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Audiophile Amplification Gains From GaN

News

Exceptional switching characteristics of GaN FETs underpin a new era in high-fidelity amplification

BY LEO AYZENSHTAT FROM ORCHARD AUDIO

FOR MORE THAN half a century lovers of hi-fidelity have argued over the best technology for making audio amplifiers. Sitting on one side of the divide are the valve aficionados, who claim that tubes are the key to providing an engaging, unfatiguing and rewarding listening experience. In the other camp are the fans of the transistor, who view this as by far the better option - one that delivers a realistic, powerful and faithful delivery of the recorded medium.

For those that prefer solid-state technology to valves, a decision now awaits. Do they hold on to their cherished amplifier that sports silicon transistors, or do they trade it in for a new breed, built around wide bandgap devices? It is not a difficult decision, because if they do invest in the future, they will reap many rewards.

The benefits are not limited to a better sound for the outlay, but extend to practical gains, such as a far smaller footprint and a higher efficiency that trims household bills.


GaN devices from GaN Systems lie at the heart of the Orchard Audio Starkrimson Ultra product range.

Over the last decade or so, there has been an increase in sales of all forms of Class-D audio amplifier, which operate at high switching frequencies. With this mode of operation it is challenging to realize an acceptable level of total harmonic distortion + noise (THD+N), due to the need for faster, cleaner switching transitions. When class D amplifiers are based on silicon MOSFETs, they incorporate substantial feedback circuitry to compensate for the poor open-loop performance and subsequent noise. While it is possible to reduce this with larger devices, this comes at the expense of higher switching losses, diminished efficiency, an increase system size and higher material costs.

All these issues are not just of concern to high-end audiophiles, who will pay thousands and thousands of dollars for an amplifier. Over the last few years home audio has changed, partly due to the pandemic-driven shut-down of traditional entertainment sources, such as movie theatres and live music venues. Many of us are now spending more time with our audio systems - whether we are streaming movies, playing games, or listening to music - and this has heighten our awareness of how high-quality home audio systems can enhance our listening experience.

Market analysis supports this view. Those in the know are pointing out that demand for high-quality audio is fuelling the growth of the Class-D audio amplifier market, which is tipped to reach $4.92 billion by 2026. This class of amplifier is being deployed in ever more audio applications, including home theatres, high-power smart speakers, pro-touring amplifiers, portable speakers, automotive, marine, and power sports.

At Orchard Audio of Succasunna, NJ, we are playing our part in the audio revolution by launching a portfolio of products that feature amplification with GaN transistors. We have adopted these devices because they have exceptional switching speeds. Several benefits result from this attribute: very fast slew rates, which are much valued in a class D amplifier, because this narrows the gap to the ideal square wave (see Figure 1); incredibly precise timing, critical to realizing high-quality audio; and improved efficiency, with amplifier topologies being able to operate with a much shorter dead time, an approach that leads to a much lower cross-over distortion (see Figure 2).