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

I found in comparing the Xs preamp with the XP-30 that Wayne met all of his goals in improving sound quality and other improvements, as well. The XP-30 is a truly great preamp, but the Xs preamp is a better preamp at every level. It provided an audible margin of musical realism that was progressively more audible as speaker quality improved over a broad range of recordings with a variety of different front-end components and power amplifiers. (I used my Wilson Alexias and Legacy Aeris speakers, an aging pair of Spendor BC-1s, a pair of older Electrovoice horn speakers, and a friend’s Quad 2905s—a friend crazy enough to actually bring his speakers to my listening room.)

Could I hear more realistic musical energy and dynamics at every level from my best recordings? Yes. Was there more musical life? Yes. Did I hear more soundstage detail with the recordings that really have one? Yes. Was there even more freedom from even a touch of upper-midrange hardness without softening strings, solo piano, or woodwinds? Yes, again. Was there slightly more electronic silence? Yes, although at an almost sub-audible level compared to the XP-30—and at only slight improvements over my memory of the sound of the XP-10 and XP-20.

The already exceptional highs of the XP-30 were even more natural. Bass definition was slightly improved in the mid and upper bass, along with the transition to the lower midrange. Male and female voice were equally excellent and somewhat more open and natural. Complex organ passages were a bit cleaner, and so were complex orchestral dynamics. I’ve never found recordings of large jazz bands to quite live up to the live listening experience, but the Xs preamp sometimes almost forced me to pay close attention to just how creative some passages of big band music can be.

This is an ideal preamp if you want to get the very best sound from your best LPs and for testing the limits of high-definition digital downloads. More importantly, it is a preamp that allows you to fully appreciate both the fun the Modern Jazz Quartet could have with the right music, and the subtleties of the best recordings of Bach’s most complex choral music.

I did keep trying to pin down exactly why the Xs preamp sounded better than the XP-30, and I kept finding that the improvements in the Xs were limited and not confined to any one area. They did, however, make the Xs consistently more musically natural and involving.

At a given point, however, describing the improvements in transparency and neutrality becomes an exercise similar to trying to write a long essay on different shades of red. You can try to make the prose exciting, but you really can’t describe the color red.

As for trying to rank or quantify such improvements, I ultimately found myself reacting to such efforts in the same way that I do to attempts to precisely rate wines from 1 to 100 with difference scored down to the last digit. Saying one bottle ranks a 91 and the other ranks a 92 implies you can really measure such difference consistently. Throwing references to the taste of wild raspberries, forest mushrooms, and oak trees, doesn’t help. (Query: Would a wine snob really know an edible forest mushroom from a poisonous one? How many oak tress and wild raspberries has he actually eaten?) Each level of improvement in Pass Labs or other preamps is audible, but if you begin with excellent overall sound quality, trying to quantify the level of subjective improvement is simply impossible.

The Pass Xs 300 Mono Amplifier
As you may already expect, I had much the same experience with the Xs 300 mono amplifiers. The differences, were, however, more dramatic because I was comparing amps with such different power levels. The Xs 300 mono amps were not only better sounding in every respect than the XA-160.5s, but they had nearly twice the power: 300 watts into 8 ohms, 600 watts into 4 ohms, and 48 amps worth of peak output current. In contrast, the XA-160.5s deliver 160 watts into 8 ohms, 320 watts into 4 ohms, and 36 amps of peak output current.

I had originally chosen the Pass XA-160.5 Class A mono amplifiers over the more powerful Pass Labs X600.5 and other outstanding amps that were then available from other manufacturers that were not Class A because the overall mix of trade-offs was audibly worth it with the system and speakers I had at the time. I knew from long experience that this would mean a slight trade-off in the most exciting and detailed aspects of musical dynamics, but I felt it more than made up for this in other aspects of sound quality—particularly in lower-midrange realism and warmth, and in putting an end to any trace of edge in the upper midrange.

In the case of the Xs 300, however, the increase in power really makes a difference in both apparent musical “speed” and detail, especially in high-level dynamic peaks with top modern speaker designs like the Wilson Alexia. It was apparent with the sound from the woofers and other drivers on my Legacy Aeris, even though they have the equivalent of built-in amplified subwoofers. It helped improve the resolution of musical energy and dynamics, from microdynamics to the highest-level peaks, which good speakers like the Quad 2905s can resolve without distorting. Good as the XA-160.5s are, the Xs 300s made them seem just slightly polite and forgiving in contrast.

The Xs 300s do involve a major increase in size and weight. Each mono amp has a separate power-supply and gain unit; each unit is 19" x 11.5" x 27.5". The gain unit weighs 168 pounds and the power supply 130 pounds; both consume some 1000 watts of AC. This may pose placement problems, but the styling and new meters are both restrained and visually impressive.

The Xs 300s are the kind of components that make a real visual statement to other audiophiles. That really shouldn’t matter. However, if you do happen to be an authoritarian leader and high-end audiophile who is seeking to intimidate other high-end authoritarians—and to do so with style and dignity—these are the amps for you, and they match the Xs preamp!