Entferner LE – Low-Pass Filter

Entferner LE is a mono, resonant, and self-oscillating 12dB low-pass filter.

It is a simplified but more aggressive sounding version of the Entferner L.

Entferner filters, in general, are based on a cascade of very versatile 6dB filters. In the case of the Entferner LE filter solely two of the filters are used, and the algorithm is tuned to be capable of an even more aggressive sound when activating the resonance color mode.

Since the filter is using internal saturation, the sound is highly dependent on the input voltages. Red LED lights beside the ports indicate any voltage overdrive. If the LED is blinking from time to time, the filter is operating in its sweet spot. If the LED is continuously red, the filter will still work but might result in a harsh sound or unwanted behavior.


  • The self-oscillation is not pitch-perfect over the whole filter range.
  • Some aliasing may occur in case of extreme cutoff, resonance and/or drive values.
  • Audio rate modulation is possible, but the filter behaves differently to what you might expect.
CutoffThe cutoff frequency controls the spectral content of the sound. A cutoff can be entered in the range of 10Hz-18kHz.
Cutoff – ColorAlter the sound based on the cutoff frequency.
Cutoff – External ModulationControl the cutoff frequency based on the signal coming in at the external modulation port. A setting of ±100% equals 1V/oct. Even using high modulation voltages will not increase the cutoff frequency above 18kHz.
DriveDrive controls the amount of the internal saturation. Drive is entered in the range of ±100%. It will not drastically in-/decrease the overall volume of the filtered sound. When lowering the drive amount the resonance gets more prominent. When raising the drive the sound will get more saturated.
ResonanceResonance controls the amount of feedback at the cutoff point in the spectral content. Resonance is entered in the range of 0%-100%. Where 0% is no resonance and 100% is the maximum. If the resonance is set to a high value the filter will start to self oscillate.
Resonance – ColorAlters the resonance when activated. This enables even more prominent resonance when using high drive values.
Resonance – External ModulationControl the resonance based on the signal coming in at the external modulation port. Even using extreme modulation voltages will not result in resonance outside of the allowed range.

Tips & Tricks


With sufficient resonance the Entferner filters are self-oscillating. To use the filter as a playable oscillator you only have to set the CV port of the Cutoff to e.g. 100% (and thus 1V/oct) and wire it up.

Red cable = modulates (in this case) the Cutoff

Blue cable = the OUT port is the oscillator signal

Hint: You can use the Cutoff to tune the oscillator to your needs.

Note: The Entferner LE package is available via the VCV Rack library.

Note: The Entferner LE package is sold via the VCV Rack library.

Version History

Version 2.0.6 (2021-12-10)

  • Improved lights when the module is bypassed

Version 2.0.5 (2021-12-04)

  • Rack 2.0 compatible version
  • Supports “Bypass”
  • Supports “Light bloom” settings
  • Optimized graphics performance (GPU usage)

Version 1.0.3 (2020-07-07)

  • Entferner LE: fixed; modulation could have caused a 0.0Hz cutoff frequency
  • added link to the online manual in the popup menu

Version 1.0.2 (2020-06-26)

  • Entferner LE: performance improvements
  • Entferner LE: optimized self-oscillation handling

Version 1.0.1 (2020-06-25)

  • Initial release


Oxidlab holds the copyright for the product concept, algorithm, and support material (e.g., manual).

Visual Concept and Artwork: Chris Corrado