Sanyo LCD TV speaker hum at low volume

Question

Just got a new LCD for the bedroom because it’s in the bedroom we use it a low volume most of the time...it has a constant hum that is really noticeable and annoying at low volume..The TV is not currently connected to any other devices and makes the noise even if the antenna is not plugged in.....I have already tried: - Replacement unit ...... no change- AC plug with no earth lug ..... no change- Different Speaker (the unit has a separate speaker enclosure attached to the bottom with speaker wire from the TV) ...no change- Ferrite Clamps on the speaker wires ....no change- Head Phones.....the hum is not present when listening with head phones I have read a lot about Ground Earth Loop Isolators but as I only have the AC power, Antenna and Speaker connections I don’t have anywhere to connect one. I suspect the noise is internal from the TV I guess I am looking for a device that will isolate the hum from the speaker cables...any help or suggestions appreciated.