[sdiy] Soloist vs. Pro Soloist vs. DGX - was Best Filter pissing contest

[Gene Stopp]

I am curious about something on Phil's web page...

I know (not in a biblical sense, but in a synth-guts-geek sense) the Soloist
and the Pro Soloist. I have one of each in nicely used condition, and
they've both been under the soldering iron to get them back to nominal
operation. I know that the Soloist has a "real" VCO (wide-range tempco'd
exponential) and a regular 1v/oct resistor-string keyboard circuit. I know
that the Pro has a digital keypress detection thing plus some kind of PLL
and stairstep-sawtooth oscillator, which I will prefer not to call a "real"
VCO.

Anybody have a decent rundown of how the Pro does it's keyboard keypress to
audio generation? I have the schemos but I have never studied them or put a
scope in there, since I never had to. It's been trouble-free all this time,
including key contacts which is unusual for a vintage piece. Benefits of
digital key decoding I guess...

But Phil's site mentions (in his replacement submodule section) that the Pro
DGX uses a 4027 for the VCO. Did the Pro Soloist keyboard/VCO design go by
the wayside and get replaced with a digital-DAC keyboard interface plus a
"real" VCO? I mean I know about the digital patch select buttons replacing
the series-wired bat-handle switches, but I thought that the funky PLL-VCO
thing was still there in the DGX.

- Gene (uh oh might have to look for a DGX)

>
> http://www.discretesynthesizers.com/arptronics/Arptronics.htm