Solid State Power Amp Reviews

Soon after I took over preparing Stereophile's biannual Recommended Components listing from the magazine's founder, J. Gordon Holt, in 1986, I ran into a problem. With so many products listed, the magazine was running out of the necessary pages to include them all. To solve this problem, I looked at how long a typical product remained on the market before being updated or replaced. The answer was 3–4 years. I therefore implemented a policy that unless one of the magazine's editors or reviewers had continued experience with a product, it would be dropped from Recommended Components after three years.

Just in case you didn't know this when you bought the Parasound HCA-3500, it says on the cover of the owner's manual: "Designed in California, USA by John Curl." Described as an "audio design legend," an appellation with which he seems quite uncomfortable, John Curl has certainly been around the audio business longer than most. He's been employed by or has consulted for some of the biggest names in consumer and professional audio—including Harman/Kardon, Ampex, and Mark Levinson—and was the designer of at least two classic products: the Mark Levinson JC-2 preamplifier and his own Vendetta">http://www.stereophile.com/phonopreamps/640">Vendetta Research phono stage, still considered by many people to be the best phono stage ever built.

In December 2023, I took the train from New York to Los Angeles to attend the Los Angeles & Orange County Audiophile Society's 30th annual Gala. I took the trip because it is both stimulating and satisfying to spend an afternoon in the company of more than 200 audiophiles and music lovers; I also wanted to see John Curl presented with the Society's fourth Innovation Award, by George and Carolyn Counnas of Zesto. John was given the award "for his groundbreaking contributions to the field of solid-state audio amplifiers, circuit innovation, mastering recorders and much more."

I first met John more than 40 years ago, at a Consumer Electronics Show in Chicago, where I was blown away by John's intuitive and innovative approach to circuit design.

The Aleph Null, or 0, represents Nelson Pass's maiden product under the Pass Laboratories banner. When he left Threshold several years ago, Pass had the luxury of starting over with a clean slate, and decided immediately that he wanted to design a single-ended MOSFET amp. The result is aptly named after Georg Cantor's first transfinite number: Aleph Null, the gateway to higher-order infinities. Just as Cantor's transfinite mathematics stretched minds with its novel conceptual view of the infinite, the Pass Aleph 0 tantalizes the imagination with a new dimension in the future of solid-state amplification: a single-ended output stage.

It was almost seven years ago that Nelson Pass, whose talks and exhibits I'd covered at many a Bay Area Burning Amp DIY event and audio show, surprised me with a loan of two Pass Laboratories' XA 160.5 class-A monoblock amplifiers. Ten months later, after I'd commented that my system had challenged the XA 160.5s in the bass department, he sent me a pair of XA200.5 monos. I connected those bigger babies to Wilson Audio Sophia 3 loudspeakers and some now-discontinued digital components with Nordost Odin 1 interconnects and speaker cables. Then came my way, toward the end of 2016, the XA200.8 monoblocks ($42,000/pair).

Years ago, when I was young and foolish (instead of old and foolish, as now), I was hanging out with a friend at a strip-mall strip club in a small southeastern city. A youngish lady approached our table in G-string and pasties and did a tableside dance. My friend's jaw scraped the floor; I, noting her lack of enthusiasm, was unmoved. The stripper noted my impassivity and stated, with irony that at the time I somehow missed, "You're a hard man."

John Atkinson, too, is a hard man, at least when it comes to audio gear. When, in January 2014, he reviewed the Pass Laboratories XA60.5 monoblock amplifier, he concluded, "It is the best-sounding amplifier I have ever used." High praise.

Everyone's going crazy for single-ended power amplifiers. What's the big deal? What is it about these relatively low-powered contraptions that could make everybody so nutso? And has Pass Labs' Nelson Pass completely lost his marbles, selling a 30Wpc amplifier for a price that can buy a high-quality 200Wpc amp? Isn't that 200W amp seven times as loud—and seven times as good—as a 30W amp?