Headphone amplifier review

The project idea: I wanted to make an amplifier capable of driving various high impedance headphones, with as little distortion as possible. One key feature that I had in mind for this design was the very high-quality component selection, which gave my device a competitive advantage in terms of quality to price ratio in comparison to other market alternatives. The amplifier's maximum gain is 20dB with a THD of 0.03%. Circuit description: The power input (5-16V) is protected against short circuit and overvoltage. A single to double power supply converter circuit consisting of a TLE2141 and a push-pull power stage (BD139 and BD140) is supplying the voltages to the rest of the audio circuit. The audio signal goes through a non-inverting voltage amplifier (LM4562) and a class AB diode biased power stage (BD139 and BD140, 1N4148) with negative feedback provided by an unity-gain buffer amplifier (LM4562). The power supply bypass and signal output decoupling capacitors are Nichicon Muse (KZ series) and the signal input decoupling capacitors are Wima (MKS 4 series). The layer stackup is, from top to bottom: ground, power, signal, ground.