The book apparently has you make the toroidal transformer yourself... "No commercial available toroid will do, we stack cores, do the maths on the cross sectio

The book apparently has you make the toroidal transformer yourself... "No commercial available toroid will do, we stack cores, do the maths on the cross section mm/2...We wind the large toroid by hand, ...as no commercial winding machine can get into our stacked cores. We mylar tape and epoxy each winding..."