Hear, hear.
Power buffering is of course what all amps do but hybrid amps usually use small-signal valves and feedback in the output stage. The F4 uses no feedback and no voltage gain. To be specific then, the concept would ask for a DHT SET (tube chosen for its sonics rather than output power or drive) coupled to a no-feedback, class A, no voltage-gain transistor buffer, the latter loading the tube to operate optimally. In the external F4 concept, that has to be accomplished with a resistor across the SET outputs which feed the inputs for the follower amp. Perhaps Roger could explain how one would ideally do this in a hybrid circuit designed to work together?
It seems a 45 for example generates a nice amount of gain. If that could be coupled to an impedance and voltage/current converter transistor buffer to give us low output impedance and current, we might hear DHTs in a different light? Of course part of the recognizable SET sound often is a function of high output impedance - and B.K. Butler's Monad A100s sound more transistor than tube, perhaps as a result of it?
Anyway, the SET/F4 combo does sound fantastic, hence here's another plea for at least a concept brief on how to accomplish something equivalent in one single chassis.
