A. A number of stereo decks, particularly older models, do not have a front-panel jack to connect an iPhone, tablet or smartphone to play a stored music list. Since the front panels of most stereos are of the same dimensions, you might want to consider upgrading to a new set. Alternatively, you can install a bulkhead-mount MP3, iPhone and tablet adapter like the Poly-Planar IC3.5PM audio port ($15), which connects to the auxiliary input jacks found on the rear panel of most stereos. This will allow easy plug-in connection for any smartphone, Apple or Android device.