ULTRA AUDIO -- Archived Article

September 15, 2005

Pass Labs XA-160 Mono Amplifiers

I had some expectations of and preconceptions about Pass Labs’ XA-160 monoblock power amplifiers ($18,000 USD per pair) before I heard one note from them. My own past experiences listening to offerings from Pass Labs’ Aleph and X series gave me an idea of the sort of things to expect from Nelson Pass and his team. I thought I could make a reasonable prediction of the XA-160s’ sound from Pass Labs’ own declaration that the design combined the sweetness of the Alephs with the low-end control and dynamic clout of the X-series amps.

But expectations for any particular component, no matter how seemingly logical or rational, can be frustrated or exceeded due to other variables in a given sound system. I found this to be true with the XA-160. Fed the right diet of cables (interconnects, speaker cables and power cords), the XA-160 exceeded my expectations. Careless cable or component matching quickly reversed those findings and had me judging this fine amplifier unfairly.


Pass Labs X and XA amplifiers are gorgeous components. Apply whatever slang term you choose -- eye candy or audio jewelry -- the Pass XA-160 is aesthetically pleasing. Pass’s famous blue meter glowing in the exquisitely machined faceplate and punctuating that muscular frame -- it all makes a bold and beautiful statement. Yes, sound is the first priority, but if a component can be equally attractive to the eye, it’s a plus.

The XA-160 is physically imposing. Tall, deep, and heavy, it stands 19"W x 11"H x 22"D and weighs 130 pounds. It’s no one-man installation job unless you buy your arthritis cream from Barry Bonds’ supplier. I suggest you solicit a little help from your friends when you uncrate and install these amps.

I have been closely following and have heard a number of the newer "compact" amplifiers, ranging from the new digital amps to the ICEpower amps ( la Jeff Rowland Design Group) to the newest "non-ICE," "nondigital" compact amplifiers from Kharma. The Kharmas are so small -- if surprisingly heavy -- that they’re sure to elicit the proverbial "aren’t they cute" from the female side while triggering a divergently different response from the average testosterone-driven, Tim Taylor-ish male audiophile. As you have likely gathered, the Pass XA-160 is not of this compact genre but is a classic beefy, analog, class-A amplifier with a gargantuan transformer and the huge heatsinks necessary to dissipate the enormous amount of heat generated by 160W of pure class-A power. However, anyone with 2- or 4-ohm speaker loads hoping to get the XA-160 to double down into decreasing impedances need not apply. The XA-160 puts out a Pass-rated 160W of class-A power into any load.

The XA-160 is fully balanced, and accepts both single-ended and XLR inputs. A small switch on the rear panel places the amp in standby mode, and the round button in the middle of the faceplate illuminates the blue meter and brings the amp to full power. My experience was that, after initial burn-in, the XA-160 needed at least 45 minutes to settle in and sound its best. I also very much appreciated the speaker binding posts, which are easily tightened by hand. Other than the hernia I suffered installing the amps myself, the XA-160s were a breeze to set up. Finally, the fact that the three-year parts and labor warranty is transferable is a big plus, if you want or need to re-sell.

My review system was as follows: Speakers were Kharma Exquisite 1D-E.d; preamplification was handled by the EMM Labs Switchman II, Conrad-Johnson ART-2, or Reimyo CAT-777, along with the Aesthetix Io Signature phono preamp. My digital source was Reimyo’s CDP-777 CD player, my analog source the SME 30 turntable with SME IV tonearm and Dynavector XV-1s cartridge. The first interconnects I used were the Harmonix SUS GP-101 XLRs, between the Reimyo CDP-777 and EMM Labs Switchman and from the Switchman to the Pass XA-160s. Between the Aesthetix Io and the Switchman was a Nordost Valhalla with RCAs. I later used Silversmith Silver and Palladium, Nordost Valhalla, and Kharma Enigma interconnects. Speaker cables at all times were the Kharma Enigma (specially designed for my speakers, which are also wired with Enigma internally). All power cords were Harmonix X-DC Studio Masters.

A study in contrasts

The XA-160s followed a pair of Tenor Audio HP-300 hybrid monoblocks in my system. The Tenor amps retailed for $34,000 per pair, the XA-160 for $18,000 per pair. Although Tenor Audio is no longer in business, its chief designer/engineer and senior technical assistant are now at CDF Audio in Canada, which continues to service Tenor components and offer upgrades and assistance to former Tenor customers.

The Tenor amps, while sounding fabulous, are slightly on the "white" or lean side of neutral, with bass that’s almost too tightly controlled. Unless mated with the proper cables, the Tenors can also sound a little glassy or lean in the upper frequencies. I nonetheless installed the Pass XA-160s using the same cables as with the Tenors, so as to change only one variable at a time.

From the first note of Vernon Handley and the Ulster Orchestra’s beautiful rendering of E.J. Moeran’s Symphony in G Minor [Chandos CHAN 7106], it was immediately evident that the Pass XA-160s were vastly different from the Tenors. Not a trace of glassiness or "whiteness" was to be heard, and the music floated in such a silky and velvety way, with notes so richly rendered, that my initial reaction was that my shoulders lowered as I relaxed into the voluptuous presentation.

What also struck me right away, and set the big Pass Labs amps apart from many competitors, is how they eschewed the usual audiophile tricks, concentrating on the forest instead of the trees. It was as if the amplifiers were exclaiming, "Music is woven together as a whole and is not simply the sum of a vast number of individual threads!" I don’t mean to imply that voices or instruments congealed into an indecipherable mass, or that I could not highlight or home in on individual performers. It was simply that the amps emphasized the organic whole rather than self-indulgently calling attention to themselves.

