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.

Associated gear
Click to view my Virtual System
teajay
just b/c the amps act differently when plugged into same outlet does not mean that DC isn't the problem. could simply be one amp is more susceptible to DC. get a multimeter and check if you're getting DC out of the outlet.

if no DC and you'd like to try self service, try tightening the mounting bolt of the tranny (prob need to remove top cover of amp, though might be able to from the bottom without removing anything). another option, more invasive (and your dealer should handle) is to take the bolt out of the tranny, raise it up a tad and put some damping material b/w the tranny and the bottom of the chassis--this is mechanical decoupling, and usually effective).

very unlikely anything is wrong w/ the amp. buzzing trannys are a very common problem IME.
I have the XA160.5. Like Teajay, I hear a VERY slight hum from each amp if I put my ear directly on the top plate above the transformer. I assume this is normal. It was slightly louder with my old XA160. I'd talk to the dealer and then Kent at Pass Labs.
Wonderfully informative review; wonder if you plan ever to review your pair of SA/1s? I'm thinking about a Soderberg-ed s/500 (his modification to Class A channels, if I ken him right, is the one-chassis equivalent to an SA/1 pair). I'm thinking of this, vs just getting an XA30.5, since both would come to about the same total on the 'Gon. I'm assuming similarity other than raw power between 30.5 and your 60.5, which is why I'm interested in your own assessment of the SA/1s. And just out of curiosity, have you ever switched the SA/1s for the XA30.5s on your MG20s?

Thanks, Doug
Hi Doug, thanks for your kind words towards my review. To address your questions:

1) Because the SA-1's have been around for almost twenty years I never felt the desire to write a review on them. They still very favorable compare to the best SS amps built today, including Pass's own designs. Smooth, rich, natural timbres,great sound staging, with great bass contol and punch. I believe they might not be quite as detailed/transparent or quick/fast as the XA-.5 series. However, if you get the full monty upgrade from Soderberg it might be very interesting which amps you might like better. I not replaced anything in my pair of SA-1's, including caps, however I'm waiting for new caps from John to install in my pair to see what these better caps will give me sonicly.

2) No, I have not switched out the XA-60.5's with the SA-1's to power my system, but will try that experiement when the new caps are installed. The SA-1's deliver terrific current so they are great bass amps on my MG-20's bass panels, so I have always used them in this way after I got the Aleph 1's for the midrange and high end which sounded better then the other way around.
Thanks for your [again informative] reply. I'll try to remember to keep tabs on your system over time to see what you find out. Haven't seen an s/500 of the later serial #s that Jon requires to enable him to do that F Monty mod [hey, a great name - you'll haveta suggest it to him] for quite some time, so maybe I'll pull the trigger on an XA30.5, since they keep showing up used.

Thanks again,

Doug