The input sensitivity of the VTL MB 450-iii is a function of damping factor but at the setting I use (minimum damping) is a low 775mV hence one needs to be very careful in setting the level on the Vivaldi. Luckily dCS provide a 0.6V (and a 0.2V) setting as well as 2V and 6V.
I currently use 0.6V with my active pre-amp and find that this works well with the volumes I like to listen at (i.e. operating the amp at close to unity gain in effect) so my presumption is this would be the best place to start with a direct connection so as to minimize the amount of cut I need to take in the DAC volume control and more importantly avoid the danger of over driving the speakers with catastrophic effect (this has happened to me in the past when I had a cable short and it blew the woofers in a set of Magico V3s)
I currently use 0.6V with my active pre-amp and find that this works well with the volumes I like to listen at (i.e. operating the amp at close to unity gain in effect) so my presumption is this would be the best place to start with a direct connection so as to minimize the amount of cut I need to take in the DAC volume control and more importantly avoid the danger of over driving the speakers with catastrophic effect (this has happened to me in the past when I had a cable short and it blew the woofers in a set of Magico V3s)