I am designing a 5-pole low-pass butterworth filter to have a cutoff frequency of ~50 Hz. It has a source impedance of ~1 Ohm, and a load impedance of ~50 Ohm (The load impedance can be changed around if that will help later). Because of these, I am using the "T" configuration. I used the table in the back of The Art of Electronics by Horowitz and Hill, to determine the following values: L1=245.9 mH C2= 107.9 uF L3 = 220 mH C4 = 56.9 uF L5 = 49.18 mH The problem, however, is that I am unable/unwilling to order custom parts with these exact values. Thus, I have chosen parts with the following values: L1=250 mH C2 = 100 uF L3 = 220 mH C4 = 56 uF L5 = 50 mH My question is now what will be the actual cutoff frequency for these values? I have thus far been unable to track down an equation that will help me find this.