[sdiy] FatMan Hacking ( and I dont mean hitting me with an Axe!)

[Magnus Danielson]

From: harry <harrybissell at prodigy.net>
Subject: Re: [sdiy] FatMan Hacking ( and I dont mean hitting me with an Axe!)
Date: Sat, 27 Oct 2001 15:47:00 -0400

> I have not seen an 18db State Variable Filter...
> 
> I do not have sufficient "guru" points to say that it cannot be done...

Well, I don't know if I have sufficient guru points either, but I will
stick out my big nose (I guess it is preferred over my big fanny) and
say that it can be done, you can also set up a 4-pole if you really
want to.

I've seen loooooong leapfrog ladder filters, which to some degree is
quite related, so it should indeed be possible.

I would actually take a peek at the Matrix-12/Xpander filter section,
I beleive they did something similar. That filter section is among the
most flexible I've seen. Haven't spent quality time over the schematic
thought.

> but the SVF is basically a summing amp and two inverting integrators...

Well, the integrators does not have to be inverters, that's just the
variant of the SVF which saves op-amps and grown to become popular. If
you run with OTA outputs with buffers (such as CA3094 or indeed the
popular 13600/13700) you skip over the inverting side and run
non-inverting mode.

> If you add one more the feedback is going to get VERY funny... at least.

Without another integrator? No, not that much fun...

> Why not just build a clone of the TB-303 filter and ADD it to the fatman...
> that would comemuch closer to the sound u want.

Possibly.

Cheers,
Magnus