subject: Ideas For Buying The Right Audio Amplifier [print this page] Picking a good audio amplifier for your speakers is not a trivial task. You want to ensure that your amp matches your speakers. I will explain some basic amplifier terms and give some pointers to help you pick the best amplifier.
Audio amplifiers come in all different shapes and sizes. They use different technologies and have many technical specs. This makes it difficult to decide which model to pick. You don't have to be an expert. Just follow some simple guidelines and you should be satisfied with your amp.
The most apparent parameter is the size of the amplifier. There are models that are as big as half your living room while some of the newest mini amplifier models are as small as a bar of soap. A large number of amps are the size of a standard rack. This allows your amp to be stacked on top of your other audio devices.
There are some core amplifier technologies available. One technology is called "solid-state". Solid-state amps now account for the majority of audio amplifiers. In the past, tube amplifiers have been popular. Even today tube amplifiers are still available. Tube amplifiers, however, have a fairly high amount of harmonic distortion. Harmonic distortion refers to how much the audio signal is degraded while being amplified. This term is often used while comparing the audio quality of amplifiers.
Tube amps will have audio distortion of up to 10%. Solid state amplifiers will have lower audio distortion depending on the amplifier technology that is used. The most traditional amps use a "Class-A" and "Class-AB" technology. These amplifiers are also called "analog amplifiers". This technology offers fairly low audio distortion. However, the power efficiency is only 10 to 30%. This means that most of the electrical power supplied to the amplifier is wasted as heat while a small fraction is used to amplify the audio signal.
Another technology is called "Class-D". This technology offers far higher power efficiency than analog amplifiers, typically around 80 to 90%. "Class-D" amplifiers are also called "digital amplifiers". Due to the switching output stage, digital amplifiers typically have higher harmonic distortion than analog amplifiers. However, some of the latest models are able to reduce distortion to 0.05% and less by employing a feedback mechanism.
The amplifier should be able to deliver enough output power to sufficiently drive your speakers which will depend not only on how much power your speakers can handle but also on the size of your listening environment. Speaker power handling is given as peak power which describes the maximum amount of power during short bursts while average power refers to how much power the speakers can handle continuously.
If your listening environment is fairly small then you may not need to drive your speaker to its rated power handling value. You would probably be good having an amplifier that can deliver 20 to 50 Watts even though your speakers may be able to handle 100 Watts of power. Note though that speakers differ in their sensitivity. Typically a low-impedance speaker will be easier to drive to high volume than a high-impedance speaker. Be sure that your amp can drive your speaker impedance. You can easily find the rated speaker impedance range in your amplifier's user manual.
Other important parameters are the signal-to-noise ratio and frequency response which should be in the order of at least 100 dB signal-to-noise ratio and 20 Hz to 20 kHz frequency response for high-quality amplifiers.
