Pass Xs Preamp and Xs 300 Mono Power Amplifiers

Major New Challenges to the State of the Art

Equipment report
Solid-state power amplifiers,
Solid-state preamplifiers
Pass Laboratories Xs,
Pass Laboratories Xs 300
Pass Xs Preamp and Xs 300 Mono Power Amplifiers

This is a case where I need to begin a review by reminding the reader that the name of this magazine is The Absolute Sound, not the Cost-Effective Sound. Both products I’m reviewing—the Pass Xs preamp and Pass Xs 300 power amplifier—are efforts to provide that absolute sound without compromise in either quality or price. They are new top-of-the-line components that push the state of art in audio to its limits, and they are priced accordingly. The Pass Xs Preamp sells for $38,000, and the Pass Xs 300 mono power amplifiers sell for $85,000 a pair.

As might be expected from Pass Labs’ history, both components meet their goal. At the risk of eliminating any suspense from this review, they are the two best-sounding examples of a preamp and power amp I have yet heard. The kind of gear most audiophiles dream about—which only the truly lucky can afford—and that redefine the perceptions of reviewers during the all-too-brief time they pass through their systems.

A Case Study in Searching for the Limits to the High End
There is, however, a broader purpose to this review than simply praising the Xs preamp and Xs 300 amps. I’ve been reviewing Pass Labs components for years, and Nelson Pass’ amplifier designs since the peak of high-end audio’s popularity during the early Fillmore Administration. I use a Pass XP-30 preamp and a pair of Pass XA-160.5 Class A mono amplifiers in my reference system. Reviewing the Xs preamp and the Xs 300 mono amps gave me the opportunity to put the merits of two true new assaults on state of the art in perspective. It allowed me to focus on the level of improvement you actually get from designs with a total cost of $123,000, when my reference XP-30 preamp and XA-160.5 mono amplifiers cost $38,500, and other truly excellent Pass components like the XP-10 preamp and XP-150.5 stereo amp cost a total of $10,750, and the superb INT-150 integrated amplifier a mere $7150.

The answers to these questions aren’t simple, and they are discouraging to audiophiles on much tougher budgets. Every Pass preamp and power amplifier I’ve heard has been remarkably neutral, worked easily with a wide range of front-end components and loudspeakers, was free of any solid-state coloration, and was transparent and neutral in sound quality. You begin with truly musical components, and they get better and better. Moreover— as is the case with every other top manufacturer of high-end preamps and amps—the level of improvement in sound quality relative to price is a matter of steadily diminishing returns. You have to pay more and more for less and less improvement.

I wouldn’t be a high-end-audio reviewer or an audiophile, however, if I had an accountant’s objectivity in measuring the incremental benefits from investing in top-of-the-line equipment. Like car freaks, wine snobs, and stamp perforation-edge perfectionists, my goals are not to be cost-effective, but to go to the limits of the sound quality I can afford—and all too often beyond. Real audiophiles pursue the limits of the high end for its own sake. We share a hobby or “sport” that largely ignores the reality of diminishing returns with each additional dollar spent. Success or “winning” consists of getting the best possible musical experience within a given personal budget. If you want to be cost-effective investing in Pass Labs equipment, buy the INT-150 and read TAS simply for your dreams.

The Pass Xs Preamp
So let me begin with the Pass Xs preamp, and try to explain why I soon came to feel the level of sonic improvement was both real and worth it to audiophiles who can afford it. Let me also set the stage by noting that virtually all high-end manufacturers tend to voice their equipment to a consistent standard. That standard tends to evolve with time and becomes steadily more realistic and musically enjoyable, but years of reviewing have taught me that given manufacturers and designers have consistent biases in the sonic nuances they voice into their equipment.

Equipment that measures “flat” using steady-state sinewaves into a fixed load does not sound flat reproducing complex musical signals into real-world loudspeakers. Some manufacturers voice for a slight bass boost, some add a slight boost for midrange or treble detail. Some voice for a more dynamic sound or more detail. Some voice for the warm and forgiving. I’m in the camp that says preamps and amplifiers can’t affect tempo or rhythm— and modern digital electronics and the best turntables are incredibly accurate in this domain—but a slight upper midrange rise can give the music more apparent life.

This voicing of electronics also affects soundstage width, imaging size, and back-to-front realism and perspective. Some manufacturers voice for a wide, more front-of-the-hall soundstage. Some seem to play with imaging, and a few seem to play with depth. Centerfill is another related issue, and one I suspect we understate in reviews because—like depth—it is usually dominated by the recordings, speaker, and room setup.

To me, the best electronics have as little of this characteristic voicing as possible. I’m a mid-hall listener, unless I’m reviewing; I listen almost exclusively to acoustic music and small jazz groups, classical groups, and soloists, rather than band, orchestra, opera, etc. With a library of music that involves thousands of mediocre to excellent recordings going from the 1930s to the present, I don’t want someone else’s biases to give me apparent “insights” into part of my recordings, and mask or color the majority of the rest.

This is one reason that I minimize references to the sound of individual recordings in my reviews. My concern is sound using a musical library, and far too often I find that a sudden “insight” into the music on a given recording usually proves to be a warning of a broader problem in listening to a full range of music. I have enough problems dealing with the voicing in my recordings, the sharper colorations in front-end components, and the unavoidable problems in matching even the best speakers to a given room and listening position.

At a different level, attention to electronic and physical noise and hum also varies, although any such problems have become far less audible over time. Like most audiophiles today, I want and expect my music to come out of a “black hole” of silence. I now find even a trace of electronic hum, noise, and hiss annoying—particularly with solo instruments in the quiet of the night. Some of my friends—particularly audiophiles who prefer the tube classics of the 1950s and 1960s—will listen gladly through such problems.

Moreover, the more I review, the more I come to distrust what I have come to regard as “trick” electronics. Preamps that minimize features to the point they don’t even have a balance— to me an “imaging” or “soundstage” control—or enough XLR and RCA inputs and the equivalent of a tape loop; preamps and amplifiers that are remarkably sensitive to given cables and loads; underpowered amplifiers that work well only with some music on a handful of speakers; and particularly amplifiers whose wattage rating are not matched by high current, extension into the deep bass, and the ability to tightly control a wide range of speakers.