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Top 10 Reasons Why an Amp Keeps Cutting Out

It goes without saying that if you want your music to be loud, and most importantly, crisp and clear, an amplifier is definitely part of the picture. That is, when it works, as there’s nothing quite as frustrating as having an amp that keeps cutting out every now and then.

If you’ve ever had a similar issue, you know how annoying it can be, and you’re definitely going to want to get it fixed immediately.

If you are experiencing frequent cutting out of your amplifier, you may be questioning if the power output (amplification) is costing you quality. Do not regret your amp just yet!

Why does an amp keep cutting out? Well, a car amp may cut out for one of many reasons, including but not limited to:

  • Bad ground
  • Amp starvation (Inadequate wiring kit)
  • Loose connection
  • Amp in Protect mode
  • Impedance mismatch
  • Shorted or blown speaker(s)
  • Amp clipping
  • Voltage drop
  • …etc

Want more details about how each of these can make your amp cut out? Read on …

10 Reasons Why an Amp Keeps Cutting Out

1. Bad ground

There’s no denying that when installing a car amplifier, the ground wire can make or break your sound system. Improper or loose grounding is the one of the most common cause of amplifier problems.

Essentially, grounding completes the electrical circuit powering your amplifier. Therefore, if the ground connection is poor, or if it isn’t connected at all, the amp may fail to turn on or not work very well.

Furthermore, a proper ground also prevents amplifier clipping, blowing fuses, ground loop noise (engine whine), current draw, dimming headlights, and a host of other issues.

To make sure bad ground isn’t the root cause of your amplifier cutting out, trace your ground wire to where it’s attached to the chassis. Thoroughly check the wire for any damage such as crimping, kinks, tear, fraying or cuts in the insulation…etc.

If the wire appears in good shape, check the connection point. If the ground itself isn’t completely secure, and allowed to move in the slightest, it won’t provide an adequate completion of the circuit, making your amplifier cut out especially at high volume. So, use extra screws, a lock washer, a star washer, and any other technique that’ll hold this connection tight and secure, and most importantly electrically conducting.

Furthermore, you need to make sure the distance between the amplifier and the grounding point is no more than 18 inches, the shorter the length of wire the better.

Moreover, in order to assure proper current flow, the gauge of the ground wire must match the gauge of the power wire.

Last but not least, the grounding point should be sanded down to bare metal or scraped clean of any paint or primer, so the ground connection will be bare metal to bare metal.

2. Amp starvation (Inadequate wiring kit)

It goes without saying that for an amp to operate efficiently, its power and ground wires must be large enough to accommodate its demand for electrical current, otherwise the amp won’t operate properly or put out its rated power.

When a car amplifier cuts out at high volume or when bass hits hard, it’s highly likely that it isn’t getting the juice it needs to run the speakers or subs at that level.

When the amp is grasping for more power, and can’t draw any more from the electrical system, it may experience thermal shutdown, blow the fuse, or go into protect mode to prevent serious damage, making the sound cut out.

It should be noted that the wiring kit you use to hook up your amplifier to your car sound system is as important as choosing the right car amplifier.

For this reason, and in order to prevent amp starvation, make sure you’re using good amp wiring that’s not too thin or made of low quality materials.

As a general recommendation, use the chart below as a quick reference in determining the appropriate wire gauge for your amp.

Wire Gauge SizeTotal Amplifier RMS Wattage
0/1 AWG1000+ Watts
4 AWG400-1000 Watts
8 AWG200-400 Watts
10 AWG100-200 Watts

 

3. Amp in protect mode

One of the most annoying car stereo problems can be when the amplifier goes into protection mode. One minute the amp is working great and the next minute it’s not, usually with the protect indicator blinking or the green power LED turning to red or orange.

Protect mode is meant to prevent serious damage to the internal component of the amplifier when something goes wrong. It’s essentially just a shutdown state that car amplifiers can go into for several reasons including:

  • Impedance mismatch (amp overloaded)
  • Overheating (thermal overload)
  • Bad ground
  • Blown speaker
  • Shorted out or loose speaker wires
  • Wrong amp wiring
  • Incorrect gain setting
  • Faulty amplifier
  • …etc.

