[sdiy] Square to Sine

[rburnett at richieburnett.co.uk]

Hi Tom,

Tom Wiltshire wrote:
> 
> From the document:
> 
> "Present implementations limit magic sinewaves to power line
> frequencies, possibly up to 400 Hertz."
> 
> and
> 
> "Unusual programming techniques are required as each and every
> microprocessor clock cycle is critical."
> 
> Sounds like exactly the sort of thing the SDIY list would get into!
> 
> and
> 
> "As many as 44,000 or more microprocessor instructions may be needed
> per power line cycle."
> 
> So it looks like full audio might be pretty demanding. Not impossible,
> perhaps, but at least demanding. For generating sines for a Hammond
> organ (just to take totally random example…) we'd only need up to
> 6KHz. Assuming the 44K-instructions-per-cycle guideline from above,
> that's a 264MHz processor!

Thanks for your comments and analysis.  I have to confess that I didn't 
read all of the particular document that I linked to, I just tried to 
quickly find something that described the technology I was thinking of.  
 From what is written in that document and your analysis it doesn't sound 
so tempting for audio rate sinewave generation.

> Still, like you, I can't help thinking there must be a (simpler) way…

Sending a digital sinewave from a lookup table straight to a DAC :-)

-Richie,