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Jon Broskie says they are the same

Posted by Lew on August 14, 2020 at 11:54:37:
If you read Tubecad, Broskie, who doesn't shy away from making provocative generalizations, says the circlotron and the Futterman output stages are fundamentally the same. I personally cannot see how that could be true, but I'd love to see Ralph's take on the idea. My last pair of Futterman amplifiers were Prodigy amplifiers, out of Texas. They sounded excellent driving the Sound Lab M1s I owned at that time (early 90s). Arguably, the Sound Labs are "modern". However, they presented a booby trap for either type of OTL, there was a very low impedance dip at midrange frequencies, as low as 2 ohms at between 1kHz and 2kHz. Neither Futterman nor circlotron is happy with that load at those frequencies.