if you are handy with soldering... if you use headphone around 32ohm get a pair of 5-10uH small inductor to bypass the 10ohm output protection resistor on TPA6120. It would lower the output impedance signifacntly on audio band and improve the control to the headphone driver. It definitely need to be tested, if it is stable (not osciallating, the TPA chip stay warm not hot and the high frequency stay the same or better, then it is not oscillating). I did once on my amp that is based on the same chip. the improvement is not small.