<div dir="auto">How noisy is it, compared to an LM13700 for example?</div><div dir="auto"><br></div><div dir="auto">I'm looking for a simple 2x4 channel waveform mixer so this two-transistor vca looks interresting. My waveforms are already unipolar (0 to -3.3v). I don't mind some distortion unless it turns my triangle into a sine or square :)</div><div dir="auto"><br></div><div dir="auto">By the way, regarding VCA noise, there's a lot about minimizing distortion in LM13700 designs, but what about noise? I understand higher input level gives less noise for more distortion, but what about Iabc? Does lowering Iabc from say 500uA to 250uA (and doubling the gain in the I-V opamp buffer) give better or worse noise performance? And how about other pros and cons? According to my sims, a lower Iabc at least gives less cv bleed-through.</div><div dir="auto"><br></div><div dir="auto">Cheers</div><div dir="auto">/Jonatan</div><div dir="auto"><br></div><div><br><div class="gmail_quote"><div dir="ltr" class="gmail_attr">On Fri, 7 Apr 2023 at 13:57, René Schmitz <<a href="mailto:synth@schmitzbits.de">synth@schmitzbits.de</a>> wrote:<br></div><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left-width:1px;border-left-style:solid;padding-left:1ex;border-left-color:rgb(204,204,204)">
<div>
<div>
<p>You'll find the same VCA in the 909 in a few places. (Bassdrum
, Toms, Clap..)<br>
</p>
<p>Note how far the signal is divided down. <br>
</p>
<p>It's noisy, and nonlinear, and has some control feedthrough.
Show what you can get away with for a single monophonic signal.
<br>
</p>
</div>
<div>The MS10 had the single transistor, the
early "Korg35" MS20 had the same. <br>
</div>
<div>The later MS20 had a second transistor,
which makes things more linear/symmetrical and you can run larger
amplitudes -> less noise. <br>
</div>
<div><br>
</div>
<div>According to the schematics the
transistors shall be selected. jx3p also says "SEL". <br>
</div>
<div><br>
</div>
<div>Anyone would know what for? Equal gain?
<br>
</div>
<div><br>
</div>
<div><br>
</div>
<div>Best,</div>
<div> René<br>
</div></div><div>
<div><br>
</div>
<div>On 07.04.2023 11:04, Adam (synthDIY)
wrote:<br>
</div>
<blockquote type="cite">
<div style="line-break:after-white-space"><br>
<div>David G Dixon via Synth-diy pisze:<br>
<blockquote type="cite">
<div>
<blockquote type="cite" style="font-family:Helvetica;font-size:13px;font-style:normal;font-variant-caps:normal;font-weight:400;letter-spacing:normal;text-align:start;text-indent:0px;text-transform:none;white-space:normal;word-spacing:0px;text-decoration:none">
<blockquote type="cite" style="font-family:Helvetica">
<blockquote type="cite" style="font-family:Helvetica">Whatever the VCA is in the
Korg MS-20 really warms up the sound of that
synthesizer. You can find the schematic on the
internet. I have something redrawn by a fellow
named Marjan Urekar that I looked at years ago. It
involves two transistors. It is evidently also the
VCA used in the Roland JX-3P.</blockquote>
</blockquote>
</blockquote>
</div>
</blockquote>
</div>
<br>
<div><br>
</div>
<div>Interesting.... here's the JX3P version</div>
<div><br>
</div>
<div><img alt="grab 2023-04-07 at 6.57.54 pm.png" src="cid:1875bbae818ad05191f1" style="width:1030px;max-width:100%"></div>
</div>
</blockquote>
<p><br>
</p>
<br>
<p><br>
</p>
<p><br>
</p>
<blockquote type="cite">
<br>
<fieldset></fieldset>
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<pre cols="72" style="font-family:monospace">--
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</blockquote></div></div>-- <br><div dir="ltr" class="gmail_signature" data-smartmail="gmail_signature">/Jonatan<br><a href="http://kymatica.com" target="_blank">http://kymatica.com</a></div>