The A-121 is a multimode voltage controlled filter (VCF) with a cut-off slope of -12 dB/octave. It provides four simultaneous output, each with different characteristics: low-pass, band-pass, high-pass and notch (or band reject). The cut-off frequency determines the point at which the respective filter effects appear. The frequency can be adjusted manually, or by voltage control (filter modulation, for instance by an LFO or ADSR). Two CV inputs are available, whose control voltages are summed. Resonance (Emphasis or Q ) can be adjusted manually, or by voltage control (VCQ), right up to self-oscillation, in which case it will behave like a sine wave oscillator.
- Width: 12TE/12HP/60.6 mm
- Depth: 55 mm measured from the rear of the front panel
- Current draw: 30mA
A-121 Multimode Filter (VCF2) at Doepfer Musikelektronik