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<p>Hi Kevin,</p>
<p><br>
</p>
<p>You may want to look into a voltage controllable envelope
generator design.</p>
<p>A good example is Juergen Haible's VC HADSR:</p>
<p><a class="moz-txt-link-freetext" href="http://jhaible.com/legacy/tonline_stuff/hj_vc_hadsr.html">http://jhaible.com/legacy/tonline_stuff/hj_vc_hadsr.html</a></p>
<p><br>
</p>
<p>- Oren<br>
</p>
<p><br>
</p>
<div class="moz-cite-prefix">On 4/27/20 8:45 PM, Kevin Walsh wrote:<br>
</div>
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<span>Hi all,<br>
</span>
<div><br>
</div>
<div>I have never posted a question here but I have been
subscribed for several years and I have learned a lot from
reading the threads. Thank you all for this.
<br>
</div>
<div><br>
</div>
<div>I am an sdiy hobbyist who enjoys making modules for my own
use. I occasionally make music and I have played a few gigs
out locally.<br>
</div>
<div><br>
</div>
<div>I have recently finished my own version of the Thomas Henry
'Clangora'. I couldn't find NE566's (VCO's) so I just swapped
them out for LM13700's and done the same with the NE571
(VCA's) while I was at it.<br>
</div>
<div><br>
</div>
<div>I also added the XOR noise source and VCF's from Ken
Stone's Cynare circuit.
<br>
</div>
<div><br>
</div>
<div>It was looking like a huge module so I decided to not add
CV control on version one. Now that it is finished I am really
happy with how it sounds and I want to add CV control to the
next version.<br>
</div>
<div><br>
</div>
<div>I know how to stick in a OTA VCA here and there to add CV
control to the Sweep and FM etc but I can't get my head around
how to use an OTA to replace the variable resistors that are
controlling the open and closed decay times.<br>
</div>
<div><br>
</div>
<div>I know I could use a vactrol but these are pricey, bulky
and slow etc so I'd rather not have to use them.
<br>
</div>
<div><br>
</div>
<div>My guess after looking at the LM13700 datasheet would be
that I need to use the 'floating vc resistor' configuration.<br>
</div>
<div><br>
</div>
<div>I am no EE so I am totally patching bits of circuits from
my Thomas Henry books together and hoping it sounds good :D<br>
</div>
<div><br>
</div>
<div>Is it the 'floating VC resistor' configuration that I need
to use in place of the open and closed decay resistors or is
it something crazy complicated that's not in the datasheet?<br>
</div>
<div><br>
</div>
<div><span style="font-family: Calibri, Helvetica, sans-serif;
background-color: rgb(255, 255, 255); display: inline
!important">Any advice on what I need to do here would be
greatly appreciated.</span><br>
</div>
<div><span style="font-family: Calibri, Helvetica, sans-serif;
background-color: rgb(255, 255, 255); display: inline
!important"><br>
</span></div>
<div><span style="font-family: Calibri, Helvetica, sans-serif;
background-color: rgb(255, 255, 255); display: inline
!important"><span style="font-family: Calibri, Helvetica,
sans-serif; background-color: rgb(255, 255, 255); display:
inline !important">Many thanks in advance for any advice.</span><br>
</span></div>
<div><span style="font-family: Calibri, Helvetica, sans-serif;
background-color: rgb(255, 255, 255); display: inline
!important"><br>
</span></div>
<div>Here's the trigger logic and envelope generator section of
the original circuit which I downloaded in a PDF from
Nuts&Volts (Nov2003):<br>
</div>
<div><a class="moz-txt-link-freetext" href="https://i.imgur.com/GXw9KVR.jpg">https://i.imgur.com/GXw9KVR.jpg</a><br>
</div>
<div><br>
</div>
<div>My sketchy block diagram:<br>
</div>
<div><a class="moz-txt-link-freetext" href="https://i.imgur.com/absDij1.png">https://i.imgur.com/absDij1.png</a><br>
</div>
<div><br>
</div>
<div>A video of my first version of this module:<br>
</div>
<div><a class="moz-txt-link-freetext" href="https://youtu.be/mq05zgHSYso">https://youtu.be/mq05zgHSYso</a><br>
</div>
<div><br>
</div>
<div>And my (slightly ridiculous) intended layout for the
version two front panel:<br>
</div>
<div><a class="moz-txt-link-freetext" href="https://i.imgur.com/n0LzEoq.png">https://i.imgur.com/n0LzEoq.png</a><br>
</div>
<div><br>
</div>
<div>My whole synth (last year):<br>
</div>
<div><a class="moz-txt-link-freetext" href="https://i.imgur.com/lcdscrw.jpg">https://i.imgur.com/lcdscrw.jpg</a><br>
</div>
<div><br>
</div>
<div>Best regards,<br>
</div>
<div>Kevin Walsh.<br>
</div>
<span></span></div>
<div>
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<div><br>
</div>
<div>-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------</div>
<div><br>
</div>
</div>
</div>
</div>
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