When Pass labs introduced the dual chassis Xs monoblocks a couple of years ago, they raised the bar for other components, and in the process even raised the bar for their own, already excellent XP30. We could end the review here by saying that on one level the difference between the XP30 and the XsPre is very much like the difference between the XA.8 series power amplifiers and the Xs monoblocks; everything is bigger, bolder, cleaner and quieter than what has come before.

Taking the financial aspect out of the equation, with the XsPre tipping the scale at $38,000 and the XP30 less than half of that at $16,500, the XsPre offers a lot more, if you have the room, system and software able to resolve the difference. For those that are familiar, think of the XP30 as a standard Porsche 911 and the XsPre as a fully geeked out GT3. You don’t need it to get the job done, but if it won’t affect your meal plan to acquire, you won’t be disappointed.

It’s no secret our publisher is incredibly enthusiastic about Pass amplifiers.  While the company’s flagship Xs300 monoblocks have been serving dual duty as his reference amplifiers and the furnace for the TONEAudio studio for some time now, his relationship with Nelson Pass is more than a mere bromance. It goes all the way back to the early 1980s, when we lived on Milwaukee’s East Side and he talked me into helping him carry his new Threshold 4000A power amplifier up a few flights of stairs.

I’m a tube guy; I’ve always been a tube guy – the tubey-er, the better. Back in 1980-something, that Threshold was a mind-bender because this massive solid-state amplifier made the room warmer than any tube amplifier I had ever experienced, sounded as musical as anything with glowing bottles, yet had killer bass output and control. It even sported an awesome set of red LED power output meters! The 4000A stayed in my system for a long time after our publisher’s terrier-like nose for all things audiophile led him sniffing down other paths and, as with one of my prized BMW 2002s, I still regret selling it.

It’s all about control

Don’t let Nelson Pass’s easy demeanor fool you; he wants control. At least control of your speakers’ cones. The major benefit to the massive power supplies and output stages in the two-chassis Xs amplifiers is the amount of control they enforce on your loudspeakers. Not letting the drivers act in a willy-nilly manner keeps distortion and non-linearity at bay, resulting in a cleaner, clearer, less fatiguing sound. Pass is fond of saying that he likes the sound of tubes without the hassle, and the Xs300s deliver this in abundance. But at almost $90K per pair they are not within the reach of every audio enthusiast.

Enter the XA160.8 monoblocks at $29,000/pair. Building on the success of the .5 series (you can read our review of the XA160.5 monoblocks here[1] and the XA200.5 monoblocks here[2] ) the .8 series of Pass amplifiers takes these designs a major step further. Larger power supplies and a more refined circuit allow these new amplifiers to be biased further into class-A territory. The changes draw more power from your wall, and generate more heat – something we put to good use here in the Pacific Northwest. The results put the 160.8 closer in sound to the massive, two-chassis Xs amplifiers than before. The price tag is still not pocket change, but a far cry from what the four-chassis, big boys will set you back.

Pass makes it a point to let you know that these are not cookie-cutter amplifiers, with each version sharing an input stage followed by progressively larger output stages. Every model in the .8 series is individually designed from the ground up with all nine amplifiers in the range using different input and driver circuitry optimized for progressively larger output stages. A peek inside the case reveals a prodigious bank of power supply capacitors flanked by equally huge heat sinks, each with “more output transistors than necessary.”

With balanced XLR inputs (the XA160.8 is a fully balanced design) and RCA inputs, this amplifier works well with any preamplifier. My ARC REF 5 proves a perfect match for the XA160.8, but after spending a bit of time with the top-of-the-line Xs Pre, I’m guessing it’s upgrade time again.  Even my standby CJ PV-12 turns in an amazing performance with these amplifiers and reminds me of when I used the Threshold 4000A with a CJ PV-2a preamplifier. Time does fly when you’re having fun. Watch for our review of that piece very soon. Suffice it to say that the XA160.8 will never be the weak link in your hifi system!

Taking care of business

Vicariously sampling the last four or five Pass amplifiers that have been in for review, it’s time to put the latest models front and center in my reference system and flog them. Rage Against the Machine’s “Take the Power Back” does the trick, as the intro kick drum beats and bass riffs occupy separate spots in the soundstage, neither losing their focus as I turn the volume up, up, up – pushing my head back against the couch. Yet near the end of the track as the pace settles to light cymbal work, the delicacy and texture rendered stops me dead. It’s so quiet and precise, everything appears to settle into nothing.

Sporting the big, blue circular meters that adorn the face of all the Pass power amplifiers, the 125 pound (each) XA160.8s are a breeze to move after the Xs300s. However, they’re probably a stretch for one person lifting, so you should consider getting some help to keep your back in order. For those not familiar with Pass amplifiers, the meter needle stays centered, indicating that the amplifier is operating fully in class-A mode, which for the 160.8, is 328 peak watts. So when that needle starts to bounce, these amplifiers are indeed producing major power.

Driving my Vandersteen 5As with the XA160.8s is absolutely peachy and the synergy with the Audio Research REF5SE is near perfection as well. I have spent some time with the Pass Xs Pre that is here for review, and that’s even more revealing. It goes without saying that you won’t go wrong with an all-Pass system, and as Mr. Pass says, you’ll never have to look for tubes again.

