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<div class="moz-cite-prefix">On 10/5/18 11:23 PM, David G Dixon
wrote:<br>
</div>
<blockquote type="cite"
cite="mid:A281021A1453412D8149B53F4958C2A9@galvanox01">
<blockquote type="cite" style="color: #000000;">
<pre wrap="">Seems even many that tried to help you with this, you didn't
even say "thanks" after they took the time to try and help you.
</pre>
</blockquote>
<pre wrap="">Um, I guess you didn't see my previous message in response to Don Tillman
(who is the only one who offered any concrete answers to my actual
questions):
</pre>
</blockquote>
no, this one:
<div dir="ltr" align="left"><span class="765185304-05102018"><font
face="Arial" size="2" color="#0000ff">Yes, I realized the next
morning that I had overlooked the loop gain factor, but
couldn't get on email until now.</font></span></div>
<br>
<div dir="ltr" class="OutlookMessageHeader" align="left"
lang="en-us">
<hr tabindex="-1"> <font face="Tahoma" size="2"><b>From:</b>
Donald Tillman [<a class="moz-txt-link-freetext" href="mailto:don@till.com">mailto:don@till.com</a>] <br>
<b>Sent:</b> Thursday, October 04, 2018 7:08 PM<br>
<b>To:</b> David G Dixon<br>
<b>Cc:</b> <a class="moz-txt-link-abbreviated" href="mailto:synth-diy@synth-diy.org">synth-diy@synth-diy.org</a><br>
<b>Subject:</b> Re: [sdiy] Polymoog resonator question<br>
</font><br>
</div>
<div>Hey Dave,</div>
<div><br>
</div>
<div>The inverter stage in those filters attenuates, reducing the
loop gain by a factor of 10, lowering the tuned frequency by a
factor of the square root of 10. </div>
<div><br>
</div>
<div>On a more philosophical note, this is because a state variable
filter isn't R's and C's; it's two integrators and an inversion in
a loop. It doesn't matter how those parts are implemented, the
overall equation is the same. </div>
<div><br>
</div>
<div>In this case, the attenuation in the inverter stage is
equivalent to each of the integrators tuned down by sqrt(10).</div>
<div><br>
</div>
<div> -- Don</div>
<div>--<br>
Donald Tillman, Palo Alto, California<br>
<a href="http://www.till.com">http://www.till.com</a></div>
<span class="765185304-05102018"></span>
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