[sdiy] Continuously variable waveshaping (was Behringer Neutron)

[Rutger Vlek]

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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