Ground Q/A sticky

Hi, I signed up on this site just to talk to you, Rob.

I've been tryin to figure out this problem for about a week, and I'm just stumped.

2006 Chevy colorado

Pioneer DEH...something or another... headunit

I had 2 bazooka subs, upgraded to the crunches, then i wired it differently, but wired them right back to the way I normally had them (i'm thinking i wired them at a lower impedence when i changed). Ever since then I had alot of engine noise, and everytime I cut on and off my amp I get a thud. Also, when i cut the volume from 0 to 1 there's a pop.

I tried a few things, a ground loop isolator (which cut out the sound...but also the music), then tried my buddy's 1200w RMS audiobahn amp, and it didn't cut it out either....now he's saying that he has road noise with it back in his car, too...but I'm not sure, he may just be paranoid.

With the engine off, I can hear the noise of the cd spinning, anything electical (blinkers, etc), and even if i tap on the head unit, i can hear it all through the subs.

I've noticed that the traffic in this room has slowed, but I'm hoping that somebody will help me out with my problem.

I just bought a new Audiobahn head unit with 4v preouts (as opposed to my Pioneer's 2v), which should be here in about a week, I'll see if it helps.

Please, anybody, let me know that my money hasn't gone down the drain, and I can recover my system.

I really need some help here. I believe I have a ground problem but cannot figure it out.

First, here's my set up: 2004 jeep wrangler X, alpine cda-9857 cd player w/ I-pod hook up, PPI pcx-2200, PPI pcx-280, JL 12w6v2, diamond audio 3-way hex component set in the front run off of the ppi pcx 280, and a set of diamond audio mid-bass run off of the head unit.

The problem I have is a whining/clicking sound when the car is turned on as well as alternator noise. When you run the stereo with the car off there is almost no noise. Also, when you change from the radio to cd, or cd to ipod, etc... there is a loud thump. The thump also occurs when the volume is turned all the way down, but not when the radio is turned on or off.

So far I have rewired all of the speakers thinking there might be a short in one of them, and re-grounded the headunit and amps. I also changed the location of the cross-overs. I may have wasted a bunch of money, but I replaced all my cables with really good monster rca's and twisted speaker cable. The HU is grounded directly to the firewall and powered directly from the battery. The amps have 4-guage cable both in and out and are grounded at a single point about a foot away.  

Any ideas or suggestions would really help, THANKS!!