understanding some terms and theory

[Paul Maddox]

All,

>
>Just wanted to straighten out my understanding of wavetables -
>

ooo, my favourite subject.

>A wavetable just holds a certain ammount of samples for a given
>waveform, right?  So no matter what the playback frequency you're
>getting the same number of samples per period?
>

sort of.. you have a single cycle of a wave form with say 64 samples. 
the table then consists of modifications to this wave form, so would 
have 32 waves each with 64 samples, this is a table... to play it back 
you cycle 64 samples, this plays 1 cycle, you play this for a while and 
then progress to the next wave in the table.. the idea/concept being you 
have 32 "snippets" of a sound and wherever you play it on the keyboard 
it wont sound like micky mouse or a robot.. its kinda like time 
stretching, but cheating a little..

>How is the number of samples determined and how is the number of 
>samples described?
>

This depends on the synth.
PPG use 64 samples per half wave (use they only bother with half cycles, 
simply invert and play backwards to get second half) the pulse/wave use 
128 samples per half wave. I suspect many low end wavetable modules 
(sound cards) dont use anywhere near this resolution.

as for the how its determined, I dunno, I guess its down to eprom size 
VS Quality of instrument balance, or even cost VS Quality.

>Thanks.  dave moylan
>

Hope this helps
Paul Maddox (nut on wave tables)



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