Hello Steve,
Looks like you need someone to reply to your post.
I have also built several of John’s headphone designs. Often there are magic resistor values to optimize something. This HP circuit is no exception, for example the 221R resistor is likely calculated with Chris Paul’s formula to maximize the Push Pull of the output triodes into the 300 ohm headphones.
Some interesting things to me are:
The top triode in the voltage amplifier or input section is MIA. Typically the section is a Half-mu. As it is show the plate resistor takes the place of the second triode the typical Aikido.
The noise canceling voltage divider at the bottom triode of the output tube is goofy. There is no top resistor of the typical voltage divider in the orginal post regarding Aikido Push Pull headphone amplifiers. All of the B+ noise is injected at the grid, not the typical magically calculated voltage divider. Makes me wonder if this noise injection / cancellation still needs some tweaks.
Take a look at this blog post to compare the items above.
Aikido Push-Pull
DT