How Small Will They Get? – The Latest Super-Mini Audio Amps
New generation super-miniature amplifiers are a result of the same miniaturization that has caused computers and cell phones to shrink. Everything is becoming smaller and vendors are packing more and more features into the same space. The bulk of audio amplifiers would be tube amps in the past. Even though a large number of fanatics still is fond of tube amplifiers, they have been substituted by solid state amps for the most part.
Today’s amps combine traditional pre-amps and power amps and arrange everything neatly in a single box no larger than a VCR. New developments in audio technology in regard to power efficiency of have permitted the development of a new generation of super-miniature audio amplifiers, such as Amphony’s microFidelity Model 100. These mini amps take up no more room than a deck of cards but deliver up to 50 Watts, which is plenty to drive a speaker to high volume.
“Class-A” and “Class-AB” amplifier topologies were the two primary amplifier architectures of previous audio amplifiers. These technologies have rather low power efficiency. Analog audio amplifiers by nature only convert a small percentage of the power they consume – typically in the order of 20% to 30% – into audio while a large part is dissipated as heat. This requires that depending on the supported output power, analog audio amps have to provide extensive cooling which is achieved by utilizing heat sinks. These heat sinks do not allow these amplifiers to be made very small.
“Class-D” amplifiers are based on a digital design which can provide larger power efficiency than “Class-A” or “Class-AB” amplifiers – normally 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 progress of “Class-D” amplifiers is audio distortion which is caused by nonlinearities of the switching output stage.
More recent “Class-T” and newer “Class-D” amplifier architectures, such as Amphony’s Model 100, incorporate a feedback mechanism where the output of the amplifier is fed back to the input. Using this design, the amplifier is capable to compensate for errors brought on by the switching output stage. Amplifiers based on this design are able to achieve low audio distortion similar to previous analog amplifiers but at the same time the power efficiency of digital amplifiers.
These latest miniature audio amplifiers open up applications where traditional 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.
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