[sdiy] Korg Volca Bass service manual

[Sean Ellis]

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
[cid:63275c5a-01f4-4d2b-97e6-8a33682977f9]

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From: Synth-diy <synth-diy-bounces at synth-diy.org> on behalf of Andrey Salomatin via Synth-diy <synth-diy at synth-diy.org>
Sent: Tuesday, 27 October 2026 11:14 AM
To: Synth-diy Mailing List <synth-diy at synth-diy.org>
Subject: Re: [sdiy] Korg Volca Bass service manual

Very interesting! Thank you for sharing!

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?

Andrey

On 26. Oct 2026, at 22:00, Sean Ellis via Synth-diy <synth-diy at synth-diy.org> wrote:

https://cdn.hackaday.io/files/1698407266434560/korg_volca_bass_sm.pdf

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.
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