Pass First Watt models ... confused

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,
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.
Charles,

"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.