new tv hook up for surround sound + cable +dvd

We're trying to hook up a new tv with our Sharp Home Cinema HT-CN300 surround sound with a digital cable box and a sharp dvd player. It all worked together with our old tv but required a rf modualtor. The new tv doesn't need the rf modulator. With out the modualtor, the dvd image and sound won't show up when we switch over on the surround sound. Any suggestions? UGH! Help! Thanks!