I have Tivo box connected to surround sound by optical cable plays OK from TV signal but will not play from recordings e.g. Recorded Glastonbury, picture ok no sound, sound ok via HDMI link to TV, any ideas??
there is a help page for Tivo sound issues if you click here. The following section seems relevant to your situation:
No sound on some recordings
If you're getting no sound on recordings from some HD channels when using external sound equipment connected via an optical connection, like an amp or surround sound system, change the audio setting from Dolby Digital to Dolby Digital to PCM.
To change this setting on your TiVo box, press Home on your TiVo remote then select Help & Settings > Settings > Audio > Dolby Digital > Dolby Digital to PCM.
Disclaimer - I don't work for Virgin Media. I'm just another VM user trying to help out so my answers may be wrong If you do like my answer please mark it as helpful as it may help others My setup: Vivid 200 Optical fibre with Superhub 2 in modem mode connected to a Netgear R7000 router. Telewest/VM user since 2001.