Well, in referring to fig. 6, I was interested in the triode/tetrode second stage as driven by the cathode follower input. I quoted this particular patent as the second and third stages essentially correspond to the website description (in the webpage, the first stage is replaced with White cathode followers, and there is only feedback signal and no input at e1, and the connection to the output stage is DC coupled with current mirror, and there is stuff on the secondary 119). Now, there's probably more to it, given a comment at audioasylum (
http://www.audioasylum.com/scripts/t...ubediy&m=51536), but...
Now I have four specific questions, please:
a) About the cross-coupled phase splitter -- the way I understand it, a mere CSS loading the triode also has the benefit of appearing like infinite plate impedance, so what's the point of doing it the way in the schematic? The only thing I see is that the positive feedback from the third stage cathodes makes for very high gain, allowing very high feedback (and very high frequency problems from this are dealt with by the feedback from the output through capacitors 122). Can't such positive feedback be done without this third stage, saving on tubes and complexity?
b) Capacitors 104 can be replaced by DC coupling through level shifting such as by a zener(as in other figs in the patent); what about capacitors 123 -- given it's in a local feedback loop, it's still in the signal path; any way to do away with it?
c) What about using this configuration in an OTL amp? Adding a negative rail, the load could be connected between the output devices, like the balanced single ended Aleph-X amps. But what if the output was to be unbalanced? How would the third stage outputs be properly coupled to a single output device? I'm asking because I have specific applications in mind.
d) In an OTL, since there's no tetriary winding 120, where would the main NFB be sourced? And in a way so that balanced input can be done without input transformers -- where would the main NFB be injected?
Yeah, I edited this message like five times...