oscillation, in which case it behaves as a sine wave oscillator.
The main features of the Doepfer A-121-2 Multi Mode Filter Modular Synthesizer include: