Hi, a question just out of curiosity (Sorry if this is not suitable here).

I found the sine waves from uVCF’s LPF, BPF, and HPF jacks are phase-shifted by pi/2. Is this because uVCF is designed so? Or is there some physics under the hood?

Hi, a question just out of curiosity (Sorry if this is not suitable here).

I found the sine waves from uVCF’s LPF, BPF, and HPF jacks are phase-shifted by pi/2. Is this because uVCF is designed so? Or is there some physics under the hood?

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The uVCF is a state variable filter topology. A good explanation of SVFs, including schematics is here: https://www.electronics-tutorials.ws/filter/state-variable-filter.html

Even without knowing the circuitry, you can see from each of the diagrams that basically ever mode of the filter is tapped from a different stage of the overall circuit. This page doesn’t go into it much, but each stage introduces its own phase shift to the signal, hence why the sine waves are also phase shifted.

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