[sdiy] Octave divider for guitar/bass

[Happy Harry]

No you're all wet...   (snicker...)

Are you going to use a regular guitar pickup. The octave thing
can be done very well if you cannot plat multiple notes...
so using a hex pickup with switching of strings is strongly
recommended.

Switching the strings lets you use more agressive filters.

See the Akimatu Patent for the method used by Roland, Boss, etc.
It works after a fashion...

See the Gold Patent (assigned to New England Digital) for the method
that the Synclavier guitar interface used. This method works very
well (it does not jump octaves, instead it reverses phase... MUCH less
obnoxious sounding)... But it will work only over a limited range, like 
about 1.5 - 2 octaves... Not enough to do the entire guitar spectrum.

Craig Anderton had an octave divider schematic, also check R. Keen
for units tike the Korg Octave divider, the E-H MicroSynthesizer (guitar) 
etc. Write back for more info after you get some of this
stuff and you want to chat...

H^)  harry


>From: Antti Huovilainen <ajhuovil at cc.hut.fi>
>To: synth-diy at node12b53.a2000.nl
>Subject: [sdiy] Octave divider for guitar/bass
>Date: Fri, 16 Mar 2001 16:30:11 +0200 (EET)
>
>Hi
>
>After doing some research about MXR BlueBox, I found out that it's not
>really a octave divider (more like random octave + fuzz), so I'm stuck
>with designing my own.
>
>Are there any schematics (even partial) for guitar octave dividers on the
>net? Has anyone else on the list tried this?
>
>I'm thinking of something like this:
>
>in +-> agc -> comparator -> divide by 2/4 -> vca -> mix with dry -> output
>    |                                          ^
>    \-> env detector --------------------------/
>
>Since vca input is just square wave, I can replace it with a single
>transistor (switch env detector output on/off). The tricky part is
>implementing AGC and the comparator.
>
>I can't use zero-crossing as a clock for the divider since at first the
>waveform crosses zero four times in one period but later only twice.
>Detection from peaks would work in the beginning but later (about same
>time as extra zero crossings disappear) the peak becomes almost flat with
>a slight dip, so that won't work either. Would some hybrid solution
>work? Say, switching when waveform crosses 2/3 of peak?
>
>Any thoughts / ideas? Am I on the right track at all?
>
>Antti
>
>"If you don't eat yer meat, you can't have any pudding!
>  How can you have any pudding if you don't eat yer meat!?"
>    - Roger Waters
>

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