Document Macintosh USB audio workaround

examples/HardwareTesting/PassThroughUSB/PassThroughUSB.ino

 void loop() {
   // TODO: make PC's volume setting control the SGTL5000 volume...
 }
+
+// A known problem occurs on Macintosh computers, where the Mac's driver
+// does not seem to be able to adapt and transmit horribly distorted
+// audio to Teensy after a matter of minutes.  An imperfect workaround
+// can be enabled by editing usb_audio.cpp.  Find and uncomment
+// "#define MACOSX_ADAPTIVE_LIMIT".  More detailed info is available here:
+// https://forum.pjrc.com/threads/34855-Distorted-audio-when-using-USB-input-on-Teensy-3-1?p=110392&viewfull=1#post110392
+

examples/HardwareTesting/WavFilePlayerUSB/WavFilePlayerUSB.ino

   playFile("SDTEST4.WAV");
   delay(1500);
 }
+
+// A known problem occurs on Macintosh computers, where the Mac's driver
+// does not seem to be able to adapt and transmit horribly distorted
+// audio to Teensy after a matter of minutes.  An imperfect workaround
+// can be enabled by editing usb_audio.cpp.  Find and uncomment
+// "#define MACOSX_ADAPTIVE_LIMIT".  More detailed info is available here:
+// https://forum.pjrc.com/threads/34855-Distorted-audio-when-using-USB-input-on-Teensy-3-1?p=110392&viewfull=1#post110392

gui/index.html

 	<p>USB input &amp; output does not cause the Teensy Audio Library to
 		update.  At least one non-USB input or output object must be
 		present for the entire library to update properly.</p>
+	<p>A known problem exists with USB audio from Macintosh computers.
+		An imperfect <a href="https://forum.pjrc.com/threads/34855-Distorted-audio-when-using-USB-input-on-Teensy-3-1?p=110392&viewfull=1#post110392">workaround
+		can be enabled by editing usb_audio.cpp</a>.
+		Find and uncomment "#define MACOSX_ADAPTIVE_LIMIT".</p>
 </script>
 <script type="text/x-red" data-template-name="AudioInputUSB">
 	<div class="form-row">
 	<p>USB input &amp; output does not cause the Teensy Audio Library to
 		update.  At least one non-USB input or output object must be
 		present for the entire library to update properly.</p>
+	<p>A known problem exists with USB audio from Macintosh computers.
+		An imperfect <a href="https://forum.pjrc.com/threads/34855-Distorted-audio-when-using-USB-input-on-Teensy-3-1?p=110392&viewfull=1#post110392">workaround
+		can be enabled by editing usb_audio.cpp</a>.
+		Find and uncomment "#define MACOSX_ADAPTIVE_LIMIT".</p>
 </script>
 <script type="text/x-red" data-template-name="AudioOutputUSB">
 	<div class="form-row">