SV: Re: SV: RE: Re: [sdiy] Rene's ms20 filter clone

[harrybissell]

The MS-20 filter is a Sallen-Key design... it should be screaming at you

and trying to tear your face off at most settings.  If it seems "subtle"

to you, its not working right yet...

H^) harry

Karl Ekdahl wrote:

> The problem is that there isn't really a point where
> thing start/stop happening, it's just decaying
> linearly in volume & *i think* cutoff. I can hear and,
> very much, see (I have a soundcard-scope) the
> resonance though so that is working now.  and it seems
> to me that there are no sub-frequencies laying
> around..
>
> thanks!
>
> Karl
>
> --- jays at aracnet.com skrev:
>
> > Karl,
> >
> > That might be the way it works.
> >
> > There is not a lot in the expo circuit to control
> > the scaling and base freq. So it could drive the
> > frequency down to very low (sub-audio) and you
> > wouldn't hear anything or it could even cut the
> > signal off completely.
> >
> > Here's an experiment. Put a very low freq signal
> > (20-30Hz) into the filter, turn the freq pot to
> > where you see a difference in the signal on a scope
> > or hear a difference in the sound. Do the same with
> > a high freq (12 kHz or more). Measure the voltage at
> > the pot wipper in each case. Ok if you know the
> > frequency and the voltage you can figure out where
> > the minimum and maximum usable voltage is and figure
> > out what the scale is (whether its really 1V/oct).
> >
> > If you don't have a scope or frequency counter but
> > do have a computer with audio software you might be
> > able to figure the frequencies you're using.
> >
> > Jay S.
> >
> > Karl Ekdahl wrote:
> >
> > > After looking at the schematic i can't possibly
> > > understand how it would *not* work as a vca? Where
> > is
> > > the signal supposed to go when the cutoff is
> > turned to
> > > -15v? I found a shorted-out cap and a 470 ohm
> > resistor
> > > instead of 470k at the base of the expo-converter,
> > so
> > > now i can hear suttle resonance and frequency
> > changes
> > > while turning the pots. But still the volume goes
> > to
> > > zero while turning the CV pot all the way down?
> > Where
> > > am i supposed to find the signal when it's turned
> > > down??
> > >
> > > Karl
> > >
> >
> >