How to solve a ground loop without a ground loop isolator

[bbroecker37]

I have a Pioneer 4200nex aftermarket radio and I get this weird clicking noise coming from the front and rear tweeters only. I do have a good ground and its connected to a bolt that goes into the tube running through the dash. The noise doesn't play when the car is in ACC. It does play when the car is in the "On" position but no engine and with the engine on I get the same noise. Doesn't matter if the volume is up or down it just stays the same. The noise is present on all inputs radio, Apple carplay, xm radio and aux. I tried leaving the antenna unplugged but still no. So that makes me think one of the car computers is sending it RF radiation somehow through the wires. So I installed Ferrite beads on the Yellow, red ACC and orange illumination wire power wires. This did nothing so I installed them on the RCA cables and still nothing. I really don't want to use a ground loop isolator. I heard they reduce sound quality and are just a band-aid. I want to fix the problem from the source. I have tried another radio (JVC KW-V820BT) and it made the same noise. I'm about ready to give up but it might be my amplifier? Any help would be greatly appreciated!

Also, when I turn on my lights (doesn't matter if its the parking lights or low beams) I get a high pitch but not that noticeable noise.

My car is a 2008 Nissan Altima with factory Bose amplifier. I'm using the Metra 70-7553 to convert the receivers pre-outs to the factory amp. I feel like this is the problem. The noise goes away if I unplug the pre-outs. Let me know and I can make a video of the noise. It sounds like a ground loop and makes a ticking noise every 2 seconds and stays the same even at different RPM levels.

Edit: I looked at the service manual and it says on page 159 that pin 10 is for a shield. Should I connect that to the radio chassis? I believe it might be for the RCA cables. https://drive.google.com/file/d/1uqSI5oc7c_czuu2mk_Bb8wxv5SCc6nvm/view?usp=sharing

[bullonwheels]

Try using Ferrite bead.

[Towger]

Try using Ferrite bead.

Between the head and amp, just before the amp. 

The cheap car audio isolation transformers do work, even if you don't like them.  Just trying one will help to track down the cause.

[ArthurDent]

Even if the 'click' is radiated there is a possibility that it's strong enough so that disconnecting the antenna won't stop it. Try using a portable radio in your car with it not tuned to a station so you can pick up weak background noise and see if you can find the same clicks on the portable. If you can't find the click on the portable then it is probably coming into the radio over the connecting cable.

Try to figure what might be on with the switch in that position. There may be car protection stuff or outside temp sensors, fuel pressure sensors, etc., that are on. Finding the cause and then stopping the problem may not be easy.

[bbroecker37]

I did a lot of research yesterday and found that the factory radio uses balanced wires to connect to the amp. The aftermarket radio is unbalanced so the signal that is being sent to the amp is getting interference making the clicking noise. Also the shield for the audio signal (pin 10 and pin 20 are not connected to anything). I used a multimeter on pin 10 and 20 to the chassis of the old radio and found they have continuity.

I would love to try the portable radio but I don't have one lmao but if I find one I will definitely try that.

I was thinking of using the speaker line outputs instead of the RCA. Run them through the Scosche OEA4 to adjust the gain so it wont blow the amp. So would that make the signal running to the amp balanced because I would have an in-phase signal and an out of phase signal? Then take the shield wires and ground them to the radio chassis. I feel like that could work.

[macboy]

Note that a ground loop breaking transformer also acts very nicely as a balun (balanced to unbalanced converter), in either direction.
I also completely agree about trying ferrites.