Friday, June 24, 2011

Isolating the ferrite inductor

In my previous design for notch-blend filter, I by necessity use a ferrite core inductor, since values like 127mH would be mind bogglingly huge in air core (even a 10mH air core weighs a bunch and sells for $77, now imagine having 13 of those).

Maybe I'm thinking about this wrongly, but it seems it might help the midrange to "isolate" the choke by putting capacitors on either side, instead of just on one side.  So instead of having one 1800pF capacitor, I could have two 3600pF capacitors, one on either side of the choke.  Thus only very high frequencies see the inductor in the first place.

The reason why this might not be true is that electrical circuits are "networks", and one part doesn't see other parts until they are actually in a full circuit, and once there is a full circuit, it doesn't matter where you put the nasty part, the nastyness will be everywhere.

Or another reason might be that even with the capacitor just on one side, the choke is effectively out-of-circuit at high freqencies.

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