Solid State Power Amp Reviews

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.

The No.331 is the latest iteration in a series of Mark Levinson 100Wpc, solid-state, stereo power amplifiers. Extensive cosmetic alterations, internal structural changes, and new circuit designs make it quite different from the No.27 and No.27.5 models that preceded it. These design refinements emanate from Madrigal Audio Laboratories' latest flagship amplifier, the $32,000/pair, 300W RMS Mark Levinson No.33 Reference.

What is it about a component that makes the blasé High Ender sit up and say, "Hey, this is special!"? What elements of its reproduction reach out to you and won't let go? How does the intrepid audio reviewer find a way to describe these hopefully recurring moments of musical discovery which define the high-end experience? How many times, after all, can you say, "Ooooo, ahhhhh, that's the best [insert some part of the frequency range here]," ad nauseam? How much difference is there, anyway? Therein lies the tale...

High-tech, compact, and lightweight, Chord's entry-level SPM 650 power amplifier ($4995) promises robust power output, low distortion and noise, flat and ultra-wideband frequency response, and bulletproof reliability—all in what seems an impossibly small package measuring 16.4" wide by 3.4" high by 13.8" deep and weighing only 22 lbs.

Musical Fidelity's "Supercharger" concept is simple, which is perhaps why no one had thought of it before: If you love the sound of your low-powered amplifier but your speakers are insensitive, or you just need more loudness, you insert the high-power Supercharger amplifier between your low-powered amp and speakers. The Supercharger loads the small amplifier with an easy-to-drive 50 ohms, and, in theory, has so little sonic signature itself that it passes on the sonic signature of the small amp unchanged, but louder.

Founded in 1925, Luxman has long been one of Japan's most highly regarded audio manufacturers. Throughout the 1970s and into the 1980s, Luxman's tube preamplifiers and power amplifiers occupied the top shelves of high-performance audio retailers, and to many older American audiophiles, the Luxman name is as familiar and esteemed as those of such storied American brands as McIntosh and Marantz. Luxman's combination of rich, warm sound, superb build quality, and indelible industrial design made its products fully competitive with other brands then considered among the world's best.

Yet another amp from Colorado! This is the third amp to come my way from that state (the others being the Spectrascan and the Rowland Research), and at this point, after living with it for a couple of months, I'm quite comfortable in declaring the Boulder 500 to be one helluvan amp.