update XLR entries

add info describing difference in electrical impedance between analog and digital audio XLR cables, how to identify

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@@ -1020,7 +1020,7 @@ <h3><a href="pinouts.html#xlr">Balanced XLR</a></h3>
  <img src="images/Audio/xlr_cork_port.jpg" data-toggle="tooltip" data-placement="bottom" title="http://jp.music-group.com/TCE/CR/StudioKonnekt48/images/main_out_xlr_large.jpg">
  <img src="images/Audio/xlr_bottle_port.jpg" data-toggle="tooltip" data-placement="bottom" title="http://proaudioblog.co.uk/wp-content/uploads/2014/06/XLR-Input.jpg">
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- <p>A three-pin connector favored for long balanced cables in pro audio equipment.</p>
+ <p>A three-pin connector favored for long balanced cables in pro audio equipment. Tradionally, analog XLR audio connectors had an electrical impedance of 75 ohms (75 Ω). Digital audio signals using the XLR connector required a higher impedance (110 Ω), but this would have no effect on analog signals - therefore, 110 Ω XLR cables intended for digital audio can safely be used for balanced analog audio connections as well. See <a href="#aes-3">AES-3</a>.</p>
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@@ -1194,16 +1194,16 @@ <h4 id="aes-3">AES-3</h4>
  <h5>Balanced</h5>
 
 <!-- AES-3 Balanced XLR -->
-<span data-toggle="modal" data-target="#aes-3_balanced_xlr"><button type="button" class="btn btn-default"><img src="images/Audio/xlr_cork_bottle_cable.jpg" class="img-responsive" style="max-height:100px; width:auto;">XLR</button></span>
+<span data-toggle="modal" data-target="#aes-3_balanced_xlr"><button type="button" class="btn btn-default"><img src="images/Audio/aes_xlr_cork_bottle.jpg" class="img-responsive" style="max-height:100px; width:auto;">XLR</button></span>
 <div id="aes-3_balanced_xlr" class="modal fade" tabindex="-1" role="dialog">
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  <h3><a href="pinouts.html#xlr">AES-3 XLR</a></h3>
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- <img src="images/Audio/xlr_cork_bottle_cable.jpg" data-toggle="tooltip" data-placement="bottom" title="https://upload.wikimedia.org/wikipedia/commons/1/15/Xlr-connectors.jpg">
+ <img src="images/Audio/aes_xlr_cork_bottle.jpg" data-toggle="tooltip" data-placement="bottom" title="https://d3d71ba2asa5oz.cloudfront.net/33000510/images/sapgx-ends_1000.jpg">
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- <p>The most common variant of AES-3 connection, found with professional installations and equipment.</p>
+ <p>The most common variant of AES-3 connection, found with professional installations and equipment. Compared to their <a href="#balanced-xlr">analog</a> equivalents, digital AES cables used an XLR connector with higher electrical impedance (110 ohm instead of 75). Using a 75 ohm cable intended for analog use with a digital audio signal like AES-3 could result in the introduction of extra noise and fuzziness into the signal. 110 ohm XLR cables intended for AES-3 were sometimes identified by gold plating such as those pictured, but not always. If in doubt as to whether an XLR cable is 75 or 110 ohm, one must directly <a href="https://www.wikihow.com/Use-an-Ohmmeter">measure</a> the connector's electrical impedance.</p>
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