Datavideo TBC-1000 outputs?
 

Wondering whether there is any reason not to simultaneously use more than one of the TBC-1000 S-Video outputs when capturing analog VHS or Hi8 tapes. In other words, is the S-Video signal freely going to all four outputs such that using 2, 3, or 4 at the same time would not affect the quality of the others, or does the signal get negatively affected by having it split into more than one stream because it gets "drawn" like AC power once a device is attached to an output?

The TBC-100 card is married to a VP-299 distribution amp, thus creating the TBC-1000.
So the distro amp is 4 outputs of same signal.

The idea of a splitter harming quality is an old video myth, dating back to at least the 1980s. It can, but inherently does not.