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Fer has a filter built around these:</div>
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<a href="https://doepfer.de/a1016.htm">Https://doepfer.de/a1016.htm</a></div>
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<b>From:</b> Synth-diy <synth-diy-bounces@synth-diy.org> on behalf of mark verbos via Synth-diy <synth-diy@synth-diy.org><br>
<b>Sent:</b> Friday, 24 October 2025 10:26 AM<br>
<b>To:</b> Mike Bryant <mbryant@futurehorizons.com><br>
<b>Cc:</b> synth-diy@synth-diy.org <synth-diy@synth-diy.org><br>
<b>Subject:</b> Re: [sdiy] Vactrol vs H11F1M optoFET</div>
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<div>These are an interesting subject. I thought they might be a drop in replacement for a Vactrol, so I tried them out. I put 2 of them in a Sallen Key lowpass, like a lopass gate. The output from the filter was like the signal was going through a linear ramped
integrator, rather than a filter. So, while it was filtering out the highs, it was not operating the same as a Vactrol would. This is beyond my understanding, but I guess it is because the Vactrols in a lopass gate are simply resistors and have signal flowing
in both directions where as this is more like the transistors in an MS-20 filter. However, in an MS-20 the signal is reduced way down before going through the transistors, where as in a lopass gate the signal is full level all the way through. So, in that
respect it’s as if there is a comparator before the opto.</div>
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<div>I imagine they would do just fine in more pedestrian applications.</div>
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<div>Mark</div>
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<div>On Oct 24, 2025, at 00:38, Mike Bryant <mbryant@futurehorizons.com> wrote:</div>
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On a related note, has anybody experience using these :</div>
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<a data-auth="NotApplicable" originalsrc="https://www.digikey.co.uk/en/products/detail/onsemi/H11F1M/1793945" class="OWAAutoLink" id="OWA0d6c1292-2a0b-1a0d-a5a2-08f70aae5d4a" href="https://www.digikey.co.uk/en/products/detail/onsemi/H11F1M/1793945">https://www.digikey.co.uk/en/products/detail/onsemi/H11F1M/1793945</a></div>
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Upsides and downsides ?</div>
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<b>From:</b> Synth-diy <<a class="OWAAutoLink" id="OWA187bdaeb-7ac0-23d7-dafd-34b73a81c740" href="mailto:synth-diy-bounces@synth-diy.org">synth-diy-bounces@synth-diy.org</a>> on behalf of crystal via Synth-diy <<a class="OWAAutoLink" id="OWA0719a6b6-71c4-9d84-74fd-e2c49690b203" href="mailto:synth-diy@synth-diy.org">synth-diy@synth-diy.org</a>><br>
<b>Sent:</b> 23 October 2025 22:31<br>
<b>To:</b> mark verbos <<a class="OWAAutoLink" id="OWA47ed46c8-0ebc-eb99-5a64-e76adb37c8b6" href="mailto:markverbos@gmail.com">markverbos@gmail.com</a>><br>
<b>Cc:</b> <a class="OWAAutoLink" id="OWA5eb26a81-5e4d-2738-e62f-96ec119e5fd9" href="mailto:synth-diy@synth-diy.org">synth-diy@synth-diy.org</a> <<a class="OWAAutoLink" id="OWA3750a9f5-f0df-a908-a8ba-a6a93b230426" href="mailto:synth-diy@synth-diy.org">synth-diy@synth-diy.org</a>><br>
<b>Subject:</b> Re: [sdiy] opto isolator "Vactrol" tester</div>
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They're not labeled, but, i think they are that same part. I had some very mixed results , but, since i bought a large bag of them, i just threw the really slow parts in their own envelope. Since they were for my own circuits i liked the (occasional) lower
on resistance.</div>
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Hadn't though to shine a light on them externally. Next time...</div>
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Crystal</div>
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On 10/20/2025 5:06 AM, mark verbos wrote:</div>
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I have had VERY unreliable experience with the Silonex parts. I used NSL-32SR3 which are meant to be the fast ones but I had places where they would take several seconds to decay. Oddly, it made a difference if I had them in an inline resistor verses as one
part of a voltage divider. Also, not necessarily a bad thing, but their on resistance is much lower than in the Vactec/PerkinElmer/Excilitas ones.</div>
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Mark</div>
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On Oct 19, 2025, at 10:58, crystal via Synth-diy <a class="x_x_moz-txt-link-rfc2396E OWAAutoLink" id="OWAa245e3da-6051-b730-ad52-198339c5a975" href="mailto:synth-diy@synth-diy.org">
<synth-diy@synth-diy.org></a> wrote:</div>
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Can someone point to a testing circuit for "Vactrols?"</div>
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I bought a bag full of Siliconex optos years ago, they are all over the map in response time.</div>
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I had tested quite a few in a very crude breadboard setup, mostly just looking at on/off resistance timing and off resistance and then putting them in envelopes with details written on them. I'm sure i could do that again, i'm just wondering if it's been done
better.</div>
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thanks,</div>
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Crystal</div>
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