<div dir="auto"><div>Hi David,</div><div dir="auto"><br></div><div dir="auto">Here are some thoughts your original post triggered. They may or may not be helpful:</div><div dir="auto"><br></div><div dir="auto">1. I recall reading about some manufacturer of ladder filters clones, explaining how they deliberately did not match all transistor pairs in the ladder. I vaguely recall only the first (and perhaps last) pairs were matched... With the rationale that things became to sterile with everything tightly matched.</div><div dir="auto">2. As others have said: input level plays a crucial role</div><div dir="auto">3. What is your personal reference for the Moog ladder sound? Could it be one of the more recent bass-compensated versions?</div><div dir="auto">4. The VCA into which the VCF feeds, also plays a role in the sound of the Minimoog. Could that be what you're missing?</div><div dir="auto"><br></div><div dir="auto">Regards,</div><div dir="auto"><br></div><div dir="auto">Rutger</div><div dir="auto"><br></div><div dir="auto"><br><div class="gmail_quote" dir="auto"><div dir="ltr" class="gmail_attr">Op za 10 jun. 2023 15:04 schreef Jean-Pierre Desrochers <<a href="mailto:jpdesroc@oricom.ca">jpdesroc@oricom.ca</a>>:<br></div><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><div lang="FR-CA" link="blue" vlink="purple" style="word-wrap:break-word"><div class="m_163878690543440365WordSection1"><p class="MsoNormal"><span>In 2016 I built a Moog 904A VCLPF clone<u></u><u></u></span></p><p class="MsoNormal"><span>from Moog’s modular original schematics.<br>I’m VERY happy about the resulting behaviour of it.<br>Very fatty and precise sound !<br>I used matched pairs of BC550C NPN’s for the ladder job.<br>I supposed the 904A VCF design is very close to the one the minimoog uses..<br>Anyway, all my projects files are open source for anybody..<br><br><u></u><u></u></span></p><p class="MsoNormal"><span><a href="http://www.arcenson.com/projects/Modular/M104A_Lowpass_Filter_Moog_904A_clone/Specifications/M104A_VCLPF_schematic.pdf" target="_blank" rel="noreferrer">http://www.arcenson.com/projects/Modular/M104A_Lowpass_Filter_Moog_904A_clone/Specifications/M104A_VCLPF_schematic.pdf</a><u></u><u></u></span></p><p class="MsoNormal"><span><u></u> <u></u></span></p><p class="MsoNormal"><span><img border="0" width="822" height="625" style="width:8.5625in;height:6.5104in" id="m_163878690543440365Image_x0020_2" src="cid:image001.jpg@01D99B7A.2077AE50"></span><span><br><img border="0" width="299" height="613" style="width:3.1145in;height:6.3854in" id="m_163878690543440365Image_x0020_3" src="cid:image002.jpg@01D99B7A.2077AE50"><u></u><u></u></span></p><p class="MsoNormal"><span><u></u> <u></u></span></p><div style="border:none;border-left:solid blue 1.5pt;padding:0cm 0cm 0cm 4.0pt"><div><div style="border:none;border-top:solid #e1e1e1 1.0pt;padding:3.0pt 0cm 0cm 0cm"><p class="MsoNormal"><b><span lang="FR">De :</span></b><span lang="FR"> Synth-diy <<a href="mailto:synth-diy-bounces@synth-diy.org" target="_blank" rel="noreferrer">synth-diy-bounces@synth-diy.org</a>> <b>De la part de</b> David G Dixon via Synth-diy<br><b>Envoyé :</b> 10 juin 2023 00:09<br><b>À :</b> <a href="mailto:synth-diy@synth-diy.org" target="_blank" rel="noreferrer">synth-diy@synth-diy.org</a><br><b>Objet :</b> [sdiy] Yves Usson's Minimoog Filter<u></u><u></u></span></p></div></div><p class="MsoNormal"><u></u> <u></u></p><div><p class="MsoNormal">Hello SDIY Team,<u></u><u></u></p></div><div><p class="MsoNormal"> <u></u><u></u></p></div><div><p class="MsoNormal">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.<u></u><u></u></p></div><div><p class="MsoNormal"> <u></u><u></u></p></div><div><p class="MsoNormal">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.<u></u><u></u></p></div><div><p class="MsoNormal"> <u></u><u></u></p></div><div><p class="MsoNormal">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.<u></u><u></u></p></div><div><p class="MsoNormal"> <u></u><u></u></p></div><div><p class="MsoNormal">Dave Dixon<u></u><u></u></p></div></div></div></div>_______________________________________________<br>
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