[Arran]

The output transformer primary connections you describe sound like an ordinary push-pull type output transformer primary, like they have had around since the late 1920s at least. I thought that Williamson type output transformers also had extra windings, or taps, for feedback? Maybe whomever posted the item on their website got the Dynaco model numbers mixed up because there is no mistaking an ultra linear output transformer with a regular push-pull type. Hammond, and Edcore both sell ones with feedback windings. You would think that with all the computer age aids to assist there would be fewer goof ups but if anything there seems to be more of this going on.
Regards
Arran