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Review: Pass Labs XA-100 monoblocks Amplifier

Category: Amplifiers

I first would like to share a very brief history of what amps I have used before, in a bi-amped configuration, that came before the Pass Labs XA-100 monoblocks, to bring a perspective of why I believe these monoblocks are the best amps I have ever had in my system.

I have always bi-amped my MG-20's, which have been in my system for over 14 years. I still use a pair of Threshold SA-1's to power the bass panels. I used a pair of Pass Labs Aleph 1's for close to 9 years to power the midrange and ribbon tweeters of the 20's. I loved the warmth/musicality/richness of the Aleph's in my system, but became curious about some of new SS designs that were being highly regarded. At the same time Pass Labs had come out with their new X series amps, which I found to be much more dynamic/detailed/transparent then my Alephs, but were somewhat "cool" for my sonic taste and not as musical as the Aleph 1's. Finally, I auditioned an Edge NL-10, that was a terrific amp in that it had all the virtues of SS design, dynamics/details/extension, and still offered a very "musical/silky" sonic signature. So, I made the change and was very satisfied for over two years.

Then Mr. Nelson Pass and his team At Pass Labs came out with his XA series and X-.5 series. When I auditioned the 350.5 it knocked my "sonic socks" off because it had all the virtues of the Edge NL-10, dynamics/transparency/extension to a somewhat better degree, but added more realistic timbres, more air around players in a larger soundstage and finally what I just like to refer to as "musicality/liquidity" that just sounds more like real music to me. The 350.5 offered a few watts of single-ended class A before going into the next 50 watts of class A before finally going A/B biasing. So what would the XA amp's offer sonically, that only offer and stay in single-ended class A mode?

All the Pass Labs amps are beautifully built and are real gems visually, including the XA-100 monoblocks. I never in any of my reviews spend time on design or mechanics because its easy to go the website to get those details, I rather just share the sonics of the piece I have auditioned or have decided to put in my system. I believe informed audiophiles know that Nelson Pass is a genuis and his products have the highest build quality and engineering in high end audio.

I could give you paragraphs of audiophile cliches regarding the beauty of XA-100's, but I'll spare you and be succient regarding the details of their sonics. Everything that the 350.5, which still is a wonderful amp, had to offer was improved in what I call the "analytical" categories that audiophiles use to dissect the sound of amps. Yes, the Xa-100's were great in those areas, such as details, total and complete transparency, the most realistic and natural timbres I have ever heard, a top end that is airy and natural, midrange bloom but without losing mico-dynamics and decays, rock solid imaging on a realistic sized sound stage with most air and a three-dimensionality to the players that I have ever heard in my system. Good stuff.

But, what really amazed and delighted me was the "pure", I know this a very subjective, "musicality/effortlessness" of these monoblocks. Not "layed back" or a "fat tube sound", but just a true beauty that allows you just to relax and enjoy the music and not be aware of any specific aspect of the overall listening experience. Now, don't get me wrong, the dynamics,prat,drive of the music is there, but is offered in an overall perspective which just seems more natural compared to any other amp I have ever auditioned in my home system. Peter, one of the good guys at Pass Labs, had a great way to describe this quality," the XA amps just invite you into the music, more then other amps", its a great way to put the experience into words.

Please, I'm not saying these are the GREATEST amps in the world, their is no GREATEST, but the XA-100's I believe rank right up their with the other world class reference amps available today. If what I wrote has conveyed to any great degree what the XA-100's have to offer, I hope you might now be curious to hear them yourself and come to your own conclusions regarding their sonic virtues. These monoblocks are going to stay put in my home rig and I feel lucky that I could muster up the cash to keep them.

A final note. Through the years I have found the people at Pass Labs, including Nelson Pass, to be generous with their time on the phone, always willing to answer any qusetions, and I believe to be very honest regarding their products. Both Peter and Kent are fine gentleman, this time I spent more time harassing Peter regarding all kinds of matters regarding the XA amps, and he always answered my questions in a very informative and friendly way. Thanks Peter.

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teajay

Showing 10 responses by teajay

teajay OP
1,655 posts
 
Cwlondon, I politely disagree with Guidocorona, the sweet spot in Pass Lab .5 series is the 350.5 when it comes to a performance/cost ratio.

