For the last two weeks I am using model SDHD 556-B (white small STB)
Booting time as usual 20 to 30 seconds, menu and channel changing sluggish. Recording and Live tv functions l feel better. Recorded files are working fine in my 32 GB pen drive. Audio video quality much better than my old 2011 model. I felt that Dolby Digital Sound quality through HDMI as well as SPDIF better than my old model.