A-155 Analog/Trigger Sequencer

The A-155 Analog / Trigger Sequencer is a well-equipped 2 x 8 step sequencer with three trigger tracks, one gate track and two control voltage tracks. Triggers 1 and 2 are always alternative, as are trigger 3 and the gate signal. Separate settings for “glide” (portamento) can be made for the two control voltages. In … Read more

A-101-2 Vactrol Lowpass Gate

A Lowpass Gate (LPG) is an odd device. It uses a vactrol circuit and couples a low pass filter to an amplifier (VCA). Then why not just use a filter and an amplifier separately? The LPG can be switched between VCF, VCA and the combination VCF / VCA! In addition, the module is built with … Read more

A-133-2 Dual VC Polarizer

The A-133-2 is a dual voltage controlled polarizer, meaning its input signals (audio or control voltages) can be amplified like a traditional VCA. With a negative control voltage or a corresponding manual setting, the input signals are amplified in inverted form. An input, a control voltage input, an output, as well as a manual controller … Read more

A-143-4 Quad VCLFO/VCO

The Quad VCLFO is actually almost a “real” VCO: It even has temperature compensation, which allows it to remain in tune even with external temperature fluctuations. Doepfer points out that the A-143-4 is not quite as accurate as the VCOs of the A-110 or A-111 series, but from my point of view it can be … Read more

A-141-4 Quad Poly VCADSR

The A-141-4 is a quadruple ADSR that is only 8 TE wide and is primarily intended for polyphonic applications. Therefore, there is only one set of controls for the envelope’s parameters – attack, decay, sustain and release, which affect all four envelopes equally. In addition, we find four control voltage inputs with bipolar attenuators for … Read more

A-110-1 Standard VCO

The A-110-1 is Doepfer’s “standard” oscillator. The “standard” sounds a bit disrespectful, is that something like a “cheap VCO with economy sound”? In terms of sound, the A-110-1 does not have to hide, not even from significantly more expensive oscillators! First of all, the waveforms on the oscilloscope don’t all look “exactly mathematical”, especially the … Read more

A-105-4 Quad Poly SSI VCF

The A-105-4 is a polyphonic filter module based on the SSM2024 integrated circuit (or its replica SSI2144). In principle, we have four A-105 filters with a common control in front of us: Cutoff frequency, resonance (called “Q” here) and input level can be set in the same way for all four filters or also controlled … Read more

A-111-4 Quad Precision VCO

The family of A-111 oscillators now includes an impressive 6 variants, all of which use the Curtis chip CEM3340 (or replica) with its triangular core and allow very precise tracking over 10 octaves and more. The A-111-4 is – nomen est omen – designed fourfold and also has a common “master” section, which affects all … Read more

A-132-8 Octal Poly VCA

The A-132-8 is a module designed for polyphonic operation with 4 voices with a total of 8 VCAs. Why so many VCAs, one might ask, wouldn’t 4 be enough? Two VCAs connected in series are responsible for each of the four synthesizer voices on the A-132-8: The first VCA always works linearly, the VCA afterwards … Read more