Newest models of super mini audio amplifiers underline the ongoing trend of miniaturization of consumer devices such as cell phones or computers. While the features are growing, the size of today's consumer products is getting smaller and smaller. The majority of audio amplifiers would be tube amps in the past. Even though large number of fanatics still is fond of tube amplifiers, they have been replace 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. Thanks to latest developments in audio technology in regard to amplifier power efficiency, a new generation of super-miniature audio amplifiers has become possible. Even though these amps are as small as a deck of cards, they are able to deliver up to 50 Watts power and easily drive a speaker to full volume.
Past audio amplifiers with "Class-A" and "Class-AB" architectures have fairly low power efficiency. Analog audio amplifiers will only convert between 20% to 30% of the consumed power into audio while the remaining portion is dissipated as heat. Analog amplifiers therefore require significant cooling which is done by heat sinks that are often bulky and prevent the amplifier from being made very small.
The "Class-D" topology of digital amplifiers offers higher efficiency than analog amps. The efficiency typically ranges between 80% and 95%. This allows digital amps to be minaturized. "Class-D" amplifiers employ a switching output stage. This stage introduces nonlinearities which causes audio distortion. This problem has had an impact on the success of digital amplifiers.
Newer amplifier technologies have emerged such as "Class-T" and newer "Class-D" architectures. These technologies provide for a feedback of the output signal to the amplifier input. By using this feedback, the amplifier can compensate for nonlinearities of the output stage. This allows the distortion to be reduced to levels similar to analog audio amplifiers. At the same time the amplifier offers the high power efficiency of digital amplifiers.
These new generation miniature audio amplifiers are suited for a range of new applications where previous audio amplifiers have failed. These applications include installations, such as in-ceiling installations, with minimum space or connecting speakers to a cable box or DVD/MP3 player where minimum space is key.
Therefore the high efficiency of modern power amps is key to obtaining the small form factor but at the same time sufficiently high audio power.
You can find additional information regarding small power amplifier products from Amphony's website.
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