Pass Labs XA-25 Audiophile Power Amplifier Reviewed

How many people back in the day really knew how special a car designed by Enzo Ferrari was? Today, years after his death, an Enzo-era design from Modena is almost always more than a million-dollar investment. When it comes to audiophile amplifiers, Nelson Pass reminds me of Enzo Ferrari a bit. I say that since Nelson has been pushing the performance limits of what an audiophile amplifier can do for decades upon decades (they make some killer stereo preamps too) for brands such as Threshold, Forte, Adcom, Pass Labs, and even his kitchen-sink project, First Watt. The world of audiophile amplifiers is a better place because of a man like Nelson Pass.  

The Pass Labs XA-25 is a really cool bit of audiophile gear in that it is an entry level, somewhat-low-gain, fully Class-A audiophile amplifier from the company. It isn’t balanced. It is fully Class-A to about 25 watts. The build quality is excellent. but the signature and super-sexy gauge included on the front plate of most Pass Labs gear is missing here, which saves significant cost but makes no sonic impact. Nelson and his team went all out on sound but cut costs where possible to deliver his best possible, most-signature sound (or lack thereof) at a price that is attainable for many. Let’s find out what makes this somewhat quirky audiophile amp such a cult favorite.  

What Makes the Pass Labs XA25 Amplifier So Special?

• Fans of tubes often are converted over to the world of solid-state power amplifiers because of Class-A technology. Amps aren’t supposed to impose their sound on an audiophile system. Class-A amps provide that detailed and airy musical reproduction that you get from SET (single ended triode) tube amps but without the maintenance and coloration of the sound. 
• The Pass Labs XA25 is modest in size (three rack spaces), not super heavy (under 50 pounds), and is narrow enough to fit into a professional equipment rack. 
• While missing the gorgeous gauge, the build quality of the Pass Labs XA-25 is simply fantastic, including a super-simple but very handsome looking faceplate. The heatsinks are beefy too, like a mini-Threshold amp for the modern era. And make no mistake, dispersing heat is a key concept for any Class-A designed amp, no matter the brand. 
• The design of the Pass Labs XA25 is push-pull. That isn’t the most efficient design in terms of power consumption versus output but what you do get for output is very accurate.
• The feet on the Pass Labs XA25 are quite robust. They make it so that you can place this amp on any reasonably solid surface and have it feel right at home. No aftermarket cones or other tricky parts are needed to get this amp sounding its best or installed correctly. 
• Forget break-in time because it isn’t a thing with the Pass Labs XA25. Right out of the box, the Pass Labs XA25 sounds like a world-beater. Your ears might need a few hours to get used to what you are listening to, but your amp is up for the challenge as soon as you hit the On button. Pass Labs says that they can measure a little bit of improvement at about 30 minutes of warm-up but I couldn’t hear the difference their tools can measure. Even the engineers at Pass suggest that the change for a warmed-up amp is quite modest. 
• I had no problems powering full-sized audiophile speakers with the XA25. Both pairs of big speakers that I have in my system right now are around 90 dB efficient (Revel F228 BEs and Bowers & Wilkins 802 D4s – read the reviews). Once I upped my preamp’s gain a bit (the Pass Labs XA25 is a bit low-gain by design) I was able to drive either pair at rock-solid volumes.. 

Why Should You Care About the Pass Labs XA25?

If you have a taste for the absolute best of the best but sometimes can’t always swing the cost of entry, then the Pass Labs XA25 is something that you might care about. This is a high end-and audiophile amplifier, from its legacy to its design to its phenomenal build quality. Pass Labs just wants to offer more and more people a place to start and get a taste of what they do. 

Many Pass Labs fans that own many of Nelson’s legacy amps as well as bigger versions of his more exotic amps have said that dollar-for-dollar and note-for-note, the Pass Labs XA25 might just be the best sounding amplifier that he’s ever designed. I’ve seen stacks of Pass Labs monoblocks that tower five feet tall and I’d like to hear what they can do (on someone else’s electric bill) but I get what these Pass Labs enthusiasts are getting at as the sound of the Pass XA25 is pretty special.  

Some Things You Might Not Like About the Pass Labs XA25

• Heat is always an issue with a Class-A design, but even behind a closed door as I have it installed, the amp doesn’t get too crazy-hot. Fans help if you can pull it off without making much/any sound as I have done in my mechanical room where my gear is installed. Otherwise, be sure to leave a good six inches or more of space to allow the amp to breathe a bit.
• The Pass Labs is a little bit low in terms of gain as I mentioned before. This wasn’t an issue with the Classé Delta Stereo Preamp that I use, as all I needed to do to compare the Pass Labs XA25 to the Classé Delta stereo amp was to crank up the volume. The only time that you might have an issue is if somehow your preamp didn’t have enough gain and I think that would be a pretty rare instance. 
• Class-A amps drink power from the wall and as such aren’t very green. By design, Class-A power amps draw all of the power that they need from the wall but tend to output only a small fraction of that power to your speakers. That’s just the nature of Class-A and why those amps tend to have such a pure sound. My solution to the energy issue is to not leave the amp on as I normally do with other amplifier designs like Class-D or Class-AB power amps. I don’t listen all day, every day, so when I do, I use the power that I need. When I am down the hall in my office, I use a different system and save the Pass Labs for later in the evening. 
• The Pass Labs XA25 isn’t balanced in terms of design or connection. For some, a fully-balanced design is a must-have, but not me. I like the fact that this amp saves parts cost by skipping XLR inputs when the amp isn’t balanced by design. 

