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Amplifiers: How to Suppress Noise

Electrically speaking, your car is a pretty active place. Every piece of electronic equipment in your car, such as power windows, your windshield wipers, and the alternator, generates its own small electrical field. These fields can be conducted through the metal that makes up your car's body and chassis. They're not really a problem until they sneak into the audio components of your stereo system and become noise.

Check all connections
You can solve almost all noise problems, without the need for adding noise filters, by making sure that every component is installed properly, that high-quality equipment is used, and that the car's charging system is working properly.

Loose grounds cause noise
Before you begin poking around your sound system for the source of the noise, you should first check your vehicle's electrical system.

  • Check the battery fluid level and fill, if necessary
  • Make sure the battery leads are tight to their posts
  • Make sure the battery's negative-to-chassis ground cable is sturdy, intact, and tightly secured

Often, tightening or replacing a vehicle's ground cables will clear up the noise issue in the sound system.


How to diagnose and eliminate noise
Use the following diagram to diagnose and cure the most common noise problems associated with systems with outboard amplifiers. The idea is to isolate the specific cause of the noise so you can eliminate it. For a more detailed explanation on how to eliminate noise, see our Car Audio Noise Suppression Guide. If these tips don't solve the problem, it's helpful to be able to call on a Crutchfield Technical Advisor. If you purchased your gear from Crutchfield, or purchased tech support separately, you can contact them toll-free between 8 a.m. and midnight Eastern Time, seven days a week.

The Big Three
Finally, for those mechanically inclined, another good option is to perform the "Big Three" electrical wiring upgrade to your vehicle's charging system. This upgrade augments the battery's ground wire, the engine-to-chassis ground wire, and the alternator's positive lead wire with heavier (1/0- or 4-gauge) wire. This greatly improves your system's current flow and signal integrity, and reduces noise significantly.

Noise suppression diagramAmerican International AS100 Antenna noise filter Click to see graphic. American International S-25A Power line noise filters American International S-15A Power line noise filters Stereo Patch Cables PAC SNI-1 RCA Ground Loop Noise Isolator
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