Doepfer A-101-1 Steiner VCF

Module A-101-1 is a multimode filter that makes use of a non-inverting amplifier design. Up to three audio signals can be introduced simultaneously to various portions of the circuit and emitted from a common output. Each input corresponds to a different filter type: LP, BP, and HP—giving users plenty of options for sculpting unique sounds.
The source signal can consist of three entirely separate sounds or parsings of a single signal fed into each input. And since each of the inputs are normalled to the other, users can rest assured that they will have a wide pallette of sounds at their disposal. Additionally, the module features two outputs, one that uses the original circuit and another that implements an additional vactrol that is directly connected to the vactrol governing the resonance. In the case of the latter, the added vactrol can act as an attenuator or crude VCA that compensates for higher levels as the resonance increases.
A-101-1 FEATURES
Vactrol-based multimode filter
Three inputs, one for each filter configuration
2 LEDs for frequency and resonance indication
Two outputs, one of which utilizes an additional vactrol