Hey!
Have a wireless headphone set that uses a 9 V battery for the transmitter. An option is a 12 V, 200mA AC/DC Adapter. I have an adapter that has the correct plug for this unit, but the adapter is 12 V 400 mA. Can this 400 mA adapter be used without damaging the unit?
Ken

Yes, you can use the adapter if the plug and the polarity (center positive or center negative) are correct. The 200ma would be the minimum.