[sdiy] Ray Wilson Filter question

[harrybissell]

you have the 100K / 1K divider on the audio signal. on the other input, add a 1M /
1K
divider, tie the input to the wiper of a trimpot from +15 to -15  (maybe a 100K
trimpot)

This lets you introduce a DC offset to correct for the offset of the OTA.  It will
never be perfect
but it can be a big improvement, especially if you have fast attack times (thump)

H^) harry

synth at oldmail.charlielamm.com wrote:

> At the risk of sounding dense....I'm having trouble visualizing this
> 1M/1K mod....Do you mean run a 1M resistor from IC-2B pin 14 to ground, in
> addition to what's already there?
>
> > Adding a 1M resistor to this input (ie 1M / 1K divider) will allow
> > you to add
> > a trimming voltage to reduce the DC offset as well !   From my experience, you
> > need only
> > add the trimmer to one stage.
> >
> > H^) harry
> >
> > synth at oldmail.charlielamm.com wrote:
> >
> > > I am trying to use this Ray Wilson filter in something I am building:
> > >
> > > http://www.musicfromouterspace.com/analogsynth/statevariablefilter.html
> > >
> > > I am using +/- 15V instead of +/- 12V.
> > >
> > > I am also using mod CV of 0 to 5V--the circuit looks to me like it expects
> > > 0-10V for a good sounding filter freq sweep?
> > >
> > > To make this work, I think I need to change R6 to about 47K for the 0-5V
> > > CV for freq mod, and R14 to about 180K to accommodate the greater supply
> > > V's.  I can't think of any other mod necessary.
> > >
> > > Can anyone else?  Are my subs OK?
> > >
> > > Thanks in advance for any help.  --Charlie Lamm
> >