I recently modified a Musical Fidelity X-CAN V3 headphone amplifier. My goal was to see what sort of improvements I could make without spending too much cash.
The X-CAN V3 uses bipolar output devices, with a tube driver stage. The tube driver stage is a JAN (Joint Army/Navy) 6922 mil-spec dual-triode tube, per channel. These tubes run in class-A and give the voltage gain necessary to drive a pair of BD139/BD140 bipolar transistors.… Read more