<div dir="ltr"><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><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><div dir="ltr"><span style="color:rgb(34,34,34);text-transform:none;text-indent:0px;letter-spacing:normal;font-family:arial,sans-serif;font-size:12.8px;font-style:normal;font-weight:400;word-spacing:0px;float:none;display:inline;white-space:normal;background-color:rgb(255,255,255);font-variant-caps:normal;font-variant-ligatures:normal;text-decoration-style:initial;text-decoration-color:initial">" 'High </span><span style="color:rgb(34,34,34);text-transform:none;text-indent:0px;letter-spacing:normal;font-family:arial,sans-serif;font-size:12.8px;font-style:normal;font-weight:400;word-spacing:0px;float:none;display:inline;white-space:normal;background-color:rgb(255,255,255);font-variant-caps:normal;font-variant-ligatures:normal;text-decoration-style:initial;text-decoration-color:initial">frequency hash' is a direct quote from Ken Stone's description of that</span><br style="color:rgb(34,34,34);text-transform:none;text-indent:0px;letter-spacing:normal;font-family:arial,sans-serif;font-size:12.8px;font-style:normal;font-weight:400;word-spacing:0px;white-space:normal;background-color:rgb(255,255,255);font-variant-caps:normal;font-variant-ligatures:normal;text-decoration-style:initial;text-decoration-color:initial"><span style="color:rgb(34,34,34);text-transform:none;text-indent:0px;letter-spacing:normal;font-family:arial,sans-serif;font-size:12.8px;font-style:normal;font-weight:400;word-spacing:0px;float:none;display:inline;white-space:normal;background-color:rgb(255,255,255);font-variant-caps:normal;font-variant-ligatures:normal;text-decoration-style:initial;text-decoration-color:initial">circuit, by the way."</span><div><span style="color:rgb(34,34,34);text-transform:none;text-indent:0px;letter-spacing:normal;font-family:arial,sans-serif;font-size:12.8px;font-style:normal;font-weight:400;word-spacing:0px;float:none;display:inline;white-space:normal;background-color:rgb(255,255,255);font-variant-caps:normal;font-variant-ligatures:normal;text-decoration-style:initial;text-decoration-color:initial"><br></span></div><div><span style="color:rgb(34,34,34);text-transform:none;text-indent:0px;letter-spacing:normal;font-family:arial,sans-serif;font-size:12.8px;font-style:normal;font-weight:400;word-spacing:0px;float:none;display:inline;white-space:normal;background-color:rgb(255,255,255);font-variant-caps:normal;font-variant-ligatures:normal;text-decoration-style:initial;text-decoration-color:initial">- and the band name for my new EDM / free jazz group. </span></div><div><span style="color:rgb(34,34,34);text-transform:none;text-indent:0px;letter-spacing:normal;font-family:arial,sans-serif;font-size:12.8px;font-style:normal;font-weight:400;word-spacing:0px;float:none;display:inline;white-space:normal;background-color:rgb(255,255,255);font-variant-caps:normal;font-variant-ligatures:normal;text-decoration-style:initial;text-decoration-color:initial"><br></span></div><div><br></div><div class="gmail_extra"><div><div class="m_6681943215784096788gmail_signature" data-smartmail="gmail_signature"><div dir="ltr"><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><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;padding-left:1ex;border-left-color:rgb(204,204,204);border-left-width:1px;border-left-style:solid"><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>
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