Any help appreciated.
stevem8: Thanks for help.
The source is a Sony Bravia integrated tuner - 46W4000 model. The optical output is set to "Auto" mode. If it is set to PCM you always get 2ch and there is no issue, but obviously no 5.1 either.
Th strange thing is that the optical input shows as a 6.1 (not 5.1) source on the AVR front panel (FL,FR,C,LFE,SR, SL + SB). I'm pretty sure it previously showed as 5.1. On reading the AVR manual it doesn't look as though it can take a 6.1 source down to 5.1 which would explain what is happening as I only have the 5 speakers+LFE.
But, it used to work. I can't see what has changed.
Involuntary autocorrect in operation on mobile device. Apologies in advance.