I fully respect what you are saying but initial invention of OTL amp as far as I know creation of J.Futtermam, it means the wheel already has been invented ! talented guys like yourselfs improve /re create OTL Amp Design Such as Berning makes Delicious OTL Amps Acuhorn makes OTL Amps and many more, but I sincerely do not understand why we are discussing OTL Amps, my initial question was SET Amps and Horns and really wanted to hear from SET Amps and horn lovers or enthusiasts . kindest regards.SabihActually the first OTL patents in the US preceded Futterman's patent. He did not invent the technology, he developed a means of positive feedback to help the drive of the top tube in the output section to be driven as well as the bottom one.
We got around the problem entirely by a different circuit. I got the idea during a dream back in 1976. At the time I had no idea who Futterman was. FWIW the Berning amplifier is brilliant, but not an OTL as it has both semiconductors and an output transformer in its output section.
My last two posts here (including this one) are corrections to set the record straight. FWIW your opening post does not suggest that this thread is about SETs; it simply asks about 'old school designs' and whether we are re-inventing the wheel (the answer to the latter question is rather obviously 'no.').