[sdiy] SAW core VCO flyback time

[rsdio at audiobanshee.com]

There are two aspects of digital synthesis that require deviation from the "ideal" (or naive) waveform.

The most important issue is that any harmonic above the Nyquist frequency will be folded back down below Nyquist and appear as aliasing, no matter how fancy the DAC and reconstruction filter. In other words, a naive "square" or "saw" sample stream, generated in a simple manner, will have aliasing built in - and the aliased harmonics cannot be removed because they're in between the harmonics that are still at their natural frequency. To combat this problem, band-limited synthesis is used in the digital realm to more accurately reproduce an ideal analog waveform that is sampled correctly.

A secondary issue is modeling the imperfections of specific analog oscillator implementations. However, if the above issue of aliasing is not handled properly, then any attempt to model analog imperfections will be ruined by digital aliasing.

Brian Willoughby


On Aug 30, 2016, at 10:21 AM, Richie Burnett <rburnett at richieburnett.co.uk> wrote:
> BTW, I think it's fascinating how the analogue designers strive to achieve perfection in the form of "instantaneous" sawtooth resets, low-distortion sinewaves, and symmetrical triangle waveforms without the little nipple at the peak.  Whilst digital synthesiser designers strive to model the imperfections of old analogue oscillators because they are somehow perceived to be the reason for their unique character.  Taken to the limit, analogue oscillators will become perfect and sterile, whilst VA models will inherit all of the "character" ;-)
>