Hmm, maybe I can answer my own question.
From what I understand, sort of, a passive preamp is more affected by the input impedance of a CD player and its output impedance into the amplifier than an active preamp. The interconnects also need to be of a relatively low capacitance so that the source can "drive" the signal through the passive and into the amplifier. I hope I have that right. I am no electrical engineer, but I have read a few books (I sound like a Holiday Inn commercial). So, the act of changing the volume actually affects the resistance of the input and output impedances.
The more I think about it, the more I realize I have no idea what I'm trying to explain. Maybe someone else with more wisdom and experience can chime in.
Bottom line--a passive preamp (in theory) will add no coloration to the sound because it is simply passing the signal from the source into the amplifier.
Anyway, still curious about the HT bypass. . .
