[Roofus] had an older car, and unfortunately his stereo’s cassette player just wasn’t doing it for him. He always wanted to simply get into his car, pull out his cell phone, and have his music ready to play without any fuss. After messing around with all sorts of different tape adapters, he got fed up and decided to rig up an A2DP (Stereo Bluetooth Audio) adapter on his own.
He pulled the head unit out and started looking around to see how he could wire an adapter in. He figured the best course of action would be to remove the tape deck, and fool the stereo into thinking that a tape had been inserted. After spending some time tracing wires and studying how his old tape adapters worked, [Roofus] had an A2DP connection wired in and was ready to rock out.
Greeted with nothing but silence, he turned to his favorite hacking site (Hackaday, naturally) for assistance. Some friendly forum-goers helped him identify a ground loop issue, and he set off to his nearest RadioShack for a pair of isolation transformers that would fix his problem.
Once he knocked out the ground loop issues, his adapter worked like a charm. He put everything back together, and aside from a tiny switch he installed to toggle between audio sources, you would never know it was there.