[sdiy] Newbie alert :-)

[René Schmitz]

Hi John and Nicolai,

john mahoney wrote:
> Addendum #1

> P.S. to Rene: You may want to update your link to Scott as found on
> http://www.uni-bonn.de/~uzs159/vco4069.html

Thanks for the hint. Done that!

Nicolai, Welcome to SDIY!
My advice would be to get yourself a simple amplifier and a speaker to 
be able to monitor your sounds. An "active PC multimedia speaker set" 
would work, for example. Don't use your precious HiFi speakers, there is 
always a risk of damage.
Usually synth circuits aren't designed to drive speakers (or low 
impedance headphones) directly. With 600ohms headphones this is usually 
ok, though.
You can use your soundcard to view waveforms on the PC. THere are some 
programs out there that allow that. For serious work, get a scope.
Also you need a suitable (read: dual) power source for your experiments. 
For starters two batteries might do. As a beginner I simply used two 
wallwarts for that.

About the VCO4069, I think that it is pretty much as simple as it can 
get. Also it does work amazingly well for the little effort. And there 
is a complete layout that shows how to build it on a piece of perfboard.
If you work systematically, there shouldn't be trouble duplicating it.
As others have pointed out you can leave out the pulse shaper, if you 
want it more "basic". There are probably simpler circuits, that are 
voltage controllable, but usually these don't meet the requirements for 
a musical use. That is the frequency as a function of voltage should be 
either linear or exponential. So that the frequency, or the perceived 
pitch are directly proportional to the applied control voltage.
But if it makes you happy, you can apply a control voltage to the 
"control voltage" pin of your 555 oscillator, and change its frequency 
by that. But the tuning range is relatively narrow, and the frequency 
doesn't change neither linearly nor exponential with the applied voltage.

Cheers,
  René

PS. My schemos were drawn with Corel Draw. But nowadays I use XFig for that.

-- 
uzs159 at uni-bonn.de
http://www.uni-bonn.de/~uzs159