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<DIV dir=ltr align=left><SPAN class=789021419-11062023><FONT face=Helvetica>Hi
Jay,</FONT></SPAN></DIV>
<DIV dir=ltr align=left><SPAN class=789021419-11062023><FONT
face=Helvetica></FONT></SPAN> </DIV>
<DIV dir=ltr align=left><SPAN class=789021419-11062023><FONT
face=Helvetica>First of all, thanks to everyone for your comments. I
haven't had time to formulate a suitable response yet, but I'm taking them
all under advisement.</FONT></SPAN></DIV>
<DIV dir=ltr align=left><SPAN class=789021419-11062023><FONT
face=Helvetica></FONT></SPAN> </DIV>
<DIV dir=ltr align=left><SPAN class=789021419-11062023><FONT
face=Helvetica>Concerning pinouts, I'm well aware that 3904/3906 and 547/557 are
opposite pinouts with respect to the flat side of the TO-92 package (another
thing that just flabbergasts me about the abject stupidity of electronic
packaging, along with the fact that most common quad opamp ICs are upsidedown
with respect to the power pins -- clearly, it would have taken 10 seconds for
the designers to check on the correct pinouts, instead of creating a situation
where every user for 50 years onward has to remember that quad opamp chips go in
upsidedown).</FONT></SPAN></DIV>
<DIV dir=ltr align=left><SPAN class=789021419-11062023><FONT
face=Helvetica></FONT></SPAN> </DIV>
<DIV dir=ltr align=left><SPAN class=789021419-11062023><FONT face=Helvetica>The
filter works -- it just doesn't work well. It doesn't have very pleasing
resonance -- it goes from almost nothing to screaming like a banshee (and, yes,
I've used the correct pots). It also doesn't respond to CV very
well. I can't get it to respond to an envelope in the normal way.
Also, it just doesn't sound like anything -- my Roland-style Dr. Octature filter
sounds infinitely more Moogy.</FONT></SPAN></DIV>
<DIV dir=ltr align=left><SPAN class=789021419-11062023><FONT
face=Helvetica></FONT></SPAN> </DIV>
<DIV dir=ltr align=left><SPAN class=789021419-11062023><FONT face=Helvetica>Of
all the suggestions, I think that upping the input drive is the best one, and
I'm gonna try that as soon as I have time to get back out into the
workshop. I will replace that 56k feedback resistor with 120k to at least
make the input inverter unity gain. I'm also wondering about that 10k
resistor feeding into the 10uF cap on the input to the ladder -- that resistor
will divide down the input a lot, given that it then feeds into 470R + 220R to
ground. I'm thinking about shorting that 10k resistor to see what
happens.</FONT></SPAN></DIV>
<DIV dir=ltr align=left><SPAN class=789021419-11062023><FONT
face=Helvetica></FONT></SPAN> </DIV>
<DIV dir=ltr align=left><SPAN class=789021419-11062023><FONT face=Helvetica>This
is the problem I always have when I build circuits that I don't understand (and
I really don't understand how this ladder filter works, and my Multisim
simulations have been no help at all). I generally avoid doing so, but I
really wanted a Minimoog filter in my system. I'm tempted to do a
complete mathematical analysis of the filter, so I can get a handle on how it
works, but I just haven't had time.</FONT></SPAN></DIV>
<DIV dir=ltr align=left><SPAN class=789021419-11062023><FONT
face=Helvetica></FONT></SPAN> </DIV>
<DIV dir=ltr align=left><SPAN class=789021419-11062023><FONT
face=Helvetica>Cheers,</FONT></SPAN></DIV>
<DIV dir=ltr align=left><SPAN class=789021419-11062023><FONT
face=Helvetica>Dave</FONT></SPAN></DIV><BR>
<DIV dir=ltr lang=en-us class=OutlookMessageHeader align=left>
<HR tabIndex=-1>
<FONT size=2 face=Tahoma><B>From:</B> Jay Schwichtenberg
[mailto:jschwich53@comcast.net] <BR><B>Sent:</B> Sunday, June 11, 2023 10:33
AM<BR><B>To:</B> David G Dixon; David G Dixon via Synth-diy<BR><B>Subject:</B>
Re: [sdiy] Yves Usson's Minimoog Filter<BR></FONT><BR></DIV>
<DIV></DIV>
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<DIV><SPAN style="FONT-FAMILY: helvetica; FONT-SIZE: 14pt">Going with something
simple. They have different pin outs?</SPAN> </DIV>
<DIV class=default-style> </DIV>
<DIV class=default-style><SPAN
style="FONT-FAMILY: helvetica; FONT-SIZE: 14pt">Jay S.</SPAN> </DIV>
<BLOCKQUOTE type="cite">
<DIV>On 06/09/2023 9:08 PM PDT David G Dixon via Synth-diy
<synth-diy@synth-diy.org> wrote: </DIV>
<DIV> </DIV>
<DIV> </DIV>
<DIV><SPAN class=776105503-10062023>Hello SDIY Team,</SPAN> </DIV>
<DIV> </DIV>
<DIV><SPAN class=776105503-10062023>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.</SPAN> </DIV>
<DIV> </DIV>
<DIV><SPAN class=776105503-10062023>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.</SPAN> </DIV>
<DIV> </DIV>
<DIV><SPAN class=776105503-10062023>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 appreciated.</SPAN> </DIV>
<DIV> </DIV>
<DIV><SPAN class=776105503-10062023>Dave Dixon</SPAN>
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