<html><head><meta http-equiv="content-type" content="text/html; charset=utf-8"></head><body style="overflow-wrap: break-word; -webkit-nbsp-mode: space; line-break: after-white-space;">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><br></div><div>I imagine they would do just fine in more pedestrian applications.</div><div><br></div><div><br></div><div>Mark</div><div> <div><br><div><br></div><div><br></div><div><br id="lineBreakAtBeginningOfMessage"><div><br><blockquote type="cite"><div>On Oct 24, 2025, at 00:38, Mike Bryant <mbryant@futurehorizons.com> wrote:</div><br class="Apple-interchange-newline"><div><meta charset="UTF-8"><div class="elementToProof" style="font-style: normal; font-variant-caps: normal; font-weight: 400; letter-spacing: normal; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; word-spacing: 0px; -webkit-text-stroke-width: 0px; text-decoration: none; font-family: Aptos, Aptos_EmbeddedFont, Aptos_MSFontService, Calibri, Helvetica, sans-serif; font-size: 12pt;">On a related note, has anybody experience using these :</div><div class="elementToProof" style="font-style: normal; font-variant-caps: normal; font-weight: 400; letter-spacing: normal; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; word-spacing: 0px; -webkit-text-stroke-width: 0px; text-decoration: none; font-family: Aptos, Aptos_EmbeddedFont, Aptos_MSFontService, Calibri, Helvetica, sans-serif; font-size: 12pt;"><br></div><div class="elementToProof" style="font-style: normal; font-variant-caps: normal; font-weight: 400; letter-spacing: normal; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; word-spacing: 0px; -webkit-text-stroke-width: 0px; text-decoration: none; font-family: Aptos, Aptos_EmbeddedFont, Aptos_MSFontService, Calibri, Helvetica, sans-serif; font-size: 12pt;"><a 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><div class="elementToProof" style="font-style: normal; font-variant-caps: normal; font-weight: 400; letter-spacing: normal; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; word-spacing: 0px; -webkit-text-stroke-width: 0px; text-decoration: none; font-family: Aptos, Aptos_EmbeddedFont, Aptos_MSFontService, Calibri, Helvetica, sans-serif; font-size: 12pt;"><br></div><div class="elementToProof" style="font-style: normal; font-variant-caps: normal; font-weight: 400; letter-spacing: normal; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; word-spacing: 0px; -webkit-text-stroke-width: 0px; text-decoration: none; font-family: Aptos, Aptos_EmbeddedFont, Aptos_MSFontService, Calibri, Helvetica, sans-serif; font-size: 12pt;">Upsides and downsides ?</div><div id="appendonsend" style="caret-color: rgb(0, 0, 0); font-family: Helvetica; font-size: 12px; font-style: normal; font-variant-caps: normal; font-weight: 400; letter-spacing: normal; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; word-spacing: 0px; -webkit-text-stroke-width: 0px; text-decoration: none;"></div><hr tabindex="-1" style="font-family: Helvetica; font-size: 12px; font-style: normal; font-variant-caps: normal; font-weight: 400; letter-spacing: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: auto; word-spacing: 0px; -webkit-text-stroke-width: 0px; text-decoration: none; display: inline-block; width: 1294.578125px;"><span style="caret-color: rgb(0, 0, 0); font-family: Helvetica; font-size: 12px; font-style: normal; font-variant-caps: normal; font-weight: 400; letter-spacing: normal; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; word-spacing: 0px; -webkit-text-stroke-width: 0px; text-decoration: none; float: none; display: inline !important;"></span><div id="divRplyFwdMsg" dir="ltr" style="caret-color: rgb(0, 0, 0); font-family: Helvetica; font-size: 12px; font-style: normal; font-variant-caps: normal; font-weight: 400; letter-spacing: normal; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; word-spacing: 