Break-in has been the same experience we’ve had with all other Pass amplifiers; they sound great straight out of the box and improve linearly over about 300 hours, with a minimal increase in clarity after that. Though solid state, they take as long as, if not longer than, a vacuum tube amplifier to fully “warm up.” Due to the power draw (550 watts per monoblock) and heat generated, most owners will not want to leave them on all the time. The XA160.8s take about 90 minutes to come out of the gentle mist exhibited at initial power up that dissipates after they reach full operating temperature. You’ll notice it in the smoothness of the upper register and the depth of the soundfield portrayed – getting deeper and deeper, drawing you further in to the presentation as they stabilize.

The 160.8s are consistent at low, medium and high volume. They never run out of steam when cranking AC/DC to near-concert levels, yet when listening to solo vocals or piano at levels barely above a whisper, maintain depth and a tonal richness that you’d expect from a flea watt SET amplifier. To say these amplifiers are incredibly linear and dynamic is an understatement.

In the end

We’re all worm food. But for now, if you find yourself asking the venerable question, “tubes or transistors,” this tube guy says buy the XA160.8 from Pass Labs. Unless you can afford the Xs monos, then of course you know what you must do.

Additional Listening: Jeff Dorgay

Selfishly, it’s always wonderful when someone else shares my enthusiasm for a piece of audio gear, and in this case, it’s been an ongoing argument between myself and Mr. O’Brien for a couple of decades now. While I agree with his analysis, because of the nature of the Vandersteen 5As only needing to be powered from about 80hz up, (because of their internally powered woofers) these speakers don’t give the full scale of the XA160.8s’ performance. And, of course, we like to perform amplifier reviews with as wide of a range of speaker systems as possible to see if there are any rocks in the road. I assure you there are none.

As with all the other Pass amplifiers we’ve auditioned, the XA160.8 continues the tradition of being able to drive any load effortlessly. I began my listening with the toughest speakers in my collection, the Magnepan 1.7s and the Acoustat 2+2s. Both passed with flying colors, and it was an interesting comparison to play the 2+2s with both the XA160.8s and a recently restored Threshold 400A that I used to use with my 2+2s in the ’80s. The more powerful, heavier, 4000A only stayed in my system briefly, but the 400A stayed for quite some time and was always a favorite.

Thanks to so much current on tap, the 2+2s now sound like there is a subwoofer in the room, but more importantly, these speakers, known for their somewhat loose and flabby lower registers are exhibiting taut, tuneful bass in a way they never have. Thomas Dolby’s “Pulp Culture” shakes the listening room with authority. An even tougher test is acoustic bass, and again the vintage ESL’s dance through all of my favorite Stanley Clarke tunes.

Moving through the gaggle of great speakers we currently have here from Dali, Dynaudio, GamuT, Eggleston and a few others, the XA160.8s have no limitations. To get them to (softly) clip requires ear shattering volume, or perhaps a pair of horribly inefficient speakers. In that case, there are always the XA200.8s and the Xs amplifiers.

No matter what music is served, the XA160.8s perform effortlessly and get out of the way for your enjoyment of it. The biggest delight, aside from knowing you’ll never have to hunt down matched quartets of power tubes again, is just how much of the flagship Xs300s capability is locked up inside these two boxes at one third of the price. Mind you in a “cost no object” system, the difference between the XS160.8 and the Xs300 will still be easily apparent, but it’s like the difference between an $85,000 Carrera and a $175,000 GT3RS – it’s easy to see, feel and hear the lineage,  and for those who don’t want to go all the way, will still find the lower-priced sibling still highly enjoyable.

I’ve hinted that the Pass XA160.8s have the slightest bit of warmth in their overall character, which they do. However, this additional richness and palpability is not at the expense of softness, or compromise in transient attack. If you want a strictly “nothing but the facts” the Pass sound may not be for you, but if you’ve always loved a touch of the glow that the world’s best vacuum tube amplifiers possess without having to chase the glass bottles, you must audition the XA160.8 I guarantee you will be highly impressed.

The Pass XA160.8

$29,000/pair

www.passlabs.com

PERIPHERALS

Analog Source	SME 20/SME V arm     Koetsu Urushi Blue
Digital Source	Simaudio MOON 650D    MacBook Pro
Amplification	ARC REF 5     Pass Xs Pre
Speakers	Vandersteen 5A
Cable	Cardas Clear

All things must eventually come to an end, but this time the breakup is not sweet sorrow.  Living with the Pass Labs XA160.5 Class-A monoblocks has been a wonderful experience, and the heat that these massive monoblocks let off is a small drawback compared to the glorious sound they produce.  In a year and a half of flawless performance, driving every kind of loudspeaker imaginable, I didn’t jot down a single complaint in my mental logbook.  The XA160.5s even proved more engaging than a number of vacuum-tube power amplifiers parked here for various reviews and personal auditions, supporting Nelson Pass’ claim that listening to his amplifiers are like “listening to tubes, but without the hassle.”

