I've been using
this AMZ splitter / buffer in many bass-builds. Works and sounds great! Maybe you could integrate it into your layout?
Here's a small layout I did for it.
If anyone finds it useful, I've been hooking it up like this:
input - splitter
output 1 - distortion circuit
output 2 - blend pot lug 1 (or 3)
distortion circuit output - blend pot lug 3 (or 1)
blend lug 2 - output (or to volume pot)
I can't remember which lugs excatly or value of the pot though..
So you need to experiment alittle there.
cheers
/ Fredrik
check out my building blog at www.parasitstudio.se