Recent models of audio super-mini amplifiers prove that audio technology has gone the same route as computer technology and cell phones. Everything is becoming smaller and vendors are packing more and more features into the same space. The majority 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.

Modern solid-state amplifiers combine the conventional pre amp and power amp stages into a neat single box no larger than a DVD player. Thanks to latest developments in audio technology regarding amplifier power efficiency, a new generation of super-miniature amps has become feasible, such as the Amphony Model 100 microFidelity amp. 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.

In the past, audio amplifiers would possess fairly low power efficiency due to the “Class-A” and “Class-AB” architecture of analog amplifiers. Only a small percentage of the consumed power – typically in the order of 20% to 30% – is in fact transformed into audio by analog amplifiers. The left over portion is radiated as heat. This requires that depending on the supported output power, analog audio amps have to afford substantial cooling which is achieved by using 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 allows higher power efficiency than “Class-A” or “Class-AB” amplifiers – usually in the order of 80% to 95%. As a result only a small portion is wasted as heat which was the key in being able to miniaturize audio amplifier designs. One major drawback of “Class-D” amplifiers is the fact that digital “Class-D” amplifiers use a switching stage at the output which causes non-linearity and as a result some amount of distortion of the audio signal. This drawback has slowed the advance of digital amplifiers.

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. 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 latest 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.