The 350.5 will easily drive a MG 1.6, 3.6, 20.1 or your older Maggies to a wonderful level of performance.
teajay OP
1,655 posts
 
Guidocorona, I too was concerned regarding if the XA amps would have enough current/drive to adequately power my MG-20's, that's why I first went with the 350.5 with great results. Remember, I bi-amp so the 350.5 was only driving the midrange panels and ribbon tweeters, not the bass panels. However, regardless of the type of music or volume levels that I normal listen to, the 350.5 never really moved out of its 50 watts of class A and maybe crossed over into A/B for a very few watts on the largest transient peaks. So, this lead to many discussions regarding the nominal ohm rating of Maggies, which is six, that they are not necessarly a hard load, but love current and finally their not the most efficient speakers as you stated in your post. Well, and I'm thrilled about this, I hear absolutly no strain, compression or distortion on any type of music or volume levels in my system.

To address your three main questions regarding the sonic differences between the XA-100's and the X-350.5 which lead me to make the change:

1) The soundstage is not smaller or bigger with the XA-100's compared to the 350.5, but I believe more accurately gives you what the recording has to offer. Also, since the XA-100's have the greatest image density and air around individual players with a three dimensionality I have ever heard in my system, the amps give you a sense of "intimacy" that kinda brings you closer to the source without shrinking the soundstage. If your listening to a big band recorded in a large acoustic space you get it, if if its a quartet in a small club that's what you hear. Now, remember, up to hearing the XA-100's in my system the 350.5 produced the best soundstage I had ever heard, compared to my Edge NL-10 a fine amp that came no were close to the 350.5's soundstage both in height or width and layering in the acoustic space, but the XA-100's are qualitatively better in my opinion.

2) I do not like to write descriptions of the sonics of different gear in highly subjective or mumbo-jumbo ways, however, sometimes its hard to describe special qualities only in analytical/objective semantics. In this case, its regarding your question conerning the authority of the XA-100's. Well, how about this fractured analogy, the XA-100's are the proverbial " iron fist in a silk glove". They offer great dynamics with terrific weight to the different players, yet at the same time are easy, relaxed, and airy at the same time. Hope that makes some sense to you.

3) The reason I decided to make the switch from the 350.5 to the XA-100's, and feel very fortunate that I can, mainly comes from a very special aspect that you get with the XA-100's, which the 350.5 offered a small taste of, which is these sense of "easyness/effortlessness/liquidity" that just lets me in a more natural way get more into the music. I'm not talking about an euphonic coloration or a fat over ripe richness I have heard with certain tube amps, but a wonderful ease and natural presentation that makes it easer to relax and enjoy the music I'm listening to. That does not mean that these amps lack impact or prat, I was just listening to Charlie Hunter's, Steady Groovin', and the music was rocking my room, but that special quality of drawing you in to the music was still making it easer to get into, in this case, the groove.

I enjoyed totally my time with the 350.5 powering my system for over a year and a half. I still think it's one of the best SS amps out on the market and will compete with virtually anything in a highly competitive way. The XA- amps will not power as well some very difficult speaker loads, were the 350.5 well sound and work better, but if XA-amps can control the speaker, I believe they offer something very few amps have in their sonic signture. Remember, at this level of gear , their are many great sounding pieces, so personnal taste and synergy are really the final determinant. For me the XA-100's are the best I have heard in my system. Please, Guidocorona, if I'm still not answering your questions specifically enough let me know and I'll try my best to address them in a more helpful way.
teajay OP
1,655 posts
 
Well Cdma, if you have the XA-100's already, I'm sure your system offers beautiful music to listen to on a daily basis!

I have always driven my MG-20's bi-amped and never purchased the passive crossover but always used a Bryston active crossover. The passive crossover from Magnapan is no longer available. In the past my experience has been that MG-20's have always sounded better when bi-amped then being driven by one amp through their own passive crossover. Besides, I'm using another Nelson Pass gem on my bass panels, a pair of Threshold SA-1's that I still great amps in their own right.
teajay OP
1,655 posts
 
Just wanted to share that I now have close to 200 hours running time on the XA-100's and the amps' sonic virtues are becoming more apparent as they break-in.

Even more of a commanding presence with rock solid images and great air around individual players, and yet they sound even smoother with greater liquidity then they did earlier on. Well, can they even improve more? I don't know, but boy, they sound pretty terrific right now.
teajay OP
1,655 posts
 
My major audiophile friend and buddy who has great ear's, always tells the truth, and is very experienced with Pass Labs gear just spent 4 hours listening to the XA-100's in my system.

