Oh yeah there’s a difference alright. The fender pre is very bright and the treble roll off doesn’t do much. It also mellows the pickups quite a bit. The east really improved the individual pickup settings and made them useful by themselves, and the bass benefits a great deal from the treble control which boosts at a higher frequency than it cuts. The sweepable mid helps to dial in a lower end precision punch with the neck and a higher mid jazz sound with the bridge. Plus the buffered(?) blend control makes it so that the pickups aren’t fully soloed until dialed fully one way or the other. The fender blend control is basically a three way switch.
Ya'll....someone buy this. The John East pre is amazing! So good that I'm putting one in a custom bass I'm building. I've also owed a Jazz bass with a J-Retro and I gutted my Lakland 55-02 and put in a Uni-Pre. Same thing is going in my new bass. Best preamp I've every used!