Converting an electric signal into mechanical movement takes energy. Thus, current needs to flow from the audio amplifier in the CD player to the headphones. In electronic terms: the headphones have a low impedance (AC resistance).
Due to a poorly designed circuit in the CD player, noise is introduced when current flows. So the more current is flowing, the more noise. Driving a dynamic load is not hard, it has been solved for a long time. The vendor just chose a poor design, probably to shave a couple tenths of a cent from the material bill.
A proper designed amplifier requires very little current (ideally none) on the input. In electronic terms: the amplifier has a high impedance. Thus the amplifier causes very little noise when connected to the cheap CD player.
The OP build a better amplifier that causes less noise when current is drawn from it, so using that results in a better quality sound.
Due to a poorly designed circuit in the CD player, noise is introduced when current flows. So the more current is flowing, the more noise. Driving a dynamic load is not hard, it has been solved for a long time. The vendor just chose a poor design, probably to shave a couple tenths of a cent from the material bill.
A proper designed amplifier requires very little current (ideally none) on the input. In electronic terms: the amplifier has a high impedance. Thus the amplifier causes very little noise when connected to the cheap CD player.
The OP build a better amplifier that causes less noise when current is drawn from it, so using that results in a better quality sound.