I’m so glad you are enjoying your Percolator!
Those mods sound nice. But I hope you ran a load line on the circuit to see if your transformer is within range to work for it. I don’t know anything about the Defender 5, but I hope that mod isn’t damaging your tube. Another customer tried to change the output transformer on this amp and ended up killing the tube and a resistor or 2. So I’m nervous about customers modding the OPT now, but you sound like you know what you are doing.
I made the frequency response of this amp a little wider than most amps, to make it sound “fatter” and “bigger” than it really is. After all these years, I can’t remember what frequency cut-offs I used. Most amps I design, I limit the bandwidth to allow it to fit in the mix within the context of a band, so it will cut through the mix better and be heard easier…more mid-range. I didn’t figure the Percolator would be played in any kind of ensemble, but rather in someone’s bedroom by themself where it’s nice to have a wide bandwidth, or in the studio where you can EQ it to fit into your recording.
-Brach