David McGown wrote:
I am not sure my reply ever posted but I would like to point out that just because you take output from the source or cathode does not mean the topology is the same. Remember, there are no complementary pairs of tubes, whereas the Pass F4 uses NPN/PNP Mosfets in a source follower. Rosenblit's design is a Circlotron, right?. Completely different animals. There is no patent on which way you take output on a device, just because the connections look the same at a high level doesn't mean the circuits are the same or even similar in operation. The difference is in the details, not the superficial similarities.
David
I was only referring to the output stage. Bruce’s design is based on Futterman/totem-pole which is similar to F4 output stage. I was wrong to imply Bruce invented the design, he got the patent for stabilizing the design and making it reliable.
BTW, you should try out an OTL amp. I built Bruce’s 15W SonOf Beast from the kit. I am never going back to transformer coupled amps again. I know there is a huge attraction for SETs, but why not a transformerless OTL.