TVC preamps: good or bad?

I don't know if they introduce colorations and aberrations, but they do seem to be very transparent and quiet and don't appear to be much bother by impedance matching issues that you sometimes get with resistor based passives. Some folks with pretty good equipment seem to swear by them, especially the Bent units and those made with S&B transformers.

What was the system setting when you tried the TVC?

This thread is a bit old and the Bent TAp with autoformer has been released. I did not own the previous version with the S&B trannies, but I did own a highly regarded S&B passive by K&K. I don't know if the difference is due to the difference in manufacturer, but I find the autoformer version of the TAP clearly superior to the S&B passive I previously owned. No leaness I can detect running my Music Reference RM9SE and incredible presentation of intonation by which I mean tracking changing levels of volume and and pitch which to me is critical to getting the musical message; that is, the new Bent Tap is very musically articulate. No loss of dynamics that I can detect compared with some highly regarded tube actives I have owned. With the right matching amp and source voltage, this passive is about as good as it gets; I think - worth an audition, especially if you own a tube amp with a 100kohm or higher input impedance and sensitivity half the output voltage of your source.

The BBAM is between DAC and BENT. That is the recommended approach?

If I understand Bobby correctly, the BBAM is almost always preferred no matter what preamp you are using.