[sdiy] Interesting article on top octave generators.

[Tom Wiltshire]

> On 27 Dec 2024, at 07:35, Donald Tillman <don at till.com> wrote:
> 
> On Dec 26, 2024, at 8:42 AM, The SynthiMuse via Synth-diy <synth-diy at synth-diy.org> wrote:
>> 
>> I guess there's a big overlap between synth-diy people and visitors to Hackaday but just in case anyone is interested; good article ( with some links to other articles embedded ) on Top Octave Generators.
>> 
>> https://hackaday.com/2024/12/24/the-mystery-of-the-messed-up-hammond-x5/ <https://hackaday.com/2024/12/24/the-mystery-of-the-messed-up-hammond-x5/>
> Interesting.
> 
> There *must* be some spare MM5833's out there.  At the very least from dead Hammond X5's or other organs that have been parts'd out.  Or maybe a different TOG chip could be found and adapted.
> 
> But y'know... I can't help but think that it's downright weird to replace a TOG chip with a computer.  Of course if it works, it works; certainly.  It's just that the technological limitations of the day were so fundamental to the very nature of these instruments.
> 
> If it was me, I would have directly emulated the chip with, say, 6 CD4040's and some diodes.  Which is probably exactly what the Hammond engineers did while they were building prototypes and waiting for the TOG chips to be delivered.

I agree that it does seem a bit crazy to replace some basic logic with a whole uP, but the arguments for doing it are pretty convincing. Doing twelve 9-bit dividers in hardware is going to be a lot of chips, whereas the uP is only one. That makes it much easier to fit inside whatever it is you're fixing. And it's cheaper - a boardful of simple logic costs *more* than a processor these days because of the economies of scale. It *is* crazy to use a million transistors when 10,000 would do, but when they all come on one chip and costs pennies, it starts to make a lot of sense.

It terms of the technological limitations, all of the uP-based divider solutions I've seen are pretty much exact clones and just as limited as the original chips! They certainly keep the original division ratios and consequent frequency error.

There are a few original divider chips out there, but the people that have them want $30 a chip or worse for them. $1 processor wins over that every time.

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