This video from a youtube member shows that the Grass Valley CVR600 a.k.a Snell & Wilcox TBS190 can be used as a classic analog TBC in passthrough mode, Though it will give better results if the signal is kept digital and fed to the HDD using a SDI interface. I recently acquired two of these babies and I will be doing extensive testing in analog passthrough and in digital passthrough, though analog passthrough is not my prefered method since it has a slight loss of quality. I will report back.
The models I got are slightly different, they have analog audio inputs and an ethernet port for ftp control, The one in the video doesn't have analog audio input and have USB 2.0 for control, Never the less all models are fully controled from the front panel and its display.