You will get no sound effects when sending DD from the TiVo. This was even the case ten years ago. Only now, with digital programming, DD is the norm. When going straight to the TV it will typically be sending a stereo pcm signal which you will hear the sound effects from.
I know on my cable system everything is sent as dolby digital. Whether it's 1.0 or up to 5.1, it's all in DD on FiOS.
Roamio Pro (5TB)
TiVo Mini x4
Roamio Basic OTA (1TB)
53TB unRAID2--38TB unRAID3--33TB unRAID1a