LM3900-based VCF

Gogledd

Hi all;

I've recently been trying to build a two-pole VCF with the LM3900 as the voltage control element, just to see how it would do. I'm basing the filter structure and CV system on an Osamu Hoshuyama phaser design, so I can't take credit for how it actually works!

I'm getting some rather unpredictable distortions whenever the filter is tuned to low frequencies (audio example attached). They seem asymmetrical and are influenced by whether the CV is rising or falling. I feel like I'm missing something obvious here.

Any ideas where I'm going wrong? Any guidance would be appreciated. Thanks!

Untitled.png

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Schematic for LM3900-based VCF

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output.wav

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LTSpice audio output for described circuit

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output.wav

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