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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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Thanx, d.<br>
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<div id="divRplyFwdMsg" dir="ltr"><font face="Calibri, sans-serif" style="font-size:11pt" color="#000000"><b>From:</b> Synth-diy <synth-diy-bounces@synth-diy.org> on behalf of cheater cheater via Synth-diy <synth-diy@synth-diy.org><br>
<b>Sent:</b> May 21, 2021 5:45 PM<br>
<b>To:</b> synth-diy <synth-diy@synth-diy.org><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 <mark.erdle@gmail.com><br>
Date: Fri, May 21, 2021 at 2:14 PM<br>
Subject: [funwithtubes] Vacuum Tube Multitasking - The Erla Superflex<br>
To: <main@funwithtubes.groups.io><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 href="https://youtu.be/Lva1lwUUUpw">https://youtu.be/Lva1lwUUUpw</a><br>
<br>
Mark<br>
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