Pass Labs AMP’s- What is the best Pass Amp Sound for You from past 10 years


So I have an XA-25 and its outstanding. I’ve tested the XA60.8 mono’s and there was not enough difference to move to them; no jaw dropping moments. Don’t get me wrong they were fantastic, but so is the XA25. Looking at the 350.8 or 250.8, etc.... even in comparison the Integrated INT-250... If you love it; want to explain what you like and why? I’m wondering what others are thinking... 
My set up: Wilson Sophia II’s, XA-25, Pass Labs XP-22 pre, Merging+NADAC. 
jahatl513
With Wilson’s you want x250.8 
Kind of disappointed that more Pass owners didn't join in and discuss their amps.  I have Pass on my radar lately.  I guess we could just go ahead and give the stock answer "Pass owners are too busy enjoying their systems to write about them".

I believe my speakers are on the border of medium and low efficiency, so I was wondering if anyone who has the XA25 that found they could use a little more power.  So far it seems enough power for everyone who has written about the amp.
Nelson Pass is a true genius when it comes to solid state amplification.  I have been a life long owner of Threshold SA-1 mono-blocks, Aleph 1 mono-blocks, XA-100.5 mono-blocks, reviewed and bought the XA-60.8 mono-blocks, XA-25, and reviewed both the class A integrated amplifier and the 250.8 single chassis amp.

Recently I have gotten two pristine refurbished Threshold s/350e and a s/550e which still are wonderful amplifiers.

As I stated in my review on the XA-25, also made it a product of the year award winner, even though its the least expensive of the current .8 series amps its my personal favorite because of its rendering of timbres/tonality, and the image density that it creates.  It also drops over 60 watts into 8 ohms and 120 watts into 4 ohms, so unless you drive very difficult speaker loads you might be shocked on how much power it can drop if needed.

I love/enjoy all my Pass Labs amplifiers and feel lucky that they are part of my stable of amplifiers.
Hi teajay, did you mean above that the XA25 is your favorite .8 series amp or your favorite of all pass amps? If its not your favorite and I am not inadvertently putting you on the spot do you mind me asking which is? Thanks

I'm thinking this may not be a fair question.


Hey Jetter,

When Nelson Pass has been asked what is his all time favorite amplifier that he created/designed he says all of them!

As I stated it's my personal favorite of the .8 generation of amplifiers.  However, I have a soft spot in my audiophile heart for the Threshold SA-1 mono-blocks because they too were warm,full, and sweet sounding but with great dynamics.

I forget to mention I also own a First Watt SIT2 that's also a wonderful music maker.  Each of Nelson's creations offer slightly different "flavors" and the matching of the amps with the right speaker load also is very important.  I loved the XA-25 on Tekton Double Impacts-pure magic, but found that my much larger 21 driver ULf's, that are easy to drive but love high current, did not match up as well with the XA-25 that's were the X-250.8 sounded better.

So, it's not the amplifier in isolation, but the matching/synergy to different speaker loads that tells the tail of the sonic tape.  Still, the XA-25, with the right speakers is a "gem" of an amplifier at a reasonable price.
The best Pass Labs is First Watt. Nuf said.
Jetter,  you need to call Pass and Mark at Reno HiFI, then go listen to some amps...
Hey Teajay...you owned so many of Nelson's babies, you don't even remember them all :o)

Don't forget you also own(ed) the...
Threshold Stasis 1
Pass XA100 (prior to the .5 that you had)
Pass X350.5
...and the SIT2

Brother Mike,

Your right!  At my age this were you start to forget your old girlfriend's names and what pieces of gear you owned throughout having fun is this crazy hobby.
250.8.  Outstanding.
Only owned and listened to one, Pass INT-150, which is my current amp.  Did own the Pass designed Adcom GFA-5802 (2 of them in a bi-amp system driving Infinity IRS Gammas).  I owned them a few years apart and drastically different speakers, so I can't make any meaningful comparison.  Have to say I am a fan of Pass Labs.  Not changing any time soon.
jl35, everything in good time. I will either eventually do a home trial with Reno HIFi or maybe wait for the dust to settle a little and pick up one on the used market, but I don't want to hurry the decision too much.  It was not that long ago when I wanted a Luxman Integrated.
Pass 350.8 i owned it wonderful ,powerful and  great sound.
makes sense Jetter, as these Pass threads are up, pretty much every model has been liked and not liked by someone else...
I have the X250.8 and XP-22 and very happy...
I've owned a Pass Labs XA30.5 the last couple of years.I like it mainly because it got me off the amp merry go round and had great synergy with both my vintage KEF 107s and more recent Spatial Audio M3s. The only other amp that came close to the 30.5 for me was the Rowland Model 2 (another lower powered amp).
I tend to lean towards higher quality watts than quantity and the 30.5 offers plenty of quality.
Yes I agree all Pass amps have to be mated to the appropriate speaker In order to determine what Pass amp would be best suited for the loudspeaker  based on the loudspeakers efficiency.  In our store which is called Sound Insight on Long Island We have over 20 different brands of loud speakers that can be auditioned with Pass amps.
Well, I’ve had an X250.8 since 2015 and think it is fabulous! I run it with an XP-20 preamp and use balanced cables between the 2.

