[sdiy] Yves Usson's Minimoog Filter

David G Dixon dixon at mail.ubc.ca
Tue Jun 13 00:44:22 CEST 2023


So, I replaced a couple of the trimmers on my Minimoog filter board -- the
1k and 500R trimmers were one-turn wonders, and the 500R was actually a 470R
cheapo flat trimmer that shorted out every time I put a screwdriver in it.
I replaced them with proper 18-turn trimmers, and I think the circuit works
better now.
 
So, it seemed to work pretty well.  I was getting good filtering.  It still
didn't sound much like a Minimoog to me.  Also, I don't really like the way
that it responds to high resonance.
 
Then I swapped the feedback resistors on the input and output amplifiers
(56k to 120k on the input, 120k to 56k on the output) to make them both
unity gain and drive the filter a bit more.  This certainly did not improve
things.  At the highest input attenuator setting, the filter just sounds
harsh and unpleasant.  At a middle setting, it sounds much better, but
simply isn't loud enough.  Hence, that was a bad idea, and I will swap them
back.
 
Then, using the same VCO and ADSR settings, I switched to my Dr. Octature
Roland-style filter (but with gain cells to eliminate signal droop with
resonance) -- this filter simply sounds brilliant (to me).  It's loud,
snappy, has much more pleasing resonance, and "she responds like a limousine
brought alive on the silver screen" to incoming CV from the ADSR.
 
Maybe I just don't need a Minimoog filter.  Or maybe there is still
something wrong with it.  I don't know.  I'm half done building the same
board with 547/557 instead of 3904/3906.  I'm going to finish that board and
put it in the module to see if it is any better.  If not, then I will
probably just abandon the whole idea of building a Minimoog filter.
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://synth-diy.org/pipermail/synth-diy/attachments/20230612/a1a0b19f/attachment.htm>


More information about the Synth-diy mailing list