Solid State Power Amp Reviews

In the fall of 1982, I had just become the Editor of the English magazine Hi-Fi News & Record Review. Hi-fi was in a state of flux. The Compact Disc had just made its debut in Japan, but the British and American launches were six months and a year away, respectively. The Linn orthodoxy prevailed about the role of the source in system performance, but there was no agreement about what was and was not important when it came to enhancing the musical experience. "Objectivists" insisted that amplifiers and even loudspeakers had pretty much reached a design plateau where no further improvement was necessary or even desirable, while "subjectivists" were fragmented. All I was aware of was that my system, based on Celestion SL6 loudspeakers, needed more of an undefinable something.

When it comes to amplifiers, ya gotcher tubes, yer solid-states, and yer hybrids. Although amplifier manufacturers would have you believe otherwise, the majority of designs within each category are variations on a few fairly-well-known themes. Everyone agrees that the power supply is extremely important. Most designers try to obtain the amplifier's desired frequency response and distortion characteristics with a minimum of negative feedback. It's also agreed—at least among designers of solid-state amps—that the ability to drive a variety of speakers, including those that present a low-impedance and/or reactive load, is an important priority.

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...

Amplifier designers have frequently looked for ways to marry the advantages of tubes to those of solid-state devices. Hybrid designs of various stripes have appeared over the years, most of them using tube input stages with transistor output stages, eliminating the major weaknesses of tube amplifiers: eg, they run hot, are unreliable in that tubes have a finite life, are more expensive than a similarly powerful solid-state design, and have power-hungry output tubes and output transformers.

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.

The Federal Express delivery man was having a hard time carrying the box containing the Krell KSA-100S up the front steps.

There's always a certain amount of jockeying for position at the very top of the High End. Every few months, a new star burns brightly, getting all the attention. While the constant turnover at the cutting edge helps to define the state of the art, audiophiles should keep their eyes on the longer term. It's a company's track record—examined over a period of years—which defines its position in the market and the credibility of its products.