But then the XA200.5 monoblocks arrived.  “More devices and more power equals more control,” says Pass Labs’ Desmond Harrington when asked about the difference between the XA160.5, the XA200.5 and the soon-to-arrive XS amplifiers.  If there was ever a case of specs not telling the whole story, this is it.  You might think there would be barely any difference between these two amplifiers—one delivering 160 watts per channel and the other delivering 200 per channel—but fire up the drum solo in Zeppelin’s “Moby Dick,” and the XA200.5 paints an entirely different picture.  “Stairway” is pretty damn good, too.

Hey, Ho, Let’s Go

Tony Levin’s bass playing on the Black Light Syndrome album, from Levin, Steve Stevens and Terry Bozzio, illustrates this perfectly.  This album offers some of the heaviest prog rock available; a dense, driving orchestral soup in which these three virtuosos repeatedly lay down notes like they’re firing automatic weapons.  Levin is solidly anchored, while his bandmates careen off to the far edges of the soundstage from start to finish.  Keeping all three musicians straight without blur is a tough task, but the XA200.5s handle it effortlessly, even at high levels.

The low, grumbling undercurrent of Burial’s “In McDonalds” takes on a more visceral feel through these amps, helping the listener truly feel the track’s deep bass and low-level texture in a way few amplifiers can muster.  The overblown bass in Cash Money and Marvelous’ “Ugly People Be Quiet” loses none of its rawness and boom, while rumbling the woofers in the GamuT S9 speakers as if a subwoofer has been added to the system.  Many audiophile amplifiers suffer from too much control and damping in such instances, taking the soul of the music with it, but the XA200.5s are true to the music, no matter what the genre.  Even a lousy-sounding record like Teenage Fanclub’s Bandwagonesque is better sorted through these amps—this thick, compressed recording actually gives up some dynamics, with a little help from the dCS Vivaldi source.

With two pairs of world-class reference speakers at my disposal (the GamuT S9 and the Sonus faber Aida), these amplifiers play to a painfully loud level without distortion.  Whether using the S9 (89 dB sensitivity) or the Aida (92 dB), the XA160.5s can be driven to a point of compression; the XA200.5s have no limit in my system.  But man cannot live by bass alone—transient prowess is another area at which the XA200.5s excel.  Romping through the title track from Carsten Dahl’s Bebopish Rubbish Rabbit, these amplifiers provide not only control, but also acceleration.  They equally render drum transients and brushwork with the proper scale and finesse.

On one level, a component can really only be evaluated in the context of a system, and it’s tough to attach a sound to said component without seeing how it reacts to the known performance of a number of other preamplifiers and speakers.  Having lived with a variety of Pass amplifiers for a few years now, I would characterize their overall sound as ever so slightly on the warm and harmonically rich side of the scale.

The XA200.5, like all of the other XA-series amplifiers I’ve auditioned, paints a big, spacious, three-dimensional soundstage—again, much like your favorite tube amplifiers do, but with considerably more dynamics, grip and control.  On the title track from Leni Stern’s album Smoke, No Fire, the XA200.5s capture her delicate guitar playing with every bit of the gradation she presents in a live show, while layer upon layer of overdubbed vocals hang in mid air, meticulously spaced between each other.  Too often, mediocre solid-state amplifiers fail musically when presented with these kinds of recordings, because their inability to resolve spatial information results in an overly flat and sterile picture.  Modestly powered tube amplifiers excel at this kind of thing, but are unable to produce the giant dynamic swings required to capture a large orchestra or driving rock band.  The XA200.5s excel here, providing the best of both worlds.  Thanks to their massive power supplies and big banks of output transistors, these amplifiers retain inner detail while simultaneously carrying a heavy bass line or the roll of a kettledrum.

A is A

The Pass Labs website simply states in the FAQ section that the reason the company produces Class-A amplifiers is “because they sound better.”  I love this firmness of conviction.  I must also admit to a bias towards high-powered Class-A solid-state power amplifiers in the same way someone might prefer tubes, SET amplifiers or a pair of Quad 57s.  At the end of the day, we all have a preference, and I won’t apologize for this one.  Pass’ large Class-AB amplifiers, as well as a few other massive AB amplifiers I’ve experienced (like the Simaudio 880Ms also reviewed in this issue), still have slightly faster acceleration and ultimate dynamic swing, but this always comes at the expense of that last bit of inner sweetness.  That being said, one person will always prefer the slightly softer ride of a standard Mercedes to the AMG version with sport suspension.

Pass Labs’ relatively recent .5 series of Class-A amplifiers come as close to offering it all as anything I’ve experienced.  While I still treasure my Pass Labs Aleph 3 (from the ’90s) and Threshold 400A (one of Nelson Pass’ first Class-A designs from the late ’70s—also a big favorite), comparing them to the XA200.5s clearly illustrates where Mr. Pass has built on his initial strengths, constantly refining the sonic delivery of today’s models.

