Well I finally got my first car registered to me! A 1975 Dodge D100 pickup. The first thing I wanted to do was fix up my radio so I could listen to music from my phone through the speakers. I had one of those cassette adapters, which worked fine but only if you could jiggle it just right and not hit any bumps in the road. So I put in an AUX jack, wired straight to the board where the cassette head leads. It works, but if my phone is turned up any louder than 2, the sound becomes very loud and distorted and if I plug my CD player into it, the motor from that causes loud staticy interference.
I think I might need to add something to stop it, but I'm not fully sure what... I opened the cassette adapter to see what it had, but there's nothing in it but wires going straight to the head. Does the head act like a diode (making the signal one way)? Or do I need capacitors or resistors and what value?
This is my radio by the way, if that helps any.
https://www.allpar.com/stereo/1980/index.html