Doepfer Module A-103 (VCF 6) is a voltage controlled lowpass filter with a cut-off slope of -18dB/octave. It filters out the higher parts of the sound spectrum and lets lower frequencies pass through. The Cut-Off Frequency determines the point at which filtering takes effect. You can control this manually, or by voltage control (filter modulation, for instance by an LFO). Three CV inputs are available, and the sum of the voltages from these affects the filter cut-off. Resonance (or Emphasis) is adjustable all the way up to self-oscillation – in which case the filter behaves like a sine wave oscillator. A-103 uses a so-called transistor ladder with a slope of 18 dB/Octave as frequency controlling element. It is very similar to the transistor ladder of the A-120 (24dB Moog type low pass) but the ladder of the A-103 is a modification of the original Moog ladder and identical to the ladder used in the Roland TB-303 (base and collector of each transistor are connected).