<html><head><meta http-equiv="Content-Type" content="text/html; charset=UTF-8"></head><body dir="auto"><div dir="auto">Hello Dave,</div><div dir="auto"><br></div><div dir="auto">Ihad pretty good luck with ladderfilters ,I suppose :-)</div><div dir="auto">I've used 2N3904 for a Taurus vcf+vca, and I believe BC547 in a minimoog vcf+vca clone.</div><div dir="auto">For both of the builds I did, I matched both pairs of transistors across, but also matched the caps. It might be that they did not have to match the caps at the time, since they could simply buy them with a tight tolerance, but thats a bit harder these days.</div><div dir="auto">As others have mentioned, the vca is a big part of the sound as well. I built mine of the schematic by Marjan Urekar, so not quite adjusted to eurorack signal levels, it distorts REALLY nicely! I have used an attenuator in front to dial it back. And, I changed the order, as they are two sequential vca's. Footpedal in one, actual envelope in the other, not sure which one is first in mine, footpedal input is simply a pot.</div><div dir="auto"><br></div><div dir="auto"><br></div><div dir="auto"><br></div><div dir="auto"><br></div><div dir="auto"><br></div><div id="composer_signature" dir="auto"><div style="font-size:12px;color:#575757" dir="auto">Sent from my Galaxy</div></div><div dir="auto"><br></div><div><br></div><div align="left" dir="auto" style="font-size:100%;color:#000000"><div>-------- Original message --------</div><div>From: David G Dixon via Synth-diy <synth-diy@synth-diy.org> </div><div>Date: 10/06/2023 06:11 (GMT+01:00) </div><div>To: synth-diy@synth-diy.org </div><div>Subject: [sdiy] Yves Usson's Minimoog Filter </div><div><br></div></div>
<div><span class="776105503-10062023">Hello SDIY Team,</span></div>
<div><span class="776105503-10062023"></span> </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><span class="776105503-10062023"></span> </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><span class="776105503-10062023"></span> </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><span class="776105503-10062023"></span> </div>
<div><span class="776105503-10062023">Dave Dixon</span></div>
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