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
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.
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, thanks for the review. I currently use the X250.5. Hopefully when finances allow, I'll follow your path to the XA's! The 250.5 was mind-bogglingly good compared to my previous amps. Nelson Pass is a genius indeed.
Teajay,
I agree with your perspectives on the X350.5. I've had one for a year or so and agree that it's very good. However, it lacks that certain something that I had with my Aleph 5, which was supplanted by an X350 due to its lack of power. The 350.5 is a very significant improvement over the X350 throughout the spectrum and in listening ease, but it lacks the naturalness that the single-ended Alephs provided. I'm now considering an XA100 for just that reason.

One thing that I can't answer and one that gives me some pause is the XA100's performance on bass. The 350.5 is great in the bass department (although I wish it didn't have such a high damping factor). Biamping, using a 350.5 to drive just the mids and treble seems a huge overkill, but that's your business. I have speakers that are 90 db efficient into 8 ohms and dip no lower than about 7.

Since you don't use your XA100s in that regard, I suppose you can't tell me about their performance driving full-range speakers, but do you know anyone who has used them in that regard?
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.