subject: Choosing The Right Audio Amplifier For Your Home [print this page] Choosing The Right Audio Amplifier For Your Home
Choosing the perfect audio amplifier can be overwhelming given the large number of different types and technologies. Regardless of your application, I will explain some essential amplifiers terms which will be useful when picking the right model.
An audio amplifier will connect your audio source with your speakers by converting the fairly weak source signal into a strong enough signal 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 today's 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, amplifier wattage is not everything. Good sound quality is probably more important than raw power. A 20 to 50 Watt amp should be sufficient for most real-world applications.
There are two conventions for specifying amplifier wattage. The first one specifies how much power the amplifier is able to deliver continuously. That number is often called rms or continuous power. The second number is called peak or maximum power and tells how much the amp can deliver for short bursts. 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.
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. No amplifier is absolutely perfect and the amplified signal will include some error components which will distort the signal to some degree. THD is either 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%.
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. Consumer-grade amps will have a signal-to-noise ratio (SNR) of at least 80 dB. Higher-end amps will have an SNR of 100 dB or more. Audiophile amps will have an SNR of close to 120 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. Some of today's mini amplifiers are no larger than a deck of cards. However, when picking a Class-D (digital) amplifier, be sure that the amplifier has low distortion and a high signal-to-noise ratio.
