Squinting my eyes, I can see it is a First Watt F1. You might want to revise your post to reflect that. If you post a
link to more info, people can look up the specs on the F1 as well. It's not your usual run of the mill amp, as the output impedance is 80 ohms and it is a current source or power transconductance amplifier appropriate more for full range drivers like Lowthers, etc...
Best,
Anand.