[sdiy] How to make wavetables? What size?

[Glen]

At 11:34 AM 5/19/2005 , Oakley Sound wrote:
>
>> With a 256-frame wavetable, the spectral content is limited to
>128 harmonics. At a fundamental frequency of 50 Hz (the low G on
>a bass), the spectrum stops at 6.4 kHz.
>
>I don't think this is true.
>
>Nyquist and all that does say that the uppermost frequency in any sampled 
>waveform should be limited in such way, but there is no such limit here. 
>What you will hear is the aliasing in all its glory. Harmonically 
>related, these 'wrap around' frequencies are very much audible and are 
>what gives this sort of synthesis a very distinctive sound.

I think Andre might actually have a valid point there. With only a 2 byte
wavetable length, you can create a square wave and have harmonics that
extend well beyond 20 kKz, but to *accurately* specify the amplitudes of
all the individual harmonics, you would need a longer wavetable. The longer
the wavetable, I would suspect, the better the accuracy of your harmonics,
or the higher the frequency you could accurately specify.

This is just idle speculation on my part, but I would think that wavetable
length *does* have a big impact on the quality of your *useable* upper
harmonics.. I just don't know the math behind this sort of thing.

take care,
Glen