New generation super-miniature amplifiers are a result of the same miniaturization that has caused computers and cell phones to shrink. While the features are growing, the size of today’s consumer products is becoming smaller and smaller. In the past, tube amps would be commonplace and take up a big 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 Nonetheless they have been replaced by solid-state amps for the most part. Modern solid-state amplifiers merge the conventional pre amp and power amp stages into a neat single box no larger than a DVD player. New developments in audio technology in regard to power efficiency of have allowed the development of a new generation of super-miniature audio amplifiers, such as Amphony’s microFidelity Model 100. These mini amps use no more room than a deck of cards but deliver up to 50 Watts, which is enough to drive a speaker to high volume. In the past, audio amplifiers would have comparatively low power efficiency due to the “Class-A” and “Class-AB” structure of analog amplifiers. Analog audio amplifiers by nature only convert a small portion of the power they consume – typically in the order of 20% to 30% – into audio while a large part is dissipated as heat. Therefore analog amplifiers require a reasonable 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 can provide larger power efficiency than “Class-A” or “Class-AB” amplifiers – typically 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. “Class-D” amplifiers utilize a switching output stage. This stage introduces nonlinearities which causes audio distortion. This difficulty has had an influence on the success 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. This feedback permits the amplifier to compensate for nonlinearities of the output switching stage and therefore lower audio distortion to similar levels of analog amplifiers while preserving the audio efficiency of digital amplifiers.
These new generation miniature audio amplifiers open up applications where traditional amplifiers would fail, such as speaker installations where space is premium, such as in-ceiling speakers and applications that attach speakers to a cable box or DVD/MP3 player.