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Doepfer Musikelektonik logo

Analogue  Modular  System  A-100







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Owners Manual

48db/oct  Voltage Controlled Filter  (LP/BP)

The A-108 is a voltage controlled low pass filter based on the Moog transistor ladder design, buy has an 8 stage low pass filter with different slopes available: 6, 12, 18, 24, 30, 36, 42 and 48 dB per octave. In addition it features a band pass output. The 4 output assignments of the 8 filter stages are set with 4 jumper pairs (default for the 4 outputs is 12, 24, 36 and 48dB). Resonance can be adjusted up to self-oscillation, with an external feedback input enables the insertion of additional processing into the feedback path.

The frequency can be adjusted manually, or by voltage control. Three CV inputs (CV1, CV2, CV3) are available. CV2 and CV3 are equipped with attenuators. The filter audio input is very sensitive so that distortion - if desired. Self oscillation will break off at high distortion levels as the internal feedback signal is drowned out by the distorted audio signal. This feature may intentionally be used to create new sounds. In combination with the Voltage Controlled Mixer A-135 and the Morphing Controller A-144 a filter with voltage controlled slope can be realized (i.e. controlling the slope from 6dB to 48dB via CV).

Each of the 4 outputs can be jumpered to the one of the following filter stages (with jumpers available on the pcb, i.e. no wiring necessary):
Output 1: 6dB (only one jumper setting possible)
Output 2: 12 dB or 18dB
Output 3: 24 or 30 or 36 dB
Output 4: 42 or 48 dB

Other custom assignments (e.g. output 1 = 12 dB or output 4 = 24dB) can be hard-wired across the pcb header pins on the pcb.








Doepfer A-108