[sdiy] Continuously variable waveshaping (was Behringer Neutron)

[Rutger Vlek]

It's an interesting read, this patent! And I wasn't even aware Moog was actively filing new patents in recent years.

@David: I didn't know that about the Dixie. And I'm not sure if I understand you correctly. You mean the Dixie runs on a triangle core, and the implementation of the tri-core requires a comparator that provides you a pulse output of which you can modulate the duty cycle? How can that change rise and fall time of the triangle, then? It would have to be combined with a change in the expo CV right to achieve that? Or am I missing something?

Regards,

Rutger



On 10 apr 2018, at 19:59, David G Dixon wrote:

> All I could see of the patent were the figures, but based on that, it looks a lot like what happens in the Dixie.  All of the "modes" shown in the final figure could be obtained simply by duty-cycle control of the driving square waves in a tri-square oscillator.
> 
> From: Synth-diy [mailto:synth-diy-bounces at synth-diy.org] On Behalf Of Rutger Vlek
> Sent: Tuesday, April 10, 2018 6:34 AM
> To: Tim Parkhurst
> Cc: synth-diy at synth-diy org
> Subject: Re: [sdiy] Continuously variable waveshaping (was Behringer Neutron)
> 
> I recently stumbled on this recent patent by Moog: https://patents.google.com/patent/US20160335998A1/un
> 
> It concerns continuously variable waveforms, but implements it at the core of a VCO rather than by crossfading the outputs (waveshapers) of one. The idea is awesome, but I have my reservations about the real-world feasibility of the method (given component tolerances and accuracies).
> 
> Rutger
> 
> 
> 
> 2018-04-08 21:09 GMT+02:00 Tim Parkhurst <tim.parkhurst at gmail.com>:
> " 'High frequency hash' is a direct quote from Ken Stone's description of that
> circuit, by the way."
> 
> - and the band name for my new EDM / free jazz group. 
> 
> 
> Tim (add in some corned beef and you've got a tasty breakfast) Servo
> ---
> "Imagination is more important than knowledge." - Albert Einstein
> 
> 
> 
> 
> On Sun, Apr 8, 2018 at 11:36 AM, Guy McCusker <guy.mccusker at gmail.com> wrote:
> On Sun, Apr 8, 2018 at 6:54 PM, David G Dixon <dixon at mail.ubc.ca> wrote:
> > My wavefolder (as found in the Intellijel uFold) uses TL072, and doesn't
> > generate "high-frequency hash".  Also, I've achieved what looks a lot like a
> > resonant filter output with a sawtooth wave, without a filter.  Given the
> > way that this folder works (with diode "turnaround" circuits) I'm not sure
> > that slew rate is a significant factor.  The opamp outputs in the folder
> > chain are confined to relatively small voltages -- the first one to about 3V
> > or less, and the subsequent ones much less.  Other folders may have
> > significantly different modes of operation where slew rate is important, but
> > not the ones based on diode turnarounds.
> 
> There's a bit of talking at cross-purposes here I think. The wave
> folder in the CGS29 and also the Serge wave multiplier (middle
> section) also does not generate "high frequency hash" and works fine
> with a fast op amp. Their design is also similar to your "turnaround"
> idea, as it happens.
> 
> The "high frequency hash" business concerns a different part of the
> CGS29, the Grinder section, which exploits op amp overshoot and
> ringing. It makes sense that slew rate is a factor there. ("High
> frequency hash" is a direct quote from Ken Stone's description of that
> circuit, by the way.)
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