[sdiy] Casio CZ resonant waveforms / Windowed Sync

[Adam Inglis]

Sounds gorgeous! - sometimes the rez waves on the CZ can sound a bit  
brittle, but not these.

Now I want a filter-sweep knob on my CZ101... ;-)

On 24/07/2011, at 11:56 PM, Tom Wiltshire wrote:

> Hi All,
>
> I've been messing with using the windowed sync technique that Casio  
> used for 'resonant waveforms' on the CZ synthesizers:
>
> http://www.electricdruid.net/images/cz/czresonantwaves.mov
>
> (6.5Mb mov)
>
> The technique is described on the CZ wiki page, but the Deep  
> Synthesis site has much more detail:
>
> http://en.wikipedia.org/wiki/Casio_CZ_synthesizers
> http://homepage.mac.com/synth_seal/html/cz1.html
>
> In short, it's a simple digital hard sync effect, but multiplied by  
> a 'window waveform' to avoid the alias-causing discontinuity. In  
> this case, the window is a simple downwards ramp, so that the  
> waveform tapers to zero where the discontinuity would have appeared.
>
> What shape window you use changes the sound considerably since  
> you're doing a multiplication in the time domain(ring mod) which is  
> equivalent to a convolution in the frequency domain. In English,  
> roughly, the harmonics of the window shape get multiplied by the  
> harmonics of the waveshape.
>
> It's very simple to do, and gives a pretty good result. What you're  
> hearing is 16-bit 48KHz, with an analog lowpass after it at about  
> 1KHz or so (I repurposed some LFO hardware I'd designed). There's  
> some distortion from my speakers being too loud for the computers  
> mic, and the video is back-to-front, but neither of those bugs are  
> the algorithm's fault! You could easily double the sample rate and  
> give yourself another alias-free octave, and for the sine-based  
> waveform, that would be enough.
>
> Hope you like it.
>
> Regards,
> Tom
>
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>



regards
Adam Inglis
http://www.adambaby.com