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<DIV dir=ltr align=left><SPAN class=615142219-11042018><FONT color=#0000ff
size=2 face=Arial>@Rutger: The Dixie is a tricore with a comparator, zeners to
provide a 5Vpp square wave, and an expo 2164 VCA controls the loop current
for 1V/Oct and Expo FM. A additional linear VCA in the loop provides
Linear FM. The square wave is fixed at 50% duty cycle by the comparator,
unless the comparator input is synced. However, all sorts of things are
possible with this configuration, and altering it to get Moog's waveforms
wouldn't be that much of a struggle. I'll just leave it at
that.</FONT></SPAN></DIV><BR>
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<FONT size=2 face=Tahoma><B>From:</B> Rutger Vlek
[mailto:rutgervlek@gmail.com] <BR><B>Sent:</B> Wednesday, April 11, 2018 1:39
AM<BR><B>To:</B> David G Dixon<BR><B>Cc:</B> 'Tim Parkhurst';
'synth-diy@synth-diy org'<BR><B>Subject:</B> Re: [sdiy] Continuously variable
waveshaping (was Behringer Neutron)<BR></FONT><BR></DIV>
<DIV></DIV>It's an interesting read, this patent! And I wasn't even aware Moog
was actively filing new patents in recent years.
<DIV><BR></DIV>
<DIV>@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?</DIV>
<DIV><BR></DIV>
<DIV>Regards,</DIV>
<DIV><BR></DIV>
<DIV>Rutger</DIV>
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<DIV>On 10 apr 2018, at 19:59, David G Dixon wrote:</DIV><BR
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<DIV dir=ltr align=left><SPAN class=732225517-10042018><FONT color=#0000ff
size=2 face=Arial>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.</FONT></SPAN></DIV><BR>
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<FONT size=2 face=Tahoma><B>From:</B> Synth-diy
[mailto:synth-diy-bounces@synth-diy.org] <B>On Behalf Of </B>Rutger
Vlek<BR><B>Sent:</B> Tuesday, April 10, 2018 6:34 AM<BR><B>To:</B> Tim
Parkhurst<BR><B>Cc:</B> synth-diy@synth-diy org<BR><B>Subject:</B> Re:
[sdiy] Continuously variable waveshaping (was Behringer
Neutron)<BR></FONT><BR></DIV>
<DIV></DIV>
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<DIV>I recently stumbled on this recent patent by Moog: <A
href="https://patents.google.com/patent/US20160335998A1/un">https://patents.google.com/patent/US20160335998A1/un</A></DIV>
<DIV><BR></DIV>
<DIV>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).</DIV>
<DIV><BR></DIV>
<DIV>Rutger</DIV>
<DIV><BR></DIV>
<DIV><BR></DIV></DIV>
<DIV class=gmail_extra><BR>
<DIV class=gmail_quote>2018-04-08 21:09 GMT+02:00 Tim Parkhurst <SPAN
dir=ltr><<A href="mailto:tim.parkhurst@gmail.com"
target=_blank>tim.parkhurst@gmail.com</A>></SPAN>:<BR>
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<DIV dir=ltr><SPAN
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'High </SPAN><SPAN
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hash' is a direct quote from Ken Stone's description of that</SPAN><BR
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by the way."</SPAN>
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and the band name for my new EDM / free jazz group. </SPAN></DIV>
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<DIV>
<DIV dir=ltr>Tim (add in some corned beef and you've got a tasty
breakfast) Servo<BR>---<BR>"Imagination is more important than
knowledge." - Albert
Einstein<BR><BR><BR><BR></DIV></DIV></DIV></DIV></DIV>
<DIV>
<DIV class=h5><BR>
<DIV class=gmail_quote>On Sun, Apr 8, 2018 at 11:36 AM, Guy McCusker
<SPAN dir=ltr><<A href="mailto:guy.mccusker@gmail.com"
target=_blank>guy.mccusker@gmail.com</A>></SPAN> wrote:<BR>
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class=gmail_quote><SPAN>On Sun, Apr 8, 2018 at 6:54 PM, David G Dixon
<<A href="mailto:dixon@mail.ubc.ca"
target=_blank>dixon@mail.ubc.ca</A>> wrote:<BR>> My wavefolder
(as found in the Intellijel uFold) uses TL072, and doesn't<BR>>
generate "high-frequency hash". Also, I've achieved what looks a
lot like a<BR>> resonant filter output with a sawtooth wave,
without a filter. Given the<BR>> way that this folder works
(with diode "turnaround" circuits) I'm not sure<BR>> that slew rate
is a significant factor. The opamp outputs in the folder<BR>>
chain are confined to relatively small voltages -- the first one to
about 3V<BR>> or less, and the subsequent ones much less.
Other folders may have<BR>> significantly different modes of
operation where slew rate is important, but<BR>> not the ones based
on diode turnarounds.<BR><BR></SPAN>There's a bit of talking at
cross-purposes here I think. The wave<BR>folder in the CGS29 and also
the Serge wave multiplier (middle<BR>section) also does not generate
"high frequency hash" and works fine<BR>with a fast op amp. Their
design is also similar to your "turnaround"<BR>idea, as it
happens.<BR><BR>The "high frequency hash" business concerns a
different part of the<BR>CGS29, the Grinder section, which exploits op
amp overshoot and<BR>ringing. It makes sense that slew rate is a
factor there. ("High<BR>frequency hash" is a direct quote from Ken
Stone's description of that<BR>circuit, by the way.)<BR>
<DIV class=m_6681943215784096788HOEnZb>
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