Not as ultra-low frequency as the last filter I published, but it's 2nd order; 12dB/octave, and gets into the upper audio band with tiny inductors. It's still quite easy to adjust once you see which side to adjust first.
Oh wait... it's dependent on the op-amp's exact gain. That is not good at all. :/ Op-amp gain varies with frequency, even in high-speed op-amps.
