[sdiy] Additive Synthesis questions

[Aaron Lanterman]

I think Ian Fritz's doubledecka module lets you do that sort of thing

Sent from my iPhone

On Apr 8, 2010, at 2:38 PM, Scott Nordlund <gsn10 at hotmail.com> wrote:

>
>>> 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?
>
> That's how the RMI Harmonic Synthesizer does it, with some
> additional filtering.  It's quite crude, though, and will leave
> with a lot of higher harmonics (maybe not a bad thing if you've
> only got 16 to work with).
>
>>> 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?
>
> Walsh functions would be the easiest, but don't assume will be
> simple, efficient, or really that exciting.  You could get similar
> results clocking an analog sequencer with a high frequency VCO.
> The output of the RMI additive engine was a 32 step waveform, so
> you could get all the same results (and more, actually) by drawing
> the waveform directly with the sequencer.  It's not as easy to work
> with, but it's a great deal simpler, electronically.
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