So while dealing with an amp in protect mode may be a pain in the butt, it might actually save you from a much bigger headache in the the long run.

That said, if your amplifier is cutting out, check if it’s in protect mode. If it is, you need to do some detective work to figure out and fix whatever is causing the protection circuit to engage.

Fully troubleshooting a problem like this might not be that easy especially for inexperienced guys. You might want to refer to our detailed and all-inclusive guide on how to get your amp out of protect mode.

4. Amp overloaded (Impedance mismatch)

Speaker impedance – measured in ohm – refers to the amount of electrical resistance, or load, a speaker offers to the current supplied by an amplifier. The lower the impedance, the higher the load on the amp (and the harder it has to work).

Amp overload occurs when an amplifier is presented with a very low impedance that far exceeds its capabilities. When this happens, the amplifier tries to keep up with that load, but heats up due to the extra power it’s trying to push out. Once it overheats, it shuts down to protect itself.

One of the most common impedance mismatch we come across very often is hooking up a 2-ohm subwoofer up to a 4-ohm amplifier that’s not stable at 2 ohm load, or wiring a couple of 4 ohms speakers in parallel and end up with a 2 ohm load, then bridging a 4 ohm amp to that load.

So, always make sure your speakers’ overall impedance is within the capability of the amplifier.

5. Shorted speaker(s) wires

If your amplifier keeps cutting out especially when the car is moving, there’s a good chance you’re dealing with a damaged wire that connects intermittently; a loose or chafed speaker wire touching metal can cause the speaker to short out.

Car speaker wires run through the cabin, and connect each speaker to the head unit (or the amplifier). They’re often routed behind panels and trim pieces, under seats, and beneath the carpet, which makes it difficult to visibly inspect them.

Each car is different, so depending on your situation, it may be easier to check for continuity between one end of each wire at the amp and the other end at each speaker. If there’s no continuity between the two ends of the wire, that means the wire is broken somewhere. On the other hand, if there’s continuity to ground, then you’re dealing with a shorted wire.

If your speakers are mounted in doors, then a common point of failure is the rubber grommet through which the speaker wires pass between the door and the door frame.

Something that drove me nuts a while ago was a speaker shortage due to a rubber grommet damage, and the wire rubbing on the hold through the door. This caused a ground short on one of my speakers. However, it still worked as the power and signal still got there, but as soon as I turn it up, and the short became too much for the amp, the latter would drop into protected mode.

With that in mind, it’s highly recommended to check for continuity and shorts with the doors both open and closed. If any of your speakers happen to be shorted to ground in that manner, that can actually cause your amplifier to cut out.

6. Blown speaker

A speaker that’s blown or grounded to the chassis is another thing that could make your amp cut out. This is because the amplifier will still try to send power to it. And when it does, it “sees” a condition that triggers its protection circuit.

If the speaker wires aren’t broken, and the speaker hasn’t totally bit the dust, ensure your speakers are tightly mounted in their mounting holes, and that none of the speakers magnet is touching the door metal.

Generally speaking, it’s easy to tell if a speaker is broken or not. However, it must be noted that there are varying degrees of blown-out speakers. For instance, a car speaker that’s completely blown out will stop working and make no sound at all. Whereas, a partially blown speaker will no longer sound normal. In other words, you’ll experience a lot of distortion in the form of crackling, rattling, buzzing, hissing …etc. This is especially true when you increase the volume.

Furthermore, to pinpoint a blown speaker you could also check each speaker individually by using the balance and fader controls on the receiver.

If you couldn’t tell whether a speaker is blown out or not, use a multimeter and check for continuity between the speaker terminals. If there isn’t any continuity, that usually means it’s blown.

7. Amp overheating

If your amplifier is cutting out after an exceptionally long listening session, there’s a good chance it may have just overheated.

The most common cause of overheating is a lack of airflow. However, an amplifier could also overheat for a wide variety of reasons including but not limited:

  • Poor build quality
  • Improper mounting
  • Lack of air flow
  • Clipping
  • Blown/grounded speaker
  • Gain/punch bass control settings too high
  • Impedance overload
  • …etc.

Regardless of the cause, thermal overload isn’t something you want to let linger. Your amplifier could sustain serious, if not permanent, damage.

