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.
QRV08 A surface mounted current feedback headphone amplifier design (QRV06) which has super regulators and transformers. May be a headphone amp with the most advanced power supply units in the world right now.