<html><head><meta http-equiv="Content-Type" content="text/html; charset=utf-8"></head><body style="word-wrap: break-word; -webkit-nbsp-mode: space; line-break: after-white-space;" class="">I in no way meant to give the impression that it was the same circuit. I meant that it was by design intended to resonate and effect the sound. Serge was an assistant to Subotnick at CalArts and designed his system to do much of what the Buchla did, but at a much lower price so the students could own one. Ironic, given how expensive Serge systems got later.<div class=""><br class=""></div><div class="">Mark</div><div class=""><br class=""></div><div class=""><br class=""><div class=""><br class=""></div><div class=""><br class=""></div><div class=""><br class=""><div><br class=""><blockquote type="cite" class=""><div class="">On 26. Nov 2022, at 23:16, S Ridley via Synth-diy <<a href="mailto:synth-diy@synth-diy.org" class="">synth-diy@synth-diy.org</a>> wrote:</div><br class="Apple-interchange-newline"><div class=""><div dir="ltr" class="">Just for the record, the Serge resonant filter used a different circuit - used 2 pole MFB filters (spaced maj. 7th).<div class="">The EMS filter band (stand-alone and Synth 100) used 2 pole Sallen Key LP and HP stages. </div><div class=""><br class=""></div><div class="">Steve</div></div><br class=""><div class="gmail_quote"><div dir="ltr" class="gmail_attr">On Tue, 22 Nov 2022 at 11:23, mark verbos <<a href="mailto:mark@verboselectronics.com" target="_blank" class="">mark@verboselectronics.com</a>> wrote:<br class=""></div><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex"><div class="">I have one of these. Definitely has “dramatic changes in sound”. In fact, everything that goes through it sounds like it went down the tube of a vacuum cleaner. The pots on the filters are trims, not on the panel and just regular single pots. The panel controls are just level sliders. It is pretty similar to the Serge Resonant EQ, which I’m sure is no accident. It does a good job of taking normal synth sounds and making them more weird, acoustic and less placeable as normal synth sounds. Buchla’s later filterbank, 296 Spectral Processor does a much better job of leaving the signal alone when all the bands are zeroed. But, those filters are 3 stages deep and the module has almost a million trim pots.<div class=""><br class=""></div><div class="">Mark</div><div class=""><br class=""></div><div class=""><br class=""><div class=""><br class=""></div><div class=""><br class=""></div><div class=""><br class=""></div><div class=""><br class=""><div class=""><br class=""><blockquote type="cite" class=""><div class="">On Nov 22, 2022, at 12:08 PM, Mike Bryant <<a href="mailto:mbryant@futurehorizons.com" target="_blank" class="">mbryant@futurehorizons.com</a>> wrote:</div><br class=""><div class="">
<div dir="ltr" class="">
<div style="font-family:Calibri,Arial,Helvetica,sans-serif;font-size:12pt;background-color:rgb(255,255,255)" class="">
yes that was what I thought. But surely for the traditional comb effect you need to sweep the frequency up and down with the keyboard. This would just kill certain frequencies pretty dead forever. Of course you can adjust the Q and freq of the resonance
to move these dead-spots, but that's on a per filter basis so couldn't be ganged pots (I assume unless they built a special megagang pot)<br class="">
</div>
<div id="m_-2882856511452786995m_4555582649120982379appendonsend" class=""></div>
<hr style="display:inline-block;width:98%" class="">
<div id="m_-2882856511452786995m_4555582649120982379divRplyFwdMsg" dir="ltr" class=""><font face="Calibri, sans-serif" style="font-size:11pt" class=""><b class="">From:</b> Roman Sowa <<a href="mailto:modular@go2.pl" target="_blank" class="">modular@go2.pl</a>><br class="">
<b class="">Sent:</b> 22 November 2022 10:58<br class="">
<b class="">To:</b> Mike Bryant <<a href="mailto:mbryant@futurehorizons.com" target="_blank" class="">mbryant@futurehorizons.com</a>>; synth-diy mailing list <<a href="mailto:synth-diy@synth-diy.org" target="_blank" class="">synth-diy@synth-diy.org</a>>; Lanterman, Aaron D <<a href="mailto:lanterma@ece.gatech.edu" target="_blank" class="">lanterma@ece.gatech.edu</a>><br class="">
<b class="">Subject:</b> Re: [sdiy] Buchla 295 10-band comb filter topology</font>
<div class=""> </div>
</div>
<div class=""><font size="2" class=""><span style="font-size:11pt" class="">
<div class="">I believe they are inverted like that to cause more dramatic changes to
<br class="">
the sound as some frequencies will be canceled out between bands.<br class="">
Otherwise it would be just plain boring graphic equalizer.<br class="">
<br class="">
Roman<br class="">
<br class="">
W dniu 2022-11-22 o 11:41, Mike Bryant pisze:<br class="">
> They are just bandpass filters - one pot in the feedback changes the <br class="">
> freq and one changes the Q. And they both interact with each other of <br class="">
> course.<br class="">
> <br class="">
