32pfl407h, TV sound falls when switching from TV to DVD

[mipg]

Hello,

My TV is a 32pfl407h. Sound is perfect when viewing TV, however it drops to a to-low-level
when viewing a DVD. I have tried up to three DVDs. And I have managed both the sound control
(put up to 60, the maximun) and the configuration, but the sound doesn't improve.

Any ideas what should I try more?

Thanks.