To clarify...

Steve Deckert of Decware (www.decware.com): Single Ended Tube amps: Zen A, B, C and Select; and Zen Monos

Nelson Pass of PassLabs (www.passlabs.com): MOSFET power amps: Zen, Zen revised, Son of Zen, (maybe even Zen Cousins)!

The Son of Zen is a single gain stage differential MOSFET pair biased by power resistors. To see the circuit:

Web page
http://www.passlabs.com/projects/sonofzen.htm
or PDF (page 2)
http://www.passlabs.com/pdf/sonofzen.pdf

Hope this helps,
I like to be of assistance now and zen, ;-)
Cheers,
Jeff