I know Dave Gilmour uses the F-2b and has been for years.  The gilmour web-site said they changed capacitor values to make it less bassy and added a preamp tube...any suggestions.

Was the F-2b in his regular rig?
 I remember reading it was used for the Leslie signal path.

I don't know Elwood; but a quick google found this.

Thanks Dave,
...and Welcome Eric...good question,  
   I wonder if the extra tube stage was added in the front, if so you might be able to simulate what Gilmour was getting by putting something like a BK tube driver before the F-2B.

I use an F-2B through a Mesa 50/50, along with a Demeter Real Tube Reverb and a SF-2 in my guitar rack rig.  The F-2B works fine as a guitar preamp.  In fact, IIRC, the F-2B is based on the Fender Dual Showman, a guitar amp.
 
Bill, tgo

Thanks guys...I googled this topic for our and got many different opinions...It sounds great now but I just like to tweak on things

just googled gilmour alembic mods and got my answer.  The tube was added as a cathode follower to lower impedence

Cool,
I see that mentioned in the thread here
 I see how a lower impedance would be good for Gilmour's rig considering how many pedals/processors might follow the F-2B.
 
 
Half way down this page it mentions:
To optimize the unit for guitar, it was modified by adding an extra tube in the preamp section for a little more drive, lowering the impedance in the output and changing the capacitor in the bottom end to eliminate some of the lows to prevent ?boominess? in closed-back cabinets.

Mine is set up so you can easily cascade the first tube stage into the next, but it does not do anything exciting for me that way.