Romping through a plethora of recorded male and female vocalists underscores these amplifiers’ combination of power, delicacy and tonal accuracy.  Anne Bisson’s gentle vocal stylings on the title track of her recent Blue Mind album are reproduced perfectly though the XA200.5s, as are the piano and soft drum work that accompany her.  If not for the enormous heat sinks on the side of each amplifier, you’d swear that the grain-free tonal texture that the XA200.5s provide is due to some vacuum tubes inside the box.  And that’s the entertaining paradox:  These amplifiers have too much sheer grunt to be tubed.  Like Nelson Pass said…

Setup and Synergy

During our time with these amps, we had the opportunity to power about 30 different sets of speakers, from a pair of freshly refurbished MartinLogan Aerius i speakers to Sonus faber’s flagship Aidas.  Nothing poses a challenge to these amplifiers or affects their performance.

The amp’s balanced XLR and single-ended inputs have an impedance of 30k ohms, which makes them easily mated to the preamplifiers at our disposal from Audio Research, Burmester, Conrad-Johnson, Robert Koda and Simaudio.  Cardas Clear cabling was used for the bulk of our listening tests, yet both speaker cables and power cords affect the XA200.5 less than many other high-powered amplifiers in recent memory.

One thing the XA200.5s benefit from, if you have the luxury, is dedicated power.  Drawing 700 watts each all the time, they will work connected to a standard 15-amp circuit, but will work better with a 20-amp line and better still with a pair of dedicated 20-amp circuits—one for each amplifier, if you really like to twist the volume control.  I’d suggest having your electrician install a pair of 20-amp outlets for your XA200.5s before you drop a few thousand dollars on exotic power cords.

Fortunately, these 159-pound monsters have conveniently placed handles on the rear panel, though (unless you’re incredibly buff) you will still need a friend to help you unpack these amplifiers.  Once you’ve installed the amps, be sure they have plenty of ventilation, because they do get warm.

The Big, Big Money

This extra power and control doesn’t exactly come cheap.  The XA200.5s have an MSRP of $34,100 per pair, compared to $24,000 per pair for the XA160.5s.  It’s always easy for me to spend your money, but if you can find a way to come up with the extra $10,000, you will not be disappointed—this is truly a case where absolute power corrupts absolutely.  The XA160.5s are no slouch by any means, and tonally identical to the XA200.5; yet, even at modest volume levels, the effortlessness provided by the bigger, beefier output stage and larger power supply is instantly evident.

If you are looking for a pair of monstrous Class-A amplifiers that take no prisoners, consider the Pass XA200.5 monoblocks, or stick around for a few more issues—the XS two-box monoblocks have just arrived for review!

Pass Labs XA200.5 Monoblocks

MSRP: $34,100 per pair

www.passlabs.com

Peripherals

Analog source	AVID Acutus Reference SP turntable    TriPlanar tonearm    Lyra Atlas cartridge    AMG V12 turntable    AMG tonearm    Clearaudio Goldfinger cartridge
Digital source	dCS Vivaldi    Meridian Sooloos Control 15    Aurender S10
Phonostage	ARC Reference Phono 2 SE    Indigo Qualia
Speakers	GamuT S9    Sonus faber Aida    Sonus faber Elipsa SE
Cable	Cardas Clear
Power	IsoTek
Accessories	Furutech DeMag and DeStat    Audio Desk Systeme RCM    GIK room treatments

Even with a track that is not bass heavy, the Pass Xs 300 amplifiers immediately show their superiority.  Sinéad O’Connor’s luscious voice on “Bewitched, Bothered and Bewildered,” from her album Am I Not Your Girl? lingers in the air between the KEF Blades in a way that it never has before—her voice is bigger and airier, with a higher degree of “reach out and touch it” than I’m used to.  And when Michael Jackson takes us through a time warp with minimal accompaniment, courtesy of The Stripped Mixes, he truly feels right in the listening room about five feet in front of the couch.  The realism is staggering.

In the world of high-end audio, where Internet-forum pundits loudly proclaim that expensive gear is not worth the money and that its curve of performance versus diminishing returns is incredibly steep, I must strongly disagree in favor of the Xs 300s.  Having lived with Pass Labs’ $22,000-per-pair XA160.5s monoblocks for over a year, and then having stepped up to the $34,100-per-pair XA200.5s (a huge jump in performance) and now taking the leap to the $85,000-per-pair Xs 300 two-chassis monoblocks, I’m still staggered at how much more of everything is available with Pass’ flagship amplifiers.

Here in Portland, Oregon, one of America’s greenest cities, my aging hipster friends would mess themselves if they knew I had a pair of amplifiers that draw 1,000 watts each, all the time.  Okay, so I’ve thrown concerns about my carbon footprint out the window with these amps, but I do walk to work and I’ve replaced all 22 of the 50-watt halogen bulbs in my studio ceiling (along with the 15 in the house) with LEDs that only draw 7 watts each.  That just about makes up for the power that these massive monos consume.  I’d light the place with candles and eat dirt before I’d give up these amplifiers!

