[sdiy] rene's ms20 filter clone questions

[René Schmitz]

Hi Christian and all,

creekree at gmx.de wrote:
> the thing is, that i am not really sure if i actually have some use for 
> that sort of filter.
> i want to know if i can use the filter to process audio (be it from an 
> elecric guitar, a x0xb0x, a bassdrum, a turntable or whatever) or if 
> this filter
> is only useful in a "modular" environment - with vcos and vcas and all 
> that (which i dont have - yet).

You can process any audio signals with it. However it might be useful to 
amplify external audio signals somewhat (A gain of maybe 5-10), else the 
resonance would scream way louder than the input signal when you push it 
into self oscillations. Levels of about 5Vpp are perhaps best.

> also: there is a point labelled "pitch" which is an input, i guess. what 
> does it do and what am i supposed to input in it?

Pitch refers to external control of the main cutoff frequency. (But 
since its not the only control, I call that "pitch" instead of 
frequency. Its the input which moves the frequency around.
Pitch -> Tonlage.) Usually this will come from a control source, like a 
keyboard (on Formant schematics you find the name Keyboard Output 
Voltage KOV) or a midi to voltage convertor.

If you don't need external control, you can leave the input open, or 
connect it to GND.

> furthermore there are two potis labelled Cv1 and Cv2 - cutoff? but why 
> two of them? ah wait - this is a stereo pot, yes?

No, these are control signals that you can attenuate with these. You 
might put an envelope and/or LFO signal there, and set the depth of the 
modulation. Or leave the inputs open if you don't use them.

Cheers,
  René

-- 
uzs159 at uni-bonn.de
http://www.uni-bonn.de/~uzs159