Unsupported Browser
The web browser that you are currently using is no longer supported, and as such features of this website may not work as expected. We advise you to update to a currently supported browser (such as Chrome, Edge, or Firefox) to improve your security, speed, and overall experience.
Key Features
The Doepfer A-101-1 Vactrol Steiner Filter is a flexible and highly functional modular filter with three distinct modes, designed to work with your Eurorack synthesizer. Taking a classic design from the '70s, the Doepfer A-101-1 creates the same unique, warm and smooth filtering as the original with the bonus of improved versatility. Using Sallen-key topology, the Doepfer A-101-1 Vactrol Steiner Filter offers a multi-mode design, capable of performing as a low-pass, high-pass and band-pass filter simultaneously. Normalised inputs allow you to copy your audio signal from one input to the rest to create a unique mix of all three filter styles, resulting in a notch filter.
Improving on the original design, the Doepfer's resonance control follows a smooth and powerful response but can be driven into oscillation at extreme levels. To ensure the natural and smooth filtering is maintained, a dual-output design has been created whereby the original output is powered by the resonance control and increases the output levels and the other is a compensated output that maintains output levels despite resonance increases.
Product Ref: 220466
In traditional Steiner-style filters, resistors are used for the frequency controls, however, in the A-101-1 these are replaced with vactrols. These vactrols are controlled by a logarithmic current source for the internal LEDs. Vactrols are a non-linear source with an extremely slow response time that injects slew into the attack and release of your sound source. Whilst not as responsive as other controllers, they do inject a distinctive sound within your audio. A sharp attack can be softened and a quick release can be expanded. When applied to a filter such as the low-pass filter within the A-101-1, you can add thick and luscious bass melodies to the foundation of your tracks.
Taking inspiration from the original design, the Doepfer A-101-1 goes one step further by offering the ability to patch in all three filter types simultaneously instead of having these selected via a switch. Three normalised inputs with attenuators for low-pass, band-pass and high-pass allow you to copy one audio input source to the rest of the inputs if nothing is patched in. The result of this is some very interesting mixing of filtering types to create unique sounds for your productions. You can patch in a typical sawtooth wave and blend between both filter types to create a distinctive notch filter or 'frequency panning' that smooths out some harsh frequencies to sit within your mix.