[sdiy] BLIT/BLEP virtual analogue synthesis

[cheater cheater]

On Tue, Aug 3, 2010 at 16:54, Olivier Gillet <ol.gillet at gmail.com> wrote:
> Hi,
>
> I've already played with these techniques, but in the software world.
> I toyed a bit with the idea of doing this on an AVR for the Shruthi,
> but this is the kind of things that can quickly get extremely costly -
> over the simpler method of generating band-limited wavetables for
> saw/square and crossfading between them, Korg DWGS-style).

Not if you want sync or any real modulation

> The major
> lesson I got from the paper is that once you have a decent band
> limited saw and square, you can move on to other waveforms from it by
> integration, difference with a phase-shifted version...

The problem here is numerical accuracy

> But if you're looking at this for software, these things are a bit
> outdated compared to BLEP / polyBLEP anyway.
>
> Now back to your question. A 8kHz square wave has harmonics at 8 kHz,
> 24 kHz, 40 kHz, etc... If you sample it at 44.1 kHz with a soundcard
> with good brickwall filters, you'll see a sine wave at 8kHz. Heck, you
> won't be able to hear the difference between a sine and square at
> 8kHz, unless you have superman's ears. You'll hear the difference
> between a sine and a sawtooth if you can hear up to 16 kHz - I don't.

No, but your distortion pedal can and then you can too.

> So at those frequency, don't expect to see anything happening besides
> sine waves, but this is not really a problem.
>
> Given that BLEP gets more and more expensive as the signal frequency
> increases (more tails from bleps active at a given point in time), you
> could maybe setup something that progressively degrade to wavetables
> of band-limited signals as frequency increases to clear up CPU.

Can't you fix that with a multisampled BLEP table?

Cheers,
D.