Pete Millet tube mic preamplifier - B+ PS is confusing me - please help

[kagliostro]

Few days ago I discovered this Pete Millet project

http://www.pmillett.com/micpre.htm

and it is intriguing me

BUT

the Power Supply uses SS circuit and I'm able to understand only the filament section

about the B+ section absolute dark for me

can you give help and explain how can B+ exit from that circuit ?

and more, which will be the estimated B+ ??

MANY THANKS IN ADVANCE

Kagliostro

[FYL]

PM uses two DC/DC switching power supplies in order to derive 6V3 heater and 200V plate voltages from a 48V rail.