Alright, finally got my new HU a 7894 and yanked out the old sony. Pretty easy install I figured, hook up all the speaker wires..etc..etc. It worked fine for about 30 seconds then the sound from the speakers cut off. It was right after I had pressed the media xpander button. Thinking I had just muted it or something I started playing around w/the filters and turned MX back off. But it still had no sound, throughout all of this the subwoofers worked. It's like there's no signal going to my speakers. Could my factory amp be screwing things ups? It's a 97' F-150 Lariat w.the "Premium Sound System".