There's two parts of this, the existing preamp and the East.
It's a 1999 US Lakland and has the slightly darker Bartolini pups and original preamp ... I don't know if it was just me, or just my ears but I couldn't get on with the original preamp... the bass boost turned everything to mush, the mid cut turned the bass off, there were 4 different settings for the mids inside and I couldn't get any of them sounding great... What was wrong with it? Not sure. I think mainly how my ears were hearing it, and probably the it needed more input or something cos it seemed to sound better the louder I hit the strings. After 4-6 months of fiddling It was annoying enough that the bass was going to go... but the core sound unplugged of the bass is really nice... so....
The East was worth trying out. His preamps (IMO) are amazing. I find the Uni pre to be really really clean sounding. By that I mean not much distortion or colouration to the sound. I'm using a very good DI signal and Hellborg preamp I used to own as my yardstick to what a clean bass sound sounds like. It's high fidelity without putting very much colouration in at all. I've tried the Glockenklang 2 band... and if you boosted anything then you could tell it's sound signature and the fact it was a Glockenklang - the east doesn't do that. Active buffered blend, so the pickups aren't interacting from each other.... a tunable bass and treble control... plus a bright pick attack switch to instantly push the bass into a completely different sound (really good with the slightly darker sound pups) swept mids - which I find super easy to use... and a passive roll off too.... From spending ages playing with the old preamp I now have a setting for each pickup setting, and then can use the passive tone to taste... which is great. (bare in mind I've not really been playing much this year! :D) For balance... the Eq is clean like a PA desk - and powerful too... I think it was @peteb who pointed out that +15db of bass boost, in the wrong hands is not going to be good at all. So if you're someone who likes a preamp to give a certain colour, or want to turn everything full up... there might be better preamps for you...