Hello: we have a 2013 sony KDL40ex640 hd digital tv. I want to plug headphones to listen that way, and have the builtin speakers silent. 1) the tv has an open usb2 port. can I buy a usb-bluetooth tx dongle and headphones, and that will do the job? or 2) I have an old wireless sennheiser headphone w/transmitter, using RCA input jacks. The sony tv has a single RCA appearing audio-out jack. I plugged in one only of the sennheiser transmitter rca jacks to the sony, but nothing came out. 3) I looked at tv settings and found nothing about the audio jack. I wonder if the jack is a dummy? Or is there something I can adjust to get sound out of that sennheiser (and turn off internal tv speakers)? 4) yes, I tested the sennheiser, it works fine on my a-v setup. Yes, I called sony tech support, she did not have an answer on any of the above.Thank you, stay safe.