Paul, doesn't your supratek use a passive resistor volume control? When you turn that knob to control the volume isn't that a variable resistor? Why is that killer and what you call a passive is not?
Amfibius, your problem with dynamics had nothing to do with the fact that the preamp was passive. If the volume is all the way up and it isn't loud enough you didn't have enough overall gain for your combination of source-speakers-room. Adding an active preamp with gain solved that problem.
Here is the bottom line. Most don't understand that ALL volume controls are passive. They may be in a box with active gain stages so we call it an active preamp, but the thing that controls the volume (resistor voltage divider, TVC) is ALWAYS passive. Designing it as a unit and using an active stage to buffer the input and/or output of the control removes variables for the uninformed audiophile and they often get better results with an active stage. Not because active is superior but because they didnt properly implement the passive control. Most actives are plug_and_play because the standard is high input and low output impedance. This is easy to achieve with active buffer circuits in the preamp but adding an active stage must also degrade the performance in other ways. Passives cant always follow these rules so what comes before and after is critical to their performance.
As stated above careful attention must be paid to impedances and cabling to maximize the performance of the passive. This is exactly what the designer of an active stage does for you, but if you are knowledgeable about what is going on and you dont need the extra gain going passive is always superior.
