Nelson Pass to put it lightly, is a f&*king superhero of HiFi! The legacy of amazing gear, his annual "amp camp" , and of course First Watt! Not only does the man sincerely encourage DIY cloning of his designs, he will personally assist you in doing so via his message board. Ive had my eye on a DIY kit for the "Aleph" amp im hoping to put together soon. Wonderful human being!

I really like your approach with emphasis on simplicity and good quality design.

I owned the XA25 for almost 2 years and thought it was fabulous! The only reason I let it go was for the SIT3 Amp which is slightly richer with more bloom.. The XA25 is transparent without sounding sterile or edgy. It has weight and great bass control with a realistic midrange. Plenty of power for most speakers and renders piano better than any other amp I have heard to date.. Simple design with less being more pays off big in SQ.. Another masterpiece by Nelson and company..

Another great video, Harley! It was a pleasure having you visit my showroom in West London :) I like your philosophy on simplicity and getting the power amplifier right - this approach is also very useful as source components (especially digital front ends and DACs) are changing so fast one may want to upgrade those after a few years - and a good power amp (or an integrated with no digital inputs) will remain a constant.

Very nice review. Simple and straightforward as usual. Lots of wisdom. Thanks for sharing. Really want to try your speakers one of these days.

Thanks Harley for another insightful review of this Pass XA-25 Power Amplifier I really enjoyed it.

Thanks for another great review, Harley. I live in New Zealand and own a PureAudio pre-amplifier and, perhaps amazingly, I had no idea that Gary Morrison had passed away, so I was obviously immensely sorry to hear about that. It will be a great loss to the local hi-end audio industry. The pre-amplifier is outstandingly good. You might also be interested in hearing that I've built my own class A amplifiers, based on the John Linsley Hood design from the 1960s that has been updated by Geoff Moss who has provided a more up-to-date method for accurately adjusting the quiescent current and output offset voltage as well as increasing the power output to around 50 watts into 8 ohms by doubling the number of output transistors. It's a really lovely sounding amplifier and I built two for a monoblock configuration. Furthermore, they are as silent as the grave when idling.

The local audio society is holding an audio meet in October and the Sibelius is the guest of honor... In preparation I auditioned a demo pair and I have to say that these speakers are just what I expected them to be (in a positive sense): accurate tone, very fast transient response, pinpoint soundstage and just enough of quality low bass to not need a sub for most music. They sounded really clean driven by the LTA Z10 integrated amplifier with 12wpc from a push-pull EL84. This amp features the Berning ZOTL switchmode impedance matching circuit but it sounded just like any other EL84 amp I've heard: clean and musical with excellent bass control. The Z10 has a tube preamp section and linear power supply and it's internally shielded to minimize noise. The attention to detail in its construction is very obvious. We did try the bigger EL34 ZOTL power amp with 40wpc and it did not impress us during the short listen. Perhaps the setup wasn't perfect to judge that amp, but what we heard from the smaller Z10 was really good so we finished the audition with it. The Sibelius speakers did not need more power in the small (maybe 20x20 ft) room with extensive acoustic treatment. I hope to try another Nelson Pass amp with the Sibelius. It's the single-ended Zen with the current source load, minimized to 3wpc (while burning 65 watts, not very efficient...) into 8 ohms and tweaked heavily (for example, bare electrolytics with Blu-Tak for vibration control). That amp works great with my DIY single-driver speakers (vintage drivers, not MarkAudio) and I expect it to sound just as good - or better - with the Sibelius.

In my HiFi journey I had for a few months a Pass X350.8 and I’m sorry to say that I came to the conclusion that it started sounding, for lack of a better word, generic. I’m on Conrad Johnson Premiere 12 mono blocks with a CJ Premiere 17LS preamp and I’m almost there but still doing setup. I think I’m really a tube guy although sometimes the Pass sounded phenomenal but I couldn’t live with it. It wasn’t for classical music.

Excellent review. I run my Sibelius speakers with the same amplifier. Your review is spot on!

Another simple, to the point, lack of hyperbole video from you. Great work. Wish to sample this amp sometime.

Great review Harley, certainly a stereo system to lust for, thanks!

I hope I don't come across as a troll and bother you here too much! I just want to make a technical comment about the XA25. The website says it's Push-Pul Class A. So it's not pure Class A. In fact, it is difficult to make an amplifier with transistors, be they FET or Mos-Fet, in pure class A. Push-Pull Class A is not actually Class A, that is, it is and it is not. The amplifier has a splitter that divides the signal into positive and negative alternating which is distributed to two amplifier branches, but these branches are already biased to class A, that is, the transistors on these branches are already open all the time and just waiting for the signal. In class AB or B, these two branches after the splitter are biased with a very small current that does not fully open them, and practically the transistors open and are fully biased only when the audio signal appears. So we are dealing here with a trick, which is welcome here, which reduces the noise and associated distortions that Class B biased transistors produce when they switch on and off when the audio signal is applied to them.

What a wonderful video...!!! (as usual) Thank you....

Another great review Harley. I jumped into the Song from Tidal right after and can duplicate everything you said except I couldn’t pin point the locations of male and female singers behind and it seems really close together. Also drum, harmony and back singers are close behind not way behind in my system which consists of a Linn Klimax DS/ Lavardin p62/mono blocks driving a pair vintage JBL 4343. Very wide front baffle of JBL are not great for pin point image but Lavardin helps bringing some of them back. Thanks again!

Nelson is to Amplifiers as Einstein is to physics.

Nelson Pass is a legend.

