[sdiy] Dual VCO mixing. / first synth DIY project.

[cacofone]

At 03:38 PM 8/31/01, you wrote:

>Hi cacofone!
>
>At 00:08 31.08.01 -0500, cacofone wrote:
> >Magnus,
> >Yes, sounds pretty clear :) Gonna get started on making some VCO's and go
> >from there. I'll keep the sdiy list updated. I found a good VCO schematic
> >on the Emusic DIY page that has  tri, sq, sine, and I think it also had
> >ramp (might be wrong on the ramp) Can you suggest a VCO schematic that's
> >versatile and not that terribly hard for a beginner, or is the one there
> >recommended? I'd really like to have at least triangle, square, and I
> >really want sine, even though I know, yes, tri/square are easiest, and
> >perhaps I can add the sine in later after I've implemented square. I assume
> >I'd start with square and get that to function, then add the triangle
> >followed by sine.
> >
> >Any advice is greatly appreciated.
>
>You might check out the VCO3 at my website. (link is at the end of this
>message)

Great! Thanks for the info there.

>Usually the designs start either with a sawtooth (or ramp which is the
>same), or with a triangle oscillator from which the other waveforms are
>derrived.
>(The square is a by-product for a triangle oscillator, and thus pulsewidth
>can't be modified.)
>A sawtooth is frequently turned into a triangle by fullwave rectifying it.
>Then you can get a sinewave from that by applying a nonlinear function onto
>the triangle.
>The pulse waveform is usually derrived from the sawtooth by a voltage
>comparator.
>The VCO3 follows that design pattern.


Yeah, I've studied enough (and lurked on the list) long enough to learn the 
basic concepts of how to do it, but it's always nice and easy to follow a 
good schematic. I think some of the most important learning I do will be 
from the actual process of it, as I go along and choose to improve and add 
stuff to it.


> >I also assume that these can be compounded using the opamps to add more
> >VCO's in the future? I've got a fairly large case that I'm intending to
> >fill (used to be a tape deck cabinet), and this is my first DIY synth
>project.
> >
> >I read somewhere to do the power supply first, though I've seen pre-made
> >ones that are cheap, supposedly reliably, and wouldn't "waste" time. Any
> >thoughts?
>
>If they're dual ones (+/- 15V or so) then that is fine.

Yay! any suggested sources?

> >Can you or someone else elaborate a little more on what you mean by
> >inverted? I assume the polarity (-/+) but if I wanted to re-invert it, how
> >would I do so?
>
>You're right about polarity, everything is just upside-down.
>Another inverting opamp stage will re-invert your signal. But I wouldn't
>bother, for audio there is no difference.

Good to know I can eliminate redundant steps :)

>Cheers,
>  René
>--
>uzs159 at uni-bonn.de
>http://www.uni-bonn.de/~uzs159

Thanks for the link René.

Joshua K

>

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