YBA-1 bridged T circuit

[jmcd]

I picked up a lovely Traynor YBA 1 that has a bridged T circuit between the second and third gain stages along with a plate-driven tone stack. I've read through the TUT3 chapter on the Bass Master, but I'd like to know more about the bridged T circuit (what it does, how it does it, and what sorts of component value changes are possible).