> But why he inverts every other band into the summing amplifier is a <br class="">
> mystery to me.<br class="">
> <br class="">
> ------------------------------------------------------------------------<br class="">
> *From:* Synth-diy <<a href="mailto:synth-diy-bounces@synth-diy.org" target="_blank" class="">synth-diy-bounces@synth-diy.org</a>> on behalf of <br class="">
> Lanterman, Aaron D via Synth-diy <<a href="mailto:synth-diy@synth-diy.org" target="_blank" class="">synth-diy@synth-diy.org</a>><br class="">
> *Sent:* 22 November 2022 10:01<br class="">
> *To:* synth-diy mailing list <<a href="mailto:synth-diy@synth-diy.org" target="_blank" class="">synth-diy@synth-diy.org</a>><br class="">
> *Subject:* [sdiy] Buchla 295 10-band comb filter topology<br class="">
> Does anyone recognize the topology Don is using here in the bandpass <br class="">
> sections?<br class="">
> <br class="">
> <a href="http://fluxmonkey.com/historicBuchla/buchlaFiles/Buchla_2950_200.jpg" target="_blank" class="">
http://fluxmonkey.com/historicBuchla/buchlaFiles/Buchla_2950_200.jpg</a> <br class="">
> <<a href="http://fluxmonkey.com/historicBuchla/buchlaFiles/Buchla_2950_200.jpg" target="_blank" class="">http://fluxmonkey.com/historicBuchla/buchlaFiles/Buchla_2950_200.jpg</a>><br class="">
> <br class="">
> The low and high bands are 3-pole Sallen-Keys, but I’m not sure what’s <br class="">
> going on in the middle filters. It looks kind of like a multiple <br class="">
> feedback filter, but instead of having a resistor to ground like in <br class="">
> Figure 1 here:<br class="">
> <br class="">
> <a href="https://sound-au.com/project63.htm" target="_blank" class="">https://sound-au.com/project63.htm</a> <<a href="https://sound-au.com/project63.htm" target="_blank" class="">https://sound-au.com/project63.htm</a>><br class="">
> <br class="">
> There’s some weirdness with a 3rd capacitor connecting to the resistive <br class="">
> feedback back.<br class="">
> <br class="">
> Aaron Lanterman, Prof. of ECE, Georgia Tech<br class="">
> My blog on Education and Innovation: <br class="">
> <a href="https://edupocalypsenow.wordpress.com/" target="_blank" class="">https://edupocalypsenow.wordpress.com</a>
<br class="">
> <<a href="https://edupocalypsenow.wordpress.com/" target="_blank" class="">https://edupocalypsenow.wordpress.com</a>><br class="">
> My blog on Electronics and Programming: <br class="">
> <a href="https://lantertronics.blogspot.com/" target="_blank" class="">https://lantertronics.blogspot.com</a> <<a href="https://lantertronics.blogspot.com/" target="_blank" class="">https://lantertronics.blogspot.com</a>><br class="">
> My YouTube channel on Electronics and Programming: <br class="">
> <a href="https://www.youtube.com/c/lantertronics" target="_blank" class="">https://www.youtube.com/c/lantertronics</a>
<br class="">
> <<a href="https://www.youtube.com/c/lantertronics" target="_blank" class="">https://www.youtube.com/c/lantertronics</a>><br class="">
> <br class="">
> <br class="">
> <br class="">
> <br class="">
> _______________________________________________<br class="">
> Synth-diy mailing list<br class="">
> <a href="mailto:Synth-diy@synth-diy.org" target="_blank" class="">Synth-diy@synth-diy.org</a><br class="">
> <a href="http://synth-diy.org/mailman/listinfo/synth-diy" target="_blank" class="">http://synth-diy.org/mailman/listinfo/synth-diy</a><br class="">
> Selling or trading? Use <a href="mailto:marketplace@synth-diy.org" target="_blank" class="">marketplace@synth-diy.org</a><br class="">
> <br class="">
</div>
</span></font></div>
</div>
_______________________________________________<br class="">Synth-diy mailing list<br class=""><a href="mailto:Synth-diy@synth-diy.org" target="_blank" class="">Synth-diy@synth-diy.org</a><br class=""><a href="http://synth-diy.org/mailman/listinfo/synth-diy" target="_blank" class="">http://synth-diy.org/mailman/listinfo/synth-diy</a><br class="">Selling or trading? Use <a href="mailto:marketplace@synth-diy.org" target="_blank" class="">marketplace@synth-diy.org</a><br class=""></div></blockquote></div><br class=""></div></div></div>_______________________________________________<br class="">
Synth-diy mailing list<br class="">
<a href="mailto:Synth-diy@synth-diy.org" target="_blank" class="">Synth-diy@synth-diy.org</a><br class="">
<a href="http://synth-diy.org/mailman/listinfo/synth-diy" rel="noreferrer" target="_blank" class="">http://synth-diy.org/mailman/listinfo/synth-diy</a><br class="">
Selling or trading? Use <a href="mailto:marketplace@synth-diy.org" target="_blank" class="">marketplace@synth-diy.org</a><br class="">
</blockquote></div>
_______________________________________________<br class="">Synth-diy mailing list<br class=""><a href="mailto:Synth-diy@synth-diy.org" class="">Synth-diy@synth-diy.org</a><br class="">http://synth-diy.org/mailman/listinfo/synth-diy<br class="">Selling or trading? Use marketplace@synth-diy.org<br class=""></div></blockquote></div><br class=""></div></div></body></html>