Gotta love Nelson Pass

Many of his products have very different appropriate applications.

Hello, @unsound  - will you please elaborate on that? 

Everything explained on firstwatt.com , even about discontinued models. For example my F2J current source power amp is designed for crossover-less, high sensitive speakers (full range drivers) and not suitable for the speakers with crossover. For traditional speakers he has different amps. 

^Yes, even some of the Pass Labs branded amps, like some of the Alephs have some limited applications.

Right, current source amps vs. volage source amps is a big difference. 

Active gain preamps vs. passive preamps with no gain at all is a big difference too. He has passive preamps which became active after the volume turned up to 9 o'clock (the aleph L series). 

But if you know what you need for your particular speakers then it's a benefit. For example i don't need much power for my full range crossover-less speakers with 101db sensitivity. Nelson said he use Zu Audio speakers himself (among others). So for my need current source F2J power amp of 5w per channel is enough. And absolutely neutral First Watt B1 buffer preamp (pretty small box) is good match for F2J power amp. 

Everyone should learn more about FW or Pass Labs products, but Nelson can help with a great support for his products.