Samsung PN51E6500EFXZA - Manual (Page 106)

may fluctuate each time you change
the channel. This feature automatically
adjusts the volume of a channel by
lowering the sound output when the
modulation signal is high or by raising
the sound output when the modulation
signal is low.
N To use the volume control of a
connected source device, set Auto
Volume to Off . If Auto Volume is
set to Normal or Night , adjusting