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<p class=MsoNormal><font size=2 face=Arial><span lang=SV style='font-size:10.0pt;
font-family:Arial'>Hi all!<br>
<br>
<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'>I have constructed a jitter measurement device (called the
jitterbug, actually ;-) with a resolution down to 100ns. I have done some initial
measurements on the synths I have at home. No conclusive results yet. But the jitterbug
works very well. My plan is to measure all different VCO topologies I can get
my hands on and present the results on a web page with statistical analysis,
distribution diagrams and everything. <o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'>However, I need your help with the trigger circuit. It uses
a LM311. There is an image of the current design here:<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'><a href="http://www.minod.com/jitter/schemo.gif">http://www.minod.com/jitter/schemo.gif</a><o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'>The problem is that it has to be trimmed in with an
oscilloscope before each measurement as to remove oscillation and false
triggers. My scope goes up to 20MHz and has no memory, so it is very difficult
to see when the trig pulse is ok. It is not impossible though. <o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'>I want the trigger circuit to be useable without using a
scope and without a very pure input waveform if possible. Right now I have to
hack into the VCO core itself, since the slopes at the audio output of the
synth often is not very sharp. Most synths cannot open the filter enough it
seems. <o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'>So, for the benefit of science and our future VCO constructions
please help me with the trigger circuit!<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'>Fredrik C<o:p></o:p></span></font></p>
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