[sdiy] Simplest stuff to begin with, and a few questions

[harrybissell]

The reason that FEW people choose variable caps as the tuning
element is that they are only available in very small values, with a
very small tuning range.

You should consider that... look for those caps you want to use
before doing the design. Its very easy to design something that
you find (later) you cannot manufacture...

...especially if you use computer simulation (spice)

H^) harry

Robotboy8 at aol.com wrote:

> I noticed you mentioned variable caps in your oscillator... most
> people try
> to avoid this technique for synths.  There's nothing wrong with
> building an
> oscillator this way, but it'll be hard to get voltage control of the
> rate.
> It will probably work fine as an LFO, but you may find there are
> better
> oscillators to use as your main VCOs.

I realize this, but I'm not really looking for CV at this point - more
at something simple enough that I can actually finish it, and something
with a low enough parts count I could build many of them (I'm looking at
8, with xfades between each set of two for real-time morphing by hand).
In other words, at this point I'm mainly just trying to see if this
proposed oscillator will indeed oscillate.  And if all it's good for is
an LFO, at least it'll be a working LFO - as opposed to the countless
unworking audio-frequency oscillators I've started and never finished.

Basically, it's two transistors turning each other on and off.  I'm not
sure if the jack is placed in the right place.  I'm not sure where to
get variable caps.  I'm not sure what value the resistors next to the
caps should be.  I don't know why there are so many damn types of
transistor, other than NPN and PNP - and I"m unsure if I have those
switched around.  All I know is that I need an SPST switch to turn it on
and off, basically - I know what the components do, but not much about
the laws surrounding them.  I've tried and I've tried to comprehend
them, but it's just too much at once as soon as I try to do more than
one thing with Ohm's law.... but then, I tend to think better by doing
than staring, so I'm trying to jump in and do something I can actually
get done.

As for the signal levels, you're right but if I design all the modules
myself they'll all be working at +/-4.5v anyway.

Schematics now online:
www.geocites.com/tranoschem/oschem.gif