I just bought the aux cable to connect my I phone 4 to my cde-9881 alpine stereo but when I hooked it up my iPhone connects to the head unit but only plays music thru the speaker on the phone. Why??

SOURCE: Installing an aftermarket head unit into a 1994 Ford Bronco

are you using and after market harness to go from your bronco to the harness to the new radio. if so make sure all the colors are matched up (e.i. purple to purple, purple/black to purple/black). did the speakers work before the aftermarket unit. Also check the wiring at the oem speakers

SOURCE: After installing the alpine cde 9870 car stereo

In this situation 8 times out of 10 the problem is not with the radio, it's that there are factory amplifiers. Many cars have them, and most require a little work, or an adapter to get going. Tell me the year, make, and model of the car, and perhaps I can give you more info.

SOURCE: I have an Alpine head unit and a 30gb iPod

What model Alpine do you have? Have you gone into the setup menu and poke around and see if you have a setting (AUX +) and if you do turn it off and see. Than if that doesn't do the trick if you have an Alpine dealer close by see if you can "borrow" a KCA-422 full speed iPod cable and quickly plug that in and if it works than it is the cable. But if it still does not recognize the iPod it is a problem in the head unit and needs to be repaired..

SOURCE: connecting a car stereo to an amplifier

you have to connect your 4 speakers to 4 speakers output direct to your car stereo no need of amplifier to 4 speaker but speakers should be small not like a woofer, and you have to connect your sub woofer by using amplifier don't connect direct. connect the output of your car stereo (using 2 RCA) to the 2 RCA inputs of amplifier. If u connect your 4 speakers to your amplifier then your car stereo does not support Left Right channel.
You can also connect your laptop or iPod direct to your amplifier.
Good Luck
enjoy music

Testimonial: "very helpful. Thank you"

SOURCE: Play Ipod thru JVC CD car stereo using RCA cable?

JVC KD-S731R does not have the option of connecting an ipod. The RCA ports on the rear of the unit are a Line-Out. These RCA's only OUTPUT sound. Not an INPUT RCA that you require. The only other method of using an ipod with this stereo is to purchase an FM-Modulator to connect the ipod. Once purchased, you must connect the antenna wire coming from the vehicle to the module, then you must connect the antenna wire coming from the module to the stereo. The other wire will be connected to either a jack or a ipod specific plug depending on the type of modulator used.