[sdiy] top octave gneration

[Theo]

As I suggested earlier;
you can do that with a AVR.
Or rather 12 AVRs that are also the dividers.

Theo

Cross tread remark:
PIC have other applications ;)



From: Don Tillman <don at till.com>

> Brock Russell wrote:
>
> > Just happen to have the 9 bit top octave divide list on my desk.
> > (2 MHz typical input)
> > Equal tempered scale; a few Just scales from Vanessa Else (Polyphony May
84)
> > C (hi)  239             210     360     630     24
> > B       253             224     384     672     26
> > A#      268             240     400     720     27
> > A       284             252     432     756     28
> > G#      301             270     450     810     30
> > G       319             280     480     840     32
> > F#      338             330     512     900     33
> > F       358             315     540     945     36
> > E       379             336     576     1008    39
> > D#      402             360     600     1080    40
> > D       426             378     640     1120    42
> > C#      451             405     675     1225    44
> > C (lo)  478             420     720     1260    48
>
> I'm sure I've said it a couple times before whenever the topic of top
octave
> generators comes up, but it's been a while...
>
> The divide-by-239 to divide-by-478 is the classic top octave chip, like
the
> 5024.  It has roughly twice the error of the gear-based Hammond organ tone
> generator (that's 1938 technology!)
>
> The reason is that instead of a 1/N approach the Hammond uses a pair of
gears
> for each note, and thus an M/N approach, which gives you bettter accuracy
with
> smallish integers.
>
> This suggests a couple things.  One is that you might want to aim for
better
> accuracy than a 1938 organ.  Another is that it might be fun to copy the
Hammond
> ratios exactly with twelve 4046 PLLs and 24 dividers.
>
>   -- Don
>
> --
> Don Tillman
> Palo Alto, California, USA
> don at till.com
> http://www.till.com
>
>
>