Just recently acquired an old Denon AVR-800 5.1 surround receiver from work for free. However, being free, it is lacking any sort of manual. Anyway - On to the point. I get it home, hook up my 5 speakers, and go to plug the sub in - but then realize there is nowhere to plug the sub in to... How do I go about hooking my sub up to this thing? Any suggestions? If you need a pic of the back of the receiver, I can do that. Thanks.