the primary culprit behind sound distortion
Electronic components, such as smartphones and DAC, exhibit relatively small distortion ratio (+- 1dB), whereas those transducers such as earphones, headphones
and loudspeakers that transform electrical signals to acoustic signals exhibit much greater distortion ratio (+- 20dB).
The foregoing explains why sound quality varies most conspicuously according to which headphones,
earphones or loudspeakers compressed audio pipes through.