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

[Magnus Danielson]

From: cacofone <pulse8 at goodtimetribe.com>
Subject: [sdiy] Dual VCO mixing. / first synth DIY project.
Date: Fri, 31 Aug 2001 00:08:25 -0500

> Magnus,

Hi.... (what ever your first name really is)

> Yes, sounds pretty clear :)

Goodie!

> 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.

It is customary to use a sawtooth (more common name than ramp)
waveform core in VCOs and then waveshape pulse, triangle and sine.

However, the triangle (and thus sine) does not get very well when
cooking it from sawtooth. However, cooking sawtooth out of triangle
and square should be fine.

> Any advice is greatly appreciated.

Check out the ASM-1 synth among others. This is a pretty good standard
oscillator.

> 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?

Either way, get a power supply early, you want to have it around to
test out the VCOs as you get them done.

> 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?

Toss it through a similar setup but with only one input.

That is, if you *really* require the right polarity.

Cheers,
Magnus