[sdiy] Sine VCO

[Magnus Danielson]

From: Michael Zacherl <sdiy-mz01 at arsprototo.at>
Subject: Re: [sdiy] Sine VCO
Date: Fri, 28 Mar 2003 10:51:56 +0100

> Hi,
> I'd be interested too!
> 
> Since a waveformconverter for a good sinewave is 
> rather componentintensive a set of "classic" VCOs 
> for additive synthesis would be expensive (IMHO).
> 
> Besides linear FM (err .. did you mean linear?) 
> are you looking for Oct./V characteristics as well?
> 
> How about modifying the charge/discharge part of 
> the sawtooth circuit, to get a triangle instead of 
> a saw and to smoothen it out afterwards?
> (Just a rough, ugly, untested thought).

This is how the Buchla 258 and 259 oscillators actually worked. They had a
triangle VCO core, but generated the sawtooth out of the tri and square
waveforms. The triangle you get this way is better than what most saw-to-tri
converters do, so you get closer only on that part alone.

> How clean do you need this sine wave? Has it to be 
> an ideal one?

There are more advanced diode/resistor networks which have less distorsion
from ideal curve. The arctan distorsion often used isn't that perfect.

The SAS-VCO has the classical saw-tri-sine chain.

The Buchla schematics you find though my webpages...

Cheers,
Magnus