Pass Labs XA30.5 power amplifier Page 2
All of the true class-A amplifiers I've had in my system have shared a few characteristics that I can now tick off on my fingers: a smooth, distortion-free purity to the sound that is most obvious across a gorgeous midrange; tonal balances that are often a bit dark, due to a softened and truncated high end; bass reproduction that typically lacks a bit of punch and extension; slightly softened dynamics; and soundstages that are deep but recessed, particularly at the center. The mix and extent of these characteristics have varied from amp to amp, but all have always been present to some degree.
The XA30.5 had the lifelike smoothness and purity in spades. It's easy, on a steady diet of recorded music, to "listen around" too-common distortions. We turn the volume down a bit to tame a bit of harshness in closely miked trumpets or a steeliness in crescendos of massed violins, and learn to accept a forceful but indistinct impact when a bass drum is first struck. The absence of these insidious distortions is one reason that live music is so immediately and obviously different from recordings. But within the first few seconds of listening with the XA30.5 in the system, it was clear that these distortions had been dramatically reduced. There was a natural ease to the sound, and a level of inner detail that hadn't been distinguishable before.
One evening, Dave Grusin's album of Glenn Miller classics, In the Digital Mood (CD, GRP Digital Master, GRP-A-1002), provided a few great examples of these differences. Before installing the XA30.5 in my system, the sound of this album had been dynamic, with a bright, sunny feel. The orchestra had sounded tight and well paced, with a foot-tapping kind of drive. Installing the Pass changed this feel to one of effortlessly smooth swing. It was as if the band members had relaxed, lowered their shoulders, and taken a deep breath. The trumpet crescendos in the halting, expanded runs midway through "In the Mood" sounded less forced through the Pass, and a slight glare was now gone, leaving the images of individual instruments more distinct and harmonically more rich. The musicians gained body and depth, and there was a sense of the spaces between them. I could picture the individual musicians and imagine the air moving through each instrument. Whenever I replaced the Pass with a different amplifier, the images flattened and the slight glare returned. Although these differences were subtle, I was surprised at how badly the glare smeared or obscured inner detail during the loudest passages.
The XA30.5 extended this effortless purity and portrayal of inner detail from the midrange out to the frequency extremes. The cymbals on the Grusin disc had a sweet timbre and long, delicate decays. Their crashes seemed a little attenuated, though, so I wondered if the Pass might be softening transients or rolling off the highest frequencies. The drum set on Test CD 2 (Stereophile STPH004-2) is a more natural recording, and showed that the Pass didn't lack extension. It was just removing a splashy overemphasis from the leading edges of hard transientssuch as those cymbal crashes. In fact, the XA30.5 reproduced the initial cymbal stroke well enough that I could easily hear both the initial impact of the drumstick and the bell-like ringing within the transient.
I heard less of this ringing in the cymbals when I switched to other amps, though the differences weren't huge. With my VTL Ichibans, for example, the cymbals still sounded like cymbals, though with a bit less ring and a bit more dense, metallic hiss. They had a complex timbre and structure, just not as sweet or as focused as they'd been with the Pass, or quite as three-dimensional. Switching from the Pass to other amps also seemed to truncate the cymbals' decay, preventing me from hearing the last, faintest traces of the shimmer dissolving into the background. Again, however, the differences were subtle.
The Pass did a great job of reproducing harmonic and inner detail on the bottom end as well, although here the XA30.5 did lack a bit of weight and extension in comparison to more powerful amps. Returning to Russ Henry's drum kit on Test CD 2, the Pass beautifully captured the round, booming nature of the bass drum, but didn't really convey the sense of a moving pressure wave. In a run down succeedingly larger toms, the Pass gave each drum a distinct location, size, and shape, each described by a clear and unique blend of elastic skin sound and trailing body resonances. The toms had more punch through other amps, and increasingly so as they dropped in pitch, but with neither the precision nor the tonal and textural detail they had through the XA30.5.
The Pass's effortless, almost lazy feel did lack some of the snap and energy I heard with other amps. Instead of turning the volume down a bit to tame the crescendos, with the Pass I was constantly turning the volume uppartially because there was no glare to tone down, but also in a quest for more impact and drive. Parsing it into audiophile terms, the XA30.5's macrodynamicsthe big swings and huge crescendosweren't as large as with my other, far more powerful amps. Where my VTL Ichibans would transition from, say, ppp to ffff, the Pass would go only from ppp to perhaps ff. Don't get me wrongthe XA30.5 had dynamic range, just not as much as my larger, pricier, class-AB goliaths.
To be fair, I was running the XA30.5 well out of its comfort zone. Nelson Pass explained to me that the front-panel meter, which indicates the amount of current being drawn from the wall, "should sit somewhere in the middle" and "won't move if you're running in class-A." During most of my listening sessions, the meter would bounce between the middle and, say, the three-quarters point of its range. When I was listening to and for large dynamic swings, the meter would frequently be pegged. This didn't seem to bother Pass when we discussed it, though he did say, "Hmmm...so you're pulling a lot of juice." Well, maybe if I'd gotten those XA200.5 monoblocks...