So, make sure your amplifier isn’t mounted in a confined space such as underneath the seats or under the carpet, and most importantly make sure it is driven within its limits.

If your amplifier is constantly overheating, you might want to refer to our detailed and all-inclusive guide on how to keep your amp from overheating.

8. Clipping 

Clipping goes hand in hand with overheating. To put it simply, it occurs when an amplifier is driven beyond its ability and attempts to generate enough voltage or current to reproduce the original signal to your speakers.

When an amp is overdriven and its maximum amount of power supply voltage has been reached, it becomes impossible for it to amplify the incoming signal without compromising its original form. This is often caused by improper amp gain setting, or because the volume is too high.

To put it less simply, instead of delivering a sinusoidal waveform that’s smooth at the peaks and troughs (the highest and lowest points of the sound), the amp produces a waveform with flat peaks.

For instance, when the gain on an amplifier is increased beyond a level that the speakers can handle, it causes the sine output signal to lose its rounded peaks and troughs. In other words the highest and lowest points of the sound wave are clipped off, causing distortion.

Clipping can be caused by a wide variety of things including:

  • Input sensitivity (gain) set too high
  • Bad ground
  • Inadequate wire gauge
  • The need for a bigger alternator
  • Over-equalization of the source signal
  • …etc

If you’re experiencing clipping, the first thing to do is to properly adjust your amp gain setting, and make sure the RMS power rating on your amp matches what your speakers are designed to handle.

Clipping isn’t a direct cause of amp cutting out. However, excessive clipping leads to overheating, which in turn causes the protection circuit to engage making the amp cut out.

9. Voltage drop

If your amp cuts out at high volume, there’s a good chance it’s because of voltage drop. This is especially true if it happens often with really loud bass notes.

It goes without saying that powerful amps are power hungry. Fortunately, most cars produce more power than they need, which is how your car can keep its battery charged even if you have accessories like air conditioner, car speakers, headlights, windshield wipers, car stereo …etc turned on.

Unfortunately, the alternator isn’t an infinite source of power. There comes a point where the alternator is no longer able to keep up with the increased power demand, and that point is often the installation of a dedicated subwoofer amplifier.

So, when you have a big subwoofer or multiple subs driven by a powerful amplifier, but the electrical system isn’t up to the task, the amp will simply keep cutting out. This leaves you with two basic solutions: downgrade your sound system, or upgrade your electrical system.

If you notice that the bass performance decreases when you crank the volume up, or that the lights are dimming even when the engine is “revved up”, it’s almost certainly your car is suffering from a voltage drop problem.

To make sure it is the culprit, use a multimeter to measure the voltage at the amplifier when it’s playing normally and then under the conditions that cause it to cut out.

If the power output at the amp is the same during both conditions, it’s safe to say that voltage drop isn’t the causal factor. However, if it’s dipping below 12 volts when then there’s your answer. A heavy-duty alternator and a strong battery (or multiple batteries) might be required to maintain a stable supply of power.

10. Faulty Amp

If everything checks out okay, and you’ve ruled out all the potential causes mentioned above, you’re probably dealing with a faulty amplifier.

A defective amplifier should be sent back to the manufacturer for repairs if it’s still under warranty, or find a local repair shop that can diagnose the problem for you. With any luck, you’ll be jamming again in no time.

Final Thoughts

There’s no denying that figuring out the reason why an amp is cutting out might be over your head especially if you’re a relative greenhorn when it comes to car audio. There’s a ton of things to check and inspect, which makes it a daunting task.

Not all car stereo system are built the same. This makes it hard to tell where the problem might be lying exactly without having some information about you overall sound system. However, the things we listed above should help you fix most problems of this kind for the most part.

Keep in mind that sometimes, the smallest things like a few strands of wire touching the metal can wreak havoc in a car stereo system.

Alex Brown

Hey There, my name is Alex Brown, I'm an LA-based sound engineer with over 10 years experience installing, troubleshooting, and repairing commercial, automotive, and household sound equipment. I've installed highly competitive car audio systems, and everything from navigation systems to full car stereo systems, remote starters, alarms and beyond. I enjoy creating solutions and simplifying everyday needs. I also love helping people get great sounding gear, thereby, saving the world from bad sound one customer at a time.

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