Solid State Power Amp Reviews

Before the advent of big-screen projection televisions, manhood was measured more conventionally: by the size of one's crate-sized, boat-anchor-heavy, brushed-aluminum-fronted power amplifiers. Those days are long gone.

Over the course of his 30-plus years in high-end audio, Nelson Pass's designs have never been far from the leading edge. In his first Threshold amplifiers he pioneered the use of dynamically adjusting bias and cascode circuitry; then, in the later Stasis models, he switched gears to the simpler approach of pure class-A. All were innovative designs, and among the very best-sounding amps of their time, but were just warmups for what was to come. In 1991, Pass Labs introduced the Aleph 0, a class-A amplifier that was a startling departure from conventional solid-state designs and combined design elements generally thought mutually exclusive: transistors, single-ended operation, and the ability to output 75Wpc into an 8-ohm load. Not surprisingly, the Aleph 0 sounded like nothing else, and became the basis for the widely acclaimed series of Pass Labs amplifiers that evolved over the next decade.

Whereas the Pass Labs preamplifiers are designed by Wayne Colburn, the power amplifiers are the work of company founder and high-end audio veteran Nelson Pass, who even lays out his own circuit boards. The X-model amplifiers, beginning with the X1000 in 1998, were the first implementation of Nelson Pass's patented Supersymmetry topology (see "Nelson Pass on the Patents of Pass"). The XA series, which debuted in 2002, combined Supersymmetry with the single-ended class-A operation of the Aleph series. The XA.5 models offer detail improvements over the XAs.

When Jim Austin offered the Plinius Reference A-150 stereo amplifier ($14,995) for review, it felt like a welcome blast from the past. Plinius has, lately, maintained a low profile in the US, likely due to several changes in US distributorship...Under the auspices of Ralph Abramo and California-based Plinius Audio Sales and Repair, Plinius's US profile seems to be rising again.

Man, you've got to watch out for those preconceived notions—they'll kill you every time. For the last several years I've seen Plinius amplifiers at hi-fi shows and—even though I didn't know the first thing about the company or its products—figured that I knew what they were all about. Spotting their brawny façades festooned with feathery heatsinks, I smugly assured myself that they were some kind of antipodean pretender to the muscle-amp throne—Krell or Threshold wannabes.

When most of us think about the folks who populate the high-end audio industry, we tend to conjure up the designers—the names above the titles, as it were. Or, in many cases, the names that are the titles: Richard">http://www.stereophile.com/interviews/688vandersteen">Richard Vandersteen, Jim">http://www.stereophile.com/interviews/221">Jim Thiel, Bill Conrad and Lew Johnson, Mike Creek, to name just a few.

These days, listeners the wide world over enjoy hearing their music recreated for them by equipment whose origins are international; trade isolationists might consider the example of PrimaLuna. This Holland-based company's operations span three continents, with designers from Floyd Design and Durob Audio in the Netherlands, manufacturing in China, and input from California-based Harmonia Distribution.