[sdiy] Continuously variable waveshaping (was Behringer Neutron)

David G Dixon dixon at mail.ubc.ca
Tue Apr 10 19:59:20 CEST 2018


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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