[sdiy] Analysis of frequency variation in analogue synths

[Richard Wentk]

On 3 May 2007, at 15:37, Colin f wrote:

> My point is that there is an untested assumption here about the  
> degree to
> which it depends on the kind of modulation.
> Before you go to the effort of carefully analysing all the possible
> influences, it's worth testing empirically whether a fairly simple
> combination of low and high speed cyclic variation plus a random  
> component
> modulating a digital oscillator's pitch and amplitude sounds any  
> more or
> less analogue than a real analogue VCO.
> Reproducing detail that you can't hear is wasted effort.

Yes, but this assumes that a steady state unfiltered waveform is  
likely to be audibly analogue.

Does that seem like a convincing assumption? Might it not be the way  
as much about the dynamics of the sound - pitch being only a small  
part - than the harmonic content?

> The failure of analogue modelling so far to fool the hard-core of  
> analogue
> fans is probably more economic than technical.

It depends on the quality of the models. If the models aren't  
detailed enough, the sound won't be convincing.

Considering that many softsynths use either the simplest possible  
model, or very nearly the simplest possible model, some differences  
are inevitable.

> Digital photos 10 years ago looked crap, but now they rival the  
> best 35mm
> film cameras.
> There's nothing spectacularly new being done - just increased  
> resolution.

But it's a much simpler problem. And anyone with a trained eye can  
still spot the difference between film and digital without too much  
trouble.

> I'd be amazed if anyone could pick out a modern digital envelope  
> generator
> from a hardware analogue EG in a blind test, with all other things  
> equal,
> i.e. CPU driving DAC driving VCA versus EG chip driving VCA.

Considering that many modulation circuits are clocked at a different  
rates which makes fast envelopes impossible, I wouldn't.

E.g. I find Reaktor frustrating because the default envelopes aren't  
nearly punchy enough.

And how many softsynth designers deliberately build in modulation  
breakthrough to add an extra transient click or thump to the start of  
the sound?

Richard