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Altar description

Crossfade smoothly between Band-pass, Low-pass & High-pass

Altar filter configuration can be smoothly crossfaded from BP to LP to HP. This unusual filter type arrangement brings out very nice harmonics and nuances. It is really suited for CV control. The CV input has an attenuverter.

Resonance is under voltage control with attenuverter as well allowing for great timbre modulations. It is particularly useful to create accent patterns à la 303 which boost the resonance a bit.

You can beef up the signal at Altar‘s input with the gain knob. It will distort the filter core for wild sounds.

The filter tracks 1V/oct for 4-5 octaves and can turn into a very sweet sine oscillator. Try using it with Miasma as a waveshaper!

Altar has been designed by Mathieu Fröhlich (creator of Squarp’s Hermod) as part of a dream synth he is working on.

Altar back

in action

Specs &


  • Gain control to distort the filter core
  • Color knob to crossfade from band pass to low pass to high pass filter
  • Resonance
  • Frequency with 1V/Oct control
  • Attenuverters on Color, Resonance and Frequency CV

Technical characteristics

  • 3-pole filter
  • 18dB/oct cut
  • 1V/Oct with trimmer on the PCB, tracks up to 4-5 octaves
Power35mA @ +12V
30mA @ -12V
0mA @ +5V
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ManualComing soon