Archive of the former Yahoo!Groups mailing list: MOTM

What's the low-frequency limit for the '420 and '440 filters? I see the
inputs are AC coupled, and I'm wondering if the bipolar buffers limit the
low-frequency response as well.

I'm interested in filtering control voltages, inspired partly by the '101
vibrato circuit and partly by trying to make a PLL with two '300's and the
ring modulator from the '110. I used the '820 lag as a cv filter for the
PLL with interesting results; depending on how you adjust the frequency and
tracking on the oscillator in the loop along with the lag time you get some
interesting 'wobble' early in the note, and it changes the timbre of the
note overall (like FM, I'd guess). But as I understand it, the '820 would
have a -6dB/oct response unlike the other filters.

Are there any filters in the works that will go down to DC or are they all
strictly audio filters?

...Craig