[sdiy] Sine-wave VCOs?

[Magnus Danielson]

From: Metrophage <c0r3dump23 at yahoo.com>
Subject: [sdiy] Sine-wave VCOs?
Date: Mon, 3 May 2004 08:15:57 -0700 (PDT)
Message-ID: <20040503151557.6086.qmail at web21408.mail.yahoo.com>

Hi CJ!

> I can't help but notice that practically every synth circuit I see
> which has a sine output was achieved by shaping another wave, typically
> the triangle. Is it really so hard to make sine VCOs, or are they just
> not desired? Of course, many schematics I have seen are just "function
> generators", probably precise but with no voltage control. How does a
> keyboard tracking VCF which self-resonates compare? I am not so much
> into subtractive synthesis, but it seems to me that filters might
> suggest ways to build sine VCOs

You are not far off. One way to generate a sine (and cosine) is to set up a
state-variable filter in ring-mod and then have a AGC that allows for the
amplitude to rise and stabilize. This is no magic. You should be able to
modify say the ASM-1 VCF to do it.

Cheers,
Magnus