[sdiy] Experiment with bandlimited ramps

[Richard Wentk]

On 7 Jan 2009, at 00:49, Tom Wiltshire wrote:

> My own oscillator uses only 64 harmonics, no interpolation between  
> table samples, and no interpolation between tables. On the face of  
> it, you'd think it sounds awful, but in fact it's quite passably  
> good. I was encouraged to keep going by the Korg DW series synths  
> which inspired me - these used no interpolation either, plus being  
> only 8-bit at 50KHz sample rate, and yet sounded pretty good. I was  
> able to increase the resolution to 16-bit and the sample rate a  
> little to 62.5KHz.

I find that rolling off the top end of digital sources can reliably  
make them sound more 'analog' - so band limiting wouldn't necessarily  
be a problem. A brickwall lopass FFT filter can be an unexpectedly  
good way to make drum loops sound warmer and fatter.

Realistically, most of the Moog stuff is horrible by modern  
standards, with bargain basement op-amps and other nasties. So the  
bandwidth is limited anyway, especially if it's being recorded to  
tape. (Or played back from tape or vinyl.)

Sonically the animation is more important than the bandwidth. So far  
as I can tell that's a combination of noisy traditional pitch  
wandering with slight decorrelation among the upper harmonics.

If you synthesize saws with a slightly noisy harmonic spread, they  
sound rather livelier than a fixed single-cycle waveform.

Richard