These are general rules or tips which will prevent or reduce the problems with engine noise (Whining).
1. Run the patch cords on the opposite side of the vehicle from the main power and remote output wires.
2. Make sure that all of the audio components are well grounded to an area that has has been cleared of all paint, primer and other protective coatings.
3. Don't use the factory wiring for the head unit's (HU) ground connection. Ground the HU to the chassis (body) of the vehicle. If the HU isn't mounted directly to a solid, GROUNDED metal structure, ground the case of the HU to the same point that the HU's ground wire is connected.
4. Do not extend the ground wires of any component unless it's absolutely necessary. If the device's manufacturer designed a high quality input circuit, extending the ground wire will only cause more problems. If all else fails, and you have one audio component which is allowing noise to enter the system, you can then try different grounding points to see if they make a difference.
5. If the insulation on the patch cord is damaged and is allowed to touch to ground, it will likely allow noise to enter the audio signal path. If the patch cord is pinched under the back seat or where it crosses over any sharp metal (where it enters the trunk) it will cause noise problems.
6. An amplifier's speaker output generally has one speaker wire with the audio signal and another (the reference) which is connected to the audio ground inside of the amplifier. If the reference is allowed to come in contact with ground (in the door or back deck of the vehicle), a ground loop may be created allowing noise to enter the system. This is not very common but it has happened.
7. Set the amplifier's gain controls properly. Setting the gains too high will only make a problem with noise worse.
NOTE:
DO NOT make any connection (RCA or otherwise) with the system switched on. Doing so may cause damage to speakers or amplifiers.
