(4th order, 24 dB/octave, Lowpass)
R=4.7k-10kΩ
<math>Ca=Cc=2 \times Cb</math>
<math>Cb=Cd=\frac {1}{\sqrt{2\pi} \times Fc \times R}</math>
Units: R [Ω], Cx [F], Fc [Hz]
