Hi all, i've been using this older teac ag-v6200 for many years with just 2 speakers hooked up, now i am wanting two up top two on the floor and one center speaker. Im good with electronics, but cant seem to get the center speaker to work. plugging one in, a pioneer "center speaker" and trying the buttons on the front, nothing happens. on the back is A and B, right and left front and rear and center. what do i need to do to get it working so i can utilize the surround sound features it has? its not a huge deal but i have a total of 7 speakers that would probably make a movie sound out of this world but i can only use 4 right now...the buttons confuse...and dont say go buy another receiver lol. thanks for any help.