[sdiy] need help with a filter

Nugent, Allison C. (NIH/NIMH) [E] nugenta at mail.nih.gov
Mon Dec 23 04:07:57 CET 2013

For some reason, that distorted the input; perhaps I misunderstood exactly what to do.

In any case, I tried caps from the negative and positive power pins of the TL072 the virtual ground, (something I'd missed from the original filter schematics) and it worked. I'm keeping it isolated on its own chip and its own virtual ground.  The fact that this relatively new breadboard seems to be becoming increasingly flaky was also not helping matters.  Now I just have to fix up my protoboard diagram, solder everything on, and hope for a Christmas miracle that no further debugging is required.

Thank you *so* much for all the help and pointing a complete neophyte with really stupid questions in the right direction.


From: cheater00 . [cheater00 at gmail.com]
Sent: Saturday, December 21, 2013 11:45 PM
To: Nugent, Allison C. (NIH/NIMH) [E]
Cc: Paul Schreiber; synth-diy
Subject: RE: [sdiy] need help with a filter

Put a resistor in series with the voltage rail and one in series with gnd. On the filter side of both resistors add a capacitor. Make the resistors 10-100x higher than the capacitor's ESR. If that works remove the ground resistor.


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