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

[jays at aracnet.com]

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
>