How Small Will They Get? – The Latest Super-Miniature Audio Amps
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 getting smaller and smaller. You most likely still remember the good old tube amps which would dominate the living room. While tube amps are still well-liked among fanatics, audio amplifiers nowadays are solid-state amps for the most part.
Modern solid-state amplifiers merge the traditional 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 possible due to new developments in audio technology regarding power efficiency. Even though these mini amps deliver up to 50 Watts – sufficiently to drive a speaker to high volume, they are no larger than a deck of cards.
“Class-A” and “Class-AB” amplifier topologies were the two primary amplifier architectures of historical audio amplifiers. These technologies have relatively low power efficiency. 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 portion is dissipated as heat. Analog amplifiers hence require considerable 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 normally ranges between 80% and 95%. This allows digital amps to be miniaturized. “Class-D” amplifiers utilize a switching output stage. This stage introduces nonlinearities which creates audio distortion. This problem has had an influence on the success of digital amplifiers.
Some new amplifier technologies have emerged. Among those are “Class-T” and newer generation “Class-D” architectures. These types of new architectures, such as the technology used in Amphony’s Model 100 use a feedback mechanism. The output signal is fed back 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 provides the high power 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, including in-ceiling speakers and applications that connect speakers to a cable box or DVD/MP3 player.