"my sound bar has started switching from Digital1 to PCM by itself. It goes silent for a second each1 answer10/31/1002/24/11

believe it or not this is completely normal. i own this soundbar and
this happens all the time. PCM is an audio format going to the
soundbar. when the source (tv, DVD) has a pcm output signal, the
soundbar will recognize it and adjust. there is absolutely nothing
wrong with the sound bar. Happy Listening Happy P.S. if you are still
confused, just ask me to leave another comment explaining better."

More at http://www.samsung.com/us/support/owners/product/HW-C451/XAA and be sure the firmware is current (be sure the model numbers match!)