Great video. Wish i could own one, but it is a lot of money. I have sugden A21 SE now and i feel it has the magic for less then half (considering you have to buy a pre amp as well)the money.

I put it against my First Watt M2 and it’s a different profile altogether. Oddly I have preferred to listen to the M2. The INT25 is worth a listen I understand. Good for an integrated based system…

Nelson Pass designs amplifiers to be as musical 10 years later from the day of release. It usually works something like that. I believe that an x-30.8 was just released and that's not quite 10 years. But it's around 8+.

Wonderful video brilliant.thank you sir music on.

Ya know, I’ve been so burned by guys doing reviews like the Tekton speakers I bought but Harley is different because he speaks like a musician and because of him my next rig is going to be a Pass with Sibelius speakers. I’ll just add that when I wrote Pass Labs, Nelson wrote me back himself.

Measurments show that Nelson is very conservative with the power rating and that it realistically putting out around 80 Watts continously with music and ca. 70 with a sinewave, and thats not even what it is able to dynamically swing in short bursts. In short - more than you will ever need for almost all speakers out there.

PassLabs XA25. Yeah, but it is really important to tell us what preamplifier and what front-end, Turntable-cartridge-phono pre-interconnect cables you have used. Most of the sound signature of any audio system comes from the front end and pre.

I love this Amp

Nelson Pass has a different amplifier for every day of the week and no two sound exactly alike.

Pass makes beautiful amplifiers. If you have the opportunity, I'd suggest having a listen to Riviera Labs -- newish Italian brand making some incredible Class A amplifiers.

Nice review! Have you tried the XA25 without a preamp and directly from a variable level soruce? This way usualy sounds cleaner but sometimes, and with very clean sounding amps, may sound a bit lean or sterile...I love to know if this amp keeps sounding clean but not lean or sterile used that way. Thanks!

When an amplifier sounds right ..................few are...............modern loudspeakers need amplifiers that kick them in the but. For pure high end sound ..........NOT for natural sounding speakers who play MUSIC ! That's why they like class AB .............class A will flower and develop their flavour with speakers like yours. High took another road..............speakers and amplifiers should be build like instruments ........

Hi Harley. How would you compare the Pass labs XA25 with say the Sugden A21SE Signature Integrated Amplifier?

Hi Harley its Paul t.

If you think an X-25 is good, try a XA-100.8 along with a Pass Labs XP-22 front end. When you play this combo, broken in, you’ll wonder why you didn’t do it sooner. As the saying goes, time lost is never found again. Why subject yourself to anything less than superlative?

Are you willing to try an experiment...? should work on full range drivers like that I've done it on tweeters soft dome and works very well. Plus you could pull the driver Down half an octave without losing any top end I think the Nelson pass amplifier would work well with KR audio preamplifier p135 opinions! should be a good match that's a good preamplifier How does a chord amplifiers work with your speakers and a ACT amplifiers. UNISON research integrated amplifier unico might work quite well have you tried it?

Harley, really love this channel, thanks for taken the time to make it. Have a question for you, if you don’t mind. I am running Supratek Cabernet pre into Belles SA30 class A power amp into my Graham Audio LS 5/9 speakers, unfortunately the gain on the pre and the power amp is a mismatch, the pre is from the designer info “Output z is less than 100 ohms, voltage on 300b is about 6v” now the Belles only need 0,7v for full output, so you can see that I don’t have mush volume adjustment before it gets too loud. The Belles has no problem driving my speakers, do you think the Pass Labs would match better with my pre amp ? Thanks! Ps. Love the videos you did discussing albums and the way they are produced and sound, would like more of those if possible, the last years I been listening more and more to jazz and classical, probably something to do with passing the big fifty 🤔

Hey Harley. Great video as always. How are you liking Accuphase amplifiers?

I have an XA25 arriving in a couple of days. Now, how do I get a pair of your speakers in Southern California???

Thanks!

Hello. I’ve only just made aware of your speakers and your channel (thank you algorithm) and I find them both very interesting. You mentioned the cone types of your speakers in this video and just wondered if you still made the Sibelius “P” with the paper cones? When I click on the corresponding page on your site, it just comes up with a 404 error. Thanks 👍🙂

🙂 listen to his model F8!

Great video thank you, what is the preamp that you are using.

May I know what kind of preamp using with XA25?

Very timely video. Just heard from my local distributor that my XA-25 is about to ship! Looking forward to hooking it up to the Sibelius with the PrimaLuna EVO 300 as the preamp. In the US the XA-25 is a bit cheaper, at "only" US$4,900. There is also a saying of "Buy once, cry once". I remember form past videos that you commented about heat output and summer vs. winter amps. The class A design indicates lots of excess heat, but at relatively low power rating of 25W it may not be that much. Would you consider it only a winter amp, or an all season amp?

Great review! How warm does the amp get after several hours? Thank you.

Audi A6 is a nice(r) VW :-)

Yikes if its like an Audi A6 its going to bore the socks off me. Best stick to my valve amps!

My Pass Labs INT-25 pairs perfectly with my Sibelius loudspeakers. As I understand it, the INT-25 is the simple-philosophy version of the XA-25 but as an integrated amp. Sound is liquid perfect and yeah, 25 Pass Labs watts feels more than enough. Volume meter goes up to 63 and I've never pushed it past 50. 30-42 is a good listening range. I forgot ear fatigue was a thing.

Gryphon audio is another great company

How would this compare to Lyngdorf 3400?

Problem with Audi A6 analogy is it’s not reliable, like all German cars.

Talk a lot, and say nothing.