I could have had the same situation with my cable box coax going right into the TV and having the TV send out a digital audio signal to the Onkyo; but the paperwok that came with the new HD box recommended using the component video into the TV rather than the cable coax.....but then there's no digital input to the TV to send thru, as our TV won't accept a digital audio input other than what resides on cable coax!
Comes down to coax for all, and let the TV send out audio; or send picture to the TV and sound to the receiver.
So I flipped a coin....and it worked!!
....nice to have options.
And "YUP" reading and re-reading the manuals if Fun...and informative....even moreso after a couple of days rest and data digestion!
Rich.
