Picking The Best Audio Amplifier For Your Home Theater
Audio amplifiers are available in a flood of different technologies and models. Choosing the perfect model for a particular application seems to be a daunting task. Regardless of your application, I will explain some essential amplifiers terms which will be useful when picking the right model.
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. There are some miniature amplifier models available. These models are small enough to hide 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. However, be careful not to overdrive your speakers. This can damage your speakers beyond repair.
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. You should choose an amplifier that has sufficient rms power, although 10 to 30 Watts should be plenty for most applications but has enough headroom for peaks that occur in music signals.
Audio quality is just as important as having enough audio power and therefore you should also look at figures such as total harmonic distortion or THD. No amplifier is perfect. There will be some amount of signal distortion which is caused by the amplifier. The amount of distortion is expressed in percent or dB. A high-quality amplifier will have a low distortion figure. The amount of distortion will be less than 0.05% for a high-quality amplifier. Consumer type amplifiers have higher distortion figures. Typical figures are up to 10% depending on the output power.
Another figure related to audio quality is known as signal-to-noise ratio and describes the amount of unwanted noise the amplifier will add to the signal. Audiophile-grade amps will have an SNR of 100 dB or higher. Consumer-grade amps will have at least 80 dB signal-to-noise ratio.
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. Class-A and Class-AB amplifiers require a fair amount of heat sinking and therefore are typically fairly large and heavy. In contrast, amplifiers based on the Class-D technology are small and lightweight. Some of today's smallest mini amplifiers are no larger 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.
Gunter Fellbaum has been engineering audio and electronic products for over a decade. You can find additional information about audio amplifier technologies and mini amplifier products from Amphony's website.