How the heck does the MS-50 filter WORK?
costello at seanet.com
Sun Jul 19 06:13:38 CEST 1998
Another embarassing post where I reveal how little I know about the
schematics on my own site. Anyway...
How the heck does the MS-50 filter work? I'm looking at the schematic
(which you can find at my site - http://www.seanet.com/~costello) and
realizing I don't know what is going on with it at all. I can figure
out some of it - it's a Sallen-and-Key filter (to be precise, it looks
like a variant of the "equal component value Sallen Key filter" in Don
Lancaster's book, "Active Filter Cookbook"). However, what is the diode
ring doing? And why the two op-amps providing the control voltage? I
would really be thankful if some DIY brainiac out there could do an
analysis of the filter, that I could put up on the web site if the
author approves (along the lines of "diodes x y and z act as the first
resistor following the first capacitor, which is this cap").
Another question: What do the diodes in the feedback loop do? I mean,
obviously they provide a clipping type of limiting, but what does that
do for the circuit? They are in the MS-20 too; what do they do there?
And finally: How do I adapt the circuit for +9 volts? ;)
P.S. My +9 volt obsession is simply out of wanting a compact pedal that
does this stuff. I'd like to have something that fits in a Budd box to
use with my guitar, or to fit on a tabletop for my TR-606.
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