Whine from Radio Speakers

[Pulsar]

I have an '01 Taurus with a decent head deck, speakers, and subs in the trunk. Ever since hooking up the subs, I get a nasty whine on the AM. I've known the 'fix', but I'm not exactly sure where to place it.

Here is a diagram of my setup:

http://www.freeimagehosting.net/uploads/0ed9eac1ff.jpg

The whine is only in the speakers from the head deck. When I pull the RCA's leading back to the amp, the whine does NOT go away. When I pull the fuse from the amplifier, the whine goes away completely.

This tells me that there is either:
1. Feedback through the power line leading from the battery to the amp that is getting to the radio.
2. Voltage being transmitted through the amplifier ground to the stereo ground and muck that up.

My question is, this is obvious a ground-loop issue, but do I put a ground loop isolator on:
1. The amp power line to prevent the feedback to the battery terminal?
2. The radio power line to prevent it from going into the radio?
3. The signal amp power line?
4. I have heard that grounding the rca wire ground will also ground the radio...... should I try this before the isolator?

Note - the amp is powered from the battery as well. Missed that connection =)

 

[BassBomb]

Did you ground the deck to chassis or to the harness?

 

[jtvang125]

Make sure the ground wire to amp is as short as possible. Also make sure at the point of contact with the chassis all paint around that point is scraped off to ensure good contact.

 

[Pulsar]

I did not ground the deck: The installation was done by the store I purchased the radio from, since the 01 Taurus has a wonder setup where you must replace the AC controls as well when you change from the factory deck.