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Troubleshooting and avoiding amplifier noise


Erin Blanton

Erin Blanton wrote about mobile A/V gear at Crutchfield for several years, and worked as a Sales Advisor in our contact center before that. She left Crutchfield to open her own toy store, Pufferbellies, in nearby Staunton, Virginia, which continues to keep her busy.

More from Erin Blanton

Amplifier noise can be tough to track down! Sometimes it seems like you've tried everything, but that high-pitched whine or ugly clicking sound just won't go away. I sat down with a Crutchfield senior technical advisor for the inside scoop on how to get rid of pesky amp noise — and how to avoid it in the first place.

Grounding — think ahead to avoid noise.
Crutchfield tech advisors report that when customers call to ask for help with amplifier noise, the problem can most often be traced to an inadequate ground. But your system doesn't have to end up this way. Think carefully about how and where to ground your amp, and you're likely to come out noise-free.

Ideally, all your audio components should be grounded to the same location. However, many people choose not to do this, especially when it comes to the in-dash receiver. Who wants to run a ground lead from the receiver all the way to the amp grounding location, anyway? Well, if the receiver has a very solid ground in the front of the vehicle, you may certainly be OK grounding it separately from the amplifier. But if you're using your car's factory radio wiring harness, the in-dash receiver is probably grounded with many of the other dash components (turn signal switch, lights, etc), and those components can introduce noise into your audio system.

If your in-dash receiver and amplifier are grounded to different locations, a ground loop may occur. In this situation, the multiple ground paths can, in effect, act as an antenna for interference. The interference is turned into noise, and you hear it in your system.

Grounding your components to a heavy-duty bolt can help you banish noise from your system.

How can you avoid ground loop problems when your components are grounded separately? Ground your amplifier using as short a piece of cable as possible, and to as thick a piece of metal as possible. The longer the ground cable, the more resistance can build up — and that can spell noise problems. A common mistake is to ground the amplifier to thin sheet metal; this can introduce noise into the system, too. Crutchfield techs recommend that you ground your amp to a heavy-duty bolt, like a seat bolt or a seat belt anchor.

One important point about ground cable: it should be exactly the same size as the power cable that's going in to the amp. If you've got 4-gauge power cable going in, you should have 4-gauge ground cable going out. 8-gauge going in? 8-gauge going out. No exceptions.

Expensive cables sure look pretty, and can really make a difference when it comes to noise reduction.

How important are the patch cables?
"Platinum-tipped GatorGrip connectors!" ... "3-core Gamma Geometry!" ... "HyperTwist construction!" ... "Phase Perfect Teflon insulation!" Um...huh? Sounds like stuff you'd find on the space shuttle, right? Nope. Those are all technologies you'll find in RCA patch cables — the cords that carry the music from your in-dash receiver to your amplifier.

Shopping for patch cables can be a little intimidating — do you have to spend hundreds of dollars on cables with fancy, trademarked technologies, just to get noise-free results? The answer is pretty simple: You don't. But that doesn't mean that you should use the rock-bottom cheapest cables, either. Good-quality cables have features that can help your system sound great (and stay noise-free). Look for patch cables with sturdy connectors and durable, flexible insulation. Well-constructed cables are typically easier to route, and will last longer than cheap ones. Another big plus is noise-rejecting twisted-pair construction — the good news is that almost all mid- to high-priced cables have it.

The way you run the patch cables can also help keep noise away. Crutchfield recommends that you run the signal cables down the opposite side of the vehicle from the power cable. The power cable may tend to emit electrical noise, which the patch cables can pick up and amplify. And don't use longer patch cables than you need — extra cable stored in loops can be a source of noise problems, too.

Your amp's power cable can radiate electrical noise. Run the signal cables down the opposite side of the vehicle.

When it comes to cables, the bottom line is this: Go for good quality, but don't feel like you have to spend a fortune on the most expensive cables out there. Choose patch cables that match your installation — a good rule of thumb is to devote somewhere between 5-10% of your total budget on patch cables. Spend time planning a wiring route that will minimize the amount of noise the cables can pick up. If your system isn't wired correctly, upgrading the patch cables to more expensive ones probably won't help; only re-wiring will.

This flow chart from Crutchfield's Learning Center can help you track down and eliminate noise from your audio system.

Got noise? Troubleshoot.
If you do wind up with noise problems after installing your new amplifier, first take a deep breath. Then, troubleshoot the problem systematically until you find the solution.

Crutchfield sells power and antenna noise filters, and material to shield your in-dash receiver from radiated noise. Check out the Car A/V Learning Center for a helpful flow chart that walks you through troubleshooting noise problems, and for advice on choosing a noise suppressor.

More good news: if you've purchased your amplifier from Crutchfield, the same technicians who provided me with the information above are on call to help you, too — all you have to do is pick up the phone.

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