As TONE staff member Jerold O’Brien helps me unpack these super-sized beasts, which weigh in at 168 pounds for the power supply and 130 pounds for the output stage, we become awestruck:  The Xs 300s have six banks of output devices per channel and Pass has increased the bias current by a factor of 10 compared to the XA amplifiers.  And as Pass Labs’ Desmond Harrington is fond of saying, “This means more control.”  Interestingly enough, Jeff Nelson of Boulder Amplifiers says the same thing, and both the Boulder 3050 monoblocks and the Xs 300s are definitely the two most incredible amplifiers I’ve ever heard (for those of us who are not worried about the price tag).

Where the mighty Boulders take more of a “just the facts, ma’am” approach, the Xs 300s sound more like a gigantic tube power amplifier with tighter grip and more bass grunt, while retaining the airy character and ravishing tonality that you would normally associate with vacuum tubes.  I’d happily put the Xs 300s up against any vacuum-tube power amplifier on the market, regardless of price, and I’d still prefer them to tube power.  The Xs 300s are equally yummy, and knowing you’ll never have to forage for power tubes again is a major bonus.

Love at First Listen

O’Brien and I are both equally stunned when we begin to hook up the Xs 300s.  Way too anxious to just let one stack sit there while taking the photos for this review, we connect one of them to the GamuT S9s.  We look at each other and O’Brien exclaims, “Dude, your system sounds better in mono with one of these than it does with the pair of XA200.5s.”

Strong words indeed; this is the level of performance increase that comes with spending twice as much money with a reputable company.  If you’ve ever fallen deeply in love at first sight then you know how this is.  The Xs 300s are love at first listen.  (After months of using them with an incredibly wide range of speakers, from the $1,500-per-pair KEF LS50s to the $150,000-per-pair GamuT S9s, I’m even more smitten with them now than the day I unpacked them.)

By the time we have the photos done and the second channel connected, it’s time for some shut-eye, so the Xs300s are left to play all night, and we’ll reinvestigate them in the morning.  As is the standard procedure with massive class-A power amplifiers if they are going to be on all night, no heat is needed in the studio.

The next day’s listening session begins with a comfortably toasty listening room, but more importantly, the amplifiers are now thoroughly warmed up.  Normally, we always leave solid-state power amplifiers on 24/7, but this is just not practical with the Xs 300s, because they produce such a prodigious amount of heat.

Boxes Ticked

The amount of sheer control the Xs300s provide is unbelievable—there is truly nothing they won’t do.  When we swap out a few of the other amplifiers we have on hand for the Xs300s (even the awesome XA200.5s), it feels as if a subwoofer has been added to the system, even with the tiny KEF LS50s—which, incidentally, sound amazing through these four-box wonders.

It isn’t just all power and punch, though:  These amplifiers offer the magic of incredibly high resolution, without throwing delicate tonality out the window.  You’ll notice tasty little nuances in your favorite well-worn recordings, prompting the desire to revisit as many of them as possible.  I predict many late-evening listening sessions once you get these fully broken in.

A perfect example is Ornette Coleman’s Ornette on Tenor. This straightforward bop record features great interplay between Coleman on sax and Don Cherry on trumpet, backed up with bass and drums—a sparse mix to be sure.  The sax and trumpet tear it up across the wide stereo mix, with the drums and bass exploding from the left and right channels, respectively.  The scale at which all of this takes place, especially in the way the Xs 300s render height, makes it all sound so convincing.

The Hammond organ sounds fabulous as it creeps into the mix at the beginning of War’s “The World is a Ghetto.”  The Hammond is barely there, just skating in and out of your consciousness, but it adds an unmistakable texture to the track—all the better in 24-bit/192-kHz resolution courtesy of HDtracks.  All the while, the funky, wah-pedal-laden guitars segue in over layer upon layer of horns.  Backing up to “The Cisco Kid” proves equally enlightening.  When a piece of gear can render a track that you’ve heard way too many times and still keep you riveted, you know you’re onto something special.  This is what the top of the mountain looks like, or rather sounds like—and it’s good.  No, it’s wonderful.

Those who live and die by the sword of pace and timing will be equally enthralled with the Xs300s.  The needle in the gigantic round meter on the front panel of the amplifier chassis stays firmly planted in the center, indicating that the amp is staying in single-ended class-A operation.  Until pushed well past reasonable and prudent levels, the needle barely ever budges, as is the case when powering the 90-dB-per-watt KEF Blade speakers.

Jazzman Marc Ribot’s Silent Movies is a collection of atonal tracks that exhibit laser-sharp focus through the Xs 300s.  The decay of Ribot’s heavily processed guitar on “Natalia in Eb Major” is so realistic that I’m magically transported back to the 10th row at the Montreal Jazz Festival as I soak it all in.  As Ribot switches from distorted electric guitar to clean acoustic, the Xs 300s allow the notes to just linger in the air so that you can feel the strings resonate.

Comfortable at All Levels

Even at practically intolerable volume levels, the Xs 300s hold their poise completely, with no soundstage collapse whatsoever.  Audioslave’s “Gasoline” is by no means an audiophile darling, and it’s actually somewhat compressed; yet, on a great system this track can be unraveled.  With the meters just beginning to budge from their stops, I can feel my brain rattling around inside my head from the sheer sound-pressure level, but the pounding drums and lead guitars stay in place and Chris Cornell’s high-octane scream stays anchored, drilling itself into my being.  These amplifiers remain composed, even at these elevated levels.