i had an X150.8 previously. The X250.8 is much more than simply a more powerful version of the X150.8. The X250.8 has a nuance rarely found in other amps.

It’s a rock solid winner of an amp 
I have the 260.8 monoblocks. I have never been happier. They stay in class A till about 34 watts.

jtucker - Can you comment on the INT 150 sound? 
douglas_schroeder  - I spoke with Nelson Pass when I wanted a First Watt for the Wilson Sophia's and he directed me to the Pass XA-25. Said that it was a mix of First Watt and Pass; something that First Watt just could not execute like Pass can so it became Pass XA-25 and recommended I try it first. 

Thanks for jumping in markum01, I was hoping somebody would mention the 260.8 monoblocks, which are sort of on my radar.  I assume the 260.8 monos offer as much as the 250.8 stereo amp, plus some? Any comparisons between the 260.8 monoblocks and the 350.8?
How about the X260.8 monoblocks????  Has anyone heard them?

XA-160.5 vs 160.8?
I am currently waiting for delivery for my first (and hopefully my last) amp upgrade. I elected to go with the 260.8 mono's and Tuesdays delivery cannot get here soon enuf
For me the pass Int-250,or X-250.5 (monoblocks XA 200.8) in combination with the preamp from EAR 868,912 or 918. A perfect combination.
jahatl513, yes, but the 25 doesn't have balanced inputs. That is a serious drawback to me as a reviewer. I build lots of systems with XLR, and that would cut out half of them. 

That may have been a tactical move on the part of Pass labs. If they were to stuff them with XLR then the unit might cut into the big boy amps in terms of sales. A company has to manage its products, and I respect that. Or, they might march the changes up the line and add XLR to follow on the lower model. 

I am currently running a pair of J2's as monos; only using 1 channel for each, and doubling up the speaker cable to the PureAudioProject Trio15 Horn 1 Speaker (reviewed). It's impressive to say the least, especially with a pair of Legacy Audio XTREME XD Subwoofers. Total of 8 15" woofers and horn system. When I apply my Schroeder Method of Interconnect Placement it becomes a completely different ball game.  

Pass/First Watt products are pretty easy to make sound respectable, and have good potential to be stunning. 
I purchased the 260.8 in dec and am happy....

I previously had in same system pass integrated 250 and difference is considerable.

The integrated is very good for an integrated but prefer tube integrated...

The monoblocks throw a massive soundstage and wonderful instrument separation and voices sound real.....sounds pretty neutral too...

I think each model should be considered on own merits and not generalize about company sound....also each room sounds different and rest of equipment synergy important.....i keep it simple buying same preamp company as amp ....

I tried the EAR 912 with the 260.8 with my harbeth 40.2 and found was sublime for jazz or vocals but bass was not good for modern rock

I thought of auditioning a different phono preamp than pass xp17 but like same company same current model synergy.....xp27 would be better still but way pricier and system already great sounding...

Will say system really began hitting all cylinders after upgrading power cable on pass preamp and fuses in pass preamp and phono (mono fuses cant be changed).....

Douglas_schroeder - your use of one amp..... sounds interesting and I’d like to understand it exactly.  Can you elaborate the details or is there a place to read up??  
Coming from the Conrad Johnson world. Everything is single ended so initially my pre was an excellent match for the XA25. Also the little amp is built to punch with authority way above its weight and an unusual onfiguration or deviation from the rest of the heard.  I’ve since updated to Pass XP-22 and all important inputs are on XLR into it and a significant upgrade.  
Teajay,

For the Ulf’s, do you prefer the Pass x250, the Aric SET KT88, or are there other amps that bring out their maximum capabilities?  I’m planning on significant upgrades 18 months out and currently doing my due diligence.  Thanks.
I'm really fond of the SIT-3.
jahatl513, I believe I go into the use of one channel on each amp in the review of the First Watt J2 I wrote for dagogo.com 

Hey 64voxac30,

My three favorite amplifiers in a ranked order on the Ulf's are:

