Hybrid Headphone Amp

Potentially, headphone listening can be technically superior since room reflections are eliminated and the intimate contact between transducer and ear mean that only tiny amounts of power are required. The small power requirement means that transducers can be operated at a small fraction of their full excursion capabilities thus reducing THD and other non-linear distortions.
This design of a dedicated headphones amplifier is potentially controversial in that (1) it has unity voltage gain and (2) employs valves and transistors in the same design.