The class of 2006. The amp class of Class D. Is that "D for doom"? As in "death to all other classes of amplification"? Is that "D for destitute"? As in "I can't design my own amp from scratch so turn-key module here I come"? While the cynics amongst us could feel - um, destitute, the sheer case evidence is rather mounting to doomsday. When the last purveyor of non-switching amps has at least one Class D amp in their arsenal. The latest bona fide amp manufacturers who joined the "digital amp" parade from what I've been able to follow are Cary Audio and Rotel. Both clearly know how to design conventional amps. Both have done so for years.
Now they've included analog switching amps to their lineups. Is that just keeping up with the Joneses? In order to offer mid-priced high-power transistor amps, does one nowadays have to go Class D, to remain competitive in similar fashion as speaker designers who simply must outsource in China to remain in the value sector of the game? Is it a function of reduced R&D investment when ready-to-roll amp modules are available from a variety of vendors? Is it a function of scrapping the heavy and expensive power transformer to drive down build costs and retails?
It's perhaps a little bit of everything, with the balance shifting depending on who we're talking about. In general, it's fair to say that the technology has matured to the point where high-profile and fully established manufacturers no longer see sonic, credibility or other issues preventing them from embracing it. There are still stalwarts like Bryston, Krell, Classe, Pass Labs and Levinson in the US and Canada who remain exclusively committed to Class A solid-state architectures. They may well see no good reason to change colors across the board or just in part any time soon or ever.
But make no mistake, their numbers are dwindling. Rapidly. It's far too early to claim that Class D has replaced the "pre-digital" ways of building amplifiers. In fact, it may never replace 'em. However and as things stand today -- epitomized by Bel Canto, Boz, Jeff Rowland, Kharma, NuForce, TacT and others -- Class D has become just as viable to offer designers and consumers alike valid and credible options. In February 2000, I covered Bel Canto's embrace of Tripath Digital Power Processing in a column I wrote for SoundStage!. 5+ years later, that shocking move for a tube amp maker turns out to have been eerily visionary and preemptive. It's really quite amazing how far things have shifted; how entrenched switching amplifiers have become since.
The genre has moved well outside the cheap'n'cheerful perception which accorded it usefulness in subwoofer, HT receiver and mini system applications then but still held that for serious purposes, it simply wasn't adequate. Today, top reviews in any audio publication include Class D performers sitting proud on the same page as the most famous Class A denizens of the good book. That's quite a maturation process for the technology. Each time a high-end manufacturer adopts it to perhaps tweak a basic module; to throw away the stock power supply and build his own; or somehow or other get involved to massage the basic recipe; the genre of digital amps gets a slight uphill push. Vendors take note. They incorporate tweaks and mods they hear about in the field. New advances stand on the shoulders of those who came before. As long as people use these modules, they keep getting better. They can clearly already be implemented such as to compete head-to-head with old-style designs. What could happen in another five years? It's a truly charged question to ponder, isn't it?