He loves the 350.5 amp and thought before he sat down to listen to the XA-100's that they would not be that much better then the single chassis 350.5.

Well, to use his words, " these amps take everything to another level of refinement". He found them to be another step towards musicality and "ease" that is so pleasurable to experience when you hear it. He still thinks the 350.5 is a great amp, but now believes the XA amps offer even more "special stuff" then the .5 series amps.
teajay OP
1,655 posts
 
Islandbird, I wish I could refer you to someone I know who uses the XA-100's to drive their speaker full range, but I don't know anyone who uses them that way.

My strong hunch is that if your speakers do not go below six ohms and are 90 db efficient the XA-100's would have no problems powering your system. Also, you would be enthralled with their overall sonic signature, in that they have the magic of the older Aleph design with the dynamics/clarity/extension of the X series, and the bass is both gutsy with accurate timbres.
teajay OP
1,655 posts
 
Cwlondon, if you wish to go with monoblocks then you are talking about either the XA-160's or the X-600.5's if you are not going to bi-amp your maggies.

In my system I am able to use XA-100's, and saved close to $5000.00, because I only use the XA monoblocks to power the midrange and ribbon tweeter in my MG-20's. However, if you are going full range with your Maggies you would have to go up to the XA-160's or the X-600.5's to power them. Both sets of monoblocks retail for $18000.00.

Take a look at the last issue of the Absolute Sound were Anthony H. Cordesman wrote a great piece on both sets of monoblocks and compared the 600.5's to the older 600's. Their is no doubt that the new .5 series is a dramatic improvement over the older X series, however the XA series are still the best in the Pass Labs lineup, with the BIG if being they have enough current/watts to drive your speakers. Remember, the XA amps are single ended class A and do not double down into lower impedence loads, that's were the .5 amps come in that will drive any speaker load.
teajay OP
1,655 posts
 
Cwlondon, I would not necessary say that the Threshold SA-1's power my MG-20's bass panels better then a pair of Pass Labs X-600.5's would, but how much better would be the question.

Most Threshold and Nelson Pass fans agree that the best sounding amps that Threshold ever produced were the SA-1's. Remember, the SA-1's average 40amps and can put out 60amps, that's tons of current, which make them great bass amps with alot of control over any bass driver.

So, to replace my beloved Classic SA-1's, would cost me alot of cash, for not much of a change in overall performance. I see someone is selling a pair of SA-1's here on the Gon for around $3000.00 in mint shape, you might want to go for it, if you seriously considering biamping your Maggies.
teajay OP
1,655 posts
 
Cwlondon, I don't know if their is the "BEST WAY" to fill your room with monoblocks to power your system, but if we are talking about the greatest performance for the buck, I would recommend the following.

1) A pair of XA-100's on top with a pair of the older X-600's on the bottom.

2) A pair of XA-100's on top with a pair of Threshold SA-1's on the Bottom.

3) A pair of XA-100's on top with a single chassis X-350.5 on the bottom.

4) A pair of XA-100's on the top and your ML-23.5 on the bottom.

I believe that biamping your Maggies with Pass Labs XA amps on top would bring your system to a totally higher sonic level then you have now with the 23.5 running full range.

On a totally different topic, I looked at your system, and would highly recommend that you might audition Acoustic Zen's Silver/Matrix reference II IC's and Satori speaker wire to replace your Transparent wires. I used to run reference level Transparent wires in my system and found the Acoustic Zen wires to be a wonderful match/synergy with both the Pass gear and Maggies.
teajay OP
1,655 posts
 
I just got through reading the only professional review that I know of regarding the XA-100's, from the French journal, Haute Fidelite, written by Mr. Laurent Thorin.

Mr. Thorin, stated the following," Low end incredulous energy and precise... Mids were astonishly rich and fluid... Voices were unsettling real... Highs materialized with subtlety and delicacy". He also noted that the XA-100's, " sounded 2 or 3 times more powerful then their actual 100 watt rating". Thorin bestowed the highest honor that his journal offers, the "Haute Fidelite Reference Designation" on the XA-100's.

I guess he liked the XA-100's to say the least! It's fun for me to hear/read how other audiophiles use language to describe their experience of gear that I am already familiar with. Mr. Thorin uses a different vocabulary then I did in my review, but came to the same conclusion, the Pass Labs XA-100's are one beautiful sounding pair of monoblocks.
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