> does the G&L L-5500 have the same schematics as the L-2000 or the L-2500?? In that I mean the 3 switch and 3 knob configuration. No. The L-5500 has 2 EMG soapbars and 3 knobs (volume/pan/bass-treble stack [BTC]). The 2000 & 2500 have the G&L MFD's and the switches for phase, series/parallel, etc.
> will the sound of the preamp dramatically change the sound of my jazz bass? No & Yes. The J-Retro "can" dramatically change the sound of your bass IF you choose to (i.e. if you crank the bass, mid , treble settings), however, it is designed to retain the original Jazz bass sound with the controls all at the center detent (0 cut/boost). It does have a built-in slope but does not alter the tone very much IMO.
> i get the impression that it'll make it become a P bass or somethin! No. But you can get a better facsimile P bass sound by panning neck pup only, kicking up the bass & treble a tad and setting the mid freq. sweep to the low mid "thump" and boosting it a little. Not exactly a P, but better then what you can currently get. Your J will still sound like a J, but your palette of tones with the J-Retro is huge!
-- Gil