Did you ever find the need for a variable frequency low cut filter?
If so, this will give you a slope of 12 db per octace below the selected
cutoff frequency. There is even an adjustment for the "Q" of the filter.
Here is the schematic
Parts list
C1 .1uf
C2 .1uf
R1 47k
R2 4.7k
R3 4.7k
R4 10k
R5 5.6k
U1, U2, U3 are 3 sections of a quad op amp
VR1, VR2 Dual 100k potentiometer from radio shack
Specs:
Cutoff freq 18 hz to 350 hz
Q range 0.5 to 3.0
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