How Tiny Can They Get? - The New Generation Super-Miniature Audio Amps
Newest models of super-mini audio amplifiers underline the continuing trend of miniaturization of consumer products such as cell phones or computers. While the features are growing, the size of today’s consumer products is becoming smaller and smaller. The majority of audio amplifiers would be tube amps in the past. Although a large number of fanatics still is fond of tube amplifiers, they have been substituted by solid state amps for the most part.
Modern solid-state amplifiers merge the conventional pre amp and power amp stages into a neat single package no larger than a DVD player. 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. Even though these amps are as small as a deck of cards, they are capable to deliver up to 50 Watts power and without difficulty drive a speaker to full volume.
“Class-A” and “Class-AB” amplifier topologies were the two crucial amplifier architectures of previous audio amplifiers. These technologies have fairly 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 whereas a large part is dissipated as heat. Analog amplifiers hence need substantial 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 provides higher efficiency than analog amps. The efficiency normally ranges between 80% and 95%. This allows digital amps to be miniaturized. One major difficulty which has slowed the growth 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 able to compensate for errors caused by the switching output stage. Amplifiers based on this design are capable to achieve low audio distortion similar to previous analog amplifiers but at the same time the power efficiency of digital amplifiers.
These new miniature audio amplifiers open up applications where previous amplifiers have failed. They are suited in particular for installations with minimum space, such as in ceiling speakers. Other applications include connecting speakers to a DVD/MP3 player or cable box.