Car Audio Buff

An amplifier’s function is to convert the audio signal from your source unit to a higher output level capable of driving speakers without changing the sonic characteristics of the audio signal. Sounds simple, doesn’t it? Actually it is quite a complex process. Fortunately for us, we do not need to know how an amplifier works to pick one that is right for our needs. This article will cover the features of amplifiers and how to choose the right amplifier to fit your needs.

Amplifier Class

Amplifier Class refers to the circuit topology of the amplifier. The common classes of amplifiers are Class A, Class B, Class AB, Class D and Class H. Class A, Class B and Class AB are variations of analog amplifier circuit design. Class D and Class H amplifiers are different implementations of digital driven amplifiers designs.

Class A amplifiers are the most inefficient but typically have the best sound quality. Their efficiency rate can be as low as 25%. That means the other 75% is wasted in heat! A typical Class A amplifier similar in size to a Class AB amplifier will only deliver about half the power. Only choose a Class A amplifier if your goal is ultimate sound quality without regard to cost and power output. Class B amplifiers are much more efficient but have the problem of notch distortion. Class AB amplifiers are a combination of Class A and Class B design yielding the best combination of amplifier efficiency and sound quality. Typical amplifier efficiency for a good Class AB design is about 60% efficiency. This is the most common choice for an amplifier that needs to reproduce the entire audible frequency range.

If you have checked out high-powered subwoofer amplifiers chances are you have heard the term Class D amplifier design. A Class D amplifiers best feature is its efficiency. Good Class D designs can meet and even exceed 80% efficiency, drawing less battery power when compared to a Class AB design. More important, they routinely have over double the efficiency of Class AB designs when running less than full power. The problem with Class D amplifiers is that they are not so good (even bad) at powering midrange and tweeter speakers. As a result, most Class D amplifiers are bandwidth limited to frequencies for subwoofers. Class H amplifiers are a newer version of digital amplifiers designs. They share the efficiency of the Class D amplifiers plus they can be very competent at powering midrange and tweeter speakers.

Number of Channels

This is one of the most important aspects of your amplifier purchase decision. There are many different configurations of amplifiers. Amplifiers range from signal channel mono-blocks to 8 channels total system amplifiers. The most common configurations are 2-channel and 4-channel amplifiers. The first step to choosing the right amplifier (or amplifiers) for your system is to first determine the number of speakers you plan to use in your vehicle. In an average system, this would consist on speakers in the front of the vehicle, amplifiers in the rear with one or two subwoofers. For this example, let’s create a simple system that uses nice set of front component speakers with a single 4-ohm subwoofer. We will look at several different options: one amplifier for the entire system, or two separate amplifiers.

Two amplifiers vs. one multi-channel amplifier

Deciding between the two possible amplifier choices will depend on comparing the benefits and advantages of two amplifiers versus one multi-channel amplifier. Multi-channel amplifiers have several advantages. The most obvious is ease of installation. Installing one box is always easier that installing two. Multi-channel amplifiers with a common power supply can also provide extra current for subwoofers when the amplifier duty is split between powering midrange and tweeters on two channels and subwoofers on the other channels. The multi-channel amplifier can make the system simpler by needed only one set of RCA signal wires and one set of power cables. Of course the most obvious benefit is cost. Multi-channel amplifiers will most often cost less for the same power as separate amplifiers of the same power and brand. If “bank for the buck” is most important, multi-channel amplifiers are the right choice.

On the other hand, separate amplifiers also have their benefits. Separate amplifiers have less cross-talk (signal bleed between channels). If the subwoofer amplifier distorts, you do not have to worry about that distortion adversely affecting the sound quality of the other amplifier. Separate amplifiers typically have more heat sink area for better heat dissipation. Another benefit is the ability to better select amplifiers for a given task. Class D amplifiers, known for their high power versus current draw from your electrical system, are perfect for subwoofers but not so good for midrange and tweeters. With separate amplifiers, each amplifier can be chosen for optimal performance in the system. If cost and space is no object, separate amplifiers are the way to go. Next, we need to match the performance of the amplifier to the impedance of the speakers and subwoofers.

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