Solid State Power Amp Reviews

Back in 1970, one Julian Vereker decided to record some musician friends in his house in Salisbury, England. Using standard, off-the-shelf electronics and tape machines, he was startled at how dissimilar the recording was to the sound of live instruments. As a result, he started designing his own recording electronics, including a recording console, of which he sold several to local broadcast facilities.

Michael, who might be termed our typical audiophile (if anything in Santa Fe can be termed "typical"), may have found his digital processor, but he's still in a quandary about choosing the right power amp to drive his new loudspeakers. He has listened to a number of them over the past few months, and has been unable to find one which satisfies him in every way. I suspect he has a lot of company. The thorny problems of room acoustics and placement aside, loudspeakers are easier. Their signatures are pronounced and generate strong feelings one way or another; it's usually no problem to narrow down one's choices in this category.

In the January 2015 edition of "Music in the Round," I reviewed NAD's latest Masters Series preamplifier-processor and multichannel power amplifier, respectively the M17 ($5499) and M27 ($3999). I was taken with both, but the M27 made a special impression. In many ways, it personified what a modern power amp should be: quiet, transparent, cool running, and compact. Its neat package of seven 180W channels inspired me to consider that stereo or mono versions of such a thing could supplant the ungainly monster amps I was using in my main system. So I asked NAD to send me not just one but two samples of their new two-channel power amplifier, the Masters Series M22 ($2999): Although this is a review of a stereo amplifier, I did want to have my front three speakers identically voiced.

Was it more surprising that, in 2015, PS Audio would produce a monoblock class-AB power amplifier containing vacuum tubes, or that PS Audio would release a monoblock power amplifier at all? I'm not sure.

In 1974, Paul McGowan and Stan Warren founded the company to produce and market a standalone phono preamplifier, sold directly to consumers for $59.95. From there they naturally progressed to a series of line-level preamplifiers. Toward the end of the '70s, PS Audio produced the Model One, the company's first power amplifier. In the mid-1980s came the high-performance, moderately priced ($495) 4.5 and 4.6 preamplifiers. I reviewed—and bought—a 4.6 a few years after I began reviewing gear for The Abso!ute Sound; Tom Norton reviewed the 4.6 for the September 1988 issue of Stereophile.

I first saw Benchmark's AHB2 stereo power amplifier at the 2013 Convention of the Audio Engineering Society, in New York City. On silent display in Benchmark's booth on the convention floor, its compact size and comprehensive features made the amp immediately attractive, and the design was described as a departure from traditional analog and digital amplifiers. It was also explained to me that the AHB2 was based on designs by Benchmark's founder, Allen H. Burdick (whose initials it bears). By the time of Burdick's retirement, in 2006, Benchmark didn't yet offer a power amplifier, but the company used a prototype based on his work to evaluate their new digital products, and that amp was soon developed as a commercial product; Burdick died just weeks before the AHB2, now named in his honor, was shown at the 2013 AES convention.

Class-A amplifiers have a well-deserved reputation for being power guzzlers that run hot enough to burn fingers. They're inherently inefficient because their output devices conduct full current at all times, and much of that current is dissipated as heat—requiring, in the case of class-A solid-state amplifiers, massive heatsinks. This is why class-A amps tend to produce relatively low power, and tend to be heavy and expensive to buy and run. And these days, energy inefficiency is out of fashion.

Imagine if you can a power amplifier with the bass richness, midrange liquidity, and high-end accuracy of the best tube amplifiers, and the inner detail, transient attack, and bass solidity and range of the best solid-state amplifiers. If you can imagine that, you can visualize what this amplifier sounds like.