carvin offers a piezo upgrade. sounds like absolute dogmeat. what happened was, the bass i ordered had "problems" and they offered me this other bass that was in stock with options i diddnt pay for, for the same price. i took it, and one of the things i did not pay for was the $100 or so piezo upgrade. it sounds like absolute dogmeat, like a bad synthesizer trying to emulate an acoustic bass or something. maybe thats just the carvin one, but i cant immagine anything similar being usefull.
my 2 cents.
Had similar experience with my 5 string Carvin. Took awhile to work out setting on guitar and amp to make it sound reasonable. Ultimately worked it out so I use it often after some string changes, etc. It didn't have a piezo though.
See posts about EUB's (piezo equipped) and the right/matching amp. Euphonics are mentioned...