When you say "switch to tv," are you referring to cable, satellite, or is the system literally hooked directly to the TV when you "switch to tv?" USUALLY when something like this happens, it's because the source is only sending a specific number of channels for audio. Odd that it's one channel, so my last question would be, when you switch to TV, what exactly (and with what cable(s)) is hooked into the Bose system?