Saturday, January 16, 2016

Doepfer A-121 Multimode Filter Re-Design

A-121-2 Re-design
We all knew a re-design of the Doepfer A-121 Multimode Filter has been in the pipeline for a while, due to the unavailability of certain chips inside.

Since the beginning this has always been one of my favourite filters, because of it's sophisticated sound and the VC infut for resonance control. Oh, and the multiple simultanuous outputs...

At Namm 2016 Doepfer will present the A-121-2, the successor of the obsolete module A-121.
The circuitry is totally different from the A-121 which used the obsolete CEM3320 filter circuit. 

Module A-121 is a voltage-controlled multi-mode filter with a cut-off slope of -12 dB / octave.
Four simultaneous outputs are available, 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, right up to self-oscillation, in which case it will behave like a sine wave oscillator.

The sound of the new module A-121-2 is identical to filter of the Dark Energy II but has been expanded by the voltage controlled resonance feature (like the original A-121).

Read all about the specs of the original A-121 at

The modules will cost Euro 120.00 and will be available around March 2016


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