He altered the head unit to play MP3 files from USB and added an auxiliary line-in ... work he did to create a false button hiding the audio jack, and a false cassette hiding the USB port and ...

1/4'' to 3.5mm Audio Jack Adapters allow a 6.35mm stereo port to connect a 3.5mm plug aux cable Connect audio devices such as guitar amplifiers and AV receivers to headphones or MP3 Players with 6 ...

Cutting off the plastic case can help too. Depending on your choice of audio player, you may prefer a 3.5 mm aux jack, or you might want to go with Bluetooth audio if your smartphone no longer has ...