I have a Panasonic Viera TX37LZD81 that I have connected by the optical output to my stereo two channel amplifier (a Peachtree Nova). This works fine with SD television and also taking the audio from my bluray player by HDMI from the bluray player to the television. However, whenever I tune to a HD channel on the built-in Freesat tuner, all I get it distortion. I assume this is because the television is outputting a 5.1 surround sound signal when the amplifier can only receive a 2.0 signal. However, I cannot find any settings on the television to change the sound ouput to PCM. Any ideas?