[sdiy] VCO reset time

[Magnus Danielson]

From: Don Tillman <don at till.com>
Subject: Re: [sdiy] VCO reset time
Date: 05 Jun 2004 00:47:46 -0700
Message-ID: <m2brjy8mzh.fsf at till.com>

>    > Date: Fri, 4 Jun 2004 09:37:40 -0400 (EDT)
>    > From: Tony Clark <clark at andrews.edu>
>    > 
>    > Before settling on a sawtooth core years ago, I had played around
>    > with triangle cores, but I found that I had a problem with the
>    > waveshaping aspect.  The tri-to-saw conversion is not good in
>    > that, in typical circuits, the wave is at double frequency to the
>    > triangle wave.
> 
> Double frequency?  Heh-heh.
> 
>    > However, if you use a bit more circuitry you can achieve a
>    > corrected frequency sawtooth, but the waveform is glitchy and
>    > unsuitable for LFO applications.
> 
> There are ways to do it without glitches.  Buchla's VCO for instance. 

Check out
http://rubidium.dyndns.org/~magnus/synths/companies/buchla

The 258 and 259 schematics should be of primary interest.

> The triangle-to-saw and saw-to-triangle converters are actually very
> similar at some basic level -- they both switch between inverted and
> noninverted versions of the original waveform with offsets.

Yeah, put the benefit from a standard triangle core is that you got the
correct phase of the squarewave to start from.

Cheers,
Magnus