Listening to the Pass Labs XA25 Power Amp… 

One of the key questions that I had about the Pass Labs XA25 was its ability to keep up with bigger, more powerful Class-AB amps like the Classe Delta amp that I recently reviewed. No sing record embodies the subtleties paired with big-time dynamics more than Pink Floyd’s The Wall. On the album version of “Empty Spaces,” you can hear all of the details in the atmospheric opening with incredible resolution, but it is a little later in the track (around the 0:50 mark) when Roger Waters’ bass kicks in and you can additionally hear the incredible bass control that the Pass Labs XA25 brings to the musical party. The details on the bass scales right before the opening lyrics are of specific note. You can hear every visceral detail of the bass riff as if you were in the studio. I expected the higher-frequency details to be crystal clear when auditioning a Class-A amp but I was shocked to hear how amazing the control of the bass on my Bowers & Wilkins 802 D4s sounded with the Pass Labs XA25 in the loop.  The number of time that I’ve heard Dire Straits’ Brothers In Arms is not calculable. This, along with Eric Clapton’s MTV Unplugged, was the never-ending soundtrack to my early days at the stereo store as a teenaged audiophile salesman in the very early 1990s. And there’s a damn good reason why these recordings are so popular. On the upbeat hit “Walk of Life,” I kept repeating the opening few guitar chords as I simply couldn’t believe how resonant and three-dimensional they sounded. I’ve heard this song 14,000 times (if once) and I’ve never heard the chords sound so engaging.  Later in the track, I was impressed by the musical layering of the organ sound, the fancy-picking rhythm guitar, lead vocals, and backup vocals. If you were to play a system like this for someone who’s never heard an audiophile system, they’d immediately be able to hear the specific details and the high levels of musical engagement. 

Not being one to let well enough alone with great results, I cranked up my favorite new audiophile demo track from guitarist Tom Morello (Rage Against the Machine, Audioslave) and his ballsy cover ofJimi Hendrix’s “Voodoo Chile.” OMG, this is an audio tour de force. Morello uses the familiar melody as a template to just go off, but the moment you know the Pass Labs XA25 is the real deal is right after the somewhat restrained and muffled opening (0:29) when the whole band sieges into the mix and blows the musical dynamic window open like a 2,000 pound J-DAM bomb.  I just finished editing an article from our staff audiologist about hearing loss so the fact that I am cranking this jam up to 100 dB plus levels is a bit crazy, but I can’t help it, and the Pass Labs XA25 is more than up for the challenge. Let’s leave it at this: there are amps with a lot more power and headroom than the Pass Labs XA25, but will this $5,150 amp leave you hanging when you are rocking out to the most over-the-top dynamic music that has ever been recorded? Nope. 

Will the Pass Labs XA25 Amplifier Hold Its Value?

There are some that think that resale is a little bit of an issue because of some dealers shipping the product around the country, but I am not convinced that there is a problem at all. I’ve had personal experience with selling a Pass Labs XA-30.5 Class-A amp a few years back when I closed up our offices on Wilshire Boulevard in Brentwood. I posted the Pass Labs XA 30.5 amp at more than 50 cents on the dollar from its retail price on Audiogon.com and I had three offers in mere minutes. The amp sold in less than an hour, complete with a wire transfer and shipping completed the day of. I can’t imagine how much better things can get for resale value on an audiophile component.  

Who Is the Competition for the Pass Labs XA25 Amplifier?

I recently reviewed the Classé Delta stereo amp which is priced at $13,000. It has more overall headroom. with over 250 watts of Class-AB power. The amp can drive tough speakers while still having that open-airy Class-A sound for the first 10 watts or so. I like the look of the Pass Labs (even without the gauge) better and I feel even more strongly about the price. The Classé amp is balanced and is a big-ass amp that took two men to install into a Middle Atlantic equipment rack. 

The AMPED 2400 is a Class-D switching amp at $5,000 that uses the lauded Pascal chip, which provides a ton of power as a switching amp but has a slightly more tube-like demeanor than most typical switching amps. The AMPED 2400 can power any speaker out there today. There are no limits really, as this amp has so much reserve power. The looks of the AMPED 2400 are pretty pedestrian, but that is not why you buy that amp. 

The AGD Productions Tempo Amp ($5,700) is a GaN or Gallium Nitride design. This world-beater amplifier is making a name for itself in terms of its efficiency, its stunning measurements, and its Class-A-like performance. These GaN amps are over 90-percent efficient. They produce close to no heat. They aren’t heavy. They do a lot right and they’ve got a number of audiophiles rethinking what defines an audiophile amplifier. At 100 total watts, the AGD Tempo doesn’t have a ton of power, but it does double down int 4 as well as 2 ohms. The ADG Productions Tempo can also be bridged to double its overall power but that obviously doubles the cost for your amplifier.  

Final Thoughts on the Pass Labs XA25 Amplifier

Over the years, I have been blessed to own Pass Labs amps in my office system. Today, I have an invoice to be paid for this Pass Labs XA25, which I am going to purchase. While there are bigger amps (plenty in the Pass Line up as well as elsewhere) that have more power, few have the colorless, open, and resolute sound that you get with an XA25. 

At a reasonably affordable  price, audiophiles who save their pretty-pennies can get themselves a taste of the good stuff when it comes to the $5,150 Pass Labs XA25 power amp. With the ability to power most of today’s best speakers with ease, owning one of Nelson’s best designs is now within reach in an audiophile market that is out of control with cost-no-object component options. The road to a truly fantastic amplifier for any high-end audio system in need of super-accurate power is waiting for you. The Pass Labs XA25 is as good as the rumors suggest. I’ve tested the sucker out. Now, I am buying it.