<html><body style="word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space;" class=""><br class=""><div class=""><div class=""><br class=""><blockquote type="cite" class=""><div class="">Am 09.02.2024 um 21:42 schrieb Mike Bryant <<a href="mailto:mbryant@futurehorizons.com" class="">mbryant@futurehorizons.com</a>>:</div><br class="Apple-interchange-newline"><div class=""><div class="elementToProof" style="font-family: Aptos, Aptos_EmbeddedFont, Aptos_MSFontService, Calibri, Helvetica, sans-serif; font-size: 12pt;">R5 C4 VR1 also form a variable frequency element as well as controlling the feedback level. Hence the waa effect.<br class=""></div><div id="appendonsend" class=""></div><hr tabindex="-1" class="" style="display: inline-block; width: 1106.40625px;"><div id="divRplyFwdMsg" dir="ltr" class=""><font face="Calibri, sans-serif" class="" style="font-size: 11pt;"><b class="">From:</b> Synth-diy <<a href="mailto:synth-diy-bounces@synth-diy.org" class="">synth-diy-bounces@synth-diy.org</a>> on behalf of Ingo Debus via Synth-diy <<a href="mailto:synth-diy@synth-diy.org" class="">synth-diy@synth-diy.org</a>><br class=""><b class="">Sent:</b> 09 February 2024 20:28<br class=""><b class="">To:</b> SDIY List <<a href="mailto:synth-diy@synth-diy.org" class="">synth-diy@synth-diy.org</a>><br class=""><b class="">Subject:</b> Re: [sdiy] Unique sounding modules that can't have voltage control?</font><div class=""> </div></div><div class="" style="word-wrap: break-word; line-break: after-white-space;"></div></div></blockquote>[…]<br class=""><blockquote type="cite" class=""><div class=""><div class="" style="word-wrap: break-word; line-break: after-white-space;"><div class="">Looking at this description of the Cry Baby:</div><div class=""><a href="https://www.electrosmash.com/crybaby-gcb-95" class="">https://www.electrosmash.com/crybaby-gcb-95</a></div><div class=""><br class=""></div><div class="">It seems to me that the pot just sets the amount of feedback. This could be easily replaced by a VCA. Am I missing something?</div></div><br class="Apple-interchange-newline"></div></blockquote></div><br class=""><div class="">So I downloaded the LTSpice model of the Cry Baby here:</div><div class=""><a href="https://cushychicken.github.io/ltspice-dunlop-crybaby/" class="">https://cushychicken.github.io/ltspice-dunlop-crybaby/</a></div><div class=""><br class=""></div><div class="">Here’s the frequency plot for various positions of the potentiometer:</div><div class=""><img apple-inline="yes" id="99E833FA-3A34-4C36-B708-C846E35593A4" class="" width="320" height="177" src="cid:ACFF5095-0F86-474D-9117-36E1831AD156"></div><div class=""><br class=""></div><div class="">Then I replaced the potentiometer R14/R12 with a „voltage controlled voltage source“, emulating an ideal VCA. The gain was set to the same values the (unloaded) potentiometer would yield. Here’s the result:</div><div class=""><img apple-inline="yes" id="B95C0AD9-D823-4D03-9981-E75E4BAB561E" class="" width="320" height="175" src="cid:F7EB41B7-E3E9-4204-B6C2-959EAAB9C87B"></div><div class=""><br class=""></div><div class="">Almost the same as the real thing. The peaks at the low frequencies are slightly higher.</div><div class="">So my conclusion is, the pot in the Cry Baby can be replaced by a VCA without altering the performance very much.</div><div class=""><br class=""></div><div class="">Ingo</div></div></body></html>