push-pull power converter, selecting frequency and core

[Jesset1996.5]

Hello all, I am trying to reverse engineer this power converter for a LV-80 amp. I am having difficulty deciding what frequency to run this at and deciding what toroidal core to go with. I do know that I will need a rather large core, around 3 in id or so. The transistor specified is a 2n1146c.
Thanks

[David Hess]

The operating frequency is determined by saturation of the transformer core.  That is a Royer based inverter.

https://en.wikipedia.org/wiki/Royer_oscillator