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How To Choose An Amp

An amplifier modulates power from your car battery to supply your car stereo system with the juice it needs to keep the bass booming and the speakers crooning. There are many aspects to consider when selecting an amplifier for your car stereo system. Here is quick list of what you should keep in mind.

  • First Choose your Speakers and Subs

Once you have settled on what types of speakers and subwoofers you will be running, you will now be able to choose an amp based on the speaker’s power ratings, impedance, efficiency, and voice coil configurations. This will help you figure out how much power you will need from your car amplifier and in planning how you will go about wiring your amp. For example, if you are only choosing one subwoofer, you will want to know if you can bridge the 2-channel amp that you have in mind.

  • A Powerful Amp Will “Amp” Up Your System

The higher the impedance of the speakers, the higher the impedance you must run the amp at. Along with that, the higher the impedance an amplifier runs at, the lesser the amount of power generated by the amp. Many amplifiers can run at either 2 ohm or 4 ohm loads, but some are stable at 1 ohm loads for optimal RMS performance.

Be sure to pay attention to the RMS power ratings, which refers to the amount of continuous power produced by an amplifier. Ignore the peak power ratings, these ratings are totally insignificant when trying to match up an amplifier with subs and speakers.

  • Efficiency Matters

The ratio of power output to power input, expressed as a percentage. For example, consider a Class A amplifier that produces 100 watts of power output from 200 watts of power input. This amplifier is rated at 50% efficiency.

To measure an amplifier’s efficiency, you need to know the power output and input levels, the car battery voltage, and the amp fuse size (measured in amperes). In the example above, assume the Class A amp uses a fuse size that is 10A and the car battery voltage is 14.4 volts. Multiplying 14.4v times 10A gives 144 watts in. 100 watts out divided by 144 watts in equals .6944. This means an amplifier with a 10A fuse and 14.4 v battery will need to be rated at 70% efficiency to produce 100 watts.

Since this is way beyond the realm of possibility, you will need to find an amplifier with a higher fuse rating to produce 100 watts. For example, take the same Class A amplifier above except imagine it with a 15A fuse instead of a 10A. 15A multiplied by 14.4v equals 216 watts in. 100 watts divided by 216 equals .4629, which means a Class A amp with a more realistic requirement of only 47% efficiency is needed to produce 100 watts.

Remember, Class A Amplifiers only offer a theoretical maximum of 50% efficiency. Class B amplifiers have a maximum theoretical efficiency of 78.5%, and Class D amps can operate at levels between 80-95% efficiency. This is important to note when considering the fuse sizes and power ratings of an amplifier.

  • Heat Sink Keeps Amplifier Temperature in Check

Consider the size and quality of the heat sink. The heat sink is used to dissipate heat and to keep the amplifier running efficiently. A heavy duty heat sink will provide better thermal stability. To further help prevent the amplifier from overheating, check out amps with cooling fans.

  • Damping Factor: Control Your Speakers

The damping factor measures how well the amp will control unwanted movement of the speaker coil. The higher the damping factor, the better the amplifier will be in controlling the speaker’s undesired movements. To calculate damping factor, divide the speaker’s impedance by the amp’s output impedance.

  • Speaker Level Inputs and RCA Terminals

An amplifier with speaker level inputs will allow you to run your amplifier from a factory receiver. Additionally, if you have no remaining preamp outputs left on your aftermarket car receiver, you can use the amp’s speaker level inputs. You want to make sure the speaker level inputs and the RCA connection terminals are secure, since your amp will have to survive the bumps and dips in the road.

  • Price

Make sure you plan your budget ahead of time. To install your amplifier, you will need amplifier wiring kits, and other accessories. You may also consider purchasing digital capacitors or other items to keep your system running at full throttle. We can help you choose which amplifier is right for you. Give us a call at 1-877-289-7664.

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Staff writers at Sonic Electronix are experts in their field. In addition to a complete in-house training program, these experts typically have many years of hands-on experience in their specialty. Some come from car audio installer backgrounds, while others come with extensive retail experience.

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