[sdiy] LC filter formula questions

[jhaible]

>Why are you not using a leap-frog realisation? It's not that hard to
generate
>and it is a cool way to make filters. It takes some exercise to debug, but
it
>is doable (just learn to lift the feedback loops to get a cleaner
response).

Is "Leapfrog" = FDNR ?

Asuming it is, then for the simple (uncoupled) Line I found it's better
to just use inductors. (See the discussion at
http://www.oldcrows.net/~jhaible/scanner_vibrato/jh_scanner_vibrato.html
)
Cheap opamps won't do it, and expensive opamps are - well - more
expensive than inductors.

For a version with coupled inductors that would be an entirely different
story, of course.

Best Regards,

JH.