Publisher Profile

Pass Laboratories XA160.5 Monoblock Amplifiers Review

By: |

With the Salk Soundscape 10 speakers

A nice contrast to the Whisper DSW is the Salk Soundscape 10 which I have reviewed. This is in some respects quite the opposite design, and as such shows the dexterity of the XA160.5 in handling divergent speakers. The Soundscape 10 employs from the top down, a RAAL ribbon tweeter, ceramic Accuton midrange, custom 10-inch long-throw woofer and twin custom passive radiators. The radiators are side firing, and the mid and tweeter can be configured with their physically separated cabinet either open or closed at the back. Though both speakers are a nominal 4 Ohms impedance, one of the most telling specifications between the two speakers is the 84 dB sensitivity rating of the Soundscape 10 versus 95 dB sensitivity for the Whisper DSW.

Here is where Class A earns its keep. Put a low bias class A/B amp, even one with 300 or more Watts on such a speaker and it will seem like an invisible power sponge has sopped up half the amp’s energy. You’ll have to turn the dial up, and keep turning it up until at times it seems you’re going to break something. In most cases nothing will be broken –- except the sound. The impact of the bass may falter, the dynamic thrust of the low end might stall and often the sound will grow more strident, more strained. When I employ the twin Pathos Classic One MkIII tube hybrid integrated amps in Mono mode to drive the Kingsound King ESL speakers, which have comparable low sensitivity of 83 dB, the demand on the Pathos units is considerable. The digital readout on the volume control is nearly double the reading as when using the Whisper DSW!

Another amp which can be taken to its limit with the King ESL is the Cambridge Audio Azur 840C, which is rated at 350 wpc into 4 Ohms stereo, and a whopping 800 Wpc into 4 Ohms when bridged. I purchased two of these amps thinking 800 wpc would be terrific. Later, when I acquired the King speakers I discovered a limitation as the amp is incapable of handling the sub-2 Ohm load; when I tried running them with the King the bridged 840W’s didn’t even get out of the starting gate –- they crashed, tripping the protection circuitry. Cambridge’s clever protection circuitry was well worth the money, as no harm was done and minutes later I was up and running, but in stereo, not mono. C’est la Vie, there goes a potential 800 wpc.

All it takes is one experience like that to give a person a profound appreciation for the “nuke-proof” operation of the XA160.5. Essentially, if you put one of those “pretty boy” low current amps on a tough mother of a speaker, they cave. Not so the Pass; if the speaker resists, the amp pushes harder –- always. No speaker sounds anemic with this amp. I’ll say that one more time in case you didn’t catch the importance of it; no speaker sounds anemic with the XA160.5 .

Why is that such a big deal? Because anemic sounding speakers tend to be either boring or irritating, they lose impact, and often timbral correctness. It is not uncommon when an amp is driven closer to its limit that the music becomes flattened and shrill. I’m exaggerating a bit, as it’s not as though a flute begins to sound like a bagpipe. However, the movement of the sound is in that direction. When the current is high enough, as in the XA160.5, all the music floats through the speakers as though carried on a mighty river. Does the Mississippi river slow down whether it’s carrying a small sight-seeing boat or a large barge? No, and with the high current, high bias of the Pass, no speaker presents a significant enough burden to slow the amp down appreciably.

Pass Laboratories XA160.5 Class A monoblock amplifiers

With the Kingsound King ESL speakers

What they say about power and panels is true; you need lots of it to get the best out of an electrostatic or magnetic planar speaker. I have concluded as a casual rule of thumb that 250-300wpc is needed for these kind of speakers to sound their best. Often, the audiophile has to make trade-offs, typically in the area of dollars for Watts. One could go the low power/high efficiency speaker route, but that will not get you panel sound, or if it does, the speaker will suffer in terms of macrodynamics, and likely microdynamics as well.

However, usually one has to attain such power via a Class A/B or Class D amplifier. That is a problem, as most are noticeably more veiled, lacking in that virtuous quality in audio called clarity. Rarely have I found cleanness of sound in an A/B amp approaching that of the XA160.5. In comparison with the amps I currently am using, such as the Cambridge Audio Azur 840W, the hybrid Pathos Classic One MkIII, and even the venerable VAC Phi 200, the Pass shines brightly in this area. The Class D amps I have used have a lovely quiet and precise character, but leave something to be desired in terms of the robustness and richness of their tonality. The VAC is weightier and as rich, but is not as pristine. The Classic One MkIII in Mono mode, even when streamlining the system by eschewing a separate preamp, still is not quite as clean as the XA160.5.

