I have the transmitter part in all sorts of places around the plasma TV portrayed - there is always a more or less AC hum it. Only if I would make it to the station on the TV set, I had a trouble-free sound. But that is too shaky, especially when the headset is switched off at the transmitter. Once the headphones exclusively used my deaf grandma and for them the sound with a slight hum is ok, I'll keep the headphones.
