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A Beginner’s Guide to Choose a Satisfactory Power Amplifier

Written by the Research & Development Team
Tuesday, 27 March 2012, 10:30

The car audio, serving as a mobile concert hall, has turned the solitary trip to an enjoyable experience. For the most of us when facing the metallic equipments, we shall be deeply attracted by the unique magnetic properties of a car stereo, no matter whether we are car audio enthusiasts or not. However, to the majority of the people, perhaps, how to choose a satisfactory car stereo is a difficult topic.

As what we introduced in the previous section, the three major components of a car radio are the unit head, the power amplifier and the speakers. In this section, we will focus on tips on the power amplifier selection of a car audio system.

Before making the right choice, we need to determine some guides on the power amplifier comparison, which are supposed to serve as the baselines for selection.

Of all parameters of the car audio system, power is the most important, which shows the load capacity. This is also the primary point of consideration for the purchase of a car radio system. However, in terms of other features, it is often difficult to make an objective comparison of different products, if we are lack of sufficient knowledge on the benchmark to identify the performance of an original car audio system. When reading the instruction label a power amplifier, the following three points are supposed to be aware of.

1. The battery voltage.

The most two common power amplifiers are of 14.4V/100W and 12V/100W. The voltage of a car battery is constantly changing, but basically maintains at around 12V during the moving process. Therefore, the 12V/100W option performs better, as the supplied voltage from a car battery is closer to its working condition. Furthermore, the 12V/100W option can reach up to 12V or even more to get more power for an original car stereo.

2. The total harmonic distortion (THD).

The comparison of the continuous power output of the power amplifiers is supposed to be conducted under the same or similar total harmonic distortion (THD) value. The sound quality of a car stereo system varies obviously under different THD values. Sometimes, the instruction on a power amplifier shows a high power maximum, however, most likely its distortion and noise are also very high. Therefore, when checking the max power output of an auto radio, we should be aware of the identified THD value.

3. The frequency range.

The testing of the continuous power output of a power amplifier of a car audio system is supposed to be within the frequency range of the actual use. It is meaningless to identify only a small frequency range on the label, while a full scope of testing should be marked on the instruction label.

With the above basis, we can now compare the output power of the power amplifiers. Generally speaking, choosing a good one follows the principle of max power output. With a greater output power, a power amplifier has a stronger ability to drive speakers in a car audio system. The output power is supposed to be greater than that of the speakers. Otherwise, if the designed output power is small but is forced to output high power in a long term, the whole auto radio system will result in poor sound quality, and failure of distortion.

Below is a list of factors of a good power amplifier.

Of course, it is not easy to identify whether a power amplifier is good or bad for a car audio system just by a text description of high power output. A high-quality option must also able to quickly reflect the peak of the music signal, correspond strong bass and provide a smooth output under low distortion and low noise conditions. To meet these requirements, a power amplifier must have the following features.

First of all, power is important throughout the whole car radio system. This is the key to determine the sound quality of a power amplifier. The power and the amplifier part must be designed separately, to reduce the noise. A large transformer can improve the supply of the stable current and a large capacitor can quickly respond to supply the amplification required current.

Secondly, the built-in parametric equalizer is also important. Unlike the home audio speaks, the installation space of a car audio is limited. Therefore, the sound regulation is very important. In addition, the chaotic sound waves caused by the headrest and the window to reduce the sound effect, as well as the installation angle of the bass speaker, will influence the sound quality of the car stereo system. Then it is the parametric equalizer to balance the impact by the above-mentioned reasons, to compensate the peaks and troughs and adjust the smoothness of the sound field.

Furthermore, it is the built-in frequency divider. No matter how excellent a power amplifier is, it cannot achieve the best results of an original car radio system due to a wide range of audio problems in the actual installation in the car. To overcome these issues, a built-in frequency divider is required. There are two advantages of a built-in frequency divider: (1) the scalability of the system, which can combine the speakers and the power amplifier as needed and (2) the easier adjustment, which will improve the sound quality of the entire auto radio system. An external frequency divider is not recommended for an auto radio system due to the complex wiring installation and the easy mixing with the noise. What’s more, an external power amplifier requires larger installation space and higher cost.

Besides knowing the above factors of a good power amplifier, we should also understand the different purposes of it.

It is not enough to select the power amplifier for an original auto radio system just by the simple parameters given by the instructions. The selection should be based on the entire sound system, the advice of professionals, and the user’s needs. By the different application purposes, the power amplifiers can be divided into the following categories.

1. The one specially design to promote the subwoofer amplifier, with built-in infrasonic filter while eliminating the external filters.

2. The one with equalizer. User can adjust the tone according to personal preference or different car space.

3. The one with 5-channel amplifier for a speaker connection. Generally, the 2-channel or 4-channel amplifier is used to drive the front and rear speakers, and another amplifier to drive the subwoofer. However, this proposal occupied too much space for installation; while a 5-channel power amplifier can solve the problem easily.

4. The one with multi-chip X-card. The unique X-card for the power amplifier to provide a various choice of crossover: high pass, low pass or even super audio filter.

5. The one with the electronic crossover module. The control module can let users select the preferred kind of signal for a power amplifier and the RCA output. By replacing the module, a power amplifier be adjusted flexibly.

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Last Updated on Tuesday, 27 March 2012, 17:30