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. 
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.


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!