[sdiy] Frequency shifted from BBD?

[Tom Wiltshire]

At the time that this was a tough problem, people were trying to solve "the pitchshifting problem" using entirely analogue means. The problem didn't really get solved until Eventide did it digitally with the Harmonizer.

But we don't have the same limitations today. It seems to me that a BBD-based pitch shifter would be possible if you had a uP to produce the required control voltages. Of course, such a thing is still *ludicrous* by most measures, but it would be *possible*. You need at least two and possibly several BBD delay lines with voltage-controlled clocks and VCAs on their outputs. Each delay line then has a CV for the clock rate, and a CV for the volume. A decent uP+DAC and a decent programmer can then generate a pile of control voltages to give you up/downshifted delayed signals, and all the necessary crossfading to avoid the glitches when the ramps jump back to zero.

I'll have to think harder about this to work out for how long a given delay line length can give you a specific pitch shift. That'll help determine how many delaylines would be required. More shift is steeper ramps (e.g. higher modulation frequency) and probably more BBDs required?


> On 6 Oct 2024, at 19:05, Michael E Caloroso via Synth-diy <synth-diy at synth-diy.org> wrote:
> 
> I can't find my hard copy, but Roland had a US patent for a BBD based pitch shifter.
> 
> MC
> 
> On Sun, Oct 6, 2024 at 2:55 AM houshu--- via Synth-diy <synth-diy at synth-diy.org <mailto:synth-diy at synth-diy.org>> wrote:
> Hello Didier,
> 
> 
> A set of schematics of BBD based pitch shifter is here:
> 
> 
> 
> https://www.experimentalistsanonymous.com/diy/index.php?dir=Schematics/Vibrato%20and%20Pitch%20Shift <https://www.experimentalistsanonymous.com/diy/index.php?dir=Schematics/Vibrato%20and%20Pitch%20Shift>
> 
> Please check Wacky harmonizer (an article from a Japanese magazine).
> 
> As discussed here, cross fading seems to be a problem.
> 
> 
> 
> Osamu Sam Hoshuyama
> 
> Kawasaki JAPAN. 
> 
> 
> 
> 
> ------ Original Message ------
> 差出人: "Didier Leplae via Synth-diy" <synth-diy at synth-diy.org <mailto:synth-diy at synth-diy.org>>
> To: "synth-diy at synth-diy org" <synth-diy at synth-diy.org <mailto:synth-diy at synth-diy.org>>
> 送信済み: 土曜日, 2024/10/5  02:44
> 件名: [sdiy] Frequency shifted from BBD?
> 
> I recently re-read the section in Barry Klein’s Electronic Music Circuits on bucket brigade devices and noticed a brief mention of using them as a frequency shifter by modulating with a ramp wave.
> 
> He acknowledges that there will always be an audible glitch and some noise issues. 
> 
> I experimented with this idea a little to minimal success, but curious if anyone else has tried this or seen it used in interesting ways.
> 
> 
> 
> 
> 
> 
> 
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