I’ve had a couple of different TVC things and neither stayed long.
They both did that nice transformer midrange trick that is very enjoyable but the bass was pish and had no real timing
I think my main problem was that they really seemed to work best when driven by something with zero output impedance and loaded with something with low input impedance.
As I use valve Phono and pre with non-zero output impedance and then a valve power with 100k input it really didn’t work.
The option of switching to sand based phono or sand based buffers was against my religious beliefs, so the TVCs moved swiftly along.
Ymmv obs