[sdiy] Prophet 08 sub oscillator mod?

[Paul Maddox]

D,

  why not email him asking for it?
he may include it in a future OS, or may tell you if it could be done  
easily.

Paul

On 3 Jan 2009, at 16:40, cheater cheater wrote:

>> 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.
>>
>>
>>
>>
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