So, since I lost my first lowpass filter, I decided to remake it. One of the things I despised about my first design was that one of my legs on the potentiometer went unused which, in my eyes, is a waste of potential, so I decided to crop out the LED output to remove the slight drop in voltage it probably caused and add a dual half-wave LED output circuit that turns on when you put the filter to its highest setting.

Another "improvement" I decided I'd try on this model was adding a capacitor that is about 160 times larger than the last, clocking in at a decent 470 microfarads, rather than my other tiny little ceramic capacitor I used on V1. This doesn't sound like it makes a difference when I plug headphones in, but then again, I am using a dog collar LED blinker as an oscillator, so it's not really a good case for the circuit.

back - https://www.furaffinity.net/view/35709061/
diagram - https://www.furaffinity.net/view/35709405/