[sdiy] High frequency VCO as BBD clock

[Guy McCusker]

Right, but if you tap pins 5 and 6 then the S&H timing needs to be
fixed otherwise the first tap is silent because it is never sampled.
It is plausible to imagine that is what happened during construction /
debugging and rather than fix the timing, someone tried tapping the
first SAD1024 half way, got sounds out, and there you go.

On Fri, Feb 10, 2023 at 10:33 AM mark verbos <markverbos at gmail.com> wrote:
>
> It’s like that on the actual module? I assume it’s a tracing error. Serge could have just tapped the first SAD1024 the same way he tapped the second one (ie pins 5 &6).
>
> Mark
>
>
>
>
>
>
> > On Feb 10, 2023, at 11:28 AM, Guy McCusker <guy.mccusker at gmail.com> wrote:
> >
> > Mark is right of course -- there are some serious bits of weirdness in
> > the WAD schematic.
> >
> > It turns out that the way the sample and hold is done after the BBD
> > taps means that one of the two taps in the first half never makes it
> > to the output. So the "short" delay tap is 1/4 of the "long" and not
> > 1/2 as claimed in the Serge marketing literature.
> >
> > On Fri, Feb 10, 2023 at 10:09 AM mark verbos via Synth-diy
> > <synth-diy at synth-diy.org> wrote:
> >>
> >> Kinda off the subject, but I find it really hard to believe the way the taps are coming off of those BBDs. The long looks ok, but….
> >>
> >> Mark
> >>
> >>
> >>
> >>
> >> On Feb 9, 2023, at 8:13 PM, S Ridley via Synth-diy <synth-diy at synth-diy.org> wrote:
> >>
> >> The Serge WAD (Wilson Analog Delay) might be worth a look - high frequency VCO driving two SAD1024s.
> >>
> >> https://www.elby-designs.com/webtek/cgs/serge/cgs208/cgs208_schematic.gif
> >>
> >> Spec says delays down to 0.5mS, dunno how well it tracks.  HF VCO is expo converter driving a CMOS oscillator.
> >>
> >> Steve
> >>
> >>
> >>
> >> On Tue, 7 Feb 2023 at 18:21, Rutger Vlek via Synth-diy <synth-diy at synth-diy.org> wrote:
> >>>
> >>> Dear list,
> >>>
> >>> For a while I've been working on a guitar pedal board for personal use. I'm about to build the second revision of a solid state pre-amp, and was thinking about possible modulation effects too. I would love a nice (stereo) BBD flanger/chorus, but felt a bit fed-up with all the 'classic' designs, particularly the traditional clocking scheme, usually with a limited range, lack of current drive (to overcome capacitance of the BBD clock input) and strictly linear modulation (calling for a hyper-triangle modulation source).
> >>>
> >>> Having some experience with designing saw- and tri-core VCO's around the 2164, I was wondering how easy it would be to push the design of a typical tri-core VCO with an 2164-based expo converter into higher frequencies (let's say up to 500kHz) and use it to clock a BBD? Has anyone tried? Or are there fundamental reasons why such frequencies are not possible? I've never (intentionally) worked with circuits outside of the audio bandwidth...
> >>>
> >>> Rutger
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