When we were requested to develop a headphone amplifier, for sure that had to be something special . Especially considering that it had to be complimentary to our Octave DAC MKII.
The result is the Aurix. Not a common design with like many before it but a real improvement on existing principles. Rather than using transistors or tubes for amplification a special step-up transformer is used. Said solution solves many problems that are found in regular low gain amplifier designs and provides a very transparent sound image.
Only two FET transistors are in the signal path as an impedance converter ( source follower, no amplification ) and it is this property where a FET transistor can do an extremely good job and delivers a very high bandwidth having low noise and low distortion . The first Fet is used as an impedance converter to drive the step-up transformer. The second FET is used to drive the headphone. The circuits are running in full " Class A " so that a relatively large heatsink is required to flow the heat . Besides the amplifier part we have used a lot of electronics just for creating the right conditions for the amplifier part and protecting your headphone against subsonics , offsets , pops and clicks. The result is a sound that is mainly determined by the connected source.