Aircraft Headphone Wiring Diagram - This is a scaled-down version of Nelson Pass' Zen power amplifier for my headphones. For this use, the Zen topology is perfect excellent sound quality, simplicity, linearity and no multi-stage feedback.. This is simple to build audiophile class-A tube headphone amplifier. It is based around 12AU7 / ECC82 audiophile vacuum tube that provides warm, rich and smooth sound expected from audiophile amplifiers. The 12AU7 (ECC82) is a Twin Triode vacuum tube, it is very popular in the audio world because it is rather rugged and can be operated at lower voltages..