The subject line says it all, unfortunately. In addition to the native speakers/sound being lack luster, sometimes the digital optical output on many of the HDTVs is not ideal for what you need to accomplish.
In your case I need to know a little more info just to verify what's happening and the equipment involved. Is the HDTV tuning in a signal and passing it along to the amp(?) Or is there a separate cable or satellite box involved too you could use? That is the ideal scenario for good audio quality- avoiding passing it back from a TV.
I see on p.15 of the LG amplifier/receiver user manual that there appear to be some digital optical audio settings accessible via the remote. Is yours currently set to 'AUX OPT'? Here's the link to the user manual so you can check that as well-
Also, in the manual for your HDTV, I read that you have to set it so the HDTV's built-in speakers are off. [TV Speakers option -off in the Audio menu] See p.44 & p.110 of the manual here-
Let me know if that works. There was also a reference to 'Audio Copy Protection' on that HDTV for certain types of content. Perhaps that's what's going on here. Sorry I am not familiar enough yet with what you guys have across the pond from your cable & satellite providers ;).
I have an LG 32LE5300 LED tv - great picture, sound lacks depth.
So I've also bought an LG HT321DH 2.1 home cinema amplifier. The TV only has headphone out or optical out, so I'm using the optical. It does work but intermittently only the left channel being picked up by the amp. It can be corrected by switching amp input using the remote and then going back to optical. It always just outputs left channel when the amp is already on and the TV is switched on. If the TV is already on and the amp is switched on, then no problem. I've tested the amp with another optical source and the same problem isn't there, so it seems to be the TV that's causing the problem - or it's only apparent with the TV.
I'd have thought really that with optical it's all or nothing as the signal is multiplexed into one stream. As I say, the amp is fine on all other input channels and other sources.
So, does anyone know what's causing this? Is this a common problem? Is the TV faulty? It is under warranty. Could it be the cable? It's only a cheap one.