Grounding and noise

Thank you guys!

In fact, I'm not sure about what gauge the ground wire is. It is about 1.5-2mm in diameter. Go figure. Same diameter as the ground wire of the OEM harness.

Unfortunately switching HU is not as easy, I don't have access to them, and purchased this one on the Internet from Japan.

However, the fact that it makes noise when it touches the metal of the car, and popping when it is not, makes me think that it may not be a headunit issue. Otherwise it would be doing something constantly, no?

Forbidden: Thanks for the suggestion, I'll try and hook up a speaker directly to the speaker output of the headunit. See what happens. And again, when it is not in the cavity, it pops when switching between songs, but no noise when engine running. If it is in the cavity, but not bolted to the mounts, same thing, when bolts are in place, there's this noise, but no popping. Go figure.

And in order to connect it to the existing car harness, I had to actually make my own connector, matching the one on the OEM radio. Used plasticine, epoxy and contacts, then soldered it to the Sony harness.

Thanks again.

Thanks Geepherder, but no, I am not feeding factory amplifier with speaker output signal.

Sony does have two sets of preamp outputs, and that's what I'm feeding the amp with, through the factory harness.

Besides, I believe that if the signal was too strong, it would be the case regardless of the engine state.

But you're right, above mentioned problems were not present with the factory head unit.

Thanks again for your input!

Just as a follow up.

Connected HU to the chassis (seat mount bolt) with 10 gauge cable, no difference, noise is there, just as when HU touches the metal of the car.

Tried hooking up speaker directly to one of the speaker output of the head unit. Noise is NOT there.

Last thought is to re-run the amplifier ground closer to HU? Does that make any sense at all? Amplifier works with no noise with the OEM radio.

So challenging!

Thanks in advance

Thanks Forbidden,

I'm not sure what do you mean by monster hot signal.

I kind of thought that line output is pretty much the same everywhere. And, as I mentioned earlier, speaker outputs of the head unit are normally left not connected.

What I'm feeding amplifier with, is the preamp output from SONY, which has four RCA at the back, front and rear. And otherwise sound is very clear and good, which wouldn't be the case if the signal was way out of amplifier range.. Or am i wrong?

Thank you again!

Not necessarily.  The factory deck may put out a lower level signal than the new deck.  Some line out converters are adjustable which could give your amp a usable signal.

You can also try linking your headunit ground to the amp ground.