@autospec Will, please give Classic Tone Transformers a call as well. Both they and Edcor do custom work, and take those needs seriously. Heyboer also seemed willing, but again, my results with them fall behind the other two. The rub I had with Edcor was in setting up an account, I needed to provide them far more (government issued information - federal and state tax IDs on official letterhead) than I did with any entity I’ve ever dealt with to prove I was not just a hobbyist. I have my own thoughts on the more esoteric winders as well as ultralinear taps, but I’ll hold them for now.
In regard to your feedback winding, is it possible they get tripped up by your nomenclature? Are you actually requesting a completely separate winding, or just the typical 4 ohm tap to run your feedback loop off? If the latter, they churn them out that way all day long, and should add but a couple of dollars to a single tap output transformer. A separate output winding would be different than most audio or guitar output transformers even if their power transformers get built that way, and my question then becomes, do you truly need a solution that elaborate?
In regard to your feedback winding, is it possible they get tripped up by your nomenclature? Are you actually requesting a completely separate winding, or just the typical 4 ohm tap to run your feedback loop off? If the latter, they churn them out that way all day long, and should add but a couple of dollars to a single tap output transformer. A separate output winding would be different than most audio or guitar output transformers even if their power transformers get built that way, and my question then becomes, do you truly need a solution that elaborate?