Trouble with Multiplex Playback

[rockmanX69]

I am playing through a laptop using the head phone out, using an 1/8" inch to stereo RCA cable. I am going into a Technics receiver. However when I play a Multiplex track, the ones with graphics behind the words, if I don't play the audio as the combined output I can not get the audio level to change using the master volume on the computer. Using either just the left or right channel the audio level with change for a split second when I change it but will then return to a very low level. The overall changes in volume with effect the combined audio if it is returned to that from the left or right channel. My question is if the problem is the cdgs themselves, or if it is hoster? Or if the cable I am using could be the problem? Any assistance would be much appreciated. Thank you very much.