OK. I installed my D3, and I've got an interference type noise coming through all my speakers. I'm running all 4 with an external amp, and with my old head unit, there was a very faint whiny ground loop type noise, so faint I didn't even worry about it. But after installing the D3, there's a very loud noise coming from all 4 speakers. It was first grounded through the car's radio harness, so I moved the ground, mute wire, and parking brake wire so they are grounded directly to the body of the car. I double checked both my amps grounds, and they're solid. So now I'm stuck.

Where should I go next? I don't want to put ground loop isolators on the RCA's because I've used them before and wasn't happy with how much they degraded the sound quality.

I've heard some say to try grounding the RCA's. I'm not sire what exactly the process is with that. How is that done, and do you think it will help?

I'm going to try running a set of speakers through my sub amp to dee if it's the amp itself causing th noise. But I don't think that's the problem, because the noise wasn't there with the old head unit.

Any ideas?

What kind of amp?

It's a Profile Clarus 640 (75W X 4) amplifier.

What kind of shape is this amp in? It's probably at least 4 years old, since they stopped making it in 2004. Try using an iPod hooked up to the inputs on the amp with an adapter cable. See if you have noise.

quick fix- take a 3 ft 16- 22g wire and ground it if your really lazy shove it in the fm antenna slot so it touches the metal of the unit and the oustide of the antenna shield. now take the other end of the wire and touch it to the shield of your rca's. if it makes the noise better than id check the pins on the plug. but if your really lazy like i am with my own ride you use the same fm technique with the rca shield.

thats about the best i can explain how to trouble shoot amp noise over the internet

Well, like I said, I'm fairly certain the amp isn't the problem, as everything was perfectly fine with my old head unit, and then when I installed the D3 the noise showed up. I never touched any part of the amplification system during the install except for the RCA cables where they plug into the head unit.

Ground your RCAs as stated above

Well, I'm not going to have time to ground the RCA's any time soon. I'm remodeling the basement at my mom's house and I'm going to be getting home around 8 or 9 at night for at least a week and a half...

But what I did do was hook up a portable CD player to each channel of my amp, and all 4 speakers play loud and clear with no interference what so ever. So the amp works fine.

Hopefully when I get a chance to ground the RCA's it will fix the problem.

For now I'll just turn up the volume to cover the noise.