Are Class-D Amps Coming of Age?

To Doug Schneider,

In some of your recent speaker reviews it appears that you have used a class-D audio amplifier as part of your equipment setup.

The better energy efficiency of class-D amplification is appealing, but most of what I have read over the years has stated that although often quite powerful, class-D amps are somewhat harsh or stale sounding compared to traditional class-AB amp designs.

From your experiences, is class-D amplification gradually coming of age? Or, in other words, is the sound quality and refinement of more recent class-D amplification finally approaching that of class-AB amplifiers?


If you look at the history of innovation in audio, new technologies are often dismissed by certain detractors, particularly if there are flaws when the technology debuts. But, over time, as that technology is refined, it often becomes as good or better than what's currently there and gets widely adopted (although there will always be a certain segment of the market who will never adopt it).

For example, despite being almost 48 years old, I'm still too young to have been there when the transistor debuted and began replacing vacuum tubes. Still, from what I understand, many audio enthusiasts thought early solid-state designs sounded pretty bad and dismissed the technology altogether. In fact, some still do, which is why vacuum tubes remain popular. So that puts class-AB of yesterday in the same boat as class-D technology today. But as we all know, solid-state devices continued to improve and class-AB amplification is what's most popular today and sets the standard. Digital playback is another area -- CD, whose introduction I do remember, certainly wasn't praised by everyone.

I don't doubt that some of the earliest class-D amplifier designs probably sounded pretty bad as well, but things have improved greatly since then. The best example would probably be Devialet's D-Premier that combines class-A and class-D technologies in a unique way that, to my ears, produces the very best sound you can hear today. Granted, it's not a pure class-D amp, but class-D technology is an important part of it and helps to show what can be achieved with some original thinking. Using the D-Premier as an example, class-AB sound hasn't simply been approached, it's been far surpassed. I encourage you to hear it for yourself and see if you agree.

What's more, traditional tube and solid-state design work is pretty much at a standstill -- many of the tube and solid-state amps on the market today are similar to those produced decades ago -- but there's still a lot of work being done with class-D-based designs, and there will continue to be quite far in the future. Right now I'm listening to the Eximus S1 amplifier, which is what you've probably seen mentioned in some of my reviews. It uses B&O's latest ICEpower module and sounds very refined -- harsh and stale aren't words I'd use to describe it.

So has class-D technology come of age? Definitely -- the D-Premier is proof of it. But it will also continue to improve and, more than likely, get even better. . . . Doug Schneider