Here, I think I'm gonna build this next:
(http://www.runoffgroove.com/dbf.png)
now I don't know if I'll get this transformer 42TM018 in Munich, but they also say you don't need it, when you don't have any buffered effect before this one.
So now, what is a buffered effect? (is the Boss MT-2 one?)
I presume a 'buffered effect' is an effect with a output stage designed to drive currents down long cable/into lower impedances etc. A common buffer is a simple Commen collecter BJT stage. Atleast i think thats right
Basically, the transformer simulates the impedance of a guitar pickup.
Like a Fuzz Face, the Bazz Fuss (and Deluxe Bazz Fuss) sounds best when driven by a higher impedance device. When following a low-impedance output effect (such as a Boss pedal), the characteristic sound of the DBF will be diminished.
The transformer isn't necessary if you are just going to be plugging the guitar directly into the DBF.
If the transformer is hard to locate, try using the Gez wah output buffer in its place: http://runoffgroove.com/wahmods.html