[sdiy] Filter Help

Tom Wiltshire tom at electricdruid.net
Fri Feb 23 15:02:36 CET 2018


+1 what Olivier said. Inverting op-amp mixer ahead of the CV input to get the scaling right and flip the signal so it’s the way up you expect and you’re good. The addition of diodes (half-wave precision rectifier) to protect against negative voltage on the Ripples schematic is a nice touch too.

The Shruthi design can do that stuff in software, so it saves the parts, but for something exposed to the outside world, that should all go in.

Tom

==================
       Electric Druid
Synth & Stompbox DIY
==================

> On 23 Feb 2018, at 08:34, Olivier Gillet <ol.gillet at gmail.com> wrote:
> 
> The Shruthi is 0.46878 V/Octave (128 semitones mapped to 5V). That's why you must find it very sensitive to CV!
> 
> For a 2164 CV scaling circuit with V/O adjustment, check the Ripples schematics:
> https://mutable-instruments.net/modules/ripples/downloads/Ripples-v40.pdf
> (Around B2).
> 
> It's not specific to any filter type.
> 
> On Fri, Feb 23, 2018 at 1:41 AM, Tim Ressel <timr at circuitabbey.com> wrote:
> Hi
> 
> I am trying to get a 2164 SVF design to behave. I can't seem to get the frequency scaling right. It is very sensitive to CV. I thought you can make a volt/oct filter out of it. btw I am going off the Shruti schematic. Anyone got some stick time on this puppy?
> 
> -- 
> --Tim Ressel
> Circuit Abbey
> timr at circuitabbey.com
> 
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