The pairing of Class A and ESL, if the amp is powerful enough, is quite rewarding, especially for lighter acoustic and vocal pieces. My wife enjoys Joni Mitchell’s “Night Ride Home,” which features crickets chirping in the background as Mitchell croons in a trill-like fashion. The mood of the piece is supposed to be soft, gentle, as still as a moonlit night, and the ultra-clean XA160.5 does not occlude the mood. One can rest assured that whatever speaker the Pass amp is used with it will not stolidly stomp, but rather tiptoe through the music.

Welterweight sound

I have used the boxing analogy previously in articles to give some sense of the gravitas of the sound of a component. Using the classic categories of “Lightweight, Welterweight, and Heavyweight,” these terms economize in description of what others call body, heft, presence, etc. One might think that the XA160.5 would, by virtue of its being a high current, high bias design, be a heavyweight amp. While it does weigh a lot, it is not sonically heavy-handed, but rather middling. It is evident that a great deal more fortitude is available than the XA160.5 delivers, considering that the company makes their own A/B designs up to 1,000wpc!

To determine, then, if the XA160.5 or a larger Pass amplifier must be procured, the customer needs to determine for themselves which characteristic is most influential in their enjoyment of the music; the cleanness or the impact? To make a rough analogy, visualize the Pass X and XA series of amps as differing weights to be dropped on the floor of your listening room from ceiling height. Consider the ”X” series to be particularly powerful sounding when they smack into the floor, and the “XA” series to be particularly clean sounding when they smash into it. Obviously, the beefier the amp, the more “impactful” it will be. In the most simplistic of terms, the degree of cleanness is determined by the type of amp, but the amount of slam is determined by the force of the amp. A Class A, 160-Watt amp will typically produce more Glam than a comparably built A/B design at 160wpc, while the A/B design will typically produce more Slam. However, the great advantage of the Pass XA160.5 is that it is better designed and built than most A/B designs, and consequently renders a sensation that it is impressively impactful for its power, as well as being ultra-clean, in other words, slam-glam!

Nelson summarizes his philosophy regarding his Class A amps, “I’m not here to pound loudspeakers into submission, rather I want to exhibit the same smooth linearity at high power levels that I get at low power.”

Applying these descriptions to the experience of listening to music, a nearly violent musical score — the Pirates of the Caribbean: The Curse of the Black Pearl soundtrack — is chock full of monstrously large low end barrages. I use track 7, “Barbossa Is Hungry,” to assess how much of the seeming mishmash can be straightened out. Systems will typically lean one way or the other, either toward the dynamic impact end of the spectrum with a high degree of opacity to the symphonic crescendos, or conversely clarify them but lighten up their impact. The XA160.5 does both well, allowing the identification of individual notes rather than one long, roiling sea of low frequency breakers upon the shore of my ears.

Memorable experience

Hearing a Pass Amplifier is a memorable experience, whether at a dealership, a show or in the home. There were several memorable moments in using the XA160.5, and among the best was hearing older selections sounding as though they had undergone “highlighting” treatment. By use of the word highlight, I mean an acoustic process not dissimilar to highlighting text in a book. When one wants the message to stand out a highlighter brings attention to it, whereas a permanent marker obscures unwanted text. Similarly, an amp will either have the effect of highlighting or obscuring the “text” of the music. One can hear precisely how much of a highlighting or obscuring effect is happening by switching amplifiers in an otherwise stable system.

To that end, a person who wishes to spend a lot of time with older, more poorly recorded media will want to consider the Pass XA.5 Class A amplifier lineup. Typically, older recordings to my ear lack the spunkiness, the vivacity of contemporary recordings. Whereas many amps can make them more defined, the XA160.5 makes them more noticeable in terms of not only definition, but also timbre and pace. A good example is Alan Parson’s Amonia Avenue, which has typically come off as fairly dead and flat, seemingly mastered by some obscure relative rather than the master himself. I had all but given up on this disc and title track, thinking it a poor reflection of Parson’s skills – until I put the Pass amps into the rig. The highlighting effect took the piece from obscurity to vibrancy, dispensing with a sense of “electronic lactic acid,” as it were.

