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    <div class="moz-cite-prefix">Darren Shorsky via Synth-diy:<br>
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        Interesting question......  I'd love to know more.</div>
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        Hopefully the likes of Eric Barbour come by on occasion.</div>
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        I think this is the first time I've seen/heard anything about
        tubes on the list.</div>
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    <br>
    Well, a couple years ago I linked to this beauty (or the
    predecessor):<br>
    <a class="moz-txt-link-freetext" href="http://knifaudio.com/knifonium/">http://knifaudio.com/knifonium/</a><br>
    <br>
    Don't look at the price tag :D<br>
    <br>
    <a class="moz-txt-link-freetext" href="https://www.youtube.com/watch?v=ZDbQYz5hit8">https://www.youtube.com/watch?v=ZDbQYz5hit8</a><br>
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        Thanx, d.<br>
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      <div id="divRplyFwdMsg" dir="ltr"><font style="font-size:11pt"
          face="Calibri, sans-serif" color="#000000"><b>From:</b>
          Synth-diy <a class="moz-txt-link-rfc2396E" href="mailto:synth-diy-bounces@synth-diy.org"><synth-diy-bounces@synth-diy.org></a> on behalf of
          cheater cheater via Synth-diy <a class="moz-txt-link-rfc2396E" href="mailto:synth-diy@synth-diy.org"><synth-diy@synth-diy.org></a><br>
          <b>Sent:</b> May 21, 2021 5:45 PM<br>
          <b>To:</b> synth-diy <a class="moz-txt-link-rfc2396E" href="mailto:synth-diy@synth-diy.org"><synth-diy@synth-diy.org></a><br>
          <b>Subject:</b> [sdiy] Fwd: [funwithtubes] Vacuum Tube
          Multitasking - The Erla Superflex</font>
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            <div class="PlainText">I seem to remember a filter design
              where the audio and the CV were in<br>
              the same signal, and the CV was very large compared to the
              audio,<br>
              essentially a bias, that set the cut-off. Was that the
              Moog filter<br>
              perhaps?<br>
              <br>
              I wonder if this is where the inspiration for such a
              filter came from.<br>
              <br>
              Cheers<br>
              <br>
              ---------- Forwarded message ---------<br>
              From: Mark <a class="moz-txt-link-rfc2396E" href="mailto:mark.erdle@gmail.com"><mark.erdle@gmail.com></a><br>
              Date: Fri, May 21, 2021 at 2:14 PM<br>
              Subject: [funwithtubes] Vacuum Tube Multitasking - The
              Erla Superflex<br>
              To: <a class="moz-txt-link-rfc2396E" href="mailto:main@funwithtubes.groups.io"><main@funwithtubes.groups.io></a><br>
              <br>
              <br>
              In the early 1920s vacuum tubes and the circuitry to
              operate them were<br>
              expensive items, so there was a great incentive to get the
              most bang<br>
              for the buck out of each tube. As early as 1915, engineers
              realized<br>
              that it was possible to have a single triode vacuum tube
              amplify audio<br>
              and radio frequency signals at the same time. One of the
              more<br>
              successful reflex radio kits was the Erla Superflex of
              1924/25, but<br>
              with the price of vacuum tubes dropping after an RCA
              patent expired,<br>
              the reflex design became obsolete by mid 1925 and the TRF
              and<br>
              superheterodyne took over the radio market.<br>
              <br>
              Robert Lozier takes a look at an Erla Superflex in this
              video:<br>
              <a moz-do-not-send="true"
                href="https://youtu.be/Lva1lwUUUpw">https://youtu.be/Lva1lwUUUpw</a><br>
              <br>
              Mark<br>
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