[sdiy] Prophet 08 sub oscillator mod?

[cheater cheater]

> It's a tiresome way to recreate work that Dave Smith has already done. But
> you'd have a cool custom Prophet at the end of it...
hehe, yes, well, it doesn't hurt to foray into dreamworld every now and then.
As far as the sub octave goes: mopho does it; it's supposedly almost
the same thing as a single p08 voice; i don't see why it wouldn't be
possible with the p08 then; i don't suppose they had a special chip
made for the mopho.
Any idea how that monosynth does it?

Cheers
D.

On Sat, Jan 3, 2009 at 4:19 PM, Tom Wiltshire <tom at electricdruid.net> wrote:
>
> On 3 Jan 2009, at 15:26, cheater cheater wrote:
>
>> Wow, synth porn.
>> At least you know how your enemy looks from the inside... or something.
>>
>> Tim:
>>>
>>> Adding the hardware to create sub-octaves: big job
>>
>> What are you basing this on? Is there a schematic you are following?
>> What would be involved?
>
> You need a minimum of a flip-flop per oscillator (at least 8 dual flip-flop
> chips - 4013 or similar). You also need a way back into the output VCA. This
> might be the more difficult part, since there is no guarantee that this
> input is available on a pin. It may be internal to the DSI voice chip (top
> of the photo). There's loads of sub-oscillator schematics available you
> could use; the SH101 has a nice one, or the Korg Poly6 is another example.
>
>>> Reverse engineering and reprogramming the operating system and adding the
>>> hardware to allow control of the suboctaves: HUGE job.
>>
>> Oh yes, definitely.
>> But on the other hand, we're talking about a simple uC program here.
>> This isn't a supercomputer. People have reverse engineered bigger
>> things; the problem is that ASM isn't as popular nowadays, so if you
>> run into trouble, you might be hard pressed to find someone who knows
>> what to do :)
>
> Reverse engineering will be made even harder by the fact that you won't be
> able to get even the assembled code out of the uPs. It'll be code-protected.
> So instead you've got to write code that will do the same job from scratch
> without knowing anything about the hardware beyond what you can see.
> It's a tiresome way to recreate work that Dave Smith has already done. But
> you'd have a cool custom Prophet at the end of it...
>
> T.
>
>
>
>