Sound problems with TV HD channels played through Amplifier

april_fool

I have a TV that plays through external speakers via an Onkyo amplifier. The TV connects to the amp with an optical cable. Sound is good for all channels with the exception of BBC1 HD in particular (sometimes other HD channels). Sometimes it works fine, sometimes sound comes out of one channel (eg music but no voices), and sometimes no sound comes out at all. Nothing changes in the set-up, and this has been going since we bought it (2 years ago). Is there anything that I can do about this (other than turn up the volume on the TV, which is what we have been doing)?

Tiexen

Have you tried changing the cable?

I_have_spoken

Freeview HD carries some programmes with 5.1 surround sound (e.g. films) which is usually OK if your TV is connected to AV Receiver by an HDMI cable.

Using optical from the TV is a bit hit and miss as Freeview HD doesn't use Dolby Digital.

See if your TV has an option to set '2-channel mix down' or 'PCM stereo' or something similar on the optical output so the Onkyo isn't getting the HE-AAC 5.1 protocol.

almillar

Above is good, but I see very little 5.1 content on BBC1HD. I've never really heard of problems with optical cables, so would have to guess that there's dirt in either end of the cable or connectors, or the cable is a bit broken. These cables can be fragile, and they carry light. You're not meant to bend them too tightly.
Test - do you have a set top box of any sort with an optical out that you could plug the cable into as a source instead of the TV?

april_fool

Thanks for responses and sorry for delay in getting back. I will look at TV/amp options as recommended by 2nd answer, but might otherwise be a damaged cable. If so, this is unfortunate, as cable is now built in to the wall behind the wall-mounted TV and the cabinet :-(

AnthonyUK

Freeview HD uses HE-AAC sound on the HD channels, many modern Freeview HD tvs and set top boxes transcode this to Dolby Digital 5.1 and 2.0 stereo and will pass this out on optical and coaxial digital outputs as a full blown DD audio bitstream;between different programme output 5.1 surround switching to 2.0 stereo you will notice changes, some amps automatically switch to Dolby Pro Logic II surround mode on stereo non 5.1 output and go back to full DD5.1 when sound changes to full blown 5.1 surround sound. Newer films are often broadcast in 5.1 on the HD channels as is Later With Jools Holland and some drama programmes and live events like Eurovision Song Contest are also that way as well.:)