[sdiy] Sine VCO - tri to sine converter

[Richard Wentk]

At 09:29 29/03/2003 -0800, Tim Ressel wrote:
>Yo,
>
>Richard maked an excellent point here. I keep falling
>into my "HP-lab-perfect" mode and try to make
>everything as sterile as possible. But this is
>subtractive synthesis: harmonically-rich waveforms are
>filtered to create timbres. If your ramps are as
>curve-free as Catherine Zeta-Jones, and your filters
>are as clean as rap lyrics, so what?

More than that it's the imperfections that give synths their character.

I *hate* the idea of having a modular with perfectly stable VCOs. If I want 
that kind of precision I'll use Csound or Reaktor. Slight random drifting 
is what makes analogue analogue. It doesn't sound the same without it.

>I have learned something recently: what is important
>is that our circuits are **Well Behaved**. The VCA has
>no bumps or pops, the filters don't wig out past 6
>volts, that kind of thing.

I'd agree about the filters. But I suspect a big part of the punchy sound 
of our favourite modulars comes from small amounts of CV breakthrough.

I think there's a huge difference between designing for musicality and 
character and designing for textbook perfection. I remember one VCO design 
I was working on took on a very unappealing character as soon as I buffered 
the outputs with TLO72s. Of course the textbook says that distortion is 
negligible. But is it *really* negligible when presented with a dynamic 
signal with a varying timbre and complex transients? You can't test for 
that kind of thing with a sine wave test tone.

I think we all recognise that some opamps sound different to others. I also 
think no one has much of a clue why.

As an interesting experiment, try breadboarding a textbook perfect op-amp 
buffer and then put a very short voltage spike through it. Even allowing 
for bandwidth limiting, what you get out often doesn't look much like what 
went in.

My ideal modular wouldn't just have a selection of modules, but a selection 
of modules with different sound characters. e.g. many different kinds of VCOs.

>Also, it's important to HAVE FUN!!!!

That too. :-)

Richard