In contrast, the Tenor amps tend to highlight individual performers and reveal the most minute details in a way that almost always first calls attention to individual aspects of the music. Their leaner sound gives an immediate impression of their being more nimble-footed and "fast" and presenting seemingly more detail, space, pinpoint focus, and a wider soundstage. However, this apparent perception could be misleading. The harmonically richer, fuller Pass XA-160s provided more pixels to the sonic screen. This filled in more of the spaces around instruments and voices and thus gave an initial illusion of less detail or less space. But that’s how the XA-160s sounded at first. Only after extended listening did I come to fully appreciate what the XA-160s brought to the table.

Over the last three years, during my visits to Consumer Electronics Shows and other audio events and during my listening sessions with local audio clubs, dealers, and friends, there seems to have been a growing trend of listening preferences toward systems that exhibit ultra-detail, super-resolution, razor-sharp focus and imaging, and lightning-fast transients. There also seems to be a growing preoccupation with soundstage width and depth. I have no issue with anyone preferring these qualities, but I can’t help wondering, as we assemble systems with more and more resolution, detail, and focus, with greater leading-edge definition and wider and deeper soundstages, if we are not at the same time getting farther away from sonic truth and accuracy. It is also true that during these last three years I have heard more and more live, unamplified music. It occurs to me that I, too, had been seeking the Holy Grail of ultra-detail, super-resolution, and increased focus and imaging, without realizing that it was antithetical to what I was hearing during the live sessions I had been enjoying. Once we get on the roller-coaster of "high-end audio," it’s not too difficult to start concentrating more on the sound than the music.

When I inserted the Pass XA-160s into my system, I found myself ignoring those audiophile tricks and simply enjoying the "whole" of the musical message. When I put my reviewer hat on I could start picking apart the XA-160s, but even then, those nits and gnats were more the product of analyzing the pieces than appreciating the whole.

Getting back to the particulars, when I hooked up the XA-160s to my system with the Harmonix interconnects, the harmonic overtones and instrumental timbres were so rich and full-bodied that I struggled with my initial reactions, which told me there wasn’t enough space, air or detail. So I started playing around, first with interconnects and then with line stages. I found that inserting a Nordost Valhalla or Silversmith Silver interconnect between my CD player and line stage, or between the line stage and the XA-160s, gave an immediate impression of sharper transients, more articulate bass, and greater detail and space. Replacing the EMM Labs Switchman II with the Reimyo CAT-777 line stage gave an even more open and airy presentation, with even greater perceived detail and articulation. I say "perceived" because long-term listening proved to me that, even though the Valhalla-Silversmith-Reimyo combo provided sharper transient attack and greater articulation, it did not provide greater resolution or detail. Instead, the leaner, more neutral, or faster character of this chain gave the perception of greater detail, while what I believe was actually happening was that my audio screen now had fewer pixels.

Whichever sort of sound you prefer, it was clear to me that the sound of the system with the XA-160s was very dependent on the partnering cables and components. Regardless of which cables I used, however, it was equally clear that the XA-160s always maintained that richly rendered, silky-smooth emphasis on the whole sound over the sum of its parts. In other words, the Pass XA-160s, while never sounding dark or rolled-off in any way, appealed to my holistic preferences. That, my friends, was a very good thing, and brought me more musical and emotional enjoyment from my system, even if it proved to be a reviewer’s nightmare.

Discs that sounded tizzy or glaring at moderate or loud volumes through the Tenor amps, such as Tower of Power’s newest offering, Oakland Zone [Or. Music B00008NFAG], lost their glare yet none of their musical detail through the XA-160s. I did notice a slight narrowing of the soundstage with the XA-160s, and, as mentioned above, that perception of greater focus and pinpoint imaging through the Tenors. However, that perception of hearing fewer audiophile tricks from the Pass Labs amps was more than offset by their more enjoyable rendering of the whole musical message. The Tower of Power brass section was more organically rich while retaining that natural bite of brass, yet the sibilant edge the vocals had through the Tenor amps was gone. While the bass was more articulate and had sharper transients through the Tenors, it was no less enjoyable through the XA-160s, whose more rounded yet powerful presentation, to a certain extent, fit better within the entire musical context. While through the Tenors each instrument seemed to hang in space, more easily lending itself to critical analysis of the sound’s component parts, the XA-160s’ more intertwined and velvety instrumental and vocal textures reached me from a more emotional perspective.

A tale of two amplifiers

I hesitate to suggest that the Pass Labs XA-160s appealed only to the emotions, if by that you might think I mean that they could not provide sufficient detail or articulation. The XA-160s had plenty of detail, sufficient slam, and provided enough of a soundstage to satisfy all but the most analytical audiophiles. If you prize detail above all else and require the ultimate in soundstage width, an ultra-detailed and razor-sharp sound, and musical parts highlighted at the cost of the musical whole, check out a used pair of the Tenor HP-300s. However, if you appreciate a holistic musical message, you owe it to yourself to audition the Pass Labs XA-160s and see if, like me, they take you back to your emotional musical roots.

…Frank Peraino

Pass Labs XA-160 Mono Amplifiers
Price: $18,000 USD per pair.
Warranty: Three years parts and labor (transferable).

Pass Laboratories
P.O. Box 219, Foresthill Road
Foresthill, CA 95631
Phone: (530) 367-3690
Fax: (530) 367-2193

E-mail: jsammut@passlabs.com
Website: www.passlabs.com

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