[sdiy] FatMan Hacking

[Tony Allgood]

>The ladder filter normally has unity resonant frequency gain.

Two ways that I, and others, have used to overcome this:

1. Increase the overall gain of the filter as resonance is increased.
The Roland SH-2000 does this, as did the System 101 I think. And my own
VCF-1, of which I thought was very clever and unique until I saw the
schems for the SH2000. This has the benefit of keeping S/N high too.

2. As you say Don, simply adding the resonance path to the output
signal. This works well and is easy to do with OTAs. I did this in my
SuperLadder. The early schematics are still on Tony Clark's archive
site.

On a side note: I believe the Korg Polysix actually turns up the volume
of the whole instrument to compensate for the drop in passband gain when
Q is turned up.

Regards,

Tony Allgood, Penrith, Cumbria, England

Oakley Modular Synth and TB3030:
www.oakleysound.com/projects.htm
My music: www.mp3.com/taklamakan