[sdiy] very simple vco

[harrybissell]

Hello Luca

your question is (lol)... to simple as well

A simple VCO is very easy (and we can help) but if you are looking
for a VCO that is 'musically' useful as well, it is much more complex
(as you have seen).

Most VCO are a current controlled oscillator, and a voltage to current converter,
usually
with exponential response.

It is the exponential response which makes the oscillator most useful for music
(there will
be some differing opinions)... and the expo circuit is the most difficult to build
as well.
Expo controlled oscillators will respond in equal 'octaves' to a linear voltage
input.  So that
if 1V = C then 2V, 3V, 4V are all higher C notes as well.

A very simple VCO is found in National Semiconductor applications note AN72,
figure
50.  It is shown with the LM3900 (now quite rare) but it can be built with other
opamps
as well.  It would probably not be an ideal synthesizer VCO... but might be useful
as a low
frequency oscillator, where the faults of the design would not be noticible.

H^) harry

luca rossini wrote:

> dear community,
> i am an unexperienced (except an am radio..) italian physics student who wants
> to build a simple analog sinth.
> decidinc to start from the basics, i'd like now to build a simple, almost
> primordial VCO, but i can find only very complex ones on the web. could You
> help me in my research? how to?
>
> thank you very much
> luca rossini
>
>