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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 5 responses by islandbird

islandbird
15 posts
 
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
15 posts
 
Teajay,
Thanks for the perspectives. I was also considering the XA160 for the extra wattage, but reasoned they are just too large and crank out too much heat to justify those 60 extra watts. Another sixty isn't all that much anyway once you have that first 100 in place.

I know I'll love the sound of the XA100, but I'm trying to get a handle on what I might miss (if anything) that the 350.5 provided before it slips away. Sort of trying to second guess myself in advance for a change.

I'd considered an Aleph 2 before I bought the X350.5 but reasoned that most available units had already had too much current over the dam. The only pristine pair I saw advertized was snapped up in a hurry. The XA100 was the logical alternative....wish I'd followed my instincts. Once one gets used to that SE sound, it's tough to settle for anything else.
islandbird
15 posts
 
According to Nelson Pass, himself, the X600.5 is the best all-around amp he has ever designed. SA-1 fans can join the Threshold SL-10 preamp fans and stasis fans, etc. but there's no getting around the fact that the current amps are better in almost all respects. Just read some of the "white papers" Pass has written concerning the evolution of his designs and class A designs in general. Some of the best aspects of his earlier designs have carried over, while he has repudiated many others as wanderings down blind alleys to make certain aspects of specific designs work, but they ultimately proved to not work as well as his simpler approaches.

From what I've managed to glean from all sources, the XA amps are the best sounding amps his primary outfits have ever produced (given the known power/compatibility caveats), and the X350.5 being the best stereo amp and the X600.5 being the best mono and therefore the best X.5 amp in the lineup. The X350.5 is the best bang for the buck in the current line-up and is all the amp most of us will ever need, and it will drive anything from Maggies to MBL's.

As for the XA amps, there are those that claim the XA160 offers the best balance of sound quality, price and power. However, within it's power band, the XA100 is the sweetest, cleanest and therefore the best sounding amp of all.
islandbird
15 posts
 
Tboooe,

I've had the 802 (standard) in the house for an extended audition and they are very lively speakers. IMO the XA160 would sound the best with that speaker as the BW's could use a little softening and warmth. Power is still an issue, but I think you'd be happy with it provided you don't have a very large room (over 150 cu meters) and like to listen at 95db average and above. The 600.5 would be very good as well and would never be lacking for power with any speaker in anything short of an auditorium. I'll bet the X350.5 would also be a great match at about half the price.

I doubt if you'll get anyone at Pass to recommend an amp for those speakers as there are too many variables. Even if they were to recommend an amp they would likely err on the side of more power.

Not knowing what your tastes/room situation are, I or anyone else can only tell you what we like, it's up to you to identify what type of sound/listening you prefer and narrow your options accordingly. People claim that there's a Pass "house sound" but the X.5 and XA amps are distinctively different in what to me are some critical areas. Anyone forming opinions based upon experience with the original X series really needs to update their perspective.
islandbird
15 posts
 
I'm not surprised, they will always recommend a healthy surplus of power. If I recall correctly, the claimed specs for at least the earlier 802 were somewhat optimisted as it had at least one dip down into the 3 ohm range. If so, the XA160 might have been cutting it too close.

As I said before, I prefer the sound of the SE amps, but if you really like your 802's, you'll love what the 600.5's do for them. However, if price were more of an issue, I definitely think you would find that the 350.5 has all the power you need.
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