Inline power filters filter out any unwanted frequencies that cause interference. These will only work if the power wires are delivering “dirty power” or a wide range of power abnormalities present that your head unit may be experiencing. The only way to find out it will work for you is to buy it and try it. If you want to try this option, follow the installation instructions provided in the packaging.
If the noise does not go away:
It is possible that the head unit may be defective and have an internal grounding issue. This is a common issue in Pioneer head units since they have an internal ground fuse to protect them.
If the RCA cables are plugged in after the head unit’s power harness is connected, the internal fuse may blow.
If the fuse is blown, the unit will have to be sent to an authorized repair facility to be replaced. To avoid this, connect all of the RCA cables before plugging in the head unit’s power harness.