1) Coda No.8 2) Threshold S/550e 3) Pass Labs XA-25

The XA-25's harmonics/tonality are beautiful on the Ulf speakers.  However, because it does not drop as much current as the other two amplifiers it just misses out on the total control of the speaker that the other amps offer.  
The XP25 is NOT part of the .8 series. The info I got from Nelson are those :Question : Just found you have a XA25 amp as "entry line". It seems to be from 2016 but the name XA25 would make me think it is from the same generation than the XA60 so 2006 Is it the case ?
And how would you rate the first watt against the .8 knowing I don't need
power (my very old speakers have a 97dB sensitivity @ 4ohms) ? Seems the SIT-3 is almost sold out and the last SIT amp. So it's now or never.
" The XA25 design is different from theX and XA amplifiers previously.  It does not operate in balanced mode, there is anRCA unbalanced input, and the black output connector goes to ground.
Also, the design eliminates the degenerating resistors usually found in
amplifiers for the purpose of locally minimizing gain and giving stability to parallel transistors.
Additionally, the amplifier's output stage bias is controlled by a new
circuit which keeps the bias current constant over a wide range of temperature and other conditions so as to allow operation without having degeneration in the output stage.
It is very different from the SIT-3.  The XA25 is a "third harmonic" sort of
amplifier, and the SIT-3 is "second harmonic".  The SIT-3 is relatively warm and polite and the XA25 is very dynamic and detailed.
Fortunately the SIT-3 is very happy with 4 ohms, and so either amplifier should be ablework well.  It comes down to your personal taste."
Question : So the X25 would be closer to what I'm looking for : as neutral as possible, WYHIWIOTS (What You Hear Is What Is On The Support) and musics : classical and acoustic jazz, mainly piano. 35 years of piano have (mis?)educated my ears as I like better faithfulness than shear pleasure.
" Both XA (30.5 and 30.8) amplifiers are a mix of 2nd and 3rd, depending on the load and the level.  They start out as 2nd (harmonics) at low levels and are 3rd a high levels.  The XA.8 products have more 2nd in proportion at low levels than XA.5 product"
Question :"Which would you consider as the most neutral ?
They all have the low order harmonics, just in different proportion.
Sonically the XA25 and XA30.5 are roughly equivalent in this regard.
The biggest difference in my opinion is that the XA25 has interesting
character is dynamics, largely due to lack of degeneration in circuit."
Question : So you like better the X25 than the X30.5 according to what I'm looking for. 
" I like them both.  XA30.5 is a little more relaxed."

Question :
And compared to the X30.8 ?" I think XA30.8 is better, has a little more 2nd to 3rd ratio.  Also bigger
supply and more heat sinks and bias current."

More to come I hope.
Lesonaussie2- Then I have a question. Of the big Pass amps, is there one that shares those characteristics of the XA25? 

douglas_schroeder - 
My Sophia II's are single wired, and per your article and in general - 
     [the speaker is single wired, not bi-wireable. So, simply use one channel of each amp for each speaker.Take the single interconnect Left or Right out from the preamp and direct it to only one input of the amp. One channel goes unused. The output from the single channel is sent by the one speaker cable to the single pair of binding posts of the respective speaker, and only one channel per speaker, providing better performance than one stereo amp]
Did Nelson ever comment on this? Do you get the full power to the one channel being used? Does this change anything with respect to Ohlm's and speaker? I am curious and have wondered about this. Is there a better way? 
Big fan of the J2. I switched from tubes to the J2 about 4 years ago and have never looked back. I couldn't imagine two, the heat from one warms the room. Currently driving the M3 Triode Masters and am quite satisfied. If your in the market for an amp and have reasonably efficient speakers First Watt is worth a look.
Another happy 250.8 owner with the XP 10 pre handles Maggie's 3.7i extremely well.
Hi all,

I am considering purchasing the Verity Otello’s and specs are as follows:
100 watts of music power, 93db @ 1w and 1m, Impedance: 8 nominal and 3.8 minimum. Based on these specs I am looking to match a Pass Lab or First Watt
amp. I like the warmness, tubelike sound of the Pass Lab. So far considering the INT 250 or maybe separates like the X250.8, but want to match the best amp to the speakers mentioned. I listen to a lot of vocals and music with heavy brass, so looking for something warm but not lacking in detail. All suggestions are welcome, please include reason for your preferrence.
Over the past decade I've used or demo'd a variety of Pass products during my speaker/amp journey...  Thiel 2.4s (Classe CAP-151, McIntosh MC402, Pass X250.5, Pass XA30.5... eventually settled on a Pass INT-30A), Coincident Super Eclipse IIIs (Pass INT-30A, First Watt SIT2... eventually settled on Coincident Frankenstein 300b Monos), & Coincident Pure Reference Extremes (Coincident Franks, Lyndgdorf TDAI-3400, Atma-Sphere M60 Monos, Pass Labs XA25... eventually settled on First Watt F4 Monos).  

