Pass Labs XP-25 Phono Preamp (TAS 209)

Equipment report
Pass Laboratories XP-25
Pass Labs XP-25 Phono Preamp (TAS 209)

There are times when I think this strange hobby of ours borders on the insane. I feel this way every time I read an ad that promises miracles from an accessory that clearly defies the laws of physics. I feel it every time I hear a system that costs more than a few thousands dollars that is so skewed in sound quality that virtually any home AV system sounds more realistic. I feel it every time I encounter a high-end system in the hands of someone who is all equipment and no music, and feel it when I see a mirror image of the pursuit of the absolute sound in a photographer who is obsessed with his equipment and does nothing meaningful with it.

And yet, there are occasion when it all seems worthwhile. At the low end of the high end, one of my friend’s daughters is a young teenager who has put her system together out of her earnings and yard sale shopping: A NAD amplifier, an old Thorens automatic turntable, a cheap Grado cartridge, and a pair of Electrovoice Two loudspeakers. Not only does the system sound alarmingly good for $300 and change, she is a pianist who has not lost sight of music. She has learned to haunt yard sales in wealthier, older neighborhoods, and talk her way into buying the sellers’ collection of LPs for virtually nothing. She’s networked with her friends to find parents who are getting rid of their LPs. Well over four hundred LPs of the music she likes. In fact, she may well be the “audiophile of the year” for well under $1000.

And, at the other end of the spectrum, there are products like the new Pass XP-25 phono preamp. Every time I feel that analogue electronics have reached the point of diminishing returns, and I should invest only in speakers or my front-end equipment, someone goes out and proves me embarrassingly wrong. It may not the sanest pursuit in the world, but there always is another advance out there that brings you closer to the music, and that takes you out of the realm of disposable new toys and almost compels you to listen.

The XP-25 does push the cost envelope. It sells for $10,600, and most audiophiles my have to opt for Pass’ less expensive XP-15 ($3800), or something far cheaper than that. At the same time, it is the quietest, most musically realistic phono preamp I’ve yet heard, and it provides a series of front-panel gain and loading choices that make it remarkably easy to adjust to a given cartridge and a given system. It may push its price tag, but it also pushes the state of the art in ways that quickly become addictive.

The Technical Details

As you should expect at these prices, the XP-25 is superbly built, both inside and out. It is a two-chassis design with an exceptionally large power supply. Unlike many competing units, it does not have a moving-magnet or moving-coil setting. It instead has three levels of gain: 53dB, 66dB, and 76dB. It also has switched front panel settings for cartridge resistive loads of 30 ohms, 50 ohms, 100 ohms, 160 ohms, 250 ohms, 320 ohms, 500 ohms, 1000 ohms, and 47,000 ohms. It also has impedance loads of 100pf, 200pf, 320pf, 430pf, 530pf, and 750pf. This covers virtually any mix of moving-magnet, moving-iron, and moving-coil cartridges, although a few cartridge collectors may have older cartridge designs (really older cartridge designs) that some audiophiles feel prefer 68,000 and 100,000 ohm loads.

I’ll get to the importance of these features in a moment, but it is also important to point out that the XP25 is a complete new phono stage design by Wayne Colburn and is not based on the previous Pass Ono or Xono phono preamps.

Sound Quality

I should begin with a couple of caveats—some important and some less so. This is an RIAA phono preamp. It does not have equalization settings for 78 rpm or really old LPs. I don’t find this particularly important. I admire 78-rpm collectors, but I grew up changing cactus needles in my father’s system and bid farewell to 78 rpm without a tear of regret. (I also have a functioning Edison cylinder record player, so I still win over 78-rpm addicts on points). I lost virtually all my non-RIAA LPs during a few moments of unpleasantness in Iraq during the early 1970s, and there are very few audiophiles around with a meaningful collection of pre-1970 LPs that require special LP equalization curves. It is an important area for those who have historical collections, but irrelevant to at least 95% of high end audiophiles in the US.

The XP-25 also has two sets of RCA inputs and no XLR inputs. Having experimented with XLR terminations of tonearms, I’m not impressed by this option. Readers may have had a different experience, but I find well-designed tonearms provide more predictable grounding, and lower risk of residual hum, with regular RCA cables. The main issue is not XLR vs. RCA; it is to use as short an interconnect as possible, one that does not affect loading and is properly shielded, and to work very carefully with grounding options and AC polarization to get the lowest possible noise, and to avoid using loading and gain settings that are noise vulnerable or alter the signal-to-noise ratio in ways that raise noise.

The first caveat that I do feel matters is the statement in the otherwise excellent instruction manual that, “moving magnet and moving iron cartridges typically work very well with a series loading of 47,000 ohms and 100 pf of parallel capacitance.” It is true up to a point, but there are a few moving-magnet and moving-iron cartridges out there that need different resistive loading, and a much larger number that need a close capacitance match to flatten their upper-frequency response. This may or may not be important to you. The amount of musical energy at the frequencies involved can be small, but some cartridges will peak around 10kHz, or you’ll get a dip in frequency response. Given the number of cartridges out there, I can’t give you any meaningful guidance. The manufacturer’s recommended capacitive loading (including the interconnect) is a good start, however, and so is a Web search. A number of audiophiles provide Web sites with useful measurements of given cartridges.

The second caveat is that every aspect of a phono front end is remarkably interactive. I did not find any compatibility problems between the XP-25 and my cartridges or those in my friend’s systems. I did not encounter any noise or hum problems with properly set-up cartridges, tonearms, turntables, and sanely designed interconnects (I don’t like unshielded, high-impedance, trick “black box” terminator, or floating-ground interconnect designs in any part of a system, and they are particularly bad in a phono interconnect.)

