How Small Will They Get? – The New Generation Super-Miniature Audio Amps

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New generation super-miniature amplifiers are a result of the same miniaturization that has caused computers and cell phones to shrink. Everything is becoming smaller and manufacturers are packing more and more features into the same space. You probably still recall the good old tube amps which would dominate the living room. While tube amps are even now popular among fanatics, audio amplifiers these days are solid-state amps for the most part.

While historically 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. New developments in audio technology in regard to power efficiency of have permitted the development of a new generation of super-miniature audio amplifiers, such as Amphony’s microFidelity Model 100. 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.

In history, audio amplifiers would have rather low power efficiency due to the “Class-A” and “Class-AB” structure of analog amplifiers. Analog audio amplifiers by nature only convert a small percentage of the power they consume – normally in the order of 20% to 30% – into audio while a large part 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.

“Class-D” amplifiers are based on a digital design which provides higher power efficiency than “Class-A” or “Class-AB” amplifiers – usually in the order of 80% to 95%. Thus only a small portion is wasted as heat which was the key in being able to miniaturize audio amplifier designs. “Class-D” amplifiers use a switching output stage. This stage introduces nonlinearities which creates 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, such as the one used in Amphony’s Model 100 provide for a feedback of the output signal to the amplifier input. Using this design, the amplifier is capable to compensate for errors brought on by the switching output stage. Amplifiers based on this design are able to achieve low audio distortion comparable to traditional analog amplifiers but at the same time the power efficiency of digital amplifiers.

These new generation miniature audio amplifiers open up applications where previous 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.

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