subject: Selecting The Right Audio Amplifier For Your Home Theater [print this page] Choosing the perfect audio amplifier can be overwhelming given the large number of different types and technologies. I will help you understand some of the basic amplifier jargon terms. This knowledge will help you choose the perfect amplifier.
Audio amplifiers are essential since your audio source such as your DVD or Blu-Ray player does not deliver a signal strong enough to drive your speakers. The amplifier will be the connecting element to your speakers. It will convert the weak source signal to a signal powerful enough to drive your speakers.
Even though some audio sources have already a built-in amplifier, a separate amplifier gives you more flexibility for picking the model that best complements your speakers. Some of todays mini amplifier models are small enough to hide them virtually anywhere.
When picking an amplifier, your first consideration probably is the amplifier output wattage. You will need a high wattage if you are driving speakers with a low sensitivity (expressed in dB/W), for driving speakers in large rooms or for outdoor speakers. You shouldn't use an amplifier with significantly higher output power than your speakers can handle. Overdriving your speakers can do irreparable damage to your speakers.
However, a 20 to 50 Watt amplifier will give you more than enough power in most situations so don't be overly concerned about the rated amplifier wattage.
Amplifier output power is given as Watts rms (continuous) and Watts peak. The rms or continuous value tells you how much power the amplifier can deliver continuously while the peak power figure tells the maximum wattage that the amplifier can deliver for short periods of time. Typically you should select an amplifier based on rms power. However, make sure that the amplifier has sufficient headroom or peak power to avoid clipping of music signals.
There are other parameters that are more important than wattage when selecting an amplifier. One important parameter is called total harmonic distortion or THD in short. Every amplifier will introduce some imperfections into the audio signal which is known as distortion and expressed in percent or dB. The amount of distortion varies between amplifier models. A smaller distortion means higher audio quality. Audiophile amplifiers will have distortion numbers of typically less than 0.05%. Consumer-grade amplifiers will have distortion figures of up to 10%.
Signal-to-noise ratio is another amplifier characteristic. This number describes the amount of noise which the amplified will add to the audio. The figure is expressed in dB. Higher-end amplifiers will achieve a signal-to-noise ratio of at least 100 dB while consumer grade amplifiers will typically have a signal ratio of at least 80 dB.
There are several amplifier technologies available. Today's amplifiers are mostly Class-D amplifiers. Class-D amplifiers have a high power efficiency and waste little energy as heat. High power efficiency has led to the development of very small amplifiers. Some of these latest mini amplifiers are no bigger than a deck of cards. Class-D type amplifiers often have higher distortion and a lower signal-to-noise ratio than Class-A or Class-AB amplifiers. Some latest digital amplifier models, however, come very close to the audio quality of analog amps. Make certain that the amp has low distortion and a high SNR if you pick a Class-D amp.
