2-Channel Line Output Converter – High To Low Level Speaker Impedance Adapter, RCA

Adding an amp to a factory stereo?

You need this little box.

2-channel high-to-low level converter—takes speaker signal and gives you clean RCA outputs.

Brand new, no-name brand, but it does exactly what it's supposed to.

Small, easy to hide, no external power needed.

If your stock head unit doesn't have preouts, this is the workaround.