A-101-1 Vactrol Multitype Input VCF

The Vactrol filter has several special features. Most striking: There is a separate input for each of the operating modes lowpass, bandpass and highpass. This allows several very different sound sources to be treated differently in a single filter. Only the cutoff-frequency and the resonance (and resonance control) are common. If that’s too much for … Read more

A-108 6/12/24/48dB Low Pass Filter

Like the A-120, the A-108 filter is also based on the Moog transistor cascade, but uses not only 4 poles, but 8 and can therefore have a maximum slope of 48 dB. That sounds sensational at first, but in real synthesizer life it’s not that extremely spectacular. What is striking, however, is the fantastic and … Read more

A-124 Wasp Filter

The Wasp Filter uses the somewhat idiosyncratic filter circuitry of the 1978 EDP Wasp synthesizer. The 12 dB filter produces very peculiar, “wild” distortions at higher resonances, which, however, always remain very easy to control. Possibilities and structure of the module (but not the layout of the front panel) are similar to the A-106-5 SEM … 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-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