This topic area may be a little too broad for this thread, but I'm not totally sure what the problem is.
Quick walkthrough of my project: I'm attempting to use Arduino to take an audio signal that has been run through an RC low pass filter, multiply it in the code, and pass the data to an LED strip. Final product will be a bass-sensitive LED strip for my car. This whole process works fine when the audio source is a 3.5mm headphone jack coming from a phone, but when I attempt to use a Bluetooth-to-AUX device, the Arduino does not pick up any signal.
I've done some analyzing and I BELIEVE the problem is the low pass filter. When I bypass the filter, the Arduino picks up the signal okay, it just picks up the whole signal, not just the bass.
Perhaps the problem is my lack of understanding of RC filters and capacitors, but I have no explanation for why audio signal from a Bluetooth receiver doesn't pass through a low pass filter.
What I figured the difference would be is voltage/current differing between a phone output and Bluetooth receiver output, but I couldn't find anything after a lot of Google searching.
I would appreciate any help on this.