A massive class A headphone amplifier design. Lot's of tweak potential.

A multiple feedback headphone amplifier which can be altered to fit anyone. It was called in the beginning CMOY deluxe.

A patented current feedback headphone amplifier design. Used with permission. Mr Mark Alexander designed it long time ago.

A surface mounted class A biased headphone amplifier design. Main parts OPA627/OPA134/AD8610 plus BUF634.