6..36dB VCF Lowpass/Highpass

6..36dB VCF Lowpass/Highpass
6..36dB VCF Lowpass/Highpass

This is the Eurorack version of my NGF 36dB VCF. I have brought out the 6dB, 12dB, 18dB, 24dB, 30dB and 36dB poles. You have two audio inputs for easy mixing sound sources. And CV inputs for linear TM, log TM, envelope, V/Oct tracking and emphasis. The exponential circuit is temperature compensated with KTY81-110. If the 12dB output is patched back to input 2 the filter can serve as a sine oscillator.

Specs and features

  • 36dB voltage controlled low pass and high pass filter
  • Two inputs for easy mixing
  • 6dB, 12dB, 18dB, 24dB 30dB, 36dB output
  • HP/LP switch
  • Positive and negative ENV control with sign changer
  • Temperature compensation with KTY81-110
  • CV inputs for linear TM, log TM, envelope, V/Oct tracking and emphasis
  • Usable as sine oscillator
  • Runs on +/-12V and +/-15V (with minor resistor value changes for best performance)
  • Power consumption around 60mA negative rail, 65mA positive rail

The documentation and the Gerber files for download can be found in my website.

6..36db VCF Highpass/Lowpass: Main board schematic
6..36db VCF Highpass/Lowpass: Main board schematic
6..36db VCF Highpass/Lowpass: Control board schematic
6..36db VCF Highpass/Lowpass: Control board schematic

Straight forward design. Six state variable filter cells are connected together in series, The output of each filter cell is brought out. There are a lot descriptions of those state variable filters out there. I feel no need to add another one.

6..36db VCF Highpass/Lowpass: Side view
6..36db VCF Highpass/Lowpass: Side view
6..36db VCF Highpass/Lowpass: Populated control PCB
6..36db VCF Highpass/Lowpass: Populated control PCB
6..36db VCF Highpass/Lowpass: Populated main PCB
6..36db VCF Highpass/Lowpass: Populated main PCB

2 thoughts on “6..36dB VCF Lowpass/Highpass

  1. Wow! this filter is impressive, I wish I could hear it.

    Just a random question, on top of this blog page appeared a 16 step sequencer picture, it is done? I cannot found the information here, I’m curious after seen it

    • This was my first build when I came back to SDIY. A three row/16 step sequencer. Completely build on stripboard. Still working after all this years. Only hand sketched schematics. Nothing to publish. Pictures only. The next post.

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