Yes, this kind of listening is bad for your eardrums, but being able to pressurize your listening room at near concert levels (no matter what kind of music you enjoy) is enthralling to say the least, so use the Xs 300s with care.  A sound-level meter would be an apt accessory for these amps.

In the end, every aspect of music reproduction sounds more convincing with these amplifiers.  Pass Labs founder Nelson Pass has always been a proponent of the “first watt” methodology (i.e. if the first watt doesn’t sound great, why bother with the rest?), and he went so far as to built a pair of small power amplifiers bearing that name.  We’ve reviewed most of the First Watt amplifiers and they are superb; the massive Xs 300s manage to retain that same level of delicacy while still providing major power.  There are just some speakers with which 15 watts per channel simply won’t cut it.

Setup and Stuff

If you think you really don’t need 300 watts per channel of class-A power, think again.  The combination of speed, control and bone-crushing dynamics offers an experience you just don’t get with less power, even at low listening levels—it’s more about the control these big amplifiers provide than just power.  Incredible acceleration is an added benefit of all this power, along with the ability to stop instantly.  The Xs 300s are lightning fast with no hangover or fatigue.  They’ve been playing nearly nonstop since they arrived, and at the end of a 16-hour day I can still keep going back to the record rack for just one more.

Like the other Pass amplifiers we’ve used, the Xs300s require about 100 hours of play to be all they can be, but they are damn good straight out of the box.  Once you become intimately familiar with them, you will notice that they sound slightly hazy at first turn on, and gently yet linearly they come out of the fog over the course of about 90 minutes.  Everything just gets easier as they reach operating temperature.

Because of the heat they generate, these amplifiers need ventilation, and Pass confirms that you can stack the chassis one on top of the other, but be sure to give them plenty of room.  And if you are in tight quarters, make sure you have decent HVAC.

The Xs 300s can be used with balanced or RCA inputs, though they are fully balanced amplifiers.  The ARC REF 5 SE and Robert Koda K-10 preamplifiers work fantastic, as do the Simaudio MOON Evolution 850P and Burmester 011.  Even my vintage ARC SP-11 Mk. 2 works well, but the high resolution of the Xs 300s does reveal the limitations of this great vintage piece.  The only real downside to the Xs 300s is that you’re likely to find yourself wanting linestage and source upgrades.

A pair of enormous cables connects the chassis with the biggest Neutrik connectors I’ve ever seen.  I plug each monoblock set into a dedicated 20-amp line, even though the power cords are of the 15-amp variety—there’s no point in putting regular gas in your Aston Martin, right?  The four speaker binding posts are the super-coolio Furutech carbon-fiber jobs that ratchet tight and click when you’ve reached the proper torque, which is a nice touch.

The $85,000 Question

Though saying so may result in some hate mail, the Pass Xs 300s are worth every penny of their $85,000 price tag.  Considering a few other amps on the market that I’ve sampled, Pass could probably charge an even 100 grand for them and easily get away with it.

But you have to ask yourself a couple of questions before making this kind of a purchase decision:  Do these amplifiers take you somewhere you’ve never been before, giving you an experience that you just can’t get with a lesser product?  Are they built with a level of precision, care and attention to detail commensurate with other products at a similar price?

Yes and yes—and then some.  Fortunately, I’ve had the privilege of listening to a lot of fantastic amplifiers in the $20k-to-$40k range over the last few years, and the Xs 300s are considerably better.  They reveal more music and are more transparent, with bottomless dynamic power and they present no problem driving any of the speakers I have at my disposal.

So if you’ve got the system, the software and the scratch, buy these babies—you won’t regret it one bit.  And the couple of readers I’ve talked to who have jumped off the cliff agree with me.  These are indeed very special amplifiers.

Pass Labs Xs 300 monoblocks

MSRP: $85,000 per pair

Pass Laboratories

www.passlabs.com

Peripherals

Analog Source	AVID Acutus Reference SP turntable    TriPlanar and SME V tonearms    Lyra Atlas and Clearaudio Goldfinger SP cartridges
Phono Preamplifier	ARC REF Phono 2 SE    Indigo Qualia    Pass Labs XP-25    Simaudio MOON 810LP
Digital Source	dCS Vivaldi    Sooloos Control 15    Aurender S10
Speakers	GamuT S9    KEF Blade    Sonus faber Aida    Sonus faber Guarneri Evolution
Cable	Cardas Clear
Power	IsoTek Super Titan

No matter your drug of choice—chemical, horsepower, audio—with prolonged use, you always reach a plateau at which you believe you just can’t get any higher. But sooner or later, something else enters your reality that restarts the cycle, and you’re off and running again. Such is my experience with the Pass Labs XA160.5 monoblocks.

If you are new to the world of high-end audio, you can get the condensed history of Pass Labs here: http://www.passlabs.com/about.htm. The shorter version is simple: Nelson Pass is a genius. He’s probably got more patents for amplifier design than almost everyone else combined. And he’s got a great sense of humor, too. The owner’s manual describes the new amplifier as “tending to run heavy and hot, but elicit high performance and reliability from simple circuits.”

