audio There are a few things to consider when purchasing a portable amplifier for iPhone to car audio. The first is the size of the amplifier. Some amplifiers are small enough to fit in a small pocket, while others are larger and require a larger storage space. Additionally, the amplifier should be able to output a good quality audio signal. Some amplifiers are designed to output audio in both mono and stereo formats, which can be helpful if you want to connect your iPhone to a car audio system.