simple PAIA keyboard scanner/arpeggiator (was Re: [sdiy] trying to understand appregiators in late 70's synths)

[Dave Manley]

Dave Manley wrote:
> Florian Anwander wrote:
>> Hi Dan
>>
>>> forgive for being an idiot, but how can i incorporate this into an 
>>> arppregiator?
>> Yep. your doubts aren't wrong. This keyboard is only the first step, but
>> it delivers a key as digital 6-bit word. This has to be 'postproduced'
>> somehow.
>>
>>> due to my lack of german...is it a mono keyboard?
>> Hmm, yes and no. If you'd put a D/A direct behind the Latch then it
>> would be monophonic and would always send the highest note.
>>
>> But one might add further logic to make it polyphonic and need this for
>> the arpeggiator too. I am only brainstorming (as far as there is any
>> brain to storm inside my old head ;-)) to the mail client now...: e.g.
>> for eight voices you need eight latches. The trigger from the 4051 must
>> be advanced with each new pressed note to the next latch. But then I am
>> not sure how to act on, if more than eight keys are pressed.
>>
>
> Years and years ago, there was a Paia keyboard scanner circuit that 
> you could use as a simple arpeggiator (IIRC) by controlling the scan 
> clock. Normally, the scan clock was running so the entire keyboard was 
> being scanned every ~1 ms.  In this mode the scan clock was stopped 
> when a depressed key was found, and then re-enabled based on the 
> arppegiator rate.  As it scanned the keyboard from low to high, it 
> would output the digital code for each currently depressed key, pause, 
> and then go to the next key.  It looks like the elektor circuit could 
> probably do the same with some mods.  If you get a little clever, you 
> could probably change the direction of scanning for up or down 
> arpeggios (and if really clever up/down or random).  I think this was 
> described in one of John Simonton's lab notes when he started 
> introducing the digital keyboard/computer/quash/etc.
>
> -Dave
>
>
Digging through the files, this arpeggiator option is described in 
Simonton's 'Friendly Stories about Computers/Synthesizers' on pages 
8-13.  These were scanned by Anders Sponton, and at some point I grabbed 
a copy.  I can't find them with "The Google" - does anyone have a link?  
If not, and someone is interested I can make them available.

BTW, the pause circuit is even simpler than a 555. It is an RC.

-Dave