G-Storm Electro Pro VCF, Recreation Of The Sequential Pro-One Filter As Eurorack Module

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G-Storm Electro Pro VCF, based on the Alfa AS3320 chip is an analog recreation of the Sequential Pro-One filter as Eurorack module

The Sequential Pro-One is one of the best vintage monophonic synthesizers, especially for very intense and fat bass sounds. So it is no wonder that Behringer wants to bring this classic black on the market as Pro-1 in a Eurorack version, similar to the Model D. But we are still waiting for the release date. One of the highlights of the Pro-One is certainly its noble filter which can score especially with a brilliant resonance.

If you do not want to immerse yourself in the Behringer world, there is now an option to get this great filter for the Eurorack format, even before the Behringer version. G-Storm Electro, an indie developer has released Pro VCF, a faithful recreation of the iconic 4-pole Pro-1 filter in Eurorack format.

G-Storm Electro Pro VCF


The Pro VCF module features two selectable filter slopes, the original 24dB/oct and a 12dB/oct. The core lies on the Alfa AS3320 filter chip based on the original Curtis. This chip can be found in countless synthesizers like the Sequential Pro-One, Prophet 5 rev3, Drumtraks, Crumar Trilogy, Stratus, Elka Synthex…

It includes in total 3 CV inputs including two for the cutoff frequency and one for the resonance, each with an attenuator. With the help of two signal inputs also with attenuators, you can overdrive the filter. At full resonance, the Pro VCF can also self-oscillate.


  • Inputs – 2 Audio Inputs, 3 CV Inputs
  • Outputs – 1 Mono Output
  • Current – 10mA +12V, 11 -12V, 0mA +5V (not used)
  • Depth – 22mm
  • Width – 8HP, 40.5mm

G-Storm Electro Pro VCF is available now for $120 USD + shipping exclusively from their Reverb.com webshop.

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