Obviously, from many of the posts, they do, which indicates that there is not a good match between the passive preamp, and the amp in use. As I understand it,Resister based units will change what the amp is seeing base upon where the volume is set, and what resistor is in the audio path. The advantage of the TVC is that this variable is removed.
Assuming a good match between the source, the TVC, and the amplifer in question, it pretty much seems like a no brainer that a TVC will allow more of the music, or whatever else in in the signal to get to the amp. This is the very basis of the single ended amplifier designs that are so much more common these days, KISS, or fewer passive and active components to "muck up" the sound, as the Brits like to say. I am of the opinion that they work best with higher efficiency systems, such as I am using, but that is merely an opinion, not born out by extensive comparisons, as so far, only one system in my past experience has come close to what a single ended high efficiency system can provide the listener.
Assuming a good match between the source, the TVC, and the amplifer in question, it pretty much seems like a no brainer that a TVC will allow more of the music, or whatever else in in the signal to get to the amp. This is the very basis of the single ended amplifier designs that are so much more common these days, KISS, or fewer passive and active components to "muck up" the sound, as the Brits like to say. I am of the opinion that they work best with higher efficiency systems, such as I am using, but that is merely an opinion, not born out by extensive comparisons, as so far, only one system in my past experience has come close to what a single ended high efficiency system can provide the listener.