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Simple filter and offset, Korg seems to be fine without using DACs for some of their synths. The Arp Odyssey reissue has a similar setup just using PWM</div>
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<b>From:</b> Synth-diy <synth-diy-bounces@synth-diy.org> on behalf of Andrey Salomatin via Synth-diy <synth-diy@synth-diy.org><br>
<b>Sent:</b> Tuesday, 27 October 2026 11:14 AM<br>
<b>To:</b> Synth-diy Mailing List <synth-diy@synth-diy.org><br>
<b>Subject:</b> Re: [sdiy] Korg Volca Bass service manual</div>
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<div>Very interesting! Thank you for sharing!</div>
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<div>Any ideas on what that input circuit for the VCO CV is and does? Looks like a summing amplifier and a filter, but it’s non-inverting? Is it doing some PWM conditioning magic?</div>
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<div>Andrey</div>
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<div>On 26. Oct 2026, at 22:00, Sean Ellis via Synth-diy <synth-diy@synth-diy.org> wrote:</div>
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<a href="https://cdn.hackaday.io/files/1698407266434560/korg_volca_bass_sm.pdf" id="OWA7c9cf023-9b69-9313-2ce4-422c948139ff" class="OWAAutoLink" originalsrc="https://cdn.hackaday.io/files/1698407266434560/korg_volca_bass_sm.pdf" data-auth="NotApplicable">https://cdn.hackaday.io/files/1698407266434560/korg_volca_bass_sm.pdf</a></div>
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Not sure if this has been shared but here's the manual, as usual some interesting circuits from Korg. Schmitt-trigger in the VCO and a very low parts count on the VCF, not a trimpot on board! Has anyone heard one of these? I'd be interested in how the filter
 sounds.  </div>
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