ULTRA AUDIO -- Archived Article

February 15, 2003

Pass Labs X2.5 Preamplifier

"To every thing, turn, turn, turn . . ."

Flash back to the fall of 1982, the first day of my freshman year of high school. My nervous eyes scan the crowded hallways anxiously searching out a familiar face. Then, as if someone had flipped on a slow-motion switch, a heavenly creature parted the crowded hallway like Moses parting the Red Sea. As she glided down the hall, she left throngs of slack-jawed pubescent boys paralyzed and bug-eyed with desire in her wake. Ambivalent to her newfound powers, she approached, her eyes locked with mine.

"Hi Greg, how was your summer?"

More than a little confused as to whom this gorgeous girl was and why in God’s name she was talking to me, I sputtered, "F-f-fine I guess, I don’t know, sorta OK."

"Well, maybe I’ll see you at lunch," she replied, oh so casually.

While the scent of watermelon lip smackers and Charlie perfume hung gently in the air, she gracefully disappeared into the crowd. After that instant, which seemed an eternity, it dawned on me that it was little Kimmy Bowers! This was the pudgy, cherub-faced little girl who just three months before was so spectacularly unspectacular.

You are probably wondering, "What does this have to do with the new Pass Labs X2.5 preamp?" Well, much like the stunning transformation of plain-Jane Kimmy Bowers into Kimberly "The Goddess" Bowers, the Pass X2.5 represents the stunning transformation of the sub-$5k solid-state preamp genre into a stunning musical vixen.

Can’t live with ’em, can’t live without ’em

Preamps have always puzzled me. At first glance, they appear to be relatively simple devices with simple objectives: route the incoming source signal to the selected output and along the way offer a little boost in volume. Yet in high-end audio, as with women, nothing is as simple as it seems. Next to digital devices, modestly priced high-end analog preamps, particularly of the solid-state persuasion, have experienced a rather slow ascent through a protracted adolescence. Only in the last year have I heard anything that indicates that this class of solid-state component has blossomed into musically satisfying maturity.

I have auditioned a couple of sub-5k preamps recently in the hopes that I could make a solid recommendation to friends shopping in this price range. The standout among the group turns out to be the subject of this review, the Pass Labs X2.5. At $3900 USD, the X2.5 is a striking product, both physically and sonically. For those who have not seen a Pass product up close, they embody a high level of engineering and quality fit’n’finish, along with restrained industrial design, that inspires a quiet confidence as well as long-term pride in ownership. Pass Labs has not abandoned its aesthetic roots in favor of flash in the design of the X2.5. The preamp is compact, yet massive. While I typically favor a more forward design approach, I really dig the utilitarian, almost lab-grade look that the X2.5 sports.

Where its big brother, the X1, houses its power supply in a separate chassis, the X2.5 is a single-chassis design. Milled from anodized aluminum, the X2.5 is identical in its proportions to the line-stage portion of the X1. The remote control is a model of simplicity itself. A robust, rectangular steel case houses four large, round buttons that navigate the X2.5’s functions. This thing will never be confused with the needlessly complicated remotes offered by mass-market manufacturers. There are two available gain settings, channel balance, input selection, phase, and of course volume adjustments in 1dB increments.

Pass Labs' Supersymmetry circuit topology developed in the X Series amplifiers is featured in the X2.5. Each channel uses completely balanced circuitry through the entire signal path. The Supersymmetry circuit is designed to improve the performance of the preamp by precisely matching the distortion characteristics of the class-A circuit. Pass intends this design to make noise and distortion insignificant at the balanced outputs. They also say it allows the preamp to have significantly lower distortion without resorting to high feedback.

There are a total of four inputs, two of which can be single-ended or balanced, and one balanced/single-ended connection for tape and main outputs. One input can be set for unity gain, allowing for a home-theater processor to be used in conjunction with the X2.5.

The sound of one preamp clapping

The first thing that struck me about the X2.5 was its deafening silence. As noteworthy as the sounds that pass through the X2.5 are, what doesn’t come through is just as relevant. Distortions and noise of varying pedigrees -- poof -- flat-out disappear. No kidding, this thing is a magic wand concerning the subtle and not-so-subtle distortions imparted by other preamps. What is left is the feeling of a direct connection to the music; a rare blend of musical of involvement that is both visceral and intellectual.

Much like its sibling X Series amplifiers, the X2.5 renders images with fantastic dimensionality and an uncanny sense of separation within the soundstage. It beautifully delineates Aaron Neville on "It Feels Like Rain" from Warm Your Heart [A&M 75021-5354-2], along with the surrounding instruments. And when the background singers chime in on the chorus, the soundstage grows a solid six feet to the rear. This is the kind of tape-measure precision that can only be had by serious powers of resolution. Though perhaps lacking the last measure of bloom and harmonic glow, the X2.5 will never bore you, nor will it run you out of the room by way of any inherent edginess or brightness. Precise without being cold in nature, the X2.5 quickly gets out of the way allowing for the suspension of disbelief and an intimate relationship with the music.

