What I'm thinking of is a semi-universal add-on output xfmr for adding Cathode Feedback (CFB) function to any standard CXPP (or GXPP) output transformer (OT). This would be a CXPP25 or GXPP15 size xfmr, with around a 1250 Ohm P-P primary and a 16 Ohm single secondary. The xfmr would need say twice the interleaves of a normal P-P OT to equalize HF coupling (leakage L on each side) and winding resistance for both sides of the primary. (or another option would be to use a split bobbin design)
In practice, the add-on OT primary sides would become the cathode windings for CFB with another main OT for plate windings. The secondary would connect in parallel with the secondary of the main (plate windings) output xfmr. The 16 Ohm secondary could be connected to the 16 Ohm terminals of the main OT for 1250 (K-K) Ohm cathode windings, or it could be connected to the 8 Ohm terminals of the main OT for 625 (K-K) Ohm cathode windings.
This way CFB function could be added to most any CXPP (or GXPP) OT without having to redesign the whole product line. (note, by keeping the Add-On xfmr primary low Z, it has a relatively small effect on the output Z spec of the main OT)
In practice, the add-on OT primary sides would become the cathode windings for CFB with another main OT for plate windings. The secondary would connect in parallel with the secondary of the main (plate windings) output xfmr. The 16 Ohm secondary could be connected to the 16 Ohm terminals of the main OT for 1250 (K-K) Ohm cathode windings, or it could be connected to the 8 Ohm terminals of the main OT for 625 (K-K) Ohm cathode windings.
This way CFB function could be added to most any CXPP (or GXPP) OT without having to redesign the whole product line. (note, by keeping the Add-On xfmr primary low Z, it has a relatively small effect on the output Z spec of the main OT)
