Is there a way to have LEDs react to sound from a stereo without using a Mic? Id love to splice into the wires for a speaker to get my input but im not sure what all i would need to filter out noise. Want to install some sound reactive LEDs to my car lol
Why not? It’s an analog signal, and most micro’s can do analog. You would have to make sure the voltage’s are converted and made safe for your circuit but honestly, signal noise wouldn’t be too big a problem I would think. It might be weird though, depending on your sample rate. I guess I don’t know what you want to do with the signals.
I suspect it’s easier to just use a mic planted near a speaker though. Probably less complicated circuitry.
Try out one of these:
That guy also sells a mono version for a few bucks less if you don’t need stereo. But why not get stereo, right? 
[I supported this seller originally when he did these as Kickstarter, and now he sells them on ebay which I think is great.]
@Peter_Buelow unfortunately a Mic is completely drowned by the vibrations coming from the motor in a car lol
@marmil oh snap i was actually looking to buy some of those MSGEQ7 spectrum analizers but i can only buy them 100 at a time. This is great should definitely work for what i need!
Another thought if using a Teensy is adding the audio board.
https://www.pjrc.com/store/teensy3_audio.html
Maybe overkill but could be another option.
I was hoping to use 1 of my Attiny controllers but i can probably do with an Arduino nano. I havent messed with Teensy’s at all yet.
Teensy + audio board + line level inputs would be an easy option