If you are unable to hear any sound from the PSB M4U series headphones when 3-Position Power Switch is either ON or ANC mode, verify the following:
- Audio source – The audio source is powered on, not muted.
- Bluetooth – When paired with Bluetooth, ensure the source device is within 10m range (Obstructions and radio wave conditions may affect the actual range).
- Cable – Connect using other cables supplied with the headphone. (Connect the standard analog cable – 3.5mm straight connector to both right or left earcup inputs and the 90-degree plug end to the audio source)
- Charging – Connect the USB cable to the right ear cup to recharge the internal AAA batteries (3-Position Power Switch LED blinks Red when charging).
- Battery – Replace batteries (check for polarity).