0px; -webkit-text-stroke-width: 0px; text-decoration: none;"><font face="Calibri, sans-serif" style="font-size: 11pt;"><b>From:</b><span class="Apple-converted-space"> </span>Synth-diy <<a href="mailto:synth-diy-bounces@synth-diy.org">synth-diy-bounces@synth-diy.org</a>> on behalf of crystal via Synth-diy <<a href="mailto:synth-diy@synth-diy.org">synth-diy@synth-diy.org</a>><br><b>Sent:</b><span class="Apple-converted-space"> </span>23 October 2025 22:31<br><b>To:</b><span class="Apple-converted-space"> </span>mark verbos <<a href="mailto:markverbos@gmail.com">markverbos@gmail.com</a>><br><b>Cc:</b><span class="Apple-converted-space"> </span><a href="mailto:synth-diy@synth-diy.org">synth-diy@synth-diy.org</a><span class="Apple-converted-space"> </span><<a href="mailto:synth-diy@synth-diy.org">synth-diy@synth-diy.org</a>><br><b>Subject:</b><span class="Apple-converted-space"> </span>Re: [sdiy] opto isolator "Vactrol" tester</font><div> </div></div><div style="caret-color: rgb(0, 0, 0); font-family: Helvetica; font-size: 12px; font-style: normal; font-variant-caps: normal; font-weight: 400; letter-spacing: normal; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; word-spacing: 0px; -webkit-text-stroke-width: 0px; text-decoration: none; background-color: rgb(255, 255, 255);"><div style="margin-top: 0px; margin-bottom: 0px;"><font size="4">They're not labeled, but, i think they are that same part. </font><font size="4">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 </font><font size="4">(occasional)<span class="Apple-converted-space"> </span></font><font size="4">lower on resistance.</font></div><div style="margin-top: 0px; margin-bottom: 0px;"><font size="4">Hadn't though to shine a light on them externally. Next time...</font></div><div style="margin-top: 0px; margin-bottom: 0px;">Crystal</div><div class="x_moz-cite-prefix">On 10/20/2025 5:06 AM, mark verbos wrote:<br></div><blockquote type="cite">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><br></div><div>Mark<br><div><br></div><div><br></div><div><br id="x_lineBreakAtBeginningOfMessage"><div><br><blockquote type="cite"><div>On Oct 19, 2025, at 10:58, crystal via Synth-diy<span class="Apple-converted-space"> </span><a class="x_moz-txt-link-rfc2396E" href="mailto:synth-diy@synth-diy.org"><synth-diy@synth-diy.org></a><span class="Apple-converted-space"> </span>wrote:</div><br class="x_Apple-interchange-newline"><div><div bgcolor="#FFFFFF"><div style="margin-top: 0px; margin-bottom: 0px;"><font size="4">Can someone point to a testing circuit for "Vactrols?"</font></div><div style="margin-top: 0px; margin-bottom: 0px;"><font size="4">I bought a bag full of Siliconex optos years ago, they are all over the map in response time.</font></div><div style="margin-top: 0px; margin-bottom: 0px;"><font size="4">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.</font></div><div style="margin-top: 0px; margin-bottom: 0px;"><font size="4"><br></font></div><div style="margin-top: 0px; margin-bottom: 0px;"><font size="4">thanks,</font></div><div style="margin-top: 0px; margin-bottom: 0px;"><font size="4"> Crystal</font></div></div>________________________________________________________<br>This is the Synth-diy mailing list<br>Submit email to:<span class="Apple-converted-space"> </span><a class="x_moz-txt-link-abbreviated" href="mailto:Synth-diy@synth-diy.org">Synth-diy@synth-diy.org</a><br>View archive at:<span class="Apple-converted-space"> </span><a class="x_moz-txt-link-freetext" href="https://synth-diy.org/pipermail/synth-diy/">https://synth-diy.org/pipermail/synth-diy/</a><br>Check your settings at:<span class="Apple-converted-space"> </span><a class="x_moz-txt-link-freetext" href="https://synth-diy.org/mailman/listinfo/synth-diy">https://synth-diy.org/mailman/listinfo/synth-diy</a><br>Selling or trading? 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