Okay, today I witnessed it working. I used a dual supply, and a 9v home power supply. It was the twin T filter.
I got 51mV at 50hz
134mV at 40hz
but a few odd things:
the upper side(above 50hz) was not the same as the rear side behind 50. The front side had less steep of a slope. For instance a 60hz I got like 70mV and also the hill kept climbing and climbing intill it got to about 1.1V near 1khz! Basically, no symetry.
I'm wondering why it came out this way.
I used 47n for C1,C2
and 2 47n caps in paralell for 2*C
68k for R1, R2
34k for the 2/R combining 30k, 3k, and 1k in series for the value.
I'm also trying to figure out what I will do for making the filter compatible with other peoples audio setup since their amplifier's power will varry.