[sdiy] Octave divider for guitar/bass

[Antti Huovilainen]

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