[sdiy] Divide down question

[cheater cheater]

Tom,
extremely interesting! I should think about that for a while. This
'multiply up' as I would call it is especially cool. Any sound
examples?

Which makes me wonder: can you do that with pulse waves..?

I think you could almost certainly do that with sawtooth waves.

D.

On Mon, Aug 24, 2009 at 5:53 PM, Tom Wiltshire<tom at electricdruid.net> wrote:
>
> On 24 Aug 2009, at 16:00, cheater cheater wrote:
>
>> Hey guys,
>> in a divide-down architecture, every key has a divide-down 'level'
>> which then gets used in the same note but an octave lower.
>>
>> Does any amplification happen at each stage?
>
> Not really, or at least not in the analog sense. The division is done by
> flip-flops, e.g. digital circuits, which means the output is the same level
> as the input, so no amplification is required.
>
> As an aside, I once considered doing a "divide up" scheme, using a triangle
> wave master oscillator at a low frequency fed to a series of precision
> rectifiers. This provides triangles in octaves going up, and does require
> gain, since the rectifiers cut the signal level in half. I hoped that the
> reduced harmonic content of triangles when compared with square waves would
> give me a smoother tone. I built the circuit and proved the concept, but
> never did anything with it.
>
>> If I press multiple keys from the same 'class' (e.g. C1, C2, C3) will
>> any 'amplitude stealing' happen?
>
> No. Essentially all the tones are fed to a big mixer. Imagine a simple
> inverting op-amp mixer with lots of 100K input resistors and 100K feedback
> resistor for unity gain. Now imagine what happens if you feed the same tone
> into two of the input resistors. Those two resistors are effectively
> paralleled, which will halve their joint value and cause the signal fed to
> them to double in level - exactly what is required.
>
>> Where can I read more about divide-down synths? I am not yet good
>> enough to read the schematics just like that; I tried googling around
>> but couldn't find much of substance.
>
> You might have better luck looking at some combo organ sites, since they're
> mostly done this way.
>
> Good luck!
> T.
>
>
>