[sdiy] Rick Jansen's Moog ladder filter design question...

Tim Ressel timr at circuitabbey.com
Thu Mar 13 19:26:03 CET 2014


HI,

Probably just need to change R17 to get the correct range. The change should be ratiometric, so a good place to start would be 590 ohms.


Tim Ressel
Circuit Abbey
503-750-9331
timr at circuitabbey.com




________________________________
From: Jean-Pierre Desrochers <jpdesroc at oricom.ca>
To: Synth-diy at dropmix.xs4all.nl 
Sent: Thursday, March 13, 2014 10:41 AM
Subject: [sdiy] Rick Jansen's Moog ladder filter design question...


I'm about to build the modified Moog ladder filter you posted here:

http://dropmix.xs4all.nl/rick/Emusic/Moog/moogvcf_schematic.gif

I would like to change the resistor R15 2k37 1% for a 1k 1% 3300ppm tempco
but this will change the overall
A3 opamp gain and screw up the 1v/oct ratio on input called "KOV"
and all the other CV inputs.
Since I don't know the exact mv/oct value this schematic needs at Q1 base
for a good oscillation tracking, can you help ?
I think I'll just have to also change both P3 & R17 values right ?
But to what values ?

Thanks !
JP

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