Pass First Watt models ... confused

I'm curious about the First Watt products. I'm a very happy owner of a Pass x250.5 AB amp but interested in experiencing full class A. No plans to sell my less than 1 year old x250.5, and I'm not rich so I won't be sinking cash into the exorbitant prices of a new XA series. A used Aleph is a possibility, but those are getting fairly old and I wonder about maintenance issues.

Therefore I am looking at the reasonably-priced First Watt line from Nelson. But I'm quite confused by all the different models. Can anyone help clarify this puzzle for me? Thanks.
Srajan Ebaen has done a very thorough and systematic review of each of
the First Watt models at 6 there are comparisons between the
various models, you won't find a more comprehensive source. Beginning
with the F1 all the way to the current SIT amplifiers! They're all covered.
I haven't looked at the 6Moons reviews Charles referenced, but I would caution that some of the First Watt models are suitable for use only with a relatively limited number of carefully chosen speakers.

The comparison chart on this page provides a good starting point. The "output ohms" column refers to the output impedance of the amplifier, output impedance corresponding to damping factor divided into 8 ohms. Several of the models have extremely high output impedances (and therefore extremely low damping factors), which cause them to act essentially as current sources (rather than as voltage sources, which is how most solid state amplifiers behave). Most solid state amplifiers, including your X250.5, have near zero output impedances, and high damping factors. Most speakers are not designed to be driven by amplifiers having very high output impedances. There are exceptions, of course.

As you can see from the numbers in the chart, that is particularly a concern for the F1, F1J, F2, F2J. And to a lesser degree (but one which may still may be significant with many speakers) for the SIT-1 and SIT-2.

The manuals that are available at the First Watt site for many of these models discuss what kinds of speakers tend to be suitable for use with them.

Also, note that none of the models listed are rated to provide more than 25 watts into 8 ohms.

Hope that helps. Regards,

-- Al
Al has it right; most of these are special purpose amplifiers, and you would be wise to carefully read the manual for each before purchasing.

Also, if you call Mark at Reno Hi-Fi, he can help point you to a suitable model for your setup, if one is appropriate.
You're right about the limitations and the need to have appropriate
speakers to get the most from these amplifiers. The 6 Moons articles-
reviews spell this out very clearly. Apparently with the proper speaker
match these amplifiers are quite exceptional. No surprise actually, great
designer, class A, very simple circuit with fewer parts (but good quality) =
good sound.
"A used Aleph is a possibility, but those are getting fairly old and I wonder about maintenance issues."

Those amps are made pretty well. If you need more power, it would probably be a better choice. I had the 0 and was rated at 40 watts/ch. It was a very powerful amp. It easily drove my old B&W 802 S3's and my Martin Logan SL-3's. I put it next to the 3 and the 5 and it definitely had more power and I thought the sound quality was better as well.
While the Aleph's run hot, I would not worry about their longevity. Eventually, you'll have to replace the supply caps but that's about it. Nothing else to adjust.

And they do put out more power than the First Watt amps.
This is very thoughtful and reasonable feedback. Thanks and I will read up on them. My speakers are the older B&W Matrix 803 series 2. 8 ohm speakers, 90 db sensitivity. Keep the feedback coming if anybody has anything to add.
I've owned the Aleph 3, 30, 60s, and 2s. And an X150.5.
I also owned the Aleph J2. It sounded good.
I bought an XA-30.5 from a friend, recently.
For the money, I like the XA-30.5. It's true Class A, and it will drive almost any speaker, for a little bit more money (used) than the current First Watt amps.
So....What are the acceptable parameters for speaker sensitivity for these amps?
I've got the J2 mated to some Gallo Strada2s (90db efficiency). I absolutely love the amp. It's very much a SET-like sound with good bass and is completely quiet. I've had some very expensive SET amps and prefer the J2 to all of them. Assuming your room isn't incredibly large, 25 watts should be plenty.
"I also owned the Aleph J2. It sounded good."

Did you mean the Aleph J or the First Watt J2?

My mistake. I had the First Watt J2...
Which current model is closest to the Aleph J? Can't buy an Aleph J anymore.
Abrew, you should just email Pass... always informative and accurate comments from them.
So, with an output impedance of 80ohms might the F1 be a match for the Quad ESL?



can we get a list of loudspeakers that are compatible w/ these amps? Keep me posted & Happy Listening!
It will depend, amp by amp. The First Watt website should steer you well. As can the threads on DIY Audio, to which Pass frequently contributes. The 6moons reviews are also pretty informative. The info is out there.
Agree with Roscoeiii, each First Watt amplifier is unique. They have different design objectives and are not of equal utility with a given speaker load. Some models have NFB and others do not. Some are voltage sourced, others current sourced. 6 Moons has covered and compared each one of them comprehensively.