[sdiy] Yves Usson's Minimoog Filter

David G Dixon dixon at mail.ubc.ca
Sat Jun 10 06:08:36 CEST 2023

Hello SDIY Team,
I've built a ladder filter on my own PCB layout from Yves Usson's Minimoog
ladder filter schematic, and I must confess that the results are less than
stellar.  The filter works, but not terribly well, and it sounds nothing
like a Minimoog.  I used 2N3904 and 2N3906 instead of BC547 and BC557, but I
matched all of the transistor pairs in the ladder, and matched the four
transistors at the top and bottom of the ladder as well as the other four
transistors, using Ian Fritz's transistor matching circuit (which I also
laid out and built on a PCB).  I did not try to match the one PNP to the
current driving NPN below the bottom of the ladder.
Does anyone here have any experience with this schematic?  Will it change
anything if I replace the 3904s with 547s, etc?  Everything else was exactly
as specified in the schematic.  This was my second attempt to build from an
Yves Usson ladder filter schematic.  My "Raging Bull" Taurus filter didn't
work at all.
I just want to know if there is some fundamental flaw in this schematic
before I spend too much more time with it.  Any insights would be most
Dave Dixon
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