[sdiy] 566 , was Re: Midwest Analog Product Books

[john mahoney]

Michael Bacich wrote:
>
> What if you were to simply use a much larger main timing capacitor?
I'm
> thinking something like about 10 times the size of the cap in Tom's
original
> design.  That would effectively move the whole range of the VCO down
...

> P.S. -- BTW, I haven't seen his circuit, but if the accuracy of the
> quadrature outputs is somewhat frequency-dependent...

Thanks for your input. Changing the cap is one of the things that I'd
try. Yes, it's so basic that even I would try it! :-) It's just not
clear from the text whether the "slumping" triangle shape is inherent
to the 566 at low frequencies. We'll see, eventually. I'll try to
breadboard it soon.


> P.S. -- BTW, I haven't seen his circuit, but if the accuracy of the
> quadrature outputs is somewhat frequency-dependent, then you might
also have to
> accordingly adjust some cap and resistor values in that part of the
circuit as well,
> if you want to range everything down into LFO territory.

It's mainly dependent on the shape of the triangle wave. Using the
standard comparator technique, you convert the tri to a square; this
additional square wave will then be 90 degrees out of phase with the
chip's built-in square output, as long as the triangle has a good
waveshape.
--
john

P.S. to Harry: While although can be useful, too, I find that but
usually works better, though however and also sometimes get the nod.
:-)