[Piers]

Have a Sony DH510, when playing mp3/SD video stuff the volume is quiet and when playing ac3/dts/HD the volume is way too loud (have to turn the amp down 20 points).

Anyone have any ideas on this?

I looked through the manual but couldn't find an option for auto volume levelling or similar.

[bobo1on1]

This is probably because the volume setting in the operating system you're using is set too low, which doesn't affect passthrough.