[sdiy] GRP Genesi

[Tom Wiltshire]

Isn't it just the typical adding-up-a-load-of-octave-squarewaves to make a staircase "ramp" waveform? 6 bits in this case, iirc.

Ah, yes, here it is, from the service manual:



> On 6 Jul 2026, at 13:01, Mike Bryant <mbryant at futurehorizons.com> wrote:
> 
> Actually one of the cleverest bits is probably converting the down-scaled squarewaves to sawtooths whilst keeping the levels consistent across the whole frequency range.  No mention of how they did they - presumably by programming a constant current source with the key and octave number ?
> From: Synth-diy <synth-diy-bounces at synth-diy.org> on behalf of Roman Sowa via Synth-diy <synth-diy at synth-diy.org>
> Sent: 06 July 2026 12:06
> To: synth-diy at synth-diy.org <synth-diy at synth-diy.org>
> Subject: Re: [sdiy] GRP Genesi
>  
> At first glimpse, just looking at block diagram, it looks like typical 
> PLL, but instead of phase comparator it uses F-to-V conversion and 
> voltage comparator. Same divider ratio is used in the feedback as in the 
> vaweform output, so the VCO works only within 1 octave while overall 
> output spans over many octaves.
> 
> Roman
> 
> W dniu 2026-07-05 o 11:26, Neil Johnson via Synth-diy pisze:
> > Michael E Caloroso wrote:
> > 
> >     US 3,930,429
> > 
> > 
> > Don did a write-up of it here: 
> > https://till.com/articles/arp/patents.html#US03930429 <https://till.com/articles/arp/patents.html#US03930429> 
> > <https://till.com/articles/arp/patents.html#US03930429 <https://till.com/articles/arp/patents.html#US03930429>>
> > Very weird architecture indeed!
> > 
> > Neil
> > 
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