Hi, so I have been looking at some schematics for a bunch of preamps and small amplifiers lately, and noticed that many have a resistor bridged across the positive and negative signal inputs (to set input impedance) that many people install across the 2 terminals on an rca input jack. Is that necessary to have a good sounding preamp? I built a passive preamp a while ago with just a dpdt switch to switch between 2 inputs and also a 100K alps potentiometer. Would adding resistors across the positive and negative signals help the sound a lot, and in what way? The passive sounds clean, just a little bit like a boom box at times :-p It is clear, but somewhat congested/bland sounding. Thanks!