circuit redesign: borrowing from the 5E5

So the Fender amp circuit which is closest to my new proposed design (in terms of power amp), seems to be the 5E5.  This is a Tweed with push-pull 6L6 pair, cathode-biased, and cathodyne phase inverter.  However, this circuit had no negative feedback.

Cathode resistor was shared between both 6L6 tubes, 250 Ohms @ 10W.  (And 25uF cap.)  This was with B+, at the output transformer center tap, of +395v.  We will have +525v.  So I'm thinking, maybe 2 x 330 Ohms @ 10W, just by mindlessly scaling up by a little over 20% for the higher voltage.

The 5E5 used a 12AX7 for the PI, with a standard gain stage in front of the cathodyne stage.  The obvious approach would be to send NFB to the cathode of this gain stage, with master volume ahead of both.  However, I'm wanting to reserve the extra 12AX7 stage for switchable boost in the preamp, thus MV between the two stages (and VTX preamp output also feeding in at this point, ahead of the MV).  So instead, I'm looking at a circuit I haven't seen anywhere else, feeding the NFB in at the cathode of the cathodyne PI.  Seems like it should work...  Of course, the phase will be opposite, but I can compensate by simply swapping the two PI output lines to the 6L6s.


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