As pure current sources with no voltage gain, the F4s are clearly not for everyone/everyspeaker, but they excel on my PREs.  As I have pointed out elsewhere, the 6moons summary description is pretty spot on.... "relaxed ultra resolution."  They have a bit of the sweetness of my 300b SET amps, but both clarity and bass control that beats out all the other amps I've auditioned on these speakers.  The soundstage is expansive, imaging is precise, and there is absolutely no harshness or grain... an important quality with the accuton ceramic tweeters on the PREs.  

I got my first F4 (actually I built it) to serve as a zero-gain bass amp to augment my Coincident Franks, but unfortunately biamping on the PREs just kills their coherency (I've tried both active, with the Lygdorf, and passive, with the F4)... even with the Franks providing the F4's input signal from their speaker posts.  When I finally ran the F4 alone I was shocked to find that it was better than all the other amps I'd tried with the PREs. 

Previously, the Franks (currently up for sale) had won every shootout, but they simply don't have enough bass control for the PREs and I was forced to move on.  Super happy that I stumbled onto this amazing speaker/amp synergy, however. 

Thanks Nelson, for coming up for the design, and making it possible for people like me to build their own (along with help from the amazing community over at diyaudio) now that the amp is no longer being produced.
jahatl513, in an exchange with Nelson he suggested that I would get an even better result by tuning the J2s into Monos. Split the input to each amp, obviously using only L input split for one amp and R input split for the other, and then sum the outputs for each amp to make a mono. No doubt this would greatly improve the performance by doubling the current. I will likely try it.


@teajay

The XA25 isn’t a .8 series amp. That’s why it’s not called the XA 25.8 It doesn’t feature a balanced topology nor supersymmetry feedback. It’s a 3 stage, unbalanced, complementary topology utilizing current feedback. It’s basically an F5 using different output FETs that have higher gate capacitance that require an intermediate driver stage.

But onward to the point of the thread....
Yep... I’ve got an F5 of my own making. It’s paired with Focal 936’s and I like it. That’s probably not news to anybody, but I don’t feel like I ever say much about how it sounds.

At the moment I’m listening to Tool’s 10,000 Days album and it’s a well produced and mastered album. The Focal/F5 combo gets it right. The imaging is clear, deep and focused while being vast and enveloping. The details are present, crisp and balanced. Adams guitars leap forward as they should with the gritty, crunchiness you hear at the shows and Danny’s drums are towering and resonant, clearly set back. The music just sounds right, like you know it should sound.

The F5 is in no small part responsible for getting this level of quality. The speakers are good, often noted for letting an amp speak, which they do, and the amp has something to say. It’s something that took a lot of time, listening, and adjusting to find. The amp is well behaved and grips the Focals well, but it has a voice you can play with. It’s a good amp built and adjusted to it’s peak performance, but it may be a better amp when it’s not. The addition of some negative phase 2nd order distortion breaths a rich dimensionality into it that it lacks when adjusted for it’s .002% distortion spec. And that works very well with these speakers, creating space and warmth and atmosphere, the likes of which I’ve heard vastly more costly combinations fail to reproduce.

I chose to build this amp in particular initially for it’s ability to scale in power, but I’ve grown to love it for making these relatively modest speakers do what I’ve heard $25,000 speakers fail at; making the music I love exciting to listen to. I listen at night before I go to bed and I often crawl in bed feeling truly fortunate to be able to listen so well and looking forward to tomorrow when I can listen again. It’s a stereo that makes me ponder what I’ll treat myself to on my way home from work. That seems like a high level of satisfaction to me. That’s what a good stereo should do, isn’t it? So I say with confidence, "That’s a REALLY freaking nice amp!!!".
@kosst_amojan Definitely, that's a win. Congrats!
Recently acquired First Watt F7. Using with Avalon Ascendant ll in medium/small room. Incredible combination. Pre is Rowland Capri. 
I've been through three Audio Research line stages on one X350.

Every year I talk about upgrading the X350 but so far it really hasn't given me a good excuse to. And I don't really need much of an excuse. Maybe next year I'll finally get a .8.
I’ve recently added a Cary SLP 97 F1 pre for use with the XA25. The Cary is an absolute gift in musicality and I have also added a Tara Labs power cord to the XA which has truly added bass to the setup. I rarely use my XP22 pre now. 
I wonder if an Aleph 1 or 2 mono would be a nice addition???