Weighing in at about 130 pounds each and $24,000 per pair, the XA160.5s are not for the light of wallet—or bicep. Or, for that matter, air-conditioning capacity. The power draw isn’t huge, but each unit sucks 600 watts from the power line, whether idling or at full power. Because they only produce 160 watts per channel into 8 ohms, doubling into a 4-ohm load, they get very warm to the touch. Yes, this behavior is normal for a class A design. The extra heat was welcome in March when the amplifiers arrived, as it kept our studio toasty. Yet, as days got longer, the amps forced us to run the A/C well before we normally would.

Super Yet Simple

Pass has always advocated keeping things as simple as possible. While squarely looking at the enormous monoblocks might cause you to question whether he still believes in this basics-minded philosophy, thanks to Pass’ patented SuperSymmetry design, the amplifier has only two gain stages. At the risk of oversimplifying, the SuperSymmetry approach achieves low distortion (and tonal purity) by making each half of the balanced amplifier as close to identical as possible so that the resulting distortion from each half of the amplifier circuit cancels out in balanced mode.

To achieve maximum performance, the amplifier must be run in balanced operation. Fortunately, the ARC REF 5 offers balanced and single-ended outputs, which makes comparisons a snap. And Pass is right again: Utilizing the XA160.5 in single-ended mode proved very good, but it featured a layer of grain not present in balanced mode. Whether you use a Pass Labs preamplifier or a model from another manufacturer, make sure to take the balanced route.

Coming Full Circle

My first experience with Pass’ class A amplifiers came in 1979. I combined a Threshold 400A with a Conrad Johnson PV-2 preamplifier driving a pair of Acoustats, making both an incredibly natural combination and excellent case for pairing a solid-state power amplifier with a tube preamplifier. While many combinations have since passed through my room, the tube pre/solid-state power amplifier is always the one to which I’m drawn, especially when it involves a class A amplifier.

The XA160.5s symbiotically works with all of the preamplifiers at my disposal, but the match with the Audio Research REF 5 linestage and REF Phono 2 preamplifier is heaven-sent. Pass Labs president Desmond Harrington tells me that many customers use the company’s amplifiers with tube preamplifiers. “It’s a popular combination, but when it comes to power, we like to see our amplifiers offering the tube sound without the tears.” Truer words haven’t been spoken.

As someone who’s purchased more than a fair share of power tubes, I am relieved to know that the sound of the XA160.5’s will never change. And, you won’t have to buy new power tubes every year. Continuous operation cuts down on tube life. If only Costco sold tubes by the palette.

Like Luke, I Ignored Yoda Just Once

Pass’ instruction manual cautions against using the XA160.5s with a power conditioner. Nonetheless, I plugged them directly into the wall and then into my Running Springs Maxim power conditioner, with the latter providing an even cleaner presentation. The soundstage opened up significantly, and I didn’t experience any loss of dynamics. Yes, the stock power cords that come with the XA160.5s are very good, but aftermarket power cords (Shunyata and Running Springs models yielded excellent results) offered up a slightly clearer window to the music.

In all fairness, think of superior power cords as being able to take an amplifier that goes to 11 up to 11.2. Besides, you wouldn’t put regular gas in your Porsche, would you?

Super and Scrumptious

Unlike a non-class A solid-state amplifier, the XA160.5s shouldn’t be powered on for 24 hours a day. They generate too much heat. Still, just like a tube amplifier, the XA160.5s need an hour to warm up and stabilize. At first turn on, they still sound great, but once you get used to them, you’ll notice a slight haziness that softly dissipates as the clock ticks. Coincidentally, the ARC REF 5 and REF Phono 2 need an hour to sound their best, too, so if you are using a tube front end, everything will warm up at the same pace.

I initially listened to familiar digital tracks from the Sooloos music server/dCS Paganini combination. I was immediately taken aback by the additional weight and depth, even more so with high-resolution digital files. All of the class A amplifiers with which I’ve lived share a tonal richness that other solid-state amplifiers do not possess. Some might refer to this quality as warmth, but I prefer to call it tonal richness. I associate warmth with slowness, lack of pace, and rounded-off treble; the XA160.5s exhibited none of these characteristics. The Pass monoblocks sport the equivalent of a great guitar’s ability to sustain a note. On a choice Gibson Les Paul, for example, music just seems to hang in the air a little longer.

Switching back and forth between amplifiers at my disposal revealed that the XA160.5s are indeed very special. It was as if the particular characteristics from my favorite amplifiers have somehow taken up residency in one model. Thanks to their monoblock design and huge power supplies (the 160.5 is claimed to have a significantly larger power supply than the 160 it replaces), these amplifiers throw a soundstage that is prodigious in all three dimensions. Image width really stands out.

I noticed such traits on all program material, but they became more obvious when listening to classical. Conveying the size of a symphony orchestra—much wider than most listening rooms—is one of the toughest feats to ask a system to accomplish. When listening to Sir Arnold Bax’s sixth symphony, it felt as if the sidewalls in my listening room had been each moved out about six feet. Not realistic, of course, but much more convincing than without the XA160.5s.

