No sound to rear speakers when using DOLBY TRUEHD Bluray from SONY player and ONKYO amp
I have a SONY BDP-S760 Bluray player feeding through to a ONKYO TX-NR809 amp. When the player is outputting the disc in DOLBY TRUEHD the ONKYO shows the output is in DOLBY TRUEHD on the display, but there is no sound from the rear speakers at all. The speakers work fine with PL11X, etc, but just nothing with DOLBY TRUEHD. I'm a bit new at this game, so am obviously missing a setting in the ONKYO somewhere, but I've looked through the, none to helpful manual, and can't find it. All help appreciated.