[sdiy] low voltage filters

[Ben Bradley]

I made a really crude VCF when I was in college (circa 1980), I
remember the schematic (mostly), I've been meaning to wire it up and
test it out again. I remember thinking "this thing works a lot better
than I could have imagined, seeing how crude the control element is."

I didn't know at the time that I wasn't the first to use a forward
biased diode, varying the the dynamic resistance with a current.

On Wed, Apr 19, 2017 at 3:38 PM, Chris McDowell <declareupdate at gmail.com> wrote:
> Howdy list!
>
> Wondering if anyone is aware of, or has any tips towards, some low voltage VCF designs. I've seen reports of people using LM13700s with a single 5V supply for VCAs, and their one-off forum posts made them seem happy, heh. I realize this would have very little headroom. I've also checked out Hoshuyama's site, which has a few battery-powered designs. Some things I've considered:
>
> - Perhaps LM13700 just works at 5V ¯\_(ツ)_/¯ (avoiding breadboard as long as possible…)
> - Discrete OTA with BJTs
> - MS-20 Style, like the monotron
> - Vactrol, H11F1, or similar
>
> The point of this is that I have DCOs and ADSRs working wonderfully in a 3.3V environment. Some dirt is okay, I say. Super ideally, I want to implement an SVF with a single 3.3V supply, suggestions toward reality / sacrifices are welcome. I imagine this would work fine with vactrols, but I don't want to design anything with parts I can't buy from mouser, hehe.
>
> Cheers,
> Chris
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