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<div class="moz-cite-prefix">On 09.04.2023 01:52, Richie Burnett
wrote:<br>
</div>
<blockquote type="cite"
cite="mid:g0n1ea4319tta1nvo9ptkysp.1680997971072@email.android.com">
<blockquote type="cite">
<pre class="moz-quote-pre" wrap="">I couldn't find the 2SD1469 ... what's the part designation on the schematic?
</pre>
</blockquote>
<pre class="moz-quote-pre" wrap="">
Q47 and Q48 underneath where it says "Snare Drum" on the Voicing Board schematic.
I noticed that people online building hardware comes of the 909 snare drum voicing circuitry recommend fitting ZTX1051A devices in these locations. That is a 4A rated switching transistor! Apparently a general purpose small-signal NPN transistor here doesn't give the right sound, but they don't say why!
</pre>
</blockquote>
<p><br>
</p>
<p>I wouldn't interpret too much into this. Has someone really made
a double blind study with statistical significance? <br>
</p>
<p>Our ears are so easily fooled by our expectations. <br>
</p>
<p><br>
</p>
<p>The ZTX seems to come from the 909 clone of Trevor Page.</p>
<p>He writes:<br>
</p>
<p><span style="left: 21.18%; top: 9.58%; font-size:
calc(var(--scale-factor)*7.20px); font-family: sans-serif;
transform: scaleX(1.14754);" role="presentation" dir="ltr">"A
number of transistors were tried in place of the 2SD1469;
ZTX1051A worked the best.</span><br role="presentation">
<span style="left: 21.18%; top: 11.01%; font-size:
calc(var(--scale-factor)*7.20px); font-family: sans-serif;
transform: scaleX(1.11615);" role="presentation" dir="ltr">These
transistors are available from Rapid Electronics in the UK.</span>"</p>
<p>I read that as: "I use it because I liked it and I know where to
get them".</p>
<p>The rest is copy pasta. RE-909 mentions the same part. The origin
story eventually gets lost and myths are created.<br>
</p>
<p>BC635 would be a closer match, and would have the same pinout. <br>
</p>
<p><br>
</p>
<p>The reason to use a switching transistor could be it's lower
Vce(sat). Which would maybe reduce the DC offset / feed through. <br>
</p>
<p>Then again these tend to have lower beta, which makes more DC
feed through. <br>
</p>
<p><br>
</p>
<p>As we said before, most of the artefacts would be masked anyway,
and hence I can't see how it would make a significant difference
to use this extra part. <br>
</p>
<p>That it potentially makes a difference now, when you try to
recreate the 909 sound (or as said above maybe it's actually
"season to taste") is a different question, <br>
</p>
<p>compared to back in the day where the designers had the freedom
to define what that sound is to begin with.<br>
</p>
<p><br>
</p>
<p>Why they used different parts in different places?<br>
</p>
<p>Totally hypothetically: <br>
</p>
<p>The designer originally intended to use 2SD1469 for all these
VCAs. <br>
</p>
<p>Then at a time it was realized they could use the same jellybean
NPN.</p>
<p>And overlooked to change the ones in the snare. (Maybe this was
done with pen and paper still...) <br>
</p>
<p>OR</p>
<p>There were several people working on different parts, and the guy
doing the snare had different preferences then the one doing the
bass or clap. <br>
</p>
<p>OR <br>
</p>
<p>The designer changed his mind mid way, and didn't want to re-test
parts that had already been finalized. <br>
</p>
<br>
<p></p>
<p>What I'm trying to say is, that there are possibly more mundane
explanations for certain part choices. <br>
</p>
<p><br>
</p>
<p>Best,</p>
<p> René<br>
</p>
<p><br>
</p>
<pre class="moz-signature" cols="72">--
<a class="moz-txt-link-abbreviated" href="mailto:synth@schmitzbits.de">synth@schmitzbits.de</a>
<a class="moz-txt-link-freetext" href="http://schmitzbits.de">http://schmitzbits.de</a></pre>
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