To me this metaphoriacal expression: "muddy sound" means lack of selectivity, lack of sharpness. With my playing it was usually experienced on low frequencies, when low notes was playing on low position.I play on Marshall VBC412 cabinet, and I think that pickups such as Antiquity II was not the best for my style of playing, because it was little muddy as I said, when I wanted to boos low frequencies. I know that jazz bass sound excellent on bright settings, like Marcus Miller slap style but I was looking for powerfull low but cutting or sharp sound. Original pickups on my 2005 Jazz Bass was'nt so powerfull and Antiquity II I think was too muddy, maybe its from their demagnetization. Don't get me wrong it wasn't bad sound but I knew that there must be something better for me. Firstly I was blaming my amp, because I heard that they can slow down or get muddy, but its no the case. Now I exchanged my jbass for Music Man Stingray with Piezo and this is the sound what I was looking for. It is very powerfull bass guitar with strong punch but with lots of clear and sharp low frequencies. My amp and cab greatly corresponds with this bass. Thats all.