Car Stereos: Subwoofer and Amp. Noises, rockford fosgate amp, high output alternator

Question
QUESTION: Hi, i have a completely aftermarket stereo system. Jensen UV8 7" touchscreen head unit, Sony Xplod 6x9's in the back, Infiniti Kappa 6.5"'s in the front doors and pioneer Tweeters in the Front doors as well, 500 Watt Rockford Fosgate Amp., 12" JL Audio W7 Subwoofer, and a .5 Farad Capacitor. Also i have a high output alternator with an AEM underdrive pulley on it. I have serval problems. First, when i turn the volume up high the head unit shuts off but im guessing the amp. in the head unit cant push out enough power. 2nd, i get a lot of feedback in the subwoofer when i change songs on a cd. 3rd, the amp. makes a high pitched tone that can be heard through the speakers. My head unit has an aux. port where i play my ipod through, and theres some feedback there as well. Also i had tried hooking up a Lanzar 1000W Amp. to the speakers and there was a very loud high pitched noise when i played music and got much worse when i turned the headlights on.

ANSWER: Hi Tom,

#1: I'm not sure why you'd get a high output alternator and then underdrive it -- you're entirely defeating the purpose.

#2: Most weird sounds and feedback come from bad/unclean ground.  Make sure your ground wires are at least as heavy a gauge as the power wire, and are grounded out cleanly to unwelded, sanded, bare metal.  Different spots on the chassis might prove to be better grounds than others.

#3: The other possibility is that your amps' gain are turned up too high and they're overamplifying slight input noise.  You can try noise blockers, but your better bet is to get the system nicely tuned.

Justin

---------- FOLLOW-UP ----------

QUESTION: Well when my car idles the voltage drops significantly, do you think this is because the underdrive pulley is not letting the alternator spin as fast as it needs to? that seems to be the most serious problem. i cant have the stereo blasted when im stopped or the car dies. also one more question, its for my girlfriends car. her antenna wire looks like it was cut where it plugs into the head unit and the frayed wires are just pushed back and was shoved in the head unit. do they sell the plug that goes in the head unit that just splices into the wire or would i need to buy a whole new wire and run it from the antenna back to the head unit?
thanks

Answer
To your first question, you unequivocally do NOT want to underdrive a bigger alternator, especially if you're doing any kind of significant power draw.  Replace it with its stock pulley.

And for the second issue, you'll need to replace the wire.  Antenna wires are incredibly finicky, and you can't splice them like other wires; they lose too much signal.

Justin