Well the East Uni-Pre arrived yesterday and I got it installed today. It would have been a simple install but unfortunately my Roscoe cavity only had large deeper round routes around where each preamp pot mounts and the East preamp boards bottomed out on the thicker areas (outside the deeper round routes). Of course that prevented the threaded shaft of the pots from going fully through the body holes (so I could thread on the washer and nut). Nothing that a little routing wouldn't solve but it's certainly not for the faint of heart (or inexperienced techs).
Once I got the cavity ready the install went smooth and the preamp sounds excellent! I had spoken to Max at BBG earlier this week and he stated that the Roscoe Barts would work fine with in the passive mode of the East Uni-Pre. I had my doubts but as usual, Max was indeed correct. The bass sounds great in the passive mode!!! The passive tone control works really good (in both the active and passive mode). This preamp provides some excellent tone shaping capability! Awesome highs, Smooth deep lows and the ability to use the Mid-Freq knob and zero in on the mid freq. to boost or cut. The highs really remind me of the Demeter Pre. Really glassy and clear sounding.
I'll record some sound clips later in the week and post them. Until then you can look at the pics.