Doepfer A-121-2 12b Multimode Filter Eurorack Module

Module A-121 is a voltage-controlled multi-mode filter with a cut-off slope of -12 dB / octave. It is the successor of the obsolete module A-121. The circuitry is different from the A-121 which used the obsolete CEM3320 filter circuit. The sound of the new module A-121-2 is identical to filter of the Dark Energy II/III.

These are the most important features of the module:

voltage-controlled multi-mode filter with a cut-off slope of -12 dB / octave (idential to the filter of the Dark Energy II/III but has been expanded by the voltage controlled resonance feature)
four simultaneous outputs are available, each with different characteristics: low-pass (LP), high-pass (HP), band-pass (BP) and notch (N)
manual control Frq. for the cut-off frequency of the filter (the cut-off frequency determines the point at which the respective filter effect appears)
two inputs for frequency control by means of external control voltages (frequency modulation, e.g. by ADSR or LFO):
control voltage input FCV1 without attenuator, about 1V/octave sensitivity
control voltage input FCV2 with attenuator FCV for the adjustment of the modulation depth of input FCV2
frequency range about 10Hz ... 20kHz
Manual control Q for the resonance of the filter
control voltage input FCQ without attenuator for external voltage control of the resonance
resonance up to self-oscillation, in which case the module will behave like a sine wave oscillator even without audio input signal
audio input Audio In with attenuator Lev. for the adjustment of the filter input level (beyond about pos. 5 clipping/distortion occurs with typical A-100 audio levels)