[sdiy] Dithering 8-bit waveforms (was Re: PPG or Prophet VS waves for class)

rburnett at richieburnett.co.uk rburnett at richieburnett.co.uk
Wed Jul 18 12:09:52 CEST 2012


Okay, thanks for clarifying.

If your aim is to force low-order harmonics down in amplitude, have you 
looked at magic sinewave techniques?  There might be something of use in 
this technique:

http://www.tinaja.com/magsn01.shtml

These are effective in 1-bit PWM applications like motor drives for 
forcing low-order harmonics of the coded sinewave to zero.

-Richie,


On 2012-07-18 10:59, Olivier Gillet wrote:
>> I'm not sure how adding noise to a short wavetable of say 256 
>> samples can
>> de-correlate the quantisation noise.
>
> I have never claimed that what I was doing was truly decorrelating 
> the
> noise. I just aim at changing its spectral shape. Actually my mistake
> is to call this "dithering" while the technical term is more
> "noise-shaping" (though both often go hands in hands). What is
> happening here is that the quantization noise stays cyclic of course
> (it's in the wavetable), but its shape changes from something with
> high lower harmonics, to something "buzzy" and "thin" with a flatter
> spectrum.
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