[sdiy] VCO Jitter, Slop ...

cheater00 . cheater00 at gmail.com
Wed Jun 12 14:44:12 CEST 2013


On Tue, Jun 11, 2013 at 11:40 AM, Fast TriggerFish
<fasttriggerfish at gmail.com> wrote:
> What if you started on the assumption that the sound of classic VCOs
> can be closely replicated by feeding a perfect VCO into one saturation
> stage followed by a linear filter and a third saturation stage ?
> Then parameterise each section ( say input and ouput levels for 2*tanh
> sections, and a 4 band parametric eq for the filtering stage ).
> Feed a few periods of various perfect waveforms through it ( with
> adequate oversampling ) at various key frequencies and regress the
> parameters against classic VCO waveforms so that the output of the
> final stage matches the classic waveform in a well chosen measure ( I
> have to admit I'm not sure which one, maybe the least squares of the
> ampitudes and phases of an FFT ? )
> Maybe also regress some form of bleed of 50/60hz and harmonics into
> the oscillators.
> Then once you have regressed all your parameters for a set of key
> frequencies, decide on a way to interpolate them.
> Finally, check if the ears agree with your resulting VCO, and maybe
> tweak things by ear a little.
> If it works you may be able to store the final "regressed VCO" output
> into tables so that you don't have to actually compute these stages
> each time.
>
> Just thinking aloud here, If I was a DSP developer with access to
> hardware and wanted fat oscillators that's probably thing that I would
> try first.
> Does that sound reasonable ?
>
> JT

Given that you have hardware in front of you, have a go at it!


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