I am using Yamaha emx-200+mordaunt short floor stage,aiwa bookshelf spk and Kenwood center...this audio setup I am using for my PC desktop,unfortunately when I ply any thing from my PC thy is only 2 speaker or 4 speaker working...and I Dolby test my system the speaker seems like can't identify the correct device(when it shows the Left front speaKer suppose to working but the both front speaker voice out)a...need help...