Things aren't as impressive when you plug-in a pair of headphones. Stereo crosstalk, which increases rapidly, volume levels decrease and intermodulation distortion starts creeping in. The general result is still decent, but we've certainly seen better here.
可能是手機內建的功率放大器推力不足吧, 推不太動低主抗耳機(該網站測試用耳機為AKG headphones with impedance of 32 ohms) 所以要維持好音色, 可以試試看加上耳擴(輸入阻抗高, 較接近無負載狀況), 或是選用較高主抗的耳機試試.