I also found the XP-25’s variable gain, resistive loading, and capacitive loading to be of immense value in getting the best out of given cartridges and preamps. Gain mismatch is a serious problem in phono sound quality. If the gain is too low, it kills life and dynamics and brings up noise. If it is too high, the midrange tends to harden and lower-level dynamics become too loud.

The 53dB, 66dB, and 76dB settings in the XP-25 can’t cover every extreme, but they did cover my mix of moving-magnet, moving-iron, and moving-coil cartridges well enough that I was not about to try messing with internal gain, even if it were possible. Moreover, all three settings were dead quiet in a well-set up system. Not only could I get a gain match, I could get it without even the kind of subconscious noise (and perhaps perception of distortion) I hear with some other top phonostages.

I should acknowledge, however, that the very best tube units do offer important trade-offs. They are not ones I favor, but they provide the same superb dynamics as the XP-25 with a somewhat softer, more forgiving form of transient and harmonic detail. I feel this is offset by the resulting loss of realistic definition and life, and by the fact that many such designs seem to slightly compress the overall musical signal and reduce low-level dynamic contrasts. It is, however, an area where many of my friends disagree. I also am particularly sensitive to even traces of tube noise, particularly when it is added to older LPs with tape hiss in their background. Many audiophiles with moving-coil cartridges don’t care or listen through such trace noise.

I’ll take solid-state, particularly when I can’t hear any sacrifice in sound quality and the end result is more musically realistic. The XP-25 could not somehow transform my LP collection to the point where it could make Gustav Mahler and 1000 of his closest friends sound natural in my living room. What is could do was give a much more natural musical match of a home listening room a touch more realism at every level.

I also am talking about the vast majority of good LPs—not just audiophile recordings. I have a large collection of Accent LP’s recorded in sites I know well from living in Belgium and Blue Note jazz LPs in a wide range of reincarnations. Throw in several hundred other musically realistic jazz, chamber music, and solo instrument and voice recordings, and I have a collection where I can at least imagine the illusion of a live performance that could actually occur in a real-world listening room. The XP-25 did not make any dramatic sonic differences over the XP-15, the Xono, a Krell Phono Preamp, or an older conrad-johnson tube design, but everything at this level of performance is about musically realistic nuance—not simply hearing some minor difference in sound.

This is what got my attention. It made slight, but consistent improvements, in a system optimized to get a natural a balance of timbre, sound stage, dynamic life, and detail from voice and acoustic instruments in “small music” at natural listening distances. Bass was better defined and had more natural power from deep to upper bass. This is the best bass from a variety of records in a variety of systems that I have yet heard from any phono preamp. Treble was as open, life-like, and dynamic as the rest of my system and the limits in most LPs permit.

What really captured my attention, however, was the combination of natural midrange timbre and energy and soundstage and low-level detail. Again, the changes were slight and much depended on record quality and the cartridge. Nevertheless, if you audition this unit, bring your best cello, flute, harpsichord, and piano recordings. Bring really demanding female voice, preferably in the context of the more complex Baroque era music so the mix of voice and instruments is both complex and natural. Throw in the usual jazz, but add some LA4 and MJQ just to be sure. I believe you will hear as realistic an illusion as the rest of the system and the recording permits.

I also don’t want to slight Gustav and his 1000 friends, or the ability of the XP-25 to reproduce even the loudest, most complex, and most Mel Gibson-like passages of Wagner. The XP did superbly with these, with demanding organ music, and with dynamic nightmares like Saint Saëns’ Symphony No. 3. Moreover, while I am not a loud rock fan, the replacement-generation listeners in my family assure me it is excellent in these areas as well.

Moreover, these are areas where variable resistance and impedance loads proved even more critical in getting a realistic illusion of music from a range of cartridges than the variable gain settings. It really, really does pay to experiment, and far more than playing around with settings like cartridge VTA.

As I have mentioned earlier, you should both research and listen to the impact of different capacitive settings for moving-magnet and moving-iron cartridges. I am not going to tell you what to select because it is likely to be system specific, but it definitely matters with Shure cartridges and will help with Grado. As for moving coils, I really would follow the instructions in pages 7-9 of the instruction manual. I can assure you that a few days making sure you have the best setting for your preferred mix of illusions with a wide range of LPs will truly pay off, and may well convince you that cartridge loading is as important in many ways as the choice of cartridge.

The only caution I would give you is that many audiophiles raise the loading impedance too high to get what seems to be a wider soundstage and more “detail” and “life.” Cartridge loading is to some extent an equalizer that affects both timbre and dynamics, but it is important to understand the trade-offs involved. First, too high a resistance does not produce musically realistic detail or life, it emphasizes the highs and produces detail that seems more the result of distortion that anything you hear with natural acoustic music. Second, imaging becomes larger and/or less stable. Third, depth is more limited. Going too low dulls the music, affects dynamics, over-softens the highs, and can affect signal-to-noise with really low-output cartridges. So go for musical realism and not for apparent detail. Also, go for the mean loading with a wide range of records to get the best out of your overall collection and do not concentrate on some favorite records. You may even find that the reason they are favorites is not their inherent quality but your previous system set up.

Summary Judgment

A must audition, if you have the money or simply want to hear a great example of the state of the art. The XP-15 offers most of the same advantages at a much lower but still significant price. Do, however, remember the teenager that I began this review with. Great as this level of equipment is, the journey does not have to begin at the destination.

Specs & Pricing

Gain: 53, 66, 76dB
Maximum output: 22V RMS
Output impedance: 150 ohms
Loading: 100pF–750 pF, 30-47k ohms
Price: $10,600

PO Box 219
24449 Foresthill Rd.
Foresthill, CA 95631 USA
(530) 367-3690