[sdiy] topoctave generator

[adam at hoodmusic.net]

i thought about playing with these for another project awhile back, they are
used for the DCOs in the juno60 i beleive, they make a surprisingly nice and
grity sound for what they are, but they would create phaselock, and one synth
with phase lock is enough for me.

adam

Theo wrote:

> How about 8054 timers as TOG.
> Each 8054 holds 3 16bit timers so 4 of those are needed for an octave.
> You would need a uC to set the division factors, allowing all kind of
> scales.
> And the clock inputs could be used for easy fine tuning.
>
> BTW you want the uC anyway for midi input,
> and a truck load cmos switches as key contacts ;)
>
> One problem though, I don't know if the 8054 is still available.
> It comes from times when even the 7to11 sold TOG ICs.
>
> Another keen and cunning plan,
> The same as above, but using 12 (or 6) Atiny AVRs (8 pin DIL).
> Small PICs would do too.
> Each uC programmed as 16bit divider(s) IC and driven from a central clock.
> With clock I mean a master-tuning clock, _not_ the uC clock.
>
> Wait even better, same scenario but with twelve 90S1200 AVRs.
> Each uC generating a pitch and performing the octave divisions.
>
> Lets see, 15 I/O pins:
> One for the master tuning clock input and 10 for the octave outputs.
> Leaves 4 inputs for things like scale selection and dutycycle select
> e.g. 50% for organ, 25% for strings or 0% for saw-waves.
> (set the uC output as OC and give a short pulse to discharge a cap,
> recharge the cap with a fixed resistor to VCC = saw)
>
> Or when 5 or 6 octaves are enough you may have multiple outputs for each
> octave.
> For example, one set of outputs gives 50% dutycycle pulse
> and another set outputs give short pulses for the saw wave trick.
>
> Mmm, a only 12 ICs for a multiple waveform main oscillator.
> Well probably a few more, for the master clock and some opamps as
> buffers and comparators (saw+comparator = pwm)
> Sounds good to me :)
>
> Theo