I got a cookie jar full of amazingly large inductors, so of course I want to try and build a passive low pass filter. Variable stepwise.
Here’s a Youtube of me testing inductors with noise[…
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Oddly well timed. I was just looking into passive filters and came across the inductor method. Neat stuff.
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Well, it’s moving along. Soldered together a playable prototype… 
Very simple:
• Selector center switch changes capacitors and connects more and more of the inductors in series.
• Toggle switch changes which (inductor or capacitor) goes to earth and out respectively; making it either highpass or lowpass.
• Resistors compensate for volume loss per frequency and for “Flat”.
Sorry for the low volume on the Youtube example, I’ll be back with some more musical tests soon… 
Here’s a testrun:
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