[sdiy] Additive Synthesis questions

[Scott Gravenhorst]

Ian Smith <taciturn_unquiet at hotmail.com> wrote:
>
>Hey all,
>
>This is more of a hypothetical sort of thing at the moment since 
>I'm working on a couple big projects at the moment. Anyway, I was 
>reading Cheater's thing on stretched harmonics, and I was 
>wondering about additive synthesis. 
>
>I think my biggest question is: Is there a noticable difference 
>between adding up a bunch of sine waves and sculpting a waveform 
>with a, my mind fails me on the name, but a quickly sequenced 
>series of voltages fed through a D/A converter or R/2R ladder? 

Walsh functions?

>If I was going to make an analogue additive synthesizer, is there 
>a simple way of building a sine wave oscillator with just a few 
>parts that aren't some expensive special function chips? 
>
>What would be a good number of sine waves for analogue additive 
>synthesis? 4, 7, as many as can be crammed on a panel? 
>
>thanks all,
>
>Ian (always bloody curious) Smith

In a digital world experiment I did, I used 16 sines and then 32 to attempt the same
waveform/timbre.  The difference is quite noticable.  When the oscillators are running at lower
frequencies, it is apparent that upper harmonics are missing because the sound isn't "bright".  32
oscillators improves this.  So I would suggest as many as you can afford or have space for.  

The experiment was performed using an FPGA producing the sinewaves (18 bit signed) at a sample rate
of 250 KHz.
 		 	   		  
-- ScottG
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-- Scott Gravenhorst
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