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
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teajay
Hi Dev, it's good to hear from you. I have called you at least a couple of times in the the last 3 to 4 months to get your opinion regarding a few things audio, but was not able to get of hold of you. I have not replaced the fuses in my MBL transport. Please share what sonic benefits you heard when you did. Talk to you in the future.
I have XA-30.5 driving JM Labs Electra. It's a very musical sounding amp. Bass handling is just phenomenal. It excels in macro dynamics, but not a slouch in micro dynamics. But I think my previous Pass amp, First Watt F5 was better in micro dynamics and delicacy. F5 has a lot of similar qualities of good SET amps. They both sound warm and liquid. In fact I think XA-30.5 sounds warmer and F5 sounds more neutral. They are both great amps.
Teajay,

Thank you for the excellent review. I use four Quicksilver V4 tube amps to power the mids and highs of my custom 3-way active Magnepan 3.6s. They are wonderful amps--pure beauty in the midrange--but I feel like I'm missing out on the last word in top-end extension and dynamics.

It seems like I could get away with two XA 30.5 amps, seeing as I'd need a channel for each driver. However, I wonder if there would be any sonic detriment to going with a non-monoblock configuration.

-- Nils (neuro on the Planar Asylum)
Hi Teajay,

Great review on the XA60.5, it certainly help me in my decision for getting a pair.
i just received the pair from the local deal and I am enjoying it very much like what you described. Breaking in seems a long time for now.

I have a concern though as my audio room is not huge which is about 4mx3m and I am sitting about 2m from where the XA60.5 are placed.
on one of the mono block, I could hear humming sound when switched on and when the no music is played. The room is quiet but it seems one of the mono block has a louder hum than the other. Thinking this should not be normal.

Have you had experiences with your pair of XA60.5?
I am thinking hard how this can be rectified, does connecting the gounding pin at the back of the humming amp solve this?

Cheers
Hi Elmerpoh, my assumption regarding the hum is that it's the transformer that you are hearing. I'm a little confused regarding what you refer to as the grounding pin, if your running RCA's single ended IC's the grounding pin on the XLR's has to be in place. So, if you are running single ended cables by all means put the grounding pin in place.

Otherwise I would call Pass and talk to Kent about the noise you are hearing. If I put my ear right above the chassis of my amps I can hear a very slight hum from the transformer, but I mean very/very slight hum. So, check the pin and if its in place and you still get a noticable hum give Pass a call.

I hope you are enjoying the sound of your 60's as much as I do and congrats on your new babies!