Audio amplifiers are electronic devices that take a relatively low-level audio signal and magnify its strength to a level that can drive speakers. This device is typically the last stage in the signal chain of an audio system that begins with the audio source. The audio source is often referred to as the head unit, and this device is often a combination of a radio and a compact disc player. In a basic setup, the signal from the head unit goes into the car stereo amplifier, which then outputs at least two independent audio channels.
Characteristics
Amplifiers have three main characteristics: power output, power supply regulation and input sensitivity. The kind of speakers that can be driven by a particular amplifier is largely dependent on the maximum power it can put out. A car stereo amplifier's power supply unit is designed to convert the 12-volt DC generated by a car's electrical system. Some amplifiers can regulate this incoming supply of electricity, while others don't. Finally, there is the amplifier's input sensitivity. This feature, together with the amplifier's maximum power output, determine how much the amplifier can magnify an audio source signal.
Speaker Match
Amplifiers should have an adequate power output to match the speakers' capacity. When speakers are driven by an amplifier that has a weak power output, the listener tends to increase the volume to get a bigger sound. The amplifier then quickly reaches its limit and distorted sound comes out of the speakers. Distortion can cause the AC signal being put out by the amplifier to transform into DC, which can blow out the speakers.
Regulated Power
Regulation in an amplifier's power supply unit is an important feature because car electrical systems can sometimes fluctuate below or above 12 volts. An amplifier subjected to voltage fluctuations is easily damaged. With regulation, the amplifier can maintain a steady output despite inconsistent electrical input. Sometimes a stiffening capacitor can be installed in a car's electrical system to keep it consistent. In such cases a car stereo amplifier with unregulated power supply would be sufficient.
Input Sensitivity Level
To set a car stereo amplifier's input sensitivity at the right level, begin by turning the knob that controls this feature all the way down. Then gradually increase the audio source's volume until it reaches the highest possible level without distortion. Now that the audio source is putting out its maximum clean signal, gradually turn up the input sensitivity until it also reaches the highest possible level without distortion. This input sensitivity level is the minimum amount of amplification necessary to produce full volume with the least amount of noise.
Other Features
Secondary characteristics that affect a car stereo amplifier's performance are tri-mode, total harmonic distortion (THD) and pre-amp outputs. Tri-mode refers to an amplifier's ability to drive a pair of high-frequency speakers with two audio channels and still use the same two channels to power one low-frequency speaker (called a subwoofer). THD is the amount of distortion an amplifier puts out at a given power output. It is often stated this way: "40watts @ 0.01% THD"--where 40 watts is the given power output and 0.01 percent is the amount of distortion at that output level. Pre-amp outputs are connections that allow several amplifiers to be strung together without splitting the signal from the audio source. This is useful when several speakers of various frequencies need to be driven by specific amplifiers.
Tags: audio source, power output, stereo amplifier, input sensitivity, power supply, amount distortion