This is a brief overview of some of the most frequently encountered noises and some useful troubleshooting techniques.

  1. Alternator: Some of the rectifying diodes have failed, or are on their way out. This allows more ripple (A/C voltage) to be present on the alternator output. The older the vehicle, the more suspect it becomes for basic charging system problems. A great starting point is to load-test the alternator and battery. This will help ensure that the charging system is functioning normally. Most automotive parts stores can do this for you, often free of charge.
  2. Alternator: Your newly Installed high-output alternator didn’t get rid of the whine? High-output alternators are capable of generating just as much noise as stock units.
  3. Battery: Your battery is near death, and needs replacement. A fatigued battery places more of a load on the alternator, which decreases as the battery returns to its normal state of charge. During these low-voltage situations, the capacitance of the battery drops, thus decreasing its ability to filter some of A/C that gets past the rectifying diodes in the alternator. Secondly, as the alternator begins working harder, its output-to-noise ratio increases.
  4. RCA Cables: Shielding of low-level signal cables does no good. In fact, shields will act as an antenna to induce noise into the low-voltage audio signal. Twisted-pair cables (no shielding is necessary) are the way to go to prevent noise from being picked up by the low-level signal cables. You can easily purchase RCA jacks in bulk, and make your own, using high-quality 12-14-gauge wire. To twist the wire, have someone hold one end of the pair, and insert the other end in your drill chuck, tighten the chuck and go! The easiest route is to BUY Memphis Connection UTPF cable!
  5. Component Chassis: If any of the system components are mounted to the metal chassis of the vehicle, then you have the potential for a ground loop. Unbolt any components mounted to metal and see if the noise remains. In this case, you must isolate the chassis of the component in question from the vehicle. A small sheet of MDF or other wood will do the job. Simply mount the wood to the chassis, and then mount the component to the wood.
  6. Passive Crossovers: The coils used in passive crossover components can pick up radiated noise from the electrical system of a vehicle. Simply move the passive components away from their existing location(s) and listen for noise. If the noise is gone, then move the crossover(s).
  7. Source Chassis: The metal chassis of a source unit can pick up radiated noise from the wiring in the dash. To check for this, simply remove the source unit from its mounting area, leaving all wiring connected. With the system playing, move the source unit away from its mounting location. If the noise goes away; re-locate the source unit; or shield the chassis of the source unit with some type of metal with a high iron content; or try alternate sources for the ground and constant and switched 12 volts; or try another source unit.
  8. The crossover did it: Everyone wants to blame the signal processor(s)! Inserting a signal processor into a system might just offer a path for noise to enter, but it is very unlikely that the component ‘caused’ the noise. Each time a low-level signal path is broken, ground loops can form. RCA Barrel connectors can even cause noise, due to the signal cable halves being moved farther away from each other.