my amp makes a loud hum

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A lot of TV's dont have an earth (double insulated) so my guess that what you can hear is the frame sync pulses leaking throught to the audio. This is typically at mains frequency (50 or 60Hz) but is NOT phase locked. I have come across this (in fact it happens without fail :rolleyes: ) with CRT televisions and assumed it to be due to scan coils but you may be getting it with a LCD too :bawling: :bawling:

Can you hear this with a decent pair of 'phones plugged in instead ??

Also, do you have any kind of cable tv / broadband connected to the tv ??
 
If the TV doesn't have earth unconnect all other cales but the power to see if it helps. My guess is the antenna cable is connected to the same ground as the RCA or headphone.
Doesn't help you much but if it is the antenna then it is possible to build a hp filter to block the 50Hz.
 
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