[sdiy] ODP: Hammond Aurora Keybeds

[Roman Sowa]

Exactly.
Logic driven keyboards are nothing new. But it's really cheaper and 
easier to put a micro into the task today. You have to enjoy the beauty 
of logic design to go that route, and then it becomes timeless classic.

Examples that come to mind now: not so vintage yet, but MacBeth touch 
keyboard is just self running, no-program, logic circuit. Or the most 
advanced one I've seen, the one designed by Dave Rossum - velocity 
scanning keyboard for Oberheim, with 64us scanning cycle and 12-bit 
precison velocity sensing. Really massive design with I think 40 ICs in 
it. Well, the old 4 Voice from Oberheim, also Dave's design, was also a 
bunch of logic. A counter driving a mux, and when key was pressed, a 
pulse appeared at the time when counter state was representing the key 
number.
Or my keyboard I did in 1990 when I didn't know how microprocessors work 
at all, very similar idea to 4Voice, only about 15 CMOS 4000 chips. 
There's a schematics somewhere in the web if anybody interested.

Roman

W dniu 2025-05-15 o 17:15, Phillip Gallo pisze:
> ... and as memory serves, Allen Organ company did just that in the late 
> 1970's, switching to matrixing keyboards in the early 1980's.
> 
> My first DIY digital keyboard (~1980) was a CMOS counter driving a raft 
> of CD4051 muxes to encode an old Vox Continental clavier.
> 1st keypress stopped the counter, latched the count value to a CD4050 
> buffer which drove 6 binary weighted resistor values (the 2 smallest 
> values getting two parallel buffers).
> This 6 bit  keyboard eliminated years of Sample and Hold frustrations.  
> A second version switched to CD 4067 mux's to reduce chip count.
> p
> 
> 
> 
> On Wed, May 14, 2025 at 11:53 PM Roman via Synth-diy 
> <synth-diy at synth-diy.org <mailto:synth-diy at synth-diy.org>> wrote:
> 
>     The best what you can do today is scan the keyboard digitally and
>     use DAC as CV source. No analog keyboard circuitry ever designed
>     will be comparably reliable. They would have gladly make keyboards
>     that way back in the 1970's as well but the technology needed was
>     too expensive.
> 
> 
>     Roman
> 
> 
> 
>     ---- Użytkownik drheqx via Synth-diy napisał ----
> 
>     Hi all,
> 
>     I have the keybeds and draw bars etc. from a Hammond Aurora organ.
> 
>     These are not matrix type keybeds. Each key closes a switch to a
>     common bus.
> 
>     Is this a good time for me to consider doing a volt
>     /octave keyboard controller?
> 
>     I definitely don't want to midify these. That would be a waste.   I
>     was considering building a voice per key synth because i love these
>     key beds and it would be so unique, but I'm short on time like so
>     many of us.
> 
>     Anyone know of a good kit to make a 1v/ oct controller, maybe with
>     some added features.
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