[sdiy] Frequency shifted from BBD?

[Kylee Kennedy]

You get a temporary pitch shift when you change the delay speed on a BBD
manually. So I bet if you set up a scanner that goes through several BBDs
that are shifting the speed as it scans you could replicate this effect.
Each BBD acts as a playback head on that device. Probably phlanging would
be included if there isn't a hard switch between BBDs via the scanner steps.

- Kylee

On Sun, Oct 20, 2024 at 11:12 PM Didier Leplae via Synth-diy <
synth-diy at synth-diy.org> wrote:

> Yes! That’s surprisingly simple solution for pitch shifting on tape. I’m
> trying to think if such a brilliantly simple solution is possible for BBD
> though.
>
>
>
> On Oct 20, 2024, at 7:45 PM, Ben Stuyts via Synth-diy <
> synth-diy at synth-diy.org> wrote:
>
> For all you frequency shifter and tape delay aficionados:
> https://youtu.be/U-4AMxkpyh0
> That’s brilliant! :-)
>
> Ben
>
> On 9 Oct 2024, at 07:07, Mike Bryant <mbryant at futurehorizons.com> wrote:
>
> 
>
>    - Besides the point that Tom raises, there's another consideration:
>    Using an MCU to program a complex digital signal is often more wasteful
>    (think: battery-draining) than judicious use of logic gates.
>
>
> Sorry but this usually isn't the case.  Unless you are switching at a very
> low rate, discrete logic gates have to drive the capacitances on the PCB
> between each other whereas MCUs do all the work internally and just output
> the final waveform.   10 cent OTP MCUs cost less than many logic gates due
> to higher volumes and usually use less power and PCB area so system cost is
> lower.
> ------------------------------
> *From:* Synth-diy <synth-diy-bounces at synth-diy.org> on behalf of brianw <
> brianw at audiobanshee.com>
> *Sent:* 09 October 2024 05:14
> *To:* SDIY <synth-diy at synth-diy.org>
> *Subject:* Re: [sdiy] Frequency shifted from BBD?
>
>
>
> On Oct 6, 2024, at 4:09 PM, Benjamin Tremblay wrote:
> > Why not generate the clocks with the MCU and skip voltage control?
>
> Besides the point that Tom raises, there's another consideration: Using an
> MCU to program a complex digital signal is often more wasteful (think:
> battery-draining) than judicious use of logic gates.
>
> A counter can divide down a higher clock rate. A couple of AND gates plus
> an inverter can generate non-overlapping clock signals from the two LSB
> outputs of the counter. Gates like these are cheap in CMOS.
>
> Doing the same with an MCU would be unwieldy unless you have hardware
> support. It might be possible to convince the timer/counter motor control
> peripheral of certain MCU chips to create non-overlapping clocks at
> identical rates.
>
>
> > I just assumed Eventide used a digital pathway.
>
> I'm sure Eventide did use a digital pathway, but it was almost surely
> built on a lot of discrete logic instead of pure software.
>
>
> > As a teenager I got one of those Radio Shack kits to build the SAD1024
> BBD delay.
>
> I also built a DIY BBD delay. I fudged many of the potentiometer values to
> get longer delays - a much lower fidelity than a commercial product would
> allow. Super fun experimentation. Basically, I allowed the clock to be
> cranked much lower than the original schematic. I knew it would sound bad,
> but I wanted the flexibility. That box had very sensitive controls, because
> each pot spanned a much wider range than would be considered ergonomic
> design.
>
>
> > Anyways… I have thought it would be fun to get a huge BBD with 4096+
> stages and run it at a really high speed.
> > If I understand, there’s a problem with speed; the sample/hold cells
> have slew rate caused by their capacitance, right?
>
> The FET switches between each pair of cells have some "on" resistance,
> albeit small, so the RC circuit formed by the on resistance and the
> capacitor put a limit on the clock speed. You can clock faster, but the
> cells will not be fully charged. If the signal is low amplitude, then it
> might pass through, but a high amplitude signal would require big changes
> in the cell charge, and the voltages would not get through in full.
>
> > It seems like a lot of work to get a mid-quality sound.
>
> Don't forget the noise - you get a lot of noise, too.
>
> > Benjamin
>
>
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