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<DIV><SPAN class=651430921-04072005><FONT face=Arial color=#0000ff size=2>Hi
guys</FONT></SPAN></DIV>
<DIV><SPAN class=651430921-04072005><FONT face=Arial color=#0000ff size=2>Thanks
for the advice...very much appreciated....the board is laided out much larger
than a potted module, I have checked back to 4012 skis, I did have -13V on the
output at one stage, but the offset trims this out nicely, the filter
refuses to oscillate (high resonance is causing signal cancellation rather than
+ feedback). A CV op amp summer would be a good improvement, once I get the
ladder to be frequency controlled. A 4035 replica is on the drawing board...but
I am determined to get this 4012 working first!</FONT></SPAN></DIV>
<DIV><SPAN class=651430921-04072005><FONT face=Arial color=#0000ff
size=2></FONT></SPAN> </DIV>
<DIV><SPAN class=651430921-04072005><FONT face=Arial color=#0000ff size=2>Can
anyone point me to an article that explains how a ladder transistor filter
works? The current sink for the filter seems to be the problem, as it is static
at 8mA with varying CV's. The ladder seems okay as it has a signal output on
both sides at the top (5mV), + and - phase.</FONT></SPAN></DIV>
<DIV><SPAN class=651430921-04072005><FONT face=Arial color=#0000ff
size=2></FONT></SPAN> </DIV>
<DIV><SPAN class=651430921-04072005><FONT face=Arial color=#0000ff size=2>The
expo converter around T14/15 could be a problem. Anyone know what voltage the
base of T3 should be at?</FONT></SPAN></DIV>
<DIV><SPAN class=651430921-04072005><FONT face=Arial color=#0000ff
size=2></FONT></SPAN> </DIV>
<DIV><SPAN class=651430921-04072005><FONT face=Arial color=#0000ff size=2><A
href="http://www.emulatorarchive.com/assets/4012.jpg">http://www.emulatorarchive.com/assets/4012.jpg</A></FONT></SPAN></DIV>
<DIV><SPAN class=651430921-04072005><FONT face=Arial color=#0000ff
size=2></FONT></SPAN> </DIV>
<DIV><SPAN class=651430921-04072005><FONT face=Arial color=#0000ff
size=2>Regards</FONT></SPAN></DIV>
<DIV><SPAN class=651430921-04072005><FONT face=Arial color=#0000ff
size=2>Rob</FONT></SPAN></DIV><!-- |**|end egp html banner|**| --></BODY></HTML>