Pass Labs 1st Watt Rundown

I have become intrigued with the 1st Watt series and I am trying to wrap my head around the series and the differences within the series, but the internet discussions seem shallow.

Can anyone give me a rundown of the different models, versions, whatever?

What are the differences from one to another?

Did the newer iterations correct problems of the previous models and what were they, or did they simply address differences in power?

Stereo? Monoblocks?

What pre's and the sensitivity of the speakers you used with them.

Anything else you can think of as to characteristics of the different models.




It's not the direct answer you're looking for, but on the first watt home page, they list all the reviews. I found 6moons reviews go into quite a bit of depth on each model. That gives you a feel for the different sound characteristics, as well as acknowledging the limited repair parts (held at First Watt for future service) for the SIT3 models.

A random gotcha is that the F7 has a very low amp impedance, so many tube preamps aren't a good match. 

I was in the same boat as your recently, and just went thru many reviews one leisurely afternoon.


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Yes, I have read the 1st watt page and several reviews. I find myself not trusting professional reviews anymore than I trust politicians. 😀

So I'd just like some honest comments from my brothers and sisters on the Gon.

I have owned two First Watt amps, the M2 and the Sit-3.  I would like to hear an F8.  Agree that the 6moons review goes into great detail and does a nice job comparing several models.  Of the two, the M2 had a bit more power (25 watts into 8 ohms) vs 18 into 8 ohms for the sit-3. I preferred the M2 to my Rogue Stereo 100 amp, despite the rogue having much more power. Better soundstage and detail.  So I sold the rogue amp.

I then got a sit-3 and thought it was again a bit more detailed with a larger soundstage.  I recently got some caintuck open baffle speakers, and in my small room (11x 14), the Sit-3 and the open baffles sound phenomenal, with jazz, folk, rock, piano music, ambient…  I think the sit-3 sounded better with the open baffles (94 dB sensitivity) than my ported bookshelf speakers (87 dB sensitivity), so they may do better with higher sensitivity speakers. 

i sold the M2s and kept the sit-3. Hope this helps

I built an F6 clone from the DIYaudio web site a couple of years ago. great site, great members and highly expd with great advice and willingness to help. It cost about $800 in parts and the cabinet, I think the F6 from First Watt is about 3500. Nelson is also active on the DIYaudio forums which is pretty cool. The amp sounds great, very musical and as I put it in a large housing with big heat sinks it doesn’t run that hot (it’s a pure class A amp). Like many of his amp it has a lower than average input sensitivity so when compared to other amps you may find you’ll need to run your pre- amp volume higher than typical, though if you’re running very efficient speakers it’s a moot point.

For what it's worth, I have owned and listened to the M2 since 2014, and I adore it. It is simply a wonderful amp that I will never sell. I drive it with a Quicksilver preamp and it powers my 89db-sensitivity Spendor 1/2s with all of the dynamics I could want. This amp is a gem among rocks!

The Pass XA-25 seems more in the realm of the First Watt stuff than any other Pass amp, and since the XA-25 sounds so damn good I've never been tempted by a First Watt amp. Maybe if my XA-25 explodes or something...However, I like the way old Nelson thinks, and it is unique that a namesake and designer of a major brand like Pass Labs designs quirky, great sounding other (First Watt) stuff,  and even shares his designs with the DIY community. 

Steve Guttenberg did a video comparing a number of First Watt Amps and the Pass Labs XA-25.   Link below



Steve Guttenberg owns four of the First Watt amps, and also the XA-25, and he reviews and compares them on his youtube channel. Hes also has some really great interviews with Nelson Pass. I see jaduio1 already posted a link. :)



I have both the Pass XA25 and the First Watt SIT-3. They are both good amps in very different ways. The Pass is clear/liquid and transparent, the SIT-3 is very good with tone and texture. I think the Pass pairs better with conventional speakers and the First Watt pairs better with Horns. I've paired the SIT-3 with a Cary SLP-98 and a Battery powered Dodd preamp with good results. If you're looking for an amp that sounds close to tubes, the SIT-3 is your amp. My speakers are 102 db efficient. Also remember that adding resistance across the terminals can tighten the sound of the SIT-3 if its necessary. According to Nelson and I agree the SIT-3 prefers a 4ohm load, but that should be determined on a case by case basis.


I agree that the diyaudio site is fantastic for folks like me that enjoy building stuff or folks that are thinking about it. I'm finishing up a F5 stereo amp and look forward to pairing it with my Fyne F703 speakers. Pass Labs Threads

You simply have to take the plunge. No matter someone’s experience, that doesn’t inform you of what yours will be. 

Me, I’ve owned the J2 and F5. Each were very good amps. And I was driving Martin Logan’s at the time. But 25 watts was more than enough to drive the 91dB ML’s. 

I have a 20x20 family room that serves as my Pass/First Watt DIY venue. If there is a common denominator it is what I hear as purity of sound. A friend likes to say that power and purity are at odds in audio equipment. He’s a low-power tube and First Watt fan. I suppose you can have both if you spend enough money. But in general,  You simply decide that you accept power limitations and some heat  in exchange for a carefully curated Class A sound.I paired a set of 95-db speakers with an M2 diy versión and a Pass NuTube preamp, also a diy project, and find absolutely nothing to complain about. I have also used that amp/pre combo to drive small Magnepans, not to very loud levels but to very satisfying results. Rock & roll? Forget it. Classical, folk, acoustic jazz trio? Go for it. 

@tonydennison there’s a nice XA30.5 on USAM here

This would be my choice in the $3000 price range, now that you’re talking Pass Labs amps here, before any of the First Watt offerings (and as a continuation of your other thread). I’m not saying it sounds like tubes, but…it’s warm, detailed, musical, with incredible mids and throws a nice holographic soundstage. It’s a higher end amp than the First Watt. Class A up to 30w, then A/B up to around 90w into 8ohms. It’s less likely to run out of juice and is a more universal amp than the FW. I drove my Wilson Audio Sabrina with the XA30.8, the latest iteration of XA30 amps. Great sound. Something to consider as an alternative to First Watt. 


Do you have experience with the AX25? can you compare it to the XA30?

In my mind, If I decided to leave tubes I would first try Pass and these two seem to be where I would start.



@tonydennison I do not have experience with XA25 but there are reviews comparing the XA25 to XA30.8 if I’m not mistaking. Should give you an idea. In any case I don’t think you can go wrong with any of the XA amps provided these amps are a good match with your speakers from the rated power and stability into the load your speakers present. I think with klipsch these Pass amps are going to be a very nice match.

One more piece of information to consider - if you plan on running an XA amp single ended (RCA cables), make sure you have and use the XLR jumpers. Running these amps single ended without the jumpers in place will result in increased noise and they just won’t sound as good. If you end up buying an XA amp used and the jumpers are missing, call Pass Labs and they will send you a pair. Customer support is one of, if not the, best in the industry.