Recorded live and flush with ambience, Hugh Masekela’s “Stimela (The Coal Train)” from Analogue Productions’ 45RPM 2LP version of Hope provides an excellent test. Having just heard Masekela perform the song at the Montreal International Jazz Festival in June, the recorded version via the Pass amps colored me impressed. While the live version claimed a slightly different arrangement, the XA160.5s pushed my GamuT S9s to a realistic sound level and conveyed such nuance and tonal contrast, I felt like I was back in Montreal’s Club Soda venue. Even at the high volume level, the front panel’s deep-blue backlit oval meter barely flinched from its center position, indicating that the amplifier never left class A mode.

Of course, man cannot live on jazz alone. At prime operating temperature, the XA160.5s did not miss a beat on a Japanese vinyl pressing of Michael Schenker’s Built to Destroy. No matter how hard I pushed, I could not destroy the amps or my speakers. And yes, that’s a very good thing. Staying in Japanese LP mode, Bruce Springsteen’s The Wild, The Innocent, and the E-Street Shuffle proved tough to resist, as did David Bowie’s Aladdin Sane. These old favorites never sounded better, and when I quickly switched back to the gear I’ve lived with for some time, across-the-range performance boosts became manifest.

Staggering Pace and Tonality

While classical music plays to one group of the XA160.5s strengths, revisiting the recently remastered Beatles catalog plays to another: These amplifiers offer rock-solid pace. Violins in the mono version of “Eleanor Rigby” (from Revolver) were strongly anchored, and Lennon and McCartney’s voices unwavering. There was so much depth, it almost sounded like a stereo recording! Speaking of the latter, the stereo version of “Penny Lane” from Magical Mystery Tour turned out to be just as exciting. Ringo Starr’s drumming and McCartney’s bass held true throughout the psychedelic soundscape.

I am easily swayed by the big sound of these amplifiers, yet that characteristic only scratches the surface of their capabilities. Concerning tonal accuracy and texture? Spot on. Acoustic instruments sound correct, whether listening to wind, string, or percussion instruments. Dynamic contrasts equate to the best I’ve experienced. A few TONE writers whose tastes skew towards classical remain astonished at the lifelike piano reproduction.

Music fans that crave vocal performances will benefit from the XA160.5’s picture-perfect tonality and resolution. Again, the extra tonal body almost feels as if one is listening to an SET—albeit an SET with nearly unlimited power that you can use with real-world speakers. The extra low-level resolution goes a long way, especially when spinning marginal discs. An ideal example comes courtesy of Keith Richards’ Talk is Cheap. Richards is not known for possessing a terribly strong lead vocal. Yet, when put through the XA160.5s, it actually has some depth. Such is the XA160.5s’ allure. They hover at the optimum point of boasting maximum resolution without being harsh, sounding full bodied and musically natural without introducing tonal distortion— a difficult balancing act.

Bass response keeps in line with the exceptional performance found elsewhere in the frequency range. While the XA160.5s have more than ample weight and slam, the bass reveals a level of texture and detail that I’ve only experienced with a small handful of amplifiers. Remember: It’s easy to confuse “audiophile bass” (usually over-damped and distinguishable from the real thing that has life, texture, and resonance); the XA160.5’s are the genuine article. A cursory listen to your favorite acoustic bassist reveals the way these amplifiers allow the instrument to breath, and brings you that much closer to the actual performance.

Top Contenders

Two years ago, I proclaimed the Burmester 911 Mk.3’s the best amplifiers I’ve heard. And over the course of hundreds of product reviews, I’ve used that dreaded “B” word just once in the absolute sense. After conveying my enthusiasm for these amplifiers to Harrington, he responded, “The 160’s are amazing, but you need to hear the 200s.” So just when I thought I couldn’t get any higher, the quest begins again.

It’s always tough to make comparisons, yet the XA160.5 combines the virtues of my three favorite amplifiers into one (actually two) boxes:  the delicacy of the Wavac EC300B, the texture and dimensionality of the ARC REF 150, and the power, control, and composure of the Burmester 911s.

Independent of the “B” word, the Pass Labs XA160.5 monoblocks orbit the top stratosphere of amplifier design at any price. If you would like that je ne sais quoi that you thought required a vacuum-tube amplifier, these are a consummate alternative. There is nothing that the XA160.5s do not do.

The Pass Labs XA160.5 monoblocks

MSRP:  $24,000/pr.

www.passlabs.com

Peripherals

Analog Source	Audio Research REF Phono 2     AVID Acutus Reference SP w/SME V tonearm and Koetsu Urushi Blue cartridge    AVID Volvere SP w/SME 309 tonearm and Grado Statement1 cartridge
Digital Source	dCS Paganini stack    Sooloos Control 15
Preamplifier	Burmester 011    Burmester 088    ARC REF 5    McIntosh C500   Conrad Johnson ET5
Speakers	GamuT S9
Power	Running Springs Dmitri    Running Springs Maxim
Accessories	Furutech DeMag    Loricraft RCM