No they don't. They also can drive fairly long interconnect and maintain dynamics at all volumn settings
Some of my best listening time is late at night when the household is asleep. I play my Ypsilon TVC preamp at very low volumes and feel that I'm missing nothing from the recording. To be fair, the Esoteric front end is a big contributor to this fine low level sound. Although I'm a dealer for both of these products, this is what I hear.
The windings on the primary remain the same but the secondary windings are tapped. That means that the input and output impedance both change but maybe not relevant if buffered by the preamp.
Where a RVC converts to heat, a TVC or AVC convert voltage to current. The inductive part of a TVC is reduced at lower settings. A series inductor acts as a high pass filter but we're talking ultrasonic for these values.
The most noticeable difference at low volume will be Fletcher-Munson, which should have nothing to do with the preamp.