The PSB M4U2 headphones feature two jacks that you can plug BTUnes into. Make sure that you plug BTunes into the left jack and not the right. The design of the M4U2 has a great deal of electronics without shielding in the right side of the headphone. Those electronics can produce interference with bluetooth and degrade the quality of sound you get with BTunes. This interference occurs when the headphone's active or ANC modes are turned on.