The second trait of the X2.5 that hit me was how fast and dynamic the sound was. There is a confidence and surefootedness to the sound; a real feel that all the musicians are all on the same page. Compared to my Jeff Rowland Design Group Coherence II, the Pass was more immediate with an emphasis on transients and fine detail. Music moved along with an almost manic energy. Track 1, "Drum Trip," from Rusted Root’s When I Woke [Polygram 522713] blasted its way through my room with an array of tom-toms and drums firing off riff after riff after riff. Building up to a near meltdown, thanks in no small part to the dynamic capabilities of the Talon Khorus X speakers, the Pass X2.5 permitted the music to get louder and louder with what seemed like an unlimited amount of effortless headroom. By comparison, the Coherence II is a touch more laid-back, favoring harmonic bloom, texture, and tonal color. Through the Rowland, the soundstage opens up behind the plane of the speakers; the X2.5 tends to place images nearer to the plane.

Another defining quality of the X2.5 would have to be its way with the bass. The X2.5 has harnessed its open and dimensional midband to a B-1 bomber of bass control and extension. This thing opens the throttle to the lower registers where lesser products flameout, flattening dynamics and restricting bass extension. As a result, all kinds of hi-fi fun and sonic high jinks ensue. You like tympani strikes? Check out the finale of Fritz Reiner conducting the Chicago Symphony Orchestra performing Scheherazade [RCA 09026]. Or if you get a kick out of kick drums, "Tell Me I’m Your Man" off Robben Ford & the Blue Line [GRP STD 1102] might do you right. Any way you cut it, the X2.5 really rocks.

Then again, a couple of solid-state preamps offer at least a fair measure of the bass control and extension served up by the X2.5. Where the X2.5 sets itself apart and demonstrates its maturity is in the heart of the midrange. The X2.5 is uncolored and has resolution galore without any of the enhanced midband "sheen" of most tube preamps I have heard in the X2.5’s price range. Margo Timmins aptly displays these qualities with the hypnotic, talking-in-her-sleep delivery that graces every track of Cowboy Junkies’ Lay It Down [Geffen 24952]. The X2.5 delivers track 2, "A Common Disaster," with more than enough vocal detail and energy to bring Timmins into the room, while maintaining the strangely beautiful, organic, and mysterious nature of her vocal timbre. When used in the same system as the Sonus Faber Amati Homage speakers, the X2.5 adds some welcome precision and surefootedness to the lush bloom of the Amati’s tonal balance.

Moving into the treble, the X2.5 remains open and free of any obfuscation or glare. The sonic fabric is of one piece in the critical transition from the upper midrange on up. Thanks to this quality, the X2.5 exposed disc after disc with stark precision while remaining musical and inviting. Remember, however, that these remarks are framed by the presence of the Linn Sondek CD12 CD player and its ability to show off all components in their best possible light. That is not to say that lesser associated gear would not benefit from the X2.5; most systems would. Just don’t expect the X2.5 to cure the inherent flaws of front ends, cables, or any other part of the component chain. In my experience with it, the X2.5 will show you the whole picture in a very enthusiastic fashion, regardless of what amplifier or speaker it is affiliated with.

Is there anything about the X2.5 I didn’t care for? Nothing is perfect, and that includes the X2.5. First off, while essentially neutral and transparent, the X2.5 lacks the last word in organic naturalness and the beguiling dimensionality and tonal color of the $14k Jeff Rowland Design Group Coherence II. Not a huge surprise considering the disparity in price. Without the Rowland to compare directly to the X2.5, this may not be an issue. Second, the X2.5 does not highlight an instrument’s texture or enhance the sense of air in the recorded space. This will be more of a problem for those who are used to tube preamps or those who place a priority on these traits.

"I can see clearly now . . ."

I have had the Pass Labs X2.5 for the last six months. I have used it with four different amplifiers, three different sets of interconnects, and three speaker systems. I have also compared it to what must be considered one of the best and most expensive preamps on the planet. And there it sits, unfazed and rock steady. There wasn’t one situation or configuration I could throw at the X2.5 that caught it off guard. If you are looking for a preamp you and your system can grow with, one that won’t cause more problems than it cures, look no further. The Pass Labs X2.5 is a seriously grown-up component. Like the vision of little Kimmy Bowers gliding down the hall, my time with the X2.5 made one hell of an impression that is sure to linger fondly in my mind for some time to come.

…Greg Petan

Pass Labs X2.5 Preamplifier
Price: $3900 USD.
Warranty: Three years parts and labor.

Pass Laboratories
PO Box 219
24449 Foresthill Rd.,
Foresthill, CA 95631
Phone: (530) 367-3690
Fax: (530) 367-2193

Website: www.passlabs.com  


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