Perform the following steps to enable/disable the Bluetooth availability in NAD C 338:
Bluetooth OFF (invisible) – Press and hold the button of the AMP3 remote control until the BT/Wi-Fi display icon blinks twice.
Bluetooth ON (discoverable) (if you want to turn it back on again) – Press and hold the 
button of the AMP3 remote control until the BT/Wi-Fi display icon blinks thrice.