Most cable boxes have a volume control, and yours may be set to a low volume. Try increasing the volume in the cable box and see if that doesn't increase the volume.
Keep me posted.
So I bought the LN40A500 around xmas and have been happy with it so far, but last week I tried to hook it up to my surround sound using the TV's audio out red/white port. The sound that came out was VERY low. To give you an idea I had to turn my system all the way up to even hear that it was on and even then the sound that came out was very distorted. And the system I use is very loud I normally never put it up over 40% volume or so. It also works fine with all my other products but not my TV for some reason.
So I said wth I need a surround sound system anyway so yesterday I went out and bought a 5.1 surround sound and connected and I have the same issue. I have the home theater hooked up to the TV two ways. The first is through HDMI for when I'm watching movies directly from the home theater system. The second way is through red/white video cables for my cable box sound. the sound that comes out is very low.
When I'm watching a movie through the systems hdmi cables it sounds great. I never have to put the volume over level 13 or so. but when I'm trying to watch my cable box I have to turn the system up to around level 30 to watch tv. Anyone know a way to fix this?