Review: Pass Labs XA60.5 monobloks Amplifier

Category: Amplifiers

Over the last twenty years I have had power amps designed and built by the audio legend Nelson Pass in my system. I still use Threshold SA-1's to power my MG-20's bass panels. I had Aleph 1's for over nine years, until I replaced it with an Edge NL-10, the only generation of Nelson Pass amps I did not like was the original X series, hence the NL-10. When Mr. Pass came out with the XA and X.5 series he won my sonic heart back. This will be my third review here on the GON of a Pass Labs amp. The progression of reviews started with the X-350.5 stereo amp, then the XA-100 monoblocks and now the XA-60.5 monoblocks. I believe that fans of Pass Labs amps come to a point were it gets harder to believe that Nelson can build that much better sounding of an amp then the last generation, but he does!

I never get into technological details because you can go to the website for that information yourself. The XA-60.5's are extremely well built, I find them to be "eye candy". Pass has made many important changes to this generation of XA.5 amps regarding parts, power conditioning/isolation, and the type of transistors used in the front end of these amps. The older AX series was class A but did not double down as speaker impedence dropped down. So, the XA amps were not a great match for very current hungry or difficult impedence load speakers. In hind sight it's amazing the XA-100's drove and sounded as wonderful with my MG-20's. My hunch is, since I biamp, that I had just enough watts/current to drive the midrange/tweeter without missing out to much on Macrodynamics on most music. The XA.5 series do double down into lower impedence loads and have much greater current ability. Since my MG-20's are a four ohms load, there is much better synergy between this amp and the 20's.

The most important part of any audio review, how did the freaking piece sound! Well, to express it in a calm way, the XA60.5's are the best amps I have ever had the pleasure to listen to in my system. Now the details why I feel this way:

1) The most natural/realistic timbres I have ever heard in my system. My all time favorite sax player is the late great Johnny Griffin the "little giant", who I had the pleasure of hearing live on more then twenty occasions, with the XA60.5's it's the closet I have heard to what he actually sounded like in my system.

2) I can't say that the soundstage got bigger with the XA60.5's compared with the XA100's, but the air around individual players and the layering became much more like the real thing.

3) These monoblocks have the lowest noise floor of any amp I have ever heard in my system. The music just floats out of a totally black background, therefore microdetails and decay trails are so much easier to hear.

4) The PRAT and dynamics of my whole system was taken to a much higher level, this is probably based on the XA60.5's having great current ability.

5) Image density and how 3-D each player sounds, yet not etched out, but intergrated with the stream of the music.

6) The last quality I want to share is also the most subjective and the most difficult to put into words. The XA60.5's are the most "musical" amps I have ever heard in the context of my system. They have an "easyness/liquidity/effortless" quality that just allows you to relax into the music and enjoy it. The XA-100's have this quality, but no were close to the level that the XA60.5's produce. Remember, this is not at the cost of microdynamics/prat or just making things sound euphonic/pretty, but the very subjective factor of "naturalness" whatever that is. Or to quote Robert Harley of the absolute sound, this from his review of the XA100.5's, " something extraordinarily beautiful about the sound. It was like slipping into a hot tub on a cold night; the music seemed warm, inviting, and enveloping. A stunning rendering of instrumental timbre,had an unparalleled sense of ease, and coupled a sense of delicacy with unfettered dynamics." I experienced the same qualities with the XA60.5's in my system.

I have said in every review I have ever written that there is no "BEST" when it comes to reference level gear because of personnal taste and system synergy. My perspective has not changed, I just would add the XA60.5's to the list of some of the most beautiful sounding amps produced today.

Finally, I would like to thank Kent of Pass Labs for always being patient with all my questions and Mark of Reno Hi-Fi for making everything so easy to get these amps in my system. Thanks, Guys.

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Onemug, it's been my experience that biamped MG-20's or 20.1's always sound/perform on a higher sonic level mainly because of using an active x-over vs. the passive stock one. Many owners of 3.6's have gone this way also, active x-crossover and a pair of amps.

I believe that the XA-60.5's would have enough current/watts to drive the 20's full range very well indeed, however for the above stated reasons I would not get the best performance because of that rather mediocre passive x-crossover. In my system I still have not found a better amp then the Threshold SA-1's for driving the bass panels of the 20's because of the hugh amuont of current that these amps can deliver.

I agree that it is really is great that starting with Nelson Pass himself and his co-workers for years, Kent and Peter, and now Mark at Reno Hi-Fi are all great guys who know there stuff, are totally honest and are great to do business with.

I wonder how do 60.5s handle microdynamics. I have had X-350.5, and although it was a nice sounding amp, what finally made me sell it, was the fact that it was just dead microdynamics wise.
Teajay, The reason I am curious is I am experimenting, in another system, with an active x/o driving 2 different amps driving my 2 way speakers.

I love the active x/o way, it makes amps happy. No doubt a powerful amp for the bass and something sweet and musical for the mid on up is a great way to go.

For my 2 way, I cross over around 3k so the experiment is with the "blend" of the 2 amps at that x/o and the octave above and below of course. I had good results with ss on the bottom and tubes on the top but I get a better blend with tubes top and bottom. Probably would work with ss top and bottom also but these speakers are great with tubes. It seems logical in that ss and tubes each have their own characteristics and asking them to shake hands from 2k to 6k might not give the best feel where tube to tube or ss to ss might be better. Remember the old saying, "better is enemy of good." It's a great hobby :-)

You may well have the best of the best. I used to listen to the SA-1's driving Apogee Duetta Sigs at my dealers way back when. I loved that sound. The X series didn't seem to have that "magic" but the XA.5's sure do so I'm sure your "blend" is fantastic and going back thru the old passive would not be a fair fight.

BTW, I agree with you on the "mediocre" stock x/o. The stock Maggie still remains a phenominal value but anyone interested in the next level should address the x/o. In my case, a friend (he used to be an authorised Maggie tech) sent me a pair of his customised x/o's. He believes in the active route but said this would get me close if I had enough power. With the XA100.5's, I'm pretty happy with it.
Elberoth2, since I had the 350.5 in my system at one time I can objectively tell you that the XA-60.5's are in a totally different sonic league and that would include microdynamics. The 60.5's have the lowest noise floor I have ever experienced in my system so you hear the smallest details emerging/floating from blackness. These details emerge with speed/quickness, these amps are the most dynamic I have yet had in my system.
Teajay, I just bought a s/h 30.5 to evaluate it in the context of my system. So far, no transistor amp I have tried (and I owned such an exotic amps as Lamm M1.2 Reference among others) could match the microdynamics and sonic purity of a good SET amp. The closest one I found so far is Dartzeel NHB-108. We will see how does the Pass XA.5 compare to the Dart.