Lactic acid is an agonizingly frustrating reality to serious athletes, as it saps energy and motivation; the muscles are pushed harder yet work less efficiently. But there are the odd exceptions, in particular Dean Karnazes, otherwise known as the “Ultramarathon Man.” Dean is a freak, as his lactic acid level actually drops as he pushes his body harder during exercise. Consequently, he says he feels better after a 50-mile run than before! Why can’t I have this problem?

The sluggishness, the latent dullness of some amps strikes me as being similar to lactic acid; it stiffens the performance. The XA160.5, however, is like Dean: a lean, mean, performing machine. It’s strong but nimble, and digs deeper to retrieve nuances than any amp I have used in seven years of reviewing. Consequently, there is no listening fatigue, no being worn out by the blunt trauma of forceful but indistinct bass, nor the temptation to run and hide to escape an etched top end. From the start, the XA160.5 is a winner, one which I never tired of hearing.

“Can’t Go Wrong” amplifier

There are a fair number of things which can go wrong when selecting components to assemble a very high end system. While a myriad of combinations make sound, many are “wrong” in fundamental aspects in that, if paired together, a major compromise will result. Select the wrong amp and you will find yourself fighting to make things sound right. The fundamental rightness of the XA160.5 makes it a superior selection for nearly any serious stereo and speaker technologies including dynamic, planar and horn.

When a sale is assuredly complementary to the customer, the phrase, “You can’t go wrong,” is often applied. In some cases it is true, while in many cases it is not. In the case of the XA160.5 the elegantly designed, high quality internals make it a true statement. You can’t go wrong with it because it is the epitome of good design, producing an ultra-refined sound suitable for a wide range of speaker applications. It is powerful enough to tackle inefficient speakers. It is also affordable enough to the extreme audiophile that it can be a ‘statement’ piece for any system without embarrassment, able to redeem countless numbers of attending components from audio purgatory. I used it in rigs averaging $75K to $100K and can in good conscience recommend it in systems well above that level. It is the kind of device you do not want to give up, whether or not a well-heeled stranger in a Rolls Royce asks you for it. I suspect that once one graces our system you may swap other components, but the XA160.5 will stay!

Associated Components:

Source: Simaudio Moon Evolution 750D DAC/Player; Cambridge Audio 840C; Denon 2900 Universal Player; Sonos Digital Music System; Oppo DV-970HD
NAS: Buffalo Linkstation 500G
DAC: Eastern Electric Minimax DAC Plus with Burson and Dexa NewClassD Discrete Opamp Upgrade
Preamp: VAC Renaissance Signature Preamplifier MkII; Purity Audio Design Silver Statement; Cambridge Audio 840E
Amps: VAC Phi 200; Jones Audio PA-M300-1-2 Monoblocks; Cambrige Audio Azur 840W
Integrated: Pathos Classic One MkIII stereo tube hybrid (two units bridged to mono); Peachtree Audio Nova
Speakers: King’s Audio Kingsound King; Legacy Audio Whisper DSW; Kings Audio King Tower Omnidirectional; Daedalus Audio Ulysses; Eminent Technology LFT-8b
Subwoofers: Daedalus Audio BOW
IC’s: Clarity Cable Organic RCA/XLR; Tara Labs RSC Air1 series 2; Wireworld Equinox; Wireworld Silver Eclipse; Wireworld Platinum Eclipse
Speaker Cables: Clarity Cable Organic Speaker; Tara Labs RSC Air1; Wireworld Equinox 5; Wireworld Silver Eclipse
Digital Cables: Clarity Cable Organic Digital; Tara Labs RSC Air 75; Wire World Startlight 6; Wireworld Gold Starlight 5, Wireworld Gold Starlight 6
Power Cables: Clarity Cable Vortex; MIT Oracle ZIII; Tara Labs RSC Air; Xindak PF-Gold; Wireworld Stratus 5, Electra 5 and Silver Electra
Power Conditioning: Wireworld Matrix Power Cord Extender; Tara Labs ISM Power Screen; Tice Audio Solo

Leave a Reply

Your email address will not be published. Required fields are marked *

This site uses Akismet to reduce spam. Learn how your comment data is processed.

Popups Powered By :