AW(2): Re: butter and pole locations

[Don Tillman]

   From: Haible_Juergen
   Date: Fri, 31 May 96 10:40:00 PDT

   > Maybe it is interesting to be able to change the relative positions
   > of the poles with pots on a filter ?
   > Is that really relevant in timbre characteristics ?

Yes.

   Build a 4-pole with discrete OTA's and give each OTA a separate
   expo converter.

OR, if you want to stick with a Moog ladder filter topology it's
obviously possible to use a swtich to select different cap values for
the ladder stages.

But why do something with a switch when you can voltage control it?
You can add some dc current source pairs and inject these currents
into the different ladder stages to raise the frequencies of the poles
of those stages (as well as the ones above).

  -- Don