What makes the David Berning amp so special?The output section topology gets around the traditional limitations of conventional transformers and so allows much wider bandwidth from the output section, regardless of power output. If you are wanting single-ended, this is arguably the best way to go. If you want a bit more power its especially useful, as the traditional issues that limit SET power and bandwidth simply don't exist.
It might be more accurate to call it 'Radio Frequency coupling'. The technique has produced IMO some of the best tube amplifiers made.