On the other hand, the XA30.5 beautifully rendered the subtle, microdynamic nuances in more intimate material. With the volume set at a level that seemed correct for the material, my megaton class-AB amps would quickly and cleanly step between ppp and pp, but lost focus and detail at the lowest, pppp, levels. They sounded perfectly fineuntil I compared them to the Pass. With the XA30.5 again set to a level appropriate for the material, the difference between ppp and pp was, instead of a step, a continuous spectrum of subtly different levelseven the faintest, barely audible sounds were detailed. The unearthly voices of "Yulunga," from Dead Can Dance's Into the Labyrinth (CD, 4AD 45384-2), were exactly that through the Pass: voices rather than sounds. There were now different layers of microdynamic nuance within these voices' tonal components, which gave them a more natural complexity than I was used to hearing from this track. The balance of these layers would shift as the voice changed pitch or level, thus giving it a slightly different character. It's difficult to describe what the XA30.5 did in audiophile terms, but the way it reproduced these nuances flipped some internal switch of mine: instead of synthesizer, I was now thinking vocal cords.
Pure class-A amplifiers are often thought of as having a slightly dark tonal balance, but that wasn't the case with the Pass. Though it definitely wasn't bright, the XA30.5's tonality sounded pretty neutral to me. Male and female voices sounded correct, as did orchestral instruments from the cello up to the violin and piccolo. One of the most compelling aspects of the Pass's performance was how well it re-created both voice and instrument in a solo acoustic performance. One of my favorite examples was Townes Van Zandt's performance of his "Pancho and Lefty," on Together at the Bluebird Café, a benefit concert album by Van Zandt, Steve Earle, and Guy Clark (CD, American Originals SDPCD161). Not only were the tonal balances of his voice and guitar spot on, I left my listening room absolutely convinced that I would recognize his guitarthat specific instrumentif I heard it somewhere else. Another, similar combination that the Pass handled uncannily well was Diana Krall's voice and piano on her debut album, Stepping Out (CD, Justin Time 50). Both seemed exactly right, alone and mixed in a common acoustic space, and sounded consistently so across very wide ranges in pitch and level.
One characteristic that I have observed in a lot of class-A amps is a distinctive spatial presentation that can be grossly described as being deeper and wider, slightly more recessed in the center, and filled with smaller-than-normal images. This definitely did not describe the XA30.5's soundstageit was both wide and deep, with excellent resolution to the outer edges in both dimensions. If anything, there was an occasional tendency for soloists at center stage to be a bit more forward than with other amps, though in all cases, images were correctly sized.
With simple recordings made in real acoustic spaces, the distances and perspectives all seemed correct. While listening to one of my favorite opera recordings, soprano Mady Mesplé's performance in Delibes' Lakmé, with conductor Alain Lombard and the Paris Opéra Comique (LP, Seraphim SIC-6082), I noted how well all the pieces were tied together. I could place myself in the audience, in the hall; the characters were the right size, and moving around on a stage that was consistent with both their size and my vantage point. Even the orchestra pit was sized and placed correctly, without any spotlighting or segregation of soloists. The Pass's spatial performance was just as impressive with studio tricks. The barking dog at the beginning of "The Ballad of Bill Hubbard," from Roger Waters' Amused to Death (CD, Columbia 468761), wasn't next door, it was in the next countyand the infamous breaking glass in "Private Investigations," from Dire Straits' Love Over Gold (CD, Warner Bros. 47772-2), was not just across the street but at the far end of the alley.
The Pass Labs XA30.5 is the latest in a long line of brilliant designs from Nelson Pass. Its innovative circuit combines the best attributes of single-ended and push-pull architectures while sidestepping their respective weaknesses. It's a pure class-A amplifier with the power to drive insensitive loudspeakers while avoiding most of the stereotypical weaknesses associated with class-A operation. The design is a simple, three-stage configuration, but the elements that permit that simplicity to be practically realized are the subjects of multiple patents.
Most of all, the XA30.5 is a superb-sounding amplifier. I absolutely loved listening to music through it, album after album and night after night. It's simple to operate, nice to look at, and extremely well built. It will almost certainly extend the bulletproof reliability I experienced over the short term to a lifetime of use, and add to the stellar reputation that previous Threshold and Pass Labs components have established. Plus, in today's high-end audio world, the XA30.5 is a steal. Compared to what else is out there, a price of $5500 is low for an amplifier of this quality. No, I probably wouldn't buy one, but only because I think that a larger, more expensive Pass Labs model would work better in my system. Absolutely, positively, and enthusiastically recommended!