Wednesday, December 4, 2013

Buying Guidelines For Audio Amplifier Products

By Mike Heller


Selecting a good amplifier for your loudspeakers is not a trivial chore. You wish to guarantee that your amplifier matches your speakers. I will describe some fundamental amplifier language and give some pointers to assist you select the right amplifier.

It is difficult to select the perfect audio amplifier as a result of the large quantity of types. All of these models have different specs. They are based on different technologies and are available in all kinds of shapes and sizes. This makes it hard to decide which type to choose. You don't have to be a specialist. Just follow some straightforward rules and you ought to be satisfied with your amp.

The huge majority of recent audio amplifiers are solid state amplifiers as opposed to more conventional tube amps. Tube amplifiers have been dominant a decade or so ago. Regrettably, tube amps have fairly high audio distortion which describes how much the audio signal is degraded by the amplifier.

Harmonic distortion of tube amplifiers is frequently as large as 10%. Solid-state amplifiers will have lower audio distortion. Still, distortion will depend on the particular audio amplifier technology. Some of the most popular technologies in the past have been "Class-A" and "Class-AB" technologies. These technologies use different arrangements to amplify the audio. Amps based on any of these technologies are also known as "analog amplifiers". While amplifiers using these technologies usually have low audio distortion, power efficiency is merely 10% to 30%. Power efficiency refers to how much of the electrical power is actually used to amplify the signal. The left over part is wasted as heat. An amp with low power efficiency will radiate the majority of its power as heat.

In comparison, "Class-D" amplifiers which are also called "digital amplifiers" offer a power efficiency of usually 80 to 90%. This permits the amplifier and power supply to be made a good deal smaller than analog amplifiers. Because of the switching output stage, digital amplifiers usually have larger harmonic distortion than analog amplifiers. On the other hand, some of the newest models are capable to lower distortion to 0.05% and less by employing a feedback mechanism.

Another technology is referred to as "Class-D". This technology offers much higher power efficiency than analog amplifiers, typically around 80 to 90%. "Class-D" amplifiers are also named "digital amplifiers". The downside is that many digital amps have higher audio distortion than analog amplifiers although some of the most recent models make use of a feedback mechanism to reduce distortion to levels of 0.05% and less. Your amp should deliver sufficient power to drive your loudspeakers. The amount of power will depend on the power handling rating of your speakers. An additional parameter is the size of your room. There are two values for speaker power handling: peak and average power handling. The peak value shows how much power the speaker can handle for small periods of time. The average value on the other hand describes how much power the loudspeaker can handle constantly without harm.

If your listening environment is fairly small then you may not need to drive your speaker to its rated power handling value. You would almost certainly be ok getting an amp that can offer 20 to 50 Watts while your loudspeakers might be able to tolerate 100 Watts of power. Note though that loudspeakers vary in their sensitivity. Usually a low-impedance speaker will be less difficult to drive to high volume than a high-impedance speaker. Be sure that your amp can drive your loudspeaker impedance. You can without problems find the rated speaker impedance range in your amplifier's user manual.

Last but not least, be sure that your amp introduces little noise and has a broad enough frequency response. High-quality amps will have a signal-to-noise ratio of no less than 100 dB and a frequency response of no less than 20 Hz to 20 kHz.




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