Latest models of audio super-mini amplifiers confirm that audio technology has gone the same path as computer technology and cell phones. Products are shrinking at a rapid pace. At the same time, manufacturers are packing in more and more features. In the past, tube amps would be commonplace and take up a large part of the living room. Tube amps still have their fair share of fanatics. Nonetheless they have been replaced by solid-state amps for the most part.
While traditionally there would be separate pre amp and power amp stages, today's solid-state amp combine everything into a neat box no larger than the size of a VCR. A new generation of super-miniature amplifiers, such as the Amphony Model 100 microFidelity amp, has become feasible due to new developments in audio technology regarding power efficiency. These mini amps take up no more space than a deck of cards but deliver up to 50 Watts, which is adequate to drive a speaker to high volume.
"Class-A" and "Class-AB" amplifier topologies were the two crucial amplifier architectures of past audio amplifiers. These technologies have relatively low power efficiency. Analog audio amplifiers by nature only convert a small percentage of the power they consume - normally in the order of 20% to 30% - into audio whereas a large part is dissipated as heat. Therefore analog amplifiers require a fair amount of cooling. The amount of cooling depends on the amplifier rated output power. These heat sinks prevent the amplifier to be built into a small form factor.
"Class-D" amplifiers are based on a digital design which provides larger power efficiency than "Class-A" or "Class-AB" amplifiers - typically in the order of 80% to 95%. Thus only a small portion is wasted as heat which was the key in being able to miniaturize audio amplifier designs. One major problem which has slowed the growth of "Class-D" amplifiers is audio distortion which is caused by nonlinearities of the switching output stage.
Newer amplifier technologies have emerged such as "Class-T" and newer "Class-D" architectures. These technologies, such as the one used in Amphony's Model 100 provide for a feedback of the output signal to the amplifier input. This feedback enables the amplifier to compensate for nonlinearities of the output switching stage and as a result lower audio distortion to comparable levels of analog amplifiers whilst preserving the audio efficiency of digital amplifiers. This high efficiency allows for the amplifier to be built into a very small enclosure. Although not having any ventilation, the audio amplifier will not run hot.
These new miniature audio amplifiers open up applications where previous amplifiers have failed. They are suited in particular for installations with minimal space, such as in ceiling speakers. Other applications include connecting speakers to a DVD/MP3 player or cable box.
Author Resource:
Gunter Fellbaum has been engineering audio and electronic products for over a decade. You can find further information regarding mini amplifiers and other audio amplifiers from Amphony's website.
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