[sdiy] Korg DW synths and phase in wavetables

[ASSI]

On Freitag 04 Januar 2008, Tom Wiltshire wrote:
> This does bring up one question though; If you generate wavetables
> with all the harmonics starting at the same phase (0) then the
> wavetables will always have this property of rotational symmetry
> around the central point, which allows you to use half as much memory
> to store them.

Actually you can use two distinct phase values: 0° and 180°.  This can 
be used to minimize amplitude with respect to spectral power.

> Given that the human ear can't really hear phase (only 
> phase differences and the effects they cause) and can't tell the
> difference between a true square wave and any of the other waves that
> include the same amount of those odd harmonics, is there any reason
> why I _might_ want to store an entire cycle of a waveform in a
> wavetable synth?

Playing them back is slightly less complicated if you don't need to care 
about the lookup reversal and sign flipping (depending on which format 
you use to represent negative numbers).  Half-cycle wavetables with a 
power-of-two length must be midpoint-sampled BTW, otherwise you can't 
stitch them together correctly.  If you forget to do this, the result 
is a very ugly noise artefact...


Achim.
-- 
+<[Q+ Matrix-12 WAVE#46+305 Neuron microQkb Andromeda XTk]>+

SD adaptations for KORG EX-800 and Poly-800MkII V0.9:
http://Synth.Stromeko.net/Downloads.html#KorgSDada