I've got a 2009 Honda with an aftermarket amp and subwoofer setup I installed about 5 years ago. Recently started hearing this high-pitched whining noise that gets louder when I rev the engine. It's coming through the speakers pretty badly. Is this a grounding issue or something else I can actually fix myself?
Don't start by replacing the alternator or amp - that's throwing money at the problem. Alternator whine is almost always a grounding or shielding issue, not a bad component. The noise gets louder with revs because the alternator's output frequency changes, and any weak ground connection amplifies that signal into your audio system.
First thing to check is your main ground wire from the negative battery terminal. After five years, it might have corroded where it connects to the chassis. Pop the hood and inspect the ground cable end - if it's got white/blue crusty buildup, disconnect it and scrub the connection and the chassis contact point with a wire brush until it's shiny metal on metal. Reconnect it tight. While you're at it, make sure your amp's ground cable is equally solid - same process. Both grounds need to go to clean, unpainted metal on the chassis, preferably near where power enters.
If that doesn't kill the whine, your RCA cables from the head unit to the amp might be picking up alternator noise. Run them separately from power cables - they should never bundle together. If they're already twisted together, separate them or get shielded RCA cables. Some folks also add a capacitor (0.5 to 1 farad) on the amp's power line near the battery, which helps filter out voltage fluctuations. It's cheap and pretty easy to install. If none of that works, your amp might need a ground loop isolator between the head unit and amp, though that's usually a last resort.
Log into answer.
