Interesting Output Stage?

[Synchrodyne]

The technique was also described in “Radio and Television Engineers’ Reference Book”, 4th Edition, 1963.  See p.14-47, which refers to its use in some Murphy stereograms.  The A674SR was one such model.

Here is the pertinent page from that book.  It provides a succinct explanation of the technique.

     
 
I wonder if any maker used this circuit with an ultralinear (UL) output.  It should have been possible, as the use of an UL main transformer would not have interfered with the basic process.  Also, UL outputs, both push-pull and single-ended, were sometimes used in the class of equipment in which orthogonal amplifiers were found.
 
Cheers,
 
Steve