Electronic Music 411 - filter circuit

filter circuit
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thread starter

05/06/08 + jp

does anybody here know of a not to complicated filter circuit. like a VCF? i'd like to add a voltage controlled filter to some of my diy stuff.

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Replies

05/06/08 + daswesen

the steiner parker filter, also called the synthacon filter, is sweetz. There is an opamp version lying around as well:

link

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05/06/08 + jp

thanks!
have you tried this filter circuit?

do you have also - ah - something with - ah - less components?

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05/06/08 + daswesen

here's the opamp version without the mixer volume thing for the inputs, much more manageable.

link

cheers, manuel

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05/06/08 + jp

that's great, thank you!

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05/06/08 + ricemutt

this is what i'vae been looking into making:
link

link

a sallen key filter. From what i've seen, it's the simplest "reso" filter. But i'm a n00b. The first link there is a sallen key filter you can use without a bipolar power supply, which seems to be a requirement for most Op amp based circuits. Then again, i'm a noob ;P

link

good luck, let us know what you end up going with, I am planning on working out some filters too!

I'm sure you've tried using basic RC filters right? Those are super easy but not too versatile, i've found.

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05/06/08 + flies

the filter on the wsg was recommended to me. here's the schem: link everyting after R11 is the filter. it has one advantage in being powered by +9V only.

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edited: May 07 2008 + daswesen

The difference between circuits with bipolar power supply and not is most of the time pretty "simple". Your audio signal oscillates around a certain voltage, 0V in bipolar, and something often called Vb (bias voltage) (or Vr in that first ms20 circuit i think). So in the wsg circuits, you can see that the virtual ground of the filter opamp is held at Vb at the middle of 9V and 0V, giving a Vbias of 4.5V. That's ok to hold it there this way cause the opamp has a very very big input impedance. If you start to mix Vb stuff with circuits that eat up power though, Vb will get pulled around so in the end, unipolar circuits are more difficult to handle than a bipolar one. Also, you Vbias is more prone to getting noise than if you have a real GND.

EDIT: My point being: it's worth it building a bipolar power supply

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05/07/08 + jp

these are great circuits. i think i try one of the vactrol designs at the beginning. looking forward to having my diy crap filtered. i will post results as soon as it's working.

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edited: May 07 2008 + flies

her's a simple VCF, also from tim escobedo: link

everybody needs more CV!

re this circuit, see link <- really odd behavior!

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