[sdiy] Digital oscillators

[Antti Huovilainen]

On Sun, 28 Dec 2008, Tom Wiltshire wrote:

> I don't exactly how good the technique is supposed to be, but I'd be bloody 
> astounded if it could generate an alias-free square wave at half the sample 
> rate.

Getting right up to nyquist is somewhat tricky, but say 0.95x nyquist is 
no problem (wasteful for resources but in no way difficult). With BLEP the 
problem is reduced to FIR filter design.

> To be honest, I''d be impressed if you could generate a noise-free 
> *sine* wave at that frequency without heavy filtering afterwards. I know 
> (from bitter experience!) that it isn't as easy as I thought it would 
> be, even with a 60+KHz sample rate and a 2048-entry wavetable.

You did use interpolation I hope?
With linear interp, you shouldn't need larger than 64..256 entry lookup 
table.

I'll try to get around to posting simple example code for alias free 
sawtooth synthesis with BLEP once I get back from holidays.

Antti

"No boom today. Boom tomorrow. There's always a boom tomorrow"
   -- Lt. Cmdr. Ivanova