Randy or Sherry Guttery wrote:

As far as "basic" operation - the use of the buffer tube isolates
...

.... and that's important sometimes because it's hard to get good enough
balance between the reactance windings to prevent troublesome coupling
of the output voltage into the control winding.

--
John Doty, Noqsi Aerospace, Ltd.
http://www.noqsi.com/
--
Specialization is for robots.