sansui av receiver rz-9700avd, Vocal isn't coming out,need HELP

[ziamax]

hi All,
Hows it going? Im new user here. Im having problem with my sansui av receiver RZ- 9700avd. I dont have user manual or anything like that. The problem is when i play DVD, Vocal (voice) doesn't come out, only background music comes out perfectly (like karaoke, no vocal only music). I pressed all the button from my remote control, still the same. Im not a GURU in hometheare system, so i need you guys help plz. Could anyone help me plz?!!!!!

one more thing, I have this "Subwoffer pre out" on back of my sansui av receiver (RZ- 9700avd).what this does? Can i be able to plug my receiver(NOTE:receiver it self an amp) to another amp ? I have a TEAC PLS-66 5.1 amp,I would like to connect it with my Sansui AV receiver. How can i do that?
will be realy glad if anyone helps me out.have a nice day.
cheers
Max, Australia

[MCH]

I assume you are talking about DVD movies. Do you have 5 speakers that includes a center channel speaker? I don't know the Sansui receiver or if its 5.1 capable.
I'm guessing here. But if you only have two speakers (mains left and right). When watching a DVD, in the Main Menu select the Stereo 2 Channel sound.
From what you describe it sounds like you are selecting DD 5.1 or DTS 5.1 and have only 2 main speakers. Therefore the Karaoke effect.
that's my best guess