After having reviewed a lot of gear over the years, two things jump out at me as being really important: Input impedance, and sweepable hi pass filtering. I currently use amps with a roughly 5MegOhm input impedance because that's what tends to sound best with my basses, and carry a preamp with me that has the same when I travel. Part of the reason that the impedance is so important is that it represents a kind of baked in HP filtering before you even hit the preamp. Here's my question/topic starter - since a lot of people seem to feel that these things are important, what is involved in creating a particular input impedance? Could this be incorporated into, for instance, a patch cable? I would ask similar questions about HP filtering: How big does that circuit really need to be, and does it need to be active (i.e. - involve a battery?). I would be interested in finding out what the smallest form factor for carrying my own input impedance and HP filter with me would be.