@tiofelon diyaudio.com/passlabs is a good source for finding out more esoteric details regarding first watt offerings. In the below thread, they state:. "The F5 has a gain of 6times.The clipping voltage of the F5 is ~ 21Vpk, or 14.7Vac."
https://www.diyaudio.com/forums/pass-labs/218770-diy-f5-questions.html
https://www.diyaudio.com/forums/pass-labs/218770-diy-f5-questions.html